The present invention relates to a valve, in particular an actuatable valve. The valve may to actuated to be open or closed to fluid flow through the valve. Preferably the valve is an actuatable control valve which allows variations between full flow and no flow in the pressure drop across the valve (i.e. variations in flow rate through the valve), for instance a substantially continuous variation in flow resistance between full flow resistance and minimum flow resistance.

Actuatable control valves which can be operated under all pressure conditions and all differential pressures with low operating forces are known, for example in

CA 872, 106. Such valves comprise an outer housing which defines an inlet opening and an outlet opening as well as an inner housing which houses a restrictor for restricting fluid flow along a fluid flow path through the valve. The restrictor is actuatable by an actuation rod from outside of the valve or by other means, for example by an electric actuator (see for example US 2013/0068976). In all cases the outer and inner housings are integral, being made by a single casting. Once the casting has been made, the actuatable restrictor can be inserted through the inlet and/or outlet opening and fixed inside the inner housing. The actuator typically comprises a piston which is engagable with a surface defining the fluid flow path thereby to block the fluid flow path. Because the piston must be inserted through one of the inlet opening and outlet opening it is often necessary to provide a bush for reducing the inner diameter of the outlet opening formed in the outer housing so that the piston can be inserted into the outer housing through the outlet opening. A bush is often screw fitted into the outlet housing. Such an arrangement is described in US

2006/0202428 in which the bush is connected to a throttle cage which allows the valve to vary the restriction to fluid flow along the fluid flow path in a substantially continuous manner.

The present invention provides an actuatable valve, comprising: an outer housing defining a fluid flow path through the valve; an actuatable restrictor in the housing which is translatable between an open position in which the fluid flow path is open and a closed position in which the fluid flow path is blocked by the actuatable restrictor; and at least one elongate supporting member mounted for translation relative to the actuatable restrictor and arranged to guide a leading portion of the actuatable restrictor as the actuatable restrictor moves from the open position to the closed position. Without the at least one elongate supporting member the actuatable restrictor may drift off axis and not engage with the parts of the actuatable valve it is designed to engage with in the correct position. Therefore, in the present invention, the actuatable restrictor is more likely to arrive in the closed position in the correct position. Engaging in the incorrect position can lead to premature wear of components and in the worst case scenario in the actuatable restrictor not blocking the fluid flow path in the closed position.

In an embodiment the at least one elongate supporting member extends through a front of the actuatable restrictor in the open position. This geometry allows the at least one elongate supporting member to guide and/or support the leading portion of the actuatable restrictor with better mechanical advantage than the case where the at least one elongate supporting member does not extend through the front of the actuatable restrictor in the open position.

In an embodiment the at least one elongate supporting member extends through a front of the actuatable restrictor in the closed position. This geometry means that the at least one elongate supporting member guides the leading portion of the actuatable restrictor for the whole movement between the open and closed positions thereby providing good guide and/or support geometry. This also allows the at least one elongate supporting member easily to be supported at both ends. That increases strength and/or stiffness of the elongate supporting member and it improves its functionality as a guide.

In an embodiment the at least one elongate supporting member comprises a plurality of elongate supporting members spaced around a longitudinal axis of the actuatable restrictor. This means that the actuatable restrictor is guided on all sides, thereby improving the guiding performance.

In an embodiment the at least one elongate supporting member is mounted stationary relative to the outer housing. Although the guiding function of the at least one elongate supporting member can be performed if the elongate supporting member is not mounted stationary relative to the outer housing (for example it is allowed to rotate around the central axis of the valve), the best guiding performance is achieved if the at least one elongate supporting member is mounted stationary relative to the outer housing.

In an embodiment, in the closed position, the actuatable restrictor blocks the fluid flow path by engagement with the outer housing. This arrangement is most preferred as it leads to the most reliable seal. In this embodiment an elastically deformable seal such as an o-ring may be mounted at the position of engagement of the actuatable restrictor with the outer housing, either on the actuatable restrictor itself or in the outer housing, or both.

In an embodiment the actuatable valve further comprises an inner housing element inside the outer housing, for housing the actuatable restrictor. The provision of an inner housing element is an easy way to arrange for actuation of the actuatable restrictor from outside of the actuatable valve. Additionally it simplifies the design in terms of making the valve a pressure balanced valve in which all axial end surfaces of the moving components of the actuatable restrictor are exposed to the same fluid pressure, in all positions of the actuatable valve.

Preferably the at least one elongate supporting member is mounted to the inner housing. This may be a direct mounting or an indirect mounting. In this way at least one end of the at least one elongate supporting member is secured to the outer housing (as the inner housing is itself secured to the outer housing).

In an embodiment the actuatable valve further comprises a piston housing in the inner housing for housing a piston rod of the actuatable restrictor. In that case it is preferable that the at least one elongate supporting member is mounted on the piston housing, for example an integral element of the piston housing or secured to a flange of the piston housing.

In an embodiment the actuatable restrictor comprises a piston cap which defines a front of the actuatable restrictor and the at least one elongate supporting member passes through a throughole in the piston cap. This feature allows the at least one elongate supporting member to extend as far as necessary to guide the leading portion of the actuatable restrictor as the actuatable restrictor approaches the closed position. This is also a convenient way to get the at least one elongate supporting member to guide the leading portion of the actuatable restrictor. Additionally it allows the at least one elongate supporting member easily to be secured at the far end to the outer housing.

Preferably the at least one elongate supporting member guides the leading portion of the actuatable restrictor by contact between the at least one elongate supporting member and the piston cap. This contact may be by way of a low friction bearing and this is a convenient way to arrange for the at least one elongate supporting member to guide the leading portion of the actuatable restrictor as it approaches the closed position. In an embodiment the actuatable restrictor comprises a guide ring axially mounted on the leading portion, the at least one elongate supporting member interacting with the guide ring, thereby to guide the leading portion. The guide ring provides a convenient surface against which the at least one elongate supporting member may bear.

