US20080121101A1 - Double check valve having floating function - Google Patents

Double check valve having floating function Download PDF

Info

Publication number
US20080121101A1
US20080121101A1 US11/825,637 US82563707A US2008121101A1 US 20080121101 A1 US20080121101 A1 US 20080121101A1 US 82563707 A US82563707 A US 82563707A US 2008121101 A1 US2008121101 A1 US 2008121101A1
Authority
US
United States
Prior art keywords
check valve
hydraulic cylinder
flow paths
double check
control valve
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Abandoned
Application number
US11/825,637
Inventor
Sung Bok Park
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Volvo Construction Equipment AB
Original Assignee
Volvo Construction Equipment AB
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Volvo Construction Equipment AB filed Critical Volvo Construction Equipment AB
Assigned to VOLVO CONSTRUCTION EQUIPMENT HOLDING SWEDEN AB reassignment VOLVO CONSTRUCTION EQUIPMENT HOLDING SWEDEN AB ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: PARK, SUNG BOK
Publication of US20080121101A1 publication Critical patent/US20080121101A1/en
Abandoned legal-status Critical Current

Links

Images

Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B11/00—Servomotor systems without provision for follow-up action; Circuits therefor
    • F15B11/02—Systems essentially incorporating special features for controlling the speed or actuating force of an output member
    • F15B11/024—Systems essentially incorporating special features for controlling the speed or actuating force of an output member by means of differential connection of the servomotor lines, e.g. regenerative circuits
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B13/00—Details of servomotor systems ; Valves for servomotor systems
    • F15B13/01—Locking-valves or other detent i.e. load-holding devices
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/20—Fluid pressure source, e.g. accumulator or variable axial piston pump
    • F15B2211/205—Systems with pumps
    • F15B2211/20576—Systems with pumps with multiple pumps
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/30—Directional control
    • F15B2211/305—Directional control characterised by the type of valves
    • F15B2211/30505—Non-return valves, i.e. check valves
    • F15B2211/3051—Cross-check valves
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/30—Directional control
    • F15B2211/305—Directional control characterised by the type of valves
    • F15B2211/30525—Directional control valves, e.g. 4/3-directional control valve
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/30—Directional control
    • F15B2211/31—Directional control characterised by the positions of the valve element
    • F15B2211/3105—Neutral or centre positions
    • F15B2211/3111—Neutral or centre positions the pump port being closed in the centre position, e.g. so-called closed centre
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/30—Directional control
    • F15B2211/31—Directional control characterised by the positions of the valve element
    • F15B2211/3122—Special positions other than the pump port being connected to working ports or the working ports being connected to the return line
    • F15B2211/3127—Floating position connecting the working ports and the return line
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/30—Directional control
    • F15B2211/315—Directional control characterised by the connections of the valve or valves in the circuit
    • F15B2211/3157—Directional control characterised by the connections of the valve or valves in the circuit being connected to a pressure source, an output member and a return line
    • F15B2211/31576—Directional control characterised by the connections of the valve or valves in the circuit being connected to a pressure source, an output member and a return line having a single pressure source and a single output member
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/30—Directional control
    • F15B2211/32—Directional control characterised by the type of actuation
    • F15B2211/327—Directional control characterised by the type of actuation electrically or electronically
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/30—Directional control
    • F15B2211/32—Directional control characterised by the type of actuation
    • F15B2211/329—Directional control characterised by the type of actuation actuated by fluid pressure
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/30—Directional control
    • F15B2211/35—Directional control combined with flow control

