Abstract: A rocking cylinder assembly comprising a cylinder, rotatable about a rocking axis between first and second end positions, having a cylinder bore terminating at a cylinder bearing surface and a cylinder aperture, and a bearing component having a component bore terminating at a component bearing surface and a component aperture. The ratio of the area of the second one of the apertures to the square of the maximum extent of the second one of the apertures in a direction perpendicular to the rocking axis and perpendicular to a second axis for fluid flow is greater than the ratio of the area of the first one of the apertures to the square of the maximum extent of the first one of the apertures in a direction perpendicular to the rocking axis and perpendicular to a first axis for fluid flow.

Abstract: In a fluid-working machine having a high-pressure line and a working chamber, a valve arrangement is arranged to control fluid flow from the high-pressure line to the working chamber. The valve arrangement comprises a main valve having a valve element arranged to provide sealing contact with a valve seat, and an auxiliary valve comprising an electromagnetically-movable valve member for equalising pressure on either side of the main valve by placing the working chamber in direct fluid communication with the high-pressure line. The electromagnetically-movable valve member may comprise a spool valve member or a poppet valve member.

Abstract: A hydraulic machine has at least one working chamber (11) of cyclically changing volume, and low-pressure and high pressure valves (15, 13) to control the connection of each of the at least one working chambers to low-pressure and high-pressure lines (16, 14) respectively. A method of operating the machine includes holding the low-pressure valve means (15) closed during at least an entire cycle of the chamber (11), starting at minimum chamber volume, such that gas dissolved in liquid in the chamber is released therefrom during an expansion of the chamber volume and re-dissolved during a reduction thereof.

Abstract: An electronically actuatable valve assembly including a valve member comprising a ferromagnetic member, and a magnetic circuit adapted to direct magnetic flux through the ferromagnetic member when the valve member is spaced apart from its valve seat, to hold the primary valve open.

Abstract: An electronically actuatable valve assembly having a primary face seating valve, including a primary valve member, and a secondary valve, including a secondary valve member. The secondary valve opens before the primary valve to equilibrate pressure across the primary valve member and thereby facilitate opening of the primary valve member. The secondary valve is coupled to an armature which moves from a first position to a second position, in use, attracted by an electromagnet. The coupling between the armature and the secondary valve is configured to enable the armature to begin to move from the first position without movement of the secondary valve.

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: A ring cam for a fluid-working machine is formed from a plurality of segments. The segments comprise a leading cooperating formation which has a piston facing surface which forms part of the working surface, at a trailing end, and which is recessed from the working surface at a leading end, and a trailing cooperating formation which has a piston facing surface which forms part of the working surface at a leading end, and which is recessed from the working surface at a trailing end. The segments having piston facing surfaces which are in compressive stress such as to partially or fully compensate for tensile stress arising from the action of rollers in use. The segments form a wavelike cam surface and attachment means are provided, through the working surface, on whichever of the leading or trailing surfaces thereof is subject to lowest forces from pistons in use.

Abstract: A fluid-working machine comprising a ring cam, at least one piston defining a working chamber, and at least one valve associated with the or each working chamber for connecting the working chamber alternately to low and high pressure manifolds in phased relationship to cycles of working chamber volume. The ring cam has a wave-like cam working surface for operative engagement with the at least one piston. The waves of the wave-like cam surface each having a leading face and a trailing face and discontinuities, such as apertures to retain bolts, are located in the working surface on whichever of the leading face and the trailing face the at least one piston does least work during normal operation resulting from the flow of fluid into and out of the working chamber in phased relationship to cycles of working chamber volume.

Abstract: A ring cam for a fluid-working machine is formed from a plurality of segments. The segments have piston facing surfaces together defining a working surface of the fluid-working machine. The segments comprise a leading cooperating formation which has a piston facing surface which forms part of the working surface, at a trailing end, and which is recessed from the working surface at a leading end, and a trailing cooperating formation which has a piston facing surface which forms part of the working surface at a leading end, and which is recessed from the working surface at a trailing end. The cooperating formations interlock and rollers are thereby handed over smoothly from one segment to the next irrespective of slight variations in alignment due to manufacturing tolerance or wear.

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: 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: 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 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 variable displacement fluid working machine includes an inward ring and an outward ring, one of the inward ring and the outward ring including a rotatable ring cam coupled to a drive shaft, the other including a plurality of radially extending piston cylinders circumferentially spaced around the respective ring. The outward ring has first and second axially spaced structural members and a plurality of demountable blocks demountably retainable therebetween, the demountable blocks having either piston cylinders or ring cam segments. The demountable blocks are removable radially to facilitate maintenance and repair and to facilitate radial access to the inward ring.

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 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.