GB2549335A

GB2549335A - A sealing arrangement

Info

Publication number: GB2549335A
Application number: GB1606663.1A
Authority: GB
Inventors: Scott Edward; Kerr Peter; Tyldesley-Worster Richard
Original assignee: Micromass UK Ltd
Current assignee: Micromass UK Ltd
Priority date: 2016-04-15
Filing date: 2016-04-15
Publication date: 2017-10-18

Abstract

A sealing arrangement comprising a sealing gasket (Fig.1, 2) arranged between first and second housing members 3, 4, the gasket having opposing first and second surfaces (Fig.2, 5, 6). A first inner seal 17 and a first outer seal 18 is provided on the first surface of the sealing gasket, for defining a first plenum 30 between the first inner seal, first outer seal and first housing member in use. A second inner seal 19 and a second outer seal 20 is provided on the second surface of the sealing gasket, for defining a second plenum 31 similar to the first. The first and second plenums are configured for fluid communication with at least one pumping arrangement 40, in use, for pumping the first and second plenums to a sub-atmospheric first pressure. A transfer channel 32 may be provided between the two plenums for fluid communication. This arrangement is suitable for use in an ultra-high vacuum (UHV) system, e.g. a turbo molecular pump.

Description

Title: A SEALING ARRANGEMENT Description of Invention

The present invention relates to a sealing arrangement, particularly to a sealing arrangement comprising a sealing gasket for arrangement between first and second housing members. The invention also relates to a system comprising the sealing arrangement, and to a sealing gasket. A known vacuum flange comprises a flange plate provided on a housing member. Two adjacent housing members having vacuum flanges can be connected together, to connect a vacuum chamber of one or each housing member to another, or to connect a vacuum chamber to a pump. Known vacuum flanges are genderless.

To ensure a good seal between the two flanges, it is known to provide a sealing arrangement therebetween. In a known “ISO” flange sealing arrangement, a centring ring and an elastomeric O-ring are provided between the two flanges. The flanges are clamped together, thereby compressing the O-ring and creating a seal. The clamping force may be provided by an external clamping mechanism and/or by the provision of bolts passing through the respective flange plates.

An ISO flange, incorporating an elastomeric O-ring, is able to prevent (or reduce to a tolerable level) leakage across the seal in high vacuum (HV) systems.

The extent of leakage across an O-ring is related, at least in part, to the pressure imbalance across the seal, between the vacuum of the system on one side and the external atmospheric pressure on the other. The greater the pressure imbalance, the greater then leak might be.

There is often a need for systems capable of operating with an ultra-high vacuum (UHV). Unacceptable levels of leakage are often experienced when adopting ISO flanges in UHV systems. Accordingly, particularly in UHV applications, it is known instead to adopt a ConFlat (CF) sealing arrangement. Each flange plate of a CF sealing arrangement comprises a ridge, effectively providing a ‘knife-edge’, and a copper gasket is arranged between the flange plates. As the flange plates are urged together (e.g. by an external clamping force), each of the knives cuts into the softer material of the gasket, providing a substantially leak tight, metal-to-metal seal therebetween. Accordingly, CF arrangements are suitable for UHV applications.

However, CF gaskets are consumable items, which cannot be reused once the seal is broken.

An improved sealing arrangement is needed.

It has previously been proposed, in WO2014/016551, to provide a ‘two-stage’ sealing arrangement, in which inner and outer sealing O-rings are provided, to provide an intermediate plenum between the two O-rings. The plenum is pumped to a sub-atmospheric intermediate pressure. Accordingly, the pressure imbalance across each of the respective O-rings is lower. Specifically, the pressure imbalance across the outer ring is equal to the difference between the atmospheric pressure and the intermediate pressure. The pressure imbalance across the inner ring is equal to the pressure imbalance between the intermediate pressure and the system (ultimate) pressure. Accordingly, the leak rate of each of the O-ring seals is lower than that of a single seal of the known ISO flange sealing arrangement. A technical difficulty with the arrangement disclosed in WO’551 is how the sub-atmospheric pressure is provided in the plenum between the inner and outer seals. As shown in figure 4 of WO’551, the preferred embodiment is to fluidly connect the intermediate plenum to the system pressure via an internal channel provided in the housing member. Figure 3 of WO’551 discloses an alternative arrangement whereby the plenum is connected to an external pumping arrangement via a channel formed in the housing member.

