Method and apparatus for assembling an expandable and disposable media filter

#The invention relates generally to air filters and, more particularly, to expandable air filters for use in furnaces.

#The use of disposable air filters in the air distribution system of a building has provided an efficient and economical method of removing undesirable particulate matter from the air. In its simplest form, a rectangular piece of filter media material is mounted in a cardboard framework, with the combination then being mounted in a filter cabinet or an air duct somewhere in the air distribution system. With a hot air furnace, it is common practice to place the filter in a filter cabinet just upstream of the fan so as to filter the return air as it enters the furnace from the return air duct. When the filter is spent, i.e. when it has collected a sufficient amount of particulate matter as to be considered “full”, then it is removed and replaced with a new filter.

#One way to increase the surface area of a filter is to make it multi-dimensional, with a plurality of accordion-like pleats. Such a pleated media filter is thicker than a non pleated filter and therefore provides more active surface area, making it more effective and longer lasting. It can be rechargeable, i.e. cleanable, or disposable depending primarily on the type of material used for the filter media. A disposable material, however, tends to be less durable and strong, and many such materials will not be suitable for providing the necessary support structure that is necessary to secure and maintain the installed position of the disposable portion of the filter in the nondisposable support framework. Further, a homeowner should be able to simply and easily remove, replace and dispose of a dirty filter.

#FIG. 1 is an exploded, perspective view of the filter structure in accordance with the present invention.

#FIG. 3 is an exploded, perspective view of a portion of the filter structure in accordance with the present invention.

#FIG. 2 is a sectional view of an side cap portion of the filter structure as seen along lines 2—2 of FIG. 1.

#Referring now to FIG. 1, an air filter structure is shown generally at 10 as comprising a media filter element 11, a pair of end plates 12 and 13, and a pair of side caps 14 and 16. The side caps 14 and 16 are formed of a plastic material and are reusable, whereas the combination of the media filter element 11 and its associated end plates 12 and 13 are made of polypropylene and cardboard materials, respectively, and are intended to be disposable and replaceable at the time when the filter is considered to be “full” or “dirty”.

#The side caps 14 and 16 are identical and comprise a substantially planer base element 17, normally extending sidewalls 18 and 19, and normally extending end walls 21 and 22, the combination of which defines a cover for receiving one end of the filter element 11 as will be described hereinafter. As part of the base element 17 of each of the side caps 14 and 16, of there are provided a pair of spaced handles or grips 23 and 24 which are molded into the base element 17 as shown. Also, on the outer surfaces of the end walls 21 and 22, there are provided a pair of molded clearance ribs 26 and 27 which serve to reduce sliding friction when the filter assembly is being installed into its operating position within a duct or the like.

#As shown in FIG. 1 and also in FIG. 2, the side caps 14 and 16 each include at each end thereof a pair of spacer flanges 28 extending normally from the base element 17 and a locking boss 29 on the inner side of the end walls 21 and 22. Each of the spacer flanges 28 includes a beveled portion 31 angled inwardly from the wall, 21 and 22, respectively, as shown in FIG. 2. The spacer flanges 28 are designed to establish and maintain the proper expanse of the filter element 11 when it is installed into the unit in the expanded state, whereas the locking bosses 29 are provided to secure the filter element in its installed position within the side caps 16 and 17 as will be more clearly explained hereinafter.