RU115535U1 - SMOKE SENSOR - Google Patents

Abstract

A smoke sensor containing an optical radiation source, a photodetector, a registration system and a warning system, characterized in that it additionally contains a beam splitter, a second photodetector, N corner reflectors, the registration system contains a divider, a comparator, a reference signal source, while the beam splitter is located on the optical axis of the optical radiation source, the second photodetector is located on the path of the optical radiation reflected from the beam splitter, the corner reflectors are sequentially located on the optical axis of the optical radiation source after the beam splitter, the output of the Nth corner reflector is optically connected to the photodetector, the photodetector output is connected to the first input of the divider, the output of the second photodetector is connected to the second input of the divider, the output of the divider is connected to the first input of the comparator, the output of the reference signal source is connected to the second input of the comparator, the output of the comparator is connected to the input of the warning system, where N is an integer, and 1 ≤N <∞.

Description

The utility model relates to fire fighting equipment and can be used to alert the onset of a fire or smoldering of spontaneous combustion materials.

Known radioisotope (ionization) smoke detector [1], which uses the ability of free ions in the air to attract smoke particles. The sensor has a special chamber where in an electric field the air is specially ionized by a weak radioactive source. Ions are charged and contribute to the flow between the electrodes of an electric current. As soon as smoke appears, the current intensity decreases, and the sensor generates a warning signal about the start of a fire. A disadvantage of the known smoke detector is its low speed, due to the need for smoke to enter the space between the electrodes. If this smoke detector is not located above the source of ignition, but to the side of it, then a certain time is required for the appearance of smoke between the electrodes.

Known optical smoke detector using light scattering by smoke particles and measuring the radiation power, scattered smoke [2]. The optical radiation receiver in the normal state is not lit, as the light source is directed in the opposite direction. The emerging smoke particles scatter a narrow beam of light, and the photodetector picks up the optical radiation reflected on the smoke particles, and the fire alarm sensor sends a signal to the warning system. A disadvantage of the known smoke detector is its low speed, due to the need for smoke to enter the space where light is scattered by the smoke particles. If this smoke detector is not located above the source of ignition, but to the side of it, then a certain time is required for the appearance of smoke particles in the region of scattering of optical radiation by the smoke particles.

The closest in technical essence to the claimed device is an optical smoke detector using light absorption on smoke particles [3]. The operation of this sensor is based on the response to a decrease in the intensity of the light flux, since smoke prevents the spread of optical radiation. The optical axis of the light source is directed to the photodetector. When smoke appears between the source and the photodetector, the signal at the output of the photodetector decreases, which leads to the inclusion of a warning system. A disadvantage of the known smoke detector is its low speed, due to the need for smoke to enter between the light source and the photodetector. If this smoke detector is not located above the source of ignition, but to the side of it, then a certain time is required for the appearance of smoke particles between the light source and the photodetector.

The objective of the utility model is to increase consumer properties by improving performance.

The solution to this problem is provided by the fact that in the known device containing an optical radiation source, a photodetector, a registration system and a warning system, the following improvements are made: it further comprises a beam splitter, a second photodetector, N corner reflectors, the registration system contains a divider, a comparator, a reference signal source wherein the beam splitter is located on the optical axis of the optical radiation source, the second photodetector is located on the path reflected from the beam splitter op radiation, the corner reflectors are sequentially located on the optical axis of the optical radiation source after the beam splitter, the output of the Nth corner reflector is optically connected to the photodetector, the output of the photodetector is connected to the first input of the divider, the output of the second photodetector is connected to the second input of the divider, the output of the divider is connected to the first input comparator, the output of the source of the reference signal is connected to the second input of the comparator, the output of the comparator is connected to the input of the warning system, where N is an integer, with 1≤N < ∞.

This construction of the smoke detector allows to increase consumer properties by increasing speed: in case of fire, smoke rising up will reach one (several) light beam (s) in a minimum time, regardless of the position of the ignition source indoors.

The essence of the utility model is illustrated by the description of the embodiment of the claimed device and the attached drawing, which shows the smoke detector circuit.

The smoke detector contains an optical radiation source 1, a photodetector 2, a registration system 3 and a warning system 4. It further comprises a beam splitter 5, a second photodetector 6, N corner reflectors 7, a registration system 3 includes a divider 8, a comparator 9, a source of a reference signal 10, the beam splitter 5 is located on the optical axis of the optical radiation source 1, the second photodetector 6 is located on the path of the optical radiation reflected from the beam splitter 5, the corner reflectors 7 are sequentially located on the optical axis of the optical radiation source 1 after the beam splitter 5, the output of the Nth corner reflector 7 is optically connected to the photodetector 2, the output of the photodetector 2 is connected to the first input of the divider 8, the output of the second photodetector 6 is connected to the second input of the divider 8, the output of the divider 8 is connected to the first the input of the comparator 9, the output of the source 10 of the reference signal is connected to the second input of the comparator 9, the output of the comparator 9 is connected to the input of the warning system 4. The optical radiation source 1, a beam splitter 5, corner reflectors 7 and a photodetector 2 are installed on the ceiling of the protected room or indoors near the ceiling.

