Patent Description:
In fluid flow systems such as pipes and conduits, e.g. as can be found in many different industrial situations such as the oil and gas industry, there is a need to control the flow of fluid in a fluid flow stream through the conduit. Devices such as fluid flow control valves and pressure regulators may be used to control or regulate the fluid flow or pressure through the conduit. Such devices may deliver a desired flow rate, or an upstream or downstream pressure, and thus may be controllable in a range between a fully open and fully closed position. Alternatively, such devices may simply act as shut-off valves, being moved between a fully open and fully closed position.

The valve member, the moving part in such valves which is controlled to open and close the valve, is typically actuated by an external mechanical actuator via a stem that protrudes through the valve body and is mechanically coupled to the valve member. However, this mechanical coupling is a potential point of weakness for the valve. Such couplings suffer from failures in, for example, the gearbox or linkage between the valve stem and the valve closure member, the gearbox or linkages within the external actuator, the stem packing that seals against the stem, etc.. Such failures can lead to the valve failing to operate or leakage of the fluid flowing in the conduit from the valve. In the oil and gas industry, in particular, leakage of oil or gas is to be avoided as this can be extremely costly, both environmentally and financially.

It is an object of the invention to provide an improved device for controlling the flow of a fluid through a conduit.

<CIT> discloses a prefabricated high-pressure flow control device according to the preamble of claim <NUM>, the device comprising an inflow housing, an outflow housing, and a flow rate control housing.

<CIT> discloses a fluid lift valve with a worm gear and a threaded spindle, wherein the worm gear has openings for the fluid flow.

<CIT> discloses an in-line control valve including a piston-type valve assembly and a plurality of control chambers controlled by one or more control ports.

<NPL>) discloses a 3D position sensor for sensing a magnet moving in its surrounding through the measurement and processing of the three spatial components of the magnetic flux density vector.

When viewed from a first aspect the invention provides a device as claimed in claim <NUM>.

The present invention provides a device for controlling (e.g. acting to open or shut off) the flow of fluid through a conduit (e.g. in which the device is placed). The flow of fluid through the device is controlled between an upstream side of the device and a downstream side of the device. The device is made up of three main parts, which are formed separately as discrete components: an upstream valve casing, a downstream valve casing and a valve core. These three parts are assembled and secured together to form the device.

The upstream casing defines an (upstream) inlet into the device through which fluid enters the device and the downstream casing defines a (downstream) outlet aperture through which fluid exits the device. The upstream valve casing, the downstream valve casing and the valve core thus together (when assembled) form a flow path through the device from the upstream side to the downstream side.

The flow of fluid through the outlet aperture, and thus through the device from the upstream side to the downstream side, is controlled by a valve member that is movably mounted on a housing that is formed as part of the valve core. The valve member is arranged in the device upstream of the outlet aperture (and thus preferably the housing is also arranged upstream of the outlet aperture) and the valve member is arranged to move reciprocally on the housing of the valve core to selectively open and close the outlet aperture.

The valve member is the movable part of the valve and comprises a closure member which may be arranged to engage with the outlet aperture. The valve member may comprise a piston head that is acted on by the fluid pressure in the control volume. In this arrangement, preferably the closure member and the piston head are kinematically linked (e.g. connected) by a piston shaft (e.g. which are integrally formed together as the valve member).

The housing (e.g. together with the valve member) defines a control volume. A fluid pressure is introduced into the control volume through an input line defined in the valve core (e.g. from a fluid pressure source external to the device). The control volume fluid pressure acts on (e.g. a piston head of) the valve member, so that its movement (and thus position) is controlled by the fluid pressure.

Thus it will be appreciated that the device (e.g. control valve) of the present invention provides a fluid flow control device, the main structural (e.g. static) components of which are three (primary) discrete components: the upstream and downstream casings and the valve core. Such a split piece design is easier to assemble because, in at least preferred embodiments of the present invention, the valve member can be assembled to mount it on the housing of the valve core before the valve core is secured to the upstream and downstream casings (which then surround the valve core and valve member). This contrasts to a conventional design with an integrally cast body in which the upstream and downstream casings and the valve core are formed as one part which, in addition to making it complicated to manufacture, means that the valve member has to be mounted "blind" inside the integrally cast body. This imposes deleterious constraints on such conventional devices. A split piece design therefore gives much greater design freedom to the device as a whole and makes it easier to manufacture and maintain.

In addition to the split piece design, the valve member is actuated using a control fluid, rather than conventional mechanically actuated devices that use mechanical linkages that extend through the valve housing, core and/or casing to an external actuator. Providing a fluid flow control device that does not rely on an external mechanical input simplifies the device owing, in at least preferred embodiments, to the lack of mechanical linkages and gearings. This results in fewer ways in which the device may fail.

Furthermore, using a fluid pressure to control the valve member, and removing the need for a mechanical linkage, helps to reduce the overall size of the fluid flow control system and its weight, and to reduce the likelihood of any fluid (e.g. oil or gas) leakages from the conduit (e.g. a pipe), owing to the lack of a fluid path out of the device via any mechanical linkages. This is very important in the oil and gas industry where it is imperative to prevent leaks.

Using a fluid pressure to control the valve member also helps to provide a fast acting, and thus responsive, fluid flow control device, and may allow higher forces to be applied to the valve member.

The device may be suitable to be used in any type of fluid flow system, and thus may be configured to be installed in any suitable and desired type of conduit. For example, the device may be used in a conduit (e.g. pipeline) for conveying air, water, oil, gas, chemical fluids, etc.. Thus the device may be configured to control the flow of air, water, oil, gas, chemical fluids, etc., therethrough.

The device and the components thereof may be arranged in any suitable and desired way. In a preferred embodiment the device comprises an axial flow device. Thus preferably the inlet, the valve member and the outlet aperture (and preferably also the housing) are arranged coaxially with respect to each other about an axis. In a preferred embodiment the inlet, the valve member and the outlet aperture (and preferably also the housing) are substantially rotationally symmetric about the axis. Preferably the axis extends in a direction collinearly with the general (e.g. average) direction of fluid flow through the outlet aperture.

Preferably the axis of the device is parallel to, e.g. collinear with, the axis of the conduit (e.g. pipe) in which the device is arranged. It will be appreciated that this arrangement allows the device to be easily fitted within an existing pipe, e.g. inserted inside a pipe at a flange or even in a continuous section of pipework, as the largest dimension of the device is likely to be in that in which the valve member moves. Therefore, no additional space may be required to house the device and it can be retro-fitted rapidly and at low cost in most sections of pipework or at most pipe joints without any significant alteration in the pipework. This contrasts to conventional devices with large mechanical control linkages that may require the pipework layout to be redesigned for the new flow control equipment to be incorporated.

Devices in accordance the present invention can therefore significantly reduce the cost and work required to incorporate them into an existing system. The arrangements mentioned above, in particular, as well as other embodiments, also allow devices in accordance with the present invention to facilitate very high mass flows for a given conduit diameter and pressure compared to conventional mechanically actuated axial flow devices. This creates a very flexible device which can be used for many different applications.

The upstream casing preferably comprises a flange for mounting to a conduit, e.g. using a flange bolt circle. Preferably the upstream casing comprises a flange for mounting to the valve core, e.g. using a flange bolt circle. Preferably the flange(s) extend radially from the upstream casing. Preferably the inner dimension (e.g. diameter) of the upstream casing at the flange for mounting to the valve core is greater than the inner dimension (e.g. diameter) of the upstream casing at the flange for mounting to the conduit.

The downstream casing preferably comprises a flange for mounting to a conduit, e.g. using a flange bolt circle. Preferably the downstream casing comprises a flange for mounting to the valve core, e.g. using a flange bolt circle. Preferably the flange(s) extend radially from the downstream casing. Preferably the inner dimension (e.g. diameter) of the downstream casing at the flange for mounting to the valve core is greater than the inner dimension (e.g. diameter) of the downstream casing at the flange for mounting to the conduit.

The valve core preferably comprises flanges for mounting to and securing between the upstream and downstream casings, e.g. using a flange bolt circle. Thus, for example, the valve core, comprising the housing with the valve member mounted thereon, is sandwiched between the upstream and downstream casings of the device. Preferably the flange(s) extend radially from the valve core.

The upstream valve casing, the downstream valve casing and the valve core are (each) formed as discrete parts. Thus preferably the device is manufactured in its separate component parts (i.e. the upstream valve casing, the downstream valve casing and the valve core, etc.) and then the device is assembled from these discrete parts. Preferably, when assembling the device, first the valve member is mounted on the housing, and then the downstream valve casing (and preferably also the upstream valve casing) are connected and secured to the valve core, thus surrounding the valve core, housing and valve member.

