SIEVE CASE STRUCTURE FOR THRESHING APPARATUS

PROBLEM TO BE SOLVED: To provide a sieve case structure designed to avoid such an unfavorableness that a chaff sieve as a whole, despite being of weight-sensing type, unnecessarily shakes as a result of the significant fluttering of chaff lip plates on the closer side of a crank mechanism due to the swing movement of the sieve case. SOLUTION: This sieve case structure for a threshing apparatus is such that the chaff lip plates 17A, as a group, of a chaff sieve 17 are connected in an interlockingly swingable way at the corresponding supports P3 on the upper ends of the respective lip plates 17A so as to allow their open degrees to be regulable, and there are provided respective springs 31 impelling to closing side the group of the chaff lip plates 17A so that the open degrees vary according to the weight of a to-be-treated object on the chaff sieve 17; wherein the sieve case 6 is subjected to reciprocating driving swing through a crank mechanism disposed therebehind and a swing arm disposed in front thereof, and the group of the chaff lip plates 17A are designed to be gradually thinner and lighter toward the rear side thereof.