Process for making a container of a given shape from sheet material

A process for obtaining a container (100) of a given shape from sheet material, comprising the steps of:

• providing a sheet (110);
• providing a mould (20) having a forming cavity (20A), which defines a reference axis (R) and has a shape corresponding to said given shape of said container (100);
• positioning said sheet (110) over said forming cavity (20A);
• providing a forming device (40) having a first forming member (41) and a second forming member (42) arranged on the side of said sheet opposite to said forming cavity, and operating said first and second forming members for inserting said sheet (110) into said forming cavity (20A) to deform it until a container blank is obtained (101) having a shape approximating said given shape;
• and
• blowing a gas under pressure into said forming cavity (20A) to deform said container blank (101) until said container (100) with said given shape is obtained;
• said process being characterized in that said step of inserting said sheet (110) into said forming cavity includes:
• gripping said sheet between a top surface of said mould and a bottom surface of the forming device;
• setting in contact with said sheet a first operating surface (S1) of said first and second forming members (41, 42) and pushing through said first operating surface (S1) said sheet (110) into said forming cavity (20A), with respect to said top and bottom surfaces, for a first stretch (H1) along said reference axis (R), wherein said sheet is deformed as a result of said pushing through said first operating surface (S1) said sheet (110) into said forming cavity (20A), with respect to said top and bottom surfaces, for a first stretch (H1) along said reference axis (R);
• and
• further pushing said sheet (110) into said forming cavity (20A) by way of a second operating surface (S2) of said first and second forming members (41, 42), which is of smaller size than said first surface (S1), with respect to said top and bottom surfaces, for a second stretch (H2) along said reference axis (R), wherein said first and second forming members (41, 42) can be driven along said reference axis (R) separately or simultaneously and wherein said sheet is further deformed as a result of said further pushing said sheet (110) into said forming cavity (20A) by way of a second operating surface (S2) of a forming member (41, 42), which is of smaller size than said first surface (S1), with respect to said top and bottom surfaces, for a second stretch (H2) along said reference axis (R),
• said process including:
• setting said first and second forming members (41, 42) substantially in one and the same position along said reference axis (R) so that they define together said first operating surface (S1);
• in this condition, feeding with respect to said top and bottom surfaces said first and second forming members (41, 42) in a fixed way with respect to one another along said reference axis (R), for said first stretch (H1);
• and
• keeping said first forming member (42) stationary and further feeding said second forming member (41) along said reference axis (R), with respect to said top and bottom surfaces, for said second stretch (H2), one end (41A) of said second member defining said second operating surface (S2), wherein, in said forming device (40):
• said first and second forming members (41, 42) are mounted inside one another in a telescopic way;
• and
• said first forming member (42) has a tubular conformation, and said second forming member (41) has a cylindrical conformation, said first and second members (41, 42) presenting the corresponding axes aligned with said reference axis;
• said process including:
• setting corresponding ends (41A, 42A), facing said mould cavity (20A), of said first and second forming members (41, 42) substantially in one and the same position along said reference axis (R) to form said first operating surface (S1),
• in said condition, feeding said first and second forming members (41, 42) with respect to said top and bottom surfaces, along said reference axis (R), in a fixed way with respect to one another, for said first stretch (H1);
• and
• keeping said first forming member (42) stationary, and feeding said second forming member (41) with respect to said top and bottom surfaces, further along said reference axis (R), for said second stretch (H2), getting said second forming member (41) to project from said first forming member (42).