Abstract: For supplying a large volumetric flow into a particular hydraulic actuator without requiring a directional control valve to be large-sized and without making large a pressure difference between a pump discharge pressure and a load pressure or reducing the pressure loss when a large volumetric flow is flushed out into a tank, a flow control apparatus in a hydraulic circuit is designed to supply a pressurized discharge fluid from the hydraulic pump (10) via a directional control valve (15) and a pressure compensation valve (18) to a plurality of hydraulic actuators (16) which are arranged in parallel to one another, the apparatus in its construction including an auxiliary control valve (30) for supplying the pressurized fluid to a particular one of the hydraulic actuators (16), which is supplied with the pressurized discharge fluid from the hydraulic pump (10) via the said auxiliary directional control valve (30) and the directional control valve (15), or whose return fluid out of that particular hydraulic actu

Abstract: A working machine fall preventive valve apparatus is constructed with a cylinder side passage, a valve body, a check valve, a flow rate control valve, and a safety valve. The cylinder side passage is adapted to communicate with a cylinder port which is open to a cylinder side mounting surface. The valve body has a directional control valve side passage which is adapted to communicate with a directional control valve port. The check valve is provided in the valve body and prevents a pressure fluid from flowing into the directional control valve side passage from the cylinder side passage. The flow rate control valve provided in the valve body normally blocks communication between the directional control valve side passage and the cylinder side passage is responsive to an external signal for establishing the above mentioned communication. The safety valve is provided in the valve body and relieves a high pressure in the cylinder side passage.

Abstract: A flow reinforcement directional control valve that is capable of reinforcing a pressure fluid to two actuators, can be formed as compact and yet is capable of flowing a return fluid out of a single actuator into a tank is provided, wherein a valve block 20 has a spool bore 21 in which a first spool (22) and a second spool (23) are slidably inserted; in which the first spool (22) is adapted to be held at a neutral position thereof by a first spring (36) and to be displaced by a pressure fluid in a second pressure receiving chamber (47) to a position thereof for supplying the fluid to an actuator; and in which the above mentioned second spool (23) is adapted to be held at a neutral position thereof by a second spring (41) and to be displaced by a pressure fluid in a first pressure receiving chamber (42) to a position thereof for flowing a return fluid into a tank and to be displaced by a pressure fluid in a third pressure receiving chamber (52) to a position thereof for supplying a pressure fluid to an actuato

Abstract: In a displacement control system for a variable displacement type hydraulic pump for supplying a discharge pressurized fluid of the variable displacement type hydraulic pump to an actuator via a direction control valve and then controlling a displacement of said variable displacement type hydraulic pump for maintaining a pressure difference between a discharge pressure of said variable displacement type hydraulic pump 1 and a load pressure at a portion between a direction control valve and an actuator, wherein an inlet side pressure of said direction control valve is detected as said discharge pressure.

Abstract: A multiple valve includes first and second valve units respectively having first and second valve bodies. The first and second valve bodies have respective spool bores therein; and a respective spool is inserted in the spool bore of each of the first and second valve bodies. The first and second valve bodies of the first and second valve units also have inlet ports, tank ports, and first and second blocks having mounting holes, the blocks and a respective valve body being fixedly coupled together by means of stud bolts. The first block has a first threaded hole on one side surface thereof for receiving the stud bolt, and a second threaded hole on another side surface thereof for receiving a cover bolt. A pump passage, a main passage and a tank passage extend between the one side surface and the another side surface of the first block, and a stud bolt extends through the second block and is engaged with the first threaded hole.

Abstract: A hydraulic pilot valve consisting of a pair of pressure-reducing valves, wherein a stopper which can freely adjust maximum control inputs of operating levers (23, 24) of the hydraulic pilot valve is provided to make maximum pilot pressures output from the pair of pressure-reducing valves freely adjustable. Furthermore, in the hydraulic pilot valve, a stopper member for limiting a maximum control input of an operating lever is fixed to the operating levers (23, 24), so that an operating force during a maximum operation of an operating lever is received by the stopper member. Furthermore, in the hydraulic pilot valve, an erroneous operation due to vibrations and the like is prevented by a damper mechanism (50) interposed between a lever fixed to each of the operating levers (23, 24) and a main body (1) of the valve.

