A divergent type grader for cocoa pods (Theobroma cacao L.)

Abstract

The size distribution of cocoa pods was measured and the average length and breadth were 147.5 and 74.2 mm, respectively.  Based on length, the pods were categorized as less than 120 mm, 120 to 140 mm and above 140 mm, which were 28, 37 and 35% of the whole lot. The breadth varied from 60 mm to 110 mm and the major contribution was 18, 28, 36, 12, 4 and 2% for the ranges, below 70 mm, 70-80 mm, 80-85 mm, 85-90 mm, 90-100 mm and 100-110 mm, respectively.  A direct proportion between the length and breadth was noted.   The sphericity and aspect ratio ranged 0.54 to 0.68 and 0.4 to 0.57. The coefficient of static friction increased in the range 0.503 to 0.738 with moisture content range of 50.3 to 76.4% (d.b.) against various surfaces, also the rolling angle varied as 15.66 to 19.7° at this moisture range. Based on the distribution of the breadth of cocoa pod, a gravity fed divergent type grader was developed to grade the pods according to breadth and evaluated for capacity and effectiveness at 22.5, 24 and 25.5° slopes. The capacity of the grader and the effectiveness of grading are found significant with slope of operation.  The capacity of the grader was 253.1, 268.9 and 277.7 kg/h at operating slopes of 22.5, 24 and 25.5°, respectively and the effectiveness of grader was 0.767, 0.787 and 0.745. Operating at 24° slope, yields the highest effectiveness of 0.787 at a capacity of 268.9 kg/h.