Abstract:
A one-way valve includes a plate and a flexible vane. The plate has a vent opening of a first size and shape. The plate has a first curvature. The flexible vane has a second curvature distinct from the first curvature. The vane is fixed to the plate in a manner facilitating the deflection of the vane between an open position and a closed position. The vane is in a bent condition in the closed position. The vane conforms to the first curvature of the plate over the vent opening, and covers the vent opening in the closed position. The vane is elastic throughout a range of deflection associated with the vane moving between the closed position and the open position.

Description:
This application claims the benefit of U.S. Provisional Application No. 60/136,469 filed May 28, 1999. 
    
    
     FIELD OF THE INVENTION 
     The invention is directed to one-way anti-back flow valves, and more particularly to anti-backflow valves suited for use as passenger vehicle cabin exhaust valves. 
     BACKGROUND OF THE INVENTION 
     One-way or anti-back flow valves are used in many different applications and have many different forms. One such application is as a valve for preventing the back flow of air, into passenger vehicle cabins. The valve both seals the cabin against the entry of poisonous fumes and the like, and vents the cabin to prevent or relieve an undesired increase of pressure therein. Such pressure increases can be caused by the operation of the heating, ventilating and air conditioning system, or by the slamming of a door of a vehicle when all of the windows are rolled up. Valves designed to serve as cabin air exhausters must both seal against back pressure, permitting very little air to leak into the cabin, and must open at very low cabin pressure to prevent or quickly reduce any significant increase in cabin pressure. Standards for acceptable flow rates are established by automotive companies. 
     Cabin air exhausters are typically spring or gravity operated flapper valves, with the flapper being formed of a relative soft rubber or rubber-like material. The flappers are hinged along a top edge in some manner, and hang vertically responsive to gravity. Back pressure tends to force the flappers against the supporting plate. Elevated cabin pressure pushes the flapper away from the plate, allowing cabin air to escape. One problem with such valves is that the desired level of sealing is difficult to consistently achieve. A limitation of valves relying exclusively on gravity to close is that gravity biased valves are sensitive to orientation. The valves must typically be oriented in an upright position on a vertical surface to operate. Another concern is that the flapper may flutter, creating undesired noise when open when air is passing through at a high rate of flow. If a spring is used to provide a more positive closing of the flapper than is possible with gravity, the cabin pressure needed to initiate exhausting will be undesirably increased. 
     It is desired to provide a one way valve which seals effectively against back flow from a first side while opening at relatively low positive pressures on the second side independent of orientation. 
     SUMMARY OF THE INVENTION 
     A one-way valve includes a plate and a flexible vane. The plate has a vent opening of a first size and shape. The plate has a first curvature. The flexible vane has a second curvature distinct from the first curvature. The vane is fixed to the plate in a manner facilitating the deflection of the vane between an open position and a closed position. The vane is in a bent condition in the closed position. The vane conforms to the first curvature of the plate over the vent opening, and covers the vent opening in the closed position. The vane is elastic throughout a range of deflection associated with the vane moving between the closed position and the open position. 
     A one-way valve includes a plate and a flexible vane. The plate has a vent opening of a first size and shape. The plate has a first curvature. The flexible vane has a second curvature distinct from the first curvature. The vane is fixed to the plate by a tab extending from a side of the vane. The vane is in a bent condition in a closed position. The vane covers the vent opening in the closed position. The vane conforms to the first curvature of the plate over the vent opening and covers the vent opening in the closed position. The vane is elastic throughout a range of deflection between the closed position and an open position. The tab is formed integral and unitary with the vane wherein the tab is a living hinge about which the vane pivots between the open position and the closed position. 
     A one-way valve includes a concave plate, a flexible vane, and a means for attaching. The concave plate has a vent opening of a first size and shape. The flexible vane has a substantially flat shape in a free state. The vane covers the opening. The vane is sufficiently flexible that it conforms to a curvature of the plate in a closed position. The vane is elastic throughout a range of deflection between the closed position and the open position. The vane is sufficiently stiff to develop a desired sealing load when forced to conform to the concave plate. The means for attaching is for attaching the flexible vane to the concave plate and enables the desired deflection of the vane between the open position and the closed position. 
     A one-way valve is provided which seals effectively against back flow from a first side while opening at relatively low positive pressures on the second side independent of orientation. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a plan view of a first embodiment of a one-way anti-backflow valve in the closed condition. 
