vacuum pump

Abstract

A vacuum pump comprising: a stator (114) having one or more stator walls (122, 124, 126) defining a pump chamber (118); a heat transfer device (130) coupled to one or more stator walls (122, 124, 126); the heat transfer device (139) comprising: a heat conductor (126, 500); and a conduit (132) penetrating the heat conductor, through which purge gas passes during use, thereby heating the purge gas.

Description

Technical Field

[0001] The present invention relates to a vacuum pump.

Background Art

[0002] Vacuum pumps are used in various technical processes to discharge process gases from a process chamber, thereby creating the low-pressure state required for each process. The process gas may include by-products of the process. The by-products may enter the pump chamber of the vacuum pump and may solidify or condense there. The solidified by-products may deposit on the surfaces inside the pump chamber, such as the inner wall of the pump chamber and the circumferential surface of the rotor. The deposited by-products may narrow the gaps between the rotors. The deposited by-products may cause a decrease in pump efficiency, damage to the bearings, and ultimately failure of the vacuum pump.

[0003] To prevent or impede the deposition of solidified by-products, it is known to use a purge gas or a flushing gas. The purge gas can be discharged into the pump chamber through a purge gas line during pump operation. Preferably, the purge gas is supplied at high speed through a nozzle. The flow of the purge gas prevents the deposition of solid particles in the pump chamber and helps to carry those solid particles out of the pump chamber.

[0004] It is known to use a mechanical booster pump in combination with a vacuum pump. One or two or more mechanical booster pumps can be mechanically coupled to the vacuum pump, for example, at the inlet of the vacuum pump, and the mechanical booster pump is adapted to increase the pressure of the fluid entering the vacuum pump during operation.

Summary of the Invention

Means for Solving the Problems

[0005] By heating the stator of the vacuum pump, condensation and deposition of by-products in the pump chamber can be prevented.

[0006] However, the inventors recognize that introducing purge gas into the pump chamber can lower the temperature inside the pump chamber and / or the temperature of the stator wall, thereby potentially causing condensation of by-products present inside the pump chamber. Furthermore, the inventors recognize that preheating the pump chamber before introducing the purge gas tends to reduce the cooling effect caused by the introduction of the purge gas, thereby reducing the condensation and accumulation of by-products inside the pump chamber.

[0007] Furthermore, the inventors recognize that heat exchangers can be adapted to the walls of pump stators such as booster pumps and can be used to preheat purge gas before it is introduced into the pump chamber of a vacuum pump, for example, a further pump downstream of the booster pump. Furthermore, the inventors recognize that heaters can be adapted to the walls of pump stators such as booster pumps and can be used to heat the stator walls, thereby heating the purge gas passing through the pump chamber of the booster pump and the heat exchanger.

[0008] In a first embodiment, a vacuum pump stator is provided, comprising one or more walls defining a pump chamber, and a heat exchanger including conduits passing through at least one or more walls, through which a purge gas passes during use, thereby heating the purge gas.

[0009] The conduit may have a conduit inlet and a conduit outlet. The conduit inlet may be located on the outer surface of one or more walls. The conduit connecting the conduit inlet and the conduit outlet may be separated from the pump room by at least one of one or more walls.

[0010] One or more walls may comprise a first wall, a second wall opposite the first wall, and one or more further walls positioned between the first and second walls. The vacuum pump stator may further comprise a pump chamber inlet defined in the first wall and a pump chamber outlet defined in the second wall. Conduits may be embedded in or integrally formed with one or more further walls.

[0011] The vacuum pump stator may further include one or more heaters configured to heat at least a portion of one or more walls.

[0012] One or more heaters can be embedded at least partially in one or more walls.

[0013] A conduit can be defined by a flow path formed on the outer surface of one or more walls, and a cover that covers at least a portion of the flow path and is fixedly attached to one or more walls.

[0014] The conduits can be intricately intertwined (convoluted, spiral-shaped).

[0015] In another embodiment, a vacuum pump is provided comprising a stator according to any of the above embodiments, one or more rotors arranged in a pump chamber, and one or more shafts that at least partially penetrate the pump chamber. One or more rotors are fixed to each of the one or more shafts.

[0016] In another embodiment, a system is provided comprising a vacuum pump according to any of the above embodiments and a purge gas source configured to supply purge gas into a conduit.

[0017] The pump chamber may include a first pump chamber inlet and a first pump chamber outlet. The system may further include a further vacuum pump. The further vacuum pump may include a further pump chamber. The further pump chamber may include a second pump chamber inlet and a second pump chamber outlet. The first pump chamber outlet may be connected to the second pump chamber inlet, and when in use, fluid is pumped from the pump chamber to the further pump chamber. A heat exchanger may be connected to the further pump chamber, and when in use, heated purge gas is supplied to the further pump chamber.

[0018] A vacuum pump can be used as a booster pump.

[0019] In another embodiment, a method is provided which includes the steps of: preparing a vacuum pump according to any of the above embodiments; pumping a fluid using the vacuum pump, the fluid being pumped through the pump chamber of the vacuum pump; and causing a purge gas to flow through a conduit of a heat exchanger. As the purge gas flows through the conduit, heat is transferred to the purge gas from one or more walls, thereby heating the purge gas.

[0020] The purge gas can be nitrogen.

[0021] This method may further include the step of heating at least a portion of one or more walls with one or more heaters.

[0022] This method may further include the step of removing the heated purge gas from the heat exchanger to a further vacuum pump.

[0023] In another aspect, a vacuum pump is provided that includes a stator and a heat transfer device. The stator includes one or more stator walls that define a pump chamber. The heat transfer device is coupled to the one or more stator walls. The heat transfer device includes a heat conductor and a conduit that passes through the heat conductor. The conduit is, in use, a conduit through which a purge gas passes and thereby heats the purge gas.

[0024] The heat transfer device can be attached (e.g., by fasteners) to the outer surface of the one or more stator walls.

[0025] The conduit can include a pipe embedded within the heat conductor. The pipe can be partially embedded within the heat conductor, for example, the pipe can be press-fitted into a groove formed on the surface of the heat conductor. Alternatively, the pipe can be fully embedded within the heat conductor, for example, the pipe can be cast into a solid mass of the heat conductor. The pipe can be a stainless steel pipe.

