WO2018006949A1

WO2018006949A1 - A check valve and a method for controlling a flow of fluid by fluid pressure

Info

Publication number: WO2018006949A1
Application number: PCT/EP2016/065883
Authority: WO
Inventors: Mats Persson
Original assignee: Wapro Ab
Priority date: 2016-07-05
Filing date: 2016-07-05
Publication date: 2018-01-11

Abstract

A check valve (10) for controlling a flow of fluid by fluid pressure, comprising a tubular housing (11) and a resilient flexible valve element (12) operatively arranged inside the housing (11), wherein the valve element (12) is hollow and comprises an open wide end (17) and a closed narrow end (18), and wherein the wide end (17) of the valve element (12), in a default configuration, engages an inner surface of the housing (11) to close the check valve (10) and is deformable by a predetermined fluid pressure from the inlet (13) to open the check valve (10). The valve element (12) is formed as a longitudinally tapered body (15) being terminated in a radially outwardly projecting flange (16) at the wide end (17), wherein the housing (11) is formed with a recess (21) for receiving the flange (16). Also, an interior circumferential edge portion (22) at the wide end (17) of the tapered body (15) is arranged in an oblique angle to the longitudinal axis (A).

Description

A CHECK VALVE AND A METHOD FOR CONTROLLING A FLOW OF FLUID BY FLUID PRESSURE

FIELD OF THE INVENTION

The invention relates to a check valve and a method for controlling a flow of fluid by fluid pressure. Check valves are one-way valves that allows fluids to flow through the check valve in only one direction, wherein a flow of fluid in a first direction is allowed and a flow of fluid in an opposite second direction is prevented.

This type of check valves and methods are generally used for controlling a flow of fluid in the form of liquids and/or gases. Such check valves can be used to prevent backflow in pipe systems and networks, such as domestic pipe systems and municipal and private pipe networks, e.g. in the form of wastewater or storm water pipe systems. Further, such check valves can be used to stop odours spreading, e.g. in pipe systems or through an inlet to a chamber or container. For example, this type of check valves can be used to protect wastewater and storm water pipe systems from backflow caused by high water levels in rivers, lakes, tidal areas and similar. Also insects and small animals can be prevented from entering such pipe systems by means of such check valves.

PRIOR ART There are several different types of check valves for controlling a flow of fluid by fluid pressure in the prior art. One such type of check valve is for example disclosed in EP1244882. The check valve disclosed in EP1244882 comprises conduit and a resilient flexible valve element operatively arranged therein by means of pressure. The valve element is arranged to allow a nor- mal flow of fluid from an inlet towards an outlet of the conduit and to prevent a backflow in the opposite direction. The valve element comprises a hollow body with a tubular portion and a tapered portion, wherein the tubular portion has an open end and the tapered portion has a closed end. In a default configuration, when a fluid pressure on both sides of the valve element is sub- stantially equal, the tubular portion of the valve element engages the inner surface of the conduit around its entire circumference for closing the valve. When the fluid pressure against the outside of the tapered end portion is increased by a normal flow the valve element will be deformed from its default configuration to open the valve. When the fluid pressure from the normal flow decreases the valve element will return to its default configuration by means of inherent resilient properties of the valve element. When the fluid pressure increases in an opposite direction by a backflow the valve element will be filled with fluid and forced against the inner surface of the conduit to keep the valve closed. Even though the check valve according to EP1244882 has many advantages there is always a need to further improve the function and operation of such check valves.

SUMMARY OF THE INVENTION An object of the present invention is to further improve check valves of the prior art. The check valve according to the invention results in improved operation both to prevent backflow and to allow the normal flow. The present invention results in an increased ability to withstand backflow pressure without leakage. Further, the present invention results in improved opening of the check valve for the normal flow, wherein the check valve according to the present invention will open more easily. A check valve opening for a flow in the normal direction at lower fluid pressure results in improved operation and also a wider field of use compared to prior art check valves.

