EP0519116B1 - Method for covering a stack of articles with a stretchfoil hood and device for carrying out the method - Google Patents

Abstract

The invention relates to a method for covering a stack of articles with stretch-film hoods, in which a hood which has been prestressed in the direction of the circumference is pulled over the stack of articles and its lower edge is folded under the stack of articles or a pallet supporting the stack of articles and fastened there. The invention also relates to a device for implementing the method. So that the stretched-film hood can be kept free of folds and can be pulled over a stack of articles in such a way that the hood can also accommodate diagonal forces, once the hood has been pulled over, its lower edge is to be taken hold of, restretched in the longitudinal direction of the hood and then folded over. <IMAGE>

Description

The invention relates to a method for covering stretch film hoods over a stack of goods, in which a hood biased in the circumferential direction is pulled over the stack of goods and its lower edge is knocked under the stack of goods or a pallet carrying the stack of goods and fastened there. The invention also relates to an apparatus for performing the method.

In a generic method, a stretch film hood is gathered in the longitudinal direction like an accordion and placed on rod-shaped holding elements of a tenter frame. The holding elements are then moved apart with the aid of a tensioning drive, as a result of which the stretch film hood is pretensioned in the circumferential direction. In this state, the tensioning frame is moved downwards along the stack of goods, the gathered stretch film hood being pulled off the holding elements and resting against the outside of the stack of goods. Brakes that engage the hood sections between the holding elements control the tension of the Stretch film hood (DE-GM 90 01 319). Although extensive control of the tension distribution in the stretch film hood is possible with the brakes, it is frequently observed that the hood folds, in particular in the central region of the sides of the stack of goods, that is to say is not preloaded uniformly in all directions. However, a wrinkled hood cannot transmit forces evenly in all directions, in particular it cannot transmit diagonal forces.

The object of the invention is to pull a stretch film hood wrinkle-free and so over a stack of goods that the hood can also absorb diagonal forces.

This object is achieved in that after covering the lower edge of the hood is grasped and re-tensioned in the longitudinal direction of the hood and then turned over. In particular, the lower edge in the central region of at least two opposite sides of the stack of goods is to be gripped and re-tensioned. The easiest way of tightening is to hold the lower edge of the hood stationary and to lift the stack of goods during tightening. By re-tensioning in the longitudinal direction of the hood, all folds of the hood that have arisen during pulling over are reliably eliminated and, at the same time, the hood is also pretensioned in the longitudinal direction of the hood in the desired manner before its lower edge is folded over under the stack of goods or the pallet and fastened there. If, as stated, the lower edge of the hood is held stationary and the stack of goods is lifted, the stroke of the stack of goods can be dimensioned sufficiently large to compensate for all folds and the set the desired preload. Brakes that work together with the stenter frame can be dispensed with. As a result, the stack of goods is covered by a stretch film hood which is stretched uniformly on all sides and in all directions, so that it can absorb forces in all directions, even in diagonal directions.

The method according to the invention can advantageously be carried out with a device for covering stretch film hoods over a stack of goods, with a clamping frame which can move along the stack of goods and which has a clamping drive which can be adjusted relative to one another and which engage in the opened hood, with a vertically adjustable carrier for the Stack of goods and with a device arranged under the stack of goods or its support for fastening the lower edge of the hood to the stack of goods, and which is characterized in that devices for retensioning the hood are arranged between the holding elements of at least two opposite sides of the stack of goods. In particular, the devices for re-tensioning should be arranged in the central area between adjacent holding elements.

According to a preferred embodiment of the invention, the devices for retensioning have pliers, the opening gap of which is directed essentially vertically for gripping the lower edge of the hood guided by the holding elements. The lower edge of the hood is then inserted directly into the opened tongs when the tensioning frame holding elements are pulled over and is held by the closed tongs when the tensioning frame holding elements have been removed.

The stack of goods is then raised to retighten the hood. After the stack of goods covered with the hood has been lifted off, the pliers are moved under the stack of goods, so that the lower edge of the retensioned hood lies under the stack of goods or under the pallet and can be fastened there.

