EP2733076A1

EP2733076A1 - Device and method for sealing and heat-shrinking a multi-pack wrapped in a sheet of heat-shrinkable material

Info

Publication number: EP2733076A1
Application number: EP12192845.1A
Authority: EP
Inventors: Federico Corazza; Marco Piccinini
Original assignee: Tetra Laval Holdings and Finance SA
Current assignee: Tetra Laval Holdings and Finance SA
Priority date: 2012-11-15
Filing date: 2012-11-15
Publication date: 2014-05-21
Also published as: WO2014075918A2; WO2014075918A3

Abstract

The invention relates to a heating station for:
i) receiving batches of packages (4) loosely wrapped in sheets (5) of a heat-shrinkable material, opposite ends of the latter overlapping and being interposed between the packages (4) and a porous conveying surface (P); and
ii) sealing the overlapping opposite ends and heat-shrinking the sheets (5) about the batches;

comprising a first and a second heat applicators (19, 20) operatively distinct from each other, for independently supplying a first and second thermal flows to the batches advancing on the porous conveying surface (P); the first heat applicator (19) being arranged below the porous conveying surface (P) to supply heat to the overlapping opposite ends, thereby sealing the sheets (5); the second heat applicator (20) being arranged above the porous conveying surface (P) to supply heat to the sheets (5) and complete the wrapping thereof.

Description

The present invention relates to a heating station of the type forming part of a unit for manufacturing a multi-pack comprising a plurality of packages wrapped in a sheet of heat-shrinkable material. Furthermore, the invention relates to a unit and method for manufacturing a such multi-pack.
Many food products, such as fruit juice, pasteurized or UHT (ultra-high-temperature treated) milk, wine, tomato sauce, etc., are commonly sold in packages made of sterilized packaging material.
A typical example of this type of package is the parallelepiped-shaped package for liquid or pourable food products known as Tetra Brik Aseptic (registered trademark), which is made by folding and sealing laminated strip packaging material.
The packaging material has a multilayer structure substantially comprising a base layer intended to confer stiffness and strength and which may comprise a layer of fibrous material, e.g. paper, or of mineral-filled polypropylene material; and a number of layers of heat-seal plastic material, e.g. polyethylene film, covering both sides of the base layer.
In the case of aseptic packages for long-storage products, such as UHT milk, the packaging material also comprises a layer of gas- and light-barrier material, e.g. aluminium foil or ethyl vinyl alcohol (EVOH), which is superimposed on a layer of heat-seal plastic material, and is in turn covered with another layer of heat-seal plastic material forming the inner face of the package eventually contacting the food product.
As is known, packages of this sort are produced on fully automatic packaging machines, on which a continuous tube is formed from the web-fed packaging material; the web of packaging material is sterilized on the packaging machine, e.g. by applying a chemical sterilizing agent, such as a hydrogen peroxide solution, which, once sterilization is completed, is removed from the surfaces of the packaging material, e.g. evaporated by heating; and the web of packaging material so sterilized is maintained in a closed, sterile environment, and is folded and sealed longitudinally to form a vertical tube.
The tube is filled continuously downwards with the sterilized or sterile-processed food product, and is sealed and then cut along equally spaced cross sections to form pillow packs, which are then fed to a folding unit to form the finished, e.g. substantially parallelepiped-shaped packages.
As is known, a certain number of folded packages, for example three, may be grouped in a batch and shrink-wrapped, so as to form a multi-pack.
For this purpose, a unit for manufacturing multi-packs is arranged downstream of the folding station.
In general, a multi-pack manufacturing unit substantially comprises:

means for conveying/aligning one or more rows of packages along given direction(s);
means for forming, from the one or more rows of packages, batches of packages to be wrapped;
a wrapping station for loosely wrapping the heat-shrinkable material around the batches of packages; and
a heating station to heat-shrink the material which loosely wraps the batches, so as to complete the formation of relative multi-packs, operatively coupled with a conveyor that receives the wrapped batches and delivers them downstream from the heating station.

