Smoke detector with photo-responsive means for increasing the sensitivity during darkness

• US 4,112,310 A
• Filed: 05/19/1977
• Issued: 09/05/1978
• Est. Priority Date: 05/19/1977
• Status: Expired due to Term

• Current Assignee: Graviner Limited
• Original Assignee: Chloride Incorporated
• Inventors: Malinowski, William J.
• Primary Examiner(s): Nelms, David C.
• Application Number:
  US05/798,582
• Time in Patent Office: 474 Days
• Field of Search: 340/237 R, 340/237 P, 340/237 S, 250/564, 250/573, 250/574, 356/207, 356/208
• US Class Current: 250/574
• CPC Class Codes: G08B 17/107 for detecting light-scattering due to smoke

Abstract

A particle detector which during periods of high ambient light is responsive to a particle concentration of a predetermined value to provide an output signal and during periods of low ambient light, is responsive to a substantially lesser particle concentration to sound an alarm.

Claims

1. A particle detector, in which means is provided responsive to the presence of particles to produce an output signal, said detector having two modes of operation and being responsive in a first mode to a predetermined concentration of particles to produce an alarm signal, and being responsive in a second mode to produce an alarm signal at a particle concentration substantially less than said predetermined concentration, in which the detector shifts automatically from one mode to another with a substantial change in the ambient light level.

2. A particle detector responsive to the presence of particles to provide an output signal, in which means is provided responsive to increases and decreases in ambient light level to decrease and increase, respectively, the sensitivity of the detector.

3. A smoke detector having means for actuating signal means at a smoke concentration of a predetermined level when the ambient light is at one intensity, and for actuating the signal means at a substantially lesser smoke concentration when the ambient light is at a lower intensity.

4. A smoke detector, comprising a light source illuminating a space, a first photo-responsive device and associated electrical circuitry producing an output signal in response to the receipt by said photo-responsive device of light reflected from said smoke particles, means responsive to an output signal above a predetermined value to energize alarm actuating means, and a second photo-responsive cell positioned to view ambient light, said second photo-responsive device being so connected into said circuitry as to cause a given smoke concentration to produce a greater output signal when the ambient light level decreases below a predetermined intensity compared to the output signal produced by said given smoke concentration when the ambient light level has a substantially higher intensity.

5. An ionization smoke detector, comprising a circuit including an ionization chamber having a pair of electrodes and a radioactive source and connected across power leads in series through a junction with a loading element, a gating device having a gate electrode connected to said junction, said gating device being responsive to an input signal from said junction of a predetermined value to cause conduction through said gating device, a photo-responsive device viewing ambient light, said photo-responsive device being so connected into said circuit that when the ambient light level is low, the signal at said gating device for a given amount of smoke is substantially higher than when the ambient light level is high.

6. A smoke detector, comprising detector means responsive to the presence of smoke to provide an output signal which is a function of smoke concentration, amplifier means receiving said output signal and producing an amplified output signal which is a function of the value of the output signal from the detector means, level detector means responsive to the amplified output of a predetermined level to actuate alarm energizing means, and photo-responsive means so associated with the detector that when the ambient light falling on said cell decreases to a predetermined value, the alarm is energized at a lower smoke concentration than the concentration at which the alarm is energized under conditions of substantial ambient light.

7. A smoke detector as set out in claim 6 in which the photo-responsive means is connected into the circuit so as to cause the output signal at a given smoke concentration to be substantially less under conditions of low ambient light than under conditions of high ambient light.

8. A smoke detector as set out in claim 6 in which said photo-responsive means is connected into said circuit so as to cause the output of the amplifier means to be greater for a given amount of smoke concentration during periods of darkness or low ambient light than during periods of daylight or high ambient light.

9. A smoke detector as set out in claim 6 in which said photo-responsive means is so connected into said circuit as to cause the level detector to be responsive to a lower output signal from the detector means during periods of low ambient light than during periods of high ambient light.