Smoke detector of the ionization type
First Claim
1. A smoke detector of the ionization type comprising a chamber containing a measuring electrode, the voltage on the measuring electrode being a function of the smoke concentration in the chamber, means responsive to a predetermined change in smoke concentration in a predetermined time in the chamber to produce an output signal to one input of an AND gate, pulse generating means providing an intermittent signal at the other terminal of the gate, a counter, means responsive to simultaneous pulse and output signals at the gate inputs to advance the counter one count, said counter having a reset terminal, means applying each pulse to the reset terminal except when the gate produces an output, and means responsive to accumulation in said counter of more than two counts for energizing alarm means.
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Accused Products
Abstract
An ionization type smoke detector (10) includes a chamber having a measuring electrode (12), the voltage on the measuring electrode being a function of the concentration of smoke in the chamber, and further includes a comparison device (A3) for comparing the voltage measured on electrode (12) at two different times, and an output device (K) for producing an output signal if the voltages differ by a predetermined value.
69 Citations
7 Claims
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1. A smoke detector of the ionization type comprising a chamber containing a measuring electrode, the voltage on the measuring electrode being a function of the smoke concentration in the chamber, means responsive to a predetermined change in smoke concentration in a predetermined time in the chamber to produce an output signal to one input of an AND gate, pulse generating means providing an intermittent signal at the other terminal of the gate, a counter, means responsive to simultaneous pulse and output signals at the gate inputs to advance the counter one count, said counter having a reset terminal, means applying each pulse to the reset terminal except when the gate produces an output, and means responsive to accumulation in said counter of more than two counts for energizing alarm means.
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2. A smoke detection system comprising
a smoke detector of the ionization type and comprising a chamber and a measuring electrode in the chamber, the voltage on the measuring electrode being a function of the smoke concentration in the chamber, alarm means and a signal processing channel responsive to the rate of increase of smoke concentration sensed by said detector connected in circuit between said smoke detector and said alarm means comprising pulse generating means, sample and hold circuit means responsive to said pulse generating means for storing a reference smoke concentration value as a function of the voltage on said measuring electrode, comparator means responsive to a predetermined offset voltage on said measuring electrode from said stored reference value for generating an interim signal and updating the reference value stored in said sample and hold circuit means to the current output voltage on said measuring electrode, counter means for accumulating said interim signals, and means responsive to accumulation in said counter means of a plurality of said interim signals for energizing said alarm means.
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5. A smoke detector system comprising
a smoke detector, said detector having an output as a function of the sensed smoke concentration, alarm actuating means, and a signal processing channel responsive to the rate of increase of smoke concentration sensed by said detector connected in circuit between said detector and said alarm actuating means comprising means for storing a reference smoke concentration value as a function of the output of said detector, means responsive to a detector output signal indicating an increase in smoke concentration from said stored reference value for generating an interim signal and concurrently updating the stored reference value to the current smoke concentration output of said detector, accumulator means for accumulating said interim signals, and means responsive to accumulation of a plurality of said interim signals by said accumulator means for energizing said alarm actuating means.
Specification