EP1275581A1 - Method and apparatus for wrapping a stack of products in a stretchable foil cover - Google Patents

Abstract

The method for fitting a hood of stretch film over a stack (3) of articles comprises stretching and folding tubular film (7) from a roll (4) to form a bellows shape which is wider than the stack. It is then welded together at the top and cut off, after which it is fitted over the stack. The novelty is that in the unstretched state the circumference of the film is at least 25% less than that of the stack and in the stretched state the thickness of the film at the top corners is more than 50% of its initial thickness. An Independent claim is included for a machine for carrying out the method.

Description

The present invention relates to a method for covering a stretch film hood via a stack of goods in which the tubular film fed from a film supply is opened and of reefing fingers that move in the horizontal and vertical directions and engage in the film taken over and bellows-like on this and with which the supplied Foil for forming the hose hood with a seam at a distance from its lower end provided and separated from the film supply, the film by spreading the reefing fingers on a larger floor plan than that of the stack of goods and stretched down the reefing finger to rest on the long sides of the stack of goods from the reefing fingers is released.

Such a method is known for example from DE 43 07 287 C1 and serves the Wrapping the stack of goods, which usually consists of a plurality of side by side and piece goods stacked one on top of the other on a pallet. With the generic The supplied tubular film is moved over the stack of goods before it is pulled over on a larger floor plan than that of the stack and then under Release of the reefing fingers pulled over the stack. The foil hood lies down due to their elastic properties close to the outer peripheral surface of the stack and connects - if several piece goods form the stack - these into one packaging unit. The stability of the packaging unit caused by the coated film depends on it among other things from the elastic stretch of the coated film on the long sides. The required longitudinal expansion of the tubular film is, for example in the method known from US Pat. No. 4,050,219 by causing to impact the film provided, lying on the reefing fingers with the interposition of the film during reefing Reef rollers are effective and the release of the tubular film by the reefing fingers to oppose some resistance. The hose has therefore only been exceeded a certain longitudinal tension released by the reefing fingers, whereby the desired longitudinal expansion is achieved on the hood side walls.

The relationships described above, known per se, are last with EP-0 344 815 B1 has been taken up again, taking into account the best possible stability the packaging unit, especially if the stack of goods is made up of piece goods filled sacks is formed, which settles or deflates during storage, suggests the film hood before covering at least in the area of the hood side walls additionally in the vertical direction by 5%, preferably by 10 to 15% of their vertical To stretch the initial length in the stretched state in the longitudinal direction. The increased However, longitudinal stretching of the stretch film hood on the side surfaces of the stack of goods brings the use of films with a higher thickness of the film in the supplied state, i.e. in the unstretched State with itself. This is the case for the method known from EP-0 344 815 B1 the use of a film with a thickness of 100 µm in the fed state up to 250 µm suggested. These thick foils offer a sufficient material reserve, so that there is no fear that even with excessive local stretching of the film the film is weakened so that it tears, or that for reliable coverage of the stack of goods is below the required minimum thickness.

For ecological as well as economic reasons and also in consideration of that Problem of disposal of the film after removing it from the stack of goods in practice, however, the lowest possible use of film material is sought. The conflicting ones Interests for the lowest possible film thickness of the supplied film on the one hand and at the greatest possible longitudinal expansion on the side surfaces of the stack of goods on the other hand, the previously known solution proposals were not or not sufficient considered. There is still an urgent need in practice for one Method and a device suitable for carrying out the method, which the above Disadvantages indicated do not have and are particularly suitable, thinner films with high proportions of stretch on the long side of the stack of goods.

The present invention is therefore based on the problem of a method and an apparatus To provide, by means of which a reliable with less use of film material Wrapping the stack of goods is possible.

In order to solve the above problem procedurally, the present invention further developed the generic method according to its first aspect in that a film is used which in the unstretched initial state has a minimum of 25% has a smaller scope than the stack of goods to be wrapped and in this way over the stack of goods that the thickness of the film is drawn on top of the stack of goods in the area of its Corners is greater than 50% of the thickness of the film in the initial state.