Preferably each of the upstream valve casing and the downstream valve casing are integrally formed. Thus preferably the rim of the upstream valve casing forming the inlet of the upstream valve casing is integrally formed with the rest of the upstream valve casing (and not an insert which is attached as a separate part thereto). Preferably the rim of the downstream valve casing forming the outlet aperture of the downstream valve casing is integrally formed with the rest of the downstream valve casing (and not an insert which is attached as a separate part thereto).

Preferably the dimension (e.g. diameter) of the outlet aperture (e.g. in a radial direction perpendicular to the main axis of the device (and the outlet aperture) is less than the (e.g. maximum) corresponding dimension (e.g. diameter) of the valve housing (e.g. in a radial direction perpendicular to the main axis of the device (and to the valve member)). Such an arrangement in which the valve housing is larger than the outlet aperture (particularly in a device in which the outlet aperture is an integral part of the downstream valve casing) means that while the valve housing may have to be assembled (and, e.g. the valve member mounted on the housing) prior to the downstream valve casing being attached to the valve core (e.g. because the valve housing and, e.g. valve member, may be too large to be inserted and assembled through the outlet aperture), the valve housing (and, e.g., valve member) may be able to have a larger (relative) size than in conventional devices, thus helping the device to allow a greater flow capacity (e.g. for a device of a particular size) than conventional devices.

The housing may be formed in any suitable and desired way as part of the valve core. In some embodiments, at least part (e.g. all) of the housing is integrally formed with the rest of the valve core (e.g. with the part of the valve core in which the fluid input line is defined and which is secured between (e.g. contacts) the upstream and downstream casings). In some embodiments, at least part (e.g. all) of the housing is formed as a separate part from the rest of the valve core and is attached thereto. Preferably, at least part of the part of the housing defining the (e.g. upstream side of the) control volume may be formed as a separate part from the rest of the valve core and attached to the rest of the (e.g. housing of the) valve core to form the control volume. This may allow access to assemble the valve member in the housing and then to attach this part (e.g. upstream side) of the housing to enclose the control volume.

The fluid pressure in the control volume acts on the valve member. Preferably the fluid pressure in the control volume acts directly on the valve member. Thus preferably (e.g. a face of) the valve member defines (e.g. a wall of) the control volume together with the housing. Preferably the valve member comprises a piston head that is arranged to move within the control volume. Preferably the fluid pressure acts on (e.g. a face of) the piston head. Preferably (e.g. a face of) the piston head defines (e.g. a wall of) the control volume together with the housing.

The device may comprise a piston liner, arranged around (e.g. the piston head of) the valve member. The piston liner may define (e.g. a boundary of) the control volume. The piston liner may be mounted on the housing. It may be mounted on the valve member. The piston liner may be arranged (e.g. radially) between the (e.g. piston head of the) valve member and the housing. The piston liner may comprise a hollow sleeve. The (e.g. piston head of the) valve member may be arranged to move longitudinally within the piston liner.

Preferably the piston liner and the housing are discrete components. Providing a separate piston liner may help to reduce the complexity of manufacturing. The piston liner may at least partially define the control volume. If the control volume is defined by the piston liner, rather than the housing, then it is possible that the housing may be manufactured to a lower tolerance, thus helping to reduce manufacturing time and costs.

The piston liner may be replaceably mounted. This means that the piston liner can be removed and replaced if it becomes worn or damaged, which can increase the service life of the device.

The valve member, which is movably mounted on the housing and positioned on the upstream side of the outlet aperture, may be arranged in the device in any suitable and desired way in which it achieves its purpose of moving in a reciprocal manner to open and close the outlet aperture, to thereby control flow of the fluid through the outlet aperture. As the valve member is positioned on the upstream side of the outlet aperture and mounted on the housing, preferably the housing is also positioned on the upstream side of the outlet aperture.

In a preferred embodiment the valve member is mounted (e.g. coaxially) on the inside of the housing. Thus preferably the valve member is arranged to move (e.g. axially) out from the housing towards the outlet aperture to close the outlet aperture and arranged to move (e.g. axially) into the housing towards the outlet aperture to open the outlet aperture.

Preferably the valve member is arranged to be movably mounted such that it comes into contact with the downstream casing (e.g. the rim of the outlet aperture) to close the outlet aperture. The valve member comprises a closure member that is attached to the piston of the valve member.

Preferably the closure member is cylindrical, e.g. with a circular cross section, and, e.g., having an axis of symmetry (along which the cross-sectional shape of the cylinder is projected and the closure member moves) along the main axis of the device. Thus preferably the closure member comprises a cylindrical sleeve mounted on the housing of the valve core and attached to the rest of the valve member. As above, preferably the dimension (e.g. diameter) of the outlet aperture (e.g. in a radial direction perpendicular to the main axis of the device (and the outlet aperture) is less than the (e.g. maximum) corresponding dimension (e.g. diameter) of the valve housing (e.g. in a radial direction perpendicular to the main axis of the device (and the valve housing).

Preferably the closure member engages with the downstream casing around an annulus at the distal (downstream) end of the closure member. Thus preferably the closure member comprises a (e.g. annular) seal at (e.g. around) the distal (downstream) end of the closure member, for sealing against the downstream casing. The downstream casing may comprise a (e.g. hardened metal) detachable rim against which the closure member is arranged to engage (and thus seal against). In this embodiment the closure member engages with and seals against the detachable rim rather than the main body of the downstream casing. Providing a detachable rim as an insert for the valve seat enables a different (e.g. hardened) material to be provided which is more suitable for such a high wear region and also allows the detachable rim to be removed and replaced, when necessary.

Preferably the closure member comprises an end face at the distal (downstream) end of the closure member. Preferably the end face is substantially perpendicular to the axis of symmetry of the closure member (e.g. lies in the radial direction of the device). Preferably the closure member is attached to the rest of the valve member (e.g. to the piston of the valve member) via the end face of the closure member.

Preferably the end face of the closure member comprises one or more apertures formed therein to allow fluid in the conduit (e.g. from the downstream side) to pass therethrough (e.g. into the housing but preferably not through to the upstream side of the device). This helps to pressure balance the valve member, e.g. so that the upstream pressure in the conduit does not apply any significant opening or closing forces on the closure member and valve member, and does not, in at least some embodiments, act to apply any forces on the valve member when there are changes in the upstream pressure in the conduit. As will be discussed below, the aperture(s) formed in the end face of the closure member also allows the downstream pressure in the conduit to act on the (e.g. piston head of the) valve member, e.g. in addition to the control fluid pressure.

The fluid pressure may be introduced through the input line in the valve core into the control volume in any suitable and desired way. In a preferred embodiment the device comprises a fluid pressure control system for supplying a fluid through the input line into the control volume to provide the fluid pressure in the control volume to act on the valve member. Preferably the fluid pressure control system is arranged to control (e.g. set) the fluid pressure in the control volume, i.e. to control the position of the valve member.

The fluid pressure control system may be provided in any suitable and desired way. Preferably the fluid pressure control system comprises a source of fluid. The source of fluid may be provided locally to (and, e.g., dedicated (e.g. solely) to) the device or the source of fluid may comprise a (e.g. distributed) fluid line into which the device is plumbed.

Preferably the fluid pressure control system comprises a pump fluidly connected to the input line (and, e.g. to the source of fluid), wherein the pump is arranged to control the (e.g. volumetric rate of) fluid input into (or removed from) the control volume (i.e. in order to control the fluid pressure in the control volume and thus the position (and, e.g., rate of movement) of the valve member). The device may comprise its own (e.g. dedicated) pump, e.g. when the source of fluid is provided locally to the device. Alternatively, e.g. when the device is plumbed into a fluid line, the fluid line may comprise a pump for the whole of the fluid line and thus the device may not comprise a separate pump.

Preferably the fluid pressure control system comprises an electronic control arranged to control the operation of the pump. In one embodiment the electronic control may simply comprise a (e.g. manually operated) switch. In other embodiments, e.g. when the fluid pressure control system receives input(s) from sensor(s), the electronic control may comprise a processing circuit arranged to control the operation of the pump (e.g. in response to the input(s)).

The electronic control may be provided locally to the device (e.g. when the pump is manually operated). In one embodiment the electronic control is remote from the device, e.g. in a control room.

The (e.g. electronic control of the) fluid pressure control system may receive (and thus the device may comprise) one or more inputs, e.g. which the fluid pressure control system uses to control (e.g. set) the fluid pressure in the control volume (e.g. by the electronic control controlling operation of the pump to set the fluid pressure).

For example, the device may comprise an upstream pressure sensor arranged to determine the pressure in the conduit upstream of the device and/or a downstream pressure sensor arranged to determine the pressure in the conduit downstream of the device. Preferably the upstream pressure sensor and/or the downstream pressure sensor are connected to the fluid pressure control system (and thus preferably the fluid pressure control system is arranged to receive the determined upstream pressure and/or downstream pressure from the upstream pressure sensor and/or the downstream pressure sensor respectively). Preferably the fluid pressure control system uses the upstream and/or downstream pressure of the fluid in the conduit (e.g. as determined by and received from the upstream pressure sensor and/or the downstream pressure sensor respectively) to control the fluid pressure in the control volume (to thus control the position of the valve member).

