EP0667288B1 - Method and apparatus for packaging products in hermetic, reclosable packages - Google Patents

Abstract

A continuous band of film (1) is unrolled and folded longitudinally onto itself into the form of a tube and joined by welding the two longitudinal edges. A closing section (6) is welded on the film. The tubular film is then welded transversely at regular intervals along a welded joint. The film is then cut transversely in the place of the transverse weld joint so as to individualise and separate the sachets. Two belt and pulley assemblies (19) take hold of a continuous section of film (6) and pass it in front of cutters (22) combined with upstream (21) and downstream (22) guides. On leaving the cutters individual segments are obtained, of length equal to the total length of the sachet reduced by a value equal to double the dimension, in the longitudinal direction , of the transverse welding zone. These segments are immediately introduced between two leaves (3,4) which synchronously drive the segments towards the welding station (7).

Description

un profilé de fermeture.The invention relates to the packaging of products in sealed reclosable packages consisting of a flexible rectangular bag formed by two portions of film provided with

a closing profile.

Such sachets generally include two portions of a film folded back on itself, closed longitudinally by welding and welded transversely on lateral sides parallel to each other and orthogonal to the longitudinal weld and to the closing profile. The longitudinal closure profile is generally attached and welded to the film, parallel to the longitudinal weld.

The closure profile is generally a waterproof profile resealable comprising a male part and a female part already engaged or not, this profile can also be optionally provided ribs or other profiles allowing easy opening of the packaging.

Furthermore, although the invention will be described in the context of packaging of a product operated simultaneously with the manufacture of sachet, the invention can also be applied to the manufacture of empty sachets, simply by omitting the step of placement of the product to be packaged.

One of the difficulties in this type of packaging is the the closure profile creates at each of its ends a annoying extra thickness to achieve transverse welding on both sides side of the bag.

These end thicknesses can generate in the region of the closure profile of the sealing problems and, in addition, slow down the process due to the special precautions that it necessary to take, which has an obvious impact on the cadences of manufacturing and machine performance.

To overcome this particular difficulty, the solution generally adopted, and which is set out in particular in the documents US-A-4,756,629, US-A-5,024,537 and EP-A-0 302,144, consists of providing, between the step of transferring and welding the profile onto the film of the bag and that of transverse welding of the lateral sides, an intermediate step of pre-crushing of the ends of the profiles in the critical region located in the extension of the lateral sides.

This technique, which will be explained later in more detail when we will describe Figures 1 and 2 and also called "pre-welding", is however difficult to achieve. It is usually obtained by overwhelming by heating and mechanical pressure, ultrasonic, hydraulic or pneumatic the part of the profile which will be in the welded region lateral sides.

This is to flatten the projections of the profile as well as possible distribute or spread them in the welding part of the film if it is a film complex, or in the film itself if it is a single layer film.

However, the material can not disappear, this step of pre-welding always causes surface unevenness, which can create during the subsequent transverse welding of the sides of the bag of leaks detrimental to the tightness of the finished bag.

In addition, the subsequent welding step should be slowed down because the amount of material provided by this part of the crushed profile requires an additional thermal contribution, therefore a longer application time along the welding jaws.

The document EP-A-0 528 721 proposes a different technique, consisting in feeding the profile no longer continuously, but by profile sections of length less than that of the bag to hold account for the distance between the transverse welds.

These profile sections are brought to the machine on a support strip whose dimensions are greater than those of the profiles, both in the longitudinal direction and in the transverse direction; the profile is no longer welded directly to the bag, but via of this backing strip, which only creates in the end regions only a little extra thickness.

However, this process presents a number disadvantages.

First, although the support strip is, in section, more uniform than the profile, it nevertheless creates an extra thickness, so than the disadvantages of the usual technique (with crushing edges of the profiles), if they are attenuated, they are not deleted.

Second, the synchronization of the film supply plastic with the backing strip is very delicate, and any offset (whether due to desynchronization or, for example, poor control of the elongation under tension of the support strip and of the film) causes a risk of welding on the profiles and therefore leakage.

Finally, this process is ill-suited to changes in length bag, profile width, etc., the preconditioning of the support strip and the machine setting to be changed each time time.

