Method and device for shrinking a heat shrink film placed around a stack of items, in particular a palleted stack of items

The invention relates to a method for shrinking a heat-shrinkable film shell arranged around, especially palletized, a stack of goods by means of at least one, moved vertically on a stand, shaped in particular in the form of a shrinking frame, a shrinking device for shrinking the shrink film by heating, the jacket being shrink film protrudes from above at least beyond the upper edge of the stack of goods to shrink the top, and on top of the stack of goods is placed, preferably protruding beyond the edge of the stack of goods, a top sheet of foil that is heat-sealed with a shrink film.

Such methods are used, for example, in the paper industry. Here, pallets of various sizes are used, which must be packed on one packaging line with shrinking. The shrinking takes place after laying the top sheet of foil on top of the stack of goods and then putting on the shrink wrap. The overhanging ends or edges of the top sheet of foil and the underside foil possibly placed additionally between the pallet and the pile of goods are clamped between the shrink film jacket and the pile of goods or the pallet. To prevent moisture ingress, sufficient protection against climatic factors must be ensured. This only occurs if sufficiently good welding is guaranteed between the stacked top sheet of film and the shrink film jacket formed in the form of a band.

This type of method is known from DE-A-19011080.

The object of the invention is to develop a method by which the abovementioned disadvantages can be avoided and sufficient protection against climatic factors is ensured by better welding of the top foil sheet and the heat-shrinkable film envelope.

This task is solved in such a way that in the first stage hot gases rising along the sides of the stack of goods are directed inwards through a combination of heat control and pressure assembly placed above the stack of goods in order to heat and bend inside the heat shrink film and heat shrink film the top sheet of film in the area of ​​the upper side of the stack of goods in a direction extending at least approximately parallel to the upper side of the stack of goods, and in the second stage, the layers of the folded heat shrink film allowance and the top sheet film are resting on each other, at least in the upper part of the stack of goods are joined by pressing the still not completely cooled, resting on each other layers of the shrink film and the top foil sheet behind by means of a combined heat and pressure control unit.

By means of the method according to the invention, hot gases, which rise normally quickly upwards, are guided by a combined heat-directing and pressing unit through the surface of the stack of goods towards its center, so that already when the sides of the stack of goods are shrinked, heating of the top sheet occurs when the upward shrinking unit moves upwards. in the upper side area and heating of the heat shrink wrap film. At the same time, this allowance is rolled inside.

In addition, by means of the combined heat-guiding and pressing unit, the not yet completely cooled, resting on each other layers of the heat-shrinkable film sheath and the outer sheet of the film are joined by mutual pressure. The pressure exerted by mutual pressure can be changed. This results in particularly good welding of the layers lying together, and thus very good protection against climatic factors.

The top of the foil sheet is at least large enough that after folding the allowance, a circumferential contact is ensured between the layered allowance of the heat-shrinkable foil jacket and the top foil sheet. Preferably, the top foil sheet is larger than the stack of goods, so that the top foil sheet is lowered down from all sides.

Of course, the shrink wrap can also protrude beyond the bottom edge of the stack of goods to shrink the bottom. If a bottom seal is also desired, it can also be placed between the pallet and the stack of goods which protrudes preferably beyond the edge of the bottom film, which is welded to the shrink film jacket when shrinking the bottom.

For shrinking, the shrink assembly can be moved first up to shrink up and then down to shrink down.

In a particular embodiment of the method, the shrinking begins at approximately half the height of the stack. The shrink assembly moves first to half the height of the stack of goods. The shrink assembly is then started and moved first up to shrink the top and then down to shrink the bottom.

In a preferred embodiment of the method, it is proposed that at least at the beginning of the shrinking process, a vertical overhang of the heat-shrinkable film overhang above the upper edge of the stack of goods is positioned, in particular by means of a heat and pressure assembly produced by the combined heat and pressure assembly, directed directly or indirectly outwards air stream. In this embodiment, it is possible, for example, to place a fan in the area of ​​the combined heat and pressure control unit, which is switched on to blow in to adjust the allowance vertically. The air stream falling on the upper side is directed outside and provides the arrangement. In the remainder of the shrinking process, for example when top shrinking and bottom shrinking are performed, the fan can be switched to suction.

