Abstract: A filter element comprising a first planar layer (1) and a second planar layer (2), the layers (1, 2) being joined to one another to form at least one volume and at least one opening (3), and the layers (1, 2) being spaced apart from one another in places by means (4). With regard to the object of providing a filter assembly which is easily manufactured and ensures proper operation, the invention is characterized in that the means (4) are formed from at least one layer (1, 2). An assembly comprising a filter element and a frame is also described. Also described is a layer (1, 2) having deep-drawn areas.

Abstract: A method and apparatus for manufacturing a pleatable filter material from a thermally bonded non-woven fabric which has spacers, formed from the filter material itself, for folds. To produce the filter material, a fibrous web is formed from drawn and undrawn synthetic fibers and subsequently calendered. The fibrous web, which is not flat bonded, is bonded in a tension-free manner between profiled calender rolls without inhomogeneities over the cross-section of the non-woven fabric.

Abstract: A filter element that is able to be sealingly secured in position in a filter housing, comprising an accordion fold pack. The oncoming-flow side of accordion fold pack is covered by a latticed protective mask. The protective mask is sealingly joined to all fold backs of accordion fold pack on the clean-air side. In this manner, the fold edges are protected from damage during the periodic cleaning in the face of the back-blasted air used for that purpose.

Abstract: A cartridge filter having a cylindrical filter element, which is pleated parallel to its axis and is made of a layered non-woven unitary fabric. The fabric is permeable by air flow in the radial direction and is used in fresh air-supply filtration with initial pressure losses of less than 300 Pa at air flow rates through the filter medium of less than 250 m.sup.3 /m.sup.2 h. The non-woven fabric has a mass per unit area of 100 to 500 g/m.sup.2, and a thickness of 1.5-7.0 mm mm. It is made of layered staple fibers of a titer of 0.1 to 50 decitex, which are bonded by a thermally softened binding agent. A bottom layer bordering on the downstream side is contained in the non-woven fabric, having a thickness of 10 to 60% of the overall thickness, and is compressed two to ten times as much as a top layer bordering on the upstream flow side having a thickness of 10-60% of the overall thickness. One or more intermediate layers link the top and bottom layers to one another.