EP1191496A1 - Light scattering smoke detector - Google Patents

Abstract

A scattered light smoke-detector includes a light-source (1) and a light pick-up (2) which are arranged so that the scatter point (4) from the light-source and the light pick-up lies outside of the scattered light smoke-detector in the open-air. The scattered light smoke-detector has a cover (3) for protecting the light-source and the light pick-up and the device for distinguishing between smoke and other foreign bodies located in an area around the scatter point (4).

Description

State of the art

The invention is based on a scattered light smoke detector the genus of the independent claim.

It is already known to use scattered light smoke detectors the scattering point of the light transmitter and Light receiver outside of the scattered light smoke detector in the Free lies. This has the advantage that there is no measuring chamber a labyrinth must be provided. Smoke detector with Labyrinth have the disadvantage that the labyrinth is through Pollution can become clogged.

Advantages of the invention

The scattered light smoke detector according to the invention with the features the independent claim has the Advantage that a distinction between permanent Foreign objects in the scattering point of the scattered light smoke detector and actual smoke is possible. Such foreign objects can e.g. Ladders that are parked for handicrafts, or boxes stacked up to the ceiling. Also Spiders can be found in narrow shafts in the free space of the Scattered Smoke Detectors build their network and by chance in the scattering point of the scattered light smoke detector permanently linger. The scattered light smoke detector according to the invention recognizes such foreign bodies and eliminates them from the Measurement signals so that false fire reports are avoided become.

By those listed in the dependent claims Measures and further training are advantageous Improvements in the independent claim specified scattered smoke detector possible.

It is particularly advantageous that the means for Differentiation between smoke and other foreign bodies Processor for analyzing the time course of received signals of the light receiver, wherein the processor to the Light receiver is connected. Based on the passage of time it is advantageously possible to determine whether smoke or another foreign object in the scattered light smoke detector is present. With smoke, it increases with time Intensity of the scattered light signal registered, while at Penetration of a foreign body into the scattering point a kind Jump function occurs briefly, then back in again solid signal to pass. This distinction in view so a jump in the time function allows on easy way of distinguishing between smoke and one other foreign body. It is still an advantage that an existing scattered light smoke detector is only about software must be added, which this temporal analysis of the Received signal from the light receiver. So that's the Scattered light detectors according to the invention in a simple manner realizable.

Furthermore, it is advantageous that around the light receiver an optic, preferably a faceted mirror, attached is the scatter signals from an area around the scatter point in couples the light receiver. The total signal on Light receiver is the integral of the signals from all Scattering areas in this area. By suitable Faceted mirror, it is possible to spatially many to detect spreading areas in which the Detector reacts sensitively to stray light. If there is of smoke it can be assumed that all spreading areas in the Essentially homogeneous with the corresponding smoke density deliver a share of the scattered light signal, while a Spider locally scatters a partial signal on the receiver. With such an arrangement can be done by simple Amplitude comparison distinguished a spider from smoke become.

In addition, it is advantageous that the light receiver is designed as a photo receiver array, the Photo receiver array at least two photo receiver elements having. It is therefore advantageously possible, and not only an integral of signals from different scattering points too measure, but a spatial distribution of the scatter signals take. Because of this spatial distribution, it is advantageously possible between smoke, small animals and Distinguish objects. You still get one Information about the distribution of smoke density and the Distance of the particles from the scattered light smoke detector. With help of cross-correlation techniques, which are based on a processor Scattered light smoke detectors are still implemented the speed of the smoke or objects measurable near the scattered light smoke detector. By a suitable optics, preferably a lens, will be the recording enables the spatial distribution of the scatter signals.

