Filtration apparatus with a sealing device

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, the slide plate being translatable across the bore of the extrusion or molding machine, said annular seal having a thrust surface located at an opposite axial end of said seal from the sealing surface, said thrust surface being angled in relation to said sealing surface;
• and
• a spring assembly including first and second springs with each spring having a length oriented parallel to an axis of the extrusion or injection molding machine, each spring further having a gap, an outside surface, an underside surface, and a push surface between said outside and underside surfaces, and said second spring being positioned within an inside diameter of said first spring in overlapping relationship wherein said gap of said second spring is oriented so as not to overlap said gap of said first spring thereby forming a first radial closure between said first and second springs to seal against passage of polymer melt upon expansion and contraction of said springs caused by a change in pressure of polymer melt in the bore, and further wherein said push surfaces of said first and second springs form a closed ring contacting flush to said thrust surface of said annular seal, so that increasing pressure of polymer melt in the bore forces said closed ring of said push surfaces of the first and second contacting springs to move against said thrust surface of said annular seal causing said annular seal to be uniformly biased against said slide plate to secure the axial closure.

A filtration apparatus for an extrusion machine or injection molding machine having a bore for passing molten resin, said filtration apparatus including a slide plate and a sealing device for sealing the 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 in relation to said sealing surface;
• and
• a spring means having a length oriented parallel to an axis of the extrusion or molding machine establishing a barrier to form a dynamic radial closure to prevent radial passage of molten resin upon expansion and contraction of said spring means caused by a change in pressure of molten resin in the bore, and wherein said spring means includes a push surface contacting said thrust surface in a closed ring that is pressed against said thrust surface, being operable so that increasing pressure of polymer melt in the bore is transferred by said push surface of said spring means against said thrust surface of said annular seal causing said annular seal to be further biased along the axis of the extrusion or molding machine and against said slide plate for a secure axial closure between said sealing surface of said annular seal and said slide plate.