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History mineral lamp
Coal mining has always been dangerous. In the early 1800s, miners' lamps or candles ignited the gases or coal dust trapped in the mines and caused massive explosions. Finally, in England in 1812, after 92 men and boys were killed in one terrible explosion, a society was formed to study and prevent mine explosions. Ultimately, that society approached Sir Humphrey Davey for help.
Davey found that burning gases cool when they traveled through a fine wire netting and that if the air was still, the flame from a lamp wouldn't spread. Using those discoveries, in 1816 Davey fabricated his first safety lamp. That lamp utilized a wick surrounded by cylindrical netting eight inches high and two inches around. However, the lamp did not provide much light, and it was not safe if there were drafts in the mine.
Over the years, others changed Davey's early lamp. One "improved" model, which produced a brighter light, substituted gasoline for oil. However, many engineers considered that model more dangerous because the gasoline lamps tended to get hotter, especially where the air was gassy, and its glass cylinders broke more frequently than those on oil lamps. To offset the problems, designers increased both the size of the lamp and its weight. They also substituted thinner glass in the cylinders because thinner glass was less likely to break from uneven expansion than the heavier glass; however, the thinner glass broke more often when a miner dropped his lamp and could trigger an explosion. Another danger of the gasoline model was that the flame went out more frequently, thus requiring a miner to relight it -- again risking an explosion.
Over the years other inventors worked on different versions of the safety lamp, and while those improved lamps did lessen the danger of explosions, they did not eliminate them. In 1906, nearly 53 percent of mine explosions were still caused by miners' lamps, and in 1912, the U.S. Bureau of Mines reported that at least two disasters had been caused by safety lamps.
The electric lamp was still in the experimental stage in the early 1900s. Inventors had not been able to develop a successful portable electric mine lamp until tungsten lamps replaced carbon filament lamps. Because tungsten lamps used less current, the batteries were small and light enough that miners could carry them and still move about freely.
In addition, inventors needed to address a host of other problems. Could lamps be made so they would not ignite mine gasses? Could they produce enough steady and uninterrupted light for at least one shift? Would they burn in any position? Were they light in weight, simple to operate, and durable? Was the battery easy to charge and inspect? It was a real challenge to develop a suitable electric lamp.
In 1912, the British government offered a prize to the person who could design an acceptable electric safety lamp for miners. A German engineer won the prize for his "Ceag" or "Cage" lamp. Outwardly, the electric Cage lamp resembled the old safety lamp, but the resemblance ended there. The Cage lamp was safe where gasses had collected; it produced twice as much light as the safety lamp; its storage battery provided enough electrical energy to last sixteen hours, or two shifts; and it was tough enough to withstand rough treatment.
The Cage lamp's upper section held an incandescent light, and a lower section held a storage battery. Its cylindrical exterior casing, made from heavy corrugated tin, was strong and resisted warping, and it had no projections to catch on clothing. The bulb was held in place between two opposing spiral springs and was protected by a thick glass cover. The battery was secured by a band of celluloid paper and was easy to replace. Power was turned on and off by rotating the top of the lamp.
In 1913, in the United States, Thomas Edison won the Ratheman Medal for developing another miner's safety lamp. Edison's lamp used a light-weight storage battery that a miner could easily carry on his back. Illumination was provided by a tungsten lamp that had "a parabolic reflector and a heavy lens to distribute the light over the proper area." The light itself could be fastened to the miner's hat, and a flexible cord connected the battery and the lamp. Because the cord locked in place and could not easily be pulled out, it was difficult for a miner to disconnect the wires and cause a spark that could ignite gases or dust in a mine.
Despite these and other
advances, however, it was many years before electric lamps came into
wide use in the mines. Over the years, other lamps were tried and
discarded until, finally, today's sophisticated lamps evolved.
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