For the purpose of fastening the lower edge, it is advantageous if each device for retensioning has two pliers arranged at a distance from one another and an adhesive spraying device is arranged under the stack of material, which sprays the lower edge of the hood with adhesive in the area between the pliers. If the lower edge is then folded over under the stack of goods or under the pallet, it is immediately liable. The liability can be further improved if a pressure roller which can be displaced with the tongs and is pressed against the underside of the stack of goods or the pallet is provided between the tongs of each device. The pressure roller can be resiliently mounted; in a preferred embodiment, the pressure roller is assigned a pressure cylinder.

To secure the lower edge of stretch film hoods drawn over palletized material stacks, it has already been proposed (DE-GM 90 01 319) to press the lower edge of the hood against the pallet by means of a heating roller, so that the film material in under the action of pressure and heat plastic state is transferred and the film connects to the pallet material. In the case of wooden pallets in particular, the film is pressed into the rough surface of the wood, with a toothing between wood and foil material. This allows the lower edge of the hood to be fixed on the side of the pallet as well as on the bottom of the pallet. The corresponding surfaces of the pallet not only have a rough surface, but generally also an irregular or corrugated surface, so that the desired success is achieved inadequately or not with a heating roller guided over the surface.

So that the lower edge of the film hood can be reliably secured, a further proposal of the invention is that groups of mutually coaxial heating disks are arranged in the region of at least two pallet sides, the axes of which extend parallel to the sides of the pallet, and that each group of Heating disks is assigned a drive with which the heating disks are guided in a rolling motion in the longitudinal direction of the film hood. The lower edge of the film hood is only attached to the pallet in strips. Depending on the width of the heating discs, which can be between 5 and 15 mm, fastening strips are formed between the film material and the pallet material, which extend in the longitudinal direction of the film hood. With this orientation of the fastening strips, the forces transmitted by the film thereon are optimally absorbed, so that even thin areas of the film material do not have a negative effect.

The heating disks are preferably pressed resiliently against the pallet. This can be achieved in particular in that the heating disks are mounted on associated pivot levers, which in turn are articulated on a slide movable by the drive, and in that the pivot levers are supported on the slide by springs. Accordingly, the heating disks can follow bumps on the assigned surface of the pallet during their rolling movement and produce a continuous fastening strip between the film material and the pallet material.

A practical embodiment is characterized in that return springs are arranged between the heating disks and their pivoting levers, which return the heating disks to their retirement when the pressure on the assigned pallet surface subsides. In particular, the heating discs move against the action of the return springs and the return movement of the heating discs is supported by the return springs.

The heating disks can preferably be heated using heating tapes which are laid on the circumference of the heating disks. This enables simple construction of the heating disks and simple electrical connections.

If, as usual, the lower edge of a film hood pulled over the stack of goods and the pallet is folded under the pallet, the heating disks can attack the underside of the pallet. If the palletized stack of goods is transported by a roller conveyor, it is expedient if the heating disks are arranged between the transport rollers of the conveyor.

If the lower edge of the film hood pulled over the stack of goods and the pallet is not folded under the pallet, but ends on the sides of the pallet, then can also engage the heating discs on the sides of the pallet.

Fig. 1

schematisch eine Ansicht einer Vorrichtung zum Überziehen von Stretchfolienhauben über einen Gutstapel,

Fig. 2

den Gegenstand nach Fig. 1 in einer anderen Funktionsstellung,

Fig. 3

den Gegenstand nach Fig. 1 in einer weiteren Funktionsstellung,

Fig. 4

eine andere Ansicht des Gegenstandes nach Fig. 2,

Fig. 5

schematisch die Ansicht einer Vorrichtung zum Sichern des unteren Randes von über palettierte Gutstape gezogene Folienhauben,

Fig. 6

teilweise und im vergrößerten Maßstab ein Detail des Gegenstandes der Fig. 1,

Fig. 7

den Gegenstand nach Fig. 6 in anderer Funktionsstellung,

Fig. 8

schematisch und in perspektivischer Darstellung die Ansicht eines palettierten Gutstapels mit darüber gezogener Folienhaube, deren unterer Rand gesichert ist

