Links 1 and 2 are connected by turning pairs A and B to the base, and their turning axes intersect at angle α. Links 1 and 2 contact each other through round cylinders a and b whose axes intersect the turning axes of links 1 and 2. A device, consisting of screw d and arc-shaped guide e, enable angle α, between the turning axes of links 1 and 2, to be varied.
$521$SL,CL$