U.S. patent application number 11/786692 was filed with the patent office on 2007-11-08 for vacuum pump.
This patent application is currently assigned to Pfeiffer Vacuum GmbH. Invention is credited to Bernd Hofmann, Tobias Stoll.
Application Number | 20070258836 11/786692 |
Document ID | / |
Family ID | 38051882 |
Filed Date | 2007-11-08 |
United States Patent
Application |
20070258836 |
Kind Code |
A1 |
Hofmann; Bernd ; et
al. |
November 8, 2007 |
Vacuum pump
Abstract
A vacuum pump includes a housing, a rotor located in the housing
and having a shaft and pump-active elements supported on the shaft,
a stator having pump-active elements and located in a separate
housing part of the housing, for driving the pump, bearings for
rotatably supporting the rotor shaft, and at least one vacuum
chamber located in the housing.
Inventors: |
Hofmann; Bernd;
(Greifenstein, DE) ; Stoll; Tobias;
(Angelburg-Goennern, DE) |
Correspondence
Address: |
ABELMAN, FRAYNE & SCHWAB
666 THIRD AVENUE, 10TH FLOOR
NEW YORK
NY
10017
US
|
Assignee: |
Pfeiffer Vacuum GmbH
|
Family ID: |
38051882 |
Appl. No.: |
11/786692 |
Filed: |
April 11, 2007 |
Current U.S.
Class: |
417/423.4 |
Current CPC
Class: |
F04D 19/042 20130101;
F04D 29/601 20130101; F04D 19/046 20130101 |
Class at
Publication: |
417/423.4 |
International
Class: |
F04B 17/00 20060101
F04B017/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 4, 2006 |
DE |
10 2006 020 710.6 |
Claims
1. A vacuum pump, comprising a housing; a rotor located in the
housing and having a shaft and pump-active elements supported on
the shaft; a stator located in the housing and having pump-active
elements, the housing having a housing part for holding the
pump-active elements of the stator; drive means for driving the
pump; bearing means for rotatably supporting the rotor shaft; and
at least one vacuum chamber located in the housing part.
2. A vacuum pump, according to claim 1, wherein the housing part
contains at least one part of the bearing means and drive means and
connectable with the housing.
3. A vacuum pump according to claim 1, comprising at least two
pumping stages, and at least one further vacuum chamber located in
the housing, and wherein the at least one and the further vacuum
chambers are connected with each other and with a respective
pumping stage.
4. A vacuum pump according to claim 3, wherein the gas pressure in
the at least one and further vacuum chambers is not the same.
5. A vacuum pump according to claim 1, wherein the bearing means
comprises a permanent magnet bearing for supporting an end of the
rotor shaft.
6. A vacuum pump according to claim 3, wherein the pump-active
rotor elements and the pump-active stator elements includes blades
forming at least one pumping stage.
7. A vacuum pump according to claim 1, wherein the at least one
vacuum chamber has an opening, the vacuum pump further comprising a
releasable cover for closing the opening, and at least two seals
for sealing the opening.
8. A vacuum pump according to claim 7, comprising an annular
channel arranged between the two seals and in which vacuum is
produced.
9. A vacuum pump according to claim 8, comprising a connection
conduit integrated in the housing between the annular channel and
one of pumping stage and gas outlet channel.
10. A vacuum pump according to claim 1, further comprising at least
one further vacuum chamber, at least one of the at least one and
further vacuum chambers being located in an insertable module.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a vacuum pump including a
housing, a rotor located in the housing and having a shaft and
pump-active elements supported on the shaft, a stator located in
the housing and having pump-active elements, with the housing
having a housing part for holding the pump-active elements of the
stator, drive means for driving the pump and bearing means for
rotatably supporting the rotor shaft.
[0003] 2. Description of the Prior Art
[0004] Vacuum pumps form, together with vacuum chambers, vacuum
systems with which numerous tasks can be performed. These tasks
range from manufacturing monolithic layers through analyses of
gases, and up to optical columns of high-resolution electronic
microscopes. The technical developments put higher and higher
requirements to the vacuum tightness and compactness of the vacuum
systems.
