EP1706321A1

EP1706321A1 - A mulit-stage unit for processing a packaging material web

Info

Publication number: EP1706321A1
Application number: EP04800382A
Authority: EP
Inventors: Magnus Skörvald; Per Svanberg; Fredrik Kullgren
Original assignee: Tetra Laval Holdings and Finance SA
Current assignee: Tetra Laval Holdings and Finance SA
Priority date: 2004-01-13
Filing date: 2004-11-24
Publication date: 2006-10-04
Anticipated expiration: 2024-11-24
Also published as: JP4284365B2; DE602004011570T2; RU2006115917A; JP2007513025A; SE526408C2; WO2005068298A1; ATE384668T1; SE0400042L; DE602004011570D1; MXPA06005531A; SE0400042D0; RU2344055C2; EP1706321B1

Abstract

The disclosure relates to a multi-stage unit (1) for processing a web (2) of packaging material, comprising a first processing station (3) where first processing steps are carried out on the material web (2) and a second processing station (5) where a second processing step is carried out on the material web (2). The first processing station (3) includes a first processing tool (3a) and at least one second processing tool (3b) placed downstream of the first, and the second processing station (5) comprises a first processing tool (5a). The multi-stage unit (1) also includes a web-tensioning device (21) for the material web (2) which is disposed between the first and the second processing stations (3, 5). Both of said first processing tools (3a, 5a) are fixedly disposed in their respective station and the at least second processing tool (3b) in the first processing station (3) is moveable in relation to the first processing tool (3a) in a direction along the material web (2) and the web-tensioning device (21) is moveable in relation to the processing tools (3a-3c) in the first processing station (3).

Description

A MULTI-STAGE UNIT FOR PROCESSING A PACKAGING MATERIAL WEB

TECHNICAL FIELD The present invention relates to a multi-stage unit for processing a web of packaging material, comprising a first and a second processing station.

BACKGROUND ART Within the food packaging industry, use has long been made of packages produced from a packaging material comprising a core layer of, for example, paper or paperboard and outer, liquid-tight coatings of plastic. Sometimes the material also includes a gas barrier, for example in the form of an aluminium layer. Such packaging containers are sometimes produced in that a web of packaging material is reformed into a tube in a forming unit in a filling machine where the one longitudinal edge of the material web is joined together in overlap with the second longitudinal edge, whereafter the tube is filled with the intended contents and sealed along transverse sealing zones disposed in spaced apart relationship to one another. The sealed portions of the tube thus containing contents are thereafter separated from the tube by means of cuts in the sealing zones and are formed, where applicable, by folding to a desired geometric configuration depending upon how the two seals disposed transversely of the longitudinal direction of the tube are oriented. Upstream of the forming unit, the material web may be fed through a multi-stage unit for processing in several sequential operations. For example, if the produced packages are to be provided with opening devices, for example screw caps, foldable tops or pull tabs, these operations can comprise punching so as to create holes at desired positions along the web, and mounting of the opening device over these holes. The opening devices may be mounted in position in that they are injection moulded direct on the holes, for example in accordance with the description in WO 98/18609. Another alternative is to glue or hot melt fuse the device in position on the packaging material. US 6,386,851 discloses a multi-stage unit comprising a processing station in which holes are punched in the packaging material web, and a processing station in which opening devices are injection moulded in the holes. Both of the stations each include a number of processing tools positioned with a certain mutual spacing along the path of the material web. With this design, simultaneous processing is permitted of a distance of the packaging material web corresponding to a number of future packages. With, for example, a punching station comprising three punching tools, three holes may be punched simultaneously, one in each web portion to be formed into a package, i.e. in each of three future packages. The mutual spacing between the processing tools thus depends upon the relevant packaging volume, i.e. the size of the package being produced, so that each respective hole is punched at a given place on each future package. The mutual spacing between the processing tools also depends upon how the web is indexed and, in a number of cases, the processing tools are thereby positioned at a distance corresponding to one packaging web portion from one another, in other cases at a distance corresponding to two or more packaging web portions. On adaptation of the filling machine to different packaging volumes, the multi-stage unit must thus, in many cases, be replaced or rebuilt, which, in certain cases, may take up considerable time.

