Method and apparatus in unwinding

Abstract

In the method in splicing in a continuous unwind, the surface speed of a new machine reel (R2) which is brought to the unwind and closed with a leading splice is accelerated in the initial acceleration to make the speed correspond to the speed of the old machine reel (R1) that is becoming empty, so that the fastening splice of the new machine reel can be joined to the web of the old machine reel. The loading affecting the leading splice and/or fastening splice of the new machine reel (R2) during the initial acceleration is reduced. The present invention also relates to an apparatus for implementing the method.

Description

[0001] The present invention relates to a method and apparatus in unwinding. The invention relates to a situation preceding the splicing stage in a continuous unwind, which terminates when the web of a new machine reel brought to the unwind is attached at full speed to the web of a machine reel that is becoming empty, by pressing the web of the machine reel that is becoming empty against a splice in the new machine reel, and the old web has been cut. Unwinding devices and measures conducted in connection with the reel change are described for example in Finnish patents FI 100323 and FI 101875.

[0002] In this application, the term leading splice is used to describe the arrangement that keeps the web attached to the surface of a new machine reel before splicing. The term fastening splice is used to describe the arrangement that fastens the web of a new machine reel to the web coming from the old machine reel that is becoming empty. The leading splice and the fastening splice can form two discrete sections, or they can be parts of the same fastening arrangement. The leading splice and the fastening splice can, for example, form the different sides of a two-sided adhesive tape, if the tape is attached to the end of the web of a new machine reel in such a manner that part of the tape extends over the length of the web fixing the end of the web to the new machine reel. In this application, the concept of a splicing gap refers to the point extending on the entire width of the web between the new machine reel and the splicing roll, in which point the distance between the new machine reel and the splicing roll is the shortest. In a splicing situation, the splicing gap is closed when the splicing roll strikes against the surface of the new machine roll to attain splicing. Furthermore, in this application the term initial acceleration refers to the stage of accelerating the speed of a full machine reel and/or the rotation of the same before splicing.

[0003] In off-machine coating machines for paper, a continuous unwind is used in which a new, full machine reel that is brought to the unwind is attached to the end of the paper web in the machine reel that is becoming empty. In present-day fast coating machines the splicing method is essentially the same, i.e. a fastening splice is prepared in the leading end of the web of a new machine reel by means of a two-sided adhesive tape, coated with a binding agent, the splice being attached on the surface of the reel by means of a leading splice, for example with pieces of fastening tape. The surface speed of the new machine reel is accelerated to be equal to the running speed of the machine, i.e. to the web speed of the paper web discharged from the machine reel that is becoming empty, whereafter the web of the reel that is becoming empty is pressed against the aforementioned fastening splice for example by means of a roll or a brush. The old web is cut with a blade above the splice.

[0004] In the splicing, the splicing roll is rapidly struck against the surface of a new machine reel, wherein a tension peak occurs in the web. The aim is to keep the tension peak caused by the stroke of the roll on a low level, by using a small splicing gap (8 to 12 mm), which causes a strong phenomenon of negative pressure. Because the present running speeds are very high, even over 1600 m/min, situations easily occur in which the travel of the web is disturbed and the web may break. Because the loading stressing the leading splice is directly proportional to the square of the running speed, and the adhesive attraction of the fastening splice is directly proportional to the adhesion time, which, of course, is reduced when running speeds are increased, it is obvious that splicing is problematic at high running speeds.

[0005] The negative pressure which is generated in the splicing gap between the splicing roll and the machine reel tends to draw the old web partly against the fastening splice already before splicing. The negative pressure may be pulsating when the new machine reel is out of round. Furthermore, the negative pressure tends to detach the leading splice from the surface of the new machine reel, wherein the new machine reel is unwound before splicing.

[0006] One solution for stabilizing the run of the web is presented in the patent publication U.S. Pat. No. 5,779,184 and in the corresponding European publication 0732287. By means of the method according to the publication, the run of the web is stabilized in such a manner that before the splicing gap there is a suction box, equal in width with the web, and the web touches this suction box when passing by the same. The suction is directed away from the web, wherein the negative pressure keeps the web on the surface of the suction box, thereby stabilizing its run. By means of this arrangement, it is not, however, possible to eliminate all effects of the negative pressure in the splicing gap.

