PURPOSE: To speed up press operation by arranging bell-cranks which interlock connectors and are symmetric to the centerline and plungers, making all of mechanisms symmetric right and left and setting kinetic moments equal on right and left.

CONSTITUTION: Connectors 2, 3 and a connector 4 are arranged so that they are opposite in the eccentric direction and equal in the eccentric amount to a crank shaft 1. 1st and 2nd crank 6, 7 are fitted respectively to the connectors 2, 3 and the connector 4 and, further, plungers 18, 19 which are driven in the vertical direction through a link mechanism are arranged. When the crank shaft 1 rotates, the connectors 2, 3 and the connector 4 reciprocate in a reverse phase, while the bell-cranks 6, 7 and the plungers 18, 19 make a vertical motion in the same phase. In this case, a ram 20 moves up and down for press working. Since the mechanism is symmetric to the centerline and inertia force is always set off by the equillbrium of the kinetic moment, the press operation is speeded-up.