Patent GB-1449992-A (GB)
Title: Circuit breaker with resettable latch and trip means
IPC: H01H71/12
Filed: 1974-01-28
Abstract: 1449992 Circuit breaker latching mechanism WESTINGHOUSE ELECTRIC CORP 28 Jan 1974 [30 Jan 1973] 03819/74 Heading H1N A circuit breaker has a releasable trip member 61 latched into a latching device 67 which comprises interlocking latching members 101 and 117, held in the latched position by a third latch member 131, which can be tripped to effect unlatching of the device and release the trip member 61, thus tripping the over-centre spring- toggle mechanism 29, to open the circuit breaker. Fig. 1 shows the circuit breaker with the latching device in the latched position immediately prior to contact closure; whilst Fig. 4 shows the tripping device operated and the latching device in the unlatched position. The latching device comprises a U-shaped bracket 67 supporting pivot pins 103 and 123 for the latches 101 and 117, which each have spaced apart limbs joined by bight portions 107 and 121. The latch 101 is biased anticlockwise by spring 115, whilst latch 117 is biased clockwise by spring 158. Latch 101 carries a pair of outer rollers 113 for engagement in a notch 127 in each limb of the latch 117 and an inner roller 109 for engagement with the releasable trip 61 when the device is latched. Latching is effected by counter-clockwise movement of the circuit breaker handle 77 which moves an operating lever 69 having an arm carrying a pin 91 which engages a shoulder 93 of the trip member 61 to move it counter-clockwise from the position shown in Fig. 4, into and beyond, the position shown in Fig. 1. During this movement the end of trip 61 engages the bight portion 107 of latch 101 thus moving it clockwise until the roller 113 is in line with the notch 127, whilst the spring 158 moves the latch 117 into the horixontal position so that the roller engages in the notch. The tip of the trip member 61 is then latched by roller 109. At the same time the shroud 81 on the handle 77 engages a leg 163 of a T-shaped member 165, pivoted at 141 and having another leg 169, which is thus moved clockwise to press back the armature 148 of a magnetic trip actuator 147. This allows leg 133 of the third latch 131 to be moved clockwise into a vertical position where a projection 145 on the bight portion 121 of the latch 117 engages in an aperture 135 in the leg 133 to retain all three latches in position. The clockwise movement of the member 131 is obtained by a spring 160 which lifts the arm 137, and simultaneously lifts a pin 175 thus re-setting a screw-adjusted test button 179. Overload tripping is effected by a pulse from a current transformer 155 fed via a circuit board 153 to a magnetic actuator 147. This causes release of the armature 148 which is impelled by spring 149 so that the shoulder 150 strikes the leg 133 to unlatch the device and trip the breaker. The circuit breaker contact mechanism is of known type and comprises three pole units in a moulded casing with insulating partitions, the three contact arms 37 being linked by a bar 51 for simultaneous operation by a single actuating and tripping mechanism; arcing contacts 45, 25 and an arcing structure with magnetic plates 87 being provided.