U.S. patent application number 15/251567 was filed with the patent office on 2018-03-01 for hermetic vacuum pump isolation valve.
The applicant listed for this patent is Agilent Technologies, Inc.. Invention is credited to John Calhoun, Ronald J. Forni, George Galica, Vannie Lu.
Application Number | 20180058453 15/251567 |
Document ID | / |
Family ID | 61166773 |
Filed Date | 2018-03-01 |
United States Patent
Application |
20180058453 |
Kind Code |
A1 |
Galica; George ; et
al. |
March 1, 2018 |
HERMETIC VACUUM PUMP ISOLATION VALVE
Abstract
A vacuum pump isolation (VPI) valve is interposed between a
vacuum pump and a vacuum chamber. During normal operation of the
vacuum pump, the VPI valve is open, allowing fluid communication
between the vacuum pump and the vacuum chamber. When the vacuum
pump becomes non-operational such as by losing power, the VPI valve
closes, thereby isolating the vacuum chamber from the vacuum pump.
The closing of the VPI valve is driven by the exhaust gas pressure
of the vacuum pump. The VPI valve becomes exposed to the exhaust
gas pressure by the opening of a pilot valve, which may occur as a
result of the vacuum pump ceasing to operate. By this
configuration, the VPI valve is hermetic and does not require
ambient air for its operation.
Inventors: |
Galica; George; (Worcester,
MA) ; Calhoun; John; (Lexington, MA) ; Forni;
Ronald J.; (Lexington, MA) ; Lu; Vannie;
(Billerica, MA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Agilent Technologies, Inc. |
Santa Clara |
CA |
US |
|
|
Family ID: |
61166773 |
Appl. No.: |
15/251567 |
Filed: |
August 30, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F04C 18/0215 20130101;
F04C 2220/10 20130101; F04C 18/126 20130101; F04C 2240/40 20130101;
F04C 23/005 20130101; F04C 28/24 20130101; F04C 29/12 20130101;
F04C 28/28 20130101; F04C 18/30 20130101; F04C 25/02 20130101 |
International
Class: |
F04C 28/24 20060101
F04C028/24; F04C 18/02 20060101 F04C018/02; F04C 25/02 20060101
F04C025/02; F04C 29/12 20060101 F04C029/12 |
Claims
1. A vacuum pump isolation (VPI) valve, comprising: a pump inlet
housing enclosing an inlet interior; a valve element disposed in
the inlet interior, the valve element configured for switching
between an open state of the VPI valve and a closed state of the
VPI valve and configured for switching to the closed state in
response to pressure, wherein at the open state the valve element
allows fluid flow between a vacuum pump and a vacuum chamber via
the inlet interior, and at the closed state the valve element
blocks fluid flow between the vacuum pump and the vacuum chamber;
and a pilot valve configured for communicating with the inlet
interior and an internal exhaust gas line of the vacuum pump, the
pilot valve switchable between an open pilot valve position and a
closed pilot valve position, wherein at the open pilot valve
position the pilot valve allows exhaust gas from the internal
exhaust gas line to apply a pressure to the valve element effective
to switch the valve element to the closed state, and at the closed
pilot valve position the pilot valve blocks exhaust gas flow from
the internal exhaust gas line to the valve element.
2. The VPI valve of claim 1, comprising a valve seat disposed in
the inlet interior, wherein the valve element comprises a piston
movable between an open piston position corresponding to the open
state of the VPI valve and a closed piston position corresponding
to the closed state of the VPI valve, and at the closed piston
position the piston contacts the valve seat.
3. The VPI valve of claim 2, comprising a control volume chamber
disposed in the inlet interior and at least partially bounded by
the piston, wherein movement of the piston varies a volume of the
control volume chamber.
4. The VPI valve of claim 3, comprising a flexible diaphragm
attached to the pump inlet housing and the piston and at least
partially bounding the control volume chamber, wherein the flexible
diaphragm moves with movement of the piston.
5. The VPI valve of claim 3, wherein the control volume chamber is
enclosed such that the control volume chamber is at least partially
fluidly isolated from the vacuum chamber.
6. The VPI valve of claim 3, comprising an inlet port in
communication between the inlet interior and the vacuum pump, and a
conductance-limiting orifice in communication between the inlet
port and the control volume chamber.
7. The VPI valve of claim 1, comprising a flexible diaphragm
disposed in the inlet interior and configured to at least partially
fluidly isolate the pilot valve from a portion of the inlet
interior communicating with the vacuum chamber.
8. The VPI valve of claim 1, comprising a spring configured for
biasing the valve element into switching to the open state.
9. The VPI valve of claim 1, wherein the pilot valve is configured
to be normally open and to switch to the closed pilot valve
position in response to receiving power.
10. A vacuum pump, comprising: the VPI valve according to claim 1;
a pump body, wherein the internal exhaust gas line is disposed in
the pump body; a first exhaust gas transfer line providing fluid
communication between the internal exhaust gas line and the pilot
valve; and a second exhaust gas transfer line providing fluid
communication between the pilot valve and the control volume
chamber.
11. The vacuum pump of claim 10, wherein the pilot valve is
configured to be held at the closed pilot valve state in response
to receiving power, and further comprising a pumping element, a
motor configured for driving movement of the pumping element, and a
power source configured for supplying power to both the vacuum pump
and the pilot valve and cutting off power to the pilot valve in
response to the motor ceasing operation.
