Stretch hood system

Abstract

The present disclosure relates to a stretch hood arrangement (200) enclosing a stack of articles (201) arranged on a pallet (203) in multiple layers including a base layer (207), a top layer (209) and one or more intermediate layers, said stretch hood arrangement (200) comprising: a polymer film tubular band (215) stretched around at least the base layer (207) of the stack; a polymer film stretch hood (213) enclosing the top and sides of the stack; characterized in that the polymer film of the tubular band (215) has a higher elasticity than the polymer film of the stretch hood. The present disclosure further relates to the use of a the stretch hood arrangement for collection and transport of a stack of articles (201), preferably for collection and transport of a stack of bottles arranged on a pallet (203) in multiple layers.

Claims

1. A stretch hood arrangement enclosing a stack of articles arranged on a pallet in multiple layers including a base layer, a top layer and one or more intermediate layers, the stretch hood arrangement comprising: a polymer film tubular band stretched around at least the base layer of the stack; a polymer film stretch hood enclosing a top and sides of the stack; wherein the polymer film of the tubular band has a higher elasticity than the polymer film of the stretch hood, such that said tubular band applies a holding force to at least the base layer and acts to prevent deformation of at least the base layer of the stack of articles.

2. The stretch hood arrangement according to claim 1, wherein the elasticity of the polymer films is defined as the elastic recovery of the polymer films.

3. The stretch hood arrangement according to claim 1, wherein the polymer film of the stretch hood applies a holding force on the top and the sides of the stack of articles, and wherein the holding force of the polymer film of the stretch hood is higher than the holding force of the polymer film of the tubular band.

4. The stretch hood arrangement according to claim 1, wherein the layers of the stack are separated by sheets of a rigid material.

5. The stretch hood arrangement according to claim 1, wherein the weight of the stack of articles is at least 500 kg.

6. The stretch hood arrangement according to claim 1, wherein the height:base width ratio of the articles is at least 2:1.

7. The stretch hood arrangement according to claim 1, wherein the articles have a base diameter D larger than a top diameter d.

8. The stretch hood arrangement according to claim 1, wherein the height of the stack is in the range of 1 to 3 meters.

9. The stretch hood arrangement according to claim 1, wherein the polymer film tubular band is stretched around the base layer and at least one intermediate layer of the stack.

10. The stretch hood arrangement according to claim 1, wherein the height of the tubular band is less than 50% of the height of the stack.

11. The stretch hood arrangement according to claim 1, wherein the height of the tubular band is between 60-100 cm.

12. Use of a stretch hood arrangement according to claim 1 for collection and transport of a stack of articles, arranged on a pallet in multiple layers.

13. The stretch hood arrangement according to claim 1, wherein the height of the tubular band is between 70-90 cm.

14. The stretch hood arrangement according to claim 1, wherein the height of the tubular band is between 75-95 cm.

15. A method for enclosing a stack of articles, arranged on a pallet in multiple layers including a base layer, a top layer and one or more intermediate layers, said method comprising the steps: a) applying a polymer film tubular band stretched around at least a base layer of the stack; b) applying a polymer film stretch hood enclosing a top and sides of the stack; wherein the polymer film of the tubular band has a higher elasticity than the polymer film of the stretch hood, such that said tubular band applies a holding force to at least the base layer and acts to prevent deformation of at least the base layer of the stack of articles.

16. The method according to claim 15, wherein the steps a) and b) are performed in sequence.

17. The method according to claim 16, wherein the steps a) and b) are both performed by a stretch hood machine.

18. The method according to claim 17, wherein the step of applying the polymer film tubular band further comprises feeding the tubular band from a supply to a pull-down device, pre-stretching the tubular band to 60-90% elongation, pulling the tubular band with the device down over the at least a base layer of the stack, releasing the tubular band from the pull-down device and relaxing the tubular band over at least the base layer of the stack, the tubular band in a relaxed state applying a holding force of 3-7 N/20 mm to a least the base layer of the stack and the step of applying the polymer film stretch hood further comprises feeding the stretch hood from a supply to a pull-down device, pre-stretching the stretch hood to 30-60% elongation, pulling the stretch hood with the device down over the top and sides of the stack, releasing the stretch hood from the pull-down device and relaxing the stretch hood over the top and sides of the stack, the stretch hood in a relaxed state applying a holding force of 6-10 N/20 mm to the top and sides of the stack.

