HUOTARINEN, Jari (Salomaantie 49 E, Valkeakoski, FI-37630, FI)
| Claims: 1. A method for placing a sealing strip (4a) onto package material (3) provided with openings, in which method - the first end of a continuous sealing strip web (4) and, following it, a span of the continuous sealing strip web (4) having the length of at least one opening (3c) in the package material is transferred by transfer devices (7-10, 12a, 12b) onto the pack- age material (3) so that at least one opening (3c) in the package material (3) can be substantially covered by placing this span of the sealing strip web (4) and the package material (3) against each other, - the sealing strip web (4) and the package material (3) are attached to each other and cut by a fixing and cutting device (13) so that the sealing strip (4a) attached to the package material (3) and cut off from the sealing strip web (4) covers primarily at least one opening (3c) in the package material (3), characterized in that - the sealing strip web (4) is guided into a guiding device (11 ) comprising at least one guide surface (23a, 23b, 23c, 23d) to guide the sealing strip web (4) against the package material (3) so that a span, having the length of at least one opening (3c) in the package material, from the end of the sealing strip web (4) is placed primarily at said at least one opening (3c) in the package material (3), above or underneath the same, and that - both edges of the sealing strip web (4) are guided with guide surfaces (23c, 23d) in the guiding device (11 ). 2. The method according to claim 1 , characterized in that the sealing strip web (4) is supported in the guiding device (11 ) by the guide surfaces (23a, 23d) which guide the sealing strip web (4) at least from above and from below. 3. The method according to claim 1 or 2, characterized in that the sealing strip web (4) is cut off and attached to the package material web (3) immediately after the guiding device (11 ). 4. The method according to claim 3, characterized in that the sealing strip web (4) is cut off so that a pull-out flap separate from the package material web (3) is left in the sealing strip (4a). 5. An apparatus for placing a sealing strip (4a) onto package material (3) provided with openings, comprising - transfer devices (7-10, 12a, 12b) for transferring the first end of a continuous sealing strip web (4) and, after it, a span of the sealing strip web (4) having the length of at least one opening (3c) in the package material (3), in relation to the opening (3c) in the package material (3) so that the opening (3c) can be substantially covered by placing the span of the sealing strip web (4) and the package material (3) against each other, - a fixing and cutting device (13) for fixing the sealing strip web and the package material against each other and cutting them so that a sealing strip (4a) attached to the package material (3) and cut off the sealing strip web (4) covers said at least one opening (3c) in the package material (3), characterized in that the apparatus further comprises: - a guiding device (11 ) comprising at least one guide surface (23a, 23b, 23c, 23d) for guiding the sealing strip web (4) against the package material (3) so that a span having the length of at least one opening (3c) in the package material, from the end of the sealing strip web (4), is placed primarily at said at least one opening (3c) in the package material (3), above or underneath the same, and which guiding device (1 1 ) comprises guide surfaces (23c, 23d) that guide both edges of the sealing strip web (4). 6. The apparatus according to claim 5, characterized in that drawing rollers (12a, 12b) for moving the sealing strip web (4) are provided in connection with the guiding device (11 ). 7. The apparatus according to claim 5 or 6, characterized in that the apparatus comprises a guiding device (11 ) with at least one guide surface (23a) for guiding the sealing strip web (4) from below and at least one guide surface (23d) for guiding the sealing strip web (4) from above. 8. The apparatus according to claim 7, characterized in that the guiding device is a guide casing (11 ), inside which the sealing strip web (4) can be fitted without relatively any clearance but in an easily movable way. 9. The apparatus according to claim 8, characterized in that the guide cas- ing (11 ) is a piece that is open at its ends in the running direction of the sealing strip web and has a primarily rectangular cross-section. 10. The apparatus according to claim 8 or 9, characterized in that the guide casing (11 ) comprises drawing roller openings (21 , 25) for fitting drawing rollers inside the guide casing (11 ). 11. The apparatus according to any of the claims 8 to 10, characterized in that the guide casing (11 ) comprises at least one finger opening (24a, 24b) for moving the sealing strip web (4) manually inside the guide casing (11 ). 12. The apparatus according to any of the claims 8 to 11 , characterized in that a guiding turnover roller (10) is provided in front of the guide casing (11 ), for guiding the sealing strip web (4) into the guide casing (11 ). 13. The apparatus according to any of the claims 8 to 12, characterized in that a shear surface (27a) is provided at the rear edge (27) of the guide casing (11 ), for cutting the sealing strip web (4) after the guide casing (11 ). 14. The apparatus according to claim 13, characterized in that the rear edge (27) of the guide casing (11 ) is curved for forming detachment wings in the sealing strip (4a) to be cut off from the sealing strip web (4). |
The invention relates to a method according to the preamble of claim 1 and an apparatus according to the preamble of claim 5.