12. The vacuum pump of claim 10, wherein the first exhaust gas
transfer line and the second exhaust gas transfer line are fluidly
isolated from an ambient environment outside the vacuum pump.
13. The vacuum pump of claim 10, comprising a scroll pumping stage
disposed in the pump body and communicating with the inlet interior
and the internal exhaust gas line.
14. A vacuum pump isolation (VPI) valve, comprising: a valve seat
disposed in the inlet interior; a piston disposed in the inlet
interior, the piston movable between an open piston state and a
closed piston state, wherein at the open piston state the piston
allows fluid flow between a vacuum pump and a vacuum chamber via
the inlet interior, and at the closed piston state the piston
contacts the valve seat and blocks fluid flow between the vacuum
pump and the vacuum chamber; a control volume chamber disposed in
the inlet interior and at least partially bounded by the piston,
wherein movement of the piston varies a volume of the control
volume chamber; and a pilot valve configured for communicating with
the control volume chamber and an internal exhaust gas line of the
vacuum pump, the pilot valve switchable between an open pilot valve
position and a closed pilot valve position, wherein at the open
pilot valve position the pilot valve allows exhaust gas from the
internal exhaust gas line to pressurize the control volume chamber
to a pressure effective to move the piston to the closed piston
state, and at the closed pilot valve position the pilot valve
blocks exhaust gas flow from the internal exhaust gas line to the
control volume chamber.
15. A vacuum pump, comprising: the VPI valve according to claim 14;
a pump body, wherein the internal exhaust gas line is disposed in
the pump body; a first exhaust gas transfer line providing fluid
communication between the internal exhaust gas line and the pilot
valve; and a second exhaust gas transfer line providing fluid
communication between the pilot valve and the inlet interior.
16. A vacuum system, comprising: a vacuum pump comprising an
internal exhaust gas line; a vacuum chamber; a vacuum isolation
(VPI) valve switchable between an open VPI valve state and a closed
VPI valve state, wherein at the open VPI valve state the VPI valve
allows fluid flow between the vacuum pump and the vacuum chamber,
and at the closed VPI valve state the VPI valve blocks fluid flow
between the vacuum pump and the vacuum chamber; and a pilot valve
communicating with the internal exhaust gas line and the VPI valve,
the pilot valve switchable between an open pilot valve state and a
closed pilot valve state, wherein at the open pilot valve state the
pilot valve allows exhaust gas to flow from the internal exhaust
gas line to the VPI valve at a pressure effective to switch the VPI
valve to the closed VPI valve state, and at the closed pilot valve
state the pilot valve blocks exhaust gas flow from the internal
exhaust gas line to the VPI valve.
17. The vacuum system of claim 16, wherein the VPI valve comprises:
a pump inlet housing enclosing an inlet interior; a valve element
disposed in the inlet interior, the valve element configured for
switching between the open VPI valve state and the closed VPI valve
state and configured for switching to the closed VPI valve state in
response to pressure, wherein at the open pilot valve state the
pilot valve allows the exhaust gas from the internal exhaust gas
line to apply a pressure to the valve element.
18. The vacuum system of claim 16, wherein the VPI valve comprises:
a pump inlet housing enclosing an inlet interior; a valve seat
disposed in the inlet interior; a piston disposed in the inlet
interior, the piston movable between a first position corresponding
to the open VPI valve state and a second position corresponding to
the closed VPI valve state, wherein at the first position the
piston allows fluid flow between the vacuum pump and the vacuum
chamber via the inlet interior, and at the second position the
piston contacts the valve seat and blocks fluid flow between the
vacuum pump and the vacuum chamber; and a control volume chamber
disposed in the inlet interior and at least partially bounded by
the piston, wherein movement of the piston varies a volume of the
control volume chamber, wherein at the open pilot valve state the
pilot valve allows the exhaust gas to pressurize the control volume
chamber.
19. The vacuum system of claim 16, comprising a first exhaust gas
transfer line providing fluid communication between the internal
exhaust gas line and the pilot valve, and a second exhaust gas
transfer line providing fluid communication between the pilot valve
and the VPI valve.
20. The vacuum system of claim 16, wherein the vacuum pump is a
backing pump, and further comprising a high-vacuum pump
communicating with the vacuum chamber, and wherein: at the open VPI
valve state the VPI valve allows fluid flow between the backing
pump and the high-vacuum pump, and at the closed VPI valve state
the VPI valve blocks fluid flow between the backing pump and the
high-vacuum pump.
Description
TECHNICAL FIELD
[0001] The present invention relates generally to an isolation
valve utilized with a vacuum pump to protect an associated vacuum
system in the event of a vacuum pump shut-down. More particularly,
the invention relates to an isolation valve that is driven to close
by gas pressure internal to the vacuum pump.
BACKGROUND
[0002] Various systems include one or more internal chambers that
are required to operate at a high-vacuum (very low, sub-atmospheric
pressure) level such as, for example, lower than 10.sup.-3 Torr.
Such systems include, for example, spectrometry systems, leak
testing systems, microscope (e.g., electron microscope) systems,
microfabrication (e.g., vacuum deposition) systems, etc. The
internal vacuum chambers of these systems are evacuated by one or
more vacuum pumps. For example, a vacuum system may include a
"roughing" pump or "backing" pump configured for bringing the
vacuum system down to a rough vacuum level, for example, down to
about 10.sup.-3 Torr. The vacuum system may further include one or
more high-vacuum pumps configured for bringing the vacuum system
further down to a high-vacuum level. In such a system, the roughing
pump serves as a first stage of vacuum pump-down, and may be
necessary for operation of the further stage(s) of high-vacuum
pump-down implemented by the high-vacuum pump.
