GB429183A - Improvements in or relating to electric welding apparatus - Google Patents

Abstract

429,183. Electric welding ; electric switches ; electric supply apparatus. HOLLAND, E. W., and CAESAR, T. W., 95, Kentish Town Road, HASELDEN, G. A., and TOOLS & MACHINERY SUPPLIES, Ltd., 54, Fetter Lane, both in London. Nov. 24, 1933, No. 32958. [Class 83 (iv)] [See also Groups XXXV and XXXVII] An electric spotwelding apparatus comprises a hand frame carrying electrodes with flexible leads connected to a source of current together with an operatoroperated switch for initiating the current flow and an automatic switch for breaking the circuit after a predetermined time interval. Small irregularly shaped articles such as dental plates may thus be welded. The electrodes 18, 19 are carried by insulating bushes and secured by screws in the split ends of a pincer-like hand frame 17. The flexible leads 15, 16 are connected to the terminals of the secondary 14 of a transformer, the primary 13 of which is connected to the supply terminals 11, 12 through a foot switch 33 and an automatic switch 31. The switch 31 is normally closed, but is opened after the desired interval by an electromagnet 34 connected through the switch 33 and in parallel with the primary circuit 13. The core 37 of the magnet, which is preferably arranged vertically, is normally urged downwards by gravity and by a spring. The switch 31 consists of a gapped rotary member 44 connected to the lead 30 and normally engaging a contact spring 45 connected to the lead 32. The member 44 is connected to the core by a rod 42 and crank pin 43. After the work has been adjusted between the electrodes the foot switch is closed to complete the welding circuit. At the same time the electromagnet is energized, thus causing the member 44 to be rotated by the crank pin to bring the gap 57 opposite the contact 45 and so to break the welding circuit after the desired interval. The electromagnet remains energized until the foot switch is released. The spindle of the member 44 is mounted at one side in a bracket 47 and at the other side in a slidable hollow rod 48 provided with a disc 51 and knob 50. A spring 53 separates the members 44, 51 and also resets the member 44, which has a stop 54 adapted to engage a stop 52 on the disc 51. In order to vary the duration of the current, the disc 51 has a series of holes 61 engageable with a peg 62 on the bracket 49 supporting the rod 48. Adjustment is effected by pushing forward and then rotating the rod 48 to required position, the rod being returned by the spring 53. Specification 397,157 is referred to.