GB1590945A - Non-return valve - Google Patents

Description

(54) NON-RETURN VALVE (71) We, UNIVERSITY COURT OF THE UNIVERSITY OF EDINBURGH, incorporated under the Universities (Scotland) Act 1889, of Old College, South Bridge, Edinburgh EH8 9YL, Scotland, do hereby declare the inven- tion, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to an improved fluid control valve and in particular to a nonreturn flap valve of the kind comprising a seating defined within a valve duct and seating obturating means turnably mounted in the duct to move to and from a closed position in which it seals to the seating in the duct.

In the specifications of U.K. Patents 1327371 and 1447871 there are described fluid flow control valves of the same general kind to which this invention relates these previously-described valves being primarily intended for the control of body fluids (e.g.

as an artificial heart valve) but which have wider applications in commerce or industry.

The obturating means used in valves of the kind described in the earlier-mentioned U.K.

specifications can be expensive to produce and although the cost of production is acceptable in the case of precision equipment like a heart valve it may not be acceptable in the case of industrial valves particularly where the call is for a range of valves of different sizes (and thus the need for the construction of a range of obturating means of different sizes).

The design of the control valves described in the aforementioned patent specifications becomes less suitable where the fluid flow to be controlled contains suspended solids. With the designs described in the afore-mentioned specifications, the clearances between the obturating means and the valve duct increase only gradually as the obturating means moves away from its closed position so that, in practice, these designs are only suitable where there is no solid phase material in the flow medium.

This invention relates to an improved form of fluid control valve which although operating in broadly the manner described in the aforementioned specifications and in particular having a low flow resistance and a flow passage which is unobstructed by protrusions at the valve duct wall, gives rise to a design of valve which is more suitable for industrial applications particularly where the flow medium to be controlled contains solid phase particles.

According to the invention a non-return flap valve comprises an apertured seating, seating obturating means disposed to move about a turn-axis to and from a closed position, in which closed position the obturating means substantially completely fills the aperture of the seating with an annular region of the obturating means contacting the seating, the turn axis being spaced from the closest chord of the annular region which is normal to the turn axis by an amount which is not less than 5% of the length of the said closest chord, which axis is off-set from the longest chord of the annular region which is normal to said closest chord whereby the obturating member will turn from the closed position on the appearance of a sufficient pressure difference across it, the obturating member including or being connected to a lift generator which generates, from medium flowing through the aperture of the seating, a turning moment which acts on the obturating member to urge the latter away from the closed position.

Conveniently the seating forms a frustoconical duct, the turn axis then being located on the side of the closest chord which is towards the broad end of the frusto-conical duct. In the case of a frusto-conical duct, the turn axis has to be located within the triangular space defined in the longitudinal plane of the duct which contains said closest chord, the shape being defined between the normal to the duct wall from one end of the closest chord, that duct wall, and the extension of the normal from the duct wall at the other end of the closest chord.

The obturating means can be a circular (or elliptical) plate which conveniently is of slight concave shape on the side facing towards the flow direction. The obturating means can be made of any convenient material which will naturally be chosen having regard to its working environment (e.g.

temperature and chemical composition of the flow medium).

The spacing of the turn axis from the closest chord will control the rate at which the clearance around the obturating means increases as the latter turns from the closed position and spacings in the range 10 to 20% of the length of the closest chord would be typical.

The lift generator can be a member of generally aerofoil cross-section attached to the obturating means (conveniently on the side which is "downstream" having regard to normal fluid flow through the valve).

Embodiments of non-return flap valve in accordance with this invention will now be described, by way of example, with reference to the drawing accompanying the provisional specification, in which: Figure 1 is a partially sectioned perspective view of a first valve shown in the closed position and Figure 2 is a section on the line II--II of Figure 1. and the accompanying drawing, in which Figure 3 is a partially sectioned perspective view of a second valve shown in the closed position.

The valve illustrated in Figures 1 and 2 comprises a housing 1 which defines a frustoconical passage 2 extending between plane sealing faces la and ib. The housing is bored with holes 3 to enable it to be clamped between duct parts (not shown) which define the path of a fluid medium through the housing.

Turnably mounted within the housing 1 and supported between spaced-apart screw 4a and 4b is an obturating means 5 and a lift generator 6.