In the method according to the invention, medium to high elasticity are preferred Stretch films are used that are at least 25% smaller in size than that Have enveloping stacks of goods and which are suitable for the stack of goods to be wrapped to be narrowly comprehensively. It was completely surprising that Use of such a film also thins the film material to the Side surfaces on film thicknesses that can no longer be tolerated can thereby be avoided can that the thickness of the film in the area of the corners on the top of the stack of goods in any case is greater than 50% of the thickness of the film in the initial state. The specified Limit of more than 50% of the thickness of the supplied film refers to the thickness the film due to plastic deformation, i.e. without elastic parts and can after Removing the film from the stack of goods can be measured at the respective areas. As The area of the corners in the sense of the present invention is in particular the area viewed from the corner with a longitudinal extension of 1/8 to 1/10 the length of the diagonals connecting the two opposite corners extends along the diagonal to the center of the stack.

According to a second aspect, the Present invention proposed to develop the generic method by that the film is released by the reefing fingers when it is opened. While in State of the art regularly when stretching the film as far as possible across stretched, i.e. the present should suggest stretching as far as possible in the circumferential direction Invention in departure from previous approaches, at least one Release part of the tubular film placed on the reefing fingers when reefing the film. As a result, the top of the hose hood formed during cross stretching, which is initially has a larger floor plan than the stack of goods to be wrapped, with a smaller one Stretching stretched. When the hose hood is subsequently pulled over the The majority of the top of the hose hood lies on the stack of crops Top of the stack of goods, however, part is on the side surfaces of the stack of goods created. It has been shown that even with such an inventive Procedural procedure an inadmissible thinning of the film with the risk of failure the film can be avoided. can be.

The two parallel proposed solutions of the present invention are surprising Based on the knowledge that to limit the film stretch at least in the the upper area of its long sides, the stretching of the top of the hood when open after stretching and / or when placing on top of the stack of goods must be checked.

Preferred developments of the method according to the invention with its first and second aspect are given in dependent claims 3 to 7. These subclaims specify various procedural measures, such as releasing the film can be influenced by the reefing fingers in an advantageous manner when clamping the same can.

In the development according to claim 3, those reefing means which are the film Apply bellows-shaped to the film, before stretching the film from the reefing fingers moved away. In other words, the reefing means are not in theirs when reefing taken active position, so that the film when stretching against the reef direction can slide freely from the spreading fingers and is released. Such a preferred Procedural procedures regularly set up equipment on the reefing fingers ahead, which will be discussed below.

In the development according to claim 4, the aforementioned reefing agents remain effective, i.e. lie against the reefing fingers with the film in between and become relative to the reefing fingers moved to release the slide. The reefing agents move accordingly one direction opposite to the reefing movement and release foil.

While the aforementioned training according to claim 4 leaves the possibility open that the reefing means when stretching the film freely by pulling off the reefing fingers Foil are moved, which in the case of the reefing rollers usually provided as reefing means means that they rotate freely, according to a further preferred embodiment of the inventive method proposed that the reefing means when clamping of the film are driven to release the film. The reefing agents can during the entire transverse movement of the reefing fingers against their reefing movement become. However, it is also conceivable to drive the reefing means only gradually, sufficient, but not too high, stretch on the top of the hood the covering over the piece goods stack to produce, for example, the hood as possible smooth, but with a thickness that is as uniform as possible on the top of the stack to apply.

For relaxation of local sources of tension, especially in the top of the hood the covering over the piece goods stack, it can be advantageous to use the reefing agents during cross stretching the film alternately to drive the film in a reflective and releasing manner, like this is proposed according to a further preferred embodiment.

It has also been shown that the thinning of the film after it has been deposited correlates the piece goods stack with the tension generated when the film is stretched. Accordingly according to a further preferred embodiment of the present invention proposed to drive the reefing means in dependence on a voltage that is applied to the reefing fingers through the stretched film. The voltage determined in this way becomes the reef fingers via sensors on the reef fingers or on the actuators measured and via a control and regulating device for the position of the reefing means and / or Transfer reef finger.

