Turbomolecular pump

Details Turbomolecular pump Turbomolecular pump

1998-08-13

2001-04-24

Yuen, Henry C. (Department: 3747)

Pumps

Motor driven

Electric or magnetic motor

C417S295000

Reexamination Certificate

active

06220831

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a turbomolecular pump which enables exhaust of a gas by interaction between rotary blades and stationary blades and/or a threaded rotor rotating at a high speed and a stator.
A general structure of a conventional turbomolecular pump is illustrated in FIG.
6
. The conventional turbomolecular pump comprises a rotor R including a main shaft
10
and a rotary cylinder
12
fixed to the main shaft for rotating integrally therewith, a stator S including a fixed cylinder
14
surrounding the shaft
10
, and a cylindrical casing
16
surrounding the rotary cylinder
12
, which are assembled on a base B. A conductance adjusting valve
100
and a gate valve
110
are provided in the space between the turbomolecular pump and an apparatus A to be evacuated provided on the upstream side of the turbomolecular pump.
In the conventional turbomolecular pump as described above, however, driving mechanisms
101
and
111
for the individual valve units
100
and
110
are provided adjacent to the turbomolecular pump and in the proximity of the valves. This has posed a problem of scaling-up of the valve units and results in a larger overall structure of the turbomolecular pump including these valves. It is conceivable, on the other hand, to form the valve unit integrally with the turbomolecular pump, but this may lead to contamination of the apparatus to be evacuated by particles arising from the valve driving mechanism.
SUMMARY OF THE INVENTION
The present invention was made to solve the problem described above, and has its object the provision of a turbomolecular pump which has a compact overall construction including valve units, and which is able to prevent contamination by the valve driving mechanism.
To accomplish the above object, according to a first aspect the invention, a turbomolecular pump is provided which comprises a rotor and a stator housed in a casing and forming an exhaust channel therebetween, and a suction port and an exhaust port formed in said casing, wherein the turbomolecular pump has a valve body for opening and closing the suction port, the valve body is movable in an axial direction of the turbomolecular pump, a valve driving mechanism for driving the valve body via a valve body supporting member which extends through a throughhole formed in the rotor and/or the stator, and bearing units for supporting the valve body supporting member within the throughhole. This arrangement enables a compact construction of the entire pump apparatus including the valve unit, since the valve unit is integrally formed with the pump.
The said bearing unit comprises a magnetic bearing unit for non-contactingly supporting the valve body supporting member. This arrangement permits prevention of contamination by particles arising from the supporting mechanism while stably supporting the valve body, because the valve body is driven by the valve driving mechanism while being non-contactingly supported by the magnetic bearing units via the valve body supporting member.
According to a second aspect of the invention, in a turbomolecular pump according to the first aspect, the rotor is non-contactingly supported by a rotor magnetic bearing, and a screw thread sealing mechanism which inhibits gas flow into the rotor magnetic bearing is provided between the rotor and the stator. This makes it possible to prevent corrosive exhaust gas from flowing into the rotor magnetic bearing, thus preventing corrosion of these members, and hence achievement of a turbomolecular pump having high durability can be accomplished.
According to a third aspect of the invention in a turbomolecular pump according to the first aspect, a gas feeding channel for feeding an inert gas is provided at a prescribed position between the rotor and the stator for inhibiting a gas flow into the bearing units by the inert gas. This provides a turbomolecular pump which prevents a corrosive exhaust gas from flowing into the rotor magnetic bearing while maintaining an inert atmosphere around the rotor magnetic bearing and, hence, has high durability.
According to a fourth aspect of the invention, in a turbomolecular pump according to the first aspect, there is provided gas deposition preventing means which prevents deposition of gas components at a contact portion between the suction port and the valve body by heating the suction port and/or the valve body. This permits maintenance of air-tightness of the valve body, thus ensuring safe operation.
The above and other objects, features and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which preferred embodiments of the present invention are shown by way of illustrative examples.


REFERENCES:
patent: 4637433 (1987-01-01), Stoll
patent: 4873833 (1989-10-01), Pfeiffer et al.
patent: 4919599 (1990-04-01), Reich et al.
patent: 4926648 (1990-05-01), Okumura et al.
patent: 5166566 (1992-11-01), Bernhardt et al.
patent: 5354172 (1994-10-01), Schofield
patent: 5443368 (1995-08-01), Weeks et al.
patent: 0 332 107 (1989-09-01), None
patent: 0 397 051 (1990-11-01), None
patent: 8-68389 (1996-03-01), None
Patent Abstracts of Japan; vol. 18, No. 249 (M-1604), May 12, 1994 & JP 06 033874 A (Ulvac Kuraio KK) *abstract*.

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