Classifications

• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
  • D21F5/00—Dryer section of machines for making continuous webs of paper
  • D21F5/18—Drying webs by hot air
  • D21F5/181—Drying webs by hot air on Yankee cylinder
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
  • D21F5/00—Dryer section of machines for making continuous webs of paper
  • D21F5/02—Drying on cylinders
  • D21F5/021—Construction of the cylinders

Definitions

• the present invention relates to a Yankee drying cylinder for drying a fibrous web such as a tissue paper web.
• the invention also relates to a method of making the inventive Yankee drying cylinder.
• Yankee drying cylinders are used in the manufacturing of paper, in particular tissue paper.
• a cylinder is designed to be supplied with hot steam to the interior of the cylinder such that the Yankee drying cylinders is heated.
• the Yankee drying cylinder When installed in a paper making machine such as a tissue machine, the Yankee drying cylinder is arranged to be rotated.
• a wet fibrous web coming from the forming section of the paper making machine is transferred to the outer surface of the Yankee drying cylinder and follows the surface of the Yankee drying cylinder as the cylinder rotates.
• the fibrous web is in contact with the outer (external) surface of the Yankee drying cylinder, the fibrous web is dried since the external surface of the Yankee drying cylinder is hot due to the hot steam that is supplied to the interior of the cylinder.
• the dried fibrous web then leaves the external surface of the Yankee drying cylinder and is sent further to a following station, for example to a reel-up where the fibrous web is reeled into a paper roll.
• a following station for example to a reel-up where the fibrous web is reeled into a paper roll.
• other equipment may be located between the Yankee drying cylinder, for example measuring equipment for measuring various properties of the paper web, for example thickness of the paper web, dryness of the web or dryness variations of the web in the cross-machine direction.
• Yankee drying cylinders were commonly manufactured by casting and in which end walls are connected to a cast cylindrical shell by such elements as bolts. It has also been suggested that Yankee drying cylinders be manufactured by methods in which steel plates rather than cast iron is used. An example of such a manufacturing method is disclosed in, for example, US patent No. 4320582. It has also been suggested that Yankee drying cylinders of steel may be manufactured in a process in which the end walls of the Yankee drying cylinder are welded to the cylindrical shell and an example of such a method is disclosed in for example US patent No. 8438752.
• a technical problem in connection with Yankee drying cylinders is that the heat energy that is supplied to the Yankee drying cylinder, and which normally comes in the shape of hot steam, must not be lost other than through heat transfer to the wet fibrous web.
• Another problem is that the Yankee drying cylinder must have a design that contributes to a long life, i.e. that the Yankee drying cylinder can be in operation over many years. Furthermore, it is desirable that the Yankee drying cylinder can be manufactured in a way that is fast and time-efficient.
• the inventive Yankee drying cylinder is intended for the purpose of drying a fibrous web such as a tissue paper web.
• the Yankee drying cylinder according to the invention comprise a circular cylindrical shell with a first and a second axial end, an internal surface and an external surface. For each axial end of the circular cylindrical shell, an end wall is joined to the circular cylindrical shell such that the circular cylindrical shell and the end walls define an enclosed space.
• the inventive Yankee drying cylinder also comprises a central tie member that extends between the end walls and is joined to the end walls. According to the invention, the central tie member is joined to the end walls by weld joints.
• the end walls are also connected to the circular cylindrical shell by weld joints such that the entire structure comprising the circular cylindrical shell, the end walls and the central tie member is held together by weld joints.
• the central tie member is joined to at least one of the end walls by at least one weld joint inside the enclosed space although embodiments are conceivable in which the central tie member is joined to the end walls only by external weld joints/weld seams.
• the tie member is joined to each end wall element not only by internal weld joints/weld seams but also by at least one welding joint/weld seam that is located outside the enclosed space.
• the internal surface of the circular cylindrical shell is provided with internal circumferential grooves.
• embodiments without such circumferential grooves are conceivable.
• the central tie member may take many different forms but, in advantageous
• the tubular structure may be formed by or comprise a tubular structure that is connected to or connectable to connectable to a source of hot steam outside the Yankee drying cylinder.
• the tubular structure may optionally be provided with openings (through-holes in the wall of the tubular structure) such that hot steam can enter the Yankee drying cylinder through the tubular structure and reach the inner surface of the circular cylindrical shell through the openings in the tubular structure.
• the invention also relates to an inventive method of making a Yankee drying cylinder.
• the method comprises the steps of providing a circular cylindrical shell with a first and a second axial end; providing a first and a second end wall element, each end wall element having a circular cylindrical outer perimeter and a central opening; providing a tie member extending between a first longitudinal end of the tie member and a second longitudinal end of the tie member and wherein the distance between the longitudinal ends of the tie member corresponds to the axial length of the circular cylindrical shell.
