GB557817A - Improvements in and relating to electric arc welding - Google Patents

Abstract

557,817. Control systems for welding arcs; regulating switches; control of D.C. motors. WILSON WELDER & METALS CO. June 1, 1942, No. 7385. [Class 38 (iv)] I[Also in Group XXXVII] To avoid crater formation the current in a welding arc is faded out by varying a resistance in series with the arc circuit and oppositely varying a resistance in parallel at the same time. Several welders may thus be operated from a common source. Fig. 7 shows a potentiometer 13 the movable tapping of which is coupled and connected to the movable tapping of a resistance 15 in series with the arc. A motor actuated, distant controlled regulator for this purpose comprises a rectilinear brush carriage 21 actuated by an endless chain passing over a sprocket driven by a reversible motor 46. The carriage 21 and a stop on the chain co-operate respectively with limit switches 53, 56 to prevent overrun of the carriage and with a further limit switch 59 cooperating with a second carriage 51 which defines the open circuit voltage of the arc circuit. The operator holds a housing 86 at the end of a cable 87 and by varying pressure upon a handle 88 he may selectively energize the motor 46 through limit switch 53 to restore the open circuit voltage fade out the arc at a desired speed or through limit switch 53 to restore the open circuit voltage to its predetermined value. This value is set by the position of the limit switch 59, carriage 51 being normally locked by a brake 69 ; by actuating a member 97 in either of two directions the operator may energize relay 81 or 82 to move this carriage to a position giving a lower or higher no-load voltage, a solenoid 67 being simultaneously operated to free the brake and couple the two carriages. A switch 68 is closed only when the solenoid operates.