Electro-hydraulic systems and hydraulic valves

Abstract

An electro-hydraulic system (1) comprises a first cam connected such that rotation of the rotor (6) of an electric motor (2) causes movement of the first cam (8); a first hydraulic valve (12) arranged such that movement of the first cam (8) causes movement of the first valve (12) from a first to a second configuration; and a second hydraulic valve (14) arranged such that rotation of the rotor (6) causes movement of the second valve (14) from a third to a fourth configuration. Also disclosed is a hydraulic valve (12) comprising a cam follower (32) connected to a valve member (42) such that rotation of a cam (8) in a first direction from a closed to an open position causes the valve (12) to move from a closed to an open configuration. As the cam (8) rotates from the closed position to the open position, the displacement of the cam follower (32) with respect to the axis of rotation of the cam (8) increases to a maximum and then decreases.

Description

[0001] Electro-hydraulic systems and hydraulic valves

[0002] Field of the Invention

[0003] The present invention concerns electro-hydraulic systems and hydraulic valves. More particularly, but not exclusively, this invention concerns electro- hydraulic systems in which an electric motor is used to operate hydraulic valve(s). The invention also concerns a method of operating such a system. Additionally or alternatively, more particularly, this invention concerns a bistable hydraulic valve.

[0004] Background of the Invention

[0005] An electro-hydraulic system comprises at least one hydraulic valve that controls the flow of a fluid through the system and an electric motor arranged to control that valve. Electro-hydraulic systems may comprise other hydraulic elements, for example accumulators, pumps, motors and / or actuators. Electro-hydraulic systems may comprise one or more external ports via which the system is connected to a supply of pressurised fluid, a low-pressure reservoir, and / or an external hydraulic element. An electro-hydraulic system may be a self-contained unit. For example, the system may comprise a housing that contains the hydraulic valve(s), electric motor(s), accumulate^ s), fluid reservoir(s), hydraulic pump(s), hydraulic motor(s), actuator(s) and / or any other elements of the system.

[0006] As the complexity of the system increases more and different types of valve are required to control the flow of fluid through the system. In prior art systems, each valve is controlled by a different electric motor. The operation of the different valves is then synchronized by a control system that controls the operation of the various motors. This may limit the speed at which the valve can switch between different configurations.

[0007] A servo valve typically comprises a moving element (spool) and a fixed element (for example a housing, sleeve or manifold) including fluid inlets and outlets (flow ports). The relative movement of these two elements controls the flow of fluid through the valve and thereby the system of which the valve forms a part. A servo valve can control the flow of fluid to or from two or more hydraulic elements, but will suffer from a constant leakage of fluid around the spool. This constant leakage can be considered an energy loss which decreases the efficiency of the system. Thus, it would be advantageous to provide a more energy-efficient way of controlling the flow of fluid within complex electro-hydraulic systems.

[0008] In many systems, the design of electro-hydraulic systems is constrained by available space. Accordingly, it is generally desirable to reduce the size of system required for a given flow rate. Additionally or alternatively, it is generally desirable to reduce the mechanical complexity of a system.

[0009] The present invention seeks to mitigate the above-mentioned problems. Alternatively or additionally, the present invention seeks to provide an improved electro-hydraulic system and method of operating such a system. Alternatively or additionally, the present invention seeks to provide an improved hydraulic valve and method of operating such a valve.

[0010] Summary of the Invention

[0011] The present invention provides, according to a first aspect an electro-hydraulic system comprising: an electric motor comprising a stator and a rotor mounted for rotation with respect to the stator; a first cam connected to the rotor such that rotation of the rotor causes movement of the first cam; a first hydraulic valve arranged such that movement of the first cam causes movement of the first valve from a first configuration to a second configuration; and / or a second hydraulic valve arranged such that rotation of the rotor causes movement of the second valve from a third configuration to a fourth configuration.

[0012] Thus, electro-hydraulic systems in accordance with the present invention may have at least two hydraulic valves which are moved between different configurations by the rotor of the same motor. This may allow the operation of the valves to be synchronized. Additionally or alternatively, synchronizing via the rotor may allow a single motor to control multiple valves and / or for synchronization to be achieved in a mechanically simple, compact and / or robust manner. The use of a cam may allow for different types of valves to be operated by the same rotor and / or provide additional flexibility in the layout of the valves relative to the rotor. For brevity, as used herein, ‘valve’ refers to a hydraulic valve unless otherwise stated. It may be that the fluid is a liquid.

[0013] A configuration may be an open configuration. An open configuration may be defined as a configuration in which fluid is able to flow through the valve along a flow path. A valve may have more than one open configuration. A valve may have an open configuration in which fluid is able to flow through the valve along a flow path, and another open configuration in which fluid is able to flow through the valve along the same flow path but in which the valve provides an increased resistance to flow in comparison with the other open configuration. A valve may have further open configurations in which fluid is able to flow through the valve along the same flow path but in which the valve provides an altered resistance to flow in comparison with the first open configuration. A valve may have a discrete number of different open configurations providing different flow resistance. Alternatively, a valve may have a continuum of open configurations with the flow resistance varying across said range. Thus, a valve may be a proportional control valve. A valve may have an open configuration, in which fluid is able to flow through the valve along a flow path and another open configuration in which fluid is able to flow through the valve along a different flow path. A valve may have further open configurations, in which fluid is able to flow through the valve along further, different, flow paths. Thus, a valve may be a multiway valve, for example a three or four-way valve. A valve may have a closed configuration. A closed configuration may be defined as a configuration in which the flow of fluid through the valve is prevented. It will be appreciated that in some valves, the intended flow paths through the valve are closed off in a closed configuration, but there will nevertheless be some leakage. For example, when a spool valve is in a closed configuration the flow paths between the ports via the spool are closed off, but there will be some quiescent leakage around the spool. It may be that the closed configuration is a shut-off configuration, being a closed configuration in which there is no leakage through the valve.

[0014] It may be that each first, second and / or further (if present) valve is arranged such that movement of the rotor (and / or a first, second or further cam, if present) causes movement of the valve from one of the above configurations to another of the above configurations. Each valve may have one or more open configurations that provide a different flow resistance along the same flow path and / or one or more open configurations that provide different flow paths. For clarity, numbering (e.g. first, second, third, fourth, further, etc.) may be used to refer to different configurations and / or different open configurations of different valves.

[0015] The system may be configured such that, in use, the or each valve has a connection to a supply of pressurised fluid, for example from another hydraulic element within the system (e.g. an accumulator or pump) or via one or more external ports of the system connectable to a supply of pressurised fluid. The system may be configured such that, in use, the or each valve has a connection to tank or return, for example from another hydraulic element within the system (e.g. a reservoir) or via one or more external ports of the system connectable to an external retum / tank. The system may be configured such that, in use, the or each valve has one or more service connections, for example a connection via which fluid is provided to another hydraulic element internal or external to the system e.g. an actuator. A valve may have a single service connection, or multiple service connections. It may be that different open configurations provide flow paths between different combinations of the pressure, return / tank, first service (if present) and / or second service (if present) connections. A closed configuration may prevent flow between pressure and a service connection, between a service and a tank / retum connection and / or between a pressure and a tank / return connection. It may be that said connections are made via the flow ports of a valve.

[0016] It may be that each of the first, second and / or further (if present) valves are spaced apart along the longitudinal axis of the rotor. It may be that the or each valve is associated with a different cam.

[0017] Alternatively, it may be that the first, second and / or further (if present) valves are arranged such that movement of the first cam causes movement of each of said valves from one of the above configurations to another of the above configurations. For example, there may be a plurality of hydraulic valves arranged such that rotation of the same cam (e.g. the first cam) moves each of the hydraulic valves from one configuration to another.

[0018] It may be that the first configuration is an open configuration (e.g. a first open configuration) and the second configuration is a closed configuration, or vice versa. Alternatively, it may be that, the first configuration is a first open configuration in which fluid is able to flow through the valve along a first flow path and the second configuration is a second open configuration in which either (i) fluid is able to flow through the valve along the first flow path but with an altered flow resistance as compared to the first open configuration and / or (ii) fluid is able to flow through the valve along a second, different, flow path. The first valve may have further configurations, e.g. a closed configuration in addition to the first and second open configurations, and / or further open configurations in which fluid can flow along further, different, flow paths and / or with differing flow resistance along one of the first, second and / or further flow paths. The first valve may be arranged such the movement of the first cam causes movement of the first valve from the first configuration to the second configuration and / or to further (if present) configurations.

