Pleated filter element and integral shield and method for making same

The method of making a filter element characterized by the steps of:

• providing a cylindrical receptacle having inwardly facing annular flanges to define a circumferentially extending basin;
• placing liquid plastic material of a foamable character in said receptacle;
• rotating said cylindrical receptacle about its longitudinal axis to distribute said plastic material evenly about the inner cylindrical surface of said basin;
• suspending a paper filter media having a plurality of V-shaped pleats radially within said receptacle and spaced a selected distance from said liquid plastic material;
• foaming said plastic material and expanding its volume so that said plastic material contacts said filter media at the apex of each V-shaped pleat to embed each pleat therein;
• and
• solidifying said plastic material into an annular shape-retaining solid such that said filter media is integrally bonded to said plastic and forms a unitary structure.

An integral filter element comprising:

• a sheet of filtering media, said filtering media sheet having a multiplicity of substantially parallel elongated folds therein, said folds being successively disposed in opposite directions to provide a plurality of elongated V-shaped pleats in said filtering media sheet, said pleats defining like-disposed folds, said sheet being joined at its ends and rolled to define an annular filter with its pleats parallel to the axis of the annulus;
• and
• a fluid-permeable, shape-retaining, structurally self-supporting shield circumscribing the outside of said annular filter and integrally bonded to the like-disposed folds of said filtering media sheet, said shield being formed of a shape-retaining, structurally self-supporting, fluidpermeable cellular plastic and laterally extending from one like-disposed fold to the next adjacent like-disposed fold so as to space apart said folds, said shield further extending longitudinally along said like-disposed folds and providing a substantially continuous bond between said shield and said like-disposed folds to restrain like-disposed folds from movement relative to said shield, said bond being formed by partially embedding the apex of each V-shaped pleat into said shield during the transition of the shield from a foamed liquid to said shape-retaining solid, said shield being of a closed-cell character, said shield including a multiplicity of perforations therethrough.