WO2008060168A1

WO2008060168A1 - A hydraulic valve and a double acting hydraulic actuator

Info

Publication number: WO2008060168A1
Application number: PCT/NZ2007/000337
Authority: WO
Inventors: William Steven Gillanders
Original assignee: William Steven Gillanders
Priority date: 2006-11-15
Filing date: 2007-11-15
Publication date: 2008-05-22
Also published as: NZ551311A

Abstract

A hydraulic valve (100) is disclosed. The valve (100) has a body (1) provided with an internal chamber (2). A first port (3) is provided at a first end of the chamber (2), a second port (5) at a second end of the chamber (2) and a third port (7) in a side of the chamber. A shuttle member (9) is substantially sealingly engaged with the chamber (2) and has a first channel (10) extending from a first end to an opposite second end which provides a flow path between the first and second ports. The shuttle (9) is slideable between a first position wherein it substantially closes the third port (7) and a second position wherein the third port (7) is open. A double acting hydraulic actuator incorporating the valve is also disclosed.

Description

A HYDRAULIC VALVE AND A DOUBLE ACTING HYDRAULIC ACTUATOR

Field of the Invention

The present invention relates to machinery using hydraulics in which quick movement of the piston of a hydraulic actuator is required. It relates in particular, but not exclusively, to equipment which can be retrofitted to a digger or other power source for use in driving piles or posts or breaking rocks.

Background to the Invention

Pile drivers operate by using a hydraulic actuator (also referred to as a hydraulic ram or a hydraulic cylinder) to lift a weight, known as a hammer, and then releasing the pressure on the ram so that the weight accelerates under the influence of gravity towards the object to be driven.

If the oil can not be removed fast enough from the side of the hydraulic actuator which lifts the weight, then the rate of fall of the weight will be insufficient to drive the tool or object. Current dedicated pile driver designs overcome this problem by using pumps which are capable of handling relatively high flows, and by dumping the hydraulic fluid to a tank when the weight is dropped. Flow rates of around 300 litres per minute may be typical in this phase.

A problem arises if a digger is to be retrofitted with a pile driver or related earth working equipment. The hydraulic systems of most diggers are adapted to work under relatively high pressure but relatively low flow rates (around 50 to 100 litres per minute). Object of the Invention

It is an object of a preferred embodiment of the invention to provide a valve which will overcome or ameliorate problems with such hydraulic systems at present, or at least one which will provide the public with a useful choice.

It is an alternative object of the invention to provide a double acting hydraulic actuator which will overcome or ameliorate problems with such hydraulic systems at present, or at least one which will provide the public with a useful choice.

Other objects of the present invention may become apparent from the following description, which is given by way of example only.

Summary of the Invention

According to a first aspect of the present invention there is provided a hydraulic valve including a body provided with an internal chamber, the body including a first port at a first end of said chamber, a second port at a second end of the chamber opposite the first end, and a third port in a side of the chamber, the valve further including a shuttle member substantially sealingly engaged with the chamber and having a first channel extending from a first end to an opposite second end which provides a flow path between said first and second ports, wherein the shuttle is slideable between a first position wherein the shuttle substantially closes the third port and a second position wherein the third port is open.

Preferably the shuttle is biased towards the first position. Preferably the first channel is provided with one way valve means adapted to allow fluid flow through the first channel from the first port to the second port, but not from the second port to the first port, and the shuttle is provided with a bleed means in parallel with the one way valve means.

Preferably wherein the bleed means includes a second channel extending from the first end of the shuttle to the second end.

Preferably the bleed means includes a clearance space around the one way valve means.

Preferably the second end of the chamber includes seat means for the shuttle.

According to a second aspect of the present invention there is provided a double acting hydraulic actuator provided with the hydraulic valve of any one of the six immediately preceding paragraphs.

According to a third aspect of the present invention there is provided a double acting hydraulic actuator including a body provided with a bore defining a first chamber, a piston sealingly and slideably engaged with the bore, the piston dividing the bore into a first chamber portion and a second chamber portion, and a piston shaft extending through the first chamber portion from the piston to the exterior of the body, the body of the hydraulic cylinder further provided with a second chamber having a first port at a first end, the first port in fluid communication with a first inlet/outlet means, a second port at a second end of the second chamber opposite the first end, the second port in fluid communication with the first chamber portion, a first conduit connecting a third port in a side of the second chamber in fluid communication with the second chamber portion, the first conduit provided with a second inlet/outlet means, a shuttle member substantially sealingly engaged with the second chamber and having a first channel extending from a first end to an opposite second end which provides a flow path between said first and second ports, wherein the shuttle is slideabie between a first position wherein the shuttle substantially closes the third port and a second position wherein the third port is open.

