US3248678A - Rotary variable resistor - Google Patents

Description

April 26, 1966 c. F. REMUS ROTARY VARIABLE RESISTOR Filed May 1, 1963 INVENTOR.

CASIMER F. REMUS United States Patent 3,248,678 ROTARY VARIABLE RESISTOR Casimer F. Remus, Tunkhannocir, Pa., assignor to The Bendix Corporation, South Montrose, Pa., a corporation of Delaware Filed May 1, 1963, Ser. No. 277,274 11 Claims. (Cl. 338164) This invention relates to electrical apparatus, and more particularly relates to a variable resistor. In the illustrative embodiment of apparatus in accordance with the invention, the variable resistor is specifically an hermetically sealed potentiometer.

The invention has among its objects the provision of a novel variable resistor which fulfills all of the conventional requirements of such devices.

Another object of the present invention is to provide a novelly constructed variable resistor or potentiometer which will obviate the occurrence of errors between upscale and down-scale readings and errors between input and output.

A further object resides in the provision of a novel variable resistor of the type wherein a movable contact engages an extended resistance at a selectively variable location therealong.

Another object of the invention resides in the provision of a variable resistor of such construction that the engagement between the movable contact and the resistance minimizes wear imposed upon the resistance and the contact.

Yet another object of the invention is the provision of a novel variable resistor wherein the zone of engagement between the resistance and the contact is hermetically sealed from the atmosphere.

A still further object of the invention lies in the provision of a variable resistor wherein the relative motion between an extended resistance and a contact movable therealong is such as to permit the use of fixedly connected flexible sealing means novelly combined with relatively rotatable parts.

The above and further objects and novel features of the invention will more fully appear from the following description when the same is read in connection with the accompanying drawings. stood, however, that the drawings are for the purpose of illustration only, and are not intended as a definition of the limits of the invention.

In the drawings, wherein like reference characters refer to like parts throughout the several views,

FIG. 1 is a view in longitudinal section through a potentiometer made in accordance with the invention, certain of the parts being shown in elevation and the section being taken on line 1-1 of FIG. 2;

FIG. 2 is a view in end elevation of the potentiometer of FIG. 1, the View being taken in a direction from left to right in FIG. 1, the resistance, the movable contact, and the connections between such elements and the terminals of the potentiometer being shown schematically;

FIG. 3 is a view in transverse section through the potentiometer of FIG. 1, the section being taken along the line 3-3 of FIG. 1; and

FIGS. 4 and 5 are detail views, partly in section, illustrating a modified form of wiper contact that may be used in the device of FIG. 1.

The apparatus of the invention is illustrated herein as an hermetically sealed potentiometer, wherein the zone of engagement between an extended resistance and a movable wiper contact is sealed from the atmosphere. It is to be understood that the invention is not limited It is to -be expressly under- ICC . the novel manner of adjusting the location of engagement betweenthe movable contact and the extended resistance, are applicable to variable resistors which need not be hermetically sealed and to other specifically different electrical devices, such as switches.

Turning now to the drawing, the illustrative potentiom- I eter is generally designated by the reference character 10. Such potentiometer has a circular cylindrical housing designated 11, such housing having acylindrical sidewall 12 made, for example, of metal such as steel. The housing 11 is completed by arear end wall 14 and aforward end wall 15, both of such end walls being generally of disc shape. Theend walls 14 and 15 are secured and sealed to theperipheral wall 12 byannular welds 16 and 17 therebetween, as shown in FIG. 1.

Disposed within the housing and spaced from the inner wall ofhousing part 12 is anextended resistance 19 in the form of a helical or toroidal winding supported on an .annular core 18 of suitable insulation, such as ceramic,

or of metal covered with insulation.Resistance 19 andcore 18 are supported by having the forward annular edge thereof imbedded in and sealed to anannular mass 20 of potting compound, such annular mass being located within and sealed to the wall of anannular recess 21 in an annular supporting member 22. Member 22 has an annular flange orpilot 24 extending forwardly from its forward Wall,flange 24 telescoping within a rearwardly extendingannular flange 25 on the rear face of the forwardend closure member 15. One or more radially extendingheaded pins 26 are pressed into mating radial holes inflanges 24 and 25 so as to secure the supporting member 22 and theresistance assembly 19, 20 supported thereby in the position shown in FIG. 1.

