EP0344815B2 - Method and device for wrapping products, in particular stacks of products, in a stretchable film cover - Google Patents

Description

The invention relates to a method according to the preamble of claim 1 and a device suitable therefor according to the preamble of claim 12.

For wrapping piece goods, in particular piece goods stacks, for example made of cement, chemical goods or the like. filled bags exist and are formed by means of a palletizing device, packaging methods are known in which the piece goods or the piece goods stack is wrapped with so-called shrink film, which is applied with heat after wrapping and then firmly shrinks onto the piece goods or the relevant one Stack of piece goods creates In the context of these known processes, so-called winding processes are known in which flat film is wrapped around the piece goods to be wrapped, and so-called hood processes are known in which at least one (possibly also two) film hood (s) is pulled over the stack and then shrinking it.

Significant disadvantages of shrink film packaging processes include in that the piece goods wrapped in the shrink film must be subjected to heat for the purpose of shrinking. This not only leads to correspondingly high energy costs, but when exposed to a flame it also means that these processes are unsuitable for flammable goods, such as are widely available in the chemical industry, for example, because of the otherwise associated dangers.

A further disadvantage of all shrinking methods is that, due to the required film thicknesses, a relatively high amount of material is required, which leads to relatively high packaging costs, since film material has become very expensive as a petroleum product, particularly since the known energy crises.

In addition, shrinkage is often perceived as not being very environmentally friendly, since this creates exhaust gases to a not inconsiderable extent, and because the operators are exposed to considerable noise pollution.

In addition, when shrinking, gluing can take place with the goods, which then often leads to corresponding damage to the piece goods parts when unpacking them, and is particularly disadvantageous if, for example, they consist of bags filled with bulk goods.

In order to avoid the aforementioned and other disadvantages, one has accordingly already started to use so-called stretch films instead of the shrink film, which do not require any heat to adhere to the piece goods to be packaged. Rather, it is sufficient if the stretch film material is "stretched" before wrapping the piece goods, which after the wrapping causes the film material to contract again and accordingly - as desired - firmly attaches to the piece goods to be wrapped or packaged. Significant "stretching" is understood to mean considerable stretching to an extent which, after wrapping, leads to sufficiently large forces being generated by the film material which ensure sufficient stack strength in the case of stacked piece goods, without it (also possibly after multiple wrapping of a wrapped packaging unit) for mutual sliding of piece goods and the like. is coming.

Here, the so-called winding stretching has become known, in which stretch film - similar to winding shrinkage - is wrapped around the piece goods to be wrapped. Despite the advantages achieved compared to shrinking, winding stretching is also associated with not inconsiderable disadvantages. These are, in particular, that the handling is relatively incomprehensible and time-consuming, and that the film consumption - although less than the shrinking - is still perceived as unsatisfactory for cost reasons, this being caused in particular by the fact that overlaps of adjacent layers are required in each case in the winding stretch.

The stack strength is also still unsatisfactory, especially if the piece goods stack is only wrapped "in one direction" (then generally horizontally) with web-like stretch film, since then no significant normal forces are generated between adjacent piece goods layers, which only prevent shifting of piece goods layers due to correspondingly increased friction. The internal vertical forces generated by "diagonal" winding are not sufficient for this. A "vertical" wrap would, however, leave two side surfaces of a general cargo stack free, that is, surfaces that would be difficult to cover with sheet films. A double (horizontal and vertical) wrap is out of the question for cost reasons.

EP-OS 0 081 328 has already proposed for hand winding stretching to stretch the web-shaped stretch film material in its longitudinal direction by 55% and the resulting contraction of the film web by 30-25% of its original width by an additional stretching to partially compensate transversely to the longitudinal direction in order to save film material, so that the (film) "loss" resulting from the longitudinal stretching can be reduced from 30-25% to approximately 15%, but manual stretching with a two-dimensionally stretched has become Film proved to be hardly practical, since it is hardly possible to wrap general cargo with a two-dimensionally stretched film.