[0003] The vacuum system may include a vacuum pump isolation (VPI)
valve configured to automatically isolate and protect components of
the high-vacuum system from high pressures (e.g. ambient, or
atmospheric, pressure) in the event that the backing pump loses
power, and thereafter reopen only after the backing pump restarts
and establishes a sufficient level of vacuum that is safe for
further operation of the components of the high-vacuum system. For
example, high-vacuum pumps such as turbomolecular pumps will be
damaged beyond repair if exposed to pressures much above about 200
mTorr when running at full speed. Typically, a VPI valve is
separate from the backing pump and communicates with the ambient,
i.e. the environment outside of the backing pump and the rest of
the vacuum system. Hence, use of the conventional VPI valve results
in a non-hermetic system.
[0004] FIG. 1 is a schematic view of an example of a vacuum system
100 utilizing a conventional VPI valve 114. The vacuum system 100
includes a backing pump 118 communicating with a high-vacuum stage
122 of the vacuum system 100 via the VPI valve 114. The backing
pump 118 is typically a mechanical pump such as, for example, a
scroll pump, rotary vane pump, diaphragm pump, Roots blower
(positive displacement lobe), etc. The high-vacuum stage 122
includes one or more vacuum chambers 126, i.e. interior spaces to
be evacuated, communicating with the backing pump 118. The
high-vacuum stage 122 further includes one or more high-vacuum
pumps 130 (e.g., turbomolecular pump, sputter ion pump, etc.)
configured for evacuating the vacuum chamber(s) 126 to a level of
vacuum beyond that which is achievable by the backing pump 118
alone. During a normal operation of the vacuum system 110, the VPI
valve 114 is open, i.e., provides an unrestricted working gas flow
path from the high-vacuum stage 122 to an inlet 134 of the backing
pump 118. The VPI valve 114 typically includes a movable piston
that is open (unseated) during the normal operation of the vacuum
system 100. The backing pump 118 discharges gas at an outlet 138
thereof into a gas exhaust line 142.
[0005] The vacuum system 100 further includes another valve, for
example a solenoid valve 146, providing selective communication
between the ambient and the VPI valve 114 (specifically, between
the ambient and the side of the VPI valve piston opposite to the
working gas flow path between the high-vacuum stage 122 and the
backing pump 118). The solenoid valve 146 is typically a normally
open valve in the sense that it requires electrical power to be
actively held in a closed state that isolates the VPI valve 114
from the ambient. The same power source may be utilized to supply
power both to the solenoid valve 146 and to the backing pump 118.
During the normal operation of the vacuum system 100, the solenoid
valve 146 is closed. If, however, the backing pump 118 loses power,
the solenoid valve 146 opens, thereby allowing ambient air 150 to
flow into the VPI valve 114. The resulting pressure differential
across the piston of the VPI valve 114 forces the piston to become
seated, thereby closing off the working gas flow path between the
high-vacuum stage 122 and the backing pump 118 and isolating the
high-vacuum stage 122 from the higher pressure developing as a
result of the shut-down of the backing pump 118.
[0006] More specific examples of the foregoing VPI configuration
are described in U.S. Pat. No. 4,785,851.
[0007] As evident from the foregoing, the conventional
configuration of the vacuum system 100 is non-hermetic in that the
isolation/protection phase of operation entails exposure to the
ambient. There are many applications, however, in which exposure to
the ambient is disadvantageous, such as applications entailing the
recirculation of helium or certain chemicals in which air should
not be permitted to enter the system and working gas should not be
permitted to exit the system. Therefore, there is a need for vacuum
systems entailing the use of a VPI valve that are hermetic.
SUMMARY
[0008] To address the foregoing problems, in whole or in part,
and/or other problems that may have been observed by persons
skilled in the art, the present disclosure provides methods,
processes, systems, apparatus, instruments, and/or devices, as
described by way of example in implementations set forth below.
[0009] According to one embodiment, a vacuum pump isolation (VPI)
valve includes: a pump inlet housing enclosing an inlet interior; a
valve element disposed in the inlet interior, the valve element
configured for switching between an open state of the VPI valve and
a closed state of the VPI valve and configured for switching to the
closed state in response to pressure, wherein at the open state the
valve element allows fluid flow between a vacuum pump and a vacuum
chamber via the inlet interior, and at the closed state the valve
element blocks fluid flow between the vacuum pump and the vacuum
chamber; and a pilot valve configured for communicating with the
inlet interior and an internal exhaust gas line of the vacuum pump,
the pilot valve switchable between an open pilot valve position and
a closed pilot valve position, wherein at the open pilot valve
position the pilot valve allows exhaust gas from the internal
exhaust gas line to apply a pressure to the valve element effective
to switch the valve element to the closed state, and at the closed
pilot valve position the pilot valve blocks exhaust gas flow from
the internal exhaust gas line to the valve element.
[0010] According to another embodiment, a vacuum pump includes: a
VPI valve according to any of the embodiments disclosed herein; a
pump body, wherein the internal exhaust gas line is disposed in the
pump body; a first exhaust gas transfer line providing fluid
communication between the internal exhaust gas line and the pilot
valve; and a second exhaust gas transfer line providing fluid
communication between the pilot valve and the control volume
chamber.