[0026] The heat conductor can be a plate or block of a heat conductive material such as metal. The heat conductor can include aluminum, for example, the heat conductor can be a plate of substantially aluminum or an aluminum alloy.

[0027] The conduit can be a complex, meandering, or serpentine conduit.

[0028] The heat transfer device can further include one or more heaters embedded therein. The heaters can be elongated heaters, each housed within a corresponding hole passing through the heat conductive material. The heat transfer device can include a plurality of heaters spaced apart from each other. The conduit can be a complex conduit passing through one or more spaces between the heaters. The one or more heaters and the conduit can be arranged in a common layer or plane within the heat conductive material. Alternatively, the heater(s) and the conduit can be arranged in different layers or planes substantially parallel to each other within the heat conductive material.

[0029] The heat transfer device can further include an additional conduit that passes through the heat conductor, and during use, a cooling fluid (such as water) passes through this conduit to cool the heat conductor. The additional conduit can be a complex, winding, or serpentine conduit.

[0030] The heat transfer device can include an additional conduit that passes through the heat conductor and is arranged to receive the cooling fluid (during use, it receives the cooling fluid and the cooling fluid passes through the heat conductor to effect cooling). The additional conduit can be arranged as a first layer (for example, substantially within a first plane) within the heat conductor. The heat transfer device can include a plurality of heaters arranged as a second layer (for example, substantially within a second plane) within the heat conductor. The second layer can be substantially parallel to the first layer. The conduit can be arranged as a third layer (for example, substantially within a third plane) within the heat conductor. The third layer can be substantially parallel to the first layer and the second layer. The third layer may be arranged between the first layer and the second layer. Alternatively, the second layer may be arranged between the first layer and the third layer.

[0031] The conduit can have an inlet on or adjacent to a first side of the heat transfer device and an outlet on or adjacent to a second side of the heat transfer device, where the second side is opposite the first side. The first side corresponds to the low vacuum side of a vacuum pump and the second side corresponds to the high vacuum side of the vacuum pump. Alternatively, the first side corresponds to the high vacuum side of the vacuum pump and the second side corresponds to the low vacuum side of the vacuum pump. In other words, the stator can have a high vacuum end and a low vacuum end, and the conduit can have an inlet on or adjacent to one of the high vacuum end or the low vacuum end and an outlet on or adjacent to the other of the high vacuum end or the low vacuum end.

[0032] In another aspect, a system is provided that includes a vacuum pump in any of the above aspects and a purge gas supply source configured to supply purge gas into the conduit.

[0033] In another embodiment, a method is provided which includes the steps of: preparing a vacuum pump according to any of the above embodiments; pumping a fluid using the vacuum pump, the fluid being pumped through the pump chamber of the vacuum pump; and causing a purge gas to flow through a conduit of a heat transfer device. As the purge gas flows through the conduit, heat is transferred from the stator to the purge gas via a heat conductor, thereby heating the purge gas. [Brief explanation of the drawing]

[0034] [Figure 1] This is a schematic diagram of a vacuum pump system (not to scale). [Figure 2] This is a schematic diagram showing an exploded perspective view of the first stator of the first vacuum pump (not to scale). [Figure 3] This is a process flow diagram showing specific steps in a process performed by a vacuum pump system. [Figure 4] This is a schematic diagram showing a perspective view of a vacuum pump equipped with a heat transfer device (not to scale). [Figure 5] This is a schematic diagram showing a heat transfer device (not to scale). [Figure 6] This is a schematic diagram showing a heat transfer device (not to scale). [Figure 7] This is a schematic diagram showing another heat transfer device (not to scale). [Figure 8] This is a schematic diagram showing yet another heat transfer device (not to scale). [Figure 9] This is a schematic diagram showing a cross-section of yet another heat transfer device (not to scale). [Modes for carrying out the invention]

[0035] In this specification, relative terms such as top and bottom, horizontal and vertical, upper and lower, front and rear are used to facilitate reference to the drawings, and these terms are not limited in that sense, and may give any two different directions or positions, etc., rather than true top and bottom, horizontal and vertical, upper and lower, etc.

[0036] Figure 1 is a schematic diagram of the vacuum pump system 100 (not to scale).

[0037] The vacuum pump system 100 comprises equipment 101, a first vacuum pump 102, a second vacuum pump 104, and a purge gas supply source 106.

[0038] Equipment 101 can be any suitable type of equipment, such as semiconductor manufacturing equipment. Equipment 101 is connected to a vacuum pump system comprising a first vacuum pump 102 and a second vacuum pump 104. The vacuum pump system 100 is configured to establish a vacuum or low-pressure environment in equipment 101 by drawing gas (e.g., air or process gas) from equipment 101.

[0039] The first vacuum pump 102 is a mechanical booster pump. The first vacuum pump 102 can be any suitable type of booster pump, such as a Roots type or Roots vacuum pump. The first vacuum pump 102 can be a positive displacement pump. The first vacuum pump 102 is operationally coupled between the equipment 101 and the second vacuum pump 104. The first vacuum pump 102 is configured to pump fluid (e.g., gas) out of the equipment 101, as indicated by the arrow and reference numeral 108 in Figure 1. Furthermore, the first vacuum pump 102 is configured to pump its fluid to the second vacuum pump 104 via the fluid line 110, as indicated by the arrow and reference numeral 112 in Figure 1. The first vacuum pump 102 is configured to increase the pressure of the pumped fluid flowing into the second vacuum pump 104. Such operation of the first vacuum pump 102 tends to increase the pumping efficiency of the second vacuum pump 104.

[0040] The first vacuum pump 102 comprises a first housing or stator 114. The first stator 114 comprises one or more walls defining a first fluid inlet 116, a first pump chamber 118, and a first fluid outlet 120.

[0041] More specifically, in this embodiment, the first stator 114 comprises a first wall or upper wall 122, a second wall or lower wall 124 facing the first wall 122, and one or more further walls or side walls 126 positioned between the first wall 122 and the second wall 124. A first fluid inlet 116 is formed through the first wall 122. A first fluid outlet 120 is formed through the second wall 124.

[0042] The first vacuum pump 102 further comprises a first pumping means 128 located within a first pump chamber 118. The first pumping means 128 can be any suitable type of pumping means and may include one or more rotors, such as a plurality of rotors that mesh with or cooperate with each other. One or more rotors can be mounted on shafts that at least partially penetrate the first pump chamber 118. These shafts, and therefore the rotors, can be rotated by some suitable means, such as an electric motor, thereby pumping fluid through the first pump chamber 118.

