Alarm silencing circuitry for photoelectric smoke detectors

• US 5,422,629 A
• Filed: 03/03/1992
• Issued: 06/06/1995
• Est. Priority Date: 03/30/1992
• Status: Expired due to Term

• Current Assignee: BRK Brands Incorporated (Newell Brands Inc.)
• Original Assignee: BRK Brands Incorporated (Newell Brands Inc.)
• Inventors: Minnis, David A.
• Primary Examiner(s): Hofsass, Jeffery A.
• Application Number:
  US07/860,452
• Time in Patent Office: 1,190 Days
• Field of Search: 340/628, 340/629, 340/630, 340/632, 340/501, 340/511, 340/512, 340/514, 356/438, 250/564, 250/573, 250/574
• US Class Current: 340/630
• 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 17/107 for detecting light-scattering due to smoke
• CPC Class Codes: G08B 29/145 of fire detection circuits

Abstract

A silencable photoelectric-type detector includes a source of radiant energy and a detector. A generator circuit provides a sequence of pulses to energize the source. A biasing circuit biases the detector. The detector can be temporarily silenced, when in alarm, by reducing the energy level of the pulses or altering the bias point of the detector for a period of time. The period of time can be established by an RC circuit. The effect of the energy level reduction or the bias point alteration is to reduce the sensitivity level of the detector temporarily.

Claims

1. A condition detecting unit with an alterable sensitivity parameter usable to temporarily silence a unit which has generated an undesirable alarm, the unit comprising:

a condition detector including an energizable source of electromagnetic radiant energy and a biasable sensor of radiant electromagnetic energy;

circuitry, coupled to said source, for intermittently energizing same to emit discrete quantities of electromagnetic radiant energy;

circuitry coupled to said sensor, for biasing same to convert received radiant energy into an electrical signal;

am activation element; and

sensitivity altering circuitry, coupled to and responsive to said element, for temporarily altering a sensitivity parameter of said detector so as to temporarily silence the unit for a predetermined period of time wherein

said altering circuitry includes one of, circuitry for changing said bias of said sensor for said predetermined period of time so as to reduce said electrical signal for said predetermined period of time, or circuitry for altering said energization of said source for said predetermined period of time so as to reduce said emitted radiant energy for said predetermined period of time wherein

said altering circuitry includes at least one switching element for carrying out said reducing function with a resistor-capacitor timing circuit coupled thereto to establish said predetermined period of time.

2. A condition detecting unit as in claim 1 wherein said biasing circuitry supplies a first biasing current to said sensor and wherein said bias changing circuitry includes timing circuitry for altering said first current for a predetermined of time.

3. A condition detecting unit as in claim 1 wherein said bias altering circuitry includes circuitry for increasing a voltage applied to said sensor for said predetermined period of time.

4. A condition detecting unit as in claim 1 wherein said energizing circuitry provides electrical energy at a first level to said source and wherein said energization altering circuitry includes circuitry for changing said energy level for a predetermined period of time.

5. A condition detecting unit as in claim 4 wherein said energy level changing circuitry includes circuitry for reducing said energy level for said predetermined period of time.

6. A condition detecting unit as in claim 1 wherein said activation element includes a manually operable member.