U.S. patent application number 10/014141 was filed with the patent office on 2002-07-25 for disc for a turbomolecular pump.
Invention is credited to Stoll, Tobias.
Application Number | 20020098088 10/014141 |
Document ID | / |
Family ID | 7660850 |
Filed Date | 2002-07-25 |
United States Patent
Application |
20020098088 |
Kind Code |
A1 |
Stoll, Tobias |
July 25, 2002 |
Disc for a turbomolecular pump
Abstract
A disc for a turbomolecular pump formed of a plurality of disc
elements assembled in an axial direction and each having a support
ring, a plurality of vanes supported on the support ring and
inclined to a plane of the support ring, and a plurality of
radially extending slots provided between the vanes, with the
support rings of the disc elements forming the support ring of the
disc, the vanes of the disc elements forming the disc vanes, and
the radial slots provided between the vanes of the disc elements
forming the radially extending slots between the disc vanes, and
with the vanes of one of disc elements least partially covering the
radially extending slots of an adjacent disc element.
Inventors: |
Stoll, Tobias; (Bad Endbach,
DE) |
Correspondence
Address: |
SIDLEY AUSTIN BROWN & WOOD LLP
875 Third Avenue
New York
NY
10022
US
|
Family ID: |
7660850 |
Appl. No.: |
10/014141 |
Filed: |
October 8, 2001 |
Current U.S.
Class: |
416/183 ;
415/90 |
Current CPC
Class: |
F04D 29/542 20130101;
F05D 2230/54 20130101; F05D 2300/171 20130101; F04D 29/544
20130101; F04D 29/321 20130101; F04D 19/042 20130101 |
Class at
Publication: |
416/183 ;
415/90 |
International
Class: |
F04D 019/04; F01D
001/36 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 24, 2000 |
DE |
100 52 637.3 |
Claims
What is claimed is:
1. A disc for a turbomolecular pump, comprising a support ring; a
plurality of vanes supported on the support rings, inclined to a
plane of the support disc, and forming a circle; and a plurality of
radially extending slots provided between the vanes, Wherein the
disc is formed of a plurality of disc elements assembled in an
axial direction and each having a support ring, a plurality of
vanes supported on the support ring and inclined to a plane of the
support ring, and a plurality of radially extending slots provided
between the vanes, Wherein the support rings of the disc elements
form the support ring of the disc, the vanes of the disc elements
form the disc vanes, and the radially extending slots provided
between the vanes of the disc elements form the radially extending
slots between the disc vanes, and Wherein in the assembled
condition of the disc, the vanes of one of the plurality of disc
elements at least partially cover the radially extending slots of
an adjacent disc element.
2. A disc as set forth in claim 1, wherein the vanes of the disc
elements forming an optically infermeable surface in the axial
direction.
3. A disc as set forth in claim 1, wherein the disc elements are
formed as sheet metal body, with the vanes being stamped out of a
disc element plane.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to discs for turbomolecular
pumps and including a support ring, a plurality of vanes supported
on the support rings, inclined to a plane of the support disc, and
forming a circle, and a plurality of radially extending slots
provided between the vanes.
[0003] 2. Description of the Prior Art
[0004] A turbomolecular pump is formed of rotor and stator discs
alternatively arranged one behind the other and having each a vane
crown. The pumping effect is based on transmission of pulses by the
vanes of rotor discs to molecules of a pumped gas in the pumping
direction. Both essential pumping characteristics, the suction
capacity and the pressure ratio, substantially depend on the
rotational speed of the rotor discs. The suction capacity linearly
depends o the rotational speed, whereas the pressure ratio depends
exponentially on the rotational speed. In order to achieve an
optimal pumping effect, the rotational speed of the rotor should be
as high as possible. As a result, the vanes of the rotor discs have
to meet very high requirements with respect to their geometry,
mechanical strength, and stability.
[0005] A further prerequisite for obtaining optimal pump
characteristics is a minimal thickness of the vanes. Moreover, in
addition to providing a large passing cross-section, which
increases the suction capacity, an important role is played by
strength considerations taken into account in designing the vanes
and in selecting the rotational speed. While striving for a high
rotational speed, one must insure, at the same time, that a
centrifugal force, which acts on the vanes, vane base, and inner
diameter of the rotor disc, is kept at a minimum.
[0006] A further criterium of optimal pump characteristics is an
optical density of separate discs. In increased optical density
prevents axial backflow within the disc stack.
[0007] At present, essentially two types of discs for
turbomolecular pumps are known. With one type, the discs are formed
as massive discs with radially extending, inclined to the disc
plane, vanes being milled out. With the other type, the discs are
formed of sheet material, with the vanes being stamped out of the
disc plane. The milled discs are formed of aluminum as this
material is easily milled. However, in many cases in which the
turbomolecular pumps are used, highly corrosive gases need to be
pumped. As aluminum is not corrosion-resistant, the aluminum disc
can be used in pumps operable in a corrosive environment. They can
be used only if they are provided with a corrosion-resistant
coating. This, however, substantially increases manufacturing
costs.