     FIG. 2 is an elevational view of the valve of FIG.  1 . 
     FIG. 3 is a plan view of the valve of FIG. 1 in a low pressure exhaust mode. 
     FIG. 4 is an elevational view of the valve of FIG.  3 . 
     FIG. 5 is a plan view of the valve of FIG. 1 in a high pressure exhaust mode. 
     FIG. 6 is an elevational view of the valve of FIG.  5 . 
     FIG. 7 is a plan view of a second embodiment of a one-way anti-backflow valve in a closed condition. 
     FIG. 8 is an elevational view of the valve of FIG.  7 . 
     FIG. 9 is a plan view of the valve of FIG. 7 in a low-pressure exhaust mode. 
     FIG. 10 is an elevational view of a valve of FIG.  9 . 
     FIG. 11 is a plan view of the valve of FIG. 7 in a high-pressure exhaust mode. 
     FIG. 12 is an elevational view of the valve of FIG.  11 . 
     FIG. 13 is a plan view of a third embodiment of a one-way anti-backflow valve in a closed condition. 
     FIG. 14 is an elevational view of the valve of FIG. 13 in a high-pressure exhaust mode. 
     FIG. 15 is a side elevational view of the valve of FIG. 14 in the direction of arrow  15 . 
     FIG. 16 is a schematic diagram of a system employing the inventive valve. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     FIG. 1-5 shows a first embodiment of an inventive valve  10 . Valve  10  can be used variously as a cabin exhaust valve, a pressure relief valve, an all purpose air exhauster valve, a check valve, an anti-backflow valve, a vane valve or flapper valve. 
     Vane or flapper  12  is mounted to a plate  14 . Plate  14  is rigid and can be formed out of any appropriate material, including steel or plastic. Vane  12  is cut from a thin sheet of material to enhance the vane&#39;s flexibility, or ability to bend. Vane  12  must be made of material sufficiently elastic so that when bent or deflected to the degree anticipated, vane  12  returns to its previous undeflected condition. Vane  12  must be formed of material that also has a sufficiently high modulus of elasticity or stiffness to generate the desired sealing loads when it is bent or bowed. Mylar® polyester film of 0.003 to 0.005 inches (0.08 to 0.13 mm) thick has been successfully employed in testing. Polycarbonate film is an alternative material for the vane. It is preferred that the film have a coefficient of thermal expansion the same or nearly the same as the material chosen for the plate. If plate  14  is formed of talc-filled polypropylene, then polycarbonate film is best suited for the vane material. If the plate is steel, polyester film is the preferred vane material because its coefficient of thermal expansion is relatively close to that of steel. For many applications, it is preferred that plate  14  be formed of a material which is paintable. It is possible to employ plate and vane materials with mismatched coefficients of thermal expansion, so long as vane  12  is connected with plate  14  by a means that accommodates the relative expansion and contraction. 
     It is also preferable that the vane material be temperature stabilized so that it does not distort with temperature changes. Temperature stabilization is particularly important for valves that are going to be used in applications exposing the valves to a wide range of temperatures. 
     Valve plate  14  is curved about an axis of curvature  16  which extends parallel to plate  14  and about which plate  14  is curved. Vane  12  is fixed to a vane side  18  of plate  14  which is the same side on which axis  16  is disposed. Valve plate  14  has a valve opening  20  passing therethrough. Vane  12  is shaped to cover valve opening  20 . Valve opening  20  may be divided by one or more support ribs  21 . Ribs  21  help support vane  12  when valve  10  is subjected to back pressure, preventing vane  12  from being pushed through opening  20 . The need for, the number of and the size of ribs  21  varies with the size of opening  20  and the stiffness of vane  12 . 
     Vane  12  has two vane mounting tabs  22  formed from the same sheet of material as vane  12  which are fixed or bonded to valve plate  14 . Samples tested to date have had tabs  22  adhesively bonded to the plate, but other means of retention, such as rivets, screws, or clips could be used. Tabs  22  could be heat staked to plate  14 . Yet alternatively, tabs  22  could be held against plate  14  by a bracket fixed to plate  14 . The precise means of fixing vane  12  to plate  14  is not critical to the operation of valve  10 . What is important to the operation of valve  10  is that tabs  22  be configured to provide adequate retention of vane  12  to plate  14 , and to provide an adequate restoring force biasing vane  12  to a closed condition, and to enable the desired mode of deflection of vane  12  in a high pressure or full open condition illustrated in FIGS. 5 and 6. In the embodiment of FIGS. 1-6, tabs  22  function as living hinges, allowing pivoting of vane  12  to the full open position responsive to an application of high pressure and providing a restoring force tending to return vane  12  to a closed position. Tabs have radii on each side of the base of tabs  22 . The radii help prevent cracks from developing between tabs  22  and the rest of vane  12  after repeated cycling of vane  12  between the open and closed positions. 
