EP1072514A1 - Method and apparatus for wrapping products, particularly stacks of products, with a sleeve of stretch foil - Google Patents

Abstract

The method involves forming a hood from a tube from a tube storage device with a circumference at least 10 per cent less than that of the item to be wrapped, pulling it over the item, spreading the hood in several steps to achieve uniform stretching, transversely stretching the hood. The tube is shaped with a stretch of at least 50 per cent before a transverse seam is welded. An Independent claim is also included for an arrangement for wrapping items, especially item stacks, with stretched foil.

Description

• daß zwei i.w. gleich lange, parallele erste Kanten der Hauben-Aufspeiz-Querschnittsfläche parallel zur Quernaht der Haube sowie zu den die Breite des Stückgutes bestimmenden Stückgut-Seitenflächen verlaufen,
• daß zwei i.w. gleich lange, parallele zweite Kanten (
  
  Bezugskanten") der HaubenAufspreiz-Querschnittsfläche i.w. rechtwinklig zu den ersten Kanten verlaufen,
• und daß der Haubendeckel von drei übereinander liegenden Folienlagen gebildet wird, nämlich von
  • einer über ihre gesamte Breite mittig von der Quernaht durchsetzten, rechtwinkligen oberen Folienlage, deren Größe und Form gleich der Hauben-AufspreizQuerschnittsfläche ist,
  • zwei die mittlere Folienlage bildenden, einander spiegelsymmetrisch gegenüberliegenden Folienabschnitten in Form jeweils eines gleichschenkligen Dreiecks, deren Höhenlinie jeweils von einem äußeren Abschnitt der Quernaht gebildet ist, und deren Grundlinie jeweils in einer Bezugskante (= zweite Kante) liegt, und
  • zwei die untere Folienlage bildenden, zu den mittleren dreiecksförmigen Folienabschnitten kongruenten, dreiecksförmigen unteren Folienabschnitten, die jeweils mit dem darüber liegenden dreiecksförmigen mittleren Folienabschnitt des Deckels eine an der Dreieck-Grundlinie offene Folientasche bilden;

und bei dem die so aufgespreizte, i.w. noch ungedehnte Haube sodann auf einen zum Überziehen erforderlichen Überziehquerschnitt quergestretcht wird, indem die zunächst das Aufspreizen und sodann das Querstretchen bewirkenden Elemente aus ihrer Stellung, in welcher sie die Haubenseitenwände i.w. ungedehnt aufspreizen, jeweils horizontal in Diagonalrichtung nach außen in eine Überziehposition bewegt werden, in welcher die quergestretchten Haubenseitenwände jeweils in einem Überzieh-Sicherheitsabstand zu der ihnen jeweils benachbarten Stückgut-Seitenwand stehen, der i.a. umlaufend i.w. konstant ist, so daß der Abstand der Eckkanten der Haube in deren Überziehzustand zu der ihnen jeweils benachbarten Eckkante des Stückgutes jeweils i.w. gleich groß ist.The invention relates to a method for wrapping piece goods with generally rectangular horizontal cross-sectional area, in particular cuboid or cube-shaped piece goods, with a horizontally cross-stretched (plastic film) hood made of stretch film, in particular from a stretch film side gusseted tube, in which one of A (tube) supply fed, in the stocked state, flat film tube, the unstretched circumference of which is at least 10% smaller than the circumference of the piece goods to be wrapped, is first formed (before cross-stretching) by the film tube being spaced apart from its free supply end a transverse seam is welded off and then severed above the transverse seam; in which the hood thus formed is pulled over the piece goods to be wrapped in such a way that its closed end in the finished wrapping state (= hood installation state) rests as a hood cover under a biaxial (hood cover) horizontal expansion caused by transverse expansion of the hood side walls at the top of the piece goods; in which the hood, in order to achieve a generally uniform circumferential expansion of its side walls when stretching transversely before stretching and covering it over the piece goods to be wrapped - if necessary in several steps - is initially expanded completely unexpanded so that the horizontal cross-sectional area of the hood spreading enclosed by the hood side walls iw is geometrically similar to the horizontal general cargo cross-sectional area and is thus arranged (spread),

• that two parallel first edges of the hood-splice cross-sectional area of generally the same length run parallel to the transverse seam of the hood and to the general cargo side surfaces which determine the width of the cargo,
• that two parallel edges of equal length (
  
  Reference edges ") of the hood expansion cross-sectional area are generally perpendicular to the first edges,
• and that the hood cover is formed by three layers of film lying one above the other, namely by
  • a right-angled upper layer of film penetrated in the middle by the transverse seam over its entire width, the size and shape of which is equal to the hood spreading cross-sectional area,
  • two film sections which form the middle film layer and are mirror-symmetrically opposite one another in the form of an isosceles triangle, the contour of which is formed by an outer section of the transverse seam and the base line of which lies in a reference edge (= second edge), and
  • two triangular-shaped lower film sections forming the lower film layer, congruent to the central triangular film sections, each forming an open film pocket on the triangular base line with the triangular-shaped central film section of the cover lying above it;

and in which the hood, which is in this way still largely unstretched, is then cross-stretched to an over-pulling cross-section required for pulling-on, by the elements which first cause the spreading and then cross-stretching from their position in which they spread the hood side walls, unstretched, each horizontally in the diagonal direction are moved outside into a pull-over position, in which the cross-stretched hood side walls are each at a pull-over safety distance from the adjacent bulk goods side wall, which is generally constant all around, so that the distance between the corner edges of the hood in their pull-over state to that of them neighboring corner edge of the piece goods is generally the same size.

The invention further relates to a device for performing the above generic packaging method described.

After the shrink hood packaging technology in the late 80s / early 90s within a short time i.w. thanks to the stretch hood packaging technology has been replaced it has been in this state of the art for a long time well-known, but in practice hardly / not yet practiced packaging technology yet considerable problems in the manufacture of loading units over many years, since both technologies only seemingly i.w. are the same.

One of these problems was that it was in the hood cover due to this when Cross stretches of the hood side walls embossed stretching and resulting Tension to film tears and / or came to the fact that the tops of the already fully spread open a stretch film hood in its V-shaped lid or triangular-shaped foil pockets in the shape of a lump. This was and is after as before not only highly undesirable for aesthetic reasons, but can in turn in particular lead to film tears when such loading units, for example by means of a forklift stacked on top of each other for storage or for transport or again be unstacked, as e.g. the forks of the lifting device the high-lying film tips can damage.

According to the technical teaching disclosed in EP 0 399 540 A1, these were disadvantageous Apparitions in general in one - in relation to the width of the piece goods to be wrapped or General cargo stack - based on short cross weld seam, more precisely in the tension of the Hood cover, which during cross stretching due to a too short weld in the Adjust the lid. They were able to do so by means of the invention disclosed in this publication be avoided that the gusseted hose used for hood formation with a Cross seam is provided, the length of which is at least about 85-90% of that parallel to the cross seam Width of the piece goods / piece goods stack to be wrapped is selected, preferably at least approx. 95% of the stack width or i.w. equal to the width of the stack, with no tearing of the film came to a point-like rising of the film in the area of the film pockets, because the hood cover is stretched so that the upper film sections the V-shaped double areas under appropriate tension to the top of the stack invest.

