Niels Christensen
Encyclopedia
Niels Christensen was a Danish-American inventor whose principal invention was the O-ring
, the ubiquitous hydraulic seal
.
, 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, now the University of Copenhagen Faculty of Science
. In 1891, Christensen immigrated to the United States
when he was 26 years old.
in Chicago
, a manufacturer of machinery for industry, mining, and transportation. He worked briefly on electrical systems for Chicago’s Columbian Exposition and then was hired by the E. P. Allis Company
of Milwaukee.
In 1933, working in his basement, Christensen 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 United States 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. Litigation resulted in a $100,000 payment to his heirs in 1971, 19 years after his death.
O-ring
An O-ring, also known as a packing, or a toric joint, is a mechanical gasket in the shape of a torus; it is a loop of elastomer with a disc-shaped cross-section, designed to be seated in a groove and compressed during assembly between two or more parts, creating a seal at the interface.The O-ring...
, the ubiquitous hydraulic seal
Hydraulic seal
A hydraulic seal is a relatively soft, non-metallic ring captured in a groove or fixed in a combination of rings, forming a seal assembly, to block or separate fluid in reciprocating motion applications. Hydraulic seals are vital in machinery...
.
Early years
Niels Anton Christensen was born on a farm in Tørring-Uldum MunicipalityTørring-Uldum municipality
Until January 1, 2007 Tørring-Uldum municipality was a municipality in the former Vejle County on the Jutland peninsula in central Denmark. The municipality covered an area of 189 km², and had a total population of 12,519 . Its last mayor was Kirsten Terkelsen, a member of the Venstre political...
, Denmark
Denmark
Denmark is a Scandinavian country in Northern Europe. The countries of Denmark and Greenland, as well as the Faroe Islands, constitute the Kingdom of Denmark . It is the southernmost of the Nordic countries, southwest of Sweden and south of Norway, and bordered to the south by Germany. Denmark...
. He showed an early aptitude for mechanics
Mechanics
Mechanics is the branch of physics concerned with the behavior of physical bodies when subjected to forces or displacements, and the subsequent effects of the bodies on their environment....
and apprenticed to a machinist in Vejle, Denmark. After completing his apprenticeship, he entered the Technical Institute of Copenhagen, now the University of Copenhagen Faculty of Science
University of Copenhagen Faculty of Science
The Faculty of Science at the University of Copenhagen consists of both mathematical and natural sciences, and is divided into 11 institutes including the Natural History Museum of Denmark...
. In 1891, Christensen immigrated to the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
when he was 26 years old.
The invention
Christensen became a leading draftsman at Fraser and ChalmersAllis-Chalmers
The Allis-Chalmers Manufacturing Co. of West Allis, Wisconsin, is an American company known for its past as a manufacturer with diverse interests, perhaps most famous for their bright Persian Orange farm tractors...
in Chicago
Chicago
Chicago is the largest city in the US state of Illinois. With nearly 2.7 million residents, it is the most populous city in the Midwestern United States and the third most populous in the US, after New York City and Los Angeles...
, a manufacturer of machinery for industry, mining, and transportation. He worked briefly on electrical systems for Chicago’s Columbian Exposition and then was hired by the E. P. Allis Company
Allis-Chalmers
The Allis-Chalmers Manufacturing Co. of West Allis, Wisconsin, is an American company known for its past as a manufacturer with diverse interests, perhaps most famous for their bright Persian Orange farm tractors...
of Milwaukee.
In 1933, working in his basement, Christensen discovered by trial and error that a ring-shaped piece of rubber
Rubber
Natural rubber, also called India rubber or caoutchouc, is an elastomer that was originally derived from latex, a milky colloid produced by some plants. The plants would be ‘tapped’, that is, an incision made into the bark of the tree and the sticky, milk colored latex sap collected and refined...
in a groove one and a half times long as the minor radius of the ring made a reliable, tight seal of a piston
Piston
A piston is a component of reciprocating engines, reciprocating pumps, gas compressors and pneumatic cylinders, among other similar mechanisms. It is the moving component that is contained by a cylinder and is made gas-tight by piston rings. In an engine, its purpose is to transfer force from...
sliding in a cylinder
Cylinder (engine)
A cylinder is the central working part of a reciprocating engine or pump, the space in which a piston travels. Multiple cylinders are commonly arranged side by side in a bank, or engine block, which is typically cast from aluminum or cast iron before receiving precision machine work...
. He applied for a U.S. patent in 1937 and it was granted two years later.
After Pearl Harbor
Pearl Harbor
Pearl Harbor, known to Hawaiians as Puuloa, is a lagoon harbor on the island of Oahu, Hawaii, west of Honolulu. Much of the harbor and surrounding lands is a United States Navy deep-water naval base. It is also the headquarters of the U.S. Pacific Fleet...
, the United States 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. Litigation resulted in a $100,000 payment to his heirs in 1971, 19 years after his death.
Related reading
- Weber, Robert John and David N. Perkins Inventive minds: creativity in technology (Volume 49. Oxford University Press. 1992)
- Christensen, Niels A. U. S. Patent 2,180,795 (Packing. November 21, 1939)