Round trunnions b of link 3 slide along oval guides a of link 1. Barrel-shaped link 4 slides along square body c of link 3. The cylindrical surface of link 4 fits into cylindrical guides d of link 2. With respect to each other, links 1 and 2 accomplish two turning motions about perpendicular axes x-x and z-z, and three translational motions along perpendicular axes x-x, y-y and z-z.
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