USRE30849E - Anti-siphon and backflow prevention valve - Google Patents

Abstract

An anti-siphon and back-flow prevention valve having a main valve chamber including air ports, an inlet at its lower end and an outlet at its upper end. Contained within the main valve chamber is a check valve including a check valve seat, through which the flow of liquid in the valve must pass. The check valve seat has a flexible diaphragm which mates with the check valve seat and functions to block any back flow of liquid from the main valve chamber into the inlet. A flexible ring is also contained in the main valve chamber and mates with the air ports to function as an air valve, allowing air to enter the main valve chamber during low pressure conditions down stream from the valve. The check valve and air valve operate independently of each other, responding to the various air and liquid pressures in and around the main valve chamber. Both valves are normally held closed by the force of gravity and static water pressure within the main valve chamber during no-flow conditions.

Description

BACKGROUND OF THE INVENTION

The present invention relates to an improved anti-siphon and back flow prevention valve for use in plumbing systems and more specifically to such a valve having an air valve and check valve where both valves operate independently of each other.

Anti-siphon and back flow prevention valves have been in use for some time and are generally used in plumbing systems. Such valves are often required by local health and sanitary codes. The valves prevent the contamination of the liquid supply upstream from the valve due to liquid back-flow and contamination of the supply line downstream from the valve due to siphoning.

Such valves commonly incorporate an air valve to permit the entry of air into line under pressure conditions that would otherwise permit a liquid to siphon upstream to the valve. They also incorporate a check valve to prevent liquid from passing upstream through the valve to the supply.

Such valves frequently use diaphragms, springs and cams to detect water pressure upstream from the valve and to close a normally open air valve before liquid reaches the valve, in order to prevent the liquid from leaking through the air valve during normal flow conditions. In such valves the possibility of leakage under low liquid pressure conditions or when the flow is started is always present. Moreover, these valves are often large and expensive and tend to reduce the liquid pressure across the valve. This renders these valves particularly unsuitable for plumbing installations in areas of limited space and possible low liquid pressure conditions such as in mobile homes and other similar recreational vehicles. The possibility of leakage from the air ports under low liquid pressure conditions likewise limits the utility and consumer acceptance of such valves in these applications.

Most existing valves use a single diaphragm to provide both the air valve and check valve functions and are therefore subject to the above limitations, notably leakage during low pressure conditions and start-up and pressure reduction through the valve. U.S. Pat. No. 2,174,742 discloses a valve which incorporates separate diaphragms for the air valve and check valve. In this valve, however, both diaphragms are normally open during no-flow conditions. The check valve closes only upon the start of backflow, thereby permitting an initial contamination of the line upstream. The air valve requires a finite amount of liquid pressure acting on it before it closes off its air ports completely. Therefore, leakage of liquid through the air valve is possible under low liquid pressure conditions or when the liquid flow has initially started.

SUMMARY OF THE INVENTION

The improved valve consists of a main valve chamber, including a check valve chamber and an air valve chamber. At the lower end of the main valve chamber there is an inlet permitting the entry of liquid and at the upper end is an outlet permitting the exit of liquid from the main valve chamber. Contained in the check valve chamber is a check valve seat. A plurality of air ports surround the inlet in the body of the main valve chamber and a flexible ring is located in the air valve chamber and can mate with the air ports. Located above the check valve seat and able to mate with it, is a flexible diaphragm.

During no-flow conditions, the flexible ring is held against the air ports by the force of gravity and the weight of liquid above it in the air valve chamber. This blocks the entry of air into, and the exit of liquid from, the air valve chamber. The leakage of liquid through the air ports is thereby prevented during these conditions.

Whenever there is negative pressure downstream of the valve, the pressure differential forces the ring away from the air ports permitting the entry of air through these air ports into the main valve chamber. This equalizes the pressure differential and prevents the occurrence of siphoning.

During no-flow conditions the flexible diaphragm mates with the check valve seat and is held in contact with the seat by the weight of liquid above it and the force of gravity. This action blocks the passage through the check valve seat and prevents the liquid in the line downstream, from flowing back upstream. In addition, the ring is flexible and tends to seat in conformity with the shape of the check valve seat providing a seal which is not subject to leakage as a result of the presence of any foreign matter on the check valve seat.

During normal flow conditions, the liquid pressure in the inlet of the main valve chamber pushes the disphragm away from the check valve seat allowing the flow of liquid out of the valve into the check valve chamber and then downstream.

