Flexible storage device for packaging particulate solid substances or liquids, method for manufacturing this device and packaging method using this device

A flexible storage device (1), for the packaging of particulate solids or liquids, having a bottom and side walls defining a substantially parallelepiped storage volume, said apparatus comprising:

• suspension loops (25) in the upper part for lifting
• a unit (3) comprising:
• a flexible outer envelope (30), forming at least the four side walls (31, 32, 33, 34) of the storage volume, and optionally the bottom wall of the storage volume,
• a tubular, flexible inner envelope (40), secured by vertical attachment lines (41, 42, 43, 44) on the four side walls (31, 32, 33, 34) of the outer envelope (30) dividing the storage volume into five vertical compartments (C1, C2, C3, C4, C5), including a central compartment C1, defined by the interior volume of the inner envelope, and four peripheral compartments (C2, C3, C4, C5), respectively defined between the side walls of the outer envelope (30) and the side walls of the inner envelope (40), and wherein the inner envelope (40) has an upper edge (50) defining the upper mouth of said central compartment C1 and a lower edge (51) defining the lower mouth of said central compartment (C), the upper edge (50) of the inner envelope (40) being located at the same height or below the upper edge of the side walls of the storage volume, so that the upper edge (50) of the inner envelope constitutes an overflow allowing the discharge of material from the central compartment C1 to the peripheral compartments (C2 to C5),
• and wherein the outer envelope (30) is constituted by a first polymer film and the inner envelope (40) is constituted by a second polymer film, said vertical attachment lines being the weld lines between the first polymer film and the second polymer film.