GB2244545A

GB2244545A - Check valve

Info

Publication number: GB2244545A
Application number: GB9110138A
Authority: GB
Inventors: Peter Carter
Original assignee: GSA IND
Current assignee: GSA IND
Priority date: 1990-05-15
Filing date: 1991-05-10
Publication date: 1991-12-04
Also published as: GB9110138D0

Abstract

A check valve (1) comprises a valve body (2) having an inlet (4), an outlet (5) and a flow passage (3) connecting the inlet (4) to the outlet (5), a valve seat (6) around the flow passage (3), and a valve closure member (10) movable relative to the valve seat (6) between a closed position in which the closure member (10) seals against the valve seat (6) and an open position in which fluid flow from the inlet (4) to the outlet (5) is possible, the valve closure member (10) including a head (12) of aerodynamic form which allows fluid to flow through the flow passage (3) past the head (12) without creating undue turbulence in the fluid. <IMAGE>

Description

CHECK VALVE This invention relates to a check valve, sometimes known as a non-return valve, which operates automatically to prevent return flow of fluid passing therethrough.

Check valves are used in many applications and generally include a valve body of some description having a flow passage therethrough, and a valve closure member cooperable with a valve seat which surrounds the flow passage. The valve closure member is arranged to move to an open position to allow flow of fluid in one direction through the passage, and automatically move to a closed position if the direction of flow of fluid through the passage begins to reverse at any time.

Generally, a biasing spring of some description is used to bias the valve closure member to its closed position and fluid flowing through the valve when the valve closure member is in its open position must overcome the force of the spring to keep the valve open, resulting in a pressure drop across the valve. Clearly, the greater the spring force, the greater will be the fluid pressure necessary to open the valve and, in turn, the greater will be the pressure drop across the valve. However, in many prior art arrangements a significant spring force is required if the check valve is to operate effectively.

In many prior art check valves the valve closure member is in the form of a flat plate or disc. It has been found that the dynamics of fluid flow through a valve having a valve closure member of this general form results in the valve closure member being subjected to stress of substantial magnitude. To accommodate these stresses the components of prior art check valves have been made of high strength materials and robust form. This increases the cost of prior art check valves unnecessarily.

It is an object of this invention to provide a simple check valve which operates at low pressures and can be of relatively lightweight construction.

A check valve according to the present invention comprises a valve body, an inlet to the body and an outlet from the body, a flow passage through the body connecting the inlet to the outlet, a valve seat adjacent the flow passage, and a valve closure member movable relative to the valve seat between a closed position in which the closure member seals against the valve seat to close the flow passage and an open position in which fluid flow from the inlet to the outlet is possible, said valve closure member including a head of aerodynamic form which will-allow fluid to flow through the flow passage past the head without creating undue turbulence in that fluid.

An embodiment of the invention is described in detail, by way of example only, in the following passages of the specification which refer to the accompanying drawings, in which:- Figure 1 shows a cross-sectional side view, taken along the line I-I of Figure 2, through a check valve according to the present invention; Figure 2 shows a rear end view of the check valve shown in Figure 1; and Figure 3 shows an enlarged cross-sectional side view of the valve closure member for the check valve of Figure 1.

In the embodiment of the invention shown in the drawings a check valve 1 includes a hollow valve body 2 having a flow passage 3 therethrough and an inlet 4 into and outlet 5 from the flow passage 3. A valve seat 6 is defined around the flow passage 3 within the valve body 2, and that valve seat may be formed by an elastomeric 0-ring seal 7 which locates in a groove 8 formed in.the wall 9 of the flow passage.

A valve closure member 10 is supported by the valve body 2. The valve closure member 10 preferably is in the form of a plunger comprising a stem 11 and a head 12, and the stem 11 and head 12 are preferably integrally formed.

The head 12 is arranged to co-operate with the O-ring seal 7 in order to close the flow passage 3 through the valve body 2, and the valve closure member 10 is movable in an axial direction relative to the valve body 2 in order to open and close the valve. The flow passage 3 and valve closure member 10 are preferably circular in cross-section having a coincident axis 13. The direction of movement of the valve closure member 10 is along the axis 13.

The valve body 2 preferably includes a cup-shaped boss 14 with an axial bore 15 therethrough in which the stem 11 of the valve closure member 10 locates, the stem 11 being slidable within the bore 15 when the valve closure member 10 moves relatively to the valve body 2. The boss 14 may be connected to the remainder of the valve body 2 by a plurality of arms 16 and the outlet 5 from the check valve 1 is preferably defined between those arms 16.

The face 17 of the head 12 of the valve closure member 10 which faces upstream of the check valve 1 has an aerodynamic configuration. That aerodynamic configuration is preferably of a symmetrical 'conical form which is slightly convex and terminates in a pointed tip 18 which lies on the axis 13 of the flow passage through the valve body. This convex conical configuration of the upstream face 17 of the valve closure member 10 forms an aerofoil shape for the valve closure member 10 and this shape affects the manner in which the valve closure member 10 operates when fluid is flowing through the check valve 1 as will be described in more detail herebelow.

The radially outer edge 19 of the head 12 of the valve closure member preferably has short cylindrical section 20.

