Shrink tunnel system and associated method for shrinking a shrink film onto package formations

Abstract

An apparatus for shrinking a shrink film onto a package formation includes a shrink tunnel-system having gas conductors that direct hot gas into the tunnel's interior along first and second flow-directions that are opposite to each other and parallel to a direction in which the package formation is conveyed through the shrink tunnel.

Claims

1. An apparatus for shrinking a shrink film onto a package formation, said apparatus comprising a shrink tunnel-system, wherein said shrink tunnel-system comprises a tunnel housing, a conveyor, and gas conductors, wherein said tunnel housing encloses a tunnel interior, wherein said conveyor moves a package formation wrapped with shrink film through said tunnel interior along a conveying direction, wherein said gas conductors direct hot-gas into said tunnel interior along a first flow-direction and a second flow-direction, wherein said first flow-direction is parallel to said conveying direction, and wherein said second flow-direction is opposite said first flow-direction.

2. The apparatus of claim 1, wherein said gas conductors direct hot gas into said tunnel interior in a first direction, wherein some of said gas conductors direct hot gas into said tunnel interior in said first flow-direction, and wherein others of said gas conductors direct hot gas into said tunnel interior in said second flow-direction.

3. The apparatus of claim 1, wherein, in operation, an average flow of hot gas within said tunnel housing is equal to zero, wherein said average flow is a volume integral of a flow field within said tunnel interior.

4. The apparatus of claim 1, wherein said tunnel interior comprises an inlet zone and an outlet zone, wherein said inlet zone adjoins said outlet zone, wherein said gas conductors comprise a first set of gas conductors and a second set of gas conductors, wherein gas conductors in said first set of gas conductors are disposed in said inlet zone, wherein gas conductors in said second set of gas conductors are disposed in said outlet zone, wherein said gas conductors in said first set of gas conductors introduce said hot-gas flow in said first flow-direction, and wherein gas conductors in said second set of gas conductors introduce said hot-gas flow in said second flow-direction.

5. The apparatus of claim 1, wherein said gas conductors are configured to cause hot-gas flow to rise constantly along said conveying direction.

6. The apparatus of claim 1, wherein further comprising a first lateral tunnel-wall and a second lateral tunnel-wall, wherein said gas conductors are arranged along said lateral tunnel-walls, and wherein said lateral tunnel-walls at least in part define said tunnel interior.

7. The apparatus of claim 1, wherein said gas conductors are formed at least in part by lateral tunnel-walls that define at least in part said tunnel interior.

8. The apparatus of claim 1, wherein said gas conductors are integrated into lateral tunnel-walls that at least in part define said tunnel interior.

9. The apparatus of claim 1, wherein said gas conductors are configured to cause said hot-gas flow to be distributed evenly along a height of said tunnel interior.

10. The apparatus of claim 1, further comprising a lateral tunnel-wall that at least in part defines said tunnel interior, wherein said gas conductors comprise a set of openings in said lateral tunnel-wall, wherein said set of openings comprises a first opening and a second opening.

11. The apparatus of claim 10, wherein said first opening directs hot gas along said first flow-direction, and wherein said second opening directs hot gas along said second flow-direction.

12. The apparatus of claim 10, further comprising a set of areas in said lateral tunnel-wall, wherein said set of areas comprises a first area, wherein said first area surrounds said first opening, and wherein each area in said set of areas is bowed so as to protrude into said tunnel interior.

13. The apparatus of claim 12, wherein said first area comprises a structural feature indicative of said first area having been embossed.

14. The apparatus of claim 10, further comprising a set of nozzles in said lateral tunnel-wall, and a set of areas in said lateral tunnel-wall, wherein said set of areas comprises a first area, wherein said set of nozzles comprises a first nozzle, wherein said first area surrounds said first opening, and wherein said first nozzle comprises said first area and said first opening.

15. The apparatus of claim 10, wherein said first opening comprises a structural feature indicative of a manner in which said first opening was made, and wherein said structural feature indicates said first opening having been made by a laser.

16. The apparatus of claim 10, wherein said tunnel housing defines an axis, wherein said openings in said set of openings have diameters, wherein each opening has a position along said axis, wherein diameters of said openings vary as a function of a position of said opening on said axis, and wherein said diameters increase monotonically with position.

17. The apparatus of claim 10, wherein said set of openings comprises slots, and wherein said slots are adjacent to said conveyor.

