AU606060B2

AU606060B2 - Water supply back flow preventer

Info

Publication number: AU606060B2
Application number: AU73188/87A
Authority: AU
Inventors: Donald Leonard Fayers
Original assignee: DONSON IND Pty Ltd
Current assignee: DONSON INDUSTRIES PTY Ltd
Priority date: 1986-05-22
Filing date: 1987-05-19
Publication date: 1991-01-31
Anticipated expiration: 2007-05-19
Also published as: AU7318887A

Description

PHILLIPS ORMONDE AN' FITZPATRICK Patent and Trade Mark Attorneys 367 Collins Street Melbourne, Australia P17/2/83 Y, I AUSTRAL IA Patents Act 6'06060 COMPLETE SPECIFICATION

(ORIGINAL)

Class Int. Class Application Number: Lodged: -7 3 *Complete Specification Lodged: Accepted: 0 0. '99 Priority 0- Published: Reae Art: This document contain t& amendments mtidc- tJr7c; Section 419 and is c:orrtxt i(ji P JfJZ4~nf~

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APPLICANT'S REF.: CAP of PH 6045/86 Name(s) of Applicant(s): DONSON INDUSTRIES PTY. LTD.

Address(es) of Applicant(s).

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090 105 NEWLANDS ROAD, COBURG, Victoria 3058 Actual Inventor(s), DONALD LFONARD FAYERS Address for Service is: PHILLIPS, ORMONDE AND FITZPATRICK Patent and Trade Mark Attorneys 367 Collins Street Melbourne, Australia, 3000 Complete Specification for thc Invention entitled, "WATE~R SUPPLY BACK FLOW PREVENTER" The following statement is a full description of this inventio~n, ir;clnd3~ig the best method of performing it known to applicant(s)., Patent and Trade NMark Attorneys 367 Collins Street Melbourne, Australia The present invention relates to valves particularly non-return valves.

Whilst numerous types of non-return valve are known in the prior art, valves for use with mains pressure water supply lines for example present particular difficulties.

Water supply authorities place particular restrictions on the form of mains water supply non-return valves due to the possibility of contamination of the water mains should the main supply fail via back flow or back syphonage of water.

In recent times there has been a dramatic increase in the Snumber of cases of water being contaminated in water supply pipes due to back flow.

Back flow can happen when a water main fails (usually a broken pipe) which allows the water to drain from the main and in doing so syphons the water backwards from the house pipes, If this happened at the time that someone was filling a swimming pool, laundry trough or washing machine with a hose that was immersed in the water, then contaminated water could syphon back through the open tap Sand into the supply pipes.

S* Back flow prevention valves known in the prior art are the subject of severe wear difficulties and may fail under the severe pressure drops which may occur when a main supply fails.

It is accordingly an object of the present invention to overcome or at least alleviate one or more of the difficulties related to the prior art, Accordingly, in a first aspect, there is provided a backflow prevention valve comprising: a valve body having a chamber and an inlet into and an outlet from said chamber, a piston moveable in the chamber and having a fluid passage therethrough, a first non-return valve member located in the fluid passage and, at least one relief port from the chamber intermediate the inlet and outlet, 2a the piston being moveable between a first position wherein the relief port is closed and fluid is able to flow from the inlet through the fluid passage to the outlet, and the second position where reverse flow through the passage is prevented by the non-return valve member and the relief port is opened and fluid is able to flow from said outlet to said relief port, the piston adopting the first position when fluid pressure at the inlet is greater than at the outlet, and adopting the second position when the fluid pressure at the outlet is greater than the inlet, and wherein said piston includes a cap member proximate the inlet such that fluid acting on the cap member causes the piston to adopt the first position.

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0 3 wherein the relief port is closed and fluid is ableJflow from the inlet through the fluid passage to t let, and the second position where rev ie flow through the passage is prevented by the non-r n valve member and the relief port is opened and id is able to flow from said outlet to said reli ort, the piston adopting the first position when id pressure at the inlet is greater than at the ou and adopting the second position when the fluid In a preferred aspect of the present invention the backflow prevention valve includes a second non-return valve member in the outlet is located in the valve, said second non-return valve member being mounted in the outlet and being operative to prevent flow of fluid from the outlet to ego the chamber.

The second non-return valve member may be of the diaphragm type.

In another preferred aspect of the present invention the piston has a shoulder proximate the outlet and the chamber has a valve seat proximate the outlet, such that when the piston adopts the first position the shoulder and the valve seat engage to form a seal to prevent fluid from flowing out the relief port.

In yet another preferred aspect of the present invention the chamber is in the form of a cylindrical bore and the piston is slideable within the bore and an annular sealing means is interposed between the piston and the bore to prevent fluid flow around the periphery of the piston.

The piston may include an annular groove around its periphery and said groove has a sealing ring located therein.

The sealing ring may be of any suitable form° The sealing ring maybe of the ring type. The sealing ring' may be of the "bucket washer" type. Double sided bucket washers may be used.

The first non-return valve member may be positioned within the outlet section of the piston. The first

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4 non-return valve member may be positioned proximate the inlet end of the outlet section of the first valve member.

The first non-return valve member, and where present, the second non-return valve member may be of the diaphragm type. The first and second non-return valves may be of the lift check valve or "pop" valve type.

