Patent GB-912137-A (GB)
Title: Improvements in or relating to methods of and apparatus for electrical welding
IPC: C07D409/12
Filed: 1959-08-24
Abstract: 912,137. Welding by pressure. OMARK INDUSTRIES Inc. Aug. 24, 1959 [Sept. 8, 1958], No. 28839/59. Class 83 (4). In arc stud welding a stud to a workpiece a refractory ferrule surrounds the stud and the zone between the stud and workpiece in which the arc is struck, the ferrule having a smooth edge facing and spaced from the workpiece during the welding cycle. A gun G, Fig. 1, with a plastic or insulated metal casing 20 supported on legs 22 carrying from a support a ferrule F comprises a stud chuck carrying plunger rod 26 pressed downwardly by a spring 29 and a clutch assembly comprising a solenoid 21 fixed to the casing and an armature 28 fixed to the rod. The flat plate W is connected to one side of a supply S, e.g. a generator with a D.C. drooping voltage characteristic and the rod 26 is connected via a switch 35.2 to the other side of the supply and a control circuit E supplied from an A.C. source A is controlled by a switch 30 in the handle of the gun. In operation a welding stud w with a fusible tip t on a conical end face of the stud is inserted in the chuck and pressed on to the work to engage spacers 22 with the work, the ferrule, which is spaced from the stud by a gap h, Fig. 3a, being spaced from the work by a gap g. The operator presses the switch 30 and the solenoid is energized to attract the armature 28 and hold the rod and then welding current is switched on. The tip fuses and the arc forms and after a predetermined period the solenoid is de-energized and the spring 29 presses the stud into the workpiece. Subsequently the welding current is cut off. The gun which may be hand held or mounted on a rigid support may comprise three legs with adjustable extensions 73, Fig. 4, carrying a plate 75 having a ferrule holding copper sleeve 75. The armature 28 comprises radially movable keys or fixed rods and the solenoid 21 is mounted in and insulated from a magnetic circuit element 91, the welding current cable 101 being connected to the element 91 which is connected to the rod via a wire 105 and sleeve 106. The spring 29 rests between a holder 95 on the casing and a holder 96 adjustably mounted on the rod. In a modification the solenoid coil 121, Fig. 8, is mounted in a magnetic element 191 having an inner sleeve 191.1. The plunger rod 126 has fixed in a bore 126 therein a stainless steel or bronze tube 128 guided at its upper end by a stem 129 fixed to the housing and containing a spring 135. An annular conically recessed member 141 is fixed above the solenoid and a conical slotted sleeve 151 is slidable on the tube 128 in the member 141, being secured at its base to an armature plate 161. When the coil is energized the plate 161 is attracted downwardly to pull the sleeve down to grip the rod. The spring effect of the legs of the slotted sleeve moves the sleeve upwardly when the coil is de-energized. The stud may be of mild steel and its tip may be on a flat end face and if alternating welding current is used the tip may be of metal, e.g. titanium or aluminium dissimilar to that of the stud or a slotted tube of aluminium or an aluminium disc #1, Fig. 14, may be applied to the tip.