[0001] This invention relates to a valve assembly for use in controlling a fluid flow through a fluid pathway.

BACKGROUND

[0002] WO 2004090508 discloses a method and device for taking micro-samples of a pressurised fluid contained in a container. An electromagnetic actuator is used to move a mobile piston of a valve between an open position and a closed position. In this way, the amount of fluid taken under pressure can be controlled by varying the duration between two consecutive displacements of the mobile piston in opposite directions.

[0003] Typically, valves of the prior art, making use of electromagnetic actuators, have undesirably long times between consecutive displacements of the mobile piston in opposite directions, in part due to the inertia of the mobile piston and corresponding portion of the electromagnetic actuator. Therefore, it can sometimes be difficult to reliably take only very small and precise volumetric samples of a pressurised fluid. In order to reduce the size of sample, valves of the prior art make use of small-diameter connecting passageways through which the pressurised fluid is to be extracted. The connecting passageways are sometimes referred to as capillary tubes. Such capillary tubes can easily become blocked by particulates or contaminants in the pressurised fluid, which can reduce the amount of a sample extracted from the pressurised fluid. In some cases, the valve can become entirely dysfunctional when the connecting passageways are completely blocked, preventing the extraction of any liquid samples until the connecting passageway can be unblocked.

[0004] The present disclosure provides at least an alternative to the valve assembly of the prior art.

BRIEF SUMMARY OF THE DISCLOSURE

[0005] In accordance with the present inventions there is provided a valve assembly for controlling a high-pressure fluid flow through a fluid pathway. The valve assembly comprises a valve housing, defining a first port and a second port configured to be fluidly connected to the first port via a fluid pathway. The valve assembly further comprises a flow control member controllably moveable in the valve housing to alter a fluid flow restriction in the fluid pathway between the first port and the second port, and a piezoelectric actuator, when activated, configured to cause the flow control member to move whereby to alter the fluid flow restriction. The piezoelectric actuator is a bending-type piezoelectric actuator. [0006] Thus, there is provided a valve assembly which can control fluid flow of a high- pressure fluid through a fluid pathway. The use of a bending-type piezoelectric actuator ensures that the controlled movement of the flow control member occurs in a responsive manner, and that sufficient force can be exerted on the flow control member to alter the fluid flow restriction in the fluid pathway. In comparison to the device of WO 2004090508 of the prior art, the fluid flow restriction of the claimed valve assembly can be opened for a reliably short amount of time, allowing more precise control of the high-pressure fluid flow through the fluid pathway. In one example, the claimed valve assembly allows for a smaller amount of fluid to pass through the fluid flow restriction compared to valves of the prior art. In another example, the claimed valve assembly allows for a larger connecting

passageway to be connected to the first port and/or the second port, compared to the valves of the prior art, whilst maintaining the amount of fluid passing through the fluid flow restriction, therefore reducing the likelihood of blockage of the connecting passageway.

[0007] It will be understood that a bending-type piezoelectric actuator is to be understood to be any piezoelectric actuator where activation of the piezoelectric actuator by

application of a voltage thereto, results in bending of at least a portion of the piezoelectric actuator. The flow control member may be a piston moveable within a piston housing. Movement of the fluid flow restriction will typically change a flow rate of the fluid flow between the first port and the second port. The fluid flow restriction may be provided by the flow control member.

[0008] The piezoelectric actuator may define a first surface and a second surface, opposite the first surface, each arranged to bend on activation of the piezoelectric actuator. The flow control member may be separate from the piezoelectric actuator and may extend substantially transverse from the first surface. Thus, during bending of the piezoelectric actuator, the first surface will be displaced in a direction having at least a component normal to the first surface, thereby causing the flow control member to be moved in the direction. In other words, the flow control member may be caused to move in a direction substantially transverse to the first surface of the piezoelectric actuator. For example, the flow control member may be caused to move in a direction substantially perpendicular to the first surface of the piezoelectric actuator.

[0009] The first surface and the second surface of the piezoelectric actuator may have defined therein a through-hole for engagement by an engaging portion of the flow control member, whereby activation of the piezoelectric actuator causes movement of the flow control member via engagement of a boundary of the through-hole with the engaging portion of the flow control member. Thus, a hole in the piezoelectric actuator can be used to mechanically connect the engaging portion of the flow control member to the piezoelectric actuator, such that movement of the piezoelectric actuator causes movement of the flow control member. It will be understood that alternative mounting methods may be used to mechanically connect the engaging portion of the flow control member to the piezoelectric actuator, for example adhesive.

[0010] The flow control member may extend from substantially a centre of the first surface. The valve assembly may be configured to support an outer boundary of the first surface of the piezoelectric actuator at a substantially fixed location relative to the valve housing. Thus, on activation of the piezoelectric actuator, a magnitude of a displacement of the centre of the first surface in an axial direction transverse to the first surface is greater than a displacement of any other location on the first surface in the axial direction. The piezoelectric transducer may be substantially disc-shaped. In other words, the first surface of the piezoelectric transducer may define a circle.

