EP1376504A1 - Light scattering smoke detector - Google Patents

Abstract

The device has an optical measurement chamber with a sensor arrangement with a light source(s) and a receiver(s) in their own elongated housings with small window openings and a labyrinth system. The light source(s) and receiver(s) are arranged in the rear parts of their housings so that there is a relatively large distance between the window openings and the optical surfaces of the light source(s) and receiver(s) through which light passes. The device has an optical measurement chamber with a sensor arrangement (2) with at least one light source (12') and receiver (11) in their own housings (13,14) and a labyrinth system (7). The elongated housings have small window openings. The at least one light source and receiver are arranged in the rear parts of their housings so that there is a relatively large distance between the window openings and the optical surfaces of the at least one source and receiver through which light passes.

Description

The present invention relates to a scattered light smoke detector with an optical measuring chamber, which a sensor arrangement with at least one light source and a light receiver and a labyrinth system with apertures disposed at the periphery of the measuring chamber, wherein the at least one light source and the light receiver each in a housing are arranged.

In the case of scattered light smoke detectors, which may have one next to the optical measuring chamber another sensor, such as a temperature sensor may contain, is known to be the optical measuring chamber designed so that disturbing ambient light is not and smoke very easily in this can penetrate. The at least one light source and the light receiver are arranged that no light rays on the direct way from the at least one light source for Receiver can arrive. In the presence of smoke particles in the beam path is the Light scattered the at least one light source to this and a portion of this scattered light is noticeable the light receiver and causes an electrical signal.

It is obvious that the reliability and false alarm safety of such scattered light smoke detectors depends substantially on their constant sensitivity. In addition to the aging of opto-electronic Components are in particular soiling of the light-permeated optical surfaces of said components, which negatively affects the sensitivity influence.

The invention will now be given a scattered light smoke detector of the type mentioned in which the light-penetrating optical surfaces pollute as little as possible, so that the detector has a constant sensitivity.

The stated object is achieved according to the invention that the said housing have an elongated shape and have a small window opening, and that the at least a light source and the light receiver are arranged in the rear part of their housing, so that between the window openings of the housing and the light-penetrated optical Areas of the at least one light source and / or the light receiver a relative large distance is formed.

Practical experiments have shown that through the small window openings of the housing and by the arrangement of the opto-electronic components in the rear part of their housing the optical surfaces are so well protected against contamination that the relevant detector have a constant sensitivity.

Another advantage of the inventive arrangement is that the respective beam have a relatively small cross-section, so that the reaching to the light receiver Scattering light with high safety of smoke particles in the center of the measuring chamber and not from dust particles deposited on its bottom.

A first preferred embodiment of the inventive smoke detector is characterized characterized in that said distance is greater than the diameter of said optical surfaces.

A second preferred embodiment of the smoke detector according to the invention is characterized characterized in that the measuring chamber is bounded above by a carrier disk, of which protrude said housing down, and that the labyrinth system is a lid-like, fixable on the support plate and having a bottom and a side wall Component forms, which can be plugged from below onto the carrier disk.

A third preferred embodiment of the smoke detector according to the invention is characterized characterized in that at least one of the window openings of said housing of enclosed in a one-piece frame

A fourth preferred embodiment of the smoke detector according to the invention is characterized characterized in that said housing except the window openings down are open and that the bottom of said component has covers for the housing.

According to a fifth preferred embodiment is in the measuring chamber between the Light exit or light entry side of the housing and the opposite aperture compact, exposed spreading room formed.

A further preferred embodiment of the smoke detector according to the invention is characterized characterized in that on the carrier disk, a contact strip for the electrical connection the detector is arranged with a provided in a detector base connector strip, and that said electrical connection by a tangential movement of contact strip and / or power strip. Preferably, the contact strip on the top of the carrier disk integrated in so-called insert technology.