Hot gases, rising along the sides of the stack of goods and guided in a direction parallel to the upper surface of the stack of goods, can be sucked, especially by means of a combined heat control and pressure assembly. Of course, other forms of implementation are also possible.

At least when moving the shrinking element vertically downwards, resting layers of the heat-shrinkable film sheath and the top sheet of film can be joined at least in the area of ​​the upper side of the stack of goods by pressing the still not completely cooled, resting on each other layers of the heat-shrinkable film and the top sheet of foil.

Alternatively, resting layers of the heat-shrinkable film sheath and the top sheet of film can be joined at least in the upper side of the stack of goods by pressing still not completely cooled, resting on each other layers of the shrink film and the top film sheet at least when shrinking the bottom .

The invention also relates to a shrinking device wrapped around, in particular a palletized, stack of heat-shrinkable film sheath, with at least one vertically displaced on the rack, shaped in particular as a shrinking frame, a shrinking assembly for shrinking the heat-shrinkable film sheath, wherein shrink film jacket protrudes at least above the upper edge of the stack of goods, and on top of the stack of goods there is preferably a top sheet of film protruding beyond the edge of the stack of goods, heat-sealable with a heat-shrinkable film sheath.

Such devices are used, for example, in the paper industry. Here, pallets of various sizes are used, which must be packed on one packaging line with shrinking. The shrinking takes place after the top foil sheet has been put on top of the stack of goods and the next shrink wrap has been put on. The overhanging ends or edges of the top sheet of foil and possibly additionally provided between the pallet and the stack of underlayer goods are clamped between the shrink film jacket and the stack of goods or the pallet. To prevent moisture ingress, sufficient protection against climatic factors must be ensured. This only occurs if sufficiently good welding is guaranteed between the stacked top sheet of film and the shrink film jacket formed in the form of a band.

The object of the invention is to develop a device with which it is possible to eliminate the said drawbacks, and which guarantees shrinking with sufficient protection against climatic factors due to better welding of the top foil sheet and the excess of the heat shrink film.

This task is solved in such a way that above the stack of goods a combined heat and pressure control unit is placed, on the one hand, to guide hot gases rising along the sides of the stack of goods in a direction running at least approximately parallel to the upper side of the stack of goods in order to heating and bending inward heat shrink film and to heat the top sheet of film in the upper side of the stack of goods, on the other hand, for the subsequent joining of the rolled shrink wrap allowance and the top sheet of film, at least in the area of ​​the upper side of the stack of goods, by pushing the not yet completely cooled, resting on each other layers of the shrink film and the top sheet of foil.

By means of the device according to the invention, hot gases, which rise normally quickly upwards, are guided by a combined heat-directing and pressing unit through the surface of the stack of goods towards its center, so that when the sides of the stack of goods are already shrinking, the surface heating of the shrinking unit takes place during the upward movement of the shrinking unit. a sheet of foil in the area of ​​the upper side and heating the heat shrinkage of the shrink film. At the same time, this allowance is rolled in.

In addition, by means of the combined heat-guiding and pressing unit, the not yet completely cooled, resting on each other layers of the heat-shrinkable film sheath and the outer sheet of the film are joined by mutual pressure. The pressure exerted by mutual pressure can be changed. This results in particularly good welding of the layers lying together, and thus very good protection against climatic factors.

The top foil sheet is at least large enough that after folding the allowance, a circumferential contact is ensured between the layered allowance of the heat-shrinkable foil jacket and the top foil sheet. Preferably, the top foil sheet is larger than the stack of goods, so that the top foil sheet is lowered down from all sides.

Of course, the shrink wrap can also protrude beyond the bottom edge of the stack of goods to shrink the bottom. If a bottom seal is also desired, it can also be placed between the pallet and the stack of goods which protrudes preferably beyond the edge of the bottom film, which is welded to the shrink film jacket when shrinking the bottom.

Preferably, the combined heat control and pressure assembly may be a plate parallel to the upper surface of the stack of goods.

At least in contact with the upper side of the stack of goods, the area of ​​the combined heat control and pressure assembly is slightly smaller than the internal dimensions of the shrink assembly to ensure that the shrink device can move sufficiently during shrinking.

The plate may advantageously be provided with a coating, preferably a Teflon coating, on the side facing the stack of goods.