BRIEF SUMMARY OF THE INVENTION One object of the present invention has thus been to realise a multi- stage unit which, in a simple, rapid and operationally reliable manner, may be set so as to permit processing of packaging material webs formed for the production of different packaging sizes respectively. The multi-stage unit according to the present invention comprises, for processing a web of packaging material, a first processing station where a first processing step is carried out on the material web, a second processing station where a second processing step is carried out on the material web, the first processing station comprising a first processing tool and at least one second processing tool placed downstream of the first, the second processing station comprising a first processing tool, and the multi-stage unit also comprising a web tensioning device for the material web which is placed between the first and the second processing stations. The present invention is characterised in that both of said first processing tools are fixedly disposed in their respective station, that the at least one second processing tool in the first processing station is moveable in relation to the first processing tool in a direction along the material web and is adapted to be located at a first distance from the first processing tool, and that the web tensioning device is moveable and adapted so that it substantially constantly is located at a second distance from the processing tool in the first processing station disposed most proximal the web tensioning device which constitutes said first distance multiplied by a factor f ₌ ι + _n 2 where m is a whole number multiple of the number of web portions located in the first processing station, and where n is the number of processing tools in the first processing station. Employing the present invention, it is possible in a simple manner to adapt the multi-stage unit to different packaging volumes by moving the processing tools along the material web. By, for example, moving apart the processing tools so that thereby the distance between them increases, a material web intended for larger packaging sizes can be processed. In addition, the moveable web tensioning device makes it possible that complete processing cycles in the multi-stage unit can be maintained. Thus, both of the first processing tools in the first and second processing station can process the same package which, in the event of production stoppage, facilitates the check that no package departs from the multi-stage unit unprocessed or semi-processed and which also increases the precision between punching and injection moulding. Preferably, the processing tools in the first processing station are interconnected in such a manner that, in a first change of the distance between the first processing tool and the second processing tool, there will be obtained a corresponding change of each respective distance between any possible additional processing tools in the first processing station, and a second change of the distance between the web tensioning device and the processing tool located most proximal the web tensioning device which is said first change multiplied by the factor f = 1 + n 2 where m is a whole number multiple of the number of web portions located in the first processing station, and where n is the number of processing tools in the first processing station. The present invention also encompasses a multi-stage unit for processing a web of packaging material, comprising a first processing station where a first processing step is carried out on the material web, a second processing station where a second processing step is carried out on the material web, the first processing station comprising a first and at least one second processing tool placed downstream of the first, the second processing station comprising a first processing tool, and the multi-stage unit also comprises a web-tensioning device for the material web which is placed between the first and the second processing stations. The present invention is characterised in that both of said first processing tools are fixedly disposed in their respective station, that the at least one second processing tool in the first processing station is moveable in relation to the first processing tool in a direction along the material web and is adapted to be located at a first distance from the first processing tool, that the processing tools in the first processing station are interconnected in such a manner that, on a first change of the distance between the first processing tool and the second processing tool there will be obtained a corresponding change of each respective distance between any possible additional processing tools in the first processing station, as well as a second change of the distance between the web-tensioning device and the processing tool disposed most proximal the web-tensioning device, which is said first change multiplied by the factor f ₌ ι + _n 2 where m is a whole number multiple of the number of web portions located in the first processing station, and where n is the number of processing tools in the first processing station. This embodiment makes it possible to design the multi-stage unit so that it will be adjustable as described above even if the entire unit as such is limited to a certain height or length so as to fit in the filling machine. The processing tools and/or the web- tensioning device may be positioned offset, i.e. may be displaced from the centre of linkage intersections in a linkage arrangement which entails that the unit will be adjustable. Preferably, the web-tensioning device is a tensioning device for the material web comprising a tensioning roller which cooperates with the packaging material and resilient support members for this tensioning roller. This construction is conventional and simple. Preferably, the first processing station is a punching station where holes are made in the material web. Preferably, the second processing station is an injection moulding station for injection moulding of opening devices on said holes.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS Presently preferred embodiments of the present invention will now be described in greater detail hereinbelow, with reference to the accompanying Drawings. In the accompanying Drawings: Fig. 1 schematically shows a side elevation of a multi-stage unit comprising a first processing station and a second processing station; Fig. 2 schematically shows two views, one in side elevation and one in perspective, of a linkage arrangement which interconnects the respective processing tools in the first station and the web-tensioning device; Fig. 3 schematically shows two views, where the left-hand view shows where a tensioning roller with radius r_s is to be placed in relation to a linkage intersection in order that the theoretical model be attained, and the right-hand view shows how a bending roller with radius fy affects the system; Fig. 4 schematically illustrates the factor f, i.e. the relationship between the positioning of the web-tensioning device and the processing tools; Fig. 5 schematically illustrates the factor f, and Fig. 6 schematically illustrates the factor f.

