GB2243431A

GB2243431A - Improvements in or relating to a pressure relief valve

Info

Publication number: GB2243431A
Application number: GB9006570A
Authority: GB
Inventors: Martin Keith Partridge
Original assignee: BROWNELL Ltd
Current assignee: BROWNELL Ltd
Priority date: 1990-03-23
Filing date: 1990-03-23
Publication date: 1991-10-30
Also published as: GB9006570D0

Abstract

A low pressure relief valve has an annular element 25 which carries a resilient annular seal 26 and a valve element 29 has an inclined conical face and is biassed by a spring 23 into engagement with the seal. The valve may be mounted in a container, so that when the valve element is pressed against the seal, the container is hermetically sealed, the valve being opened in response to a predetermined pressure differential between the interior and exterior of the container. In another embodiment two reverse-oriented valve elements are provided, one nested within the other so that any excess of pressure on the interior or the exterior of the container may be vented. <IMAGE>

Description

DESCRIPTION OF INVENTION "Improvements in or relating to a Pressure Relief Valve THE PRESENT INVENTION relates to a pressure relief valve and more particularly relates to a low pressure relief valve, adapted to relieve a differential gas or air pressure.

In this Specification the words "low pressure relief valve" are intended to mean a relief valve which is self-operating and which operates whenever there is a pressure differential, across the valve, in the appro 2 priate sense of approximately 3.5 kN/m . Thus such a valve may well operate whenever the pressure differential across the valve is in the region of approximately 2-7kN/m2 There is, at the present time, a need to maintain different items of equipment and apparatus within a carefully controlled environment, particularly with regard to the humidity of the environment. This is especially the case in connection with delicate equipment which may, in many instances, be fitted in aeroplanes.

Whilst it would be possible to provide such equipment within sealed containers, these containers would have to be made to be very sturdy to withstand the different applied air pressures experienced between ground level and the operating height of the aeroplane.

Thus the containers would be very heavy which is clearly undesirable in the context of apparatus to be mounted in an aeroplane, which should be as light as possible.

It has thus been proposed to provide containers which contain such equipment with internal desiccators, and with pressure relief valves which serve to operate only when there is a predetermined pressure differential between the interior of the container and the exterior of the container, the valves permitting a sufficient flow of air to reduce any imbalance in air pressure between the interior of the container and the exterior of the container.

Small quantities of air may thus enter the container on operation of the pressure relief valve, that air bringing with it moisture in the form of humidity present within the air. However, such moisture may be absorbed by the desiccator within the container or the air may be caused to pass through a desiccant as the air enters the container. By providing the pressure relief valves a minimum flow of air is ensured, thus assisting in maintaining the quality of the environment within the container, whilst still enabling the container to be fabricated of a light-weight material, since the container will not be subjected to any severe pressure differential.

A typical prior proposed relief valve is illustrated, in cross-section, in Figure 1 of the accompanying drawings. Referring to Figure 1 a pressure relief valve comprises a substantially cylindrical housing 1 having an outer wall presenting a radially outwardly extending protruberance 2. A fixing ring 3 is provided adapted to engage the protruberance, the fixing ring being provided with a plurality of apertures 4 and being associated with a resilient gasket 5. To mount the valve in position a bore or aperture may be formed in the wall of a casing to receive the cylindrical housing 1, and the fixing ring 3 may then be pressed against the outside of the housing to trap the gasket 5 between the fixing ring in the housing and bolts may be passed through the apertures 4 and further bolt holes aligned therewith formed in the wall of the container to secure the fixing ring in place.

Within the cylindrical housing 1 there is provided an inwardly directed protruberance 6. In engagement with the lower end of the protruberance 6, as illustrated in Figure 1, is the outer periphery of an annular spider 7 which comprises an outer periphery, associated with inwardly directed arms 8 supporting a central boss 9. Adjacent the spider 7 is a mesh or scrim 10. The spider and the mesh may be secured in position by means of an adhesive.

Located abutting the upper end of the protruberance 6 is a valve seat support member 11. The valve seat support member comprises an outer annular ring 12 presenting an outer upwardly directed flange 13 and also presenting, on its lower surface, an annular elastomeric sealing element 14 formed of silicone rubber for example. The outer ring 12 carries inwardly directed radially extending arms 15 which carry a hollow boss 16, a portion of which extends axially downwardly to provide a guide for a valve element 17.

A mesh or scrim 18 is provided located above the upwardly extending flange 13 and engaging the upper end of the spigot 16. The scrim may be held in position by means of a circlip or "C" ring 19 or may be secured in position by means of an adhesive.

The valve element consists of a closed tubular part 20 which is slidingly mounted on the lower part of the cylindrical boss 16, and which carries at its upper end a radially outwardly extending disc 21 which terminates with an upwardly extending flange 22 which tapers to a knife edge adapted to engage with the elastomeric sealing element 14.

A spring 23 is provided engaging between the central boss 9 and a step provided underneath the disc 21 of the valve element. The spring 23 serves to bias the valve element so that the tapering flange 22 becomes engaged with the elastomeric sealing element 14.