[0007] It is an aim of the solution of the present application that the end of a new machine reel remains attached to the surface of a new machine reel by its leading splice, and that the new machine reel endures the initial acceleration without being unwound. On the other hand, the leading splice has to be detached easily when the splicing roll is struck against the surface of the new machine reel, and the fastening splice adheres to the web coming from the old machine reel that is becoming empty, the old web is cut and the discharge of the web from the new machine reel begins. A substantially uniform loading is exerted on the leading splice on the entire width of the web, which loading can, however, vary as a function of time for example due to said pulsating negative pressure. The loading exerted on the leading splice consists of the loading caused by air friction, centrifugal tension and the tension caused by the negative pressure in the splicing gap. In addition, the fastening splice must have a good adherence capacity to the web. Most significant part of the loading that exerted on the leading splice is the tension caused by the negative pressure prevailing in the splicing gap.

[0008] The tension caused by air friction can be calculated according to the following formula

T fric ={fraction (1/2)}·Cf·ρa·V2·I,

[0009] in which

[0010] Tfric=tension caused by air friction (N/m)

[0011] Cf=coefficient of resistance ˜0,0025

[0012] ρa=air density (kg/m3)

[0013] v=running speed (m/s)

[0014] l=web length (m)

[0015] The centrifugal tension can be calculated according to the formula

T CP =(MWEB+MAIR)·V2,

[0016] in which

[0017] TCP=centrifugal tension (N/m)

[0018] MWEB=grammage of paper (kg/m2)

[0019] MAIR=mass of air conveyed by paper (kg/m2)

[0020] v=running speed

[0021] The tension caused by the negative pressure prevailing in the splicing gap is calculated according to the formula

T VAC ≈Δp·r,

[0022] in which

[0023] TVAC=tension caused by negative pressure (N/m)

[0024] Δp=the difference between the pressure of the splicing gap and the pressure prevailing inside the reel (normal pressure), i.e. the negative pressure (Pa) prevailing in the splicing gap

[0025] r=radius of the reel to be accelerated (m)

[0026] The negative pressure prevailing in the splicing gap is calculated according to the formula

Δ≈{fraction (1/2)}·ρa·va2,

[0027] in which

[0028] ρa=air density (kg/m3)

[0029] va=flow rate of air in the splicing gap (m/s)

[0030] By means of the method and apparatus according to the invention it is possible to affect the loading exerted on the leading splice and/or fastening splice of the new machine reel. The method is characterized in that the loading affecting the leading splice and/or fastening splice of the new machine reel during the initial acceleration is reduced. The apparatus is characterized in that it comprises means for reducing the loading applied to the leading splice and/or fastening splice of the new machine reel.

[0031] By means of the new high speed splicing arrangement according to the invention, it is possible to considerably reduce the loading exerted on the leading splice and/or fastening splice, especially the negative pressure prevailing in the splicing gap. Furthermore, it is possible to adjust the temperature of the leading splice and/or fastening splice to adjust their adhesion.

[0032] The effect of the loading exerted on the leading splice and/or fastening splice, for example the tension caused by air friction and the tension prevailing in the splicing gap, can be reduced by passive and/or active actuators. By means of active actuators the loading is reduced by producing counter loading for said loading, and the passive actuators function as obstacles so that the air current causing the negative pressure would not enter the splicing gap. Generally, the actuators extend over the entire width of the web, but it is also possible that the actuators only extend on a part of the width of the web.

[0033] To reduce the tension caused by the negative pressure prevailing in the splicing gap, the aim is to reduce or prevent the generation of negative pressure. The generation of negative pressure can be prevented or it can be reduced for example

[0034] by directing an air blow in the splicing gap, the direction of which is substantially opposite to the flow direction of the air flowing in the splicing gap. The amount of air blow is adjusted so that the flow rate of air in the splicing gap is approximately substantially zero, or

[0035] by arranging moving or stationary mechanical obstacles, which prevent or reduce the generation of negative pressure in the splicing gap, or

[0036] by directing air suction away from the splicing gap, the direction of which is substantially opposite to the flow direction of the air flowing in the splicing gap. The amount of air suction is adjusted so that the flow rate of air in the splicing gap is approximately substantially zero, or

[0037] by blowing air along the surface of a new, full machine reel against the direction of rotation of the machine reel and/or by blowing air along the surface of a web coming from the old machine reel that is becoming empty against the travel direction of the web.

