Ultraviolet light flame detector

BACKGROUND OF THE INVENTION

0001The subject invention relates to fire detection systems. More particularly, the subject invention relates to fire detection systems utilizing ultraviolet sensors.

0002Fire detection systems are available to sense various attributes of a fire and to warn individuals when a fire is detected. For example, smoke detectors include sensors adapted to sense smoke associated with a fire and to trigger an alarm when a selected level of smoke is detected. Other detectors sense other attributes associated with a fire.

0003Flame detector systems utilizing ultraviolet (UV) sensors are known. In a flame detector system, UV radiation emitted from the flames of a fire is detected by the detector's UV sensor. When a selected amount of UV radiation is detected, the flame detector system triggers an alarm.

0004UV flame detectors are tested periodically to ensure proper detector function. The test includes typically includes pulsing a small Neon/Hydrogen UV emitter to deliver short wavelength UV radiation pulses of a broad spectrum of wavelengths of about 180 nM to 350 nM to the UV photocell of the detector. The UV emitter is part of the detector, and as such, the UV radiation pulses are transmitted through a UV window of the detector, and reflected back through the UV window and to the UV photocell, producing a response in the UV photocell. If the response is not within an expected range, the detector goes into fault. Typically the Neon/Hydrogen UV emitter requires an amount of radioactive gas, such as Krypton 85, to ensure reliable function of the emitter in all required operating conditions, and within a very short time period, often less than 10 msec. This is especially true when the UV emitter is stored in or operated in an environment of complete darkness, since no stray light is available to trigger operation of the UV emitter. Changes in international regulations surrounding the use and shipment of radioactive materials, such as Krypton 85, have made it difficult to ship UV emitters containing radioactive materials at a level that ensures reliable operation of the UV emitter.

BRIEF DESCRIPTION

0005In one embodiment, a flame detector includes an ultraviolet (UV) sensor to detect UV radiation emitted by a flame; a testing apparatus to periodically test function of the flame detector. The testing apparatus includes a UV light emitting diode (UVLED) emitter to emit a test signal and a mirror to reflect the test signal emitted from the UVLED emitter to the UV sensor.

0006In another embodiment, a method of testing an ultraviolet (UV) flame detector includes transmitting a test signal from a UV light emitting diode (UVLED) emitter. The test signal is reflected toward a UV sensor of the flame detector, and the test signal received at the UV sensor is evaluated.

0007In yet another embodiment, a flame detector includes a housing, an ultraviolet (UV) sensor located in the housing to detect UV radiation emitted by a flame, and a testing apparatus to periodically test function of the flame detector. The testing apparatus includes a UV light emitting diode (UVLED) emitter positioned in the housing to emit a test signal at a wavelength between 220 nM and 240 nM. A mirror reflects the test signal emitted from the UVLED emitter toward the UV sensor. A UV window is located at the housing interposed between the mirror and the UV sensor and between the UVLED emitter and the mirror. The test signal is transmitted through the UV window to the mirror reflected off of the mirror and through the UV window toward the UV sensor.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawing in which:

<figref idref="DRAWINGS">FIG. 1</figref> is a schematic view of an embodiment of a flame detector; and

<figref idref="DRAWINGS">FIG. 2</figref> is another schematic view of an embodiment of a flame detector.

DETAILED DESCRIPTION

0011Shown in the <figref idref="DRAWINGS">FIG. 1</figref> is an exemplary embodiment of a flame detector <b>10</b>. The flame detector <b>10</b> includes a sensor, for example, an ultraviolet (UV) photocell <b>12</b> positioned in a housing <b>14</b> behind a UV window <b>16</b>. The flame detector <b>10</b> further includes a controller <b>18</b> and a power supply <b>20</b> connected to the UV photocell <b>12</b>, and further an alarm <b>22</b>, such as a light, buzzer or other audible or visual alarm.

0012In operation, the photocell <b>12</b> detects UV radiation <b>24</b> emitted by a flame <b>26</b>, through the UV window <b>16</b>. The photocell <b>12</b> is configured to detect light in the UV wavelength range. Once a selected level of UV radiation <b>24</b> is detected by the photocell <b>12</b>, the photocell <b>12</b> transmits an alarm signal to an electronic circuit in the controller <b>18</b>. The alarm signal may be transmitted from the controller <b>18</b>, to the power supply <b>20</b> to supply power to the alarm <b>22</b>.

0013Referring now to <figref idref="DRAWINGS">FIG. 2</figref>, the flame detector <b>10</b> is periodically tested to ensure function and reliability of the flame detector <b>10</b>. To do so, the flame detector <b>10</b> includes a UV emitter <b>28</b>. UV test signal <b>30</b> from the UV emitter <b>28</b> is directed through the UV window <b>16</b> to an optical integrity (OI) mirror <b>32</b>, which reflects the UV test light <b>30</b> back through the UV window <b>16</b> to the photocell <b>12</b>. The photocell <b>12</b> detects the UV test signal <b>30</b> and transmits a signal to the controller <b>18</b> where this signal is compared with a setpoint. If the setpoint condition is not met, the controller <b>18</b> sets a fault condition in the detection system. This process tests the operation of the photocell <b>12</b> as well as transmission through and condition of the UV window <b>16</b>. Since this UV light is generated at a known time, the alarm <b>22</b> is not activated and does not signal a state of fire emergency to the user. Rather, the failure to detect the proper level of UV light at this known time triggers a fault condition to alert the user of a failure in the detection system.

0014The UV emitter <b>28</b> of the embodiment of <figref idref="DRAWINGS">FIG. 2</figref> is a UV light emitting diode (UVLED) emitter <b>28</b>. In some embodiments, the UVLED emitter <b>28</b> is configured to transmit UV test signal <b>30</b> in the wavelength of about 220 nM to about 240 nM. It is to be appreciated, however, that this wavelength range is merely exemplary, and UV test signals <b>30</b> outside of this range may be utilized and are contemplated within the scope of the present disclosure. In some embodiments, the UVLED emitter <b>28</b> is pulsed, or flashed at a rate of about 10 mSec per cycle.

0015The UVLED emitter <b>28</b> offers significant advantage over the prior art Neon/Hydrogen/Krypton UV emitter. First, it contains no radioactive materials thereby alleviating regulatory and shipping difficulties associated with radioactive materials. Further, the use of the UVLED emitter <b>28</b> makes the emitter less susceptible to faulty optical integrity evaluation. The optical integrity fault results from the presence of dust and/or other contaminants on the UV window <b>16</b>. Contamination of the UV window <b>16</b> can scatter very short wavelength light transmitted from the emitter back to the photocell <b>12</b> without first reflecting off the OI mirror <b>32</b>, thus resulting in an errant evaluation of occlusion of the UV window <b>16</b>, because the detector erroneously evaluated the UV window <b>16</b> as not occluded. The UVLED emitter <b>28</b> transmits light at a slightly longer wavelength than the previous Neon/Hydrogen/Krypton emitter, which transmits at a broad spectrum of light from 180 to 240 nM in wavelength, thus reducing scattering of the UV test signal <b>30</b> by the contaminants on the UV window <b>16</b>, thus making the test more reliable.

0016While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.