Patent Publication Number: US-2011062644-A1

Title: Conveyor belt clamp

Description:
This application claims the benefit of the filing date of U.S. Provisional Patent Application No. 61/242,110 entitled “CONVEYOR BELT CLAMP” filed Sep. 14, 2009, which is hereby incorporated herein by reference in its entirety. 
    
    
     The present invention relates to a belt clamp and, in particular, to a conveyor belt clamp. 
     Conveyor belt clamps are widely used to attach a pulling device to the end of a conveyor belt for the purpose of moving the end of the conveyor belt to another location by pulling longitudinally, i.e. in the direction the belt normally travels when used as a conveyor. For example, a belt may be pulled to install the belt onto a conveyor system or to remove the belt from the conveyor system. Typically, conventional belt clamps only effectively pull the edges of the belt, which can cause damage to the belt and/or generate uneven pulling forces across the width of the belt. 
     In a conveyor, it is often necessary to pull the ends of a conveyor belt towards one another so that the ends can be joined or spliced. To have a good joining, e.g., a splice, the two ends to be joined should be straight and aligned, whether the ends are cut transverse to the direction of belt travel at a right angle or at another angle, so that the ends meet along their entire lengths where the joint is to be made. If the belt is pulled more at its edges, then the end of the belt will tend to become concave as it is pulled and the edges of the end of the belt will meet before the centers of the ends of the belt meet, thereby making a uniform and strong joint (splice) more difficult to achieve. 
     In the present state of the art, mechanical belt clamps consist of two basic types. One type employs two simple beams, one adjacent to each surface of a conveyor belt, that span the width of the belt with the belt between them. Clamping mechanisms exterior to each edge of the belt are employed to force the respective ends of the two beams together outboard of or near the edges of the belt. As the ends of the beams are forced together to clamp the belt between the beams, the edges of the belt tend to act as pivot points, thereby causing one or both of the beams to deflect (bend) slightly and/or the edge of the belt to compress slightly. As a result, the conventional clamped beams exert greater force on the edges of the belt than at the center of the belt. Thus, when the belt is pulled by pulling on the conventional belt clamp, the edges of the belt tend to be pulled to a greater extent than does the center of the belt, resulting in uneven forces pulling the belt across its width. 
     When the belt being clamped is of sufficient width, e.g., 48″ (about 1.2 m.) and wider, the forces across the width of the belt are not consistent (not uniform) and can vary to the point where it is difficult to pull the ends of the belt together accurately. Many belts are more than 96″ (about 2.4 m.) wide, which makes it even more difficult to obtain even pulling forces to accurately pull together and join the ends of the belt. 
     The second type of conventional belt clamp has two separate clamps that are independently clamped to the opposing edges of the conveyor belt. These clamps exert all of the pulling force at the edge of the belt and none in the center, and so necessarily experience the uneven pulling force problem as described. 
     Thus there is a need for a conveyor belt clamp that can reduce the non-uniformity of force across the width of the belt. 
     To this end, a conveyor belt clamp may comprise: first and second clamp beams for being placed against a conveyor belt, one or both of the clamp beams may be pre-stressed for deflecting a central region along the length of the clamp beam; first and second end clamps are for being placed over the ends of the clamp beams, and each of the end clamps includes a tightening device for forcing the ends of the clamp beams closer together. The pre-stressed clamp beam is placed with its convex side against a conveyor belt. 
     In another aspect, a method for clamping a conveyor belt may comprise:
         providing first and second clamp beams, one or both of which is pre-stressed for having a convex side;   placing the first and second clamp beams transversely across a conveyor belt with the conveyor belt therebetween and with the convex side of the one or both clamp beams adjacent the conveyor belt;   placing a first end clamp over first ends of the first and second clamp beams;   placing a second end clamp over second ends of the first and second clamp beams; and   tightening the first and second end clamps for forcing the ends of the first and second clamp beams closer together for clamping the conveyor belt therebetween.       