In packages for liquid or various bulk materials, such as packages for various beverages or powders, sealing strips that can be ripped off in various ways are normally used for closing a drain hole in a lid or wall. At present, it is known to place and fix a sealing strip onto package material to be used as the material for a lid or side walls of packages already before the assembly of the package. Normally, the sealing strip is fixed to the package material by the so-called heat sealing method, because the method is fast and easily automated.
When the sealing strip is attached by the heat sealing method, the sealing strip is placed onto an opening in the package material and compressed and heated around the edges of the opening so that sealing plastic applied onto the surface of the sealing strip and/or the package material melts, wherein the sealing strip and the package material are connected to each other in a liquid and air proof manner. For example, US patent 6,722,104 discloses a method of prior art for manufacturing a cylindrical liquid package equipped with a drain hole sealed with a sealing strip. In this case, a side wall blank that forms the side walls of the package is first formed of a continuous package material web. After this, the first of the lids for its ends is attached to the side wall blank, the lid being also made of a continuous package material web (so-called lid web) by cutting off lid blanks having the cross-section of the side wall blank, i.e. a circular shape, by means of a suitable punch. The lid blanks are clearly larger in diameter than the inner diameter of the side wall blank, so that a heat sealable form joint can be formed between them and the side wall blank. After the fixing of the first lid, the package is filled with the liquid to be contained therein, and first after this, the package is provided with the second lid. The drain hole of the package is placed in the first lid. The drain hole is made in the lid web and the sealing strip to close the same is attached onto the drain hole before the lid blanks are cut off the lid web. The sealing strip is made of a continuous sealing strip web, whose material may be, for example, aluminium or a laminate. When attached, the sealing strip has not yet been dispensed from the sealing strip web. The sealing strip is normally dispensed by cutting off the sealing strip web after it has been attached.
At present, it is also known (among other things, from the packaging machines of prior art manufactured by the applicant) to guide the sealing strip made of a continuous sealing strip web to the drain hole in the package material web by means of guide rollers moving the sealing strip web. After the end of the sealing strip web has moved to a suitable position with respect to the hole, the sealing strip web is pressed by a ram-type tool against the package material web. However, a thin laminar sealing strip made of, for example, aluminium may bend between the rollers that guide and move it, and be wrinkled or curled around the guiding and/or drawing rollers. It may also be guided more or less off the package material web after the last rollers. In such a case, it cannot be aligned either at all or sufficiently accurately between the ram tool and the drain hole in the package material web. This problem has caused, among other things, various malfunctions and production breaks on production lines of packages to be sealed with sealing strips. Furthermore, the sealing strip web guided poorly between the ram tool and the package material web may adhere to an unwanted point in the package material, in other words, slightly or to some extent to the side of the drain hole. In this case, the adhesion and sealing of the drain hole of the package do not necessarily meet the requirements set for them.
