Actuators for pilot valves

Abstract

An actuator (1) for a pilot valve (26) comprises a housing (2), a piston (4) movably mounted in the housing (2), and an actuator chamber (20) defined between the piston (4) and the housing (2). The actuator (1) comprises a control fluid supply (16) for introducing fluid into the actuator chamber (20) to control fluid pressure, and the fluid pressure acts on the piston (4). The actuator (1) also comprises an actuating member for acting on the pilot valve (26) and a loading spring (6) located between the piston (4) and the actuating member. The loading spring (6) is arranged to resist the fluid pressure in the actuator chamber (20) to bias the piston (4). The control fluid supply (16) controls the fluid pressure, so that the fluid pressure acts on the piston (4) to resist the bias of the loading spring (6) to control the biasing force.

Description

Technical Field

[0001] The present invention relates to an actuator for a pilot valve, and in particular to a spring-loaded actuator suitable for acting on a pilot valve diaphragm. Background Art

[0002] Pilot valves are used in fluid control systems to regulate the supply of control fluid to control valves and pressure regulating devices. Pilot valves, which are usually small and easy to operate, are able to control the operation of larger valves, such as control valves or pressure regulators, which would otherwise require greater force to actuate.

[0003] A pilot valve may include a diaphragm and poppet assembly that moves between an open position that allows fluid to flow through the pilot valve and a closed position that restricts fluid flow. Pilot valves may be used to implement a variety of different control strategies. These may include control of pressure downstream of a control valve or pressure regulator (commonly referred to as pressure relief) and control of pressure upstream of a control valve (commonly referred to as pressure holding).

[0004] In a pressure relief pilot valve, the pressure downstream of the pilot valve acts on the diaphragm against the force of the loading spring. The force exerted by the loading spring on the pilot diaphragm can be adjusted by compressing or resetting the loading spring. This determines the set target pressure or set point for the fluid flowing out of the pilot valve.

[0005] If the downstream pressure exceeds the set point, the force of the downstream pressure on the diaphragm will be greater than the opposing force of the loading spring, so that the diaphragm and poppet valve will be biased to restrict the flow through the pilot valve. The reduction in flow through the pilot valve causes a change in the control pressure transmitted to the control valve or pressure regulator that is fluidly connected to the pilot valve. This, in turn, causes the control valve or pressure regulator to close, thereby reducing the flow through the control or pressure regulator and subsequently reducing the downstream pressure.

[0006] Conversely, if the downstream pressure is less than the set value, the force of the loading spring on the diaphragm will be greater than the opposing force of the downstream pressure on the diaphragm, so that the diaphragm and poppet valve will be biased to increase the flow through the pilot valve. The increase in the flow of control fluid through the pilot valve causes a change in the control pressure transmitted to the control valve or pressure regulator. This, in turn, causes the control valve or pressure regulator to open, thereby increasing the flow through the control or pressure regulator and subsequently increasing the downstream pressure.

[0007] The setting can be adjusted by compressing or returning the loading spring using an actuator, thereby increasing or decreasing the biasing force acting on the diaphragm and poppet setting, respectively.

[0008] Figure 1Such an actuator 41 is shown, which includes an adjustment bolt 42 disposed at the end of a loading spring 43, so that when the bolt 42 is rotated, the loading spring 43 is compressed or reset. The compression of the loading spring 43 exerts a biasing force on the pilot diaphragm 44 and the poppet 45 of the pilot valve 46, which can be adjusted to determine the desired setting. This approach may not allow for precise or remote control of the pilot valve setting.

[0009] Alternatively, the actuator may include an actuator diaphragm to which control pressure is supplied by fluid flow from a control source through a flexible hose. The force generated by this control pressure is transmitted from the actuator diaphragm to the loading spring through a pin, thereby compressing the loading spring. The compression of the loading spring exerts a force on the pilot diaphragm and the poppet valve, thereby acting to bias the pilot valve to control the set point.

[0010] As will be appreciated, the above solution is complex and has multiple points of failure. For example, the actuator diaphragm is susceptible to rupture, resulting in leakage of the control fluid and a corresponding loss of pressure. This can significantly reduce the efficiency of the valve. In addition, the limited travel of the actuator diaphragm and pin arrangement means that the compression range of the loading spring is limited, thereby limiting the range of possible setting values.

[0011] Additionally, the flexible hoses connecting the control fluid source to the diaphragms are often a significant source of leaks and pressure losses. Summary of the invention

[0012] The present invention aims to provide an improved actuator for a pilot valve.