According to the claimed invention, the device comprises a position sensor (e.g. comprising a control unit) arranged to determine (e.g. detect) the position of the valve member (e.g. relative to the housing and/or the outlet aperture). This helps the device to position the valve member as desired, using the fluid pressure in the control volume, to control the flow of fluid through the device.

The magnetic field sensor(s) may be mounted on the housing, e.g. in a fixed position relative to the outlet aperture, such that the magnet is moved by the valve member relative the magnetic field sensor(s). The magnetic field sensor(s) may be arranged to detect the changes in the magnetic field it experiences from the magnet as it moves relative to the sensor(s), which allows the position of the valve member to be determined.

The position sensor comprises one or more multiple magnetic field sensors. It will be appreciated that by providing multiple magnetic field sensors, a more accurate determination of the position of the valve member may be made (e.g. owing to the more accurate measurement of the movement of the magnetic field of the magnet that may be made). In at least preferred embodiments, providing multiple magnetic field sensors may allow the measurements to be automatically calibrated for changes (e.g. degradation) of the magnetic field of the magnet with time and/or temperature.

The magnet may comprise any suitable and desired magnet. Preferably the magnet comprises a permanent magnet. Preferably the device comprises a sheath surrounding the magnet. The sheath helps to protect the magnet, which may be quite brittle. The sheath may help to avoid contact of the magnet with the working fluid of the device (i.e. the fluid flowing through the conduit whose flow is being controlled). This may be required, for example, when the device is used in the water industry, for regulatory approval. The sheath may also help to reduce the friction of the magnet as it is displaced.

Preferably the magnet is longitudinally extended (i.e. having a length greater than its width (e.g. diameter)), e.g. in the direction in which the valve member (and thus the magnet) is arranged to be displaced. Preferably the magnet is cylindrical, e.g. being longitudinally extended in the direction in which the cross-section of the cylinder is projected (along the length of the cylinder).

The magnet may be mounted on the valve member in any suitable and desired way. In a preferred set of embodiments, the magnet is mounted such that the magnet retains the same circumferential and/or radial position (e.g. relative to the housing and/or axis of the device) when the magnet is displaced by the valve member, e.g. even when the valve member rotates (circumferentially) relative to the housing.

The magnet retaining the same circumferential and/or radial position during operation helps to maintain the same positional relationship between the magnet and the magnetic field sensors (apart from the intended (e.g. axial) displacement of the magnet with the valve member) and thus maintains a consistent environment for (e.g. the (e.g. non-ferrous) material (such as plastic or metal) of the device between) the magnet and the magnetic field sensors. This helps the position of the valve member to be determined accurately, e.g. even when the valve member rotates (circumferentially) relative to the housing (which can be common during operation), because the magnetic field strength and angle experienced by the magnetic field sensors does not vary with rotation of the valve member. Furthermore, the fixed circumferential and/or radial position helps to preserve the magnetic field angle experienced by the magnetic field sensors as the magnet deteriorates.

The magnet may be mounted along the axis of the valve member Thus, for example, the magnet may be longitudinally extended along the axis of the valve member. The magnet may comprise an annular (e.g. circumferentially symmetric) magnet, e.g. mounted around the (e.g. axis of the) valve member. Providing a magnet at the central axis of the valve member or circumferentially extending around the central axis of the valve member helps to retain the magnet at the same circumferential and radial position.

The magnet may be any suitable and desired size. Preferably the magnet has a length (e.g. in the axial direction) that is greater than the maximum (e.g. axial) displacement of the valve member. This helps to provide a (e.g. axial) position on the (e.g. housing of the) fluid flow control device at which the magnet overlaps at all (e.g. axial) displacements of the valve member (and thus the magnet). Preferably the length of the magnet is greater than or equal to the sum of the maximum (e.g. axial) displacement of the valve member and the (e.g. axial) spread of the magnetic field sensors. This allows the magnetic field sensors to be (and in an embodiment they are) positioned such that they overlap with the magnet at all (e.g. axial) displacements of the valve member.

The plurality of magnetic field sensors may be mounted at the plurality of different positions on the valve housing in any suitable and desired way. In one embodiment the plurality of magnetic field sensors are mounted on an outer casing of the valve housing. This allows easy access to the magnetic field sensors, e.g. for attaching readout wiring thereto. In a preferred set of embodiments, the plurality of magnetic field sensors are mounted on or in the valve core of the housing. This may allow the magnetic field sensors to be located close to the magnet.

In one embodiment, the magnetic field sensors are mounted within <NUM> of the magnet (e.g. in the radial direction), e.g. approximately <NUM> from the magnet.

In one embodiment the (e.g. valve core of the) valve housing comprises one or more cavities in which the magnetic field sensors are located. The plurality of magnetic field sensors may be arranged in the same cavity or in a plurality of respective cavities.

Preferably the magnetic field sensors (and thus, for example, the one or more cavities for the magnetic field sensors) are arranged at (e.g. exposed to) atmospheric pressure. Preferably the magnetic field sensors are isolated from (i.e. not exposed to) the (e.g. fluid pressure of the) working fluid of the fluid flow control device, e.g. owing to where on or in the valve housing they are mounted. This allows the magnetic field sensors (and, e.g., any associated electronics) to operate in a relatively safe environment and be accessed relatively easily. The magnetic field sensors may, for example, not require complicated sealing mechanisms.

In a preferred set of embodiments, the plurality of magnetic field sensors are fixedly (e.g. rigidly) mounted on the valve housing. Providing static magnetic field sensors helps, for example, to simplify any connecting wiring and/or electronics. It may also allow static seals (which are relatively simple and safe, e.g. compared to dynamic seals) to be used to seal the magnetic fields sensors in the housing.

The plurality of magnetic field sensors may be provided at a plurality of different (respective) positions in any suitable and desired way, e.g. so that they experience different magnetic field strength of the magnet from each other. In one embodiment the plurality of magnetic field sensors are radially spaced from each other. Preferably the plurality of magnetic field sensors are axially spaced from each other. In other embodiments the magnetic field sensors are angled between the radial and axial directions. Preferably the magnetic field sensors are angled so that the radial field lines from the magnet cut through the tops of the magnetic (e.g. Hall effect) sensors.

The plurality of magnetic field sensors may be spaced from each other by mounting them on a plurality of different (respective) substrates (e.g. printed circuit boards), e.g. for locating them in a plurality of different cavities in the valve housing. Alternatively, the plurality of magnetic field sensors are mounted, but spaced from each other, on the same substrate (e.g. printed circuit board), e.g. for locating the magnetic field sensors in the same cavity.

Thus, as appropriate, the one or more cavities may be longitudinally extended, e.g. radially or axially. For example, when the plurality of magnetic field sensors are located in the same cavity, the cavity may extend longitudinally in the axial direction (and thus the magnetic field sensors may be spaced axially from each other). Or, for example, when the plurality of magnetic field sensors are located in a plurality of cavities, the cavities may be spaced axially from each other (e.g. at the same circumferential position) but extend radially.

The plurality of magnetic field sensors may be spaced from each other by any suitable and desired distance. Preferably the magnetic field sensors are positioned on the valve housing within the maximum (e.g. axial) displacement of the magnet, e.g. when the magnetic field sensors are axially spaced from each other. This allows the magnetic field sensors to overlap with the magnet at all displacements of the magnet. As the magnetic field sensors are multiple axis sensors, it may be possible to use a smaller magnet.

The magnetic field sensors may be any suitable and desired type of magnetic field sensors. In one set of embodiments the magnetic field sensors comprise a plurality of magnetic Hall effect sensors. According to the claimed invention, the magnetic field sensors comprise multiple axis sensors. The multiple axis sensors may be configured to determine the magnitude of the magnetic field in two (e.g. horizontal and vertical) axes. A magnetic field angle may be calculated from the output of the multiple axis magnetic field sensors. A position of the valve member may be determined by (e.g. the control unit of) the position sensor from a calculated or a measured magnetic field angle. Using a magnetic field angle to determine the position of the valve member, rather than a magnitude of the magnetic field, can improve the range of displacements of the valve member that may be determined. Furthermore, the determination may be independent of fluctuations in temperature.

In one embodiment, the magnetic field sensors may comprise Hall effect switches (e.g. in addition to other magnetic field sensors). The Hall effect switches are preferably positioned on the valve housing at or outside the maximum (e.g. axial) displacement of the magnet (e.g. in either direction). The Hall effect switches may thus use the discontinuity in the magnet field of the magnet to detect that the magnet has reached its maximum (e.g. axial) displacement (in either direction).

Using Hall effect switches in this way may be suitable for an on-off or shut-off valve, or to calibrate the measurements from the (e.g. intermediately positioned) other magnetic field sensors.

