EP1055603A1

EP1055603A1 - Method and machine for wrapping a product in a sheet of heat-shrink wrapping material

Info

Publication number: EP1055603A1
Application number: EP00111211A
Authority: EP
Inventors: Fiorenzo Draghetti; Saverio Martini
Original assignee: GD SpA
Current assignee: GD SpA
Priority date: 1999-05-27
Filing date: 2000-05-24
Publication date: 2000-11-29
Also published as: IT1309272B1; ITBO990294A1; ITBO990294A0

Abstract

A method and machine for wrapping a product (2) in a sheet (3) of heat-shrink wrapping material, whereby the product (2) is wrapped in the sheet (3) of wrapping material to form an overwrapped product (27), which is fed to a station (32) where two opposite surfaces (30) of the overwrapped product (27) are brought into contact with respective heated endless conveyors (34).

Description

The present invention relates to a method of wrapping a product in a sheet of heat-shrink wrapping material.
The present invention is particularly advantageous for use on machines for cellophaning packets of cigarettes, to which the following description refers purely by way of example.
Known machines for cellophaning packets of cigarettes normally comprise a first wrapping wheel, on which a sheet of heat-shrink wrapping material is folded about a packet of cigarettes to form a tubular wrapping, which is stabilized by means of a longitudinal seal and has two tubular end portions, each projecting from a respective end wall of the packet.
At the output of the first wrapping wheel, the packet and respective tubular wrapping are normally fed through a folding station where each projecting tubular portion of the tubular wrapping is folded onto the respective end wall to form a closed outer overwrapping, which, as it is conveyed, together with the respective packet, on a second wrapping wheel, is stabilized by two end seals.
Finally, the overwrapped packet is fed to an output station of the cellophaning machine, where it is normally heat treated to shrink the sheet of wrapping material about the packet.
The heat treatment normally comprises feeding the overwrapped packet along a tunnel maintained at a given temperature by a stream of hot air or by a beam of infrared radiation.
Heat-shrinking as described above involves several drawbacks, mainly due to the whole surface of the outer wrapping of each packet being exposed to a poorly controlled amount of heat, which shrinks the wrapping not only to the extent of deforming the packet and later making the wrapping difficult to remove, but also unequally from one point to another, thus resulting in the formation of wrinkles.
It is an object of the present invention to provide a method of wrapping a product in a sheet of heat-shrink wrapping material, designed to eliminate the aforementioned drawbacks.
According to the present invention, there is provided a method of wrapping a product in a sheet of heat-shrink wrapping material, the method comprising the steps of wrapping the product in said sheet of wrapping material to form an overwrapped product having an outer wrapping comprising at least two opposite surfaces substantially parallel to each other; and feeding said overwrapped product through a heat-shrink station; and being characterized in that the overwrapped product, as it is fed through said heat-shrink station, travels with the two opposite surfaces of said outer wrapping directly contacting respective heated surfaces defining, in between, a channel for the passage of said overwrapped product through the heat-shrink station.
Preferably, the overwrapped product is fed through said heat-shrink station by means of two heated endless conveyors facing each other, and each having a conveying portion contacting a respective one of said two opposite surfaces; each said conveying portion defining a respective said heated surface.
In a preferred embodiment of the above method, each said opposite surface is defined by a respective continuous, i.e. seamless, portion of the sheet of wrapping material.
By contact heating only the continuous opposite surfaces - normally the major lateral surfaces - of the outer wrapping, it is possible not only to accurately control shrinkage of the outer wrapping by transferring, by contact, a controlled amount of heat to the sheet of wrapping material, but also to prevent heat being transmitted to the lateral surface - normally a minor lateral surface - of the outer wrapping sealed longitudinally to stabilize the tubular wrapping, and so prevent any unevenness along the longitudinal seal from resulting in the formation of unacceptable creases or wrinkles in the course of the heat-shrink operation.
The present invention also relates to a machine for wrapping a product in a sheet of heat-shrink wrapping material.
According to the present invention, there is provided a machine for wrapping a product in a sheet of heat-shrink wrapping material, the machine comprising wrapping means for wrapping the product in said sheet of wrapping material and forming an overwrapped product having an outer wrapping comprising at least two opposite surfaces substantially parallel to each other; and a heat-shrink station; and being characterized by comprising two heated surfaces located at said heat-shrink station and defining, in between, a channel for the passage of said overwrapped product; each said heated surface coming into direct contact with a respective said opposite surface as said overwrapped product is fed through said heat-shrink station.
In a preferred embodiment of the above machine, said two heated surfaces are so located as to engage respective continuous, i.e. seamless, portions of the sheet of wrapping material; each said continuous portion defining a respective one of said two opposite surfaces of the outer wrapping.
Preferably, each said heated surface is defined by a conveying portion of a respective heated endless conveyor.
The present invention will be described with reference to the accompanying drawing, which shows a schematic side view, with enlarged details and parts removed for clarity, of a non-limiting embodiment.
Number 1 in the accompanying drawing indicates as a whole a cellophaning machine for wrapping a packet 2 of cigarettes in a respective sheet 3 of transparent heat-shrink wrapping material.
