The invention also relates to a device for implementing the afore- mentioned method according to the preamble of the appended claim 13.

A continuous paper web of several meters in width which is passed directly from a paper machine or from a finishing treatment apparatus connected thereto in a continuous, on-line type manner, or from a separate off-line type finishing treatment apparatus is reeled in the reel- up to form successive so-called machine reels around reeling cores (reel spools). These large machine reels, which substantially comply with the width of production of paper, function as kind of intermediate storages for the paper web between off-line type finishing processes.

Such further processing may relate for example to coating and calen- dering of paper. At a later off-line treatment stage of a full-width paper web, the web reeled on the machine reels substantially in the produc- tion width is unwound and cut in the longitudinal direction into narrower part webs of which customer rolls are formed. The width and size of the customer rolls are adjusted to comply with the requirements of the customer and the further use of the rolls.

The state of art currently in use in the reeling up is described for exam- ple in the book by Mikko Jokio: Papermaking Part 3 Finishing, pub- lished by Fapet Oy, ISBN 952-5216-10-1,1999, pp. 143-183.

There are various known reel-up solutions, of which a reel-up type generally used at present in the reeling up of large-sized, large-mass machine reels is a so-called center drive assisted reel-up. The afore- mentioned reel-up type utilizes either a stationary or moving reeling cylinder equipped with a center drive and a growing machine reel in a reeling position in a so-called nip contact with said reeling cylinder. The paper web is guided on the machine reel via a nip formed between said reeling cylinder and the machine reel that is being formed. In center

drive assisted reel-ups, to improve the control of the reeling process, the reel spool functioning as a reeling core for the machine reel is provided with a separate center drive of its own in addition to the fact that the aforementioned reeling cylinder is rotated with a center drive.

In reel-ups of earlier level of development, in so-called surface drive reel-ups (Pope-type reel-ups), the machine reel that is being formed obtains the impetus necessary for its rotation merely via the nip con- tact, in other words by means of friction from the reeling cylinder through the paper web. In center drive assisted reel-ups the properties of the machine reel that is being formed are affected during the reeling up process in a known manner by means of control variables, which are, for example the nip force (linear load) of the reeling nip, the pe- ripheral force exerted on the paper web by the machine reel, and the web tension of the paper web determined before the nip and the reel- ing cylinder. The nip force is adjusted by loading the machine reel that is being formed and the reeling cylinder against each other for example by means of hydraulic cylinders, or the like. By adjusting the torque of the center drive of the machine reel it is possible to affect the peripheral force exerted on the paper web that is being reeled up. The torque of the center drive of the reeling cylinder is utilized to affect the web tension of the paper web on the free section of the paper web pre- ceding the nip.

The present invention is especially intended to be used in connection with the aforementioned center drive assisted reel-ups. The machine reel formed in center drive assisted reel-ups can, when located in the reeling position during the reeling up process, be arranged to move with respect to the reeling cylinder to adjust the nip force between the machine reel and said reeling cylinder, and/or to take into account the changing diameter of the growing machine reel. The adjustment of the nip force can also be implemented by moving the reeling cylinder. A known reel-up is also a reel-up used for reeling up of machine reels in which the machine reel rotates in its position, and the reeling cylinder is loaded against the reel to adjust the nip force and moved in accor- dance with the growth of the machine reel. Instead of the actual reeling cylinder it is possible to use other known mechanical solutions in the

reel-up that function in a nip-like manner, for example a combination of a reeling cylinder and a belt.

High web speeds of present papermaking and finishing processes set extremely high demands for the function of reel-ups, so that the paper web stored on the machine reels would be as flawless as possible, and loss as small as possible. The so-called change sequence that is con- ducted when the machine reel that is being formed becomes full, is one of the most critical stages of the reeling up process. In the change se- quence the reeling up is changed from the machine reel that is be- coming full by cutting the paper web, to an empty reeling core brought in connection with the reeling cylinder, and the reeling up continues to said empty reeling core. In present processes the aim is to conduct the change sequence as a so-called flying change, wherein the web speed of the paper web is not substantially reduced for the duration of the change. Disturbance-free implementation of a change sequence as a flying change to avoid broke requires faultless performance of the ac- tuators and automatics at present web speeds of typically over 25 m/s.

