Classifications

• • G—PHYSICS
  • G08—SIGNALLING
  • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
  • G08B17/00—Fire alarms; Alarms responsive to explosion
  • G08B17/10—Actuation by presence of smoke or gases, e.g. automatic alarm devices for analysing flowing fluid materials by the use of optical means
  • G08B17/103—Actuation by presence of smoke or gases, e.g. automatic alarm devices for analysing flowing fluid materials by the use of optical means using a light emitting and receiving device
  • G08B17/107—Actuation by presence of smoke or gases, e.g. automatic alarm devices for analysing flowing fluid materials by the use of optical means using a light emitting and receiving device for detecting light-scattering due to smoke
• • G—PHYSICS
  • G08—SIGNALLING
  • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
  • G08B17/00—Fire alarms; Alarms responsive to explosion
  • G08B17/10—Actuation by presence of smoke or gases, e.g. automatic alarm devices for analysing flowing fluid materials by the use of optical means
  • G08B17/11—Actuation by presence of smoke or gases, e.g. automatic alarm devices for analysing flowing fluid materials by the use of optical means using an ionisation chamber for detecting smoke or gas
  • G08B17/113—Constructional details

Definitions

• the invention relates to a smoke detector with a detector insert which can be fastened in a base and has an optical module which has a light source, a light receiver, a measuring chamber, a central diaphragm, a base and a labyrinth system with diaphragms arranged on the periphery of the measuring chamber.
• smoke detectors of this type which are referred to as scattered-light smoke detectors, and which may optionally contain a further sensor, for example a temperature sensor, in addition to the optical module
• the optical module is designed in such a way that disturbing extraneous light cannot penetrate and smoke can very easily penetrate the measuring chamber.
• the light source and light receiver are arranged in such a way that no light rays can get directly from the source to the receiver. In the presence of smoke particles in the beam path, the light from the light source is scattered thereon and part of this scattered light falls on the light receiver and causes an electrical signal.
• the false alarm security of such scattered-light smoke detectors depends, among other things, to a large extent on the fact that light from the light source that is actually only scattered on smoke particles reaches the light receiver, and that the so-called background light - whether this is extraneous light from outside or on parts of the optical module or on light other than scattered on smoke particles , is suppressed.
• the background light is suppressed in the known optical smoke detectors, for example also in the one described in DE-A-44 12 212, by absorption of the background light on matt surfaces, for which purpose the corresponding parts of the optical module made of a black plastic with a matt surface consist.
• the invention is now intended to provide a smoke detector of the type mentioned in the introduction, in which the basic pulse is significantly reduced compared to the smoke detectors known today.
• the object is achieved according to the invention in that certain parts of the optical module which are critical with regard to the generation of background light have a glossy surface and are designed such that the light which is not absorbed is reflected in a defined direction.
• the solution according to the invention brings about a drastic reduction in the basic pulse, because the defined direction mentioned can be selected such that light reflected in it certainly does not interfere. For example, you can choose this direction so that the non-absorbed light is reflected several times and is practically completely destroyed. Because only about 5% of the striking light is not absorbed and reflected by the glossy black surfaces, only a few reflections are required until there is only a fraction of the original background light that is no longer distracting.
• a first preferred embodiment of the smoke detector according to the invention is characterized in that the parts of the optical module mentioned comprise the peripheral diaphragms, the central diaphragm and the ceiling of the measuring chamber opposite the floor.
• a second preferred embodiment is characterized in that further parts or the entire inside of the optical module have a glossy surface.
• the optical module is produced with an injection molding tool which, at least on the parts provided for producing the aforementioned glossy surfaces, has a surface quality sufficient to achieve a glossy surface.
• a fourth preferred embodiment of the smoke detector according to the invention is characterized in that the injection molding tool has a polished surface on the parts mentioned.
• FIG. 2 shows a schematic section along the line II-II of FIG. 1 on a scale reduced compared to FIG. 1.
• the scattered-light smoke detector shown consists in a known manner of a detector insert 1, which can be fastened in a base (not shown) which is preferably mounted on the ceiling of the room to be monitored, and a detector hood 2 which is placed over the detector insert 1 and which is in the area of its in the operating state of the Detector against the space to be monitored is provided with smoke inlet slots 3.
• the detector insert 1 essentially comprises a box-like base body, on the side facing the tip of an optical module 5 surrounded by a side wall 4 and on the side facing the detector base a printed circuit board with evaluation electronics (not shown) are arranged. This detector structure is known and will not be described in more detail here. In this context, reference is made, for example, to the detectors of the AlgoRex series (AlgoRex - registered trademark of Cerberus AG) and to European patent application No. 95117405.1.
• the optics module 5 essentially consists of a light source 6, a light receiver 7, a measuring chamber 8, a labyrinth system consisting of peripheral diaphragms 9 arranged on the inside of the side wall 4, a central diaphragm 10 and a bottom 11.
• the optical axes of the by an infrared light emitting diode (IRED) formed light Source 6 and the light receiver 7 are not on a common straight line, but have a bent course, the central diaphragm 10 being arranged close to the intersection.
• IRED infrared light emitting diode
• the side wall 4 and the bottom 11 shield the measuring chamber 8 against external light from the outside, and the peripheral diaphragms 9 and the central diaphragm 10 prevent light rays from being able to reach the light receiver 7 in a direct way from the light source 6.
• the peripheral diaphragms 9 also serve to suppress the so-called background light, which is caused by undesired scattering or reflections. The better the background light is suppressed, the lower the basic pulse, that is the signal that is detected when there is no smoke in the measuring chamber 8.
• the intersection of the beam of rays emitted by the light source 6 and the field of view of the light receiver 7 form the actual measurement area, hereinafter referred to as the scattering space.
