METHOD AND TAPE FOR JOINING PAPER WEBS

Abstract: This invention relates to a method and tape for joining paper webs. In paper production, a paper web is accidentally broken or cut, in which case the ends are joined together by means of a tape. In the known junction, the ends of the webs are located one on top of the other, and there is a two-sided tape therebetween. On account of faults in work, the paper does not always completely cover the tape, wherefore the junction point in the roll will adhere to the paper on top and underneath, which will result in a web rupture. This disadvantage can be avoided by using one-sided tape (1) whose protective film is divided into two parts (5, 6), whereby a butt joint can be made which involves no danger of sticking.

Description: Method and tape for joining paper webs This invention relates to a method for joining paper webs by means of tapes provided with a protective film, in accordance with which an adhesive surface of a first tape is exposed, said tape is attached subs¬ tantially transversely to a first web at a distance from the end edge of the web so that .it will extend from one longitudinal edge of the web to the other, the end portion of the web between the tape and the end edge of the web is removed, the same steps are repeated for a second web, and the junction point between the webs is covered with a second tape. The invention also relates to a tape used in the method. After a paper web has been produced it will in general be immediately subjected to re-checks wherein for example holes and impurities are removed from the paper. Thereby the paper web is cut at the defective points and the end edges thus produced are joined together by means of at least one substantially trans¬ verse, self-adhesive tape. According to the most often employed method, the joining is carried out with a two-sided tape. Thereby a two-sided tape furnished with a protective film covering one side _.s fixed "o "the fitst paper web in the vicinity of the end edge thereof, whereafter the part of the web between the tape and the end edge of the web, the so called tail, is torn away by hand along the edge of the tape. Thereafter the protective film on the tape is removed and the other paper web is fixed on top of the tape and the end portion is torn away. This known method has the disadvantage that the torn end edge of the paper web does not always exactly follow the edge of the adhesive surface of the tape, but the edge may have notches resulting from inaccurate tearing, on account of which some of the adhesive sur¬ face of the tape will appear. This will result in that the junction points on the paper web wound on a roll will adhere to the ply on top and the ply underneath. This can be prevented for the outer side of the junc¬ tion by covering the junction with a one-sided tape, but a corresponding operation cannot be carried out on the lower side of the junction, since it rests against the previous ply on the roll. Thus the known method explained above has the disadvantage that the paper web will often adhere at the junction at least to the ply of the paper web underneath, wherefore the paper web may be broken when it is removed from the roll. The junction point is also relatively thick, since there are superimposed therein two layers of paper and one or two layers of tape. The thickness of the web thus changes abruptly at this point, on account of which the printing roll may even be broken as a result of the impact thereupon. The object of this invention is to provide a method for joining paper webs, wherewith a junction is produced which involves no danger of adhesion between the paper plies and which is still equally thin as, or thinner than, the junction produced by the known method. he method of the invention is characterized in that both paper webs are fixed end to end onto the same side of the first tape and that the adhesive surface of the first tape is exposed in steps so that prior to the fixing of the tape to the first paper web a lon- gitudinal adhesive zone having a width smaller than the width of the adhesive surface of the tape is exposed, and the remainder of the adhesive surface is exposed after the removal of the end portion of the first web prior to the fixing of the tape to the second web. With the method of the invention, a butt joint covered on each side with one-sided tapes whose adhesive surface faces the paper is produced, and thus no outwardly exposed adhesive surfaces which could adhere to the other plies of the roll can be produced at the junction point. Furthermore, because of the butt joint between the paper webs the junction point is as thin as, or thinner than, the junction point produced with the previously known method, and the structure of the junction is gradually enlarging in thickness, wherefore the junction point will enter and leave the printing rolls softly. To produce the butt joint, the preferable procedure is that the adhesive zone located adjacent the longitudinal edge of the tape which is remote from the end edge of the first paper web is exposed first, and thereafter the adhesive zone adjacent the opposite longitudinal edge is exposed. The invention also relates to a tape for joining paper webs, one side of said tape having an adhesive surface covered with a removable protective film. The tape according to the invention is characterized in that the protective film comprises two longitudinal parts which can be separately removed from the adhesive surface. In order that the protective film for the -tape would be easily removable in two steps, according to one embodiment of the invention the protective film has a longitudinal slot or weakening line which separates the different parts of the film. In order for both paper webs to adhere to the tape equally strongly, it is preferred that the parts of the film are substan¬ tially equally broad and that the combined width there¬ of corresponds to the width of the tape. One advantageous embodiment of the invention is explained more closely in the following with reference to the accompanying drawing wherein Figures 1 to 6 illustrate the different steps of the method of the invention. Figure 7 shows a cross-section of a produced junction. Figure 8 shows a top view of a tape used in the method, and Figure 9 shows a magnified cross-section of the middle portion of the tape. When a defective point, such as a hole or a point deviating in colour from the other parts of the web, is found in the paper web to be handled, this point is removed by cutting the paper web on both sides of the defective o s whereafter the paper webs are again joined by means of a tape. The method of the invention is explained in the following with reference to Figures 1 to 6. In accord¬ ance with Figure 1, one takes a one-sided tape 1 as shown in Figures 8 and 9, whereof a longitudinal zone of the adhesive surface 2 is exposed, the width of said zone being substantially half of the width of the tape and being delimited by that edge of the tape which is remote from the end edge 4 of the first paper web 3. When the tape 1 is fastened to the paper web 3 by means of the adhesive zone 2, the end portion of "the paper web which is located between the end edge 4 and the edge of the adhesive zone 2 which is closest to this end edge is torn off from the paper web, whereby the situation shown in Figure 2 is created. The tearing is done by hand, and it is made possible by the portion 5 of the protective film which still partly covers the tape. The removed part of the protective film is indi¬ cated by reference numeral 6. When the paper web 3 is fixed to the tape 1, part 5 of the protective film is removed from the adhesive surface 2 of the tape, whereby a second lon¬ gitudinal zone of the adhesive surface is exposed. Thereafter the second paper web 7 is fixed to the second adhesive zone of the tape similarly as web 3, and also in this case the end portion of the web is torn off as shown in Figure 4. The accurate tearing, i.e. trimming, of the end portion is now made possible by the edge of the first torn web. Thus both ends are accurately laid face to face without gaps or over- lapping paper. The result is a butt joint between the paper webs 3,7 as shown in Figure 5, wherein the end edges of the webs are face to face, fixed to the same one-sided tape 1. Finally, the junction is covered by an one-sided tape 8 from the side opposite tape 1. The tape 8 is preferably substantially narrower than tape 1. After the tapes have been cut, the junction shown in Figure 7 is ready. The tape used in the method of the invention has been shown more closely in Figures 8 and 9. The adhesive surface 2 of the one-sided tape is covered by parts 5,6 of the protective film, which in the shown embodiment are equally broad and whose combined width corresponds to the width of the tape 1. There is a slot 9 between parts 5,6 of the protective film, on account of which parts 5,6 can be removed from "the tape independently and at separate points of time. Both the slot 9 and parts 5, 6 of the protective film are conti¬ nuous in the longitudinal direction of the tape and extend to the edges of the tape. The bearing layer of the tape is indicated with the reference numeral 10 in Figure 9. The above presents a preferred embodiment of the method of the invention and the tape used therein, and it is obvious that the invention may differ in its details considerably from what has been presented above. Thus the slot 9 may be replaced for instance by a weakening line or some other arrangement which makes it possible to remove the protective film in steps from the tape. Further, it is to be noted that the tape need not be fixed exactly transverse to the paper webs, but often it is advantageous to fix it to the webs somewhat diagonally, as has been shown in the figures, whereby the impact on the printing roll is weakened. The inven¬ tion is particularly suitable for use in connection with thin and thick paper qualities, whereby the most suitable thickness for the bearing layer 10 of the tape is selected in view of the required tensile strength and the total thickness of the junction, but it can also be used in connection with other equivalent mater- ials. The width of parts 5,6 of the protective film can be varied according to need.