[0013] From a first aspect, the present invention provides an actuator for a pilot valve, the actuator comprising:

[0014] case;

[0015] a piston movably mounted in the housing;

[0016] an actuator chamber defined between the piston and the housing;

[0017] a control fluid supply for introducing fluid into the actuator chamber to selectively control fluid pressure in the actuator chamber, wherein the piston is arranged to be acted upon by the fluid pressure in the actuator chamber;

[0018] an actuator acting on the pilot valve; and

[0019] a loading spring between the piston and the actuator, wherein the loading spring is configured to bias the piston against fluid pressure in the actuator chamber;

[0020] Therein, the control fluid supply is arranged to control the fluid pressure in the actuator chamber, so that the fluid pressure acts on the piston against the bias of the loading spring to control the biasing force exerted by the loading spring on the actuator to actuate the pilot valve.

[0021] The present invention provides an actuator for a pilot valve, which thus enables the setting of the pilot valve to be adjusted. The setting of the pilot valve is controlled by controlling the compression of a loading spring extending between a piston and an actuator (which is arranged to act on the pilot valve (e.g., its diaphragm)) to exert a biasing force on the actuator.

[0022] The piston is mounted in a housing which together with the piston defines an actuator chamber. The brake chamber is fluidly connected to a control fluid supply which enables the fluid pressure in the (brake) chamber to be selectively controlled. The fluid pressure acts on the piston against the bias of the loading spring. Thus, the increased pressure in the actuator chamber acts on the piston to compress the loading spring.

[0023] Controlling the fluid pressure in the actuator chamber controls the compression of the loading spring, which in turn controls the biasing force that the actuator can exert on the pilot valve (e.g., the diaphragm of the pilot valve). This allows the fluid pressure in the actuator chamber to be used to control the actuation of the pilot valve, for example, depending on the pressure in the pilot valve on the opposite side of the diaphragm.

[0024] It will be appreciated that providing a piston in the actuator, for example, in place of a diaphragm and pin arrangement, helps the actuator of the present invention provide a wider (and potentially more sensitive) range of settings for the pilot valve, since the piston's travel range is potentially greater than the limited range of the diaphragm. Additionally, the piston does not flex in the same manner as the diaphragm and is therefore not subject to rupture and the resulting loss of fluid pressure, thereby helping to improve the reliability of the actuator.

[0025] The housing of the actuator may have any suitable and desired form, so as to mount the piston and define an actuator chamber together with the piston. Preferably, the housing is cylindrical (e.g., having an axis along which the cylinder extends in a direction parallel to the direction in which the piston is movable). Preferably, the housing defines an internal volume (e.g., a space) and the piston is mounted in the internal volume of the housing. Therefore, preferably, the housing includes an outer wall (e.g., cylindrical) that defines the internal volume, and the piston is exemplarily mounted on the outer wall (e.g., inner surface) of the housing. Preferably, the actuator chamber includes a portion of the internal volume of the housing.

[0026] The housing can be made of any suitable and desired material. In one embodiment, the housing is made of metal, such as stainless steel. In one embodiment, the housing is made of plastic.

[0027] The piston may be movably mounted in the housing in any suitable and desired manner. Preferably, the piston is cylindrical (e.g., having an axis along which the cylinder extends in a direction parallel to the direction in which the piston can move), e.g., to complement the cylindrical housing in which it is mounted.

[0028] Preferably, the piston comprises a piston head which is arranged to be acted upon by the fluid pressure in the actuator chamber. Thus, preferably, the actuator chamber is defined between the piston head and the housing. Preferably, the piston head is cylindrical (eg disc-shaped).

[0029] Preferably, the piston comprises a piston shaft. Preferably, the loading spring is (mounted) between the piston shaft and the actuator. Preferably, the piston shaft comprises a recess, for example, the piston shaft comprises an inner volume to receive the loading spring. Thus, preferably, the piston shaft comprises a hollow cylinder.

[0030] Preferably, the piston head is wider than the piston shaft in a direction perpendicular to the movable direction of the piston (e.g., has a larger diameter). Therefore, preferably, the housing defines an internal volume, which includes a first internal volume portion (away from the actuator) and a second internal volume portion (close to the actuator), wherein the first internal volume portion is wider than the second internal volume portion in a direction perpendicular to the movable direction of the piston (e.g., has a larger diameter), and wherein the piston head is movably mounted in the first internal volume portion (e.g., on the inner surface of the wall of the first internal volume portion) and the piston shaft is at least partially movably mounted in the second internal volume portion (e.g., on the inner surface of the wall of the second internal volume portion).

[0031] Preferably, the actuator chamber comprises a part of the first inner volume portion. Preferably, the loading spring extends at least partially through the second inner volume portion. Thus, preferably, the loading spring is mounted in a housing, e.g. the housing comprises a spring box. Preferably, the housing is arranged to mount the actuator to the pilot valve. Thus, preferably, the housing extends from the actuator chamber (e.g. from a control fluid supply, e.g. from an inlet and outlet conduit and / or a valve) to the pilot valve. Preferably, the actuator is mounted in the housing.

