Abstract: A filter element for gas or liquid comprises a layer of glass, ceramic, metal, mineral wool or organic fibres containing, wholly within the layer, an apertured sheet, for example of steel or aluminum, the fibres being bound to one another throughout the layer and through the apertures, as well as to the sheet itself, by a synthetic resin such as silicone resin or polyurethane. The filter element is formed by mounting the apertured sheet a selected distance above a filter surface on which the fibres build up while a slurry containing the fibres is drained through the filter surface. When the fibres have built up to a predetermined distance above the sheet, the fibres containing the sheet are removed and the assembly impregnated with a synthetic resin and cured. Two or more grades of slurry mixture may be used in succession to produce a density grading through the thickness of the fibrous layer.

Abstract: Filter elements are described in which a pleated cylindrical sheet of non-woven microporous glass fibre filter material impregnated with a binder, which may be silicone, polyurethane, phenolic resin or epoxy resin, is mounted in contact with a cylindrical supporting sheet of, for example, expanded metal for maintaining the filter material against shock pressure loads. To protect the filter material during assembly a porous layer of protective material may be interposed between the filter material and the supporting cylinder. The supporting cylinder may be a simple cylinder or pleated so as to fit the filter material. An activated carbon layer for removing odors during air filtration may be added to the filter material. When the air contains oil mist, a layer containing dye that will be taken up by the oil and discolor the filter element as a warning indication that the filter has become saturated, may be interposed between the filter material and the activated carbon layer.