It is an aim of the present invention to provide a new method to improve the prior art and to eliminate the above-mentioned problems relating to the guiding of the sealing strip in web form as well as its placement on and adhesion to the package material. In particular, it is aim of the invention to provide a method by which a sealing strip in web form can be guided and placed onto a drain hole in a package material in a way that is more reliable and accurate than before. Yet another aim of the invention is to present an apparatus for implementing the method of the invention.
The inventive idea of the method and apparatus according to the invention is that the sealing strip web is guided by guide surfaces guiding both edges of the sealing strip web and by at least one such a guiding device equipped with a guide surface that forces the sealing strip web to pass straight before and after the drawing rollers, wherein it cannot bend, be wrinkled or curl around the drawing rollers. To put it more precisely, the method according to the invention is characterized in what will be presented i n th e characterizing part of claim 1 , and the apparatus according to the invention is characterized in what will be presented in the characterizing part of claim 5.
The method according to the invention has the advantage that in use, the sealing strip web to be guided and placed onto a drain hole in the package material cannot bend, be wrinkled or curl around the drawing rollers when it is between the guiding and drawing rollers of the apparatus, wherein mal- functions and production breaks caused to these problems are avoided. The method also has the advantage that in use, the sealing strip web can be guided and placed onto a drain hole in the package material in a way that is more reliable and accurate than before, wherein the drain hole to be sealed with the sealing strip to be cut off the sealing strip web is sealed in a more reliable way than before so that the sealed drain hole meets the requirements of sealing and pressure tightness. Yet another advantage of the method according to the invention is that the apparatus according to it is simple and inexpensive and it can be easily retrofitted in existing apparatuses for attaching sealing strips.
In the following, the invention will be described in more detail with reference to the appended drawings, in which
Fig. 1 shows a side view of a lid web machine intended for the processing of package material in web form, comprising an apparatus according to the invention,
Fig. 2 shows a side view of an apparatus for fixing sealing strips as part of the lid web machine shown in Fig. 1 ,
Fig. 3a shows a top view of the bottom side of the guide casing of the apparatus shown in Fig. 2,
Fig. 3b shows the cross-section A-A of the bottom side of the guide casing of the apparatus of Fig. 2, as shown in Fig. 3a,
Fig. 3c shows the top side of the guide casing of the apparatus shown in Fig. 2 seen from below, and Fig. 3d shows the cross-section B-B of the top side of the guide casing of the apparatus of Fig. 2, as shown in Fig. 3c.
Figure 1 shows a lid web machine 1 used for the manufacture of lids for liquid packages, wherein drain holes 3c in the package material web equipped with drain holes 3c, i.e. in the lid web 3, are sealed with sealing strips 4 formed of a sealing strip web 4. The machine comprises two successive lid web rolls 3a and 3b, the first being mounted on an unwinder 1 a and the sec- ond in a re-reel up 1 b. Between the unwinder 1 a and the re-reel up 1 b, devices 2 are provided for implementing the operations to be carried out on the lid web 3. Of these devices 2, the most interesting one in view of this invention is the device 2a for fixing sealing strips, whereby the sealing strips are attached onto the drain holes 3c at regular intervals in the lid web 3. In addition to the device 2a for fixing sealing strips, the devices 2 comprise, among other things, extension tables after the unwinder 1 a and before the re-reel up 1 b, several turnover rollers and nips, as well as dancing rollers responsible for the tension of the lid web, mounted on the frame 1 c of the lid web machine 1 so that the lid web 3 can be introduced in a way known as such to the device 2a for fixing sealing strips and, after the fixing of the sealing strips, guided to the re-reel up 1 b, from which the lid web rolls equipped with sealing strips can be transferred to be packed and further to a product storage to wait for transportation to a client. Furthermore, it should be noted that the devices 1 a, 1 b and 2 used for moving the lid web 3 and the device 2a for fixing sealing strips are controlled in the lid web machine 1 according to Fig. 1 by the same control system, known as such (not shown in the figures). This control system comprises the necessary measuring, adjusting and control devices, known as such, by means of which the device 2a for fixing sealing strips can be made to operate in synchronization with the other parts of the lid web machine 1.
