USRE28437E - Work-head with automatic motions controls - Google Patents

Abstract

56. AUTOMATICALLY CONTROLLED APPARATUS, INCLUDING A WORK DEVICE, MEANS FOR TRANSPORTING SAID WORK DEVICE THROUGH THREE-DIMENSIONAL RANGES OF POSITIONS, AND CONTROL MEANS FOR SAID WORK DEVICE AND SAID TRANSPORTING MEANS, SAID CONTROL MEANS INCLUDING A FIRST SOURCE OF CONTROL INFORMATION FOR DETERMINING A PRESCRIBED PROGRAM OF MOTIONS OF SAID WORK DEVICE IN THREE-DIMENSIONAL SPACE, A FURTHER SOURCE OF CONTROL INFORMATION INDEPENDENT OF SAID TRANSPORTING MEANS FOR GENERATING, DURING OPERATION OF SAID FIRST SOURCE, OFFSET INFORMATION THAT VARIES IN THE COURSE OF THE PROGRAM PROVIDED BY SAID FIRST SOURCE OF CONTROL INFORMATION, AND MEANS COMBINING AND RESPONSIVE JOINTLY TO SAID FIRST AND FURTHER SOURCES OF CONTROL INFORMATION FOR CONTROLLING SAID TRANSPORTING MEANS TO EXECUTE SAID PRESCRIBED PROGRAM OF MOTIONS MODIFIED BY THE GENERATED OFFSET INFORMATION.

Description

June 3, 1975 I 5. c. DEVOL EI'AL Re. 28,437

WORK-HEAD WITH AUTOMATIC MOTIONS CONTROLS Original Filed July 30, 1968 6 Sheets-Sheet 1 m an,

Juno 3, 1915 I c, DEVQL h TAL Re. 28,437

WORK-HEAD WITH AUTOMATIC MOTIONS CONTROLS Original Filed July 50, 1968 6 Sheets-Sheet 4 lllllhlll'i'mllllll 2/4 2/0m 244 245 WORK-HEAD WITH AUTOMATIC MOTIONS CONTROLS Original Filed July so, 1968 G. C. DEVOL ET AL Juno 3, 1975 6 Sheets-Sheet 5 i I I -JEA' WORK-HEAD WITH AUTOMATIC MOTIONS CONTROLS Original Filed July 30, 1968 June 3, 1975 a. c.DEVOL ETAL 6 Sheets-Sheet 6 m 0 Z 8 0Z 4 x a 2 a J u 8 3 J a aMW 6 3 22 a a E- 3 6 |!..l 7 2 F2 a 5 7 2 3 3 5 a 8 3 M 5 3 5 United States Patent;

e. 28,437 Reissued June 3, 1975 28,437 WORK-HEAD WITH AUTOMATIC MOTIONS CONTROLS George C. Devol, 990 Ridgefield Road, Wilton, Conn. 06897, and Paul S. Martin, 189-54 43 Road, Flushing, N.Y. 11358 Original No. 3,543,910, dated Dec. 1, 1970, Ser. No. 748,703, July 30, 1968. Application for reissue Nov. 30, 1972, Ser. No. 310,769

Int. Cl. B65g 47/08 US. Cl. 198-34 68 Claims Nlatter enclosed in heavy brackets If appears in the original patent but forms no part of this reissue specification; matter printed in italics indicates the additions made by reissue.

ABSTRACT OF THE DISCLOSURE The disclosed apparatus has a work-head movable in program-controlled three-dimensional paths by an extendable and retractable arm that is movable through angles both in azimuth and elevation. The Work-head may be any of various tools. As shown, the work-head has article gripping jaws. The work-head is also operable about horizontal and vertical axes at the end of the arm. Each motion is produced by a respective drive unit, especially a hydraulic actuator, and has a corresponding control. Inverse angular controls can be used to enforce equal and opposite angular movements of the work-head about its axes corresponding to the angular motions of the arm in elevation and azimuth.

In one form of the apparatus, the control information is supplied directly to the respective polar-coordinate controls, in polar form. In another form of the apparatus, the control information is supplied in rectangular coordinates and controls the operation of a manipulating unit having respective parts movable in mutually perpendicular direc tions, and the manipulating unit operates a lever that is movable in elevation and azimuth and operable lengthwise by elongation and contraction, and in turn, the lever acts as a converter or as part of a converter in operating the polar-coordinate controls of the work-head operating apparatus.

There is a linear-motion control in both forms of apparatus additional to the controls already mentioned for producing a control eifect to cause straight-line motion of the work-head in a direction that involves lengthwise and angular motion of the arm that carries the work-head. Information can be supplied to this linear-motion control in increments, as in pallet loading; or it can be supplied continuously to enable the work-head to carry out a program of control informationin relation to a work space on a continuous conveyor. There is a converter in the polar-coordinate apparatus that responds to the linearmotion control and provides polar-coordinate output for introducing off-set input into the polar-coordinate controls that otherwise respond to the polar coordinate control information. In the rectangular-coordinate apparatus, the linear-motion control introduces an off-set in the manipulating unit that responds otherwise to its input con trol information.

This application is a reissue of Pat. No. 3,543,910 which matured from application Ser. No. 748,703 filed July 10, 1968.

The present invention relates to apparatus in which a Work head is operable automatically to execute a sequence of motions. The work head may assume various forms, such as a drill, or a paint-spray gun, or an assembling tool, or jaws of a resistance welder; but the features of the i.nvention are described below primarily in relation to ar ticle-transfer-apparatus in which the work head has an article gripper.

Apparatus of this type has been developed for operatlon under program control to execute prescribed sequences of operation. The apparatus is very flexible, since it can be adapted to new uses merely by developing a new program. Typically it includes a work head that is carried through space in a primary three-dimensional pattern of motions and the Work head itself is operable in secondary motions to assume various attitudes as it is carried through its pattern of motions. Examples of such apparatus are shown in US. patents issued to G. C. Devol, Nos. 2,988,- 237, 3,251,483, 3,279,624 and 3,306,471.

A particularly useful form of construction involves an arm that carries the work head where the arm is operable about at least one axis. In a commercial program-controlled article-transfer apparatus, there are three primary motions of the arm, about vertical and horizontal axes, and telescopic elongation and retraction of the arm; and in addition a unit carried by the arm is capable of moving the work head in what may be called secondary motions, such as a wrist-bend motion. In an application filed concurrently herewith by George C. Devol, one of the applicants herein, a related improvement is disclosed, providing for automatic correlation of a work head pivotally carried by an arm that is itself operable about a parallel pivot, to maintain constant aim of the work head.

Because of the primary angular motions involved in that type of apparatus, the straight-line motion of the work head in any one direction involves a certain amount of complexity. The problems are further complicated where there is a sequence of positions to which the work head is to move which are related to each other in a basically rectangular-coordinate system. Each required motion of the head along a line parallel to an axis in a rectangular coordinate system must include control constituents that take into account the angular motions of the arm and the armlength change. For example, an article transfer apparatus may be applied to the loading or unloading of pallets with articles in a rectangular pattern of rows, columns and layers. In another example, a work head may be required to keep up with one section of a conveyor moving along a straight line. The latter problem is dealt with in one manner in Pat. No. 3,283,918 to G. C. Devol, wherein the program-controlled apparatus is bodily shifted in synchronized motion with one segment after another of the conveyor to execute its program cycle.

Accordingly, an object of the present invention resides in providing motion-control apparatus that responds to linear control information for controlling a Work head carrying an arm that is movable about at least one axis and wherein the arm is operable lengthwise to extend and retract the work head, and more particularly wherein the arm is movable about two mutually perpendicular axes.

A further object of the invention resides in providing motion control apparatus that is adapted to respond to instructions given in terms of rectangular coordinates in a plane or in space for controlling the motions of an arm that moves a work head to various extended and retracted positions and about at' least one axis, and more particularly where the apparatus is one that has an arm operable about mutually perpendicular axes.

As indicated above, program-controlled apparatus has heretofore been available commercially that has an arm operable about horizontal and vertical axes and carries a work head capable of angular motion on the arm. The unit carried by the arms has been capable of executing a wrist-hen motion. The Work head itself has been capable of twist motion.

An object of this invention resides in providing such apparatus with increased capability, by adding a further wrist-bend motions about mutually perpendicular axes.

The twist motion'may be retained if desired.

An object related to theforegoing feature resides in providing means for coordinating the operations of a work head through changes in both azimuth and elevation angles in' relation to a supporting arm with changes in the angles of azimuth and elevation of the arm for maintaining constant aim or attitude of the work head as it is bodily transported by its'supportingla'rm through complex motions in space.

A still further object-resides in providing a means for modifying the operation of apparatus having an arm movable through an angle about an axis and carrying a work head to extended and retracted positions, and Wherein the worlc'head itself is operable about a parallel axis, so that the angle of the arm and its length change, and the angle of the work head relative to the arm changes, so as-to move the Work head along a straight-line path, to maintain a constant relationhip of the work'hea'd with a point in. space that is moving along a straight line. For example, the point may be'identified with-a discrete portion of a conveyor moving along a straight-line path.

A further object of this invention resides inmodifying the operation of apparatus of such construction to execute a program of operation established initially in a stationarycspace", where the space is then set in motion along a line passing the apparatus.

A further object resides in adapting apparatus of the type having an arm that can extend and retract a work head and Where the arm is operable through-angles of azimuth and elevation, and where the work head is operable relative to the arm through angles crazimuth and elevation, so that the work head can maintain a constant relationship with a point in space that moves along a straight line. A still further object is to adapt such apparatus to execute a program of operations in relation to a segment of a conveyor in motion where the program was established in relation to a stationary volume or space.

The cooperation of program-controlled apparatus of the construction considered above with a conveyor is but one example of automatic operation under a program control, modified by a second source of control informationpMore generally expressed, an object of the present-invention resides in providing apparatus normally operable under control of a main source of control information to move a work head through prescribed patterns of motion, with off-set control means and a supplementary source of offset control information to modify the pattern of motions that would otherwise be executed under control of the main source of control information.

Another object related to the foregoing resides in adapting such apparatus to alternate operation with and without control by the ofi-set source of information. Such a situation arises (for example) where an article transfer unit is to transfer a seriesof articles from a stationary supply point or a pattern of stationary supply points to a point or a series of spaced-apart points all of which are identified in the program of the apparatus, butwhere the delivery point or points are set in motion on a conveyor. The article holder operates solely under control of the program in approaching the stationary supply point time after time, but it moves to'a progressively advancing point or to progressively advancing mutually separateddelivery points in alternation with its motions to the supply point or points under an off-set control that represents the .motion of the conveyor, and where the oif-set control is alternately in effect and removed from effect.

