Sod harvesters can have hydraulic systems that are configured to actuate components with precise timing. The hydraulic system of a sod harvester can be configured to maintain the temperature of hydraulic fluid both during harvesting and while harvesting is paused to thereby eliminate or minimize the occurrence of periods of variation in the timing of actuation of the components that the hydraulic fluid drives. As a result, these components can be consistently actuated with precise timing even after harvesting has been paused. Additionally, such configurations can minimize the amount of time required to warm the hydraulic fluid to a steady operational temperature.

A hydraulic machine includes a tank; a working device including a boom; a boom cylinder which operates the boom and has a large chamber and a small chamber; a floating hydraulic circuit connected to the large chamber, the small chamber, and the tank so as to enable the large chamber, the small chamber, and the tank to communicate with each other; and an operator input device for receiving, from a driver, a request for turning on or turning off the floating hydraulic circuit. In the case of a boom down operation for lowering the boom, it is determined whether the working device floats in the air, and when it is determined that the working device floats in the air, the floating hydraulic circuit can be turned off, even if the request for turning on the floating hydraulic circuit is input to the operator input device.

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).

The present disclosure relates to a hydraulic circuit, comprising: a hydraulic displacement unit for driving an implement; a hydraulic machine fluidly connected or selectively fluidly connected with the hydraulic displacement unit the hydraulic machine having a fixed hydraulic displacement; an electric machine drivingly engaged or selectively drivingly engaged with the hydraulic machine; a hydraulic pump fluidly connected or selectively fluidly connected with the hydraulic displacement unit, the hydraulic pump having a variable hydraulic displacement; and an electric motor drivingly engaged or selectively drivingly engaged with the hydraulic pump.

Provided is a work machine which can increase the operation speed of an actuator by a regeneration function while securing the position control accuracy of the actuator. A controller is configured to calculate a regeneration flow rate on the basis of an input amount of an operation lever and a target actuator flow rate, subtract the regeneration flow rate from the target actuator flow rate to calculate a target actuator supply flow rate, calculate a target flow rate control valve opening amount on the basis of the target actuator supply flow rate, calculate a target pump flow rate that is equal to or higher than a total target actuator supply flow rate, control a selector valve on the basis of the input amount of the operation lever, control a flow rate control valve according to the target flow rate control valve opening amount, and control a hydraulic pump according to the target pump flow rate.

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).

Provided is a construction machine that can prevent a machine body from being lowered since a blade is not put into a float state even where a misoperation is made by an operator when the machine body is in a jacked-up state, and that can perform a favorable leveling operation by putting the blade into the float state in accordance with an operator's operation when the machine body is not in the jacked-up state. A hydraulic excavator includes a controller 42 that determines whether or not the machine body is in a jacked-up state and controls a float valve 41. In the case where it is determined that the machine body is not in the jacked-up state, the controller 42 changes over the float valve 41 to a float position V and invalidates an operation of a blade control valve 22, in accordance with a float instruction. In the case where it is determined that the machine body is in the jacked-up state, the controller 42 holds the float valve 41 in a reference position IV and validates the operation of the blade control valve 22, irrespectively of the presence or absence of the float instruction.

Provided is an electrohydrostatic actuation system including an emergency shut-off circuit to be actuated stably with a simple configuration. The electrohydrostatic actuation system includes: a hydraulic cylinder (24) including a piston (25) to which a valve element is connected, a first chamber (24A), and a second chamber (24B); a hydraulic pump (21) configured to supply hydraulic fluid to the first chamber (24A) or the second chamber (24B); a servo motor (M) configured to drive the hydraulic pump (21); a shuttle valve (11) configured to establish communication to a downstream side under a state in which a hydraulic pressure generated by the hydraulic pump (21) is maintained; a solenoid valve (12) configured to receive the hydraulic pressure via the shuttle valve (11) as a pilot pressure; and a logic valve (13) including a first port configured to receive the pilot pressure from the solenoid valve (12), and a second port to be communicated to the first chamber (24A) of the hydraulic cylinder (24). When the solenoid valve (12) is brought to a de-energized state, the pilot pressure of the logic valve (13) is released, and the logic valve (13) causes the hydraulic fluid in the first chamber (24A) communicated to the second port to flow into the second chamber (24B) so that emergency shut-off of the valve element is achieved by a return spring (26).

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.

An actuator system for an aircraft includes an actuator, and a control valve system operatively connected to the actuator. The control valve system includes a first direct drive valve (DDV) mechanically connected to a second DDV. A backup valve system is operatively connected to the actuator. The backup valve system includes one of an electro-hydraulic servovalve (EHSV) and a DDV.