EP1103487A1 - Packaging bag with reclosable opening - Google Patents

Abstract

The packaging sachet (10) for foods stuffs has a first layer and a heat weldable layer between which is a layer of permanent adhesive. The sheet defines a seating (20) with a passage (18) initially closed by a heat weld (16) between the sheet and a complementary support behind the weldable layer . The weld line forms a stress concentration when the sachet is subjected to opening forces. The heat weld can form pointed failure lines along its edges.

Description

The present invention relates to a packaging bag of the type comprising at least one packaging sheet comprising a primer associated with a welding layer between which is interposed, at the minus a marked area, a layer of permanent adhesive, which sheet at least partially delimits a housing provided with a passage initially closed by a weld strip established between said sheet and an additional support along said weldable layer.

Packages and sachets with a packaging sheet allowing easy opening and reclosing are currently used, for example, for packaging food products. The structure such sheets are described in particular in patent application FR-A-95-14117.

In this document, the laminated sheet used to allow the opening and the reclosure of the packaging has two layers of polymer between which a layer of permanent adhesive is interposed. One of layers, called "weldable or weldable layer" is intended to be oriented towards the inside of the package. It is suitable to be welded on the edge peripheral of a tray. The other layer, called the "support layer", is intended to form the external face of the packaging, this layer possibly being printed.

A sheet of this type can also be used to form sachets as described in document EP-A-0.516.276.

When the bag is opened, the sealing layer of the sheet tears on either side of the welded region. After opening the bag, it remains on the inner face of the facing sheet, a residual welded bead, consisting of the welded part of the welding layer.

The opening of the bag being obtained by rupture of the sealing layer, it should be chosen so that it has characteristics of rupture compatible with the conditions of use of the packaging.

In particular, the welding layer should be able to be torn manually, without the need to exert too much tensile force important on the packaging sheet. So the welding layers used are rather of reduced thickness.

However, the weldable layer should also have good welding characteristics to ensure a reliable bond between the sheets next to the bag. In addition, the welding layer must be is compatible with the permanent adhesive interposed between the two leaf layers. To meet this condition, choose a rather thick layer.

It can therefore be seen that the choice of the welding layer is relatively delicate, due to the many constraints it must meet. This choice is particularly dictated by the possibility that the diaper is torn manually. However, this characteristic is difficult to reconcile with the other properties necessary for the layer.

Thus, we see that it is generally difficult to open a sachet resealable since it is necessary to apply a very intense force to cause rupture of the welding layer.

The object of the invention is to provide a resealable packaging sachet, whose opening is easy and requires only the application of a reduced force to ensure opening.

To this end, the subject of the invention is a packaging bag of the aforementioned type, characterized in that said weld strip has according to its length, on its outer edge, a profile comprising at least one point inflection forming a stress accumulation point during opening of the sachet by spacing the packaging sheet and the additional support.

• ledit profil de la bande de soudure comporte une succession de points de rebroussement disposés au sommet de pointes s'étendant sensiblement transversalement à la bande de soudure ;
• la bande de soudure décrit un parcours sinueux ;
• ledit parcours sinueux présente une succession de régions courbes de concavités opposées ;
• lesdites régions courbes ont un rayon de courbure compris entre 1 mm et 3 mm ;
• la bande de soudure comporte au moins un tronçon qui, sur son bord extérieur, présente un angle obtus ; et
• la bande de soudure comporte essentiellement deux tronçons rectilignes reliés par un coude délimitant ledit angle obtus.

According to particular embodiments, the packaging bag includes one or more of the following characteristics:

• said profile of the weld strip comprises a succession of cusps placed at the top of points extending substantially transversely to the weld strip;
• the weld strip describes a sinuous course;
• said sinuous course presents a succession of curved regions of opposite concavities;
• said curved regions have a radius of curvature of between 1 mm and 3 mm;
• the weld strip comprises at least one section which, on its outer edge, has an obtuse angle; and
• the weld strip essentially comprises two straight sections connected by a bend delimiting said obtuse angle.

