Blade for a refiner, and refiner comprising such a blade

Abstract

The present invention relates to a blade for a refiner, the blade (10) comprising a plurality of refiner bars (14) separated by grooves (15), and also comprising a plurality of refiner dams (16) arranged across the grooves (15) to connect refiner bars (14) on either side of the grooves (15) to each other, and further5 comprising at least one through-hole (18) in at least one of the refiner dams (16) for enabling a flow along the groove (15) through the dam (16).The invention also relates to a refiner comprising such a blade (10) and to a method for manufacturing the blade (10).

Description

[0001] BLADE FOR A REFINER, AND REFINER COMPRISING SUCH A BLADE

[0002] TECHNICAL FIELD

[0003] The present invention relates to a blade for a refiner for refining lignocellulosic material, wherein the blade comprises a plurality of refiner bars separated by grooves and a plurality of refiner dams arranged across the grooves to connect refiner bars on either side of the grooves to each other.

[0004] BACKGROUND

[0005] A disc refiner is commonly used within the pulping industry for refining lignocellulosic material used in the production of fibrous material such as paper and board.

[0006] The disc refiner comprises two or more opposite refining elements, at least one of which is rotatable. The rotating refining dement can be referred to as a rotor or a rotor side blade, whereas the non-rotating or stationary refining element can be referred to as a stator or a stator side blade. Between the refining elements is a refining gap, where the material to be refined is ground against the refining surfaces. The refining surface of the refining elements comprises a plurality of bars, separated by grooves, that serve to refine the lignocellulosic material during use.

[0007] In some applications, the rotor side blade and the stator side blade are circular blades that are mounted on one stationary and one rotary frame element in the refiner, such that they face each other during use. Often, the stator side blade and the rotor side blade are divided into many smaller blade segments that each cover a sector of the frame element and that when mounted together form the circular blades. There is generally an opening at the center of at least one of the circular blades for insertion of the lignocellulosic material, such that the material enters at the center and is transported in a radial direction during refining.

[0008] While refiner bars serve to refine the lignocellulosic material, the refiner dams instead serve to lift the material up from the grooves towards the refining gap to ensure a thorough and uniform refining of the material. Due to the high pressure and elevated temperature between the blades, moisture present in the lignocellulosic material forms steam, but the presence of the steam may hinder progress of the lignocellulosic material across the blade, in particular when approaching a pressure peak in the refining gap between the inner and the outer periphery of the blades. The extremely high pressure at the pressure peak typically causes steam to flow backwards towards the inner periphery, thereby preventing an efficient flow of lignocellulosic material across the pressure peak. This in turn decreases refining efficiency and leads to higher costs as well as excessive wear on the blades, thereby decreasing their lifetime and requiring frequent maintenance. Also, local pressure maxima may arise and cause excessive wear or damage to the blade.

[0009] There are at present no efficient solutions for mitigating these problems.

[0010] SUMMARY

[0011] The object of the present invention is to eliminate or at least to minimize the problems discussed above. This is achieved by a blade for a refiner, a refiner, and a method for manufacturing a blade according to the appended independent claims.

[0012] The blade of the invention comprises a plurality of refiner bars separated by grooves, and also comprises a plurality of refiner dams arranged across the grooves to connect refiner bars on either side of the grooves to each other. Furthermore, the blade comprises at least one through- hole in at least one of the refiner dams for enabling a flow along the groove through the dam.

[0013] By providing at least one dam with a through-hole, the blade of the present invention enables a flow of lignocellulosic material to be lifted by the dam into the refiner gap when operating inside a refiner, while at the same time allowing steam to flow through the through-hole and thereby pass the dam without interrupting the flow of lignocellulosic material. This is highly advantageous in improving operation of a refiner and in achieving an efficient refining while limiting energy consumption and extending the lifetime of the refiner blade. Suitably, the through-hole has a width that differs less than 10 % from a width of the groove. Thereby, the through- hole has a width that is close to the width of the groove itself, and this enables a large flow of steam through the through- hole.

[0014] Alternatively, the through-hole has a width that is less than 80 % of a width of the groove, preferably less than 60 % and more preferably less than 40 %. Thereby, a narrower through-hole is achieved, rendering the dam itself more robust and stable while at the same time allowing a flow of steam through the through-hole.