Abstract: A pressurized fluid supply system, in which a plurality of pressure compensation valves are connected to a pump discharge line of a hydraulic pump in parallel, and direction control valves are provided at the outlet side of each pressure compensation valve to supply a discharged pressurized fluid from the hydraulic pump to a plurality of actuators. The pressure compensation valves include a check valve portion establishing and blocking communication between the pump discharge line and the inlet port of the direction control valve, and a pressure reduction valve portion for supplying a reduced pressure from the pump discharge line. The check valve portion shifts in a valve opening direction in response to an inlet pressure and shifts in a valve closing direction in response to an outlet pressure. The pressure reduction valve portion has a first and a second pressure chamber.

Abstract: Simultaneous operation efficiency in a case where a plurality of actuators are operated by one or a plurality of hydraulic pumps is improved. A delivery pressure passage (1a) of one hydraulic pump (1) and that (1a) of the other hydraulic pump (1) communicate with each other through a first short-circuit passage (39) via a pair of check valves (38, 38), and an unload valve (40) is provided in this first short-circuit passage (39). The load pressure introduction passages (6, 6) on the left and right hydraulic pumps (1, 1) communicate with each other through a second short-circuit passage (36) via a pair of check valves (35, 35), and a relief valve (37) is provided in this short-circuit passage (36).

Abstract: A hydraulic circuit including a pressure compensating valve, which aims at preventing the delay in operation of the valve due to the time required for the inflow of fluid in amount corresponding to stroke volume thereof, thereby improving the response of thereof. This hydraulic circuit includes a pressure compensating valve (3) provided between the delivery side of a hydraulic pump (1) and the inlet of a directional control valve (4), the pressure compensating valve (3) being arranged to be urged by the pressure applied to first pressure receiving portion (6) to position (D) where the area of opening thereof is kept maximum, and also urged by the pressure applied to second pressure receiving portion (8) to position (E) where the area of opening thereof is kept minimum, the portions (6) and (8) being connected with the outlet and inlet sides of the valve (4).

Abstract: A hydraulic circuit for a swivel working machine, in which the operation of the working unit is speeded up when the swiveling body and the working unit are simultaneously operated, includes, for this purpose, first and second operating valves (15.sub.1 and 15.sub.2) connecting the delivery conduit of a hydraulic pump (10) to a swiveling hydraulic motor (16.sub.1) and to a working unit cylinder (16.sub.2), and pressure compensating valves (18) provided between the first operating valve (15.sub.1) and the swiveling hydraulic motor (16.sub.1) and between the second operating valve (15.sub.2) and the working unit cylinder (16.sub.2), the load pressure of the swiveling hydraulic motor (16.sub.1) and the load pressure of the working unit cylinder (16.sub.

Abstract: This invention provides a hydraulic circuit system capable of reducing the flow rate distribution error in supplying pressurized fluid from a single hydraulic pump into a plurality of hydraulic actuators, and also supplying pressurized fluid quickly. The circuit is simplified to reduce manufacturing costs.

Abstract: A pressure control system in which a pressure in a back pressure chamber of a flow control valve is controlled according to a throttle opening of a pilot valve to locate stationary the valve body of the flow control valve at a position corresponding to the throttle opening of the pilot valve. In the system, a fixed throttle is provided in an oil passage extended to the back pressure chamber of the flow control valve, thereby applying a dampering action to the valve body.

Abstract: A pressure control system in which a pressure in a back pressure chamber of a flow control valve is controlled according to a throttle opening of a pilot valve to locate stationary the valve body of the flow control valve at a position corresponding to the throttle opening of the pilot valve. In the system, a fixed throttle is provided in an oil passage extended to the back pressure chamber of the flow control valve, thereby applying a dampering action to the valve body.