"The foregoing and other objects, advantages and features are realized in the illustrative apparatus described below and shown in the accompanying drawings that form part of the disclosure of such apparatus. Generally, two embodiments are shown. A basic structure useful in both embodiments includes an arm that is carried on a rotata-" ble post and pivoted on the post about a transverse axis to'r'aiseand ower=a ork-head'carriecl'byth arm/That two axes are involved is of distinct advantage but broader aspects of the invention apply to a'structure' in which the arm is bodily moved, linearly, for raising and lowering the work head. The work head is carried by the arm for corresponding movements about horizontal and vertical angles of tilt and swing, these being the motions referred to above as doublewrist bends. The 'work head itself may be arrang'd to rotate about its axis 'and it may have its own further adjustments or controlled ,actuato'rs, as may be needed. In the illustrative structure, the tilt angle and theswing angle are coordinated in several ways withrthe angles of elevation of the arm and turn of the arm-supporting post.v 4

The control apparatus for. such a structure for adapting it to respond to linear-motion control information is described in connection with two illustrative embodiments showninthe drawings. Each includes a converter" that responds to linear control operation and provides output control for .the required motions, of the arm thatcarries the work head. 1

1' The converter includes a. lever-having the same motion capabilities-as the arm that carries the work-head; The

lever operates servo-master controls, while the actuators of the arm in its various motions are controlled bywhat mayxbe considered servo slave units. The master and slave controls are coupled to each other variously, e.g., electrically and electromechanically. I

i In one of these embodiments, the converter responds to three-dimensional rectangular-coordinate control information. This information may come from various sources, as from a recorded program, or a computer, or both. In one of its coordinates there is an off-set input of linear control, from the conveyor. The pattern of operations of the work head in space is controlled by information from the main source of control information, here the program drum, and the operations then ensue in relation to a stationary space. The identical motions are executed in relation to a moving space: as a result of off-set-information supplied to the converter-by a servo link to the conveyor. The converter automatically changes the angles of elevation and azimuth ofthe arm, and its length, asneeded, either for keeping the work head in constant cooperation witha pointin space that moves with the conveyor, of for enabling the-work head :to keep pace withthe-advancihg pattern of points that are involved in the program.

In a second embodiment the program control information is provided directly toeach control for the actuators that tilt, swing and extend the arm which carries the work head. Aconverter is provided that-has a linear input control operated by a servo link to a conveyor, and the lever of the converter operates controls that introduce an appropriate off-set into each of the actuator'controls of the arm for keeping the Work head on the arm in step with a point or a pattern of points on the conveyor.

The nature of the invention in its various aspects is more readily understood andappreciated. from the following detailed description of the illustrative apparatus shown in the accompanying drawings.

In the drawings: t a

FIG. 1 is a lateral elevation of an article-handling apparatus shown partly in cross-section and showing in broken lines a position assumed by one of its parts in the course of operation;

FIG. 1A is an enlarged cross-section of part of the apparatus of FIG. 1 as viewed from the plane 1A1A in FIG 1;

FIG; 2 is a top plan view of theapparatus of FIG. 1, showing in broken lines a position assumed-by part of the apparatus in the course of its operation;

"FIG. 2A is a fragmentary View of aportion oyFlG. 2, drawn-to larger sc'ale," i

FIG; 3 "is an enlarged lateral cross-section of a detail in FIG. I, viewed from a vertical plane atright angles to FIG. 1;

FIG 4 is an enlarged view of part of the control structure inunits 86 and 88 of FIG. 2;

FIGS. 4A, 4B and 4C are modifications of the control apparatus of FIG. 4;

FIG. 5 is a block diagram showing the coordinating and program-control apparatus for the apparatus of FIGS. 1 and 2;

FIG. 6 is a somewhat diagrammatic lateral elevation of the apparatus of FIGS. 1-4, modified to include further features of the invention;

FIG. 6A is a diagram illustrating a manner of operation of the apparatus of FIG. 6;

FIG. 7 is a plan view, partly in cross-section, of the converter in FIG. 6;

FIG. 8 is an end view of the converter of FIG. 7;

FIG. 9 is a top plan view of a detail of the converter of FIG. 8;

FIG. 10 is a perspective of a pallet loaded with cartons which the apparatus of FIGS. 6-9 is useful;

FIG. 11 is a diagram of a portion of the control mechanism useful in the embodiment of FIG. 7 to enable alternate operation of the apparatus with off-set for synchronized operation with the conveyor and for elimination of such oif-set;

FIG. 12 is a lateral somewhat diagrammatic view of apparatus as shown in FIGS. 14 modified to include certain additional features of the invention;

FIG. 12A is a diagram illustrating the operation of the apparatus of FIG. 12;

FIG. 13 is the elevation of part of the apparatus in FIG. 12, drawn to somewhat larger scale;

FIG. 14 is a plan cross-section of the apparatus in FIG. 13 as viewed from the section line 14-14;

FIG. 15 is a fragmentary perspective of the apparatus of FIGS. 13 and 14, in a modified operating state; and

FIG. 16 is a detail of a portion of the control apparatus linking the converter of FIGS. 13-15 with the rest of the apparatus in FIG. 12.

Referring now to FIGS. 1, 1A, 2 and 2A, anarticletransfer apparatus 10 is shown including abase 12, avertical post 14, and anarm 16 carryinghead unit 18.Base 12 contains adrive motor 20 which operates through chains 22 to rotate thecenter shaft 24 ofpost 14 about its vertical axis.Shaft 24 rotates within astationary sleeve 26 onbase 12, and is supported for rotation bybearings 28 and 30. Ashell 32 is secured toshaft 24 above bearing 28, and rotates with the shaft.

Hydraulic actuator 34 (which may be simply a piston Operating in a cylinder with hydraulic lines to its extremities) has apivotal connection 34a torotary shell 32, andactuator 34 is connected byrod 34b toarm 16. By proper control of the pressure supply of hydraulic fluid to the respective ends ofactuator 34,rod 34b will elevate orlower arm 16 about itspivot 16a, as desired, or hold the arm at any angle of elevation.

Ann 16 containshydraulic actuator 38 comprisingpistonrod 38a and piston 38b, the cylinder in which piston 38b works being secured toarm 16 androd 38a being secured tohead unit 18. Radial motion ofhead unit 18 is controlled by admitting hydraulic fluid under pressure to the appropriate side of piston 38b, discharging fluid from the other side of the piston. Twotubes 36a and 36b are telescopically received intubes 36c and 36d andsupport head unit 18. Shafts intubes 36a and 36b have telescopic splined connections to drive shafts 50' and 68, respectively. These two telescopic drive shafts cause a swinging motion ofwork head 18a about the axis ofshaft 18d and tilting motion about the horizontal axis ofshaft 18c. These axes intersect with each other at a point along the axis ofrod 38a which may be called the longitudinal axis ofarm 16. The axis ofrod 38a passes through the axis ofpivot 16a, which is the pivotal axis ofarm 16. The telescopic shafts maintain the described drive connections throughout the range of radial motion ofhead unit 18 produced byactuator 38.Shaft 18c remains horizontal and parallel 6 to pivot 16a.Shaft 18d can tilt, but it can also be made vertical and parallel to post 14 despite sloping positions ofarm 16.

Horizontal shaft 18c has its extremities in bearings inU-shaped head frame 18b and is rotated by the shaft intube 36a via bevel gears 40.Shaft 18d operates intube 18f that is united toshaft 180. Rotation ofshaft 18c about its horizontal axis causes tilting ofshaft 18d.

The drive shaft intube 36b operatesbevel gear 42 for rotating a bevel gear unit comprisingbevel gears 44a and 44b united to the ends of a sleeve 44d that forms a bearing onshaft 18c.Bevel gear 440 meshes withbevel gear 44b, and becausegear 44c is fixed toshaft 18d, rotation of the drive shaft intube 36b causes swinging ofwork head 18a about itsshaft 18d.

Ayoke 18a is secured to the ends ofshaft 18d and to gear 44c.Yoke 18e swings through a large arc and, if necessary,yoke 18e may be made large enough to swing about the gear-containing portion ofhead unit 18. At the end ofyoke 18c remote fromarm 16 there is a drive unit 46 carrying article-grippingjaws 48. Drive unit 46 can be arranged to rotatejaws 48 about an axis passing through the intersection of the axes ofshafts 18c and 18d. Unit 46 contains suitable means (not shown) for operat ing the jaws to grip and release an article.

When equipped withjaws 48,apparatus 10 is operable for transferring articles from place to place as desired.laws 48 may be replaced by a suction cup as another form of article gripper. Other devices such as a drill, a pair of welding jaws, and other work devices may be mounted on unit 46 in place ofjaws 48. Still further, unit 46 may itself contain a driving element for shiftingjaws 48 or a substitute tool along the axis of rotary drive unit 46. Such endwise motion is useful, for example, for causing lengthwise drive of a drill carried by unit 46.

The apparatus thus far described involves a number of independent motions, each of which may be termed a degree of freedom.Post 14 is rotatable bymotor 20 about a vertical axis for operatingarm 16 through various angles of azimuth.Actuator 34 operatesarm 16 through a range of angles of elevation. Operation ofactuator 38 shifts head 18 radially. These may be termed three primary degrees of freedom. In addition, the swinging motion ofwork head 18a about itsaxis 18d and the tilting motion ofwork head 18a about its horizontal axis provide two secondary degrees of freedom. Rotation of unit 46 about its axis represents a sixth degree of freedom. Another degree of freedom would be represented by the shift ofjaws 48 bodily along the axis of unit 46.

The following means is provided for rotating the shaft intube 36b, in order to swingyoke 18c about the axis ofshaft 18d.Shaft 50 is coupled to gear 42 throughdifferential 79 andshaft 50 via internal telescopic splined shafts.Shaft 50 is rotated by bevel grears 52 and 54, the latter gear being operated bydual sprocket 56,chains 58 and by a reverse-acting pair ofhydraulic actuators 60. Each of these actuators provides a power stroke in the direction to pull the related end ofchain 58, thereby to rotatesprocket 56 and gears 54 and 52.

Gears 40 are driven via splined shafts inarm 16 extending to shaft 68 at the opposite end ofarm 16. Shaft 68 is rotated bybevel gears 70 and 72, adual sprocket 74,chains 76 and dualhydraulic cylinder actuators 78, the construction and operation of which is the same as that described forhydraulic cylinders 60 and 62 and the parts driven thereby.

Any rotation of shaft 68 causesshaft 18c to rotate about its horizontal axis and thereby causesshaft 18d to tilt. However, if this occurs at a time whenbevel gear 42 is fixed, thereby fixingbevel gears 44a, 44b, and 440, then the tilting ofshaft 18d would result in travel ofbevel gear 44c aboutgear 44b, and would inherently causeyoke 18a to swing about tiltingshaft 18d. This is avoided here by providing adifferential gear unit 79 having input couplings from both shaft 68 andshaft 60 and having its output shaft coupled togear 42. In case shaft 68 shouldnot rotate, any rotation ofshaft 50 would be transmitted via thedifferential gear assembly 79 to gear'42'. This 'shaft e v i a Apparatus includes a poweractuator in each degree of freedom, and is program-controlled in each degree of freedom. In the form illustrated, "rotatable shaft 24 of'post 14 is' operated bymotor'20 and carries a gear 809. that meshes withgear 80b tooperate unit 706; This unit contains a digital shaft-position encoder or analog-todigital converter and other devices described below. Rotation ofshaft 24 by motor is monitored by the digital encoder, and can be interrupted or otherwise controlled by the relationship in effect at any moment between the digital encoder and a control program.Motor 20 may be stopped when the encoder matches the program code, or the program code can be replaced by the'nex't code when match occurs, as desired. Similarly, the elevation ofarm 16by actuator 34 is' monitored by means of agear sector 92a fixed toarm 16 and operable aboutpivot 16a.Sector 82a meshes withpinion 82b for operatingdefv (5 82c.

This'device (described below in detail) includesa digital encoder. Still further, the radial motion ofarm 16 caused byactuator 38 is monitored by aunit 84 that' con tains a digital encoder.Unit 84 is operated by agear 84a driven by apinion 84b secured to drum 84c. An internal'wind-up spring is contained indrum 84c, and thisdrurn is ar-Units 86 and 88 geared to shafts and 68 similarly contain digital encoders to'rep'resentthe absolute positions orshafts 18c and' 18d about their respective axes, for adapting the apparatus to program control. Details of these units appear below.

