Patent GB-709165-A (GB)
Title: Improvements in or relating to electric circuit breakers
IPC: H01H33/32
Filed: 1952-06-13
Abstract: 709,165. Automatic circuit-breakers. WESTINGHOUSE ELECTRIC INTERNATIONAL CO. June 13, 1952 [June 21, 1951], No. 14942/52. Class 38(5) A circuit-breaker has both trip-free and non-tripfree latch means so that it may be tripped either by the trip-free latch means permitting the " breaking " of a main toggle interconnecting the movable contacts and a power operating means, or by the non-trip-free latch means releasing the mechanism so that the circuit-breaker opens with the main toggle set, selecting means being provided to select one or other latch means for operation by a common trip coil. In Fig. 2 the moving contact-member is biased towards the open position by a spring 13 and is connected to an operating piston 23 by linkage including the main toggle links 33, 35 which have pivots 37, 39 guided for vertical linear movement in a frame 47. The links 33; 35 are pivoted together and to a tripping toggle 73, 71 at 41. This tripping toggle comprises a link 73 pivoted at 83 to a link 71 having a fixed pivot 79, and is normally maintained in the underset position shown by the trip-free latch 75. The circuit-breaker is maintained closed by the tripping toggle holding the main toggle 33, 35 set and by a main latch 51 engaging a member 59 carried on the piston rod 25, the latch 51 being normally maintained in latching position against the upward thrust of a spring 147 by the non-trip-free latch 76. When the latch 76 is moved aside by the action of the trip coil 95, the upward thrust of the spring 147 forces the main latch 51 out of engagement with the member 59 and the springs 13, 147 open the circuit-breaker, the main toggle 33, 35 being maintained set by the link 73 which pivots about the spindle 83. When the trip-free latch 75 is turned anticlockwise about its pivot 85 by the action of the coil 95, the tripping toggle 71, 73 is released and collapses so permitting the main toggle to collapse as shown in Fig. 7, the spring 13 causing this collapse and opening the contacts. During this opening motion, a projection 155 on the latch 75 engages and moves the latch 76 to its unlatching position, the spring 147 then forcing the latch 51 aside and moving the piston 23 and rod 25 upwardly. Since the pivot pins 37, 39 are constrained to move in a straight line, the upward movement of the link 33 causes the link 35 to turn anticlockwise about its pivot 39 to reset the main and tripping toggles. The choice of the trip-free latch 75 or non-trip-free latch 76 is made by means of a selector-bar 101 which may be axially positioned so that a projection 137, Fig. 1, engages an arm 86 of the latch 76 or a projection 141 engages an arm 119 of the latch 75, the tripping of the chosen latch being effected by the plunger 99 of. the coil 95 raising the bar 101. Normally the bar 101 is positioned as shown in Fig. 1 so that tripping is controlled by the non-trip-free latch 76 and a rapid reclosing operation may be effected. When the circuitbreaker is being closed and pressure fluid is applied to the cylinder 17 by means of a solenoid-operated valve assembly 195, a small piston (not shown) in the valve assembly turns a lever 121 against the bias of a spring 135 to position the selector-bar 101 so that the projection 141 is moved below the arm 119 of the latch 75. This enables the circuit-breaker to be tripped out by the latch 75 in a trip-free manner whilst the cylinder 17 is charged with pressure fluid so preventing non-trip-free tripping. A latch checking switch 113 is operated by the arm 119 of the latch 75. The valve assembly 195 also includes a main piston-operated inlet valve, a dump valve, a throttle valve which reduces the flow of pressure fluid to the cylinder 17 during the initial part of the closing operation, and a solenoid-operated pilot control valve, Figs. 4, 5 and 6 (not shown).