Patent GB-619962-A (GB)
Title: Improvements in apparatus for electric arc welding
IPC: B23K9/20
Filed: 1946-05-17
Abstract: 619,962. Electric welding. ENGLISH ELECTRIC CO., Ltd., and BARLOW, K. F. May 17, 1946, No. 14916. [Class 83 (iv)] [Also in Group XXXV] A stud-welding gun comprises a housing into which the stud-holder is axially withdrawable against a biassing force by pressing the end of the stud against a plate, adjustable plate-engaging members on the housing for determining the inward movement of the stud-holder, an actuating member movable in the housing a predetermined distance towards and away from the plate, and electromagnetic clutch means operative to connect the stud-holder to the actuating member so that the latter retracts the stud from the plate. The housing 1, which carries a stirrup handle 3 provided with a welding control switch 4 and a supply cable 13, has a threaded end of reduced diameter to receive a tripod stand 5 with adjustable legs 6. Slidable in the housing is an insulated flanged sleeve 7 which is pressed upward by a spring 16 through an insulating ring, the sleeve carrying an electromagnetic clutch consisting of two C-shaped ferro-magnetic members 9, 10, with pole faces in sliding contact with each other and of which 9 is movable with the sleeve and 10 is free to move axially relatively thereto and is locked to the spindle 11 to which the stud-carrying chuck is fixed. The spindle is normally pressed by a spring 14 engaging a collar 15 thereon so that the stud projects beyond the ends of the legs 6. The casing is provided with a tubular part 19 containing an electromagnet for withdrawing an armature 20 from a hole 25 in the sleeve, the armature being normally pressed forward by a spring 21. In operation the sleeve together with the member 9 is first pushed down by a push button 24 against the action of the spring 16 and is held in such position by the armature 20. The gun with the stud in place in the chuck is then pressed against the plate to force the spindle inwards until the tripod legs contact the plate. The switch 4 is then closed to start the weld, whereupon the current through the spindle magnetizes the members 9, 10 so as to lock them to the spindle. A short time afterwards the coil 22 is energized to disengage the armature 20 whereupon the spring 16 moves the sleeve 7 with the parts 9, 10 and spindle until the sleeve engages an adjustable stop 18 so as to form an arc between the stud and plate. After a predetermined time the welding current is switched off, whereupon the members 9, 10 are demagnetized and the spring 14 moves the spindle forwards to press the stud on the plate to complete the weld. The members 9, 10 mav be laminated and in order to eliminate creep of the spindle relative to the member 9 with A.C. current, copper shading rings may be let into the pole faces of one of the members 9, 10. The member 18 may be provided with a gap filled with non-magnetic material such as brazing alloy, or the pole faces may be separated by a layer of non-magnetic material. The operation may be controlled by an automatic timer after hand operation of the switch 4 and the armature 20 may be arranged to operate a further switch in series with the switch 4 to ensure that the timing circuit is completed only when the armature engages the hole 25 in the sleeve. In a modification the electromagnetic clutch 26, 27 comprises a ferro-magnetic member 21 carried by the spindle 11 and having end flanges 26a, 26b constituting axially-separated pole faces, and carrying a magnetizing coil 28, and a member 27 movable with the flanged sleeve. If desired, the coil 28 may be de-energized just before the welding current is cut off, so that the stud engages the plate while the current is still flowing. The members have grooves on the surface of different pitch or one set may be a square-section helical thread. The grooves may be filled with non-magnetic material. The supply cable 13 is attached to the connecting lug 29. The gun, instead of being portable, may form part of a machine and be pressed down by a hand lever or pedal against the action of a spring or gravity, or may be raised and lowered by a fluid-pressure servomotor controlled by an operator's valve. Specifications 584,695 and 601,567 are referred to in the Provisional Specification. According to the Provisional Specification the spring 16 may be replaced by an electromagnet.