Each of the motions described is ordinarily subject to independent program control. However, it is sometimes desirable to link certain motions. For example,jaws 48 may grip an article in What may be called a nor'mal attirestore the rotor of synchro transmitter to anormal starting angular position.

tude, and it may be important for this attitude to be maintaineddespite a change in the angle of elevation ofarm 16 to the broken-line position 18 in FIG. 1. correspondingly, it may be desirable to maintain the attitude of'an'article injaws 48 unchanged, despite the swing ofarm 16 about the vertical axis ofpost 14 in carryinghead 18 to its broken-line position 18" (FIG. 2). The axis of unit 46 a Oct-11, 1965, now Patent No. 3,525,094 by G. Leonard. Agear 94 is normally freely rotatable onshaft 92. A magnetic. clutch 96 has one plate fixed to gear 94 and another plate fixed to shaft'92. Theclutch, when energized, couples gear 94t0 shaft 92. When this occurs, .gear 94drives pinion 98, and rotates a servo master control, for example synchro torque transmitter 100. When clutch Unit c is likeunit 82c, in that unit 80c contains both a digital encoder and an optionally operative synchro torque transmitter.

Units 86 and 88 are made alike, for example as shown iHFIG. 4 v

Plate 103 supports analogto-digital encoderll04 of the same construction asencoder 90, and a servo slave unit such as asynchro torquereceiver 108.Encoder 104 is coupled by gearing 105 to one shaft ofdifferential gearing unit 107. Another shaft of the differential gearing unit"107 is connected to synchro'receiver-108. The"third shaft 1 12 of the differential gearing-unit iscb'nne'cted-lto sprocket '56 or sprocket74, where the unit shown in FIG. 4 is used asunit 86 or 88 in FIGS. 1 and 2.

Sodoirg assynchro'receiver 108*is held inwha't-may be called itszeroposition;the-position ofshaft 112 corresponds to the code output'of encoder 104.Rotation ofsynchro receiver- 104 introduces" an offset irr'that' relationship. The offset angleas measured at shaft 1l 2is -madeequ'al and opposite to the .angle through which synchro transmitter 100 is'operated from the start to the end of' a program-controlledangular motion'ofarm 16, provided that there is no change in the value -'a'gainst which encoder'104'is compared 'and matched. The change thus'introduced means that there is'no longer theoriginal relationship between' the position of the operatedpart ofthe apparatus and the value represented by the related encoder. During an offset operation of this 'type,arm 16 changes'its angle of elevation, butwork head 18a remains "parallel to its original position at the start of the changeof-elevation travel of thearm 16, by reversely changing its angular relationship toarm 16.

.A. spring mechanismbiases servo receiver 108 to a Zero or home position. In that s'ta te,.there is an absolute relationship between the code produced inencoder 104 and the position of the component to, which the encoder is geared. Thus, with .servo receiver 108 in its home position and withshaft 112 coupled tosprocket 56, the angular position ofwork head 18a aboutshaft 18d is digitally represented by the code output ofencoder 104.'This spring mechanism includes a pair of torsion-spring units 109 and 111 having the outer ends of internal wound leaf springs fixed to their cases and having the inner ends of the springs fixedto arms 109a and 111a on respective shafts at the centers of the spring cases. In the home position of the servo'recei-ver, arms 109a and 111a bear agaiHSL the opposite. faces of fixedstop 113, and they also bear against opposite sides of I pins 115a and 1151: .projectingfrom gear. 115.Gear 108a ofthe servo receiver 10S meshe with gear 115. I When theservoreceiver is rotated, gear 115 forcibly lifts one of .the arms.,'109a.0r 111a away fromstop 103,

andincreases the..,spring tensionofthe relatedspring unit.

$ubsequentlywhemthe servo; receiver is de'energized, the spring reset meehaiiiSIh described firmly returns the operated arrri 109a'or11lafinto contact with stopl03, thereby restoring theservo receiver 108 to its homeli position.

;;- A modification of the apparatus of FIG. 4.is.shown in FIG. 4A.Digital encoder 104 vin FIG. 4Af-is shown mounted on plate106, which also supportssynchro torque receiver 108.Units 104 and Y108 in FlG. 4A have input shafts'to differential gearassembly l lO for operatingshaft 112, as in FIG. 4.,This-.shaft represents vthe shaft ofsprocket 56 or sprocket 74 (FIGS. Land 2).

A precise arrangement is provided forreturningservo 108. tofzero. For this purpose, synchrotorque receiver 108'ope'rates anassembly 114 of discs that are coupled together in the manner of odometer wheels so. that the disc closest to synchro receiver. 108 operates at-,highest speedand the others are scaled .down toiindex one step for each ten, hundred, and thousand .rotations of the units ,disc 114a. As .shown in broken lin'e end view in FIG. 4, the discs are generally round but have a flat,

and all of the flats are aligned horizontally whenunit 108 is in its normal zero position.

Cooperating with all of the discs ofassembly 114 is a pair of normally open contacts 116 (shown in broken lines 116) that are closed so long as any one of the discs is out of its zero position.Contacts 118 and 120 are normally open, and either of these contacts closes when the flat portion of units disc 114a rotates through a significant angle away from its zero position. The adjustment ofcontacts 116 in relation tocontacts 118 and 120 is such that, upon rotation of disc 114a in either direction,contacts 116 close after the closing of one of the two pairs ofcontacts 118 or 120, depending upon the direction of rotation of disc 114a.

Closing of'contacts 116 and 120 occurs when disc 114a rotates counterclockwise, considering the end-view representation 1143. in FIG. 4A. When this occurs, power is connected fromline 122,contacts 120 andrelay contacts 124a to relay 126 and to terminal 122'. When this occurs, relay 126' is energized and closes its own holding contacts 12Gb which maintainrelay 126 energized vialine 128 so long ascontacts 116 remain closed. Whenrelay 126 has once been energized, itscontacts 126a open and thereby break the circuit fromcontacts 116 viacontacts 118 that might otherwise be established to relay 124. Consequently, continued rotation of disc 114a in a counterclockwise direction, ultimately allowingcontacts 118 to close, would not cause energization ofrelay 124. On the other hand, ifdisc 114 should rotate clockwise, thereby closing bothcontacts 116 and 118 initially, then a series circuit is formed fromline 122 throughcontacts 116 and 126-a to relay 124 and terminal 122'. This has the effect of closing its holding contacts 124b, thereby maintainingrelay 124 energized so long ascontacts 116 remain closed. Energization ofrelay 124 also openscontacts 124a and thereby prevents subsequent energization ofrelay 126 whencontacts 120 close later in the continued rotation of disc 114-a. Thus, either relay 124 orrelay 126 is energized, depending upon the direction of rotation of disc 114a away from its zero position and the selected relay remains energized so long as any one of the discs inassembly line 114 is not in its zero position. On the other hand, when all of the discs are restored to-their zero position by restoring synchroreceiver 108,contacts 116 open, and then the energizing connection for the holding-contact circuits is broken and the energized relay is deenergized.

Relay 124 has a pair of contacts 1240 which, when closed, operate a reversingrelay 130. Normally, reversingswitch 130 provides an energizing connection from asignal source 132 via contacts 134a of relay 134 when closed. At that time, and if reversingswitch 130 is then in its normal condition, then synchroreceiver 108 rotates in a first direction. Incase contacts 124c should be closed when closing of contacts 134a occurs, then synchroreceiver 108 rotates in the opposite direction.

Relay 134 can be energized by closing itscontrol contacts 138 momentarily. When this is done,relay holding contacts 134b are closed, to complete a holding circuit vialead 128 throughcontacts 116 to energizingterminal 122. So long as the synchro receiver is in its home position,contacts 116 are open andrelay holding contacts 134b cannot energize relay 134.

A further modification of the apparatus of FIG. 4 is shown in FIG. 4B. Here the case 104' of a digital encoder (in all respects like encoder 104) has its frame or housing mounted for rotation withshaft 112 that corresponds toshaft 112 in FIG. 4. The movable shaft 1400f the encoder is coupled bygears 142 to synchrotorque receiver 108 whose case is stationary.Gear 108a couples the synchro torque receiver to gear '115, this being part of a torsion spring restoring mechanism exactly the same as in FIG. 4.

The operation of the apparatus in FIG. 3 and each of FIGS. 4, 4A and 4B may now be described, in their relationship to the equipment of FIGS. 1 and 2. The appa- 10 ratus of FIG. 3 is contained in each of units c,and 820 of FIG. 1, and any one of the assemblies in FIGS. 4, 4A or 4B is contained inunits 86 and 88. It may be assumed that the apparatus has been programmed so that work head 46 is horizontal andjaws 48 grip an articlein its horizontal attitude.Shafts 16a and 18c are parallel to each other.Arm 16 is initially horizontal or at any other angle of elevation. Let it be assumed further that it. is desired to maintainjaws 48 horizontal despite swinging ofarm 16 through a substantial vertical angle for raising or lowering the article. The horizontal attitude of the article shall not change during this operation. (The assumption that Work head 46 is horizontal is only an example of its possible attitudes in the ensuing operations.)

At the start of the operation, clutch 96 (FIG. 3) is energized under program control. Any rotation ofgear sector 82a representing the change in the program-controlled elevation ofarm 16 causes rotation ofpinion 82b and gears 94 and 98 so as to operate synchro transmitter 100. This has the effect of correspondingly rotatingsynchro receiver 108. A program-controlled motion ofarm 16 through a vertical angle would cause a corresponding angular motion ofjaws 48 when there is no change in the code that is supplied to control the jaws. Stated otherwise, ifjaws 48 were aligned witharm 16 and ifarm 16 changes its angle of elevation,jaws 48 ordinarily move through the same angle, still aligned with arm 16assuming the same control code is supplied to the head motion control at the start and end of this motion. However, rotation of synchroreceiver 108 introduces a dilferential effect betweendigital encoder 104 and the tilt-control drive ofhead 18a. This causeshydraulic actuator 78 to operate for maintainingencoder 104 in condition to match the program instruction. As a result,shaft 112 operates in such direction as to compensate for the changed attitude ofarm 116 and maintain constant the attitude ofjaws 48 and the article carried by those jaws.

The same effect is realized in relation to the horizontal swing ofarm 116 from the initial position in FIG. 2 to that represented by the broken-line position 18". Consequently, despite controlled motions ofarm 16 in both azimuth and elevation angles, it is possible to maintain constant the attitude of the article gripped betweenjaws 48. At the start of such parallel-motion mode of operation ofwork head 18,shaft 180 is inherently parallel toshaft 16a.Shaft 18d should be made parallel to post 14 where azimuth parallel-motion operations are to be executed.Jaws 48 can be mounted so as to be capable of tilting onwork head 18, if desired, so that requiringshaft 18d to be vertical in the parallel-motion mode of operation is not a serious handicap.

It is important that the initial absolute digital program control over the positions ofshafts 18c and 18dbe restorable, following a parallel-motion mode of operation, to, undo the offsetting effect of the synchro transmitter and receiver (or other servo master and slave) just described. For this purpose, it is necessary to restore the synchro receiver -108 to its zero condition, thereby reestablishing the initial relationship between each encoder 104 inunits 86 and 88 andshaft 112. This is done in FIG. 4 and 4B by deenergizing the synchro receiver so thatspring 109 or 111 operates. In FIG. 4A this is done by momentarily closingcontacts 138, thereby energizing relay 134 and closing contacts 134a. This applies a restoring-motion signal to synchroreceiver 108, which operates in the correct direction as previously described for restoring the assembly ofdiscs 114 to the true zero condition. When that condition is reached,contacts 116 open, relay 134 is deenergized, and operation of synchroreceiver 108 is arrested. It is also desirable to restore synchro transmitter to its normal angular position. This restoration is effected simply bytension spring 102, clutch 96 being deenergized at this time.

