FIELD OF THE INVENTION

The present invention relates to delivering purge gas to vacuum pumps, and more particularly to stators having purge gas flow paths for delivering purge gas to vacuum pumps.

BACKGROUND

Vacuum pumps are often purged with a purge gas, thereby removing working fluid from the vacuum pump. Purging may be performed, for example, in preparation for maintenance of the vacuum pump, before beginning operation of the vacuum pump, or before shut-down of the vacuum pump. Purging may be used, for example, to reduce the risk of (e.g., hazardous) working fluids being released from the vacuum pump or being undesirably mixing with other working fluids during subsequent pump operation, or to perform leak tests, or to reduce the risk of deposit and/or condensation formation or unwanted chemical reactions within the vacuum pump which may detrimentally affect performance of the vacuum pump.

Delivery of purge gas to a vacuum pumping chamber tends to mitigate formation of deposits and/or condensation of working fluid, e.g. of residual working fluid present in the chamber after pumping. Purge gas which is delivered at temperatures significantly lower than that of the working fluid in the vacuum pump may however detrimentally affect the extent to which formation of deposits and/or condensation is mitigated, or even increase the risk of deposits and/or condensation.

SUMMARY OF THE INVENTION

In an aspect, there is provided a stator for use in a vacuum pump. The stator comprises an inlet stator part comprising a working fluid inlet. The stator further comprises an exhaust stator part comprising: a working fluid outlet; a first purge gas inlet; and a first purge gas channel extending through the exhaust stator part from the first purge gas inlet. The inlet stator part and the exhaust stator part define a first pumping chamber between the working fluid inlet and the working fluid outlet. The first purge gas inlet is distinct from each of the working fluid inlet and the working fluid outlet, and is disposed on a surface of the exhaust stator part external to the first pumping chamber. The first purge gas channel extends from the first purge gas inlet towards the first pumping chamber and forms at least a part of a first purge gas flow path. The first purge gas flow path fluidly connects the first purge gas inlet to the first pumping chamber.

A second purge gas channel may be formed between the inlet stator part and the exhaust stator part and may be formed outside the first pumping chamber. The second purge gas channel may be at least in part defined by a first groove in the exhaust stator part. The first purge gas channel and the second purge gas channel may be fluidly connected and may together define the first purge gas flow path.

The second purge gas channel may be formed at a first side of the exhaust stator part, the first side being opposite a second side of the exhaust stator part at which the first purge gas inlet is disposed. Advantageously, this tends to provide the first purge gas flow path with a lengthened path of travel through the stator than if the second purge gas channel was formed at the same side as the first purge gas inlet, thereby providing improved heating of purge gas passing therethrough.

The first purge gas flow path may be a bent, meandering or convoluted path. Advantageously, this tends to lengthen the first purge gas flow path, thereby providing improved heating of purge gas passing therethrough. The first purge gas flow path may be a serpentine path. There may be disposed along the first purge gas flow path one or more fins. Advantageously, the one or more fins tend to improve a rate of heat transfer across the first purge gas flow path, thereby providing improved heating of purge gas passing therethrough. The exhaust stator part may further comprise a second purge gas inlet and a third purge gas channel extending through the exhaust stator part from the second purge gas inlet. The inlet stator part and the exhaust stator part may define a second pumping chamber between the working fluid inlet and the working fluid outlet. The first and second pumping chambers may correspond to, e.g. at least in part define, respective pumping stages of the vacuum pump. The second purge gas inlet may be distinct from each of the working fluid inlet and the working fluid outlet and may be disposed on a surface of the exhaust stator part external to the second pumping chamber. The third purge gas channel may extend from the second purge gas inlet towards the second pumping chamber and may form at least a part of a second purge gas flow path. The second purge gas flow path may fluidly connect the second purge gas inlet to the second pumping chamber.

A fourth purge gas channel may be formed between the inlet stator part and the exhaust stator part and may be formed outside the second pumping chamber. The fourth purge gas channel may be at least in part defined by a second groove in the exhaust stator part. The third purge gas channel and the fourth purge gas channel may be fluidly connected and may together define the second purge gas flow path.

The first pumping chamber and the second pumping chamber may be displaced in an axial direction and may be in fluid communication. One or both of the second purge gas channel and the fourth purge gas channel may extend through the exhaust stator part in the axial direction. The first purge gas channel and the third purge gas channel may be substantially parallel.

The second purge gas inlet may be formed in the surface of the exhaust stator part at the first side of the exhaust stator part opposite the second side of the exhaust stator part. Advantageously, this tends to provide the second purge gas flow path with a lengthened path of travel through the stator than if the second purge gas inlet was formed away from the first side of the exhaust stator part, thereby providing improved heating of purge gas passing therethrough. The second purge gas flow path may be a bent, meandering or convoluted path. Advantageously, this tends to lengthen the second purge gas flow path, thereby providing improved heating of purge gas passing therethrough. The second purge gas flow path may be a serpentine path. There may be disposed along the second purge gas flow path a further one or more fins. Advantageously, the further one or more fins tend to improve a rate of heat transfer across the second purge gas flow path, thereby providing improved heating of purge gas passing therethrough.

A first temperature of the inlet stator part may be less than a second temperature of the exhaust stator part.

The second temperature may be approximately 30 degrees Celsius greater than the first temperature.

The vacuum pump may be a Roots dry pump.

The exhaust stator part may further comprise a further first purge gas channel extending through the exhaust stator part from the first purge gas inlet. The further first purge gas channel may extend from the first purge gas inlet towards the first pumping chamber and may form at least a part of a further first purge gas flow path, the further first purge gas flow path fluidly connecting the first purge gas inlet to the first pumping chamber. The further first purge gas flow path may be distinct from the first purge gas flow path.

A further second purge gas channel may be formed between the inlet stator part and the exhaust stator part and may be formed outside the first pumping chamber. The further second purge gas channel may be at least in part defined by a further first groove in the exhaust stator part. The further first purge gas channel and the further second purge gas channel may be fluidly connected and may together define the further first purge gas flow path.

In a further aspect, there is provided a method of introducing a purge gas to a vacuum pump via the stator of the preceding aspect. The method comprising passing the purge gas along the first purge gas flow path from the first purge gas inlet to the first pumping chamber. The stator may comprise a second purge gas inlet and a third purge gas channel extending through the exhaust stator part from the second purge gas inlet. The inlet stator part and the exhaust stator part may define a second pumping chamber between the working fluid inlet and the working fluid outlet. The first and second pumping chambers may correspond to, e.g. at least in part define, respective pumping stages of the vacuum pump. The second purge gas inlet may be distinct from each of the working fluid inlet and the working fluid outlet and may be disposed on a surface of the exhaust stator part external to the second pumping chamber. The third purge gas channel may extend from the second purge gas inlet towards the second pumping chamber and may form at least a part of a second purge gas flow path. The second purge gas flow path may fluidly connect the second purge gas inlet to the second pumping chamber. The method may further comprise passing the purge gas along the second purge gas flow path from the second purge gas inlet to the second pumping chamber.