One or more projections 24 may be provided at the end of the cylindrical housing 1 to ensure that even if containers are stacked one-upon-the-other there is always a free air-way leading to the upper side of the valve member 17.

Should the pressure within the container, that is to say underneath the housing 1 as illustrated in Figure 1, fall beneath the pressure on the exterior of the container by a predetermined amount the valve 17 should move against the spring bias provided by the spring 23 to permit a small amount of air to "bleed" into the container, thus equalising the pressure. It is found, however, that in use the flange 22 forms a groove within the annular sealing element 14. Thus the valve element tends to "stick" to the sealing element or, at least, a degree of friction is created between the pointed flange 22 and the sealing element 14. The result, in either event, is that the valve does not open at the desired pressure differential. This can be extremely disadvantageous bearing in mind that the valve is intended to open at a relatively low pressure differ ential.It is not practicable to use a valve member with a flat ended flange, since at the spring pressures utilised, this will not provide an air-tight seal.

The present invention seeks to provide an improved pressure relief valve.

According to this invention there is provided a low pressure relief valve, said valve comprising an annular element carrying an annular resilient seal, a valve element with an inclined conical face, resilient means to bias the valve element into engagement with the resilient seal, with the seal contacting said inclined face, and means for mounting the valve in or on a container so that, when the valve element is pressed against the seal the container is substantially hermetically sealed, the valve element being separable from the seal against the bias of the resilient means in response to a predetermined pressure differential between the interior and exterior of the container to permit a flow of air past the valve element.

Preferably said inclined conical face is in 0 clined at an angle between 40 and 60 to the axis of movement of the valve element when being separated from the seal.

Conveniently the angle of inclination of the 0 said face is 50 to the said axis of movement.

Preferably the valve further comprises a cylindrical housing, the said annular element being mounted co-axially within the housing, the housing further containing a spider which engages said resilient means.

Advantageously the housing is provided with an inwardly directed protrusion, the said element and the said spider engaging opposed ends of said protrusion and being secured in position.

Peferably the said housing carries an outer protrusion, a mounting flange being provided engaging said protrusion and carrying a seal and being adapted to mount the valve in position on the side wall of a container.

Conveniently the housing has at at least one end thereof, one or more axial projections.

Preferably the said valve element defines a central aperture and carries a second annular resilient seal defining said aperture, a second valve element being provided, again presenting an inclined conical face, further resilient means being provided engaging the first valve element and the second valve element to bias the second valve element into engagement with the said resilient seal, with the seal contacting said inclined face, the valve thus comprising a double-acting valve.

In order that the invention may be more readily understood, and so that further features thereof may be appreciated, the invention will now be described, by way of example, with reference to the accompanying drawings in which FIGURE 2 is a sectional view of a valve in accordance with the invention, and FIGURE 3 is a sectional view of another embodiment of a valve in accordance with the invention.

Referring now to Figure 2 of the accompanying drawings, it is to be observed that the design of the housing 1, the retaining ring 3, the lower spider 7 and the associated scrim 10, the upper scrim 18 and the associated circlip or "C" ring 19 are the same as in the prior art arrangement described with reference to Figure 1. Thus these components will not be re-described here.

It is to be observed that engaged with the upper end of the inner protruberance 6 of the housing 1 is an annular element 25 of substantially rectangular cross-section having a cut-out at the lower inner corner thereof. The cut-out carries an insert 26 formed of elastomeric material such as silicone rubber or the like again of substantially square cross-section, the insert thus presenting a point which is directed downwardly and inwardly. This point may, in certain embodiments of the invention, be cut-away to present a substantially flat land directed downwardly and inwardly.

The described embodiment of the invention incorporates a valve element 27 which has an axially extending stem 28 carrying an enlarged head 29 which presents an outer sealing surface which is of conical tapering form 30, and which is dimensioned to engage the downwardly and inwardly directed point or land to form a seal.

Preferably the angle of inclination of the sides of the tapering portion extends at approximately 0 50 from the axis of the described arrangement, although the angle of inclination may be selected to be between 40 and 600 from the axis.

The spring 23 again biases the valve element upwardly, as illustrated, so that the valve is closed.

It is to be appreciated that the valve operates generally in the manner as described with reference to the prior art arrangement illustrated in Figure 1, but since the sealing element 26 makes effectively point contact with the tapering or inwardly sloping exterior surface 30 of the head 29 of the valve 27, no friction or sticking effect is observed and the valve thus tends to open substantially at the intended operating pressure.

It is to be appreciated that the valve, as described with reference to Figure 2, will only permit air to enter the container when there is an appropriate excess of pressure on the exterior of the container. A container may be provided with two similar valves, one having the reverse orientation to that illustrated in Figure 2. This reverse orientation is achieved by removing the housing 1, together with all the components assembled therein, from the mounting ring 3, inverting the housing 1 and re-inserting it in the mounting ring 3. A valve, when in this orientation, will serve to permit air to escape from the container whenever the pressure in the container is greater than the pressure on the exterior of the container.Thus typically, a container is provided with two valves, one in each orientation, so that the pressure within the container is always substantially equal to the pressure outside the container.

