WO2017077318A1

WO2017077318A1 - Fluid valve

Info

Publication number: WO2017077318A1
Application number: PCT/GB2016/053433
Authority: WO
Inventors: Mark Edward Byers Sealy; Martin Denmark; Murray Schofield
Original assignee: Norgren Limited
Priority date: 2015-11-05
Filing date: 2016-11-04
Publication date: 2017-05-11
Also published as: GB201519519D0

Abstract

A fluid valve (14) having a valve member (40) configured for movement in translation and a bellows (60) that is configured to contract and extend via pressure change in order to move the valve member (40) in translation. The bellows (60) also contribute to guiding of the valve member (40). The valve member (40) is retained in a manner which allows it to rock a few degrees about the main movement axis to ensure it seats properly.

Description

FLUID VALVE

TECHNICAL FIELD

The embodiments described below relate to fluid valves, in particular actuation of fluid valves having a valve member moveable in translation relative to a valve seat, sometimes known as 'poppet valves', most particularly valves for controlling the flow of hot gases such as those exhausted from internal combustion engines.

BACKGROUND ART FR 2689201 discloses a three-way valve having a sliding bearing for a lift valve member moveable in translation by means of a bellows actuator. JP 2012-172519 discloses an exhaust gas recirculation (EGR) valve in which a bellows serves not as an actuator but rather as a pressure balancing mechanism to allow a smaller electric actuator to be used.

DISCLOSURE OF THE INVENTION

According to a first aspect of the invention, there is provided a fluid valve comprising

a valve member configured for movement in translation; and

a bellows that is configured to both move and guide the valve member in translation.

Such a bellows configured to extend, contract and guide the valve member in translation reduces or eliminates the need for rotating or sliding guides for the valve member as known e.g. from the aforementioned FR 2689201. Such guides can be vulnerable to corrosion or sticking due to contaminants, particularly in high-temperature applications where the use of bearings and/or lubricants is limited.

A bellows has the additional advantage of sealing functionality, being weldable into a fabrication so as to provide complete containment. This can reduce or eliminate the need for sliding seals, which may leak exhaust externally and which may require costly machined surfaces.

The valve may comprise a valve seat, the valve member being configured for movement in translation relative thereto so as to restrict flow between the member and the seat. In such circumstances, a bellows that is configured to extend, contract and guide the valve member in translation allows lateral compliance, i.e. compliance transverse to the translation movement of the valve member, which in turn allows the valve member to be presented correctly on the valve seat, thereby ensuring a good seal.

The valve may comprise a first and second valve seats 51,52 spaced in the direction of translation of the valve member, the valve member being configured for movement in translation relative thereto so as to restrict flow between the member and the first or the second valve seat.

The first and/or second valve seat may be annular. The first and/or second valve seat may be conical. The first and/or second valve seat may be planar.

The valve member may be circularly symmetric about the direction of translation. The first and/or second valve seat may be circularly symmetric about the direction of translation. The outer annular periphery of the valve member may taper in the direction of the second valve seat. The second valve seat may taper in the direction away from the valve member. The first valve seat may be planar and extend perpendicular to the direction of translation.

The bellows may be circularly symmetric about - and configured to expand and contract in - the direction of translation. The valve may comprise a compression spring configured to bias the valve member into engagement with a valve seat. The spring may be coaxial with the bellows.

The valve may comprise a first, second and third flow passageways 30,31,32, the first valve seat 51 being located between the first and second passageways 30,31 and the second valve seat 52 being located between the first and third passageways 30,32.

The spring may be located in the same passageway as the bellows. The spring may be located in a different passageway to the bellows. The bellows and spring may be located in the second and first passageways 31, 30 respectively. The bellows and spring may be located in the second and third passageways 31, 32 respectively.

The valve may comprise a shield configured to shield the bellows from fluid flow. The shield may comprise a cylinder. The cylinder may be coaxial with the bellows.

The valve may be configured to move the valve member by increasing a control pressure. The increasing control pressure may be applied to the external surface of the bellows, causing the bellows to contract. The valve may comprise a housing, the increasing control pressure being applied between the external surface of the bellows and the housing. The increasing control pressure may be applied between the external surface of the bellows and the internal surface of the cylinder.

