Smoke detector

• US 3,917,956 A
• Filed: 03/08/1974
• Issued: 11/04/1975
• Est. Priority Date: 03/08/1974
• Status: Expired due to Term

• Current Assignee: Graviner Inc (Carrier Global Corporation)
• Original Assignee: William J. Malinowski
• Inventors: Malinowski, William J.
• Primary Examiner(s): Lawrence, James W.
• Assistant Examiner(s): La Roche, E. R.
• Application Number:
  US05/449,362
• Time in Patent Office: 606 Days
• Field of Search: 250/214,551,554,564,573,574 340/237R,237S
• US Class Current: 250/564
• CPC Class Codes: G08B 17/107 for detecting light-scattering due to smoke

Abstract

A smoke detector of the type utilizing photo-electric detection of light reflected from smoke particles, in which a lightgenerating device is energized intermittently and a photoresponsive device and an associated amplifier produce energy pulses when smoke is present. The energy pulses are utilized to actuate an alarm. To prevent power supply voltage changes from affecting the operation of the amplifier, a capacitor is provided across the power leads to the amplifier, and means is provided between the capacitor and the power supply for electrically isolating the amplifier and capacitor from the transient voltages from the power supply, which are caused by the turning on of the light generating device, or from other causes. In one embodiment of the invention said means comprises a choke coil in the line to the capacitor and a second choke coil in the line to the light generating device. In another embodiment of the invention the isolating means may be Zener diodes in place of choke coils. In a third embodiment of the invention the means comprises a switch in the power line between the capacitor and the power supply, with means being provided to open the switch when the light generating device is energized. In each embodiment, the amplifier is isolated from transient voltage changes during the time the light generating device is energized, so that the pulse of energy required to power the amplifier is provided by the capacitor.

Claims

1. In a smoke detector of the type utilizing photo-electric detection of light reflected from smoke particles (in which) having a light source which is energized intermittently, first means including a photo-responsive device (is provided) and an amplifier to produce energy pulses in response to light pulses refected from smoke particles, and second means utilizing said energy pulses to control a signalling device, the improvement comprising a voltage supply for said first means, a capacitor connected across the voltage supply, and third means between the capacitor and the voltage supply for isolating the (amplifier) first means and the capacitor from voltage pulses occurring at the power supply at least during the time that the light source is emitting light.

2. A smoke detector as set out in claim 1 in which said third means allows current flow when the light source is not producing light, but effectively prevents the passing of voltage pulses in the frequency range to which the amplifier is responsive.

3. A smoke detector as set out in claim 1 in which means is provided for energizing said amplifier only while the light source is emitting light, and said third means allows current flow to charge the capacitor While the amplifier is de-energized but does not allow a voltage pulse to pass therethrough during the period that the amplifier is energized, whereby the amplifier draws power substantially only from the capacitor when it is energized.

4. A smoke detector as set out in claim 1 in which said third means is a switch, and means is provided to open said switch when the light source is energized and to close said switch when the light source is de-energized.

5. In a smoke detector of the type utilizing photo-electric detection of light reflected from smoke particles, in which a pulse generator pulses a light generating device, a photo-voltaic cell is positioned to produce voltage pulses from the pulsed light reflected from smoke particles, means is provided for amplifying said voltage pulses, and means is provided for utilizing said amplified pulses to control a signalling device, the improvement comprising said pulse generator and said amplifier being supplied by separate leads from a common power source, means rendering said amplifier operative substantially only during the time the pulse generator is on, a storage capacitor connected across the leads to the amplifier and an impedence device disposed between the storage capacitor and the power source, whereby when the amplifier is turned on, it draws power principally from the storage capacitor, and the impedence means isolates the amplifier from voltage transients at the power source due to the turning on of the pulse generator and the light generating device.

6. A smoke detector as set out in claim 5 in which said impedence means comprises an inductance having electrical characteristics such that it prevents passage of voltage pulses in the frequency range to which the amplifier is responsive.

7. A smoke detector having a light source, means energizing the light source intermittently, photo-responsive means positioned to receive light reflected from smoke particles illuminated by the light source, and amplifier means for amplifying voltage pulses resulting therefrom, a power source, means providing power therefrom to the light source and to the amplifier by first and second power leads, first and second capacitors associated with said first and second power leads respectively, and means between each capacitor and so as to be charged by said power supply the power supply for isolating said capacitors from transient voltages occuring at the power supply during the period that the light source is emitting light so that during said period the voltages on said first and second capacitors remain substantially equal.

8. A smoke detector as set out in claim 7 in which said means for isolating from the power supply the capacitor associated with the power lead to the amplifier includes a switch in said lead and means for opening and closing said switch with energization and de-energization of the light source.

9. A smoke detector comprising a light source, a photo-responsive device positioned to view light reflected from smoke particles illuminated by the light source, a pulse generator for providing energizing pulses to the light source, amplifier means for amplifying pulses created by the photoresponsive device, said pulse generator providing a pulse to render said amplifier operative only when said light source is energized, said pulse generator and said light source being energized by a first lead from a power source and said amplifier being energized by a second lead from said power source, a first capacitor connected in parallel with said amplifier and a second capacitor connected in parallel with the pulse generator, and means maintaining the voltage on said capacitors substantially equal while the light source is energized and the amplifier is operable.