Patent Publication Number: US-2003234480-A1

Title: Plank cramp and clamp assembly

Description:
[0001] THIS INVENTION relates to a plank cramp and a clamp assembly.  
       [0002] The invention has particular application to a plank cramp and a clamp assembly for use in cramping a plurality of aluminium builders planks together to form a platform. However, the plank cramp could be used with timber planks and could also have other applications such as a floor cramp, while the clamp assembly could be used with an L-shaped member as a slide clamp to provide an alternative to existing slide clamps or G-clamps.  
       [0003] While plank cramps are known, they typically are not as effective in use or as efficient to fit and, remove as desired.  
       [0004] The present invention aims to provide a plank cramp and a clamp assembly for a plank cramp which will be more effective and/or more efficient and/or safer than the presently available plank cramps and clamp assemblies.  
       [0005] With the foregoing in view, the present invention in one aspect resides broadly in a plank cramp including:  
       [0006] an elongate member adapted to support thereon in side-by-side abutting relationship two or more builders planks or other articles to be cramped; said elongate member having retaining means secured thereto at or adjacent one end adapted to engage with a side face and/or an upper face of the adjacent one of the planks to be clamped;  
       [0007] a clamp assembly mounted on said elongate member for holding said two or more builders planks together on said elongate member, said clamp assembly including a gripping part having a passage therethrough and said elongate member passing slidably through said passage, and engagement means for engaging an upper face and a lower face of said elongate member for securing said clamp assembly in a predetermined desired position along said elongate member, and clamping means operatively connected to said gripping part for pivoting movement towards and away from the upper face of said elongate member about a first pivot axis, and a cam operatively connected to said gripping part for at least partial rotation relative thereto about a second pivot axis substantially parallel to said first pivot axis, said cam being adapted to engage said clamping means to force said clamping means into engagement with the upper face and/or the side face of the plank adjacent said clamp assembly to force the two or more planks to be cramped together and said engagement means into engagement with the upper and lower faces of said elongate member, and actuation means for actuating said cam.  
       [0008] In another aspect the invention resides broadly in a clamp assembly including:  
       [0009] a gripping part having a passage for slidably receiving therethrough an elongate member, and engagement means for engaging an upper face and a lower face of the elongate member to which the gripping part is fitted to secure the clamp assembly in a predetermined desired position along the elongate member;  
       [0010] clamping means operatively connected to said gripping part for pivoting movement towards and away from the upper face of the elongate member about a first pivot axis;  
       [0011] a cam operatively connected to said gripping part for rotation relative thereto about a second pivot axis substantially parallel to said first pivot axis, said cam being adapted to engage said clamping means to force said clamping means into engagement with the upper face and/or the side face of a plank to be clamped and said engagement means into engagement with the upper and lower faces of the elongate member, and  
       [0012] actuation means for actuating said cam.  
       [0013] Terms such as upper, lower, side, top, base and the like are used for the purpose of description and illustration of the invention in the position it would normally be used in cramping builders planks together to form a platform and are not intended to limit the invention to use in any particular attitude.  
       [0014] Preferably said engagement means is constituted by spaced apart bars defining the upper and lower boundaries of said passage, said bars being also spaced apart in the direction along the elongate member on which the clamp assembly is mounted, and the upper bar being rearward of the lower bar and also rearward of the first pivot axis. Advantageously this arrangement allows the gripping part to pivot about the lower bar thereby forcing the upper bar into engagement with the upper face of the elongate member, while the lower bar engages with the lower face of the elongate member. It will be appreciated that as the cam forces the clamping means into engagement with the side face and/or the upper face of the adjacent plank, the reaction of the gripping part is to lift at its forward end thereby forcing the upper and lower bars into tight engagement with the elongate member.  
       [0015] Preferably the cam is shaped with a lobe for forcing the clamping means into engagement with the upper face and/or the side face of a plank followed by a dwell portion adapted to effectively lock the clamping means in the cramping position, the dwell portion preventing self release.  
       [0016] Preferably the clamping means is an L-shaped member which is pivotally mounted to the gripping part forward of the upper bar, the L being suitably sized and shaped to capture the upper edge of the plank in the enclosed corner of the L-shaped member. Suitably this shape allows the L-shaped member to force the plank downwardly onto the elongate member and also against the adjacent plank and so on to clamp against the retaining means at the other end of the elongate member. 
     
