WO2015128812A1

WO2015128812A1 - Packing method and unit for folding a sheet of packing material around a parallelepipedal product

Info

Publication number: WO2015128812A1
Application number: PCT/IB2015/051399
Authority: WO
Inventors: Gilberto Spirito; Stefano Negrini
Original assignee: G.D Societa' Per Azioni
Priority date: 2014-02-25
Filing date: 2015-02-25
Publication date: 2015-09-03
Also published as: DE112015000960T5

Abstract

A packing method and unit (11) for folding a sheet (9) of packing material around a parallelepiped-shaped product (2); the sheet (9) of packing material is folded around the product (2) to form a package (1) having at least one open end (16; 38). where the sheet (9) of packing material has two opposite parallel central portions (17; 39) projecting from the product (2) and at least one lateral portion (18; 40) which projects from the product (2) and is perpendicular to and connects the two central portions (17; 39); the two central portions (17; 39) of the sheet (9) of packing material are folded towards each other by means of two central folding devices (24; 41), so as to superimpose the two central portions (17; 39) to form a fin (25; 42); and, by means of a lateral folding device (26; 43) separate from and independent of the central folding devices (24; 41), the lateral portion (18; 40) of the sheet (9) of packing material is folded into a 'V' shape.

Description

"PACKING ME THOD AND UNI T FOR FOLDING A SHEE T OF PACKING MATERIAL AROUND A PARALLELE PI PEDAL PRODUCT"

TECHNICAL FIELD

The present invention relates to a packing method and unit for folding a sheet of packing material around a parallelepipedal product .

The present invention finds advantageous application in the folding of a sheet of heat-sealable packing material around a group of cigarettes, to which the following description will make explicit reference, but without any loss of generality.

PRIOR ART

A packet of cigarettes generally comprises an inner package, which is composed of a group of cigarettes wrapped in an inner wrapping sheet, and outer packaging, which contains the inner package and can be composed of an external wrapping sheet folded around the inner package and have an open receptacle- like shape (soft type of cigarette packet), or be composed of a rigid box with a hinged lid formed by folding a rigid blank around the inner package (rigid type of cigarette packet) .

In a traditional cigarette packet, the group of cigarettes is internally wrapped in a rectangular inner wrapping sheet of metalized paper without glue and externally wrapped in a rectangular outer wrapping sheet that is stabilized by gluing.

Tobacco is very sensitive to the effects of the outside environment, as contact with the atmosphere tends to alter its organoleptic characteristics, due both to variations in humidity (the tobacco can become too dry or absorb too much humidity) and the evaporation of volatile substances with which the tobacco has been impregnated (especially in the case of cigarettes aromatized with particular flavours such as cloves) . To preserve the integrity of the tobacco in the cigarettes, the cigarette packets are wrapped in cellophane, i.e. are covered with a heat-sealed external overwrapping made of an impermeable plastic material. However, the heat-sealed external overwrapping might not be sufficient to completely conserve the organoleptic characteristics of the tobacco contained in a packet of cigarettes, especially when the packet of cigarettes is smoked after a certain period of time from its production. Furthermore, the external overwrapping is removed when the packet is first opened and therefore the tobacco in the cigarettes contained in the packet comes into contact with the outside environment; if the cigarettes contained in the packet are not quickly smoked after the packet is first opened, the organoleptic characteristics of the remaining cigarettes can deteriorate.

To try to obviate the above-described drawback, a rigid cigarette packet has been proposed in patent US4300676A1, in which the inner package is impermeable and is constituted by a heat-sealable, impermeable sheet of packing material having an a opening for cigarette extraction that is closed by a reusable closing tab.

It has been observed that the folding of the inner wrapping sheet around the group of cigarettes can damage the ends of the cigarettes, causing localized deformation (both on the filter end and the end where the tobacco is visible) and/or loss of tobacco (i.e. emptying of the tips, obviously only at the end opposite to the filter where the tobacco is visible) . In particular, damage to the cigarettes caused by the folding of the inner wrapping sheet around the group of cigarettes is worst on the cigarettes positioned at the vertices of the group of cigarettes and, in any case, is evident in all the externally positioned cigarettes, i.e. arranged along the fold lines of the inner wrapping sheet. The folding of an impermeable inner wrapping sheet is particularly damaging to the cigarettes, as the impermeable inner wrapping sheet has a greater thickness (and therefore rigidity) than traditional inner wrapping sheets composed of metalized paper.

Furthermore, the heat-sealing of the superimposed portions of the inner wrapping sheet can also damage the underlying cigarettes, as in order to perform good quality heat sealing

(i.e. to ensure effective sealing) in short times (modern packing machines process more than 500 packets per minute and so heat sealing must be completed in a fraction of a second) , it is necessary to press the superimposed portions using high pressures, which are inevitably transmitted to the underlying cigarettes with evident risks of their permanent deformation and it is necessary to heat the superimposed portions to a high temperature, with evident risks of excessively overheating the tobacco contained in the underlying cigarettes

(excessive overheating of the tobacco can cause local drying that alters the organoleptic characteristics) .

To reduce damage to the cigarettes caused by folding an impermeable inner wrapping sheet and the subsequent heat sealing of the superimposed portions of the impermeable inner wrapping sheet, it has been proposed to use so-called fin folding' , whereby two portions of the inner wrapping sheet are folded towards each other so as to superimpose the two portions to form a fin perpendicular to an underlying surface of the group of cigarettes. Some examples of inner cigarette packages having fin folds' are illustrated in the following documents: EP2544958A1, EP2456685A1, EP1686060A1, US4789060A1, GB1471086A1 and US3948389A1.

