Sideseam joint for a carton

Abstract

Unwanted adhesion between a second panel and a first panel attendant the formation of the sideseam joint is eliminated by providing the second panel with a notch. The notch corresponds in form to the triangular notch or truncated portion at the tapered end of the sideseam forming fifth panel. In this way, when compression of the first panel against the sideseam panel occurs, there is no hot and sticky exposed area of the first panel which will adhere to the second panel.

Description

This application is a continuation of Ser. No. 09/928,359, filed on Aug. 14, 2001, now abandoned.

BACKGROUND OF THE INVENTION

This invention relates to paperboard containers of the type often used for the packaging of liquids such as milk and fruit juices. Such containers are fashioned from a unitary blank of paperboard, usually coated on both its interior and exterior surfaces with one or more barrier layer materials, cut and scored, erected and filled on automatic machinery to form gable top liquid packages. Such containers have a flat bottom and a gable top upper or roof section, the latter being adapted to form a pour spout when opened, all as known. An intermediate step in making such containers is the formation of a tube structure from the blank, with the steps of forming the end closures and filling with liquid taking place after tube formation.

In the formation of a gable top containers from a unitary blank having a plurality of wall forming panels serially arranged, one step involves forming a tube by folding the blank so that the fifth or sideseam forming panel is superposed over an edge zone of the free edge portion of the first sidewall forming panel. A part of the carton interior forming surface of the first panel has been heated so as to partially melt the usual polyethylene coating and make the latter sticky. Similarly, that portion of the fifth or sideseam panel which is to be in surface contact with the first panel free edge zone has also been heated so as to make its polyethylene coating sticky. The transverse cross sectional configuration of the now folded blank is substantially that of a shallow diamond, with a force applied to the upper two panels collapsing the diamond shaped tube, resulting in a force applied to the sideseam flap or panel to seal it to the edge zone portion of the first panel.

Often, the sideseam is skived, with the particular skiving process/apparatus employed unavoidably resulting in a taper at one end of the sideseam forming or fifth panel, at the bottom carton closure. This taper causes a partial triangular uncovering of the first panel edge zone, so that when the panels are pushed downwardly to compress and seal the sideseam (fifth) panel against an edge zone of the fist panel, a portion of the second panel will contact an exposed hot and sticky triangular portion of the first panel and cause an unwanted adhesion between a triangular portion of the first panel, near the tapered end of the sideseam panel, and the triangular portion of the second panel.

In order to avoid unwanted adhesion, the temperature of the heated first panel edge portion and the temperature of the fifth or sideseam forming panel is reduced to decrease the stickiness. While solving the problem of unwanted adhesion, such temperature reduction diminished the strength and quality of the seal between the sideseam panel and the first panel. This lowered quality becomes unacceptable with extended shelf life liquid cartons.

SUMMARY OF THE INVENTION

According to the practice of this invention, the noted unwanted adhesion between the second panel and the first panel attendant the formation of the sideseam joint is eliminated by providing the second panel with a notch. The notch corresponds in form to the triangular notch or truncated portion at the tapered end of the sideseam forming fifth panel. In this way, when compression of the first panel against the sideseam panel occurs, there is no hot and sticky exposed area of the first panel which will adhere to the second panel.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a prior unitary paperboard blank for forming a gable top liquid carton;

FIG. 2 is a perspective view of the tubular carton being collapsed;

FIG. 3 is a plan view of a unitary blank of paperboard provided with a notch in the first panel;

FIG. 4 is a perspective view of a tubular carton formed form the blank of FIG. 2 being collapsed;

FIG. 5 is a plan view of a unitary blank of paperboard provided with a notch in the second panel; and

FIG. 6 is a perspective view of a tubular carton formed form the blank of FIG. 5 being collapsed;

DETAILED DESCRIPTION OF THE INVENTION

Referring now to FIG. 1, a unitary paperboard 10 includes first, second, third, and fourth sidewall forming panels and a fifth, sideseam forming panel. These panels are denoted as 12, 14, 16, 18, and 20 respectively. The upper ends form a gable top when folded and erected, while the lower ends of the panels form a bottom closure. The lower ends are formed by first 112, second 114, third 116 and fourth 118 panels. Each closure panel is connected to a sidewall panel by a fold line. The second 114 and fourth 118 panels each contain a pair of diagonal fold lines, as is conventional. Tab 24 is conventional, and taper 28 is formed during the left or free edge skiving of fifth or sideseam forming panel 20. Taper 28 is formed as the bottom edge of the sideseal panel 20 extends upwardly from the fold line between the panel 20 and the fourth closure panel 118.

Right edge zone 40 of first panel 12 denotes a sealing area that contacts sealing panel 20 when the blank in folded into a tube form. An imaginary triangular zone, later to be described, is bounded by imaginary lines 32 and 34. Both surfaces of the blank are provided with barrier layer coatings, such as polyethylene, as is conventional.

FIG. 2 illustrates a step in the formation of a tube from paperboard blank 10 for forming a gable top container. The paperboard blank is folded to have sideseam panel 20 overlap a part or zone 40 of the edge of panel 12. Prior to this, the lower surface of sideseam forming panel 20, as viewed at FIG. 2, has been heated, as by flame or other treatment, as has been that portion of panel 12 (see area 40 of FIG. 1) which will be in surface contact with sideseam panel 20. These two heated surfaces are at a higher temperature (not necessarily the same) than their respective surfaces on opposite sides of the blank. Second panel 14 and third panel 16 are now pressed downwardly, so that panel 14 overlies panel 12. This presses the heated surface of sideseam forming panel 20 against the locally heated edge portion 40 of first panel 12. The thermoplastic on these portions of panels 20 and 12, because they have been heated, are tacky, resulting in a joint or seam between first panel 12 and sideseam panel 20.