The diameter of this cylindrical section 20 is substantially the same, although slightly smaller, than the diameter of the flow passage in order that the cylindrical section 20 is a sliding fit within the flow passage. When the valve closure member 10 moves into its closed position, the cylindrical section 20 locates just within the downstream end of the flow passage 3, and the radially outer edge 19 of the convex conical face 17 of the head 12 engages the valve seat 6 in order to form a seal therewith and thereby close the valve preventing return flow through the valve. The radially outer corner 21 of the downstream side of the head 12 of the valve closure member 10 is preferably bevelled to enhance the flow characteristics of the valve closure member 10.

The valve closure member 10 is preferably spring biased to its closed position. The spring 22 for providing that biasing force preferably comprises a compression coil spring which locates underneath the head 12 of the valve closure member and reacts between the underside 25 of the head and the boss 14. The boss 14, as previously mentioned, is cup-shaped and the mouth 23 of that cup shape faces towards the head 12 of the valve closure member. The compression spring 22 locates within the mouth 23 and is housed in the cup-shaped boss 14. The cup-shaped boss thus has a cylindrically shaped inner surface 24 which defines a containment for the compression spring 22 located therein.

It is preferred that the compression spring 22 has a relatively weak spring force so that the valve closure member 10 is able to move easily from its closed position to its open position.

The aerofoil configuration of the upstream face 17 of the valve closure member 10 curves from the outer diameter to the fine point 18 on the end of the valve closure member 10, that point lying on the axis 13. The configuration of the aerofoil face 17 is selected so that separation of flow of fluid through the valve occurs at a point well upstream of the valve and fluid thus flows over the valve closure member with a minimum of pressure differential on the surface of the closure member. The aerofoil curvature is selected to ensure that laminar or near laminar flow of fluid occurs as the fluid passes over the head of the closure member and the laminar flow continues past the cylindrical section of the closure member.

As flow of fluid continues past the head of the closure member shear of the laminar flow at the point downstream of the cylindrical section seeds a vortex formation behind and inwardly of the cylindrical section causing a low pressure area underneath the head 12 of the closure member 10. This low pressure area causes the valve closure member to move to a fully open position even at a very low flow rate through the valve. The ability to move to a fully open position is enhanced by the fact that the compression spring 22 selected for biasing the closure member 10 to its closed position has a relatively weak spring force.

In addition, the laminar flow of fluid over the closure member 10 allows the closure member to remain open and "fly" in the flow achieving dynamic stability within the flow without the need for rigid guides or vanes. Thus, when fluid is flowing through the valve, the valve closure member is suspended in its open position by the fluid pressure interacting with the different surfaces on the head 12 of the valve closure member, the fluid dynamics resulting in an equilibrium of fprces acting on the valve closure member. When flow through the flow passage 3 stops, the compression spring will urge the valve closure member to return to its closed position and thereby prevent return flow through the check valve 1.

Because the valve closure member 10 is able to "fly" and remain open due to its aerofoil form when fluid is flowing through the valve it can be made of a lightweight material and thus the compression spring 22 can be relatively weak. It will be appreciated that the simple arrangement of having the head 12 of aerodynamic form enables the check valve to be of simple construction and to operate efficiently without excess pressure drop across the valve. Also, because of the lightweight nature of the closure member or plunger and the spring the valve is easily able to move to its open position ensuring that no pressure buildup is allowed to occur upstream of the valve 1. The valve 1 can thus operate at very low flow rates.

It is preferred that both the valve body and the valve closure member are made from a plastics material and both components may be made using a suitable moulding process.

Claims

1. A check valve comprising a valve body, an inlet to the body and an outlet from the body, a flow passage through the body connecting the inlet to the outlet, a valve seat adjacent the flow passage, and a valve closure member movable relative to the valve seat between a closed position in which the closure member seals against the valve seat to close the flow passage and an open position in which fluid flow from the inlet to the outlet is possible, said valve closure member including a head of aerodynamic form which will allow fluid to flow through the flow passage past the head without creating undue turbulence in that fluid.

2. A check valve according to claim 1 wherein said valve closure member includes a stem projecting from said head in a direction away from said inlet, with a boss being supported on said body and said stem being slidably located in said boss.

3. A check valve according to claim 1 or claim 2 wherein said head is of conical form tapering divergently in a downstream direction.

4. A check valve according to claim 3 wherein the upstream face of the head is of convex shape.

5. A check valve according to any preceding claim wherein the valve closure member is spring biased towards the closed position

6. A check valve according to any preceding claim wherein the valve seat is of circular form, the axis of the valve seat being coincident with an axis of the flow passage, and the valve closure member being of circular cross-sectional form and being movable back and forth along the line of said coincident axes between said closed and open positions.

7. A check valve according to any preceding claim wherein said valve closure member is formed of a relatively rigid plastics material.

8. A check valve according to any preceding claim wherein said valve closure member is of a form such that when fluid flows through the valve from the inlet to the outlet, fluid forces acting on the closure member result in the closure member moving to an open position and remaining suspended in that open position as a result of the interactive effect of fluid pressure acting on different surfaces of the closure member.

9. A check valve substantially as hereinbefore described with reference to the accompanying drawings.