[0005] In some common applications, so-called differential pumps
are used. With differential pumps, a system is formed of vacuum
pumps connected with each other, with separate vacuum chambers
being held at different gas pressures.
[0006] A noticeable simplification of formation of a pump system
for differential pumps is disclosed in German Patent DE-PS 43 31
589. Instead of a plurality of pumps, a single vacuum pump takes
over evacuation of vacuum chambers.
[0007] European Patent EP-PS 1 090 231 discloses a vacuum pump with
a double housing. An inner housing combines a rotor/stator region
and a drive/bearing region of the pump. The inner housing is then
pushed into an outer housing that is adapted to a particular use.
However, the latter solution has serious drawbacks, a double
housing is expensive as more parts are used than with a single-part
housing. This increases both expenses associated with manufacturing
of the housing components and expenses associated with the assembly
of numerous components. The contact surfaces of the two housings
must be machined with a high precision. The danger of a virtual
leak increases with an increase of number of components needed for
the housing. Between the two separate housings, seals must be
provided which, because of their large number, increase the risk of
leakage. For a double housing, additional space should be provided,
which makes gas feeding more expensive. These problems are
independent of the number of vacuum chambers provided in the vacuum
system.
[0008] Accordingly, an object of the invention is a vacuum pump in
which the problems, which are associated with a double housing, are
eliminated.
[0009] Another object of the invention is a vacuum pump having a
compact construction and requiring a small number of parts.
SUMMARY OF THE INVENTION
[0010] These and other objects of the present invention, which will
become apparent hereinafter, are achieved by providing a vacuum
pump in which the housing part which serves for holding pump-active
stator elements, has at least one vacuum chamber. This noticeably
reduces the number of necessary parts. A smaller number of flanges
and other housing transition elements becomes necessary, whereby
vacuum tightness increases and expenses decreases. Generally, a
very compact unit is provided. Because a flange connection between
the vacuum chamber and vacuum pump, which is necessary in the
existing state of the art, is eliminated, the vacuum tightness is
noticeably increased. This permits to achieve lower end pressures
with the inventive vacuum pump.
[0011] A further reduction of the number of parts is achieved when
the separate housing part further holds at least one component of
bearing and drive means.
[0012] According to the invention, the inventive vacuum pump has a
plurality of pumping stages with each of which a vacuum chamber is
connected, with the vacuum chambers being also connected with each
other. Thereby, a single component, such as a housing, is necessary
for all chambers in the vacuum pump, which reduces costs and
increases tightness. With the gas pressure in the respective
chambers being different, a plurality of differential pumps are
provided in the vacuum pump.
[0013] According to the invention the bearing means includes a
permanent magnet bearing for supporting an end of the rotor shaft.
This bearing does not require lubrication and is wear-free and,
thus, can be used in the high-vacuum region of a vacuum pump.
[0014] According to a further modification of the present
invention, for production of the high vacuum, the pump-active rotor
elements and the pump-active stator elements includes blades
forming at least one high-vacuum pumping stage. This is
particularly suitable for obtaining low pressures.
[0015] According to a further development of the present invention,
the at least one vacuum chamber has an opening, and the vacuum pump
further includes a releasable cover for closing the opening, and at
least two seals for sealing the opening. The opening provides for
an easy access to the vacuum chamber so that, e.g., maintenance
becomes possible, or the components located in the vacuum chamber,
e.g., of some experiment, can be very easily replaced. The
opening-sealing seals insure the vacuum tightness.
[0016] The arrangement discussed above can be further improved by
providing an annular channel between the two seals and in which
vacuum is produced. Thereby, the pressure drop between the
atmospheric pressure and vacuum takes place in stages, which
reduces forces acting on the seals. Because the leakage rate of a
leak depends on the pressure difference between the inner and outer
sides, and the stagewise pressure drops means a smaller pressure
difference across a seal, smaller leaks play a smaller role. By
measuring the power consumption of a pump used for producing
vacuum, leakage at the seals can be determined.