One way of implementing the change sequence when using a center drive assisted reel-up is presented in the earlier publication WO 9611868 of the applicant. In the method presented in said publication the machine reel that is being formed is transferred from the reeling position to a so-called change position, in other words transferred off the reeling cylinder and the nip contact, and the reeling up to the ma- chine reel that is being formed continues until the paper web is cut in full width by means of a cutting member located after the reeling cylin- der in the travel direction of the web. The cut paper web is guided in a flying change to an empty reeling core brought in connection with the reeling cylinder, and after this change the reeling up continues without interruptions to the new machine reel formed on said reeling core. The finished full machine reel is decelerated and transferred away from the reel-up. In the method described in the publication W09611868 the cutting of the paper web is conducted by means of a cutting member placed after the reeling cylinder in the travel direction of the paper web, but there are also known solutions in which the cutting of the web is

conducted by means of a cutting member located before the reeling cylinder.

In the above-described change method according to prior art as well as in other known change methods in which the machine reel that is becoming full is transferred away from the nip contact before the paper web is cut, i. e. in so-called open nip changes, problems are caused by the fact that accurate tension information of the paper web is not obtained from the section of the paper web succeeding the reeling cyl- inder, which information would be necessary for instance in the control of the center drive of the machine reel. This results from that according to prior art, the tension measurement of the paper web is only con- ducted in the section of the paper web preceding the reeling cylinder and the nip contact in the travel direction of the paper web, wherein said tension information can be used in the adjustment of the actual reeling up process in the reeling position, for example in the control of the center drives of the reeling cylinder and the machine reel. However, in a situation where the machine reel that is becoming full is located in the change position, i. e. away from the nip contact, the paper web reeled on said machine reel travels via the reeling cylinder, possibly in interaction with the empty reeling core which is already brought in nip contact with the reeling cylinder, wherein tension measurement of prior art does not describe the situation in the section of the paper web suc- ceeding the reeling cylinder in a reliable manner. This means that for the optimal control of the center drive of the machine reel that is be- coming full, accurate tension information of the paper web is not avail- able in this situation. This causes significant problems that affect the quality of the machine reel that is being formed and the control of the change process. The present invention provides a solution for these problems which will be described in more detail hereinbelow.

In solutions of prior art the failure to be able to optimally control the center drive of the machine reel in the change position after disen- gagement of the nip contact and before cutting the paper web, consid- erably impairs the quality of the paper web reeled on said machine reel during the period of time in question. In the worst case, inaccurate

center torque of the machine reel that is defined without proper tension information of the paper web and used in the control of the center drive can cause an uncontrolled and premature breaking of the paper web, or damaging of the paper layers reeled on the machine reel at an ear- lier stage if the reeling up of the surface layers is too slack (peripheral force too small) or too tight (peripheral force too high). Poorly reeled surface layers of the machine reel rotating at high speed may be loosened entirely and broken due to the effect of centrifugal force before said machine reel that is becoming full is stopped, which causes losses as well as a need to clean up the surroundings of the reel-up.

The use of too small a peripheral force increases the tendency of air drifting underneath the paper web that is being reeled up, especially when coated and/or calendered paper grades are reeled up. Too large a peripheral force may, in turn, cause tearing of the paper web that is being reeled up, and/or damaging of the lower layers that have already been reeled on the machine reel. Poorly reeled surface layers can also complicate the intermediate storing of the machine reel and affect the treatment endurance and storage life of the same, and at later treatment stages of the machine reel at the latest, they cause ad- ditional work and losses.

In addition to the problems caused to the actual machine reel that is being formed, inaccurate tension of the paper web in the change situa- tion after the reeling cylinder may also complicate accurate cutting of the paper web when the cutting is conducted in the section of the paper web located after the reeling cylinder. Successful cutting of the paper web is important so that the paper web can be guided successfully around a new reeling core and the reeling up to the aforementioned reeling core can be started. Successful and accurately performed reel- ing up of first, so-called bottom layers accumulated on the empty reel- ing core is an important factor when the aim is to produce a machine reel of good quality that maintains the properties of the reeled up paper web as well as possible, thus reducing losses at each later stage of the treatment of the paper web stored on the machine reel.