The present invention relates to a check valve for controlling a flow of fluid by fluid pressure, comprising a tubular housing and a resilient flexible valve element arranged inside the housing, wherein the housing forms a conduit having a longitudinal axis for the fluid and comprises an inlet and an outlet for the fluid, wherein the valve element is hollow and comprises an open wide end directed towards the outlet and a closed narrow end directed towards the inlet, and wherein the wide end of the valve element, in a default configuration, engages an inner surface of the housing to close the check valve and is deformable by a predetermined fluid pressure from the inlet to open the check valve, characterised in that the valve element is formed as a longitudinally tapered body having the open wide end and the closed narrow end, that the tapered body is terminated in a radially outwardly projecting flange at the wide end, that an interior circumferential edge portion at the wide end of the tapered body is arranged in an oblique angle to the longitudinal axis, and that the housing is formed with a recess for receiving the flange. The combination of the valve element and recess structure results in that the valve element is easily deformed for improved opening of the check valve while backflow is efficiently prevented. The valve element being formed as a tapered body, such as substantially a cone or an oblique cone, being terminated with the flange results in reliable and efficient deformation of the valve element at relatively low fluid pressure in the normal flow direction to open the check valve. Simultaneously, the oblique interior edge portion, such as a chamfer around at least a portion of the interior circumference, results in that a backflow pressure forces the valve element against the interior side of the housing to further seal the check valve and keep the valve element in position. Hence, both operation for allowing normal flow and preventing backflow are improved, wherein normal flow at low fluid pressures are allowed while backflow even at high fluid pressures are efficiently prevented. The flange can be rounded, e.g. arranged substantially as an external part of an o-ring with semicircular section or a section like a circular sector, wherein at least a portion of the recess is formed with a corresponding shape towards the inlet to extend around and partially enclose the flange. The flange and the recess can be formed with a distinct edge towards the inlet, such as in the portions of the flange and recess being closest to the inlet. This shape has been found to efficiently seal the check valve and prevent backflow as the flange is pressed against the inside of the housing in the recess during high backflow pressures. The distinct edge of the flange in combination with the oblique interior edge portion efficiently prevents the flange from leaving the recess during backflows. The distinct edge can be arranged between the interior edge portion and the inlet. The distinct edge can terminate the recess in a direction towards the inlet. Further, the flange can be arranged in a material being more flexible, such as softer, than the tapered body or the remaining part of the tapered body, so that the flange more easily can be deformed and compressed. With the flange being softer than the rest of the valve element the pressure required to deform the valve element and open the check valve in the normal flow direction can be reduced. Further, the flexibility or softness of the flange can be adapted to a desired opening pressure. Also, with a softer flange the flange can be made with a larger diameter and squeezed into the recess under compression of the flange, which can result in an improved ability to withstand backflow pressure, seal the check valve and keep the valve element in position during backflow. The recess or at least a portion of the recess can be arranged with a tapering portion towards the outlet to prevent debris from accumulating in the recess. Hence, due to the shape of the recess a normal flow results in turbulence in the recess and debris is washed out from the recess and transported towards the outlet through the tapering portion of the recess. The housing can be formed with a radially inwards projecting projection adjacent the recess and between the recess and the inlet to further support the valve element and prevent the flange from leaving the recess and also prevent axial displacement of the valve element inside the housing due to high backflow pressures. The projection can be arranged around at least a part of the interior circumference of the housing, such as around the oblique part or lower part of the tapered body when it is formed as an oblique cone.

Disclosed is also a method for controlling a flow of fluid by fluid pressure, comprising the steps of

a) conducting fluid to an inlet in a tubular housing of a check valve, the housing having a longitudinal axis (A),

b) inside the housing conducting the fluid into contact with a resilient flexible valve element formed as a hollow longitudinally tapered body having an open wide end towards an outlet of the housing and a closed narrow end towards the inlet,

c) increasing the fluid pressure against the valve element to a predetermined threshold value, d) by means of the fluid pressure deforming the valve element from a default configuration, in which a circumferential flange terminating the tapered body at the wide end is engaged in a recess in the housing to close the check valve, to a deformed configuration, in which the flange is disengaged from the recess around a portion of the circumference and thereby opening the check valve,

e) conducting fluid out from the housing through the outlet, and f) returning the valve element to its default configuration by means of inherent resilient properties of the valve element when the fluid pressure is reduced to a level below the predetermined threshold value.

