PCT WORLD INTELLECTUAL PROPERTY ORGANIZATION International Bureau

INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PC

(51) International Patent Classification 4 (11) International Publication Number: WO 89/1 F16K 24/04, 24/00, E03C 1/10 Al (43) International Publication Date : 2 November 1989 (02.

(21) International Application Number: PCT/AU89/00174 (81) Designated States : AT (European patent), AU, BE pean patent), BR, CH, CH (European patent), D

(22) International Filing Date: 21 April 1989 (21.04.89) ropean patent), DK, FR (European patent), GB pean patent), IT (European patent), JP, LU (Eur patent), NL (European patent), SE (European p

(30) Priority data: US.

PI 7865 22 April 1988 (22.04.88) AU

Published

(71) Applicant (for all designated States except US): BURNETTA With international search report.

PTY. LTD. [AU/AU]; 161 Reynolds Roads, Mt. Pleas¬ ant, W.A. 6153 (AU).

(72) Inventor; and

(75) Inventor/Applicant (for US only) : BEATTIE, David, Dow- ley [AU/AU]; 3 Medhurst Crescent, Nollamara, W.A. 6061 (AU).

(74) Agent: COLLISON & CO.; 117 King William Street, Ade¬ laide, S.A. 5000 (AU).

(54) Title: BACKFLOW PREVENTION VALVE

(57) Abstract

A backflow prevention valve having a hollow housing (1) having an inlet check valve (5) and an outlet check valve (16) for fluids flowing through the housing and having a drain (4) from the housing with a drain valve (10) coupled to the inlet check valve (5) to open the drain valve (10) when the inlet check valve (5) is positioned to close the inlet (2) and optionally an atmos¬ pheric vent valve (9) to the hollow of the housing.

FOR THE PURPOSES OFINFORMAΗON ONLY

Codes used to identify States party to the PCT on the frontpages of pamphlets publishing international appli- cations under the PCT.

AT Austria πt France ML Mali

AU Australia GA Gabon MS Mauritania -

BB Barbados GB United Kingdom MW Malawi

BE Belgium HU Hungary NL Netherlands

BG Bulgaria IT Italy NO Norway

BJ Benin JP Japan RO Romania

BR Brazil KP Democratic People's Republic SD Sudan

CF Central African Republic ofKorea SE Sweden

CG Congo KR Republic ofKorea SN Senegal

CH Switzerland LI Liechtenstein su Soviet Union

CM Cameroon LK Sri Lanka TD Chad

DE Germany, Federal Republic of LU Luxembourg TG Togo

DK Denmar MC Monaco US United States of America

BACKFLOWPREVENTIONVALVE

This invention relates to a backflow prevention valve for pressure fluids and in particular it relates to a valve adapted to be inserted between a pressure fluid supply and a consumer area.

A problem with, for instance, domestic supplies or supplies to industrial areas is that, should a backflow occur in a mains fluid supply, such as a water supply, contamination will take place of the supply source by backflow from the consumer area.

Such a condition is highly undesirable and while for instance it is possible to have a non-return valve in a pressure supply line, such valves are not in themselves acceptable because, in the event of a leak or malfunction, backflow can take place when the supply pressure drops below that of the consumer area.

To overcome this problem, valves have been proposed in which, as well as using a nonreturn valve, an air admission valve is included which breaks backflow should the nonreturn valve fail, such a valve being shown for instance in the specification of U.K. Patent GB 2181819A of Bjorn Andersson in which a chamber is used between the pressure source and the consumer area, and in the chamber is positioned a valve arranged to allow air to flow into the chamber to prevent flow from the fouled consumer area to the pressure source.

A similar assembly is shown in U.S. Patent No 3,951 ,164 of Buckley Crist which uses a pair of disc valves in a chamber, one to act as a backflow preventor, the other to bleed air units into the system to prevent flow to a fouled pressure source from the fouled consumer area.

It is an object of this invention to provide a form of valve, which although it is connected between a pressure source and a consumer source, has improved safety factors, in that where the fouled consumer area backflow is above atmospheric pressure and pressure source pressure no fouling of the pressure source area occurs.

This is achieved according to this invention by so arranging valve means that outflow from a drain valve to the atmosphere occurs when the pressure in the consumer source exceeds that in the supply source or when both pressures are equal but less than atmospheric at both points, and preferably the chamber is connected to the atmosphere when the pressure of the pressure source fails below the pressure at the consumer area.

