EP0510251B1

Movatterモバイル変換

Info

Publication number: EP0510251B1
Application number: EP19910116658
Authority: EP
Inventors: Thomas Meyer
Original assignee: Joa Curt G Inc
Current assignee: Joa Curt G Inc
Priority date: 1991-04-24
Filing date: 1991-09-30
Publication date: 1995-06-14
Anticipated expiration: 2011-09-30
Also published as: EP0510251A1; DE69110451T2; DE69110451D1; ES2075292T3; CA2052180A1

Description

Background of the Invention

The invention disclosed herein pertains to an accumulator for accumulating a substantial length of a running web such that if the infeed to the accumulator is stopped or slowed for a short interval, the web in storage is paid out continuously to a web utilizing machine so the machine has a constant supply and need not be stopped or slowed during any part of the interval.
One common use of a web accumulator is where a web is fed from a primary supply reel and it is necessary to splice the leading end of the web from a standby supply reel to the trailing end of a web from the primary supply reel in a manner which will not cause interruption of the web supply to a web consuming or utilizing device. In some known accumulators there is a row of spaced apart rollers on one swingable arm cooperating with another row of rollers which may be stationary or swingable on another arm. When the one arm with a row of spaced apart rollers on it is swung away from stationary rollers or the row of rollers on the other arm and the web is looped around the two sets of rollers, a substantial length of web can be accumulated. During normal running of the web, the arms will be urged to their maximum separation from each other for accumulating and storing the maximum length of web. If the supply of web to the accumulator is stopped for a short interval, the tension due to drawing web from the outfeed end of the accumulator causes the sets of rollers to move toward each other while the length of web in storage is paid out. After the end of the interval during which web infeed to the accumulator is stopped, the two relatively movable sets of rollers separate again to accumulate and store another length of web.
There is another general type of accumulator which has a set of rollers mounted on a movable carriage which can run linearly toward or away from a set of corresponding stationary rollers. The web is looped back and forth between the rollers on the movable and stationary components so that web is accumulated as the movable carriage moves away from the stationary assembly.
In application of web accumulators where web tension is of concern, designers must face the problems associated with friction and inertia. The consequence of these two factors may be appreciated when it is realized that the web may be running at a very high rate of speed when suddenly, for some reason, such as when making a splice, the infeeding web is stopped or decelerated. This change in web motion will result in a reaction by the components of the accumulator. Most notable of these reactions is the motion imparted to the movable assembly of the accumulator, whether swinging arm or linear carriage. Minimizing the inertia and friction associated with this reaction will minimize tension transients, and is a prime advantage of the invention described herein.
Also notable is the change in speed of the individual rollers. While roller inertia can actually be of benefit during a sudden deceleration, it must also be overcome when the infeeding web is returned to the original running speed. The roller nearest the infeed may have come to a complete stop, while each succeeding roller has slowed to some speed slightly higher than the roller preceding it. As the web at the infeed is accelerated it can only be drawn into the accumulator as fast as the rollers can resume their original speeds. Since the force to accelerate these rollers is provided only by the tension in the web, it can be seen that minimizing the number of rollers and their inertias can allow a given system to operate successfully at lower web tensions. In prior art machines, friction and inertia are significant factors which limit their usefulness at low tensions. Thus, there is an important need for a web accumulator which provides the benefits of low friction and minimized inertia, allowing it to handle the most delicate of webs at high speeds without breakage or loss of control.
A known web accumulator is disclosed in Patent Number US-A-3540641, which embodies all the features in the preamble of claim 1. The piston of a double acting fluid cylinder carries a rack, which engages a sprocket on one of the axle shafts. Thus linear movement of the piston rod causes a proportional change in the angle of the arms when the tension in the web changes.

