Impregnated fiber air filter and method of making same

Claim 1

AN AIR FILTER CARTRIDGE COMPRISING AN ANNULAR BAND OF TWO CONCENTRICALLY DISPOSED RINGS HAVING MATING SURFACES, SAID RINGS BEING AXIALLY COMPRESSIBLE, EACH RING BEING COMPOSED OF RANDOMLY DISPOSED SYNTHETIC FILAMENTS AND BEING OF THE SAME HEIGHT AND RADIAL THICKNESS, THE INNER RING HAVING MORE FILAMENTS THEREIN AND BEING CLOSELY COMPACTED AND OF A MORE DENSE CHARACTER THAN THE OUTER RING, THE RINGS BEING IMPREGNATED WITH A LIQUID RESIN THROUGHOUT AND ON ALL SURFACES THEREOF BONDING THE FILAMENTS AND THE MATING SURFACES TOGETHER THUS MAKING A RIGID STRUCTURE AND PROVIDING CLOSED END FLAT FACES, A FORAMINOUS RIGID TUBE ENGAGING AND BEING BONDED TO THE INNER SURFACE OF THE INNER RING AND BEING OF LESS HEIGHT THAN THE BAND, EACH BAND HAVING END PORTIONS, THE END PORTIONS BEING COMPLEMENTARILY SKIVED SO THAT WHEN JOINED THE END PORTIONS WILL BE OF THE SAME THICKNESS AS THE REMAINDER OF THE RING, THE ENTIRE BAND BEING IMPREGNATED WITH A FIREPROOFING COMPOUND AND THE CLOSED END FACES COMPRISING A GASKET TO ENGAGE A HOUSING STRUCTURE AND WITH THE RIGID INNER TUBE ALLOWING COMPRESSION OF THE BAND, SEALS THE BAND IN THE HOUSING.