The invention relates to a variable air flow valve. More specifically, the invention relates to a valve that operates to enable variation of the flow- through volume capacity depending on the prevailing conditions and thus facilitate harraonisation in ventilation systems.

In ventilation systems the air pressure in ducting can vary over time and depending on location, e.g. as a consequence of differential flow through/into areas of ducting and aspects such as the distance and, particularly, the height between inlets, ducting sections and out let /expulsion points {such as extractor fans) or any point at which air is propelled. This may particularly be the case for multi-branch ventilation systems in which there may be an inter-dependency between zones, for example a roof-top extractor-fan ventilation system that serves rooms on each floor of a multi-storey building.

Variation in air pressure and air flow through ducting can lead to undesirable inconsistency in the volume of air passing through a valve over time, potentially leading to a sub-optimal ventilation environment which may be particularly acute for rooms that are vertically furthest removed from mechanical propellers/extractors. Thus, a fan situated on the roof of multi-storey building and extracting air from ventilation ducting on all floors will, other factors being equal, naturally draw more air from ducting that is nearer to it because less force is required, particularly with respect to vertical distance. Such factors can therefore make it comparatively more difficult to achieve the desired turnover of air in certain regions of multi-storey buildings, e.g. the lower floors, while other areas (higher floors) may be subject to higher rates of air flow than necessary. Given that ventilation is a specific aspect of building regulations this can give rise to difficulties for constructors and developers,

The present invention aims to address such shortcomirigs in vent i1at ion systems ,

According to an aspect of the present invention there is provided a variable air flow valve for controlling flow volume through a duct in a ventilation system, wherein the valve comprises a movable member for inhibiting fluid flow from the upstream side to the downstream side and a frame which comprises a seat bordering an opening for fluid flow through the valve, the movable member being movable with respect to the valve seat find being reversibly movable between an inhibitory position which at least partially obstructs the opening and a position which is proportionately less obstructive, and wherein the member is arranged to be propelled towards the inhibitory position under action of upstream fluid force against the valve, so that as flow rate through the valve varies the available flow path through the valve is adjusted.

It will be appreciated that the valve could theoretically be used with any liquid or gas and all are encompassed within the term, fluid. However the intended application of the invention is specifically in ventilation ducting in order to enable moderation of air flow in different parts of a ventilation system.

As elucidated below it will be appreciated that the movable member may optionally take a range of positions, for example depending on air flow strength. Further, though the position of the movable member may be indirectly influenced it is preferable that it is affected by fluid flow without there being intervening components. Conveniently the movable member is on the upstream side of the opening. The fluid flow opening may optionally be partially, more fully or even (essentially) completely obstructed by the movable member in the inhibitory position (as discussed further below) . Conveniently the inhibitory position is ad acent to the valve seat.

The valve seat defines the fluid flow opening and the movable member is arranged to naturally, when the valve is in use, take a position removed from the valve seat when there is no or relatively low air-flow against the valve, such that there is greater access to the opening (and hence room for fluid flow through the opening) when there is lower speed/force of fluid flow from the upstream direction. Accordingly, in use, the movable member is conveniently biased away from the inhibitory position. Conveniently the movable member is biased away from the val e seat by gravity when there is no or relatively low air-flow against it. When the valve is fitted in ducting the valve seat may hence preferably be at an inclined angle.

The invention allows for adjustment of fluid flow volume depending on the relative strength/ speed of fluid (air) flow upstream of the valve. Thus 'when there is sufficiently fast/strong air flow the movable member will close (such that it moves closer to the opening, e.g. becomes seated in the body of the valve), and so the passage of air across the valve will be restricted. Contrastingly, -when the pressure/speed of upstream. airflow is low (or absent) the movable member will be able to open (potentially solely due to gravity) , resulting in greater access to the opening and hence a greater opportunity for air/fluid to flow through the valve . I this way the i vention allows for automatic adjustment of air flow volume, improving system consistency. For example, if a valve according to the invention is used in ventilation ducting on a top floor (or floors) of a multi-storey building then the amount of air which may be drawn across the valve by a rooftop extractor could be reduced by the movable member acting to inhibit air flow, Consequently, with less air coming from, upper floors the extractor would hence be able to draw more air from lower floors than would otherwise nave been the case, thereby providing a more balanced air flow system by enabling greater turnover of air in parts of buildings which may otherwise be less well served. Due to its function of enabling differential fluid flow the invention could be used in many/all different areas of a building (e.g. higher and lower floors) but it is anticipated it may have greatest applicability to areas nearer to extractor systems. Further, as is discussed more below, valves of the invention may be developed to utilise an intermediate degree of flow inhibition, such that a movable member may, in use, not necessarily be intended to be completely 'open' or 'closed' ^' (in a binary fashion) with respect to a fluid-flow opening. Valve geometry could also mean that flow volume undulates as the movable member position/orientation progresses.