In the device 2a for fixing sealing strips, shown in more detail in Fig. 2, the sealing strips are cut from a continuous sealing strip web 4 that is unwound from a sealing strip web roll 5. In this case, the device 2a for fixing sealing strips comprises a separate fixing frame 6 mounted on the frame 1 c of the lid web machine 1 , an unwinder 7, a lower turnover roller 8, an upper turnover roller 9, a control turnover roller 10, a control casing 1 1 , drawing rollers 12a and 12b, a cutting and fixing device 13, a device 14 for finishing the attachment, and a marking punch 15 for the lid web.
In the lid web machine 1 shown in Fig. 1 , the unwinder 7 is mounted on the frame 1 c of the machine, on the front side of the mounting frame 6 for the device for fixing sealing strips, slightly higher than the other parts of the device 2c for fixing sealing strips. The unwinder 7 is an unwinder known as such and suitable for the storage of the sealing strip web 4, on which unwinder the sealing strip web roll 5 can be mounted by opening a locking disc 17 fixed by a thumb screw 16 at the end of the central shaft of the unwinder 7 and by fitting the sealing strip roll 5 onto a mandrel 18 mounted on bearings on the central shaft. The mandrel 18 is also implemented in such a way that the rotation of the sealing strip web roll 5 in relation to the mandrel 18 is prevented when the locking disc 17 is fixed in its place. Fur- thermore, the mandrel 18 is decelerated by a breaking device (not shown in the figures) known as such and provided with adjustable braking power, so that the sealing strip web roll 5 cannot be unwound in an uncontrolled manner but the sealing strip web 4 remains under a suitable tension all the time during its unwinding.
The lower 8, upper 9 and guiding turnover 10 rollers placed after the unwinder 7 are also rollers known as such, made of e.g. nylon plastic and suitable for guiding a web-like material, by which rollers the sealing strip web 4 is guided to run in a desired direction. The lower 8 and upper 9 turnover rollers are provided with collars known as such, to prevent the sealing strip web 4 from moving in the side direction. The sealing strip web 4 is guided to run in a way shown in Fig. 1 , underneath the lower turnover roller 8 following the unwinder 7, so that the lower turnover roller 8 guides the sealing strip web 4 diagonally upwards. After this, the sealing strip web 4 is guided to run above the upper turnover roller 9 that is next so that the sealing strip web 4 is guided, after the upper turnover roller 9, down again towards the next guiding turnover roller 10.
As seen in Fig. 2, the guiding turnover roller 10 is placed in front of the guide casing 1 1 so that the sealing strip web 4 can be turned underneath the guiding turnover roller 10 in between the drawing rollers 12a and 12b in connection with the guide casing 11 , in parallel to the guide casing 11 ; in other words, the lowest point of the guide turnover roller 10 is approximately at the level of the upper surface of the inner space of the guide casing 11.
In this embodiment, the guiding device to guide the sealing strip web 4 to the lid web 3 consists of the guide casing 11 that guides the sealing strip web 4 moved by the drawing rollers 12a and 12b to a fixing and cutting device 13 after the guide casing. In this case, the guide casing 1 1 consists of a lower part 19a and an upper part 19b which are separate from each other. The structure of the guide casing 11 is seen in more detail in Figures 3a-d which show its lower part 19a and upper part 19 separated from each other.
The lower part 19a of the guide casing, shown in Figs. 3a and 3b, comprises a lower wall 20a and edge parts 20b and 20c provided on its both sides. In the part after the midpoint of the lower wall 20a (in the running direction of the sealing strip web), a lower drawing roll opening 21 is provided for the lower drawing roll 12a. Furthermore, the lower part 19a is provided with threaded holes 22a and 22b placed in the middle of the edge parts, for screws (not shown in the figures) for fixing the guide casing. The top surface of the lower wall 20a forms a lower guide surface 23a for guiding the sealing strip web 4, and the inner surfaces of the edge parts 20b and 20c constitute the guide surfaces 23b and 23c for guiding the edges of the sealing strip web 4. In this embodiment, the height of the edge parts 20b and 20c is about 1.5 mm. However, the height of the edge parts 20b and 20c may vary in different embodiments of the invention, depending, for example, on the type of the sealing strip web used.
