Patent GB-667068-A (GB)
Title: Improvements in and relating to automatic electric circuit opening device
IPC: H01H71/44
Filed: 1948-11-26
Abstract: 667,068. Automatic circuit-breakers; protective cut-out arrangements. BRITISH THOMSON-HOUSTON CO., Ltd. Nov. 26, 1948. [Nov. 28, 1947] No. 30738/48. Class 38 (v). A number of sub-branches 62 of a distribution system are connected to a branch 61 which is in turn connected to a supply line, the branch 61 and each of the sub-branches 62 having a circuit-breaker 65, 66, these breakers being connected in series with a main automaticallyreclosing circuit-breaker, or multi-shot fuse contact, 63, which is opened on fault before the breaker in the faulty part of the circuit is opened, the main breaker then reclosing to restore the supply to the sound parts of the system. The breakers 76, 66 open in response to a different number of interruptions of the main breaker, so that only the faulty branch or sub-branch is cut out. Each breaker comprises a modification of that of Specification 650,509, the contacts being held closed by the engagement of the armature 29 in a space between a latch arm 52 of a notched disc 33 integral therewith. The disc 33 is urged counterclockwise, Fig. 3, so that the latch 52 abuts against a pin 53 which is adjustable into any of positions 53, 53<SP>1</SP>, 53<SP>11</SP> to vary the number of interruptions of the main breaker necessary before the release of the branch breaker. As shown, the pin is in position 53, thus making the breaker suitable for use in the supply line between the branch 61 and the main breaker 63, i.e. at 64. On a fault, e.g. at X in branch 61, the armature 29 of each of breakers 64, 65 is attracted and a spring-pressed pawl 30 thereon engages, and rotates, a ratchet wheel 32 fixed to the disc 33 so as to rotate the latter one step. As soon as the breaker 63 opens, the armature 29 drops and a projection 34 on a plunger armature 31 is moved to the right, Fig. 2, by a spring 35, so as to enter one of the notches in disc 33 and so prevent the disc from returning to its normal position. The breaker 65 is arranged to open on the second operation of main breaker 63 and, accordingly, the pin 53 is in position 53<SP>1</SP>, with notch 1 in disc 33 initially opposite the projection 34. As soon as breaker 63 re-closes, the armatures 29, 31 are attracted, the latter to disengage the disc and the former to move it on another step. This moves latch 52 from under armature 29 so that when the breaker 63 re-opens, the armature 29 drops to the Fig. 5 position and so opens the breaker 65. On restoration of the normal supply, plunger 31 is withdrawn and latch 52 returns to its initial position. The breaker is reclosed on removal of the fault by lifting the armature 29 to reclose the contacts and allow latch 52 to re-engage underneath it. In a modification, Fig. 9, the breaker is held closed by a lip 89 on a latch arm 88 engaging the armature 77. A second armature 94 carrying a pawl 98 is movable in a slot 74 in the armature 77 and is urged to the left by a spring 96. The pawl 98 co-operates with a ratchet 85 on one end of a piston rod 84 movable through a slot 97 in the armature 94. On overload, the armatures 77, 94 are attracted, the former to lift the ratchet against the pawl 98, and the latter to move the rod 84 to the right, by means of the ratchet, against the action of a spring 83 in a dashpot 76. The right hand end of rod 84 is thus moved towards or into engagement with an adjustable screw 92. When the main breaker 63 opens, the armatures 77, 94 are released, and the ratchet is disengaged so that the rod 84 moves slowly to the left at a rate set by the size of holes in a valve disc 82 thereon. The arrangement is such that the movement to the left before the breaker 63 recloses is not as great as that to the right. Consequently, one or more successive movements to the right, depending on the position of screw 92, cause rod 84 to push lip 89 from under armature 77, so that the breaker opens when the armature is released by its coil.