The arrangements in FIGS. 4 and 4A involve adifferential gear assembly 107 or 110. This is a, complication,

but has the advantage of modifying the effect ofdigital encoder 104 without bodily rotating the frame of the encoderjlnasmuch as many wires are often involved in the typical encoder, fixed mounting of the encoder is an advantage because it avoids the use of troublesome slip rings for providing connections to the encoder. However, there are some forms of encoders where this condition is not of controlling importance; and in that event, the configuration of parts in the encoder and the offset means in FIG. 4B may be desirable. A still further alternative may be desired, interchanging encoder 104' andsynchro torque transmitter 108 in FIG. 4B, thereby mounting the housing of the encoder fixedly and mounting the housing of the offset-introducing synchro receiver onrotating shaft 140. This is shown and more fully described in an application filed concurrently herewith by George C. Devol.

FIG. 4C shows a still further approach to the problem of achieving a parallel-motion mode of operation, for maintaining constant aim ofwork head 18a despite changes in the angle of elevation ofarm 16. Identical apparatus is useful for maintaining constant aim ofwork head 18a despite angular motion ofarm 16 aboutpost 14, whereshaft 18d is vertical at the start of the parallelmotion mode of operation.Actuator 34 in FIG. 4C is controlled byencoder 90,program input unit 90a, and acomparator 90b in which the difference between the encoder and the program instruction is derived.Comparator 90b controls avalve 34a to cause operation ofactuator 34 in the appropriate direction in dependence on the algebraic sign of the difference, and to shut the valve when the difference reaches zero. This is the normal control means for the elevation ofarm 16. An example of such control is shown in US. Pat. 2,927,258 issued to B. Lippel.Actuator 60 provides the drive effort to tilthead 18a.Valve 60a controlsactuator 60.Program input unit 104a supplies the usual input control for the tilt motion ofwork head 18a, to be compared with theencoder 104 that monitors the tilt position.Comparator 104b provides output for controlling thevalve 60a.Comparator 104b responds to input values from the encoder and the program input unit, and provides an output representing the difference, so as to operateactuator 60 in the appropriate direction and to shutvalve 60a when the input values are alike.

In FIG. 4C, anumerical combining unit 108 is included to introduce a parallel-motion offset, comparable to the effect of synchroreceiver 108. When switching means 108b is closed, register and [added] adder 108' takes the algebraic sum of the output ofencoder 104 and the numerical difference of the number of pulses needed to reduce to zero the difference betweenencoder 90 which represents the initial elevation ofarm 16 andprogram unit 90a which represents the final elevation ofarm 16 at the end of the motion to be executed. Adder 108' supplies this algebraic sum tocomparator 104b with its algebraic sign reversed, to be compared with the program input. Assuming this to be a parallel-motion mode of operation, the program input fromunit 104a does not change, andactuator 60 causes an angular tilt motion ofwork head 18a that is equal and opposite to the change-of-elevation motion ofarm 16 to be carried out or being carried out byactuator 34. Succeeding operations ofarm 16 by itsactuator 34 and ofwork head 18a by itstilt actuator 60 in the parallel-motion mode are carried out in the same way.

At the end of a parallel-motion mode of one operation or a series of such operations, the absolute relationship betweenencoder 104 andtilt actuator 60 is to be restored. This is executed by opening switching means 108b andactuating reset element 108a to restore to zero the input register inunit 108 that stores input fromcomparator 90b. Thereafter, absolute position input data fromprogram unit 104a has its original significance in controlling the aim ofWork head 18a, not altered by unit 108'.

The apparatus involvingdigital encoders 90 and 104 as Well as digital encoders for other degrees of freedom in the apparatus described represents a highly reliable form of program-controlled equipment, in which there is an absolute position for each numerical instruction for each degree of freedom. The program as established is repeatable reliably on a point-to-point basis, free of errors such as might be introduced in other forms of program control. In another form of program control, the motion in any one degree of freedom from one point to the next is established by counting the number of steps of advance. Each new position is established as an increment in relation to the previous position. In such a system there is a possibility of errors arising due to spurious pulses and due to pulses being lost, a cumulative source of error, and therefore the absolute-coordinate system as described in the preferred type of control. However, it will be readily recognized that the parallel-motion controls 100 and 108 in FIGS. 3 and 4 and the circuit of FIG. 4C can readily be used or adapted with the well-known incremental pointto-point control systems, and with other forms of programcontrolled motions.

The extent of motion in each degree of freedom when carried out under program control in each respective degree of freedom may be called a program-controlled motion. The parallel-motion mode of operation is brought into effect under program control, as by energizing clutch 96 (FIG. 3), or by closing switching means 108b for rendering added 108' operative. It represents a program-controlled mode of operation and it is another program-controlled motion. There is a tying-together of two degrees of freedom wherein control of a primary degree of freedom causes movement through a program-controlled arc while the linked degree of freedom moves through an incremental are from its initial position. When the parallelmotion mode is in operation, the primary control such as elevation ofarm 16 is linked to a related degree of freedom such as tilt ofhead unit 18a. The latter is a dependent degree of freedom during the parallel-motion mode. The secondary motions ofwork head 18a are equal and opposite to the primary motions ofarm 16 in the parallel-motion mode of operation.

It will be appreciated that program control signals in FIG. 4C that control the operation of arm-tiltingactuator 34 are also used, inversely, to control the work-head tilting actuator 50. Stated otherwise, there is no need for a separate program of signals for tilting the work head in the parallel-motion mode of operation, since the signals that control the arm elevation are used also to control the attitude ofwork head 18a. This kind of operation of the apparatus in FIG. 4C is applicable not only when the whole apparatus is being operated under program control, but also during the preparatory phase, when the program is being recorded, an operation more fully described below in connection with FIG. 5. In that case, the values inencoders 90 and 104 at the start of the parallel-motion mode of operation are entered in intermediate storage registers forming part ofprogram units 90a and 104a. Thereafter, during the time whenactuator 34 is being operated byvalve 34a under manual control to teach a motion sequence by recording the manually controlled motions, the numerical changes produced byencoder 90 are derived bycomparator 90b and used (with reversed sign) to control the operation of valve a as already described.

This kind of operation is a distinct advantage, since the automatic parallel-motion mode of operation thus realized avoids the burden of manually controlling the attitude ofwork head 18a during the program-recording operations.

FIG. 5 is a simplified illustration of a form of program-control equipment suitable for the apparatus of FIG. 1. This includes a rotary drum 146 having a surface of readily magnetizable and magnetically retentive material. This drum may be either a continuously rotating type of storage drum, or it may be a form of magnetic drum that indexes from one control position to the next.

13 The drum as shown is equipped with a first set of magnetic senslng or readheads 148 and another set of magnetizing or writeheads 150, but it will be understood that a single series of heads can readily be utilized for both sensing and recording. The control areas that are sensed at any one moment by the series ofheads 148 may be called a slot While the series of areas sensed in successlon by any one of theheads 148 is called a track.Heads 148 are divided into as many groups as there are I degrees of freedom, plus a few heads that are allocated to provided bydigital encoder 154, typical of the several encoders in the equipment of FIG. 1 such as encoder 90 (FIG. 3) and encoder 104 (FIG. 4). The ditference between the coded numerical representation provided by sensingheads 148a and the position of actuated part of the apparatus, such as the elevation of arm'16 byactuator 34 as represented byencoder 154, is derived by means ofsubtraction unit 156. The operation control means 158 of the actuator in each degree of freedom is controlled byunit 156. Advantageously,unit 156 provides not only the on and off control but also the direction of operation, corresponding to the algebraic sign or sense of the difference between the values applied tosubtraction unit 156 by thetemporary storage unit 152 and thedigital encoder 154. The details of this digital form of control are separately well known and may take a variety of different forms as, for example, in Pat. No. 2,927,258 issued Mar. 1, 1960 to B. Lippel. Still further, the apparatus may be of a design to impart not only on and off control, and direction or sense control, but also to provide rate control so as to decelerate the operation of the controlled actuator in the related degree of freedom as the end-point of the motion comes close. The magnetic memory represented .vantage. In the illustrated apparatus, when the subtraction shows that there is correspondence between the tempo- .rary storage and the sensed coordinate for which the apparatus of FIG. 1 has been programmed to operate, as one point in the series that make up the program of motions, the next function or the next program step becomes effective. The controlled actuator may arrest the operated part, or motion of the actuated part may continue under control of the next slot of the program drum.

There are as many groups ofheads 148 as there are degrees of freedom, as previously mentioned,group 148a being assigned to one degree of freedom,group 148 being assigned to another degree of freedom, etc. Each additional group of heads 148b is associated with a duplicate system like that described for the group ofheads 148a. Additionally, there is a group ofheads 148c whose purpose is to provide control functions for the apparatus. Thus, for example, at some part in the program it might be desired to institute a parallel-motion mode of operation. To do this, eachsynchro transmitter 90 is connected to itsreceiver 108, and each clutch 96 is activated, under control of a recording sensed by a head 148e, this control 96' optionally including a temporary storage register.Reset control 157 of theregister 152 that temporarily stores sensed digital codes can be rendered operative under thesame control 148c to prevent the value stored intemporary storage register 152 from being changed in the sensing operations that follow. In the ensuing operation of the apparatus of FIG. 1 (when the next slot of the drum is in effect) the parallel-motion mode of operation would then come into efl ect. At the end of such parallel-motion mode of operation, or at the end of a sequence of such operations, another sensing head of the group 1480 may provide a signal to disconnect the servo transmitters and receivers, to deenergizeclutches 96, and in the device of FIG. 4A, to closecontacts 138, for restoringsynchro receiver 108 to its normal position. Concurrently this restoresshaft 112 to the position corresponding to that prevailing at the start of the parallel-motion operation. Where (as here) absolute coordinates are represented by the related digital encoder, the offset introduced by the parallel-motion mode of operation is eliminated, and absolute-value relationship betweenencoder 104 andshaft 112 is restored. The following operations in the program are controlled by the sensing heads 148a, 148b, etc.

Restoration of the synchro receiver 108 (or its equivalent) to the starting position at the end of a parallelmotion step or series of steps in a program may well be desired even Where theencoder 104 is omitted in favor of a variety of other forms of program-responsive drive controls that may not involve an encoder of absolute positions. A device for controlling or monitoring a programcontrolled motion as an incremental displacement or as a discrete series of steps from the previous program-controlled position is an example of another form of control with which the parallel-motion mode of operation is useful, and still others are known.

The program on drum 146 is recorded as is discussed in greater detail in the above-identified Devol patents. Briefly, however, a new program can quickly be taught to the memory drum by manually controlling the apparatus of FIG. 1 to execute the desired program and, at each step of the sequence of motions that is desired, causing the coordinates of that position to be recorded. For this purpose,digital encoder 154 may be connected by switch to thecontrol circuit 162 of the related group ofrecording heads 150a. These heads (when energized) record the code combination represented inencoder 154, as to each step in the program, for each of the different degrees of freedom. Additionally, it is understood that appropriate manually controlled means are to be provided for causing recording heads 150s to record the necessary function control portions of the recorded program. During program-controlled operation of the apparatus, the drum-advancing means 161 operates under control of subtraction means 156 and a function-control sensing head 148e, viaswitch 163. This switch is shifted to manual control during the teach activities.

The apparatus of FIGS. 15 inclusive represents a highly flexible type of equipment that is readily adapted to perform a variety of functions, as already mentioned. The foregoing parallel-motion mode of operation is especially important in the apparatus shown in FIGS. 6 and 12 and their related figures.