The method can also include the steps of bringing a backflow of fluid entering through the outlet to engage an interior circumferential edge portion at the wide end of the tapered body, and forcing the edge portion radially outwards by means of the edge portion being arranged in an oblique angle to the longitudinal axis and thereby pressing the flange into the recess.

The disclosed check valve can easily be installed in a pipeline or chamber. It can be installed horizontally or vertically or at any angle and can be used to prevent substantially any types of backflow. Flow in the normal direction causes a pressure buildup against the valve element which causes the valve element to deform just enough to allow the normal flow to pass. When backflow occurs the valve element is filled with fluid, such as liquid and/or gas, and forces the valve element outwards to seal the check valve and prevent backflow.

Further characteristics and advantages of the present invention will become apparent from the description of the embodiments below, the appended drawings and the dependent claims.

SHORT DESCRIPTION OF THE DRAWINGS

The invention will now be described more in detail with the aid of embodiments and with reference to the appended drawings, in which Fig. 1 is a schematic perspective view obliquely from an inlet side of a check valve for controlling a flow of fluid by fluid pressure according to one embodiment, showing a tubular housing and a part of a valve element of the check valve,

Fig. 2 is a schematic view from an outlet side of the check valve according to Fig. 1 , wherein the check valve is closed,

Fig. 3 is a schematic perspective view from the inlet side of the valve element of the check valve according to Fig. 1 , wherein the valve element is in a default configuration,

Fig. 4 is a schematic top view of the valve element according to Fig. 3, Fig. 5 is a schematic longitudinal section view of the check valve according to one embodiment, wherein the check valve is closed,

Fig. 6 is a schematic longitudinal section view, showing the check valve of Fig. 5 arranged in a pipe system and in closed configuration, wherein a fluid flow through the inlet is illustrated,

Fig. 7 is a schematic longitudinal section view, showing the check valve of Fig. 6 in open configuration, wherein the fluid is flowing through the check valve,

Fig. 8 is a schematic longitudinal section view, showing the check valve of Fig. 6 in closed configuration preventing a backflow,

Fig. 9 is a schematic longitudinal section view of the tubular housing accord- ing to one embodiment,

Fig. 10 is a schematic longitudinal section view of the valve element according to one embodiment, Fig. 1 1 is a schematic longitudinal section view of the check valve according to one alternative embodiment, Fig. 12 is a schematic longitudinal section view of the check valve according to another alternative embodiment, wherein the check valve is closed,

Fig. 13 is a schematic view from the inlet side of the check valve according to Fig. 12, wherein the check valve is closed, and

Fig. 14 is a schematic section view of a portion of the check valve according to one embodiment.

THE INVENTION

With reference to Fig. 1 and Fig. 2 a check valve 10 for controlling a flow of fluid by fluid pressure according to one embodiment is illustrated schematically. The check valve 10 is arranged for allowing a fluid flow in one direction, a so called normal direction, and prevent a backflow in the opposite direction, a so called backflow direction. For example, the check valve 10 is arranged for installation in or as part of a pipe system, such as a domestic, private or municipal water supply system, waste water system, a sewerage or similar. Alternatively, the check valve 10 is arranged for installation in any gas and/or liquid pipe system or container system for handling gas and/or liquid with or without debris or other wastes. For example, the check valve 10 is arranged for installation in a vacuum sewage system to allow passage of sewage in one direction and prevent a backflow of odour in the opposite direction. Hence, fluid as used herein includes liquids, gases and combinations thereof, optionally also including solid or semi-liquid material, such as debris, mud, wastes and similar.

