GB645875A - Electric stud welding apparatus - Google Patents

Abstract

645,875. Electromagnets. ENGLISH ELECTRIC CO., Ltd. April 29, 1947, No. 11444. [Class 35] [Also in Group XXII] The piston 9 of a welding-machine has an annular energizing coil 10 fitted on a reduced part of the piston which when energized serves magnetically to hold the piston in its rear position against the action of a spring 8. An asymmetric distribution of the magnetic flux round the pole faces is produced so that the maximum density is at one side of the body and thus pulls the piston over against the body. This may be produced by forming a number of holes 11 substantially half-way round the flange of the piston so as to increase the reluctance of the magnetic circuit on this side, or by forming the reduced part of the piston eccentric to the pole faces or forming a part of the end flanges of the piston of reduced diameter or with a flat on part of the circumference, or by providing thereon an insert of non-magnetic material. In welding, the piston is pushed upwards against action of the spring 8, whereupon contacts 20 on the coil engage spring plungers 14, 15 connected to a timing device. When the tripod 3 engages the work a push-button 17 is closed and the timer 18 operates to energize the coil 10 and pass welding current through the stud to the work. After a predetermined short interval the coil is de-energized and the welding current flow stopped and the stud forced by the spring into contact with the work to effect the weld. The Provisional Specification refers to Specification 584,695, and Specification 645,903 also is referred to.