U.S. patent application number 13/851641 was filed with the patent office on 2013-10-03 for pumping system for evacuating gas from a plurality of chambers and method for controlling the pumping system.
This patent application is currently assigned to Pfeiffer Vaccum GmbH. The applicant listed for this patent is PFEIFFER VACCUM GMBH. Invention is credited to Thorsten BURGGRAF, Jan HOFMANN, Tobias STOLL.
Application Number | 20130259711 13/851641 |
Document ID | / |
Family ID | 47757425 |
Filed Date | 2013-10-03 |
United States Patent
Application |
20130259711 |
Kind Code |
A1 |
BURGGRAF; Thorsten ; et
al. |
October 3, 2013 |
PUMPING SYSTEM FOR EVACUATING GAS FROM A PLURALITY OF CHAMBERS AND
METHOD FOR CONTROLLING THE PUMPING SYSTEM
Abstract
A pumping system for evacuating gas from a plurality of
chambers, includes at least one turbomolecular pump, at least two
fore-vacuum pumps, at least one connection conduit extending
between the at least two fore-vacuum pumps. and at least one
transverse constriction for at least one of reducing and regulating
gas flow.
Inventors: |
BURGGRAF; Thorsten; (Runkel,
DE) ; HOFMANN; Jan; (Gruenberg, DE) ; STOLL;
Tobias; (Hohenahr, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
PFEIFFER VACCUM GMBH |
Asslar |
|
DE |
|
|
Assignee: |
Pfeiffer Vaccum GmbH
Asslar
DE
|
Family ID: |
47757425 |
Appl. No.: |
13/851641 |
Filed: |
March 27, 2013 |
Current U.S.
Class: |
417/53 ;
417/199.1 |
Current CPC
Class: |
F04D 19/042 20130101;
F04D 27/009 20130101; F04D 27/0253 20130101; F04B 23/08 20130101;
F04D 19/046 20130101; F04D 25/16 20130101; F04D 27/0269
20130101 |
Class at
Publication: |
417/53 ;
417/199.1 |
International
Class: |
F04B 23/08 20060101
F04B023/08 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 30, 2012 |
DE |
102012102761.7 |
Jul 4, 2012 |
DE |
102012105951.9 |
Claims
1. A pumping system for evacuating gas from a plurality of
chambers, comprising at least one turbomolecular pump; at least two
fore-vacuum pumps; at least one connection conduit extending
between the at least two fore-vacuum pumps; and at least one
transverse constriction for at least one of reducing and regulating
gas flow.
2. A pumping system according to claim 1, wherein the at least one
transverse constriction is formed as an adjustable
constriction.
3. A pumping system according to claim 1, comprising a further
turbomolecular pump constructively identical to the at least one
turbomolecular pump.
4. A pumping system according to claim 1, wherein at least one
transverse constriction is formed as one of throttle orifice,
throttle valve, and gas flow controller.
5. A pumping system according to claim 1, wherein the at least one
transverse constriction is formed as one of regulated and
switchable valves.
6. A pumping system according to claim 1, comprising a plurality of
transverse constrictions switchingly arranged one of seriesly and
parallel to each other.
7. A pumping system according to claim 1, wherein there is provided
a superordination process control for regulating the at least one
transverse constriction.
8. A pumping system according to claim 1, wherein a device for
measuring one of actual vacuum and gas flow rate is provided at
least at one of a point of at least one chamber of the plurality of
chambers, in the at least one conduit, and pump connections
provided to that end.
9. A pumping system according to claim 1, wherein the at least one
turbomolecular pump is formed as an exhaust pressure-dependent
pump.
10. A pumping system according to claim 1, wherein the pumping
system is designed for evacuating gas from a plurality of chambers
comprising at least two chambers connected with each other.
11. A pumping system according to claim 10, wherein one of the at
least two fore-vacuum pumps is located immediately adjacent to one
of the at least two chambers.