Conveniently the movable member is a flap.

It will be understood by a person skilled in the art that various aspects such as the size and weight of the movable member and its (e.g. hanging) position may all be modified and have an effect on the fluid flow capacity. Accordingly, movable members may optionally be specifically designed and/or selected for different systems, depending on their characteristics. This may be particularly the case for flaps.

Preferably the valve may comprise one or more airflow apertures which remain unobstructed by the movable member. In this way there may always be a minimum potential degree of fluid passage across the valve, even when the movable member is in the inhibitory position. Such airflow apertures may variously be part of /continuous with the area obstructed by the movable member (e.g. a flap or other movable member may have a smaller relevant surface area than the fluid flow opening which it obstructs), and/or may be separated from the area obstructed by the movable member. For example, the valve seat may border an unobstructed airflow aperture; the seat may define a fluid flow opening which is bigger than the (relevant dimensions of) the movable member and so cannot be completely obstructed by the movable member. Another option is for an aperture to be defined by another part of the valve frame, in which case optionally the fluid flow opening may potentially be more fully (or even essentially completely) obstructed by the movable member when in the inhibitory position.

As discussed further below, such airflow apertures may be adjustable and the movable member itself may optionally comprise one or more airflow apertures.

The movable member is preferably attached to the valve frame (another option may, for example, be to attach it in situ in ducting) . Optionally the movable member may be attached to the valve seat part of the valve frame. In this regard, it will be understood that depending on structure the valve frame and seat may optionally be thought of as synonymous.

One of the simplest designs may be to have a flap as the movable member. Preferably a flap may be pivotally mounted on the valve frame . Conveniently the flap may be hinged to the valve frame.

There is preferably at least an unobstructed airflow aperture adjacent to the opening (area) which is obstructed by the movable member, either separate to or continuous with the obstructed opening. As discussed elsewhere, such an aperture may be considered an unobstructed part of the opening obstructed by the movable member. Such an aperture may, for example, be above the flap or other movable member.

Conveniently the forward movement of the flap (or other movable member) may be restricted by abutting the valve seat (the valve frame around the opening) . Depending on the dimensions of the opening border the movable member may not necessarily contact the frame consistently at points adjacent to the frame and hence gaps may purposefully remain through which fluid may pass. For example, acting as a pendulum, a flap may potentially only contact the frame at the lowest point. Another option for limiting the forward movement of a flap may be to restrict the movement allowed by one or more pivot points.

One or more weights may be attached to the flap (or other movable member) in order to vary the relative air pressure needed to effect its displacement. Since the mass of applied weights could easily be varied this could be a convenient way of tailoring a valve for differing prevailing conditions. A convenient mode of attachment may be a screw or nut and bolt mechanism whereby one or more screws/bolts pass through holes in both the weight and the flap or other movable member.

The movable member may comprise one or more airflow apertures through which air may flow irrespective of the position of the movable member. Preferably an airflow aperture is adjustable whereby it may be closed, open and open to varying degrees. The movable member, e.g. a flap even when fully seated in the body of the valve, may thus optionally allow for a minimum relative degree of fluid passage as 'well as, conveniently, the variable adjustment of such a minimum. Equally, the size of any opening/airflow aperture on the valve may be adjustable. Conveniently an airflow aperture (and/or any opening) may be closable and openable to varying degrees by operation of a movable and/or extendable screen. A single screen may potentially operate to vary multiple airflow apertures. Conveniently such screens may be sliding screens and a screen itself may optionally comprise one or more airflow apertures . Accordingly the proportion of exposed airflow aperture may potentially be affected by (a) screen aperture (s) and the screen edges. Optionally a sliding screen may be attached to the flap by a flange which projects through a slot on the flap (at an angle of approximately 90 degrees to the flap) , and/or by a screw which passes through the flap and screen and secures the screen to the flap. Preferably the horizontal position of a screw may be varied by moving it along a slot in the flap. In this way the position of a screen, and hence the size of a flap airflow aperture, may conveniently be adjusted by use of a single screwdriver while the valve remains in situ in ducting .

