EP0399540B1 - Method and device for wrapping products in a hood of stretchable film and packaging unit shaped with this - Google Patents

Abstract

The invention relates to a method for wrapping products (2) - in particular stacked product parts such as, and in particular, substantially parallelipipedic or cubic product stacks consisting of a plurality of superposed and substantially flush layers of product - by means of a tubular section (1) of stretchable film whose original circumference is less than the circumference of the product (2) to be wrapped which, before being drawn over the product, is stretched in its circumferential direction to an extent which makes it possible to draw it effortlessly over the product, and which, after being drawn over, rests closely on the product with the expansion being retained, the section of stretchable film being sealed off at one of its ends, with the formation of a welded joint (13), to form a hood (1') of (stretchable) film, the weld extending, after wrapping, substantially centrally and parallel to two mutually opposite edges of the end faces (17) of the product, the length L of the welded joint being at least about 85 to 90% of the length of the edges of the end faces of the product stack which, in the wrapped state, are parallel to the said weld, and a device for carrying out the abovementioned method and a packaging unit to be formed by means of the abovementioned method and/or of the abovementioned device. <IMAGE>

Description

The invention relates to a method for wrapping general cargo - in particular stacked general cargo parts such as and in particular i.a. by means of a palletizing device, essentially cuboid or cube-shaped stacks of goods, which consist of several superposed, generally there are essentially congruent layers of general cargo, by means of a tubular stretch film section, the unstretched original circumference of which is smaller than the circumference of the general cargo to be encased, which is stretched in its circumferential direction by an amount prior to being coated over the general cargo to be encased, which is an effortless covering over the encased item General cargo enables, and which, after being pulled over, remains tightly stretched against the general cargo, with the tubular stretch film section being welded at one end to form a closed (stretch) film hood to form a weld seam, which after wrapping is essentially centered and parallel runs to two opposite edges of the end faces of the piece goods to be wrapped.

The invention further relates to a device for wrapping piece goods according to the above method, which u.a. four (spread) fingers or the like has, which are to be introduced into the interior of the tubular film before wrapping.

The invention further relates to a packaging unit to be formed in particular by the above method and / or using the above device.

For wrapping piece goods, in particular palletized piece goods stacks, for example made of cement or chemical bulk goods or the like. filled sacks and i.a. are formed by means of a palletizing device, packaging processes are known in which the piece goods or the piece goods stack is wrapped with so-called shrink film, which is applied after the wrapping with heat and then shrinks firmly against the piece goods to be wrapped / the piece goods stack to be wrapped .

Within the scope of these known processes, i.a. So-called winding processes are known in which flat film is wrapped around the piece goods / stack of pieces to be wrapped, and so-called hood processes are also known in which at least one (possibly also two) film hood (s) is pulled over the piece goods to be wrapped and then shrinking it.

The main disadvantages of the shrink film packaging process include in that the piece goods wrapped with shrink film must be subjected to heat for the purpose of shrinking. This not only leads to correspondingly high energy costs, but also, in particular when exposed to an open flame, to the fact that these processes are not suitable for flammable goods, such as those that are available, for example, and especially in the chemical industry, because of the associated dangers are suitable.

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 good, which then often leads to corresponding damage to the piece goods parts when unpacking and is particularly disadvantageous if, for example, they consist of bags filled with bulk goods.

In order to avoid the above and other disadvantages, it has accordingly also started to use so-called stretch films instead of the shrink films, 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" (= stretched) before the piece goods are wrapped, whereby the (technical) term "stretching" does not generally mean any slight stretch of the starting material, but rather a considerable stretch of ia at least 10% and more, which in the wrapping state is then also able to ensure the dimensional stability required for the required stack strength of packaged goods. Such stretching leads, after the wrapping, to the fact that the film material contracts again and thereby firmly attaches to the piece goods to be wrapped or packaged.

Here, the so-called winding stretching has become known, in which web-shaped 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 lie, for example, in the fact that the desired good load securing is still unsatisfactory, since winding stretching produces only horizontal or only vertical tensioning forces if the piece goods to be wrapped are not wrapped in both directions. However, the latter leads to a disproportionately high hen use of materials with corresponding costs. Also, the film consumption - although lower than the shrinkage - is still perceived as unsatisfactory for cost reasons, this being caused in particular by the fact that not inconsiderable overlaps of two mutually adjacent film webs are required in each case in the stretching process.

