GB2622602A

GB2622602A - Sealing gasket

Info

Publication number: GB2622602A
Application number: GB2213812.7A
Authority: GB
Inventors: Ernest Kinnaird Holbrook Alan; Hockley Robin; Kolenyak Jan
Original assignee: Edwards Ltd
Current assignee: Edwards Ltd
Priority date: 2022-09-22
Filing date: 2022-09-22
Publication date: 2024-03-27
Also published as: GB2622662A; GB2622664A; GB202308570D0; GB202213812D0; GB202308566D0; GB202308577D0; GB2622663A

Abstract

A sealing gasket 20 for a vacuum pump is provided. The sealing gasket 20 comprises: a first annular sealing member 22 comprising: a first annular surface 30; a second annular surface 32 opposite the first annular surface 30; a first radially inner surface 34; and a first radially outer surface 36 opposite to the first radially inner surface 34, the first radially inner surface 34 and the first radially outer surface 36 being disposed between the first annular surface 30 and the second annular surface 32; a second annular sealing member 24 comprising: a third annular surface 40 ; a fourth annular surface 42 opposite the third annular surface 40; a second radially inner surface 44; and a second radially outer surface 46 opposite to the second radially inner surface 44, the second radially inner surface 44 and the second radially outer surface 46 being disposed between the third annular surface 40 and the fourth annular surface 42; a first longitudinal sealing member 26 connected between the first radially outer surface 36 and the second radially outer surface 46; and a second longitudinal sealing member 28 connected between the first radially outer surface 36 and the second radially outer surface 46.

Description

SEALING GASKET

FIELD OF THE INVENTION

The field of the invention relates to a sealing gasket for a vacuum pump, 5 a vacuum pump and method.

BACKGROUND

Rotating machines, such as compressors or pumps, need to be carefully designed and manufactured in order for the moving parts to cooperate with each other accurately. Providing effective seals to seal the machine tends to be problematic, particularly when fluid flow is encouraged by a pressure difference between the machine and ambient environment, such as in a vacuum pump. It is desired to provide an improved seal for such applications.

SUMMARY OF THE INVENTION

In an aspect, there is provided a sealing gasket for a vacuum pump. The sealing gasket comprises: a first annular sealing member comprising: a first annular surface; a second annular surface opposite the first annular surface; a first radially inner surface; and a first radially outer surface opposite to the first radially inner surface, wherein the first radially inner surface and the first radially outer surface are disposed between the first annular surface and the second annular surface; a second annular sealing member comprising: a third annular surface; a fourth annular surface opposite the third annular surface; a second radially inner surface; and a second radially outer surface opposite to the second radially inner surface, wherein the second radially inner surface and the second radially outer surface are disposed between the third annular surface and the fourth annular surface; a first longitudinal sealing member connected between the first radially outer surface and the second radially outer surface; and a second longitudinal sealing member connected between the first radially outer surface and the second radially outer surface. -2 -

The sealing gasket may further comprise one or more curved surface portions and/or one or more planar surface portions disposed between one or more of the annular sealing members and one or more of the longitudinal sealing members, each of the one or more curved surface portions and/or the one or more planar surface portions being located at an interface between the one or more annular sealing members and the one or more longitudinal sealing members.

The sealing gasket may further comprise one or more curved surface portions and/or one or more planar surface portions disposed between one or more of the radially outer surfaces and one or more of the longitudinal sealing members, and located at interfaces between the one or more radially outer surfaces and the one or more longitudinal sealing members.

The sealing gasket may further comprise, at an interface between a radially outer surface and the longitudinal sealing member connected thereto, a continuous curved surface portion arranged to provide a smooth continuous transition between the radially outer surface and the longitudinal sealing member connected thereto.

The sealing gasket may further comprise, at an interface between a radially outer surface and the longitudinal sealing member connected thereto, a curved surface portion and a discontinuity, the curved surface portion and the discontinuity being disposed between the radially outer surface and the longitudinal sealing member connected thereto.

The sealing gasket may further comprise, at an interface between a radially outer surface and the longitudinal sealing member connected thereto, one or more discrete planar surface portions disposed between the radially outer surface and the longitudinal sealing member connected thereto. In some aspects, there may be only one discrete planar surface portion (e.g. a chamfer) disposed between the radially outer surface and the longitudinal sealing member connected thereto. In some aspects, there may be multiple discrete planar surface portions (i.e. a multi-faceted portion) disposed between the radially outer surface and the longitudinal sealing member connected thereto. -3 -

In a further aspect, there is provided a sealing gasket for a vacuum pump. The sealing gasket comprises: a first annular sealing member; a second annular sealing member; a first longitudinal sealing member connected between the first annular sealing member and the second annular sealing member; a second longitudinal sealing member connected between the first annular sealing member and the annular sealing member; and one or more curved surface portions and/or one or more planar surface portions disposed between one or more of the annular sealing members and one or more of the longitudinal sealing members, and located at one or more interfaces between the one or more annular sealing members and the one or more longitudinal sealing members.