     The size and shape of valve vane  12  and opening  20 , the tab configuration, including the number and location of tabs  22 , the stiffness of the vane material and a size of radius R of curvature of plate  14  all contribute to the sealing force of opposing a back pressure force directed against a back side  24  of plate  14 . However, it is the concave curvature of the valve plate which is of particular benefit. If the valve plate was not curved, the vane would only cover opening  20 , but would not be pressed against it. Tabs  14  would resist movement of vane  12 , but would not provide any sealing force against plate  14 . The sealing force attributably to the curvature of plate  14  is very important to the effectiveness of valve  10  in blocking the backflow of fluids. With plate  14  being curved, vane  12  is pressed against bowed plate  14  and induces sealing forces between vane  12  and plate  14 . The spring force of vane  12  attributable to the bending strength of the vane about the axis of curvature  16  acts against the curved plate  14 , inducing the sealing force of vane  12  against plate  14 . Vane  12  is just slightly larger than the opening  12  in the plate, with sealing occurring between the outer periphery of vane  12  and the portion of the plate  14  overlapped by vane  12 . The small overlap results in greater sealing pressure between vane  12  and plate  14  than if a large overlap is employed. 
     Testing has been conducted with plate  14  having radius R of 9 inches (230 mm). While FIG. 1 shows plate  14  having a single constant radius, that characteristic is not critical to the invention. Plate  14  must be generally concave on vane side  18  for valve  10  to function as intended. However, plate  14  may employ a curvature of multiple radii, or may even include flat portions. Valve  10  may operate adequately with a portion of the curvature being reversed or convex, however such reverse curvature must be sized and oriented so as not to prevent sealing. While such variations may not be optimal, they will still be functional. 
     The shape and location of tab  22  is important to maintaining vane  12  against plate  14  in the closed condition. Tab  22  must be stiff enough to keep vane  12  pressed against plate  14 . The desired stiffness of tabs  22  may be achieved by forming tab  22  of sufficient width. Alternatively, the stiffness of tabs  22  could be increased by laminating a layer of materials to tabs  22  to increase their thickness. The necessary stiffness of tabs  22  will be a function of the stiffness or resistance to bowing of vane  12 , and of the radius of curvature of plate  14 . A smaller radius of curvature will require a stiffer tab to keep vane  12  pressed against the plate  14 . If there are two tabs  22 , with each located near the ends of vane  22 , then the tabs  21  resistance to twisting as well as their resistance to bending may also be important. If tabs  22  can twist excessively, vane  12  may not be properly seated at the center in an unloaded condition. 
     If the curvature of vane  22  is reversed on opening, a near stable open position can be obtained, and very little force is required to maintain the open condition. It is possible to build a bi-stable valve, which remains open or closed until some force applied to the valve moves the vane to the opposite position. However, care must be taken to ensure that a bi-stable structure is not created unintentionally, lest vane  12  unintentionally become stuck in the open position. 
     The location of tabs  22  may influence the shape of vane  12 . With tabs  22  located at the ends of vane  12 , as shown in the FIGS. 1-6, vane  12  can have a straight edge on a side  26  with the tabs. However, for a valve having a single tab  122  at the center of vane  112  as shown in FIGS. 7-12, it is preferable to have a curved edge on the side  126  with the tabs. The radius of the curved edge is approximately that of the curvature of plate  114  to prevent interference between the ends or corners  128  of vane  112  and the curved plate  114  when vane  114  is deflected to the fully open position. However, in some applications, it may be desirable to have the interference that would result from having the side of the vane with the tabs extend in a straight line. The resulting engagement of the corners with the plate in the open condition would provide an increased restoring force biasing the vane back toward the closed position. It should also be appreciated that single tab configurations will be less sensitive to mismatches in the coefficient of thermal expansion between vane  12  and plate  14 . 
