Abstract
Disclosed is a refiner filling piece for a refiner having a rotor that rotates about an axis of rotation and cooperates with a stator to mechanically treat a pulp containing cellulosic fibers. The refiner filling piece is mountable to the rotor or the stator. The refiner filling piece comprises a base and a plurality of spaced-apart refiner bars, each refiner bar being defined by a bar length and a bar height. At least some of the refiner bars have a surface coated with a stepped coating. The surface having the stepped coating may be the leading surface of the refiner bar.
Claims
1. A refiner filling piece for a refiner having a rotor that rotates about an axis of rotation and cooperates with a stator to mechanically treat a pulp containing cellulosic fibers, the refiner filling piece being mountable to the rotor or the stator, the refiner filling piece comprising: a base; a plurality of spaced-apart refiner bars, each refiner bar being defined by a bar length and a bar height; and wherein at least some of the refiner bars have a surface coated with a stepped coating.
2. The refiner filling piece of claim 1 wherein the stepped coating has a first coating thickness over a first portion of the bar height and a second coating thickness over a second portion of the bar height.
3. The refiner filling piece of claim 2 comprising an uncoated portion extending from the base to the stepped coating.
4. The refiner filling piece of claim 3 wherein the stepped coating extends to a top end of the refiner bar.
5. The refiner filling piece of claim 1 wherein the surface that is coated with the stepped coating is a leading surface of the refiner bar.
6. The refiner filling piece of claim 1 wherein the second portion of the bar height having the second coating thickness is taller than the first portion of the bar height having the first coating thickness.
7. The refiner filling piece of claim 1 wherein the stepped coating has a first coating thickness along a first portion of the bar length and a second coating thickness along a second portion of the bar length.
8. The refiner filling piece of claim 7 comprising an uncoated portion extending from a radially inner end of the refiner bar to the stepped coating.
9. The refiner filling piece of claim 8 wherein the stepped coating extends to a radially outer end of the refiner bar.
10. The refiner filling piece of claim 7 wherein the surface that is coated with the stepped coating is a leading surface of the refiner bar.
11. The refiner filling piece of claim 7 wherein the first portion of the bar length having the first coating thickness is longer than the second portion of the bar length having the second coating thickness.
12. A refiner comprising: a housing; a stator supported within the housing; a rotor that rotates about an axis of rotation and cooperating with the stator to mechanically treat a pulp containing cellulosic fibers; a first refiner filling piece fastened to the rotor; and a second refiner filling piece fastened to the stator, wherein the refiner filling piece comprises: a base; a plurality of spaced-apart refiner bars, each refiner bar being defined by a bar length and a bar height; and wherein at least some of the refiner bars have a surface coated with a stepped coating.
13. The refiner of claim 12 wherein the stepped coating has a first coating thickness over a first portion of the bar height and a second coating thickness over a second portion of the bar height.
14. The refiner of claim 13 wherein the refiner bar comprises an uncoated portion extending from the base to the stepped coating.
15. The refiner of claim 14 wherein the stepped coating extends to a top end of the refiner bar.
16. The refiner of claim 12 wherein the surface that is coated with the stepped coating is a leading surface of the refiner bar.
17. The refiner of claim 12 wherein the second portion of the bar height having the second coating thickness is taller than the first portion of the bar height having the first coating thickness.
18. The refiner of claim 12 wherein the stepped coating has a first coating thickness along a first portion of the bar length and a second coating thickness along a second portion of the bar length.
19. The refiner of claim 18 wherein the refiner bar comprises an uncoated portion extending from a radially inner end of the refiner bar to the stepped coating.
20. The refiner of claim 19 wherein the stepped coating extends to a radially outer end of the refiner bar.
21. The refiner of claim 18 wherein the surface that is coated with the stepped coating is a leading surface of the refiner bar.
22. The refiner of claim 18 wherein the first portion of the bar length having the first coating thickness is longer than the second portion of the bar length having the second coating thickness.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] Further features and advantages of the present technology will become apparent from the following detailed description, taken in combination with the appended drawings, in which:
[0011] FIG. 1 is a perspective view of a refiner having a rotor and stator in accordance with an embodiment of the present invention showing the replacement of a refiner filling piece on the stator.
[0012] FIG. 2 is another perspective view of the refiner of FIG. 1 showing the replacement of a refiner filling piece on the rotor.
