Vacuum pump

Abstract

A vacuum pump, comprising a pump assembly (110), an inlet means (120) and an outlet means (130), and an enclosure (140) for containing the pump assembly (110), the enclosure (140) comprising a first-end part (141), a second-end part (142), and sleeve means (143) arranged between the first-end part (141) and the second-end part (142), wherein the sleeve means (143) comprises a bellows means (143a) for accommodating a thermal expansion of the vacuum pump (100).

Description

[0001] VACUUM PUMP

[0002] FIELD OF THE INVENTION

[0003] The field of the invention relates to vacuum pumps, and more specifically to vacuum pumps comprising ‘seal-free’ pump assemblies.

[0004] BACKGROUND

[0005] Vacuum pumps are typically employed as a component of a vacuum system to evacuate working gases from the system. These pumps can be used to evacuate fabrication equipment used in, for example, the production of semiconductors. Rather than performing compression from a vacuum to atmosphere in a single stage using a single pump, it is common in such applications to provide multi-stage vacuum pumps wherein each stage performs a portion of the compression range required to transition from a vacuum to atmospheric pressure.

[0006] Examples of vacuum pumps include clamshell pumps and screw pumps, both of which are examples of multi-stage pumps. A pump assembly of a clamshell pump typically requires the use of two stator shell halves and two end plates (also known as head plates) on the two sides of the stator halves to enclose the pumping area. Traditionally, longitudinal and annular seals are used between the two stator halves and between the stator halves and the two end plates, respectively, to prevent leakages between the pump assembly and the surrounding environment. A pump assembly of a screw pump comprises two cooperative screw rotors contained within a stator having an inlet and an outlet. The stator interfaces with end plates (also known as head plates) to effectively seal the plurality of pump chambers defined by the stator and screw rotors, from an exterior of the pump assembly. The stator and end plates are typically clamped together (for instance using bolts) with annular seals therebetween.

[0007] Traditionally, elastomer seals (such as o-rings) are used to seal assembly components of a pump assembly together in a fluid-tight manner. However, it can still be difficult to achieve an effective seal. Moreover, there are applications where the use of elastomer seals is not desirable. For example, they may be susceptible to degradation and loss of sealing at certain operational temperatures and under certain corrosive process gas environments. Further, elastomer seals may be susceptible to outgassing and have unacceptable gas permeability under certain conditions.

[0008] Even at low temperature operation, the removal of elastomer seals can yield desirable benefits such as reducing the cost of a vacuum pump, mitigating the need for frequent service intervals, and increasing the overall lifespan of a vacuum pump. However, the removal of elastomer seals to provide a ‘seal-free’ pump can result in increased leakage of process gas from the pump assembly into the external environment within which the vacuum pump is deployed. Moreover, gases such as Oxygen may leak into the pump assembly from the external environment. This is problematic where a pump assembly is exhausting process gases that could react with the Oxygen (i.e., where the process gas comprises Hydrogen).

[0009] An approach considered in W02023 / 001718A1 is to provide a safety device enveloping at least the stator elements of a vacuum-pump to form a containment volume for a pumped gas. Another approach, considered in GB2118904.8, is to provide an enclosure around the entirety of a seal-free pump-assembly of a vacuum-pump, that may be filled with an inert purge gas.

[0010] However, certain aspects of the practical implementation of an enclosure for vacuum pump remain to be addressed. More specifically, during operation of a vacuum pump, a thermal expansion of components can occur. This may be in the pump assembly itself, the head-plates, the top and bottom covers of the vacuum pump, or the inlet and outlet pipes, which may be transporting and / or processing heated process gas.

[0011] Therefore, it is desirable to provide a vacuum pump that mitigates these issues. SUMMARY OF THE INVENTION

[0012] In an aspect, there is provided a vacuum pump, comprising: a pump assembly having an inlet and an outlet, the pump assembly comprising a stator means and a rotor means arranged to define at least one pump chamber between the inlet and the outlet, the rotor means being arranged to rotate, in- use, about a pump-axis, to exhaust a process gas from the inlet to the outlet; an inlet means for connecting the inlet to a first exterior pipework of a vacuum pump assembly, such that the process gas can flow into the pump assembly from the first exterior pipework; an outlet means for connecting the outlet to a second exterior pipework of the vacuum pump assembly, such that the process gas can flow out of the pump assembly to the second exterior pipework; and an enclosure for containing the pump assembly, the enclosure comprising: a first- end part; a second-end part; and sleeve means arranged between the first-end part and the second-end part, wherein the sleeve means comprises a bellows means for accommodating a thermal expansion of the vacuum pump.

[0013] The pump assemblies of vacuum pumps, particularly pump assemblies without elastomer seals (also known as ‘seal-free vacuum pumps’), can be prone to gas leakage into and out of the pump assemblies. This introduces safety concerns in applications where a process gas (the gas being exhausted by the vacuum pump) could react with gases in the external environment leaking into the pump assembly. An example of such a process gas is Hydrogen, which may react with Oxygen leaking into the pump assembly. This leakage of gas and the associated risks introduce a conflict with safety specifications for vacuum pumps.

[0014] The inventors have realised in GB2118904.8, which is hereby incorporated by reference, that a solution to such a problem is to provide a pump assembly of a ‘seal-free’ vacuum pump, within a further hermetically sealed environment i.e., within a further enclosure. The invention described herein tends to provide a practical design for such an enclosure that considers the operational conditions of a vacuum pump, tends to be applicable to any vertical or horizontally positioned vacuum pump, and tends to have minimal impact on the current footprint of vacuum pump designs. More specifically, the enclosure provided by the invention comprises a bellows means that tends to accommodate a thermal expansion of the vacuum pump (i.e., can accommodate a thermal expansion of one of more components of the vacuum pump).