FIG. 6 illustrates, somewhat diagrammatically, apparatus that is broadly similar to that of FIG. 1, in thatunit 10a also has abase 12, avertical post 14 that is rotatable about its vertical axis, anarm 16 that is pivoted to move through various angles of elevation about apivot 16a at the top ofpost 14, andhead 18 having awork head 18a including article-grippingjaws 48. The head and the jaws in FIG. 6 are capable of both tilting and swinging motions and have control means identical to that in FIGS. 1-5 (omitted from the drawing in FIG. 6) adapting the head to both program-controlled operation and operation in what has been called the parallel-motion mode. In FIG. 6, theactuator 34 for controlling the angle of elevation ofarm 16 has a hydraulicservo control valve 166 that is capable of operatingarm 16 up and down, decelerating the motion of the arm as each desired position is approached.

The hydraulic actuator inarm 16, such asactuator 38 in FIG. 2, is controlled by a hydraulic valve 168 in FIG. 6. Acontrol arm 170 is operable about apivot 172. The control end ofvalve 166 and its body are connected toarms 16 and 170 so as to remain parallel to post 14.Valve 166 andactuator 34 act as a hydraulic servo system so that operation ofcontrol arm 170 is reproducedpost 14causes master control 192 to control the servoslave motor base 12 to rotatepost 14 correspondingly. Preferably a master valve is used ascontrol 192 with a ,slave hydraulic .motor inbase 12. Accordingly, motions ofarm 170 about the axis ofpost 14 are reproduced by the post and byarm 16 so thatarms 16 and 170 remain in a common plane that passes through the axis of the post.

Arod 175 is slidably mounted withinarm 170. One end of acable 178 is secured to therod 38a which moveshead 18 radially, in the sense of a systemof motions in polar coordinates.Cable 178 extends about apulley 180 coaxial with the, pivot ofarm 16. The other end ofcable 178 is wound aboutadrum 182 that is secured to post 14, and has a bearing axis parallel to that ofpulley 180. A second cable.1-86 has one end wound aboutdrum 184,

the latter being half the diameter ofdrum 182 and v se cured thereto.Cable 186 extends about a pulley-188' coaxial withpivot 172, and the oppositeendof thiscable is secured to the control portion of valve 168, the body of which is secured torod 175. Pulley 188 is helf the diameter ofpulley 180. Suitable means represented by spring 190 acts on the part-of valve 168 to whichcable 186 is attached, for maintaining the cable under tension. For example, this spring represents a pneumatic cylinder inarm 170 whose piston is connected torod 175 and constantlybiases rod 176 toward the right in FIG. 6. Valve 168 and the radial actuator of arm 16 (seeactuator 38, FIG. 2) form a hydraulic servo drive. When thevalve control shaft 176 is shifted out of its normal position in relation to the body portion of the valve, then the actuator inarm 16 causesrod 38a to operatecables 178 and 186 as a feedback servo connection in the direction to restore the normal condition between the valve body and the control part of valve 168. Move ments ofrod 176 along its length are accordingly reproduced as proportional movements ofhead 18 alongarm 16.

Rod 176 represents what may be called a master lever 'for controlling the threevalves 166, 168 and 192 that 'control the primary motions of elevation, azimuth and will be reviewed below.

The mechanically operatedvalve 166 for servo "actuator 34, and the mechanically coupled master 168 with itsslave actuator 38, and the mechanically actuatedvalve 192 and itsslave motor 12 are direct and effective, but. by no means unique. Thus, if the mechanical coupling between each master and slave as shown were considered objectionable, master and slave potentiometers in a bridge can be used to control the direction and operation of each of these actuator controls 166, 168 and 192, and a variety of other servos can be used between each ofoutput points 166, 168 and 192 of thecontrol converter 170, 196 and the respective controls for the actuators that operateapparatus 12, 14 and 18.

The details ofapparatus 196 are shown in FIGS. 7, 8 r

and 9.Unite 196 comprises a-pair ofrails 200 ,which slidablysupport bearing members 202 and' 2022; of abridge bar 204. The oppositely extending endsfofhydraulic actuator 206 operate achain 208 that extends aboutsprockets 210 and 212. These sprockets are secllffid l0 l1,af1 .214 and 216 which carry pairs of sprockets .bydigital encoder 232..

slidable inblock 242.

" and 220 that are twice the diameter ofsprockets 210 At th l ft in FIGS; 7 and s, shaft'230ex ndinaparallel .torails 200 is longitudinally grooved or pined and has suitable end bearings for rotatably supporting the shaft.Shaft 230 is coupled towshaft-position encoder 232 and to drivemotor 234 by suitable gearing.Sprocket 236 has lateral bearings inbridge bar 204 and lidable alongshaft 230.Sprocket 236 is internallylkeyed. o. as

.to be rotated byshaft 230. A chain 238 driven -bysprocket 236 and extending aboutsprocket 240 hasits. extremities fixed to ablock 242 that has slide bearings for operation alongbar 204. Accordingly, operation ofmotor 234 is efiectivetoshift block 242 horizontally alongbar 204, and the position ofbar 242 alongbar 204. isf. rii onit r.ed

At the rightin FIGS. 7 .and 8,. afurthepshaftlZj U tending parallel torails 200 is longitudinally grooyed or splined and has rotary;.end bearings. Shafti'244, is rotated by motor246 and theangular position ofshaft 244 is monitored by an analog-to-digital converter onencoder 248. An additionalsplined shaft 250 parallel to bridgebar 204 has its ends suitably supported in bearings onbridge bar 204.Shafts 244 and 250 ar'ef coupled bybevel gearing 252. Apinion 254 having latera l'bearings inblock 242 is slidable alongshaft 250 and is'internally keyed so as to be rotated bysplined shaft 250.Pinion 254 meshes with avertical rack 256. that is accurately It will be understood that in all of the foregoing drive couplings in FIGS. 7 and 8, due precautions will be observed for avoiding looseness or backlash at thegearing and for assuring accurately controlled sliding motionfree of looseness where this is needed. p

At the top ofrack 256 there is a rotatably mountedcollar 258, and the forked end of master lever 176 (see FIG. 6) has snug-fitting bearings incollar 158.Motors 206, 234 and 246move rack 256 along X, Y and Z coordinates, and correspondingly move the operatingend of'master lever 176 of the apparatus in FIG. 6. The "position ofrack 256 in each of these coordinates is'lnonit'ored by respectivedigital encoders 224, 232 and 248.

Themaster lever 170 and its associatedcable 186 and its pulley 188 and its wind-up drum 186 are all accurately made to half-scale that of arm 1638a, pulley 18'0and wind up drum 82. To complete the symmetry between arm 1'638a and master lever 170-176,- thedistance betweenpivots 16a and the axisof these drums is'twicethe distance betweenpivot 172 and the axis of these drums. 'Accordingly the'motio'n's of control head2'58 correspond to those ofarm 16 in angles of elevation and azimuth,and the radial extent ofwork head 18 remains twice that of control head258. I p

It has been indicated that the apparatus o f'FIG. "6 is very similar, basically, to that of FIG. 1. It should therefore be'understood that th'e'servo transmitters and receiv- "and azimuth, Despite the rectangular controls use'din FIG.

' 6'for the primary motions of the arm,"the'parallel'-motion mode of operating work head 18'is ffully effective.

The apparatus of FIGS. 7 and is program-controlled byfapparatus of the type shown in FIG. j iandidescribed above. However, while polancoordinates are used in the programfor the apparatus of FIG. 1, the. elevation, the azimuth, and the radial extension of.head unit 18a, are

- 17 expressed in the program for the apparatus of FIG. 6 in terms of rectangular coordinates, i.e., digits that define the coordinates ofcontrol head 258 at the top ofrack 256 and at the end of themaster lever 176. The polar-coordinateoperating unit 12, 14, 16, etc., of FIG. 6 is controlled bymaster servo lever 176, and thisis operated by a rectangular-coordinate manipulator 196 (FIGS. 7 and 8) that is program-controlled.

A program can be taught to the program storage drum in the following manner.Head 18 can be shifted to various desired positions by controllingmotors 206, 234 and 246 manually.Arm 16 responds in its basic motions of azimuth, elevation and length. When each desired position ofhead unit 18 is thus established, the rectangular coordinates as represented bydigital encoders 224, 232 and 248 are recorded. These three coordinates may represent only part of the recording that is effective with reference to each location ofhead unit 18, for at each such location the other program entries may also be needed, representing related operations such as jaw-opening or closing controls, and one such recording is the start and end of the parallel-motion mode controls. If the apparatus is then changed to its automatic program-controlled mode of operation, the motions executed byhead unit 18 andjaws 48 will then accurately repeat the taught motions under control of the drum recording. The recorded program relates to an article A (FIG. 6) that is assumed to be at rest.

In FIG. 6,work head 18a is shown as being cooperable with an article A on aconveyor 260 which is operated by adrive motor 262 andsprockets 264 onshaft 266. Aservo transmitter 268 monitors the advance ofconveyor 260. During all of the recording of a program to enable head unit 1821 to execute a series of operations on article A,conveyor 260 will be at rest.

The conveyor can then be started, and an article can be mounted on the conveyor at an accurately known location. At the same'time, the signal generated by synchrotransmitter 268 will be coupled to synchroreceiver 226. Accordingly, the position ofbridge bar 204 along its rails will be modified progressively so as to introduce a departure between the actual position ofcontrol head 258 and, correspondingly, the actual positions of those parts in the at rest" program that is recorded on the drum. In an example, article A in FIG. 6 may represent a pallet (FIG. 10) and thejaws 48 of the apparatus in FIG. 6 may be automatically operated so as to seize, transport and discharge a succession of articles carried by the conveyor. In another example, thejaws 48 are formed as welding jaws, programmed for making a series of Welds at different spots on an article carried by the conveyor; or a glue-spotting tool can replacejaws 48, and so forth. The program that was taught to the apparatus while the conveyor was at rest is modified by the off-set factor introduced byservo system 226, 268 to represent the speed of the conveyor. Of course,servo motor 226 drivesbridge bar 204 alongrails 200 at half the speed of the conveyor by properly proportioning the gearing that drivesbridge bar 204. The program is thus executed successfully and accurately despite the motion of the conveyor that takes place while the program is being executed automatically, and despite the fact that the program was recorded with the article A at rest.

There may be no requirement for the secondary" degrees of freedom represented by tilt and swing ofWork head 18a (FIGS. 1 and 2) to be subject to independent control in the apparatus of FIG. 6. Instead workhead 18a may be constrained to a fixed attitude in space using the parallel-motion mode of operation and control means of FIGS. l5. In that event, the tilt and swing control recordings would remains unchanged for all motions ofarm 16. These two recordings should establish a horizontal attitude of the axis ofwork head 18a. The axis of the work head as shown passes midway betweenjaws 48 and passes perpendicularly throughshafts 18c and 18d which should be parallel to pivot 16a and post 14 ofarm 16 in this 18 operation.Work head 18a would then move through tilt and swing angles that are equal and opposite to the elevation and azimuth angles ofarm 16.

As shown in FIG. 6A,work head 18a at the start of a motion (solid lines) moves through an angle A in reaching thefinal position 18a that equals the change in elevation B ofarm 16. FIG. 6A demonstrates a latitude of flexibility of the apparatus. By mounting, adjusting or operatingjaws 48 movably relative to 18a so that the jaws aim down (or otherwise) whileshaft 18d is parallel to post 14, the attitude of the head can be maintained consent throughout a sequence of motions in the parallel-motion mode. Thus, the apparatus is not inherently limited to the aforementioned horizontal attitude in operatingwork head 18a.

The parallel-motion servos are maintained constantly in operation for this type of operation, not only during the program-controlled operation but also during the teach" procedure of recording a control program for the apparatus. If desired, just before each program cycle of operations in the parallel-motion mode starts, the attitude of work head 1821 may be normalized to eliminate errors that could arise, i.e., in case the master and slave servos and 108 (FIGS. 3 and 4) were to fall out of step. One of the heads c may be used to record a control for'such an operation on the program of drum 146. In this normalizing operation,arm 16 is ideally perpendicular toconveyor 260 and the axis ofwork head 18a is aligned witharm 16 and both are horizontal.

