KR20000064238A - Smoke alarm - Google Patents

Abstract

The smoke detector has a fixing socket in which a detector insert with an optical module is fitted. The optical module has a light source (6) and a photodetector (7) contained within a measuring chamber having a base (11). The module further has a labyrinth system provided by plates (9) projecting inwards from the periphery of the measuring chamber. The base of the measuring chamber has a conical or pyramid shape so that its centre lies at a greater distance from the plane containing the light source and the photodetector than its periphery.

Description

Smoke alarm

Scattered light smoke alarms are known, and in smoke alarms of the type including temperature sensors in addition to optical modules, interfering light from external sources cannot pass through the measuring chamber, but the optical module is designed to allow smoke to pass through very easily. It is known. The light source and the optical receiver are arranged so that light does not reach the receiver directly from the light source. When smoke particles are present in the beam path, the light from the light source is scattered and a portion of the scattered light is transmitted to the optical receiver to generate an electrical signal.

The reliability of the scattered light smoke alarm device, which indicates the degree to which false alarms can be prevented, is highly dependent on the fact that no other particles except smoke particles can enter the measuring chamber since the light from the light source is scattered only on the smoke particles. . The term particles should be understood broadly, including insects. The problem with insects has long been recognized and solved by the insect screens surrounding the measuring chamber.

The scattered light smoke alarm described in DE-A-44 12 212 includes a measuring chamber in the form of a round box, which is fixed in front to a plate connected to the ceiling of the room for monitoring and the side wall of the chamber is formed of an insect screen. . The front part of the measuring chamber facing the detection dome and spaced from the plate is covered with a flat base.

Using a scattered light smoke alarm having a flat, cylindrical measuring chamber can increase the frequency with which the detector generates false alarms as the service life increases. This is because the light of the light source can be scattered from the dust particles accumulated in the measurement chamber and act as if the smoke particles are present. In order not to generate false alarms, the detection device must be cleaned to remove dust, which is an undesirable additional expense.

The present invention comprises a labyrinth system having a screen disposed around the measuring chamber and an optical module comprising a base, a central screen, a measuring chamber, an optical receiver and a light source, and an alarm unit which can be fixed to the base. It relates to an alarm device.

1 is a cross-sectional view of a scattered light smoke alarm device at the height of the optical axis of the optical module, looking towards the base of the optical module,

FIG. 2 is a cross-sectional view taken along line II-II of FIG.

* Code Description

1 ... alarm unit 2 ... detection cover

3 ... smoke inlet slit 4 ... side wall

5 ... light module 6 ... light source

7 ... light detector 8 ... measuring chamber

9 ... perimeter screen 10 ... center screen

11 ... Base 12 ... Rib

13 ... grid structure 14, 15 ... sheet

16 ... Housing 18 ... Windows

It is an object of the present invention to provide a smoke alarm device of the type described in the beginning, which can prolong the maintenance interval by completely preventing or greatly reducing false alarm operation caused by light scattering on dust particles.

This object is achieved according to the invention in which the base is formed so as to be spaced farther from the plane defined by the light receiver and the light source at the center than at the edges.

The solution according to the invention reduces the possibility of light scattering on the dust particles reaching the measuring chamber since the dust particles are more spaced apart in the actual measurement area and can significantly reduce the interference effect of the dust particles.

As is known, the optical axes of the light source and the optical receiver intersect in the central region of the measurement chamber and the central region of the base. In the corner or peak area, the base is far from the measurement plane, and dust accumulates in the base area so that the light emitted by the light source cannot reach the dust particles accumulated in the corner of the base and cannot be scattered into the measurement chamber. .

A feature of the smoke alarm device according to the first preferred embodiment of the present invention is that the base is funnel shaped and can take on the corner or pyramid shape.

In the smoke alarm device according to the second preferred embodiment of the present invention, the base comprises a grating structure and acts as an insect screen. This embodiment has the advantage that the smoke detection apparatus is cheaper than the conventional apparatus.

