EP1376504B1 - 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 has a sensor arrangement with at least one light source and a light receiver and a labyrinth system with arranged on the periphery of the measuring chamber aperture, wherein the at least one light source and the light receiver are each arranged in a housing.

In the case of scattered light smoke detectors, which may optionally contain a further sensor, for example a temperature sensor, in addition to the optical measuring chamber, it is known that the optical measuring chamber is designed such that disturbing ambient light can not and smoke very easily penetrate into it. The at least one light source and the light receiver are arranged so that no light rays can pass directly from the at least one light source to the receiver. In the presence of smoke particles in the beam path, the light of the at least one light source is scattered to this and a portion of this scattered light is incident on the light receiver and causes an electrical signal.

It is obvious that the reliability and false alarm safety of such scattered light smoke detectors essentially depends on their constant sensitivity. In addition to the aging of the opto-electronic components, it is particularly soiling of the light-penetrated optical surfaces of said components, which adversely affect the sensitivity.

The document EP 0880118 discloses a scattered light smoke detector according to the preamble of claim 1.

The invention should now be a scattered light smoke detector of the type mentioned above, in which the light-penetrated optical surfaces, as little as possible dirty, so that the detector has a constant sensitivity.

The object is achieved according to the invention in that the said housing have an elongated shape and have a small window opening, and that the at least one 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 surfaces of the at least one light source and / or the light receiver, a relatively large distance is formed.

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

A further advantage of the arrangement according to the invention is that the respective bundles of rays have a relatively small cross section, so that the scattered light reaching the light receiver is obtained with high certainty from smoke particles in the center of the measuring chamber and not from dust particles deposited on its bottom.

The inventive smoke detector is characterized in that said distance is greater than the diameter of said optical surfaces.

The smoke detector according to the invention is further characterized in that the measuring chamber is bounded above by a carrier disk from which said housing project downwards, and that the labyrinth system forms a lid-like, fixable on the carrier disk and having a bottom and a side wall component, which can be plugged from below onto the carrier disk.

A first preferred embodiment of the inventive smoke detector is characterized in that at least one of the window openings of said housing is enclosed by a one-piece frame, and
in that said casings are open at the bottom, with the exception of the window openings, and in that the bottom of said component has covers for the casings.
According to a further preferred embodiment, a compact, free scattering space is formed in the measuring chamber between the light exit or light entry side of the housing and the opposing diaphragms.
A further preferred embodiment of the inventive smoke detector is characterized in that a contact strip for the electrical connection of the detector with a provided in a detector base connector strip is arranged on the support disk, and that said electrical connection is effected by a tangential movement of the contact strip and / or connector strip. Preferably, the contact strip is integrated on the upper side of the carrier disk in so-called insert technique.

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 Rauchmeider shown in Figures 1 to 4 consists in a known manner of three main components, a base 1, an optical sensor system 2 and a housing 3. This structure is best seen in Fig. 3. FIG. 2 shows a view of a part of the optical sensor system 2 in a cross section through the detector as seen from below.

The base 1 is intended for mounting on the ceiling of the room to be monitored, with the installation either directly on a flush box or surface-mounted with or without base addition. The base 1, which essentially consists of a circular plate and a downwardly projecting edge web, contains inter alia a plug connector 4 (FIGS. 3, 4) which is provided for receiving a contact strip 5 (FIG. 4) connected to the sensor system ,

The optical sensor system 2 includes a plate-shaped carrier 6 for the optical sensor, a fixed to the underside of the carrier 6 lid-shaped labyrinth 7, arranged on the base 1 facing the upper side of the carrier 6 arranged circuit board 8 with the transmitter and a printed circuit board 8 am Edge and upwardly covering cover 9, which forms part of the housing 3. The contact strip 5 is an integral part of the support plate 6 and protrudes from this upwards. 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 the contact strip 5, so that this projects into the plane of the socket 1 arranged in the socket strip 4.

The optical sensor shown in FIG. 2 includes a measuring chamber formed by the carrier 6 and the labyrinth 7 with a light receiver 11 and two light sources 12, 12 ', which are each arranged in a housing 13, 14, 15. These housings consist of a bottom part, in which the respective diode (photodiode or IRED) is held, and which has a window opening for the entrance or exit of light at its front side facing the center of the measuring chamber. As can be seen from the figure, the scattering space formed in the measuring chamber in the region in front of the mentioned window-like openings of the housings 13, 14, 15 is compact and exposed. This arrangement and shape makes the detector for the use of a usable in this scattering space transparent body for smoke simulation best suited. Such transparent bodies are used to adjust or test for smoke sensitivity in the manufacture of the detectors (see EP-B-0 658 264).