In der Zeichnung ist ein Gutstapel 1 wiedergegeben, der auf einer Palette 2 angeordnet ist. Der palletierte Gutstapel 1 wird auf einer Rollenbahn 3 eines Förderers 4 transportiert, bis er in dem Bereich einer im einzelnen nicht dargestellten Vorrichtung zum Überziehen einer Stretchfolienhaube 5 über den Gutstapel 1 gelangt.In the following an embodiment of the invention shown in the drawing is explained; show it:

Fig. 1

schematically a view of a device for covering stretch film hoods over a stack of goods,

Fig. 2

1 in a different functional position,

Fig. 3

1 in a further functional position,

Fig. 4

another view of the object of FIG. 2,

Fig. 5

schematically the view of a device for securing the lower edge of film hoods pulled over palletized Gutstape,

Fig. 6

partially and on an enlarged scale a detail of the subject of FIG. 1,

Fig. 7

6 in a different functional position,

Fig. 8

schematically and in perspective the view of a palletized stack of goods with a film hood pulled over it, the lower edge of which is secured

In the drawing, a stack of goods 1 is shown, which is arranged on a pallet 2. The stacked stack of goods 1 is transported on a roller conveyor 3 of a conveyor 4 until it passes over the stack of goods 1 in the area of a device (not shown in detail) for covering a stretch film hood 5.

The device for covering includes a tensioning frame, of which only holding elements 6 are shown, which in the embodiment shown consist of fingers pointing downwards. The holding elements 6 are located in the area of the four floor plan corners of the stack of goods 1. The opened stretch film hood is gathered in the longitudinal direction like an accordion and placed on the holding elements 6. The holding elements 6 are then moved apart with the aid of a tensioning drive, as a result of which the stretch film hood 5 is pretensioned in the circumferential direction. In this state, the tensioning frame with the holding elements 6 is moved downwards along the stack of goods 1, the gathered stretch film hood 5 being pulled off the holding elements 6 and resting on the outer sides of the stack of goods 1. The stack of goods 1 with the pallet 2 is lifted off the roller conveyor 3 of the conveyor 4 by means of a lifting device 7. 1 shows this state.

Devices 8 for tensioning the stretch film hood 5 are arranged on both sides of the conveyor 4 and possibly also in the region of the end face of the stack of goods 1. Only one device 8 for retensioning is shown.

Each device 8 for retensioning consists of one Carriage 9, which can be moved horizontally on a bracket 10 of the conveyor 4 with the aid of a lifting cylinder 11. On the carriage 9, two pliers 12 are arranged at a mutual distance such that their opening gap extends substantially vertically and the lower edge 13 of the stretch film hood 5 is transferred from the holding elements 6 into the opening gap of the pliers 12 or falls into it when the holding elements 6 have reached their lowest position, in which the lower edge 13 of the stretch film hood 5 detaches from the holding elements 6. The pliers 12 are then closed with the aid of associated drives 14. The tenter with the holding elements 6 moves upwards again (Fig. 2).

Now the palletized stack of goods 1 is moved upwards with the aid of the lifting device 7. The stretch film hood 5 is then retensioned because the tongs 12 do not follow the upward movement.

Under the palletized stack of goods 1 and in the embodiment shown is connected to the supporting elements of the lifting device 7 is an adhesive spray device 15 which sprays the inside of the lower edge 13 of the stretch film hood 5 in the area between the two tongs 12 and optionally also at other points with an adhesive. Then the lower edge 13 of the stretched stretch film hood 5 is knocked under the pallet 2, in which the carriage 9 is moved with the pliers 12 by actuating the lifting cylinder 11 under the raised, palletized stack of goods 1. On the carriage 9, a pressure roller 16 is arranged between the two pliers 12, which in the embodiment shown on an arm 17 pivotally mounted, double-armed lever is mounted, on the other arm 18 engages a lifting cylinder 19 as a drive. When the slide 9 is moved, the lifting cylinder 19 is also actuated, so that at least the portion of the lower edge 13 of the stretch film hood 5 provided with adhesive is pressed against the underside of the pallet 2 and fastened thereon (FIG. 3). The pliers 12 are opened as soon as the pressure roller 16 has reached the necessary pressure force. The tensioning frame with the holding elements 6 has meanwhile moved upward and is available for receiving a new stretch film hood 5.

