Interrupting chamber of a circuit-breaker having two compression volumes

A current interrupting chamber, for use in a circuit-breaker and filled with a dielectric fluid, including:

• a moving assembly which is axially displaceable between a start position and an end position of an operation of opening the circuit-breaker, the moving assembly comprising:
• a) a first compression chamber, the volume of which diminishes between the start position of an operation of opening the circuit-breaker and a position corresponding to the completion of the compression process in the first compression chamber;
• b) a hollow drive tube having at one end at least one first arcing contact adapted to cooperate with a second arcing contact, and further having ports for bringing the interior of the drive tube into communication with the outside of the current interrupting chamber, the interior of the drive tube being in communication with the first compression chamber between a position corresponding to the separation of the two arcing contacts and the end position of an operation of opening the circuit-breaker;
• c) a second compression chamber, which is in communication at a first end thereof with the first compression chamber, and the volume of which diminishes between the start position and the end position of an operation of opening the circuit-breaker being adapted to inject dielectric fluid into the first compression chamber between the position corresponding to the separation of the two arcing contacts and the end position of an operation of opening the circuit-breaker, when the pressure in the first compression chamber is lower than the pressure in the second compression chamber;
• and
• d) means for obstructing the ports in the drive tube from the start position of an operation of opening the circuit-breaker up to an intermediate position which is attained between the position corresponding to the separation of the two arcing contacts and the end position of an operation of opening the circuit-breaker;
• the position corresponding to the completion of the compression process in the first compression chamber being attained before the end position of an operation of opening the circuit-breaker, and a position corresponding to the completion of the compression process in the second compression chamber being attained after the position corresponding to the completion of the compression process in the first compression chamber.