The object of the invention is to overcome all of the disadvantages of known techniques, by proposing a method and a packaging machine to completely eliminate the step pre-welding of conventional processes, ensuring positioning perfect profile without any risk of loss of sealing at the ends of it, and which is very easily modifiable according to the choice of profile and bag length.

The method of the invention is therefore of the generic type comprising the steps, carried out step by step and synchronously, consisting in: (a) unwinding longitudinally a continuous strip of film: (b) longitudinally folding this strip of film over it- even, in tubular form and join by welding the two longitudinal edges of the film; (c) longitudinally welding a closure profile to the film; (d) transversely weld the tubular film at regular intervals, along d a solder joint; and (e) cut the film transversely at the location of the transverse seal so as to individualize and separate the bags;

Characteristically of the invention, the closure profile is sectioned in a sequence of length equal to the length of the bag minus the width, in transverse direction, of the weld joint produced at the step (d) and prior to step (c) the individualized segments of the closure profile are introduced between two adjacent sheets of the film folded back on itself, so that the film training participates in the synchronous drive of said segments of closure profiles up to at the welding station carrying out the step (c) and that the transverse welds are formed in the intervals separating the successive segments.

The closing profile can be routed on the film under shape of precut segments.

However according to another advantageous characteristic of the invention the closing profile is preferably conveyed in the form of a continuous strip cut into segments during an intermediate stage prior to l step (c), also offset step by step and in synchronism with the other steps.

Preferably, before step (c), there is further provided a step additional consisting in checking the longitudinal positioning of the profile segment relative to the film.

The invention also relates to a packaging machine, comprising the means of synchronized implementation of the different above steps.

L invention finally relates to sachets of packaging obtained by the implementation of this process.

Other characteristics and advantages of the invention will appear on reading the description below, made with reference to the accompanying drawings.

Figure 1 is a partial plan view of a sachet obtained by implementing a conventional packaging process.

Figure 2 illustrates a machine for the implementation of such a conventional process.

Figures 3, 4, 5 and 6 are schematic sections taken at level of lines III-III, IV-IV, V-V and VI-VI of figure 2.

FIG. 7 illustrates a machine for implementing the method of the invention.

Figure 8 shows in more detail the upper part of the machine of figure 7.

Figure 9 is equivalent to Figure 1, for a bag made by implementing the method of the invention.

Figure 10 schematically illustrates the relationship between the advance successive segments of cut profile and advances in lengths not sachets.

Figure 1 is a partial view of a bag made by setting work of a conventional process, such as that described by the documents US-A-4,756,629, US-A-5,024,537 and EP-A-0 302,144 cited above, by means of the machine illustrated schematically in Figure 2.

The raw material is a reel of film, printed or not, continuously supplied from an unwinder delivering a flat sheet 1. This flat sheet is brought to a forming and filling station 2 where the tablecloth is folded on itself so as to form on a compound tube essentially two continuous sheets 3, 4 which will constitute the two walls of the bag when it is individualized. At the same time, we preferably at this same station, filling the product with condition 5, which will be enclosed between the two sheets 3, 4 of film folded by the forming neck of station 2.

Simultaneously, we unroll, continuously and at the same speed as the film, the closure profile 6 which is inserted for example over a region edge of the two sheets 3 and 4 just downstream of the forming neck of station 2. Film strip 3, 4 and profile 6 progress step by step at the same rate, each step corresponding to a length of sachet to be carried out and the stops for sealing allowing to seal the sides of the bags to different workstations that we will describe now.

The first welding station, referenced 7, is used to fix the longitudinal edges of the film, to longitudinally close the tube thus formed. This welding station 7 can also be used to fix the closing profile 6 on the sheets 3, 4 of the film when this profile 6 is placed in an edge region of the film. As a variant, the closure profile 6 can be fixed to the film 1 to 1. using additional welding means, similar to means 7, when the closure profile 6 is placed at a distance from the edge region of the film. This stage does not pose any particular difficulty, since it is carried out over a length of film and section of uniform section, without protrusion; the heating jaws 8 are positioned in the direction of the unwinding of the film and carry out the welding by thermal input and transverse pressure, as can be seen in the section of FIG. 3.

The next item called "pre-welding", referenced 9, is essential in this conventional machine to crush ends of the profiles in the area where the welding will be carried out transverse, as explained in detail in the introduction to the present description.