19. The method according to claim 15, wherein the steps a) and b) are both performed by a stretch hood machine.

20. The method according to claim 19, wherein the step of applying the polymer film tubular band further comprises feeding the tubular band from a supply to a pull-down device, pre-stretching the tubular band to 60-90% elongation, pulling the tubular band with the device down over the at least a base layer of the stack, releasing the tubular band from the pull-down device and relaxing the tubular band over at least the base layer of the stack, the tubular band in a relaxed state applying a holding force of 3-7 N/20 mm to a least the base layer of the stack and the step of applying the polymer film stretch hood further comprises feeding the stretch hood from a supply to a pull-down device, pre-stretching the stretch hood to 30-60% elongation, pulling the stretch hood with the device down over the top and sides of the stack, releasing the stretch hood from the pull-down device and relaxing the stretch hood over the top and sides of the stack, the stretch hood in a relaxed state applying a holding force of 6-10 N/20 mm to the top and sides of the stack.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Referring now to the figures, which are exemplary embodiments, and wherein the like elements are numbered alike:

(2) FIG. 1 shows a common problem in the prior art, where the base layer of the stack of articles have been partially overbalanced thus deforming the base layer of the stack.

(3) FIG. 2 is a perspective view of an embodiment of the inventive stretch hood arrangement enclosing a stack of articles arranged on a pallet in multiple layers.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(4) FIG. 1 shows a situation that commonly appears in prior art solutions (100) during transport of a stack of articles (101) arranged on a pallet (103). The stack of articles (101) is arranged on a pallet (103) in multiple layers separated by sheets (105) of rigid material. The stack of articles has a base layer (107), at least one intermediate layer, a top layer (109) and four side walls. The layers have four substantially quadrangular side walls and a substantially quadrangular cross-section. Substantially quadrangular in the present disclosure should be understood as substantially rectangular or substantially quadratic. The stack of articles (101) is enclosed by a polymer film (113), for example by a stretch hood film or a shrink hood film.

(5) The situation depicted in FIG. 1 may occur when the stack of articles (101) have been subjected to a rapid deceleration during transport. The base layer (107) has deformed by partial tipping of the articles therein. The intermediate and top layers have deformed to a lesser degree. The deformed base layer (107) exerts a force on the polymer film (113) enclosing the articles. Articles that are in contact with the polymer film (113) may exert a punctual load on the polymer film. This load may be large enough to rupture the film, which may cause the articles to fall out of the stack and break.

(6) The polymer film (113) in the prior art solution may for example be a polymer film shrink hood or a polymer film stretch hood. Both these films are suitable for applying to a stack of articles. When applied to the stack of articles (101), the polymer film (113) comprises a substantially quadrangular closed top and four side walls. The horizontal cross section circumference of the polymer film shrink hood is typically larger than the horizontal cross section circumference of the stack of articles. The polymer film (113) is typically pulled down over the stack so that it encloses the top and sides of the stack. The polymer film is typically top welded just before mounting to form a hood. If the polymer film is a shrink hood, heat may then be applied to the polymer film (113) which may cause the shrink hood to shrink so that it is in contact with the stack of articles (101) and exerts a holding force on the top and sides of the stack of articles. When mounted to the stack of articles (101), the polymer film (113) exerts a holding force on the stack of articles (101). Shrink hoods often get irregularly folded during mounting and heat crimping, especially at the corners, and these folds may act as breaking lines when exerted to a force from the stack of articles during for example heavy braking.

(7) FIG. 2 shows an embodiment of the inventive stretch hood arrangement (200). The stretch hood arrangement (200) is depicted in a state where it is applied to a stack of articles (201). The stack of articles (201) is arranged on a pallet (203) in multiple layers separated by sheets (205) of rigid material. The stack of articles has a base layer (207), at least one intermediate layer, a top layer (209) and four side walls. The layers have four substantially quadrangular side walls and a substantially quadrangular cross-section. Substantially quadrangular in the present disclosure should be understood as substantially rectangular or substantially quadratic.

(8) The stretch hood arrangement (200) comprises a polymer film stretch hood (213) and a polymer film tubular band (215). The polymer film tubular band (215) is configured to be stretched around all four side walls of at least the base layer (207) of the stack of articles. The tubular band (215) is not closed at its top or bottom. When applied to the stack of articles (201) the tubular band (215) comprises four side walls of substantially the same height. This height of the tubular band (215) is in the present disclosure to be understood as the height of these side walls. The polymer film stretch hood (213) is configured to enclose the top and all four side walls of the stack of articles (201). When applied to the stack of articles (201) the stretch hood (213) comprises a substantially quadrangular top and four side walls. The top of the stretch hood (213) is preferably formed by welding.