According to a further aspect of the invention a hydraulic valve is substantially as herein described with reference to the accompanying figures.

Further aspects of the invention, which should be considered in all its novel aspects, will become apparent from the following description given by way of example of possible embodiments of the invention.

Brief Description of the Drawings

Figure 1 Is a diagrammatic cross section side view of a hydraulic valve according to one embodiment of the present invention, with a shuttle shown in a first position.

Figure 2 Is a diagrammatic cross section of the valve of Figure 1 with the shuttle in a second position, with the check valve, bleed passage and spring omitted.

Figure 3 Is a diagrammatic cross section of the valve of Figure 1 with the shuttle in a third position, with the check valve, bleed passage and spring omitted. Figure 4 Is a schematic diagram of the valve of Figure 1 in use directing hydraulic fluid to a first side of a double acting hydraulic actuator.

Figure 5 Is a schematic diagram of the valve of Figure 1 in use directing fluid from the first side of the hydraulic actuator to the second side.

Best Modes For Performing The Invention

Referring first to Figure 1 , a hydraulic valve according to one embodiment of the present invention is generally referenced 100. The valve 100 is preferably used as a hydraulic control valve.

The valve 100 has a body 1 provided with an internal chamber 2. The body has a first port 3 at a first end 4 of the chamber 2 and a second port 5 at a second end 6 of the chamber 2 opposite the first end 4. A third port 7 is provided in a side wall 8 of the chamber 2.

A shuttle .9 is provided within the chamber 2 and is slidingly and sealingly engaged with the chamber 2. The shuttle 9 has at least one channel 10 therethrough which allows fluid communication between the first port 3 and the second port 5.

The embodiment shown in Figure 1 is provided with an optional spring 10a which biases the shuttle 9 towards the second end 6 of the chamber 2. The shuttle 9 is also provided with an optional one way valve 10b which allows fluid to flow though the channel 10 from the first port 3 to the second port 5, but does not allow fluid to flow from the second port 5 to the first port 3. Embodiments provided with a one way valve 10b are preferably also provided with a small or

"bleed" bypass around the one way valve 10b. In the Figure 1 the bypass is provided by a second channel 10c provided in parallel with the channel 10, but in other embodiments the bypass may be provided by a clearance space around the one way valve 10b which allows fluid from the second port 5 to the first port 3. The flow through the bypass is preferably restricted so that only very low flow rates are possible.

The shuttle 9 is dimensioned so as to be able to slide into a first position whereby it completely blocks the third port 7, as shown in Figure 1.

As shown in Figure 2, the shuttle can be moved to a second position in which it completely uncovers the third port 7, or a third position in which it only partially covers the third port 7, as shown in Figure 3.

Referring next to Figures 4 and 5, the operation of the valve 100 will be explained with reference to its use with a pile driver (not shown) in which a weight has to be raised, dropped or lowered gently.

The first port 3 of the valve 100 is connected to a first reversible hydraulic fluid supply 11 and acts as an inlet our outlet depending on the direction of flow of the hydraulic fluid. The second port 5 is in fluid communication with a first chamber portion on a first side 12 of the piston 15 of a two way hydraulic actuator, generally referenced 200. Two way hydraulic actuators, also referred to as hydraulic cylinders or hydraulic rams, are well known to those skilled in the art. The third port 7 is connected by a conduit to a second chamber portion on a second side 13 of the piston 15 of the hydrauiic actuator 200. A second reversible hydrauiic fluid supply 14 is connected to a combined inlet/outlet provided between the third port 7 and the second side 13 of the piston 15.

When fluid pressure is supplied to the first port 3 the shuttle 9 moves downward to the first position, blocking the third port 7 as shown in Figure 1. The fluid flows through the channel 10 to the second port 5, and from there to the first side 12 of the hydraulic actuator 200. The pressure of the hydraulic fluid acts on the piston 15 inside the actuator 200 which moves upward, thereby lifting a weight which is connected to the piston shaft 16 by a suitable mechanism such as a rope (not shown).

The second reversible hydraulic supply 14 removes fluid displaced from the second side 13 of the hydraulic actuator 200, and any fluid which leaks past the shuttle 9 and out the third port 7.

