Filtering materials which provide reasonable efficiencies in the removal of the relatively finer foreign particles have relatively high resistance to the flow of air there through. As a result it is generally desirable to provide an area of filtering media for the air to flow through which is greater than the-area of the air inlet duct to the air conditioning or supply system. To accomplish this, it is common practice to corrugate or pleat the filtering media thereby increasing the area of filtering media through which the air may flow. Most types of filtering media which are effective against finer dirt particles are not sufficiently rigid to be self-supporting in this corrugated or pleated configuration, with the result that some apparatus must be supplied to support the filtering media.
While various expedients have been used to provide this support, including Wire baskets, rigid frameworks which carry supporting wires and the like, the least expensive and most widely used have been various cardboard members used as a frame work to support the filtering media in a self-contained cartridge. Such cartridges, however, have certain objectionable features. For example, the cardboard support is such that the adjacent pleats of media are flexed by the air stream so as to cling one to the other thereby reducing the effective area of filtering material available for air to pass through. To partially avoid this, it is necessary that the space between the pleats and/or `the angle between the pleats must be relatively large thereby restricting the area of filtering material.
In order for a filtering cartridge to be sufficiently inexpensive to be disposable after replacement, the materials used must be inexpensive, the quantity of materials minimized, and the manufacture of the cartridge must be relatively rapid and inexpensive. In accordance with the present invention, there is provided a self-contained disposable filter cartridge which is relatively efficient against finer dirt particles. This cartridge incorporates inexpensive materials which may be inexpensively assembled. Further, the filtering media is sufficiently supported in its pleated condition to obtain a maximum effective area of filtering media for a given size of filter cartridge consistent with a low resistance to air flow through the filter cartridge.
Turned it off immediately. 