(9) The tubular band (215) is typically applied to the stack of articles (201) before the stretch hood (213) is applied. The stretch hood (213) is preferably applied so that it also encloses the tubular band (215). When applied to a stack of articles (201), the stretch hood arrangement (200) is substantially rain and dust proof.

(10) The tubular band (215) is stretched around at least the base layer of the stack of articles (201) by feeding an appropriate length of a tube of polymer film from a roll onto a pull-down device. The circumference of the tube is lower than the horizontal circumference of the stack of articles (201). The pull-down device arranges the tube in a shape corresponding to the geometry of the horizontal cross section of the stack of articles (201). The tube is then cut off from the feed roll, thus forming a tubular band (215). The pull-down device stretches the circumference of the tubular band (215) to a predetermined pre-stretch elongation degree, typically in the range of 60-120%, such as 90-100%, such as about 95%, such that the tubular band (215) in the stretched state has a circumference which is greater than the horizontal circumference of the stack of articles (201). The tubular band (215) is then pulled over at least the base layer (207) of the stack of articles (201), preferably the base layer and one and a half intermediate layers. The tubular band (215) can be applied from the bottom upwards, or from the top down. The tubular band (215) may be doubled over its full height, or parts thereof. The tubular band (215) can for example be applied from bottom to top and back, i.e. in 2 layers, or in one layer on an upper part, and two layers on lower part. The tubular band (215) is then gradually released from the pull-down device. The tubular band (215) will then retract until it is stretched around at least the base layer (207) of the stack of articles (201). The retraction is typically a fast process; a preferable time-frame is less than 1 second. After retraction the tubular band (215) typically has a residual elongation in the range of 50-80%, such as 65-75%, for example about 72%. The residual elongation allows the stretch hood to exert a holding force to at least the base layer of the stack of articles (201). The residual elongation typically comprises both an elastic and a plastic deformation component. Preferably, the plastic deformation component is substantially small. The elastic component of the residual elongation allows the stretch hood to exert a holding force to the top and sides of the stack of articles (201). Residual elongation is supposed to be understood as the elongation of the circumference of the film when the film is applied to the stack of articles (201).

(11) The stretch hood is applied to the stack of articles (201) by feeding an appropriate length of a tube of polymer film from a roll onto a pull-down device. The circumference of the tube is lower than the horizontal circumference of the stack of articles (201). The pull-down device arranges the tube in a shape corresponding to the geometry of the horizontal cross section of the stack. The tube is cut off from the film roll and the cut-off end is joined together by plastic welding forming a top weld (211), thus forming the closed top of the stretch hood. The welding is performed by means well known in the art, for example by electrical induction heated bars. The pull-down device stretches the circumference of the stretch hood to a predetermined pre-stretch degree, typically in the range of 20-60%, such as 40-50%, for example about 44%, such that the stretch hood in the stretched state has a circumference which is greater than the horizontal circumference of the stack of articles (201). The predetermined pre-stretch degree is lower for the stretch hood than for the tubular band (215). The stretch hood is then pulled over the top and sides of the stack of articles (201) and, the stretch hood is gradually released from the pull-down device. The stretch hood will then retract until it is encloses the top and sides of the stack of articles (201). The retraction process typically takes longer time for the stretch hood than for the tubular band (215), preferably a few seconds. After retraction, the stretch hood typically has a residual elongation in the range of 15-30%, such as 20-25%, for example about 22%. The residual elongation is typically caused by both an elastic and a plastic deformation component. Preferably, the plastic deformation component is substantially small, however in practise the elastic recovery of stiff stretch hoods is typically only partial, for example about of the original deformation. The elastic component of the residual elongation allows the stretch hood to exert a holding force to the top and sides of the stack of articles (201).

(12) The polymer film tubular band (215) has a higher elasticity than the polymer film stretch hood. A higher elasticity typically means a higher elastic recovery. The elastic recovery in the present disclosure is measured in accordance with the elastic recovery and holding force test method as defined herein.

(13) Elastic recovery and holding force in the present disclosure is measured in accordance with an elastic recovery and holding force test method. The elastic recovery and holding force test method in the present disclosure is defined as follows: A film strip of approximately 20 mm width and length (L) is placed with 100 mm distance between holders in a tensile testing machine well known in the art. The tensile testing machine is of the type defined in the International standard ISO 527-3. The machine stretches the film at a rate of 500 mm/min until the film reaches a predetermined first length (L1), typically to a length in the range of 160-220% of the original length L depending on the film material. The film is kept at the first length (L1) for 60 seconds. The elongation is then reduced 20% to a second length (L2) and kept there for an additional 60 seconds. L2 represents the residual elongation. The load on the sample is then measured and converted to a corresponding force. This force is the holding force [N/20 mm] of the sample. The sample is then released from the holders and after the film has completely relaxed a third length (L3) is measured. The elastic recovery is defined as

(14) $\frac{L1-L3}{L}100\left[\%\right].$

(15) The polymer film tubular band (215) preferably has an elastic recovery in the range of 60 to 100% as measured by the elastic recovery and holding force test method as defined herein. The polymer film stretch hood typically has a lower elastic recovery, and the elastic recovery is only partial, for example only about of the original deformation.