In a further aspect, there is provided a vacuum pumping system comprising the stator of the foremost aspect above. The vacuum pumping system further comprises a purge gas source fluidly connected to the first purge gas inlet.

The stator may comprise a second purge gas inlet and a third purge gas channel extending through the exhaust stator part from the second purge gas inlet. The inlet stator part and the exhaust stator part may define a second pumping chamber between the working fluid inlet and the working fluid outlet. The first and second pumping chambers may correspond to, e.g. at least in part define, respective pumping stages of the vacuum pump. The second purge gas inlet may be distinct from each of the working fluid inlet and the working fluid outlet and may be disposed on a surface of the exhaust stator part external to the second pumping chamber. The third purge gas channel may extend from the second purge gas inlet towards the second pumping chamber and may form at least a part of a second purge gas flow path. The second purge gas flow path may fluidly connect the second purge gas inlet to the second pumping chamber. The purge gas source may be fluidly connected to the second purge gas inlet. The purge gas source may supply the same purge gas to the first purge gas inlet as to the second purge gas inlet. The purge gas source may supply a different purge gas to the first purge gas inlet as to the second purge gas inlet. The second purge gas inlet may be supplied purge gas by a different or distinct purge gas source than that which supplies the first purge gas inlet with purge gas. The distinct purge gas sources may supply the same purge gas to the first and second purge gas inlets. The distinct purge gas sources may supply different respective purge gases to the first and second purge gas inlets.

In a further aspect, there is provided an exhaust stator part for a vacuum pump stator. The exhaust stator part comprises a working fluid inlet, a working fluid outlet, a first purge gas inlet, and a first purge gas channel extending through the exhaust stator part from the purge gas inlet. The first purge gas inlet is distinct from each of the working fluid inlet and the working fluid outlet. The first purge gas inlet is disposed on a surface of the exhaust stator part opposite the working fluid inlet. The first purge gas channel extends from the first purge gas inlet and forms at least a part of a first purge gas flow path.

The first purge gas flow path may fluidly connect the first purge gas inlet to the working fluid inlet.

The first purge gas flow path may further comprise a second purge gas channel at least in part defined by a first groove in the exhaust stator part.

The exhaust stator part may further comprise a second purge gas inlet, and a third purge gas channel extending through the exhaust stator part from the second purge gas inlet. The second purge gas inlet may be distinct from each of the working fluid inlet and the working fluid outlet. The second purge gas inlet may be disposed on the surface of the exhaust stator part opposite the working fluid inlet. The third purge gas channel may extend from the second purge gas inlet and may form at least a part of a second purge gas flow path. The second purge gas flow path may fluidly connect the second purge gas inlet to the working fluid inlet. The second purge gas flow path may further comprise a fourth purge gas channel at least in part defined by a second groove in the exhaust stator part.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is a perspective view (not to scale) of an exemplary vacuum pump known in the art;

Figure 2 is a front (axial) view cross-section (not to scale) of the vacuum pump;

Figure 3 is a perspective view cross-section (not to scale) of the vacuum pump;

Figure 4 is a plan view (not to scale) of an exhaust stator of the vacuum pump;

Figure 5 is a perspective view (not to scale) of the exhaust stator of the vacuum pump;

Figure 6 is a perspective view (not to scale) of a further vacuum pump according to the present invention;

Figure 7 is a front (axial) view cross-section (not to scale) of the further vacuum pump;

Figure 8 is a perspective view cross-section (not to scale) of the further vacuum pump;

Figure 9 is a plan view (not to scale) of an exhaust stator of the further vacuum pump;

Figure 10 is a perspective view (not to scale) of the exhaust stator of the further vacuum pump; and

Figure 11 is a process flow chart depicting steps of a method for purging the further vacuum pump using a purge gas. DETAILED DESCRIPTION

Figure 1 is a perspective view (not to scale) of an exemplary vacuum pump 100 known in the art. In this example, the vacuum pump 100 is a dry vacuum pump, and specifically a Roots-type vacuum pump.

The vacuum pump 100 comprises a housing 102 defining a front side 104, a back side 106, a top side 108, a bottom side 110, a first lateral side 112, and a second lateral side 113. The front side 104 opposes the back side 106. The top side 108 and the bottom side 110 oppose each other and extend between the front and back sides 104, 106. The first lateral side 112 and the second lateral side 113 oppose each other and extend between the front and back sides 104, 106. The housing 102 is formed of an inlet stator 122 and an exhaust stator 124. The inlet stator 122 may be considered a top stator, i.e. the inlet stator 122 defines the top side 108 of the housing 102. The inlet stator 122 and the exhaust stator 124 are substantially contiguous, e.g. along the line 126 of Figure 1 , and form therebetween one or more pumping chambers (not shown in Figure 1 ) of the vacuum pump 100. The exhaust stator 124 may be considered a bottom stator, i.e. the exhaust stator 124 defines the bottom side 110 of the housing 102. The inlet stator 122 comprises a working fluid inlet of the one or more pumping chambers. The exhaust stator 124 comprises a working fluid outlet of the one or more pumping chambers, and may thus be considered an outlet stator.

The vacuum pump 100 further comprises, at the top side 108 of the housing 102, a plurality of purge gas inlets 128. In this example, the plurality of purge gas inlets 128 are spaced in an axial direction 130 along the top side 108 of the housing 102.

The inlet stator 122 comprises a first plurality of channels 132, each channel of which extends, through an interior of the inlet stator 122, from a respective one of the plurality of purge gas inlets 128, away from the top side 108 in a substantially diagonal direction towards the bottom side 110 and first lateral side 112. The channels of the first plurality of channels 132 are axially displaced, i.e. displaced in the axial direction 130. In this example, the channels of the first plurality of channels 132 are substantially parallel.

The inlet stator 122 further comprises a second plurality of channels 134, each channel of which extends, through the interior of the inlet stator 122, from a respective one of the plurality of purge gas inlets 128, away from the top side 108 in a substantially diagonal direction towards the bottom side 110 and second lateral side 113. The channels of the second plurality of channels 134 are axially displaced, i.e. displaced in the axial direction 130. In this example, the channels of the second plurality of channels 134 are substantially parallel.