Summary of the Invention

The present invention provides a web accumulator comprising:
a base;
first and second axle shafts arranged with their axes in parallel and journalled for turning relative to said base, the axes of the axle shafts being spaced from each other along a common centreline;
first and second arms fastened to said axle shafts respectively, for swinging in spaced apart parallel planes in response to turning of said axle shafts, said arms extending in generally opposite directions from the respective shaft axes;
first and second wheel means fastened to said first and second axle shafts respectively;
a force producing actuator;
a flexible member formed in a closed loop around both of said wheel means and engaged with said wheel means for turning said wheel means and the arms with said axle shafts in response to translation of said flexible member resulting from one axle shaft being driven rotationally, the rotation of said one axle shaft causing one arm to swing through an angle away from one side of said centreline and the other arm to swing away through a corresponding angle from the other side of said centreline until the arms attain a predetermined maximum angle; and
a series of spaced apart rollers supported on each arm, the rollers on each arm extending from the plane in which that arm swings towards the plane in which the other arm swings to provide for a web being looped around rollers on opposite arms in succession such that the maximum length of web accumulated in said accumulator occurs when the arms are swung to their said maximum angle;
CHARACTERIZED BY further comprising:
a web infeed roller rotatable on the first axle shaft and a web outfeed roller rotatable on the second axle shaft;
a torque arm fastened to one axle shaft and having a curved profile surface whose radius from the axis of said axle shaft varies over the length of the surface; and
a flexible element connected between said actuator and said curved surface whereby said flexible element is maintained in tangential contact with said curved surface at points along said surface having radii of different lengths as said torque arm is rotated owing to tension developed in said flexible element that results from actuation of said actuator;
wherein changes in the moment of force, defined by the length of the radius at the point of tangency times the tension in the flexible element, cause the torsional force on the axle shaft and first and second arms to vary in correspondence with the angle of the arms with respect to said centreline.
An important feature of the invention is that a constant force applied by the actuator can produce a torsional force on the arms that varies with angular position. The varying radii of the torque arm can be selected to compensate for the varying force vector between the web and arm angles, resulting in an effectively constant web tension, regardless of arm position.

Description of the Drawings

FIGURE 1 is a front elevational, mostly diagrammatic, view of a web handling machine in which the new accumulator may be installed;
FIGURE 2 is a front elevational view of the accumulator with its roller carrying arms angulated to the position in which the maximum length of web is accumulated;
FIGURE 3 is similar to FIGURE 2 except that the arms of the accumulator would be moving towards each other as would he the case when infeed of web is stopped and the great length of web which is stored in the accumulator is being paid out;
FIGURE 4 is a view taken on the line 4--4 in FIGURE 5 of the mechanism for driving the arms apart in unison to effect accumulation of a length of web;
FIGURE 5 is a side elevational view taken on the line 5--5 in FIGURE 4, of the assembled accumulator with some parts being shown in section;
FIGURE 6 shows the two arms of the accumulator swung past each other to provide a clear passageway for threading the web into the accumulator at the start of a web run;
FIGURE 7 shows the position of the arms immediately after the web has been threaded into the accumulator and separation of the arms is underway to increase the length of the web which is to be held in storage;
FIGURE 8 is a front elevational view of an alternate but preferred embodiment of the new accumulator;
FIGURE 9 is similar to FIGURE 8 except that the arms are swung to a position wherein a substantially minimum amount of web would be in storage; and
FIGURE 10 is a view, partly in section, taken on a line corresponding with 10-10 in FIGURE 9.