[0015] In some embodiments, the sleeve means comprises a first sleeve extending continuously from the first-end part to the second-end part in a direction parallel to the pump-axis. The provision of a first sleeve that extends from the first-end part to the second-end part of the enclosure tends to allow for easier assembly of the vacuum pump with a minimal number of enclosure components. More specifically, a pump assembly and other components of the vacuum pump can be assembled ‘into’ the enclosure, with the sleeve being slid over, or arranged over, the pump assembly and other components. For instance, the motor, headplate, stator and rotor, can be arranged onto the first- end or second-end part, the first sleeve slid over the components, and then the second-end or first-end part arranged atop the first sleeve.

[0016] In some embodiments, the bellows means comprises a first bellows arranged as at least part of the first sleeve, the first bellows extending in the direction parallel to the pump-axis. The first bellows may be considered integrally formed with the first sleeve and may extend part-way or entirely along the first sleeve in the direction of the pump-axis. For instance, in some embodiments, the first sleeve may be entirely formed of a bellows construction. This allows for greater accommodation of thermal expansion of the vacuum pump or one or more components thereof.

[0017] In some embodiments, the inlet means and the outlet means comprise respective inlet and outlet pipes, the inlet and outlet pipes extending through either of the first end-part, the second end-part, or the first sleeve. The inlet and outlet pipes may extend through the same or different parts of the enclosure, to connect with exterior pipework providing process gases to and from the pump assembly. This allows process gases to reach the pump assembly located and sealed within the enclosure of the vacuum pump. In some embodiments, the inlet pipe and / or the outlet pipe extend through the first sleeve, and wherein the bellows means comprises a second bellows protruding from the first sleeve to surround the inlet and / or outlet pipe. The inlet pipe and / or outlet pipe may be used to transport heated gases to and / or from the pump assembly of the vacuum pump. By providing the second bellows protruding from the first sleeve around the inlet and / or outlet pipe, thermal expansion in the vicinity of the inlet and / or outlet pipe can be accommodated by the enclosure.

[0018] In some embodiments, the second bellows is attached to the first sleeve using a face seal, preferably an elastomer face seal. The face seal tends to provide a mitigation of leakage at the join of the first sleeve to the second bellows in a radial direction with respect to the axis of the seal. An elastomer face seal tends to be preferable because it is low cost, can be re-used during assembly and disassembly, and requires a relatively lower clamping force compared to, for instance, a metal seal.

[0019] In some embodiments, the second bellows is attached to the inlet pipe and / or outlet pipe using a metal seal. A metal seal tends to provide a seal that can withstand high temperatures.

[0020] In some embodiments the second bellows comprises stainless steel. The use of stainless steel for the second bellows tends to have the advantage of having a low thermal conductivity. Hence a thermal break effect tends to be achieved.

[0021] In some embodiments, the inlet pipe extends through an inlet channel provided in the first-end part or the second-end part, wherein an outer diameter of the inlet pipe is less than an inner diameter of the inlet channel, such that a first gap is provided between an outer surface of the inlet pipe and an inner surface of the inlet channel; and / or the outlet pipe extends through an outlet channel provided in the first-end part or the second-end part, wherein an outer diameter of the outlet pipe is less than an inner diameter of the outlet channel, such that a second gap is provided between an outer surface of the outlet pipe and an inner surface of the outlet channel. The inlet pipe and / or outlet pipe extending through the first-end part and / or second-end part could lead to direct contact of the inlet and / or outlet pipe with the first-end part and / or second-end part. This could provide a route for heat transfer i.e. , heat loss from the inlet and / or outlet pipe to the first-end part and / or second-end part. In vacuum pumps, this can lead to process gas condensation in the inlet and / or outlet pipes, which can affect exhaust efficiency of the vacuum pump. The first gap and / or second gap acts as a thermal gap to prevent heating of the first-end part and / or the second-end part. This mitigates the risk of condensation of process gases, but also mitigates the risk of the first- end part and / or second-end part (and the components attached to or contained therein) overheating. Put differently, the enclosure can be thermally isolated from not only the pump assembly itself but also the inlet and outlet pipes.

[0022] In some embodiments, a first purge gas channel is provided in the first end-part and / or the second end-part, the first purge gas channel fluidly connecting the first gap and / or the second gap to a first purge gas supply for supplying a first purge gas. In some embodiments the first purge gas is an inert gas. In some embodiments, the first purge gas is Nitrogen.

[0023] The first gap and / or second gap provide a potential route for gases to leak into and out of the enclosure. Whilst the first gap and / or second gap may form a tortuous path for such gas leakage (i.e., a labyrinth type seal), the gas leakage can be further mitigated by providing a first purge gas into the first gap and / or second gap. This tends to ensure the first gap and / or second gap is filled with a positive pressure relative to gas attempting to leak into the enclosure from the environment exterior to the vacuum pump. By providing the first purge gas an as inert gas, the first purge gas leaking into the enclosure and potentially into the pump assembly, does not raise safety concerns. Put differently, the inert gas will not react with the process gases being exhausted by the pump assembly. The use of Nitrogen as the process gas tends to have the advantage of being a relatively low-cost, widely available, inert gas.