[0017] According to further development of the present invention,
there is provided a push-in or insertable module in which at least
one of the vacuum chambers is located. The insertable module is
pushed in a bore formed in the vacuum pump housing and is retained
there. Thereby, it is possible to replace the vacuum chamber system
of the inventive vacuum pump and adapt it to other requirements. In
addition, it is possible to have the vacuum chambers and the vacuum
pump produced by different manufactures. This reduces costs because
manufacturing steps take place parallel with each other and
respective professional skills and knowledge are optimally
used.
[0018] According to a further advantageous embodiment of the
present invention, for producing vacuum in the annular channel,
there is provided a connection conduit integrated in the housing
between the annular channel and one of pumping stages and gas
outlet channel.
[0019] The novel features of the present invention, which are
considered as characteristic for the invention, are set forth in
the appended claims. The invention itself, however, both as to its
construction and its mode of operation, together with additional
advantages and objects thereof, will be best understood from the
following detailed description of preferred embodiments, when read
with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] The drawings show:
[0021] FIG. 1 a cross-sectional view of a first embodiment of a
vacuum pump according to the present invention;
[0022] FIG. 2 a cross-sectional view of a second embodiment of a
vacuum pump according to the present invention; and
[0023] FIG. 3 a cross-sectional view of a third embodiment of a
vacuum pump according to the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0024] A vacuum pump 1 according to the present invention, a first
embodiment of which is shown in FIG. 1, has a housing 2 and a lower
housing part 3. A shaft 4 is supported at one of its ends by
bearing means 8 and at its another opposite end by a permanent
magnetic bearing 17. The permanent magnetic bearing 17 is located
at a high-vacuum side of the pump system and is secured thereat by
a support structure 16. The pump system includes pump-active rotor
elements 5 supported on the shaft 4, and stationary pump-active
stator elements 6. In the embodiment shown in the drawings, rotor
and stator elements are formed as blade-carrying discs, whereby a
vacuum pump in accordance with a known constructional principle of
turbomolecular pumps is formed. However, the present invention is
not limited to this type of a vacuum pump, rather it is applicable
to a combination of different types in accordance with a pressure
region that should be obtained. E.g., the invention is applicable
to Holweck stages and the like. The stator has, in addition to
pump-active elements 6, spacers 7 which determine the axial
distance of the stator elements from each other. The stator
components are first inserted through the housing 2 of the vacuum
pump 1, mounted in their respective positions and are held there.
Without the housing 2, this mounting is not given, the remaining
pump part is not itself operational.
[0025] In the housing part 3, in addition to bearing means 8, there
is provided drive means 9, e.g., electrical coils which cooperate
with permanent magnets arranged on the shaft 4, setting the shaft
in rapid rotation. The bearing means 8 can be formed as a ball
bearing, magnetic bearing, or gas bearing. The lower housing part 3
also includes a gas outlet channel 30 leading to a gas outlet
union. When the vacuum pump itself is not compressed to the
atmospheric pressure, a forevacuum pump is connected with this gas
outlet union.
[0026] Also are arranged in the housing 2, a first vacuum chamber
20 and a second vacuum chamber 21, with a lower pressure being
produced in the first vacuum chamber 20 than in the second vacuum
chamber 21.
[0027] The first vacuum chamber 20 is directly connected with the
first pumping stage 22 of the pump system. The second vacuum
chamber 21 is connected by a suction channel 10 with an
intermediate inlet 18. Through the intermediate inlet 18, gas can
be fed to the second pumping stage 23. Thus, gas from the first
vacuum chamber 20 is fed into both the first pumping stage 22 and
the second pumping stage 23 and is compressed there, whereas gas
from the second vacuum chamber 21 is compressed only in the second
pumping stage 23. This principle can be expanded further by
providing further vacuum chambers in the housing 2. The further
vacuum chambers can be connected with further intermediate inlets
of the pump system. Likewise, one of the chambers can be connected
with the gas outlet channel 30 by a channel formed in the housing.
The first and second vacuum chambers 20 and 21 are connected with
each other by a connection passage 25. The passage 25 can be formed
as a bore in the housing 2 or as a throttle. The second vacuum
chamber 21 has an opening 26 through which, e.g., a to-be-analyzed
gas or a particle stream can flow in.