Preferably the at least one elongate supporting member is secured at both ends to the outer housing. This increases the stiffness of the elongate supporting member along its length thereby resulting in better guiding performance. In an embodiment the at least one supporting member is secured at one end by one or more vanes extending between the at least one supporting member and an outlet opening of the inner housing.

The at least one elongate supporting member of the present invention can be used with any type of actuatable valve, including valves which are made of an integral outer housing and inner housing (i.e. those valves made by a single casting). Additionally the at least one elongate supporting member may be used with valves which are comprised of several parts, for example valves of the type disclosed in PCT Application No.

PCT/GB2014/052982.

In an embodiment the valve comprises an outer housing; an upstream element of the outer housing defining an inlet opening; a downstream element of the outer housing defining an outlet opening; and an inner housing element inside the outer housing for housing the actuatable restrictor; wherein the inner housing element is non-integral with at least one of the upstream and downstream elements.

Therefore, the inner housing element is not integral with the outer housing. The separate nature of the inner housing element from the outer housing means that during assembly of the valve the inner housing must be mounted to the upstream and downstream elements of the outer housing. However, this arrangement, despite requiring extra assembly steps to achieve an inner housing in an outer housing, has several advantages, due to the discrete nature of the inner housing element. The first advantage is that the integrity of the inner housing can be more easily determined and manufacturing steps such as surface grinding, polishing, applying coatings etc. can be more easily performed on the inner housing. This is because access to the inner housing is not through the inlet or outlet opening of the outer housing. Inspection of the integrity of the outer housing to determine the integrity/presence or otherwise of defects is also more easily performed, such as dye penetration techniques, radiography (for which there must be space around the object being inspected) and magnetic particle inspection (if a magnetic material is being used). All of those non destructive inspection techniques require adequate access of the surface being inspected. If the inner housing is outside of the outer housing this is much more readily achievable. An additional advantage is that the restrictor can be assembled in the inner housing prior to the inner housing being inserted into the outer housing, which is much more convenient. In some embodiments it is no longer necessary to provide a bush to reduce the diameter of the inlet or outlet opening as is necessary for example in the valve of US 2006/0202428. This is advantageous as the use of a bush can make a sealing surface (where the valve seals against pipework) uneven, making the valve face where it should seal with a gasket or metallic seal against mating pipework a potential leak path to atmosphere.

A further advantage is that the outer housing and inner housing can be made by processes other than casting. For example, at least some elements of the inner or outer housing may be made by forging, for example closed die forging. Additionally the valve design of the present invention has the benefit of allowing a degree of modularity in that different combinations outer housing and inner housing elements can be selected dependent upon the required valve performance such as operating pressure, maximum flow rate etc.

Although it is possible to cast the inner and outer housings in one integral casting as has been done previously, this can be difficult as effectively the operator is trying to make a casting within a casting. Typically this results in a poor feed path for molten metal to the inner housing element, making it prone to having volumetric defects. The design of the cast therefore is more complicated. Due to the single piece design it is impossible to get access properly to inspect the surfaces on valves with a small bore (i.e. 50mm or smaller) with larger sized bores (i.e. 300mm and greater) being extremely difficult and time consuming to inspect and repair due to very restricted access to the area between the outer wall of the inner housing and the inner wall of the outer housing. If during testing any defects are found in the inner housing (or the inner surface of the outer housing), these defects can be harder to repair as all repairs must be performed through the inlet opening or outlet opening of the outer housing (e.g. by welding).

By re-designing the valve with separate, discrete inner and outer housings, the valve can be made of a modular construction. Even by having more constituent parts, significant manufacturing cost reduction can be achieved. This is because by

manufacturing the constituent parts as individual components the components can be produced by forging or casting methods, and by not trying to make a casting within a casting, fewer machining steps and lower subsequent difficulty in repairing and inspecting the item can be expected. This results in much lower cost per unit due to higher integrity of the casting by practically eliminating the cause from which the need to repair arises in the first instance. Additionally because of this higher quality, parts can be produced in a much shorter timescale due to this manufacturing methodology. A typical casting manufacturing lead time for the existing design with a pattern already in existence would be typically 24 - 40 weeks duration. In contrast, by eliminating the manufacturability issues with the existing design, castings or forgings could be procured in 8 - 12 weeks, giving a significant competitive advantage in manufacturing lead time with the inventive steps taken.

In an embodiment the inner housing element is non-integral with the upstream and downstream elements. This provides the advantage that the upstream and downstream elements of the outer housing are both separate from the inner housing element so that the inner housing element can be prepared entirely separately from the upstream and downstream elements. When the three elements are ready to be assembled, the inner housing element and attached restrictor do not need to pass through the inlet opening or outlet opening defined in the upstream and downstream elements. Therefore, the inlet and outlet openings defined by the upstream and downstream elements can be sized and machined exactly for use during manufacture so that the surface defining the inlet and outlet openings can be integral with the other parts of the upstream and downstream elements (for example flanges for connecting the valve to pipework). In this way it is not necessary for a bush to be present in the inlet or outlet opening and a flat (even) sealing surface can easily be formed on the upstream and/or downstream elements.

In an embodiment the valve further comprises a central element of the outer housing between the upstream and downstream elements. In an embodiment the inner housing element is mounted to the central element of the outer housing. This allows easier assembly as attaching the inner housing element to only the central element whilst the upstream elements and/or downstream elements are not present is simpler (because it is not necessary to work through the inlet opening or outlet opening). In an embodiment the inner housing element is integral to the central element of the outer housing. For example, the inner housing element and central element of the outer housing may be cast or forged as one integral element (discrete from the upstream and downstream elements of the outer housing). This reduces the number of assembly steps as it is not necessary to use, for example, screw fixing means for mounting the inner housing element to the outer housing. One way of assembling the outer housing is to provide at least two of the upstream, downstream and central elements of the outer housing with flanges which are through bolted thereby to join the elements together and form the outer housing.

In an embodiment the central element of the outer housing is integral with at least one of the upstream and downstream elements of the outer housing. This may be advantageous in that the valve has fewer parts. It may be that only the upstream or downstream side of the inner housing requires really good access and access to the other of the upstream and downstream side of the inner housing through one of the inlet opening and outlet opening may be acceptable in order to perform any necessary machining, assembly, defect inspection and repair.

