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By Allen Dong and Roger J. Edberg I-Tech, P.O. Box 795, Davis, California 95617

Note: This document is part of the public disclosure of an Invention. This Invention becomes PUBLIC DOMAIN on the day of the disclosure, August 9, 1989. This document is dedicated to the people of the third world.

Introduction: There are several machine designs for hulling rice. One common design is the two rubber roller system, with each roller rotating in opposite direction and different speed. Hulls are slipped off the kernels when grants are passed between the two rollers. (Gariboldi, 1974). Another rice huller design is the horizontal abrasive disk system, using one rotating disk and one stationary disk (Fig. Ib) (Gariboldi , 1974). The advantages of using rubber rollers are higher percentage of hulling, and less kernel breakage. The advantages of the abrasive disk system are ease of fabrication and of repair of the abrasive surface when it wears out.

The I-Tech design, disclosed here, tasks a vertical abrasive disk system, (a hand mill, Fig. 2a) to hull rice and spelt `wheat. The advantage of using rubber surface is incorporated in this design by replacing the stationary disk with it gum rubber disk. The abrasive rotating disk remains unaltered. The replacement of the stationary disk with rubber disk is not permanent so the original purpose of the hand mill/grain is retained.

Materials: Materials required are one steel washer, one sheet of gum rubber, cyanoacrylate glue and a hand mill. The hand mills and stone disks described here are available from R&R Mill Co., 45 West First North Street, Smithfield, UT 84335, USA. (Mention of company names or products is for the benefit of the reader and does not imply endorsement by I-tech).

Method: (i) Remove auger and rotating disk from the hand mill (Fig. 2b).

(2) Remove stationary disk from mill, by detaching three screws.

(3) Determine the outside diameter of the stationary disk and obtain a suitable sized steel washer. The "Corona " and {Quaker City " hand mills use a nominal 13/4 Inch wash«, which corresponds to 1 7/8 Inch Inside diameter and 4 Inch outside diameter.

(4) Drill and countersink three holes on the washer for mounting washer on to the grain mill.

(5) Obtain a sheet of 1/8 inch thick gum rubber of sufficient size to cover the washer. Cut out a rubber disk with a hole to the shape of the washer. Rough up one side of the gum rubber and washer with a The. Remove all and dirt from the rubber surfaces and washer surfaces with acetone, lacquer remover or paint thinner. Glue the rubber disk on to the washer with cyanoacrylate glue (e.g. Krazy Glue )

(6) Bevy the Inner edge of the gum rubber using a razor blade. Cut out mounting holes on rubber disk (Fig. 2c).

(7) Attach gum rubber + washer on to grain mill. Insert auger and. rotating disk on mill (Ag. 2d).

Results: Percentage of rice and spelt w heat hulled can be as high as 95% depending on the spacing between the stationary rubber disk and rotating abrasive disk. Closer spacing Increases hulling percentages and kernel breakage but decreases the percent of kernel breakage and unhulled grains. Well made hand mills have bearings on both ends of the shaft and are able to maintain the disks parallel.

The described rice and spat wheat huller using a hand mill is relatively inexpensive, easy to maintain and worn rubber disks are simple to replace. It Is Ideal for home, small scale farm and village usage.

Reference: Gariboldi, F. (1974) Rice milling equipment operation and maintenance. FAO Agricultural Services Bulletin #22. Food and Agriculture Organization of the United Nations, Rome.

Acknowledgments: The authors thank the Student Experimental Farm and the Cooperative Extension of the University of California, Davis. for technical support; Lorenz Schaller of Kusa research Foundation. Opal. California, for providing spelt wheat; and Leonard Diggs of Sacramento, California, for providing rice.

Copyright © 1989