These difficulties came about because when you switched from the shrink hood packaging technology to the stretch hood packaging technology before May 1989 the formatting of the side gusset hoses used to form the hood initially according to the formatting for the shrink hood packaging technology had provided, namely in such a way that the (still unstretched) fully expanded side gusseted tube spans or limits a hood-expansion cross-sectional area that i.w. is geometrically similar to the general cargo cross-sectional area. The length of the edges was the Hood-spreading cross-sectional area of a shrink film hood each by a certain one Factor greater than the respectively adjacent, parallel edge of the stack cross-sectional area, so that a shrink hood in the spread state already had a covering state in which their hood side walls all around an i.w. constant safety distance from the general cargo stack had.

At the time, therefore, one also initially had stretch hood packaging technology the the side gusseted hoses intended for use are formatted so that they can be Expanded state a hood-expanded cross-sectional area that is geometrically similar to the stack cross-sectional area spanned or limited, but of course with the difference to shrink hood packaging technology that the side edges of the hood expansion cross-sectional area each i.w. smaller by the same factor than the neighboring one, parallel stack side surface, and has the formatted and fed stretch film side gusseted tube welded with a cross seam when forming the hood.

As a result, the length of the cross weld seam was the same as that formatted feed width of the gusseted tube was, and for example only 75% of the stack width was, if a transverse stretch of the hood is provided in its installation state of 25% was. With such short transverse weld seams, however - as in EP 0 399 540 A1 in individual is executed - to the problems already mentioned above.

Nevertheless, this way of working, which was initially envisaged, had one technical logic ", because efforts were made to use the properties / possibilities offered by the selected stretch film as fully as possible, and therefore already when stretching the stretch film hood from its generally unexpanded spreading state to its transversely overstretched state (and not only in the system state) Obviously, this is only possible if the cross-sectional area of the hood-expansion in the area of the side walls of the hood is geometrically similar to the cross-sectional area of the stack, and if this geometric similarity is generally maintained when stepping sideways.

The process also likes to make use of this goal and this knowledge. EP 0 399 540 A1 Use when stretching the hood side walls, but only with a vertical distance to the closed hood end (= hood cover), which is used to achieve a longer Cross seam or a larger cross seam ratio (= length of the cross seam to the stack width) of at least approx. 85 - 90% and thus more favorable tension conditions in the lid acc. EP 0 399 540 A1 has already been formatted geometrically dissimilar in the feed state (then the spreading and cross stretching of the hood not on the outer edges of the Side gusseted hose or starting from this, but not in the area folded hose side surfaces), or before cross seam formation in the cross seam area is reformatted according to the feed condition.

The teaching according to EP 0 399 540 A1 has also proven its worth over the past decade: when used, film tears in the hood cover as well as tip formation in the area of the two film pockets could be effectively avoided, and not only with a relatively low transverse stretch of, for example. 12% or 15%, which is only a few percent larger than the limit transverse elongation of about 10%, above which one can actually be used in practice Stretch "speaks, but also with transverse stretch values in the range from 20 to about 30% and more, which (for example DE-A-37 07 877) were still considered practical by the experts in view of the film properties at the time.

In the meantime, the relevant supplier industry has now developed stretch films that Enduring cross stretch values of 50% and (significantly) more without damage, even then, if a vertical longitudinal stretch is superimposed on the transverse stretch, i.e. the stretch film hood is stretched biaxially on the finished loading unit in the system state, like this one from the EP 0 344 815 is known. However, it has now been found that for such high transverse stretch values of about 50% and (possibly considerably) more according to the teaching. EP 0 399 540 A1 or B2 is obviously to be expanded or modified, since it has been found that it is in such a large transverse stretch even to the dreaded tip formation in the hood cover and possibly even tearing of the film, if acc. EP 0 399 540 worked becomes. Because with such cross stretch ratios, it can not only be too short Welding seams, but problems may also arise if the transverse seams are too long.

The present invention is accordingly. the task is based on a procedure and a To create device for its implementation, in the / whose application the described Problems can be reliably avoided even with very large transverse stretch.

The procedural part of this task is solved according to the invention. in the fact that the hose supplied in the laid-flat state from the hose supply with a relatively large transverse stretch of the hood to be formed of at least about 50% of its side walls in the state of contact with the fully encased piece goods for the purpose of hood formation by welding off the transverse seam and severing the free seam provided with the transverse seam lower hose section with respect to its width when laying the transverse seam (at least in the area of the transverse seam to be formed before it is formed) is formatted such that the two legs of the same length of the two V- or triangular-shaped, pocket-forming film double areas of the hood cover are still largely unexpanded The state of expansion of the hood extends at least approximately to the respective adjacent second edge of the hood-expansion cross-sectional area, which runs below the cross-seam area and is geometrically similar to the horizontal piece goods cross-welding surface ken, preferably extend with one leg section into this hood-expanding cross-sectional area, the Schenekl section length X of these leg sections in each case being approximately at least as large as the corner edge distance Y between a corner edge of two adjacent hood side walls in the still unexpanded state of expansion and this Corner edge adjacent outer corner edge of the corresponding gusset, the corner edge distance Y, the one Expansion reserve "of the hood cover characterizes (such that the horizontal expansion of the cover when stretching the hood side walls loosely in the cover area only begins or becomes significant when this occurs Expansion reserve "is exhausted, i.e. the cover is under horizontal tension) is always> 0 (as already taught by EP 0 399 540 for transverse stretch values 10% ≦ σ _q ≈ 30 - 40%), but it should also be noted that the relative hood cover Expansion reserve characteristic value Y / X> 1, namely / and preferably at σ _q ≈ 50% Y / X ≈1, and increasing with increasing σ _q , at σ _q ≈ 100% (or possibly more) Y / X » 1, where the leg section length X can possibly go to zero.

Fig. 1 bzw. Fig. 1'

eine Seitenansicht auf eine durch Querabschweißung aus einem Seitenfaltenschlauch gebildete Stretchfolienhaube an ihrem mit der Quernaht versehenen oberen Endabschnitt im noch ungedehnten, nicht aufgespreizten Zustand gem. Fig. 2 bzw. Fig. 2';

Fig. 2 bzw. Fig. 2'

einen Schnitt durch die Stretchfolienhaube gern. Fig. 1 bzw. Fig. 1'in Richtung der Schnittlinie II-II bzw. II'-II' gesehen, wobei die Haube in Fig. 2 bzw. Fig. 2' (abweichend von ihrem tatsächlichen Zustand) bereits etwas aufgespreizt dargestellt ist, um die seitlich eingefalteten V-förmigen Seitenfalten erkennen zu können; und

Fig. 3 bzw. Fig. 3'

eine Draufsicht auf die (noch ungedehnt) vollständig aufgespreizte Haube in Richtung des Pfeiles III bzw. III' in Fig. 1 bzw. Fig. 1' gesehen, sowie auf den mittig/zentrisch unter der Haube befindlichen zu umhüllenden Stückgutstapel,

wobei der Darstellung gern. den Fig. 1 - 3 bzw. den Fig. 1' - 3' Stapel-Querschnittsabmessungen gern. den Abmessungen einer Euro-Palette zugrundeliegen, also eine parallel zur Querschweißnaht vorhandene Stapelbreite B = 1.200 mm sowie eine Stapeltiefe T = 800 mm, und wobei ein Querstretch σ_q = 30 % vorgesehen ist, so daß bei dem vorhandenen Stapelumfang U_st = 4.000 mm ein Umfang des ungedehnten Schlauches U₃

= 3.077 mm zu wählen ist, und für die Länge bzw. Tiefe h der Seitenfalten jeweils ein Wert von 308 mm, so daß die Länge t = 2 h der beiden rechtwinklig zur Querschweißnaht 6 verlaufenden ersten Kanten der gem. Fig. 3 vollständig aufgespreizten Stretchfolienhaube 3