The fluid flow control device may comprise any suitable and desired number of magnetic field sensors. In a preferred set of embodiments, the fluid flow control device comprises two or more magnetic field sensors, e.g. three or more magnetic field sensors. Having three or more magnetic field sensors provides some redundancy, e.g. were one of the sensors to stop working.

In a preferred set of embodiments, the position sensor comprises a control unit arranged to receive an output (e.g. a measurement of the magnetic field (e.g. strength and/or angle) of the magnet) from the magnetic field sensors. The control unit may be connected via a wired or wireless connection to the magnetic field sensors. Preferably the control unit is arranged to determine the position of the valve member, from the output received from the magnetic field sensors. Preferably the control unit comprises processing circuitry arranged to receive the output received from the magnetic field sensors and to calculate the position of the valve member from the measured magnetic field (e.g. strength and/or angle). Preferably the processing circuitry is arranged to perform one or more (e.g. all) of the functions of the control unit, as appropriate.

The position of the valve member may be determined in any suitable and desired way. Measuring the position of the valve member helps to provide reassurance (e.g. to a user) that a valve aperture is fully open or fully closed, as desired. The position of the valve member may be used to determine the amount by which the valve member is throttling the flow of fluid through the valve aperture. This, in turn, may allow the valve member to be positioned in a particular position, e.g. to deliver a desired amount of throttling. The position of the valve member may be used to allow the flow rate through the fluid flow control device to be determined (or estimated). The position of the valve member may be used as part of health checks and/or condition monitoring of the fluid flow control device.

In a preferred set of embodiments, the determined position of the valve member is used as part of a (e.g. active) feedback control loop. Thus preferably the (e.g. control unit of the) position sensor is arranged to control operation of the fluid flow control device using the determined position of the valve member, e.g. to position the valve member at a particular position. This may be done in any suitable and desired way, e.g. owing to the type of fluid flow control device being used. For example, the (e.g. control unit of the) position sensor may (e.g. control a pilot valve to) set a control pressure in the fluid flow control device (e.g. using the determined position of the valve member) to displace the valve member to a particular position.

Thus preferably the (e.g. control unit of the) position sensor is connected to the (e.g. electronic control of the) fluid pressure control system (and thus preferably the fluid pressure control system is arranged to receive the determined position of the valve member from the (e.g. control unit of the) position sensor). Preferably the (e.g. electronic control of the) fluid pressure control system uses the position of the valve member (e.g. as determined by and received from the (e.g. control unit of the) position sensor) to control the fluid pressure in the control volume (e.g. by the electronic control operating the pump to set the fluid pressure). This allows the position of the valve member to be actively adjusted, so that, for example, that the fluid flow control valve may be controlled to operate in a particular way, e.g. at a constant flow rate.

In a preferred set of embodiments, the (e.g. control unit of the) position sensor is arranged to perform error minimisation on the output from the magnetic field sensors to determine the position of the valve member. The error minimisation exploits the multiple measurements from the multiple magnetic field sensors and helps to account for any changes of the magnet with temperature or time. Furthermore, depending on the error minimisation algorithm used, the temperature and/or the magnetisation of the magnet may also be determined (and thus in an embodiment the (e.g. control unit of the) position sensor is arranged to determine the temperature and/or the magnetisation of the magnet using the output from the magnetic field sensors).

The fluid in the control volume could be any suitable and desired fluid, e.g. a liquid (thus applying a hydraulic pressure) or a gas (thus applying a pneumatic pressure). The choice of fluid to use may depend on the desired operation of the device and the fluid pressure that is to be provided. Preferably the "control" fluid in the control volume comprises a fluid that is less damaging environmentally than the fluid flowing in the conduit that is being controlled by the device. It will be appreciated that the control fluid is likely to have a limited volume (e.g. compared to the volume of fluid flowing through the conduit) and so if this leaks, the environmental damage this causes may be minimised.

The fluid to introduce into the control volume could be taken from the fluid in the conduit whose flow is being controlled by the device. However, in a preferred embodiment the device is configured to keep the fluid in the conduit (whose flow is being controlled by the device) separate from the fluid in the control volume. This helps to reduce contamination (in either direction) between the control fluid and the line fluid (the fluid in the conduit).

Preferably the fluid in the control volume (and the input line) is isolated from the fluid in the conduit. Thus preferably the control volume and the input line are sealed, e.g. from the fluid in the conduit. Preferably the device comprises one or more seals for sealing the control volume, e.g. between the valve member (e.g. the part of the valve member which moves in the control volume, e.g. the piston head) and the housing (e.g. the part thereof which defines the control volume). The seal(s) may be provided on the housing and/or on the valve member.

In some embodiments the device comprises a (e.g. compression) spring (e.g. within the housing) arranged to act on the valve member (i.e. in addition to the fluid pressure). It will be appreciated that the split piece nature of the device is particularly convenient for including and assembling a spring in the device, as the spring may be (and preferably is) assembled with the valve member and the housing, before the valve core is secured between the upstream and downstream casings.

The spring may be arranged to act on any suitable and desired part of the valve member, and in any suitable and desired direction. Preferably (e.g. when the fluid pressure acts on only one side of the valve member) the spring is arranged to act on the valve member in the opposite (e.g. axial) direction to the direction in which the fluid pressure acts on the valve member. Thus preferably the valve member is acted on by (at least) the fluid pressure and the spring force to control the position of the valve member.

In one embodiment the spring is arranged to act to bias the valve member in the downstream direction (i.e. to bias the valve member towards closing the outlet aperture). Preferably, in this embodiment, the spring is located between (and thus engages and exerts a force against) the housing of the valve core and the closure member.

In one embodiment the spring is arranged to act to bias the valve member in the upstream direction (i.e. to bias the valve member towards opening the outlet aperture). Preferably, in this embodiment, the spring is located between (and thus engages and exerts a force against) the housing of the valve core and the piston head of the valve member.

The device may be arranged to have defined operating characteristics, e.g. particularly with regard to its "fail safe" mode of operation. This is preferably to provide the device with a defined mode of operation in the event of a loss of (or significant reduction in) the fluid pressure. This may be caused, for example, by a loss of power to the device (e.g. to the fluid pressure control system) or by a leak of the control fluid from the control volume (e.g. owing to a failure of a seal for the control volume). In the former situation, the fluid pressure in the control volume is likely to be reduced to below the pressure acting on the valve member in the opposite direction. In the latter situation, the leak of the control fluid is likely to lead to the equalisation of the fluid pressure acting on the valve member in each direction. In these situations, the failure mode of the valve may also depend on whether the device comprises a spring acting on the valve member.

In one embodiment, in a "fail closed" design, the device is configured to (e.g. move the valve member to) close the outlet aperture when there is a loss of (or significant reduction in) the fluid pressure.

In one embodiment, in a "fail open" design, the device is configured to (e.g. move the valve member to) open the outlet aperture when there is a loss of (or significant reduction in) the fluid pressure.

When the device is configured to fail closed or open, preferably the valve member is biased (e.g. by a spring) in the downstream or upstream direction respectively.

In one embodiment, in a "fail in position" design, the device is configured to retain the valve member in the same position when there is a loss of (or significant reduction in) the fluid pressure (i.e. in the position the valve member is in when the loss of fluid pressure occurs).

Such "fail safe" modes of operation may be chosen depending on the operating requirements of the system in which the device is installed.

In one set of (e.g. "fail closed") embodiments, the control volume is arranged such that the fluid pressure acts to bias (and thus move) the valve member in the upstream direction (i.e. to open the outlet aperture), e.g. such that the fluid pressure acts on a downstream face of the (e.g. piston head of the) valve member. Thus, in the event of a loss of fluid pressure, the valve member experiences a drop in the pressure acting on it that would ordinarily bias it in the upstream direction, thus preferably moving the valve member in the downstream direction to close the valve aperture.

In this set of embodiments, preferably the device (e.g. the housing and valve member) is arranged such that the downstream pressure of the fluid in the conduit acts to bias (and thus move) the valve member in the downstream direction (i.e. to close the outlet aperture) (e.g. differentially with the control fluid pressure acting in the opposite direction on the valve member). Preferably the valve member is acted on by the downstream pressure in the conduit and the fluid pressure in the control volume so as to be moved (inter alia) by the difference between these pressures to control the position of the valve member.

Preferably an upstream face of the (e.g. piston head of the) valve member is exposed to the downstream pressure, e.g. such that the downstream pressure acts on the upstream face of the (e.g. piston head of the) valve member. Thus, in the event of a loss of fluid pressure, the downstream pressure acts on the valve member to move the valve member in the downstream direction to close the valve aperture.