DESCRIPTION OF PREFERRED EMBODIMENTS The present invention will now first be described in outline with the aid of Fig. 1 in which the multi-stage unit has been given reference numeral 1. The multi-stage unit is employed for processing a web 2 of packaging material and is included in a filling machine (not shown) for producing packages, in particular food packages. The web 2 is fed through the multistage unit 1 along a path P. In the examples which will be described below, the advancement takes place by 3:3 indexing of the web, i.e. three web portions are advanced in each processing cycle. The term web portion is taken to signify that length of the packaging material which is consumed to form one package. The multi-stage unit 1 includes a first processing station 3 where a first processing step is carried out on the material web 2. The first processing station 3 is placed along a first vertical section P-i of the path P of the material web. In those examples which will be described below, said first processing station is a punching station 3 in which openings or holes 4 are punched in the packaging material 2. The openings or holes 4 which, for example, are circular in configuration, are punched with uniform distribution along the web 2. The distance between the openings or holes is normally called the distribution length and is normally defined as the distance between one point on the web, for example a point where an opening is to be punched, to the next such point, i.e. where the next opening or hole is to be made. In those examples which will be described hereinbelow, the distribution length is as long as a web portion, whereby an opening or hole 4 is being punched in each future package. In the examples, for simplicity's sake, the openings or holes 4 are made substantially centrally on the web portion, and thus the distribution lengths begin and end in a point centrally on the web portion. Hence, it should be perceived that one distribution length and one web portion need not begin at the same point on the web. This will be described in greater detail below. In the examples, the first processing station 3 includes a first processing tool 3a and at least one second processing tool 3b placed downstream of the first. The station 3 also includes a third processing tool 3c placed downstream of the second. The number of processing tools corresponds to the number of web portions indexed in each cycle. The processing tools work "in parallel", i.e. in one and the same operation, or in a rapid series, an opening or hole 4 can be punched in each of three web portions. In the case with 3:3 indexing, three web portions are punched in succession. The term "tool" is here taken to signify the entire punching unit, including int. al. a punching element (i.e. that part which is forced through the material), a surrounding housing, drive means etc. The unit 1 further includes a second processing station 5 where a second processing step is carried out on the material web. Said second station is placed downstream of the first station along a horizontal section P₂ of the path P of the material web. In the example, the second station is an injection moulding station 5 where opening devices 6 of thermoplastic material are injection moulded on the material web 2 at its opening 4. The second processing station 5 includes a first processing tool 5a. The station 5 also includes a second and a third processing tool 5b and 5c, i.e. the number of processing tools in the second station 5 is preferably equal to the number of processing tools in the first station 3. Reference numeral 7 relates generically to a system for the stepped advancement of the web 2 through the multi-stage unit 1. This advancement system 7 includes a pair of infeed rollers 8, 9 which act one on each side of the material web 2. The roller 8 is driven by a first servomotor 10 by the intermediary of a first synchronous transmission 11 , for example a gear belt transmission. The roller 9 is preferably idle and only journalled. The infeed rollers 8 and 9 lie upstream of the first processing station 3 along the path P of the material web. The servomotor 10 is controlled so that the web 2 is advanced stepwise by a control unit 14 which receives a first input signal Si from an optical indicator 15 which is located in the proximity of the first processing tool 3a. The signal Si may, for example, be generated by a bar code or the like on the material web. The advancement system 7 also displays a pair of discharge rollers 16, 17 which lie downstream of the first processing station 3 along the path P. These discharge rollers 16 and 17 act one on each side of the material web 2. A servomotor 18 drives the roller 16 by the intermediary of a second synchronous transmission 19, for example a gear belt transmission. The roller 17 is preferably idle and merely journalled. The servomotor 18 is controlled by the control unit 14 which receives a second input signal S₂ from an optical indicator 20 which is positioned in the proximity of the second processing station 5, for example directly upstream of the first injection moulding tool 5a. The indicator 20 can thereby read-off, for example, the position of those holes 4 which are made by the punching tools 3a-c and cause the control unit 14 to stop the servomotor 18 on the basis of the signals from the indicator 20 so that the holes 4 are positioned within a permitted tolerance inside each respective injection moulding cavity in the injection moulding tools 