616 mm beträgt, und die Länge der beiden zur Quernaht 6 parallelen zweiten Kanten C_h bzw. C_v der gem. Fig. 3 vollständig aufgespreizten Haube 3 jeweils 923 mm. Die rechteckige Hauben-Aufspreiz-Querschnittsfläche der Haube 3 ist mithin geometrisch ähnlich zur Stapel-Querschnittsfläche gewählt. Denn multipliziert man den Wert b = ch =cv mit dem sich aus dem vorgesehenen Querstretch von 30 % ergebenden Dehnungsfaktor f^* von 1,3, so ergibt sich ein Wert von 1.200 mm = B, während sich bei Multiplikation des Wertes t = 2 h = 616 mm mit dem Dehnungsfaktor f* von 1,3 die Stapeltiefe T = 800 mm ergibt.Before the present invention is explained further in general below or on the basis of exemplary embodiments, it appears to be expedient or necessary, inter alia / in particular. To explain or clarify the terms used above and below with the aid of a drawing for better / easier understanding. First of all shows

Fig. 1 and Fig. 1 '

a side view of a stretch film hood formed by transverse welding from a gusseted tube at its upper end portion provided with the transverse seam in the still unexpanded, non-expanded state according to FIG. Fig. 2 and Fig. 2 ';

Fig. 2 and Fig. 2 '

like a cut through the stretch film hood. Fig. 1 and Fig. 1 'seen in the direction of section line II-II or II'-II', the hood in Fig. 2 or Fig. 2 '(deviating from its actual state) is already shown slightly spread out in order to be able to recognize the laterally folded V-shaped gussets; and

Fig. 3 or Fig. 3 '

a top view of the (still unexpanded) fully spread hood seen in the direction of arrow III or III 'in Fig. 1 or Fig. 1', and on the stack of items to be wrapped in the center / center under the hood,

being happy to present. 1 - 3 and FIGS. 1 '- 3' stack cross-sectional dimensions like. are based on the dimensions of a Euro pallet, i.e. a stack width B = 1,200 mm parallel to the cross weld seam and a stack depth T = 800 mm, and a transverse stretch σ _q = 30% is provided, so that with the existing stack circumference U _st = 4,000 mm a circumference of the unstretched hose U ₃

= 3,077 mm is to be selected, and for the length or depth h of the gussets a value of 308 mm, so that the length t = 2 h of the two first edges of the gem. 3 fully expanded stretch film hood 3

616 mm, and the length of the two parallel edges 6 to the transverse seam C _h or C _{v of} the gem. 3 fully spread hood 3 each 923 mm. The rectangular hood expansion cross-sectional area of the hood 3 is therefore chosen geometrically similar to the stack cross-sectional area. Because you multiply the value b = c H = c v with the stretch factor f ^* of 1.3 resulting from the intended transverse stretch of 30%, the result is a value of 1,200 mm = B, while multiplying the value t = 2 h = 616 mm with the expansion factor f * of 1.3 gives the stack depth T = 800 mm.

This spreading (and later stretching) of the stretch film hood 3 takes place by means of spreading and stretching elements 7, which can be designed as vertical fingers or stirrups, and onto which a hood 3 after the transverse seam 6 has been placed and the lower tube section has been separated forming free end portion of the gusseted tube is wrinkled before laying (welding) the transverse seam 6.

Since the length l _{6 of} the transverse seam 6 is equal to the hose feed width b, because the side gusseted hose is welded with its formatting in the feed state, the length of the transverse seam 6 is therefore also 923 mm, so that the transverse seam ratio Q = b / B is (only) about 0.77, so the length of the transverse seam 6 is (only) 77% of the width B of the stack 2 parallel to it.

Fig. 4a

die obere Folienlage F_O des ungedehnt aufgespreizten Foliendeckels einer Haube gern. den Fig. 1 - 3 in einer Draufsicht;

Fig. 4b

die obere Folienlage f_o gem. Fig. 4a im quergestretchten Zustand f'_o, wobei zusätzlich die Kontur der oberen Folienlage f_O im noch ungedehnten Aufspreizzustand (gern. Fig. 4a) eingezeichnet ist;

Fig. 5a

die unter der oberen Folienlage f_O liegende mittlere Folienlage f_M des Haubendeckels im ungedehnten Aufspreizzustand;

Fig. 5b

die mittlere Folienlage f_M des Haubendeckels im quergedehnten Zustand f'_M, wobei zusätzlich die noch ungedehnte Form der mittleren Folienlage f_M im Aufspreizzustand (Fig. 5a) eingezeichnet ist;

Fig. 6a

die untere Folienlage f_U des ungedehnten Haubendeckels in der Aufspreizstellung;

Fig. 6b

die untere Folienlage f_U im quergestretchten Zustand f'_U, wobei zusätzlich die untere Folienlage f_U um ungedehnten Aufspreizzustand eingezeichnet ist (Fig. 6a), und

Fig. 6c

eine Draufsicht auf die Oberseite 2 des zu umhüllenden Stückgutstapels 2, der der besseren Übersicht halber in Fig. 6 links neben Fig. 6a gezeichnet ist, dessen Oberseite 2 sich aber im Aufspreiz- und späteren Anlagezustand unmittelbar unterhalb der unteren Folienlage f'_U befindet,

wobei in den Fig. 4 - 6 die jeweils betroffene Fläche des Haubendeckels kreuzschraffiert ist, und wobei die in den Fig. 4 - 6 dargestellten Verhältnisse hinsichtlich der Haubenformatierung im Quernahtbereich einem Beispiel entsprechen, welches vor Schaffung des Verfahrens nach der EP 0 399 540 den Stand der Technik der Stretchhauben-Verpackungstechnologie dargestellt hat, was hier aber - bei der Verdeutlichung der Ausbildung des Haubendeckels hinsichtlich seines Aufbaus - unerheblich ist.Are the elements 7 from their hood-spread position acc. Fig. 3 horizontally and acc. through the corner edges e ₁ to e _{4 of} the piece goods stack 2 running (movement) arrows diagonally in the overdrawn state of the hood 3 shown with dotted lines in FIG. 3 Moving outwards, starting from the triangular tips Q or P _r located in the hood cover in the area of the cross weld 6, tensions occur due to the stresses impressed on the hood cover by the transverse stretching of the hood side walls, and the top sections have already been raised in a zigzag shape of the two film pockets formed in the hood cover, which are to be explained below with the aid of further drawing figures, since their relatively complicated, geometric structure is particularly important in relation to the problem at hand here. In this respect shows

Fig. 4a

the upper film layer F _{O of} the unexpanded film lid of a hood is happy. Figures 1-3 in a plan view.

Fig. 4b

the upper foil layer f _o acc. FIG. 4a f in quergestretchten state _'o, in addition, the contour of the upper film layer f _O in the still unstretched spread state is located (like FIG. 4a.);

Fig. 5a

the central film layer f _{M of} the hood cover lying underneath the upper film layer f _O in the unexpanded expanded state;

Fig. 5b

the middle film layer f _{M of} the hood cover in the transversely stretched state f ' _M , the additionally unexpanded shape of the middle film layer f _{M being shown} in the expanded state (FIG. 5a);

Fig. 6a

the lower film layer f _{U of} the unstretched hood cover in the spread position;

Fig. 6b

the lower film layer f _U in the cross-stretched state f ' _U , the lower film layer f _U being additionally drawn in by the unexpanded spreading state (FIG. 6a), and

Fig. 6c

a top view of the top 2 of the piece goods stack 2 to be encased, which is drawn in FIG. 6 to the left of FIG but is in the spreading and later installation state immediately below the lower film layer f ' _U ,

4-6, the area of the hood cover concerned is cross-hatched, and the relationships shown in FIGS. 4-6 with regard to hood formatting in the transverse seam area correspond to an example which was used before the method according to EP 0 399 540 was created State of the art of stretch hood packaging technology has shown, but what is irrelevant here - when clarifying the design of the hood cover with regard to its structure.