In addition, in order to protect the surface 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. This can cause corrugations in the area of such a cover sheet and, in particular, damage if the cover is turned over several times, since such a cover sheet is not under tension on the piece goods.

Overall, it should therefore be noted that packaged goods packed by stretch wrapping 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 incomplete if it is often unavoidable when wrapping Wrinkling comes.

One has therefore already gone over to covering packaged goods to be packaged or packs of packaged goods to be packaged with a film hood made of stretch film, as was known in principle from shrink film packaging. However, considerable problems have arisen, particularly in the area of the weld seam, which have not yet been satisfactorily solved.

A weld seam is just as unavoidable with stretch film hoods, which are each formed from a section of a tubular film material for reasons of economy, as is the case with shrink film hood processes, whereby the difficulties detailed below with shrink film packaging using film hoods are probably due to the Heat exposure and the restructuring of the molecules taking place here have not shown nearly as much as has been the case up to now with stretch film hood processes.

Such tubular film material is known to have a folded, as it were flat initial state, in which the tubular film material has two mutually parallel first side surfaces and two V-shaped inwardly folded second side surfaces. This folding is therefore useful in order to be able to store such tubular film material in a space-saving manner (and thus also with a relatively small width) rolled up into rolls. l.ü. It has been shown that such tubular film material folded in the stock state can be opened better than is the case when the tubular film material is fed to a hood former in the unfolded state, in which the tubular film width is therefore equal to half the circumference of the tubular film.

In a method previously practiced by the applicant (as well as by competitors), a tubular film section was welded in the as-yet unstretched original state in such a way that the corresponding end section of the tubular film section was welded practically in the form supplied (and thus also the corresponding storage width of the tubular film) , the weld seam therefore having a length which corresponded to the width of the mutually parallel first side faces of the tubular film.

Since the circumference of the tubular film in the non-vertical original state is intended to be significantly smaller (in some cases quite considerably) than the length of the front edges of the piece goods / piece goods stack, with which the weld seam runs parallel in the wrapped state, the weld seam in this way of working during stretching is inevitable and necessarily one subjected to very considerable stretching, and not only when (cross) stretching before wrapping the piece goods / piece goods stack, in which the tubular film must be widened to such an extent that it can be easily pulled over the piece goods / piece goods stack, but also afterwards in the wrapped state. This is evident from the fact that a stretch film hood is still under (sometimes considerable) elongation when it is firmly attached to the piece goods / piece goods stack, whereby stretches of up to 30% and more can be provided (see, for example, DE-A-37 07 877) .

This procedure then, as has already been indicated, leads to problems in the area of the weld seam, in particular at the points at which the tips which inevitably arise in the case of such a tubular film hood lie on one another in the wrapped state on the relevant end face of the piece goods / piece goods stack.

In the process known from DE-A-37 07 877, already mentioned above, a completely different route has been chosen (presumably in an effort to avoid the problems outlined above), namely the film opened before welding and (cross) stretched and only then separated and welded from the tubular film supply in the desired length, i.e. practically in the no longer folded and already stretched state, which inevitably results in a weld seam, the length of which in the stretched state before the covering is (considerably) greater than the length of the one in the wrapped state State parallel to the front edge of the piece goods / piece goods stack to be wrapped.

Such a formation of the weld seam can, however, result in that in the film material existing internal tensions in the plasticizing of the film material occurring during the welding process are lost (largely or even substantially completely), so that they are practically no longer present in the welded section even after the welding process has ended, but remain in the remaining film material so that it tearing or even tearing can occur, especially in the border areas between the weld seam and the adjacent film material, in particular when the packaging units formed in this way are turned over several times, which, if there are corresponding tears, can lead to a loss of the required stack strength and always to a loss of the desired tightness.

The present invention has for its object to improve the known methods and devices and thus last but not least the packaging units to be formed therewith in such a way that the problems previously occurring in the weld seam area and in the adjacent areas are avoided or at least considerably reduced to a harmless level.