In addition, in order to protect the top surface (and possibly the underside) of a packaging unit wrapped on its side surfaces with stretch film, a flat film has to be applied as a cover sheet, and a separate cover sheet feeder with a corresponding work step is required for this.

Overall, it should be noted that packaged goods packed by stretch wrap are often not adequately weather-resistant, since moisture can often penetrate into the packaging unit at the edges of the film, and that the view of the packaged packaged goods is often imperfect, when it is unwinding into a generally hardly avoidable crease comes.

Therefore, considerations have already been made to cover the piece goods or piece goods stack to be packed with a film hood made of stretch film, as is known in principle for shrink film material. However, despite extensive development work, these efforts have so far yielded only extremely unsatisfactory results, since a stretch film hood was first inserted into a reefing device by hand in order to accomplish a reefing process (i.e. an accordion-like folding of the hood side sections), and then the film hood that was shirred in its sides so-called reefing frame (manual or possibly mechanical) had to be transferred to a second place or work station so that the shirred and pre-stretched film hood could be pulled over a stack of piece goods.

All of this clearly leads to a relatively large amount of effort (if only because of the two required workstations, on the one hand the hood is prepared and on the other hand the hood is pulled over the general cargo stack), among other things, The space required for this may be disadvantageous, but also the effort to be carried out and, among other things. the low work output that can only be achieved with this is also perceived as unsatisfactory.

To avoid the above disadvantages, DE-OS 27 06 955 and 31 01 310 have made known devices which are also suitable for wrapping piece goods (stacking) with a stretch film hood, as is expressly mentioned in DE-OS 27 06 955 . When using these previously known devices, however, there is only a considerable scheduled stretching of the tubular stretch film material or a stretch film hood in the horizontal transverse direction (= perpendicular to the vertical longitudinal axis of the piece goods stack and thus the stretch film hood), so that there is then a tight covering General cargo stacks with a stretch film hood first come to an (apparently) satisfactory (because smooth) packaging unit with a film wrapper that seems to take into account the requirements for durability or stack strength on the one hand and the tightness of the wrapper on the other hand, but this occurs particularly with stacked goods which, for example, with cement or the like. filled sacks exist, not only when forming the piece goods stack to vent the sacks not completely filled with bulk goods, but it has been shown that with such piece goods stacks a delayed post-venting can also take place (in particular with repeated handling with, for example, relatively jerky Put on the piece goods stack), so that the stack volume is changed during this post-venting, in particular due to a reduction in the stack height. In the case of one-dimensionally stretched film material, this inevitably leads to a corresponding slackness at least in the vertical direction, which may even result in wrinkling.

In addition, the vertical forces exerted by the film hood, which may arise when the film hood is pulled over the stack of items due to a certain slight expansion, when the hood is pulled and the film material slides over guides, are irrelevant or for the creation of a sufficient one Inadequate stacking strength, especially if the piece goods are filled sacks that are later refilled during handling. This also applies to the subject of DE-OS 30 03 052. Here, the stretch film hood is pulled down after the horizontal transverse stretching out of the state of being gained by the guide bracket and slides under it with a certain amount of friction, so that there is a certain vertical expansion can if the tensile forces are to be greater than the frictional forces, but this does not result in significant longitudinal stretching and thus also does not result in the desired dimensional stability of the wrapped piece of goods stack, in particular if these consist of filled sacks.

The present invention is accordingly based on the object of improving the known methods and devices of the type in question while avoiding in particular the disadvantages discussed above and to provide a method and a device suitable and specific for carrying out this method, by means of which packaging units the here The type in question can be created using the advantageous stretch film hoods, which do not lose their dimensional stability even in the case of "problem piece goods" and possibly repeated handling.

According to the invention, the procedural part of the above object is achieved by the characterizing features of claim 1, while the device-related part of the above task is solved by the characterizing features of claim 12, preferred embodiments of the present invention being described in the method and device subclaims are.

