Sealing supported by pressurized air

A sealing station comprising:

• a lower tool provided with a lower sealing surface;
• an upper tool provided with an upper sealing surface and arranged above the lower tool;
• a drive unit configured to move the lower tool and the upper tool towards each other, or to move one of the lower and upper tools toward the other, so that a packaging tray and a cover film for closing the packaging tray may be pressed together between the lower sealing surface and the upper sealing surface when the packaging tray and the cover film are positioned between the lower tool and the upper tool;
• a pressurized-gas source;
• a valve;
• and
• a control unit;
• wherein the lower sealing surface or the upper sealing surface has provided therein a pressurized-gas aperture, which is configured to allow an escape of pressurized gas provided by the pressurized-gas source, the valve is configured to selectively prevent or allow a flow of the pressurized gas from the pressurized-gas source to the pressurized-gas aperture, and the control unit is configured to control the drive unit for pressing the packaging tray and the cover film together by means of the lower sealing surface and the upper sealing surface and to control the valve for allowing the flow of the pressurized gas to the pressurized-gas aperture after the cover film and the packaging tray have been pressed together at least for a predetermined first period of time.

A method of closing a packaging tray, the method comprising:

• arranging a packaging tray, which is filled with a product to be packed, between a lower tool and an upper tool of a sealing station;
• positioning a cover film above the packaging tray between the lower tool and the upper tool of the sealing station;
• and
• pressing together the cover film and the packaging tray by a lower sealing surface of the lower tool and an upper sealing surface of the upper tool cooperating with the lower sealing surface, a connection between the cover film and the packaging tray being established along a sealing seam during the pressing together;
• wherein an overpressure is locally generated by supplying pressurized gas from a pressurized-gas source while the cover film and the packaging tray are being pressed together, the overpressure cooperating as a counterpressure with the lower sealing surface or with the upper sealing surface so as to press the cover film and the packaging tray together, wherein the packaging tray comprises at least two superimposed material layers, and wherein the overpressure is generated in an area in which at least one material layer of the packaging tray is omitted.