Stator for a vacuum pump

Abstract

A vacuum pump stator 114 comprises one or more walls 122, 124, 126 defining a pumping chamber 118, and a heat exchanger 130 comprising a conduit 132 through at least one of the walls which, in use, a

Description

FIELD OF THE INVENTION The present invention relates to stators for vacuum pumps. BACKGROUND Vacuum pumps are used in various technical processes to pump process gases out of process chambers, thereby to create low-pressure conditions for the respective processes. The process gas may contain by-products of the processes. The by-products may proceed into the pumping chamber of the vacuum pump where they may solidify or condense. The solidified by-products may settle on surfaces within the pumping chamber, such as interior walls of the pumping chamber and peripheral surfaces of the rotors. The deposited byproducts may constrict the gap situated between the rotors. The deposited byproducts may lead to reduced pumping efficiency, bearing damage and, ultimately, to the failure of the vacuum pump. It is known to use purge or flushing gas to prevent or oppose build-up of solidified by-products. The purge gas may be discharged into the pump chamber via a purge gas line during the operation of the pump. Preferably, the purge gas is delivered at high speed, for example, via a nozzle. The flow of purge gas prevents the settling of solid particles within the pump chamber and facilitate in the conveyance of said solid particles out of the pumping chamber. It is known to use mechanical booster pumps in conjunction with vacuum pumps. One or more mechanical booster pumps may be mechanically coupled to the vacuum pump, for example at the inlet of the vacuum pump, such that, in operation, the mechanical booster pump increases the pressure of the fluid entering the vacuum pump. 05 10 23 Heating the stator of the vacuum pump may prevent condensation and deposition of the by-products within the pumping chamber. The present inventors have realised, however, that the introduction of a purge gas into the pumping chamber may lower the temperature within the pumping chamber and / or the temperature of the stator walls, thereby causing by-products present within the pumping chamber to condense. The present inventors have further realised that pre-heating the purge gas prior to its introduction into a pumping chamber tends to reduce the cooling effect of the purge gas introduction, thereby reducing condensation and deposition of byproducts within the pumping chamber. The present inventors have further realised that heat exchangers may be accommodated in the walls of pump stators, such as the stators of booster pumps, and may be used to pre-heat a purge gas prior to that purge gas being introduced into the pumping chamber of a vacuum pump, e.g. a further pump downstream of the booster pump. The present inventors have further realised that heaters may also be accommodated in the walls of pump stators, such as the stators of booster pumps, and may be used to heat the stator walls, thereby to heat the pumping chamber of the booster pump as well as the purge gas flowing through the heat exchanger. In a first aspect, there is provided a vacuum pump stator according to claim 1. The conduit may comprise a conduit inlet, and a conduit outlet. The conduit inlet may be located at an external surface of the one or more walls. The conduit outlet may be located at an external surface of the one or more walls. The conduit connected between the conduit inlet and conduit outlet may be separated from the pumping chamber by the at least one of the one or more walls. The one or more walls may comprise a first wall, a second wall opposite to the first wall, and one or more further walls disposed between the first wall and the second wall. The vacuum pump stator may further comprise a pumping chamber inlet defined in the first wall, and a pumping chamber outlet defined in 05 10 23 the second wall. The conduit may be embedded in or integrally formed with the one or more further walls. The vacuum pump stator may further comprise one or more heaters configured to heat at least a portion of the one or more walls. 5 The one or more heaters may be at least partially embedded in the one or more walls. The conduit may be a convoluted conduit. In a further aspect, there is provided a vacuum pump comprising a stator according to any preceding aspect, one or more rotors arranged in the pumping 10 chamber, and one or more shafts extending at least partially though the pumping chamber. The one or more rotors are fixed to a respective one of the one or more shafts. In a further aspect, there is provided a system comprising the vacuum pump of any preceding aspect, and a purge gas source configured to supply the 15 purge gas into the conduit. The pumping chamber may comprise a first pumping chamber inlet and a first pumping chamber outlet. The system may further comprise a further vacuum pump. The further vacuum pump may comprise a further pumping chamber. The further pumping chamber may