SE1150723A1 - A machine for making Tissue paper and a method of running such a machine - Google Patents

Abstract

The invention relates to a paper machine for producing tissue paper. The machine comprises a former (2) and a press (11) with a first press part (12) and a second press part (13) arranged to form a dewatering nip (PN) with the first press part (12). A fi lt (7) is arranged to pass through the drainage nip (PN). Entork cylinder (14) is arranged to form a transfer nip (TN) with the pre-press part (12) and a belt (15) forming a loop around the first press part (12) so that the belt (15) passes through the dewatering nip (PN) and the transfer nip ( TN). The first press member (12) is a long nip roll having an flexable sheath (17) forming a loop and an flexable support body (18) within the loop of the flexable sheath (17). The flavable support body (18) can be pushed to push the flexable sheath (17) radially outwards and the flexable support body (18) is positioned in the center motor cylinder (14) so that the flexable support body (18) can press the fl exible sheath (17) against the drying cylinder ) to end the transfer nip (TN). The invention also relates to a method of running the machine.

Description

A PAPER MAKING MACHINE AND A METHOD OF OPERATING A PAPERMAKING MACHINE FIELD OF THE INVENTION The present inVention relates to a paper making machine for making tissue paper. The inVention also relates to a method of operating such a machine.

BACKGROUND OF THE INVENTION A paper making machine for the production of tissue paper is known from U.S. patentNo. 5393384. The paper machine shown therein has a belt imperrneable to water whichruns in a loop through an extended press nip formed by a shoe press and a counter roll.A press felt is conveyed through the press nip. In one embodiment, a shoe press hasbeen placed such that the press shoe is capable of acting on the tissue drying cylinder. Itis stated that the drying effect of the shoe press generates a considerably higher degreeof drying than a corresponding roll press and that this, in the conjunction with anonabsorbent belt which avoids remoistening of the web results in considerablyincreased drying capacities of a press unit.

Another paper making machine for soft paper such as tissue is disclosed in U.S. patentNo. 6547924. The paper making machine shown in that patent also uses a substantiallyimperrneable belt but this belt is a texturing belt which has a web-contacting surfacedefining a multitude of regularly distributed depressions and surface portions locatedbetween the depressions. The belt is used for the purpose of texturing a relief pattem ina f1brous web in order to increase its bulk. The substantially imperrneable belt runs in aloop through a press with a shoe press roll and a counter roll and around a transfer rollthat forms a transfer nip with a Yankee dryer.

Yet another paper making machine is shown in US patent No. 7811418. The papermaking machine shown in that patent uses a transfer belt that may have depressions anda perrneable structuring fabric which is arranged to transfer the wet paper web to adrying cylinder. In embodiments described in that document, a shoe press is used inwhich the transfer belt passes through a press nip between a shoe press roll and a counter roll.

The above mentioned patents include a large number of components. It is desirable to reduce the number of components used in the machine.

U.S. patent No. 4144124 discloses a machine for manufacturing paper such a tissuepaper. The machine disclosed in that patent comprises a twin-wire former and a pressnip between an inner and an outer press roll. The upper or outer press roll is a suctionroll which, together with a Yankee cylinder forms a second nip. An endless fabric suchas a wire suitable for pattem embossing is may be used and is said to produceimpressions in the paper at the press nips. This machine can use uses fewer rolls in thepress section since the suction roll is used two nips, one nip with the so called “inner roll” and one nip with the Yankee cylinder.

It is an object of the present invention to provide a paper making machine for tissuepaper which has a simple design and few parts and which is capable of producing atissue paper web that has a high bulk. These and other objects are achieved by means of the present invention as will be explained.

DISCLOSURE OF THE INVENTION The invention relates to a paper making machine for making tissue paper. The inventivemachine comprises a former in which a fibrous web may be formed. The former has aforming roll, a forrning fabric and a felt. The machine further comprises a press with afirst press member and a second press member. The second press member is arranged toform a dewatering nip with the first press member and the felt (i.e. the same felt as isused in the former) is arranged to pass through the dewatering nip. The machine furthercomprises a drying cylinder which is arranged to form a transfer nip with the first pressmember. A belt forms a loop around the first press member such that the belt passesthrough the dewatering nip and the transfer nip. According to the invention, the firstpress member is an extended nip roll that has a flexible jacket that forms a loop and aflexible support body within the loop of the flexible jacket. The flexible support bodycan be caused to press the flexible jacket radially outwards. Moreover, the flexiblesupport body is placed opposite the drying cylinder such that the support body can pressthe flexible jacket towards the drying cylinder to close the transfer nip. The first pressmember is also movable in relation to the drying cylinder such that the distance betweenthe drying cylinder and the first press member can be increased in a separatingmovement or decreased in a closing movement. The paper making machine further comprises a mechanical stop arranged to halt the closing movement.

In embodiments of the inVention, the mechanical stop is arranged to halt the closingmovement in a position Where the transfer nip is not yet closed. Closure of the transfernip Will then require that flexible support body presses the flexible jacket radially outWards.

In embodiments of the inVention, the flexible support body comprises or is supported byat least one flexible hose extending in a cross machine direction and connected to asource of pressurized fluid such that pressurization of the at least one flexible hose Willcause the flexible support body to either expand or move radially outWards.

The belt may be an imperrneable belt Which has a smooth surface on the side that, in thetransfer nip, faces the drying cylinder.

The belt can also be an imperrneable belt Which has a textured surface on the side that,in the transfer nip, faces the drying cylinder.

In other embodiments, the belt may be a perrneable belt Which has a textured surface onthe side that, in the transfer nip, faces the drying cylinder.

