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 present invention relates to a fire detector.
• Fire alarm systems generally comprise a control unit which manages peripheral units, usually sensors/detectors, over a two-wire line or by means of radio systems.
• optical-thermal detectors ensure better coverage of a broader range of types of fire.
• Optical sensors particularly photoelectric ones, use the principle according to which an electromagnetic radiation which is incident to a particle suspended in a fluid is partly absorbed and partly diffused by the particle.
• the structure of these detectors comprises an optical chamber which has a box-like structure and is perimetrically formed by access ducts for the fluid; a light source, advantageously an LED, and a light receiver, advantageously a photodiode, are arranged in said chamber.
• the fluid access ducts are provided so as to block as much as possible the penetration of ambient light in the optical chamber, in order to avoid affecting the sensing of the photodiode.
• the transmitter is constituted by an LED which emits a light pulse in which the ratio between the width and the period is very low.
• the light emitted by the LED is partially diffused by the particles suspended in the fluid, is detected by the photodiode, and is converted into an electrical signal which is then amplified and processed by an electronic circuit.
• the LED and the photodiode are arranged so as to avoid a line-of-sight configuration but are arranged so that their respective emission and reception fields mutually intersect in a point which lies inside the optical chamber.
• the emitter-receiver pair is fitted on the printed circuit board by through-hole mounting.
• GB-A-2 306 218 discloses a fire detector comprising a printed circuit board on which at least one optical transmitter and at least one optical receiver are surface-mounted, said transmitter and said receiver being arranged so as to avoid a line-of-sight arrangement, their respective emission and reception fields intersecting each other, said board being associated with a box-like optical chamber, said chamber being formed perimetrically by a plurality of partitions which form access ducts for the fluid.
• the aim of the present invention is to eliminate or substantially reduce the problems of conventional fire detectors.
• an important object of the invention is to provide a fire detector which ensures manufacturing and assembly at high speed and low cost.
• Another object is to provide a detector characterized by low sensitivity to radio-frequency noise.
• Another important object is to provide a fire detector whose overall quality at least equals or exceeds that of conventional detectors.
• a fire detector characterized in that it comprises a printed circuit board on which at least one optical transmitter and at least one optical receiver are surface-mounted with a method known commercially as SMD, said transmitter and said receiver being arranged so as to avoid a line-of-sight arrangement, their respective emission and reception fields intersecting each other, said board being associated with a box-like optical chamber which is composed of a fluid detection portion and a fluid circulation portion, said detection portion being arranged through a corresponding through hole formed in the printed circuit board and being provided with openings which are formed in the perimetric wall for the corresponding transmitters and receivers, whose respective emission and reception fields mutually intersect inside it, said circulation portion being arranged on the opposite side with respect to the detection portion and being formed perimetrically by a plurality of partitions which form access ducts for the fluid.
• a fire detector according to the invention is generally designated by the reference numeral 10.
• the tapering upper portion 12 is provided with lateral openings 13.
• the assembly 14 comprises a printed circuit board 15 on which a transmitter 17, advantageously constituted by an LED, and a receiver 16, advantageously constituted by a photodiode, are surface-mounted; said receiver and said transmitter operate in the infrared part of the spectrum.
• the transmitter 17 and the receiver 16 are arranged on the board 15 so as to avoid a line-of-sight configuration but so that the emission and reception fields mutually intersect.
• the emission and reception fields are arranged at 45° with respect to the line-of-sight position.
• a second LED 18, which is visible from outside, and a thermistor 19 are further arranged on the printed circuit board 15.
• the board 15 is associated, by means of a removable interlocking coupling, with a first cover 20 for protecting the electronic components which lies perimetrically and is monolithic with an optical chamber 21.
• the optical chamber 21 is constituted by a lower portion 22 for detection of the fluid and by an upper portion 23 for circulation of the fluid.
• the detection portion 22 extends downward beyond the dimensions of the first cover 20, through a corresponding through hole 24 formed in the printed circuit board 15.
• the detection portion 22 is further provided with two openings 25 provided in the perimetric wall 26 for the LED 17 and the photodiode 16, whose emission and reception fields accordingly intersect inside the portion 22.
• the internal perimetric wall 26 of the lower portion 22 has tooth-like projections 27 so as to minimize the signal produced by internal reflections collected by the photodiode 16.
• the lower portion 22 is shaped with lateral recesses 28 at the openings 25 for advantageously accommodating the LED 17 and the photodiode 16.
• the upper circulation portion 23 lies on the opposite side to where the lower portion 22 lies with respect to the first cover 20, is substantially cylindrical and is formed perimetrically by a plurality of access ducts 29 for the fluid.
• the upper ends 31 of the partitions 30 are accommodated in corresponding seats 32 formed in the flat inner portion of a second cover 33 for the upper portion 23.
• the second cover 33 has a perimetric portion 34 which lies at right angles to its plane of arrangement and is made of mesh, as required by the standards, adapted to cover the plurality of ducts 29 for controlled access of fluid inside the optical chamber 21.
• the flat inner portion of the second cover 33 is also provided with tooth-like projections 35.
• the printed circuit board 15 is associated, with a removable interlocking coupling, with the first cover 20; the removable interlocking coupling is allowed by flexible elastic teeth 36 which protrude monolithically with respect to the first cover 20 and at right angles to its plane of arrangement.
• the printed circuit board 15 has, in addition to the photodiode 16 and the LED 17, a second LED 18 and a thermistor 19.
• the thermistor 19 is constituted by a sensitive portion 38, which in this embodiment is made of a material having a negative temperature coefficient, and is associated with a support 39 which lies at right angles to the printed circuit board 15 and passes through the optical chamber 21 and finally through a through hole 40 of the second cover 33.
• the sensitive portion 38 is external to the optical chamber 21 but is contained within the box-like body 11 at its upper portion 12 provided with lateral openings 13.
• the above-described detector 10 is a detector of the optical-thermal type.
• the sensor detects the presence of the smoke by means of the emitter-receiver pair, which operates in the infrared part of the spectrum.
• the transmitter 17 (LED) and the receiver 16 (photodiode) are arranged in the optical chamber 21 so that they are not in a line-of-sight configuration: when smoke enters the volume that corresponds to the intersection of the beam emitted by the LED 17 and of the viewing field of the photodiode 16, it diffuses part of the incident light emitted by the transmitter 17, which is detected and converted into an electrical signal (current) by the photodiode 16.
• the thermistor 19, supported by a support 39, is arranged outside the profile of the optical chamber 21.
• the LED 17 and the photodiode 16 can be replaced with a transmitter and a receiver which operate in the visible part of the spectrum.
• this particular embodiment also allows to obtain a detector whose sensitivity to radio-frequency noise is particularly low, since the length of the connections of the various electronic components is very limited.
• the total height of the optical chamber has been kept as great as possible, to the extent allowed by the bounding mechanical constraints, so as to space the active volume from the second cover of said chamber.
• the materials employed, as well as the dimensions, so long as they are compatible with the contingent use may be any according to requirements.