A feature of a smoke alarm device according to a third preferred embodiment of the present invention is that the base has a plurality of vertically upwardly projecting thin plates on the inner side facing the measuring chamber and is transferred to the base before reaching the base. The arrangement, number, height and mutual distance of the thin plates is selected so that light reaches one of the thin plates, and all optical receivers of the base are thin plates.

The shape of the base according to the invention with the upward facing thin plate can reduce the light generated from the light path scattered in the measurement chamber on the dust particles accumulated on the base. This is because dust particles accumulate not on the thin plate, but on the base, i.e. in the area blocked by the thin plate from light generated from the measuring chamber. In addition, the thin plate serves as a screen to block light generated from an external source, which increases the measurement reliability of the smoke alarm device according to the present invention.

An advantage of absorbing the light produced by the second scattering or reflection, known as backlight, is that the need for production tolerances is relatively low. That is, as more back light is absorbed, the need for positional accuracy of the light source and optical receiver is reduced.

The invention is explained in detail on the basis of the following examples and figures.

The scattered light smoke alarm device consists of an alarm unit (1) which can be fixed to a base mounted on the ceiling of the room for monitoring and a detection cover (2) covering the alarm unit (1), the cover being in operation state. The smoke inflow slit 3 is provided in the corner area which faces the room for monitoring. The alarm unit 1 comprises a box-shaped base body in which the side of the base body facing the detection cone is arranged in the optical module 5 surrounded by the side wall 4 and the side of the base body facing the detection base is analyzed. It is disposed on a printed circuit board having an electronic device. The detection unit is known and will not be described in detail. See, for example, the alarm device of European Patent No. 95117405.1 and Algorex (registered trade name of Cerberus AG).

The optical module 5 consists of a light source 6, an optical receiver 7, a measurement chamber 8, a peripheral screen 9 arranged inside the side wall 4, a center screen 10 and a base 11. It consists of a labyrinth system. The optical axes of the light source 6 and the optical receiver 7 formed of the infrared light emitting diode IRD are not arranged on the same line but have a winding path, and the center screen 10 is disposed adjacent to the intersection. The side wall 4 and the base 11 block the measuring chamber 8 from external light generated from the outside, and the peripheral screen 9 and the center screen 10 are beamed directly from the light source 6 to the light receiver 7. Prevent this from reaching. The peripheral screen 9 has a function of suppressing backlight caused by undesired scattering or reflection. The more the backlight is suppressed, the lower the base pulse. That is, a signal is detected in the measuring chamber 8 when there is no smoke. The region of intersection of the light rays emitted from the light source 6 and the visible region of the optical receiver 7 forms an actual measurement section called the scattering zone.

The light source 6 emits short, strong light pulses into the scattering zone, so that the optical receiver 7 observes the scattering area, not the light source 6. Light emitted from the light source 6 is scattered by the smoke passing through the scattering area, and part of the scattered light is transmitted to the optical receiver 7. Thus, the receiver signal generated is processed by the electronic device. In general, the smoke detector may include a temperature sensor and / or a gas sensor in addition to the light sensor system included in the optical module 5.

If smoke is generated in the monitored room and ascends to the smoke alarm, the smoke passes through the smoke inlet slit 3 and flows horizontally into the funnel-shaped base 11. The base 11 includes a grid-like structure and has a rib 12 arranged in a star shape on the outer side, through which the smoke is directed to the base. As a result, the smoke flows in the vertical direction into the measuring chamber 8 and the scattering zone. Because of the funnel structure, the base 11 is farther away from the measurement chamber than when the base is flat. Dust particles that act like smoke particles through the measuring chamber 8, which scatters the light emitted from the light source 5, collect in the corners of the base 11 outside the incidence zone emitted from the light source 6, thereby causing dust. The interference effect of the particles is significantly reduced.

As shown in the accompanying drawings, the funnel-shaped base 11 region takes the form of a pyramid or pyramid, with all sides of the pyramid comprising the grid structure described above. Only the grid structure 13 on one side of the pyramid surface is shown in FIG. 1. The rib 12 located outside of the base 11 is preferably arranged along the side edges of the pyramid.