5. The multi-stage unit 1 further includes a web-tensioning device 21 for the material web 2. Its task is to take up differences which may occur as a result of the fact that the stepwise advancement of the material web 2 in the infeed rollers 8, 9 is independent of the advancement in the discharge rollers 16, 17. The web-tensioning device 21 is placed along the path P between the first and the second processing stations 3, 5. Those differences which the web-tensioning device 21 normally need to take up are slight and are to be found within a given narrow interval. The web-tensioning device 21 is a tensioning device for the material web 2 comprising a tensioning roller 23, with a radius r_s, which cooperates with the packaging material 2 and resilient support members (not shown) for this tensioning roller 23. The tensioning device also includes a support frame 22. The material web 2 abuts with a circumferential angle of substantially 180° around the tensioning roller 23 so that the direction of the web is changed and the web 2 is guided up to a bending roller 24 with a radius /&. At the bending roller 24, the section P₂ of the path P begins. The material web 2 abuts with a circumferential angle of substantially 90° around the bending roller 24. The tensioning roller 23 may rotate about an axis A which, in the examples, is at right angles to both of the web sections Pi and P₂, see Fig. 2. The axis of rotation A lies in a shaft (not shown) which, in both ends, is connected to arms 28 which are journalled about an axis B in the support frame 22. Each arm 28 is pre-tensioned by one of the resilient support members, this resilient support member being disposed between the journal points of the arm 28 in the support frame 22 and the anchorage of the tensioning roller 22 in the arm 28. This arrangement imparts to the material web 2 a pre-set, substantially constant tension. Differences in the web advancement at the infeed rollers 8, 9 and the discharge rollers 16, 17, respectively, as a result of the fact that they do not advance the web 2 completely synchronously are taken up by the "floating" movement of the tensioning roller 23 in the web-tensioning device 21. In order for it to be possible to take up differences in the advancement, there is a material web loop, a slack, between the first and second processing stations 3, 5. The length of the material web loop corresponds in the example to the length of one indexing, i.e. corresponding to three web portions, so that an opening or hole 4 which is punched in the first processing tool 3a will subsequently be injection moulded in the first processing tool 5a in the second processing station 5. The same result may also be achieved in those cases where the length of the material web loop is a whole number multiple of the number of web portions which are located in the first processing station 3, as will be described in greater detail below. Each respective processing tool 3a-c in the first processing station 3 and the web-tensioning device 21 are interconnected by a linkage arrangement 25 of conventional gantry type as shown in Fig. 2 and as will be described in greater detail below. A linkage arrangement 25 of this type will be protractable and retractable, respectively, with a uniform spacing between the inner and outer linkage intersections 26, 27, respectively. The distance between a first inner linkage intersection 26a and a second inner linkage intersection 26b is designated l_ι. The distance between the second inner linkage intersection 26b and a third linkage intersection 26c is designated L₂. The processing tools 3a-c are placed on these linkage intersections. The web-tensioning device is also secured to a linkage intersection and the distance between the third linkage intersection 26c and that linkage intersection to which the web-tensioning device 21 is secured is designated L_τ. In the following disclosure, a theoretical model of the present invention will be described where the radius r_s of the tensioning roller and the radius ti_> of the bending roller are both very small, i.e. substantially zero. The processing tools 3a-c and the web-tensioning device 21 are placed on the linkage intersections so that the punching elements and that point which constitutes the "tensioning roller" (r_s close to or equal to zero) are located at the same height, i.e. in line with a respective linkage intersection. However, it will be perceived by a person skilled in the art that in a more practical model of the present invention, the tensioning roller 23 normally displays a considerable radius r_s and arch length B_s. In order that the practical model behave like the theoretical model, account must be taken of the radius r_s and the reasoning which follows is illustrated in Fig. 3. Since the arc length B_s of the tensioning roller 23 will be longer, see the left-hand view, than a corresponding vertical extent in the theoretical model, the tensioning roller 23 must be displaced a distance k towards the first station 3, this distance k being calculated in accordance with k = B. J The radius r_s also entails that the second station 5 must be displaced a horizontal distance 2r_s in relation to the positioning in the theoretical model. In the practical model, the bending roller 24 also displays a considerable radius rt, and this implies that the second station 5 must be displaced a further distance a in the horizontal direction, the distance a being calculated in accordance with α = 2r. ^■ B_b = 2-^