The side edges of the combined heat control and pressure assembly may approximately coincide with the side edges of a stack of goods. A solution is also possible in which the combined heat-guiding and pressing unit is slightly smaller than the dimensions of the stack of goods. In this case, appropriate measures should be provided to enable hot gases to be directed.

Preferably, the combined heat control and pressure assembly projects laterally beyond the outline of the stack of goods.

The combined heat control and pressure assembly may have at least one, preferably located approximately in the middle of the combined heat control and pressure assembly, a recess to discharge hot gases flowing up towards the center parallel to the top side of the stack of goods. By this recess, hot gases, guided from the top edge towards the center, are discharged upwards. The resulting flow velocities also strengthen the bending of the oversizes and welding the oversize to the top sheet of film. It is of course also possible that, especially along the length of the combined heat control and pressure assembly, two recesses are provided, one after the other.

Preferably, the position of the at least one recess can be variable to change the point at which hot gases, flowing initially parallel to the surface of the stack of goods, are directed upwards. An embodiment is possible in which the recess is, for example, part of a cover sheet or a sliding sheet, displaced in a horizontal direction relative to the combined heat control and pressure assembly within the contour of the opening provided in the combined heat control and pressure assembly.

Advantageously, a transport device may be provided for suctioning hot gases flowing parallel to the upper side of the stack of goods towards the center of the stack by at least one recess. The transport device causes that in the area of ​​the upper side of the stack of goods, the combined heat and pressure control assembly generates a vacuum, so that in the area between this upper side and the combined heat control and pressure assembly a larger amount of hot gases is sucked and directed. At the same time, the transport device can also be used for blowing, which is used for the initial possible vertical alignment of the heat shrink film sleeve.

A throttling flap may be used in the area of ​​at least one recess. When applying the combined heat-guiding and pressure assembly, i.e. when the not-completely-cooled, resting on each other layers of the thermosensitive film jacket and the outer foil sheet are pressed together, it is in the closed position. This prevents the top foil sheet from being pulled up in the recess area due to the thermic hot air rising from the hot surface of the top foil sheet. At the same time, the throttle flap allows you to control the volume of the stream during shrinking.

To prevent overheating of the combined heat control and pressure assembly at high palletizing capacities, at least that area of ​​the combined heat control and pressure assembly that is in contact with still not completely cooled, resting on each other layers of the heat-shrinkable film sheath and the top foil sheet, be cooled. It is possible, for example, a cooling system provided in the underside of the combined heat control and pressure assembly, cooled by water, air or other suitable refrigerant.

If stacks of goods of various sizes are to be packaged with the device according to the invention, it is advantageous if, in order to adjust the distance between the stack of goods on one side and at least one, extending essentially parallel to the respective side surface of the stack of goods, a shaped heating strip constituting shrinking assembly on the other hand, at least one heating bar has a variable position by moving in a direction substantially perpendicular to this side surface. This adjustment ensures that the stack of goods in the area of ​​all side surfaces is supplied with substantially the same heating power to achieve an even shrinking result.

If only one adjustment is desired with respect to the length or width of the stack of goods, then it is sufficient if only one heating bar is movable. Alternatively, two opposite heating strips of the shrinking frame, consisting of four heating strips, can be movable relative to each other. When adapting to the width and length of a stack of goods, at least two contacting heating strips are movable.

Preferably, at least one of the two heating strips, arranged substantially perpendicular to the direction of transport of the stack of goods, has a variable position by displacement to adjust the distance between the stack of goods on one side and at least one of both heating strips extending substantially perpendicular to the direction of transport of a stack of goods

The heating strip movable relative to the rest of the shrinking frame can be placed on at least one rail provided in the rest of the shrinking frame, and a drive can be provided for movement. The rail can be placed either on top or bottom of the shrinking frame, whereby the heating strip is mounted on the rail by appropriate means. It is also possible that the heating strip at both ends has rollers that run on a rail mounted on the upper side of the shrinking frame. A kind of conveyor belt is also possible, which is led between two return rollers and on which the heating strip is mounted.

To ensure that the combined heat control and pressure assembly , especially when adhering to the top of the stack of goods, is positioned approximately horizontally, an assembly can be provided which prevents the combined heat control and pressure assembly from pivoting, especially when adhered to the top of the stack. goods.

