Provided is a double nozzle type positioner, which includes a flapper (1), a first nozzle (2) and a second nozzle (3) disposed at both sides based on the flapper (1), a first orifice (4) configured to maintain a constant pressure of the first nozzle (2), a second orifice (5) configured to maintain a constant pressure of the second nozzle (3), a first pilot valve (6) having an input portion connected to a feed pressure, a second pilot valve (7) having an input portion connected to an output portion of the first pilot valve (6), a discharge hole (8) connected to an output portion of the second pilot valve (7), and an actuator (9) connected to the output portion of the first pilot valve (6) and the input portion of the second pilot valve (7). If the first nozzle (2) is opened due to the movement of the flapper (1), the second nozzle (3) is closed, and if the first nozzle (2) is closed, the second nozzle (3) is opened.

A manual override assembly for a hydraulic power source operates to override an actuator of a hydraulic power source. The assembly includes a lever arm and connecting rods. The lever arm pivotally moves relative to a valve body of the hydraulic power source. The lever arm is connected to valve spools via the connecting rods, respectively. Each spool has a bore with an off-set opening for inserting one end of the connecting rod.

A hydraulic valve assembly includes a first spool valve and a first selector valve for actuating a first hydraulic consumer port or a second hydraulic consumer port, and a second spool valve and a second selector valve for actuating a third hydraulic consumer port or a fourth hydraulic consumer port. A shut-off valve is arranged in a common pressure channel. A branch channel with first and second pressure branch channels branches off the pressure channel upstream of the shut-off valve. The first selector valve connects the first pressure branch channel to a first connection line in a first switching position and connects the second pressure branch channel to a second connection line in a second switching position. The second selector valve, in a first switching position, connects the first connection line to the control channel and, in a second switching position, connects the second connection line to the control channel.

A torsion bridge for use in a servovalve includes a body extending along and adapted to rotate about a first axis; a passage extending through the body along a second axis substantially perpendicular to the first axis, the passage defining a first cylindrical surface having a radius R.sub.1; an annular groove formed in the first cylindrical surface. The annular groove includes: a second cylindrical surface extending substantially in the direction of the second axis, the second cylindrical surface having first and second ends and a radius R.sub.2, where R.sub.2 is greater than R.sub.1; a first annular surface joining the first cylindrical surface to the first end of the second cylindrical surface; and a second annular surface joining the second end of the second cylindrical surface to the first cylindrical surface.

A valve body for a servovalve is provided comprising: a first surface adapted to extend parallel and adjacent to a substantially flat pole piece surface of a pole piece in use; and attachment features provided on the first surface for attaching the valve body to the pole piece in use, wherein the first surface is contoured such that, in use, an area of the first surface surrounding the attachment features is in contact with the substantially flat pole piece surface and an area of the first surface removed from the attachment features is not in contact with the substantially flat pole piece surface.

An electropneumatic valve assembly comprises an electropneumatic pilot stage and a pneumatic power stage which is actuated by the pilot stage. Each pilot valve switches at least two power valves, and the valve assembly has a housing with an electrical signal input, with a compressed-air port, at least one vent port and at least one working outlet. The housing is layered with a pilot stage housing and a power stage housing connected along a substantially planar parting surface. At least one sealing element is between the pilot stage housing and power stage housing surrounding a control pressure region between the pilot stage housing and power stage housing. The control pressure region has two actuation regions for two power valves and has a duct-like connection with a defined flow cross section between the two actuation regions. An outlet of the associated pilot valve opens into the control pressure region.

A proportional valve is provided having a pilot control valve that can be controlled by means of a control signal and having a booster valve that can be actuated by means of the pilot control valve. The proportional valve has a compressed-air connection for connecting a compressed-air supply, a working connection, and an air-removal connection. The booster valve has three valve elements, which are arranged one after the other and can each be moved in an axial direction against a spring force.

A manual override assembly for a hydraulic power source operates to override an actuator of a hydraulic power source. The assembly includes a lever arm and connecting rods. The lever arm pivotally moves relative to a valve body of the hydraulic power source. The lever arm is connected to valve spools via the connecting rods, respectively. Each spool has a bore with an off-set opening for inserting one end of the connecting rod.

A valve body for a servovalve is provided comprising: a first surface adapted to extend parallel and adjacent to a substantially flat pole piece surface of a pole piece in use; and attachment features provided on the first surface for attaching the valve body to the pole piece in use, wherein the first surface is contoured such that, in use, an area of the first surface surrounding the attachment features is in contact with the substantially flat pole piece surface and an area of the first surface removed from the attachment features is not in contact with the substantially flat pole piece surface.

A torsion bridge for use in a servovalve includes a body extending along and adapted to rotate about a first axis; a passage extending through the body along a second axis substantially perpendicular to the first axis, the passage defining a first cylindrical surface having a radius R.sub.1; an annular groove formed in the first cylindrical surface. The annular groove includes: a second cylindrical surface extending substantially in the direction of the second axis, the second cylindrical surface having first and second ends and a radius R.sub.2, where R.sub.2 is greater than R.sub.1; a first annular surface joining the first cylindrical surface to the first end of the second cylindrical surface; and a second annular surface joining the second end of the second cylindrical surface to the first cylindrical surface.