Definitions

  • the present invention relates to a double check valve having a floating function, whereby a working device (e.g., a dozer blade) that is used for a land readjustment work on a work surface can perform a floating function.
  • a working device e.g., a dozer blade
  • floating function means that a working device in a non-load state (that a large chamber and a small chamber of a hydraulic cylinder for operating the working device (e.g., a dozer blade) are connected to each other) is operated depending on the ruggedness of a work surface or road surface in a state that the supply of hydraulic fluid from a hydraulic pump to the hydraulic cylinder is temporarily intercepted.
  • a large chamber d 1 and a small chamber d 2 of a hydraulic cylinder d are connected to each other through a pipe h. Accordingly, when the equipment having a working device f mounted thereon travels along the rugged ground and is on a downhill road, the working device f descends due to its own weight, and thus the hydraulic cylinder d is driven to be extended. By contrast, when the equipment is on an uphill road, the hydraulic cylinder d is driven to be contracted.
  • the construction equipment having a conventional double check valve includes a hydraulic pump P; a hydraulic cylinder d connected to the hydraulic pump P to operate a dozer blade f; a control valve a installed in flow paths between the hydraulic pump P and the hydraulic cylinder d and shifted to control a start, a stop, and a direction change of the hydraulic cylinder d; and a double check valve k installed to open/close flow paths between the control valve a and the hydraulic cylinder d, and having a pair of check valves b and c supported by pressing members f 1 and f 2 that are elastically supported by first and second elastic members (e.g., compression coil springs) e 1 and e 2 , respectively, and a plunger h slidably installed between the check valves b and c to prevent the dozer blade f from sinking.
  • first and second elastic members e.g., compression coil springs
  • the double check valve k serves as a check valve through the check valves b and c elastically supported by the first and second elastic members e 1 and e 2 and the pressing members f 1 and f 2 .
  • the check valve b blocks first flow paths s 1 and s 3 that connect the control valve a to the small chamber d 2 of the hydraulic cylinder d
  • the check valve c blocks second flow paths S 2 and s 4 that connect the control valve a to the large chamber d 1 of the hydraulic cylinder d.
  • the hydraulic fluid bed from the hydraulic pump P is not supplied to the hydraulic cylinder d. Also, the hydraulic fluid fed from the hydraulic cylinder d is not returned to the hydraulic tank.
  • the dozer blade f is prevented from sinking.
  • the hydraulic fluid in the first flow path s 1 acts upon a diaphragm n 1 to shift the plunger h in the left direction, and presses the check valve b in the right direction as shown in the drawing to remove the check function (at this time, the first elastic member e 1 receives the compression force). That is, the first flow paths s 1 and s 3 of the check valve k are connected to each other.
  • the plunger h is shifted to press the check valve c in the left direction as shown in the drawing to remove the check function (at this time, the second elastic member e 2 receives the compression force). That is, the second flow paths S 2 and S 4 of the check valve k are connected to each other.
  • the hydraulic fluid fed from the hydraulic pump P is supplied to the small chamber d 2 of the hydraulic cylinder d after passing through the control valve a and the first flow paths s 1 and s 3 of the check valve k in order.
  • the hydraulic fluid fed from the large chamber d 1 of the hydraulic cylinder d is returned to the hydraulic tank after passing through the check valve c of which the check function has been removed, the second flow paths S 2 and S 4 , and the control valve a in order.
  • the hydraulic cylinder d is driven to be contracted by the hydraulic fluid from the hydraulic pump P.
  • the hydraulic fluid in the second flow path s 2 acts upon a diaphragm n 2 to shift the plunger h in the right direction, and presses the check valve c in the left direction as shown in the drawing to remove the check function (at this time, the second elastic member e 2 receives the compression force). That is, the second flow paths s 2 and s 4 of the check valve k are connected to each other.
  • the plunger h is shifted to press the check valve b in the right direction as shown in the drawing to remove the check function (at this time, the first elastic member e 1 receives the compression force). That is, the first flow paths S 1 and S 3 of the check valve k are connected to each other.
  • the hydraulic fluid fed from the hydraulic pump P is supplied to the large chamber d 1 of the hydraulic cylinder d after passing through the control valve a and the second flow paths s 2 and s 4 of the check valve k in order.
  • the hydraulic fluid fed from the small chamber d 2 of the hydraulic cylinder d is returned to the hydraulic tank after passing through the check valve b of which the check function has been removed, the first flow paths S 1 and S 3 , and the control valve a in order.
  • the hydraulic cylinder d is driven to be extended by the hydraulic fluid fed from the hydraulic pump P.
  • the construction equipment having the conventional double check valve has the problems that in the case where the control valve a is kept in a neutral state, the large chamber d 1 and the small chamber d 2 of the hydraulic cylinder d cannot be connected to each other through the check function of the check valves b and c installed in the double check valve k. Accordingly, in the case where the dozer blade f requires the floating function depending on the working condition, it is impossible to perform the floating function.
  • the present invention has been made to solve the above-mentioned problems occurring in the prior art while advantages achieved by the prior art are maintained intact.
  • One object of the present invention is to provide a double check valve having a floating function, whereby a working device that is operated by a hydraulic cylinder having a double check valve can perform a floating function when the working device performs land readjustment of a work surface, and thereby improving the workability.
  • a double check valve having a floating function which includes a hydraulic pump; a hydraulic cylinder connected to the hydraulic pump to operate a working device; a control valve installed to open/close flow paths between the hydraulic pump and the hydraulic cylinder and shifted to control a start, a stop, and a direction change of the hydraulic cylinder; and a double check valve installed in flow paths between the control valve and the hydraulic cylinder, and having a pair of plungers dividedly formed to be shifted in opposite directions to each other when a signal pressure is applied from an outside, and a pair of check valves being pressed to remove their check functions through a shifting of the plungers; wherein in the case where the control valve is shifted to a neutral state and a floating function mode of the working device is selected, a large chamber and a small chamber of the hydraulic cylinder are connected to each other by the double check valve.
  • the double check valve may further include a housing in which first flow paths connecting the control valve to the small chamber of the hydraulic cylinder and second flow paths connecting the control valve to the large chamber of the hydraulic cylinder are formed; a signal pressure flow path to which a signal pressure for shifting the plungers is supplied; a pressing member pressing the check valve for opening/closing the first flow paths; a first elastic member elastically supporting the pressing member so as to elastically bias the first flow paths, which have been blocked by the check valve, to their initial states; a pressing member pressing the check valve for opening/closing the second flow paths; and a second elastic member elastically supporting the pressing member so as to elastically bias the second flow paths, which have been blocked by the check valve, to their initial states.
