Process for closing a container in metal sheet

A process for closing a container in metal sheet, of the type which comprises a tubular body formed by a peripheral lateral wall having an upper end portion and a lower end portion, to which an upper end wall and a lower end wall are respectively affixed, characterized in that it comprises the steps of:

• conforming a metal sheet portion to define the peripheral lateral wall of the tubular body;
• conforming the peripheral lateral wall so as to provide, in its upper end portion, an upper peripheral edge which is outwardly and downwardly bent, defining an upper retention hook with a profile in the form of an inverted U;
• and, in its lower end portion, a lower peripheral edge which is bent to define a lower retention hook;
• peripherally affixing the lower end wall to the lower retention hook of the tubular body;
• conforming a metal sheet portion to define an upper end wall having a median panel and a peripheral upper skirt which presents an end edge which is outwardly, downwardly and inwardly bent, so as to define an upper closure hook with a profile in the form of an inverted U;
• fitting and seating the peripheral upper skirt in the interior of the upper end portion, with the container being empty or already filled with the product, so as to seat the upper closure hook onto the upper retention hook sandwiching an elastic sealing element previously provided between said hooks;
• and
• submitting the upper closure hook and the upper retention hook and also a portion of the peripheral upper skirt and a confronting region of the upper end portion to a simultaneous deformation operation, in order to seam the upper closure hook onto the upper retention hook, compressing the elastic sealing element, and to form at least one outer circumferential retention rib in the peripheral upper skirt and a corresponding inner circumferential retention groove in the upper end portion of the peripheral lateral wall, tightly fitting the retention rib.