The upper part 19b of the guide casing, shown in Figs. 3c and 3d, comprises an upper wall 2Od and fixing recesses 2Oe and 2Of of the edge parts. The bottom surface of the upper part 19b forms an upper guide surface 23d for the sealing strip web 4. The upper wall 2Od, slightly on the rear side of the midpoint of the guide casing 11 (in the running direction of the sealing strip), a first finger opening 24a is provided, and in this case at a distance of about 15 mm from it, a second finger opening 24b is provided to extend slightly to the rear side of the midpoint of the upper wall. The function of these finger openings is to facilitate the fitting of the sealing strip web 4 between the drawing rollers 12a and 12b when a new sealing strip web is inserted. Following the finger openings 24a and 24b, an upper drawing roller opening 25 is provided for the upper drawing roller 12b. In this case, the upper drawing roller opening 25 is larger than the lower drawing roller opening 21 in the lower part 19a, but placed in alignment with this so that the drawing rollers 12a and 12b can be fitted against each other via the drawing roller openings 21 and 25. The upper part 19b is also provided with holes 26a and 26b for fixing screws to be installed in threaded holes 22a and 22b at the midpoint of the edge parts of the lower part 19a. These holes 26a and 26b formed in the midpoint of the fixing recesses 2Oe and 2Of formed at the edges of the upper part extend through the upper part 19b so that the fixing screws of the guide casing 11 can be fitted via them into the threaded holes 22a and 22b in the lower part 19a when the lower part 19a and the upper part 19b are joined to each other.
In this case, the rear edge 27 of both the lower part 19a and the upper part 19b of the guide casing 11 has a preferably curved shape. However, the rear edge may also be, for example, straight. Thanks to the curved shape, the front edge of the sealing strip 4a to be cut from the sealing strip web 4 can be provided with detachment wings which remain off the package material at the fixing stage and which are easy to grip for opening the drain hole 3c in the lid of the finished package. Furthermore, the rear edges of both parts 19a and 19b of the guide casing 11 (the edges on the side of the cutting and fixing device 13) are designed to have a flat surface and a uniform shape so that the front edge of the cutting tool of the cutting and fixing device 13 to be moved along them and the rear edge 27 of the guide casing 1 1 constitute shear surfaces that cut easily to this shape. Further, at the front edge of the guide casing 11 (the edge at the end on the side of the unwinder), the ends of the walls of the lower part 19a and the upper part 19b are slightly rounded so that the sealing strip web 4 can be threaded more easily into the guide casing 11 at the stage of introducing the sealing strip web 4.
When the sealing strip is in the installed position in the fixing device, the lower part 19a and the upper part 19b of the guide casing are fixed to each other by fixing screws. Furthermore, the guide casing 1 1 is fixed at its front edge in the way shown in Fig. 2 to the mounting structure of the guide turnover roller 10 and, at its rear part, to the mounting structures of the cutting and fixing device 13. It should also be noted that the rear edge of the lower part 19a of the guide casing 11 is, in this embodiment, provided with a bevel 28 so that the rear edge of the guide casing 1 1 directed diagonally to the lid web can be supported as stably and immovably as possible to the lower surface of a lead-through 29 in the mounting structure of the cutting and fixing device 13. This improves the shearability and the cutting finish of the sealing strip web 4.