     According to another aspect, a conveyor belt clamp may comprise: first and second elongated clamp beams; at least one center clamp on at least one of the first and second elongated clamp beams at a location between the first and second ends thereof; first and second end clamps each comprising a frame and a tightening device, the frame of the end clamp for being placed over an end of each of the first and second elongated clamp beams, wherein the tightening device is tightenable for forcing the ends of the first and second elongated clamp beams closer together; and the at least one center clamp is tightenable for applying clamping force to the conveyor belt at the location between the first and second ends of the first and second elongated clamp beams. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       The detailed description of the preferred embodiment(s) will be more easily and better understood when read in conjunction with the FIGURES of the Drawing which include: 
         FIG. 1  is an isometric view of an example embodiment of a conveyor belt clamp that is clamped to a cut end of a conveyor belt for pulling the cut end of the belt; 
         FIG. 2  is an isometric view of two of the example conveyor belt clamps of  FIG. 1  that are clamped to opposing cut ends of a conveyor belt for pulling the cut ends of the belt together for splicing; 
         FIG. 3  includes  FIGS. 3A through 3D  wherein: 
         FIG. 3A  is a side elevation view of the example conveyor belt clamp of  FIG. 1  with pre-stressed upper and lower clamp bars in position prior to contact with the conveyor belt; 
         FIG. 3B  is a side elevation view of the example conveyor belt clamp of  FIG. 3  with pre-stressed upper and lower clamp bars in position of making initial contact with the conveyor belt and the two end clamps in position to exert clamping force on the ends of the upper and lower clamp bars; 
         FIG. 3C  is a side elevation view of the example conveyor belt clamp of  FIGS. 3-4  with the upper and lower clamp bars in the clamped condition in contact with the conveyor belt and with the two end clamps forcing the ends of the upper and lower clamp bars together; 
         FIG. 3D  is a side elevation view of the example conveyor belt clamp of  FIGS. 3-5  with the upper and lower clamp bars in the clamped condition in contact with the conveyor belt and the end clamps forcing the ends of the upper and lower clamp bars together, wherein the center clamp device is exerting force on the center of the conveyor belt to force the upper and lower clamp bars into reverse deflection; 
         FIG. 4  is an end view of an example end clamp of the conveyor belt clamp of  FIG. 1  showing details of the end clamp; 
         FIG. 5  includes  FIGS. 5A and 5B  that are cross-ways and longitudinal sectional views, respectively, of a clamp beam that show an example arrangement of tensioning rods therein; 
         FIG. 6  is an isometric view of a prior art conveyor belt clamp clamped to a conveyor belt to illustrate the uneven distribution of pulling forces across the width of a conveyor belt obtained thereby; 
         FIG. 7  is an isometric view of an example conveyor belt clamp of  FIG. 1  clamped to a conveyor belt to illustrate the relatively more even distribution of pulling forces across the width of the conveyor belt obtained thereby; and 
         FIG. 8  is an isometric view of an example embodiment of a conveyor belt clamp having plural intermediate clamping devices along its length and that is clamped to a cut end of a conveyor belt for pulling the cut end of the belt. 
     
    
    
     In the Drawing, where an element or feature is shown in more than one drawing figure, the same alphanumeric designation may be used to designate such element or feature in each figure, and where a closely related or modified element is shown in a figure, the same alphanumerical designation primed or designated “a” or “b” or the like may be used to designate the modified element or feature. It is noted that, according to common practice, the various features of the drawing are not to scale, and the dimensions of the various features are arbitrarily expanded or reduced for clarity, and any value stated in any Figure is given by way of example only. 
     DESCRIPTION OF THE PREFERRED EMBODIMENT(S) 
     The conveyor belt clamp of the present arrangement pre-stresses the beams that are used for clamping the belt so that they exert forces in the center of the belt as well as at the edges of the belt, thereby to provide a more even and effective force distribution across the width of the belt than is provided by a conventional belt clamp 
     The conveyor belt clamp of the present arrangement tends to mitigate the disadvantages of the prior art belt clamps by utilizing one or more pre-tensioned (pre-stressed) beams that together will tend to exert a relatively more uniform force across the width of the belt when clamping forces are applied to the beams at the edges of the belt. One of the beams, usually the one positioned as the upper beam, may have an additional clamping device near the center of its length so as to create additional clamping force near the center of the belt, and/or may have plural additional clamping devices at intermediate locations across the width of the belt, as might be advantageous for longer beams intended for use with wider belts. 
       FIG. 1  is an isometric view of an example embodiment of a conveyor belt clamp  100  that is clamped to a cut end  54  of a conveyor belt  50  for pulling the cut end  54  of the belt  50 . The first and second bars  110 ,  110 ′ of the conveyor belt clamp  100 , also referred to as the upper and lower bars thereof, are generally identical except that one of the bars  110 , typically the first bar or the bar placed in the upper bar position, typically has a clamping device or pusher  120  located generally near the center thereof. The central pusher device  120  allows clamping pressure to be applied near the center of the conveyor belt  50  in cooperation with the two end clamps  130  which are located near the opposite ends of the clamping bars, e.g., outboard of the edges  52  of the conveyor belt  50 . 
     Placing of the first and second bars with the conveyor belt therebetween, and with the end clamps located at the ends of the first and second bars, is described in relation to  FIGS. 3-6  below. It is noted that tightening the screws or bolts  136  of the end clamps  130  causes the conveyor belt  50  to be clamped between the upper an lower bars  110 ,  110 ′, generally with an even pressure on conveyor belt  50  due to the pre-stress on the first and second bars  110 ,  110 ′ which causes a slight bowing so that the center of the bars contact the conveyor belt first. Then the screw or bolt  126  of the clamping device located generally near to the center of the first and second bars  110 ,  110 ′, and generally near to the center of the conveyor belt  50 , may be tightened to further improve the uniformity of the pressure with which the conveyor belt clamp grasps the conveyor belt. The clamping device  120  is preferably located on the upper bar, generally near to the center thereof. 
     Each end clamp has an eye or lug  140 ,  142  or other feature to which a cable or other means can be attached for pulling on the conveyor belt  50  by pulling on the conveyor belt clamp  100  according to the described arrangement. The conveyor belt clamp  100  is generally clamped to the conveyor belt  50  in the vicinity of an end  54  thereof, typically near a cut end  54  intended for being spliced. 
       FIG. 2  is an isometric view of two of the example conveyor belt clamps  100   a ,  100   b  of  FIG. 1  that are clamped to opposing cut ends of a conveyor belt for pulling the cut ends of the belt together for splicing, as indicated by the arrows Fa, Fb extending along the conveyor belt from the respective pulling eyes  140  of the two conveyor belt clamps. 