The main purpose of the present invention is to attain a method by means of which it is possible in the reeling up process, during a change sequence conducted with an open nip to better control the tension of the paper web on the section succeeding the reeling cylinder, thus avoiding the above-described problems caused by the inaccurate ten- sion of the paper web on said section. It is also an aim of the invention to provide a device implementing the aforementioned method.

To attain this purpose, the method according to the invention is primar- ily characterized in what will be presented in the characterizing part of the independent claim 1.

The device according to the invention, in turn, is primarily characterized in what will be presented in the characterizing part of the independent claim 13.

The other dependent claims present some preferred embodiments of the invention.

The invention is based on the idea that when the machine reel that is being formed is transferred from the reeling cylinder or another mem- ber functioning in a nip-like manner, in other words away from a nip contact in general, and when the reeling up is continues to said ma- chine reel until the paper web in continuous motion is cut, tension measurement is used in the free section of the paper web after said member that functions in a nip-like manner. The tension measurement member, which can comply with prior art as such, is thus placed in the area of the paper web between the aforementioned member, such as a reeling cylinder, that functions in a nip-like manner and the machine reel that is becoming full.

On the basis of the tension information given by the tension measure- ment implemented according to the invention it is, for example possible to optimally control the center drive of the machine reel that is be- coming full in such a manner that the tension of the paper web in the aforementioned section of the paper web can be made suitable both for

the reeling up of the final surface layers of the machine reel that is be- coming full and other measures included in the change sequence, such as cutting and threading of the paper web.

In a preferred embodiment of the invention, the operating principle of the tension measurement member complies with an earlier publication EP0367901 of the applicant. In said method the paper web is in a direction transverse to its travel direction provided with a guiding sur- face, such as a beam, the paper web moving with respect to the guid- ing surface producing a thin layer of air between itself and said guiding member, and the tension of the paper web is determined from the air pressure of said layer of air by means of local pressure measurements.

The method according to the invention can be advantageously imple- mented by connecting/fastening the tension measurement member to another member to be used in connection with the change sequence, which said member is transferred to such a position during the change sequence in which the tension measurement member con- nected/fastened thereto is in an operating position with respect to the paper web to conduct tension measurement above and/or below the paper web. The aforementioned member can be a cutting device lo- cated after the reeling cylinder in the travel direction of the paper web or a turnup member used for guiding the end of the paper web to a new reeling core. Said member can also be a so-called pressing device to be moved on the surface of the machine reel in connection with the change sequence, the purpose of which pressing device is to prevent the slackening of the surface layers of the machine reel and the access of air underneath the same during the change sequence. Furthermore, it is also possible to fasten the tension measurement member to a pri- mary reeling device, by means of which the empty reeling core is brought in connection with the reeling cylinder during the change se- quence, and by means of which reeling up on said empty reeling core is started after the cutting of the paper web.

In a preferred embodiment of the invention, the tension measurement member positioned according to the invention is, in addition to the ten- sion measurement, used as a guiding member for the paper web.

In the following, the invention will be described in more detail with ref- erence to the appended drawings, in which Fig. 1 shows in a principled side-view the essential parts of a cen- ter drive assisted reel-up as well as a tension measurement member positioned in accordance with prior art, Fig. 2 shows in a side-view the essential parts of a center drive assisted reel-up in a change situation with an open nip, as well as a tension measurement member positioned in ac- cordance with an embodiment of the invention, Figs. 3 to 5illustrate in principled side-views in more detail the temporal progression of the embodiment according to Fig. 2 during a change sequence, Fig. 6 shows in a principled side-view a second embodiment of the invention, Fig. 7 shows in a principled side-view a third embodiment of the invention, Figs. 8 to 10 show in a principled side-view the temporal pro- gression of a fourth embodiment of the invention during a change sequence, Fig. 11 shows in a principled side-view a fifth embodiment of the invention, Fig. 12 shows in a principled diagram the use of measurement data given by the tension measurement conducted according to the invention in the control of reeling up.