[0015] The through- hole suitably has a lower end that is at a height from a bottom of the groove of less than 50 % of a dam height, preferably less than 20 %, and more preferably less than 10 %. Thereby, the through-hole is provided close to the bottom of the groove, and this is advantageous in enabling a smooth flow of steam that is separated from the flow of lignocellulosic material lifted into the refiner gap.

[0016] Also, the through-hole suitably has a through-hole height that is less than half a dam height of the refiner dam, preferably less than one third of the dam height. Thereby, the refiner dam maintains stability and is able to lift the flow of lignocellulosic material without being unduly damaged or broken.

[0017] The through-hole also suitably has a through-hole height that is at least one fourth of a dam height of the refiner dam. Thereby, the through-hole is rendered large enough to enable a large flow of steam in a reliable and efficient way.

[0018] Suitably, a plurality of the refiner dams comprise a through-hole. This improves the flow of steam across the blade. In some embodiments, at least 50 % of the refiner dams comprise at least one through- hole. Thereby, the flow of steam across the blade as a whole is further improved.

[0019] Furthermore, a plurality of refiner dams may suitably be arranged along one groove and comprise through- holes that are aligned to create a channel along the groove. This improves the flow of steam since lifting of steam into the refiner gap is avoided where through-holes are provided, so that steam is able to flow along the groove whereas the lignocellulosic material is regularly lifted into the refiner gap whenever it encounters a refiner dam.

[0020] Suitably, at least one refiner dam at an outer periphery of the blade is solid and lacks through-holes. Thereby, both steam and lignocellulosic material is lifted by the refiner dam as it nears the outer periphery. This is advantageous in improving the flow of material from the blade after refining is completed.

[0021] In some embodiments, each dam adjacent to the outer periphery of the blade is solid and lacks through-holes. This achieves the advantage disclosed above over the entire circumference of the blade.

[0022] Suitably, at least one of the refiner dams extends downwards into the groove at an angle to a flow direction along the groove, said angle being less than 90°, preferably less than 60° and more preferably less than 45°. Thereby, steam is guided into the through-hole to improve the flow through the hole.

[0023] At least one refiner dam has a dam height that is less than 80 %, preferably less than 65 % of a refiner bar height. Thereby, the advantages of the through- hole in the refiner dam are achieved also for half dams or subsurface dams.

[0024] Suitably, the blade comprises a peak region between an inner periphery and outer periphery of the blade, and each of the through- holes in refiner dams is arranged between the peak region and the inner periphery. Thereby, the flow of steam through the through-hole is enabled between the inner periphery and the peak region, so that a backwards flow of steam that typically arises when pressure increases can take place. This in turn decreases energy consumption and improves refining since the lignocellulosic material is guided towards the peak region in a more efficient manned than in prior art solutions.

[0025] Also, all refiner dams of the blade suitably comprise at least one through- hole. Thereby, the flow of steam is further improved on the blade.

[0026] Suitably, all grooves are connected to each other. This is achieved by through- holes distributed in a plurality of the refiner dams and provides the advantage that pressure is distributed more evenly on the blade. The blade may be a blade portion having a central angle of 10° - 360°.

[0027] The present invention also relates to a refiner for refining lignocellulosic material where the refiner comprises at least one blade according to the invention.

[0028] Suitably, the blade according to the invention is arranged as a rotor side blade in the refiner. Thereby, the flow of steam across the blade when in use is rendered particularly advantageous since the steam typically flows in the grooves of the blade that is rotating to a higher degree than in the blade that is stationary.

[0029] The invention also relates to a method for manufacturing the blade of the invention. The method comprises the following:

[0030] - providing production data of the blade,

[0031] - supplying the production data to a 3D printer, and

[0032] - 3D printing a pattern of the blade.

[0033] This enables manufacturing of the blade with the through- hole in at least one refiner dam through additive manufacturing (3D printing). Thereby, dimensions and placement of the through-hole is achieved with high precision so that the advantages of the invention are realised in a particularly advantageous manner.

[0034] Many additional benefits and advantages of the present invention will be readily understood by the skilled person in view of the detailed description below.

[0035] DRAWINGS

[0036] The invention will now be described in more detail with reference to the appended drawings, wherein:

[0037] Fig. 1 discloses a planar view from above of a portion of a blade according to a first embodiment of the invention; Fig. 2 discloses a perspective view from the inner periphery of the blade of Fig. 1;

[0038] Fig. 3 discloses a perspective view from the side of the blade of Fig. 1;

[0039] Fig. 4 discloses a planar view from the inner periphery of the blade of Fig.

