| 摘要 |
A tubular, moving contact element (11) is surrounded by a blowout nozzle (27) which moves with it and is connected to the outlet (17) of a pump cylinder (19) which moves with it, can be displaced on a pump piston (21) and contains an extinguishing gas. The blowout nozzle (27) has a blowout space (30) which is supported at a distance in front of the free end of the contact element (11) and, when the circuit breaker is in the switched-on position, is closed by a fixed-position switching pin (35) which is engaged with the moving contact element (11). The moving contact element (11), which passes through the pump piston (21), has a blowout opening (16), which originates from the interior (44) of said contact element (11), at a distance from its free end. In order that the precompression of the extinguishing gas which is located in this internal space (44), in the same way as that which is located in the pump cylinder (19), is supported at the start of the switching-off movement by the pressure surge which is produced at the start of the time period for which the switching arc burns, the separation (41) between the blowout opening (16) and the base (18) of the pump cylinder (19) is shorter than the length of the switching movement (40), while the thickness of the pump piston (21) at the point (24) through which the contact element (11) passes corresponds approximately to the size (42) of the blowout opening (16), measured in the movement direction of the moving contact element (11). <IMAGE>
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