In an embodiment the inner housing is non-integral with the elements of the outer housing. This advantageously allows all around access to the inner housing for machining, polishing, defect analysis, repair and assembly. Preferably the actuatable valve further comprises a connector member formed at an upstream end of the inner housing, and fastening means fixing the connector member to the outer housing. Preferably the connector member is comprised of a plurality of webs extending radially and axially from the inner housing to an outer ring. More preferably the outer ring is fitted in the inlet opening.

In an embodiment at least one web extends between the inner housing element and outer housing and the inner housing element is fixed to the outer housing via the at least one web. The web may be integral to one or both of the inner housing element and outer housing and supports the inner housing element within the outer housing.

In an embodiment the fluid flow path of the valve is substantially in an axial direction between the inlet and outlet openings and substantially annular around the inner housing.

In an embodiment the actuatable restrictor comprises a piston engagable with a portion of an inner surface of the outer housing defining the fluid flow path thereby to block the fluid flow path. In this way the actuatable restrictor can be actuated to open or close the valve. Preferably the portion of the inner surface of the outer housing is defined by material integral to a flange of the upstream element for connecting the valve to pipework. This avoids the need for a bush and difficulties which that might entail in particular in terms of accurate dimensioning of the inner surface of the outer housing and any mating surface of the outer housing which mates with pipework to which the valve is connected.

In an embodiment the valve further comprises a throttle cage in the form of a tube with a plurality of axially spaced through holes through walls of the tube, the piston being translatable axially in the tube thereby to vary the number of the plurality of through holes through which fluid can flow and thereby to vary the restriction to fluid flow along the fluid flow path. This allows the valve to be a flow control valve in the sense that the restriction to the flow of fluid of the valve can be varied between being on and off, for example substantially continuously and preferably in a substantially linear manner.

In an embodiment the actuatable restrictor comprises a piston rod at least partly housed in a piston housing (the piston housing may be part of/integral to the inner housing). Preferably the piston housing comprises a seal in a groove for sealing against the piston rod. Such an arrangement is advantageous over the situation where the seal is fitted to the piston rod and results in better sealing performance (integrity and life) at the expense of requiring the piston rod to be a little longer as in the fully actuated condition a surface against which the seal in the piston rod can bear is needed. This is particularly the case where surfaces of the piston rod are specifically prepared (e.g. have a surface hardening treatment such as laser hard facing applied, followed by grinding) to act as a bearing surface where the seals in the grooves of the piston housing contact the piston rod.

In an embodiment the piston housing is integral with the inner housing. This is advantageous in that it reduces the number of components of the valve. It is particularly suitable for the case in which the inner housing is non integral with elements of the outer housing.

Preferably leading and trailing surfaces of moving components of the actuatable restrictor which are of equal area are in fluid communication with fluid on the same side of the actuatable valve in all positions such that pressures on either side of the moving components are equal. Preferably the actuatable restrictor comprises a piston engagable with a portion of an inner surface of the outer housing defining the fluid flow path thereby to block the fluid flow path and at least one through-hole is provided in a front downstream axial face of the piston so that fluid passes through the front face of the piston. Preferably the actuatable restrictor comprises a piston rod at least partly housed in a piston housing and at least one passage is provided in the inner housing providing communication between an upstream cavity in which the piston sits in a fully retracted state and a downstream cavity on the downstream side of the inner housing in which an upstream axial end of the piston rod is positioned.

The actuatable restrictor may comprise a piston rod at least partly housed in a piston housing and a passageway through the piston rod between an upstream cavity in which the piston sits in a fully retracted state and a downstream cavity on the downstream side of the inner housing in which an upstream axial end of the piston rod is positioned.

Preferably the valve is an internally pressure balanced valve.

Preferably the valve is a mechanically actuated valve.

Preferably the restrictor is actuatable by an actuation rod from outside of the valve. The actuatable restrictor may comprise a piston rod at least partly housed in a piston housing and the piston rod can be moved in the axial direction of the valve using the actuator rod. The actuator rod may have a toothed surface which interacts with a toothed surface of the piston rod. The actuating rod may be rotatable. The valve may further comprise an actuator rack housing in a recess of the outer housing. The valve may further comprise a pinion rack held onto the actuator rod which engages with a rack on a side of the piston rod.

At least some of the elements may be at least partly fixed together by welds.

The present invention will now be described by way of example only with reference to the following drawings:

Figure 1 is an expanded perspective view of a valve;

Figure 2 is a cut-away perspective view of the assembled valve of Figure 1;

Figure 3 is a cross-sectional view of the valve of Figure 1;

Figure 4 is a perspective view of a throttle cage;

Figure 5 is an expanded perspective view of a valve;

Figure 6 is a cut-away perspective view of the assembled valve of Figure 5; Figure 7 is a cross-sectional view taken across the axial direction of the valve of Figure 5;

Figure 8 is a cross-sectional view in the vertical plane in the axial direction of the valve of Figure 5;

Figure 9 is a cross-sectional view in the horizontal plane in the axial direction of the valve of Figure 5; and

Figure 10 is a cut-away perspective view of a detail of a valve according to the present invention in the open position;

Figure 11 is a cut-away perspective view of the valve of Figure 10 in the closed position;

Figure 12 is a cut-away perspective view of a second embodiment of a valve according to the present invention, in the open position; and

Figure 13 is a cut-away perspective view of the valve of Figure 12 in the closed position.

An actuatable valve will now be described with reference to Figures 1-3.

The valve 1 of the present invention operates in substantially the same way as the valves disclosed in CA 872, 106, US 2006/0202428 and US 2013/0068976. Those documents are all incorporated herein by reference in their entirety. Those valves and the valve 1 of the present invention are designed such that both the leading and trailing surfaces (surfaces not parallel to the axial direction) of moving components of an actuatable restrictor 300 for restricting fluid flow along a fluid flow path through the valve 1 are in fluid communication with fluid on the upstream side. Thus, the pressures on either side of the moving components are equal and low actuation forces are needed to actuate the restrictor. Thus, the valves are pressure balanced valves. The valves may be for use in the oil or chemical industries, for example.

