Patent GB-682564-A (GB)
Title: Improvements in or relating to automatic electric circuit breakers
IPC: H01H71/44
Filed: 1950-12-06
Abstract: 682,564. Automatic circuit-breakers. WESTING- HOUSE ELECTRIC INTERNATIONAL CO. Dec. 6, 1950 [Jan. 28, 1950], No. 29833/50. Class 38 (v) The tripping time of a circuit-breaker is controlled by a time delay element comprising a chamber having a number of valves, of which one is arranged to admit air to the chamber at a certain rate so as to produce a certain delay, whilst the additional valves are automatically operated in accordance with the current to increase the rate of fluid flow so as to reduce the delay. The contacts 23, 33, 25, 35 are normally latched by underset toggles 83, 85 and 85, 87 which are retained, the one by a link 101 pivoted at 103 to a lever 99 retained by a roller 111 on a lever 105 which is latched by a part 115 on a lever 117, and the other by a support 131 pivoted at 107. Tripping is produced automatically on overload by upward movement of a trip rod 199 which engages an adjustable screw 127 on the lever 117, which is thereby tilted counter-clockwise to release the lever 105, and, consequently, lever 99, thereby allowing collapsing of the toggle 83, 85 by spring 57. An ear 153 eventually moves the support 131 from under the pin 93 of the toggle 85, 87 which also collapses under the action of a spring 129 and a weighted armature 171 pivoted at 93. The toggle 83, 85 is reset during this latter movement and the latches 99, 105, 115 are restored. The lever 117 may alternatively be moved manually to trip by rotation in one direction of a cam 149 on a handle shaft 137 which is normally centralised by a spring 145. The trip coil 189 acts on an armature 191 slidable on a sleeve 205 surrounding the trip rod 199, the force of the armature being transmitted through a spring 209 to the sleeve 205 and then through a washer 207 to the rod 199. The latter carries at its lower end a sleeve 231 secured to a member 225, between which and a member 227 is clamped a diaphragm 213 in a chamber 215. The space above the diaphragm is at atmospheric pressure, the time delay being the time taken for air to be admitted to the space below the diaphragm, and three inlet valves are provided, viz. a long time delay valve 235, a short time delay valve 237, and an instantaneous valve. The valve 235, Fig. 2, comprises a conical seating 241 formed on the housing part 219 and surrounded by a metal member 243 moulded into part 219 and threaded internally to receive a member 245 co-operating with the seating 241. The gap between members 245 and 241 is adjustable by means of a knob 249 biased against a flange 247 on the member 245 by a spring 251 and having serrations 263 co-operating with some on the member 245. The outer edge of knob 249 co-operates with a flange 255 on the part 219 to support a filter 257, through which air passes to a groove 259 in the part 245, and then through the space between parts 241, 245, and through a bore 261 to the under-side of the diaphragm 213. Rotation of the knob 249 is limited to about 360 degrees by a pin 265 on the knob engaging a pin 267 on the part 219, the knob being held in adjusted position by a spring pawl 271 engaging serrations 269 on the knob. The valve 237, Fig. 4, comprises a part 281 with a tapered end 285 and slidable in a sleeve 273 having an axial passage 283 co-operating with the end 285, and an enlarged head 277 with bores 287 the passage 283 being connected to the upper-side of the diaphragm 213 over a passage 289, and the bores 287 being connected to the under-side of the diaphragm over a passage 291. The part 281 is actuated to the open position by an armature 293 which is biased downwards by a spring 294 and upwardly by the trip coil 189. The armature 293, carries a bracket 299 having a D-shaped hole 303 engaging a notch 305 in the part 281, which has a D-shaped head 307. The hole 303 and head 307 are normally out of alignment but can be brought into alignment for removal of the valve. The amount of opening of the valve is limited by the engagement of the end of the armature 293 with a stop 311 formed on an S-shaped member 309 adjustable by means of a screw 315 and carrying a pointer 337 co-operating with a scale (not shown). The instantaneous valve 239 is operated by an armature 375 and is similar to valve 237 but the tapered portion 285 and the stop 311 of the latter are omitted. The operating currents of the armature 293, 375 of the valves 237 and 239 are varied by adjusting the tension of springs 294 by screws 395, 397 co-operating with non-rotatable members 391, 393 having pointers 401, 403. The armature 191 is biased down by springs 405 which act on a member 407 pivoted in grooved studs 409 and engaging in a groove 413 in the armature. The tension of the springs 405 is adjustable by a screw 417 engaging a non-rotatable member 415 having a pointer 412. The time delay element may be adjusted so that on overloads up to 500 per cent or 600 per cent of normal current only the valve 235 is open, on overloads between 500 per cent or 600 per cent and 1,000 per cent, the valves 235 and 237 are open, and of 1,000 per cent or more, all the valves are open. The contacts may be reclosed by manual or automatic energisation of a coil 175 to cause upward movement of the armature 171 so as to reset the toggle 85, 77, the support 131 being restored by its spring 133. Alternatively, the cam 149 may be rotated in the direction opposite to that for tripping so as to engage a cam 95 on the link 87, so that the toggle is reset.