EP3277596B1 - Method for continuously manufacturing a plastic bag for food products - Google Patents

Description

The invention relates to the technical sector of plastic packaging bags, especially for the packaging of food products.

More particularly, the invention relates to a preformed flexible plastic bag, in particular obtained from a film having a thickness of less than about 200 μm.

This type of bag comprises a front wall and a rear wall assembled at their lateral sides, in combination with bellows, delimiting a bottom and a filling opening.

In known manner, these preformed bags are made continuously, from a single plastic film, such as PE with or without added OPP, or PE added with PET, or any other materials perfectly known for a skilled in the art commonly employed in the field of food packaging.

The plastic film is subjected continuously to successive operations of folding and welding, to make a bag as such, with as indicated, a bottom, two walls, joined by bellows, and a filling opening opposite to background.

Generally, the external pleats, at the bellows and wall connections, are assembled by continuous welding lines. The bottom of the bag is made by any known and appropriate means.

Under a filling effect of the bag, the side gussets are spread apart, thus giving volume to the shape of the bag, and indirectly, participate in the formation of a bottom, to allow to maintain the bag in a vertical position, or substantially vertical.

It appears, however, that the formation of the bottom often requires folding operations, and does not constitute a base capable of ensuring perfect stability in vertical position, or substantially vertical bag.

This problem of stability can pose significant problems when packaging the bag, after filling, on an automatic machine. Indeed, it is important that the bags can remain perfectly stable, for example, during their transport of positions in positions, in order to subject them, under good conditions, to the selected operations, and to avoid any phenomena of reversal of their content.

This stability is also important for the storage and presentation of bags.

In an attempt to remedy these disadvantages, a solution emerges, for example, from the teaching of the patent FR 2 833 928 , which provides for creating, on at least one of the walls of the bag, a marking line, capable of constituting a fold zone determined to form and delimit the bottom relative to the walls, by creating a support base under the effect of the spacing of the bellows.

This solution is effective, but essentially suitable when the bottom results from a folding operation and welding at the bottom of the walls of the bag. Other methods of manufacturing plastic bags are known from the documents US 3,119,548 and FR 2 672 033 .

The invention proposes an alternative solution to solve the problem of improving stability, while aiming to reduce the thickness, and improve the aesthetics of the bag.

• on soumet le film à des opérations de pliages successifs pour réaliser des soufflets latéraux entre deux parois,
• on réalise une ligne de soudure longitudinale au niveau du raccordement des bords externes des soufflets avec les parois,
• on réalise à intervalles réguliers une ligne de soudure transversale constituant un fond,
• on réalise à intervalles réguliers une ligne de soudure oblique entre les bords externes des soufflets et la ligne de soudure transversale constituant le fond,
• on découpe une zone triangulaire résultant des lignes de soudures obliques et de fond,
• on réalise une coupe au niveau du fond présentant symétriquement, de part et d'autre, les lignes obliques, pour former une ouverture du sac.

To solve such a problem, it has been designed and developed a method for continuously manufacturing a food packaging bag from a plastic film sheath, a method according to which:

• the film is subjected to successive bending operations to produce lateral gussets between two walls,
• a longitudinal weld line is made at the connection of the external edges of the bellows with the walls,
• a transverse weld line constituting a bottom is produced at regular intervals,
• an oblique welding line is made at regular intervals between the outer edges of the bellows and the transverse weld line constituting the bottom,
• a triangular zone resulting from the lines of oblique and bottom welds is cut out,
• a cut is made at the bottom symmetrically, on either side, the oblique lines, to form an opening of the bag.

The manufacturing method according to the invention is characterized in that the cutting of each triangular zone is performed from the outer edge of the bellows, along the outer edge of the oblique welding line, to the outer edge of the line of transverse welding, then the cutting is continued transversely towards the inside of the plastic film sheath along the outer edge of the transverse welding line to make a semicircle away from the transverse welding line to return back and continue cutting transversely to the outer edge of the sheath, parallel to the transverse weld line.

Thus, the plastic food product packaging bag obtained comprises a front wall and a rear wall assembled, on the one hand, at their lateral sides, in combination with bellows forming two folds, and secondly at one of their transverse side with said bellows, to form a bottom.