[0013] FIG. 2A is a plan view of four refiner filling pieces shaped as four arcuate segments as one example of segmented filling pieces for a disc-type refiner.
[0014] FIG. 3 is a cross-sectional view of a refiner filling piece having a variable coating on a leading surface of the bars.
[0015] FIG. 4 is a cross-sectional view of a refiner filling piece having a variable coating on a leading surface of the bars.
[0016] FIG. 5 is a cross-sectional view of a refiner filling piece having a variable coating on a leading surface of the bars.
[0017] FIG. 6 is a cross-sectional view of a refiner filling piece having a variable coating on a leading surface and a thinner variable coating on the trailing surface.
[0018] FIG. 7 is a cross-sectional view of a refiner filling piece having a variable coating on a leading surface and a thinner variable coating on the trailing surface.
[0019] FIG. 8 is a cross-sectional view of a refiner filling piece having a variable coating on a leading surface and a thinner variable coating on the trailing surface.
[0020] FIG. 9 is a top view of a refiner filling piece in accordance with one embodiment of the invention in which the variable coating varies linearly along a bar length on the leading surface.
[0021] FIG. 10 is a top view of a refiner filling piece in accordance with another embodiment of the invention in which the variable coating varies linearly along a bar length on the leading surface and a thinner variable coating varies along the bar length on the trailing surface.
[0022] FIG. 11 depicts a conical refiner filling piece to which a variable coating may be applied in accordance with another embodiment of the invention.
[0023] FIG. 12 is a cross-sectional view of a refiner filling piece having stepped coatings on the refiner bars in accordance with another embodiment of the invention.
[0024] FIG. 13 is a top view of a refiner filling piece in accordance with another embodiment of the invention in which the stepped coating is stepped along the radial length of the refiner bars.
[0025] FIG. 14 is a cross-sectional view of a refiner filling piece having stepped coatings on the refiner bars in which the stepped coatings comprise three steps in accordance with another embodiment of the invention.
[0026] FIG. 15 is a cross-sectional view of a refiner filling piece having stepped coatings on the refiner bars in which the stepped coatings comprise three steps above an uncoated lower portion in accordance with another embodiment of the invention.
[0027] FIG. 16 is a cross-sectional view of a refiner filling piece having stepped coatings on the refiner bars in which the stepped coatings comprise two steps above and below uncoated portions in accordance with another embodiment of the invention.
[0028] FIG. 17 is a cross-sectional view of a refiner filling piece in which the refiner bars have both stepped coatings and linearly variable coatings in accordance with another embodiment of the invention.
[0029] FIG. 18 is a cross-sectional view of a refiner filling piece in which the refiner bars have both stepped coatings and nonlinearly variable coatings in accordance with another embodiment of the invention.
[0030] FIG. 19 is a cross-sectional view of a refiner filling piece in which the refiner bars have stepped coatings on both the leading surfaces and the trailing surfaces.
[0031] FIG. 20 is a perspective view of a refiner bar showing gaps between steps of a stepped coating in accordance with another embodiment of the invention.
[0032] It will be noted that throughout the appended drawings, like features are identified by like reference numerals.
DETAILED DESCRIPTION
[0033] Disclosed herein are various embodiments of a refiner filling piece having refiner bars that are coated with a variable coating or with a stepped coating. The present specification also discloses a refiner having one or more refiner filling pieces that include the refiner bars coated with the variable coating or with the stepped coating.
[0034] FIG. 1 is a perspective view of a refiner generally denoted by reference numeral 10 in accordance with one embodiment of the present invention. In the embodiment depicted in FIG. 1, the refiner 10 has a housing 12, a stator 14 and a rotor 16. The rotor rotates about an axis of rotation and cooperates with the stator to mechanically treat a pulp (or pulp suspension) containing cellulosic fibers. The axis of rotation defines an axial direction and a radial direction. In the illustrated embodiment of FIG. 1, the refiner is a disc-type refiner having a replaceable refiner filling. The refiner filling is composed of a plurality of refiner filling pieces. In the example of FIG. 1, the refiner filling pieces are segments of a generally flat, annular disc-like or plate-like structure (also referred to herein as a plate). However, it will be appreciated that the refiner filling pieces may be conical filling pieces in a conical refiner. For the purposes of this specification, the expression refiner filling piece shall be construed as encompassing a flat disc-like plate or an arcuate segment thereof, or a conical structure or an angular segment thereof. For a disc-type refiner, the refiner filling piece may be a one-piece circular plate, an annular plate or an arcuate segment that is assembled with other arcuate segments to form the complete circular or annular plate. Analogously, for a conical refiner, the refiner filling piece may be a one-piece conical (or frusto-conical) structure or an angular segment of a cone (or frustum) that is assembled with other such angular segments to form a complete conical (or frusto-conical) structure. From the foregoing, it is to be understood that a refiner filling piece may be circular, annular or conical (i.e. defining a complete 360-degree component) or segmented (i.e. defining an arcuate or angular component of less than 360 degrees that is designed to be assembled with other such segments to form the complete circular or annular plate or to form the cone, as the case may be).