According to a second aspect of the invention, there is provided a fluid valve comprising first and second valve seats spaced along a first axis; a substantially planar valve member located on the first axis between the first and second valve seats; and a bellows configured to move the valve member in translation along the first axis so as to restrict flow between the member and the first or the second valve seat.

The second aspect may be particularized by features of the first aspect.

The fluid valve may comprise first and second flow passageways with the first valve seat therebetween, the first and second passageways having respective longitudinal axes inclined at a first angle greater than 0° and less than 90° to the first axis. The respective longitudinal axes may be inclined at a first angle of around 45° to the first axis.

The first and second flow passageways may each be defined by respective first and second tubular conduits with respective longitudinal axes, the conduits intersecting at a plane P inclined at a second angle greater than 0° and less than 90° to the longitudinal axis of each conduit. The second angle may be the same for each conduit. The second angle may be around 45°:

The respective longitudinal axes of the first and second tubular conduits may extend in the same plane. The first and second tubular conduits may extend to the same side of the first axis. The first and second tubular conduits extend to different sides of the first axis.

The valve element can be attached to the shaft with a connection allowing some rocking motion, or the valve element and shaft assembly can de designed with a small rocking movement to allow the valve element freedom to seat precisely on its valve seats in all operating conditions, even if the valve element is not initially presented perfectly onto the seats.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic view of a vehicle heat recovery system incorporating an exhaust diverter valve; FIG. 2 A is a sectional perspective view of a valve according to a first embodiment of the invention in a first position;

FIG. 2B is a sectional perspective view of a valve according to a first embodiment of the invention in a second position;

FIG. 3 is a detail sectional view of FIG. 2A;

FIG. 4 is a sectional view of a valve according to a second embodiment of the invention;

FIG. 5 is a sectional view of a valve according to a third embodiment of the invention;

FIG. 6 A is a sectional view taken along line D-D in FIG. 6B, which is in turn a perspective view of a valve according to a fourth embodiment of the invention;

FIG. 7 is a perspective view of a valve according to a fifth embodiment of the invention. DETAILED DESCRIPTION OF THE INVENTION

The figures and following description depict specific examples to teach those skilled in the art how to make and use the best mode of embodiments of a valve. For the purpose of teaching inventive principles, some conventional aspects have been simplified or omitted. Those skilled in the art will appreciate variations from these examples that fall within the scope of the present description. Those skilled in the art will also appreciate that the features described below can be combined in various ways to form multiple variations of the valve. As a result, the embodiments described below are not limited to the specific examples described below, but only by the claims.

The valve of the invention is particularly suitable for use as an exhaust diverter valve, in particular an exhaust diverter valve for a heat recovery system for commercial vehicles of the kind known, e.g. from WO2015/007859, incorporated by reference. As shown in the heavily simplified depiction of FIG. 1, such a system has an evaporator 124 which transfers heat from the exhaust flow 102 of an IC engine 101 to a working fluid such as ethanol to drive an expander 122 before returning to evaporator 124, the kinetic power output of the expander being fed back to the IC engine 101 as indicated at 130. The evaporator 124 is in fluid communication with the expander 122 via fluid and/or vapor control modules, pumps, and condensers but for clarity, the fluid communication is represented in a simplified manner by conduits 126a,b. Exhaust diverter valve 14 controls (typically in dependence on a signal 140 from the expander) the amount of exhaust fed through the evaporator before reaching (via exhaust return 102b) the vehicle tailpipe 102, the remainder being directed to the tailpipe via a bypass conduit 102a.

Referring to FIGS. 2 A and 2B, valve 14 comprises a housing 20 having an inlet

30, a first outlet 31 and second outlet 32. In the particular heat recovery application shown in FIG. 1, inlet 30 will be connected to the IC engine 101, first outlet 31 will be connected to the evaporator 124 and second outlet 32 will be connected to the bypass conduit 102a.