Description of a Preferred Embodiment

FIGURE 1 illustrates an arrangement in which the new accumulator, generally designated by thenumeral 10, can be used advantageously. In this figure,web 11 is being fed from asupply reel 12 from which the web runs to asplicer 13. The splicer may be any of a variety of conventional splicers which can join the leading end 14 of a web from astandby supply reel 15 to the trailing end of the web from the primary supply reel when the web is just about ready to run out from the primary supply reel. A pair oftranslating belt devices 16 and 17 are provided for rotating the primary and standby supply reels, respectively, for the purpose of feeding out the web to the accumulator downstream.Typical reel driver 16 comprises a belt 18 running onrollers 19 and 20. Roller 20 is fixed to ashaft 21 which is driven rotationally by a motor, not visible, which is behind thefront plate 22 of the machine. The belt and rollers are carried on a frame 23 which has anarm 24 connected to thepiston rod 25 of apneumatic actuator 26. Theactuator 26 is used to push the belt 18 into frictional driving relationship with the periphery of roll of web on the supply reel. This supplyreel drive device 16 is a well known type. After the web passes throughaccumulator 10 it goes through a metering device 27 which is symbolically represented. From the metering device, the web is drawn in the direction of thearrow 28 into a web utilizing device, not shown, which could be a disposable diaper making machine.
Normally, theweb 11 after leavingsplicer 13, will continue overidler rollers 29 and 30 to the infeedroller 35 of theaccumulator 10. And, after being looped back and forth in the accumulator to lengthen the amount of web in storage, the web continues from theoutfeed roller 36 ofaccumulator 10.
When the web onprimary supply reel 12 is depleted to the extent that its trailing end is about to unwind from the reel, drive 16 deceleratesreel 12 so as to bring it to a stop, at which time thesplicer 13 splices the leading end of the web onreel 15 to the expiring web. It is quite typical that conventional splicers would simultaneously sever the expiring web, leaving what is now a continuous web running from thereel 15 through to the web accumulator. After a short interval, during which said splicing action occurs, the run of web betweensplicer 13 and theinfeed roller 35 is not moving, and is under essentially the same tension as it is in regular feeding of the web. Of course, at this time the great length of web which is formed within the several loops in the accumulator is being paid out of the accumulator fromoutfeed roller 36.
Attention is now invited to FIGURE 2 wherein the parts of the accumulator are in the position in which they would be during storage of the maximum amount of web as is the case when the web is being drawn out of the accumulator and is being fed into the accumulator at the same rate. In other words, in this example, the swingingarms 37 and 38 are swung apart as far as is practical in FIGURE 2 to store the maximum amount ofweb 11 in the form of loops running back and forth between the arms.Arms 37 and 38 are clamped toaxle shafts 39 and 40, respectively, for rotating with the axle shafts. The axes of theaxle shafts 39 and 40 lie on a center line which is marked 41 in FIGURE 2. As will be explained shortly hereinafter,axle shafts 39 and 40 are driven apart in unison so that the arms always maintain the same angular separation fromcommon center line 41. Thearms 37 and 38 turn clockwise together and counterclockwise together.
Attention is now invited to FIGURES 2, 4 and 5 for a discussion of how the arms are driven apart to bring about the accumulation of web and how the arms swing toward each other to pay out accumulated web to the outfeed when infeed of web is stopped for a short interval. First refer to FIGURE 4 which shows that the mechanism for operating thearms 37 and 38 is contained within a housing whosefront wall 42 appears in FIGURE 4 and whoserear wall 43 appears in FIGURE 5. In the latter figure the end walls 44 and 45 of the housing are also visible. The housing is much like a box whoserear wall 43 is fastened to thefront face plate 22 of the machine depicted in FIGURE 1.
Considering FIGURES 4 and 5, primarily, one may see that therotatable axle shafts 39 and 40 have tooth wheels in the form ofsprockets 46 and 47 fastened to them.Sprocket 46 is bolted to aclamp 48 which provides for clamping the sprocket toaxle shaft 39 by way of tightening a clampingscrew 49. A key and keyway, not visible, may also engage the sprocket to the axle shaft. Theother sprocket 47 is similarly bolted to a clamping member 50 which is provided with ascrew 51 which can be tightened to clamp the sprocket toaxle shaft 40.Axle shaft 40 is journaled inball bearings 52 and 53 which are set in suitable counterbored holes in the front andrear walls 42 and 43, respectively, of the drive mechanism housing. Theother axle shaft 39 is similarly journaled for rotation inball bearings 54 and 55. Swingingarm 37 is clamped toaxle shaft 39 by means of a clamping element 56 which is essentially a split ring that is engaged to the shaft by tightening amachine screw 57. Swingingarm 38 is similarly clamped toaxle shaft 40 by means of a clampingmember 58. The previously mentionedoutfeed roller 36 is shown in FIGURE 5 to be journaled for rotation onaxle shaft 39 by means of twointernal bearings 59 and 60. The roller is secured against shifting axially bycollars 61 and 62 which are clamped toaxle shaft 39.Tubular roller 36 is preferably composed of a strong lightweight material so the roller has low inertia and requires the least amount of torque to start and stop. Previously mentionedinfeed roller 35, as shown in FIGURE 5, is journaled for rotation onaxle shaft 40.Roller 35 is prevented shifting axially onaxle shaft 40 by means of axially spaced apartcollars 64 and 65 which are clamped toaxle shaft 40. From inspection of FIGURE 5, it will be evident thatarms 37 and 38 swing in planes which are parallel to each other.