Landscapes

• Analytical Chemistry (AREA)
• Business, Economics & Management (AREA)
• Emergency Management (AREA)
• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Chemical & Material Sciences (AREA)
• Fire-Detection Mechanisms (AREA)
• Fire Alarms (AREA)
• Structures Of Non-Positive Displacement Pumps (AREA)
• Investigating Or Analysing Materials By Optical Means (AREA)
• Eye Examination Apparatus (AREA)
• Exchange Systems With Centralized Control (AREA)
• Induction Machinery (AREA)
• Camera Bodies And Camera Details Or Accessories (AREA)
• Studio Devices (AREA)

Applications Claiming Priority (3)

Publications (2)

Family

ID=11451906

Family Applications (1)

Country Status (14)

Families Citing this family (12)

Family Cites Families (4)

• 2000
  • 2000-04-11 IT IT2000PD000083A patent/IT1315417B1/it active
• 2001
  • 2001-04-06 CN CNB018077420A patent/CN100438308C/zh not_active Expired - Fee Related
  • 2001-04-10 CA CA002405713A patent/CA2405713A1/en not_active Abandoned
  • 2001-04-10 AU AU2001246755A patent/AU2001246755A1/en not_active Abandoned
  • 2001-04-10 DE DE60100756T patent/DE60100756T2/de not_active Expired - Fee Related
  • 2001-04-10 PT PT01919696T patent/PT1272992E/pt unknown
  • 2001-04-10 CZ CZ20023374A patent/CZ20023374A3/cs unknown
  • 2001-04-10 AT AT01919696T patent/ATE249668T1/de not_active IP Right Cessation
  • 2001-04-10 RU RU2002129506/09A patent/RU2002129506A/ru not_active Application Discontinuation
  • 2001-04-10 DK DK01919696T patent/DK1272992T3/da active
  • 2001-04-10 EP EP01919696A patent/EP1272992B1/en not_active Expired - Lifetime
  • 2001-04-10 ES ES01919696T patent/ES2206415T3/es not_active Expired - Lifetime
  • 2001-04-10 WO PCT/IB2001/000591 patent/WO2001078031A1/en active IP Right Grant
• 2002
  • 2002-10-10 NO NO20024896A patent/NO20024896L/no not_active Application Discontinuation

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