  • a pilot signal pressure which is supplied from the hydraulic pump to the signal pressure flow path, is used as a signal pressure for shifting the plungers.
  • FIG. 1 is a view explaining a floating function of a working device
  • FIG. 2 is a schematic view of construction equipment having a conventional double check valve installed thereon;
  • FIG. 3 is a view illustrating the use state of the double check valve when the control valve as illustrated in FIG. 2 is in a neutral state;
  • FIG. 4 is a view illustrating the use state of the double check valve when the control valve as illustrated in FIG. 2 is shifted;
  • FIG. 5 is a view illustrating the use state of the double check valve when the control valve as illustrated in FIG. 2 is shifted;
  • FIG. 6 is a sectional view of a double check valve having a floating function according to an embodiment of the present invention.
  • FIG. 7 is a view illustrating the use state of the double check valve when the control valve as illustrated in FIG. 6 is shifted;
  • FIG. 8 is a view illustrating the use state of the double check valve when the control valve as illustrated in FIG. 6 is shifted.
  • FIG. 9 is a view illustrating the use state of the double check valve when the control valve as illustrated in FIG. 6 is in a neutral state.
  • a double check valve having a floating function includes a hydraulic pump P; a hydraulic cylinder d connected to the hydraulic pump P to operate a working device; a control valve a installed in flow paths between the hydraulic pump P and the hydraulic cylinder d and shifted to control a start, a stop, and a direction change of the hydraulic cylinder d; and a double check valve k installed in first flow paths S 1 and s 3 and second flow paths S 2 and s 4 between the control valve a and the hydraulic cylinder d, and having a pair of plungers h 1 and h 2 dividedly formed to be shifted in opposite directions to each other when a signal pressure is applied from an outside to diaphragms n 3 and n 4 , and a pair of check valves b and c (e.g., ball type or poppet valves) being pressed to remove their check functions through a shifting of the plungers h 1 and h 2 .
  • a double check valve k installed in first flow paths S 1 and
  • a large chamber d 1 and a small chamber d 2 of the hydraulic cylinder d are connected to each other by the double check valve k.
  • the double check valve k may further include a housing m in which the first flow paths s 1 and s 3 connecting the control valve a to the small chamber d 2 of the hydraulic cylinder d and the second flow paths S 2 and s 4 connecting the control valve a to the large chamber d 1 of the hydraulic cylinder d are formed; a signal pressure flow path j to which a signal pressure for shifting the plungers is supplied from a pilot pump Pp; a pressing member f 1 pressing the check valve b for opening/closing the first flow paths s 1 and s 3 ; a first elastic member e 1 elastically supporting the pressing member f 1 so as to elastically bias the first flow paths s 1 and s 3 , which have been blocked by the check valve b, to their initial states; a pressing member f 2 pressing the check valve c for opening/closing the second flow paths s 2 and s 4 ; and a second elastic member f 2 elastically supporting the pressing member f 2 so as to elastically bias the second flow
  • a pilot signal pressure which is supplied from the hydraulic pump Pp to the signal pressure flow path j, is used as a signal pressure for shifting the plungers h 1 and h 2 .
  • the double check valve k may be driven by the hydraulic fluid fed from the hydraulic pump P or air pressure applied from a compressed air source (not illustrated).
  • the double check valve k serves as a check valve through the check valves b and c elastically supported by the first and second elastic members e 1 and e 2 and the pressing members f 1 and f 2 .
  • the pair of plungers h 1 and h 2 dividedly formed are kept in close contact with each other.
  • the check valve b blocks the first flow paths s 1 and s 3 that connect the control valve a to the small chamber d 2 of the hydraulic cylinder d
  • the check valve c blocks the second flow paths S 2 and s 4 that connect the control valve a to the large chamber d 1 of the hydraulic cylinder d.
  • the hydraulic fluid bed from the hydraulic pump P is not supplied to the hydraulic cylinder d. Also, the hydraulic fluid fed from the hydraulic cylinder d is not returned to the hydraulic tank.
  • the dozer blade f is prevented from sinking.
  • the check valve b is pressed to remove the check function, and the first flow paths s 1 and s 3 are connected to each other. Accordingly, the hydraulic fluid fed from the hydraulic pump P is supplied to the small chamber d 2 of the hydraulic cylinder d after passing through the control valve a and the first flow paths s 1 and s 3 in order.
  • the check valve c is pressed to remove the check function, and the second flow paths s 2 and s 4 are connected to each other. Accordingly, the hydraulic fluid fed from large chamber d 1 of the hydraulic cylinder d is returned to the hydraulic tank after passing through the second flow paths s 2 and s 4 and the control valve a in order.
  • the check valve c is pressed to remove the check function, and the second flow paths s 2 and s 4 are connected to each other. Accordingly, the hydraulic fluid fed from the hydraulic pump P is supplied to the large chamber d 1 of the hydraulic cylinder d after passing through the control valve a and the second flow paths s 2 and s 4 in order.
  • the check valve b is pressed to remove the check function, and the second flow paths s 2 and s 4 are connected to each other. Accordingly, the hydraulic fluid fed from small chamber d 2 of the hydraulic cylinder d is returned to the hydraulic tank after passing through the first flow paths s 1 and s 3 and the control valve a in order.
  • FIG. 9 is a view illustrating the use state of the double check valve when the control valve a is shifted to a neutral state and the floating function of the dozer blade f is selected.
  • the check valve b is pressed in the right direction to remove its check function (at this time, the first elastic member e 1 receives the compression force). That is, the first flow paths s 1 and s 3 of the check valve k are connected to each other.
  • the check valve c is pressed in the left direction to remove its check function (at this time, the second elastic member e 2 receives the compression force). That is, the second flow paths s 2 and s 4 of the check valve k are connected to each other.
  • control valve a and the small chamber d 2 of the hydraulic cylinder d are connected to each other by the first flow paths s 1 and s 3
  • control valve a and the large chamber d 1 of the hydraulic cylinder d are connected to each other by the second flow paths s 2 and s 4 .
  • the small chamber d 2 and the large chamber d 1 of the hydraulic cylinder d are connected to each other. That is, in the case where the hydraulic fluid fed from the large chamber d 1 of the hydraulic cylinder d in a non-load state is transferred to the small chamber d 2 of the hydraulic cylinder d (as indicated by an arrow) after passing through the second flow paths s 4 and s 2 , the control valve a, and the first flow paths s 1 and s 3 in order, the hydraulic cylinder d is driven to be contracted.
  • the double check valve having a floating function has the following advantages.