Alead wire 27, connected to one end of thewound resistance 19, is connected to aterminal 29 which extends through an insulating seal of glass, ceramic or the like mounted in and sealed to the rearend closure member 14 of the housing. The other .end of thewound resistance 19 is connected by alead wire 30 to asimilar terminal 31, which is likewise mounted in a sealing insulator sealed to member 14 (FIG. 2):

If theresistance wire 19 is insulated, a central inner peripheral zone of the winding is bated at anannular zone 33, indicated by phantom lines, so as to cooperate with a movableresilient wiper contact 32 which is novelly mounted and so movable as to engage a selected part ofsuch zone 33 of the resistance. Themovable contact 32 is of annular shape and is mounted upon an eccentric or crank means disposed on ashaft 34 mounted axially of the housing, whereby turning of the shaft progressively changes the location of the point of engagement of the contact with the resistance winding. Shaft 34 is rotatably mounted in an anti-friction bearing 35 mounted in theforward closure member 15 of the housing and in a similar bearing 39 mounted inanannular support 40 mounted on therear closure member 14 of the housing.Bearing 35 is retained in abore 36 inmember 15 by means of asplit spring ring 37 which is snapped into an annular groove adjacent the forward end ofbore 36.Thesupporting member 40 for the rear bearing is of cup-like shape, such supporting member being accurately received within a centralcircular recess 41 in the inner wall ofmember 14 as shown.

The eccentric or crank onshaft 34 on whichcontact 32 is mounted is designated 42. Eccentric 42 preferably has an antifriction bearing 44 mounted thereon as shown, the inner race of such bearing being carried by the eccentric and the outer race of such bearingmounting contact 32 through an interposedannular insulating member 46. Thecontact 32 may be in the form of the rim of a wheel having a partially rolled orrounded rim 49 and a radially inwardly directedinner flange 47 which is imbedded in insulatingmember 46 or otherwise suitably mounted onhearing 44.Contact 32 is made of spring metal, such as beryllium copper, whereby the rim or" the contact may resiliently yield somewhat as it engagesresistance 19, thereby insuring secure electrical engagement between the contact and the resistance.

It will be seen that as theshaft 34 is rotated, as by a suitable knob (not shown) secured to the forward end of the shaft protruding from the housing, theannular contact 32 moves bodily eccentrically with respect toshaft 32 without appreciable rotation upon its own axis so that the engagement between the contact and the resistance alongzone 33 is progressively changed. One revo- -lution ofshaft 34 causes thecontact 32 to traverse the entire annular extent ofzone 33 of the resistance, and thus causes the resistance betweencontact 32 and each ofterminals 29 and 31, to vary from a maximum to a minimum and viceversa, respectively. Thus, as the shaft rotates the contact has a combined wiping and rolling engagement with the turns of winding 19. Thecontact 32 has a hook-like terminal 50 thereon,terminal 50 being connected by aflexible lead wire 51 to aterminal 52 which is mounted in an insulating bushing, such as a glass or ceramic seal, supported by and sealed to theend closure member 14.Wire 51 need only be sufficiently long to permitterminal 50 to move in a small circle having a diameter equal to the difference between the diameter ofshaft 34 and eccentric 42.

The space within housing 11 which includes the zone of engagement between thebrush 32, 49 and theresistance 19 is hermetically sealed from the atmosphere, and may be filled, if desired, with an inert gas. In the illustrative embodiment, the sealing means includes a forward flexible pleated metal sleeve orbellows 55 and a similar rear sleeve orbellows 56, the sleeves being sealed at the end-s thereof lying intermediate the length of the housing to the annularcontact supporting member 45 and at their outer ends to the forwardend closure member 15 and the bearing supportingmember 40. In order to effect such sealing connections, the ends of the sleeves are bent over annular flanges on the respective members to which the sleeves are attached and are brazed or welded thereto. Thus, theforward end closure 15 is provided with an inwardly extendingannular flange 57 having a radially extendingflange 58 on its inner end.Member 45 hasannular flanges 59 and 60, on its opposite ends, and hearing supportingmember 40 has aflange 61 on its inner end for this purpose.

When theshaft 34 of the potentiometer is turned, in order to vary the location of the point of engagement between thecontact 32 and theresistance 19, theflexible sleeves 55 and 56 are called upon to flex only to a relatively small degree without rotation as thecontact support 45 travels eccentrically. The bellows thus hold the Wiper contact assembly against rotation about its own axis whenshaft 34 is rotated. It will be seen that the annular space within the housing outwardly ofsleeves 55 and 56 is thus sealed from the atmosphere, and that no provision must be made for providing a seal at the forward bearing 35.

