Method and apparatus for forming carton blanks with hemmed edges

In a paper box folding machine for forming individually and successively planar carton blanks into folded cartons, said machine including conveyor means for transporting successive, spaced blanks along a paper line axis in a horizontal plane and means for forming a coplanar edge portion of each carton blank parallel to the paper line axis into a hemmed edge, at least said edge portion having upper and lower sides thereof coated with a thermoplastic coating and said edge portion being divided into inner and outer halves that extend parallel to the paper line axis with the inner half being intermediate the outer half and the remainder of the blank, the improvement of apparatus for acting seriatim to form a hemmed edge on each blank, said hemmed edge forming apparatus comprising:

• A. skiving means for removing at least 50% of the blank from the lower side of the outer half of the edge portion,
• B. scoring means for forming a score line in the blank parallel to the paper line axis and at the boundary of the outer and inner halves of the edge portion,
• C. first folding means for folding the outer half about the score line onto the lower side of the inner half,
• D. means for compressing the folded outer and inner halves,
• E. second folding means for returning the outer half of the edge portion to lie in a substantially vertical predetermined plane,
• F. air supply means for providing superheated air,
• G. air directing means located below the plane of the paper line axis for directing a series of air streams toward the lower side of inner half of the edge portion, each said air stream being formed as a planar stream elongated to be parallel to, and said air streams being spaced along a line parallel to, the paper line axis thereby to limit activation of thermoplastic coating to that present on the lower side of the inner half of the edge portion,
• H. third folding means for folding the outer half of the edge portion onto the lower side of the inner half,
• I. means for tacking the outer half to the inner half, and
• J. sealing means for pressing the outer and inner halves of edge portion thereby to effect a seal therebetween whereby substantially all of the skived outer half seals to the thermoplastic coating on the inner half of the edge portion.

In a method for forming individually and successively planar carton blanks into folded cartons as they are transported in successive, spaced fashion along a paper line axis wherein each carton has a coplanar edge portion with opposite sides to be formed into a hemmed edge and has, on at least opposite sides at said edge portion, a thermoplastic coating and said edge portion being divided into inner and outer halves that extend parallel to the paper line axis with the inner half being intermediate the outer half and the remainder of the blank, the improvement steps for forming the hemmed edge comprising:

• A. skiving the outer half of the edge portion,
• B. stably positioning the outer half of the edge portion of a blank in a predetermined plane that intersects the plane of that blank and that exposes the inner half of the edge portion,
• C. activating exclusively the thermoplastic coating at the inner half of the edge portion adjacent the skived portion, and
• D. sealing the skived outer half of the edge portion onto the inner half thereby to seal substantially all of the skived outer half to the thermoplastic coating on the inner half of the edge portion.

A method forming a hemmed edge along one edge of a paper box planar carton blanks as they are formed individually and successively into folded cartons during transport along a paper line axis in a horizontal plane, at least each edge portion of each blank having upper and lower sides thereof coated with a thermoplastic coating and said edge portion being divided into inner and outer halves that extend parallel to the paper line axis with the inner half being intermediate the outer half and the remainder of the blank, said method comprising the steps of:

• A. skiving at least 50% of the blank from the lower side of the outer half of the edge portion,
• B. scoring a line in the blank parallel to the paper line axis and at the boundary of the outer and inner halves edge portion,
• C. folding the outer half of the edge portion about the score line onto the lower side of the inner half thereby to form a hem,
• D. compressing the folded outer and inner halves of the edge portion,
• E. opening the hem to return the outer half of the edge portion to lie in a substantially vertical, predetermined plane,
• F. directing a series of superheated air streams toward the lower side of inner half of the edge portion, the air streams being formed as individual laminar-like air streams elongated and spaced along a line parallel to the paper line axis thereby to limit activation of thermoplastic coating to that present on the lower side of the inner half of the edge portion,
• G. producing a third folding of the outer half of the edge portion half onto the lower side of the inner half,
• H. tacking the outer half to the inner half, and
• I. pressing the outer and inner halves of edge portion thereby to effect a seal therebetween whereby substantially all of the skived outer half seals to the thermoplastic coating on the inner half of the edge portion.