Fig. 1 shows in a principled side-view the essential parts of a center drive assisted reel-up as well as a tension measurement member posi- tioned in accordance with prior art. For the sake of clarity, Fig. 1, as well as Figs. 2 to 11 hereinbelow, do not describe the parts and func- tions of the reel-up that are irrelevant in view of the present invention, such as for example frame structures and supporting structures or moving mechanisms and operating mechanisms. These can be any solutions of prior art as such, in which the mutual mode of operation of the machine reel that becomes full during the change sequence and the member functioning in a nip-like manner, such as a reeling cylinder, is, however, in principle, similar to the one presented above, in other words, the change sequence is conducted as a so-called open nip change.

In Fig. 1 the reeling cylinder 11 rotates at peripheral speed corre- sponding to the speed of the paper web W, and by means of axles lo- cated at the ends it is mounted on bearings to the frame of the reeling device or to a member fixed to the frame. The reeling cylinder 11 can also be located in movable carriages or corresponding movable struc- tures. The reeling cylinder 11 is coupled to a center drive device via the other end of the cylinder, which center drive device, in turn, is linked to the operation of the part of the systemthat feeds the paper web W, in such a manner that the peripheral speed of the reeling cylinder 11 can be adjusted so that it corresponds to the speed of the web W fed to the reel-up. For this adjustment of the center drive of the reeling cylinder 11 it is, according to prior art, possible to use a tension measurement member TM1 before the reeling cylinder 11 in the travel direction of the paper web W, said tension measurement member being arranged to measure the tension of the paper web W. The paper web W is accu- mulated on a reeling core 12 located in the reeling position to form a machine reel 13, and the machine reel 13 is loaded at the same time in a known manner against the reeling cylinder 11 to attain the desired nip force. To the reeling core 12, which may be a so-called reel spool with a metal frame and which is journalled pivotable in bearing hous- ings at its ends, is provided with a center drive of its own via the other

end of the roll. By adjusting the torque of said center drive on the basis of the measurement information given by the tension measurement member TM1 it is possible to affect the peripheral force exerted on the paper web that is being reeled up in a known manner.

Fig. 2 illustrates in a principled side-view the basic idea of the present invention in a change situation in which a full machine reel 13 that is about to be completed is transferred away from the nip contact (in other words to an open nip situation) and the empty reeling core 21 is brought in a position of readiness for cutting of the paper web W. In a solution of prior art, the section of the paper web W after the reeling cylinder 11 does not give exact tension information for the control of the center drive of the machine reel 13 in the situation of Fig. 2. The reason for this is that when the tension measurement of the paper web is conducted according to the state of art, the tension measurement of the paper web by means of the tension measurement member TM1, or in another manner in which the tension and/or the speed of the paper web W for the part of the section preceding the reeling cylinder 11 is defined, the information measured/defined in said manner does not in a reliable manner describe the situation in the section of the paper web succeeding the reeling cylinder 11. When the tension of the paper web W is defined according to the invention by means of the tension measurement member TM2, exact information is, however, obtained for control of the center drive of the machine reel 13, because the in- teraction of the paper web W with the reeling cylinder 11 and the empty reeling core 21 possibly already brought in nip contact with the reeling cylinder 11 does not disturb the act of defining the tension of the paper web W at said point of location of the paper web.

In the open nip situation the information obtained from the tension measurement member TM2 enables the control of the center drive of the machine reel 13 by feedback coupling in such a manner that the structure of the machine reel 13 remains optimal also for the part of the final surface layers that are reeled up. In other words, a suitable pe- ripheral force exerted on the paper web W that is being reeled up by the machine reel 13 prevents the surface layers of the machine reel

from being reeled up too tightly or too loosely, which causes problems that have been described earlier in this text. The use of the information given by the tension measurement in controlling the reeling up process in an open nip situation will be described in more detail later in this text by means of Fig. 12.

