Low-voltage limiting circuit breaker with leaktight extinguishing chamber

Claim 1

A limiting device of an electric current, comprising: a leaktight extinguishing chamber, a pair of separable contacts housed in said extinguishing chamber, an insulating shield slidingly mounted in said extinguishing chamber between two end positions, one active position in which said shield is inserted between said separable contacts in open position and subdividing said extinguishing chamber into two independent parts each of which containing one of said contacts, and the other inactive end position of retreat of the shield allowing the closing of said contacts and a communication between said two parts of the extinguishing chamber, a piston securedly united to said shield having a face subjected to the action of pressure in said extinguishing chamber to move the shield to the active position when said pressure increases due to the action of an arc drawn when said contacts separate, the volume of said extinguishing chamber substantially corresponding to the dimensions of said contacts in separated position in order to reduce to a minimum the gas volume contained in said chamber and to obtain a fast pressure increase of this gas due to the arc action.