| 摘要 |
Perforated sheet or drum produced from such a sheet, employed in screens and presses for the crude paper pulp industry and for the papermaking industry, the holes made in the said sheet being either round holes or elongate slots, the said sheet being furthermore completely planar or provided with ribs, ridges, projections, grooves or the like and being characterised in that at least a proportion of the filter surfaces of the said sheet 1 is equipped with a hard surface layer provided with a diffusion coating.
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