FIGS. 7a-9b show partial representations of the hood cover corresponding to FIGS. 4a-6b in the cross-seam area according to FIG. of the hood formatted in EP 0 399 540, where Fig. 7a corresponds to Fig. 4a, Fig. 7b, 4b, Fig. 5a, 8a, ..., and Fig. 9b, 6b.

10-12 show, compared to FIGS. 4-9, an enlarged representation of the upper foil layer f _O (FIG. 10), the middle foil layer f _M (FIG. 11), and the lower foil layer f _U (FIG. 12) ) of the hood cover in the still unexpanded expansion state, in each case in a graphic overlay on the one hand according to the formatting according to EP 0 399 540, and on the other hand acc. the previous state of the art according to creation of the method. EP 0 399 540, that is to say in a respective overview of FIGS. 4a and 7a (FIG. 10), or FIGS. 5a and 8a (FIG. 11), or FIGS. 6a and 9a (FIG. 12).

If you have a gusseted hose 3 acc. 1 and 2 or FIGS. 1 'and 2' of a respective feed width b of its two sides 8, 8 not folded in in the supply and feed state, and with a pleat depth on both sides h = t / 2 supplies the welding device to a stretch film hood packaging machine in order to form the free end section of the tube 3 in order to form a stretch film hood 3 to be welded with a transverse seam 6 and then to be separated from the hose supply behind this, and if the hood 3 thus formed is then on their outer vertical corner edges (in plan view: Corners ") e ₁ - e ₄ (see FIGS. 3, 3 '), it is known that at the closed hood end - in addition to the four surfaces formed by the hood side walls - a fifth surface for the stretch film packaging of a stack of packaged goods 2 a ( Hood) cover.

• einer durchgehenden oberen Folienlage f_O, welche mittig die parallel zu den Haubenseitenflächen 8, 8 verlaufende Quernaht 6 enthält (s. Fig. 4a bzw. Fig. 7a bzw. Fig. 11),
• weiterhin aus einer mittleren Folienlage f_M, die aus zwei V-förmigen bzw. dreiecksförmigen Folienabschnitten Q-B-C bzw. P-A-D besteht, die sich jeweils von den rechtwinkling zur Quernaht verlaufenden Seitenkanten a_l bzw. a_r (s. Fig. 3, 3') des Haubendeckels aus zur Mitte hin erstrecken, spiegelsymmetrisch zueinander angeordnet sind, und jeweils an einem in der Quernaht 6 liegenden Punkt Q_M bzw. P_M enden,
• sowie schließlich aus einer unteren Folienlage f_U, die aus zwei V-förmigen bzw. dreiecksförmigen unteren Folienabschnitten besteht, die jeweils unter einem dreiecksförmigen Folienabschnitt der mittleren Folienlage f_M liegen und kongruent (= deckungsgleich) zu diesem sind,
• wobei jeder der beiden mittleren dreiecksförmigen Folienabschnitte Q_M-B_M-C_M (s. Fig. 5a) bzw. P_M-A_M-D_M mit dem jeweils zu ihm kongruenten, unter ihm liegenden unteren dreiecksförmigen Folienabschnitt Q_U-B_U-C_U bzw. P_U-A_U-D_U eine zum jeweiligen Rand B-C bzw. A-D hin offene Folientasche bildet, deren jeweils von dem mittleren dreiecksförmigen Folienabschnitt Q_M-B_M-C_M bzw. P_M-A_M-D_M sowie dem darüber liegenden dreiecksförmigen Folienabschnitt Q_O-B_O-C_O bzw. P_O-A_O-D_O der rechtwinkligen oberen Folienlage f_O des Haubendeckels gebildete Taschen-Oberseite bei einer idealen Verpackung des Stapels 2 mit einer Haube 3 (horizontal) eben, also parallel zur Stückgutoberseite 2 verläuft, die sich aber ggf. zipfelförmig aufstellen kann, wenn die Länge l₆ der Quernaht 6 in Relation zur Breite B des Stapels 2 (und damit das Quernahtverhältnis l₆/B) unterhalb eines in der EP 0 399 540 definierten Grenzwertes liegt, wenn der Querstretch σ_q etwa zwischen 10 und 40 %, maximal etwa 50 % liegt.

The hood cover basically consists of

• a continuous upper film layer f _O , which contains the central seam 6 running parallel to the hood side surfaces 8, 8 (see FIGS. 4a and 7a and 11),
• furthermore from a central film layer f _M , which consists of two V-shaped or triangular film sections QBC or PAD, each of which extends from the side edges a _l or a _r running at right angles to the transverse seam (see FIGS. 3, 3 ') of the hood cover extend towards the center, are arranged mirror-symmetrically to one another, and each end at a point Q _M or P _M lying in the transverse seam 6,
• and finally a lower film layer f _U , which consists of two V-shaped or triangular lower film sections, each of which is below a triangular film section of the central film layer f _M and is congruent (= congruent) with this,
• wherein each of the two central triangular film sections Q _M -B _M -C _M (see FIG. 5a) or P _M -A _M -D _M with the lower triangular film section Q _U -B _U, which is congruent to it and lies below it -C _U or P _U -A _U -D _{U forms} a film pocket which is open towards the respective edge BC or AD, the respective pocket of which, from the central triangular film section Q _M -B _M -C _M or P _M -A _M -D _M and the triangular-shaped film section Q _O -B _O -C _O or P _O -A _O -D _{O of} the right-angled upper film layer f _{O of} the hood cover formed the top of the pocket with an ideal packaging of the stack 2 with a hood 3 (horizontal) even, i.e. parallel to the top of the general cargo 2 runs, which may, however, be lumpy if the length l _{6 of} the transverse seam 6 in relation to the width B of the stack 2 (and thus the transverse seam ratio l ₆ / B) is below a limit value defined in EP 0 399 540 if the transverse stretch σ _{q is} approximately between 10 and 40%, a maximum of approximately 50%.

The hood cover, which later lies on the top of the piece goods in the horizontally biaxially stretched state, therefore already has two V-shaped or triangular-shaped film double regions Qe ₁ -e ₂ or Pe ₃ -e ₄ (see FIG. 3) in the unexpanded state of expansion ), or with the designations of FIGS. 4 to 12 QBC or PAD which differ somewhat with regard to the corner points.

So if a stretch film hood 3 formed from a gusseted tube at its vertical corner edges e ₁ - e ₄ (FIGS. 3, 3 ') or at its corner points A - C (FIGS. 4 - 12), the base lines of the triangular foil duplication areas or of the edges a _r or a _l open film pockets, which form isosceles triangles e ₁ -Qe ₂ and e ₃ -Pe ₄ (see Fig. 3) not only in the side edges a _l or a _{r of} the hood cover, but also with respect to match their length with these. The triangles e ₁ -Qe ₂ and e ₃ -Pe ₄ mentioned above are - as will be shown later - different from when the teaching is implemented according to. EP 0 399 540: The triangles have relatively large edges; their legs of equal length e ₁ -Q and e ₂ -Q or e ₃ -P and e ₄ -P run in the corner edges e ₁ - e _{4 of} the hood cover, or its corner points AD.