In greater detail, the wrapping station is arranged upstream from the heating station and is adapted to receive and loosely wind around a batch of packages a sheet of heat-shrinkable material so that opposite ends of the sheet overlap and are ultimately interposed between the conveyor and the bottom walls of the packages of the respective batch. Typically, to this purpose, the wrapping station comprises means for storing, feeding and cutting lengths of a film of a heat-shrinkable material.
In particular, each sheet of heat-shrinkable material comprises:

a main, centrally arranged, portion which is made to at least loosely cooperate with bottom and top walls of the packages in a batch; and
end portions opposite to one another, protruding from the main portion and substantially not cooperating, prior to the shrinking operation, with the packages in the batch.

A such batch shall consist of a number of juxtaposed packages in one or more rows, loosely wrapped in a sheet of heat-shrinkable material, the opposite ends of the sheet overlapping underneath the batch. In practice, the width of the heat-shrinkable material length is greater than the overall width of the batch of packages, whereby end portions thereof project off the batch.
Upon application of heat, the projecting ends shrink and bend over the edges of the batch and come to cooperate with it laterally. Accordingly, proper stability of the multi-pack can be conveniently achieved, in that the relative motion of packages within the multi-pack is thus prevented.
In practice, prior to heat application, the sheet of heat-shrinkable material is kept loosely wrapped around the batch by the very weight of the packages in the batch, which rest onto the overlapping ends of the sheet against the surface of the conveyor.
The heating station then receives and heats the batches loosely wrapped in their relative sheets, so causing a) the sealing of the latter via local melting of the relative overlapping ends; and b) the overall heat-shrinking of the sheets about the respective batches, which substantially completes the formation of the multi-packs.
In greater detail, formation of a multi-pack requires that, in the heating station, heat be supplied:

to the overlapping ends of the heat-shrinkable material sheet (sealing area) so that sealing can be achieved through localized partial melting;
to the whole of the heat-shrinkable material sheet to induce shrinking and proper wrapping around the batch of packages.

In view of this twofold technical requirement, proper control of operations in the heating station is not straightforward. In fact, higher operating temperatures are desirable in that they favour a tight shrinking of the wrapping sheet about the packages, which results in a greater stability of the multi-packs. On the other hand, however, prolonged exposure to air at high temperatures tends to overheat the conveying surface upon which the wrapped batches of containers lie, which is typically defined by a metal conveyor belt, e.g. a chain-driven wire mesh conveyor belt. As a consequence, overheating may cause a more extensive softening/partial melting of the heat-shrinkable material, which consequently sticks to, and accumulates on, the metallic mesh of the conveyor. This is clearly greatly undesirable, because the molten plastic material tends to obstruct the metallic mesh, therefore supply of hot air from below to the heat-shrinkable material may be hindered, if not made impossible altogether. This results in the multi-packs no longer being sealed properly.
Moreover, plastic materials may even make the relative motion of chain segments of the conveyor about the conveyor idler rollers impossible. In practice, molten plastics may solidify between the idler rollers and the conveyor chain segments, which results in a complete blockage of the heating station and may cause definitive breakages.
Furthermore, replacement of the metallic mesh becomes necessary when the flow of hot air through the mesh is compromised or when the conveyor chain gets blocked, therefore production needs to be interrupted and maintenance costs and times are undesirably increased.
A need is therefore felt within the industry for a heating station that makes it possible to overcome the above drawbacks. In particular, the need is felt for a heating station of a unit for manufacturing a multi-pack that substantially prevents, or at least significantly hinders, overheating of the metallic mesh and the consequent melting of the heat-shrinkable material wrapped about the batches of packages.
At the same time, a need is felt within the industry for a heating station that helps reduce the occurrence of machine downtime made necessary for reasons of maintenance and/or replacement of parts.
It is an object of the present invention to provide a heating station of a unit for manufacturing a multi-pack of the type comprising a plurality of packages wrapped in a sheet of heat-shrinkable material that is designed to meet at least one of the above-identified needs.
According to the present invention, the above object is achieved through the provision of a heating station as claimed in Claim 1. Furthermore, according to the present invention, there is provided a unit for manufacturing a multi-pack of the type comprising a plurality of packages wrapped in a sheet of heat-shrinkable material, as claimed in Claim 11.
The present invention also relates to a method for manufacturing a multi-pack of the type comprising a plurality of packages wrapped in a sheet of heat-shrinkable material, as claimed in Claim 12.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred embodiment is hereinafter disclosed for a better understanding of the present invention, by mere way of non-limitative example and with reference to the accompanying drawings, in which:

