(57) A pulverizing mill (10) having a grinding bowl (12) mounted so as to be rotatable
about a central axis (14), and a frustoconical grinding roll (20) which is in parallel
relationship with the grinding surface of the bowl. The bowl is mounted at an angle
(15-60°) to the horizontal. The bowl and roll are constructed such that the ratio
of the horizontal radial distance from the axis of the bowl to the lower, inner end
of the roll where it lies adjacent to the bowl surface (Ri), compared to the radius
of that point from the axis about which the roll rotates (ri), is equal to the ratio
of the horizontal radial distance from the axis of the bowl to the upper end of the
roll at the point where it lies adjacent to the bowl surface (R2), compared to the radius of that point from the axis about which the roll rotates
(r2), so that as the bowl and roll rotate about their respective axes (14, 22), the roll
surface moves across the bowl surface with only rolling movement, rather than a combination
of rolling and sliding movement, to thereby reduce the wear on these surfaces.
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