EP0461667B1 - Method and apparatus for wrapping products in stretchable film - Google Patents

Description

The invention relates to a method for wrapping piece goods with a tubular or hood-shaped stretch film according to the preamble of claim 1 and a device suitable for this according to the preamble of claim 3.

When pulling a stretch film hood over a stack of general cargo possibly arranged on a pallet, it has been shown that the lower edge region of the film, which is intended to reach under the general cargo or the pallet itself with a so-called understretch, in order to create a weather-resistant and transport-safe loading unit , has the tendency to pull up at least partially over the pallet or the underside of the piece goods. This is particularly the case when the film material is not only subjected to horizontal transverse stretching but also to vertical longitudinal stretching.

This disadvantageous effect results when the film held and guided by the lifting frame during the pulling process already slides off the lifting frame in the lower end section of the film wrapping when the film section above it has not yet been able to firmly attach to the piece goods or the pallet.

In order to prevent the lower edge of the film from sliding up, it is known from DE 90 01 319 U1 to provide movable clamping jaws which press the film in the lowest position of the lifting frame against the piece goods or the pallet arranged below it, before the lower edge of the film Swivel brackets of the lifting frame is released, which have pulled the film hood over the stack of goods.

Such jaws, including their drive and their control, require considerable additional effort. In addition, it has been shown that there can be difficulties when working with a relatively high pulling speed, as is desirable in order to achieve a corresponding throughput, and that the desired understretch does not come about at least in part because the film is over pulls up the underside of the pallet or piece goods after it has detached itself from the lifting frame, in particular if a considerable vertical stretch is provided.

DE 40 19 041 C1 has proposed a method and a device for wrapping piece goods with stretch film, by means of which the lower edge section of the wrapping is to be reinforced compared to the rest of the wrapping during the wrapping process. For this purpose, the lower edge section of the stretch film hood, in the case of essentially already completely wrapped article side surfaces or the wrapped pallet, before reaching under the piece goods or the pallet, forming a double-layered film edge section extending beyond the underside of the piece goods or the pallet from a first lowered position, the under the general cargo or in the area of the pallet, raised again and only then released. In this case, the reversible drivable reefing rollers can optionally serve as an alternative, in the second lowered position, again with the film in To be brought into engagement in order to bring about the desired folding effect in order to strengthen the lower edge of the film. However, they have no influence on the above problem.

The present invention is based on the object of specifying a method by means of which the desired understretch can be carried out simply and reliably under a wide variety of structural conditions. In addition, the generic device is to be simplified considerably.

As a solution to the procedural part of the above object, the invention provides that the pulling speed is reduced in the pulling final phase. This ensures that the film has sufficient time to contact the stack or the pallet with appropriate contraction and to securely grasp the latter with the understretch.

In addition, the film can be moved inward relative to its covering contour below the pressing area or also in the pressing area, for example when using a generic device, in that the bow-like frame sections of the lifting frame are moved inwards, as shown below is explained further. As a result of this measure, the film is correspondingly relaxed in its lower edge area, accordingly fits well in the understretch area and can then no longer be pulled up over the underside of the pallet or the piece goods.

As a solution to the device-related part of the task, the invention provides that the drive of the lifting frame - at least in the lowering or pulling over phase - is to be switched from a first operating speed (= relatively high normal pulling speed) to a reduced second operating speed, and that the reefing rollers are used as the pressing device. By this measure, one can do without additional jaws or the like and comes to Reef rollers are used. This measure makes it possible to dispense with additional clamping jaws or the like and considerably simplifies the construction.

According to one embodiment, the lifting frame can be provided with line openings which open in the area of its engagement surface with the film, the line openings being pressurized in the pressing phase in order to hold the film on the lifting frame in the final pull-over phase.

Fig. 1

eine etwas schematische räumliche Darstellung eines mit einer Stretchfolienhaube zu überziehenden Stückgutstapels, wobei die Stretchfolienhaube aus einem Seitenfaltenschlauch gebildet wird, der in Fig. 1 an seinem freien Endabschnitt bereits von dem Hubrahmen aufgenommen worden ist;

Fig. 2

in einer Fig. 1 entsprechenden Darstellung die Anordnung gemäß Fig. 1 nach Bilden einer Stretchfolienhaube;

Fig. 3

in einer Darstellung gemäß den Fig. 1 und 2 die gemäß Fig. 2 gebildete Stretchfolienhaube nach dem/beim Querstretchen;

Fig. 4

in einer Darstellung gemäß den Fig. 1 bis 3 einen Zwischenzustand beim Überziehen des Stückgutstapels mit einer Stretchfolienhaube;

Fig. 5

eine Seitenansicht eines bügelförmigen (Hub-)Rahmenabschnittes nebst dessen Stütze in Richtung des Pfeiles V in Fig. 6 gesehen;

Fig. 6

eine Draufsicht auf zwei (von vier) bügelförmige (Hub-)Rahmenabschnitte;

Fig. 7

eine teilweise schematisierte Seitenansicht auf einen auf einer Palette abgestützten Stückgutstapel mit einem bügelförmigen Rahmenabschnitt sowie einer Andrückeinrichtung in der Überzieh-Endphase; und

Fig. 8

in einer Darstellung gemäß Fig. 7 (ausschnittsweise) die fertige Ladeeinheit.