The sealing may comprise, at an interface between an annular sealing member and a longitudinal sealing member connected thereto, a continuous curved surface portion arranged to provide a smooth continuous transition between the annular sealing member and a longitudinal sealing member connected thereto.

In any of the preceding aspects, the sealing gasket may be a one-piece gasket. The sealing gasket may be a moulded gasket. Some or all of the sealing gasket may have square or rectangular cross-section. The sealing gasket may be deformable. The sealing gasket may be made of or comprise an elastomer.

In a further aspect, there is provided a vacuum pump, comprising: shell stators defining at least one pumping chamber; end pieces mountable at either end of the shell stator; and the sealing gasket of any preceding aspect.

In a further aspect, there is provided a shell stator for a vacuum pump, The shell stator comprises: a first sealing groove disposed along a joining surface of the shell stator, the joining surface being for receiving a further shell stator thereby to define at least one pumping chamber; and a second sealing groove disposed in an end surface of the shell stator, the end surface being for receiving an end piece; wherein the first and second sealing grooves are connected at an edge of the shell stator via a transitional groove portion that -4 -comprises one or more curved surface portions and/or one or more planar surface portions.

The first and second sealing grooves may be connected at the edge of the shell stator via a multi-faceted transitional groove portion comprising multiple planar surface portions.

The first and second sealing grooves may be connected at the edge of the shell stator via a chamfered transitional groove portion comprising only a single planar surface portion.

The first and second sealing grooves may be connected at the edge of the shell stator via a continuous transitional groove portion comprising only a continuous curved surface portion.

The first and second sealing grooves may be connected at the edge of the shell stator via a transitional groove portion comprising a curved surface portion and a discontinuity. The discontinuity may be disposed between the curved surface portion and either the first or second sealing groove.

The first and second sealing grooves may be connected at the edge of the shell stator via a transitional groove portion comprising a curved surface portion and a planar surface portion. The planar surface portion may be disposed between the curved surface portion and either the first or second sealing groove.

The first and second sealing grooves may be connected at the edge of the shell stator via a transitional groove portion comprising a curved surface portion and two planar surface portions. Each planar surface portion may be disposed between the curved surface portion and a respective one of the first and second sealing grooves.

In a further aspect, there is provided a shell stator for a vacuum pump. The shell stator comprises: a joining surface of the shell stator, the joining surface being for receiving a further shell stator thereby to define at least one pumping chamber; a sealing groove disposed in an end surface of the shell stator, the end surface being for receiving an end piece; and a transitional -5 -groove portion disposed between the joining surface and the sealing groove at an edge of the shell stator, the transitional groove portion comprising one or more curved surface portions and/or one or more planar surface portions.

The transitional groove portion may be a multi-faceted transitional groove portion comprising multiple planar surface portions.

The transitional groove portion may be a chamfered transitional groove portion comprising only a single planar surface portion.

The transitional groove portion may be a continuous transitional groove portion comprising only a continuous curved surface portion.

to The transitional groove portion may comprise a curved surface portion and a discontinuity. The discontinuity may be disposed between the curved surface portion and either the sealing groove or the joining surface.

The transitional groove portion may comprise a curved surface portion and a planar surface portion. The planar surface portion may be disposed between the curved surface portion and either the sealing groove or the joining surface.

The transitional groove portion may comprise a curved surface portion and two planar surface portions. Each planar surface portion may be disposed between the curved surface portion and a respective one of the sealing groove and the joining surface.

In a further aspect, there is provided a vacuum pump comprising: shell stators defining at least one pumping chamber; end pieces mountable at either end of the shell stator; and a sealing gasket disposed between the shell stators and the end pieces. One or more of the shell stators is a shell stator according to any of the preceding aspects. For example, both of the shell stators may be in accordance with one of the proceeding aspects, e.g., different aspects. The sealing gasket may be in accordance with any of the preceding aspects.

BRIEF DESCRIPTION OF THE DRAWINGS -6 -

The present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a schematic illustration (not to scale) showing a housing of a vacuum pump, Figure 2 is a schematic illustration (not to scale) of a sealing gasket; Figure 3 is a further schematic illustration (not to scale) of the sealing gasket; Figure 4 is a process flow chart showing certain steps of a method of incorporating the sealing gasket into the housing; Figure 5 is a schematic illustration (not to scale) showing sealing gasket incorporated into the housing; Figures 6a-c are schematic illustrations (not to scale) showing further detail of the sealing gasket incorporated into the housing in the vicinity of a 1-joint; Figures 7a and 7b are schematic illustrations (not to scale) showing a portion of an alternative shell stator for the housing; Figures 8a and 8b are schematic illustrations (not to scale) showing a portion of an alternative shell stator for the housing; Figures 9a and 9b are schematic illustrations (not to scale) showing a portion of an alternative shell stator for the housing; Figures 10a and 10b are schematic illustrations (not to scale) showing a portion of an alternative shell stator for the housing; Figures 11a and 11b are schematic illustrations (not to scale) showing a portion of an alternative shell stator for the housing; Figures 12a and 12b are schematic illustrations (not to scale) showing a portion of an alternative shell stator for the housing; Figure 13 is a schematic illustration (not to scale) showing an alternative mould cavity for the sealing gasket; and -7 -Figure 14 is a schematic illustration (not to scale) showing an alternative mould cavity for the sealing gasket.

