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: 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: 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: 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 hydraulic pump for use in driving a load with a control modulation system which modulates a primary control signal in order to accommodate variations in secondary changeable parameters which require control at a higher frequency or have a lower latency.

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: According to a first aspect of the invention there is provided a thermodynamic machine operating according to the Brayton cycle and including a closed loop fluid circuit for circulating working fluid. A fluid compressor (8) and a fluid expander (10) are independently controllable variable positive displacement machines. The variable positive displacement machines incorporate working chambers of cyclically varying volume, the net fluid displacement of each working chamber being selectable on a cycle by cycle basis. The compressor and expander axles are linked and the compressor and expander can be controlled to independently vary the displacement of the compressor, the displacement of the expander and the net torque exerted on the axle. The machine works efficiently with a wide range of heat source and heat sink temperatures and can respond to varying power demands, including transient changes to power demand.

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 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: 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: 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 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 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: 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.