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1. WO2014175808 - A REEL-UP FOR WINDING A PAPER WEB INTO A ROLL AND A METHOD OF WINDING A PAPER WEB TO FORM A ROLL

Note: Text based on automatic Optical Character Recognition processes. Please use the PDF version for legal matters

[ EN ]

A REEL-UP FOR WINDING A PAPER WEB INTO A ROLL AND A METHOD OF WINDING A PAPER WEB TO FORM A ROLL

FIELD OF THE INVENTION

The present invention relates to a reel-up for winding a paper web into a roll and to a method of winding a paper web to form a roll.

BACKGROUND OF THE INVENTION

In a paper making machine, the ready-dried web is brought to a reel-up and wound on a reel spool to a roll of paper. This is often made in a Pope-type reel-up in which the paper web rests on and is driven by a supporting cylinder whose peripheral speed is equal to that of the paper web. Examples of such a Pope-type reel-up are disclosed in, for example, US patent No. 3743199 and US patent No. 5251835. In such reel-ups, the paper roll forms a nip with the supporting cylinder and a load is applied in the nip. In order to ensure that the paper roll being formed is substantially uniform, the nip pressure should be controlled. When nip pressure cannot be sufficiently controlled, this may result in paper rolls in which the paper has not been uniformly wound. This may also affect the paper properties. Especially tissue paper webs may be particularly sensitive to this problem.

To ensure a uniform winding, it has been suggested in for example US patent No. 5901918 that the supporting cylinder be replaced by a flexible member such as a belt such that the paper web is engaged by the flexible member against the reel spool during winding.

In a reel-up of the kind disclosed in US patent No. 5901918, i.e. a reel-up in which a flexible member such as a belt is used, it is of importance that the paper web adheres properly to the belt such that it does not become destabilized which could lead to wandering or wrinkles in the web. At the same time, the web should not adhere too strongly to the belt since that could lead to difficulties in transferring the paper web to the reel spool. To ensure a proper degree of adherence of the web to the belt, it has been suggested in US patent No. 7,398,943 that the static electricity of at least one of the belt and the paper web be measured by a static measurement probe and that at least one static induction device be used. The static induction device should then be used for

inducing a static charge into at least one of the endless flexible belt and the paper web. According to the '943 patent, the static charge difference between the web and the belt should be at least 6 kV or more in order to avoid poor web handling. However, the '943 patent also states that the static charge difference should be kept below 20 kV in order to avoid difficulties in connection with web transfer from the belt to the reel spool.

The object of the present invention is to provide a belt reel-up belt with improved control of the adherence of the paper web to the belt such that winding can be carried out in a controlled way.

DISCLOSURE OF THE INVENTION

The object of the invention is achieved by the inventive reel-up for receiving and winding into a roll a paper web that arrives from a drying cylinder in a paper making machine. The inventive reel-up comprises a rotatably mounted reel spool onto which a paper web can be wound to create a paper roll of increasing diameter and an endless flexible belt mounted for rotation along a predetermined path of travel such that the flexible belt forms a loop. The flexible belt is positioned adjacent to the reel spool to engage the paper web against the reel spool during winding such that the flexible belt is deflected from the predetermined path of travel when a paper roll is formed on the reel spool. In principle, the flexible belt will be deflected by an amount relative to the amount of paper material wound on the reel spool but the deflection can be kept constant or kept within predetermined limits if the distance between the reel spool and the predetermined path of the belt is increased as the diameter of the paper roll grows.

According to the invention, the endless flexible belt comprises electrically conductive material such that static electricity in the flexible belt is dissipated away from the flexible belt.

In an embodiment of the invention, the flexible belt is a woven fabric which is permeable to air and has a plurality of warp yarns and a plurality of weft yarns interwoven with the plurality of warp yarns and wherein at least some of the yarns are electrically conductive and preferably at least some of the weft yarns are electrically conductive.

In yet another embodiment of the invention, the flexible belt is a spiral link belt which is permeable to air and which comprises electrically conductive elements that have been inserted into the spiral link belt and extend in a cross-machine direction.