The individual layers f _O , f _M and f _U for a gusseted _tube formatting roughly according to. 1 - 3 are shown in Figs. 4 - 6, namely in the drawing figures marked with a) in the stretch-free state, and in the drawing figures marked with b) during horizontal transverse stretching (also in these figures) for a better comparison, the unexpanded expansion state is also shown in each case according to the respective a) representation), in which the four hoods 3 arranged at the corners of the rectangle ABCD are shown first stretch-free spreading finger or bow-like elements 7 acc. the arrows shown in FIGS. 4b, 5b and 6b can be moved from their spread position to the pull-over position via the intermediate position shown in FIGS. 4b, 5b and 6b. 6b and 6c, the hood side walls are shown dotted in the top view in this pull-over position. As can be seen from FIG. 6c, the hood side walls are circumferentially spaced apart from the respectively adjacent, parallel hood side wall. This distance ü is regularly about 10 - 15 cm. It is provided in order to reliably avoid a collision of the lifting frame holding the reefing, spreading and stretching elements 7 with the stack 2 when the lifting frame is lowered during the pulling-over process.

As can be seen, for example, from FIG. 5a, the length l _{6 of} the cross weld 6 is equal to the feed width b of the gusseted tube, and the height h of the film triangles BCQ or APD is equal to the depth of fold h of the gusseted tube (see FIG. 2).

The side gusset tube 3 that is spread out unstretched Rectangle ABCD formed in the top view or in a horizontal cross section is geometrically similar to each horizontal cross-sectional area of the piece goods stack 2 (that is, also to its top side 2 ) and to the cross-sectional area spanned by the hood side walls in the covering state (see dotted lines in FIG. 6c). Because the cross seam ratio Q = 1 6 / B is only 0.77 with a transverse stretch σ _q of approx. 30%, the transverse stretching (see FIGS. 4b, 5b and 6b) results in the V-shaped or triangular-shaped film pockets rising up in a lobed shape, which are separated from the triangular-shaped film section B _M -Q _M -C _{M of} the middle film layer f _M and the overlying section B _O -Q _O -C _{O of} the upper film layer f _O or the triangular-shaped film section A _M -P _M -D _{M of} the middle film layer m _M and the section A _O -P _O -D _{O of} the upper film layer f _O lying above it, and starting from the triangular tips Q and P to film tears.

These phenomena are acc. of EP 0 399 540 should be avoided if, with a transverse stretch σ _q of still 30% (up to approx. 50%) at i.ü. same conditions with regard to the stack cross-section and the circumference of the unstretched gusseted tube, as illustrated in FIGS. 7-9, which in turn represent the foil layers f _O , f _M and f _{U of} the hood cover in corresponding representations to FIGS. 4-6, whereby the gusseted hose used for hood formation but acc. EP 0 399 540 is either already formatted in the state in which it is in stock, or else before the transverse seam formation is formatted at least in its section intended for the transverse seam formation so that the length l ₆ the cross weld 6 and thus the cross seam ratio Q is greater than in the example according to 4 - 6. The latter is in the embodiment according to. 7-9 namely 0.935; the length l ₆ the cross weld 6 is therefore 93.5% of the stack size B parallel to it.

_O bzw. A _M-B _M-C _M-D _M bzw. A _U-B _U-C _U-D _U aufspannen.In order to achieve a uniform circumferential expansion of the hood side walls, the spreading, reefing and stretching elements 7 are already in their pull-over position 3 before and during transverse stretching (see Fig. 8a) again positioned so that in the unexpanded spread position (see Fig. 7a, 8a and 9a, and additionally drawn in Figs. 7b, 8b and 9b) a geometrically similar rectangle A _O -B _O -C _O -D _O or A _O -B _O -C _O -D

_O or A _M -B _M -C _M -D _M or A _U -B _U -C _U -D Open _U.

For geometrical reasons, this inevitably means that - despite the greater length l _{6 of} the transverse weld 6 - the height h of the isosceles triangles BCQ or APD becomes smaller and therefore the length m of the middle section of the weld 6 between points Q and P is (considerably) larger than in the execution. 1 - 3.

These relationships become particularly clear when looking at FIGS. 10 to 12, in which the two exemplary embodiments according to FIGS. 4 to 6, on the one hand, and FIGS. 7 to 9, on the other hand, are shown enlarged and superimposed on one another, with the same reference numbers again being chosen, of course have been made to differentiate the reference numerals for the embodiment according to. 7 - 9 are underlined. The corresponding points naturally coincide in part. It is among others / esp. It can be seen that the triangles which determine the two film pockets of the hood cover with regard to their geometrical shape with the same circumferences of the stack 2 on the one hand and the hood 3 on the other hand (and thus the same circumferential expansion in the condition of the finished loading unit) with gem. EP 0 399 540 formatted hood 3 become significantly smaller in the transverse seam area and correspondingly longer transverse weld seam 6, since the length h of the side gussets (see FIGS. 4-6) must necessarily be smaller, and the size of the triangles, as already stated, is determined by the side fold depth h , which is equal to the height h of the two equal triangles QBC and PAD.

sowie das SchenkelabschnittLängenmaß X=Q M -K=Q M -M=P M -P=P M -N=Q U -K=Q U -M=P U -P=P U -N geworfen, da diese (insb. in Relation zueinander) erfindungsgemäß (gleichsam als Kenn-Parameter") für die (Seitefalten-)Schlauchformatierung im Bereich der Quernaht 6 bei großen Querdehnungen im Bereich von 50 % und (ggf. deutlich) darüber insofern eine Rolle spielen, weil mit ihrer Hilfe/unter Bezugnahme auf diese Hilfslängen" erfindungsgemäß eine gegenüber der EP 0 399 540 erweiterte Lehre gefunden wurde, mittels welcher Zipfelbildungen und Folieneinrisse im Deckel einer Stretchfolienhaube auch bei hohem und ggf. auch sehr großem Querstretch σ_q um bspw. 60 %, 70 % oder 100 % und mehr zu vermeiden sind.Attention should already be paid to the length dimension entered in FIGS. 10 - 12 ( Corner edge distance ")

as well as the leg section X = Q M -K = Q M -M = P M -P = P M -N = Q U -K = Q U -M = P U -P = P U -N thrown, since these (especially in relation to each other) according to the invention (as it were as Characteristic parameters ") for the (side gusset) hose formatting in the area of the transverse seam 6 with large transverse stretches in the area of 50% and (possibly significantly) above play a role in so far because with their help / with reference to this Auxiliary lengths "According to the invention, a teaching has been found which is expanded compared to EP 0 399 540, by means of which tip formation and film tears in the cover of a stretch film hood increase by, for example, 60%, 70% or 100% and more, even with high and possibly also very large transverse stretch σ _q are to be avoided.

The embodiment according to FIG. Fig. 13 (iw scale representation) for a piece of stack 2 to be wrapped with a stretch film hood 3 ', the width B = 1,200 mm and the depth T = 1,000 mm, so that the stack circumference U _st = 4,400 mm, while the circumference U ₃ 'of the unstretched (gusseted) hose is 2,700 mm, so that the transverse stretch σ _{q is} about 63% in the applied state, and approximately in the overdrawn state, which is shown in FIG. 13 with thick dotted lines and labeled 3 _ü 85%.

