Patent Publication Number: US-3877657-A

Title: Leverage weight control for torque generating mechanism

Description:
United States Patent 1 Zebley, deceased LEVERAGE WEIGHT CONTROL FOR TORQUE GENERATING MECHANISM [75] Inventor: Donald Dane Zebley, deceased, late of Greenville, S.C., by Mildred S.  
 Zebley, executrix [73] Assignee: United Merchants and Manufacturers, lnc., New York, N.Y.  
 [22] Filed: Mar. 20, 1974 [21] Appl. No.: 452,937  
 [52] US. Cl 242/75.5; 242/7543 [51] Int. Cl B65h 25/04; B65h 25/22 [58] Field of Search 242/755, 75.43, 75, 75.2,  
 [ 51 Apr. 15, 1975 Zcblcy 139/311 Zebley 242/755 [5 7] ABSTRACT A device for automatically positioning a weight on a lever arm in response to the diameteral change in a roll of sheet material which is rotatively driven by a torque generating mechanism which includes the weight as the primary motive force component thereof. The weight is mounted upon a lever arm of the torque generating mechanism and positioning of the weight controls the amount of torque produced to drive the roll. A sensing device responsive to buildup of sheet material being wound upon the roll temporarily releases a brake mechanism holding the weight in position upon the lever arm thereby permitting adjustment of the weight moment arm in response to roll enlargement.  
 12 Claims, 2 Drawing Figures PATENTECAPRISEFS 3,877, 657 sum 1 0f 2 FATENTEEAPR 1 51575 3,877,, sum 2 pf 2 FIG. 2  
 LEVERAGE WEIGHT CONTROL FOR TORQUE GENERATING MECHANISM BACKGROUND OF THE INVENTION The present invention relates generally to a mechanism for driving a take-up roll upon which sheet material, such as textile fabric from a loom, is being wound, and more particularly to a leverage weight contol device which adjusts the position of a weight operative as the motive element of a torque generating mechanism which drives the take-up roll. Particularly. the present invention disclosed in U.S. Pat. No. 3,792,826, incorporated herein by reference. Although it will be clear from the description which follows that the present invention may be applied in various environments, it is primarily intended for application in textile facilities in connection with the winding of textile fabric into compact, uniform, tightly-wound rolls.  
  In textile installations, weavedfabric is brought from a loom and is wound upon take-up rolls which may extend several feet in length and which usually comprise diameters of about 20 inches or more. ln most installations, the mechanism comprising the take-up roll is located remotely from the loom, for example, in a basement where it receives the fabric which passes through a slot in the floor of the loom room.  
 Due to the remote location and size of the take-up roll, problems may develop resulting in improper alignment of the fabric on the roll. Additionally, if the tension on the fabric web as it is being drawn from the loom on to the take-up roll is not uniformly maintained, there may result a roll which is lacking in desired compactness, tightness, and alignment. Other problems which may be encountered result from the&#39;fact that power equipment, such as electric motorsfiare used in driving such take-up rolls. Not only is it difficult with such equipment to maintain uniform fabric tension, but disadvantages also arise due to substantial heat which is emitted from the numerous drive motors which are usually required for a large textile mill. Because of such heat generation, use of airconditioning equipment may become essential, thus further increasing the operating cost of driving the equipment.  
  In order to overcome these and other problems, it has been proposed in the invention of U.S. Pat. No. 3,753,452, incorporated herein by reference, to utilize a torque generating mechanism which applies the potential energy force of a falling weight mounted on a lever arm to rotatively drive the shaft upon which the fabric take-up roll is mounted. This eliminates much of the need for power equipment and gives rise to several advantages among which are decrease in power requirements and in heat generation at the installation site.  
  A further proposal which is the subject of U.S. Pat. No. 3,707,996, incorporated herein by reference, in volves the utilization of a compacting roller assembly which controls the direction of the textile cloth incoming to the take-up roll and which derives a compacting force from tension in the incoming fabric, with this tension-derived compacting force being applied to assist in the formation of the fabric roll. The compacting assembly generally involves a triad of rollers through which the incoming fabric is wound, and a pivotal mounting arrangement supporting the roller triad forrotation about an axis parallel to but spaced from theax&#39;is of the take-up roll. Thus, as the fabric builds up upon the take-up roll, and the diameter of the fabric roll increases, the roller triad rotates about its pivotal mounting and moves away from the center of the take-up roll.  