[0040] 1;

[0041] Fig. 5a discloses a planar view from the side of a refiner dam with a through-hole according to the invention;

[0042] Fig. 5b discloses a planar view from the side of another design of a refiner dam with a through-hole according to the invention;

[0043] Fig. 5c discloses a planar view from the side of yet another design of a refiner dam with a through-hole according to the invention;

[0044] Fig. 6a discloses a planar view from the side of a dam of the blade according to the first embodiment;

[0045] Fig. 6b discloses a planar view from the side of a dam of the blade according to a second embodiment;

[0046] Fig. 6c discloses a planar view from the side of a dam of the blade according to a third embodiment;

[0047] Fig. 6d discloses a planar view from the side of a dam of the blade according to a fourth embodiment; and

[0048] Fig. 7 discloses schematically the steps of the method according to the invention.

[0049] All the figures are schematic, not necessarily to scale, and generally only show parts which are necessary in order to elucidate the respective embodiments, whereas other parts may be omitted or merely suggested. Any reference number appearing in multiple drawings refers to the same object or feature throughout the drawings, unless otherwise indicated.

[0050] DETAILED DESCRIPTION Fig. 1 discloses a portion of a blade 10 for a refiner according to a first embodiment of the invention. The blade 10 comprises an inner periphery 11 and an outer periphery 12, and between them a refining surface 13 is arranged and comprises a plurality of refiner bars 14 for refining lignocellulosic material. The refiner bars 14 are separated by grooves 15 and are connected by refiner dams 16 that may connect only two adjacent refiner bars 14 as shown in Fig. 1 or may alternatively extend across a plurality of grooves 15 to connect a plurality of refiner bars 14. At least one of the refiner dams 16 of the blade 10 comprises a through-hole 18 as will be explained below with reference to Fig. 2 onwards. As is well known in the art, the refiner bars 14 serve to refine lignocellulosic material whereas refiner dams 16 serve to ensure that the lignocellulosic material transported in the grooves 15 is lifted towards the refining surface 13 at upper ends 20 of the refiner bars 14 so that refining can take place. The refining surface 13 at the upper ends 20 of the refiner bars 14 typically defines a refiner gap together with a refining surface on an opposing blade when the blade 10 is mounted in a refiner.

[0051] The through- hole 18 is defined as an opening that extends through the refiner dam 16 so that a connection is established between the groove 15 on one side of the refiner dam 16 and the groove 15 on an opposite side of the refiner dam 16. Hie through-hole 18 is delimited by material of the refiner dam 16 and also in some embodiments by material of the refiner bars 14 that are connected by the refiner dam 16 and by a bottom 19 of the groove 15. This will be explained in more detail below with reference to Fig. 5a-5c. It is in particular to be noted that the through-hole 18 is delimited by material around its entire circumference, i.e. that the through-hole 18 is not in the form of a notch, a groove or an indentation.

[0052] During operation in a refiner, the blade 10 is arranged as a stator side blade or as a rotor side blade. Lignocellulosic material is fed into the refiner and reaches the blade 10 at the inner periphery 11. It then moves across the blade 10 towards the outer periphery 12 and is refined by contact with the refiner bars 14 in the refiner gap formed between the refining surface 13 of the rotor side blade and the stator side blade. The design and arrangement of the refiner bars 14 and refiner dams 16 may differ in different sections of the blade 10.

[0053] When it is stated herein that lignocellulosic material is lifted to the refiner gap or that refining takes place at the refiner gap, this is to be understood as being in a space delimited by the upper ends 20 of the refiner bars 14 on one blade 10 and extending to upper ends of refiner bars on an opposing blade that can be a blade according to the present invention or another kind of refiner blade.

[0054] The term lignocellulosic material is used herein to mean materials containing lignin, cellulose and hemicellulose. One example of such materials is wood, others include other agricultural or forestry wastes.

[0055] In the following, when it is said that one feature or dimension of the blade 10 (such as e.g. a height or width of one feature) is “substantially” the same as another, this is to be understood as being the same within manufacturing tolerances or at least not differing more than 10 %.