comprise a second pumping 20 chamber inlet and a second pumping chamber outlet. The first pumping chamber outlet may be coupled to the second pumping chamber inlet such that, in use, a fluid is pumped from the pumping chamber to the further pumping chamber. The heat exchanger may be coupled to the further pumping chamber such that, in use, the heated purge gas is supplied into the further pumping 25 chamber. The vacuum pump may be a booster pump. In a further aspect, there is provided a method comprising: providing a vacuum pump, the vacuum pump being in accordance with any preceding aspect; pumping, using the vacuum pump, a fluid, the fluid being pumped 30 through the pumping chamber of the vacuum pump; and causing a purge gas to 05 10 23 flow through the conduit of the heat exchanger. As the purge gas flows through the conduit, heat is transferred to the purge gas from the one or more walls thereby to heat the purge gas. The purge gas may be nitrogen. 5 The method may further comprise heating, by one or more heaters, at least a portion of the one or more walls. The method may further comprise outputting, to a further vacuum pump, from the heat exchanger, the heated purge gas. 10 BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic illustration (not to scale) of a vacuum pumping system; Figure 2 is a schematic illustration (not to scale) showing an exploded perspective view of a first stator of the first vacuum pump; and 15 Figure 3 is a process flow chart showing certain steps of a process performed by the vacuum pumping system. DETAILED DESCRIPTION It will be appreciated that relative terms such as above and below, 20 horizontal and vertical, top and bottom, front and back, and so on, are used herein merely for ease of reference to the Figures, and these terms are not limiting as such, and any two differing directions or positions and so on may be implemented rather than truly above and below, horizontal and vertical, top and bottom, and so on. 25 Figure 1 is a schematic illustration (not to scale) of a vacuum pumping system 100. The vacuum pumping system 100 comprises a facility 101, a first vacuum pump 102, a second vacuum pump 104, and a purge gas source 106. 05 10 23 The facility 101 may be any appropriate type of facility, for example a semiconductor fabrication facility. The facility 101 is coupled to a vacuum pumping system comprising the first vacuum pump 102 and the second vacuum pump 104. The vacuum pumping system 100 is configured to establish a 5 vacuum or low-pressure environment at the facility 101 by drawing gas (for example, air or process gases) from the facility 101. The first vacuum pump 102 is a mechanical booster pump. The first vacuum pump 102 may be any appropriate type of booster pump such as a Roots-type or Roots vacuum pump. The first vacuum pump 102 may be a 10 positive displacement pump. The first vacuum pump 102 is operatively coupled between the facility 101 and the second vacuum pump 104. The first vacuum pump 102 is configured to pump fluid (e.g. gas) out of the facility 101, as indicated in Figure 1 by an arrow and reference numeral 108. The first vacuum pump 102 is further configured to pump that fluid, via a fluid line 110, to the 15 second vacuum pump 104, as indicated in Figure 1 by an arrow and reference numeral 112. The first vacuum pump 102 is configured to increase the pressure of the pumped fluid entering the second vacuum pump 104. Such operation of the first vacuum pump 102 tends to increase the pumping effectiveness of the second vacuum pump 104. 20 The first vacuum pump 102 comprises a first housing or stator 114. The first stator 114 comprises one or more walls which define a first fluid inlet 116, a first pumping chamber 118, and a first fluid outlet 120. In particular, in this embodiment, the first stator 114 comprises a first or top wall 122, a second or bottom wall 124 opposite to the first wall 122, and one 25 or more further walls, or side walls, 126 disposed between the first wall 122 and the second wall 124. The first fluid inlet 116 is formed through the first wall 122. The first fluid outlet 120 is formed through the second wall 124. The first vacuum pump 102 further comprises a first pumping means 128 located within the first pumping chamber 118. The first pumping means 128 30 may be any appropriate type of pumping means and may include, for example, one or more rotors such as a plurality of intermeshing or cooperating rotors. The 05 10 23 one or more rotors may be fixed to respective shafts extending at least partially though the first pumping chamber 118. The shafts, and thereby the rotors, may be rotated by any appropriate means, such as an electric motor, whereby to pump fluid through the first pumping chamber 118. 5 The first pumping chamber 118 (and the first pumping means 128 therein) are connected between the first fluid inlet 116 and first fluid outlet 120 such that, in operation, the fluid is pumped, by the first pumping means 128 into the first fluid inlet 116, from the first fluid inlet 116 to the first fluid outlet 120, and out of the first fluid outlet 122. 