Synchro transmitter 268 andsynchro receiver 226 are to be initiated in operation under program control from a starting condition at the start of the program, and they are to be restored to their starting condition at the end of the program. This is accomplished in precisely the manner as that described above in connection with FIGS. 1-5, and particularly with respect to FIG. 4. It follows that the apparatus in FIG. 6 will operate under control of a set of rectangular coordinates in the magnetic memory represented by drum 146 despite the essentially polar character of theapparatus 12, 14, 16 and 38. The motion of the conveyor does not introduce any changes in the recorded rectangular coordinates of the program, and yet the execution of the program by the polar apparatus takes into account all of the complex and progressive changes of azimuth, elevation and lengthwise changes ofarm 16 that are necessary forjaws 48 to reach predetermined parts of an article and to keep the jaws moving in step with particular parts of an article when carried in the straightline path of the conveyor.

The coordination of the conveyor in FIG. 6 with the rest of the apparatus in that figure represents a distinctive feature of the invention, but this apparatus has still other advantages, apart from the conveyor. Thus, it may be desired to develop a series of pallet-loading or pallet-unloading techniques where there are many rows of articles on a pallet, many columns of articles, and many layers of articles on that pallet (FIG. 10). It would be relatively tedious to carry out the manually controlled motions of the apparatus for teaching such a program. The apparatus of FIG. 6 with its rectangular manipulator (FIGS. 7 and 8) has the distinct advantage of being able to operate during a teach mode by using the X, Y" andZ encoders 224, 232 and 248, together with a means for executing a sequence of steps defined by successive increments introduced into a rudimentary computer. The dimensions of each carton are known, and hence center-to-center distribution of the cartons along the X axis, along the Y axis,

and along the Z axis is also known. The X, Y and Z.

coordinates of the first carton location are readily determined by manually operating the apparatus to deposit a carton at that location. This set of coordinates can be fed into a computer, together with the three center-to-center X, Y and Z distances desired for the carton spacing within a row, for the row-to-row spacing, and for the layer-to layer spacing, plus the number of cartons in each row, the number of rows, and the number of layers. After the first carton has been spotted physically by operating the apparatus, and the coordinates of that location are entered in the program drum 146, then the computer can supply the X, Y and Z digital coordinates to be entered into successive slots of the program drum. Each new program becomes a simple matter. Indeed, a computer can be used to record a series of programs on tape for each difierent grouping of articles to be palletized, and each such program can be transferred into drum 146 when needed or such tapes can even be used in lieu of such a program on drum 146 for controlling the automatic operation of the apparatus of FIGS. 6-9. Other modes of control of the elevation, azimuth and radial positions ofapparatus 10 by means of theX-Y-Z control apparatus 196 can be devised for such patterned-location operations such as palletizing, where X, Y and Z information of the patterned locations is available.

It may at times be important for the program-controlled apparatus to execute a program involving a number of operations on an article on a moving conveyor, and to cooperate with one or more stationary locations. Thus, for example, it may be desirable for articles at one supply point or a series of articles located at spaced-apart supply points adjacent to a conveyor to be picked up in a prescribed sequence and transferred to an article being transported on a moving conveyor, as for assembling parts to a machine being assembled while the machine base is advancing on the conveyor or for loading a pallet on the conveyor. Similarly, it may be desired to remove a series of articles from a pattern of locations within a modular area of a moving conveyor, and to transport those articles and deposit them in succession at a delivery point or in a prescribed pattern of delivery locations. Such a program can be recorded with the conveyor at rest. Under manual control, theapparatus 10a is caused to execute operations in any required sequence with respect to the article or modular area to be advanced by the conveyor, and with respect to one or more fixed locations adjacent to the conveyor. Then the automatic operation can be accomplished by having the control apparatus equipped with a means for introducing an off-set in the programcontrolled motions that are executed in relation to a moving conveyor and, for each motion that is to be executed in relation to a stationary location, to restore the program-control means to the more usual form of control in which there is no such off-set. This character of operation can be achieved by incorporating the structure of FIG. 11 in that of FIG. 7, as a modification of a part of FIG. 7.

The apparatus of FIG. 11 includesdigital encoder 224, synchroreceiver 226, anddifferential gearing unit 228 that introduces an off-set provided by synchroreceiver 226 between the value ofencoder 224 and the position ofshaft 216. Amechanism 261 is interposed betweensynchro receiver 226 anddifferential gearing 228. The purpose ofmechanism 261 is to enablesynchro receiver 226 to introduce a progressive off-set in proportion to the extent of motion of the conveyor from a starting time of a complete program of motions including conveyor-related motions, and to restore the program free of off-set during the execution of operations not concerned with conveyor motion. In this way the apparatus can perform motions related to stationary articles and devices at stationary locations adjacent to the conveyor, and to catch up with a progressively advancing discrete area of the moving conveyor. The entire travel of the conveyor from start of the program is taken into account, without special concern for the time taken by the apparatus in executing program-controlled motions related to stationary locations.

Mechanism 261 includesgear 263 that is supported on ashaft 265 and meshes with thepinion 267 that provides offset input todifferential gearing unit 228. Ablock 269 extends laterally fromgear 263 and is in driving engagement with apin 271 that extends laterally from anothergear 273. This driving engagement is true for only one direction of rotation ofgear 263. Atorsion spring unit 275 has one end of the internal spring connected toshaft 265, and the other end of the internal spring connected totubular shaft 277 that is rotatably supported onshaft 265.Gear 273 is fixed toshaft 277.Torsion spring unit 275 biases gears 263 and 273 in the required directions to maintain driving connection betweenblock 269 andpin 271.Pinion 279 that meshes withgear 273 is rotated by synchroreceiver 226 in the direction to drivepin 271 away fromblock 269. As synchroreceiver 226 operatesgear 279,gear 273 rotates and, due totorsion spring unit 275, gear 263' rotates likewise. This introduces the previously described off-set into therectangular manipulator 196 of FIGS. 6, 7 and 8 to compensate the pre-recorded program for the motion of the conveyor.

Gear 263 has apin 281 that is in engagement with astop 283 at the start of the program. Atorque motor 285 is connected to gear 263 andshaft 265 and is effective when energized to drivegear 263 so that itspin 281 bears againststop 283.

At the start of the program, synchroreceiver 226 is not energized.Torque motor 285 is energized under control of the program on drum 126 (FIG. 5) topress pin 281 againststop 283, and then motor 285 is deenergized. Under program control, synchroreceiver 226 is energized and starts to rotate coordinately with the travel of the conveyor. Thecoupling mechanism 261 is then effective to transmit the off-set provided by synchroreceiver 226 to thedifferential gearing unit 228. Consequently, the motions ofapparatus unit 12, 14, 16, etc., will execute the originally recorded program, modified to introduce the off-set for compensating the program for conveyor travel.Synchro receiver 226 continues to rotate and to rotate gear 273' during the execution of the entire program. However, if at some time in the course of the program, theapparatus unit 12, 14, 16, etc., is to execute an originally recorded program motion in relation to a fixed location alongside the conveyor, thentorque motor 285 is energized under program control to restoregear 263 to its starting position. This restores the direct relationship betweenencoder 224 andshaft 216 that existed during recording of the program, free of any off-set. When it is next desired to execute another operation in relation to the conveyor,torque motor 285 is deenergized, and the torsion provided byspring unit 275 is then effective to restore the off-set corresponding to the actual conveyor advance from the start of the program.Spring unit 275 advancesgear 263 to the extent limited to engagement of itsblock 269 withpin 271 ongear 273 that has been continuously driven by synchroreceiver 226. In this way, an entire program can be pre-recorded to include operations of the transfer unit which relate to stationary locations, and other operations that relate to a discrete moving section of a conveyor; and later the program can be executed automatically, with the conveyor operations alternating with the stationary operations executed by the transfer apparatus. When the mechanism of FIG. 11 is utilized, the apparatus in FIG. 5 is to include a recording head 1500 and asensing head 148c with a related circuit for controllingtorque motor 285.

A further embodiment of various aspects of the invention is illustrated in FIGS. 12, 12A, and 1316. The article-handling unit 10b of FIG. 12 includes a base 12', a post 14' that is rotatable about a vertical axis, an arm 16' that moves about ahorizontal pivot 16a, and ahead 18 on the end of ashaft 38a that moveshead 18 to various radial lengths, measured frompivot 16a.Work head 18a carries a pair ofjaws 48.Head 18 has the same actuating means as in FIG. 1 so that the jaws can be moved through various tilting motions about a horizontal axis (parallel to pivot 16a) and various swinging motions about an axis perpendicular to the tilting axis. The same encoders and off-set servo receivers are provided in the apparatus of FIG. 12 for the swinging motion ofwork head 18a and for the tilting motion ofwork head 18a as in FIG. 1.

Transfer apparatus 10b is capable of being taught a program of motions with respect to a stationary space, e.g., the space containing an article A while at rest, and then thetransfer apparatus 10b is capable of executing that program on article A when the article is carried on a movingconveyor 260 as in FIG. 6. In common with the apparatus in FIG. 1,apparatus 10b includes anazimuth angle encoder 290 which monitors the rotation of post 14' about its vertical axis, and it includes anencoder 292 that monitors the angle of elevation ofarm 16, and it further includes a radial-position or arm-length encoder 294 that monitors the distance betweenpivot 16a andhead 18.Motor 20 rotates post 14 about its vertical axis,actuator 34 operates arm 16' aboutpivot 16a, and a hydraulic actuator in arm 16' (as in FIG. 1) operatesshaft 38a outward and inward, all subject to the same program control when article A is at rest as the apparatus of FIG. 1.

Apparatus 10b in FIG. 12 has an off-setservo receiver 296 that is coupled through adifferential gearing unit 298 toencoder 290 and to post 14' viapinion 80b andgear 80a. Similarly, an off-setservo receiver 300 is coupled viadifferential gearing unit 302 toencoder 292 and to gearsector 304 that is rigidly connected to arm 16'. Finally,encoder 294 that monitors the length ofarm 16', 38a is coupled to an off-setservo receiver 306 and to drum 84c (as in FIG. 1) via differential gearing unit 308. Off-setservo receivers 296, 300 and 306 are included for introducing a compensating factor that adjusts the operation ofapparatus 10b for the motion of the article A on a conveyor, after the apparatus has been taught a program with respect to a stationary article A. These compensations will be appreciated from a consideration of FIG. 12A.

It is understood that a program has been recorded in the memory of the apparatus (FIG. While an article was at rest on conveyor 260 (FIGS. 12 and 12A). This program involves a motion of thehead 18 to position 18-1. Then there is a dwell, the article and the head remaining at rest for a time interval during the teaching of the program. The dwell may allow for a Welding operation or for a drilling operation by a drill that moves outward relative to head 18, or a spot-coating operation, or the like. Subsequently,head 18 is moved to a second programcontrolled position 18-2 and there another dwell is required in this illustrative pro-gram. Any further steps follow, as needed.

After the whole program has been recorded with article A at rest, the program is executed with the article onconveyor 260 which is then set in motion. The apparatus b moveshead 18 to position 18.-1 at the start of the program, witharm 16 in position 16-1. During the first dwell of the program,arm 16 moves through an angle to position 16-1a, to keephead 18 in constant position in relation to the moving article. Thereafter, instead ofarm 16 carryinghead 18 to position 18-2, no such motion is undertaken. This is because the at-rest position 18-2 ofhead 18 has now been changed by motion of the conveyor during the dwell. Programmed position 18-2 has now become position 18-2a. Accordingly,arm 16 should move to position 16-2a. During the second dwell, to remain in cooperation with the same p-art of the article represented by original coordinate 18-2,arm 16 must move from position 16-2a to position 16-2b. Prominent compensations are needed between the record-controlled positions and the program carried out in relation to the moving article.