It has surprisingly been found that two-dimensional stretching - in contrast to winding stretching processes - is not only practicable at all, but also solves practically all previous problems with hood stretching processes if the film material is first stretched by 15-20% and this transverse stretching then a (based on the then contracted vertical unit length) a vertical stretch of at least 5% (preferably about 10 - 15%) is superimposed, whereby the required stack strength is achieved sustainably and yet even with sensitive piece goods (e.g. bottles standing on documents as General cargo position) does not lead to adverse effects as before, because up to now, due to the lack of longitudinal stretch, it had to rely on very high transverse stretch in order to be able to form reasonably usable packaging units.

• Fig. 1 eine Seitenansicht einer erfindungsgemäßen Vorrichtung in einem Zustand, in dem die mittels einer Abzugseinrichtung von einem (Schlauch-)Folienvorrat abgezogene (Schlauch-)Folie von einer Spreizeinrichtung bereits erfaßt ist;
• Fig. 2 eine Darstellung gemäß Fig. 1, wobei der vom Folienvorrat abgezogene Folienabschnitt bereits von der Spreizeinrichtung auseinandergezogen ist und der freie Randabschnitt des Folienabschnittes einer Reffeinrichtung zugeführt ist;
• Fig. 3 eine Darstellung gemäß den Fig. 1 und 2 nach dem Reffen der später die Seitenwände der Folienhaube bildenden Abschnitte beim Schweißen der Haubennaht vor dem Abtrennen der Haube von dem Folienvorrat;
• Fig. 4 eine Darstellung gemäß den Fig. 1 bis 3, wobei die Folie nach dem Abschneiden zu Ende gerefft worden ist und ein neuer Folienabschnitt gleichzeitig von der Spreizeinrichtung erfaßt ist;
• Fig.5 ein Horizontalstretchen der Folienhaube mittels einer Stretcheinrichtung, wobei der das Reffen bewirkende Teil der Reffeinrichtung ausgeschwenkt ist;
• Fig. 6 das Überziehen der gestretchten Folienhaube über einen darunter befindlichen Stückgutstapel, wobei zugleich ein vertikales Stretchen der Seitenwände der Folienhaube erfolgt;
• Fig. 7 den mit der Stretchfolienhaube umhüllten Stückgutstapel (mit zwei Varianten an der der Palette zugekehrten Seite);

The invention is further explained below with the aid of an exemplary embodiment with reference to a schematic drawing, the explanations given in the description of the exemplary embodiment also evidently being of general importance with regard to the invention. It shows:

• 1 shows a side view of a device according to the invention in a state in which the (tube) foil drawn off from a (tube) foil supply by means of a removal device has already been gripped by a spreading means;
• FIG. 2 shows a representation according to FIG. 1, the film section drawn off from the film supply having already been pulled apart by the spreading device and the free edge section of the film section being fed to a reefing device;
• 3 shows a representation according to FIGS. 1 and 2 after the reefing of the sections which later form the side walls of the film hood when welding the hood seam before the hood is separated from the film supply;
• 4 shows a representation according to FIGS. 1 to 3, the film having been reefed to the end after being cut off and a new film section being simultaneously gripped by the spreading device;
• 5 shows a horizontal stretching of the film hood by means of a stretching device, the part of the reefing device causing the reefing being pivoted out;
• 6 shows the stretching of the stretched film hood over a stack of general cargo located underneath, at the same time vertical stretching of the side walls of the film hood taking place;
• 7 shows the piece goods stack wrapped with the stretch film hood (with two variants on the side facing the pallet);

The drawing shows a device designated by 1 for the automatic or automatic wrapping of piece goods by means of a stretch film hood, more precisely of piece goods stacks 2, which consist of stacked piece goods parts (for example bags filled with bulk goods) and have been formed by means of a palletizing device.

