Patent GB-461699-A (GB)
Title: Improvements in and relating to electric liquid-blast circuit breakers
IPC: H01H33/92
Filed: 1935-08-28
Abstract: 461,699. Liquid - blast switches. BRITISH THOMSON-HOUSTON CO., Ltd. Aug. 28, 1935, No. 24079. Convention date, Aug. 28, 1934. [Class 38 (v)] Automatic circuit-breakers ; electric motor actuation ; springs, arrangement and dispoeition of.-In a circuit-breaker including separable contacts and a piston for directing arcextinguishing liquid between the contacts on separation thereof, a single operating means, effects separation of the contacts and a working stroke of the piston, and a retarding driver decelerates the movable contact after predetermined contact-separation without affecting the working stroke of the piston. The fixed contact 4 co-operates with a tubular movable contact 3 passing through an insulating baffle 12 in a metal container 5 filled to the level shown with oil or other arc-extinguishing liquid. When 3 moves upwardly to open the circuit, oil is forced over the break-space, through the contact 3 and out of ports 14 therein The blast is produced by a piston 6 normally urged upwardly against a plate 7 by means of a spring 8 surrounding the rod 10 and bearing on the plate 7 and on a flange 9 on the rod. Free movement of oil is permitted by aperture 15 and ports 71, 61 in the plate 7 and piston 6, respectively, except during the blast-action when a simple disc valve 16 closes the ports 6<1>. The operating rod 19 of contact 3 is connected to a lever 34 having a fixed pivot 35 and a link connection 33 with a floating lever 30, which is in turn pivoted at 29 to a lever 26 having a fixed pivot 27 and acted on by a compression-spring 22. The lever 30 also has a pin 36 engaging a slot 37 in rod 10, and a pin 31 or roller releasably engaging a trip latch 32 under control of an overload coil 46. Due to the engagement between 31, 32, the spring 22 acts on lever 30 in a counterclockwise direction and through link 33 causes 3 to be held in fast engagement with 4, Fig. 1. When the latch 32 is tripped on overload, however, the spring 22 causes 30 to rotate clockwise about 36, which, owing to inertia of the piston 6 and oil, becomes a momentary fulcrum, so that the contact 3 rises until a slot 41 in a link 38 connected to lever 34 engages a pin 40 on an arm 39, which is pivoted at 45 to an oil-dashpot housing 44. The plunger 42 has a through-bore 43 and a notch 42<1> engaged by an extension 391 of lever 39, so that when 40 is engaged by 41, the piston 42 is slowly depressed and declerates the contact 3. At this point the fulcrum of 30 may be regarded as having moved to the yielding pin 33<1>, so that the spring 22 now acts through pin 36 to drive the piston 6 downwards and drive oil across the separating contacts, Fig. 2. To reset the parts ready for reclosure, spring 22 is compressed by means of a pitman 55 which is pivoted to 30 at 56 and has a roller 54 engaging slot 52 in a cam gear 50 driven by motor 23 in a clockwise direction. The end 52<1> of the slot pulls on the pitman 55 in a direction tending to keep the pin 33<1> raised, and swings the lever 30 counterclockwise thereabout. The motor 23 is de-energized at the top dead-centre position of pitman 55. in which position, Fig. 3, the spring 22 is compressed, the spring 8 has restored piston 6 to its upper position, and roller 31 is above the latch 32. To reclose, the motor is again started and moves 55 past the dead-centre position, so that spring 22 acts to move 31 into engagement with 32 and lever 30 is caused to rotate counterclockwise about 31 and depress the rod 19. The closing action is retarded by the return of the dashpot piston 42 to the initial position.