U.S. patent application number 13/090804 was filed with the patent office on 2011-11-24 for vacuum pump.
This patent application is currently assigned to Oerlikon Leybold Vacuum GmbH. Invention is credited to Holger Dietz, Gerhard-Wilhelm Walter.
Application Number | 20110286833 13/090804 |
Document ID | / |
Family ID | 44900420 |
Filed Date | 2011-11-24 |
United States Patent
Application |
20110286833 |
Kind Code |
A1 |
Dietz; Holger ; et
al. |
November 24, 2011 |
VACUUM PUMP
Abstract
A vacuum pump has the outer side of the pump housing provided
with retaining elements. These serve to receive at least one mass
element. With these mass elements, which are preferably arranged
asymmetrically with respect to the longitudinal axis of the vacuum
pump, vibrations that occur can be suppressed.
Inventors: |
Dietz; Holger; (Cologne,
DE) ; Walter; Gerhard-Wilhelm; (Kerpen, DE) |
Assignee: |
Oerlikon Leybold Vacuum
GmbH
|
Family ID: |
44900420 |
Appl. No.: |
13/090804 |
Filed: |
April 20, 2011 |
Current U.S.
Class: |
415/90 |
Current CPC
Class: |
F04D 19/04 20130101;
F04D 29/662 20130101; F04D 29/668 20130101 |
Class at
Publication: |
415/90 |
International
Class: |
F01D 1/36 20060101
F01D001/36 |
Foreign Application Data
Date |
Code |
Application Number |
May 21, 2010 |
DE |
10 2010 021 241.8 |
Claims
1. A vacuum pump, in particular a turbo-molecular pump, comprising:
a pump housing defining a suction chamber, and at least one pumping
element arranged in the suction chamber, wherein at least one
retaining element is provided for receiving at least one mass
element, said retaining element being connected to the pump
housing.
2. The vacuum pump of claim 1, wherein said retaining element
comprises a plurality of recesses and/or compartments for
respectively receiving at least one mass element.
3. The vacuum pump of claim 1, wherein the recesses and/or
compartments are arranged asymmetrically with respect to a
longitudinal axis of the vacuum pump.
4. The vacuum pump of claim 1, wherein the mass elements have
different weights.
5. The vacuum pump of claim 1, wherein a plurality of in particular
different mass elements may be arranged in a recess and/or
compartment.
6. The vacuum pump of claim 1, wherein the mass elements are
rod-shaped.
7. The vacuum pump of claim 1, wherein the mass elements may be
arranged in the compartments as a bulk material, in particular a
ball bulk material.
8. The vacuum pump of claim 1, wherein liquids are provided as the
mass elements, in particular liquids of different viscosities.
9. The vacuum pump of claim 1, wherein at least one retaining
element is rod-shaped so as to receive disc-shaped mass
elements.
10. The vacuum pump of claim 1, wherein the mass elements are
removably arranged in and/or connected with the recesses and/or the
compartments and/or the rod-shaped retaining elements.
11. The vacuum pump of claim 1, wherein at least one retaining
element is arranged at a front end face of the pump housing and
preferably extends all over the front end face.
12. The vacuum pump of claim 1, wherein said one retaining element
surrounds the vacuum pump at least party, and wherein it is in
particular of annular shape.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The present invention claims the priority of German Patent
Application no. DE 10 2010 021 241.5 filed on May 21, 2010, the
disclosures of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The invention refers to a vacuum pump, in particular a
turbo-molecular pump.
[0004] 2. Description of the Prior Art
[0005] Vacuum pumps are used, for example, to evacuate chambers of
an installation serving the optical or electronic examination of
samples. These installations may be, for instance, mass
spectrometers, electron microscopes, installations for coating
processes, etc. Such installations frequently have a very high
resolution of 1 to 2 nm, for instance. The vacuum pump may transmit
vibrations to the installation, resulting in a corruption of the
measurement results. Resonances may be excited as well, which may,
for example, generate noises or cause structural damages. Such
vibrations may be due, for example, to an imbalance of the rotating
pump elements. Even with pump elements that are balanced very
precisely, there is always a risk that undesired vibrations are
still transmitted to the installation. Further, vibrations and
movements in the pump can be caused by the pump being
asymmetrically connected with connection elements or attachments.
