Rotary kinetic fluid motors or pumps – Smooth runner surface for working fluid frictional contact
Patent
1994-11-16
1996-09-10
Look, Edward K.
Rotary kinetic fluid motors or pumps
Smooth runner surface for working fluid frictional contact
415143, F01D 0136
Patent
active
055539980
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a gas friction vacuum pump with at least two differently configured pump stages, each comprising a rotor section and a stator section.
Molecular and turbomolecular vacuum pumps are friction pumps. In molecular pumps, a moving rotor wall and a resting stator wall are configured and spaced apart in such a way that the pulses transferred from the walls to gas molecules disposed between the walls have a preferred direction. Normally, rotor and/or stator walls are provided with thread-like recesses or projections. Turbomolecular vacuum pumps are provided with intermeshed rows of stator and rotor blades, much like a turbine.
Turbomolecular pumps have a relatively low compression (pressure ratio between pressure on the pressure side and the suction side) and a relatively high suction capacity (pumping speed, volume flow per unit of time). Their manufacture and installation is complex and expensive. Moreover, they require a forevacuum pressure of approximately 10.sup.-2 mbar. Molecular pumps are provided with a relatively high compression but their suction capacity is relatively small.
They deliver pressures of up to 10 mbar and more so that the required complexity for the generation of the forevacuum is less than in turbomolecular pumps. It is therefore known to provide gas friction vacuum pumps with differently configured pump stages, with the pump stage on the forevacuum side usually being a molecular pump stage because of the better critical forepressure.
SUMMARY OF THE INVENTION
It is the object of the present invention to create a gas friction vacuum pump of the type mentioned in the beginning, which can be adapted to various applications in a simple manner.
According to the invention this object is solved by providing a gas friction pump that has a vacuum side and a pressure side, that together define a respective direction of flow of a gas through the pump. The pump includes at least three differently configured pump stages sequentially and releasably connected to each other, each comprising a housing section, and a rotor located within the respective housing section. One of the pump stages is a molecular pump stage located on the pressure side of the pump, with the rotor of the molecular pump stage having a frustoconical hub tapering away from the pressure side. Another of the pump stages is a filling stage preceding the molecular pump stage in a direction toward the vacuum side. The housing section of the filling stage constitutes a stator that surrounds the rotor of the filling stage. The rotor of the filling stage comprises a frustoconical, central hub that tapers away from the pressure side and adjoins the frustoconical hub of the molecular pump stage so that the two adjoining hubs form a continuous, frustoconical shape. The rotor of the filling stage further includes a plurality of radial, helical webs attached to the central hub. Each helical web has a pitch and a width that decreases in a direction toward the pressure side for the pumping of the gas. Another of the pump stages is a turbo molecular pump stage that precedes the filling pump stage and is on the vacuum side of the pump.
The measures which are proposed offer the advantage that the ultimate pressure behavior of the pump can be influenced in a graduated manner by means of simple variations of the rotor and stator components. By means of modularly attachable turbomolecular pump stages on a molecular pump stage alone it is possible to clearly influence the pumping properties of the entire pump. The basic configuration of the molecular pump switched downstream is not influenced.
BRIEF DESCRIPTION OF THE DRAWINGS
Further advantages and details of the invention will be explained by way of embodiments illustrated in the FIGS. 1 through 4. These show:
FIG. 1 a section through a friction pump according to the invention configured as a molecular pump,
FIG. 2 a partial section through a friction pump according to FIG. 1 which is provided with a turbomolecular pump stage disposed on the hig
REFERENCES:
patent: 3947193 (1976-03-01), Maurice
patent: 4732529 (1988-03-01), Narita et al.
patent: 4826393 (1989-05-01), Miki
patent: 5165872 (1992-11-01), Fleischmann et al.
Fleischmann Frank
Kabelitz Hans-Peter
Kriechel Hans
Muhlhoff Martin
Leybold AG
Look Edward K.
Sgantzos Mark
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