GB2049883A - Improvements in valves - Google Patents

Abstract

The present invention relates to valves for use in a high pressure liquid jet producing apparatus. A valve has an inlet chamber 6 communicating with outlet chambers 8,9 by coaxial ports 10,11. A valve member assembly 12 comprising a spindle coaxial with the ports, carrying valve members 21,20, for sealing against the ports 11,10 when in first and second positions respectively. Oppositely directed surface areas of the valve member assembly are exposed to pressure so that the valve member assembly is biased at all times towards its first position which corresponds to liquid escape at low pressure with the jet not in use. <IMAGE>

Description

SPECIFICATION Improvement in valves The present invention relates to improvements in valves, particularly but not exclusively for use in an apparatus or gun for producing a high pressure liquid jet.

Such a gun comprises a high pressure nozzle supplied with high pressure liquid, e.g. water, via a valve on the body on which the nozzle is mounted and which is operated manually by a trigger mounted on the valve. The valve has two positions, in one of which the valve is "open" and water flows to the nozzle to produce a high pressure jet, and in the other of which the valve is "close,d" and no water flows to the nozzle. For reasons of safety it has been proposed that, when the valve is "closed", the inlet to the valve should be connected to a "dump" outlet connected to a low pressure nozzle or reservoir. Also for reasons of safety, the valve should be biased to its "closed" position so that, as soon as the trigger is released, water supply to the nozzle is cut off.

Particularly with high liquid input pressures, for example of the order of 700 bars (10,000 psi), this requirement can result in the imposition of a high nett load or biasing force on the trigger because the valve has to be held closed against a high input pressure. Under such circumstances, the operator has to squeeze the trigger very hard to hold the valve "open" and can lose control of the valve in so doing.

According to one aspect of the present invention there is provided a valve assembly comprising a valve body having an inlet, a first outlet, a second outlet, and a valve member assembly movable within said body between a first position in which communication between said inlet and said first outlet is established and a second position in which communication between said inlet and said second outlet is established, said valve member assembly being movable in the direction of flow of fluid through said valve body and being arranged so as to provide oppositely directed areas which are, in use, subject to the pressure of fluid flowing through said valve and which are arranged to provide in all positions of said valve member assembly in said valve body a differential area subject to the pressure of the fluid and directed so that a force is exerted by the fluid pressure biasing said valve member assembly to its first position.

It is thus possible to provide a valve assembly in which the valve member assembly has a permanent bias to one of its positions, the bias being closely calculable and can be arranged to be sufficiently small that it can be overcome without difficulty. Preferably the biasing force varies in dependence on the position of the valve member assembly in the valve body and for example may be arranged to decrease as said valve member assembly moves from its first position to its second position.

According to another aspect of the present invention there is provided a high pressure liquid gun comprising a valve assembly as defined above and wherein said second outlet of said valve assembly is connected to a nozzle for producing a high pressure liquid jet and said first outlet is connected to low pressure means.

Preferably said gun includes an operating trigger for moving said valve member assembly from its first position to its second position and said valve assembly is arranged such that the biasing force on said valve member assembly, to be overcome by the operator operating said trigger, is small.

In a preferred embodiment of said valve assembly, said valve body defines an inlet chamber communicating with said inlet and with a first and a second outlet chamber by respective first and second coaxial valve ports, said outlet chambers communicating with-said first and second outlets. Said valve member assembly comprises a spindle coaxial with and extending through said valve ports and axially movable in said valve body. End portions of said spindle may be sealingly received in bores in the walls of said outlet chambers in said valve body and, intermediate its ends, said spindle may be associated with one or more valve members providing surfaces for sealing against seats on said valve ports. The or each valve members may lie in the inlet chamber or in respective said outlet chambers and may be fixed to or movable relative to said spindle.

The movement of said spindle from the first position of said valve member assembly to said second position can be obtained by any suitable means depending on the use of said valve assembly.

In one embodiment, the areas of said ports determine the areas of surfaces of said valve members exposed to fluid pressure when said valve members close their respective said ports.

To obtain the required bias on said valve member assembly, the area of the end portion of said spindle adjacent the first outlet chamber may be larger than the area of the other end portion of said spindle adjacent said second outlet chamber and may be larger than the area of said second outlet port, and said area of said first outlet port may be larger than the area of the other end portion of said spindle adjacent said second outlet chamber. The areas of said ports may be different or may, for convenience of manufacture, be equal.