  In the torque generating mechanism whic drives the take-up roll, the applied rotative moment of force may be adjusted by controlling the position of the weight on the lever arm. As the diameter of the fabric roll increases, it is generally preferable to move the weight further away from the pivot point, of the lever arm in order to increase the torque applied to the enlarging take-up roll. Among other things, this has the advantage of tending to maintain a more uniform tension in the incoming fabric, since as the force required to turn the larger take-up roll increase, the applied torque is commensurately increased to maintain a uniform pull on the fabric.  
  Inasmuch as the compacting assembly operates in a manner whereby its roller triad is in contact with the outer circumference of the fabric roll throughout the operation of the overall mechanism, this element may be advantageously utilized as sensing means to determine increases in roll diameter. Thus, the control system which adjusts the position of the weight on the lever arm of the torque generating mechanism may be operatively associated with the compacting assembly to control positioning of the weight in response to the pivotal motion of the compactingassembly.  
 SUMMARY OF THE INVENTION Briefly, the present invention may be described as a torque control device for rotatively driving a roll adapted to have flexible material wound thereabout comprising lever means having a free end and an end opposite said free end, said lever means being rotatively mounted at said opposite end about a pivot point for pivotal motion between a first angular position and a second angular position vertically displaced from said first position, a weight mounted on said lever means for positioning between said free end and said pivoted end, said lever means being arranged to be driven from said first to said second angular position by the&#39;gravitational force of said weight, means for driving said lever means from said second to said first position, means for transmitting to said roll torque developed by said lever means during motion thereof between said first and said second position, means for sensing the diameter of said material roll, releasable brake means for holding said weight fixed upon said lever means, and means interconnecting said brake means and said diameter sensing means for effecting release of said brake means in response to changes in the diameter of said material roll to permit relocation of said weight on said lever means, said brake means being biased to become reengaged after movement of said weight relative to said lever means in response to said roll diameter change.  
  The present invention is more specifically directed to the releasable brake means and the control mechanism associated therewith which enables positioning of the weight on the lever means to be effected in correspondance with the size of the material roll. The brake means of the invention are structurally configured to include spring means which bias the brake means toward a position tending to hold the weight in place on the lever arm. A capable system interconnects the releasable brake means with the roll diameter sensing means. As the diameter of the roll increases, the cable means exert a pull upon the brake spring means thereby re leasing the brake and enabling the weight to slide freely on the lever arm. So long as the tension in the cable is maintained, the brake means will be held in their released condition. When the weight has moved to a new location at which tension in the cable is relieved, the brake means will re-engage and hold the weight at its new position until further changes in the diameter roll cause additional tension in the cable to again release the brake means.  
  Thus, the weight may be adjusted in position on the lever arm in response to changes in the roll diameter to apply a desired torque to drive the fabric roll with a force commensurate with the size of the roll.  
 DESCRIPTION OF THE DRAWINGS The present invention will be better understood by reference to the following detailed description ofa preferred embodiment thereof taken in connection with the accompanying drawings wherein:  
  FIG. 1 is a side elevation of a torque generating mechanism for driving a fabric roll inclulding a compacting assembly which also operates as a sensing means responsive to diameter changes in the roll and a leverage weight control device in accordance with the present invention for effecting a desired positioning of the leverage weight of the torque generating mechanism; and  
  FIG. 2 is a cross-sectional view showing in greater detail the leverage weight and releasable brake means of the present invention.  
 DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 1 of the drawings, there is shown a take-up roll assembly which comprises a floormounted frame 1 supporting a rotatively driven fabric roll 10. Fabric incoming to the roll is derived from a loom room (not shown) and is first wound through a roller triad l2 and then about the roll 10. The roll 10 is mounted upon a drive shaft 14 which receives power through a chain 16 from a driving sprocket 18. Power for turning the sprocket 18 is derived from a torque generating mechanism which includes a pair of pivoted lever arms 20 and 22 each having mounted thereon, respectively, a leverage weight 24 and 26.  
  Each of the lever arms 20 and 22 is mounted at one end thereof for pivotal motion about a pivotal mounting 28 and 30, respectively. A pawl and ratchet mechansim (not shown) operates to transmit torque from the lever arm 20 and 22 to rotatively drive the sprocket 18.  
