Abstract:
A one directional flow valve assembly for a fluid system. The valve assembly is comprised of a valve body having an internal valve chamber in communication with the ambient environment with a valve seat of a predetermined configuration. The assembly further has a cap structure with means to position and align a sealing membrane with respect to the valve seat. A flexible elastomeric sealing diaphragm is provided which is under tension when the diaphragm is in a sealing configuration. A carrier plate structure may be provided to position the sealing diaphragm. The sealing member is in tension adjacent to the sealing seat when in a sealing position.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates generally to a one directional flow valve assembly for a fluid system and particularly for permitting the ambient environment to equalize negative pressure differentials within the fluid system while preventing positive pressure gases from escaping into the ambient environment. The invention is particularly useful in providing an air admittance valve assembly for a plumbing system, such as an air admittance valve assembly constructed and arranged to provide an automatic one-way valve assembly for low pressure differentials to the drain portion of a plumbing system. The valve assemblies of the invention provide responsive and sensitive air inlet valves, constructed and arranged for indoor use environments to vent into plumbing systems. 
     A typical plumbing system supplies water and carries away waste. Water is supplied under pressure to the plumbing fixtures and drain pipes carry waste water from the fixtures to the main drain which empties into a sewer system, septic tank or the like. Ambient atmospheric pressure is typically maintained in the drainage system and gases are vented from the system by vent pipes that extend through the roof of the building structure. A drainage system may be referred to as the drain-waste-vent system (or DWV) in that it drains water, carries away solid waste and vents gasses outside the system. Each plumbing fixture typically has a trap which contains water to prevent gasses from entering the building through the fixture, e.g. sink or tub. The trap of a typical fixture is connected to a drain pipe, i.e., 1½ or 2 inch diameter. Waste from toilets is typically discharged through a 3 or 4 inch diameter soil pipe connected to the main drain. 
     At each trap of a fixture a vent extends from the drainage system to maintain atmospheric pressure. The vent at the toilet typically extends from the soil pipe and is referred to as the soil stack. Other fixtures are typically vented by a secondary vent or revent, i.e., 1½ inch diameter pipe which is connected to the main vent or they may be vented by a main vent extending through the roof. 
     Venting a plumbing system allows make-up air to enter the system to prevent a vacuum from forming which would pull water from the traps and into the drain pipes. Thus, plumbing systems typically have at least one main vent and preferably a vent at each fixture. Plumbing codes usually specify the requirements for venting plumbing installations. 
     It is presently common procedure in the construction and plumbing industries to utilize roof vent pipes for providing make up air when negative pressures are realized in drain and waste plumbing systems, such as when a sink is drained or a toilet is flushed. The installation of vent pipes, particularly secondary vents, is a time consuming and costly procedure in the building construction process. Particularly in home remodeling projects, for example, vent pipes are normally placed within the interior of wall structures and extend to the main vent or through the roof. Further, where wall space restrictions exist, such as in pre-manufactured homes, mobile homes and in other motor vehicles having plumbing drain and waste systems, vent pipes are cumbersome and difficult to install and utilize. 
     Building codes in several countries outside the United States permit the use of vent valve assemblies for venting drain and waste systems. Further, several States in geographic areas in the United States now also permit the use of vent valve assemblies for venting drain and waste systems. However, various codes and requirements must be met for use of such valve assemblies. For example, the American Society of Sanitary Engineering for Plumbing and Sanitary Research (ASSE) has promulgated performance requirements for air admittance valves for venting DWV Systems and venting drainage systems, i.e., ASSE/ANSI 1051. These performance requirements are increasingly being utilized by governmental and local regulatory agencies in promulgating and enforcing plumbing codes. 
     A clear need exists in the plumbing industry for an automatic valve assembly for reliably venting into a low pressure plumbing drain and waste system and several such assemblies have been proposed and utilized. However, these prior art valve assemblies have drawbacks and difficulties. For example, the reliability of these valve structures and the proper sealing at low pressures have been problematic in such prior art devices. Other valve structures utilize mechanical means to operate the sealing members and they utilize elements that may be attacked by environmental hazards and, thus, may become unreliable over time. 