Fig. 1

eine perspektivische Darstellung eines Ausführungsbeispiels eines erfindungsgemässen Melders von vorne unten gesehen,

Fig. 2

eine perspektivische Darstellung eines Querschnitts durch den Melder von Fig. 1,

Fig. 3

eine perspektivische Darstellung eines Axialschnitts durch den Melder von Fig. 1; und

Fig. 4

eine perspektivische Darstellung einer Draufsicht auf den Melder von Fig. 1 ohne Sockel.

In the following the invention will be explained in more detail with reference to embodiments and the drawings; it shows:

Fig. 1

a perspective view of an embodiment of an inventive detector seen from the front bottom,

Fig. 2

3 a perspective view of a cross section through the detector of FIG. 1,

Fig. 3

a perspective view of an axial section through the detector of Fig. 1; and

Fig. 4

a perspective view of a plan view of the detector of FIG. 1 without base.

The smoke detector shown in Figures 1 to 4 consists in a known manner of three Main components, a socket 1, an optical sensor system 2 and a housing. 3 This structure is best seen in Fig. 3. Fig. 2 shows in a cross section through the Detector looking from below a view of part of the optical sensor system. 2

The base 1 is intended for mounting on the ceiling of the space to be monitored, wherein Mounting either directly on a flush-mounted box or surface-mounted with or without additional pedestal he follows. The base 1, which consists essentially of a circular plate and a down protruding edge web, contains, inter alia, a connector strip 4 (Fig. 3, 4), which for Receiving a connected to the sensor system contact strip 5 (Fig. 4) is provided.

The optical sensor system 2 includes a plate-shaped support 6 for the optical sensor, a fixed to the underside of the carrier 6 lid-shaped labyrinth 7, one at the base 1 facing upper side of the carrier 6 arranged circuit board 8 with the transmitter and the circuit board 8 at the edge and upwardly covering cover 9, which Part of the housing 3 forms. The contact strip 5 is an integral part of the support plate 6 and sticks out of it. The cover 9 has substantially the shape of a plate with a peripheral collar at the edge and with an opening 10 for the passage of Contact strip 5, so that this protrudes into the plane of the socket 1 arranged in the socket 1.

The apparent from Fig. 2 optical sensor includes a through the support 6 and the labyrinth. 7 formed measuring chamber with a light receiver 11 and two light sources 12, 12 ', respectively in a housing 13, 14, 15 are arranged. These housings consist of a bottom part, in which the respective diode (photodiode or IRED) is held, and at its the center the measuring chamber facing front a window opening for the light inlet or light exit having. As the figure can be seen, is in the measuring chamber in the area in front of the said window-like openings of the housing 13, 14, 15 formed scattering space compact and exposed trained. This arrangement and design makes the detector for use a transparent body for smoke simulation which can be used in this scattering room best for. Such transparent bodies are used to balance or test the Smoke sensitivity used in the manufacture of the detectors (see EP-B-0 658 264).

The frames of the window openings are formed integrally at least in the housings 14 and 15, whereby the tolerances for the smoke sensitivity are reduced. At acquaintances Stray light smoke detectors, the window frames consist of two parts, one of which the ceiling and the other is attached to the bottom of the measuring chamber. When putting on of the floor pass difficulties and it comes to variable window sizes and to form a light gap between the two halves of the window and thus unwanted interference of the transmitting and the receiving light. In the one-piece housing windows Disruptions of this kind are excluded and there can be no problems with the Positioning accuracy of window halves occur. The windows are rectangular or square and between the window openings and the associated light source 12, 12 'and the Lens of the associated light receiver 11 is a relatively large distance, resulting in a gives relatively small aperture angle of the respective light beams. A small opening angle the light rays has the advantage that on the one hand hardly light of the light sources 12, 12 'on the Ground meets and on the other hand, the light receiver 11 does not "see" the ground, so that on the Soil deposited dust particles can not produce disturbing stray light. Another advantage the large distance between the windows and the light source 12, 12 'and the lens of the light receiver 11 is that the light-penetrated optical surfaces lie relatively deep inside the housing and are thus well protected against contamination, which results in a constant sensitivity of the opto-electronic elements.

