A filter assembly for a servo valve. The filter assembly has a filter body defining a chamber; a first end cap having a first fluid outlet at a first end of the filter body and a second end cap having a second fluid outlet at a second end of the filter body. A flow restrictor restricts fluid flow between the filter body and each of the first and second fluid outlets. A spacer in the chamber spaces the first end cap from the second end cap.

There is provided a method of assembling a torque motor. The method comprises fastening the torque motor to a support such that any magnetic elements of the torque motor are substantially fixed in position with respect to the support, but without securing an armature to the torque motor, locating the armature of the torque motor around a fixed element of the torque motor such that the armature is able to move with respect to the fixed element, moving the armature with respect to the fixed element whilst the magnetic elements of the torque motor are substantially fixed in position with respect to the support, so as to position the armature in an in use orientation or position, and then attaching the armature to the fixed element in the in use orientation or position.

A servovalve includes a torque motor section and a hydraulic section. The torque motor section may comprise first and second opposing pole pieces and first and second permanent magnets may be positioned between these first and second pole pieces. The torque motor section also comprises an armature/flapper assembly which comprises a torsion bridge, an armature plate and a flapper that is connected at a first end to the armature plate. The flapper extends from said armature plate along a first longitudinal axis X. The armature plate may extend between the first and second permanent magnets and along a second longitudinal axis Y that is perpendicular to the first axis X. The hydraulic section comprises: a housing that comprises a body section and a chimney section. The chimney section extends from the body section to a first end.

A servo valve comprises a valve housing, a cavity formed in the valve housing and defining a longitudinal axis (X), and a member disposed in the cavity and axially-moveable therein, wherein the member comprises a portion with first and second cylindrical sections having a first diameter (R1, R2), a central section located between the first and second cylindrical sections and having a second diameter (R3), and first and second frusto-conical sections connecting the first and second sections to the central section and forming respective first and second frusto-conical surfaces. A plurality of ports, each form a fluid passage through the valve housing and have first and second nozzles with first and second nozzle openings.

The present disclosure provides a heat exchanger system for a servovalve, comprising a base comprising a supply port in fluid communication with a return port, a first passage for fluid connection to a source of cooling fluid, and a second passage in fluid communication with the return port. The system further comprises one or more pipes located over a surface of the base, the one or more pipes fluidly connected between the first passage and the second passage, such that in use cooling fluid may flow from the first passage to the second passage via the network of pipes.

A torque motor for use in a servovalve wherein only two holes must be provided through each of the pole pieces in order to assemble the torque motor together. The torque motor comprises first and second opposing pole pieces, first and second permanent magnets positioned between the first and second pole pieces; an armature comprising a magnetic plate and a flapper, the magnetic plate being positioned between the first and second permanent magnets, the flapper being connected at one end to the magnetic plate; and further comprising: first and second fastening means each extending through the first pole piece, the armature and the second pole piece to thereby fasten the torque motor together.

The disclosure provides a method of securing a feedback spring relative to a spool of a servovalve, the method comprising inserting the feedback spring at least partially into an internal cavity of the spool, inserting two fixing members into the internal cavity such that they each oppose a portion of the feedback spring, bringing the fixing members into respective set positions, such that the fixing members clamp the feedback spring and prevent relative movement between the feedback spring and the spool, and securing the fixing members in their respective set positions, such that the fixing members remain in their clamping positions and prevent relative movement between the feedback spring and the spool.

A torque motor assembly comprising two or more pole piece pairs, each pair comprising two opposing pole pieces each having an end facing an end of the opposite pole piece, the ends separated by a gap; and a magnetic plate extending between the pole piece pairs and located in the gap, the magnetic plate having surface portions facing the respective pole piece ends; wherein the surface portions of the magnetic plate and the respective pole piece ends are non-parallel with respect to each other.

A servo valve includes: a fluid transfer valve assembly comprising a supply port and a control port (P.sub.A, P.sub.B); a moveable valve spool arranged to regulate flow of fluid from the supply port to the control port in response to a control signal; and a drive means configured to axially move the valve spool relative to the fluid transfer assembly in response to the control signal to regulate the fluid flow. The drive means comprises an elongate member arranged to rotate in response to the control signal. The elongate member has a cam profile in the fluid flow path such as to vary the pressure acting on the ends of the spool as the cam profile rotates.

A system uses a two-stage, four-way electrohydraulic servo valve that includes an additional control port that commands a fail-fixed valve to lock the position of a device in the last commanded position. The additional port is modulated by an existing land on the EHSV valve element, adding little to no complexity. Major technical benefits of the disclosed system are that it adds little to no cost, complexity, size, or weight the device being controlled. The disclosed configuration allows for the use of a relatively small and simple fail-fixed valve, and the control ports on the controlled device keep “drift” to a minimum, when transitioning between normal operating mode and fail-fixed operating mode.