Abstract: Provided is a hydraulic driving apparatus for a working machine, preventing an excessive decrease in pressure on a meter-in side and moving a load at a stable speed in a lowering direction. The apparatus comprises: a hydraulic pump; a hydraulic actuator; a manipulation device; a working hydraulic circuit including a meter-in flow passage and a meter-out flow passage; a control valve for changing a state of supply of hydraulic fluid to drive the hydraulic actuator at a speed designated by the manipulation device; a meter-in flow adjuster and a meter-out flow adjuster adapted to adjust a meter-in flow rate and meter-in flow rate respectively to respective value corresponding to the speed designated by the manipulation device; and a relief valve. The meter-in and meter-out flow adjusters have respective flow adjustment characteristics such that the meter-in flow rate is greater than the meter-out flow rate.

Abstract: Provided is an apparatus to lower a load, comprising a hydraulic pump, a hydraulic actuator having first and second ports, a manipulation device, a hydraulic circuit including meter-in and meter-out flow passages for the first and second ports respectively and a regeneration flow passage with a check valve, a control valve, a meter-out flow controller adjusting a meter-out flow rate according to the manipulation device, a back pressure valve, and a non-regeneration operation relief valve whose set pressure is not less than a sum of a minimum set pressure of the back pressure valve, an inlet-outlet pressure difference of the meter-out flow controller when the meter-out flow rate is maximum and a discharge flow rate of the hydraulic pump is maximum, and an actuator pressure difference for driving the hydraulic actuator with no load, and not less than a maximum set pressure of the back pressure valve.

Abstract: Provided is an apparatus provided in a working machine to lower a load, comprising a hydraulic pump, a hydraulic actuator, a manipulation device having a manipulation member, a meter-in flow control device, a meter-out flow control device, a back pressure valve, a regeneration fluid passage branched from the meter-out fluid passage at a position upstream of the back pressure valve and merged with the meter-in fluid passage, and a check valve. The meter-in flow control device controls a meter-in flow rate in a region of the meter-in fluid passage upstream of a merging point with the regeneration fluid passage. The meter-out flow control device controls a meter-out flow rate in a region of the meter-out fluid passage upstream of a branching point of the regeneration fluid passage so as to make the meter-out flow rate be greater than the meter-in flow rate.

Abstract: Disclosed is a construction machine which comprises: a command changing regulation section; a loading device for imposing, on an engine, a load for raising an exhaust temperature of the engine up to a value at which particulate matter accumulated in a filter is burnt; and an instruction section for instructing the loading device to perform an operation for loading the engine. The instruction section prohibits the loading device from changing a loading level on the engine, during a period where a manipulation-state detection section detects a presence of a manipulation of a manipulation section. The command changing regulation section is set to a changing permission mode for permitting a value of a command which is to be assigned to an actuator control valve, to be changed according to changing a value of a command to be output from a manipulation device, during a period where the loading level is constant.

Abstract: Second-gear blocking switching valves 101 to 104 are provided in pipe lines providing communication between remote control valves 22, 24 and pilot operation portions of valve sections of second-gear spools of control valves. A switching selection means 105 switches the second-gear blocking switching valves 101 to 104. Proportional pressure reduction valves 111 to 114 change secondary pressure to be outputted in accordance with secondary pressure of the remote control valves. Secondary pressure changing switching valves 116 to 119 are provided in pipe lines providing communication between the remote control valves and pilot operation portions of valve sections of first-gear spools of the control valves.

Abstract: Provided is an apparatus provided in a working machine to lower a load, comprising a hydraulic pump, a hydraulic actuator, a manipulation device having a manipulation member, a meter-in flow control device, a meter-out flow control device, a back pressure valve, a regeneration fluid passage branched from the meter-out fluid passage at a position upstream of the back pressure valve and merged with the meter-in fluid passage, and a check valve. The meter-in flow control device controls a meter-in flow rate in a region of the meter-in fluid passage upstream of a merging point with the regeneration fluid passage. The meter-out flow control device controls a meter-out flow rate in a region of the meter-out fluid passage upstream of a branching point of the regeneration fluid passage so as to make the meter-out flow rate be greater than the meter-in flow rate.

Abstract: Provided is an apparatus to lower a load, comprising a hydraulic pump, a hydraulic actuator having first and second ports, a manipulation device, a hydraulic circuit including meter-in and meter-out flow passages for the first and second ports respectively and a regeneration flow passage with a check valve, a control valve, a meter-out flow controller adjusting a meter-out flow rate according to the manipulation device, a back pressure valve, and a non-regeneration operation relief valve whose set pressure is not less than a sum of a minimum set pressure of the back pressure valve, an inlet-outlet pressure difference of the meter-out flow controller when the meter-out flow rate is maximum and a discharge flow rate of the hydraulic pump is maximum, and an actuator pressure difference for driving the hydraulic actuator with no load, and not less than a maximum set pressure of the back pressure valve.

Abstract: Disclosed is a construction machine which comprises: a command changing regulation section; a loading device for imposing, on an engine, a load for raising an exhaust temperature of the engine up to a value at which particulate matter accumulated in a filter is burnt; and an instruction section for instructing the loading device to perform an operation for loading the engine. The instruction section prohibits the loading device from changing a loading level on the engine, during a period where a manipulation-state detection section detects a presence of a manipulation of a manipulation section. The command changing regulation section is set to a changing permission mode for permitting a value of a command which is to be assigned to an actuator control valve, to be changed according to changing a value of a command to be output from a manipulation device, during a period where the loading level is constant.

Abstract: Second-gear blocking switching valves 101 to 104 are provided in pipe lines providing communication between remote control valves 22, 24 and pilot operation portions of valve sections of second-gear spools of control valves. A switching selection means 105 switches the second-gear blocking switching valves 101 to 104. Proportional pressure reduction valves 111 to 114 change secondary pressure to be outputted in accordance with secondary pressure of the remote control valves. Secondary pressure changing switching valves 116 to 119 are provided in pipe lines providing communication between the remote control valves and pilot operation portions of valve sections of first-gear spools of the control valves.

Abstract: The present invention provides a hydraulic circuit for a crane wherein a switching valve is provided between a plurality of motor circuits connected in series within the same actuator group, and at the time of simultaneous operation of the motor circuits, the switching valve is switched from a first position to a second position whereby the series connection between the motor circuits is cut off, and they are driven by each of separate hydraulic sources, thereby enabling prevention of pressure interference at the time of simultaneous operation of the motor circuits within the same actuator group without increasing hydraulic sources.

Abstract: The present invention provides a hydraulic circuit for a crane wherein a switching valve is provided between a plurality of motor circuits connected in series within the same actuator group, and at the time of simultaneous operation of the motor circuits, the switching valve is switched from a first position to a second position whereby the series connection between the motor circuits is cut off, and they are driven by each of separate hydraulic sources, thereby enabling prevention of pressure interference at the time of simultaneous operation of the motor circuits within the same actuator group without increasing hydraulic sources.

Abstract: A hydraulic winch in which a piston rod of a brake cylinder constituting a hydraulic winch is connected in a state capable of being moved only in a range fixedly controlled in axial and diametral directions relative to a pressure plate to control an axial movement of the piston alone when a mode is switched and not to exert an unreasonable load to the connected portion. Thereby, it is possible to prevent an overstroke of the piston of the brake cylinder and to improve the switching responsiveness when switched to the brake release state again.