The present invention seeks to provide an alternative sealing arrangement.

Accordingly, the present invention provides a sealing arrangement comprising: a sealing gasket for arrangement between first and second housing members, the gasket having opposing first and second surfaces; a first inner seal and a first outer seal provided on the first surface of the sealing gasket, for defining a first plenum between the first inner seal, first outer seal and first housing member in use; and a second inner seal and a second outer seal provided on the second surface of the sealing gasket, for defining a second plenum between the second inner seal, second outer seal and second housing member in use, wherein the first and second plenums are configured for fluid communication with at least one pumping arrangement, in use, for pumping the first and second plenums to a sub-atmospheric first pressure.

Preferably, the sealing arrangement further comprises a transfer channel extending through the sealing gasket from the first side to the second side, such that the first and second plenums are fluidly connected in use.

Preferably, the sealing arrangement further comprises a vacuum supply port, for fluid communication between said pumping arrangement and at least one of the first and second plenums in use.

Preferably, the vacuum supply port is provided on a side face of the sealing gasket, between the first and second surfaces, for fluid communication with said pumping arrangement in use.

Preferably, the sealing arrangement further comprises a vacuum supply channel fluidly connected between the vacuum supply port and the transfer channel.

Preferably, the first and second surfaces are substantially planar and parallel to one another.

Preferably, the inner and outer seals are received in annular grooves provided on the first and second surfaces.

Preferably, the inner and outer seals are O-rings.

In another embodiment, there is provided a system comprising: a first housing member; a second housing member; and a sealing arrangement, comprising: a sealing gasket arranged between said first and second housing members, the gasket having opposing first and second surfaces; a first inner seal and a first outer seal provided on the first surface of the sealing gasket, defining a first plenum between the first inner seal, first outer seal and first housing member; and a second inner seal and a second outer seal provided on the second surface of the sealing gasket, defining a second plenum between the second inner seal, second outer seal and second housing member.

Preferably, the system further comprises at least one pumping arrangement in fluid communication with said first and second plenums and configured to pump the first and second plenums to a sub-atmospheric first pressure.

Preferably, the system further comprises: a transfer channel extending through the sealing gasket from the first side to the second side, such that the first and second plenums are fluidly connected; and at least one vacuum supply channel provided in at least one of the first and second housing members, for fluid communication between a pumping arrangement, in use, and at least one of the first and second plenums.

Preferably, the vacuum supply channel is provided with a vacuum supply port, for connection to the pumping arrangement.

Preferably, at least one of the first and second housing members comprises a vacuum chamber, held under a sub-atmospheric second pressure, wherein the vacuum chamber and the first and second plenums are fluidly separated by the respective first and second inner seals.

Preferably, the second pressure is lower than the first pressure.

Preferably, wherein the second pressure is a high vacuum (HV) or ultra-high vacuum (UHV).

Preferably, the first pressure is substantially mid-way between the second pressure and atmospheric pressure.

Preferably, the other of the first and second housings comprises a turbo molecular pump.

In another embodiment, there is provided a sealing gasket for arrangement between first and second housing members of a sealing arrangement, the gasket having opposing first and second surfaces; the first surface configured to receive a first inner seal and a first outer seal on the first surface, for defining a first plenum between the first inner seal, first outer seal and first housing member in use; and the second surface configured to receive a second inner seal and a second outer seal, for defining a second plenum between the second inner seal, second outer seal and second housing member in use, wherein the first and second plenums are configured for fluid communication with at least one pumping arrangement, in use, for pumping the first and second plenums to a sub-atmospheric pressure.