     The air admittance valve of the present invention utilizes a very low-pressure seal that is gravity activated. The valve assembly includes an air inlet valve chamber and means to align the sealing membrane with respect to the valve seat of the valve chamber. The flexible sealing membrane is comprised of a thin membrane having different configurations and which are placed in a tensioned state when sealing. The flexible, tension membrane reduces the need for high precision and debris intolerant parts in the valve assembly while providing tight and reliable sealing at low pressure differentials, i.e. at 0.01 psi. This sensitive sealing result can be attained without the requirement for dust catching sealing adjuncts such as silicone oil or silicone grease. The air admittance valves according to the teachings of this invention permit valve opening and air admittance at negative pressure differentials of less than 0.02 psi. 
     Prior art valves either do not reliably seal to current American Society of Sanitary Engineering standard 1051 (ASSE/ANSI 1051) or require sealing adjuncts such as grease or oil to effect sealing at the 0.01 psi. standard. Prior art valve assemblies typically incorporate cantilevered elastomeric sealing structures which are structurally stiff enough in flexure to seal in the range of pressures that the air admittance valve is subject to. However, the prior art sealing structures must be soft enough in flexure to overcome manufacturing variability and, therefore, have inherent performance shortcomings. 
     In contrast to the sealing structures of the prior art, the tensioned membrane of the present invention is structurally soft in flexure which, therefore, is tolerant of manufacturing variability, e.g. of the valve seat, valve membrane guide, and sealing membrane structures. Performance of the present invention is less critical of manufacturing tolerances associated with the sealing interface than those of the previous art. The single sealing surface also permits higher contact pressures than dual sealing surfaces. 
     Specifically, for thin shell shapes of thickness t, flexural stiffness is approximately proportional to t 3  while strength in tension is proportional to t. Thus, the structure of the sealing membranes of the present invention are as soft in flexural stiffness as necessary to allow for manufacturing variances while maintaining adequate tensile strength to prevent failure of the sealing member in use. Prior art air admittance valves with cantilever sealing structures must trade off adequate flexural stiffness to handle the range of pressures that the air admittance valve is subjected to while simultaneously being soft enough flexurally to tolerate manufacturing variability. Consequently, these prior art cantilever designs require tighter manufacturing tolerances to attain similar sealing performance. 
     Because of the mathematical relationship between the membrane flexural stiffness and tensile strength as a function of membrane thickness, the sealing membrane of the present invention provides a very soft flexural structure with an adequately strong tension structure. Further, because of the cooperation of the sealing membrane with the structure beneath the sealing ring, excessive strain on the membrane is limited even at high pressures, e.g. greater than 50 psi. Thus a novel air admittance valve is provided by the teachings of the present invention. 
     It is the object of the present invention to provide an automatic air admittance valve which effectively and reliably permits ambient make up air under ambient pressure to enter and equalize a negative pressure differential in a plumbing drain and waste system while preventing the discharge of contaminated and undesirable gasses under positive pressure conditions. It is further the object of the present invention to provide a flexible sealing diaphragm for a gravity controlled low pressure air admittance valve assembly which is reliable and effective for venting into such plumbing systems. 
     SUMMARY OF THE INVENTION 
     The present invention provides an automatic, one-way air admittance valve assembly for low pressure venting into a closed system, such as a plumbing drain and waste system. 
     The air admittance valve is comprised of a valve body having an internally positioned valve chamber which is constructed and arranged to form an annular valve seat. An elastomeric flexible sealing membrane is provided for flexibly sealing against the sealing surface of the annular valve seat. The annular valve seat has a sealing edge with a predetermined sloping configuration. A valve cap is provided for attachment to the valve body and has means to position and guide the flexible sealing membrane with respect to the valve seat. 