The check valve 10 comprises a tubular housing 1 1 and a valve element 12 operatively arranged inside the housing 1 1 . The housing 1 1 is formed as a conduit or pipe element having an inlet 13 and an outlet 14 for the fluid, wherein a direction from the inlet 13 to the outlet 14 is the normal direction and the opposite direction is the backflow direction. The housing 1 1 is arranged with a rounded cross section. In the illustrated embodiment the housing 1 1 is arranged with circular cross section. Alternatively, the housing 1 1 is arranged with an oval or elliptic cross section. For example, the housing 1 1 is arranged in plastic materials, such as polyethylene, PVC or other suitable plastic materials. Alternatively, the housing 1 1 is arranged in metal or a metal alloy, such as stainless steel, aluminium or other suitable alloys.

The valve element 12 is arranged inside the housing 1 1 and is connected to the interior of the housing 1 1 to keep the valve element 12 in place therein. The valve element 12 is illustrated without the housing 1 1 in Figs. 3 and 4. The valve element 12 is arranged in a resilient flexible material, such as an elastomer material, rubber or similar, wherein it is deformable from a default configuration to a deformed configuration upon application of a force and then returns to its default configuration when the application of the force ceases. For example, the valve element 12 is formed in silicone, ethylene- propylene rubber, polyurethane or similar materials. The valve element 12 is impermeable to water or at least substantially impermeable to water. For example, the valve element 12 is also impermeable to gas, such as methane gas and other odorous gases. Hence, according to one embodiment the valve element 12 is both liquid and gas proof. The valve element 12 comprises a tapered body 15 and an outwardly projecting flange 16. The tapered body 15 has a wide end 17 and a narrow end 18. In the illustrated embodiment the tapered body 15 is continuously tapered between the wide and narrow ends, e.g. with the same angle from the wide end 17 to the narrow end 18. For example, the tapered body 15 is formed substantially as a cone with a somewhat rounded apex. In the illustrated embodiment, the tapered body 15 is formed as an oblique circular cone. The tapered body 15 is terminated with the flange 16 at the wide end thereof. Hence, in the illustrated embodiment the outer circumference adjacent to the base of the cone shaped ta- pered body 15 is formed with the flange 16. The flange 15 extends around the circumference of the tapered body 15, such as around the entire circumference of the wide end 17 of the tapered body 15, wherein the flange 16 is continuous, closed and ring shaped. For example, the flange 16 is rounded. According to one embodiment the flange 16 is arranged softer than the tapered body 15 or the remaining part of the valve element 12, wherein the flange 16 is more flexible and more easily deformable than the tapered body 15. For example, the valve element 12 is arranged in two different materials having different flexibility or softness properties, wherein the tapered body 15 is formed in a first material and the flange 16 is formed in a second material being softer than the first material.

With reference to Fig. 5 a section view along a longitudinal axis A of the check valve 10 is illustrated schematically. For example, the housing 1 1 extends in the longitudinal direction A and is, e.g. straight, wherein the inlet 13 and the outlet 14 are aligned, longitudinally displaced and arranged in parallel, so that they are spaced apart to form a gap between them. Alternatively, the housing 1 1 is bent, wherein the inlet 13 and outlet 14 are angularly displaced and/or displaced in the radial direction in relation to each other. The check valve 10 is arranged to be mounted with its longitudinal axis at any angle, such as horizontally, vertically or at an oblique angle.

