Abstract: There are two different kinds of classical pantograph mechanisms called Sylvester pantograph mechanism and Shay Nel pantograph mechanism. The first one has one input point and one output point, and the two points don’t need to lay on a same line. The second one, the Shay Nel pantograph mechanism has one input point and two output points, but they have to stay in the same line. Both mechanisms are planar 5-bar parallelogram mechanisms. Based on the topologies of planar 5-bar mechanism and the fact that pantograph can scale any graphs, necessary condition is set up for the pantograph by giving some particular input curves. And then a new type of planar 5-bar pantograph mechanism is proposed, which unifies the two classical pantograph mechanisms.

Key words: pantograph mechanism, parallelogram mechanisms