[0019] It may be that the third configuration is an open configuration (e.g. a third open configuration) and the fourth configuration is a closed configuration, for example a shut-off configuration, or vice versa. Alternatively, it may be that, the third configuration is a third open configuration in which fluid is able to flow through the valve along a third flow path and the fourth configuration is fourth open configuration in which either (i) fluid is able to flow through the valve along the third flow path but with an altered flow resistance as compared to the third open configuration and / or (ii) fluid is able to flow through the valve along a fourth, different, flow path. The second valve may have further configurations, e.g. a closed configuration in addition to the third and fourth open configurations, and / or further open configurations in which fluid can flow along further, different, flow paths and / or with differing flow resistance along one of the third, fourth, and / or further flow paths. The second valve may be arranged such the movement of the rotor (and second cam, if present) causes movement of the second valve from the third configuration to the fourth and / or to further (if present) configurations.

[0020] It may be that the electro-hydraulic system comprises a cam connected to the rotor such that rotation of the rotor causes movement of the second cam. It may be that the second hydraulic valve is arranged such that movement of the second cam causes movement of the second hydraulic valve from the third configuration to the fourth configuration.

[0021] The first valve and first cam may be arranged such that rotation of the rotor in a first direction from a first position to a second position causes the first valve to move from the first configuration to the second configuration. The second valve (and / or second cam, if present) may be arranged such that rotation of the rotor in the first direction causes the second valve to move from the third configuration to the fourth configuration. The rotation in the first direction to move the second valve may be a rotation from the first position to the second position (i.e. the second valve may be moving during the same motion of the rotor as the first valve), or a rotation from a third position to a fourth position. The third position may be between the first and second positions. Alternatively, the third position may be after the second position in the first direction. Alternatively, the second valve (and / or second cam, if present) may be arranged such that rotation of the rotor in a second, opposite, direction (e.g. from the second position to the first position, or from the fourth position to the third position, or from the first position to a fifth position) causes the second valve to move from the third configuration to the fourth configuration.

[0022] It may be that the first valve moves from the first configuration to the second configuration (and vice versa) as the rotor rotates through a first angular range, and the second valve moves from the third configuration to the fourth configuration (and vice versa) as the rotor rotates through a second, different, angular range. The angular ranges may be overlapping (e.g. one valve is opening as another is closing) and / or sequential (one valve opens and then another valve closes). For example, the valves and cam(s) may be configured such that the first valve moves from the first configuration to the second configuration over a first angular range, and then continued rotation of the rotor in the first direction over a second angular range causes the second valve to move from the third configuration to the fourth configuration.

[0023] It may be that the or each cam (e.g. the first, second, third (if present) and / or any further cam (if present) is connected to the rotor such that rotation of the rotor causes rotation of the cam. It may be that the cam and rotor are connected such that the cam rotates with the rotor. Thus, references herein to the movement of the cam in particular directions and / or between particular positions may also be understood as describing the movement of the rotor in said directions and / or between said positions, and vice versa. It may be that the rotor comprises the or each cam. It may be that the or each cam is a portion of the rotor.

[0024] It may be that each cam has an axis of rotation. It may be that each cam has a cam surface arranged to control the movement of the valve. For example, it may be that when the rotor is in one position (e.g. a first, second, third or fourth position), the cam / cam surface is spaced apart from the valve, for example a valve member (see below) of the valve. It may be that as the rotor rotates (in the first or second direction) to another position, the cam is brought into contact with the valve, for example the valve member, and thereby exerts a force on the valve member that causes the valve to move from one configuration to another. For example, the cam may urge the valve member in the first direction. It may be that the cam / cam surface abuts the valve member, for example a distal end of the valve member as the rotor rotates to said another position. It may be that as the rotor rotates from said another position to its original position, the cam moves such that it no longer exerts a force on the valve and / or no longer urges the valve member in the first direction, for example it may be that the cam moves away from the valve. The valve may be configured to return to its original configuration, for example under the pressure of a fluid flowing through the valve, a biasing mechanism and / or gravity, in the absence of a force from the cam. The valve may be biased to return to its original configuration in the absence of the cam urging the valve towards the other configuration.

[0025] The cam surface and rotor may be concentric, for example coaxial. The cam surface may be normal to the axis of rotation. The cam surface may extend circumferentially around the cam. It may be that the radial distance between the axis of rotation of the cam and the cam surface varies circumferentially (e.g. around the circumference of the cam). The cam surface may comprise one or more regions of decreasing radius (e.g. regions in which the radius is decreasing with distance in a first direction of rotation) and one or more regions of increasing radius (e.g. regions in which the radius is increasing with distance in the first direction of rotation).

[0026] The cam surface of the or each cam may extend around the circumference, for example the whole of the circumference, of the rotor at a location along the longitudinal axis of the rotor. For example, the cam may be a region of the rotor having an enlarged radius.

[0027] It may be that the electro-hydraulic system comprises a third valve, the third valve being arranged such that rotation of the rotor causes movement of the third valve from a fifth configuration to a sixth configuration. The fifth and sixth configurations may be any of the configurations discussed above. It may be that the electro-hydraulic system comprises one or more further valves, each further valve being arranged such that rotation of the rotor causes movement of the further valve from one further configuration to another further configuration. Each further configuration may be any of the configurations discussed above.

[0028] It may be that the electro-hydraulic system comprises a third cam, the third cam being connected to the rotor such that rotation of the rotor causes movement of the third cam. It may be that the third valve is arranged such that movement of the third cam causes movement of the third hydraulic valve from the fifth configuration to the sixth configuration. It may be that the electro-hydraulic system comprises one or more further cams, each further cam being connected to the rotor such that rotation of the rotor causes movement of the cam. It may be that each further valve is arranged such that movement of the further cam causes movement of the further hydraulic valve from one further configuration to another.

[0029] It may be that the second hydraulic valve differs from the first hydraulic valve. It may be that the second hydraulic valve differs from the first hydraulic valve in respect to the type and / or construction of the valve. It may be that the second hydraulic valve is of a different construction to the first hydraulic valve. It may be that the second hydraulic valve is of a different type to the first hydraulic valve. By way of example only, valves of the same type (e.g. servo valves, poppet valves) may have different construction (e.g. a different sleeve, valve member, ports and / or a different arrangement of any of the foregoing).

[0030] It may be that the first and / or second hydraulic valve differs (in construction and / or type) from any further hydraulic valve.

[0031] It may be that the first, second and / or any further hydraulic valve is a spool valve or a poppet valve.

[0032] It may be that the first, second and / or any further hydraulic valve is a shut-off valve. A shut-off valve is a valve that can provide a shut-off configuration. It may be that the shut off valve comprises a valve member and / or valve seat as described below.

[0033] It may be that the first, second, third and / or any further valve is a spool valve. A spool valve comprises a spool mounted for movement with respect to a fixed element comprising one or more flow ports. A flow port may be defined as an aperture via which fluid can flow into and / or out of a cavity in which the spool is located. The fixed element may be a sleeve which is itself received within a manifold of the electro-hydraulic system. Alternatively, the fixed element may be a manifold of the electro-hydraulic system. The manifold and / or sleeve may comprise one or more flow galleries (passageways) connected to the flow ports such that fluid can flow into or out of a flow gallery via a flow ports. A flow port may be an inlet (via which, in use, fluid flows into the cavity), an outlet (via which, in use, fluid flows out of the cavity), or bidirectional (i.e. fluid flows into or out of the cavity via the port depending on the state of the system). A spool valve may comprise at least two flow ports selected from inlet ports, outlet ports, and bidirectional ports such that, in use, fluid can flow in at least one direction along a least one flow path between said at least two ports. It may be that the surface of the spool comprises one or more grooves or passageways along which fluid can flow to or from a flow port. In use, movement of the spool may bring the grooves and / or passageways into or out of alignment with the flow port(s) to create and / or alter the flow path followed by fluid through the valve.

[0034] The spool valve may be arranged such that rotation of the rotor causes movement of the spool relative to the flow ports and thereby moves the valve from one configuration to another. Said movement of the spool may be a translation or a rotation. The spool valve may be a rotary spool valve comprising a spool mounted for rotation relative to the fixed element defining the flow ports. By rotating the spool relative to the flow ports a flow path between ports may be provided or altered thereby allowing control of the flow of fluid through the valve. The spool valve may be a linear servo valve comprising a spool mounted for translation, e.g. axial displacement, relative to the fixed element defining the flow ports. By moving the spool back and forth relative to the flow ports a flow path between the flow ports may be provided or altered thereby allowing control of the flow of fluid through the valve.

[0035] It may be that the longitudinal axis of the spool (the axis about which the spool rotates, or along which it translates) is parallel to the longitudinal axis of the rotor. It may be that the longitudinal axis of the spool and the longitudinal axis of the rotor extend along a common axis (a first axis).

