A drive system of a construction machine includes: a controller that controls a fuel injection valve, so an actual rotation speed of an engine is adjusted to a setting rotation speed; a hydraulic circuit including a boom cylinder supplied with hydraulic oil from a pump driven by the engine, configured so energy is regenerated as motive power owing to the pump being driven by pressurized oil discharged from the boom cylinder at boom lowering; and a boom operation device including a boom operation lever. At boom lowering, the controller cuts a fuel supply to the engine when a cutting condition is satisfied, which is defined to include that an operating amount of the lever is less than or equal to a first threshold, and resumes the fuel supply when the cutting condition stops being satisfied or when the actual rotation speed of the engine becomes less than a second threshold.

A control device is disclosed for at least one hydraulic working section (A, B), which can be connected to a pressure supply source (P) and a return flow (T) via a hydraulic supply circuit and a control valve (34) supplied with a pilot pressure, the device comprising an emergency shutdown system (32) having a pilot solenoid valve (16) and an additional valve (14). Said control device is characterised in that both the hydraulic energy flow from the pressure supply source (P) to at least one of the respective working sections (A, B) and the pilot pressure supply to the control valve (34) can be suppressed by means of the pilot solenoid valve (16) via the additional valve (14).

In a hydraulic drive of a tool piston in a cylinder first and second flat contact areas each are contiguous, when moving into and in the open position of the valve member between the detent element and the valve member, wherein a pressure-limiting valve that can be loaded with the pressure in the cylinder from a closed position to an open position and a detent element loaded by a spring in the locking direction to positively hold a neck of a valve member of the pressure-limiting valve are arranged in the open position, wherein the detent element at least via the tool piston at its return to a released position can be moved and, when moving the valve member to the open position of the pressure-limiting valve, non-positively acts on the valve member.

A manipulator for concrete pumps having an articulated boom with at least two boom arms and a hydraulic drive that pivots one or more of the boom arms. A hydraulic cylinder has piston and rod side working volumes. A hydraulic circuit has a first switching state in which the hydraulic circuit connects a first working port for feed or discharge of hydraulic fluid to the rod-side working volume and connects a second working port for feed or discharge of hydraulic fluid to the piston-side working volume. In a second switching state, the hydraulic circuit separates the first working port from the first fluid channel and thereby connects the first fluid channel to the second fluid channel for the feed of hydraulic fluid from the rod-side to the piston side working volume. A sensor acquires an operating state variable based upon which an activation assembly sets the switching state.

Power machines having hydraulic systems and controllers configured to prohibit, limit, or allow full operation of the hydraulic systems based upon measured temperature of the hydraulic oil in the system are provided. Also included are methods of controlling the hydraulic systems. In the methods implemented by the controllers, determinations are made as to whether the temperature of the hydraulic oil is below a first (and lowest) set point temperature, above a second (and higher) set point temperature, or between the first and second set point temperatures. The controllers then either prohibit hydraulic system operation, allow limited hydraulic system operation, or allow full hydraulic system operation, based upon the measured temperature in comparison to the two or more set point temperatures.

A forklift includes forks, cylinders for causing the forks to perform an ascending/descending operation in accordance with the flow rate of hydraulic oil, a first valve for controlling the flow rate of the hydraulic oil in accordance with an energizing current, a second valve 6 for regulating the flow rate of the hydraulic oil in accordance with cylinder pressure, and a control portion that calculates the flow rate to be regulated by the second valve, on the basis of cylinder pressure detected by a pressure sensor, calculates a current command value for the energizing current, with the flow rate to be controlled by the first valve being set equal to the regulated flow rate, and changes the energizing current in two stages, with the current command value as the upper limit of the energizing current, thereby decelerating the forks in two stages when stopping the ascending/descending operation.

A car wash system including a hydraulic pump, the pump being overcapacity for the rotating cleaning elements to which it is connected. An output from the hydraulic pump is connected to a hydraulic motor, which is, in turn, connected to a generator. The generator is connected to a service panel. Thus, some of the spare capacity of the hydraulic pump may be used to generate electricity which may be returned to the grid, reducing operating costs of the automated car wash.

This disclosure includes systems and methods for actuating hydraulically-actuated devices.

A hydraulic system in a work machine includes a hydraulic pump to supply pilot hydraulic oil. A work hydraulic actuator is to move a work device of the work machine. A control valve is to control the work hydraulic actuator based on a pilot pressure of the pilot hydraulic oil. A target pilot pressure of the pilot hydraulic oil is input through the work operation device to control, according to the target pilot pressure, the pilot pressure supplied from the hydraulic pump to the control valve. A pilot oil path connects the work operation device and the control valve to supply the pilot pressure to the control valve. A drain oil path is divided from the pilot oil path. A pressure adjustment valve is provided in the drain oil path to adjust the pilot pressure to be less than the target pilot pressure when a condition is satisfied.

A hydraulic drive system of a construction machine includes: an over-center pump connected to a turning motor; a regulator that adjusts tilting angle of the over-center pump; a main pump coupled to over-center pump; and a controller that controls the regulator such that when a turning deceleration operation is performed, the over-center pump's tilting angle decreases in accordance with decrease in a turning operation signal outputted from a turning operation device. The controller: when a pressure accumulation condition satisfied, switches a switching valve to pressure accumulation position to bring an accumulator into communication with a delivery line of the main pump; when a pressure release condition is satisfied, switches the switching valve to a pressure release position to bring accumulator into communication with a suction line of main pump; and when neither the pressure accumulation condition nor pressure release condition is satisfied, switches the switching valve to a neutral position.