Hart's inversor

Hart's inversor is one of two mechanisms that provides a perfect straight line motion without sliding guides.[1] They were invented and published by Harry Hart in 1874–5.[1][2]

Hart's (first) inversor. Links of the same color are the same length. The relative position of the fixed point, the input, and the output along their links is the same (half, here).
Hart's A-frame, or Hart's second inversor. The short links are half the length of the long ones. The center link is one quarter of the way down the long links. A fixed link along the bottom of the same length as the long links is not shown.

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.[1][3]

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.

Example dimensions
    • AB = AC = BD = 4
    • CE = ED = 2
    • Af = Bg = 3
    • fC = gD = 1
    • fg = 2
    • AB = Bg = 2
    • CE = FD = 6
    • CA = AE = 3
    • CD = EF = 12
    • Cp = pD = Eg = gF = 6

See also

References
  1. "True straight-line linkages having a rectlinear translating bar" (PDF).
  2. Ceccarelli, Marco (23 November 2007). International Symposium on History of Machines and Mechanisms. ISBN 9781402022043.
  3. "Harts inversor (Has draggable animation)".
  • bham.ac.uk – Hart's A-frame (draggable animation) 6-bar linkage


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