[0036] It may be that the spool is connected, for example directly connected, to the rotor such that rotation of the rotor causes rotation or translation of the spool. It may be that the rotor comprises the spool. It may be that the spool is a portion of the rotor. It may be that the spool and the rotor are integrally formed in a single piece construction. It may be that the longitudinal axis of the spool (the axis about which the spool rotates, or along which it translates) is perpendicular to the longitudinal axis of the rotor.

[0037] It may be that the spool valve comprises a flexure. The flexure may be integrally formed with the spool or connected thereto. Thus, references to moving with or relative to the spool in the following should be understood as encompassing moving with the rest of, or relative to the rest of, the spool. The valve may be arranged such that movement of the flexure in a direction parallel to the longitudinal axis of the spool causes movement of the spool in a first direction, for example from one configuration to another (e.g. from the first to the second configuration, or from the third to the fourth configuration). It may be that the flexure and the spool move in phase parallel to the longitudinal axis of the spool. Thus, moving the flexure parallel to the longitudinal axis of the spool moves the spool. It may be that the flexure is configured for movement relative to the spool in a direction perpendicular to the longitudinal axis of the spool. Thus, the flexure may absorb motion exerted on the spool in a direction perpendicular to the longitudinal axis of the spool. Absorbing the perpendicular motion may be advantageous in that a linear, axial movement of the spool may reduce perpendicular forces between the spool and the manifold and result in less wear and consequently a longer lifespan for the valve. The flexure may also reduce backlash caused by forces transmitted from the spool to the drive member.

[0038] The flexure and the spool may be integrally formed in a single-piece (monolithic) construction.

[0039] It may be that the flexure is attached to the spool at only one end, e.g. a second end opposite the first end. Thus, the flexure may be a cantilever. Alternatively, it may be that the flexure is attached to the rest of the spool at both ends of the flexure.

[0040] The valve may be arranged such that the as the rotor rotates, the rotor contacts the flexure and thereby moves the spool. The flexure may include an aperture, for example at the first end or in the (lengthwise) centre of the spool. A portion of the rotor may be located in the aperture, for example the rotor may extend through the aperture. In use, the rotor may contact the flexure at the inner edge of the aperture during at least part of a rotation of the rotor. For example, rotation of the rotor may bring the rotor into (and out of) contact with the flexure at the edge of the aperture. It may be that the portion of the rotor and / or the aperture are shaped such that rotation of the rotor relative to the aperture causes the rotor to exert a force on the flexure, which moves the flexure in a first direction parallel to the longitudinal axis of the spool and thereby results in translation of the spool. The potion of the rotor may comprise a cam that urges the flexure in a first or second direction as the rotor rotates. The portion of the rotor may comprise a crank, the crank having rotational symmetry about an axis spaced apart from the longitudinal axis of the rest of the rotor, such that the as the rotor turns the crank moves along an arcuate path. It may be that the flexure absorbs any motion of the rotor that is not axial to the spool. As a result, the rotary motion of the rotor may be translated into a translation of the spool with the non-axial components absorbed by flexing of the flexure. That may advantageously reduce wear as the spool moves in the manifold, prolonging the life of the valve.

[0041] It may be that rotation of the rotor from a first position to a second position causes the rotor to exert a force on the flexure, which moves the flexure in a first direction parallel to the longitudinal axis of the spool and thereby results in translation of the spool and movement of the valve from its original configuration (e.g. the first or third configuration) to a different configuration (e.g. the second or fourth configuration). It may be that continued rotation of the rotor in the first direction from the second position to the first position causes the rotor to exert a force on the flexure, which moves the flexure in a second, opposite, direction parallel to the longitudinal axis of the spool and thereby results in translation of the spool and movement of the valve from the different configuration back to the original configuration. Alternatively, it may be that rotation of the rotor in a second, opposite, direction from the second position to the first position causes the rotor to exert a force on the flexure, which moves the flexure in a second, opposite, direction parallel to the longitudinal axis of the spool and thereby results in translation of the spool and movement of the valve from the different configuration back to the original configuration.

[0042] It may be that the spool is hollow, for example the spool may have an inner spool cavity. The flexure may extend into the spool cavity. The flexure may extend across the length of the spool cavity. The spool cavity and / or flexure may extend along the majority of the length of the spool. By providing the flexure within a cavity in the spool rather than mounting the flexure on the outside of the spool, the flexure may advantageously exert a more axial force on the spool. For example, that may reduce bending moments that would otherwise occur if the flexure was mounted off-axis on the spool. Reducing the bending moments may advantageously further reduce wear between the spool and the manifold.

[0043] The flexure may be substantially planar. The flexure may have a length parallel to the longitudinal axis of the spool. The flexure may have a height defined as the extent of the flexure parallel to the longitudinal axis of the drive member. The flexure may have a thickness. The length of the flexure may be very much greater than the height. The height of the flexure may be very much greater than the thickness. Alternatively, the flexure may be substantially round in cross-section. Thus, the length of the flexure may be very much greater than the radius.

[0044] It may be the valve comprises a valve member mounted for movement relative to a valve seat. It may be that in a closed configuration the valve member abuts the valve seat. It may be that in a shut-off configuration the valve member abuts the valve seat such that leakage through the valve is prevented. It may be that in each open configuration, the valve member is spaced apart from the valve seat. For example, movement of the valve member relative to the valve seat may be used to control the flow resistance of the valve.

[0045] The valve may be arranged such that rotation of the rotor causes a (first, second or further) cam to exert a force on the valve member and thereby move the valve member in a first direction relative to the valve seat (e.g. away from the valve seat), for example from an original configuration (e.g. a first or third configuration) to another configuration (e.g. a second or fourth configuration). It may be that valve is configured such that the valve member moves in a second, opposite, direction (e.g. towards the valve seat) in the absence of the force from the cam, for example as a result of a fluid pressure on the valve member, under the action of gravity or as a result of a biasing mechanism. It may be that valve comprises a resilient member (for example a spring or block of resilient material) configured to move the valve member in a second, opposite, direction (e.g. towards the valve seat) in the absence of the force from the cam. Thus, the resilient member may act to return the valve member to its original configuration. Other biasing mechanisms will be well known to the skilled person. The original configuration may be a closed configuration, for example a shutoff configuration. Said another configuration may be an open configuration. The electro-hydraulic system may comprise a manifold. The manifold may comprise one or more cavities. The or each hydraulic valve may be received (at least in part) within a cavity. The electric motor may be received within a cavity. The manifold may comprise one or more flow galleries, for example channels or passageways, along which, in use, fluid flows. The manifold may have a single-piece construction.

[0046] The electro-hydraulic system may comprise a housing containing the manifold, the electric motor and / or the first and second valves (and any other valves, if present). It may be that the rest of the electro-hydraulic system is contained within the housing.

[0047] The electric motor may comprise a plurality of coils and a plurality of magnets. It may be that either the plurality of magnets or the plurality of coils is mounted on the stator and the other of the plurality of magnets and the plurality of coils is mounted on the rotor. The rotor may comprise a rotor body being a region of the rotor having one of the plurality of magnets and plurality of coils mounted around its circumference. The rotor body may be integrally formed with the rest of the rotor, in a single-piece construction. The rotor body may have a larger radius that the rest of the rotor.

[0048] The electro-hydraulic system may comprise a control system configured to control the operation of the motor, for example, in response to a user input and / or a signal received from a feedback system. The pump may comprise a feedback system, for example an electrical feedback system, configured to provide information on the position of the rotor, speed of the rotor and / or the state of the first, second, third and / or any further hydraulic valves. The control system may comprise a processor and an associated memory. It may be that the processor is configured to cause the electro-hydraulic system to perform the method of the invention by executing instructions stored in the associated memory and / or controlling the motor.

[0049] If present, one or more of the valve member, valve seat, rotor, cam, spool, flexure and manifold may be formed using additive manufacturing.

[0050] In an embodiment, there is provided an electro-hydraulic system comprising: an electric motor comprising a stator and a rotor mounted for rotation with respect to the stator; a first cam being a portion of the rotor; a first hydraulic valve comprising a valve member mounted for movement relative to a valve seat, arranged such that rotation of the first cam in a first direction causes movement of the first valve from a first configuration to a second configuration; and a first spool valve (a second hydraulic valve), comprising a spool mounted for rotation with respect to one or more flow ports, wherein the spool is a portion of the rotor, such that rotation of the rotor causes movement of the spool valve from a third configuration to a fourth configuration.

