Patent GB-244744-A (GB)
Title: Improvements in and relating to electric cut-outs
IPC: H01H85/40
Filed: 1925-12-02
Abstract: 244,744. British Thomson-Houston Co., Ltd., (Assignees of Lincks, G. F.). Dec. 17, 1924, [Convention date]. Oil-switches; bases; contacts. - A fusible cut-out for protecting high capacity circuits comprises a closed tank A of heavy boiler plate nearly filled with oil or other arc-suppressing fluid, a shell or cartridge fuse B, and means C for raising the, cartridge out of the oil and lowering it again into engagement with its fixed contacts D. The cartridge B comprises a barrel 1 of horn fibre or other insulating material divided by a partition 4 into an explosion and spring chamber 5, 6, respectively, the partition being pressed against a shoulder 7 by a sleeve 8 which, with the barrel 1, is bored at 9 to permit the flow of oil while small holes 10 in the barrel allow slow ingress of oil to the explosion chamber 5. The partition 4 has an aperture 12 normally closed by a plunger 13 having a circular head 14 from which projects a semi-cylindrical part 15 co-operating with a similar part 16 to clamp the fuse link 11. The latter is a flat strip having one end straight, an adjacent reduced cross-section 23, and a head 22 which is passed through a keyhole slot 24 in the wall 25 of the end cap 2. Fig. 6, and secured in the slot portion of the keyhole against the tension of a spring 19. The thimble 26 is screwed against the head 22 to ensure good contact and, as shown in Fig. 7, the link may be reinforced with a steel wire 27. The spring 19 seats in a groove in the head 14 and behind a projection 20 on a thimble 20<1> screwed on the end cap 3, flexible shunts 21 between the thimble and plunger relieving the spring of heating effects due to current passing through. The tank is made so as to withstand explosive shocks and has a lid 28 secured by hinged bolts 29, the insulator bushings 30 for the connectors 31 extending through the walls and being secured by metal rings 32, cemented to the bushings, and bolts 33, with oiltight packing 34. The connectors 31 comprise metal shells 35 engaged by clamping rings 36 which screw on nuts 37 in turn screwing on conductors 38, which are connected to fulcrum blocks 39 for the contact D. The. blocks 39 have washers 40 receiving shunts 41 and between the washers 40 and shoulders 43<1> on the bushings 30 are packing rings 43 the whole being secured by screws 42. The contacts Dare formed as sheet metal jlates 47, to which are riveted stud brackets 49, the studs of which enter the blocks 39 and are cleft longitudinally to straddle the pins 46 which, with pins 50, allow limited universal tilting of the bracket 49. Springs 51 press the contacts D towards one another and, owing to shunts 41, are relieved of carrying current. The elevating means C comprise a rock shaft 52 provided with cranks 53 - - 55, of which 53, 54 are of insulation and carry U-shaped leaf springs 56 apertured at their ends to engage diametrical studs 57 in the end caps 2, 3. The shaft 52 is of insulation 59, as is also a bolt 58 connecting the cranks 53, 54:, to prevent their carrying arcing currents. The crank 55 carries a handle 60 movable therein under control of a helical spring 61 tending to move its tip 62 into locking relation with stops 63, 64 on the tank to retain the fuse in or out of engagement with contacts D. When the lid 28 is off, the fuse, may be swung over the top of the tank for replacement. The tank is lined with insulation 65 and carries cannisters 66 with packing rings 68 and sections 67 to be soldered to the cable, sheath. The top of the cannister is pierced to permit pouring in insulating material and stopper plugs 70 are then inserted, and a vent pipe 71 releives the tank of any gas pressure. On small overloads the tension spring 19 pulls the link 11 in case of a softening of the fuse metal, whereas on shortcircuit the gas pressure in the chamber 5 displaces the plunger 13 before the spring has time to act. As the arc approaches the aperture 12 in the partition 4, it is cooled and put out by the violent rush of oil, the oil acting likewise to cushion the explosion and relieve the barrel 1 from excessive shock.