10 The first vacuum pump 102 further comprises a heat exchanger 130. The heat exchanger 130 comprises a conduit 132. In this embodiment, the conduit 132 comprises a conduit inlet 134 and a conduit outlet 136. The conduit inlet 134 is located at an external surface of the first stator 114. In particular, in this embodiment, the conduit inlet 134 is located 15 at an external surface of the one or more further walls 126. The conduit outlet 136 is located at an external surface of the first stator 114. In particular, in this embodiment, the conduit outlet 136 is located at an external surface of the one or more further walls 126. The conduit inlet 134 is coupled to the purge gas source 106 such that, 20 in operation, a purge gas is received at the conduit inlet 134 from the purge gas source 106, as indicated in Figure 1 by an arrow and the reference numeral 138. The conduit 132 is configured to convey the received purge gas therethrough, from the conduit inlet 134 to the conduit outlet 136, as indicated in Figure 1 by an arrow and the reference numeral 140. The conduit outlet 136 is 25 coupled to the second vacuum pump 104 such that, in operation, purge gas exiting the conduit 132 of the heat exchanger 130 via the conduit outlet 136 is conveyed to the second vacuum pump 104, as indicated in Figure 1 by an arrow and the reference numeral 142. In this embodiment, the conduit 132, connected between the conduit inlet 30 134 and conduit outlet 136, is separated from the pumping chamber 118 by the walls of the first stator 114. In other words, within the confines or boundary of 05 10 23 the first stator 114, in this embodiment, the conduit 132 is fluidly isolated or independent from the first pumping chamber 118. Thus, in this embodiment, fluid cannot flow between from the conduit 132 to the first pumping chamber 118, or vice versa, through the walls of the first stator 114. In this embodiment, the conduit 132 is a convoluted, meandering, or serpentine conduit. This can be more clearly seen in Figure 2. Further details of the heat exchanger 130 and its operation are described in more detail later below with reference to Figures 2 and 3. The second vacuum pump 104 may be any appropriate type of vacuum pump such as a dry vacuum pump. The second vacuum pump 104 is configured to pump the fluid from the first vacuum pump 102, as indicated in Figure 1 by an arrow and the reference numeral 112. Thus, a vacuum or low-pressure environment is created at the facility 101. The second vacuum pump 104 is configured to exhaust or output the pumped fluid, as indicated in Figure 1 by an arrow and the reference numeral 144. The pumped fluid may be exhausted to any appropriate entity, depending on application. For example, the pumped fluid may be output to an abatement system, or to the environment. The second vacuum pump 104 comprises a second housing or stator 146. The second stator 146 comprises one or more walls which define a second fluid inlet 148, a second pumping chamber 150, and a second fluid outlet 152. The second vacuum pump 104 further comprises a second pumping means (not shown in the figures) located within the second pumping chamber. The second pumping means may be any appropriate type of pumping means. The second vacuum pump 104 further comprises a nozzle 154. The nozzle 154 is disposed through the one or more walls of the second stator 146. The nozzle 154 is coupled to the conduit outlet 136 such that, in operation, a flow of purge gas is received by the nozzle 154. The nozzle 154 is further configured to deliver the received purge gas into the second pumping chamber 150, as indicated in Figure 1 by arrows and the reference numeral 156. 05 10 23 Figure 2 is a schematic illustration (not to scale) showing an exploded perspective view of the first stator 114 of the first vacuum pump 102. In this embodiment, the heat exchanger 130 is located on a first side wall 200 of the first stator 114. The first side wall 200 is disposed between the first 5 wall 122 and the second wall 124. In accordance with the present invention, the conduit 132 of the heat exchanger 130 is defined by one or more channels 202 formed on an external surface of the first side wall 200, and a cover 204 that covers the one or more channels 202, thereby to define the conduit 132. 