More specifically, two heating jaws 10 (shown in section on FIG. 4) come, by mechanical, ultrasonic pressure, hydraulic or pneumatic, crush the section of profiles 6 which will later find in region 11 of the transverse weld operated downstream. It is, as can be seen in Figure 1, to flatten to better region 12 in order to standardize the transverse profile as much as possible of the bag in region 11 where the sides of the bag will be welded.

Figure 5 shows the appearance of the film-profile assembly after passage to the pre-welding station 9, with the crushed regions 13 and 14: as we can see, as it is a simple crush without removal of material, and as we just spread it, it will always remain, in transverse profile, surface inequalities which can later create leaks detrimental to the seal of the bag completed.

The next step, carried out at station 15, consists in carrying out the transverse weld (edge region 11 of the bag), which will thus seal packaging. This is done by compression between transverse heating jaws 16 (shown in section in the figure 6).

Despite the pre-welding carried out upstream at station 9, this step weld, however, poses the risk of imperfections, because it is carried out, as we have just explained, on a surface presenting at profile level a spread of material generating an extra thickness (referenced 17 in the section of FIG. 6) preventing a distribution uniform pressure support and heat transfer required to good weld quality. On the other hand, due to the greater amount of material present in this region, the duration of application of jaws 16 should be extended, further slowing the rate of machine production.

The final step is to separate the bags 18, now individualized, by means of a separation blade which detaches the bags by separating them from the initial strip.

We will now describe the improvement brought by the invention to this process, an improvement which, as will be seen, eliminates the pre-welding stage completely (item 9 of the conventional process) and all the drawbacks attached thereto.

To this end, the invention essentially proposes to delete part of the profile in the transverse weld area this weld can then be carried out on a section with constant profile, without any extra thickness since the packaging obtained will no longer have a profile in this area. The welding times will be reduced (because the sections to weld will have a constant profile) and the quality will be significantly improved, by eliminating any risk of flight to these regions.

To do this, according to an advantageous embodiment, provision is made, as illustrated in FIGS. 7 and 8, to place closure profiles routed in the form of d in the running circuit. a continuous strip, immediately upstream of the forming neck of station 2, a system making it possible to cut segments of sections simultaneously with their routing. More specifically, this system, referenced 18, comprises two assemblies 19 with belt and pulley coming to grip the continuous profile 6 and pass it in front of a shears 20 combined with upstream guides 21 and downstream 22. At the output of this system 18, one obtains individualized segments 23 of profile, of longitudinal dimension equal to the total length of the bag (itself equal to the step p of advance of the machine) minus a value x equal to twice the dimension, in longitudinal direction, of the transverse sealing area required for one of the two sides of the bag (see Figure 10).

These profile segments are immediately introduced between the two sheets of film 3, 4, so that they participate in the synchronous drive of these segments to the associated welding station. This welding station can be formed from station 7 if the closure profile is placed on an edge region of the film, as indicated previously, or else an additional welding station. So according to l invention he n it is not necessary to provide special means for supporting the individualized segments of closure profile during this process; downstream of this welding station 7, the profile segments are in the film and travel at the same time as the latter and at the same speed.

The synchronization of station 18 with the rest of the machine is made, in itself known manner, from coders, cells photoelectric, etc. and possibly automatons adapted to precision required.

Advantageously, means are provided to verify the correct longitudinal positioning of the profile segments relative to the film, in order to immediately notify the operator in the event of a shift so that he can intervene immediately and adjust the machine setting.

The sachet obtained, illustrated in FIG. 9, present in the region end 12 of the transverse welding zone 11 a thickness perfectly uniform and flawless, closing profile 6 stops just before this end region 12 and not encroaching on it.

An additional advantage of the development of the invention is due to the fact that it can be directly adapted to a machine pre-existing, simply by adding the cutting system synchronized 18 immediately upstream of the forming neck of station 2 and by removing or deactivating the pre-welding station 9 (shown for this reason in dotted lines in Figure 7), now become unnecessary.

According to a second implementation variant, the closure profile 6 n is not routed in a continuous strip and cut in situ step by step immediately before the welding station using means 18, but the closure profile 6 is precut on a separate machine. In this case, the cutting station 18 n is not necessary upstream of the forming neck 2.