[0024] Some embodiments further comprise at least two piston rings arranged in the first gap and / or the second gap, wherein the first purge gas channel is fluidly connected to the first gap and / or second gap at a location in-between the at least two piston rings.

[0025] The at least two piston rings provide a tortuous path for gases attempting to leak into the enclosure from the exterior of the vacuum pump. Moreover, the at least two piston rings provide a minimal contact surface to the first-end part and / or the second end-part and the inlet pipe and / or outlet pipe. This minimises heat transfer. By providing the first purge gas between the at least two piston rings, the first purge gas is substantially trapped between the piston rings in a gas pocket. This mitigates the first purge gas leaking into the enclosure and / or to the exterior of the vacuum pump, whilst maintaining the tortuous labyrinth type seal between the inlet pipe and / or outlet pipe, and the first-end part and / or second-end part.

[0026] In some embodiments, the sleeve means comprises: a third sleeve extending in a direction parallel the pump-axis, from the first-end part to a first protruding rim of the stator means; and a fourth sleeve extending in a direction parallel the pump-axis, from the second-end part to the first protruding rim of the stator means; wherein the inlet means and the outlet means extend through the first protruding rim for connecting to the first exterior pipework and second exterior pipework of the vacuum pump assembly; wherein the bellows means comprises a third bellows arranged as at least part of the third sleeve and extending in the direction parallel the pump-axis, and / or a fourth bellows arranged as at least part of the fourth sleeve and extending in the direction parallel the pump-axis.

[0027] In certain designs of vacuum pumps and their pump assemblies, the stator itself comprises the inlet means and outlet means. For instance, the inlet means and the outlet means may be embedded in / casted in the stator and protrude therefrom. The sleeve means may, for such stator designs, necessarily be formed of two sleeves: one sleeve extending from one of the end parts of the enclosure to the rim, the other extending from the other end part to the rim. In these embodiments, the inlet and outlet means do not need to pass through the enclosure per se, which can avoid the difficulty of sealing the enclosure around the inlet means and outlet means. Hence the enclosure can be made easier to manufacture as two sleeve pieces, either of which, or both, comprising a bellows for accommodating thermal expansion.

[0028] In some embodiments, the third and fourth sleeves are attached to the respective first-end part and second-end part using face seals, preferably elastomer face seals. The face seal tends to provide a mitigation of leakage at the join of the first sleeve to the second bellows in a radial direction with respect to the axis of the seal. An elastomer face seal tends to be preferable because it is low cost, can be re-used during assembly and disassembly, and requires a relatively lower clamping force compared to, for instance, a metal seal.

[0029] In some embodiments, the first-end part comprises a recess for accommodating at least one of: a motor of the vacuum pump; a cooling means for the motor of the vacuum pump; one or more electrical cables of the vacuum pump; and any other pipework of the vacuum pump. This allows for a more compact vacuum pump design and integration of the components of the vacuum pump with the enclosure.

[0030] In some embodiments, the second-end part is a top cover of the vacuum pump, the top cover comprising a second protruding rim for attaching to the sleeve means. Vacuum pumps traditionally comprise a top cover. By providing a protruding rim on the top cover (i.e., extending the top cover), the enclosure can be integrated into the vacuum pump design without the requirement for a further cover piece. This tends to reduce the number of additional components comprising the enclosure, simplifying manufacture and reducing manufacturing costs.

[0031] Some embodiments further comprise a second purge gas supply channel provided in the first-end part and / or the second-end part, the second purge gas supply channel fluidly connecting an interior volume of the enclosure to a second purge gas supply for supplying a second purge gas. In some embodiments the second purge gas is an inert gas. In some embodiments the second purge gas is Nitrogen.

[0032] By providing a second purge gas into the enclosure itself, the pump assembly is further protected from gases, exterior to the vacuum pump, leaking into the pump assembly. This is because the second purge gas provides a positive pressure within the enclosure relative to the exterior of the vacuum pump. By selecting the second purge gas as an inert gas, the risks associated with the second purge gas leaking into the pump assembly are also mitigated (i.e. , the inert gas tends not to react with the process gases being exhausted by the pump assembly). The selection of Nitrogen has the benefit of being a relatively low-cost inert gas that is also widely available. The second purge gas supply may be mounted to the first-end part and / or second-end part, for instance.

[0033] In even more preferred embodiments, a pressure sensor may be arranged within the interior volume of the enclosure for monitoring a pressure in the enclosure. The pressure sensor may be electrically connected to the second purge gas supply for regulating the supply of the second purge gas.

[0034] In even more preferred embodiments, a one-way valve may be provided in either of the first-end part, second-end part, or sleeve means, for evacuating the interior volume of the enclosure to an exterior of the vacuum pump, during use of the second purge gas supply (i.e., during filling of the interior volume with the second purge gas).

[0035] According to a further aspect of the invention, there is provided a method of manufacturing a vacuum pump, the method comprising: providing a pump assembly having an inlet and an outlet, the pump assembly comprising a stator means and a rotor means arranged to define at least one pump chamber between the inlet and the outlet, the rotor means being arranged to rotate, in- use, about a pump-axis, to exhaust a process gas from the inlet to the outlet; arranging the pump assembly onto a first-end part of an enclosure for containing the pump assembly; arranging a sleeve means of the enclosure onto the first-end part to surround the pump assembly, wherein the sleeve means comprises a bellows means for accommodating a thermal expansion of the vacuum pump; arranging a second-end part of the enclosure onto the sleeve means, thereby enclosing the pump assembly; and arranging an inlet means and an outlet means to respectively fluidly connect the inlet and the outlet to first and second exterior pipework of a vacuum pump assembly, such that the process gas can flow into the pump assembly from the first exterior pipework, and such that the process gas can flow out of the pump assembly to the second exterior pipework.