[0011] The piezoelectric actuator may comprise a plurality of piezoelectric elements, each configured to be extensible in a first direction, and mounted parallel to the other piezoelectric elements of the plurality of piezoelectric elements, wherein, when the piezoelectric actuator is activated with a first voltage, the piezoelectric actuator is configured to bend in a first angular direction, and wherein, when the piezoelectric actuator is activated with a second voltage, the piezoelectric actuator is configured to bend in a second angular direction, opposite the first angular direction. Thus, the piezoelectric actuator can be formed from a plurality of parallel piezoelectric layers, ensuring that the required displacement of the flow control member can be achieved.

[0012] In some examples, the piezoelectric actuator may be a bimorph piezoelectric actuator. In other words, the plurality of piezoelectric elements comprises only a first piezoelectric element and a second piezoelectric element. The piezoelectric actuator may comprise a first electrode and a second electrode in electrical contact with opposing surfaces of the plurality of piezoelectric elements, such that the first piezoelectric element and the second piezoelectric element are provided between the first electrode and the second electrode. The first piezoelectric element may be mounted directly to the second piezoelectric element, for example by adhesive or sintering. Alternatively, the first piezoelectric element may be separated from the second piezoelectric element by a third electrode. Thus, the piezoelectric actuator may be a serial or a parallel bimorph bending- type piezoelectric actuator.

[0013] In some examples, the plurality of piezoelectric elements may comprise more than two piezoelectric elements. This can be referred to as a multilayer bending-type piezoelectric actuator, a multilayer piezoelectric actuator or a multimorph piezoelectric actuator. Again, the piezoelectric actuator typically comprises a first electrode and a second electrode to sandwich the plurality of piezoelectric elements therebetween and a third electrode provided within the plurality of piezoelectric elements. In some examples, the piezoelectric actuator may comprise a plurality of electrodes arranged in an

interdigitated arrangement. In other words, each of the plurality of piezoelectric elements may be provided with a first electrode in electrical contact with a first planar surface of the piezoelectric element and a second electrode in electrical contact with a second planar surface of the piezoelectric element. The electrodes from several of the plurality of piezoelectric elements may be electrically connected in a predetermined arrangement such that the piezoelectric actuator comprises a first electrical contact, a second electrical contact and a third electrical contact. The electrical contacts may be connected to the electrodes of each of the plurality of piezoelectric elements such that when a first voltage is applied to the first electrical contact and a second voltage, negative relative to the first voltage is applied to the second electrical contact, a third voltage between the first voltage and the second voltage, when applied to the third electrical contact, causes the

piezoelectric actuator to bend in the first angular direction or the second angular direction in dependence on the third voltage. In particular, when the third voltage is exactly equidistant between the first voltage and the second voltage, the piezoelectric actuator may be configured not to bend away from an equilibrium position. The first voltage and the second voltage may each be spaced by a substantially identical magnitude from a ground voltage.

[0014] The valve housing may further define a third port configured to be fluidly connected to the first port via a further fluid pathway. Thus, with three ports in the valve housing, the valve assembly may be for a sampling valve for extracting a sample of the high-pressure fluid. Typically, the high-pressure fluid is arranged to flow between the first port and the third port. When a sample of the fluid is required, the piezoelectric actuator can be activated to direct some of the fluid to the second port as the sample. It will be understood that the valve assembly may alternatively be used as an injection valve to inject an amount of a fluid injection component into the fluid flowing between the first port and the third port. The fluid injection component may be injected into the fluid via the second port on activation of the piezoelectric actuator.

[0015] The piezoelectric actuator may be configured to cause the flow control member to move to change a sealing condition of the fluid pathway between the first port and the second port between a sealed configuration in which the first port is sealed from the second port and an unsealed configuration in which fluid can flow between the first port and the second port. Thus, in embodiments the valve assembly can provide full sealing between the first port and the second port to prevent fluid flow therebetween, even for high-pressure fluid flows.

[0016] When the fluid pathway between the first port and the second port is in the unsealed configuration, the further fluid pathway between the third port and the first port may be in an unsealed configuration in which fluid can flow between the first port and the third port. Thus, when the fluid flow through the second port is at a higher pressure than a fluid flow between the first port and the third port, fluid can be sampled from a high- pressure system, connected to the valve assembly via the second port, at the second port, and removed from the valve assembly by a carrier fluid flowing between the first port and the third port. It will be understood that this can also be thought of as an injection valve, since the fluid injection component (the sample from the system) is injected into the fluid flowing between the first port and the third port (the carrier fluid).

[0017] The first port and the third port may be configured to be at a lower pressure than the second port, whereby to provide a sampling valve for withdrawing a fluid sample from a pressurised system through the second port to a fluid carrier passing between the first port and the third port.

[0018] The first port and the third port may be configured to be at a higher pressure than the second port, whereby to provide an injection valve for introducing a fluid component into a pressurised system through the second port from a fluid carrier passing between the first port and the third port.

[0019] Thus, it will be understood that the valve assembly can function as a sampling valve or a dosing/injection valve depending on the pressures and fluid flows connected to the ports of the valve assembly.

[0020] The piezoelectric actuator may be configured to cause the flow control member to apply a predetermined sealing force to seal the first port from the second port when the fluid pathway between the first port and the second port is in the sealed configuration.

Thus, the predetermined sealing force may be determined to be sufficient to provide a full seal between the first port and the second port when the fluid pathway between the first port and the second port is in the sealed configuration.