The belt is can also be a perrneable belt Which has a smooth surface on the side that, inthe transfer nip, faces the drying cylinder.

Within the loop of the flexible jacket, the extended nip roll may optionally alsocomprise a flexible support body that is placed opposite the second press member tocooperate With the second press member to form the dewatering nip.

The second press member may be a grooved roll.

In embodiments of the inVention, the first press member is supported in bearinghousings. In such embodiments, the paper making machine may further comprise atleast one actuator arranged to act on the bearing housings of the first press member toincrease or decrease the distance between the first press member and the dryingcylinder.

When the paper making machine uses an extended nip roll that has a flexible supportbody arranged to form a transfer nip With the drying cylinder as described above, theinvention can also be described in terms of a method of operating such a machine. Themethod comprises moving the first press member from a first position at a first distancefrom the drying cylinder to a second position defined by the mechanical stop While theflexible support body has still not pressed the flexible jacket radially outWards.Subsequently, the flexible support body is caused to press the flexible jacket radially outWards such that it acts against the drying cylinder in the transfer nip (i.e. such thatthe transfer nip is loaded With a certain linear load).

As explained above, there are embodiments Where, Within the loop of the flexiblejacket, the extended nip roll also comprises a flexible support body that is placedopposite the second press member to cooperate With the second press member to formthe deWatering nip. In such embodiments, the inventive method may comprise operatingthe deWatering nip at a linear load in the range of 100 kN/m - 600 kN/m and a peakpressure of 6 MPa.

According to the inventive method, the drying cylinder may be rotating already beforethe transfer nip is closed. In such cases, the belt that passes through the transfer nip (andthus forms a loop around the first press member) may be used to drive the flexiblejacket such that the flexible jacket rotates before the transfer nip is closed.

The belt can be used to drive the flexible jacket to a speed that matches that of thedrying cylinder before the transfer nip is closed or at least before the belt contacts thesurface of the drying cylinder.

Preferably, the belt is used to drive the flexible jacket to match the speed of the dryingcylinder While the outer surface of the flexible jacket is still at a distance of at least 40mm from the surface of the drying cylinder.

Altematively, the inventive paper making machine may be defined in the followingterms. The machine comprises a former in Which a fibrous Web may be formed. Theformer has a forming roll, a forrning fabric and a felt. The machine further has a firstpress member and a second press member arranged to form a deWatering nip With thefirst press member. The felt (i.e. the same felt as used in the former) is arranged to passthrough the deWatering nip. A drying cylinder is arranged to form a transfer nip With thefirst press member. Furthermore, a belt forms a loop around the first press member suchthat the belt passes through the deWatering nip and the transfer nip. According to theinvention, one of the first press member and the second press member is an extendednip roll that has a flexible jacket that forms a loop and a flexible support body Within theloop of the flexible jacket. The flexible support body can be caused to press the flexiblejacket radially outWards. Moreover, the support body fiarther is placed opposite theother press member such that the support body can press the flexible jacket towards theother press member to close the deWatering nip. Either of the first press member and the second press member may be an extended nip roll.

BRIEF DESCRIPTION OF THE DRAWINGSFigure 1 shows a layout of a paper making machine according to one embodiment.

Figure 2 is a schematic representation of a press nip and a transfer nip in a paper making machine.Figure 3 shows a cross section of a support body used in the press nip of Figure 2.

Figure 4 shows a cross section similar to Figure 3 but illustrating another way ofarranging a support body for the press nip.

Figure 5 is a schematic representation of a part of the paper making machine in which apress member is placed in a first position.

Figure 6 is a schematic representation similar to Figure 5 but with the same press member placed in a second position.

Figure 7 is a figure similar to Figure 5 and Figure 6 but showing an altemative design ofone of the components used.

Figure 8 is a schematic cross-sectional representation of the situation before the transfernip has been closed.

Figure 9 is a schematic cross-sectional representation of how the transfer nip has beenclosed.

Figure l0a is a schematic representation substantially corresponding to Figure 5 but where second press member is shown.

Figure 10 b is a schematic representation similar to Figure 10 a but showing the firstpress member in a position where it has moved closer to the drying cylinder.

Figure 10 c is a schematic representation substantially similar to Figure 10a and 10b butwhere the flexible support bodies have been activated to act in the transfer nip and the press nip.Figure 11a is a schematic representation of an embodiment of the invention.

Figure 11b is a Figure similar to Figure 10a but showing a perspective view of the same components.

Figure 12 shows a layout of a paper making machine according to an altemative embodiment.

DETAILED DESCRIPTION OF THE INVENTION With reference to Figure 1, the invention relates to a paper making machine 1 formaking paper, in particular tissue paper. As used herein, the term “tissue paper” relatesto paper having a relatively low basis weight. In most cases, this means a basis weightin the range of 10 g/mz - 50 g/mz although examples of tissue paper webs are knownwhere the basis weight may lie outside this range. Unlike paperboard, tissue paper doesnot have to be stiff and tissue can therefore have a lower basis weight. In most cases, thebasis weight for tissue paper may lie in the range of 15 g/mz - 40 g/mz and typicalvalues may lie in the range of 15 g /mz - 30 g/mz or 20 g/mz - 30 g/mz. Such paper canbe used as, for example, facial tissue, toilet paper or absorbent paper towel (e.g. kitchentowel). The machine according to the invention comprises a former 2 in which a f1brousweb may be formed. As can be seen in Figure 1, the former 2 has a forming roll 4, aforming fabric 5 and a felt 7. The forrning fabric 5 is suitably a perrneable wire. Theforming fabric 5 is guided in a loop by guide rolls 6 and the felt 7 is guided in a looppartially by guide rolls 8 but also by the forming roll 4 and by a press member 13. Theformer 2 also has a head box 3 arranged to inject stock in a gap formed between theforming fabric 5 and the felt 7 as is known in the art. One or several felt dewateringdevices 26 may be arranged to remove water from the felt 7 as is known in the art towhich the invention pertains. The dewatering device 26 may be, for example, a Uhlebox.