     The invention operates in the following manner. Valve  10  is mounted as shown schematically in FIG. 16 to or formed in a surface  32  separating a first chamber  34  from a second region  36 . It is desired to permit fluid to flow out of first chamber  34 , to second region  36 , and to block flow from second region  36  into first chamber  34 . A source of fluid flowing from chamber  34  through valve  10  is a fan or pump  38 . Fan  38  forces air into chamber  34  which exhausts through valve  10 . One exemplary chamber is an automobile passenger cabin, with the outside environment constituting the second region. The fan of the heating, ventilating and air conditioning (HVAC) system corresponds to fan  38 . Operation of the fan, in most operating modes of the HVAC system, forces air into the cabin which causes air in the cabin to be exhausted through valve  10 . Another chamber and region combination is a furnace flue and the outside environment. Many other such applications are readily apparent. The vane side  18  of plate  14  is exposed to the environment, and the back side  24  of plate  14  is disposed toward the chamber. 
     When the pressures inside and outside the chamber are in equilibrium, vane  12  is held against plate  14  by the bending force of tabs  22 . Both vane  12  and plate  14  preferably have a smooth finish to facilitate sealing therebetween. With pressure outside the chamber exceeding that inside the chamber, the fluid acts against vane  12 , pressing it even more firmly against plate  14  than just the force of the tabs  22  alone. 
     Shifting the pressure balance so that the pressure inside the chamber is greater than outside causes the fluid to unseat vane  12 . The fluid flows out of the chamber through valve  10 , past vane  12 . With the pressure in the chamber greater than the pressure outside by only a small amount, vane  12  deflects in the low pressure mode illustrated in FIGS. 3 and 4. With tabs  22  still resisting deflection, vane  12  deflects at the location furthest from tabs  22  which is the center of vane  12 . Vane  12  curves away from plate  14 . Fluid flows from the chamber, through the now open gaps between the sides of vane  12  and plate  14 , as shown in FIG. 4, into the second region. When the pressure inside the chamber is increased to a predetermined level, the resistance of tabs  22  is overcome, and vane  22  swings open about a hinge axis or axes defined by tabs  22  as shown in FIGS. 5 and 6. The hinge axis or axes are normal to axis of curvature  16 . Although not shown in FIGS. 5 or  6 , vane  12  would likely retain its reverse bow shape when fully unseated from plate  14  because tabs  22  are too close to each other to allow vane  12  to assume a flat shape. When the pressure inside the chamber drops, the force induced by tabs  22  pivots vane  12  back into contact and conformance with plate  14 . 
     The embodiment of valve  110  shown in FIGS. 7 through 12 operates in a substantially identical manner to that of the embodiment of FIGS. 1-6. FIGS. 7 and 8 show vane  112  in a closed position against plate  114 . FIGS. 9 and 10 show vane  112  deflected in a low pressure mode, with the ends of vane  112 , now the parts most distal to tab  122 , bowing away from plate  114 . In the high pressure mode, vane  112  would assume a more nearly flat shape than vane  12 , as the ends of vane  112  are free to extend outward. 
     In the valve  210  embodiment shown in FIGS. 13-15, there are a pair of “twinned” vanes  212  and  212 ′ joined to a plate  214  by common tabs  222 . The closed position or mode is shown only in FIG.  13 . Vent openings  220  and  220 ′ and vanes  212  and  212 ′ are mirror images of each other on either side of an imaginary plane  230  separating the two sides and approximating a hinge axis. Imaginary plane  230  is normal to axis of curvature  216 . Tabs  222  bias vanes  212  against plate  214 . The low pressure mode of deflection of each of vanes  212  is similar to that illustrated in FIGS. 3 and 4. The high pressure mode of deflection of vanes  212  is illustrated in FIGS. 14 and 15. As with vane  12 , vanes  212  have reverse curvature in the high pressure mode. Vanes  212  are able to contact each other in the high pressure mode, with contact occurring at the apex of the arched vanes  212 . The contact between vanes  212  and  212 ′ enable vanes  212  and  212 ′ to stabilize each other in the high pressure mode. The contact eliminates valve flutter which might otherwise occur. 
     It is anticipated that for some applications it will be desirable to form plate  14 ,  114 ,  214  as part of a housing which would in turn be mounted to the chamber which is to be unidirectionally vented. Such housings could be designed for mounting on either an outside surface or an inside surface. The housings would preferably be provided with a means of sealing to the surface to which they are mounted. Failure to provide an adequate housing seal would result in undesired backflow into the chamber in spite of the seal provided by the vane against the plate. 