Figure 1 shows a schematic perspective view, with parts removed for the sake of a better understanding, of an embodiment of a heating station of a unit for manufacturing a multi-pack of the type comprising a plurality of packages wrapped in a sheet of heat-shrinkable material according to the present invention;
Figure 2 shows a schematic side section of the heating station of Figure 1;
Figure 3 shows a larger-scale detail of the metallic conveyor of the heating station of Figures 1 and 2;
Figure 4 shows a larger-scale, schematic perspective view of a batch of packages wrapped in a sheet of heat-shrinkable material of the type handled by the manufacturing unit of Figures 1 and 2;
Figure 5 shows a larger-scale, schematic perspective view of the batch of packages of Figure 4 after provision of heat in the heating station of Figures 1 and 2, whereby a multi-pack is formed; and
Figure 6 shows a schematic side section of an alternative embodiment of a heating station of a unit for manufacturing a multi-pack of the type comprising a plurality of packages wrapped in a sheet of heat-shrinkable material according to the present invention; and
Figure 7 shows a schematic side section of a heating section according to the present invention in two different configurations.

BEST MODE FOR CARRYING OUT THE INVENTION

In Figures 1 and 2 numeral 1 indicates as a whole a heating station adapted to form part of a unit for manufacturing a multi-pack 3 (see also Figure 5) of the type comprising a plurality of packages 4 wrapped in a sheet 5 of heat-shrinkable material.
A multi-pack manufacturing unit (not illustrated) generally comprises:

means for conveying/aligning one or more rows of packages 4 along (a) given direction(s);
means for forming, from the one or more rows of packages 4, batches of packages 4 to be wrapped;
a wrapping station for wrapping the heat-shrinkable material around the batches of packages 4; and
a heating station 1 to heat-shrink the material to wrap the batches, so as to complete the formation of relative multi-packs.