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

Fig. 1

a somewhat schematic spatial representation of a piece of goods to be covered with a stretch film hood, the stretch film hood being formed from a gusseted tube which has already been received by the lifting frame in FIG. 1 at its free end section;

Fig. 2

in a representation corresponding to FIG. 1, the arrangement according to FIG. 1 after forming a stretch film hood;

Fig. 3

in a representation according to FIGS. 1 and 2, the stretch film hood formed according to FIG. 2 after / during transverse stretching;

Fig. 4

in an illustration according to Figures 1 to 3, an intermediate state when covering the piece goods stack with a stretch film hood.

Fig. 5

a side view of a bow-shaped (lifting) frame section and its support seen in the direction of arrow V in Fig. 6;

Fig. 6

a plan view of two (out of four) bow-shaped (lifting) frame sections;

Fig. 7

a partially schematic side view of a piece of goods supported on a pallet with a bow-shaped frame section and a pressing device in the final pull-over phase; and

Fig. 8

7 (detail) of the finished loading unit.

1 shows a block-shaped piece goods stack, designated as a whole by 1, which consists of several layers of piece goods parts which are intended to be wrapped with a stretch film hood 2 in order to form a loading unit. The stretch film hood 2 is formed from a gusseted tube 3, which is fed to the device according to the arrows 8 from a gusseted tube supply, not shown, the free end of the gusseted tube 3 according to FIG 3) has been included.

As has been indicated in Fig. 2, the gusseted tube 3 is welded at a distance from its free end by means of a welding device 4, which consists essentially of two welding strips, so that a transverse seam 5 is formed, and above the transverse seam 5 by means of a not shown Separating device separated to form a stretch film hood 2, the side surfaces of which, in the state shown in FIG. 2, have already been substantially raised onto the lifting frame 9 (by means of a reefing device).

From the state shown in FIG. 2, the four frame-like (lifting) frame sections 9 'essentially forming the lifting frame and assigned to the corner regions of the piece goods stack 1 are moved apart in the direction of arrows 6 for the purpose of transverse stretching of the stretch film hood 2. After that 4 is stretched across the piece goods stack 1 by means of the lifting frame 9, which at the same time forms a reefing frame, FIG. 4 showing an intermediate state in which the piece goods stack 1 is already half-wrapped.

In the intermediate position according to FIG. 4 and beyond, the lifting frame 9, which can be driven by means of a drive (not shown), initially moves downward at a normal first operating speed, which is as high as possible, taking into account the strength or elasticity properties of the film material used to be able to achieve a correspondingly high throughput of the machine, and finally in one position, as can be seen in FIG. 7, wherein only a single bow-like frame section 9 'can be seen in FIG. 7, but the other bow-like frame sections 9' are designed accordingly and are at the same level.

7, the lowering speed of the lifting frame 9 is considerably reduced, so that the pulling-on process in the pulling-over end phase is carried out at a reduced second operating speed, with the result that the stretch film is given the possibility of being in the desired position To put on the stack of goods or the pallet and does not pull up.

Before the wrapping process is explained in more detail below, in particular with reference to FIGS. 5 and 6, the specific configuration of the bow-like frame sections 9 'of the lifting frame 9 in the exemplary embodiment shown is explained further, and reference should first be made to the fact that the piece goods stack 1 - As can be seen from FIGS. 1 to 4 - is supported on a (one-way) pallet 10 with a plate top 10 '.

As has already been stated, the lifting frame 9 consists of four substantially C-shaped bracket-like frame sections 9 ', each of which is provided with a plurality of through-bores 13, which are connected to a vacuum source, and in each case engages with films during operation located section of the outside of the relevant lifting frame section 9 'open. The vacuum source indicated schematically in FIG. 6 is designated by 14.

Each bow-shaped frame section 9 'is supported by a support 17 (see FIGS. 5 and 6) formed by a curved, conical sheet metal, the supports 17 each having a recess 18 in the central region. Otherwise, the through bores 13 connected to the vacuum source 14 are connected to a control device 16 (see FIG. 6), by means of which the vacuum can be controlled.

As can be seen from Fig. 7, the bracket-like frame sections 9 'of the lifting frame 9 are moved in the illustrated embodiment during the pulling process to slightly below the top 10' of the pallet 10, with Fig. 7 showing that the already in this intermediate position Side gusset tube 3 or the (side surfaces of) stretch film hood 2 essentially envelop the piece goods stack. Nevertheless - as can be seen from FIG. 7 - the film 2 or 3, which is still in frictional engagement with the bracket-like frame sections 9 'of the lifting frame 9, does not yet adhere to these in the region of the lower section 1' of the piece goods stack 1 and not yet applied to the pallet 10. If, in the state according to FIG. 7, the lifting frame 9 were disengaged from the film, in particular when the film 2 or 3 was stretched vertically, this could be the case even in the second phase, which is provided in the final pulling phase and reduced in comparison with the initial first operating speed Operating speed have the consequence that this extends up to over the underside of the piece goods stack 1 or the pallet top 10, at least the top layer 11 of the pallet 10, so that there is no desired bottom stretch in which the film 2 or 3 Top layer 11 engages under pallet 10 (see FIG. 8).