DETAILED DESCRIPTION

Figure 1 is a schematic illustration (not to scale) showing a housing 10 of a vacuum pump, according to one embodiment. The housing 10 comprises a pair of shell stators 12, 14 and a pair of end plates 16, 18. The shell stators 12, 14 define recesses which receive components of the vacuum pump. The shell stators 12, 14 are brought together to retain the components in those recesses.

The end plates 16, 18 are then brought to retain the shell stators 12, 14. This provides for particularly convenient assembly of the vacuum pump.

In other words, the housing 10 of the vacuum pump may be formed from multiple component parts, including shells 12, 14 and end plates 16, 18 which need to be sealed upon assembly. In the arrangement shown in Figure 1, the stator is formed by bringing together the two housing parts or shells 12, 14 which are then retained between the pair of end plates 16, 18.

As will be explained in more detail below, in this embodiment, to adequately seal the shell stators 12, 14 together, one or more (e.g. two) longitudinal seals are located along the joining faces of the shell stators 12, 14.

Also, to ensure adequate sealing between the shell stators 12, 14 and the respective end plates 16, 18, a pair of annular seals is located between the end plates 16,18 and the shell stators 12, 14.

Figure 2 is a schematic illustration (not to scale) of a sealing gasket 20 for sealing the housing 10, according to one embodiment.

The sealing gasket 20 comprises a first annular sealing member 22, a second annular sealing member 24, a first longitudinal sealing member 26, and a second longitudinal sealing member 28.

The first annular sealing member 22 comprises a first annular surface 30, a second annular surface 32 opposite the first annular surface 30, a first radially inner surface 34, and a first radially outer surface 36 opposite to the first radially -8 -inner surface 34. The first radially inner surface 34 and the first radially outer surface 36 are disposed between the first annular surface 30 and the second annular surface 32.

The second annular sealing member 24 comprises a third annular surface 40, a fourth annular surface 42 opposite the third annular surface 40, a second radially inner surface 44, a second radially outer surface 46 opposite to the second radially inner surface 44. The second radially inner surface 44 and the second radially outer surface 46 are disposed between the third annular surface 40 and the fourth annular surface 42.

to The first longitudinal sealing member 26 is connected or attached between the first radially outer surface 36 (of the first annular sealing member 22) and the second radially outer surface 46 (of the second annular sealing member 24).

The second longitudinal sealing member 28 is connected or attached between the first radially outer surface 36 (of the first annular sealing member 22) and the second radially outer surface 46 (of the second annular sealing member 24).

The second longitudinal sealing member 28 is arranged opposite to the first longitudinal sealing member 26. That is to say, the second longitudinal sealing member 28 is connected to the first and second annular sealing members 22, 24 and at an opposite side of the first and second annular sealing members 22, 24 to the side at which the first longitudinal sealing member 26 is connected to the first and second annular sealing members 22, 24.

The first annular seal member 22 is a ring-shaped sealing member. The 25 first annular seal member 22 has a square or rectangular cross-section.

The second annular seal member 24 is a ring-shaped sealing member. The second annular seal member 24 has a square or rectangular cross-section.

The first longitudinal sealing member 26 may be an 0-ring cord. The first longitudinal sealing member 26 has a square or rectangular cross-section. -g -

The second longitudinal sealing member 28 may be an 0-ring cord. The second longitudinal sealing member 28 has a square or rectangular cross-section.

In this embodiment, the sealing gasket 20 is a continuous one-piece sealing gasket.

In this embodiment, the sealing gasket comprises curved surface portions 48a-d at the interfaces between the annular sealing members 22, 24 and the longitudinal sealing members 26, 28. In particular, there are curved surface portions 48a between the first radially outer surface 36 and the first longitudinal sealing member 26 at the interface between the first annular sealing member 22 and the first longitudinal sealing member 26. Also, there are curved surface portions 48b between the first radially outer surface 36 and the second longitudinal sealing member 28 at the interface between the first annular sealing member 22 and the second longitudinal sealing member 28. Also, there are curved surface portions 48c between the second radially outer surface 46 and the first longitudinal sealing member 26 at the interface between the second annular sealing member 24 and the first longitudinal sealing member 26. Also, there are curved surface portions 48d between the second radially outer surface 46 and the second longitudinal sealing member 28 at the interface between the second annular sealing member 24 and the second longitudinal sealing member 28.

