Roll-Concave Shelling Machine

a machine for shelling or hulling (separating the outer coverings from the kernel) buckwheat and millet. The principal components of a roll-concave shelling machine are the feeder, the horizontal rotating cylinder (roll), and the fixed concave or board (see Figure 1). Grain entering the machine is trapped by the roll and is drawn into the adjustable working area between the roll and and the concave; it is simultaneously subject to compressive and shearing strains. The outer coverings are cracked or crushed, whereupon the kernel falls out easily.

Figure 1. Roll-concave shelling machine.

The roll and concave used for shelling buckwheat are made of fine-grained natural quartz that is periodically processed to create a rough surface. For shelling millet, the roll is fabricated from an abrasive substance, and the concave is made from industrial rubber with fabric (cord) layers. The action of a shelling machine is continuous. Some machines have two concaves with a single roll. The roll diameter is 500 mm, its length is 600 mm, and the length of the arc in the working area of the concave is 220-300 mm. (The span angle of the concave is 40°-70°.) The specific productivity per cm of length of roll element when processing buckwheat is 240 kg per day; when processing millet, it is 400 kg per day.