When the lower edge 13 of the stretch film hood 5 is fastened under the pallet 2, the slide 9 with the units arranged thereon is moved back into the rest position shown in FIG. 1. The palletized stack of goods 1 is lowered onto the roller conveyor 3 of the conveyor 4 and transported away, the adhesive connection between the lower edge 13 of the stretch film hood 5 and the underside of the pallet being further improved by contact with the roller conveyor 3.

The device shown in FIG. 5 belongs to a device for covering stretch film hoods 101 over a stack of goods 103 arranged on a pallet 102, as described in principle in DE-GM 90 03 319. The palletized stack of goods 102, 103 is transported on a roller conveyor, on the transport rollers 104 of which the pallet 102 is supported with its underside. In the area of the roller conveyor, a lifting device 105 is provided, with which the stacked goods stack 102, 103 is raised so that the stretch film hood 101 can be pulled over it and its lower edge 106 can be knocked under the underside of the pallet 102. The facilities required for this are not shown. Movable clamping jaws 107 hold assigned sections of the stretch film hood 101 until the lower edge 106 has been folded under the pallet 102.

The device described below serves to secure the lower edge 106 of the stretch film hood 101. This device includes, in the area of each long side of the pallet 102, heating disks 108 arranged coaxially to one another, which in the embodiment shown (see in particular FIGS. 6, 7) each have a circular sector-shaped plan and which are covered on the circumference with heating tapes 109, to which electrical connections 110 are assigned are.

The heating disks 108 are arranged between the transport rollers 104 of the roller conveyor and are rotatably mounted on associated pivot levers 111, which in turn are articulated at 112 to a carriage 113. The carriage 113 is displaceable on a support 114 fixed to the frame parallel to the axis of the transport rollers 104 or to the underside of a pallet, with the aid of a drive 115, which in the embodiment shown is a lifting cylinder.

The pivot levers 111 are supported on the slide 113 by means of compression springs 116. In addition, a return spring 117 extends between each heating disc 108 and the associated pivot lever 111.

The heating disks 108 or their heating tapes 109 have a width of 5 to 15 mm.

The device described so far works as follows: If the stretch film hood 101 has been covered over the palletized stack of goods 102, 103 raised with the lifting device 105 and its lower edge 106 has been folded over under the pallet, the palletised stack of goods 102, 103 is lowered until it rests on the transport rollers 104. Then the drives 115 of the carriages 113 are actuated so that the carriages 113 move in the direction of the arrow 118 (FIG. 6). When the heating disks 108 with their heating tapes 109 reach the area of the underside of the pallet 102, they roll on the underside of the pallet 102 or on the edge 106 of the stretch film hood 101 located there. In the area of the heating disks 108 or the heating tapes 109, the film material is heated and softened, so that it forms a connection with the pallet material. In the case of pallets made of wood, the film material is pressed into the rough surface of the wood, creating a toothing between the wood and the film material. Ultimately, fastening strips 119 (FIG. 8) are formed which extend in the longitudinal direction of the stretch film hood 101.

When the drives 115 of the carriages 113 are reversed, the carriages 113 are withdrawn again, the heating disks 108 rolling in the opposite direction. As soon as the heating disks 108 come free from the underside of the pallet 102, they are returned by the return springs 117 to the rest position shown in FIG. 6.