The obturating means 5 defines the cap of a hollow sphere, an annular region 5a thereof providing the seal against the passage 2 when the valve is in the closed position. The line 5b shown in Figure 2 represents the chord of the region 5a which is closest and normal to the turn axis defined by the screws 4a and 4b and it will be seen from Figure 2 that this is spaced from the turn axis by a distance x. In the embodiment shown x is 15% of the length of the closest chord 5b and this off-setting of the turn axis from the obturating means ensures a more rapid opening of the clearances between the annular region Sa and the passage 2 as the obturating means moves away from its closed position.

The lift generator is shown as a circular disc of general aerofoil cross-section and is spaced from the obturating means 5 by pillars 7.

By separating the obturating means and the lift generator in the manner shown, the cost of producing the obturating means can be dramatically reduced and the same lift generator can be used for a variety of different valve sizes. Although a disc of general aerofoil section has been shown for the lift generator 6 in the illustrated embodiment, it will be appreciated that a wide variety of different lift generators can be used. In the simplest case a strip of suitably bent metal can be disposed on one side of the obturating means, its purpose merely being to maintain the obturating means away from the closed position as flow of medium through the passage 2 builds up following initial movement of the obturating means 5 from its closed position.

An important additional advantage of separating the obturating means and the lift generator is that the lift generator can be of simpler form because the position of the centre of lift need not here be close to the axis of symmetry.

Valves of the kind illustrated are suitable in a wide range of different sizes to 450 mm in diameter and beyond.

In the case of a frusto-conical duct is is important that the turn axis be located in the area "A" shown shaded in Figure 2, this area beng defined in a longitudinal plane of the passage 2 which includes the closest chord 5b and is defined between the normal (extended) to the duct from one end of the chord 5b, the normal to the duct from the other end of the chord 5b and the duct wall. As can be seen from Figure 2, the boundary of the area "A" diverges from the normals to the ends of the chord 5b at distances from the point X in Figure 2.The precise shape of the area "A" is difficult to compute but guidance as to the method used can be obtained from an article entitled "The Geometry of Smooth Bore Non-Return Valves for Controlling Blood Flow" by Norman Maclead published on pages 98-110 of "Mechanisms 1971" the proceeedings of a one day sumposium of the mechanics group of the Institute of Mechanical Engineers. It will be appreciated that if the turn axis is located in the area "A" it is displaced to one side of the longest chord which is normal to the closest chord 5b, this longest chord lying in a longitudinal plane of the duct normal to the line 5b which passes through the point X in Figure 2.

Figure 2 shows the flow direction with the arrow Y and the fully open position of the valve in dash lines.

The passageway 2 need not be of frustoconical form but where it is, semi-angles in the range 15 to 25 are preferred.

Figure 3 shows a slightly modified embodiment of valve which is particularly suited to the manufacture of valves having a cross sectional size of 150 mm and above and provides the following features: (a) a positive stop, limiting the opening movement of the obturating means 5; (b) a counterpoised obturating means 5, closing automatically under gravity; and (c) freedom for the obturating means 5 in its closed position to seat positively under the action of back-pressure.

The valve shown in Figure 3 is intended for horizontal mounting. The obturating means 5 is part of a spherical shell of relatively thin gauge material which is mounted rigidly on a cylindrical shank 8, attached normally to the geometrical centre of the means 5. The shank 8 is a sliding fit in a tubular guide 9 which is fixed to a concavo-convex lift generator 6 of aerofoil cross-section, The generator 6 is journalled on trunnions or bearing supports, of which only one 4a is shown in Figure 3.

The trunnions define a turn axis (shown dotted), chordal to the generator 6, about which the generator 6 can rotate freely. The turn axis is at right angles to, and is placed from, the centre line of the axis of symmetry of the flow-channel (which axis coincides with that of the frusto-conical seating 2). The position of the turn axis relative to the vertex of the frusto-conical seating 2 is determined in accordance with the geometrical principles given in the paper from "Mechanisms 1971 previously discussed. The assembly comprises ing integers 5, 6, 8 and 9 can rotate about the turn axis under the influence of an excess fluid pressure acting on the concave side of 5.

The frusto-conical edge of integer 5 moves freely out of engagement with the seating by this rotation even though 5 and 2 are in perfect coincidence at the commencement of this motion (as is explained in the reference cited above).

As this rotation proceeds, the angle between 5 (and 6) and the flow direction diminishes, and the members 5 and 6 tend towards alignment with ffe flow. The rotation is initiated by static fluid pressure forces whose resultant acts through the centre of the obturating means 5 and therefore gives rise to a turning moment about the turn axis. The alignment of the means 5 with the stream continues under the action of drag forces, and is completed by the joint action of forces of drag and lift. In particular, the lift force on the generator 6 acts through a point which, though relatively near the forward stagnation point for an aerofoil of this simple symmetrical shape, lies downstream of the turn axis.