As a solution to the procedural part of this object, the invention provides that the length of the weld seam is selected so that it is at least approximately 85 to 90% of the length of the end edges of the piece goods to be encased which are parallel to it in the encased state, and this is preferred provided that it is at least about 95% of the length of the front edges of the piece goods parallel to it in the wrapped state, a highly preferred embodiment being that the length of the weld seam is substantially equal to the length of the front edges of the wrapped state parallel to it Piece goods is, the weld seam preferably being formed before (transverse) stretching.

Particularly in the case of the most preferred method, in which the length of the weld seam before the (transverse) stretching is formed with a length which is practically equal to the length of the end edges of the piece goods parallel to it in the wrapped state, no harmful tensions occur in the finished wrapping state of the packaging unit more and there are still no tears, unwanted corrugations and the like, because the weld seam in the unstretched (unstretched) initial state before stretching the film material has more or less exactly the same length as in the wrapping state. This gives (in particular compared to an embodiment in which the weld seam length is significantly smaller than the corresponding stack length) the considerable advantage that the stresses occur essentially perpendicular to the weld seam and no longer at any or random angles to the weld seam, the latter in particular in the V-shaped double areas of the film can lead to overstretching, in particular in such a way that greater stresses occur in the film below than in the upper film section. On the other hand, in the configuration according to the invention, the inner film tensions in the upper film section are greater than in the lower one (which can be largely free of tension), so that the lower film sections in the V-shaped double region are readily under the tension of the upper film sections Apply to the piece goods and the tensioned upper film sections ensure a smooth surface.

The practically unstretched condition of the welded-off area also does not have any adverse side effects, because in this area no stretch tensions are required for the desired tight or tight wrapping of the piece goods.

Even if this condition is strictly achieved only if the length of the weld seam is chosen to be equal to the length of the front edges of the piece goods to be encased which are parallel to it in the encased condition, this effect of a considerable improvement over the previously known generic methods can already be seen qualitatively and can be achieved to a quantitatively most remarkable and noticeable extent if the length of the weld seam is chosen to be only slightly smaller than the length of the end edges of the piece goods to be encased parallel to it in the encased state, i.e. 95% of this length.

In order to achieve the aim of the invention, when using the customary folded film tube material, which has two mutually parallel first side faces and two second side faces each folded in a V-shape, it can be advantageous, if necessary, to weld the tubular film material at its end section to be welded off before welding. to be deformed so that the two mutually parallel first side surfaces have the desired length of the weld seam while reducing the size of the V-shaped, inwardly folded second side surfaces (or possibly increasing the size of the V-shaped second side surfaces). The storage width of the tubular film material before the welding process (and preferably before the stretching) is then generally increased to the desired size of the weld seam, and the relevant tubular film section is then stretched with the appropriate weld seam length after welding and thereby onto a piece goods (stack) concerned adapted shape so that the stretch film hood formed in this way can be easily pulled over the piece goods to be wrapped. When stretching to oversize, the weld seam area is then generally stretched somewhat, but due to the dimensioning of the weld seam in accordance with the invention, this stretched state practically goes back to zero, since the unstretched weld seam length According to the invention essentially equal to the length of the end wall edges parallel to the weld seam in the encased state.

In order to be able to implement this adaptation of the tubular film material kept in stock to the desired welding width in a particularly expedient manner, there is a device for carrying out the method according to the invention which generally has four (spreading) fingers or the like. has, which are to be introduced into the interior of the tubular film in order to open it fully and (cross) it, designed according to the invention in such a way that the fingers can first be moved into a first position or working position in which the length of the mutually parallel first side walls the tubular film has the desired length of the weld seam, and that the fingers or the like. only afterwards (namely after welding) can be moved into a second position in which the tubular film is stretched into its covering state.

Preferred embodiments of the present invention are described in subclaims.

