Patent GB-560726-A (GB)
Title: Improvements in or relating to methods of and apparatus for electric resistance welding
IPC: B23K11/24
Filed: 1942-11-21
Abstract: 560,726. Welding cans &c. CARTNER, J., and STUCHBERY, A. L. Nov. 21, 1942, No. 16490. [Class 83 (iv)] In resistance welding the seams of sheet metal articles such as cans &c. for foodstuffs, drums &c. by means of electrodes arranged in pairs, the electrodes are applied to the seam simultaneously so as to hold the articles in welding position, and the welding current is passed through the seam at right angles to its length from one electrode of each pair to the other electrode of said pair, each pair of electrodes being energized in sequence through a separate circuit individual to each pair, while carrying out the welding operation by means of all the electrodes simultaneously. Square cans or drums made in halves connected by two diagonally opposed longitudinal lock seams have their seams spot welded by placing them over an electrically conductive mandrel 2 with their seams in contact with opposite sides thereof and welding is effected by three pairs of electrodes 6, 6a, each pair being connected to the terminals of the secondary of a separate transformer the primaries of which are connected to the respective phases of a three phase current supply. The electrodes 6, 6a respectively weld spots on the upper and lower seams and the work is then fed along to a new position and another set of welds effected. The mandrel, which is of copper, is of skeleton form with upper and lower bars 2a in sections separated by insulation 3 and electrically connected in pairs by members 4. The electrodes are carried by plungers 7 connected to one end of levers 10, 10a, which are pivoted at 11, 11 a and connected at their other ends by rods 14, 14a, respectively to pneumatically operated cylinders 15 and pistons 17 so as to move the upper and lower electrodes in opposite directions The cylinders are provided with ports 20, 20a connected to a valve so that either end may be connected to supply or exhaust. In a modification each rod 14, 14a may be provided with a separate piston reciprocated outwards pneumatically in a fixed cylinder and returned pneumatically or by springs. The transformer secondaries 21 are disposed axially of the pairs of electrodes, the middle one being arranged on the upper electrode plunger and the outer ones on the lower electrode plungers, so that the electrodes may be spaced close together. When 'making continuous welds the reciprocating electrodes are replaced by roller electrodes, the mandrel being provided with rollers co-operating with the electrode rollers. When making continuous welds on a single seam, roller electrodes, electrically connected as above, are used, the rolls of each pair engaging opposite sides of the seam. Flanged ends may be similarly welded by roller electrodes in the ends of cylindrical drums, the pairs of electrodes, electrically connected as above, being spaced 120‹ apart round a circle having a diameter equal to that of the drum. The electrodes are carried by pneumatically operated pivoted arms. After the seam is welded solder may be applied between the welds to' ensure a complete seal.