The present invention refers to a method for manufacturing cardboard boxes, and to a box obtained with this method.

A method for manufacturing cardboard boxes, which is described in Spanish Patent application no. 9300188 (PAPER, S.A.), publication number ES 2067382, starts from separate sheets, with lugs on the sides and flaps at the ends facing each other two by two. These sheets are applied onto the external faces of a mandrel, along which the various steps of the method are carried out to provide a rectangular prismatic body whose bases are provided with open flaps and whose edges are reinforced by folded lugs glued to the sides of the body, beside the edges.

In addition to achieving reinforced boxes capable of withstanding the stresses to which they will be subjected during utilization, the method object of the aforesaid patent provides other advantages which are, in summary: the possibility of some sides of the box being of different quality and thickness than the others, or presenting fibres running in different directions in order to withstand stresses in any direction.

Despite these advantages, various tests carried out with this type of box have shown that it is possible to increase their strength and thus extend their field of utilization.

Thus, in order to increase the strength of the boxes manufactured using the method described, the new method constituting the object of the present invention has been developed.

The method of the invention is characterized in that the lugs which project from the sides of the sheets are applied and joined together over chamfered edges provided on the mandrel. These chamfered edges are situated between two adjacent sides of the mandrel.

At least one of the pairs of sheets from which the box is obtained presents prolongations from the respective lugs. These prolongations are applied and joined to an adjacent zone of the sheet, immediately beside the chamfered edges upon which the lugs in question are applied.

In one possible embodiment, all the sheets from which the box is obtained present prolongations from their respective lugs. These prolongations are applied and joined to a zone of the sheet immediately adjacent to the chamfered edges upon which the lugs in question are applied.

The box obtained with the method described is provided with chamfered edges (or chamfers) between its sides and on which are superimposed and glued the folded lugs of the adjacent sheets, forming two cant edges between each pair of sheets.

At least one of the superimposed lugs forming the chamfered edges of the box presents a prolongation folded and glued onto the adjacent side, beside the chamfered edges.

It is further envisaged that each of the superimposed lugs which form the chamfered edges of the box present corresponding prolongations folded and glued onto the adjacent side, beside the chamfered edges.

For a better understanding of all that has been set forth in this specification, there are attached some drawings in which, solely by way of example, a practical case of embodiment of the method and the corresponding box is shown.

In said drawings Figure 1 is a schematic cross-section showing the moulding core and a pair of sheets with their lugs prior to application against the chamfered edges of the moulding core; Figure 2 is a similar view showing another pair of sheets with their lugs extended, on the point of being applied and glued to the lugs of the first two sheets; Figure 3 is a view similar to the previous two, showing the lugs which form each chamfered edge glued together; Figure 4 is a view similar to that of Figure 3, but in this example two of the sheets have their corresponding prolongations folded and glued to the adjacent sheets; Figure 5 is a view very similar to that of Figure 4, but in this case it is the other two sheets which present the corresponding prolongations to their lugs; Figure is a view similar to those of Figures 4 and 5, showing a version in which all the sheets present lugs with prolongations folded and glued to the adjacent sides; Figure 7 is a perspective view showing one of the chamfered edges of the box obtained according to the method of the invention.

The method for manufacturing of boxes consists, according to the representation shown in the drawings, in applying successively two pairs of sheets -1- and -2- against the sides of a moulding core -3- provided with chamfered edges -4- situated between sides -5- of the moulding core. The sheets -1- have some lugs -6- on both sides, while the sheets -2- have similar lugs -7-. Optionally, the lugs -6- and -7- have prolongations -6a- and -7a-, respectively.

It is envisaged that at least the lugs -6, 7- and, optionally, their prolongations -6a, 7a-, together with the zones of the sheets -1, 2- immediately adjacent to the respective lugs, be glued. Then the application of these lugs and, optionally, their prolongations, against the chamfered edges -4- of the moulding core -1- and against the sides -5- of same is carried out, using countermoulds, rollers or any other similar mechanism (not shown). Finally the body obtained is removed from the moulding core -1-, and constitutes the box, whose particular feature consists in it being provided with reinforced chamfered edges -8-, formed by the lugs -6, 7- glued together, which alternate with sides -9- (Figure 7).

If the lugs -6, 7- have prolongations -6a, 7a-, the sides -9- will also be reinforced by said prolongations glued beside the chamfered edges -8-.

In any case, between the chamfered edges -8- of the box are formed pairs of cant edges -8a- which lend the box a great stiffness, so that it withstands the compression stresses to which it will be subjected during utilization.