GB2190466A

GB2190466A - Improved valve member

Info

Publication number: GB2190466A
Application number: GB08611887A
Authority: GB
Inventors: Joseph Anthony Griffiths
Original assignee: C R M DESIGN SERVICES Ltd
Current assignee: C R M DESIGN SERVICES Ltd
Priority date: 1986-05-15
Filing date: 1986-05-15
Publication date: 1987-11-18
Also published as: GB8611887D0

Abstract

In a flexible one-piece moulded valve having a mouth (5) at one end which is normally closed but which opens on demand, the mouth is shaped (preferably U-shaped) so that the upper and lower lips thereof (5a, 5b) are pre-stressed so that they are always returned to their fully closed position after the mouth has been opened, even when there is no pressure differential across the mouth.The valve is preferably moulded from a natural or synthetic rubber material.

Description

SPECIFICATION Improved valve member This invention relates to a demand or non return valve and particu la rly to a simple one-piece valve moulded in aflexible natural orsyntheticmaterial.

Demand valves are known comprising a length of tubing, one end of which has been flattened so that the opposite walls thereof lay against each other to form a mouth which is normally closed. These valves allow fluid to pass through them on demand butthey require a pressure differential across the mouth to ensure that it closes again. Thus, such valves are not suitableforuse in situations where there would not normally be any pressure differential to keep the valve mouth closed.

This problem is particularly noticeable in the context of venting fuel tanks for vehicles. Normally, the entry pipeto the fuel tank is closed byafillercap which has a hole in it so that the contents of the fuel tank are vented to atmosphere at all times. For normal road use, this arrangement works satisfactorily but ifthe vehicle is parked on a steep slope, the fuel can reach the vent hole and leak out of the tankth rough it. This problem is particularly noticeable in off-road vehicles which are designed to travel across undulating terrain. In such vehicles therefore, it is desireable to fit a non-return one-way valve in a pipe leading from the airvent hole in the fuel filler cap to overcome this problem.

It is an object of the invention therefore to provide asimpleone-wayvalvewhich is reliable in use and cheap to manufacture.

According to the invention there is provided a onepiece moulded flexible one-way valve having a mouth atone end which, in use, is normallyclosed but which opens on demand, said mouth being shaped so that it is pre-stressed to return it to its fully closed condition after it has been opened, even when there is no pressure differential across the mouth.

Preferrablythe valve is generally tubular in cross section at one end but u-shaped in cross section at the other end where the mouth is located, the cross section gradually changing from tubularto u-shaped along the length of the valve.

In a preferred embodiment, the cross section of one half of the valve remains constant whereas the other half changes along the length of the valve.

Desireablythe mouth is u-shaped butotherconfigurations are possible.

In a preferred embodiment, the valve is formed at an end wall which is cut along its length to provide the mouth.

A preferred embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure lisa perspective view of a valve of the invention, Figure2 is a longitudinal cross section through the valve shown in Figure 1, Figure 3 is a top plan view ofthe valve shown in Figures 1 and 2, and, Figure 4 is an underneath view of the valve shown in Figures 1 to3.

Referring to the drawings, there is shown a valve member 1 comprising a generally tubular body2 and an end collar3. The collar3 is formed internallywith an annular recess 4 which is adapted to co-operate with a raised annular bead 11 provided on the end of a pipe 10 to which the valve member is to be fitted.

When fitted thereto, the bead 11 fits into the recess 4 to provide a seal therewith.

At point 12wherethe generallytubular body meets the collar 3, the transverse cross-section of the valve body is circular. However, the upper part of the tubular member 2 is formed with a scalloped shaped depression 7 therein which results in the cross sec tion of thetubular member2 changing along length from circular at point 12 to u-shaped at the end remote from the collar 3. This u-shaped end provides a mouth Swhich is slitat6 along its length to provide an upper lip 5a and a lower lip 5b. Although a small gap is shown in Figure 2 between the upper lip 5a and the lower lip 5b this isforthe purposes of illustration only.In practice, the upper lip 5a and the lower lip 5b would be pressed tightly together to form a seal with each other.

The valve member illustrated in the drawings is moulded from a synthetic or natural rubber material or from a synthetic plastic material. Which ever material is used, it will be seen that the valve member itself is flexible and accordingly, fluid can flow through the mouth Sin the direction of arrow becausethe mouth will deform to permit passage ofthe fluid. However, once the fluid flow has ceased, the pressure generated by the pre-stressed mouth 5 itselfwill result in the upper and lower lips being closed up again to their normal sealed position.Because ofthe design of the valve, it is not possiblefor fluid to fiow in the opposite direction to that shown bythearrowA. butin any event, such flowwould only encouragethe lipsto close which isthe purpose required of the valve.

It is the pre-stressing of the mouth 5 which forms the essence of the invention because making the mouth u-shaped results in tension being applied to both lipsSa and Sbforcing them to return to their closed seal position. In prior art valves, the mouth is normally a horizontal slit with the resultthat once the mouth has been opened to permit the passage of fluid therethrough the resilience of the material from which the mouth is made returns the mouth backto its closed position. The problem with this however is that in the absence of any pressure differential, the more the mouth closes, the less tension is applied to it so the recovery rate is extremely slow and a proper seal cannot be guaranteed. Such valves are normally used in situations where the fluid itself exerts pressure on the valve to ensure that it closes. Underwater diving equipment often uses valves of this type which open to permit waste air to be exhausted but the pressure ofthe surrounding water ensures that the valve closes again.

The advantage of the valve of the present invention is that it does not require any pressure differential across the mouth 5 to ensure that the lips 5a, 5b return to their closed position because the mouth 5 is naturally pre-stressed by its shape to en surethatthis happens.

Claims

1. A one-piece moulded flexible one-wayvalve having a mouth at one end which, in use, is normally closed but which opens on demand, said mouth being shaped so that it is pre-stressed to return itto its fully closed position after it has been opened, even when there is no pressure differential across the mouth.

2. Valve as claimed in claim 1 wherein the valve is generallytubular in cross section at one end but u-shaped at the other end where the mouth is located.

3. Avalve as claimed in claim 2 wherein the cross section gradually changes from tubularto u-shaped along the length of the valve.

4. Avalve as claimed in anyone of claims 1 to 3 wherein the cross section of one half of the valve remains constant whereas the other half changes along its length.

5. Avalve as claimed in anyone of claims 1 to 4 wherein the mouth is u-shaped.

6. Avalve as claimed in anyone of claims 1 to 5 wherein the valve has an end wall which is cut along its length to provide the mouth.

7. A valve as claimed in anyone of claims 1 to 6 moulded from a natural or synthetic rubber material.

8. Avalve member substantially as herein described with reference to the accompanying drawings.