As illustrated in Fig. 5 the valve element 12 is formed with the wide end 17 open and the narrow end 18 closed, wherein the valve element 12 is hollow and the tapered body 15 is open in a direction towards the outlet 14 and closed in a direction towards the inlet 13. Hence, the tapered body 15 is tapered in the longitudinal direction A towards the inlet 13. In the illustrated embodiment the narrow end 18 of the tapered body 15 is displaced radially from the longitudinal centre axis A. For example, a first portion 19 of the tapered body 15 is arranged in the longitudinal direction along the inner surface of the housing 1 1 , wherein a radially opposite second portion 20 of the tapered body 15 is inclined in relation to the longitudinal axis A. In the illustrated embodiment, the first portion 19 of the tapered body 15 engages the inner surface of the housing 1 1 and is arranged in parallel therewith and in parallel with the longitudinal axis A, wherein the second portion 20 extends substan- tially diagonally through the housing 1 1 . For example, the first portion 19 is a top portion when the longitudinal axis A is horizontal. The flange 16 of the valve element 12 is received in a recess 21 in the housing 1 1 to prevent longitudinal displacement of the valve element 12 inside the housing 1 1 . The recess 21 extends in the radial direction and conforms at least partially to the shape of the flange 16. For example, the recess 21 extends around the inner circumference of the housing 1 1 , such as around the entire inner circumference so that the recess 21 continuous. For example, the flange 16 is formed as a distinct outwardly projecting bulge having a distinct edge towards the tapered body 15. For example, the flange 16 is substantially and at least partially formed with a semicircular shape extend- ing radially outwards. In the illustrated embodiment the recess 21 is formed with a corresponding rounded shape in a direction towards the inlet 13 to prevent longitudinal displacement of the valve element towards the inlet 13. Hence, the recess 21 is, e.g. formed with a distinct edge in a direction towards the inlet 14. Further, in the illustrated embodiment the recess 21 is tapered towards the outlet 14 to prevent material from accumulating in the recess 21 . Hence, the recess 21 is deeper towards the inlet 13 than towards the outlet 14.

The valve element 12 comprises a circumferential interior edge portion 22. The interior edge portion 22 is arranged at the wide end 17 of the tapered body 15. The interior edge portion 22 is arranged opposite to the flange 16, wherein the flange 16 projects radially outwardly at the wide end 17 of the tapered body 15 while the interior edge portion 22 is arranged on the interior side of the wide end 17. Hence, the tapered body 15 is terminated at the wide end 17 with the flange 16 on the outer side and the interior edge portion 22 on the inner side. The interior edge portion 22 is arranged in an oblique angle to the longitudinal axis A to form a chamfer of the tapered body 15, at least around a portion of its circumference, at the inner side of the wide end 17. Hence, the interior edge portion 22 is arranged in an oblique angle outwards in relation to the longitudinal axis A to further widen the wide end 17. In the illustrated embodiment the interior edge portion 22 adjacent to the first portion 19 of the tapered body 15, e.g. being a top portion, is inclined in relation to said first portion 19, wherein the interior edge portion 22 adjacent to the inclined second portion 20 of the tapered body 15, e.g. being a lower portion, is arranged as a continuation of said second portion 20.

With reference to Fig. 6 a part of a pipe system is illustrated schematically according to one embodiment, wherein the check valve 10 is arranged between a first pipe 23 and a second pipe 24. Hence, the illustrated embodiment is an inline installation. Alternatively, the check valve 10 is arranged at an inlet or outlet in a pipe system, wherein the check valve 10 is arranged in an inlet installation or an outlet installation. Alternatively, the check valve 10 is arranged at an inlet or outlet to a container, chamber or similar, wherein the check valve 10 is arranged in a chamber installation.

In Fig. 6 a fluid, such as waste water which can include liquids, gases, and/or semiliquid materials possibly in combination also with solid materials, is indicated by means of the wavy line F. The fluid F is entering the check valve 10 through the inlet 13 from the first pipe 23 in a direction illustrated by means of the arrow N, wherein the arrow N illustrates a normal flow direction. In Fig. 6 the check valve 10 is closed, wherein the valve element 12 is in its default configuration and the flange 16 is received in the recess 21 and engages the inner side of the housing 1 1 around the entire circumference thereof. In the illustrated embodiment, the narrow end 18 of the tapered body 15 is arranged towards the inlet 13. Hence, in the default configuration of the valve element 12 the wide end 18 of the tapered body 15 engages the inner surface of the housing 1 1 to close the check valve 10. The fluid flow into the check valve 10 results in a fluid pressure against the valve element 12. The fluid flow into the check valve 10 from the inlet 13 results in a fluid pressure against the exterior surface of the tapered body 15. Hence, the fluid flow engages the exterior inclined surface of the tapered body 15, i.e. the surface of the tapered body 15 obliquely facing the inlet 13. When the fluid pressure against the exterior side of the tapered body 15 exceeds a threshold value for deforming the valve element 12 the valve element 12 deforms to open the check valve 10, which is illustrated schematically in Fig. 7. Hence, in Fig. 7 the valve element 12 is deformed by fluid pressure against it from the inlet 13, wherein the check valve 10 is open to let the fluid pass in the normal direction from the inlet 13 to the outlet 14 as illustrated by the arrow N. Accord- ing to one embodiment, the fluid pressure required for opening the check valve 10 by deformation of the valve element 12 is predetermined, such as by adapting the material properties and thickness of the valve element 12, which e.g. is made in a conventional manner by a skilled person in view of the present disclosure. When the fluid pressure against the exterior surface of the valve element 12 is decreased the valve element 12 returns to its closed default position by the inherent resilient flexible properties thereof.