10 The one or more channels 202 may be channels or grooves that have been machined or etched into the external surface of the first side wall 200. The one or more channels 202 may define one or more convolute paths between the conduit inlet 134 and the conduit outlet 136. The cover 204 may be a substantially flat sheet or plate. The cover 204 15 may be formed from the same material as that from which the walls (e.g., the first side wall 200) of the first stator 114 are formed. This material may be a heat conducting material, such as a metal. The cover 204 may be attached to the first side wall 200 by any appropriate attachments means, such as using one or more fasteners. Attachment of the cover 204 to the first side wall 200 is 20 indicated in Figure 2 by dashed arrows and the reference numeral 206. In some embodiments, a seal or gasket, such as an O-ring, is disposed between the cover 204 and the first side wall 200 thereby to reduce or eliminate leakage of the purge gas from the heat exchanger 130. In this embodiment, the first stator 114 further comprises two heaters 25 208. The heaters 208 are disposed or received in respective voids 210 in the one or more walls of the first stator 114. Thus, the heaters 208 are at least partially embedded in the first stator 114. In this embodiment, the heaters 208 and the voids 210 in which they are received are elongate. Insertion of the heaters 208 into the voids 210 is indicated in Figure 2 by dashed arrows and 30 the reference numeral 212. 05 10 23 In this embodiment, the voids 210 are formed in the first side wall 200. The voids 210 are positioned proximate the heat exchanger 130, in particular proximate the one or more channels 202. More specifically, in this embodiment, the voids 210 are positioned at opposite sides of the one or more channels 202, 5 and adjacent to the channels 202. The voids 210 may be defined by respective grooves formed (e.g. by machining) on an external surface of the first side wall 200, and the cover 204 that covers those grooves, thereby to define the voids 210. The heaters 208 may be any appropriate type of heater, including but not 10 limited to electric heaters. The heaters 208 are configured to heat, i.e. raise the temperature of, at least a portion of the one or more walls of the first stator 114. Preferably, the heaters 208 are configured to heat at least a portion of the first side wall 200 that forms conduit 132. The heaters 208 may be controlled by a controller (not shown in the 15 Figures). In some embodiments, the first stator 114 further comprises one or more temperature sensors, which may be disposed on or embedded in the one or more walls of the first stator 114. The one or more temperature sensors may be configured to measure a temperature of the one or more walls of the first stator. Operation of the heaters 208 may be performed based on some function 20 of the temperature measurements taken by the one or more temperature sensors. For example, in some embodiments, the heaters 208 may be controlled to heat at least a portion of the first side wall 200 (e.g., at least a part that forms the heat exchanger 130) until a temperature of that portion of the first side wall 200, as measured by one or more temperature sensors, reaches a 25 threshold value, at which point the heaters 208 may be controlled to stop or reduce heating. The heaters 208 may be controlled to maintain the temperature of the portion of the first side wall 200 at about the threshold value. In some embodiments, the distribution of heaters over the first stator is such that the temperature of the first stator is substantially uniform over the 30 body of the first stator. Heaters may be distributed over the first stator at 05 10 23 substantially uniform intervals. The heaters may be controlled by a common controller to achieve the desired uniform temperature of the first stator. Heaters may be distributed over the first stator in an arrangement that is substantially symmetrical about the first stator axis. One or more heaters may 5 be located in the end covers and / or head plates of the first stator. Figure 3 is a process flow chart showing certain steps of a process 300 performed by the vacuum pumping system 100. It should be noted that certain of the process steps depicted in the flowchart of Figure 3 and described below may be omitted or such process 10 steps may be performed in differing order to that presented below and shown in Figure 3. Furthermore, although all the process steps have, for convenience and ease of understanding, been depicted as discrete temporally-sequential steps, nevertheless some of the process steps may in fact be performed simultaneously or at least overlapping to some extent temporally. 15 At step s302, the first vacuum pump 102 pumps a fluid out of the facility 101. The fluid is pumped, by the first vacuum pump 102, into the first fluid inlet 116, through the first pumping chamber 118, and out of the first fluid outlet 120. This fluid is pumped to the second vacuum pump 104 via the fluid line 110. The first vacuum pump 102 increases the pressure of the pumped fluid entering the 20 second vacuum pump 104. In this embodiment, the pumping of the fluid by the first vacuum pump 102 tends to cause a temperature of the one or more walls of the first stator 114 to increase above ambient temperature. This increase in temperature tends to be due to the relatively high temperature of the fluid received by the first 25 vacuum pump 102 from the facility 101 and / or friction within the first vacuum pump 102, e.g. between the fluid and the parts of the first vacuum pump 102. At step s304, optionally, the heaters 208 may be controlled to heat or further heater at least a