Method of adjusting the pressure balance or a control device, in particular of a servo valve, the requisite adjusting movement being applied by a disc translator.

A valve may have a fluid inlet and a fluid outlet. The valve may include a valve stem having a lumen extending from a first opening at a proximal portion of the valve stem to a second opening at a distal end of the valve stem. A plurality of seals may be positioned relative to the valve stem. The valve stem and seals may be configured so that a fluid entering the inlet is prevented from flowing to the outlet in a first position of the valve stem and relative to the inlet and the outlet. The valve stem and the seals may be configured so that a fluid entering the inlet flows to the outlet in a second position of the valve stem relative to the inlet and the outlet, the second position being more distal than the first position relative to the inlet and the outlet.

The subject matter of this specification can be embodied in, among other things, a fluid valve assembly that includes a first fluid port, a second fluid port, a third fluid port, a valve spool configured to be positioned at a first position, a second position away from the first position, a third position away from the first position opposite the second valve position, the valve spool defining a first fluid duct configured to fluidly connect the first fluid port to the second fluid port in the first valve position, a second fluid duct configured to fluidly connect the first fluid port to the third fluid port in the second valve position, and a third fluid duct configured to fluidly connect the first fluid port to the second fluid port in the third valve position.

A valve may have a fluid inlet and a fluid outlet. The valve may include a valve stem having a lumen extending from a first opening at a proximal portion of the valve stem to a second opening at a distal end of the valve stem. A plurality of seals may be positioned relative to the valve stem. The valve stem and seals may be configured so that a fluid entering the inlet is prevented from flowing to the outlet in a first position of the valve stem and relative to the inlet and the outlet. The valve stem and the seals may be configured so that a fluid entering the inlet flows to the outlet in a second position of the valve stem relative to the inlet and the outlet, the second position being more distal than the first position relative to the inlet and the outlet.

A four-position switching valve includes first and second pistons for driving a spool in a valve body, and a spool moving mechanism part that moves the spool to first and second intermediate switching positions between one-end side and the other-end-side switching positions. The spool moving mechanism part includes a compression spring that moves the spool back in the opposite direction by moving to the switching position on one end side and the other end side of the spool. The compression spring moves the spool to the first intermediate switching position when the spool moves to one-end-side switching position and the pressure on the second piston is released, and moves the spool to the second intermediate switching position when the spool moves to the other-end-side switching position and the pressure on the first piston is released.

A valve assembly includes a valve body defining a cylindrical passage therein about an axis. An inlet port is defined in or near a first end of the valve body. First and second outlet ports are defined in the valve body extending radially outward from the cylindrical passage. A cylindrical valve spool having a central passage is positioned within, and sealingly engaged with, the cylindrical passage. The valve spool is moveable along the axis among: a first position wherein the inlet port is in fluid communication with the first outlet port but not the second outlet port, a second position wherein the inlet port is in fluid communication with the second outlet port but not the first outlet port, and an intermediate position between the first and second positions wherein the inlet port is in fluid communication with both of the first and second outlet ports.

A piezoelectric ring bender servo valve assembly reduces mechanical wear by removing mechanical components used in prior art servo valves. The assembly does not use torque motor, flapper, and feedback spring. In this manner, no moving parts are required, which reduces maintenance and costs. A pair of piezoelectric ring benders mount adjacently to a pair of nozzles. The piezoelectric ring benders independently regulate the flow of fluid through the nozzles by moving between an open position to enable flowage, and a closed position to restrict flowage. A linear position sensing device measures and provides feedback about the spool position to a valve controller. The valve controller allows the spool valve to move until valve position achieves command position and the force on the spool valve is in equilibrium with pressure difference across spool valve. An H-bridge operable to switch the polarity of a differential pressure applied across to a load.

A non-curable injectable ester containing packing material for use in the repair of leaking valves contains a calcium sulfonate grease containing at least one polyalphaolefin, an ester, an anti-wear/anti-galling agent, a binding/thickening agent and a plasticizing agent.

An example spool includes a shaft varying in diameter along a length of the shaft, and a plurality of annular lands formed on the shaft and spaced-apart by respective reduced diameter annular neck portions. The plurality of annular lands comprise at least one annular metering land, and wherein the at least one annular metering land comprises: one or more sine notches formed as a portion of a sine wave, and one or more additional notches having a different shape from the one or more sine notches.

A four-position switching valve includes first and second pistons for driving a spool in a valve body, and a spool moving mechanism part that moves the spool to first and second intermediate switching positions between one-end side and the other-end-side switching positions. The spool moving mechanism part includes a compression spring that moves the spool back in the opposite direction by moving to the switching position on one end side and the other end side of the spool. The compression spring moves the spool to the first intermediate switching position when the spool moves to one-end-side switching position and the pressure on the second piston is released, and moves the spool to the second intermediate switching position when the spool moves to the other-end-side switching position and the pressure on the first piston is released.