GB545111A - Improvements in or relating to gas blast electric circuit breakers - Google Patents

Abstract

545,111. Automatic circuit-breakers ; gas-blast switches. BRITISH THOMSON-HOUSTON CO., Ltd. Aug. 27, 1941, No. 10919. Convention date, Aug. 28, 1940. [Class 38 (v)] A gas-blast switch wherein the blast is operative in both the opening and closing stroke, as in Specifications 541,165 and 1536/41, as open to inspection under Sect. 91, has means for independent adjustment of the duration and time of initiation of the blast during the two operations, whereby the most advantageous conditions may be obtained for each operation. The switch shown is of the crossblast type and has an arc-chute substantially as described in Specification 544,017, the blast-pipe. 19 being connected to reservoir 11 over a blastvalve 12 comprising also a pilot valve 59 and trip valve 60. Valve 59 is opened either electromagnetically by solenoid 63 ormechanically, in response to the closure of the breaker, by a linkage 83 ... 86, this linkage being also adapted to " take over " from the solenoid 63 when the opening movement of the breaker has commenced and opened contacts 90. The function of the latter is as follows. Just after valve 12 opens to provide the opening blast, valve 60 opens to admit gas to the pneumatic trip device 61 for the retaining latch 50 of the breaker, the connection including a further valve 93 opened by the solenoid 94 which is energized at the same time as solenoid 63. Since the valve 60 would also be opened under control of the closing movement of the breaker and would trip the latch 50 regardless of whether there was an overload or not, the solenoids 63, 94 are de-energized in all but the closed position of the breaker. The common operating rod 28 of all poles of the breaker is connected to, so as to rotate, a sector 65, Fig. 2, pivoted at 66 and carrying adjustable and inter-changeable closing and opening cams 70, 71 which cooperate with a cam-follower roller 73 on a lever 74. A pin 81 on lever 74 co-operates with cam surfaces 72a, 72b according as the breaker is being closed or opened, so positioning roller 73 for co-operating with cam 70 or 71, the lever 74 being normally centred by springs 77 about its pivot 75 on a rotatable U-shaped member 76 which is pivoted at 78 in a support 79. The arrangement is such that each time the roller 73 engages a cam 70 or 71 it rotates 76 clockwise against spring-action 80, as seen in Fig. 2, and, through universal joint 82 and linkage 83 ... 86, opens valve 59. The parts are shown in breaker-closed position and when 66 rotates counter-clockwise a cam 91 moves clear of contact 90 which is opened by spring 92. The breaker is closed by opening an electromagnetically-operated valve 58 to admit gas to a piston 34 the rod of which engages a roller 36 on a toggle 40, 41 to move it to the overset position shown, in which it is held by stop 53. The upper pivot of the toggle link 40 is held by a lever 42 pivoted at 43 and norinally retained by the pneumatically-trippable catch 50. The lower pivot of link 41 is connected to a lever 45 having a fixed pivot 46 and link-connected at 47 to a lever 26. This has a fixed pivot 26<SP>1</SP> and is pivoted to a floating lever 22a guided at 23a. in guides 24a and connected to the contact-rod 21a. A dashpot 54 and pad 25a cushion the opening and closing strokesrespectively. Rod 28 is pivoted to lever 26 and to a lever 27 which is pivoted to the lever 22b of another pole and. has a fixed pivot 27<SP>1</SP>, Lever 27 is acted on by an opening spring 29 and plunger 31, engaging roller 32, and by 'a balancing spring 30.