In order to solve the above problem in the device, the present invention a device with the features of claim 8 specified. This points in a known manner Way a film supply for tubular film and a separating or cutting device to form a sealed top and separated from the film stock Hose hood on. Furthermore, the device has a spreading device for opening the Tubular film and a covering device that can be inserted into the tubular film and for transverse stretching of the same, the reefing fingers to be moved apart which are relative to the Longitudinal side of the stack of goods are movable and reefing means which can be driven for bellows-like operation Place the supplied tubular film on the reefing fingers. This on The known device has means provided on the reefing fingers according to the invention to reduce the friction compared to the film wrapping around the reefing finger.

The area of the reefing fingers wrapped in the film is where the film is stretched from a substantially parallel to the side surfaces of the stack of goods extending alignment in a substantially parallel to the top of the stack of goods extending orientation is redirected when spanning the same. There will be the reefing fingers when stretching regularly at an angle of about 90 ° from the film entwined. With longitudinal stretching, the wrap angle is significantly lower. At this Special measures are provided in the state of the art, the straight to prevent the film from sliding undesirably from the reefing fingers. So is proposed for example in EP-0 344 815 B1, at the top end of the Refffinger provide a resistance stirrup, which the desired Ensure longitudinal expansion on the long side of the stack of goods. Of this the present invention also applies to the solution principle known from US Pat. No. 4,050,219 with their device aspect completely. The invention The device has means for precisely where the film slides off the reefing fingers Reduction in friction. The high longitudinal strains that may be required can be achieved on the side surfaces of the stack of goods, for example, that the Reffmittel are effective when pulling the hose hood on the piece goods stack and by applying a defined holding force, the film slides off the reefing fingers to be avoided at least until the desired longitudinal expansion is reached.

The agents according to the invention for reducing the friction lead to a friction between the film and the reef finger when stretching the film, which is less than in State of the art is where the spreading fingers at least on their wrapped in the film Sections are made of steel or aluminum.

According to a preferred embodiment of the present invention, the means for Reduction of friction is formed by the surface wrapped in the film the reefing finger is made of a plastic. A suitable plastic can for example polytetrafluoroethylene. The plastic can be a layer on the surface be provided on the reefing fingers at least on those surface areas that are wrapped in the film. Alternatively, the reefing fingers can also be used in sections from a solid plastic material, if necessary, to increase the strength, a fiber composite plastic be educated.

According to a preferred development of the present invention, the reefing fingers Means for generating a rolling friction to the film wrapping around the reefing fingers. Such means can be formed, for example, by rotatably driven rollers be arranged at the upper end of the reefing fingers and wrapped in the film and which allow control of the film length released when the film is stretched. In the case of such a preferred embodiment, the degree of the clamping the top of the hood and cross stretch of the film released film length, for example can be predetermined and controlled by the reefing means, as in the dependent claim 13 is specified. With regard to the simplest possible design of the invention However, the device is preferred to be freely rotatable on the reefing fingers Stored rollers to provide the reefing fingers at the ends wrapped in the film are arranged.

According to a further preferred embodiment, which slides relatively flat Foil when stretching the same and especially when placing the foil on the side surfaces of the stack of goods allowed, the rollers are provided on a reefing bracket, the End sections approximately at right angles to each other and each parallel to adjacent long sides of the stack of goods to be wrapped are arranged. The as such, for example EP-0 344 815 B1 as well as DE 43 27 450 C1 known reefing bracket is in this aforementioned prior art as a means of increasing the friction between the Foil and the reefing bracket provided. In contrast, after the further development of the invention proposed the aforementioned reefing bracket as a means of reducing surface friction provided. This preferred further development is realized in particular by that several freely rotatable, preferably spherical rollers, the curved The course of the reef bracket are arranged one behind the other. With this configuration becomes essentially the entire circumferential surface of the reef bracket known per se formed by the peripheral surfaces of the freely rotatable rollers.

Figur 1

eine Seitenansicht eines Ausführungsbeispiels einer erfindungsgemäßen Vorrichtung;

Figur 2

eine Draufsicht auf ein erstes Ausführungsbeispiel eines Refffingers;

Figur 3

eine Seitenansicht des in Figur 2 gezeigten Refffingers;

Figur 4

eine Draufsicht auf ein zweites Ausführungsbeispiel eines Refffingers; und

Figur 5-7

einen Teilbereich der in Figur 1 gezeigten Vorrichtung in verschiedenen Verfahrensstadien beim Überziehen einer Stretchfolienhaube.

