Sealing gasket for a vacuum pump, vacuum pump and method

Abstract

A sealing gasket 100 for a vacuum pump comprises a first annular sealing member 110 comprising first and second opposed annular surfaces 112, 114, a second annular sealing member 120 spaced apart from

Description

FIELD OF THE INVENTION The field of the invention relates to vacuum pumps, and more specifically 5 to sealing gaskets for vacuum pumps. BACKGROUND LO CXI Vacuum pumps are typically employed as a component of a vacuum system to evacuate working gases from the system. These pumps can be used 10 to evacuate fabrication equipment used in, for example, the production of semiconductors. Whilst compression from a vacuum to atmosphere may be performed 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 15 atmospheric pressure. Vacuum pumps need to be carefully designed and manufactured in order to ensure the moving parts (i.e., the rotor / s) and the static parts (i.e., the stator) cooperate with each other accurately. Certain components of the vacuum pump are required to be sealed to each other such that a fluid flow can be encouraged 20 through the vacuum pump owing to pressure differences between the pump inlet and the pump outlet. Traditionally, elastomer seals (more specifically T-seals) have been used to seal between the top and bottom stators and end-plates of clamshell roots pumps. An example of a four-piece elastomer T-seal is provided in 25 GB201701268A. Generally, fluorocarbon-based fluoro-elastomer materials such as FKM and FFKM are used for their good temperature stability and chemical resistance to process gases. SUMMARY OF THE INVENTION As vacuum pump applications become more demanding with desires to operating at ever higher temperatures, elastomer seals can become prone to degradation. This can lead to leakage and eventual failure of their function as 5 seals. It is desirable to provide a sealing gasket that mitigates these issues. In a first aspect, there is provided a sealing gasket for a vacuum pump according to claim 1. A problem arises with elastomer seals in respect of their temperature applicability to demanding vacuum pump applications. By way of example, 10 elastomer seals are generally only applicable to maximum operating temperatures of 250°C if they are to be expected to have a moderate operational life. Higher rates of degradation of elastomer seals can typically be expected above temperatures of 270°C. This degradation can be further exacerbated by toxic / corrosive process gases (i.e., for harsher applications 15 such as semiconductor manufacturing, the degradation can occur at much lower temperatures). As a result of this degradation, the sealing properties (i.e., chemical resistance, compression / sealing force, elongation, permeation outgassing, thermal stability) of elastomer seals worsen leading to leakage and failure of the seals entirely. Presently there is no sealing solution for vacuum 20 pumps operating at these higher temperatures. Furthermore, elastomer seals can comprise per- or poly-fluorinated alkl substances (PFAS) that are often referred to as “forever chemicals” owing to their extreme persistence in the environment. The sealing gasket disclosed comprises metal which tends to allow the 25 sealing gasket to be used in harsher or more challenging applications of vacuum pumps. More specifically, the sealing gasket tends to be able to be used with vacuum pumps operating at higher temperatures and / or in more corrosive environments than functionally achievable with elastomer seals. This tends to be achieved without the sealing gasket sealing properties degrading. Furthermore, the sealing gasket disclosed herein does not contain PFAS chemicals or substances, thereby reducing the usage of forever chemicals that would otherwise persist in the environment. In addition, there is a desire to mitigate the build-up of deposits from 5 process gases in vacuum pumps. This deposition can result in the gaps between rotors and stators reducing, eventually to a point where the rotor and stator meet and vacuum pump operation is stopped. In some applications, enabling a vacuum pump to operate at higher temperatures results in conditions less favourable to deposition being created within the vacuum pump. Hence, 10 deposition from process gases in such applications tends to be reduced, improving vacuum pump lifetime and serviceability (i.e., service intervals, service cost). The first continuous surface may comprise a portion of the first annular surface and a portion of the third annular surface. The second continuous 15 surface may comprise another portion of the first annular surface and another portion of the third annular surface. The first and second longitudinal sealing members may each be connected between the first annular surface and the third annular surface to define respective T-shaped joints. 20 The sealing gasket tends to provide an effective T-shaped seal for a vacuum pump. The first continuous surface may comprise a plurality of first curved surface portions, the first curved surface portions being disposed where the first and second longitudinal sealing members respectively connect to the first 25 annular surface and the third annular surface. In additional or alternatively the second continuous surface may comprise a plurality of second curved surface portions, the plurality of second curved surface portions being disposed where the first and second longitudinal sealing members respectively connect to the first annular surface and the third annular surface. 30 The first and / or second curved surface portions tend to provide improved and more uniform sealing than abrupt linear changes in angle. In this regard the curved surface portions tend to provide a continuous transition from the annular surfaces to the longitudinal surfaces. Hence compressive loads when the sealing gasket is clamped between stator components of a vacuum pump are applied / distributed in a more unform manner. 5 A hollow section may be provided in at least one of: a part or the whole of the first annular sealing member; a part or the whole of the second annular sealing member; a part or the whole of the first longitudinal sealing member; and a part or the whole of the second longitudinal sealing member. The hollow section is configured to receive an inert gas, such as Nitrogen. 