Patent GB-1141843-A (GB)
Title: Method of and apparatus for the fabrication of individual metal joists
Inventor: CAPE RICHARD ALLAN GORDON
IPC: E04C3/08
Filed: 1965-05-10
Abstract: 1,141,843. Making lattice girders; welding by pressure; bending. DOMINION BRIDGE CO. Ltd. 8 Aug., 1966 [10 May, 1965], No. 19584/65. Headings B3A, B3F and B3R. A lattice metal joist is made by bringing top and bottom chord members A, B into contact with a web member E of shorter length than the chords in such a way that the ends of the chords extend beyond both ends of the web member, welding the chords to the web member at their contacting surfaces, bonding the ends of one of the chord into contact with the ends of the other chord and welding the contacting ends together. The chords A, B are released singly from magazines positioned one each side of a web forming machine, Fig. 5 (not shown). Each magazine comprises a pair of rollers (29), Fig. 8 (not shown), which are reciprocated by a piston (31). When the rollers are in their upper position a pair of fingers (22) beneath the lowest chord of each stack are moved outwards and the rollers lowered. As the rollers (29) are lowered the fingers engage under the second from bottom chord and the lowest chord is lowered on the rollers (29). The chord is then fed longitudinally by driven rollers successively to a chord welding station wherein successive chords from the magazine are welded together using three carbon blocks as a backing by the CO 2  solid wire welding process and to a shearing station wherein the chords are cut to the desired length. Chord shearing.-The shearing is performed by an hydraulic shear mounted on a carriage. The carriage normally is urged against a stop by means of pulleys and counter-weights. When the chord strikes a limit switch the shear blade starts to descend and a pneumatic chisel grips the chord. After shearing the chord to the desired length it is fed longitudinally until it abuts a limit switch (36), Fig. 9 (not shown), and is discharged transversally on to an inclined roller bed at the end of which it is rotated on to its side and held in position by rollers (46)-(48). Simultaneous with the chord welding and shearing on one side of the apparatus the chords from the second magazine have been welded and sheared and fed transversely into spaced relationship with the chord from the first magazine, Fig. 5 (not shown). The web E is formed from rods (50), Fig. 10 (not shown), which are fed longitudinally from a magazine (10) to rod shearing and welding stations. The ends of each rod are cut at an angle of 11 degrees and alternate rods rotated through 180 degrees to form a butt-joint which is welded by the metal inert gas process. The rods of-the desired length are then fed by rollers (57) to a rod bending apparatus. Rod bending.-The apparatus consists of a fixed table 64, Fig. 11, and a movable carrier 65. Pivotally mounted on the table and the carrier are a pair of arms 66, 67 pivotally connected together at 68. The position of the arms 66, 67 in their inner position is adjustable. The web is produced from a straight rod 49 which is fed to the bending apparatus with the carriage 65 in its retracted position, i.e. the arms 66, 67 in a straight line. The leading end of the rod is positioned 4 inches past the hinge 70 and the carriage 65 advanced and retracted. The rod is advanced until the bent end fits into the slot formed between the table mandrel 80 and the anvils 81, 82. The carriage is again advanced and retracted to produce the first wave portion. Successive bends are created in the same manner, the last bend being formed at the hinge 80. After each bending operation plungers 96, 97 on the carriage and the table raise the formed web out from between the mandrels and the anvils. The formed web 61 is fed between the chords, Fig. 14, to the welding station. The welding apparatus consists of two resistance welding machines 126, 127 located side by side and adjustable longitudinally and transversely of the apparatus respectively. The chords are fed against stops 144, 145 and the web 61 positioned to bring the bent joint 147 in line with the retracting electrode 137 which co-operates with a fixed electrode 140 to weld the web to the chord A. The web and the chord A are then moved forward to a preset stop 146 and the next bend welded to the chord A. The sequence of welding is repeated until the bend 148 adjacent the chord B arrives in the welding machine 127 whereupon the web is welded to chords A, B simultaneously. In practice a controlled camber is applied to the chord A by clamps 150. The welded chords and web are then fed to a chord bending machine, Fig. 17 (not shown), wherein the ends of the bottom chord B are bent into contact with the ends of the chord A and welded thereto. The bending is performed by a reciprocating bender (168) which is activated hydraulically. A joist entering the bending machine is stopped and heated by oxygen torches (187), Fig. 7 (not shown), and the chord is clamped by anvils (183), 186, Fig. 18 (not shown). Simultaneously the end of the chord is bent by an anvil 168 on the hydraulic ram 156. The chords A, B are tack welded together while under load. The trailing end of the joist is bent similarly on the left-hand side of ram. After formation the joist passes to a paint booth 18, Fig. 5 (not shown), and on to drying skids.