Portable sheet bending brake
This is a continuation of application Ser. No. 423,459, filed Sept. 24, 1982, now U.S. Pat. No. 4,494,397, which is, in turn, a continuation-in-part of application Ser. No. 359,566 filed Mar. 18, 1982, now U.S. Pat. No. 4,489,583. 
    
    
     This invention relates to sheet bending brakes and particularly to portable sheet bending brakes. 
     BACKGROUND AND SUMMARY OF THE INVENTION 
     In the handling of sheet material such as is used for building construction, it has been common in recent times to provide a portable sheet bending brake wherein sheet material is clamped between an anvil member and a clamping surface and a bending member is hinged for bending the sheet material about the anvil member. Typical sheet bending brakes are disclosed in U.S. Pat. Nos. 3,161,223, 3,481,174, 3,482,427, 3,559,444, 3,817,075 and 4,240,279. 
     As shown, for example, in the aforementioned U.S. Pat. Nos. 3,161,223, 3,559,444, 3,817,075 and 4,240,279, the anvil member is clamped into position by means of a backing plate that has inclined cams underlying a portion of the fixed frame so that when the plate is moved longitudinally by a hand lever, the cams are moved into and out of position clamping and unclamping the backing plate. 
     In the aforementioned U.S. Pat. Nos. 3,481,174 and 3,482,427, the anvil is supported by pivoted bars that, in turn, are connected by links to a handle that is pivoted on the frame of the brake so that rotation of the handle moves the bars and, in turn, the anvil into and out of clamping position. 
     It has also heretofore been suggested that eccentric cams be utilized for moving the anvil member into and out of position as shown, for example, in U.S. Pat. Nos. 3,383,899, 4,092,841 and 4,081,986. 
     One of the problems with prior sheet bending brakes utilizing eccentric cams is that of adjusting the cams on the shaft. Thus, it is common to provide some type of clamp for holding the cams in position. Any such arrangement results in difficulty in adjustment and also the tendency of the clamp arrangement to loosen resulting in a loss of adjustment. 
     In one arrangement, the cams are adjustably mounted by bolts which can be loosened to permit rotation of the cams about the shaft. Such an arrangement operates satisfactorily but is subject to loss of adjustment in use necessitating frequent adjustment. 
     Accordingly, among the objectives of the present invention are to provide a portable sheet bending brake incorporating a construction wherein the eccentric cam positions can be readily adjusted and will remain adjusted; which is low in cost; and which can be adjusted without the use of heavy tools. 
     In accordance with the invention, the shaft and eccentric cams are provided with circumferentially spaced teeth extending axially so that the cams are locked in any adjusted position. The position of a cam can be adjusted by moving the cam axially relative to the shaft to disengage the teeth on the cam from the teeth on the shaft, rotating the cam to the desired adjusted position and moving the cam axially to reengage the teeth. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a fragmentary perspective view of a sheet bending brake embodying the invention. 
     FIG. 2 is a fragmentary part sectional rear elevational view. 
     FIG. 3 is a fragmentary sectional view taken along the line 3--3 in FIG. 2. 
     FIG. 4 is a perspective view of a portion of the sheet bending brake during adjustment. 
     FIG. 5 is an enlarged view of a portion of the brake. 
    
    
     DESCRIPTION 
     Referring to FIGS. 1, 2 and 3, the sheet bending brake embodying the invention comprises a plurality of longitudinally spaced C-shaped frame members 10 which are preferably injection molded of reinforced plastic such as 30% glass filled nylon. Each frame member 10 includes a lower arm 11 and an upper arm 12 with a connecting portion 13, the upper arm 12 being shorter than the lower arm 11. Each frame member 10 includes a rearwardly extending recess or notch defined by a horizontal surface 14 and a vertical surface 15 for receiving an extruded aluminum square rear rail 16. As shown in FIG. 2, portion 13 includes laterally extending flanges 17 overlying the upper surface of the rear rail 16 through which screws 18 extend to fasten the rear rail to the frame members. 