     In the illustrated arrangement, both beams  110  have one or more tension rods installed internally in the beam. The tension rods are installed using end plates at each end of each beam and at least one tension nut that can be tightened to pre-stress the tension rod for pre-stressing the beam. The tension rods are located off of the beam neutral axis, so that when the tension rods are tensioned the beam deflects or bends. As a result, the beams when placed with their convex sides adjacent the conveyor belt will have their respective ends slightly further away from the edges of the conveyor belt than is the center of the beams from the center of the conveyor belt. 
     When the ends of the beams are forced together by the tightening of the end clamps  130 , the center of the pre-stressed beam or beams  110  will contact the center of the conveyor belt  50  first. Then as the ends of the beams are brought together as the end clamps  130  are tightened further, the clamping force against the belt from the upper and lower beams will become distributed evenly across the width of the belt, e.g., more evenly than with a conventional belt clamp. The optional center pusher clamp  120  may be used to apply additional force or pressure near the center of the conveyor belt  50  in order to get additional clamping pressure between the clamp bars  110 ,  110 ′ and the conveyor belt  50 . 
     In general, the holding of the conveyor belt between the clamping bars is produced by the clamping force of the bars of the conveyor belt clamp against the conveyor belt and by the friction between the bars and the conveyor belt. A more even distribution of clamping force along the length of the clamping bars will, in general, produce a more even distribution of the pulling force across the width of the conveyor belt when the conveyor belt clamp is pulled, e.g., by the eyes thereof. 
       FIG. 3  includes  FIGS. 3A through 3D  illustrating a typical sequence of positioning and successively tightening the conveyor belt clamp on a conveyor belt. In practice, these usually are not stopping points, but are “snapshots” at various stages during the tightening process. 
       FIG. 3A  is a side elevation view of the example conveyor belt clamp  100  of  FIG. 1  with pre-stressed upper and lower clamp bars  110  in position prior to coming into contact with the conveyor belt  50 . In this example, both the upper and lower bars  110  are pre-stressed by their respective tension bars  116 , and so both are slightly curved so that the centers thereof are closer to the conveyor belt than are the ends thereof. The one tensioned bar positioned above the top of the belt preferably has an optional additional clamping device  120  near the center thereof which can be tightened so as to apply additional clamping force near the center of the conveyor belt. The other tensioned bar positioned below the conveyor belt typically does not include an additional clamping device. 
     While both the upper and lower bars  110  are illustrated as being pre-stressed or tensioned so as to have a slight curvature away from the conveyor belt at their ends, it is sufficient in many applications that only one of the two bars  110 ,  110 ′ be a pre-stressed or tensioned bar. Further, where the conveyor belt is relatively wide, one or more additional clamping devices  120  may be provided on one of the bars  110 ,  110 ′, generally but not necessarily, on the upper bar as a matter of convenience in being able to access the device for tightening it. The additional clamping devices typically include a screw or bolt or other mechanism  126  for increasing and decreasing the force they apply to the conveyor belt. Preferably, the optional additional clamping device or devices  120  is/are retracted when the upper bar or other bar including such optional clamping device is initially placed against the belt and as the bars are subsequently, at least initially, clamped together. 
       FIG. 3B  is a side elevation view of the example conveyor belt clamp  100  of  FIG. 3A  with pre-stressed upper and lower clamp bars  110  in a condition of making initial contact with the conveyor belt  50  and the two end clamps  130  in position to exert clamping force on the ends of the upper and lower clamp bars  110 . This condition obtains as the end clamps  130  are slipped over the ends of the two bars  110  and are initially tightened from the condition of  FIG. 3A  until the upper and lower bars come into contact with the conveyor belt. Rotating the bolt  136  of the end clamp  130  so that it advances into the end clamp causes the bearing plate  138  therein to move towards the beams to exert a force that presses the bars together against the frame  132  of the end clamp. 
     Because both the upper and lower bars are pre-stressed or tensioned in this example, each is slightly bowed and is placed so as to present a convex side  110   c  toward the conveyor belt. As a result, the centers of both the upper and lower beams tend to contact the conveyor belt first and to do so near the center of the belt, if the clamp bars  110  are placed as shown, which is not necessary. Where only one of the beams  110 ,  110 ′ is tensioned, then only that beam  110  would have a convex side  110   c  that is placed into contact with the conveyor belt. 
     Optional center clamp  120  includes a frame  122  that may be attached, e.g., by welding or bolts or other fasteners, to clamp beam  110  and a threaded hole  124  through which a bolt or other threaded member  126  may be threaded. Center clamp  120  applies clamping force to conveyor belt  50  when tightening device  126  is rotated in hole  124  to advance toward conveyor belt  50  thereby to press pressure plate  128  against belt  50 , and clamping force is reduced or removed by rotating tightening device  126  in the opposite direction so that it withdraws away from conveyor belt  50 . 
       FIG. 3C  is a side elevation view of the example conveyor belt clamp  100  of  FIGS. 3A-3B  with the upper and lower clamp bars  110  in the clamped condition in contact with the conveyor belt  50  and with the two end clamps  130  tightened to force or draw the ends of the upper and lower clamp bars  110  together. The two end clamps  130  are both tightened against the pre-stress of the tensioned bars to draw the respective ends of the bars closer together, e.g., at least until the sides  110   c  adjacent the conveyor belt are substantially parallel as shown. The center clamp  120  is preferably not yet tightened. 