The at least one heating bar may consist of several heating segments, preferably of several separately activated heating segments. With separate activation, the heating segments can therefore be independently connected or disconnected. This embodiment is advantageous because it is then possible to switch off the heating segments of the heating strips which no longer act on the area covered by the movable heating bar (movable heating bars) and, optionally, the fixed heating bar (fixed heating bars) or parts thereof.

An embodiment of the invention is explained below, shown in the drawings in which:

Fig. 1 is a side view of the device according to the invention with a shrinking frame and combined heat-guiding and pressing unit, Figs. 2-7 different positions of the shrinking frame and a combined heat-guiding and pressing unit, Fig. 8 Figs. 9-12 Fig. 13 from above, the object of Fig. 1 a side view of another embodiment of the device according to the invention, a top view of the object of Figs. 11 and 12, and Fig. 14, a top view of the object of Figs. 9 and 10.

In all figures of drawings, identical references have been used to designate identical or identical elements.

Fig. 1 shows a side view of the device according to the invention for shrinking wrapped around a stack of goods 1 of a heat shrink film 2. In the illustrated embodiment, the stack of 1 goods stands on the bottom of the pallet 3. The pallet 3 itself rests on the conveyor 4.

The bottom foil 5 is first laid on an empty pallet, with the bottom foil projecting beyond the pallet at the edges

3. A stack of goods, for example paper, is placed on the back film 5. From the top, a top sheet 6 of film is applied to the stack of 1 goods, with the top sheet 6 of the film also protruding beyond the edge of the stack of 1 goods. Usually, the top foil sheet 6 is cut off from the endless foil roll. Both the hanging edge 7 of the bottom film 5 and the hanging edge 8 of the top sheet 6 of the film are folded down.

In the next stage of the method not shown, a heat-shrinkable film jacket 2 is laid around the stack of goods. For this purpose, the stack of 1 goods can, for example, be moved in the direction of a foil curtain made of a heat-shrinkable film, which extends transversely to the direction of transport. When passing, the shrink film is laid around a stack of 1 goods. In the area opposite to the direction of transport, the heat-shrinkable film jacket wrapped in this way around the stack of 1 goods is usually welded by means of a vertically oriented welding beam. In this way, a band is formed, as shown in Fig. 1.

From above as well as from below, the shrink film jacket 2 protrudes beyond the upper edge or lower edge of the stack of goods 1 to form an allowance 9 or 10 for subsequent shrinking of the top and bottom. The folded edges 8, 7 of the top sheet 6 of the foil and the bottom foil 5 are located between the jacket 2 of shrink foil and a stack of 1 goods or a pallet 3.

In the vicinity of the conveyor 4 on the stand 11 a shrinking frame 14, consisting of four heating strips 14a for shrinking by heating the jacket 2 from heat-shrinkable film is provided, moved vertically (arrow 13) by means of the drive 12. At the same time, on the stand 11 there is also a movable in the vertical direction (arrow 13) combined heat and pressure control assembly 15. It consists in the illustrated embodiment of a plate 16 arranged parallel to the upper side of the stack of 1 goods, wherein the plate 16 in the illustrated embodiment projects about 50 mm on all sides beyond the outline of the stack of 1 goods.

On the side facing the stack of goods 1, plate 16 has a coating, e.g., a Teflon coating, to prevent sticking to the top sheet 6 of the film. In the embodiment shown in Figs. 1 to 8, the plate 16 has a central recess 17 for escaping hot gases. With this recess 17 a channel section 18 is connected from above, in which the throttling flap 19 and the transport assembly 20 formed as a fan are located.

Fig. 8 shows in detail the configuration of the combined heat-guiding and pressing unit. As can be seen in this figure, the combined heat control and pressure assembly 15 is mounted on two oblique supports 21, which for their part are connected to the stand 11. The oblique supports 21 are fixed by means of transverse supports 22.

Retaining elements 23 are provided on the oblique supports 21, at the bottom of which a quadrangular frame 24 is mounted. In each corner the frame 24 has an outwardly facing retaining plate 25, each with an opening 26.

