Patent ID: 7195121

Claim:
A sifting device for a sieve box comprising: a) a drive coupled to the sieve box; b) a fundamental oscillation system having a plurality of substantially horizontal first transverse carriers coupled to the sieve box; c) a supplementary oscillation system coupled to the sieve box, the system comprising: i) at least two curved receiving parts positioned essentially parallel to a set of faces on the sieve box; ii) a plurality of substantially horizontal second transverse carriers which are coupled to each other in their end regions via said at least two curved receiving parts, and positioned substantially parallel to said plurality of substantially horizontal first transverse carriers and which are each positioned between at least two of said plurality of substantially horizontal first transverse carriers; iii) a plurality of stretchable sieve liner strips for coupling said plurality of substantially horizontal second transverse carriers together and wherein said at least two curved receiving parts have distributed fixations for coupling together said plurality of substantially horizontal second transverse carriers; d) a pendulum axle; e) a plurality of pendulum arms coupled to said pendulum axle, said pendulum arms being movably coupled to the sieve box and also coupled to said at least two curved receiving parts, wherein a transverse carrier that is closer to a feeding side is higher than a subsequent transverse carrier which is closer to a discharge side, and wherein said sifting device is in the form of at least two sections, wherein a height difference between the centers of gravity of two sequential transverse carriers is greater in a feeding side section than in a discharge side section such that said oscillation system is pivotally mounted around said pendulum axle via said pendulum arms to form a sieve surface as a curved plane formed by said stretchable sieve liner strips.