Gas blast circuit breaker of the axial blast type

Claim 1

An electric circuit breaker of the axial-blast, gas blast type comprising: a. a pair of separable current-carrying contacts through which most of the circuit-breaker current flows when said currentcarrying contacts are engaged, b. a pair of separable arcing contacts electrically connected in parallel with said current-carrying contacts and maintained in an engaged position when the circuit breaker is closed, c. opening means for separating said arcing contacts after said current-carrying contacts separate during an interrupting operation, thereby drawing an arc between said arcing contacts, d. a nozzle having a flow passage, e. an exhaust channel communicating at its upstream end with said flow passage, f. a housing adapted to contain pressurized gas in which is located said current-carrying and arcing contacts, said flow passage, and said exhaust channel, g. a normally-closed blast valve at the downstream end of said exhaust channel openable during said interrupting operation to produce through said nozzle flow passage and said exhaust channel a blast of gas that forces said arc into a position where the arc extends through said flow passage, h. said nozzle comprising an orifice member substantially surrounding said flow passage and serving as one of said arcing contacts, i. the other of said arcing contacts being a member that engages said orifice member when said circuit breaker is closed and acts while engaging said orifice member to restrict flow through said nozzle flow passage even though said blast valve has opened, j. said opening means delaying separation of said arcing contacts until after said blast valve has opened and caused a large reduction in the pressure in said exhaust channel.