The present invention will be more fully understood from the following description of embodiments thereof, given by way of example only, with reference to the accompanying drawings.

In the drawings: Figure 1 is a section through an embodiment of a valve assembly according to the present invention; Figure 2 is a section through part of another embodiment of a valve assembly according to the present invention; Figure 3 is a section through part of a further embodiment of a valve assembly according to the present invention; Figure 4 is an enlargement of part of the valve assembly of Figure 3; and Figure 5 is a diagrammatic side view of a high pressure liquid gun incorporating an embodiment of a valve assembly according to the present invention.

As shown in Figure 1, the valve assembly 1 comprises a valve body 2 having an inlet 3 and first and second outlets 4, 5. The valve body defines a central inlet chamber 6 communicating by a duct 7 with the inlet 3, and two outlet chambers 8,9 each communicating with the chamber 6 by a port 10, 11, which ports are coaxial.

A valve member assembly 12 is received in the valve body 2 and extends coaxially through ports 10, 11 and is movable axially thereof in the direction of the arrow 13. The valve member assembly 12 comprises a spindle, the end portions 14, 1 5 of which are slidably received in bores 16, 1 7 in the body 2 and are sealed thereagainst by annular seals 18, 1 9. The spindle is associated with one or more, as shown 2, valve members 20, 21 providing surfaces which seat against seats provided on the ports 10, 11 to close the respective ports. As shown in Figure 1, the valve members 20, 21 are in the form of enlargements fixed to or integral with the spindle and they lie each in a respective outlet chamber 8, 9.

For the purposes of manufacture, the valve body comprises a block 22 provided with a through bore 23 in which a plurality of annular elements are received. These annular elements are retained at one end of the bore 23 by a step 24 and at the other end of the bore by members 25 and 26, of which member 25 defines the bore 17 and member 26 closes the end of the bore 17. The remaining annular members comprise two members 27, 28 defining the ports 10 and 11, a member 29 defining bore 16 and apertured spacer members 30,31 and 32 in each of the chambers 8, 6 and 9 respectively. The valve member assembly 12 is also made in two parts which are threaded together to enable assembly of the valve member assembly with the various annular members 25 to 32.

As shown in Figure 1, the valve member assembly 1 2 is in its second or "open" position with the inlet 3 in communication with the outlet 5 and the port 10 closed by the valve member 20.

The valve member assembly 12 is movable to a first or "closed" position in which the valve member 21 seats against and closes port 11 and valve member 20 has moved away to open port 10 to place input 3 in communication with outlet 4. The valve member assembly 12 is arranged so that, in all positions of the valve member assembly, there is a differential area exposed to inlet fluid pressure and facing in a direction such as to create a bias in a direction to move the valve member assembly 1 2 towards its first position.To obtain this, the area of the end portion 14 of the spindle is larger than the area of the port 11 (to obtain the required bias when the valve member assembly is in its first position), the area of the port 10 is larger than the area of the end portion 1 5 of the spindle (to obtain the required bias when the valve member assembly is in its second position), and the area of the end portion 14 of the spindle is larger than the area of the end portion 1 5 of the spindle (to obtain the required bias when the valve member assembly is in an intermediate position). For conveniece of manufacture, the areas of the two ports 10, 11 can be made the same so that, when the valve assembly is assembled, there is no possibility of assembling the annular members 27 and 28 the wrong way round.With the ports 10, 11 of the same area, the area of the end portion 14 of the spindle is larger than the area of the ports 10 and 11 which are in turn larger than the area of the end portion 15 of the spindle. The extent to which one area exceeds another is calculated so as to provide the required magnitude of bias and so as to provide any required variation in the magnitude of the bias as the valve member moves between its first and second positions.

In a preferred embodiment, the diameter of the ports 10, 11 is 13 mm, the diameter of the end portion 1 5 of the spindle is 12.7 mm and the diameter of the end portion 14 of the spindle is 1 4.3 mm. Thus in this preferred embodiment the bias on the valve member assembly in the second position of the valve member assembly is less than that in the first position of the valve member assembly so that the resistance to "opening" the valve decreases when the valve member assembly is in its second position, but is still positive.