[0028] The housing 2 has an opening that can be closed by a cover
11 and which is connected with the first vacuum chamber. The cover
11 permits to monitor components which are located in the first
vacuum chamber 20. Around this opening, two seals are provided,
with a first seal 12 surrounding the opening and the second seal 13
surrounding the first seal 12. An annular channel 14 is provided
between the seals 12 and 13 and in which vacuum is produced. For
producing the vacuum, there is provided a connection conduit 15
that opens either in one of the pumping stages of the vacuum pump
or in the gas outlet channel 30. When the connection conduit opens
not in front of the first pumping stage but at the other location
of the pump system, the vacuum, which is produced between the two
seals 12 and 13, is between the pressure in the first vacuum
chamber 20 and the pressure of the vacuum pump environment.
Thereby, the load, which act on separate seals, is noticeably
reduced as the pressure drop across a respective seal is smaller.
Measurement of drive power of the pump or the pumping stage
necessary for producing the vacuum permits to make a conclusion
about leakage and whether the seals are defective.
[0029] The vacuum pump according to the first embodiment has a
further advantage achieved with the present invention, namely, when
all of vacuum conduits between the chambers, chambers and pumping
stages, and to the annular channel in the housing are integrated,
only one forevacuum flange is necessary. Additional expensive
conduits, which should be attached later, are eliminated.
[0030] In the vacuum pump according to a second embodiment, which
is shown in FIG. 2, the invention is applied to a three-chamber
system. There are provided in the housing 2 of the vacuum pump a
first chamber 31 in which a high vacuum is produced, a second
chamber 32 in which a medium vacuum is produced, and a third
chamber 33. The third vacuum chamber 33 is retained at a forevacuum
level. The third vacuum chamber 33 is connected via a forevacuum
inlet 37 with the gas outlet channel 30 of the vacuum pump. A
middle inlet 36 connects the second vacuum chamber 32 with the
pumping system of the vacuum pump. A high vacuum inlet 35 connects
the first vacuum chamber 31 with the pump system. Gas, which
reaches the pump system through the high vacuum inlet 35 should
flow over all of the parts of the pump system. The stationary
components, stator discs 6 and spacers 7 should only be mounted in
the housing 2 and retained in their positions. Without the housing
2, this mounting of stationary components is not possible, and
remaining pump components themselves are not operational. As a
rule, it is necessary to optimize conductance between the chambers
and the respective parts of the pump system. A parameter which
permits to achieve optimization, is angle .alpha. between the rotor
axis 40 and the chamber axis 41. This parameter can vary between
0.degree., i.e., with parallel arrangement, and 90.degree., i.e.,
with a mutually perpendicular arrangement.
[0031] A third embodiment of a vacuum pump according to the present
invention is shown in FIG. 3. The third embodiment differs from the
second embodiment by the vacuum chambers. At least one of the
vacuum chambers, here, two vacuum chambers 32 and 33 are arranged
in an insertable module 44. This module 44 is inserted through a
bore formed in the housing 2 of the vacuum pump 1 and is secured in
the housing 2. To provide for servicing or exchange of the module,
the module 44 can be releasably secured, e.g., with screws. Seals
45 seal the module 44 against the housing 2. The vacuum chambers
32, 33 are connected with each other as the chambers 32 and 31 that
is formed in the housing 2. All or, as shown in FIG. 3, only some
of the chambers can be provided in the insertable module. Suction
channels 42, 43 connect the vacuum chambers 32, 33 with different
parts of the pump system of the vacuum pump, so that different
pressure can be produced in the vacuum chambers.
[0032] Though the present invention was shown and described with
references to the preferred embodiments, such are merely
illustrative of the present invention and are not to be construed
as a limitation thereof and various modifications of the present
invention will be apparent to those skilled in the art. It is
therefore not intended that the present invention be limited to the
disclosed embodiments or details thereof, and the present invention
includes all variations and/or alternative embodiments within the
spirit and scope of the present invention as defined by the
appended claims.
* * * * *