In the position shown in FIG. 2A, a circular valve member 40 - specifically a first (lower) annular peripheral region 40' thereof - engages a first annular valve seat 51 so as to seal off flow to the first outlet 31 , thereby allowing flow to the second outlet as indicated by arrows A. As indicated by arrow T in FIG. 2B, valve member 40 moves in linear translation along its axis of circular symmetry so as to disengage the first valve seat 51, thereby allowing flow to the first outlet 31 as indicated by arrows B, and engages a second (upper) annular peripheral region 40" with a second annular valve seat 52 so as to seal off flow to the second outlet 32.

In the particular embodiment shown, the outer annular periphery of the substantially planar valve member is convex in radial cross-section, tapering (i.e. narrowing in diameter) in the direction of the second valve seat 52, which itself is conical, increasing in diameter in the direction of the valve member 40. Consequently, engagement between the second (upper) annular peripheral region 40" with a second annular valve seat 52, as shown in FIG. 2B, is predominantly over a conical area. In contrast, the first valve seat 51 is planar and extends perpendicular to the axis T, with the result that engagement between valve member and the first planar valve seat 4 is substantially a line contact.

As shown in more detail in FIG. 3, valve member 40 is moved in translation by an - advantageously metal - bellows 60 which sits inside a cylinder 70, the upper end 61 of the bellows being sealed to the upper end 71 of the cylinder and the lower end 62 of the bellows being sealed to the lower end 82 of a plunger 80 carrying the valve member 40 at its upper end 81. In the embodiment shown, both bellows and cylinder are circular in cross-section. A compression spring 90 located inside the bellows 60 and around the plunger 80 similarly has an upper end 91 that engages the upper end 71 of the cylinder and a lower end 92 that engages the lower end 82 of the plunger, thereby biasing the plunger downwards as shown in FIG. 3 and the valve member 40 into engagement with the first valve seat 51. This is the fail-safe position of the valve shown in FIG. 2A and in which, in the particular application of FIG. 1, exhaust from the engine 101 bypasses directly to the tailpipe 102 rather than heating the evaporator 124.

However, pressurized fluid - preferably air - supplied into the cylinder through port 100 at the lower end 72 of the cylinder acts on the outside of the bellows to compress the bellows 60, drive the plunger 80 upwards and translate the valve member 40 along a straight line into engagement with the second valve seat 52 spaced along the axis T of translation of the valve member shown in FIG. 2B. It will be appreciated that control of the pressure in the bellows acting against spring 90 allows (according to Hooke's law) positions of the valve member intermediate the two valve seats to be achieved, with a valve member position sensor (not shown) facilitating control.

In contrast to the prior art acknowledged above, valve member 40 has no sliding bearings. Rather, it is supported in the housing 20 - via plunger 80 - solely by the substantially vertically oriented bellows 60 (and, to a lesser extent, the spring 90).

Moreover - and again in contrast to the sliding bearings of the aforementioned prior art - the bellows (and spring) permit a certain amount of rocking movement transverse to the translation direction T, which in turn allows the valve member to be presented correctly on the valve seat, thereby ensuring a good seal.

FIG. 4 is a sectional view of a valve according to a second embodiment of the invention, those features common with FIGS. 2A,B and 3 being indicated by common reference signs. Valve 14 comprises a housing 20 having an inlet 30, a first outlet 31 and second outlet 32. In the example shown, the inlet and outlet passageways are circular in cross-section. In the particular heat recovery application shown in FIG. 1, inlet 30 will be connected to the IC engine 101, first outlet 31 will be connected to the evaporator 124 and second outlet 32 will be connected to the bypass conduit 102a.

