The subject matter of this specification can be embodied in, among other things, an electrohydraulic positioning control system that includes a shuttle valve configured to direct fluid flow between a selectable one of a first fluid port and a second fluid port, and a fluid outlet configured to be fluidically connected to a fluid actuator, a first servo valve controllable to selectably permit and block flow between the first fluid port, a fluid source, and a fluid drain, a second servo valve controllable to selectably permit and block flow between the second fluid port, the fluid source, and the fluid drain, a first servo controller configured to provide a first health signal and control the first servo valve based on a second health signal, and a second servo controller configured to provide the second health signal and control the second servo valve based on the first health signal.

The subject matter of this specification can be embodied in, among other things, a method that includes actuating a closure member at a predetermined first velocity a predetermined first number of cycles between a first configuration and a second configuration, actuating the closure member at a predetermined second velocity a predetermined second number of cycles between the first and the second configuration, actuating the closure member at a predetermined third velocity a predetermined third number of cycles and the second configuration, actuating the closure member at a predetermined fourth velocity a predetermined fourth number of cycles and the second configuration, and actuating the closure member to the second configuration at a predetermined fifth velocity for a predetermined flushing period.

An injection molding apparatus including: a valve pin driven by an actuator, the valve pin extending axially through at least a portion of the channel length of the fluid flow channel, the fluid flow channel and the valve pin being configured or adapted such that the valve pin is movable axially upstream and downstream between an upstream position where the downstream flow of the injection fluid is restricted by a bulbous protrusion (B) of the pin being axially aligned (AL) with the throat (T) of the channel, an intermediate position where downstream flow of injection fluid is unrestricted (WG) and a fully downstream position where downstream flow of injection fluid is stopped at both the gate and at the throat.

A servo valve assembly includes a housing defining a cylindrical cavity having a central axis, and a spool disposed in the cavity and co-axially aligned with the central axis. A pair of transition portions define opposing conical cavity surfaces each connect a respective one of first and second cylindrical cavity portions with a third cylindrical cavity portion. The spool comprises a pair of blocking members projecting radially, and each of the blocking members defines a conical blocking surface opposing a respective one of the conical cavity surfaces to define a fluid flow passage therebetween. A cone angle of each conical blocking surface relative to the central is equal to a cone angle of the opposing conical cavity surface relative to the central axis. The spool is moveable along the central axis to vary a flow area of the flow passages between the conical blocking surfaces and the conical cavity surfaces.

Systems and methods for auto-commissioning first and second valve assemblies associated with an actuator in an electro-hydraulic system are disclosed. In one method, a controller performs an automatic test protocol to determine a bulk modulus over fluid volume parameter used by the controller to control the valve assemblies. In one aspect, the test protocol can include pressurizing each side of the actuator to two different pressures with one of the first and second valve assemblies and blocking the other side of the actuator with the other of the first and second valve assemblies. The bulk modulus over fluid volume parameter for each valve assembly can be calculated based on recorded fluid pressures at the actuator and consumed flow at the first and second valve assemblies.

A hydraulic valve assembly includes an algorithm stored in an internal memory of the hydraulic valve assembly that determines a spool correction command based on a flow demand which is calculated for obtaining a target single port pressure or a target delta pressure using one or more port pressure measurements. The spool correction command is sent to an upper level controller of the hydraulic valve assembly, and the upper level controller uses the spool correction command to obtain an optimal displacement of a spool inside the valve assembly.

An example valve includes: a pressure compensation spool configured to be subjected to a first fluid force of fluid received at an inlet port of the valve; a sleeve having a cavity and at least one throttling cross-hole; a throttling spool disposed in the cavity of the sleeve and configured to be axially movable therein, wherein the throttling spool blocks the at least one throttling cross-hole when the valve is unactuated; and a pressure compensation chamber, wherein when the valve is actuated, the throttling spool moves in the proximal direction to form a throttling flow area between a distal end face of the throttling spool and an edge of the at least one throttling cross-hole, allowing fluid flow from the inlet port to the pressure compensation chamber, thereby causing a second fluid force to be applied on the pressure compensation spool, allowing flow to an outlet port of the valve.

An example valve includes: a pressure compensation spool configured to be subjected to a first fluid force of fluid received at an inlet port of the valve; a sleeve having a cavity and at least one throttling cross-hole; a throttling spool disposed in the cavity of the sleeve and configured to be axially movable therein, wherein the throttling spool blocks the at least one throttling cross-hole when the valve is unactuated; and a pressure compensation chamber, wherein when the valve is actuated, the throttling spool moves in the proximal direction to form a throttling flow area between a distal end face of the throttling spool and an edge of the at least one throttling cross-hole, allowing fluid flow from the inlet port to the pressure compensation chamber, thereby causing a second fluid force to be applied on the pressure compensation spool, allowing flow to an outlet port of the valve.

A first flow path area at a position where one of multiple openings of a sleeve and one of multiple grooves of a spool overlap with each other is different in size from a second flow path area at a position where another one of the openings of the sleeve and another one of the grooves of the spool overlap with each other. The one opening and the one groove form a flow path for connecting one of one pressure chamber and the other pressure chamber to a fluid supply source, due to displacement of the spool. The other opening and the other groove form a flow path for connecting another one of the other pressure chamber and the one pressure chamber to a fluid discharge port, due to the displacement of the spool.

Hydraulic systems and associated methods configured to reduce leakage past a spool valve when the system is in a neutral state. Leakage reduction is achieved by shifting the spool valve within the spool bore. The amount of shifting can be controlled by a pressure controller that sets one or pressures in the system and actively/dynamically adjusts the system to achieve a desired pressure or set of pressures by shifting the spool valve.