| 摘要 |
A tumbling mill includes an inlet area, an outlet area, and a tumbling area between the inlet and outlet areas. The mill is formed as a tri-cyclical member having an outer cylinder extending along the tumbling and outlet areas, and an inner cylinder concentric with the outer cylinder and extending through the inlet, outlet and tumbling areas. The inner and outer cylinders define a space therebetween. The inner cylinder is perforated to allow sand to fall into the space between the inner and outer cylinders. The inner cylinder includes an inner helical vane to urge sand, media, and castings toward the outlet area, and an outer helical vane to urge sand and media toward the inlet area. A reclassifying screen is provided in the inlet area to classify sand. Sand particles that are sufficiently small passes through the screen and out a chute. Sand particles that are not small enough are recirculated through the tumbling mill to be further broken down. A shell is positioned in the inlet area between the inner cylinder and the screen to hold the segments which form the inner cylinder together under heavy tumbling. The shell includes a plurality of relatively large openings to allow any sand that falls enters the shell to fall through to the screen. A third helical vane is positioned between the shell and the screen. Preferably, the edges of the third helical vane are aligned with the openings in the shell. The shell is sufficiently thick (preferably between +E,fra 3/8+EE '' to 1'') to prevent said segments from separating under pressure of extensive tumbling.
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