The subject matter of this specification can be embodied in, among other things, a fluid valve assembly that includes a first fluid port, a second fluid port, a third fluid port, a valve spool configured to be positioned at a first position, a second position away from the first position, a third position away from the first position opposite the second valve position, the valve spool defining a first fluid duct configured to fluidly connect the first fluid port to the second fluid port in the first valve position, a second fluid duct configured to fluidly connect the first fluid port to the third fluid port in the second valve position, and a third fluid duct configured to fluidly connect the first fluid port to the second fluid port in the third valve position.

The object of the present invention is to provide an inventive energy recovery method for a hydraulic system comprising a hydraulic cylinder (1), a pump (2), a tank (3), a supply conduit (4), a return conduit (5), and a hydraulic accumulator (7), the method comprises the steps of charging said hydraulic accumulator (7), and storing fluid in said hydraulic accumulator (7), wherein said energy recovery method comprises the step of directing fluid from said hydraulic accumulator (7) into an expanding chamber (8, 9) of said hydraulic cylinder (1) during an overrunning load condition.

Disclosed is a hydraulic system for performing land preparation works by means of a simultaneous boom-up and arm-in operation. The hydraulic system according to the present invention includes: an arm cylinder and a boom cylinder that are connected to first and second hydraulic pumps, respectively; a first boom control valve that is disposed in the discharge flow path of the second hydraulic pump; a second boom control valve that is disposed in the discharge flow path of the first hydraulic pump and causes the working fluid of the first hydraulic pump to converge with the working fluid which is supplied from the second hydraulic pump to the boom cylinder; a first arm control valve that is disposed in the discharge flow path of the first hydraulic pump; a second arm control valve that is disposed in the discharge flow path of the second hydraulic pump and causes the working fluid of the second hydraulic pump to converge with the working fluid which is supplied from the first hydraulic pump to the arm cylinder; a recycle valve that is disposed in the flow path between the working fluid inlet port of the first arm control valve and a hydraulic tank; and a second boom control valve spool having a parallel pressure section in which the boom-up pilot pressure does not increase with respect to the boom-up strokes during the simultaneous boom-up and arm-in operation.

A closed loop feedback circle drive system utilized onboard a motor grader includes an operator input device, a blade, and a multi-speed hydraulic motor having a motor output shaft. The motor output shaft is mechanically linked to blade such that motor output shaft rotation drives rotation of the blade about a blade rotation axis. A controller is operably coupled to the operator input device and to the multi-speed hydraulic motor. The controller is configured to: (i) receive blade rotation commands via the operator input device to rotate the blade about the rotation axis in a commanded manner; and (ii) control the multi-speed hydraulic motor to implement the blade rotation commands, while repeatedly adjusting the rotational speed of the motor output shaft to reduce variations in a rotational velocity of the blade due to changes in blade loading conditions occurring during motor grader operation.

A hydraulic control system for a work vehicle includes one or more processors configured to receive an indication of a pump flow provided by a pump of the hydraulic control system. The one or more processors are also configured to receive an additional indication of a current input position of an input device of the hydraulic control system. The one or more processors are further configured to apply a dynamic valve map to control a valve position of a valve of the hydraulic control system based on the pump flow and the current input position of the input device.

A stage assembly (10) includes a stage (14), and a fluid actuator assembly (24) that moves the stage (14). The fluid actuator assembly (24) includes a piston housing (32) that defines a piston chamber (34); (ii) a piston (36) that separates the piston chamber (34) into a first chamber (34A) and a second chamber (34B); (iii) a supply valve (38C) that controls the flow of the working fluid (40) into the first chamber (34A); and (iv) an exhaust valve (38D) that controls the flow of the working fluid (40) out of the first chamber (34A). The supply valve (38C) has a supply orifice (250G) having a supply orifice area, and the exhaust valve (38D) has an exhaust orifice (352G) having an exhaust orifice area. Moreover, the supply orifice area is different from the exhaust orifice area. Further multiple valves of different sizes can be used in combination for the supply and exhaust for each chamber (34A), (34B).

The subject matter of this specification can be embodied in, among other things, a fluid valve assembly that includes a first fluid port, a second fluid port, a third fluid port, a valve spool configured to be positioned at a first position, a second position away from the first position, a third position away from the first position opposite the second valve position, the valve spool defining a first fluid duct configured to fluidly connect the first fluid port to the second fluid port in the first valve position, a second fluid duct configured to fluidly connect the first fluid port to the third fluid port in the second valve position, and a third fluid duct configured to fluidly connect the first fluid port to the second fluid port in the third valve position.

A closed loop feedback circle drive system utilized onboard a motor grader includes an operator input device, a blade, and a multi-speed hydraulic motor having a motor output shaft. The motor output shaft is mechanically linked to blade such that motor output shaft rotation drives rotation of the blade about a blade rotation axis. A controller is operably coupled to the operator input device and to the multi-speed hydraulic motor. The controller is configured to: (i) receive blade rotation commands via the operator input device to rotate the blade about the rotation axis in a commanded manner; and (ii) control the multi-speed hydraulic motor to implement the blade rotation commands, while repeatedly adjusting the rotational speed of the motor output shaft to reduce variations in a rotational velocity of the blade due to changes in blade loading conditions occurring during motor grader operation.

A stage assembly (10) includes a stage (14), and a fluid actuator assembly (24) that moves the stage (14). The fluid actuator assembly (24) includes a piston housing (32) that defines a piston chamber (34); (ii) a piston (36) that separates the piston chamber (34) into a first chamber (34A) and a second chamber (34B); (iii) a supply valve (38C) that controls the flow of the working fluid (40) into the first chamber (34A); and (iv) an exhaust valve (38D) that controls the flow of the working fluid (40) out of the first chamber (34A). The supply valve (38C) has a supply orifice (250G) having a supply orifice area, and the exhaust valve (38D) has an exhaust orifice (352G) having an exhaust orifice area. Moreover, the supply orifice area is different from the exhaust orifice area. Further multiple valves of different sizes can be used in combination for the supply and exhaust for each chamber (34A), (34B).

The invention relates to a controlled three-way proportional valve unit comprising: a valve assembly with two individual valves; an actuating device actuating valves of the valve assembly; and a control unit acting upon the actuating device and having a control signal input, the valves of the valve assembly being designed as poppet valves arranged on opposite sides and having counter-rotatable valve spindles. The valve spindles are prestressed relative each other in opposite directions by a prestressing element such that, when the actuating unit is inactive, a first poppet valve is open and the second poppet valve is closed. The actuating device comprises an actuator common to both poppet valves, acts upon the two valve spindles and changes the position of the valve spindles counter to the effect of the prestressing element.