Referring further to FIGURE 5,arm 37 has mounted to itseveral rollers 70, 71, 72 and 73. These rollers are freely rotatable onrespective shafts 74, 75, 76 and 77.Arm 38 has mounted to it an equal number of rollers 78-81. These rollers are mounted for rotation onrespective shafts 82, 83, 84 and 85.Roller 78 is typical. It is also preferably composed of a lightweight rigid material for the sake of minimizing inertia.Roller 78 is journaled for rotation onshaft 82 by means of twoball bearings 86 and 87. The outboard end ofshaft 82 is provided with a c-ring 88 for retainingbearing 87 on the shaft. Theother bearing 86 is pressed on the shaft and retained against axial movement by abutting ashoulder 89 on theshaft 82.Typical roller shaft 82 is mounted toarm 38 by means of amachine screw 90.
As will be explained in detail later,arms 37 and 38 are driven rotationally, in this illustrative embodiment, by means of twopneumatic actuators 96 and 97, whosepiston rods 98 and 104 are interconnected by twochains 115 and 118. The chains engage the toothed wheels orsprockets 46 and 47 for rotating theaxle shafts 39 and 40 and thearms 37 and 38 thereon to accumulate web in response to movement of thepistons 100 and 101. When infeed of web to the accumulator stops, the continued draw on the web at the outfeed causes the arms to swing toward each other. Twopneumatic actuators 96 and 97 are illustrated but it should be understood that either actuator could be removed and replaced with a section of chain and the remaining actuator could be replaced by a single actuator of sufficiently larger piston area to produce the actuating force which is the sum of the forces of the two actuators.
In FIGURE 2,arms 37 and 38 are both rotated through an angle relative toimaginary center line 41 which provides for storing the maximum length ofweb 11 in the loops of web spanning between the arms.Arms 37 and 38 are swung by the greatest angular amount as in FIGURE 2 whenweb 11 is being fed intoinfeed roll 35 and is being drawn out of the accumulator overoutfeed roll 36. In FIGURE 7,arms 37 and 38 are swung close to each other which is a condition that occurs when infeed ofweb 11 is stopped and the accumulator has paid out just about all of the web it is permitted to pay out over theoutfeed roller 36 before infeed of web must continue. The manner in which thearms 37 and 38 are induced to swing out as in FIGURE 2 for storing the maximum amount and are allowed to yield toward each other as in FIGURE 7 to give up the stored amount of web will now be discussed in more detail in reference to FIGURES 4 and 5.
As previously mentioned in respect to FIGURE 4, asprocket 47 is fastened toaxle shaft 40 for theinfeed roller 36 and anothersprocket 46 is fastened to the outfeedroller axle shaft 39. Twopneumatic actuators 96 and 97 are mounted to thewall 42 of the housing.Actuator 96 has apiston rod 98 which extends slidably and sealably through both ends of the cylinder ofactuator 96. The piston fixed torod 98 is drawn in solid lines and is marked 100. Under ordinary operating conditions, that is, whenarms 37 and 38 are swung through the maximum angle relative tocenter line 41,piston 100 will be shifted by air pressure to its phantom line position designated by the numeral 100'. Actuator 97 is similar toactuator 96. They drive and yield together and each contributes one-half of the force for swingingarms 37 and 38. Thus, when thepiston 100 inactuator 96 is in its solid line position,piston 101 in actuator 97 is positioned as shown in hidden lines. The volume 102 on one side ofpiston 100 is occupied by air under pressure under all operating conditions of the accumulator. The pressure tends to forcepiston 100 to the left to develop a force which is translated to web tension. Similarly, when thevolume 103 on the left side ofpiston 101 in actuator 97 is subjected to the same air pressure,piston 101 is biased to the right in FIGURE 4. The piston rod 104 of actuator 97 also extends through both ends of the actuator cylinder 105. Pressurized air is supplied to the pressurizingvolumes 102 and 103 of the actuators through asupply line 106. The pressurized air enters actuator 97 by way ofinlet elbow 107 and pressurized air entersactuator 96 through anelbow 108. There arefilter devices 109 and 110 connected to therespective cylinders 99 and 105 to allow exhaust of air when the pistons shift from their home position as depicted in FIGURE 4. The filters also prevent air containing contaminants from being drawn into the actuator cylinders when the pistons retract to their home positions depicted in FIGURE 4. A flexible member in the form of achain 115 has one of itsend 116 connected to an end ofpiston rod 98 ofactuator 96 and has itsother end 117 connected to an end of piston rod 104 of actuator 97.Chain 115 is engaged withsprocket 46 for drivingaxle shaft 39. Anotherchain 118, has one of itsends 119 fastened topiston rod 98 ofactuator 96 and the other of its ends 120 fastened to the piston rod 104 of actuator 97. It would be possible to use toothed pulleys in place ofsprockets 46 and 47 and to use toothed timing belts in conjunction with the pulleys instead of using chains.