       FIG. 3D  is a side elevation view of the example conveyor belt clamp  100  of  FIGS. 3A-3C  with the upper and lower clamp bars  110  in the fully clamped condition in contact with the conveyor belt  50  and the end clamps  130  forcing the ends of the upper and lower clamp bars together, wherein the ends of the clamp bars  110  are tightened sufficiently to apply a desired holding force at the edges  52  of the conveyor belt  50 . The center clamp device  120  is tightened so as to exert force at the center of the conveyor belt to force the upper and lower clamp bars  110  into reverse deflection. 
     At this final stage of tightening of end clamps  130  and the center clamp  120 , each has preferably been tightened to a predetermined degree so that the gripping of the conveyor belt  50  is relatively more uniform across the width of the conveyor belt. This can be controlled, e.g., by tightening the respective bolts  136 ,  126  of the end clamps  130  and of the center clamp  120  to a pre-determined torque, as might be done using a torque wrench or other torque applying device. 
       FIG. 4  is an end view of an example end clamp  130  of the conveyor belt clamp of  FIG. 1  showing details of the end clamp  130 . The end clamp  130  comprises a frame  132  suitable for placing a tightening device  136  against one of the clamp bars  110  and for holding the other of the clamp bars  110  so that force can be applied to both to draw them closer together. The clamp frame  132  may be rectangular as illustrated or may be another suitable shape, e.g., a “C” shape. 
     A threaded opening  134  at one end of the clamp frame  132  receives a clamp bolt  136  that can be rotated therein for advancing the clamp bolt  136  and the pressure plate  138  at its end to force the clamp bars  110  closer together, and for withdrawing the clamp bolt  136  for loosening and releasing the clamp bars  110 , e.g., by applying a wrench to the head of the clamp bolt  136 . The threaded opening  134  may be provided by a threaded hole through the clamp frame, or by a nut  134  attached thereto, e.g., by welding, or by a nut or other element  134  extending the length of the threaded opening provided by the threaded hole in the clamp frame and the nut. 
     The clamp frame  132  preferably includes a pulling eye or pulling lug  140  as a convenience for attaching a cable or other device, e.g., placed in the opening  142  of the pulling lug  140 , for pulling on the clamp bar  100  and the conveyor belt  50  on which it is clamped. Absent a pulling lug  140 , a cable loop could be placed over the tightened clamp bars for exerting pulling forces on the clamp bars and the conveyor belt. 
       FIG. 4  also illustrates a detail of the end of the clamp bars  110  which include an end plate  114  disposed at the respective ends of the clamp bars  110 . The end plates  114  have one or more openings which are offset towards the same edge of the end plate  114  through which ends of the tensioning rods  116  extend for having a nut or other fastener  118  placed thereon that can be tightened to pre-tension the clamp bars  110 . Tightening of the tensioning nuts  118  tends to place the tensioning rods  116  in tension which, because they are offset relative to the longitudinal center CL, NA of the clamp bars, tend to compress one of the long sides of the clamp bars relative to the opposing long side thereof, whereby the clamp bar will bend or distort in a pre-stressed or tensioned condition. 
       FIG. 5  includes  FIGS. 5A and 5B  that are cross-ways and longitudinal sectional views, respectively, of a clamp beam  110  that show the arrangement of tensioning rods  116  therein. While beams  110 ,  112  may have walls of the same thickness, it is preferred that one wall be thicker than the other three walls, and that the thicker wall  110   c  provide the convex side  110   c  that is to be placed adjacent to or against the conveyor belt  50 . Because one wall is thicker than the other walls, the neutral axis NA of the beam  112  is offset from the centerline CL of the beam  112  towards the thicker wall  110   c . The centerline CL is the physical center, e.g., the mid-point, between opposing outer surfaces of the beam, whereas the neutral axis NA is where longitudinal tensioning forces, if applied, would compress the beam  112  without bending the beam one way or the other. If the beam  112  is symmetrical, then the centerline CL and the neutral axis NA would coincide. The centerline CL and neutral axis NA are shown in one direction for explaining the bending of beam  110 ,  112  under tension, and the coincident centerline and neutral axis in the direction perpendicular to those shown in this example are not shown. 
     A tensioning force applied offset from the neutral axis NA in the direction away from the thicker wall  110   c  will cause beam  110 ,  112  to bend in a direction that bows the thicker wall  110   c  outward to produce a convex side  110   c . Where two tensioning rods  116  are employed as illustrated, they are disposed symmetrically about the un-shown centerline so that beam  110 ,  112  bends in the desired direction and remains straight in the other direction. Preferably tensioning force is applied by alternatingly tightening the tensioning nuts  118  against end plates  114  so that the tensioning force applied by each tensioning rod  116  remain relatively even. If only one tensioning rod  116  were to be employed, it would be offset from the neutral axis NA and on the un-shown centerline in the perpendicular direction, i.e. symmetrical with respect to the opposing thinner walls of beam  112 . 
