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 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 fluid working machine comprises a controller and a working chamber of cyclically varying volume having an electronically controllable primary low pressure valve and a secondary low pressure port 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. 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 and in parallel during a portion of at least some cycles of working chamber volume, including at the point in the expansion or contraction stroke where the rate of change of volume of the working chamber is greatest.

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 characterized 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 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 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, characterized 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: 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 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: 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 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: 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: 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: 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.