Abstract: A radial piston pump has a plurality of cylinders within which pistons reciprocally move. Each cylinder is connected to a first port by an inlet passage that has an inlet check valve, and is connected to a second port by an outlet passage that has an outlet check valve. A throttling plate extends across the inlet passages and has a separate aperture associated with each inlet passage. Rotation of the throttling plate varies the degree of alignment of each aperture with the associated inlet passage, thereby forming variable orifices for altering displacement of the pump. Uniquely shaped apertures specifically affect the rate at which the variable orifices close with throttle plate movement, so that the closure rate decreases with increased closure of the variable orifices.

Abstract: A system for operating a single acting hydraulic cylinder includes a directional valve that has one extreme position in which a workport is connected to a tank return conduit, another extreme position where the workport is connected to a pump supply conduit, and a closed intermediate a position where the workport is disconnected from both the pump and the tank. The directional valve is pilot operated and is biased toward the one extreme position by a spring. An electrically operated primary applies pilot pressure to the directional valve alternately from the pump supply conduit and the tank return conduit. A pilot operated check valve has a first state which restricts fluid flow only from the workport toward the chamber and a second state in which fluid can flows from the chamber to the workport. The system has a pressure compensation that also provides self priming of the directional valve.

Abstract: A system has a variable displacement pump that supplies pressurized fluid to power a plurality of hydraulic functions. Each hydraulic function has a control valve with a variable source orifice controlling fluid flow between the pump and a flow summation node, and a variable metering orifice controlling fluid flow between the flow summation node and a hydraulic actuator. Variable bypass orifices in the control valves are connected in series between the flow summation node and a tank. As the metering orifice in a control valve enlarges, the source orifice enlarges and the bypass orifice shrinks. This alters pressure at the flow summation node, which is used to control the output of the pump. Components are provided to give selected hydraulic functions different levels of priority with respect to consuming fluid flow from the pump.

Abstract: An apparatus includes a first plurality of cylinders, each coupled to a shared first port by a separate first valve and to a shared second port by a separate second valve. Each first and second valve has a chamber to which pressure from either the associated cylinder or the respective port is dynamically applied to select different operating modes. Each one of a second plurality of cylinders is coupled to the first port by a separate third valve and to a shared third port by a separate fourth valve. Each third and fourth valve has a chamber to which pressure from either the associated cylinder or the respective port is dynamically applied to select different operating modes. Selecting an operating mode enables the apparatus to act as a bidirectional pump or a hydraulic motor. Selectively controller the valves can deactivate an individual cylinder, while other cylinders remain active.

Abstract: A hydraulic machine has a cylinder body with first and second ports and a plurality of cylinder bores disposed radially with openings through a side surface. Deformation regions, formed around each cylinder bore opening, expand and contract in response to pressure changes in the cylinder bores. A continuous band extends around the cylinder body closing the cylinder bore openings and applying a pre-stress compressive force to each deformation region. A plurality of pistons are slideably received in the plurality of cylinder bores and a plurality of valve arrangement couple the cylinder bores to the first and second ports. A shaft with an eccentric cam drives the pistons to slide within the cylinder bores. Each deformation region distorts in response to pressure in the associated cylinder bore wherein the circumference of that cylinder bore becomes more circular as the cylinder pressure increases.

Abstract: A pump system has a piston pump. The piston pump has a cylinder block with an inlet port, an outlet port, and a plurality of cylinders. Each cylinder in the plurality of cylinders is connected to the inlet port by an inlet passage and to the outlet port by an outlet passage. The piston pump has a plurality of pistons disposed in the plurality of cylinders. A drive shaft drives the pistons within the cylinders. A throttle member independently throttles flow in each inlet passage. The pump system has an electrohydraulic actuator governing movement of the throttle member.

Abstract: A hydraulic system has a pump that furnishes pressurized fluid to a supply node connected to a plurality of functions. Each function includes hydraulic actuator and a control valve assembly through which fluid flows both from the supply node to the hydraulic actuator and from the hydraulic actuator to a return line. A control method involves receiving a plurality of commands, each designating desired operation of a function. Each command is separately used to derive a flow value designating an amount of flow for the respective function, a load value indicating a load magnitude related to the respective function, and a pressure value denoting a supply pressure for the respective function. Then, the control valve assembly for each given hydraulic function is operated in response to the flow and load values for that function and in response to the pressure value that is greatest among the plurality of functions.