[0032] The piston can be made of any suitable and desired material. In one embodiment, the piston is made of metal, such as stainless steel. In one embodiment, the piston is made of plastic.

[0033] An actuator chamber defined between a piston (e.g., a piston head) and a housing (e.g., a first internal volume portion thereof) preferably includes a seal between the piston and the housing, for example, to (substantially) prevent fluid from leaking from the actuator chamber (e.g., to the other side of the piston). The seal may be provided in any suitable and desired manner. Preferably, the seal is located between the piston head and the housing (e.g., the inner surface of its wall). Preferably, the seal is located in a (e.g., circumferentially extending) groove defined in the piston (e.g., in the piston head). Preferably, the seal comprises an O-ring. In one embodiment, the seal comprises an elastomer, such as a nitrile, seal. In one embodiment, the seal comprises polytetrafluoroethylene (PTFE) or polyurethane.

[0034] It will be appreciated that the volume of the actuator chamber varies as the piston moves to change the fluid pressure in the actuator chamber (under control of the control fluid supply). Preferably, the housing is arranged to define a maximum and minimum volume of the actuator chamber. Preferably, the housing includes a stop (e.g., a shoulder, e.g., at a boundary between the first and second internal volume portions) for the piston (e.g., a piston head). Preferably, the stop defines a position at which the piston (e.g., a piston head) has a maximum volume in the actuator chamber, e.g., at a maximum travel distance of the piston.

[0035] In a preferred embodiment (e.g. when the actuator chamber is sealed to prevent control fluid from leaking to the other side of the piston (e.g. into the second interior volume)), the second interior volume is set at atmospheric pressure. This can be done in any suitable and desired manner. For example, the housing can include a hole in (the wall of) the housing, for example, from the second interior volume to the atmosphere.

[0036] The fluid used in the actuator chamber may be any suitable and desired fluid.Preferably, the fluid comprises an incompressible fluid, for example an incompressible liquid such as water or oil, or a gas such as air.

[0037] The fluid may be provided from any suitable and desired (e.g., pressurized fluid) source; preferably, the control fluid supply is fluidically connected to a fluid source for supplying fluid into the actuator chamber. In one embodiment, the fluid is supplied from a separate (e.g., pressurized) fluid source. In a preferred embodiment, the fluid is drawn from a working fluid of a fluid flow control device (e.g., a control valve or a pressure regulator) controlled by a pilot valve controlled by the actuator. Therefore, preferably, the control fluid supply is fluidically connected to a pipeline (e.g., the upstream side), wherein the fluid flow control device controls the flow of fluid through the pipeline, wherein the fluid flow control device is controlled by a pilot valve, whose set point is controlled by the actuator of the present invention.

[0038] Fluid can be introduced into the actuator chamber in any suitable and desired manner by controlling the fluid supply. In a preferred embodiment, the control fluid supply includes an inlet valve for controlling the flow of fluid into the actuator chamber (e.g., via an inlet conduit) and an outlet valve for controlling the flow of fluid out of the actuator chamber (e.g., via an outlet conduit). Therefore, preferably, the control fluid supply includes an inlet conduit and an outlet conduit (each conduit being fluidically connected to the actuator chamber). Preferably, the inlet conduit is fluidically connected to a (e.g., pressurized) fluid source. Preferably, the outlet conduit is arranged to discharge the fluid that can flow out of the actuator chamber, for example, to the atmosphere.

[0039] It will be appreciated that by actuating the inlet valve, the control fluid supply may supply fluid into the actuator chamber to pressurize the actuator chamber, thereby acting on the piston against the bias of the loading spring to move the piston (i.e., by increasing the volume of fluid in the actuator chamber) to compress the loading spring, thereby increasing the force on the actuator member. By actuating the outlet valve, the control fluid supply may cause fluid to flow out of the actuator chamber to depressurize the actuator chamber, thereby reducing the force from the pressurized fluid against the bias of the loading spring, thereby moving the piston away from the pilot valve (e.g., its diaphragm) (i.e., by reducing the volume of fluid in the actuator chamber) to reset the loading spring, thereby reducing the force on the actuator member.

[0040] Preferably, the inlet valve and the outlet valve are arranged (e.g., in their closed position) to seal the actuation chamber (e.g., by sealing the inlet conduit and the outlet conduit). It will therefore be appreciated that, in at least preferred embodiments, the control fluid supply may only need to be operated (e.g., to actuate the inlet valve and the outlet valve) when the fluid pressure in the actuation chamber is desired to be changed. In between, the actuation chamber is preferably arranged to maintain its fluid pressure.