The exhaust stator 124 further comprises a first plurality of grooves and a second plurality of grooves (not shown in Figure 1 ). Each groove of the first plurality of grooves is formed proximate a top edge of the exhaust stator 124 (i.e. proximate the line 126 indicated in Figure 1 ) and connects a respective one of the first plurality of channels 132 to the one or more pumping chambers. Each groove of the second plurality of grooves is formed proximate the top edge of the exhaust stator 124 (i.e. proximate the line 126 indicated in Figure 1 ) and connects a respective one of the second plurality of channels 134 to the one or more pumping chambers.

In this example, each groove of the first plurality of grooves connects a respective one of the first plurality of channels 132 to a respective pumping chamber of the one or more pumping chambers. Each groove of the second plurality of grooves connects a respective one of the second plurality of channels 134 to a respective pumping chamber of the one or more pumping chambers. Each groove of the first plurality of grooves and the second plurality of grooves, together with a lower surface of the inlet stator 122 proximate the line 126, forms a respective conduit or channel which extends through the vacuum pump 100 to the respective pumping chamber.

In this example, the first plurality of channels 132 comprises four channels, the first plurality of grooves comprises four grooves, and the one or more pumping chambers comprises four pumping chambers. The one or more pumping chambers, comprising four pumping chambers in this example, are hence hereinafter referred to as “the pumping chambers”.

More specifically, in this example, each of the four channels 132 is connected by a respective one of the first plurality of grooves to a respective one of the pumping chambers.

Similarly, in this example, the second plurality of channels 134 comprises four channels, and the second plurality of grooves comprises four grooves. In particular, in this example, each of the four channels 134 is connected by a respective one of the second plurality of grooves to a respective one of the pumping chambers. That is to say that, in this example, each of the (four) pumping chambers is contiguous and in fluid communication with two grooves, one groove being a respective groove of the first plurality of grooves, the other groove being a respective groove of the second plurality of grooves.

However, in other examples, the first plurality of channels 132 may comprise a different number of channels other than four, e.g. two, or three, or five, or six, or more channels, or the first plurality of channels 132 may be replaced by a single channel. The second plurality of channels 134 may comprise a different number of channels other than four, e.g. two, or three, or five, or six, or more channels, or the second plurality of channels 134 may be replaced by a single channel.

In other examples, the first plurality of grooves may comprise a different number of grooves other than four, e.g. two, or three, or five, or six, or more grooves, or the first plurality of grooves may be replaced by a single groove. The second plurality of grooves may comprise a different number of grooves other than four, e.g. two, or three, or five, or six, or more grooves, or the first plurality of grooves may be replaced by a single groove.

In other examples, the one or more pumping chambers may comprise a different number of pumping chambers other than four, e.g. one, or two, or three, or five, or six, or more pumping chambers. In these and other examples, each chamber of the one or more pumping chambers may be contiguous and in fluid communication with a different number of grooves of the first plurality of grooves other than one, e.g. zero, or two, or more grooves, and/or may be contiguous and in fluid communication with a different number of grooves of the second plurality of grooves other than one, e.g. zero, or two, or more grooves.

The vacuum pump 100 may be configured to, in use, receive a working fluid via an inlet (not shown) to the one or more pumping chambers, the inlet being formed in the inlet stator 122. The vacuum pump 100 may be further configured to, in use, pump the working fluid through the one or more pumping chambers, and expel the working fluid from the vacuum pump 100 via an outlet (not shown) of the one or more pumping chambers, the outlet being formed in the exhaust stator 124.

The vacuum pump 100 is further configured such that the one or more pumping chambers may be purged of working fluid, e.g. before or after pumping working fluid.

During purging, the vacuum pump 100 receives, from one or more purge gas sources (not shown), a purge gas via the plurality of purge gas inlets 128. The purge gas may be nitrogen, or another, preferably inert, gas.

During purging, the purge gas is delivered along the first and second plurality of channels 132, 134 and the first and second plurality of grooves to the one or more pumping chambers. In particular, in this example, during purging, each of the four pumping chambers receives purge gas via a respective pair of channels (that is, one channel of the first plurality of channels 132 and one channel of the second plurality of channels 134) and a respective pair of grooves (that is, one groove of the first plurality of grooves and one groove of the second plurality of grooves).

During purging, the purge gas is pumped through each pumping chamber and expelled from the exhaust stator 124 via the working fluid outlet.

Thus, there is provided an exemplary vacuum pump 100 configured to be purged by a purge gas.

In this example, during purging, a purge gas is received by each inlet of the plurality of purge gas inlets 128 and delivered to each pumping chamber of the pumping chambers, i.e. each pumping chamber receives the same purge gas. In other examples, however, at least one inlet of the plurality of inlets 128 may receive a different purge gas than at least one other inlet of the plurality of purge gas inlets 128. At least one pumping chamber of the pumping chambers may receive a different purge gas than at least one other pumping chamber of the pumping chambers. In some embodiments, one or more of the respective inlets of the plurality of inlets 128 do not receive a purge gas.

Figure 2 is a front (axial) view cross-section (not to scale) of the vacuum pump 100. The cross-section is taken along a lateral plane perpendicular to the axial direction 130.

In particular, Figure 2 illustrates a pair of channels comprising a first channel 202 belonging to the first plurality of channels 132 and a second channel 204 belonging to the second plurality of channels 134. A first purge gas inlet 205 of the plurality of purge gas inlet 128 is in fluid communication with each of the first channel 202 and the second channel 204.

Figure 2 also illustrates one pair of grooves comprising a first groove 206 belonging to the first plurality of grooves and a second groove 208 belonging to the second plurality of grooves.

Figure 2 also illustrates a first pumping chamber 210 of the pumping chambers. The pumping chamber 210 is shown in phantom to illustrate that it lies behind the plane of the cross-section viewed in Figure 2. That is to say that, in this example, the first channel 202, second channel 204, first groove 206, and second groove 208, whose cross-section can be seen in the plane of the front view cross-section depicted in Figure 2, are not located in the same plane as any portion of the first pumping chamber 210. In particular, the first pumping chamber 210 is axially displaced from the plane of the cross section viewed in Figure 2.

A pair of rotor shafts 212 extend through the first pumping chamber 210 in the axial direction, and their cross-section is shown in Figure 2. The shafts of the pair of rotor shafts 212 are laterally displaced, i.e. displaced from each other in a direction from the first lateral side 112 to the second lateral side 113, within the first pumping chamber 210.

