Patent ID: 8656551

Claim:
A filter bag for use in vacuum cleaning apparatus, which bag comprises fine planar filtration means comprising a filter web arranged in the form of a collection bag and coarse planar filtration means comprising at least one sheet of fibre felt or web material disposed inside said bag, wherein an inlet port is provided through the fine filter web so as to permit airflow access to the coarse filtration means in the interior of the bag when the bag is placed in the path of a suction-induced air stream, with the coarse filtration means disposed generally upstream of the fine filtration means, wherein the fine filtration means serves to provide a fine filter for retaining dust fine particles and wherein the relatively coarse filter sheet material has a thickness of at least 4 mm thereby to provide a matrix volume in which dust may be collected, and wherein the coarse filtration means comprises a plurality of sheets or a folded web of material, and peripheral edge regions of the sheets or web are not closed, so that air may spill around from one sheet side to the other when the filter is in use.