In particular, the wrapping station is arranged upstream from heating station 1 and is adapted to receive and loosely wrap around a batch of packages 4 a sheet 5 of heat-shrinkable material so that opposite ends of the sheet overlap and are interposed between conveyor 10 and the bottom walls of packages 4 of the respective batch when the batch is delivered to heating station 1.
In this context, by "loosely wrapped", reference is made to a condition where the sheet of heat-shrinkable material has been wound around the batch of packages, yet not properly (i.e. tightly) wrapped about the packages, which are - as a consequence - still free to move relative to each other, at least along a direction transversal to the main advancement direction X.
Heating station 1 is adapted to receive and heat batches of packages 4 loosely wrapped in their respective sheets 5, opposite ends of the latter overlapping and being interposed between packages 4 (in particular, the relative bottom walls) and a conveying surface upon which they lie, so as to cause a) the sealing of sheets 5 at a relative sealing area (substantially defined by the overlapping ends); and b) the overall heat-shrinking of sheets 5 about the respective batches, thereby completing the formation of multi-packs.
The conveying surface is defined by a porous conveyor 10 operatively coupled with heating station and defining a substantially horizontal plane P, for receiving from the wrapping station batches of packages 4 loosely wrapped in sheet 5 of heat-shrinkable material with opposite ends overlapping and interposed between conveyor 10 and packages 4 of the respective batch and for delivering fully formed multi-packs at an output end 11 of heating station 1.
In greater detail, conveyor 10 is typically a metal conveyor belt, e.g. a chain-driven wire mesh conveyor belt, of a known type.
Advantageously, heating station 1 comprises a first and a second heat applicators 19 and 20 for independently supplying respective first and second thermal flows to the wrapped batches of containers 4 as they are advanced, along a main direction X of advancement, by porous conveyor 10; the first heat applicator 19 being arranged underneath plane P of conveyor 10; the second heat applicator 20 being arranged above plane P of conveyor 10.
In greater detail, with respect to the main advancement direction X, second heat applicator 20 is arranged downstream of first heat applicator 19.
Preferably, first and second heat applicators 19, 20 are connectable to one or more heat sources 14, 15, which may e.g. consist of independent sources of a heating medium, such as hot air.
In the embodiment shown in Figures 1 and 2, heating station 1 comprises a first and a second heating chamber 12 and 13 internally defining, together with conveyor 10, operatively distinct volumes V1 and V2. First and second heating chambers 12 and 13 are operatively coupled with first and second heat applicators 19, 20, respectively, and may be materially divided by a separation member 16 that allows batches on conveyor 10 to advance from one chamber to the other, such as a curtain-like element of the type commonly used in known shrink tunnels.
In greater detail, in the embodiment illustrated schematically in Figures 2 and 4, heating station 1 comprises a tunnel housing 17, having an inlet 18_in and an outlet 18_out, and defining internally first and second chambers 12, 13 with the aid of conveyor 10, which delimits inferiorly the relative volumes V1 and V2, and of separation member 16, which materially divides volume V1 from volume V2.
Separation member 16 may preferably be a curtain of a reinforced silicone rubber, which is known to be able to withstand the operating temperatures at which heat-shrinking is carried out, while minimising heat loss, which helps accurately control temperature within both chambers 12, 13.
First chamber 12 is operatively coupled with first heat applicator 19. Preferably, as is the case with the embodiment illustrated in Figures 1 and 2, first heat applicator 19 is defined by first distributing means, fluidly connectable with a first source 14 of a heating medium and arranged immediately underneath conveyor 10 for directing a substantially homogeneous flow of heating medium through the mesh of conveyor 10 and into first volume V1 of first chamber 12. In particular, distributing means 19 may comprise a relative distribution chamber 19a fluidically connectable with first source 14 (e.g. a blower) and opening in an upper portion thereof (in other words, superiorly) into a plurality of holes. In practice, the top wall of distribution chamber 19a may consist of a perforated plate, which allows for a homogenous distribution of the heating medium over the sealing area, i.e. onto the overlapping ends of the sheet of heat-shrinkable material wrapped around the batches, as illustrated by the arrows in Figures 2 and 4.