A pair of rotors 214 are disposed within the first pumping chamber 210. Each rotor of the pair of rotors is drivingly connected to a respective one of the pair of rotor shafts 212, such that rotation of each one of the pair of rotor shafts 208 causes rotation of each one of the pair of rotors 214.

Each rotor shaft of the pair of rotor shafts 212 is configured to be counter-rotated relative to the other rotor shaft, such that simultaneous rotation of the pair of rotor shafts 212 causes counter-rotation of the pair of rotors 214. In this example, the rotors of the pair of rotors 214 are lobed rotors.

During operation of the vacuum pump 100, counter-rotation of the pair of rotors 214 causes axial movement of working fluid (and, if present, purge gas) across the first pumping chamber 210.

As illustrated in Figure 2, purge gas may be delivered from the first purge gas inlet 205 of the plurality of purge gas inlets 128 to the first pumping chamber 210 along a first purge gas flow path (indicated with single-headed arrows and the reference numeral 220) and a second purge gas flow path (indicated by single-headed arrows and the reference numeral 222). The first purge gas flow path 220 is defined by the continuous path formed, from the first purge gas inlet 205 to the first pumping chamber 210, by the first channel 202 and the first groove 206. The second purge gas flow path 222 is defined by the continuous path formed, from the first purge gas inlet 205 to the first pumping chamber 210, by the second channel 204 and the second groove 208.

The connection point of the first groove 206 to the first pumping chamber 210 is not indicated in Figure 2 because, in this example, the first groove 206 extends, from a first lower channel end 224 of the first channel 202 proximate the line 126, in the axial direction (i.e., out of the plane of the cross-section viewed in Figure 2) before adjoining the first pumping chamber 210. Thus, only some of the first purge gas flow path 220 is viewable in the cross-section of Figure 2. The connection point of the second groove 208 to the first pumping chamber 210 is not indicated in Figure 2 because, in this example, the second groove 208 extends, from a second lower channel end 226 of the second channel 204 proximate the line 126, in the axial direction (i.e., out of the plane of the cross-section viewed in Figure 2) before adjoining the first pumping chamber 210. Thus, only some of the second purge gas flow path 222 is viewable in the cross-section of Figure 2.

Figure 3 is a perspective view cross-section (not to scale) of the vacuum pump 100. The cross-section is taken along the lateral plane perpendicular to the axial direction 130.

Figure 3, similarly to Figure 2, shows only a portion of the first purge gas flow path 220 and a portion of the second purge gas flow path 222 through the vacuum pump 100. A further portion of the first purge gas flow path 220 and a further portion of the second purge gas flow path 222 are each omitted from Figure 3. This is because, as above, the first and second grooves 206, 208 each extend, from the first lower channel end 224 and the second lower channel end 226 (respectively) in the axial direction 130 (i.e., out of the plane of the cross-section viewed in Figure 3) before adjoining the first pumping chamber 210. Thus, only some of the first purge gas flow path 220 and some of the second purge gas flow path 222 is viewable in the cross-section of Figure 3.

Figure 4 is a plan view (not to scale) of the exhaust stator 124 of the vacuum pump 100, shown in isolation from the inlet stator 122.

Figure 4 depicts in particular the pumping chambers 400 (including the first pumping chamber 210), the first plurality of grooves 402 (including the first groove 206), and the second plurality of grooves 404 (including the second groove 208). Each groove of the first plurality of grooves 402 extends, along the axial direction 130, from a respective groove inlet to a respective groove outlet. Each groove outlet fluidly connects a respective pumping chamber of the pumping chambers 400 to the corresponding groove.

For example, the first groove 206 extends from a first groove inlet 406 to a first groove outlet 408, thereby to define the further portion of the first purge gas flow path 220 omitted from Figures 2 and 3. The second groove 208 extends from a second groove inlet 410 to a second groove outlet 412, thereby to define the further portion of the second purge gas flow path 222 omitted from Figures 2 and 3.

Figure 5 is a perspective view (not to scale) of the exhaust stator 124 of the vacuum pump 100, shown in isolation from the inlet stator 122. Features corresponding to those shown in Figure 4 are denoted by like reference numerals, and repeat descriptions thereof are omitted.

Thus, a known exemplary vacuum pump 100 is provided. The vacuum pump 100 is configured to allow pumping of a working fluid and purging by a purge gas.

Where the working fluid of such a vacuum pump is a process gas, e.g. in the case where the vacuum pump is used in a semiconductor manufacturing and/or abatement facility, a build-up of said process gas within the pumping chambers during operation, i.e. an increase in the pressure of the process gas, tends to increase the likelihood of undesirable condensation of said process gas. Build-up of condensation within the pumping chambers tends to cause problems including reduced pumping efficiency and pumping failure. To address these issues, the pumping chambers are intermittently or continuously purged with inert purge gas, thereby reducing the partial pressure of the process gas and mitigating condensation.

Furthermore, it is desirable that the temperature of the vacuum pump 100 and process gas to be maintained within an optimal temperature range. The optimal temperature range will vary depending on, amongst other factors, the process gas being pumped and the purge gas being used. If the temperature of the vacuum pump 100 and purge gas falls below this range, condensation becomes more likely. If the temperature the vacuum pump 100 and purge gas rises above this range, thermal decomposition of the process gas may undesirably occur, which decomposition may result in the release of harmful gases from the vacuum pump and/or condensation of decomposition products. The present inventors have realised that it is desirable for the purge gas to be delivered to the pumping chambers at a temperature at or close to an optimal temperature range, thereby improving condensation mitigation.

The present inventors have further realised that, in vacuum pumps such as the vacuum pump 100 in which the exhaust stator 124 typically has a higher temperature than the inlet stator 122, it is desirable for a temperature of the exhaust stator 124 to be within an optimal temperature difference or deviation range from a temperature of the inlet stator 122. If the temperature of the exhaust stator 124 is greater than the temperature of the inlet stator 122 by more than the optimal temperature difference or deviation range, pumping efficiency tends to be reduced.

Figure 6 is a perspective view (not to scale) of a further vacuum pump 600 according to the present invention. In this embodiment, the further vacuum pump 600 is a dry vacuum pump, and specifically a Roots-type vacuum pump.

The further vacuum pump 600 shares certain features with the vacuum pump 100. Similarities and differences between the further vacuum pump 600 and the vacuum pump 100 are described below. Features of the further vacuum pump 600 corresponding to those appearing in the vacuum pump 100 are denoted with like wording, but are given updated reference numerals in Figure 6.

