Pocket type filter

Claim 1

A pocket type fluid filter comprising: two approximately equal sized sections of a fibrous fluid-permeable batt-scrim laminate, said scrim portion of said laminate being a thermoplastic material; a heat seal joining said sections of laminate together in facing relationship along their abutting outer side peripheries and closed at one end to define a pocket filter, said outer side peripheries being folded over upon themselves to form four layers of batt scrim laminate, the remaining portion of their outer peripheries forming an open upstream entrance means, said heat seal being comprised of two portions: (1) a fluid impermeable scrim-impregnated batt portion, and contiguous thereto, (2) a fluid impervious thermoplastic portion defining the outer extremity of said seal, said heat seal being effective to secure the outer peripheries of said laminate sections together in a fluid impervious seam and prevent fluid leakage therethrough; and selectively spaced fluid impervious seams forming a plurality of parallel pockets joining said sections of batt scrim laminate, said seams being essentially normal to said entrance means and extending a major portion of the distance from the downstream most juncture of said sections toward said entrance means.