[0035] FIG. 1 depicts the replacement of a refiner filling piece 20 on the stator 14. The refiner filling piece 20 may be mounted to the stator 14 using fasteners, e.g. threaded fasteners, as shown. In this example, a plurality of refiner filling pieces 20 are mounted to the stator 14 in an annular arrangement to constitute a stator-side refiner plate. In the embodiment depicted in FIG. 1, the stator 14 is mounted to a door-like cover 15 that pivots about a hinge mechanism to enable replacement of the refiner filling piece(s) 20.
[0036] FIG. 2 is another perspective view of the refiner 10 of FIG. 1 showing the replacement of a refiner filling piece 20 on the rotor 16. The refiner filling piece 20 may be mounted to the rotor 16 using fasteners, e.g. threaded fasteners, as shown. A plurality of refiner filling pieces 20 are mounted to the rotor 16 in an annular arrangement to constitute a rotor-side refiner plate. In the embodiment depicted in FIG. 2, the rotor 16 is mounted inside the housing 12 of the refiner 10.
[0037] In the embodiment of FIGS. 1 and 2, the refiner filling piece 20 is a replaceable refiner filling piece having a segmented plate-like shape. When servicing the refiner, the refiner filling may be replaced, if worn, by replacing the assembly of refiner filling pieces that constitute the filling. For example, as shown in FIG. 2A, four refiner filling pieces shaped as four arcuate segments may be assembled to provide a complete annular plate structure for a disc-type refiner. The angular arc of each arcuate or segmented filling piece may be varied from what is shown in these examples. The angular arc of the filling piece may be, for example, 360 degrees, 180 degrees, 90 degrees, 45 degrees, 30 degrees, 22.5 degrees, 20 degrees, 15 degrees, 10 degrees, etc. so that when assembled they constitute an annular arrangement having a full 360 degrees. FIG. 2A also shows that the annular refiner filling piece may be characterized by an inner diameter (ID) and an outer diameter (OD). The refiner filling piece thus extends radially from the inner diameter to the outer diameter. It will also be appreciated that a complete plate or annulus of arcuate or segmented filling pieces may be composed of filling pieces of different shapes, e.g. one 180-degree filling plus two 90-degree filling pieces, two 90-degree filling pieces plus four 45-degree filling pieces, three 60-degree filling pieces plus six 30-degree filling pieces, and so on.
[0038] As illustrated in FIGS. 3-10, the refiner filling piece 20 has a base 22. The base may have a uniform thickness in an axial direction in some embodiments although it may alternatively have a non-uniform thickness. The base extends radially from an inner diameter ID to an outer diameter OD as depicted in FIG. 2A. The refiner filling piece 20 has a plurality of spaced-apart refiner bars 30 (also known as blades). The bars may be spaced apart with a uniform or non-uniform groove width, i.e. the spacing between adjacent bars may vary or be constant. Optionally, the refiner bars are spaced apart by spacers 24 although in other implementations, there may be no spacers. Each bar is defined by a bar length BL extending toward the outer diameter, i.e. extending generally radially, and is defined by a bar height BH protruding generally axially from the base. The bar height may be constant or varying. In some implementations, the bar height may be, for example, a value that is within the range of 3 to 14 mm. At least some of the refiner bars 30 have a leading surface 32 coated with a variable coating 34 in an embodiment of this invention.
[0039] The variable coating is applied non-uniformly, unlike the prior art, on the leading surface of the bar and optionally also, or alternatively, on the trailing surface of the bar. The coating is variable in thickness, i.e. the coating varies dimensionally or geometrically. The thickness of the coating varies so that the coating is thickest in areas where it provides maximum wear resistance and minimizing or eliminating application in areas with limited value or where excess coating may be detrimental.