Landscapes

  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Check Valves (AREA)
  • Fluid-Pressure Circuits (AREA)
  • Operation Control Of Excavators (AREA)
  • Valve Device For Special Equipments (AREA)

Abstract

A double check valve having a floating function is disclosed, whereby a working device that is operated by a hydraulic cylinder having a double check valve (e.g., a dozer blade) can perform a floating function when the working device performs land readjustment of a work surface. The double check valve having a floating function includes a hydraulic pump, a hydraulic cylinder operating a working device, a control valve controlling a start, a stop, and a direction change of the hydraulic cylinder, and a double check valve installed to open/close flow paths between the control valve and the hydraulic cylinder, and having a pair of plungers dividedly formed to be shifted in opposite directions to each other when a signal pressure is applied thereto, and a pair of check valves being pressed to remove their check functions through a shifting of the plungers. When the control valve is shifted to a neutral state and a floating function mode is selected, a large chamber and a small chamber of the hydraulic cylinder are connected to each other by the double check valve.

Description

    CROSS-REFERENCE TO RELATED APPLICATION
  • This application is based on and claims priority from Korean Patent Application No. 10-2006-119035, filed on Nov. 29, 2006 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
    • BACKGROUND OF THE INVENTION
  • 1. Field of the Invention
  • The present invention relates to a double check valve having a floating function, whereby a working device (e.g., a dozer blade) that is used for a land readjustment work on a work surface can perform a floating function.
  • The term “floating” function means that a working device in a non-load state (that a large chamber and a small chamber of a hydraulic cylinder for operating the working device (e.g., a dozer blade) are connected to each other) is operated depending on the ruggedness of a work surface or road surface in a state that the supply of hydraulic fluid from a hydraulic pump to the hydraulic cylinder is temporarily intercepted.
  • 2. Description of the Prior Art
  • As shown in FIG. 1, in construction equipment, a large chamber d1 and a small chamber d2 of a hydraulic cylinder d are connected to each other through a pipe h. Accordingly, when the equipment having a working device f mounted thereon travels along the rugged ground and is on a downhill road, the working device f descends due to its own weight, and thus the hydraulic cylinder d is driven to be extended. By contrast, when the equipment is on an uphill road, the hydraulic cylinder d is driven to be contracted.
  • In other words, even in the case where hydraulic fluid fed from a hydraulic pump is not supplied to the hydraulic cylinder d that operates the working device f, the working device f is repeatedly operated depending on the ruggedness of the ground.
  • AS shown in FIGS. 2 to 5, the construction equipment having a conventional double check valve includes a hydraulic pump P; a hydraulic cylinder d connected to the hydraulic pump P to operate a dozer blade f; a control valve a installed in flow paths between the hydraulic pump P and the hydraulic cylinder d and shifted to control a start, a stop, and a direction change of the hydraulic cylinder d; and a double check valve k installed to open/close flow paths between the control valve a and the hydraulic cylinder d, and having a pair of check valves b and c supported by pressing members f1 and f2 that are elastically supported by first and second elastic members (e.g., compression coil springs) e1 and e2, respectively, and a plunger h slidably installed between the check valves b and c to prevent the dozer blade f from sinking.
  • As shown in FIG. 3, when the control valve a is kept in a neutral state, the double check valve k serves as a check valve through the check valves b and c elastically supported by the first and second elastic members e1 and e2 and the pressing members f1 and f2.
  • Specifically, the check valve b blocks first flow paths s1 and s3 that connect the control valve a to the small chamber d2 of the hydraulic cylinder d, and the check valve c blocks second flow paths S2 and s4 that connect the control valve a to the large chamber d1 of the hydraulic cylinder d.
  • Accordingly, the hydraulic fluid bed from the hydraulic pump P is not supplied to the hydraulic cylinder d. Also, the hydraulic fluid fed from the hydraulic cylinder d is not returned to the hydraulic tank.
  • Thus, the dozer blade f is prevented from sinking.
  • As shown in FIG. 4, when the control valve a is shifted in the right direction by a signal pressure being applied from an outside, the hydraulic fluid fed from the hydraulic pump P is supplied to the first flow path s1 of the double check valve k through the control valve a.
  • The hydraulic fluid in the first flow path s1 acts upon a diaphragm n1 to shift the plunger h in the left direction, and presses the check valve b in the right direction as shown in the drawing to remove the check function (at this time, the first elastic member e1 receives the compression force). That is, the first flow paths s1 and s3 of the check valve k are connected to each other.
  • In this case, the plunger h is shifted to press the check valve c in the left direction as shown in the drawing to remove the check function (at this time, the second elastic member e2 receives the compression force). That is, the second flow paths S2 and S4 of the check valve k are connected to each other.
  • Accordingly, the hydraulic fluid fed from the hydraulic pump P is supplied to the small chamber d2 of the hydraulic cylinder d after passing through the control valve a and the first flow paths s1 and s3 of the check valve k in order. In this case, the hydraulic fluid fed from the large chamber d1 of the hydraulic cylinder d is returned to the hydraulic tank after passing through the check valve c of which the check function has been removed, the second flow paths S2 and S4, and the control valve a in order.
  • Accordingly, the hydraulic cylinder d is driven to be contracted by the hydraulic fluid from the hydraulic pump P.
  • As shown in FIG. 5, when the control valve a is shifted in the left direction by a signal pressure being applied from an outside, the hydraulic fluid fed from the hydraulic pump P is supplied to the second flow path s2 of the double check valve k through the control valve a.
  • The hydraulic fluid in the second flow path s2 acts upon a diaphragm n2 to shift the plunger h in the right direction, and presses the check valve c in the left direction as shown in the drawing to remove the check function (at this time, the second elastic member e2 receives the compression force). That is, the second flow paths s2 and s4 of the check valve k are connected to each other.
  • In this case, the plunger h is shifted to press the check valve b in the right direction as shown in the drawing to remove the check function (at this time, the first elastic member e1 receives the compression force). That is, the first flow paths S1 and S3 of the check valve k are connected to each other.
  • Accordingly, the hydraulic fluid fed from the hydraulic pump P is supplied to the large chamber d1 of the hydraulic cylinder d after passing through the control valve a and the second flow paths s2 and s4 of the check valve k in order. In this case, the hydraulic fluid fed from the small chamber d2 of the hydraulic cylinder d is returned to the hydraulic tank after passing through the check valve b of which the check function has been removed, the first flow paths S1 and S3, and the control valve a in order.
  • Accordingly, the hydraulic cylinder d is driven to be extended by the hydraulic fluid fed from the hydraulic pump P.
  • As described above, the construction equipment having the conventional double check valve has the problems that in the case where the control valve a is kept in a neutral state, the large chamber d1 and the small chamber d2 of the hydraulic cylinder d cannot be connected to each other through the check function of the check valves b and c installed in the double check valve k. Accordingly, in the case where the dozer blade f requires the floating function depending on the working condition, it is impossible to perform the floating function.
    • SUMMARY OF THE INVENTION
  • Accordingly, the present invention has been made to solve the above-mentioned problems occurring in the prior art while advantages achieved by the prior art are maintained intact.
  • One object of the present invention is to provide a double check valve having a floating function, whereby a working device that is operated by a hydraulic cylinder having a double check valve can perform a floating function when the working device performs land readjustment of a work surface, and thereby improving the workability.
  • In order to accomplish these objects, there is provided a double check valve having a floating function, according to one aspect of the present invention, which includes a hydraulic pump; a hydraulic cylinder connected to the hydraulic pump to operate a working device; a control valve installed to open/close flow paths between the hydraulic pump and the hydraulic cylinder and shifted to control a start, a stop, and a direction change of the hydraulic cylinder; and a double check valve installed in flow paths between the control valve and the hydraulic cylinder, and having a pair of plungers dividedly formed to be shifted in opposite directions to each other when a signal pressure is applied from an outside, and a pair of check valves being pressed to remove their check functions through a shifting of the plungers; wherein in the case where the control valve is shifted to a neutral state and a floating function mode of the working device is selected, a large chamber and a small chamber of the hydraulic cylinder are connected to each other by the double check valve.
  • The double check valve may further include a housing in which first flow paths connecting the control valve to the small chamber of the hydraulic cylinder and second flow paths connecting the control valve to the large chamber of the hydraulic cylinder are formed; a signal pressure flow path to which a signal pressure for shifting the plungers is supplied; a pressing member pressing the check valve for opening/closing the first flow paths; a first elastic member elastically supporting the pressing member so as to elastically bias the first flow paths, which have been blocked by the check valve, to their initial states; a pressing member pressing the check valve for opening/closing the second flow paths; and a second elastic member elastically supporting the pressing member so as to elastically bias the second flow paths, which have been blocked by the check valve, to their initial states.
  • A pilot signal pressure, which is supplied from the hydraulic pump to the signal pressure flow path, is used as a signal pressure for shifting the plungers.
    • BRIEF DESCRIPTION OF THE DRAWINGS
  • The above and other objects, features and advantages of the present invention will be more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which:
