GB430023A - Improvements in or relating to electric welding machines - Google Patents

Abstract

430,023. Welding. HOLDEN, T. F., Cox's Lane, Old Hill, Staffordshire. Dec. 12, 1933, No. 34916. [Class 83 (iv)] In an electric welding - machine wherein the movement required to bring the electrodes into welding position and to apply the welding pressure is effected by the normally moving part of an electromagnet, the magnet is itself movably mounted against the resistance of a force applied thereto, which force is preferably adjustable and limits the welding pressure. The machine comprises a lever 4 pivoted to the frame 3 at 5 and acting on a slide 2 which carries the movable electrode 1, but in a modification the movable electrode is carried directly by the lever 4. A laminated armature 7 of an electromagnet is pivoted at 6 on the lever and is normally pressed by a spring 9 against an adjustable abutment 12 attached to a link 11 pivoted to the lever, the spring compression being adjustable by a nut 10. A keeper 16 for the magnet is also pivoted to the lever at 6 and carries a roller 20 engaging a slot 21 in the machine frame so that when the keeper is rocked towards the armature 7 it will act as a toggle to raise the right hand end of the lever and press the electrode 1 against the work. The roller 20 and slot 21 may be replaced by a toggle, crank, cam, wedge, &c., such as the toggle link 16<a>. The keeper 16 has a portion 17 concentric with the pivot 6 which moves over the curved portion 18 of the armature 7 to increase the power of the magnet and a stop may be provided to limit the outward movement of the keeper. The keeper may be returned to inoperative position by gravity or a spring. In operation, the magnet 7 is energized by means of a rotary switch 22<a> which may be operated by hand or foot for a single weld or may be driven by an electric motor and variable speed gearing for a series of welds. The keeper is rocked towards the armature 7 to press the electrode 1 against the work, first with a gentle pressure and finally with a strong pressure. When further movement of the electrode is prevented by the resistance of the work 26, the armature is rocked about the pivot 6 towards the keeper against the pressure of the spring 9, thereby closing a switch 15<a> to energize a solenoid-operated time switch 23 controlling the main switch 24 for the primary of the welding transformer 25. After a predetermined interval of time, varying from a fraction of a second to several seconds, the switch 23 opens the switch 24 to stop the welding current and the switch 22<a> is then opened to allow the parts to return to inoperative position. The pressure exerted by the electrodes on the work may be varied by adjusting the pressure of the spring 9 and by varying the number of turns on the electromagnet 7. The time switch may comprise clock-work, or an electric motor, &c., or alternatively the machine may be controlled by the amount of current flowing through the electromagnet 7 or the main welding circuit by means of an ampere, ampere-hour, watt or other power-factor meter carrying adjustable contacts acting either directly or through delayed operation devices on the electromagnet or primary or secondary transformer circuit. These controls may effect single spot welds or continuous intermittent welds for seams, in the latter case the machine remaining in operation so long as the current is switched on. For a very rapid series of welds, the time switch 23 may be short-circuited by a switch 27 so as to put the welding current switch 24 under direct control of the automatic switch 15a. The machine may be used for butt welding by substituting vice jaws for the electrodes, and for flash butt welding the current to the electromagnet 7 may be controlled automatically by means, such as a rheostat, so as to give the necessary movements of the work-pieces to and from each other in order to produce the flash.