The outer lateral edges of the bellows are connected to the bottom by oblique cutting lines, so that after filling of the bag corresponding to the spacing of the bellows, said oblique lines form symmetrically, on either side of the bottom, a clearance in triangle, without overthickness, thus improving the stability of said bag in vertical filling position.

It follows from these characteristics that the triangle-shaped clearances are located on either side of the median zone of the bottom avoiding any extra thickness, since the fold is limited in length, and is located, as indicated, only at the the middle part of the bottom. It is also possible to equip the bottom, labels or others.

According to other features, the oblique cut lines are formed from the bottom and the median line of the two folds of each bellows.

The outer edges of the bellows, at their connection with the walls, including the oblique cutting lines, have a weld zone.

• la figure 1 est une vue en perspective d'un sac, obtenu grâce au procédé selon l'invention,
• la figure 2 est une vue à plat et de face du film,
• la figure 3 est une vue de côté, correspondant à la figure 2, en position écartée des plis de l'un des soufflets,
• la figure 4 est une vue de face du sac, en position remplie,
• la figure 5 est une vue de côté, correspondant à la figure 4,
• la figure 6 est une vue de dessous, correspondant à la figure 4,
• la figure 7 est une vue en plan, à caractère schématique, montrant le procédé de fabrication en continu d'un sac, selon les caractéristiques de l'invention,
• la figure 8 est une vue de détail de la zone encerclée apparaissant sur la figure 7, illustrant la découpe d'une zone triangulaire, et la découpe avec la double lame.

The invention is described below in more detail with reference to the figures of the accompanying drawings, in which:

• the figure 1 is a perspective view of a bag, obtained by means of the process according to the invention,
• the figure 2 is a flat and front view of the film,
• the figure 3 is a side view, corresponding to the figure 2 , in a position away from the folds of one of the bellows,
• the figure 4 is a front view of the bag, in the filled position,
• the figure 5 is a side view, corresponding to the figure 4 ,
• the figure 6 is a view from below, corresponding to the figure 4 ,
• the figure 7 is a plan view, schematic, showing the continuous manufacturing process of a bag, according to the features of the invention,
• the figure 8 is a detailed view of the circled area appearing on the figure 7 , illustrating the cutting of a triangular area, and the cutting with the double blade.

In a perfectly known manner, the food bag designated as a whole by (1) is made of a flexible plastic material, in particular of thickness less than 200 microns. The bag is, in a perfectly known manner, obtained from a roll of film unrolled continuously, and subjected to various operations, including automatic folding and welding.

As a result, the bag obtained has a front wall (1a) and a rear wall (1b) assembled at their lateral sides in combination with bellows (1c,) and (1d). The bag has, moreover, a bottom (1e) and a filling opening (1f).

Each of the bellows (1c) and (1d) form two folds (a) and (b). The bottom (1e) is welded at the connection of one of the transverse sides of the walls, with the bellows.

According to the invention, the external lateral edges of the bellows (1c) and (1d), at their connection with the front and rear walls of the bag, are connected to the bottom (1e) by oblique cutting lines (1c1) ( 1c2) and (1d1) and (ld2) ( Figures 2, 3 and 6 ).

The oblique cutting lines are formed from the bottom (1e) and the median line (c) of the two folds (a) and (b) of each bellows.

The external lateral edges of the bellows (1c, 1d), at their connection with the front (1a) and rear (1b) walls, including at the oblique cutting lines, have a weld line (L).

It follows from these characteristics, that after filling the bag, corresponding to the spacing of the bellows (1c, 1d), the different oblique lines form symmetrically, on either side of the bottom (1e), a clearance in the form of triangle (T), figure 6 . These clearances in the form of a triangle are located symmetrically, on either side of the bottom (1e) and have no extra thickness. The extra thickness, constituted by the bottom (1e), is limited between the two clearances triangle (T), in other words, over a reduced length.

We refer to the figure 7 which shows the method of continuously manufacturing a food packaging bag, according to the features of the invention from a sheath of a plastic film.

The film is subjected to successive bending operations to achieve the lateral bellows between two walls.

A longitudinal weld line (L1) is made at the connection of the external edges of the bellows with the front and rear walls.

