WO2000068128A1

WO2000068128A1 - Device for joining together two packaging films for packaging machines of the 'flow-pack' type

Info

Publication number: WO2000068128A1
Application number: PCT/IT2000/000169
Authority: WO
Inventors: Paolo Roso
Original assignee: PFM SpA
Current assignee: PFM SpA
Priority date: 1999-05-06
Filing date: 2000-05-04
Publication date: 2000-11-16
Anticipated expiration: 2001-11-06
Also published as: ITVR990041A1; AU4610400A; IT1309358B1

Abstract

A device for joining together the head and tail edges of packaging films (63, 65) coming from different reels (62, 64) in a packaging machine, advantageously a machine of the 'flow-pack' type with continuous advance movement of the articles to be packaged, comprises a frame (61) fixed to the frame of said packaging machine, a device (70) for joining the start edge of a film (65) to the end edge of another film (63), as well as a storing device (80) for realising a reserve of film having a predetermined length, in order to allow both the film to advance and the articles to be packaged during the joining phase of the start and end edges of said films (63, 65). Said storing device (80) comprises a carriage (81) movable along rectilinear guides and including a first series of rolls (86, 87) and a second series of rolls (86, 87) which the film to be stored is made to pass upon, and it further comprises a third series of rolls (88, 89, 90) and a fourth series of rolls (91, 92) which are fixed to said frame (61) and which the film to be stored is made to pass upon, the movement of the carriage (81) from a first position towards a second position generating a reserve of a given film length inside of said storing device (80).

Description

DEVICE FOR JOINING TOGETHER TWO PACKAGING FILMS FOR PACKAGING MACHINES OF THE "FLOW- PACK" TYPE .

* * * * *

TECHNICAL FIELD

The present invention relates to a device for joining together two packaging films for packaging machines of the "flow-pack" type.

More particularly, the present invention relates to a device allowing the respective head and tail edges of a pair of films made of synthetic material which are wound on respective reels, to be joined together during the operation of a high speed packaging machine of the so- called "flow-pack" type, and this without causing said machine to be stopped.

The invention may be mainly applied in the field of mechanic industry, in particularly in the field of manufacturing of packaging machines.

BACKGROUND ART Packaging machines provided with a feeding movement along a horizontal line, of a type which is commonly defined as "flow-pack" type, are well known in the art.

By means of these packaging machines a given article, that is placed in a horizontal or vertical position, is moved on a suitable conveyor while a plastic film is simultaneously unwound from a suitable supporting reel and suitably shaped in order to cover said article.

A "flow-pack" machine is provided with a suitable shaping means, that is generally constituted by tubular sheet which is suitable for folding the plastic film in such a way that the article to be packed can be inserted into said tubular sheet and, thereafter, wrapped by the plastic film.

While the article is advancing within the shaping device, the plastic film is firstly welded along a longitudinal line relative to the feeding direction of the article. This first welding operation is generally carried out by means of a plurality of rolls which are coupled and facing each other on each side of the article in order to act on both edges of the plastic packaging film.

More particularly, said rolls normally comprise a first pair of rolls acting as guides for facilitating the film movement, a second pair of rolls which carry out the longitudinal welding operation along the feeding direction of the article, a third pair of rolls which are provided with a cutting blade in order to eliminate the portions of film beyond the welded edges, and a fourth pair of rolls, which are generally made of rubber, for driving the film.

Said first welding operation may be carried out, according to other forms of embodiment, through different means in respect of the already described ones, e.g. through welding blocks .

Once the first longitudinal welding operation is ended, a second welding operation is carried out in a transversal direction in respect of the feeding direction of the article, in order to obtain the first short side of a given packaging; this second welding operation is carried out by means of a pair of welding plates which are placed downstream of said rolls.

In case of continuous feeding movement of the article, said welding plates are assembled on a movable mechanism which is driven parallel to the article, in such a way that the plates engage the film to be welded for a predetermined time; in case of intermittent feeding movement, the welding plates are provided with a reciprocating movement to and from each other. Once said second welding operation is ended, the plates are opened and, in case of intermittent feeding movement, the article is advanced by one step so that said welding plates are closed again downstream of the article in order to carry out a third welding operation, that is made transversally in respect of the feeding direction, thereby realising the second short side of the package .

In case of a continuous feeding movement of the article, the mechanism on which the welding plates are mounted causes a backward movement of the latter, as well as their closure in correspondance of the second transversal side to be welded.