     The dual low pressure/high pressure exhaust mode characteristic of the valves described allows low pressure/low flow rate exhaust as may required, while also accommodating a high pressure/high flow rate event such as exhausting the cabin to account for air being pumped into the passenger cabin by the heating, ventilating and air conditioning system of the vehicle, without sacrificing the sealing capabilities of the valve. Additionally, because the vane seals by bowing against the plate, and because of the light weight of the vane, the valve can be located without regard to the orientation of the valve. This is contrasted with valves which rely on gravity for closure, or for spring loaded valves with relative heavy vanes, the sealing capabilities of which may be adversely affected by gravity. 
     In tests, the backflow of air past the seal of the vane against the plate was well within the test objectives. The forward flow exceeded the test objectives at pressures equal to 0.1 and 0.5 inches of water pressure. The results were the same, independent of the orientation of the valve. Testing was performed in a wind tunnel testing fixture designed for testing automotive cabin exhauster valves. 
     Many alternative constructions of the valve are readily apparent. Alternative configurations may employ composite vane assemblies. For example, metal vanes may be used in combination with polymer tabs or hinges. In one version of the inventive valve, a vane could be attached on opposite sides at or near the center of its associate plate so that the ends of the vane would deflect in the same mode as shown in FIG.  10 . With the vane attached on two sides, it would be unable to pivot up to the high pressure mode shown in FIGS. 11 and 12. Similarly, a vane could be attached to a plate on just one end instead of at it center. However, both versions would still provide the desired sealing against back pressure, and would exhaust at relatively low pressures. Such valves may suffer from restricted high pressure flow capacity, and susceptibility to flutter of the free ends of the vane. Also, the vane need not necessarily be flat in its free condition. It could alternatively have a pre-set curvature radius greater than that of the plate, and be oriented with its concave side either facing or opposite the concave plate to achieve either higher or lower sealing loads respectively than a flat vane. If the vane has it concave side oriented toward the concave plate, the free curvature radius of the vane may be even smaller than the plate&#39;s radius of curvature. Versions of the valve employing a flat or a convex plate are also anticipated. While the embodiments discussed to this point all employ a concave plate, it should be appreciated that it is the difference in curvature between the plate and the vane which results in the sealing force of the vane being applied against the plate. For example, a convex plate having a radius of 9 inches (230 mm) could be used in combination with a vane formed to have a permanent radius in a free or unloaded condition of 6 inches (150 mm). Fixing the curved vane to the concave plate results in the vane exerting a load against the pressure plate just like the loads exerted by vanes  12 ,  112  and  212  against plates  14 ,  114 , and  214 . Similarly, if the plate is flat, a curved vane could be used to achieve the desired sealing load, as long as the concave side of the vane is pressed against the plate. It is understood that the amount of curvature of the vane will vary with other parameters of the vane, such as the stiffness of the vane and the size and shape of the vane. What is common to each of the possible combinations of plate curvature and the free curvature of the vane is that the vane has a curvature distinct from the plate, and when the vane is pressed into conformance with the plate at the opening, the vane is forced to bend and thereby generate a sealing load around the opening in the plate. 
     The word curvature as used herein refers to surfaces that are flat as well as curved. The curvature of the plates and vanes may be thought of as being positive or negative to indicate whether it is a convex or concave surface and may have a magnitude indicator as well corresponding to a radius. A flat surface would be characterized as a curvature having an radius equal to infinity. Therefore the term curvature is not exclusive of flat surfaces. Again, as noted above in the discussion of FIGS. 1-6, the curvature is not limited to constant radius curves. 
     The basic valve structure is suitable for many different types of valves. The vane material must be chosen to suit the application, the fluid to be controlled, temperature, pressure, environmental and flow requirements. It can function as a check valve in gas or liquid pumps, venting devices or systems, anti-backflow valve for breathing devices, medical infusion systems, plumbing systems, clothes dryers, sanitary vents, range hood vents, building vents. The list is nearly endless. 
     The embodiments disclosed herein have been discussed for the purpose of familiarizing the reader with the novel aspects of the invention. Although preferred embodiments of the invention have been shown and disclosed, many changes, modifications and substitutions may be made by one having ordinary skill in the art without necessarily departing from the spirit and scope of the invention as described in the following claims.