Resin-coated foam prefilter for a paper-based air filter - to inhibit premature choking by dust

摘要

An air filter based on a concertina pattern paper element is fitted with a preliminary filter of porous material coated with a (tacky) resin (I). Esp. suitable for air intake filters for internal combustion engines, to prevent the paper filter becoming choked with dust or smoke. Pref. the prefilter is a strip of open-celled polyurethane foam; the ratio of the thickness of the foam prefilter to the depth of the paper fold pattern being about 1:2.5.