• la figure 1 est une vue en élévation d'un sachet d'emballage selon l'invention;
• la figure 2 est une vue en section de la région soudée d'obturation du sachet de la figure 1 prise suivant la ligne II-II ;
• les figures 3 et 4 sont des vues en section analogues à celles de la figure 2, prises respectivement après ouverture initiale du sachet, et après refermeture de celui-ci ;
• la figure 5 est une vue en élévation d'une variante de réalisation du sachet d'emballage de la figure 1 ;
• la figure 6 est une vue à plus grande échelle du profil de la soudure d'obturation du sachet de la figure 5 ; et
• la figure 7 est une vue en élévation d'encore une variante de réalisation du sachet selon l'invention.

The invention will be better understood on reading the description which follows, given solely by way of example, and made with reference to the drawings in which:

• Figure 1 is an elevational view of a packaging bag according to the invention;
• Figure 2 is a sectional view of the welded closure region of the bag of Figure 1 taken along line II-II;
• Figures 3 and 4 are sectional views similar to those of Figure 2, taken respectively after initial opening of the bag, and after reclosing thereof;
• Figure 5 is an elevational view of an alternative embodiment of the packaging bag of Figure 1;
• Figure 6 is an enlarged view of the profile of the closure seal of the bag of Figure 5; and
• Figure 7 is an elevational view of yet another alternative embodiment of the bag according to the invention.

The bag 10 shown in Figure 1 is made from a single sheet 11 folded back on itself. The two longitudinal edges of the sheet are welded to each other in a median longitudinal weld 12.

At its lower end, the bag has transversely a straight weld strip 14. Similarly, it has at its upper end a weld strip 16 closing off an access 18 to a delimited housing 20 inside the bag. Thus, the bag has two sections extending between which a closed space is defined.

The sheet 11 of the bag extends at its upper end beyond of the weld strip 16 over a range of 1 to 3 cm in width, forming gripping areas facilitating the opening of the bag.

As shown in Figure 2, the sheet constituting the bag 10 has a layered structure. It has a primary layer 30 turned outwards and a weldable layer 32 facing inward of the bag. Between the primary layer 30 and the welding layer 32 is disposed a layer 34 of a permanent adhesive.

The longitudinal weld 12, produced between the two opposite faces of the welding layer 32, is a weld of the flesh against flesh type. The two opposite end edges of the welding layer 32 are welded one against each other by heat sealing.

Likewise, the welded strips 14 and 16 are obtained by heat sealing. of parts opposite the welding layer 32.

According to the invention, the weld strip 16 sealing the bag 20 has on its external profile at least one inflection point, forming a point of accumulation of stresses in the welding layer 32 during opening from the sachet.

More specifically, in the embodiment of Figure 1, the edge outside of the weld strip 16 has a succession of points 36 extending transversely. These are regularly spaced on the entire length of the weld strip. They each present their vertex a cusp 38 directed towards the upper end of the bag.

The width of the weld strip is between 5 mm and 10 mm. The height of the points 36 is between 20 and 50% of the width average welded strip 16.

To open the bag, the operator enters in each hand an extension of the sheet 11 located beyond the weld strip 16. He then spreads the opposite sides of the bag in order to cause the opening from the sachet. When pulling the two extensions in the opposite direction, high stresses are applied in the region of the cusps 38 located at the top of the points 36.

Indeed, the tensile force applied between the two extensions is distributes exclusively over the cusps 38 and not over the entire length of the outer contour of the welded region 16. Thus, constraints very high are applied to 38 cusps in the region welded. Under the action of these constraints, the welding layer 32 tears initially around the cusps 38.

Thus, the presence of the turning points 38 along the contour outside of the welded strip 16 facilitates the tearing of the welding layer 32, allowing an accumulation of constraints in just certain points along the length of the outer contour of the welded strip.

The tear then propagates along the outer contour of the weld 16 under the continuous action of the traction of the two extensions in opposite directions. The tear progresses from each turning point 38 to the bottom of the slots delimited between two points, leading thus to the complete tearing of the welding layer 32 according to the outer contour of the weld strip 16.

During the next phase of separation of the two extensions, the portion of the welded layer 32, which remains linked to the opposite sides separates gradually permanent adhesive 34, which remains bonded to the primer 30.