Figure 3 illustrates, by way of example, a detail of a possible configuration of the metallic mesh 10a of conveyor 10 as it is driven over the perforated plate of distribution chamber 19a.
Second chamber 13 is operatively coupled with second heat applicator 20. Preferably, as is the case with the embodiment illustrated in Figures 1 and 2, second heat applicator 20 is defined by second distributing means, fluidly connectable with a second source 15 of a heating medium and arranged above conveyor 10 in a top portion of tunnel housing 17, for directing a substantially homogeneous flow of heating medium into second volume V2 of second chamber 13 all over the wrapped and sealed batches received from first chamber 12. In particular, distributing means 20 may comprise a relative distribution chamber 20a fluidically connectable with second source 15 (e.g. a blower) and opening in a lower portion thereof (in other words, inferiorly) into a plurality of holes. In practice, the bottom wall of distribution chamber 20a may consist of a perforated plate, as illustrated by the arrows in Figures 2 and 5, which allows for a homogenous distribution of the heating medium all over the batch, which favours proper and tight wrapping of the heat-shrinkable material about packages 4.
In an alternative embodiment, both first and second heat applicators 19, 20 may be connected to a same heat source. By way of example, heat applicators 19, 20 may be defined by distinct distribution means both connected to a same source of a heating medium, heating station 1 optionally comprising further means for varying the temperature of one flow of heating medium directed to one of heat applicators 19, 20 with respect to the temperature of the other flow of heating medium directed to the other one of heat applicators 20, 19.
Preferably, first and second heat applicators 19, 20 are adapted and configured to supply heat at two different temperatures. In practice, first and second heat applicators 19, 20 are preferably connectable to distinct first and second sources 14,15 of heating medium adapted and configured to supply heating medium at two different temperatures.
Preferably, the temperature of the heating medium supplied from the first source 14 is set such that the temperature of the metallic mesh of conveyor 10 at the exit from first chamber 12 never exceeds, in use, a threshold value. In particular, the temperature of the heating medium supplied from the first source 14 is set such that sealing of the sheet of heat-shrinkable material is conveniently achieved, while preventing the heat-shrinkable material from sticking to conveyor 10.
Similarly, the temperature of the heating medium supplied from the second source 15 is set such that the temperature of the heat-shrinkable material is brought, and maintained for a given time, above a given threshold value which can be associated with proper and complete shrinking/wrapping about the batch of packages 4.
Number 1' in Figure 7 indicates an alternative embodiment of a heating station in accordance with the present invention.
Heating station 1' is similar to heating station 1, and is described below only insofar as it differs from the latter, and using, wherever possible, the same reference numbers for identical or corresponding parts of heating stations 1, 1'.
More specifically, heating station 1' differs from heating station 1 in that it comprises only one heating chamber 13' internally defining, together with conveyor 10, a volume V3, and being operatively coupled with second heat applicator 20.
In greater detail, heating station 1' comprises a tunnel housing 17, having an inlet 18_in and an outlet 18_out, and defining internally heating chamber 13' with the aid of conveyor 10, which delimits inferiorly the relative volume V3.
Figure 7 shows a further view of a heating station 1" comprising a tunnel housing 17, having an inlet 18_in and an outlet 18_out, and defining internally a heating chamber 13. Advantageously, tunnel housing 17 is movable between a first operative position (indicated by the dashed line), wherein it is in slidable cooperation with conveyor 10, and a second operative position, which is vertically superior with respect to the first operative position.