[0041] Preferably, the inlet and outlet conduits are integrally formed in the housing. This helps reduce leakage of fluid from the actuator (e.g., the control fluid may be supplied via a flexible hose that is prone to leakage, compared to conventional actuators). This in turn helps reduce the number of times the inlet and outlet valves must be actuated, e.g., to maintain fluid pressure in the actuation chamber (actuator chamber). This thus helps reduce the power consumption of the inlet and outlet valves and helps increase the service life of the inlet and outlet valves, e.g., they may have a lifespan of a limited number of actuations.

[0042] The inlet valve and the outlet valve can be operated in any suitable and desired manner. Preferably, the inlet valve and the outlet valve are connected to a power source, such as wired to a main power source. In one embodiment, the actuator includes a battery power source for supplying power to the inlet valve and the outlet valve. When the actuator includes a battery power source, it will be appreciated that reducing leakage of fluid from the actuator helps increase the life of the battery power source.

[0043] The inlet (valve) and outlet valves may comprise any suitable and desired valves. In a preferred embodiment, the inlet valve comprises an inlet solenoid valve and / or the outlet valve comprises an outlet solenoid valve. Preferably, the inlet solenoid valve comprises an inlet direct-acting solenoid valve. Preferably, the outlet solenoid valve comprises an outlet direct-acting solenoid valve. Thus preferably, the inlet solenoid valve is actuated (e.g., pulsed) to allow fluid to flow into the actuator chamber, and preferably the outlet solenoid valve is actuated (e.g., pulsed) to allow fluid to flow out of the actuator chamber.

[0044] Preferably, the inlet (e.g. solenoid) valve and / or the outlet (e.g. solenoid) valve are mounted directly (e.g. integrally) on the housing. Preferably, the inlet (e.g. solenoid) valve and / or the outlet (e.g. solenoid) valve are arranged to directly act on (open and close) the inlet duct and the outlet duct, respectively, e.g. they are integrally formed in the housing. This helps, e.g. together with the integrally formed inlet duct and outlet duct, to reduce leakage of the control fluid from the actuator. This is because, in these embodiments, it is not necessary for the valve (e.g. solenoid valve) to be connected to the actuator via a flexible hose (i.e. as may be provided in conventional actuators) which is prone to leakage.

[0045] Preferably, the inlet (e.g. solenoid) valve and the outlet (e.g. solenoid) valve are biased closed (causing both the inlet conduit and the outlet conduit to be sealed closed to seal the actuator chamber), for example, by respective springs. Preferably, the inlet valve and the outlet valve are arranged to remain or move into a closed position upon failure (or power loss) of the inlet valve and / or the outlet valve. This helps to keep the actuator (and the pilot valve) in the same position upon failure (or power loss) of the inlet valve and / or the outlet valve, thereby helping, for example, to avoid loss of control pressure from the pilot valve (e.g., causing the fluid flow control device controlled by the pilot valve to fully open or close).

[0046] The loading spring located between the piston (e.g., piston head) and the actuator is preferably a compression spring, such as a helical compression spring or a flat wire compression spring. Preferably, the loading spring is arranged to extend between the piston head and the actuator, such as from the first internal volume portion into the second internal volume portion of the housing. Preferably, the end of the loading spring remote from the actuator (e.g., in the first internal volume portion) is at least partially located within the internal volume of the piston shaft (e.g., a hollow cylinder).

[0047] The other end of the loading spring is arranged to abut against the actuator. Preferably, the housing (e.g. the base thereof) comprises a hole through which the loading spring extends so that it can act on the actuator. Preferably, the actuator comprises a (e.g. annular) groove for receiving the loading spring. Thus, this end of the loading spring is located at the annular groove in the actuator. Since the moving part of the actuator (e.g. the piston) is separated from the pilot poppet and the diaphragm by means of the loading spring, no additional friction is added to the main control element of the pilot valve.

[0048] The actuator can be provided in any suitable and desired manner. Preferably, the actuator is arranged between the loading spring and the pilot valve (e.g., the pilot poppet valve). Therefore, movement of the actuator (e.g., as a result of the relative force of the loading spring and the fluid pressure in the pilot valve) actuates the pilot valve (e.g., its pilot poppet valve). In one embodiment, the actuator includes a plate. In one embodiment, the actuator includes a diaphragm. Providing a diaphragm helps to seal the fluid that controls the self-actuator (e.g., the second internal volume portion of the actuator) through the pilot valve. The diaphragm also helps to provide a (relatively large) surface area for the fluid pressure of the pilot valve to resist or counter the force of the self-loading spring.

[0049] In a preferred embodiment, the actuator comprises a diaphragm and a diaphragm plate.Preferably, the actuator acts directly on the (diaphragm) plate to bias the diaphragm against fluid pressure in the pilot valve (and, for example, spring force of the pilot poppet valve).