In the center of the center M _i (more precisely to the vertical central axis of the stack 2), the hose 3 or the hood 3 'is drawn in FIG. 13 with thick solid lines (spread out without stretching by the spreading, reefing and stretching elements 7), that the existing in this expansion-free expanded-hood cross-sectional area between its corner points or corner edges formed by the four elements 7 is geometrically similar to the cross-sectional area of the stack 2, that is also to the top 2 'thereof. The width b of the hood 3 ', which is spread out without stretching geometrically similar to the stack cross-sectional area, or its side walls, is 756 mm if the stack width B = 1,200 mm and if the transverse stretch σ _{q is} 63% in the state of contact. Following the corresponding consideration, the depth t of the hose 3 'in this spread position is 630 mm, since the depth of the stack 2 T = 1,000 mm.

From this spread-out position - as has already been repeatedly stated above - the elements 7 arranged on the vertical corner edges e ₁ , e ₂ , e ₃ and e ₄ in the area of the hood side walls are preferred. the arrows shown in Fig. 13 with solid lines are moved horizontally and diagonally with transverse stretching (transverse stretch) of the hood side walls to the outside that they are stretched iw evenly. The elements 7 first reach the vertical corner edges e ' ₁ , e' ₂ , e ' ₃ and e' _{4 of} the stack 2, and finally in their overdrawn position 7 '' shown with thick dotted lines, the ones with e '' ₁ and e '' ₂ or e '' ₃ or e '' ₄ designated vertical corner edges of the hood side walls in the overdrawn position of the hood 3 'designated with 3 _ü .

Now, however (insofar in accordance with the teaching known from EP 0 399 540), the hood 3 'in the area of the transverse weld seam 6 provided is not roughly gem-welded before it is welded off. of the unexpanded spreading position described above, shown with thick solid lines in FIG. 13 [since the length l _{6 of} the transverse weld seam 6 would then only be 63% of the width B of the stack 2 parallel to it, whereby their as it were active length "QP (similar to the exemplary embodiment. FIGS. 1-6) would be extremely small, since in the event that the gusseted tube used for hood formation would be supplied with such formatting, the two triangles e ₁ -Qe ₂ or e ₃ -Pe ₄ would be very large in relation to the hood-spreading cross-sectional area: their legs e ₁ -Q, e ₂ -Q, e ₃ -P and e ₄ -P, each of the same length, would each - as described above of another, similar example executed - run through the vertical corner edges e ₁ or e ₂ or e3 or e ₄ ], but in such a way that the conditions already mentioned will switch on, as will be explained in more detail below.

At this point, for further explanation and, as it were, for reasons of delimitation, reference should be made to the fact that a gusseted hose with the same circumference U _{3 'could,} at least theoretically, have a gusset depth in the limit case that is equal to half the feed width, as is shown in FIG. 13 with thin dotted lines is shown if the folded-in side folds should not overlap each other when stored. With this feed formatting, they would therefore lie against one another with the fold vertices in the longitudinal central axis M ₁ .

Such formatting generally makes little sense, since feed formatting alone acc. 13 with thick solid or thick dashed lines in FIG shown formatting status with regard to the weld seam length and the caused thereby Problems (lumpy erection of the tops of the film pockets; tearing the film in the hood cover) makes no sense.

In the other conceivable limit case, in which the fold depth h of the gussets is zero, i.e. no gusseted tube is used anymore, but an unfolded flat tube, the feed width would be b 3'max = U 3 '/ 2 = a + b , whereby this case, which in principle may be practically practicable, is mentioned here in particular in order to clarify that the hood formatting in the transverse seam area before the transverse seam 6 is placed can lie between the two limit traps described above, whereby it is again expressly pointed out that - Regardless of which formatting is selected in each case - the cross-stretching by means of the elements 7 (or possibly other elements which replace the elements 7 in cross-stretching, as it were) each preferably takes place mainly from points or vertical lines of the hood side walls parallel to the transverse seam 6, which lie on the (reference) lines L _A and L _B shown in thick dash-two-dot lines in FIG. 13, because all hood side walls are to be uniformly stretched or stretched evenly when stretching from the unexpanded spreading position to the pull-over position .

For example, the hood is formatted in the area of the transverse seam 6 to be made by welding in accordance with 13 with thin dash-dotted lines, so that the length l _{6 of} the transverse seam 6 extends between the points 40 and 41, so it is clearly larger than b with the same hose circumference and the same transverse expansion provided, and the two Triangles of the pocket-forming V-shaped duplication areas between points 42, 43 and 44 (see left part of FIG. 13; the same applies correspondingly in mirror symmetry on the right) are clearly smaller than with formatting according to the embodiment shown in Fig. 13 with thick dashed lines, in which the transverse seam length l 6 = b is. It will be appreciated that the above with reference to FIGS. 10 - 12 explained leg portion length value X (= length of the leg portion with which the legs 43-42 and 43-44 extend beyond the line L _A addition inwardly ) makes up about half the total length of the legs 43-44 or 43-42, each of the same length, and that the corner edge distance Y (= side length section of the film in the hood cover between the vertical corner edges), also explained above with reference to FIGS. 10-12 e ₁ and 42 or e ₂ and 44; the same again applies, of course, to the right part of the relationships in FIG. 13 with respect to the corner edges e ₃ and e ₄ ), which is greater than zero, as in the case in FIG thick solid and dashed lines formatting would be the case.

It has now been recognized according to the invention that under these conditions there is neither Tear the foil hood cover, also to a lump-shaped raising of the The top of the foil pockets comes because not only - as already mentioned in the teaching. the EP 0 399 540 - Y> 0, but also the condition prescribed according to the invention is satisfied that X ≧ Y, as indicated above in the solution of that of the present Invention underlying task according to the characterizing part of the main claim (in other words) has been communicated.

If, for example, one turns to the case in which the hood 3 'in FIG. 13 is shown with thin dashed lines (likewise, of course, centered on the central longitudinal axis M _i ), in which the length of the transverse weld 6 would be equal to the stack width B, then without further notice that the triangular V-shaped double areas of the film, which are also drawn with broken lines, are extremely small. Their tips 45 and 46 obviously do not nearly reach the line L _A or L _B assigned to them, so that the value X is equal to zero "(ie does not exist at all, and mathematically expressed as negative size "would have to be specified), although the length value Y (for this case not shown in FIG. 13 for the sake of clarity) between the point or the vertical edge 47 of the hose 3 'and the corner edge e ₁ (the same applies evidently correspondingly for the other three corner edge areas) has a considerable size. Since the transverse stretch is to be σ _q = 63%, ie is still adjacent to the limit value of ≈ 50% (and because it is far away from extreme values σ _q ≈ 100%), Y / X ≈1.