[0051] In an embodiment, there is provided an electro-hydraulic system comprising: an electric motor comprising a stator and a rotor mounted for rotation with respect to the stator; a first cam and a second cam, each cam being a portion of the rotor; a first hydraulic valve comprising a first valve member mounted for movement relative to a first valve seat, arranged such that rotation of the first cam in a first direction causes movement of the first valve from a first configuration to a second configuration; a second hydraulic valve being a first spool valve, the first spool valve comprising a first spool mounted for translational movement with respect to one or more flow ports, the first spool being connected to the rotor such that rotation of the rotor causes translation of the first spool to move the first spool valve from a third configuration to a fourth configuration; a third hydraulic valve comprising a second valve member mounted for movement relative to a second valve seat, arranged such that rotation of the second cam in the first direction causes movement of the third valve from a fifth configuration to a sixth configuration.

[0052] In an embodiment, there is provided an electro-hydraulic system comprising: an electric motor comprising a stator and a rotor mounted for rotation with respect to the stator; a first cam being a portion of the rotor; a plurality of hydraulic valves (a first hydraulic valve, a second hydraulic valve, a third hydraulic valve and optionally further hydraulic valves) arranged such that rotation of the first cam moves each of the hydraulic valves from one configuration to another, wherein the longitudinal axis of each valve is perpendicular to the axis of rotation of the rotor. The above embodiments may have any of the features described above with reference to the first aspect. In a second aspect of the disclosure, there is provided a method of operating an electro-hydraulic system comprising a first hydraulic valve, a second hydraulic valve, a first cam and / or an electric motor, for example an electric motor having a stator and a rotor mounted for rotation with respect to the stator. It may be that the method comprises rotation of the rotor causing: (i) rotation of the first cam which in turn causes the first hydraulic valve to move from a first configuration to a second configuration; and / or (ii) the second hydraulic valve to move from a third configuration to a fourth configuration. The system and method of the second aspect may have any of the features described above with reference to the first aspect, or vice versa.

[0053] It may be that rotation of the rotor in a first direction causes rotation of the first cam which in turn causes the first hydraulic valve to move from the first configuration to the second configuration; and then as the rotor rotates in a second, opposite, direction, the first hydraulic valve moves from the second configuration to the first configuration. For example, rotation of the rotor in the second direction may cause rotation of the first cam in the second direction which in turn causes the first hydraulic valve to move from the second configuration the first configuration.

[0054] It may be that rotation of the rotor in a direction causes rotation of the or each cam in said direction. It may be that said rotation of the cam in turn causes the associated valve to move from one configuration to another.

[0055] It may be that rotation of the rotor in one of the first direction and a second, opposite, direction causes the second hydraulic valve to move from the third configuration to the fourth configuration; and then as the rotor rotates in the other of the first and second directions, the second hydraulic valve moves from the fourth configuration to the third configuration. For example, rotation of the rotor may cause rotation of the second cam which in turn causes the second hydraulic valve to move between the configurations.

[0056] Where, in the present specification, roman numerals are used to refer to steps, it should be appreciated that the order of the numerals does not imply any limitation of the order of the steps. For example, steps (i) and (ii) may take place in series (in either order) or simultaneously.

[0057] It may be that rotation of the rotor in one direction (e.g. the first direction) causes the first hydraulic valve to move from the first configuration to the second configuration and then from the second configuration to the first configuration. It may be that rotation of the rotor in one direction (e.g. the first or second direction) causes the second hydraulic valve to move from the third configuration to the fourth configuration and then from the fourth configuration to the third configuration. It may be that a single complete rotation (i.e. a rotation of 360 degrees) of the rotor in one direction causes (i) the first hydraulic valve to move from the first configuration to the second configuration and then from the second configuration to the first configuration; and (ii) the second hydraulic valve to move from the third configuration to the fourth configuration and then from the fourth configuration to the third configuration.

[0058] It may be that the first hydraulic valve comprises a valve member and a valve seat. It may be that rotation of the rotor in the first direction causes the first cam to urge the valve member in a first direction, such that the valve moves from the first to the second configuration. It may be that rotation of the rotor in the first direction causes the first cam to exert a force on the valve member and thereby move the valve member in the first direction. It may be that the first direction (of the valve member) is a direction away from the valve seat. Thus, it may be that rotation of the rotor in the first direction causes the first cam to exert a force on the valve member that moves the first valve from a closed configuration, for example a shut-off configuration, in which the valve member abuts the valve seat, to an open configuration in which the valve member is spaced apart from the valve seat. It may be that as the rotor continues to rotate in the first direction and / or rotates in a second opposite direction, the first cam ceases to urge the valve member in the first direction. For example, it may be that the radius of the cam decreases with continued rotation in the first direction. It may be that the first hydraulic valve returns to the first configuration, for example the valve member moves in a second, opposite, direction, in the absence of a force from the first cam / when the first cam ceases to urge the valve member in the first direction. It may be that the resilient member urges the valve member in the second, opposite, direction. Thus, as the rotor rotates and the first cam ceases to exert a force on the valve member, it may be that the resilient member urges the valve member in a second, opposite, direction to return the valve to the third configuration.

[0059] It may be that the second hydraulic valve is a spool valve comprising a spool. It may be that rotation of the rotor, for example in the first direction, causes movement of the spool relative to one or more flow ports and thereby moves the valve from the third configuration to the fourth configuration. It may be that the third configuration is a third open configuration in which fluid is able to flow through the valve along a third flow path and the fourth configuration is a fourth open configuration in which (i) fluid is able to flow through the valve along the third flow path but with an altered flow resistance as compared to the third open configuration and / or (ii) fluid is able to flow through the valve along a fourth, different, flow path.

[0060] The method may comprise operating the electric motor to rotate the rotor. The method may comprise current being supplied to the electric motor to cause the rotor to rotate relative to the stator. The method may comprise the rotor rotating in a first direction. The method may comprise the rotor rotating in a second, opposite, direction. The method may comprise controlling, for example the control system controlling, the motor to rotate the rotor and / or to change the direction of rotation of the rotor.

[0061] In a third aspect of the disclosure, there is provided a hydraulic valve comprising: a valve seat, and valve member mounted for movement with respect to the valve seat; a cam mounted for rotation with respect to the valve seat; and a cam follower. It may be that the cam follower is connected to the valve member such that rotation of the cam in a first direction from a closed position to an open position causes the valve to move from (i) a closed configuration in which the valve member contacts the valve seat such that the flow of fluid through the valve is prevented to (ii) an open configuration in which the valve member is spaced apart from the valve seat such that fluid is able to flow through the valve. It may be that the valve is arranged such that: the cam urges the cam follower in a first direction, while the cam follower is biased to move in a second, opposite, direction; further movement of the cam in the first direction is prevented when the cam is in the open position; and / or as the cam rotates in the first direction from the closed position to the open position, the displacement of the cam follower with respect to the axis of rotation of the cam increases to a maximum and then decreases.

[0062] Thus, valves in accordance with the present aspect may be stable towards the open configuration once the cam is between the open position and the point at which the displacement of the cam follower is at a maximum (the point of maximum displacement). At this stage, unless work is done to the cam to move it in a second, opposite, direction, the valve cannot return to the closed configuration against the biasing of the cam follower. Thus, in the event of a loss of power to e.g. the electric motor rotating the cam, the valve moves to or remains in the open configuration if the cam is between the point of maximum displacement and the open position. Such a valve may find application in safety-critical situations. Additionally or alternatively, such a valve may allow for increased energy efficiency, for example because the motor controlling the valve can be switched off when the valve is required to be in the open configuration for longer periods.

[0063] It may be that the hydraulic valve of the third aspect is a first, second, third or further hydraulic valve as described above in connection with the first or second aspects, or has any of the features of such valves. Equally, it will be appreciated that the valve of the present aspect may find application separately from the electro- hydraulic system of the first and second aspects.

[0064] It will be appreciated that the displacement of the cam follower is at a maximum when the portion of the cam follower that contacts the cam is at the greatest distance in the first direction from its positions when the cam is in the open and closed positions.

[0065] It may be that further movement of the cam in a second direction, being opposite to the first direction, is prevented when the cam is in the closed position.

[0066] Thus, valves in accordance with the present aspect may be stable towards the closed configuration once the cam is between the closed position and the point of maximum displacement. At this stage, unless work is done to the cam to move it in the second direction the valve cannot return to the open configuration against the biasing of the cam follower. Thus, in the event of a loss of power to e.g. the electric motor rotating the cam, the valve moves to or remains in the closed configuration if the cam is between the closed configuration and the point of maximum displacement. Thus, the valve may be a bi-stable valve which ‘fails’ open or closed depending on its state at the time at which power is lost. Such a valve may find application in safety- critical situations. Additionally or alternatively, such a valve may allow for increased energy efficiency, for example because a motor controlling the valve can be switched off when the valve is required to be in the open or closed configuration for longer periods.