With reference to Figure 1, Figure 11a and Figure 11b, the machine 1 also comprises apress 11 with a first press member 12 and a second press member 13. The second pressmember 13 is arranged to form a dewatering nip PN with the first press member 12 (seealso Figure 11b and Figure 11b). The felt 7 is arranged to pass through the dewateringnip PN. As can be seen in Figure 1, the felt 7 forms a loop around the seconddewatering member 13. In the dewatering nip PN, water is pressed from the wet paperweb and absorbed by the felt 7. One or several further felt dewatering devices, forexample Uhle boxes, may be arranged to dewater the felt 7 while the felt runs from thepress 11 back to the forrning roll (these further dewatering devices are not shown inFigure 1).

The machine also comprises a drying cylinder 14. The drying cylinder may suitably be aYankee drying cylinder which is intemally heated by steam. The drying cylinder 14 canalso be heated by other means, for example by infrared heaters (not shown). The dryingcylinder 14 is arranged to form a transfer nip TN with the first press member 12 (seeFigure 11a and Figure 11b). A belt 15 forms a loop around the first press member 12such that the belt 15 passes through the dewatering nip PN and the transfer nip TN. Ascan be seen in Figure 1, guide rolls 16 may be arranged to guide the belt 15. The belt 15may also be provided with a cleaning device (not shown) for cleaning the belt duringoperation of the machine. According to the invention, the first press member 12 is anextended nip roll that has a flexible jacket 17 that forms a loop and a flexible supportbody 18 within the loop of the flexible jacket 17 as is also shown in Figure 11b andFigure 1 lb. As can be seen more clearly in Figure 1 la and Figure 1 lb, the first pressmember 12 may comprise two flexible support bodies 18, 19 in which case a firstflexible support body 18 is arranged to act against the drying cylinder 14 and a secondflexible support body 19 is arranged to act against the second press member 13. Eachflexible support body 18, 19 can be caused to press the flexible jacket 17 radiallyoutwards. That the support body 18, 19 is a flexible support body should be understoodas meaning that, at least to some extent, it can adapt its shape to follow the contour ofan opposing element such as the drying cylinder 14 or the second press member 13. Thesecond press member 13 is suitably a roll. In advantageous embodiments of theinvention, the second press member 13 may be provided with grooves 28 as best seen inFigure 11 b. The use of a grooved roll in this position improves dewatering. In otherembodiments, the second press member may be a press roll with a smooth surface, forexample a roll with a cover, e.g. an elastic cover such as a cover of rubber or a materialwith properties similar to rubber. The cover could also be a ceramic cover. The press member 13 may also be a roll without a cover.

The belt 15 may be an imperrneable textured belt. For example, it may be animperrneable textured belt of the kind disclosed in U.S. patent No. 6547924, i.e. at leastthe surface facing the paper web is textured. The use of a textured belt can improve thebulk of the web by imparting a three-dimensional structure to the web.

The belt 15 may also be a belt with a substantially smooth surface (i.e. at least thesurface facing the paper web is smooth). In this context, “smooth” should be understoodas meaning that the belt 15 has no texturing structure that is arranged to form a texturedpattem in the paper web. The belt could be a belt of, for example, the kind disclosed inU.S. patent No. 5298124.

It should be understood that the belt 15 is typically made of a material that iscompressible to a certain degree and the belt 15 is often made of a material that may beheat sensitive. This is especially the case when the belt contains polymer materials. Thebelt 15 preferably comprises polyurethane such that at least the surface that contacts thepaper web may be made of polyurethane, at least in part.

The extended nip roll and the flexible support body 18 (and optionally also the secondflexible support body 19) may be designed in a way shown in, for example, U.S. patentNo. 7527708, the disclosure of which is hereby incorporated by reference. The design ofsuch an extended nip roll and flexible support body will also be explained withreference to Figure 2 and Figure 3. As can be seen in Figure 2, the flexible support body18 is placed within the loop of a flexible jacket 17 that can be made wholly or in part of,for example, polyurethane or a material with properties similar to polyurethane. Theflexible jacket 17 may thus comprise polyurethane but possibly also other components.The extemal surface of the flexible jacket 17 may be smooth or substantially smooth butembodiments are conceivable where the flexible jacket 17 does not have a smooth outersurface. For example, the extemal face of the flexible jacket 17 may have grooves. Ascan be seen in Figure 3, that flexible support body 18 may be formed by or comprise abody that can be described as a flexible hose with an intemal cavity 31 that can bepressurized intemally by means of pressurized fluid that is caused to flow into theintemal cavity 31 from a source 22 of pressurized fluid that is connected to the intemalcavity 31. The source of pressurized fluid 22 may be controlled by a control device 32.The control device 32 may be, for example, a computer. In Figure 3, the support bodies18, 19 are schematically shown as being connected to the same source 22 of pressurizedfluid. It should be understood that each flexible support body 18, 19 may be connectedto its own source 22 of pressurized fluid. As can be seen in Figure 3, the flexiblesupport body 18 may be placed in a channel 30 of a holder 29. It should be understoodthat the support body 18 may be sealed at its axial ends. The flexible support body 18 ispreferably made of an elastic material such that either the entire support body 18 or atleast a part of is made of an elastic material such that the flexible support body iselastically deformable. The support body 18 can be made of, for example, plastic orrubber material such as polymers, possibly reinforced polymers. If pressurized fluid isfed into the intemal cavity 31, the flexible support body 18 will expand radiallyoutwards. In Figure 3, the flexible jacket 17 is not shown but it should be understoodthat the flexible jacket 17 runs over the flexible support body 18. When the flexiblesupport body 18 expands radially outwards, it will press against the flexible jacket 17such that also the flexible jacket 17 is pressed outwards. It should be understood that the flexible support body 18 which has an inner cavity 31 as described above also extends in the cross machine direction.

