Combustion – Timer – programmer – retarder or condition responsive control – By combustion destructible element – e.g. – fusible plug – etc.
Reexamination Certificate
2000-05-30
2001-07-03
Yeung, James C. (Department: 3743)
Combustion
Timer, programmer, retarder or condition responsive control
By combustion destructible element, e.g., fusible plug, etc.
C431S033000, C431S319000, C126S096000, C126S287500
Reexamination Certificate
active
06254380
ABSTRACT:
BACKGROUND—CROSS-REFERENCE TO RELATED APPLICATIONS
This invention is an improvement over the inventions of several earlier applications, to-wit:
Ser. No. 08/130,290, filed Oct. 4, 1993 now U.S. Pat. No. 5,338,185, granted Aug. 16, 1994 in the names of Richard W. Henderson and George R. Lightsey;
Ser. No. 08/247,925, filed May 23, 1994 now U.S. Pat. No. 5,456,595, granted Oct. 10, 1995 in the name of Richard W. Henderson;
Ser. No. 08/297,048, filed Sept. 30, 1994 now U.S. Pat. No. 5,409,370, granted Apr. 25, 1995 in the name of Richard W. Henderson;
Ser. No. 08/365,804, filed Dec. 29, 1994 now U.S. Pat. No. 5,549,470, granted Aug. 27, 1996 in the name of Richard W. Henderson;
Ser. No. 08/514,583, filed Aug. 14, 1995 now U.S. Pat. No. 5,662,468, granted Sep. 2, 1997 in the name of Richard W. Henderson.
Ser. No. 08/559,922, filed Nov. 17, 1995 now U.S. Pat. No. 5,551,865, granted Sep. 3, 1996 in the names of Richard W. Henderson and Samuel R. Henderson;
Ser. No. 08/684,131, filed Jul. 19, 1996 now U.S. Pat. No. 5,730,115, granted Mar. 24, 1998 in the name of Richard W. Henderson;
Ser. No. 08/684,132, filed Jul. 19, 1996 now U.S. Pat. No. 5,772,425, granted Jun. 30, 1998 in the name of Richard W. Henderson;
Ser. No. 08/829,037, filed Mar. 31, 1997 now U.S. Pat. No. 5,899,682, granted May 4, 1999 in the names of Richard W. Henderson and Kerryl L. Henderson; and
Ser. No. 08/916,764, filed Aug. 19, 1997 now U.S. Pat. No. 5,551,865, granted Oct. 19, 1999 in the names of Richard W. Henderson and E. Randolph Lucas.
BACKGROUND—FIELD OF INVENTION
This invention relates to safety devices, specifically to a mechanism for prevention of flareup in barometric-type wick-fed liquid fuel burners.
BACKGROUND—DISCUSSION OF PRIOR ART
Wick-fed liquid fuel burners, such as kerosene heaters, are used for space or area heating in homes, businesses, cabins, manufactured housing, and the like. In such burners liquid fuel from a fuel chamber is supplied to a wick which is exposed to the oxygen of the atmosphere within a wick-receiving combustion chamber. Once the wick has been ignited, flame intensity and heat generation are controlled by adjusting the length of the exposed wick.
A common type of kerosene heater is the barometric style, in which gravity causes liquid fuel to be delivered to a horizontal fuel chamber from a vertically-oriented, removable fuel tank inserted into a mating well, or sump, in a top surface of the fuel chamber. In some cases a sight gauge is mounted on the side of the removable tank to monitor the fuel level in that tank when the tank is filled, and during operation of the burner. The flow of fuel from the removable tank into the fuel chamber is governed by a barometric, or fuel release, valve in the cap on the removable tank, which, in normal operation, maintains the level of the fuel in the fuel chamber at the level of the barometric valve. A partial vacuum above the fuel in the removable tank prevents the fuel from flowing into the fuel chamber until the fuel level in the fuel chamber drops below the barometric valve, which then allows air to enter the removable tank. As air enters the removable tank through the barometric valve, fuel in the removable tank flows into the fuel chamber until its level in the fuel chamber rises and covers the barometric valve, causing fuel flow from the removable tank to cease.
