Patent ID: 7563301

Claim:
A filter comprising: a hollow frame comprising a first face, a second face and an interior passageway extending therebetween; a first screen extending across the passageway at the first face; a first partial-depth, open-cell stabilizer extending across and into the passageway, wherein the stabilizer comprises a matrix formed by a plurality of walls defining a plurality of open cells therebetween, a second screen extending across the passageway at the second face; a second partial-depth, open-cell stabilizer extending across and into the passageway, wherein the stabilizer comprises a matrix formed by a plurality of walls defining a plurality of open cells therebetween; and granular filter materials tightly packed within the passageway, between the first screen and the second screen; wherein the distance between the first screen and the second screen defines the depth of the filter; wherein the aggregate depth of the first partial-depth, open-cell stabilizer and the second partial-depth, open-cell stabilizer are collectively less than the depth of the filter; and wherein the depths of the first and second partial-depth, open-cell stabilizers, the number, size and cross-section of their open cells, the depth of the filter, the composition of the granular filter materials, and the tightness of packing of the granular filter materials, are all balanced vis-à-vis one another in order to provide improved stabilization for the granular filter materials without creating excessive wall chimney effects.