GB828853A - Improvements in hydraulic operating devices for electric circuit breakers - Google Patents

Abstract

828,853. Automatic circuit-breakers; protective cut-out arrangements. ALLIS-CHALMERS MANUFACTURING CO. Jan. 16, 1957 [Jan. 23, 1956], No. 1639/57. Class 38 (5). A circuit-breaker has an hydraulic operating device comprising a piston 104 movable in a cylinder 106 in one direction under liquid pressure to close the circuit-breaker contacts and biased by a spring 110 in the other direction to return to its initial position and a motordriven pump 102 for supplying pressure liquid to the cylinder 106 through a pipe 108, the pressure liquid being directly returned to the pump through the same pipe upon de-energization of the motor when the piston reaches the end of a predetermined travel in the contact closing direction. To close the circuit-breaker a push-button switch 135, Fig. 5, is pressed to complete a circuit over contacts 125, 126 of a switch 121 and contacts 139, 140 of an " antipumping " relay 114 to energize the coil 116 of a relay 113 which closes its contacts 142, 143 to start the motor 101. The liquid under pressure supplied to the cylinder 106 forces up the piston 104 and piston-rod 109 which lifts a member 80. The end of a slot 83 in the member 80 moves a pin 82 on a pivoted trip bar 67 and causes the bar 67 to pivot anti-clockwise about a fixed axis 69 so that a cam surface 72 on the bar 67 acts on a roller 71 to close the circuit-breaker contacts (not shown). An arm 122 rigid with the bar 67 actuates the switch 121 as the circuit-breaker contacts close and a latch 57 engages a pin 66 on the bar 67 to maintain the circuit-breaker contacts closed. When the switch 121 is actuated it opens contacts 125, 126 and closes contacts 123, 124 to complete a circuit through contacts 144, 145 of the relay 113 to energize the coil 119 of the relay 114. This relay opens contacts 139, 140 to de-energize the coil 116 of relay 113 which opens to de-energize the motor 101. The spring 110 is then able to force the piston 104 down, returning the liquid through the pump 102 to the reservoir 103. The circuit-breaker may be closed manually by turning a handle (not shown) attached to a spindle 77 so that a cam 78 on the spindle acts on a roller 81 to raise the member 80. The operating and tripping linkage and the contact arrangement of the circuit-breaker are similar to those described in Specification 775,940.