As indicated by arrow T, a substantially planar valve member 40 (specifically an annular peripheral region on a second side thereof, 40") is moveable in linear translation towards (and potentially into engagement with) a second annular valve seat 52 formed in the housing around the periphery of second outlet 32 so as to restrict (and potentially seal off) flow through the second outlet 32. Such movement is effected by the expansion of a bellows 60, a first, upper end 61 of the bellows being sealed to a first, opposite side 40' of the valve member 40 and a second, lower end 62 of the bellows being sealed to a cantilever support 200 formed in the housing 20, extending into the bore of the first outlet passageway 31 and having a conduit 100 for supply of pressurized fluid, preferably compressed air. Bellows 60 acts against a compression spring 90, secured between the second side 40" of the valve member 40 and a cantilever support 210 formed in the housing and extending into the bore of the second outlet 32. When the pressure in bellows 60 is reduced, spring 90 urges an annular peripheral region 40' on the first side of valve member 40 towards a first annular valve seat 51 formed in the housing around the first outlet 31 so as to restrict (and potentially seal off) flow through the second outlet 31 to the evaporator and open the bypass path 32 to the tail pipe. As in the previous embodiment, this is the fail-safe position, with intermediate positions of the valve member being possible by regulation of the pressure in the bellows, optionally controlled by a valve member position sensor (not shown).

FIG. 5 is a sectional view of a valve according to a third embodiment of the invention, those features common with FIGS. 2A,B, 3 and 4 being indicated by common reference signs. Valve 14 comprises a housing 20 having an inlet 30, a first outlet 31 and second outlet 32. In the example shown, inlet and outlets are circular in cross-section. In the particular heat recovery application shown in FIG. 1, inlet 30 will be connected to the IC engine 101 , first outlet 31 will be connected to the evaporator 124 and second outlet 32 will be connected to the bypass conduit 102a.

A valve assembly 40 comprises first and second substantially planar members 41, 42 spaced along an axis of linear translation movement T which, as shown, is coaxial with the inlet 30. In the position shown, valve assembly 40 is biased by compression spring 90 such that member 41 (specifically an annular peripheral region on a first side thereof, 41 ') engages a first annular valve seat 51 formed in the housing around the first outlet 31 so as to at least restrict and, as shown, seal off flow through the second outlet 31 to the evaporator and open the bypass path 32 to the tail pipe. Spring 90 is supported at the opposite end to the valve assembly by a cantilever support 220 formed in the housing and extending into the bore of the inlet 30.

A bellows 60 has a first end 61 sealed to the first side 41 ' of member 41 and a second end 62 sealed to a cantilever support 200 formed in the housing 20 and extending into the bore of the first outlet 31. Supply of pressurized fluid, preferably compressed air, into the bellows 60 via a conduit 100 formed in the support extends the bellows against the action of the compression spring 90, moving the first side 4 of valve assembly away from valve seat 51 and the second side 42' of planar member 42 (facing in the opposite axial direction to the first side 4 ) towards coaxial valve seats 50, 52 formed in the housing around the inlet 30 and second outlet 32 respectively. This at least restricts (and potentially seals off) flow through the inlet 30 to the second outlet 32, while a passageway 230 formed in the valve member 40 between planar members 41,42 allows flow between the inlet 30, past valve seat 51 and into the first outlet 31.

As in the previous embodiment, FIG. 5 shows the fail-safe position in which exhaust flow bypasses the evaporator and is fed directly to the tail pipe. However, intermediate positions of the valve member 40 are possible by regulation of the pressure in the bellows, optionally controlled by a valve member position sensor (not shown).

In the embodiments described above, the bellows actuator 60 sits downstream of the annular sealing surface of the valve member and within the first outlet passageway 31. In the particular embodiment of FIG. 3, compression spring 90 also sits downstream of the sealing surface of the valve member and within the first outlet passageway 31. Specifically, spring 90 sits within the bellows 60. In the embodiment of FIG. 4, spring 90 sits downstream of the sealing surface of the valve member and within the second outlet passageway 32. In the embodiment FIG. 5, spring 90 sits upstream of the valve member and within the inlet passageway 30. In all three embodiments, the valve member is guided solely by a guide arrangement that consists, i.e. comprises solely, of the bellows and the spring, with the bellows the predominant guide.