12. A pumping system according to claim 1, comprising a plurality
of turbomolecular pumps, wherein at least one of the fore-vacuum
pumps is arranged in front of at least one of the turbomolecular
pumps.
13. A pumping system according to claim 1, comprising a plurality
of turbomolecular pumps, and wherein the at least two fore-vacuum
pumps are arranged, at least one off together and separately, in
front of one of a part of the turbomolecular pumps and all of the
turbomolecular pumps.
14. A pumping system according to claim 1, comprising a plurality
of turbomolecular pumps, and wherein at least one of the plurality
of turbomolecular pumps has two inlets.
15. A method of controlling a pumping system for evacuating gas
from a plurality of chambers, comprising at least one
turbomolecular pump; at least two fore-vacuum pumps; at least one
connection conduit extending between the at least two fore-vacuum
pumps; and at least one transverse constriction for at least one of
reducing and regulating gas flow, the method comprising the steps
of measuring one of vacuum and gas flow rate at at least one of a
point of at least one chamber, in the at least one conduit, and
pump connections provided to that end; and using the at least one
of measured variables for controlling the at least one transverse
constriction.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The invention relates to a pumping system for evacuating gas
from a plurality of chambers and to a method of controlling the
pumping system.
[0003] 2. Description of the Prior Art
[0004] Practically, the entire system consists of one or more
vacuum chambers (recipients). These chambers can be used
separately, however, they may be connected, at least partially,
with each other. In this case, at a set pressure difference, a
substantial gas flow takes place therebetween through an opening
formed in a common wall between two process chambers or through a
tubular conduit connecting the chambers. One or several chambers
can also be subjected to gas loads which can also result from
connection with the chamber environment (atmosphere), from gas
loads transmitted from upstream-located chambers, from otherwise
generated, mostly process-dependent, gas flows, and also from
admitted inert or process gases such as helium, from desorption
from workpieces, test pieces placed into a chamber, and/or chamber
components, and/or from reaction products actively produced in a
process.
[0005] In order to maintain the process in each chamber, the
chambers should be evacuated by respective vacuum pump systems
connected therewith at a predetermined vacuum that should be
maintained as constant as possible. The separate vacuum pump
systems are formed either of a separate pump or of several pumps
which are connected seriesly or parallel to each other. Dependent
on the gas flow, several chambers can be simultaneously evacuated
by a single pump or by several pumps with a common fore-vacuum
pump. The connections between the chambers and the pumps can be
formed as series connections, parallel connections, or any
arbitrary combinations of those connections.
[0006] The state-of-the-art (WO2011/121322A2) discloses that pumps
can be arranged in suitable manner so that they mutually support
each other, with the pumps being connected to a different pressure
level within the other pump.
[0007] For the most part, the processes in multi-chambers systems
require a high gas load at a low pressure, so that there large
fore-vacuum pumps must be used in order to be able to maintain a
desired vacuum. The low pressure means that a high suction capacity
need be available. Simultaneously, other chambers of such a system
can maintain vacuum with very small expenditures, and a smaller
pump can suffice. The greater is the gas load a pump should handle,
the higher is the energy consumption and the associated therewith
cooling requirements, and electrical and mechanical losses caused
by gas friction.
[0008] Because of environmental and boundary conditions, e.g., a
limited constructional space, allowable heat output, noise and
vibration generation, it can be advantageous to use several small
pumps instead of a large one. It is further advantageous to be able
to distribute the loads as uniformly as possible to insure a high
efficiency of the pumps.
[0009] In actual cases, the gas loads and vacuum differ greatly
from chamber to chamber, and adaptation of the noise reduction to
existing possibilities while maintaining the desired process
characteristics, is difficult and only possible when considering
the balance of interests. One type of solution is described in the
state-of-the art (WO2011/121322 A2). However, the proposed solution
requires the use of special pumps with matching intermediate
connections.