At regular intervals, a transverse weld line (L2) constituting the bottom (1e) and an oblique weld line (L3) between the outer walls of each of the bellows and the weld line (L2) constituting the bottom are produced at regular intervals. , [step (A)].

The oblique weld lines (L3) and the transverse weld lines (L2) are made one after the other in separate steps, and with separate tools. The order in which these lines is not important. The oblique weld lines (L3) can be made before or after the transverse weld lines (L2). The fact that the oblique weld lines (L3) are made independently of the transverse weld lines (L2), and with separate tools, makes it possible to adapt or adjust as necessary the position of the lines of oblique welds (L3) with respect to transverse weld lines (L2). Thus, the method is more flexible in that it is possible to vary the inclination of the oblique welds or to move them transversely, and thus to modify the manufactured bag, without having to change tools. These characteristics also make it possible to adjust the position of the oblique lines (L3) according to the dimensional differences found in the manufacturing process. The manufacturing process is simple, fast, and accurate.

Then, the triangular zone (T) resulting from the weld lines (L1) (L2) and (L3), [step (B)] is cut.

Note that the cut can be shaped so as to achieve rounded edges, or not.

In addition, according to the invention and with reference to figure 8 , the cut is made from the outer edge of the bellows (1c, 1d), along the outer edge of the oblique weld line (L3), to the outer edge of the transverse weld line (L2), then the cut is continued transversely to the inside of the plastic film sheath along the outer edge of the transverse weld line (L2) to a semicircle away from the transverse weld line (L2) for go back and continue cutting transversely to the outer edge of the sheath, parallel to the transverse weld line (L2).

Then, in a known manner, a section is produced at the level of the weld line (L2), symmetrically presenting on both sides the oblique weld lines (L3) to form the opening of the bag [step (C)] .

Preferably, this cutting is performed by a double blade, the spacing of the blades allows for a cut by sealing on either side the transverse cuts made during the cutting of the triangular areas (see figure 8 ). In other words, the transverse weld lines formed during the cutting of the triangular areas are found arranged between the two blades during the double cutting.

In this way, the cutting with the double blade, around the transverse cuts made during the cutting of the triangular areas, allows for an optimal finish of the bag, with rounded edges and without protruding part.

• l'esthétique obtenue,
• une diminution des épaisseurs,
• la stabilité obtenue,
• la possibilité de mettre des étiquettes ou des marquages, au niveau du fond.

The advantages are apparent from the description. In particular, we emphasize and remind:

• the aesthetics obtained,
• a decrease in thicknesses,
• the stability obtained,
• the possibility of putting labels or markings at the bottom.

Claims (3)

1. Process of continuous production of a bag for packaging food products, from a tubular film of plastic material, according to which:

   • one submits the film to successive folding operations to produce lateral gussets (1c, 1d) between two walls (1a, 1b);

   • one produces a longitudinal weld line (L1) at the joint between the exterior edges of the gussets (1c, 1d) with walls (1a, 1b);

   • one produces - at regular intervals - a transversal weld line (L2) constituting a bottom (1e);

   • one produces an oblique weld line (L3) at regular intervals between the exterior edges of the gussets (1c, 1d) and the transversal weld line (L2) constituting the bottom (1e);

   • one cuts out a triangular area resulting from the oblique weld lines (L3) and bottom (1e);

   • one makes a cut at the bottom (1e) with oblique lines, symmetrically, on either side, to form an opening in the bag;

   production process characterized by the fact that the cutting-out of each triangular area is performed starting from the exterior edge of the gussets (1c, 1d) and along the exterior edge of the oblique weld line (L3), and the cut is then continued transversally towards the interior of the plastic tubular film and along the exterior edge of the transversal weld line (L2) until a semi-circle is performed while becoming more-distant from the transversal weld line (L2), until returning backwards and continuing the cut transversally until the exterior edge of the tubular film, in parallel to the transversal weld line (L2).
2. Process in accordance with claim 1, characterized by the fact that the cutting-out of the triangular areas is formed in such a manner as to procure rounded edges.
3. Process in accordance with claim 1, characterized by the fact that the cut-out at the bottom (1e) is produced with a dual blade, with the gap between the two blades being such that, during the double cut, the transversal cut-outs produced during the cutting-out of the triangular areas are positioned between the aforesaid two blades.

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