Another advantageous approach, the scattered light smoke detector train such that a distinction between smoke and other foreign bodies is possible is the formation of the Light source with adjustable wavelength. So that will advantageously exploited the effect that the Rayleigh scattering is the scattering behavior of the wavelength of the Radiation is dependent. When using a tunable Lasers are obtained for the presence of smoke particles the Rayleigh scattering different signal intensities as a function of wavelength. For particles that are large compared to the wavelength, the scatter does not depend or only slightly depending on the wavelength, therefore at tuning the light transmitter is not significant Effect occur with the scatter signals. With small ones Particles like smoke particles, this effect is the Intensity variation depending on the wavelength clearly measurable. It is thus advantageously possible distinguish such smoke particles from larger parts. This distinction is then made by a processor in the Scattered light smoke detector according to the invention performed.

Another advantage is that the light transmitter with is connected to an amplitude modulator. On the one hand, amplitude-modulated light signals enable due to the phase shift between broadcast and received signals, these are the impulses that come from the Amplitude modulation arose Distance determination from the scattering object while a pulse broadening, i.e. a dispersion, a measure of is a diffuse scattering body, like one in particular Cloud of smoke is. So it is advantageous possible that depending on the pulse broadening It can be determined whether smoke or another foreign body is present.

Finally, it is also an advantage that the Scattered light smoke detector has an ultrasonic sensor, the ultrasonic sensor being a transmitter and a receiver has and wherein the ultrasonic sensor is arranged in such a way is so that the ultrasonic sensor covers the area around the Scatter point monitored. The ultrasonic sensor monitors it advantageously the optical scattering range of the Scattered light detector. There is a solid foreign body in the scattering range, the ultrasonic sensor and the Scattered light sensor a signal. Is there smoke in the Scattering point, only the scattered light sensor receives a signal but not the ultrasonic sensor. For this procedure Ultrasonic sensors in the megahertz range are particularly suitable work because these ultrasonic sensors are a very have good directivity. With the help of It is also advantageous for the ultrasonic sensor determine whether there is a foreign body in an area the smoke detector, which may be a Influencing the flow conditions for the Fire detection means. This can serve as a warning from the Headquarters are issued.

drawing

Embodiments of the invention are in the drawing are shown and are described in the following description explained in more detail. Figure 1 shows a first embodiment of the scattered light smoke detector according to the invention, FIG. 2 a second embodiment of the invention Scattered light smoke detector with a facet mirror, Figure 3 a third embodiment of the invention Scattered light smoke detector with a photo receiver array, figure 4 shows a fourth embodiment of the invention Scattered light smoke detector with an amplitude modulator, figure 5 shows a fifth embodiment of the invention Scattered light smoke detector with an ellipsoid, Figure 6 a amplitude-modulated optical signal for determining a Distance, Figure 7 amplitude-modulated optical signals to identify a cloud of smoke and Figure 8 the Scattered light smoke detector according to the invention with a Ultrasonic detection for foreign bodies.

description

Scattered light smoke detectors, which are used as fire detectors, have the advantage, independent of stray light sources, Dust, pollution, insects, short-term smoke and briefly introduced foreign bodies in the measuring point, such as e.g. Cleaning equipment to be. Longer term Clouds of smoke, such as those that arise during a fire, provide the scattered light smoke detector for a clear scatter signal, which is recognized as a fire detection signal, for example by comparison with a predetermined threshold. at permanent retention of objects at the measuring point, that is the scatter point, becomes the scattered light smoke detector however, functionally report a fire. According to the invention is therefore a scattered light smoke detector proposed that has means to switch between smoke and distinguish other foreign objects. Such means relate in particular to a processor, the timing received signals from the light receiver. Other options include the use of Faceted mirrors to an area around the scattering point capture a photo receiver array to obtain a spatial resolution achieve a tunable light source to wavelength-dependent To detect scatter signals, a Amplitude modulator to use amplitude modulated Light signals the distinction between foreign bodies and Smoke hit and an ultrasonic sensor that detects the area monitored around the scattering point.