[0011] According to another embodiment, a vacuum pump isolation
(VPI) valve includes: a valve seat disposed in the inlet interior;
a piston disposed in the inlet interior, the piston movable between
an open piston state and a closed piston state, wherein at the open
piston state the piston allows fluid flow between a vacuum pump and
a vacuum chamber via the inlet interior, and at the closed piston
state the piston contacts the valve seat and blocks fluid flow
between the vacuum pump and the vacuum chamber; a control volume
chamber disposed in the inlet interior and at least partially
bounded by the piston, wherein movement of the piston varies a
volume of the control volume chamber; and a pilot valve configured
for communicating with the control volume chamber and an internal
exhaust gas line of the vacuum pump, the pilot valve switchable
between an open pilot valve position and a closed pilot valve
position, wherein at the open pilot valve position the pilot valve
allows exhaust gas from the internal exhaust gas line to pressurize
the control volume chamber to a pressure effective to move the
piston to the closed piston state, and at the closed pilot valve
position the pilot valve blocks exhaust gas flow from the internal
exhaust gas line to the control volume chamber.
[0012] According to another embodiment, a vacuum pump includes: a
VPI valve according to any of the embodiments disclosed herein; a
pump body, wherein the internal exhaust gas line is disposed in the
pump body; a first exhaust gas transfer line providing fluid
communication between the internal exhaust gas line and the pilot
valve; and a second exhaust gas transfer line providing fluid
communication between the pilot valve and the inlet interior.
[0013] According to another embodiment, a vacuum system includes: a
vacuum pump comprising an internal exhaust gas line; a vacuum
chamber; and a VPI valve according to any of the embodiments
disclosed herein.
[0014] The vacuum pump may include a pumping stage disposed in the
pump body and communicating with the inlet interior and the
internal exhaust gas line. The pumping stage may include one or
more stationary pumping elements and moving pumping elements. The
moving pumping element(s) may be driven (powered) by a motor (e.g.,
an electric motor) of the vacuum pump. In some embodiments, the
vacuum pump is a scroll pump. The scroll pump may have a scroll
pumping stage. The scroll pumping stage may include a stationary
scroll and an orbiting scroll drivable to orbit relative to the
stationary scroll, as appreciated by persons skilled in the
art.
[0015] Other devices, apparatus, systems, methods, features and
advantages of the invention will be or will become apparent to one
with skill in the art upon examination of the following figures and
detailed description. It is intended that all such additional
systems, methods, features and advantages be included within this
description, be within the scope of the invention, and be protected
by the accompanying claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] The invention can be better understood by referring to the
following figures. The components in the figures are not
necessarily to scale, emphasis instead being placed upon
illustrating the principles of the invention. In the figures, like
reference numerals designate corresponding parts throughout the
different views.
[0017] FIG. 1 is a schematic view of an example of a vacuum system
utilizing a conventional vacuum pump isolation (VPI) valve.
[0018] FIG. 2 is a schematic view of an example of a vacuum system
according to an embodiment disclosed herein.
[0019] FIG. 3A is a partially cut-away perspective view of an
example of a part of a vacuum pump according to an embodiment
disclosed herein, illustrating a VPI valve of the vacuum pump in an
open position.
[0020] FIG. 3B is a partially cut-away perspective view of the
vacuum pump similar to the view of FIG. 3A, but illustrating the
VPI valve in a closed position.
[0021] FIG. 4 is a partially cut-away side view of the vacuum pump
illustrated in FIGS. 3A and 3B.
[0022] FIG. 5 is a partially cut-away top view of the vacuum pump
illustrated in FIGS. 3A, 3B, and 4, with the VPI valve and an
associated pump inlet of the vacuum pump removed.
DETAILED DESCRIPTION
[0023] As used herein, the term "vacuum chamber" encompasses a
chamber (i.e., an enclosed space capable of being fluidly sealed in
a vacuum-tight manner) that is part of or in fluid communication
with a vacuum pump as disclosed herein. Depending on the context or
stage of operation, a "vacuum chamber" is at a vacuum pressure
(e.g., at a sub-atmospheric pressure down to 10.sup.-9 Torr or
lower) as result of operating the vacuum pump (i.e., the vacuum
chamber has been evacuated), or is at least capable of being pumped
down to a vacuum pressure due to being part of or in fluid
communication with the vacuum pump. Generally, depending on the
application, the vacuum chamber may be, or be part of, any device
or system that utilizes an evacuated region such as a scientific
instrument or a fabrication instrument. Examples of scientific
instruments include, but are not limited to, mass spectrometers,
ion mobility spectrometers, gas leak detectors, and electron
microscopes. Examples of fabrication instruments include, but are
not limited to, instruments that utilize evacuated reaction
chambers to fabricate components for microelectronics,
microelectromechanical systems (MEMS), microfluidics, and the like.
Such fabrication instruments may, for example, utilize techniques
involving vacuum deposition, plasma generation, electron beam
generation, molecular beam generation, ion implantation, and the
like as appreciated by persons skilled in the art.
