Multi-layer filter element for filtering pleated filter medium in hydraulic element, has filtering medium charged with lower depressing rate of fluid filtration during fluid flow at lower surface

摘要

The element (1) has alternating sequence of a set of filter folds (5) provided with fold height (h1) and another set of the filter folds (7) provided with another fold height (h2) where effective filter surface area is higher than uniform wrinkle height of the filter folds, so that a filtering medium (3) is charged with lower depressing rate of fluid filtration during the fluid flow at a lower surface. The filter medium comprises non-woven filter layers with differing electron donation properties, and/or electron-receiving properties.