Abstract: Two or more flow control valves may be used to provide redundant flow control for a hydraulic actuator or servoactuator. The flow control valves include a sleeve, a bypass control spool, and a primary control spool. Under normal operating conditions, each bypass control spool is stationary relative to the sleeve and the flow control valve functions as a four-way hydraulic flow control valve. Each flow control valve is connected to a bypass-shutoff valve including a bypass spool that is moveable from a shut-off position to a bypass position. Upon supply pressure failure to one flow control valve, the bypass spool moves to the bypass position, reducing pressure in the corresponding actuator piston chambers. When a primary control spool becomes jammed, the corresponding bypass control spool moves within its sleeve allowing a bypass groove to port control pressure to the return line, thereby reducing pressure in the corresponding actuator piston chambers.

Abstract: A locking hydraulic actuator has a cylinder and a main piston that is movable from an extend position to a retract position by a hydraulic circuit. The actuator has a locking mechanism that includes a lock piston that slides within a lock piston bore of the main piston. One or more lock segments are held by slots within the main piston and may be radially constrained within a tailstock housing and cylinder. The lock segments maintain the main piston in a locked position. The lock segments have two straight tapers, one on a proximal face and the other on a distal face, which transmit axial loading forces to and from the cylinder and main piston by distributed loading, thereby avoiding point-contact loading and material deformation. The lock piston, lock segments, piston, and cylinder may have different hardnesses.

Abstract: A locking hydraulic actuator has a cylinder and a main piston that is movable from an extend position to a retract position by a hydraulic circuit. The actuator has a locking mechanism that includes a lock piston that slides within a lock piston bore of the main piston. One or more lock segments are held by slots within the main piston and may be radially constrained within a tailstock housing and cylinder. The lock segments maintain the main piston in a locked position. The lock segments have two straight tapers, one on a proximal face and the other on a distal face, which transmit axial loading forces to and from the cylinder and main piston by distributed loading, thereby avoiding point-contact loading and material deformation. The lock piston, lock segments, piston, and cylinder may have different hardnesses.

Abstract: A hydraulic warming system for low ambient temperature (0° to −65° F.) operation includes a hydraulic motor integrated in a valve manifold and driven by a two-stage jet pipe flow control electro-hydraulic servovalve mounted on the valve manifold in proximity thereof via a multi-port lapped spool-sleeve bypass-shutoff valve having a pre-loaded return spring. The spool is driven by a solenoid valve mounted on the valve manifold and coupled to the bypass-shutoff valve thereto between a first position and a second position. The first position utilizes the warmed low flow rate hydraulic leakage fluid from the servovalve to provide continuous warming of the internal rotating components of the hydraulic motor when the hydraulic motor is not operational. The second position includes diverting the warmed low flow rate hydraulic leakage fluid from the servovalve directly to hydraulic system return bypassing the internal rotating components of the hydraulic motor when the hydraulic motor is operational.