Protracted-blast electric circuit-breaker for alternating currents

An electric circuit-breaker for alternating currents:

• in which the arc extinction chamber containing the fixed and moving contacts is filled with a liquid dielectric consisting of liquefied SF6 gas under pressure;
• in which, when the circuit-breaker is in the switched-in position, the moving contact bears against the fixed contact solely by axial pressure exerted by thrust-exerting actuating means;
• and in which said moving contact has an axial passage therethrough which forms a nozzle for centripetal blasting of the liquid dielectric having port adjacent to and between the contacts;
• said circuit-breaker being characterized in that the moving contact is supported by a first piston which cooperates with a second coaxial or blast piston, the two said pistons sliding one within the other and the assembly formed by said coaxial pistons being slidable within a bore formed through the end-face of the arc extinction chamber;
• in that each of the pistons has one face in contact with the dielectric under pressure contained in the arc extinction chamber;
• in that said assembly is controlled by said actuating means and in that stop means limit the travel of the first piston to less than the travel of the second piston;
• whereby the blast process is prolonged beyond the instant at which the moving contact supported by the first piston reaches its position of maximum spacing from the fixed contact.