Patent GB-1309289-A (GB)
Title: Electric arc welding apparatus having means for controlling the supply of weld metal
IPC: B23K9/127
Filed: 1970-06-15
Abstract: 1309289 Welding by fusion MESSER GRIESHEIM GmbH 15 June 1970 [13 June 1969] 28876/70 Heading B3R In an electric arc welding apparatus the rate of supply of welding metal to a weld gap is controlled by signals derived from sensing means which respond to variations in weld gap dimension. As described and shown in Fig. 1, a roller 10 on a lever 12 runs along one edge 13 of the joint, pivoting of the lever 12 being used to move the wiper 17 of a variable resistor 18 whereby the electrode feed motor 22 is controlled to increase or decrease electrode feed rate. The resistor can equally be in circuit to control a parameter of the welding circuit, or the speed of advance of torch 16. Alternatively, resistor 18 can be replaced by a. variable inductor or capacitor which is used to vary the wire feed rate and/or welding current and/or welding voltage and/or speed of advance of torch 16. In a second embodiment (Fig. 2, not shown), in which welding is performed overhead, the sensing roller engages a deposited weld bead. The pivoted lever provides wipers for a respective one of two resistors (28, 29) the former being in the circuit of the wire feed motor while the latter is in circuit with the welding current source. The latter may be a constant potential rectifier with transductor current control, and a rectifier with electromechanical current control. In a third embodiment (Fig. 3, not shown), the sensing roller is on a vertically-slidable pushrod (30) and the torch is carried on a carriage (33) which rides on rails parallel to the joint. The speed of the carriage motor is controlled in dependence upon the position of a push-rodoperated wiper (36) of a resistor (37). In a fourth embodiment (Fig. 4, not shown), a pair of spaced sensing rollers (39, 40) on a common shaft are intended to run along respective joint flanks. The rollers are spring-urged apart and mounted on a carriage (42) which runs on wheels on the workpiece surfaces. Affixed to one roller is a resistor (48) whose wiper (49) is on the other roller; alternatively, the resistor and wiper can be on respective ends of the spring (41) between the rollers. The resistor is in circuit with the wire feed motor. In a fifth embodiment (Fig. 5, not shown), respective ones of a pair of sensing rollers are mounted on respective inclined shafts (52, 53) having a lower common pivot (55). The shafts are supported by a wheeled carriage, and their upper ends define respective resistor wipers of resistors in circuit with the wire feed motor. In the embodiments described above, the resistor(s) can, alternatively, control the speed of advance of the torch. Also, they can be used during overhead welding or for vertical welding, e.g. in welding of tanks. Welding is by the automatic MIG process. In other embodiments (not shown, nor described in detail), the circuit element, e.g. resistor, capacitor or inductor, controlling a parameter which will affect the metal deposition, can be in a bridge circuit of which the differential voltage is used to effect the desired control; the resistor, capacitor or inductor can have a non-linear characteristic; and the sensing rollers may be replaced by capacitative and/or inductive sensors which detune the frequency of an HF transmitter circuit whose frequency is used to effect the desired control.