  • FIG. 1 is a view explaining a floating function of a working device;
  • FIG. 2 is a schematic view of construction equipment having a conventional double check valve installed thereon;
  • FIG. 3 is a view illustrating the use state of the double check valve when the control valve as illustrated in FIG. 2 is in a neutral state;
  • FIG. 4 is a view illustrating the use state of the double check valve when the control valve as illustrated in FIG. 2 is shifted;
  • FIG. 5 is a view illustrating the use state of the double check valve when the control valve as illustrated in FIG. 2 is shifted;
  • FIG. 6 is a sectional view of a double check valve having a floating function according to an embodiment of the present invention;
  • FIG. 7 is a view illustrating the use state of the double check valve when the control valve as illustrated in FIG. 6 is shifted;
  • FIG. 8 is a view illustrating the use state of the double check valve when the control valve as illustrated in FIG. 6 is shifted; and
  • FIG. 9 is a view illustrating the use state of the double check valve when the control valve as illustrated in FIG. 6 is in a neutral state.
    •  DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
  • Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. The matters defined in the description, such as the detailed construction and elements, are nothing but specific details provided to assist those of ordinary skill in the art in a comprehensive understanding of the invention, and thus the present invention is not limited thereto.
  • As shown in FIGS. 6 to 9, a double check valve having a floating function according to an embodiment of the present invention includes a hydraulic pump P; a hydraulic cylinder d connected to the hydraulic pump P to operate a working device; a control valve a installed in flow paths between the hydraulic pump P and the hydraulic cylinder d and shifted to control a start, a stop, and a direction change of the hydraulic cylinder d; and a double check valve k installed in first flow paths S1 and s3 and second flow paths S2 and s4 between the control valve a and the hydraulic cylinder d, and having a pair of plungers h1 and h2 dividedly formed to be shifted in opposite directions to each other when a signal pressure is applied from an outside to diaphragms n3 and n4, and a pair of check valves b and c (e.g., ball type or poppet valves) being pressed to remove their check functions through a shifting of the plungers h1 and h2.
  • In the case where the control valve a is shifted to a neutral state and a floating function mode of the working device (e.g., a dozer blade) is selected, a large chamber d1 and a small chamber d2 of the hydraulic cylinder d are connected to each other by the double check valve k.
  • The double check valve k may further include a housing m in which the first flow paths s1 and s3 connecting the control valve a to the small chamber d2 of the hydraulic cylinder d and the second flow paths S2 and s4 connecting the control valve a to the large chamber d1 of the hydraulic cylinder d are formed; a signal pressure flow path j to which a signal pressure for shifting the plungers is supplied from a pilot pump Pp; a pressing member f1 pressing the check valve b for opening/closing the first flow paths s1 and s3; a first elastic member e1 elastically supporting the pressing member f1 so as to elastically bias the first flow paths s1 and s3, which have been blocked by the check valve b, to their initial states; a pressing member f2 pressing the check valve c for opening/closing the second flow paths s2 and s4; and a second elastic member f2 elastically supporting the pressing member f2 so as to elastically bias the second flow paths s2 and s4, which have been blocked by the check valve c, to their initial states.
  • A pilot signal pressure, which is supplied from the hydraulic pump Pp to the signal pressure flow path j, is used as a signal pressure for shifting the plungers h1 and h2.
  • The double check valve k may be driven by the hydraulic fluid fed from the hydraulic pump P or air pressure applied from a compressed air source (not illustrated).
  • Hereinafter, the operation of the double check valve having a floating function according to an embodiment of the present invention will be described with reference to the accompanying drawings.
  • As shown in FIG. 6, when the control valve a is kept in a neutral state, the double check valve k serves as a check valve through the check valves b and c elastically supported by the first and second elastic members e1 and e2 and the pressing members f1 and f2. In this case, the pair of plungers h1 and h2 dividedly formed are kept in close contact with each other.
  • Specifically, the check valve b blocks the first flow paths s1 and s3 that connect the control valve a to the small chamber d2 of the hydraulic cylinder d, and the check valve c blocks the second flow paths S2 and s4 that connect the control valve a to the large chamber d1 of the hydraulic cylinder d.
  • Accordingly, the hydraulic fluid bed from the hydraulic pump P is not supplied to the hydraulic cylinder d. Also, the hydraulic fluid fed from the hydraulic cylinder d is not returned to the hydraulic tank.
  • Thus, the dozer blade f is prevented from sinking.
  • As shown in FIG. 7, when the control valve a is shifted in the right direction by a signal pressure being applied from an outside, the hydraulic fluid fed from the hydraulic pump P is supplied to the first flow path s1 of the double check valve k through the control valve a. In this case, the pair of plungers h1 and h2, which are kept in close contact with each other, are slidably moved and shifted in the left direction.
  • As the hydraulic fluid in the second flow path s1 acts upon a diaphragm n1 to shift the plungers h1 and h2 in the left direction as shown in the drawing, the check valve b is pressed to remove the check function, and the first flow paths s1 and s3 are connected to each other. Accordingly, the hydraulic fluid fed from the hydraulic pump P is supplied to the small chamber d2 of the hydraulic cylinder d after passing through the control valve a and the first flow paths s1 and s3 in order.
  • Simultaneously, due to the shifting of the plungers h1 and h2, the check valve c is pressed to remove the check function, and the second flow paths s2 and s4 are connected to each other. Accordingly, the hydraulic fluid fed from large chamber d1 of the hydraulic cylinder d is returned to the hydraulic tank after passing through the second flow paths s2 and s4 and the control valve a in order.
  • As shown in FIG. 8, when the control valve a is shifted in the left direction by a signal pressure being applied from an outside, the hydraulic fluid fed from the hydraulic pump P is supplied to the second flow path s2 of the double check valve k through the control valve a. In this case, the plungers h1 and h2, which are in close contact with each other, are slidably moved and shifted in the right direction.
  • As the hydraulic fluid in the second flow path s2 acts upon a diaphragm n2 to shift the plungers h1 and h2 in the right direction as shown in the drawing, the check valve c is pressed to remove the check function, and the second flow paths s2 and s4 are connected to each other. Accordingly, the hydraulic fluid fed from the hydraulic pump P is supplied to the large chamber d1 of the hydraulic cylinder d after passing through the control valve a and the second flow paths s2 and s4 in order.
  • Simultaneously, due to the shifting of the plungers h1 and h2, the check valve b is pressed to remove the check function, and the second flow paths s2 and s4 are connected to each other. Accordingly, the hydraulic fluid fed from small chamber d2 of the hydraulic cylinder d is returned to the hydraulic tank after passing through the first flow paths s1 and s3 and the control valve a in order.
  • FIG. 9 is a view illustrating the use state of the double check valve when the control valve a is shifted to a neutral state and the floating function of the dozer blade f is selected.
  • When the pilot signal pressure from the hydraulic pump Pp is applied to the signal pressure flow path j formed in the check valve k, the plungers h1 and h2 dividedly formed are simultaneously shifted in opposite directions to each other.
  • Specifically, as the plunger h1 is shifted in the right direction as shown in the drawing by the pilot signal pressure acting upon the diaphragm n3 of the plunger h1, the check valve b is pressed in the right direction to remove its check function (at this time, the first elastic member e1 receives the compression force). That is, the first flow paths s1 and s3 of the check valve k are connected to each other.
  • Simultaneously, as the plunger h2 is shifted in the left direction as shown in the drawing by the pilot signal pressure acting upon the diaphragm n4 of the plunger h2, the check valve c is pressed in the left direction to remove its check function (at this time, the second elastic member e2 receives the compression force). That is, the second flow paths s2 and s4 of the check valve k are connected to each other.
  • Accordingly, the control valve a and the small chamber d2 of the hydraulic cylinder d are connected to each other by the first flow paths s1 and s3, and the control valve a and the large chamber d1 of the hydraulic cylinder d are connected to each other by the second flow paths s2 and s4.
  • Accordingly, the small chamber d2 and the large chamber d1 of the hydraulic cylinder d are connected to each other. That is, in the case where the hydraulic fluid fed from the large chamber d1 of the hydraulic cylinder d in a non-load state is transferred to the small chamber d2 of the hydraulic cylinder d (as indicated by an arrow) after passing through the second flow paths s4 and s2, the control valve a, and the first flow paths s1 and s3 in order, the hydraulic cylinder d is driven to be contracted.
  • By contrast, in the case where the hydraulic fluid fed from the small chamber d2 of the hydraulic cylinder d in a non-load load state is transferred to the large chamber d1 of the hydraulic cylinder d (as indicated by an arrow) after passing through the first flow paths s3 and s1, the control valve a second flow paths s4 and s2, the control valve a, and the second flow paths s2 and s4 in order, the hydraulic cylinder d is driven to be extended.
  • Consequently, in the case where the equipment having the dozer blade f mounted thereon travels along the ground g, the displacement of the hydraulic cylinder d in a non-load state is automatically adjusted depending on the ruggedness of the ground g, and thus the floating function can be performed.
  • As described above, the double check valve having a floating function according to an embodiment of the present invention has the following advantages.
  • In the case where a working device that is operated by a hydraulic cylinder having a double check valve performs a land readjustment work for making the ground even, it performs a floating function to improve the workability and reliability of the equipment.
  • Although a preferred embodiment of the present invention has been described for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Claims (5)

