O-rings are a small part of many products, but their importance is bigger than you might think. The global seals and gaskets market is worth $63.2 billion in 2017, and is expanding at a compound annual growth rate of 5.8 percent, on track to reach a value of $84 billion by 2022, Transparency Market Research projects. The quest for eco-friendly solutions in the automotive and energy industries is helping fuel innovation and drive demand. Electrical and electronics applications will also contribute to this growth, says Stratistics MRC.
There are many different uses for o-rings, which is why manufacturer Apple Rubber makes customized o-rings in over 8,000 different sizes out of a wide variety of materials. O-rings have far more utility than most people realize, and they have a very colorful history. Here are three surprising facts you probably didn’t know about o-rings.
Thomas Edison Developed Early Prototypes for O-Rings
With 1,093 patents for his own inventions and 2,332 patents in all, Thomas Edison left his mark on many technologies, so it’s not surprising that he should figure into the story of the o-ring. When Edison was inventing the light bulb, one of the challenges he faced was the fact that the carbon thread he used as filament would burn in the presence of oxygen. To prevent this, after the bulb was assembled, Edison used a vacuum pump to remove oxygen through a thin glass tube. Keeping the bulb free of oxygen required designing it with an air-tight seal. To create this seal, Edison developed a prototype of what we now call the o-ring. The design for a light bulb Edison patented in 1882 shows the neck of the bulb sealed off by a round rubber ring.
Another 1882 patent Edison obtained for a water faucet shows a gas-sealing ring. Edison apparently based this idea on gaskets made of india rubber that were being used on waterworks pipes in the mid-19th century.
O-Rings Helped Win World War II
While Edison’s sealing rings were similar in function to o-rings, the first actual o-ring patent was awarded to Swedish inventor J.O. Lundberg in 1896. However, it was not Lundberg, but Danish-American inventor Niels Christensen who invented the direct ancestor of today’s o-ring in 1933.
Christensen had a background inventing an airbrake system for electric-powered streetcars. While working in this area, he figured out how to seal a piston’s cylinder by setting a rubber ring in a groove slightly larger than the ring’s minor radius. Christen developed his invention for several years before applying for a patent in 1937, which was approved in 1939. Christensen intended to profit from his invention by licensing it in 1941 to United Aircraft, who planned to use it as a seal for hydraulic cylinders in planes.
But Christensen’s plans were interrupted by Pearl Harbor. The United States government considered his invention critical to the war effort, and seized the rights to his patent. He received $75,000 in compensation, with his heirs later receiving an additional $100,000. The government allowed U.S. military contractors to begin using o-rings, and their use became widespread in the aircraft industry and later in other industries.
Today, aircraft manufacturers continue to use o-rings as seals in hydraulic systems for brakes, as well as wing flaps and landing gear. O-rings are made out of special synthetic rubber that has been designed to withstand the high temperatures and extreme conditions of aerospace applications, which is why they are used in airplanes as well as space shuttles and rockets.
O-Rings Save Lives
O-rings also have important applications in medicine that help save lives. An example is hydraulic rescue tools such as Jaws of Life used to save victims trapped in vehicles following crashes. These types of tools can be used to cut through a door or roof, spread open a wedged door or ram a dashboard off a victim’s body. Since these tools are powered by hydraulics, they rely on o-rings.
O-rings are also used as medical seals for a wide variety of devices. These include medical appliances, pump seals, feeding devices, IV components, dialysers and implant materials. O-rings designed for these purposes typically use special medical-grade rubber that has heat-resistant and chemical-resistant properties to prevent cracking, bacteria and toxicity.