GB249232A - Improvements in electric switchgear - Google Patents

Abstract

249,232. Cox, F. B.. Dec. 29, 1924. Automatic current-breakers. - An electric switch, particularly suitable for use as a motorstarter, comprises a primary arm and one or more secondary arms mounted on the same or adjacent axes, each secondary arm being connected to the primary arm by a spring which, when the primary arm is swung into position, pulls the secondary member into making or breaking position when released, or given an initial movement, by an automatic no-volt or overload device. Fig. 1 shows a simple form of the switch, the full lines indicating the " off " position. When the primary arm A is moved in the direction of the arrow 4, the spring S crosses the common axis C and draws up the secondary arm B to close the contacts E. The arm is held in this position by the no-volt device F which will prevent breaking the circuit when the arm A is moved back, until the arm B is released by the no-volt device. In the form shown in Fig 3A, the arm A is held in the position in which it " makes " the contacts D, by a catch a<3>, the spring S failing to cross the axis C to pull down the arm B until the overload device F<1> imparts an initial movement to the arm B. Fig. 4 shows a simple form of motorstarter. The arm A is swung downwards to " make " the starting contact D where it is retained by the no-volt device F<2> against the returning spring S<1>. This causes the spring S to cross the axis C, and after a predetermined time the no-volt device F ceases to function, allowing the arm B to be pulled down to complete the running circuit at E<1> and " break " the starting circuit at E. The no-volt device F<2> then ceases to function and the arm A is returned to its initial position by the spring S<1>, the spring S re-crossing the axis C and pulling up the arm B to its initial position when the running circuit is no longer required, a no-volt device (not shown) holding the arm B in position. Fig. 6 shows an arrangement wherein both arms A and B co-operate with two contacts D<2>, D<3>, E<2>, E<3>, D<2> and E<2> are connected in series to one of the two circuits to be controlled, and D<3> and E<3> are connected in series to the other. In the form shown in Fig. 9, the arm A is operated by a handle H<1> mounted on the common axis C and connected to the arm A by a toggle T, T<1>. When the handle is swung to cause the arm A to " make " the contact D, the spring S crosses the axis C and the spring p<4> crosses the axis p<2> on which is mounted a striker P. The handle is held against the return action of the spring S<2>, by the catch p'. When the novolt device F releases the arm B, the spring S pulls it away from the contact E to the contact E'. When the no-bolt device p<5> ceases to function, the spring p<4> rocks the striker P which collapses the toggle T, T' and releases the catch p<7> to be pulled back by its spring p<9>. The spring S<2> then pulls the arm A away from the contact D to its initial position. In addition to the above applications of the switch to motor-starters having single-starting and single-running positions, the device may be used with a rheostat D<6>, Fig. 10.