The reason is that the packaging material web 2 in the theoretical model changes direction at point x which gives a length 2r, in relation to the arc length B_& which the material web follows if the bending roller 24 has a radius r_b (which is not close to or equal to zero). In the following disclosure, the theoretical model will be described in greater detail and thereby the radius r_s of the tensioning roller and the radius /i, of the bending roller must both be extremely slight, i.e. substantially zero. It should, however, be observed that Fig. 1 , to which reference is now made, does not show the theoretical model but shows a multi-stage unit which is compensated for in accordance with the foregoing so as to be able to behave as the theoretical model. In the example, the centre of the punching element in the first processing tool 3a is placed at the same height as, i.e. lies flush with, the first inner linkage intersection 26a. Correspondingly, the centre of the punching element in the second processing tool 3b is placed at the same height as , i.e. lies flush with, the second inner linkage intersection 26b. Similarly, the centre of the third punching element is placed at the same height as the third inner linkage intersection 26c. Further, the web-tensioning device 21 is, in the example, placed on a fourth linkage intersection 26d, as will be described in greater detail below, and that point which constitutes the "tensioning roller" is located on the same height, i.e. flush with this fourth linkage intersection 26d. Here, (_ι and L₂ correspond to the previously mentioned distribution length and the distances U and L₂ are equal. Hereafter, the mutual spacing between the tools will therefore only be designated Li. The mutual spacing between the processing tools 5a-c, i.e. the distribution length, is preferably substantially the same as in the first processing station, i.e. the spacing corresponds to the distance L-i. By such means, in 3:3 indexing, three mutually subsequent punched openings or holes 4 may be processed. The multi-stage unit 1 according to the present invention is flexible and can be adjusted for the production of different packaging sizes. This implies 5 that the mutual distance L| between the processing tools in the first and second stations 3, 5, which is the same as the distribution length, is adjustable. In the example with 3:3 indexing and where the distribution length is equal to the length of the web portion, it applies that the distribution length between the tools is slight when small packages are produced and larger

