| 摘要 |
A filter element comprises coaxial inner and outer relatively rigid, permeable cylinders (5, 8), each cylinder being circumferentially continuous and sandwiched between the two cylinders, a spirally-wound cylindrical filter structure comprising a plurality of layers of microporous non-woven fibrous material (9), each pair of adjacent layers being separated by a layer of strong, fluid-permeable, flexible support material (10), the filter structure being under substantially uniform radial compression over the whole of its area. The compression is preferably such as to compress the filter structure by from 25% to 45% of its original thickness, and materially increases the efficiency of filters incorporating the structure. A method of effecting the compression during manufacture is also described. |
