Abstract: A servo actuator system and method of operating the same includes a dual acting actuator comprising an actuator body and a movable member movable in the actuator body to define a first and second chamber on each side of the movable member. A first port is fluidly coupled to the first chamber and a second port is fluidly coupled to the second chamber. A fluid pump having a return is provided. A proportional valve assembly is fluidly coupled to the fluid pump, return and the first and second ports. The proportional valve assembly includes a plurality of metering orifices. A controller is operably coupled to the proportional valve assembly to control the plurality of metering orifices to generate a load vector having magnitude and direction and wherein an actual position of a movable member in an actuator body is indeterminate.

Abstract: A hydraulic system, especially in a high-pressure application, comprises a pressurized-fluid tank, a pressurized-fluid pump driven by a drive unit, at least one hydraulic load that can be pressurized thereby and a control and/or distribution unit connected fluidically between the pressurized-fluid pump and the load. This unit is provided with a housing and a core received therein and connected rigidly with the housing, which core bears with part of its surface in the region of a common, closed, especially cylindrical joint face with the housing on a corresponding inside face of a housing opening. Surface groove-like flow ducts are provided on the core and/or the housing in the region of the joint face, and the pressurized-fluid pump is directly built onto the control and/or distribution unit in the region of a free end face of the core.

Abstract: The hydraulic flotation circuit for the header of a windrower or other harvester utilizes a pair of precharged gas accumulators that are always in open communication with the flotation cylinders of the circuit. One of the accumulators is set at a relatively high precharge pressure, while the other is set at a much lower precharge pressure. If the header chosen for attachment to the harvester is relatively heavy, the accumulator with the higher precharge pressure provides the flotation bias, while if the header is relatively light, the accumulator having the lower precharge pressure comes into play.

Abstract: The windrower or other harvester has a hydraulic lift circuit for its header that includes a pair of double-acting cylinders which operate in concert to raise the header and provide a solid, lower limit for downward swinging of the header. The two cylinders are connected to one another in a master-slave relationship, and the slave cylinder has its return line normally blocked by a one-way check valve so that a body of fluid is trapped against the piston of the slave cylinder during field operations. This stabilizes the two cylinders to reduce header bounce.

Abstract: A hydraulic control valve has a two position body shifted by rotation. The shaft of the valve body carries a drive wheel segment extending through an arc that corresponds to the shift angle of the valve. A spring is provided to bias, at least in the final stage of rotation in either direction, the wheel segment in the opposite direction of rotation. This enables the valve body to be positioned into the other position in a reliable manner.

Abstract: A hydraulic pump and valve unit is disclosed which is particularly useful in a system using a hydraulic cylinder for raising and lowering the cab of a truck. The unit includes a pump which is connected to a valve intake chamber which, in turn, opens axially into a flat end of a larger valve chamber. An annular thrust seal is slidably mounted in the valve intake chamber, and spring means biases the thrust seal against the flat end of a valve spool which is rotatably mounted in the valve chamber. The valve spool has a pair of flow passages therein which connect respective ports in the flat end of the valve spool with corresponding ports in the cylindrical surface of the valve spool. The ports in the cylindrical surface of the valve spool register with a second pair of cooperating flow passages which deliver hydraulic fluid under pressure from the unit to a system such as a hydraulic cylinder, and return hydraulic fluid from such system to the unit.