Filter

Claim 1

A FILTER FRAME COMPRISING AN INTEGRAL BASE MEMBER HAVING ONE WALL IN THE FORM OF A CLOSED FIGURE AND SPACED INNER AND OUTER FLANGES PERPENDICULAR TO SAID WALL EXTENDING AROUND THE PERIMETER OF SAID WALL, A TOP MEMBER COMPRISING A PLURALITY OF PARTS ADAPTED TO FIT WITHIN THE PERIMETER OF SAID OUTER FLANGE WITH THE ENDS THEREOF IN ABUTTING RELATIONSHIP, EACH OF SAID PARTS HAVING AN OUTER WALL WITH ITS LOWER EDGE FITTING SNUGLY BETWEEN SAID FLANGES AND HAVING A SURFACE TO SURFACE ENGAGEMENT WITH BOTH OF SAID FLANGES, AND INTERENGAGEABLE MEANS ON SAID OUTER WALL AND ONE OF SAID FLANGES TO HOLD SAID FRAME MEMBERS AGAINST ACCIDENTAL SEPARATION, EACH OF SAID PARTS HAVING A WALL SECTION PARALLEL TO THE WALL OF SAID BASE MEMBER INWARDLY OF SAID INNER FLANGE, AND LONGITUDINALLY EXTENDING RIBS ON THE WALL OF SAID BASE MEMBER AND SAID WALL SECTION PROJECTING TOWARD EACH OTHER, THE RIBS ON THE WALL OF SAID BASE MEMBER AND THE RIBS ON SAID WALL SECTION BEING OFFSET RELATIVE TO EACH OTHER AND OVERLAPPING VERTICALLY WHEN SAID BASE AND TOP MEMBERS ARE ASSEMBLED, WHEREBY THE RIBBED PORTIONS OF THE WALL OF SAID BASE MEMBER AND SAID WALL SECTION ARE ADAPTED TO COOPERATE WITH EACH OTHER TO HOLD AN EDGE OF A FILTER MEDIA BETWEEN SAID FIRST MENTIONED WALL AND SAID WALL SECTION.