Abstract A particulate filter bed in which the particles define a generally uniform gradient of removal ratings of decreasing coarseness from top to bottom, and a method of producing the filter particles therefor are provided. The bed comprises a multiplicity of particles of uniformly decreasing size and increasing specific gravity from top to bottom. The particles have cores of approximately equal size and specific gravity and outer coatings of varying thicknesses, but equal specific gravity. The specific gravity of the outer coating is substantially less than the specific gravity of the core, so that the overall specific gravity of the larger particles is less than that of the smaller particles. The method comprises encapsulating the higher specific gravity core material with lesser specific gravity material by spray coating or the like.
Particulate filter media according to claim 1, in which the specific gravity of the core material is at least twice the specific gravity of the outer coating material.
Claim 2
Dependent Claim
16 words
Particulate filter media according to claim 1, in which the outer coating material is thermoplastic resin.
Claim 3
Dependent Claim
15 words
Particulate filter media according to claim 1, in which the core material is silica sand.
Claim 4
Dependent Claim
15 words
Particulate filter media according to claim 1, in which the cores are of irregular shape.
Claim 5
Dependent Claim
43 words
Particulate filter media according to claim 1, in which the cores have diameters in the range of about 0.005 inches to about 0.050 inches; and the overall particle sizes are randomly distributed over the range of about 0.005 inches to about 0.125 inches.
Claim 6
Dependent Claim
140 words
A filter assembly comprising: a housing having an inlet at the top and an outlet at the bottom; and a bed of particulate filter media disposed in the housing in the line of flow from the inlet to the outlet; the particles of said bed defining a generally uniform gradient of decreasing removal ratings ranging from coarser on top to finer on the bottom, said bed comprising a multiplicity of particles of generally decreasing size and increasing specific gravity from top to bottom; said particles having cores of approximately equal size and specific gravity and outer coatings of varying thickness but approximately equal specific gravity, the specific gravity of the outer coating being substantially less than the specific gravity of the core, so that the overall specific gravity of the larger particles is less than that of the smaller particles.