Simultanously to the third welding operation the plastic film is cut and the worked article is then suitably packaged and it is ready for the subsequent packaging and storing operations .

Said packaging operations may be carried out on both a article that is moved as vertically placed on the conveyor, and on a article having its larger surface that lays on the conveyor plan.

The packaging machines of the above-described type may be sorted into different categories, depending on the type and dimensions of the article to be packaged, as well as on the required packaging speed.

By way of example, a known packaging machine of the above-described type is suitable for packaging foodstuffs such as snacks, bars, biscuits and similar articles at a relatively high speed which, in case of short articles (i.e. about 50 mm or less), can even be higher than thousand packagings per minute. Packaging machines of this kind are characterised by a relatively high consumption of packaging film, therefore the reels forming the supports on which said films are wound need to be frequently replaced.

An obsolete technology, though rather used yet, requires that the machine is stopped once the film has been completely unwound from the reel. Thereafter, the empty reel is removed from its support and a new film reel is mounted.

It appears to be obvious that this technology causes very long machine stops, and consequent losses of time, labour and productivity.

Furthermore, if the machine necessarily needs to carry out a continuous work (for instance when the machine is placed downstream of an extruder) , said technology may not be applied, unless the whole packaging plant is temporarily stopped.

In order to enhance the general productvity and to allow a continuous operation of packaging machines, some devices have been developed, which are applied to said packaging machines allowing the machine to be kept in operation, though at a substantially reduced speed, when a reel needs to be replaced.

These devices carry out a head/tail joint between the end edge of the film that has already been unwound, and that leaves its reel, and the head edge of a second reel which is supported on the packaging machine.

In order to allow said film portions to be welded together, a known device forms, during the normal operation of the machine, a film reserve of a predetermined length between the area where the film ends are joined, and the packaging area.

The provision of a film reserve between said areas allows the machine to be kept in operation during the respective steps of reducing the film speed, welding and accelerating, which are necessary in order to join the ends of the two films, the reserve being rapidly taken up during said working steps.

Film joining devices operating in the above- described way are normally defined as reel-replacing devices . Generally speaking, a known reel-replacing device comprises a first series of rolls parallel to each other, the ends of which are respectively fixed to the device frame, and a second series of rolls which are parallel to each other (and to the rolls of the first series) , fixed to a pair of parallel bars, one end of which is free, while the other one is fixed to the device frame and constitutes a rotation pivot for the pair of bars.

The film that is unwound from the first reel is made to pass between a roll of the first series and a roll of the second series, then it is fed again to a roll of the first series and so on for all the device rolls; the film coming out of the last roll is finally directly sent to the shaping device (i.e. to the device determining the shape of the package) .

From the foregoing it can be deduced that if the rotation of the rolls of the second series around said pivot is suitably controlled, away from the rolls of the first series, a given film length is stored as a reserve between the joining area and the packaging area.

Now, as already mentioned, when the rolls of the second series are moved towards the rolls of the first series, the film portion that is close to the joining area may temporarily be braked until it stops for a short time in said joining area, while in the packaging area the tape is driven, though at a reduced speed in respect of the normal working speed, but the machine is never stopped.

A schematic general layout of said device is illustrated in figures 1 and 2, which respectively show the normal working mode (fig. 1) and the film storing phase (fig. 2) that immediately precedes the head/tail joining operation of the edges of film 11 coming from the quite empty reel 10, and of film 21 belonging to the new reel 20.

Reference sign 30 indicates the joining area (where suitable welding means are present, which are well known to skilled people) , reference sign 40 indicates the film storing device and reference sign 50 indicates the rolls which just precede the area where the articles are packaged. A device of this kind offers rather satisfactory results only if the machine speed (in terms of packages per minute) is not too high, i.e. about 500 to 600 packages per minute.

However, in the case where the film has to keep a very high speed (i.e. at a speed equal to or even higher than thousand packages per minute for articles whose length is comprised between 20 and 50 mm) , the above- described device is not satisfactory, since it is not possible to create a film reserve that is sufficient for allowing the subsequent operations of braking, head/tail welding of the films to be joined, and accelerating, to be reliably carried out in the limited laps of time during which the drive rolls of the packaging machines take up all the length of film stored by means of said device . On the other hand, it is not possible to rotate said second series of upper rolls about a given angle in order to avoid undesired contact, and on encumbrancy grounds.

