Stretch wrapping machine and method for stretch wrapping

Abstract

 The present invention relates to a stretch wrapping machine and a device for stretch wrapping products which must breathe during their storage and transport process. The stretch wrapping machine comprises a rotating base (1) configured to support the palletized load and a fixed column (2) next to the rotating base (1) comprising a first reel (3) of an extendable sheet (5), said first reel (3) being movable along said column (2). The stretch wrapping machine additionally comprises a second reel (4) of a non-extendable sheet (6), said second reel (4) being movable along said column (2). As a result of the transpiration features of the extendable sheet (5), the preservation of the load will be optimal. The method of the invention comprises stretch wrapping the load with the extendable sheet (5) to subsequently stretch wrap the load with a layer formed on the inside by the non-extendable sheet (6) and on the outside by the extendable sheet (5).

Description

Field of the Invention

[0001] The present invention belongs to the field of stretch wrapping machines and of methods for stretch wrapping a palletized load. More specifically, it relates to a stretch wrapping machine capable of stretch wrapping products, such as potatoes, onions or other vegetables and/or tubers, which must breathe during the storage or transport process on the pallet by means of the combined use of an extendable material such as raffia and a non-extendable material such as paper.

Background of the Invention

[0002] The process of stretch wrapping a palletized load is known in the state of the art. The load is typically deposited on pallets for the purpose of more easily moving them with machinery designed for such purpose. Given the height that the load on the pallet reaches and the vibrations or blows the pallet may be exposed to, it is necessary to stretch wrap the load, i.e., providing it with a wrapping which groups and binds the load together and with the pallet.

[0003] The most widespread solution to this problem is stretch wrapping the load with pre-stretched plastic sheets, such that once the plastic has been applied, it compacts the load, preventing the relative movement therein. This solution, described for example in patent applications such as DE 19601668 A1, EP 1520784 A1 and US 2006/0260279 A1, have the drawback that the layer of pre-stretched plastic does not allow the load to transpire or breathe, such that in the case of transporting loads which need said transpiration for proper preservation, such as potatoes for example, the solution obtained with said inventions is not optimal.

Description of the Invention

[0004] In a first aspect, the invention relates to a stretch wrapping machine capable of stretch wrapping products such that the respiration of said products is possible. The stretch wrapping machine of the invention comprises a rotating base configured to support a palletized load and a fixed column next to the rotating base comprising a first reel of an extendable sheet, said first reel being movable along said column. The invention will be described such that it is the base which rotates, the column remaining fixed, it also being possible for the column to rotate around the pallet while the pallet remains fixed on the base. As in the stretch wrapping machines of the state of the art, the first reel will travel the entire height of the load as it covers the load with the extendable sheet. Extendable sheet shall be understood throughout the present invention as a sheet capable of being subjected to a certain stretching without the sheet tearing. Likewise, the sheet must allow the load to breathe. The material of said extendable layer could be, for example, a woven polypropylene or a polyethylene mesh, generically referred to throughout the invention as raffia.

[0005] According to the invention, the column of the stretch wrapping machine additionally comprises a second reel of a non-extendable sheet. As in the previous case, the second reel can move along the column. Throughout the invention, non-extendable sheet will be understood as a sheet which cannot be pulled on without tearing, which cannot be heat-welded and which must additionally protect the load from ultraviolet rays. Paper can be a possible material for making said non-extendable sheet. In the same manner, the non-extendable sheet could be a complex formed by several materials, all of which comply with the conditions discussed in this paragraph.

[0006] Therefore, the load stretch wrapped with the stretch wrapping machine described above can breathe given that the extendable sheet allows the load to breathe, additionally having protection against ultraviolet rays as a result of the non-extendable sheet.

[0007] The two previously discussed reels can be arranged at the same height of the column, such that both reels move together, whereby the sheets which are unwound will cover the same area of the load. Thus, in the case of wanting to stretch wrap with a layer combining the extendable and non-extendable sheets, the stretch wrapping can be done directly since both sheets are arranged at the same height.

[0008] For the purpose of finishing the stretch wrapping of the load, there may be cutting means for both the non-extendable sheet and for the extendable sheet. In the case of the non-extendable sheet, said cutting means could be a blade.

[0009] The stretch wrapping machine can comprise a blowing device (9) configured to provide constant airflow so that the extendable reel and the non-extendable reel remain in contact during the stretch wrapping. Therefore, if the stretch wrapping is first done with the extendable sheet and then the non-extendable sheet is added, it will not be necessary to have any additional element so that both sheets stretch wrap the load simultaneously because the airflow will secure the contact between both sheets during the entire process, from start to finish.