Abstract: A hydraulic system includes a first pump and a plurality of valves that control fluid flow from the first pump to several actuators. Variable source orifices in the control valves are connected in parallel between the first pump and a node, and variable bypass orifices in the control valves are connected in series between the node and a tank. Pressure at the node controls displacement of the first pump. Each control valve also has a metering orifice for varying fluid flow between the node and one of the actuators. A hydrostatic pump-motor, coupled between two ports of a given actuator, is driven in a motoring mode by fluid exiting one of those ports. In a pumping mode, the hydrostatic pump-motor forces lower pressure fluid exhausting from one port into the other port of the given actuator.

Abstract: A hydraulic system has several valve sections, each having a directional valve that controls fluid flow from a pump to a hydraulic actuator. A mechanism senses a greatest pressure among the hydraulic actuators to provide a load sense pressure. One valve sections has a pressure compensation apparatus includes a pressure compensation valve that reduces fluid flow between a given directional valve and an associated hydraulic actuator in response to pressure at a control port, and a pressure regulating valve that responds to the load sense pressure and pressure in the associated hydraulic actuator by selectively applying output pressure from the pump and the load sense pressure to the control port.

Abstract: The hitch on a vehicle is moved by a hydraulic actuator. A method for controlling the hydraulic actuator defines a draft force setpoint in response to separately averaging two forces acting on lateral sides of the hitch, while operating in a configuration mode. During regular operation, a draft load is calculated from sensing those two forces and deriving a draft force error from difference between the draft load and the draft force setpoint. The draft force error is used to control fluid flow to and from the hydraulic actuator. One aspect of the control method derates the draft force error as the hitch moves beyond a predefined threshold position.

Abstract: A control valve includes a main poppet that moves in response to pressure in a primary control chamber and thereby controls the flow of fluid through a valve seat between first and second ports. A passageway extends between the second port and the primary control chamber and includes a variable flow restriction that decreases as the main poppet moves away from the valve seat. An electrohydraulic pilot valve has a pilot poppet which controls fluid flow from the primary control chamber to the first port in response to pressure in a pilot control chamber. A sub-pilot valve selectively releases pressure in the pilot control chamber to operate the pilot poppet to open and close a path between the inlet and the outlet. Using an electrohydraulic pilot valve enables the main poppet to operate quickly in controlling large fluid flow rates. Unidirectional and bidirectional versions of the control valve are described.

Abstract: A valve assembly couples a plurality of hydraulic actuators to a variable displacement pump and to a tank. A separate valve is associated with each hydraulic actuator and comprises a variable flow source orifice between the supply conduit and a summation node coupled to a pump control port, a variable metering orifice between the summation node and the associated hydraulic actuator, and a variable bypass orifice between the summation node and the tank. As a valve operates to enlarge the metering orifice, the flow source orifice also enlarges, and the bypass orifice shrinks. When the valve operates to shrink the metering orifice, the flow source orifice also shrinks and the bypass orifice enlarges. Those operations vary fluid flow in and out of the summation node, which alters pressure applied to the pump control, thereby causing the pump output to vary as required to drive the associated hydraulic actuator.

Abstract: A high efficiency diametrically compact, radial oriented piston hydraulic machine includes a cylinder block with a plurality of cylinders coupled to a first port by a first valve and to a second port by a second valve. A drive shaft with an eccentric cam, is rotatably received in the cylinder block and a cam bearing extend around the eccentric cam. A separate piston is slideably received in each cylinder. A piston rod is coupled at one end to the piston and a curved shoe at the other end abuts the cam bearing. The curved shoe distributes force from the piston rod onto a relatively large area of the cam bearing and a retaining ring holds each shoe against the cam bearing. The cylinder block has opposing ends with a side surface there between through which every cylinder opens. A band engages the side surface closing the openings of the cylinders.

