说明
Watt's linkage (also known as the parallel linkage) is a type of mechanical linkage invented by James Watt (19 January 1736 – 25 August 1819) to constrain the movement of a steam engine piston in a straight line.The idea of its genesis using links is contained in a letter he wrote to Matthew Boulton in June 1784.I have got a glimpse of a method of causing a piston rod to move up and down perpendicularly by only fixing it to a piece of iron upon the beam, without chains or perpendicular guides <...> and one of the most ingenious simple pieces of mechanics I have invented. This linkage does not generate a true straight line motion, and indeed Watt did not claim it did so. In a letter to Boulton on 11 September 1784 he describes the linkage as follows