Tubular film is unwound from a tubular film supply 3 by means of a pair of drivable rollers 5 as a pull-off device in the direction of arrow 4 and fed to a spreading device 6 which has spreading plates 7 tapering against the direction of travel of the film, so that the tubular film (see FIG. 2) can be pulled apart . The free edge section of the film section drawn off from the tubular film supply 3 is pressed and held against the expansion plates 7 by pressing means 8 in the direction of the arrows 8 '.

The spreading device 6 is followed by a reefing device, generally designated 9, which is used for reefing, that is to say for the concertina-shaped folding of the tubular film section 3 'which later forms a hood, over a vertical distance h which is less than the length of the film section 3'.

A welding device 10 (see FIG. 3) for forming a horizontal seam 11 is indicated between the spreading device 6 and the reefing device 9, and between the welding device 10 and the spreading device 6 there is a cutting device 12 for cutting off the film hood which forms after welding Foil section 3 '' (see Fig. 4).

Furthermore, the device 1 has a stretch device by means of which the film section 3 'is to be stretched. The stretch device itself consists of two individual devices, on the one hand a device for horizontal stretching and on the other hand a device for vertical stretching, as will be described further below.

Finally, there is also a lifting device with which the hood 3 ″, which is closed at its upper end, can be pulled over the piece goods stack 2.

Concerning. the reefing device 9 should be added that it has a movable reefing jaw 13 or the like. Containing reefing frame 14 which is vertically movable and forms part of the lifting device. The reefing frame 14 also forms part of the stretching device, as will be explained further below.

After the free end section of the film section 3 'is inserted from the tubular film supply 3 into the spreading device 6, where it can be held by means of the pressing means 8, 8 (see FIG. 1), the process continues Pulled off the film from the tubular film supply 3 and by means of the pressing means 8, 8 which, for example, from suction jaws or the like, but also from clamping jaws or the like. can exist, with simultaneous spreading of the tubular film downwards, so that the pressing means 8, 8 per se form pressing and holding means (for the film) (see FIG. 2).

After the free edge section of the film section 3 'has been transferred into the reefing device (more precisely, between the outer reefing jaws 13' and reefing rollers 15 of swiveling reefing units 16), the reefing takes place according to FIG. 3, the reefed film between the outer reefing jaws 13 'and inner reef jaws 13 '' accordion-shaped.

The welding device 10 (see FIGS. 3, 10) then functions to form the seam 11 and the film hood 3 ″ thus formed can be cut off from the film supply by means of the cutting device 12 (see FIG. 3).

The remaining section of the side sections forming the side walls of the film hood 3 ″ is then reefed (see FIG. 4) until the section forming the bottom 17 of the film hood 3 ″ runs horizontally (that is to say it is tensioned), as is the case here 4, so that afterwards the reefing units 16 according to FIG. 5 can be pivoted outwards and a transverse stretching can take place in the horizontal direction (see FIG. 5), in which the reefing jaws 13 are moved outwards according to the arrows 18 .

Then the film hood 3 ″ stretched in the transverse or horizontal direction can be pulled over the piece goods stack 2 (see FIG. 6) by lowering the reefing jaws 13 guided on vertical bars 19 according to the arrows 20. In this process, vertical stretching of the film hood 3 '' then takes place, but this can also take place when the film is removed from the film stock. Later stretching has the advantage that the film is not yet stretched in the vertical or longitudinal direction during horizontal stretching and accordingly initially is even easier to handle.

In the present case, the film hood 3 ″, which is shirred and horizontally stretched in accordance with FIG. 5, is pulled over the (longitudinal) stretch bracket 24 when the piece goods stack 2 is pulled over, when it is stretched in the vertical longitudinal direction according to arrow 25 when the reefing unit 16 is lowered is, with a defined longitudinal stretching by about 12% of the already stretched film.

The lowering of the stretch jaws 13 forming part of the lifting device takes place below the pallet 21 on which the stack of packaged goods 2 is arranged, so that the stretch film hood 3 ″ lies under the pallet with its free edge section or engages under it (see FIG. 7).