To allow for a pivoting movement a flap may be hinged to the valve frame. There are a number of ways this may be achieved. For example, protrusions on either side of the flap may extend into holes in the valve frame. Another option may be to hinge the flap along its top to the frame.

It will be appreciated that a valve could comprise a plurality of movable members, valve seats and/or openings etc. For example, a valve may comprise a plurality of hinged flaps as discussed above. In this way the degree of regulation of fluid flow may be more nuanced , For example, depending on aspects such as flap size, weight and position, different flaps may be variously open or closed in different air speed conditions. Flaps may optionally be located on/within bigger flaps if desired. It is thought probable that the most convenient structure will be embodiments with a single movable member varying the availability of a single opening, however,

In use, the valve may be appropriately positioned in ducting (potentially at an incline) by virtue of its dimensions; it may be positioned by a push-fit. For example, frictional forces of the edges of the valve against one or more of the inside surfaces (e.g. top, bottom, either side) of the ducting may act to keep the valve in place. Valves of different sizes and shapes may thus be made for ducting of different dimensions. For example, a valve with rounded sides could be used for circular tubing. Further, a valve need not necessarily occupy all of the ducting cross-sectional area. One or more gaps between valve edges and ducting surfaces may optionally be used deliberately as a measure for helping to ensure there is always a minimum potential air flow through ducting.

A further approach to securing a valve in ducting may be to use a form of fixing, such as one or more clips. Also tape could be applied to the outside of the valve and used to adhere it and/or wedge it into position. Fixings may be used in conjunction with appropriate valve dimensions.

In addition to or instead of the approaches discussed above a valve may be fitted into ducting using an adaptor, which optionally could be integrated as part of the valve. Such an adaptor may itself variably permit /obstruct fluid flow.

A further approach to using the valve could be to integrate it into ducting, e.g. such that the outside of the valve forms part of the piping conveying fluid.

Instead of necessarily being within ducting the valve could similarly be attached to or incorporated into a ventilation grille. The approaches for ducting discussed above may equally apply to association with ventilation grilles.

A movable member may be biased away from a valve opening using gravity. Alternatively or in addition to gravity the valve may comprise biasing means for displacing one or more movable members . For example, components such as o e or more springs and/or magnets may be used. Accordingly, the valve may comprise a spring which biases the (or a) movable member towards remaining open. In this way the relative force needed to reduce fluid flow may potentially be increased since the fluid flow against the movable member would nave to be strong enough to compress the spring. Thus use of a spring may enable more appropriate flow regulation in varying circumstances. As an example, one end of a spring may be connected to the downstream side of a flap. This could be direct or may be via an additional component or components such as a rod. The spring may conveniently be connected to one edge of the flap and to facilitate this a nook may be formed in the side of the valve frame seat by 'which the spring or connecting component passes .

The other end of the spring, that further away from the flap, may be supported by being attached to ducting in situ. Another option would be for the rear end of the spring to be attached to the valve frame, for example using a rearwardly projected support / ^' platform.

Optionally, instead of (or in addition to) a spring, magnets could be used in a similar manner . Thus, one magnet could be positioned behind the flap. As discussed above with respect to the spring, it may be attached to ducti g in situ or to a rearward valve component such as the end of a rod. Another magnet may be connected directly or indirectly, e.g. via a rod, to the flap. In this way the natural inter-repellence of the magnets can operate to bias the flap to remain open. As for a spring, the extra influence of the repellent forces of magnets may allow for different resistance levels in differing conditions.

It villi be appreciated that embodiments of the invention using means such as magnets and/or a spring (s) may be configured to operate with or without gravity acting to open the movable member. For example, a valve could be positioned vertically such that a flap; would not naturally hang open; instead the biasing towards an open position in low air flow conditions may be dependent only upon the action of the spring, magnets or other appropriate means.