In the embodiment of FIG. 3, cylinder 70 also serves as a shield, shielding actuator bellows 60 (and, indirectly, spring 90 contained therein) from the flow of hot exhaust gas. The lower end 72 of the cylinder 70 is closed by a wall of the valve housing 20, while the top end 71 of the cylinder is closed by an annular plate 73 having a central hole 74. The top annular end 61 of the bellows seals to the annular plate while plunger 80, to which the bottom annular bellows end 62 is sealed, is able to move up and down through the hole to move the valve member 40 between valve seats 51 and 52. In the embodiment shown, planar annular plate 73 and planar annular valve seat 51 are co-axial and integral, being connected by radial spokes indicated at 75 in FIG. 2B. FIG. 6A is a sectional view taken along line D-D in FIG. 6B, which is in turn a perspective view of a valve according to a fourth embodiment of the invention that shares many features in common with the embodiment of FIGS. 2A,B and 3, common features being indicated by common reference signs.

Valve 14 comprises a housing 20 having an inlet 30, a first outlet 31 and second outlet 32. In the example shown, inlet and outlets are circular in cross-section. In the particular heat recovery application shown in FIG. 1, inlet 30 will be connected to the IC engine 101, first outlet 31 will be connected to the evaporator 124 and second outlet 32 will be connected to the bypass conduit 102a.

In the position shown in FIG. 6 A, a circular, substantially planar valve member 40

- specifically a first annular peripheral region 40' thereof - engages a first annular valve seat 51 so as to seal off flow to the first outlet 31, thereby allowing flow to the second outlet 32 as indicated by arrow A. As indicated by arrow T, valve member 40 can be moved in linear translation along its axis of circular symmetry so as to disengage the first valve seat 51, allowing flow to the first outlet 31 as indicated by arrow B in FIG. 6B.

Linear translation of the valve member 40 is again effected by an - advantageously metal - bellows 60 which sits inside a cylinder 70, the (left-hand) end 61 of the bellows being sealed to one end 71 of the cylinder proximate the valve member 40 and the other (right-hand) end 62 of the bellows being sealed to one (right-hand) end 82 - remote from the valve member - of a shaft 80 carrying the valve member 40 at its opposite (left-hand) end 81. In the embodiment shown, both bellows and cylinder are circular in cross-section. A compression spring 90 located inside the bellows 60 and around the shaft 80 similarly has one end 91 that engages the end 71 of the cylinder and another end 92 that engages the lower end 82 of the shaft, thereby biasing the plunger to the right as viewed in FIG. 6A and the valve member 40 into engagement with the first valve seat 51. This is the failsafe position of the valve in which, in the particular application of FIG. 1, exhaust from the engine 101 bypasses directly to the tailpipe 102 rather than heating the evaporator 124.

Pressurized fluid - preferably air - is supplied into the cylinder 70 through port 100 to act on the outside of the bellows, thereby compressing the bellows 60 and driving the shaft 80 to the left. This translates the valve member 40 along a straight line into engagement with the second valve seat 52 spaced along the axis T of translation of the valve member. It will be appreciated that control of the pressure in the bellows acting against spring 90 allows (according to Hooke's law) positions of the valve member intermediate the two valve seats to be achieved, with a valve member position sensor (not shown) facilitating control.

In the embodiment of FIGS. 2A,B and 3, the longitudinal axes of the inlet 30 and first outlet 31 (and which substantially correspond to the direction of flow into /out of the inlet / first outlet) extend substantially parallel to the planes of the valve member 40 and valve seat 51 and substantially perpendicular to the direction T of translation of the valve member 40.

By contrast, the longitudinal axes 30A,31A of inlet and first outlet 30,31 of the embodiment of FIGS. 6 A and B are inclined at an angle greater than 0° and less than 90° to direction T (and indeed to the plane of the valve member 40 and valve seat 51). In the particular embodiment shown, the longitudinal axes 30A,31A of inlet and first outlet 30,31 are inclined at angles Θ of around 45° to axis T.

Moreover, inlet 30 and first outlet 31 are each defined by respective tubular conduits 21,22 with respective longitudinal axes 30A,31A, the conduits intersecting (in the example shown at a flanged and welded joint 610) at a plane P inclined at an angle β greater than 0° and less than 90° to the longitudinal axis of each conduit. Cylinder 70 and second outlet 32 are each sealingly secured in the wall of a conduit - as shown along a common axis T, the substantially horizontal orientation of which necessitates a sliding support or bearing 600 for the plunger 81. As shown, bearing 600 supports that end 81 of the shaft 80 proximate the valve member and is itself fixed relative to the valve seat 51 and housing 20 by means of radial spokes shown at 75 in FIG. 6B.