In the improved valve the air valve and check valve operate independently. Both valves are normally closed during no-flow conditions, preventing the back flow of liquid upstream from the valve and also preventing the leakage of liquid from the valve through the air ports, both during these conditions and during initial flow conditions when the liquid pressure may be temporarily small.

Moreover; due to the light weight of the flexible diaphragm and its free movement above the check valve seat there is a relatively low liquid pressure drop through the check valve chamber. Similarly, the flexible ring is responsive to small pressure differentials and thereby provides positive protection against siphoning. Because of its simplicity of operation, the valve can be manufactured in a small and inexpensive package and is therefore particularly suitable for application in recreational vehicles or other facilities of limited space.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded view of the valve;

FIG. 2 is a top plan view of the valve;

FIG. 3 is a vertical cross sectional view of the valve along theline 3--3 of FIG. 2 showing the valve during normal flow conditions with the air valve closed and the check valve open;

FIG. 4 is a cross sectional view of the valve along theline 4--4 in FIG. 3;

FIG. 5 is a partial vertical cross section of the valve, similar to FIG. 3 but showing the air valve in the open position and the check valve in the closed position, in a mode to prevent siphoning;

FIG. 6 is a partial vertical cross section of the valve, similar to FIG. 3 showing both the air valve and check valve in the closed position, during no-flow conditions.

Referring to the drawings, an anti-siphon and back-flow prevention valve 10, desirably formed primarily of plastic, includes avalve body 12 defined in part by a tubularexternal wall 14. Thisexternal wall 14 surrounds and defines amain valve chamber 16 within thevalve 10. Thewall 14 carriesthreads 18 on its exterior so that it may be mated into a plumbing system.

Depending downwardly from the integral with thevalve body 12 is aninlet 20, of tubular configuration. Theinlet 20 is also externally threaded as at 22 for mating into the plumbing system. Theinlet 20 has aninternal passageway 24 which leads generally into thevalve chamber 16.

A check valve, generally 26, is situated within thevalve body 12 and includes acheck valve seat 28, acheck valve diaphragm 30, and a checkvalve diaphragm retainer 32. Thecheck valve seat 28 includes a lowertubular stem 34 and anupper funnel 36, the funnel terminating at its upper end in aflat 37, through which aninternal passageway 38 runs. The stem is tapered at its lower end, and thestem 34 fits snugly into an enlarged diameterupper portion 40 of theinlet passageway 24. Thecheck valve diaphragm 30 is relatively thin and flexible, being desirably composed of a low durometer rubber. If any obstacle such as foreign debris should become located on the check valve seat, the diaphragm will collapse about it, substantially checking reverse flow. It is retained in alignment with thecheck valve seat 28 by the checkvalve diaphragm retainer 32, also located within thevalve body 12. The retainer includes anupper ring 40, having an external circumference which fits snugly into ashoulder 42 internally situated at the upper end or theoutlet 43 of thevalve body 12.

A number, desirably four,legs 44 depend downwardly from thering 40, and terminate coextensively at theupper flat 37 of thefunnel 36 of thecheck valve seat 28. About midway of their lengths, thelegs 44 join to aretainer plate 46, the plate as best seen in FIG. 3 being located below the upper end of thevalve body 12 and above thecheck valve seat 36. Thecheck valve diaphragm 30 is held against lateral movement by the portions of thelegs 44 below theplate 46, and is limited in its upper movement by theplate 46.Openings 48 defined by the ring and the plate enable flow through the check valve. Theretainer 32 and thecheck valve seat 28 all define a check valve chamber within which thecheck valve diaphragm 30 moves, to open and close thecheck valve 26.

Thevalve body 14 has abottom wall 50 which surrounds theinlet 20, and which has a number, desirably six,air ports 52 therein, see FIG. 4. The upper portions of theair ports 52 are depressed as at 54. Situated over theair ports 52, and surrounding thestem 34 of thecheck valve seat 28 is anair valve ring 56. The upper face of thebottom wall 50, the inner face of thevalve body wall 14 and the outer face of thecheck valve seat 28 at itsfunnel 36 all define an air valve chamber, serving to limit movement of theair valve ring 56. The check valve seat, at its funnel-shapedportion 36, overhangs theair valve ring 56, preventing flow effects, such as back flow or turbulence from acting on the ring. Desirably, thering 56 or theair ports 52 are covered with a thin layer of a lubricant such as silicone grease. This prevents sticking at low pressures, and prevents sticking after long periods of non-use.

Having described the various structural components of the valve, its operation may now be briefly reviewed.