The frames of the window openings are integrally formed at least in the housings 14 and 15, whereby the tolerances for the smoke sensitivity are reduced. In known scattered light smoke detectors, the window frames consist of two parts, one of which is worked on the ceiling and the other at the bottom of the measuring chamber. When putting the floor pass difficulties occur again and it comes to variable window sizes and the formation of a 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 disturbances of this kind are excluded and there can be no problems with the positioning accuracy of window halves. 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 relatively small opening angle of the respective light beams. A small opening angle of the light beams has the advantage that, on the one hand, hardly any light of the light sources 12, 12 'hits the ground and, on the other hand, the light receiver 11 does not "see" the ground, so that dust particles deposited on the floor can not generate disturbing scattered light. Another advantage of 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 are relatively deep inside the housing and are thus well protected against contamination, resulting in a constant sensitivity the opto-electronic elements result.

The labyrinth 7 consists of a bottom and peripherally arranged aperture 16 and it contains flat cover for said housing 13, 14, 15. The bottom and the panels 16 serve to shield the measuring chamber against extraneous light from the outside and to suppress 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 configuration. Due to the shape and arrangement of the aperture 16, in particular by their mutual distance, it is ensured that the measuring chamber is adequately shielded from extraneous light and still their function can be checked with an optical test device (EP-B-0 636 266). 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 only a little light fall on such an edge and can be reflected. Floor and ceiling of the measuring chamber, so the facing surfaces of the carrier 6 and the labyrinth 7, are fluted, and all surfaces in the measuring chamber, in particular the aperture 16 and the said fluted surfaces are shiny and act like black mirrors. This has the advantage that incident light is not diffusely scattered but reflected directionally.

The arrangement of the two light sources 12 and 12 'is selected so that the optical axis of the light receiver 11 with the optical axis of the one light source, according to the light source 12, a blunt and with the optical axis of the other light source, according to the light source 12', includes an acute angle. The light of the light source 12, 12 'is scattered by penetrating into the measuring chamber smoke and a portion of this scattered light is incident 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 an acute angle between the optical axes of backward scattering speaks.

It is known that the scattered light generated by forward scattering is substantially larger than that produced by backward scattering, the two scattered light portions being characteristically different for different types of fires. This phenomenon is known, for example, from WO-A-84/01950 (= US Pat. No. 4,642,471), which discloses, inter alia, that the ratio of scattering at a small scattering angle to scattering at a larger scattering angle is different for different types of smoke Make use of the smoke type detection. The larger spread angle can also be selected over 90 °, so that the forward and the backward scattering is evaluated. The evaluation of the scattered light components originating from the two light sources 12 and 12 'does not form the subject of the present application and will therefore not be described in more detail here.

For better discrimination between different aerosols can be provided in the beam path transmitter and / or receiver side active or passive polarizing filter. The carrier 6 is prepared accordingly and has provided in the housings 13, 14 and 15 grooves (not shown) in which polarizing filter can be fixed. As a further option, as light sources 12, 12 'diodes can be used, which emit 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 substantially in two parts and consists of the already mentioned cover 9 and a sensor sensor system 2 comprehensive detector hood 17. The latter consists of an upper annular portion and a spaced therefrom, the tip of the detector forming plate which is connected to the upper annular part by arcuate or rib-like webs 18. The space designated by the reference numeral 19 between the upper and the lower part of the detector hood 17 forms a running over the entire housing circumference opening for the entry of air and thus smoke to the optical sensor system 2, said opening is interrupted only by the relatively narrow webs 18 , There is an even number of webs 18 is provided, according to four.

The detector hood 17 and the cover 9 are fixed to the carrier 6 via hook-type snap fasteners (not shown) and the entire detector is fastened in the base 1. In the upper part of the detector hood 17, a ring 20 is inserted, which carries an insect screen 21 made of a suitable flexible material. When attaching the detector hood 17, the carrier 6 is pressed against the ring 20, whereby the insect screen 21 is fixed in the detector. The attachment of 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 possible due to a formed by guide ribs and guide grooves mechanical coding only in a single relative position between the detector and socket. Then, the detector in the base 1 is rotated by an angle of about 20 ° (Fig. 4), whereby the part of the carrier 6 forming and projecting upwardly from this contact strip 5 inserted tangentially 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 the detector and socket is made. Subsequently, the mechanical fixation of the detector in the base 1 is effected by the aforementioned bayonet closure.

