Fluid handling – Combustion failure responsive fuel safety cut-off for burners – Thermo-electric
Reexamination Certificate
1998-07-16
2001-02-27
Walton, George L. (Department: 3754)
Fluid handling
Combustion failure responsive fuel safety cut-off for burners
Thermo-electric
C251S207000, C431S255000
Reexamination Certificate
active
06192913
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates in general to gas valves for gas burners and in particular to an improved gas valve for a pilotless gas burner.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
There are many burner systems that use a pilot light adjacent the main burner to ignite the main burner. Such systems have shown to be unsafe because there may be a burner flame-out and an accumulation of gas which may cause an explosion.
Thus, pilotless burner systems have been developed. Such systems are shown in U.S. Pat. Nos. 3,344,835; 3,582,249; and 4,207,054. In these patents, there are no gas flow paths through the valve that will allow different amounts of gas to be fed to the burner for ignition, running at low temperatures, and running at high temperatures. Further, they have only emergency manual controls.
Typical designs of convection heaters provide gas flow into an automatic control valve that divides the gas flow into two independent circuits, the pilot burner and the main burner.
Following ignition of the pilot burner, a thermocouple responds to the presence of the flame and provides power to the automatic control valve. The power flowing into the automatic control valve allows the valve to remain open and gas to flow into the main burner. Downstream from the automatic control valve in the main burner gas circuit is a manual control valve used to control the amount of fuel to the main burner. The operator adjusts the manual control valve to provide the desired amount of heat.
There are a number of concerns with this type of arrangement. First, proper operator involvement with the multiple valve system is very important. Failure to follow operating instructions could result in accidental starting of the main burner, delayed ignition of the main burner, and operation beyond the specified range.
Accidental ignition of the main burner occurs if the pilot burner flame proves the thermocouple and the manual control valve is not in the OFF position. Delayed ignition of the main burner can occur due to improper operation of the manual control valve. Failure to open the manual control valve to the full open position during ignition may cause delayed ignition. The operator can partially close the manual control valve, which reduces main burner gas flow below a specified input rate. Operation at reduced input rate can create high carbon monoxide, odor, and/or soot from incomplete combustion.
Further, flame supervision for the pilot burner causes additional concerns such as nuisance pilot burner outage and unsupervised operation of the main burner. Heaters may be subjected to nuisance outage due to drafts extinguishing the pilot burner. Pilot burner outage deprives the thermocouple of heat necessary to produce electrical power. The loss of electrical power causes the automatic control valve to interrupt the gas flow to all burners. In addition, the unsupervised main burner may operate below minimum input rate until the heater is manually shut down. In some cases, the main burner flame could become extinguished but still the system could flow gas because the thermocouple is supervising the pilot burner.
It would be advantageous to have a single automatic control valve system wherein the automatic safety control and the manual adjustment of the main control valve are contained within one control thus reducing the number of components.
SUMMARY OF THE INVENTION
The present invention provides a single automatic control valve system wherein the automatic control of the valve and manual adjustment of the valve are provided within one control body thus reducing the number of components in the system. In order to start the heater, the operator need only to rotate a control knob to an indicated “low” position and depress. After ignition of the burner system with piezoignition, the control knob is released and the thermocouple holds the valve open. In order to change the heat output of the heater from the low position, the operator need only to rotate the control knob to the desired heat setting. Unlike variable valves used on other heaters, the variable automatic control valve of the present invention has defined low, medium, and high positions. Previous designs were subject to the operator's interpretation of operating instructions. Unlike manual valves used on other heaters, the variable automatic control valve has limited operating positions and prohibit operation beyond a specified range. With this valve, there is pilotless ignition and the main burner is directly ignited, not indirectly with a pilot flame. Since the main burner is ignited, it is monitored directly with the thermocouple. Thus, the present valve includes fewer parts to assemble and maintain.
It is, therefore, an object of the present invention to provide a gas burner control valve for a pilotless ignition system in which the valve has a gas inlet valve and a single gas outlet valve to the gas burner with a manual gas flow control mechanism within the body or housing.
It is another object of the present invention to provide a gas control valve that has a gas metering sleeve between the gas input port and the single gas output port for controlling the amount of gas being coupled between the gas input port and the gas output port.
It is still another object of the present invention to provide a manual control for the valve for ignition and control of the amount of the gas flowing to the burner.
It is also an object of the present invention to provide both automatic shutdown of the valve and manual control of the valve in the same housing.
Thus, the present invention relates to a gas valve for a pilotless gas burner system comprising a valve body, a gas input port in the valve body, a single gas output port in the valve body for providing gas to the gas burner, a hollow gas metering sleeve having a wall and a gas input orifice, the sleeve being positioned between the gas input port and the single gas output port. A first ignition orifice is formed in the sleeve wall for providing sufficient gas to the single gas output port to ignite the gas burner. A second “run” orifice in the sleeve wall adds sufficient gas to that provided by the first orifice to enable the gas burner to provide a first minimum heat. At least a third orifice in the sleeve adds gas to that provided by the first and second orifices to increase the heat output of the burner system. A manually operated control shaft is associated with the sleeve for selectively coupling the first, second, and third sleeve orifices to the single gas output port. A thermocouple controlled solenoid holds the valve open as long as the gas burner is lit but automatically shuts off the gas flow when the burner is not lit.
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Fielder Ricky J.
Kaltenmark Eric M.
Willey John R.
Desa International
Jones Day Reavis & Pogue
Walton George L.
LandOfFree
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