Mold base provided with a central movable insert

Method for manufacturing a container (2) that has a bottom (8) that is provided with a seat (9) and a central area (10) that is raised in relation to the seat (9), by blow molding or stretch blow molding, in a mold (1) of a blank (3) made of plastic material that was heated in advance to a temperature that is higher than the glass transition temperature of the material, which method comprises:

• An operation for inserting the blank (3) into said mold (1), which mold comprises a side wall (16) that bears the impression of a body (4) of the container (2) and a mold base (20) that completes, with the side wall (16), the impression of the container (2) that is to be obtained, with this mold base (20) comprising a base unit (21) that has a molding face (22) in relief bearing the impression of at least the seat (9) of the container (2) and is provided with a central opening (28), with this mold base (20) also comprising an insert (29), mounted in the central opening (28) and provided with an end face (30) that bears the impression of the central area (10) of the bottom (8) of the container (2), which insert (29) can be moved in relation to the unit (21) between:
• A retracted position in which the end face (30) extends in continuation of the molding face (22) of the unit (21), thus completing with the latter the impression of the bottom (8) of the container (2);
• A protruding position in which the insert (29) projects in relation to the central opening (28);
• further comprising:
• A pressurization phase that comprises the injection, in the blank (3), in the retracted position of the insert (29), of a pressurized fluid to form the container (2);
• A depressurization phase that comprises the linking of the thus formed container (2) with the atmosphere,
• A boxing operation of the central area (10) of the bottom (8) of the container (2) that is thus formed and that consists, during or after the depressurization phase, in moving the insert (29) toward its protruding position in such a way as to exert pressure against said central area (10) of the bottom (8) of the container (2) and to increase the clearance of said central area (10) in relation to the clearance that it has at the end of the blow molding.