10 The hollow section / s tend to allow for the provision of a purge gas or other cooling mechanism. This tends to further mitigate degradation of the sealing gasket when subjected to higher vacuum pump operating temperatures, thereby providing seal protection. The purge gas can also be combined with a gas ballast (i.e., supply the purge gas into the pump stages of a vacuum pump 15 to lower the partial pressure of the process gases) to prevent condensation, increase corrosion resistance, and reduce flammable safety risks related to flammable gases. Alternatively, there may be no hollow sections and a protective purge gas or other cooling may be providing around the sealing gasket when deployed (i.e., into grooves of stator components receiving the 20 sealing gasket). At least one of the first longitudinal sealing member and the second longitudinal sealing member may comprise a laterally deviating section. The laterally deviating section tends to accommodate axial tolerances of various vacuum pump components and thermal expansion mismatches. During 25 use, the sealing gasket may expand axially. If the axial expansion cannot be accommodated the sealing gasket could buckle, fracture, or more generally worsen in respect of its sealing characteristics. The laterally deviating section may be a lateral deviation along the length of the longitudinal sealing member / s such as a kink, curved part, radial step, a step outwards or inwards (relative to 30 the longitudinal axis of the sealing gasket), a step outwards and then inwards or vice versa. A deformable material may be disposed where the first and second longitudinal sealing members respectively connect to the first annular surface and / or the third annular surface. The deformable material may, alternatively, be disposed anywhere along the first and / or second continuous surfaces. 5 The deformable material tends to further improve the sealing performance of the sealing gasket. An example of a deformable material is a sealant or glue. The first annular sealing member, second annular sealing member, first longitudinal sealing member, and second longitudinal sealing member, may be 10 together formed as a single piece. The first annular sealing member, second annular sealing member, first longitudinal sealing member, second longitudinal sealing member, may be formed entirely from the first metal. The first metal may be a metal selected from the listed of metals 15 consisting of: Stainless steel; Nickel; Nickel alloy; Cast Iron. The sealing gasket comprises a first continuous sealing member arranged to extend along the first continuous surface, wherein the first continuous sealing member is conformal to the first continuous surface; and a second continuous sealing member arranged to extend along the second 20 continuous surface, wherein the second continuous sealing member is conformal to the second continuous surface; wherein the first continuous sealing member and the second continuous sealing member comprise a second metal. The first continuous sealing member and second continuous sealing 25 member tend to provide improved leak tightness by assisting the even distribution of clamping force across the sealing gasket when the sealing gasket is used to seal between components of a vacuum pump. More generally, the first continuous sealing member and the second continuous sealing member provide an improved sealing interface. The first continuous sealing member and 30 second continuous sealing member may be ‘bent’ to match the first continuous surface and second continuous surface and the substrate of the vacuum pump components to which they abut, in use. The first and second continuous sealing members tend to not have sharp edges that would otherwise present challenging sealing interfaces. The first continuous sealing member and the second continuous sealing 5 member may be formed entirely from the second metal. The second metal may be a metal selected from the listed of metals consisting of: Aluminium; Nickel; Nickel Alloy; Graphite. The first continuous sealing member may comprise one or more first curved portions for cooperating with respective first curved surface portions of 10 the first continuous surface; and / or the second continuous sealing member may comprise one or more second curved portions for cooperating with respective second curved surface portions of the second continuous surface. The one or more first and / or second curved portions tends to ensure the first continuous sealing member and second continuous sealing member are 15 conformal to the first and second continuous surfaces. Furthermore, said curved portions tend to allow for the uniform distribution of clamping forces when the sealing gasket is used between components of a vacuum pump. The first continuous sealing member and the second continuous sealing member may have a rectangular, circular or oval cross-section. The circular or 20 oval cross-sections may be preferred owing to their improved compression characteristics (i.e., compression loads tend to be more uniform). Furthermore, the first and / or second continuous sealing members may have open-section forms i.e., C-section, E-section, V-section or other open section forms. The sealing gasket may comprise a third continuous sealing member 25 arranged to extend along the second annular surface; and a fourth continuous sealing member arranged to extend along the fourth annular surface; wherein the third continuous sealing member and fourth continuous sealing member comprise a third metal. The third and fourth continuous sealing members tend to provide 30 improved sealing of the second and fourth annular surface to end-plates / head-plates of a vacuum pump. The third continuous sealing member and fourth continuous sealing member may be formed entirely from the third metal. The third metal may be a metal selected from the listed of metals consisting of: Aluminium; Nickel, Nickel Alloy, Graphite. 5 The third continuous sealing member and the fourth continuous sealing member may have a rectangular, circular or oval cross-section. Furthermore, the third and / or fourth continuous sealing members may have open-section forms i.e., C-section, E-section, V-section or other open section forms. According to a second aspect, there is provided a vacuum pump, 10 comprising: a shell stator comprising a first shell stator component attached to a second shell stator component to define at least one internal pumping chamber; a rotor arranged within the at least one pumping chamber; a first end plate mounted to a first end of the shell stator; and a second end plate mounted to a second end of the shell stator; wherein the vacuum pump further comprises the 15 sealing gasket according to the first aspect, wherein the first continuous surface of the sealing gasket is arranged opposing the first shell stator component, the second continuous surface of the sealing gasket is arranged opposing the second shell stator component, the first annular sealing member is arranged between the first end plate and first end of the shell stator, and the second 20 annular sealing member is arranged between the second end plate and the second end of the shell stator. The vacuum pump may be of the clamshell type design wherein the sealing gasket provides a single piece seal between the stator components and end-plates (also referred to as headplates). 