Self-spacing pleated filter insert
A replaceable, self-spacing, pleated, filter insert that can be easily installed in a reusable filter frame without the aid of a secondary spacing structure includes reversibly collapsible and expandable filter media including a plurality of pleats that expand uniformly when the filter is expanded. When the filter is expanded to the length of the filter frame, the filter is under tension and behaves like a spring, thereby allowing the length of the filter to be readily adjusted to match the length of the frame and allowing the pleats to be aligned with corresponding ribs provided in the frame.
1. A self-spacing pleated filter insert for use with a frame having a length and a plurality of equally spaced transverse ribs that mesh with the expanded pleats of the filter insert, said self-spacing pleated filter insert comprising a reversibly collapsible and expandable self-supporting fibrous nonwoven polypropylene filter media including a plurality of pleats formed by heat setting and are generally uniformly spaced upon expansion and release of said pleated filter insert, wherein when said pleated filter insert is expanded to the length of the filter frame, said pleated filter insert is under tension, and when said pleated filter insert is released, it will return to an equilibrium length that is no greater than the length of the frame.
2. A pleated filter insert as defined in claim 1 , wherein said filter media has a basis weight of 50–80 g/m 2.
3. A pleated filter insert as defined in claim 2 , wherein said filter media has a thickness of 0.5–0.63 mm.
4. A pleated filter insert as defined in claim 3 , wherein said filter media has a permeability of 690–1024 cfm.
5. A pleated filter insert as defined in claim 1 , further comprising attachment members along opposed first and second ends of said filter media for securing said pleated filter insert into a frame.
6. A pleated filter insert as defined in claim 5 , wherein said attachment members contain holes adapted to mate with respective projections on the frame.
7. A pleated filter insert as defined in claim 6 , wherein said attachment members contain an asymmetric hole pattern that allows the pleated filter insert to be attached to the frame in only one orientation.