Figure 3 illustrates a modified embodiment of the invention, which is a double-acting valve which both permits the flow of air out of the container when the pressure within the container is relatively high, having regard to the pressure on the exterior of the container, and the flow of air into the container when the flow of air on the exterior of the container is relatively high having regard to the pressure of air inside the con tainer.

Referring now to Figure 3, it is to be observed that the illustrated valve effectively comprises a valve element 39, which corresponds to the valve element 29, save that the valve element 39 carries a further elastomeric sealing element 40 at a position surrounding an aperture 41 which extends through the valve element 39.

The elastomeric element 40 forms a sealing strip for a second inverted valve element 42 which has a stem 43 which carries, at its lower end, a washer 44 held in position by means of a nut 45. A spring 46 engages between the washer and an abutment 47 defined on the valve member 39. The valve member 42 has an outer face 48 again inclined at approximately 500 to the axis of the valve which engages with the elastomeric element 40.

It is to be appreciated that in the valve of Figure 3 if the pressure on the exterior of the container is greater than the pressure on the interior, the valve member 39 will move downwardly, against the bias of the spring 23, thus permitting air to enter the container. However, should pressure within the container be greater than the pressure of air outside the container the valve member 42 will move upwardly, against the bias provided by the spring 46, thus permitting air to exit from the container.

Claims

CLAIMS:

1. A low pressure relief valve, said valve comprising an annular element carrying an annular resilient seal, a valve element with an inclined conical face, resilient means to bias the valve element into engagement with the resilient seal, with the seal contacting said inclined face, and means for mounting the valve in or on a container so that, when the valve element is pressed against the seal the container is substantially hermetically sealed, the valve element being separable from the seal against the bias of the resilient means in response to a predetermined pressure differential between the interior and exterior of the container to permit a flow of air past the valve element.

2. A valve according to Claim 1 wherein said inclined conical face is inclined at an angle between 40 and 600 to the axis of movement of the valve element when being separated from the seal.

3. A valve according to Claim 2 wherein the angle of inclination of the said face is 500 to the said axis of movement.

4. A valve according to any one of the preceding Claims wherein the valve further comprises a cylindrical housing, the said annular element being mounted co-axially within the housing, the housing further containing a spider which engages said resilient means.

5. A valve according to Claim 4 wherein the housing is provided with an inwardly directed protrusion, the said element and the said spider engaging opposed ends of said protrusion and being secured in position.

6. A low pressure relief valve substantially as herein described with reference to and as shown in Figure 2 of the accompanying drawings.

6. A valve according to Claim 4 or 5 wherein the said housing carries an outer protrusion, a mounting flange being provided engaging said protrusion and carrying a seal and being adapted to mount the valve in position on the side wall of a container.

7. A valve according to any one of Claims 4 to 6 wherein the housing has at at least one end thereof, one or more axial projections.

8. A valve according to any one of the preceding Claims wherein the said valve element defines a central aperture and carries a second annular resilient seal defining said aperture, a second valve element being provided, again presenting an inclined conical face, further resilient means being provided engaging the first valve element and the second valve element to bias the second valve element into engagement with the said resilient seal, with the seal contacting said inclined face, the valve thus comprising a double-acting valve.

9. A low pressure relief valve substantially as herein described with reference to and as shown in Figure 2 of the accompanying drawings.

10. A low pressure relief valve substantially as herein described with reference to and as shown in Figure 3 of the accompanying drawings.

11. Any novel feature or combination of features disclosed herein.

AMENDMENTS TO THE CLAIMS HAVE BEEN FILED AS FOLLOWS 1. A low pressure double-acting relief valve, said valve comprising a tubular cylindrical housing, a first annular element mounted co-axially within the housing carrying an annular resilient seal, a first valve element with an inclined conical face, resilient means to bias the first valve element into engagement with the first resilient seal, with the first seal contacting said inclined face, the resilient means engaging a spider within the housing, the said first valve element carrying a second annular resilient seal defining an aperture through the said first valve element, a second valve element being provided, again presenting an inclined conical face, further resilient means being provided engaging the first valve element and the second valve element to bias the second valve element into engagement with the said second annular resilient seal, with the seal contacting said inclined face, the said housing having means for mounting the valve in or on a container so that, when the two valve elements are pressed against the respective seals the container is substantially hermetically sealed, each valve element being separable from its associated seal against the bias of the respective resilient means in response to a predetermined pressure differential between the interior and the exterior of the container to permit a flow of air through the valve.

2. A valve according to Claim 1 wherein each inclined conical face is inclined at an angle between 40 and 600 to the axis of movement of the respective valve element when being separated from the respective seal.

4. A valve according to any one of the preceding Claims, wherein the said housing carries an outer protrusion, a mounting flange being provided engaging said protrusion and carrying a seal and being adapted to mount the valve in position on the side wall of a container.

5. A valve according to any one of the preceding Claims, wherein the housing has at least one end thereof, one or more axial projections.