The labyrinth 7 consists of a bottom and peripherally arranged apertures 16 and it contains flat lid for said housing 13, 14, 15. The bottom and the panels 16 are used for shielding the measuring chamber against extraneous light from the outside and for suppression of the so-called background light (see also EP-A-0 821 330 and EP-A-1 087 352). The peripherally arranged aperture 16 each consist of two legs and have an L-shaped Build up. Due to the shape and the arrangement of the aperture 16, in particular also by their mutual distance, it is ensured that the measuring chamber is sufficient shielded against extraneous light and still their function with an optical test device (EP-B-0 636 266) can be checked. In addition, the panels 16 are arranged asymmetrically, so that smoke from all directions can penetrate similarly well into the measuring chamber.

The directed against the measuring chamber leading edge of the aperture 16 is formed as sharp as possible, so that little light can fall on such an edge and be reflected. ground and ceiling of the measuring chamber, so the facing surfaces of the carrier 6 and labyrinth 7, are grooved, and all surfaces in the measuring chamber, in particular the Apertures 16 and the aforementioned fluted surfaces are shiny and look like black Mirror. This has the advantage that incident light is not diffused but directed is reflected.

The arrangement of the two light sources 12 and 12 'is chosen so that the optical axis of Light receiver 11 with the optical axis of a light source, according to the representation Light source 12, one blunt and with the optical axis of the other light source, according to the representation the light source 12 ', an acute angle includes. The light of the light source 12, 12 'is scattered by penetrating into the measuring chamber smoke and a part of this Stray light falls on the light receiver 11, wherein at an obtuse angle between the optical axes of light source and light receiver of forward scattering and at a acute angle between the optical axes of backward scattering speaks.

It is known that the scattered light generated by forward scattering is significantly larger than which generated by backward scattering, the two scattered light components for different Types of fires are characteristically different. This phenomenon is for example from WO-A-84/01950 (= US-A-4 642 471), where disclosed inter alia is that different for different types of smoke ratio of dispersion at Use a small scattering angle for scattering with a larger scattering angle to detect the type of smoke leaves. The larger spread angle can also be chosen over 90 ° so that the forward angle and the backward scatter is evaluated. The evaluation of the two Light sources 12 and 12 'derived stray light components does not form the subject of the present Registration and will therefore not be described here.

For better discrimination between different aerosols in the beam path transmitter and / or receiver side active or passive polarization filter can be provided. Of the Carrier 6 is prepared accordingly and has provided in the housings 13, 14 and 15 Grooves (not shown) in which polarizing filters can be fixed. As another Option can be used as light sources 12, 12 'diodes, which radiation in the wavelength range of visible light (see EP-A-0 926 646), or the light sources can emit radiation of different wavelengths, for example the one Light source red and the other blue light.

The housing 3 of the smoke detector is constructed essentially in two parts and consists of the already mentioned cover 9 and the optical sensor system 2 comprehensive detector hood 17. The latter consists of an upper annular part and a distance from this, the dome of the detector forming plate, which with the upper annular part is connected by arched or rib-like webs 18. The designated by the reference numeral 19 Gap between the upper and the lower part of the detector hood 17th forms an over the entire housing circumference opening for the ingress of air and Thus, smoke to the optical sensor system 2, this opening only by the relatively narrow Webs 18 is interrupted. There is an even number of webs 18 provided, as shown there are four.

