Patent GB-250583-A (GB)
Title: Improvements in electric welding machines and in methods of providing an electric current for welding purposes
IPC: B23K11/31
Filed: 1926-04-06
Abstract: 250,583. Leslie, F. H. April 11, 1925, [Convention date]. Inductor - alternators; rotary machines; producing short current impulses by means external to the machine. - An electric resistance welding machine consists of a rotatable member magnetically associated with a welding circuit so that when the rotatable member is magnetically excited its kinetic energy is transformed into a large momentary current in the welding circuit. In the form shown in Figs. 1 and 2, the rotating member is an H-shaped electromagnet mounted on a shaft 13 with its poles 16 rotating within a laminated yoke 19 and excited through slip-rings 23 from a generator 24 on the shaft. The shaft carries fast and loose pulleys 14, 15 and a heavy flywheel 25, the whole being mounted on pedestals on a stand 10 in which a treadle lever 36 is pivoted. Linked with the yoke is a single turn, constituting the welding circuit in which alternating current is induced bv the rotating magnet and composed of a conductor 26 attached at one end by a flexible strip 27 to the upper electrode bar 28 and at the other to a fixed copper block 33 on which the lower electrode bar 32 is adjustably mounted. The upper bar is insulated from and carried by a bracket 29, extensions 30 of which straddle the upper bar 28 and are journaled in members 31 extending from the yoke. Pivoted on the bracket 29 is an arm 39 carrying one member of a switch 44 in the exciting circuit of the dynamo 24 and normally drawn towards the bracket 29 by an adjustable spring 42. Depression of the treadle rocks the arm 39 and bracket 29 jointly about the pivots 30<a> and lowers the upper electrode ready to make the weld. Further depression of the treadle overcomes the spring 42 and closes the switch 44, thereby exciting the dynamo and rotating magnet and effecting the weld. The switch 44, as shown in Fig. 4, has two contact members 46, 47 pivoted on a base on the bracket 29 and normally held apart by a spring 48. The member 46 is also spring-supported at 49 and the member 47 has a lug 47b engaged by an operating-lever 50 pivoted on the arm 39. Upward movement of the arm 39 causes the lever to close the contacts and then ride over the lugs, allowing the contacts to open. When the arm 39 is moved downwards after the welding operation the lever 50 rides over the lug 47b against the action of a spring 53. Alternative arrangements of the machine are described in which the secondary welding turn is embedded in slots in a stationary magnetic yoke opposite the rotating magnet and in slots in a stationary yoke surrounded by a rotating magnet having internal poles. Also a form is described in which the welding turn and the exciting coils are both carried on a stationary core surrounded by a rotating iron ring having inner poles. Fig. 7 shows a form in which the turn 70 is linked with a stationary yoke 68 having an exciting coil 69, the flux pulsations being produced by an inductor 71 on the flywheel shaft. The yoke 68 may, alternatively, be of ordinary bipolar dynamo form with a plain bar inductor rotating in its bore. The switch 44, Figs. 1 and 4, may be in the circuit of the rotating magnet instead f the exciting circuit of the dynamo 24, and the magnet may be excited from an external supply instead of from a dynamo on the welding machine.