In this case, in the exemplary embodiment dealt with in FIG. 13, the side fold depth h is only 150 mm. Although the transverse seam ratio Q is therefore> 0.85 (or 85%) and even greater than 0.95 (or 95%), namely 1.0 or 100%, as was the case for transverse strains in the previously usual range of about 15 - 30% is not only sufficient, but according to EP 0 399 540 is even particularly expedient in order to avoid the disadvantageous phenomena in the hood cover which have already been repeatedly described above, this condition is not sufficient for large transverse stretching from approximately 50% (in the present case: 63%) in order to avoid these adverse effects in the hood cover to avoid due to the stresses there, which arise automatically when the hood side walls are stretched. With such a high transverse stretch, as is naturally to be preferred, in order to achieve a high dimensional stability of the finished loading units and the best possible use of the film material (with the least possible use of material), the condition must - as already stated X> Y at Y> 0 (at least iw) must be fulfilled, whereby with a transverse stretch σ _q from about σ _q = 50% upwards, if the condition reproduced formally is observed, the individual sections of the film cover are only stretched so much that no film tears occur in the hood cover, and so on are stretched so that the upper film sections of the hood cover extend horizontally in the triangular V-shaped (film) double regions, namely, they rest against the top of the stack 2 '. This happens when the stresses in the individual layers f _o , f _M and f _{U of} the hood cover, which arise due to the transverse expansion of the hood side walls in the hood cover, set so that the triangular top film sections characterized by the triangular corner points QBC or PAD are relative Tension the underlying triangular foil sections in the V-shaped double areas, thus preventing them from straightening up with the less stretched overlying foil sections.

It should be pointed out again that the dimensioning or. Formatting conditions not to avoid the adverse effects in the hood cover original, but indirectly responsible for the fact that loading units are highly satisfactory result because the original sizes to create or avoid these disadvantageous Effects in the hood cover are of course the tensions in the hood cover, which in turn due to the expansion of the hood side walls, but that the conditions, in which satisfactory loading units can be obtained, describe in the manner described let, and thus also give a technical lesson for the professional world, by this can be easily implemented and complied with.

The same was already true for the one conveyed by EP 0 399 540 technical teaching, the (relative) length of the weld seam or the transverse seam ratio is not original for the tension or elongation conditions in the hood cover and the resulting effects responsible, but also only indirectly as a characteristic measure to indicate suitable conditions and their delimitation against unsuitable conditions, as is already known in technical teaching. EP 0 399 540 the size of the triangular V-shaped film double areas e.g. with regard to the triangle height h or the leg length as a characteristic measure can choose.

With reference to FIG. 13, the case drawn there with dash-three-dot lines is briefly discussed, in which the side-gusseted tube (of course again having the same circumference U ₃ '= 2,700 m) already before the transverse seam 6 is welded off and for the purpose of welding it off is formatted in the feed state, or before laying the transverse seam 6, so that the tips 50 or 51 of the triangular, V-shaped double areas of the film in the hood cover, which are defined by the triangle corner points 50-52-53 or 51 -54-55 are marked, lie straight on line L _A or line L _B , so that the length value X is just zero. Since a smooth hood cover also results in this limit case, the above condition can therefore be expanded as follows: 0 ≦ X ≧ Y at Y> 0, where (in individual cases, if necessary, to be determined empirically) the limit condition for relatively low cross-stretch values σ _q in the present cross-stretch range σ _q > 50% X ≈Y, and - especially in the case of extremely large transverse stretches in the system state, around 100% ( which, under normal conditions, even corresponds to a transverse stretch in the order of approximately 125% in the pull-over state), if necessary a smooth hood cover can also be achieved without tears if the tips of the triangular or V-shaped double regions are somewhat outside of the one in Fig. 13 with the corner points e ₁ -e ₂ -e ₃ -e _4, rectangles drawn with thick solid lines, i.e. the value X does not exist or is slightly negative ".

Such a case is shown in FIG. 14, with a stack of piece goods having a square cross section 2 with an edge length of 1,380 mm (i.e. with a circumference of 5,520 mm) with a Stretch film hood of a format 1,050 x 300 mm (tube circumference = 2,700 mm) wrapped the transverse expansion of the hood in the system state is 104% and in the pulling-on process is even about 125%.

In the geometrically similar unexpanded expansion state, which in turn is characterized in FIG. 14 (as in FIG. 13) in the right part by the vertical corner edges e ₃ and e _{4 of} the hood side walls, the hose or hood width b as well as the hose respectively. Hood depth t each 675 mm, as can be seen from the stack dimensions and the planned transverse expansion of 104% in the system state. The spreading, ripening and stretching elements 7 likewise drawn in on the right-hand part of FIG. 14 therefore lie on the corner edges e ₃ and e _{4 of} the spread-out stretch film hood 3 'and become beyond the corner edges e' ₃ and e ' ₄ when stretching moved horizontally and diagonally outwards, for covering even beyond the vertical corner edges e ' ₃ or e' ₄ into the covering position, which is shown in FIG. 13 with thick dotted lines and is omitted in FIG. 14. The conditions on the other (left) side are of course (mirror symmetrical) corresponding.

The tube formatting in the section provided for the transverse seam 6 is however selected (deviating from the unexpanded expansion state of the hood side walls) in such a way that the length l _{6 of} the transverse weld seam 6 is not equal to b, as would be the case if the side gusseted tube were fed with a feed width b and would be welded in this width, which would result in a cross seam ratio Q = 0.49. Rather, a larger transverse seam ratio Q is chosen, as can be seen from the left part of FIG. 14, where Y 0 0 can be seen, and X has the limit value X = 0 (the tip 50 of the triangle 50-52-53 lies on that Line L _A ).

The cross-sectional area spanned by the elements 7 in the unexpanded expanded state with 736 x 614 mm is not exactly geometrically similar to the horizontal Cross-sectional area of stack 2, but still i.w. geometrically similar, so that the Cross stretches in the hood sides i.w. horizontal tensions of equal magnitude and thus Set even transverse strains, which are then applied to the stack anyway are even because the difference in elongation or tension in the Hood sidewalls are compensated for at the latest when a height-related hood section of the hood side walls when sliding over the elements 7 and slides is temporarily in the air before it is under the specified transverse stretch of 104% on the side surfaces of the stack 2, and there due to the resulting Frictional forces between the inside of the hood and the stack ensure stable investment conditions the film hood 3 'arise.

In the formatting limit case shown in the left part of FIG. 14 (X = 0) is formed also a smooth lid without the formation of lobes, although the basic lines of triangular hood pockets of the hood cover - as is otherwise the case with such a large one Querstretch -, that is in Fig. 14 between points 52-53 and 54-55 running lines not in the system state, for example, at the side edge determining the depth T of the stack 2 lie, but with (considerable) distance to them.

15 shows yet another exemplary embodiment in which a piece goods stack 2 is one Width B 1,200 mm and depth T = 1,000 mm covered with a stretch film hood should be made from a gusseted tube with the dimensions 1,050 x 300 mm (2 x 150 mm) or 950 x 400 mm (2 x 200 mm), i.e. a hose or a hood 3 'with an unstretched circumference of 2,700 mm, so that the transverse stretch is 63% in the stacked state and 84% in the overdrawn state the first-mentioned case is shown in the left part of FIG. 15, and the second-mentioned case Case in the right part of Fig. 15. Of course, the respective conditions are on the other side (mirror symmetrical) accordingly.

While in the former case (see Fig. 15 left) a weld seam length of 87.5% of the results in stack width B parallel to the transverse seam, the transverse seam ratio is in the second mentioned Case (see Fig. 15 right) 0.79 or 79%.

In the left part of FIG. 15 it can be seen that the limit case X = 0 is again present here, and in the right part of Fig. 15, a case where X> Y is present. As with corresponding Attempts have resulted in a smooth hood cover without a lobed shape upstanding film bag tops in the area of the triangular or V-shaped Areas of film as desired, and there are also no tears. The triangular film double areas of the hood cover are thus in the system state stretched so that due to the tension in the hood cover, that result from the transverse stretch of the hood side walls, smooth to the top Place 2 'of stack 2. The embossed in the upper film sections of the hood cover Tensions are therefore greater than in the underlying film areas, however are the tensions impressed on the lid when stretching the side walls of the hood everywhere below the tear strength limit, so that it is despite the enormously high film stretch no film tears occur.