18. The apparatus of claim 1, further comprising a lateral tunnel-wall that at least in part defines said tunnel interior, wherein said lateral tunnel-wall comprises a metal panel, wherein said gas conductors comprise a set of openings formed in said metal panel, and wherein said set of openings comprises a first opening and a second opening.

19. The apparatus of claim 18, wherein said first opening comprises a structural feature indicative of a manner in which said first opening was made, and wherein said structural feature indicates said first opening having been made by a metal punch.

20. A method for shrinking a shrink film onto a package formation, said method comprising moving a package formation that has been loosely wrapped with shrink film through a tunnel interior along a conveying direction, and, while said package formation is in said tunnel interior, exposing said package formation to hot-gas flow that is directed along a first direction and to hot-gas flow that is directed along a second direction that is opposite to said first direction, wherein said first direction is parallel to said conveying direction.

21. The method of claim 20, wherein exposing said package formation to hot-gas flow that is directed along a first direction and to hot-gas flow that is directed along a second direction that is opposite to said first direction comprises passing said package formation through an inlet zone, at said inlet zone, exposing said package formation to said hot-gas flow that is directed along said first direction, passing said package formation through an outlet zone, and, at said outlet zone, exposing said package formation to said hot-gas flow that is directed along said second direction.

22. The method of claim 20, wherein exposing said package formation to hot-gas flow that is directed along a first direction comprises causing hot gas to enter said tunnel interior through gas conductors provided on lateral walls that at least in part define said tunnel interior.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) These and other features of the invention will be apparent from the following detailed description and the accompanying figures, in which:

(2) FIG. 1 shows a simplified schematic longitudinal section through a shrink-tunnel system according to the invention,

(3) FIG. 2 shows a view from above a lateral wall of the tunnel housing shown in FIG. 1,

(4) FIG. 3 shows a section along the axis I-I through the lateral wall shown in FIG. 2,

(5) FIG. 4 shows a simplified schematic cross-section through the shrink-tunnel system of FIG. 1,

(6) FIG. 5 shows a view from above an alternative embodiment of the lateral wall shown in FIG. 2, and

(7) FIG. 6 shows a section along the axis II-II through the lateral wall shown in FIG. 5.

DETAILED DESCRIPTION

(8) FIGS. 1 and 3 show a shrink-tunnel system 1 for shrinking a shrink film 2 onto a package formation 3.

(9) As used herein, a package formation 3 includes sets of packaged goods that are to be packaged with shrink film. Examples include sets of containers, bottles, cans or similar individual packages that, upon being bound together by shrink film 2, form a packaging unit 4 or a cluster pack. In some embodiments, the shrink film 2 is a printed film.

(10) The shrink-tunnel system 1 includes a tunnel housing 5. In some embodiments, the tunnel housing 5 has multiple parts. In either case, the tunnel housing 5 defines a tunnel interior 6 that is separated from the exterior by at least first and second lateral tunnel-walls 5.1, 5.2 opposite each other, and a top and bottom tunnel-wall 5.3, 5.4. In some embodiments, the tunnel-walls 5.1-5.4 are held in the tunnel housing 5. In other embodiments, the tunnel-walls 5.1-5.4 at least in part form the tunnel housing 5.

(11) Referring to FIG. 1, a conveyor 7 carries a package formation 3 that has been loosely wrapped with shrink film 2. The conveyor 7 carries this package formation 3 through a tunnel inlet 5a and into an inlet zone EZ within the tunnel interior 6. It continues carrying the package formation into an adjoining outlet zone EZ and on out through a tunnel outlet 5b. In some embodiments, the conveyor 7 is a conveyor belt.

(12) Within the tunnel interior 6, the package formation 3 encounters a flow 8 of hot air. This hot-air flow 8 shrinks the shrink film 2 tightly so that the resulting packaging unit 4 approximates the external shape of the package formation 3.

(13) Hot air used for the hot-air flow 8 comes from a heating/blower arrangement 9, 9, which is preferably located above the tunnel interior 6. A pipe distribution system 10 feeds this hot air into the tunnel interior 6 through first openings 11 and second openings 12. The first openings 11 are in the lateral tunnel-walls 5.1, 5.2. The second openings 12 are in the bottom tunnel wall 5.4.

(14) The heating/blower arrangement 9, 9 draws partially-cooled hot air from the tunnel interior 6 through an extractor opening 13 in the top tunnel wall 5.3, as shown in FIG. 1. The heating/blower arrangement 9, 9 then heats this partially-cooled hot air all over again and recirculates it. Preferably, the hot air is heated to a temperature in the range of approximately 320 F. to 450 F. for shrinking the shrink film 2.