The flexible support body 18 must not necessarily be shaped as in U.S. patent No.7527708. Another kind of flexible support body arrangement is shown in Figure 4. Inthe embodiment of Figure 4, the flexible support body 18 is a thin shoe with a concavesurface. The concave surface faces outwards such that it can cooperate with a convexcounter element such as a roll in order to forrn a nip with the convex counter element.The thin shoe that forrns the flexible support body may be made of, for example,aluminum, and be suff1ciently thin to allow the shoe to adapt to a large extent to thecontour of a counter roll (such as a Yankee drying cylinder). The thin shoe is supportedby one, two or more flexible hoses 33 that can be made of an elastic material or amaterial that is only flexible but not elastic. The flexible hose or flexible hoses 33extend in the cross machine direction and are connected to a source of pressurized fluid22 in the same way as described with reference to Figure 2 and Figure 3. In someembodiments, a further thin sheet 35 and a number of separate interrnediate pieces 34may optionally be placed between the flexible support body 18 and the flexible hose(s)33. The thin sheet 35 may serve to protect the flexible hoses 33 from the interrnediatepieces 35. The interrnediate pieces 34 can be capable of moving relative to each other inthe radial direction (i.e. substantially in the press plane). Thereby, the flexible supportbody 18 can more easily adapt to the shape of a counter element such as a Yankeecylinder 14. If the flexible hose(s) 33 is (are) filled with pressurized fluid, this maycause the flexible hose(s) to expand and thereby cause the flexible support body 18 tomove outwards against the inner surface of the flexible jacket 17 such that also theflexible jacket 17 is pressed radially outwards. An arrangement substantially asdescribed with reference to Figure 4 is also disclosed in EP 2085513 and such an arrangement may also be used in the present invention.

In embodiments of the invention, the flexible support body 18 can thus be described ascomprising or being supported by at least one flexible hose extending in a crossmachine direction and connected to a source of pressurized fluid such thatpressurization of the at least one flexible hose will cause the flexible support body 18 to either expand or move radially outwards.

It should be understood that, regardless of how the flexible support body is designedand arranged, the extended nip roll may have an intemal lubrication arrangement (notshown) to supply lubrication fluid (e. g. oil) to the inner surface of the flexible jacket 17such that there will be a thin film of lubrication fluid between the flexible support body 18 (or support element 18) and the inner surface of the flexible jacket 17. Thereby,friction between the flexible jacket 17 and the flexible support body may be reduced.Various arrangements for supplying a lubricant in an extended nip press are known inthe art.

According to the invention, the first flexible support body 18 is further placed oppositethe drying cylinder 14 such that the flexible support body 18 can press the flexiblejacket 17 towards the drying cylinder 14. Thereby, the flexible support body 18 can close the transfer nip TN.

According to the invention, the first press member 12 is movable in relation to thedrying cylinder 14. Thereby, the distance between the drying cylinder 14 and the firstpress member 12 can be increased in a separating movement or decreased in a closingmovement. With reference to Figure 5, the first press member 12 is shown in a firstposition at a distance from the drying cylinder 14. When the first press member 12 is inthis position, activation of the first flexible support body 18 is not sufficient to close thetransfer nip TN since the distance between the flexible jacket 17 and the surface of thedrying cylinder is too large. In practice, the distance may be 40 mm or more. It shouldbe noted that, while the belt 15 that passes in a loop around the first press member 12 isnot shown in Figure 5, the belt 15 will be there. To simplify the information in Figure 5,Figure 6 and Figure 7, the belt 15 has been left out from those figures. It should beunderstood that, in Figure 5, the second press member 13 as seen in Figure 11a has alsobeen left out but it would norrnally be present, even if not visible in Figure 5.

It should be understood that the drying cylinder 14 is norrnally heated already before thetransfer nip TN is closed. If the heating cylinder 14 is a Yankee cylinder, it will beheated from the inside by hot steam. If the belt 15 and the flexible jacket 17 of the firstpress member are too close to the Yankee cylinder while the belt 15 and the flexiblejacket 17 have not yet started to move, this may cause heat damage to the belt 15 andpossible also to the flexible jacket 17 of the first press member. Therefore, a certaindistance should be kept if the belt 15 must be stopped for any reason.

With reference to Figure 6, the first press member 12 is shown in a second position,close to the surface of the drying cylinder 14. In Figure 6, the first press member 12 andthe belt 15 are shown at a certain distance from the drying cylinder (i.e. there is still agap). However, it should be understood that already in the second position, the belt 15may optionally be in contact with the surface of the drying cylinder 14 even though thefirst flexible support body 18 has not yet been activated to press against the drying cylinder 14 and from a proper nip. 11 It is also possible that the first flexible support body 18 has already been activated to alimited extent when the first press member 12 reaches its second position although butthat the first flexible support body 18 it is not fully activated until after the first pressmember 12 has reached its second position which is defined by the mechanical stop 23.