portion of the one or more walls of the first stator 114. The heaters 208 may be controlled to heat at least a portion of the one or more 30 walls of the first stator 114 to a predetermined temperature. The heaters 208 may be controlled to heat at least a portion of the first side wall 200 that forms 05 10 23 the heat exchanger 130, i.e. the portion of the first side wall that defines the conduit 132 or one or more channels 202. At step s306, a purge gas is pumped through the heat exchanger 130. More specifically, the purge gas is pumped from the purge gas source 106 and 5 into the conduit 132 via the conduit inlet 134. The purge gas is then pumped through the conduit 132, from the conduit inlet 134 to the conduit outlet 136. The purge gas is then pumped out of the conduit outlet 136. The purge gas may be pumped by any appropriate pumping means. For example, in some embodiments, the purge gas source 106 comprises a pump 10 configured to pump the purge gas. The purge gas may be any appropriate purge gas. Preferably, the purge gas is an inert gas. An example of a purge gas is nitrogen gas. At step s308, as the purge gas travels through the conduit 132 of the heat exchanger 130, the heat exchanger 130 heats, i.e. increases the 15 temperature of, the purge gas. More specifically, heat is transferred from the relatively hot first side wall 200 that at least partially forms the conduit 132, to the relatively cool purge gas flowing through the conduit 132. Thus, in this embodiment, the temperature of the purge gas exiting the heat exchanger 130 at the conduit outlet 136 is higher than that of the purge 20 gas entering the heat exchanger 130 at the conduit inlet 134. In some embodiments, the heaters 208 are controlled to heat the portion of the walls of the first stator 114 that forms the heat exchanger 130 such that a temperature of the purge gas exiting the heat exchanger 130 is equal to or exceeds a predefined threshold temperature. This predefined threshold 25 temperature may be any appropriate temperature, for example, a temperature between about 180°C and about 250°C, or more preferably between about 180°C and about 200°C. The predefined threshold temperature may be a temperature selected from the group of temperatures consisting of 180°C, 190°C, 200°C, 210°C, 220°C, 230°C, 240°C, and 250°C. 05 10 23 At step s310, the second vacuum pump 104 pumps the fluid received via the fluid line 110. The fluid is pumped, by the second vacuum pump 104, into the second fluid inlet 148, through the second pumping chamber 150, and out of the second fluid outlet 152. This fluid is pumped out of the second 5 vacuum pump 104 to any appropriate entity, depending on application. At step s312, the heated purge gas is pumped from the heat exchanger 130 to the second vacuum pump 104. The heated purge gas is received at the nozzle 154 of the second vacuum pump 104. At step s314, the nozzle delivers or disperses the heated purge gas into 10 the second pumping chamber 150 of the second vacuum pump 104. Preferably, the heated purge gas is delivered at high speed into the second pumping chamber 150. This delivery of the heated purge gas into the second pumping chamber 150 advantageously tends to remove solid matter that has been deposited on 15 components within the second pumping chamber 150. Such solid matter may include, by-products of processes performed by the facility 101 that may have condensed and settled within the second pumping chamber 150, or dust, etc. Advantageously, the delivery of heated purge gas into the second pumping chamber 150 tends to prevent the settling of solid particles within the second 20 pumping chamber 150 and convey of the solid particles out of the second pumping chamber 150. The relatively high temperature of the purge gas tends to reduce or eliminate a reduction of a temperature within the second pumping chamber 150 and / or a temperature of the walls of the second stator 146 and / or the pumping 25 means housed therein. This advantageously tends to reduce or eliminate condensation of by-products present within the pumped fluid. Accordingly, the deposition of solidified by-products within the second pumping chamber 150 tends to be reduced. The temperature within the second pumping chamber 150 and / or a temperature of the walls of the second stator 146 and / or the pumping 30 means housed therein may be, for example, a temperature selected from the 05 10 23 group of temperatures consisting of 180°C, 190°C, 200°C, 210°C, 220°C, 230°C, 240°C, and 250°C. Thus, the process 300 performed by the vacuum pumping system 100 is provided. 