In the particular embodiment shown, angle β is the same for each conduit at around 45°: not least, this allows the same tooling to be used to produce each conduit 21,22.

In addition, the wall of each conduit adjacent the intersection P may be curved so as to facilitate gas flow.

Moreover, different relative locations of inlet and outlets may be achieved simply by varying the relative position of the two conduits about an axis (corresponding to axis T in the embodiment of figure 6A) normal to the plane of intersection P. For example, inlet 30 and outlet 31 may both extend upwardly and in the same plane as shown in figure 6B. Alternatively, inlet 30 and outlet 31 may extend in opposite directions and in the same plane as shown in figure 7. Although specific embodiments are described herein for illustrative purposes, various equivalent modifications are possible within the scope of the present description, as those skilled in the relevant art will recognize. For example, the system could work without a spring, two bellows working in opposition being used instead. The teachings provided herein can also be applied to other valves, and not just to the embodiments described above and shown in the accompanying figures. For example, the invention may be applicable to valves having fewer (i.e. two) or a greater number of ports than the three ports of the examples above. Moreover, the valve may have vehicle or industrial applications beyond the specific waste heat recovery application discussed above. Accordingly, the scope of the embodiments described above should be determined from the following claims.

Claims

1. A fluid valve comprising

a valve member configured for movement in translation; and

a bellows that is configured to contract and extend via pressure change in order to move the valve member in translation, wherein the bellows are configured to guide the valve member in translation, and wherein the valve member is retained in a manner which allows the valve member to rock a few degrees about a translation axis to ensure the valve member provides a good seal.

2. Fluid valve according to claim 1, wherein the valve comprises a valve seat, the valve member being configured for movement in translation relative thereto so as to restrict flow between the member and the seat.

3. Fluid valve according to claim 2 and comprising first and second valve seats spaced in the direction of translation of the valve member, the valve member being configured for movement in translation relative thereto so as to restrict flow between the member and the first or the second valve seat.

4. Fluid valve according to claim 2 or claim 3, wherein the first and/or second valve seat is annular and/or conical and/or planar.

5. Fluid valve according to any preceding claim, wherein at least one of the valve member, first valve seat and second valve seat is circularly symmetric about the direction of translation.

6. Fluid valve according to claim 5, wherein the first valve seat is planar and extends perpendicular to the direction of translation.

7. Fluid valve according to claim 5, wherein the outer annular periphery of the valve member tapers in the direction of the second valve seat and the second valve seat tapers in the direction away from the valve member.

8. Fluid valve according to any preceding claim, wherein the bellows is circularly symmetric about - and configured to expand and contract in - the direction of translation.

9. Fluid valve according to any preceding claim, wherein the valve comprises a spring configured to bias the valve member into engagement with a valve seat.

10. Fluid valve according to claim 9, wherein the spring is coaxial with the bellows.

1 1. Fluid valve according to any one of claims 3 to 10 and comprising first, second and third flow passageways, the first valve seat being located between the first and second passageways and the second valve seat being located between the first and third passageways.

12. Fluid valve according to claim 1 1, wherein the spring is located in the same passageway as the bellows.

13. Fluid valve according to claim 1 1, wherein the spring is located in a different passageway to the bellows.

14. Fluid valve according to claim 13, wherein the bellows and spring are located in the second and first passageways respectively.

15. Fluid valve according to claim 13, wherein the bellows and spring are located in the second and third passageways respectively.

16. Fluid valve according to any preceding claim, wherein the valve comprises a shield configured to shield the bellows from fluid flow.

17. Fluid valve according to claim 16, wherein the shield comprises a cylinder.

18 Fluid valve according to claim 17, wherein the cylinder is coaxial with the bellows.

19. Fluid valve according to any preceding claim and configured to move the valve member by increasing a control pressure.

20. Fluid valve according to claim 19, wherein the increasing control pressure is applied to the internal surface of the bellows, causing the bellows to expand.