1. A double check valve having a floating function, comprising:
a hydraulic pump;
a hydraulic cylinder connected to the hydraulic pump to operate a working device;
a control valve installed in flow paths between the hydraulic pump and the hydraulic cylinder and shifted to control a start, a stop, and a direction change of the hydraulic cylinder; and
a double check valve installed in flow paths between the control valve and the hydraulic cylinder, and having a pair of plungers dividedly formed to be shifted in opposite directions to each other when a signal pressure is applied from an outside, and a pair of check valves being pressed to remove their check functions through a shifting of the plungers;
wherein in the case where the control valve is shifted to a neutral state and a floating function mode of the working device is selected, a large chamber and a small chamber of the hydraulic cylinder are connected to each other by the double check valve.
2. The double check valve of claim 1, wherein the double check valve further comprises:
a housing in which first flow paths connecting the control valve to the small chamber of the hydraulic cylinder and second flow paths connecting the control valve to the large chamber of the hydraulic cylinder are formed;
a signal pressure flow path to which a signal pressure for shifting the plungers is supplied;
a pressing member pressing the check valve for opening/closing the first flow paths;
a first elastic member elastically supporting the pressing member so as to elastically bias the first flow paths, which have been blocked by the check valve, to their initial states,
a pressing member pressing the check valve for opening/closing the second flow paths; and
a second elastic member elastically supporting the pressing member so as to elastically bias the second flow paths, which have been blocked by the check valve, to their initial states.
3. The double check valve of claim 1, wherein a pilot signal pressure, which is supplied from the hydraulic pump to the signal pressure flow path, is used as a signal pressure for shifting the plungers.
4. The double check valve of claim 1, wherein a ball type or poppet valve is used as the check valve.
5. The double check valve of claim 2, wherein a ball type or poppet valve is used as the check valve.
US11/825,637 2006-11-29 2007-07-06 Double check valve having floating function Abandoned US20080121101A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
KR10-2006-0119035 2006-11-29
KR1020060119035A KR100849500B1 (en) 2006-11-29 2006-11-29 double check valve with floating function

