EP0142457A2 - Method of shaping the bottom of a bag of flexible synthetic material starting from a cushion filled with a liquid - Google Patents

Abstract

1. A process for forming the bottom of a bag made of flexible synthetic material from a cushion (1) made of synthetic material and filled with liquid, and for giving the bag stability, this process involving gripping each of the two lower corners (3, 4) of the cushion (1) by means of tongs (5), winding the said corner on itself about the pin supporting the tongs according to a specific number of revolutions, and then finally, after immobilization and removal of the tongs, welding the roll thus formed.

Description

The subject of the present invention is a process for forming the bottom of a flexible plastic bag from a plastic cushion filled with liquid, and for giving it stability. The subject of the invention is also the sachets obtained according to this method and the device for its implementation.

When making flexible plastic containers, one of the problems posed is that of the stability of the bag, obtained by a specific conformation of the bottom of the bag to allow it to be placed on a flat surface.

Multiple structures have been proposed and are satisfactory.

Thus, for example, as in French application 75.18358 in the name of the plaintiff, the bottom of the sachet is shaped like a W by folding the plastic film before filling.

In the same way, French patent 71.20879 proposes to shape the bottom by welding and cutting the angles forming ears after folding the bottom. In these embodiments, it is imperative that the bag is empty.

If the W-shaped bottom allows continuous work on a horizontal routing machine, the structure of patent 71.20879 cannot be obtained continuously.

In addition, the two proposed embodiments are necessarily made from empty bags, at a given stage of their conformation.

The same is true of the US patent. 382 9007 which offers stabilization by lateral folding then welding. Here too, it is imperative to work on an empty sachet.

There is therefore a need for a process allowing continuous production of bags with a flat bottom, with the same advantages as the W-shaped bottom, while allowing intervention on a filled sachet, in the intermediate cushion state, more particularly for a vertical tracking process, leading to a succession of cushions from a continuous roll of film.

According to the invention, this result is obtained with a process for forming the bottom of a flexible synthetic bag, from a cushion of synthetic material filled with liquid, and for giving it stability, which consists in pinch each of the two lower corners of the cushion with pliers, to wrap said corner around itself around the axis supporting the pliers, according to a determined number of rotations, then finally, after immobilization and removal of the pliers, to weld the roller thus formed.

• - la figure 1 est une vue schématique de la prise d'un coin d'un coussin par une pince,
• - la figure 2 illustre l'enroulement du coin sur lui-même,
• - la figure 3 illustre l'immobilisation avant retrait de la pince,
• - la figure 4 illustre la soudure finale.

The invention will be better understood with the aid of the description below of a non-limiting mode of implementation, with reference to the appended drawings in which:

• FIG. 1 is a schematic view of the grip of a corner of a cushion by a clamp,
• - Figure 2 illustrates the winding of the corner on itself,
• FIG. 3 illustrates the immobilization before removal of the clamp,
• - Figure 4 illustrates the final weld.

We will first refer to Figure 1:

A cushion (1) filled with liquid (2) is intended to be shaped into a sachet, from a continuous vertical or horizontal path, in this case preferably vertical.

To give shape and stability to the bag, it is envisaged to wind the two corners (3,4) of the cushion on themselves so as to form stabilization rollers.

To do this, each of the corners (3,4) is grasped using a clamp (5) integral in rotation with an axis, shown, driven by a motor; the clamp opening and closing controls are inside the axis. A device allows the release of the axis and the clamp after winding.

When the wedge, for example (3), is pinched, the rotation of the axis is controlled and the wedge is wound up in a winding (6) by expelling the liquid towards the inside of the sachet (FIG. 2).

Then the rotation is stopped and the roller (6) is locked in position, applying light pressure by a jaw (7,8). We then remove the axis, and therefore the clamp (Figure 3).
Finally, a heat of welding is applied to the roller (6), the jaw (7,8) possibly being, for example, a welding tongs (FIG. 4).

This produces a bag bottom delimited by two opposite rollers which give the desired shape and stability.

Claims (2)

1. Method for forming the bottom of a flexible plastic bag from a plastic cushion filled with liquid, and for giving it stability, characterized in that it consists in pinching each of the two lower corners (3,4) of the cushion (1) by a clamp (5), to wind said corner around itself around the axis supporting the clamp, according to a determined number of rotations, then finally, after immobilization and removal of the pliers, to weld the roll thus formed. 2. Device for implementing the method according to claim 1, characterized in that it essentially comprises a clamp (5) secured to an axis driven by a motor and movable in rotation with said axis, said clamp being provided with opening and closing controls inside the axis, the axis being able to be released laterally after winding the corner (3,4).

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