Further details, advantages and features of the present invention result from the following description of an exemplary embodiment in conjunction with the drawing. In this show:

Figure 1

a side view of an embodiment of a device according to the invention;

Figure 2

a plan view of a first embodiment of a reef finger;

Figure 3

a side view of the reef finger shown in Figure 2;

Figure 4

a plan view of a second embodiment of a reef finger; and

Figure 5-7

a portion of the device shown in Figure 1 in different stages of the process when covering a stretch film hood.

The embodiment shown in Figure 1 of a device according to the invention comprises a device frame 1, a lane 2 between the vertical stands for feeding and removing stacked articles 3, each consisting of a plurality of one above the other arranged general cargo parts are formed, is arranged. On the fixture frame 1, a roll 4 is mounted on which a tubular film 5 is wound. The side edges of the tubular film 5 are folded in the wound state (Gusseted tube). The tubular film 5 is passed over deflection rollers 6 and take-off rollers 7 fed to a threading device which has vertically movable guide elements 8. The The device further comprises a separating device 9 and a welding device 10th

Below the guide elements 8 are in a known manner on both sides of the device frame 1 roof-shaped double conveyor belts 11 as a means of opening arranged the film, the upper receiving ends immediately below the guide elements 8 are in their vertically lowered position.

On the four stands of the device frame 1 are slides 12 in a vertical direction or longitudinal direction of the supplied tubular film 5 movably mounted, on each a reef finger 13 is attached. The present supported on the four stands Reefing fingers 13 have horizontally extending reefing brackets 14, each approximately arranged at right angles to one another and parallel to the side faces of the stack 3 have extending temple ends. Each reef finger 13 is via a drive device 15 attached to the corresponding carriage 12. The drive device 15 is in the present case formed from a hydraulic cylinder, with all the longitudinal axes of the hydraulic cylinder aligned approximately to the center of the device frame are and lie in an approximately horizontal plane. The reefing fingers 13 are each one assigned externally arranged reef roller 16, which is mounted on the carriage 12 and which are movable in the horizontal or transverse direction and relative to the respective reefing finger 13 is. In the embodiment shown, the longitudinal axis of the Reef roller 16 parallel to a respective side surface of the stack 3.

Figures 2 and 3 show a reefing bracket 14 with a reefing finger 13. The reefing bracket 14 is located at the upper end of the reefing finger 13 and extends essentially parallel to the top of the batch of pieces to be wrapped, i.e. horizontal. How out FIG. 2 shows the reefing bracket 14 has two substantially at right angles to one another extending legs 14a, 14b which are substantially parallel to the side surfaces of the stack of goods to be wrapped are aligned.

The exemplary embodiment of a reefing finger shown in FIGS. 2 and 3 is suitable in particular to introduce high longitudinal strains parallel to the long sides of the enveloping stack of goods when placing the film on these long sides and instructs its essentially extending parallel to the long sides of the stack of goods outer contact surface 13a on a concave trough 13b through a cylindrical surface 13c is limited. The concave trough 13b extends parallel to the axial one Extension of the reef roller 16, which is indicated in FIG. 3 with a dashed line. Between the outer peripheral surface of the reef roller 16 and the cylindrical surface 13c an annular segment-shaped gap 17 is formed.

In the embodiment shown in Figures 2 and 3, the reefing finger is off Steel formed and has on the surface of the reef bracket 14 on a steel core applied plastic surface.

In Figure 4 is a plan view of an alternative embodiment of a reefing bracket 14, which is substantially in accordance with that in FIGS. 2 and 3 shown embodiment is associated with a reefing finger, not shown here. In the embodiment shown in Figure 4, the peripheral surface of the reef bracket 14 formed by five consecutively arranged freely rotatable rollers 21. This Rollers 21 each have a convexly curved outer peripheral surface and are with their axis of rotation each offset angularly to each other, so that the outer Circumferential surfaces of the rollers 21 form approximately a circular arc segment. The two outer rollers 21a, 21e are substantially rectangular with their respective axes arranged to each other. Between the respective rollers 21e, 21f or on the front Ends of the outer rollers 21 can be connected to the remaining part of the reefing finger 13 Supports 22 are provided, which carry the rollers 21 and these with the Connect the remaining part of the reefing fingers 13. At least one of these supports 22 can Cylinder surface 13c for the reef roller 16 and also one in the conveying direction of the Form the film behind the contact surface 13a.