[0050] The present invention also extends to a system for controlling a pilot valve setting, wherein the system comprises:

[0051] pilot valve; and

[0052] An actuator acting on a pilot valve, the actuator comprising:

[0053] case;

[0054] a piston movably mounted in the housing;

[0055] an actuator chamber defined between the piston and the housing;

[0056] a control fluid supply for introducing fluid into the actuator chamber to selectively control fluid pressure in the actuator chamber, wherein the piston is arranged to be acted upon by the fluid pressure in the actuator chamber;

[0057] an actuator acting on the pilot valve; and

[0058] a loading spring between the piston and the actuator, wherein the loading spring is configured to bias the piston against fluid pressure in the actuator chamber;

[0059] The control fluid supply is configured to control the fluid pressure in the actuator chamber, whereby the fluid pressure acts on the piston against the bias of the loading spring to control the biasing force applied by the loading spring to the actuator to actuate the pilot valve. Thus, the actuator is configured to control the biasing force applied by the loading spring to the actuator to control the setting value of the pilot valve.

[0060] Preferably, the pilot valve comprises an inlet conduit and an outlet conduit, and a pilot valve member, wherein the pilot valve member is acted upon by an actuator of the actuator to selectively control the flow of fluid from the inlet conduit to the outlet conduit of the pilot valve. The control pressure of the control valve or pressure regulator can be taken from the upstream or downstream side of the pilot valve.

[0061] In some embodiments, the actuator comprises a secondary spring extending between the housing and the piston, for example within the second inner volume portion of the housing. Thus, preferably, the secondary spring is mounted in the housing. Preferably, the secondary spring is arranged to bias the piston against the fluid pressure in the actuator chamber.

[0062] The secondary spring is provided to reduce the force transmitted through the pilot loading spring and can be used to offset friction within the piston assembly. This can help set the setting of the pilot valve to zero. This is because the secondary spring opposes the friction and weight of the piston by acting on the housing rather than on the actuator (i.e., what the primary loading spring acts on). Therefore, when the fluid pressure in the actuator chamber is reduced to atmospheric pressure, the second spring helps to reduce the force transmitted to the actuator through the loading spring, for example, so that the loading spring is not compressed. Setting the setting to zero can cause the pilot valve to be fully closed because the force acting through the loading spring can be offset.

[0063] Preferably, the secondary spring surrounds (e.g. is located radially outside) the loading spring. Preferably, the secondary spring (i.e. the end thereof closer to the actuator) is mounted on an inwardly protruding rim (e.g. at the base) of the housing, e.g. around the hole through which the loading spring passes to act on the actuator. The other end of the secondary spring (away from the actuator) preferably abuts the piston (e.g. the base of the piston shaft).

[0064] The secondary spring may comprise any suitable and desired type of spring.Preferably, the secondary spring comprises a compression spring, such as a flat wire compression spring or a helical compression spring.

[0065] The control fluid supply is arranged to control the fluid pressure in the actuator chamber so that the fluid pressure acts on the piston against the bias of the loading spring (and, for example, the secondary spring). Increasing the fluid flow into the actuator chamber increases the pressure acting on the actuator piston, while flowing the fluid out of the actuator chamber decreases the pressure acting on the actuator piston. The control fluid supply thus controls the displacement of the actuator piston, thereby controlling the preload of the loading spring, so that the setting value of the pilot valve can be controlled.

[0066] In some embodiments, the control fluid supply (e.g., inlet valve and outlet valve (e.g., solenoid)) can be connected (e.g., provide feedback) to the control unit. This can be, for example, via a wireless or wired connection. Thus, the actuator can be remotely operated by the control unit, either manually or automatically (e.g., as part of a feedback loop).

[0067] In some embodiments, a fluid flow control device (e.g., a control valve or pressure regulator) controlled by a pilot valve (the pilot valve being actuated by the actuator of the present invention) may have one or more of its operating parameters (e.g., upstream and / or downstream pressure, fluid flow through the device, valve member position, control volume pressure, pilot valve pressure) monitored. Sensors measuring these operating parameters are preferably connected (e.g., provide feedback) to a control unit.

[0068] Preferably, the actuator is operated by a control unit based on operating parameters of the fluid flow device. This helps to enable the fluid flow device to be controlled more accurately.

[0069] Because, at least in preferred embodiments, the piston has a greater range of travel than conventional diaphragms, the present invention may be able to operate over a wider range of pressures than conventional actuators. For example, while a typical system including a diaphragm actuator may adjust the pilot valve set point between 2 bar and 4 bar, certain embodiments of the present invention may enable adjustment of set point pressures within a range of 0 bar to 7 bar. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] With reference now to the accompanying drawings, preferred embodiments of the present invention will now be described, by way of example only, in which:

[0071] Figure 1 A conventional actuator for a pilot valve is shown; and

[0072] Figure 2 and Figure 3 A cross-sectional view of an actuator for a pilot valve according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0073] Pilot valves can be used in fluid control systems to control higher pressure and / or higher flow fluid flow control devices (e.g., control valves or pressure regulators). Using a pilot valve is beneficial because it is typically smaller and easier to operate than larger downstream devices, which in turn require greater force to actuate. The pilot valve itself is typically controlled by an actuator that determines the set target pressure or set point of the pilot valve.