• Fig. 1 eine Seitenansicht auf einen Schlauchabschnitt, wie er üblicherweise zur Bildung einer Folienhaube verwendet wird;
• Fig. 2 eine Draufsicht auf den Folienabschnitt gemäß Fig. 1 in leicht geöffneter Stellung in Richtung des Pfeiles II in Fig. 1 gesehen;
• Fig. 3 eine Seitenansicht auf einen zu umhüllenden Stückgutstapel mit darüber angeordneter, zu einer Folienhaube zu verarbeitender, von einem aufgerollten Folienvorrat zugeführter Schlauchfolie;
• Fig. 4 eine Draufsicht auf die Schlauchfolie gemäß Fig. 2, nachdem (Spreiz-)Finger in das Innere der leicht geöffneten Schlauchfolie eingefahren sind;
• Fig. 5 die Schlauchfolie gemäß Fig. 4, nachdem ihre ersten Seitenflächen (unterVerkürzung derV-förmig eingefalteten zweiten Seitenflächen) wenigstens am Abschweiß-Endabschnitt auf eine Länge gebracht worden sind, die der Länge der zu bildenden Schweißnaht entspricht;
• Fig. 6a eine Seitenansicht auf die Schlauchfolie gemäß Fig. 5 in Richtung des Pfeiles VI gesehen nach Anlegen von Schweißbacken;
• Fig. 6b nach Bildung der Schweißnaht; und
• Fig. 6c in (quer-)gestretchter Übergröße vor dem Überziehen;
• Fig. 7a eine Draufsicht auf den mit der Stretchfolienhaube umhüllten Stapel nach dem Überziehen der Folienhaube; und
• Fig. 7b im Vergleich dazu eine Ansicht gemäß Fig. 7a des mit einer Folienhaube überzogenen Stückgutstapels, dessen Folienhaube in konventioneller Weise mit einer Schweißnaht versehen ist, welche vor dem Stretchen in einer der Breite des zugeführten Folienschlauches entsprechenden Länge ausgeführt worden ist.

The invention is explained below using an exemplary embodiment with reference to a drawing. It shows:

• Figure 1 is a side view of a tube section, as is usually used to form a film hood.
• FIG. 2 shows a top view of the film section according to FIG. 1 in a slightly open position in the direction of arrow II in FIG. 1;
• 3 shows a side view of a stack of piece goods to be wrapped, with a tubular film arranged above it, to be processed into a film hood, and fed from a rolled-up film supply;
• FIG. 4 shows a plan view of the tubular film according to FIG. 2 after (spreading) fingers have been moved into the interior of the slightly opened tubular film;
• 5 shows the tubular film according to FIG. 4 after its first side faces (shortening the V-shaped folded second side faces) have been brought to a length at least at the welding end section which corresponds to the length of the weld seam to be formed;
• 6a shows a side view of the tubular film according to FIG. 5 in the direction of arrow VI after the application of welding jaws;
• 6b after formation of the weld seam; and
• Fig. 6c in (cross) stretched oversize before covering;
• 7a shows a plan view of the stack covered with the stretch film hood after the film hood has been pulled over; and
• 7b in comparison, a view according to FIG. 7a of the stack of articles covered with a film hood, the film hood of which is provided in a conventional manner with a weld seam, which was carried out before stretching in a length corresponding to the width of the supplied film tube.

1 to 4 show the free end section of the tubular film 1 formed as a stretch film, which comes from a roll-up reel of tubular film and which is supplied with a width B corresponding to the storage width to a piece goods stack 2 according to the arrow 3 in FIG. 3 from the center, and which has two mutually parallel first side faces 4.1 and 4.2 and two second side faces 5.1 and 5.2 folded inwards in a V-shape in the folded storage and supply state, each of which has two legs 6.1.1 and 6.1.2 or 6.2.1 and 6.2.2 exist.

1 shows a side view of the tubular film 1 in the direction of the arrow in FIG. 2 and FIG. 2 shows a section through the tubular film 1 according to FIG. 1 in the direction of the section line 11-11, but already in a slightly opened state , in the (spread) fingers or the like (see Fig. 4 and 5) or the like. can be inserted into the interior of the tubular film 1. Such opening of the tubular film 1 from the storage state, in which adjacent first and second side surfaces 4 and 5 lie against one another with mutual contact, can be done, for example, by means of suction bars 8 or the like. (see FIG. 2), which are placed on the free end section of the tubular film 1 from the outside on the first side faces 4 and can then be moved apart by a corresponding amount according to the arrows 9 (see FIG. 2).