[0010] For the purpose of the ending of the stretch wrapping, the stretch wrapping machine may comprise at least one movable roller in the direction of the column. Said at least one movable roller will work such that with its movement it will group the extendable sheet forming a cord. The stretch wrapping machine may have a single roller, therefore said roller must push one end of the extendable sheet towards its other end to form the cord, or it may have two, in which case the first roller may act as a stop whereas the second one pushes the sheet against the first one, the cord thus being formed. The position in which the cord will be arranged will therefore depend on the position in which the roller ends up in the event that the stretch wrapping machine has a single roller, or the one occupied by the roller acting as a stop in the case of having two stops.

[0011] For the same task of ending the stretch wrapping, the stretch wrapping machine may comprise separating means for separating the cord from the palletized load. Said separating means could be a flat bar configured to be located close to the palletized load at a pre-defined height. Thus, when the rotating base rotates and when the cord is at the same height, as a result of at least one movable roller, the cord formed by the extendable sheet could be wrapped several times around said flat bar. There can also be holding means (13) for holding the cord, for example a clamp, such that the cord can be held in the clamp. Therefore, the ending of the stretch wrapping could be done more comfortably having the cord separated in a first turn and held by the clamp in a second turn.

[0012] To end the stretch wrapping, all that is left to do is weld two of these which are grouped in the aforementioned sheet, typically the first one which is grouped and the second one held by the clamp, cutting the excess cord, which could be used, since it is held in the clamp, to begin stretch wrapping a new pallet. The welding can be performed, for example, with a pulse welding electrode.

[0013] The stretch wrapping machine can have a synchronizer to synchronize the extendable sheet feed, the non-extendable sheet feed and the rotation of the rotating base, such that the amount of extendable sheet and of non-extendable sheet does not exceed the calculated necessary amount taking into account the rotation speed of the rotating base.

[0014] In a second aspect, the present invention relates to a method for stretch wrapping a palletized load comprising a first step of placing the palletized load on a rotating base.

[0015] According to the invention, the method additionally comprises a step of stretch wrapping the palletized load with an extendable sheet, wrapping the palletized load with said extendable sheet, and another step of jointly stretch wrapping the palletized load with a non-extendable sheet on the inside and with the extendable sheet on the outside, wrapping the palletized load with the non-extendable sheet and the extendable sheet. Therefore, the load thus stretch wrapped will be transpirable as a result of the extendable sheet, and it will furthermore be protected against ultraviolet rays as a result of the non-extendable sheet.

[0016] The method described above can include an additional step in which the non-extendable sheet is cut and the stretch wrapping of the load ends with the extendable sheet, wrapping the palletized load with said extendable sheet.

[0017] During the entire process for stretch wrapping, the extendable and non-extendable sheets can be unwound from reels located at the same height in a fixed column located next to the rotating platform.

[0018] In the combined stretch wrapping with the non-extendable sheet and the extendable sheet, a blowing device can provide constant airflow so that the extendable reel and the non-extendable reel remain in contact, without it being necessary to have any mechanism for achieving a double-sheet stretch wrapping, one of them, the innermost one, being non-extendable sheet, and the outermost being extendable sheet.

[0019] For the purpose of ending the stretch wrapping, once the previous steps have been performed, the extendable sheet could be converted into a cord at a pre-defined height. Said cord can subsequently be separated after a stretch wrapping cycle, defined by a complete turn of the pallet, to weld the separated cord with the same separated cord formed after the new stretch wrapping cycle. Once the welding is done, the cord, and therefore the extendable sheet, can be cut.

Description of the Drawings

[0020] To complement the description being made and for the purpose of aiding to better understand the features of the invention, a set of drawings is attached as an integral part of said description in which the following is depicted with an illustrative and non-limiting character:

Figure 1 shows a simplified view of the stretch wrapping machine of the invention, in which the rotating base and the column with the two reels of extendable sheet and non-extendable sheet are depicted.

Figure 2 shows a top view of the column of the stretch wrapping machine of the invention.

Figure 3 shows a view of the separating flat bar in which the separated cord can be observed.

Figure 4 shows a view of the cutting means for cutting the cord, as well as the clamp for the cord.

Preferred Embodiment of the Invention

[0021] A preferred embodiment of the stretch wrapping machine forming the object of this invention is described below with reference to the drawings.

[0022] Figure 1 shows a stretch wrapping machine according to the present invention. Said figure does not show the pallet or palletized load which can be stretch wrapped by the invention, which load must be located on the rotating base (1) of the stretch wrapping machine.