From Fig. 7 it can also be seen that on the underside of the piece goods stack (in the illustrated embodiment between piece goods stack 2 and pallet 21) a flat film can also be applied to protect the piece goods stack 2 from below. According to the left part of FIG. 7, this can be done in such a way that the edge 22 'of the flat film 22 is applied upwards to the piece goods stack or, as shown in the right part of FIG. 7, is brought down to the pallet. The latter is somewhat simpler in terms of work, but the solution shown in the left part of FIG. 7 can in principle also be accomplished without difficulty.

With reference to Fig. 4 of the drawing, it should be added that during the final horizontal reefing, tubular film can already be removed from the film supply and fed to the spreading device 6, so that after the stack of packaged goods has been wrapped (FIG. 7), the stack of packaged goods is transported away on a conveyor 23 and the transport of a further stack of piece goods 2, a new wrapping process can begin immediately, so that not only the considerable advantages described above can be achieved with the device and the method according to the invention, but also an extraordinarily high work output.

Due to the defined longitudinal stretching of the film material according to the invention in addition to the transverse stretching, even with relatively heavy and heavily ventilated piece goods, such as sacks filled with cement, packaging units are obtained which, even after being folded several times, still have excellent stacking strength, while also being relatively sensitive General cargo stacks, the general cargo layers of which, for example, consist of bottles on intermediate layers, can be handled in an optimal manner according to the invention, since on the one hand the transverse stretch no longer needs to be made as large as it was previously required in hood stretching processes in order to provide at least reasonably satisfactory packaging units Realize (but the transverse forces generated by the transverse stretch were then usually too large for sensitive piece goods), because because of the longitudinal stretching even after subsequent ventilation, it is still common e piece goods harmless, but sufficiently large normal forces are applied by the film wrapping, which ensure a corresponding increase in the frictional forces, so that there is no longer a mutual displacement of adjacent piece goods positions. It has been shown that, contrary to expectations, in contrast to winding stretching, two-dimensional stretching when stretching the hood is practicable, especially if the initially stretched hood is stretched lengthwise immediately when the stack of goods is pulled over, which is easily defined or taken using suitable measures given size is possible, since the hood with its (top) bottom is to be held firmly on the piece goods stack and forms a corresponding abutment, and since it is also easily possible to achieve the desired, appropriate longitudinal stretch by means of friction rollers, friction rollers or the like. to apply, which act on the hood abutting an abutment.

Claims (20)

