The present invention relates to valves and is particularly concerned with locating and biasing valve bodies within their housings.

Valves are used in many different applications across a broad range of industries. A common use is within fluid conduits in which a valve can be used to open or close the conduit to fluid flow through the conduit. Other types of valve can regulate the fluid flow by changing the degree to which the conduit is open. Another type of valve can switch a fluid flow from an inlet conduit to one of two outlet conduits. Similarly, multi-way valves can switch between multiple fluid paths.

There are many different types of valve configuration dependent on the application requirements, for example fluid pressure, temperature, space. A typical fluid flow valve 10 is shown in Figure 1 comprising a fluid conduit 12, for example a hollow cylinder, with an incoming fluid flow 14. The conduit 12 includes a valve seat 16 in the form of a flange or projection extending radially inwardly of the conduit walls and with an aperture 18 to allow, in an open configuration of the valve 10, an outgoing fluid flow 20 through a downstream portion of the conduit 12. Between the upstream and downstream portions of the conduit 12 is a valve body 22 in the form of a solid cylinder of smaller diameter than the conduit 12. The valve body 22 is spaced from the walls of the conduit 12 and located in relation to them by spacers 24, which also act as sliding guides during operation of the valve 10.

The valve body 22 is moveable, by any suitable actuating means (not shown) such as a spring or hydraulic piston, between a first configuration shown in solid lines and a second configuration shown in broken lines. In the first configuration the valve body 22 is spaced apart from the valve seat 16 and fluid is able to flow through the aperture 18 substantially unrestricted. In the second configuration the valve body 22 abuts the valve seat 16 to close the fluid conduit 12 to fluid flow. An end stop (not shown) may be provided to locate the valve body 22 in the first configuration.

One disadvantage of using spacers 24 to space the valve body 22 from and locate it with respect to the walls of the conduit 12, and to act as sliding guides is that there is a sliding joint between the spacers 24 and the valve body 22. Any sliding joint is a source of wear and friction, which reduces the life of the components. There are also associated problems such as slower operation, particularly as the components wear, higher manufacturing costs and a requirement for more wear resistant materials to slow the wearing process. Alternative spacers 24, for example springs, can suffer from fatigue. Any spacer 24 is prone to dirt ingress which damages the spacer 24 or valve body 22 and can prevent the components from sliding as designed. Some spacers 24 are not suitable for applications at high temperatures or under high pressures.

The present invention seeks to provide an apparatus to space a valve body from the conduit that seeks to address the aforementioned problems.

Accordingly the present invention provides a valve arrangement comprising an internal member and an external member that are relatively moveable characterised in that at least part of an external surface of the internal member and at least part of an internal surface of the external member comprise means to generate a magnetic field, thereby generating a mutually repulsive force to maintain a desired radial spacing between the internal member and the external member. This obviates the need for spacing and sliding guides that wear against the moving member and slow its movement.

Preferably the external surface of the internal member and the internal surface of the external member each comprise at least two axially spaced magnetic portions, the magnetic portions being arranged to generate a mutually repulsive force between the internal member and the external member, the magnetic portions being further arranged such that there is an axial offset between at least one of a first magnetic portion of the internal member and a first magnetic portion of the external member and

a second magnetic portion of the internal member and a second magnetic portion of the external member,

to provide an axial bias to the valve arrangement.

Preferably the magnetic portions are further arranged such that the first magnetic portion of the internal member is axially aligned with the first magnetic portion of the external member and the second magnetic portion of the internal member is axially offset from the second magnetic portion of the external member to provide an axial bias to the valve arrangement.

Preferably at least one of the internal and external members is cylindrical. This enables an entirely symmetrical magnetic field to be generated.

Preferably the entire external surface of the internal member comprises means to generate a magnetic field. More preferably the entire internal surface of the external member comprises means to generate a magnetic field. This provides a centring function for the internal member. Alternatively only portions of the external surface of the internal member and / or the internal surface of the external member comprise means to generate the magnetic field.

