| 摘要 |
A strip of filter material is folded so as to form two closely adjacent strip portions which are of one piece and have aligned longitudinally extending free edges and longitudinally extending second edges transversely spaced from the free edges and unitary with one another. The strip is coiled so that each of the strip portions forms a plurality of convolutions which alternate with the convolutions of the other strip portion. Means is provided in the region of the second edges for preventing liquid being filtered from forcing contaminant particles through the filter material.
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