In Figure 1 is a first embodiment of the Scattered light smoke detector according to the invention as a block diagram shown. A cover 3 protects the Scattering smoke detector against moisture, aggressive gases and mechanical damage. The cover 3 is as made of transparent plastic. Alternatively it is possible to use glass. The cover 3 is like this procure so that it is for the light for the Scattered light measurement is transparent. It can also be used as a Filters for unwanted interference. In particular if infrared radiation is used, it is Ambient light easily through the cover 3 and Light receiver 2 filterable. Located behind the cover 3 on the one hand a light transmitter 1, here a light emitting diode Infrared. Alternatively, a laser is also preferred a semiconductor laser, and / or other wavelength ranges possible, which is controlled by a transmitter control 5. The transmitter control 5 is therefore a driver circuit for the light transmitter 1. In the case of a laser, it is one typical laser driver circuit with temperature and Bias compensation. The control 5 is a second output connected to a processor 7. The Processor 7 is connected to a data input / output Memory 8 connected in the permanently stored Reference signals are stored and that for storage of intermediate values is used. About a second The processor 7 with a data input Receive evaluation 6 connected. Via a data output the processor 7 to a signaling device 9 connected. An input of the reception evaluation 6 is with connected to a light receiver 2. The light receiver 2 is here is a photodiode. The light emitting diode 1 and the photodiode 2 are arranged such that a scattering point 4 outside the Scattered smoke detector is located outdoors.

At scatter point 4 it is detected whether smoke is present or Not. If there is smoke, this is indicated by scatter signals from the Detected photodiode 2, and the processor 7 then carries along the signaling device 9 a signaling regarding a fire. The reception evaluation is 6 here a receive amplifier and an analog / digital conversion. The signaling device 9 can be a Light, a siren or a communication module, a signaling to a center, preferably via a bus transmits. This is particularly advantageous if several scattered light smoke detectors are used, the are connected to the control center via the bus to a central monitoring of a building.

The processor 7 now carries out a time profile analysis of the Receive signals of the photodiode 2 through. Smoke occurs in the Scatter point 4, this leads to a continuous Increase in the intensity of the scattered light received by the Photodiode 2. However, if a foreign object is in the scattering point 4 is introduced, then when inserting the foreign body in the scatter point 4 a jump in the course of time Intensity function of the received signals by the Photodiode 2 take place, then after the introduction and the Remain of the foreign body in the scattering point 4 again to produce a flat signal plateau. A brief appearance of a foreign body in the scattering point 4 calls a short one Impulse in the reception function of the scatter signals and is thus recognized as a signal that is not used for Alarm triggering is used.

So occurs in the time function of the intensity of Received signals a jump on, this is on introducing of a foreign body. This can be done by software can be recognized by the processor 7 and then via the Communication module 9 to transmit the center, so that it is reported here that the scattered light smoke detector is due to of a foreign body no longer function properly can, so the optimal flow conditions again are to be produced.

Other signals are, for example, in spider webs and Spiders can be expected directly at the scattering point. Because of the slow The actual construction of the Spider web through the in the scattered light smoke detectors Usual drift compensation compensated. The usual Drift compensation is that very slow Signal changes in the range of 6 to 8 hours suppressed become. The simplest embodiment is a high pass with a correspondingly small time constant. A drift occurs in conventional fire detectors due to aging of the components and especially due to slow pollution of the Inside the labyrinth. So that's one Realization of rest value realized.

Fluctuations in the spider web, e.g. by a draft, but can lead to interference signals or if the spider moving slowly to the scattering point, this can be too Lead false signals. However, this becomes a kink result in the intensity function, so such Changes in intensity can be recognized by the processor 7.

In Figure 2 is a second embodiment of the Scattered smoke detector according to the invention shown, wherein around the light receiver 2 a faceted mirror of two concave mirrors (concave mirror segments) 10 and 11 attached is. The concave mirrors 10 and 11 collect light from one Area around its own scattering point and couple it into the light receiver 2 a. The or the scatter points are Strictly speaking, volume areas where the light beam of the Radiation source and the receiving lobe of the light receiver to cut. There are two scattering points here, as it is for the optical axes of the two mirrors 10 and 11 and the optical axis of the light transmitter 1 two each Intersection points.