Preferably the housing comprises a channel from the downstream side of the housing (and, e.g., the valve member) that is fluidly connected to the upstream face of the (e.g. piston head of the) valve member. This provides a fluid route through for the downstream pressure to act on an upstream face of the valve member. Preferably, when the closure member of the valve member comprises aperture(s) therethrough, the aperture(s) are fluidly connected, e.g. via a channel, to the upstream side of the (e.g. piston head of the) valve member. Thus, even when the valve member has (e.g. fully) closed the outlet aperture, the downstream pressure can act on the upstream face of the valve member.

Preferably, when the device comprises a spring, the spring is arranged to act to bias the valve member in the downstream direction (i.e. to bias the valve member towards closing the outlet aperture). Thus preferably the spring acts on the valve member, along with the downstream pressure, to bias the valve member in the downstream direction against the control fluid pressure, such that the valve member closes the outlet aperture in the event of a loss of (or significant drop in) the control fluid pressure.

In one set of (e.g. "fail open") embodiments, the control volume is arranged such that the fluid pressure acts to bias (and thus move) the valve member in the downstream direction (i.e. to close the outlet aperture), e.g. such that the fluid pressure acts on an upstream face of the (e.g. piston head of the) valve member. Thus, in the event of a loss of fluid pressure, the valve member experiences a drop in the pressure acting on it that would ordinarily bias it in the downstream direction, thus preferably moving the valve member in the upstream direction to open the valve aperture.

In this set of embodiments, preferably the device (e.g. the housing and valve member) is arranged such that the downstream pressure of the fluid in the conduit acts to bias (and thus move) the valve member in the upstream direction (i.e. to open the outlet aperture) (e.g. differentially with the control fluid pressure acting in the opposite direction on the valve member). Preferably a downstream face of the (e.g. piston head of the) valve member is exposed to the downstream pressure, e.g. such that the downstream pressure acts on the downstream face of the (e.g. piston head of the) valve member. Thus, in the event of a loss of fluid pressure, the downstream pressure acts on the valve member to move the valve member in the upstream direction to open the valve aperture.

Preferably the housing comprises a channel from the downstream side of the housing (and, e.g., the valve member) that is fluidly connected to the downstream face of the (e.g. piston head of the) valve member. This provides a fluid route through for the downstream pressure to act on a downstream face of the valve member. Preferably, when the closure member of the valve member comprises aperture(s) therethrough, the aperture(s) are fluidly connected, e.g. via a channel, to the downstream side of the (e.g. piston head of the) valve member. Thus, even when the valve member has (e.g. fully) closed the outlet aperture, the downstream pressure can act on the downstream face of the valve member.

Preferably, when the device comprises a spring, the spring is arranged to act to bias the valve member in the upstream direction (i.e. to bias the valve member towards opening the outlet aperture). Thus preferably the spring acts on the valve member, along with the downstream pressure, to bias the valve member in the upstream direction against the control fluid pressure, such that the valve member opens the outlet aperture in the event of a loss of (or significant drop in) the control fluid pressure.

In one set of (e.g. "fail in position") embodiments, the device comprises two control volumes. Preferably the device comprises two (e.g. fluidly separate) input lines defined in the valve core for introducing fluid pressures into the two control volumes respectively. Preferably the valve member is acted on by the difference in the fluid pressures in the two control volumes to control the position of the valve member.

Preferably the device comprises a fluid pressure control system for (e.g. independently) supplying a fluid through the two input lines into the two control volumes respective to provide the fluid pressures in the respective control volumes to act on the valve member. Thus each input line and control volume may have fluid supplied thereto by a separate control system or the same control system may be arranged to supply fluid to both input lines and respective control volumes, e.g. independently. Preferably the fluid pressure control system is arranged to control (e.g. set) the fluid pressure in each of the control volumes, i.e. to control the position of the valve member.

One of the control volumes is preferably arranged such that the fluid pressure acts to bias (and thus move) the valve member in the upstream direction (i.e. to open the outlet aperture), e.g. such that the fluid pressure acts on a downstream face of the (e.g. piston head of the) valve member. The other of the control volumes is preferably arranged such that the fluid pressure acts to bias (and thus move) the valve member in the downstream direction (i.e. to close the outlet aperture), e.g. such that the fluid pressure acts on an upstream face of the (e.g. piston head of the) valve member. Thus, in the event of a loss of fluid pressure, the valve member experiences a drop in the pressure acting on both of its sides. The valve member is thus preferably arranged to remain in the position when the loss of fluid pressure occurred.

In this set of embodiments, preferably the device (e.g. the housing and valve member) is arranged such that the downstream pressure of the fluid in the conduit does not act to bias the valve member. Preferably the closure member of the valve member is pressure balanced, e.g. preferably the closure member comprises aperture(s) therethrough. This means that although the closure member may be exposed to the downstream pressure of the fluid in the conduit, this does not cause a net force to act in either the upstream or downstream direction on the valve member.

In these embodiments, the device may comprise a spring, wherein the spring is arranged to act to bias the valve member in either the upstream or the downstream direction. Such an arrangement may therefore be arranged to bias the valve member in the upstream or the downstream direction respectively, e.g. in order to move the valve member into the fully closed or fully open position when there is a loss of fluid pressure in both the control volumes.

In the above embodiments the device may be (and preferably is) operated simply as an on-off valve, e.g. using the control fluid pressure to move the valve member to open or close the outlet aperture. However, it will be appreciated that the fluid pressure may be controlled to move the valve member into a position between its fully open and its fully closed configurations. The device may then be operated as a control valve.

In some embodiments the device is adapted further to help it to control the flow of fluid therethrough with more fine control than simply having the valve member open or closed. In a preferred embodiment the device comprises a cage that extends across the flow path between the housing and the outlet aperture, wherein the cage comprises a plurality of apertures (e.g. holes or slots) to allow fluid to flow through. Preferably the cage is arranged such that movement of the valve member selectively allows fluid to flow through a lesser or greater proportion of the plurality of apertures in the cage. This acts to throttle the flow of fluid through the device (and thus through the outlet aperture), therefore helping to control the flow of fluid through the device.

The cage (e.g. a valve trim) may be provided in any suitable and desired way to control the flow of fluid therethrough according to the movement and position of the valve member. In one embodiment the cage is attached to (and, e.g., projects from) the valve member. Therefore, preferably, as the valve member moves towards and away from the outlet aperture, a lesser or greater (respectively) number of apertures in the cage are exposed to the flow path through the device, thus controlling the flow of fluid through the outlet aperture.

In one embodiment the cage is attached to (and, e.g., extends between) the housing and the downstream casing (e.g. the rim of the outlet aperture). In this embodiment, preferably the valve member moves relative to the cage (e.g. the cage is fixed stationary in the device). Therefore, preferably, as the valve member moves towards and away from the outlet aperture, the apertures in the cage are selectively opened and closed, thus controlling the flow of fluid through the outlet aperture.

The arrangement of (e.g. the size and distribution of) the apertures in the cage may be chosen to provide a particular profile for the control of the flow of fluid through the outlet aperture.

Certain preferred embodiments for the invention will now be described, by way of example only, with reference to the accompanying drawings in which:.

There are many different industrial situations in which there is a desire to control the flow rate in a fluid flow stream through a conduit. In such systems, a device is required to control the output flow rate by opening and/or closing an outlet (e.g. valve) aperture. As will now be described, embodiments of the present invention provide devices that are able to provide this control for the fluid flow.

<FIG> and <FIG> show a cross-sectional view of a fluid flow device <NUM> in accordance with an embodiment of the present invention. <FIG> shows the device <NUM> in its fully-open position and <FIG> shows the device <NUM> in its fully-closed position. The device <NUM> comprises a valve core <NUM>, an upstream valve casing <NUM> and a downstream valve casing <NUM>, which are formed as three separate components. The device <NUM> is mounted in a pipe <NUM> that extends either side of the upstream and downstream valve casings <NUM>, <NUM>.

To assemble the device <NUM>, the valve core <NUM> is mounted and sealed between the upstream and downstream valve casings <NUM>, <NUM> and is clamped in place by means of a flange bolt circle <NUM>. This provides an advantage over one-piece cast valve bodies, in which the valve member must be smaller in diameter than the ends of the valve in order for it to be inserted through the inlet or outlet aperture. Whereas, with the present three-piece design, it is possible to accommodate a larger valve core and valve member capable of supporting higher hydraulic control pressures.

The upstream valve casing <NUM> defines an inlet aperture <NUM> and the downstream valve casing <NUM> comprises a valve seat <NUM> surrounding and defining an outlet aperture <NUM>. The flow of fluid in <FIG> and <FIG> is from left to right, following a conduit <NUM> defined within the valve casings <NUM>, <NUM>.

The valve core <NUM> comprises four main components: a piston <NUM>, a closure member <NUM>, a control fluid feed <NUM> and a housing <NUM>. The piston <NUM> and the closure member <NUM> together form a valve member. The housing <NUM> and the piston <NUM> together define a control fluid pressure chamber <NUM> and a downstream pressure chamber <NUM>.

