Forward scatter smoke detector

• US 4,430,646 A
• Filed: 12/31/1980
• Issued: 02/07/1984
• Est. Priority Date: 12/31/1980
• Status: Expired

• Current Assignee: Sentrol Incorporated (Carrier Global Corporation), University of Florida (State University System of Florida)
• Original Assignee: American District Telegraph Company (Johnson Controls International plc)
• Inventors: Enemark, Robert B.
• Primary Examiner(s): Caldwell, Sr., John W.
• Assistant Examiner(s): Myer, Daniel
• Application Number:
  US06/221,524
• Time in Patent Office: 1,133 Days
• Field of Search: 340/630, 340/380, 250/574, 356/338, 356/339, 356/247, 356/438, 356/439
• US Class Current: 340/630
• CPC Class Codes: G01N 21/53 within a flowing fluid, e.g. smoke
• CPC Class Codes: G01N 2201/0642 Light traps; baffles

Abstract

An optical smoke detector having a conical masking body located directly between a light source and a light receiver. The masking body is provided with a reflecting surface so that rays from the light source are diverted into a reaction zone to supplement direct rays from the light source to the zone. In one embodiment the reflecting surface is cuspidate while in another embodiment a second masking body is added which shadows the light receiver from viewing the base of the first masking body.

Claims

1. A particle detector comprising:

a source of light directed on a first path accessible to particles;

a photocell having a photosensitive area viewing on a second path into a zone of intersection of the two paths and responsive to light scattered from particles in the zone; and

a body masking direct light from the source to the photosensitive area and having a periphery outside which light passes to the intersection zone;

wherein the detector includes a reflective surface disposed between the masking body periphery and the light source having reflective components at an angle relative to direct rays from the source toward the masking body such as to direct such rays away from the body into a substantial value of the intersection zone; and

wherein the reflective surface is cone like.

2. A detector according to claim 1 wherein the reflective surface is a surface of axial revolution.

3. A detector according to claim 2 wherein the reflective surface is a surface of revolution of a curved line.

4. A detector according to claim 2 wherein the light source and photocell are on the axis of revolution.

5. A detector according to claim 1 wherein the surface has a conical apex directed toward the light source and the surface flares away from the light source.