The height ofhead 18 above the horizontal x, y plane (through thepivot 16a of arm 16) remains constant during the first dwell, whilehead 18 moves from position 18-1 to position 18-1a. This is a straight-line motion, parallel to the path ofconveyor 260. Initially, as arm 16-1 swings toward vertical plane x, 2,arm 16', 38a becomes shorter so as to involve an arm-length correction C-1. Thereafter, ashead 18 moves from the x-z plane to position 18-1a, the arm length will increase to the extent of compensation 0-2. (In the chosen operation, arni 16 has moved through a greater angle beyond plane x, z in reaching position 16-1a than it traversed from position 16-1 to plane x, 2.) C-1 represents a decrease in arm length and C-2 represents an increase in arm length, as compared with the recorded arm length.

During the swing of arm 16' from the position 16-1 to the vertical plane x, 2, there is an increase in the angleof-elevation ofarm 16. This is because the radial extent ofhead 18 has changed, from position 18-1 to a shorter radial position and it has maintained a constant distance from the x, y plane (i.e., conveyor 260). The angle of elevation of arm 16' decreases asarm 16 moves beyond plane x, z to position 16-1a. The changes in angle of elevation to keephead 18 at the position 18-1 required by the recorded program involve further compensations.

From position 18-1a,head 18 must not move to the originally programmed position 18-2 but, instead,head 18 must move directly to position 18-2a to take into account the travel of the conveyor during the first dwell. Position 18-2 in this example is originally at the far side of plane x, z. By thetime head 18 has moved to the position 18-2a (located along a straight line parallel toconveyor 260, from position 18-2) it has become necessary for the length of the arm to increase by a compensation distance C-3. The angle of elevation ofhead 18 has decreased a little (compared to the angle of elevation at position 18-2 of the at-rest program) and of course there has been a sweep ofarm 16 through a substantial azimuth angle to reach position 16-2a. Thereafter, whenhead 18 moves from position 18-2a to position 18-2b, there is further elongation of the arm requiring an armlength compensation C-4, compared to the original programmed arm length. There has also been a change in azimuth angle, and there has been a reduction in angle of elevation.

Mechanism 310 which is best illustrated in FIGS. 12 to 16, inclusive, provides all these compensations. This mechanism includes anarm 312 that is pivoted aboutaxis 312 on abracket 314 carried on acollar 316 that is coaxial withshaft 14 but rotatable on shaft 14' about the vertical axis. Acompanion arm 312a is similarly carried by a suitable bracket oncollar 316a that is rotatable about astationary shaft 14a parallel to post 14 but spaced laterally from that post. Anarm extension 318 is telescopically received inarm 312 and, similarly, anarm extension 318a is telescopically received inarm 312a. Aspherical bearing 320 fixed toshaft 322 is captive in a suitable socket in the end ofarm 318. Aspherical bearing 320a also fixed toshaft 322 is supported byarm extension 318a.Arms 312 and 312a are parallel to each other at all times.Balls 320 and 320a rotate in their sockets. Ashaft 323 is supported bybrackets 325 and 327 depending fromarms 312 and 312a, spaced substantially belowarm 324.Pinions 329 in these brackets mesh with rack teeth alongarm extensions 318 and 318a.Shaft 323 connectspinions 329 so that both pinions rotate in unison, maintainingarm extensions 318 and 318a equal in length.Shaft 323 has a flexible or a universal rotary drive connection to eachpinion 329 that accommodates angular shift ofarms 312 and 312a in relation to the shaft.

Athird arm 324 is carried on pivot 324' extending perpendicularly through post 14'.Arm extension 326 is received telescopically Withinarm 324. An externallyspherical unit 328 on threadedshaft 322 is carried in a socket inextension 326, and is keyed against rotation inextension 326. In operation,parts 320, 320a and 328 pivot about axes perpendicular toshaft 322 and to their supporting arm extensions. A servoreceiver torque motor 330 is carried byshaft 322 and is arranged to operateshaft 322 in the direction to drivenut 328 away from thecompanion part 320. Anarcuate part 330a extends fromarm extension 318 to constrain the motor frame from rotating. As will be seen, the position ofarm 312 and itsextension 318 represents the original programmed 23 azimuth, elevation and length of the arm, whereas the angular position ofarm 324 and itsextension 326 represents the actual or compensated azimuth, elevation and length ofarm 16, 38a.

Afourth arm 332 is supported on the horizontal pivot ofarm 324. Anannular plate 334 is carried by aslide bearing 335 onpost 14. Raisedbrackets 336 and 337 ofarms 312 and 332, respectively, engageplate 334. This plate is biased againstbracket 336, by gravity for example, whilearm 332 is suitably biased upward so that itsbracket 337 bears againstplate 334.Plate 334 is thus effective to maintainarm 332 at the same angle as that assumed byarm 312.Plate 334 is spaced fromarm 324 to provide clearance forarm 324 to assume larger angles of elevation thanarm 312. Arm 332 carries aservo torque transmitter 338 whose rotor carries apinion 348 meshing with agear sector 342 carried by abracket 344 upstanding fromarm 324. The angle through whichgear sector 342 operatesservo transmitter 338 is a measure of the change of elevation ofarm 324 relative to the programmed elevation represented by the elevation ofarm 312. This change provides a compensation signal during conveyor operation, and is discussed more fully below.

Anarm 345 extends rigidly frompost 14 and supports aservo transmitter 346. Afurther arm 348 extends frombracket 316. One end of a rack orgear sector 350 is secured tobracket 348. Apinion 352 on the shaft of theservo transmitter 346 meshes withgear sector 350. When angularity develops betweenarms 312 and 324, as represented by their axes 312' and 324 (FIG. 15) this angularity is measured by the rotation ofservo transmitter 346. The signal ofservo transmitter 346 represents the azimuth compensation between the programmed position ofarm 16 and its compensated position during conveyor operation.

Motor 330 is a servo torque receiver that drivesnut 328 alongshaft 322 in synchronism with the conveyor travel.

Arms 312 and 324carry servo transmitters 354 and 356, respectively, e.g., synchro torque transmitters. These servo transmitters havepinions 329 and 357 which mesh with rack teeth alongextensions 318 and 326, respectively.

Referring once again to FIG. 12, acable 360 is shown having one end secured toshaft 38a that moves withhead 18.Cable 360 passes around apulley 362 coaxial withshaft 16a, and then around adrum 364 that is mounted on post 14'. Wind-updrum 364 has an internal tensioner such as a torque motor to maintaincable 360 under tension. Anothercable 366 is wound about adrum 368 coaxial withdrum 364 and fixed thereto.Cable 366 extends about apulley 370 that is rotatably mounted on post 14', and the remote end ofcable 366 is secured to abracket portion 372 of extension 326 (FIG. 15). An internal compression coil spring or fluid-pressure cylinder inarm 324 pressesextension 326 outward and maintainscable 366 tensioned.

A rod 374 (FIGS. 12 and 15) extends betweenarm 16 andarm 324 for maintaining these arms parallel, as to their angle of elevation.Rod 374 is parallel to post 14'.

The operation of the apparatus thus far described may be considered at this point. Servotorque receiver motor 330 onshaft 322 receives a signal from theservo torque transmitter 368 coupled to theconveyor 360, so thatmotor 330 rotates at a rate that represents the speed of a conveyor. Rotation ofmotor 330 drivesarm 326 away fromarm 318. The proportions ofcompensator 310 including its arm lengths,pulley 370, and drum 368 are all scaled down, for example, to one-half ofarm 16, 38a,pulley 362 anddrum 364; and the distance betweenpulley 370 and drum 368 is accordingly half that betweenpulley 362 anddrum 364. Servotorque receiver motor 330 advances the end ofextension 326 along threadedshaft 322 accordingly at one-half the linear speed of advance of the conveyor. The length ofshaft 322 betweenextensions 318 and 318a is made sutficient for the apparatus to execute the programmed sequence of operations during the travel of an article on the conveyorpast apparatus 10b.

The apparatus that includesmotor 20 anddigital encoder 290 that are coupled to the vertical post 14' tends to operate that vertical post as if the article A with which head 18 is to cooperate were not moving. However, operation of the conveyor rotatesservo torque transmitter 268 and operatestorque receiver motor 330 correspondingly, and as a result, an angle develops betweenarms 312 and 324 (FIG. 15). An equal angle develops betweenarms 345 and 348 (FIG. 14), with the result thatservo torque transmitter 346 produces an output that is a measure of this angle.Torque transmitter 346 is coupled to servo torque receiver 296 (FIG. 12). Theservo system 346, 296, acts throughdifferential gearing 298 to introduce an off-set between the actual azimuth angle of post 14' and that which is represented byencoder 290, to an extent that accommodates the travel (at any given instant) of article A onconveyor 260 from the start of the recorded program. A suitable index element on the conveyor, or on article A, may be used to trigger the start of the programmed operation ofapparatus 10b, as in Pat. No. 3,283,918.

Arms 324 and 16. are both pivoted toshaft 14, and they both swing through equal azimuth angles concurrently. The actual position ofarm 16 at any given point in the program is actually the recorded azimuth angle, subject to the off-set introduced byservo system 346, 296. Accordingly,arm 312 lagsarm 324 by this off-set angle; and the angular position ofarm 312 is, consequently, the position thatarm 16 would have assumed if there had been no off-set azimuth angle.

Theradial length oflarm 16, 38a tends to operate under program control in accordance withencoder 294. However, an off-set length is introduced byservo torque receiver 306, for adjusting the radial position ofhead 18 in accordance with the recorded program and in accordance with the compensation or correction required to take into account the motion of the conveyor. The signal for synchrotorque receiver 306 is supplied in the following manner. The radially outward bias of the internal spring or air cylinder withinarm 324 acting onextension 326 pressesshaft 322 transversely, tending to moveshaft 322 away from post 14'.Arms 312 and 312a are also preferably equipped wth internal biasing means for urgingextension 318 and 318a outward, tending to move transverse threadedshaft 322 bodily away fromposts 14' and 14a. This outward bias maintainscable 366 under tension. Accordingly, the radial extent ofhead 18 frompivot 16a ofarm 16', 38a remains proportional to the length ofarm 324, 326.Servo torque transmitters 354 and 356 (FIG. 14) onarms 312 and 324 operatesynchro torque receivers 375 and 376 (FIG. 16). These synchro receivers are connected to adifferential gear unit 378 arranged to operate asynchro torque transmitter 380 in accordance with the difference between the rotations of eachsynchro torque transmitter 354 and 356. The output of synchro torque transmitter 380 (geareddown to the one-half scale ofunit 310 compared toarm 16', 38a) operates synchro torque receiver 306 (FIG. 12)Differentials 378 and 308 may be direct-connected it convenient, omittingservo units 306 and 380.

So long asarm 324 and itsextension 325 are face-toface witharm 312 and itsextension 318, then there is no difference in the rotation betweenservo torque transmitter 354 and 356, irrespective of the length ofextension 326 as determined bycables 366 and 360. However, when servotorque receiver motor 330 operates to shiftextension 326 away from extension 318 (FIG. 15) then a difference develops between the length ofarm 312, 318 andarm 324, 326. This difference is derived by the servo elements in FIG. 16 and introduced byservo receiver 306 as an off-set or departure between the actual length ofarm 16', 38a and the length of that arm called for by the program. This difference results from the effect ofservo torque receiver 330 and represents the necessary compensation inlength ofarm 16', 38a, to accommodate the recorded vprogram to the travel of the conveyor.

