GB2099111A

GB2099111A - Shut-off valve for filter

Info

Publication number: GB2099111A
Application number: GB8208021A
Authority: GB
Original assignee: WHITE WILLIAM ERIC
Current assignee: WHITE WILLIAM ERIC
Priority date: 1981-05-22
Filing date: 1982-03-19
Publication date: 1982-12-01
Also published as: GB2099111B

Abstract

The valve includes a housing (31), and a spool (32). The housing includes a tapered internal seating face (15). The spool has a correspondingly tapered external face (22) provided with a recess (23) and a sealing O-ring (24). The spool also includes a portion (18) slidable in the portion (13) of the housing, and a larger-diameter portion (19) slidable in the portion (14) of the housing. The portion (19) includes a recess (20) and a sealing O-ring (21). A spring (34) urges the spool in the direction to cause engagement between the two tapered sealing faces and thus to close the valve. The spool is moved in the opposite direction to open the valve when a filter element is fitted in the check valve. The design of the valve is also such that liquid pressure forces in the valve tend to move the spool in the direction to close the valve. <IMAGE>

Description

SPECIFICATION Improvements in or relating to check valves This invention relates to check valves, and it is an object of the invention to provide a valve which will normally serve to cut off communication between an inlet and an outlet, but which will respond to a mechanical force to allow substantially uninhibited flow of liquid from the inlet to the outlet. One particular application of check valves of this kind is in connection with the filtration of liquids. It is common practice to provide a check valve in a filter system, the arrangement being such that the system will not allow the passage of liquid therethrough if the filter element is not in position. Thus, in an arrangement of this kind, the check valve is normally closed, but is mechanically opened when the filter element is placed in position.

Filtration systems of this kind mentioned above are used in particular in the supply of clean liquids from a reservoir to a final usage point. The reservoir may be, for example, a refuelling tanker containing aviation fuel, and the final usage point referred to may be the fuel tank of an aircraft. In such a situation, the filtration system is provided to ensure that any water or dirt in the refuelling tanker is prevented from entering the aircraft fuel tank.

One particular example of a filtration system for use in re-fuelling aircraft is shown in Figure 1 of the accompanying diagrammatic drawings. It will be seen that fuel from the refuelling tanker is pumped into one end 1 of a pressure housing 2 through an inlet 3 and is fed from the pressure housing to the aircraft tanks through an outlet 4 at the other end 8 of the housing. The two ends of the housing which are referredto respectively as the "dirty end" and the "clean end" are separated by a sealed bulk-head or deck plate 5. A pressure gauge 40 is provided to measure the pressure in the dirty end 1 and a pressure gauge 41 is provided to measure the pressure in the clean end 2. In addition a drain 42 is provided to emty the dirty end 1 and a drain 43 is provided to empty the clean end 2.

A plurality of check valves 6 are mounted in the deck plate 5, and a filter element 7 is fitted into each check valve. The filter elements are generally cylindrical and hollow, and are arranged so that fuel can pass from the exterior to the interior of the element, whereas, water and dirt are prevented from so doing. The interior of each filter element is in communication with the interior of the corresponding check valve and, provided the filter element is in position, the check valve is opened to allow fuel to pass from the interior of the check valve into the clean end of the pressure housing. If any filter element is not inserted in a check valve, that valve automatically closes to prevent fuel passing through it from the dirty end of the pressure housing to the clean end.Ideally each check valve should allow uninterrupted flow of fuel through it when the filter element is in position and provide complete cut off under pumping pressure if the filter element is not in position.

Many known check valves suffer from the disadvantage that they do not fulfill this requirement. In particular, a check valve may fail to close completely when the filter element is removed, or may fail to allow unimpeded passage of the fuel when the filter element is in position.

It is an object of the present invention to provide a check valve which does not suffer from either of these disadvantages.

From one aspect the invention consists in a check valve including a housing and a spool, wherein the housing includes a tapered internal sealing face, and the spool includes a correspondingly-tapered external face provided with a sealing ring capable of being urged by liquid pressure forces into liquid-tight engagement with said sealing face, and of being urged by mechanical pressure out of engagement with said sealing face.

From another aspect the invention consists in a check valve comprising a generally cylindrical housing and a hollow spool slidable within said housing, wherein the housing includes a first open-ended portion having a first internal diameter; a second closed-ended portion having a second internal diameter greater than said first internal diameter, means being provided in said second portion to allow communication between the interior of said second portion and the exterior thereof; and a third portion intermediate between said first and second portions, the internal diameter of said third portion increasing linearly from said first diameter to said second diameter, wherein the spool includes a first portion which is freely slidable within the first portion of the housing, means being provided in said first portion to allow communication between the hollow interior of the spool and the exterior thereof; a second portion provided with sealing means slidable within the second portion of the housing; and a third frusto-conical portion intermediate between said first and second portions and provided with sealing means capable of forming a liquid-tight seal with the third portion of the housing, and wherein the arrangement is such that, if liquid is introduced under pressure through the open end of said housing, the resulting forces acting on said spool to move said sealing means of said frusto-conical portion into engagement with the third portion of the housing are greater than the resulting forces urging the spool in the opposite direction.