(16) When applied to the stack of articles (201), the tubular band (215) and the stretch hood each apply a holding force to the stack. The tubular band (215) applies a holding force to at least the base layer (207) of the stack. When applied to the top and sides of the stack, the stretch hood applies a holding force to the top and sides of the stack of articles (201). All holding forces in the present disclosure are measured according to the elastic recovery and holding force test method as defined herein.

(17) The polymer film of the stretch hood typically has holding force is in the range of 6-12 N/20 mm, preferably approximately 9-10 N/20 mm.

(18) The polymer film of the tubular band (215) is typically has a holding force in the range of 3-7 N/20 mm, such as 3-5 N/20 mm or 4-7 N/20 mm.

(19) If the holding force exceeds a maximum value the layers in the stack of articles (201), particularly in the top layers may deform to an ellipsoidal shape. Thus, it is advantageous if the holding force of the stretch hood does not exceed this maximum value. The combined holding force of the tubular band (215) and the stretch hood is exerted only on the at least a base layer (207) onto which the tubular band (215) is stretched around. These layers are less prone to reshape to an ellipsoidal shape by internal relocation of the articles in the layer, due to the accumulated weight of the higher layers exerting pressure on the lower layers.

(20) The relatively elastic recovery of the tubular band (215) may allow the base layer (207) of the stack of articles (201) to return to its resting position after a dynamic deformation of the stack of articles (201) due to for example rapid deceleration during transportation.

(21) Polymer films suitable for stretch hood applications are well known to the person skilled in the art. Commonly used films are single layer or coextruded blown polyethylene based films. The films typically comprise at least three layers, such as a core layer and two outer skin layers.

(22) The polymer film tubular band (215) advantageously has a thickness in the range of 60-120 m. The polymer film tubular band (215) may comprise a single layer (mono) or coextruded (coex) film. The polymer film is preferably comprising an elastomeric polyolefin, with a high elasticity such as a propylene-ethylene rubber, or a mixture of this with a high-vinylacetate copolymer with ethylene (EVA), or a ethylene-vinylacetate copolymer with a very high co-monomer content, or a compound of a polyolefin and a thermoplastic elastomer. The coextruded polymer film tubular band (215) may comprise several layers, such as in the range of 2-6 layers. The layers may all be of the same polymer film material or they may be of different polymer film materials.

(23) The polymer film stretch hood advantageously has a thickness in the range of 100-150 m. The thickness of the stretch hood polymer film is typically larger than the thickness of the polymer film of the tubular band (215). The film may be a single layer (mono) or coextruded (coex) film. The polymer film is preferably made of ethylene-based copolymers or an elastomeric polyolefin. The coextruded polymer film stretch hood may comprise several layers, such as in the range of 2-6 layers. The layers may all be of the same polymer film material or they may be of different polymer film materials. Preferably, the stretch hood film is a 3-layer film, comprising two so called skin layers on each side of a so called core layer. The skin layers are typically suited for welding and advantageously rich in metallocene-based Linear Low Density polyethylene (mLLDPE), and optionally comprise conventional Low density polyethylene or long-chain branched LDPE. The core layer is typically rich in ethylene-vinyl acetate copolymers (EVA) or ethylene butyl acrylate copolymers (EBA), and/or elastomeric polyolefins, or mixtures of these materials.

(24) The stack of articles (201) is typically arranged on a pallet (203) for transport in for example a truck. The pallet (203) could be a standard Euro-pallet of 12080 cm, an industrial pallet of 100120 cm, a semi-pallets of 6080 cm or a quarter pallet of 6040 cm in size. The pallet may also be of other dimensions known in the art. The height of the stack is typically in the range of 150-300 cm, such as 150-250 cm. The stack of articles (201) typically comprises 3-10 layers of articles.

(25) The size stack of articles (201) may advantageously be scaled to correspond to suitable pallet (203) size, for example a standard Euro-pallet of 12080 cm. When arranged on a Euro-pallet, the stack of articles (201) preferably defines a maximum volume of 2.5 m.sup.3.