Abstract: An operating lever device constructed such that the members thereof having a comparatively high rigidity can be used in such a way as to minimize the wear-down thereof and enable the angle of inclination of the lever to be detected precisely over a long period of time. The operating lever device is arranged such that any one of a plurality of rod members (22) which are inserted slidably while they are constantly urged upward into the device body (10) can be pushed down by the tilting of a lever (20) so as to rotate either a first shaft (23) or a second shaft (24) through a retaining member (27) or (28) held in contact with the lower end of the rod member (22). Thus, the angle of inclination of the lever (20) can be detected precisely by either one of rotational angle sensors (25, 26) mounted on at least one end of each of the first and second shafts.

Abstract: The object of the inventioin is to provide a pilot valve which is compact, prevents erroneous operation, and is inexpensive to manufacture. The pilot valve includes a valve body (1), inlet port (2) and outlet ports (3) formed in the valve body, spools (4) operable to interrupt/establish communication between the inlet port (2) and the outlet port (3), pistons (8) for slidably moving the spools (4), a lever (15), and a disk (14) adapted to transmit movement of the lever (15) and having a downwardly directed spherical recess (23). The valve body has a spherical projection (20) pivotably received in the spherical recess (23). A lever mounting shaft (13) is prevented from rotating about its own axis during operation of the lever.

Abstract: An apparatus for supplying a pressure oil to a plurality of hydraulic cylinders of a working machine such as power shovels provided with working equipment such as shovels, wherein the cylinders are contracted at the same speed to move down or lower the working equipments at the same speed, so that the working equipment are prevented from suddenly dropping off in operation even if pressure oil passages (a, b) supplying the pressure oil to the cylinders are damaged during operation. The apparatus comprises: a lock valve assembly (B) provided with a valve housing (70) mounted on a cylinder tube of each of the hydraulic cylinders, in which valve housing (70) a check valve (77), a poppet valve (78) and a pilot valve (79) are mounted; and a directional control valve assembly (C) for selectively supplying the pressure oil to a lifting-movement pressure chamber (9a) and a lowering-movement pressure chamber (9b) of each of the hydraulic cylinders through the pressure oil passages (a, b), respectively.

Abstract: A poppet valve device according to the present invention is adapted to sequentially operate a plurality of poppet valves the switching operation of a pilot valve, for example, an electromagnetic solenoid or the like which operates in response to an external input signal. The above-mentioned poppet valve device includes first and second poppet valves (A, B) each of which is constructed so that a poppet (32) for communicating or intercepting an inlet port (30) and an outlet port (31) with or from each other may be moved towards a communicating position by an inlet port side pressure acting upon its pressure receiving portion (32a). The poppet (32) may be moved towards an intercepting position by a pressure acting upon its back pressure chamber (38a, 38b).

Abstract: In a pilot operated control valve system provided with a plurality of valves for controlling a plurality of hydraulic devices such as hydraulic cylinders, there is employed a plurality of valves each of which does not interfere with each other in operation and requires a minimum mounting space in the system to enable the system to be a small system having a construction easily adapted to control a plurality of hydraulic devices and also adapted to simultaneously supply the pressure oil to the hydraulic devices from a pair of hydraulic pumps through the same hydraulic circuit as needs require.

Abstract: In a control valve system provided with a plurality of valves for controlling a hydraulic equipment such as hydraulic cylinders, there are employed a plurality of valves each of which does not interfere with each other in operation and requires a minimum mounting space in the system to enable the system to be a small-sized system having a construction easily adapted to control a plurality of hydraulic equipments.

Abstract: In a pilot operated control valve system provided with a plurality of valves for controlling hydraulic equipment such as hydraulic cylinders, there are employed a plurality of valves each of which does not interfere with each other in operation and requires a minimum mounting space in said system to enable said system to be a small-sized system having a construction easily adapted to control a plurality of hydraulic equipments.