Any suitable means may be provided to move the valve member assembly against the biasing force to its second or open position and these means may for example be electrical or mechanical and automatically or manually operated. As shown in Figure 1, the end portion 14 of the spindle projects beyond the bore 23 in the valve block 22 and is engaged by a lever 33 pivoted at 34 on the block 22.

As shown, the valve assembly also includes a spring 35, for example in the form of a stack of Belville discs, which additionally biases the valve member assembly 12 to its first position to ensure that the valve member assembly 12 moves to its first position in the absence of supply of fluid under pressure to the inlet 3.

A modification of the valve shown in Figures 1 is shown in Figure 2 and, in Figure 2, the parts which are the same or equivalent to parts shown in Figure 1 have been given the same reference numerals. The main difference between the valve assembly of Figure 1 and that of Figure 2 is that, in Figure 2 instead of having the valve members 20, 21 in the respective outlet chambers 8, 9, these valve members 36, 37 are arranged to lie in the inlet chamber 6. The valve assembly operates in an exactly similar manner to the valve assembly of Figure 1 and has the same requirements for areas of the end portions 14 and 15 of the valve member assembly spindle and of the ports 10 and 11.

In the foregoing description, in considering the cross-sectional areas at the ports 10, 11, it will be appreciated that it is the areas of these ports which determine the areas of the valve members exposed to fluid pressure when each is in a position closing the respective port. This arises by virtue of the particular shaping of the valve members in relation to the ports and the manner of seating of these valve members on the ports. As a generality, the areas to be considered are those of the valve members which are exposed to fluid pressure when the valve member is in a position closing the respective port. It will also be appreciated that the shaping of the valve members relative to the ports may take other forms and the manner of seating of these valve members on seats on the ports may take other forms.For example, the valve members may be sealingly received within the ports, making sealing contact along cylindrical surfaces.

For use with very high pressure water, the above described valve assemblies are preferably made of stainless steel with the annular members 27 and 28 defining the ports 10 and 11 made of aluminium bronze. Seats of tungsten carbide may be provided on the ports 10, 11 and the contacting surfaces of the valve members of the valve member assembly may also be made of tungsten carbide.

In the above described valve assemblies, particularly when used with high pressure fluids, e.g. at pressures of the order of 700 bars, the valve assembly components have to be made to very small tolerances so that they are closely concentric to prevent leakage of fluid through the port 10 when the valve member assembly is in its second or "open" position. Additionally, with wear of the seat provided on the port 10 and of the corresponding surface of the valve member 20 or 35, the effective area of the valve member 20 or 35 subject to the pressure of the fluid when the valve member is in a position closing the port 10 can vary with time, relatively small variations producing substantial variations in the nett load or bias on the valve member assembly.

The valve assembly shown in Figures 3 and 4 is similar to that shown in Figure 1 but with modifications to overcome the above problems. In Figures 3 and 4 parts corresponding to parts in the embodiment of Figure 1 have been identified by the same reference numerals.

The main difference between the valve assembly of Figure 1 and that of Figures 3 and 4 is that the valve member 20 fixed to the spindle in Figure 1 has been replaced by a floating valve member 50 which is received with a small clearance on the spindle of the valve member assembly 12 so that its axis can diverge from the axis of the spindle to take up any lack of concentricity between the spindle and the port 10.

When the valve member assembly is in its first position, as shown in the lower half of Figures 3 and 4-, the valve member 50 liies within outlet chamber 8 in an inoperative position. When the valve member assembly is moved to its second position, as shown in the upper half of Figures 3 and 4, the valve member 50 is held by the spindle against the seat on port 10 to close the port and will make fuil sealing contact with the port even if the port is not exactly coaxial with the spindle.The seat on port 10 is provided by a frusto-conical surface 51 having a cone angle of for example 600 and the corresponding surface 52 on valve member 50 is also frusto-conical but with a slightly smaller cone angle, for example of 550, to ensure that the surfaces make sealing contact at the inner edge 53 of the frusto-conical surface of the seat and thus to ensure that the effective area of the valve member 50 subject to the pressure of the fluid when the valve member assembly is in its second position, is and remains equal to the area of the port 10.Additionally the member 50 abuts against the spindle at its other end by similarly frusto-conical surfaces 54, 55, the frusto-conical surface 54 of the spindle having a cone angle of for example 550 and the frusto conical surface 55 of the member having a larger cone angle of for example 600 so that again the member and spindle make sealing contact along the line at the inner edge 56 of the frusto-conical surface 55 of the valve member. The seat on port 10 is made of a material harder than that of member 50 and member 50 is made of a material harder than that of the spindle to ensure that even with wear of the valve member relative to the seat and of the spindle relative to the valve member sealing contact between the seat, valve member and spindle is always made along the edges 53, 56.