(26) The layers of the stack are typically separated by separator sheets (205). The sheets (205) separating the layers in the stack of articles (201) are typically made of a rigid material such as a thermoplastic or corrugated cardboard but it could also be a metal, ceramic or a wood material. The sheets (205) are scaled to correspond to suitable pallet (203) size. It is preferable that the sheets (205) do not extend outside the perimeter of the pallet (203). Preferably, the corners of the sheets (205) are rounded. When the articles are arranged on a Euro-pallet, the sheets (205) typically measures a maximum of 12080 cm, preferably somewhat less. It is advantageous if the sheets (205) have the same aspect ratio as the pallet (203).

(27) The stretch hood arrangement (200) is particularly useful for packaging of heavy duty loads weighing more than 500 kg. Typically the combined weight of the stack of articles (201) may be in the range of 500-1200 kg, for example 800-1000 kg.

(28) The stretch hood arrangement (200) is particularly useful for packaging articles that are susceptible to tipping during for example a rapid deceleration during transport. The stretch hood arrangement (200) is typically suitable for enclosing a stack of articles (201) wherein the articles have a height-to-base width ratio at least of 2:1. The base width is measured at the narrowest part of the base. The base of the articles typically has a circular shape but it could also have a polygonal shape, such as a triangular, quadrangular or hexagonal shape. The base width of the articles typically is in the range of 3-20 cm. The height of the articles typically is in the range of 15-50 cm.

(29) Typically, the articles have a tapered form where the base width is larger the top width. The articles are advantageously wine bottles, but could also be beer bottles, soft drink bottles, water bottles, vacuum flasks, home furnishings, designer objects, laboratory glassware, Erlenmeyer flasks, flower pots or flower vases.

(30) One advantage of the stretch hood arrangement (200) described above is that it may alleviate some of the potential damage associated with the situation depicted in FIG. 1. Load securing of articles which are capable of moving or dislocating internally in the stack of articles (201) is becoming increasingly important in the art. Guidelines for load securing are described in for example the European standard EN 12195. EN 12195 also considers dynamic deformations during emergency situations. If the situation depicted in FIG. 1 occurs due to a rapid deceleration during transport, the flexible tubular band (215) can cause the deformed base layer (207) to re-bounce i.e. that the articles return to a non deformed state, thus the pressure exerted on the film is relaxed. This is achieved by the elastic deformation properties of the tubular band (215). When subjected to a force, for example from a deformed base layer (207) of a stack of articles (201), the tubular band (215) will deform elastically and stretch. After reaching a maximum elongation the tubular band (215) will retract and thus exert a force on the deformed base layer (207) that allows the articles in the base layer (207) to re-bounce and return to a non deformed state. The rapid deceleration may for example subject the stack of articles (201) to a force of 0.5 G, which is used in the dynamic tests according to for example the European standard EN 12642, Appendix B with 0.5 G lateral and rearward forces.

(31) While the invention has been described with reference to various exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.

Example

(32) A standard industrial pallet of 12001000 mm size was stacked with empty glass bottles, in 7 layers using plastic separator sheets of 3 mm thickness. Approx. 300 bottles were stacked in each layer. The total height of the load was about 200 cm. D to d ratio of the glass bottles was approx. 2.5:1. Aspect ratio (height-to-base) of the glass bottles was 3.4:1.

(33) A polymer film tubular band of 90 m film thickness made as a 3-layer coex film having a circumference of 2560 mm, gusseted, with a core layer comprising a elastomeric polypropylene based copolymer with ethylene, and skin layers of metallocene-based Linear Low Density Polyethylene, was stretched around approximately 60 cm height of the stack of articles, plus about 10 cm on the pallet, using a pre-stretch of 95% and 100 mm void space between pallet and grippers in outer position. The tubular band covered 2 layers in height. Active unrolling on a stretch hood machine, from bottom upwards was used. Residual elongation after mounting of the tubular band was 72%.

(34) For the stretch hood, tubular polymer film of 120 m thickness, having a circumference of 3600 mm was used. The gusseted, stiff film was made as a 3-layer co-ex with an EVA core layer (comonomer content of 8%), and skin layers made dominantly of metallocene-based Linear Low Density Polyethylene. The stretch hood was top welded, pre-stretched 44% and mounted. Residual elongation after mounting of the stretch hood was 22%.

(35) The tubular band and stretch hood enclosed stack of articles was then subjected to a deceleration test, under which the stack was deformed causing tipping of articles in the base layer of about 16. The articled then re-bounced totally to the original upright position, without causing any rupture or other permanent damage in the stretch hood