Heating device for heat-sealing bottom portions of containers

A heat device for heat-sealing bottom portions of containers comprising a hot air nozzle positionable as opposed to a bottom forming end portion of a tubular blank for heating a region of the blank end portion, at least one of the end portion and the hot air nozzle being movable toward and away from the other, the hot air nozzle having a plurality of orifices, the orifices of the hot air nozzle being directed toward a plurality of parts within the region when the nozzle is positioned close to the end portions, the heating device being characterized in that the nozzle orifices comprises first orifices directed toward a first part of the region remote from an extremity of the blank when the blank is so positioned and second orifices directed toward a second part of the region proximate to the blank extremity when the blank is so positioned,

• said first orifices being of greater diameter than said second orifices,
• a first open area ratio being a ratio of total area of the first orifices to an entire area of the first part, a second open area ratio being a ratio of total area of the second orifices to an entire area of the second part,
• said first open area ratio being greater than said second open area ratio.