Elliptic motion driving apparatus for a step screen

An elliptic motion driving apparatus for a step screen in which elliptic motion of an elliptic motion driving unit is transferred to a driven link so as to make a plurality of movable plates, connected by a movable column, perform an elliptical movement in a longitudinal direction of the movable column, the apparatus comprising:

• a worm reduction gear which is driven by a drive motor for driving a power transmission;
• a driving rotation cam having a first end coupled to said power transmission shaft and includes a second end;
• a horizontal motion guiding rail;
• a vertical motion guide rail;
• an eccentric shaft for horizontal motion axially connected to said second end of said driving rotation cam, said eccentric shaft having a horizontal eccentric bearing for horizontal motion thereof which is movable horizontally along said horizontal motion guiding rail upon rotation of said driving rotation cam, said eccentric shaft having a vertical eccentric beating;
• and
• an eccentric shaft for vertical motion and an eccentric rotation cam mounted on said eccentric shaft for vertical motion and being engagable with said eccentric shaft for horizontal motion through said eccentric rotation cam such that said vertical eccentric bearing of the eccentric shaft for vertical motion moves vertically along said vertical motion guiding rail upon rotation of said eccentric shaft for horizontal motion.