Block bottom bag

Claim 1

A BAG WHICH IS FOLDABLE INTO A FLAT CONDITION WHEN EMPTY AND HAS A PARALLELEPIPEDAL SHAPE WHEN FILLED, SAID BAG COMPRISING, WHEN EMPTY, A FLATTENED TUBE FORMED FROM HEAT-SEALABLE THERMOPLASTIC MATERIAL AND HAVING PARALLEL ENDS WHICH ARE AT RIGHT ANGLES TO THE AXIS OF THE TUBE, A FIRST FOLD LINE EXTENDING TRANSVERSELY ACROSS ONE SIDE OF SAID TUBE NEAR EACH END THEREOF, THE FIRST FOLD LINES BEING PARALLEL TO ONE ANOTHER AND EQUIDISTANTLY SPACED FROM THEIR RESPECTIVE ENDS OF THE TUBE, A SECOND SET OF FOLD LINES IN EACH SIDE OF THE TUBE EXTENDING AT AN ANGLE OF 45 DEGREES TO THE AXIS OF THE TUBE FROM THE TWO POINTS OF INTERSECTION OF EACH OF SAID FIRST FOLD LINES WITH THE SIDES OF SAID TUBE, AND A RECTANGULAR BOTTOM FOR EACH END OF THE TUBE, EACH BOTTOM BEING FORMED FROM THERMOPLASTIC HEAT-SEALABLE MATERIAL AND BEING NON-INTEGRAL WITH SAID TUBE, EACH OF SAID BOTTOMS BEING JOINED BY AT LEAST THREE LINES OF HEAT-SEALING, EXTENDING ALONG THREE OF ITS EDGES, TO THREE OF THE EDGES OF THE RECTANGLE FORMED BY SEPARATING ONE OF THE ENDS OF THE TUBE AND FOLDING IT (A) ALONG THE FIRST FOLD LINE AND (B) ALONG THE TWO FOLD LINES AT 45 DEGREES THERETO, IN WHICH A GENERALLY RECTANGULAR INWARDLY EXTEINDING VALVE FLAP, OF THE SAME WIDTH BUT SHORTER LENGTH THAN THE RECTANGLE FORMED BY SEPARATING AND FOLDING ONE OF THE ENDS OF THE TUBE, IS INTERPOSED BETWEEN SAID RECTANGLE AND THE RECTANGULAR BOTTOM JOINED TO SAID RECTANGLE, IS ALIGNED WITH SAID RECTANGLE AT ONE CORNER THEREOF AND IS JOINED TO SAID CORNER OF SAID RECTANGLE BY THREE LINES OF HEAT-SEALING EXTENDING ALONG THE THREE OUTER EDGES OF ITS PERIPHERY, AND IN WHICH THE SAID VALVE FLAP IS JOINED TO SAID RECTANGULAR BOTTOM BY LINES OF HEAT-SEALING EXTENDING ALONG TWO OF THE THREE OUTER EDGES OF ITS PERIPHERY BUT NOT ALONG THE THIRD ONE, AND IN WHICH SAID VALVE FLAP IS ADDITIONALLY JOINED TO SAID RECTANGULAR BOTTOM BY TWO PARALLEL LINES OF HEAT-SEALING EXTEINDING PARALLEL TO BUT INWARDLY SPACED FROM THE SAID TWO LINES OF HEATSEALING JOINING EDGES OF THE RECTANGULAR VALVE FLAP TO THE RECTANGULAR BOTTOM.