Apparatus and method to form hollow containers

Method to form hollow containers suitable in particular to contain one or more liquid or semi-liquid food products, starting from parisons made of thermoplastic material, wherein said method comprises:

• a step of positioning one of said parisons in a matrix defined by a pair of molds cooperating with each other to define a cavity, shaped like the container to be made, and a support channel, configured to define an additional portion of said container intended to be removed to allow said container to be filled, said support channel being connected to said cavity in correspondence with a connection zone and being provided with an aperture, on the opposite side with respect to said cavity, in communication with the outside;
• a step of introducing a forming punch, in a direction parallel to a longitudinal axis, through said support channel in said cavity, to thrust and blow said parison against the walls of said cavity to form said container, and against the walls of said support channel to form said additional portion, said forming punch having an extension in the direction of said longitudinal axis and being provided with a thrusting end portion which is introduced into said cavity;
• wherein at the end of said introduction step, said thrusting end portion contacts said container in the process of being formed, at least in correspondence with said connection zone to confer a desired size on it, and a cutting portion of said forming punch, positioned upstream of said thrusting end portion, delimits said parison in correspondence with said aperture, and an auxiliary portion of said forming punch which is interposed between said thrusting end portion and said cutting portion (19), to allow said thrusting portion (18) to reach and contact said connection zone;
• and
• a step of extracting said forming punch from said cavity through said support channel in a direction parallel to said longitudinal axis, when the forming of said container and of said additional portion is completed.