Puffer type gas circuit

Claim 1

A puffer type gas circuit breaker comprising: a housing having a first end and a second end; a rod-shaped stationary arcing contact immovably set at said first end of the housing and extending axially therefrom toward said second end of the housing; a stationary puffer piston immovably set at said second end of the housing, at a distance from the stationary arcing contact and in axial alignment with the stationary arcing contact, and extending therefrom toward said first end of the housing; a movable puffer cylinder having at a first end a forward end wall with a hole therethrough and at a second end an opening, said stationary puffer piston being inserted through said opening, thus defining a cylinder chamber between said forward end wall and said stationary puffer piston; arc extinguishing gas filled in the cylinder chamber; means for reciprocating the movable puffer cylinder in the axial direction thereof; a substantially ring-shaped movable arcing contact attached to said first end of the movable puffer cylinder in axial alingment with the movable puffer cylinder, said stationary arcing contact being inserted into the movable arcing contact and thus put into slidable and electrical contact therewith when the movable puffer cylinder is moved in one direction and being pulled out of the movable arcing contact and thus put out of slidable and electrical contact therewith when the movable puffer cylinder is moved in the other direction; conductor means for supplying the stationary and movable arcing contacts with current to be interrupted; a cup-shaped nozzle made of electrically insulative material, positioned at said first end of the movable puffer cylinder, surrounding said movable arcing contact and extending coaxially with the movable puffer cylinder, a passage being formed between said cup-shaped nozzle and the movable arcing contact, said cup-shaped nozzle having at one end a throat through which the stationary arcing contact extends, said throat having a diameter larger than that of the stationary arcing contact so that a ring-shaped gap is provided between the throat and the stationary arcing contact, and said cylinder chamber communicating with an area outside the cup-shaped nozzle through said ring-shaped gap, the passage between the cup-shaped nozzle and the movable arcing contact and the hole of said forward end wall; a first arc resisting member made of arc resisting material, attached to that end face of the movable arcing contact which faces the throat of the cup-shaped nozzle and to that part of the inner periphery of the movable arcing contact which is continuous with said one end face; a second arc resisting member made of arc resisting material and attached to the end of the stationary arcing contact extending toward said second end of the housing, said second arc resisting member extending to at least that portion of the stationary arcing contact which defines said ring-shaped gap with the throat of the cup-shaped nozzle, when the stationary arcing contact is moved relative to the movable arcing contact to a position where the stationary arcing contact leaves the movable arcing contact, the first arc resisting member and the second arc resisting member being in electric contact with each other even when the movable arcing contact is engaged with the stationary arcing contact to the deepest extent; and main contact means connected in parallel to both arcing contacts for opening the external circuit before opening both arcing contacts; whereby as long as said stationary and movable arcing contacts are kept in mutual contact, both arc resisting members contact each other, and arc generated only between the first and second arc resisting member when both arcing contacts leave each other is extinguished by arc extinguishing gas supplied from said cylinder chamber and flowing along said stationary arcing contact, the arc extinguishing gas passed through the arc being exhausted through said gap supplied at the time just after the movable arcing contact leaves the stationary arcing contact.