Patent GB-466967-A (GB)
Title: Improvements in and relating to electric circuit breakers
IPC: H01H33/985
Filed: 1936-02-03
Abstract: 466,967. High-tension switches ; automatic circuit-breakers. BRITISH THOMSONHOUSTON CO., Ltd. Feb. 3, 1936, No. 3226. Convention date, Feb. 1, 1935. [Class 38 (v)] In a circuit-breaker of the kind comprising fixed and movable contacts 15, 16 enclosed by walls of pressure resistant material forming a compression chamber, valve means are associated with the operating means for the movable contact for gas-tightly sealing the chamber when the movable contact is in the open position. In the construction shown, the compression chamber comprises a metal cylinder 14 with a fibre lining 17. The fixed contact 15 is secured in one end of the cylinder in a gas-tight manner by providing insulating bushings 18, 19 and a cup-shaped member 20 of soft copper arranged between a flange 21 on the contact 15 and an inwardlyextending flange on one end of the cylinder 14. On tightening up the nut 24, the member 20 is spread to form a gas-tight seal between the contact 15 and the liner 17. A corrugated insulating washer 25 is placed between the nut 24 and the end of the cylinder. The lower end of the cylinder is closed by a cylindrical cap 26 which is screwed into the cylinder, a sealing gasket 27 being provided. In order substantially to seal this end of the cylinder while providing for snapaction of the movable contact 16, flexible washers 29, 30 are provided, the washer 30 having an inwardly projecting cylindrical extension which exerts a wiping action on the contact 16. The valve for completely sealing the compression chamber when the movable contact is in the open position is formed by a shoulder 32 on the movable contact which co-operates with a conical valve seat 31 formed in the inner face of the cap 26 or in a separate member 33 supported by the cap. To provide a lost-motion connection with the operating mechanism to permit of snap action movement of the contact 16, a pin 67 under control of a spring housed in a chamber 71 in the stem of the contact extends through a slot in a block 70 rigidly secured to the stem and serves as the means of connecting the movable contact to the operating mechanism. Specification 420,042 is referred to. The Specification as open to inspection under Sect. 91 describes also operating and trip mechanism for the circuit-breaker. The operating mechanism includes a U-shaped operating member 53, Fig. 2 (Cancelled), which is pivoted at 50 and provided with a handle 55, a pair of spaced parallel arms 53 pivoted at 49, and a pair of triangular toggle links 54 pivoted at 51. The arms 52 carry an operating pin 58 which extends through slots 59 in the toggle links 54, and each of the latter is connected to a second toggle link 62 the other end of which engages a pin 63 carried by a member 64 secured to a pivoted cross-bar 65 which extends across the three poles of the circuit-breaker for simultaneously operating the movable contacts 16 between open and closed position. Overcentre springs are provided for making and breaking the toggles with a snap action. For automatic operation a U-shaped tripping member 80 is provided, the member 80 being pivoted at 50 and normally latched by the trip mechanism. The tripping member 80 is provided with a pair of extending fingers 82 which are adapted to engage the operating pin 58 and break the toggles under the action of springs 87 when the tripping member is released. The tripping member is reset by moving the handle 55 downwardly. The trip mechanism comprises a latch plate 93 pivoted at 93a, a U-shaped impact member 94 pivoted at 94a and a U- shaped reset member 95 pivoted at 95a. The latch plate is provided with a finger 96 arranged to engage the yoke portion 81 of the tripping member 80 in latching relation, and the impact member 94 is provided with an overturned part 97 engaging a portion of the latch plate. Springs are provided for operating the impact member and causing it to strike the latch plate a hammer-like blow to release the tripping member 80. The impact member is normally held in the position shown by a trip bar 103, which is adapted to be moved about its pivot 103a on overload either by the bending of a bimetallic element 106 carrying the current, or by the attraction of an armature 109 by a U-shaped magnet 108 which partly surrounds one of the conductors 39. This subject-matter does not appear in the Specification as accepted.