In this embodiment, the curved surface portions 48a-d tend to provide the radially outer surfaces 36, 46 of the annular sealing members 22, 24 are continuous with surfaces of the longitudinal sealing members 26, 28. There are smooth, continuous transitions between the radially outer surfaces 36, 46 of the annular sealing members 22, 24 and the longitudinal sealing members 26, 28. The curved surface portions 48a-d smooth the transitions, and moreover provide a continuous transition, between the radially outer surfaces 36, 46 of the annular sealing members 22, 24 and the longitudinal sealing members 26, 28.

-10 -The sealing gasket 20 is made of a deformable or flexible material, such as an elastomer material (e.g. a fluoroelastomers (FKM/FPM) or a perfluoroelastomer (FFKM)) or silicon, such that the sealing gasket 20 is deformable or flexible. Thus, the sealing gasket 20 may be deformed into a desired shape or configuration suitable for use as a seal for the housing 10.

Figure 3 is a schematic illustration (not to scale) showing the sealing gasket 20 that has been deformed into a configuration that may be suitable for sealing the housing 10.

In this configuration, the annular sealing members 22, 24 are square to ring-shaped members with curved corners. The configuration has major faces (which are the first radially inner surface 34 and the first radially outer surface 36 of the first annular sealing member 22, and the second radially inner surface 44 and the second radially outer surface 46 of the second annular sealing member 24) which, in use, abut against major faces of the end plates 16, 18 and the adjacent faces of the shell stators 12, 14. In this example, the annular sealing members 22, 24 have substantially planar, axially outer faces, provided by the first radially inner surface 34 and the second radially inner surface 44 respectively. The annular sealing members 22, 24 have substantially planar, axially inner faces, provided by the first radially outer surface 36 and the second radially outer surface 46 respectively. The longitudinal sealing members 26 are connected between the facing axially inner faces of the annular sealing members 22, 24 (i.e., between the first radially outer surface 36 and the second radially outer surface 46). The annular sealing members 22, 24 have substantially constant thicknesses.

Figure 4 is a process flow chart showing certain steps (s40 -s48) of a method of fitting, installing, or incorporating the sealing gasket 20 into the housing 10.

Figure 5 is a schematic illustration (not to scale) illustrating the incorporation of the sealing gasket 20 into the housing 10, useful in understanding the process of Figure 4.

At step s40, the shell stator 14 is provided, into which components (not shown) of the vacuum pump may be assembled.

At step s42, the sealing gasket 20 is positioned relative to the shell stator 14 such that the first and second longitudinal sealing members 26, 28 are located along the joining face of shell stator 14, typically in seal grooves extending along the joining face of shell stator 14. This may be as depicted in Figure 5.

At step s44, the shell stator 12 is brought into close contact with the longitudinal sealing members 26, 28.

Referring to Figure 5, the shell stator 12 may be moved onto the longitudinal sealing members 26, 28 towards the joining face of shell stator 14, as indicated in Figure 5 by an arrow and the reference numeral 50.

At step s46, the shell stators 12, 14 are clamped together, which compresses the longitudinal sealing members 26, 28.

Thus, after step s46, the annular sealing members 22, 24 tend to extend or protrude axially from the axial ends of the assembled together shell stators 12, 14.

At step s48, the end plates 16, 18 are brought together to compress the annular seals 26, 28 in the axial (i.e. longitudinal) direction.

The annular sealing members 22, 24 may be located in annular seal grooves located in the shell stators 12, 14 and/or the end plates 16, 18.

Referring to Figure 5, the end plate 18 is shown having been moved onto the first annular sealing member 22 at a first end of the assembled together shell stators 12, 14. The end plate 16 may be moved onto the second annular sealing member 24 at a second end (opposite to the first end) of the assembled together shell stators 12, 14, as indicated in Figure 5 by an arrow and the reference numeral 52.

Thus, a method of fitting, installing, or incorporating the sealing gasket 20 into the housing 10 is provided.

-12 -Pumps which have an axial split-line along the stators typically require a seal at each end of the split-line, which is referred to as a T joint. Embodiments provide a sealing gasket, e.g. a single piece elastomer gasket, for providing a 1-joint sealing arrangement for metal, plated or coated clam pumps.

Figures 6a-c are schematic illustrations (not to scale) showing further detail of the sealing gasket 20 incorporated into the housing 10 in the vicinity of a T-joint. Although only one of the 1-joints are depicted in Figures 6a-c, it will be appreciated by those skilled in the art that corresponding or similar features may be present at the location of the other T-joints of the assembly, and in the other shell stator 12.

In particular, Figure 6a shows the sealing gasket 20 incorporated into the housing 10 in the vicinity of the T-joint. Figure 6b shows the shell stator 14 in the vicinity of the T-joint (i.e. the same region as Figure 6a, with the sealing gasket 20 omitted). Figure 6c shown a side view cross section of the portion of the shell stator 14 shown in Figure 6b.