[0043] Since the first pump chamber 118 (and the first pumping means 128 located inside it) is connected between the first fluid inlet 116 and the first fluid outlet 120, when in operation, the fluid is pumped by the first pumping means 128 to the first fluid inlet 116, from the first fluid inlet 116 to the first fluid outlet 120, and from the first fluid outlet 120 to the outside.

[0044] The first vacuum pump 102 further comprises a heat exchanger 130. The heat exchanger 130 includes conduits 132 (e.g., embedded or integrally formed) passing through at least one of the one or more walls of the first stator 114. In particular, in this embodiment, the conduits 132 are embedded in or integrally formed with one or more further walls 126. The conduits 132 can be entirely inside one or more further walls 126.

[0045] In this embodiment, the conduit 132 comprises a conduit inlet 134 and a conduit outlet 136. The conduit inlet 134 is located on the outer surface of the first stator 114. More specifically, in this embodiment, the conduit inlet 134 is located on the outer surface of one or more further walls 126. The conduit outlet 136 is located on the outer surface of the first stator 114. More specifically, in this embodiment, the conduit outlet 136 is located on the outer surface of one or more further walls 126.

[0046] Since the conduit inlet 134 is connected to the purge gas supply source 106, when in operation, the purge gas from the purge gas supply source 106 is received at the conduit inlet 134, as shown by the arrow and reference numeral 138 in Figure 1. As shown by the arrow and reference numeral 140 in Figure 1, the conduit 132 is configured to carry the received purge gas from the conduit inlet 134 to the conduit outlet 136. Since the conduit outlet 136 is connected to the second vacuum pump 104, when in operation, the purge gas discharged from the conduit 132 of the heat exchanger 130 through the conduit outlet 136 is carried to the second vacuum pump 104, as shown by the arrow and reference numeral 142 in Figure 1.

[0047] In this embodiment, the conduit 132 connected between the conduit inlet 134 and the conduit outlet 136 is isolated from the pump chamber 118 by the wall of the first stator 114. In other words, in this embodiment, within the range or boundary of the first stator 114, the conduit 132 is fluidically isolated or independent from the first pump chamber 118. Therefore, in this embodiment, fluid cannot flow through the wall of the first stator 114 from the conduit 132 to the first pump chamber 118 (and vice versa).

[0048] In this embodiment, the conduit 132 is a complex, winding, or meandering conduit. This can be seen more clearly in Figure 2.

[0049] Details of the heat exchanger 130 and its operation will be explained in more detail later with reference to Figures 2 and 3.

[0050] The second vacuum pump 104 can be any suitable type of vacuum pump, such as a dry vacuum pump. The second vacuum pump 104 is configured to pump fluid from the first vacuum pump 102, as indicated by the arrow and reference numeral 112 in Figure 1. Thus, a vacuum or low-pressure environment is created within the facility 101. The second vacuum pump 104 is configured to discharge or send out the pumped fluid, as indicated by the arrow and reference numeral 144 in Figure 1. The pumped fluid can be discharged to any suitable entity depending on the application. For example, the pumped fluid can be sent to a pollution control system or the environment.

[0051] The second vacuum pump 104 comprises a second housing or stator 146. The second stator 146 comprises one or more walls defining a second fluid inlet 148, a second pump chamber 150, and a second fluid outlet 152.

[0052] The second vacuum pump 104 further comprises a second pumping means (not shown) located in the second pump chamber. The second pumping means can be any suitable type of pumping means.

[0053] The second vacuum pump 104 further comprises a nozzle 154. The nozzle 154 is positioned to penetrate one or more walls of the second stator 146. The nozzle 154 is connected to a conduit outlet 136, and when in operation, the flow of purge gas is received by the nozzle 154. The nozzle 154 is further configured to supply the received purge gas to the second pump chamber 150, as indicated by the arrow and reference numeral 156 in Figure 1.

[0054] Figure 2 is a schematic diagram showing an exploded perspective view of the first stator 114 of the first vacuum pump 102 (not to scale).

[0055] In this embodiment, the heat exchanger 130 is positioned on the first side wall 200 of the first stator 114. The first side wall 200 is positioned between the first wall 122 and the second wall 124.

[0056] In this embodiment, the conduit 132 of the heat exchanger 130 is defined by one or more flow channels 202 formed on the outer surface of the first side wall 200 and a cover 204 that covers the one or more flow channels 202, thereby defining the conduit 132.

[0057] One or more flow channels 202 can be channels or grooves machined or etched onto the outer surface of the first side wall 200. One or more flow channels 202 can define one or more complex, interwoven paths between the conduit inlet 134 and the conduit outlet 136.

[0058] The cover 204 can be a substantially flat sheet or plate. The cover 204 can be made from the same material as the wall of the first stator 114 (e.g., the first side wall 200) which is formed from this material. This material can be a thermally conductive material such as a metal. The cover 204 can be attached to the first side wall 200 by some suitable fastening means, for example, using one or more fasteners. The attachment of the cover 204 to the first side wall 200 is indicated by the dashed arrow and reference numeral 206 in Figure 2. In some embodiments, a seal or gasket, such as an O-ring, is placed between the cover 204 and the first side wall 200 to reduce or eliminate the leakage of purge gas from the heat exchanger 130.

[0059] In this embodiment, the first stator 114 further comprises two heaters 208. The heaters 208 are positioned or housed in the respective voids 210 of 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 housed are elongated. The insertion of the heaters 208 into the voids 210 is indicated by the dashed arrows and reference numeral 212 in Figure 2.

[0060] In this embodiment, the void 210 is formed in the first side wall 200. The void 210 is positioned close to the heat exchanger 130, and more specifically close to one or more flow channels 202. More specifically, in this embodiment, the void 210 is positioned adjacent to the flow channels 202 on both sides of one or more flow channels 202.

[0061] The void 210 is defined by grooves formed (for example, by machining) on ​​the outer surface of the first side wall 200 and a cover 204 that covers these grooves, thereby defining the void 210.

[0062] The heater 208 can be any suitable type of heater, including but not limited to an electric heater. The heater 208 is configured to heat, i.e., raise the temperature of at least a portion of one or more walls of the first stator 114. Preferably, the heater 208 is configured to heat at least a portion of the first side wall 200 that forms the conduit 132.

