Patent GB-534501-A (GB)
Title: Improvements in and relating to gas blast electric circuit breakers
IPC: H01H33/91
Filed: 1939-11-03
Abstract: 534,501. Valves. BRITISH THOMSONHOUSTON CO., Ltd. Nov. 3, 1939, No. 29318. Convention date, Nov. 3, 1938. [Class 135] [Also in Group XXXVII] The movable contact 2, Fig. 2, is held closed against spring-action 10 by a latch 25 connected by trip mechanism 12 to a piston 13, which is maintained in the closed position shown by gaspressure admitted to cylinder 14 through a pipe 29 and a manually or remote-controlled valve 15. The remote end of cylinder 14 is closed by a valve V held against its seating 35 by a spring 36, the valve V having a bleed hole 34 whereby the space beneath it is normally at the same pressure as the cylinder 14. When the switch is to be opened, a solenoid 31 energized from the line transformer 30, opens a valve 33 and exhausts the space beneath the valve V, whereupon the pressure in 14, acting on the shoulder of V, opens the blast passage 4 to the contacts, the piston 13 being also driven by its spring 16 to sustain the blast. The piston rod 20 is connected at 19 to a crank 17 which has a fixed pivot 18 and has pivoted to it at 23 a trip magnet 21, its armature 22, and the latch 25, which lies a pin and slot connection 28 with the armature. A spring connection 24 biases 21, 17 apart to a limited extent, and a similar one 27 biases the latch 25 outwards into latching position. When the trip magnet is energized, with a slight time-delay, the latch is lowered to release contact 2, and the movement of 13 causes the trip mechanism 12 to swing bodily clockwise into a position in which the latch again engages behind the contact rod 11, and at the same time the valve 15 is automatically closed by means not shown. When 15 is opened again, the piston 13 is moved back and rotates the mechanism 12 clockwise, so reclosing the switch, in which position a valve-seating 131 prevents leakage of gas past the piston. In the open position both contacts 1, 2 are in pockets 7, 8 providing special outlets for metal vapour given off from the contacts, and ensuring that the minimum amount of such vapour is present in that part of the arc subject to the blast. The arrangement is also such that the maximum blastvelocity is at the mouth of the arc-splitters 6. In Fig. 3, the movable contact 2 is held closed by gas-pressure acting on piston. 8 and opened when the pressure is released to provide the blast. Pressure is admitted behind the piston by.means of a valve 15 which comprises parts 15a, 15b separated by a reduced part 15c. To close, therefore, a solenoid 19 is energized by a push-button 20 and moves the valve to the left against spring action 21, so placing the supply 14 in communication with the piston 8 through a non-return valve 18. The parts 15a, 15b act as pistons which are held by the gas-pressure in the displaced position after button 20 is released. When the switch is to be opened, solenoid 25 restores the valve 15 to the position shown, in which the chamber 16 beneath valve 12 is exhausted at 26. The pressure in conduit 11 then opens the valve 12, as in Fig. 2, and the spring 7 opens the contact and supplements the gas blast due to the pressure in the conduit. Specification 334,321, [Class 38 (v)], is referred to. The Specification as open to inspection under Sect. 91 also included a double-break arrangement of contacts, each break having an arcchute and being actuated from a common blast-producing piston, Fig. 3 (Cancelled, not shown). This subject-matter does not appear in the Specification as accepted.