Abstract: An air filter of the accordion-pleated type with successive media pleats providing substantially parallel walls held in spaced relation by corrugated spaces and sealed within a square or rectangular frame. The spacers which separate the media in the upstream direction are of higher amplitude than the spacers separating the media walls on the downstream side. The upstream spacers are preferably about 2 to 21/2 times greater in amplitude than the downstream spacers. The filters are particularly advantageous in applications where the loading or dust collection rate is accelerated and the final pressure drop is uncommonly high. Dust holding capacity is significantly increased over similar, prior art filters having equal spacing of the media walls in the upstream and downstream directors.

Abstract: A cartridge including a sheet of filtering media in annular form through which air is passed as it moves in a generally toroidal path within an enclosed housing due to rotation of a computer tape disc, or the like, mounted adjacent the cartridge within the housing. The cartridge includes a rigid body portion supporting the filter media in a generally conical plane within the annular body. The body portion is initially formed as two separate, mating halves which engage the media about its inner and outer peripheries when joined.