• the method further comprises the step of joining the circular cylindrical shell, the end wall elements and the tie member to each other such that the end wall elements close the axial ends of the circular cylindrical shell to define an enclosed space and the tie member extends between the end wall elements and connect them to each other.
• the tie member is joined to the end wall elements in such a way that the longitudinal ends of the tie member are fitted into the central openings of the first and second end wall element respectively and welded to the end walls elements such that each end wall element is joined to the tie member by one or several welds (weld joints/weld seams).
• the longitudinal ends of the tie member are joined to the end wall elements by making welding joints located inside the enclosed space.
• the longitudinal ends of the tie member are joined to the end wall elements also by welding joints located outside the enclosed space.
• the circular cylindrical shell, the end wall elements and the tie member are joined to each other in a sequence.
• the sequence comprises the steps of performing a machining operation on the first end of the tie member such that the external shape of the first end of the tie member can fit into the central opening of the first wall element and fitting the now machined first end of the tie member into the central opening of the first wall element.
• the sequence further comprises the steps of aligning the tie member with the first wall element and welding the first end of the tie member to the first wall element with a first weld between the tie member and the first wall element in the area where that first end of the tie member is inserted into the first wall element.
• the method further comprises the following steps:
• Figure 1 is a side view which gives a schematic representation of a Yankee drying cylinder on operation.
• FIG. 2 is a schematic representation of different components used in the
• Figure 3 is a schematic representation of one of the initial steps of the inventive method.
• Figure 4 is a schematic representation of a part of the sequence following the method step shown in Figure 3.
• Figure 5 shows a part of the sequence after the sequence step of Figure 4.
• Figure 6 is a schematic representation a part of the manufacturing sequence immediately following the one of Figure 5.
• Figure 7 is a view corresponding to Figure 6 and shows a subsequent step of the sequence.
• Figure 8 is a view corresponding to Figure 7 and illustrating the next part of the manufacturing sequence.
• Figure 9 is a schematic side view illustrating how the end walls are being provided with external welds.
• Figure 10 is a view corresponding to Figure 8 and showing the Yankee drying cylinder after the external welding operation indicated in Figure 9.
• Figure 11 is a view corresponding to Figure 10 and representing the following part of the manufacturing sequence.
• Figure 12 is a view corresponding to Figure 11 and indicating one of the final steps in the manufacturing sequence.
• a Yankee drying cylinder 1 is shown in operation.
• the Yankee drying cylinder 1 may in a Yankee drying cylinder according to the present invention and Figure 1 gives an example of how such a Yankee drying cylinder may be used in practice.
• a fibrous web W is carried by a fabric 50 to a nip between a roll 51 and the Yankee drying cylinder 1.
• the fabric 50 may be a felt which is permeable to air and water and capable of receiving water.
• the roll 51 may be, for example, a suction roll or a shoe press roll but it may also be some other kind of roll such as a deflection-compensated roll.
• the fibrous web W is transferred to the external surface 7 of the Yankee drying cylinder 1.
• the Yankee drying cylinder 1 has a smooth outer surface 7.
• the web W will be transferred from the fabric 50 the surface 7 of the Yankee drying cylinder 1.
• the fibrous web W has a strong tendency to follow a smooth surface rather than a rough surface and the smoothness of the outer surface 7 of the Yankee drying cylinder 1 results in a very strong tendency of the fibrous web W to follow the outer surface 7 of the Yankee drying cylinder.
• the outer surface 7 of the Yankee drying cylinder 1 is normally made smooth special surface treatment such as, for example, grinding while the fabric 50 normally has a surface that is rough, at least compared to that of the outer surface 7 of the Yankee drying cylinder 1.
• the fibrous web W follows the surface of the Yankee drying cylinder 1 as the Yankee drying cylinder rotates in the direction of arrow R.
• the Yankee drying cylinder 1 is heated and normally heated from within by a heating medium such as hot steam.
• a source of hot steam is symbolically indicated by the reference numeral 16.
• the hot surface 7 of the Yankee drying cylinder 1 will cause water in the fibrous web W to evaporate such that the fibrous web W is dried.
• the fibrous web W may then be removed from the surface 7 of the Yankee drying cylinder 1. For example, it may be creped away from the outer surface 7 by means of a doctor 53 as schematically indicated in Figure 1.
• a doctor 53 indicates a journal for the Yankee drying cylinder 1.
• the Yankee drying cylinder of the present invention is intended for drying wet fibrous webs and may be used in the way explained with reference to Figure 1 and the Yankee drying cylinder of Figure 1 may be understood as a representation of the inventive Yankee drying cylinder.
• the Yankee drying cylinder may be followed by other equipment such as a reel-up.
• the inventor of the present invention has found that, in known Yankee drying cylinders, there may be heat losses resulting from the leakage of steam from the Yankee drying cylinder.
