Incipient fire detector II
First Claim
1. A new and improved incipient fire detector having sample gas selector valve and conduit system means for selectively sampling the gaseous atmospheres in a multiplicity of different volumetric spaces automatically and sequentially supplying the sampled gases to a centrally located small particle detector, said gaseous atmosphere sampling conduit system including an improved gas sample flow rate deviation detector which operates in a stable manner over a wide range of temperatures to detect any variation in flow rate of the sampled gases through the sampling conduct system from a preset norm, and wherein said gas flow rate deviation detector comprises a pair of self-heating thermistors each having the same resistance value at a known reference temperature but which have different free air dissipation constants, the thermistor with the smaller free air dissipation constant being physically mounted in the gaseous atmosphere sampling conduit system for monitoring the flow rate therethrough and the remaining thermistor being physically mounted in a region that is at the same temperature as the gaseous atmosphere being sampled but is not in a flowing stream of sampled gas, and both thermistors being electrically interconnected in a measurement circuit for deriving an output signal indicative of any deviation in the sampling flow rate of the sampled gaseous atmospheres from a preset norm, and an improved system operating condition checking sub-system comprised by particle generator means connected to the automatically operated sample gas selector valve and conduit system means for selectively injecting small particles into the samples of gaseous atmospheres supplied to the centrally located particle detector that periodically operates to sequentially sample and test the sample gases from the respective zones for the presence of particles, timing and control means coupled to the particle generator means and synchronized with the operation of the respective zone sampling periods for activating the particle generator means for a short time interval relative to the sampling period of each respective zone at the end thereof for injecting into the sample conduit system for delivering a burst of small particles to the centrally located particle detector whereby continued normal operation of the system can be indicated in low particle background environments.
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Accused Products
Abstract
An improved incipient fire detector that employs a sub-micrometer size particle detector of the Wilson cloud chamber type in conjunction with a continuous on-the-fly sequential selector valve assembly and sample gas conduit system for monitoring a plurality of different enclosed spaces (zones). The sampling line for each zone can have up to ten heads, and delivers air or other gaseous atmosphere samples from the respective parts of the zone to the centrally located particle detector at a continuous flow rate of about 14 liters a minute. Each zone line is sampled sequentially by an electronically controlled selector valve assembly for a 15 second interval, once a minute. The cloud chamber particle detector operates at a cycling rate of about once per second and provides a continuous analog voltage corresponding to small particle concentration in the portions of the zone being sampled. The alarm sensitivity can be different for each zone and can be changed with time by means of an external timer to provide increased sensitivity at night, for example. A pre-alarm warning is provided for each zone with the alarm and warning states indicated by separate lights and alarm contact closures for each zone located at a centrally located control panel. The IFD incorporates several diagnostic circuits to monitor its operation, and in case of a problem a trouble indication is provided together with an indication on a diagnostic panel which shows the source of the problem.
38 Citations
28 Claims
- 1. A new and improved incipient fire detector having sample gas selector valve and conduit system means for selectively sampling the gaseous atmospheres in a multiplicity of different volumetric spaces automatically and sequentially supplying the sampled gases to a centrally located small particle detector, said gaseous atmosphere sampling conduit system including an improved gas sample flow rate deviation detector which operates in a stable manner over a wide range of temperatures to detect any variation in flow rate of the sampled gases through the sampling conduct system from a preset norm, and wherein said gas flow rate deviation detector comprises a pair of self-heating thermistors each having the same resistance value at a known reference temperature but which have different free air dissipation constants, the thermistor with the smaller free air dissipation constant being physically mounted in the gaseous atmosphere sampling conduit system for monitoring the flow rate therethrough and the remaining thermistor being physically mounted in a region that is at the same temperature as the gaseous atmosphere being sampled but is not in a flowing stream of sampled gas, and both thermistors being electrically interconnected in a measurement circuit for deriving an output signal indicative of any deviation in the sampling flow rate of the sampled gaseous atmospheres from a preset norm, and an improved system operating condition checking sub-system comprised by particle generator means connected to the automatically operated sample gas selector valve and conduit system means for selectively injecting small particles into the samples of gaseous atmospheres supplied to the centrally located particle detector that periodically operates to sequentially sample and test the sample gases from the respective zones for the presence of particles, timing and control means coupled to the particle generator means and synchronized with the operation of the respective zone sampling periods for activating the particle generator means for a short time interval relative to the sampling period of each respective zone at the end thereof for injecting into the sample conduit system for delivering a burst of small particles to the centrally located particle detector whereby continued normal operation of the system can be indicated in low particle background environments.