    
    
     [0017] In order that this invention may be more readily understood and put into practical effect, reference will now be made to the accompanying drawings which illustrate preferred embodiments of the invention and wherein:  
     [0018]FIG. 1 is a pictorial representation of a plank cramp according to the invention;  
     [0019]FIG. 2 is a side elevation of the elongate member of the plank cramp of FIG. 1;  
     [0020]FIG. 3 is a side elevation of the clamp assembly of the plank cramp of FIG. 1;  
     [0021]FIG. 4 is a front elevation of the clamp assembly of FIG. 3;  
     [0022]FIG. 5 is a side elevation of the cam of the clamp assembly of FIG. 3;  
     [0023]FIG. 6 is a front elevation of the cam of FIG. 5;  
     [0024]FIG. 7 is a side elevation of one side plate of the clamp assembly of FIG. 3;  
     [0025]FIG. 8 is a side elevation of the plank cramp of FIG. 1 in use with one plank, and  
     [0026]FIG. 9 is a side elevation of an alternative clamp assembly according to the invention. 
    
    
     [0027] The plank cramp  10  illustrated in FIG. 1 includes an elongate member  111  constructed of 50 mm×25 mm×2 mm Rectangular Hollow Section(RHS) steel tube which has an end stop  112  welded thereto, the end stop being constructed of 30 mm×30 mm×2 mm RHS and having a top lug  113  extending towards the free end above the elongate member  111 . The lug is spaced from the elongate member by a distance of approximately 51 mm so that a standard aluminium builders plank can be rested on the elongate member and retained or held thereto by the lug.  
     [0028] A clamp assembly  116  is mounted on the elongate member for sliding movement towards and away from the end stop. The assembly includes two side plates  117  and  118  which are spaced apart by a distance slightly greater than 25 mm so that the elongate member  111  can be received therebetween in a loose sliding fit. An upper bar  119  and a lower bar  120  extend between the side plates and are welded thereto to hold them in the desired spaced apart relationship.  
     [0029] A shaft  121  extends between the side plates directly forward of the upper bar  119  towards the end stop and is pivotally mounted in aligned apertures  122  and  123  provided therein respectively. An L-shaped tongue  124  is welded to the shaft so that it can pivot with the shaft about the shaft axis  126 .  
     [0030] A cam  131  is mounted on another shaft  132  above and intermediate the upper bar and the shaft  121  and is arranged to engage with the tongue to cause it to pivot about the shaft axis  126  thereby moving it towards die end stop  112  and downwardly towards the upper face of the elongate member  111 . The cam has a lobe portion  131   a  which defines the maximum movement of the tongue and a dwell portion  133  which prevents self release of the cam from the tongue. That is to say, once the cam reaches the maximum engagement position it can be rotated further in the dwell portion while maintaining the tongue in the same position. Full rotation of the cam against the tongue is prevented by a stop pin  137  which limits rotation of the cam shaft about its axis. The cam is actuated by the handle  136  which extends through an aperture provided in a protruding head  135  of the cam shaft The stop pin is a dowel which extends through the head of the cam shaft parallel to the shaft axis and engages in an arcuate slot  138  provided in side plate  117  as more clearly shown in FIG. 7.  
     [0031] In use, a plank or planks, preferably two, are rested on the upper face of the elongate member  111  with lug  113  extending just over an upper edge of the immediately adjacent plank, with the other plank being placed side by side the first plank. The clamp assembly  110  is then slid onto the elongate member with the short leg of the tongue  124  resting just over the upper edge of the second plank in a manner similar to that shown in FIG. 8 for the single plank  139 . The cam is then rotated from the position shown in FIG. 1 and FIG. 3 through 180° to cramp the planks together by use of the handle  136 . Under this action, as the tongue  124  pivots towards the end stop  112  and the upper face of the elongate member  111   a, the rest of the clamp assembly lifts slightly so that the lower bar  120  engages with the lower face  111   b  of the elongate member and tilts slightly away from the end stop until the upper bar  119  engages with the upper face  111   a  and the elongate member is effectively gripped between the upper and lower bars. Continued rotation of the cam through the full 180° available effectively locks the tongue in place due to the dwell portion of the cam.  
     [0032] In order to release the planks, the cam is rotated through 180° in the opposite direction whereupon the clamp assembly can be moved away from the planks or even removed from the elongate member altogether.  
     [0033] The clamp assembly illustrated in FIG. 9 is very similar to the one previously described, except that instead of the passage through which the elongate shaft extends being defined by the upper and lower pins  119  and  120  and the two side plates  117  and  118 , it is defined by a rectangular tubular portion  141  which is welded to the bottom pin  120  for pivoting movement about the axis of that pin, while the shaft  121  is mounted to the box section rather than the side plates. In this form of the invention, the upper pin  119  still grips the upper face of the elongate member but the lower wall of the tubular member  141  grips the lower face. In other respects the clamp assembly operates in much the same manner as that previously described.  
     [0034] While the foregoing description has been given by way of illustrative example of the invention, all modifications and variations thereto as would be apparent to persons skilled in the art are deemed to fall within the broad scope and ambit of the invention as defined in the appended claims.