A hydraulic assembly for an extendable lift arm assembly can include an extension cylinder, a leveling cylinder, a main control valve, a flow combiner/divider, and one or more flow-blocking arrangements. The main control valve can be configured to control commanded movement of the extension and leveling cylinders of the lift arm assembly. The flow combiner/divider can be configured to hydraulically link the extension cylinder with the leveling cylinder for synchronized operation of the extension cylinder and the leveling cylinder. The one or more flow-blocking arrangements can be configured to restrict flow from rod or base ends of the leveling or extension cylinders during commanded extension or retraction of the leveling and extension cylinders, or in the absence of commanded movement of the leveling and extension cylinders, to maintain synchronized orientation of the leveling and extension cylinders.

A method for automatically adjusting the position of an implement of a lift assembly of a work vehicle includes determining a tilt transition boom angle for the lift assembly, determining a closed-loop control signal associated with controlling movement of the implement based at least in part on the tilt transition boom angle, generating a valve command signal based at least in part on the closed-loop control signal, and controlling an operation of at least one valve associated with the implement based at least in part on the valve command signal to maintain the implement at a target implement angle as a boom of the lift assembly is being moved across a boom travel range.

A hydraulic assembly for an extendable lift arm assembly can include an extension cylinder, a leveling cylinder, a main control valve, a flow combiner/divider, and one or more flow-blocking arrangements. The main control valve can be configured to control commanded movement of the extension and leveling cylinders of the lift arm assembly. The flow combiner/divider can be configured to hydraulically link the extension cylinder with the leveling cylinder for synchronized operation of the extension cylinder and the leveling cylinder. The one or more flow-blocking arrangements can be configured to restrict flow from rod or base ends of the leveling or extension cylinders during commanded extension or retraction of the leveling and extension cylinders, or in the absence of commanded movement of the leveling and extension cylinders, to maintain synchronized orientation of the leveling and extension cylinders.

A lift arm structure for a power machine with a frame can include a multi-bar linkage that is pivotally secured to the frame and a leveling link that is pivotally secured to the multi-bar linkage. The leveling link can be configured to transmit force from the leveling link to an implement as the multi-bar linkage is actuated to raise or lower the implement, including via a multi joint member that is pivotally secured to the leveling link, the multi-bar linkage, and an actuator that is configured to move the implement.

Disclosed embodiments include power machines, such as front-end loaders and utility vehicles, with a lift arm and a bucket leveling system utilizing four-bar linkages which mechanically level an attached implement as the lift arm is raised and lowered.

A work machine includes a mainframe, a boom moveable relative to the mainframe, a work implement coupled to and moveable relative to the boom. The work machine further includes a work-implement operator control configured to transmit a signal indicative of a work-implement movement command, a boom operator control configured to transmit a signal indicative of a boom movement command, and a boom sensor configured to detect a movement of the boom and transmit a signal indicative of the detected movement of the boom. The work implement further includes a controller configured to receive signals from the work-implement operator control, the boom operator control, and the boom sensor. The controller is further configured transmit a signal to cause movement the work implement relative to the boom based on the detected movement of the boom and the work-implement movement command.

A hydraulic system includes: a boom cylinder to move a boom; a working tool cylinder to move a working tool attached to the boom; a boom control valve to control the boom cylinder; a working tool control valve to control the working tool cylinder; a horizontal control valve having: an activating position to allow a horizontalizing operation of the working tool; and a stopping position to stop the horizontalizing operation; and a controller device having: a first information obtaining portion to obtain permission and non-permission to the horizontalizing operation; a second information obtaining portion to obtain at least one of upward operation and upward movement of the boom; and a horizontal controller to set the horizontal control valve to the stopping position when the first information obtaining portion obtains the non-permission and the second information obtaining portion obtains one of the upward operation and the upward movement.

The invention provides a wheel loader front unit including a frame, the wheel loader front unit further including two hub supporting elements, each hub supporting element being arranged on opposite sides outside of the frame for supporting a respective hub unit, a lift arm for supporting an implement of the wheel loader, the lift arm being arranged to be pivoted around a pivot connection to the frame by a main hydraulic cylinder, and a tilting hydraulic cylinder arranged to actuate a tilting movement of the implement in relation to the lift arm, wherein the wheel loader front unit further includes a slave hydraulic cylinder hydraulically connected to the tilting hydraulic cylinder for controlling the tilting movement of the implement when the lift arm is pivoted by the main hydraulic cylinder, wherein the slave hydraulic cylinder extends between the lift arm and one of the hub supporting elements.

A hydraulic system includes first and second control valves controlling a flow rate of operation fluid to be supplied to first and second hydraulic actuators, respectively, a supply fluid tube connecting the first control valve and the second control valve and being connected to a return fluid tube, and a discharge fluid tube connected to the second control valve. The second control valve is switched between primary, secondary, and tertiary positions, the primary position blocking between the supply fluid tube and the discharge fluid tube and allowing return fluid to be supplied to the second hydraulic actuator, the secondary position communicating between the supply fluid tube and the discharge fluid tube and stopping supplying the return fluid to the second hydraulic actuator, and the tertiary position communicating between the supply fluid tube and the discharge fluid tube and allowing the return fluid to be supplied to the second hydraulic actuator.

A lift arm structure for a power machine with a frame can include a multi-bar linkage that is pivotally secured to the frame and a leveling link that is pivotally secured to the multi-bar linkage. The leveling link can be configured to transmit force from the leveling link to an implement as the multi-bar linkage is actuated to raise or lower the implement, including via a multi joint member that is pivotally secured to the leveling link, the multi-bar linkage, and an actuator that is configured to move the implement.