[0024] FIG. 2 is a schematic view of an example of a vacuum system
200 according to an embodiment disclosed herein. The vacuum system
200 includes at least one vacuum pump. In the present embodiment,
the vacuum system 200 includes a backing pump 218. The backing pump
218 includes a vacuum pump isolation (VPI) valve 214, a pump inlet
234 communicating with a high-vacuum stage 222 of the vacuum system
200 via the VPI valve 214, and a pump outlet 238 that discharges
gas into a main exhaust gas line 242. The backing pump 218 may be a
mechanical pump as described above. The high-vacuum stage 222
includes one or more vacuum chambers 226 communicating with the
backing pump 218. The high-vacuum stage 222 may further include one
or more high-vacuum pumps 230 as described above. The backing pump
218 further includes a first exhaust gas transfer line or port 254
that provides fluid communication between the main exhaust gas line
242 and a pilot valve 246, and a second exhaust gas transfer line
or port 258 that provides fluid communication between the pilot
valve 246 and the VPI valve 214. The VPI valve 214 and the exhaust
gas transfer lines 254 and 258 are schematically depicted
separately from the backing pump 218 for illustrative purposes. In
some embodiments, however, the VPI valve 214 is integrated with or
internal to the main structure or housing of the backing pump 218.
The exhaust gas transfer lines 254 and 258 may also be integrated
with or internal to the main structure or housing of the backing
pump 218. In other embodiments, all or part of the first exhaust
gas transfer line 254 and the pilot valve 246 may be disposed
outside of the main structure or housing of the backing pump
218.
[0025] Generally, the pilot valve 246 may be any type of valve
capable of being actuated into an open state and a closed state. In
a typical yet non-exclusive embodiment, the pilot valve 246 is
configured as a normally open valve, i.e., the pilot valve 246
requires electrical power to be actively held in the closed state.
As one example, the pilot valve 246 may be a solenoid-actuated
valve. The same power source (e.g., a 24-V power supply) may be
utilized to supply power both to the pilot valve 246 and to the
backing pump 218.
[0026] An example of operating the vacuum system 200 will now be
described. In this example, the vacuum system 200 includes both the
backing pump 218 providing a first vacuum pumping stage and at
least one high-vacuum pump 230 providing at least one additional
vacuum pumping stage.
[0027] Starting with the backing pump 218 off, interior regions of
the vacuum system 200 such as the backing pump 218 and the vacuum
chamber 226 are at atmospheric pressure, and the VPI valve 214 is
open. The VPI valve 214 typically includes a movable valve element
such as a piston that may be biased to an open (unseated) position
by a spring, as described further below. The normally open pilot
valve 246 is also open at this time. When the backing pump 218 is
then started, power is supplied to the pilot valve 246 causing the
pilot valve 246 to close (e.g., by energizing a solenoid), thereby
isolating the VPI valve 214 from the discharge/exhaust side of the
backing pump 218. The VPI valve 214 remains open at this time. As
the backing pump 218 operates, vacuum begins to develop in the
high-vacuum stage 222. Subsequent operation of the high-vacuum pump
230 brings the vacuum to the level required for the intended use of
the vacuum chamber 226.
[0028] If, then, the backing pump 218 loses power, for example is
turned off or shuts off due to power failure or power supply fault,
the pilot valve 246 opens. For example, in the case of a
solenoid-based pilot valve the pilot valve 246 likewise loses
power, whereby the solenoid is de-energized causing the pilot valve
246 to move to its normally open position. With the pilot valve 246
open, one side of the VPI valve 214 is now exposed to the pressure
of the exhaust gas via the first exhaust gas transfer line 254, the
pilot valve 246, and the second exhaust gas transfer line 258. The
exhaust gas pressure may be, for example, at or around atmospheric
pressure, but in any case is much higher than the pressure in the
evacuated regions on the other side of the VPI valve 214. As a
result, a pressure differential develops across the VPI valve 214
that is large enough to close the VPI valve 214. For example, as
described further herein the VPI valve 214 may include a
spring-biased piston that is forced by the exhaust gas pressure to
become seated against the biasing force of the spring. The VPI
valve 214 may be configured to close rapidly (e.g., in a few
milliseconds) upon the opening of the pilot valve 246. The closing
of the VPI valve 214 closes off the working gas flow path (lines
262 and 266 in FIG. 2) between the high-vacuum stage 222 and the
backing pump 218. In this way, the high level of vacuum in the
high-vacuum stage 222 maintained until the backing pump 218 becomes
operational again.
[0029] When the backing pump 218 is restarted, the pilot valve 246
is closed again. Exhaust gas is removed from the VPI valve 214 and
drawn into the pump inlet 234 of the backing pump 218. When the
pressure in the VPI valve 214 becomes low enough, the VPI valve 214
opens back up, thereby re-coupling the high-vacuum stage 222 with
the backing pump 218.
[0030] From the foregoing it is evident that the VPI valve 214 is
driven to close by an internal mechanism, namely the pressure of an
internally routed flow of exhaust gas. Ambient air is not utilized
and does not enter the vacuum system 200. Therefore, the backing
pump 218 provides a hermetic solution for vacuum pump
isolation.
[0031] FIG. 3A is a partially cut-away perspective view of an
example of a part of a vacuum pump 318 that includes a VPI valve
314 according to an embodiment. The vacuum pump 318 and the VPI
valve 314 may be provided as part of a vacuum system. Accordingly,
as an example, the vacuum pump 318 and the VPI valve 314 may
correspond to the backing pump 218 and the VPI valve 214 of the
vacuum system 200 described above and illustrated in FIG. 2.
[0032] The vacuum pump 318 generally includes a pump body 320
enclosing a pump interior 324. Stationary and moving pumping
elements (not shown) are disposed in the pump interior 324. The
configuration of the pumping elements (e.g., scrolls, vanes, lobes,
etc.) depends on the particular embodiment of the vacuum pump 318.
