Patent GB-647671-A (GB)
Title: Apparatus for assembling and securing together by spot welding sheet metal profiles to produce a hollow beam
IPC: B23K11/08
Filed: 1948-04-13
Abstract: 647,671. Making beams; electric welding. BUDD CO. April 13, 1948, No. 10196. Convention date, May 10, 1947. [Classes 83 (ii) and 83 (iv)] Spot-welding apparatus for assembling and securing together sheet-metal profiles to produce a hollow beam comprises spaced supports 29 having means for holding the profiles in predetermined relationship and a spot-welding unit 26 movable longitudinally of the beam. The welding unit is traversed along rails 22 having stops 23 at their ends by means of pinions 27 engaging racks 25 supported by I-sections 24 between the rails and the supports 29 are pivoted on transverse shafts 30 attached to the I-sections so that they may be swung down out of the path of the welding unit. Welding unit. The welding unit carries five pairs of vertical electrodes 54, 55, 56, Fig. 18, two pairs of horizontal electrodes 68, 69, Figs. 5 and 18, and, at each end, work supports 43, Figs. 2 and 3, comprising four pairs of rollers 44, 45, 46, 47. The upper vertical electrodes are carried by the piston-rods of hydraulic cylinders 51, 52, 53 and the lower aligned electrodes are connected to hydraulic cylinders 51<SP>1</SP>, 52<SP>1</SP>, 53<SP>1</SP>. The inner electrodes of the pairs of horizontal electrodes 68, 69 are each mounted on the inner arms of pairs of yokes 63, 64 and the outer electrodes are mounted on the piston-rods of hydraulic cylinders 67 or 67<SP>1</SP> attached to the outer arms of the yokes; one pair of electrodes on each side'is at a lower level than the others. to give a staggered weld. The yokes are pivoted outside their centres of gravity on shafts 62 and when an outer electrode is retracted by its cylinder, the corresponding yoke pivots under its own weight until it meets a stop on the frame, thus withdrawing the inner electrode. A motor-driven pump 78, Fig. 2, on the unit supplies pressure to the cylinders. The electrodes on one side of the machine and the central electrodes 54, 541 are connected to a transformer 72 and a transformer 73 supplies the other electrodes. The pinions 27 engaging the racks 25 are mounted on shafts 81 geared to a transverse shaft 83 and, for step-by-step movement of the unit along the rails, a ratchet mechanism 96, 88 having a pawl member with a pair of pawls 97, is connected to a hydraulic cylinder controlled by a solenoid-operated valve 102. A gear 87 on the ratchet spindle is connected to a gear 84 on the shaft 83 through meshing gears 90, 91 on a lever 92 which can be set in three positions by means of a spring-loaded plug 93 engaging holes 94 on the frame. In the lower position of the lever, the drive is direct through the gear 90, in the mid-position, the drive is disconnected and, in the upper position, the gear 90 engages the gear 88 and the gear 91 engages the gear 84, to give a reverse drive. For rapid movement of the unit, the shaft may also be driven by a motor 105 coupled to it by a clutch 103 and a switch is fitted to cut out the motor if the lever is not in the mid-position. A squared end 85 on the shaft 83 also permits movement of the unit by means of a hand crank. Work-supports. Each work-support 29, Fig. 12, comprises a frame supported by a shaft 30 pivoted on the I-sections 24 and carries a pair of side supports 114 hinged on a vertical axis, a hinged upper clamp 117 and a centre support 112. For swinging each support down out of the way of the welding unit, a gear sector 124 is rotatably mounted on the shaft 30 and engages a rack 125 interconnected with similar racks for the other supports, all the racks being movable by a, single hydraulic cylinder 129, Fig. 1. Each support may be independently connected to its rack by a rod 132 moved axially by a square-ended operating shaft 135 into engagement with one of two holes spaced at 90 degrees from each other on the gear sector. When the support is in the upright position, the rod 132 is withdrawn from the gear sector and engages in a bracket 137 on an I-section 24, so that the support is locked upright. By setting the rack appropriately, with the gear sector disengaged from the support, one or other hole 136 is available for engagement with the rod 132 so that the support can be swung down to right or to left. Operation. Five cams 141-145, Fig. 18, on a continuously-rotating shaft 140 operate hydraulic valves which control the sequential operation of the hydraulic cylinders to move the electrodes into engagement with the work and, at the same time, cams 151-155 on the same shaft energize the appropriate electrodes through a timer 156. After a set of welds has been completed, a further cam 156<SP>1</SP> energizes the solenoid 102, causing the cylinder 100 to move the welding unit along by one step. The cylinder 129 for moving the supports 29 is controlled by four-way valves 131, one at each support station. To prevent the supply of current to electrodes which are either not yet in engagement with. the work or have passed beyond the end of the work, switches 157, 158, 159 are operated by cam surfaces 161 adjustably fitted on the ends of the rails 22.