Abstract: A valve housing of a multiple valve device is formed by being split into two parts, that is, a first housing block and a second housing block abutting against and separated away from each other at positions of facing joining surfaces. Three or more spool sliding bores are provided on the first housing block forming a three-dimensional structure. The other spool sliding bores are provided on the second housing block forming a three-dimensional structure. A relief valve for suppressing maximum pressures in a plurality of oil passages to a predetermined set pressure or less is provided on one of the first and second housing blocks. This relief valve is arranged at a position closer to the joining surfaces than each of the spool sliding bores provided in the one of housing blocks.

Abstract: A valve housing of a multiple valve device is formed by being split into two parts, that is, a first housing block and a second housing block abutting against and separated away from each other at positions of facing joining surfaces. Three or more spool sliding bores are provided on the first housing block forming a three-dimensional structure. The other spool sliding bores are provided on the second housing block forming a three-dimensional structure. A relief valve for suppressing maximum pressures in a plurality of oil passages to a predetermined set pressure or less is provided on one of the first and second housing blocks. This relief valve is arranged at a position closer to the joining surfaces than each of the spool sliding bores provided in the one of housing blocks.

Abstract: A control valve has a pressure chamber 24 causing a pressure to act on a valve element 21 of a check valve 20, an oil chamber 39 around the valve 21, a slot 40 formed in the valve element 21 and interconnecting the oil chamber 39 and the pressure chamber 24with each other and, a control valve 25 connected directly to a divergence portion 17 and the oil chamber 39 and capable of permitting or cutting off communication between the divergence portion 17 and the oil chamber 39 and changing an opening degree of the communication, an intra-valve-element passage 42, a slot 41 formed in an outer peripheral wall of the valve element 21 and communicating the passage 42 and the chamber 39 with each other, and a spring-return auxiliary check valve 43 for allowing pressure oil to flow from a supply passage 15 into the intra-valve-element passage 42.

Abstract: [PROBLEM] To provide a directional control valve assembly, in which a check valve for controlling a flow rate of pressure oil to be guided to a directional control valve as a main valve and a control means for limiting an opening degree of the check valve by a pressure are integrated with the directional control valve and therefore, a flow hardly occurs in the pressure oil that produces the pressure.

Abstract: A joystick for an electro-hydraulic control system is provided with a rotary potentiometer having a pivotable arm. This pivotable arm is integrally arranged on a rotary shaft and pivots responsive to pivotal control of a joystick in a predetermined direction or a direction opposite to the predetermined direction. The joystick is also provided with a torsion coil spring for normally holding the pivotable arm in a neutral position, a pin arranged on the pivotable arm and capable of expanding the torsion coil spring upon pivotal movement of the pivotable arm, a holding pin for holding the torsion coil spring at its coil portion, and a cover member having a pair of guide portions for limiting movements of the coil portion of the torsion coil spring in the predetermined direction and the opposition direction when the torsion coil spring is in its neutral position.

Abstract: A joystick for an electro-hydraulic control system is provided with a rotary potentiometer having a pivotable arm. This pivotable arm is integrally arranged on a rotary shaft and pivots responsive to pivotal control of a joystick in a predetermined direction or a direction opposite to the predetermined direction. The joystick is also provided with a torsion coil spring for normally holding the pivotable arm in a neutral position, a pin arranged on the pivotable arm and capable of expanding the torsion coil spring upon pivotal movement of the pivotable arm, a holding pin for holding the torsion coil spring at its coil portion, and a cover member having a pair of guide portions for limiting movements of the coil portion of the torsion coil spring in the predetermined direction and the opposition direction when the torsion coil spring is in its neutral position.

Abstract: A spool 33 provided with a flange 39 is inserted in a spool bore 32, and a pressing force of a spring 52 is always applied through the flange 39 to the spool 33 at its one end in a second pressure chamber 35. A fluid groove 60 is formed in an inner peripheral surface of the spool bore 32 at a position near an abutment surface 51. A hydraulic fluid under the same pressure P2 as that in the second pressure chamber 35 is introduced to the fluid groove 60 through a fluid passage 61 formed in a valve body 31. When the flange 39 and the abutment surface 51 are in contact with each other, the hydraulic fluid is allowed to enter the interface between them through the fluid groove 60. A rise of the cracking pressure, which occurs upon the flange coming into tightly close contact with the abutment surface, can be prevented without reducing the strength of the flange 39, and stable opening/closing characteristics of the spool 33 can be achieved.

Abstract: A spool 33 provided with a flange 39 is inserted in a spool bore 32, and a pressing force of a spring 52 is always applied through the flange 39 to the spool 33 at its one end in a second pressure chamber 35. A fluid groove 60 is formed in an inner peripheral surface of the spool bore 32 at a position near an abutment surface 51. A hydraulic fluid under the same pressure P2 as that in the second pressure chamber 35 is introduced to the fluid groove 60 through a fluid passage 61 formed in a valve body 31. When the flange 39 and the abutment surface 51 are in contact with each other, the hydraulic fluid is allowed to enter the interface between them through the fluid groove 60. A rise of the cracking pressure, which occurs upon the flange coming into tightly close contact with the abutment surface, can be prevented without reducing the strength of the flange 39, and stable opening/closing characteristics of the spool 33 can be achieved.

