High tension circuit breaker including a dielectric gas used for blasting

A high tension circuit breaker having a dielectric gas under pressure, the circuit breaker being of the type including at least one circuit breaking chamber comprising an insulating envelope filled with said gas and containing a fixed assembly comprising a fixed main contact and a fixed arcing contact, and a moving assembly comprising in particular a moving main contact and a moving arcing contact, the circuit-breaking chamber further including a pair of secondary contacts and a blast cylinder opening out into a blast nozzle, wherein said blast cylinder is deliminted by a first cylinder constituting the moving arcing contact, a second cylinder constituting the fixed main contact, and a first piston sliding between said first and second cylinders, said first piston being urged by a spring to come into abutment against a part fixed to the fixed assembly, the cylinder constituting the moving arcing contact and a tube connected to the fixed assembly and coaxial with said cylinder together delimiting, on the other side of the piston closing the blast cylinder, a variable volume closed at one end by said first piston and at its other end by an annular end piston connected to said first cylinder and sliding along said tube, said volume enclosing said secondary contacts, a first secondary contact being fixed to said tube and the second secondary contact being entrained by said first cylinder.