Patent GB-191005765-A (GB)
Title: Improvements in Electric Motor Starting and Controlling Apparatus.
Inventor: HIRST JOHN ARTHUR
IPC: H02P1/20
Filed: 1910-03-08
Granted: 1911-04-10
Abstract: 5765. Hirst, J. A., and Brook, P. S. March 8. Automatic circuit - breakers; switches, interlocking.-A double-pole " no-volt " release circuit-breaker is mechanically interlocked with a rheostat arm, and excess current devices are provided for de-energizing the no-volt circuit. The main current is completed between terminals a<1>, a<2>, Fig. 2, when eccentrically pivoted disks c<1> are rotated to engage rollers c<2> on the ends of double - pole switch - arms a<3>. Each arm is pivoted at a<7>, is connected by a strap a<4> with the terminals a', and is maintained against a contact a<5> on the other terminal a<2> by a magnet E<2>. An auxiliary renewable carbon contact b<2> takes the spark at the break and is arranged between the cheeks b<1> of a blow-out magnet B. The handle shaft c<4>, Fig. 1, is connected to the shaft of the disks c<1> by means of a pin c<5> on a crank on the shaft c<4>, which engages with a gab lever c<6> on the shaft c<3>. When the handle has been operated to close the main switch, it is returned to the " off " position by a spring c<7>, the switch remaining held on by the magnet. The switch is interlocked with the rheostat arm by means of a vertically movable rod s<4>, which is connected above to one end of a lever s<5>, and abuts below on one arm s<1> of a bell-crank lever. The other arm s<2> of the bell crank is hooked and engages a projection s<3> on the handle shaft when the rod is maintained in the raised position, thus preventing the main switch handle from being moved to complete the circuit. Assuming the rheostat arm D to have been returned to the " off " position illustrated in Fig. 1, the rod-maintaining quadrant d' on the arm will have disengaged a hook s<15> on the lever s<5> and a spring s<6> will have pulled down the rod s<4> and tripped the bell-crank rocking-lever. The handle C is then free to throw the main switch while the hook s<15> locks the rheostat arm. The resetting-spring c' for the handle moves a projection s' to raise the rod s<4> and allow the rheostat arm to cut out the resistance. The rheostat arm has an auxiliary spring-bow end contact d<3> to take the spark against roller contacts d<4> connected to the main contacts d. Specification 1491/08, [Class 37, Electricity, Measuring &c.], is referred to. Electro-magnetic switches with optional hand actuation. An overload relay device for breaking the " no-volt" circuit consists of a strip f connecting contacts f<2>, f<3>, and raised to break the circuit by an overload magnet f<1>, or, when desired, by pushing a hand button f<4>. Thermal switches.-A thermal device operated by excess current to open or close a circuit consists of contacts g<2>, g<5>, Fig. 4, which are connected to a conducting bridge g<4>. A screw g<6> can be adjusted in the bridge by means of a handle having a pointer g<7> travelling over a graduated scale g<8>, thereby varying the distance of the screw point from a bowed strip g<1> which carries the main current. The curvature of the bowed strip is increased by an excess current, the strip finally making contact with the screw. By reversing the curvature of the strip and threading the circuit through the contacts g<2>, g<5>, the strip may be arranged to break the circuit. Cut-out arrangements. - The " no-volt " coil of the circuit-breaker is controlled by the electro-magnetic and thermal overload devices above described. A moderate overload acting for a given time causes the thermal device to open or short-circuit the " no-volt " release, whereas a heavy excess current causes the electro-magnetic device to act immediately and open the " novolt " circuit.