Figure 6, however, shows how the first press member 12 has reached its second positionwhile there is still a small gap between the first press member 12 and the dryingcylinder 14 such that there is still a small gap separating the belt 15 from the surface ofthe drying cylinder 14.

In the embodiment shown in Figure 5 and Figure 6, the machine 1 has at least oneactuator 25 to move the first press member from its first position away from the dryingcylinder 14 to its second position closer to the drying cylinder 14. The at least oneactuator 25 may be a hydraulic cylinder. In the embodiment shown in Figure 5 andFigure 6, two hydraulic cylinders are used as actuators 25 to move the first press member 12 in a closing movement in the direction of arrow A in Figure 5.

In the embodiment shown in Figure 5 and Figure 6, the first press member 12 issupported in bearing housings 24, i.e. the first press member has axial ends that aresupported in bearing housings as is well known in the art of extended nip presses. The atleast one actuator 25 may be arranged to act on the bearing housings 24 of the first pressmember 12 to increase or decrease the distance between the first press member 12 andthe drying cylinder 14.

In the embodiment shown in Figure 5 and Figure 6, the closing movement is shown as alinear movement but it should be understood that, in many embodiments, a tumingmovement, i.e. a movement in which the press member 12 moves along an arcuate(curved) path may be chosen or even preferred. The first press member 12 may be arranged to tum about a hinged connection (not shown).

In order to provide a well defined position for the first press member, the paper makingmachine further comprises a mechanical stop 23 that is arranged to halt the closingmovement. This can be made in a position where the flexible jacket 17 of the first pressmember 12 does not close the transfer nip TN unless the flexible support body 18presses the flexible jacket 17 radially outwards. Altematively, the mechanical stop 23can be positioned such that there is a certain degree of contact between the belt 15 andthe drying cylinder 14 already before the first flexible support body 18 has been causedto press against the drying cylinder 14. It should be understood that the mechanical stop 23 is a stationary machine part which blocks/prevents further movement of the first 12 press member 12 when a part of the first press member comes into contact with themechanical stop 23. The mechanical stop 23 may be secured to a fixed structure. Forexample, the mechanical stop 23 may be secured to the floor on which the paper making machine stands or it may be secured to the machine frame of the paper making machine.

With reference to Figure 7, the mechanical stop 23 may be designed to limit movementof the first press member in more than one direction. In Figure 7, this is represented by amechanical stop 23 that has a V-shaped groove to receive a corresponding V-shapedprojection on the bearing housing 24. In practice, the actuator or actuators 25 will oftencontinue to press the first press member against the mechanical stop also duringoperation. In the embodiments shown, the mechanical stop 23 acts against the bearinghousings 24. In principle, the mechanical stop 23 could also act on some other part ofthe first bearing housing. For example, it could act on a joumal extending beyond thebearing housing 24.

From an initial situation where the flexible jacket l7 is not moving and the transfer nipTN is not yet closed, or at least not fully activated, the starting sequence may be asfollows. Initially, the first press member l2 is in the position shown in Figure 5, i.e. at afirst distance from the drying cylinder l4. The drying cylinder l4 is driven (i.e. itrotates). The belt 15 will now be driven by a drive arrangement. The drive arrangementfor the belt 15 is not explicitly shown but the drive could be arranged in many differentways. For example, one or several guide rolls 16 for the belt 15 could be driven rolls.The belt 15 can then be used to drive the flexible jacket l7 of the first press member l2.Thereby, the flexible jacket l7 can be caused to rotate before the transfer nip TN isclosed. Preferably, the belt 15 is driven to a speed that matches that of the surface of thedrying cylinder. Thereby, it can also drive the flexible jacket to the same speed. This ispreferably done while the distance between the outer surface of the flexible jacket 17 isstill at a distance of at least 40 mm away from the surface of the drying cylinder l4.

The first press member l2 is then moved from its first position to a second positiondefined by the mechanical stop 23. At this stage, the flexible support body 18 has stillnot pressed the flexible jacket l7 radially outwards. Altematively, it may be activatedbut only to a very limited degree. Therefore, the transfer nip may still be open such thatbelt 15 is not yet in contact with the drying cylinder. Altematively, there is only a lightcontact between the belt 15 and the drying cylinder l4 but the transfer nip TN is not yetloaded. When the first press member is in its second position, there may be a distance(gap) between the outer surface of the flexible jacket 17 and the surface of the drying cylinder 14 which may be on the order of about 5 mm (the exact distance may of course 13 vary from case to case). The belt 15 is somewhat closer since the belt 15 also has acertain thickness. Possibly, there is actually a light contact between the belt 15 and thesurface of the cylinder 14.

Reference will now be made to Figure 8. Figure 8 shows the situation after the firstpress member 12 has been brought to the position defined by the mechanical stop 23. InFigure 8, a certain gap is shown but there may optionally also be a light contact betweenthe belt 15 and the cylinder 14. The arrows in Figure 8 indicate the direction ofmovement of the belt 15, the flexible jacket 17 that is driven by the belt 15 and thedirection of rotation of the drying cylinder 14. From this position, the flexible supportbody will be caused to press the flexible jacket radially 17 outwards in order to actagainst the drying cylinder 14. If there is a initially a gap between the belt 15 and thedrying cylinder 14, activation of the first flexible support body 18 will cause this gap tobe closed. The activation of the first flexible support body 18 and the effect of this willnow be explained with reference to Figure 9.