     In one embodiment the flexible elastomeric sealing member is a tensioned membrane while sealing and in another embodiment the flexible sealing membrane has an interior portion and exterior and intermediate concentric portions of a specified cross-sectional profile. The latter embodiment is also tensioned while sealing. The valve cap further has means to guide the carrier structure to thereby position and place the sealing diaphragm onto the sealing surface of the annular valve seat. In one embodiment a carrier plate structure is provided for guiding the elastomeric diaphragm and for sealing the flexible diaphragm against the valve seat. The carrier structure has an annular body configuration for attachment to the diaphragm. The carrier structure further has a plurality of radiating structural ribs which extend upward toward the center hub. 
     Further provided are valve body configurations and, particularly, valve seat and cooperating flexible sealing diaphragm configurations which repeatedly seal so as to permit an air admittance valve to function in a low pressure plumbing environment. 
     It is an object of the invention to provide air admittance valve assemblies which are responsive at low pressures to comply with various plumbing codes and regulatory agencies. 
    
    
     These and other benefits of this invention will become clear from the following description by reference to the drawings. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a top plan view of the air admittance valve assembly of the present invention; 
     FIG. 2 is a sectional view of the valve assembly taken along line  2 — 2  of FIG. 1; 
     FIG. 2A is a sectional view of the valve assembly of FIG.  2  and showing the air inlet path of the air admittance valve; 
     FIG. 3 is a sectional view taken along line  3 — 3  of FIG. 1; 
     FIG. 3A is a sectional view of the valve assembly of FIG.  3  and showing the air admittance path of the valve assembly into the plumbing system; 
     FIG. 4 is an enlarged sectional view of the valve seat of the air admittance valve assembly; 
     FIG. 5 is a top view of the valve body of the air admittance valve assembly; 
     FIG. 6 is a lateral view of the valve body of FIG. 5; 
     FIG. 7 is a bottom view of the valve body of FIG. 5; 
     FIG. 8 is a perspective view taken from the top and side of the valve body of FIG. 5; 
     FIG. 9 is a perspective view taken from the bottom and side of the valve body of FIG. 5; 
     FIG. 10 is a top view of the cap member of the air admittance valve assembly of FIG. 1; 
     FIG. 11 is a sectional view of the cap member of FIG. 10; 
     FIG. 12 is a bottom view of the cap member of FIG. 10; 
     FIG. 13 is a top view of the carrier structure of the air admittance valve of FIG. 1; 
     FIG. 14 is a lateral sectional view of the carrier structure of FIG. 13; 
     FIG. 15 is a bottom view of the carrier structure of FIG. 13; 
     FIG. 16 is a sectional view of the sealing membrane taken along line  16 — 16  of FIG. 17; 
     FIG. 17 is a top view of the sealing membrane of the air admittance valve assembly of FIG. 1; 
     FIG. 18 is a top plan view of another embodiment of the air admittance valve assembly of the invention; 
     FIG. 19 is a sectional view of the air admittance valve taken along line  19 — 19  of FIG. 18; 
     FIG. 19A is a sectional view of the valve assembly of FIG.  19  and showing the air inlet path of the air admittance valve; 
     FIG. 20 is a sectional view taken along line  20 — 20  of FIG. 18; 
     FIG. 20A is a sectional view of the valve assembly of FIG.  20  and showing the air admittance path from the valve assembly into the plumbing system; 
     FIG. 21 is an enlarged view showing the sealing membrane of the air admittance valve assembly of FIG. 18 captured between the valve body and the valve cap; 
     FIG. 22 is a top view of the cap member of the air admittance valve assembly of FIG. 18; 
     FIG. 23 is a sectional view of the cap member of FIG. 22; 
     FIG. 24 is a bottom view of the cap member of FIG. 22; 
     FIG. 25 is a sectional view of the sealing membrane taken along line  25 — 25  of FIG. 26; and 
     FIG. 26 is a bottom view of the sealing membrane of the air admittance valve assembly of FIG.  18 ; 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIGS. 1-3, the one-way valve assembly  10  is shown comprising a valve body  11  and a cap member  12  mounted thereon. The valve body  11  has a bottom connecting portion  13  which by means of external threads  24 , for example, is connected to a closed system, such as a plumbing system. The valve assembly  10  is constructed and arranged for connection to the vent portion of a drain-waste-vent (DWV) plumbing system to permit ambient air to enter the system during negative pressure or vacuum conditions and to seal the drainage system during positive pressure conditions to thereby prevent gases from entering the ambient environment. The valve assembly  10  is constructed for connection to other systems requiring one-way venting from the ambient environment under low differential pressures, i.e., in the order of 0.01 psi. 
