| 摘要 |
<p>638,132. Air-break switches. BRITISH THOMSON-HOUSTON CO., Ltd. Nov. 29, 1945, No. 32287. Convention date, Nov. 30, 1944. [Class 38 (v)] In a fluid-blast circuit-breaker, fluid-actuated arcing contacts 2, 3 reclose once before the series isolating switch 4, 5 is opened, previous. opening of the latter being prevented by energization of a coil 63 which shuts off the opening blast, a time delay device 66 causing the blast valve 18, and thus the contacts 2, 3 to reclose. On a fault, the valve 18 is opened by a coil 32, and the arcing contacts 2, 3 are opened. Simultaneously, the coil 63 is energized, thereby blocking a conduit 59 and preventing the exhausting of a cylinder 50 and movement of a piston 49 to permit the supply of fluid to an isolator-operating piston 40. Fluid also acts on a piston 79 having an annular recess 89 and a central bore 88, so that the pressure builds up before the piston moves downwards against the action of an adjustable spring 85. This causes counter-clockwise rotation of a cam-shaft 84, so that a cam 100 acts on a roller 102 to open a switch 67 in the circuit of the coil 32, thus shutting off the blast and allowing the contacts 2, 3 to reclose. Further movement of the camshaft 84 opens a switch 69, 74 to de-energize the coil 63, and then closes a switch 68, 76 to provide an alternative circuit for coil 32 and cause re-opening of valve 18 if the fault persists. In this latter event, the circuit is again broken at 2, 3 and fluid is now supplied to the piston 40 to open the isolator 4, 5. Movement of the rack 42 opens a switch 70 and again de-energizes coil 32. The spring 85 returns the device 66 to the position shown, and the arrangement is such that the switches 68, 69 are restored simultaneously with the switch 67. A manual switch 73 can be changed over to provide the normal arrangement wherein the contacts 4, 5 open every time contacts 2, 3 open. The downward movement of the piston 79 may be intermediately retarded by providing an accumulator chamber 92. A similar chamber 93 ensures an adequate gas supply to ensure completion of the operation of the time delay device 66. Switches held set and freed mechanically.- Opening of the switch 69 is caused by a cam surface 112 acting on a roller 111 on a rocking cam 105 which is pivoted at 106 and bears on a roller 108. The surface 109 of cam 105 holds 69 in its new position while allowing a considerable reverse movement of cam 110 before the cam surface 113 engages a roller 115 on the cam 105.</p> |
