Patent ID: 7226276

Claim:
A multi-stage reciprocating vacuum pump, comprising a housing ( 1 ); at least one first pump chamber ( 2 ) and at least one second pump chamber ( 4 ) provided in the housing ( 1 ) and each having a suction side ( 16 , 17 ) and an outlet side ( 15 , 19 ); a first piston ( 6 ) reciprocating in the at least one first pump chamber ( 2 ) and a second piston ( 8 ) reciprocating in the at least one second pump chamber ( 4 ); a valve ( 10 , 11 ) provided at the outlet side ( 15 , 19 ) of each of the at least one first pump chamber ( 2 ) and the at least one second pump chamber ( 4 ); a first conduit ( 14 ) for communicating the outlet side ( 15 ) of the at least one first pump chamber ( 2 ) with the suction side ( 17 ) of the at least one second pump chamber ( 4 ); a second conduit ( 20 ) for communicating the suction side ( 16 ) of the at least one first pump chamber ( 2 ) with the suction side ( 17 ) of the at least one second pump chamber ( 4 ); and means ( 18 , 21 ; 25 ) for selectively connecting the first conduit ( 14 ) and the second conduit ( 20 ) with the suction side ( 17 ) of the at least one second pump chamber ( 4 ), the first and second conduits ( 14 and 20 ) and the selectively connecting means ( 18 , 21 ; 25 ) being located in the housing ( 1 ), wherein selectively connecting means comprises a three-way cock ( 25 ) provided at an intersection of the first and second conduits ( 14 and 20 ) and having a first position in which gas entering through the suction side ( 16 ) of the at least one first pump chamber ( 2 ) is pumped, in parallel, in the at least one first pump chamber ( 2 ) and the at least one second pump chambers ( 4 ) and is expelled through the respective outer valves ( 10 , 11 ) provided at the outlet sides ( 15 , 19 ) of the at least one first pump chamber ( 2 ) and the at least one second pump chamber ( 4 ), and a second position in which gas entering through the suction side ( 16 ) of the at least one first pump chamber ( 2 ) is compressed in the at least one first pump chamber ( 2 ), with an entire compress gas volume flowing therefrom through the first conduit ( 14 ) into the at least one second pump chamber ( 4 ), is further compressed therein, and is expelled through the valve ( 11 ) provided at the outlet side ( 19 ) of the at least one second pump chamber ( 4 ).