The Chebyshev linkage is a mechanical linkage that converts rotational motion to approximate straight-line motion.
It was invented by the nineteenth-century mathematician Pafnuty Chebyshev, who studied theoretical problems in kinematic mechanisms. One of the problems was the construction of a linkage that converts a rotary motion into an approximate straight-line motion. This was also studied by James Watt in his improvements to the steam engine. Van helsing, CC BY-SA 3.0 http://creativecommons.org/licenses/by-sa/3.0/&, via Wikimedia Commons