[0021] The predetermined sealing force may be determined in dependence on a number of times the fluid pathway has previously been in the sealed configuration. Thus, the piezoelectric actuator can be controlled to deflect by an increased amount during ageing and any degradation of a sealing member that may form part of the fluid flow restriction, for example between the first port and the second port. [0022] A tip of the flow control member may comprise a sealing member arranged to block the second port in the sealed configuration. It will be understood that the sealing member may alternatively be comprised in the valve housing to be engaged by the tip of the flow control member. In some examples, the tip may comprise a first sealing member and the valve housing may comprise a second sealing member arranged to engage with the first sealing member when the fluid pathway between the first port and the second port is in the sealed configuration. The sealing member may be formed from a resiliently deformable material. The sealing member may be in the form of a convex tip to engage with a substantially circular boundary of a sealing orifice in the fluid pathway between the first port and the second port. The convex tip may form a portion of a substantially spherical shape. The sealing member may be formed from a plastics material, for example a polymeric material. The sealing member may be formed from a metal material, for example a soft metal such as gold.

[0023] A cross-sectional area of the second port through which fluid can pass in the unsealed configuration may be less than 0.5 square millimetres. The cross-sectional area of the second port may be less than 0.1 square millimetres. The cross-sectional area of the second port may be less than 0.05 square millimetres. Thus, the second port is sized to allow a very small volumetric flow rate to pass therethrough. This makes it easier to allow only very precise amounts of fluid to pass between the first port and the second port by controlling the operation of the piezoelectric actuator to move the flow control member to alter the fluid flow restriction.

[0024] The valve assembly may further comprise a controller configured to provide one or more control signals to activate the piezoelectric actuator in one of at least three predetermined configurations. Thus, the piezoelectric actuator can be controlled to have more than two predetermined configurations, corresponding to more than two

predetermined positions of the flow control member. In other words, the valve assembly can operate in a configuration other than fully sealed and fully unsealed for the fluid flow restriction. For example, a further possible configuration is where the fluid flow restriction restricts the fluid flow more than in the fully unsealed configuration, but does not fully stop the fluid flow as in the fully sealed configuration. This may be referred to sometimes as a partially unsealed configuration.

[0025] The piezoelectric actuator may be configured to maintain a position of the flow control member at an intermediate position between a first position providing a first fluid flow restriction in the fluid pathway and a second position providing a second fluid flow restriction in the fluid pathway. Thus, the flow control member can be held by operation of the piezoelectric actuator in a position which only partially throttles a fluid flow between the first port and the second port.

[0026] The valve assembly may further comprise temperature control means, operable to control a temperature of the fluid between the second port and the first port to be within a predetermined temperature range. The predetermined temperature range may have a lower bound greater than 100 degrees Celsius. The predetermined temperature range may have a lower bound greater than 200 degrees Celsius. The predetermined temperature range may have an upper bound less than 300 degrees Celsius. For example, the temperature control means may comprise a heater. Thus, the environment in the valve assembly can be maintained in a suitable condition for sampling or dosing using the valve assembly. The temperature control means may further comprise a temperature controller, for example comprising a control unit and one or more temperature sensors in data communication with the control unit. The temperature controller may control the heater to provide a controlled and stable temperature of the fluid between the second port and the first port.

[0027] The valve assembly may further comprise a further actuation means configured to, when engaged, retain the flow control member in a position caused by activation of the piezoelectric actuator, even when the piezoelectric actuator is subsequently deactivated. Thus, it may be possible to retain the flow control member in a desired position, such as in the sealed or unsealed configuration, without maintaining constant power to the piezoelectric actuator.

[0028] The further actuation means may be a latch, for example a safety latch. The further actuation means may be a passive actuation means, which does not require any power to maintain the position of the flow control member once activated. For example, the passive actuation means may comprise at least one of a solenoid and a rotary actuator. Thus, it is possible to retain the flow control member in a desired position, such as in the sealed or unsealed configuration, without maintaining constant power to the further actuation means. In an example, the further actuation means may be configured to maintain the flow control member in a sealed configuration without maintaining power to the further actuation means.

[0029] Viewed from another aspect, the present disclosure provides a kit of parts for forming the valve assembly described hereinbefore. The kit of parts comprises a valve housing, defining: a first port; and a second port configured to be fluidly connected to the first port via a fluid pathway. The kit of parts further comprises a flow control member configured to be controllably moveable in the valve housing to alter a fluid flow restriction in the fluid pathway between the first port and the second port; and a piezoelectric actuator, when activated, configured to cause the flow control member to move whereby to alter the fluid flow restriction. The piezoelectric actuator is a bending-type piezoelectric actuator. Thus, the valve assembly can be provided in an unassembled condition and assembled from the component parts in the kit.

[0030] As used herein, the term high pressure will be understood to mean pressures exceeding 5 megapascals (5 x 10 ⁶ pascals). In some cases, high pressure may mean pressures up to 50 megapascals, 70 megapascals, 100 megapascals, or even greater.

