An air admittance valve

Abstract: The air admittance valve shown comprises a body 1 which has a closed end 2 and an open end 5 adapted to be mounted on a stack pipe 3, the body 1 including air admittance means 6 through which air can pass from the atmosphere into the pipe 3 and a valve member 7 movable relative to the air admittance means 6 in response to pressure variation in use in the pipe 3 to open or to close the air admittance means 6, which air admittance means 6 comprises an aperture preferably a plurality of apertures 8 contained in a wall portion 9 of the body 1, the internal surface 11 of the wall portion 9 defining a sealing surface 11 and the valve member 7 comprising a resilient membrane 7 which is complementary in shape to the sealing surface 11 and sealably engageable therewith to obdurate the apertures 8.

Description: The invention relates to an air admittance valve, particularly to the kind commonly found on stack pipes forming part of drainage systems. Many air admittance valves currently on the market consist of numerous working parts, are mechanically complex, and are therefore expensive and difficult to manufacture. Examples of prior art valves can be found in WO-A-86/04399, particularly Fig. 6, which discloses a valve tube unit, and an associated end cap which is formed integrally with the valve tube unit. That unit comprises a cylindrical valve tube arranged for fitting in a socket of a pipework system. The upper end of the tube carries an integrally formed frusto-conically shaped annular wall which projects outwardly of the tube to provide a stop for limiting the insertion of the tube into the socket 16, and inwardly of the tube to provide a downwardly-facing frusto-conical valve seating. According to the invention there is provided an air admittance valve comprising a body which has one end closed by a cap member and an open end which is adapted to be mounted on a pipe, the body including air admittance means through which air can pass from the atmosphere into the pipe and a valve member comprising a resilient membrane movable relative to the air admittance means in response to pressure variation in use in the pipe to open or to close the air admittance means, the air admittance means comprising a frusto-conical wall portion having a plurality of through apertures and an upstanding circular flange, the membrane having a frusto-conical part of complementary shape to an internal surface of the wall portion and sealably engageable therewith to obturate the apertures, characterised by the membrane having an annular integrally formed portion with a downwardly open channel portion which fits over the circular flange and by the cap member defining the closed end which is snap-engaged with the circular flange to secure channel portion which fits over the circular flange and by the cap member defining the closed end which is snap-engaged with the circular flange to secure the membrane and the air admittance means together. The aperture may comprise a grille-like structure. The cap may comprise a depending skirt. An air admittance valve is hereinafter described, by way of example, with reference to the accompanying drawing. The drawing shows a longitudinal view through an air admittance valve in accordance with the invention, the left hand portion being in elevation. Referring to the drawing the air admittance valve shown comprises a body 1 which has a closed end 2 and an open end 5 adapted to be mounted on a stack pipe 3, the body 1 including air admittance means 6 through which air can pass from the atmosphere into the pipe 3 and a valve member 7 movable relative to the air admittance means 6 in response to pressure variation in use, in the pipe 3 to open or to close the air admittance means 6, which air admittance means 6 comprises an aperture preferably a plurality of apertures 8 contained in a wall portion 9 of the body 1, the internal surface 11 of the wall portion 9 defining a sealing surface 11 and the valve member 7 comprising a resilient membrane 7 which is complementary in shape to the sealing surface 11 and sealably engageable therewith to obdurate the apertures 8. The wall portion 9 is substantially frusto-conical in shape and the resilient membrane 7 is of matching frusto-conical configuration. The wall portion 9 comprises a grille-like structure, wherein the slots 8 between adjacent grille members define a plurality of apertures 8. The resilient membrane 7 also contains an integrally formed portion 14 by means of which it can be retained in position against the frusto-conical wall portion 9. This integrally formed portion 14 corresponds in shape to a circular flange 12 which is joined to the lower in use frusto-conical wall portion. The circular flange has at its outer upper periphery a recessed shoulder 13. The integrally formed portion 14 of the resilient membrane 7 has an upper channel section member which fits over the top of the circular flange 12 and the outer portion 15 of the channel shown lies in the recessed shoulder of the circular flange 12. The body 1 is closed at one end by a cap 16 which has a downwardly in use extending and slightly outwardly directed skirt 17. The skirt has on its inside a lip 18 which is arranged to extend under the outer periphery of the point where the frusto-conical wall portion 9 joins the circular flange 12. By this means the cap 16 may be made a snap fit onto the body. In use the body 1 is mounted on the open end 5 of the stack pipe 3. The body 1 may be an interference fit on the stack pipe 3 or may be secured thereto by means of adhesive if appropriate. When there is a positive air pressure in the stack pipe 3, this puts pressure on the inner surface of the resilient membrane 7 and thus causes it to bias into sealable engagement with the frusto-conical wall portion 9 thereby sealing the slots 8 and preventing the escape of noxious gases. When a negative pressure exists in the stack pipe 3 the ambient pressure is greater than this and the resilient membrane 7 is therefore lifted away from the sealing surface 11 and permits air to enter into the system through the slots 8 thereby relieving the reduced pressure and, more importantly, keeping the noxious gases in the stack pipe so that they do not escape to atmosphere. When the pressure in the stack pipe is at least equalised with ambient air, the resilient membrane returns to seat on the sealing surface again to obviate escape of noxious gases.

Claims: An air admittance valve comprising a body (1) which has one end closed by a cap member (16) and an open end (5) which is adapted to be mounted on a pipe (3), the body (1) including air admittance means (6) through which air can pass from the atmosphere into the pipe (3) and a valve member comprising a resilient membrane (7) movable relative to the air admittance means (6) in response to pressure variation in use in the pipe (3) to open or to close the air admittance means (6), the air admittance means (6) comprising a frusto-conical wall portion (9) having a plurality of through apertures (8), and an upstanding circular flange (12), the membrane having a frusto-conical part of complementary shape to an internal surface of the wall portion and sealably engageable therewith to obturate the apertures, characterised by the membrane (7) having an annular integrally formed portion (14) with a downwardly open channel portion which fits over the circular flange (12) and by the cap member (16) defining the closed end which is snap-engaged with the circular flange (12) to secure the membrane (7) and the air admittance means (6) together. An air admittance valve according to Claim 1, characterised in that the apertures (9) comprise a grille-like structure (4). An air admittance valve according to Claim 2, characterised in that the cap (16) comprises a depending skirt (17). An air admittance valve according to Claim 3 characterised in that the depending skirt (17) is arranged to extend under the outer periphery of the point where the frusto-conical wall portion (9) joins the circular flange (12).

Inventors: EARL RAYMOND FREDERICK, EARL, RAYMOND FREDERICK
Applicants: POLYPIPE PLC
Application year: 1992
Main classification: F16K24
IPC codes: F16K24