A process for packing pasty, liquid or semiliquid products, comprising the steps of:
- forward nonstop feeding a pair of sheets (1 ,2), respectively above and under a plurality of injection feeding ducts (3) that feed a pasty, liquid or semiliquid material to be packed (M), said ducts (3) being arranged in an array extending parallel to the forwards run of said sheets (1, 2) and ending in respective injection nozzles (4);
- longitudinally nonstop sealing said pair of sheets (1, 2) to each other by forming continuous beads (5) having spaced widening portions (10), longitudinally sealed at both sides of each of said feeding ducts (3) producing oblong hollow wrappers or sleeves laterally limited by said beads (5);
- forming longitudinally sealed narrowing portions (7) at longitudinally regular intervals on said wrappers or sleeves (6), without shaping higher and lower walls of the oblong wrappers or sleeves, each of said longitudinally sealed narrowing portions (7) having a width sufficient to let pass one of said feeding ducts (3), so that relatively long wide lengths are defined within said wrappers or sleeves (6), said wide lengths (8) are connected to each other by narrow areas (9), corresponding to said longitudinally sealed narrowing portions (7);
- nonstop injecting, under pressure, material to be packed (M) from said nozzles (4) into said wrappers or sleeves (6) to form unit (28) of packed material (M), while the sheets (1, 2) are running forward, and
- closing under pressure and cross sealing at regular intervals said wrappers or sleeves (6) at said narrow areas (9);
- and
- wherein said pair of sheets (1,2) are of a thermoplastic material and the beads (5), together with said widening portions (10) are longitudinally nonstop sealed by welding both sheets (1, 2) through heat and pressure to the areas conforming them, said heat and pressure are respectively provided by a heating roller (11) and a pressing roller (12) having on their respective cylindrical surfaces (13, 14) circumferential grooves (15, 16) facing each other and shaped for configuring said wrappers or sleeves (6), and wherein said sheets (1, 2), sealed to each other, are moved forwards with the higher and lower walls of the wrappers or sleeves (6) leaning on each other, leaving only a central space (8, 9) in said wrappers or sleeves (6) for the passage of the feeding ducts (3) up to the end thereof, where said injection nozzles (4) are located through which the material to be packed (M) is nonstop injected, filling completely and inflating said wrappers or sleeves (6) at said wide lengths (8) and at said narrow areas (9), and
- wherein said higher and lower walls of the wrappers or sleeves (6) at said wide lengths (8) and at said narrow areas (9) are pressed against each other and against the external surfaces of the feeding ducts (3) by means of a pair of closing rollers (20, 21) provided with circumferential grooves (22), facing each other, having a suitable cross section, at their respective cylindrical surfaces, just before where the injection nozzles (4) are located in order to prevent the material (M) from flowing rearwards and the air from entering the wrappers or sleeves (6) which have been filled.