Preferably the internal member is a valve body and the external member is a housing. More preferably the internal member is moveable and the external member is fixed. Alternatively the internal member is fixed and the external member is moveable.

The means to generate a magnetic field may comprise at least one permanent magnet, at least one electromagnet or at least one Halbach array. The valve arrangement may be arranged to provide a fluid to at least one component of a gas turbine engine.

The valve arrangement may comprise actuation means. Preferably this is one of the group comprising mechanical, pneumatic, hydraulic and magnetic actuation means. More preferably the magnetic actuation means comprises one or more of the group comprising a ferromagnet, a permanent magnet and an electromagnet. Use of magnetic actuation means that both centring / spacing and actuation is accomplished using magnets and no extra components are required within the flow path through the valve arrangement.

The valve arrangement may comprise an end stop. This prevents the valve body moving too far when actuated and is normally situated at the opposite axial end to a valve seat.

The present invention will be more fully described by way of example with reference to the accompanying drawings, in which:

Figure 1 is a schematic view of a valve according to the prior art;

Figure 2 is a schematic view of a radially stable valve in the first configuration according to the present invention;

Figure 3 is a schematic view of a first embodiment of a radially and axially stable valve according to the present invention;

Figure 4 is a schematic view of the valve of Figure 3 coupled to magnetic actuation means; and

Figure 5 is a schematic view of a second embodiment of a radially and axially stable valve according to the present invention. An exemplary embodiment of the present invention is shown in Figure 2, in which a valve arrangement 10 is shown that is similar to the prior art arrangement shown in Figure 1. For the purposes of clarity the valve body 22 is shown in the first configuration only, although it is to be understood that the valve body 22 can be moved by any suitable actuating means (not shown) to the second configuration in which it abuts the valve seat 16 to prevent fluid flow through the aperture 18 and thence into the downstream portion of the fluid conduit 12. There are no spacers 24 in the arrangement of the present invention. Instead, spacing and centring of the valve body 22 is achieved by repelling magnetic flux. It will be understood that the movement of the valve body 22 is axial, as indicated by the orientation arrows in Figure 2, and the components are substantially symmetrical about this axis unless otherwise specified. The conduit or housing 12 is radially outside the valve body 22.

The external surface of the valve body 22 is magnetised to alternate north and south polarity, known as a Halbach array. A Halbach array is an arrangement of permanent magnets that augments the magnetic field on one side whilst cancelling the field on the other side to produce a one-sided flux. This arrangement can be rolled into a "Halbach cylinder" and thus provide a valve body 22 with no internal magnetic field and / or a housing 12 with no magnetic field on its external surface. Beneficially, such a cylinder has a spatially alternating magnetic polarity along its axial length. The internal surface of the conduit or housing 12 is also magnetised to a matching Halbach array. Thus, the magnetic flux generated by the two surfaces repels one another. Since in the preferred embodiment of the valve arrangement 10 both the valve body 22 and the conduit or housing 12 are cylindrical, this means that the magnetic repulsion force is equal in all directions and therefore the valve body 22 rests in a radially stable equilibrium position that is concentric with the conduit 12. Any radial movement of the valve body 22, for example caused by fluid eddies or uneven pressure, will be corrected by the magnetic repulsion force. This arrangement is beneficial over the prior art arrangement since it removes the requirement for mechanical spacing and location means, and the resultant wear problems. It also removes the spacers 24 from the fluid flow path around the valve body 22 meaning that there is less obstruction to the flow than in the prior art arrangement.

Although the conduit or housing 12 and the valve body 22 are preferably cylindrical, other complementary shapes are susceptible to application of the present invention. For example, conduit or housing 12 and the valve body 22 may resemble, in cross- section, concentric squares, oblongs, triangles or any regular polygon. Regular shapes are preferred, as are identical but scaled shapes, to maximise the stability of the valve body 22 to disturbances within the conduit or housing 12. The magnetic repulsion force ensures that the valve body 22 and conduit or housing 12 remain substantially coaxial with a concentric cross-sectional profile.