The course of the method for wrapping a piece goods stack 3 is described below in particular explained with reference to FIGS. 1 and 5 and 7:

The flat tubular film 5 is in a manner known per se by the take-off rollers 7 threaded over the guide elements 8. At the lower end of the guide elements 8 is each folded edge of the tubular film 5 is passed between a double conveyor belt 11, to open the hose. After the lower end of the tubular film 5 a piece has run out of the double conveyor belts 11, the take-off rollers 7 and the double conveyor belts 11 stopped and the reefing fingers 13 are in the hose end retracted. When the reefing fingers 13 have reached a predetermined position the reefing rollers 16 moved up to the reefing fingers 13. Part of the circumferential surface moves of the respective reefing rollers 16 into the depression 13b of the associated reefing finger 13 and clamps the tubular film 5 in the gap 17 (Figure 5). After that, the reef rolls 16 put into operation together with the take-off rollers 7 and the double conveyor belts 11, up to a predetermined length of tubular film 5 like a bellows, i.e. meandering is placed over the reefing finger 13 (FIG. 6). The one when the film hits the supply peeled off and applied to the reefing fingers 13 meandering in the area the contact surface 13a (see FIG. 3) of the reefing finger.

Now the separating and welding devices 9 and 10 are actuated in order to remove the below the separating and welding devices 9, 11 section of the Tubular film 5 to a tubular hood 18 of predetermined length closed at the top to build. Then the double conveyor belts 11 are driven again to the rest To release part of the formed hose hood 18, preferably by simultaneous approach of the reef rollers 16 brought into a predetermined starting position and can be stretched over the reefing bracket 14.

Starting from this starting position, the reefing fingers 13 are moved apart in the transverse direction. Before that, however, the reef rollers 16 in the exemplary embodiments shown deducted from the reefing fingers 13 so that the reefing rollers 16 in one Non-use position are arranged. When the reefing fingers move apart 13 to a floor plan that is larger than the floor plan of the stack 3 a part of the tubular film 5 torn onto the reefing finger 13 due to reduced Frictional properties of the reefing bracket 14 with respect to the film of the reefing bracket 14 slide. Accordingly, excessive stretching of the film when stretched the top of the closed tubular film 18 can be prevented.

After the film is stretched transversely by moving the reefing fingers 13 diagonally apart has been reached, the position shown in Figure 1 is reached. In this is the now stretched hose hood with its upper side essentially parallel to the top of the stack 3, but has a floor plan that is larger than that Floor plan of the general cargo stack 3 is. Now the four on the corner The reefing finger 13 together with the reefing rollers 16 moves relative to the piece goods stack. in the In the present case, the piece goods stack is predominantly fixed, whereas the Reef finger 13 to be moved down. During the downward movement of the reefing fingers 13 first the top of the hose hood 18 closed at the top lies against the Top of the piece goods stack 3 and also lies against the side surface thereof, before further tubular film 5 against the resistance of those pressing against the reefing fingers 13 Reef rollers 16 is released by the reefing fingers 13. With continuous downward movement the reefing finger 13 becomes the film 5 against the contact pressure of the reefing rollers 16 deducted from the reefing fingers 13 and for contact with the long sides of the General cargo stack 3 brought. Finally, the previously formed hose hood is total pulled over the general cargo stack 3.

The device according to the invention and the corresponding method are not available the previously described embodiments limited. For example, the Relative movement between the film hood and the stack of goods take place in that the film is arranged in a fixed position, whereas the general cargo stack for covering with the foil hood is raised. Furthermore, the hose hood can first be welded and then be thrown on the reefing fingers.

