AU644243B2

AU644243B2 - Reduced pressure zone valve

Info

Publication number: AU644243B2
Application number: AU88185/91A
Authority: AU
Inventors: Donald Hardie Smith
Original assignee: QUEENSLAND PLUMBING Pty Ltd
Current assignee: QUEENSLAND PLUMBING Pty Ltd
Priority date: 1990-11-29
Filing date: 1991-11-26
Publication date: 1993-12-02
Anticipated expiration: 2009-12-05
Also published as: AU8818591A

Description

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AUSTRALIA

Patents Act 1990 Name of Applicant QUEENSLAND PLUMBING PTY. LTD.

Actual Inventor(s) DONALD HARDIE SMITH Address for Service GRANT ADAMS COMPANY, Patent Trade Mark Attorneys Level 9, National Mutual Centre, 144 Edward Street, BRISBANE. QLD. 4000

AUSTRALIA.

Invention Title "REDUCED PRESSURE ZONE VALVE" Details of Associated Provisional Applications Numbers PK 3605 The following statement is a full description of the invention including the best method of performing it known to me.

THIS INVENTION relates to a reduced pressure zone valve.

Patent Application No. 45842/89 (618862) describes and illustrates a reduced pressure zone valve assembly for the prevention of back-syphonage and back pressure flow such as may occur when a water main is fractured or disconnected. When a mains fails there is the possibility that the consequent drop in mains pressure may allow contaminated water to flow back into the main.

The general object of the invention is to provide, certain improvements in reduced pressure zone valves as claimed in Patent Application No. 45842/89 (618862) for improving their operation.

With the foregoing and other objects in view, the invention resides broadly in a reduced pressure zone valve assembly for connection between a water supply line from a water main and a water delivery line including: a non-return valve connected to the supply line; a hydraulic cylinder; a first water inlet to the hydraulic cylinder, connected to the supply line up-stream of the non-return 25 valve; a second water inlet to the hydraulic cylinder, connected down-stream of the non-return valve; a piston in the hydraulic cylinder between the

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first and second water inlets, thereto dividing the S 30 cylinder into first and second ends; an outlet from the hydraulic cylinder to the water delivery line at the same second end of the cylinder as is the second water inlet; a passage from the hydraulic cylinder at the second end to atmosphere; a valve connected to the piston to close the said passage when the piston is acted on by water under pressure in the supply line, and for opening the said passage when the pressure of the water in the supply line is reduced below that at the outlet; and the piston being sealed to the cylinder at two spaced apart points therealong, the space between the two points being vented by a passage through the piston to the passage and thereby to atmosphere.

In order that a preferred embodim-nt of the invention may be readily understood and carried into practical effect, reference is now made to the accompanying drawings, wherein:- FIG. 1 is a partly broken-away side elevational view of a reduced pressure zone valve according to the invention, in its normal or inoperative position; and FIG. 2 is a similar view of the valve in its operative position preventing back-flow of water.

The reduced pressure zone valve assembly shown in the drawings is connected between a water supply line 10 from a water mains system and a water delivery pipe 11 conducted into premises required to have the reduced pressure zone back-flow prevention device installed.

25 The valve assembly between the water supply line 10 and the delivery pipe 11 includes, connected in series, an inlet ±2 to a first non-return valve 13, a valve chamber 14, and a second non-return valve 15, and an outlet 15 therefrom. The non-return valves are of well-known type permitting flow of water under pressure in the direction indicated by arrows but preventing return flow of the water. Test valves 17 are connected to the inlet 12 of the first non-return valve 13 and the *0 outlet 16 from the second non-return valve 15, for the purpose of testing the assembly, as may from time to time be required. A third similar test-valve (not shown) may also be connected to the valve chamber 14.

The valve chamber 14, interposed between the first and second non-return valves, is cylindrical with its axis perpendicular to the axes of the inlet and outlet pipes 10 and 11. The valve chamber is provided with sealed top and bottom end caps 18 and 19 screwed onto the valve chamber. The top end cap 18 secures, within the upper part of the chamber 14, a cylindrical piston sleeve 20 with a top peripheral flange located on top of the chamber. The outlet of the first non-return valve 13 communicates with the valve chamber 14 by way of a chamber inlet 21 leading perpendicularly into the ~middle of the chamber 14, a chamber outlet 22 coaxial 15 with the inlet 21 leading to the second non-return valve Ss The inlet 12 to the first non-return valve 13 is connected by a by-pass line 23 to an inlet 24 leading coaxially through the top end cap 18 of the chamber 14.