In the following, some preferred embodiments of the invention will be described in more detail by means of Figs 3 to 11. It is obvious that the present invention is not limited solely to the embodiments presented in the following, but it can be modified within the scope of the appended claims.

Figs. 3 to 5 illustrate in principled side-views the temporal progression of the change sequence in an embodiment of the invention in more detail.

In Fig. 3, the machine reel 13 that is becoming full is pulled away from the nip contact, in other words off the reeling cylinder 11, in the begin- ning of the change sequence. According to the invention, the tension measurement member TM2 is brought in contact with the paper web W in the area between the reeling cylinder 11 and said machine reel 13 that is becoming full. In the situation of Fig. 3 the empty reeling core 21 is brought to the vicinity of the reeling cylinder 11 to be ready for the change. According to prior art, the machine reel 13 can in the situation of Fig. 3 be supported at its ends on a carriage, reeling carriages, etc. that move for example on rails, or the machine reel 13 may also be supported at its ends on rails directly by means of bearing housings located at the ends of the reeling core 12. The machine reel 13 is ro- tated by means of a center drive. The empty reeling core 21 is, in turn, fixed to a so-called primary reeling device, which, according to prior art, comprises a separate center drive for the reeling core 21. The main purpose of the primary reeling device, which, since it does not consti- tute a part of the invention, is not described in Figs 3 to 5, is to receive the empty reeling core 21 from a storage containing reeling cores, which storage can be located for example above the reeling cylinder 11 and the paper web with respect to the reeling cylinder 11, and to

transfer said reeling core 21 to the vicinity of the reeling cylinder 11 to change the reeling up to an empty reeling core. According to the inven- tion, the tension measurement member TM2 placed on the free section of the paper web after the reeling cylinder 11, is fixed to a moving mechanism (not shown in Figs 3 to 5), which makes it possible to transfer the tension measurement member TM2 to a measuring posi- tion with respect to the paper web W. Said moving mechanism can be for example a mechanism which is fixed to a carriage or a correspond- ing mechanism used for transferring the machine reel 13.

In Fig. 4 the empty reeling core 21 is turned to a position of readiness by means of the primary reeling device, in other words from above the reeling cylinder 11 closer to the paper web W and closer to the section of the paper web between the reeling cylinder 11 and the machine reel 13. At this stage the reeling core 21 is accelerated to the web speed by means of a center drive affecting the center of the reeling core 21 of the primary reeling device (hereinbelow shortly primary drive). The nip between the empty reeling core 21 and the reeling cylinder 11 (herein- below shortly primary nip) can still be open at this stage.

In Fig. 5, when the full machine reel 13 has been transferred further away from the reeling cylinder 11, thus giving room for the primary reeling device, the primary reeling device and the reeling core 21 at- tached thereto turn further against the paper web W to a position suit- able for the cutting and threading of the paper web. The afore- mentioned primary nip is closed at this stage at the latest. Before the paper web is cut, the reeling core 21 may have been turned into its ex- treme position, in other words on rails or other members used for sup- porting the machine reel 13, but the cutting, tail change and reeling up of the paper web to the reeling core 21 can also be started in such a manner that the primary reeling device is only partly turned, according to the principle shown in Fig. 4.

In the situation of Fig. 5, the cutting member conducting the cutting of the paper web is transferred to a working position, if the applied solu- tion of prior art is such that the cutting member is not located fixedly in

a suitable position, or it has not been transferred to said position al- ready at an earlier stage of the change sequence. The cutting of the paper web W can be conducted according to prior art known as such vertically or diagonally with respect to the travel direction of the paper web W, by cutting the paper web at once in full width or by means of one or more blade members moving in the transverse direction of the paper web. The cutting member may be based either in the use of mechanical blade/blades or a jet of pressurized air or water can also function as a blade member. Furthermore, the cutting can be based on controlled tearing of the paper web after the initial cut is made by means of the aforementioned cutting member. The cutting member, which in Fig. 5 is marked in a simplified manner by means of arrows B1 and B2, can be located either after the reeling cylinder, i. e. cutting member B2, or before the reeling cylinder, i. e. cutting member B1, in the travel direction of the paper web.