Embodiments of the present invention will now be described, by way of nonlimiting example only, with reference to the figures in which:

Figure 1 shows a side view of sealing gasket of/for a sealing arrangement according to a first embodiment of the present invention;

Figure 2 shows a cross-sectional view of the sealing gasket of figure 1;

Figure 3 shows a side view of sealing gasket of/for a sealing arrangement according to a second embodiment of the present invention;

Figure 4 shows a cross-sectional view of the sealing gasket of figure 3;

Figure 5 schematically illustrates a cross-sectional view of a sealing arrangement according to a first embodiment of the present invention;

Figure 6 schematically illustrates a cross-sectional view of a sealing arrangement according to a second embodiment of the present invention;

Figure 7 shows a sealing gasket according to a first embodiment of the present invention connected to a vacuum chamber;

Figure 8 shows the vacuum chamber of figure 7 with a turbo molecular pump attached thereto; and

Figure 9 shows a cross-sectional view of the arrangement of figure 8.

Figure 5 schematically illustrates a sealing arrangement 1 according to a first embodiment of the present invention. The sealing arrangement 1 comprises a sealing gasket 2 for arrangement between a first 3 and second 4 housing member. The gasket 2 is shown in isolation in Figures 1 and 2.

It should be noted that figures 2 and 5 illustrate a cross-sectional view of the gasket 2. For the purposes of clarity, the cross-sectional view only illustrates a ‘slice’ of the gasket 2. By virtue of the preferred toroidal shape of the gasket 2, the cross-section plane dissects the gasket 2 in two locations (180 degrees apart).

For the sake of clarity, some reference numbers are shown in the figures on one part of the cross-section, and other reference numbers are shown on the other part of the cross-section. The cross-section of the gasket 2 may or may not be identical at each dissected location.

The gasket 2 comprises first 5 and second 6 opposing axial surfaces, which are substantially planar and parallel to one another. The first surface 5 of the sealing gasket 2 comprises a first inner annular groove 7 and a first outer annular groove 8. Similarly, the second surface 6 of the sealing gasket 2 comprises a second inner annular groove 9 and a second outer annular groove 10. Preferably, the outer annular grooves 8, 10, are substantially concentric with the inner annular grooves 7, 9. A first inner seal 17 is seated within the first inner groove 7. A first outer seal 18 is seating within the first outer groove 8. A second inner seal 19 is seated within the second inner groove 9. A second outer seal 20 is seated within the second outer groove 10. The grooves 7-10 are illustrated in the figures as having a semi-circular cross-section. This is not essential. The grooves 7-10 are preferably configured so as to retain the seals 17 - 20 in place in use. The grooves 7-10 may be shallower or deeper than those shown in the figures, and may take other forms.

Preferably, the inner 17, 19 and outer 18, 20 seals comprise elastomeric O-rings.

Only a part of the first 3 and second 4 housing members are illustrated schematically in figure 5. The first housing member 3 provides a sealing face 23, which preferably comprises the sealing face of a known sealing flange. Likewise, the second housing member 4 provides a second sealing face 24, which preferably comprises the sealing face of a known sealing flange.

As illustrated in figure 5, the sealing gasket is arranged between the first 3 and second 4 housing members with the seals 17-20 provided in the grooves 7 - 10. When the first 3 and second 4 housing members are urged together, the seals 17 -20 are compressed, thereby forming a seal between the sealing interfaces. A first plenum 30 is defined between the first inner seal 17, the first outer seal 18, the part of the sealing face 23 of the first housing member 3 bounded by the first inner seal 17 and the first outer seal 18, and the part of the first surface 5 of the sealing gasket 2 bounded by the first inner seal 17 and the first outer seal 18.

Similarly, a second plenum 31 is defined between the second inner seal 19, the second outer seal 20, the part of the sealing face 24 of the second housing member 4 bounded by the second inner seal 19 and the second outer seal 20, and the part of the second surface 6 of the sealing gasket 2 bounded by the second inner seal 19 and the second outer seal 20.

The first 30 and second 31 plenums are toroidal.

At least one transfer channel 32 is provided in the sealing gasket 2, extending through the sealing gasket 2 from the first side 5 to the second side 6, such that the first 30 and second 31 plenums are fluidly connected by the transfer channel(s) 32 in use.