[0063] The heater 208 can be controlled by a controller (not shown). In some embodiments, the first stator 114 further comprises one or more temperature sensors, which can be placed on or embedded in one or more walls of the first stator 114. The one or more temperature sensors can be configured to measure the temperature of one or more walls of the first stator. The operation of the heater 208 can be performed based on some function of the measured temperature values ​​obtained by the one or more temperature sensors. For example, in some embodiments, the heater 208 can be controlled to heat at least a portion of the first side wall 200 (e.g., at least a portion forming the heat exchanger 130), which continues until the temperature of that portion of the first side wall 200, as measured by one or more temperature sensors, reaches a threshold, at which point the heater 208 can be controlled to stop or reduce heating. The heater 208 can be controlled to maintain the temperature of that portion of the first side wall 200 near the threshold.

[0064] In some embodiments, the distribution of heaters on the first stator is such that the temperature on the body of the first stator is substantially uniform. The heaters can be distributed at substantially uniform intervals on the first stator. The heaters can be controlled by a common controller to achieve a desired uniform temperature on the first stator.

[0065] The heaters can be distributed on the first stator in a substantially symmetrical arrangement around the first stator shaft. One or more heaters can be located on the end cover and / or head plate of the first stator.

[0066] Figure 3 is a process flow diagram showing specific steps of process 300 performed by the vacuum pump system 100.

[0067] Please note that some of the process steps shown in the flowchart of Figure 3 and described below may be omitted, or may be performed in a different order than that shown in Figure 3. Furthermore, for convenience and ease of understanding, all process steps are shown as separate steps that occur consecutively in time, but in reality, some process steps may be performed simultaneously or at least overlap to some extent in time.

[0068] In step s302, the first vacuum pump 102 pumps fluid out of the equipment 101. The fluid is pumped by the first vacuum pump 102 to the first fluid inlet 116, through the first pump chamber 118, and out of the first fluid outlet 120. This fluid is pumped through the fluid line 110 to the second vacuum pump 104. The first vacuum pump 102 increases the pressure of the pumped fluid entering the second vacuum pump 104.

[0069] In this embodiment, the pumping action of the fluid by the first vacuum pump 102 tends to raise the temperature of one or more walls of the first stator 114 above the ambient temperature. This temperature rise tends to be mainly due to the relatively high temperature of the fluid that the first vacuum pump 102 receives from the equipment 101, and / or friction inside the first vacuum pump 102, such as friction between the fluid and the components of the first vacuum pump 102.

[0070] In step s304, the heater 208 can be optionally controlled to heat or further heat at least a portion of one or more walls of the first stator 114. The heater 208 can be controlled to heat at least a portion of one or more walls of the first stator 114 to a predetermined temperature. The heater 208 can be controlled to heat at least a portion of the first side wall 200 that forms the heat exchanger 130, i.e., the portion of the first side wall that defines the conduit 132 or one or more flow paths 202.

[0071] In step s306, the purge gas is pumped through the heat exchanger 130. Specifically, the purge gas is pumped from the purge gas source 106 through the conduit inlet 134 to the conduit 132. Next, the purge gas is pumped through the conduit 132 from the conduit inlet 134 to the conduit outlet 136. Finally, the purge gas is pumped out of the conduit outlet 136.

[0072] The purge gas can be pumped by some suitable pumping means. For example, in some embodiments, the purge gas supply source 106 includes a pump configured to pump the purge gas.

[0073] The purge gas is some suitable purge gas. Preferably, the purge gas is an inert gas. An example of a purge gas is nitrogen gas.

[0074] In step s308, as the purge gas moves through the conduit 132 of the heat exchanger 130, the heat exchanger 130 heats the purge gas, that is, raises the temperature of the purge gas. Specifically, heat is transferred from the relatively hot first side wall 200, which forms at least partially the conduit 132, to the relatively cold purge gas passing through the conduit 132.

[0075] Therefore, in this embodiment, the temperature of the purge gas exiting the heat exchanger 130 at the conduit outlet 136 is higher than the temperature of the purge gas entering the heat exchanger 130 at the conduit inlet 134.

[0076] In some embodiments, the heater 208 is controlled to heat a portion of the wall of the first stator 114 forming the heat exchanger 130 such that the temperature of the purge gas exiting the heat exchanger 130 is above a preset threshold temperature. This preset threshold temperature can be any suitable temperature, for example, between approximately 180°C and approximately 250°C, more preferably between approximately 180°C and approximately 200°C. The preset threshold temperature can be a temperature selected from the group consisting of 180°C, 190°C, 200°C, 210°C, 220°C, 230°C, 240°C, and 250°C.

[0077] In 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 to the second fluid inlet 148, through the second pump chamber 150, and out of the second fluid outlet 152. Depending on the application, this fluid is pumped from the second vacuum pump 104 to some appropriate device.

[0078] In 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 by the nozzle 154 of the second vacuum pump 104.

[0079] In step s314, the nozzle supplies or disperses the heated purge gas to the second pump chamber 150 of the second vacuum pump 104. Preferably, the heated purge gas is supplied to the second pump chamber 150 at high speed.

[0080] The supply of heated purge gas to the second pump chamber 150 is advantageous in that it tends to remove solids that have accumulated on the components within the second pump chamber 150. Such solids may include by-products of processes performed in the equipment 101, or dust, which can condense and accumulate within the second pump chamber 150. Advantageously, supplying heated purge gas to the second pump chamber 150 prevents solid particles from accumulating within the second pump chamber 150 and tends to carry the solid particles out of the second pump chamber 150.

[0081] The relatively high temperature of the purge gas tends to reduce or eliminate the temperature drop in the second pump chamber 150 and / or the temperature drop in the walls of the second stator 146 and / or the pumping means housed therein. This advantageously tends to reduce or eliminate the condensation of by-products present in the pump fluid. Consequently, the accumulation of solidified by-products in the second pump chamber 150 tends to be reduced. The temperature in the second pump chamber 150 and / or the temperature of the walls of the second stator 146 and / or the temperature of the pumping means housed therein is a temperature selected from the group consisting of, for example, 180°C, 190°C, 200°C, 210°C, 220°C, 230°C, 240°C, and 250°C.

[0082] Therefore, a process 300 is provided that is performed by the vacuum pump system 100.