  A torque generating mechanism such as utilized in connection with the present invention is more fully described in US. Pat No. 3,753,452, incorporated herein by reference, and reference should be had thereto for a better understanding of the detailed construction of the means whereby the levers 20 and 22 operate to drive the sprocket 18 thereby to effect rotation of the fabric roll 10. Since a detailed description thereof is not necessary for an understanding of the present invention, certain details have been eliminated.  
  Each of the lever arms 20 and 22 pivots between a first upper angular position and a second lower angular position. In the drawing of FIG. 1, the lever arm 20 is shown in its first upper angular position and the lever arm 22 is shown in its second lower angular position.  
 With the lever arm 20 in the position shown, the ratchet mechanism becomes engaged and as the lever arm 20 falls downwardly pivoting about the pivotal mounting 28 due to the gravitational force exerted by virtue of the weight 24, a rotative torque is transmitted to the sprocket 18 through the ratchet mechanism.  
  While the lever 20 is falling from its first angular position to its second angular position, the lever 22 is simultaneously being raised from its second angular position, in which it is depicted in FIG. 1, to its upper first angular position. During travel of the lever 22 from the lower second angular position to the upper first angular position, the ratchet mechanism is not engaged and no force is transmitted by the lever 22 to the sprocket 18.  
  The levers 20 and 22 operated in tandem with one lever moving from its upper first postition to its lower second position while the other lever moves from its lower second position to its upper first position. The rachet mechanism, which is not shown in the drawing, engages and disengages in such manner, as more fully explained in U.S. Pat. No. 3,753,452, that torque is continually transmitted to the sprocket 18. As soon as one of the lever arms 20 or 22 has reached its lower second angular position, the other lever arm is at its upper first angular position and by operation of the ratchet mechanism one or the other of the lever arms is always applying torque to the sprocket 18 during movement downwardly from the upper first angular position to the lower second angular position.  
  Each of the lever arms 20 and 22 are raised from their lower second angular positions to their upper first angular positions by a pneumatic mechanism (not shown) which is also more fully described in U.S. Pat. No. 3,753,452. This pneumatic mechanism operates to alternately apply a lifting force to each of the lever arms 20 and 22 as soon as they have reached their respective lower second angular positions.  
  Thus, by virtue of the torque applied to the sprocket 18 by the lever arms 20 and 22, the fabric roll 10 is continuously driven to wind thereabout incoming fabric. It will be apparent that the amount of torque which is applied by the lever arms 20 and 22 will be controlled by the position of the weights 24 and 26 relative to the pivotal mountings 28 and 30. The greater the distance between the pivotal mountings 28 and 30 and the weights 24 and 26, respectively, the greater will be the moment arm of each of the levers 20 and 22 and, therefore, the greater will be the torque which is generated. As the fabric roll 10 grows larger in diameter, a greater amount of torque will be necessary to draw the incoming fabric about the fabric roll 10. Thus, if the weights 24 and 26 are moved outwardly along the lever arms 20 and 22, respectively, as the diameter of roll 10 grows larger, a constant pulling force may be applied to the incoming fabric thereby maintaining the fabric with a uniform tension. This will tend to produce greater uniformity in the wound roll 10, with the wound fabric being more uniformly distributed from the center of the roll to its periphery. This uniformity is obtained by operation of the present invention by gradually moving the weights 24 and 26 outwardly along the lever arms 20 and 22, respectively, as the diameter of the fabric roll 10 increases, in a manner to be more fully described hereinafter.  
  The frame 1 has mounted thereon a tiltable frame member 40 which may be rotated about a pivotal support 42 located in the upper portion of the frame 1. A  
 pinned latching mechanism 44 holds the frame member 40 in the position shown in FlG. 1 while the fabric roll is winding, but by release of the latch mechanism 44, the frame 40 may be swung out of the way to permit removal of a completed roll 10. When the frame 40 is in the position shown, it supports at its upper end a compacting assembly 50 is pivotally mounted to the upper end of the frame member 40 along a pivot axis 52 which is generally parallel to the axis of the drive shaft 14. The compacting assembly 50 includes an arm 54 which extends from the pivotal mounting 52 having the roller triad 12 mounted at its free end. The lowermost roll of the roll triad 12 rests against the periphery of the roll 10 and it will be apparent that as the diameter of the roll 10 increases the roll triad 12 will be moved outwardly away from the center of the roll thereby causing the arm to pivot counterclockwise about the pivot axis 52.  
