Film bag and method of producing a film bag

Description:

The invention relates to a film bag formed by folding and sealing a piece of film, with two front sides, two V-shaped side gussets, a bottom gusset and a bag opening at the top.

Film bags of this type are known from patent specifications DE 12 38 650 and DE 196 12 102 C2, for example. A problem that frequently arises with the traditional folding of side gusset bags is that the bags do not unfold completely when filled. This applies particularly when stiffer composite films are used. Ideally, the film bag will be precisely cuboid in shape with a flat base if possible. If the bag deviates too greatly from this ideal shape, problems frequently emerge in the subsequent packing process. Hence, for instance, the filled bags will tip over if they are not guided. This can lead to an automatic filling process being brought to a standstill and thereby cause a reduction in output.

A film bag with the features described above is known from specification EP 1 323 639 A1 , in which the folding areas of the base are pre-treated using heat or refrigeration prior to folding. This is intended to increase the stability of the film bag standing on the base. However, this measure does not yet give the bag the desired standing properties needed in order to guarantee a trouble-free packing process.

The invention is based on the object of identifying a film bag with a base that can be easily unfolded and, in addition, has good standing properties.

The object is solved according to the invention by a film bag formed by folding and sealing a piece of film, with two front sides, two V-shaped side gussets, a base and a bag opening at the top, wherein the standing properties of the film bag standing on the base are improved by a continuous, blind heat-sealed seam that must be folded over when the base is unfolded, close to which there is, in addition, a separately produced, continuous, mechanical weakening. The

term "blind heat-sealed seam" means that this process does involve the joining of any layers of film, but simply a local weakening of the film material due to the effects of the heat during the blind heat-sealing process. According to the invention, a mechanical weakening is carried out in addition close to the blind heat-sealed seam, which follows on separately from the blind heat-sealing process. While a blind heat-sealing process or mechanical weakening alone does not produce the desired standing properties in the film bag, the combination of a blind heat-sealed seam and separate mechanical weakening according to the invention guarantees that the blind heat-sealed seam is very easily folded over to produce the base. Due to the easily foldable edges, the film bag according to the invention stands securely on its base and has no tendency to tip over.

The mechanical weakening is preferably produced by means of light punching, small cut-outs, stamping or by laser treatment. The film may also have punchings at the ends, which lie down once the film close to the base is folded and thereby reduce by area the number of film layers forming the base. The smaller number of film layers advantageously guarantees smaller jumps in thickness around the base, thereby guaranteeing a flat base surface.

The object of the invention is, in addition, a method of manufacturing a film bag in accordance with claim 4. Advantageous embodiments of this method are described in claims 5 to 8.

The invention is described below by means of a drawing showing only one exemplary embodiment. In the drawing

Fig. 1 shows a film bag according to the invention before its side gussets have been folded,

Fig. 2 shows the film bag depicted in Fig. 1 after the side gussets have been folded,

Fig. 3 shows the film bag depicted in Fig. 2 after the base area has been sealed,

Fig. 4 shows a bottom view of the film bag with the base folded over and

Fig. 5 shows a perspective depiction of the film bag.

Figs. 1 to 5 show a method of producing a film bag from plastic, which has two front sides 1 , two V-shaped side gussets 2, a base 3 and a bag opening at the top 4. In this case, a continuous web of film 5 is provided with a blind heat- sealed seam 6 running perpendicular to the web 5 and extending over the entire width of the web 5. The film web 5 is additionally provided with a separately produced mechanical weakening 7 close to the blind heat-sealed seam 6, which likewise extends over the entire width of the web (Fig. 1 ). In addition, the continuous film tube 5 is provided with punchings 12, which will be considered in greater detail later. In order to guarantee the smooth running of the film web 5 even after punching, a narrow strip 16 is initially left alongside the punching 12 on the right-hand edge. The V-shaped side gussets are then folded, the film web welded into a film tube 5' with a longitudinal heat-sealed seam 13 and the narrow strip 16 detached. The longitudinal heat-sealed seam 13 is located on a corner between a front side 1 and a side gusset 2. Blind heat-sealed seams 13' are provided on the other corresponding edges of the film bag (Fig. 2). The side gussets 2, just as with the front sides 1 of the continuous film tube 5', are then sealed at the base with heat-sealed seams 8, 9, 10 (Fig. 3). A blank 5" for an individual film bag is then produced by cutting a piece from the continuous film tube 5'. In the exemplary embodiment, the blank 5" is produced by stamping along the dividing lines 14. The blank 5" has a zipper 15 to close the opening 4, which has already been welded onto the continuous film web 5 (Fig. 1 ). As an alternative to a zipper, a slider may also be welded on. It can be seen from Fig. 3 that the heat-sealed seams 9, 10 used to seal the front sides 1 are spaced from one another and run parallel to one another. On an individual blank 5", the base 3 of the film bag is formed by folding over the continuous blind heat-sealed seam 6 (Fig. 4). By comparing Figs. 4 and 5, it can be seen that the end section of the film tube 5 sealed by the heat-sealed seams 9, 10 is folded towards the base 3 and adhered to the latter. The corresponding folding line X is shown as a dotted line in Figs. 3 to 5. It runs parallel to the heat-sealed seams 9, 10. In order to minimise the number of film layers in the base, the end section 11 is provided with punchings 12, which are preferably made in the form of windows in the film web 5 where the side gussets 2 have not yet been inserted (Fig. 1 ). The heat-sealed seams 8 sealing the side gussets 2 at the base run slantwise to the film tube 5'.