Filter assembly

Claim 1

A filter assembly which comprises (A) a housing interposed between opposed, aligned end surfaces of a polymer melt inlet manifold and a polymer melt outlet manifold; (B) at least two filter pods, each containing a plurality of filter elements, the pods being retained within said housing in side-by-side relationship, and adapted to be moved successively into tight register with inlet and outlet manifolds to define alternate polymer melt flow paths and a plurality of intermediate polymer melt flow paths in which varying proportions of adjacent pods are utilized; (C) a primary seal device, located in a rabbet at at least one of the interfaces of the inlet and outlet manifolds with the housing, and having a cross-section the outer surface of which is generally U-shaped, the dimensions of the device being such that (i) the convex surface of the device defines part of the polymer melt path, (ii) one outer surface of the member providing one leg of the U-shape bears against the wall of the rabbet, and (iii) the surface providing the other leg of the U-shape provides a sealing surface which bears against an opposed wall to form a seal between the housing and the manifold, the tightness of which is determined in part by the pressure exerted in use by the melt flow on the convex surface of the device, (D) means for achieving a controlled movement of the filter pods into successive exclusive register with the inlet and outlet manifolds; and (E) means connecting inlet and outlet manifolds adapted to urge the manifolds axially towards and away from each other so as to tighten the seal at the interfaces of the manifolds and the interposed housing.