The light receiver 2 is therefore sensitive all around, so that the light receiver 2 now consists of several diodes that light can receive from different directions, is composed. The cover 3 in turn protects the Scattered light smoke detector against external attacks.

The light receiver 2 is through its output with the Receive evaluation 6 connected via its data output is connected to the processor 7. The processor 7 is connected to the memory 8 via a data input / output. The processor 7 is connected to the via a data output Signaling device 9 connected. To a second The data input of the processor 7 is the transmitter control 5 connected. A second output of the transmitter control 5 leads to the light transmitter 1, here again a light emitting diode is. A laser can also be used here.

By using the concave mirrors 10 and 11 as Faceted mirror is the integral of the captured Scattered areas formed by the light receiver 2. at Presence of smoke is assumed to be everyone Scattering areas essentially homogeneous with the corresponding Provide smoke density a share of the scattered light signal, while a spider only locally sends a partial signal to the Recipient scatters. With such an arrangement, can by a simple amplitude comparison of the received signals by the processor 7 a spider as a foreign body of smoke be distinguished. The evaluation can in particular also by evaluating the time signal. Smoke there a continuous signal while an insect as an example for a foreign body a signal jump when leaving and Enter each segment. An insect would become a pulse train when crossing through the scattering area produce. There is then a threshold value in the memory 8 to provide, which specifies a threshold for the amplitude the smoke is considered recognized. A spider would be a signal result that is below the threshold. The threshold is determined based on experimental data.

FIG. 3 shows a third embodiment of the Sreulich smoke detector according to the invention shown. The Cover 3 again protects the scattered light smoke detector external attacks. The light transmitter 1 is via its entrance connected to the transmitter control 5. The transmitter control 5 is connected to processor 7 via a second output connected. The processor 7 is via a data input / output connected to the memory 8. To a second data input of processor 7 is a photo receiver array evaluation 13 connected. At a data output of the processor 7 a signaling device 9 connected. The Photo receiver array evaluation 13 is connected via its input connected to a photo receiver array 12. The photo receiver array 12 consists of an array of photodiodes. It can alternatively also a CCD (Charged Coupled Device) line, CCD matrix or a CMOS matrix. A lens 14 is between cover 3 and photoreceptor array 12 arranged. The lens 14 is arranged such that the Photo diodes of the photoreceptor array 12 have several local areas Detect around scattering point 4.

The photo receiver array evaluation 13 asks the individual Signals from the photodiodes and digitized them to then to be transferred to the processor 7, which is therefore a Spatial resolution of the received signals around the scattering point 4 performs. It is possible not only the integral of the Receive signals from the area around the scattering point 4 measure, but with the lens 14 a local distribution of Record signals. Through rays 15, 16, 17 and 18 are examples of two local areas, which by the Photo receiver diode array 12 are detected, shown. This spatial resolution can now clearly between Smoke that will be homogeneous, small animals that are only in individual areas popping up, and items differ. For items that are slightly larger, will the received intensity signal between two photodiodes of the photo receiver array a jump in the received Cause light intensity. It is also possible that when inserting an object several photodiodes of the Photo receiver arrays are wandered through and in time interval produces a typical signal pattern what is due to the insertion of an object into the Stray field of the scattered light smoke detector.

FIG. 4 shows a fourth embodiment of the Scattered smoke detector according to the invention shown. The Cover 3 in turn protects the scattered light smoke detector external intervention. The light transmitter 1 is above its Input connected to an amplitude modulator 19. On Data output of the amplitude modulator 19 leads to a first data input of the processor 7. The transmitter control 5 is at a data input of the amplitude modulator 19 connected. A second output of the transmitter control 5 leads to a second data input of the processor 7. The Processor 7 is connected to the via its third data input Receiver evaluation 6 connected. Via a data input / output the processor 7 is connected to the memory 8. Via a data output of the processor 7 Signaling device 9 connected. At an entrance the receiver evaluation 6 is the light receiver 2 connected. The light transmitter 1 and the light receiver 2 are arranged so that the scattering point 4 outside the Scattered smoke detector is located outdoors.