Patent application JP2002284110A describes a packing unit for forming a sealed package around a parallelepipedal product 1 by folding a heat-sealable wrapping sheet 2. In a folding station 100, the packaging sheet 2 is first folded into a ^λυ' and then into a tube around the product 1 to form a tubular package having two open ends 2a. In a folding station 200 located downstream of folding station 100, each open end 2a is flattened by two drawing elements 228 and 243, which are inserted in the open ends 2a and, by moving in opposite directions, draw each open end 2a to form a flat fin that is subsequently heat sealed.

However, producing fin folds' according to currently known packaging methods is not very efficient, or rather does not allow achieving high productivity if it is wished to maintain high final quality for the package.

DESCRIPTION OF INVENTION

The object of the present invention is to provide a packing method and unit for folding a sheet of packing material around a parallelepipedal product, the packing method and unit being devoid of the above-described drawbacks and, at the same time, simple and inexpensive to implement.

In accordance with the present invention, a packing method and unit are provided for folding a sheet of packing material around a parallelepipedal product, as set forth in the appended claims.

BRIEF DESCRIPTION OF DRAWINGS

The present invention will now be described with reference to the attached drawings, which illustrate some non-limitative embodiments, in which:

Figure 1 shows a front perspective view of a cigarette package produced according to the packing method of the present invention;

- Figure 2 shows a perspective view of a group of cigarettes contained in the package in Figure 1 ;

- Figure 3 shows a perspective view of a stiffening element that can be contained in the package in Figure 1 ;

- Figure 4 shows a plan view of a sheet of packing material used to make the package in Figure 1; - Figure 5 shows a schematic, perspective view of a packing unit that produces the package in Figure 1 ;

- Figure 6 shows a perspective view, on an enlarged scale, of a longitudinal folding path in Figure 5;

- Figure 7 shows a perspective view, on an enlarged scale, of a detail of Figure 6;

- Figure 8 shows a perspective view, on an enlarged scale, of a transverse folding path in Figure 5;

- Figure 9 shows a schematic, perspective view of the packing unit in Figure 5 modified to produce a variant of the package in Figure 1 ;

- Figure 10 shows a perspective view, on an enlarged scale, of a longitudinal folding path in Figure 9;

- Figure 11 shows a perspective view, on an enlarged scale, of a detail of Figure 10;

- Figure 12 shows a perspective view, on an enlarged scale, of a transverse folding path in Figure 9;

- Figure 13 shows a schematic plan view of the longitudinal folding path in Figures 6 and 10;

- Figure 14 schematically shows part of a feed conveyor of the longitudinal folding path in Figures 6 and 10;

- Figure 15 shows a schematic plan view of a folding device of the longitudinal folding path in Figures 6 and 10 in two different operating configurations (the top half of Figure 15 regards the embodiment shown in Figures 9-12, while the bottom half of Figure 15 regards the embodiment shown in Figures 5- 8) ;

- Figure 16 shows a schematic, perspective view of a tubular body supported by fixed folders of the longitudinal folding path in Figures 6 and 10;

- Figures 17-20 are four cross-sectional views of the tubular body in Figure 16;

Figures 21, 22 and 23 are three different schematic, perspective views of a folding device of the transverse folding path in Figures 8 and 12;

- Figures 24, 25 and 26 are three different views from the front, side and top, respectively, of the folding device in Figures 21, 22 and 23;

- Figure 27 is a schematic, perspective view of an alternative embodiment of the packing unit in Figure 5; and

- Figure 28 is a schematic, perspective view of a variant of a formation path of the packing unit in Figure 27.

PREFERRED EMBODIMENTS OF THE INVENTION

In Figure 1, reference numeral 1 indicates, as a whole, a sealed cigarette package, for example, of the type described in patent US4300676A1.

According to that shown in Figure 2, the cigarette package 1 contains a parallelepiped-shaped group of cigarettes 2 and has a top surface 3 and a bottom surface 4 that are constituted by the tips of the cigarettes and are parallel to and facing each other, two larger lateral surfaces 5 that are constituted by the lateral cylindrical surfaces of the cigarettes and are parallel to and facing each other, and two smaller lateral surfaces 6 that are constituted by the lateral cylindrical surfaces of the cigarettes and are parallel to and facing each other .

According to that shown in Figure 1, the package 1 has a top front opening 7 for the extraction of cigarettes (visible in Figure 4), which is delimited by a pre-weakened tearable line, is closed by a reusable closing tab 8 and involves a portion of a front surface of the package 1 and a portion of a top surface of the package 1. According to a preferred embodiment, the closing tab 8 is fastened to the cigarette package 1 by non-drying repositionable adhesive, which is applied to the lower surface of the closing tab 8 and all around the extraction opening 7 to enable the closing tab 8 to be partially separated from the package 1 multiple times and then fastened again to the package 1. According to another embodiment that is not shown, the package 1 does not have the extraction opening 7 and associated closing tab 8, but a removable top portion, which is separated from the rest of the package 1 by a pre-weakened tearable line and torn off when the package 1 is first opened; in this embodiment, the package 1 is preferably provided with a tear- off ribbon to aid tearing the package 1 along the pre-weakened line . The package 1 is obtained by folding a sheet 9 of packing material (shown in Figure 4), which is rectangular in shape, comprises at least one layer of a heat-sealable, airtight plastic material, and is folded directly around the group of cigarettes 2 so as to be in direct contact with the cigarettes. Once the sheet 9 of packing material has been folded around the group of cigarettes 2 to form the package 1, the shape of the package 1 is stabilized by heat sealing superimposed portions of the sheet 9 of packing material. Before being folded around the group of cigarettes 2, the sheet 9 of packing material is pre-cut to define the extraction opening 7; then the closing tab 8 is applied to the sheet 9 of packing material, the closing tab 8 being gummed at the bottom, i.e. provided with a repositionable adhesive on its lower surface that, inside the extraction opening 7, causes permanent gluing of the inner portion of the sheet 9 of packing material to the closing tab 8 and, outside the extraction opening 7, causes removable gluing of the sheet 9 of packing material to the closing tab 8