In practice, heating station 1" comprises means 21 for lifting/holding tunnel housing 17 at a raised position where it does not cooperate with conveyor 10 and direct access to volume V3 and its content is made possible, e.g. for maintenance or inspection operations. Preferably, lifting/holding means 21 allow tunnel housing 17 to be raised above plane P by a height at least equal to the height of packages 4 being processed.
In use, a batch of packages 4 loosely wrapped in its respective sheet 5 of heat-shrinkable material with the relative opposite ends overlapping and interposed inferiorly between the batch and a porous conveying surface is fed to heating station 1, whereby the opposite overlapping ends of the sheet 5 of heat-shrinkable material are sealed and the sheet 5 of heat-shrinkable material is shrunk about the batch of packages 4 to form a multi-pack.
Advantageously, a first and a second thermal flows are independently supplied to the wrapped batch of containers 4 as they are advanced, along main direction X of advancement, by the porous conveying surface; the first thermal flow being supplied by a first heat applicator 19 arranged below the porous conveying surface so as to cause sealing of the sheet of heat-shrinkable material; the second thermal flow being supplied by a second heat applicator 20 arranged above the porous conveying surface so as to cause a substantially full shrinking of the heat-shrinkable material about the batch.
Preferably, the first and second thermal flows are supplied as distinct first and second flows of a thermal medium, the first and second flows of heating medium being at two different temperatures.
Preferably, the temperature of the heating medium in the first flow is set such that the temperature of the conveying surface never exceeds, at a given position along direction X, a threshold value.
Similarly, the temperature of the heating medium in the second flow is set such that the temperature of the heat-shrinkable material is brought, and maintained for a given time, above a given threshold value which can be associated with proper and complete shrinking/wrapping about the batch of packages 4.
From an analysis of the features of heating station 1, of a manufacturing unit comprising heating station 1 and of the method outlined above, the advantages which can be obtained from the present invention shall be apparent.
In particular, accurate and distinct temperature control for the two operations that need to be carried out is made possible.
In fact, direct supply of heat at the sealing area, e.g. by means of a flow of air at high temperature distributed from a source arranged underneath the porous conveyor, makes it possible to very quickly induce a localised partial melting of the heat-shrinkable material and, therefore, precise and reliable sealing of the multi-pack, without overheating the conveyor surface. Furthermore, this also dramatically reduces the time needed for reaching the set-point operating conditions at start-up with respect to traditional heating stations. In fact, with a conventional heating station as described before, it is necessary to bring substantially the whole of the inner volume of the sealing/shrinking environment to a temperature sufficient for effectively carrying out both operations, which may require an overall pre-heating time of as long as 30 minutes. On the other hand, with the heating station and method of the present invention, a much shorter pre-heating time, in the range 0.5÷1 minute, has been found to be sufficient for getting the heating station ready to operate properly.
Furthermore, independent temperature control for the shrinking operation conveniently results in a fully satisfactory (tight) wrapping of the heat-shrinkable material about the packages 4, while the likelihood of melting and sticking to the mesh of conveyor 10 on the part of the heat-shrinkable material is greatly reduced, if not virtually eliminated.
Accordingly, the need for machine downtime for replacement of the conveyor is practically eliminated.
Finally, it is clear that modifications and variants not departing from the scope of protection of the independent claims can be made to the heating station, manufacturing unit and manufacturing method disclosed herein.
By way of example, it shall appear that, while focus has been placed here mainly on embodiments where heat is supplied by means of flows of a thermal medium, different types of heat applicators may be used, such as infrared heat applicators. Different heat supply mechanisms may even be used for the first and second heat applicator.