In assembling the potentiometer of the invention, the sub-assembly comprising the two bellows andparts 15, 40 and 45 is first made, thecontact 32 being already mounted on'ring 45. Thesub-assembly comprising members 18, 19, 26 and 22 is then mounted uponplate 15 to form a further, intermediate assembly.Bearings 39 and 44 are next installed, followed by installation ofshaft 34. The latter has annular flanges which position the bearings, the dimensions of the par-ts preferably being such as to pre-load the center bearing 44 and avoid backlash or end shake. Bearing 35 is now put in place and locked in position against a collar on the shaft by thesplit ring 37. After leads 27, 3t and 51 are connected to their respective terminals onrear cover 14, thecylindrical casing member 12 is slipped into position and welded at 16 and 17. By providing additional bearing support inplate 15 forshaft 34, the left side of supportingmember 45 could be closed and the left end of the shaft withhearing 39 could be eliminated.

Theend closure member 14 is provided with ahole 62 therethrough, such hole communicating with the space within the housing lying radially outwardly ofsleeves 55 and 56. Such annular space to be sealed within the housing may be evacuated throughhole 62, and any desired gaseous medium introduced into the housing through such hole in a manner Well known to the art. Aplug 64 may then be inserted intohole 62 and welded toend closure member 14 in order finally to seal the space with in the enclosure or a tube may be mounted in said hole and then pinched closed and sealed when the casing has been backfilled.

In FIGS. 4 and 5 there is illustrated a modified form of annular wiper cont-act which may be substituted forwiper contact 32, 49. As shown, said contact comprises a ring orannulus 66 made of resilient material and a con tact orwiper ring 67 secured to the outer periphery thereof.Annulus 66 is preferably made of a high temperature spring material, such as Inconel, and comprises a disc-like portion 68 which may be embedded in insulatingmass 46 and an axially directed flange portion having a plurality ofslots 70 to form a series ofspring fingers 69. Theslots 70 between the fingers preferably extend somewhat intodisc portion 68.Contact ring 67 is secured by soldering or other suitable means to some or all offingers 69.Ring 67 may thus engageresistance 19 under resilient pressure the same ascontact 32, 49.

The device of the invention is particularly characterized by its simplicity, long life, and the ruggedness of its parts. The described novel manner of mounting of the wiper contact, whereby the contact moves in a planetary manner within theresistance 19, distributes the wearing of the contact over its entire periphery, thereby insuring long, trouble-free operation of the contact. As the contact moves in such manner, it has both a rolling and wiping contact with thezone 33 of the resistance, whereby wearing of both the contact and the resistance is minimized while providing a satisfactory and desirable amount of sliding or wiping engagement.

Although only a limited number of embodiments of the invention have been illustrated in the accompanying drawings and described in the foregoing specification, it is to be expressly understood that changes may be made therein. For example, neither the resistance winding assembly nor the wiper contact need form a complete annulus andshaft 34 need not be rotatable through a complete revolution. If desired, the shaft may be supported at only one side of the wiper contact assembly, such as by a pair of spaced bearings, and thus said assembly may be mounted at the end of the shaft, in which case the eccentric movement of the contact may be realized by having the end portion of the shaft extend at an angle to the axis of rotation. In such modification, only one bellows or sealing sleeve is required and the contact supporting member forms a solid end closure therefor. If desired, a rigid wiper contact may be loosely mounted on insulatingsupport 46 with an interposed resilient support, such as a split wavy leaf spring, to provide .the desirable resilient contacting force. Additionally, a series of circumferentially spaced contacts may be substituted forresistance 19 to provide a rotary switch. Various other changes such as in the relative dimensions of the parts, materials used, and the like, as well as in the suggested use of the apparatus of the invention, may also be made without departing from the spirit and scope of the invention as will now be apparent to those skilled in the art.

What is claimed is:

1. A variable resistor comprising an extended annular resistance member, a contact supporting member disposed within the resistance member, laterally flexible means for holding said contact supporting member against rotation about its own axis, and arcuate contact mounted on the periphery of the contact supporting member and tangentially resiliently engaged with the inner peripheral surface of the resistance member, and eccentric means rotatable about the axis of the resistance member and freely within said contact supporting member for oscillating the contact supporting member and the contact relative to the axis of the resistance member to vary the point of engagernent of said contact along said resistance member.