10 when larger packages are produced. With the selected indexing, the smallest packaging size that can be produced is limited by the extent of each respective tool along the path of the web, i.e. the smallest distribution length is obtained in the position where the processing tools have been moved as close to one another as possible and, as a result, their housings abut.

15 The both above mentioned first processing tools 3a, 5a are fixedly disposed in their respective processing stations 3, 5. This implies that the housing in the first punching tool 3a is fixedly anchored in the frame of the filling machine, like the housing for the first injection moulding tool 5a. Further, the second processing tool 3b in the first processing station 3 is

20 moveable in relation to the first processing tool 3a in a direction along the material web 2. Similarly, the third processing tool 3c is moveable in relation to the second processing tool 3b in a direction along the material web 2. Further, the web-tensioning device 21 is moveable in relation to the third processing tool 3c.

25 As was mentioned above, the web-tensioning device 21 is secured in a linkage intersection at a distance l_τ from that linkage intersection 26c to which the third processing tool 3c is secured. Which linkage intersection is relevant depends upon a number of factors. The distance Lγ is the distance Li multiplied by the factor f, where where m is a whole number multiple of the number of web portions located in the first processing station 3, and where n is the number of processing tools in the first processing station 3. The variable m relates to the length of the material loop, how many times it is longer in relation to the length of the 35 relevant number of web portions in the first station 3, and in the described example, the number of web portions in the first processing station is equal to the number of web portions in the material loop, in which event m is equal to 1. Further, there are three processing tools in the first processing station 3 and n will therefore be 3. Thus, the factor f by which the distance l_ι is to be multiplied will thus be 1. Consequently, the distance L_τ in this case will be equal to the distance L|. Since there is an equal distance between the linkage intersections, the web-tensioning device 21 may thus be interconnected to a fourth inner linkage intersection 26d, see Fig. 4. As a result of the linkage arrangement, the movement of the processing tools 3a-c in the first processing station 3 and the web-tensioning device 21 is facilitated. The linkage arrangement is designed in such a manner that, on a change of the distance l_ι between the first processing tool 3a and the second processing tool 3b, there will be obtained a corresponding change of the distance L₂ between the second processing tool 3b and the third tool 3c. Similarly, there will be obtained a change of the distance L_τ between the web-tensioning device 21 and the third processing tool 3c. This change is obtained by multiplying the first change by the previously mentioned factor /where f fi = ι1 +^ ^{m _ 1} n 2 where m is a whole number multiple of the number of web portions located in the first processing station (three in number) and where n is the number of processing tools in the first processing station (three in number). In this case, f will, like before, be 1 in which event the changes are of equal size. The geometry entails that the total change of the distance from the first processing tool 3a to the web-tensioning device 21 is as large as the total change of the material web distance between the web-tensioning device and the first tool 5a in the second processing station 5. Fig. 1 shows a position where the processing tools 3a-c in the first processing station 3 are positioned in spaced apart relationship from one another. The second and third processing tools 3b, 3c have therefore been displaced away from the first, fixedly disposed processing tool 3a in a direction along the material web 2, and the web-tensioning device 21 has been placed a distance from the third processing tool 3c. The circle markings in the figure relate to punched openings 4, i.e. the beginning and end of each respective distribution length. The dashes at right angles to the material web 2 relate to the beginning and end of each respective web portion. It may be seen that the first web portion begins immediately ahead of the first processing tool 3a in the first station 3 and the third ends immediately after the third processing tool 3c. Thus, the first distribution length begins in on half of the first web portion. The fourth web portion is folded over a point which relates to "tensioning roller 23" (which, in the theoretical model, has the radius r_s close to or equal to zero) so that an opening or hole 4 arrives substantially in said point, i.e. the third distribution length ends substantially centrally on the web-tensioning device 21. The seventh web portion begins immediately ahead of the first processing tool 5a in the second processing station 5 and the sixth distribution length begins centrally thereof, i.e. the opening or hole 4 is located centred under the first injection moulding tool 5a. There will thus be located as many punched openings or holes 4 in the material loop as in the first and second processing stations 3, 5, respectively. The linkage arrangement will be described in the following disclosure and with reference to Fig. 2. It should however be observed that the linkage arrangement which is shown in the figure does not fully correspond to the theoretical model, since it can be seen that neither the punching elements nor the web-tensioning device are correctly positioned in relation to the centre of the linkage intersections. The second and third tools 3b, 3c, as well as the web-tensioning device 21 are moveable along guides 29 and the displacement proper is realised with the aid of ball screws 30 secured in the housing of the third tool. The ball screws 30 are driven by a servomotor (not shown). In order that no force is applied on the linkage system during operation of the multi-stage unit, i.e. when the tools and the web-tensioning device are ready-adjusted, two locking devices 31 are disposed between the third tool 3c and the web-tensioning device 21. These locking devices 31 each include a compressed air cylinder 32 which each surround a shaft 33. No further locking between the first and second tools 3a, 3b and between the second and third tools 3b, 3c, respectively is needed, since the geometry of the linkage system automatically provides locking of all linkages through the locking devices 31. As was mentioned previously, the positioning of the web-tensioning device 21 in relation to the third processing tool 3c in the first processing station 3 is calculated using the factor f. The factor depends upon n and m, i.e. if the number of processing tools in the first processing station is changed and/or the number of web portions in the material loop is changed, the factor is correspondingly changed. In table 1 can be seen different values of the factor /for different m and n.

