adjacent bars bound a gap for the passage of the material, characterised in that the bars (2) are arranged in two parallel rows, the bars (2b) of the second row being offset transversely from the bars (2a) of the first row so that one gap is bounded by a pair consisting of two bars, one (2a) of which belongs to the first row and the other (2b) to the second row, and the bar ends are secured to ...
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