The mechanism of the invention is such that if a malfunction occurs and the pressure at the consumer area is higher than the pressure at the pressure source, or either or both pressures are less than atmospheric, an outlet valve closes but at the same time a drain valve opens to cause outflow from the valve to the atmosphere, while the inlet valve also closes and according to a preferred form an atmospheric vent valve opens to place a chamber in a housing which is disposed between a fluid inlet to the valve and the fluid outlet therefrom to be maintained at atmospheric pressure-

Basically the backflow prevention valve of this invention comprises a housing having a chamber therein and having an inlet for fluid thereinto and an outlet for fluid therefrom and including at least a check valve in the inlet to prevent backflow through the inlet, characterised by a drain in the housing to drain fluid from the chamber in the housing, and by a drain valve in the housing to control flow through the drain, the check valve in the inlet being coupled to the drain valve to open the drain when the inlet check valve in the inlet is closed.

The backflow prevention valve can be constructed in various ways but preferably comprises a housing which has at one end an inlet for the fluid and in the inlet a non-return check valve movable to allow flow into the chamber under normal pressure conditions, the outlet allowing flow to the consumer device, but this inlet valve is coupled to a drain valve by a special arrangement which closes the drain valve when the inlet valve is open but to open the drain valve when the inlet valve is closed, the coupling preferably using both mechanical means and fluid pressure contact to effect the control to ensure that backflow is prevented.

In the preferred form the invention also relates to the use of a check valve in the outlet and to an atmospheric vent valve in the housing to vent the chamber in the housing to allow air flow into the chamber when the drain valve is open to drain fluid from the chamber of the housing.

The method of the invention comprises bypassing the fluid from the chamber of the housing to atmosphere through the drain valve when flow through the chamber is toward the inlet, and optionally admitting air into the chamber through air atmospheric vent valve during such flow.

To enable the actual construction of the invention to be better appreciated, an embodiment of the invention will now be described with reference to the accompanying drawing in which:

FIG. 1 is a longitudinal section of such a valve,

FIGS. 2 and 3 show respectively at a reduced scale the main valve components in a exploded view and in plan,

FIGS 4, 5, 6 and 7 show schematically the functional positions of the valves under selected conditions, FIG. 4 showing the valve in a static condition with the various valves in their spring loaded locations, FIG. 5 showing the valve positions in a normal flow arrangement, FIG. 6 showing the back pressure position, and FIG. 7 indicating how atmospheric air is admitted to the chamber.

The valve comprises a housing 1 defining with a closure cap 1a a chamber which has at a first end, an inlet 2 for fluids, and at a second end an outlet 3 for fluids and a drain 4 to discharge fluids from the chamber, an inlet check valve 5 normally closing the fluid inlet 2 through the action of a spring 6 between the inlet check valve 5 and an apertured platform 7 which is positioned across the chamber in the housing 1 has an annular circumferential channel 8 which communicates with the atmosphere through an opening 8a in the housing 1 through an atmospheric vent valve 9 when the platform 7 is at rest in a lower position as shown in FIG. 1. The atmospheric vent valve 9 has a sealing washer 9a on it to engage a seat on platform 7.

The drain valve 10 which is positioned in the drain 4, has at its top a spray baffle 11 which is apertured at its edge to allow controlled fluid flow past it, and this drain valve 10 is loaded toward an open position by a spring 12 which is confined between the lower end of the housing 1 and the drain valve 10 but this valve also has a spring 13 between it and a push member 14 which is coupled by push rods 15 to the inlet check valve 5 so that when the inlet check valve 5 is pushed down by pressure to allow water flow into the chamber of the housing 1 , the drain valve 10 is moved to a closed position by the push member 14 engaging the spray baffle 11 on the drain valve 10 so that the drain valve 10 is held shut against pressure of the spring 12 during the normal supply of pressure fluid to the inlet. The drain valve 10 has a sealing washer 10a which engages a face on the housing 1 when the drain valve 10 is closed.

The outlet check valve 16 is disposed in the fluid outlet 3 at the base of the chamber 1 and is loaded by a spring 17 to a closed position, and when backflow occurs normally prevents backflow into the chamber of the housing 1 , but if leakage occurs in this outlet check valve 16 under conditions where backflow would take place into the chamber of the housing 1 , which happens when the inlet pressure is lower than the outlet pressure, the drain valve 10 is opened by pressure of the spring 12 but also by pressure against the spring baffle 11 which extends, excepting for peripheral bleed apertures 18, across the chamber in the housing 1 and which of course co-acts with the push member 1 and thus the push rods 15 to move the inlet check valve 5 to its closed position. The outlet check valve 16 has an "O" ring 16a encircling it.

Disposed within the platform 7 is the atmospheric vent valve 9 which is spring loaded, there being a spring 19 between it and the platform 7 tending to open the valve, and a spring 20 which engages the inlet check valve 5 and is so balanced that when the inlet check valve 5 is closed, the atmospheric vent valve 9 is opened to allow the chamber of the housing 1 to be at atmospheric pressure, the balance however being such that the atmospheric vent valve 9 is closed during normal flow of fluid past the inlet check valve 5 to the chamber of the housing 1. The atmospheric vent valve 9 carries a sealing washer 9a.