In figures 1, 2 and 5, a transfer channel 32 is illustrated in both parts of the cross-sectional view. This is not essential. In one embodiment, there is only a single transfer channel 32 between the first 30 and second 31 plenums. In another embodiment, there may be a plurality of transfer channels 32, circumferentially distributed around the plenums 30, 31. The transfer channel 32 may comprise a cylindrical bore, or take other forms. A transfer channel 32 may be substantially arcuate (when viewed in plan), and extend around the sealing gasket 2 by a predetermined angle. With reference to Figure 2, it will be appreciated that if the transfer channel 32 extended around the entire circumference of the sealing gasket 2, at least one connecting rib (not shown) would be necessary to connect the inner and outer parts of the gasket together.

Although the transfer channel 32 is shown as being substantially equidistant between the inner seals 17, 19 and the outer seals 18, 20, this is not essential. All that matters is that the transfer channel 32 is able to fluidly connect the first 30 and second 31 plenums in use.

In the first embodiment shown in figures 1, 2 and 5, the sealing gasket 2 further comprises a vacuum supply port 42, provided on the side face of the sealing gasket 2, between the first 5 and second 6 surfaces. Preferably, the vacuum supply port 42 is provided on a radial outer side face of the sealing gasket 2. In use, a pumping arrangement 40 (shown schematically) is fluidly connected to the vacuum supply port 42 by a conduit 41. The vacuum supply port 42 may be provided with any suitable connector, such as a push-fit or threaded connector.

The sealing gasket 2 of the first embodiment further comprises a vacuum supply channel 33, fluidly connected between the vacuum supply port 42 and the transfer channel 32. The vacuum supply channel 33 preferably connects at substantially the mid-point of the transfer channel 32. However, this is not essential.

As will best be seen from Figure 7, the sealing gasket 2 of the first embodiment illustrated in Figures 1, 2 and 5 only comprises one vacuum supply channel 33 and vacuum supply port 42. However, in other embodiments, more than one vacuum supply channel 33 and/or vacuum supply port 42 may be provided.

In another embodiment, not shown, the vacuum supply channel 33 may be fluidly connected between the vacuum supply port 42 and one of the first 30 and second 31 plenums. The first 30 and second 31 plenums are, in turn, fluidly connected through the transfer channel 32. In a further embodiment, not shown, the vacuum supply channel 33 may be bifurcated along its length so as to connect the vacuum supply port 42 to each of the respective first 30 and second 31 plenums.

In use, the pumping arrangement 40 is configured to pump the first 30 and second 31 plenums to a sub-atmospheric first pressure.

Preferably, at least one of the first 3 and second 4 housing members comprises a vacuum chamber 50, held under a sub-atmospheric second pressure. The vacuum chamber 50, at a second pressure, is separated from the first 30 and second 31 plenums by the respective first and second inner seals 17, 19.

Preferably, the second pressure is lower than the first pressure. Preferably, the second pressure is a high vacuum (HV) or an ultra-high vacuum (UHV). Preferably, the first pressure is substantially midway between the second pressure and atmospheric pressure. The pressure imbalance across the inner seals 17, 19 is equal to the pressure imbalance between the first and second pressures. The pressure imbalance across the outer seals 18, 20 is equal to the pressure imbalance between the first and external (e.g. atmospheric) pressures. Accordingly, the leak rate across the seals is lower than that of a single seal of the known ISO flange sealing arrangement.

Figure 6 schematically illustrates a sealing arrangement 101 according to a second embodiment of the present invention. The sealing gasket 102 of the second embodiment generally corresponds to the sealing gasket 2 of the first embedment. Like references are used to refer to like features.

Unlike the sealing gasket 2 of the first embodiment, the sealing gasket 102 of the second embodiment does not comprise a vacuum supply channel 33 in the sealing gasket 102.

As illustrated in figure 6, the first housing member 103 comprises a vacuum supply channel 133, for fluid communication between a pumping arrangement 40 (shown schematically) and the first plenum 30. The first 30 and second 31 plenums are fluidly connected to one another via the transfer channel 32.

