EP1927759A1

EP1927759A1 - Double check valve having floating function

Info

Publication number: EP1927759A1
Application number: EP07014738A
Authority: EP
Inventors: Sung Bok Park
Original assignee: Volvo Construction Equipment AB
Current assignee: Volvo Construction Equipment AB
Priority date: 2006-11-29
Filing date: 2007-07-27
Publication date: 2008-06-04
Also published as: KR100849500B1; CN101191506A; JP2008138870A; KR20080048711A; US20080121101A1

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 November 29, 2006 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.

BACKGROUND OF THE INVENTION

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.

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 α 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 α 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 α 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 α 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 α 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 α 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 α.
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 α 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 α 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 α 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 α.
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 α 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 α 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 α 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 α 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 α 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 α 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 α to the small chamber d2 of the hydraulic cylinder d and the second flow paths S2 and s4 connecting the control valve α 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 α 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 α 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 α 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 α 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 α. 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 α 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 α in order.
As shown in FIG. 8, when the control valve α 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 α. 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 α 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 α in order.
FIG. 9 is a view illustrating the use state of the double check valve when the control valve α 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 α 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 α 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 α, 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 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 α second flow paths s4 and s2, the control valve α, 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

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.
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.
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.
The double check valve of claim 1 or 2, wherein a ball type or poppet valve is used as the check valve.