The detector hood 17 and the cover 9 are on the carrier 6 via hook-like snap closures Fixed (not shown) and the entire detector is mounted in the base 1. In the upper Part of the detector hood 17, a ring 20 is inserted, which is an insect screen 21 from a wearing suitable flexible material. When attaching the detector hood 17, the carrier 6 against pressed the ring 20, whereby the insect screen 21 is fixed in the detector. The attachment the detector in the base 1 is done by a kind of bayonet lock. The detector is from below pushed into the base 1, which is due to a guide ribs and guide grooves formed mechanical coding only in a single relative position between detectors and

Socket is possible. Then, the detector in the base 1 by an angle of about 20 ° (Fig. 4) rotated, whereby the part of the carrier 6 forming and upwardly projecting from this contact strip 5 tangentially inserted into the socket strip mounted in the socket 1 and the electrical Contact between the connector strip 4 and the contact strip 5 and thus between detectors and

Base is made. Subsequently, by the mentioned bayonet catch the Mechanical fixation of the detector in the base 1.

The contact strip 5 is integrated on the upper side of the carrier 6 in so-called insert technique and made in one piece with the carrier 6. Of the plug contacts of the contact strip 5 are the electrical connections to a cast into the carrier 6 stamped part with metallic, conducted against each other insulated metal conductors. The free ends of these metal conductors protrude in addition to the contact strip 5 from the carrier 6 and form contact points for the production of Soldered connections to the evaluation electronics on the printed circuit board 8.

• Für die Herstellung der Steckverbindung ist nur eine einfache Mechanik erforderlich und es muss insbesondere keine Umsetzung einer Rotations- in eine Translationsbewegung erfolgen.
• Die kompakte Steckverbindung erlaubt einfache Schlaufkontakte und besitzt ausgezeichnete Eigenschaften hinsichtlich elektro-magnetischer Verträglichkeit (EMV).

The electrical connection between detector and socket through the two elements connector strip 4 and contact strip 5 has a number of advantages:

• For the production of the connector only a simple mechanism is required and there must be no particular implementation of a rotational in a translational movement.
• The compact connector allows simple loop contacts and has excellent properties with regard to electro-magnetic compatibility (EMC).

As can be seen in FIG. 3, a component is formed on the bottom of the component forming the labyrinth 7 Fastened light conductor 22, on the one hand up to the circuit board 8 and on the other hand by a Bore in the lower part of the detector hood 17 protrudes from the detector hood. The detector hood is in Area of said bore provided with a spherical recess 23, which is the free Surrounds the end of the light guide 22. The light guide 22 serves as a so-called alarm indicator for visual display of alarm conditions of the detector. On the circuit board 8 is for this purpose an LED (not shown) is provided, which is activated in an alarm condition and the Light guide 22 applied with light.

The alarm indicator requires little power and it is because it is in the area of the detector's apex lies, practically visible on all sides. The all-round visibility is only from a perspective from 20 ° to the horizontal, but since the detector is mounted on the ceiling, this is Condition fulfilled in most cases. As can be seen in particular FIG. 2, is the Optical fiber 22 is guided in the region between the housings 14 and 15 through the measuring chamber. The two housings 14 and 15 are connected to each other at their front side and thus form with their inner side surfaces and the connecting surface between these one the light guide 22 surrounding wall, which the scattering space of the measuring chamber against the light guide 22 largely shields.

The smoke detector described so far is a purely optical detector with smoke detection based on the scattered light caused by smoke particles that have penetrated into the measuring chamber. Optionally, the detector can be designed as a two-criteria detector and additionally contain a temperature sensor. According to FIGS. 1 and 2, two temperature sensors 24 formed by NTC resistors are provided, which are arranged in the region of two mutually opposite webs 18. The webs 18 have in the middle of an elongated recess 25, in which from above the temperature sensors 24 protrude, which are mounted on the circuit board 8. Optical thermal detectors are known, so that a description of the signal evaluation is omitted here. Of course, the detector could contain other sensors, such as a fire gas sensor (CO, NO _x ), which could be arranged at correspondingly small dimensions within the measuring chamber.

