Patent Publication Number: US-2012025123-A1

Title: High Capacity Air Admittance Valve for Sanitary Waste Pipe System

Description:
FIELD OF THE INVENTION  
     This invention relates to a high capacity air admittance valve to be connected to a sanitary waste pipe system in order to protect the water traps in the system and to prevent communication between waste pipes or sewers systems with surrounding atmosphere, said valve opens automatically to admit outside atmospheric air into the pipe system upon presence of a pressure drop within said pipe system. 
     A building drainage and vent system involves, in normal operating conditions, the establishment of an induced air flow within the vertical stacks of the system due to the unsteady water downfall generated by any appliance discharge. In order to protect the habitable space against contaminated odours, each appliance is normally protected by a water trap seal. Variation due to water downfall within the drainage system, generates occasional variations in air pressure that are often capable of disturbing these water trap seals either by siphonage due to a sudden under-pressure in the system or as a result of back pressures following air path closures by water surcharge. 
     DESCRIPTION OF THE PRIOR ART  
     Several air admittance valves have already been proposed to avoid said inconveniences and also offers the possibility of avoiding the necessity to vent the waste pipe system outside the roof of the building as said valves only open in response to sub-atmospheric pressure conditions in the waste pipe system. 
     Preferably, said valves are designed to assure a maximum possible air inlet flow from the air inlet of the valve to the waste pipe system while passing through the temporary opened valve membrane. 
     The patent document U.S. Pat. No. 4,232,706, in the name of the applicant, discloses an automatic valve device in which a vertical tube, constituting the body of the valve, comprises at its upper end a constriction in the form of a Venturi which co-operates with a cover so as to form a peripheral air inlet provided with an annular valve member situated at the exterior of the constriction and which can be tilted when a negative pressure occurs in the pipes while permitting the fresh air to penetrate into the vertical waste water pipe and which, when the pressure is equilibrated or when there is overpressure, occupies a closed position in which the escape of contaminated air is prevented. 
     Said valve comprises an annular peripheral opening which distributes the air inlet, in case of lifting of the annular valve member, towards the vertical tube in connection with the waste pipe. Although this device gives generally very good results with an increased air inlet capacity due to the venturi shaped tube, it may happen, in heavy duty circumstances that some turbulence may occur between the annular air inlet opening and the passage to the waste pipe. Said turbulence may occur when all of the air flow coming from the outer diameter of the annular valve member, in lifted position, is forced to be concentrated into a central tube portion of the pipe system having a smaller diameter and generally a smaller section than the overall annular valve section and will reduce, in some extend, the air inlet capacity. 
     In valves of this kind, the circular or annular valve member is generally resting on two concentric valve seats having each a circular sealing surface. In case of deformation or distortion of the valve member, problems could occur with the necessary airtight closure of said valve member with at least one of the two sealing surfaces. 
     Document U.S. Pat. No. 6,532,988 discloses a valve having a valve body with at least two air inlet openings in communication with the atmospheric air, each of the opening alternating with a passage toward the waste water pipe system; the openings and passages being equally distributed within the valve housing viewed in horizontal cross-section about the valve seat level. In normal position, the valve member is resting on a valve seat separating the openings from the passages. Said valve member having a substantially butterfly shaped sealing surface for a valve embodiment having two diametrically opposed air openings situated perpendicular respectively to two diametrically opposed air passages. The particular shape of the air distribution within the valve provides a maximum and well equilibrated air inlet and venting of the sewage system, however the manufacture of the housing and butterfly shaped valve member is rather difficult and costly. Moreover, a perfect horizontal level of the valve member and the valve seat, having a complicated peripheral circumference, is not always achieved with moulded plastic elements causing possible tightness problems of the valve. 
     SUMMARY OF THE INVENTION 
     The main object of the present invention is to solve the above mentioned drawbacks by providing automatic air admittance valves with easy to manufacture valve closing members and corresponding valve seats, whereby the air flow capacity remains equal or is even increased for a valve having substantially the same outer dimensions. 
     The above objects are achieved in accordance with the technical features of the present invention which are described more particularly in the annexed set of claims. 
     The characteristics, advantages and features of the invention will appear from the following description of an embodiment of the valve according to the invention and in which reference is made to drawings in which: 
       FIG. 1 : is an exploded view of a valve according to the invention, showing the main components; 
       FIG. 2 : is a detailed sectional view along a vertical, longitudinal central plane of the valve in normal closed position; 
       FIG. 3 : is a detailed sectional view along a vertical, longitudinal central plane of the valve in open position; 
       FIG. 4 : is a view from above of the valve housing taken without the cover and without the closing valve members. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     As shown in  FIGS. 1 to 4 , the air admittance valve, according to the present invention, comprises a body having an oblong bowl-shaped valve housing  10  and a lower portion comprising a vertical tubular member  12  extending downwards and adapted to be connected to a pipe (not shown) being part of a sanitary waste water pipe system. Usually the inner part of the tubular member  12  is provided with guiding members  13  designed for connecting pipes having different diameters. 
     The valve housing  10  is closed at its upper portion or upper end by means of an oblong shaped cover  14  (seen from above). 
     The central portion  16  of the housing  10 , situated between the cover  14  and the tubular member  12 , contains an inner space  18  in which are usually located the valve function elements, such as the valve seat and the movable valve member. Said inner space  18  is open towards the tubular member  12  (and the waste pipe system) by means of apertures  17  separated by internal grids  19  to avoid intrusion of undesired elements or insects into the valve housing  10 . 