[0031] Although the present disclosure has described a piezoelectric actuator of a bending type for actuating the flow control member, it will be understood that other suitable actuators may be used. However, in the present applications, any other actuator must be sufficiently responsive, and/or able to exert sufficient force. It is also an advantage if the actuator is able to operate at low voltages. As will be understood, a low voltage is safer than a high voltage. Furthermore, a power supply for providing a low voltage is less expensive than a power supply for providing a high voltage. It is a further advantage if the actuator is sufficiently controllable. Thus, viewed another way, the present disclosure provides a valve assembly for controlling a high-pressure fluid flow through a fluid pathway. The valve assembly comprises: a valve housing defining a first port and a second port configured to be fluidly connected to the first port via a fluid pathway; a flow control member controllably moveable to alter a fluid flow restriction in the fluid pathway between the first port and the second port; and an actuator. When activated, the actuator is configured to cause the flow control member to move whereby to alter the fluid flow restriction. The actuator may be configured to maintain a position of the flow control member at a plurality of positions between a first position providing a first fluid flow restriction in the fluid pathway and a second position providing a second fluid flow restriction in the fluid pathway. The actuator may be configured to move the flow control member between the first position and the second position in less than 10ms, for example less than 5ms, preferably less than 2ms. The actuator may be configured to apply a force to the flow control member of at least 10N. The actuator may be configured to move the flow control member by a distance of at least 0.05 millimetres, for example at least 0.1 millimetres. The actuator may be configured to move the flow control member by a distance of approximately 0.3 millimetres. The actuator may be configured to move the flow control member by a distance of less than 2 millimetres, for example less than 1 millimetre. The actuator may be configured to be activated by a voltage having an absolute voltage lower than 100 volts, for example -30V to 30V. [0032] Although the present disclosure has been described in relation to a high-pressure valve, it will be understood that the valve may be used in any system where a valve is required.

BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Embodiments of the invention are further described hereinafter with reference to the accompanying drawings, in which:

Figure 1 is an illustration of a valve assembly;

Figure 2 is an illustration of a cross-sectional view through the valve assembly shown in Figure 1 ;

Figure 3 is an enlarged illustration of a cross-sectional view through a portion of the valve assembly shown in Figures 1 and 2;

Figures 4a and 4b are illustrations of a cross-sectional view through a lower portion of the valve assembly shown in Figures 1 to 3, shown in an unsealed configuration (Figure 4a) and a sealed configuration (Figure 4b);

Figure 5 is an illustration of a cross-sectional view through a further valve assembly; and

Figured 6 is an enlarged illustration of a cross-sectional view though a portion of the valve assembly shown in Figure 5.

DETAILED DESCRIPTION

[0034] Figure 1 is an illustration of a valve assembly 100. The valve assembly is for controlling the flow of a fluid. The valve assembly 100 is suitable to be used in a high- pressure system, where the pressure of the system may exceed 5 megapascals or even exceed 50 megapascals, as described elsewhere herein. The valve assembly 100 is typically a separate add-on to a high-pressure system. However, it will be understood that the valve assembly 100 can alternatively be an integral part of a system.

[0035] The valve assembly 100 comprises a valve housing 110 which defines a fluid pathway for the fluid through the valve assembly. In particular, the valve housing 110 defines a first port 112 and a second port 114. The first port 112 and the second port 114 are each for receiving fluid therethrough. As can be seen in Figures 2 and 3, the second port 114 is configured to be fluidly connected to the first port 112 via a fluid pathway. As will be explained further in relation to Figures 4a and 4b hereinafter, in some configurations the second port 114 will be sealed from the first port 112, such that there is selectively no fluid pathway between the first port 112 and the second port 114. [0036] The valve assembly 100 further comprises a flow control member 120, and an actuator 130 in the form of a piezoelectric actuator 130. The piezoelectric actuator 130, when activated, is configured to cause the flow control member 120 to move. As will be explained further in relation to Figure 2 hereinafter, the flow control member 120 is controllably moveable in the valve housing 110 to alter a fluid flow restriction in the fluid pathway between the first port 112 and the second port 114. In this way, activation of the piezoelectric actuator 130 alters the fluid flow restriction. The piezoelectric actuator 130 is a bending-type piezoelectric actuator 130 in this example, though it will be understood that other actuation means may be used to achieve at least some of the same benefits described herein over valve assemblies of the prior art. In this example, the piezoelectric actuator 130 is provided away from the first port 112 and the second port 114 to prevent heat transfer between the high-pressure fluid in fluid connection with one or both of the first port 112 and the second port 114, for example from the high-pressure fluid to the piezoelectric actuator 130.

[0037] A controller (not shown) to provide control signals to control activation of the piezoelectric actuator 130 can also be provided away from the first port 112 and the second port 114. In this example, the piezoelectric actuator 130 is provided in an actuator housing 140, separate from the valve housing 110. As explained more fully in relation to Figure 2 hereinafter, the actuator housing 140 is spaced from the valve housing 110 by a spacer 150, for example in the form of a cooling portion 150. In this example, the spacer 150 is made from a substantially non-heat-conductive material (such as a non-metallic material). A suitable material is a high-temperature resistant plastic, ceramic, etc. The material is chosen to have a substantially similar linear thermal expansion coefficient (e.g., 3 ppm/°C.-7ppm/C.) as the valve housing 110 and the actuator housing 140. As a result, thermal expansion/contraction of each of the valve housing 110, the actuator housing 140 and the spacer 150, may occur similarly and/or substantially equally, to substantially avoid leakage of fluid flow from the system. The spacer 150 may also be formed from any other suitable material, for example a metal.

[0038] An electrical connection port 160 is provided to receive electrical control signals for controlling the piezoelectric actuator 130. Thus, a demountable electrical connector (not shown) can be used to connect to the valve assembly 100 via the electrical connection port 160 to provide the control signals to the piezoelectric actuator 130.