Consequently, the torque about the turn axis due to this can rotate integers 5 and 6 into full alignment with the flow.

The rotation of the moving assembly in the valve of Figure 3 is positively limited when the head 8a of the shank 8 comes into contact with the tip of a cylindrical peg or stop 10 fixed in the wall of the flow channel. A short compression spring (not shown) interposed at 11 between the enlarged head 8a and the end of the guide 9 buffers the shock of this arrest of the final phase of the opening motion due to the lift generator 6.

When the valve is used with the flow axis and the turn axis both horizontal, the gravitational turning moment due to the weight of that part of the shank 8 shown lying to the right of the generator 6 in Figure 3 is arranged slightly to exceed that due to the weight of the means 5 and that part of the shank 8 lying between 5 and 6. The shank 8 can be drilled out (as shown at 8b in Figure 3) to give the desired out-of-balance arrangement. The entire assembly pivoted about the turn axis thus tends to assume the position shown in Figure 3 as soon as forward flow ceases. The attainment of this closed position is accelerated by fluid forces generated on flow reversal.

Closure of the valve is therefore rapid and consequently relatively free from the shock associated with the eventual abrupt destruction of fluid kinetic energy attained during a prolonged phase of back flow.

After the valve has attained the closed position, the obturating means 5 is pushed firmly into leak-tight engagement with its seating 2, against the force of the spring at 11, by the fluid back-pressure acting on the convex face of the means 5.

Although Figures 1 and 3 show pointed screws defining the turn axis, it should be realised that pairs of cross-spring flexure mechanisms can replace the pivot points.

WHAT WE CLAIM IS: 1. A non-return flap valve comprising an apertured seating, seating obturating means disposed to moe about a turn-axis to and from a closed position, in which closed position the obturating means substantially completely fills the aperture of the seating with an annular region of the obturating means contacting the seating, the turn axis being spaced from the closest chord of the annular region which is normal to the turn axis by an amount which is not less than 5% of the length of the said closest chord, which axis is off-set from the longest chord of the annular region which is normal to said closest chord whereby the obturating member will turn from the closed position on the appearance of a sufficient pressure difference across it, the obturating member including or being connected to a lift generator which generates, from medium flowing through the aperture of the seating, a turning moment which acts on the obturating member to urge the latter away from the closed position.

2. A flap valve as claimed in claim 1, in which the seating forms a frusto-conical duct with the turn axis located on the side of the closest chord which is towards the broad end of the frusto-conical duct.

3. A flap valve as claimed in claim 2, in which the turn axis is located within the

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (12)

1. **WARNING** start of CLMS field may overlap end of DESC **.

   (a) a positive stop, limiting the opening movement of the obturating means 5; (b) a counterpoised obturating means 5, closing automatically under gravity; and (c) freedom for the obturating means 5 in its closed position to seat positively under the action of back-pressure.

   The valve shown in Figure 3 is intended for horizontal mounting. The obturating means 5 is part of a spherical shell of relatively thin gauge material which is mounted rigidly on a cylindrical shank 8, attached normally to the geometrical centre of the means 5. The shank 8 is a sliding fit in a tubular guide 9 which is fixed to a concavo-convex lift generator 6 of aerofoil cross-section, The generator 6 is journalled on trunnions or bearing supports, of which only one 4a is shown in Figure 3.

   The trunnions define a turn axis (shown dotted), chordal to the generator 6, about which the generator 6 can rotate freely. The turn axis is at right angles to, and is placed from, the centre line of the axis of symmetry of the flow-channel (which axis coincides with that of the frusto-conical seating 2). The position of the turn axis relative to the vertex of the frusto-conical seating 2 is determined in accordance with the geometrical principles given in the paper from "Mechanisms 1971 previously discussed. The assembly comprises ing integers 5, 6, 8 and 9 can rotate about the turn axis under the influence of an excess fluid pressure acting on the concave side of 5.

   The frusto-conical edge of integer 5 moves freely out of engagement with the seating by this rotation even though 5 and 2 are in perfect coincidence at the commencement of this motion (as is explained in the reference cited above).

