A drive system for hydraulically driven working mechanisms of a working machine includes an axial piston pump, the pump capacity and flow direction of which is varied by changing the pivot angle of the axial piston pump. The drive system includes a hydraulic motor connected via a line to the axial piston pump and drivably connected to the working mechanisms, a control unit operated to set the pump capacity of the axial piston pump to zero and a control valve arrangement that is actuated by the control unit to actuate a limiting device such that the pivot angle of the axial piston pump can be mechanically set to zero degrees (0°).

A servo-control having at least one movable cylinder that includes a hydraulic directional control valve. The hydraulic valve includes a control shaft that is rotatable about a longitudinal axis, the control shaft being connected to a distributor slide. The servo-control including a stationary abutment member secured to a cylinder and an input lever situated outside the cylinder. The input lever is connected to the control shaft and includes a stop portion arranged in the abutment member. The servo-control includes movement means for moving the input lever longitudinally, a first abutment surface of the abutment member limiting a travel amplitude of the stop portion when the input lever is in a first position.

Disclosed is a hydraulic construction machinery capable of operating a travel apparatus and a swing apparatus, when same are to be operated in combination, by means of working fluids supplied at the maximum discharge flow rate from a plurality of hydraulic pumps. A hydraulic construction machinery according to the present invention comprises: first and second hydraulic pumps; travel and swing motors connected to the first hydraulic pump; a hydraulic actuator connected to the second hydraulic pump; a main control valve comprising a first control valve and a second control valve, the first control valve controlling a working fluid supplied from the first hydraulic pump to the travel and swing motors, and the second control valve controlling the working fluid supplied from the second hydraulic pump to the hydraulic actuator; a first regulating valve, disposed on the most upstream side of a supply channel of the second hydraulic pump, for switching when the travel and swing motors are operated simultaneously so that the working fluid of the first hydraulic pump is supplied to the travel motor and the working fluid of the second hydraulic pump is supplied to the swing motor; a second regulating valve, disposed on the most downstream side of a supply channel of the second hydraulic pump, for switching when the travel and swing motors are operated simultaneously so as to close the most downstream opening of the supply channel of the second hydraulic pump; and an electronic proportional valve for outputting a control signal, corresponding to a control signal from a controller, to the first and second regulating valves when a manipulation signal, sensing whether the travel and swing motors are manipulated, is entered in the controller.

A hydraulic drive, preferably for a hydraulic press, having a first synchronized cylinder that comprises a piston between first and second pressure chambers; at least one hydraulic pump whereby the pump outlet is hydraulically connected with the first pressure chamber of the first synchronized cylinder and the pump inlet is hydraulically connected with the second pressure chamber of the first synchronized cylinder; at least a second synchronized cylinder that comprises a piston between first and a second pressure chambers; whereby the piston of the first synchronized cylinder is mechanically movably coupled with the piston of the second synchronized cylinder; whereby the first pressure chamber of the second synchronized cylinder is hydraulically connected with the pump outlet; and whereby the second pressure chamber of the second synchronized cylinder can be connected with the pump inlet when a pressure limit in the second pressure chamber of the second synchronized cylinder is exceeded.

Disclosed is a flow control valve for construction machinery, the flow control valve being adapted to reduce pressure loss due to flow on return to a hydraulic tank during the boom-down operation of a large-scale excavator. The flow control valve for construction machinery according to the present invention comprises: first and second boom spools which are respectively coupled to first and second boom valve blocks, and which regulate working fluid that is respectively supplied from first and second hydraulic pumps to a boom cylinder during direction reversal; a boom-up flow-adjusting means which, in direction reversal of the first and second boom spools for boom-up drive, supplies working fluid from the first and second hydraulic pumps into a large chamber of the boom cylinder via the first and second boom spools respectively, and causes part of the flow of working fluid from the second hydraulic pump to pass via the second boom spool so as to be combined with working fluid being supplied from the first hydraulic pump to the large chamber of the boom cylinder due to direction reversal of the first boom spool; and a boom-down flow-adjusting means which, in direction reversal of the first and second boom spools for boom-down drive, causes part of the flow of working fluid coming back from the large chamber of the boom cylinder to return to the hydraulic tank via the first and second boom spools respectively, and causes part of the flow of working fluid coming back from the large chamber of the boom cylinder to combine as respective regenerative flows for working fluid on the small chamber side of the boom cylinder.

A control system for a hydraulic system including an accumulator and a hydraulic transformer coordinates flow sharing within the hydraulic system. The hydraulic transformer includes first and second variable displacement pump/motor units mounted on a rotatable shaft. The rotatable shaft has an end adapted for connection to a first external load. The first variable displacement pump/motor unit includes a first side that fluidly connects to a pump and a second side that fluidly connects to a tank. The second variable displacement pump/motor unit includes a first side that fluidly connects to the accumulator and a second side that fluidly connects with the tank. A second external load may be hydraulically connected to the hydraulic system. Energy may be transferred to/from the pump, the accumulator, the first external load, and/or the second external load, as directed by the control system.

A power system for a working machine includes a transmission for driving the working machine, the transmission including a continuously variable gear box having a gear unit and a hydraulic variator unit; a work hydraulic circuit for controlling at least one hydraulic actuator of the working machine; wherein the hydraulic variator unit is hydraulically connected to the work hydraulic circuit to hydraulically transfer energy from the hydraulic variator unit to the work hydraulic circuit.

A hydrostatic drive system (1) with a hydrostatic pump (3) driven by a drive motor (2) and connected in a closed circuit with a hydrostatic motor (4). The hydrostatic motor (4) is connected with a consumer (5). The closed circuit is formed by a first hydraulic connection (6a) and a second hydraulic connection (6b). A pressure accumulator device (30) can be connected with the two hydraulic connections (6a, 6b) for the storage of energy and the output of energy. The pressure accumulator device (30) is a double piston accumulator (31) having a high-pressure-side pressure chamber (32) and a low-pressure-side pressure chamber (33). The high-pressure-side pressure chamber (32) can be connected with one of the two hydraulic connections (6a, 6b) of the closed circuit and simultaneously the low-pressure-side pressure chamber (33) can be connected with the respective other hydraulic connection (6b, 6a) of the closed circuit.

The present invention relates to a closed hydraulic circuit between a hydraulic pump and a hydraulic motor that are connected to one another via working lines, a flushing pump being provided in order to feed a pressure medium into the working lines, and an output connection being provided in order to discharge excess pressure medium from the working lines. At least one hydraulic consumer, which is provided to convert at least some of the volume flow discharged from the hydraulic circuit into mechanical power, is connected downstream of the output connection.

A blowout preventer control system comprising: a blowout preventer comprising one or more casing shear rams and one or more blind shear rams; a casing shear ram close chamber; a blind shear ram close chamber; a first SPM valve; a second SPM valve; a first solenoid valve; a microprocessor; and a hydraulic fluid source.