[0036] According to a further aspect of the invention, there is provided a method of sealing a pipe to an enclosure of a vacuum pump, the method comprising: providing a channel through an enclosure for a vacuum pump, the channel having an inner diameter greater than an outer diameter of a pipe; arranging the pipe within the channel and extending through the enclosure, such that a gap is provided between an inner surface of the channel and an outer surface of the pipe; and providing a purge gas into the gap.

[0037] Some embodiments further comprise providing at least two piston rings arranged in the gap; and providing the purge gas to a location in-between the at least two piston rings.

[0038] It will be appreciated that particular features of different aspects of the invention tend to share the technical effects and benefits of corresponding features of other aspects of the invention. More specifically, the methods described herein share the same technical benefits as the vacuum pump described herein.

[0039] It will also be appreciated that the use of the terms “first” and “second”, and the like, are merely intended to help distinguish between similar features and are not intended to indicate a relative importance of one feature over another, unless otherwise specified.

[0040] BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0042] Figure 1 A shows a first embodiment of a vacuum pump;

[0043] Figure 1 B shows in cross-section, an outlet pipe extending through an enclosure of the vacuum pump of Figure 1 A;

[0044] Figure 1C shows in a further cross-section, an outlet pipe extending through an enclosure of the vacuum pump of Figure 1 A; Figure 2A shows a second embodiment of a vacuum pump;

[0045] Figure 2B shows a partial view of the vacuum pump 200 of Figure 2A;

[0046] Figure 3 shows a third embodiment of a vacuum pump;

[0047] Figure 4 shows an embodiment of a method of manufacturing a vacuum pump; and

[0048] Figure 5 shows an embodiment of a method of sealing a pipe to an enclosure of a vacuum pump.

[0049] DETAILED DESCRIPTION

[0050] Figure 1A illustrates a first embodiment of a vacuum pump 100 in accordance with the invention described herein. The vacuum pump 100 is illustrated in partial cross-section.

[0051] The vacuum pump 100 comprises a pump assembly 110 having an inlet 111 and an outlet 112. The pump assembly 110 itself comprises a stator means 113 (i.e., a stator) and a rotor means (i.e., a rotor) arranged between head plates 114 and 115, to define at least one pump chamber between the inlet 111 and outlet 112. The rotor means (not visible) is arranged to rotate, in-use, about a pump axis ‘A, to exhaust a process gas from the inlet 111 to the outlet 112. The pump assembly 110 represents a ‘seal-free’ pump assembly. Put differently, the pump assembly 110 does not comprise elastomer seals such as o-rings or gaskets between the stator 113 and head plates 114, 115. The pump assembly 110 may therefore be prone to gas-leakage into the pump assembly 110.

[0052] The vacuum pump 100 further comprises an inlet means 120 for connecting the inlet 111 to a first exterior pipework (not visible in the Figure) of a vacuum pump assembly (not visible in the Figure). This allows a process gas to flow into the pump assembly 110 from the first exterior pipework.

[0053] The vacuum pump 100 further comprises an outlet means 130 for connecting the outlet 112 to a second exterior pipework (not visible in the Figure) of a vacuum pump assembly (not visible in the Figure). This allows the process gas to flow out of the pump assembly 110 to the second exterior pipework.

[0054] The vacuum pump 100 also comprises an enclosure 140 into which the pump assembly 110 can be assembled and contained. For instance, the pump assembly 110 may be vertically assembled into the enclosure 140. The enclosure 140 comprises a first-end part 141 , a second-end part 142, and a sleeve means 143 arranged between the first-end part 141 and the second-end part 142. The sleeve means 143 comprises a bellows means 143a for accommodating a thermal expansion of the vacuum pump 100.

[0055] The first-end part 141 constitutes a base where a motor 150 of the vacuum pump 100 is accommodated. Also accommodated in the first-end part 141 are peripherals 160 such as cooling apparatus for the motor 150, electrical cables etc, which are embedded into or traverse through the first-end part 141 to the exterior 170 of the vacuum pump 100. Any interface of the peripherals 160 with the exterior 170 is sealed using piston rings. The pump assembly 110 is connected to the first-end part 141 using bolts 183, for instance, through the head plate 113.

[0056] The second-end part 142 comprises a top cover for the vacuum pump 100. The second-end part 142 is enlarged to comprise a protruding rim 142a for attaching to the sleeve means 143. Hence the top cover for the vacuum pump 100 also acts as a top or cover for the enclosure 140.

[0057] The sleeve means 143 comprises a single sleeve (i.e. , only a first sleeve) extending continuously from the first-end part 141 to the second-end part 142 in a direction parallel to the pump-axis ‘A. The bellows means 143a comprises only a single bellows (i.e., a first bellows) arranged as at least a part of the first sleeve and extending in the direction parallel to the pump-axis ‘A’. The sleeve means 143 is attached to the first-end part 141 and the second-end part 142 using elastomer face seals 181 , 182.

[0058] In this embodiment of a vacuum pump 100, the inlet means 120 and the outlet means 130 comprise respective inlet and outlet pipes 120, 130. Hence, as described herein, the reference numerals 120, 130 will also be used to refer directly to the inlet and outlet pipes 120, 130. The inlet pipe 120 extends through the second-end part 142. The outlet pipe 130 extends through the first- end part 141.