As can be seen in Fig. 8, for example in conjunction with Fig. 4, the plate 16 of the combined heat-guiding and pressing unit 15 is suspended at a distance from the bottom of the frame 24, creating a free space 27. To this end, mounting pins are formed on the upper side of the plate 16 28 with an end bead 29. Each attachment pin 28 is guided in its associated hole 26, the bead 29 being larger than the diameter of the hole 28 and above the holding plate 25.

Upon contact of the plate 16 with the upper side of the stack of goods 1, the fixing pins 28 are moved in the holes 26, thus reducing the free space 27. In order to allow this displacement of the plate 16 relative to the frame 24, also the channel section 18 is shaped accordingly. As it results from fig. 4, the channel section 18 is divided into a lower partial channel section 18a with a smaller contour and an upper partial channel section 18b with a larger contour, so that both partial channel sections 18aa, 18b are movable with each other.

This special embodiment of the combined heat-guiding and pressing unit 15 allows the pressing to take place only under the actual weight of the plate 16. Only after traveling through the free space 27 can work be carried out with greater pressure, because then, in addition to the weight of the other parts of the combined steering unit 15 heat and pressing force still operates the drive 12.

The operating principle of Figures 1 to 7 is as follows:

In Fig. 1, the wrapped stack of 1 goods is ready for shrinking. The allowance 9 protruding upwards from the upper edge of the stack of goods 1 is not yet straightened, that is, it partly stands upright, and partly it is rolled out or inward.

Then the shrinking frame 14 moves to the position shown in Fig. 2, which corresponds to approximately half the height of the stack of 1 goods. It is only when this position is reached that the shrinking frame 14 is started, which is shown in cross-section in Figures 2 to 7. Hot gases flow in the direction of the arrow 30 up along the sides of the stack of 1 goods. The transport device 20 is here set to blow, so that air is blown out in the direction of the arrow 31 to the upper side, causing the vertical allowance 9 to be positioned on the upper side. The throttling flap 19 is in the open position.

When lifting the shrinking frame 14, as shown in Fig. 3, the distance between the combined heat-guiding and pressing unit 15 and the upper side of the stack of goods 1 decreases. In Fig. 2 this distance is about 500 mm. In Fig. 3, the gap is reduced to approx

200 mm.

In the position shown in Fig. 3, the transport device 20 is already set for suction, so that hot gases flowing along the sides upwards (arrows 30) are guided in a direction parallel to the upper side of the stack of goods 1 (arrows 32). As a result, also the heat shrink film jacket 2 and the top foil sheet 6 in the upper side area are heated sufficiently for good shrinking of the top.

In Fig. 4, the shrinking frame 14 has reached its highest position. The shrinking frame 14 then moves to shrink the sides, especially in the lower area of ​​the stack of goods 1, vertically downwards as shown in Fig.

5. With this vertical downward movement, hot gases are sucked as before (arrows 32) by the transport device 20 by recessing 17 in the direction of arrows 33.

In Fig. 6, the shrinking frame 14 has reached its lowest position for carrying out the shrinking of the pit. In the position shown in Fig. 6 the transport device 20 is turned off and the throttling flap 19 is closed. The combined heat-guiding and pressing unit 15 is pressed in the direction of arrow 34 to the upper side of the stack 1 of goods, whereby the layers of the heat shrink film 2 and the foil top sheet 6 lying on top of each other in the upper side area are joined together by pressing not yet fully cooled resting on each other layers. Of course, pressing can also take place earlier.

After the shrinking process, the shrinking frame 14 and combined heat-guiding and pressing unit 15 are again moved to the position shown in Fig. 7, and the wrapped and shrunk stack of goods 1 is discharged by means of a conveyor 4.

Figures 9 to 14 show another embodiment of the device according to the invention. The heating bar 14a arranged perpendicular to the direction of transport 35 is movable in relation to the remaining part of the shrinking frame 14. This makes it possible to adjust the distance between the stack of 1 goods on one side and the movable heating bar 14a made as the shrinking assembly of the shrinking frame 14. This possibility of movement is advantageous if stacks of 1 goods of various dimensions, for example lengths, are to be packed.

Figures 9, 10 and 11 show a stack of 1 goods of smaller length. Therefore, the left heating bar 14a shown in Figs. 9 and 10 has been moved towards the opposite heating bar 14a in the direction of movement 36 substantially perpendicular to this side surface. In this case, the direction of transport 35 and the direction of travel 36 match.

