AU623547B2 - Reduced pressure zone valve - Google Patents

Description

COMMONWEALTH OF AUSTRALIA Patents Act 1952 Name of Applicant Address of App~licant Actual Inventor Address for Service QUEENSLAND PLUMBING PTY LTD 22 Prospect Street, Fortitude Valley, Queensland, 4006,

AUSTRALIA.

DONALD HiARDIE SMITH GR~ANT ADAMS COMPANY Patent Trade Mark Attorneys Level 9 NATIONAL MUTUAL CENTRE 144 Edward Street Brisbane, Queensland, 4000

AUSTRALIA.

COMPLETE SPECIFICATION FOR THE INVENTION ENTITLED: "REDUCED PRESSURE ZONE VALVE" The following statement is a full description of the invention including the best method of performing it 'known to the applicant.

i THIS INVENTION relates to a reduced pressure zone valve.

In many water supply installations, it is required to instal reduced pressure zone valve assemblies for the prevention of back-syphonage and back pressure flow such as may occur when a water main is fractured or disconnected, with the possibility that the consequent drop in pressure may draw contaminated water into the main.

The general object of the invention is to provide, for this purpose, a reduced. pressure zone valve which is particularly efficient and positive in operation. Other objects achievable in preferred embodiments of the invention are to provide such a valve assembly which is particularly simple and economical in construction and durable and trouble-free in use.

With the foregoing and other objects in view, the invention resides broadly in a reduced pressure Sor.' valve assembly for connection between a water supply line from a water main and a water delivery line including: a valve chamber connected between first and second spring-loaded or equivalent non-return valves; a first hydraulic cylinder connected to the valve chamber; a first water inlet to the first hydraulic cylinder, connected to the water supply line up-stream of the first non-return valve; 0,^o a second water inlet to the first hydraulic :30 cylinder from the valve chamber; 0 0 a piston in the first hydraulic cylinder between the first and second water inlets thereto; a second hydraulic cylinder opening from the valve chamber and with a drainage vent to the atmosphere; c I 7 t ot 0 0*4t 00000) 0 (0 (0 0 01 0 a first valve for closing the second hydraulic cylinder from the valve chamber; a third hydraulic cylinder communicating with the valve chamber; a second valve for closing the third hydraulic cylinder; means for conveying water under pressure from the valve chamber to the third hydraulic cylinder to equalise water pressure in the two; and actuating means operatively connecting the first and second valves operatively to the piston so that, while the piston is advanced in the first hydraulic cylinder by higher water pressure in the water supply line than in the valve chamber, the first valve 15 closes the second hydraulic cylinder and the second valve closes the third hydraulic cylinder, and when the piston is retracted in the first hydraulic cylinder by lower water pressure in the supply line than in the valve chamber the first valve and the second valve are moved to open positions and water in the valve chamber can drain through the vent of the second hydraulic cylinder.

Other features of the invention will become apparent from the following description.

In order that a preferred embodiment 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 30 view of a reduced pressure zone valve according to the invention, in its normal inactive position; and FIG 2 is a similar view of the valve in its active position preventing back-flow of water.

The reduced pressure zone valve assembly illustrated is connected between a water supply line from a water mains system and a water delivery pipe 11.

r conducted into an establishment required to have the reduced pressure zone back-flow prevention device installed.

9 0 0 909 09 9 9B 9 o 9 o 9o o o i o 0 oao o 0 6 l 0 0 6 D B O ft o The valve assembly between the water supply line 10 and the delivery pipe 11 includes a first nonreturn valve 12, a main valve chamber 13 and a second non-return valve 14, both of the non-return valves being of well-known spring-loaded type permitting flow of water under pressure in the direction indicated by arrows but preventing flow of the watrr.

The valve chamber 13 interposed between the first and second non-return valves 12 and 14 is cruciform, having an inlet 15 from the non-return valve 12 and a coaxial outlet 16 to the non-return valve 14 15 and, perpendicularly to these, a cylindrical upper arm 17 and a coaxial lower arm 18.

An upper or first cylinder 19 is fitted closely in the upper arm 17 of the main valve chamber 15, and is formed integrally with a coaxial top cap which is screwed onto, and sealed to, the top of the upper arm 17.

A lower or second cylinder 21 is closely engaged in the lower arm 18 of the chamber 15 and is formed integrally with a coaxial bottom cap 22 which is 25 screwed onto, and sealed to, the bottom end of the lower arm 18, An inner or third cylinder 28 is fixed and sealed through a central aperture in the bottom cap 22 and for the greater part is located coaxially within, 30 and spaced from, the lower cylinder 21. Its bottom end is closed by a closure cap 24.

