Combustion – Timer – programmer – retarder or condition responsive control – By combustion or combustion zone sensor
Utility Patent
1999-03-04
2001-01-02
Lazarus, Ira S. (Department: 3743)
Combustion
Timer, programmer, retarder or condition responsive control
By combustion or combustion zone sensor
C340S578000
Utility Patent
active
06168419
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a flame monitor for blue-burning flames of gas or oil burners, which is intended not only to confirm the presence of the flame but also to monitor the combustion process.
DESCRIPTION OF RELATED ART
For safety reasons, a flame monitor should operate not only in the visible light band, but also in a spectral band beyond visible light. It is therefore known for sensors to be chosen for this purpose which supply a signal which is sufficiently above the noise level in the near-ultraviolet band. The signal supplied from the sensor is evaluated in an evaluation circuit which is designed such that the fuel supply is inhibited if the flame signal remains below 500 nm.
A flame which burns in the blue band in normal operation has a correctly set fuel/air ratio, in which optimum combustion is ensured, with essentially stoichiometric combustion and low CO emissions. If this ratio is disturbed, the color of the flame moves toward longer wavelengths, that is to say into the green-yellow-red band of the spectrum. At the same time, the output signal from the photosensor also increases and indicates a stable burner operation even though, in reality, a disturbance exists in that the flame is no longer burning optimally, and is thus no longer blue.
German Patent 3,108,409 has disclosed a flame monitor which uses a UV tube and a photosensor as sensors for flame monitoring, whose signals are each supplied via a frequency/voltage converter having a maximum selection circuit, with only the respectively larger signal being used for measurement and evaluation purposes. This means that it is not possible to tell whether the burner is operating in a stable manner, with a blue flame.
SUMMARY OF THE INVENTION
The object of the invention is to provide a flame monitor which makes it possible to tell whether the burner is operating in a stable manner with a blue flame.
The invention thus provides a flame monitor having a photosensor, which detects the flame radiation and whose sensitivity rises sharply from ultraviolet to infrared, and an evaluation circuit which is connected downstream of the photosensor and switches off the fuel supply when (i) there is radiation in the band from 200 to 500 nm or (ii) the increase in the detected radiation intensity above 500 nm indicates movement out of the blue band. Photosensors of the said type are available, for example, as silicon photodiodes under the designation SFH 191 from Siemens, Munich, as well as from other Companies which produce semiconductor components.
The evaluation circuit may comprise, in particular, a first channel for signal components at a relatively high frequency, which represent signal components from ultraviolet radiation up to 500 nm, and a second channel for signal components at a relatively low frequency, which represent visible and infrared radiation, in which case the output signal from the first channel, which enables the fuel supply, can be inhibited by an output signal, whose magnitude can be predetermined, on the second channel.
Other refinements of the invention can be found in the following description and the dependent claims.
The invention is explained in more detail in the following text, with reference to an exemplary embodiment which is illustrated in the attached figures.
REFERENCES:
patent: 3301308 (1967-01-01), Briggs
patent: 3304989 (1967-02-01), Alexander et al.
patent: 3748083 (1973-07-01), Finger
patent: 5480298 (1996-01-01), Brown
patent: 3108 409 C3 (1982-09-01), None
patent: 4-64806 (1992-02-01), None
Alix Yale & Ristas, LLP
Clarke Sara
Giersch GmbH
Lazarus Ira S.
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