• the light source 6 sends short, intense light pulses into the scattering space, the light receiver 7 "seeing" the scattering space but not the light source 6.
• the light from the light source 6 is scattered by smoke penetrating into the scattering space, and part of this scattered light falls on the light receiver 7.
• the receiver signal generated thereby is processed by the electronics.
• the smoke detector can also contain further sensors, for example a temperature and / or a gas sensor.
• the bottom 11 has a sieve or lattice-like structure and is on it Provided on the outside with ribs 12 arranged in a star shape, through which the smoke is brought to the floor. As a result, the smoke flows in the vertical direction into the measuring chamber 8 and into the scattering space. Due to the funnel-shaped design, the base 11 is at a considerably greater distance from the measuring chamber than is the case with a flat base.
• the funnel-shaped region of the base 11 has the shape of a pyramid or a truncated pyramid, all the side surfaces of the pyramid having the sieve-like or lattice-like structure already mentioned.
• a lattice-like structure 13 is indicated schematically only in one of the pyramid surfaces for reasons of clearer recognition.
• the ribs 12 on the outside of the base 11 are preferably arranged along the side of the pyramid.
• the likelihood of interference from dust particles deposited on the floor 11 is further reduced by a special design of the floor.
• the floor 11 is provided on its inner surface with a Niel number of vertically upwardly projecting lamellae 14, 15, their arrangement, number, height and mutual distance being selected such that light falling from the measuring chamber onto the floor is present Reaching the floor meets one of the slats, and that the light receiver 7 sees only the slats 14, 15 from the floor 11.
• the lamellae 14, 15 shield the light receiver 7 against external light from the outside.
• not all pyramid surfaces are provided with lamellae, but only that of the light source 6 and that opposite the light receiver 7 and the pyramid surface enclosed between these two surfaces.
• the pyramid surfaces opposite the light source 6 and the light receiver 7 are provided with longitudinal lamellae 14 oriented parallel to the base edge of the pyramid and the Chen enclosed pyramid surface is provided with at least one longitudinal lamella 14 and with a plurality of transverse lamellae 15 oriented perpendicular to this.
• the longitudinal lamellae 14 run at least approximately perpendicular to the optical axis of the opposite light source or the opposite light receiver.
• the transverse fins 15 serve primarily for the optical decoupling of light source 6 and light receiver 7.
• At least certain parts of the optical module 5, in particular the peripheral diaphragms 9, the central diaphragm 10 and the ceiling of the measuring chamber 8 opposite the floor 11, have a glossy, i.e. reflective, surfaces on.
• other parts or the entire inside of the optical module 5 can have a glossy surface.
• glossy surfaces are used, then they act like black mirrors and reflect the unabsorbed light onto another of these surfaces, for example the neighboring peripheral diaphragm. Since the reflecting surfaces are black and therefore only reflect about 5% of the incident radiation, this can be virtually completely eliminated by repeated reflection between such surfaces.
• the glossy surfaces are produced by an injection molding Stuff that has a suitable, preferably polished, surface at least on the surfaces that should shine.
• peripheral diaphragms 9 are not arranged rotationally symmetrically but in such a way that the angle of incidence of the light beam emitted by the light source 6 and that received by the light receiver 7 is on this aperture is constant.
• Peripheral diaphragms 9 arranged in a rotationally symmetrical manner would be those which are formed by rotating an aperture around the center.
• the four peripheral diaphragms 9 adjacent to the light source 6 and the light receiver 7 are not rotationally symmetrical.
• the opening angle is selected so that the incident and non-absorbed light is reflected as often as possible between the peripheral diaphragms 9.
• the peripheral screens 9 each consist of two angled partial surfaces, the mutual inclination and the distance and the length of the peripheral screens 9 being selected such that the light emitted to the peripheral screens 9 cannot reach the inner surface of the side wall 4 directly, but in each Case strikes a peripheral diaphragm 9 and is reflected by this on the adjacent peripheral diaphragm.
• the non-rotationally symmetrical arrangement of the plurality of peripheral diaphragms 9 also leads to better absorption of the background light and thus to less stringent requirements for the positioning and component accuracy of light source 6 and light receiver 7 and to a detector which is less susceptible to contamination.
• the peripheral diaphragms 9 are formed as sharp as possible on their inner edge directed against the central diaphragm 10. This has the advantage that only a little light falls on such a sharp edge and therefore less light is reflected in a multitude of directions.
• the sharpness of an edge is limited by the thickness of the wire used, which does not meet the requirements for the inner edges of the peripheral screens 9.
• the desired sharpness of the inner edges is achieved by inserting a core into the injection molding tool, which has a stepped (serrated or serrated) contour on the periphery provided for forming said inner edges.
• peripheral diaphragms 9 with sharp inner edges and optical module parts (peripheral diaphragms 9, central diaphragm 10, ceiling of the measuring chamber 8) with a glossy surface leads to a marked reduction in the basic pulse, and that the detector is less susceptible to dust and condensation is.
• the light source 6 and the light receiver 7 are each arranged in a housing 16 and 17, respectively.
• the two housings 16 and 17, which are worked onto the ceiling of the measuring chamber 8, are open at the bottom and are covered on their open side by the floor 11.
• the housings 16 and 17 are each closed by a window with a light exit or light entry opening.
• These windows differ from the housing windows of known scattered-light smoke detectors in that they are made in one piece.
• the windows consist of two parts, one of which is attached to the ceiling of the measuring chamber and the other to the floor. When fitting the floor, fitting problems occur again and again and there is a gap in the light between the two halves of the window and thus to undesirable interference in the transmission and reception light. With the one-piece housing windows, malfunctions of this type are excluded and there can be no problems with the positioning accuracy of the two window halves.
• the injection molding tool can be designed without a side pull in such a way that a separate shaped element is provided for each of the two halves of the light emission and light entry opening which are offset with respect to one another, so that a precisely defined shape and a clean surface of these openings is achieved.

