Abstract: A hydraulic control apparatus 1 includes a switch valve 11, a valve support chamber 35, a flow control valve 12 movable within the valve support chamber 35, an on-off valve 13 movable within the communication path chamber 12a, and a valve control device 14. The flow control valve 12 has a communication path chamber 12a and a back pressure chamber 12d. The on-off valve 13 is capable of opening and shutting off a communication path X between a cylinder line 32 and a switch valve line 33. A restrictor is formed between the flow control valve 12 and a wall defining the valve support chamber 35. The restrictor connects the cylinder line 32 and the communication path chamber 12a to each other. The opening degree of the restrictor is changed in correspondence with movement of the flow control valve 12.

Abstract: A valve seat 20 is arranged between the supply circuit 8 and a downstream circuit 18. A valve body 21 blocks a fluid flow between the supply circuit 8 and the downstream circuit 18 by contacting the valve seat 20. The valve body 21 connects the supply circuit 8 to the downstream circuit 18 for supplying the fluid to the downstream circuit 18 by separating from the valve seat 20. A through hole 24 extends through the valve body 21 and thus defines a part of the supply circuit 8. The through hole 24 is defined in such a manner that the fluid that has flowed from the through hole 24 proceeds between the valve seat 20 and the valve body 21 and is thus supplied to the downstream circuit 18. The valve body 21 is formed in such a manner that a pressure receiving area at an upstream side of the through hole 24 is smaller than a pressure receiving area at a downstream side of the through hole 24.

Abstract: A hydraulic control apparatus 1 includes a switch valve 11, an adjustment valve 12, and a valve control device 13. The adjustment valve 12 has a fluid chamber 15, a valve body 14, and a back pressure chamber 17. A restrictor is formed between the valve body 14 and a wall defining the fluid chamber 15 and connects the cylinder line 32 to the switch valve line 33. The opening degree of the restrictor changes in correspondence with movement of the valve body 14. When the switch valve 11 is located at a neutral position or a supply position, the valve control device 13 applies the fluid pressure in the cylinder line 32 to the back pressure chamber 17. When the switch valve 11 is located at a drainage position, the valve control device 13 applies a pilot pressure lower than the fluid pressure in the cylinder line 32 to the back pressure chamber 17.

Abstract: A supply passage, a discharge passage, an actuator passage, and a spool bore are defined in a housing. The spool bore accommodates a spool and communicates with the supply passage, the discharge passage, and the actuator passage. Load pressure detection circuit sections of load pressure detection circuit are provided in correspondence with two switch. Each of the load pressure detection circuit sections detects load pressure when the actuator passage is connected to the supply passage. Each load pressure detection circuit section is defined by a through hole provided in the housing and connected to the spool bore. Check valves are each arranged in a corresponding one of the load pressure detection circuit sections. This simplifies the configuration of each load pressure detection circuit 21 and saves the space for arranging the load pressure detection circuit 21., resulting in a relatively compact housing.

Abstract: A flow divider includes a spool for distributing fluid from a supply flow path to priority and surplus flow paths. First and second surplus restrictions vary flow rate in accordance with the movement of the spool and restrict the flow rate to the surplus flow path respectively from first and second supply passages. The second surplus restriction is formed to restrict the flow rate in at least two steps. The spool includes a cross-sectional area changing portion located at a position corresponding to the second surplus restriction. Therefore, the circuit structure is prevented from becoming complicated and the fluid force acting as a spool urging force is suppressed.

Abstract: A hydraulic control apparatus for a single action cylinder includes a switch valve for supplying fluid to and draining fluid from the cylinder, a cylinder side passage connected to the cylinder, a switch valve side passage connected to the switch valve, and a valve body accommodation chamber. The valve body accommodation chamber linearly extends between the cylinder side passage and the switch valve side passage. An on-off valve is located in a vicinity of a first end of the valve body accommodation chamber. The on-off valve defines a first back pressure chamber. A flow control valve is located in a vicinity of a second end that is opposite to the first end. The flow control valve defines a second back pressure chamber. The on-off valve and the flow control valve are separated from each other by a partitioning member.

