Ultraviolet wavelength smoke detector
Patent 3982130 Issued on September 21, 1976. Estimated Expiration Date: 
September 21, 1993. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.
September 21, 1993. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.Patent References 2369966 3770356 3857641 InventorAssigneeApplicationNo. 05/621338 filed on 10/10/1975US Classes:250/373, With means to transmission-test contained fluent material340/630, Photoelectric356/434, Photoelectric (e.g., sequential viewing)356/439, Contained356/51INFRARED AND ULTRAVIOLETExaminersPrimary: Smith, Alfred E.Assistant: Grigsby, T. N. Attorney, Agent or FirmInternational ClassesG08B 17/103 (20060101)G01N 21/53 (20060101) G01N 21/47 (20060101) AbstractCollimated ultraviolet light radiation at wavelengths of 2537A and 3129A is alternately directed across the space to be monitored for smoke indicative of a fire. A "cats eye" mirror at the far side of the monitored space returns the ultraviolet rays to a photomultiplier detector adjacent the light source. Smoke, for example pine smoke having a particle mean diameter of 1.4 to 3.0 micrometers, will attenuate the shorter wavelength beam much more than the longer wavelength beam. Approximately 1.3 times greater attenuation is inflicted on the 2537A beam than on the 3129A by the pine smoke. Thus, returning beam signals having this ratio of signal levels will provide an indication of a pine fire. Particles of a different diameter intercepting the beam will produce a different ratio of attenuated signals. | |
