Coiled filter body - has a layer with better drainage structured with denser zones across the wood direction

摘要

The filter structure of a deep fitler body, which can be back rinsed, is composed of at least two non-woven layers with different drainage characteristics, wound in a coil. the layer with better drainage has at least one zone of a denser material across the wound direction, for reduced permeability by the fluid passing at a tangent in the layer with better drainage compated to the radially neighbouring layer. Also claimed is a mfg. process where the layer with the better drainage, before winding into a coiled filter body or during winding, is continuously compressed along a zone to give reduce permeability within limits. USE/ADVANTAGE - The filter body is a wound coil of material which can be back rinsed and cleaned, and gives a deep filter action. The filter gives an effective filtering action, which retains the filtered matter without the fluid passing by the layers. It is easily cleaned and is made cost-effectively.