August 17, 1915 – Charles Kettering Patents the Electric Ignition

On this day in engineering history, Charles Franklin Kettering received U.S. patent 1150523 for an "engine starting device" that revolutionized the American automobile.

Ultimately, Kettering's all-electric starter would replace the hand crank, a difficult and dangerous device that could break the user's arm if the engine backfired. Indeed, as Henry Ford popularized his affordable Model T, American doctors coined a new term for these hand-crank injuries – "Ford Fractures".

Cadillac Dreams

Charles F. Kettering's filed his patent application for an electric ignition on June 15, 1911. A year later, the Ohio inventor joined Henry Leland, a Vermont-born machinist who had once worked for Colt, in developing a self-starter for a Cadillac.

Together, the American inventors won the Dewar Trophy, a cup awarded by British parliamentarian Sir Thomas R. Dewar "to the motor car which should successfully complete the most meritorious performance or test" to advance the interests of the automobile industry.

Clutch Performance

In his patent application, Charles F. Kettering described "a foot pedal which is adapted to cause the coupling of the starting device to the engine". This "normally disconnected" pedal controlled a "transmission clutch" and also served as "safety device". By preventing the "inadvertent or accidental" forward-movement of the vehicle, the actuated pedal eliminated another danger posed by hand-cranking.

Kettering's motor-generator, accumulator, and electrical connections were used with a controller switch that, "when thrown into its first, or starting position", connected the accumulator's cells in series with the motor-generator. When the controller switch was "thrown into the second, or charging position", the connections were broken.

Kettering and Gearing

The motor-generator or "dynamo electric machine", as Kettering called it, was designed to "operate as a motor to crank the engine of the automobile through the medium of intermediate gears". The gearing that was selected was also an important consideration.

"In the present instance," Kettering explained, "the motor connection for starting permits the driving of the motor at a high rate of speed, and the turning of the engine at a low rate of speed, thus developing a powerful starting torque with a comparatively small motor".

Resources:

http://www.google.com/patents?id=7TllAAAAEBAJ&printsec=drawing&zoom=4#v=onepage&q&f=false

http://en.wikipedia.org/wiki/Charles_F._Kettering

http://simple.wikipedia.org/wiki/Ford_Model_T

http://en.wikipedia.org/wiki/Dewar_Trophy