[0038] The adhesion of the fastening splice to the web of the old machine reel can be improved by adjusting the temperature of the ambient air in the fastening splice and/or the temperature of the fastening splice. The temperature of the ambient air in the fastening splice and/or the temperature of the fastening splice can be increased by means of infrared heating, by blowing heated air from a blow box or the like, by microwave heating or inductively by heating up the fastening splice that contains metal. The act of reducing the negative pressure in the splicing gap and the heating of the fastening splice can be combined in one actuator in such a manner that the blowing of the heated air is arranged to a suitable location from which air is blown to reduce the air flow in the splicing gap.

[0039] The effect of the tension caused by air friction can be reduced by directing air blows to suitable points in the direction of the periphery of the new machine reel and in the direction of rotation of the reel within a given section on the periphery, that does not extend close to the splicing gap, in the vicinity of which air is blown substantially against the aforementioned direction.

[0040] In the following, the invention will be described with reference to the appended drawings, in which,

[0041] FIG. 1 shows a side-view of a full machine reel,

[0042] FIG. 2 shows an unwinding apparatus and an embodiment of the invention,

[0043] FIGS. 3 to 7 shows embodiments of the invention, and

[0044] FIG. 8 shows an arrangement to reduce air friction.

[0045] FIG. 1 shows a side-view of a full machine reel R2 that enters the unwind. The drawing also shows as an example how leading splices and fastening splices can be formed on the surface of the full machine reel R2. The paper web is reeled around a reeling shaft K, and the end E of the paper web W (marked with a dotted line in the drawing) is attached to the surface of the reel R2 by means of a leading splice P. The end E of the paper web W remains underneath the splices according to FIG. 1. On the surface of the reel R2 there is a ready-made fastening splice F, from which the new machine reel R2 is attached to the end of the web W of an old machine reel R1.

[0046] FIG. 2 shows a side-view of an apparatus whose splicing arrangement is of the type presented in the Finnish patent 100323. In the apparatus, the web W is continuously unwound from machine reels brought to thereto, said machine reels being formed at an earlier reeling stage, and the web W is guided to a finishing apparatus of paper web, for example to a coating machine. The apparatus comprises a secondary drive 2 which rotates the machine reel R1 that is becoming empty and a primary drive 1 which rotates a new, full machine reel R2 brought to the apparatus. The main principle of the continuous unwinding is to bring reels successively into the apparatus in such a manner that a full reel is brought therein to be rotated by the primary drive 1, the paper web of the reel is attached to the web W coming from the reel that is becoming empty, which is rotated by the secondary drive 2, and the web is cut, whereafter it is unwound from the full reel rotated by the primary drive 1. When a particular amount of paper remains on the reel rotated by the primary drive 1, the reel is transferred to be rotated by the secondary drive 2, and a new full machine reel is brought to the primary drive, whereafter the webs are attached to each other again in the above-described manner. The transfer of the full reel R2 to the primary drive 1, the removal of the empty reel R1 from the secondary drive 2 and the change of the unwound reel from the primary drive 1 to the secondary drive 2 can be performed by using known solutions, and since they are not part of the invention, they will not be described in more detail in this context.

[0047] FIG. 2 describes a situation before the change, in which the web of the full machine reel R2 that has been brought to a primary station in the primary drive 1 is joined to a web W discharged from the machine reel R1 that is becoming empty in the secondary drive 2. The circumference of the full machine reel R2 touches a splicing station provided with a splicing roll 3 which guides the web W discharged from the reel R1 that is becoming empty in close proximity to the outer surface of the circumference in the full machine reel R2 rotated by the primary drive 1, in such a way that a splicing gap of a given width is formed between the web and the machine reel R2. The splicing is performed by striking the splicing roll 3 rapidly towards the opposite surface of the reel, wherein the splicing gap is closed. The splicing stroke is synchronized by striking the web W against the surface of the full machine reel R2 when the attachment point on the surface of the reel, for example a splicing tape, enters the splicing station. This point is marked with the letter S. The tape assembly in question can be for example a tape assembly in the transverse direction of the web by means of a tape whose both sides are adhesive, the tape assembly being attached to the end of the web of a full machine reel R2, and it typically has the shape of a saw blade or the like for the purpose of improving the grip. Furthermore, the cutting of the web to be discharged is conducted in a synchronized manner with the splicing stroke by utilizing a cutting device illustrated by arrow C, which cutting device performs the cutting stroke and is located before the splicing roll 3 in the travel direction of the web. The cutting device can be for example a striking blade cutting device. The drawing also illustrates an auxiliary roll 4 cooperating with the actual splicing roll 3 and guiding the discharged web W after the splicing station (splicing gap). The auxiliary roll is attached together with the splicing roll 3 to a common lever 5 articulated at an articulation point 5a located between the axes of the rolls 3 and 4. When the splicing roll 3 is struck against the surface of the full machine reel R2 by means of an actuator (not shown), the motion is transmitted to the auxiliary roll 4 by means of the lever, this motion of the auxiliary roll backwards along a path determined by the point of articulation compensating the stretch otherwise produced on the web.