Preferably the valve may be made of a metallic material . Metal can create less static than other- materials and so may not attract particulate matter such as dust to such a high degree.

According to another aspect of the present invention there is provided an assembly of ducting comprising a valve as disclosed herein. Preferably the ducting is ventilation ducting.

In use, the valve may be appropriately positioned in ducting {at an inclined angle) by virtue of its dimensions. For example, frictional forces of the edges of the valve against one or more of the inside surfaces (e.g. top, bottom, either side) of the ducting may act to keep the valve in place. Valves of different sizes and shapes may thus be made for ducting of different dimensions. For example, a valve with more rounded sides could optionally be used for circular tubing.

Further, a valve need not necessarily occupy all of the ducting cross-sectional area. One or more gaps between valve edges and ducting surfaces may optionally be used deliberately as a measure for helping to ensure there is always a minimum potential air flow through ducting . A further approach to securing a valve in ducting may be to use a form of fixing, such as one or more clips. Fixings may be used in conjunction with appropriate valve dimensions.

Other options for fitting/integrating a valve in ducting are discussed elsewhere and it will be appreciated that they may apply to all aspects of the invention .

According to another aspect of the present invention there is provided a ventilation system, comprising one or more valves and/or ducting assemblies as disclosed herein. The use of valves according to the invention allows the flow rates of air in different parts of a system to be better balanced,

It will be understood that any valve embodiment as disclosed herein may be installed in ducting and/or used in a ventilation system. A ventilation system according to the invention may comprise a fan, a plurality of ducts and one or more valves as disclosed herein, the valve or valves being located to enhance balancing of the relative air flow in different parts of the system.

An embodiment of the invention will now be described with reference to the accompanying drawings, of which:

Figure 1 shows an embodiment of the invention from a front-on view in situ.

Figure 2 s ows a side-on view of the embodiment of Figure 1 with certain ducting walls omitted for clarity.

Figure 3 shows a rear-angled view of an embodiment of the invention with ducting walls omitted for c1ar ity ,

Figure 4 shows a rear-angled view of another embodiment of the present invention, again with ducting walls omitted for clarity. Figure 5 shows {photographically) a preferred tubular embodiment of the present invention.

Figure 6 shows a graph indicating how air flow across, in litres per second, varies across a valve such as that indicated in Figure 5 as the air pressure { in Pasca1 s ) against the f1ap increases.

Figure 7 indicates the relative positioning of the flap at the corresponding points annotated on the Figure 6 graph.

Figure 8 s ows another representation of the embodiment of Figure 5 with different shading/highlighting to enhance clarity of some features .

As may be seen in Figures 1 to 3, a valve 1 has a movable member which in this case is a flap 2 which, when closed, covers fluid flow opening 3 that is defined by valve seat 21 of frame 22. The flap is hinged to the valve frame 22 such that it is able to move with respect to other parts of the valve under the influence of gravity. The valve is positioned diagonally (inclined) in ducting 4 such that under low {or no) air flow conditions the flap naturally hangs open towards the upstream direction. The relative dimensions of the valve and the ducting mean there is a frictional force with respect to the top/bottom/sides of the ducting keeping the valve in position.

The indicative passage of air through the valve is represented by large open-headed arrows (see Figure 2) . Thus, as may be seen, when there is low ambient air speed/force there would be little pressure against the flap and so it would hang open. Air could thus flow around the flap and through opening 3. In circumstances of faster/stronger air flow, however, there would be greater force against the flap which may then be closed, preventing air flowing through opening 3. For this embodiment the closure of the flap cannot prohibit all air flow, however, since the valve also comprises a second opening, airflow aperture 5, 'which has no obstruction. Further, in different embodiments flaps optionally may (see Figures 1, 2, 5 and 8) or may not {see Figures 3 and 4) comprise one or more window openings, see airflow apertures 6, 6a and 6b, which may be closed, opened and the size of which may be adjusted by variable positioning of screen 7. By allowing air to flow through the flap, having an aperture on the flap may increase both the air speed/force needed to close the flap and the minimal volume of air that would flow across the valve when the flap is closed. In relevant examples the position of screen 7 may hence be determined by particular conditions where the valve is to be used.

