Load-handling vehicle comprising: a load-handling member, a jack (4) for lifting the load-handling member, comprising a lifting chamber (5) and a lowering chamber (6), a fluid source (7), a first fluid connection (8) from the lifting chamber (5) to the source (7), a second fluid connection (9) from the lowering chamber (6) to the source (7), the first connection (8) comprising a safety valve (10) that is open in the direction of the fluid source (7) towards the lifting chamber (5), and that is normally closed in the direction of the lifting chamber (5) towards the fluid source (7). A valve (11) arranged on the second link (9) is sensitive to the pressure of the portion of the first link (8) extending between the valve (10) and the source (7), and a unidirectional fluid circulation line (12), which can be closed according to the pressure weighing on the portion of the second fluid connection (9) between the valve (11) and the source (7), connects the first and second connections (8, 9).

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 relates to a timber handling vehicle (1) and a timber grip, wherein said timber handling vehicle includes a load compartment (2), a crane (3) a timber grip (4), a hydraulic cylinder (4c), a hydraulic system (11, 12), a pump (15), a tank (16), a control valve (18) with which a fluid flow set under a pump feed pressure (P) is directed to a plus side (15:1) via a first pipe (15A) respectively a minus side (15:2) via a second pipe (15B). For efficient timber handling, the hydraulic system (11, 12) includes a third pipe (15C), which results in a regenerative fluid flow from the minus side (15:2) to the plus side (15:1) of the hydraulic cylinder (4c), a valve means (21) in the second pipe (15B), which valve means (21) is configured to; drive in a first operating condition, where the valve means (21) is closed and fluid flow from the minus side (15:2) to the plus side (15:1) of the hydraulic cylinder is directed via said third pipe (15C), receive a pressure indication that indicates a pump feed pressure (P) on the plus side (15:1) of the hydraulic cylinder (4c), determine whether the pump feed pressure (P) exceeds a first operating condition threshold value (Z1) and, if so, drive in a second operating condition, where the valve means (21) is open, and fluid flow from the minus side (15:2) of the hydraulic cylinder (4c) is directed to the tank (16).

The present disclosure shows a hydraulic regeneration circuit for a hydraulic cylinder that enables multiple extension speeds for the cylinder even while using fixed displacement pumps. The regeneration circuit uses the expelled fluid to drive a hydraulic pump/motor combination to create 4 or more speeds, as opposed to the 2 speeds typical in regeneration circuits. By using directional flow control valves, the fluid can be combined in such a way that the operator can choose a speed multiplier for the hydraulic cylinder to operate at.

A hydraulic system includes: a cylinder in which an interior of a tube is divided by a piston into a first pressure chamber and a second pressure chamber; a first bidirectional pump connected to the first pressure chamber by a first supply/discharge line; a second bidirectional pump connected to the second pressure chamber by a second supply/discharge line and coupled to the first bidirectional pump in a manner enabling torque to be transmitted between the first and second bidirectional pumps; a relay line connecting the first and second bidirectional pumps such that a hydraulic liquid discharged from one of the first and second bidirectional pumps is introduced into the other of the first and second bidirectional pumps; and an electric motor that drives the first or second bidirectional pump. At least one of the first and second bidirectional pumps is a variable displacement pump whose delivery capacity per rotation is freely variable.

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 hydraulic system can include a hydraulic actuator including a piston rod slidably disposed within a housing having a base-side port and a rod-side port, a hydraulic pump, a hydraulic reservoir, an accumulator, a first control valve operable to selectively control flow from the pump to the base-side port and from the base-side port to the reservoir, a second control valve operable to selectively control flow from the pump to the rod-side port and from the rod-side port to the reservoir, a third control valve operable to selectively allow flow between the base-side port and the accumulator, and a controller for operating the hydraulic system and including a ride control mode in which damping is provided to the hydraulic actuator by operation of the first, second, and third control valves.

A hydraulic system, mining machine and method of controlling a hydraulic actuator. The hydraulic system (HS) is provided with a control valve (23) for controlling movement direction and speed of a hydraulic actuator (HA) connected to the system. Generated force of the hydraulic actuator is controlled independently relative to the control valve by means of counterbalance valves (Cb1, Cb2) and servo valves (Sv1, Sv2) controlling their opening pressure. The counterbalance valves and the servo valves operate as a meter-out control assembly which controls flow of hydraulic fluid discharged from working pressure spaces (16a, 16b) of the hydraulic actuator. The disclosed system may be implemented to control a mining boom (3) of a mining machine (1).

A hydraulic system, mining machine and method of controlling a hydraulic actuator. The hydraulic system (HS) is provided with a control valve (23) for controlling movement direction and speed of a hydraulic actuator (HA) connected to the system. Generated force of the hydraulic actuator is controlled independently relative to the control valve by means of counterbalance valves (Cb1, Cb2) and servo valves (Sv1, Sv2) controlling their opening pressure. The counterbalance valves and the servo valves operate as a meter-out control assembly which controls flow of hydraulic fluid discharged from working pressure spaces (16a, 16b) of the hydraulic actuator. The disclosed system may be implemented to control a mining boom (3) of a mining machine (1).

Disclosed are a fork leveling system and a method thereof, and a telescopic boom forklift. The fork leveling system includes an active leveling oil cylinder, a passive leveling oil cylinder and an electric control oil supplement valve, where a rodless cavity of the active leveling oil cylinder is communicated with a rodless cavity of the passive leveling oil cylinder, and a rod cavity of the active leveling oil cylinder is communicated with a rod cavity of the passive leveling oil cylinder; and an oil inlet of the electric control oil supplement valve is connected to an oil pump, and an oil outlet of the electric control oil supplement valve is connected to the rodless cavity of the active leveling oil cylinder and the rod cavity of the active leveling oil cylinder.