A further drawback of the above-described device is constituted by the fact that each reel is provided with a single sensor that delivers a signal when it detects the passage of the film edge, whereby the welding operation is carried out between said edge and the head of the film which is wound on the new reel; however, in the very frequent case where some areas of the film are provided with graphic signs of different nature, i.e for example with the figure of the packed article, or its ingredients, it happens that the welding operation of the two film edges is carried out without taking these graphic signs into due account; consequently, portions of the sign can be omitted or overlap other graphic portions, whereby this exerts a negative influence either on the aesthetic result of the final package, or on law dispositions (in case of omission of specific indications, for example).

Yet, in case of packaging some articles coming from continuously operating machines (e.g. from extruders), it appears to be clear that the packaging machine that is placed downstream of the extruders should continuously be operated too and, when possible, without significantly slowing down its speed; however, where the articles are small-dimensioned and the packaging machine has to be driven at a high speed (for instance in order to produce and package bon bons and similar items) , the known solutions do not offer any reliable solution in order to carry out a safe and accurate joint of the film edges. Finally, it is worth to mention that other packaging plants are known, which are suitable for packaging particular items, such as for instance tubular-shaped articles as cigars or cigarettes, or tea pouches. These plants are fully automatized and work at very high speed. These plants are also provided with automatic reel replacing devices which store a film reserve.

However, these plants are characterised by remarkable overall dimensions and, contrary to the packaging machines of the ^v flow-pack" type, this important bulk does not play any significant role; furthermore, these plants do not have to solve the problem of precisely aligning to each other the graphic signs which are present on the packaging films, since they only use completely transparent packaging films. DESCRIPTION OF THE INVENTION

The present invention aims to set aside the inconveniences and drawbacks which are typical of the prior art, and to provide thus for a device for joining packaging films for packaging machines ot the "flow-pack" type allowing the films to be joined together in machines operating at high speed, said device having a reduced bulk and carrying out very accurate film joints in which the graphic signs which are possibly present in the films to be joined are perfectly aligned to each other.

This is achieved by means of a device having the features disclosed in the main claim.

The dependent claims outline particularly advantageous forms of embodiment of the device according to the invention.

The device according to the present invention comprises a carriage that is movable along rectilinear guides between a first position, that is relatively close to a fixed frame, and a second position, that is relatively far away from said frame.

Said carriage and said frame are respectively provided with rolls which the film coming from an unwinding reel and directed towards the packaging area of the articles is made to pass upon.

According to the invention, the translating movement of the carriage on said rectilinar guides in the direction away from the fixed frame causes a predetermined film length to be stored as a reserve, that is later taken up during the reel replacement operation, where the respective tail edge of a film and head edge of a second film are joined and welded together, and this without stopping the packaging operation and only slightly reducing the machine speed. According to a particularly advantageous form of embodiment of the invention, both the carriage and the fixed frame are provided with two series of rolls which have different diameters but which are respectively aligned to each other, in such a way that they can store, for the same distance that is run by the carriage between the start and end positions, a reserve of film that has a length which is about the double in respect of the film length that can be stored without said two series of rolls.

In this way the two films can be joined together in a safe and reliable way, without stopping the packaging machine that continuously operates at high speed.

ILLUSTRATION OF DRAWINGS Other features and advantages of the invention will become apparent from reading the following description of a form of embodiment of the invention, given as a non- limiting example, with the help of the figures illustrated in the attached sheets, in which figures 1 and 2 have previously been described and: figure 3 shows a schematical plan view of a device for replacing a reel in a packaging machine of the "flow-pack" type according to the present invention; and - figures 4a and 4b show two side sections of one of the film joining groups of the device according to fig. 3.

DESCRIPTION OF A FORM OF EMBODIMENT In figure 3, reference sign 60 generally indicates a device for replacing a reel of a high-speed packaging machine of the "flow-pack" type according to the present invention .

Device 60 comprises a frame 61 that is integral to the frame of the packaging machine (not shown in the figure), which is provided with a first reel 62, on which a first packaging film 63 is wound, as well as with a second reel 64 on which a second packaging film 65 is wound .

During the operation of the packaging machine, one of the respective packaging films 63, 65 is unrolled from its reel and crosses a joining area 70 in which, once the unwinding of the film that is present on a reel has been ended, the tail edge of said film is joined to the head edge of the film that is starting to be unrolled from the other reel, in a way that will later be described in detail.

Thereafter, the film is unrolled along a predetermined path inside a film storing device 80, by means of which a reserve of film is formed, that is used while the reel is being replaced; the film reserve is used in a way that is similar to the one that has already been described with reference to the background art.

