The invention relates to a fluid control valve; particularly to an anti-backflow, anti-siphon vacuum breaker valve.
There are many fluid flow systems that supply fluid from a clean source for use in a potentially contaminated fluid environment. These systems are regulated by local laws to comply with certain industrial codes, standards and specifications to protect the clean source of fluid for other uses and users. These codes and laws generally require that none of the contaminated fluid is permitted to backflow into the clean (or potable) source of fluid. This requires a fluid control valve having a vacuum breaker vent to prevent any back-siphoning of the contaminated fluid, as well as a direct anti-backflow valve to prevent any backflow of the contaminated fluid from flowing into the clean source of fluid.
Some examples of such systems include agricultural water irrigation systems, home dialysis installations and other medical applications, solvent cleaning systems, industrial water and chemical applications, and numerous home and industrial plumbing and sewage handling applications.
There are many prior art devices, that have been developed for use in these applications and environments. Some examples of such devices include the Watts 188A for irrigation systems, the Watts 288A for hot or cold water anti-siphon vacuum breakers, and the Watts N338 for hot and cold water anti-siphon vacuum breaker having bottom inlet and outlet connections. There are numerous other manufacturers and suppliers of such devices.
The prior art devices, because of the venting design, usually require that the device be installed as the last component before the discharge end, and with no downstream shutoff valve, and not less than 12 inches above the discharge outlet. These requirements present design limitations for many fluid control systems.
A common problem associated with the prior art devices is that in certain backflow conditions, even though they comply with the anti-backflow requirements to protect the clean source, they permit the contaminated backflow fluid to flow through the vent into the open environment. This may not present a problem in outside irrigation applications or in industrial controlled spillage environments; but this is a major problem in many laboratory and home installations.
As shown in FIG. 1 (Prior Art), a typical example of a prior art device includes an anti-siphon vacuum breaker valve 10, having an inlet 12, an outlet 14, and an atmospheric vent 16. The valve includes an internal chamber having an inlet valve seat 18 and an upper vent seat 20, and a dual action disc valve 22. The valve is slidable on a vertical guide stem 24 and has a lower valve seal 26 and an upper vent seal 28.
In operations, the lower valve seat 18 is normally closed, and the upper vent seat 20 is normally open; when water pressure is supplied to the inlet (not shown), the disc valve 22 is elevated on the stem to open the water inlet valve seat 18 and the upper seal 28 engages the vent seat 20 to close the vent 16. When the water pressure at the inlet is discontinued, the disc valve 22 returns to the lower position. Also in operation, when backflow is applied through the outlet 14, the valve seal 26 engages the valve seat 18 and prevents contaminated flow from entering the inlet source fluid, but the vent seat 20 can not be sealed; and the contaminated fluid is permitted to flow through the vent 16 into the environment and onto the floor of the home or laboratory. This is a major mess, and potential health threat to the home or laboratory.
In view of the foregoing, it is an object of the present invention to provide an anti-siphon, anti-backflow, vacuum breaker valve that prevents any backflow of contaminated fluid into a clean (potable) fluid source, and prevents any backflow of contaminated fluid through the vent and into the environment and onto the floor of the home, laboratory or commercial facility.
It is another object to provide an anti-siphon anti-backflow vacuum breaker valve that is compact, economical to produce, and reliable and durable in operation.
It is another object to provide an anti-siphon anti-backflow vacuum breaker valve that can be installed in any sequence, including forward of a shut-off valve, and at any elevation, relative to the discharge end, in a fluid flow system.