The Peaucellier–Lipkin cell, also known simply as Peaucellier’s
cell, consists of seven links and is driven by the rocking motion
of the central link (yellow). Note that the spacing between the
cell’s two points of attachment to the supporting structure
needs to be equal to the length of the central link.
The Peaucellier–Lipkin cell works on the principle of
inversion of a circle (with the central link tracing part of it),
and it was one of the first linkages capable of producing
perfectly linear motion. Its invention was crucial for the
development of 19th-century industry and, most notably,
for its use in steam engines.