[0067] It may be the valve comprises an end stop that prevents further movement of the cam in the first direction when the cam is in the open position. For example a portion of the cam and / or rotor may abut the end stop to prevent further movement of the rotor and cam. It may be the valve comprises an end stop that prevents further movement of the cam in the second direction when the cam is in the closed position. The valve may comprise a body, for example which is a portion of the manifold of the electro-hydraulic system and / or a sleeve received therein. The body may define the valve seat. The body may comprise an end stop, for example a protrusion arranged to abut a portion of the cam and / or rotor when the cam (and / or rotor) is in the open or closed position so as to prevent further movement of the cam in the first or second direction.

[0068] It may be that the cam follower and the valve member are directly connected, for example such that the valve member moves with the cam follower. Thus, references herein to the movement of the cam follower in certain directions may also be understood as describing the movement of the valve member in said directions. It may be that the valve member comprises the cam follower. It may be that the valve member and the cam follower are integrally formed in a single piece construction, for example using additive manufacturing.

[0069] The valve may comprise a biasing mechanism which urges the cam follower in the second direction. The biasing mechanism may comprise a resilient member, for example a spring (e.g. a helical or leaf spring) or a block of resilient material, arranged to urge the cam follower in the second direction. Additionally or alternatively, the valve may be configured such that fluid pressure in the valve acts to urge the cam follower in the second direction. Additionally or alternatively, the valve may be configured such that gravity acts to urge the cam follower in the second direction.

[0070] In a fourth aspect of the invention, there is provided an electro-hydraulic system comprising the valve of the third aspect, or an electro-hydraulic system of the first or second aspect comprising a valve of the third aspect. The system may comprise an electric motor comprising a stator and a rotor mounted for rotation with respect to the stator. It may be that the cam is connected to the rotor such that rotation of the rotor causes rotation of the cam, for example wherein the rotor comprises the cam.

[0071] In a fifth aspect of the invention, there is provided a method of operating an electro-hydraulic system comprising a hydraulic vale and an electric motor. It may be that the hydraulic valve comprises a valve seat, a valve member, a cam follower and / or a cam. It may be that the electric motor comprises a stator and a rotor mounted for rotation with respect to the stator. The method may comprise rotation of the rotor in a first direction causing rotation of the cam in a first direction from a closed position to an open position in which further rotation of the cam in the first direction is prevented by an end stop. It may be that said rotation of the cam causes the valve to move from (i) a closed configuration in which the valve member contacts the valve seat such that the flow of fluid through the valve is prevented to (ii) an open configuration in which the valve member is spaced apart from the valve seat such that fluid flows through the valve. It may be that as the cam rotates in the first direction from the closed position to the open position, the increasing radius of the cam urges the cam follower in a first direction until a maximum displacement of the cam follower is reached. It may be that the cam follower is biased to move in a second, opposite, direction as the radius of the cam then decreases with continuing rotation of the cam in the first direction, such that once the cam has rotated in the first direction past the point at which the maximum displacement of the cam follower is reached the valve member moves to or remains in the open configuration in the event of a loss of power to the rotor.

[0072] It may be that the method further comprises rotation of the rotor in a second, opposite, direction causing rotation of the cam in a second direction from the open position to the closed position. It may be that in the closed position further rotation of the cam in the second direction is prevented by an end stop. It may be that said rotation of the cam causes the valve to move from (i) the open configuration to (ii) the closed configuration. It may be that as the cam rotates in the second direction from the open position to the closed position, the increasing radius of the cam urges the cam follower in the first direction until a maximum displacement of the cam follower is reached. It may be that the cam follower is biased to move in the second, opposite, direction as the radius of the cam then decreases with continuing rotation of the cam in the second direction, such that once the cam has rotated in the second direction past the point at which the maximum displacement of the cam follower is reached the valve member moves to or remains in the closed configuration in the event of a loss of power to the rotor.

[0073] It will of course be appreciated that features described in relation to one aspect of the present invention may be incorporated into other aspects of the present invention. For example, the method of the invention may incorporate any of the features described with reference to the apparatus of the invention and vice versa. Description of the Drawings

[0074] Embodiments of the present invention will now be described by way of example only with reference to the accompanying schematic drawings of which:

[0075] Figure 1 shows a schematic view of an electro-hydraulic system in accordance with a first example embodiment;

[0076] Figure 2 shows a schematic view of an electro-hydraulic system 1 in accordance with a second example embodiment;

[0077] Figure 3 shows a rotor suitable for use in an electro-hydraulic system in accordance with a third example embodiment;

[0078] Figure 4 shows a cross-sectional view of the rotor of Figure 3 in an electro- hydraulic system in accordance with a fourth example embodiment;

[0079] Figure 5 shows a cross-sectional view of an electro-hydraulic system 1 in accordance with a fifth example embodiment;

[0080] Figure 6 shows a cross-sectional view of an electro-hydraulic system 1 in accordance with a sixth example embodiment;

[0081] Figure 7 shows a flow chart of an example method of operating an electro- hydraulic system;

[0082] Figures 8(a) to 8(d) show a hydraulic valve in accordance with a seventh example embodiment, at various stages of operation; and

[0083] Figure 9 shows a flow chart of an example method of operating a hydraulic valve.

[0084] Detailed Description

[0085] Figure 1 shows a schematic view of an electro-hydraulic system 1 in accordance with a first example embodiment of the disclosure. The system 1 comprises a motor 2 having a stator 4 and a rotor 6. The rotor 6 is connected to a first cam 8 and a second cam 10. A first hydraulic valve 12 is associated with the first cam 8. A second hydraulic valve 14 is associated with the second cam 10. In use, movement of the rotor 6 causes movement of the first and second cams 8, 10 and thereby movement of the first and second hydraulic valves 12,14 from one configuration to another. Thus, electro-hydraulic systems in accordance with Figure 1 may allow for coordinated operation of multiple hydraulic valves by using cams connected to the rotor of the same motor. In some embodiments, rotor 6, first cam 8 and second cam 10 rotate together, for example by having the rotor 6, first cam 8 and second cam 10 integrally formed as a single member. The first and second hydraulic valves 12,14 are shown as being on the same side of the first and second cams 8, 10 in Figure 1. It will be appreciated that the disclosure is not limited to this arrangement.

[0086] Figure 2 shows a schematic view of an electro-hydraulic system 1 in accordance with a second example embodiment of the disclosure. Like reference numerals denote like elements as between the first and second embodiments (e.g. the rotor is labelled 6 in Figures 1 and 2). Only those aspects of the second embodiment which differ from and / or have not been discussed in connection with the first embodiment are discussed here. In contrast to the first embodiment, the second embodiment does not include a second cam 10. Instead, the second hydraulic valve 14 is directly connected to the rotor 6. In use, movement of the rotor 6 causes movement of the first cam 8 (and thereby movement of the first hydraulic valve 12 from one configuration to another) and movement of the second hydraulic valve 14 from one configuration to another. Thus, electro-hydraulic systems in accordance with Figure 2 may allow for coordinated operation of multiple hydraulic valves using a cam and a hydraulic valve differently connected to the rotor. In some embodiments, rotor 6, first cam 8 and part of the second hydraulic valve 14, for example a spool, rotate together, for example by having the rotor 6, first cam 8 and spool integrally formed as a single member.

[0087] Figure 3 shows a rotor 6 suitable for use in an electro-hydraulic system in accordance with a third example embodiment. Like reference numerals denote like elements as between the first and third embodiments. Figure 3 shows a rotor 6 having the form of a single member comprising a rotor body 16, a first cam 8 and a spool 18. The rotor 6 is generally cylindrical and has regions of different diameter. The first cam 8 is located in-between, and spaced apart from, the rotor body 16 and the spool 18 along the longitudinal axis (axis of rotation) of the rotor 6. Rotor body 16 is located at a first end of the rotor 6 and is a region of enlarged radius having magnets (not shown) spaced apart around its circumference. The first cam 8 comprises a cam surface 20 that extends circumferentially around the rotor 6. The radial distance between the cam surface 20 and the longitudinal axis of the rotor 6 varies with angle around the longitudinal axis (i.e. the cam surface 20 is eccentric with respect to the axis of rotation of the rotor). The spool 18 extends away from a second end of the rotor 6, towards the first cam 8. The spool 18 is a region of the rotor 6 having reduced diameter compared to the rest of the rotor 6 and comprises one or more groves 22 in its exterior surface and / or ports 24 leading to flow passages (not shown) within the spool 18.

