GB394758A - Improvements relating to electric spot welding machines - Google Patents

Abstract

394,758. Welding-machines. DORRAT, J. A., 9, Kenwood Road, Stretford, Manchester, and ASSOCIATED ELECTRICAL INDUSTRIES, Ltd., Crown House, Aldwych, London. Feb. 23,1932, No. 5436. [Class 83 (iv).] A multiple spot-welding machine, particularly for use in the manufacture of meter box parts, is provided with electrodes 1, 2, 3, Fig. 3, which can be moved simultaneously to operative position towards a fixed set of electrodes 1a, 2a, 3a and retained there during the welding operation by a rotary cam 4 which is actuated by a continuously operated electric motor 29 through a magnetic clutch 30. Engagement of the clutch and the motor is effected initially by means of a push-button 44, Fig. 1, or other manual or pedal device, and thereafter maintained automatically by an electric switch 39-41, which is closed by the action of a cam 37, until the main cam 4 has rotated through 345‹. The welding circuit is established and maintained during rotation of the main cam through 270‹ by the action of a cam 38 on contacts 40, 42, the latter energizing a coil 46 adapted to close the main contact 45 of a welding transformer 35. When the welding circuit is broken, the cam 4 exerts an increased force on the movable electrodes to upset the weld and then permits their withdrawal to inoperative position under the action of springs, whereupon contact of a braking device 43 with the retracted clutch 30 brings the cam to rest after one complete revolution. The duration of the weld can be adjusted by providing a rheostat 48 to vary the speed of the motor or by adjustment of the ratio of gearing between a constant speed motor and the cam shaft. The welding current mav be varied by adjusting the voltage tap of the welding current transformer to accommodate different thicknesses of work. The movable electrodes may be subjected to the same predetermined pressure by interposing spring-loaded plungers 19, 20, 21, Fig. 3, between the electrodes and the cam 4. In a modification, Fig. 5 (not shown), a combined multiple electrode is moved towards a set of fixed electrodes by similar means.