To assist sealing between the member 50 and the spindle, an O-ring seal 57 may be provided in the spindle and contacting the member 50 upstream of the conical surface 54 and the line of sealing contact between the member 50 and the spindle. The action of the seal may be improved by reducing the clearance between the member 50 and the spindle immediately downstream of the seal 57. This is effected, as shown by increasing the diameter of the spindle in region 58. This reduction in clearance will not affect the floating action of the member 50 because it is provided close to the zone in which the member 50 pivots on the spindle.

As in the embodiment of Figure 1, the diameter of end portion 14 of the spindle is slightly larger than the diameter of end portion 1 5 of the spindle and the diameter of port 10 is larger than the diameter of portion 1 5, and the diameter of portion 14 is larger than the diameter of port 11, so that in operation there is a positive bias on the valve member assembly tending to move it towards its first position. Preferably again the bias is less when the valve member assembly is in its second position than when it is in its first position.

In a preferred embodiment the diameter of portion 14 is 12.76 mm, the diameter of port 10 is 12.8 mm, the diameter of port 11 is 12.66 mm and the diameter of portion 1 5 is 12.70 mm.

As in the embodiment of Figure 1, the valve assembly of Figures 3 and 4 may include a spring biasing the valve member assembly towards its first position so that the valve member assembly returns to this position even in the absence of pressurised fluid connected to the inlet.

It will be appreciated that the second valve member 21 may also be replaced by a floating valve member similar to member 50 with a corresponding modification of the shape of the port 11.

Figure 5 illustrates a high pressure liquid gun incorporating a valve assembly 1 as described in any of the preceding figures. The gun includes rigid pipes 40, 41 and 42 which are threaded into the inlet 3 and outlets 4, 5. Pipe 40 serves as a handle for the gun and has a flexible hose connected to its free end for supply of high pressure liquid thereto. Pipe 42 is provided at its end with a nozzle for producing a high pressure jet of liquid and pipe 41 is provided with a nozzle of sufficientiy large orifice to produce only a low pressure jet which is harmless and can, for example, be used for rinsing, or pipe 41 may be donnected by a flexible hose to the reservoir or to waste.An angled plate 43 extends between and is fixed to pipes 40 and 41 and serves as a trigger guard, the lever 33 in Figure 1 being extended to form a trigger which is manually grasped by the operator. For convenience of use, a shoulder support 44 is threaded into a blind bore 45 (Figure 1) provided in valve block 22. In use of the above described gun, the first position of the valve member assembly is that in which the inlet 3 is connected to the low pressure outlet 4. The trigger 33 is operated to move the valve member assembly from its first "closed" position to its second "open" position in which the inlet 3 is connected to outlet 5, pipe 42 and the high pressure nozzle.

There are thus provided valve assemblies in which the valve member assembly has a permanent but variable bias urging the valve member assembly towards one of its two positions and that bias, by judicious selection of the various areas of the valve member assembly exposed to fluid pressure in the various positions of the valve member assembly, may be graded to be lower when the valve member assembly is in its other positions than when it is in its one position.

The valve assembly is particularly suited and adapted for use with a high pressure liquid jet producing gun because it can be arranged to have a permanent bias to the "closed" position of the gun, with the bias being of a magnitude such that the valve assembly can be opened easily by manual operation and then easily held open.

Claims (23)

1. A valve assembly comprising a valve body having an inlet, a first outlet, a second outlet, and a valve member assembly movable within said body between a first position in which communication between said inlet and said first outlet is established and a second position in which communication between said inlet and said second outlet is established, said valve member assembly being movable in the direction of flow of fluid through said valve body and being arranged so as to provide oppositely directed areas which are, in use, subject to the pressure of fluid flowing through said valve and which are arranged to provide in all positions of said valve member assembly in said valve body a differential area subject to the pressure of the fluid and directed so that the force is exerted by the fluid pressure biasing said valve member assembly to said first position.