- 15. In a new and improved incipient fire detector having means for selectively sampling the gaseous atmospheres in a multiplicity of different volumetric spaces on a sequential basis and supplying the sampled gases via a selector valve and conduit system to a centrally located sensor, said gaseous atmosphere sampling conduit system including an improved gas flow rate deviation detector which operates in a stable manner over a wide range of temperatures to detect any variation in flow rate of the sampled gases through the sampling conduit system from a preset norm, and wherein said gas flow rate deviation detector comprises a pair of self-heating thermistors each having the same resistance value at a known reference temperature but which have different free air dissipation constants, the thermistor with the smaller free air dissipation constant being physically mounted in the gaseous atmosphere sampling conduit system for monitoring the flow rate therethrough and the remaining thermistor being physically mounted in a region that is at the same temperature as the gaseous atmosphere being sampled but is not in a flowing stream of sampled gas, and both thermistors being electrically interconnected in a measurement circuit for deriving an output signal indicative of any deviation in the sampling flow rate of the sampled gaseous atmospheres from a preset norm.
- 19. In a new and improved incipient fire detector intended for use in clean rooms and other low particle background environments, an improved system operating condition checking sub-system comprised by particle generator means connected to a sample gas conduit and automatically operated selector valve system for sequentially supplying samples of the gaseous atmospheres of a plurality of zones being monitored to a centrally located particle detector type sensor that periodically operates to sequentially sample and test the sample gases from the respective zones for the presence of particles, timing and control means coupled to the particle generator means and synchronized with the operation of the respective zone sampling periods for activating the particle generator means for a short time interval relative to the sampling period of each respective zone at the end thereof for injecting into the sample conduit system a burst of particles for detection for delivery to the centrally located particle detector type sensor whereby continued normal operation of the system can be indicated in low particle background environments.
- 25. In a new and improved incipient fire detector having means for selectively sampling the gaseous atmospheres in a multiplicity of different volumetric spaces on a sequential and continuous periodic basis and supplying the sampled gases via a sample selector valve and gas conduit system to a centrally located particle detector type sensor, and wherein the particle detector comprises an improved Wilson Cloud Chamber particle detector having an improved inlet and outlet cloud chamber valving system for sequential supply of the gaseous samples to the cloud chamber for detection of particles therein, said improved inlet and outlet valving system comprising a first cloud chamber inlet valve for supply of gas samples to the cloud chamber through a humidifier via the sample gas selector valve and gas conduit system means, a second cloud chamber inlet valve bypassing the first cloud chamber inlet valve and humidifier, a first cloud chamber outlet valve in series with a flow restriction intermediate the output from the cloud chamber and the cloud chamber vacuum pump, and a second cloud chamber outlet valve bypassing the first cloud chamber outlet valve and series connected from resistance, and cloud chamber inlet and outlet valve control means for sequentially opening the first inlet and the first outlet cloud chamber valves during a flush and fill cycle and thereafter closing them, after a short dwell time opening the second outlet valve momentarily and then closing it to reduce the pressure in the cloud chamber to create an expansion of the gaseous sample in the cloud chamber, and then releasing the reduced pressure by opening the second inlet valve before initiating a new cycle of operation of the cloud chamber particle detector.
Specification