According to that shown in Figure 3, the package 1 could comprises a strengthening element 10, which is made of rigid cardstock or cardboard, is U-shaped and is placed inside the package 1 in contact with the group of cigarettes 2. The function of the strengthening element 10 is to provide greater rigidity and greater stability of shape to the package 1 in order to prevent the package 1 from collapsing after some of the cigarettes contained in the package 1 have been extracted, which would complicate extraction of the remaining cigarettes and, in particular, make the opening and subsequent closing of the closing tab 8 extremely complicated. A further function of the strengthening element 10 is to provide mechanical protection for the cigarettes during the folding of the sheet 9 of packing material, mechanical and thermal protection for the cigarettes during the heat sealing of the superimposed portions of the sheet 9 of packing material, and mechanical protection for the cigarettes when handling the package 1.

In Figure 5, reference numeral 11 indicates, as a whole, a packing unit that is part of a packing machine and is designed to produce the above-described package 1.

It is important to underline that the packing machine could comprise only the packing unit 11 (in this case, each above- described package 1 is a finished product and can be directly marketed) ; alternatively, the packing machine could comprise a further packing unit of known type to wrap a respective outer packaging around each package 1; the outer packaging would contain the package 1 and could be composed of an external wrapping sheet folded around the package 1 and have an open receptacle-like shape (soft type of cigarette packet), or be composed of a rigid box with a hinged lid formed by folding a rigid blank around the package 1 (rigid type of cigarette packet) . The packing unit 11 comprises a group-forming station 12 in which groups of cigarettes 2 are formed in succession, a preliminary folding station 13 in which a corresponding sheet 9 of packing material is folded into a ^λυ' around each group of cigarettes 2, a longitudinal folding station 14 in which each sheet 9 of packing material is folded longitudinally at the smaller lateral surfaces 6 of the respective group of cigarettes 2, and a transverse folding station 15 in which each sheet 9 of packing material is folded transversely at the bottom surface 4 of the respective group of cigarettes 2. The group-forming station 12 for the groups of cigarettes 2 comprises a hopper equipped with three outlets to simultaneously feed three groups of cigarettes 2 to respective pockets of a group-forming conveyor that advances along a straight group-forming path PI in large steps. By way of example, the group-forming conveyor comprises a belt, which is wrapped around end pulleys (one of which is powered) and moves along a closed-loop path in large steps.

The preliminary folding station 13 is located along the group- forming conveyor downstream of the group-forming station 12. In the preliminary folding station 13, each group of cigarettes 2 is combined with the corresponding outstretched sheet 9 of packing material, by resting a central part of the sheet 9 of packing material (corresponding to the extraction opening 7) against the top surface 3 of the group of cigarettes 2; then, as better shown in Figure 6, the sheet 9 of packing material is folded into a ^λυ' around the corresponding group of cigarettes 2 (after contact between the central part of the sheet 9 of packing material and the top surface 3 of the group of cigarettes 2) to form a U-shaped package 1 having two open lateral ends 16, which leave the corresponding smaller lateral surfaces 6 of the group of cigarettes 2 visible. Each open lateral end 16 has two central portions 17 that project from the group of cigarettes 2 (and constitute the continuation of the larger lateral surfaces 5) and a single lateral portion 18 that projects from the group of cigarettes 2 (and constitutes the continuation of the top surface 3 of the group of cigarettes 2), and is perpendicularly to and connects the two central portions 17.

It is important to underline that each sheet 9 of packing material is folded into a ^λυ' around the corresponding group of cigarettes 2 by means of interposition of the walls of the pocket of the group-forming conveyor; in this way, the fold lines of the sheet 9 of packing material are at least partially formed against rigid elements of the pocket, avoiding mechanical stress on the cigarettes in the group of cigarettes 2 during the folding of the sheet 9 of packing material .