The possibility of interference effects of dust particles accumulated on the base 11 is reduced by the special type of base. Because the base 11 is provided with a plurality of thin plates 14, 15 protruding upwards vertically on the inner surface, the light generated in the base from the measuring chamber before reaching the base is arranged to reach one of the thin plates, This is because the number, height, and mutual distance are selected, and the optical receiver 7 observes only the thin plates 14, 15 of the base 11. As a result, since dust is retained more on the base than is attached to the vertical walls of the thin plates, the risk of light scattering on the dust particles is somewhat less. The base 11 is blocked from light generated in the measurement chamber 8, and the thin plate 14 blocks the optical receiver 7 from external light generated from the outside.

As shown in the figures, not all pyramidal surfaces have thin plates. Only the pyramidal surface facing the light source 6 and the surface facing the optical receiver 7 and the pyramid surface surrounded between the two surfaces are provided with thin plates. The pyramidal surface opposite the light source 6 and the optical receiver 7 comprises longitudinal thin plates 14 oriented parallel to the base edge of the pyramid, wherein the pyramid surfaces surrounded between the surfaces are one or more longitudinal thin plates. 14 and a plurality of transverse thin plates 15 arranged at right angles to the thin plates 14. The longitudinal thin plates 14 are perpendicular to the optical axis of the opposing optical receiver and the opposing light source. The main function of the transverse thin plate 15 is to optically separate the light source 6 and the light receiver 7.

Except for the light source 6 and the optical receiver 7, the base 11, made of a suitable plastic and made of injection molded parts, like the entire alarm device 1, comprises several snap organs on the edges, which are optical The side wall 4 of the module 5 and the base 11 are detachably coupled (FIG. 2).

In order to absorb more back light, the cover of the measurement chamber 8 opposite the particular part of the optical module 5, in particular the peripheral screen 9, the center screen 10 and the base 11, is replaced with a conventional matt surface. Includes a glossy reflective surface. Generally, some or the entire inner surface of the optical module 5 can be polished.

Backlight can be most lost by absorption on the matte surface, but it can be presumed that it can be overlooked that light diffuses and scatters on the matte surface to reach out of control in the measurement chamber. On the other hand, if a glossy surface is used, it acts like black glass and reflects nonabsorbed light in a defined non-interfering direction, for example to an adjacent peripheral screen. Since the reflecting surface is black and reflects only about 5% of the incident light, it can be almost completely lost to repeated reflections between the surfaces. Glossy surfaces are formed by injection molding, which in turn imparts adequate gloss on the surface to be glossy.

An important feature for improving the measurement reliability of the smoke alarm device shown in the figure is that the incident angle of the light beam received by the light receiver 7 and emitted by the light source 6 without the peripheral screen 9 being arranged rotationally symmetrically It is arranged to be always constant on the screen. Peripheral screens 9 arranged in rotational symmetry are formed by rotating the screen about its center. In FIG. 1, four peripheral screens 9 adjacent to the light source 6 and four screens adjacent to the optical receiver 7 are not formed rotationally symmetric. The incident angle is selected so that the incident light and the non-absorbed light are highly reflected between the peripheral screen 9.

Since each of the peripheral screens 9 consists of two angled surfaces, light emitted to the peripheral screen 9 cannot reach the inner surface of the side wall 4 directly, but in each case reaches the peripheral screen 9. The mutual inclination and distance, and the length of the peripheral screen 9 are determined to be reflected by the screen to adjacent peripheral screens. In addition, the non-rotational symmetrical arrangement of most peripheral screens 9 absorbs more back light, requiring less position and component accuracy of the light receiver 7 and light source 6 and making the smoke alarm unit operate more accurately.

In FIG. 1, the peripheral screen 9 is configured to have as pointed edges as possible at the inner edges facing the center screen 10. This has the advantage that only a small amount of light reaches the pointed edge so that light is not reflected in various directions.