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• Chemical & Material Sciences (AREA)
• Analytical Chemistry (AREA)
• Business, Economics & Management (AREA)
• Emergency Management (AREA)
• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Fire-Detection Mechanisms (AREA)
• Investigating Or Analysing Materials By Optical Means (AREA)

Priority Applications (4)

Applications Claiming Priority (2)

Publications (1)

Family

ID=8223020

Family Applications (1)

Country Status (12)

Cited By (1)

Families Citing this family (4)

Citations (3)

• 1996
  • 1996-07-22 ES ES96111752T patent/ES2185728T3/es not_active Expired - Lifetime
  • 1996-07-22 EP EP96111752A patent/EP0821331B1/de not_active Expired - Lifetime
  • 1996-07-22 AT AT96111752T patent/ATE227041T1/de active
  • 1996-07-22 DE DE59609838T patent/DE59609838D1/de not_active Expired - Lifetime
• 1997
  • 1997-06-03 ZA ZA9705812A patent/ZA975812B/xx unknown
  • 1997-07-15 CN CN97190938A patent/CN1198238A/zh active Pending
  • 1997-07-15 UA UA98031426A patent/UA52618C2/uk unknown
  • 1997-07-15 KR KR10-1998-0701679A patent/KR100467129B1/ko not_active IP Right Cessation
  • 1997-07-15 RU RU98107635/09A patent/RU2189639C2/ru not_active IP Right Cessation
  • 1997-07-15 WO PCT/CH1997/000270 patent/WO1998003947A1/de active IP Right Grant
  • 1997-07-15 AU AU33328/97A patent/AU725326B2/en not_active Ceased
  • 1997-07-15 PL PL97325922A patent/PL184227B1/pl not_active IP Right Cessation

Patent Citations (3)

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