HERMETIC VACUUM PUMP ISOLATION VALVE
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.
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.
BACKGROUNDVarious 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 10−3 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 10−3 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.
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.
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.
More specific examples of the foregoing VPI configuration are described in U.S. Pat. No. 4,785,851.
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.
SUMMARYTo 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.
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.
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.
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.
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.
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.
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.
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.
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.
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 10−9 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.
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.
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.
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.
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
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.
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.
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
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
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.
As in the embodiment described above and illustrated in
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 (
In the embodiment specifically illustrated in
The vacuum pump 318 generally may operate as described above in relation to the embodiment shown in
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
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
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.
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.
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.
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.
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.
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.
Type: Application
Filed: Aug 30, 2016
Publication Date: Mar 1, 2018
Inventors: George Galica (Worcester, MA), John Calhoun (Lexington, MA), Ronald J. Forni (Lexington, MA), Vannie Lu (Billerica, MA)
Application Number: 15/251,567