The longitudinal folding station 14 comprises a longitudinal folding conveyor 19 (shown in Figure 13), which feeds the packages 1 (each composed of a sheet 9 of packing material folded into a ^λυ' around a corresponding group of cigarettes 2) in succession along a straight longitudinal folding path P2 perpendicular to the group-forming path PI. In other words, the longitudinal packaging conveyor 19 receives the packages 1 from the group-forming conveyor in succession, in a transfer area; the groups of cigarettes 2 are fed transversely along the group-forming conveyor (i.e. the cigarettes are arranged perpendicularly to the group-forming path PI), while along the longitudinal folding conveyor 19 the groups of cigarettes 2 are fed longitudinally (i.e. the cigarettes are arranged parallel to the longitudinal folding path P2) . According to that shown in Figures 13 and 14, the longitudinal packaging conveyor 19 comprises a endless-loop conveyor belt 20 (partially shown) , which is wrapped around respective end pulleys (not shown) , is located beneath the longitudinal folding path P2 and supports a plurality of pushers 21 that are designed to push on the bottom surface 4 of a corresponding group of cigarettes 2 to push the group of cigarettes 2 along the longitudinal folding path P2. In addition, the longitudinal packaging conveyor 19 comprises a fixed surface 22 (i.e. without moving parts and shown in Figure 16) that is positioned above the conveyor belt 20 and slidingly supports each package 1 (i.e. each group of cigarettes 2 combined with the corresponding sheet 9 of packing material) ; in other words, each package 1 is pushed along the longitudinal folding path P2 by a pusher 21 to slide on the fixed surface 22. The fixed surface 22 has a through slit arranged parallel to the longitudinal folding path P2 and inside which support rods pass, each of which mechanically connects a pusher 21 to the underlying conveyor belt 20.

According to a preferred embodiment shown in Figures 14 and 15, each pusher 21 has a pair of stabilizer teeth 23, which are arranged on opposite sides of the group of cigarettes 2 and which slot into the open spaces at the sides of the intermediate layer of cigarettes (having one cigarette less with respect the outer layers of cigarettes) to keep the shape of the group of cigarettes 2 stable. According to that shown in Figures 14 and 15, each drawer of the group-forming conveyor has a through slit at the bottom, arranged parallel to the longitudinal folding path P2 and inside which the support rods pass, each of which mechanically connects a pusher 21 to the underlying conveyor belt 20; in this way, each pusher 21 can extract a package 1 (i.e. a group of cigarettes 2 combined with the corresponding sheet 9 of packing material) from the drawer (shown on the right) of the group-forming conveyor.

According to that shown in Figures 16-20, the longitudinal folding station 14 comprises a pair of fixed central folding devices 24 on each side of the longitudinal folding path P2 that push, at the respective open lateral end 16 of the package 1, the two central portions 17 of the sheet 9 of packing material towards each other so as to superimpose the two central portions 17 to form a longitudinal fin 25 (shown in Figures 10 and 20) arranged perpendicularly to an underlying smaller lateral surface 6 of the group of cigarettes 2. According to that shown in Figures 13 and 15, the longitudinal folding station 14 comprises a lateral folding device 26 on each side of the longitudinal folding path P2 that is separate from and independent of the central folding devices 24, and folds the lateral portion 18 of the sheet 9 of packing material to give a V-shape to the lateral portion 18 at least at the start of the folding of the two central portions 17 of the sheet 9 of packing material towards each other. In other words, when the folding of the two central portions 17 of the sheet 9 of packing material towards each other starts in each open lateral end 16 under the action of the central folding devices 24, at the same time the lateral folding device 26 folds the lateral portion 18 of the sheet 9 of packing material to give a V-shape to the lateral portion 18. It is important to note that each lateral folding device 26 intervenes at least at the start of the folding of the central portions 17 of the sheet 9 of packing material towards each other and preferably accompanies the folding of the central portions 17 of the sheet 9 of packing material during most of the folding in synchronization with operation of the central folding devices 24 (i.e. each lateral folding device 26 only leaves the corresponding lateral portion 18 of the sheet 9 of packing material when the central portions 17 of the sheet 9 of packing material are so close together that there is no longer the space necessary to accommodate the lateral folding device 26) .

As already stated in the foregoing, the central folding devices 24 are fixed and positioned along the longitudinal folding path P2; on the contrary, each lateral folding device 26 is advanced along the longitudinal folding path P2 in synchronization with a corresponding package 1 (i.e. with a corresponding group of cigarettes 2 combined with a sheet 9 of packing material) . According to a preferred embodiment shown in Figures 13 and 15, each lateral folding device 26 is carried by a belt conveyor 27 that cyclically advances the lateral folding device 26 along an annular path and is positioned along the longitudinal folding path P2. In particular, each belt conveyor 27 comprises an endless-loop conveyor belt 28 that is wrapped around two pulleys 29 (one of which is powered) mounted to rotate about respective axes 30 of rotation arranged perpendicularly with respect to the longitudinal folding path P2.

In the embodiment shown in Figures 5-8 and in the lower half of Figure 15, each lateral folding device 26 folds the lateral portion 18 of the sheet 9 of packing material outwardly from the two central portions 17 of the sheet 9 of packing material in such a way that the lateral portion 18 does not become caught between the two central portions 17 (as clearly visible in Figure 7) . In this embodiment, the longitudinal packaging conveyor 19 feeds each group of cigarettes 2 combined with a sheet 9 of packing material along the longitudinal folding path P2 at a speed VI (schematically shown in Figure 15); whereas each belt conveyor 27 advances the corresponding lateral folding device 26 along the longitudinal folding path P2 at a speed V2 higher than speed VI, such that the lateral folding device 26 pushes on a surface of the lateral portion 18 of the sheet 9 of packing material facing the central portions 17 of the sheet 9 of packing material (i.e. it pushes the lateral portion 18 outwards from the inside to make it assume the ^λν' shape shown in Figure 7) .