Figure 9 illustrates an embodiment where the flexible support body 18 is designed in theway explained with reference to Figure 3 but substantially the same procedure could beused with other embodiments of the flexible support body. In Figure 9, the intemalcavity 31 of the flexible support body has been filled with pressurized fluid to such anextent that the support body 18 has expanded radially outwards. As a consequence, theflexible jacket 17 and the belt 15 have been pressed in a direction towards the dryingcylinder 14 to act against the drying cylinder 14. Thereby, the transfer nip TN has beenproperly activated, i.e. loaded, (and closed if there was an initial gap) and the paper webwill now be pressed against the drying cylinder 14 in the transfer nip TN and betransferred from the belt 15 to the surface of the drying cylinder 14. It should beunderstood that the holder 29 in which the flexible support body 18 is placed norrnallyremains stationary while the flexible support body 18 expands radially outwards toactivate the transfer nip TN (the holder 29 is norrnally a component that is fixed withinthe extended nip roll).

With reference to Figures 10a - 10c, it can be seen that when the first press member 12is moved towards the frying cylinder 14, it also moves towards the second pressmember 13. Figure 10a is a schematic representation substantially corresponding to thesituation depicted in Figure 5. In Figure 10b, the first press member 12 has been movedcloser to the drying cylinder 14 and, at the same time, also closer to the second pressmember 13. In this position, there may still be a small gap between the flexible jacket 17 and the drying cylinder 14 or a small gap between the flexible jacket 17 and the 14 second press element 13 but the flexible support bodies 18 and 19 have not yet beenactivated. It is also possible that there is a light contact between the flexible jacket 17and one or both of the drying cylinder 14 and the second press member 13 but also inthis case, the flexible support elements 18, 19 have not been activated, there aresubstantially no forces in the transfer nip TN or the press nip PN. In this situation, itwould norrnally be so that no paper is running through the machine or at least no paperweb is passing between the press elements 12, 13. The flexible support bodies 18, 19are then activated to load the press nip PN and the transfer nip TN as indicated by thearrows in Figure 10c. Thereafter, paper may pass through the nips. For simplicity, thebelt 15 and the felt 7 are not shown in Figures 10a - 10c. Nevertheless, it should beunderstood that they are there. The same is true of the mechanical stop 23.

With reference to Figure 1 la, a doctor blade 27 has been arranged to crepe the paperweb W from the drying cylinder 14. The inventors have discovered that the use of aflexible support body in the transfer nip has the surprising effect that the bulk of thepaper web is improved. Since bulk is often a desired property for tissue paper, this is ofgreat practical value. Without wishing to be bound by theory, it is believed by theinventors that the use of a flexible support body causes the paper web to adhere strongerto the surface of the drying cylinder. The following creping operation by the doctorblade 27 may then have a greater effect on the paper such that bulk is increased.

With reference to Figure 1 lb and Figure 1 lb, it can be seen that, within the loop of theflexible jacket 17, the first press member 12 may also comprise a second flexiblesupport body 19. The second flexible support body 19 is placed opposite the secondpress member 13 to cooperate with the second press member 13 in order to form the dewatering nip PN.

Instead of the second flexible support body 19, a substantially rigid shoe as in aconventional shoe press may also be used for the dewatering nip PN. The second pressmember 13 may be a roll with grooves 28 as shown in Figure 11b. It may also be, forexample, a suction roll or a deflection-compensated roll.

When the dewatering nip PN is formed with a flexible support body 19, the dewateringnip PN may suitably be operated at a linear load in the range of 100 kN/m - 600 kN/mand a peak pressure of 6 MPa. In one embodiment contemplated by the inventors, thedewatering nip PN formed by a flexible support body may have a nip length of 125 mm- 140 mm and a linear load of 150 kN/m.

When the deWatering nip is formed With a rigid shoe (i.e. a conventional metal shoe thatmay have a concave surface facing to opposite press member), the machine directionlength of such a rigid shoe may be in the range of 50 mm - 150 mm While the linearload of the deWatering nip in such a case may be in the range of 200 kN/m - 1000kN/m, preferably 300 kN/m - 1000 kN/m. In many realistic embodiments, the linearload may be in the range of 400 kN/m - 600 kN/m When a rigid concave shoe (e.g. asteel shoe) is used in the deWatering nip PN. This Which can give an adequate deWatering Without causing unnecessary bulk reduction.

The transfer nip TN may be operated at a linear load Which is, for example, in the rangeof 50 kN/m - 100 kN/m but it is believed by the inventors that higher linear loads (andhigher pressure levels) in the transfer nip TN may actually have the benefit ofimproving the bulk since a higher linear load can cause the Web W to adhere stronger tothe surface of the drying cylinder 14. When the flexible support body 18 in the transfernip TN is formed by a flexible hose With an intemal cavity 31 (see Figure 3), the lengthof the transfer nip TN in the machine direction may suitably be in the range of 30 mm -100 mm and preferably 30 mm - 80 mm. It is believed by the inventors that a length inthis range is advantageous for achieving good adhesion of the Web to the dryingcylinder While avoiding unnecessarily large dimensions of the components used. Thismay also be a suitable length for the transfer nip TN When the flexible body 18 isarranged according to the embodiment of Figure 4. A suitable highest pressure in thetransfer nip TN may be in the range of 1 MPa - 3 MPa. In one embodimentcontemplated by the inventors, the highest pressure in the transfer nip TN may be 2MPa or about 2 MPa. HoWever, it is believed by the inventors that higher peakpressures could result in even better adhesion of the Web to the surface of the dryingcylinder 14. Therefore, peak pressures up to 6 MPa may be tested or possibly evenhigher peak pressures.