• a central tie member which is usually shaped as a tubular element is used to connect the end walls of the Yankee drying cylinder.
• the inventor has found that leakage of steam may occur in the area where the central tie member is joined to the end walls and that this is related to the way in which the central tie member is joined to the end walls.
• the conventional way of securing the central tie member to the end walls is by screws and/or bolts and this method of fastening has traditionally always been used but the inventor of the present invention has found that an alternative way of fastening the tie member to the end walls should be used.
• the Yankee drying cylinder 1 comprises a circular cylindrical shell 2 that has an axial extension E ( Figure 2), a first axial end 4 and a second axial end 5.
• the cylindrical shell 2 has an internal surface 6 and an external surface 7.
• an end wall 8, 9 is joined to the circular cylindrical shell 2 such that the circular cylindrical shell 2 and the end walls 8, 9 define an enclosed space 13 (see Figure 12).
• a central tie member 14 extends between the end walls 8, 9 and is joined to the end walls 8, 9. According to the present invention, the central tie member 14 is joined to the end walls 8, 9 by weld joints 19, 24, 25, 26 (see Figure 12).
• the end walls 8, 9 are connected also to the circular cylindrical shell 2 by weld joints 20, 21, 22, 23 such that the entire structure comprising the circular cylindrical shell 2, the end walls 8, 9 and the central tie member 14 is held together by weld joints 19, 20, 21, 22, 23, 24, 25, 26 (see Figure 12).
• the central tie member 14 is joined to at least one of the end walls 8, 9 by at least one weld joint 19, 25 that is placed inside the enclosed space 13.
• the tie member 14 is additionally joined to each end wall element 8, 9 by at least one welding joint 24, 26 that is located outside the enclosed space 13.
• each end wall 8, 9 has a central opening into which the longitudinal ends 15a, 15b of the tie member 14 are fitted and the tie member 14 is welded to the end walls 8, 9 by both internal and external welds, the advantage is gained that the tie member 14 can be securely held in place. This contributes to giving the Yankee drying cylinder a long service life. The manufacturing process will also be time-efficient.
• the internal surface 6 of the circular cylindrical shell 2 may be provided with internal circumferential grooves 3.
• the circumferential grooves 3 serve to improve heat transfer to the outer surface 7 of the cylindrical shell 2 when the Yankee drying cylinder 1 is being used.
• a heating medium such as hot steam is sent into the enclosed space 13 the steam will condensate against the internal surface 6 and heat energy will be transferred to the cylindrical shell 2.
• the central tie member 14 is formed by or comprises a tubular structure that is connectable to a source 16 of hot steam outside the Yankee drying cylinder 1 (see Figure 1).
• the tubular structure is provided with openings 17 such that hot steam can enter the Yankee drying cylinder 1 via the tubular structure of the tie member 14, pass through the openings 17 in the tubular structure and reach the inner surface 6 of the circular cylindrical shell 2.
• the initial steps of the method comprises: providing a circular cylindrical shell 2 with a first and a second axial end 4, 5; providing a first and a second end wall element 8, 9, each end wall element 8, 9 having a circular cylindrical outer perimeter 10 and a central opening 11, 12; providing a tie member 14 extending between a first longitudinal end 15a of the tie member and a second longitudinal end 15b of the tie member 14 and wherein the distance between the longitudinal ends 15a, 15b of the tie member 14 corresponds to the axial length (or extension E) of the circular cylindrical shell 2.
• the tie member 14 may be subjected to a machining operation at its first longitudinal end 15a.
• machining operation should be understood as an operation in which material is removed from the tie member 14.
• the reference numeral 18 is used to indicate a machine tool such as a tool used for turning.
• the machining operation is carried out to such an extent that the external shape of the first end 15a of the tie member 14 is such that it fits into the central opening 11 of the first wall element 8.
• the tie member 14 is aligned with the central opening 11 of the first wall element 8 and moved in the direction of arrow B such that the first end 15a of the tie member 14 is fitted into the central opening 11 of the first wall member 8.
• the tie member 14 is joined to the fist wall element by a first weld 19 which is preferably a circumferential weld joint/weld seam that goes all around the circumference of the tie member 14 such that the tie member 14 is joined to the first wall element 8 along its entire circumference.
• first weld 19 is placed 8 in the area where the first end 15a of the tie member 14 is inserted into the first wall element 8.
• second end 15b of the tie member 14 is given such a shape that it can fit into the central opening 12 of the second wall element 9.
• the circular cylindrical shell 2 may be aligned with the first wall element 8 and the second wall element 9 may subsequently be aligned with the circular cylindrical shell 2 and with the tie member 14 such that the now machined second end 15b of the tie member 14 fits into the central opening 12 of the second wall member 9.