In the embodiment shown in Figures 9-12 and in the upper half of Figure 15, each lateral folding device 26 folds the lateral portion 18 of the sheet 9 of packing material inwardly to the two central portions 17 of the sheet 9 of packing material in such a way that the lateral portion 18 becomes caught between the two central portions 17 (as clearly visible in Figure 11) . In this embodiment, the longitudinal packaging conveyor 19 feeds each group of cigarettes 2 combined with the sheet 9 of packing material along the longitudinal folding path P2 at a speed VI (schematically shown in Figure 15); whereas each belt conveyor 27 advances the corresponding lateral folding device 26 along the longitudinal folding path P2 at a speed V3 lower than speed VI, such that the lateral folding device 26 pushes a surface of the lateral portion 18 of the sheet 9 of packing material opposite to the central portions 17 of the sheet 9 of packing material (i.e. it pushes the lateral portion 18 inwards from the outside to make it assume the ^λν' shape shown in Figure 11) .

It is important to note that there is no type of physical change between the embodiment shown in Figures 5-8 and in the lower half of Figure 15 and the embodiment shown in Figures 9- 12 and in the upper half of Figure 15 (i.e. the structure remains the same) , but only a change in the timing of the two belt conveyors 27 with respect to the timing of the longitudinal packaging conveyor 19. In other words, in the embodiment shown in Figures 5-8 and in the lower half of Figure 15, each lateral folding device 26 is delayed and faster with respect to the longitudinal packaging conveyor 19, whereas in the embodiment shown in Figures 9-12 and in the upper half of Figure 15, each lateral folding device 26 is in advance and slower with respect to the longitudinal packaging conveyor 19. This timing change can be conveniently performed by acting just on the control software, without requiring any physical change to the packing unit 11.

According to a preferred (but not mandatory) embodiment shown in Figure 16, the central folding devices 24 are incorporated in a fixed tubular body 31 that has an inner channel 32 (aligned parallel to the longitudinal folding path P2) inside which the packages 1 (i.e. the groups of cigarettes 2 combined with the corresponding sheets 9 of packing material) are made to advance in succession. The tubular body 31 has a truncated- cone shape with a cross-section (shown in Figures 17-20) progressively decreasing along the longitudinal folding path P2. As clearly shown in Figures 13 and 15, each belt conveyor 27 is inclined to follow the truncated-cone shape of the tubular body 31 (i.e. to maintain a constant distance from the tubular body 31) . According to that shown in Figure 16, the tubular body 31 has, on each side, a corresponding through slit 33 that is aligned parallel to the longitudinal folding path P2 and is designed to allow the passage of a corresponding lateral folding device 26. Each through slit 33 physically separates the two corresponding central folding devices 24, which are positioned to face each other from opposite sides of the through slit 33. The tubular body 31 is composed of a number of separate parts (due to the presence of the lateral slits 33 and the bottom slit) and preferably can be opened at the top to facilitate cleaning operations.

According to that shown in Figure 13, the longitudinal folding station 14 comprises a heat-sealing device 34 (schematically shown in Figure 13) of known type that seals together the two superimposed two central portions 17 on each side of the package 1 so as to stabilize the longitudinal fin 25. By way of example, the heat-sealing device 34 could comprise heat- sealing grippers that grip the longitudinal fins 25 together (preferred solution when the packing unit 11 works intermittently, cyclically alternating motion steps and stationary steps), or the heat-sealing device 34 could comprise heat-sealing rollers between which the longitudinal fins 25 are compressed (preferred solution when the packing unit 11 works continuously) . According to that shown in Figure 13, the longitudinal folding station 14 comprises a folding device 35 (of known type and normally comprising fixed folding profiles), which is arranged downstream of the heat-sealing device 34 on opposite sides of the longitudinal folding path P2 to fold each longitudinal fin 25 by 90° so that the longitudinal fin 25 rests against the package 1 (i.e. to make the longitudinal fin 25 parallel to an underlying smaller lateral surface 6 of the group of cigarettes 2 ) .

In the embodiment shown in Figures 5-8, each longitudinal fin 25 comprises two top ends 36 (i.e. two 'ears' , as better seen in Figure 6) , each of which protrudes beyond the underlying smaller lateral surface 6 of the group of cigarettes 2 (i.e. protrudes beyond the top surface 3 of the group of cigarettes 2) . In this embodiment and as shown in Figure 13, the longitudinal folding station 14 comprises a folding device 37 (of known type and normally comprising movable folding profiles), which is arranged downstream of the folding device 35 on opposite sides of the longitudinal folding path P2 to fold each top end 36 of a corresponding longitudinal fin 25 by 180° so as to fold back the top end 36 onto the longitudinal fin 25. Obviously, the folding device 37 is not present (or deactivated) in the embodiment shown in Figures 9-12, as in this embodiment the longitudinal fins 25 are devoid of the top ends 36 due to the different way of folding the lateral portions 18 of the sheet 9 of packing material.

According to that shown in Figure 21, at the end of the longitudinal folding station 14 (i.e. at the entrance to the transverse folding station 15) , each package 1 has an open bottom end 38, which leaves the bottom surface 4 of the group of cigarettes 2 visible. The open bottom end 38 has two central portions 39 that project from the group of cigarettes 2 (and constitute the continuation of the larger lateral surfaces 5 of the group of cigarettes 2) and two lateral portions 40 that project from the group of cigarettes 2 (and constitute the continuation of the smaller lateral surfaces 6 of the group of cigarettes 2), each of which is perpendicular to and connects the two central portions 39. The transverse folding station 15 comprises a transverse folding conveyor (known and not shown), which feeds the packages 1 in succession (each one composed of a sheet 9 of packing material folded in a tube around a corresponding group of cigarettes 2) along the transverse folding path P3, which is straight and perpendicular to the longitudinal folding path P2 (and therefore parallel to the group-forming path PI) . In other words, the transverse folding conveyor receives the packages 1 from the longitudinal packaging conveyor 19 in succession in a transfer area; the groups of cigarettes 2 are fed longitudinally along the longitudinal folding conveyor 19 (i.e. the cigarettes are arranged parallel to the longitudinal folding path P2), while along the transverse folding conveyor the groups of cigarettes 2 are fed transversely (i.e. the cigarettes are arranged perpendicularly to the transverse folding path P3) .