25 The first continuous sealing member is arranged to extend along the first continuous surface between the first continuous surface and the first shell stator component, wherein the first continuous sealing member is conformal to the first continuous surface and the first shell stator component; and the second continuous sealing member is arranged to extend along the second continuous 30 surface between the second continuous surface and the second stator shell component, wherein the second continuous sealing member is conformal to the second continuous surface and the second shell stator component. One or more grooves for receiving the sealing gasket may be provided in at least one of: the first shell stator component; the second shell stator component; the first end plate; and the second end plate. The one or more grooves tend to mitigate any changes in position of the 5 rotor of the vacuum pump relative to the stator owing to the inclusion of the sealing gasket. In this respect, the sealing gasket may be considered to be recessed into the grooves. The one or more grooves may be provided in one or both of the stators and / or head plates, for instance. The one or more grooves may be cut all around the stator and endplate components (i.e., a continuous 10 groove may be formed when the vacuum pump components are attached together). The one or more grooves further tend to enable easier alignment and fitting of the sealing gasket to the vacuum pump. The first shell stator component and / or second shell stator component 15 may comprise respective first grooves; and the first groove of a respective shell stator component extends around an edge of the respective shell stator component via a transitional groove portion. The transitional groove portion may comprise at least one of: a multifaceted transitional groove portion comprising multiple planar surface portions; 20 a chamfered transitional groove portion comprising a single planar surface portion; a continuous curved surface portion; a curved surface portion and a discontinuity; and a curved surface portion and at least one planar surface portion. The transitional groove portion tends to avoid sudden abrupt changes in 25 direction or angle of the one or more grooves. Such sudden abrupt changes in direction or angle can present poor sealing interfaces for the sealing gasket and lead to non-uniform sealing. By providing the transitional groove portion the sealing of the sealing gasket through changes in direction (i.e., at the interfaces of the first grooves) tends to be smooth, continuous and improved. Furthermore, 30 the combination of transitional groove portions and curved portions of the sealing gasket tend to allow the sealing gasket to distort or flow around the edges of the shell stator without losing firm contact therewith. Hence the arrangement tends to be tolerant of all compression scenarios. A single planar surface portion may be disposed between parts of the curved surface portion. Two planar surface portions may be used, with each 5 being disposed between the curved surface portion the first groove / s. In a third aspect, there is provided a method of sealing a vacuum pump, comprising: providing a sealing gasket according to the first aspect; providing a first shell stator component of a shell stator of a vacuum pump; arranging the sealing gasket with the first shell stator component such that the first continuous 10 surface of the sealing gasket opposes the first shell stator component; providing a second shell stator component of the shell stator; arranging the second shell stator component such that the second continuous surface of the sealing gasket opposes the second shell stator component; attaching the second shell stator component to the first shell stator component to define at least one internal 15 pumping chamber; attaching a first end plate to a first end of the shell stator, such that the first annular sealing member of the sealing gasket is arranged between the first end plate and the shell stator; attaching a second end plate to a second end of the shell stator, such that the second annular sealing member of the sealing gasket is arranged between the second end plate and the shell 20 stator. The arranging of the sealing gasket with the first shell stator component may comprises arranging a first continuous sealing member between the first continuous surface and the first shell stator component; and the arranging of the second shell stator component may comprise arranging a second continuous 25 sealing member between the second continuous surface and the second shell stator component. 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 30 described herein share the same technical benefits as the vacuum pump described herein. 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. 5 BRIEF DESCRIPTION OF THE DRAWINGS The present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1A shows an example, in isometric view, of a sealing gasket 10 according to aspects of the present disclosure. Figure 1B shows the example of Figure 1A in side-view. Figure 1C shows an example, in isometric view, of first and second continuous sealing members according to aspects of the present disclosure. Figure 2 shows an example, in plan-view, of a laterally deviating section. 15 Figure 3A shows an example, in cross-sectional view, of a vacuum pump comprising a sealing gasket according to aspects of the present disclosure. Figure 3B shows an example, in isometric-view, of a clamshell stator as used in the example of Figure 3A. Figure 3C shows an example, in isometric view, of a transitional groove 20 portion as used in the clamshell stator of Figure 3B. Figure 3D shows an example, in side-view, of a corner area provided in the example of Figure 3A. Figure 4 shows an example of a method. 