A description will now be given of the construction of two valves. However, the use of at least one elongate supporting member of the present invention is not limited to use in the types of valves illustrated in Figures 1-9. Indeed, the at least one elongate supporting member described with reference to Figures 10-13 can be used with any type of valve including those disclosed in CA 872, 106, US 2006/0202428 and US 2013/0068976. However, it is preferable that the at least one elongate supporting member described with reference to Figures 10-13 is used in combination with a valve such as described in relation to Figures 1-9 and for this reason a detailed description of those types of valve is given below without reference to the at least one elongate supporting member.

The actuatable valve 1 of Figures 1-3 may be in the form of an on/off valve as illustrated. Alternatively and particularly with the addition of a throttle cage 400 such as that described in GB 2,054,103 hereby incorporated in its entirety by reference and as described below in further detail with reference to Figure 4, may be in the form of a flow control valve in which the flow rate fluid through the valve (or the pressure drop across the valve) may be varied substantially continuously. Achieving this is in theory possible without a throttle cage 400, but the throttle cage 400 enables a choice of flow variation with the piston position and/or pressure drop with axial movement of the restrictor 300.

The valve comprises an outer housing 100, an inner housing 200 and a restrictor

300.

The outer housing 100 comprises an upstream flange 114 and a downstream flange 112. The upstream and downstream flanges 114, 112 have through holes 113 in them for bolts 115 (for example four or more circumferentially spaced around the flange 114, 112) to pass therethrough. The bolts 115 pass through through holes in a flange of pipework to which the valve 1 is to be connected. Mating surfaces 116 at the axial ends of the valve 1 mate with a corresponding mating surface of the pipework to which the valve 1 is to be connected. The mating surfaces 116 may include the provision therein of a seal (not illustrated). The mating surfaces 116 may include a groove 117 for the provision to be welded to the abutting mating pipe work, "weld prep end" (not illustrated).

The housing 100 defines an inlet opening 104 and an outlet opening 102 for fluid flow into and out of the valve (though the flow direction may be reversed (the valve 1 is a two-way valve)).

The outer housing 100 is made up of a upstream element 140 and a downstream element 120. The upstream and downstream elements 140, 120 of the outer housing 100 define the inlet opening 104 and outlet opening 102 respectively. Additionally, the upstream and downstream elements 140, 120 each comprise the associated flange 114, 112 for connecting the valve 1 to pipework.

The inner housing element 200 is in a separate component from the upstream element 140 and the downstream element 120 of the outer housing 100. Those three elements 120, 140, 200 are discrete in that they are not formed integrally (they are non- integral) and are formed as disunited components which can be mounted (and demounted, or attached/detached) to each other.

The fact that the inner housing 200 is separate from the upstream and downstream elements 140, 120 of the outer housing 100 allows the inner housing 200 to be machined, inspected for defects and repaired more easily. This is because access to the inner housing 200 does not have to be through the inlet or outlet opening 104, 102. Additionally, assembly of the actuatable restrictor 300 or insertion of the actuatable restrictor 300 into the inner housing 200 does not need to be performed through one or both of the inlet opening 104 and outlet opening 102. This makes assembly easier.

The outer housing 130 also has a central element 134. When the outer housing 100 is assembled, the central element 134 forms a central part of the outer housing 100 and is positioned between the upstream and downstream elements 140, 120. Each of the upstream, downstream and central elements 120, 140, 130 has a flange 122, 142, 132 with through holes which in the assembled state are aligned and bolts 150 (for example at least six circumferentially spaced bolts) hold the outer housing 100 together. A dowel 151 is in a through hole of the flange 132 of the central element 130 and in recesses in the flanges 142, 122 of the upstream and downstream elements 140, 120. The dowel 151 is used for alignment of those three elements 120, 130, 140. The bolts 150 are tightened up to form the outer housing.

Ring seals 152, 153 may be positioned between the central element 130 and upstream element 140 and between the central element 130 and downstream element 120. A backup seal 154 may also be provided. In this way the outer housing 100 defines a flow path for fluid through the valve 1 from the inlet opening 140 to the outlet opening 120. It should be noted that the valve 1 may have fluid flowing through it in either the direction and when the term inlet opening is used herein it may also be read as an outlet opening and vice versa. The normal flow direction would be from inlet 140 to outlet 120, the valve would also operate if the flow changed direction and seal in the reverse flow direction, in the reverse flow direction the flow path through the valve would be less favourable.

In the embodiment of Figures 1-3, the inner housing 200 is formed integrally with the central element 130 of the outer housing 100. The central element 130 and inner housing 200 may be formed by casting or forging or any other method. Following casting or forging, machining and/or polishing of the component may take place. The surfaces which are machined and/or polished are typically those surfaces which abut against other components of the valve 1. For example, the faces of the flange 132 which abut with the flanges 142, 122 of the upstream and downstream elements 140, 120 would be machined to ensure a flat surface and good mating.

The inner housing 200 is attached to the central element 130 via at least two webs 220, 230. There may only be one web or there may be more than two webs. The fluid flow path through the valve 1 allows fluid flow between the inner housing 200 and the inner surface of the outer housing 100 at all locations apart from the locations of the webs 220, 230 extending between the inner housing 200 and the outer housing 100. Therefore, the fluid flow path through the valve is substantially in an axial direction (A-G in Figure 3) between the inlet and outlet openings 102, 104 and has a substantially annular cross- section around the inner housing 200.