Abstract: A hydraulic control apparatus 1 includes a switch valve 11, a valve support chamber 35, a flow control valve 12 movable within the valve support chamber 35, an on-off valve 13 movable within the communication path chamber 12a, and a valve control device 14. The flow control valve 12 has a communication path chamber 12a and a back pressure chamber 12d. The on-off valve 13 is capable of opening and shutting off a communication path X between a cylinder line 32 and a switch valve line 33. A restrictor is formed between the flow control valve 12 and a wall defining the valve support chamber 35. The restrictor connects the cylinder line 32 and the communication path chamber 12a to each other. The opening degree of the restrictor is changed in correspondence with movement of the flow control valve 12.

Abstract: A hydraulic control apparatus 1 includes a switch valve 11, an adjustment valve 12, and a valve control device 13. The adjustment valve 12 has a fluid chamber 15, a valve body 14, and a back pressure chamber 17. A restrictor is formed between the valve body 14 and a wall defining the fluid chamber 15 and connects the cylinder line 32 to the switch valve line 33. The opening degree of the restrictor changes in correspondence with movement of the valve body 14. When the switch valve 11 is located at a neutral position or a supply position, the valve control device 13 applies the fluid pressure in the cylinder line 32 to the back pressure chamber 17. When the switch valve 11 is located at a drainage position, the valve control device 13 applies a pilot pressure lower than the fluid pressure in the cylinder line 32 to the back pressure chamber 17.

Abstract: A flow divider includes a spool for distributing fluid from a supply flow path to priority and surplus flow paths. First and second surplus restrictions vary flow rate in accordance with the movement of the spool and restrict the flow rate to the surplus flow path respectively from first and second supply passages. The second surplus restriction is formed to restrict the flow rate in at least two steps. The spool includes a cross-sectional area changing portion located at a position corresponding to the second surplus restriction. Therefore, the circuit structure is prevented from becoming complicated and the fluid force acting as a spool urging force is suppressed.

Abstract: A flow rate switching type flow divider for distributing fluid from a pump to a priority flow circuit and a surplus flow circuit. A flow divider valve arranged along a first line includes a first restriction to restrict flow rate of the fluid from the supply flow path to the priority flow path. A switch valve is arranged along a second line that differs from the first line so as to communicate with the supply flow path through the flow divider valve at a location upstream from the first restriction. The switch valve switches an opening amount of a connection flow path that bypasses the first restriction and extends from the supply flow path to the priority flow path. The switch valve includes a second restriction arranged in the switch valve for restricting flow rate of fluid flowing through the connection flow path.

Abstract: A supply passage 32, a discharge passage 33, an actuator passage 34, and a spool bore 36 are defined in a housing 31. The spool bore 36 accommodates a spool 35 and communicates with the supply passage 32, the discharge passage 33, and the actuator passage 34. Load pressure detection circuit sections 21a, 21b of load pressure detection circuit 21 are provided in correspondence with switch positions 13b, 13c. Each of the load pressure detection circuit sections 21a, 21b detects load pressure when the actuator passage 34 is connected to the supply passage 32. Each load pressure detection circuit section 21a, 21b is defined by a through hole provided in the housing 31 and connected to the spool bore 36. Check valves 22 are each arranged in a corresponding one of the load pressure detection circuit sections 21a, 21b. This simplifies the configuration of each load pressure detection circuit 21 and saves the space for arranging the load pressure detection circuit 21.

Abstract: A valve seat 20 is arranged between the supply circuit 8 and a downstream circuit 18. A valve body 21 blocks a fluid flow between the supply circuit 8 and the downstream circuit 18 by contacting the valve seat 20. The valve body 21 connects the supply circuit 8 to the downstream circuit 18 for supplying the fluid to the downstream circuit 18 by separating from the valve seat 20. A through hole 24 extends through the valve body 21 and thus defines a part of the supply circuit 8. The through hole 24 is defined in such a manner that the fluid that has flowed from the through hole 24 proceeds between the valve seat 20 and the valve body 21 and is thus supplied to the downstream circuit 18. The valve body 21 is formed in such a manner that a pressure receiving area at an upstream side of the through hole 24 is smaller than a pressure receiving area at a downstream side of the through hole 24.

