Combustion – Timer – programmer – retarder or condition responsive control – By combustion or combustion zone sensor
Reexamination Certificate
1999-12-02
2001-07-17
Price, Carl D. (Department: 3743)
Combustion
Timer, programmer, retarder or condition responsive control
By combustion or combustion zone sensor
C431S018000, C431S075000, C126S512000
Reexamination Certificate
active
06261087
ABSTRACT:
BACKGROUND OF THE INVENTION
Gas and oil burners of all types use a controller to safely initiate, monitor, control, and shut down combustion. Simple systems such as those for gas water heaters use mechanical controllers and thermostats for this function. This is possible because the water tank receiving heat is close to the burner providing that heat. Where the heat from the burner is delivered for use at a point remote from the burner as is typical for a home furnace, the thermostat for sensing demand for heat must be located remote from the burner in a room where the heat is delivered. It is not convenient to use a mechanical controller and thermostat in such situations, so it is customary to use an electrically operated controller and thermostatic switch wired to the controller.
Again conventionally, it is customary to use a 24 v. transformer to power electrical burner controllers. But there are also systems which generate their own power using thermopiles, see U.S. Pat. Nos. 4,770,629 and 4,696,639, both by Bohan. There are substantial advantages for such self-powered systems. In the first place, the expense of wiring the controller with line power is avoided. Secondly, the burner continues to operate safely even during power outages. While typical central hot air and hydronic heating systems need line power to operate properly, auxiliary gas burning heaters which have no fan or pump can profitably employ a self-powered controller.
One example of an auxiliary gas burning heater is the gas fireplace. While wood-burning fireplaces are very common, they have a number of drawbacks such as inconvenient fueling, ashes removal and disposal, creosote buildup in the chimney, and environmental pollution. Accordingly, the gas fireplace, typically using natural gas as fuel, has been developed as an alternative to wood-burning fireplaces. In a gas fireplace, natural gas is piped to a burner element typically hidden behind a simulated log. Burning this gas from the burner creates a flame which is both realistic and very safe. Gas fireplaces are also relatively inexpensive to install or retrofit into a wood-burning fireplace, they burn cleanly and efficiently, and they require little or no maintenance. These gas fireplaces can be designed to produce heat efficiently for the room in which they are installed, so they can serve as relatively high capacity auxiliary heat sources, something that has always been difficult for wood-burning fireplaces to achieve.
Early gas fireplace units required manual lighting each time the user wanted operation, but more recent units have a standing pilot flame, so that the fireplace can be turned on by simply opening a valve for the main gas flow. This usually requires operating a valve within the fireplace which is inconvenient for a number of reasons.
Gas fireplaces are one type of auxiliary heat source which can profitably use a self-powered controller, as can wall-mounted supplementary heat sources also. In either case, the heat outputs are large enough to make thermostatically control burner operation desirable. More so in retrofit situations, it is difficult to install the conductor pair between the remotely located thermostat or activator and the burner control which is located within the fireplace or within the housing of a conventional auxiliary heater. 24 v. systems are now available which use a battery-powered portable control with an integral thermostat function which communicates with the controller by an RF signal, thereby avoiding the need for a wired thermostat or physical access to the controller itself.
Thus, state of the art self-powered burner controllers must be wired to a remote thermostatic switch or activator. Line powered controllers of course require wiring for low voltage power, but can operate with wireless remote activation.
BRIEF DESCRIPTION OF THE INVENTION
We have developed an improved self-powered burner control system which operates the burner in response to demand from a remote wireless thermostat or other activator. Such a system is intended for a burner unit having a main burner and a standing pilot burner. A controller for such a system includes a power source for operating the electronic components of the controller. The controller is particularly suitable for electrical generators and other power sources having low output. A preferred version of an electrical generator having a relatively low power output comprises a thermopile mounted to receive heat from the pilot burner flame, and in response to this heat, provide a power voltage. We intend the term “thermopile” in this context to refer to any device which can convert heat energy to electric power in sufficient quantity to operate an electronic burner control. Other electrical generators with low power output such as photovoltaic elements convert radiant energy from the pilot flame to electrical power. Even electrical power storage devices such as batteries might in appropriate circumstances serve as a power source for some controller designs. Where the electrical generator is unable to directly provide adequate voltage to operate available electronic circuitry, the generator can include a DC to DC converter to provide a second, higher voltage to the electronic circuitry.
An electrically controlled fuel valve receives fuel from a fuel source and controls fuel flow to the main burner. The valve has an open state responsive to presence of a valve operating voltage at a control terminal and a closed state responsive to absence of the valve operating voltage at the control terminal. Fuel is allowed to flow or prevented from flowing to the main burner from the fuel source accordingly as the valve is in its open or closed states.
A wireless signal receiver receives the second power voltage. The receiver converts a coded wireless burner control signal having a control code therein specifying an operating condition for the burner unit, to a burner control signal encoding the control code. A transmitter which can in one embodiment be operated manually by a user and in another comprises a thermostat, includes a switch which when closed causes the wireless burner control signal to radiate. The receiver when close enough to the transmitter receives this signal.
A logic unit, typically a microprocessor, receives the burner control signal from the receiver, and also receives the second power voltage. Responsive to a preselected value of the control code in the burner control signal, provides a first switch closure signal. A valve switch is connected to provide power from the thermopile to the valve. When the logic unit provides the first switch closure signal to the valve switch, the switch connects the thermopile to the valve. The thermopile then provides at least a portion of the valve operating voltage to the valve when the valve switch is closed.
The generators currently available have power output barely able to operate the controllers which we can presently devise in addition to holding the valve open. To address this problem we provide a receiver switch having a first power terminal connected to receive power from the generator, a second power terminal connected to the receiver's first power terminus, and a control terminal. A second switch closure signal at the receiver switch control terminal electrically connects the receiver switch's first and second power terminals, thereby providing generator power to the receiver. The logic unit is designed to periodically provide the second switch closure signal to the receiver switch control terminal. By providing the second switch closure signal for a small percentage of the time, receiver power consumption can be substantially reduced.
REFERENCES:
patent: 4433719 (1984-02-01), Cherry et al.
patent: 4696639 (1987-09-01), Bohan, Jr.
patent: 4734658 (1988-03-01), Bohan, Jr.
patent: 4770629 (1988-09-01), Bohan, Jr.
patent: 4773847 (1988-09-01), Shukla et al.
patent: 4984981 (1991-01-01), Pottebaum
patent: 5051089 (1991-09-01), Jayaram
patent: 5081981 (1992-01-01), Beal
patent: 5092519 (1992-03-01), Staats
patent: 54508
Bird Douglas D.
Bohan, Jr. John E.
Gonia Patrick S.
Honeywell International , Inc.
Price Carl D.
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