The vacuum pump 318 includes a pump inlet 334. In the present
embodiment, the pump inlet 334 is defined by a pump inlet housing
(or pump inlet flange) 336 that is coupled to the pump body 320 in
a vacuum-tight manner. The pump inlet housing 336 is configured to
be fluidly coupled to a vacuum system (a high-vacuum stage as
described above) as indicated by an arrow 322 in FIG. 3. The pump
inlet housing 336 includes a pump inlet port 340 in which the VPI
valve 314 is positioned. The VPI valve 314 is positioned such that
the pump inlet 334 selectively provides fluid communication between
the pump interior 324 and the rest of the vacuum system
(high-vacuum stage) 322 depending on the state of the VPI valve
314.
[0033] FIG. 3A illustrates the VPI valve 314 in an open state. In
the open state, the VPI valve 314 allows gas to flow freely (due to
operation of the pumping elements of the vacuum pump 318) from the
vacuum system 322 into the pump inlet 334, and into the pump
interior 324 via the pump inlet port 340, as generally indicated by
an arrow 344. For this purpose, the VPI valve 314 may include a
movable member that is movable between an open position
corresponding to the open state and a closed position corresponding
to the closed state. The closed position of the movable member, and
thus the closed state of the VPI valve 314, are illustrated in FIG.
3B, described further below.
[0034] In the present embodiment, the VPI valve 314 includes a
movable member in the form of a piston 348. The piston 348 is
movable linearly (in the vertical direction, from the perspective
of FIG. 3A) between the open position (FIG. 3A) to the closed
position (FIG. 3B). The linear movement or translation of the
piston 348 may be guided by a piston guide 352. In the present
embodiment, the piston guide 352 is in the form of a stationary pin
that is elongated in the direction of piston movement and extends
into a central bore of the piston 348. The piston 348 may be biased
toward the illustrated open position by an appropriate spring 356
that surrounds the piston 348 and is retained by one or more outer
surfaces of the piston 348 and inner surfaces of the pump inlet
housing 336. Also in the present embodiment, the piston 348
includes a first piston portion (or main piston body) 360 and a
second piston portion 364 (or piston nut) attached (e.g., by
threaded engagement) to the first piston portion 360. The piston
guide 352 extends through a central bore of the second piston
portion 364 and into a central bore of the first piston portion
360.
[0035] The VPI valve 314 further includes an annular diaphragm 368
composed of a suitably flexible material (e.g., rubber). The
diaphragm 368 is attached to the piston 348 and to the pump inlet
housing 336 and/or the pump body 320. More specifically in the
illustrated embodiment, the inner peripheral region of the
diaphragm 368 is clamped between the first piston portion 360 and
the second piston portion 364, and the outer peripheral region of
the diaphragm 368 is clamped between the pump inlet housing 336 and
the pump body 320. As illustrated, the outer peripheral region of
the diaphragm 368 may include an annular bead that is positioned in
an annular groove of the pump inlet housing 336.
[0036] FIG. 3B is a partially cut-away perspective view of the
vacuum pump 318 similar to the view of FIG. 3A, but illustrating
the VPI valve 314 in a closed position. As best shown in FIG. 3B, a
variable-volume control volume chamber 372 is defined (bounded) by
the piston 348 (specifically the second piston portion 364), the
diaphragm 368, and a surface 376 of the pump body 320 axially
opposite to and facing the piston 348 (specifically the second
piston portion 364). From the perspective of FIGS. 3A and 3B, the
control volume chamber 372 is positioned under the piston 348 and
the diaphragm 368. The volume of the control volume chamber 370 is
at a minimum value when the piston 348 is in the open position
(FIG. 3A), which is its lowermost position from the perspective of
FIGS. 3A and 3B. At the open position the piston 348 (specifically
the second piston portion 364) may abut the pump body surface 376.
In some embodiments and as illustrated in FIG. 3A, at the open
position a portion of the diaphragm 368 may be folded onto itself.
On the other hand, the volume of the control volume chamber 370
expands out to a maximum when the piston 348 is moved to the closed
position (FIG. 3B), which is its uppermost position from the
perspective of FIGS. 3A and 3B. As shown in FIG. 3B, at the closed
position the piston 348 (specifically the first piston portion 360)
abuts an annular valve seat 380. The valve seat 380 may be formed
on an inside surface of the pump inlet housing 336. To enhance the
sealing interface between the piston 348 and the valve seat 380 at
the closed position, the valve seat 380 may be engineered (e.g.,
machined) to have a smoother surface (of less surface roughness)
than other interior surfaces not utilized for sealing. Moreover,
the piston 348 may include a sealing element 384 (for example, an
O-ring positioned in an annular groove of the first piston portion
360) that contacts the valve seat 380 and may be deformed to some
extent between the piston 348 and the valve seat 380 upon
contacting the valve seat 380. As further shown in FIG. 3B, the
spring 356 is compressed at the closed position.
[0037] As in the embodiment described above and illustrated in FIG.
2, the vacuum pump 318 includes an exhaust gas transfer line
running from a main exhaust gas line of the vacuum pump 318 to the
VPI valve 314, and a pilot valve operatively positioned in the
exhaust gas transfer line to alternately close (block gas flow
through) the exhaust gas transfer line and open (allow gas flow
through) the exhaust gas transfer line. Examples of components
making up the exhaust gas transfer line and the pilot valve will
now be described with reference to FIGS. 3A, 3B, 4, and 5.
[0038] FIG. 4 is a partially cut-away side view of the vacuum pump
318 illustrated in FIGS. 3A and 3B. Relative to the view of FIGS.