A series of drainage holes 25 are formed through the bottom cap 22 about the inner cylinder 23.

A by-pass line 26 is connected between the water supply line 10 upstream of the first non-return 7 valve 12 and a central opening 27 through the top cap A piston 28 is slidable in the upper cylinder 19 and is mounted on a stem 29 of which the lower end, reduced in diameter, is slidable in a stem guide formed integrally with the closure cap 24.

Fixed on the stem 29 are a disc valve 31 and, below it, a plunger valve 32. When the piston 28 is brought to its lowered or retracted position as shown in FIG 1, the disc valve 31 bears on and closes the top of the second or lower cylinder 21 and the plunger valve 32 enters and closes the third or inner cylinder 28.

The piston 28 is biased to its retracted or raised position as shown in FIG 2 by a light helical compression spring 33 about the reduced-diameter lower part of the stem 29, its upper end bearing against a stop disc 34 fixed on the stem and its lower end bearing on an adjustment nut 35 screwed into the threaded lower part of the bore of the inner cylinder 23 and formed from its underside with apertures to facilitate its rotation by a suitable tool to adjust the compression of the spring 33.

+The stem 29 is formed with an axial passage 36 and inlet holes 37 enter this passage at a position between the piston 28 and the disc valve 31, and outlet holes 38 lead from the bottom of the passage into the third or inner cylinder 28 below the plunger valve 32.

When the reduced pressure zone valve is installed and functioning, water under pressure will 30 flow through the assembly, from the water supply line 4 S to the delivery pipe 11 whenever water is drawn from any of the outlets of the premises to which the delivery pipe is connected. The piston 28 will remain, under normal circumstances, in the advanced or lowered position shown in FIG 1, as there is pressure differential between water in the supply line 10 and 7 water in the valve chamber 13 below the piston, due to the spring-loading of non-return valve 12. Also, as the lower cylinder 20 is vented to atmosphere through the drainage holes 25, water pressure within the valve chamber 13 will maintain the disc valve 31 firmly on its seat and the piston 28 lowered. The plunger valve 32 closes the third or inner cylinder 28 and the passages 36, 37 and 38 in the stem 29 ensure that water pressure within the inner cylinder 28 is equalised with that within the valve chamber 13. The spring 33 is held fully compressed.

These conditions apply unless or until there is a drop in the mains pressure, due to break or disconnection of the water main so that the water pressure in the supply line 10 and the by-pass line 26 0 fall correspondingly. Thereupon, the then relatively high water pressure within the valve chamber 13 below the piston, and in the inner or third cylinder 21, 0supplemented by the pressure exerted by the spring 33, cause the pistn to be qugickly retracted or raised to its full extent in the upper cylinder 19. The disc valve 31 and the plunger valve 32 are simultaneously unseated from the lower cylinder 21 and the inner cylinder 23 respectively, so that water in the chamber 13 can drain through the drainage holes 25. The valve assembly, then, maintains a reduced pressure zone between the incoming mains. pressure on one side of the ]i valve chamber 13 and the pressure on the opposed side of the chamber. When normal mains pressure is resumed, the 30 piston 28 is driven immediately to its normal position shown in FIG 1, bringing the disc valve 31 and the plunger valve 32 to their closed positions, closing the second cylinder 21 and the third or inner cylinder 28.

The piston 28 is formed with a small waterway 40 from the bottom of the piston to its side, between its two peripheral sealing rings 41 to reduce friction which otherwise could arise from pressure differential above and below the piston.

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

It will, of course, be understood that the embodiment of the invention herein described and illustrated may be subject to many modifications of constructional detail and design without departing from the scope of the invention hereinafter claimed.

o 6 4 9 4

Claims (3)

1. 2. A reduced pressure zone valve assembly according to Claim 1 wherein: the third hydraulic cylinder is spaced coaxially within the second hydraulic cylinder; the actuating means includes a stem extending coaxially from the piston and into the second and third hydraulic cylinders; the first and second valves being fixed on the stem.
2. 3. A reduced pressure zone valve assembly according to Claim 2 wherein: S, 15 a spring in the third hydraulic cylinder applies pressure to the stem to bias the piston to its retracted position.
3. 4. A reduced pressure zone assembly according to Claim 3 wherein: adjustment means are provided for varying the pressure applied by the spring. A reduced pressure zone assembly substantially S as herein described with reference to the accompanying t" drawings. DATED this sixteenth day of August 1990. QUEENSLAND PLUMBING PTY LTD r,0 4 By their Patent Attorneys c. GRANT ADAMS COMPANY. Y