Abstract: A fluid-working machine for a renewable energy generation device, the fluid-working machine comprising a ring cam and a plurality of working chambers, the ring cam having an annular working surface extending around an axis of rotation of the ring cam, the annular working surface defining a plurality of waves, each working chamber having a piston, each piston in operative engagement with the ring cam working surface, the ring cam and working chambers being mounted to rotate relative to each other, cycles of working chamber volume being thereby coupled to rotation of the ring cam relative to the working chambers, characterised in that the individual waves of the ring cam working surface have an asymmetric profile.

Abstract: A fluid-working machine comprises at least one primary working chamber such as a cylinder (4) of cyclically changing volume and primary valves (7) to control the connection of the at least one chamber to low (10)- and high (9)-pressure manifolds. The machine has at least one secondary working chamber (5) of cyclically changing volume and a secondary valve (12, 21) for placing the secondary chamber in communication with the primary chamber (4) in an active state of the secondary chamber (5) and for isolating it therefrom in an idling state of the secondary chamber.

Abstract: The present invention provides a method of controlling a fluid working machine (12) having a plurality of working cylinders (14) having pistons (16) therein and arranged to drive a shaft (18), in which said cylinders are supplied with pressurized working fluid via a manifold (24), the contents of which may be 5 purged by a de-pressurizer taking one of a number for forms such as to allow re-activation of said machine (10).

Abstract: An electromagnetic actuator comprises a core (1), a ferromagnetic component (2) movable in a gap (5) in the core, and a magnet (4) for attracting the component to one side of the gap. A flux concentrator (12) concentrates the magnetic flux on that side of the gap (5) and a solenoid (8) produces magnetic flux in the gap. A magnetic circuit of the solenoid is defined by part of the core (1), part of the gap (5) and by a further gap (6) between the ferromagnetic component (2) and the core (1). A demagnetiser (7) has a magnetic circuit defined by another part of the core (1), another part of the gap (5) and by the further gap (6). The demagnetiser is arranged to demagnetise the magnet (4) at least to the extent that the magnetic flux produced by the solenoid (8) is diverted from the flux concentrator (12) into the further gap (6) and the movable component (2) is movable away from the magnet (4) under the magnetic force of the solenoid (8).

Abstract: The present invention provides a fluid system (99) comprising a source of hydraulic fluid under pressure supplying a hydraulic fluid consumer (103) together with a valve passing fluid between said source and said fluid consumer (102). A first fluid compliance (105) is situated between said source (100) and said valve (102) and a variable restrictor (110) is provided for varying the cross sectional area available for flow of fluid through said valve (102) and is movable between a first position (A) with a larger said area and a second position (B) with a smaller said area. A bias means (117) biases said restrictor (110) towards said second position whilst an opening means (Fa) urges said restrictor (110) against said bias (117) when fluid flows through said valve (102) and a damping means (126) damps movement of said restrictor between said first and second positions and provides a resistance which increases with the velocity of displacement of said restrictor (110).

Abstract: A valvetrain control arrangement for an internal combustion engine. A fluid-working machine (1) has working chambers (3) of cyclically varying volume, each connected to a piston actuator (4) which is capable of moving an intake or exhaust valve in the internal combustion engine. The engine crankshaft (2) drives a crankshaft of the fluid-working machine at the same speed as the engine. Each working chamber (3) is linked to a low-pressure manifold (7) by a venting valve (6), the venting valve being normally open but electromagnetically closable by a signal from an electronic sequencing means (8) which operates in timed relationship to the engine crankshaft phase.

Abstract: In an energy extraction device and method for extracting energy from a fluctuating energy flow from a renewable energy source, a hydraulic pump is driven by a rotating shaft, driven in turn by a renewable energy source. A hydraulic motor drives a load and a high pressure manifold communicates between the pump, motor and an elastically deformable fluid retaining body. The hydraulic pump and hydraulic motor comprise working chambers displacing a volume of working fluid selectable on each cycle of working chamber volume by the control of electronic valves. The pressure in the high pressure manifold is measured and the net rate of displacement of working fluid by the hydraulic pump is selected responsive thereto to regulate the torque applied to the said rotating shaft.

Abstract: A hydraulic pump is driven by a rotating shaft, driven in turn by a renewable energy source. A hydraulic motor drives a load and a high pressure manifold communicates between the pump, motor and an elastically deformable fluid retaining body. The pressure in the high pressure manifold is measured and the net rate of displacement of working fluid by the hydraulic pump is selected responsive thereto to regulate the torque applied to the rotating shaft. The net rate of displacement of working fluid by the hydraulic motor is selected to smooth the energy flow to the load. The net rate of displacement of working fluid by the hydraulic motor is selected to regulate the pressure in the high pressure manifold to remain within an acceptable pressure range.

Abstract: In a method of operating a fluid-working machine, the volume of working fluid displaced during each cycle of working chamber volume is selected taking into account the availability of other working chambers. The status of each working chamber is monitored and a working chamber treated as unavailable if it is found to be malfunctioning. A working chamber may be treated as unavailable if it is allocated to an alternative working function. A fault may be detected in a working chamber by determining whether a measured output parameter of the fluid working machine fulfils at least one acceptable function criterion taking into account the previously selected net displacement of working fluid by a working chamber during a cycle of working chamber volume to carry out the working function.

Abstract: The present invention relates to a fluid working machine comprising a controller and a working chamber, an electronically controllable low pressure valve associated therewith and a fast high pressure valve associated therewith, characterised in that the working chamber has associated therewith a slow high pressure valve for controlling the connection of the working chamber to a secondary high pressure manifold. A fluid working machine according to the invention may be operated to rotate its shaft to a certain position, for example to allow easy maintenance of a wind turbine generator.

