Link 1 turns about fixed axis A and is connected by sliding pair B to link 3. Roller 2 rotates about axis D-D. When link 1 turns about axis A, roller 2, cutting into the surface of the drawing with its sharp edge, moves during each instant along the line of intersection of the planes of the drawing and of roller 2. The envelope of the successive positions of this straight line is an involute with the polar equation, with respect to pole A, R = aϕ where R=B͞K, a=A͞͞B, ϕ = angle of rotat ion of link 1.
$1235$LG,Ge$