Stabilizer for stabilizing the gas pressure in an air blast circuit breaker

A gas pressure stabilizer for an air-blast circuit breaker, said stabilizer including a first passage for communicating a compressed gas source with the circuit breaker, a first valve disposed in the first passage to control the passage of the gas therein, said stabilizer further including:

• first means communicating with the circuit breaker and being sensitive to the gas pressure therein for keeping said first valve closed when the pressure of the gas in the circuit breaker is higher than a first predetermined value P.sub.1, P.sub.1 being lower than the pressure of the gas which comes from the source, and for keeping the first valve open when the pressure of the gas in the circuit breaker is lower than P.sub.1 ;
• a second passage for communicating the circuit breaker with atmospheric air;
• a second valve disposed in the second passage to control the passing of the gas in said second passage;
• and second means communicating with the circuit breaker and being sensitive to the pressure of the gas therein for keeping the second valve closed when the pressure of the gas in the circuit breaker is lower than a second predetermined value P.sub.2, P.sub.2 being higher than P.sub.1, and for keeping the second valve open when the pressure of the gas in the circuit breaker is higher than P.sub.2, said first means including a first cylinder having opposed first and second plane surfaces, a first piston provided within said first cylinder and having an axial rod which passes through said first plane surface of said first cylinder and dividing said first cylinder into two parts, a first part located on the side nearest the first plane surface and a second part located on the side nearest the second plane surface of the first cylinder, said second part communicating by a first duct with the internal volume of the circuit breaker, said first means including first resilient means disposed in said first part and exerting on said first piston a bias pressure which opposes the pressure of the gas with which the second part is filled, so that the position of the first piston in the first cylinder depends on the pressure of the gas in the circuit breaker, and a transmission unit actuated by the first piston and capable of opening the first valve when the first piston is located in the first cylinder between the second plane surface and the first position which corresponds to a pressure P.sub.1 of the gas in the circuit breaker.