     A first fixed extruded aluminum member 20 is provided on the front end of the lower arms 11 as presently described and comprises an upper generally triangular portion 21 defining a horizontal clamping surface 22 and a lower C-shaped portion 23 that has upper and lower walls that telescope over the free ends of the lower arms 11. Screws fasten the fixed member 20 on the arms 11. 
     An extruded aluminum bending member 24 as hinged to a portion of the fixed member 20 by a hinge defined by intermeshing projections on the members 24, 20, respectively. A hinge pin extends through aligned openings in the projections to complete the hinge. The bending member 24 further includes a laterally extending L-shaped portion 25 that receives the lower end of an extruded floating member 26 yieldingly urged by a spring 26 against the hinge. The member 26 engages the sheet to be bent and minimizes marring during the bending as more fully described in U.S. Pat. Nos. 3,481,174 and 3,482,427 which are incorporated herein by reference. The bending member 24 further includes a C-shaped portion that supports an adapter 36 for receiving a tubular handle 27. 
     The sheet bending brake further includes a plurality of extruded aluminum bars 30, a bar 30 being pivoted to each frame member 10 by a bolt 31 at the area of juncture of the rear of the arm 12 and the upper part of the connecting portion 13. Each bar 30 includes an upper flange 32, a lower flange 33, and a vertical wall 34. An extruded aluminum shaft 35 is journalled in the forward ends of the upper arms 12 by plastic bearings and extend through enlarged openings in the vertical walls of the bars 30. A plurality of plastic eccentric cams 36 are fixed on shaft 44 so that they are positioned between the upper and lower flanges 32, 33 of each bar. Each frame member 10 has axially extending bosses surrounding the opening through which shaft 35 extends. A collar 37 holds shaft 35 axially against a boss. 
     The bars 30 support an anvil member 39 that includes an upper horizontal portion bolted to the lower flange 33 of the bars, and inclined portion and a V-shaped nose portion having a horizontal bottom surface and an inclined upper surface. As shown in FIG. 3, a protective strip 40 of sheet metal such as rolled stainless steel is provided. 
     A handle 41 is provided for rotating the shaft 44 to rotate cams 45 to move anvil member 60 into and out of clamping relation to surface 22. The handle 41 comprises a U-shaped tube. 
     The sheet bending brake heretofore described is substantially like that described in pending Canadian Patent Application Ser. No. 423,598 filed Mar. 15, 1983. 
     In accordance with the invention, the shaft and eccentric cams are provided with circumferentially spaced teeth extending axially so that the cams are locked in any adjusted position. The position of a cam can be adjusted by moving the cam axially relative to the shaft to disengage the teeth on the cam from the teeth on the shaft, rotating the cam to the desired adjusted position and moving the cam axially to reengage the teeth. 
     More specifically shaft 35 is formed with axially extending grooves 45 defining teeth 46 and a collar 47 having complementary teeth 48 is provided on the shaft 35 with the teeth 48 engaging the teeth 46. Each cam 36 has an eccentric opening formed with a plurality of V-shaped teeth 49 which engage complementary V-shaped teeth 50 on collar 47. 
     In order to adjust the cam positions on shaft 35, each cam 36 is moved axially relative to the shaft 35 to dis engage the teeth 49, 50, is thereafter rotated to the desired adjusted position and moved axially to reengage the teeth 49, 50. The number of teeth 49, 50 is such that small accurate adjustments can be made. For example, the size of the teeth can be such as to provide 5° increments of adjustment. The lower flange 33 of each bar 30 is made sufficiently wide to permit the cam 36 to be disengaged. A retainer 51 is removably fastened to the upper flange 32 by a screw 52 and has a downwardly extending lip 53 which retains the cam 36 against axial movement during normal operation. During adjustment, the retainer is removed and a screw 54 holds the collar 47 against axial movement when the cam 36 is moved axially to disengage the teeth. 
     The number of teeth can vary but, as shown in the drawings comprises two opposed arcuate segments separated by arcuate areas 49a, 49b without teeth which have an arcuate extent of approximately thirty degrees. 
     It can thus be seen that there has been provided a sheet bending brake wherein the positions of the eccentric cams can be readily adjusted and will remain adjusted, which is low in cost, and which can be adjusted without the use of heavy tools.