LIST OF REFERENCE NUMBERS

1

device stand

2

roadway

3

stack of packaged goods

4

role

5

tubular film

6

idler pulley

7

off rollers

8th

baffles

9

separator

10

welding equipment

11

Double conveyor belt

12

carriage

13

reefing fingers

13a

contact surface

13b

trough

13c

Cylinder surface

14

folding frame

14a

leg

14b

leg

15

driving means

16

furling foil

17

gap

18

tubular hood

19

presser

21

roll

22

Support

Claims (13)

Process for covering a stretch film hood over a stack of goods, in which the tubular film fed from a film supply is opened and taken over by reefing fingers that move in the horizontal and vertical direction and engage in the film and are folded onto it in bellows fashion, and in which the supplied film to form the hose hood is spaced apart provided with a seam at its lower end and is separated from the film supply, the film is stretched across by spreading the reefing fingers to a larger plan than that of the stack of goods and when the reefing fingers are moved down to rest on the long sides of the stack of goods, the reefing fingers release them
characterized in that a film is used which, in the unstretched initial state, is at least 25% smaller in circumference than the stack of goods to be wrapped and is stretched and pulled over the stack of goods in such a way that the thickness of the film on the top of the stack of goods in the region of its corners is greater than 50% of the thickness of the film in the initial state. Process for covering stretch film hoods over a stack of goods, in which the tubular film supplied from a film supply is opened and taken over by reefing fingers that move in the horizontal and vertical direction and engage in the film and are folded onto the bellows in a bellows-like manner and in which the supplied film for forming the tubular hood is spaced apart provided with a seam at its lower end and separated from the film supply, the film is stretched across by spreading the reefing fingers to a larger plan than that of the stack of goods and when the reefing fingers are shut down to rest against the long sides of the stack of goods, the reefing fingers release them, especially after Claim 1
characterized in that the film is released by the reefing fingers when stretching. A method according to claim 1 or 2, characterized in that reefing means which convey the film to the reefing fingers like a bellows are moved away from the reefing fingers before the film is stretched crosswise. A method according to claim 1 or 2, characterized in that reefing means, which convey the film like bellows onto the reefing fingers, are placed against the reefing fingers when the film is stretched with the film interposed, and are moved relative to the reefing fingers to release the film. A method according to claim 4, characterized in that the reefing means are driven when stretching the film to release the film. A method according to claim 4 or 5, characterized in that the reefing means are alternately driven reefing and releasing the film when stretching the film. A method according to claim 6, characterized in that the reefing means are driven as a function of a voltage applied to the reefing fingers by the stretched film. Device for covering a stretch film hood over a stack of goods (3) with a film supply (4) for tubular film (5) and a separating and cutting device (9, 10) for forming a hose hood which is closed on the top and separated from the film supply, and a spreading device (11) To open the tubular film and a covering device, reefing fingers (13) that can be inserted extensively into the tubular film and spread apart to move them, that are movable relative to the long side of the stack of goods (2) and that can be driven by reefing means (16) for storing the supplied tubular film in the manner of a bellows. 5) are assigned to the reefing fingers (13),
characterized in that the reefing fingers (13) have means for reducing the friction (21) compared to the tubular film (5) wrapping around the reefing fingers (13). Apparatus according to claim 8, characterized in that the surface of the reefing fingers (13) wrapped around by the tubular film (5) is formed from a plastic. Apparatus according to claim 8 or 9, characterized in that the reefing fingers (13) have means for generating a rolling friction (21) to the tubular film (5) wrapping around the reefing fingers (13). Apparatus according to claim 10, characterized in that the reefing fingers (13) have rollers (21) which are freely rotatably mounted on their ends wrapped in the tubular film (5). Apparatus according to claim 11, characterized in that the rollers (21) are provided on a reefing bracket (14), the end sections of which are arranged approximately at right angles to one another and approximately parallel to the opposite longitudinal sides of the stack of goods (3). Device according to one of the preceding claims, characterized in that the drivable reefing means (16) are controlled in such a way that they lie against the reefing fingers (13) when the tubular film (5) is stretched across, with the tubular film (5) being interposed, and are freely rotatable or counter-rotating Reef movement of the reefing means (16) are driven.

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