Patent ID: 7891498

Claim:
A length grading machine comprising: a rotatable member extending about and along a longitudinal axis, the rotatable member including an interior surface, an interior space surrounded by the interior surface, and a plurality of lifting pockets located along the interior surface and extending over an axial length of the rotatable member, the lifting pockets for lifting granules in a particular size range from a lower position to a higher position within the interior space of the rotatable member, when the rotatable member rotates; an inlet passageway opening into the interior space of the rotatable member, the inlet passageway for delivering a stream of granules into the interior space; and a trough mounted within the interior space of the rotatable member, the trough comprising: a first end wall located in proximity to the inlet passageway, a second end wall opposing the first end wall, a first longitudinal wall extending between the first and second end walls, a second longitudinal wall opposing the first longitudinal wall and extending between the first and second end walls, and a bottom wall extending from the first end wall to the second end wall and from the first longitudinal wall to the second longitudinal wall; and an upper opening to receive the lifted granules in the particular size range, the upper opening bounded by an upper edge of each of the first and second end walls, and by an upper edge of each of the first and second longitudinal walls; wherein the upper edge of the first end wall of the trough is located at a first distance, along the longitudinal axis, from the inlet opening; and an intersection of the bottom wall with the first end wall of the trough is located a second distance, along the longitudinal axis, from the inlet opening; and the second distance is greater than the first distance; wherein the first longitudinal wall of the trough includes a first longitudinal section and a second longitudinal section; the first longitudinal section extends from an intersection with the first end wall toward the second longitudinal section, and upward from the bottom wall toward the upper edge of the first longitudinal wall of the trough at a first angle with respect to the bottom wall; the second longitudinal section extends from the first longitudinal section toward the second end wall of the trough, and upward from the bottom wall toward the upper edge of the first longitudinal wall of the trough at a second angle with respect to the bottom wall; and the first angle being less than the second angle, and the first and second longitudinal sections being conterminous at the upper edge of the first longitudinal wall.