With reference to Fig. 8 a backflow is illustrated wherein the fluid F enters through the outlet 14 and flows into the check valve 10 in a direction il- lustrated by means of the arrow B. The backflow enters into the interior of the hollow tapered body 15 through the wide end 17 thereof, wherein the check valve 10 remains closed and the backflow is stopped. The backflow fluid engages the oblique interior edge portion 22 of the tapered body 15 and forces the edge portion 22 towards the inner surface of the housing 1 1 , which is il- lustrated by means of the arrow P. Hence, the backflow exerts a pressure on the edge portion 22 and presses the flange 16 on the exterior side of the wide end 17 of the tapered body 15 into the recess 21 to keep the check valve 10 closed. The inclined edge portion 22 results in a force directed obliquely outwards in the radial direction to press the wide end 17 of the ta- pered body 15 in the corresponding direction and force the flange 16 in the recess 21 towards the inner surface of the housing 1 1 to prevent the back- flow from leaking. In Fig. 8 the backflow is illustrated schematically. For example, the backflow fills the tapered body 15 and exerts a pressure around the entire circumference of the wide end 17 and towards the entire edge por- tion 22. When the backflow pressure increases the force applied on the edge portion 22 is also increased to keep the check valve 10 closed.

With reference to Fig. 9 the housing 1 1 is illustrated separately without the valve element 12 according to one embodiment, wherein the housing 1 1 is formed with the recess 21 for receiving the flange 16. The recess 21 is formed in the interior side of the housing 1 1 , is tapered towards the outlet 14 and is formed with a distinct edge 25 towards the inlet 13. For example, the recess 21 extends at least perpendicular into the housing wall, such as in a direction 90 degrees or more from the longitudinal axis A. For example, after the distinct edge 25 the recess 21 is rounded into the tapering portion towards the outlet 14. In the illustrated embodiment and seen in a direction from the inlet 13, the recess 21 extends distinctly and substantially in the radial direction to form the distinct edge 25 and is then rounded into the taper- ing portion towards the outlet 14.

With reference to Fig. 10 the valve element 12 is illustrated separately without the housing 1 1 according to one embodiment. The valve element 12 is formed with suitable dimensions for the desired application. For example, the check valve 10 is arranged for pipes having an inner diameter of 10-2000 mm, wherein a largest outer diameter D of the valve element 12 is 10-2000 mm or slightly more. For example, the diameter D is 102 mm. For example, the length L of the valve element 12 is larger than the diameter D, such as about 25% larger. For a valve element 12 having the diameter D of 102 mm the length is, e.g. 125 mm. For example, the valve element 12 is arranged with an angle a between the first portion 19 and the second portion 20 of 20- 50 degrees, such as 30-40 degrees or about 35 degrees. For example, a thickness T of the wall of the tapered body 15, excluding the flange 16 and the oblique edge portion 22, is 2-10 mm, such as 5 mm for a valve element 12 having a length L of 125 mm and a diameter D of 102 mm. For such a valve element 12 the outer radius R4 of the flange 16 is, e.g. 4 mm, wherein the outer radius R5 of the narrow end 18 is 5 mm and the inner radius R3 of the narrow end 18 is 3 mm.

