Scattered-light smoke detector with a two-color light-emitting diode

Patent metadata

Field	Value
Publication number	US-9541501-B2
Application number	US-201514955101-A
Country	US
Kind code	B2
Filing date	Dec 1, 2015
Priority date	Dec 1, 2014
Publication date	Jan 10, 2017
Grant date	Jan 10, 2017

Abstract

A scattered-light smoke detector includes a detector unit that operates according to the scattered-light principle. The detector unit includes a light-emitting diode (LED) to irradiate particles to be detected and a spectrally sensitive photosensor to detect the light scattered by the particles. The LED and photosensor are aligned such that a principal optical axis of the LED and a principal optical axis of the photosensor define a scattered-light angle. The LED includes a first and a second LED chip for emitting first and second light beams with light in a first wavelength range and a different second wavelength range, and an LED chip carrier arranged orthogonally to the principal optical axis. The two LED chips are arranged side-by-side on the LED chip carrier. The LED is rotated such that a chip axis extending through the two LED chips is orthogonal to an angle plane defined by the two optical axes.

First claim

What is claimed is:

1. A scattered-light smoke detector with a detector unit that works according to the scattered-light principle, the scattered-light smoke detector comprising:
a light-emitting diode configured to irradiate particles to be detected, and
a photosensor that is spectrally sensitive to the particles to detect light scattered by the particles,
wherein the light-emitting diode has a principal optical axis and the photosensor has an optical receiving axis, wherein the light-emitting diode and the photosensor are arranged and aligned with respect to each other such that the principal optical axis of the light-emitting diode and the optical receiving axis of the photosensor define a scattered-light angle,
wherein the light-emitting diode comprises a first LED chip configured to emit a first light beam with light in a first wavelength range and a second LED chip configured to emit a second light beam with light in a second wavelength range different from the first wavelength range,
wherein the light-emitting diode comprises an LED chip carrier arranged orthogonally to the principal optical axis of the light-emitting diode ,
wherein the two LED chips are arranged side-by-side on the LED chip carrier, and
wherein the light-emitting diode is rotated about the principal optical axis such that a chip axis extending through the first and second LED chips is orthogonal to an angle plane defined by the principal optical axis of the light-emitting diode and the optical receiving axis of the photosensor.

2. The scattered-light smoke detector of claim 1 , wherein the first and second LED chips are located at the same distance from the principal optical axis of the light-emitting diode.

3. The scattered-light smoke detector of claim 1 , wherein the first and second LED chips are arranged side-by-side such that the chip axis extends through both the principal optical axis of the light-emitting diode and through a geometric center of the first and second LED chips.

4. The scattered-light smoke of claim 1 , wherein the first and second LED chips are aligned orthogonally to the principal optical axis of the light-emitting diode on the chip carrier.

5. The scattered-light smoke detector of claim 1 , wherein the light-emitting diode comprises at least two terminal contacts extending from a housing of the light-emitting diode, wherein the terminal contacts are in contact with the first and second LED chips for electrically controlling the first and second LED chips.

6. The scattered-light smoke detector of claim 1 , wherein a ratio of an optically active surface of the first LED chip to an optically active surface of the second LED chip is within a range of from 1.3 to 12.

7. The scattered-light smoke detector of claim 1 , wherein the first LED chip is configured to emit light in the wavelength range of 350 nm to 500 nm, and wherein the second LED chip is configured to emit light in the wavelength range of 665 nm to 1000 nm.

8. The scattered-light smoke detector of claim 7 , wherein the first LED chip is configured to emit light with a wavelength of 460 nm±40 nm or 390 nm±40 nm, and the second LED chip is configured to emit light with a wavelength of 940 nm±40 nm or 860 nm±40 nm.

9. The scattered-light smoke detector of claim 1 , wherein:
the detector unit is shielded against ambient light but permeable to particles to be detected,
the light-emitting diode, the photosensor, and a diaphragm mechanism are arranged in the detector unit, wherein the diaphragm mechanism comprises a diaphragm aperture and is disposed and aligned such that a large part of the light emitted by the first and second LED chips passes through the diaphragm aperture in a range of between 50% and 85%.

10. The scattered-light smoke detector of claim 9 , wherein:
light-emitting diode comprises a housing made of a transparent plastic, and
the housing forms an optical lens in a region between the light outlet from the first and second LED chips and the light outlet on the outside of the housing.

11. The scattered-light smoke detector of claim 9 , comprising an optical lens unit arranged between the light-emitting diode and the diaphragm aperture.

12. The scattered-light smoke detector of claim 1 , comprising an electronic control unit connected to the light-emitting diode and to the photosensor, wherein the control unit is configured to output at least one of a warning or an alarm in response to detecting a minimum concentration value of smoke.

13. The scattered-light smoke detector of claim 12 , wherein the electronic control unit is configured to control the first and second LED chips using alternative pulsing.

14. The scattered-light smoke detector of claim 1 , wherein the photosensor comprises a silicon PIN photodiode.

15. The scattered-light smoke detector of claim 1 , wherein the light-emitting diode and the photosensor form a forward scattered-light arrangement with a scattered-light angle within a range of 20° to 90°, or a backward scattered-light arrangement with a scattered-light angle within a range of greater than 90° to 160°.

Assignees

• Siemens Schweiz Ag

Inventors

• Allemann Martin
• Schmid Brigitt
• Walker Stefan

Classifications

• G01N21/53 Primary

  within a flowing fluid, e.g. smoke · CPC title

• G08B17/113

  Constructional details · CPC title

• G08B17/107

  for detecting light-scattering due to smoke · CPC title

• G01N2201/0621

  Supply · CPC title

• G01N2201/0696

  Pulsed · CPC title