Detectors 197
Detectors 197 : Particle Detectors: (4.26) Smoke Detector: (1) History: The first automatic electric fire alarm was invented in 1890 by Francis Robbins Upton (US patent no. 436,961). Upton was an associate of Thomas Edison, but there is no evidence that Edison contributed to this project. George Andrew Darby patented the first electrical heat detector and smoke detector in 1902 in Birmingham, England. In the late 1930s the Swiss physicist Walter Jaeger tried to invent a sensor for poison gas. He expected that gas entering the sensor would bind to ionized air molecules and thereby alter an electric current in a circuit in the instrument. His device failed: small concentrations of gas had no effect on the sensor's conductivity. Frustrated, Jaeger lit a cigaretteand was soon surprised to notice that a meter on the instrument had registered a drop in current. Smoke particles had apparently done what poison gas could not. Jaeger's experiment was one of the advances that paved the way for the modern smoke detector. It was 30 years, however, before progress in nuclear chemistry and solid-state electronics made a cheap sensor possible. While home smoke detectors were available during most of the 1960s, the price of these devices was rather high. Before that, alarms were so expensive that only major businesses and theaters could afford them. The first truly affordable home smoke detector was invented by Duane D. Pearsall and Stanley B. Peterson in 1965, featuring an individual battery powered unit that could be easily installed and replaced. The first units for mass production came from Duane Pearsall's company, Statitrol Corporation, in Lakewood, Colorado. These first units were made from strong fire resistant steel and shaped much like a bee's hive. The assembly line was designed by Stanley's son Daniel B. Peterson. He called it the 'Slideline' named for the way the circuit boards moved from each assembly person to another. At the end of the line the completed circuit boards were lifted onto a Flow-Solder machine to adhere the parts to the circuit. After the Flow-Solder the boards went to an automated clipping tool that looked like an upside-down box with a flat horizontal saw hovering just the right hight above the board. The circuit board was held down by a vacuum controlled by the user. Boards were then sent to inspection, test, and then final assembly before shipping. The first battery was a rechargeable specialized unit created by Gates Energy Corporation, the same as Gates Rubber Company. Stanley B. Peterson had a personal and professional friendship with Charlie Gates during this period which facilitated the design of these batteries. The need for a quick replace battery didn't take long to show itself and the rechargeable was replaced with a pair of AA batteries along with a plastic shell encasing the detector. The small assembly line sent close to 500 units per day before Statitrol sold its invention to Emerson Electric in 1980 and Sears's retailers picked up full distribution of the 'now required in every home' smoke detector
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