  Attached upon the arm 54 at a point intermediate its ends is a cable attachment member 56 which includes a screw means 58 which may be loosened and tightened to adjust the position of the cable attachement member 56 along the arm 54, as indicated by the arrows. A second cable attachment member 60 is mounted upon the frame member 40, and it is likewise adjustably mounted by screw means 62 which enable the member 60 to be moved along the length of the member 40 in the directions indicated by the arrows. A pair of control cables 64 and 66 extend from a fixed attachment on the member 56 about a pulley 70 of the cable attachment member 60. The cables then pass beneath a pulley 72 mounted on the member 40 and about another pulley 74 attached on the upper part of frame 1.  
  The cable 64 extends from the pully 74 through pulleys 76, 78, and 80 to a fixed connection 82 on the outer side of the weight 24.  
  The cable 66 extends from the pulley 74 about the pulleys 84, 86, and 88 to a fixed connection 90 on the outer side of the weight 26. It should be noted that each of the cables 64 and 66, respectively, must pass through the center of rotation of the arms and 22 in order that the lengths of the cables extending, respectively, between the pulleys 78, 86 and the pulleys 80, 88 will remain unchanged when the lever arms 20 and 22 effect their pivotal motions.  
  Thus it will be seen that the cables 64 and 66 are connected, in the case of the cable 64, between the connection 82 and the cable attachment member 56 and in the case of the cable 66. between the attachment point 90 and the cable attachment member 56. Thus, it will also be seen that as the compacting assembly 50 is swung counterclockwise about the pivot axis 52, the ends of the cables 64 and 66 attached to the member 56 will be pulled upwardly as the diameter of the roll 10 increases. It will be apparent from the arrangement of the cables 64 and 66 that the pulling action exerted thereon as a result of the diameter expansion of the roll 10 will cause a force to be applied to the connection points 82 and 90 in a direction outwardly of the lever arms 20 and 22. As will be. explained more fully hereinafter with reference to FIG. 2, this pulling force controls the releasable brake mechanisms to efiect desired positioning of the weights 24 and 26 on the lever arms 20 and 22, respectively.  
  Referring now to FIG. 2, there is shown in more detail the structure of the weight 24 and of the releasable braking system operatively associated therewith. Al-  
 though the weight 24 alone is shown in FIG. 2, it is to be understood that the structure and arrangement of the weight 26 and of the braking mechanism operatively associated therewith, is identical to that to be described in connection with the weight 24 and that, as will be apparent from the description which follows, the operating mode for both devices is the same.  
  The lever arm 20 is formed as a hollow body and is arranged to have the cable 64 extending interiorly thereof. The pulley is freely rotatively mounted on the free end of the lever arm 20 by a pin which has its ends firmly fixed in the body of lever arm 20. Lever arm 20 is formed with an opening 102 through which the pulley 80 extends and which will allow the cable 64 to pass outwardly from within the lever arm 20 to the end connection point 82.  
  The weight 24 is formed with an opening 104 extending completely therethrough. The size of the opening 104 is made slightly larger than the outer dimension of the lever arm 20 thereby permitting a gap or space 107 to exist between the surface of the opening 104 and the outer surface of the lever arm 20. Thus, it will be apparent that, unless otherwise restrained, the weight 24 will be freely slideable along the lever arm 20.  
  The weight 24 includes a pair of threaded bolts 106 extending through the body thereof and adaptable to be threadedly brought into engagement with the underside of the lever arm 20 in order to firmly frictionally maintain the weight 24 in a desired position. A pair of adust nuts 108 are also provided and together with the bolts 106 they may be threadedly adjusted to maintain the weight 24 at a desired location on the lever arm 20 when a mode of operation involving a fixed positioning of the weight 24 on the arm 20 is desired. However, this mode of operation essentially operates to render inoperative the releasable brake mechanism of the present invention and it is not utilized under ordinary circumstances. Thus, ordinarily, the nuts and bolts 108, 106 will be maintained in the position shown in FIG. 2 out of engagement with the lever arm 20.  
  The weight 24 has fixedly attached at opposite ends thereof a pair of bifurcated support arms 110 and 112 located beneath the lever arm 20. On the opposite side of the lever arm 20, a mounting screw 147 threadedly engaged within the weight 24 serves as attachment means for a spring member 116 which is stretched in tension between the weight 24 and a brake arm 118 to which an end of the spring 116 is connected by connecting means 120. The brake arm 118 has afixed thereto a pin 122 about which the end of the cable 64 is looped in order to form the cable connection 82 which enables tension in the cable 64 to be applied as a pulling force upon the arm 118 acting against the tension of the spring 116.  