Abstract: A hydraulic control apparatus for a single action cylinder includes a switch valve for supplying fluid to and draining fluid from the cylinder, a cylinder side passage connected to the cylinder, a switch valve side passage connected to the switch valve, and a valve body accommodation chamber. The valve body accommodation chamber linearly extends between the cylinder side passage and the switch valve side passage. An on-off valve is located in a vicinity of a first end of the valve body accommodation chamber. The on-off valve defines a first back pressure chamber. A flow control valve is located in a vicinity of a second end that is opposite to the first end. The flow control valve defines a second back pressure chamber. The on-off valve and the flow control valve are separated from each other by a partitioning member.

Abstract: A main spool is located in a bypass line connecting a pump line to a return line. The main spool moves in an axial direction according to the pressure in a spring chamber and the pressure in a pilot chamber, thereby adjusting the opening degree of the bypass line. A pilot switching valve is located in a pressure control passage connecting the spring chamber to the return line. The pilot switching valve controls the flow rate of hydraulic oil that flows from the spring chamber to the return line in accordance with the load pressure of a hydraulic actuator, thereby adjusting the pressure of hydraulic oil in the spring chamber. As a result, the range of the flow rate of hydraulic oil supplied to the hydraulic actuator, which range precludes the influence of the load pressure of the hydraulic actuator, is expanded.

Abstract: A main spool is located in a bypass line connecting a pump line to a return line. The main spool moves in an axial direction according to the pressure in a spring chamber and the pressure in a pilot chamber, thereby adjusting the opening degree of the bypass line. A pilot switching valve is located in a pressure control passage connecting the spring chamber to the return line. The pilot switching valve controls the flow rate of hydraulic oil that flows from the spring chamber to the return line in accordance with the load pressure of a hydraulic actuator, thereby adjusting the pressure of hydraulic oil in the spring chamber. As a result, the range of the flow rate of hydraulic oil supplied to the hydraulic actuator, which range precludes the influence of the load pressure of the hydraulic actuator, is expanded.

Abstract: A tilt control device for a fork lift truck comprises a tilt spool for operating the tilt cylinder, a pilot operation type flow rate control valve connected to the hydraulic pump via the tilt spool and adapted to be switched between a fully opened position and a half opened position which are different in opening from each other in response to addition/deletion of a pilot pressure, a pilot operation type logic valve disposed between the rod side oil compartment of the tilt cylinder and the flow rate control valve and adapted to permit hydraulic oil to flow into the rod side oil compartment and to be operated so as to open/close relative to hydraulic oil flowing out of the rod side oil compartment in response to the addition/deletion of the pilot pressure, and an electromagnetic switching valve for controlling the addition/deletion of the pilot pressure to the flow rate control valve and the logic valve.

Abstract: A lift control valve is switched based on the manipulation of a lift lever, so that a lift cylinder extends or retracts to move a fork, supported on a mast, to move up or down. A check valve, which is actuated with a pilot pressure, is placed between the lift control valve and the lift cylinder. A pilot pipe led out from a pipe directly coupled to an oil tank is connected to a port of the check valve. A tilt control valve is switched based on the manipulation of a tilt lever, so that a tilt cylinder extends or retracts to tilt the mast. An electromagnetic valve is disposed between the tilt cylinder and the tilt control valve. When values necessary to drive the fork are detected, a controller control the electromagnetic valve based on those values.

Abstract: A hydraulic device for a forklift is disclosed. The forklift includes a tilting mast and a fork supported by the mast so that the fork is lifted and lowered. A tilt cylinder operates to tilt the mast by means of oil supplied by a tilt valve. A restricting valve is arranged in an oil passage connecting the tilt cylinder with the tilt valve. When the mast is tilted with the fork carrying an object and located higher than a predetermined reference position, the restricting valve closes the oil passage so that the angle of the tilting mast is limited. A check valve is arranged between the tilt cylinder and the restricting valve. The check valve blocks oil flow from the tilt cylinder to the restricting valve so that the position of the mast is maintained. This prevents unintentional movement of the mast.