Link 1, turning about fixed axis A, is connected by a sliding pair to link 3 which, in turn, is connected by turning pair B to slider 4. Slider 4 moves along fixed guides a-a whose axis is parallel to axis Ay. Cross-piece Bt of link 3 is connected by a sliding pair to link 5. Link 5 is connected by turning pair E to slider 2 which moves along fixed ways b-b whose axis is also parallel to axis Ay. Centre A is placed at the common focus of the parabolas to be enveloped, the axis of guides a-a is made to coincide with the directrix of parabola q-q and the axis of guides b-b is located at a distance from point A equal to c=(p+p')/2, where p and p' are the distances from directrices to the focus of parabolas q-q and q' -q'. When link 1 turns about axis A, cross-pieces Bt and En of links 3 and 5 simultaneously envelop confocal parabolas q-q and q' -q'.
$1098$LG,Ge$