According to that shown in Figures 21, 22 and 23, the transverse folding station 15 comprises a pair of movable central folding devices 41 (cooperating with each other) on one side only of the transverse folding path P3 that fold, at the open bottom end 38 of the package 1, the two central portions 39 of each sheet 9 of packing material towards each other so as to superimpose the two central portions 39 on each other to form a transverse fin 42 (partially shown in Figures 8 and 12) perpendicular to an underlying bottom surface 4 of the group of cigarettes 2. In other words, the two central folding devices 41 are movable, and are moved towards each other to grip the two central portions 39 of the sheet 9 of packing material between them and thus form the transverse fin 42. When the packing unit 11 works intermittently, cyclically alternating motion steps and stationary steps, the central folding devices 41 grips the two central portions 39 of each package 1 together during a stationary step (i.e. when the package 1 is stationary in front of the central folding devices 41) ; when the packing unit 11 works continuously, the central folding devices 41 move along the transverse folding path P3 in synchronization with the transverse folding path P3 to follow each package 1 during a stage of its advancement.

According to that shown in Figures 21, 22 and 23, the transverse folding station 15 comprises a pair of lateral folding devices 43 on one side only of the transverse folding path P3, which are separate from and independent of the central folding devices 41, and fold the lateral portions 40 of the sheet 9 of packing material to give a V-shape to the lateral portions 40 at the start of the folding of the two central portions 39 of the sheet 9 of packing material towards each other. In other words, when the folding of the two central portions 39 of the sheet 9 of packing material towards each other starts in each open bottom end 38 under the action of the central folding devices 41, each lateral folding device 43 folds the corresponding lateral portion 40 of the sheet 9 of packing material to give a V-shape to the lateral portion 40. The two lateral folding devices 43 can move towards each other and are moved towards the lateral portions 40 of the sheet 9 of packing material to give a V-shape to the lateral portions 40. According to a preferred embodiment shown in Figures 21, 22 and 23, each lateral folding device 43 has a wedge-like shape with the tip oriented towards the corresponding lateral portion 40 of the sheet 9 of packing material. It is important to note that each lateral folding device 43 intervenes at least at the start of the folding of the central portions 39 of the sheet 9 of packing material towards each other and preferably accompanies the folding of the central portions 39 of the sheet 9 of packing material during most of the folding in synchronization with operation of the central folding devices 41 (i.e. each lateral folding device 43 only leaves the corresponding lateral portion 40 of the sheet 9 of packing material when the central portions 39 of the sheet 9 of packing material are so close together that there is no longer the space necessary to accommodate the lateral folding device 43) . According to a preferred embodiment, the two central folding devices 41 are also heated (for example, internally equipped with electric heat resistances) to also act as heat sealers, i.e. for heat sealing two superimposed central portions 39 to stabilize the transverse fin 42; in other words, the heat- sealing device that stabilizes the transverse fin 42 is integrated into the two central folding devices 41. According to one possible embodiment, an additional (gripper or roller) heat-sealing device that further repeats (i.e. completes) the heat sealing of the transverse fin 42 could be provided immediately downstream of the two central folding devices 41.

According to a preferred embodiment shown in Figures 24, 25 and 26, in a folding movement (in which the two central portions 39 are superimposed on each other) , each central folding device 41 moves according to (i.e. follows) a circular trajectory Tl such that the part of the central folding device 41 in contact with a corresponding central portion 39 of the sheet 9 of packing material covers an arc of a circle centred on a fold line 44 (visible in Figures 22 and 23) of the central portion 39 located along an edge of the group of cigarettes 2. Preferably, the circular trajectory Tl of each central folding device 41 has a radius equal to the distance between the fold line 44 (visible in Figures 22 and 23) of the corresponding central portion 39 of the sheet 9 of packing material and a corresponding inner edge 45 (visible in Figures 22 and 23) of the transverse fin 42 (i.e. the inner edge 45 of the transverse fin 42 facing the fold line 44) . Preferably (but not mandatorily) , in a return movement following the folding movement, each central folding device 41 follows the circular trajectory Tl backwards.

According to a preferred embodiment shown in Figures 24, 25 and 26, in a folding movement (in which a lateral portion 40 of the sheet 9 of packing material is folded into a ^λν' ) , each lateral folding device 43 moves according to (i.e. follows) a circular trajectory T2 such that a point of the lateral folding device 43 in contact with the corresponding lateral portion 40 of the sheet 9 of packing material covers an arc of a circle centred on a fold line 46 (visible in Figures 22 and 23) of the lateral portion 40 located along an edge of the group of cigarettes 2. Preferably, the circular trajectory T2 of each lateral folding device 43 has a radius equal to the distance between the fold line 46 (visible in Figures 22 and 23) of the corresponding lateral portion 40 of the sheet 9 of packing material and a corresponding inner edge 47 (visible in Figures 22 and 23) of the transverse fin 42 (i.e. the inner edge 47 of the transverse fin 42 facing the fold line 46) . In a return movement following the folding movement, each lateral folding device 43 moves according to (i.e. follows) a straight trajectory T3, which is clearly different from the circular trajectory T2; in this way, mechanical interference between the lateral folding devices 43 and the transverse fin 42 just formed is avoided. Due to the circular movement (i.e. along an arc of a circle) of the folding devices 41 and 43, it is possible to improve the folding quality of the sheet 9 of packing material as the folding devices 41 and 43 follow and support the natural deformation of the sheet 9 of packing material.

