Communications: electrical – Condition responsive indicating system – Specific condition
Reexamination Certificate
1999-05-27
2002-04-16
Mullen, Thomas (Department: 2632)
Communications: electrical
Condition responsive indicating system
Specific condition
C250S339150
Reexamination Certificate
active
06373393
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a flame detecting device of a detector and a flame detecting method, in which generation of a fire is automatically detected making use of the physical phenomena (heat, smoke and flame) caused by a fire.
2. Description of the Related Art
Among conventional infrared ray type flame detection devices (hereinafter, referred to as “flame detection device”), a flame detection device as illustrated in
FIG. 8
is known as an example. In
FIG. 8
,
1
denotes a detection element,
2
denotes a frequency filter,
3
denotes a comparator, and
4
denotes an optical wavelength band pass filter. In practical applications, an amplifier, etc. for signal amplification is included, but omitted here for simplifying the description.
In the conventional flame detection device, the infrared ray energy in a monitoring area is converted into the electric signal by the detection element
1
. The “prescribed low frequency component” of the electric signal is taken out by the frequency filter
2
. When the level of the low frequency component exceeds the reference level, the fire detection signal is outputted. The “prescribed low frequency component” means the component including the frequency fc of the flicker (or shaking) of the infrared ray energy to be radiated from the flame, and fc is the extremely low frequency of several Hz or under.
FIG. 9
is a schematic view of how the flame burns. Generally speaking, the flame follows the growing process in which the flame is small immediately after the ignition, then, becomes gradually larger, and smaller as the combustible is exhausted, and is finally extinguished. However, when viewed in a short time, the size of the flame repeats the growth and deflation at a certain period. That is, as indicated in FIG.
9
, the periodic fluctuation is repeated, wherein the burned-up flame takes in oxygen therearound and grows, while it becomes smaller for a moment once oxygen in its surrounding is reduced in amount, and then, grows again by the supply of oxygen from its outer side. It is proved that the repetitive cycle (the frequency fc) is characterized in that it is inversely proportional to the square root of the fire length for the combustible, e.g., liquid fuel. For example, the cycle is expressed by the following formula {circle around (1)} according to “Report on Fire-fighting Research, Vol. 53, No. 24 (1982)” (by Kunihiro Yamashita).
fc=k/{square root over ( )}L[Hz] {circle around (1)}
Where, k is a coefficient according to the kind of the fuel, and L is a value to express the quantity (fire length) of the fire. In general fire model, fc is e.g. about 2.5 Hz or 1.8 Hz. Thus, in a construction of
FIG. 8
, the “flame” caused by a fire can be detected if the passing frequency of a frequency filter
2
is 2.5 Hz, 1.8 Hz or each of these frequencies.
However, in the above-mentioned conventional flame detection device, the flame has been detected and judged based only on the level of the “prescribed low frequency component” including the single frequency fc given by the formula {circle around (1)}. Thus, for the below-mentioned reasons, errors occur with a physical phenomenon which is not related to a fire, and thus there is a problem that of reliability of the conventional flame detectors is not sufficient.
FIG. 10
a-c
is a diagram to indicate the temporal fluctuation of the infrared ray energy, where (a) denotes a flame, (b) denotes a mercury lamp, and (c) is a rotary lamp. The flame is of course an object to be monitored because the flame detection device is used for detecting the flame, and in addition, the mercury lamp is often used for illumination of roads. The rotary lamp is often used in an emergency car as well as an alarm for an entrance or an exit of a parking lot or for road construction, and for a guide of a store. These mercury lamp and rotary lamp are examples of an infrared ray energy radiation body which are seen in a daily life.
FIG. 10
indicates the output of the infrared ray energy of the flame, the mercury lamp and the rotary lamp taken out through a chopper. In
FIG. 10
(
a
) the infrared ray energy of the flame flickers at the frequency in the frequency band including the extremely low frequency fc, based on the above-mentioned reason. On the other hand, the infrared ray energy of the mercury lamp is maintained at the prescribed level (neglecting the fluctuation in power supply and noise) as indicated in
FIG. 10
(
b
) and the frequency of the flicker is approximately 0 Hz (only DC part). Further, the infrared ray energy of the rotary lamp is clearly accompanied by, the periodic fluctuation as indicated in
FIG. 10
(
c
) and its frequency is synchronous with the revolution of the rotary lamp. The rotary lamp is diversified in kind, including one. In which one lamp is turned in one direction at the prescribed speed (about two turns a second), and one in which a plurality of lamps are turned in a synchronous or asynchronous manner, and their frequency component is also diversified, but the rotary lamp of any kind is same in that it is periodically operated.
FIG. 11
a-c
shows an observation of the infrared ray energy of the flame, the mercury lamp and the rotary lamp (e.g., the output taken out as the temperature information through the chopper) relative to the frequency axis. Similar to
FIG. 10
, (
a
) denotes the flame, (b) denotes the mercury lamp, and (c) denotes the rotary lamp. The axis of abscissa means the frequency, and the origin means 0 Hz (DC part). The level in the vicinity of the origin is fairly large in (a), (b) and (c), and the peak is too high to be described in a graph, and omitted due to limitations of space.
Attention is paid to the flame in (a) and the mercury lamp in (b), and it is understood that their difference is quite obvious. That is, the flame has several levels in a frequency range
6
exceeding 0 Hz while the level in a similar frequency range
7
of the mercury lamp is approximately 0. Thus, the flame can be discriminated from the mercury lamp by comparing the level of the two using the frequency fc in the conventional technology.
However, in the rotary lamp in (c), similarity to the flame in (a) is high in that it has several levels in a frequency range
8
exceeding 0 Hz. When the level of the “flame”, the “mercury lamp” and the “rotary lamp” is compared with each other using the frequency fc in the conventional technology, it has been difficult to clearly discriminate the flame from the rotary lamp though the flame can be discriminated from the mercury lamp, or the mercury lamp can be discriminated from the rotary lamp. This indicates that the fire detection signal can be mistakenly outputted if, for example, an emergency car having the rotary lamp approaches a place where a conventional flame detection device is installed. It thus means that there is a technological problem which must by solved by all means from the viewpoint of the reliability of a fire-fighting device or apparatus.
A flame detection device to solve the problem is also proposed. This device made use of not the phenomenon known as the CO
2
resonance, but the radiation phenomenon that a peak appears in the vicinity of 4.4 &mgr;m in the spectrum distribution of the infrared ray to be irradiated from an infrared ray radiation body accompanied by the flame. This flame detection device comprises, for example, a band pass filter for center extraction to pass the infrared ray of the wavelength around 4.4 &mgr;m, and one or a plurality of band pass filters for periphery extraction to pass the infrared ray of the wavelength not including those close to 4.4 &mgr;m so that these band pass filters can be switched by a switching mechanism such as a rotary plate. (Japanese Unexamined Patent Publication No. 50-2497, Japanese Unexamined Patent Publication No. 53-44937). Alternatively, the flame detection device comprises a detection element in which a band pass filter for center extraction is arranged on its forward side, and a detec
Aizawa Masato
Matsukuma Hidenari
Shima Hiroshi
Hochiki Kabushiki Kaisha
Lackenbach Siegel Marzullo Aronson & Greenspan P.C.
Mullen Thomas
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