GB1260991A - Improvements in and relating to apparatus, for use in conjunction with an electric switch, comprising movable members and gas dampers - Google Patents

Abstract

1,260,991. Pneumatic dashpots. " COQ " N.V. 12 March, 1970 [14 March, 1969], No. 11916/70. Heading F2S. [Also in Divisions F1 and H1] The movement of a member such as a rod 3 operating an electric switch (not shown) is damped by attaching to it a piston 11 which, at least at the end of a predetermined range of movement of the member, enters a cylinder 9 from which gas is expelled through a non-return valve 19 which is biased by a gas cushion 36. In the case of electric circuit breaker operation, the whole assembly may be in an atmosphere of SF 6 to prevent arcing of the switch contacts, and the SF 6 also serves as the damping medium. In Fig. 1, an operating piston 2 in a cylinder 1 is acted on by gas from a source 30 under the control of valves 28, 29 to move from one end to the other of the cylinder. The operating piston carries two damping pistons 10, 11 which, in combination with respective cylinders 8, 9 effectively act as end stops for the operating piston. Each of these end stops constitutes a pneumatic damper in which a respective non- return valve 18 or 19 opens to allow gas to escape whenever the cylinder pressure exceeds a predetermined value. The value of this predetermined pressure depends on the pressure of the gas cushion and the latter should therefore be adjustable to allow for different operating pressure values. As shown it is self-adjusting, since the gas cushion and the main cylinder both receive pressure from the same source 30, so that the operating pressure and the biasing pressure are maintained in an appropriate relationship. Figs. 2 and 3 (not shown) depict modifications of Fig. 1 in which the floating piston 33 bounding the gas cushion is replaced by a diaphragm or bellows. In Fig. 1, but not in Figs. 2 and 3, the biasing force due to gas pressure is augmented by the bias of a spring 17.