Filter element, unit, cartridge and insert

Claim 1

IN A FILTER HAVING A FILTER ELEMENT COMPRISING TWO FILTER LEAVES SECURED TOGETHER AT THEIR PERIPHERIES OF WHICH LEAVES AT LEAST ONE IS PROVIDED AT ITS INTERIOR WITH AN OUTLET OPENING FOR DISCHARGING FROM THE INTERIOR OF THE ELEMENT LIQUID FILTERED THERINTO THROUGH SAID LEAVES, THE IMPROVEMENT WHICH COMPRISES SPACING MEANS BETWEEN SAID TWO LEAVES, SAID SPACING MEANS HAVING AN INTERIOR APERTURE IN REGISTER WITH SAID OUTLET OPENING, SAID SPACING MEANS CONSISTING OF TWO LAYERS OF SINGLE-FACED CORRUGATED PAPERBOARD WITH THEIR CORRUGATIONS SUBSTANTIALLY AT RIGHT ANGLES TO EACH OTHER, EACH LAYER COMPRISING A CORRUGATED SHEET SECURED TO A FACING SHEET, THE TWO FACING SHEETS BEING IN FACIAL CONTACT, EACH LAYER HAVING CORRUGATIONS WHICH COMMUNICATE WITH SAID APERTURE AND CORRUGATIONS WHICH BY-PASS SAID APERTURE, EACH LAYER HAVING A PLURALITY OF CHANNELS CROSSING SUBSTANTIALLY ALL OF THE CORRUGATIONS WHICH BY-PASS SAID APERTURE, THE CHANNELS OF EACH LAYER EXTENDING THROUGH THE FACING SHEET OF SAID LAYER, THE BOTTOMS OF THE CHANNELS OF EACH LAYER BEING THE FACING SHEET OF THE OTHER LAYER, SAID CROSSING CHANNELS HAVING DIRECT COMMUNICATION WITH SAID APERTURE.