[0039] The actuator housing 140 in this example comprises a cover member 142. The cover member 142 is to cover an upper opening in the actuator housing 140. Although the cover member 142 is formed from a substantially transparent material in this example, such as glass or a transparent plastics material, it will be understood that this is not essential, and any other material can be used. In this example, the cover member 142 ensures that there are no atmospheric contaminants (for example dust or dirt) passing into the actuator housing 140 which could interfere with operation of the piezoelectric actuator 130.

[0040] A further actuation means, such as a latch, for example in the form of a safety latch (not shown) can additionally be provided to retain the flow control member 120 in a desired position, such as in the sealed configuration. The further actuation means can be positioned between the cover member 142 and the flow control member 120. The further actuation means is typically arranged such that a solenoid and a rotary actuator, such as a cam, will be in constant contact with a resiliently deformable element, such as a spring element, located around the flow control member 120, when no power is applied to maintain the position of the flow control member. This mechanism will function to compress the flow control member 120 by a sufficient amount of force to fully seal the valve. In other words, without any power being applied to the piezoelectric actuator (including during any electrical failure of the piezoelectric actuator), flow will still be prevented through the valve assembly 100. Once power is applied to the further actuation means, the rotary actuator will change position to allow a flow path through the valve assembly 100 to be unsealed, thereby allowing the flow control member to be controlled by the controller.

[0041] Figure 2 is an illustration of a cross-sectional view through the valve assembly 100 shown in Figure 1. The cross-section is sliced down a longitudinal axis of the flow control member 120, and also illustrates the inner structure of the valve assembly 100 within the valve housing 110. It will be understood that the opposite side of the valve assembly 100 (that hidden in the cross-sectional view of Figure 2, is substantially a mirror image of the view in Figure 2. The piezoelectric actuator 130 is arranged such that activation of the piezoelectric actuator 130 will cause bending of a first planar surface 132 of the piezoelectric actuator 130. The flow control member 120 extends substantially transverse from the first planar surface 132 of the piezoelectric actuator 130. The flow control member 120 is engaged with the first planar surface 132 of the piezoelectric actuator 130 such that activation of the piezoelectric actuator 130 necessarily causes movement of the flow control member 120. The first planar surface 132 of the piezoelectric actuator 130 has defined therein a through-hole 134 through which the flow control member 120 passes. The flow control member 120 is fixedly secured to the piezoelectric actuator 130 at the through-hole 134 by engagement between an engaging portion 122 of the flow control member 120 and a boundary of the through-hole 134 on the first planar surface 132. It will be understood that similar engagement between a further engaging portion of the flow control member 120 and the boundary of the through-hole 134 on a second planar surface 136 of the piezoelectric actuator 130 ensures that the flow control member 120 can be caused to move axially in either direction by controlled activation of the piezoelectric actuator 130. The through-hole 134 is located substantially centrally within the piezoelectric actuator 130.

[0042] The piezoelectric actuator 130 is supported around at least part of an outer boundary thereof by a first support member 144 and a second support member 146, which restrict movement of the outer boundary of the piezoelectric actuator 130 in an axial direction of the flow control member 120. The first support member 144 and the second support member 146 are arranged to substantially pin the outer boundary of the piezoelectric actuator 130 therebetween. In this way, activation of the piezoelectric actuator 130 causes movement of the flow control member 120 axially. The first support member 144 and the second support member 146 are each configured to allow angular movement of the piezoelectric actuator 130 in a portion of the piezoelectric actuator 130 provided between the first support member 144 and the second support member 146, even when the portion is pinned therebetween, to provide a sufficient axial movement range of the flow control member 120. Were the first support member 144 and the second support member 146 to rigidly clamp the piezoelectric actuator 130 therebetween, such that angular movement of the piezoelectric actuator 130 in the portion of the piezoelectric actuator 130 provided between the first support member 144 and the second support member 146 was restricted, then it will be understood that the axial movement range of the piezoelectric actuator 130 would be reduced. Nevertheless, either configuration is possible. The second support member 146 is arranged to support the second planar surface 136 of the piezoelectric actuator 130. In this example, one of the first support member 144 and the second support member 146, in particular the second support member 146, is formed from a resiliently deformable material, such as an O-ring, which ensures that the piezoelectric actuator 130 is held securely in place in any configuration of the piezoelectric actuator 130, resulting in more precise control for the valve assembly 100.