[0008] On the other hand, high corrosion-resistant materials, such
as alloyed steel, not particularly suitable for milling. However,
the sheet metal can be stamped rather easily.
[0009] However, one of the main drawbacks of the discs made of
sheet material with stamped and shaped vanes consists in that these
discs are not optically dense. This leads to high backflow losses
in a pump. A further drawback consists in that an entire mass of
vanes of a disc is relatively big with respect to the radial
surface of the support ring. This lead to large centrifugal forces
acting on the supporting which limits the rotational speed of the
pump and, thus, its output capacity.
[0010] Accordingly, an object of the present invention is to
provide a turbomolecular pump disc which is formed of a
corrosion-resistant material, can be cost-effectively produced, and
is devoid of the above-discussed drawbacks.
[0011] Another object of the present invention is to proved a
turbomolecular pump disc having a high optical density. A further
object of the present invention is to provide a turbomolecular pump
disc with which the load resulting from the action of the
centrifugal forces is kept within acceptable limits while the pump
operates with a maximal possible rotational speed.
SUMMARY OF THE INVENTION
[0012] These and other objects of the present invention, which will
become apparent hereinafter, are achieved by providing a disc
formed of a plurality of disc elements assembled in an axial
direction and each having a support ring, a plurality of vanes
supported on the support ring and inclined to a plane of the
support ring, and a plurality of radially extending slots provided
between the vanes, with where the support rings of the disc
elements forming the support ring of the disc, the vanes of the
disc elements forming the disc vanes, and the radially extending
slots provided between the vanes of the disc elements forming the
radially extending slots between the disc vanes, and with the vanes
of one of the plurality of disc elements at least partially
covering the radially extending slots of an adjacent disc element
in the assembled condition of the disc.
[0013] The disc according to the present invention can be formed of
corrosion-resistant materials, with the gas delivery structure
being formed by stamping out of the radial slots and by stamping
the vanes out of the disc plane, with subsequent appropriate
shaping of the vanes. The assembly of the disc of several disc
elements insures a high optical density of the disc, which prevents
backflows both within the disc itself and within the entire disc
stack. In addition, the disc elements can be formed with a reduced
number of vanes than when a solid disc is formed, while obtaining
the same optical density.
[0014] Because in the disc according to the present invention, the
load, which is caused by the centrifugal force and acts on the vane
case and the supporting, is reduced to a minimum, the pump can
operate with a higher rotational speed which insures obtaining
optimal pump characteristics. The advantage of the inventive disc
also consists in that that the vanes can be made thinner than in a
disc with milled out vanes, which permits to increase the passing
cross-section of the pump, further improving the pump
characteristics. Thinner vanes also contributes to the reduction of
the centrifugal force acting on the vane base and the support
disc.
[0015] 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 is
construction and its mode of operation, together with additional
advantages and objects thereof, will be best understood from the
following detailed description of preferred embodiment, when read
with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] The drawings show:
[0017] FIG. 1 an exploded view of a two-part rotor disc according
to the present invention for a turbomolecular pump;
[0018] FIG. 2 a perspective view of the two-part rotor disc shorn
in FIG. 1 in a semi-assembled condition; and
[0019] FIG. 3 a perspective view of the two-part rotor disc shown
in FIG. 1 in an assembled condition.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0020] A rotor disc according to the present invention, which is
shown in FIGS. 1-3, is formed of two disc elements 11 and 12. Each
of the disc elements 11, 12 has a support ring 21, 22,
respectively, and a plurality of vanes 31, 32 secured to the
respective support ring 21, 22. The vanes 31, 32 are inclined to a
plane of the respective disc elements 11, 12 and are so shaped that
they form a gas delivery structure. A plurality of openings in a
form of radially extending slots 41, 42 are provided between
respective vanes 31, 32. The two disc elements 11, 12 are assembled
together, forming a rotor disc shown in FIG. 3. A position of the
two disc elements 11 and 12, in which they are already engaged in
each other but are not yet fixedly connected with each other, is
shown in FIG. 2. In FIG. 3, both disc elements 11, 12 are joined
with each other with aid of joining clips 51, 52, forming a rotor
disc 1. The two support rings 21, 22 form an inner support disc 2,
and the vanes 31, 32 form rotor disc vanes 3 supported on the
support ring 2 at an angle to the plane of the rotor disc 1, with
radially extending slots 4 formed between the vanes 3. However, in
the axial direction of the rotor disc 1, the vanes 3 form an
optically impermeable surface. The disc elements 11-12 are formed
as a sheet metal body, with the vanes 31-32 being formed by being
stamped out of the disc element plane.
[0021] In the embodiment shown in the drawings, the rotor disc
according to the present invention is formed of two disc elements.
However, a rotor disc can be formed of more than two disc
elements.
[0022] It is to be noted that stator disc of a turbomolecular pump
can be formed in a similar manner. In this case, as a rule, the
vanes are located radially within the support ring.
[0023] Through the present invention was shown and described with
references to the preferred embodiment, 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 embodiment or details thereof, and the present
invention includes all variations and/or alternative embodiment
within the spirit and scope of the present invention as defined by
the appended claims.
* * * * *