In advantageous embodiments of the invention, the reel-up further comprises: a deflection sensor mounted adjacent to the flexible belt and being arranged to measure the amount of deflection of the flexible belt from the predetermined path of travel; an actuator for positioning the reel spool and the flexible belt relative to each other to vary the amount of deflection of the flexible belt; and a controller connected to the deflection sensor and the actuator for controlling the amount of deflection of the flexible belt as the paper roll increases in diameter.

In embodiments using a flexible belt that is permeable to air, the reel-up may further comprise at least one source of underpressure located inside the loop of the flexible belt.

The invention may be used in, for example, a paper making machine for making tissue paper and which comprises a Yankee drying cylinder and a doctor blade arranged to crepe a paper web from the surface of the Yankee drying cylinder, and wherein, downstream of the Yankee drying cylinder, the paper making machine further comprises a reel-up according to the invention.

The invention also relates to a method of winding a paper web to form a roll. The inventive method comprises the steps of: engaging an endless flexible belt against a reel spool; moving the endless flexible belt along a predetermined path of travel; rotating the reel spool such that the surface of the reel spool moves together with the flexible belt and forms a nip with the flexible belt; and advancing the paper web into the nip and directing the web around the reel spool to form a roll of increasing diameter. In the inventive method, the endless flexible belt is a belt that comprises electrically conductive material such that static electricity in the endless flexible belt is dissipated away from the endless flexible belt.

In embodiments of the inventive method, the paper web is first creped from a Yankee drying cylinder and subsequently conveyed to the endless flexible belt to be wound to a roll.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a schematic side view of a part of a reel-up of the type that the present invention relates to.

Figure 2 is a side view of a reel-up placed in the dry end of a paper making machine

Figure 3 is a side view similar to Figure 2 but in larger scale and showing some details in one embodiment of the present invention.

Figure 4 is a schematic side view of a part of a paper machine with a different layout and in which the inventive reel-up could be used.

Figure 5 is a schematic side view similar to Figure 5 but with an alternative layout.

Figure 6 shows schematically and from above, a first embodiment of a belt for use in the present invention.

Figure 7 shows, schematically and from above, a second embodiment of a belt for use in the present invention.

Figure 8 is a side view of the belt of Figure 7.

DETAILED DESCRIPTION OF THE INVENTION

With reference to Figure 1 and to Figure 2, a reel-up 2 is shown which is arranged for receiving and winding into a roll 3 a paper web W that arrives from a drying cylinder 17 in a paper making machine. The reel-up 2 is a belt reel 2 that comprises a rotatably mounted reel spool 4 onto which a paper web W can be wound to create a paper roll 3 of increasing diameter and an endless flexible belt 5 mounted for rotation along a predetermined path of travel such that the flexible belt 5 forms a loop. The flexible belt 5 is positioned adjacent to the reel spool 4 to engage the paper web W against the reel spool 4 during winding such that the flexible belt 5 is deflected from the predetermined path of travel when a paper roll 3 is formed, i.e. when the paper roll 3 starts to build up on the reel spool 4. Of course, once the web W has started to become wound on the reel spool 4 and form a paper roll 3 on the reel spool 4, new paper web that arrives will be engaged against the reel spool 4 through the paper roll 3 that is being formed on the reel spool 4. In the context of this patent application and any patent granted on this patent application, the expression "engage the web against the reel spool" should thus be understood as including the case where the web that arrives to the nip point C is engaged by the flexible belt 5 against the paper roll 3 that is wound on the reel spool 4. New paper web that arrives to the nip point C is engaged against the reel spool 4 and any paper roll 3 already formed on the reel spool 4. In order for the paper web W to have the correct degree of adhesion to the flexible belt 5, it has previously been suggested in US patent No. 7,398,943 that static electricity of at least one of the belt and the paper web be measured by a static measurement probe and that one or several static induction devices be used and that the static charge difference between the web and the belt should be kept in the range of 6 kV - 20 kV. Such a method may achieve its purpose but the inventors have found that the previously known method is not optimal for achieving a correct degree of adherence of the paper web W to the flexible belt 5. The operation becomes dependent on the reliability of the measurement probe and the induction device or induction devices. One problem is that the static electricity in the flexible belt 5 and/or paper web W may lead to uncontrolled electric discharges that disturb the operation of the measurement probe and/or the static induction device(s). Moreover, if the reeling is carried out in an environment with large amounts of dust in the air, this may also disturb the operation of the measurement probe and the induction device or induction devices. In particular in such cases where the paper web W has been creped from a drying cylinder, for example a Yankee drying cylinder, there may be large amounts of dust in the air since the creping operation generates large quantities of dust that fill the air in the dry end of the machine where the reel 2 is located. Even without a static induction device, the belt may become charged with static electricity due to friction between the belt and guide rolls that are used to guide the belt in its loop but the actual level of the static electricity may vary considerably which can lead to variations in the adherence of the paper web to the belt. The inventors have found that, generally, more static electricity seems to be generated due to friction when the dryness level of the paper web is high. In particular, the inventors have noted that much static electricity is generated when the moisture content of the web that arrives to the reel-up is no more than 3 % by weight but the actual level or amount of static electricity can be difficult to predict. This is in particular the case for production of high bulk tissue products on for example TAD machines. The difficulties may be further aggravated by the fact that static electricity and dust disturb the function of measurement probes and induction devices. The actual charge difference between the web W and the flexible belt 5 can therefore vary in ways that are difficult to predict and the control of the charge difference may be less than satisfactory.

