Internally supported multi-stage sleeve filter

A self-supporting, self-gasketing, multi-stage, variable density fiber glass sleeve filter of rectangular configuration comprising:

• a. a rigid, rectangular, internal reusable wire frame;
• b. a composite, low velocity, fluid entry filter member on one side of said frame having a first fluid permeable, puffed glass fiber outer filter layer and a second fluid permeable, puffed glass fiber inner filter layer contiguous with said first filter layer and positioned inwardly thereof;
• c. said first fluid permeable filter layer defining the fluid entry surface of the filter and having a thickness and density less than the thickness and density of said second fluid permeable filter layer;
• d. a fluid egress member disposed on the other side of said frame comprising a flat, fibrous surfacing mat having a thickness less than the thickness of either of the layers of said entry filter;
• e. said entry filter member and said egress filter member each extending transversely beyond the longitudinal edges of said frame and being joined to one another by stitching exteriorly of said frame along longitudinal edge portions on opposed sides thereof so as to form an open ended sleeve that can be slid on and off of said reusable frame;
• and
• f. said sleeve being dimensional such that when it is slid onto said frame, the fluid entry layer is tensioned across said wire frame and assumes an outwardly curved configuration with respect to said fluid egress member, said fluid egress member lying flat and tensioned across said frame.