[0083] Advantageously, the above systems and methods tend to reduce or eliminate the accumulation of potentially flammable, corrosive, or harmful particulate matter in the second vacuum pump. Furthermore, the resistance (impedance) of the pumping means of the second vacuum pump, such as the rotor, tends to be reduced or eliminated. Consequently, the pumping efficiency of the second vacuum pump tends to be improved.

[0084] Heating the first stator by the heater tends to reduce or eliminate the condensation of by-products present in the pump fluid within the first pump chamber. Consequently, the accumulation of solidified by-products in the first pump chamber tends to be reduced. Therefore, the pumping efficiency of the first vacuum pump tends to improve.

[0085] Advantageously, uniform heating of the first stator by the heater tends to be achieved. The net shape of the casting forming the first stator 114 tends to allow for even distribution of the heater to achieve uniform heating.

[0086] Advantageously, the above-mentioned purge gas heating can be non-electric, which tends to simplify the power supply on the pump.

[0087] In the above embodiment, the first vacuum pump is a mechanical booster pump and can be a Roots type or Roots vacuum pump. However, in other embodiments, the first vacuum pump can be a different type of vacuum pump. The first vacuum pump can have, for example, any number of stages, pump chambers, rotors, and rotor shafts.

[0088] In the above embodiment, the conduits of the heat exchanger are formed in the side walls of the first stator. However, in other embodiments, the conduits are formed in one or more other walls of the first stator instead of, or in addition to, the side walls of the stator. For example, at least a portion of the conduits may be formed in the upper or lower walls of the first stator.

[0089] In the embodiments described above, the conduit is a complex, winding, or meandering conduit. However, in other embodiments, the conduit may have a different appropriate shape. In some embodiments, the conduit includes one or more features that facilitate heat transfer to the purge gas, such as one or more fins that increase the surface area of ​​the conduit wall and / or one or more limiters that slow down the flow of purge gas through the conduit.

[0090] In the above embodiment, the heat exchanger comprises a single conduit. However, in other embodiments, the heat exchanger comprises multiple conduits.

[0091] In the above embodiment, the first stator comprises a single heat exchanger for heating the purge gas flow. However, in other embodiments, the first stator comprises multiple such heat exchangers.

[0092] In the above embodiment, the first stator comprises two heaters. However, in other embodiments, the stator comprises a different number of heaters, for example, one heater or three or more heaters. In some embodiments, heaters are omitted.

[0093] In the embodiments described above, the heaters are positioned close to the conduits. More specifically, the heaters are positioned adjacent to the conduits on both sides thereof. However, in other embodiments, one or more heaters occupy different locations on the first stator. In some embodiments, the heaters can be distributed (e.g., uniformly) on the first stator to provide substantially uniform heating to the walls of the first stator.

[0094] In the embodiments described above, the preheated purge gas is supplied from the first vacuum pump to the second vacuum pump, specifically to the second pump chamber of the second vacuum pump. However, in other embodiments, some or all of the preheated purge gas is supplied to a different location instead of, or in addition to, the second pump chamber of the second vacuum pump. For example, in some embodiments, the heated purge gas can be supplied to the respective pump chambers of one or more further vacuum pumps, in addition to the second pump chamber of the second vacuum pump. In some embodiments, the heated purge gas is supplied to the first pump chamber of the first vacuum pump. In some embodiments, the heated purge gas is not supplied to the second vacuum pump, and the second vacuum pump may be omitted.

[0095] In the above embodiment, the conduit of the heat exchanger is defined by one or more flow paths and a cover that encloses these flow paths. However, in other embodiments, the conduit is formed in a different manner.

[0096] In the above embodiment, the heater is embedded in one or more of the walls of the first stator. However, in other embodiments, the heater is coupled to the stator wall(s) in a different manner. For example, one or more of the heaters may be mounted on the outer surface of the wall of the first stator.

[0097] An alternative embodiment is described with reference to Figures 4 to 8, in which a heat exchanger conduit through which a purge gas can be heated is located within a heat transfer device that can be detachably attached to the vacuum pump stator.

[0098] Figure 4 is a schematic diagram showing a perspective view of one embodiment of the vacuum pump 400 (not to scale).

[0099] The vacuum pump 400 can be implemented as the first vacuum pump 102 or the second vacuum pump 104 in the above embodiment.

[0100] In this embodiment, the vacuum pump 400 comprises a stator 402 including a plurality of stator walls 404 that define the pump chamber.

[0101] The vacuum pump 400 further comprises a heat transfer device 406 thermally coupled to the stator 402. The heat transfer device 406 is detachably attached to one or more outer surfaces of the stator wall 404 by a plurality of fasteners 408.

[0102] Figure 4 shows a single heat transfer device 406 positioned on the side wall of the stator 402, but it should be understood that multiple such heat transfer devices can be implemented. One or more heat transfer devices may be attached to one or more other walls 404 of the stator 402, including, but not limited to, the upper, lower, and / or outer surfaces of the side walls of the stator.

[0103] Figures 5 and 6 are schematic diagrams showing the heat transfer device 406 of this embodiment (not to scale).

[0104] The heat transfer device 406 comprises a heat conductor 500 and a conduit 502 that penetrates the heat conductor.

[0105] The heat conductor 500 is a plate or block of a heat conductive material. The heat conductor 500 can be a heat transfer plate. In this embodiment, it is desirable that the heat conductor 500 is a single plate made of metal, preferably aluminum or an aluminum alloy.

[0106] Conduit 502 is a pipe through which purge gas (e.g., nitrogen) passes during use and is heated, as described above with reference to Figures 1 to 3 for details.

[0107] The conduit 502 is a pipe that is intricately intertwined, winding, or meandering. Preferably, the conduit 502 is a integrally molded pipe that is bent into an intricately intertwined or meandering shape.

[0108] The conduit 502 is embedded within the heat conductor 500. In this embodiment, the conduit 502 is cast into the heat conductor 500, thereby embedding the conduit 502 within the heat conductor 500. However, in other embodiments, the conduit 502 can be embedded within the heat conductor 500 in a different way, such as by pressing or pushing the conduit 502 into a groove formed on the surface of the heat conductor 500.

