Patent GB-558359-A (GB)
Title: Improvements in or relating to switching systems for electric circuits particularly applicable to resistance welding and high frequency heating apparatus
IPC: B23K11/24
Filed: 1942-06-23
Abstract: 558,359. Supply systems for resistance welding, induction furnaces &c. ; electric discharge apparatus; converting. WESTINGHOUSE ELECTRIC INTERNATIONAL CO. June 23, 1942, No. 8627. Convention date, June 24, 1941. [Classes 38 (ii) and 38 (iv)] [Also in Group XL] Thermionic and like control.-A circuit between two terminals subject to varying voltage, such as 19', 20<SP>1</SP>, is closed at a definite proportion of that voltage by the controlled breakdown of a spacedischarge device such as 26, having a fixed breakdown voltage and consisting of two plate-electrodes 28, 29 of an alloy (such as iron-nickelcobalt), separated by an annular insulator 30, say 1 mm. thick and united by a ring of glass 31 to form a sealed vessel which is exhausted and preferably filled with suitable gas at low pressure such as 1 to 15 cms of mercury. According to Fig. 2 an alternating current generator 23 is connected to charge a condenser 14 during a portion of each half cycle determined by the adjustment of a tap 54 on an impedance 33 so that the fixed voltage at which device 27, similar to 26, conducts will be a predetermined portion of the maximum circuit voltage, the device 26 being prevented by its shunting impedance from completing the circuit until 27 had broken down. Similar means 58 may connect the circuit of a high frequency furnace across the condenser during each charging period when the condenser becomes sufficiently charged. Means similar to 25, 27, 33 may also be connected in the exciting circuit of an ignitron or of ignitrons reversely connected in parallel circuit with a welding transparent side as 15, Fig. 11, to obtain high frequency energization thereof from the condenser 14 at each charge thereof. A condenser such as 126 may shunt the discharge devices in respect of the high frequency current. A condenser such as 125 may replace one of the discharge devices and means other than 33 may control the voltage relation between that across the circuit terminals and that across the discharge device. In one form the device is connected across an adjustable inductance or condenser forming part of a series resonant circuit across the terminals; this may be used in combination with the variably tapped shunt 33. Two variable inductances or condensers may be connected each across one of two serially connected devices. The variable secondary winding of a transformer may be connected across a device in series with a condenser and in a parallel circuit across the terminals, a resistance in series with the primary winding of the transformer. Fig. 11 shows a resistance welding circuit in which a transformer, energized with a voltage derived from a phase shifting circuit 130 across the generator 23, has its secondary connected across a discharge device 124 so that when a short-circuiting control switch 117 is opened the alternating charges given to the condenser 14 may discharge at high frequency for portions of each generator half cycle determined by the transformer tapping or the phase setting through ignitrons 118, 119 and a welding transformer 15. A choke 24 limits the generator current during discharge of the condenser 14 and an inductance 22, 57, Fig. 2, may be used to determine the oscillation frequency.