[0043] In this example, the piezoelectric actuator 130 is substantially disc-shaped, otherwise referred to as circular. The bending-type piezoelectric actuator 130 in this example is a multilayer bending-type piezoelectric actuator 130, having at least three layers formed from a piezoelectric material and comprising three electrical contacts (not shown) which can each be separately electrically activated. It will be understood that the skilled person is aware of the structure and function of a number of different types of multilayer bending-type piezoelectric actuators. In one particular example, each of the layers formed from the piezoelectric material is provided with a first electrode in electrical contact with a first planar surface of the layer and a second electrode in electrical contact with a second planar surface of the layer. The layers can be stacked together such that the first planar surface and the second planar surface of adjacent layers are facing and opposing. The electrodes from several of the plurality of layers may be electrically connected in a predetermined arrangement to one of the first electrical contact, the second electrical contact and the third electrical contact. In other words, each of the electrodes is connected to only one of the electrical contacts, and each electrical contact is connected to at least one electrode. The electrical contacts are connected to particular electrodes of each of the plurality of layers such that when a first voltage is applied to the first electrical contact and a second voltage, negative relative to the first voltage is applied to the second electrical contact, a third voltage between the first voltage and the second voltage, when applied to the third electrical contact, causes the piezoelectric actuator to bend in a first direction or a second direction, opposite the first direction, in dependence on the third voltage. In particular, when the third voltage is exactly equidistant between the first voltage and the second voltage, the piezoelectric actuator is configured not to bend away from an equilibrium position. The first voltage and the second voltage may each be spaced by a substantially identical magnitude from a ground voltage. Although the present disclosure relates to a piezoelectric actuator 130 capable of actuating in either direction from an inactive configuration, it will be understood that other examples of the valve assembly 100 may use a piezoelectric actuator which is only actively moveable in the first direction, but having a spring or other passive element to provide a restoring force to move the piezoelectric actuator in the second direction when the piezoelectric actuator is not activated.

[0044] Although the present disclosure mentions a multilayer bending-type piezoelectric actuator, it will be understood that other types of bending-type piezoelectric actuators may instead be used, for example bimorphs.

[0045] As described briefly hereinbefore, the cover member 142 covers an upper opening of the actuator housing 140 to ensure that there are no atmospheric contaminants (for example dust or dirt) passing into the actuator housing 140, via the upper opening of the actuator housing 140, which could interfere with operation of the piezoelectric actuator 130. A lower surface of the actuator housing 140 is, in this example, not sealed from the atmosphere. One or more airflow channels are provided in the actuator housing 140 to allow air to pass between a first cavity on a first side of the piezoelectric actuator 130 and a second cavity on a second side of the piezoelectric actuator 130. In this way, the pressures on both sides of the piezoelectric actuator 130 remain substantially equalised with the atmospheric pressure outside the actuator housing 140, ensuring that movement of the piezoelectric actuator 130 is not resisted by a pressure differential between the two sides of the piezoelectric actuator 130.

[0046] Although the present disclosure mentions a safety latch constitute by a solenoid and a rotary actuator, it will be understood that other types of mechanism may instead be used, for example an air actuator device with a spring, a rotary solenoid and a cam or just a manual element.

[0047] The spacer 150 in the form of the cooling portion 150 comprises one or more cooling protuberances 152, in the form of one or more cooling fins 152, for example a plurality of cooling fins 152. In this way, heat from the system (or elsewhere) which may heat the valve housing 110, and can be transferred to a first portion of the spacer 150 in contact with the valve housing 110 can be dissipated into the ambient environment via the relatively large surface area provided in contact with the ambient environment provided by the plurality of cooling fins 152. Therefore, the amount of heat passing through the spacer 150 to the actuator housing 140 via a second portion of the spacer 150, opposite the first portion, and in contact with the actuator housing 140, is reduced, protecting the piezoelectric actuator 130 and any associated electrical components in the actuator housing 140. Furthermore, any thermal energy in the flow control member can also be transferred to the cooling portion 150. As can be seen in Figure 2, in this example, the valve housing 110 further defines a third port 116. As will be explained further with reference to Figure 3 hereinafter, the first port 112 and the third port 116 are arranged to be in fluid communication independent of whether the first port 112 is in fluid

communication with the second port 114. The operation of the valve assembly 100 will be explained further with reference to Figures 4a and 4b hereinafter.

[0048] Although not shown, it will be understood that the valve housing 110 may further comprise temperature control means, for example a heater, which can be operated to control a temperature of fluid in the valve housing 110 to be within a predetermined temperature range. The temperature control means can comprise a heater and a temperature sensor to ensure the temperature remains within the predetermined temperature range. The temperature control means may be located within the valve housing 110, for example in a hole defined therein to ensure that the heater and the temperature sensor are each located proximate the fluid pathway between the first port 112 and the second port 114.

[0049] Figure 3 is an enlarged illustration of a cross-sectional view through a portion of the valve assembly 100 shown in Figures 1 and 2. As will be explained further with reference to Figures 4a and 4b hereinafter, the flow control member 120 is arranged in the sealed configuration in Figure 3. The flow control member 120 is substantially cylindrical in profile, and extends to a tip 124 to be positioned in the valve housing 110 and comprising a sealing member 126. Thus, in the sealed configuration, it can be seen that there is no fluid pathway between the first port 112 and the second port 114. However, an outer profile of the flow control member 120, for example an outer diameter of the flow control member 120 is smaller than the void in the valve housing 110 in the region of the first port 112 and the third port 116, such that there remains a further fluid pathway between the first port 112 and the third port 116, circumferentially around the flow control member 120. Thus, regardless of the position of the flow control member 120, fluid can continue to flow between the first port 112 and the third port 116. It will be understood that the flow control member 120 is substantially sealed relative to an outer connection from the valve housing 110, for example via the spacer 150. In this way, fluid flowing between the first port 112 and the third port 116 cannot leak out of the valve housing 110. It will be understood that a seal can be provided surrounding the flow control member 120, between the spacer 150 and the valve housing 110, whereby to ensure substantially no fluid leakage out of the valve housing 110 via any space between the valve housing and the spacer 150 or between the spacer 150 and the flow control member 120.

