Combustion – Timer – programmer – retarder or condition responsive control – Providing repeated start attempts prior to shutdown upon...
Reexamination Certificate
1999-06-08
2001-11-27
Lazarus, Ira S. (Department: 3743)
Combustion
Timer, programmer, retarder or condition responsive control
Providing repeated start attempts prior to shutdown upon...
C431S028000, C431S078000, C431S081000, C431S082000, C431S069000, C137S066000, C126S0390BA
Reexamination Certificate
active
06322352
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a safety system for gas burners and, more particularly to a device for ensuring the operational safety of a gas burner station.
More particularly, the invention relates to a gas burner system with improved security against the release of unburned fuel gas in an arrangement in which the supply line to the burner includes a manually operated valve, an electromagnetic valve in addition to the manually operated valve and which shuts off the gas supply to the burner upon extinction of the flame, and a spark igniter or spark plug which ignites the gas and which signals when gas is released unburned.
BACKGROUND OF THE INVENTION
There are various systems available for preventing the release of fuel gas unburned from or burner. A gas valve with a magnetic control can be provided in combination with a temperature responsive element, for example, a bimetallic element or thermocouple, to generate an electric current while a gas flame remains lit to supply the magnetically operated valve and maintain the spring loaded valve open as long as the gas flame heats the sensor tip of the thermal element. Should the gas flame be extinguished at the burner the temperature of the flame is no longer detectable by the tip of the sensor and the gas valve can automatically close by the action of the spring to shut off the supply of gas to the burner.
This system has the drawback that the gas valve is operated via a stem which is depressed manually and must be held in until the electric current generated by the thermal element is sufficient to retain the magnetic valve in the open position. In most instances, it is necessary to depress the stem or plunger for up to 10 seconds before the valve will be retained in its open state.
Another drawback is that, upon extinction of the flame at the burner, the closure of the gas valve may take up to 90 seconds so that over this period of time unburned gas can be released into the atmosphere from the burner. Furthermore, the way in which the thermoelement must be mounted on the burner can be comparatively expensive and, with time, the sensor tip of the thermal element can be damaged or soiled and can become unusable.
Another approach, with a burner having no automatic shutoff is to provide for ionization ignition by a spark plug at the burner. An electric amplifier measures the current between the spark plug at the burner and a burner covered and the degree of ionization thus measured can indicate whether the gas flame is present or if a gas flame is absent where a gas flame is found to be absent by this system, the spark plug is triggered to reignite the burner. In this case, if a train of ignition pulses is transmitted to the spark plug after the gas flame has been extinguished and the flame is not reignited, unburned gas continues to flow out of the burner during the period. The gas supply then can be cutoff only by manual operation of the gas cook. In the case of a defective burner, removal or loss of the burner cover or even partial blockage of gas outlet openings, the spark generating igniter can fire without igniting the gas so that the gas can flow unburned from the burner.
OBJECTS OF THE INVENTION
It is the principal object of the present invention to provide an improved safety system for gas burners which prevents the escape of unburned fuel gas at a gas-cooking station, thereby automatically and rapidly interrupting the outflow of gas as soon as a dangerous condition can arise.
Another object of the invention is to provide a significant reduction in the duration over which unburned gas can be released from a burner in the event a gas burner flame is extinguished or is not ignited.
SUMMARY OF THE INVENTION
These objects and others which will become apparent hereinafter are attained, in accordance with the invention, in a system of the type described in which an electronic controller is provided between an electromagnetic valve in the burner supply line and the spark plug which, in response to the detection of a failure of the burner flame, will send a train of trigger pulses to the spark plug to generate respective sparks and if reignition is not possible, will then cut off the electromagnetic valve. More particularly, the electromagnetic valve and the spark igniter are connected with an electronic controller which shuts off the flow of unburned fuel gas within a predetermined time period or after a certain number of reignition attempts following detection of the extinguishing of the burner flame. With the system of the invention, the construction of the assembly is simple but reliability is greatly enhanced, especially when the rotation current maintaining the electromagnetic valve in its open state is produced by the control device.
Preferably, the retention of the spring loaded electromagnetic valve in its open state is triggered by a single depression or actuation of the swinging stem of the manually operated valve also connected in the gas supply line. The stem may be connected to a switch, especially a microswitch, to turn on and off the controller.
More particularly, a gas burner system according to the invention can comprise:
a gas burner;
a gas supply line connected to the gas burner for supply a fuel gas thereto;
an electromagnetic valve connected in the gas supply line for shutting off a supply of gas to the burner upon extinguishing of a burner flame;
a spark generator at the burner receiving a voltage pulse for producing a spark to ignite the flame at the burner and for signaling discharge of unburned fuel gas therefrom; and
an electronic controller connected between the spark generator and the electromagnetic valve for automatically triggering a series of voltage pulses producing respective sparks to attempt to ignite unburned fuel gas and, upon a failure of ignition within a predetermined time interval or after a predetermined number of pulses, closing the electromagnetic valve.
The electrocontroller generates a retention current maintaining the electromagnetic valve in an open state over an entire duration of the burner flame.
The electromagnetic valve is spring biased toward a closed state and the system further comprises a manually operable valve connected in the line, the manually operable valve having a valve stem producing, upon a single actuation of the stem, a retention current maintaining the electromagnetic valve in an open state over an entire duration of the burner flame.
The manually operated valve can have a housing in which the electromagnetic valve is located. The burner can be one of a plurality of such burners and only those of the plurality which are not reignitable by the train of pulses can be shut off from the gas supply by the electric controller.
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Cocks Josiah C.
Dubno Herbert
Isphording Germany GmbH
Lazarus Ira S.
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