  The lower end of the brake arm 118 is fixedly attached by welding or the like to an eccentric cam member which is eccentrically rotatively mounted upon the bifurcated support arm 110. The cam 124 is generally configured as a circular cylindrical member having a geometrical axis indicated as 126. However, the cam 124 is pivotally mounted upon support arm 110 by a pin or other mounting means which enables the cam 124 to pivot relative to the arm 1 10 about a pivotal axis 128 which is spaced from the axis 126. Thus, it will be apparent that movement of the brake arm 118 which has its lower end firmly connected as shown to the cam 124 will effect pivotal motion of the eccentric cam 124 about the pivotal axis 128.  
  The cam 124 is arranged so that the spring 116 may exert a force upon the brake arm 118 tending to rotate the cam 124 about the axis 128 to bring the upper surface 130 of the cam 124 into engagement with the lower surface 132 of the lever arm 20. The force thus exerted by the cam 124 tends to pull or force the upper inner surface 134 of the opening 104 formed in the weight 24 against the upper outer surface 136 of the lever 20. As the surfaces 134 and 136 are brought into engagement, a frictional braking force is created which tends to maintain the weight 24 firmly fixed in position upon the lever arm 20. It will be apparent that the surfaces 134 and 136 extend over a substantial area and accordingly the frictional braking force which is created by their engagement will be of relatively substantial amount effective to firmly hold the weight 24 upon the lever arm 20.  
  Thus, when the cable 64 fails to exert a pulling force upon the pin 122 to rotate the brake arm 118 in a clockwise direction as viewed in FIG. 2, the spring 116 will pull the brake arm 118 in a counterclockwise direction thereby maintaining the cam 124 in engagement with the underside of the lever arm to apply the previously described braking force maintaining the weight 24 in position upon the arm 20. However, when tension is created in the cable 64, the end of the cable located at the end connection 82 will tend to pull upon the pin 122 driving the brake arm 118 against the force of the spring 116 in a clockwise direction. When this occurs, the cam 124 will, because of its eccentric mounting, be pulled away from engagement with the surface 132 of the lever arm 20 thereby releasing the braking force created between the surfaces 134 and 136 to permit the weight 24 to slide longitudinally along the lever arm 20.  
  It will be apparent that when this occurs, reengagement of the braking force created by the tension in the spring 116 will be automatically re-established by motion of the weight 24 outwardly or to the right as viewed in FIG. 2, along the lever arm 20. It will be clear that when the cable 64 pulls the lever arm 118 to the right as viewed in FIG. 2, motion of the weight 24 rightwardly will compensate for the pull of the cable 64 thereby re-establishing the spring force tending to drive the surface 130 of the cam 124 against the surface 132 of the lever arm 20 to re-establish the frictional braking force holding the weight 24 in position.  
  Accordingly, each time that a tug or pull is applied through the cable 64, the braking force will be momentarily released allowing the weight 24 to move rightwardly toward the free end of the lever arm 20 an incremental distance determined by the amount of pull established in the cable 64. Once this pulling force has been depleted by motion of the weight 24, the braking force created by the spring 116 is re-established and the weight 24 is once again firmly held in its relocation position.  
  Referring back to the description of the mechanism shown in FIG. 1, it will be seen that a pulling force upon the cable 64 tending to release the brake force of the spring 116 occurs when the compacting assembly 50 is moved in counterclockwise direction about the pivotal mounting 52 caused by an increase in the diameter of the roll 10. Each time that an incremental increase in roll diameter occurs, a pulling force representative of the amount of diameter increase is generated, and this force is transmitted to the brake arm 118 to release the brake mechanism holding the weight 24 in position. From the description previously set forth, it will be clear that the amount of movement of the weight 24, which is commensurate with the amount of pull generated in the cable 64, will be determined by the incremental increase in the diameter of the roll 10. Thus, the weight 24 will be positioned upon the lever arm 20 at a location determined by the diameter of the roll 10 in order thereby to generate a torque driving roll 10 which is sufficient to compensate for increase in the weight of fabric being formed upon the roll thereby to maintain a generally constant tension in the incoming fabric.  