[0059] The inlet pipe 120 is connected through the second-end part 142 using a piston seal 183. The outlet pipe 130 is connected through the first-end part 141 using a sealing arrangement 184 as will be later discussed in greater detail with reference to Figure 1 B and 1 C. The positions of the inlet pipe 120 and the outlet pipe 130 are however, changeable (i.e., either could be routed through the first- end part 141 or the second-end part 142).

[0060] The enclosure 140 hermetically seals the pump assembly 110 from the exterior 170 of the vacuum pump 100. The enclosure 140 defines an interior volume V that is filled with Nitrogen as a purge gas (although any other inert gas can be used). The Nitrogen is provided into the enclosure 140 via a purge gas supply channel 190 provided in the second-end part 142. The purge gas supply (not shown) may be mounted to the second-end part 142. Furthermore, a pressure sensor (not shown) may be located within the enclosure 140 to regulate the flow of Nitrogen through the supply channel 190. A one-direction valve (not shown) may also be equipped on either the first-end part 141 or the second-end part 142 to assist with evacuating the enclosure 140 to the exterior 170 during filling of the enclosure 140 with the Nitrogen purge gas.

[0061] The enclosure 140 itself is provided with pump stand 195 to allow for either a vertically (as illustrated) or horizontally positioned pump deployment. The pump stands 195 can be fixed to the first-end part 141 and second-end part 142. For instance, after assembling in the vertical configuration (as illustrated), the pump 100 may be rotated to the horizontal for deployment.

[0062] It will be understood, that for the vacuum pump 100 shown, during use a process gas will pass through the inlet pipe 120 and into the inlet 111 of the pump assembly 110. The pump assembly 110 will exhaust the process gas to the outlet 112 and out of the vacuum pump 100 through the outlet pipe 130. To avoid gases leaking into the pump assembly 110 from the exterior 170 of the vacuum pump 100, the enclosure 140 is filled with a Nitrogen purge gas. This exerts a positive pressure within the enclosure 140 preventing leakage into the enclosure 140 whilst ensuring that any gas leakage into the pump assembly 110, if at all, comprises only the inert Nitrogen gas. Moreover, the bellows 143a ensures the enclosure 140 can accommodate the thermal expansion of the vacuum pump 100 during use.

[0063] Owing to the isolation of the enclosure 140 from direct contact with the hot pump assembly 110 and outlet pipe 130. The seals 181 , 182 of the enclosure 140 illustrated can be low-temperature seals such as elastomer seals.

[0064] Figure 1 B illustrates in cross-section, the outlet pipe 130 of Figure 1A extending through the enclosure 140 of Figure 1A. More specifically, the Figure shows a view of the sealing mechanism 184 provided between the outlet pipe 130 and the enclosure 140.

[0065] The outlet pipe 130 is shown as extending through an outlet channel 184a provided in the first-end part 141. The outer diameter of the outlet pipe 130 is configured to be less than an inner diameter of the outlet channel 184a. The creates a gap 184b between an outer surface of the outlet pipe 130 and an inner surface of the outlet channel 184a.

[0066] Figure 1C illustrates in a further cross-section, the outlet pipe 130 extending through the enclosure 140 of Figure 1A. The cross-section shown in Figures 1 B and 1C are orthogonal each other.

[0067] The outlet pipe 130 extends through the outlet channel 184a provided in the first-end part 141. The gap 184b is shown between the outer surface of outlet pipe 130 and the inner surface of the outlet channel 184a.

[0068] A purge gas channel 184c is provided in the first end-part 141 fluidly connecting the gap 184b to a purge gas supply (not shown) for supplying a purge gas, which in this embodiment is Nitrogen. Two piston rings 184d are arranged in the gap 184b. The purge gas channel 184c is fluidly connected to the gap 184b at a location in-between the two piston rings 184d.

[0069] As shown in Figure 1 C, the intention of the sealing mechanism 184 is to avoid a direct contact of the outlet pipe 130 with the first-end part 141 . The only contact made is via the piston rings 184d. This provides a thermal gap i.e., tends to mitigate heat transfer between the outlet pipe 130 and the first-end part 141 . This tends to avoid heat from a hot exhaust gas heating the outlet pipe 130 and that heat being transferred to the first-end part 141 , resulting in condensation of the exhaust gas in the outlet pipe 130. This tends to improve exhaust efficiency of the vacuum pump 100 of Figure 1A. As a further advantage, this also tends to mitigate the external temperature of, for instance, the first-end part 141 , exceeding safety regulations (i.e., by preventing heat transfer to the end part 141 , the end part 141 can be kept relatively cool, particularly where the end part 141 may be touchable / come into contact with a user). The presence of the purge gas between the two piston rings 184d mitigates gas leakage into the enclosure 140 of Figure 1 and furthermore tends to prevent process gases leaking out of the enclosure 140. The gap 184b also assists in preventing thermal overload of components that may be located / accommodated within the first-end part 141 .

[0070] Figure 2A illustrates a second embodiment of a vacuum pump 200. The vacuum pump 200 is illustrated in partial cross-section.

[0071] The vacuum pump comprises a pump assembly 210 that is the same as the pump assembly 110 of Figure 1A. The pump assembly 210 may reach approximately 400°C temperatures during operation.