[0023] As can be seen, the rotating base (1) is located in the vicinity of a column (2) in which there are arranged, at the same height, two reels (3, 4), one with an extendable sheet (5) and the other with a non-extendable sheet (6). A top view of said reels (3, 4) can be seen in Figure 2.

[0024] The non-extendable sheet (6) is a sheet of paper (6), in the same way that the extendable sheet (5) will be a sheet of raffia (5), the palletized load being a pallet of bags of potatoes. The stretch wrapping machine of the invention could alternatively be applied to bags of onions or any other type of vegetables or tubers with similar preservation requirements.

[0025] First, the pallet with bags of potatoes will be stretch wrapped following a conventional method with raffia (5). The bags of potatoes can breathe with this layer, their preservation conditions thus being improved. The layer of raffia (5) also allows the stretch wrapping of the bags because it has the necessary consistency to prevent the bags from moving from the position defined in the process for loading the pallet. As can be seen in Figure 1, the reel (3) of raffia (5) will be the one farthest away from the rotating base (1), as will be discussed below.

[0026] In addition to allowing the bags of potatoes to breathe as a result of the raffia (5), the present invention provides protection against ultraviolet rays as a result of a layer of paper (6). Said paper (6) is applied in the method for stretch wrapping as follows.

[0027] Once the bags of potatoes are correctly stretch wrapped and the reel (3) of raffia (5) has swept the column (2) from the lowest position of the column (2) to the highest, for example, the reel (4) of paper (6) will start to let out paper (6) for the purpose of stretch wrapping the bags with said paper (6). In this case the two reels (3, 4) will sweep the column (2) from the highest position to the lowest. A blowing device (9) provides constant airflow in order for the paper (6) to act together with the raffia (5) such that the paper (6) is fixed to the raffia (5) by the air stream. The arrangement of said blowing device (9) can be seen in Figure 2. In this second sweeping that is performed, the raffia (5) will thus continue to be on the outside of the load, whereas the paper (6) will be located between the outside raffia (5) and the first layer of raffia (5).

[0028] Once the paper (6) reaches the end of its path, shears (8) will cut the paper (6), the raffia (5) again being the element used for stretch wrapping the load.

[0029] At this time the last steps of the stretch wrapping are performed and are aimed at closing or joining the free ends of the raffia (5) to the stretch wrapping, such that the stretch wrapping cannot accidentally come undone.

[0030] First, two rollers will encircle the raffia (5), one at the top and one at the bottom, forcing it to form a highly resistant plastic cord (10), the rollers being in a predetermined position when said cord (10) is formed, in the case of the present embodiment, the rollers being in the bottom area of the load, approximately in the top area of the pallet on which the load is supported.

[0031] In the event that the raffia (5) is made of woven polypropylene, this material cannot easily be welded. Therefore, in order to perform the welding described in the preceding paragraph, it is necessary to form the described cord (10). Grouping the raffia in a cord (10) will thus make it possible to weld such cord.

[0032] The two rollers will be arranged immediately after the exit from the reel (3) of raffia (5). The cord (10) will always thus be located around the load at the same point. However, once the cord (10) is formed, as can be seen in Figure 3, separating means (11) formed by a flat bar (11) will be located in the path of cord (10), such that the cord (10) will be separated from the load at this point. Once the cord (10) has been separated, another flat bar could be located at the same height of the flat bar (11) which forms part of a clamp (13), such that the cord (10) can be held by said clamp (13) in the next pass of the cord (10).

[0033] Figure 3 depicts the moment prior to when the clamp (13) grabs the cord (10). As can be seen, the cord (10) is separated by the flat bar (11), whereas the second flat bar, the one forming part of the clamp (13), waits for the next pass to hold the cord (10). The welding of the cord (10) and the cutting thereof is thus made easier.

[0034] Figure 4 shows the clamp (13) as well as the cutting tool (7) and welding tool (12). The closeness of the separating flat bar (11) and the clamp (13) makes it easier to weld the cord (10) between the pass of the separated cord (10) and the second pass. At a point before the welding tool or means (12), which welding is performed with a welding electrode (12), the raffia (5) can be cut using a cutting resistance (7), the end at which the stretch wrapping of the next pallet of bags of potatoes will begin then being in the clamp (13). There will be certain allowance in the welded cord (10) of raffia (5), as much allowance as distance between the pallet and the position of the flat bar (11).

