EP0667288A1 - 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

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

Such bags generally comprise 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 seal and to the closure profile. The longitudinal closure profile is generally attached and welded to the film, parallel to the longitudinal weld.

The closure profile is generally a reclosable waterproof profile comprising a male part and a female part already engaged or not, this profile possibly being also possibly provided with ribs or other profiles allowing easy opening of the packages.

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

One of the difficulties in this type of packaging is that the closure profile creates an annoying excess thickness at each of its ends in order to achieve transverse sealing on the two lateral sides of the bag.

These end thicknesses can cause sealing problems in the region of the closing profile and, moreover, slow down the process due to the special precautions which it is necessary to take, which has an obvious effect on the rates of manufacturing and machine performance.

To overcome this particular difficulty, the generally adopted solution, which is set out in particular in 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 the ends of the profiles in the critical region situated in the extension of the lateral sides.

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

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

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

In addition, the subsequent welding step must be slowed down because the quantity of material provided by this part of the crushed profile requires additional heat input, therefore a longer application time of the welding jaws.

The document EP-A-0 528 721 proposes a different technique, consisting of feeding the profile no longer continuously, but through sections of length shorter than that of the bag to take account of 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 then no longer welded directly to the bag, but via this support strip, which thus creates in the end regions only a small excess thickness.

However, this process has a number of drawbacks.

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

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

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

The object of the invention is to overcome all the drawbacks of known techniques, by proposing a method and a packaging machine making it possible to completely eliminate the pre-welding step from conventional methods, by ensuring perfect positioning of the profile without no risk of loss of sealing at the ends thereof, and which is very easily modifiable depending on the choice of profile and length of bag.

The method of the invention is therefore of the generic type comprising the steps, executed 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 welding the tubular film at regular intervals, along a weld joint and (e) transversely cutting the film at the location of the transverse weld joint so as to individualize and separate the bags;

Characteristically of the invention, the closure profile is sectioned in sequence of length equal to the length of the bag. reduced by the width, in transverse direction, of the weld joint produced in step (d) and before 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 drive participates in the synchronous drive of said closure profile segments to the welding station performing step (c).

The closure profile can be conveyed on the film in the form of precut segments.

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

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

The invention also relates to a packaging machine, comprising the means for synchronized implementation of the various aforementioned stages.

The invention finally relates to the packaging sachets 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 bag obtained by implementing a conventional packaging process.

Figure 2 illustrates a machine for implementing such a conventional method.

Figures 3, 4, 5 and 6 are schematic sections taken at 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.

FIG. 8 shows in greater detail the upper part of the machine of FIG. 7.

FIG. 9 is equivalent to FIG. 1, for a sachet produced by implementing the method of the invention.

FIG. 10 schematically illustrates the relationship between the advance of the successive segments of cut section and the advances of the lengths of pitch of the sachets.

FIG. 1 is a partial view of a sachet produced by implementing a conventional method, such as that described by 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 diagrammatically in FIG.

The raw material is a reel of film, printed or not, fed continuously from an unwinder delivering a flat sheet 1. This flat sheet is brought to a station 2 for forming and filling where the sheet is folded over it. even so as to form on a tube composed essentially of two continuous sheets 3, 4 which will constitute the two walls of the sachet when the latter is individualized. At the same time, this same station is preferably filled with the product to be packaged 5, which will be enclosed between the two sheets of film 3, 4 folded back by the forming neck of the station 2.

Simultaneously, the closure profile 6 is unrolled, continuously and at the same speed as the film, which is inserted for example on an edge region of the two sheets 3 and 4 just downstream of the forming neck of the station 2. film 3, 4 and profile 6 progress step by step at the same rate, each step corresponding to a length of bag to be made and the stops for welding allowing the sides of the bags to be sealed at the different workstations that are going 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 using additional welding means, similar to the 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 following post known as "pre-welding", referenced 9, is essential in this conventional machine to crush the ends of the profiles in the area where the transverse welding will be carried out, as explained in detail in the introduction to the present description.

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

FIG. 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 can be seen, as it is a simple crushing without removal of material, and as we are content to spread it, there will always remain, in transverse profile, surface unevenness which can subsequently create leaks detrimental to the sealing of the finished bag.

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

Despite the pre-welding carried out upstream at station 9, this final welding step nevertheless presents risks of imperfections, because it is carried out, as has just been explained, on a surface having at the level of the profile a spreading of material generating an additional thickness (referenced 17 in the section of FIG. 6) preventing a uniform distribution of the support pressure and of the heat transfer necessary for good weld quality. On the other hand, due to the greater quantity of material present in this region, the duration of application of the jaws 16 must be extended, slowing down the production rate of the machine accordingly.

The final step consists in separating the sachets 18, now individualized, by means of a separation blade which detaches the sachets by separating them from the initial strip.

We will now describe the improvement provided by the invention to this process, an improvement which, as will be seen, makes it possible to completely overcome the pre-welding step (item 9 of the conventional process) and all the drawbacks which are attached to it.