       FIG. 6  is an isometric view of a prior art conveyor belt clamp clamped to a conveyor belt  50  to illustrate the uneven distribution of pulling forces across the width of a conveyor belt obtained thereby. The prior art clamp employs clamping bars that are hollow, or that may be solid, but that are not pre-tensioned. Thus, the prior art clamp bars tend to bow away from the conveyor belt when tightened to pull their ends together, and so they clamp relatively more tightly at the edges  52  of the conveyor belt  50  and relatively less tightly at and near the center of the conveyor belt. This produces a non-uniform or uneven distribution of force across the width of the conveyor belt as indicated by the arrows of differing length extending from the conveyor belt in the direction opposite to the direction it is pulled by pulling on the clamp. 
       FIG. 7  is an isometric view of an example conveyor belt clamp  100  of  FIG. 1  clamped to a conveyor belt  50  to illustrate the relatively more even distribution of pulling forces across the width of the conveyor belt  50  obtained thereby. The present belt clamp  100  employs one or both clamping bars  110  that are pre-stressed or pre-tensioned. Thus, the present clamp bars  110  tend to bow towards the conveyor belt  50  at its center and when tightened to pull their ends together, to continue to exert substantial clamping force at and near the center of the conveyor belt  50 . This produces a relatively uniform or even distribution of force across the width of the conveyor belt as indicated by the arrows of similar length extending from the conveyor belt in the direction opposite to the direction it is pulled by pulling on the clamp bar  100 . 
       FIG. 8  is an isometric view of an example embodiment of a conveyor belt clamp  100 ′ having plural intermediate clamping devices  120  along its length and that is clamped to a cut end  54  of a conveyor belt for pulling the cut end of the belt. The upper bar  110  thereof has two center clamps  120  spaced along its length so as to be tightenable after the ends of the upper and lower clamp bars  110  are pulled together by the tightening of the end clamps  130 . While this clamping arrangement including end clamps  130  and upper and lower clamp bars  110 , at least one of which is pre-stressed or tensioned so as to bow toward the conveyor belt  50  near its center, does provide a more uniform distribution of pulling force across the width of the conveyor belt, in view of the greater width of the conveyor belt, two tightenable center clamps  120  are provided instead of only one near the center. The two center clamps  120  are preferably symmetrically offset to either side from the center of the clamping bar  110 , e.g., at about the one-third and two-thirds positions along the length of the upper clamping bar  110 . 
     In the conveyor belt clamp  100  described herein, one or both of the upper and lower clamp beams  110  are pre-stressed so that greater force is transferred to the center of the conveyor belt  50  when the upper and lower beams  110  are clamped together. It is noted that only one beam  110 , preferably the top beam, has to be pre-stressed for the clamps to operate as desired. Preferably the upper and lower beams  110  are pre-stressed such that their ends are deflected away from the surface of the belt prior tightening of the end clamps  130 . When the end clamps  130  are tightened, a region of the convex side  110   c  of the pre-stressed clamp beam  110  away from the ends thereof, e.g., generally near the center of the pre-stressed clamp beam if the end clamps  130  are tightened relatively evenly, and the centers of the pre-stressed beams  110  generally contact the belt first. Contact between the two beams  110  and the belt  50  progresses from the center of the belt  50  towards the edges of the belt as the end clamps  130  are progressively tightened. The conveyor belt clamp  100  may have one or more clamping mechanisms (clamping devices)  120  on the beams  110  thereof across the width of the conveyor belt  50 . The conveyor belt clamp  100  preferably has a relatively consistent (uniform) clamping force across the width of the belt. The conveyor belt clamp  100  may have tension rods  116  installed in the upper beam  110 , in the lower beam  110 , or in both the upper and lower beams  110 . A conveyor belt  50  is installed between the upper and lower beams  110 , and the belt clamp  100  provides relatively even distribution of pulling force across the width of the belt  50 . 
     In an example conveyor belt clamp suitable for use with a 30 inch (76.2 cm) wide conveyor belt, the two pre-stressed beams are aluminum and are about 34 inches (about 86.4 cm) long and about 2 inches by 3 inches (about 5.1 cm by 7.6 cm) in cross-section. The tensioning rods are ⅜ inch (about 0.95 cm) diameter steel rods with 16-NC threads for receiving 16-NC tensioning nuts at each end thereof. The end clamps are steel and are about 4 inches by 6 inches by 2 inches (about 10.2 cm by 15.2 cm by 5.1 cm) and the steel tightening bolts are 1-inch ACME thread bolts. Where the walls are of different thicknesses, the thin walls are about ¼ inch (about 0.64 cm) thick and the thicker wall is about ⅜ inch (about 0.95 cm) thick. 