[0074] Figure 2 A cross-sectional view of an actuator 1 for a pressure relief pilot valve according to an embodiment of the present invention is shown, wherein the setting value of the pilot valve is at a minimum value. Figure 3 A cross-sectional view of the actuator 1 is shown, wherein the setting of the pilot valve is at a maximum value.

[0075] like Figure 2 and 3 As illustrated, a typical pilot valve 26 may include a diaphragm 14 with a poppet 28 extending vertically therefrom through a bore 30 fluidly connecting an inlet pilot fluid supply 32 to an outlet pilot fluid supply 34. The pilot valve 26 may be connected to a fluid control system that, in turn, controls a higher pressure and / or higher flow fluid control device (e.g., a control valve or pressure regulator).

[0076] For the pressure relief pilot valve, the pressure of the pilot flow downstream of the orifice 30 acts upward on the lower side of the diaphragm 14. This is opposite to the downward force applied to the upper side of the diaphragm 14 by the loading spring 6 through the actuator 13 (ie, the diaphragm plate).

[0077] The force applied by the loading spring 6 through the diaphragm plate 13 on the pilot diaphragm 14 can be adjusted by compressing or resetting the loading spring 6. This determines the set pressure or set point of the pilot valve 26. If the downstream pressure acting on the underside of the pilot diaphragm 14 exceeds the set point, the force acting upward on the underside of the diaphragm 14 will be greater than the downward force of the loading spring 6 acting on the diaphragm 14 through the diaphragm plate 13. The diaphragm 14 will then be forced upward, causing the poppet 28 to rise, effectively narrowing the pilot orifice 30 and restricting the flow through the orifice 30 and the outlet pilot flow supply 34. The reduction in flow through the outlet pilot flow supply 34 results in a change in the control pressure transmitted to the control valve or pressure regulator to which the pilot valve 26 is fluidly connected. This in turn causes the control valve / pressure regulator to close, thereby reducing the flow through the control valve and subsequently reducing the downstream pressure.

[0078] Conversely, if the downstream pressure is below the set value, the downward force of the loading spring 6 acting on the diaphragm 14 through the diaphragm plate 13 will be greater than the upward force of the downstream pressure acting on the underside of the diaphragm 14. Subsequently, the diaphragm 14 will be forced downward, causing the poppet 28 to drop, effectively widening the pilot hole 30 and increasing the flow through the hole 30 and the outlet pilot flow supply 34. The increase in flow through the outlet pilot flow supply 34 causes a change in the control pressure transmitted to the control valve or pressure regulator to which the pilot valve 26 is fluidly connected. This in turn causes the control valve or pressure regulator to open, thereby increasing the flow through the control valve and subsequently increasing the downstream pressure.

[0079] The setting of the pilot valve can be set in this manner by means of the actuator 4, which compresses and returns the loading spring 6. As will now be described, embodiments of the present invention are directed to providing an improved actuator for a pilot valve.

[0080] Figure 2 A cross-sectional view of the actuator 1 mounted on the pilot valve 26 is shown, as described above, with the setting of the pilot valve 26 at a minimum. The actuator 1 includes a housing 2, an actuator piston 4, an inlet solenoid 10, and an outlet solenoid 12. The housing 2 defines a control fluid inlet supply 16 and a control fluid outlet supply 18. The housing 2 and the actuator piston 4 together define an actuator chamber 20. The control fluid inlet supply 16 and the control fluid outlet supply 18 are fluidly connected to the actuator chamber 20 through an inlet channel 17 and an outlet channel 19, respectively. Flow through the inlet channel 17 is controlled by the inlet solenoid 10 and flow through the outlet channel 19 is controlled by the outlet solenoid 12. The inlet and outlet solenoids 10, 12 open and close to control the flow of fluid into and out of the actuator chamber 20.

[0081] The inlet solenoid 10 and the outlet solenoid 12 are integrated directly into the pilot housing 2, thereby minimizing the number of potential leak points from the actuator chamber 20. This also has the advantage of reducing power consumption and increasing the life of the inlet solenoid 10 and the outlet solenoid 12, as they do not need to be removed as frequently to replace any control fluid that may leak from the actuator chamber 20.