The control fluid pressure chamber <NUM> is downstream of the piston head <NUM> and is fluidly connected to the control fluid feed <NUM> for supplying a control fluid (and thus a control fluid pressure) into the control fluid pressure chamber <NUM>, such that the control fluid pressure acts on the downstream face <NUM> of the piston head <NUM>. The downstream pressure chamber <NUM> is upstream of the piston head <NUM> and is fluidly connected to the downstream side of the conduit <NUM> via an upstream piston cavity balance hole <NUM> and closure member balance holes <NUM>. This allows the fluid on the downstream side of the conduit <NUM> (and thus a downstream fluid pressure) to be supplied into the downstream pressure chamber <NUM> (via the upstream piston cavity balance hole <NUM> and the closure member balance holes <NUM>), such that the pressure in the upstream portion of the downstream pressure chamber <NUM> (and thus acting on the upstream face of the piston head <NUM>) is equal to the downstream pressure at the outlet aperture <NUM>. The housing <NUM> further defines a piston shaft aperture <NUM> and a closure member chamber <NUM>.

The control fluid feed <NUM> is connected to a source of control fluid <NUM> (e.g. hydraulic fluid, pneumatic fluid or fluid taken from within the pipe <NUM>) which is controlled by a control system <NUM>, e.g. to set the pressure of the control fluid in the control fluid pressure chamber <NUM>. The control system <NUM> may use feedback data collected by a position sensor <NUM> that determines the position of the piston <NUM> relative to the housing <NUM> and/or the outlet aperture <NUM>.

The piston <NUM> comprises a piston head <NUM> and a piston shaft <NUM>, which projects perpendicularly from the downstream surface <NUM> of the piston head <NUM> through the piston shaft aperture <NUM> into the closure member chamber <NUM>. The piston head <NUM> is sealed against the housing <NUM> by piston seals <NUM> and the piston shaft <NUM> is sealed within the piston shaft aperture <NUM> by piston shaft seals <NUM>. This prevents the control fluid from leaking into the downstream pressure chamber <NUM> and the closure member chamber <NUM> respectively.

The closure member <NUM> is attached to the downstream end of the piston shaft <NUM> such that the closure member <NUM> moves longitudinally with the piston <NUM>. The closure member <NUM> has a cylindrical sleeve portion <NUM> and an end portion <NUM>. The end portion <NUM> comprises shut off seals <NUM>, mounted on the outside surface of the closure member end portion <NUM>, and a number of closure member balance holes <NUM> that allow fluid to pass from the downstream side of the conduit <NUM> through the closure member chamber <NUM> and into the downstream pressure chamber <NUM> via the upstream piston cavity balance hole <NUM>. The closure member <NUM> is arranged to move reciprocally along the inner surface <NUM> of the housing <NUM> within the closure member chamber <NUM>.

The cylindrical sleeve portion <NUM> of the closure member <NUM> has a hollow central bore in which a helical spring <NUM> is positioned around the piston shaft <NUM>. The helical spring <NUM> is a compression spring which is held between the housing <NUM> and the closure member <NUM> to bias the closure member <NUM> to close the outlet aperture <NUM>.

The closure member <NUM> is moveable between two extreme positions: a fully-open position, as shown in <FIG>, and a fully-closed position, as shown in <FIG>. In the fully-open position, the upstream surface <NUM> of the piston head <NUM> abuts the upstream inner face <NUM> of the housing <NUM> and the end portion <NUM> of the closure member <NUM> is located within the closure member chamber <NUM>, leaving a flow path for the flow of fluid through the outlet aperture <NUM> from the upstream side of the device <NUM> to the downstream side. In the fully-closed position, the downstream surface <NUM> of the piston head <NUM> abuts the downstream inner surface <NUM> of the housing <NUM> and the end portion <NUM> of the closure member <NUM> is moved such that the outer surface of the end portion <NUM> of the closure member <NUM> is sealed against the valve seat <NUM> by shut off seals <NUM>. This prevents the fluid from flowing through device <NUM> via the outlet aperture <NUM>.

Operation of the fluid flow device <NUM> shown in <FIG> and <FIG> will now be described.

<FIG> shows the device <NUM> in its fully-closed state, in which the control fluid pressure in the control fluid pressure chamber <NUM> is set to a low value by the control fluid source <NUM> (controlled by the control system <NUM>). The combined force from the downstream pressure acting on the upstream surface <NUM> of the piston head <NUM> and the spring force from the helical spring <NUM> is greater than the control fluid pressure acting on the downstream surface <NUM> of the piston head <NUM>. Thus the piston <NUM> is moved to the right of <FIG>, moving the end portion <NUM> of the closure member <NUM> to be sealed against the valve seat <NUM> by the shut off seals <NUM>. This prevents the fluid from flowing through the device <NUM> via the outlet aperture <NUM>.

In order to place the device <NUM> in the fully-open position, as shown in <FIG>, the control fluid pressure is raised to a value sufficient to cause the force acting on the downstream surface <NUM> of the piston head <NUM> to be greater than the combined opposing forces caused by the helical spring <NUM> and the downstream pressure acting on the upstream surface <NUM> of the piston head <NUM>. As a result, the upstream surface <NUM> of the piston head <NUM> is moved to the position in which it abuts the upstream inner surface <NUM> of the housing <NUM>, thus moving the closure member <NUM> to be located within the closure member chamber <NUM>, leaving a flow path for the flow of fluid through the outlet aperture <NUM>.

In the event of failure of one or more of the piston seals <NUM> or piston shaft seals <NUM>, causing the pressure acting on the upstream surface <NUM> of the piston head <NUM> to become equal to the pressure acting on the downstream surface <NUM> of the piston head <NUM>, the helical spring <NUM> acts to bias the closure member <NUM> to the right of <FIG> and <FIG> into the fully-closed position. In the event of a loss of control fluid pressure (e.g. owing to a loss of power in the hydraulic and/or control systems <NUM>), the downstream pressure acting on the upstream surface <NUM> of the piston head <NUM> is greater than the control pressure acting on the downstream surface <NUM> of the piston head <NUM>. Furthermore, the helical spring <NUM> acts to bias the closure member <NUM> towards the right of <FIG>. Thus, in both of these failure modes of the fluid flow device <NUM>, the piston <NUM> is moved to the right of <FIG>, moving the end portion <NUM> of the closure member <NUM> to be sealed against the valve seat <NUM> by the shut off seals <NUM>. This prevents the fluid from flowing through device <NUM> via the outlet aperture <NUM>, thus representing a "fail closed" mode of the device.

<FIG> and <FIG> show a device <NUM> in accordance with a further embodiment of the present invention, which is a variant of the device <NUM> shown in <FIG> and <FIG>. <FIG> shows the device <NUM> in its fully-open position and <FIG> shows the device <NUM> in its fully-closed position.

The embodiment has the same three-piece design as the embodiment shown in <FIG> and <FIG>. However, the device <NUM> varies from device <NUM> in a number of ways.

First, the control fluid pressure chamber <NUM> is on the upstream side of the piston head <NUM> and the downstream pressure chamber <NUM> is on the downstream side of the piston head <NUM>. The downstream pressure chamber <NUM> in the device <NUM> is defined by the housing <NUM>, the downstream surface <NUM> of the piston head <NUM> and the inner surface of a cylindrical spring housing <NUM>. The spring housing <NUM> extends through the piston shaft aperture <NUM> from the piston chamber <NUM> to the closure member chamber <NUM>.

The spring housing <NUM> comprises a central bore <NUM> and an end aperture <NUM>, wherein the end aperture <NUM> is proportioned to accommodate the piston shaft <NUM>. A helical spring <NUM> is positioned within the central bore <NUM> such that it encompasses the piston shaft <NUM> and extends between the downstream surface <NUM> of the piston head <NUM> and the downstream inner surface of the spring housing <NUM>. The helical sprint <NUM> thus acts to bias the closure member <NUM> to open the outlet aperture <NUM>.

Second, the housing <NUM> of device <NUM> does not define an upstream cavity balance hole. Instead, the downstream pressure chamber <NUM> is fluidly connected to the outlet aperture <NUM> via the end aperture <NUM> of the spring housing <NUM> and the closure member balance holes <NUM>. The downstream pressure thus acts on the downstream face <NUM> of the piston head <NUM>.

<FIG> shows the device <NUM> in its fully-open state, in which the control fluid pressure in the control fluid pressure chamber <NUM> is set to a low value by the hydraulic source <NUM> (controlled by the control system <NUM>). The combined force from the downstream pressure acting on the downstream surface <NUM> of the piston head <NUM> and the spring force from the helical spring <NUM> is greater than the control fluid pressure acting on the upstream surface <NUM> of the piston head <NUM>. As a result, the upstream surface <NUM> of the piston head <NUM> is moved to the position in which it abuts the upstream inner surface <NUM> of the housing <NUM>, thus moving the end portion <NUM> of the closure member <NUM> to be located within the closure member chamber <NUM>, leaving a flow path for the flow of fluid through the outlet aperture <NUM>. It will be appreciated that this arrangement is the reverse of the arrangement shown in <FIG> and described above, where the device <NUM> is designed to fully close when the control fluid pressure is low.