Therefore, the inventors have found that the paper web W should be made to adhere correctly to the belt without relying on measurement probes for static electricity and/or static induction devices.

Instead of static induction devices, the present invention uses an endless flexible belt 5 that comprises electrically conductive material such that static electricity in the flexible belt 5 is dissipated away from the flexible belt 5. In this way, static electricity can be dissipated away from the flexible belt and the paper web. As a consequence, the level of the static charge will be low or zero and can be disregarded. This means that static charge is predictable (since it is zero or too small to be of significance) and that there will be no substantial variations in the static charge that could lead to variations in the adherence of the paper web W to the flexible belt 5.

Instead of achieving adherence by means of a difference in static charge, adherence of the paper web to the flexible belt should be achieved by means that are not dependent on electronic equipment that can be disturbed by static electricity in the flexible belt or the paper web. One solution may be to use a flexible belt 5 which is substantially impermeable and has a smooth surface that the paper web W adheres to the flexible belt 5 due to the smooth surface of the flexible belt 5. In the smooth surface of the flexible belt 5, electrically conductive material may be placed. For example, if the flexible belt 5 is a polyurethane belt, thin electrically conductive wires may be embedded in the surface of the smooth flexible belt.

However, in preferred embodiments of the invention, the endless flexible belt 5 is a belt which is permeable to air. Such a solution is advantageous since the adherence of the paper web W can then be reliably kept on a proper level by means of suction devices arranged inside the loop of the flexible belt 5 which can be operated based on practical experience.

An embodiment of a permeable flexible belt 5 is showed in Figure 6. The flexible belt 5 which is showed in Figure 6 is a woven fabric with a plurality of warp yarns 32 that extend in the machine direction (the MD direction in Figure 6) and a plurality of weft yarns 33 that extend in a cross machine direction (the CD direction in Figure 6) and that are interwoven with the plurality of warp yarns 32. At least some of the yarns 32, 33 are electrically conductive. Preferably, it is some of the weft yarns 33 (i.e. the yarns that extend in the cross machine direction) that are electrically conductive. Suitably, every fourth weft yarn or every fifth weft yarn 33 is electrically conductive. However, it is also conceivable that every second weft yarn 33 is electrically conductive or that all weft yarns 33 are electrically conductive. Embodiments are also conceivable in which one or several warp yarns 32 that extend in the machine direction are electrically conductive. It should be understood that the flexible belt 5 of Figure 6 is permeable to air such that a suction device (for example a suction roll) or a blow box may act through the flexible belt to suck a paper web against the flexible belt 5.

An example of a fabric belt with electrically conductive yarns is disclosed in US patent No. 6790796 and a fabric substantially according to that patent could conceivably be used as a flexible belt in a reel-up according to the present invention.

Yet another possible embodiment of a suitable flexible belt 5 is shown in Figure 7 and in Figure 8. The spiral link belt may have a structure which is of a kind substantially as disclosed in WO 2008/157223 Al . The spiral link belt 5 in Figure 7 and Figure 8 may comprise spiral coils 34 that are interconnected by a series of parallel pins 35.

