Hydraulically-activated operating system for an electric circuit breaker

In a hydraulically-actuated operating system for an electric circuit breaker operable in a closing sense and an opening sense,

• (a) a fluid motor comprising a cylinder and a movable piston adapted to move in one direction within said cylinder to operate said circuit breaker in one of said senses and in a reverse direction within said cylinder to operate the circuit breaker in the other of said senses, the cylinder space at one side of said piston constituting a first breaker-operating space in which pressurized liquid can act on said piston to operate said circuit breaker in said one sense and the cylinder space at the opposite side of said piston constituting a second breaker-operating space in which pressurized liquid can act on said piston to operate said circuit breaker in said other sense,
• (b) an accumulator freely communicating with said first breaker-operating space for supplying pressurized liquid thereto during a circuit-breaker operation in said one sense,
• (c) a normally-closed valve located on the second breaker-operating space side of said piston and openable to release liquid from said second breaker-operating space so that pressurized liquid in said first breaker-operating space can drive said piston in said one direction, said valve comprising a movable valve member that is movable from a valve-closed position to a valve-open position to open said valve and is returnable to said valve-closed position to close said valve,
• (d) means operable in response to the pressure in said second breaker-operating space dropping to a predetermined level for returning said valve member to said valve-closed position following a circuit-breaker operation in said one sense,
• (e) means for causing the pressure in said second breaker-operating space to drop to said predetermined level immediately after piston motion in said one direction is terminated,
• (f) and an impeded passage affording communication between said accumulator and said second breaker-operating space for allowing pressurized liquid to flow from said accumulator to said second breaker-operating space and develop a pressure within said second breaker-operating space substantially equal to accumulator pressure when said valve member is returned to said valve-closed position following a circuit-breaker operation in said one sense, said passage affording communication between said accumulator and said second breaker-operating space during motion of said piston in said one direction but being so impeded that the flow therethrough from said accumulator into said second breaker-operating space is sufficiently low during initial motion of said piston in said one direction through a substantial portion of its operating stroke as to avoid interference with said piston motion in said one direction during said initial motion of the piston in said one direction.