The amplitude modulator 19 forms from the electrical signal the transmitter control 5 a pulse train and thereby leads an amplitude modulation. In its simplest form this is simply a switch so that a sequence of periodic light pulses in the light transmitter 1 is generated and then another blanking is carried out and this alternately in one cycle, which the amplitude modulator 19 pretends. The processor 7 then evaluates the received signals in Comparison to these transmitted signals that the Transmits amplitude modulator 19 directly to processor 7, by. As a result, processor 7 is able, on the one hand a distance determination based on the phase shift between the transmitted and the received pulses perform and check on the other hand whether it is a cloud of smoke or an object. Is at all Finding nothing at scatter point 4 except air will not Signals are scattered and the receiver 2 only receives Ambient light, which by appropriate choice of Light wavelength or the light wavelength range as well (electronic) constant light suppression eliminated can be.

FIG. 6 shows how pulse sequences, the have been sent and received in the phase differ. In Figure 6a is the pulse train sent shown by the arrow 21 on the Reflection plane 22 falls. In Figure 6b is the received one Pulse train shown. You recognize through one Time comparison that the phase shift 23 occurred is. The phase shift 23 is a measure of the Distance from the light transmitter and receiver to the Reflection plane 22. In FIG. 7a there is again a transmitted one Pulse train shown that hits a cloud of smoke 25. In FIG. 7b, on the other hand, the pulse train received is from Cloud of smoke 25 shown. Because of that many scattering centers in the cloud of smoke 25, the impulses widen the transmitted pulse train A, and there is one Pulse dispersion as shown in Figure 7b. The width of the received pulses in Figure 7b is a measure of whether smoke is present or not. This can be done using a Threshold value comparison can be determined by the processor 7. This threshold value is then specified and in memory 8 stored.

Another embodiment, objects of one Differentiating a cloud of smoke is the use of a Light source with tunable wavelength as a light transmitter 1. For example, it can be a tunable Semiconductor lasers are used in the infrared range tuned over a predetermined wavelength range to see if the scattered light signals are dependent on the wavelength. This spread will Called Rayleigh scattering. With small particles, as in there is a cloud of smoke, this is Rayleigh scattering wavelength dependent. The processor 7 is thus on the Transmitter control 5 over the currently used wavelength informed, then the received signals as a function of Analyze transmission wavelength. This function results in a Horizontal or a roughly horizontal one, then is a Object has been introduced into the scattering point 4, since large Items that are particularly large compared to those used Are wavelength, no intensity dependence on that Have wavelength. This is a clear detection possible whether a foreign body or smoke in the area around the Scattering point 4 is present.

In addition to a tunable laser, it is also possible to use one Use lamp that emits light at multiple wavelengths then emitted and through a filter these individual To select wavelengths.

FIG. 5 shows a fifth embodiment of the Scattered smoke detector according to the invention shown. The Cover 3 again protects the scattered light smoke detector external interventions. The light transmitter 1 is above its Input connected to the transmitter control 5, the Transmitter control 5 via a data output with a first Data input of the processor 7 is connected. The processor 7 is via a data input / output with the memory 8 connected. The processor is via a second data input 7 connected to the reception evaluation 6. At one Data output of processor 7 is the Signaling device 9 connected. The Light receiver 2 is at an input of the Receiver evaluation 6 connected. To the light receiver 2 an ellipsoid 20 is arranged, which ensures that as much scattered light as possible in the light receiver 2 is coupled. This improves the signal-to-noise ratio of the scattered smoke detector. An alternative method is that a stronger light transmitter 1 is used.