The further vacuum pump 600 comprises a housing 602, in accordance with the housing 102 of the vacuum pump 100, defining a front side 604, back side 606, top side 608, bottom side 610, first lateral side 612, and second lateral side 613. The housing 602 is formed of an inlet stator 622 and an exhaust stator 624. The inlet stator 622 may be considered a top stator, i.e. the inlet stator 622 defines the top side 608 of the housing 602. The exhaust stator 624 may be considered a bottom stator, i.e. the exhaust stator 624 defines the bottom side 610 of the housing 602. The inlet stator 622 and the exhaust stator 624 are substantially contiguous, e.g. along the line 626 of Figure 6, and form therebetween pumping chambers of the further vacuum pump 600. The inlet stator 622 comprises a working fluid inlet of the pumping chambers. The exhaust stator 624 comprises a working fluid outlet of the pumping chambers, and may thus be considered an outlet stator.

The further vacuum pump 600 further comprises, at the bottom side 610 of the housing 602, i.e. in the exhaust stator 624, a plurality of purge gas inlets 628 analogous to the plurality of purge gas inlets 128 of the vacuum pump 100. In this embodiment, the plurality of purge gas inlets 628 are spaced in an axial direction 630 along the bottom side 610 of the housing 102.

The exhaust stator 624 comprises a first plurality of channels 632 analogous to the first plurality of channels 132 of the vacuum pump 100. Each channel of the first plurality of channels 632 extends, through an interior of the exhaust stator 624, from a respective one of the plurality of purge gas inlets 628, away from the bottom side 610 in a diagonal direction towards the top side 608 and first lateral side 612. The channels of the first plurality of channels 632 are axially displaced, i.e. displaced in the axial direction 630, from each other. In this embodiment, the channels of the first plurality of channels 632 are substantially parallel.

The exhaust stator 624 further comprises a second plurality of channels 634 in accordance with the second plurality of channels 134 of the vacuum pump 100. Each channel of the second plurality of channels 634 extends, through the interior of the inlet stator 622, from a respective one of the plurality of purge gas inlets 628, away from the top side 608 in a diagonal direction towards the bottom side 610 and second lateral side 613. The channels of the second plurality of channels 634 are axially displaced, i.e. displaced in the axial direction 630, from each other. In this embodiment, the channels of the second plurality of channels 634 are substantially parallel.

The exhaust stator 624 further comprises a first plurality of grooves (not shown in Figure 6) and a second plurality of grooves (not shown in Figure 6) in accordance with the first and second plurality of grooves 402, 404 of the vacuum pump 100. Each groove of the first plurality of grooves is formed proximate a top edge of the exhaust stator 624 and connects a respective one of the first plurality of channels 632 to a respective pumping chamber (not shown in Figure 6). Each groove of the second plurality of grooves is formed proximate the top edge of the exhaust stator 624 and connects a respective one of the second plurality of channels 634 to a respective pumping chamber (not shown in Figure 6).

Each groove of the first plurality of grooves and the second plurality of grooves, together with a lower surface of the inlet stator 622, forms a respective conduit or channel (not shown in Figure 6) which extends through the further vacuum pump 600 to the respective pumping chamber.

In this embodiment, the first plurality of channels 632 consists of four channels, the first plurality of grooves consists of four grooves, and the pumping chambers consists of four pumping chambers. More specifically, in this embodiment, each of the four channels of the first plurality of channels 632 is connected by a respective one of the first plurality of grooves to a respective one of the pumping chambers.

Similarly, in this embodiment, the second plurality of channels 634 consists of four channels, and the second plurality of grooves consists of four grooves. More specifically, in this embodiment, each of the four channels of the second plurality of channels 634 is connected by a respective one of the second plurality of grooves to a respective one of the pumping chambers. That is to say that, as is each of the pumping chambers of the vacuum pump 100, each of the (four) pumping chambers is contiguous and in fluid communication with two grooves, one groove being a respective groove of the first plurality of grooves, the other groove being a respective groove of the second plurality of grooves.

However, in other embodiments of the further vacuum pump 600, the first plurality of channels 632 may comprise a different number of channels other than four, e.g. two, or three, or five, or six, or more channels, or the first plurality of channels may be replaced by a single channel. The second plurality of channels 634 may comprise a different number of channels other than four, e.g. two, or three, or five, or six, or more channels, or the second plurality of channels may be replaced by a single channel. In other embodiments of the further vacuum pump 600, the first plurality of grooves may comprise a different number of grooves other than four, e.g. two, or three, or five, or six, or more grooves, or the first plurality of grooves may be replaced by a single groove. The second plurality of grooves may comprise a different number of grooves other than four, e.g. two, or three, or five, or six, or more grooves, or the first plurality of grooves may be replaced by a single groove.

In other embodiments, the further vacuum pump 600 may comprise a different number of pumping chambers other than four, e.g. one, or two, or three, or five, or six, or more pumping chambers. In these and other examples, each chamber of the one or more pumping chambers may be contiguous and in fluid communication with a different number of grooves of the first plurality of grooves other than one, e.g. zero, or two, or more grooves, and/or may be contiguous and in fluid communication with a different number of grooves of the second plurality of grooves other than one, e.g. zero, or two, or more grooves.

Unlike in the vacuum pump 100, the first and second plurality of channels 632, 634 and the first and second plurality of grooves of the further vacuum pump 600 are all formed in the exhaust stator 624, as opposed to shared between the inlet and exhaust stators as in the vacuum pump 100.

The further vacuum pump 600 is, like the vacuum pump 100, configured to, in use, receive a working fluid via an inlet (not shown) to the pumping chambers, the inlet being formed in the inlet stator 622. The further vacuum pump 600 may be further configured to, in use, pump the working fluid through the pumping chambers, and expel the working fluid from the further vacuum pump 600 via an outlet (not shown) of the pumping chambers, the outlet being formed in the exhaust stator 624.

The further vacuum pump 600 is configured such that the pumping chambers may be purged of working fluid, before, during, or after pumping working fluid.

During purging, the further vacuum pump 600 receives, from one or more purge gas sources (not shown), a purge gas via the plurality of purge gas inlets 628. In this embodiment, the purge gas may be nitrogen, or another, preferably inert, gas.

During purging, the purge gas is delivered along the first and second plurality of channels 632, 634 and the first and second plurality of grooves to the one or more pumping chambers. In particular, in this example, during purging, each of the four pumping chambers receives purge gas via a respective pair of channels (that is, one channel of the first plurality of channels and one channel of the second plurality of channels) and a respective pair of grooves (that is, one groove of the first plurality of grooves and one groove of the second plurality of grooves).

During purging, the purge gas is pumped through each pumping chamber and expelled from the exhaust stator 624 via the working fluid outlet.