[0088] Figure 4 shows a cross-sectional view of the rotor 6 of Figure 3 in use in an electro-hydraulic system 1 in accordance with a fourth example embodiment. Only part of the electro-hydraulic system 1 is shown in Figure 4. Like reference numerals denote like elements as between the first to fourth embodiments. The rotor 6 is received within a manifold 26. The spool 18 is received in a cylindrical spool cavity 27 within the manifold 26. Flow galleries 28 (passageways) within the manifold 26 terminate at internal ports 30 (orifices) on the interior surface of the manifold that defines the cavity 27. The flow galleries 28 connect the internal ports 30 to other hydraulic components of the electro-hydraulic system and / or to exterior ports (not shown) via which the electro-hydraulic system is connected to other hydraulics. Rotor body 16 is concentrically located inside the stator 4 of the motor 2. The first hydraulic valve 12 which takes the form of a poppet valve having a valve stem 32 that extends perpendicular to the longitudinal axis of the rotor 6, at the same location along the longitudinal axis of the rotor 6 as the first cam 8. A spring 34 is located at the opposite end of the valve stem 32 to the rotor 6. The valve stem 32 is received within a sleeve 36 which is located within a second cavity 38 in the manifold 26. Flow galleries 28 in manifold 26 terminate at internal ports 30 on the interior surface of the manifold 26 that defines the second cavity 38. The internal ports 30 are connected to sleeve ports 38 on an interior surface of the sleeve 36 via channels (not shown) in the sleeve 36. A first set of sleeve ports 38a are formed at a first location along the length of the valve stem 32, and a second set of sleeve ports 38b are formed at a second location along the length of the valve stem. The valve stem 32 comprises an enlarged region 42 midway along its length. In a first configuration as shown in Figure 4, the enlarged region 42 abuts a valve seat 44 formed by an inner surface of the sleeve 36. The rotor 6 is mounted on bearings 46. In the fourth embodiment the manifold 26 is of a single piece construction (for example produced by additive manufacturing), but it will be appreciated that the disclosure is not limited to such manifolds.

[0089] In use, the eccentric nature of cam surface 20 means that as the rotor 6 rotates, the cam surface 20 is brought into contact with, and then pushes against, the valve stem 32 causing a translational movement of the stem 32 relative to the sleeve 36 and compression of the spring 34. As the stem 32 is pushed away from the rotor 6, the enlarged region 42 is moved away from the seat 44 thereby moving the first hydraulic valve 12 away from the first (closed) configuration to a second (open) configuration in which fluid can flow between the first set of sleeve ports 38a and the second set of sleeve ports 38b. With continued rotation of the rotor 6, cam surface 20 moves away from the valve stem 32 and spring 34 decompresses thereby returning the stem 32 to its original position in which the enlarged region 42 abuts the seat 46, and the first hydraulic valve 12 to the first (closed) configuration. At the same time, as the rotor 6 and thereby spool 18 rotates the grooves 22 and / or ports 24 are moved into an out of fluid communication with the internal ports 30, thereby changing the configuration of the valve of which spool 18 forms a part and controlling the flow of fluid through the manifold 26 / electro-hydraulic system 1. Thus, spool 18 and internal ports 30 form part of a second hydraulic valve 14 being a servo valve. Configurations of the second hydraulic valve may comprise the spool 18 being positioned so that there is no flow between the internal ports 30 (a closed configuration), the valve member being positioned so there is flow between a first pair of internal ports 30 (a first open configuration), and / or the valve member being positioned so that there is flow between a second, different, pair of internal ports 30 (a second open configuration). Various other configurations as provided by conventional servo valves will be apparent to the skilled person. In the present embodiment, the first hydraulic valve has two sets of sleeve ports, but it will be appreciated that different arrangements of internal and / or sleeve ports may be used and in some embodiments the sleeve may be absent. Similarly, the enlarged region 42 and valve seat 44 could be at different locations along the valve stem, and / or the valve seat 44 could be formed by the manifold.

[0090] Electro-hydraulic systems in accordance with the present embodiment thereby provide mechanical synchronization of the operation of hydraulic valves of different types and / or allow a single motor to control operation of multiple valves of differing types in a compact and / or mechanical. Additionally or alternatively, this is achieved in a compact and / or mechanically simple manner.

[0091] Figure 5 shows a cross-sectional view of an electro-hydraulic system 1 in accordance with a fifth example embodiment. Only part of the electro-hydraulic system 1 is shown in Figure 5. Like reference numerals denote like elements as between the first to fifth embodiments. Only those aspects of the fifth embodiment which differ from and / or have not been discussed in connection with the fourth embodiment are discussed here. In the fifth embodiment, a second hydraulic valve 14 comprises a spool 18 connected to the rotor 6 by a flexure 52. The flexure 52 is an elongate member connected at one end to the spool 50 and having an aperture 54 at the other end. The rotor 6 extends through the aperture 54, and flexure 52 extends away from the rotor 6 in a direction perpendicular to the longitudinal axis of the rotor. The spool 18 is received in a cylindrical cavity 27 within the manifold 26. Pressure flow galleries 28a, B flow galleries 28b and tank (return) flow galleries 28c within the manifold 26 terminate at internal pressure ports 30a, internal B ports 30b and internal tank ports 30c respectively on the interior surface of the manifold that defines the cavity 28. The internal pressure ports 30a are spaced apart around the circumference of the cavity 28 and all the internal pressure ports 30a are at the same location along the longitudinal axis of the cavity. The internal B ports 30b and internal tank ports 30c are similarly arranged, and each of the internal pressure ports 30a, internal B ports 30b and internal tank ports 30c are spaced apart along the longitudinal axis of the cavity 28 from the other types of internal ports. A pressure flow gallery 28a extends from the internal pressure ports 30a to the first hydraulic valve 12, which is a poppet valve of a different construction to the poppet valve of Figure 4. A first cam 8 on rotor 6 is adject one end of a valve stem 32 of the first hydraulic valve 12. In contrast to the valve of Figure 4, the valve stem 32 comprises an enlarged region 42 at the opposite end of the valve stem 32 to the rotor 6. In a first configuration as shown in Figure 5, the enlarged region 42 is spaced apart from a seat 44 formed at one end of a sleeve 36 which is located within a second cavity 38 in the manifold 26. A spring 34 is located at the opposite end of the sleeve 36 to the seat 44. The pressure flow gallery 28a connecting the second hydraulic valve 14 and the first hydraulic valve 12 terminates at an internal pressure port 30a at the end of the second cavity 38 closest to rotor 6, with another set of internal pressure ports 30a (which connect to a supply of pressurised fluid, not shown) being located at the other end of the second cavity 38. A third hydraulic valve 50 is of a similar construction to the first hydraulic valve 12 but is connected by a B flow gallery 28b to the second hydraulic valve 14, and by another B flow gallery 28b to a, for example, an actuator (not shown) . A third cam 48 on rotor 6 is located adjacent to an end of the valve stem 32 of the third hydraulic valve 50.

[0092] In use, rotation of the rotor 6 causes translation of the spool 6 and thereby allows the second hydraulic valve 14 to control the flow of fluid between the pressure flow galleries 28a and the B flow galleries 28b, and the flow of fluid between the B flow galleries 28b and the tank flow galleries 28c. In this way, an actuator or other hydraulic equipment connected to B flow galleries 28b can be controlled. Rotation of the rotor 6 also causes the valve stem 32 of the first 12 and third 50 hydraulic valves to move relative to the valve seat 44 such that at certain points of the rotation the first 12 and third 50 hydraulic valves are closed to isolate the second hydraulic valve 14 from the supply of pressurised fluid and / or the system connected to the B flow galleries 28b. In this way, quiescent leakage through the second hydraulic valve 14 can be reduced.

[0093] Figure 6 shows a cross-sectional view of an electro-hydraulic system 1 in accordance with a sixth example embodiment. Like reference numerals denote like elements as between the first to fifth embodiments. Only those aspects of the fifth embodiment which differ from and / or have not been discussed in connection with the fourth embodiment are discussed here. The sixth embodiment comprises a single cam 8, and six poppet valves 12, 14, 50, 56, 57, 58, 59, arranged around the cam 8, with the valve stem 32 of each poppet valve extending radially outwards. The construction of each poppet valve is largely as described above with reference to the fourth example embodiment. For each poppet valve, service flow galleries 28b within the manifold 26 terminate at service ports 30b which are associated with a first set of sleeve ports 38a. For each poppet valve, pressure flow galleries 28a within the manifold 26 terminate at internal pressure ports 30a which are associated with a second set of sleeve ports 38b. The service flow galleries 28b of each valve are connected to a different hydraulic element (not shown), e.g. an actuator, accumulator etc. In use, as the cam 8 rotates, the valves 12, 14, 50, 56, 57, 58, 59 open and close in series, so that each hydraulic element in turn is connected to and then isolated from the supply of pressurised fluid.