Under no-flow conditions, shown in FIG. 6, theair valve ring 56 mates with and thus closes theair ports 52, the ring being held in this position by the force of gravity and the static liquid pressure above it. Further, thecheck valve diaphragm 30 mates with thecheck valve seat 28 and thus closes thecheck valve 26, preventing any back flow of liquid upstream through theinlet 20. This of course prevents contamination of the source of liquid supply. In actual practice, both thering 56 and thediaphragm 30 come into close face-to-face contact with their opposed funnel-shaped members, but are shown somewhat ideally, i.e., non-flexed, in the drawings.

Under normal flow conditions, shown in FIG. 3, theair valve ring 56 remains in place, being out of the way of any flow, and being shielded from disturbing turbulance by the overhangingfunnel 36 of thecheck valve seat 28. Normal flow runs throughinlet 20 in the direction A, through thepassageway 38 in thecheck valve seat 28, lifts thediaphragm 30 away from said seat, and continues past thelegs 44 of the retainer, through theretainer openings 48, and then further downstream.

Should, during non-flow conditions, a low-pressure condition arise downstream, which might cause undesirable siphoning, the air valve opens. As best seen in FIG. 5, atmospheric pressure on the exterior of the air valve would press against theair valve ring 56, moving the ring away from theair ports 52 since this atmospheric pressure is greater than the low pressure existing downstream. Opening of theair ports 52 permits entry of air through the air valve chamber and then throughflow openings 48, equalizing pressure on the upstream and downstream sides of the valve. During this time, the check valve is retained closed by thediaphragm 30, being unaffected by the movement of theair valve ring 56. Since theair valve ring 56 is essentially free floating, it is able to open under low negative pressure. It is also able to close under low positive pressure.

It will thus be seen that the air valve and the check valve work completely independently of one another, each able to respond quickly to various pressures and conditions of flow, while both being closed during no flow conditions, so as to prevent accidental leaking. No leaking is therefore likely during start-up or initial sensing of a different flow or pressure condition. The foregoing has been achieved with a device having few parts, being small in size and being economical to manufacture. The latter is particularly true, since the valve is desirably formed of plastic, except for the air valve ring and the check valve diaphragm, which may be stamped from rubber.

Claims (8)

What is claimed is:

1. A valve for preventing backflow and siphoning, comprising:

a. a valve body,

b. check valve means within the valve body, the check valve means including a seat, a diaphragm in alignment with the seat, and diaphragm retaining means, said retaining means including a plate and spaced legs depending from said plate and contacting the seat, the diaphragm being captured for limited movement between the plate and the seat, and

c. air valve means within the valve body and operating independently of the check valve means, said air valve means including at least one air port in the valve body, a seat surrounding the air port, and a closing member in alignment with the air port, the member normally mating with the air port seat and opening during a downstream low pressure condition to permit equalization.

2. A valve as set forth in claim 1 wherein the air valve means is circumferentially disposed about the check valve means.

3. A valve as set forth in claim 2, wherein the check valve means include a funnel shaped check valve seat, the air valve means being disposed about the check valve seat.

4. A valve as set forth in claim 3, wherein there are a number of air ports being depressed, the air ports surrounding the check valve seat.

5. A valve as set forth in claim 4 wherein a lubricant is situated between the air valve closing member and the air ports.

6. A valve as set forth in claim 1 wherein the seat of the check valve means overhangs the air valve closing member and comprises a stop to limit movement of said closing member.

7. A valve for preventing backflow and siphoning, comprising:

a. a valve body defining a chamber, the valve body including an inlet leading into the chamber and an outlet leading out of the chamber, and at least one air port in the chamber,

b. a first flow path running from the inlet through the chamber to the outlet,

c. check valve means located within the chamber and controlling flow in .Iadd.and normally closing .Iaddend.the first flow path,

d. a second flow path running from the air port, by-passing the check valve means, through the chamber to the outlet, and

e. air valve means operable independently of the check valve means and operative hydraulically downstream of the check valve means, the air valve means including a closing member located across the second flow path in alignment over .Iadd.and normally closing .Iaddend.the air port, the closing member being mated against the air port to prevent flow in the second flow path during a positive pressure condition within the chamber and being opened by a negative pressure condition in the second flow path to permit pressure equalization.

8. A valve as set forth in claim 7 wherein the valve body includes a plurality of air ports, said air ports circumferentially surrounding the check valve, the second flow path leading from said air ports through the chamber to the outlet.

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