21. Fluid valve according to claim 19, wherein the increasing control pressure is applied to the external surface of the bellows, causing the bellows to contract.

22. Fluid valve according to claim 21 and comprising a housing, the increasing control pressure being applied between the external surface of the bellows and the housing.

23. Fluid valve according to claim 22, wherein the increasing control pressure is applied between the external surface of the bellows and the internal surface of the cylinder.

24. Fluid valve comprising

first and second valve seats spaced along a first axis;

a substantially planar valve member located on the first axis between the first and second valve seats; and

a bellows configured to move the valve member in translation along the first axis so as to restrict flow between the member and the first or the second valve seat.

25. Fluid valve according to claim 24, wherein the first and/or second valve seat is annular and/or conical and/or planar.

26. Fluid valve according to claim 24 or 25, wherein at least one of the valve member, first valve seat and second valve seat is circularly symmetric about the first axis.

27. Fluid valve according to claim 26, wherein the first valve seat is planar and extends perpendicular to the first axis.

28. Fluid valve according to any one of claims 24 to 27, wherein the outer annular periphery of the valve member tapers in the direction of the second valve seat and the second valve seat tapers in the direction away from the valve member.

29. Fluid valve according to any one of claims 24 to 28, wherein the bellows is circularly symmetric about - and configured to expand and contract in - the first axis.

30. Fluid valve according to any one of claims 24 to 29, wherein the valve comprises a spring configured to bias the valve member into engagement with a valve seat.

31. Fluid valve according to claim 30, wherein the spring is coaxial with the bellows.

32. Fluid valve according to any one of claims 24 to 31 and comprising first, second and third flow passageways, the first valve seat being located between the first and second passageways and the second valve seat being located between the first and third passageways.

33. Fluid valve according to claim 32 when dependent on claim 30 or 31, wherein the spring is located in the same passageway as the bellows.

34. Fluid valve according to claim 32 when dependent on claim 30 or 31, wherein the spring is located in a different passageway to the bellows.

35. Fluid valve according to claim 34, wherein the bellows and spring are located in the second and first passageways respectively.

36. Fluid valve according to claim 34, wherein the bellows and spring are located in the second and third passageways respectively.

37. Fluid valve according to any one of claims 24 to 36, wherein the valve comprises a shield configured to shield the bellows from fluid flow.

38. Fluid valve according to claim 37, wherein the shield comprises a cylinder.

39. Fluid valve according to claim 38, wherein the cylinder is coaxial with the bellows.

40. Fluid valve according to any one of claims 24 to 39 and configured to move the valve member by increasing a control pressure.

41. Fluid valve according to claim 40, wherein the increasing control pressure is applied to the external surface of the bellows, causing the bellows to contract.

42. Fluid valve according to claim 41 and comprising a housing, the increasing control pressure being applied between the external surface of the bellows and the housing.

43. Fluid valve according to claim 44, wherein the increasing control pressure is applied between the external surface of the bellows and the internal surface of the cylinder.

44. Fluid valve according to any one of claims 24 to 43 and comprising first and , second flow passageways with the first valve seat therebetween, the first and second passageways having respective longitudinal axes inclined at a first angle greater than 0° and less than 90° to the first axis.

45. Fluid valve according to claim 44, wherein the respective longitudinal axes are inclined at a first angle of around 45° to the first axis.

46. Fluid valve according to claim 44 or 45, wherein the first and second flow passageways are each defined by respective first and second tubular conduits with respective longitudinal axes, the conduits intersecting at a plane P inclined at a second angle greater than 0° and less than 90° to the longitudinal axis of each conduit.

47. Fluid valve according to claim 46, wherein the second angle is the same for each conduit.

48. Fluid valve according to claim 45 or 46, wherein the second angle is around 45°:

49. Fluid valve according to any one of claims 44 to 48, wherein the respective longitudinal axes of the first and second tubular conduits extend in the same plane.

50. Fluid valve according to any one of claims 44 to 49, wherein the first and second tubular conduits extend to the same side of the first axis.

51. Fluid valve according to any one of claims 44 to 49, wherein the first and second tubular conduits extend to different sides of the first axis.