Abstract:
An air admittance valve assembly for venting ambient air into a system while preventing the escape of gases within the system. A housing includes first and second passageways in fluid communication through a valve seat therebetween. A flat generally thin, flexible, preferably resilient free-floating sealing membrane is positioned for sealing engagement by gravity only atop the valve seat. Ambient air in the second passageway will freely flow into the first passageway and the system at system air pressure less than atmospheric pressure while air within the system is prevented from flowing outwardly therefrom through the valve assembly.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     Not applicable 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR  DEVELOPMENT 
     Not applicable 
     INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC 
     Not applicable 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to air admittance valves for plumbing systems and more particularly to a one-way valve designed to allow air to enter the plumbing drainage system when a pressure less than atmospheric pressure develops. 
     2. Description of Related Art 
     Individual and branch-type air admittance valves for sanitary drainage systems are devices used as vent terminals in plumbing drainage systems. These valves are not used to relieve backpressure, but to allow air to enter the system when even a slight negative internal pressure occurs. When the valve of the type of the present invention is installed in a building, at least one open vent terminal which extends to atmosphere outside of the building serves the same building drain on which these valves are installed. Therefore, the valves are designed to be used for individual fixtures or for a branch serving multiple fixtures. 
     Typical plumbing systems introduce water and carry away waste, the water being supplied under pressure to the plumbing fixtures and drain pipes carry waste and water from the fixtures to a drain emptying into sewer systems or septic tanks or the like. Atmospheric pressure is maintained in the system and gases are vented by vent pipes that open to the outside. Plumbing fixtures typically contain a trap which holds water to prevent gases from entering the building through the fixture. Such venting allows air to enter the system to prevent a vacuum from forming. Common procedure in building plumbing systems is to utilize roof vent pipes for providing air when negative pressures are realized in drain plumbing systems. 
     Related air vent valves include U.S. Pat. No. 6,234,198 to Chalich which teaches a combined vacuum relief and pressure containing valve assembly for relieving vacuum in conduits, while also serving as a check valve preventing elevated pressures from propelling fluids past the valve. Beckey, et al. teaches a one-way flow valve assembly comprised of a valve body having an internal valve chamber in communication with the ambient environment with a valve seat. The primary object of Beckey&#39;s U.S. Pat. No. 6,415,816 patent provides for an automatic air admittance valve which permits ambient air under ambient pressure to enter and equalize a negative pressure differential in a plumbing drain, while preventing the discharge of gases under positive pressure conditions. 
     In U.S. Pat. No. 5,419,366, Johnston teaches a valve assembly for automatic venting of excess negative pressure in a drain line. An elastomeric diaphragm is drawn against a valve plate having a passageway therethrough which is normally closed by the diaphragm and, at a predetermined differential pressure across the diaphragm, causes the diaphragm to lift away from the plate to open the passageway. 
     There is a need in the industry for a valve containing a movable diaphragm which quickly and reliably seats and seals air flow when closed and allows air to enter when open. The valve of the present invention includes a housing which contains a movable free-floating diaphragm which seats and seals air flow when closed and allows outside or ambient air to enter when open. 
     BRIEF SUMMARY OF THE INVENTION 
     This invention is directed to a one-way air admittance valve assembly for venting ambient air into a system while preventing the escape of gases within the system. A housing includes first and second passageways in fluid communication one to another and a valve seat defining an opening demarking the first and second passageways. A cap is sealingly engaged or engageable with an upper end of the housing to define an upper portion of the first passageway and being positioned above the valve seat. A flat generally thin flexible unsupported sealing membrane is positioned for sealing by gravity only atop the valve seat, the sealing membrane being sized to slidably fit within the upright side wall of the housing which, in combination with the cap, defines the upper portion of the first passageway wherein an uninterrupted sealing area located centrally on the sealing membrane remains in alignment over the valve seat. Ambient air in the second passageway will freely flow into the first passageway and the system at system air pressure less than atmospheric pressure while air within the system is prevented from flowing outwardly therefrom through the valve assembly. 