With reference to Fig. 1 1 the check valve 10 is illustrated according to one alternative embodiment, wherein the wide end 17 is inclined in relation to the radial direction. In the illustrated embodiment, the wide end 17 is arranged at an angle β to the radial direction, wherein the first portion 19 is displaced axially in relation to the second portion 20 of the tapered body 15. For example, the angle β is 10-30 degrees, such as 20 degrees. For example, the second portion 20 is displaced towards the inlet 13 in relation to the first portion 19. For example, the second portion 20 is a lower portion, wherein the first portion 19 is an upper portion. With reference to Figs. 12 and 13 another alternative embodiment of the check valve 10 is illustrated, wherein the housing 1 1 is formed with a projection 26. The projection 26 is arranged adjacent the recess 21 towards the inlet 13, so that the projection 26 is arranged between the inlet 13 and the recess 21 . The projection 26 s arranged to engage the flange 16 and/or the portion of the tapered body 15 adjacent the flange 16 to prevent the valve element 12 from being displaced towards the inlet 13, e.g. due to a high backflow pressure. For example, the projection 26 is also arranged to support the valve element 12 when a backflow pressure forces the wide end 17 of the tapered body 15 outwards. For example, the projection 26 is arranged around a part of the inner circumference of the housing 1 1 , such as around the second portion 20 of the tapered body 15. For example, the projection 26 is arranged around a lower half of the inner circumference of the housing 1 1 . In the illustrated embodiment the projection 26 is tapered towards the inlet 13. In the embodiment of Fig. 12 the tapering portion of the recess 21 extends around a part of the inner circumference of the housing 1 1 , such as a lower half of the inner circumference of the housing 1 1 .

With reference to Fig. 14 a part of the check valve 10 is illustrated according to another alternative embodiment, wherein the housing 1 1 is formed with the rounded and tapered recess 21 and the projection 26, and wherein the valve element 12 is formed with the rounded flange 16 and the interior edge portion 22. In the embodiment of Fig. 14 the valve element 12 is arranged as an oblique cone having the flange 16 at the wide end 17 and optionally a rounded narrow end 18, wherein the edge portion 22 is arranged substantially as a continuation of the tapered body 15 in the second portion 20 of the tapered body 15, such as the lower portion, and as a chamfer in the remaining portion of the tapered body 15. The flange 16 is a rounded protrusion at the wide end 17 of the tapered body 15 and is, e.g. substantially formed as an outer half of an o-ring, i.e. as a protrusion having a substantially semicircular section in the longitudinal direction of the check valve 10. For example, the flange 16 is arranged with a section as a circular sector having a periphery engaging the straight oblique form of the tapered body 15 extending towards the narrow end 18. The recess 21 extends around at least the portion of the flange 16 facing the inlet 13. The projection 26 is arranged around at least a portion of the inner circumference of the housing 1 1 including the second portion 20, such as a lower half of the tapered body 15. The projection 26 is tapered towards the inlet 13, wherein the thickness of the housing wall increases towards the recess 21 up to the distinct edge 25 after which the thickness of the housing wall decreases rapidly in the recess 21 to a rounded part of the recess 21 which continues in a tapered portion towards the outlet 14 wherein the thickness of the housing wall increases slowly. For example, the recess 21 is formed with a substantially semicircular portion towards the inlet 13 to prevent the flange 16 from leaving the recess 21 , e.g. during high backflow pressures. In the illustrated embodiment, the recess 21 is formed with a substantially semicircular deeper portion towards the inlet 13 continuing in a shallower tapering part towards the outlet 14 to prevent the flange from leaving the recess 21 and achieve turbulence of the fluid when the check valve 10 is open and prevent accumulation of debris in the recess 21 . Optionally the first portion 19 of the tapered body 15, such as the top portion when mounted in a horizontal conduit, is attached to the housing 1 1 also by conventional fastening means, such as adhesive, screws, etc.

