Abstract: A hydraulic actuator including a piston rod having a centering mechanism associated therewith which, upon actuation, will return the piston rod to a predetermined position even against loads and lock it in that position and hold it there even without the presence of hydraulic power. The centering and locking mechanism includes a drive mechanism and cam surfaces on the piston rod which are engaged by drive surfaces on the driving mechanism. The drive and cam surfaces are opposed ramps with one of the ramps on the drive mechanism always disposed opposite one of the ramps on the actuator, such that at any position of the stroke of the actuator piston rod the centering and locking mechanism may be actuated and is operable to return the actuator to the predetermined position and lock it in place. The cam surfaces are infinitely variable as to their position on the piston rod within the limits of the dimensions of the drive mechanism.

Abstract: A valve combining in a single unit a multiplicity of functions including isolation, thermal and pressure relief, return check and bypass. The valve includes a pair of spool valves, one slidably positioned within the other, disposed with a bore in a housing and interconnected with system pressure and return and an appropriate control valve.

Abstract: A parallel actuator pair force transmission system including a mechanical feedback apparatus capable of detecting differential movement between the actuator pair and providing a feedback signal to control valves phased in such a manner as to correct for and counteract the differential motion between the actuator pair.

Abstract: An actuator, and a system employing the same, which will continue to operate after deformation of a portion thereof which deformation would normally restrict movement between the piston and cylinder of the actuator. The piston or gland of the actuator is constructed so as to include segmented flanges which will fracture responsive to forces applied to them upon engagement of the deformation. Slots defining the segments are filled with a rubber-like material which is bonded to the piston or gland thus providing a solid structure to enable appropriate sealing while not interfering with the fracturability of the segments.