(15) The shrink-tunnel system 1 includes first and second air-conductors 14, 15 for providing a targeted hot-air flow 8 onto the shrink film 2. The first air-conductor 14 introduces hot-air flow 8 along a first flow-direction SR1 that is oriented along the conveying direction TR. The second air-conductor 15 introduces a hot-air flow 8 along a second flow-direction SR2 that is oriented opposite the conveying direction TR. In the transitional area between the inlet zone EZ and the outlet zone AZ, the direction of hot-air flow 8 changes.

(16) The first and second air-conductors 14, 15 are designed to generate a constantly-rising hot-air flow 8 with a specified direction along the inlet and outlet zone EZ, AZ. To achieve this, the first and/or second air-conductors 14, 15 are preferably arranged along the lateral tunnel-wall 5.1, 5.2. In alternative embodiments, they are partially formed by the lateral tunnel-wall 5.1, 5.2 itself. In yet other embodiments, they are integrated into the lateral tunnel-wall 5.1, 5.2. The air conductors 14, 15 are preferably also configured to generate a hot-air flow 8 that is evenly distributed along a vertical direction, at least over the height of the packaging units 4 if not over the height of the tunnel interior 6.

(17) Within the tunnel interior 6 is a lower air-layer zone under the conveyor 7. The pipe distribution system 10 directs some hot air into this zone. This air exits the lower air-layer zone through the second openings 12 in a direction perpendicular to the conveying direction TR and directed toward the top tunnel wall 5.3.

(18) It is particularly advantageous to apply the oriented hot-air flow 8 to the ends of the shrink film 2 that project laterally over the package formations. These ends will be referred to herein as the free ends.

(19) Preferably, the hot-air flow 8 is applied in alternation. In this way, the free ends are turned over such that they come to rest on the open faces 3 of the package formation 3, namely those that are not wrapped with the shrink film 2.

(20) Because the flow-directions SR1, SR2 are oriented in opposite directions, the free ends of the shrink film 2 that are oriented in the conveying direction TR and the free ends of the shrink film 2 that are on the opposite end, which are thus oriented against the conveying direction TR, are turned over on the faces 3 of the package formation 3 in an optimum manner. As a result, they can be shrunk on with reduced wrinkle formation. In this context, a window-like opening 4 arises, which provides a view of the section of the package formation not enclosed by the shrink film 2.

(21) As shown in FIG. 1, a package formation 3 enclosed by the shrink film 2 is fed to the shrink-tunnel system 1 in such a way that a first open face 3 of the package formation 3 faces the first lateral tunnel-walls 5.1 and a second open face 3 faces the second lateral tunnel wall 5.2. This direction causes hot-air flow 8 to have a velocity vector that is generally tangential to the open faces 3 of the package formation 3.

(22) In some embodiments, the lateral tunnel-walls 5.1, 5.2 are metal panels that have a multiplicity of first openings 11 to supply hot-air flow 8 into the tunnel interior 6. These openings 11 thus form the first and second air-conductors 14, 15.

(23) Within the inlet zone EZ, the first openings 11 are shaped to direct hot-air flow 8 emerging therefrom along either a first flow-direction SR1. These collectively define the first air-conductor 14. Within the outlet zone AZ, the first openings 11 are shaped to direct hot-air flow 8 emerging therefrom along the second flow-direction SR2. These collectively define the second air-conductor 15.

(24) Referring to FIGS. 2 and 3, in a preferred embodiment, a first opening 11 is made through the lateral tunnel-walls 5.1, 5.2. This can be carried out by metal punching or by a laser. Next, an embossing tool embosses an area 16 around the first opening 11. The resulting embossed area 16 has an outwardly bowed contour that protrudes into the tunnel interior 6. The position of the opening 11 within the area 16 determines the direction in which hot-air flow 8 exits the opening 11.

(25) The spacings and the diameters of the first openings 11 are selected to control the magnitude of the hot-air flow 8 needed for the shrink process. The first openings 11 are preferably arranged in a matrix of rows and columns on the lateral tunnel-walls 5.1, 5.2.

(26) The bowed contour of the areas 16 can be circular or oval. The location of the opening 11 within the bowed area can also vary. For example, the first openings 11 can be made to lie near an edge of the bowed areas 16. This will tend to increase the tangential component of the velocity vector at the cost of the normal component thereof.

