Patent ID: 8876517

Claim:
A filtration apparatus for an extrusion or injection molding machine having a bore for passage of a polymer melt, said filtration apparatus including a slide plate and a sealing device for sealing said slide plate, said sealing device comprising: an annular seal having a sealing surface which abuts against said slide plate, said slide plate being translatable across the bore of the extrusion or injection molding machine, said annular seal having a thrust surface located at an opposite axial end of said seal from said sealing surface, said thrust surface being angled relative to said sealing surface; and a first spring having a length oriented parallel to an axis of the extrusion or injection molding machine and an angled push surface contacting flush to said thrust surface of said annular seal, said push surface being a complete closed ring for biasing said sealing surface of said annular seal against said slide plate, and wherein said first spring having first and second tangs at opposing ends, each of said first and second tangs having a cross-section with an outside surface and an underside surface with its corresponding push surface therebetween, said first and second tangs are always positioned in overlapping relationship so that an outside surface of said first tang contacts said underside surface of said second tang to form a first radial closure against passage of polymer melt upon expansion and contraction of said first spring caused by a change in pressure of polymer melt in the bore, and wherein increasing radial pressure of polymer melt in the bore forces said first spring to expand so that said first spring uniformly transfers the pressure axially through said closed ring of said push surface against said thrust surface of said annular seal causing said sealing surface of said annular seal to be further biased against said slide plate forming a secure annular axial closure.