[0072] The vacuum pump 200 comprises an enclosure 240 into which the pump assembly 210 can be assembled and contained. The enclosure 240 comprises a first-end part 241 , a second-end part 242, and a sleeve means 243 arranged between the first-end part 241 and the second-end part 242. The sleeve means 243 comprises a bellows means 243a for accommodating a thermal expansion of the vacuum pump 200.

[0073] The first-end part 241 constitutes a base accommodating a motor 250 and peripherals 260 as already described for Figure 1A. The pump assembly 210 is connected to the first-end part 241 in a similar manner to that described for Figure 1A. The second-end part 242 comprises a top cover for the vacuum pump 200 as described also for Figure 1A. The sleeve means 243 comprises a straight sleeve that is attached to the first-end part 241 via a piston seal 282. Hence the pump 200 can accommodate some movement of the sleeve means 243 relative to the first-end part 241 . The piston seal 282 may be an expansion seal i.e., a relatively large cross-section o-ring (e.g., having a 10-15mm cross section). The sleeve means 243 is attached to the second-end part 242 using a face seal 281 .

[0074] The vacuum pump 200 comprises an inlet means 220 and an outlet means 230. The inlet means 220 and the outlet means 230 comprise respective inlet and outlet pipes 220, 230. Hence, as described herein, the reference numerals 220, 230 will also be used to refer directly to the inlet and outlet pipes 220, 230. The inlet pipe 220 extends through the sleeve means 243. The outlet pipe 230 extends through the sleeve means 243.

[0075] The inlet pipe 220 is attached to the sleeve means 243 using a piston seal 221. The outlet pipe 230 passes through the bellows means 243a. More specifically, the bellows means 243a comprises a bellows protruding from the sleeve means 243 and surrounding the outlet pipe 230. The bellows of the bellows means 243a is attached to the sleeve means 243 using an elastomer or polymer face seal 243b. The bellows of the bellows means 243a is attached to the outlet pipe 230 using a metal seal 243c. The bellows of the bellows means 243a comprises stainless steel i.e., a low thermal conductivity material.

[0076] As illustrated, the sleeve means 243 primarily comprises a straight jacket sleeve which may be formed from metal. This allows the majority of the sleeve means 243 to be formed at lower cost. The sleeve means 243 accommodates thermal expansion during use of the vacuum pump 200 by providing a bellows means 243a that surrounds the outlet pipe 230. The bellows means 243a will be described in greater detail with reference to Figure 2B.

[0077] Pump stands 295 are also provided in accordance with Figure 1A.

[0078] Figure 2B provides a partial view of the vacuum pump 200 of Figure 2A. In the partial view, the pump assembly 210, first-end part 241 , second-end part 242 and the sleeve means 243 are presented in a simplified manner.

[0079] The outlet pipe 230 extends from the pump assembly 210 to an exterior 270 of the vacuum pump 200. The bellows means 243a protrudes from the sleeve means 243 and surrounds the outlet pipe 230. The polymer face seal 243b connects the bellows means 243a to the sleeve means 243. The metal seal 243c connects the bellows means 243a to the outlet pipe 230. Hence, the interior volume V’ is hermetically sealed from the exterior 270 and the bellows means 243a can accommodate thermal expansion of the vacuum pump 200.

[0080] The interior volume V’ is filled with Nitrogen as a purge gas (although any other inert gas can be used) in accordance with Figure 1A.

[0081] Figure 3 illustrates a third embodiment of a vacuum pump 300. The vacuum pump 300 is illustrated in cross-section.

[0082] The vacuum pump 300 comprises a pump assembly 310 that operates in a similar manner to the pump assembly 110 of Figure 1A. More specifically, the pump assembly 310 comprises a stator means 311 .

[0083] The vacuum pump 300 also comprises an enclosure 340 into which the pump assembly 310 can be assembled and contained. The enclosure 340 comprises a first-end part 341 , a second-end part 342, and a sleeve means 343 arranged between the first-end part 341 and the second-end part 342. The sleeve means 343 comprises a bellows means for accommodating a thermal expansion of the vacuum pump 300. The sleeve means 343 and the bellows means will now be described.

[0084] The sleeve means 343 comprises a third sleeve 343’ extending in a direction parallel to a pump-axis ‘B’ of the pump assembly 310. The third sleeve 343’ extends from the first-end part 341 to a first protruding rim 311a (i.e., a flange) of the stator means 311.

[0085] The sleeve means 343 also comprises a fourth sleeve 343” extending in a direction parallel the pump-axis ‘B’, from the second-end part 342 to the first protruding rim 311 a of the stator means 311.

[0086] The vacuum pump 300 comprises an inlet means 320 and an outlet means 330. The inlet means 320 and the outlet means 330 extend through the first protruding rim 311a for connecting to first exterior pipework (not shown) and second exterior pipework (now shown) of a vacuum pump assembly (not shown).

[0087] The bellows means comprises a third bellows 343a’ arranged as at least part of the third sleeve 343’ and extending in the direction parallel the pump- axis ‘B’. The bellows means also comprises a fourth bellows 343a” arranged as at least part of the fourth sleeve 343” and extending in the direction parallel the pump-axis ‘B’.

[0088] The third and fourth sleeves 343’, 343” are shown as being attached to the respective first-end part 341 and second-end part 342 using elastomer face seals 381 , 382. The face seals 381 , 382 can be any low temperature seal. The third and further sleeves 343’, 343” are further attached to the protruding rim 311a using a high temperature metal seal 383, 384. Pump stands 395 are also provided in accordance with Figure 1A.