According to the present invention and the details shown in Figs 3 to 5, the center drive of the machine reel 13 that is becoming full (herein- below shortly secondary drive) is coupled to be controlled on the basis of the measurement information obtained from the tension measure- ment member TM2 as soon as the tension measurement member TM2 is transferred to a suitable measurement position for said measurement when the machine reel 13 disengages itself from the nip contact, in other words when the so-called secondary nip between the reeling cylinder 11 and said reel is opened. The reeling up process is contin- ued under the control of the measurement data obtained from the ten- sion measurement member TM2 until the paper web W is cut by means of the cutting member B1 or B2. A moment before the cutting of the paper web, the load of the secondary drive, in other words the speed of rotation and torque are locked into fixed values, and, if neces- sary, the tension measurement member TM2 is switched off/transferred away from the paper web W to prevent the damaging of said measurement member. The paper web W is cut according to prior art and thereafter the cut paper web W is threaded to the empty reeling core 21. The speed of rotation of the full machine reel 13 is decelerated and the rotation of the machine reel is stopped, whereafter said ma-

chine reel is transferred away from the reel-up. The reeling core 21 and the new machine reel formed thereon is, according to prior art, trans- ferred away from the control of the primary reeling device for example by changing a secondary drive to the free end of the reeling core 21, and by detaching the primary drive from the other end in such a man- ner that the torque required in the rotation of the reeling core is ramped, in other words changed gradually from said primary drive to said secondary drive. When the primary reeling device has become free, the primary reeling device returns to retrieve the next empty reel- ing core ready for the next change sequence.

In the following, other preferred embodiments of the invention will be described.

In a preferred embodiment of the invention, which is described in prin- ciple in Fig. 6, the tension measurement member TM2 is connected to the cutting member 61, and the thereby produced combination can be moved with respect to the paper web W by using one moving mecha- nism. Thus, the need to arrange separate moving mechanisms both for the tension measurement member TM2 and the cutting member 61 can be avoided. In this embodiment, the function of the tension measure- ment member TM2 is advantageously based on the measurement of air pressure between the guiding member arranged in a direction transverse with respect to the travel direction of the paper web W, as described in the earlier publication EP0367901 of the applicant, and the cutting member 61 is advantageously in a corresponding manner a blade cutting device cutting the paper web in full width, which is de- scribed in the earlier publication W09611868 of the applicant.

By means of the tension information of the paper web W obtained from the tension measurement member TM2 in an open nip situation and the feedback control of the center drive of the machine reel 13 that be- comes possible thereby, it is advantageously possible to affect the ac- tual cutting process of the paper web W as well. Before the cutting, the web tension of the paper web W in the area between the machine reel 13 and the reeling cylinder can be adjusted suitable for the cutting

method used at a given time and the paper grade that is being reeled up. Optimal tension of the paper web W in view of the cutting depends, for example on that whether the cutting is conducted by means of a mechanical blade or a water jet. It is also possible that before the ac- tual cutting the cutting member, for example the member B2 in Fig. 5 or the member 61 in Fig. 6 is transferred against the paper web W, at the same time changing its path in such a manner that the tension of the paper web W has to be adjusted in a corresponding manner to prevent premature breaking of the web. In different paper grades the optimal web tension for conducting the cutting can also vary. Certain paper grades, depending for example on the orientation of the fibres affecting the transversal tearing susceptibility of the paper web require a larger web tension so that they can be cut in a reliable manner. On the other hand, brittle and thin paper grades require the use of smaller web tension so that the cutting process would remain controlled.

In a preferred embodiment of the invention that is shown in principle in Fig. 7, the tension measurement member TM2 is connected to a so- called pressing device 71. The pressing device 71 is a member ac- cording to prior art, for example a roll arranged rotatable or a beam or the like which does not rotate as such, but is provided with a low-fric- tion surface material, which is used to press the surface of the machine reel 13 that is becoming full, thus preventing the slackening of the reeled-up surface layers and the access of air between said layers es- pecially when coated and/or calendered paper grades are reeled up.