Abstract: A fluid-working machine has a working chamber of cyclically varying volume, high and low pressure manifolds, and high and low pressure valves for regulating the flow of fluid between the working chamber and the high and low pressure manifolds respectively. A controller actively controls at least one said valve to determine the net displacement of working fluid of the working chamber on a cycle by cycle basis. At least one said valve is a variable timing valve and the controller causes the valve to open or close at a time determined taking into account one or more properties of the performance of the fluid working machine measured during an earlier cycle of working chamber volume.

Abstract: The present invention relates to a method of operating a fluid-working machine wherein the volume of working fluid displaced each cycle is selectable and wherein the volume of working fluid displaced by a first working chamber takes into account the suitability of the working chamber to displace fluid. The invention extends in further aspects to power absorbing structures such as renewable energy devices comprising such fluid working machines. The invention allows the operation of fluid working machines and power absorbing structures which are more long lived.

Abstract: A method of measuring a property of entrained gas in a hydraulic liquid received by a working chamber of a fluid working motor, wherein the said property is determined from the period of time elapsing between the closure of a first valve to isolate the working chamber and the passive opening of a second valve to bring the working chamber into fluid communication with a manifold. The property may, for example, be related to the concentration of entrained gas in the received hydraulic liquid or the compressibility or bulk modulus of the received hydraulic fluid.

Abstract: In a method of detecting a fault in a fluid-working machine including a plurality of working chambers of cyclically varying volume, each working chamber is operable to displace a volume of working fluid which is selectable for each cycle of working chamber volume to carry out a working function responsive to a received demand signal. An output parameter of the fluid working machine, which is responsive to the displacement of working fluid by one or more of the working chambers to carry out the working function, is measured. It is determined whether the measured output parameter fulfils at least one acceptable function criterion, taking into account the previously selected net displacement of working fluid by a working chamber during a cycle of working chamber volume to carry out the working function.

Abstract: A fluid-working machine for a renewable energy generation device, the fluid-working machine comprising a ring cam and a plurality of working chambers, the ring cam having an annular working surface extending around an axis of rotation of the ring cam, the annular working surface defining a plurality of waves, each working chamber having a piston, each piston in operative engagement with the ring cam working surface, the ring cam and working chambers being mounted to rotate relative to each other, cycles of working chamber volume being thereby coupled to rotation of the ring cam relative to the working chambers, characterised in that the individual waves of the ring cam working surface have an asymmetric profile.

Abstract: A fluid working machine comprises a working chamber of cyclically varying volume, a high pressure manifold, and an actuated high pressure valve for regulating the flow of fluid between the working chamber and the high pressure manifold. The actuated high pressure valve comprises a moveable valve member, operable between a closed position and at least one open position. A controllable opening mechanism provides an active urging force to urge the moveable valve member from the said closed position towards at least one said open position, the volume of the working chamber varying between a maximum volume and a minimum volume. The controllable opening mechanism provides the active urging force more than once while the volume of the working chamber is intermediate the maximum of chamber volume and the minimum of chamber volume.

Abstract: A valve assembly suitable for regulating the flow of fluid between a working chamber of a fluid-working machine and a fluid manifold. The valve assembly comprises a valve body comprising a valve seat, a fluid passage extending through the valve body, and a travelling member comprising a valve member, which valve member is operable between an open position in which the valve member is spaced apart from the valve seat and fluid can flow through the fluid passage and a closed position in which the valve member is in sealing contact with the valve seat preventing fluid from flowing through the fluid passage. The valve assembly defining a fluid flow path passing, in a first fluid flow mode, between the valve member and the valve seat, and into the fluid passage.

Abstract: A valve assembly for regulating the flow of fluid between a working chamber of a fluid-working machine and a fluid manifold. The valve assembly comprising a valve body comprising a valve seat, a fluid passage extending through the valve body, and a travelling member comprising a valve member and operable between an open position in which the valve member is spaced apart from the valve seat and fluid can flow through the fluid passage and a closed position in which the valve member is in sealing contact with the valve seat preventing fluid from flowing through the fluid passage. The valve assembly further defines a fluid flow path passing in a first fluid flow mode, between the valve member and the valve seat, and into the fluid passage. The valve assembly is characterised by a barrier upstream of the valve member, to the barrier reduces one or more forces which would otherwise act on the valve member as a result of the flow of fluid to urge the valve member towards the valve seat.

Abstract: The invention relates to a valve actuator (2), comprising a magnetic core (6) with an interspace (8) and at least one bifurcating branch (7), at least one variable magnetic field generating device (16), at least one permanent magnetic field generating device (13) and at least one movable magnetic component (12), wherein the bifurcating branch (7) defines a first region (4) and a second region (5) of said magnetic core (6).

Abstract: A fluid working machine comprises a controller (12) and a working chamber (2) of cyclically varying volume. The working, chamber has both an electronically controllable primary low pressure valve (14) and a secondary low pressure port (22) associated therewith, each of which is openable and closable in phased relation to cycles of working chamber volume to bring the working chamber into fluid communication with a low pressure manifold (16, 26). At least the primary low pressure valve is under the active control of the controller to enable the controller to determine the net displacement of fluid by the working chamber on a cycle by cycle basis. The primary low pressure valve and the secondary low pressure port are openable concurrently during a portion of at least some cycles of working chamber volume to enable fluid to flow into or out of the working chamber concurrently through both the primary low pressure valve and the secondary low pressure port.