Referring next to Figure 5, when the weight is to be dropped, the hydraulic supplies 11 , 14 are reversed. The second reversible hydraulic supply 14 supplies fluid and the first reversible hydraulic supply 11 removes the fluid as required, although this may be minimal in embodiments provided with one way valve 10b. As the fluid flows into the second side 13 of the hydraulic actuator the pressure forces the piston 15 towards the first side 12 and forces the shaft or spear 16 out of the body of the actuator. This piston movement in turn forces fluid back through the second port 5 and the difference in pressure between the fluid at the bottom 20 of the shuttle 9 relative to the top 21 moves the shuttle 9 upward to the position shown in Figure 2, thereby opening the third port 7. This allows fluid from the first side 12 of the hydraulic actuator to flow to the second side 13 of the hydraulic actuator. The weight is able to pull the piston 15 at a much higher rate than would be possible if the fluid in the first side of the hydraulic actuator 200 was removed by the first reversible hydraulic supply 11 alone. This is because the pull of the weight can assist in filling the second side 13 of the hydraulic actuator 200.

As described above with reference to Figure 1 , a preferred embodiment for some operations includes a one way valve 10b in the main channel 10. In the absence of a force from the falling weight, once there is fluid communication (as above) between the two sides of the hydraulic actuator, the pressure equalises on both sides of the piston 15. However the force on the second side 13 of the piston 15 is greater than that on the first side 12 because the area of the piston 15 against which the fluid on the first side 12 is pressing is smaller than that on the second side 13 by the area of the base of the piston shaft 16. Consequently there is a resultant force pushing the shaft outwards and any displaced fluid flows from the first side 12 to second side 13 of the actuator.

It is usual for the force of the pump providing the reversible hydraulic fluid supply to be much greater than any resistive forces of the shaft 16 so that the fluid flows through the second fluid supply 13 at an approximately constant rate. Given this situation of an approximately constant fluid flow rate; no weight pulling the shaft 16; and a negligible loss of fluid through the bleed channel 10c, the rate at which the shaft moves is approximately inversely proportional to its base or cross-sectional area. For example, halving the cross-sectional area of the shaft doubles the rate at which the piston moves because only half as much fluid needs to be pumped to fill the space vacated by the shaft. Minimising the diameter of the shaft 16 allows the piston to move at high speed. In the usual situation where the movement of the shaft is leveraged by pulleys or.other apparatus, it can be made to move faster than any hammer weight can pull it. This allows for free fall of the weight or very fast operation of other hydraulic machinery. Increasing the diameter of the bleed channel 10c reduces shaft speed because some fluid is lost through the channel.

Referring next to Figure 1 , in some applications it may be important that the shuttle 9 does not accidentally open the third port 7. For example, when the hydraulic supply 11 is supplying fluid which travels through ports 3 then 5 to side 12 of the hydraulic actuator, this retracts the piston shaft 16 and raises the weight as described earlier. In this situation any loss of fluid through port 7 reduces the speed at which the weight is raised.

Accordingly, in a preferred embodiment the second end 6 of the chamber is provided with an annular step 22 against which the bottom 20 of the shuttle 9 seats when in the first position. When the shuttle 9 is in the first position the area of the bottom 20 of the shuttle 9 which is exposed to the hydraulic fluid is less than the area of the top 21. This means that if the hydraulic fluid has an equal pressure at both ends of the shuttle 9, the shuttle will tend to stay in the first position. Any hydraulic fluid which does get between the step 22 and the bottom 20 will tend to escape through the third port 7.

In some embodiments the spring 10a or other biasing force may be useful for automatically stopping the falling weight. Hydraulic controls on diggers and other power sources have three positions. In the first position fluid is pumped so that one reversible hydraulic supply is providing fluid and the other is open to receive fluid to flow back to the holding tank. In the second position the flow in the two hydraulic supplies is reversed. Jn both these positions the operating lever must be held against a force which seeks to return the handle to the third default position in which both hydraulic supplies are closed and will not allow any fluid movement. If the weight is falling as shown in Figure 5, it may be desirable that if the operator leaves the controls then the motion of the weight is halted. In this situation the hydraulic controls return to the default position and movement through both hydraulic supplies is stopped. In the absence of a biasing force the pressure exerted by the piston 15 under the influence of the falling weight will force fluid from the first side 12, through port 5 then port 7, into the second side 13 of the hydraulic actuator. Provided there is no one way valve in the main channel 10, and the main channel is large enough to provide little resistance to movement of the shuttle 9, a biasing force such as a spring will move the shuttle 9 into the first position (as shown in Figure 1) and cut off fluid flow through port 7. As there is then nowhere for the fluid flowing from the first side 12 of the piston to go, it will press back onto the piston 15 and attempt to stop the piston movement and therefore the fall of the weight.

In practice a moving weight of reasonable size will simply create enough fluid pressure to burst the machinery unless a pressure relief valve (not shown) is provided in the supply 11 to allow the fluid to flow back to the holding tank and stop the weight gradually. Such a pressure relief valve will be set to create sufficient back pressure to allow the weight to be held stationary once it has been slowed.