The drawing rollers 12a and 12b comprise a lower drawing roller 12a above the guide casing 1 1 and an upper drawing roller 12b underneath the guide casing 11. As already mentioned above and as can be seen, for example, in Fig. 2, the drawing rollers 12a and 12b are placed in the rear part of the guide casing 1 1 , at drawing roller openings 21 and 25 formed in its upper and lower parts, so that the drawing rollers 12a and 12b can be pressed against the sealing strip web 4 left between them. The drawing roller 12b is mounted on the drive shaft of an actuator, such as an electric motor 34, mounted on the mounting frame. The drawing roller 12a, in turn, is a freely rotating roller that is mounted on bearings on the first swinging arm 36 of a lever means 35 mounted in a swivelled manner on the mounting frame, so that it can be swivelled by an actuator 38 with linear movement, mounted on a second swinging arm 37 of the lever means 35 shown in Fig. 2, in the direction towards or away from the lower drawing roller opening 21 in the lower part of the guide casing. In this way, the function of the drawing roller 12b is to move the sealing strip web 4, and the function of the drawing roller 12a is to press the sealing strip web 4 against the surface of the drawing roller 12b to produce the necessary grip between the drawing roller 12b and the sealing strip web 4. For the above-mentioned reasons, the lower drawing roller 12a is clearly smaller in diameter than the upper drawing roller 12b. Furthermore, the upper drawing roller 12b is made of, for example, a soft and elastic material, whereas the lower drawing roller 12a is made of a hard material, such as, for example, metal.
The cutting and fixing device 13 has a structure and a function that are pri- marily known as such. It comprises an actuator 30 with linear movement, mounted on the mounting frame, and its movable end 31 is provided with a ram element 32 whose rear edge is equipped with a shearing edge 33 for cutting the sealing strip web 4. Inside the ram element 32, there is an electrical resistance, by which the lower part 32 of the ram element 32 is heated so that the joint plastics in the sealing strip web 4 and in the lid web 3 can be melted to provide a sealed and sufficiently strong joint. However, the joint between the sealing strip web 4 and the lid web 3 can also be made by using another sealing method, such as, for example, ultrasonic or induction heating.
In the embodiment of Fig. 1 , after the cutting and fixing device 13 there is a device 14 for finishing the attachment that secures the adherence of the sealing strip 4a, as well as a unit 15 for notching the lid web 3. The device 14 for finishing the attachment is a device known as such that fully corresponds to the cutting and fixing device but is not provided with a cutting edge. With the device 14 for finishing the attachment, the joint between the sealing strip 4a and the lid web 3 is finished and the uniform quality and sealing of the joint is secured. The notching unit 15 is also a device known as such, for providing one edge of the sealing strip 3 with a rectangular cutting mark to be used in the next step of processing the lid web roll 5 for determining the points of cutting the lid web.
The device 14 for finishing the attachment is placed at a distance equal to the distance between two successive openings 3c in the lid web 3 (that is, the opening distance) from the cutting and fixing device 13, and the unit 15 for notching the lid web is placed at a distance slightly smaller than the opening distance forward from the device for finishing the attachment. In this way, these next steps to be carried out on the lid web 3 can be performed simultaneously with the cutting and fixing of the sealing strip web 4, that is, at the same moment when the lid web 3 is stopped for cutting and fixing of the sealing strip web 4.
In the use of the device 2a for fixing the sealing strips in the lid web machine 1 shown in Fig. 1 , the sealing strip web roll 5 is mounted on the unwinder 7 of the fixing device. If the device does not comprise a previous sealing strip web 4, it must first be threaded underneath the lower turnover roller 8 and from there above the upper turnover roller 9 to the guiding turnover roller 10 and further to the guide casing 11 , wherein it can be moved from the finger openings so that the end of the strip can be introduced between the drawing rollers 12a and 12b. When the sealing strip web 4 is between the drawing rollers 12a and 12b, the drawing rollers 12a and 12b are responsible for moving the sealing strip web 4 forward. Generally, during normal use, the threading does not need to be performed again, but after the sealing strip web roll 5 has come to an end, the movement of the lid strip 3 and the sealing strip web 4 is stopped so that the tail end of the previous sealing strip web roll remains between the lower turnover roller 8 and the unwinder 7. After this, a new sealing strip web roll is changed on the unwinder 7, and the leading end of the new sealing strip web unwound from the roll is attached by a tape to the tail end of the old sealing strip web. In this way, the leading end of the new sealing strip web is introduced with the old sealing strip web between the drawing rollers 12a and 12b without manual threading.