The smoke sensor operates as follows. The light generated by the optical radiation source 1 is divided by a beam splitter 5 into two beams. The beam passing through the beam splitter 5 passes sequentially through N corner reflectors 7 and enters the photodetector 2. The power of the light incident on the photodetector 2 is determined as follows:

J _FP = J ₀ K ₁ K _2,

where J _FP is the power of the optical radiation incident on the photodetector 2, J ₀ is the power of the optical radiation generated by the source 1, K ₁ is the transmittance of the beam splitter 5, K ₂ is the transmittance of N consecutively located corner reflectors 7. The power of the electric signal U _FP at the output of the photodetector 2 is defined as follows:

U _FP = J _FP K ₃ = J ₀ K ₁ K ₂ K ₃ ,

where K ₃ - the steepness of the characteristics of the photodetector 2. This signal hits the first input of the divider 8.

The power of the optical radiation J _FP2 incident on the second photodetector 6 is determined as follows:

J _FP2 = J ₀ / (1-K ₁ ).

The power of the electric signal U _FP2 at the output of the second photodetector 6 is determined as follows:

U _FP2 = J _FP2 K ₄ = J ₀ K ₄ / (1-K ₁ ),

where K ₄ - the steepness of the characteristics of the second photodetector 6. This signal is fed to the second input of the divider 8.

The electrical signal U _D at the output of the divider 8 is equal to the ratio of the values of the electrical signals at its first input and second input:

U _D = U _FP / U _FP2 = J ₀ K ₁ K ₂ K ₃ (1-K ₁ ) / J ₀ K ₄ = K ₁ K ₂ K ₃ (1-K ₁ ) / K ₄ .

From this relation it follows that the electric signal U _D at the output of the divider 8 is independent of the instability of the power J ₀ of the optical radiation generated by the source 1.

The electric signal at the first input of the comparator 9 is equal to U _D , the electric signal at the second output of the comparator 9 is equal to the signal U ₀ at the output of the source 10 of the reference signal.

Under normal conditions (in the absence of ignition or decay of spontaneously combustible materials), the signal U _{0 is} selected so that the ratio U _D > U _{0 is} satisfied, while the signal at the output of the comparator 9 is zero, therefore, the warning system 4 is disabled. When spontaneous ignition materials appear in a room of ignition or decay, smoke rising upward intersects one or more beams of optical radiation propagating from an optical radiation source 1 through a beam splitter 5, corner reflectors 7 to a photodetector 2. Smoke particles absorb part of the optical radiation, and the value of U _D decreases and becomes smaller than the signal U ₀ , as a result of which the comparator 9 generates an electrical signal, including a warning system 4. The threshold of the comparator 9 is determined by the magnitude of the electrical signal U ₀ at the output of the source of the reference signal 10.

INFORMATION SOURCES

1. Fire and fire alarm sensors [Text]:

http://www.pk-atlant.ru/datchiki-pozharnoj-i-pozharno-okhrannoj-signalizatsii 08/05/2011.

2. Classification of fire detectors according to the principle of operation [Text]: http://www.ingeo-2000.ru/info_slabotochk_20.html 08/05/2011.

3. Bondarenko M.A., Gavrish V.F., Krakhmalev A.K. etc. Smoke detector [Text]: RF patent No. 51770 for a utility model, prior. 04/13/2005, publ. 02/27/2006, IPC G08B 17/17 (2006.01).

Claims (1)

A smoke detector containing an optical radiation source, a photodetector, a registration system and a warning system, characterized in that it further comprises a beam splitter, a second photodetector, N corner reflectors, a registration system contains a divider, a comparator, a reference signal source, while the beam splitter is located on the optical axis the optical radiation source, the second photodetector is located on the path of the optical radiation reflected from the beam splitter, the corner reflectors are sequentially located on optical axis of the optical radiation source after the beam splitter, the output of the Nth corner reflector is optically connected to the photodetector, the output of the photodetector is connected to the first input of the divider, the output of the second photodetector is connected to the second input of the divider, the output of the divider is connected to the first input of the comparator, the output of the reference signal source is connected to the second input of the comparator, the output of the comparator is connected to the input of the warning system, where N is an integer, with 1≤N <∞.