25 DETAILED DESCRIPTION Figure 1A shows an example, in isometric view, of a sealing gasket 100 for a vacuum pump according to aspects of the present disclosure. The sealing gasket 100 comprises a first annular sealing member 110. The first annular sealing member 110 comprises a first annular surface 112 and a second annular surface 114 opposite the first annular surface 112. The first annular surface 112 may be considered to face inwards. The second annular 5 surface 114 may be considered to face outwards. The sealing gasket 100 further comprises a second annular sealing member 120 spaced apart from the first annular sealing member 110. The second annular sealing member 120 comprises a third annular surface 122 and a fourth annular surface 124 opposite the third annular surface 122. The third 10 annular surface 122 may be considered to face inwards. The fourth annular surface 124 may be considered to face outwards. LO CXI The second annular sealing member 120 is arranged such that the third annular surface 122 faces the first annular surface 112. The first annular sealing member 110 and the second annular sealing member 120 are arranged on the 15 same concentric axis such that the third annular surface 122 and the first annular surface 112 are parallel each other and in facing relations. The first annular sealing member 110 and the second annular sealing member 120 may be considered as defining a substantially annular shape in a respective geometrical plane. The first annual sealing member 110 and the 20 second annular sealing member 120 do not comprise sharp edges. The first annular sealing member 110 and the second annular sealing member 120 have a square of rectangular shaped cross section, though a circular cross section or oval cross section may alternatively be used. The annular sealing members 110, 120 are formed of metal. The annular sealing 25 members 110, 120 may have a thickness of less than or equal to 20mm, more preferably less than or equal to 10mm, even more preferably less than or equal to 5mm. The sealing gasket 100 further comprises a first longitudinal sealing member 130. The first longitudinal sealing member 130 comprises a first 30 longitudinal surface 132 and a second longitudinal surface 134 opposite the first longitudinal surface 132. The sealing gasket 100 further comprises a second longitudinal sealing member 140 spaced apart from the first longitudinal sealing member 130. The second longitudinal sealing member 140 comprises a third longitudinal surface 142 and a fourth longitudinal surface 144 opposite the third longitudinal surface 5 142. The longitudinal sealing members 130, 140 are elongate and arranged parallel but spaced apart from each other. The first and third longitudinal surfaces 132, 142 may be considered to face upwards. The second and fourth longitudinal surfaces 134, 144 may be considered to face downwards. 10 The longitudinal sealing members 130, 140 are formed from metal. The longitudinal sealing members 130, 140 have a square or rectangular cross section, though a circular or oval cross section may be used. The longitudinal sealing members 130, 140 may have a thickness of less than or equal to 20mm, more preferably less than or equal to 10mm, even more preferably less than or 15 equal to 5mm. The first and second longitudinal sealing members 130, 140 are each connected between the first annular surface 112 of the first annular sealing member 110 and the third annular surface 122 of the second annular sealing member 120. A first continuous surface is defined by the first longitudinal 20 surface 132, third longitudinal surface 142, first annular surface 112 and third annular surface 122. A second continuous surface is defined by the second longitudinal surface 134, fourth longitudinal surface 144, first annular surface 112 and third annular surface 122. The sealing gasket 100 is formed as a single-piece gasket. In this regard, 25 the annular sealing members 110, 120 and the longitudinal sealing members 130, 140 may be considered as being integrally formed. The sealing gasket 100 may be moulded as a single piece, for instance. Alternatively, the annular sealing members 110, 120 may be welded or otherwise connected to the longitudinal sealing members 130, 140. 30 The sealing gasket 100 can be used to seal a vacuum pump of the clamshell type. In-use, the sealing gasket 100 is arranged between first and second shell stator components. More specifically, a first shell stator component is received onto the first continuous surface defined by the surfaces 112, 122, 132, 142. The first shell stator component conforms to the first continuous surface and vice versa. A second shell stator component is received onto the second continuous surface defined by the surfaces 112, 122, 134, 144. The 5 second shell stator component conforms to the second continuous surface and vice versa. A first end plate of the vacuum pump is received against the second annular surface 114. A second end plate of the vacuum pump is received against the fourth annular surface 124. When the shell stator components and end plates are fastened together, the sealing gasket 100 provides a continuous 10 sealing surface between the various components. Figure 1B shows the example sealing gasket 100 of Figure 1A in sideview. LO CXI The second longitudinal sealing member 140 is shown extending from the first annular sealing member 110 and second annular sealing member 120. 15 The second longitudinal sealing member 140 extends from substantially the midpoint of the first annular sealing member 110 and second annular sealing member 120. The second longitudinal sealing member 140 extends substantially orthogonally to the first annular sealing member 110 and second annular sealing member 120 to define respective T-shaped joints. Put 20 differently, the first annular sealing member 110 and second longitudinal sealing member 140 together define a ‘T’ shape. Similarly, the second annular sealing member 120 and the second longitudinal sealing member 140 together define a T shape. This configuration may also be referred to as a ‘T seal’. An equivalent arrangement is provided for the first longitudinal sealing member 130 (not 25 shown in the Figure). The first continuous surface comprises the first longitudinal surface (not shown), third longitudinal surface 142, a portion 112a of first annular surface and a portion 122a of third annular surface. The second continuous surface comprises the second longitudinal surface (not shown), fourth longitudinal 30 surface 144, another portion 112b of the first annular surface and another portion 122b of the third annular surface. First curved surface portions 150 are disposed where the second longitudinal sealing member 140 respectively connects to the portion 112a of the first annular surface and the portion 122a of the third annular surface. Second curved surface portions 160 are disposed where the second 5 longitudinal sealing member 140 respectively connects to the another portion 112b of the first annular surface and the another portion 122b of the third annular surface. A similar arrangement is apparent from Figure 1A for the connection of the first longitudinal sealing member 130. The provision of the curved surface portions 150, 160 provides a