The contact strip 5 is integrated on the upper side of the carrier 6 in so-called insert technique and manufactured in one piece with the carrier 6. Of the plug contacts of the contact strip 5, the electrical connections are made to a cast in the carrier 6 stamped part with metallic, mutually insulated metal parts. The free ends of these Metailleiter protrude next to the contact strip 5 from the support 6 and form contact points for the production of solder joints to the transmitter on the 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 from Fig. 3, a light guide 22 is fixed to the bottom of the labyrinth 7 forming member, which projects on the one hand up to the circuit board 8 and on the other hand through a hole in the lower part of the detector hood 17 from the detector hood. The detector hood is provided in the region of said bore with a spherical recess 23 which surrounds the free end of the light guide 22. The light guide 22 serves as a so-called alarm indicator for the visual display of alarm conditions of the detector. On the circuit board 8, an LED (not shown) is provided for this purpose, which is activated in an alarm condition and the light guide 22 is exposed to light.

The alarm indicator requires little power and, because it is located in the area of the detector apex, it is practically visible on all sides. The visibility from all sides is only given from a viewing angle of 20 ° to the horizontal, but since the detector is mounted on the ceiling, this condition is met in most cases. As can be seen in particular from FIG. 2, the light guide 22 is guided through the measuring chamber in the area between the housings 14 and 15. 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 them one the light guide 22 surrounding wall, which largely shields the scattering space of the measuring chamber against the light guide 22.

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 are completely independent of direction, there is a strong directional dependence in a peripherally arranged sensor and the response depends on whether the sensor is located on the side facing the fire or on the side facing away from the detector. This problem is solved by the use of two opposing temperature sensors 24. It is essential that the detector has a homogeneous, rotationally symmetrical sensitivity independent of the direction of flow. This is achieved by the webs 18 in cooperation with the insect screen 21, the webs 18 on the one hand protect the temperature sensors 24 against mechanical forces and optimally direct the air to the sensors and on the other hand, in cooperation with the insect screen 21, the air outside along the housing along.

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

Claims (7)

1. Light scattering 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 diaphragms (16) arranged at the periphery of the measuring chamber, the at least one light source (12, 12') and the light receiver (12, 12') each being arranged in a housing (14, 15; 13) having a small window opening, and in that the at least one light source (12, 12') and the light receiver (11) are arranged in the rear part of their housings (14, 15; 13), so that between the window openings of the housings (14, 15; 13) and the optical surfaces of the at least one light source (12, 12') and/or of the light receiver (11) through which light passes there is formed a distance which is greater than the diameter of the said optical surfaces, characterized in that the measuring chamber is bounded in the upward direction by a carrier plate (6), from which the said housings (14, 15; 13) protrude downwards, and in that the labyrinth system (7) forms a cover-like component which can be fixed on the carrier plate, has a bottom and a side wall and can be fitted onto the carrier plate (6) from below.
2. Smoke detector according to Claim 1, characterized in that at least one of the window openings of the said housings (14, 15) is enclosed by a one-part frame, and in that, apart from the window openings, the said housings (14, 15; 13) are open in the downward direction and the bottom of the said component has covers for the housings (14, 15; 13).
3. Smoke detector according to Claim 2, characterized in that a compact, exposed scattering space is formed in the measuring chamber between the light exit or light entry side of the housings (14, 15 or 13) and the opposite diaphragms (16).
4. Smoke detector according to one of Claims 3, characterized in that the housings (14, 15; 13) have grooves for the fastening of polarization filters.
5. Smoke detector according to Claim 3 or 4, characterized in that the mutually facing surfaces of the carrier plate (6) and of the bottom of the component forming the labyrinth system (7) have a ribbed formation.
6. Smoke detector according to one of Claims 1 to 5,
   characterized in that a contact strip (5) for the electrical connection of the detector to a connector strip (4) provided in a detector base (1) is arranged on the carrier plate (6), and in that the said electrical connection takes place by means of a tangential movement of the contact strip (5) and/or the connector strip (4).
7. Smoke detector according to Claim 6, characterized in that the contact strip (5) is integrated on the upper side of the carrier plate (6) by the so-called insert technique.

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