AU2003100983A4

AU2003100983A4 - Valve Assembly for a Hydraulic Cylinder Assembly

Info

Publication number: AU2003100983A4
Application number: AU2003100983A
Authority: AU
Inventors: Norman Ian Mathers
Original assignee: NORMAN MATHERS
Current assignee: NORMAN MATHERS
Priority date: 2003-12-01
Filing date: 2003-12-01
Publication date: 2004-01-29
Anticipated expiration: 2011-12-01
Also published as: WO2005054688A1

Description

Norman Ian Mathers

AUSTRALIA

Patents Act 1990 COMPLETE INNOVATION PATENT Invention Title: Valve Assembly for a Hydraulic Cylinder Assembly The following statement is a full description of this invention, including the best method of performing it known to me: Valve Assembly for a Hydraulic Cylinder Assembly This invention relates to a valve assembly for controlling the flow of fluid into and out of a fluid chamber of a telescopic hydraulic cylinder assembly. In particular, the invention concerns a valve assembly for preventing a telescopic hydraulic cylinder assembly from retracting in an uncontrolled manner should there be an unexpected drop in hydraulic fluid pressure.

Background of the Invention Telescopic hydraulic cylinder assemblies are used in many different types of machines, including tip/dump trucks. A telescopic hydraulic cylinder assembly includes a cylinder forming a fluid chamber and at least one piston extendable and retractable relative to the cylinder. To extend the piston, the fluid chamber is filled with fluid, and to retract the piston, fluid is drained from the fluid chamber.

Tipping trays of tip/dump trucks are usually raised and lowered using multi-stage telescopic hydraulic cylinder assemblies. A directional control valve of the truck, employing a spool valve, may be used to direct hydraulic fluid to and from the multi-stage telescopic hydraulic cylinder assembly. The directional control valve may be connected to the air brake system of the truck and pressurised air may be used to switch the directional control valve between extension and retraction modes of operation.

Should there be an unexpected drop in hydraulic fluid pressure, due to failure of a hydraulic component of the tip/dump truck a burst or damaged hose or fitting), then an extended telescopic hydraulic cylinder assembly under load may retract in an uncontrolled manner (ie.

"free fall") and may cause damage to the hydraulic cylinder assembly, tipping tray or chassis of the truck.

Object of the Invention The present inventor has now developed a valve assembly which overcomes the problem referred to above.

Summary of the Invention According to the present invention there is provided a valve assembly for controlling the flow of fluid to and from a fluid chamber of a telescopic hydraulic cylinder assembly, said valve assembly having: a body having first and second inlets for fluid, a passage extending from the second inlet, and a piston chamber; a piston movable between resting and working positions within the piston chamber, wherein the piston is biased into the resting position and movable to the working position by fluid introduced through the first inlet; a first check valve for controlling the flow of fluid to and from the fluid chamber, the first check valve having a valve seat and a valve member biased into engagement with the valve seat, wherein the passage in the body extends between the second inlet and the valve seat, and the valve member has a passage extending therethrough for communicating fluid between the fluid chamber and the passage in the body; a second check valve located in the passage extending through the valve member for controlling the flow of fluid from the fluid chamber to the passage in the body, the second check valve having a valve member biased into engagement with a valve seat, wherein fluid may flow from the fluid chamber to the passage in the body when the valve member of the second check valve is biased out of engagement with the seat of the second check valve; and a push rod extending between the piston and the first and second check valves for moving the valve members out of engagement with the respective valve seat, wherein the push rod is normally biased out of engagement with the valve members and is movable into engagement therewith by the piston when in the working position, wherein to fill the fluid chamber with fluid, fluid is applied to the second inlet and the fluid moves the valve member of the first check valve out of engagement with the respective valve seat, and to empty the fluid chamber of fluid, fluid is applied to the first inlet and the push rod initially moves the valve member of the second check valve out of engagement with the respective valve seat.

Detailed Description of the Invention The body may be of any suitable shape and size. Preferably, the body is elongate, the first inlet is located at one end of the body and the valve seat of the first check valve is located at an opposing end of the body. The first and second inlets may correspond to one or more openings in the body. Preferably, the second inlet is located in a side wall of the body adjacent the first and second check valves. The body preferably comprises two or more attachable pieces so that internal components of the valve assembly may be accessed.