Although the valve of Figures 1-3 is shown with the outer housing formed of three elements 120, 130, 140 and the inner housing 200 being formed integrally with the central element 130, other arrangements are possible. For example, the outer housing 100 may be only formed of two elements (an upstream and a downstream element) with the inner housing 200 attached to only one of those upstream and downstream elements. For example, the upstream side of the inner housing 200 does not usually require much post casting or post forging machining on its upstream outer surface. Therefore, the inner housing 200 can be made integral with the upstream element 140 with or without the central element 130. The actuatable restrictor 300 can then easily be inserted into the inner housing 200 (from the downstream side) following any machining, polishing, defect detection or repairing. Those steps can relatively easily be carried out to the downstream side of the housing 200 as that side is fully accessible. Any defect inspection or repairing or machining to the upstream side of the housing 200 would need to take place through the inlet opening 104. Once the actuatable restrictor 300 has been assembled and attached into the inner housing 200, the downstream element 120 (and any other intervening elements which are positioned between the upstream and downstream elements 140, 120) can be attached to the upstream element 140. Other arrangements are possible so long as the inner housing 200 is discrete from at least one of the upstream and downstream elements 140, 120. In this way the inner housing 200 can be made more accessible than in the case where the inner and outer housings 200, 100 are cast as a single integral unit as in the prior art.

In manufacture of the valve 1, the upstream element 140 and downstream element 120 may be cast and/or forged separately. Any post casting or forging machining, polishing, defect detection and repairing is then carried out. The inner housing element 200 is separately produced for example by casting or forging. In the embodiment of Figures 1-3 the inner housing element 200 is cast or forged integrally with the central element 130 of the outer housing 100. Following casting or forging of the inner housing element 200, any machining, polishing, defect detection and repairing may be performed on the inner housing element 200 (and central element 130 of the outer housing 100). Because the inner housing element 200 is separate from the upstream and downstream elements 140, 120 of the outer housing 100, access to the inner housing element 200, particularly the upstream and downstream ends of the housing element 200 is easy. The actuatable restrictor 300 may then be inserted into the inner housing 200 and fixedly attached thereto. Again, this step is easy because access to the upstream side of the inner housing element 200 is unrestricted. The final stage is clamping together the outer housing elements 120, 130, 140 and thereby inserting the inner housing element 200 into the outer housing 100. This final action is performed by passing the through bolts 150 through the flanges 122, 132, 142 (after they have been aligned with dowel 151) and tightening. The ring seals 152, 153 and backup seals 154 are placed between the elements 120, 130, 140 of the outer housing 100 before the bolts 150 are inserted.

The restrictor 300 will now be described. The restrictor 300 comprises two main moveable components, namely a piston 330 and a piston rod 320. The piston 330 is moveable from a position where it does not engage (e.g. touch) with the outer housing 100 to a position where it does engage with the outer housing (as illustrated in Figure 2). The piston 330 engages with a portion 126 of the inner surface of the outer housing 100. The inner surface of the outer housing 100 defines the fluid flow path. By engaging with a portion 126 of that surface, the piston 330 blocks off the fluid flow path and thereby closes the valve 1. The portion 126 of the inner surface of the outer housing is defined by material integral to the upstream element 140. In particular, the material is integral with the material of the flange 112 which is for connecting the upstream element 140 to pipework. This is possible because of the discrete (non-integral) nature of the inner housing 200 from at least one of the upstream and downstream elements 140, 120 of the outer housing 100. That is, components of the piston do not need to be inserted through the inlet opening 104 or outlet opening 102 during assembly, such that the inlet and outlet openings 104, 102 can be formed by surfaces of the upstream and downstream elements 140, 120 In the prior art this is not possible and it is necessary to use a bush on the surface defining the inlet opening 104 for the piston to engage with so that the inlet opening defined by the outer housing casting is large enough for the piston to fit through. This can create difficulty in that the bush and the upstream element 140 of the outer housing 100 might not form a perfectly flat bearing surface 116.

The actuatable restrictor 300 also comprises the piston rod 320. The piston rod 320 has attached at one of its ends the piston 330. The piston rod 320 is held in a piston rod housing 310 which is itself attached to the inner housing element 200. The piston housing rod 310 is illustrated as being non-integral with the inner housing 200 in the embodiment of Figures 1-3. However, this is not necessarily the case and as in the embodiment of Figures 5-9, the piston rod housing 310 may be formed integrally with the inner housing element 200.

The actuatable restrictor 300 may be mechanically actuated in any way, for example the piston rod 320 can be moved in the axial direction of the valve 1 (i.e.

translated) using an actuator rod 340. The actuator rod 340 has a toothed surface (not visible in the diagrams) which interacts with a toothed surface 322 of the piston rod. When the actuator rod 340 is moved up and down (as illustrated) interaction of the toothed surface of the actuator rod 340 with the toothed surface 322 of the piston rod 320 is effective to translate the piston rod 320 and thereby the piston 330 in the axial direction to actuate the valve 1.

In order for the actuatable restrictor 300 to operate with high fluid pressures and with low actuation forces, both axial end faces of the piston rod 320 and piston 330 (i.e. the main moveable components) must be in fluid communication with fluid on the same side of the valve 1 in all positions of the piston 330 (the upstream side in the embodiments, but equally possible to be the downstream side). In order to achieve this, at least one through- hole is provided in the front downstream axial face of the piston 330 so that fluid passes through the front face of the piston 330. At least one passage (not illustrated) in the inner housing 200 provides communication between an upstream cavity 250 (in which the piston 330 sits in the fully retracted state) and a downstream cavity 240 on the downstream side of the inner housing 200 and in which the upstream axial end of the piston rod 320 is positioned. The upstream internal cavity 250 and downstream internal cavity 240 may be formed in any way including during casting/forging and/or by post casting/forging machining. The at least one passageway can additionally or alternatively be through the piston rod 320, as illustrated in Figure 6.

The piston 330 comprises a piston skirt 332. The piston skirt 332 is tubular and seals against the inner surface of the downstream cavity 240 of the inner housing 200. Seals 333 seal between the upstream cavity 250 and the piston skirt 332. An downstream seal 335 of the piston 330 is a dynamic seal formed between a leading annular end of the piston skirt 332 and a piston cap 337. The piston cap 337 and piston skirt 332 are held together by bolts, for example. The piston cap 335 has through holes in it such that fluid may flow through it. When the dynamic seal 335 abuts against a portion 126 of the downstream element 120 a seal is formed. In this position fluid cannot pass between the inner surface of the downstream element 120 or between the inner housing and the piston skirt 332 (because of seal 333) and cannot pass otherwise through the inner housing 200 (though it may extend through to the upstream cavity 250). Therefore, fluid flow through the valve 1 is blocked.

