Smoke detectors with ambient light detection and procedures

Abstract

Smoke detector (2) according to the scattering radiation principle, with a radiation transmitter (4) and a radiation receiver (6), whose radiation paths (8, 10) form a scattering volume (12), and with a filter medium for filtering out ambient light, characterized in that the smoke detector (2) is designed so that the filter medium can be temporarily deactivated, wherein the filter medium has an optical filter (14, 18) for filtering radiation reaching the radiation receiver (6).

Description

[0001] The present invention relates to a smoke detector according to the preamble of claim 1 and a method according to claim 7. State of the art

[0002] Smoke detectors detect smoke in a room using light, usually in the infrared range, which is scattered by smoke particles in front of a photodiode by an LED. To protect the photodiode from external light that could negatively affect the measurement, these smoke detectors have a smoke chamber.

[0003] A smoke detector is known from WO 2013 / 121192 A1. This smoke detector consists of a housing connected to an external environment, a light source located inside the housing that illuminates a detection volume in a first wavelength band, and a light sensor that responds to light from the sensor volume in a second wavelength band. WO 93 / 06462 A1 discloses a smoke detector with a smoke chamber through which air or another gaseous medium flows, in which smoke or other particles are detectable.

[0004] Smoke detectors without a smoke chamber are known from DE 10 2004 001 699 A1 and DE 100 66 246 A1. In such smoke detectors, a scattering volume, in which radiation is scattered by smoke particles, is located outside a housing of the smoke detector, in which a radiation emitter and a radiation receiver are arranged. The housing has a cover such that the radiation emitter and radiation receiver are arranged on one side of the cover and the scattering volume on the other side of the cover. The cover is at least partially transparent to radiation emitted by the radiation emitter.

[0005] These types of smoke detectors are designed to be unaffected by normal ambient light. Therefore, an electronic signal analysis of the light detected by the radiation receiver is performed to filter out ambient light in particular.

[0006] It is desirable to further develop a smoke detector so that, in addition to its main task of smoke detection, it also fulfills additional functions. Disclosure of the invention

[0007] Against this background, the present invention proposes a smoke detector with the features of claim 1 and a method with the features of claim 7. Advantages of the invention

[0008] A key aspect of the present invention is that a smoke detector based on the scattered radiation or light scattering principle comprises a radiation transmitter, a radiation receiver whose radiation paths form a scattering volume, and a filter medium for filtering out ambient light. Such a smoke detector can advantageously also provide information about the lighting conditions in the room being monitored by at least temporarily deactivating the filter medium for filtering out ambient light.

[0009] Smoke detectors based on the scattered radiation principle have special filter functions to protect against interfering external light, separating the signal caused by light scattering from smoke particles from ambient light. When these filter functions are deactivated, the detected signal results from the light in the room. Such a filter function can, for example, include modulating the radiation and evaluating the received radiation with regard to this modulation.

[0010] In the first operating mode of the smoke detector, the filter medium is activated, and in the second operating mode, the filter medium is deactivated. This ensures that in the first operating mode, the smoke detector provides a signal indicating smoke development, while in the second operating mode, it provides a signal indicating ambient light, from which information about the lighting conditions in the monitored room can be obtained. This information can be used for effective building management, as it relates to the lighting conditions in the monitored room, such as whether the room lighting is on or off, or what the light intensity is. This allows monitoring of whether all room lighting fixtures in a room are functioning correctly, for example.They were switched off at night, while information regarding the luminous intensity can be used to control or regulate the illuminance.

[0011] It can be provided that the operating modes are switched regularly and / or selectively. According to one embodiment, the smoke detector has a control unit (processing unit, e.g., a microcontroller) that activates and deactivates the filter medium to effect a switch from the first operating mode to the second operating mode and vice versa. This allows the smoke detector to automatically switch between the first and second operating modes, thus monitoring smoke development at times and the light conditions in the room at other times. The control unit is also expediently connected to the radiation receiver for data transmission in order to analyze the measurement signal. Furthermore, the control unit can be designed for data connection to a bus system so that the measured values ​​can be forwarded to a building control center, where they can be further processed to adjust the lighting conditions, e.g.,to switch off the lighting during the night, or to adjust the light intensity. If the filtering agents are computer-implemented, they are also expediently implemented in the control unit.

[0012] According to a further embodiment, the radiation transmitter is configured to emit modulated radiation, and the filter device is configured to allow a similarly modulated measurement signal, detected by the radiation receiver, to pass through. This ensures that interfering signals, such as light signals from a light source, can be filtered out in order to provide a signal in the event of a fire, for example, in the first operating mode, since only a measurement signal that has the same frequency and / or frequency characteristics as the modulated radiation emitted by the radiation transmitter is allowed to pass through.