[0082] The control fluid inlet supply 16 is fluidly connected to the upstream flow of working fluid in the fluid flow control device so that it receives fluid to generate a fluid pressure acting on the actuator piston 4. The control fluid pressure is greater than or equal to the pressure of the fluid flowing through the pilot hole 30. The control fluid outlet supply 18 is fluidly connected to the atmosphere so that fluid and pressure can be exhausted from the actuator chamber 20. The inlet solenoid 10 and the outlet solenoid 12 sprung closed but can be independently pulsed open to allow control fluid to flow into or out of the actuator chamber 20, respectively. Increasing the flow of fluid into the actuator chamber 20 increases the pressure acting on the actuator piston 4, while exhausting fluid from the actuator chamber reduces the pressure acting on the actuator piston 4.

[0083] The inlet solenoid 10 and the outlet solenoid 12 may be operated by a control system. The control system may also receive feedback from sensors that measure parameters of the fluid flow control device (eg, pressure, flow rate) and may be used to determine the setting of the pilot valve 26.

[0084] The actuator piston 4 and the pilot diaphragm 14 are located in the interior volume of the housing 2. The actuator piston 4 includes a circular piston head 3 and a hollow cylindrical piston shaft 5 extending vertically from the inner surface of the piston head 3. The loading spring 6 is positioned in the piston shaft 5 and extends between the actuator piston 4 and the diaphragm plate 13, and the diaphragm plate 13 is mounted on the diaphragm 14 so that the vertical displacement of the actuator piston 4 exerts a force on the diaphragm 14 through the loading spring 6 and the diaphragm plate 13. The setting value of the diaphragm 14 is selectively increased and decreased by increasing and decreasing the force exerted on the diaphragm 14 by the loading spring 6 through the diaphragm plate 13, i.e., by increasing or decreasing the fluid pressure in the actuator chamber 20, respectively.

[0085] Since the actuator piston 4 is separated from the diaphragm 14 and the poppet valve 28 by the loading spring 6 , the friction caused by the movement of the actuator piston 4 does not negatively affect the performance of the pilot valve 26 .

[0086] The actuator piston 4 can be in a static position (eg Figure 2 ) and the fully compressed position (as Figure 3 As shown), the actuator piston moves between the actuator chambers 20 and is sealed in the housing 2 by the actuator piston seal 24 to prevent the control fluid from leaking from the actuator chamber 20.

[0087] The housing 2 further includes an inwardly projecting lip ring 22 which projects into the central bore of the housing 2. The secondary actuator spring 8 is located within the central bore of the housing 2 such that it extends between the inwardly projecting lip ring 22 and the distal end of the piston shaft 5. The secondary actuator spring 8 enables the set point of the device 2 to be set to zero, as the secondary actuator spring 8 provides the additional force required to overcome the friction of the actuator piston seal 24 and the self-weight of the actuator piston 4. This causes the poppet valve 28 to completely seal the pilot bore 30, thereby preventing any fluid from flowing through the pilot bore 30 and the outlet pilot flow supply 34, and reducing the downstream pressure to zero. In embodiments where a zero set point is not required, the secondary actuator spring 8 may be omitted.

[0088] We will now describe Figure 2 and 3 The operation of the actuator device 1 is shown in FIG.

[0089] Figure 2 The actuator device 1 is shown with the actuator piston 4 in a rest position. In this position, the volume of the control fluid in the actuator chamber 20 is set to a minimum by the control system, which means that the downward force exerted by the control fluid pressure on the upper surface of the actuator piston 4 is less than the combined upward force of the loading spring 6 and the secondary actuator spring 8 acting on the actuator piston 4. As a result, the actuator piston 4 moves to a certain distance (e.g., farthest) from the diaphragm plate 13, thereby reducing the compression of the loading spring 6 to a reduced (e.g., minimum) value. The secondary actuator spring 8 resists the weight of the actuator piston 4 and the friction of the actuator seal 24, so that the weight of the actuator piston is not transferred to the diaphragm 14 through the loading spring 6 and the diaphragm plate 13, and the loading spring 6 extends to an increased (e.g., maximum) length. As a result, the downward force acting on the diaphragm 14 is reduced (e.g., minimized), thereby reducing the setting value of the pilot valve 26 to a reduced (e.g., minimum) value.

[0090] To increase the setting of the pilot valve 26, the inlet solenoid 10 is pulsed open to allow control fluid to flow into the actuator chamber 20. The pressure of the control fluid in the actuator chamber 20 exerts a force on the upper surface of the actuator piston 4 that is greater than the combined opposing force of the loading spring 6 and the secondary actuator spring 8. As a result, the actuator piston 4 is pushed toward the Figure 3 1 and the loading spring 6 and the secondary actuator spring 8 are compressed. The compression of the loading spring 6 increases the downward force on the diaphragm 14 through the diaphragm plate 13, thereby biasing the poppet valve 28 toward the open position. This causes the inlet pilot flow supply 32 to be supplied with a higher pressure through the pilot valve 26, thereby increasing the setting value of the pilot valve 26.