To ensure this, a pressure device 12, shown schematically in FIG. 7, is provided, in which it is in the illustrated embodiment, the (reefing rollers) of the reefing device, by means of which the gusseted tube 3 has previously been attached to the supports 17 of the bow-like frame sections 9 'of the lifting frame 9. The reefing rollers essentially forming the pressing device 12 are pressed in the position shown in FIG. 7 according to the arrow 15 on the piece goods 1 or in a somewhat lower position on the upper layer 11 of the pallet 10. Only then do the bow-like frame sections 9 'move downward according to the arrow 19, that is, out of engagement with the film 2 or 3, whereby they have already been moved inwards according to the arrow 20 (ie onto the piece goods 1 or the pallet 10) become.

The result of the measures according to the invention is that the film 2 or 3, owing to the reduced second operating speed on the one hand and the pressure by means of the pressing device 12 on the other hand, can “rest” with an understretch section 21 on the underside of the pallet top layer 11, the corresponding one The measure can also be seen on the lower layer 22 of the pallet, as has been indicated in FIG. 8 with respect to the lower stretch section 21 'in a dash-dotted line, or in the case of one not on a pallet 10 or the like. supported loading unit immediately below the piece goods stack 1, as is readily apparent to those skilled in the art.

It should also be pointed out that, within the scope of the inventive concept, numerous variations or modifications are evidently possible which go (far) beyond the exemplary embodiment described above and shown in the drawing. Thus, the lifting frame does not of course have to consist of bow-like sections of the type in question here (see FIGS. 5 and 6), but can, for example, consist of consist of a closed frame, the individual legs (for the purpose of cross-stretching) are telescopic.

Furthermore, the pressing device 12 can be designed in a wide variety of ways and, in particular, does not need to be a component of the reefing device, as is most expedient, but can, as has already been indicated, be realized, for example, by the fact that the lifting frame 9 is still on the lifting frame held film 2 or 3 in the negative pressure applied through the through holes 13 are held firmly on the lifting frame, while this is possibly / preferably moved from its pull-over position in the pull-over final phase closer to the packaged goods 1 and the film 2 or 3 is given the opportunity has to put firmly on the piece goods stack 1 or the pallet 10 or a part thereof, so that the understretch 21 or 21 'can then also be produced in an equivalent manner as in a normal "pressing device".

Claims (4)

1. A method of wrapping unit loads (1), which may or may not be supported on a pallet (10) or the like, with a stretch film (2) in tube or hood form, more particularly for wrapping unit load stacks (1) of parallelepipedal or cubic shape consisting of palleted unit loads stacked one upon the other in several layers, that section (3) of the film which forms the side surface wrapping being reefed and transversely stretched before being drawn over the unit load (1), while during the drawing of the film (2) over the unit load (1) and before the release of its bottom edge portion it is at least temporarily pressed laterally against an abutment in the region of the bottom edge portion (1') of the load and/or of the pallet (10) and the lateral pressure is removed when the film (2) has firmly contacted the load (1) at the full height or at least partially firmly contacted the pallet (10), characterised in that the speed at which the film is drawn over the load is reduced in the final phase of the drawing-over operation.
2. A method according to claim 1, characterised in that during the application of pressure to the film (2) the latter is moved inwardly relatively to its drawing-over contour inside or beneath the pressure-application zone.
3. Apparatus for wrapping unit loads (1), which may or may not be supported on a pallet (10) or the like, with a stretch film (2) in tube or hood form, more particularly for wrapping unit load stacks (1) of parallelepipedal or cubic shape consisting of palleted unit loads stacked one upon the other in several layers, comprising a reefing and stretching reciprocating frame (9) which is adapted to be driven and which consists of a plurality of bow-shaped frame portions (9') disposed substantially in one (horizontal) plane and constructed to be substantially L or C shaped (in plan view), and bow supports holding each such frame portion, that portion (2) of the film which forms the side surface wrapping being reefed, before being drawn over the load (1), on to the same by means of a reefing device comprising reefing rollers, the reefed film (2) being transversely stretched by said frame before the film is drawn over the unit load, the film (2, 3) being pressed, before the release of its bottom edge portion, against the unit load and/or the pallet (10) in the bottom zone of the unit load (1) by a pressure-application device (12), the latter being disengaged from the film (2, 3) when the film (2, 3) has contacted the bottom end portion of the unit load (1) and, where applicable, the top end portion (11) of the pallet (10), for performing the method according to claim 1 or 2, characterised in that the drive of the reciprocating frame (9) is switched from a first operating speed to a reduced second operating speed, at least in the lowering or drawing-over phase; and in that the reefing rollers at the same time form the pressure-application device (12).
4. Apparatus according to claim 3, characterised in that the reciprocating frame (9) is provided with conduit orifices (13) which lead into the region of the surface of engagement of the frame (9) with the film (2, 3) and in that the conduit orifices (13) are subjected to negative pressure during the pressure-application phase.

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