[0040] As depicted in FIGS. 3-10, the variable coating has a coating thickness that is variable along either the height of the refiner bar (e.g. increasing from the base to the top of the bar) or variable in the radial direction (e.g. increasing from the inner diameter ID to the outer diameter OD of the filling).
[0041] The coating thickness may be a function of bar height. For example, the coating thickness may increase with the height of the bar (e.g. the coating becomes thicker as the height increases to a maximum thickness at the top of the bar). This minimizes the stress concentration at the base of the bar where bending stresses are highest while maximizing the space at the base of the groove to maintain or improve hydraulic capacity. Furthermore, the variable coating reduces cost by not applying the coating where it is not needed or less effective.
[0042] The coating may also, or alternatively, be varied in thickness as a function of radial length, e.g. in a direction from the inner diameter ID (where the coating is least) to or toward the outer diameter OD (where is it greatest). This maximizes the open area or volume at the inner diameter ID which is very important for hydraulic capacity. Since the outer diameter OD of the filling piece typically has a peripheral velocity higher than that of the inner diameter ID (for a disc-type refiner), the outer diameter portion consumes more energy, applies more shear and compression, and performs the majority of the refining work. Accordingly, concentrating the coating in the outer region of the filling pieces will improve service life relative to the same amount of coating if uniformly applied.
[0043] FIG. 3 is a cross-sectional view of a refiner filling piece 20 having a variable coating 34 on a leading surface 32 of the bars 30. In the embodiment depicted in FIG. 3, the variable coating 34 has a coating thickness that varies axially with the bar height.
[0044] As shown in FIG. 3, the coating thickness in this example embodiment increases linearly with the bar height.
[0045] FIG. 3 also denotes a groove space that occupies the volume between a trailing surface of one bar and the coated leading surface of the bar immediately behind it. The coating on the leading surface of the bar inhibits wear of the bar and thus preserves the hydraulic capacity of the refiner by maintaining a desired groove space between adjacent bars.
[0046] Alternatively, in the embodiment depicted in FIG. 4, the variable coating 34 on the leading surface 32 of the bars 30 has a coating thickness that, for example, increases non-linearly with bar height. For example, in one specific implementation, the nonlinear coating may be coated parabolically or exponentially with the bar height. For example, the coating thickness may increase as a function of the square of the axial height.
[0047] Alternatively, in the embodiment depicted in FIG. 5, the variable coating 34 on the leading surface 32 of the bars 30 has a coating thickness that, for example, increases over a first portion of the bar height, then decreases over a second portion of the bar height and then increases over a third portion of the bar height.
[0048] FIG. 6 is a cross-sectional view of a refiner filling piece 20 having a variable coating 34 on a leading surface 32 and a thinner variable coating 36 on the trailing surface 38. In the specific example of FIG. 6, both the coatings on the leading and trailing surfaces increase linearly with the bar height although at different rates.
[0049] In the example embodiment depicted in FIG. 7, both the leading and trailing surfaces 32, 38 have respective variable coatings 34, 36 that increase nonlinearly with the bar height although at different rates.
[0050] In the example embodiment depicted in FIG. 8, the trailing surface has a thinner variable coating than the variable coating on the leading surface as in FIGS. 6 and 7. In FIG. 8, the thinner variable coating increases over the first portion of the bar height, then decreases over the second portion of the bar height and then increases over the third portion of the bar height.
[0051] FIG. 9 is a top view of a refiner filling piece 20 in accordance with one embodiment of the invention in which the variable coating 34 varies radially along a bar length BL on the leading surface 32. Specifically, in this example, the variable coating has a coating thickness that varies linearly along the bar length.
[0052] FIG. 10 is a top view of a refiner filling piece 20 in accordance with another embodiment of the invention in which the variable coating 34 varies radially along a bar length BL on the leading surface 32 and a thinner variable coating 36 varies radially along the bar length BL on the trailing surface 38. In this specific example, the variable coating has a coating thickness that varies linearly along the bar length. As shown in FIG. 10, the trailing surface has a thinner variable coating than the variable coating on the leading surface.
[0053] FIG. 11 depicts a conical refiner filling piece 20 to which a variable coating may be applied in accordance with another embodiment of the invention. The conical refiner filling piece 20 is characterized by an inner diameter ID and an outer diameter OD as denoted in FIG. 11. The refining bars 30 of the conical refiner filling piece 20 have a variable coating as described above which may vary in all of the different ways discussed above. In this example, the conical refiner filling piece 20 is a single unitary component defining the complete conical structure although it will be appreciated that the conical refiner filling piece may be a segmented conical filling piece that is assembled with other segmented conical filling pieces to constitute the complete conical (or frusto-conical) structure.