These may be electronic control elements connected to the pump,
other pumps connected, such as pre-vacuum pumps, or electric lines
which, for turbo-molecular pumps, may have a diameter of about 1 cm
and more and are therefore rather heavy. Asymmetric attachments or
connection elements may cause a tumbling or swaying of the pump in
a direction substantially perpendicular to the longitudinal axis.
Such a swaying or tumbling movement has a further disadvantage in
that, independent of the transmission of vibrations to the
installation, a relative movement occurs between the fast rotating
rotor and the housing. With mechanically supported pumps, this
causes high loads on the bearings. With electromagnetically
supported pumps, this causes loads on the electronics of the
magnetic bearings. The forces and moments thus acting on the
pumping elements, such as the rotor, may lead to permanent damage
to the pumping elements. The service life of the bearings and/or
the pumping elements is thereby compromised.
[0006] For the purpose of damping the vibrations transmitted from
the vacuum pump to the installation, it is known to provide
mechanical damping elements between the vacuum pump and the
installation. However, this can only result in a reduction of the
vibrations transmitted. In particular the transmission of
low-frequency vibrations, especially in the range of up to 200 Hz,
can be damped thereby only to a limited degree. Further, such
damping elements are difficult to adapt to the installation
condition of the vacuum pump. Moreover, it is known to actively
dampen vibrations. For this purpose, phase-shifted vibrations are
induced into the vacuum pump by a vibration generator, so that the
vibrations cancel each other. Such components are costly and do not
allow the suppression of low-frequency vibrations.
SUMMARY OF THE INVENTION
[0007] It is an object of the invention to provide a vacuum pump,
in particular a turbo-molecular pump in which the transmission of
critical, especially low-frequency vibrations to an installation is
avoided and/or the service life thereof is prolonged by reducing
relative movement between pumping elements and the housing.
[0008] The vacuum pump of the present invention, which preferably
is a turbo-molecular pump, comprises a suction chamber formed by a
pump housing. At least one pumping element is arranged in the
suction chamber, which element specifically is a rotor of a
turbo-molecular pump. For the purpose of a reduction of vibrations,
which may be caused, for example, by a remaining imbalance of the
pumping element and/or by components asymmetrically connected with
the pump housing, the invention provides for the connection of at
least one retaining element with the pump housing. The retaining
element serves to accommodate at least one mass element. By
providing at least one, preferably a plurality of mass elements
moving together with the pump housing it is possible, depending on
the arrangement and/or the weight of the mass elements, to suppress
critical vibrations or to avoid their occurrence. In particular,
this allows suppressing the especially critical vibrations in the
low-frequency range up to 200 Hz.
[0009] Preferably, several different mass elements can be connected
with the pump at respective different positions. This allows an
adaptation of the pump. Accordingly, it becomes possible in a
simple manner to adapt the vacuum pump, depending on the
application, to a respective field of application or a respective
installation, with consideration to the connections and attachments
used. According to the invention, this is achieved in a simple
manner by arranging and/or exchanging mass elements
correspondingly. A complex and costly special structure depending
on the application of the vacuum pump or the installation, to which
the vacuum pump is connected, can thus be omitted owing to the
invention. Rather, identical pumps can be used for different
applications and can be readily adapted to the respective given
application.
[0010] Preferably, the retaining element has a plurality of
recesses or compartments to accommodate a plurality of in
particular different mass elements. The mass elements may be
inserted into the same, for instance. Since the mass elements are
preferably removably retained in the recesses or compartments, the
mass elements can be changed in a simple manner. The mass elements
are also retained, for instance, by friction occurring between the
mass element and the recess or compartment, or by providing fixing
elements. Thus, the vacuum pump can be readily adapted to the
respective application. Vibrations occurring can be measured and be
changed by replacing and/or arranging the mass elements in other
recesses or compartments.