[0010] The object of the invention is a system which permits to
optimally use a largest possible number of pumps from the
economical and technical standpoints, and to distribute the
existing gas loads as uniformly as possible between a number of as
simple as possible and similar or identical pumps, without
retroactive effects on the process.
SUMMARY OF THE INVENTION
[0011] The object of the invention is achieved by a pumping system
for evacuating gas from a plurality of chambers, including at least
one turbomolecular pump, at least two fore-vacuum pumps, at least
one connection conduit extending between the at least two
fore-vacuum pumps, and at least one transverse constriction for
reducing and/or regulating gas flow; and by a method including
measuring vacuum or gas flow rate at a point of the at least one
chamber, in the at least one conduit, and pump connections provided
to that end, and using the at least one of measured variables for
controlling the at least one transverse constriction.
[0012] According to the invention, the maximum gas flow in at least
one of respective conduits, which connect a plurality of pumps
connected seriesly and/or parallel to each other, is limited by at
least one transverse constriction. Within the meaning of the
invention, the transverse constriction is also understood as a
device that completely closes the conduit.
[0013] The transverse constriction can be formed advantageously as
a simple throttle orifice. It represents a constructional component
having a definite transverse constriction over a predetermined
length of the available conduit.
[0014] In a simplest case, the flow-restricting orifice meter is
provided with a stationary constriction.
[0015] According to a further, particularly advantageous
embodiment, the constriction is adjustable within a certain region.
In this embodiment, the constriction is in form of a throttle
valve. The adjustable region can be adjusted mechanically by a hand
or electrically, pneumatically, or hydraulically by a control
drive.
[0016] The adjustment of the throttle valve is carried out
advantageously based on a previously determined calibrated scale.
However, there is no feedback of an actual cross-section of the
exemplary gas flow. To this end, advantageously, a separate or
integrated gas flow measurement follows, so that in order to be
able to regulate a predetermined gas flow, it is possible to form a
closed regulating circuit. For the most part, a corresponding
pre-set value is generated electrically as an analogue electrical
signal, e.g., voltage, current, pulse modulation, or by another
conventional method, or is transmitted as a digital signal by an
arbitrary bus system. Alternatively or additionally, the target can
be produced by a local or remote control unit with a user
interface. This device is generally called a gas flow controller.
The gas flow controller is a customary component that is also
called a mass flow controller.
[0017] The above-mentioned transverse constrictions can be formed
suitably as separate constrictions or as a combination of identical
or different constrictions arranged seriesly and/or parallel to
each other. The use of one or several valves for separating one or
several conduit sections of a formed network additionally expands
the possibilities for adaptation to different process
conditions.
[0018] According to a further advantageous embodiment of the
invention, there exists a possibility to measure the vacuum and/or
the gas flow rate at one or several points in one or several
chambers, and/or at arbitrary points inside of the conduits, or at
pump connections provided to this end, and to use the obtained
values for regulating the above-mentioned parameters. The simplest
embodiment discloses a pressure switch that generates a signal for
opening or closing a conduit section at a predetermined threshold
pressure to prevent overload of the connectable pump or the
influence of process parameters.
[0019] According to yet another advantageous embodiment of the
invention, a superordination process control is contemplated. With
a superordination process control, it is possible to use obtained,
at different locations, measurement data for process evaluation and
for influencing the process and, thereby, to optimize the process
and the load of separate pumps.
[0020] When pumps are used the pump throughput of which depend, at
least partially, on the discharge pressure, e.g., with the use of
turbomolecular pumps, it is advantageous when those have, at their
discharge side, a pump stage that delivers a constant throughput
over a large pressure region.
[0021] This stage may include, e.g., Gaede, Siegbahn, and/or
Holweck stage. The robustness of a pump against pressure
fluctuation at the discharge side permits to noticeably simplify
the lay-out of the system. Thereby, it is possible to operate with
a simple throttle orifice instead of a switchable or regulated
valve.