     A conveyor belt clamp  100  may comprise: first and second clamp beams  110 ,  110 ′ for being placed against a conveyor belt  50 , one or both of the first and second clamp beams  110  may be pre-stressed for deflecting a central region along the length of the clamp beam  110 ; a first end clamp  130  for being placed over a first end of each of the first and second clamp beams  110 , respectively, and a second end clamp  130  for being placed over an other end of each of the first and second clamp beams  110 , respectively, wherein each of the first and second end clamps  130  includes a tightening device  136  for forcing the ends of the first and second clamp beams  110  closer together; wherein the one or both of the first and second clamp beams  110  is for being placed with its convex side  110   c  against a surface of a conveyor belt  50  for clamping the conveyor belt  50 . Both of the first and second clamp beams  110  may be pre-stressed so as to have respective convex sides  110   c  for being placed against a surface of a conveyor belt  50 . The pre-stressed one  110  of the first and second clamp beams  110 ,  110 ′ may comprise: an elongated beam member  112  having a longitudinal neutral axis NA and first and second ends; and a tensioning member  116 ,  118  connected to the first and second ends of the elongated beam member  112  and offset from the longitudinal neutral axis NA thereof, for pre-stressing the elongated beam member  112 . The elongated beam member  112  may be hollow and the tensioning member  116  may be disposed within the hollow elongated beam member. Where the elongated beam member  112  is hollow, one wall  110   c  of the elongated beam member may be thicker than other walls thereof, whereby the neutral axis NA of the elongated beam member  112  is offset from the centerline CL thereof. Tensioning member  116 ,  118  may include a tensioning rod  116  attached at the first and second ends of elongated beam member  112  and a tightening device  118  for increasing and decreasing tension of tensioning rod  116 . The pre-stressed one  110  of the first and second clamp beams  110 ,  110 ′ may comprise: an elongated beam member  112  having first and second ends; and at least one center clamp  120  on the elongated beam member  110  at a location between the first and second ends thereof. The first and second end clamps  130  may each comprise: a frame  132  defining a central opening of sufficient size to receive respective ends of first and second clamp beams  110 ,  110 ′ therein; wherein tightening device  134 ,  136  may include a threaded member  136  threadingly engaging frame  132  for rotating in a first direction for advancing into the central opening of frame  132  for pressing against first and second clamp beams  110 ,  110 ′ therein and for rotating in an opposite direction for withdrawing out of the central opening. Threaded member  134 ,  136  may include a bolt  136  engaging a threaded opening  134  of frame  132 , and frame  132  may further include a pulling lug  140  on an outer surface thereof. The pre-stressed one or both of the first and second clamp beams  110 ,  110 ′ may be placed against the conveyor belt  50  with the center thereof making contact with the conveyor belt  50  in a region away from its edges  52 , and the first and second end clamps  130  may be tightened so that contact between the first and second clamp beams  110 ,  110 ′ and the conveyor belt  50  progresses from the region away from the edges  52  of the conveyor belt  50  towards the edges  52  thereof as the end clamps  130  are progressively tightened. The conveyor belt clamp  100  may further comprise one or more clamping mechanisms  120  located at one or more locations on the pre-stressed one  110  of the first and second clamp beams  110 ,  110 ′ across the width of the conveyor belt  50 . The conveyor belt clamp  100  may be in combination with a conveyor belt  50 , wherein the conveyor belt  50  is clamped between the first and second clamp beams  110 ,  110 ′ by the first and second end clamps  130 . 
     A method for clamping a conveyor belt may comprise:
         providing first and second clamp beams  110 ,  110 ′, one or both of which  110  is pre-stressed for having a convex side  110   c;      placing the first and second clamp beams  110 ,  110 ′ transversely across the width of a conveyor belt  50  with the convex side  110   c  of the one or both clamp beams  110 ,  110   c  adjacent the conveyor belt  50 ;   placing a first end clamp  130  over first ends of the first and second clamp beams  110 ,  110 ′;   placing a second end clamp  130  over second ends of the first and second clamp beams  110 ,  110 ′; and   tightening the first and second end clamps  130  for forcing the ends of the first and second clamp beams  110 ,  110 ′ closer together for clamping the conveyor belt  50  therebetween.
 
The method may further comprise: tightening a clamp device  120  located on one of the first and second clamp beams  110 ,  110 ′ for clamping the conveyor belt  50  in a region away from its edges  52 . The method may further comprise: pulling on the conveyor belt  50  by pulling on respective pulling lugs  140  of the first and second end clamps  130 . The method may further comprise: loosening the first and second end clamps  130  for releasing the clamping pressure of the first and second clamp beams  110 ,  110 ′ on the conveyor belt  50 ; and removing the first and second end clamps  130  from the first and second clamp beams  110 ,  110 ′ and the first and second clamp beams  100 ,  100 ′ from the conveyor belt  50 .
       

     A conveyor belt clamp  100  may comprise: first and second clamp beams  110 ,  110 ′, one or both of which  110  is pre-stressed for having a convex side  110   c ; wherein the first and second clamp beams  110 ,  110 ′ are placed transversely across the width of a conveyor belt  50  with the convex side  110   c  of the one or both clamp beams  110 ,  110 ′ adjacent the conveyor belt  50 ; a first end clamp  130  disposed over first ends of the first and second clamp beams  110 ,  110 ′ with the conveyor belt  50  therebetween; a second end clamp  130  disposed over second ends of the first and second clamp beams  110 ,  110 ′ with the conveyor belt  50  therebetween; and means  130  for tightening the first and second end clamps  110 ,  110 ′ for forcing the ends of the first and second clamp beams  110 ,  110 ′ closer together for clamping the conveyor belt  50  therebetween. The conveyor belt clamp  100  may further comprise means for tightening  120 ,  126  at least one additional clamp  120  for clamping a central region of the first clamp beam  110  against the conveyor belt  50 . 