     It is therefore an object of this invention to provide an improved one-way air admittance valve for venting ambient air into a system while preventing the escape of gases from the system through the valve. 
     Yet another object of this invention is to provide an improved air admittance valve for waste disposal systems which quickly responds to admit ambient air into the system responsive to negative system internal pressure while preventing noxious gases from being emitted from the system into the building. 
     Yet another object of this invention is to provide a free-floating sealing member with an air admittance valve which responds more quickly and more positively to both seal the valve from outward flow of gases from the system while allowing the free inlet of ambient air into the system as required to balance internal and ambient atmospheric pressures. 
     In accordance with these and other objects which will become apparent hereinafter, the instant invention will now be described with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S) 
         FIG. 1  is a perspective view of the valve assembly of the present invention. 
         FIG. 2  is a perspective view of  FIG. 1  with the cap removed. 
         FIG. 3  is an exploded view of  FIG. 1 . 
         FIG. 4  is an exploded broken view of the cap and housing of  FIG. 3 . 
         FIG. 5A  is a side elevation broken section view of another embodiment of the invention shown responsive to positive pressure within a system. 
         FIG. 5B  is a view of  FIG. 5A  in an ambient air admittance mode responsive to negative pressure within the system. 
         FIG. 5C  is an enlarged section view of the upper portion of the valve assembly of  FIG. 1  demonstrating both modes of operation shown in  FIGS. 5A and 5B . 
         FIGS. 6 to 11  depict various embodiments of the sealing membrane of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings, and firstly to  FIGS. 1 to 4 , the preferred embodiment of the invention is there shown generally at numeral  10  and includes a plastic molded cap  12  and a plastic molded housing  14 . The cap  12  sealingly engages over the outer smooth cylindrical barrel  20  of housing  14  preferably assisted in airtight sealing therebetween by O-ring  38  fitted into annular groove  36 . 
     The housing  14  includes external threads  18  formed on a lower portion thereof for connection to a conduit forming a part of a system for waste evacuation. The lower flanges of the cap  12  includes inward projections  48  which create spaces for engagement on either side of locking tabs  49  which prevent inadvertent rotation of the cap  12  when sealingly engaged over the housing  14 . 
     As seen in  FIGS. 5A to 5C , the lower inner portion of the housing  14  forms and defines a first air passageway  64 , an intermediate portion of which is formed by side openings  28  and  30  as best seen in  FIGS. 2 and 4 . This first passageway  64  is further defined at an upper portion thereof between the cap  12  and the housing  14  at  64   a . A second passageway is defined by a transverse air passageway  32  which extends across the upper central part of the housing  14  and is open to ambient air at the ends thereof. 
     The first and second passageways  64 / 64   a  and  32  are demarcated by an air opening  26  defining a preferably circular valve seat  24  formed through the central top panel of the second passageway  32 . This valve seat  24  may have a broad array of cross sectional configurations, the valve seat  24  preferably having a generally radiused upper surface which may also be of a wider nature or may also be sharpened by modifying the radiused section into an upwardly pointing triangular section or having a knife edge configuration as desired. 
     A sealing membrane  40  rests atop the valve seat  24  and is preferably formed of flat neoprene, silicone or gum rubber sheet material having a uniform thickness of between 0.02″ to 0.08″. The preferred embodiment of this sealing membrane  40  as also seen in  FIGS. 6 and 7 , includes closely and evenly spaced apertures  44  formed therethrough which facilitate inlet air flow as described herebelow. The outer peripheral diameter of the sealing membrane  40  is only slightly smaller in diameter than the cylindrical inner surface  56  of housing  14 , that difference in diameter being preferably in the range of about 0.03″ to 0.05″ such that sealing area  42  seen in  FIG. 6  remains overlapped and centered over the valve seat  24  regardless of lateral movement of the sealing membrane  40 . 
