Cartridge filter

Claim 1

A CARTRIDGE FILTER OF THE TYPE WHICH IS INTENDED TO BE IMMERSED IN THE FLUID TO BE FILTERED, COMPRISING: A FILTER ELEMENT COMPRISING TWO ELONGATED FACES OF FILTERING MATERIAL OF SMALL THICKNESS, A FURROWED INTERCALARY STRIP INTERPOSED BETWEEN SAID SUPPORTING SAID FILTERING MATERIAL FACES AND DEFINING THEREWITH A SERIES OF DUCTS WHICH EXTEND BETWEEN THE OUTER SIDE EDGES OF SAID FACES AND THE INNER EDGES OF SAID FACES THE SPACE BETWEEN SAID OUTER SIDE EDGES OF SAID FACES, BEING CLOSED AND THE SPACE BETWEEN SAID INNER SIDE EDGES OF SAID FACES BEING OPEN WHEREBY FLUID CAN FLOW THROUGH SAID DUCTS AND THROUGH THE SPACE BETWEEN SAID INNER SIDE EDGES; THE FILTER ELEMENT BEING FOLDED ABOUT FOLD LINES EXTENDING BETWEEN SAID SIDE EDGES SO THAT THE ELEMENT IS DIVIDED INTO HINGEDLY CONNECTED SECTIONS WHICH ALTERNATELY EXTEND IN OPPOSITE DIRECTIONS IN A GENERALLY ZIG-ZAG FASHION; THE FILTER ELEMENT BEING FOLDED, CURVED AND POSITIONED SO THAT SAID INNER SIDE EDGES OF EACH OF SAID SECTIONS ARE SUBSTANTIALLY PARALLEL TO EACH OTHER AND TO THE INNER SIDE EDGES OF THE ADJACENT SECTIONS AND FORM A CYLINDRICAL OPENING, THE INNER SIDE EDGES OF EACH SECTION BEING IN CONTINUOUS, FLUID-SEALING ENGAGEMENT WITH THE CORRESPONDING PARALLEL INNER SIDE EDGES OF THE ADJACENT SECTIONS BETWEEN THE FOLD LINES WHEREBY FLUID FLOW BETWEEN SAID SECTIONS INTO SAID CYLINDRICAL OPENING IS PREVENTED; THE FILTER ELEMENT FORMING SUBSTANTIALLY AN ANNULUS OF SUBSTANTIAL DEPTH CONSISTING OF A SINGLE LAYER OF THE FILTER ELEMENT; A PAIR OF COVERS SECURED TO THE OPPOSITE ENDS OF SAID FILTER ELEMENT ADJACENT SAID FOLD LINES AND OVERLYING OPPOSITE ENDS OF SAID CYLINDRICAL OPENING, AT LEAST ONE OF SAID COVERS HAVING CONDUIT MEANS ASSOCIATED THEREWITH IN FLUID-FLOW COMMUNICATIN WITH SAID CYLINDRICAL OPENING; SAID DUCTS BEING IN FLUID-FLOW COMMUNICATION WITH SAID CYLINDRICAL OPENING.