[0056] Pressure in the refining gap between the blades changes as the lignocellulosic material passes from the inner periphery 11 to the outer periphery 12, with a pressure peak in a peak region 17 where the pressure is at a maximum before abruptly decreasing on an outside of the peak region 17, i.e. between the peak region 17 and the outer periphery 12. Hie peak region 17 is defined as a region extending along the blade 10 in a circumferential direction and having a pressure that is higher than in any other part of the blade 10. On an inner side of the peak region 17, i.e. between the peak region 17 and the inner periphery 11, steam tends to flow countercurrent to the flow of lignocellulosic material so that steam moves towards the inner periphery. On an outer side of the peak region 17, i.e. between the peak region 17 and the outer periphery 12, steam instead flows along the current of lignocellulosic material.

[0057] Fig. 2 discloses the blade 10 in a perspective view, showing through- holes 18 in a plurality of the refiner dams 16. The through-holes 18 are in this embodiment provided at a lower end 21 of the refiner dams 16 and reach all the way to a bottom 19 of the groove 15 in which the refiner dam 16 is arranged. The through-holes 18 enable a flow along the groove 15 through the refiner dam 16 and is particularly suitable for a flow of steam generated in the refiner due to the elevated pressure between refiner blades. Thereby, steam may flow along the groove 15 whereas lignocellulosic material is lifted by the refiner dams 16 to the upper ends 20 of the refiner bars 14, i.e to the refining surface 13, to ensure on the one hand that the flow of steam does not hinder the flow of lignocellulosic material and on the other hand that the lignocellulosic material itself is brought to the refiner gap for refining. The steam typically flows towards the inner periphery 11 due to the elevated pressure in the peak region 17 forcing steam backwards, away from the peak region 17, whereas the lignocellulosic material flows across the peak region 17 towards the outer periphery 12. That the lignocellulosic material is able to move across the peak region 17 is due to the fact that the constant feeding of lignocellulosic material into the refiner prevents a backwards flow.

[0058] Fig. 3 discloses the blade 10 in a perspective view showing one groove 15 with three refiner dams 16 arranged to connect a refiner bar 14 with an adjacent refiner bar 14 (not shown). Through-holes 18 are provided in each of the refiner dams 16 to form a channel C along the groove 15 so that steam is able to flow unhindered along the length of the groove 15. This is particularly advantageous in separating the steam from the lignocellulosic material to ensure that refining in the refiner gap is rendered particularly efficient.

[0059] In some embodiments, only one of the refiner dams 16 on the blade 1 comprises a though- hole 18, but in the first embodiment a plurality of the refiner dams 16 each comprise such a through-hole 16. In fact, in the first embodiment at least 50 % of the refiner dams comprise through- holes 16.

[0060] In some embodiments, all the through-holes 18 provided in the refiner dams 16 are arranged between the peak region 17 and the inner periphery 11 to ensure that a flow of steam towards the inner periphery 11 does not interfere with the flow of lignocellulosic material towards the peak region 17. The refiner dams 16 between the peak region 17 and the outer periphery 12 are instead solid and lack through-holes 18 to ensure a maximum strength of the refiner dams 16. Since the steam and lignocellulosic material flow in the same direction after passing the peak region 17, i.e. towards the outer periphery 12, the steam does not hinder refining efficiency in the refiner gap.

[0061] It is advantageous to provide at least one refiner dam 16 close to the outer periphery 12 without through-hole 18, i.e. as a solid refiner dam 16. That way both steam and lignocellulosic material are lifted by the refiner dam 16 to the outer periphery 12 and proceed together from the blade 1. In the first embodiment, each refiner dam 16 that is adjacent to the outer periphery 12 is solid and lacks through-holes 18. This means that for a circular blade the refiner dams 16 distributed in the circumferential direction around the blade 10 at the outer periphery 12 are solid.

[0062] Fig. 4 discloses the blade 10 in a planar view from the inner periphery outwards to show the through- holes 18 more clearly. In the first embodiment, the through-holes 18 are at a bottom 19 of the grooves 15 with the refiner dams 16 then extending upwards to the upper end 20 of the refiner bars 14. The refiner dams 16 thus have a dam height dh that is substantially the same as a bar height bh (within manufacturing tolerances or at least not differing more than 10 %). This means that the refiner dams 16 are able to lift the lignocellulosic material all the way to the refiner gap when the blade 10 is in use in the refiner, i.e. to the upper ends 20 of the refiner bars 14.