[0011] The recesses or compartments are arranged with respect to
the longitudinal axis of the vacuum pump, which for a
turbo-molecular pump is the rotational axis of the rotor, such that
it is possible to asymmetrically arrange different mass elements at
a plurality of positions.
[0012] Preferably, the mass elements used have different weights.
Varying the weights can be achieved by using mass elements of
different sizes and/or different materials.
[0013] The mass elements are rod-shaped, for instance, and are thus
easily be inserted into recesses or compartments.
[0014] In another preferred embodiment of the invention, it is
further possible to provide mass elements in bulk. The
corresponding bulk, which may be spherical bulk, for instance, may
be provided in the different compartments. A very fine adjustment
of the mass provided at a certain location can be achieved by using
a bulk containing spheres of different materials and/or different
sizes, for instance.
[0015] Likewise, it is possible to use liquids as mass elements,
which in particular have different viscosities. These may also be
provided in the compartments.
[0016] A movement of the bulk or the liquids in the compartments
can be avoided by making the compartments variable in size so that
a respective compartment is always filled completely with the
liquid or the bulk. For that purpose, a side wall and/or a lid of
the compartment may be slidable, for example.
[0017] In a further preferred embodiment, the at least one
retaining element is rod-shaped and serves to receive disc-shaped,
in particular round mass elements. These can be set on the
retaining element and be fixed using a nut or the like. In this
context it is also possible to arrange asymmetric discs as mass
elements on the retaining elements.
[0018] Of course, the above described embodiments can also be
combined with each other at will.
[0019] The retaining element, which preferably comprises a
plurality of recesses, compartments and/or pin-shaped protrusions,
is preferably arranged at a front end side of the pump housing. In
particular, the front end side of the pump housing is a surface
extending perpendicularly to the longitudinal axis of the pump. It
is preferred that the retaining element has the same dimensions as
the front end side and thus extends across all of the front end
side.
[0020] In another preferred embodiment the retaining element
surrounds the vacuum pump at least partially. Preferably, the
retaining element is annular and in particular symmetrical to the
longitudinal axis. With such a retaining element it is possible to
arrange mass elements around the vacuum pump, if need be also at
different distances from the longitudinal axis. Such a retaining
element allows arranging mass elements at different distances from
the longitudinal axis of the vacuum pump and at different
positions. For this purpose, a preferred embodiment of the
retaining element has a plurality of recesses or compartments
extending parallel to or under an angle with the longitudinal
axis.
[0021] Of course, it is also possible to connect retaining elements
of different designs with one and the same vacuum pump.
[0022] Likewise, it is possible to use a retaining element to
arrange at least one mass element symmetrically to the longitudinal
axis of the vacuum pump. Here, the at least one mass element may be
arranged on the in particular rod-shaped retaining element such
that the relative position of the mass element to the retaining
element can be changed. For example, this is possible by providing
the mass element with a bore through which the retaining element
projects and by providing the bore asymmetrically in the mass
element. In particular, the mass element may be a parallelepiped,
the connection with the retaining element preferably being made at
a distance from the centre of gravity of the parallelepiped.
Thereby, simply turning the mass element around the retaining
element allows setting which vibrations are to be suppressed by the
mass element. This makes it possible to suppress critical
vibrations that particularly occur in the low-frequency range up to
100 Hz.
[0023] It is of course possible to arrange additional elements such
as vibration dampers and the like between individual mass elements.
