GB552608A - Improvements in or relating to electric circuit interrupters of the fluid blast type - Google Patents

Abstract

552,608. Gas-blast switches; actuation of switches; indicators for switches. WESTING- HOUSE ELEICTRIC INTERNATIONAL CO. Jan. 9, 1942, No. 363. Convention date, Jan. 25, 1941. [Class 38 (v)] A gas-blast switch having its contacts operated by fluidpressure motor under control of an operating valve, is provided with means dependent on the position of the blast valve for preventing the operation of the operating valve if the blast valve fails to function. The general layout, Fig. 1, comprises a framework 11 housing the control mechanism and tank 147, a container 19 for the operating fluid motor, and a disconnect switch 41 and gas-blast circuit-interrupter element 23 operated in sequence by the motor. The stationary contact 29 of the interrupter 23 is housed in an insulator 25 whereas a similar insulator 21 houses the movable contact 31 which, Fig. 3, is linked at 63 to a lever 59 pivoted at 61 to container 19 and at 73 to link 71 which in turn is pivoted to the rod 69 of the operating piston 65. The end of the closing stroke is cushioned by a dashpot 81 connected to lever 59 and having a ball valve 83 which is closed on the down stroke of the dashpot piston 79, the latter, on completing its movement, opening a valve 87 to prevent the entrapped air from reopening the switch. Pivot 61 also carries a crank arm 89 connected by levers 91, 93 to operate the shaft 95 of the disconnect switch 41. The latter comprises an arm 45 on shaft 95 pivoted at 43 to a member 97 carrying the movable blade contact 39. The sector-shaped end 99 of arm 45 has a spring-link connection 101, 105 with member 97 so as normally to cause the surface 109 to engage the sector 99 as shown in Fig. 2. When piston 65 rises to open the circuit, the first movement of shaft 95 causes the toggle 45, 39 to move upwards using the engagement with the fixed contact jaws 47 as a pivot and causing 39 to move longitudinally through the contact 47. When the pivot 43 passes over centre, the blade 39 moves to the left and leaves contact 47, whereupon spring 105 restores the parts to their original relative positions, and, in the full-open position. blade 39 engages a contact 111 to short-circuit the interrupter-contacts 29, 31. In the closing movement, the arrangement is such that the parts 39, 45 move rigidly and close just after the contacts 29, 31. The switch position is indicated by means controlled by an auxiliary switch 113 connected to the lever 59 by the lever-and-link system 115, 117, 119, 125, 127, 135, 137, 139, the rod 127, which is necessarily of insulating material, being kept always under tension by a spring 141 in a guide tube 143 coupled to an arm 145 on the shaft of cranks 119, 125. Blast-gas is supplied from tank 147 through insulators 13, 21 under control of a valve 155 operated through rocker arm 157 by a piston 161, air being admitted below the latter by way of passages 167, 171 under control of a valve 169 opened by electromagnet 173. In the event of failure of the latter, a latch arm 223 on the shaft 159 of the arm 157 remains over, and locks against movement, a lever 225, Fig. 7, connected to the switch-opening valve 179, so preventing the latter from opening. This valve and the closing valve 181 are generally similar in construction, the latter being shown in Fig. 7, and control the fluid supply through pipes 183, 191 in insulators 15, 17 to cylinder 67 above and below piston 65. The closing valve 235 is operated by a piston 241 which is engageable with the head of the valve-stem 237 and lowerable by fluid admitted under control of electromagnetically-controlled valve 243. A passage 247 is opened when the valve recloses, so as to exhaust the operating fluid from below 65. The opening valve 179 communicates by a pipe 257 with a cylinder 249 into which an extension 239 of stem 237 extends and which contains a further piston 251 slidable, like piston 241, on the stem. The surface of piston 251 is larger than that of 241 so that if both valves 179, 181 are conflictingly operated, the piston 251 overcomes 241 and holds valve 235 closed, thus ensuring the opening of the switch.