The pressing device 71 is guided to a working position against the surface of the full machine reel 13 that is about to be completed typi- cally during the change sequence, but the pressing device 71 can also be used during the rest of the reeling process, if necessary. The com- bination formed by the pressing device 71 and the tension measure- ment member TM2 can be arranged to turn/move with respect to the center of the reeling core 12 of the machine reel 13 along the surface of the machine reel 13 when the machine reel 13 moves during the change sequence further away from the reeling cylinder 11. Thus, it is possible to maintain the tension measurement member TM2 in the po- sition necessary for conducting the measurement with respect to the

paper web W also when the distance between the machine reel 13 and the reeling cylinder 11 changes during the change sequence, at the same time changing the position and angle on the periphery of the ma- chine reel 13 in which the paper web W is reeled up on the machine reel 13.

In a preferred embodiment of the invention that is shown in principle in Figs 8 to 10, the tension measurement member TM2 is connected to a primary reeling device 81. The tension measurement member TM2 is connected to the primary reeling device 81 with respect to mov- ing/turning fastening member/members 82 which, when the primary reeling device 81 turns during the change sequence, main- tains/maintain the tension measurement member TM2 in the operating position with respect to the paper web W. The tension measurement member TM2 may be connected to the primary reeling device 81 also without the moving/turning fastening member/members 82, wherein the tension measurement can be conducted only in certain positions of the primary reeling device 81.

In a preferred embodiment of the invention shown in principle in Fig.

11, the tension measurement member TM2 is used before the paper web W is cut for measuring the tension of the paper web W in the above-described manner, and after the cutting of the paper web W the tension measurement member TM2 is also used for guiding the end of the paper web on the empty reeling core 21. The aforementioned tur- nup is advantageously conducted for example by means of directional pressurized air jets, as shown in principle in Fig. 11. When the tension measurement is conducted by means of pressure measurement dis- closed in the publication EP0367901, the tension measurement mem- ber TM2 is already connected to the pressurized air inlet, because pressurized air itself is used in said measurement method for example to clean off the pressure measurement holes located in a measurement beam. The guiding blast used for turning up the cut end of the paper web W to the reeling core 21, can be intensified further by the shaping of the beam structure or the like that functions as a tension measure- ment member TM2, which beam can also be transferred after the cut-

ting of the web to a guiding position deviating from the position used in the actual tension measurement, if necessary, to guide the end of the web. The tension measurement member TM2 connected to the pri- mary reeling device 81 and shown in principle in Figs 8 to 10 as well as the fastening member 82 of the same can be utilized in a correspond- ing manner to guide the end of the paper web to the reeling core 21.

The aforementioned threading can be controlled by using pressurized air jets fixed to the fastening member 82 and/or tension measurement member TM2 and directed substantially towards the reeling core 21, and/or by shaping the fastening member 82 and/or the tension meas- urement member TM2 for said purpose in an advantageous manner that complies with the shape of the periphery of the reeling core 21.

The fastening member 82 and/or the tension measurement member TM2 can also be turned after the cutting of the paper web to a position that intensifies the threading, in which position they are utilized to force the cut end of the paper web to be better turned and guided around the reeling core 21.

Fig. 12 also shows in a principled diagram the use of measurement data given by the tension measurement conducted according to the invention in the adjustment of reeling up in an open nip situation. For the sake of clarity, Fig. 12 shows in a simplified manner only the most important interdependencies and feedback relations between the dif- ferent parts/components and system blocks.