[0048] FIGS. 2 and 3 show an embodiment of the invention, in which air is blown to the splicing gap N from a blow device 6. From the blow device 6 installed in the gap opening between the reel and the web, air is blown in the direction of the arrow B towards the splicing gap N against the travel direction of the periphery of the reel R2 and the web W. During splicing, a contact point N1 on the periphery of the splicing roll 3 and a contact point N2 on the periphery of the new machine reel R2 enter in contact with each other. The points N1 and N2 extend over the length of the splicing roll 3 and over the entire width of the web W. In a normal running situation there is a splicing gap N between these contact points N1 and N2 that extend over the entire width of the web W. The blow of air is parallel to the tangent on the periphery of the splicing roll 3 that travels via the point N1 and the tangent on the periphery of the new machine reel R2 that travels via the point N2, and it is substantially directed towards the splicing gap N between the points N1 and N2. Air is blown at such a speed that the flow rate in the splicing gap is substantially zero. Air is blown on the entire width of the web from a slit orifice or the like, at a speed which substantially equals the travel speed of the web W. Thus, it is advantageous that the air inlet of the blow device 6 is equal in size with the splicing gap N. The blow device 6 is connected to a positive pressure air source, for example to an air compressor. The blast pressure of the blow device 6 can be set as a function of the running speed, i.e. the travel speed of the web W.

[0049] FIG. 2 also shows an arrangement by means of which it is possible to measure and adjust the temperature of the air to be blown to improve the adhesion of the fastening splice or to adjust the adhesion of the leading splice and/or fastening splice. A temperature sensor 12 measures the temperature on the surface of the machine reel R2 and the adjustment device 13 for temperature is arranged to adjust the temperature of the air to be blown on the basis of the information obtained from the temperature sensor 12. The temperature sensor 12 and the adjustment device 13 for temperature are known as such, and therefore they will not be described in more detail in this context. The binding agents of the leading splices and fastening splices can be selected in such a manner that their adhesion is different in the same temperature, wherein the splices behave optimally in the splicing situation. For example the adhesion of the fastening splice may be greater than the adhesion of the leading splice in said temperature. The temperature of the air to be blown can also be changed during the period of time passed between the act of starting the initial acceleration and the splicing. Thus, the air flow blown from the device 6 can be utilized to affect both the flow conditions and the temperature conditions in the splicing gap.

[0050] FIG. 4 shows an embodiment of the invention, in which mechanical obstacles 7 are placed above and below the splicing gap to prevent the generation of negative pressure. The cross-section of the obstacles 7 can, for example, resemble the one shown in FIG. 4, but obstacles of other shapes are also possible. The cross-section of the obstacles 7 shown in FIG. 4 has a shape of the letter V with a rounded angle. The obstacles 7 are located above and below the splicing gap, i.e. in the travel direction of the periphery of the reel R2 and the web W before the splicing gap N and after the splicing gap N. The ends of the obstacles, whose cross-section has the shape of the letter V with a rounded angle, are directed towards the splicing gap N, close to the space between the points N1 and N2. One side of the obstacle 7 is close to the surface of the new machine reel R2 and the other is close to the surface of the web W. This way it is possible to reduce air flow in the splicing gap, and thereby also the negative pressure. The obstacles may be stationary or movable, wherein they can be transferred away from their position after the splicing is finished, or the position of the same can be changed for example when the size of the machine reel changes. The number of the obstacles may vary, and they extend over the entire width of the web W.

