GB2153048A

GB2153048A - Improvements in non-return valves for liquids or gases

Info

Publication number: GB2153048A
Application number: GB08402756A
Authority: GB
Inventors: James Edward Brown
Original assignee: Individual
Current assignee: Individual
Priority date: 1984-02-02
Filing date: 1984-02-02
Publication date: 1985-08-14
Also published as: GB8402756D0; GB2153048B

Abstract

A non-return valve for liquids or gases comprises a flexible tubular member (2) of elastic material having one closed end but formed with a curved slit (10) the walls of which are normally pressed closely upon each other under the action of the elasticity. The slit (10) is located longitudinally of and centrally of the width of a thin curved edge constituted by the junction of curved walls (11 and 12). In order to prevent inner wall (12) from becoming lodged behind outer wall (11) when the inner wall recovers from depressed position attained by a substantial back pressure applied to the valve, the outerwall (11) at said thin edge is raked towards the open end of the valve away from the slit, through an angle which may be about 45 DEG . <IMAGE>

Description

SPECIFICATION Improvements in non-return valves for liquids or gases This invention relates to non-return valves for liquids or gases and is concerned with valves intended to work at low pressures and to open and close with very low pressure differentials which comprise a flexible tubular member of elastic material having one end closed but formed with an aperture the walls of which are normally pressed closely upon each other under the action of the elasticity of the material of which the member is composed, the liquid or gas under pressure being admitted to the member through the open end thereof.

British Patent No. 1066508 relates to a non-return valve of this character in which the closed end of the tubular member is formed by a thin edge constituted by the junction of a curved wall portion of the member with an opposed similarly curved wall portion of the member and the aperture in the closed end is a curved slit extending longitudinally of the thin edge substantially centrally of the width thereof.

In this arrangement the curved slit is between a concave (outer) wall portion and a convex (inner) wall portion relative to the slit.

It is found with such a shape of the closed end that gaping of the slit is prevented and that the walls of the slit will close together with certainty whenever the pressure outside the closed end of the member equals or rises slightly above the pressure prevailing within the member. Moreover, the pressure required to cause the slit to open is extremely low.

Preferably, the wall thickness of the tubular member, at least for some distance back from the closed end thereof, is very thin so that the walls are highly flexible and will be displaced readily to cause full opening of the slit without disturbing the gas dissolved in a liquid such as beer the flow of which is to be controlled by the valve.

If the pressure on the outlet side of the valve builds up, the shape of the closed end of the tubular member will ensure that the seal produced by the closing together of the walls of the slit will be supplemented by the closing together in surface contact with each other of the two opposed curved walls of the member.

The tubular member may be formed from rubber, synthetic rubber or a suitable plastics material and preferably is produced by a dipping technique or injection moulding. It may be made with a thickened or rolled edge at the open end so that it may be engaged over a tubular nozzle or the like by stretching this edge, the natural elasticity of the material ensuring a tight engagement. Alternatively the open end of the tubular member may be formed with a flange adapted to be clamped between washers or nuts around the orifice to be fitted with the valve.

It has been found that when the valve described in Patent 1 066508 is subjected to a high back pressure the inner wall portion tends to move, relative to the outer portion, towards the open end of the valve. When the back pressure is released it tends to return to its normal position but there is then a tendency for the edge of the inner portion to become lodged under any step formed on the.

outer portion by the slit in the valve.

According to the present invention, the thin outside edge of the closed end of the tubular member is raked towards the open end of the valve away from the edge of the inner wall portion, through an angle which may be about 45 . The inner wall portion can then present an angled edge to the outer wall portion so that it may easily return to its normal position.

A valve according to one embodiment of the invention will now be described by way of example with reference to the accompanying drawing in which: Figure 1 shows in perspective a non-return valve according to Patent 1066508, Figure 2 shows a longitudinal section through part of the valve of Fig. 1 modified according to the present invention on a larger scale, Figure 3 shows an end view of the valve shown in Fig. 2.

Referring to the drawings a tubular member 1 is a thin-walled rubber tube 2 of circuiar cross-section at the open end 3 where it is formed with a beaded or flanged edge 4 and of semi-circular shape in cross-section at the closed end 5. Between the ends the crosssectional shape changes from a circle to a semi-circle, the wall portion above a diametral plane remaining semi-circular in cross-section throughout its length and the wall portion below this plane commencing at the part 6 near the edge 4 as a semi-circle in crosssection and changing to a semi-circle with a re-entrant curved wall portion 7 which then progressively increases in size as the closed end 5 is approached from a minute arc at the position 8 up to a full semi-circle of approximately the same radius as the upper wall portion at the position 9.

