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US 4,797,068 AGranted
Vacuum evacuation system
AssigneeHitachi, Ltd.
InventorsTadashi Hayakawa, Kazuaki Shiinoki, Sinji Mitsuhashi, Kotaro Naya
Life of this patent
Estimating the term…
Abstract
A vacuum evacuation system comprising a non-positive displacement type vacuum pump called molecular pump which obtains high pumping speed in a high vacuum range, and an oil-free, positive displacement type vacuum pump called screw vacuum pump. The non-positive displacement type vacuum pump and the positive displacement type vacuum pump are connected to each other such that the non-positive displacement type vacuum pump is located on a high vacuum side and the positive displacement type vacuum pump is located on a low pressure or atmospheric side, to thereby prevent oil from being penetrated into a system to be evacuated.
Claims9
A vacuum evacuation system comprising:
- a first vacuum pump having a rotary component which is adapted to rotate at high speeds to produce a linear velocity and against which gas molecules are caused to strike, thus giving momentum of said rotary component in a direction of the linear velocity of the rotary component to produce a gas flow in a given direction;
- a second vacuum pump having a casing provided with suction and exhaust ports between which a gas flow passage is defined and in which a pair of male and female screw rotors are supported with a minute gap between said screw rotors and said casing, the inner surface of said casing and said pair of male and femal screw rotors defining a working chamber in which said screw rotors rotate with a minute gap maintained therebetween in the absence of sealing, cooling and lubrication liquid, within said working chamber and the gas flow passage thereby producing a differential pressure between the suction and exhaust ports provided in said casing;
- means connecting said exhaust port of said first vacuum pump to said suction port of said second vacuum pump;
- and
- said suction port of said first vacuum pump being disposed on a vacuum side, and said exhaust port of said second vacuum pump being disposed on an atmospheric side.
2 more elements
A vacuum evacuation system comprising:
- first vacuum pump means having a rotor blade stage including stator blades secured to an outer case and rotor blades arranged in facing relationship with said stator blades, against which respective blades gas molecules are caused to strike to produce a gas flow in a downstream direction, and a screw pump stage including a helically grooved rotor formed at its outer peripheral surface facing the outer case with a helical groove, said helical groove serving to deliver the gas from said rotor blade stage in the downstream direction;
- second vacuum pump means having a casing provided with suction and exhaust ports between which a gas flow passage is defined and a pair of screw rotors, each having a plurality of helical irregularities at its outer peripheral surface and rotatably received within said casing in meshing relation with each other, said pair of screw rotors and the inner surface of said casing defining a working chamber in which said pair of screw rotors rotated in the absence of sealing, cooling and lubrication liquid within said working chamber and the gas flow passage and sealing means disposed between said casing and the respective shaft portions of said pair of screw rotors;
- and
- drive means for driving said first and second vacuum pump means.
1 more element
A vacuum evacuation system comprising:
- non-positive displacement-type vacuum pump means having rotor blade cascades including stator blades and rotor blades disposed in facing relation to said stator blades, for providing a gas flow in a downstream direction in a gas flow passage by causing gas molecules to strike against the rotating rotor blades, and screw pump means having a helically grooved rotor formed at its outer pheripheral surface with a helical groove, said helical groove serving to deliver the gas molecules from said rotor blade cascades;
- positive displacement-type twin screw vacuum pump means including a casing provided with suction and exhaust ports between which a gas flow pasage is defined and having an inlet in communication with said outlet of said non-positive displacement type vacuum pump means, a pair of screw rotors having meshing helical ridges and grooves at the outer peripheral surfaces thereof and rotatably received within said casing, said pair of screw rotors and the inner surface of said casing defining a working chamber in which said pair of screw rotors rotate in the absence of sealing, cooling and lubrication liquid within said working chamber and the gas flow passage, and sealing means disposed between said casing and the respective shaft portions of said screw rotors;
- and
- drive means for driving said non-positive displacement-type vacuum pump means and said positive displacement-type vacuum pump means.
1 more element
Dependencies are inferred from the claim text.