It will be evident that when air pressure is applied involumes 102 and 103 ofactuators 96 and 97, respectively,pistons 100 and 101 will shift in opposite directions and the chains running onsprockets 46 and 47 will driveaxle shafts 39 and 40 and thearms 37 and 38 thereon in unison. Whenpistons 100 and 101 are in the positions in which they are depicted in FIGURE 4,arms 37 and 38 are departed by the least angular amount from the center line which extends between the axes ofaxle shafts 39 and 40. As the pistons begin to move, thearm 38 passes through a position represented by phantom lines and marked 38'' and theother arm 37 moves through an angular position represented by the phantom lines marked 37''. When the arms are in the position represented by phantom lines 37'' and 38'' they are positioned approximately as depicted in FIGURE 3.
During normal operating conditions, that is, when the infeed of web to the accumulator corresponds with the outfeed of web, thearms 37 and 38 rotate to the position in which they are depicted in FIGURE 2 wherein they store the maximum amount of web in the loops between the rollers 70-73 and 78-81 on therespective arms 37 and 38. In typical applications, the web is fed into the accumulator at a speed regulated by the position of the arms. This will cause the infeed web speed to equal outfeed web speed when the arms are positioned for optimum web storage. This will place the arms approximately as shown in FIGURE 2, with theair cylinder piston 100 at position 100', as shown in FIGURE 4. Under any condition of infeed and outfeed velocities, the force developed by theactuators 96 and 97 is translated to rotational forces in the arms and a resultant tension in the web. If outfeed velocity exceeds infeed velocity, the differential in web travel will tend to move the arms backwardly, compressing the air in the cylinders. Pressure regulating devices (not shown) limit the increase in pressure in the cylinders and therefore regulate the tension.
It should be noted that since theaxle shafts 39 and 40 for the arms are driven together the arms always will counterbalance each other. It should also be noted that the shafts and the arms swing clockwise together as they are accumulating a length of web in loops between them and that they rotate counterclockwise together when infeed of web is interrupted and outfeed continues as a result of web being drawn by whatever web consuming or utilizing device is being supplied with the web from the accumulator.
Observe in FIGURES 4 and 5 that there is anothersprocket 125 fastened toaxle shaft 39. Achain loop 126 runs over the sprocket for the purpose of driving anothersprocket 127.Sprocket 127 is fastened to theshaft 128 of apotentiometer 129. The lead wires, not shown, come in through aconnector 132. The potentiometer is supported on abracket 130 which is clamped to thefront wall 42 of the drive mechanism housing by means of machine bolts, such as the one marked 131, which pass through slotted holes in the bracket to provide for shifting the potentiometer until the proper tension is obtained inchain 126.
The potentiometer produces an analog signal relating to the angular position of the arms. This analog signal is typically supplied to the infeed device's web speed controller, not shown. In the application depicted in FIGURE 1 the motor being controlled is the previously mentioned motor coupled to theshaft 21 of thebelt drive mechanism 16. If, during regular operation, draw of web at the outfeed of theaccumulator 10 increases such as to cause an angular change in the arm position of the accumulator, for example, the controller will cause the motor which drives thebelt drive 16 to run faster until normal arm position is restored.
A feature of the invention is the ease with which the web can be threaded through the accumulator to begin a web run without the need for zigzagging the web around the rollers on thearms 37 and 38. Attention is invited to FIGURE 6. Here it will be noted thatarms 37 and 38 are crossed over each other as compared with their angular positions in FIGURE 2 and 3, for example. Cross-over can be effected by grasping the outboard end ofarm 38, for example, and drawing it pastarm 37. Because the arms swing through an angle relative to the imaginary center line which runs through the axes ofshafts 39 and 40 and the rollers on each of the arms are offset from each other as they pass the center line, the rollers on one arm can pass through the space between rollers on the other arm . When the arms are crossed over and spaced apart as they are in FIGURE 6, it will be evident that theweb 11 can be arranged as indicated without the need for making as much as a semi-circular loop around any of the rollers.Cylinders 99 and 105 ofactuators 96 and 97 can have the normal