   As this rotation proceeds, the angle between 5 (and 6) and the flow direction diminishes, and the members 5 and 6 tend towards alignment with ffe flow. The rotation is initiated by static fluid pressure forces whose resultant acts through the centre of the obturating means 5 and therefore gives rise to a turning moment about the turn axis. The alignment of the means 5 with the stream continues under the action of drag forces, and is completed by the joint action of forces of drag and lift. In particular, the lift force on the generator 6 acts through a point which, though relatively near the forward stagnation point for an aerofoil of this simple symmetrical shape, lies downstream of the turn axis.

   Consequently, the torque about the turn axis due to this can rotate integers 5 and 6 into full alignment with the flow.

   The rotation of the moving assembly in the valve of Figure 3 is positively limited when the head 8a of the shank 8 comes into contact with the tip of a cylindrical peg or stop 10 fixed in the wall of the flow channel. A short compression spring (not shown) interposed at

   11 between the enlarged head 8a and the end of the guide 9 buffers the shock of this arrest of the final phase of the opening motion due to the lift generator 6.

   When the valve is used with the flow axis and the turn axis both horizontal, the gravitational turning moment due to the weight of that part of the shank 8 shown lying to the right of the generator 6 in Figure 3 is arranged slightly to exceed that due to the weight of the means 5 and that part of the shank 8 lying between 5 and 6. The shank 8 can be drilled out (as shown at 8b in Figure 3) to give the desired out-of-balance arrangement. The entire assembly pivoted about the turn axis thus tends to assume the position shown in Figure 3 as soon as forward flow ceases. The attainment of this closed position is accelerated by fluid forces generated on flow reversal.

   Closure of the valve is therefore rapid and consequently relatively free from the shock associated with the eventual abrupt destruction of fluid kinetic energy attained during a prolonged phase of back flow.

   After the valve has attained the closed position, the obturating means 5 is pushed firmly into leak-tight engagement with its seating 2, against the force of the spring at 11, by the fluid back-pressure acting on the convex face of the means 5.

   Although Figures 1 and 3 show pointed screws defining the turn axis, it should be realised that pairs of cross-spring flexure mechanisms can replace the pivot points.

   WHAT WE CLAIM IS: 1. A non-return flap valve comprising an apertured seating, seating obturating means disposed to moe about a turn-axis to and from a closed position, in which closed position the obturating means substantially completely fills the aperture of the seating with an annular region of the obturating means contacting the seating, the turn axis being spaced from the closest chord of the annular region which is normal to the turn axis by an amount which is not less than 5% of the length of the said closest chord, which axis is off-set from the longest chord of the annular region which is normal to said closest chord whereby the obturating member will turn from the closed position on the appearance of a sufficient pressure difference across it, the obturating member including or being connected to a lift generator which generates, from medium flowing through the aperture of the seating, a turning moment which acts on the obturating member to urge the latter away from the closed position.
2. 2. A flap valve as claimed in claim 1, in which the seating forms a frusto-conical duct with the turn axis located on the side of the closest chord which is towards the broad end of the frusto-conical duct.
3. 3. A flap valve as claimed in claim 2, in which the turn axis is located within the

   triangular shape defined in the longitudinal plane of the duct which contains said closest chord, the shape being defined between the normal to the duct wall from one end of the closest chord, that duct wall, and the extension of the normal from the duct wall at the other end of the closest chord.
4. 4. A flap valve as claimed in any preceding claim, in which the obturating means is a plate of concave shape on the side facing towards the flow direction.
5. 5. A flap valve as claimed in any preceding claim, in which the spacing of the turn axis from the closest chord is in the range 10 to 20% of the length of the closest chord.
6. 6. A flap valve as claimed in any preceding claim, in which the lift generator is a member of aerofoil shape attached to the obturating means on the side which is downstream having regard to the flow direction.
7. 7. A flap valve as claimed in claim 6, in which the obturating means is connected to the lift generator by a connection permitting the spacing, in the flow direction, between the obturating means in its closed position and the lift generator to be varied.
8. 8. A flap valve as claimed in claim 7, in which the connection comprises a shank slidably received in a tubular guide.
9. 9. A flap valve as claimed in claim 8, in which the shank is attached to the obturating means and the tubular guide to the lift generator, a spring being disposed between the guide and the shank to urge the obturating means towards the lift generator.
10. 10. A flap valve as claimed in any previous claim dependent on claim 2, in which the semi-angle of the frusto-conical duct is in the range 15 to 25".
11. 11. A flap valve substantially as hereinbefore described with reference to and as illustrated in Figures 1 and 2 of the drawings.
12. 12. A flap valve substantially as hereinbefore described with reference to and as illustrated in Figure 3 of the drawings.