     According to the invention, the inner space  18  of the central portion  16  of the valve housing  10  is provided with two circular valve seats  20  symmetrically arranged with respect to the centre of the oblong shaped upper portion of the housing. 
     The circular valve seats  20  extend downwards in order to create tubular spaces  22  connected to the valve housing  10  at their respective lower ends. A portion of the tubular space  22 , located just above the lower tubular member  12 , is closed off by means of conical walls  24  connected to the upper part of the tubular member  12 . 
     The remaining surface of the lower extremity of the tubular spaces  22  is provided with apertures  26  open to the surrounding atmosphere. Said apertures  26  are advantageously separated with external grids  28  in order to avoid intrusion of undesired objects or insects. 
     The centre of each tubular space  22  is provided with a tubular guide  30  extending upwardly from the valve housing  10  and which is designed to co-operate with a movable closing valve member. 
     Said valve member  34  is preferably a poppet kind member  34  having a bowl shaped central portion  36  and a peripheral conical edge  38  extending upwardly. The centre of the bowl shaped portion  36  is provided at its lower side with a stem  32  extending downwards in order to co-operate with the tubular guide  30  provided within the tubular space  22 . 
     Such kind of poppet valve member and corresponding seat structure, which are particularly suitable for this kind of application, have been disclosed and claimed in European Patent Application No. 09 447 002 in the name of the applicant. 
     Accordingly, the circular valve seats  20 , co-operating with such movable valve members  34  are advantageously provided with a soft annular ring  40  having an inner cantilever lip  42 . Said soft annular ring  40  being clamped on the valve seat  20  of the housing  10  by means of an annular ring  44 . 
     The  FIG. 2  shows the air admittance valve, according to the invention, in normal closed position whereby the air pressure contained within the sewage pipe system is generally equal or superior to the atmospheric pressure outside the system. In this position, the peripheral conical edge  38  of the valve member  34  is resting onto the inner cantilever lip  42  of the soft annular ring  40  positioned onto the circular seat  20 . The higher the air pressure inside the waste water pipe system will raise, the firmer the valve member  34  will be pressed against the cantilever lip  42  increasing and securing at the same time the tightness of the valve function. 
     In case the air pressure within the sewage pipe system drops suddenly below the atmospheric pressure, the valve members  34 , having their lower surface in communication with the atmospheric air pressure and their upper surface in communication with the air inside the sewage pipe system, will promptly be tilted upwards ( FIG. 3 ). 
     This will allow the atmospheric air to enter promptly through the apertures  26  into the tubular spaces  22  and both peripheral gaps, now created between the respective valve seats  20  and the peripheral conical edge  38  of the valve members  34 . Said incoming air flow will be sucked downwards passing through the apertures  17  towards the inner space of the lower tubular member  12  and into the waste water pipe system. Such incoming air flow will balance the air pressure inside the system and avoid sucking out the several water traps contained in the sanitary waste water piping. 
     The upwards movement of the valve members  34  will be limited by the central bowl shaped portion  36  of the valve members which will contact the lower surface of the cover  14  of the valve housing  10 . This will avoid the stems  32  to loose contact with their respective guiding means  30  of the valve housing  10 . 
     In order to reduce the friction between the stems  32  and the guiding means  30 , the inner surface of these portions will be provided with longitudinal ribs  31 . 
     The  FIG. 4  shows the various inner spaces, seen from above, of the air admittance valve according to the invention. It clearly shows the outer oblong (cross sectional) shape of the valve housing  10  and the location of the two circular valve seats  20 . 
     The circular valve seats  20  are extending downwards forming tubular spaces  22  which are closed off, on the one hand, from the tubular member  12  by means of the conical walls  24  and which are provided, on the other hand, with apertures  26  open towards the surrounding atmosphere and external grids  28  to avoid undesired objects or insects to enter into the valve. The centre of the tubular spaces  22  are provided with tubular guides  30  extending upwards in order to co-operate with stems  32  extending downwards from the closing valve member  34 . 
     The centre of the inner space  18  between the two tubular spaces  22 , is open towards the tubular member  12  and consequently towards the sanitary waste pipe system by means of apertures  17  separated by internal grids  19 , part of the valve housing  10 . 
     Tests have shown that the air flow capacity of the valve according to the present invention has significantly improved with respect to the existing air admittance valves. 
     The purpose of the embodiments as described herewith is only to illustrate the invention while still other variations are possible without falling out of the scope of the invention as expressed in the following claims. Consequently, it would be possible, for example, that the circular valve seats extending downwards and creating two tubular spaces and which have been illustrated as being of the same diameter, could have different diameters so as to allow each of the valve function elements to accommodate their successive or simultaneous opening according to the need of air inflow trough only one or both of the valve functions. 
     LEGEND OF THE REFERENCE NUMERALS  
       10 : valve housing 
       12 : tubular member 
       13 : internal guiding means of the tubular member  12   
       14 : cover of the valve housing 
       16 : central part of the housing 
       17 : apertures towards tubular member  12   
       18 : inner space 
       19 : internal grids 
       20 : circular valve seat 
       22 : tubular space 
       24 : conical wall 
       26 : apertures open to atmospheric air 
       28 : external grids 
       30 : guiding means 
       31 : longitudinal ribs 
       32 : stem of valve member 
       34 : valve member 
       36 : bowl shaped central portion 
       38 : peripheral conical edge of valve member 
       40 : soft annular ring 
       42 : cantilever lip 
       44 : annular ring