Figures 11, 12 and 13 show the arrangement of heating strips 14a for a stack of longer goods. Here the left heating strip 14a is almost completely extended outwards.

In the embodiments of the invention exemplified in Figures 10 and 11, the heating bar 14a can be moved to two different positions. It is of course also possible that the intermediate positions of the movable heating bar 14a can be set to increase the adaptability.

To allow displacement, rails 37 are arranged on the upper side of the shrinking frame 14. On both rails 37, a heating bar 14a is mounted slidably by means of guide slots 38. To move, the toothed bar 14a cooperates with a toothed belt 40 mounted between two return rollers 39. A proper drive for driving the toothed belt 40 is not shown. The return rollers 39 are attached with support brackets 3a on the shrinking frame 24. For better clarity, toothed belts 40 are not shown in Figs. 13 and 14.

Insofar as each of the two ends in contact with the movable heating bar 14a, the heating bars 14a with rails 37 located at the top consist of several separately controlled and equally activated heating segments, in the position of the heating bar 14a shown in Fig. 10 it is preferred, if the heating segments in the projecting region X of the heating strips 14a with the top rails 37 are turned off.

In the position of the movable heating bar 14a shown in Fig. 11, all heating segments of the heating bars 14a with the rails 37 located at the top are turned on.

As can be seen in Figs. 9 to 14, in this embodiment two recesses 17 are made in the plate 16, each of which connects the channel section 18 in which the throttling flap 19 and the transport unit 20 in the form of a fan are connected.

In the embodiment shown in Figures 9 to 14, only one of the four heating strips 14a is movable, while the remaining part of the shrinking frame 14, consisting of the other three heating strips 14a, is not movable and forms a U-shape together. it is also possible to make two or more heating strips 14a movable, which allows them to be adjusted to the length as well as the width of the stack of 1 goods.

The stack of 1 goods in the embodiment shown in Figs. 9, 10 and 14 is arranged such that the center of the stack of 1 goods roughly coincides with the center of the right recess 17. Preferably, the distance on the opposite sides of the stack of 1 goods relative to each of the adjacent and stacked parallel to these sides of the heating strips 14a is approximately the same. As for the one shown in fig. 9 and a stack of 1 goods, then the left heating bar 14a is moved towards the stack of 1 goods until this spacing is approximately equal to the distance between the remaining three heating bars 14a and the stack of 1 goods.

In the position of the heating bar 14a shown in Figs. 9, 10 and 14, the throttling flap 19 of Fig. 9 on the left of the channel section 18 is closed. As a result, the hot gases in the later suction phase are only sucked through the transport device 20 by the right recess 17 in the direction of arrows 33.

In piles 1 of goods with longer lengths, as shown in Figures 11, 12 and 13, both transport devices 20 are "active" and, for example, when suctioning both throttling flaps 19 are open because both recesses 17 are within the outline stack of 1 goods. The stack of 1 goods is arranged in such a way that the center between the recesses 17 coincides approximately with the middle of the upper side 20 of the stack of 1 goods. The working situation in Fig. 12 for the longer one and in Fig. 10 for a shorter stack of 1 goods roughly corresponds to the working situation shown in Fig. 2.

To prevent tilting of the combined heat-guiding and pressing assembly 5, especially for piles 1 of shorter length goods adjacent to the upper side of a stack of goods, assembly 41 is used. This assembly 41 is provided in the region of the edge of the plate 16, which compared to others the edges of the plate 16 usually protrude sideways relative to the stack of 1 goods.

In the embodiment shown, the assembly 41 is shaped as a cylinder 42 that cooperates with a lever arm 43 connected to the plate 16, whereby the plate 16 is lifted in the region of this edge. As a result, the plate 16 does not tilt, but is kept in an approximately horizontal position, such that approximately equal force is applied to each point of the upper surface of the stack of 1 goods.

If several heating strips 14a are movable, it is advantageous if an assembly 41 is arranged in the area of ​​each edge of the plate 16 with which the movable heating strip 14a borders.

MSK-VERPACKUNGS-SYSTEME

GESELLSCHAFT MIT BESCHRANKTER HAFTUNG

Proxy:

84P24625PL00

EP 1 940 686 B1