Electrically conductive elements 36 have been inserted into the spiral link belt and extend in a cross-machine direction. It should be understood that the flexible belt 5 of Figure 7 and Figure 8 is permeable to air such that a suction device (for example a suction roll) or a blow box may act through the flexible belt to suck a paper web against the flexible belt 5.

The function of the inventive reel-up 2 will now be explained further with reference to the drawings.

With reference to Figure 1, it can be seen that in advantageous embodiments of the invention, the reel-up 2 may optionally comprise a deflection sensor 6 mounted adjacent to the flexible belt 5 and being arranged to measure the amount of deflection of the flexible belt 5 from the predetermined path of travel. In principle, the flexible belt 5 will be deflected during winding by an amount relative to the amount of paper material wound on the reel spool 4 (i.e. by an amount relative to the growing diameter of the paper roll 3 that is being formed on the reel spool 4) but the deflection can be kept constant or within predetermined limits if the distance between the reel spool 4 and the path of travel of the flexible belt is adjusted as the paper roll 3 grows. The reel spool 4 may be resting in carriages 9, preferably one carriage 9 at each side of the machine (i.e. at each axial end of a reel spool 4). The reel-up 2 may also comprise an actuator 7 for positioning the reel spool 4 and the flexible belt 5 relative to each other to vary the amount of deflection of the flexible belt 5 and a controller 8 connected to the deflection sensor 6 and the actuator 7 for controlling the amount of deflection of the flexible belt 5 as the paper roll 3 increases in diameter. The function of such an arrangement has been described in detail in US patent No. 5901918 and exactly the same control method may be applied for the present invention. The basic principle is that, as the diameter of the paper roll 3 increases, the paper roll 3 will deflect the flexible belt 5 from its path of travel and in Figure 1, the amount of deflection is indicated by "D". The deflection is detected by the deflection sensor 6 which may be a laser sensor. The detected deflection D generates a signal that is transmitted to a controller 8 that may be, for example, a computer. The controller 8 is programmed to keep the deflection D at a predetermined level or within predetermined limits. When actual deflection D deviates from the predetermined value or range, the controller 8 causes the actuator 7 to act to adjust the positioning of the reel spool 4 and the flexible belt 5 relative to each other. This can be done by, for example, causing the actuator 7 to move the reel spool 4 along rails 20 (see Fig. 2) away from the flexible belt 5 until the deflection D of the flexible belt 5 has reached an acceptable value. In this way, the pressure in the contact point C between the flexible belt 5 and the paper roll 3 can be controlled.

The use of a deflection sensor 6 and the controller 8 is very advantageous but embodiments are also conceivable in which these elements are not used.

With reference to Figure 2, it can be seen that the reel-up 2 may be a part of a paper making machine 1 that comprises a drying cylinder 17 which may be a Yankee cylinder from which the paper web is creped by a doctor 27 as is known in the art. The Yankee cylinder may internally heated by steam and can be a Yankee cylinder of cast iron or it could be a Yankee cylinder of welded steel. The paper web W that has been creped from the hot surface of the drying cylinder 17 may optionally be passed through a calender 24 and/or a measurement device 23 that is arranged to measure such properties as, for example, basis weight or dry solids content In the embodiment of Figure 2, the paper web W is then passed in an open draw to the flexible belt 5 of the reel-up 2. The reference numeral 16 indicates a guide roll that is used to guide the paper web. The web reaches the flexible belt 5 at a point of contact P that is located at the end of the open draw. Where the web W meets the flexible belt 5, a wedge-shaped space WS may result.

As can be seen in Figure 2, the flexible belt 5 may be guided in its loop by internal guide rolls 10, 12, 13, 14 and optionally also by one or several external guide rolls 15. In Figure 2, it can also be seen that the reel-up 2 may comprise a stand supported by substantially vertical pillars 18. The pillars 18 may support parallel lower support beams 19 that carry rails 20 on which rails the carriage 9 of the reel spool 4 may be carried. The pillars 18 also support upper parallel beams 21 with rails 22 on which new reel spools 4 may be supported. The upper rail 22 may thus serve to store new reel spools 4. When a new paper roll 3 has been completely wound on its reel spool 4, a new reel spool 4 can be taken from the upper rail 22 as is known in the art.

