The length of the links comply with the conditions: E͞G=G͞F=F͞D=D͞E. Figure GFDE is a rhombus linkage. Slider 1 moves along fixed guides t-t and is connected by turning pairs E to links 3 and 6. Link 7, connected by turning pairs G to links 3 and 4, moves in sliders 2 and 8. Slider 2 is connected by turning pair C to slider 9, and slider 8 is connected by turning pairs D to links 5 and 6. Slider 9 moves along cross-piece Ee of slider 1. Point F is placed at the focus of a parabola and axis d-d of guides t-t is made to coincide with its directrix. Then, when slider 1 moves along guides t-t, point C describes parabola q-q with the distance p between the focus and directrix. At the same time, straight line DG envelops the parabola.
$1108$LG,Ge$