[0051] FIG. 5 shows an embodiment, in which a moving obstacle is placed before the splicing roll 3 on the opposite side of the web W in the travel direction of the web W, which obstacle prevents or reduces the generation of negative pressure in the splicing gap N. The obstacle is a roll 8 which has a considerably smaller diameter than the splicing roll 3, and it extends over the entire width of the web W. The roll 8 touches the web W when the web travels passes by the roll 8. The direction of rotation of the roll 8 is opposite to the direction of rotation of the splicing roll 3, and at the point closest to the new machine reel R2, the surface of the same moves to a direction opposite to the direction of motion of the surface of the machine reel, thereby preventing the flow of air towards the splicing gap in the direction of the periphery of the reel R2.

[0052] FIG. 6 shows an embodiment, in which air is sucked from the splicing gap at a suitable flow rate in such a manner that the flow rate of air in the splicing gap N is substantially zero. The suction can be performed by means of a suction device 9 extending over the entire width of the web, for example by means of a slit orifice or the like. The suction device is positioned in the closing gap formed by the reel and the web, close to the splicing gap N, in such a manner, however, that it does not touch the new machine reel R2, the splicing roll 3 or the web W. The slit orifice or corresponding suction inlet/inlets are directed towards the splicing gap. The suction is directed in such a manner that it is parallel to the tangent on the periphery of the splicing roll 3 travelling via the point N1 and the tangent on the periphery of the new machine reel R2 travelling via point N2, and it is substantially directed away from the splicing gap N between the points N1 and N2. The slit orifice or a corresponding structure extends substantially over the entire width of the web. In FIG. 6 the direction of the suction is shown with an arrow A. The suction device 9 is coupled to a negative pressure air source, for example to a vacuum pump.

[0053] FIG. 7 shows an embodiment in which air is blown in the directions shown by arrows B1 and B2, substantially in parallel to the surface of the machine reel R2 and the web W in such a manner that the blowing takes place against the direction of rotation of the machine reel R2, and against the travel direction of the web W. The blowing arrangement 10 can be for example a slit orifice or the like, which is directed in a suitable manner and extends substantially on the entire width of the web. The air currents B1 and B2 prevent the access of air currents accompanying the surface of the reel and the web to the splicing gap.

[0054] FIG. 8 shows an embodiment the aim of which is to reduce air friction. Outside the outer periphery of the new machine reel R2, close to the surface of the reel, devices 11 have been arranged at fixed intervals, which devices blow air in the direction of rotation of the machine reel R2 and extend over the entire width of the new machine reel R2. In FIG. 8, arrows B3 represent the direction in which air is blown. The air blowing devices 11 are basically of the same type with the blow arrangement 10, but they can differ from each other as far as their operating parameters, for example the flow rate of air or mass flow are concerned. As can be seen in FIG. 7, there are several successive blow devices on the sector of the periphery of the reel that begins approximately at an angular distance of 180° from the splicing gap and ends at a distance of approximately 30° from the same. The blow devices are not normally located in the splicing gap. The blow rate of air is advantageously substantially the same as the speed of the web to be unwound.

[0055] The above-described facts do not restrict the invention, but the invention may vary within the scope of the claims. The mechanical obstacles can differ from those presented in this application. The effect can also be produced solely by means of an obstacle/obstacles located before the splicing gap or solely by means of an obstacle/obstacles located after the splicing gap. The blowing or suction of air can be directed in different ways. The essential aspect is that the loading exerted on the leading splice and/or fastening splice of the new machine reel during the initial acceleration is reduced by means of an apparatus which is suitable for this purpose.

Claims

1. A method in splicing in a continuous unwind, in which method the surface speed of a new machine reel (R2) which is brought to the unwind and closed with a leading splice is accelerated in the initial acceleration to make its speed correspond to the speed of an old machine reel (R1) that is becoming empty, so that the fastening splice of the new machine reel can be joined to the web of the old machine reel, characterized in that the loading affecting a leading splice and/or fastening splice of the new machine reel (R2) during the initial acceleration is reduced by using active and/or passive actuators.

2. The method according to claim 1, characterized in that the loading is reduced by directing air blows and/or suction to suitable locations.

3. The method according to claim 2, characterized in that air is blown towards a splicing gap (N).

4. The method according to claim 3, characterized in that air is blown between contact points (N1, N2) restricting the splicing gap in such a manner that the air blow is substantially parallel to a tangent travelling via a contact point (N1) on the periphery of the splicing roll (3) and a tangent travelling via a contact point (N2) on the periphery of the new machine reel (R2).

