The mechanism is based on the four-bar link-gear linkage ABC for enveloping hyperbolas, with the addition of a double guiding element consisting of two sliders, 4 and 5, connected together by turning pair P. Point P describes the space centrode of slider 2. Sliders 2 and 4 are connected by sliding pairs to cross-shaped slider 6 which has guides perpendicular to each other. When crank 1 turns about fixed axis A, centre D of cross-shaped slider 6 describes a hyperbola, and rule t-t, secured rigidly to slider 2, simultaneously envelops the hyperbola. Pivot C is placed at a focus of the hyperbola, and pivot A at its centre. Hyperbolas of the required dimensions can be obtained by adjusting pivots B and C along slots E and G.
$1090$LG,Ge$