[0013] According to the invention, the filter medium comprises an optical filter. Preferably, the optical filter is arranged between the radiation receiver and the scattering volume, wherein the optical filter is in a first state in the first operating mode and in a second state in the second operating mode. In the first state, the optical filter is transparent only to radiation emitted by the radiation source (e.g., infrared). The radiation receiver is sensitive to the radiation emitted by the radiation source. Thus, ambient light does not interfere with the measurement of the radiation emitted by the radiation source with the radiation receiver for determining the smoke particle density. In the second state, the filter is transparent. This allows ambient light to be detected. The optical filter can, for example, be tunable or movably mounted so that it can be inserted into and removed from the beam path.

[0014] For example, the radiation receiver can output measuring light that is not usually present or only very slightly present in ambient light (e.g. IR light), and the optical filter can be a bandpass filter that allows the measuring light to pass through but not ambient light.

[0015] According to one embodiment, the radiation receiver has a sensor that is sensitive to radiation emitted by the radiation transmitter and is simultaneously light-sensitive. This allows the same sensor to detect both the radiation emitted by the radiation sensor and ambient light. Thus, the sensor has a dual function. Therefore, the smoke detector has a particularly simple design.

[0016] According to another embodiment, the radiation receiver comprises a radiation sensor sensitive to radiation emitted by the radiation source and a light-sensitive sensor. This ensures that optimally adapted sensors are used for both the radiation emitted by the radiation source and the light measurement.

[0017] Another aspect of the present invention relates to a control unit configured to control the filter medium of a smoke detector at intervals in order to effect a change from the first operating mode to the second operating mode and vice versa, wherein the control unit can be connected to the radiation receiver of the smoke detector for the transmission of measured values.

[0018] Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawing.

[0019] It is understood that the features mentioned above and those to be explained below can be used not only in the combinations specified, but also in other combinations or on their own, without leaving the scope of the present invention.

[0020] The invention is schematically illustrated in the drawing using an exemplary embodiment and is described in detail below with reference to the drawing. Brief description of the drawings Fig. Figure 1 shows a smoke detector in schematic representation, and Fig. Figure 2 shows another smoke detector in a schematic representation. embodiment(s) of the invention

[0021] The figures show identical or corresponding elements with the same reference symbols. Further explanation is omitted.

[0022] In Fig. Figure 1 shows a smoke detector 2 based on the scattering radiation principle, which is finally inserted into a recess in a ceiling 22.

[0023] According to the present embodiment, the smoke detector 2 comprises a radiation transmitter 4 and a radiation receiver 6. In this embodiment, the radiation transmitter 4 is designed to emit non-visible radiation, e.g., radiation in the infrared or ultraviolet range. In this embodiment, the radiation receiver 6 comprises a sensor that is sensitive to both radiation emitted by the radiation transmitter 6 and light-sensitive. Thus, the sensor is sensitive to light and, for example, infrared or ultraviolet radiation.

[0024] The radiation transmitter 4 and the radiation receiver 6 are arranged inside the interior 34 of a housing 24 of the smoke detector 2. The housing 24 has an opening 32 which is closed by a cover 16. The cover 16 prevents dirt, such as dust, from entering the interior 34 of the housing 24.

[0025] The cover 16 is associated with a filter medium in the form of an optical filter 14. The optical filter 14 can be brought into a first state and a second state, wherein in the first state the optical filter 14 is transparent and opaque to radiation emitted by the radiation source 4, and in the second state it is transparent. The optical filter 14 according to the present embodiment is tunable, e.g., the optical filter 14 has a liquid crystal element 18.

[0026] Furthermore, in the present embodiment, the smoke detector 2 has a control unit 20. The control unit 20 is electrically connected via control lines (not shown) to the radiation transmitter 4, the radiation receiver 6 and the optical filter 14.

[0027] In a first operating mode of the smoke detector 2, the control unit 20 activates the radiation emitter 4 at a predetermined interval to check for smoke development. The radiation emitter 4 then emits radiation in the invisible range, e.g., in the infrared or ultraviolet range, with a beam path 8. At the same time, the control unit 20 switches the optical filter 14 to the first state in which, according to the present embodiment, the optical filter 14 is transparent to radiation emitted by the radiation emitter 4, but otherwise opaque to light.

[0028] If smoke particles are present in the beam path 8, scattered light reflection occurs from the radiation emitted by the radiation transmitter 4. This establishes a beam path 10, which is directed towards the radiation receiver 10 and detected by it. The value measured by the radiation receiver is read by the control unit 20, possibly compared with a threshold value, and if the threshold value is exceeded, a fire alarm signal is generated and, if necessary, forwarded via a bus system (not shown) to a building management system (not shown).