The body may be connected to the telescopic hydraulic cylinder assembly in any suitable way.

The body may be located within a cavity or port of a wall of a cylinder of the telescopic hydraulic cylinder assembly. Alternatively, a manifold housing the valve assembly may be connected to a wall of the cylinder. Manifolds connectable to hydraulic cylinder assemblies are well known in the art. Preferably, the valve assembly is in the form of a cartridge that may be screwed into a port or cavity of the hydraulic cylinder assembly or manifold. The valve assembly may have sealing members, such as o-rings, to provide a fluid-tight fit within the port or cavity.

Preferably, fluid lines connect the first and second inlets to a directional control valve for extending and retracting the telescopic hydraulic cylinder assembly. Directional control valves employing spool valves are well known in the art. An air brake system of a vehicle may be used to control the directional control valve and to apply air to the first inlet. A hydraulic pump of the vehicle may be connected to the directional control valve and may provide the second inlet with oil.

The piston may be of any suitable shape and size. Preferably, the piston is disk shaped. The piston may be biased into the resting position in any suitable way. The valve assembly may have a spring for biasing the piston in the resting position and the spring may be located within the piston chamber. Preferably, the spring is a coil spring.

The valve member and valve seat of the first check valve may be of any suitable shape and size.

Preferably, the valve member has a sealing portion located outside the body for engaging the valve seat and a stem portion located in the passage of the body. Preferably, the passage in the valve member extends longitudinally through the sealing and stem portions, and laterally through the stem portion.

The sealing portion may be biased into engagement with the valve seat in any suitable way.

Preferably, the sealing portion is biased by a spring, such as a coil spring. The spring may extend about the stem portion within the passage of the body.

The valve member and valve seat of the second check valve may be of any suitable shape and size. The valve seat may extend laterally across the passage of the valve member and the valve member may be a ball.

The valve member of the second check valve may be biased into engagement with the valve seat in any suitable way. The valve assembly may have a spring, such as a coil spring, extending within the passage of the valve member.

The push rod may be of any suitable shape and size. The push rod may move the valve members out of engagement with the respective valve seat in any suitable way. Preferably, the push rod has an end connected to the piston. An opposing end of the push rod may extend within the passage of the valve member, in close proximity to the valve member of the second check valve. A shoulder of the push rod, intermediate the ends of the push rod, may engage the valve member of the first check valve.

The distance that the sealing portion moves from the valve seat may be varied so that the rate of fluid flow from the fluid chamber may be regulated. This may be achieved in any suitable way.

Preferably, the stroke of the piston within the piston chamber is adjustable.

Preferably, the first inlet, piston, push rod, valve member of the first check valve, and second check valve extend along a longitudinal axis of the body.

A preferred embodiment of the invention will now be described with reference to the accompanying drawings.

Brief Description of the Drawings Figure 1 depicts a valve assembly connected to a multi-stage telescopic hydraulic cylinder assembly of a tip/dump truck, according to an embodiment of the invention; Figure 2 is a longitudinal cross-sectional view of the valve assembly of Figure 1; and Figure 3 is an enlarged view of the valve assembly of Figure 2.

In the figures, like reference numerals refer to like parts.

Figure 1 depicts a valve assembly 1 connected to a multi-stage telescopic hydraulic cylinder assembly 2 of a tip/dump truck. Assembly 2 includes a cylinder 5 forming a fluid chamber 8 and a multi-stage piston (not labelled) extendable and retractable relative to cylinder 5. To extend the multi-stage piston, fluid chamber 8 is filled with fluid, and to retract the piston, fluid is drained from fluid chamber 8. A tipping tray of the truck is raised when assembly 2 extends and is lowered when assembly 2 retracts.

A manifold 4 is connected to cylinder 5. The manifold 4 has two laterally extending passages 7, 18 and a longitudinally extending passage 6.

Assembly 1 is in the form of a screw-in cartridge valve and is located within passage 6.

Various o-rings (not labelled) provide a fluid tight seal. The assembly 1 controls the flow of fluid into and out of the fluid chamber 8 via passage 7.