Claims (3)

Process for wrapping piece goods with generally rectangular cross-sectional area (2 '), in particular cuboid or cube-shaped piece goods (2), with a horizontally stretch-stretched (plastic) hood (3') made of tubular stretch film, especially from a gusseted tube (3), in the case of a film tube (3) fed from a (tube) supply and laid flat in the storage state, the unstretched circumference (U _{3 '} ) of which is at least 10% smaller than the circumference (U _st ) of the piece goods to be wrapped (2 ), a hood (3 ') is first formed by welding the film tube (3) at a distance from its free feed end with a transverse seam (6) and then severing it above the transverse seam (6); in which the hood (3 ') thus formed is pulled over the piece goods (2) to be wrapped in such a way that its closed end in the finished wrapping state (= hood installation state) as a hood cover under a biaxial (hood cover) caused by transverse expansion of the hood side walls Horizontal expansion is present at the top (2 ') of the piece goods (2); in which the hood (3 ') (to achieve a generally uniform circumferential expansion of its side walls when stretching transversely) before stretching and covering over the piece goods (2) to be wrapped - if necessary in several steps - is initially spread out completely unstretched so that the horizontal hood expansion cross-sectional area enclosed by the hood side walls is geometrically similar to the horizontal general cargo cross-sectional area (eg 2 ') and is thus arranged (expanded), that two generally identical, parallel first edges (e ₁ -e ₃ ; e ₂ -e ₄ ) of the hood-expansion cross-sectional area (e ₁ -e ₂ -e ₃ -e ₄ ) parallel to the transverse seam (6) of the hood ( 3 ') and to the side surfaces of the piece goods determining the width (B) of the piece goods (2); that two parallel edges of equal length (

Reference edges ") (e ₁ -e ₂ e ₃ -e ₄ ) of the hood expansion cross-sectional area (e ₁ -e ₂ -e ₃ -e ₄ ) iw perpendicular to the first edges (e ₁ -e3; e ₂ -e ₄ ) run; and that the hood cover is formed by three superimposed film layers (f _O , f _M , f _U ), namely by one across its entire width ( b = l6 ) centered by the transverse seam (6), right-angled upper layer of film (f _O ), the size and shape of which is equal to the hood-spreading cross-sectional area (e ₁ -e ₂ -e ₃ -e ₄ ), two, the middle film layer (f _M) forming each other mirror-symmetrically opposite film sections (B _M -O _M -C _M, A _M -P _M -D _M) in the form respectively of an isosceles triangle whose height line (Q _M -F _M; P _M -E _M ) is formed in each case by an outer section of the transverse seam (6), and its baseline (B _M -C _M ; A _M -D _M ) each in a cross-sectional area (e ₁ , e ₂ , e ₃ , e ₄ ) formed reference line (L _A or L _B ), and two triangular-shaped lower film sections (B _U -Q _U -C _U ; A) forming the lower film layer (f _U ) and congruent to the central triangular film sections (B _M -Q _M -C _M ; A _M -P _M -D _M ) _U -P _U -D _U ), each of which forms an open film pocket on the triangular baseline (BC or AD) with the triangular-shaped film section of the middle film layer (f _M ) of the hood cover; and in which the hood (3 '), which is thus still unexpanded, is then cross-stretched to an over-pulling cross-section (3 _ü ) required for covering, by first removing the elements (7) which cause the spreading and then stretching from their position in which they are Spread the hood side walls completely unstretched, move each horizontally outwards in a diagonal direction to a pull-over position in which the cross-stretched hood side walls are each at a pull-over safety distance (ü) from the adjacent general cargo side wall, which is generally constant all round. so that the distance of the corner edges (e '' ₁ , e '' ₂ , e '' ₃ , e '' ₄ ) of the hood (3 ') in its covering state to the corner edge (e' ₁ , e ' ₂ adjacent to them ₎ , e ' ₃ , e' ₄ ) of the piece goods (2) is in each case of the same size, characterized in that the hose (3) with at least a relatively large transverse stretch (σ _q ) of at least about 50% ens in the area of the transverse seam to be formed (6) is formatted such that the two legs of equal length (BQ, CQ or AP, DP) of the two V- or triangular-shaped, pocket-forming film double areas (B _M -O _M -C _M , B _U -O _U -C _U or A _M -P _M -D _M , A _U -P _U -D _U ) of the hood cover in the still unexpanded expansion state of the hood at least approximately to the one adjacent to it, at right angles to it Cross seam (6) running second edge (BC = reference line L _a ; AD = reference line L _B ) of the hood expansion cross-sectional area (e ₁ , e ₂ , e ₃ , e ₄ ) present below the transverse seam area, which is geometrically similar to the horizontal general cargo cross-sectional area, preferably with a leg section (MQ, KQ, P -P, NP) of a length (X) into this cross-sectional area of the hood-expansion, the length (X) of these leg sections (MQ, KQ, P -P, NP) is approximately at least as large as the distance (Y) between a corner point / corner edge (e ₁ , e ₂ , e ₃ , e ₄ ) of two adjacent hood side walls in the still unexpanded expanded state and the corner point / this corner edge (e ₁ or e ₂ or e ₃ or e ₄ ) adjacent outer edge (g ₁ , g ₂ , g ₃ , g ₄ ) of the corresponding side fold (9). Method according to Claim 1, characterized in that the hood cover expansion reserve characteristic value (Y / X) in the region of a transverse stretch (σ _q ) is approximately equal to 1 at approximately 50-60%, and increases with increasing transverse stretch (σ _q ), whereby it increases a transverse stretch (σ _q ) in the range around 100% is considerably greater than 1, and the length of the leg section (X), which can decrease with increasing transverse stretch (σ _q ), can go to zero or be zero. Device for wrapping piece goods with generally rectangular horizontal cross-sectional area, in particular of cuboid-shaped piece goods stacks, with a horizontally stretched (plastic film) hood made of stretch film, for carrying out the method according to one of the preceding claims, with a rolled-up hose supply and a feed device, by means of which is to be fed to the film tube laid flat in the storage state, with a welding device, by means of which the supplied film tube is to be welded with a transverse seam (6) at a distance from its free feed end, and with a separating device, by means of which the welded-off tube section above the transverse seam (6) is to be cut, as well as with spreading, reefing and stretching elements (7), by means of which the supplied film tube section intended for hood formation is folded before the transverse seam (6) is placed and the hood (3 ') formed in front of the cross stretcher Chen the hood side walls so unexpanded with a hood-spreading cross-sectional area that the hood side walls in their subsequent horizontal, diagonal movement outward stretch the hood side walls iw uniformly, the tube section forming the hood (3 ') in the area of the intended transverse seam ( 6) is formatted or, before the transverse seam (6) is placed, is formatted such that the length (l ₆ ) of the transverse seam (6) is greater than the length of the two edges of the hood-expansion cross-sectional area in the region of its side walls, characterized in that the control of the elements (7) with an intended transverse stretch (σ _q ) of at least about 50% takes place in such a way that with a transverse stretch (σ _q ) in the range of approximately 50-60% a hood cover expansion reserve characteristic value (Y / X) of about 1, and with larger transverse stretch (σ _q ) in the range around 100% a characteristic value (Y / X) »1, the length of the leg section (X) increasing with m transverse stretch (σ _q ) can go to zero or reach zero, and the corner edge distance (Y) is always> 0.

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