Fluid handling – Line condition change responsive valves – Direct response valves
Reexamination Certificate
2000-08-31
2002-07-09
Buiz, Michael Powell (Department: 3753)
Fluid handling
Line condition change responsive valves
Direct response valves
C137S323000
Reexamination Certificate
active
06415816
ABSTRACT:
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.
Beckey Thomas J.
Nyvall Peter J.
Stone Richard T.
Buiz Michael Powell
Cherne Industries Incorporated
Eggink Anthony G.
Schoenfeld Meredith H.
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