Patent GB-198985-A (GB)
Title: Improvements in centrifugally acting mechanisms for operating electric switches or circuit breakers
IPC: H01H3/26
Filed: 1923-01-01
Abstract: 198,985. British Thomson - Houston Co., Ltd., (Assignees of Walle, L. S.). June 8, 1922, [Convention date]. A u t o m a t i c circuitbreakers; electric motor and centrifugal actuation.- In order to effect the closure of heavy current circuit-breakers with a minimum of power, the closing means, which includes tripfree mechanism, is actuated by the movement of centrifugal weights speeded up by a small motor, the weights acting through toggle mechanism to give a firm closing pressure. As shown in Fig. 1, applied to an oilimmersed circuit - breaker, the circuit-breaker is held in the closed position shown by the link 6 having a slot in which a pin 26<1> carried by the operating crank 26 is adapted to move, but is held in the position shown by the trip-free toggle 7, 8 locked by catches 9, 10 and released on overload or other predetermined conditions by the electromagnetic responsive device 40. The operating crank 26 has a fixed pivot 27 and is jointed to a thrust-bearing coupling 20 at the top of a rotary operating spindle 15 the lower end of which has a cross-pin 16 guided in slots in a rotary head 14 connected by a thrust bearing 30, 36, 37 mounted on a bracket 13, with the shaft of a small motor 28 which may be of stock pattern. A pair of centrifugal weights 17, Fig. 6, is mounted on the pin 16 and constitute with the link 18 a pair of toggles, the upper ends of the links 15 being pivoted together at 19 to the rotating head. To close the circuit-breaker for the position shown in Fig. 7, the circuit of the small motor 28 is closed, causing the weights to fly out, lifting the spindle 15 and rotating the crank member 26 in the clockwise direction until, at a certain speed, the circuit-breaker is closed and the toggles 17, 18 assume an overset position limited by the engagement of projections 39 with the rotating head. This overset arrangement serves to maintain the switch closed against its normal bias to the off-position. In its closing movement, the spindle 15 opens, through links 46, 47, a small switch in the motor circuit to stop the motor. With the arrangement described, the electroresponsive trip controlled bv the toggles 7, 8 is self-resetting as the mechanism moves to the off position. In order to enable the switch to be closed again, at once, should it first be closed on overload or short-circuit, a braking surface may be arranged near the limit of outward travel of the weights so that they are stopped at once and fall when the circuit-breaker is tripped, thereby permitting the trip mechanism 7, 8 to re-set. When an instantaneous closure is required, as in synchronizing, the operating crank 26 is locked by an additional overset toggle 59, 60, Fig. 9, and, when the motor has been speeded up, the toggle is broken by hand-controlled electromagnetic means 62, as shown. The circuit-breaker may be operated. at need. by hand by means of a detachable hooked handle 56, Fig. 2, which engages with a pocket 55 in the operating crank 26, and the crank may be positively locked in the closed position by a pin on the frame passing into a hole in the crank. In a modified construction of eentrifugally-acting closing mechanism, weights 83, Fig. 17, pivoted at 84 constitute toggles with the links 85. One of the weights is capable of longitudinal motion on its bearing pin and, in the closing movement, inertia and air-friction cause it to bear laterally on a locking pin 89 and, at the limit of movement, the weight is held up by the pin, while at the same time one auxiliary switch in the motor circuit is broken and a second auxiliary switch in an alternative circuit closed. When the motor switch is reversed the weight is released from the catch pin and the circuitbreaker tripped. The application of the invention to an air-break circuit-breaker is shown in Fig. 14, in which the motor 28' is mounted on a trunnion, the toggle links 18<1> are biassed in the upset direction by springs 79, and the actuating member 74 has a catch 75 engaged by the latching member 76 to hold the switch in the closed position until the latching member is tripped.