The first housing member 103 is provided with a vacuum supply port 142 for connection to the conduit 41 in an otherwise similar manner to that of the arrangement shown in figures 1,2 and 5.

At the end of the vacuum supply channel 133 is provided a vacuum transfer port 150, which fluidly communicates with the first plenum 30.

Comparing the first and second embodiments, it will be noted that, in the first embodiment, the vacuum supply channel 33 communicates with the transfer channel 32 which, in turn, fluidly connects both the first 30 and second 31 plenums. In the second embodiment, the vacuum supply channel 133 communicates directly with the first plenum 30, which then, in turn, fluidly communicates with the second plenum 31 by the transfer channel 32.

Alternatively, the vacuum supply channel 133 may be provided in the second housing 104. In another embodiment, each of the first 103 and second 104 housing members may be provided with an internal vacuum supply channel 133. In such an embodiment, the transfer channel 32 is not necessary. Instead, the sub-atmospheric pressure may be provided in each of the first 30 and second 31 plenums by way of the designated vacuum supply channel 133 in the respective first 103 and second 104 housing members, either connected to a shared pumping arrangement or a dedicated pumping arrangement for each plenum 30, 31. Nevertheless, a transfer channel 32 may still be provided, to ensure equilibrium of pressure between the first 30 and second 31 plenums.

In both illustrated embodiments, the sealing gasket 2, 102, comprises a collar 49, which has an axial length which is larger than the distance between the first 5 and second 6 faces. Accordingly, the collar 49 projects from each of the first 5 and second 6 surfaces. The collar 49 is substantially cylindrical. The diameter of the outer surface 48 of the collar 49 is preferably equal to or smaller than the diameter of the opening of the housing member (e.g an ISO flange) into which it is located. Conveniently, the collar 49 aids assembly, by self-centring the sealing gasket 2, 102 relative to the first 3, 103, and/or second 4, 104 housing members. It also helps to ensure that the sealing gasket 2, 102 is retained in use.

An advantage of the first embodiment is that the effective seal provided by having an inner and outer seal, with an intermediate plenum therebetween, can effectively be retrofitted to an otherwise conventional ISO flange arrangement, without any modification needed to the flange plates of the housing members being connected. A sealing gasket of the present invention can conveniently be retrofitted to any third party’s housing member (e.g. vacuum chamber, vacuum pump) adopting an ISO flange. The pumping arrangement is connected directly to the sealing gasket. Should the sealing gasket, seals, and/or any of the pumping components fail, the invention conveniently allows for them to be quickly replaced without affecting the ISO flanges. By comparison, with the arrangement of WO’551, parts of the pumping arrangement are necessarily provided by the housing members. Accordingly, should any parts of the pumping arrangement in WO’551 fail, the entire housing member (e.g. pump housing) would likely need to be replaced, and can only be replaced with a similar part having the unique features of the housing member.

The embodiments illustrated and described above include two (inner and outer) seals at each sealing interface. It is envisaged that in some embodiments, there may be provided more than two seals at each sealing interface. For example, there may be provided an inner and outer seal and at least one intermediate seal, defining a plurality of plenums therebetween, each being held at a respective pressure such that the pressure imbalance across each seal is even lower than that of an arrangement comprising inner and outer seals.

Preferably, a sealing arrangement embodying the present invention further provides an electromagnetic interference shield arrangement, preferably extending across the connections between the first and second housing members and the sealing gasket.

The sealing gasket may be comprised of any suitable material, such as plastic or metal.

Figure 7 shows the sealing gasket 2 of a first embodiment of the present invention connected to a vacuum chamber 51. Figures 8 and 9 shows the addition of a turbo molecular pump 52 attached to the sealing gasket 2.

When used in this specification and claims, the terms "comprises" and "comprising" and variations thereof mean that the specified features, steps or integers are included. The terms are not to be interpreted to exclude the presence of other features, steps or components.