During the operation of the lid web machine 1 , the sealing strip web 4 runs from the unwinder 7 via the lower 8, upper 9 and guiding turnover 10 rollers to the guide casing 11 in a jerking manner in synchronization with the lid web 3. When inside the guide casing 11 , the sealing strip web 4 runs straight first between the drawing rollers 12a and 12b and from there underneath the ram element 32 of the cutting and fixing device 14. The top surface of the lower part 19a of the guide casing 1 1 , that is, the lower guide surface 23a of the guide casing, and the bottom surface of the upper part 19a, that is, the upper guide surface 23d of the guide casing 1 1 , keep the sealing strip web 4 straight all the time when it is inside the guide casing 11. Thanks to this, the sealing strip web 4 cannot bend or be wrinkled or curl around either of the drawing rollers 12a or 12b in this span. Furthermore, since the width of the sealing strip web 4 is equal to the distance between the inner surfaces of the edge parts 20b and 20c of the guide casing, that is, between the guide surfaces 23b and 23c, the sealing strip web 4 cannot be turned on the slant in the side direction either. Thus, the sealing strip web 4 is always guided from the guide casing 11 accurately underneath the ram element 32 of the cutting and fixing device 14. The control system for the device 2a for fixing the sealing strip and the device 2 for transferring the lid web 3 secures that the drain hole 3c in the lid web 3 is always underneath the ram element 32 and the lid web 3 is stopped when the sealing strip web 4 covers the drain hole 3c in the lid web 3 and extends sufficiently to the front side of the front edge of the drain hole 3c. Furthermore, the control system secures that the ram element 32 of the cutting and fixing device 14 always performs a cutting and pressing movement in this situation, wherein the sealing strip web 4 is cut off and the length of the sealing strip web cut off from the sealing strip web, that is, the finished sealing strip 4a, is attached around the edges of the drain hole 3c in the lid web 3.
The method and the apparatus according to the invention can be implemented in a way that is, in many respects, different from the example embodiment presented above. For example, the length of the guide casing, the width and height of the space inside the casing (the distances between the guide surfaces) may vary. Moreover, the guide casing for guiding the sealing strip web does not necessarily need to be completely straight, but the guide casing can be, for example, curved in its leader part so that it guides the sealing strip web supplied, for example, vertically from above, to a horizontal position before the sealing strip web exits from the front part of the guide casing. Furthermore, two or more pairs of drawing rollers may be mounted in connection with the guide casing, for example so that the first pair of rollers is in the rear part of the guide casing (close to the inlet of the sealing strip web), and the second pair of drawing rollers is in the front part of the guide casing (close to the outlet). Thus, for example the threading of the sealing strip web into the guide casing is facilitated, and the maximal traction force to be produced by the drawing rollers is increased, thanks to the better grip between the drawing rollers and the sealing strip web.
Furthermore, in an embodiment, the device for fixing the sealing strip web can be implemented, for example, in such a way that one device for fixing the sealing strip is used for attaching the sealing strip simultaneously onto two or more package material webs provided with openings. In this case, the sealing strip web can be introduced, for example, between two package material webs on top of each other, wherein the sealing strip is attached to the lower side of the package material web on top, and to the top side of the lower package material web. Alternatively, in such a device, the sealing strip web can be supplied, for example, in a transverse direction to the package material web, onto two or more package material webs adjacent to each other. In this case, the cutting and fixing of the sealing strip web can be performed by a single cutting and fixing device that cuts the sealing strips fitting in openings for the adjacent package material webs simultaneously.
The invention is not restricted to the example embodiment presented above, but it may vary within the scope of the appended claims.