[0063] In some embodiments, at least one and preferably at least some of the refiner dams 16 are instead subsurface dams, i.e. refiner dams 16 that have a dam height dh that is lower than the bar height bh. The dam height dh of such a subsurface dam is less than 80 % of the bar height bh, preferably less than 65 % of the bar height. This means that the subsurface dams are able to lift lignocellulosic material towards the upper ends 20 of the refiner bars 14 but that they do not extend all the way to the upper ends 20 themselves.

[0064] In the first embodiment, the through-holes 18 have a width w that is substantially the same as a groove width gw of the groove 15 where the through-hole 18 is arranged (i.e. where the refiner dam 16 comprising the through-hole 18 is arranged), or that at least does not differ more than 10 % from the groove width gw. Typically, refiner bars 14 are wider at the bottom 19 of the adjacent grooves 15 and taper towards the upper ends 20, and this means that the groove width gw is smaller at the bottom 19 and increases towards the upper ends 20 of the refiner bars 14. Thus, when it is stated that the width 2 of the through-hole 18 is the same as the groove width gw, this means that at any given height from the bottom 19 of the groove, the width of the through-hole 18 is the same as the groove width gw at that height.

[0065] Fig. 5a discloses one refiner dam 16 with a through-hole 18 according to the first embodiment, i.e. with a width w that is the same as the groove width gw. The through-hole 18 has a height h that is less than half of the dam height dh, preferably less than one third of the dam height dh and that extends all the way to the bottom 19 of the groove 15.

[0066] Fig. 5b discloses a refiner dam 16 where the width w of the through-hole 18 is less than the groove width gw. In this embodiment, the through-hole has a width that is less than 80 % of the groove width gw, preferably less than 60 % and more preferably less than 40 %. This renders the refiner dam 16 more stable and improves its ability to withstand the flow of steam and lignocellulosic material without breaking.

[0067] The height h of the through- hole 18 is in this embodiment less than one third of the dam height dh. In this embodiment, the through-hole 18 does not extend to the bottom 19 of the groove 15 but instead has a lower end 21 that is at a height H from the bottom 19 of the groove 15 of less than 50 % of the dam height dh, preferably less than 20 % and more preferably less than 10 %. Although the flow of steam is most efficient when it is allowed to pass unhindered at the bottom 19 of the groove 15, is it sometimes desirable to arrange the through-hole 18 higher on the refiner dam 16, in particular for preventing blockage of the through- holes 18 due to fibers of the lignocellulosic material.

[0068] Fig. 5c discloses another design that combines the width w of the through- hole 18 of the first embodiment with the through-hole being provided at the height H from the bottom 19 of the groove 15. It is advantageous for all of the embodiments described herein that the height h of the through-hole 18 is larger than one fourth of the dam height dh, since this enables a high flow of steam. At the same time, some embodiments can have a smaller height h where only a smaller flow of steam is required.

[0069] It is to be noted that the embodiments of Fig. 5a-5c are similar or identical to each other in all respects other than those explicitly stated above to differ.

[0070] It is also to be noted that the blade 10 according to any embodiments disclosed herein may comprise a plurality of through-holes 18 that differ from each other, so that some through-holes 18 may be according to the embodiment shown in Fig. 5b whereas other through-holes 18 are according to the embodiment of Fig. 5c and / or Fig. 5a. Similarly, in some embodiments, the selection of dimensions for through-holes 18 may freely be varied from one through-hole 18 to the other so that a plurality of different designs are used in the same blade 10. In other embodiments, all through-holes 18 may have the same dimensions so that only one design or embodiment is represented on the blade 10.

[0071] Fig. 6a shows the first embodiment of the refiner dam 16 from the side, with the through-hole 18 provided at the bottom 19 of the groove 15 and with an arrow S to show a flow direction of steam when the blade 10 is in use. The refiner dam 16 according to this design is provided with an outer dam surface 22 that is substantially perpendicular to a radial direction from the inner periphery 11 to the outer periphery 12. The refiner dam 16 also has an inner dam surface 23 that is angled in relation to the radial direction to form an upwards slope so that lignocellulosic material is lifted along the inner dam surface 23 in an efficient manner. An arrow M denotes the flow direction of lignocellulosic material as it reaches the refiner dam 16.

