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: An electronically controlled valve includes a valve member moveable between a first position and a second position. A valve member moving mechanism is operable to receive energy from a fluid-working machine crankshaft, or other rotating shaft, and to provide a valve member moving force to urge the valve member from the first position to the second position using the received energy. Thus, the energy used for movement of the valve against a pressure gradient is derived from the crankshaft. Energy received from the crankshaft can be stored and used subsequently to urge the valve member from the first position, allowing the valve to function despite timing differences between the availability of energy from the crankshaft and the requirement for energy to move the valve member.

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 variable transmission comprises a first fluid working machine (1) for connection to a prime mover (2), a second fluid working machine (5) for connection to a mechanical load (6) and a fluid system linking the first and second working machines, the fluid system having a high-pressure side (3) and a low-pressure side (4) each connected to both said first and said second fluid working machines (1, 5), a fluid accumulator (7) on the high-pressure side, a means to admit fluid from the reservoir to the low-pressure side and a pressure control valve to maintain the correct pressure in the low-pressure side, wherein the second fluid working machine (5) includes chambers of variable volume having electronically controllable valves such that each of said chambers has pumping, motoring and idling modes of operation, and the second fluid working machine (5) is operable to both source fluid to and sink fluid from each of said high-pressure side (3) and said low-pressure side (4).

Abstract: An electronically controlled valve for regulating the supply of fluid between a working chamber of a fluid working machine and a manifold, which valve includes a pilot valve and a pilot valve elastic member charged in use by the movement of the armature towards the electromagnet during closure of the valve to provide a return force urging the pilot valve sealing member away from the pilot valve seat. The valve is especially useful as the low pressure valve of a fluid working motor.

Abstract: An electronically controlled valve includes a travelling member with a sealing member and operable between a closed position in which the sealing member forms a seal with a valve seat, and an open position. The valve further has a decelerating mechanism operable to slow the movement of the armature during closure of the valve. The sealing member and armature are decoupled and thereby moveable relative to each other such that the armature can continue to move and decelerate due to the action of the damping mechanism after the sealing member has impacted the valve seat. The peak deceleration force on the armature is thereby reduced, increasing the lifetime of the valve or the maximum rate at which it can be closed without damage.

Abstract: An electro-magnetic mechanism comprises a spring-operated rod (1) having a recess (1a) and a latching member (2) engageable in the recess to block motion of the rod. A release member (4) retains the latching member engaged in the recess (1a) in a first position of the release member and allows the latching member to be disengaged from the recess in a second position of the release member (4). A magnet (5) retains the release member in the first position and the mechanism includes an element such as a spring (7) for urging the release member (4) to the second position. A coil (8) is arranged to demagnetize the magnet (5) at least such that the release member moves to the second position, the latching member (2) is disengaged from the recess (1a) and the rod (1) moves axially by spring force.

Abstract: A fluid working machine, operable to carry out a motoring cycle under at least some circumstances, comprises a controller (12) and a working chamber (2) of cyclically varying volume. The working chamber has a high pressure valve (18) associated therewith to control the connection of the working chamber to a high pressure manifold (20), and an electronically controllable primary low pressure valve (14) to control the connection of the working chamber to a low pressure manifold. The controller is operable to actively control at least the primary low pressure valve, in phased relationship to cycles of working chamber volume, to determine the net displacement of fluid by the working chamber on a cycle by cycle basis. The fluid working machine is adapted to release pressurised fluid from the working chamber prior to the opening of the primary low-pressure valve, during a motoring cycle. This facilitates the opening of the primary low pressure valve.

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.

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 has a plurality of working chambers, e.g., cylinders, of cyclically changing volume, a high-pressure fluid manifold and a low-pressure fluid manifold, at least one valve linking each working chamber to each manifold, and electronic sequencing means for operating said valves in timed relationship with the changing volume of each chamber, wherein the electronic sequencing means is arranged to operate the valves of each chamber in one of an idling mode, a partial mode in which only part of the usable volume of the chamber is used, and a full mode in which all of the usable volume of the chamber is used, and the electronic sequencing means is arranged to select the mode of each chamber on successive cycles so as to infinitely vary the time averaged effective flow rate of fluid through the machine.

Abstract: A valve assembly (1) operable to allow or prevent the flow of fluid to or from a working chamber of a fluid-operated machine, comprising radially spaced apart inner and outer annular valve seats (8, 15) defining an annular passage therebetween, a valve member comprising a sealing ring (21), and means (3, 7, 26, 25) for moving the valve member axially between a first position in which the sealing ring (21) is in seating engagement with the annular valve seats to close the annular passage to fluid flow therethrough and a second position in which the sealing ring (21) is spaced from the annular valve seats (8, 15) so that the annular passage is open to fluid flow therethrough. The valve assembly further comprises axially spaced apart first and second valve guide means (6) for guiding the valve member during axial movement between its first and second positions.