When m=1 , the number of web portions in the material loop is equal to the number of web portions in the first station. However, the length of the material loop can be a multiple m of the number of web portions in the first station, i.e. the number of web portions can be multiplied by a whole number m. For example, it could be possible to have three web portions in the first processing station and six web portions in the material loop (m=2). In the above example (with n=3), L_τ would thereby be Li multiplied by 2.5. The linkage system would then need to be extended so that the web-tensioning device 21 could be interconnected to a linkage intersection which is located 2.5 steps upwards, i.e. the web-tensioning device is moved from the fourth inner intersection 26d to a fifth outer intersection 27e, see Fig. 5. Correspondingly, m=3 (and n=3) would entail that the web-tensioning device 21 would need to be moved up four stages (f=4), i.e. to a seventh inner intersection 26g in the linkage arrangement, see Fig. 6. It can also be seen in the table what values f will have if the number of processing tools (n) increases to four in the first station 3. The processing tools 5a-5c in the second station 5 are preferably correspondingly moveable, i.e. the second processing too! 5b in the second processing station 5 is moveable in relation to the first processing tool 5a in a direction along the material web 2. Similarly, the third processing tool 5c is moveable in relation to the second processing tool 5b in a direction along the material web 2. The interconnection between the tools 5a-c can be into effect employing a linkage system in accordance with the foregoing or, for example, using a ball screw system where the motor is positioned on the second processing tool 5b. The theoretical model has been described with reference int. al. to Fig. 1 which actually shows the multi-stage unit when the tensioning roller 23 in the web-tensioning device 21 has a radius r_s and a brief description now follows: In order to compensate for the radius so that the multi-stage unit behaves as in the theoretical model, the web-tensioning device 21 has been moved so that its uppermost point, i.e. the tangent to the uppermost point in the circumferential surface of the tensioning roller 23 is located the distance k below the fourth linkage intersection 26d. Like the theoretical model, an opening or hole 4 will thereby be located on the uppermost point. The second station 5 has been moved a horizontal distance 2r_s to the right in the figure, i.e. in a direction away from the web-tensioning device 21. If a new radius were to be selected, a new compensation must be made, i.e. a new distance k must be calculated and the second station must be moved a distance 2Ar_s, i.e. the difference between the new and the old radius multiplied by 2. When this has been done and the parts have been locked in the multi-stage unit 1 , it functions as the theoretical model, i.e. the multi-stage unit 1 can be adapted by means of the linkage system 25 for processing another length of web portions. There are often limitations to the space in the filling machine where the multi-stage unit 1 is to be positioned and, in certain cases, it may be necessary to depart from the ideal model because the multi-stage unit 1 is, for example, limited to a given height or length. The theoretical model must then be modified and, in the following disclosure, a second, more practical embodiment will be described with reference to Fig. 2. Here, the punching elements are positioned offset, i.e. displaced from the centre of the linkage intersections, and the web-tensioning device is located so that the tensioning roller 23 is positioned with its centre point in line with its linkage intersection. The distances Li , L₂ and Lγ are still the distances between the linkage intersections, but a number of constants, for example k1~k4, must be introduced and taken into account in the system. In order that the multi-stage unit function like the theoretical model, it is necessary that the processing tools 3a-3c in the first processing station 3 be interconnected in such a manner that, on a first change of the distance l_ι between the first processing tool 3a and the second processing tool 3b, there will be obtained a corresponding change of the distance L₂ between the second and third processing tool 3b, 3c, as well as a second change of the distance In- between the web-tensioning device 21 and the third processing tool 3c which is said first change multiplied by the factor m - 1 f = 1 + n 2 where m is a whole number multiple of the number of web portions located in the first processing station 3, and where n is the number of processing tools in the first processing station 3. Only when this has been set in relation to those constants which are relevant in the system can the distances between the first tool 3a, 5a in each respective station 3, 5 be established and locked to the filling machine, i.e. the multi-stage unit 1 must be constructed in response to certain given preconditions. A multi-stage unit 1 which has been constructed in this manner will then be adjustable in the same way as the theoretical mode, i.e. k1-k4 remain constant while L|, L₂ and Lj may be varied through the linkage arrangement. However, if any of the constants k1- k4 are changed, i.e. the given preconditions, the system must be reconstructed and each respective first processing tool 3a, 5a must probably need to be moved in relation to one another. Alternatively, the position of the first and second stations 3, 5 may naturally be given from the start and then it is the constants k 1-k4 which must be adjusted so that the correct relationships are attained between the parts in the multi-stage unit 1. While the present invention has only been described with respect to one currently preferred embodiment, it should be clear to a person skilled in the art that the present invention is not restricted thereto, but that a plurality of variations and modifications are conceivable without departing from the scope of the appended Claims. For example, a multi-stage unit 1 has been described as comprising two stations 3, 5. However, it should be obvious to a person skilled in the art that the number of stations may be increased. Similarly, the number of processing tools in each station 3, 5 need not be three as in the described example, but could be a different number. For example, as many tools may be provided in both the first and second stations 3, 5. Suitably, another indexing is also selected corresponding to the number of tools, for example 4:4 indexing if the number of tools n is increased to four. In the example, 3:3 indexing has been described. It should be understood that the present invention also functions in other types of indexing. When the web portions are shorter than the smallest possible distance between the tools, the indexing 1 :5 may, for example, be put into effect. This type of indexing has been described in publication EP 1 249 399 and the indexing proper will not be described in greater detail. In 1 :5 indexing, there are six web portions in the first station 3 when the number of tools therein is three (i.e. n=3) and six web portions in the material loop (i.e. rr?=1). The factor twill then be 1. In twelve web portions in the loop (i.e. m=2), the factor f will, as described above, be f=2.5. Further, the multi-stage unit has been described as comprising a punching station and an injection moulding station, but it should, however, be understood that it can be employed in different types of practical applications and thereby contain other stations. For example, the second processing station may comprise applicators for pull tabs which are to be sealed over each respective punched hole. Another alternative for the second station may comprise applicators for opening devices of the type consisting of screw caps etc. It should further be understood that the construction of the advancement system as described may be modified without departing from the scope of the invention. Similarly, both stations of the multi-stage unit can alternatively be placed along one and the same vertical line P-i, or along one and the same horizontal line P₂. The processing tools 3a-c in the first station and the web-tensioning device 21 are interconnected to each other by means of the above described linkage system 25. Alternative apparatuses and systems for interconnection may however be employed, for example ball screws may be used. Another alternative is to connect in a servomotor to each tool as well as one to the web-tensioning device. Finally, one type of web-tensioning device 21 has been described. It should, however, be understood that its construction may be of a different type, for example an air cylinder may be employed. Alternatively, a web- tensioning device of the type described in US 6,386,851 may be employed.

