Sliding link 1 turns about fixed axis C. Slider 2, moving along link 1, carries rule D. Slider 3, moving along fixed guides G, is connected by turning pair B to slider 2. When link 1 rotates about axis C, rule D, rigidly secured to slider 2, envelops parabola H. Point C is placed at the focus of the parabola and the axis of guides G passes through its vertex. Parabolas of various sizes can be obtained by adjusting pivot C along slot E.
$1113$LG,Ge$