2. A valve assembly as claimed in claim 1, wherein different ones of said oppositely directed area are subject to the pressure of fluid flowing through said valve so that said biasing force varies in dependence on the position of said valve member assembly in said valve body.

3. A valve assembly as claimed in claim 1, wherein said oppositely directed areas are arranged so that said biasing force on said valve member assembly is less when said valve member assembly is in said second position than when said valve member assembly is in said first position.

4. A valve assembly as claimed in any one of the preceding claims, wherein said valve body defines an inlet chamber communicating with said inlet and with first and second outlet chambers by respective first and second coaxial valve ports, said first and second outlet chambers communicating respectively with said first and second outlets, and said valve member assembly comprises a spindle coaxial with the said valve ports and axially movable in said valve body.

5. A valve assembly as claimed in claim 4, wherein said spindle extends through said valve ports and end portions thereof are received in the walls of said outlet chambers and, intermediate its ends, said spindle is associated with at least one valve member providing surfaces for sealing against seats provided on said ports.

6. A valve assembly as claimed in claim 5, wherein the or each valve member lies in said inlet chamber.

7. A valve assembly as claimed in claim 5, wherein two valve members are provided one in each of said first and second outlet chambers.

8. A valve assembly as claimed in any one of claims 5 to 7, wherein the or each said valve member is provided by an enlargement fast with said spindle.

9. A valve assembly as claimed any one of claims 5 to 7, wherein said or at least one of said valve members is movable relative to said spindle.

10. A valve assembly as claimed in claim 9, wherein said valve member comprises an annular member mounted on said spindle with a clearance such that the axis thereof can diverge from the axis of said spindle, said annular member having a surface for sealing against a surface provided on the respective one of said ports and a surface for sealing against a surface of said spindle.

11. A valve assembly as claimed in claim 10, wherein said annular member has a frusto-conical surface for sealing against a frusto-conical surface provided on said port, said frusto-conical surface of said annular member having a smaller cone angle than that of said frusto-conical surface of said port.

12. A valve assembly as claimed in either claim 10 or claim 11 , wherein said valve member has a frusto conical surface for abutment with a frustoconical surface on said spindle and said frustoconical surface of said spindle has a smaller cone angle than said frusto-conical surface of said valve member.

13. A valve assembly as claimed in claim 11, wherein said frusto-conical surfaces of said valve member, said port and said spindle are arranged with said apices directed in the direction of movement of said valve member assembly from said first position to said second position.

14. A valve assembly as claimed in any one of claims 5 to 12, wherein the or each said valve member is arranged relative to the respective seats on said ports such that the areas thereof exposed to fluid pressure when said ports are closed are determined by the areas of said ports.

1 5. A valve assembly as claimed in claim 14, wherein the area of said end portion of said spindle adjacent said first outlet chamber is larger than the area of said other end portion of said spindle adjacent said second outlet chamber and is larger than the area of said second outlet port, and the area of said first outlet port is larger than the area of said other end portion of said spindle.

1 6. A valve assembly as claimed in claim 15, wherein the areas of said ports are the same.

1 7. A valve assembly as claimed in claim 15, wherein the area of said first port is larger than the area of said second port.

1 8. A high pressure liquid gun comprising a valve assembly as claimed in any one of the preceding claims, wherein said second outlet thereof is connected to a nozzle for producing a high pressure liquid jet and said first outlet is a low pressure outlet, said inlet being adapted for connection to a source of liquid under high pressure.

19. A gun as claimed in claim 18 when dependent on claim 10, wherein said one valve member movable relative to said spindle is arranged to close said first port in said second position of said valve member assembly.

20. A valve assembly substantially as herein described with reference to Figure 1 or Figure 2 of the accompanying drawings.

21. A valve assembly substantially as herein described with reference to Figures 3 and 4 of the accompanying drawings.

22. A high pressure liquid gun substantially as herein described with reference to Figures 1,2 and 5 of the accompanying drawings.

23. A high pressure liquid gun substantially as herein described with reference to Figures 3, 4 and 5 of the accompanying drawings.