2. A variable resistor as defined in claim 1, wherein the contact is resilient and circular in shape and has a relaxed diameter less than the inner diameter of the resistance member by slightly less than twice the eccentricity of said eccentric means, and the eccentric means for moving the contact supporting member is an eccentric member journalling the contact supporting member.

3. An hermatically sealed variable resistor comprising a gas impermeable support, an extended annular resistance member secured to the support, a contact supporting member arcuately movable along the resistanec member, an annular contact mounted on the contact supporting member and tangentially engaged with the inner periphery of the resistance member, means including at least a part of the support and flexible gas impermeable diaphragm means connected to the support and the contact supporting member for constantly sealing the zone of contact between the resistance member and the contact from the atmosphere, and eccentric means outwardly of the diaphragmmeans and rotatably journalled within the contact supporting member for moving the contact supporting member and the contact carried thereby arcuately along the resistance member.

4. An hermetically sealed variable resistor comprising a housing having a gas-impermeable peripheral wall, an

extended circular resistance member disposed within the housing and along the wall of the housing, a contact supporting member arcuately movable along the resistance member, a contact mounted on the contact supporting member and engaged with the resistance member, means including the peripheral wall of the housing and flexible gas impermeable diaphragm means connected to the housing and the contact supporting member for constantly sealing the zone of contact between the resistance memher and the contact from the atmosphere, and eccentric means outwardly of the diaphragm means for arcuately moving the contact supporting member and the contact carried thereby along the resistance member.

5. An hermetically sealed variable resistor comprising a housing having agas impermeable peripheral wall, an extended annular resistance member disposed within the housing, a contact supporting member disposed within the resistance member, a circular contact mounted on the contact supporting member and tangentially engaged with the inner peripheral surface of the resistance member, means including the peripheral wall of the housing and flexible impermeable diaphragm means connected to the housing and the contact supporting member for sealing the zone of engagement between the resistance member and the contact from the atmosphere and for holding the contact supporting member against rotation about its own axis while permitting transverse movement of said supporting member, and means comprising an eccentric member journalling the contact supporting member and rotatable about an axis coaxial with the axis of the resistance member, said last-named means being outside of the sealed space formed by theperipheral wall of the housing and the diaphragm means and radially within the resistance member for moving the contact supporting member and the contact carried thereby along the resistance member, said contact having a relaxed diameter less than the diameter of the resistance member by slightly less than twice the eccentricity of said eccentric member.

6. An hermetically sealed variable resistor as defined in claim 5, wherein the diaphragm means is made up of two flexible generally aligned and circular cylindrical diaphragms, said diaphragms being sealingly connected at their outer ends to the peripheral wall of the housing and at theirinner ends to the contact supporting member.

7. A variable resistor comprising an extended annular resistance member, a contact supporting member dis- .posed within'the resistance member, a circular resilient contact rotatably mounted on the contact supporting member within the resistance member, the rim of the contact being tangent to and engaged with the inner peripheral surface of the resistance member at one zone of the resistance member, a shaft coaxial of the resistance member mounting the contact supporting member eccentrically with respect to the axis of the shaft, the contact having a relaxed diameter less than the inner diameter of the resistance member by slightly less than twice the eccentricity of said supporting member, and means for holding the contact against rotation about its own axis while permitting transverse movement of said supporting member, whereby rotation of the shaft oscillates the contact relative to the axis of the shaft and causes the contact to roll along the inner peripheral surface of the resistance member.

8. Apparatus comprising a first member having a convex generally arcuate surface, a second member having a concave generally arcuate surface in substantially tangential engagement with said convex "surface, the latter having a smaller radius of curvature than said concave surface, said second member including a toroidal winding of electrical resistance wire and said first member comprising an arcuate metallic contact resiliently engageable with said Winding, rotatable means having its axis of rotation concentric with said concave surface, means eccentric to and rotatable with said rotatable means for rotatably supporting said first member, the difference between the radii of said arcuate surfaces being slightly less than the eccentricity of said eccentric means and means for holding said first member against rotary movement about its own axis while permitting transverse movement of said first member.