Adjacent to the closed end 5 where the two wall portions unite to form an edge of a thickness equal to slightly more than twice the wall thickness the passage through the tubular member is of crescent-shape in cross-section with the maximum width of the crescent diminishing to almost zero as the closed end is reached.

The curved closed end 5 is formed with a longitudinally extending slit 10 disposed centrally of its width, the slit being produced with removing any material for example by employing an extremely sharp thin blade to separate the two opposed wails 11 and 1 2 from each other over part of the length of the closed end 5. The slit preferably extends over the central portion only of this end for example symmetrically about the centre point for a total length equal to about half that of the end.

When liquid is flowing through the valve the walls of the slit 10 in the curved closed end 5 will open to an elliptical shape so that the area of the opening thus produced can be substantially equal to that of the internal cross-section of a pipe end or the like over which the valve end 3 is fitted without the external diameter of the valve being substantially larger than that of the bore of the pipe or the like.

It will be understood that both the slit 10 and the wall parts 11 and 1 2 will close together with certainty whenever the pressure outside the closed end 5 equals or rises slightly above the pressure prevailing within the member but nevertheless the pressure differential required to open the slit 10 is extremely low.

The valve of Fig. 1 will resist the flow of gas or liquid through the valve end when a high pressure in excess of the pressure within the valve member is applied to the outside of the closed end 5 of the valve. However when a large back pressure is applied in this way the wall portion 7 of the valve may be moved towards the open end of the valve, the slit remaining closed to resist flow of fluid. When the excess pressure is reduced the wall portion 7 should return to its former position but in the known valve of Fig. 1 the edge of the wall 1 2 may then become lodged behind the step adjacent the slit formed by wall 11.

This effect may be avoided by modifying the closed end of the valve as shown schematically in Fig. 2. In this modification the ends of walls 11 and 1 2 at the closed end are angled by an angle which is suitably about 45 , such that the end surfaces of walls 11 and 1 2 are raked towards the open end of the valve from the slit 1 0. With this arrangement, when the wall 1 2 recovers from its depressed position there is little or no tendency for the edge of wall 1 2 to become lodged behind wall 11 and the valve walls return to their normal positions, that is their positions when the valve is not subjected to pressure.

It is believed that with the modification of Fig. 2 when wall 1 2 returns to its normal position it presents an angled edge to wall 11 so that it may return more easily to its normal position.

Claims

1. A non-return valve for liquids or gases, the valve comprising a flexible tubular member of elastic material having one end closed but formed with an aperture the walls of which are normally pressed closely upon each other under the action of the elasticity of the material of which the member is composed, the liquid or gas under pressure being intended to be admitted to the member through an open end thereof, and the closed end of the tubular member being formed by a thin edge constituted by the junction of a curved outer wall portion of the member with an opposed similarly curved inner wall portion of the member, the aperture in the closed end being a curved slit extending longitudinally of the thin edge substantially centrally of the width thereof, and the curved outer wall portion at said edge at the closed end of the tubular member being raked towards the open end of the valve away from the edge of the inner wall portion.

2. A non-return valve as claimed in claim 1, wherein said outer wall portion at said edge of the closed end of the tubular member is raked towards the open end of the valve away from the edge of the inner wall portion through an angle of 45 .

3. A non-return valve as claimed in claim 1 or 2, wherein said inner wall portion at said closed end of the tubular member extends beyond said outer wall portion in a direction away from said open end of the valve.

4. A non-return valve as claimed in claim 1, 2 or 3, wherein the wall thickness of the tubular member, at least for some distance back from the closed end thereof, is thin so that the walls are flexible and will be displaced readily to cause full opening of the slit without disturbing the gas dissolved in a liquid the flow of which is to be controlled by the valve.

5. A non-return valve as claimed in any one of the preceding claims, in which the tubular member is formed from rubber, synthetic rubber or a plastics material.

6. A non-return valve as claimed in any one of the preceding claims, wherein the tubular member has been produced by a dipping technique or injection moulding.

7. A non-return valve as claimed in any one of the preceding claims, wherein the tubular member is made with a thickened or rolled edge at its open end.

8. A non-return valve as claimed in any -one of claims 1 to 6, wherein the open end of the tubular member is formed with a flange adapted to be clamped between washers or nuts around the orifice to be fitted with the valve.

9. A non-return valve as claimed in claim 1, substantially as hereinbefore described with reference to the accompanying drawings.