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Cruise control

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Cruise control

Cruise control (also known as speed control, cruise command, autocruise, or tempomat) is a system that automatically controls the speed of an automobile. The system is a servomechanism that takes over the car's throttle to maintain a steady speed set by the driver.

Speed control existed in early automobiles such as the Wilson-Pilcher in the early 1900s. They had a lever on the steering column that could be used to set the speed to be maintained by the engine. In 1908, the Peerless included a governor to keep the speed of the engine through an extra throttle lever on the steering wheel. Peerless successfully used a flyball governor. They advertised their system as being able to "maintain speed whether uphill or down."

A governor was used by James Watt and Matthew Boulton in 1788 to control steam engines, but the use of governors dates at least back to the 17th century. On an engine, the governor uses centrifugal force to adjust the throttle position to adapt the engine's speed to different loads (e.g., when going up a hill).

Modern cruise control (also known as a speedostat or tempomat) was invented in 1948 by the blind inventor and mechanical engineer Ralph Teetor. He came up with the idea due to being frustrated by his driver's habit of speeding up and slowing down as he talked.

A more significant factor in developing cruise control was the 35 mph (56 km/h) speed limit imposed in the United States during World War II to reduce gasoline use and tire wear. A mechanism controlled by the driver provided resistance to further pressure on the accelerator pedal when the vehicle reached the desired speed. Teetor's idea of a dashboard speed selector with a mechanism connected to the driveshaft and a device able to push against the gas pedal was patented in 1950. He added a speed lock capability that maintained the car's speed until the driver tapped the brake pedal or turned off the system.

A 1955 U.S. patent for a "constant speed regulator" was filed in 1950 by M-Sgt Frank J. Riley. He conceived the device while driving on the Pennsylvania Turnpike and installed his invention in his car in 1948.

Another inventor named Harold Exline, working independently of Riley, also invented a type of cruise control that he first installed on his car and friends' cars. Exline filed a U.S. patent for a "vacuum powered throttle control with electrically controlled air valve" in 1951, which was granted in 1956. Despite these patents, Riley, Exline, and subsequent patent holders were not able to collect royalties for any cruise control inventions.

The first car with Teetor's "speedostat" system was the 1958 Chrysler Imperial (called "auto-pilot"), using a speed control dial on the dashboard. This system calculated ground speed from the rotating speedometer cable and used a bi-directional screw-drive electric motor to vary the throttle position as needed. Cadillac soon renamed and marketed the device as "cruise control."

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