In Fig. 12, the measurement variable M which is proportional to the tension of the paper web W and which is obtained from the tension measurement member TM2 is transferred to the control and adjust- ment system CS of the reel-up. On the basis of said tension informa- tion the control and adjustment system CS forms at least a control and actuating variable C1, by means of which the center drive of the reeling core 12 of the machine reel 13 is controlled to optimize the structure of the machine reel 13 that is being formed for the part of the final paper layers that are reeled up before the paper web W is cut. As was dis- closed earlier in this text, the tension measurement according to the invention can be utilized not only to affect the structure of the machine

reel but also to cut the paper web W. In other words, the web tension of the paper web W in the free section of the paper web between the nip and the machine reel 13 is adjusted into optimal one in view of the cut- ting, and to conduct the cutting at the correct moment, the control and adjustment system can be utilized further to produce a control and ac- tuating variable C2, which variable is arranged to control the function of the cutting member B2.

In an open nip situation the cohesive forces in the surface layers of the machine reel 13 that is becoming full are produced almost solely of the force components effective in the longitudinal direction (travel direction) of the paper web W. In other words, the tangential tensioning of the machine reel 13 produces a friction force between the paper layers, said friction force retaining the surface layers of the machine reel to- gether. By increasing the torque of the center drive of the reeling core 12 temporarily in connection with the change, it is possible to im- plement the aforementioned instantaneous tangential tensioning of the surface layers of the machine reel 13, wherein the tighter surface layer that is formed thereby better retains the machine reel 13 together after the paper web W is cut during the deceleration succeeding the cutting.

The above-described tensioning can be controlled by using tension measurement according to the invention, wherein it is, for example, possible to avoid unintentional cutting of the paper web during the aforementioned tensioning.

In addition to the tensioning in the direction of the tangent of the ma- chine reel 13 produced by the torque of the center drive of the reeling core 12, it is also possible to affect the structure of the surface layers by using a pressing device 71, as was mentioned earlier in the text. It is also possible to utilize the measurement information given by the ten- sion measurement conducted according to the invention in the control of the pressing device 71. In Fig. 12, the control and adjustment sys- tem CS utilizes the tension information of the paper web W contained in the measurement variable M to produce a control and actuating vari- able C3, which variable is arranged to control the function of the pressing device 71. By means of the control and adjustment system

CS the variables C1 and C3 are arranged adjustable in such a manner that the tensioning of the surface layers of the machine reel 13 caused by the center drive (variable C1) of the reeling core 12 primarily in the direction of the tangent of the reel and the tensioning caused by the pressing device 71 (variable C3) primarily in the direction of the radius of the reel together produce the desired tight structure of the surface layers of the machine reel 13. In different paper grades the part of center drive of the reeling core 12 and the pressing device 71 in the process of tensioning the surface layers of the machine reel may vary.

It is, of course, obvious for anyone skilled in the art that the method according to the invention can also be applied in connection with other known tension measurements than the tension measurement method described in the examples above, based on the measurement of air pressure between the paper web and a beam. As for prior art, there are known mechanical methods in which the surface of the paper web is pressed with a freely rotating reel or a roll, and the tension of the paper web is defined on the basis of the relationship between the shift in the direction of said pressing movement on the path of the web and the force required therein. In a known method the speed of sound waves propagating in the paper web is measured, which propagation speed depends on the tension of the paper web. In another known method the travel of a paper web over the measurement beam is deviated by means of air blown at constant pressure via holes in the measurement beam, and the measurement holes located in the measurement beam are utilized to measure the pressure produced in the measurement holes on the basis of the distance between the paper web travelling over said beam and the beam, in other words on the basis of the tension of the paper web. The tension measurement can be conducted locally at two or more points in the transverse direction of the paper web. Said local measurement can be shifted in the transverse direction of the paper web to determine a measured value defining the tension of the paper web on the entire width of the paper web and/or the transverse tension profile of the paper web. The tension measurement can also be conducted substantially on the entire trans-

verse width of the paper web at the same moment in time to define the measured value for the tension or the transverse tension profile.

It is, of course, also obvious that the method according to the invention can also be applied in reel-ups in which a simple reeling cylinder is re- placed with a combination of a reeling cylinder and a belt, or with another mechanical solution known as such that functions in a corre- sponding nip-like manner. In the mutual arrangements of a machine reel and a member functioning in a nip-like manner, it is possible to use modes of operation known as such, including different carrier and auxiliary roll solutions. The primary reeling device can also be imple- mented in different manners of prior art.