Function test means of photoelectric type smoke detector

• US 4,647,785 A
• Filed: 03/26/1984
• Issued: 03/03/1987
• Est. Priority Date: 04/08/1983
• Status: Expired due to Fees

• Current Assignee: Nohmi Bosai Kogyo Company Limited (Secom Company Limited)
• Original Assignee: Nohmi Bosai Kogyo Company Limited (Secom Company Limited)
• Inventors: Morita, Toshikazu
• Primary Examiner(s): Nelms, David C.
• Application Number:
  US06/593,110
• Time in Patent Office: 1,072 Days
• Field of Search: 250/573, 250/574, 250/575, 250/205, 340/630, 356/438, 356/338-343
• US Class Current: 250/574
• CPC Class Codes: G08B 17/107 for detecting light-scattering due to smoke
• CPC Class Codes: G08B 29/145 of fire detection circuits

Abstract

A photoelectric smoke detector is provided with first and second radiation emitters and first and second radiation receivers. The first emitter emits pulsed radiation at a predetermined frequency. The second emitter emits pulsed radiation at twice this frequency. The first receiver receives the radiation of the second emitter directly and that of the first emitter by scattering only. When the first receiver receives alternate detection pulses reinforced by scattered radiation, an alarm is generated. The second receiver receives radiation directly from the first emitter and modulates the radiation output level of the second emitter proportionately. When the first receiver receives testing pulses between the alternating detection pulses, their level is discriminated to determine the functional state of the detecting elements and a corresponding function signal is generated.

Claims

1. A function testing means for a photoelectric smoke detector, comprising:

a first light-emitting element for smoke detection;

a first light-receiving element for smoke detection by reception of light scattered from smoke arranged at a location shielded from direct irradiation by said first light emitting element and having an output;

a second light-receiving element for monitoring radiation emitted by said first light-emitting element and having an output;

a second light-emitting element for emitting radiation in proportion to said output of said second light-receiving element toward said first light-receiving element;

function testing means for operating the photoelectric smoke detector in a test mode in which said first light-emitting element and said second light-emitting element simultaneously emit radiation;

operational means for operating the photoelectric smoke detector in a detection mode in which only said first light-emitting element emits radiation;

switching means for alternatively performing said test mode and said detection mode; and

monitor means for continuously monitoring said output of said first light-receiving element in each of said test mode and said detection mode.

2. The function testing means as defined in claim 1, further including:

alarm means for transmitting an exception-state signal to a fire control panel for generating a control signal if said output of said first light-receiving element deviates from a predetermined value when irradiated by said second light-emitting element.

3. The function testing means as defined in claim 2, further including:

reception means for receiving said control signal from said fire control panel; and

said reception means being connected to power means connected to said second light-emitting element for causing said second light-emitting element to emit radiation in excess of a value which causes said output of said first light-receiving element to exceed said predetermined value.