While arranged in the axis of the detector temperature sensors completely independent of direction are, there is a strong directional dependence in a peripherally arranged sensor and the response depends on whether the sensor is facing the fire or is located on the side facing away from this of the detector. This problem is caused by the Use of two opposing temperature sensors 24 solved. It is essential that the detector regardless of the direction of flow a homogeneous, rotationally symmetric Sensitivity. This is through the webs 18 in cooperation with reaches the insect screen 21, wherein the webs 18 on the one hand, the temperature sensors 24 against protect mechanical forces and direct the air optimally to the sensors and on the other hand, in cooperation with the insect screen 21, the air outside along the housing conduct.

As already mentioned in the introduction, today are optical, optical-thermal and thermal fire detectors in use, with these still come gas detectors can. In addition, the optical, thermal and optical thermal detectors additionally have a fire gas sensor. The detector shown covers the variants optically and optically-thermally (possibly supplemented by a fire gas sensor), wherein Of course, no temperature sensors 24 are provided in the purely optical detector. Apart from that, but is the detector structure in the two variants described so far mechanically completely the same. By using a double photodiode as a light receiver 11 optimum redundancy can be achieved (two light transmitters, two light receivers, two temperature sensors) achieve.

Claims (12)

Scattered light smoke detector with an optical measuring chamber, which has a sensor arrangement (2) with at least one light source (12, 12 ') and a light receiver (11) and a labyrinth system (7) with arranged on the periphery of the measuring chamber aperture (16), wherein the at least a light source (12, 12 ') and the light receiver (12, 12') each in a housing (14, 15, 13) are arranged, characterized in that said housing (14, 15, 13) have an elongated shape and a small window opening, and that the at least one light source (12, 12 ') and the light receiver (11) in the rear part of their housing (14, 15, 13) are arranged so that between the window openings of the housing (14, 15; 13) and the light-penetrated optical surfaces of the at least one light source (12, 12 ') and / or the light receiver (11) a relatively large distance is formed. Smoke detector according to claim 1, characterized in that said distance is greater than the diameter of said optical surfaces. Smoke detector according to claim 1 or 2, characterized in that the measuring chamber is bounded above by a carrier disc (6), from which said housing (14 15; 13) protrude downwards, and that the labyrinth system (7) a lid-like, on the carrier disc fixable and a bottom and a side wall exhibiting component forms, which from below on the carrier disc (6) can be plugged. Smoke detector according to claim 1 or 2, characterized in that at least one of the window openings of said housing (14, 15) is enclosed by a one-piece frame. A smoke detector according to claim 4, characterized in that said casings (14, 15; 13) are open at the bottom except for the window openings and that the bottom of said component has covers for the casings (14, 15; 13). Smoke detector according to one of claims 3 to 5, characterized in that in the measuring chamber between the light exit or light inlet side of the housing (14, 15 or 13) and the opposite aperture (16) is formed a compact, uncovered scattering space. Smoke detector according to one of claims 3 to 6, characterized in that the housings (14, 15, 13) have grooves for the attachment of polarization filters. Smoke detector according to one of claims 3 to 7, characterized in that the mutually facing surfaces of the carrier disc (6) and the bottom of the labyrinth system (7) forming member having a corrugation. Smoke detector according to claim 8, characterized in that the apertures (16) and the corrugated surfaces of the carrier disc (6) and the bottom of said component have a shiny surface. Smoke detector according to one of claims 1 to 9, characterized in that arranged on the periphery of the measuring chamber aperture (16) have an essentially L-shaped configuration, wherein the shorter leg is directed against the interior of the measuring chamber, and that the distance between adjacent aperture (16) is a multiple of the thickness thereof. Smoke detector according to one of Claims 3 to 10, characterized in that a contact strip (5) for the electrical connection of the detector to a plug strip (4) provided in a detector base (1) is arranged on the carrier plate (6), and in that said electrical connection by a tangential movement of the contact strip (5) and / or power strip (4). Smoke detector according to claim 11, characterized in that the contact strip (5) on the upper side of the carrier disc (6) is integrated in so-called insert technique.

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