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

To do this, according to an advantageous embodiment, provision is made, as illustrated in FIGS. 7 and 8, to place in the running circuit closing profiles conveyed in the form of a continuous strip, immediately upstream from the forming neck. from station 2, a system for cutting profile segments simultaneously with their routing. More precisely, this system, referenced 18, comprises two sets 19 with belt and pulley coming to grip the continuous profile 6 and pass it in front of a shears 20 combined with upstream and downstream guides 21 and 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 the longitudinal direction, of the transverse weld zone 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 these 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 above, or from an additional welding station. Thus according to the invention 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 the station 18 with the rest of the machine is carried out, in itself known manner, from encoders, photoelectric cells, etc. and possibly automatons adapted to the required precision.

Advantageously, means are provided for checking the correct longitudinal positioning of the profile segments relative to the film, in order to immediately warn the operator in the event of a shift so that he can intervene without delay and adjust the adjustment of the machine.

The bag obtained, illustrated in FIG. 9, has a perfectly uniform and flawless thickness in the end region 12 of the transverse welding zone 11, the closure profile 6 stopping just before this end region 12 and does not not encroaching on it.

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

According to a second implementation variant, the closure profile 6 is not conveyed in a continuous strip and cut in situ not to not immediately before the welding station using the means 18, but the closure profile 6 is precut on a separate machine. In this case, the cutting station 18 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 drive of the profile. closing towards the welding station.

Of course the present invention is not limited to the particular embodiment which has just been described but extends to any variant in accordance with its spirit.

In particular, the conveying means comprising a belt and pulley assembly 19 according to the embodiment described above can be the subject of numerous variants.

Furthermore, the longitudinal weld closing the packaging longitudinally can be provided either on an edge of the packaging leading to one end of the transverse welds, or at any point along the length of the packaging and consequently opening onto the length of the transverse welds. Likewise, the closure profile 6 can be placed either on an edge of the packaging leading to one end of the transverse welds, or at any point along the length of the packaging and consequently opening onto the length of the transverse welds.

Claims (10)

Method for packaging products in resealable sealed packages consisting of a flexible rectangular bag formed by two film portions provided with a closure profile comprising the steps, performed step by step and synchronously, consisting of: a) unwinding longitudinally a continuous strip of film (1), b) longitudinally fold this strip of film (1) back onto itself, in tubular form and join by welding the two longitudinal edges of the film, c) longitudinally weld a closure profile (6) on the film (1), d) transversely welding the tubular film (1) at regular intervals (11) along a weld joint and e) transversely cutting the film (1) at the location of the transverse sealing joint (11) so as to individualize and separate the bags, characterized in that the closure profile (6) is sectioned into segments of length equal to the length of the sachet minus the width, in transverse direction, of the solder joint produced in step d), and before step c), the individualized segments of the closure profile (6) are introduced between two adjacent sheets ( 3, 4) of the film (1) folded back on itself, so that the drive of the film participates in the synchronous drive of said segments of closure profile, up to the welding station performing step c). Method according to claim 1, characterized in that the closure profile (6) is conveyed on the film (1) in the form of precut segments. Method according to claim 1, characterized in that the closure profile (6) is conveyed in the form of a continuous strip and cut into segments during an intermediate step prior to step c), also carried out step by step and in synchronism with the other stages. Method according to one of claims 1 to 3, characterized in that it further comprises the additional step of checking the longitudinal positioning of the profile segment relative to the film. Machine for packaging products in sealed reclosable packages consisting of a flexible rectangular bag formed by two portions of film provided with a closure profile of the type comprising: - means for longitudinally unwinding a continuous strip of film (1), means for longitudinally folding this strip of film (1) onto itself, in tubular form, and joining by welding the two longitudinal edges of the film, - means for longitudinally welding a closure profile (6) on the film (1), means for transversely welding the tubular film at regular intervals along a weld joint, and - Means for transversely cutting the film at the location of the transverse weld joint so as to individualize and separate the bags, characterized in that it comprises supply means (18, 19) designed to supply the welding means of the profile, in profile segments of length equal to the length of the bag minus the width, in transverse direction, of the weld joint produced by the transverse welding means and means capable of introducing, prior to their fixing by welding, the segments individualized closure profile between two adjacent sheets (3, 4) of the film folded back on itself, so that the film drive participates in the synchronous drive of said closure profile segments to the associated welding station. Machine according to claim 5, characterized in that the supply means are adapted to convey on the film (1) segments of precut closure profile. Machine according to claim 5, characterized in that the supply means comprise means for conveying a continuous strip of closing profile, and means (20) for cutting the continuous strip of closing profile into segments, upstream of the associated welding means. Machine according to one of claims 5 to 7, characterized in that it comprises means for checking the longitudinal positioning of the cut profile segments relative to the film (1). Machine according to one of claims 5 to 8, characterized in that it comprises means for conveying segments of cut profile, between the two sheets (3, 4) of the film (1), consisting of a set ( 19) belt and pulley. Sealing resealable packaging obtained by the implementation of the process according to one of claims 1 to 4 and or using the machine according to one of claims 5 to 9.

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