Thus, there is provided a further vacuum pump 600 configured to be purged by a purge gas.

Figure 7 is a front view cross-section (not to scale) of the further vacuum pump 600. The cross-section is taken along a lateral plane perpendicular to the axial direction 630.

In particular, Figure 7 illustrates a pair of channels comprising a first channel 702 belonging to the first plurality of channels 632 and a second channel 704 belonging to the second plurality of channels 634. A first purge gas inlet 705 of the plurality of purge gas inlets 628 is in fluid communication with each of the first channel 702 and the second channel 704.

Figure 7 also illustrates a pair of grooves comprising a first groove 706 belonging to the first plurality of grooves and a second groove 708 belonging to the second plurality of grooves.

Figure 7 also illustrates a first pumping chamber 710 of the pumping chambers. The pumping chamber 710 is shown in phantom to illustrate that it lies behind the plane of the cross-section viewed in Figure 7. That is to say that, in this embodiment, the first channel 702, second channel 704, first groove 706, and second groove 708, whose cross-section can be seen in the plane of the front view cross-section depicted in Figure 7, are not located in the same plane as any portion of the first pumping chamber 710. In particular, the first pumping chamber 710 is axially displaced from the plane of the cross section viewed in Figure 7.

A pair of rotor shafts 712 extend through the first pumping chamber 710 in the axial direction, and their cross-section is shown in Figure 7. The shafts of the pair of rotor shafts 712 are laterally displaced, i.e. displaced from each other in a direction from the first lateral side 612 to the second lateral side 613, within the first pumping chamber 710.

A pair of rotors 714 are disposed within the first pumping chamber 210. Each rotor of the pair of rotors is drivingly connected to a respective one of the pair of rotor shafts 712, such that rotation of each one of the pair of rotor shafts 712 causes rotation of each one of the pair of rotors 714. The pair of rotors 714 is shown in phantom to illustrate that it lies behind the plane of the cross-section viewed in Figure 7. That is to say that, in this embodiment, the first channel 702, second channel 704, first groove 706, and second groove 708 are not located in the same plane as any portion of the pair of rotors 714. In particular, the pair of rotors 714 is axially displaced from the plane of the cross section viewed in Figure 7.

Each rotor shaft of the pair of rotor shafts 712 is configured to be counter-rotated relative to the other rotor shaft, such that simultaneous rotation of the pair of rotor shafts 712 causes counter-rotation of the pair of rotors 14. In this embodiment, the rotors of the pair of rotors 714 are lobed rotors.

During operation of the further vacuum pump 700, counter-rotation of the pair of rotors 714 causes axial movement of working fluid (and, if present, purge gas) across the first pumping chamber 710.

As illustrated in Figure 7, purge gas may be delivered from the first purge gas inlet 705 of the plurality of purge gas inlets 628 to the first pumping chamber 710 along a first purge gas flow path (indicated with single-headed arrows and the reference numeral 720) and a second purge gas flow path (indicated by single-headed arrows and the reference numeral 722). The first purge gas flow path 720 is defined by the continuous path formed, from the first purge gas inlet 705 to the first pumping chamber 710, by the first channel 702 and the first groove 706. The second purge gas flow path 722 is defined by the continuous path formed, from the first purge gas inlet 705 to the first pumping chamber 710, by the second channel 704 and the second groove 708.

The connection point of the first groove 706 to the first pumping chamber 710 is not indicated in Figure 7 because, in this embodiment, the first groove 706 extends, from a first upper channel end 724 of the first channel 702 proximate the line 626, in the axial direction 630 (i.e., out of the plane of the cross-section viewed in Figure 7) before adjoining the first pumping chamber 710. Thus, only some of the first purge gas flow path 720 is viewable in the cross-section of Figure 7.

The connection point of the second groove 708 to the first pumping chamber 710 is not indicated in Figure 7 because, in this embodiment, the second groove 708 extends, from a second upper channel end 726 of the second channel 704 proximate the line 626, in the axial direction 630 (i.e., out of the plane of the cross-section viewed in Figure 7) before adjoining the first pumping chamber 710. Thus, only some of the second purge gas flow path 722 is viewable in the cross-section of Figure 7.

Figure 8 is a perspective view cross-section (not to scale) of the further vacuum pump 600. The cross-section is taken along the lateral plane perpendicular to the axial direction 630.

Figure 8, similarly to Figure 7, shows only a portion of the first purge gas flow path 720 and a portion of the second purge gas flow path 722 through the further vacuum pump 600. A further portion of the first purge gas flow path 720 and a further portion of the second purge gas flow path 722 are each omitted from Figure 8. This is because the first and second grooves 706, 708 each extend, from the first upper channel end 724 and the second upper channel end 726 (respectively) in the axial direction 630 (i.e., out of the plane of the crosssection viewed in Figure 8) before adjoining the first pumping chamber 710. Thus, only some of the first purge gas flow path 720 and some of the second purge gas flow path 722 is viewable in the cross-section of Figure 8.

Figure 9 is a plan view (not to scale) of the exhaust stator 624 of the further vacuum pump 600, shown in isolation from the inlet stator 622.

Figure 9 depicts in particular the pumping chambers 900 (including the first pumping chamber 710), the first plurality of grooves 902 (including the first groove 706), and the second plurality of grooves 904 (including the second groove 708). Each groove of the first plurality of grooves 902 extends, along the axial direction 630, from a respective groove inlet to a respective groove outlet.

Each groove outlet fluidly connects a respective pumping chamber of the pumping chambers 900 to the corresponding groove.

For example, the first groove 706 extends from a first groove inlet 906 to a first groove outlet 908, thereby to define the further portion of the first purge gas flow path 720 omitted from Figures 7 and 8. The second groove 708 extends from a second groove inlet 910 to a second groove outlet 912, thereby to define the further portion of the second purge gas flow path 722 omitted from Figures 7 and 8.

Figure 10 is a perspective view (not to scale) of the exhaust stator 624 of the further vacuum pump 600, shown in isolation from the inlet stator 622. Features corresponding to those shown in Figure 9 are denoted by like reference numerals, and repeat descriptions thereof are omitted.

Thus, a further vacuum pump 600 is provided in which purge gas flow paths are formed in or by the exhaust stator 624. The further vacuum pump 600 is configured to allow pumping of a working fluid and purging by delivery of a purge gas along purge gas flow paths, e.g. the first and second purge gas flow paths 720, 722.

