Cartridge filter

A cartridge filter containing non-woven fabric converted into a cylindrical shape for use as the filter element, the filter element being permeable in the radial direction and comprising:

• a top layer made of fibers having a first titer and bordering on the upstream side of the filter and having a thickness of between 10%-60% of the overall thickness of the non-woven fabric;
• a bottom layer made of fibers having a second titer and bordering on the downstream side of the filter and having a thickness of between 10% to 60% of the overall thickness of the non-woven fabric, said second layer being compressed between two to ten times the first layer, the non-woven fabric having an overall mass per unit area of 100 to 500 g/m.sup.2, and an overall thickness, as measured according to DIN 53 855, of 1.5-7.0 mm;
• and
• one or more transition zones intermediate the first and second layers, the transition z-ones being formed integral with the first and the second layers so that these layers need not be separately joined together, wherein the top layer, the bottom layer, and the transition zone comprise 100% of the thickness of the filter element;
• wherein the fibers are bonded together by a thermally softenable binding agent to form the non-woven fabric, which is cylindrical in shape and which is pleated parallel to the cylindrical axis of its shape, and wherein the filter element is useable in 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.

A cylindrical filter made of non-woven fabric for use as the filter element in a cartridge filter, the filter element being permeable in the radial direction and comprising:

• a first layer made of fibers having a first titer and bordering on the upstream flow side of the filter and having a thickness of between 10%-60% of the overall thickness of the non-woven fabric;
• a second layer made of fibers having a second titer and bordering on the downstream side of the filter and having a thickness of between 10% to 60% of the overall thickness of the non-woven fabric, said second layer being compressed between two to ten times the first layer, the non-woven fabric having an overall mass per unit area of 100 to 500 g/m2, and an overall thickness, as measured according to DIN 53 855, of 1.5-7.0 mm;
• and
• a transition zone intermediate the first and second layers, the transition zone being formed integral with the first and the second layers such that the full cross-section of the filter as viewed parallel to the transition zone is available to filter gas, wherein the first layer, the second layer, and the transition zone comprise 100% of the thickness of the filter element;
• wherein the fibers are bonded together by a thermally softenable binding agent to form the non-woven fabric, which is cylindrical in shape and which is pleated parallel to the cylindrical axis of its shape, and wherein the filter element is useable in air-supply filtration with initial pressure losses of less than 300 Pa at gas flow rates through the filter medium of less than 250 m.sup.3 /m.sup.2 h.