• the first wall element 8 is welded to the circular cylindrical shell 2 with a second weld 20 which is an internal weld.
• the second wall element 9 is welded to the circular cylindrical shell 2 with a third weld 21 which is an internal weld (i.e. a weld on the inside of that which is to become a Yankee drying cylinder 1) such that the circular cylindrical shell 2, the end walls 8, 9 and the tie member 14 now form a coherent structure 27.
• the coherent structure 27 may be placed on turning rolls 28 such that the axis of the circular cylindrical shell 2 extends in a horizontal direction.
• the coherent structure is then rotated and, while it is being rotated, the first wall element 8 is welded to the circular cylindrical shell 2 with a fourth weld 22 which is a circumferential external weld and 20 the second wall element 9 is welded to the circular cylindrical shell 2 with a fifth weld 23 which is a circumferential external weld.
• first end 15a of the tie member 14 may thus be welded externally to the first wall 8 with an external weld (weld seam/weld joint) 24 which is preferably a circumferential weld 24 that goes all around the
• the reference numeral 54 refers to a welding apparatus used for making the external welds 22, 23.
• a following step may include heat treatment of the coherent structure 27 which is now a Yankee drying cylinder in the making.
• the arrows P symbolically represent heat energy transferred to the Yankee drying cylinder 1.
• the heat treatment may include heating the entire Yankee drying cylinder in the making to a temperature in the range of 580 °C - 680 °C.
• the heat treatment may include heating the Yankee drying cylinder 1 to a temperature in the range of 605 °C - 640 °C. For example, it can be heated to a
• the heating should preferably not be too quick and the inventor has found that heating should preferably take place at such a rate that the temperature of the Yankee drying cylinder is increased by 20 °C - 45 °C per hour (20 °C - 45°C/hour). More preferred, the temperature is raised at a rate of 25° C - 35 °C/hour and a suitable rate of heating may be, for example, 30 °C/hour. The rate at which the temperature is increased is held low in order to avoid harmful tensions in the material, in particular in the weld seams. When the Yankee drying cylinder has reached its final temperature, it may be kept at that temperature for a period of time.
• the Yankee drying cylinder should be kept at its final elevated temperature for about one hour per 25 mm thickness of the material. For example, if the material thickness is 75 mm, the Yankee drying cylinder should be held at the elevated temperature for about 3 hours. The Yankee drying cylinder is then allowed to cool. The Yankee drying cylinder should initially cool down at a slow rate, about 20 °C/h - 30 °C/h, until it has reached a temperature of about 200 °C after which it can be allowed to cool freely.
• the heat treatment is carried out while the second end 15b of the tie member 14 is still not welded to the second end wall 9.
• the reason is that if the second end 15b is welded to the second end wall 9 before heat treatment, shrinking in the weld seams might cause remaining mechanical tensions in the Yankee drying cylinder. If the second end 15b has not yet been welded to the second end wall 9 when the heat treatment is carried out, the second end 15b of the tie member is still free to move relative to the second end wall 9. It can then be welded to the second end wall 9 after heat treatment. In this way, the creation of mechanical tensions can be avoided.
• following method steps may thus include welding the second end 15b of the tie member 14 to the second wall element 9 by a seventh weld 25 which is an internal weld and an eighth weld 26 which is an external weld.
• the seventh weld 25 and the eighth weld 26 may be carried out before heat treatment but for reasons explained above, it is preferred that these welds are made after heat treatment of the coherent structure 27.
• the welding of the second end 15b of the tie member 14 to the second end wall 9 may advantageously (but not necessarily) be followed by a local heat treatment of the area where the second end 15b is welded to the second end wall 9.
• the end walls may be provided with special insulation, for example as disclosed in US patent No. 8398822.
• the inventive Yankee drying cylinder may be used in combination with a hot air hood, for example such a hot air hood as disclosed in US patent No. 6079115 or as disclosed in EP 2963176 Al.
• the Yankee drying cylinder may also have equipment for removing condensate water from the grooves. Examples of such equipment is disclosed in, for example, European patent No.

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• 2016
  • 2016-03-31 SE SE1650417A patent/SE540216C2/en not_active IP Right Cessation
• 2017
  • 2017-01-05 PL PL128030U patent/PL128030U1/pl unknown
  • 2017-01-05 WO PCT/SE2017/050011 patent/WO2017171602A1/en active Application Filing
  • 2017-01-05 BR BR212018070127-6U patent/BR212018070127Y1/pt not_active IP Right Cessation
  • 2017-01-05 DE DE212017000093.7U patent/DE212017000093U1/de not_active Expired - Lifetime
  • 2017-01-05 AT ATGM9004/2017U patent/AT16483U1/de not_active IP Right Cessation
  • 2017-01-05 CN CN201790000747.4U patent/CN209443296U/zh not_active Expired - Fee Related

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