| 摘要 |
PROBLEM TO BE SOLVED: To reduce a charge of installation costs and to effectively screen raw material of object particle size by, when causing undersize raw material of a screen of the previous stage to flow down in each stage from the second stage or later to screen it, feeding oversize raw material of the previous stage to the downstream side from the feed position of the undersize raw material of the previous stage to screen them together. SOLUTION: Raw material 5 is fed to the uppermost part of a screen of the upper stage 2 from a raw material feeding device 11, and it is screened while flowing down an inclined screen surface 2c, and undersize raw material 12 that has passed on the screen surface 2c is fed to the uppermost part of a screen of the lower stage 3. Oversize raw material 13 of the screen of the upper stage 2 is rolled on an inclined screen surface 2c of the screen of the upper stage 2 and is fed to an intermediate part of an inclined screen surface 3c of the screen of the lower stage 3. At this time, the undersize raw material 12 from the screen of the upper stage 2 flows down an inclined screen surface 3c of the screen of the lower stage 3, and the oversize raw material 13 from the screen of the upper stage 2 is fed thereon, and they are jointed to be screened. At this time, the intrusion of raw material containing particle size not larger than mesh opening of the screen of the lower size 3 into the oversize raw material 13 of the screen 2 of the upper stage is small and raw material containing particle size not larger than the mesh opening of the screen of the lower stage 3 is contained in a lower layer.
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