Patent GB-190904093-A (GB)
Title: Improvements in Multiple Electric Switches and Automatic Circuit Breakers, especially applicable to Motor Starters.
Inventor: BROOK PERCY SMITH
IPC: H02P1/06
Filed: 1909-02-19
Granted: 1910-02-21
Abstract: 4093. Brook, P. S., and Hirst, J. A. Feb. 19. [Cognate application, 16,678/09.] Automatic circuit-breakers ; mechanically-interconnected switches.-In multiple switches, such as motor-starters, the switches are closed in succession by means of cams &c. on a shaft, or on shafts geared together, some or all of them being retained closed by means which are released when a ' I no-volt' or overload device is operated, and one of the said shafts is rotated by a handle which, when released, returns, under the action of a spring, to one of its extreme positions, combined with means whereby, if this occurs before all the switches are closed, the ' no-volt ' device is operated. Fig. 1 shows a motor-starter with resistance switches R closed in succession by cams D on the shaft A, which is rotated by a rocking movement of the handle H and is provided with a ratchet-wheel G engaged by a pawl F to hold it against the action of the retracting-spring E, and circuit-breakers C, C' operated by a shaft S, which is driven from the shaf t A by a chain s'. The lastclosing resistance switch and the automatic circuitbreakers are constructed, as shown in Fig. 4, with a fixed renewable brush contact 3, a solid contact 2 on a pivoted arm 1, a pair of auxiliary sparking- contacts 4, 5 resembling spring buffers, and a blowout magnet with poles 8<a>. For large starters, all the resistance switches may be constructed in the same way. The pawl F, Fig. 3, is raised by the ' novolt' magnet V, a switch M' in the circuit of which. tending to be opened by the spring 16, is retained by a latch, which is displaced when struck by the released handle. If, however, the shaft has been previously advanced so as to close all the switches, an abutment 18 lies in a position to prevent the release. An alternative way of opening the novolt' switch by the released handle through levers and a compressible link is also described. The circuit-breakers C, C' are closed by cams and rollers N, Fig. 4, and are held closed by a latch Q, which is raised in the first place, along with the core of the ' no-volt' solenoid, by a cam v<2>, Fig. 3. The latch, as well as the pawl F, is subsequently held in place by the solenoid. An overload magnet w acts by opening the 'no-volt' switch M'. The arrangement of circuits is shown in Fig. 10, as connected up for starting a shunt motor Z. In a modification for stronger currents, the shaft A is unprovided with a retracting-spring. Arms having rollers transmit the closing effort successively to resistance switches through levers and toggle-links, and the automatic circuit-breakers are closed through the agency of chains s', and separate shafts with pawls arranged to become inoperative after the closure ; the no-load magnets V and detents Q then act to hold the switches closed. When the 'no volt' magnet fails, either as a consequence of diminution of current, or of the opening of the switch M' by the overload magnet or the released handle, the circuit-breakers alone open, the shafts remaining stationary. To re-open the resistance switches, a separate handle, previously inoperative, is turned, carrying back the shaft.