Patent GB-1473700-A (GB)
Title: Method and apparatus for making truss members
IPC: B21D47/01
Filed: 1974-07-25
Abstract: 1473700 Making lattice girders, angular bending C-O Inc 25 July 1974 32803/74 Headings B3A and B3E [Also in Division B5] A method of making truss members, e.g. lattice girders, from a pair of channel-section strips 10 and a third strip formed into a plurality of struts 12, comprises cutting both side edges of each of the strips 10 at longitudinally spaced points, the cut points being transversely aligned with respect to the longitudinal axes of the strips 10, and located intermediate the points where alternate apices of the third strip contact the strips 10, cutting through the truss member intermediate the cut points to leave free ends on the strips 10 and the third strip and thereafter bending the free ends inwardly toward one another. The three strips are fed from motor driven rolls (80), Fig. 1A (not shown) to a press 83 of notching dies 106, Fig. 4, by a reciprocating gripper (82). The dies are supported on a plate 107 which is yieldingly mounted between a fixed platen 112 and a movable platen 111, and on which are mounted notching die members 115. When the strips 10 are clamped by fixed notching die members 113, 114 on the platens 111, 112, air cylinders 117 are actuated to drive the die members 115 via cam plates 116  thereby forming a plurality of notches in the strip edges. The notched strips 10 pass into bending dies 104 and the third strip into die 105. The strips 10 are formed into channel section by die members 120, 121, the members 121 being mounted on a floating plate 122 located between movable and fixed platens 111, 112. The third strip is formed into channel section struts by the members 123, 124 of the die 105. The struts are bent by hammers 92, 93, Fig. 7, the hammer 92 including a movable anvil 127 co-operating with a fixed anvil 129 and a movable anvil 130 co-operating with an anvil 131 on the hammer 93. The hammer 92 is actuated first to bend a portion 12X of the strut strip downwardly and then the hammer 92 bends a portion 12Y of the strip upwardly. The notched and bent strips are fed into an assembly device (91), Fig. 1B (not shown), and then on to a welder (94) where the strut apices are welded to the strips 10. The welded assembly is fed by a gripper (95) until it reaches a limit switch (96a), Fig. 1C (not shown), whereupon the feed is interrupted and a pressure cylinder (142), Fig. 9 (not shown) swings a rotary saw blade (140) over to cut off a length of the welded assembly, which is held by a cam operated clamp. When the cutting operation has been completed, the saw is swung back and the cut truss member is advanced to tucker units, (98), (99), Fig. 1C. Each unit comprises a pair of air cylinders (152), Fig. 10 (not shown), for actuating rollers (150), which bear upon the free ends 10a-10d and 12a, 12b, of the truss member, Fig. 11. The cylinders are operated to bend the ends 10a, 12a and 10d, 12b, first and secondly the ends 10b, 10c, the strips 10 being bent at their notched portions. All the operations are controlled and timed by a rotary limit switch (118), Fig. 1A, mounted on a crankshaft (86) and the work cycle to make one complete span of the truss is completed in one full revolution of the crankshaft.