The barometric valve consists of a spring-loaded plunger, which has an enlarged head at one end. When the removable tank is inserted into the fuel chamber, the plunger head contacts a pin located in the fuel chamber, which pushes the plunger back, allowing the fuel in the removable tank to be in fluid communication with the fuel chamber.
When the tank is removed, the action of the spring on the plunger head forces it against the opening in the tank cap, sealing the opening and preventing fuel from leaving the tank. The capacity of the removable tank is typically about four to five liters (four to five quarts), while the fuel chamber can hold a maximum of about two liters (two quarts).
Various improvements have been made to such burners which make them safer to operate. For example, tip-over shut-off mechanisms, manual shut-off devices, and low-level O
2
detectors have been employed. However, these burners continue to cause fires that result in death, injury, and property loss. These fires are caused, because, under certain conditions, vapors from the sump area can be ignited by the wick flame, and in other cases, fuel can overflow the fuel chamber. When the overflowing fuel ignites, the result is an uncontrollable fire outside the heater cabinet, or flareup.
There are safety devices that drop the wick down, thereby extinguishing the flame, if the burner tips over or experiences excessive vibration, or if abnormal combustion is detected. Other safety devices detect high levels of CO
2
and low levels of O
2
in the vicinity of the heater, and use these to control burning rates. Still others regulate the position of the wick during the ignition and extinguishing operations of the heater to prevent excessive flaming during these operations. Examples are shown in U.S. Pat. No. 4,363,620, issued Dec. 14, 1982 to Nakamura; U.S. Pat. No. 4,872,831, issued Oct. 10, 1989 to Fujimoto; U.S. Pat. No. 4,797,088, issued Jan. 10, 1989 to Nakamura; U.S. Pat. No. 4,805,589, issued Feb. 21, 1989 to Nakanishi; and U.S. Pat. No. 5,165,883, issued Nov. 24, 1992 to Van Bemmel. However, not only do these devices fail to prevent flareup, they are ineffective in stopping flareup after its onset. In some cases, the safety devices require the use of electrical power and electronic circuitry for actuation: this increases the cost of the burners significantly, without rectifying the flareup problem.
It has been suggested in two publications (“Kerosene Heater Fires: Barometric Type,” R. Henderson et al.,
Fire Marshals Bulletin
(National Fire Protection Association), Vol. 87-5, p. 8 (1987); and “Barometric Kerosene Heaters,” R. Henderson,
Fire and Arson Investigator
(International Association of Arson Investigators), Vol. 39, No. 3, p. 26 (1989)) to make the size of the removable tank of barometric kerosene heaters comparable in volume to that of the fuel chamber so that flooding of the fuel chamber will not occur. To implement this suggestion, either the capacity of the removable tank must be reduced, or alternatively, that of the fuel chamber must be increased. However, reducing the capacity of the removable tank will reduce the burn time accordingly, and possibly affect the marketability of the heaters. Increasing the capacity of the fuel chamber will require that new tanks be designed and implemented.
Also, it has been suggested that a float device be introduced into the fuel chamber to be used to activate the automatic wick extinguishing mechanism, and a sight gauge be present to show dangerous fuel levels in the fuel chamber. Introduction of such a float device would also require that the fuel chamber be redesigned, as discussed above. Although some burners have sight gauges in the fuel chamber, the sight gauges are used only to indicate whether or not fuel is present, not when dangerous fuel levels are present in the fuel chamber.
In addition it was proposed that a tank block-out device be installed. In this, a float in the fuel chamber pushes a pin that moves if the removable tank is withdrawn from the heater. Once again, such a device would require a redesigning of the fuel chamber and insertion of moving parts inside a somewhat restricted space.
U.S. Pat. No. 4,797,088, issued Jan. 10, 1989 to Nakamura, claims that its device detects an excessively increased flame—which most often is due to the presence of a highly volatile fuel in the burner—and actuates an automatic wick extinguishing mechanism. However, this device has a significant disadvantage in that it re-sets after the burner cools down, which allows the burner to be re-ignited, with the dangerous fuel still inside the burner. Also, the device requires electrical circuitry for some of its operation.
U.S. Pat. 5,080,578, issued Ja
Henderson Harry H.
Henderson Richard W.
Pressman David
Yeung James C.
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