YAMAMOTO CO., LTD.

Polished rice contains not only head rice but also brokens of various sizes, rice bran, and dust. Broken rice is separated by a grader. Rice bran and dust are eliminated by an aspirator. The degree of separation of broken rice is determined acording to the demand of consumers. In many coutries, it is not necessary to separate broken rice. There are, however, markets requiring that head rice not be mixed with brokens and rice bran. In general, some percentage of broken rice inclusion is acceptable. But rice products require the elimination of dust and bran.
Types of grader are shown below.

Oscillating Sieve

Structure and operation:
It has a horizontal screen with an angle of about 4 - 12° and is vibrated to and from by a vertical eccentric drive rotating at about 3.3 - 6.6 Hz.
The screen is perforated steel sheet with round holes or wire mesh.
The single or double screes are used with different sieve openings.
The single screen divides milled rice into head rice and large brokens on the top and small brokens at the bottom. The double screen divides head rice, large brokens, and small brokens separately.

Capacity:
The separation capacity is not large, because the grains stop at the end of each swing.
The effectiveness of separation is also not so high. The machine, however, is widely used in small rice mills in Southeast Asia.