Claims

1 . A check valve (10) for controlling a flow of fluid by fluid pressure, comprising a tubular housing (1 1 ) and a resilient flexible valve element (12) arranged inside the housing (1 1 ), wherein the housing (1 1 ) forms a conduit having a longitudinal axis (A) for the fluid and comprises an inlet (13) and an outlet (14) for the fluid, wherein the valve element (12) is hollow and comprises an open wide end (17) directed towards the outlet (14) and a closed narrow end (18) directed towards the inlet (13), and wherein the wide end (17) of the valve element (12), in a default configuration, engages an inner surface of the housing (1 1 ) to close the check valve (10) and is deformable by a predetermined fluid pressure from the inlet (13) to open the check valve (10), c h a r a c t e r i s e d in

that the valve element (12) is formed as a longitudinally tapered body

(15) having the open wide end (17) and the closed narrow end

(18),

that the tapered body (15) is terminated with a radially outwardly projecting flange (16) at the wide end (17),

that an interior circumferential edge portion (22) at the wide end (17) of the tapered body (15) is arranged in an oblique angle to the longitudinal axis (A), and

that the housing (1 1 ) is formed with a recess (21 ) for receiving the flange (16).

2. A check valve according to claim 1 , wherein the flange (16) is rounded, and wherein at least a portion of the recess (21 ) directed towards the inlet (13) is formed with a corresponding rounded shape.

3. A check valve according to claim 2, wherein the flange (16) is formed with a distinct edge (25) in a direction towards the inlet (13).

4. A check valve according to claim 2 or 3, wherein the flange (16) is arranged with a circular sector shape in the longitudinal direction.

5. A check valve according any of the preceding claims, wherein at least a portion of the recess (21 ) is tapered towards the outlet (14).

6. A check valve according to any of the preceding claims, wherein the inte- rior circumferential edge portion (22) at least partially is tapered in a direction towards the outlet (14).

7. A check valve according to any of the preceding claims, wherein the valve element (12) is formed as an oblique circular cone having the flange (16) ad- jacent a base thereof.

8. A check valve according to any of the preceding claims, wherein the housing (1 1 ) is formed with a radially inwards projecting projection (26) adjacent the recess (21 ), arranged between the recess (21 ) and the inlet (13) and around at least a part of the interior circumference of the housing (1 1 ).

9. A check valve according to any of the preceding claims, wherein the flange (16) is softer than the remaining part of the valve element (12).

10. A method for controlling a flow of fluid by fluid pressure, comprising the steps of

a) conducting fluid to an inlet (13) in a tubular housing (1 1 ) of a check valve (10), the housing (1 1 ) having a longitudinal axis (A),

b) inside the housing (1 1 ) conducting the fluid into contact with a resili- ent flexible valve element (12) formed as a hollow longitudinally tapered body

(15) having an open wide end (17) towards an outlet (14) of the housing (1 1 ) and a closed narrow end (18) towards the inlet (13),

c) increasing the fluid pressure against the valve element (12) to a predetermined threshold value,

d) by means of the increased fluid pressure deforming the valve element (12) from a default configuration, in which a circumferential flange (16) terminating the tapered body (15) at the wide end (17) is engaged in a recess (21 ) in the housing (1 1 ) to close the check valve (10), to a deformed configu- ration, in which the flange (16) is disengaged from the recess (21 ) around a portion of the circumference and thereby opening the check valve (10),

e) conducting fluid out from the housing (1 1 ) through the outlet (14), and

f) returning the valve element (12) to its default configuration by means of inherent resilient properties of the valve element (12) when the fluid pressure is reduced to a level below the predetermined threshold value.

1 1 . A method according to claim 10, comprising the steps of

- bringing a backflow of fluid entering through the outlet (14) to engage an interior circumferential edge portion (22) at the wide end (17) of the tapered body (15), and

- forcing the edge portion (22) radially outwards by means of the edge portion (22) being arranged in an oblique angle to the longitudinal axis (A) and thereby pressing the flange (16) into the recess (21 ).