[0050] In this example, it can be seen that the first port 112 and the third port 116 are axially offset in the axial direction of the flow control member 120. The inventors have found that this arrangement improves the flow of fluid between the first port 112 and the third port 116. In particular, this arrangement ensures that fluid flowing between the first port 112 and the third port 116 sweeps substantially the entire volume around the flow control member 120.

[0051] As shown in Figure 2, both the first port 112 and the third port 116 define a wide mouth portion, tapering to a narrow throat portion. Thus, external tubing (not shown) can be inserted into the wide mouth portion and sealed therein to ensure that fluid flow between the first port 112 and the third port 116 continues within the connected external tubing, without escaping outside the external tubing and the first and third ports 112, 116, for example to atmosphere.

[0052] The second port 114 in this example is provided by a replaceable capillary tube 119 to be fitted within a second port orifice 118. The second port orifice 118 is sized to have fitted therein the capillary tube 119. This arrangement will be explained more fully with reference to Figures 4a and 4b hereinafter. The sealing member 126 is formed from a material suitable to seal the second port 114 when abutted against an open end of the capillary tube 119 with sufficient sealing force. In this example, the sealing member 126 is formed from a soft metal, for example gold. The material of the sealing member 126 can be chosen to ensure that the sealing member 126 does not chemically react with the fluid passing through any of the first port 112, the second port 114 and the third port 116.

Additionally or alternatively, the material of the sealing member 126 can be chosen to ensure that the sealing member 126 is thermally stable at the operating temperature of the valve assembly 100.

[0053] Figures 4a and 4b are illustrations of a cross-sectional view through a lower portion of the valve assembly 100 shown in Figures 1 to 3, shown in an unsealed configuration (Figure 4a) and a sealed configuration (Figure 4b). In particular, Figures 4a and 4b show the valve housing 110 and a lower portion of the spacer 150 of the valve assembly, showing an internal arrangement within the valve housing 110 when the valve assembly 100 is in the unsealed configuration (Figure 4a) and the sealed configuration (Figure 4b). Figure 4a shows the valve assembly 100 in the unsealed configuration. As can be seen, a gap G is provided between the sealing member 126 and the open end of the capillary tube 119 providing the second port 114, such that there exists a fluid pathway between the second port 114 and the first port 112. It should also be noted that there also exists a fluid pathway between the second port 114 and the third port 116 in this example, which includes the third port 116. Figure 4b shows the valve assembly 100 in the sealed configuration. As in Figure 3 described hereinbefore, there is no gap between the sealing member 126 and the open end of the capillary tube 119 providing the second port 114. In this way, it can be seen that there is no fluid pathway between the first port 112 and the second port 114, or between the second port 114 and the third port 116. As noted in relation to Figure 3, in the sealed configuration, there still exists the further fluid pathway between the first port 112 and the third port 116.

[0054] Figures 4a and 4b also show sealing means 170 in the form of a resiliently deformable plug 170, sometimes referred to as a ferrule 170, used to retain and seal the capillary tube 119 in place in the second port orifice 118 described in relation to Figure 3 hereinbefore. In this way, fluid can only pass between the second port 114 provided by an inner passage of the capillary tube 119 and one or more of the first port 112 and the third port 116, and cannot escape from the cavity within the valve housing 110 in any way between the second port orifice 118 and the capillary tube 119. In this example, the plug 170 is held in place by a threaded fastener 172, for example a threaded gland nut 172 which can engage with a corresponding threaded portion in the valve housing 110, and forces the plug 170 against an outer face of the valve housing 110 around the second port 114, as well as around the capillary tube 119. Thus, fluid cannot pass the plug 170 either between the plug 170 and the capillary tube 119 or between the plug 170 and the valve housing 110. Due to the high pressures in the system, the plug 170 can be formed from metal (such as Hastelloy or stainless steel) or high-temperature resistant plastic (such as Vespel or PEEK), yet still be considered resiliently deformable. The threaded gland nut 172 is typically formed of a material harder than the plug 170 in order to seal the system. Examples of such arrangements will be known to the skilled person.

[0055] The plug 170 can be removed to allow replacement of the capillary tube 119 as necessary, for example if an internal diameter of a different size is required, or if the capillary tube 119 becomes partially or completely blocked and needs to be replaced.

Once the capillary tube 119 is replaced with a new tube 119, the plug 170 can be re inserted to ensure the second port 114 remains sealed other than for fluid meant to be passing through the capillary tube 119. In some examples, the plug 170 may be a single use consumable which will need to be entirely replaced each time the capillary tube 119 is replaced.

[0056] In use, the valve assembly described hereinbefore with reference to Figures 1 to 4b is versatile, and can be used in a number of ways. Where a high-pressure system is connected to the second port 118, for example via the capillary tube 119, a precise amount of sample can be extracted from the system. In this case, a carrier fluid, such as a carrier gas, at a lower pressure is passed between the first port 112 and the third port 116 continuously, for example from the third port 116 to the first port 112 and thereafter to analysis apparatus for analysis of any sample. The piezoelectric actuator 130 is activated to move the sealing member 126 away from the open end of the capillary tube 119 by a predetermined distance for a predetermined amount of time to allow a precise amount of sample to be forced out of the high-pressure system and carried by the carrier gas to the analysis apparatus for analysis. Alternatively, the sample could be collected for analysis using equipment not connected to the valve apparatus 100. In some examples, the piezoelectric actuator 130 may be activated to reduce a sealing pressure applied between the sealing member 126 and the open end of the capillary tube 119 in order to allow a predetermined amount of fluid from the high-pressure system to seep out of the second port 118 and into the carrier gas flowing between the first port 112 and the third port 116.