In the injection molding process by erosion, the edge sharpness is limited depending on the thickness of the wire used, which does not meet the requirements of the inner edge of the peripheral screen 9. In the smoke alarm unit 1, the sharpness of the inner edge can be formed as required because the core is inserted into an injection molded portion having a toothed or zigzag contour around the edge provided to form the inner edge. Each tooth or zigzag portion is fitted into a groove formed in the injection molding to form the peripheral screen 9 and closed towards the center. As a result, a sharp edge may be formed between the groove of the injection molded part and the toothed portion of the core.

In actual testing, the use of a peripheral screen 9 with a pointed inner edge and an optical module with a glossy surface (peripheral screen 9, center screen 10, measurement chamber 8 cover) can significantly reduce the base pulse and reduce smoke. Demonstrates that the alarm is less likely to contain dust and condensate.

As can be seen in the accompanying drawings, each of the light source 6 and the optical receiver 7 is disposed in the housing 16, 17. The two housings 16, 17, which are fixed to the cover of the measuring chamber 8, open towards the bottom and close at the open side by the base 11. On the front side facing the center screen 10, the housings 16, 17 are closed by windows having light outlets and light inlets, respectively. The window differs from the housing window of the scattered light smoke alarm in that it can be made as a single part.

In the known scattered light smoke alarm, the window consists of two parts, one of which is fixed to the cover of the measuring chamber and the other of which is fixed to the base. When the base is in place, fitting problems occur repeatedly, and air gaps may be formed between the upper and lower half of the window, causing undesirable disturbances in radiant and received light. The integral housing window can prevent the kind of disturbance described above and does not have the problem of keeping the position of the window divided into two parts accurately.

As shown in FIG. 2, in the case of the window 18 of the housing 16, the upper half and the lower half of the unitary window split like two scissors blades. As a result, since the injection molding part is formed without a mold slide, an independent mounting element is provided in the light inlet and the light outlet divided into two parts, so that the correct shape can be maintained and the surface of the opening can be kept clean.

Claims (10)

An optical module 5 consisting of a labyrinth system comprising a light source 6, an optical receiver 7, a measuring chamber 8, a base 11 and a screen 9 arranged around the measuring chamber 8 is provided. In a smoke alarm device comprising an alarm unit (1), which can be fixed to the base, the base (11) so as to be spaced farther from the center than from the plane defined by the light source (6) and the optical receiver (7). Smoke alarm) characterized in that is made. 2. Smoke alarm device according to claim 1, characterized in that the base (11) is funnel shaped and takes the form of corners or pyramids. 3. Smoke alarm device according to claim 2, characterized in that the base (11) comprises a grid structure (13) and is formed of an insect screen. 4. The base 11 according to claim 1, wherein the base 11 has a plurality of upwardly protruding thin plates 14, 15 on the inner side facing the measuring chamber 8, the mutual distance, height, number of thin plates. And the arrangement is such that the light generated against the base 11 reaches one of the thin plates 14, 15 before reaching the base, and the optical receiver 7 observes only the thin plates 14, 15 of the base 11. Smoke alarm device, characterized in that selected. 5. Smoke alarm device according to claim 4, characterized in that the optical receiver (7) is blocked by the thin plates (14, 15) from external light passing from the outside through the measuring chamber. 5. Smoke alarm device according to claim 2 and 4, characterized in that the thin plates (14, 15) are arranged parallel or at right angles to the base edge of each pyramid side. 6. A smoke warning device according to claim 5, wherein the star-shaped ribs (12) are provided on the outside of the base (11), which form the side walls of the smoke-moving channel. The cover of the measuring chamber (8) according to claim 1, wherein the part of the optical module (5) which is important for backlighting, in particular against the peripheral screen (9), the center screen (10) and the base (11). And a glossy surface, wherein the non-absorbed light is made to reflect in a predetermined direction. The peripheral screen 9 according to claim 1, wherein the peripheral screen 9 is arranged such that the angle of incidence of the light beam emitted by the light source 6 and received by the optical receiver 7 remains constant over most of the screen. Smoke alarm device, characterized in that. Smoke alarm device according to claim 1, characterized in that the peripheral screen (9) has as pointed edges as possible at the front facing the center screen (10).