Fig. 3 shows a side view of the relative assignment of the free end portion of the tubular film 1 to a piece of goods to be wrapped with a stretched film hood 2, which is supported to enable understretching on its underside 10 on the substrate 11 by means of a support means 12, the area of which is smaller than the bottom 10 of the piece goods stack 2.

Since, according to the invention, the length Lder at the upper end of the stretch film section weld seam 13 (see, for example, FIG. 6b) is substantially equal to the length I of the front edges of the piece goods stack 2 parallel to it in the wrapped state, but the storage and thus the feed width B of the tubular film 1 is smaller than the length I of the relevant end edges of the piece goods stack 2, and since the weld seam 13 is expediently to be produced in the unstretched state of the tubular film material, the width B of the supplied tubular film 1, that is to say the length of its parallel first be tenflächen 4, are first enlarged accordingly.

This happens in the present case that the fingers or the like. 7, which will later be used for completely opening the tubular film 1 and for stretching, are moved into the slightly open tubular film according to FIG. 4, the lower section of which is generally used. To enable the smallest possible height, the device is folded in a zigzag shape by means of suitable devices, and that the fingers 7 are accordingly moved outwards in the direction of the arrows 14 parallel to the first side faces 4, with their enlargement and corresponding reduction of the second side faces 5, until the length B 'of the first side faces 4, at least in the designated welding area, is equal to the predetermined or envisaged length L of the weld seam to be formed, namely the length 1 of the front side edges of the stack of bulk goods 2 which are parallel to the weld seam 13.

It is clearly not necessary that the fingers 7 extend into the welding area. Rather, it can remain free, so that welding jaws 15 can be applied according to FIG. 6 to form the welding seam 13 (see FIGS. 6a and b).

Thereafter, the fingers 7 can then be extended diagonally according to the arrows 16 (see FIG. 5) with the tubular film 1 fully opened and, if necessary, also perform the (transverse) stretching process in which the film hood 1 'now formed is in relation to the piece goods stack 2 is brought to an oversize, which allows it to be subsequently pulled over the piece goods stack 2 from above, with its lower edge section shrinking the underside 10 of the piece goods stack 2 and the film hood 1 'consequently with permanent stretch on the piece goods stack 2 is present.

7a shows a plan view of the piece goods stack 2 wrapped with the film hood 1 '. It can be seen that the length of the weld seam 13 is practically equal to the length I of the face edges 17.1 and 17.2 of the piece goods stack 2 parallel to it, and that the weld seam 13 so that it again has the length I that it already had before stretching. Of course, according to FIG. 6c, it was subjected to a certain stretch in the transverse direction during the (transverse) stretching, but this stretching stretch is evidently reduced to zero due to the design according to the invention, so that the problems previously occurring in the area of the weld seam 13 are not only so reduced to a different level, but are practically completely eliminated.

In order to make this even clearer, FIG. 7b shows a view according to FIG. 7a on a piece goods stack covered with a film hood 1 ', in which the weld seam 13' has been carried out in a conventional manner before stretching in a length B which is the width of the supplied tubular film 1 corresponds. As stated, this has the consequence that the weld seam 13 '(its length is therefore considerably smaller than the length I of the face edges 17.1 and 17.2 of the piece goods stack 2 parallel to it in the wrapped state) not only when stretching to oversize (for covering the General cargo stack 2) is considerably (more) stretched, but that the weld seam 13 'remains in a considerable stretched state, especially in the wrapped state when the film hood 1' is firmly in contact with the general cargo stack 2, with the result that it is particularly in the tip regions 18 considerable stress peaks, which in turn can lead to tears, particularly in the case of multiple handling, and thus to the removal of protection against the effects of weather and possibly even to the loss of the required dimensional stability of the packaging unit.