     A conveyor belt clamp  100  may comprise: first and second clamp beams  110 ,  110 ′ for being placed against opposing surfaces of a conveyor belt  50 , at least one  110  of said first and second clamp beams  110 ,  100 ′ may comprise: an elongated beam member  112  having a longitudinal neutral axis NA and first and second ends; and a tensioning member  116 , 118  connected to the first and second ends of elongated beam member  110  and offset from the longitudinal neutral axis NA thereof for pre-stressing elongated beam member  110  and deflecting a central region  110   c  along the length thereof, whereby the at least one  110  of first and second clamp beams  110 ,  110 ′ is bent and has a convex side  110   c ; first and second end clamps  130  may each comprise a frame  132  and a tightening device  134 ,  136 , the frame  132  of first end clamp  130  for being placed over a first end of each of the first and second clamp beams  110 ,  110 ′, respectively, the frame  132  of second end clamp  130  for being placed over an other end of each of the first and second clamp beams  110 ,  110 ′, respectively, wherein the tightening device  134 ,  136  of each of first and second end clamps  130  is tightenable for forcing the ends of the first and second clamp beams  110 ,  110 ′ closer together; wherein the at least one  110  of first and second clamp beams  110 ,  110 ′ is for being placed with its convex side  110   c  against a surface of a conveyor belt  50  for clamping the conveyor belt  50 . The elongated beam member  112  may be hollow and tensioning member  116 ,  118  may be disposed within the hollow elongated beam member  112 ; or elongated beam member  112  may be hollow and one wall of elongated beam member  112  may be thicker than other walls thereof, whereby the neutral axis NA of elongated beam member  112  is offset from the centerline CL thereof; or elongated beam member  112  may be hollow and one wall of elongated beam member  112  may be thicker than other walls thereof, whereby the neutral axis NA of elongated beam member  110  may be offset from the centerline CL thereof and tensioning member  116  may be disposed within the hollow elongated beam member  112 . The at least one  110  of first and second clamp beams  100 ,  100 ′ may comprise: at least one center clamp  120  on elongated beam member  112  at a location between the first and second ends thereof. First and second end clamps  130  may each comprise: a frame  132  defining a central opening of sufficient size to receive respective ends of first and second clamp beams  110 ,  110 ′ therein; and tightening device  134 ,  136  may include a threaded member  136  threadingly engaging frame  132  for rotating in a first direction for advancing into the central opening of frame  132  for pressing against first and second clamp beams  110 ,  110 ′ therein and for rotating in an opposite direction for withdrawing out of the central opening. Threaded member  136  may include a bolt  136  engaging a threaded opening  134  of frame  132 , and frame  132  may further include a pulling lug  140  on an outer surface thereof. 
     A conveyor belt clamp  100  may comprise: first and second elongated clamp beams  110 ,  110 ′ for being placed against opposing surfaces of a conveyor belt  50 , wherein each of first and second elongated clamp beams  110 .  110 ′ comprises an elongated beam member  112  having first and second ends; at least one center clamp  120  on at least one of first and second elongated clamp beams  110 ,  110 ′ at a location between the first and second ends thereof; first and second end clamps  130  each comprising a frame  132  and a tightening device  134 ,  136 , the frame  132  of first end clamp  130  for being placed over a first end of each of the first and second elongated clamp beams  110 , 110 ′, respectively, the frame  132  of second end clamp  130  for being placed over an other end of each of the first and second elongated clamp beams,  110 , 110 ′, respectively, wherein the tightening device  134 ,  136  of each of first and second end clamps  130  is tightenable for forcing the ends of the first and second elongated clamp beams  110 ,  110 ′ closer together; and wherein at least one center clamp  120  is tightenable for applying clamping force to the conveyor belt  50  at the location between the first and second ends of the at least one of said first and second elongated clamp beams  110 ,  110 ′. Center clamp  120  may comprise: a tightening device  122 ,  124 ,  126  including a threaded member  126  threadingly engaging the at least one of first and second elongated clamp beams  110 ,  110 ′ for rotating in a first direction for advancing towards the conveyor belt  50  for pressing against the conveyor belt  50  and for rotating in an opposite direction for withdrawing away from the conveyor belt  50 . Threaded member  126  may include a bolt  126  engaging a threaded opening  122 ,  124  of the at least one of said first and second elongated clamp beams  110 ,  110 ′. Each elongated beam member  112  may have a longitudinal neutral axis NA and wherein at least one of the first and second elongated clamp beams  110 ,  110 ′ may comprise: a tensioning member  116 ,  118  connected to the first and second ends of the elongated beam member  112  thereof and offset from the longitudinal neutral axis NA thereof for pre-stressing elongated beam member  112  and deflecting a central region along the length thereof, whereby the at least one of first and second elongated clamp beams  110 ,  110 ′ is bent and has a convex side  110   c , wherein the at least one of said first and second elongated clamp beams  110 ,  110 ′ is for being placed with its convex side  110   c  against a surface of the conveyor belt  50  for clamping the conveyor belt  50 . The elongated beam member  112  may be hollow and tensioning member  116  may be disposed within the hollow elongated beam member  112 ; or elongated beam member  112  may be hollow and one wall of elongated beam member  112  may be thicker than other walls thereof, whereby the neutral axis NA of elongated beam member  112  is offset from the centerline CL thereof; or elongated beam member  112  may be hollow and one wall of elongated beam member  112  may be thicker than other walls thereof, whereby the neutral axis NA of elongated beam member  112  is offset from the centerline CL thereof and tensioning member  116  is disposed within the hollow elongated beam member  112 . First and second end clamps  130  may each comprise: a frame  130  defining a central opening of sufficient size to receive respective ends of first and second elongated clamp beams  110 ,  110 ′ therein; wherein tightening device  134 ,  136  may include a threaded member  136  threadingly engaging frame  132  for rotating in a first direction for advancing into the central opening of frame  132  for pressing against first and second elongated clamp beams  110 ,  110 ′ therein and for rotating in an opposite direction for withdrawing out of the central opening. Threaded member  136  may include a bolt  136  engaging a threaded opening  134  of frame  132 , and frame  132  may further include a pulling lug  140  on an outer surface thereof. 