5. The method according to claim 2, characterized in that air is sucked from the splicing gap (N).

6. The method according to claim 5, characterized in that air is sucked between contact points (N1, N2) restricting the splicing gap in such a manner that the suction of air is substantially parallel to a tangent travelling via a point (N1) on the periphery of the splicing roll (3) and a tangent travelling via a point (N2) on the periphery of the new machine reel (R2).

7. The method according to claim 2, characterized in that the blow of air is directed in parallel to the surface of the new machine reel (R2) against the direction of rotation of the machine reel.

8. The method according to claim 2 or 7, characterized in that the blow of air is directed in parallel to the web (W) coming from the old machine reel (R1) against the direction of rotation of the web.

9. The method according to claim 2, characterized in that the blow of air is directed in parallel to the outer periphery of the new machine reel (R2) close to the surface of the machine reel in the direction of rotation of the machine reel.

10. The method according to claim 2, characterized in that the flow of air is affected before the splicing gap (N) and/or after the splicing gap (N) by means of mechanical obstacles.

11. The method according to claim 10, characterized in that the obstacle is an article (7) shaped into a given form from a sheet-like material.

12. The method according to claim 10, characterized. in that the obstacle is a roll (8) arranged before the splicing gap, which roll touches the web (W) when the web passes by the roll.

13. The method according to claim 1, characterized in that the temperature of the fastening splice and/or leading splice is adjusted to increase the adhesion of the splices.

14. An apparatus in connection with splicing of a web (W) coming from an old machine reel (R1) and a web of a new machine reel (R2), in which splicing said webs are arranged to be connected to each other by means of a fastening splice, characterized in that the apparatus comprises means for reducing the loading applied to the leading splice and/or fastening splice of the new machine reel (R2).

15. The apparatus according to claim 14, characterized in that the means for reducing the loading applied to the leading splice and/or fastening splice of the new machine reel (R2) comprise one or more active or passive actuators.

16. The apparatus according to claim 14 or 15, characterized in that the device/devices is/are one or more devices that blow or suck air.

17. The apparatus according to claim 16, characterized in that the device is a blow device (6) which is positioned after the splicing gap and directed towards the splicing gap against the travel direction of the surface of the new machine reel (R1) and the web (W).

18. The apparatus according to claim 17, characterized in that the blow device (6) is arranged to blow air towards the splicing gap (N) between the contact points (N1, N2) in such a manner that the blow of air is substantially parallel to a tangent travelling via a contact point (N1) on the periphery of the splicing roll (3) and a tangent travelling via a contact point (N2) on the periphery of the new machine reel (R2).

19. The apparatus according to claim 16, characterized in that the device is a suction device (9) which is located after the splicing gap and directed towards the splicing gap against the travel direction of the surface of the new machine reel (R2) and the web (W).

20. The apparatus according to claim 19, characterized in that the blow device (9) is arranged to suck air from the splicing gap between the contact points (N1, N2) in such a manner that the suction of air is substantially parallel to a tangent travelling via a contact point (N1) on the periphery of the splicing roll (3) and a tangent travelling via a contact point (N2) on the periphery of the new machine reel (R2).

21. The apparatus according to claim 16, characterized in that one or more devices are arranged to blow air before the splicing gap in parallel to the surface of the new machine reel (R2) against the direction of rotation of the machine reel.

22. The apparatus according to claim 16 or 21, characterized in that the blow of air is directed in parallel to the web (W) coming from the old machine reel (R1) against the travel direction of the web.

23. The apparatus according to claim 16, characterized in that one or more devices are arranged to blow air in parallel to the outer periphery of the new machine reel (R2) close to the surface of the machine reel in the direction of rotation of the machine reel.

24. The apparatus according to claim 14 or 15, characterized in that one or more device/devices is/are one or more mechanical obstacles placed between the splicing gap and/or after the splicing gap.

25. The apparatus according to claim 24, characterized in that the obstacle is an article (7) shaped into a given form from a sheet-like material.

26. The apparatus according to claim 24, characterized in that the obstacle is a roll (8) arranged before the splicing gap, which roll touches the web (W) when the web passes by the roll.

27. The apparatus according to claim 14, characterized in that it comprises means for adjusting the temperature of the fastening splice and/or leading splice.