Today, a combative old man changes technology. The
University of Houston's College of Engineering
presents this series about the machines that make
our civilization run, and the people whose
ingenuity created them.
Two things we've found in
this series: Great inventors aren't always nice,
pleasant people, and inventiveness does not attach
to youth. Take Niels Christensen. He was harsh and
uncompromising, and he gave us his finest invention
when he was over 70.
I met that invention in 1951. I went from
engineering school straight to the Boeing Company.
Early in the game I had to design a valve. The
valve stem had to slide inside a cylinder and seal
in hydraulic fluid. An older engineer saw me trying
to select a gasket. He said: "That's no way to do
it. Use an O-ring." "What's an O-ring?" I answered.
O-rings had come into use only in WW-II. I'd never
seen one in school. An O-ring is a skinny
doughnut-shaped piece of rubber or neoprene that
fits in a square slot. The way it works is subtle.
As it mates with another surface, the ring distorts
and drags a film of lubricant onto the surface. It
also snugs down into one side of the slot and
tightly seals against leakage.
Since then, those little rings have revolutionized
sealing. They're so common today it's hard to
imagine life without them.
Christensen, their inventor, was born in Denmark in
1865. He studied as a machinist, and he came to
America in 1891. During the 1890s he invented a
fine new air brake for electric streetcars. Soon he
was up to his neck in litigation. His patent rights
passed from company to company until Westinghouse
owned them, and Christensen did not suffer
So he fought through the courts, and he went on
inventing. New gasoline engines, car and airplane
starters, more braking systems! Then in 1933 he
began looking at hydraulic system seals.
He experimented with rubber rings in slots. It took
four years and a lot of testing to get it right.
Christensen filed his first O-ring patent in 1937.
He was 72 years old.
In 1941 he licensed the patent to United Aircraft.
He was set to get rich. Then Pearl Harbor! The
government bought out all the key military patents
and gave them away to manufacturers. Christensen
got a lump payment of $75,000, and O-rings belonged
to the government. He mounted his last great court
battle. It ended in 1971, 19 years after his death,
with a $100,000 payment to his heirs.
How I hate these patent battle stories! They demean
the creative process. Christensen gave us his
greatest invention when he was 72. I want to
remember him for changing the world after the world
had begun to call him old. That's better payment
than any of the people who stole his ideas ever
I'm John Lienhard, at the University of Houston,
where we're interested in the way inventive minds