  Of course, a similar mode of operation occurs with regard to the weight 26 since the pull established in the cable 64 will likewise be established in the cable 66 since both cables are connected at an identical point upon the compacting assembly 50. Thus, each of the weights 24 and 26 will be moved outwardly on their respective lever arms 20 and 22 to a position determined by the diameter of the roll 10.  
  As previously stated, each of the lever arms 20 and 22 are continuously swung about their respective pivotal mountings 28 and 30 through an arc which extends between a first upper angular position and a second lower angular position. This swinging motion of the lever arms 20 and 22 creates a force tending to drive the weights 24 and 26 longitudinally along the arms 20 and 22. Of course, this force is overcome by the braking mechanism previously described when the braking force is in operation. However, a certain amount of play or slippage may occur, particualrly with regard to motion of the weights 24 and 26 leftwardly or toward the pivotal axis of the lever arm 20 and 22. Accordingly, in order to insure a more positive and accurate maintenance of the location of the weights upon the lever arms, a second braking member is provided at the left or inner ends of the weights 24 and 26, and, in the case of the weight 24, this second braking mechanism is mounted upon the bifurcated support arm 112 as shown in FIG. 2. Of course, it will be understood that a similar arrangement is provided in connection with the weight 26.  
  A circular cylindrical cam member 140, which is generally similar to the member 124, comprises a geometrical center 142 and is mounted upon the arm 112 for pivotal motion about an eccentric axis 144. The cam member has fixed thereto a spring engaging pin 146 with a similar spring engaging pin 148 being afixed to the arm 112. A torsion spring 150 mounted upon the arm 112 by screw means 152 applies a torsional spring force between the engaging pins 146 and 148 to maintain the cam member in engagment with the underside of the lever arm 20. As seen in FIG 2, the spring force created by the torsion spring 150 drives the upper surface 154 of the cam member 140 against the lower surface 132 of the lever arm 20 thereby creating a frictional braking force between the surfaces 134 and 136 in a manner similar to that created by the brake mechanism including the cam member 124 located at the opposite end of the weight.  
  The cam 140 is eccentrically mounted in a manner whereby the braking force applied by this cam will be greater in a direction tending to overcome motion of the weight 24 leftwardly or backwardly along the lever arm 20 in the direction of the pivotal axis 28. Accordingly, because of this eccentric mounting. movement of the weight 24 rightwardly or toward the free end of the lever arm 20 will not be adversely resisted by the cam 140 but will, instead. be controlled by the cam [24 whose eccentric mounting is generally opposite to the eccentric mounting of the cam 140. Thus, as the lever arm 20 reciprocates through its swinging motion, movement of the weight 24 towards the pivotal axis 28 will be resisted by the braking force created through the cam 140 and a movement in a rightward direction toward the free end of the arm 20 will be resisted by the cam 124 when the spring 116 is effective to create its braking force.  
  Of course, it will also be apparent that the spring 116 may be configured to apply a sufficient spring force which will tend to overcome the force tending to move the weight 24 leftwardly toward the axis 28 during the swinging motion of the arm 20. If the spring 116 is configured in a manner to generate a spring force of sufficient magnitude to overcome leftward motion of the weigh 24, then the cam 124 will be constantly maintained in engagement with the surface 132 throughout the swinging motion of the lever arm 20 unless the spring force of the spring 116 is counteracted by the pull of the cable 64. However, in order to insure that no leftward slippage occurs, the braking mechanism including the cam 140 is provided with a configuration which tends to resist leftward motion of the weight 24 but does not adversely effect leftward motion due to the particular eccentric mounting arrangement of the cam 140. Since the device of the present invention will be primarily useful in connection with an expanding fabric roll 10 rather than with an unwinding operation where the roll 10 is decreasing in diameter, the weights 24 and 26 will almost invariably involve motion out wardly from the pivot axes of the arms and 22 and not the reverse. Thus, the braking arrangement of the present invention may be applied in the manner described to generate a desired controlled torque which is applied as the driving force for the fabric roll 10.  
  When the roll 10 has been fully wound and a roll of desired diameter is achieved, the finished roll may be re moved from the frame 1 and the weights 24 and 26 may be manually readjusted to a location at which torque generation is initiated by manually alleviating the spring forces creating the braking effect. This may be accomplished by manually gripping the brake arm 118 and a similar brake arm 160 which is welded or otherwise afixed to the cam 140. With the weights 24 and 26 at their leftmost location closest to the pivot points 28 and 30, respectively, winding of new roll 10 may be commenced with the operation preceding in the manner previously described until a desired roll diameter has been achieved with the weights 24 and 26 moving incrementally outwardly along the lever arms 20 and 22 to thereby generate a desired level of torque for each level of roll diameter.  