Publications (1)

Publication Number Publication Date
US20080121101A1 true US20080121101A1 (en) 2008-05-29

Family

ID=39167691

Family Applications (1)

Application Number Title Priority Date Filing Date
US11/825,637 Abandoned US20080121101A1 (en) 2006-11-29 2007-07-06 Double check valve having floating function

Country Status (5)

Country Link
US (1) US20080121101A1 (en)
EP (1) EP1927759A1 (en)
JP (1) JP2008138870A (en)
KR (1) KR100849500B1 (en)
CN (1) CN101191506A (en)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20090078111A1 (en) * 2007-09-20 2009-03-26 Volvo Construction Equipment Holding Sweden Ab. Double check valve having floating function
US20100139791A1 (en) * 2007-06-05 2010-06-10 Masahiro Tanino Hydraulic controller
US9068322B2 (en) 2010-05-18 2015-06-30 Volvo Construction Equipment Ab Double check valve for construction equipment
AU2012397386B2 (en) * 2012-12-20 2016-05-19 Volvo Construction Equipment Ab Construction machine with floating function
US10306827B2 (en) 2014-11-04 2019-06-04 Cnh Industrial Canada, Ltd. Hydraulic system for an air cart
US11332911B2 (en) * 2017-09-29 2022-05-17 Hitachi Construction Machinery Tierra Co., Ltd. Construction machine

Families Citing this family (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2933471B1 (en) * 2008-07-03 2013-02-15 Vianney Rabhi BALANCED ELECTRO-HYDRAULIC VALVE FOR A VARIABLE COMPRESSION RATE MOTOR HYDRAULIC CONTROL UNIT
KR100985814B1 (en) 2010-02-18 2010-10-08 파카코리아 주식회사 That cavitation prevention equipment is equipped double pilot check valve
KR101294673B1 (en) * 2010-08-16 2013-08-09 국방과학연구소 Automatic shut valve for rapid transfer of flow in hydraulic cirrcuit
KR101595193B1 (en) * 2011-06-23 2016-02-17 가부시기가이샤니레꼬 Electro-hydraulic hybrid drive device
EP2696080B1 (en) * 2012-08-09 2016-12-14 HAWE Hydraulik SE Commande électro-hydraulique
KR101570390B1 (en) 2015-05-12 2015-11-19 주식회사 에프피씨 valve unit for automatic volumetric flow compensation
FR3049663B1 (en) * 2016-03-31 2018-03-16 Lohr Industrie DOUBLE-CLOSING SAFETY BLOCK FOR HYDRAULIC CYLINDER
KR101835691B1 (en) * 2017-11-06 2018-04-19 주식회사 에프피씨 Auxiliary valve for hydraulic operation