Claims (18)

1. Method of drawing stretch film hoods over a stack of articles, wherein a hood (5), which is pretensioned in the circumferential direction, is drawn over the stack of articles (1), and its lower edge (13) is driven beneath the stack of articles (1), or beneath a pallet (2) carrying the stack of articles (1), and secured there, characterised in that, after the drawing process, the lower edge (13) of the hood (5) is gripped, subsequently tensioned in the longitudinal direction of the hood and then wrapped round.
2. Method according to claim 1, characterised in that the lower edge (13) is gripped in the central region of at least two oppositely situated sides of the stack of articles (1) and subsequently tensioned.
3. Method according to claim 1 or 2, characterised in that, during the subsequent tensioning process, the lower edge (13) of the hood (5) is retained in a stationary manner, and the stack of articles (1) is raised.
4. Apparatus for accomplishing the method according to one of claims 1 to 3, including a tensioning frame, which is displaceable longitudinally of the stack of articles (1) and has retaining members (6), which are displaceable relative to one another by a tensioning drive and engage in the opened hood (5), including a vertically displaceable carrier (7) for the stack of articles (1), and a means, disposed beneath the stack of articles (1) or its carrrier (7), for securing the lower edge (13) of the hood (5) on the stack of articles (1), characterised in that means (8) for subsequently tensioning the hood (5) are disposed between the retaining members (6) of at least two oppositely situated sides of the stack of articles (1).
5. Apparatus according to claim 4, characterised in that the means (8) for the subsequent tensioning process are disposed in the central region between adjacent retaining members (6).
6. Apparatus according to claim 4 or 5, characterised in that the means (8) for the subsequent tensioning process include gripping members (12), the opening gap of which is orientated substantially vertically for gripping the lower edge (13) of the hood (5) guided by the retaining members (6).
7. Apparatus according to one of claims 4 to 6, characterised in that, after the stack of articles (1), covered with the hood (5), has been raised, the gripping members (12) are displaceable beneath the stack of articles (1).
8. Apparatus according to one of claims 4 to 7, characterised in that each means (8) for the subsequent tensioning process includes two gripping members (12), which are disposed with a mutual spacing therebetween, and in that an adhesive spraying device (15) is disposed beneath the stack of articles (1), said device spraying adhesive on the lower edge (13) of the hood (5) in the region between the gripping members (12).
9. Apparatus according to one of claims 4 to 8, characterised in that a pressure roller (16) is provided between the gripping members (12) of each means (8), said roller being displaceable with the gripping members (12) and urgeable against the underside of the stack of articles (1) or respectively of the pallet (2).
10. Apparatus according to one of claims 4 to 9, characterised in that the pressure roller (16) has a pressure cylinder (19) associated therewith.
11. Apparatus according to one of claims 4 to 10, the edge being presed against the pallet by at least one displaceable heating disc and the film material thereby being joined to the pallet material, characterised in that groups of heating discs (108), which are coaxial with one another, are disposed in the region of at least two pallet sides, the axes of said plates extending parallel to the sides of the pallet (102), and in that each group of heating discs (108) has a drive (115) associated therewith, by means of which drive the heating discs (108) are guided in a rolling movement in the longitudinal direction of the film hood (101).
12. Apparatus according to claim 11, characterised in that the heating discs (108) are pressed against the pallet (102) in a resilient manner.
13. Apparatus according to claim 11 or 12, characterised in that the heating discs (108) are mounted on associated pivot levers (111) which, in turn, are pivotally connected to a carriage (113), which is displaceable by the drive (115), and in that the pivot levers (111) are supported on the carriage (113) by springs (116).
14. Apparatus according to one of claims 11 to 13, characterised in that return springs (117) are disposed between the heating discs (108) and their pivot levers (111).
15. Apparatus according to one of claims 11 to 14, characterised in that the heating discs (108) are circumferentially covered with heating strips (109).
16. Apparatus according to one of claims 11 to 15, characterised in that the heating discs (108) engage with the underside of the pallet (102).
17. Apparatus according to claim 16, characterised in that the heating discs (108) are disposed between the conveyor rollers (104) of a conveyor.
18. Apparatus according to one of claims 11 to 15, characterised in that the heating discs (108) engage with the sides of the pallet (102).

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