Patent GB-250937-A (GB)
Title: Improvements relating to electrical circuit-breakers
IPC: H01H3/60
Filed: 1926-04-12
Abstract: 250,937. Metropolitan-Vickers Electrical Co., Ltd., (Assignees of Aalborg, C., and Macneill, J. B.). April 15, 1925, [Convention date]. Automatic circuit-breakers; oil switches; arcrupturing devices.-Loose-handle automatic circuit-breakers having their relatively movable contacts capable of moving independently of the operating mechanism are provided with means for effecting the acceleration of the contacts as they approach their maximum separation. As shown in Fig. 1, the main and auxiliary movable contacts 13, 14 which co-operate with corresponding fixed contacts 11, 12 are mounted on the end of a vertically movable rod 15 which terminates at its upper extremity in a member 36 having a lateral recess in which is held one of the rollers 59 of a latching mechanism 16, so holding the switch closed against the action of springs 31, 32. The rollers 59 with spacers 61 are contained within a transverse tube 58 and are held in latching position by a member 63 pressed upwards by a spring 65 so that its end projects through the wall of the tube under the end of a tripping lever 76 which is biassed by a spring in an anti-clockwise direction. The latching mechanism 16 is supported by links from an actuating lever 45 which has one end pivoted at 49 and the other end connected by a link 46 to a crank-arm on the manually or motor operated spindle 47. The lever 45 is normally held by a spring-pressed detent 101. If the circuit-breaker is tripped either manually by a lever 82 operated by an external member 83 or electromagnetically by the core of the solenoid 72 the lever 76 is rotated against its bias to depress the member 63 so permitting the springs 31, 32 to move down rapidly the contact rod 15, forcing aside the ball 59 engaging the recess in its upper end 36. This downward movement is at first rapidly accelerated by the joint action of both compression springs 31, 32 until the shorter spring 31 has fully extended after which its downward movement is continued with decreased acceleration until the expansion of the spring 31 is prevented by the washer 32 at its lower end being held against the fixed shoulder 41. If the kimetic energy imparted to the contact rod is sufficient, the rod will continue its downward movement and by causing the enlarged portion 34 to engage the upper washer 29 causes further compression of the spring 31 to produce a cushioning effect. This effect is assisted by dashpot action between the rounded enlargement 26 of the rod 15 and members 109 surrounding it. During the downward movement of the contact rod 15 the enlargement 34 engages a projection 104 of a pivoted lever 103 which moves aside the detent 101 and allows the lever 45 to drop to the position shown in Fig. 3, during which movement the upper end 36 of the rod 15 is re-engaged within the latching mechanism 16 so that on movement of the operating mechanism to reclose the circuit-breaker the rod 15 is held by the latching mechanism and raised until the lever 45 is again latched in position. During the downward movement of the lever 45 the tripping lever and solenoid which is carried by brackets 72 also pivoted at 49 is moved around by springs to a limited extent so that in reclosure the tripping mechanism is always operable by overload to trip the latching mechanism and the circuit-breaker cannot be held closed while such overload continues. An indicator is operated by a switch 91 connected by mechanism to a pivoted bell-crank lever 95, the free end of which is held against the upper end 55 of a member 57 pressed by a spring 56 against the upper end of the contact rod. On release of the rod the member 57 moves between the rollers 59 and the indicator switch is then changed over by the spring 95. A magnetic blow-out consisting of an energizing coil 18 and a U-shaped core 19 is supported by a rod 22 adjacent to the circuit-breaker contacts, the whole, mechanism being disposed within the oil tank 10.