Claims: AMENDED CLAIMS [received by the International Bureau on 23 May 1990 (23.05.90) original claims 3-5 replaced by arrended claim 3; claims 1 and 2 unchanged (1 page)] 1. A method for joining paper webs by means of tapes provided with a protective film, in accordance 5 with which an adhesive surface (2) of a first tape (1) is exposed, said tape is attached substantially trans¬ versely to a first web (3) at a distance from the end edge (4) of the web so that it will extend from one longitudinal edge of the web to the other, the end 0 portion of the web between the tape (1) and the end edge (4) of the web is removed, the same steps are repeated for a second web (7), and the junction point between the webs is covered with a second tape (8), c h a r a c t e r i z e d in that both paper webs (3, 5 7) are fixed end to end onto the same side of the first tape (1) and that the adhesive surface (2) of the first tape is exposed in steps so that prior to the fixing of the tape to the first paper web (3) a longitudinal adhesive zone having a width smaller than the width of 0 the adhesive surface (2) of the tape is exposed, and the remainder of the adhesive surface is exposed after the removal of the end portion of the f rst web (3) prior to the fixing of the tape to the second web ( 7 ) . 2. A method as claimed in claim 1, c h a r - 5 a c t e r i z e d in that the adhesive zone located adjacent the longitudinal edge of the tape (1) which is remote from the end edge (4) of the first paper web (3) is exposed first, and thereafter the adhesive zone adjacent the opposite longitudinal edge is disposed. 0 3. Use of a tape comprising an adhesive surface (2) covered with a removable protective film provided with a longitudinal slot (9) or weakening line dividing the pro ¬ tective film into two longitudinal parts (5,6) which can be separately removed from the adhesive surface (2), for j oin ¬ -_ ing the ends of two paper webs (3,7) to each other.

Inventors: PITKAENEN SAMI, PITKAENEN, SAMI
Applicants: LINDELL AB OY, OY LINDELL AB
Application year: 1990
Main classification: C09J7
IPC codes: B31F5, B65H19, B65H21, B65H37, C09J7