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3274902A (en) * 1965-10-22 1966-09-27 Deere & Co Hydraulic control system
US3908515A (en) * 1973-09-10 1975-09-30 Caterpillar Tractor Co Hydraulic circuit with selectively actuatable float control
US4286432A (en) * 1979-08-30 1981-09-01 Caterpillar Tractor Co. Lock valve with variable length piston and hydraulic system for a work implement using the same
US6997210B2 (en) * 1999-12-13 2006-02-14 Aladdin Engineering & Manufacturing, Inc. Valve arrangement including release valve

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4166506A (en) 1975-06-30 1979-09-04 Kabushiki Kaisha Komatsu Seisakusho Controlling apparatus for bulldozer blade
US4506700A (en) 1983-10-07 1985-03-26 Deere & Company Poppet valve with float function
JPH06128984A (en) * 1992-10-15 1994-05-10 Kubota Corp Dozer device for service car
JPH10183674A (en) 1996-12-25 1998-07-14 Toyo Umpanki Co Ltd Lifting device of earth-moving tool
DE19919014C2 (en) 1999-04-27 2001-03-01 Danfoss Fluid Power As Nordbor Hydraulic valve with a locking and a floating function

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3274902A (en) * 1965-10-22 1966-09-27 Deere & Co Hydraulic control system
US3908515A (en) * 1973-09-10 1975-09-30 Caterpillar Tractor Co Hydraulic circuit with selectively actuatable float control
US4286432A (en) * 1979-08-30 1981-09-01 Caterpillar Tractor Co. Lock valve with variable length piston and hydraulic system for a work implement using the same
US6997210B2 (en) * 1999-12-13 2006-02-14 Aladdin Engineering & Manufacturing, Inc. Valve arrangement including release valve

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20100139791A1 (en) * 2007-06-05 2010-06-10 Masahiro Tanino Hydraulic controller
US8671986B2 (en) * 2007-06-05 2014-03-18 Sanyo Kiki Co., Ltd. Hydraulic controller
US20090078111A1 (en) * 2007-09-20 2009-03-26 Volvo Construction Equipment Holding Sweden Ab. Double check valve having floating function
US8001882B2 (en) * 2007-09-20 2011-08-23 Volvo Construction Equipment Holding Sweden Ab Double check valve having floating function
US9068322B2 (en) 2010-05-18 2015-06-30 Volvo Construction Equipment Ab Double check valve for construction equipment
AU2012397386B2 (en) * 2012-12-20 2016-05-19 Volvo Construction Equipment Ab Construction machine with floating function
US10306827B2 (en) 2014-11-04 2019-06-04 Cnh Industrial Canada, Ltd. Hydraulic system for an air cart
US11330760B2 (en) 2014-11-04 2022-05-17 Cnh Industrial Canada, Ltd. Hydraulic system for an air cart
US11332911B2 (en) * 2017-09-29 2022-05-17 Hitachi Construction Machinery Tierra Co., Ltd. Construction machine

Also Published As

Publication number Publication date
CN101191506A (en) 2008-06-04
JP2008138870A (en) 2008-06-19
KR20080048711A (en) 2008-06-03
KR100849500B1 (en) 2008-07-31
EP1927759A1 (en) 2008-06-04

Similar Documents

Publication Publication Date Title
US20080121101A1 (en) Double check valve having floating function
US8001882B2 (en) Double check valve having floating function
US8875736B2 (en) Hydraulic control valve for heavy equipment
KR101737902B1 (en) Double check valve for construction equipment
JP4856131B2 (en) Hydraulic system of work machine
JP3917989B2 (en) Pilot operated relief valve
US8011387B2 (en) Pressure control device for heavy equipment
CA2852741C (en) Volume booster with seat load bias
JPH07253103A (en) Pressure compensation valve and pressure oil supply device
US8113233B2 (en) Hydraulic circuit of option device for excavator
JP6159629B2 (en) Fluid pressure control device
JP2009508066A (en) Servo-controlled metering poppet valve
JPH0755031A (en) Directional control valve for flow rate assistance
JP4222842B2 (en) Cut-off valve with variable cut-off pressure
KR20050081056A (en) Pilot poppet type relief valve
JP2015028367A (en) Hydraulic unit and hydraulic system
JPH07279905A (en) Controller for operating cylinder
CN113557339B (en) Electrohydraulic device for earthmoving machine
JPH08200308A (en) Hydraulic circuit
KR200398715Y1 (en) remote control valve assembly for a heavy equipment
JP5105845B2 (en) Hydraulic control device
KR20010009599A (en) Logic valve

Legal Events

Date Code Title Description
AS Assignment

Owner name: VOLVO CONSTRUCTION EQUIPMENT HOLDING SWEDEN AB, SW

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:PARK, SUNG BOK;REEL/FRAME:019578/0854

Effective date: 20070613

STCB Information on status: application discontinuation

Free format text: ABANDONED -- FAILURE TO RESPOND TO AN OFFICE ACTION