It will be understood that the backflow prevention valve assembly according to the present invention may function as follows: In normal use, fluid flowing from a fluid supply passes through the inlet to the chamber and acts on the cap member on the piston such that the piston S adopt the first position. The fluid flows around the cap member and into the fluid passage in through the piston.

The fluid then flows past the first non-return valve and when present, the second non-return valve and through the outlet.

When the fluid supply fails, back flow is initially retarded or prevented by the second non-return valve, when ago$ present. If the second non-return valve fails, back flow is then halted by the first non-return valve within the 0 piston. If the back flow pressure is sufficient, the piston S will be raised from its valve seat and fluid flow will pass through the relief port from the chamber in the side of the valve body.

The non-return valve assembly may be manufactured in any suitable manner and in any suitable material. A metal S. material is preferred. The valve body of the back flow prevention valve assembly may be formed in a brass material. The valve body may be cast or forged. The piston and the cap member therefor may be formed from brass rod.

The brass rod may be machined to the required shape.

The present invention will now be more fully described with reference to the accompanying drawings. It should be understood, however, that the description following is illustrative only and should not be taken in any way as a i restriction on the generality of the invention as described above.

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5 Figure 1 is a cross-sectional view of a backflow prevention valve assembly according to one embodiment of the present invention.

Figure 2 is a cross-sectional view of a backflow prevention valve assembly according to an alternative aspect of the present invention.

In more detail, and referring firstly to Figure 1, there is there illustrated a backflow prevention valve assembly comprising a valve body 1, an inlet 2 into and outlet 3 from a chamber 3a, a piston 4 located in the S chamber 3a of the valve body 1. A sealing ring 5 is provided in the peripheral groove in the piston 4. This seals the piston to the inner wall of the valve body 1.

In use, fluid flows through the inlet 2 contacts a cap member 6 on the piston 4 and passes through orifices 7 therein. Fluid then passes into a .fluid passage in the chamber through a first non-return valve 8 and, when present, a second non-return valve 9 before passing out of the outlet 3.

If backflow pressure occurs, backflow may be prevented by the second non-return valve member 9. HoWever, if this fails or is not present, the force of fluid will close the first non-return valve member 8 and if sufficient, will raise the piston 4 from the valve seat 10. Fluid vill then pass out the relief ports 11 and 12 from the chamber 3a in the side wall of the valve body to atmosphere.

With reference to Figure 2, like parts are described with like numbers. The only distinction between Figure 1 and Figure 2 is that in Figure 2 the non-return valves 13 and 14 are of the lift-check type. Guide rings 15 and 16 are provided within the fluid passage and outlet 3.

Finally, it is to be understood that various other modifications and/or alterations may be made without departing from the spiri of the present invention as outlined herein.

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Claims

1. A backflow prevention valve comprising: a valve body having a chamber and an inlet and an outlet from said chamber, a piston moveable in the chamber and having a fluid passage therethrough, a first non-return valve member located in the fluid passage and, at least one relief port from the chamber intermediate the inlet and outlet, the piston being moveable between a first position wherein the relief port is closed and fluid is able to flow from the inlet through the fluid passage to the outlet, S and a second position where reverse flow through the passage is prevented by the non-return valve member and the relief port is opened and fluid is able to flow from said outlet to said relief port, the piston adopting the first position when fluid pressure at the inlet is greater than at the outlet, and adopting the second position when the fluid pressure at the outlet is greater than the inlet, .i and wherein said piston includes a cap member proximate the inlet such that fluid acting on the cap member causes the piston to adopt the first position. S** 0 6 1. A backflow prevention valve comprising: a valve body having a chamber and an int and in outlet from said chamber, a piston moveable in the chamber and aving a fluid passage therethrough, a first non-return valve member ocated in the fluid passage and, at least one relief port f m the chamber intermediate the inlet and outlet, the piston being mo able between a first position S* wherein the relief port 's closed and fluid is able to flow from the inlet throug the fluid passage to the outlet, and a secon position where reverse flow through the passage is pre pnted by the non-return valve member and the relief port s opened and fluid is able to flow from said outlet t said relief port, the piston adopting the first positi when fluid pressure at the inlet is greater than at the utlet and adopting the second position when the fluid i S 2. A valve according to claim I wherein a second non-return valve member in the outlet is located in the valve, said second non-return valve member being mounted in the outlet and being operative to prevent flow of fluid from the outlet to the chamber.

3. A valve according to claim 1 or 2 wherein the piston has a shoulder proximate the outlet and the chamber has a valve seat proximate the outlet, such that when the piston adopts the first position the shoulder and the valve seat engage to form a seal to prevent fluid from flowing out the relief port.

4. A valve according to any one of claims 1 to 3 wherein the chamber is in the form of a cylindrical bore and the piston is slideable within the bore and an annular sealing means is interposed between the piston and the bore to RB L -7- prevent fluid flow around the periphery of the piston. A valve according to claim 4 wherein the piston includes an annular groove around its periphery and said groove has a sealing ring located therein. the piston includes a cap member -a he inlet such that fluid actin cap member causes the piston to I A valve according to any one of claims 2 to 5 wherein S the first non-return valve member and second non-return valve member are of the pop-valve type.

7. A backflow prevention valve according to claim 1 substantially as hereinbefore described with reference to any one of the drawings. DATED: 18 May, 1990 PHILLIPS ORMONDE FITZPATRICK Attorneys for:- DONSON INDUSTRIES PTY. LTD S "5796r j C