In the above situation if there is a one way valve 10b in the main channel 10, the spring or other small biasing force will be insufficient to move the shuttle 9 against the force of the fluid. In this case the weight can be stopped by moving the hydraulic controls to supply fluid through fluid supply 11 as described earlier to raise the weight. Because this moves the shuttle 9 against the force of the fluid coming from port 5, the port 7 can only be closed after the fluid from port 5 has been arrested and the hammer fall stopped. This avoids provision of a special mechanism to arrest the weight. It is also important that the weight can be lowered gently. If the channel 10 is not provided with a one way valve 10b, the channel 10 is preferably sized such that when the first hydraulic supply 11 is receiving fluid at substantially less than the maximum flow rate, and the second hydraulic supply 14 is supplying fluid aϊ substantially less than the maximum flow rate, the shuttle 9 will either not move from the first position, or will only move to the third position in which the third port 7 is only partially uncovered, as shown in Figure 3.

When the channel 10 contains a one way valve 10b, lowering of the weight is accomplished by briefly opening and closing the lever controlling fluid flow to provide small quantities through the hydraulic supply 14. The size of the bleed channel 10c affects the amount of fluid that needs to be provided as some escapes through the bleed channel.

It is important that the hammer weight not drop unexpectedly. In the case of a fault in the hydraulics of the digger causing a slow leak so that fluid supply 11 can slowly receive fluid, the weight of the hammer will force fluid from side 12 of the hydraulic actuator through port 5 and then port 3 back through supply 11 to the digger. In the case where no one way valve is present in channel 10, the slow fluid leak will allow the hammer to drop slowly. (Any vacuum which may be created in side 13 of the hydraulic actuator will generally be insufficient to stop the hammer movement).

Where a one way valve 10b is present, blocking the flow through the main channel 10₁ the force of the fluid would move the shuttle 9 from the first position to the third position, opening the third port 7 and allowing fluid to flow suddenly into side 13 of the hydraulic actuator with resultant rapid fall of the hammer. Providing a small bleed channel 10c in parallel with the one way valve 10b ensures that the fluid pressure can equalize at both ends of the shuttle 9 so that in this situation the shuttle 9 stays securely shut in the first position, preventing rapid hammer movement.

The main channel 10 may be any suitable size, and in some cases may be sufficiently large that the shuttle 9 is effectively a hollow sleeve, although the ends of the shuttle 9 need to have a cross-section with sufficient area to allow the shuttle to be moved between the first and second positions by the pressure of the hydraulic fluid.

Through use of this valve 100 a pile driver can be actuated by a digger using the digger's normal controls and hydraulic system, without being limited by the diggers relatively low hydraulic flow rate.

While the hydraulic valve in the embodiments described above is separate from the hydraulic cylinder to which it supplies fluid, in a preferred embodiment the valve may be integral with the body of the cylinder. In this embodiment the conduits between the ports in the valve and the chamber portions of the cylinder may be formed in the body of the cylinder.

Those skilled in the art will recognize machinery other than pile drivers or rock breakers which may utilize this invention.

Where in the foregoing description, reference has been made to specific components or integers of the invention having known equivalents, then such equivalents are herein incorporated as if individually set forth. Although this invention has been described by way of example and with reference to possible embodiments thereof, it is to be understood that modifications or improvements may be made thereto without departing from the scope of the appended claims,

Claims

1. A hydraulic valve including a body provided with an internal chamber, the body including a first port at a first end of said chamber, a second port at a second end of the chamber opposite the first end, and a third port in a side of the chamber, the valve further including a shuttle member substantially sealingly engaged with the chamber and having a first channel extending from a first end to an opposite second end which provides a flow path between said first and second ports, wherein the shuttle is slideable between a first position wherein the shuttle substantially closes the third port and a second position wherein the third port is open.

2. The valve of claim 1 wherein the shuttle is biased towards the first position.

3. The valve of claim 1 or 2 wherein the first channel is provided with one way valve means adapted to allow fluid flow through the first channel from the first port to the second port, but not from the second port to the first port, and the shuttle is provided with a bleed means in parallel with the one way valve means.

4. The valve of claim 3 wherein the bleed means includes a second channel extending from the first end of the shuttle to the second end.

5. The valve of claim 3 wherein the bleed means includes a clearance space around the one way valve means.

6. The valve of any one of the previous claims wherein the second end of the chamber includes seat means for the shuttle. 16

11. A hydraulic valve substantially as herein described with reference to the accompanying figures.