Patent ID: 7322882

Claim:
A drive linkage for reciprocating a sieve that is suspended within a frame of a combine harvester for movement in mutually orthogonal directions, the drive linkage comprising: a cranking mechanism, the cranking mechanism imparting a reciprocating motion to the sieve in a fore and aft movement in the direction of travel of the harvester; and a pivot arm pivotably connected at one end to one side of the sieve, the pivot arm configured to impart movement to the sieve such that the sieve moves in an arc centered on a pivot axis at the opposite end of the pivot arm as the sieve is reciprocated, wherein means are provided for displacing the pivot axis of the pivot arm relative to the frame in synchronism with the reciprocation of the sieve, further wherein the means displaces the pivot axis inwardly when the sieve is at the limits of the fore and aft movement and moved back to a central position when the sieve is at a midpoint in the fore and aft movement, in such a manner as to cause the sieve to follow a substantially rectilinear path relative to the frame.