Further, it is possible to provide spacer elements in order to vary
the distance of the individual mass elements to the pump housing or
to the longitudinal axis of the pump housing.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] A full and enabling disclosure of the present invention
including the best mode thereof, enabling one of ordinary skill in
the art to carry out the invention, is set forth in greater detail
in the following description, including reference to the
accompanying drawing in which
[0025] FIG. 1 is a much simplified illustration of a vacuum pump
arranged in an installation,
[0026] FIG. 2 is a schematic top plan view on a detail of an
annular retaining element,
[0027] FIG. 3 is a schematic top plan view on a detail of a
retaining element arranged at the front end side of the vacuum
pump,
[0028] FIG. 4 is a schematic illustration of two mass elements,
and
[0029] FIG. 5 is a schematic side elevational view on a further
embodiment of a retaining element with mass elements.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0030] A vacuum pump 10, such as a turbo-molecular pump, is
arranged at a housing 14 of an installation, e.g. via a flange 12,
so that a medium, especially gases, can be drawn by the pump from a
chamber of the installation, as indicated by an arrow 16. The
vacuum pump 10 has an outlet 18 from which the medium pumped is
discharged in the direction of an arrow 20. The outlet 18 may be
connected to a pre-vacuum pump, for instance. The outer side 22,
such as the shell surface of the housing 24 of the vacuum pump 10,
a control means 26 as well as a cable 28 may be connected.
[0031] Inside the pump housing 24 of a turbo-molecular pump, a
pumping element 30 in the form of a rotor is arranged within the
suction chamber 32 defined by the pump housing 24. The rotor 30
rotates at high speeds about a longitudinal axis 34.
[0032] Due to imbalances in the rotor 30, remaining in spite of
complex and precise balancing methods, and/or to elements fastened
asymmetrically to the housing with respect to the longitudinal axis
34, vibrations occur in all of the vacuum pump. On the one hand,
these are transmitted to the installation 14 and may, on the other
hand, cause relative movements between the rotor 30 and the pump
housing 24.
[0033] To suppress these vibrations, especially in low-frequency
ranges of up to 200 Hz, the invention provides to connect retaining
elements 36, 38 with the pump housing 24. In the embodiment
illustrated a first retaining element 36 is connected all over a
front end face 40 of the pump housing 24 so that the entire front
end face 40 is covered by the retaining element 36. In the
embodiment illustrated the second retaining element 38 is of
annular design and surrounds the pump housing 24.
[0034] As can be seen in the detail illustrated in FIG. 2, the
annular retaining element 38 has a plurality of recesses or
compartments 40, 42, 44. Rod-shaped mass elements of different
weights can be inserted into the recesses 40, 42, 44 which, in the
embodiment illustrated, are cylindrical. The mass elements are
fixed in the recesses 40, 42, 44 by friction, for instance. The
recesses 40, 42, which may of course have another cross section and
may differ in size among each other, substantially extend radially
to the longitudinal axis 34. Likewise, recesses 42 may be provided
that extend in parallel to the longitudinal axis 34.
[0035] For the sake of clarifying the various embodiments of the
invention, FIG. 2 further illustrates a compartment 44. Different
liquids and/or bulk materials can be provided as the mass element
in the compartment 44.
[0036] Correspondingly, the retaining element 46 illustrated in
FIG. 3 is also provided with recesses 40, 42, 44.
[0037] FIG. 4 schematically illustrates two mass elements 41, 43
that can be arranged in the retaining elements 40, 42 by insertion.
A ball bulk material 45 is illustrated as the mass elements in the
compartments 44.
[0038] In another embodiment (FIG. 5), rod-shaped retaining
elements 46 are connected with the pump housing 24. These may be
connected both with the front end face 40 and with the shell
surface 22 of the pump housing 24. Disc-shaped mass elements 48 can
be set on the rod-shaped retaining elements 46. The disc-shaped
mass elements 48 may have different weights. This is possible by
using different materials, different sizes or volumes. Further, the
mass elements 48 may be asymmetrical.
[0039] Although the invention has been described and illustrated
with reference to specific illustrative embodiments thereof, it is
not intended that the invention be limited to those illustrative
embodiments. Those skilled in the art will recognize that
variations and modifications can be made without departing from the
true scope of the invention as defined by the claims that follow.
It is therefore intended to include within the invention all such
variations and modifications as fall within the scope of the
appended claims and equivalents thereof.
* * * * *