Hart's inversor

Hart's inversor is one of two mechanisms that provides a perfect straight line motion without sliding guides.

They were invented and published by Harry Hart in 1874–5.

Hart's first inversor is based on an Antiparallelogram. The addition of fixed points and a driving arm make it a 6-bar linkage.

It can be used to convert rotary motion to a perfect straight line by fixing a point on one short link and driving a point on another link in a circular arc.

Hart's second inversor, also known as "Hart's A-frame", is less flexible in its dimensions, but has the useful property that the motion perpendicularly bisects the fixed base points.