The tip/dump truck has a directional control valve 3, employing a spool valve, for extending and retracting the assembly 2. The directional control valve 3 is connected to an air brake system of the truck as well as to an oil pump 14 and reservoir 15 of the truck. Pressurised air travelling through hoses 12 and 13 controls the directional control valve 3.

An air hose 9 connects the assembly 1 to directional control valve 3 and hose 12 connects the assembly 1 and the valve 3 to the air brake system. A hydraulic hose 11 is connected to passage 18 and extends to directional control valve 3. When pressurised air is directed through hose 13, oil flows from the pump supply 14 to the assembly 1 via hose 11, and assembly 2 extends. When pressurised air is directed through hoses 12 and 9, oil flows from fluid chamber 8 to tank via hoses 11 and 15, and assembly 2 retracts.

Referring now to Figures 2 and 3, the assembly 1 has a cylindrical body 20 having a threaded port 21 connected to air hose 9, ports 22 for communicating oil to passage 18, a passage 24 extending along the longitudinal axis of body 20, and a piston chamber 25. Chamber 25 has a shoulder The body 20 comprises a first cylindrical piece 50, a cap 31 screwed to the first cylindrical piece 50, a second cylindrical piece 51 screwed to the first cylindrical piece 50, and a sleeve 53 extending within pieces 50 and 51. An annular flange 49 of sleeve 53 abuts a shoulder 54 of piece 51. The screw cap 31 seals one end of the piston chamber 25 and the first port 21 extends through the cap 31.

A piston 26 is movable between resting and working positions within chamber 25. A coil spring 28 located within chamber 25 returns and biases piston 26 within the resting position against cap 31. A nut 29 is threaded onto an external thread of the piston 26. The stroke of the piston 26 is defined by cap 31 and the point at which nut 29 collides with shoulder 30. The stroke of the piston 26 is adjustable by changing the position of nut 29 relative to piston 26. A breather port 33 allows for pressure changes within chamber A first check valve 40 has a valve seat 41 and a valve member 42. Valve member 42 consists of a sealing portion 43 and a stem portion 44. The sealing portion 43 is located outside body and stem portion 44 extends within passage 24 and sleeve 53. A coil spring 45 extends around stem portion 44 and sleeve 53 and biases sealing portion 43 into engagement with valve seat 41.

Lock nuts 47, 48 extend from stem portion 44. Spring 45 extends between lock nuts 47, 48 and annular flange 49 of sleeve 53. An end of spring 45 is connected to lock nut 48.

Valve member 42 has a passage 60 extending longitudinally through sealing portion 43 and stem portion 44, and laterally through stem portion 44. Passage 60 communicates fluid between fluid chamber 8 and passage 24.

A second check valve 70 regulates the flow of fluid from fluid chamber 8 to passage 24. Check valve 70 has a ball valve member 71 and a valve seat 72. A coil spring 73 is anchored within the passage 60 and biases the ball valve member 71 into engagement with the valve seat 72.

A push rod 80 extends between piston 26 and the first and second check valves 40, 70. Push rod extends through an o-ring 84 and a narrow portion of push rod 80 extends within stem portion 44. An end 81 of push rod 80 is connected to piston 26 and the other end 82 of the rod is situated adjacent ball valve member 71. When piston 26 is moved to the working position, push rod 80 first moves ball valve member 71 out of engagement with valve seat 72, following which a shoulder 85 of push rod 80 engages stem portion 44 and moves sealing portion 43 out of engagement with valve seat 41.

In order to extend assembly 2, the engine of the truck drives the oil pump and oil is directed through hose 11 to sealing portion 43 via ports 22 and passage 24. The oil pressure causes sealing portion 43 to move out of engagement with valve seat 41, at which point oil flows through passage 7 to fluid chamber 8, and consequently the piston extends.

In order to retract the assembly 2, pressurised air is directed to chamber 25 via hoses 9 and 12 and port 21. As the part of the chamber 25 above piston 26 fills with air, piston 26 moves push rod 80 into engagement with ball valve member 71 and moves it from valve seat 72. With passage 60 open, fluid bleeds from fluid chamber 8 to hose 11 via passages 24 and 60 and ports 22. Shoulder 85 of push rod 80 also engages stem portion 44 to move sealing portion 43 out of engagement with valve seat 41, at which time fluid may also flow through valve seat 41 to ports 22. The rate at which oil flows from fluid chamber 8 may be controlled by adjusting the stroke of piston 26.