[0109] In this embodiment, the conduit 502 is partially embedded within the heat conductor 500. More specifically, several substantially linear parallel sections 504 of the conduit 502 are embedded within the heat conductor 500, while curved transition sections 506 between the linear parallel sections 504 are spaced apart from the heat conductor 500 (i.e., not embedded within the heat conductor 500). Nevertheless, in some embodiments, the conduit 502 can follow a complex, intricate path within the heat conductor 500. Also, in some embodiments, the conduit 502 may be fully embedded within the heat conductor 500.

[0110] Preferably, the conduit 502 is formed from a different material than the material on which the thermal conductor 500 is formed. The conduit 502 can be formed from, for example, stainless steel or a nickel-based alloy. The thermal conductor 500 can be formed from, for example, aluminum, an aluminum alloy, or (for example, in non-semiconductor applications) copper. Preferably, the thermal conductor 500 is formed from a material with a thermal conductivity of 200 W / mK or higher.

[0111] In this embodiment, the conduit 502 includes an inlet 508 and an outlet 510. The inlet 508 is positioned to receive a flow of purge gas from a purge gas supply source. The purge gas received at the inlet 508 passes through the conduit 502 and flows out of the conduit 502 at the outlet 510.

[0112] In this embodiment, the inlet 508 is located on or near the first side surface 512 of the heat transfer device 406. The outlet 510 is located on or near the second side surface 514 of the heat transfer device 406. The second side surface 514 is on the opposite side from the first side surface 512.

[0113] During operation, the purge gas is supplied from the purge gas source to the inlet 508 of the conduit 502 and is allowed to pass through the conduit 502. Heat is transferred from the relatively hot stator to the relatively cooler purge gas passing through the conduit 502 via the heat conductor 500 and the walls of the conduit 502. Exemplarily, the heat conductor 500 of a heat transfer device 406 attached to the stator of a hot screw pump may be heated to a temperature of approximately 250°C. The heated purge gas flows out of the conduit 502 through the outlet 510. Therefore, preheating of the purge gas is performed before it is introduced into the pump chamber of the vacuum pump.

[0114] Advantages include the avoidance of the use of active electric heating, which reduces cost and complexity. Cast-in gas-heated pipes are a low-cost, passive solution that reduces installation space and tends to be highly reliable.

[0115] While the use of active heating can be avoided, in some embodiments the heat transfer device may still include one or more heaters. Exemplarily, Figure 7 is a schematic diagram (not to scale) showing a heat transfer device 700 with one or more heaters according to a further embodiment.

[0116] The heat transfer device 700 can be thermally coupled to the stator of a vacuum pump (e.g., a first vacuum pump 102 or a second vacuum pump 104) in a manner similar to or similar to that of the heat transfer device 406 shown in Figure 4. For example, the heat transfer device 700 can be detachably attached to the outer surface of one or more stator walls 404 by a plurality of fasteners.

[0117] The heat transfer device 700 comprises a heat conductor 702 and a conduit 704 that penetrates the heat conductor 702. The heat conductor 702 can be substantially the same as the heat conductor 500. For example, the heat conductor 702 can be a metal plate or block such as aluminum or an aluminum alloy.

[0118] The conduit 704 is a pipe through which a purge gas (e.g., nitrogen) passes during use, thereby heating the purge gas. The conduit 704 can be a stainless steel pipe. In this embodiment, the conduit 704 follows a complex, intricate path within the heat conductor 702. The conduit 704 has an inlet 712 at or near the first end 714 of the heat transfer device 700, and an outlet 716 at or near the second end 718 of the heat transfer device 700, with the second end 718 being on the opposite side of the first end 714. During operation, the purge gas is supplied from a purge gas source to the inlet 712 of the conduit 704 and is allowed to pass through the conduit 704. Heat is transferred from the relatively hot stator to the relatively cooler purge gas passing through the conduit 704 via the walls of the heat conductor 702 and the conduit 704. The heated purge gas flows out of conduit 704 through outlet 716. Therefore, the purge gas is preheated before being introduced into the pump chamber of the vacuum pump.

[0119] In this embodiment, the heat transfer device 700 further comprises a plurality of heaters 708. Figure 7 shows a heat transfer device 700 comprising four heaters 708, but those skilled in the art will understand that in practice the heat transfer device 700 may contain any number of heaters 708, such as 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or 11 or more. Each heater 708 is housed in a corresponding hole or void 710. In this embodiment, the heaters 708 and the voids 710 in which they are housed are elongated in shape. The voids 710 are formed in the heat conductor 702.

[0120] The heater 708 can be any suitable type of heater, including, but is not limited to, an electric heater. The heater 708 is configured to heat, i.e., raise the temperature of, at least a portion of the heat conductor 702.

[0121] The heater 708 can be controlled by a controller (not shown). In some embodiments, the heat transfer device 700 further comprises one or more temperature sensors, which can be placed on or embedded in the heat conductor 702. One or more temperature sensors can be configured to measure the temperature of the heat conductor 702. The operation of the heater 708 can be based on some function of the temperature measurements obtained by one or more temperature sensors. For example, in some embodiments, the heater 708 can be controlled to heat at least a portion of the heat conductor 702, which continues until the temperature of that portion of the heat conductor 702, as measured by one or more temperature sensors, reaches a threshold, at which point the heater 708 can be controlled to stop or reduce heating. The heater 708 can be controlled to maintain the temperature of that portion of the heat conductor 702 near the threshold.

[0122] In some embodiments, the distribution of heaters 708 on the heat conductor 702 is such that the temperature of the heat conductor 702 is substantially uniform. The heaters 708 can be distributed at substantially uniform intervals on the first stator. The heaters can be controlled by a common control device to achieve the desired uniform temperature of the heat conductor 702.

[0123] In this embodiment, the heaters 708 are spaced apart from each other. The conduit 704 is a complex network of conduits that pass through the space between adjacent heaters 708.

[0124] In this embodiment, the heater 708 and the conduit 704 are arranged in a single common layer or plane within the heat conductor 702. Alternatively, the heater 708 and the conduit 704 can be arranged in different layers or planes within the heat conductor 702. Exemplarily, Figure 8 is a schematic diagram (not to scale) showing a heat transfer device 800 according to yet another embodiment.

[0125] The heat transfer device 800 can be thermally coupled to the stator of a vacuum pump (e.g., a first vacuum pump 102 or a second vacuum pump 104) in a manner similar to or similar to that of the heat transfer device 406 shown in Figure 4. For example, the heat transfer device 800 can be detachably attached to the outer surface of one or more stator walls 404 by a plurality of fasteners.