In some cases, the flexible support body 18 that is used for the transfer nip TN maypossibly have a longer nip length than 80 mm. In such embodiments, the flexiblesupport body 18 may have several chambers that may be individually pressurized asdisclosed in US patent No. 7527708 (such an embodiment is shown in Fig. 12 of USpatent No. 7527708). In such embodiments, nip length in the transfer nip TN may be inthe range of 50 mm - 150 mm. For such longer transfer nips, the linear load can bemade higher.

To accommodate movement of the belt 15 When the first press member 12 is moved,one or several guide rolls 16 for the belt 15 may also be movable. 16 As previously mentioned, the belt 15 may be an imperrneable belt which has a smoothsurface on the side that faces the paper web, i.e. the side that, in the transfer nip TN,faces the drying cylinder 14. Such a belt may be used in order to secure a correct webtransfer after the dewatering nip PN. The smooth surface of the belt ensures that the webfollows the belt 15 after passage of the dewatering nip PN instead of following the water-receiving felt 7.

However, the belt 15 may advantageously be an imperrneable belt which has a texturedsurface on the side that, in the transfer nip, faces the drying cylinder 14. This entails theadvantage that the bulk of the paper web W can be increased.

Embodiments are also conceivable in which the belt 15 is, at least to some extent, a beltthat is perrneable to water. This may be the case both when the belt 15 is textured andwhen it is smooth.

A different embodiment will now be explained with reference to Figure 12. In theembodiment of Figure 12, the components are largely the same as in the embodimentdescribed with reference to Figures 1 - 11b and 11b. The machine of Figure 12 thuscomprises a former 2 in which a fibrous web may be formed, the former 2 having with ahead box 3; a forming roll 4; a forrning fabric 5 which is guided in a loop by guide rolls6; and a felt 7. The forrning roll 4 may advantageously be a roll with a suction zone (thisis also the case for the embodiment shown in Figure 1). Just as in the embodiment ofFigure 1, the machine also includes a press with a first press member 12 and a secondpress member 13 arranged to form a dewatering nip PN with each other. Just as in thearrangement of Figure 1, the felt 7 that is used in the former is also arranged to passthrough the dewatering nip PN and a drying cylinder 14 is arranged to form a transfernip TN with the first press member 12. Just as in the embodiment of Figure 1, a belt 15forms a loop around the first press member 12 such that the belt 15 passes through thedewatering nip PN and the transfer nip TN. Unlike the arrangement of Figure 1, theembodiment of Figure 11 is designed such that it is the second press member 13 that isan extended nip roll. The extended nip roll may be a roll that uses a flexible supportbody as described above but it may also be a more conventional shoe press roll with asubstantially rigid and concave press shoe such as the SymBeltTM shoe press roll whichis marketed by Metso Paper OY. When a rigid and concave press shoe is used, niplength may be in the range of 50 mm - 150 mm while linear load may be in the rangeof, for example, 200 kN/m - 1000 kN/m. In the embodiment of Figure 11, either the first press member 12 or the second press member 13 may be movable against a 17 mechanical stop as described above With reference to Figures 5 - 7. A mechanical stop23 may be used as described With reference to Figure 5, Figure 6 and Figure 7.

By using one and the same roll to forrn both a transfer nip TN and a press nip PN, fewerparts are necessary even though a press With an extended nip roll is used.

Also by using the same felt in the forrning section and the deWatering nip PN, the number of components can be reduced.

By using a mechanical stop against that def1nes a position for the f1rst press member 12,the advantage is gained that the first press member has a Well-defined position beforethe transfer nip TN is activated. This is of particular importance if the f1rst pressmember 12 has two flexible support bodies 18, 19 (or a flexible support body 18 for thetransfer nip TN and a rigid shoe for the deWatering nip PN). If the f1rst press memberhas two flexible support bodies and is required to form both a press nip PN With thesecond press member 13 and a transfer nip TN With the drying cylinder, it is importantthat the position of the f1rst press member is Well defined When these nips are to beclosed/activated.

The use of a mechanical stop also entails the advantage that an operator of the machinecan control the closing of the transfer nip TN and the press nip PN more accurately. Themechanical stop makes it possible to place the f1rst press member 12 in the positiondefined by the mechanical stop but in Which it is not necessarily so that any of the nipsTN, PN is closed. The operator of the machine can then close those nips (or bring thenips to their operational load in case they are already closed) by activating the flexiblesupport bodies 18, 19. If the operator Wants to load the nips PN, TN in any specialsequence, for example loading the deWatering nip PN before the transfer nip is closed,this is also possible.

Since the f1rst press member 12 can be brought to a Well-defined position near thedrying cylinder 14 before the flexible support body 18 is activated, the risk that thepressure in the flexible hose of the support body 18 should become too high before thenip is properly closed can be avoided.

The use of a flexible support body 18 in the transfer nip TN entails the advantage thatthe bulk of the paper Web can be improved.

In all embodiments, a suitable machine speed may be up to 2200 m/minute. Forexample, machine speed may be in the range of 1000 m/minute - 2200 m/minute.

Suitable speeds Would norrnally be about 1500 m/minute - 2200 m/minute to give the 18 web a suitable dwell time for dewatering in the nip in combination with the need tokeep up a production output. However, for reasons of productivity, it may be desirableto run the machine at even higher speeds.

In many practical embodiments, the machine width may be in the range of 2 - 8 meters.

For example, machine width may be 3.5 - 7 meters. However, machines wider than 8meters are conceivable (for example machines up to a width of 10 meters or more).Machines narrower than 2 meters may also be considered. The pulp used in the processmay be, for example, chemical pulp. Depending on the end user”s needs, Virgin pulp orrecycled may be used.