Unlike in the vacuum pump 100, the first and second plurality of channels 632, 634 and the first and second plurality of grooves 902, 904 of the further vacuum pump 600 are all formed in the exhaust stator 624, as opposed to being shared between the inlet and exhaust stators as is the case in the vacuum pump 100. That is to say, purge gas flow paths of the further vacuum pump 600 (e.g., the first and second purge gas flow paths 720, 722) extend through the exhaust stator 624 and not the inlet stator 622, unlike in the vacuum pump 100 whose purge gas flow paths (e.g., the first and second purge gas flow paths 220, 222) extend through both the inlet stator 622 and the outlet stator 624. Purge gas being delivered to the pumping chambers 900 of the further vacuum pump 600 therefore passes through only the exhaust stator 624, and not the inlet stator 622, prior to entry into said pumping chambers 900.

In the above embodiment of Figures 6 to 10, the inlet stator 622 may be considered an inlet stator part comprising a working fluid inlet. The exhaust stator 624 may be considered an exhaust stator part comprising the working fluid outlet, the first purge gas inlet 705, and the first channel 702 (which may be considered a first purge gas channel 702) extending through the exhaust stator part from the first purge gas inlet 705. The inlet stator part and the exhaust stator part define the first pumping chamber 710 between the working fluid inlet and the working fluid outlet. The first purge gas inlet 705 is distinct from each of the working fluid inlet and the working fluid outlet, and is disposed on a surface of the exhaust stator part external to the first pumping chamber 710. The first purge gas channel 702 extends from the first purge gas inlet 705 towards the first pumping chamber 710 and forms at least a part of the first purge gas flow path 720, the first purge gas flow path 720 fluidly connecting the first purge gas inlet 705 to the first pumping chamber 710.

In the above embodiment shown in Figures 6 to 10, the conduit or channel defined, together with a lower surface of the inlet stator 622, by the first groove 706 may be considered a second purge gas channel formed between the inlet stator part and the exhaust stator part. The second purge gas channel at least in part defined by the first groove 706 in the exhaust stator part is formed outside the first pumping chamber 710. The first purge gas channel 702 and the second purge gas channel are fluidly connected and together define the first purge gas flow path 720.

In the above embodiment shown in Figures 6 to 10, the second purge gas channel (at least in part defined by the first groove 706 in the exhaust stator part) is formed at a first side of the exhaust stator part (namely, a top side of the exhaust stator part proximate the line 626), the first side being opposite a second side of the exhaust stator part at which the first purge gas inlet 705 is disposed (namely, a bottom side of the exhaust stator part at the bottom side 610 of the housing 602).

In the above embodiment shown in Figures 6 to 10, the first purge gas flow path 720 is a meandering or convoluted path. In some embodiments, the first purge gas flow path may be serpentine in configuration. In some embodiments, the first purge gas flow path 720 may include fins along its length, thereby to improve the rate of heat transfer across the path.

In the above embodiment shown in Figures 6 to 10, the exhaust stator part comprises a second purge gas inlet of the plurality of purge gas inlets 628 and a further purge gas channel of the first plurality of channels 622 (which may be considered a third purge gas channel) extending through the exhaust stator part from the second purge gas inlet. The inlet stator part and the exhaust stator part define a second pumping chamber of the pumping chambers 900 (which may be considered a further pumping stage distinct from a first pumping stage at the first pumping chamber 710) between the working fluid inlet and the working fluid outlet. The second purge gas inlet is distinct from each of the working fluid inlet and the working fluid outlet, and is disposed on a surface of the exhaust stator part external to the second pumping chamber. The further purge gas channel of the first plurality of channels 622 (i.e. , the third purge gas channel) extends from the second purge gas inlet towards the second pumping chamber and forms at least a part of a further purge gas flow path (which may be considered a second purge gas flow path distinct from the second purge gas flow path 722), the further purge gas flow path fluidly connecting the second purge gas inlet to the second pumping chamber.

In the above embodiment shown in Figure 6 to 10, a further conduit or channel defined, together with a lower surface of the inlet stator 622, by a further groove of the first plurality of grooves 902 may be considered a fourth purge gas channel formed between the inlet stator part and the exhaust stator part. The fourth purge gas channel at least in part defined by the further groove of the first plurality of grooves 002 in the exhaust stator part is formed outside the first and second pumping chambers The third purge gas channel and the fourth purge gas channel are fluidly connected and together define the further purge gas flow path (which may be considered a second purge gas flow path distinct from the second purge gas flow path 722), which fluidly connects the second purge gas inlet to the second pumping chamber.

In the above embodiment shown in Figures 6 to 10, the first pumping chamber 710 and the second pumping chamber of the pumping chambers 900 are displaced in the axial direction 630 and are in fluid communication. One or both of the second purge gas channel (defined by the first groove 706 of the first plurality of grooves 902) and the fourth purge gas channel (defined by the further groove of the first plurality of grooves 902) extends through the exhaust stator part in the axial direction 630.

In the above embodiment shown in Figures 6 to 10, the first purge gas channel (defined by the first channel 702 of the first plurality of channels 622) and the third purge gas channel (defined by the further purge gas channel of the first plurality of channels 622) are substantially parallel. In other embodiments, the first purge gas channel and the third purge gas channel may be oriented so as not to be parallel.

In the above embodiment shown in Figures 6 to 10, the second purge gas inlet of the plurality of purge gas inlets 628 is formed in the surface of the exhaust stator part at the first side of the exhaust stator part opposite the second side of the exhaust stator part.

In the above embodiment shown in Figures 6 to 10, the further purge gas flow path (defined by the third and fourth purge gas channels) is a meandering or convoluted path. In some embodiments, the further purge gas flow path may be serpentine in configuration. In some embodiments, the further purge gas flow path may include fins along its length, thereby to improve the rate of heat transfer across the path.

In the above embodiment shown in Figures 6 to 10, the second purge gas flow path 722 (defined by the second channel 704 of the second plurality of channels 634 and the conduit or channel formed by the second groove 708 of the second plurality of grooves 904) is a meandering or convoluted path. In some embodiments, the second purge gas flow path 722 may be serpentine in configuration. In some embodiments, the second purge gas flow path 722 may include fins along its length, thereby to improve the rate of heat transfer across the path.

In the above embodiment shown in Figures 6 to 10, a first temperature of the inlet stator part is less than a second temperature of the exhaust stator part when the further vacuum pump 600 is in operation to pump working fluid and/or purge gas therethrough.

In the above embodiment shown in Figures 6 to 10, the second temperature is approximately 10 to 50 degrees Celsius greater than the first temperature. For the example, the second temperature may be approximately 20 to 40 degrees Celsius greater than the first temperature, or approximately 25 to 35 degrees Celsius greater than the first temperature, or approximately 30 degree Celsius greater than the first temperature.