Figure 4 shows another embodiment of the present invention. In this embodiment, biasing of the flap movable member to resist closure is enhanced by the use of a spring 8 connected to the flap. The spring is connected to the flap by means of a rod 9. At one end of rod 9 is a disc 10 to 'which the spring is secured. The other end of rod fits into a socket 11 on one side of the flap. Another option would be to screw the rod to the flap. The other end of the spring {that distal from the flap) is secured to a platform 12 that projects inward from the side of the ducting. A nook 13 in the valve seat 21 ensures that movement of the rod is not hindered by the valve frame 22.

As above, when there is low ambient air speed/force there would be little pressure against the flap and so it would hang open. Air could thus flow around the flap and through the opening. In circumstances of faster/stronger air flow, however, there would be greater force against the flap which, if it is sufficient to affect both the flap and to depress the spring, may then be closed, preventing air flowing through the opening. Again, the closure of the flap cannot p ohibit all air flow, however, since the valve also comprises a second opening, airflow aperture 5, above the flap which has no obstruction,

A preferred tubular embodiment of the invention is shown in Figures 5 and 8, In this embodiment a frame 14 comprises a valve seat 15 in the form of a circumferential border that defines the opening 3. In this instance the valve seat part of the valve frame is clipped into the external tubular casing component of the frame (see e.g. notches on the top of the valve in Figures 5 and 8) .

In this example the movable member, here a flap 2, has two distinct window areas, airflow apertures 6a and 6b, separated by a division 16 in the flap. Towards the top of the flap is a slot 17 through which a flange 23 of sliding screen 7 projects. There is a window opening, airflow aperture 18, in the sliding screen which can be set to align to a varying degree with one or more corresponding apertures in the flap. In this instance opening 18 exposes 6b and the side of the screen defines the edge of 6a (see Figure 8) . The position of the screen may be varied by unscrewing screw 19 (from the reverse side to that shown in Figure 5), moving it along a slot (not shown) in the flap and then tightening it again. During adjustment the screen position may be supported by the flange 23 in the slot 17, facilitating one-handed adjustment of the window opening (s) . This may be advantageous when the valve is mounted in ducting behind a ventilation grille.

In this example the flap 2 is hinged to the valve frame 14 by lateral projections 20 extending through holes in the casing. The flap pivots about these points. Further, in this example it may be seen that airflow aperture 25 is continuous with the opening 3 instead of being discrete from it . It may thus be considered a part of opening 3 which cannot be obstructed by the flap 2 due to the relative dimensions of the flap.

The variation of air flow rate (in litres per second) across a valve such as that indicated in Figure 5 is shown, relative to the air pressure (in Pascals) upstream of the valve, in the graph of Figure 6. Further, Figure 7 indicates the relative position of the flap at the indicated different levels of air pressure in Figure 6.

As may be seen, the relationship between flow rate and air pressure is not universally linear, and the trend of flow rate variation changes (both increases and decreases at different times) as the flap moves from position I (which may be considered fully ''open) to position V {which may be considered fully closed) . The following descriptions represent what is considered to be taking place in the different positional zones: Zone 1 to 2; The flap is held in a vertical position by gravity, with weight greater at the base of the flap creating a pendulum. The air flowing past will mainly be laminar with a gentle swirl as the natural elasticity of air curves around the flap and through the space around the flap and between the valve seat /frame.

Zone 2 to 3; The flap position is elevated towards the valve opening with the weight of the flap impacting on the force of the flowing air. Turbulence of air hits critical point, the 'weight of the flap against the incoming air through the valve seat disrupting the elastic flow, causing turbulence that in itself increases the resistance of air flow.

Zone 3 to 4; Flap position is elevated towards the valve with the weight of the valve flap increasingly impacting on the force of the flowing air. The increasing pressure in these turbulent conditions gives a proportional response, providing a linear volume delivery of air against increasing or decreasing pressure .

Zone 4 to 5; Flap position against valve seat with weight of the flap being held by the force of the flowing air. All air flow is now going through predefined opening with little or no air going through the rest of the valve. The volume of air flow is now dictated by the size of the opening and the resistance that is caused through compression (Boyle's law) as it passes through the remaining orifice.

It may potentially be that the target position for the flap is to sit between positions III and IV in order to be in the more linear zone. Ventilation system characteristics {for example fan air pressure flow, length and/or depth of ducting) may hence be profiled accordingly .