[0126] The heat transfer device 800 comprises a heat conductor 802 and a conduit 804 that penetrates the heat conductor 802. The heat conductor 802 can be substantially the same as the heat conductor 500 or the heat conductor 702. For example, the heat conductor 802 can be a metal plate or block such as aluminum or an aluminum alloy.

[0127] Conduit 804 is a pipe through which a purge gas (e.g., nitrogen) passes during use, thereby heating the purge gas. Conduit 804 can be a stainless steel pipe. In this embodiment, conduit 804 follows a complex, intricate path within the heat conductor 802. Conduit 804 has an inlet 820 at or near the first end 822 of the heat transfer device 800, and an outlet 824 at or near the second end 826 of the heat transfer device 800, with the second end 826 being on the opposite side of the first end 822. During operation, the purge gas is supplied from a purge gas source to the inlet 820 of conduit 804 and is allowed to pass through conduit 804. Heat is transferred from the relatively hot stator to the relatively cooler purge gas passing through conduit 804 via the walls of the heat conductor 802 and conduit 804. The heated purge gas flows out of conduit 804 through outlet 824. Therefore, the purge gas is preheated before being introduced into the pump chamber of the vacuum pump.

[0128] In this embodiment, the heat transfer device 800 further comprises a plurality of heaters 808. Figure 8 shows a heat transfer device 800 comprising four heaters 808, but those skilled in the art will understand that in practice the heat transfer device 800 may include any number of heaters, such as 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or 11 or more. Each heater 808 is housed in a corresponding hole or void 810. In this embodiment, the heaters 808 and the voids 810 in which they are housed are elongated in shape. The voids 810 are formed in the heat conductor 802.

[0129] The heater 808 can be any suitable type of heater, including, but is not limited to, an electric heater. The heater 808 can be controlled by a controller, for example, using sensor measurements, as described above with respect to Figure 7.

[0130] In this embodiment, the heater 808 and the conduit 804 are arranged in different layers or planes within the heat conductor 802. The planes or layers can be substantially parallel to each other.

[0131] In this embodiment, the heat transfer device 800 further comprises a further conduit 812. The further conduit 812 is a pipe that penetrates the heat conductor 802 and, when in use, carries a cooling fluid (e.g., water) that cools the heat conductor 802. The further conduit 812 is preferably a complex, winding, or meandering conduit. The further conduit 812 can be considered a cooling fluid conduit. Those skilled in the art will understand that such a cooling fluid conduit can be implemented in any other embodiment of the heat transfer device described herein, for example, the heat transfer device 406 described with respect to Figures 5 and 6, or the heat transfer device 700 described with respect to Figure 7.

[0132] In this embodiment, the additional conduit 812 is located in the first layer 814 within the heat conductor 802. For example, the additional conduit 812 can be located in the first plane. Also, the multiple heaters 808 are located in the second layer 816 within the heat conductor 802. For example, the multiple heaters 808 can be located in the second plane. Also, the conduit 804 is located in the third layer 818 within the heat conductive body 802. For example, the conduit 804 can be located in the third plane. Preferably, the first, second, and third layers (or planes) 814, 816, and 818 are substantially parallel to each other. In this embodiment, the second layer 816 is located between the first layer 814 and the third layer 818. That is, the heater layer 808 is sandwiched between the layer or plane containing the additional conduit 812 and the layer or plane containing the conduit 804. The heat transfer device 800 can be mounted on the stator wall such that the third layer 818 is in contact with the stator wall and the first layer 814 is furthest from the stator.

[0133] However, in other embodiments, the order or arrangement of the layers may differ. Exemplarily, Figure 9 is a schematic diagram (not to scale) showing a cross-section of a heat transfer device 900 in which the conduit 804, heater 808, and further conduit 812 are arranged differently. In this embodiment, the layer or plane 902 containing the conduit 804 is sandwiched between the layer 904 containing the heater 808 and the layer or plane 906 containing the further conduit 812. The heat transfer device 900 can be mounted on the stator wall such that the layer 904 containing the heater 808 is in contact with the stator wall, and the layer or plane 906 containing the further conduit 812 is furthest from the stator. In this arrangement, heat loss upward from the heater 808 tends to be captured by the purge gas in the conduit 804, and the heater 808 is in close proximity to or in direct contact with the stator, improving its heating efficiency. When heater 808 is operating and the supply of cooling fluid to the further conduit 812 is stopped, the purge gas tends to create a protective layer between heater 808 and the further conduit 812 to prevent boiling, stress corrosion, and calcification of the cooling fluid in the further conduit 812.

[0134] The heat transfer devices described above tend to prevent or reduce calcification and stress corrosion. For example, the purge gas passing through conduit 804 tends to prevent the boiling of the cooling fluid (e.g., water) in the further conduit 812, which tends to be beneficial in preventing calcification and stress corrosion problems in static cooling plates where water does not flow inside.

[0135] During operation, if stator cooling is required, one or more heaters can be turned off and the flow of purge gas and cooling fluid can be turned on. During operation, if heating of the stator and / or purge gas is required, the flow of cooling fluid can be turned off and one or more heaters and the flow of purge gas can be turned on.

[0136] Advantageously, the above systems and devices tend to provide vacuum pump systems with a small footprint. For example, the need for additional, separate purge gas heating equipment can be reduced or eliminated.

[0137] The heat transfer devices described above tend to offer relatively low power consumption and / or a more uniform temperature distribution throughout the pump.

[0138] The systems and devices described above tend to allow for shorter pump warm-up times by preheating the purge gas. When the purge gas is supplied to the abatement system, this saves the power required to preheat the purge gas within the abatement system.

[0139] Advantageously, the above systems and devices tend to allow the use of more powerful heaters. This improves the preheating of the purge gas and the heating of the stator, and tends to allow for shorter pump warm-up times.

[0140] The purge gas passing through the purge gas conduit tends to disperse across the stator, reducing the likelihood of high / low temperature spots caused by localized heating by the heater.

