Liquid heaters and vaporizers – Stand boiler – And condition responsive feature
Reexamination Certificate
2002-09-26
2004-03-02
Wilson, Gregory (Department: 3749)
Liquid heaters and vaporizers
Stand boiler
And condition responsive feature
C122S018300, C122S019200, C220S567300
Reexamination Certificate
active
06698386
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to gas-powered water heaters, particularly those for residential use, and devices to shield the heating and pilot light burners from flammable vapors in the immediate area while improving air flow to the burners.
2. Description of the Relevant Art
Fuel-fired storage-type domestic water heaters are commonly used, and are popular because of their efficiency, economy and responsiveness compared with electric water heaters. Such devices are well known, and are described broadly in numerous publications, e.g. the background sections of U.S. Pat. Nos. 5,085,205 and 5,797,355. Such heaters can be used outdoors or indoors, but are typically used indoors, where the storage or spillage of flammable liquids or the like may give rise to hazards due to the close proximity of the heater pilot light, and heating burners and combustion air inlets to the floor, where such spillage typically takes place. These hazards are discussed at length in the patents just cited.
Various heater designs have been created, patented or produced to reduce or eliminate the hazards of the ignition of flammable vapors by the burners of the heater. Combustion air can be provided by direct venting from outside the heater space, which generally requires powered fans or other intake devices, takes considerable space for venting and is costly. Additionally, when a heater is provided air by venting from a distance, special control mechanisms must be provided to confirm the flow of air and the burning of the pilot light before the gas valve opens. Such controls are costly and prone to disrepair. Sealed combustion devices generally operate in a similar manner to vented systems, and have many of the same problems. Elevating a water heater on a stand at least 18 inches above the floor (in accordance with many building codes) is a simple mitigating method which is effective in many cases, but cannot prevent ignitions in all foreseeable circumstances.
Combustion air can be obtained from the immediate area of the heater via cylindrical enclosures which elevate the air intake further (resembling a “bucket”), or from elevated intake devices, collectively and informally referred to as “snorkels,” but these are not much more effective and may also increase the cost of the basic water heater installation. Various types of flame arrestor devices have been used with gas-fired water heaters to prevent the ignition of flammable vapors in the vicinity of an operating heater, but such devices impose a cost for the safety features offered, and also a burden of maintenance since they may tend to become clogged with debris or otherwise malfunction.
Hall's U.S. Pat. No. 5,085,205 discloses an elevated air intake using an open “bucket” or cylindrical enclosure. Harrigill's U.S. Pat. No. 6,035,812 discloses a heater with a bottom air intake and flame arrestor system. Bourke's U.S. Pat. No. 5,797,355 discloses several systems having flame arrestors and elevated (“snorkel”) air intakes. Heaters related to the latter patent are sold under the trademarks “FLAME GUARD” and “FLAME LOCK”.
U.S. Pat. Nos. 5,575,273; 5,533,495 and 6,058,892 are related and relevant art, disclosing representative air intake systems. Moore's '273 and '495 patents are closely related, and disclose “balanced flue” heaters for outdoor use, having air intake openings on the upper vertical face of the outer jacket and ducts to carry the air down to the burner below the tank. FIG. 3 of the '495 patent shows an essentially annular air duct, interrupted only by blocks 74, while the '273 patent (FIGS. 1 & 2) shows a more conventional vertical air duct limited to only a portion of the annular space between tank and jacket. U.S. Pat. No. 6,058,892 discloses exterior tubular air intakes with open tops.
U.S. Pat. No. 5,765,547 discloses (see FIGS. 5/6, col. 8/9) a water heater with an exterior sealed shell forming a partial annular air passage for combustion air, with air entering side-opening vents at elevated positions above the middle of the heater.
U.S. Pat. No. 5,848,586 discloses a water heater with a “fire safety collar,” including two concentric air baffles which shield the burner from flammable vapors and form an annular air duct for combustion air intake from a position above the base of the unit.
U.S. Pat. No. 5,361,729 discloses (in FIGS. 17-23 and related text) a gas water heater with a partitioned flue including rectangular air intakes. Columns 7/8 and FIG. 17 describe the use of tapered exhaust ducts to affect heat transfer.
U.S. Pat. No. 3,091,223 discloses a sealed vent water heater with a “snorkel” air intake.
U.S. Pat. No. 5,365,887 discloses an on-demand water heater and heat exchanger. FIGS. 1 and 6 show air entering the outer shell through open vents and passing downward through an apparently annular air intake to provide combustion air to a burner shielded from the exterior environment.
Bowman's U.S. Pat. Nos. 6,074,200 and 6,139,311 (the latter a CIP of the first), assigned to Gas Research Institute, disclose burner systems with the pilot light exposed to the ambient atmosphere to monitor the presence of flammable vapors and shut down the burners when necessary for safety purposes.
A large collection of patents was found which were all assigned to the same Australian company. Several of these patents are related as divisionals, continuations or continuations-in-part of older applications. Significant patents and disclosures include:
U.S. Pat. No. 6,138,613 discloses a “snorkel” intake using vertical-louvered air inlets. (Cont. Of U.S. Pat. No. 5,797,355)
U.S. Pat. No. 6,142,106 discloses air inlets with flame arrestors, designed to admit both air and extraneous vapors to the combustion chamber. U.S. Pat. No. 6,085,699, a CIP of U.S. Pat. No. 5,797,355, discloses similar air vents.
U.S. Pat. No. 5,797,355 discloses a gas water heater with a side-mounted “snorkel” intake having louvered air inlets.
U.S. Pat. No. 6,003,477 discloses snorkel intakes, both open and closed, and including flame traps. (CIP/CIP/CIP of U.S. Pat. No. 5,797,355)
U.S. Pub. No. 2001/0010209 (continuation of division of U.S. Pat. No. 5,797,355) also discloses vertical snorkel intakes with elevated louvered inlets.
U.S. Pat. No. 6,196,164, a division of U.S. Pat. No. 6,003,477, discloses vertical snorkel intakes with louvered inlets or open tops, and flame traps for use therein.
U.S. Pub. No. 2001/001529 (a continuation of division of U.S. Pat. No. 6,138,613, a continuation of U.S. Pat. No. 5,797,355) also discloses vertical snorkel intakes with elevated louvered air inlets.
U.S. Pub. No. 2001/0009144 (continuation of U.S. Pat. No. 6,196,164) discloses vertical snorkel intakes with elevated louvered air inlets and flame traps.
U.S. Pat. No. 6,293,230 discloses gas water heaters with air inlets/flame traps to admit both air and extraneous fumes to the combustion chamber.
U.S. Pat. No. 6,295,951 (CIP/CIP of U.S. Pat. No. 5,797,355) discloses side-mounted snorkel intakes with flame traps.
Clearly, despite the efforts of many designers and manufacturers in the mature industry serving the residential water heater market, there remains the need for simple, economical yet effective means of providing an efficient and responsive water heater which is reasonably safe against the hazards of flammable vapors in the vicinity. Homeowners and other purchasers are sensitive to prices for such appliances, and will normally pay only a limited premium for safe heaters, while perhaps honoring fire safety precautions more in the breach than the observance.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide apparatus which renders conventional fuel-fired water heaters safe in the presence of flammable vapors or other materials. Another object of the invention is to provide a smooth flow of combustion air from the vicinity of the heater to the combustion chamber of the heater without disruption from drafts, wind or other air disturbances, pressure fluctuations
Poole, Esq. James K.
Safetp Engineering Laboratories, Inc.
Wilson Gregory
LandOfFree
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