[0072] Fig. 6b shows a second embodiment where the inner dam surface 23 maintains an upwards slope but where the outer dam surface 22 shows a downward slope so that steam is guided into the through-hole 18. This can be denoted as the refiner dam 16 extending downwards into the groove 15 at an angle a to the flow direction along the groove, where the angle a is less than 90°. In the design of Fig. 6b, the angle a is less than 60° and preferably less than 45° to further improve guiding of the steam S into the through-hole 18.

[0073] Fig. 6c shows a third embodiment where the inner dam end 23 has the upwards slope and where the outer dam end 22 has the downwards slope but at the angle a less than 90° but not less than 60°. This provides the guiding of the steam into the through- hole 18 to a lesser degree than the design of Fig. 6b, but at the same time ensures greater stability of the refiner dam 16.

[0074] Fig. 6d shows a fourth embodiment where the inner dam end 23 has the upwards slope but where the outer dam end 22 slopes away from the through- hole 18. The refiner dam 16 of this design is a sub-surface dam so that the refiner dam 16 does not reach to the upper end 20 of the refiner bar 14.

[0075] It is to be noted that the embodiments of Fig. 6a-6d are similar or identical to each other in all other respects than those explicitly stated above to be different. Also, the blade 10 may comprise dams according to only one or to a plurality of the embodiments of Fig. 6a- 6d so that any number of designs for a refiner dam 16 may be represented on the blade 10.

[0076] In some embodiments, all refiner dams 16 of the blade 10 comprise at least one through- hole 18. This improves the flow of steam on the blade during use and also distributes pressure more evenly on the blade.

[0077] Also, in some embodiments all the grooves 15 are connected to each other. This is achieved by the through-holes 18 but may also be achieved by the refiner bars 14 being designed so that they do not extend unbroken from the inner periphery 11 to the outer periphery 12. The refiner bars 14 can thus be arranged to be shorter than a distance from the inner periphery 11 to the outer periphery 12 or may alternatively be arranged with interruptions so enable a connection of grooves 15 on either side of the refiner bar 14. By thus connecting the grooves 15 to each other, pressure distribution on the blade is improved so that local pressure maxima can be avoided or at least minimized.

[0078] For the embodiments described above, it is particularly advantageous where the through-holes 18 in the refiner dams 16 are provided to facilitate the flow of steam since this decreases the risk of local pressure maxima and improves the refining by ensuring that the lignocellulosic material is able to flow towards the peak region 17 in a smooth and efficient way.

[0079] The blade 10 of the invention is a circular blade but it may also be provided as a blade portion that has a central angle less than 360°, most suitably in the range 10° - 360° with the upper end of the range being the circular blade 10. Where the blade 10 is provided as a blade portion with a lesser central angle (typically referred to as a segment), a plurality of blade portions are provided to form the circular blade when mounted in the refiner.

[0080] When using the blade 10 in the refiner, it is particularly advantageous to arrange the blade 10 of the invention as the rotor side blade, since it has been found that steam is transported mainly along the rotor side blade. However, the blade 10 may also be arranged as the stator side blade and enable a more efficient flow of steam along the stator side blade.

[0081] The method for manufacturing the blade according to the invention will now be described with reference to Fig. 7.

[0082] The method comprises providing 101 production data of the blade 10 according to any embodiment disclosed herein.

[0083] Generally, in the present disclosure, the production data may be provided in any suitable data type. Usually, 3D printable models may be created with a computer-aided design (CAD) package, via a 3D scanner, or by a plain digital camera and photogrammetry software. 3D printed models created with CAD result in reduced errors and can be corrected before printing, allowing verification in the design of the object before it is printed. Accordingly, CAD data are preferred in the present disclosure.

[0084] In one specific embodiment of the present disclosure, a 3D model of a refiner blade is produced with a CAD program package, where the 3D refiner blade model created by the CAD program is a mathematical representation stored in a first data file with a suitable file format, e.g. a STL file. Suitable CAD program packages are, for example, Pro / Engineer and SolidWorks. Optionally but preferably, the data on the first and second data files are checked for errors and imperfections with a suitable software program package, e.g. a program package provided by the company EOS e- manufacturing solutions. Besides correcting errors in the data files, it is important that all geometrical structures in the refiner blade models are reproducible in subsequent manufacturing steps and are suitable for such manufacturing steps. Depending on the geometrical structures incorporated in the refiner segments and on the specific 3D printer and 3D printer software chosen, the data contained in the data files is mathematically sliced into layers, which can have a virtual thickness of, e.g., 0.01 mm.

