GB166914A - Improvements relating to electric welding - Google Patents

Abstract

166,914. Longbottom, B., and Greenhalgh, E. Jan. 14, 1920. Heating by electricity.-A welding electrode is connected first to a circuit of comparatively high voltage and low current capacity for striking the arc and then either by hand or preferaby by an automatic switch to a second circuit of lower voltage supplying the welding current. Fig. 1 shows an arrangement of the circuits in which the change is effected automatically. The high and low voltage mains V<1> V<3>, V<2> V<3> may be supplied by a transformer T having two secondaries t<2>, t<3>, or by continuous current generators S, W. The work piece P is connected to the main V<3>, the welding electrode E being connected to the conductor 2 which is normally connected to the main V' to enable an arc to be struck when the electrode E and work P are brought into contact. This circuit is made through a solenoid a' and conductors 3, 4, 5, and a two-way switch A. The contacts a<2> of the switch A are normallv closed as shown on the left-hand' side of Fig. 1, but when the arc is struck the current in the solenoid a<3> raises the switch armature to close the circuit through the contacts a<5> and thus connect the electrode E to the main V<2> as shown on the righthand side of Fig 1. Instead of the two-way switch A, two separate contactor switches actuated by solenoids may be used, or foot or manually-operated switches may be employed. Fig. 3 shows an arrangement in which the current is automatically broken if a short-circuit occurs in the welding circuit. The electrode E and work P are connected to the high voltage mains V<1>, V<3>, and when the arc is struck the solenoid c<2> is energized, thus closing the switch I and energising the solenoid g<2>, and closing the switch G and opening the switch D<1>. The electrode E and work P are then connected to the low voltage mains V<3>, V<4>, the opening of the switch D' deenergizing the solenoid h<2> and opening the switch H. If the current in the welding circuit becomes excessive the overload solenoid k<3> opens the switch K and de-energizes the solenoid g<2> whereupon the switch G opens, switch D' closes, but the switch H remains open. The switch K remains open until the short-circuit is removed by d'isconnecting the electrode E from the work.