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.

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

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 limitationthe invention being defined by the claims.