     The one-way valve assembly  10  is further shown to comprise a valve chamber  16  centrally disposed within the upper portion of the valve body member  11 . The valve chamber  16  is shown to comprise a hemispherical or cupped wall terminating in an upwardly extending valve seat  17 . Extending outwardly from the upper portion of the valve chamber wall is an upper peripheral portion  14  having a terminal connecting ridge  15  for receiving the bottom portion of the cap member  12 . The threaded lower outer portion  13  is provided to permit the valve assembly  10  to be secured to an internally threaded conduit or pipe, for example, or to an adapter structure connected to the top of a vent pipe. The pipe threads are preferably NPT threads (National Pipe Threads). Although threads  24  are shown, alternative connecting means of the valve assembly  10  may be utilized, i.e., the use of adhesives or other connecting means. 
     Shown particularly in FIGS. 2 and 3, the cap member  12  has alignment means to position the flexible sealing membrane  25  with respect to valve seat  17 . A centrally disposed guide member  19  is shown extending from the interior of the cap member  12 . A sliding carrier structure  20  is shown positioned about the axially aligned guide member  19 . The carrier structure  20  is comprised of a central hub  42  having a bore for sliding with respect to guide member  19 . A plurality of structural ribs  22  are shown extending from the hub  42  and to the bottom of which a peripheral support is fixed for supporting the flexible sealing membrane  25  above the valve seat  17 . The thin flexible elastomeric membrane  25  is preferably fixed to the bottom of the sliding carrier structure in a constrained state and is tensioned while sealing. In FIGS. 2 and 3, the sealing membrane  25  is shown sealingly positioned over the circumferential valve seat  17  of the valve chamber  16  thereby maintaining system gases within the valve body in communication with area  18 . 
     Referring to FIGS. 2A and 3A, the operation of the air admittance valve assembly  10  is shown. As shown, under negative pressure in the valve due to negative system pressure through valve area  18 , the sealing membrane carrier structure  20  is lifted upward from valve seat  17  thereby permitting ambient air to enter the valve chamber  16  through air inlet areas  26  and  27  shown oppositely disposed in FIG.  2 A. In FIG. 3A, which is a sectional view of the valve assembly  10  and which is 90° from that shown in FIG. 2A, the inlet air is shown entering the closed system through valve outlet portion  18  to thereby equalize the pressure differential between the closed system and the ambient environment. 
     The valve assembly  10  operation described is provided by the structural configuration of the valve body  11  further shown in FIGS. 5-9, in cooperation with the cap member  12  shown in FIGS. 10-12, the carrier assembly  20  shown in FIGS. 13-15 and the sealing membrane  25  shown in FIGS. 16 and 17. 