The fluid flows through an aperture the platform 7 and through past the edges of the spray baffle 11 on the drain valve 10 but of course the drain valve 9 has its sealing washer 9a held in a closed position by the push rods 15, the push member 14 transmitting the push from the inlet valve 5 to the push member 14 and thus to the drain valve 10 to hold it in a closed position, the spring 13 between the drain valve 10 and the push member 14 ensuring that the valve is maintained in a closed position during pressure fluid flow from the inlet to the outlet.

The inlet valve 5 has a sealing washer 5a and also has an "O" ring 5b which moves out of the inlet when the inlet valve is open, one purpose of this being to have a longer travel of the inlet check vale 5 to facilitate operation of the drain valve 10.

The platform 7 has "O" rings 7a around to locate it but is apertured at 21 to allow the push rods 15 to pass through it and to allow fluid flow through it past the push rods 15 whereby to allow flow of fluid through the platform 7 during fluid supply to the outlet 3.

Test points 22 are provided to check conditions.

In this way an assembly is provided which is schematically shown in FIGS. 4, 5, 6 and 7 in which in a static position has the inlet check valve 5 and the outlet check valve 16 closed but the atmospheric vent valve 9 and the drain valve 10 are in an open position so that the chamber in the housing 1 is at atmospheric pressure and no flow can take place through it in either direction.

As shown in FIG. 5 when pressure at the inlet 2 exceeds pressure at the outlet 3 the inlet check valve 5 opens and the movement of the inlet check valve 5 at the same time closes the vent valve 9 and the drain valve 10. The outlet check valve 16 opens so that fluid flow takes place through the chamber of the housing 1 so long as the pressure at the outlet remains less than the pressure at the inlet and neither pressure is less than atmospheric.

FIG. 6 indicates what happens if inlet pressure falls below the back pressure, which closes the outlet check valve 16, but if this outlet check valve leaks, such leakage is allowed to flow from the outlet check valve

16 through the drain valve 10 because both the drain valve 10 and the atmospheric vent vaive 9 are open under such a condition to ensure that at least the space between the platform 7 and the fluid inlet 2 is atmospheric.

FIG. 7 shows how at this stage air can flow through the atmospheric . vent valve 9 into the chamber of the housing 1 so that even if the inlet valve 5 leaks, there will be no backflow because of an air column between the fluid inlet 2 and the fluid outlet 3.

It is of course possible to considerably vary the construction of this device but maintaining the general principle of operation which is to so arrange the valve that under normal conditions flow takes place through the valve from a supply fluid to a consumer device but if pressure falls in the supply, the inlet check valve 5 is closed and, depending on conditions, should the outlet check valve 16 leak, such fluid is drained from the chamber or the housing 1 through the drain valve 10 while the chamber of the housing 1 is at atmospheric pressure to ensure that there is complete separation of any flow by such flow being bypassed to the atmosphere through the drain 4 and not to the fluid supply source.

OPERATIONAL DESCRIPTION

Situation 1

FIG. 1 shows a cross sectional view of the valve, in the unpressurised situation, the fluid inlet check valve 5 with its sealing washer 5a and associated O" ring 5b being held in the closed position under the influence of the spring 6.

The atmospheric vent valve 9 with its associated sealing washer 9a and the drain valve 10 with associated sealing washer 10a are both held open under the influence of springs 19 and 12, whilst the outlet check valve 16 and its "O" ring seal 16a are held in the closed position by the spring 17. This situation is shown diagrammaticaliy in FIG. 4.

Situation 2

Inlet pressure positive with downstream demand cock (not shown) open.

Incoming pressure will cause the inlet check valve 5 to move vertically downwards, however the internal dimensions are arranged so that sufficient force is applied to spring 20 to close the atmospheric inlet valve 9, and similarly via the push member push-rod assembly 14-15 to close the drain valve 10. Continuing movement of the inlet check valve 5 then forces the "O" ring 5b to exit the neck 2a of the housing, allowing water to flow into the chamber in the housing 1. Internal pressure then opens the outlet check valve 16 allowing water to flow to the demand point. This is shown diagrammaticaliy in FIG. 5.

Situation 3

Mains pressure drops to atmospheric or less, with outlet check valve 16 leaking and back pressure applied from the downstream supply. Back pressure leakage exists through the drain valve 10, as shown in FIG. 6.

Situation 4

As for Situation 3 above, but with inlet check valve 5 also leaking. In this situation, atmospheric air will be drawn into the chamber of the housing 1 via the atmospheric vent valve 9, as shown in FIG. 7 and wil exit into the mains supply system.

It should be noted that the invention incorporates an inbuilt vertical air gap with an interspersed spray baffle 11 , and the inlet valve 5 incorporates double protection by means of a conventional sealing washer 5a and an associated "O" ring 5b.