Figure 27 shows a variant of the packing unit 11 shown in Figures 5 and 9; this variant has two main differences: the group-forming path PI is L-shaped and the transverse folding path P3 is circular.

Figure 28 shows a variant of the group-forming station 12 of the packing unit 11 in Figure 27, in which each drawer of the group-forming conveyor has a strengthening element 10 inserted beforehand and inside which a corresponding group of cigarettes 2 will be subsequently inserted. The above-described packing unit 11 has numerous advantages.

First of all, the folding of the sheet 9 of packing material in the above-described packing unit 11 results in reduced mechanical stress on the cigarettes in the group of cigarettes 2; in consequence, even when operating at high production speeds, the cigarettes in the group of cigarettes 2 are not damaged during folding of the sheet 9 of packing material. During the folding of the sheet 9 of packing material to produce the fins 25 and 42, the group of cigarettes 2 is not subjected to any type of mechanical stress. Furthermore, due to the combined action of the central folding devices 24 and 41 and the lateral folding devices 26 and 43, the folding of the sheet 9 of packing material takes place with very high quality folds, even at high production speeds. In this way, folding of the fins 25 and 42 can be performed with high quality and in very short times (and so is compatible with the speed requirements of fast, modern packing machines) .

During the heat sealing of the fins 25 and 42, the sheet 9 of packing material is not pressed against the group of cigarettes 2, but is gripped between two metal parts; in this way, it is possible to perform the heat sealing by pressing the superimposed portions under high pressure and heating the superimposed portions to a high temperature without any damage to the cigarettes in the group of cigarettes 2. In this way, the heat sealing of the fins 25 and 42 can be performed with a high level of quality and in very short times (and so is compatible with the speed requirements of fast, modern packing machines) .

Finally, the above-described packing unit 11 is also simple and inexpensive to manufacture, as it is composed of structurally simple elements that have few, easily implemented movements .

Claims

1) A packing method for folding a sheet (9) of packing material around a parallelepiped-shaped product (2) having a top surface (3) and a bottom surface (4) opposite each other, and two opposite lateral surfaces (6); the packing method comprising the steps of:

folding the sheet (9) of packing material around the product (2) to form a package (1) having at least one open end (16; 38), where the sheet (9) of packing material has two opposite parallel central portions (17; 39) projecting from the product (2) and at least one lateral portion (18; 40), which projects from the product (2) and is perpendicular to and connects the two central portions (17; 39);

folding the two central portions (17; 39) of the sheet (9) of packing material, at the open end (16; 38) of the package (1), towards each other by means of two central folding devices (24; 41), so as to superimpose the two central portions (17;

39) to form a fin (25; 42) perpendicular to the underlying surface (6; 4) of the product (2); and

heat sealing the two superimposed central portions (17; 39) to each other to stabilize the fin (25; 42);

the packing method being characterized by comprising, at least at the start of the step of folding the two central portions (17; 39) of the sheet (9) of packing material towards each other, the further step of folding the lateral portion (18;

40) of the sheet (9) of packing material into a ^λν' shape by means of a lateral folding device (26; 43) separate from and independent of the central folding devices (24; 41) .

2) A packing method according to claim 1, wherein the lateral folding device (26; 43) folds the lateral portion (18; 40) of the sheet (9) of packing material inwards to the two central portions (17; 39) of the sheet (9) of packing material, so that the lateral portion (18; 40) is gripped between the two central portions (17; 39) . 3) A packing method according to claim 1, wherein the lateral folding device (26; 43) folds the lateral portion (18; 40) of the sheet (9) of packing material outwards from the two central portions (17; 39) of the sheet (9) of packing material, so that the lateral portion (18; 40) is not gripped between the two central portions (17; 39) .

4) A packing method according to claim 1, 2 or 3, wherein:

the product (2), with the sheet (9) of packing material applied, is fed along a longitudinal folding path (P2) ;

the central folding devices (24) are fixed and located immovably along the longitudinal folding path (P2) ; and the lateral folding device (26) is moved along the longitudinal folding path (P2) in synchronization with the product (2) with the sheet (9) of packing material applied.

5) A packing method according to claim 4, and comprising the further steps of:

feeding the product (2), with the sheet (9) of packing material applied, along the longitudinal folding path (P2) at a first speed (VI) ; and

moving the lateral folding device (26) along the longitudinal folding path (P2) at a second speed (V2) higher than the first speed (VI), so that the lateral folding device (26) pushes on a surface of the lateral portion (18) of the sheet (9) of packing material facing the central portions (17) of the sheet (9) of packing material. 6) A packing method according to claim 4, and comprising the further steps of:

moving the lateral folding device (26) along the longitudinal folding path (P2) at a third speed (V3) slower than the first speed (VI), so that the lateral folding device (26) pushes on a surface of the lateral portion (18) of the sheet (9) of packing material facing away from the central portions (17) of the sheet (9) of packing material.