smooth transition between the 10 surfaces 112a, 142 and 122a and between the surfaces 112b, 144 and 122b. Furthermore, the curved surface portions 150, 160 tend to avoid sharp or abrupt changes in direction for the first and second continuous surfaces that may otherwise prove challenging to seal. This achieves a more uniform application LO of clamping force when the sealing gasket 100 is used to seal between vacuum CXI 15 pump components. Figure 1C shows an example, in isometric view, of first 170 and second 180 continuous sealing members according to aspects of the present disclosure. The first continuous sealing member 170 is arranged to extend along the 20 first continuous surface defined by surfaces 112, 122, 132 and 142 of Figure 1A. The first continuous sealing member 170 is conformal to the first continuous surface. The second continuous sealing member 180 is arranged to extend along the second continuous surface defined by the surfaces 112, 122, 134, 144 of 25 Figure 1A. The second continuous sealing member 180 is conformal to the second continuous surface. The first continuous sealing member 170 and the second continuous sealing member 180 comprise metal. The sealing members 170, 180 are respective bent metal seals that do not comprise sharp edges. Instead, the 30 sealing members 170, 180 comprise curved edges. The bending angles of the sealing members 170, 180 should enable conformity with the first and second continuous surfaces and the stator components between which the sealing members 170, 180 will be located. The first continuous sealing member 170 comprises first 172 and second 174 looped sections for extending along portions of the first and second annular 5 surfaces 112, 122 of Figure 1A. The first and second looped sections 172, 174 are connected via first 176 and second 178 longitudinal sections. The first and second longitudinal sections are for extending along the first and third longitudinal surfaces 132, 142 of Figure 1A. The second continuous sealing member 180 comprises third 182 and 10 fourth 184 looped sections for extending along portions of the first and second annular surfaces 112, 122 of Figure 1A. The third and fourth looped sections 182, 184 are connected via third 186 and fourth 188 longitudinal sections. The third and fourth longitudinal sections 186, 188 are for extending along the second and third longitudinal surfaces 134, 144 of Figure 1A. 15 The first continuous sealing member 170 comprises one or more first curved portions 179 for cooperating with respective first curved surface portions 150 of the first continuous surface of Figure 1B. The second continuous sealing member 180 comprises one or more second curved portions 189 for cooperating with respective second curved surface portions 160 of the second 20 continuous surface of Figure 1B. The curved portions 179, 189 avoid sudden changes in angle that would be challenging to seal in use. The first and second continuous sealing members 170, 180 comprise have a circular or oval cross-section, although a square or rectangular cross section could be used. The first and second continuous sealing members 170, 25 180 have a thickness less than or equal to 20mm, more preferably less than or equal to10mm, even more preferably less than or equal to 5mm, even more preferably 3mm. In use, the first continuous sealing member 170 will be arranged between the first continuous surface (as described with respect to Figure 1A) and a first 30 stator component. The second continuous sealing member 180 will be arranged between the second continuous surface (as described with respect to Figure 1 A) and a second stator component. Improved leak tightness tends to be achieved for a gasket 100 using the sealing members 170, 180 owing to even distribution of clamping force across the sealing gasket 100 when the sealing gasket is used to seal between components of a vacuum pump. 5 Figure 2 shows an example 200, in plan-view, of a laterally deviating section. The example 200 shows first 230 and second 240 longitudinal sealing members that may be used instead of the longitudinal; sealing members 130, 140 of Figure 1A. 10 The first and second longitudinal sealing members 230, 240 comprise respective laterally deviating sections 230a, 240a. The laterally deviating sections 230a, 240a comprises a curved section that deviates outwardly away from and then inwardly towards a central axis A. The curved sections are continuous and do not comprise abrupt changes in angle. Whilst the example 15 200 show laterally deviating sections 230a, 240a that extend laterally outwards away from axis ‘A’ and then return inwards, other examples include the laterally deviating sections extending outwards and then not returning inwards, or extending inwards and then not returning outwards. The laterally deviating sections 230a, 240a enable the longitudinal sealing members 230, 240 to 20 accommodate axial expansion of vacuum pump components parallel axis ‘A’. Figure 3A shows an example, in cross-sectional view, of part of a vacuum pump 300 comprising a sealing gasket according to aspects of the present disclosure. The vacuum pump 300 comprises a shell stator comprising a first shell 25 stator component 310 attached to a second shell stator component 320 to define at least one internal pumping chamber. A rotor (not visible) is arranged within the at least one pumping chamber. The vacuum pump 300 further comprises a first end plate 330 mounted to a first end of the of the shell stator components 310, 320. 30 The vacuum pump 300 further comprises a second end plate 340 mounted to a second end of the shell stator components 310, 320. The vacuum pump 300 further comprises the sealing gasket 100 of Figure 1A. The first continuous surface of the sealing gasket 100 is arranged opposing the first shell stator component 310. The second continuous surface of the sealing gasket 100 is arranged opposing the second shell stator 5 component 320. The first annular sealing member 110 is arranged between the first end plate 330 and first end of the shell stator components 310, 320. The second annular sealing member 120 is arranged between the second end plate 340 and the second end of the shell stator components 310, 320. The sealing gasket 100 comprises the first continuous sealing member 10 170 arranged to extend along the first continuous surface between the first continuous surface and the first shell stator component 310, wherein the first continuous sealing member is conformal to the first continuous surface and the first shell stator component 310. LO CXI The sealing gasket 100 comprises the second continuous sealing 15 member 180 arranged to extend along the second continuous surface between the second continuous surface and the second stator shell component 320. The second continuous sealing member is conformal to the second continuous surface and the second shell stator component 320. The sealing gasket 100 also comprises a third continuous sealing 20 member 190 arranged between the first annular sealing member 110 and the first end plate 330. A fourth continuous sealing member 195 is arranged between the second annular sealing member 120 and the second end plate 340. The third continuous sealing member 190 and fourth continuous sealing member 195 comprise a third metal. 