To move sealing portion 43 out of engagement with valve seat 41, the piston force must be greater than the valve member 43 holding force. The piston force is equal to the air pressure within chamber 25 (above piston 26) multiplied by the surface area of piston 26 labelled as Al (see Fig. The holding force is equal to the oil pressure within passage 7 multiplied by the area of sealing portion 43 labelled as A2 (see Fig. combined with the force imparted by spring 45. To ensure that sealing portion 43 can be moved out of engagement with valve seat 41, area Al is typically four to five times larger than area A2.

Typically the air system of a truck will operate at 80-100 PSI. An air pilot supply of 80 PSI will move sealing portion 43 out of engagement with valve seat 41 as long as the pressure within the fluid chamber 8 is not greater than about 320 PSI. Typically, the tipping tray would be lifted by a pressure of 200 PSI within fluid chamber 8.

Should the holding force exceed the piston force such that check valve 40 cannot be opened, check valve 70 will nevertheless be opened by piston 26 at a pilot pressure of about 80 PSI.

This is because ball valve member 71 has a surface area about 40 times less than area Al of piston 26, and the holding force (ie. the oil pressure within passage 60 multiplied by the surface area of the ball valve member 71, combined with the force imparted by spring 73) will be far less than the piston force. An air pilot supply of 80 PSI could lower a loaded tipping tray of over 3000 PSI.

The valve assembly of the present invention can thus prevent a telescopic hydraulic cylinder assembly from retracting uncontrollably should a hydraulic hose or fitting fail. This is achieved by the valve assembly preventing fluid from leaving the fluid chamber. Furthermore, the valve assembly allows retraction to take place in a precise manner by allowing fluid to bleed from the fluid chamber at a controlled rate.

Claims

1. A valve assembly for controlling the flow of fluid to and from a fluid chamber of a telescopic hydraulic cylinder assembly, said valve assembly having: a body having first and second inlets for fluid, a passage extending from the second inlet, and a piston chamber; a piston movable between resting and working positions within the piston chamber, wherein the piston is biased into the resting position and movable to the working position by fluid introduced through the first inlet; a first check valve for controlling the flow of fluid to and from the fluid chamber, the first check valve having a valve seat and a valve member biased into engagement with the valve seat, wherein the passage in the body extends between the second inlet and the valve seat, and the valve member has a passage extending therethrough for communicating fluid between the fluid chamber and the passage in the body; a second check valve located in the passage extending through the valve member for controlling the flow of fluid from the fluid chamber to the passage in the body, the second check valve having a valve member biased into engagement with a valve seat, wherein fluid may flow from the fluid chamber to the passage in the body when the valve member of the second check valve is biased out of engagement with the seat of the second check valve; and a push rod extending between the piston and the first and second check valves for moving the valve members out of engagement with the respective valve seat, wherein the push rod is normally biased out of engagement with the valve members and is. movable into engagement therewith by the piston when in the working position, wherein to fill the fluid chamber with fluid, fluid is applied to the second inlet and the fluid moves the valve member of the first check valve out of engagement with the respective valve seat, and to empty the fluid chamber of fluid, fluid is applied to the first inlet and the push rod initially moves the valve member of the second check valve out of engagement with the respective valve seat.

2. The valve assembly of claim 1, wherein the push rod has an end connected to the piston, an opposing end extending within the passage in the valve member in close proximity to the valve member of the second check valve, and a shoulder intermediate the ends for engaging the valve member of the first check valve.

3. The valve assembly of claim 1 or claim 2, wherein the distance that the valve member of the first check valve moves relative to the respective valve seat is adjustable by varying the stroke of the piston.

4. The valve assembly of any one of the preceding claims, wherein the valve member of the first check valve has a sealing portion located outside the body for engaging the valve seat and a stem portion located in the passage in the body, and the second check valve is a ball check valve.

5. A valve assembly substantially as hereinbefore described with reference to the accompanying drawings. DATED this 1st day of December 2003 NORMAN IAN MATHERS By His Patent Attorneys CULLEN CO.