     Referring to FIGS. 5-9, the valve body member  11  is shown comprised of a tubular structure having an upper portion with a peripheral portion  14  having a ridge  15  for connection with the cap member  12 . The cup shaped or hemispherical valve chamber  16  is shown positioned centrally in the valve body  11  and having the valve seat  17  extending upwardly therefrom. The valve chamber  16  is shown comprising a wall having generally four quadrants, including opposing apertured areas having web portions  52  forming apertures  53  which form opposing air inlet portions  26  and  27 . The opposing apertured wall portions of the valve chamber  16  are shown to have a generally triangular configuration. The apertured wall portions are provided to keep debris and insects from entering the interior of the valve chamber  16  and to thereby secure the integrity of the sealing function of the sealing membrane on the valve seat  17 . The upper peripheral portion  14  includes opposing walls  55  and  56  which connect the valve chamber  16  and define opposing air outlet chambers or ports  28  and  29 . The latter outlet chambers  28  and  29  are in communication with the bottom outlet portion  18  of the valve body  11 . As further shown the exterior connecting inner walls  57  and  58  of the opposing outlet ports  28  and  29  also form and provide funneled air inlet ports to the apertured walls of the valve chamber  16 . 
     In FIGS. 10-12, the cap member  12  is shown comprised of a circular, unitary structure having a curvilinear downwardly sloping cross section. Centrally disposed is a downwardly extending guide member  19 . The unitary cap structure  12  is preferably molded of a plastic composition, such as PVC or the like, and has a lower end for connection to the valve body member  11 . Alternatively, the cap member  12  is provided as a clear molded plastic structure so that one is able to see the inner workings of the device so that users may see the parts and operation of the device. 
     In FIGS. 13-15, the carrier structure  20  is shown comprised of a central hub  42  having a guide bore  21  for slidably engaging the guide member  19  of cap member  21 . Extending angularly and downwardly from the central hub  42  are a plurality of equidistantly spaced structural ribs  22 . An annular support ring  23  is shown connected to the bottom of the structural ribs  22  and which is constructed to hold the sealing membrane thereto. The carrier structure  20  is also preferably molded of a unitary plastic composition such as PVC or the like. 
     In FIGS. 16 and 17 the sealing membrane  25  is shown comprised of a thin circular structure. The sealing membrane  25  is preferably constructed of an elastomeric material which is fixed in a constrained state to the support ring  23  of the carrier structure  20 . For example, the sealing membrane  25  may be adhesively fixed at its peripheral edge or otherwise mechanically attached by means, for example, of a formed lip to the support ring  23 . As shown in previous drawings, the sealing membrane  25  and support ring  23  have a diameter intermediate the diameters of the valve seat  17  and the bottom of the cap member  12 . This arrangement permits the support ring  23  to exert the weight of the carrier structure  20  to the sealing membrane  25  concentrically outside of the valve seat  17  to thereby flex the sealing membrane  25  about the valve seat  17 . As shown in FIG. 4, the valve seat  17  in cross section is shown to have a sealing edge formed of a rounded edge and an angled wall edge  34  which provides a relief area for the tensioned sealing membrane when in the sealing position. Thus, the thin elastomeric sealing membrane  25  is able to reliably seal against the valve seat  17  in a flexed condition. 
     An air admittance valve assembly  10  for connection to a vent structure having 1.5 inch NPT threads, exemplary dimensions for the valve body  11  constructed of a rigid PVC composition may be as follows: upper outside diameter of approximately 2.6 inches, lower connecting portion outside diameter of approximately 1.9 inches and a height of approximately 1.4 inches. The centrally disposed valve seat has a seat diameter of approximately 1.5 inches, a rounded valve seat edge having a radius of approximately 0.003 inches, sloping wall of approximately 135 degrees and a height of approximately 0.016 inches. The cap member  12  constructed of rigid PVC may have a lower outside diameter of approximately 2.5 inches, an inside diameter of approximately 2.38 inches, a height of approximately 1.26 inches and a guide member with a length of approximately 0.75 inches. The sloped portion of the cap member is disposed at approximately 51° with respect to a central axis through the guide member. The slidable carrier structure  20  is also constructed of rigid PVC has a lower outside diameter of approximately 2.14 inches, an upper hub diameter of approximately 0.50 inches with a bore of approximately 0.22 inches and an overall height of approximately 0.91 inches. The equally spaced ribs have a width of approximately 0.10 inches. The sealing membrane or diaphragm  25  is preferably constructed of a flexible elastomeric material, such as neoprene rubber or the like and has a thickness of approximately 0.030 inches and a diameter of approximately 2.20 inches. Other valve assembly dimensions, valve attachment means material and other compositions used in the valve assembly are within the purview of this invention. 