25 The first and second stator components 310, 320 comprise curved edges that conform to the sealing gasket 100. This avoids abrupt changes in angle that would otherwise prove challenging to seal. This also ensures that clamping forces are evenly distributed across the sealing gasket 100 and stator components 310, 320 providing a continuous seal. 30 As previously mentioned, the vacuum pump shown in the example 300 contains a rotor. The alignment of the rotor relative to the stator components is important for the operation of the vacuum pump. Sealing gasket configurations should not alter the alignment of the rotor and stator components. Hence, grooves may be required for seating the sealing gasket 100. The grooves may be cut or engraved across one or more (i.e., all) surfaces receiving or in abutment with the sealing gasket 100. For example, grooves may be provided 5 in either or both of the stator components 310, 320 and / or in either or both of the end plates 330, 340. When specifying the grooves, the stack-up tolerance may be considered. The stack-up tolerance control may depend on the metal seal used but in general three different dimensional tolerances are considered: groove depth; 10 thickness of the annular and longitudinal sealing members; thickness of the continuous sealing members. The first and second continuous sealing members may be recommended to have a thickness greater than or equal to 3mm to accommodate the total stack-up tolerance. 15 The provision of grooves to accommodate the sealing gasket 100 in the vacuum pump 300 will now be described. Figure 3B shows an example, in isometric-view, of a clamshell stator as used in the example of Figure 3A. More specifically Figure 3B shows the first stator component 310 and the second stator component 320 with the first end 20 plate 330 and sealing gasket 100 removed. The first shell stator component 310 and the second shell stator component 320 comprise respective first grooves 312, 322 that extend around an edge of the respective shell stator components 310, 320 via transitional groove portions 314, 324. 25 Figure 3C shows an example, in isometric view, of the transitional groove portion 324 as used in the clamshell stator component 320 of Figure 3B. The transitional groove portion 324 comprises a continuous curved surface portion extending around the edge of stator component 320. The transitional groove portion 324 may be cut into stator component 320 using two 30 straight cuts (on the respective sides of stator component 310 joining at the edge) and then jointed with a radius corner. The sealing of the sealing gasket 100 in Figure 3A through changes in direction tends to be smooth, continuous and improved as a result of the transitional groove portion 324. The sealing gasket 100 tend to be able to distort or flow around the edges of the shell stator component 320 without losing firm 5 contact therewith. Figure 3D shows an example, in cross sectional view, of a corner area from the example of Figure 3A. More specifically Figure 3D shows first stator component 310 cooperating with a first surface of first continuous sealing member 170 around 10 an edge of the first stator component 310. The edge of first stator component 310 comprises a transitional groove portion providing a smooth continuous curved transition around the edge of the first stator component 310. The first continuous sealing member 170 curves around the edge of first stator component 310 in a conformal manner. 15 Also shown is first annular sealing member 110 and first longitudinal sealing member 130 interfacing in a curved manner and defining the first continuous surface against which first continuous sealing member 170 interfaces cooperatively on a second side. The first continuous sealing member 170 can be considered as being sandwiched between first annular and 20 longitudinal sealing members 110, 130 and first stator component 310. It will be appreciated that the various curved surfaces shown in the Figure are conformal to each other and lack sudden abrupt changes in angle. Clamping forces are uniformly distributed at the various interfaces providing an improved and uniform sealing effect. 25 For completeness, the third continuous sealing member 190 is shown as being sandwiched between first annular sealing member and first end plate 330. The end plate 330 may include a groove for aligning and receiving the third continuous sealing member 190. Figure 4 shows an example of a method 400 of sealing a vacuum pump. 30 A first step 410 comprises providing a sealing gasket according to the first aspect. The sealing gasket may be the sealing gasket 100 of Figure 1A. The sealing gasket may further comprise the continuous sealing members 170, 180 of Figure 1C. A further step 420 comprises providing a first shell stator component of a shell stator of a vacuum pump. The first shell stator component may be the shell 5 stator component 310 of Figure 3A. A further step 430 comprises arranging the sealing gasket with the first shell stator component such that the first continuous surface of the sealing gasket opposes the first shell stator component. A further step 440 comprises providing a second shell stator component 10 of the shell stator. The second shell stator component may be the stator component 320 of Figure 3A. A further step 450 comprises arranging the second shell stator component such that the second continuous surface of the sealing gasket opposes the second shell stator component. 15 A further step 460 comprises attaching the second shell stator component to the first shell stator component to define at least one internal pumping chamber. A further step 470 comprises attaching a first end plate to a first end of the shell stator, such that the first annular sealing member of the sealing gasket 20 is arranged between the first end plate and the shell stator. The first end plate may be the end plate 330 of Figure 3A. A further step 480 comprises attaching a second end plate to a second end of the shell stator, such that the second annular sealing member of the sealing gasket is arranged between the second end plate and the shell stator. 