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
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
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.