[0022] The invention permits not only to prevent use of pumps the
dimensions of which vary greatly, but rather permits to use two or
more identical pumps at different positions to thereby keep the
number of different pump types in production, sale, assemblies, and
use low and, thereby, to reduce manufacturing costs and provide
cost savings for customers. The cost savings are achieved due to
low qualified expenditures. Qualified expenditures mean that the
user installs and tests several pumps of the same type which pumps
in combination are best able to meet the job requirements at the
region-specific predetermined network voltage or the
region-specific network frequency. This approach is applicable to
both pumps in the fore-vacuum region as used in the above example,
and pumps connected directly or by connection conduits with
respective chambers.
[0023] The described solution provides many advantages with
systems, e.g., so-called LCMS-systems, in which the pumps with a
small load must pump, at least in one process condition, primarily
light gases (small particle mass) as, e.g., at additional gas load,
when helium is used as a process gas. The pumping capacity
according to main pump principles depends on to-be-pumped atom,
e.g., molecular weights. Light gases with small masses are
generally more difficult to pump. The pumping capacity of such
pumps sharply increases when heavy gases, such as drag medium, are
used. In this case, the heavy particles drag the light particle in
the correct direction through the pump, thus reducing the backflow
of the light particles. While the pump generally must pump more
gas, the pump throughput of light gases noticeably increases. The
discharge of the first pump, which feeds, through a transverse
constriction, a gas flow with a smaller portion of light gases to
the second pump, causes a corresponding drag effect in the second
pump that in the described case, pumps gas with a high content of
light gases, so that the light gases can be pumped noticeably
better.
[0024] Pumps, which are connected to a local power supply, are
often driven by a frequency converter, and rotate, dependent on to
the region-specific network frequency (typically 50 Hz or 60 Hz) or
network voltage (typically 90V, 120V, 230V), with a different speed
and/or with a different maximal input power (e.g., due to
limitation of the driving current or the resulting heat input) and
change, thereby, correspondingly their maximal pump throughput.
This leads to that chambers which are evacuated directly by such a
pump, are pumped, dependent on an available power supply network,
at a different pressure level. In order to prevent this, according
to a conventional practice, up to now it was necessary to so
regulate the gas flow by adaptation of the stop-throttle valves or
orifice meters within or on the chambers that at an available or
predetermined power supply network, the desired process pressure is
achieved. Because of the complexity of the entire system, this is
not easily realized and is connected with high costs because for
the most part, several corresponding chambers are involved. This
problem is solved by providing, according to the invention, a
transverse constriction between the concerned first pump with a
variable rotational speed and/or variable input power, and second
pump that either pumps a region in which the chamber pressure is
irrelevant, and/or a pump directly connected with the chambers,
e.g., one or several turbomolecular pumps which produce a
fore-vacuum pressure, wherein those are robustly react against
pressure changes at their discharge side. A simple change or
adjustment of the above-mentioned transverse constriction equalizes
the difference in the pump throughput of the first pump so that the
concerned chamber pressure remains constant, without a need to
undertake any measure in or outside the chamber. Such adjustment
can be undertaken, as it has already been described, with
internally or externally connected control units that determine the
process condition, e.g., the vacuum in the concerned chamber, and
adjust, by adjusting the transverse constriction, the vacuum to a
value desired for an actual process condition.
[0025] The object of the invention can also be achieved by varying
the pump through-put based not on the influence of the power supply
network but rather on the difference in the operational conditions
of the pump, e.g., on heat generated during operation or on
changing environmental conditions, in particular, on the
environmental and/or cooling water temperature, and also on
different pump throughputs.