25 The second end plate may be the end plate 340 of Figure 3A. In addition to the specific advantages already described herein, conventionally the separation of T-joint sealing surfaces can occur when the compressions of a gasket and annular seal are unbalanced. This separation can cause a leak and can occur during assembly or by thermal expansion of the 30 seals. Also, conventionally, sharp edges on the ends of grooves (in the stator components, for instance) are difficult to manufacture and can cut annular seals, causing leaks. Also, conventional complex gasket profiles can have irregular distortion, which can cause leakage. The sealing gasket described herein advantageously tends to address these problems. Advantageously, the substantially constant or uniform cross-sectional 5 area of examples of the above-described sealing gasket tend to lead to reduced distortion, making the T-seal / T-joints more tolerant of a wide compression range and reducing leaks. The above-described sealing gasket tends to facilitate the use of T-seals to a higher temperature, for example in excess of 250°C, 260°C, 270°C, 280°C, 10 290°C and 300°C. Furthermore, the above-described sealing gasket tends to provide a PFAS-free solution for ‘normal’ operating temperature ranges (i.e., less than or equal to 250°C). LO CXI Although illustrative examples of the invention have been disclosed in detail herein, with reference to the accompanying drawings, it is understood that 15 the invention is not limited to the precise examples and that various changes and modifications can be effected therein by one skilled in the art without departing from the scope of the invention as defined by the appended claims and their equivalents. Whilst the examples described herein refer to the term “annular” it will be 20 appreciated that “substantially annular” configurations are within scope. Whilst the examples described herein may refer to the use of first and second continuous sealing members, it will be appreciated that the first and second continuous sealing members may be omitted and a sealing gasket be achieved using only the first and second annular sealing members and the first 25 and second longitudinal sealing members. Whilst the examples described herein may show longitudinal sealing members as being entirely linear, other examples within scope include longitudinal sealing members that comprise laterally deviating sections. Whilst the examples described herein may refer to specific dimensions, it 30 will be appreciated that the dimensions may vary dependent upon the specific application of the sealing gasket. Whilst the sealing gasket may be referred to as having a continuous one-piece construction, it may alternatively comprise multiple parts joined together, for instance by welding, adhesive, fusion or interference fit. Whilst the sealing gasket may be referred to as having a substantially 5 uniform cross-section, alternatively the cross-section may vary. Whilst the sealing gasket may be referred to as having substantially planar surfaces, alternatively the surfaces may be non-planar provided that the surfaces are suitably for engaging with adjacent surfaces of the stator components and end-plates. 10 Whilst the examples described herein show annular sealing members and longitudinal sealing members interfacing via curved portions, alternatively the curved portions may in other examples be omitted. Generally, the disclosure herein provides a sealing gasket for a vacuum pump, comprising a first annular sealing member, a second annular sealing 15 member, a first longitudinal sealing member and a second longitudinal sealing member. The first and second longitudinal sealing members are each connected between the first annular sealing member and the second annular sealing member. The first annular sealing member, second annular sealing member, first longitudinal sealing member and second longitudinal sealing 20 member comprise metal. The sealing gasket may comprise a first continuous sealing member arranged to extend along a first continuous surface defined by the first annular sealing member, first longitudinal sealing member, second longitudinal sealing member, and second annular sealing member, wherein the first continuous 25 sealing member is conformal to the first continuous surface. The sealing gasket may comprise a second continuous sealing member arranged to extend along a second continuous surface defined by the first annular sealing member, first longitudinal sealing member, second longitudinal sealing member, and second annular sealing member, wherein the second 30 continuous sealing member is conformal to the second continuous surface. The first continuous sealing member and the second continuous sealing member may comprise metal. Whilst the examples disclosed herein show first, second, third and fourth continuous sealing members formed of or comprising metal, alternative 5 materials may be used such as polymer of fibre-based materials. 10 Reference numeral list 100 sealing gasket LO 110 first annular sealing member CXI 112 first annular surface 1“ 112a portion of first annular surface 15 112b another portion of first annular surface 114 second annular surface 120 second annular sealing member 122 third annular surface 122a portion of third annular surface 20 122b another portion of third annular surface 124 fourth annular surface 130 first longitudinal sealing member 132 first longitudinal surface 134 second longitudinal surface 25 140 second longitudinal sealing member 142 third longitudinal surface 144 fourth longitudinal surface 150 first curved surface portions 160 second curved surface portions 170 first continuous sealing member 5 172 first looped section 174 second looped section 176 first longitudinal section 178 second longitudinal section 179 first curved portions 10 180 second continuous sealing member LO 182 third looped section CXI 184 fourth looped section i— i— 186 third longitudinal section 188 fourth longitudinal section 1 15 189 second curved portions 190 third continuous sealing member 195 fourth continuous sealing member 200 example 230 first longitudinal sealing member 20 230a laterally deviating section 240 second longitudinal sealing member 240a laterally deviating section 300 vacuum pump 310 first shell stator component 25 312 first grooves 314 transitional groove portions 320 second shell stator component 322 first grooves 324 transitional groove portions 330 first end plate 5 340 second end plate 400 method 410 providing step 420 providing step 430 arranging step 10 440 providing step LO 450 arranging step CXI 460 attaching step i— i— 470 attaching step 480 attaching step 1 15 20 25