In order to place the device <NUM> in the fully-closed position, as shown in <FIG>, the control fluid pressure is raised to a value sufficient to cause the force acting on the upstream surface <NUM> of the piston head <NUM> to be greater than the combined opposing forces caused by the helical spring <NUM> and the downstream pressure acting on the downstream surface <NUM> of the piston head <NUM>. As a result, the piston <NUM> is moved to the right of <FIG>, moving the end portion <NUM> of the closure member <NUM> to be sealed against the valve seat <NUM> by the shut off seals <NUM>. This prevents the fluid from flowing through the device <NUM> via the outlet aperture <NUM>.

In the event of failure of one or more of the piston seals <NUM>, causing the pressure acting on the downstream surface <NUM> of the piston head <NUM> to become equal to the pressure acting on the upstream surface <NUM> of the piston head <NUM>, the helical spring <NUM> acts to bias the closure member <NUM> to the left of <FIG> and <FIG> into the fully-open position. In the event of a loss of control fluid pressure (e.g. owing to a loss of power in the hydraulic and/or control systems <NUM>), the downstream pressure acting on the downstream surface <NUM> of the piston head <NUM> is greater than the control pressure acting on the upstream surface <NUM> of the piston head <NUM>. Furthermore, the helical spring <NUM> acts to bias the closure member <NUM> towards the left of <FIG>. Thus, in both of these failure modes of the fluid flow device <NUM>, the piston <NUM> is moved to the left of <FIG>, moving the end portion <NUM> of the closure member <NUM> to be located within the closure member chamber <NUM>, leaving a flow path for the flow of fluid through the outlet aperture <NUM>, thus representing a "fail open" mode of the device.

The housing <NUM> of device <NUM> defines two control fluid pressure chambers: an upstream control fluid pressure chamber <NUM>, located upstream of the piston head <NUM> and a downstream control fluid pressure chamber <NUM>, located downstream of the piston head <NUM>. The upstream control fluid pressure chamber <NUM> is fluidly connected to an upstream control fluid source <NUM> via an upstream control fluid feed <NUM> for supplying a control fluid (and thus a control fluid pressure) into the upstream control fluid pressure chamber <NUM>, such that the control fluid pressure acts on the upstream face of the piston head <NUM>. The downstream control fluid pressure chamber <NUM> is fluidly connected to a downstream control fluid source <NUM> via a downstream control fluid feed <NUM> for supplying a control fluid (and thus a control fluid pressure) into the downstream control fluid pressure chamber <NUM>, such that the control fluid pressure acts on the downstream face of the piston head <NUM>.

<FIG> shows the device <NUM> in its fully-closed state, in which the control fluid pressure in the downstream control fluid pressure chamber <NUM> is set to a low value by a downstream control fluid source <NUM> and the control fluid pressure in the upstream control fluid pressure chamber <NUM> is set to a high value by an upstream control fluid source <NUM>. Both the downstream control fluid source <NUM> and the upstream control fluid source <NUM> are controlled by a control system <NUM>.

The combined force from the control pressure acting on the upstream surface <NUM> of the piston head <NUM> and the spring force from the helical spring <NUM> (which acts to bias the closure member <NUM> towards the right of <FIG>) is greater than the control pressure acting on the downstream surface <NUM> of the piston head <NUM>. Thus the piston <NUM> is moved to the right of <FIG>, moving the end portion <NUM> of the closure member <NUM> to be sealed against the valve seat <NUM> by the shut off seals <NUM>. This prevents the fluid from flowing through the device <NUM> via the outlet aperture <NUM>.

In order to place the valve <NUM> in the fully-open position, as shown in <FIG>, the downstream control fluid pressure is raised by the control system <NUM> to a value sufficient to cause the force acting on the downstream surface <NUM> of the piston head <NUM> to be greater than the combined opposing forces caused by the helical spring <NUM> and the downstream control pressure acting on the upstream surface <NUM> of the piston head <NUM>. As a result, the upstream surface <NUM> of the piston head <NUM> is moved to a position in which it abuts the upstream inner surface <NUM> of the housing <NUM>, thus moving the closure member <NUM> to be located within the closure member chamber <NUM>, leaving a flow path for the flow of fluid through the outlet aperture <NUM>.

In the event of failure of one or more of the piston seals <NUM>, causing the pressures in the downstream control fluid pressure chamber <NUM> and the upstream control fluid pressure chamber <NUM> to equalise, the helical spring <NUM> acts to bias the closure member <NUM> to the right of <FIG> and <FIG> into the fully-closed position. In a further failure mode, when one or more of the piston shaft seals <NUM> fail, the downstream control fluid pressure becomes equal to the downstream pressure. In this case, the helical spring <NUM> acts to bias the closure member <NUM> to the right of <FIG> and <FIG> and move it in into the fully-closed position.

In the event of a loss of downstream control fluid pressure (e.g. owing to a loss of power in the hydraulic and/or control systems <NUM>), the piston head <NUM> is biased and moved towards the right of <FIG> and <FIG> by the combined force of the helical spring <NUM> and the upstream control pressure.

Thus, in all of the failure modes of the fluid flow device <NUM> described above, the piston <NUM> is forced to the right of <FIG>, moving the end portion <NUM> of the closure member <NUM> to be sealed against the valve seat <NUM> by the shut off seals <NUM>. This prevents the fluid from flowing through the device <NUM> via the outlet aperture <NUM>. However, it will be appreciated that the helical spring <NUM> of device <NUM> shown in <FIG> and <FIG> may be adapted to function in a manner similar to that shown in <FIG> and <FIG> so that the device operates as a "fail-open" device. Furthermore, the helical spring <NUM> may be removed completely so that, in the event of seal or power failure, the valve <NUM> is designed to fail "in-place", i.e. the valve <NUM> is not biased to either the fully-closed or the fully-open position.

<FIG> shows a device <NUM> in accordance with a further embodiment of the present invention, which is a variant of the device <NUM> shown in <FIG> and <FIG>. The device <NUM> is essentially the same as the device <NUM> discussed above. However, the helical spring <NUM> has been removed and a cylindrical cage <NUM> has been centrally attached to the end portion <NUM> of the closure member <NUM>. The embodiment has the same three-piece design as the embodiment shown in <FIG> and <FIG>.

The cylindrical cage <NUM> extends longitudinally through the outlet aperture <NUM> of the device <NUM>. The outer diameter of the cage <NUM> is equal to the outer diameter of the end portion <NUM> of the closure member <NUM> so that the cage <NUM> fills the outlet aperture <NUM>. The cage <NUM> comprises a plurality of apertures <NUM> which are distributed uniformly along the length and circumference of the cage <NUM> and fluidly connect inlet aperture <NUM> of the conduit <NUM> to the outlet aperture <NUM>.

As in previous embodiments, the closure member <NUM> is moveable longitudinally within the closure member chamber <NUM> between a fully-open position (shown in <FIG>) and a fully-closed position (not shown).

<FIG> shows the device <NUM> in its fully-open position, in which the downstream control fluid pressure in the downstream control fluid pressure chamber <NUM> is greater than the upstream control fluid pressure in the upstream control fluid pressure chamber <NUM>. As a result, the piston <NUM>, the closure member <NUM> and the cage <NUM> are moved to the left of <FIG> such that the closure member <NUM> is fully located within the closure member chamber <NUM>. In this position, a maximum number of cage apertures <NUM> are opened to allow fluid to flow through the device <NUM> at a maximum flow rate.

In order to reduce the flow rate through the device <NUM>, the upstream control pressure is increased, causing the piston <NUM>, closure member <NUM> and the cage <NUM> to move to the right of <FIG>. As the cage <NUM> is moved into the outlet aperture <NUM>, the number of cage apertures <NUM> that are closed by the valve seat <NUM> increases. This has the effect of throttling the fluid flow, as the flow rate will decrease in proportion the total area of the apertures <NUM> that remain open. Consequently, it will be appreciated that this embodiment enables more precise control of the fluid flow rate.

When the device <NUM> reaches its fully-closed position, the end portion <NUM> of the closure member <NUM> is sealed against the valve seat <NUM> by the shut off seals <NUM> and the cage <NUM> is fully encompassed by the valve seat <NUM>, thus closing all off the cage apertures <NUM>. This prevents the fluid from flowing through the device <NUM> via the outlet aperture <NUM>.