Claims

A heating station (1; 1') adapted and configured to:
a) receive and heat batches of packages (4) loosely wrapped in respective sheets (5) of a heat-shrinkable material, opposite ends of the heat-shrinkable material overlapping and being interposed between said packages (4) and a relative porous conveying surface (P) on which said packages (4) lie; and

b) cause the sealing of said overlapping opposite ends of said sheets (5) and the overall heat-shrinking of said sheets (5) about the respective batches of packages (4), such that multi-packs of packages (4) are obtained;
characterised by comprising a first and a second heat applicators (19, 20) operatively distinct from each other, for independently supplying respective first and second thermal flows to said batches of containers (4) as they are advanced, along a main direction (X) of advancement, by said porous conveying surface (P); said first heat applicator (19) being arranged below said porous conveying surface (P) to supply heat to said overlapping opposite ends and thereby sealing said sheets (5); said second heat applicator (20) being arranged above said porous conveying surface (P) to supply heat to said sheets (5) and complete the wrapping thereof.
The heating station of Claim 1, characterised in that said porous conveying surface (P) is defined by a conveyor (10), said heating station (1; 1') comprising at least one heating chamber (12; 13) operatively coupled with one of said heat applicators (19; 20).
The heating station of Claim 2, characterised by comprising a further heating chamber (12; 13), said heating chambers (12, 13) being operatively coupled with said first and second heat applicators (19, 20), respectively.
The heating station of Claim 3, characterised in that said first and second heating chambers (12, 13) are materially divided from each other by a separation member (16) that allows said batches to advance from one said chamber (12) to the other (13).
The heating station of any of Claims 2 to 4, characterised by comprising a tunnel housing (17) defining internally said at least one heating chamber (12; 13).
The heating station of any one of Claims 1 to 5, characterised by comprising at least one heat source (14; 15) operatively connected to one or both of said heat applicators (19; 20).
The heating station of Claim 6, characterised in that said at least one heat source (14) is a source of a heating medium; and characterised by comprising first distributing means defining said first heat applicator (19), fluidly connectable with said at least one source (14) and arranged immediately underneath said porous conveying surface (P) for directing a substantially homogeneous flow of heating medium through said porous conveying surface (P) onto said batch of packages (4).
The heating station of Claim 7, characterised in that said first distributing means (19) comprise a relative distribution chamber (19a) opening in its upper portion into a plurality of holes.
The heating station of any one of Claims 6 to 8, characterised by comprising a second heat source (15), said second heat source (15) being a source of a heating medium; and characterised by comprising second distributing means defining said second heat applicator (20), fluidly connectable with said second source (15) and arranged above said porous conveying surface (P) for directing a substantially homogeneous flow of heating medium to said batch of packages (4).
The heating station of Claim 9, characterised in that said second distributing means (20) comprise a relative distribution chamber (20a) opening in its lower portion into a plurality of holes.
A unit for manufacturing a multi-pack comprising a plurality of packages wrapped in a sheet of heat-shrinkable material, characterised by comprising a heating station (1) according to any one of Claims 1 to 10.
A method for manufacturing a multi-pack comprising a plurality of packages wrapped in a sheet of heat-shrinkable material, comprising the steps of:
a) feeding a batch of packages (4) loosely wrapped in a respective sheet (5) of heat-shrinkable material with the relative opposite ends overlapping and interposed inferiorly between the batch and a porous conveying surface (P) to a heating station (1); and

b) at said heating station (1) sealing the opposite overlapping ends of said sheet (5) of heat-shrinkable material and shrinking said heat-shrinkable material about said batch of packages (4) to form a multi-pack;
characterised in that said step b) of sealing and shrinking comprises independently and subsequently supplying a first and a second thermal flow to said batch of containers (4) as they are advanced along a main direction (X) of advancement on said porous conveying surface (P); said first thermal flow being applied by a first heat applicator (19) arranged below said porous conveying surface (P) so as to cause sealing of said sheet (5) of heat-shrinkable material; said second thermal flow being applied by a second heat applicator (20) arranged above said porous conveying surface (P) so as to cause a substantially full shrinking of said heat-shrinkable material about said batch.
The method according to Claim 12, characterised in that said first thermal flow is supplied as a flow of a heating medium, the temperature of the heating medium in said first flow being set such that the temperature of said porous conveying surface (P) never exceeds, at a given position along direction X, a first given threshold value.
The method according to Claim 12 or 13, characterised in that said second thermal flow is supplied as a flow of a heating medium, the temperature of the heating medium in said second flow being set such that the temperature of said heat-shrinkable material is brought, and maintained for a given time, above a second given threshold value.
A heating station (1") adapted and configured to:
a) receive and heat batches of packages (4) loosely wrapped in respective sheets (5) of a heat-shrinkable material, opposite ends of the latter overlapping and being interposed between said packages (4) and a relative porous conveying surface (P) on which said packages (4) lie; and

b) cause the sealing of said overlapping opposite ends of said sheets (5) and the overall heat-shrinking of said sheets (5) about the respective batches of packages (4), whereby multi-packs of packages (4) are obtained;
said heating station (1") comprising a tunnel housing (17) and characterised in that said tunnel housing (17) is movable between a first operative position, wherein said tunnel housing (17) is in slidable cooperation with said porous conveying surface (P) to define an inner heating volume (V2; V3), and a second operative position, which is vertically superior with respect to said first operative position and wherein direct access to said porous conveying surface (P) and to said volume (V2; V3) is made possible.