By virtue of taper 28 on sideseam forming panel 20, a triangular zone 30 on first closure panel 112 heated with the rest of the free edge portion of panel 12 is exposed. Accordingly, when panels 14 and 16 are pushed downwardly to apply pressure to form the sideseam joint or seam between panels 12 and 20, a corresponding portion 30A of second closure panel 114 becomes adhered to the hot and sticky triangular portion 30 of panel 112. This adhesion renders the tube unusable for further processing into a gable top carton. In the past, only lowering the surface thermoplastic (typically polyethylene) softening temperature of panels 12 and 20 eliminated the problem, but at the cost of an inferior sideseam joint.

Referring now to FIG. 3, the blank of U.S. Pat. No. 5,626,285 is shown and differs from the blank of FIG. 1 only by a notch formed by the removal of a triangular zone bordered by cut lines 34 and 36 from the bottom edge of the closure panel 112 extending from first panel 12.

Referring now to FIG. 4, it is seen that when panels 14 and 16 are pressed downwardly to form the sideseam joint, there will be no zone or portion of panel 112 beyond taper 28 which will stick to panel 114 at region 30A. Thus, what is shown at FIG. 4 is conventional, except for cut lines 34 and 36 and the consequent absence of triangular zone 30 of FIG. 2. The notch shown at FIGS. 3 and 4 is bordered by lines 34 and 36 and is triangular. FIG. 4 shows edges 28 and 34 as coincident. If desired however, cut line 36 could be curved or could extend straight downwardly, parallel to the edge of zone 40, instead of at an angle as shown at FIG. 3. As earlier stated, in practice the seam forming step shown at FIGS. 2 and 4 is carried out with the tube formed from the sidewalls and the fifth panel 20 rotated 180 degrees about its longitudinal axis.

When the carton described in U.S. Pat. No. 5,626,285 is utilized in small sized cartons, a difficulty has been encountered in forming the bottom of the carton prior to filling with automated machinery. The notch in the first panel has a tendency to prevent the clean folding of the gable tips formed in the second and fourth panels. It is therefore advantageous to move the notch from the first panel to the second panel but still in a position corresponding to the exposed glue on the first closure panel 112 formed by the truncation of the sideseam panel.

Referring now to FIG. 5, the blank of the invention is seen. The second closure panel 114 has a free edge 144 opposite the fold line between the second closure panel 114 and second panel 14. The third closure panel 116 has a free edge 146 opposite the fold line between the third closure panel 116 and second panel 16. The second closure panel 114 has a notch defined by edges 134, 136 in its bottom edge. Edge 134 extends from free edge 144 and joins edge 136. The edge 136 extends from the end of edge 134 to the free edge 146 of third closure panel 116. The notch removes material from the second closure panel that would otherwise adhere to the exposed adhesive 30 on the first closure panel 112 when the blank is formed into a collapsed tube. Edge 136 corresponds to a line 34 demarcating the truncated edge 28 of the glue flap 20 after it is joined to the first panel 12 to form a tubular carton.

FIG. 6 depicts the tube being flattened and the notch overlying the exposed glue area 30 created as the sideseam panel 20 overlies the glue area 40 of first panel 12. The free edge 136 of the notch corresponds to the truncated edge 28 of the glue flap 20 so that the exposed adhesive area 30 does not come in contact with the portion of the second panel of the carton 14. In this way, unwanted adhesion of the flattened tube is prevented. When flattened, the first and fourth panels 12, 18 form a lower layer and second and third panels 14 and 16 form the upper layer. The upper layer, specifically second panel 14, does not have material that may become adhered to the lower layer. The carton is shipped in this configuration until its ultimate formation into a carton filled and sealed.

While the invention has been described in the preferred embodiment, modifications and variations would be obvious to one of ordinary skill in the art without departing from the spirit of the invention. The description is not intended to be eliminating in any way, but is defined by the appended claims.

Claims

1. A blank for forming a container, comprising:

a first panel connected to a second panel along a first fold line, said second panel connected to a third panel along a second fold line, said third panel connected to a fourth panel along a third fold line, said fourth panel connected to a fifth panel along a fourth fold line,

a first, second, third and fourth closure panel connected to said first, second, third and fourth panels, respectively, by fold lines,

said second closure panel having a free edge opposite said fold line between said second panel and said second closure panels,

said third closure panel having a free edge opposite said fold line between said third panel and said third closure panels,

said fifth panel having a bottom edge extending upwardly from said fourth fold line, and

a notch in said free edge of said second panel, said notch formed by a first edge extending from said second closure panel free edge and a second edge extending upwardly from third closure panel free edge.

2. The blank of claim 1, wherein

said second edge extends passed a fold line between said second closure panel and said third closure panel.

3. The blank of claim 1, wherein

said blank is made of paperboard.

4. A collapsed tube for forming a container, comprising:

a first closure panel connected to a second closure panel along a first fold line, said second closure panel connected to a third closure panel along a second fold line, said third closure panel connected to a fourth closure panel along a third fold line, said fourth closure panel connected to a fifth panel along a fourth fold line,

said fifth panel having a bottom edge extending upwardly from said fourth fold line, said fifth panel adhered to said first closure panel,

said second panel overlying said first panel,

an area of exposed adhesive on said first panel below said fifth panel, and

a notch in said second closure panel corresponding to the portion of said second closure panel overlying said area of exposed adhesive.

5. The tube of claim 4, wherein

said area of exposed adhesive is triangular.

6. The tube of claim 4, wherein

said notch is formed by a first edge and a second edge, said second edge overlying said fifth panel bottom edge.