     As used herein, the term “about” means that dimensions, sizes, formulations, parameters, shapes and other quantities and characteristics are not and need not be exact, but may be approximate and/or larger or smaller, as desired, reflecting tolerances, conversion factors, rounding off, measurement error and the like, and other factors known to those of skill in the art. In general, a dimension, size, formulation, parameter, shape or other quantity or characteristic is “about” or “approximate” whether or not expressly stated to be such. It is noted that embodiments of very different sizes, shapes and dimensions may employ the described arrangements. 
     Although terms such as “up,” “down,” “left,” “right,” “front,” “rear,” “forward,” “backward,” “under” and/or “over,” may be used herein as a convenience in describing one or more embodiments and/or uses of the present arrangement, the articles described may be positioned in any desired orientation and/or may be utilized in any desired position and/or orientation. Such terms of position and/or orientation should be understood as being for convenience only, and not as limiting of the invention as claimed. 
     While the present invention has been described in terms of the foregoing example embodiments, variations within the scope and spirit of the present invention as defined by the claims following will be apparent to those skilled in the art. For example, either the upper beam  110  or the lower beam  110  or both may be pre-stressed or tensioned so as to exhibit a curved shape; however, each one of the beams  110  that is pre-stressed is intended to be placed with its convex side  110   c  facing the conveyor belt  50  so that clamping force is provided and maintained near the center of the belt  50 . The first and second clamp beams  110 ,  110 ′ herein include two pre-stressed clamp beams  110  or one pre-stressed clamp beam  110  and one clamp beam  110 , i.e. one or both clamp beams is a pre-stressed clamp beam  110 . 
     While it is preferred that the tensioning device  116  employed to pre-stress a clamp beam  110  be located in the hollow interior of the beam  112 , a tensioning device  116  may be located external to beam  112  because the tension produced will cause compression of the side of the beam on which the tensioning device  116  is located, thereby tending to bend the beam  112  in the direction such that the convex side  110   c  is opposite the tensioning device and is therefore exposed and available to be placed into contact with a conveyor belt  50 . 
     While end clamps  130  and center clamps  120  may utilize a simple bolt-like mechanism  134 - 136 ,  122 - 126  for clamping down on the respective ends of clamp beams  110 ,  110 ′ as is shown, any mechanism that produces a suitable clamping force, e.g., as by threads or cams or cables or other means, may be employed. While a load spreading device such as pressure plates  128 ,  138  at the contact ends of bolts  126 ,  136  may be employed, the use of such plates is optional and the size thereof is typically adjusted for the expected loading and stress. 
     The optional center clamp  120  may be omitted where the width of the conveyor belt  50  is sufficiently narrow that the one or two pre-stressed clamp beams  100  of the present conveyor belt clamp arrangement  100  provides sufficient uniformity of pulling forces across the width of the conveyor belt  50 . One or more center clamps  120  may be provided for use with relatively wider belts so that additional clamping force may be provided at one or more locations between the edges  52  of the conveyor belt  50 . 
     Typically the center clamps  120  are symmetrically provided so as to provide for a relatively uniform distribution of the pulling forces, however, other non-symmetrical placements may be utilized. While the illustrated example center clamp  120  is affixed to a pre-stressed clamp beam  110 , one or more center clamps  120  may be utilized with a pre-stressed clamp beam  110  and/or one or more center clamps  120  may be utilized with a non-pre-stressed clamp beam  110 ′ that opposes a pre-stressed clamp beam  110 . The center clamp or clamps  120  may be fixed at a predetermined location on the clamp beam  110 ,  110 ′ or may be movable to a desired position thereon. 
     The terms “upper” and “lower” are used for convenience only and are not limiting as to how the present conveyor belt clamp may be employed or utilized. The “upper” beam may be placed under the conveyor belt and the “lower” beam may be placed over the conveyor belt. The tightening bolts of the end clamps may be in any position as may be convenient, and need not be against the “upper” beam, and the two end clamps do not need to be placed on the clamping beams in the same orientation, and similar variations may apply to the one or more center clamps. 
     Each of the U.S. Provisional Applications, U.S. patent applications, and/or U.S. patents identified herein are hereby incorporated herein by reference in their entirety. 
     Finally, numerical values stated are typical or example values, are not limiting values, and do not preclude substantially larger and/or substantially smaller values. Values in any given embodiment may be substantially larger and/or may be substantially smaller than the example or typical values stated.