The piston rod housing 310 has a flange 312 with through holes in it. Bolts 314 are used to attach the piston rod housing 310, via the flange 312, to a portion of the inner housing 200. Seal 315 optionally seals between the piston rod housing 310 and the inner housing 200. The piston rod housing 310 comprises, on an inner surface, axially spaced grooves which hold a seal 317, 318 for sealing against the piston rod 320. The outer surface of the piston rod 320 is thereby sealed against the inner surface of the piston rod housing 310. This prevents fluid from entering between the piston rod 320 and the piston rod housing 310 and thereby escaping the valve 1 through a hole 134 formed in the central element 130 and in which the actuator rod 340 is positioned. The advantage of placing the groove and seal 317, 318 in the inner surface of the piston rod housing 310 rather than on the external surface of the piston rod 320 is that this results in better performance of the seal in terms of improved life and improved seal integrity. In an embodiment the piston rod 320 may be coated with a laser applied hard facing treatment applied before being diamond ground on the surfaces which come into contact with the seals 317, 318, during use. This further increases the seal 317, 318 life and integrity of the seal 317, 318.

Further seals and an actuator rack retaining plate 138 may be provided for ensuring fluid tight integrity and for the actuator rod 340 to bear against.

In order to actuate the restrictor 300, the actuator rod 340 is pushed into the valve 1 or pulled out of the valve 1. This results in the axial movement of the piston rod 320 as described above. As the piston 330 approaches the portion 126 of the downstream element 120 against which the downstream seal 335 of the piston 330 bears, the restriction to fluid flow through the valve increases. When the downstream seal 335 of the piston 330 seals against the portion 126 of the downstream element 120, the valve is closed. Even in the closed position, because of the through holes in the piston cap 335, fluid from the downstream side passes through the piston skirt 332 and into the restrictor internal cavity 240 formed in the inner housing 200. In this way the fluid pressure on the upstream and downstream sides of all components of the piston 330 is the same. Because the upstream cavity 250 is in fluid communication with the downstream cavity 240, the pressures on either side of the piston rod 320 are also equal. As a result, any actuation force required to move the piston rod 320 and piston 330 is relatively low even at very high inlet fluid pressures.

Figure 4 illustrates a throttle cage 400. The throttle cage 400 may be positioned within the valve 1 such that the piston 330 moves axially inside the throttle cage 400. The throttle cage 400 is held in the flow path upstream of the outlet opening 102 and downstream of the inner housing 200. The throttle cage 400 is in the form of a tube. A plurality of axially spaced through holes 410 are present in walls of the tube 400. The fluid flow path is through the through holes 410 in the throttle cage 400. As the piston translates axially in the tube 400 more or fewer of the through holes 410 are covered by the piston skirt 332. As the number of through holes 410 covered by the piston skirt 332 varies, so does the cross-sectional area of the flow path through the throttle cage 400 and therefore the pressure or flow rate drop of fluid through the valve 1. In this way the valve 1 can change the flow rate on a substantially continuous (or even linear) basis and is not just an on/off valve. Such a valve is termed a control valve. The valve is an axial flow control valve. A second valve will now be described. The second valve is the same as the first valve except as described below. Features of one valve may be used in the other valve and vice versa.

In the second valve of Figures 5-9, the outer housing 100 is made of a single piece. For example, the outer housing 100 may be an integrally cast element comprising the upstream element, downstream element and central element of the valve of Figures 1-3. In the valve of Figures 5-9 the outer housing may be comprised of more than one element, for example of an upstream element, a downstream element and a central element as illustrated in Figures 1-3. In the valve of Figures 5-9, the inner housing 200 is discrete from the upstream and downstream elements of the outer housing like in the first valve and is additionally discrete from the central element of the first valve. That is, the inner housing element 200 is separate from or non-integral with the outer housing 100.

The inner housing 200 is attachable or mountable within the outer housing 100. Webs may extend from the inner housing 200 to the opposing inner surface of the outer housing 100 or vice versa. Those webs may contact the opposing surface and optionally may be secured to the opposing surface for example using bolts. In the valve of Figure 5, as most clearly illustrated in Figure 6, webs only exist at a upstream end of the inner housing 200. In Figures 8 and 9 such webs 220, 230 are illustrated at a central portion of the inner housing 200, as well as at the upstream end.

In the valve of Figures 5-9 a connector member 260 is formed at the upstream end of the inner housing 200. Fastening means are used to fix the connector member 260 to the outer housing 100 thereby fix the inner housing 200 in the outer housing 100. The connector member 260 is provided for preventing movement in the axial direction of the inner housing 200 relative to the outer housing 100 and for holding the inner housing 200 in the correct radial position. The connector member 260 is comprised of a plurality of webs extending radially and axially from the inner housing 200 to an outer ring 265. The outer ring 265 is sized to fit in the inlet opening 104 of the outer housing 200. A plurality of locking keys 267 sit in through holes 266 in the outer ring 265 and in grooves formed in the inner surface of the inlet opening 104 of the outer housing 100 (not illustrated).

Locking bolts 269 maintain the locking keys 267 in place.

The inner housing 200 houses the actuatable restrictor 300 like in the first embodiment. The actuatable restrictor 300 comprises a piston 330 and piston rod 320 like in the first embodiment. In the valve illustrated in Figures 5-9, the piston housing is formed as part of (i.e. integral with) the inner housing 200. That is, the piston rod 320 is housed in a cavity within the inner housing 200 and there is no separate piston housing. The actuatable restrictor 300 can be seen as not having a piston housing.

The second valve 1 is manufactured as follows. The outer housing 100 is formed, for example by casting. The outer housing 100 may be formed integrally or may be formed by several elements joined together, for example by bolting. In that case the elements may be forged instead of cast. The inner housing 200 is formed separately to the outer housing 100. The inner housing 200 may be cast or forged. In a preferred embodiment the connector member 260 is formed integrally with the inner housing 200. However, this is not necessarily the case and the connector member 260 may be formed separately from the inner housing before being connected, for example with screw fastenings, to the inner housing 200. The connector member 260 may be formed as a single unit for example by casting or forging or may be assembled from individual separate components.

