Circuit breaker equipped with an extensible exhaust cover

A medium-, high-, or very high-voltage circuit breaker (10), comprising at least one arc-control chamber (12) and an outer casing (14) defining a space (13) in which the arc-control chamber (12) is arranged, said arc-control chamber comprising:

• a first set of electrical contacts (18a, 20a) and a second set of electrical contacts (18b, 20b), arranged at least in such a manner as to enable closing and opening operations of the circuit breaker;
• an arc blast nozzle (19);
• and
• a discharge cap (40) forming a portion of the outer wall of the arc-control chamber (12), the discharge cap being situated in the space (13) and internally defining a gas-flow chamber (31) situated at least in part downstream from the blast nozzle (19) with which it communicates, said discharge cap (40) being suitable for including one or more openings (50) for discharging the gas from the gas-flow chamber towards said space (13);
• and
• a support (60) that is electrically insulating and that mechanically connects the arc-control chamber (12) to an end wall (14a) of the outer casing (14) of the circuit breaker;
• the circuit breaker being characterized in that the discharge cap (40) comprises at least one portion (40′) that is movable under the effect of the gas pressure in the gas-flow chamber (31), so that its volume is extensible.