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The Ubiquitous Rubber Seals
| Article
# : |
19652 |
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Section : |
NATURAL SCIENCE
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| Issue
Date : |
10 / 1991 |
2,262 Words |
| Author
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David L. Burkhead
David L. Burkhead is a free-lance writer, specializing in
science and technology. He lives in Akron, Ohio. |
On January 28, 1986, at 11:39 A.M. eastern standard time, the space shuttle Challenger exploded, killing the five men and two women aboard. The cause of the explosion was a faulty O-ring connection on the solid rocket boosters. The O-ring, which is in use in the home, on the road, and throughout industry, had suddenly become the perpetrator of the worst tragedy of the American space program. Even today, more than five years after the event, the average person probably thinks of O-rings in terms of the Challenger, unaware of the intrusion of these rubber rings into virtually every field. O-rings are used on the land, in the sea, and in the air. They are employed in automobiles, submarines, and aircraft, in the food processing industry, offshore oil drilling, and nuclear power plants.
O-rings are flexible rubber rings that form a tight seal when exposed to pressure. Wherever a leak-free seal between two parts is exposed to vibration, flexing, or other stresses, the O-ring is the seal of choice.
Round rubber rings were used as sealants as early as the 1850s. Normally, they formed a seal between a cylinder and a piston in pumps, gauges, and steam engines. In these systems, the ring rolled between the pistons and cylinder walls. These designs did not work well as the rings tended to twist and stretch, breaking the seal and forming leaks. Although several attempts were made to solve the problem, none proved satisfactory. The development of the modern O-ring had to wait for Niels Christensen.
Christensen was born in Denmark in 1865. He apprenticed as a machinist and pattern maker at the age of 14 while attending technical school at night. Eventually he earned an engineering degree and entered the Royal Danish Navy as a marine engineer. After a visit to the 1891 Chicago World's Fair, he emigrated to the United States. A fatal railway accident inspired him to develop a new braking system and, in 1896, he formed his own company to market it. In five years, Christensen Engineering Company of Milwaukee had become the largest manufacturer of its kind.
Christensen discovered that too little attention had been paid to developing a truly universal sealing mechanism. He turned his energy to inventing one. To do this, he turned back to using round rubber rings, but with a difference: He placed the rings in a narrow groove so they could not roll.
Christensen began placing his new invention in a brake cylinder. In tests simulating thousands of miles
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