[0029] Subsequently, within a predefined interval, the lighting conditions in the monitored room 30 are checked in a second operating mode of the smoke detector 2. For this purpose, the control unit 20 deactivates the radiation transmitter 4 (optionally) and switches the optical filter 14 to its second state, in which, according to the present embodiment, the optical filter 14 is transparent. Now, light emitted by the light source 26 to illuminate the monitored room 30 can pass along the beam path 28 through the optical filter 14 and be detected by the radiation receiver 6. The value measured by the radiation receiver 6 is read by the control unit 20 and, if necessary, transmitted via a bus system (not shown) to a building management system (not shown).This provides the building management with information about the lighting conditions in room 30 to be monitored, which can be used to decide whether to deactivate light source 26 or adjust the luminous intensity of light source 26.

[0030] In Fig. Figure 2 shows another smoke detector 2 based on the scattered radiation principle.

[0031] The in Fig. The smoke detector shown in section 2 differs from the one in [reference missing]. Fig. The smoke detector 2 shown in 1 is distinguished by the fact that the cover 16 does not have an optical filter 14, e.g. in the form of a liquid crystal element 18. In the case of the Fig. In contrast, the control unit 20 of the smoke detector 2 shown in Figure 2 is supplemented by a filter medium in the form of an electronic or computer-implemented filter device 36. Furthermore, the cover 16 is designed to be both translucent and permeable to radiation emitted by the radiation transmitter 4.

[0032] The filter device 36 is connected to the radiation receiver 6 via lines (not shown) to transmit the measurement signal. The filter device 6 is designed to filter the measurement signal from the radiation receiver 6 in order to independently check for smoke development in the first operating mode and to obtain information about the light conditions in the monitored room 30 in the second operating mode.

[0033] To check for smoke development, the control unit 20 is configured to control the radiation transmitter 4 such that it emits radiation modulated at a specific frequency. In the event of a fire, this radiation is reflected by the scattering volume 12 and detected by the radiation receiver 6. The filter device 36 filters the measurement signal detected by the radiation receiver 6 and forwards only the measurement signal based on the modulated radiation to the control unit 20, while light signals from the light source 26 are filtered out by the filter device 36 due to their different frequency spectrum. Thus, light signals from the light source 26 do not affect the check for smoke development.

[0034] However, in order to obtain information about the light conditions in the room 30 to be monitored, e.g. alternating with the check for smoke development, the filter device 36 is deactivated and the measurement signal recorded by the radiation receiver 6 is forwarded unfiltered to the control unit 20.

[0035] The filter device 36 can comprise a hardware or a software filter. Furthermore, the filter device 36 can comprise one or more low-pass, band-pass, and / or high-pass filters, between which it is possible to switch depending on whether a check is to be carried out, whether smoke development is present, or whether information about the lighting conditions is to be obtained, in order to filter the measurement signal acquired by the radiation receiver 6.

Claims

[1] Smoke detector (2) based on the scattering principle, with a radiation transmitter (4) and a radiation receiver (6), whose radiation paths (8, 10) form a scattering volume (12), and with a filter medium for filtering out ambient light, characterized by , that the smoke detector (2) is configured to allow the filter medium to be temporarily deactivated, the filter medium having an optical filter (14, 18) for filtering radiation reaching the radiation receiver (6). [2] Smoke detector (2) according to claim 1, which is configured to be operated in two different operating modes, wherein the filter medium is activated in a first operating mode of the two different operating modes and deactivated in a second operating mode of the two different operating modes. [3] Smoke detector (2) according to one of the preceding claims, wherein the optical filter (14) is arranged between the radiation receiver (6) and the scattering volume (12), wherein the optical filter (14) is in a first state in the first operating mode and in a second state in the second operating mode, wherein in the first state the optical filter (14) is transparent to radiation emitted by the radiation transmitter (4) and opaque to ambient light, and in a second state is transparent to ambient light. [4] Smoke detector (2) according to one of the preceding claims, wherein the radiation emitter (4) is configured to emit modulated radiation and the filter medium is configured to filter out non-modulated radiation. [5] Smoke detector (2) according to one of the preceding claims, wherein the radiation receiver (6) has a sensor that is sensitive to radiation emitted by the radiation transmitter (4) and is light-sensitive, or wherein the radiation receiver (6) has a radiation sensor that is sensitive to radiation emitted by the radiation transmitter (4) and a further light-sensitive light sensor. [6] Smoke detector (2) according to one of the preceding claims, comprising a control (20) configured to activate and deactivate the filter medium. [7] Method for detecting ambient light using a smoke detector (2) according to one of the preceding claims, wherein the filter medium is deactivated. [8] Method according to claim 7, wherein the filter medium is alternately activated and deactivated.

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