5 Advantageously, the above-described system and method tends to reduce or eliminate the build-up of potentially flammable, corrosive, or otherwise hazardous particulate matter within the second vacuum pump. Furthermore, the impedance of, for example, the pumping means, e.g. rotors, of the second vacuum pump tends to be reduced or eliminated. Thus, pumping efficiency of 10 the second vacuum pump tends to be improved. The heating of the first stator by the heaters advantageously tends to reduce or eliminate condensation of by-products present within the pumped fluid within the first pumping chamber. Accordingly, the deposition of solidified by-products within the first pumping chamber tends to be reduced. Thus, 15 pumping efficiency of the first vacuum pump tends to be improved. Advantageously, uniform heating of the first stator by the heaters tends to be achieved. The net shape of the casting forming the first stator 114 tends to allow for the even placement of heaters to achieve uniform heating. Advantageously, the above-described purge gas heating may be non-20 electrical, which tends to simplify the power provision on board the pump. In the above embodiments, the first vacuum pump is a mechanical booster pump, and may be a Roots-type or Roots vacuum pump. However, in other embodiments, the first vacuum pump is a different type of vacuum pump. The first vacuum pump may have any number of stages, pumping chambers, 25 rotors and rotor shafts, for example. In the above embodiments, the conduit of the heat exchanger is formed in a side wall of the first stator. However, in other embodiments, the conduit is formed in one or more other walls of the first stator instead of or in addition to a side wall of the stator. For example, at least a part of the conduit may be formed 30 in the top or bottom wall of the first stator. 05 10 23 In the above embodiments, the conduit is a convoluted, meandering, or serpentine conduit. However, in other embodiments, the conduit has a different appropriate shape. In some embodiments, the conduit comprises one or more features that facilitate heat transfer to the purge gas, such as one or more fins 5 that increase the surface area of the conduit walls, and / or one or more restrictors that slow the flow of purge gas through the conduit. In the above embodiments, the conduit of the heat exchanger is defined by one or more channels and a cover that covers said channels. In the above embodiments, the heat exchanger comprises a single 10 conduit. However, in other embodiments, the heat exchanger comprises multiple conduits. In the above embodiments, the first stator comprises a single heat exchanger for heating a flow of purge gas. However, in other embodiments, the first stator comprises multiple such heat exchangers. 15 In the above embodiments, the first stator comprises two heaters. However, in other embodiments, the stator comprises a different number of heaters, for example only one heater or more than two heaters. In some embodiments, the heaters are omitted. In the above embodiments, the heaters are embedded in one or more of 20 the walls of the first stator. However, in other embodiments, the heaters are coupled to a stator wall or walls in a different way. For example, one or more of the heaters may be attached to an external surface of a wall of the first stator. In the above embodiments, the heaters are located proximate to the conduit. In particular, the heaters are adjacent to and on opposite sides of the 25 conduit. However, in other embodiments, one or more of the heaters occupies a different position on the first stator. In some embodiments, heaters may be distributed (e.g. uniformly) over the first stator so as to provide substantially uniform heating to the walls of the first stator. In the above embodiments, pre-heated purge gas is delivered from the 30 first vacuum pump to the second vacuum pump, and in particular to the second pumping chamber of the second vacuum pump. However, in other embodiments, some or all of the pre-heated purge gas is delivered to a different location instead of or in addition to the second pumping chamber of the second vacuum pump. For example, in some embodiments, the heated purge gas may 5 be delivered to respective pumping chambers of one or more further vacuum pumps in addition to the second pumping chamber of the second vacuum pump. In some embodiments, the heated purge gas is delivered to the first pumping chamber of the first vacuum pump. In some embodiments, the heated purge gas is not delivered to the second vacuum pump and the second vacuum 10 pump may be omitted. 05 10 23 Reference numerals 100-vacuum pumping system 100 101 - facility 102 - first vacuum pump 5 104 - second vacuum pump 106 - purge gas source 108, 112, 144-fluid flow directions 110 - fluid line 114 - first stator 10 116-firstfluid inlet 118 - first pumping chamber 120 - first fluid outlet 122 - first or top wall 124 - second or bottom wall 15 126 - one or more further walls or side walls 128 - first pumping means 130 - heat exchanger 132 - conduit 134 - conduit inlet 20 136 - conduit outlet 138, 140, 142, 156 - purge gas flow direction 146 - second stator 148 - second fluid inlet 150 - second pumping chamber 25 152 - second fluid outlet 154 - nozzle 200 - first side wall 202 - one or more channels 204 - cover 5 206 - direction of movement of cover 208 - heaters 210 - voids 212 - direction of movement of heaters 300 - process 10 s302-s314 - process steps 05 10 23