Claims (1)

1. A paper making machine (1) for making tissue paper, the machine comprising: aformer (2) in Which a fibrous Web may be formed, the former (2) having aforming roll (4), a forrning fabric (5) and a felt (7); a press (11) With a first pressmember (12) and a second press member (13) arranged to form a deWatering nip(PN) With the first press member (12) and the felt (7) being arranged to passthrough the deWatering nip (PN); a drying cylinder (14) arranged to form atransfer nip (TN) With the first press member (12); a belt (15) forrning a looparound the first press member (12) such that the belt (15) passes through thedeWatering nip (PN) and the transfer nip (TN), characterized in that the firstpress member (12) is an extended nip roll that has a flexible jacket (17) thatforms a loop and a flexible support body (18) Within the loop of the flexiblejacket (17) Which flexible support body (18) can be caused to press the flexiblejacket (17) radially outWards, the flexible support body (18) further being placedopposite the drying cylinder (14) such that the flexible support body (18) canpress the flexible jacket (17) towards the drying cylinder (14) to close thetransfer nip (TN), the first press member (12) being movable in relation to thedrying cylinder (14) such that the distance between the drying cylinder (14) andthe first press member (12) can be increased in a separating movement ordecreased in a closing movement, and in that the paper making machine further comprising a mechanical stop (23) arranged to halt the closing movement. A paper making machine according to claim 1, Wherein the mechanical stop isarranged to halt the closing movement in a position Where the transfer nip (TN)is not yet closed. A paper making machine according to claim 1, Wherein the flexible supportbody (18) comprises or is supported by at least one flexible hose extending in across machine direction and connected to a source of pressurized fluid such thatpressurization of the at least one flexible hose Will cause the flexible supportbody (18) to either expand or move radially outwards. A paper making machine according to claim 1, Wherein the belt (15) is animperrneable belt Which has a smooth surface on the side that, in the transfer nip(TN), faces the drying cylinder (14). 10. 11. 12. . A paper making machine according to claim 1, Wherein the belt (15) is an imperrneable belt Which has a textured surface on the side that, in the transfernip, faces the drying cylinder (14). A paper making machine according to claim 1, Wherein the belt (15) is aperrneable belt Which has a textured surface on the side that, in the transfer nip(TN), faces the drying cylinder (14). A paper making machine according to claim 1, Wherein the belt (15) is aperrneable belt Which has a smooth surface on the side that, in the transfer nip,faces the drying cylinder (14). A paper making machine according to claim 1, Wherein, Within the loop of theflexible jacket (17), the first press member (12) also comprises a flexible supportbody (19) that is placed opposite the second press member (13) to cooperateWith the second press member (13) to form the deWatering nip (PN). A paper making machine according to claim 1, Wherein the second press member (13) is a grooved roll. A paper making machine according to any of claims 1 - 9, Wherein the firstpress member (12) is supported in bearing housings (24) and Wherein the papermaking machine further comprises at least one actuator (25) arranged to act onthe bearing housings (24) of the first press member (12) to increase or decreasethe distance between the first press member (12) and the drying cylinder (14). A paper making machine according to claim 1, Wherein the transfer nip has a length in the range of 30 mm - 100 mm. A paper making machine for making tissue paper, the machine comprising: aformer (2) in Which a fibrous Web may be formed, the former (2) having aforming roll (4), a forrning fabric (5) and a felt (7); a press With a first pressmember (12) and a second press member (13) arranged to form a deWatering nip(PN) With the first press member (12) and the felt (7) being arranged to passthrough the deWatering nip (PN); a drying cylinder (14) arranged to form atransfer nip (TN) With the first press member (12); a belt (15) forrning a looparound the first press member (12) such that the belt (15) passes through thedeWatering nip (PN) and the transfer nip, characterized in that one of the firstpress member (12) and the second press member (13) is an extended nip roll thathas a flexible jacket (17) that forms a loop and a flexible support body (19) 13. 14. 15. 16. 17. 21 Within the loop of the flexible jacket (17) Which flexible support body (19) canbe caused to press the flexible jacket radially outWards, the support body (19)further being placed opposite the other press member such that the support body(19) can press the flexible jacket (15) towards the other press member to closethe deWatering nip (PN). A method of operating a paper machine according to any of claims 1 - 11,Wherein the method comprises moving the first press member (12) from a firstposition at a first distance from the drying cylinder (14) to a second positiondefined by the mechanical stop (23) and subsequently causing the flexiblesupport body (18) to press the flexible jacket radially (17) outWards to actagainst the during cylinder (14). A method according to claim 13, Wherein, Within the loop of the flexible jacket(17), the first press member (12) also comprises a flexible support body (19) thatis placed opposite the second press member (13) to cooperate With the secondpress member (13) and form the deWatering nip and Wherein the deWatering nip(PN) is operated at a linear load in the range of 100 kN/m - 600 kN/m and apeak pressure of 6 MPa. A method according to claim 13, Wherein the drying cylinder (14) is rotatingalready before the transfer nip (TN) is closed and Wherein the belt (15) used todrive the flexible jacket (17) such that the flexible jacket (17) rotates before thetransfer nip (TN) is closed. A method according to claim 15, Wherein the belt (15) is used to drive theflexible jacket (17) to a speed that matches that of the drying cylinder (14)before the transfer nip (TN) is closed. A method according to claim 16, Wherein the belt (15) is used to drive theflexible jacket (17) to match the speed of the drying cylinder (14) While the outersurface of the flexible jacket (17) is still at a distance of at least 40 mm from thesurface of the drying cylinder (14).