<FIG> shows a device <NUM> in accordance with a further embodiment of the present invention, which is a variant of the device <NUM> shown in <FIG>. The device <NUM> is essentially the same as the device <NUM> discussed above. However, rather than the cage <NUM> being attached to the end portion <NUM> of the closure member <NUM>, the cage <NUM> is attached to the downstream end of the closure member casing <NUM>, spanning the orifice between the closure member casing <NUM> and the valve seat <NUM>. The inner diameter of the cage <NUM> is equal to the inner diameter of the closure member casing <NUM> so that the closure member <NUM> is able to slide longitudinally within the cage <NUM>. Furthermore, the shut off seals <NUM> are mounted on the inner surface of the valve seat <NUM> rather than on the outside surface of the closure member <NUM>.

<FIG> shows the device <NUM> in its fully-open position, in which the downstream control fluid pressure in the downstream control fluid pressure chamber <NUM> is greater than the upstream control fluid pressure in the upstream control fluid pressure chamber <NUM>. As a result, the piston <NUM> and the closure member <NUM> are moved to the left of <FIG> such that the closure member <NUM> is fully located within the closure member chamber <NUM>. In this position, none of the cage apertures <NUM> are closed by the closure member <NUM>. Therefore, fluid may flow through the device <NUM> at a maximum flow rate.

In order to reduce the flow rate through the device <NUM>, the upstream control pressure is increased, causing the piston <NUM> and the control member <NUM> to move to the right of <FIG>. As the closure member <NUM> is moved towards the outlet aperture <NUM>, the number of cage apertures <NUM> that are closed by the closure member <NUM> increases. This has the effect of throttling the fluid flow, as the flow rate will decrease in proportion to the total area of the apertures <NUM> that remain open. Consequently, it will be appreciated that this embodiment enables more precise control of the fluid flow rate.

When the device <NUM> reaches its fully-closed position, the end portion <NUM> of the closure member <NUM> is sealed against the valve seat <NUM> by the shut off seals <NUM> and all of the cage apertures <NUM> are completely closed by the closure member <NUM>. This prevents the fluid from flowing through the device <NUM> via the outlet aperture <NUM>.

<FIG> shows a cross-sectional view of a fluid flow device <NUM> in accordance with an embodiment of the present invention, in which the device <NUM> comprises position sensing apparatus. The device <NUM> shown in <FIG> is substantially the same as the device <NUM> shown in <FIG>, except that the device <NUM> comprises a magnet <NUM> embedded within the piston <NUM> and a magnetic field sensor <NUM> mounted within a radial hole <NUM> in the housing <NUM>.

The radial hole <NUM> extends into the valve core <NUM> from the exterior surface of the valve core <NUM>. The radial hole <NUM> is arranged in a plane perpendicular to the control fluid feed and the piston cavity balance hole (not shown). A PCB <NUM> is located within the radial hole <NUM> and comprises three magnetic field sensors (Hall effect sensors) <NUM>. Electric cables fed through radial hole <NUM> provide power to the PCB <NUM> and allow measurements of the magnetic field strength to be sent from each of the sensors <NUM> to a position sensor control unit <NUM>.

The magnet <NUM>, extending in the axial direction, is embedded centrally within the piston <NUM>. As the magnet <NUM> is rigidly embedded within the piston <NUM>, the axial displacement of the piston <NUM> corresponds exactly to the axial displacement of the magnet <NUM>. As the magnet <NUM> is located centrally within the piston <NUM>, any circumferential movement of the valve member does not cause a change in distance between the magnet <NUM> and the sensors <NUM>.

During normal operation of the device <NUM>, the flow of fluid through the device <NUM> from the inlet aperture <NUM> to the outlet aperture <NUM> is controlled by the movement of the piston <NUM> and closure member <NUM>. As the closure member <NUM> is moved towards the valve seat <NUM>, the flow through the device <NUM> is restricted. Therefore, the fluid flow may be throttled by adjusting the axial displacement of the piston <NUM> and closure member <NUM>.

The sensors <NUM> continuously measure the strength of the magnetic field of the magnet <NUM> as it moves with the piston <NUM> and closure member <NUM>. The measurements may be processed by the position sensor control unit <NUM> using an error minimisation algorithm in order to determine the axial position of the piston <NUM> and closure member <NUM>.

<FIG> shows a cross-sectional view of a fluid flow device <NUM> in accordance with an embodiment of the present invention, in which the device <NUM> comprises position sensing apparatus. The device <NUM> is essentially the same as the device <NUM> discussed above. However, the axial magnet <NUM> has been replaced by a ring magnet <NUM> that is embedded within the piston <NUM>.

A PCB <NUM> comprising three Hall effect sensors <NUM>, electrically connected to the position sensor control unit <NUM>, is located within a radial hole <NUM>. The magnet <NUM> is positioned with the piston <NUM> such that, at all axial positions of the piston <NUM>, the sensors <NUM> are positioned within the end limits of the magnet <NUM>.

Furthermore, as the ring magnet <NUM> is embedded centrally within the piston <NUM>, any circumferential movement of the closure member <NUM> does not cause a change in distance between the magnet <NUM> and the sensors <NUM>.

During normal operation of the device <NUM>, flow through the device <NUM> is throttled by the axial displacement of the piston <NUM> and closure member <NUM>. The sensors <NUM> continuously measure the strength of the magnetic field of the ring magnet <NUM> as it moves with the piston <NUM> and closure member <NUM>. In the same way as the above embodiment, the measurements may be processed by the position sensor control unit <NUM> using an error minimisation algorithm in order to determine the axial position of the piston <NUM> and closure member <NUM>.

<FIG> shows a cross-sectional view a fluid flow device <NUM> in accordance with an embodiment of the present invention, in which the device <NUM> comprises position sensing apparatus. The device <NUM> is essentially the same as the device <NUM> discussed above. However, the valve core <NUM> comprises an additional two radial holes <NUM> which extend into the valve core <NUM> from the exterior surface of the valve core <NUM>. The radial holes <NUM> are spaced axially within the valve core <NUM>.

A PCB <NUM> comprising a Hall effect sensor <NUM>, electrically connected to the position sensor control unit <NUM>, is located within each radial hole <NUM>. The magnet <NUM> is positioned with the piston <NUM> such that, at all axial positions of the piston <NUM>, the sensors <NUM> are positioned within the end limits of the magnet <NUM>.

In the same way as the above embodiments, the sensors <NUM> continuously measure the strength of the magnetic field of the magnet <NUM> as it moves with the piston <NUM> and closure member <NUM>. The measurements may be processed by the position sensor control unit <NUM> using an error minimisation algorithm in order to determine the axial position of the piston <NUM> and closure member <NUM>. For example, the measurements may be used to determine a deviation in the magnetisation of the magnet from a nominal magnetisation, and the determined axial position may be adjusted accordingly.

The fluid flow device <NUM> further comprises a cylindrical piston liner <NUM> arranged between the housing <NUM> and the piston <NUM>.

It can be seen from the above that in at least preferred embodiments of the invention, the device is a split piece design that includes three main parts: the upstream and downstream casings, and the valve core. The valve member of the device is actuated (e.g. hydraulically or pneumatically) by a control fluid. These features help to provide a fluid flow control device which is easy to manufacture and assemble, and is less likely to cause leakage of the fluid flowing through failure of the device in the manner of conventional designs.

Claim 1:
A device (<NUM>; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>) for controlling the flow of a fluid through a conduit (<NUM>; <NUM>) from an upstream side of the device to a downstream side of the device, the device comprising:
an upstream valve casing (<NUM>) defining an inlet on the upstream side of the device;
a downstream valve casing (<NUM>) defining an outlet aperture (<NUM>; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>) on the downstream side of the device;
a valve core (<NUM>; <NUM>; <NUM>) secured between the upstream valve casing and the downstream valve casing, wherein the upstream valve casing, the downstream valve casing and the valve core are formed as discrete parts;
wherein the valve core comprises a housing (<NUM>; <NUM>; <NUM>; <NUM>; <NUM>) defining a control volume (<NUM>, <NUM>; <NUM>, <NUM>; <NUM>; <NUM>; <NUM>);
a valve member (<NUM>, <NUM>; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>) comprising a piston and a closure member (<NUM>; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>) attached to the piston, wherein the valve member is movably mounted on the housing and positioned on the upstream side of the outlet aperture, wherein the valve member is arranged to move reciprocally to selectively open and close the outlet aperture, thereby controlling flow of the fluid through the outlet aperture;
an input line (<NUM>; <NUM>) defined in the valve core for introducing a fluid pressure into the control volume, wherein the valve member is acted on by the fluid pressure in the control volume to control the position of the valve member;
characterized in that the device further comprises:
a magnet (<NUM>; <NUM>; <NUM>), embedded within the piston of the valve member such that it is displaced by the movement of the valve member in the same direction as the valve member; and
a position sensor (<NUM>; <NUM>; <NUM>; <NUM>) arranged to determine the position of the valve member, wherein the position sensor comprises one or more multiple-axis magnetic field sensors (<NUM>; <NUM>; <NUM>).