(27) FIG. 2 shows a view facing a lateral tunnel-wall 5.1, 5.2 in which openings 11 have been embossed to direct flow along the first direction SR1. FIG. 3 shows a section along the line I-I through the lateral tunnel-wall 5.1, 5.2 in FIG. 2. The first openings 11 together with the bowed areas 16 thus form a nozzle-like structure.

(28) Within the inlet zone EZ, the first openings 11 are shaped to direct gas flow 8 in a first flow-direction SR1. Meanwhile, within the outlet zone AZ, the first openings 11 are shaped to direct gas flow 8 in in a second flow-direction SR2 against the conveying direction TR.

(29) In some embodiments, the diameters of the nozzle-like first openings 11 are not all the same. In particular, the diameters increase in the conveying direction TR so that the volume of hot-air flow 8 introduced into the tunnel interior 6 by the first openings 11 increases in the conveying direction TR. Advantageously, in this way, the hot-air flow 8 is applied to the shrink films 2 alternately in and against the conveying direction TR, and thus the front or reverse of the shrink film 2 is raised from the package formation 3. This improves the result of the shrinking process.

(30) FIG. 4 shows a cross-section through the shrink-tunnel system 1. In general, a package formation 3 will have four free-ends. A first and second free-end will face the first lateral-wall 5.1 and a third and fourth free-end will face the second lateral-wall 5.2. The package formation 3 is always oriented such that the first and third free-ends are closest to the tunnel inlet 6a and the second and fourth free-ends are closest to the tunnel outlet 6b.

(31) While the package formation 3 is in the inlet zone EZ, the flow 8 is in the conveying direction TR. This flow 8 will tend to fold the first and third free-ends towards the package formation 3 and to lift the second and fourth free-ends away from the package formation 3.

(32) In the transitional area between the inlet zone EZ and the outlet zone AZ, the direction of the flow 8 changes. In the outlet zone AZ, a hot-air flow 8 oriented against the conveying direction TR is now applied to the package formation 3. The second and fourth free-ends of the shrinking film 2 are thus blown against the conveying direction TR and folded onto the package formation 3.

(33) In some embodiments, such as that shown in FIG. 1, a first heating/blower arrangement 9 serves the inlet zone EZ and a second heating/blower arrangement 9 serves the outlet zone AZ.

(34) The first heating/blower arrangement 9 has a first blower unit 9.1 and a first heating unit 9.2. At the end of the inlet zone EZ, the first blower unit 9.1 draws air out of the tunnel interior 6 through a first extractor opening 13 and feeds it to the first heating unit 9.1 for heating. The pipe distribution system 10 then routes the heated air from the first heating unit 9.1 to the first openings 11 provided in the inlet zone EZ so that the hot air can be fed back into the tunnel interior 6.

(35) Similarly, the second heating/blower arrangement 9 has a second blower unit 9.1 and a second heating unit 9.2. At the end of the outlet zone AZ, the second blower unit 9.1 draws air out of the tunnel interior 6 through a second extractor opening 13, and feed it to the second heating unit 9.2 for heating. The pipe distribution system 10 then routes the heated air from the second heating unit 9.2 to the first openings 11 arranged in the outlet zone AZ so that the hot air can be fed back into the tunnel interior 6.

(36) In some embodiments, the shrink-tunnel system 1 includes a temperature sensor for sensing the temperature of the hot air or of the gas flow 8 in the tunnel interior 6. This measured temperature can then be used to adjust heating/blower arrangements 9, 9 accordingly.

(37) In a further embodiment, shown in FIGS. 5 and 6, the first openings 11 that are closest to the conveyor 7 are slot-shaped openings 11. Each slot-shaped opening 11 on the first lateral tunnel-wall 5.1 has a corresponding slot-shaped opening on the second lateral tunnel-wall 5.2 that lies on the opposite side of the conveyor 7. A slot-shaped openings 11 is made by punching a rectangular hole in a lateral tunnel-wall 5.1, 5.2 while leaving behind a guide panel section 17 that can be bent to direct flow in a desired direction, as shown in FIG. 6.

(38) Slot-shaped openings 11 along conveyor 7 permit targeted application of the free ends of the shrink film 2 projecting on the front face. In particular, the section of the free ends of the shrink film 2 oriented in the direction of the conveyor 6 is raised and routed in the direction of the front face 3 of the package formation 3.

(39) The invention has been described above using various embodiments as examples. However, other embodiments are possible without departing from the scope of the invention as defined by the attached claims.