In this embodiment, the shell stator 14 comprises a first seal groove 60 extending along the (upper) joining face of shell stator 14 and a second seal groove 62 extending across an end surface of the shell stator 14.

In this embodiment, the sealing gasket 20 is arranged such that a longitudinal sealing member (in this case, the first longitudinal sealing member 26) is located in the first seal groove 60, and such that an annular sealing member (in this case, the second annular sealing member 24) is located in the second seal groove 62.

As shown in Figures 6b and 6c, in this embodiment, the shell stator 14 comprises curved surface portions 64 at the interfaces between the first seal groove 60 and the second seal groove 62. The curved surface portions 64 of this embodiment may be considered to be transitional groove portions between the first seal groove 60 and the second seal groove 62.

In this embodiment, the curved surface portion 64 tends to provide that the recessed surfaces (e.g. the flat bottoms) of the seal grooves 60, 62 are continuous with each other. There is a smooth, continuous transition between -13 -the first and second seal grooves 60, 62. The curved surface portion 64 provides a smooth continuous transition between the seal grooves 60, 62.

Preferably, the curved surface portions 64 between the seal grooves 60, 62 are complimentary or conform to the respective curved surface portions 48a-d of the sealing gasket 20. This tends to provide improved contact between the sealing gasket and the housing 10, and thus improved sealing.

Advantageously, the rounded or curved edge/surfaces 64 between the gasket groove (i.e. the first seal groove 60) and the annular seal groove (i.e. the second seal groove 62) tends to allows the sealing gasket to distort or flow around the edge without losing firm contact with the sealing surfaces. The arrangement tends to be tolerant of all compression scenarios. Further, the curved surfaces 64, 48a-d tend to eliminate sharp edges and create a single continuous tool path for gasket and annular seal grooves. The sealing gasket 20 tends to become self-aligning regardless of groove depths.

The sealing gasket tends to be easy to install into a housing or a vacuum pump.

Advantageously, the sealing gasket described herein tends to be relatively easy to produce or manufacture compared to conventional sealing assemblies. For example, the sealing gasket tends to be relatively easy to produce via moulding. For example, the sealing gasket can be moulded, in a mould, as a single-piece, as a substantially planar or flat item (as shown in Figure 2 and described in more detail earlier above), and then deformed or manipulated into a desired shape or configuration (e.g., such as that shown in Figure 3 and described in more detail earlier above). Moulding may be performed using a mould tool comprising a first part comprising a recess that is the desired shape of the sealing gasket; a substantially planar second part can be placed over the recess in the first part thereby to define a mould cavity in which the sealing gasket can be formed. Advantageously, the sealing gasket formed in this way tends not to have a parting line (where the two different side of the mould come together). Thus, the potential for separation of the sealing gasket tends to be greatly reduced. Moreover, any mould flash present on the -14 -moulded sealing gasket tends to be restricted to non-critical areas of the sealing gasket, such as extending outwards from the upper surface of the sealing gasket when in the orientation of Figure 2). This tends to improve robustness and stability of the sealing gasket.

Conventionally, the separation of T-joint sealing surfaces can occur when the compressions of the gasket and annular seal are unbalanced. This separation can cause a leak and can occur during assembly or by thermal expansion of the seals. Also, conventionally, sharp edges on the ends of the gasket grooves are difficult to manufacture and can cut the annular seals, causing leaks. Also, conventional complex gasket profiles of current designs can have irregular distortion, which can cause leakage. The above described methods and apparatuses advantageously tends to address these problems.

Advantageously, the substantially constant or uniforms cross-sectional of the above-described sealing gasket tends to lead to reduced distortion, making 15 the T-seal 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 up to 300 °C.

The sealing gasket can be designed slightly shorter than the longitudinal grooves in the shell stators (i.e. the gasket grooves) so that it has a low tension during assembly. This tends to make the sealing gasket self-positioning regardless of the annular groove depths.

The width/thickness of the sealing gasket may be constant in the T-seal region, which tends to lead to reduced distortion. This tends to make the T-seal more tolerant of a wide compression range, which reduces leaks. The width/thickness of the sealing gasket can also be a constant width throughout the whole sealing gasket.

Advantageously, it tends to be possible to mould the sealing gasket on its side in one plane 0.e. in the configuration of figure 2. This tends to achieve a continuous sealing surface from the side walls of the mould tool, without any split-lines, which ensures a high integrity sealing surface. This one-piece seal -15 -shape tends to be reconfigurable to fit the seal housing by using bending only and requiring no twisting of any section of the seal.

It will be appreciated that the cord and the gasket can have different shapes or thicknesses to suit the arrangement of the housing.

In the above embodiments, the sealing gasket is a continuous one-piece sealing gasket. However, in other embodiments, the sealing gasket comprises multiple separate parts that are joined together. The multiple parts may be joined together by any joining means or methods, such as using an adhesive, fusion, or via an interference fit.