air pressure applied to them at the time one arm is swung past the other manually. On the other hand, theactuator cylinders 99 and 105 can be unpressurized before a web run starts so only a small manual force is needed to cause them to cross over. It will now be appreciated why, during normal operation, when the arms are not crossed over, a free space remains between the end ofactuator cylinder 99 and the displaced piston 100'. When thearm 38 is urged into cross-over position as explained in reference to FIGURE 6, piston 100' is compelled to over travel and almost abut the adjacent end of the actuator cylinder. This amount of travel is all that is necessary to turn theaxle shafts 39 and 40 enough to cause the rollers on the two arms to pass each other. Of course, since the arms are mechanically interconnected by means of the chains when the arm, such as 38, swings through a small angle, theother arm 37 swings through a corresponding angle in the other direction relative to the center line and a small amount of movement of one arm provides a rather large gap between arms for threading the web through the accumulator when setting up for a run of the machine.
In FIGURE 7, manually deflectedarm 38 has been released and tension is being applied to the web which causes the arms to swing past each other again. The arms then slowly swing away from each other in response to the pressure that is applied to the pistons in thepneumatic actuators 96 and 97.
In the FIGURE 1-7 embodiment of the invention, the actual tension induced in the web by the torsional force applied to the arms is a trigonometric function of the angular relationship between the various web strands and the arms. As the angle between web and arm is varied from the perpendicular, relatively constant web tension can be achieved, for example, by having a microprocessor based controller, not shown, vary the actuator pressure in dependence on the signal received from thepotentiometer 129. An alternative embodiment of the accumulator depicted in FIGURES 8-10 overcomes the variable torque requirement by a purely mechanical rather than electrical method. In FIGURE 8-10 parts which are similar to parts identified in the previously discussed embodiment are given the same reference numerals.
In this embodiment, a varyingradius cam 150 is fastened toaxle shaft 40 along withsprocket 47. Aclosed loop chain 151 wraps aroundsprocket 47 and also aroundsprocket 46 which is on theother axle shaft 49. It will be evident that when one sprocket is forced to turn the other will turn through the same angle and thearms 37 and 38 will swing through a corresponding angle relative to a line passing through the centers ofaxle shafts 39 and 40. A short piece ofchain 152 is fastened at oneend 153 to the cam and is fastened at the other of itsend 154 to the end of apiston rod 155.Piston rod 155 extends from thecylinder 156 of apneumatic actuator 157.Cylinder 156 can swivel on abracket 170. The cylinder has aninlet 164 for pressurized air and a filter-muffler 165. Theend 153 of thechain 152 attaches to thecurved cam 150 at the place where the radius of theprofile 158 of the cam is minimum. The radius of the cam increases continually from thepoint 153 to theend 159 of the cam where the radius of the cam is largest. The effective radius or moment of rotation arm is that point at which the chain becomes tangent to thecam profile 158. From this, it can be seen that a constant force applied by the pneumatic actuator can produce a torsional force in the arms which varies with angular position. The varying radii of the cam are selected to compensate for the varying force vector between the web and arm angles, resulting in an effectively constant web tension, regardless of arm position.
FIGURE 9 illustrates this situation where thechain 152 is tangent to theprofile 158 of the cam at a point marked 162. The radius of the cam at this point is marked 160. In FIGURE 8 the radius extending from the center ofshaft 40 to the point of tangency between the chain and theprofile 158 of the cam is marked 163. It will be evident that theradius 160 in FIGURE 9 where the arms are close to each other is substantially greater than theradius 163 in FIGURE 8 where thearms 37 and 38 are angulated farther apart in FIGURE 8 than they are in FIGURE 9. Since the air pressure driving the piston inactuator cylinder 156 is held substantially constant, it will be evident that the tension force in thechain 152 multiplied by thetorque radius 163 in FIGURE 8 will result in a torque related to the constant tension inchain 152 multiplied bytorque arm 160.
The pressurized air is supplied toactuator cylinder 156 through atube 164. The cylinder is also provided with a combination muffler and filter 165 which prevents contaminated air being drawn into thecylinder 156 when the piston moves in opposition to the air pressure due toarms 37 and 38 being forced toward each other while web infeed is stopped for an interval.
FIGURE 10 shows howaxle shaft 40 is journaled for rotation inball bearings 52 and 53 which are set inwalls 42 and 43 of the mechanism housing as is the case in the previously described embodiment. In FIGURE 10, however,cam 150 is fastened toshaft 40 andsprocket 47 is fastened to amember 166.Chain 152 is pivotally connected tocam 150 with apin 167 as is evident from inspection.