Similarly, the welding layer 32 tears according to the inner contour of the welded region 32 when the two extensions are pulled in opposite directions.

Thus, as illustrated in FIG. 3, the two sides of the bag are then separated, one always having on the inside a welded strip 46 from weld layer 32 and the other side having a groove 48 corresponding to the imprint of the strip carried by the other panel.

It can be seen, as illustrated in FIG. 4, that the approximation of the two sides and the replacement of the welded strip 46 in the groove 48 allows the packaging to be closed again, by the action of the permanent adhesive.

In Figure 5 is shown an alternative embodiment of the bag packaging according to the invention, noted 48. In this alternative embodiment, the welded strip denoted 50, closing the access 18 inside the bag extends following a sinuous path, having substantially a sinusoidal shape.

This welded strip has, as shown on a larger scale in Figure 6, along the width of the bag a succession of curved regions 52 of opposing concavities two by two. The curved regions 52 are connected by substantially rectilinear sections 54.

Thus, along its outer contour, the welded strip 50 has a succession of vertices forming inflection regions of high curvatures.

Advantageously, the welded strip 50 has a width comprised between 10 mm and 15 mm and is advantageously equal to 13 mm. The radii of curvature at points of inflection formed by curved regions 52 are substantially between 1 mm and 3 mm and for example equal to 2 mm.

Finally, the straight sections 54 connecting the curved regions 52 delimit between them an angle substantially equal to 60 °.

In FIG. 6, an envelope of the weld formed of a succession of segments defining between them angles of 60 ° has been represented in mixed lines.

It is understood that the presence of the curved regions 52 forming summits allows the concentration of stresses when opening the sachet in only a reduced number of regions distributed along the length of the welded strip, thus facilitating the opening of the bag.

In the embodiment shown in Figure 7, the sachet noted 68 is closed by a weld strip 70, which has two sections straight 72, 74 successive connected to each other and angularly offset an obtuse angle.

Thus, over most of the width of the bag, the weld strip 70 has a rectilinear section 72 extending perpendicular to the axis of the bag. In the vicinity of a lateral edge of the bag, the weld strip 70 has an inclined weld section 74 of the same width as the section 72. Between the two sections, is formed on the outer contour of the weld a sharp angle 76 forming an inflection point 78 on the outer contour of the welding. A corresponding inflection point 80 is also delimited on the inside contour of the weld.

It is understood that in this embodiment also, by discarding extensions of the bag from each other in the region immediately above angle 76, constraints only concentrate around the angle 76. So, without a high force having to be applied, rupture of the sealing layer 32 of the bag occurs. Likewise, a second layer rupture at inflection point 80 occurs immediately after.

The ruptures in the weld layer thus initiated on either side of the weld strip 70 then progressively propagates next on the entire length of it.

Claims (7)

Packaging bag (10; 48; 68) comprising at least one sheet packaging comprising a primary layer (30) associated with a layer weldable (32) between which is interposed, in at least one marked area, a layer (34) of a permanent adhesive, which sheet defines at least partially a housing (20) provided with a passage (18) initially closed by a weld strip (16; 50; 70) established between said sheet and a additional support along said weldable layer (32), characterized in what said weld strip (16; 50; 70) has along its length, on its outer edge, a profile comprising at least one inflection point (38; 52; 78.80) forming a point of accumulation of stresses during opening of the bag by spacing the packaging sheet and the support complementary. Packaging bag according to claim 1, characterized in that said profile of the weld strip (16) comprises a succession of points cusps (38) arranged at the top of spikes (36) extending substantially transversely to the weld strip (16). Packaging bag according to claim 1, characterized in that the weld strip (50) describes a sinuous course. Packaging bag according to claim 3, characterized in that said sinuous course presents a succession of curved regions of concavities opposite. Packaging bag according to claim 4, characterized in that said curved regions have a radius of curvature between 1 mm and 3 mm. packaging bag according to claim 1, characterized in that the weld strip (70) comprises at least one section which, on its edge exterior, has an obtuse angle (78). Packaging bag according to claim 6, characterized in that the weld strip essentially comprises two straight sections connected by an elbow delimiting said obtuse angle.

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