The inner housing 200 may be machined, polished, defect inspected and/or repaired prior to the actuatable restrictor 300 being installed in/on the inner housing 200. After installation of the actuatable restrictor 300, the actuatable restrictor 300 and inner housing 200 can be inserted through the inlet opening 104 of the outer housing 100 into the outer housing 100. The inner housing 200 may then be connected to the outer housing 100 using the connector member 260 as described above.

Therefore, in the second valve, the connection between the inner housing 200 and the outer housing 100 is inside the inner housing 100. In contrast, in the first valve the connection between the non-integral elements of the valve is outside of the inner housing 200 (namely via the flanges 122, 132, 142). However, both valves offer the advantage that prior to assembly of the valve 1 the inner housing 200 is accessible for machining, polishing, defect detection, repair and installation of the actuatable restrictor 300.

The actuatable restrictor 300 of the second valve differs to that of the first valve in that the piston skirt 332 sits outside of the inner housing 200 and surrounds the inner housing 200. A downstream seal 3321 seals between the piston skirt 332 and the inner housing 200. Grooves are formed on the inner surface of the piston skirt 332 for location of the downstream seals 3321. In this way fluid from the downstream side of the valve 1 which passes through the through holes 3323 in an axial end surface of the piston 330, is prevented from passing between the inner housing 200 and the piston skirt 332. A passageway (not illustrated) may be provided through the inner housing 200 to a upstream end of the piston rod 320 to provide for pressure balancing of the piston rod 320 and/or, as illustrated, a passageway from one axial end of the piston rod 320 to the other may be provided through the piston rod 320 itself. The outer surface of the inner housing 200 against which the seals 3321 bear may be coated in a laser coated Tungsten carbide metal matrix prior to being diamond ground to ensure a good sealing surface.

An downstream seal 3325 to seal against the portion 126 of the inner surface of the outer housing 100 is provided like in the first embodiment.

In the second valve the piston 330 and piston rod 320 are illustrated as being an integral unit, though this is not necessarily the case. The piston 330 and piston rod 320 (and piston rod housing 310) may be the same as in the first embodiment.

In the valve of Figures 5-9, the actuating rod 340 is not translatable but is rotatable. An actuator rack housing 361 is provided in a recess in the outer housing 200. A retaining plate seal 362 and a flange 342 on the actuator rod completes the assembly. A pinion rack 346 held onto the actuator rod engages with a rack (illustrated in Figure 9) on a side of the piston rod 320. A similar mechanism could optionally be used in the first embodiment or the mechanism of the first embodiment could be used in the second embodiment.

The valve is therefore a pressure balanced valve which stops or limits (or alters) the flow of fluid by means of a pressure balanced sealing piston. The valve is internally pressure balanced as described above in the sense that there is no fluid pathway external of the outer housing 100. The pressure balancing is obtained by the outlet fluid pressure (or inlet fluid pressure) operating on two opposite equal areas of the moving components of the restrictor. Such pressure balancing reduces the operating forces even at high inlet pressures.

In the specification where reference is made to one element being integral with another, this can be interpreted as one element being integrally formed with another element.

The separate components of the valves described above are described as being fixed together using screw fastening means such as bolts 150 and 269. This need not be the case however and the components may be (at least partly) held together by welds. The welds may be made by TIG or laser welding or other sorts of welding, for example. In the first embodiment, the flanges 122, 132, 142 may be welded together. In the second valve, the outer ring 265 may be welded to the inside of the inlet opening 104 of the outer housing 200.

The present invention will now be described with reference to Figures 10-13. The valve illustrated in Figures 10-13 is the same as the first valve of Figures 1-3 except as described below. In the valve of Figures 10-13 no central element is provided. Instead, the inner housing 200 is formed integrally with the downstream element 120.

A potential difficulty with the valve design of Figures 1-9 is that because, apart from the piston rod 320, the actuatable restrictor 300 is completely unsupported at a leading portion during transfer from the open position (Figure 10) to the closed position (Figure 11). As a result, small changes in longitudinal axial position of the leading portion of the actuatable restrictor 300 can occur so that the downstream seal 335 of the piston 330 does not perfectly align against portion 126 of the downstream element 120 against which the downstream seal 335 abuts in the closed position. This can lead to undue wear of the downstream seal 335 and/or portion 126 of the downstream element 120 where the seal is formed and/or imperfect formation of a seal. This can result in the fluid flow path through the valve not being blocked by the actuatable restrictor 300 in the closed position.

In the present invention, as illustrated in Figures 10-13, at least one elongate supporting member 1000 is provided. The at least one elongate supporting member 1000 guides the leading portion of the actuatable restrictor 300 as the actuatable restrictor 300 moves from the open position (Figures 10 and 12) to the closed position (Figures 11 and 13).

The at least one elongate supporting member 1000 is mounted for translation relative to the actuatable restrictor 330. That is, the elongate supporting member 1000 stays substantially stationary relative to the remainder of the valve 1 as the actuatable restrictor 300 translates from the open position (Figures 10 and 12) to the closed position (Figures 11 and 13). In this way the leading portion of the actuatable restrictor 300 is supported even when the piston skirt 332 extends a long way out of the inner housing 200. Although the interaction of the piston skirt 332 and the inner housing 200 through the seal 333 provides some support for the trailing portion of the actuatable restrictor 300 as the actuatable restrictor 300 moves from the open position to the closed position, this does not prevent all movement of the leading portion of the actuatable restrictor 300 away from alignment with the axis of the piston rod housing 310. This function is provided by the at least one elongate supporting member 1000 of the present invention.