The angle of elevation of arm 16' is that produced byactuator 34 under control of the stored program and elevation-angle encoder 292. It will be recalled that link 374 constrainsarm 324 to remain parallel to arm- 16. When servotorque receiver motor 330 operatesshaft 322 and causesarm 324 to swing away fromarm 312, the angle of elevation ofarm 324 changes in relation to that ofarm 312.Arm 312 remains at a position corresponding to the actually recorded program. The net etfect of the angular movement ofarm 324 relatively away fromarm 312 results inarm 332 moving through an angle in relation toarm 324. This motion operatesservo torque transmitter 338 to transmit an elevation compensating signal toservo torque receiver 300, thereby to adjust the angle of elevation ofarm 16', 38a as it moves through the various program-controlled motions for coordination with the conveyor as illustrated in FIG. 12A.

In FIGS. 12-15, each of the primary program-controlled motions involves a mechanical feedback connection between the transfer apparatus b and its compensationsignal generator mechanism 310.Arm 324 is carried on a pivot transverse to post 14 and parallel to pivot 16a.Bracket 345 is fixed to post 14 and carries aservo torque transmitter 346 that is rotated bygear sector 350 on abracket 348, for providing the azimuth angular compensating transmission.Bracket 345 thus represents a direct feedback connection tomechanism 310 from the controlled part ofapparatus 10b.Cables 360 and 366 form a mechanical feedback connection betweenarm 16, 38a of theapparatus 10b andarm 324, 326 of thecompensation mechanism 310. This operatesservo devices 375 and 376 (FIG. 14) and 380 (FIG. 16) to provide the radial arm-length compensating transmission. Finally,rod 374 provides a mechanical feedback connection to maintain parallelism between arm 16' ofapparatus 10b andarm 324 ofmechanism 310. This arrangement is part of the means for operating servo torque transmitter 338 (FIG. 14) that provides the elevation-compensating signal.

Theentire mechanism 310, said to be half-scale compared to the length ofarm 16, 38a, could be made fullscale, as by usingarm 16 itself in place of the describedarm 324; and in that case, there would be no need for the feed-back connections since the compensation signal generating mechanism would then be directly integrated in the head-carrying apparatus.

The accommodation provided by signals frommechanism 310 to adapt the primary motions of azimuth, radial arm length and angular elevation to the conveyor-carried article are also useful for adapting the secondary motions of tilt and swing ofwork head 18a to the conveyor movement. To this end, the tilt and swing ofwork head 18a is operated by the same encoders and off-set servo torque receivers as in FIGS. 1-4, with signal input fromservo torque transmitters 338 and 346. The connections to the off-set servo torque receivers for adjusting the tilt and swing ofwork head 18a are those to produce equal and opposite compensation angles in relation to the compensation angles of the elevation of arm 16' and of the rotation of post 14'. For example, if the conveyor motion should necessitate lowering of arm 16' in FIG. 12 toward the horizontal, then workhead 18a is to be tilted upward by an equal and opposite angle in order to maintain the attitude ofwork head 18a constant in space. The attitude ofwork head 18a is basically a program-controlled mo- Themechanism 310 of FIG. 12 isdescribed above in connection with the use ofapparatus 10b with a conveyor. However, it is readily possible to take advantage of some characteristics of this apparatus even, ifthere were no conveyor present. For example, the mechanism3-10adapts the rest ofapparatus 10b to straight-line motion in one direction by providing input tomotor 330. Consequently, in case straight-line motion is wanted, suitable input to this motor will produce linear traverse motions ofwork head 18a. Further, if uniform advances'are wanted along this line from each position to the next, as in loading a pallet, then repeated equal increments to thismotor 330 will produce the desired equal linear displacements ofwork head 18a. These increments can even be provided under program control, as by makingmotor 330 part of a digital servo system controlled by the recorded program.Motor 330 may take the form of a pulse-counting motor, advancing one small but accurate step in response to each pulse and supplied with trains of equal numbers of pulses for successive equal steps ofhead 18 along a line parallel toshaft 322. Successive operations may then be carried out bywork head 18a at regular-spaced locations on one or more articles along the line without the necessity of manipulating the manual controls of the apparatus in the teach or program-recording mode, for each such location.

Theapparatus 10b of FIG. 12 is readily capable of operating between the moving conveyor and a stationary location in alternate operations, merely by incorporating the mechanism of FIG. 11 in each oif-set-introducing and position-encoding assembly in the same manner as already described in connection with FIG. 11.

In both of the embodiments, those of FIGS. 6 and 12, thepivot 16a ofarm 16 and the longitudinal axis ofarm 16 lie in a common plane. It is understood that the invention applies to equivalent apparatus. For example, there is a commercial program-controlled apparatus very similar to those illustrated in the drawings, having an arm likearm 16 herein whose longitudinal axis, when horizontal, extends along a line that is located a small but sometimes significant distance above the pivot corresponding to pivot 16a herein. This does not upset the functioning of either apparatus, provided that themanipulators 196 and 310 have corresponding configurations.

FIG. 4C shows a means for introducing a digital-value olf-set between the control information supplied by the program recording and the hydraulic actuator-and-controlvalve system that responds to the input control information. In like manner, the apparatus of FIGS. 6-9 and that of FIGS. 1216' may be equipped with three digital encoders representing the three oiT-sets to be provided, in the arm length, in the elevation and in the azimuth angle. Thus, in the embodiment of FIG. 12, unit 380 (FIG. 16), unit 338 (FIG. 13), andunit 346 may be replaced by digital encoders whose output may be introduced between theseveral encoders 294, 292 and 290 and their respec tive information input registers comparable to theencoder 104, theinput register 104a and the off-set introduction unit 108' in FIG. 4C. The same feature may be used to advantage in the apparatus of FIGS. 6 and 7. Thus,servo receiver 226 andditferential 228 which introduce an oil"- set betweenencoder 224 and the program drum may be replaced by the digital oif-set introducing arrangement in FIG. 4C.

The embodiments of FIGS. 6 and 12 involve a preferred form of control means for each of the actuators,e.g. actuators 20, 34 and 38. However, in accordance with more general aspects of the invention, other forms of actuators may be substituted, such as that in application Ser. No. 686,111, filed Nov. 28, 1967, by George C. Devol, and in that case once again, the off-set information may be generated by mechanisms shown herein, using off-set digital encoders in lieu of the servo transmitters in FIGS. 13- 15 for example, and combining the data from these encoders with the primary data furnished by the primary source of control information, in the manner of FIG. 11.

A wide latitude of further variation and varied application of the novel features of the invention will be readily devised by those skilled in the art, based on the foregoing. Consequently, the invention should be construed broadly in accordance with its full spirit and scope.

We claim:

1. Apparatus for moving a workhead through a pattern of motions, including an arm operable arcuately about a first axis, said arm having a lengthwise movable part adapting the arm to be extended and retracted, said lengthwise movable part carrying said workhead, a first angular actuator for operating said arm about said first axis and a lengthwise actuator for extending and retracting said lengthwise movable part of said arm, and control apparatus for said actuators, said control apparatus including control means individual to said actuators, respectively, a linear-motion control for providing control input representing motion of said workhead along a path requiring lengthwise adjustment of said arm and angular motion of said arm, and rectilinear-to-polar converter means in at least partial control of both said individual control means and responsive to said linear-motion control for imparting a linear component of motion to the workhead.

2. Apparatus in accordance withclaim 1, wherein said control apparatus includes a main source of motion control information for producing a sequence of motions of the workhead and separate means for providing control information to said linear motion control, for effecting a pattern of motions of said workhead as directed by the main source of motion control information, modified in accordance with the linear-motion control information.

3. Apparatus in accordance withclaim 1, wherein said control apparatus includes a main source of motion control information to respective ones of said individual control means for producing a sequence of motions of the workhead, offset coupling means in each of said individual control means controlled by said rectilinear-to-polar converter, and separate means for providing control information to said linear motion control, for effecting a pattern of motions as directed by the main source of motion control information, modified in accordance with linearmotion control information.

4. Apparatus in accordance withclaim 1, including a second linear motion control, said rectilinear-to-polar converter means including portions operable at right angles to each other, said portions being responsive to said linearmotion controls, respectively, and a main source of motion control information for said linear-motion controls for operating said converter means to impart controlled sequences of motion in at least two dimensions to said work head.

5. Apparatus in accordance withclaim 4, further including means for imposing offset motion control information on one of said linear motion controls, so that said workhead is operable through motions in accordance with said main source of motion control information as modified by the offset information means.

6. Apparatus in accordance withclaim 1, wherein said arm is operable in a coordinate additional to said lengthwise and angular motions so as to carry said workhead through three-dimensional paths, and including an additional actuator and individual control means for said additional actuator.

7. Apparatus in accordance withclaim 3, wherein said arm is operable in a coordinate additional to said lengthwise and angular motions so as to carry said workhead head through three-dimensional paths, and including an additional actuator and individual control means for said additional actuator responsive to said main source of information and to said converter means.

8. Apparatus in accordance withclaim 6, including two additional linear-motion controls in control of said converter means, said converter means including three elements operable at right angles to each other in accordance with said three linear-motion controls, respectively, and a main source of motion control information for said linearmotion controls for operating said converter means to impart controlled sequences of motion in three dimensions to said workhead.

9. Apparatus in accordance with claim 8, further including means for imposing offset motion control information on one of said linear motion controls, so that said workhead is operable through motions in accordance with said main source of motion control information as modified by the offset information means.

10. Apparatus in accordance withclaim 1, wherein said arm is operable about a second axis at right angles to said first axis, and including a second angular actuator and individual control means for said actuator at least partially controlled by said converter means.

11. Apparatus in accordance withclaim 1, wherein said arm is operable about asecond axis at right angles to said first axis, and including a second angular actuator and individual control means for said actuator at least partially controlled by said converter means, and wherein said control apparatus includes a main source of motion control information to respective ones of said individual control means for producing a sequence of motions of the workhead, offset coupling means in each of said individual control means controlled by said converter means, and separate means for providing control information to said linear motion control, for effecting a pattern of motions as directed by the main source of motion control information, modified in accordance with the linear-motion control information.

12. Apparatus in accordance withclaim 1, wherein said arm is operable about a second axis at right angles to said first axis, and including a second angular actuator and individual control means for said second angular actuator at least partially controlled by said converter means, said converter means including three portions operable rectilinearly in accordance with the three linear-motion controls respectively, said portions being operable at right angles to each other, and a main source of motion control information for said linear-motion controls for operating said converter means to impart controlled sequences of motion in three'dimensions to said workhead.

13. Apparatus in accordance withclaim 12, further including means for imposing offset motion control information on one of said linear motion controls, so that said workhead is operable through motions in accordance with said main source of motion control information as modified by the offset information means.

14. Apparatus in accordance withclaim 1, wherein said converter means includes first and second levers operable about a main lever axis, a third level parallel to said first lever and operable about another axis parallel to said main lever axis, a rod carried by said first and third levers at equal distances from said axes thereof, said second lever having an operative part on and adjustable along said rod to move the rod to various angles in relation to said first lever and to various distances from said main lever axis, said linear-motion control being arranged to determine the position of said operative part of the second lever along said rod, means enforcing conjoint angular motions of said arm and said second lever, means for maintaining a constant ratio between the lengths of said arm and said second lever, and means responsive to the angular displacement between said first and second levers for at least partially controlling the individual control means of said first angular actuator.

15. Apparatus in accordance withclaim 14, wherein each of said individual control means includes first and second control elements, and wherein said control apparatus includes a main source of control information for respective ones of said first control elements for producing a sequence of motions of the workhead and wherein said second control elements in said individual control means form respective portions of said means enforcing conjoint angular motions of the second lever and said arm and

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