One embodiment of the invention will now be described with reference to Figures 2 to 5 of the accompanying diagrammatic drawings, in which: Figure 2 is a side view, partly in section, of a check valve in accordance with the invention in the closed position; Figure 3 is a side view on a smaller-scale showing the check valve in the open position; Figure 4 is an exploded perspective view of the check valve illustrated in Figure 2; and Figure 5 is a cut-away sectional perspective view showing the valve in the closed position.

The check valve illustrated includes an outer housing 31 having a flange 10 at one end. An annular recess 1 1 is provided adjacent the flange 10 and a sealing O-ring 12 in this recess. These items together enable the check valve to be fitted in the sealed deck plate of a filtration system in a liquid-tight fashion. The housing includes a first portion 13 and a second portion 14 having an internal diameter greater than the internal diameter of the portion 1 3. These two portions are joined by a portion 15 having a conical taper. The end of the first portion of the housing is open as shown at 1 6, but the end of the portion 14 is closed and sealed by an end cap 33. A series of eight holes 17 is provided in the wall of the portion 14 adjacent to the largest diameter end of the intermediate portion 15.

The valve also includes a spool 32 including a first portion 18, the diameter of which is such that it is freely slidable with clearance in the first portion 13 of the housing. The spool also provides a second portion 19, the diameter of which is such that it is freely slidable in the second portion 14 of the housing. However, in this case, an annular recess 20 is formed in the spool and a sealing 0ring 21 is fitted in this recess. The arrangement is such that a seal is formed between the second portion of the spool and the second portion of the housing.

The spool also includes an intermediate tapered portion 22. The cone angle of the intermediate portion 22 is equal to the cone angle of the intermediate portion 1 5. A recess 23 is formed in the intermediate portion 22 and a sealing O-ring 24 is fitted in this recess. The arrangement is such that, if the intermediate portion 22 is in contact with the intermediate portion 15 a liquid-tight seal is formed by the sealing ring 24.

Between the first portion 18 and the intermediate portion 22, an annular recess 25 is formed and, in this annular recess, four holes 26 are formed.

An internal recess 27 is formed in the second portion of the spool to receive a helical spring 34.

This spring is located on a spigot 28 on the end cap 33.

The housing 31 preferably consists of aluminium, the spool 32 and the end cap 33 consist of a non-corrosive material which may be aluminium or a thermo-setting synthetic resin material, and the spring preferably consists of stainless-steel.

When a filter element is inserted into the valve, the spool 32 is pushed back into the position illustrated in Figure 3. In this position, the two tapered faces 15 and 22 are out of contact and a passage for fluid flow is provided between the open end 16 of the valve through the holes 26 in the spool and through the holes 17 in the housing.

The total area of the holes 26 and the total area of the holes 17 is arranged to be greater than the internal area of the filter element so that, under these conditions, the check valve provides free and unimpeded flow from the interior of the filter element into the clean end of the pressure housing (Figure 1).

If the filter element is not present, the return spring 34 moves the spool into the position shown in Figure 2. Under these conditions, if fluid under pressure is admitted through the opening 16, two opposing forces (apart from the force of the spring) act on the spool. One of these forces is caused by the action of the fluid on the exposed portion 29 of the intermediate portion 22. This force urges the spool in a direction to open the valve. The other force, which operates in a direction to close the valve results from the fluid pressure acting on the annular face 30 at the end of the portion 19. The force tending to open the valve depends on the cone angle of the intermediate portion 22 and the exposed area 29. The cone angle and the area 29 are arranged so that the force acting to open the valve is considerably less than the force acting to close the valve.The cone angle shown in the drawings is 600 and, in this case, the force acting to open the valve is proportional to the exposed area 29 multiplied by cos 300. However, the cone angle may vary between 400 and 800.

It will be seen that, when the spool is moved upwardly by the fluid pressure, fluid cannot pass from the open end 16 of the valve to the openings 17 because it is prevented from flowing in the downward direction by the sealing ring 24, and from passing in the upward direction by the sealing ring 21.

The use of tapered sealing faces in accordance with the invention ensures that positive sealing can be obtained without any tendancy for the valve to stick in the open position. In addition, the fluid pressure on the tapered intermediate face of the spool produces a centralising force which ensures that the spool can move freely within the housing and enables the parts to be made with relatively high manufacturing tolerances.

Claims

1. A check valve including a housing and a spool, wherein the housing includes a tapered internal sealing face, and the spool includes a correspondingly-tapered external face provided with a sealing ring capable of being urged by liquid pressure forces into liquid-tight engagement with said sealing face, and of being urged by mechanical pressure out of engagement with said sealing face.

