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 self-leveling front-end loader for attachment to a tractor. The self-leveling front-end loader includes a support structure configured to be attached to the tractor, and two extendable booms, each boom including a proximal leg, a distal leg, and a self-leveling hydraulic linkage configured to maintain the tilt angle of an accessory, such as a bucket. Each extendable boom has a boom extension hydraulic cylinder for extending the boom by up to 2 to 4 feet, a lift hydraulic cylinder to lift each boom, a self-leveling hydraulic cylinder, and a tilt hydraulic cylinder to tilt the accessory. The extendable booms enhance the capability of the front-end loader to position payload higher and farther than a standard front end loader, while preserving the stability and lifting capacity of the front-end loader. The booms have a traditional dogleg bend of 105 to 135 degrees, providing the two booms a wide range of motion.

Disclosed is a self-level mechanism for controlling a tilting movement of an equipment (15) mounted to an equipment connector (5) of a main arm (3) of a lifting arrangement of a construction machine, preferably a wheel loader (1), upon pivoting said main arm (3). The self-level mechanism is configured to at least partially compensate any tilting movement of the equipment (15).

Disclosed power machines include a lift arm structure having a first arm pivotally mounted to a frame and a second arm, coupled to an implement interface, configured to telescopically extend from and retract into the first arm. A control system controls a first actuator to raise and lower the first arm, and controls a second actuator to extend and retract the second arm relative to the first arm. The control system is configured to control the first and second actuators to implement a lift operation, responsive to an operator input. During the lift operation, the first actuator raises the first arm and the second actuator extends and retracts the second arm to maintain a substantially linear path, such as a vertical path, of the implement interface or an implement attached to the implement interface.

A method of controlling a lift arm actuator and a tilt actuator to control positioning of an implement carrier coupled to a lift arm of a power machine. An activation signal is received from an enabling input device. A lift arm control signal is received from a lift arm control input commanding movement of the lift arm. The lift arm actuator is controlled responsive to receipt of both of the activation signal and the lift arm control signal to move the lift arm to a target lift arm position and to move the implement carrier to or maintain the implement carrier at a target implement carrier orientation relative to a gravitational direction.

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.

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.

The present disclosure is directed to a control method for controlling the operation of a lift assembly of a work vehicle, wherein the lift assembly includes an implement and at least one loader arm coupled to the implement. As such, the method may generally include transmitting at least one first command signal in order to simultaneously move the loader arm and the implement towards a return position. The first command signal(s) are associated with moving the loader arms at a movement velocity. The method also includes monitoring a height of the implement relative to a driving surface of the work vehicle during simultaneous movement of the loader arm and the implement. As such, the method may also include reducing the movement velocity of the loader arm when the height is below a predetermined threshold.

Power machines and control systems used thereon include a lift cylinder, a tilt cylinder, and a slave cylinder mechanically connected to assist the lift cylinder with raising a boom. With a lift control valve controlled to cause extension of the lift cylinder to raise the boom, pressure from a hydraulic source is provided to the slave cylinder to aid in raising the boom. Resulting increased pressure on a side of the slave cylinder opens load holding valves, allowing hydraulic pressure from the tilt cylinder to be communicated to the slave cylinder such that tilt cylinder pressure due to a heavy load on an implement aids in raising the boom.

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.