8 is the scattered light smoke detector according to the invention with an ultrasound detection. The light transmitter 1 and the light receiver 2 are arranged so that the Scattering point 4 outside of the scattered light smoke detector outdoors lies. The cover 3 protects the scattered light smoke detector external attacks. At an input of the light transmitter 1 is the transmitter control 5 connected. A data output of the Transmitter control 5 leads to a first data input of the Processor 7. To a second data input of processor 7 signal processing 28 is connected, others Input an ultrasound receiver 27 is connected. The The ultrasound receiver is aimed at scatter point 4, to which an ultrasonic transmitter 26 is also aligned. The Ultrasonic transmitter is either in continuous operation or in operated periodically.

At a third input of the processor 7 Receive evaluation 6 connected. To a data output the processor 7 is connected to a signal 9. The processor 7 is connected to the processor via a data input Memory 8 connected. At an entrance to the Receiving evaluation 6, the light receiver 2 is connected.

If there is a foreign body in the area around scatter point 4, then receive both the light receiver 2 and the Ultrasound receiver 27 signals so that the processor 7 based on the received signal from the signal processor 28, which receive signals from the ultrasound receiver 27 amplified and digitized, realizes that it is a Foreign body and not smoke, which the Scattered signals, which the light receiver 2 receives, causes. So that the optical reception signal by the Ultrasound reception signal monitored. It is about Smoke, which causes the scatter signals at scatter point 4, then the ultrasound receiver receives no reception signal. Ultrasonic waves offer the ability to target an area to sound, so that false signals are unlikely.

The function of an ultrasound transmitter and receiver can can also be integrated in a component. It will be a first Ultrasound pulse emitted. Then you switch to reception around and waits for that from an existing one Object reflected signal (echo operation).

Claims (10)

Wherein the scattered light smoke detector having scattered light smoke detector a light transmitter (1) and a light receiver (2), which are arranged so that the scattering point (4) of the light transmitter (1) and the light receiver (2) lies outside the scattered light smoke detector outside, characterized characterized in that the scattered light smoke detector has a cover (3) for protecting the light transmitter and the light receiver (2) and means (7) for distinguishing between smoke and other foreign bodies which are located in an area around the scattering point (4). Scattered-light smoke detector according to Claim 1, characterized in that the means for distinguishing between smoke and other foreign bodies have a processor (7) for analyzing the time profile of received signals from the light receiver (2), the processor (7) being connectable to the light receiver (2) , Scattered light smoke detector according to claim 1 or 2, characterized in that the means for distinguishing between smoke and other foreign bodies have optics (10, 11) on the light receiver (2) which contain scatter signals from several scattering areas in an area around the scattering point (4) couples the light receiver (2). Scattered light smoke detector according to claim 1, characterized in that the optics is designed as a facet mirror (10, 11). Scattered light smoke detector according to claim 2, 3 or 4, characterized in that the light receiver is designed as a photo receiver array (12), the photo receiver array (12) having at least two photo receiver elements. Scattered light smoke detector according to claim 5, characterized in that a lens system (14) is arranged in front of the photo receiver array (12). Scattered light smoke detector according to claim 2, 3, 4, 5 or 6, characterized in that the light transmitter (1) is designed as a tunable light source, the tunable light source depending on control signals from a transmitter control (5) emitting light with a changed wavelength. Scattered light smoke detector according to one of claims 2 to 7, characterized in that the light transmitter (1) can be connected to an amplitude modulator (19). Scattered-light smoke detector according to one of claims 2 to 7, characterized in that the scattered-light smoke detector has an ultrasonic sensor, the ultrasonic sensor having an ultrasonic transmitter and an ultrasonic receiver and that the ultrasonic sensor is arranged such that the ultrasonic sensor monitors the area around the scattering point (4). Scattered light smoke detector according to claim 9, characterized in that the ultrasonic sensor can be operated in echo mode.

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