2. A check valve as claimed in Claim 1, wherein said housing is generally cylindrical, and includes a first open-ended portion having a first internal diameter; a second portion having a second internal diameter greater than said first diameter; and a cap adapted to close the end of said second portion.

3. A check valve as claimed in Claim 2, wherein means are provided in said second portion to allow communication between the interior and the exterior thereof.

4. A check valve is claimed in Claim 3, wherein said housing further includes a third intermediate between said first and second portions, the internal diameter of said third portion increasing linearly from said first diameter to said second diameter to provide said tapered internal sealing face.

5. A check valve as claimed in Claim 4, wherein the spool is hollow and includes a first portion which is freely slidable within the first portion of the housing and a second portion slidable within the second portion of the housing.

6. A check valve as claimed in Claim 5, wherein means are provided in said first portion of said spool to allow communication between the hollow interior and the exterior thereof.

7. A check valve as claimed in Claim 6, wherein sealing means are provided on said second portion of said spool to form a liquid-tight seal with the second portion of the housing.

8. A check valve as claimed in Claim 6 or Claim 7, wherein said spool further includes a third frusto-conical portion intermediate between said first and second portions, and provided with sealing means capable of forming a liquid-tight seal with the third portion of the housing, said frusto-conical portion constituting said correspondingly-tapered external face.

9. A check valve comprising a generally cylindrical housing and a hollow spool slidable within said housing, wherein the housing includes a first open-ended portion having a first internal diameter; a second closed-ended portion having a second internal diameter greater than said first internal diameter, means being provided in said second portion to allow communication between the interior of said second poriton and the exterior thereof; and a third portion intermediate between said first and second portions, the internal diameter of said third portion increasing linearly from said first diameter to said'Second diameter, wherein the spool includes a first portion which is freely slidable within the first portion of the housing, means being provided in said first portion to allow communication between the hollow interior of the spool and the exterior therof; a second portion provided with sealing means slidable within the second portion of the housing; and a third frusto-conical portion intermediate between said first and second portions and provided with sealing means capable of forming a liquid-tight seal with the third portion of the housing, and wherein the arrangement is such that, if liquid is introduced under pressure through the open end of said housing, the resulting forces acting on said spool to move said sealing means of said frusto-conical portion into engagement with the third portion of the housing are greater than the resulting forces urging the spool in the opposite direction.

10. A check valve is claimed in Claim 9, wherein said housing is provided with a flange at the open end of said first portion, and wherein an annular recess is formed adjacent to the flange, a sealing 0 ring being provided in said recess to enable the check valve to be fitted in a filtration system in a liquid-tighttashion.

11. A check valve is claimed in Claim 9 or Claim 10 wherein the means provided in the second portion of the housing to allow communication between the interior and the exterior thereof comprise a plurality of radial holes through the wall of the second portion adjacent to the largest diameter end of the third portion of the housing.

12. A check valve as claimed in Claim 9 to 1 1, wherein the sealing means provided on the second portion of the spool comprise an annular recess and a sealing O-ring fitted in said recess.

13. A check valve as claimed in any of Claims 9 to 12, wherein the cone angle of the third portion of the housing is equal to the cone angle of the third portion of the spool.

1 4. A check valve as claimed in Claim 13, wherein the sealing means provided on the third portion of the spool comprise a recess in the external surface of the spool and a sealing O-ring fitted in this recess.

15. A check valve as claimed in any of Claims 9 to 14, wherein the spool includes an annular recess between the first portion and the third portion, and wherein a plurality of holes are provided in the wall of the spool between the hollow interior thereof and said annular recess.,

16. A check valve as claimed in any of Claims 9 to 15, wherein a spring is provided to urge the third portion of the spool into engagement with the third portion of the housing.

1 7. A check valve as claimed in Claim 16, wherein a cap is provided to close and seal the end of the second portion of the housing, and wherein an internal recess is formed in the second portion of the spool to receive said spring, the other end of which is located on a sprocket on said cap.

18. A filtration system including a sealed deck plate; a plurality of check valves as claimed in any of Claims 9 to 1 7; and a filter element fitted in at least one of said check valves to move the spool in the housing so that the third portion of the spool is out of sealing contact with the third portion of the housing.

19. A filtration system as claimed in Claim 18, wherein the, or each, check valve is in accordance with Claim 11 and Claim 15, and wherein the total area of the holes in the second portion of the housing and the total area of the holes opening into the annular recess on the spool is greater than the internal area of the filter element.

20. A check valve substantially as hereinbefore described with reference to, and as illustrated in, Figures 2 to 5 of the accompanying diagrammatic drawings.

21. A filtration system as illustrated in Figure 1 including a plurality of check valves as claimed in Claim 20.

22. Any features of novelty, taken singly or in combination, of the embodiment of the invention as hereinbefore described with reference to the accompanying diagrammatic drawings.