Claims

1. A sealing gasket for a vacuum pump, comprising:a first annular sealing member comprising a first annular surface and a second annular surface opposite the first annular surface;5 a second annular sealing member spaced apart from the first annularsealing member, wherein the second annular sealing member comprises a third annular surface and a fourth annular surface opposite the third annular surface, wherein the second annular sealing member is arranged such that the third annular surface faces the first annular surface;10 a first longitudinal sealing member comprising a first longitudinal surfaceand a second longitudinal surface opposite the first longitudinal surface;LO CXIa second longitudinal sealing member spaced apart from the first longitudinal sealing member, comprising a third longitudinal surface and a fourth longitudinal surface opposite the third longitudinal surface;15 wherein the first and second longitudinal sealing members are eachconnected between the first annular surface of the first annular sealing member and the third annular surface of the second annular sealing member, such that a first continuous surface is defined by the first longitudinal surface, third longitudinal surface, first annular surface and third annular surface, and such20 that a second continuous surface is defined by the second longitudinal surface, fourth longitudinal surface, first annular surface and third annular surface;wherein the first annular sealing member, second annular sealing member, first longitudinal sealing member and second longitudinal sealing member comprise a first metal; and25 wherein the sealing gasket further comprises a first continuous sealingmember arranged to extend along the first continuous surface, wherein the first continuous sealing member is conformal to the first continuous surface; anda second continuous sealing member arranged to extend alongthe second continuous surface, wherein the second continuous sealing member30 is conformal to the second continuous surface;wherein the first continuous sealing member and the second continuous sealing member comprise a second metal.

2. The sealing gasket of any preceding claim, wherein the first and second 5 longitudinal sealing members are each connected between the first annularsurface and the third annular surface to define respective T-shaped joints.

3. The sealing gasket of any preceding claim, wherein:the first continuous surface comprises a plurality of first curved surface10 portions, the first curved surface portions being disposed where the first and second longitudinal sealing members respectively connect to the first annular surface and the third annular surface; and / orthe second continuous surface comprises a plurality of second curved surface portions, the plurality of second curved surface portions being disposed 15 where the first and second longitudinal sealing members respectively connect to the first annular surface and the third annular surface.

4. The sealing gasket of any preceding claim, wherein a hollow section is provided in at least one of:20 a part or the whole of the first annular sealing member;a part or the whole of the second annular sealing member;a part or the whole of the first longitudinal sealing member; anda part or the whole of the second longitudinal sealing member.25 5. The sealing gasket of any preceding claim, wherein at least one of thefirst longitudinal sealing member and the second longitudinal sealing member comprise a laterally deviating section.

6. The sealing gasket of any preceding claim, further comprising a deformable material disposed where the first and second longitudinal sealing members respectively connect to the first annular surface and / or the third annular surface.

57. The sealing gasket of any preceding claim, when dependent on claim 3, wherein:the first continuous sealing member comprises one or more first curved portions for cooperating with respective first curved surface portions of the first 10 continuous surface; and / orthe second continuous sealing member comprises one or more second curved portions for cooperating with respective second curved surface portions of the second continuous surface.15 8. The sealing gasket of any preceding claim, further comprising:a third continuous sealing member arranged to extend along the second annular surface; anda fourth continuous sealing member arranged to extend along the fourth annular surface;20 wherein the third continuous sealing member and fourth continuoussealing member comprise a third metal.

9. A vacuum pump, comprising:a shell stator comprising a first shell stator component attached to a25 second shell stator component to define at least one internal pumping chamber;a rotor arranged within the at least one pumping chamber;a first end plate mounted to a first end of the of the shell stator; anda second end plate mounted to a second end of the shell stator;wherein the vacuum pump further comprises the sealing gasket according to any preceding claim, wherein the first continuous surface of the sealing gasket is arranged opposing the first shell stator component, the second continuous surface of the sealing gasket is arranged opposing the second shell5 stator component, the first annular sealing member is arranged between the first end plate and first end of the shell stator, and the second annular sealing member is arranged between the second end plate and the second end of the shell stator.10 10. The vacuum pump of claim 9, wherein:the first continuous sealing member is arranged to extend along the first continuous surface between the first continuous surface and the first shell stator component, wherein the first continuous sealing member is conformal to the first continuous surface and the first shell stator component; and15 the second continuous sealing member is arranged to extend along thesecond continuous surface between the second continuous surface and the second stator shell component, wherein the second continuous sealing member is conformal to the second continuous surface and the second shell stator component.2011. The vacuum pump of any one of claims 9-10, where one or more grooves for receiving the sealing gasket are provided in at least one of:the first shell stator component;the second shell stator component;25 the first end plate; andthe second end plate.

12. The vacuum pump of claim 11, whereinthe first shell stator component and / or second shell stator component comprise respective first grooves; andthe first groove of a respective shell stator component extends around an edge of the respective shell stator component via a transitional groove portion.

513. The vacuum pump of claim 12, wherein the transitional groove portion comprises at least one of:a multi-faceted transitional groove portion comprising multiple planar surface portions;10 a chamfered transitional groove portion comprising a single planarsurface portion;a continuous curved surface portion;CM a curved surface portion and a discontinuity; and1 a curved surface portion and at least one planar surface portion,i—15"i” 14. A method of sealing a vacuum pump, comprising:providing a sealing gasket according to any one of claims 1-8;providing a first shell stator component of a shell stator of a vacuum pump;20 arranging the sealing gasket with the first shell stator component suchthat the first continuous surface of the sealing gasket opposes the first shell stator component;providing a second shell stator component of the shell stator;arranging the second shell stator component such that the second25 continuous surface of the sealing gasket opposes the second shell stator component;attaching the second shell stator component to the first shell stator component to define at least one internal pumping chamber;LO CXIattaching a first end plate to a first end of the shell stator, such that the first annular sealing member of the sealing gasket is arranged between the first end plate and the shell stator;attaching a second end plate to a second end of the shell stator, such5 that the second annular sealing member of the sealing gasket is arranged between the second end plate and the shell stator.

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