When coming out of storing device 80, the film is fed to the "flow-pack" -type packaging machine, in order to carry out a high-speed packaging operation of articles which are moved on a band conveyor.

The operating way of such a packaging machine is well known to the people who are skilled in the art, and it will not be repeated again.

We only may take a note of the fact that the device according to the invention is suitable for cooperating with a machine that continuously wraps up relatively short articles, i.e. having a length ranging from 10 to

80 mm, at a speed that may even be higher than 1000 packages per minute, and that thanks to the invention it is not necessary to reduce said speed, or else very few, during the reel replacing operation.

Device 80 for storing the film comprises a carriage

81 that is movable on suitable rectilinear guides 82, 83 (which are indicated with dotted lines in figure 3) by means of suitable motor means (not shown in the figures) between a first rest position and a second position of maximum reserve of film, the latter position substantially correponding to the position in which carriage 81 is shown in the figure.

As depicted in figure 3, carriage 81 is provided with a first series of rolls 84, 85, having a relatively larger diameter, and a second series of rolls 86, 87, having a relatively smaller diameter.

Furthermore, device 80 comprises a third series of rolls 88, 89, 90 having a relatively larger diameter, and a fourth series of rolls 91, 92 having a relatively smaller diameter, which are mounted in a fixed position on frame 61 of reel replacing device 60 according to the present invention.

Yet, when carriage 81 is driven from the rest position towards the position of maximum reserve of film, it is subjected to the action of resilient means 93 (which in the figure are represented by a pair of springs) which, during the taking up phase of the stored film (i.e. during the reel replacing phase, when the carriage is moving from the left side to the right one in the figure) , keep the film tensioned. According to the invention, said first (84, 85) and second (86, 87) series of rolls are mounted on carriage 81 in such a way that roll 84 having a relatively larger diameter and roll 86 having a relatively smaller diameter are parallel to each other and their longitudinal axes are perpendicular to the translating direction of the carriage .

In the same way, roll 85 having a relatively larger diameter and roll 87 having a relatively smaller diameter are parallel to each other and their longitudinal axes are perpendicular to the translation direction of the carriage .

As it clearly appears by examining fig. 3, the film coming from the joining area 70 is successively made to pass upon roll 84 (that is movable along a rectilinear path) , roll 91 (that is fixed in respect of the frame) , movable roll 85, fixed roll 92, movable roll 87, fixed roll 89, movable roll 86, fixed rolls 88 and 90, and it then comes to the packaging machine. Therefore, it appears to be evident that, thanks to the position of the different series of rolls, a relatively short run of carriage 81 results in a remarkable length in terms of stored film, that can be used when replacing the reel, whereby a high packaging speed is mantained.

In particular, it may be noticed that, thanks to the above-described disposition of the rolls, the overall bulk of the film storing device is very small; however, much greater lengths of stored film are achieved in respect of the known solutions, particularly in what concerns packaging machines of the flow-pack type. Furthermore, since carriage 81 is continuously subjected to a resilient force generated by resilient means 93, the film is continuously kept tensioned, thereby avoiding any tears or breaks . As previously mentioned, the main purpose of storing a great length of film is that of allowing an effective and reliable reel replacing operation to be carried out while the machine is working, i.e. during the normal operation of a high speed packaging machine of the flow- pack type.

However, are previously mentioned, said machines suffer from the disadvantage of not being provided with film joining devices which are able to keep the alignment and the continuity of the graphic signs which are present on the films that are wound on the two respective reels. The device according to the present invention allows this drawback to be set aside too, thanks to the provision of an improved device for joining the edges of the respective films . Having now reference to figure 3, inside of joining area 70 there are two identical units 71, 72 which are symmetric in respect of the vertical plane on which the two films are joined together; unit 71 is represented in detail in figures 4a and 4b. Unit 71 comprises, inside a protection container 73, a slider 74 movable along a rectilinear path between two limit positions by means of a compressed-air motor; the figures show pipes 75, 76 and 77 belonging to said motor.

In a central position relative to slider 74 there is a knife 78 which, in operation, cuts the respective films 63, 65 (see fig. 3) in correspondance of precisely defined positions.

Still, in the upper part of unit 71 there is a pad

79 which, during the final part of the advancing movement of slider 74, blocks the film against a guiding wedge 95 that is fixed to frame 61 of the reel replacement device.

Said knife 78 is suitable for crossing through an aperture 81 that is realised in said wedge 95.

In correspondance of the lower part of unit 71 there is a unit 82 for temporarily blocking the film. Said unit 82 comprises a head 83 provided of suckers 84 by means of which film 65 that starts to be unrolled from reel 64 is temporarily blocked.

