Niels Christensen

Niels Christensen (1865-1952) was a Danish-American inventor whose principal invention was the O-ring, the ubiquitous hydraulic seal.

Early years

Niels Christensen was born in 1865 in Tørring, Denmark. He showed an early aptitude for mechanics and apprenticed to a machinist in Vejle, Denmark. After completing his apprenticeship, he entered the Technical Institute of Copenhagen. He immigrated to the United States when he was 26 years old.

The invention

In 1933, working in his basement, he discovered by trial and error that a ring-shaped piece of rubber in a groove one and a half times long as the minor radius of the ring made a reliable, tight seal of a piston sliding in a cylinder. He applied for a U.S. patent in 1937 and it was granted two years later. After Pearl Harbor, the government bought the rights to many war-related patents, and made them available to manufacturers royalty-free. Christensen was paid $75,000. When the war ended (formally, in 1952) and the patent rights were transferred back to him, the patent had only four years left.

References

• Wise, George Invention and Technology Magazine Spring/Summer 1991,Volume 7, Issue
• [1]
• Christensen, Niels A. U. S. Patent 2,180,795 Packing Issued Nov. 21, 1939.