     Referring to FIGS. 18-20, another embodiment  30  of the one-way valve assembly is shown comprising a valve body  31  and a cap member  32  mounted thereon. The valve body  31  has a bottom connecting portion  33 , an air inlet valve chamber  36  and a cap member  32 . The valve body  31  having air inlet ports  40  and  41 , upper connecting portion  35  and bottom portion  33  with internal air outlet  38  and external threads  39 , is similar in structure and operation as the valve body  11  of assembly  10  described above. However, as shown, the sealing membrane  45  and cap member  32  are different in structure and operation. 
     In FIGS. 19A and 20A, the valve assembly  30  is shown to vent air into and out of the valve chamber  36  similar to the airflow path shown with respect to valve assembly  10  shown in FIGS. 2A and 3A. Sealing membrane  45  is shown upwardly moved from valve seat  37  to permit airflow through the valve body  31 . Cap member  32  is shown aligning and positioning the sealing membrane  45  by holding the circumferential edge within upper connecting end  35  of valve body  31 . As shown particularly in FIG. 21, the sealing membrane  45  has a formed peripheral ridge  46  which can be retained by either the cap member  32  or by the valve body  31 . The sealing membrane only needs to be retained in this position. It does not require an air tight seal to either the cap or to the valve body. 
     In FIGS. 22-24 the cap member  32  is shown comprised of a circular unitary structure having a flattened triangular cross-sectional configuration. The cap member  32  is shown to have a flattened top portion  54  which is constructed and arranged to receive and guide the centrally disposed thickened  47  of sealing member  45 . The unitary cap structure  32  and unitary valve body  31  are preferably molded of a plastic composition, such as PVC or the like. 
     In FIGS. 25 and 26 the sealing membrane  45  is shown comprised of a thin circular flexible structure having an inner area  48 , a sloped concentric sealing area  49  and an outer concentric area  50  having a downwardly extending edge with a peripheral ridge  46 . A cylindrical thickened portion  47  is shown centrally extending from the top surface of the sealing membrane  45 . A plurality of spaced apertures  51  are shown in outer area  50  so that internal system pressure is operative above the sealing membrane  45  for proper function of the valve assembly. This cooperating arrangement permits the thickened and weighted portion  47  to flex the concentric and sloped sealing area  49  about the valve seat  37 . The sloped sealing area  49  is preferably angled in a range of 20°-30° when viewed in a cross-section and with respect to a horizontal base line. The valve seat  37  may be angled so that the seat  37  is normal to the sloped sealing area  49  when the sealing membrane  45  is in the sealing position. The material composition of the sealing membrane is preferably a soft neoprene rubber or the like having a Shore-A durometer ranging from 15-30 and the thickness of the membrane is preferably approximately 0.030 inches. 
     In summary regarding both valve assembly embodiments discussed above, each utilizes a soft, flexible sealing membrane to seal in a tensioned state against a thin valve seat at a low negative pressure differential. For a sealing area having a 1.5 inch diameter, both sealing membranes have a weight of approximately 8-10 grams, i.e., the sealing membrane plus carrier structure in the first embodiment and the sealing membrane only in the second embodiment having the thickened center area. For other sealing areas, the membrane weight would be proportional to the area. The thin valve seat has a radius of approximately 0.003 inches having a relatively sharp edge without burs to provide a high contact pressure. Both sealing membrane embodiments have a thickness of approximately 0.030 inches, except for the thickened center of the second embodiment, and are constructed of a soft neoprene rubber or the like have a Shore-A durometer ranging from 15 to 30. 
     As many changes are possible to the embodiments of this invention utilizing the teachings thereof, the descriptions above and the accompanying drawings should be interpreted in the illustrative and not in the limited sense.