Patent GB-434071-A (GB)
Title: An improved apparatus for electric resistance welding
IPC: B23K11/31
Filed: 1934-12-18
Abstract: 434,071. Electric welding; electric switches; electric supply apparatus. BREGUET, L., 24, Rue George Bizet, Paris. Dec. 18, 1934, No. 36238. [Class 83 (iv)] [See also Groups XI, XXXV, and XXXVII] In an apparatus for electric-resistance welding of the kind in which the electrodes are connected to the secondary of a transformer, the primary of which is supplied with direct current and controlled by means so that electrical energy may be stored magnetically, a control means is provided which may be actuated so that welding current may be generated either by making the primary circuit or by breaking it or by alternately making and breaking it. A transformer having primary and secondary windings 3, 4 wound on a large core 2 has the movable and fixed electrodes 9, 10 connected to the secondary terminals. The electrode 9 is carried by a slide 16 linked to a beam 25, which is pressed down by pneumatic mechanism or, as shown, by a pedal 20 through rods 22, 23 and a shackle 24. The beam is pivoted to a slidable guide 32 and the electrode pressure is controlled by a light spring 18 and by a strong spring 28, adjusted by a nut 29. The primary circuit, which may contain an adjustable resistance 51, is controlled by a make and break switch 13 operated by an electromagnet 34 connected in shunt with the feed terminals 14, 15 and controlled by a normally closed automatic circuit breaker 36 through a control switch 35. The switch 35 has a movable arm 46 with brushes to connect either contacts a and band k and l, or c and d and i and j, or e and f and g and h, according to whether welding is to be effected by switching on and off the primary current once or several times, by switching on the primary current, or by switching off the primary current. In the first case depression of the pedal 20 first closes contacts 37 and then operates electrode 9. When electrode 9 engages the work the spring 28 is compressed and when the predetermined pressure of the electrodes on the work is reached the contacts 33 are closed so as to energize the coil 34 through 14, 37, 36, 34, k, l, 33, 15. The switch 13 is thus closed to complete the primary circuit and apply induced welding current. The coil 49 of circuit breaker 36 is energized by current shunted from the primary through 14, 37, 49, a, b, d, 50, 12, 15 and the circuit breaker 36 thus opened to open the primary. The coil 49 is thus again deenergized to allow the circuit breaker 36 to close again. In order that the weld may be completed in a given number of successive openings and closings of the circuit, the core of the circuit breaker has a pawl 39 which operates a toothed sector 40 step by step until the sector engages an angularly adjustable stop 45 which finally prevents the circuit breaker from closing. The sector is carried by a rod held by a spring 42 in contact with the end 38 of the pedal. When the pedal is released the spring 42 presses the rod down and the sector is reset by a lug 43 thereon engaging a fixed finger 44. With the control switch 35 in the second position, depression of the pedal closes the contacts 37, forces the electrode 9 against the work and when the desired pressure is obtained connects contacts 33 to close the primary circuit to effect the weld. The circuit of the coil 34, which is established through 37, 36, 34, k, i, j, l, 33, 15, however remains energized by current through 14, 37, 36, 34, i, j, l, c, d, 50, 12, 15 until after the electrodes have separated and the contacts 37 opened. With the control switch in the third position, depression of the pedal closes contacts 37, which immediately causes coil 34 to be energized through 14, 37, 36, 34, g, h, 15 to close the primary circuit. Further pressure causes the electrode 9 to be pressed into contact with the work whereupon, on the desired pressure being reached, contacts 33 are closed. The coil 49 is thus energized via 14, 37, 49, e, f, 33, 15 to open the contact breaker 36 and thus open the primary circuit to effect the weld. The contact breaker is held open by the pawl 39 and sector, which in this case is in engagement with the stop 45. The circuit breaker 36 is not closed until the electrodes are separated and the contacts 37 opened.