[0026] A conventional embodiment has two or more chambers which at
least partially connected with each other and, for the most part,
operate at different vacuum. Gas flows are produced by the fed
to-be-analyzed gases and often, by the auxiliary gases delivered in
another chambers. Alternatively, the vacuum in one or several
chambers is produced directly with a fore-vacuum pump. Otherwise,
one or several chambers is (are) evacuated by one or more
turbomolecular pumps which are supported again together and/or
separately by one or more fore-vacuum pump(s). Alternatively, at
least one of the vacuum pumps can have more than one inlet (split
flow, interstage port) connected with at least one other chamber
and the first inlet of the pump. Advantageously, the pumps have a
high robustness against the high discharge pressure. Typically, the
pressure difference between the turbomolecular pump and the
fore-vacuum pump lies in a region from 1 to 20 mbar. To relief at
least one of the at least two fore-vacuum pumps, there is provided
at least one connection with a transverse constriction between the
suction connectors of the first-mentioned fore-vacuum pump and the
second fore-vacuum pump, and which provides maximum for such gas
flow that the second fore-vacuum pump always can be retained at a
certain discharge pressure. The first, relief fore-vacuum pump can
be selected smaller than the second one so that the second one can
be better used.
[0027] 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:
[0028] The drawings show:
[0029] FIG. 1 a schematic view of a prior art pumping system;
[0030] FIG. 2 a schematic view of a first embodiment of a pumping
system according to the present invention;
[0031] FIG. 3 a schematic view of a modified embodiment, in
comparison with first embodiment, of a pumping system according to
the present invention;
[0032] FIG. 4 a schematic view of a further modified embodiment of
a pumping system according to the present invention;
[0033] FIG. 5 a schematic view of a still further modified
embodiment of a pumping system according to the present
invention;
[0034] FIG. 6 a schematic view of yet a further modified embodiment
of a pumping system according to the present invention;
[0035] FIG. 7 a schematic view of another further modified
embodiment of a pumping system according to the present invention;
and
[0036] FIG. 8 a schematic view of yet another modified embodiment
of a pumping system according to the present invention;
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE
INVENTION
[0037] FIG. 1 shows a prior art pumping system that has two
to-be-evacuated chambers 1 and 2. A turbomolecular pump 3 is
associated with the chamber 1, and a turbomolecular pump 4 is
associated with the chamber 2.
[0038] The turbomolecular pump 3 is supported by a fore-vacuum pump
5, and the turbomolecular pump 4 is supported by fore-vacuum pump
6. The drawback of the prior art pumping system consists in that
the turbomolecular pump 3 should maintain a predetermined pressure
in the chamber 1, and the turbomolecular pump 4 should maintain a
predetermined pressure in the chamber 4. Accordingly, the pumps 3,
4, 5, 6 should be correspondingly capable of performing this task.
This means that they must have a required pumping capacity under
network voltage and frequency condition for a particular
region.
[0039] Q designates a gas flow. The chambers 1 and 2 are connected
with each other. With different pressures in chambers 1 and 2,
there exists a gas flow Q between the two chambers. In the chamber
2, in addition, there is provided a gas inlet 7 for feeding a
process gas into the chamber 2.
[0040] FIG. 2 shows two chambers 1, 2 which are evacuated by
turbomolecular pumps 3, 4.
[0041] Fore-vacuum pumps 5, 6 provide support for turbomolecular
pumps 3, 4. A conduit 8 is provided between the fore-vacuum pumps 5
and 6. In the conduit 8, a throttle orifice 9, which is shown
schematically, is arranged. The throttle orifice 9 permits to
control the gas flow in the conduit 8.
[0042] By the arrangement according to the present invention, it is
possible to identically dimension the pumps 3, 4, e.g., to use
turbomolecular pumps 3, 4 of the same type. This results in relief
of the first pump 5 that delivers, via the throttle orifice 9, a
gas flow with a smaller portion of light gases to the second pump
6. This leads to a drag effect in the second fore-vacuum pump 6
that, according to FIG. 2, pumps a greater portion of light gases,
so that the light gases can be pumped noticeably better.
[0043] The same is true for the arrangement in FIG. 3, wherein a
single turbomolecular pump 4 is provided for evacuation of chamber
2.
[0044] The chamber 1 is evacuated by the fore-vacuum pump 5. For
supporting the turbomolecular pump 4, the fore-vacuum pump 6 is
provided.