Claims

A web accumulator (10) comprising:
a base (42);
first and second axle shafts (39,40) arranged with their axes in parallel and journalled for turning relative to said base (42), the axes of the axle shafts being spaced from each other along a common centreline (41);
first and second arms (37,38) fastened to said axle shafts (39,40) respectively, for swinging in spaced apart parallel planes in response to turning of said axle shafts, said arms extending in generally opposite directions from the respective shaft axes;
first and second wheel means (46,47) fastened to said first and second axle shafts (39,40) respectively;
a force producing actuator (157);
a flexible member (151) formed in a closed loop around both of said wheel means (46,47) and engaged with said wheel means for turning said wheel means and the arms (37,38) with said axle shafts in response to translation of said flexible member (151) resulting from one axle shaft (40) being driven rotationally, the rotation of said one axle shaft (40) causing one arm (38) to swing through an angle away from one side of said centreline (41) and the other arm (37) to swing away through a corresponding angle from the other side of said centreline (41) until the arms attain a predetermined maximum angle; and
a series of spaced apart rollers (70-73, 78-81) supported on each arm, the rollers on each arm extending from the plane in which that arm swings towards the plane in which the other arm swings to provide for a web (11) being looped around rollers on opposite arms in succession such that the maximum length of web (11) accumulated in said accumulator (10) occurs when the arms (37,38) are swung to their said maximum angle;
CHARACTERIZED BY further comprising:
a web infeed roller (35) rotatable on the first axle shaft (40) and a web outfeed roller (36) rotatable on the second axle shaft (39);
a torque arm (150) fastened to one axle shaft (40) and having a curved profile surface (158) whose radius from the axis of said axle shaft (40) varies over the length of the surface; and
a flexible element (152) connected between said actuator (157) and said curved surface (158) whereby said flexible element is maintained in tangential contact with said curved surface (158) at points along said surface having radii of different lengths as said torque arm (150) is rotated owing to tension developed in said flexible element (152) that results from actuation of said actuator (157);
wherein changes in the moment of force, defined by the length of the radius (160,163) at the point of tangency times the tension in the flexible element (152), cause the torsional force on the axle shaft (40) and first and second arms (37,38) to vary in correspondence with the angle of the arms with respect to said centreline (41).
A web accumulator (10) according to claim 1, wherein said flexible member (151) is a roller chain and said wheel means (46,47) are sprockets.
An accumulator (10) according to claim 1 or claim 2, wherein the actuator (157) is operated with pressurized air.
An accumulator (10) according to any preceding claim, wherein the ends of the rollers (70-73,78-81), remote from the arm (37,38) on which the rollers are supported, are free.