GB520830A - Improvements in or relating to closing mechanism for electric circuit-breakers - Google Patents

Abstract

520,830. Automatic circuit-breakers; actuation of switches. REYROLLE & CO., Ltd., A., and CHRISTIE, J. Sept. 29,'1938, No. 28298. [Class 38 (v)] Closing mechanism for a breaker comprises a gravityinfluenced inertia device operatively connected to the breaker-moving parts to close or assist closure, and means for disengaging or rendering ineffective such connection when the breaker reaches its closed position and allowing the device to continue to move and so gradually dissipate its surplus energy. The mechanism provides a smooth closing action not only against the blow-out forces produced by closure on a fault-current but also when resistance is small, as when the breaker is tripped during the closing action. The shaft 10 is connected through holding and tripping mechanism to the movable contact (not shown), and released to close by rotation of shaft 12. The shaft 10 carries a crank 17 which is connected by a toggle 18, 19 to one arm 16 of a bell-crank which is pivoted at 15 and carries a weight 13 on the other arm. In the open position of the breaker, Fig. 1, the links 18, 19 are just over the dead-centre and the line of the toggle is remote from pivot 15 and relatively near to the shaft 10, whereas when the weight 13 has moved the parts to the closed position, Fig. 2, the line of action is at right-angles to crank 17 and in line with arm 16. The torque is thus progressively applied to shaft 10 and is a maximum at the closed portion where the blow out forces are largest, whereas the rate of movement of the shaft 10 progressively decreases until, at the closed position, it may be as small as desired, any residual velocity after the retaining latch is passed being taken up by a stop. At the closed position, the pin 22 engages the link 18 whereby further downward movement of the weight causes the link 19 to rotate further and the pin 20 to travel down slot 21, thus allowing the weight to swing idly. Although the kinetic energy of the weight assists the final closing movement, its potential energy is relied upon to complete the closing movement in any circumstances. When tripped open, the shaft 10 returns to the latched position (Fig. 1), the weight being raised against the stop 23 to restore the toggle. The mechanism is applicable to a number of breakers arranged in a row by providing clutches or the equivalent for connecting it to the breaker to be closed.