摘要:
A control system has two fixed-displacement pumps for supplying pressurized fluid to a pair of steering cylinders via a steering valve and to a pair of implement cylinders via an implement valve. Connected next to the pumps is a demand valve which is pilot operated to deliver to the steering cylinder pair the pressurized fluid from only one pump upon slight displacement of the steering valve and the pressurized fluid from both pumps upon greater displacement of the steering valve. The demand valve is further pilot operated to deliver to the implement cylinder pair the pressurized fluid from only one pump when the implement valve is actuated in a direction to lower the implement assembly, and the pressurized fluid from both pumps when the implement valve is actuated in a direction to raise the implement assembly. In additional embodiments the pumps are of the variable-displacement type, with their displacement adjusted by servo controls responsive to the pressure of the fluid being drained from the demand valve.
摘要:
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.
摘要:
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.
摘要:
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. A cover is fixedly mounted on the another side surface of the first block by a cover bolt which is engaged with the second threaded hole, the cover having a cut-out groove therein for communicating the pump passage with the main passage.
摘要:
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. Furthermore, a shuttle valve interposed between the output ports of the pressure-reducing valves can simplify the construction of the hydraulic pilot valve for taking out a maximum pilot pressure out of the pilot pressures of the output ports.
摘要:
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.
摘要:
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. This system comprises a plurality of operating valves (15) provided in circuits (10a, 17) connected between a hydraulic pump (10) and a plurality of hydraulic actuators (16); a plurality of pressure compensating valves (18) which can be set at a highest value load pressures applied to the hydraulic actuators, respectively; and a load pressure detection port (37) provided in each operating valve so as to detect an intermediate value between the inlet and outlet pressures of each pressure compensating valves (18) from within the operating valves when each operating valve (15) is held at fluid supply position (I or II), the load pressure detection port being connected through a check valve (42) with a load pressure introduction conduit (23), wherein each pressure compensating valve (18) has a first pressure receiving portion (19) adapted to urge it by fluid pressure applied thereto in a direction to disconnect it and which is connected with the load pressure introduction conduit (23); and a second pressure receiving portion (21) adapted to urge it by fluid pressure applied thereto in a direction to connect it and which is connected with fluid outlet side of the operating valve (15) so that the load pressure can be detected from the fluid inlet side of the pressure compensating valve (18).
摘要:
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.
摘要:
A flow control valve assembly, for preventing the pressure oil confined in an inlet port of a valve housing from pulsating and for additionally performing a safety valve function without employing a separate safety valve, has a valve housing which is easy in machining thereof and neat in construction. In the valve housing of the flow control valve assembly is formed a valve-receiving bore (21) in which a poppet (32) and a second spool valve (51), serving as a safety valve, are axially aligned with each other in series. In the valve housing (20), a hydraulic operating oil flows to a communication port (39) of the poppet (32) through an inlet port (23) formed in the valve housing (20), and then further flows to a back-pressure chamber portions (38a, 38b) of the poppet (32) through a variable orifice (44). The pressure oil, having been received in the back-pressure chamber portion (38b), flows out of the portion (38b) to an outer peripheral portion of the second spool valve ( 51). On the other hand, the pressure oil confined in the inlet port (23) flows to a pressure-receiving chamber (56) of the second spool valve (51).
摘要:
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 actuator (16) is flushed into a tank via the auxiliary directional control valve (30) and the directional control valve (15).