Vacuum pump system including serially connected rotary and reciprocating vacuum pumps

Claim 1

A vacuum pump assembly comprising: a rotary vacuum pump including a cylindrical housing, a pair of rotors having shafts which are parallel to each other and to the axis of said housing, and inlet side and outlet side covers provided at and closing opposite axial ends of said housing, said rotor shafts being rotatably supported by said covers, said inlet and outlet side covers respectively having inlet and outlet ports of said rotary vacuum pump, said pair of rotors cooperating to axially drive air towards said outlet port from said inlet port; a reciprocating piston vacuum pump including a housing positioned at a side of said outlet side cover opposite to a side thereof at which said housing of said rotary vacuum pump is provided, and a crank shaft extending parallel to said shafts of said rotors, a first end of said crank shaft extending away from said outlet side cover and being adapted to be connected to a drive motor; a gear casing between said outlet side cover and said housing of said reciprocating piston vacuum pump, ends of said rotor shafts and a second end of said crank shaft projecting into said gear casing, said gear casing including gear means for transmitting the driving force of the drive motor from said second end of said crank shaft to said end of one of said rotor shafts to thereby drive the rotary vacuum pump at a speed different from the reciprocating piston vacuum pump, and timing gear means for transmitting said driving force from said end of said one rotor shaft to said end of said other rotor shaft; and connecting means connecting said outlet port of the rotaryu vacuum pump to the inlet of said reciprocating piston vacuum pump.