1. A method for completely wrapping products (2) by means of stretch films, more particularly stacked product parts, such as stacks of products formed, for example, and more particularly, by means of a paletting device, such stacks consisting of a plurality of superposed product layers, in which method a tubular film portion (3) of a smaller periphery than the periphery of the product (2) for wrapping, is drawn from a (tubular) film supply (3) and is opened by expansion at its free end; the side walls of the tubular film portion (3) are reefed to place them in folds extending substantially concentrically to the vertical centre-line of the product for wrapping; the tubular film portion (3) is welded at its end facing the film supply and the resulting film cover (3'') is severed from the film supply (3); the film cover (3'') is transversely stretched in the horizontal transverse direction; and the transversely stretched film cover (3'') is drawn over the product for wrapping, with a longitudinal tension which smoothes the film material and pulls it over the product, characterised in that before it is pulled over the product the film cover (3'') is longitudinally stretched at least in the area of the cover side walls in the vertical longitudinal direction additionally by at least 5% of its vertical starting length in the transversely stretched state.
2. A method according to claim 1, characterised in that the film material is longitudinally stretched by 10 - 15%.
3. A method according to claim 1 or 2, characterised in that the film in respect of its supply condition is transversely stretched in manner known per se by at least 10%.
4. A method according to claim 3, characterised in that the films are transversely stretched by about 15 - 20%.
5. A method according to any one of claims 1 to 4, characterised in that the longitudinal stretching of the film cover (3'') is effected at least partially during the drawing of the film cover over the product (2) for wrapping.
6. A method according to any one of claims 1 to 5, characterised in that the longitudinal stretching of the film cover (3'') is effected at least partially during the drawing of the tubular films from the film supply (3).
7. A method according to one or more of the preceding claims, characterised in that drawing of a tubular film from the film supply (3) to form another film cover (3'') is already initiated before the product to be wrapped prior to this is completely wrapped.
8. A method according to claim 7, characterised in that the drawing of the tubular film from the film supply (3) to form another film cover (3'') is initiated immediately after the previously formed film cover (3'') has been cut off.
9. A method according to one or more of the preceding claims, in which, to wrap the underside of the product (2) for wrapping, which underside is not to be covered by the film cover (3''), a flat film (22) is disposed immediately beneath the product (2) for wrapping, said flat film being larger than the floor area of the stack of products (2), characterised in that the edge portions (22') of the flat film (22) projecting laterally beyond the product (2) for wrapping are applied upwardly to the product stack (2) before the product is covered by the film cover.
10. A method according to one or more of claims 1 to 9, characterised by the use of a stretch film having an initial thickness of about 50 - 250 µm.
11. A method according to claim 10, characterised by the use of films having a thickness of about 100 to 12 µm.
12. Apparatus (1) for wrapping products (2) by means of stretch film (3'), more particularly stacked product parts, such as stacks of products, for example, and more particularly, stacks of products formed by means of a paletting device, such stacks consisting of a plurality of superposed product layers, comprising a (tubular) film draw-off means (5), whereby tubular stretch film (3) is drawn portion-wise from a (tubular) film supply; an expanding means (6) following the drawing-off means (5), whereby the tubular stretch film can be opened at its free end portion; a reefing means (9) following the expanding means (6) to reef the film portion over a vertical distance less than the length of the film portion; welding means (10) for welding a tubular film portion (3') withdrawn from the film supply, at its end portion facing the film supply; a cutting means (12) whereby each film cover (3'') formed during the welding operation is severed from the film supply, a transverse stretching means (13; 14) whereby the film portion is stretched in the horizontal transverse direction; and a (cover pull-over) lifting means, whereby the transversely stretched cover (3'') is pulled over the product (2) for wrapping, for performing the method according to one or more of claims 1 - 11, characterised by a longitudinal stretching means (14, 24) whereby the film portion/the film cover (3'') can be longitudinally stretched in the vertical longitudinal direction (25) by at least 5% and preferably 10 - 15%.
13. Apparatus according to claim 12, comprising a reefing frame (14) receiving the reefed film material during reefing and movable vertically during wrapping, characterised in that the reefing frame (14) is part of the longitudinal stretching means.
14. Apparatus according to claim 13, characterised in that the reefing frame (14) has longitudinal stretching means which can be frictionally engaged with the film material above the folds formed during the reefing operation and exert on the film material, during the lowering of the reefing frame (14), a predetermined traction which effects a longitudinal stretching.
15. Apparatus according to claim 14, characterised in that the longitudinal stretching means comprise longitudinal stretching elements (24) substantially of bar or rod shape, which extend substantially transversely.
16. Apparatus according to claim 15, characterised in that the longitudinal stretching elements (24) are disposed at least in the corner zones of the opened film tube.
17. Apparatus according to claim 15, chracterised in that the longitudinal stretching elements (24) are disposed on the inside of the film tube.
18. Apparatus according to one or more of claims 13 to 17, characterised in that the longitudinal stretching means comprise longitudinal stretching rolls or rollers which are drivable or adjustable in respect of their frictional resistance, whereby it is possible to impress on the film material longitudinally directed friction forces greater than the forces required to smooth the reefed film.
19. Apparatus according to claim 14, characterised in that the reefing means (9) comprise reefing rolls (15) operating against reefing jaws (13') or the like and forming part of a reefing unit (9) which can be swung away.
20. Apparatus according to claim 19, characterised in that the reefing units (9) can be swung against the product unit from the outside.

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