[0057] In an alternative mode of operation, the valve assembly may be used as an injection valve (sometimes referred to as a dosing valve) for injecting a system with a predetermined amount of a fluid injection component into the system. In this case, a stream of the fluid injection component is passed between the first port 112 and the third port 116 at first pressure greater than the pressure in the system into which the fluid injection component is to be injected. The system is connected to the valve assembly via the second port 114, in particular via the capillary tube 119. The piezoelectric actuator 130 is activated to move the sealing member 126 away from the open end of the capillary tube 119 by a predetermined distance for a predetermined amount of time to allow a precise amount of the fluid injection component to be forced into the system via the second port 114. In some examples, the piezoelectric actuator 130 may be activated to reduce a sealing pressure applied between the sealing member 126 and the open end of the capillary tube 119 in order to allow a predetermined amount of the fluid injection component passing between the first port 112 and the third port 116 under high pressure to seep into the second port 118 and thereafter into the system connected thereto.

[0058] The carrier fluid should be chosen to not react with the components of the system with which it will come into contact, such as the sample and the fluid injection component.

[0059] Figure 5 is an illustration of a cross-sectional view through a further valve assembly 200. The structure and operation of the further valve assembly 200 is substantially similar to that of the valve assembly 100 described with reference to Figures 1 to 4b hereinbefore, apart from the hereinafter noted differences. Within the actuator housing 240, the piezoelectric actuator 230 is held in place at an outer boundary thereof relative to the actuator housing 240 via a first support member 244 and a second support member 246. Both the first support member 244 and the second support member 246 are formed, from a resiliently deformable material, as an O-ring. Furthermore, two further O- rings 282, 284 are provided for engaging with the through-hole 234 in the centre of the piezoelectric actuator 230.

[0060] In this example, the actuator housing 240 is open at an upper end thereof, and the piezoelectric actuator 230 is not shielded from the ambient environment.

[0061] The spacer 250 is formed from a polymer material, in particular polyether ether ketone (PEEK) which provides an insulative function to reduce heat transfer between the valve housing 210 and the actuator housing 240. In this way, it will be appreciated that cooling fins may not be required where the material is sufficiently thermally insulating.

[0062] As can be seen in Figures 5 and 6, the first port 212 need not be provided at a different axial position to the third port 216 relative to the axial direction of the flow control member 220. In this example, the first port 212 is provided at substantially the same axial position to the third port 216 relative to the axial direction of the flow control member 220.

[0063] Figured 6 is an enlarged illustration of a cross-sectional view though a portion of the valve assembly shown in Figure 5. The second port 214 comprises a constricted section 286 having an inner diameter sufficiently small to reduce a flow rate therethrough to enable a precise amount of fluid to pass therethrough between the second port 214 and the first port 212 past the sealing member 226. Thus, the restriction section 286 is integrally formed with the valve housing 210 and is not provided by a separate capillary tube, as in the embodiment shown in Figures 1 to 4b. Furthermore, it will be seen that a portion of the valve housing 210 to be contacted by the sealing member 226 when the valve assembly 200 is provided in the sealed configuration (as shown in Figure 5 and 6), is slightly raised, whereby to reduce a surface area of the valve housing 210 around the second port 214 in contact with the sealing member 126. This ensures that a higher sealing pressure can be applied by the piezoelectric actuator 230 compared to the situation where a larger surface area of the valve housing 210 was in contact with the sealing member 226 in the sealed configuration. Yet further, the relatively small inner diameter of the constricted section 286 of the second port 214 ensures that a smaller compressive force is required to close port 214 than would be required were the constricted section 286 to have a larger inner diameter.

[0064] The operation of the valve assembly 200 shown in Figures 5 and 6 is substantially similar to the operation of the valve assembly 100 shown in Figures 1 to 4b and described with reference to those figures hereinbefore.

[0065] It will be understood that in examples including a third port, the third port can be blocked up if not desired for a particular application of the valve assembly.

[0066] Thus, there is provided a valve assembly (100, 200) for controlling a high- pressure fluid flow through a fluid pathway, the valve assembly (100, 200) comprising: a valve housing (110, 210), defining: a first port (112, 212); and a second port (114, 214) configured to be fluidly connected to the first port (112, 212) via a fluid pathway; a flow control member (120, 220) controllably moveable in the valve housing (110, 210) to alter a fluid flow restriction in the fluid pathway between the first port (112, 212) and the second port (114, 214); and a piezoelectric actuator (130, 230), when activated, configured to cause the flow control member (120, 220) to move whereby to alter the fluid flow restriction, and wherein the piezoelectric actuator (130, 230) is a bending-type

piezoelectric actuator (130, 230).

[0067] Throughout the description and claims of this specification, the words“comprise” and“contain” and variations of them mean“including but not limited to”, and they are not intended to (and do not) exclude other components, integers or steps. Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

[0068] Features, integers, characteristics or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.