Abstract: To permit forcedly stopping combining flows of pressure fluid from two hydraulic pumps when a load pressure on a combined-flow-driven actuator in which the flows of pressure fluid are combined together exceeds a predetermined pressure and hence to permit driving the combined-flow-driven actuator with the pressure fluid from only one of the hydraulic pumps, a hydraulic drive system is provided with a flow-combining valve 2 connected to a directional control valve 1 in a first group of directional control valves via a center bypass passage 3, a flow-combining circuit 5 communicating the flow-combining valve 2 and a supply port of a flow-combining directional control valve 4 with each other, and a combined-flow-driven actuator 20 controlled by the flow-combining directional control valve 4, and performs overall power control such that a total value of input torques to the two hydraulic pumps 15,18 does not exceed an output torque from an engine 30.

Abstract: To permit forcedly stopping combining flows of pressure fluid from two hydraulic pumps when a load pressure on a combined-flow-driven actuator in which the flows of pressure fluid are combined together exceeds a predetermined pressure and hence to permit driving the combined-flow-driven actuator with the pressure fluid from only one of the hydraulic pumps, a hydraulic drive system is provided with a flow-combining valve 2 connected to a directional control valve 1 in a first group of directional control valves via a center bypass passage 3, a flow-combining circuit 5 communicating the flow-combining valve 2 and a supply port of a flow-combining directional control valve 4 with each other, and a combined-flow-driven actuator 20 controlled by the flow-combining directional control valve 4, and performs overall power control such that a total value of input torques to the two hydraulic pumps 15,18 does not exceed an output torque from an engine 30.

Abstract: A hydraulic circuit system having a load sensing system including a hydraulic pump, a plurality of hydraulic actuators driven by a hydraulic fluid delivered from the hydraulic pump, a plurality of control valves disposed between the hydraulic pump and the plurality of acutators, a signal detecting hydraulic line to which a signal pressure based on a maximum load pressure among the plurality of hydraulic actuators is introduced, and pump control means for controlling a delivery pressure of the hydraulic pump to be held higher than the signal pressure by a predetermined value.

Abstract: A fixed throttle 12 is provided in a delivery line 11a of a fixed pump 11 driven by an engine 9 for rotation together with a hydraulic pump 1, and a differential pressure detecting valve 31 is provided in association with the fixed throttle 12 to detect a differential pressure across the fixed throttle 12 and to output a pressure lower than the detected differential pressure by a predetermined value. The output of the differential pressure detecting valve 31 is introduced, as a signal pressure, to a pressure bearing section 5c of a load sensing valve 5, thereby setting a target differential pressure. With that arrangement, a pressure in link with an engine revolution speed can be directly employed as the set differential pressure of the load sensing valve, and the structure of the load sensing valve can be avoided from being complicated.

Abstract: It is an object of the present invention to provide a control valve which can reduce the number of external lines connected to a hydraulic remote control valve. A control valve 1 for controlling hydraulic cylinders 2,2′ is provided, in one 26 of spool covers, with fluid passages 27,27′, a shuttle valve 28 for selecting higher one of pilot pressures to be transmitted to these fluid passages 27,27′, and a fluid passage 29 for transmitting the pressure selected by the shuttle valve 28. The fluid passages 27,27′ are in communication with pressure fluid ports 25,25′ as connection ports for pilot lines 24a,24c. The control valve 1 is also provided, in the other spool cover 32, with fluid passages 33,33′, a shuttle valve 34 for selecting higher one of pilot pressures to be transmitted to these fluid passages 33,33′, and a fluid passage 35 for transmitting the pressure selected by the shuttle valve 34.

Abstract: A hydraulic line slit 20 formed in a valve body 50 of a flow distribution valve 5-1, a control chamber 70, and a hydraulic line 31-1 are connected to a signal transmitting hydraulic line 9. A lap portion 32 is formed in the hydraulic line slit 20, the lap portion 32 having a check valve function with a lap amount X when the valve body 50 is in a cutoff position. A 2-position, 3-way valve 11 is disposed in the hydraulic line 31-1. The valve 11 connects the control chamber 70 of the flow distribution valve 5-1 to only the signal transmitting hydraulic line 9 when an external signal F is not applied, and to both the signal transmitting hydraulic line 9 and a lower-pressure detecting hydraulic line 35, which is connected an outlet passage 5b of a flow distribution valve 5-2 on the side of a hydraulic actuator 3-2, when the external signal F is applied.

Abstract: A recovery check valve 26 and a piston valve 27 are axially slidably disposed within a spool 2 in coaxial relation. An axial fluid passage 32 is formed within a cylindrical portion 27a of the piston valve 27, and a seat portion 33 for the recovery check valve is formed at an open end of the cylindrical portion 27a. The cylindrical portion 37a of the piston valve is formed with a hole 36 through which a hydraulic fluid in the fluid chamber 32 is introduced to a bridge passage 21 when the spool 2 is operated so as to introduce a hydraulic fluid from a hydraulic pump to the bottom side of a hydraulic cylinder. Fluid passages 40, 31 are formed within the spool so that a hydraulic fluid in the bridge passage 21 is introduced to the closed end of the piston valve through the fluid passages when the spool is operated in the opposite direction. With such a structure, the size of the valve apparatus can be set to the same size as the directional control valve not provided with the recovery check valve.