Patent GB-736090-A (GB)
Title: Improvements in or relating to electric circuit breakers
IPC: H01B3/16
Filed: 1952-05-20
Abstract: 736,090. Gas-blast switches. WESTINGHOUSE ELECTRIC INTERNATIONAL CO. May 20, 1952 [July 19, 1951], No. 12716/52. Class 38 (5). Arcs in a circuit interrupter are extinguished by a forced flow of a medium consisting at least partly of sulphur hexafluoride (SF6). This medium may be used with any suitable interrupter and several forms are described. In one form, Fig. 3, an explosion chamber 104 is arranged within a sealed casing 108, both being filled with the gas. The moving contact 110 cooperates with an intermediate contact 129 on a spring-urged rod 111 which is pivoted at 113 to a contact 114 pivoted to the chamber 104 at 114A. When contact 110 is withdrawn, contact 114 follows to draw an arc between contacts 114 and 115 until a stop 119 engages a barrier 128, at which point a series arc is drawn between contacts 110, 129. The first arc creates a pressure in sub-chamber 122 which passes to sub-chamber 130 to extinguish the second arc. If, on high-current interruption, the pressure is too great, a plunger 121 is depressed against spring pressure, thereby moving a contact rod 127 towards contact 114. The first arc is therefore transferred to rod 127 and is thereby shortened to reduce the pressure. A second multi-break arrangement is shown in Fig. 4, wherein the first arc is formed between contacts 141, 142 and the second arc between 138, 139, contacts 138 and 142 being attached to an operating member 135, contact 142 by way of a pantograph or lazytongs 137. The blast produced by pressure in chamber 132 passes through a vent 150 across the second arc and exhausts through a valve 134 which with low-currents is opened by cam 147 on a rod 148 attached to member 135, or by the blast itself with high currents. In a single-break arrangement, Fig. 6, a piston 47 is attached to the moving contact rod 24a and is movable in a fixed cylinder 37. The moving contact 43a is resiliently mounted in a cylinder 56 attached to the piston head 58 and extends towards an orifice member 50 forming an extension of the piston. Contacts 43a, 44 are enclosed by member 50 when closed, and upward movement of contact 43a with the piston causes a gas blast down through the piston and orifice to extinguish the arc. In a modification (Fig. 2, not shown), the moving contact is rigidly mounted on the piston. In a cross-blast arrangement, (Fig. 5, not shown), the gas is supplied from a reservoir and passes through an arc chute into an enclosure from where it is pumped back to the reservoir through a cleaner. In an axial-blast arrangement using a reservoir, (Fig. 7, not shown), the moving contact is mounted on an actuating piston which is moved by the blast to separate the contacts and open an exhaust vent leading to a cooler, a cleaner and a chimney. The invention may also be used with a single-break explosion pot breaker, (Fig. 1, not shown), or a breaker with a magnetic blow-out and arc chute. In order to prevent the production of acids by combination of arc-released fluorine and hydrogen released from resinous insulation, the latter is replaced by polymers such as polytetrafluorethylene or polychlorotrifluoroethylene. The sulphur hexafluoride may be mixed with one or more of the following gases : air, nitrogen, hydrogen, argon, helium and carbon dioxide.