It is not necessary for the whole of the external surface of the valve body 22 to be magnetised, nor the corresponding portion of the conduit or housing 12. Indeed, it is preferably for only portions of the surface of the valve body 22 and of the conduit 12 to be magnetised as a Halbach array. To retain the radial stability of the valve body 22 within the conduit 12 it is preferable that the magnetised sections extend around the entire circumference of the valve body 22 to form rings and form a similar pattern on the surface of the conduit 12.

Although the arrangement described with respect to Figure 2 is radially stable, it is not axially stable. A slight perturbation in the axial direction alters the flux paths sufficiently to propel the valve body 22 axially until it reaches an obstruction (valve seat 16 or end stop) or the minimum flux energy position is reached. Therefore, the principle illustrated by this arrangement is extended to provide a valve having both radial and axial positional stability. Figure 3 shows an axially and radially stable arrangement of the valve 10. The external surface of the valve body 22 comprises a pair of magnetised portions, axially upstream portion 22a and axially downstream portion 22c, with a non-magnetic section 22b therebetween. Similarly the conduit or housing 12 comprises axially upstream and downstream magnetised sections 12a, 12c with a non-magnetic portion 12b therebetween. The portions are so arranged that in a first configuration the axially upstream magnetic portion 22a of the valve body 22 is axially aligned with the axially upstream magnetic portion 12a of the conduit or housing 12 but the axially downstream magnetic portions 22c, 12c are axially offset. The valve body 22 may be held in this position by any suitable actuation means (not shown). Similarly, when the valve body 22 is released by the actuation means, the axial offset creates a force in the axially downstream direction that moves the valve body 22 into a second configuration. In the second configuration, both the axially upstream and downstream magnetic portions 22a, 12a, 22c, 12c are offset. The non-magnetic portions 22b, 12b must be of sufficient axial length to prevent magnetic attraction or repulsion between the axially upstream magnetic portion 22a of the valve body 22 and the axially downstream magnetic portion 12c of the conduit 12 or vice versa. Thus the axial offset biases the valve 10 to its closed position, although the offset may be reversed to bias the valve 10 to its open position. The actuation means therefore acts against the magnetic bias to move the valve body 22.

The provision of magnetised surfaces around the entire circumference of the conduit 12 and the valve body 22 provides the centring function described with respect to Figure 2. Thus there is no need for additional spacers 24 as in the prior art and hence, there is no opportunity for friction and wear of the sliding components. Instead, the valve body 22 moves in a contactless way, until abutting the valve seat 16 or an end stop (not shown), which enables quicker action than is possible in an arrangement with contact between moving parts. The arrangement shown in Figure 3 can be coupled with magnetic, rather than mechanical, actuation. This is achieved by providing an extension of the valve body 22, at either end or in the central portion 22b for the actuation arrangement 28. An embodiment of the present invention coupled with magnetic actuation 28 is shown in Figure 4, in which an extension portion 22d of the valve body 22 is provided towards the valve seat 16. The extension portion 22d of the valve body 22 comprises a ferromagnetic material having its Curie point temperature set such that the valve 10 is required to be in one configuration above that temperature and in the other configuration below it. As illustrated, the valve 10 is closed above the Curie temperature and open below it, but this can be reversed if required. The actuation arrangement 28 is such that it is the temperature of the fluid flowing through the conduit 12 that actuates the valve 10 but other arrangements are possible wherein the valve 10 is actuated by the temperature of another fluid or of a component to which it is thermally coupled. It may be necessary to provide one or more bleed passages to allow a small amount of fluid to flow when the valve 10 is closed so that the ferromagnetic material is located in flowing, not static, fluid. This improves the thermal sensitivity.