Claims

1. A vacuum pump stator comprising:one or more walls defining a pumping chamber; anda heat exchanger comprising:5 a conduit which, in use, a purge gas is passed through whereby toheat the purge gas, wherein the conduit is defined by a channel formed on an external surface of the one or more walls; anda cover covering at least a portion of the channel and fixedly attached to the one or more walls.

102. The vacuum pump stator of claim 1, wherein:the conduit comprises:a conduit inlet; anda conduit outlet;15 the conduit inlet is located at an external surface of the one or morewalls;the conduit outlet is located at an external surface of the one or more walls;the conduit connected between the conduit inlet and conduit outlet is20 separated from the pumping chamber by the at least one of the one or more walls.

3. The vacuum pump stator of any preceding claim, whereinthe one or more walls comprises:25 a first wall;a second wall opposite to the first wall; and05 10 23one or more further walls disposed between the first wall and the second wall;the vacuum pump stator further comprises:a pumping chamber inlet defined in the first wall; and5 a pumping chamber outlet defined in the second wall; andthe conduit is embedded in or integrally formed with the one or more further walls.

4. The vacuum pump stator of any preceding claim, further comprising one 10 or more heaters configured to heat at least a portion of the one or more walls.

5. The vacuum pump stator of claim 4, wherein the one or more heaters are at least partially embedded in the one or more walls.15 6. The vacuum pump stator of any preceding claim, wherein the conduit is aconvoluted conduit.

7. A vacuum pump comprising:a stator according to any preceding claim;20 one or more rotors arranged in the pumping chamber;one or more shafts extending at least partially though the pumping chamber; whereinthe one or more rotors are fixed to a respective one of the one or more shafts.

258. A system comprising:the vacuum pump of claim 7; and05 10 23a purge gas source configured to supply the purge gas into the conduit.

9. The system of claim 8, wherein:the pumping chamber comprises a first pumping chamber inlet and a first 5 pumping chamber outlet;the system further comprises a further vacuum pump; whereinthe further vacuum pump comprises a further pumping chamber;the further pumping chamber comprises a second pumping chamber inlet and a second pumping chamber outlet;10 the first pumping chamber outlet is coupled to the second pumpingchamber inlet such that, in use, a fluid is pumped from the pumping chamber to the further pumping chamber; andthe heat exchanger is coupled to the further pumping chamber such that, in use, the heated purge gas is supplied into the further pumping chamber.1510. The system of claim 9, wherein the vacuum pump is a booster pump.

11. A method comprising:providing a vacuum pump, the vacuum pump being in accordance with 20 claim 7;pumping, using the vacuum pump, a fluid, the fluid being pumped through the pumping chamber of the vacuum pump; andcausing a purge gas to flow through the conduit of the heat exchanger; wherein25 as the purge gas flows through the conduit, heat is transferred to thepurge gas from the one or more walls thereby to heat the purge gas.

12. The method of claim 11, wherein the purge gas is nitrogen.

13. The method of claim 11 or 12, further comprising heating, by one or more heaters, at least a portion of the one or more walls.

14. The method of any of claims 11 to 13, further comprising outputting, to a further vacuum pump, from the heat exchanger, the heated purge gas.10COCM

Images