Patent GB-190708504-A (GB)
Title: Improvements in Multiple Switch Controlling Apparatus for Electric Circuits specially applicable to Motor Starters.
Inventor: BROOK PERCY SMITH
Filed: 1907-04-12
Granted: 1908-04-11
Abstract: 8504. Brook, P. S., and Hirst, J. A. April 12. Switches. - Multiple switch controlling apparatus particularly applicable to motor starters have their separate switches so articulated to a shaft adapted to close them consecutively that no switch except the first can be closed until the preceding switch is firs closed, each switch being closed in opposition to a spring and held closed by an electromagnet which is energized either when the operating- handle is held in its operative position or when the last switch is closed. Figs. 1 and 2 show the connexions diagrammatically when the automatic devices are on one pole and on two poles respectively. Fig. 3 shows an elevation, and Fig. 5 an end elevation on the line B-B, Fig. 3, of the device applied to a motor starter having automatic overload and no-voltage releases of the double-pole type. Fig. 6 is a detail view of the articulating means. The operating-handle G, which is pivoted at g<1> to a shaft H, is turned about its axis g<1> to depress a lever g<3> pivoted at g<4> against the action of a spring g<5>, whereby the handle contacts g are closed, and the windings a<1> .. a<5> of the hold-on magnets A<1>. . . A<5> are energized, the hand release contacts E and the overload contacts B being normally closed. If then the handle G is oscillated, the switches S<1> ... S<5> are closed consecutively until all the sections r<1> ... r<4> of the resistance R are cut out, and each switch will remain closed as long as the handle is depressed, or until the last switch S<5> closes the circuit of the magnets A<1> ... A<5> through a contact f independently of the handle contacts g, so that releasing the handle afterwards does not break this circuit. Should the current exceed a prescribed limit, the overload solenoid b opens the contacts B, thus opening all the switches; or, the same result is obtained by opening the hand release contacts E. Fig. 2 shows one switch Sx on the one pole and the other switches on the opposite pole. The winding b of the hold-on magnet A<x> of the switch S<x> replaces the overload contacts B, and a hand tripping-gear on the switch Sx replaces the hand release contacts E. The shunt winding M of the motor M
 is connected to the end contact c', and the winding u<5> is included in this circuit. When the switch Sx is closed by the first oscillation of the handle G, it connects the motor positive terminal T+ to the positive lead L+, and the next oscillation closes the switch S' and connects the motor negative terminal T- to the negative lead L-, and, as the hold-on magnet windings a<1> ... a<4> are energized through the handle contacts, g, each succeeding switch can then be closed in order. The hold-on winding a<5> being energized through the motor shunt winding M
 independently of the handle contacts g, after the last switch is closed the handle G may be released, whereupon the switches S<1> ... S' open ; the last switch, however, cuts out all the resistance. If the voltage fails, the switch S<5> opens the motor circuit ; and, if the maximum current is exceeded, the switch S<x> opens the motor circuit. A high resistance K may be used to connect the motor shunt winding M
 across the motor terminals irrespective of the resistance R. Switches of the type described in Specification No. 13,517, A.D. 1906, are preferably used with a series of levers L' ... L<5> fulcrumed on a spindle l carried by levers l<2> from the switch spindle N, the spindle l being oscillated from the shaft H by levers h and rods h'. The switches are put on by straightening a pair of toggles P<1>, Q<1> pivoted at p against a spring s. The toggle Q<1> is provided with a pin q adapted to engage the respective lever L to straighten the toggle-joint, which is then held closed by the engagement with the tooth d on the toggle of its detent D, if the latter is held down by its magnet A. Each toggle Q has a hold-off piece W ; thus W<2> is the hold-off of the toggle Q<2>, articulated to the preceding switch and threaded on the shaft N. Thus Fig. 5 shows the hold-off W<1> preventing engagement of the lever L' with the tooth q of the toggle Q<1> until the switch S<x> is operated, whereupon a pin v on its toggle moves the hold-off W<1> clear of the lever L'. When the switch Sx is closed, Fig. 3, the lever L<x> is prevented from engaging with the tooth q by the hold-off x sliding under the lever L<x> in the absence of frictional resistance to disengagement. The whole apparatus is enclosed in a casing 1, the contacts c<1> .. c<5> being carried by a bar 2, and the contact bar C by a bar 3, with mica insulations 2<a>, 3<a>. The switches have carbon sparking-tips 6. The overload magnet A<x>, Figs. 3 and 5, raises an adjustable plunger 7, which strikes a pin 8" a smart blow and releases the detent D. A hand tripping-pin 9 is also provided. The oscillating sbaft may be actuated electrically by a solenoid from a distance.