[0045] Again, a conduit 8 extends between the fore-vacuum pumps 5,
6 and is provided with a throttle orifice 9.
[0046] FIG. 4 shows a modified embodiment with three chambers 1, 2,
and 10. As shown in FIG. 4, again, there are provided two
fore-vacuum pumps 5, 6 and a turbomolecular pump 3 for evacuation
of chamber 1. For evacuation of chambers 2 and 10, a split-flow
pump 11 is provided. The split-flow pump 11 has two inlets 12 and
12a. Again, a conduit 8, which is provided with a throttle orifice
9, extends between the fore-vacuum pumps 5 and 6.
[0047] FIG. 5 shows a further modified embodiment with six
to-be-evacuated chambers 1, 2, 10, 13, 14, 15. The chambers 2, 10,
13 have additional gas inlets 16, 17, 18 for process gases.
[0048] For evacuation of the chamber 1, a turbomolecular pump 3,
which is supported by a fore-vacuum pump 5, is provided. For
evacuation of chambers 2, 13, and 14, a split-flow pump 19 is
provided. The split-flow pump 19 is supported by a fore-vacuum pump
6.
[0049] An additional turbomolecular pump 20 is provided for
evacuation of the chamber 15.
[0050] A conduit 8 with a throttle orifice 9 extends between the
fore-vacuum pumps 5 and 6. Here likewise, a relief of the first
fore-vacuum pump 5 is provided and which delivers a gas flow with a
smaller portion of light gases to the second fore-vacuum pump 6 as
a result of a transverse constriction in form of the throttle
orifice 9 provided in the conduit 8 connecting the fore-vacuum
pumps 5 and 6. This leads to a drag effect in the second
fore-vacuum pump 6 that, in this case, pumps a greater portion of
the light gases, so that light gases can be pumped noticeably
better.
[0051] FIG. 6 shows an arrangement with four chambers 1, 2, 10, 13.
The chamber 1 is evacuated by a turbomolecular pump 3, and the
chamber 2 is evacuated by a turbomolecular pump 4. The
turbomolecular pump 3 is supported by a fore-vacuum pump 5, and the
turbomolecular pump 4 is supported by a fore-vacuum pump 6.
[0052] A conduit 8 with a throttle orifice 9 extends between the
fore-vacuum pumps 5 and 6.
[0053] For evacuation of the chambers 10, 13, a split-flow pump 11
is provided and which is supported by a fore-vacuum pump 21. An
additional conduit 22 is provided between the fore-vacuum pumps 6
and 21 and has a throttle orifice 9.
[0054] FIG. 7 shows a pump arrangement for a multi-chamber system
with six chambers 1, 2, 10, 13, 14, 15. The chambers 1, 2, 13, 14,
15 are evacuated by constructively identical turbomolecular pumps
3, 4, 20, 24, 25. The turbomolecular pump 3 is supported by a
fore-vacuum pump 5. The pumps 4, 20, 24, 25 are supported by a
fore-vacuum pump 6. Again, a conduit 8 with a throttle orifice 9
extends between the fore-vacuum pumps 5 and 6.
[0055] FIG. 8 shows a multi-chamber system with six chambers 1, 2,
10, 13, 14, 15. The chamber 1 is evacuated by a fore-vacuum pump 5.
Constructively identical turbomolecular pumps 4, 20, 24, 25
evacuate the chambers 2, 13, 14, 15. The pumps 4, 20, 24, 25 are
supported by a fore-vacuum pump 6.
[0056] A conduit 8 with a throttle orifice 9 extends between the
fore-vacuum pumps 5, 6. A device 26 for measuring an actual vacuum
is provided in the chamber 14.
[0057] A device 27 for measuring an actual vacuum is mounted on the
pump 20 on the connection provided to this end.
[0058] A device 29 for measuring a gas flow rate is provided in a
conduit 28. A device 30 for measuring a gas flow rate is provided
in the conduit 8.
[0059] 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.
* * * * *