The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims

1. A sealing arrangement comprising: a sealing gasket for arrangement between first and second housing members, the gasket having opposing first and second surfaces; a first inner seal and a first outer seal provided on the first surface of the sealing gasket, for defining a first plenum between the first inner seal, first outer seal and first housing member in use; and a second inner seal and a second outer seal provided on the second surface of the sealing gasket, for defining a second plenum between the second inner seal, second outer seal and second housing member in use, wherein the first and second plenums are configured for fluid communication with at least one pumping arrangement, in use, for pumping the first and second plenums to a sub-atmospheric first pressure.

2. A sealing arrangement according to claim 1, comprising a transfer channel extending through the sealing gasket from the first side to the second side, such that the first and second plenums are fluidly connected in use.

3. A sealing arrangement according to any preceding claim, comprising a vacuum supply port, for fluid communication between said pumping arrangement and at least one of the first and second plenums in use.

4. A sealing arrangement according to claim 3, wherein the vacuum supply port is provided on a side face of the sealing gasket, between the first and second surfaces, for fluid communication with said pumping arrangement in use.

5. A sealing arrangement according to any of claim 3 and 4 when dependent on claim 2, comprising a vacuum supply channel fluidly connected between the vacuum supply port and the transfer channel.

6. A sealing arrangement according to any preceding claim, wherein the first and second surfaces are substantially planar and parallel to one another.

7. A sealing arrangement according to any preceding claim, wherein the inner and outer seals are received in annular grooves provided on the first and second surfaces.

8. A sealing arrangement according to any preceding claim, wherein the inner and outer seals are O-rings.

9. A system comprising: a first housing member; a second housing member; and a sealing arrangement, comprising: a sealing gasket arranged between said first and second housing members, the gasket having opposing first and second surfaces; a first inner seal and a first outer seal provided on the first surface of the sealing gasket, defining a first plenum between the first inner seal, first outer seal and first housing member; and a second inner seal and a second outer seal provided on the second surface of the sealing gasket, defining a second plenum between the second inner seal, second outer seal and second housing member.

10. A system according to claim 9, further comprising at least one pumping arrangement in fluid communication with said first and second plenums and configured to pump the first and second plenums to a sub-atmospheric first pressure.

11. A system according to any of claims 9 and 10, wherein the sealing arrangement comprises the sealing arrangement of any of claims 2 to 8.

12. A system according to any of claims 9 and 10, further comprising: a transfer channel extending through the sealing gasket from the first side to the second side, such that the first and second plenums are fluidly connected; and at least one vacuum supply channel provided in at least one of the first and second housing members, for fluid communication between a pumping arrangement, in use, and at least one of the first and second plenums.

13. A system according to claim 12, wherein said vacuum supply channel is provided with a vacuum supply port, for connection to the pumping arrangement.

14. A system according to any of claims 9 to 13, wherein at least one of the first and second housing members comprises a vacuum chamber, held under a sub-atmospheric second pressure, wherein the vacuum chamber and the first and second plenums are fluidly separated by the respective first and second inner seals.

15. A system according to claim 14, wherein the second pressure is lower than the first pressure.

16. A system according to any of claims 14 and 15, wherein the second pressure is a high vacuum (HV) or ultra-high vacuum (UHV).

17. A system according to any of claims 14 to 16, wherein the first pressure is substantially mid-way between the second pressure and atmospheric pressure.

18. A system according to any of claims 14 to 17, wherein the other of the first and second housings comprises a turbo molecular pump.

19. A sealing gasket for arrangement between first and second housing members of a sealing arrangement, the gasket having opposing first and second surfaces; the first surface configured to receive a first inner seal and a first outer seal on the first surface, for defining a first plenum between the first inner seal, first outer seal and first housing member in use; and the second surface configured to receive a second inner seal and a second outer seal, for defining a second plenum between the second inner seal, second outer seal and second housing member in use, wherein the first and second plenums are configured for fluid communication with at least one pumping arrangement, in use, for pumping the first and second plenums to a sub-atmospheric pressure.

20. A sealing arrangement, system or sealing gasket substantially as herein described with reference to the figures.

21. Any novel matter or combination thereof herein described.