Liquid heaters and vaporizers – Stand boiler – And condition responsive feature
Reexamination Certificate
2000-07-06
2001-10-02
Wilson, Gregory A. (Department: 3749)
Liquid heaters and vaporizers
Stand boiler
And condition responsive feature
C431S346000
Reexamination Certificate
active
06295952
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to water heaters. More particularly, the invention relates to flammable vapor resistant gas water heaters.
BACKGROUND
Gas-fired, storage-type water heaters often include a combustion chamber and air plenum disposed below a water tank. A burner element, gas manifold tube, ignition source, thermocouple, and a pilot tube typically extend into the combustion chamber. When the temperature of the water in the tank falls below a set minimum, gas fuel is introduced into the combustion chamber through the gas manifold tube and burner element. This gas fuel is ignited by the pilot flame or other ignition source, and the flame is maintained around the burner element. Air is drawn into the plenum, and mixes with gas fuel to support combustion within the combustion chamber. The products of combustion typically flow through a flue or heat exchange tube in the water tank to heat the water by convection and conduction.
In some cases, a water heater may be positioned in an area that is also occupied by lawnmowers, chain saws, snow blowers, trimmers, and other equipment having a gasoline-powered internal combustion engine. In such cases, it is not uncommon that there be gasoline and other flammable substances (e.g., kerosene, diesel, turpentine, solvents, alcohol, propane, methane, and butane) present in the same area. Such flammable substances often emit flammable vapors.
If the flammable substances are mishandled, the flammable vapors may encounter an ignition source, such as the pilot flame or burner flame of a gas-fired water heater. As a result of the mishandling of flammable substances, the flammable vapors may ignite, and the flame may follow the flammable vapors to their source, causing an explosion and/or a fire. Proposed governmental regulations would require residential gas-fired water heaters to be flammable vapor resistant in order to help reduce the occurrence of such dangerous situations caused by the mishandling of flammable substances.
SUMMARY
The present invention provides a water heater comprising a water tank, a combustion chamber positioned beneath the water tank, a skirt wall surrounding the combustion chamber; an inner plate defining a bottom boundary of the combustion chamber, and a gas burner in the combustion chamber. In one preferred construction, the inner plate includes a depending flange that is rolled over an edge of the skirt wall to form a seam.
Preferably, the inner plate includes an opening and a raised portion surrounding the opening. The raised portion provides a seat for the flame arrestor, and thus acts as a flame arrestor retainer. The flame arrestor may be provided with a peripheral groove to receive an o-ring seal which facilitates sealing the periphery of the flame arrestor with respect to the water heater skirt. The flame arrestor is preferably sandwiched between a support member and the inner plate, and the o-ring seal provides a substantially gas tight peripheral seal between the flame arrestor and the support member. The support member may be welded to the inner plate to provide a substantially gas tight seal therebetween. The seam formed by rolling the flange portion of the inner plate over the edge of the skirt wall creates a substantially gas tight seal therebetween.
An access door may be constructed of, for example, sheet metal. Preferably, the access door is stamped with a raised portion and substantially flat portion, and is shaped to fit the contour of the water heater skirt (e.g., the door is generally curved). The access door is sized to fit over an access opening in the skirt. The substantially flat portion has a hole therein, and a sight glass is sized to fit substantially gas-tightly in the hole. The access door may also include a manifold aperture surrounded by a boot wall. A boot is slip fit over the boot wall to provide a substantially gas-tight seal between the boot and the access door. A fuel conduit extends through the boot and the manifold aperture, and is substantially gas tightly sealed to the access door by the boot. The boot permits limited movement of the fuel conduit without breaking the seal. Preferably, the boot includes an inwardly-facing recess and the boot wall has a lip. The lip and recess engage each other to resist removal of the boot.
Other features and advantages of the invention will become-apparent to those skilled in the art upon review of the following detailed description, claims, and drawings.
REFERENCES:
patent: 4924816 (1990-05-01), Moore, Jr. et al.
patent: 5533495 (1996-07-01), Moore, Jr.
patent: 5941200 (1999-08-01), Boros et al.
Cornett Nolan
Reynolds Gregory Allen
Shropshire R. Dale
Smith Herbert Edward
AOS Holding Company
Michael & Best & Friedrich LLP
Wilson Gregory A.
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