9. Electrical apparatus comprising shaft means, support means for supporting said shaft means for rotary move ment about a first axis, means eccentric to and rotatably movable with said shaft means, .a contact assembly mounted on said eccentric means to permit rotation of the latter relative to said assembly about a second axis movable around said first axis as the shaft means rotates, said assembly comprising a resilient electrical contact having an arcuate peripheral surface concentric with said second axis, means for holding said assembly against rotary movement about said second axis relative to said support means while permitting transverse movement of said assembly, and means including an electrical resistance having an arcuate surface concentric with said first axis and tangentially engageable by the arcuate peripheral surface of said contact, the arcuate surface of the contacthaving a radius less than the radius of said arcuate surface concentric with the first axis by slightly less than the eccentricity of said eccentric means, whereby said contact has combined rolling and sliding engagement with said last-named arcuate surface during rotation of said shaft means.

.10. Electrical apparatus comprising support means, shaft means having crank means and mounted for rotary movement on said support means, an annular electrical contact assembly comprising an annular metallic contact mounted on said crank means to permit rotation of the latter relative to the assembly, tubular means surrounding said shaft means and connected to said assembly and to said support means, said tubular means being flexible to permit movement of said assembly transversely of the axis of said shaft means while holding said assembly against appreciable rotary movement about its axis on said crank means relative to said support means, and an electrical resistance having a generally circular are concave surface concentric with the axis of said shaft means, said contact assembly including a generally circular arc convex surface resiliently engaging said concave surface.

11. A variable resistance comprising an extended circular arc resistance element, a contact supporting member mounted for rotation about the axis of the arcuate surface of the resistance element and having a circular portion eccentric to said axis, a resilient circulararc contact freely mounted on said eccentric portion of the supporting member with the arcuate surface thereof in face-to-face relation with the arcuate surface of the resistance element, the radius of the arcuate surface of said element being greater than the relaxed radius of the adjacent arcuate surface of said contact by slightly less than the eccentricity of said circular eccentric portion, whereby said arcuate surfaces have substantially tangential engagement, and laterally flexible means for holding said contact against angular movement about its own axis.

References Cited by the Examiner UNITED STATES PATENTS 1,569,042 1/1926 Sheriff 338-168 X 1,731,003 10/1929 De Giovanni 338-154 X 2,007,462 7/1935 Stoekle 338-202 X 2,041,380 5/1936 Stoekle 338-202 X 2,133,358 10/1938 McCormack 74-18 X 2,293,407 8/ 1942 Schirrrneister 74-804 X 2,457,814 1/1949 Gordy 338-154 2,497,867 2/1950 Cymmer 74-178 2,656,737 10/1953 Lang 74-804 X 2,798,137 7/1957 Rasmussen 338-202 X 2,873,339 2/1959 Bourns et al. 338-180 2,874,253 2/1959 Sharp et al. 338-164 2,956,254 10/1960 Burns et a1. 338-162 3,067,396 12/1962 Carlstein 338-154 3,081,022 3/1963 Miche 230-147 FOREIGN PATENTS 396,877 8/1933 Great Britain. 813,467 5/ 1959 Great Britain.

RICHARD M. WOOD, Primary Examiner.

ANTHONY BARTIS, Examiner.

Claims (1)

1. 3. AN HERMATICALLY SEALED VARIABLE RESISTOR COMPRISING A GAS IMPERMEABLE SUPPORT, AN EXTENDED ANNULAR RESISTANCE MEMBER SECURED TO THE SUPPORT, A CONTACT SUPPORTING MEMBER ARCUATELY MOVABLE ALONG THE RESISTANCE MEMBER, AN ANNULAR CONTACT MOUNTED ON THE CONTACT SUPPORTING MEMBER AND TANGENTIALLY ENGAGED WITH THE INNER PERIPHERY OF THE RESISTANCE MEMBER, MEANS INCLUDING AT LEAST A PART OF THE SUPPORT AND FLEXIBLE GAS IMPERMEABLE DIAPHRAGM MEANS CONNECTED TO THE SUPPORT AND THE CONTACT SUPPORTING MEMBER FOR CONSTANTLY SEALING THE ZONE OF CONTACT BETWEEN THE RESISTANCE MEMBER AND THE CONTACT FROM THE ATMOSPHERE, AND ECCENTRIC MEANS OUTWARDLY OF THE DIAPHRAGM MEANS AND ROTATABLY JOURNALLED WITHIN THE CONTACT SUPPORTING MEMBER FOR MOVING THE CONTACT SUPPORTING MEMBER AND THE CONTACT CARRIED THEREBY ARCUATELY ALONG THE RESISTANCE MEMBER.

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