[0094] Figure 7 shows a flow chart of an example method of operating an electro- hydraulic system, in accordance with the present disclosure. The system may have any of the features described above in connection with the other embodiments. The method comprises rotation 100 of the rotor of an electric motor causing (i) a first cam to move 102, which in turn causes a first hydraulic valve to move 104 from one configuration to another (for clarity these may be referred to a first and second configurations), and (ii) a second hydraulic valve to move 106 from one configuration to another (for clarity these may be referred to as third and fourth configurations). The steps of moving 104 the first hydraulic valve and moving 106 the second hydraulic valve may take place simultaneously or sequentially (and in either order). Optionally, movement 102 of the first cam causes the cam to push 108 against a valve member of the first hydraulic valve and thereby move 110, e.g. translate, the valve member and thereby move 104 the first hydraulic valve from the closed to the open configuration. Optionally, rotation 100 causes a valve member of the second hydraulic valve to rotate 112 and thereby move 106 the second hydraulic valve between the different open configurations.

[0095] Figures 8 (a) to 8 (d) show a hydraulic valve 12 in accordance with a seventh example embodiment, at various stages of operation. It will be appreciated that such a valve may be used as the first hydraulic valve in one of the examples above, but may also find application separately. Each of Figures 8(a) to 8(d) show (i) a cross- sectional view through the valve, perpendicular to the axis of rotation of the cam / rotor, and (ii) an end on view of the rotor. Like reference numerals denote like elements as between the present and other embodiments (e.g. the rotor is labelled 6 in Figures 1 and 8). With reference to the cross-sectional views, the first hydraulic valve 12 comprises a first cam 8 surrounding the rotor 6 and located in a cavity 27 formed in the manifold 26. A valve stem 32 acts as a cam follower, and is biased towards the first cam 8 by a spring 34 located at the opposite end of the valve stem 32 to the rotor 6. The valve stem 32 comprises an enlarged region 42 midway along its length. A valve seat 44 is integrally formed in the manifold 26. In other embodiments, the valve seat 44 may be separate from the manifold, for example may be formed in a sleeve inserted into the manifold. Flow galleries 28 in the manifold 26 lead away from the region above the valve seat 44 in Figure 7, and into the lower region of the cavity 27 below the valve seat 44. In other embodiments, the flow galleries may be differently arranged. With reference to the end-on view, the rotor 6 comprises a radially extending rotor arm 60. A first end stop 62a is located at the 8 o-clock position around the outer circumference of the rotor 6. A second end stop 62b is located at the 2 o-clock position around the outer circumference of the rotor 6.

[0096] Figure 8(a) shows the first hydraulic valve 12 in a closed position in which the rotor arm 60 abuts the first end stop 62a such that clockwise rotation is prevented. The enlarged region 42 is held in an abutting relationship against the valve seat 44 by the spring 34 such that the flow of fluid through the valve is prevented, and the first cam 8 is out of contact with the valve stem 32. As the rotor 6 rotates the first cam 8 in the anti-clockwise direction away from the closed position of Figure 8(a) the first cam 8 comes into contact with the valve stem 32, as shown in the first intermediate position shown in Figure 8(b). In Figure 8(b), the enlarged region 42 is still in contact with the valve seat 44 such that the flow of fluid through the valve is prevented. As the first cam 8 continues to rotate in the anti-clockwise direction away from the position of Figure 8(b) the first cam 8 urges the valve stem 32 upwards, until it reaches a maximum displacement as shown in Figure 8(c). The upwards movement of the valve stem 32 has resulted in the enlarged region 42 moving away from the valve seat 44 such that fluid can flow through the valve past the valve seat 44 / enlarged region 42. With continued rotation of the first cam 8 in the anticlockwise direction away from the intermediate position of Figure 8(c), the radius of the first cam 8 begins to reduce, such that the spring 34 urges the valve stem 32 downwards, maintaining contact with the first cam 8. This continues until the first cam 8 reaches the open position of Figure 8(d) in which the rotor arm 60 contacts the second end stop 62b such that further anti-clockwise movement of the rotor is prevented, and the distance between the enlarged region 42 and the valve seat 44 is reduced in comparison to Figure 8(c), but fluid can still flow through the valve past the valve seat 44 / enlarged region 42. Because the valve stem 32 has gone beyond the point of maximum displacement as the first cam 8 moves from the closed position of Figure 8(a) to the open position of Figure 8(d), in the event of a loss of power to the rotor 6, the valve will remain in the open configuration. On the other hand, if the loss of power occurs before the valve stem 32 has reached the point of maximum displacement (i.e. somewhere between Figures 8(a) and 8(c)), in the event of a loss of power to the rotor 6, the valve will move to or remain in the closed configuration of Figure 8(a). Accordingly, the hydraulic valve 12 may be described as a bistable valve because it occupies one of two configurations (the closed configuration of Figure 8(a) or the open configuration of Figure 8(d)) in the event of a loss of power and depending on which side of the point of maximum displacement the valve stem is located when power is lost.

[0097] Figure 9 shows an example method of operating a bistable hydraulic valve in accordance with the present disclosure. The method comprises rotation 202 of the cam in a first direction from a closed position to an open position causing a movement 204 of the valve from a closed configuration to an open configuration. During the movement 204, the cam follower passes 206 a point of maximum displacement. In the event a loss of power 208 to the cam / rotor occurs before the cam follower passes 206 the point of maximum displacement, the valve returns to or remains in 210 the closed configuration. In the event a loss of power 208 to the cam / rotor occurs after the cam follower passes 206 the point of maximum displacement, the valve moves to or remains in 212 the open configuration. Optionally, the method comprises rotation 214 of the cam in a second, opposite, direction from the open position to the closed position causing movement 216 of the valve from the open configuration to the closed configuration. During the movement 216, the cam follower again passes 218 the point of maximum displacement. In the event a loss of power 220 to the cam occurs before the cam follower passes 218 the point of maximum displacement, the valve returns to or remains in 222 the open configuration. In the event a loss of power 220 to the cam occurs after the cam follower passes 218 the point of maximum displacement, the valve moves to or remains in 224 the closed configuration. In some embodiments, cam 8 is connected to the rotor of an electric motor for rotation therewith. Thus, a loss of power to the cam may occur when the motor is switched off. Whilst the present invention has been described and illustrated with reference to particular embodiments, it will be appreciated by those of ordinary skill in the art that the invention lends itself to many different variations not specifically illustrated herein. By way of example only, certain possible variations will now be described.

[0098] The examples above all have a rotor on which a cam and rotor body are integrally formed as part of a single-piece construction. It will be appreciated that the rotor does not necessarily need to be of a single-piece construction, but could, by way of example, comprise one or more parts connected together.

[0099] The above examples describe servo valves, and various types of poppet valve, but it will be appreciated that other types of hydraulic valve can be used. Where in the foregoing description, integers or elements are mentioned which have known, obvious or foreseeable equivalents, then such equivalents are herein incorporated as if individually set forth. Reference should be made to the claims for determining the true scope of the present invention, which should be construed so as to encompass any such equivalents. It will also be appreciated by the reader that integers or features of the invention that are described as preferable, advantageous, convenient or the like are optional and do not limit the scope of the independent claims. Moreover, it is to be understood that such optional integers or features, whilst of possible benefit in some embodiments of the invention, may not be desirable, and may therefore be absent, in other embodiments.

Claims

Claims1. An electro-hydraulic system comprising: an electric motor comprising a stator and a rotor mounted for rotation with respect to the stator; a first cam connected to the rotor such that rotation of the rotor causes movement of the first cam; a first hydraulic valve arranged such that movement of the first cam causes movement of the first valve from a first configuration to a second configuration; and a second hydraulic valve arranged such that rotation of the rotor causes movement of the second valve from a third configuration to a fourth configuration.

2. An electro-hydraulic system according to claim 1, wherein the second hydraulic valve differs from the first hydraulic valve.

3. An electro-hydraulic system according to claim 1 or claim 2, wherein the rotor comprises the first cam, for example wherein the rotor and the cam are integrally formed in a single-piece construction.

4. An electro-hydraulic system according to any previous claim, wherein the first configuration is one of a first open configuration in which fluid is able to flow through the valve along a first flow path and a closed configuration in which the flow of fluid through the valve is prevented and the second configuration is the other the first open configuration and the closed configuration; or the first configuration is the first open configuration and the second configuration is a second open configuration in which either (i) fluid is able to flow through the valve along the first flow path but with an altered flow resistance as compared to the first open configuration and / or (ii) fluid is able to flow through the valve along a second, different, flow path.