Abstract: An array of valve sections in a hydraulic system are connected to a supply line, a tank return line, and a load sense line. One valve sections includes a control valve with a metering orifice through which fluid flows from the supply line to a valve outlet. A load sense node is coupled by a load sense orifice to the load sense line. A load sense pressure limiter prevents pressure at the load sense node from exceeding a threshold level. A pressure compensator is connected in a fluid path between the valve outlet and one of the hydraulic actuators. The pressure compensator opens and closes the fluid path in response to pressure at the valve outlet and pressure at the load sense node, thereby governing the maximum amount of pressure that the respective valve section can apply to the hydraulic actuator.

Abstract: A method provides several modes for recovering hydraulic energy produced by an overrunning load acting on cylinders connected in parallel to a machine component. In one mode, fluid from first chambers in both cylinders is routed into the accumulator, while other fluid is directed into second chambers of those cylinders. In a different mode, fluid is routed from the first chamber of only one cylinder into the accumulator, and fluid from the first chamber of the other cylinder goes into the second chambers of both cylinders. Yet another mode comprises routing fluid from the first chambers of both cylinders into the second chambers of both cylinders. In still another mode, fluid from the first chambers of both cylinders goes into the return conduit while the second chambers of both cylinders receive fluid from a supply conduit. Several modes of reusing the recovered energy are described.

Abstract: A hydraulic valve assembly includes a pressure compensating valve in which a compensator spool is slideably received in a bore. A pre-compensator gallery connected to a metering orifice, a preload gallery leading to a hydraulic actuator, an auxiliary pump supply passage, and a load sense passage all open into the bore. The compensator spool moves in response to a pressure differential between the pre-compensator gallery and the load sense passage. That movement selectively opens and closes a first path between the pre-compensator gallery and the a preload gallery, and a second path between the auxiliary supply passage and the load sense passage. Control of these paths maintains a constant pressure drop across the metering orifice and generates a pressure signal that is employed to regulate pressure at an outlet of a pump.

Abstract: A user input device is provided for a hydraulic system that has a source of pressurized fluid and a tank. The user input device includes a body with a supply passage for receiving the pressurized fluid, a tank passage for connection to the tank, and a first chamber. A handle is pivotally attached to the body and operates one or more valves within the body. In a preferred embodiment, the handle can be pivoted independently about two orthogonal axis with separate pairs of valves operated by movement about each axis. In response to the position of the handle, each valve connects a separate chamber alternately to either the supply passage or the tank passage and different pressure sensor produces an electrical signal indicating a level of pressure in the chamber of each valve. Thus an electrical signal is produced from each valve to indicate motion of the handle.

Abstract: A user input device is provided for a hydraulic system that has a source of pressurized fluid and a tank. The user input device includes a body with a supply passage for receiving the pressurized fluid, a tank passage for connection to the tank, and a first chamber. A handle is pivotally attached to the body and operates one or more valves within the body. In a preferred embodiment, the handle can be pivoted independently about two orthogonal axis with separate pairs of valves operated by movement about each axis. In response to the position of the handle, each valve connects a separate chamber alternately to either the supply passage or the tank passage and different pressure sensor produces an electrical signal indicating a level of pressure in the chamber of each valve. Thus an electrical signal is produced from each valve to indicate motion of the handle.

Abstract: A hydraulic suspension system for a vehicle includes a pair of cylinders on opposite sides of the vehicle. Each cylinder is divided by a piston into two chambers. When the vehicle is not making a significant turn, a switching valve connects the chambers in the same cylinder together and when a significant turn occurs, the switching valve cross connects the chambers of the two cylinders. That cross connection increases resistance of the suspension system to roll of the vehicle, as compared to when the cylinder chambers are not cross connected. A load leveling function also is included in the hydraulic suspension system.

Abstract: A vibration damper piston includes a piston body with a bore from which first and second apertures respectively provide paths to first and second chambers of the vibration damper. A valve spool in the bore defines a pilot chamber and controls fluid flow between the first and second apertures. First and second springs bias the valve spool in opposing directions. A control orifice provides a continuous fluid path between the first chamber and the pilot chamber, and a variable orifice provides another fluid path between the second chamber and the pilot chamber. An actuator is operably connected to adjust the variable orifice in response to a control signal.