[0091] Figure 3The actuator device 1 and the actuator piston 4 are shown moved to a position closest to the diaphragm plate 13, thereby providing an increased (e.g., maximum) compression of the loading spring 6 and the secondary actuator spring 8. In this position, the volume of the control fluid in the actuator chamber 20 is set to an increased (e.g., maximum) value by the control system.

[0092] Due to the increased (eg, maximum) compression of loading spring 6 , loading spring 6 exerts an increased (eg, maximum) force on diaphragm 14 through diaphragm plate 13 , thereby increasing the setting of pilot valve 26 to an increased (eg, maximum) value.

[0093] To reduce the setting of the pilot valve 26, the outlet solenoid 12 is pulsed open to allow control fluid to flow from the actuator chamber 20 through the control fluid outlet feed 18 to atmosphere. As a result, the pressure in the actuator chamber 20 decreases, causing the upward force exerted on the actuator piston 4 by the pilot load spring 6 and the secondary actuator spring 8 to become greater than the opposing force caused by the control fluid pressure. As a result, the actuator piston 4 is forced upward. Figure 2 The position shown is moved and the pilot loading spring 6 is subsequently extended, thereby reducing the force on the pilot diaphragm 14. As a result, the poppet valve 27 is biased towards the closed position, closing the inlet pilot flow supply 32, which means that a lower downstream pressure is required to close the orifice 30. Therefore, the setting of the pilot valve 26 is reduced.

[0094] From the above, it can be seen that in at least preferred embodiments, the present invention provides an actuator for a pilot regulator that can set a control pressure for a pressure regulator or control valve, wherein the control pressure is set by compression of a piston by a load spring. The use of an actuator piston rather than an actuator diaphragm improves the reliability of the actuator because the actuator piston is more resilient to fracture or fatigue. Further, the larger stroke size of the piston provides a greater control range for the set point of the prior art actuator.

[0095] although Figure 2 and 3 The actuator in the embodiment has been shown to be used with a specific pilot valve, but those skilled in the art will recognize that the actuator of the present invention can be used with a variety of different pilot valves. In particular, the pilot valve can be operated in different settings, for example, so that the valve is closed when the fluid pressure in the actuator chamber increases, and the valve is opened when the fluid pressure in the actuator chamber decreases.

Claims

1. An actuator for a pilot valve, the actuator comprising: case; a piston movably mounted in the housing; an actuator chamber defined between the piston and the housing; a control fluid supply for introducing fluid into the actuator chamber to selectively control fluid pressure in the actuator chamber, wherein the piston is arranged to be acted upon by the fluid pressure in the actuator chamber; an actuating member acting on a pilot valve; and a loading spring between the piston and the actuator, wherein the loading spring is configured to bias the piston against fluid pressure in the actuator chamber; wherein the control fluid supply is arranged to control the fluid pressure in the actuator chamber so that the fluid pressure acts on the piston against the bias of the loading spring to control the biasing force exerted by the loading spring on the actuator to actuate the pilot valve; and The control fluid supply comprises an inlet valve for controlling the flow of fluid into the actuator chamber and an outlet valve for controlling the flow of fluid out of the actuator chamber, wherein the inlet valve and the outlet valve are mounted directly on the housing.

2. The actuator according to claim 1, wherein: The piston includes a piston shaft having a recess defined therein to receive the loading spring.

3. The actuator according to claim 1 or 2, wherein: The actuator chamber includes a seal between the piston and the housing.

4. An actuator according to claim 1 or 2, wherein the control fluid supply is fluidly connected to a fluid source for supplying the fluid into the actuator chamber.

5. An actuator according to claim 1 or 2, wherein the control fluid supply comprises an inlet conduit and an outlet conduit, wherein the inlet conduit and the outlet conduit are integrally formed in the housing.

6. An actuator according to claim 1 or 2, wherein the inlet valve and the outlet valve are arranged to seal the actuator chamber.

7. An actuator according to claim 1 or 2, wherein the inlet valve comprises an inlet solenoid valve and the outlet valve comprises an outlet solenoid valve.

8. An actuator according to claim 1 or 2, wherein the inlet valve and the outlet valve are biased closed.

9. The actuator according to claim 1 or 2, wherein: The actuator includes a secondary spring extending between the housing and the piston, wherein the secondary spring is configured to bias the piston against fluid pressure in the actuator chamber.

10. The actuator of claim 9, wherein the secondary spring surrounds the loading spring.

11. A system for controlling a pilot valve setting, wherein the system comprises: An actuator and a pilot valve as claimed in claim 1 or 2.

Images