[0035] The clamp (13) is vertically and horizontally movable. The process for stretch wrapping the palletized load can thus begin at an intermediate height, far from both the base and the top end of the load. When the stretch wrapping in this situation begins, the initial end of both the paper and the raffia (5), used when the stretch wrapping begins, will be on the inside of the actual stretch wrapping, not being accessible from the outside of such stretch wrapping, thus making it impossible for the stretch wrapping to come undone.

[0036] In view of this description and set of figures, the person skilled in the art will understand that the invention has been described according to a preferred embodiment thereof, but that multiple variations can be introduced in said preferred embodiment without departing from the object of the invention as it has been claimed.

Claims

1. Stretch wrapping machine comprising a rotating base (1) configured to support a palletized load and a column (2) next to the rotating base (1), comprising a first reel (3) of an extendable sheet (5), said first reel (3) being movable along said column (2),
characterized in that the column (2) additionally comprises a second reel (4) of a non-extendable sheet (6), said second reel (4) being movable along said column (2).

2. Stretch wrapping machine according to claim 1, characterized in that the first reel (3) and the second reel (4) are arranged at the same height in the column (2).

3. Stretch wrapping machine according to any of claims 1-2, characterized by comprising cutting means (7, 8) for cutting the non-extendable sheet (6) and the extendable sheet (5).

4. Stretch wrapping machine according to any of claims 1-3, characterized by comprising a blowing device (9) configured to provide constant airflow so that the extendable sheet (5) and the non-extendable sheet (6) remain in contact during the stretch wrapping.

5. Stretch wrapping machine according to any of claims 1-4, characterized by comprising at least one movable roller in the direction of the column (2), said at least one movable roller being configured to convert the extendable sheet (5) into a cord (10) at a pre-defined height.

6. Stretch wrapping machine according to claim 5, characterized by comprising separating means (11) for separating the cord (10) from the palletized load.

7. Stretch wrapping machine according to claim 6, characterized in that the separating means (11) for separating the cord (10) are a flat bar (11) configured to be located close to the palletized load at the pre-defined height, the cord (10) being held in the flat bar (11).

8. Stretch wrapping machine according to any of claims 6-7, characterized by comprising ending means (12) for ending the extendable sheet (5) comprising welding means (12) for welding the cord (10) configured to weld the cord (10) held in the separating means (11).

9. Stretch wrapping machine according to claim 8, characterized in that the welding means (12) are a welding electrode (12).

10. Stretch wrapping machine according to any of claims 6-9, characterized by comprising holding means (13) for holding the cord (10).

11. Stretch wrapping machine according to claim 10, characterized in that the holding means (13) are a clamp (13), movable in the direction of the column (2) and in a direction perpendicular to said column (2).

12. Stretch wrapping machine according to any of claims 1-11, characterized by comprising a synchronizer for synchronizing the extendable sheet (5) feed, the non-extendable sheet (6) feed and the rotation of the rotating base (1).

13. Stretch wrapping machine according to any of claims 1-12, characterized in that the non-extendable sheet (6) is a non-heat-weldable material.

14. Stretch wrapping machine according to claim 13, characterized in that the non-heat-weldable material is paper (6).

15. Stretch wrapping machine according to any of claims 1-12, characterized in that the non-extendable sheet (6) is a non-heat-weldable complex.

16. Stretch wrapping machine according to any of claims 1-15, characterized in that the extendable sheet (5) is a woven polypropylene.

17. Stretch wrapping machine according to any of claims 1-15, characterized in that the extendable sheet (5) is a polyethylene mesh.

18. Stretch wrapping machine according to any of claims 1-17, characterized in that the column (2) is integral with the rotating base (1).

19. Method for stretch wrapping a palletized load comprising placing the palletized load on a rotating base (1), characterized by additionally comprising the steps of:

- stretch wrapping the palletized load with an extendable sheet (5), wrapping the palletized load with said extendable sheet (5),

- jointly stretch wrapping the palletized load with a non-extendable sheet (6) on the inside and with the extendable sheet (5) on the outside, wrapping the palletized load with the non-extendable sheet (6) and the extendable sheet (5).

20. Method according to claim 19, characterized in that an additional step of cutting the non-extendable sheet (6) and stretch wrapping with the extendable sheet (5), wrapping the palletized load with said extendable sheet (5).

21. Method according to any of claims 19-20, characterized in that the extendable sheet (5) and the non-extendable sheet (6) are unwound from reels (3, 4) located at the same height in a fixed column (2) located next to the rotating base (1).

22. Method according to any of claims 19-21, characterized in that during the joint stretch wrapping with the non-extendable sheet (6) and the extendable sheet (5) a blowing device (9) provides constant airflow so that the extendable sheet (5) and the non-extendable sheet (6) remain in contact.

Drawing