SMOKE DETECTING DEVICE UTILIZING OPTICAL FIBERS

• US 3,805,066 A
• Filed: 08/14/1972
• Issued: 04/16/1974
• Est. Priority Date: 08/14/1972
• Status: Expired due to Term

• Current Assignee: Toichi Chijuma, Yoshio Morita
• Original Assignee: Toichi Chijuma, Yoshio Morita
• Inventors: Morita, Yoshio, Chijuma, Toichi
• Primary Examiner(s): Lawrence, James W.
• Assistant Examiner(s): Nelms, D. C.
• Application Number:
  US05/280,204
• Time in Patent Office: 610 Days
• Field of Search: 250/227,218,221 350/96R,96B 340/237S 356/207,208
• US Class Current: 250/227.11
• CPC Class Codes: G01N 21/534 by measuring transmission alone, i.e. determining opacity
• CPC Class Codes: G08B 17/10 Actuation by presence of smoke or gases , e.g. automatic alarm devices for analysing flowing fluid materials by the use of optical means
• CPC Class Codes: G08B 17/103 using a light emitting and receiving device
• CPC Class Codes: G08B 17/113 Constructional details

Abstract

A smoke detecting device utilizing optical fibers is composed of a required number of optical fibers arranged in series alignment with gaps provided therebetween, a light source introducing light rays through one end of the first of the serially arranged optical fiber to the interior thereof, a photo-electric transducer for receiving light rays passed through the optical fibers and delivered from the end of the last of the serially arranged optical fiber to convert the amount of light thus received into an electric quantity, and a discriminating circuit which produces a predetermined electric signal for indicating the detection of fire whenever the variation of the electric quantity thus obtained exceeds a preset value, whereby any variation in the amount of light due to the intervention of smoke into the gaps between the optical fibers is detected electrically thereby to obtain an electric signal.

Claims

1. A smoke detecting device, comprising:

a plurality of optical fibers including a first optical fiber having a free end and a coupled end, a last optical fiber having a free end and a coupled end and intermediate optical fibers having two coupled ends in serial alignment and each pair of consecutively aligned optical fibers defining a gap between the adjacent coupled ends thereof;

a light source and focusing means positioned opposite the free end of the first of the serially aligned optical fibers for introducing light rays into the first optical fiber for transfer through the serially arranged optic fibers;

a coupling means operatively positioned between each of the adjacent optical fibers and firmly retaining the ends thereof in proper alignment and maintaining the gap therebetween, the coupling means defining a plurality of apertures appropriately positioned to allow smoke to enter therein and to pass through the gap between the adjacent ends of coupled optical fibers, diminishing the amount of light transferred from one optical fiber to the adjacent optical fiber in direct relation to the amount of smoke in the gap;

a photoelectric transducer means operatively positioned for receiving light transmitted through the serially arranged optical fibers and delivered from the unconnected end of the last optical fiber to convert the light received into an electrical voltage; and

a discriminator circuit operatively connected to the photoelectric transducer means for producing a pre-determined electric signal for indicating the detection of smoke whenever the variation of the electrical voltage caused by the diminution of received light due to the presence of smoke in the gaps exceeds a preset value.

2. The device of claim 1 wherein the light projecting means, the photoelectric transducer means and the discriminator circuit comprise a single unit.

3. The device of claim 2 wherein the connecting means comprises a box having end walls and longitudinal walls placed at each junction of two adjacent optical fibers, said box having a cylindrical optical fiber holder extended inwardly from each of the centers of two end walls of the box in a manner that the two cylindrical holders are aligned in the axial direction of the box, said box further having ventilation holes through the central portion of the longitudinal walls for introducing smoke into the box, and said two cylindrical holders maintaining the two optical fibers in their positions so that a predetermined length of gap is provided between the ends of the two optical fibers.