The purpose of temporarily blocking the film by means of unit 82 is that of placing on the starting edge of film 65 a double-adhesive tape (not illustrated in the figures) for joining it to the end edge of film 63; in order to stick the double-adhesive tape on the starting edge of film 65 an operator firstly raises unit 71 which, as it may be noticed in fig. 3, is hinged in correspondance of a corner thereof, then he places the tape on the edge of film 65 that is held by unit 82.

Once film 63 has been unrolled, the end edge thereof is cut by means of the knife that unit 72 is provided with, and the operator joins the two films together in correspondance of the double adhesive tape.

According to a particularly advantageous form of embodiment of the present invention, films 63 and 65 are provided with identification notches (not illustrated in the figures) , which are placed at regular intervals and which may be read by means of suitable respective readers 85, 86, e.g. photocell readers, which are connected to an electronic control logics .

Through a suitable selection of the distance separating the identification notches it is possible to stop respective films 63 and 65 at predetermined locations in such a way that the films are joined in a sequential and coordinated fashion, taking the graphic signs which are present on said films into due account, and warranting their continuity, thereby avoiding any overlapping or cut of the graphic signs which are typical of the joining devices as known in the art.

The invention has previously been described with reference to a form of embodiment thereof.

However, it is clear that the invention includes several variants falling within its scope, in the range of mechanical equivalences .

Claims

1. Device for joining together the head and tail edges of packaging films (63, 65) coming from different reels (62, 64) in a packaging machine, advantageously a machine of the "flow-pack" type with continuous advance movement of the articles to be packaged, comprising a frame (61) fixed to the frame of said packaging machine, a device (70) for joining the start edge of a film (65) to the end edge of another film (63), as well as a storing device (80) for realising a reserve of film having a predetermined length, in order to allow both the film to be fed and the articles to be packaged during the joining phase of the start and end edges of said films (63, 65), characterised in that said storing device (80) comprises a carriage (81) movable along rectilinear guides and including a first series of rolls (86, 87) and a second series of rolls (86, 87) which the film to be stored is made to pass upon, in that it further comprises a third series of rolls (88, 89, 90) and a fourth series of rolls (91, 92) which are fixed to said frame (61) and which the film to be stored is made to pass upon, the movement of the carriage (81) from a first position towards a second position generating a reserve of a given film length inside of said storing device (80) .

2. Device according to claim 1, characterised in that the rolls (84, 85) of said first series have a relatively larger diameter and the rolls (86, 87) have a relatively smaller diameter, and in that the disposition of said first (84, 85) and second (86, 87) series of rolls on the carriage (81) is such that the roll (84) having a relatively larger diameter and the roll (86) having a relatively smaller diameter are parallel to each other and their longitudinal axes are perpendicular to the translation direction of the carriage.

3. Device according to anyone of the preceding claims, characterised in that said carriage (81) is permanently subjected to the action of resilient means (93) in order to keep the packaging film constantly tensioned durint the respective movements of both the film and the carriage (81) .

4. Device according to anyone of the preceding claims, characterised in that it comprises a pair of identical joining units (71, 72) opposed to each other inside an area (70) in which the end edge of a film (63) is joined to the start edge of another film (65), and in that each joining unit comprises a movable knife (78) suitable for cutting the advancing film in a predetermined position.

5. Device according to claim 4, characterised in that said knife (78) is mounted on a slider (74) having a reciprocating movement between a first position in which the knife does not engage the film surface and a second position in which the knife cuts the film surface .

6. Device according to anyone of claims 4 and 5, characterised in that each unit further comprises first blocking means (79) for holding the film against a fixed element (94) during the cutting operation.

7. Device according to anyone of claims 4 to 6, characterised in that each unit comprises second means (83) for temporarily blocking the film, said means being positioned downstream of said knife (78) in order to allow an operator to place a suitable adhesive on the edge of the film that has been cut by means of said knife (78) .

8. Device according to claim 7, characterised in that said second means (83) for temporarily blocking the film comprise suckers (84) which are suitably controlled in order to hold the cut edge of the film.

9. Device according to anyone of claims 4 to 8, characterised in that each joining unit (71, 72) is movable in order to allow an operator to place an adhesive on the edge of the film that has been cut by means of said knife (78), and to successively join the head and the tail edges of the films.

10. Device according to claim 9, characterised in that each joining unit (71, 72) is rotatably movable as being hinged in correspondance of a corner thereof.