Patent GB-455406-A (GB)
Title: A method of and apparatus for welding together parallel tubes, rods, and the like
IPC: B23K11/06
Filed: 1935-12-11
Abstract: 455,406. Welding parallel tubes etc.; annealing. HEILBUT, M. H., Kennan's House, Crown Court, Cheapside, London.-(Bundy Tubing Co. ; 4815, Bellevue Avenue, Detroit, Michigan, U.S.A.) Dec. 11, 1935, No. 34308. [Classes 83 (ii) and 83 (iv)] [See also Groups II and XI] In a method of welding together parallel tubes, bars, &c., which expand differently when heated, the tubes are pressed between welding electrodes and one of them is maintained in a distorted or stressed condition in advance of the electrodes so that the differential expanding actions will be counteracted and the tubes will assume a predetermined shape on cooling. In a machine for welding a petrol feed pipe to a petrol-gauge pipe for motor vehicles, the base 1 carries welding electrodes 2, 3 whereof the latter is freely rotatable on a fixed axle and the former on an axle which is raised by a spring and fed downwards by a pneumatic cylinder 5 supplied with air by a pipe 8 and a foot-controlled valve 7. The tubes A, B to be welded together are supported in a trough 25, the lower tube being of larger diameter than the upper one and the electrodes having large and small grooves to correspond. Each electrode has a number of grooves, as shown in Fig. 3, so that they may be moved axially to present fresh grooves when one has worn, the upper electrode having four narrow grooves and the lower electrode two wide ones. The electrodes are cooled by a water supply 10 which falls on the upper electrode and collects in a trough 11 provided with an overflow pipe 12, the lower electrode dipping in the trough. A guard 13 prevents water from falling on the tubes A, B before they reach the electrodes. Welding current is supplied to the upper electrode by a laminated conductor 14, Fig. 3, and returns through the lower electrode to the frame of the machine. The tubes A, B are fed between the electrodes by means of a rack 28 carrying a bracket 26 provided with slots to receive the tubes and recesses to accommodate nipples &c., on the ends of the tubes. The rack is actuated by a pinion 36 driven by a chain 38 from an electric motor 19. In operation, with the electrode 2 raised and the motor 19 at rest, a pair of tubes A, B is placed in the bracket 26 as shown in Fig. 1, with a separator 47, Fig. 5, between them. This separator is carried by a rod 48 having a collar thereon for engagement with a bracket 49 on the plunger 4 of the cylinder 5. The pedal 9 is then depressed to supply air to the cylinder 5 and the plunger 4 and electrode 2 descend, the plunger carrying rollers 16, 18 with it to close switches 15, 17 and energize the welding circuit and motor 19 respectively. The rack 28 feeds the tubes between the electrodes until its motion is arrested by a wedge 45 thereon riding under a spring-pressed block 46 carried by the plunger 4 and simultaneously a spring plunger 40 on the rack actuates a counter 42 and a roller 22 actuates switches 20, 21 to de-energize the motor and welding circuits. During downward motion of the plunger the separator 47 descends and bends the lower tube A as shown in Fig. 5, so as to stress this tube and allow the united tubes to remain straight on cooling. The pedal 9 is then released to raise the electrode 2, the welded tubes are removed to a trough 43, and the motor reversed by a push button 51 until the roller 22 actuates a switch 23 to break the motor circuit. A push button 52 allows the motor to be stopped at any time. When the motor circuit is broken, a solenoid 59 is de-energized to allow a spring to apply a brake 56 to the motor shaft. When alternating current is used, the tubes may be " stitch " welded together. Annealing. The heat of welding anneals the major portion of the smaller tube B, which has been produced by drawing and is thereby hardened, but the projecting ends B<1> of this tube which have not been welded are annealed in a separate apparatus. In this apparatus the welded tubes are placed on an insulating table, and clamps are applied to the projecting ends B<1> of the tube B. The two terminals of a transformer secondary are connected to the clamps and a current is passed through the tube, the unsupported ends being heated sufficiently to anneal them whilst the major portion is maintained cool by the increased conductivity of the attached larger tube A. The movable portions of the clamps are spring mounted within hinged covers which are pressed down on the tube ends by the operator and carry the switches for closing the transformer secondary circuit. The tubes may be of steel made according to Specification 359,731 and both tubes may be distorted in advance of the welding electrodes.