As can be seen from all of Figures 10-13, a plurality of elongate supporting members 1000 are envisaged. The elongate supporting members 1000 are spaced around a longitudinal axis of the actuatable restrictor 300 (the central axis along which the actuatable restrictor 300 moves between the open and closed positions). By spacing the elongate supporting members 1000 around the longitudinal axis, deflection of the actuatable restrictor 300 in any direction out of the longitudinal axis can be restricted in a balanced way. In the case of the embodiment of Figures 10 and 11 it may not be necessary to provide more than one elongate supporting member in order to provide the guiding effect, but in the embodiment of Figures 12 and 13 it may be necessary to provide more than one elongate supporting members 1000 in order to prevent movement away from the longitudinal axis in all directions assuming the elongate supporting members 1000 each do not extend around a significant portion of the longitudinal axis. It may be necessary to provide at least three elongate supporting members 1000, though even with only one elongate supporting member 1000 some benefit will be present.

The elongate supporting members 1000 are positioned inside the piston skirt 332. This is convenient as they do not then intrude into the fluid flow path of the valve and thereby increase pressure drop across the valve.

As can be seen from Figures 10 and 12, in the open position the at least one elongate supporting member 1000 extends through a front (as seen during movement from the open position to the closed position) of the actuatable restrictor 300. This means that the elongate supporting members 1000 are able to extend further in the axial direction away from the the actuator rod 340 than the inner housing 200 and thereby support the leading portion of the actuatable restrictor for the whole of the distance from the open position (Figures 10 and 12) to the closed position (Figures 11 and 13).

In the embodiment illustrated in Figures 10 and 11, the at least one elongate supporting members 1000 extend through the front of the actuatable restrictor 300 in the closed position (see Figure 11). This ensures that the at least one elongate supporting members 1000 guide the leading portion of the actuatable restrictor even at the end of its stroke, in the closed position. Thus, alignment between the downstream seal 335 and the portion 126 of the downstream housing element 120 are very well aligned as the downstream seal 335 comes into contact with the portion 126 in the closed position. Also, this arrangement allows for easy supporting of the elongate supporting members 1000 at their ends furthest from the inner housing 200.

In the embodiments of Figures 10-12, the elongate supporting members 1000 are attached to the piston rod housing 310 or are part of the piston rod housing 310. This is achieved either by connecting the at least one elongate supporting members 1000 to the piston housing flange 312 or forming them integrally with the piston housing flange 312. In this way the elongate supporting members 1000 are mounted stationary relative to the outer housing 100 via the piston rod housing 310 and the inner housing 200. In an alternative embodiment the at least one elongate supporting member 1000 may be mounted directly to the inner housing 200 rather than to the inner housing 200 via the piston rod housing 310.

Referring now to the embodiment of Figures 10 and 11, the elongate supporting members 1000 have a constant cross section throughout their length, along which the piston cap 337 travels. Through holes 338 are provided in the piston cap 337 through which the elongate supporting members 1000 pass. The through holes 338 may be in a low friction bearing 339 of the piston cap 337. By contact between the at least one elongate supporting member 1000 and the piston cap 337 (for example with the low friction bearing 339), the elongate supporting member 1000 guides the leading portion of the actuatable restrictor 300 throughout its motion from the open position (Figure 10) to the closed position (Figure 11).

The elongate supporting members 1000 are supported at both ends, thereby to increase strength and stiffness of the elongate supporting members 1000.

The way in which the elongate supporting members are supported at a front end

(with respect to the direction of travel of the actuatable restrictor 300 from the open position to the closed position) will now be described. At least one vane 1012 extends from the outer housing 100 to the elongate supporting member 1000. In the illustrated embodiment, two vanes 1012 are illustrated as extending between each elongate supporting member 1000 and the outer housing 100. The vanes are separated slightly so as to form a V shape and thereby improve the stiffness of the support provided to the end of the elongate supporting member 1000. The vanes 1210 are attached at the other end to a vane ring 1010. The vane ring 1010 is located into the outlet 102 of the downstream element 120. A bolt 1013 through a vane ring provided at an end of each of the pair of vanes 1020 and into an end of the elongate supporting member 1000 connects the vanes 1020 to the elongate supporting member 1000. In this way the at least one elongate supporting member 1000 is secured at both ends to the outer housing 100.

The alternative embodiment illustrated in Figures 12 and 13 will now be described. In the embodiment of Figures 12 and 13 each of the elongate supporting members 1000 is only attached at one end to the outer housing 100. As previously described, in the embodiments of Figures 12 and 13 the elongate supporting members 1000 are attached to the outer housing 100 via the inner housing element 200 and the piston rod housing 310.

The elongate supporting members 1000 of the Figures 12 and 13 embodiments are tapered along their length. This is not necessary but is preferable as it provides improved stiffness along the length of each elongate supporting member 1000 whilst reducing the amount of material required for each elongate supporting member 1000. Although the piston cap 337 is provided with through holes 338 through which the elongate supporting members 1000 protrude in the closed position, no contact between the elongate supporting members 1000 and the piston cap 337 is necessary. However, in an embodiment there may be contact between an inner surface of the piston cap 337 defining the through hole 338 and a radially inwardly facing surface of the elongate supporting members 1000.

The main guiding is achieved in the embodiment of Figures 12 and 13 by the provision of a guide ring 1020. The guide ring 1020 is axially mounted on the piston rod 320 behind the piston cap 337. Each of the elongate supporting members 1000 interacts with the guide ring 1020. That is, the outer surface of the guide ring 1020 engages with a radially inwardly facing surface of each of the elongate supporting members 1000. The interaction of the elongate supporting members 1000 with the guide ring 1020 is effective to guide the leading portion of the actuatable restrictor 300 as it traverses from the open position to the closed position.

As can be seen in Figure 13, in the open position the elongate supporting members 1000 do not protrude through the piston cap 337 as there is no need for them to do so. Instead, in the closed position, the ends of the elongate supporting members 1000 are engaged with the guide ring 1020. In the embodiment of Figures 12 and 13 the guide ring 1020 may be made of a low friction bearing material.

In either embodiment the elongate supporting members 1000 may be made of metal or of a low friction material, such as PTFE or my be made of metal or similar structural material and coated with PTFE to ensure smooth opening and closing of the actuator member 300 despite interaction and sliding motion between the elongate supporting members 1000 and parts of the actuatable restrictor 300.