  Although the invention has been described by reference to a preferred embodiment thereof, it is to understood that modifications and variations of the specific Structure set forth may be effected within the knowledge of those skilled in the art without departing from the spirit and scope of the invention as defined in the claims appended hereto.  
 What is claimed is:  
  l. A torque control device for rotatively driving a roll adapted to have flexible sheet material wound thereabout comprising lever means having a free end and an end opposite said free end, said lever means being rotatively mounted at said opposite end about a pivot point for pivotal motion between a first angular position and a second angular position vertically displaced from said first position; a weight mounted on said lever means for positioning between said free end and said pivoted end; said lever means being arranged to. be driven from said first to said second angular position by the gravitational force of said weight; means for driving said lever means from said second to said first angular position; means for transmitting to said roll torque developed by said lever means during motion thereof between said first and said second angular positions; means for sensing the diameter of said material roll; releasable brake means for holding said weight fixed upon said lever means; and means interconnecting said brake means and said diameter sensing means for effecting release of said brake means in response to said changes in the diameter of said material roll to permit relocation of said weight on said lever means; said brake being biased to become re-engaged after motion of said weight relative to said lever means through a distance commensurate with the change in diameter of said material roll.  
  2. A device according to claim 1 wherein said releasable brake means include spring means creating a force to apply said brake means to hold said weight in position on said lever arm, and wherein said interconnecting means comprise cable means attached between said diameter sensing means and said spring means to apply a force counteracting the force of said spring means when the diameter of said material roll increases.  
  3. A device according to claim 1 wherein said releasable brake means comprise cam means pivotally mounted upon said weight and located to be pivotally brought into abutment with said lever means.  
  4. A device according to claim 3 wherein said cam means comprise an eccentrically mounted circular cylinder.  
  5. A device according to claim 1 wherein said diameter sensing means comprises an arm having one end pivotally mounted at a point fixed relative to said fabric roll and an opposite free end abutting the outer circumference of said roll, and wherein said interconnecting means comprise cable means connected between said releasable brake means and a point on said pivoted arm spaced from the pivotally mounted end thereof.  
  6. A device according to claim 1 wherein said releasable brake means are configured to bring said weight into frictional abutment with said lever means when said brake means are engaged thereby to create a braking force therebetween.  
  7. A device according to claim 1 wherein said releasable brake means comprise a cam member pivotally mounted on said weight on one side of said lever means, a brake arm having one end fixed to said cam member and another end extending to the opposite side of said lever means, a spring engaged between said weight and said other end of said arm on said opposite side of said lever means, said spring operating to apply to said arm a spring force tending to pivot said cam member into abutment with said lever means thereby to create a frictional braking force between said lever means and said weight.  
  8. A device according to claim 7 wherein said weight comprises a body having an opening extending completely therethrough with said lever means being formed as an elongated member extending completely through said opening, said opening being configured of a dimension greater than the outer peripheral dimensions of said lever means to enable said weight to be freely slideable along said lever means when said brake means are released, with abutment of said cam member against said lever means upon engagement of said brake means operating to bring the surface of said opening in said weight against the outer peripheral surface of said lever means causing a frictional force to be developed therebetween to brake said movement of said weight relative to said lever means.  
  9. A device according to claim 7 wherein said interconnecting means comprise a cable attached between said diameter sensing means and said brake arm. said cable being attached to said brake arm at a point to exert a force thereon to counteract the force of said spring when said cable is pulled by said diameter sensing means upon occurrence of an increase in the diameter of said material roll.  
  10. A device according to claim 4 wherein said circular cylinder includes a geometric central axis and an eccentrically located pivot point at which said cylinder is pivotally mounted to said weight, said pivot point being spaced from said geometric axis.  
  11. A device according to claim 3 wherein said cam means comprise a pair of cam members each mounted on opposite ends of said weight and adapted to be brought into abutment with said lever means, with one only of said cam members being arranged in engagement with a torsional spring member mounted between said one cam member and said weight to apply a spring force tending to constantly maintain said one cam member in abutment with said lever means.  
  12. A device according to claim 11 wherein said one cam member is mounted on a side of said weight closest &#39;to said opposite pivotally mounted end of said lever means.