As has already been explained above, the objective according to the invention can also be achieved qualitatively compared to the prior art if the length of the weld seam 13 in the unstretched state is not exactly the length I of the end edges 17 of the piece goods stack parallel to it , but, for example, is 5% smaller than the length L with an intended elongation of 12.5%, since it is evident that the stress conditions which arise in the conventional mode of operation are already considerably reduced, as a rule to a harmless level.

Claims (7)

1. A method of wrapping piece goods or a stack (2) thereof in a hood (1') of stretch film, in which, before stretching, a hood (1') is formed from a stretchable laterally pleated tube (1) supplied from a store and, in the storage and supply state, comprising two parallel closely adjacent first side surfaces (4, 4) having a given supply width (B) and two intermediate V-shaped inwardly folded second side surfaces (5, 5') and a smaller periphery than the piece goods or stack (2) to be wrapped, the laterally pleated tube (1) being welded in a transverse seam (13) at a distance from its free end and cut from the supply behind the portion forming the hood (1'), the hood (1') being completely opened for the purpose of wrapping the piece goods or stack (2) and stretched along substantially its entire length to the extent required for wrapping, characterised in that the laterally pleated tube (1) is given a transverse seam (13) having a length (= ideal length) substantially equal to the width (1) parallel to the transverse seam (13) of the piece goods or stack (2) to be wrapped, and in cases where the feed width (B) of the laterally pleated tube (1) is not equal to the ideal length of the transverse seam (13) to be formed, before the transverse seam is positioned at least the top end portion of the part of the laterally pleated tube (1) for subsequently forming the hood (1') is given a width equal to the ideal length of the transverse seam (13).

2. A method according to claim 1, characterised in that the length (L) of the transverse seam (13) is at least approximately 95% of the width (1) of the piece goods (2) parallel thereto.

3. A method according to claim 1 or 2, characterised in that after the transverse seam (13) has been positioned, the hood (1') formed from the laterally pleated tube portion is stretched so that the film material forming the side surfaces of the stretch film wrapping is substantially uniformly stretched at all side surfaces.

4. Adevice for wrapping piece goods or a stack (2) thereof in a hood (1') of stretch film, the device comprising a welding means (15) by means of which, before stretching, a hood (1') is formed from a laterally pleated tube (1) having a smaller periphery than the piece goods or stack (2) to be wrapped, the laterally pleated tube (1) being welded in a transverse seam at a distance from its free end, the device also comprising a cutting means for cutting the laterally pleated tube (1) behind the portion forming the hood (1'), and four expanding fingers or the like (7) which are inserted into the interior of the laterally pleated tube portion forming the hood and are moved apart for stretching, for working the method according to any of claims 1 to 3, characterised in that the expanding fingers (7) or the like, in cases where the feed width (B) of the laterally pleated tube (1) is less or greater than the ideal length of the required transverse seam (13), in a first working step (Fig. 5) are moved into a first operating position with simultaneous partial consumption or simultaneous deepening of the side pleats (6.1.1, 6.1.2; 6.2.1, 6.2.2) without stretching the film material, until the web width (B') of the laterally pleated tube (1), altered from the original feed web width (B), is equal to or slightly less than the width (1) of the stack (2) of piece goods and therefore equal to the ideal length of the transverse seam (13); and after the transverse seam (13) has been positioned, in a second working step the expanding fingers (7) are moved apart into a second operating position until the hood (1), after being completely opened, is finally stretched to a predetermined extent required for wrapping.

5. A device according to claim 4, characterised in that in the second working step, the expanding fingers (7) or the like are moved so that the film material forming the side surfaces of the hood-like stretch-film wrapping is substantially uniformly stretched at all side surfaces.

6. A unit load made up of piece goods wrapped in a hood of stretch film formed from a laterally pleated tube having a smaller periphery than the piece goods to be wrapped and provided before stretching with a transverse seam at a distance from its free end, formed by a method according to any of claims 1 to 3 and/or by a device according to claims 4 or 5, characterised in that the length (L) of the transverse seam (13) before stretching is preferably about 95% of the width (1) of the piece goods (2) parallel to the transverse seam (13).

7. A unit load according to claim 6, characterised in that the length (L) of the transverse seam (13) is substantially equal to the width (1) of the stack (2) of piece goods.

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