Abstract: A distributed hydraulic system having a plurality of hydraulic functions each including a hydraulic actuator, a valve assembly that controls flow of fluid to the hydraulic actuator, and a function controller which operates the valve assembly. The function controllers exchange messages over a communication network which has a finite bandwidth. Access to the network is controlled by determining which function controllers govern high priority operations and allowing those function controllers to send messages as often as once every first interval of time. The other function controllers are limited to sending messages no more often than once every second interval of time, which is longer than the first interval of time.

Abstract: A distributed hydraulic system having a plurality of hydraulic functions each including a hydraulic actuator, a valve assembly that controls flow of fluid to the hydraulic actuator, and a function controller which operates the valve assembly. The function controllers exchange messages over a communication network which has a finite bandwidth. Access to the network is controlled by determining which function controllers govern high priority operations and allowing those function controllers to send messages as often as once every first interval of time. The other function controllers are limited to sending messages no more often than once every second interval of time, which is longer than the first interval of time.

Abstract: A pair of hydraulic cylinders 10 which are coupled to a driven member, placed parallel to each other and extend/contract in synchronization with each other, and a control valve 20 which controls hydraulic fluid supplied to or discharged from the hydraulic cylinder 10 are provided. An elastic support mechanism 50 which supports the control valve 20 to each hydraulic cylinder between the paired hydraulic cylinders 10; metallic piping 30 and the metallic piping 40 which connect the control valve 20 with the respective hydraulic cylinders 10 and leads the hydraulic fluid controlled by the controlling valve 20; and curved portions 31c, 32, 41c, 42a which are provided at some midpoints of the piping and flexibly deform in accordance with relative deformation of each hydraulic cylinder 10 are provided. A difference in relative displacement of each hydraulic cylinder with respect to the control valve 20 is absorbed by deformation produced in the elastic support mechanism 50 and the curved portions.

Abstract: A machine has a boom, that is pivotally raised and lowered by a first cylinder, and has a load carrier that is pivoted at the end of the boom by a second cylinder. As a machine operator commands movement of the boom, the position of the load carrier is automatically altered by a controller to prevent a load from falling off the load carrier. The load carrier position with respect to the boom is altered in response to the amount of boom motion to maintain a constant position relationship between the load carrier and a chassis of the machine. Although the boom and load carrier move through different angular positions, the machine control is expressed in terms of the linear motion of the first and second cylinders.

Abstract: An apparatus is provided which has sensors that detect pressure on opposite sides of a control valve which controls the flow of hydraulic fluid from a source to a hydraulic actuator. The sensors produce electrical signals indicating those pressures. In response to the sensor signals, a controller produces an output signal the operates a proportional control valve to thereby regulate pressure at a node of the hydraulic circuit. Several mechanisms are described that react to the pressure at the node by varying the pressure of the fluid being supplied to the main valve so that a controlled pressure level is achieved.

Abstract: A hydraulic valve assembly is provided to activate and deactivate cylinder valves of a multi-cylinder engine. A plurality of electrohydraulic valves are loosely received in openings in a base plate which allows the relative positions of the valve to adjust automatically for dimensional irregularities as the assembly is installed on the engine. At the complete of that installation, elements of each electrohydraulic valve are clamped between the base plate and the engine to secure the valves in position. A flexible lead frame containing electrical conductors is secured to both the base plate and the electrohydraulic valves provides additional support while allowing movement of the valves with respect to the base plate.

Abstract: A spool valve section for a multiple valve assembly has a body with two opposing side surfaces. A plurality of mating surfaces are raised from each side surface. The mating surfaces surround the openings of fluid passages through the section and apertures for fasteners that secure the assembly together. The mating surfaces are spaced from a region of each side surface that is adjacent a bore in the body that receives a control spool. The fluid passages also are spaced from and do not intersect the spool bore. These characteristics of the spool valve section reduce distortion of the spool bore which could otherwise result from the pressure and fastening forces in the valve assembly.

Abstract: A solenoid operated valve has a valve body with a plurality of ports and a spool slidable within the valve body to interconnect the ports in different combinations. An actuator drives the spool into several operating positions. The actuator has a solenoid assembly with an aperture within which first and second tubular pole pieces are received. An armature is able to slide within the two pole pieces and a push member projects from the armature abutting the spool. The push member is secured to a rolling bearing which has a plurality of rolling elements that roll against the pole pieces to reduce resistance to movement of the armature.

Abstract: A plurality of hydraulic actuators are connected by valve assemblies to fluid supply and return conduits. Desired operating velocities are specified for the hydraulic actuators and used to define the amounts of fluid flow required by each actuator to move at the respective velocity. Provide the requisite flow amounts, fluid at related pressures must be provided at the different hydraulic actuators. In order for those pressures to occur, a pump has to furnish fluid at a greater pressure to allow for supply conduit losses. A process is provided for determining the pressure that the pump must provide to satisfy the greatest pressure that is necessary for the desired operation of all the hydraulic actuators.