In the above embodiment shown in Figure 6 to 10, the further vacuum pump 600 is a Roots-type pump having lobed rotors. In other embodiments, the further vacuum pump 600 may be some other type of vacuum pump, e.g. another type of dry vacuum pump.

In an embodiment, there is provided a vacuum pumping system comprising a stator consisting of the inlet stator part and the outer stator part described in the embodiment above with reference to Figure 6 to 10.

In this embodiment, the vacuum pumping system further comprises a purge gas source fluidly connected to the one or more purge gas inlets of the plurality of purge gas inlets 628, e.g. the first purge gas inlet 705. The purge gas source is configured to deliver purge gas to the one or more purge gas inlets, thereby to facilitate purging of the further vacuum pump 600. The purge gas may be, for example, nitrogen, or another, preferably inert, gas.

The purge gas source may be fluidly connected to the second purge gas inlet of the plurality of inlets 628, and/or to one or more (or all of) the remaining of the plurality of purge gas inlets 628. Alternatively, a different purge gas source may be fluidly connected to the second purge gas inlet of the plurality of inlets 628, and/or to one or more (or all of) the remaining of the plurality of purge gas inlets 628. The same purge gas source may be configured to deliver different purge gases to each of the first purge gas inlet 705 and the respective other one or more inlets of the plurality of inlets 628 which are connected to the purge gas source to receive purge gas, thereby to allow pumping of the first pumping chamber 710 and the respective other one or more pumping chambers of the pumping chambers 900 with different purge gases if desired.

In another embodiment, there is provided an exhaust stator part in accordance with the exhaust stator 624 of the further vacuum pump 600 described in embodiments above.

Figure 11 is a process flow chart depicting steps of a method 1100 for purging the further vacuum pump 600 using a purge gas.

The method 1100 includes, at step s1110, passing the purge gas along the first purge gas flow path 720 from the first purge gas inlet 705 to the first pumping chamber 710.

The method 1100 may include, at step s1120, passing the purge gas along the second purge gas flow path 722 from a second purge gas inlet of the plurality of purge gas inlets 628 to a second pumping chamber of the pumping chambers 900.

The method 1100 may be performed, for example, before or after operation of the further vacuum pump 600 to pump working fluid therethrough. The method 1100 may alternatively or additionally be performed during operation of the further vacuum pump 600 to pump working fluid therethrough.

Advantageously, the above-described methods and apparatuses facilitate purging a vacuum pump such that purge gas spends sufficient time in the exhaust stator, prior to entering a respective pumping chamber, to be warmed to a temperature close to or approximately equal to a temperature of the working fluid or an internal temperature of the respective pumping chamber. Undesirable cooling of the working fluid within the pumping chamber thus tends to be mitigated. This tends to reduce the risk of deposit and/or condensation formation, as well as any attendant unwanted chemical reactions, within the vacuum pump which may detrimentally affect performance of the vacuum pump.

Advantageously, the above-described methods and apparatuses tend to prevent further cooling of the inlet stator by avoiding introduction of cool purge gas via the inlet stator. Thus, an acceptable/desired temperature difference (e.g., 30 degrees Celsius) between the inlet and exhaust stators tends to be maintained, thereby improving pumping efficiency. In other words, a more uniform temperature distribution may be maintained between the inlet and exhaust stators.

Advantageously, the above-described methods and apparatuses tend to prevent the exhaust stator from overheating due to the cooling effect of heat transfer to purge gas introduced to the vacuum pump via the exhaust stator. Unwanted chemical reactions, e.g. thermal decomposition and subsequent reactions, within the vacuum pump (which may detrimentally affect performance of the vacuum pump) thus tend to be mitigated.

Advantageously, the above-described methods and apparatuses tend to eliminate a need for preheating of the purge gas before its introduction to the vacuum pump, e.g. a need for the purge gas source to include heating means. Purging the vacuum pump thus tends to be made more convenient, expeditious, and less costly.

Advantageously, the above-described methods and apparatuses provide for purge gas delivery via channels and conduits formed in or by the exhaust stator only, rather than channels and conduits whose formation is shared between the inlet and exhaust stators. Thus, exhaust stators may be manufactured whose use with standard inlet stators which do not have or require channels or conduits for purge gas delivery nevertheless facilitates purge gas delivery. Convenience of manufacture and assembly, and interoperability of purge gas-delivering exhaust stators in vacuum pump systems, hence tends to be improved. Advantageously, the above-described methods and apparatuses allow for purge gas delivery via respective purge gas flow paths which extend in both lateral (e.g., radial) and axial directions through the vacuum pump, in meandering or convoluted paths which extend between vacuum pumping stages. This tends to result in purge gas spending a longer period of time between entering the purge gas flow path via a respective purge gas inlet and delivery into a respective pumping chamber, thereby improving heat transfer from the exhaust stator to the purge gas prior to the purge gas’ entrance into a respective pumping chamber. This improved heat transfer further acts to maintain the temperature difference between the inlet and outlet stators within a desired range, as well as prevent overheating of the exhaust stator.

Reference numeral list

100 - vacuum pump

102 - housing

104 - front side

106 - back side

108 - top side

110 - bottom side

112, 113 - lateral sides

122 - inlet stator

124 - exhaust stator

126 - line

128 - plurality of purge gas inlets

130 - axial direction

132 - first plurality of channels

134 - second plurality of channels

202 - first channel

204 - second channel

205 - first purge gas inlet

206 - first groove

208 - second groove

210 - first pumping chamber

212 - pair of rotor shafts

214 - pair of rotors

220 - first purge gas flow path

222 - second purge gas flow path 224 - first lower channel end

226 - second lower channel end

400 - pumping chambers

402 - first plurality of grooves

404 - second plurality of grooves

406 - first groove inlet

408 - first groove outlet

410 - second groove inlet

412 - second groove outlet

600 - further vacuum pump

602 - housing

604 - front side

606 - back side

608 - top side

610 - bottom side

612 - first lateral side

613 - second lateral side

622 - inlet stator

624 - exhaust stator

626 - line

628 - plurality of purge gas inlets

630 - axial direction

632 - first plurality of channels

634 - second plurality of channels

702 - first channel 704 - second channel

706 - first groove

708 - second groove

710 - pumping chambers 712 - pair of rotor shafts

714 - pair of rotors

720 - first purge gas flow path

722 - second purge gas flow path

724 - first upper channel end 726 - second upper channel end

900 - pumping chambers

902 - first plurality of grooves

904 - second plurality of grooves

906 - first groove inlet 908 - first groove outlet

910 - second groove inlet

912 - second groove outlet