Patent GB-160768-A (GB)
Title: Improvements relating to electric welding
IPC: B23K11/26
Filed: 1921-02-26
Abstract: 160,768. Metropolitan-Vickers Electrical Co., Ltd., (Assignees of Chubb, L. W.). March 23, 1920, [Convention date]. Valves.-Valve heads and stems are electrically welded together by magnetically storing a predetermined amount of electrical energy and discharging the same by the passage of an electric current through the parts and then causing a percussive engagement of the parts. The parts may be connected to the secondary terminals of a transformer or to the ends of a reactance, the primary circuit of the transformer or the reactance being connected to a source of direct current, an arc being produced between the parts by a current induced in the transformer secondary or the reactance when the primary current is cut off. In the machine shown, which is for welding two wires 11, 21, the part 21, which may rest on the base 1 during welding, is mounted in a chuck, the lower part 16 of which is secured to the base and the upper portion of which is secured to a forked rod 17 pivoted at 20 and raised by a solenoid 18 against the action of a spring 22 to bring the parts 11, 21 into contact. When welding a valve the chuck holds the stem of a cup-chuck which receives the valve head. The part 11 is secured to an impact member 6 provided with plates 7, 8 guided on rods 3 secured to and insulated from the table 2. The plate 8 carries two sets of adjusting screws 12 which rest on a pair of plates 13 mounted on springs 14, so as to support the impact member resiliently. A second impact member 23 with guide plate 24 is carried by a rod 25 sliding through an adjustable spacing member 5 and is held in raised position by a pivoted latch 29 engaging an adjustable stop 28 on the rod 25, the latch forming the armature of an electromagnet 31. This member also carries a projecting strap 33 for operating the switch 32 to cut out the primary circuit of the transformer. U-shaped members 34 are provided to couple the members 23, 6 together when it is required to raise the member 6 to remove the finished work. The primary 47 of a transformer which is supplied with current from a direct current generator 42' with series field winding 43 and shunt field winding 44 in series with a variable resistance 45, has a hand switch 46<a> and a relay switch 46, which is operated by a solenoid 51 connected to the primary through the switch 32. On putting in the switches 46<a> and 55 the solenoid 31 is energized so that the latch 29 may maintain the member 23 in raised position. Current also passes through the solenoid 51 to actuate the switch 46- against the action of its spring 53 so as to put in the primary current. At the same time a switch 52 in the circuit of the solenoid 18 is closed by its spring 54 and the part 21 raised into contact with the part 11. On cutting out the switch 55, the latch 29 allows the member 23 to drop. In its motion it cuts out the switch 32, thus releasing the switch 46 to cut out the primary. A current is thus induced in the secondary 48 which. starts while the parts are in contact. The switch 46 then operates the switch 52 to open the circuit through the solenoid 18, so as to allow the spring 22 to separate the parts. An arc is thus formed by the current induced in the transformer secondary. The member 23 then strikes the member 6 which is forced down to complete the weld. Thearc may be established by movement of the upperinstead of the lower part.