Abstract: An electrically operated valve controls the flow of oil to and from a device that activates and deactivates a cylinder of a multi-cylinder engine. A first valve seat is between an inlet and a workport connected to the device and a second valve seat is between the workport and an outlet. A valve element engages the first valve seat when a solenoid actuator is energized. The valve element and the first valve seat cooperate to allow air to bleed from the inlet through the valve upon starting the engine, but prevent the oil from flowing in that path unless the solenoid actuator is energized. In one version of the valve, the valve element engages the second valve seat when disengaged from the first valve seat. In a second version, another valve element engages the second valve seat when oil flows through the first valve seat.

Abstract: An assembly of a plurality of hydraulic control valves is housed in a single-piece body. For each control valve, a spool bore and an aperture for a pressure compensation valve are provided in the monolithic body. Each spool bore is connected to several return passages and a supply passage that extend through the monolithic body. A pair of workports also is connected to each spool bore. A relief valve return passage also extends through the monolithic body and where needed, apertures for pressure relief valves extend from a surface of the monolithic body intersecting the relief valve return passage and a given workport. A load sense passage and a second supply passage also are formed in the monolithic body.

Abstract: A member that is driven by a hydraulic actuator tends oscillate when fluid flow to the hydraulic actuator is terminated. A pressure relief device reduces that oscillation by connecting first and second first relief valves to the hydraulic actuator. The first relief valve provides a relatively large first relief passage as long as pressure in the hydraulic actuator remains above a threshold. A second relief valve opens a second relief passage at substantially the same threshold pressure and thereafter remains open as long as the pressure remains above another lower threshold. A timer causes the second relief valve to close a given interval of time, if the pressure does not drop below the other lower threshold.

Abstract: A hydraulic circuit branch includes a hydraulic actuator, such as a cylinder, and an assembly of one or more electrohydraulic proportional valves connected in series between a pressurized fluid supply line and a tank return line. The force acting on the hydraulic actuator is determined by sensing fluid pressures produced by the hydraulic actuator. Pressures in the supply and tank return lines also are sensed. The sensed pressures and a desired velocity for the hydraulic actuator are employed to determine an equivalent flow coefficient, which characterizes fluid flow through the hydraulic circuit branch, either a conduction or restriction coefficient may be derived. The equivalent flow coefficient is used to determine how to activate each electrohydraulic proportional valve to achieve the desired velocity of the hydraulic actuator. The equivalent flow coefficient also is employed to control the pressure levels in the supply and tank return lines.

Abstract: In a hydraulic system that has first and second pumps, a pressure compensation circuit is provided to unload the output of the second pump when its operation is not required. The unloading reduces the power demanded of the engine that drives the pumps thus conserving energy. The first pump is directly connected to a supply line and a back flow check valve couples the second pump to the supply line. When pressure in the supply line is significantly greater than the load pressure of the actuators powered by the hydraulic fluid a bypass compensator valve opens to provide a path between the outlet of the second pump and the tank line. This action unloads the second pump and reduces its demand for engine power.

Abstract: An apparatus and method for controlling hydraulic output to a plurality of actuatable devices are disclosed. The apparatus includes a plurality of main valves coupled, respectively, to the actuatable devices and to respective secondary valves, and also an adjustment valve that is coupled between a pressure source and one or more of the secondary valves. The adjustment valve receives a first indication of a pressure at the one or more secondary valves, and a second indication related to a highest load pressure. The adjustment valve allows pressure to be provided from the pressure source to the one or more secondary valves when the second indication exceeds the first indication, such that an equal amount of fluid flow occurs with respect to each of those secondary valves that is reduced in comparison with the fluid flow to any other secondary valves that are not connected to the adjustment valve.

Abstract: The flow of fluid to a hydraulic actuator is controlled by a valve assembly which operates in different metering modes at various points in time. The metering mode to use in selected in response to the hydraulic load that acts on the valve associated with the hydraulic actuator. Specifically the load is determined and then compared to threshold levels associated with the different metering modes to choose the metering mode for use a given point in time.

Abstract: A first control valve selectively connects a first port of a double acting actuator to either a pump supply line or a tank return line, and a second control valve selectively connects a second port of the actuator to either a pump supply line or a tank return line. A first pilot operated check valve restricts fluid flow to a direction only from the first control valve to the first workport unless a pilot pressure from the second port is sufficient to open the valve for the opposite flow direction. A second pilot operated check valve restricts fluid flow to a direction only from the first control valve to the second workport unless a pilot pressure from the first port is sufficient to open the valve for the opposite flow direction. A load sense circuit is incorporated to produce signal indicating the greater pressure at the actuator ports.

Abstract: A pilot operated valve has a poppet that is held against a valve seat by pressure in a control chamber on an opposite side of the poppet and by force from a feedback spring. The force feedback spring also engages a pilot valve spool which controls the flow fluid from a control chamber. When a electrically driven actuator moves the pilot valve spool and fluid is released from the control chamber, inlet pressure acting on the poppet causes the valve to open. As the poppet moves away from the valve seat, the feedback spring exerts more force on the pilot valve spool so as to meter the fluid being released from the control chamber. When the force of the feedback spring counterbalances the actuator force, an equilibrium condition occurs and the poppet stops moving at the desired flow control position.