3A and 3B, the view of FIG. 4 is rotated about a vertical axis. As
illustrated in FIG. 4, the vacuum pump 318 includes a pilot valve
488. As described earlier in the present disclosure, the pilot
valve 488 generally may be any type of valve capable of being
actuated into an open state and a closed state. In a typical yet
non-exclusive embodiment, the pilot valve 488 is configured as a
normally open valve, i.e., the pilot valve 488 requires electrical
power to be actively held in the closed state. As one example, the
pilot valve 488 may be a solenoid-actuated valve. A power source
supplies power to the pilot valve 488 via appropriate electrical
wiring 490. The same power source (e.g., a 24-V power supply) may
be utilized to supply power both to the pilot valve 488 and to the
motor of the vacuum pump 318 that drives the movable pump
element(s) (e.g., the orbiting scroll of a scroll pump). The pilot
valve 488 may be mounted between a first gas-conducting block (or
bracket) 492 and a second gas-conducting block (or bracket) 394.
The pilot valve 488, the first gas-conducting block 492, and the
second gas-conducting block 394 may be positioned outside of the
pump body 320.
[0039] The vacuum pump 318 includes a main exhaust gas line 442
that conducts the gas worked by the pumping elements away from the
discharge side of the vacuum pump 318, as appreciated by persons
skilled in the art. As noted above, in the present embodiment the
main exhaust gas line 442 communicates with the pilot valve 488
and, in turn, with the VPI valve 314 (FIGS. 3A and 3B) via an
exhaust gas transfer line. In the present embodiment the exhaust
gas transfer line is collectively formed or defined by a plurality
of gas channels (internal passages). The gas channels are distinct
from each other in that they are disposed in different solid
structures. Adjacent gas channels communicate with each other at
fluid-sealed junctions where different solid structures are
interfaced and/or via fluidic fittings as appropriate.
[0040] In the embodiment specifically illustrated in FIG. 4, the
exhaust gas transfer line includes a first gas channel 421 disposed
in an outboard housing 423 of the pump body 320 and fluidly coupled
to the main exhaust gas line 442 (also disposed in the outboard
housing 423), a second gas channel 425 disposed in a cast frame 427
of the pump body 320 and fluidly coupled to the first gas channel
421, a third gas channel 429 (partially shown) disposed in the
first gas-conducting block 492 and fluidly coupled to the second
gas channel 425, a fourth gas channel 531 (not shown in FIG. 4,
partially shown in FIG. 5) disposed in the pilot valve 488 and
fluidly coupled to the third gas channel 429, and a fifth gas
channel 333 (not shown in FIG. 4, partially shown in FIGS. 3A and
3B) disposed in the second gas-conducting block 394 and fluidly
coupled to the fourth gas channel. While in the partial cut-way
view of FIG. 4 only a part of the third gas channel 429 is shown
and the fourth and fifth gas channels are not specifically shown,
the gas flow through the first gas-conducting block 492, the pilot
valve 488, and the second gas-conducting block 394 is schematically
depicted by a dashed line 435. The fluid couplings or interfaces
between different gas channels may be fluid-sealed by any suitable
means. As an example, FIG. 4 illustrates the provision of sealing
elements 433 such as O-rings.
[0041] FIGS. 3A and 3B illustrate the second gas-conducting block
394 and portions of its internal fifth gas channel 333. In the
embodiment specifically illustrated in FIGS. 3A and 3B, the exhaust
gas transfer line further includes a sixth gas channel 339 disposed
in the pump body 320 (for example, in the cast frame 427) and
fluidly coupled to the fifth gas channel 333. From the perspective
of FIGS. 3A and 3B, the sixth gas channel 339 includes a horizontal
portion fluidly coupled to the fifth gas channel 333 and leading to
a vertical portion that is in open communication with the control
volume chamber 370 (FIG. 3B). In the open (lowered) position of the
piston 348 shown in FIG. 3A, the piston 348 (specifically the
second piston portion 364) may or may not block fluid flow between
the sixth gas channel 339 to the control volume chamber 370. In
either case, gas flow through the exhaust gas transfer line is
dictated by the state (open or closed) of the pilot valve 488.
[0042] FIG. 5 is a partially cut-away top view of the vacuum pump
318 illustrated in FIGS. 3A, 3B, and 4, with the VPI valve 314 and
the associated pump inlet pump inlet 334 (FIGS. 3A and 3B) removed.
The cut-away is taken through a plane passing through the pilot
valve 488, second gas-conducting block 394, and a portion of the
pump body 320 underneath the control volume chamber 370 (FIG. 3B).
The cut-away plane is located such that the third gas channel 429
(FIG. 4) of the first gas-conducting block 492 is not shown, only a
portion of the fourth gas channel 531 of the pilot valve 488 is
shown, only a portion of the fifth gas channel 333 of the second
gas-conducting block 394 is shown, and only portions of the sixth
gas channel 339 (part of the horizontal portion, and the
cross-section of the vertical portion, shown in FIGS. 3A and 3B) in
the pump body 320 are shown. The gas flow through the portions of
these gas channels not shown is schematically depicted by dashed
line 535. The fourth gas channel 531 may be defined by one or more
internal passages of the pilot valve 488. Depending on its
configuration, the pilot valve 488 may include one or more valve
elements (typically at least one movable valve element) that switch
the pilot valve 488 between its open and closed states and thereby
control gas flow through the pilot valve 488 and thus the exhaust
gas transfer line.
