Fruit/vegetable floatation grading

摘要

A floatation separation method is described for separating pieces of fruit or vegetable of the same type, but wherein desirable pieces have a slightly different specific gravity from the undesirable ones, and all have a specific gravity about the same as that of water. The pieces (12, FIG. 3 ) are placed near the surface of a body of water, and a cloud (40) of tiny air bubbles is maintained in the water. As the bubbles float to the surface they encounter the articles and slightly increase their buoyancy. The increase in buoyancy is slight and uniform, so those articles having a density slightly greater than that of the water will remain at the water surface, while those of a slightly greater density cannot be floated by the air bubbles and will sink to the bottom. The cloud of air bubbles is created by allowing air at about atmospheric pressure, to emerge from apertures in a rapidly spinning rotor that open in a direction primarily opposite to the spin direction.