The extension portion 12d of the conduit 12 surrounding and offset from the ferromagnetic valve body extension portion 22d comprises a permanent magnet or an electromagnet 30. Thus, when the fluid flow 14 through the conduit 12 is relatively cool, the ferromagnetic extension portion 22d is below its Curie temperature and is magnetic. There is, therefore, a magnetic attraction force between the ferromagnetic extension portion 22d and the permanent magnet or electromagnet 30, which acts to open the valve 10. When the fluid temperature rises sufficiently to heat the ferromagnetic extension portion 22d above its Curie temperature, the extension portion 22d loses its magnetism and there is, therefore, no attraction to the permanent or electromagnet 30. Hence, the biasing axial offset described with respect to Figure 3 acts to close the valve 10 to fluid flow therethrough. Alternatively, the valve body extension portion 22d may be a permanent magnet or electromagnet and the extension portion 12d of the conduit or housing 12 may comprise a ferromagnetic material. Figure 5 shows an alternative embodiment of the bi-stable valve arrangement 10 and has similarities to Figure 3. The valve seat 16 is located intermediate the upstream and downstream ends of the valve body 22 so that the arrangement resembles a shuttle valve. There is an annular flange or member 26 extending radially outwardly from the surface of the valve body 22 which is located so as to be spaced from the valve seat 16 in the first configuration of the valve 10 and to abut the valve seat 16 in the second configuration of the valve 10. It is also to be noted that the valve body 22 has a smaller diameter than the diameter of the aperture 18 and so the valve body 22 extends through the aperture 18. As previously, any suitable actuation means may be used in conjunction with the valve 10 including mechanical, pneumatic, hydraulic and magnetic means (ferromagnetic or electromagnetic).

It will be apparent to the skilled reader that other modifications can be made to the described embodiments without diverging from the inventive concept of the present invention. For example, the valve components can be arranged to provide a bi-stable valve that has a single downstream, outlet flow 20 but two alternative inlet flows dependent on the configuration of the valve body 22. Alternatively, there may be a single upstream flow 14 and two outlet flows, which outlet receives the fluid flow being controlled by the configuration of the valve body 22.

In preferred embodiments of the present invention, magnets provide both the spacing and centring function. However, partial benefits may be obtained by using one of these functions without the other. More preferably, magnetic actuation is also used.

Although the valve arrangement 10 has been described with a fixed or static housing 12 and a moveable inner valve body 22 the benefits of the present invention are equally obtainable by reversing this arrangement. Thus, there would be a fixed central body and a moveable surrounding body. The valve seat 16 may be attached to or extend from the fixed central body. In a variation to the embodiment shown in Figure 5, the flange 26 may advantageously be attached to or extend from the moveable body and the valve seat 16 be attached to or extend from the fixed body. Although the axially stabilising magnets have been described having one set of offset magnetic portions and one set axially aligned, the same benefits are accrued, with a potentially greater force, by providing both sets of magnetic portions being axially offset in the same direction.

Valves as described herein have many applications across a range of industries including aerospace, automotive and chemical plants. For example, they may be used to provide cooling fluid to one or more components of an aero, marine or land-based gas turbine engine, e.g. a turbine blade, turbine vane or combustor. Alternatively, they may be used to provide, selectively, a heating fluid to one or more components, for example to prevent icing or to warm a gas turbine engine or vehicle engine before starting on a cold day. Heating fluid may be provided to e.g. a compressor vane, a compressor blade, an engine nosecone or a nacelle. Alternatively, the valve 10 may be used to control flow of lubricant in a gas turbine engine or other engine.

Although the valve body 22 has been described as solid it may equally be hollow to allow the fluid to flow therethrough, with consequent alteration of the valve seat 16. The absolute arrangement of the magnetic polarities is not critical provided that the relative polarities are as described herein to produce the desired magnetic field and flux patterns.

Either or both of the valve body 22 and the conduit or housing 12 may be coated with a protective layer to enable use of the valve 10 in a hostile environment, e.g. high temperature or chemically corrosive.

Partial benefits of the present invention may be obtained by utilising the magnetic centring as described with respect to Figure 2 but providing the location functionality via pins or other means that are well known in the art. This is less preferable since it reintroduces components that can wear against each other during use. Although the magnetic portions 22a, 22c, 12a, 12c have been described as on the surfaces of the valve body 22 or housing 12 the same effects can be obtained by embedding the magnetic portions within the walls of these components. The requirement being that an equivalent magnetic field is produced to that described above.