Patent GB-692095-A (GB)
Title: Automatic control for electric welding
IPC: B23K9/133
Filed: 1950-02-20
Abstract: 692,095. Automatic control systems for welding apparatus. UNION CARBIDE & CARBON CORPORATION. Feb. 20, 1950 [March 11, 1949], No. 4352/50. Class 38 (iv). [Also in Group XXIX] An electrical welding control system including a rotary compressed-air motor for feeding an electrode to the work, and a valve, responsive to the welding voltage for controlling the supply of air to the motor, is characterized in that the valve is a sliding piston valve for controlling the amount and direction of air through the motor to retract or advance the electrode to maintain the welding voltage at a substantially constant value. As shown in Fig. 1, a compressed air motor M drives a rodfeeding device F, which feeds welding rod R through a nozzle N towards the work W. The motor is controlled by a slide valve T interposed between an air supply valve A and the motor. The slide valve .T comprises a hollow piston 15 slidable in a stationary sleeve 16 having ports 17, 18, 19 in communication with the supply valve A. Circumferential grooves 20, 21, 22 are provided on the piston 15 for conducting air to the motor inlets 23, 32. Thus, when the piston is moved to the left, air flows to motor inlet 23 causing forward drive of the motor and when the piston is moved to the right, air flows to the motor inlet 32, causing reverse operation of the motor. The position of the piston is controlled by a diaphragm D and solenoid B, air being conducted by port 18, groove 21 and central bore 27 to the right-hand side of the diaphragm, the lefthand side being spring biased. The pressure allowed to build up on the right-hand side of the diaphragm D is controlled by a solenoid operated needle valve 33 which when retracted allows air to flow to exhaust valve K. As shown in Fig. 3, the solenoid is connected so that the movement of the armature carrying the needle valve is dependent on the voltage and the welding arc. The valve T is therefore positioned so that the motor M is operated in a direction to reposition the work to maintain the welding voltage constant if any deviation from a predetermined value as set by resistance 39 (Fig. 3) occurs. A contact switch J in series with a starting relay 37 controls the welding generator 38 supplying conductors 10 and 12. An inching button switch G is in series with the operating solenoids of the air supply valve A and exhaust valve K. The two operating coils of the solenoid B may be connected in series for D.C. operation and in parallel for A.C. operation. To start the weld switch G is closed, opening valve A and causing forward drive of motor M until the rod makes contact with the work when switch G is relea ed, valve A is closed, and the motor stops. Switch H and switch J are then closed, opening both valves A and K, and closing the welding current circuit by operating starter relay 37. This raises the top of the rod from the work W producing an arc and automatic control occurs. To stop, the welding switch H is opened, thereby closing valves A and B and stopping rotation of the motor M. The piston 15 returns to reverse position and depression of switch L ensures an air supply for retraction of the rod R. Specification 601,466 is referred to.