[0141] In the systems and apparatus described above, the purge gas conduit can be arranged so that the purge gas flows along the length between the low vacuum ends of the stator. For example, the heat transfer device described above can be mounted on the stator such that the inlet of the conduit is located at or adjacent to one of the high vacuum end or low vacuum end of the vacuum pump, and the outlet of the conduit is located at or adjacent to the other of the high vacuum end or low vacuum end. Under operating conditions such as high load conditions, where the high vacuum end and adjacent stages of the vacuum pump may be hotter than the low vacuum end and adjacent stages of the vacuum pump, the purge gas can be introduced into the purge gas conduit from a conduit opening closer to the high vacuum end, and the flow of purge gas through the conduit tends to transfer heat from the high vacuum end to the cooler low vacuum end. Similarly, under operating conditions such as the ultimate condition, where the low vacuum end and adjacent stages of a vacuum pump may be hotter than the high vacuum end and adjacent stages, the purge gas can be introduced into the purge gas conduit from a conduit opening near the low vacuum end, and the flow of purge gas through the conduit tends to transfer heat from the low vacuum end to the cooler high vacuum end. Advantageously, the direction of the purge gas flow through the conduit can be changed.

[0142] In the embodiments described above, the purge gas conduit can have some appropriate dimensions. For example, the purge gas conduit can have an inner diameter of about 5-10 mm, more preferably about 6 mm. In some embodiments, the purge gas conduit can have an inner diameter of 5 mm or less, for example, 2-4 mm, for example, about 3 mm.

[0143] In the embodiments described above, the heat conductors of the heat exchanger can be cast or machined. However, in other embodiments, at least a part of the heat exchanger, such as the heat conductors, can be manufactured by different methods, such as additive manufacturing (AM) techniques. For example, the heat conductors can be formed using AM so as to include a purge gas conduit network inside. Reducing the size of the purge gas conduits in the heat transfer device tends to improve the prevention of calcification and stress corrosion.

[0144] In the above embodiment, the purge gas can be nitrogen. However, in other embodiments, a different purge gas, such as air, can be used.

[0145] In the above embodiment, the cooling fluid can be water. However, in other embodiments, different cooling fluids can be used. [Explanation of Symbols]

[0146] 100 Vacuum Pump System 101 Equipment 102 First Vacuum Pump 104 Second Vacuum Pump 106 Purge gas supply source 108, 112, 144 Fluid flow direction 110 Fluid lines 114 First State 116 First fluid inlet 118 First Pump Room 120 First fluid outlet 122 First or upper wall 124 Second or lower wall 126 One or more additional walls or side walls 128 First pumping means 130 Heat exchanger 132 Conduit 134 Conduit entrance 136 Conduit outlet 138, 140, 142, 156 Purge gas flow direction 146 Second State 148 Second fluid inlet 150 Second pump room 152 Second fluid outlet 154 nozzles 200 First side wall 202 One or more flow channels 204 Cover 206 Direction of cover movement 208 Heater 210 void 212 Heater movement direction 300 processes s302-s314 Process Steps 400 Vacuum Pump 402 stater 404 Stator Wall 406 Heat transfer device 408 Fasteners 500 Thermal Conductors 502 Conduit 504 Straight parallel section 506 Curved transition section 508 Entrance 510 Exit 512 First Aspect 514 Second Aspect 700 Heat transfer device 702 Thermal Conductors 704 Conduit 708 Heater 710 void 712 Entrance 714 First end 716 Exit 718 Second end 800 Heat transfer device 802 Thermal Conductors 804 Conduit 808 Heater 810 void 812 Further conduits 814 First layer 816 Second Layer 818 The third layer 820 Entrance 822 First end 824 Exit 826 Second end 900 Heat transfer device 902, 904, 906 layers

Claims

1. A stator having one or more stator walls that define the pump chamber, A heat transfer device coupled to one or more stator walls, A vacuum pump equipped with, The heat transfer device is A heat conductor and, A conduit that penetrates the heat conductor, through which purge gas passes during use, thereby heating the purge gas, A vacuum pump equipped with the following features.

2. The vacuum pump according to claim 1, wherein the heat transfer device is attached to the outer surface of the one or more stator walls.

3. The vacuum pump according to claim 1 or 2, wherein the conduit includes a pipe embedded in the heat conductor.

4. The vacuum pump according to claim 3, wherein the pipe is a stainless steel pipe.

5. The vacuum pump according to any one of claims 1 to 4, wherein the heat conductor is a plate of a heat conductive material.

6. The vacuum pump according to any one of claims 1 to 5, wherein the heat conductor comprises aluminum.

7. The vacuum pump according to any one of claims 1 to 6, wherein the heat transfer device further comprises one or more heaters embedded inside.

8. The heat transfer device comprises a plurality of heaters arranged at intervals from one another. The vacuum pump according to claim 7, wherein the conduit is a complex network of conduits passing through one or more spaces between the heaters.

9. The vacuum pump according to any one of claims 1 to 8, wherein the conduit is a complex network of conduits.

10. The heat transfer device is A further conduit that penetrates the heat conductor and through which a cooling fluid passes during use, thereby cooling the heat conductor, A vacuum pump according to any one of claims 1 to 9, further comprising:

11. The heat transfer device is A further conduit, which penetrates the heat conductor, receives a cooling fluid and thereby cools the heat conductor, and is arranged as a first layer within the heat conductor, Multiple heaters are arranged as a second layer within the heat conductor, Equipped with, The conduit is arranged as a third layer within the heat conductor, The vacuum pump according to any one of claims 1 to 10, wherein the third layer is disposed between the first layer and the second layer.

12. The aforementioned conduit is An inlet on the first side of the heat transfer device or adjacent to the first side, An outlet on the second side of the heat transfer device or adjacent to the second side, The vacuum pump according to any one of claims 1 to 11, wherein the second side is opposite to the first side.

13. The stator is provided with a high vacuum end and a low vacuum end. The aforementioned conduit is An inlet adjacent to either the high vacuum end or the low vacuum end, The outlet at the high vacuum end or the other of the low vacuum end, or an outlet adjacent to the other, A vacuum pump according to any one of claims 1 to 12, comprising:

14. A vacuum pump according to any one of claims 1 to 13, A purge gas supply source configured to supply the purge gas to the conduit, A system equipped with these features.

15. It is a method, A step of preparing a vacuum pump according to any one of claims 1 to 13, A step of pumping a fluid using the vacuum pump, wherein the fluid is pumped through the pump chamber of the vacuum pump, The steps include: causing the purge gas to flow through the conduit of the heat transfer device; Includes, A method wherein, as the purge gas flows through the conduit, heat is transferred from the stator to the purge gas via the heat conductor, thereby heating the purge gas.

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