Claims

WHAT IS CLAIMED IS:

1. A multi-stage unit (1) for processing a web (2) of packaging material, comprising a first processing station (3) where a first processing step is carried out on the material web (2), a second processing station (5) where a second processing step is carried out on the material web (2), the first processing station (3) comprising a first processing tool (3a) and at least one second processing tool (3b) placed downstream of the first, the second processing station (5) comprising a first processing tool (5a), and said multistage unit (1) also comprising a web-tensioning device (21) for the material web (2) which is placed between the first and the second processing stations (3, 5), characterised in that both of said first processing tools (3a, 5a) are fixedly disposed in each respective station (3, 5), that said at least second processing tool (3b) in the first processing station (3) is moveable in relation to the first processing tool (3a) in a direction along the material web (2) and is adapted to be located a first distance (L-i) from the first processing tool (3a), and that the web-tensioning device (21) is moveable and adapted so that it is substantially constantly located at a second distance (L._τ) from the processing tool (3c) in the first processing station (3) most proximal the web- tensioning device (21), which is said first distance (L-i) multiplied by a factor f f fi = 1 + ^m ~ ^l n 2 where m is a whole number multiple of the number of web portions located in the first processing station (3), and where n is the number of processing tools in the first processing station (3).

2. The multi-stage unit (1) as claimed in Claim 1 , characterised in that the processing tools (3a-3c) in the first processing station (3) are interconnected in such a manner that, on a first change of the distance (L-i) between the first processing tool (3a) and the second processing tool (3b), there will be obtained a corresponding change of each respective distance (l_χ) between any possible additional processing tools in the first processing station (3), as well as a second change of the distance (L_τ) between the web-tensioning device (21) and the processing tool (3c) located most proximal the web- tensioning device (21), which is said first change multiplied by the factor f where m is a whole number multiple of the number of web portions located in the first processing station (3), and where n is the number of processing tools in the first processing station (3).

3. A multi-stage unit (1) for processing a web (2) of packaging material, comprising a first processing station (3), where a first processing step is carried out on the material web (2), a second processing station (5) where a second processing step is carried out on the material web (2), the first processing station (3) comprising a first processing tool (3a) and at least one second processing tool (3b) placed downstream of the first, the second processing station (5) comprising a first processing tool (5a), said multi-stage unit (1) also comprising a web-tensioning device (21) for the material web (2) which is placed between the first and the second processing stations (3, 5), characterised in that both of said first processing tools (3a, 5a) are fixedly disposed in their respective station (3, 5), that said at least second processing tool (3b) in the first processing station (3) is moveable in relation to the first processing tool (3a) in a direction along the material web (2) and disposed to be located at a first distance (l_ι) from the first processing tool (3a), that the processing tools (3a-3c) in the first processing station (3) are interconnected in such a manner that, on a first change of the distance (Li) between the first processing tool (3a) and the second processing tool (3b), there will be obtained a corresponding change of each respective distance (l_χ) between any possible additional processing tools in the first processing station (3), as well as a second change of the distance (L_τ) between the web- tensioning device (21) and the processing tool (3c) disposed most proximal the web-tensioning device (21), which is said first change multiplied by the factor f fi ι , ^{m _ 1} 2 where m is a whole number multiple of the number of web portions located in the first processing station (3), and where n is the number of processing tools in the first processing station (3).

4. The multi-stage unit (1) as claimed in any of the preceding Claims, characterised in that the web-tensioning device (21) is a tensioning device for the material web (2) comprising a tensioning roller (23) which cooperates with the packaging material (2) and resilient support members for said tensioning roller (23).

5. The multi-stage unit (1) as claimed in any of the preceding Claims, characterised in that the first processing station (3) is a punching station where openings (4) are made in the material web (2).

6. The multi-stage unit (1) as claimed in any of the preceding Claims, characterised in that the second processing station (5) is an injection moulding station for injection moulding of opening devices on said openings (4).