[0089] Hence, the interior volume V” is hermetically sealed from the exterior 370 and the bellows means can accommodate thermal expansion of the vacuum pump 300.

[0090] The interior volume V” is filled with Nitrogen as a purge gas (although any other inert gas can be used) in accordance with Figure 1A.

[0091] The vacuum pump 300 tends to have the advantage that the inlet means 320 and the outlet means 330 do not need to pass through the sleeve means 343. This avoids difficult sealing and the makes the enclosure 340 relatively simple in geometry. The bellows 343a’ and 343a” accommodates tolerances in the design of the enclosure 340 and the thermal expansion of the vacuum pump 300 when in-use.

[0092] Figure 4 illustrates an embodiment of a method 400 of manufacturing a vacuum pump.

[0093] A first step 410 comprises, providing a pump assembly having an inlet and an outlet, the pump assembly comprising a stator means and a rotor means arranged to define at least one pump chamber between the inlet and the outlet, the rotor means being arranged to rotate, in-use, about a pump-axis, to exhaust a process gas from the inlet to the outlet.

[0094] A further step 420 comprises, arranging the pump assembly onto a first- end part of an enclosure for containing the pump assembly.

[0095] A further step 430 comprises, arranging a sleeve means of the enclosure onto the first-end part to surround the pump assembly, wherein the sleeve means comprises a bellows means for accommodating a thermal expansion of the vacuum pump.

[0096] A further step 440 comprises, arranging a second-end part of the enclosure onto the sleeve means, thereby enclosing the pump assembly.

[0097] A further step 450 comprises, arranging an inlet means and an outlet means to respectively fluidly connect the inlet and the outlet to first and second exterior pipework of a vacuum pump assembly, such that the process gas can flow into the pump assembly from the first exterior pipework, and such that the process gas can flow out of the pump assembly to the second exterior pipework.

[0098] Figure 5 illustrates an embodiment of a method 500 of sealing a pipe to an enclosure of a vacuum pump.

[0099] A first step 510 comprises, providing a channel through an enclosure for a vacuum pump, the channel having an inner diameter greater than an outer diameter of a pipe.

[0100] A further step 520 comprises, arranging the pipe within the channel and extending through the enclosure, such that a gap is provided between an inner surface of the channel and an outer surface of the pipe.

[0101] A further step 530 comprises, providing a purge gas into the gap.

[0102] Whilst specific embodiments described herein indicate a particular number of seals between different components of the vacuum pumps, this is not intended to be limiting. A greater or lesser number of seals may be used.

[0103] Whilst specific embodiments described herein indicate a different configuration between the inlet means and outlet means, or inlet pipe and the outlet pipe, the configurations are in fact interchangeable.

[0104] Whilst specific embodiments described herein may show certain components of a vacuum pump being accommodated in the first-end part or the second-end part, other components may also be accommodated therein i.e., other purge pipework, cooling pipework, power pipework, cabling, controllers, etc. Whilst Nitrogen is referred to herein as a preferred inert gas, any other inert case could be used.

[0105] Reference numeral list

[0106] 100 - vacuum pump

[0107] 110 - pump assembly

[0108] 111 - inlet

[0109] 112 - outlet

[0110] 113 - stator means

[0111] 114, 115 - head plate

[0112] 120 - inlet means / inlet pipe

[0113] 130 - outlet means / outlet pipe

[0114] 140 - enclosure

[0115] 141 - first-end part

[0116] 142 - second-end part

[0117] 142a - second protruding rim

[0118] 143 - sleeve means

[0119] 143a - bellows means

[0120] 150 - motor

[0121] 160 - peripherals

[0122] 170 - exterior of vacuum pump

[0123] 181 , 182 - face seal

[0124] 183 - piston seal

[0125] 184 - sealing arrangement for outlet pipe

[0126] 184a - outlet channel

[0127] 184b - gap 184c - purge gas channel

[0128] 184d - piston rings

[0129] 190 - gas supply channel

[0130] 195 - pump stand

[0131] 200 - vacuum pump

[0132] 210 - pump assembly

[0133] 220 - inlet means / inlet pipe

[0134] 221 - piston seal

[0135] 230 - outlet means / outlet pipe

[0136] 240 - enclosure

[0137] 241 - first-end part

[0138] 242 - second-end part

[0139] 243 - sleeve means

[0140] 243a - bellows means

[0141] 243b - face seal

[0142] 243c - metal seal

[0143] 250 - motor

[0144] 260 - peripherals

[0145] 281 - face seal

[0146] 282 - piston seal

[0147] 295 - pump stand

[0148] V, V’, V” - interior volume of enclosure

[0149] A, B - pump-axis

[0150] 300 - vacuum pump

[0151] 310 - pump assembly

[0152] 311 - stator means 311a - first protruding rim

[0153] 320 - inlet means

[0154] 330 - outlet means

[0155] 340 - enclosure

[0156] 341 - first-end part

[0157] 342 - second-end part

[0158] 343 - sleeve means

[0159] 343’ - third sleeve

[0160] 343” - fourth sleeve

[0161] 343a’ - third bellows

[0162] 343a” - fourth bellows

[0163] 370 - exterior of vacuum pump

[0164] 381 , 382 - face seals

[0165] 383, 384 - metal seals

[0166] 400 - Method

[0167] 410-450 - Steps of method

[0168] 500 - Method

[0169] 510-530 - Steps of method

Claims

CLAIMS1. A vacuum pump, comprising: a pump assembly having an inlet and an outlet, the pump assembly comprising a stator means and a rotor means arranged to define at least one pump chamber between the inlet and the outlet, the rotor means being arranged to rotate, in-use, about a pump-axis, to exhaust a process gas from the inlet to the outlet; an inlet means for connecting the inlet to a first exterior pipework of a vacuum pump assembly, such that the process gas can flow into the pump assembly from the first exterior pipework; an outlet means for connecting the outlet to a second exterior pipework of the vacuum pump assembly, such that the process gas can flow out of the pump assembly to the second exterior pipework; and an enclosure for containing the pump assembly, the enclosure comprising: a first-end part; a second-end part; and sleeve means arranged between the first-end part and the second-end part, wherein the sleeve means comprises a bellows means for accommodating a thermal expansion of the vacuum pump.