In the above embodiments, the sealing gasket has substantially constant cross-section over its parts. However, in other embodiments, the sealing gasket has non-constant cross-section In the above embodiments, the sealing gasket has square or rectangular cross-section. However, in other embodiments, some or all of the sealing gasket has an alternative cross-section other than square or rectangular, such as circular, triangular, oval, etc. In the above embodiments, the sealing gasket may be made of an elastomer. In some embodiments, the sealing gasket may be made of a different, deformable material, for example, a metal.

Although the major faces of the sealing gasket in the above embodiments are substantially planar, it will be appreciated that they may be any shape which is suitable for engaging with the major faces of the end plates and the adjacent faces of the shell stators.

In the above embodiments, the sealing gasket comprises curved surface portions at the interfaces between the annular sealing members and the longitudinal sealing members. These curved surface portions provide continuous transitions between the annular sealing members and the longitudinal sealing members. Similarly, one or both of the shell stators comprise curved surface portions between the longitudinal gasket seal groove and the annular seal grooves. However, in other embodiments, the interfaces -16 -between the annular sealing members and the longitudinal sealing members and/or the interfaces between the stator seal grooves in a stator part are not curved and/or not continuous.

As a first example, Figures 7a and 7b illustrate the shell stators 12, 14 in accordance with an alternative embodiment.

In this embodiment, the shell stator 14 comprises a curved surface portion 70 at the interfaces between the first seal groove 60 and the second seal groove 62. The curved surface portion 70 provides a degree of continuity between the recessed surfaces (e.g. the flat bottoms) of the seal grooves 60, 62.

Also in this embodiment, the shell stator 12 comprises a seal groove 72 at its end face for receiving an annular sealing member. When the shell stators 12, 14 are assembled together, seal grooves 62 and 72 form an annular sealing groove for receiving an annular sealing member 22, 24 of the sealing gasket 20.

The seal groove 72 comprises a curved surface portion 74 at the interface between the seal groove 72 and the joining face of the shell stator 12 (i.e. the face of the shell stator 12 that joins to/faces the shell stator 14). In addition, there is a discontinuity or edge 76 disposed between the curved surface portion 74 and the joining face of the shell stator 12. This discontinuity or edge 76 tends to facilitate or enable omission of a sealing groove in the joining surface of the shell stator 12. Thus, manufacture of the shell stator 12 tends to be facilitated.

The discontinuity or edge 76 tends to provide improved contact between the sealing gasket 20 and the housing 10, and thus improved sealing.

As a second example, Figures 8a and 8b illustrate the shell stators 12, 14 in accordance with a further alternative embodiment.

In this embodiment, the shell stator 14 comprises a multi-faceted portion 80 at the interfaces between the first seal groove 60 and the second seal groove 62. In this embodiment, there are multiple discrete surfaces disposed between the first seal groove 60 and the second seal groove 62. Thus, the first and second seal grooves 60, 62 are distinct from one another, and are discrete rather than continuous. Although in this example, the multi-faceted portion 80 -17 -comprises three distinct surfaces, it will be appreciated by those skilled in the art that the multi-faceted portion 80 may comprise a different number of facets or surfaces, e.g. more than or less than three.

This multi-faceted portion 80 tends to be relatively easy to manufacture, e.g. by machining.

An equivalent multi-faceted portion may be provided in the opposing shell stator 12.

As a third example, Figures 9a and 9b illustrate the shell stators 12, 14 in accordance with a yet further alternative embodiment.

to In this embodiment, the shell stator 14 comprises only a single planar surface portion 90 at an interface between the first seal groove 60 and the second seal groove 62. The single planar surface portion 90 may be considered to be a chamfer or chamfered transition between the first seal groove 60 and the second seal groove 62. The first and second seal grooves 60, 62 are distinct from one another, and are discrete rather than continuous.

This single planar surface portion 90 tends to be relatively easy to manufacture, e.g. by machining.

An equivalent single planar surface portion may be provided in the opposing shell stator 12 As a fourth example, Figures 10a and 10b illustrate the shell stators 12, 14 in accordance with a further alternative embodiment.

In this embodiment, the shell stator 14 comprises a multi-faceted portion 100 at the interfaces between the first seal groove 60 and the second seal groove 62. In this embodiment, there are multiple discrete surfaces disposed between the first seal groove 60 and the second seal groove 62. Thus, the first and second seal grooves 60, 62 are distinct from one another, and are discrete rather than continuous. Although in this example, the multi-faceted portion 100 comprises four distinct surfaces, it will be appreciated by those skilled in the art that the multi-faceted portion 100 may comprise a different number of facets or surfaces, e.g. more than or less than four. By having more facets, the multi- -18 -faceted portion 100 may approximate a curved surface while being easier to manufacture.

As a fifth example, Figures 11a and 11 b illustrate the shell stators 12, 14 in accordance with an alternative embodiment.

