Smoke detecting apparatus and method

• US 5,898,377 A
• Filed: 04/01/1997
• Issued: 04/27/1999
• Est. Priority Date: 04/01/1996
• Status: Expired due to Fees

• Current Assignee: Hamamatsu Photonics KK
• Original Assignee: Hamamatsu Photonics KK
• Inventors: Adachi, Izumi
• Primary Examiner(s): Lefkowitz, Edward
• Application Number:
  US08/831,715
• Time in Patent Office: 756 Days
• Field of Search: 340/628, 340/630, 250/573, 250/574
• US Class Current: 340/630
• CPC Class Codes: G08B 17/107 for detecting light-scattering due to smoke
• CPC Class Codes: G08B 17/113 Constructional details
• CPC Class Codes: G08B 29/18 Prevention or correction of operating errors G08B29/02, G08B29/12 take precedence

Abstract

The smoke detecting apparatus of the present invention comprises a detection space (52) into which generated smoke is to be introduced; light-emitting means (2) for emitting a predetermined coded light pulse train into the detection space (52); light-detecting means (3) for detecting scattered light which is generated when the light emitted from the light-emitting means (2) is scattered by the smoke and generating an electric signal corresponding to the detected light; and control means (4) for generating a burst code signal composed of a pulse train coded with a reference pulse to the light-emitting means (2) and judging that the smoke exists in the detection space (52) when the pulse patterns of thus compared signals coincide with each other. According to this configuration, the apparatus can securely operate at the time of smoking and cannot detect when there is no smoke.

Claims

1. A smoke detecting apparatus comprising:

structures forming a detection space into which generated smoke is to be introduced;

light-emitting means for emitting a light pulse train which is in synchronization with a pulse of a predetermined burst code signal into the detection space;

a light-detecting means for detecting light from the light-emitting means that is scattered by smoke to be detected and generating an electric signal corresponding to the detected light; and

control means for transmitting said burst code signal composed of a pulse train which is coded with a reference pulse to said light-emitting means so as to control the emission of the light pulse train and comparing the burst code signal and the output electric signal of said light-detecting means with each other and, determining, based on the coincidence of these signals with each other or not, judging that the whether or not smoke exists in the detection space.

2. A smoke detecting apparatus according to claim 1, wherein said detection space is disposed at a portion within an electrical equipment which is prone to generate the smoke, and said control means shuts off a power supply to the electrical equipment when it judges that the smoke exists.

3. A smoke detecting apparatus according to claim 1, wherein said light-emitting means and light-detecting means are disposed within a shielding case which is shielded from electromagnetic noises, and the detection space is formed within the shielding case, while an inlet for introducing the smoke into the detection space is formed in a side wall of the shielding case.

4. A smoke detecting apparatus according to claim 3, further, comprising:

a net attached over said inlet for preventing unnecessary substances from proceeding into said detection space.

5. A smoke detecting apparatus comprising:

a detection space which is disposed within an electrical equipment and into which generated smoke is to be introduced;

a light-emitting means for emitting into said detection space a predetermined light pulse train corresponding to a burst code signal transmitted from a control section of the electrical equipment; and

a light-detecting means for detecting scattered light which is generated when the light emitted from said light-emitting means is scattered by the smoke and transmitting an electric signal corresponding to the detected light to the control section of the electrical equipment.

6. A smoke detecting method comprising the steps of:

placing within an electrical equipment structures forming a detection space for introducing generated smoke;

emitting into the detection space a predetermined light pulse train corresponding to a burst code signal transmitted from a control section of the electrical equipment;

detecting scattered light generated when the light pulse train is scattered by smoke and generating an electric signal corresponding thereto to the control section of the electrical equipment;

comparing pulse patterns of the output electric signal and the code signal; and

,

judging that the smoke exists within the detection space and not, respectively when the pulse patterns of thus compared signals coincide with each other and not.