In Figure 2, it can also be seen that a source of underpressure 11 such as a blow box or a suction box can be placed inside the loop of the flexible belt 5. It should be understood that one or several sources of underpressure 1 1 may be used. For example, there could be one, two or three blow boxes placed after each other in the machine direction. There could also be more than three blow boxes (or suction boxes) inside the loop of the flexible belt 5. Instead of blow boxes or suction boxes, suction rolls may be used. Blow boxes and/or suction boxes may also be used in combination with one or several suction rolls to act through the flexible belt 5 (which is then permeable to air).

Reference will now be made to Figure 3. In Figure 3, it can be seen that, at the contact point P where the paper web W meets the flexible belt 5, the guide roll 10 for the flexible belt 5 is a suction roll 10 with a suction zone 10c which is located in the area of the contact point P. By means of underpressure in the suction roll 10, the paper web will be caused to adhere to the flexible belt 5 when the flexible belt 5 is air permeable. The suction zone 10c of the roll 10 will also assist in removing air that has been entrained by the web or the flexible belt into the wedge-shaped space or gap WS between the web W and the flexible belt 5. In Figure 3, it can also be seen that the guide roll 12 that precedes the point where the paper roll 4 meets the flexible belt 5 may also be a suction roll and that it has a suction zone 12c. With reference to Figure 3, it can also be seen how an air deflector 25 may be placed in or adjacent the wedge-shaped gap WS to prevent boundary layer air entrained by the paper web W or the flexible belt 5 to come between the paper web W and the flexible belt 5. Such an air deflector 25 may be advantageous but is optional for the present invention. Embodiments without such an air deflector are possible. If such an air deflector 25 is used, it may be arranged such that it can be withdrawn from an active position and placed in an inactive position away from the wedge-shaped gap WS. To achieve this functionality, the air deflector 25 may be mounted on a holder which can be moved away from the wedge-shaped gap (or towards the wedge-shaped gap) by one or several hydraulic or pneumatic cylinder or some other actuator.

With reference to Figure 3, it can also be seen how an additional air deflector 26 may be placed adjacent the flexible belt 5 at a point which is located at a distance from the contact point P where the paper web W meets the flexible belt 5. This additional air deflector 26 is entirely optional. If such an additional air deflector 26 is used, it may serve to divert boundary layer air away from the flexible belt 5 and cause a flow of air in a desired direction. Such a flow of air can be used to carry dust away from the area of the reel-up.

It should be understood that the guide rolls 10, 12 do not necessarily have to be suction rolls, they could also be solid rolls. The guide roll 10 in Figure 2 and Figure 3 could also be a roll which has a suction zone only at an axial end of the roll but which is otherwise a solid roll A suction zone that is located only at the axial end of the roll 10 could be useful for tail threading.

When the flexible belt is permeable to air, sources of underpressure such as suction rolls 10, 12, suction boxes or blow boxes 1 1 can act through the flexible belt 5 such that the paper web will be caused to adhere to the flexible belt 5. Experience has showed that

such an arrangement produces a reliable adherence of the paper web W to the belt. When static electricity in the belt is dissipated away from the belt since the belt is electrically conductive, static electricity is less likely to cause unpredictable fluctuations in the adherence of the web to the flexible belt.

When the flexible belt is a woven fabric with electrically conductive yarns as shown in Figure 6, the electrically conductive yarns will cause static electricity to dissipate away from the flexible belt 5 and from the paper web W which is in contact with the flexible belt 5.

When the flexible belt 5 is a spiral link belt as shown in Figure 7, the electrically conductive elements 36 will cause static electricity in the flexible belt 5 and the paper web W to be dissipated.

When static electricity is dissipated away from the belt, this also reduces the risk that sudden discharges of electrical energy will cause disturbances in the operation of the deflection sensor 6, the controller 8 and the actuator 7 since such equipment may comprise electronic components that may be affected by electrical discharges.

Therefore, the use of a flexible belt that is electrically conductive contributes to a more reliable operation of those components. As a result, the control of the winding operation is improved. This result is achieved independently of the improved control of web adherence that is also achieved.