In this embodiment, the shell stator 14 comprises a curved surface portion 110 and a planar surface portion 112 at the interfaces between the first seal groove 60 and the second seal groove 62. The curved surface portion 70 provides a degree of continuity between the recessed surfaces (e.g. the flat bottoms) of the seal grooves 60, 62. The planar surface portion 112 is disposed between the curved surface portion 110 and the first seal groove 60.

Also in this embodiment, the shell stator 12 may comprise a seal groove at its end face for receiving an annular sealing member. This seal groove comprises a curved surface portion 114 and a planar surface portion 116 at the interface between the seal groove and the joining face of the shell stator 12. The planar surface portion 116 is disposed between the curved surface portion 114 and the joining surface of the shell stator 12.

Use of one or both of the planar surface portions 112, 116 may provide improved contact between the sealing gasket 20 and the housing 10, and thus improved sealing.

As a sixth example, Figures 12a and 12b illustrate the shell stators 12, 14 in accordance with an alternative embodiment.

In this embodiment, the shell stator 14 comprises a curved surface portion 120 and two planar surface portions 122, 124 at the interfaces between the first seal groove 60 and the second seal groove 62. The curved surface portion 120 provides a degree of continuity between the recessed surfaces (e.g. the flat bottoms) of the seal grooves 60, 62. A first planar surface portion 122 is -19 -disposed between the curved surface portion 120 and the first seal groove 60. A second planar surface portion 124 is disposed between the curved surface portion 120 and the second seal groove 62.

Also in this embodiment, the shell stator 12 may comprise a seal groove at its end face for receiving an annular sealing member. This seal groove comprises a curved surface portion 126 and two planar surface portions 127, 128 at the interface between the seal groove and the joining face of the shell stator 12. Planar surface portion 127 is disposed between the curved surface portion 126 and the joining surface of the shell stator 12. Planar surface portion 128 is disposed between the curved surface portion 126 and the seal groove at the end face of the shell stator 12.

Use one or more of the planar surface portions 122, 124, 127, 128 may provide improved contact between the sealing gasket 20 and the housing 10, and thus improved sealing.

In the above embodiments, the sealing gasket may be manufactured by moulding as a single-piece, as a substantially planar or flat item as shown in Figure 2. However, in other embodiments, the sealing gasket may be manufactured in a different way, for example by moulding as a single-piece, as a substantially planar or flat item as shown in Figure 13 (see single-piece, substantially planar or flat gasket 130) or Figure 14 (see single-piece, substantially planar or flat gasket 140).

Although illustrative embodiments of the invention have been disclosed in detail herein, with reference to the accompanying drawings, it is understood that the invention is not limited to the precise embodiment 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.

-20 -Reference numeral list 10-housing 12, 14-shell stators 16, 18 -end plates 20 -sealing gasket 22 -first annular sealing member 24 -second annular sealing member 26 -first longitudinal sealing member 28 -second longitudinal sealing member 30-first annular surface 32 -second annular surface 34 -first radially inner surface 36 -first radially outer surface 40 -third annular surface 42-fourth annular surface 44 -second radially inner surface 46 -second radially outer surface 48a-d -curved surface portions s40-s48 -method steps 50, 52 -directions -first seal groove 62 -second seal groove 64 -curved surface portion 70 -curved surface portion 72 -seal groove 74 -curved surface portion 76 -discontinuity -multi-faceted portion -planar surface portion 100-multi-faceted portion -curved surface portion 112-planar surface portion 114-curved surface portion 116-planar surface portion 120-curved surface portion 122, 124-planar surface portion 126-curved surface portion 127, 128-planar surface portion 130, 140 -sealing gasket -22 -