An annular valve seat 25 is sealed in an axial aperture through the bottom end cap 19 its bore being a drain S outlet passage 26. A vermin-proof disc 27 is fixed in the outlet passage Within the upper part of the chamber 14 is a 25 piston 28 on a downwardly extending stem 29 having on its lower end a valve 30 which, when the piston is dep-essed or retracted as shown in FIG 1, seats upon the valve seating 25 to close the drain outlet passage 26; and when in raised or extended position, as shown in FIG 2, unseats the valve 30 to open the drain outlet passage.

The piston 28 ma T be made in two diameters.

Its upper part, of lesser diameter, has a circumferential sealing ring 31 and is slidable in the piston sleeve 20, its lower part of larger diameter and having a circumferential sealing ring 32 being slidable in the chamber below the sleeve 20. A water passage 33 is formed through the valve 30, the stem 29 and into the piston 28 where it leads to radial passages 34 to the periphery of the piston between the sealing rings 31 and 32.

A fairly light helical spring 35, its lower end on the bottom end cap 19 about the valve seat its upper end engaging a flange 36 about the stem 29, biases the piston 28 to its raised position. This spring serves to counterbalance the piston and its associated parts. The flange 35 fits fairly closely in the chamber 14 and has a series of water passages 37 through it.

15 In use, water under pressure will flow through *the valve assembly, from the water supply line 10 to the delivery pipe 11 whenever water is drawn from any of the

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tap outlets of the premises supplied from the water main. The piston 28 is depressed, as shown in FIG 1 and the valve 30 is held in its closed position on the seating eooe These conditions apply unless or until there o is a drop in the mains pressure so that water can return from the top of the valve chamber 14 through the by-pass *oot: 25 23 by-passing the first non-return valve 13 which Sprevents return of water under pressure from below the Spiston. The pressure differential causes the piston to rise, as shown in FIG 2, unseating the valve 30 so that the water contained in the cylinder below the piston can escape to waste through the outlet passage 26. The device, then maintains a reduced pressure zone between the incoming mains pressure on one side of the valve chamber 14 and the mains pressure on the opposed side of the valve chamber. In the event of any leakage from the second non-return valve 15, any returning water passes to waste. When normal mains pressure is resumed the piston 28 is driven immediately to its normal position shown in FIG i, bringing the valve 30 to closed position on its seating If there should be a failure of the upper sealing ring 31 of the piston 28 so that high pressure water enters between the two sealing rinas 31 and 32, this water will escape through the water passages 34 into the axial passage 33 through the piston stem and drain through the drain outlet passage 26, thus warning that the piston requires maintenance. An unrelieved build up of water pressure between the two sealing rings could interfere with the quick response of the valve assembly to any failure in the water main.

15 Reduced pressure zone valves according to the invention will be found to be very effective in achieving the objects for which they have been devised.

.6 It will, of course, be understood that the particular embodiment of the invention herein described and illustrated may be subject to many modifications of constructional detail and design, which will be readily apparent to persons skilled in the art, without dmat departing from the spirit and scope of the invention.

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Claims

1. A reduced pressure zone valve assembly for connection between a water supply line from a water main and a water delivery line including: a non-return valve connected to the supply line; a hydraulic cylinder; a first water inlet to the hydraulic cylinder, connected to the supply line up-stream of the non-return valve; a second water inlet to the hydraulic cylinder, connected down-stream of the non-return valve; a piston in the hydraulic cylinder between the first and second water inlets thereto dividing the cylinder into first and second ends; an outlet from the hydraulic cylinder to the water delivery line at the same second end of the cylinder as is the second water inlet; a passage from the hydraulic cylinder at the second end to atmosphere; a valve connected to the piston to close the said passage when the piston is acted on by water under 25pressure in the supply line, and for opening the said 25 passage when the pressure of the water in the supply line is reduced below that at the outlet; and the piston being sealed to the cylinder at two spaced apart points therealong, the space between the two points being vented by a passage through the 30 piston to the passage and thereby to atmosphere. A reduued pressure zone valve substantially as hereinbefore described with reference to the :i accompanying drawings. DATED this twenty-fourth day of August 1993. QUEENSLAND PLUMBING PTY. LTD., by its Patent Attorneys, GRANT ADAMS COMPANY. Title: "REDUCED PRESSURE ZONE VALVE" ABSTRACT A reduced pressure zone valve assembly contains a piston (28) actioning a valve (30) by which backflow from a line (11) may be dumped to avoid syphoning into a mains Piston (28) is contained in a cylinder (14) being at mains pressure at one end and either of mains pressure or a downstream pressure, whichever is greater, at the other. Connection to the mains at the other end is via a check valve (13) oriented against flow back to the mains. j 4' S. e'