It remains important in the context of this second variant of implementation, that the segments of the closure profile are sandwiched between the two sheets 3, 4 of the film, so that these participate in the driving the closure profile towards the welding station.

Of course the present invention n is not limited to the particular embodiment which comes from be described but s extends to any variant in accordance with the object defined by the claims.

In particular, the means of routing comprising a belt and pulley assembly 19 according to the embodiment described above can make the subject to many variations.

Furthermore, the longitudinal weld closing longitudinally l packaging can be provided either on an edge of the packaging leading to one end of the transverse welds, or anywhere along the length of the packaging and therefore opening out along the length of the transverse welds. Similarly, the closure profile 6 can be placed either on an edge of the packaging leading to one end of the transverse welds, or anywhere along the length of the packaging and therefore opening out along the length of the transverse welds.

Claims (10)

1. A method of packaging products in recloseable sealed packages each constituted by a flexible rectangular bag made up of two film portions provided with a closure strip, the method comprising the following steps that are performed stepwise and synchronously:

   a) paying out longitudinally a continuous sheet of film (1);

   b) folding said sheet of film (1) over longitudinally to form a tube and uniting the two longitudinal edges of the film by heat sealing;

   c) longitudinally heat sealing a closure strip (6) to the film (1);

   d) transversely heat sealing the tubular film (1) at regular intervals (11 along respective heat seal join lines; and

   e) cutting the film (1) transversely at the transverse heat seal join lines (11) so as to separate individual bags;
      the method being characterized in that the closure strip (6) is sectioned into segments of length equal to the length of the bag minus the width in the transverse direction of each heat seal join line made in step d); and prior to step c), the individual segments of the closure strip (6) are inserted between two adjacent leaves (3, 4) of the folded-over film (1) so that the drive applied to the film contributes to synchronously driving said segments of closure strip up to the heat sealing station that performs step c); and in that the transverse heat sealing is performed in the gaps between the successive segments.
2. A method according to claim 1, characterized in that the closure strip (6) is conveyed to the film (1) in the form of precut segments.
3. A method according to claim 1, characterized in that the closure strip (6) is conveyed in the form of a continuous strip and is cut into segments during an intermediate step prior to step c), which step is likewise performed stepwise and synchronously with the other steps.
4. A method according to any one of claims 1 to 3, characterized in that it further includes the additional step which consists in checking the longitudinal positioning of each segment of strip relative to the film.
5. A machine for packaging products in recloseable sealed packages each constituted by a flexible rectangular bag formed by two film portions provided with a closure strip, and of the type comprising:

   means for paying out longitudinally a continuous sheet of film (1);

   means for folding said sheet of film (1) over longitudinally to form a tube, and for uniting the two longitudinal edges of the film by heat sealing;

   means for longitudinally heat sealing a closure strip (6) to the film (1);

   means for transversely heat sealing the tubular film at regular intervals along respective heat sealing join lines; and

   means for cutting the film transversely at the locations of the transverse heat seal join lines to separate individual bags,
      the machine being characterized in that it includes feed means (18, 19) designed to feed the means for heat sealing the strip with strip segments of length equal to the length of a bag minus the width in the transverse direction of each heat seal join line made by the transverse heat sealing means, and means suitable for inserting individual segments of closure strip prior to their fixing by heat sealing between two adjacent leaves (3, 4) of the folded-over film, such that the drive applied to the film contributes to synchronously driving said closure strip segments to the associated heat sealing station, and in that the successive segments are positioned so as to leave gaps between them for the transverse heat sealing join line.
6. A machine according to claim 5, characterized in that the feed means are adapted to convey precut segments of closure strip onto the film (1).
7. A machine according o claim 5, characterized in that the feed means include means for conveying a continuous closure strip, and means (20) for sectioning the continuous closure strip into segments, upstream from the associated heat sealing means.
8. A machine according to any one of claims 5 to 7, characterized in that it includes means for checking the longitudinal positioning of the cut strip segments relative to the film (1).
9. A machine according to any one of claims 5 to 8, characterized in that it includes means for conveying cut strip segments between the two leaves (3, 4) of the film (1), which means are constituted by a belt-and-pulley assembly (19).
10. Recloseable sealed packaging obtained by implementing the method according to any one of claims 1 to 4, and/or using the machine according to any one of claims 5 to 9.

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