Claims

CLAIMS1. A sealing gasket for a vacuum pump, the sealing gasket comprising: a first annular sealing member comprising: a first annular surface; a second annular surface opposite the first annular surface; a first radially inner surface; and a first radially outer surface opposite to the first radially inner surface, wherein the first radially inner surface and the first radially outer to surface are disposed between the first annular surface and the second annular surface; a second annular sealing member comprising: a third annular surface; a fourth annular surface opposite the third annular surface; a second radially inner surface; and a second radially outer surface opposite to the second radially inner surface, wherein the second radially inner surface and the second radially outer surface are disposed between the third annular surface and the fourth annular surface; a first longitudinal sealing member connected between the first radially outer surface and the second radially outer surface; and a second longitudinal sealing member connected between the first radially outer surface and the second radially outer surface.
2. The sealing gasket of claim 1, further comprising one or more curved surface portions and/or one or more planar surface portions disposed between one or more of the annular sealing members and one or more of the longitudinal sealing members, each of the one or more curved surface portions and/or the -23 -one or more planar surface portions being located at an interface between the one or more annular sealing members and the one or more longitudinal sealing members.
3. The sealing gasket of claim 1 or 2, further comprising one or more curved surface portions and/or one or more planar surface portions disposed between one or more of the radially outer surfaces and one or more of the longitudinal sealing members, and located at interfaces between the one or more radially outer surfaces and the one or more longitudinal sealing members.
4. The sealing gasket of any of claims 1 to 3, further comprising, at an interface between a radially outer surface and the longitudinal sealing member connected thereto, a continuous curved surface portion arranged to provide a smooth continuous transition between the radially outer surface and the longitudinal sealing member connected thereto.
5. The sealing gasket of any of claims 1 to 3, further comprising, at an interface between a radially outer surface and the longitudinal sealing member connected thereto, a curved surface portion and a discontinuity, the curved surface portion and the discontinuity being disposed between the radially outer surface and the longitudinal sealing member connected thereto.
6. The sealing gasket of any of claims 1 to 3, further comprising, at an interface between a radially outer surface and the longitudinal sealing member connected thereto, one or more discrete planar surfaces portion disposed between the radially outer surface and the longitudinal sealing member connected thereto.
7. A sealing gasket for a vacuum pump, the sealing gasket comprising: -24 -a first annular sealing member, a second annular sealing member; a first longitudinal sealing member connected between the first annular sealing member and the second annular sealing member; a second longitudinal sealing member connected between the first annular sealing member and the annular sealing member; and one or more curved surface portions and/or one or more planar surface portions disposed between one or more of the annular sealing members and one or more of the longitudinal sealing members, and located at one or more to interfaces between the one or more annular sealing members and the one or more longitudinal sealing members.
8. The sealing gasket of claim 7, comprising, at an interface between an annular sealing member and a longitudinal sealing member connected thereto, a continuous curved surface portion arranged to provide a smooth continuous transition between the annular sealing member and a longitudinal sealing member connected thereto.
9. The sealing gasket of any preceding claim, wherein the sealing gasket is a one-piece gasket.
10. The sealing gasket of any preceding claim, wherein the sealing gasket is a moulded gasket
11. The sealing gasket of any preceding claim, wherein some or all of the sealing gasket has square or rectangular cross-section.
12. The sealing gasket of any preceding claim, wherein the sealing gasket is deformable.
13. The sealing gasket of any preceding claim, wherein the sealing gasket is an elastomer.
14. A vacuum pump, comprising: shell stators defining at least one pumping chamber; end pieces mountable at either end of the shell stator; and the sealing gasket of any preceding claim.
15. A shell stator for a vacuum pump, the shell stator comprising: a first sealing groove disposed along a joining surface of the shell stator, the joining surface being for receiving a further shell stator thereby to define at least one pumping chamber; and a second sealing groove disposed in an end surface of the shell stator, the end surface being for receiving an end piece; wherein the first and second sealing grooves are connected at an edge of the shell stator via a transitional groove portion that comprises one or more curved surface portions and/or one or more planar surface portions.
16. The shell stator of claim 15, wherein the first and second sealing grooves are connected at the edge of the shell stator via a multi-faceted transitional groove portion comprising multiple planar surface portions.
17. The shell stator of claim 15, wherein the first and second sealing grooves are connected at the edge of the shell stator via a chamfered transitional groove portion comprising only a single planar surface portion. -26 -
18. The shell stator of claim 15, wherein the first and second sealing grooves are connected at the edge of the shell stator via a continuous transitional groove portion comprising only a continuous curved surface portion.
19. The shell stator of claim 15, wherein the first and second sealing grooves are connected at the edge of the shell stator via a transitional groove portion comprising a curved surface portion and a discontinuity, the discontinuity being disposed between the curved surface portion and either the first or second sealing groove.
20. The shell stator of claim 15, wherein the first and second sealing grooves are connected at the edge of the shell stator via a transitional groove portion comprising a curved surface portion and a planar surface portion, the planar surface portion being disposed between the curved surface portion and either the first or second sealing groove.
21. The shell stator of claim 15, wherein the first and second sealing grooves are connected at the edge of the shell stator via a transitional groove portion comprising a curved surface portion and two planar surface portions, each planar surface portion being disposed between the curved surface portion and a respective one of the first and second sealing grooves.
22. A shell stator for a vacuum pump, the shell stator comprising: a joining surface of the shell stator, the joining surface being for receiving a further shell stator thereby to define at least one pumping chamber; a sealing groove disposed in an end surface of the shell stator, the end surface being for receiving an end piece; and -27 -a transitional groove portion disposed between the joining surface and the sealing groove at an edge of the shell stator, the transitional groove portion comprising one or more curved surface portions and/or one or more planar surface portions.
23. A vacuum pump, comprising: shell stators defining at least one pumping chamber; end pieces mountable at either end of the shell stator; and a sealing gasket disposed between the shell stators and the end pieces; 10 wherein one or more of the shell stators is a shell stator according to any of claims 15 to 22.
24. The vacuum pump of claim 23, wherein one of the shell stators is in accordance with any of claims 15 to 21, and another of the shell stators is in accordance with claim 22.
25. The vacuum pump of claim 23 or 24, wherein the sealing gasket is in accordance with any of clams 1 to 13