Patent ID: 7017754

Claim:
An apparatus for classifying fine balls having diameters of 1 mm or less into those having predetermined diameter ranges, comprising a feeder for supplying fine balls, at least one rotatable cylindrical sieve constituted by a plate with a thickness of 200 μm or less having circular holes, said rotatable cylindrical sieve having a center axis inclined relative to a horizontal plane, and a container for receiving fine passing-through balls classified by subjecting said fine balls to falling from said cylindrical sieve, said fine balls being supplied from said feeder to an inlet of said rotating cylindrical sieve at its upper end, fine passing-through balls that have passed through the circular holes of said cylindrical sieve being subjected to falling to be recovered by said container, and fine residual balls that have not passed through said circular holes being withdrawn from an exit of said cylindrical sieve at its lower end, wherein the standard deviation σ of the inner diameter distribution of said cylindrical sieve formed with said circular holes is 0.35 μm or less.