2. The vacuum pump of claim 1 , wherein the sleeve means comprises: a first sleeve extending continuously from the first-end part to the second-end part in a direction parallel to the pump-axis.

3. The vacuum pump of claim 2, wherein the bellows means comprises: a first bellows arranged as at least part of the first sleeve, the first bellows extending in the direction parallel to the pump-axis.

4. The vacuum pump of any one of claims 2-3, wherein the inlet means and the outlet means comprise respective inlet and outlet pipes, the inlet and outlet pipes extending through either of the first end-part, the second end-part, or the first sleeve.

5. The vacuum pump of claim 4, wherein the inlet pipe and / or the outlet pipe extend through the first sleeve, wherein the bellows means comprises: a second bellows protruding from the first sleeve to surround the inlet and / or outlet pipe.

6. The vacuum pump of claim 5, wherein: the second bellows is attached to the first sleeve using a face seal, preferably an elastomer face seal; the second bellows is attached to the inlet pipe and / or outlet pipe using a metal seal; and / or the second bellows comprises stainless steel.

7. The vacuum pump of claim 4, wherein: the inlet pipe extends through an inlet channel provided in the first-end part or the second-end part, wherein an outer diameter of the inlet pipe is less than an inner diameter of the inlet channel, such that a first gap is provided between an outer surface of the inlet pipe and an inner surface of the inlet channel; and / or the outlet pipe extends through an outlet channel provided in the first-end part or the second-end part, wherein an outer diameter of the outlet pipe is less than an inner diameter of the outlet channel, such that a second gap is provided between an outer surface of the outlet pipe and an inner surface of the outlet channel.

8. The vacuum pump of claim 7, further comprising: a first purge gas channel provided in the first end-part and / or the second end-part, the first purge gas channel fluidly connecting the first gap and / or the second gap to a first purge gas supply for supplying a first purge gas, the first purge gas preferably being an inert gas and even more preferably being Nitrogen.

9. The vacuum pump of claim 8, further comprising: at least two piston rings arranged in the first gap and / or the second gap, wherein the first purge gas channel is fluidly connected to the first gap and / or second gap at a location in-between the at least two piston rings.

10. The vacuum pump of claim 1 , wherein the sleeve means comprises: a third sleeve extending in a direction parallel the pump-axis, from the first-end part to a first protruding rim of the stator means; and a fourth sleeve extending in a direction parallel the pump-axis, from the second-end part to the first protruding rim of the stator means; wherein the inlet means and the outlet means extend through the first protruding rim for connecting to the first exterior pipework and second exterior pipework of the vacuum pump assembly; wherein the bellows means comprises a third bellows arranged as at least part of the third sleeve and extending in the direction parallel the pumpaxis, and / or a fourth bellows arranged as at least part of the fourth sleeve and extending in the direction parallel the pump-axis.

11. The vacuum pump of claim 10, wherein the third and fourth sleeves are attached to the respective first-end part and second-end part using face seals, preferably elastomer face seals.

12. The vacuum pump of any preceding claim, wherein the first-end part comprises a recess for accommodating at least one of: a motor of the vacuum pump; a cooling means for the motor of the vacuum pump; one or more electrical cables of the vacuum pump; and any other pipework of the vacuum pump.

13. The vacuum pump of any preceding claim, wherein the second-end part is a top cover of the vacuum pump, the top cover comprising a second protruding rim for attaching to the sleeve means.

14. The vacuum pump of any preceding claim, further comprising: a second purge gas supply channel provided in the first-end part and / or the second-end part, the second purge gas supply channel fluidly connecting an interior volume of the enclosure to a second purge gas supply for supplying a second purge gas, the second purge gas preferably being an inert gas and even more preferably being Nitrogen.

15. A method of manufacturing a vacuum pump, the method comprising: providing a pump assembly having an inlet and an outlet, the pump assembly comprising a stator means and a rotor means arranged to define at least one pump chamber between the inlet and the outlet, the rotor means being arranged to rotate, in-use, about a pump-axis, to exhaust a process gas from the inlet to the outlet; arranging the pump assembly onto a first-end part of an enclosure for containing the pump assembly; arranging a sleeve means of the enclosure onto the first-end part to surround the pump assembly, wherein the sleeve means comprises a bellows means for accommodating a thermal expansion of the vacuum pump;arranging a second-end part of the enclosure onto the sleeve means, thereby enclosing the pump assembly; arranging an inlet means and an outlet means to respectively fluidly connect the inlet and the outlet to first and second exterior pipework of a vacuum pump assembly, such that the process gas can flow into the pump assembly from the first exterior pipework, and such that the process gas can flow out of the pump assembly to the second exterior pipework.

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