A self-energizing valve includes a valve body defining an inner chamber having an inlet and an outlet. A valve head within the inner chamber is moveable between a first position and a second position. A valve seal in fluid communication with the inlet has a sealing surface with a sealing member between the valve head and the valve seal. The sealing member is movable between a closed position where the sealing member engages with the sealing surface and an open position where the sealing member disengages from the sealing surface to allow flow through the inlet into the inner chamber. A cam is coupled to the valve head. Rotation of the cam causes movement of the valve head between the first position and the second position to move the valve head to the first position to hold the sealing member in the closed position.

Devices and methods for improving the efficiency of an axial piston hydraulic motor or other axial piston hydraulic device. In some embodiments, a valve cam, with specified geometry, is assembled to a conventional axial piston hydraulic device (e.g., hydraulic motor, hydraulic pump, hydraulic pump-motor) in a manner permitting selective rotation of the valve cam relative to the distributor valves (e.g., spool valves). The rotating valve cam facilitates variable piston stroke and can be provided in conjunction with (e.g., joint control) an adjustable swashplate according to a mathematical relationship in order to adjust the displacement of the axial piston hydraulic motor (or other device) while maintaining optimal pre-compression and decompression across a range of operating conditions. This configuration allows, for each desired effective displacement of the hydraulic motor, a set of optimal valve timing to achieve perfect pre-compression and decompression so as to eliminate associated throttling losses.

It is provided a dosage pump (10) comprising a pump housing (12), a first valve (18), a second valve (20), an actuation lever (22), wherein the actuating lever (22) is adapted to be tilted around a tilting axis (24), a disc (34) for providing a torque, wherein the disc (34) is adapted to rotate around an input axis, a first cam (26) connected to the disc (34) and a second cam (30) connected to the disc (34), wherein the actuating lever (22) comprises a first raceway (28), wherein the first raceway (28) and the second raceway (32) are formed such that at least partially during an angle of rotation of the disc (34), where the actuation lever (22) has to apply an actuation force for opening and/or closing the first valve (18) and/or the second valve (20), the first cam (26) or the second cam (30), whose contact point to its corresponding raceway (28, 32) is farer away from the tilting axis (24) of the actuation lever (22) and/or adjusted to a lower torque at the actual angle of rotation of the disc (34), provides the tilting force onto the actuation lever (22). Due to the at least two cams (26, 30) the actuation force at the valves (18, 20) can be provided by means of the cam (26, 30) with a large lever arm, so that a lower torque of the disc (34) is sufficient, which can be generated with a lower energy consumption.