[0043] The vacuum pump 318 generally may operate as described above
in relation to the embodiment shown in FIG. 2. Assuming that the
vacuum pump 318 has not been operating, the interior regions of the
vacuum pump 318 and other portions of the system communicating with
the vacuum pump 318 (such as the vacuum stage 322) are at ambient
(e.g., atmospheric) pressure. At this time, the VPI valve 314 is in
the open state due the piston 348 being biased by the spring 356 to
the open position shown in FIG. 3A. Also at this time, the normally
open pilot valve 488 is also in its open state, as no power is
being supplied to the pilot valve 488 to urge it to its closed
position.
[0044] The vacuum pump 318 may then be started by supplying power
to the motor of the vacuum pump 318. At this time power is also
supplied to the pilot valve 488, causing it to switch to and be
held at its closed state, thereby blocking exhaust gas flow in the
exhaust gas transfer line and thus isolating the VPI valve 314 from
the main exhaust gas line 442. At this time the vacuum pump 318 is
operating normally. The vacuum pump 318 develops a vacuum in its
intake (suction) side as well as in the vacuum stage 322 by drawing
gas molecules from the vacuum stage 322 into the pump interior 324
via the pump inlet 334 (as generally depicted by the arrow 344 in
FIG. 3A) and transferring the gas molecules into the main exhaust
gas line 442 in the discharge side of the vacuum pump 318. The VPI
valve 314 remains in its open state, as the gas pressure in the
control volume chamber 372 is not sufficient to overcome the
biasing force imparted to the piston 348 by the spring 356. As
shown in FIGS. 3A and 3B, the vacuum pump 318 may include a
small-diameter orifice 339 that provides gas conductance-limited
fluid communication between the pump inlet port 340 and the control
volume chamber 372. The orifice 339 may serve to equalize the
pressure in the control volume chamber 372 with the vacuum pressure
in the pump inlet port 340. Thus, during normal operation of the
vacuum pump 318, no pressure differential exists across the piston
348.
[0045] If at some point during normal operation the vacuum pump 318
shuts down either intentionally or due to an operational failure,
the pilot valve 488 also loses power and switches to its open
state. Consequently, the control volume chamber 372 communicates
with the main exhaust gas line 442 (which may be at or around
atmospheric pressure) via the now open exhaust gas transfer line,
and is rapidly pressurized by exhaust gas flowing into the control
volume chamber 372. Accordingly, a pressure differential rapidly
develops across the piston 348 and forces the piston 348 to move to
the closed position illustrated in FIG. 3B against the biasing
force of the spring 356. At the closed position, the piston 348
blocks gas flow between the vacuum stage 322 and the pump inlet
port 340 and thereby maintains vacuum pressure in the vacuum stage
322. The diaphragm 368 prevents exhaust gas from rapidly flowing
from the control volume chamber 372 into the vacuum stage 322.
However, the gas conductance-limiting orifice 339 allows exhaust
gas to slowly flow from the control volume chamber 372, through the
orifice 339, through the pump inlet port 340, and into the pump
interior 324. This small gas flow through the orifice 339 may
function to prevent the backflow of gas up from the main exhaust
gas line 442, through the pump interior 324, and into the pump
inlet port 340, and thereby prevent oil or particles from entering
the pump inlet 334.
[0046] When subsequently the vacuum pump 318 is restarted, the
pilot valve 488 is switched back to its closed state, thereby
reestablishing a fluidic seal in the exhaust gas transfer line
between the VPI valve 314 and the main exhaust gas line 442. As the
vacuum pump 318 begins to develop vacuum again during this resumed
operation, the vacuum pump 318 gradually pumps out the exhaust gas
in the control volume chamber 372 (and in the portion of the
exhaust gas transfer line between the control volume chamber 372
and the now closed pilot valve 488) via the orifice 339. The
pressure differential across the piston 348 becomes smaller and,
when the pressure in the control volume chamber 372 becomes small
enough, the piston 348 (assisted by the spring 356) moves back to
the open position thereby reestablishing fluid communication
between the vacuum pump 318 and the vacuum stage 322.
[0047] From the foregoing it is seen that the vacuum pump 318, as
in other embodiments disclosed herein, provides a VPI valve that is
hermetic and does not require ambient air for its operation.
[0048] As noted above, a vacuum pump as disclosed herein may be a
scroll pump. The pumping stage of the scroll pump may include a
stationary scroll and an orbiting scroll drivable to orbit relative
to the stationary scroll, as appreciated by persons skilled in the
art. Examples of scroll pumps are further described in, for
example, U.S. Patent Application Pub. Nos. US 2014/0271233 A1; US
2014/0271242 A1; and US 2016/0201674 A1; the contents of each of
which are hereby incorporated by reference herein in their
entireties.
[0049] It will be understood that terms such as "communicate" and
"in . . . communication with" (for example, a first component
"communicates with" or "is in communication with" a second
component) are used herein to indicate a structural, functional,
mechanical, electrical, signal, optical, magnetic, electromagnetic,
ionic or fluidic relationship between two or more components or
elements. As such, the fact that one component is said to
communicate with a second component is not intended to exclude the
possibility that additional components may be present between,
and/or operatively associated or engaged with, the first and second
components.
[0050] It will be understood that various aspects or details of the
invention may be changed without departing from the scope of the
invention. Furthermore, the foregoing description is for the
purpose of illustration only, and not for the purpose of
limitation--the invention being defined by the claims.
* * * * *