7) A packing method according to claim 4, 5 or 6, wherein the central folding devices (24) are incorporated in a fixed tubular body (31) having an inner channel (32) inside which the product (2), with the sheet (9) of packing material applied, is fed.

8) A packing method according to claim 7, wherein the tubular body (31) has a through slit (33) parallel to the longitudinal folding path (P2) and allowing passage of the lateral folding device (26) .

9) A packing method according to any one of claims 4 to 8, wherein the lateral folding device (26) is fitted to a belt conveyor (27) that cyclically advances the lateral folding device (26) along an annular path and is located along the longitudinal folding path (P2) .

10) A packing method according to any one of claims 1 to 9, and comprising the further step of placing a centre portion of the sheet (9) of packing material on the top surface (3) of the product (2) and folding the sheet (9) of packing material into a ^λυ' around the product (2), so as to form a U-shaped package (1) having two open lateral ends (16), each of which has two central portions (17) and a single lateral portion (18) located at the top surface (3) of the product (2) .

11) A packing method according to claim 1, 2 or 3, wherein: the central folding devices (41) are movable, and are moved towards each other to superimpose the two central portions (39) of the sheet (9) of packing material and so form the fin (42) ; and the lateral folding device (43) is movable, and is moved towards the lateral portion (40) of the sheet (9) of packing material to fold said lateral portion (40) into a ^λν' shape. 12) A packing method according to claim 11, wherein, in a folding movement, each central folding device (41) travels along a circular first trajectory (Tl), so that the part of the central folding device (41) in contact with the central portion (39) of the sheet (9) of packing material travels along an arc of a circle centred on a fold line (44) of the central portion (39) located along an edge of the product (2) .

13) A packing method according to claim 12, wherein the circular first trajectory (Tl) of each central folding device (41) has a radius equal to the distance between the fold line (44) of the corresponding central portion (39) of the sheet (9) of packing material and a corresponding inner edge (45) of the fin (42) . 14) A packing method according to claim 11, 12 or 13, wherein, in a folding movement, the lateral folding device (43) travels along a circular second trajectory (T2), so that a tip of the lateral folding device (43) in contact with the lateral portion (40) of the sheet (9) of packing material travels along an arc of a circle centred on a fold line (46) of the lateral portion (40) located along an edge of the product (2) .

15) A packing method according to claim 14, wherein the circular second trajectory (T2) of the lateral folding device (43) has a radius equal to the distance between the fold line (46) of the corresponding lateral portion (40) of the sheet (9) of packing material and a corresponding inner edge (47) of the fin (42) . 16) A packing method according to claim 14 or 15, wherein, in a return movement after the folding movement, the lateral folding device (43) travels along a straight third trajectory (T3) .

17) A packing method according to any one of claims 11 to 16, wherein the lateral folding device (43) is wedge-shaped with its tip oriented towards the lateral portion (40) of the sheet (9) of packing material.

18) A packing method according to any one of claims 11 to 17, and comprising the further step of placing a centre portion of the sheet (9) of packing material on the top surface (3) of the product (2) and folding the sheet (9) of packing material around the product (2), so as to form a tubular package (1) having one open end (38), which is located close to the rear surface (4) of the product (2) and has two central portions (39) and two lateral portions (40) .

19) A packing method according to any one of claims 11 to 18, wherein the two central folding devices (41) are heated to heat seal the two superimposed central portions (39) together and so stabilize the fin (42) .

20) A packing method according to any one of claims 1 to 19, and comprising the further step of folding the fin (25; 42) by 90° to make the fin (25; 42) parallel to an underlying surface (6; 4) of the product (2) .

21) A packing method according to claim 20, and comprising the further step of folding a top end (36) of the fin (25), projecting from the underlying surface (6) of the product (2), by 180° .

22) A packing method according to any one of claims 1 to 21, wherein each lateral folding device (26; 43) intervenes at least when starting to fold the central portions (17; 39) of the sheet (9) of packing material towards each other, and accompanies the folding of the central portions (17; 39) of the sheet (9) of packing material during most of the folding in synchronization with operation of the central folding devices (24; 41) .

23) A packing unit (11) for folding a sheet (9) of packing material around a parallelepiped-shaped product (2) having a top surface (3) and a bottom surface (4) opposite each other, and two opposite lateral surfaces (6) ; the packing unit (11) comprising:

a folding station (14; 15) for folding the sheet (9) of packing material around the product (2) to form a package (1) having at least one open end (16; 38) where the sheet (9) of packing material has two opposite parallel central portions (17; 39) projecting from the product (2), and at least one lateral portion (18; 40), which projects from the product (2) and is perpendicular to and connects the two central portions (17; 39) ;

two central folding devices (24; 41) for folding the two central portions (17; 39) of the sheet (9) of packing material at the open end (16; 38) of the package (1) towards each other, so as to superimpose the two central portions (17; 39) and form a fin (25; 42) perpendicular to an underlying surface

(6; 4) of the product (2) ; and

a heat-sealing device (34) for heat sealing the two superimposed central portions (17; 39) to each other to stabilize the fin (25; 42) ;

the packing unit (11) being characterized by comprising a lateral folding device (26; 43) separate from and independent of the central folding devices (24; 41), and which, at least when starting to fold the two central portions (17; 39) of the sheet (9) of packing material towards each other, folds the lateral portion (18; 40) of the sheet (9) of packing material into a ^λν' shape .