[0085] The method also comprises supplying 102 the production data to a 3D printer.

[0086] Generally, in the present disclosure, the printing step may be performed by any suitable 3D printer type. Preferred printing materials are selected from metals or metal alloys. The present invention is not limited to a specific printing material.

[0087] The method further comprises 3D printing 103 a pattern of the blade 10.

[0088] The mathematically sliced data files are thus input into a suitable 3D printer package and the refiner blade is printed using the 3D printer. Different 3D printing techniques can be employed, but a preferred technique is so-called direct metal laser sintering (DMLS), which utilizes an ytterbium (Yb) fiber laser fired into a bed of metal powder.

[0089] It is to be noted that features from the various embodiments described herein may freely be combined, unless it is explicitly stated that such a combination would be unsuitable.

Claims

CLAIMS1. Blade for a refiner, the blade (10) comprising a plurality of refiner bars(14) separated by grooves (15), and also comprising a plurality of refiner dams (16) arranged across the grooves (15) to connect refiner bars (14) on either side of the grooves (15) to each other, and further comprising at least one through- hole (18) in at least one of the refiner dams (16) for enabling a flow of steam along the groove (15) through the dam (16).

2. Blade according to claim 1, wherein the through- hole (18) has a width that differs less than 10 % from a width of the groove (15).

3. Blade according to claim 1, wherein the through- hole (18) has a width (w) that is less than 80 % of a width (gw) of the groove (15), preferably less than 60 % and more preferably less than 40 %.

4. Blade according to any previous claim, wherein the through-hole (18) has a lower end (21) that is at a height (H) from a bottom of the groove(15) of less than 50 % of a dam height (dh), preferably less than 20 %, and more preferably less than 10 %.

5. Blade according to any previous claim, wherein the through-hole (18) has a through- hole height (h) that is less than half a dam height (dh) of the refiner dam (16), preferably less than one third of the dam height (dh).

6. Blade according to any previous claim, wherein the through-hole (18) has a through- hole height (h) that is at least one fourth of a dam height (dh) of the refiner dam (16).

7. Blade according to any previous claim, wherein a plurality of the refiner dams (16) comprise a through- hole (18).

8. Blade according to claim 7, wherein at least 50 % of the refiner dams(16) comprise at least one through-hole (18).

9. Blade according to claim 7 or 8, wherein a plurality of refiner dams (16) are arranged along one groove (15) and comprise through- holes (18) that are aligned to create a channel along the groove (15).

10. Blade according to any previous claim, wherein at least one refiner dam (16) at an outer periphery (12) of the blade is solid and lacks through-holes (18).

11. Blade according to claim 10, wherein each refiner dam (16) adjacent to the outer periphery (12) of the blade is solid and lacks through-holes (18).

12. Blade according to any previous claim, wherein at least one of the refiner dams (16) extends downwards into the groove (15) such that an outer dam surface (22) is at an angle to a flow direction of steam along the groove, said angle being less than 90°, preferably less than 60°, and more preferably less than 45°.

13. Blade according to any previous claim, wherein at least one refiner dam (16) has a dam height (dh) that is less than 80 % of a refiner bar height.

14. Blade according to any previous claim, further comprising a peak region (17) between an inner periphery (11) and the outer periphery (12) of the blade (10), and wherein each of the through- holes (18) in refiner dams (16) are arranged between the peak region (17) and the inner periphery (11).

15. Blade according to any of claims 1-9 or 12-14, wherein all refiner dams (16) comprise at least one through- hole (18).

16. Blade according to any previous claim, wherein all grooves (15) are connected to each other.

17. Blade according to any previous claim, wherein the blade (10) is a blade portion having a central angle of 10° - 360°.

18. Refiner for refining lignocellulosic material, the refiner comprising at least one blade (10) according to any of claims 1-17.

19. Refiner according to claim 16, wherein the blade (10) according to any of claims 1- 17 is arranged as a rotor side blade in the refiner.

20. Method for manufacturing the blade according to any of claims 1- 17, comprising:- providing production data of the blade (10),- supplying the production data to a 3D printer, and- 3D printing a pattern of the blade.

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