Fluted filter medium and process for its manufacture

摘要

A fluted filter medium (74) comprising a corrugated filter sheet, where each flute (120) has an end closure defined by a regular fold arrangement in the corresponding corrugation. Each regular fold arrangement has at least four folds. A process for manufacturing the fluted filter medium comprising deforming a portion of each corrugation to define at least one foldable tip, and folding the said tip in order to close the corrugation.