Filter leaf support structure

Claim 1

IN A FILTER LEAF OF THE TYPE IN WHICH A RIGID SUPPORT IS SANDWICHED BETWEEN FILTERING SEPTA, A SUPPORT STRUCTURE CONSISTING ESSENTIALLY OF PAIR OF SHEETS OF PLASTIC MATERIAL EACH FORMED TO DEFINE A CORRUGATED FILTER LEAF WALL PERIPHERALLY SURROUNDED BY A U-SHAPED MARGINAL PORTION, SAID SHEETS BENG BONDED TOGETHER WITH THE PEAKS OF THE CORRUGATION AND THE EDGES OF THE MARGINAL PORTIONS OF ONE SHEET SECURED IN FACE TO FACE RELATION TO THE PEAKS OF THE CORRUGATIONS AND EDGES OF THE MARGINAL PORTIONS OF THE OTHER SHEET, THE CORRUGATIONS OF THE UNITED SHEETS BEING ARRANGED VERTICALLY TO DEFINE A SET OF VERTICAL CHANNELS UNDERLYING EACH SEPTUM, AND THE U-SHAPED MARGINAL PORTIONS OF THE UNITED SHEETS FORMING A STRENGTHENING AND RIGIDIFYING TUBULAR BORDER ABOUT THE PERIPHERY OF THE LEAF, THE TUBULAR BORDER AT THE BOTTOM ARGIN OF THE LEAF DEFINING A HORIZONTAL FILTRATE-COLLECTING CONDUIT, SAID WALLS HAVING OPENINGS ESTABLISHING FLOW PASSAGES BETWEEN THE LOWER ENDS OF SAID CHANNELS AND THE INTERIOR OF SAID CONDUIT, AND A DRAIN CONNECTED TO SAID CONDUIT.