Ralph Teetor (August 17, 1890 – February 15, 1982) was a renowned inventor who pioneered the development of the cruise control system. He served as the long-time president of The Perfect Circle Co., an automotive component manufacturing company (acquired in 1963 by Dana Holding Corporation, later sold to Mahle GmbH in 2007) in Hagerstown, Indiana, specializing in piston ring bearings.
According to family heritage information, Teetor was inspired to invent the cruise control system while riding with the family lawyer, Harry Lindsay. Lindsay had a habit of slowing down when talking and accelerating when listening. The jolts caused by this behavior frustrated Teetor to the point where he was determined to create a speed control device. In 1945, after ten years of experimentation, Ralph Teetor received his first patent for a cruise control device.
Various names were given to his invention, including “Controlmatic,” “Touchomatic,” “Pressomatic,” and “Speedostat,” with “Speedostat” eventually becoming the brand name. Teetor received the patent for “Speedostat” on August 22, 1950. The Perfect Circle device was not commercially used until Chrysler introduced it as an option for luxury models called “Auto Pilot” in 1958. Cadillac marketed the product as “Cruise Control,” and this name became the generic term for the invention.
The throttle was controlled by a bidirectional electric motor connected by a two-way screw, linking together during use through an electromagnet. A 12v column would be held in the middle near two electrical contacts on the throttle, one controlling the motor screw to increase speed and the other to decrease speed.
This column would “guide” the engine (and throttle and vehicle speed) with input from the rotational weight of the speedometer cable from the gearbox and a tensioned spring set by a cable from a disc near the steering wheel.
The first widely sold design became an industry standard for over a decade (GM switched to vacuum pumps/toggle switches/turn signal activation in 1969, although still marketed as “Speedostat”).
Teetor lived a nearly accident-free life and continued to be successful as an engineer, manufacturing manager, and accomplished entrepreneur. His other inventions included an early lawnmower, a locking mechanism, and a fishing pole clamp.
In 1936, Teetor was elected president of the Society of Automotive Engineers (SAE). In 1963, he established the Ralph R. Teetor Educational Award for SAE, awarded annually to stimulate “the relationship between young engineering faculty and practicing engineers in industry and government.”
In 1965, Teetor received two honorary doctorates, Doctor of Engineering from the Indiana Institute of Technology and Doctor of Laws from Earlham College, Indiana. He was also appointed a Fellow of the American Society of Mechanical Engineers. The astronomical observatory board and one of the residences at Earlham College bear Teetor’s name.
In 1988, Teetor was inducted into the Automotive Hall of Fame in Dearborn, Michigan, alongside other great inventors and industry contributors. This was a tribute to his many years of contributions to the automotive industry.
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