Abstract: A bag-type filter apparatus, whose elongate tubular filter bags are supported by tubular cages therewithin, is provided with an air diffuser tube extending longitudinally within each tubular cage for diffusing and distributing a periodic reverse purge air flow throughout each filter bag to dislodge from the exterior surface of each filter bag particulate material which normally collects on the filter bags. Each air diffuser tube is formed from a perforate strip of helically wound sheet metal, adjacent edges of which are interconnected by a seam in which such adjacent edges overlap each other in interlocking relationship so that the seam extends helically around the respective air diffuser tube.

Abstract: The cleaning of a tubular filter bag supported by a tubular supporting cage positioned within the filter bag is significantly enhanced by the provision of an elongate air distributor pipe extending into one end of the filter bag and longitudinally along the interior of the supporting cage and filter bag, with the air distributor pipe having a plurality of air outlet openings therein for distributing compressed air throughout the interior of the filter bag. An elongate hollow diffuser tube extends longitudinally within the supporting cage and filter bag in surrounding relation to the air distributor pipe, the diffuser tube having perforations therein for diffusing and further distributing throughout the filter bag the compressed air which is discharged from the air distributor pipe.