Machine 1 comprises a frame 4; and a wrapping wheel 5 fitted to a powered shaft 6, which in turn is fitted to frame 4 to rotate in steps, with respect to frame 4 and in a given direction (anticlockwise in the drawing), about an axis 7 perpendicular to the plane of the accompanying drawing.
Wheel 5 is a known type, and comprises a number of pockets 8 equally spaced along the periphery of wheel 5, and which are substantially U-shaped and open both radially and axially outwards.
When arrested at a loading station 9, each pocket 8 receives a respective sheet 3 of wrapping material fed to station 9 by a known feed device 10; and a respective packet 2, which is inserted, in known manner at station 9, inside respective pocket 8 so as to fold sheet 3 into a U about packet 2.
In connection with the above, it should be pointed out that, on machine 1, packet 2 is fed by wheel 5, and by successive conveying devices described later on, along a wrapping path P with the longitudinal axis 2a of the packet crosswise at all times to path P and to the plane of the accompanying drawing.
As packet 2 and respective sheet 3 are fed by wheel 5 from loading station 9 to an unloading station 11, sheet 3 is folded about packet 2 (as of said U-shaped configuration) by a known movable folding device 12a and a known fixed folding device 12b, to form a tubular wrapping 13, which is stabilized by a longitudinal edge seal made by a known sealing device 14 during one of the stops of wheel 5, and comprises two tubular end portions 15, each projecting from a respective end wall 16 of packet 2.
Wheel 5 comprises, in known manner, two coaxial, parallel disks 17 (only one shown in the accompanying drawing) fitted to shaft 6, and each having a number of peripheral seats 18, each of which, together with a corresponding seat 18 on the other disk 17, defines a respective pocket 8.
Machine 1 also comprises an endless conveyor 19, in turn comprising a belt 20 looped about a number of pulleys 21 having respective axes 22 parallel to axis 7 of wheel 5. Belt 20 comprises a number of push elements 23 equally spaced along belt 20 and defining a succession of pockets 24, each of a length at least equal to the width of a packet 2 measured parallel to path P.
One of pulleys 21 (hereinafter referred to as 21a) is powered to rotate continuously in a given direction (anticlockwise in the accompanying drawing) about respective axis 22. In a further embodiment not shown, pulley 21a may be powered to rotate in steps about axis 22. At unloading station 11, conveyor 19 extends between disks 17 of wheel 5 to enable one of push elements 23 to extract a respective packet 2 and respective tubular wrapping 13 from a respective pocket 8, and feed the packet and tubular wrapping through a folding station 25 having a number of known folding devices 26 for each of the two tubular portions 15 of tubular wrapping 13. Each number of folding devices 26 comprises two movable folding devices 26a, 26b for folding two walls, arranged crosswise to path P, of respective tubular portion 15 onto the relative end wall 16 of respective packet 2; and a fixed helical folding device 26c for folding two walls, arranged parallel to path P, of respective tubular portion 15 onto the relative end wall 16 of respective packet 2 to form an overwrapped packet 27.
At the output of station 25, overwrapped packet 27 therefore comprises a closed outer wrapping 28, which is stabilized by two end seals made as the overwrapped packet 27 travels along a portion of path P defined by the periphery of pulley 21a. For which purpose, pulley 21a comprises, in known manner, a number of pairs of facing sealing devices 29 equally spaced about pulley 21a and movable with pulley 21a in time with pockets 24. At the output of pulley 21a, each outer wrapping 28 is therefore substantially parallelepiped-shaped with a rectangular section, and with two major lateral surfaces 30 parallel to each other and each defined by a respective continuous portion of sheet 3 of wrapping material, i.e. a portion unaffected by the stabilizing seals described above.
At the output of pulley 21a, conveyor 19 feeds the overwrapped packet 27 "laid flat" - i.e. with surfaces 30 of outer wrapping 28 positioned horizontally and with axis 2a crosswise to path P - along a plate 31 and towards an output station 32 of machine 1.
Finally, machine 1 comprises a heat-shrink device 33 defining output station 32, and which provides for feeding the overwrapped packet 27 through output station 32 and simultaneously performing heat treatment to shrink sheet 3 of wrapping material about packet 2. For which purpose, device 33 comprises two belt conveyors 34 arranged one over the other beneath path P, and each comprising a respective belt 35, which travels in contact with a respective plate 36 heated to a given temperature by electric resistors (not shown) embedded in plate 36 and controlled by a known temperature control device 37. Each belt 35 is looped about a pair of pulleys 38 - one of which is powered - fitted to frame 4 to rotate about respective axes 39 parallel to axis 7.
Each belt 35 comprises a horizontal conveying portion 40 extending parallel to path P and facing the conveying portion 40 of the other belt 35 to define a channel 41, along which the overwrapped packet 27 is fed with surfaces 30 of outer wrapping 28 directly contacting conveying portions 40.
Operation of machine 1 is easily deducible from the foregoing description with no further explanation required. It should, however, be stressed that, by heating sheet 3 of wrapping material by direct contact with conveying portions 40, a given precise amount of heat can be transmitted to sheet 3, by conduction and through surfaces 30, to achieve a predetermined amount of shrinkage of outer wrapping 28 about packet 2. Moreover, by heating sheet 3 by direct contact at continuous surfaces 30 only, i.e. the surfaces with no sealed joins, it is possible not only to accurately control shrinkage of outer wrapping 28 about packet 2, but also to prevent heat being transmitted to the lateral surfaces - normally one of the minor lateral surfaces and the two end surfaces - of outer wrapping 28 having respective seals for stabilizing outer wrapping 28, and so prevent any unevenness along the seals from resulting in the formation of unacceptable creases and/or wrinkles in the course of the heat-shrink operation.