5. An electro-hydraulic system according to claim 4, wherein the closed configuration is a shut-off configuration.

6. An electro-hydraulic system according to any previous claim, wherein the third configuration is a third open configuration in which fluid is able to flow through the valve along a third flow path and the fourth configuration is a fourth open configuration in which (i) fluid is able to flow through the valve along the third flow path but with an altered flow resistance as compared to the third open configuration and / or (ii) fluid is able to flow through the valve along a fourth, different, flow path.

7. An electro-hydraulic system according to any previous claim, wherein the second hydraulic valve is a spool valve comprising a spool mounted for movement with respect to one or more flow ports, and rotation of the rotor causes movement of the spool and thereby moves the second hydraulic valve between the third configuration and the fourth configuration.

8. An electro-hydraulic system according to claim 7, wherein rotation of the rotor causes rotation of the spool valve relative to the flow ports.

9. An electro-hydraulic system according to claim 7 or claim 8, wherein the spool is a portion of the rotor, for example wherein the rotor and the spool are integrally formed in a single-piece construction;10. An electro-hydraulic system according to claim 7, wherein the second hydraulic valve comprises a flexure having an aperture, a portion of the rotor is located in the aperture, and the portion of the rotor and / or the aperture are shaped such that rotation of the rotor relative to the aperture causes the rotor to exert a force on the flexure and thereby move the flexure in a first direction parallel to the longitudinal axis of the spool which in turn results in translation of the spool relative to the flow ports and thereby moves the second hydraulic valve from the third configuration to the fourth configuration.

11. An electro-hydraulic system according to any previous claim, wherein the first hydraulic valve comprises a valve member mounted for movement relative to a valve seat, the first hydraulic valve being arranged such that rotation of the rotor causes thefirst cam to exert a force on the valve member such that the valve member moves in a first direction relative to the valve seat and thereby moves the first hydraulic valve from the first configuration to the second configuration.

12. An electro-hydraulic system according to claim 11, wherein the first hydraulic valve comprises a resilient member configured to move the valve member in a second, opposite, direction in the absence of the force from the first cam.

13. A method of operating an electro-hydraulic system comprising a first hydraulic valve, a second hydraulic valve, a first cam and an electric motor having a stator and a rotor mounted for rotation with respect to the stator, the method comprising: rotation of the rotor causing: (i) rotation of the first cam which in turn causes the first hydraulic valve to move from a first configuration to a second configuration; and (ii) the second hydraulic valve to move from a third configuration to a fourth configuration.

14. A method of operating an electro-hydraulic system according to claim 13, wherein rotation of the rotor in a first direction causes (i) rotation of the first cam which in turn causes the first hydraulic valve to move from the first configuration to the second configuration; and (ii) the second hydraulic valve to move from the third configuration to the fourth configuration; and then rotation of the rotor in a second, opposite, direction, causes (iii) rotation of the first cam which in turn causes the first hydraulic valve to move from the second configuration to the first configuration and (iv) the second hydraulic valve to move from the fourth configuration to the third configuration.

15. A method of operating an electro-hydraulic system according to claim 13, wherein rotation of the rotor in a first direction causes (i) the first hydraulic valve to move from the first configuration to the second configuration and then from the second configuration to the first configuration and (ii) the second hydraulic valve tomove from the third configuration to the fourth configuration and then from the fourth configuration to the third configuration.

16. A method of operating an electro-hydraulic system according to claim 15, wherein a single complete rotation of the rotor in the first direction causes (i) the first hydraulic valve to move from the first configuration to the second configuration and then from the second configuration to the first configuration; and (ii) the second hydraulic valve to move from the third configuration to the fourth configuration and then from the fourth configuration to the third configuration.

17. A method of operating an electro-hydraulic system according to any of claims 13 to 16, wherein the first hydraulic valve comprises a valve member and a valve seat, and rotation of the rotor in the first direction causes the first cam to urge the valve member in a first direction away from the valve seat such that the valve moves from a shut-off configuration in which the valve member abuts the valve seat to an open configuration in which the valve member is spaced apart from the valve seat.

18. A method of operating an electro-hydraulic system according to claim 17, wherein the first hydraulic valve comprises a resilient member, and as the rotor continues to rotate in the first direction and / or rotates in a second opposite direction, the first cam ceases to urge the valve member in the first direction, and the resilient member urges the valve member in a second, opposite, direction to return the valve to the shut-off configuration.

19. A method of operating an electro-hydraulic system according to any of claims 13 to 18, wherein the second hydraulic valve is a spool valve comprising a spool, and rotation of the rotor in the first direction causes movement of the spool relative to one or more flow ports and thereby moves the valve from the third configuration to the fourth configuration.

20. A method of operating an electro-hydraulic system according to claim 19 wherein the third configuration is a third open configuration in which fluid is able to flow through the valve along a third flow path and the fourth configuration is a fourthopen configuration in which (i) fluid is able to flow through the valve along the third flow path but with an altered flow resistance as compared to the third open configuration and / or (ii) fluid is able to flow through the valve along a fourth, different, flow path.

21. A hydraulic valve comprising: a valve seat, and valve member mounted for movement with respect to the valve seat; a cam mounted for rotation with respect to the valve seat; and a cam follower, the cam follower being connected to the valve member such that rotation of the cam in a first direction from a closed position to an open position causes the valve to move from (i) a closed configuration in which the valve member contacts the valve seat such that the flow of fluid through the valve is prevented to (ii) an open configuration in which the valve member is spaced apart from the valve seat such that fluid is able to flow through the valve; and the valve is arranged such that: the cam urges the cam follower in a first direction, while the cam follower is biased to move in a second, opposite, direction; and further movement of the cam in the first direction is prevented when the cam is in the open position; and as the cam rotates in the first direction from the closed position to the open position, the displacement of the cam follower with respect to the axis of rotation of the cam increases to a maximum and then decreases.

22. A hydraulic valve according to claim 21, wherein the valve is arranged such that further movement of the cam in a second direction, being opposite to the first direction, is prevented when the cam is in the closed position.

23. A hydraulic valve according to claim 21 or 22, comprising an end stop that prevents further movement of the cam in the first direction when the cam is in the open position and / or an end stop that prevents further movement of the cam in the second direction when the cam is in the closed position.

24. A hydraulic valve according to any previous claim, wherein the cam follower and the valve member are directly connected, for example wherein the valve member comprises the cam follower.

25. An electro-hydraulic system comprising the valve of any of claims 21 to 24, and an electric motor comprising a stator and a rotor mounted for rotation with respect to the stator, wherein the cam is connected to the rotor such that rotation of the rotor causes rotation of the cam, for example wherein the rotor comprises the cam.

26. A method of operating an electro-hydraulic system comprising a hydraulic vale and an electric motor, the hydraulic valve comprising a valve seat, a valve member, a cam follower and a cam, and the electric motor comprising a stator and a rotor mounted for rotation with respect to the stator, the method comprising: rotation of the rotor in a first direction causing rotation of the cam in a first direction from a closed position to an open position in which further rotation of the cam in the first direction is prevented by an end stop, said rotation of the cam causing the valve to move from (i) a closed configuration in which the valve member contacts the valve seat such that the flow of fluid through the valve is prevented to (ii) an open configuration in which the valve member is spaced apart from the valve seat such that fluid flows through the valve; and as the cam rotates in the first direction from the closed position to the open position, the increasing radius of the cam urges the cam follower in a first direction until a maximum displacement of the cam follower is reached, and the cam follower is biased to move in a second, opposite, direction as the radius of the cam decreases with continuing rotation of the cam in the first direction, such that once the cam has rotated in the first direction past the point at which the maximum displacement of the cam follower is reached the valve member moves to or remains in the open configuration in the event of a loss of power to the rotor.

27. A method according to claim 26, the method further comprising rotation of the rotor in a second, opposite, direction causing rotation of the cam in a second direction from the open position to the closed position, wherein in the closed position further rotation of the cam in the second direction is prevented by an end stop, said rotation ofthe cam causing the valve to move from (i) the open configuration to (ii) the closed configuration; and as the cam rotates in the second direction from the open position to the closed position, the increasing radius of the cam urges the cam follower in the first direction until a maximum displacement of the cam follower is reached, and the cam follower is biased to move in the second, opposite, direction as the radius of the cam decreases with continuing rotation of the cam in the second direction, such that once the cam has rotated in the second direction past the point at which the maximum displacement of the cam follower is reached the valve member moves to or remains in the closed configuration in the event of a loss of power to the rotor.

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