With reference to Figure 4, it can be seen that the inventive reel-up may also be used in a paper making machine where a Yankee drying cylinder is preceded by a through air drying cylinder 28, i.e. a TAD cylinder 28. In the configuration of Figure 4, a TAD wire 29 is arranged to carry the web W over the TAD cylinder 28 and the TAD wire 29 is guided by guide rolls 37. A press roll 38 arranged within the loop of the TAD wire 29 forms a nip with the Yankee cylinder 17. The nip formed by the press roll 38 and the Yankee cylinder 17 functions as a transfer nip in which the paper web W (especially a tissue paper web) is transferred to the Yankee cylinder 17. The TAD cylinder 28 may have a hood 30. Hot air used to dry a tissue paper web may by created by (for example) a burner (not showed in Figure 4) and a fan (not showed in the figure) may be used to force the hot air into the hood 30. The hot air is drawn through the web carried on the wire 29 and through the cylinder 28.

A machine substantially similar to the machine of Figure 4 is showed in Figure 5. The machine according to Figure 5 differs from the machine according to Figure 4 in that the TAD cylinder 28 is placed in a different position.

When a through air drying cylinder 28 is used, the hot air does not necessarily have to flow from the hood 30 to the TAD cylinder 28. Instead, it could also be so that the hot air flows from the TAD cylinder 28, through the tissue paper web and into the hood 30.

It should be understood that, in both the configuration of Figure 2, the configuration of Figure 4 and in the configuration of Figure 5, there is a forming section which is not showed.

It will now be understood that the inventive method of winding a paper web W to a paper roll comprises the steps of engaging an endless flexible belt 5 against a reel spool 4 and moving the endless flexible belt 5 along a predetermined path of travel. The reel spool 4 is rotated such that the surface of the reel spool 4 moves together with the flexible belt 5 and forms a nip with the flexible belt 5. The paper web W is advanced into the nip and directed around the reel spool 4 to form a roll 3 of increasing diameter. Since the endless flexible belt 5 comprises electrically conductive material, static electricity in the endless flexible belt 5 is dissipated away from the endless flexible belt 5. In Figure 1, the nip can be represented by the point of contact C between the flexible belt 5 and the paper roll 3.

Embodiments are conceivable in which the paper web is produced entirely without creping, for example if the only drying cylinder that is used is a through air drying cylinder. However, the invention is especially valuable in such cases where the paper web W has first been creped from a Yankee drying cylinder 17 and subsequently conveyed to the endless flexible belt 5 to be wound to a roll 3 since creping produces much dust and the use of static inductors is more difficult in such circumstances.

It should be understood that, when static electricity is dissipated away from the flexible belt 5 by means of electrically conductive materials or elements in the flexible belt 5, this will also cause static electricity to be dissipated away from the paper web W since the paper web W is in contact with the flexible belt 5. Static electricity in the flexible belt 5 will of course be discharged to ground when the flexible belt 5 comes into contact with metal objects such as rolls that are journalled in the frame of the paper making machine.

The use of a flexible belt 5 that comprises or is made of electrically conductive material can thus give a more stable and predictable adherence of the paper web to the flexible belt. This is especially the case when the flexible belt is permeable to air and sources of underpressure have been placed within the loop of the flexible belt (i.e. when at least one source of underpressure has been placed within the loop of the flexible belt 5 and adjacent the flexible belt 5 such that it can act through the flexible belt 5).

Independently of the adherence of the paper web to the flexible belt, the use of a flexible belt which comprises electrically conductive material also leads to a more reliable winding when a deflection sensor and a controller is used to control an actuator that is arranged to move the reel spool relative to the flexible belt.

The invention is particularly useful in such cases where the moisture content (water content) of the paper web that arrives to the belt reel-up is in the range of 2% - 5% and especially when the moisture content is in the range of 2 %- 3 %. In practice, the moisture content of the web will not be lower than 1% by weight. It can therefore be said that the invention is particularly useful in such cases where the paper web that arrives to the reel-up has a moisture content in the range of 1 % by weight - 5 % by weight and especially when the paper web has a moisture content in the range of 2 % v-3 %. For paper webs with a moisture content higher than about 5 %, static electricity will normally not be generated to any substantial amount.

Although the invention has been described above in terms of, a reel-up, a machine comprising the reel-up and a method of winding, it should be understood that these categories only reflect different aspects of one and the same invention. The inventive method may thus comprise such steps that would be the inevitable result of using the inventive reel-up and/or the inventive machine that comprises the inventive reel-up, regardless of whether such steps have been explicitly mentioned or not.