Claims

A method of wrapping a product in a sheet of heat-shrink wrapping material, the method comprising the steps of wrapping the product (2) in said sheet of wrapping material to form an overwrapped product (27) having an outer wrapping (28) comprising at least two opposite surfaces (30) substantially parallel to each other; and feeding said overwrapped product (27) through a heat-shrink station (32); and being characterized in that the overwrapped product (27), as it is fed through said heat-shrink station (32), travels with the two opposite surfaces (30) of said outer wrapping (28) directly contacting respective heated surfaces (40) defining, in between, a channel (41) for the passage of said overwrapped product (27) through the heat-shrink station (32).
A method as claimed in Claim 1, characterized in that said overwrapped product (27) is fed through said heat-shrink station (32) by means of two heated endless conveyors (34) facing each other, and each having a conveying portion (40) contacting a respective one of said two opposite surfaces (30); each said conveying portion (40) defining a respective said heated surface (40).
A method as claimed in claim 1 or 2, characterized in that each said opposite surface (30) is defined by a respective continuous, i.e. seamless, portion (30) of the sheet (3) of wrapping material.
A method as claimed in any one of Claims 1 to 3, characterized in that said overwrapped product (27) is substantially in the form of a rectangular-section parallelepiped having two opposite major lateral surfaces (30); each said heated surface (40) coming into direct contact with a respective said major lateral surface (30).
A method as claimed in Claim 4, characterized in that the overwrapped product (27) is fed between said heated surfaces (40) with said major lateral surfaces (30) in a substantially horizontal position.
A method as claimed in any one of Claims 2 to 5, characterized in that each said endless conveyor (34) comprises a belt conveyor (34).
A machine for wrapping a product in a sheet of heat-shrink wrapping material, the machine comprising wrapping means (5, 26, 21a) for wrapping the product (2) in said sheet (3) of wrapping material and forming an overwrapped product (27) having an outer wrapping (28) comprising at least two opposite surfaces (30) substantially parallel to each other; and a heat-shrink station (32); and being characterized by comprising two heated surfaces (40) located at said heat-shrink station (32) and defining, in between, a channel (41) for the passage of said overwrapped product (27); each said heated surface (40) coming into direct contact with a respective said opposite surface (30) as said overwrapped product (27) is fed through said heat-shrink station (32).
A machine as claimed in Claim 7, characterized in that said two heated surfaces (40) are so located as to engage respective continuous, i.e. seamless, portions (30) of the sheet (3) of wrapping material; each said continuous portion (30) defining a respective one of said two opposite surfaces (30) of the outer wrapping (28).
A machine as claimed in Claim 7 or 8, characterized in that said overwrapped product (27) is substantially in the form of a rectangular-section parallelepiped having two opposite major lateral surfaces (30); each said heated surface (40) coming into direct contact with a respective said major lateral surface (30).
A machine as claimed in any one of Claims 7 to 9, characterized in that each said heated surface (40) is defined by a conveying portion (40) of a respective heated endless conveyor (34).
A machine as claimed in Claim 10, characterized in that each said conveying portion (40) lies in a respective horizontal plane.