Expandable media filter assembly

The invention relates generally to air filters and, more particularly, to expandable air filters for use in furnaces. An expandable media filter structure is composed largely of biodegradable materials and is environmentally disposable. A plurality of pleated panels are interconnected at their edges so as to be collapsible for storage and shipping purposes but expandable for installation and use. A plurality of ribbons are ultrasonically welded to each of the panels edges, with the ribbon portions between edges being of substantially equal lengths, thereby maintaining equal spacing between the panel edges when the filter is in the expanded condition but allowing an each collapsing of the filter for storage. Forming a part of the nondisposable framework for support of the disposable filter are a pair of end plates which are C-shaped in cross section for slidably receiving an end panel of the media filter therein. The depth of the C-shaped channel is sufficient to allow a plurality of the unexpended pleats to be stored therein so that a single sized filter may be used for various sizes of cabinet openings. The end plates include a pair of slots formed near their ends for attachment to a nondisposable support structure. The nondisposable support structure includes a pair of molded plastic side caps that fit over the respective ends of the filter panels and the end plates. Each side cap has pair of flanges at its opposite ends which act to maintain the filter in its expanded condition when the end plates are placed in abutting position therewith. Each side cap also includes a boss which fits into a respective end plate slot to hold the end plates in their installed positions within the side caps.