George C. Devol, 99, a self-taught tinkerer whose invention of the robotic arm revolutionized factories around the world, died of a heart ailment Aug. 11 at his home in Wilton, Conn.

The robotic arm, which Mr. Devol dreamed up in the early 1950s, was originally called the “programmed article handling device.” It was a long name for a relatively simple and very smart machine that, in the coming decades, would become a fixture on modern assembly lines.

The Unimate, as the product became known, was designed to perform jobs that were dangerous or costly for human workers. Mr. Devol sold the first of his robotic arms in 1961 to a General Motors plant in Trenton, N.J., where it was programmed to handle the hot metal used in die casting.

Other early customers included Chrysler and Ford. Partly because of the influence of labor unions, which saw the robots as a threat to U.S. jobs, sales did not take off in the United States.

Mr. Devol’s product was wildly successful in countries such as Japan, however, and in the late 1960s the company signed a deal with Kawasaki Heavy Industries. In 2006, the Institute of Electrical and Electronics Engineers estimated that there were more than 950,000 industrial robots in operation worldwide.

Many of them are direct or indirect descendents of Unimate, said Carlene Stephens, the curator of the robot collection at the Smithsonian Institution’s National Museum of American History.

In 2005, Popular Mechanics magazine named the robotic arm one of the top 50 inventions of the past 50 years, along with the jet airliner and the television remote control.

Mr. Devol was inducted into the National Inventors Hall of Fame this year. “Devol’s patent for the first digitally operated programmable robotic arm represents the foundation of the modern robotics industry,” his induction citation reads. “Today, industrial robots have transformed factories into safer places and improved products with precision and consistency.”

Mr. Devol’s business partner was engineer Joseph F. Engelberger. Together they formed the company Unimation in Danbury, Conn.

It was, at first glance, an odd couple: The bow-tie-sporting Engelberger had degrees from Columbia University; Mr. Devol hadn’t graduated from high school. Engelberger was said to love science fiction; contrary to reports, Mr. Devol had no special love for the genre, his daughter Christine Wardlow said in an interview. Mr. Devol was too pragmatic and preferred things that could be proven to those that could not.

But like most odd couples, Engelberger and Mr. Devol had something important in common. They believed in the potential of robotics for the United States, even at a time when U.S. clients weren’t buying.

“We’re handing it to the Japanese on a platter,” Mr. Devol told The Washington Post in 1983. “I just can’t understand America.”

George Charles Devol Jr. was born Feb. 20, 1912, in Louisville. His father was a traffic manager with the Louisville & Nashville Railroad.

Mr. Devol said that his limited formal education never held him back. “I always went into areas of industry where nobody else knew anything either,” he told the publication Computerworld. “There was nowhere to go to get information, so I generated it.”

As a teenager, he started a business dealing with motion picture and sound recording, eventually applying for patents on magnetic recording devices. During World War II, he worked for a company whose products jammed German radar. He later worked on high-speed printers.

His wife of 65 years, the former Evelyn Jahelka, sometimes played a part in his work. In the 1950s, her kitchen included an early microwave, where she experimented with cooking hamburgers and other foods.

Mr. Devol’s wife died in 2003. Besides his daughter, of Littleton, Colo., survivors include three children, George C. Devol III of New Canaan, Conn., Robert Devol of Wilton and Suzanne Judkins of Brookfield, Conn.; five grandchildren; and five great-grandchildren.

When he was in his 70s, Mr. Devol began dreaming up an automatic factory that he would lease to companies.

“How can we afford to let a country as big as this go down the drain in manufacturing capability?” he said in a 1984 interview with the Miami Herald. “I’m the perpetual Don Quixote. Always flailing my arms.”