     The valve  10  is intended for use in a system wherein the valve  10  is maintained at a fixed upright orientation as shown in the Figures. The present invention capitalizes on this fixed orientation by alternately relying only upon gravity to maintain the sealing membrane  40  in a sealed relationship resting atop the valve seat  24  by virtue of only the relatively small weight of the sealing membrane  40 . At 0.028″ thick, the preferred embodiment of the sealing membrane  40  fabricated of flexible, resilient sheet material such as nitrile (Buna), EPDM or neoprene is in the range of 1.0 g. The preferred feature of resiliency enhances sealing against the valve seat  24 , especially so if they are irregularities in the valve seat  24 . By providing the small clearance between the periphery of the sealing membrane  40  and the cylindrical inner surface  56  of housing  14 , complete sealing reliability has been achieved. 
     Referring specifically to  FIGS. 5A ,  5 B and  5 C, when positive air pressure shown at arrow A is present in the first passageway  64 / 64   a  in  FIG. 5A , that positive air pressure above ambient or atmospheric pressure is transmitted at arrow B through the apertures  44  into the upper portion  64   a  of the first passageway  64  and is exerted downwardly in the direction of arrow C against the sealing membrane  40  to effect positive sealing against the valve seat  24 . As a result, virtually no airflow is experienced through the opening  26  for outward discharge through the second passageway  32 . 
     In this embodiment  10 ′ of the invention, an additional sealing weight  52  is also provided. This sealing weight  52  may be formed of any weighted material and may be rubber encapsulated as desired. The important features of this sealing weight  52  is that the outer peripheral diameter be such that, when it inadvertently is moved laterally in the direction of arrow D positioned atop the sealing membrane  40 , it will contact the inner cylindrical surface  56  of housing  14  as shown in phantom in  FIG. 5A  at  54  and will remain in weighted contact against the sealing membrane  40  over the entire diameter or periphery of the valve seat  24 . The preferred range of weight of this sealing member may be in the range of 2 to 12 g. 
     Referring to  FIG. 5B , the mode of operation of the valve  10 ′ with the added sealing weight  52  for additional insurance of reliability of this valve  10 ′is shown with the system experiencing a negative or below atmospheric pressure indicated by arrow A′ within first passageway  64  and air must be introduced into the system to avoid emptying of toilet bowls or other standing water within the system. The negative pressure within the system is felt at C′ through apertures  44  and the upper portion  64   a  of the first passageway which causes ambient air to be drawn inwardly through the second passageway  32  and upwardly through opening  26  in the direction of arrows C′. Once the negative pressure at A′ is neutralized to atmospheric pressure, the sealing membrane  40  reseals automatically against the valve seat  24  as previously described. 
     Referring now to  FIGS. 8 to 11 , alternate embodiments of the sealing member are thereshown. Sealing membrane  60  includes spaced circular apertures  62  similar to that incorporated into sealing membrane  40  except that these apertures  62  are further spaced apart and reduced in number. Sealing membrane  60  includes elongated slotted apertures  68  evenly spaced at 90° one to another while the sealing membrane  78  depicts a variety of aperture shapes at  80 ,  82 ,  84  and  86  which are shown only by example and not intended to be limiting with respect to the configuration of this feature of the invention. Moreover, inwardly extending slots  74  of sealing membrane embodiment  72  will also function to serve the dual preferred needs of the sealing member to allow ambient air to quickly pass into the valve and system while facilitating the vary minimal amount of airflow from the system into the upper first passageway  64   a  to effect quick sealing and prevention of air outflow from the system into the building. 
     While the instant invention has been shown and described herein in what are conceived to be the most practical and preferred embodiments, it is recognized that departures may be made therefrom within the scope of the invention, which is therefore not to be limited to the details disclosed herein, but is to be afforded the full scope of the claims so as to embrace any and all equivalent apparatus and articles.