Niels Anton Christensen (16 August 18655 October 1952) was a Danish-American inventor whose principal invention was the

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 round cross-section, designed to be seated in a groove and compressed during assembly between two or more par ...

, the ubiquitous hydraulic seal.

Early years

Niels Anton Christensen was born on a farm in Tørring-Uldum Municipality,

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. He showed an early aptitude for

mechanics Mechanics (from Ancient Greek: μηχανική, ''mēkhanikḗ'', "of machines") is the area of mathematics and physics concerned with the relationships between force, matter, and motion among physical objects. Forces applied to objects r ...

and apprenticed to a machinist in

Vejle, Denmark Vejle () is a city in Denmark, in the southeast of the Jutland Peninsula at the head of Vejle Fjord, where the Vejle River and Grejs River and their valleys converge. It is the site of the councils of Vejle Municipality ('' kommune'') and the R ...

. After completing his apprenticeship, he entered the Technical Institute of Copenhagen, now the

University of Copenhagen Faculty of Science The Faculty of Science ( da, Det Natur- og Biovidenskabelige Fakultet) at the University of Copenhagen houses 12 departments, including the Natural History Museum of Denmark. The faculty also encompasses several national and international research ...

. In 1891, Christensen immigrated to the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...

when he was 26 years old.

Work

Christensen became a leading draftsman at Fraser and Chalmers in

Chicago (''City in a Garden''); I Will , image_map = , map_caption = Interactive Map of Chicago , coordinates = , coordinates_footnotes = , subdivision_type = Country , subdivision_name ...

, a manufacturer of machinery for industry, mining, and transportation. While working in Chicago, he witnessed an accident of a new electric railway, which resulted in two deaths and a number of injuries because the conductor was unable to stop the rail cars in time using the mechanical brake. Christensen decided to design and build a power brake. The Christensen air brake was successfully tested on Detroit's streetcar system, but a downturn of the economy prevented Christensen from manufacturing and marketing the system. He worked briefly on electrical systems for Chicago’s

Columbian Exposition The World's Columbian Exposition (also known as the Chicago World's Fair) was a world's fair held in Chicago in 1893 to celebrate the 400th anniversary of Christopher Columbus's arrival in the New World in 1492. The centerpiece of the Fair, hel ...

and then was hired by the E. P. Allis Company of

Milwaukee Milwaukee ( ), officially the City of Milwaukee, is both the most populous and most densely populated city in the U.S. state of Wisconsin and the county seat of Milwaukee County. With a population of 577,222 at the 2020 census, Milwaukee is ...

. While at E. P. Allis, he continued to develop his air brake for electric rail cars and streetcars. In 1896 he obtained financial backing that allowed him to make an experimental test apparatus. He also secured patents on the new valve mechanism. In early 1897, he founded Christensen Engineering Company, which initially operated in the Menomonee Valley at 718 Hanover. His operations were co-located with the Seamless Structural Company at the corner of Hanover and Burnham Streets.

George Westinghouse George Westinghouse Jr. (October 6, 1846 – March 12, 1914) was an American entrepreneur and engineer based in Pennsylvania who created the railway air brake and was a pioneer of the electrical industry, receiving his first patent at the age of ...

had developed an air braking system for steam locomotives and felt that Christensen's invention constituted

patent infringement Patent infringement is the commission of a prohibited act with respect to a patented invention without permission from the patent holder. Permission may typically be granted in the form of a license. The definition of patent infringement may v ...

, suing him in December 1906.

Westinghouse Air Brake Company The Westinghouse Air Brake Company (sometimes nicknamed or abbreviated WABCO although this was also confusingly used for spinoffs) was founded on September 28, 1869 by George Westinghouse in Pittsburgh, Pennsylvania. Earlier in the year he had i ...

acquired National Electric, renaming the company the National Brake & Electric Company, which refused to pay royalties to Niels Christensen. Christensen promptly countersued, starting a 24-year legal battle that went before the US Supreme Court on three separate occasions over the rights to manufacture compressed air brake systems for streetcars. In 1933, working in his basement, Christensen discovered by trial and error that a ring-shaped piece of

rubber Rubber, also called India rubber, latex, Amazonian rubber, ''caucho'', or ''caoutchouc'', as initially produced, consists of polymers of the organic compound isoprene, with minor impurities of other organic compounds. Thailand, Malaysia, and ...

in a groove one and a half times long as the minor radius of the ring made a reliable, tight seal of a

piston A piston is a component of reciprocating engines, reciprocating pumps, gas compressors, hydraulic cylinders and pneumatic cylinders, among other similar mechanisms. It is the moving component that is contained by a cylinder and is made gas-tig ...

sliding in a

cylinder A cylinder (from ) has traditionally been a three-dimensional solid, one of the most basic of curvilinear geometric shapes. In elementary geometry, it is considered a prism with a circle as its base. A cylinder may also be defined as an infin ...

. He applied for a

U.S. patent Under United States law, a patent is a right granted to the inventor of a (1) process, machine, article of manufacture, or composition of matter, (2) that is new, useful, and non-obvious. A patent is the right to exclude others, for a limited ...

in 1937 and it was granted two years later. After

Pearl Harbor Pearl Harbor is an American lagoon harbor on the island of Oahu, Hawaii, west of Honolulu. It was often visited by the Naval fleet of the United States, before it was acquired from the Hawaiian Kingdom by the U.S. with the signing of the Re ...

, 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.''339 F2d 665 Jo. C. Calhoun, Jr., and Esther C. Young, Executors of the Estate of Niels A. Christensen (Deceased) v. United States'' (OpenJurist.org

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Selected listing of inventions

*Propeller (1369399)filed October 6, 1916; issued February 22, 1921 *Power controller for vehicle brakes (2150022)filed November 3, 1932; issued March 7, 1939 *Air compressor (2074980)filed October 17, 1932; issued March 23, 1937 *Brake mechanism (2197068)filed March 10, 1938; issued April 16, 1940 *Automobile wheel and brake mechanism (2172788)filed July 16, 1935; issued September 12, 1939

References

External links

Portrait of Niels A. Christensen
{{DEFAULTSORT:Christensen, Niels 1865 births 1952 deaths 20th-century Danish inventors 20th-century American inventors Danish emigrants to the United States

Early years

Work

Selected listing of inventions

References

Related reading

External links