[0054] In some embodiments, the leading surface of all refiner bars has the variable coating, i.e. all of the refiner bars are coated with the variable coating. In other embodiments, only some of the leading surfaces of the refiner bars have the variable coating. For example, an alternating pattern of coated and uncoated bars may be implemented. As another example, every third or fourth bar may be coated. Conversely, every third or fourth bar may be uncoated.
[0055] In some embodiments, the variable coating extends along all of the bar length. In other embodiments, the variable coating extends only partially along the bar length. For example, the variable coating may extend over 90%, 80%, 70%, 60%, 50%, 40%, 30%, 20%, 10%, etc. of the length. As another example, one bar may be coated a first percentage with the next bar being coated a different percentage. In some embodiments, the variable coating extends from the base to the top of the bar, i.e. the coating covers all of the bar height. In other embodiments, the variable coating extends only over a portion of the bar height. For example, the variable coating may begin at a point higher than the base, e.g. the midpoint, at a quarter of the height, a third of the height, three-quarters of the height, etc.
[0056] Another aspect of the disclosure is a refiner filling piece for a refiner in which at least some of the refiner bars have a stepped coating. The stepped coating is a coating having a discrete change in geometry as opposed to a variable coating that changes in a smooth or continuous fashion, such as a linearly variable or parabolically variable coating. The stepped coating may have multiple steps wherein each step has a discrete and uniform thickness. The stepped coating may have two steps, three steps or even four or more steps. In some embodiments, all refiner bars of the refiner filling piece are coated with the stepped coating. In some embodiments, the stepped coating is made entirely of the same coating material. In other embodiments, the stepped coating may be made of two or more different coating materials. The refiner filling piece with the stepped coatings on its refiner bars is mountable to the rotor and/or the stator in the same manner as was described above.
[0057] In the embodiment depicted by way of example in FIG. 12, the refiner filling piece 20 comprises a base 22, a plurality of spaced-apart refiner bars 30, each refiner bar 30 being defined by a bar length and a bar height and wherein at least some of the refiner bars 30 have a surface coated with a stepped coating 35. In this particular example, all of the refiner bars 30 have a stepped coating 35. Each stepping coating 35 has two or more discrete steps.
[0058] In the embodiment depicted by way of example in FIG. 12, the stepped coating 35 has a first coating thickness T.sub.1 over a first portion of the bar height and a second coating thickness T.sub.2 over a second portion of the bar height. The first portion defines a first step. The second portion defines a second step. In other embodiments, there may be three or more steps (i.e. three or more portions of different coating thicknesses). In this example, the first coating thickness T.sub.1 has a constant or uniform thickness and the second coating thickness T.sub.2 has a constant or uniform thickness wherein T.sub.1 is not equal to T.sub.2. Each step of the stepped coating 35 defines a flat planar surface that is parallel to the leading surface (or trailing surface) of the refiner bar. At the ends of the stepped coating and at the interface of two adjoining steps are generally or substantially perpendicular surfaces (or ledges) or sloped or curved surfaces.
[0059] In one embodiment, the second thickness T.sub.2 is twice the first thickness T.sub.1. In another embodiment, the second thickness T.sub.2 is more than twice the first thickness T.sub.1. In another embodiment, the second thickness T.sub.2 is less than twice the first thickness T.sub.1. In alternative embodiments, the first portion (lower step) may be thicker than the second portion (upper step).
[0060] In the embodiment depicted by way of example in FIG. 12, the stepped coating 35 is formed from a single coating material. In other words, the first step and the second step are both made of the same coating material. In another embodiment, the first step is made of a first coating material and the second step is made of a different coating material. In yet another embodiment, the second step may be made of a first layer of the first coating material having a thickness equal to the first step and a second layer of the second coating material that is coated on top of the first layer.
[0061] In the embodiment depicted by way of example in FIG. 12, the refiner filling piece 20 has an uncoated portion on the leading surface extending from the base 22 to the stepped coating 35. In another embodiment, the stepped coating 35 covers the entire leading surface of the refiner bar 30 (such that there is no uncoated portion).
[0062] In the embodiment depicted by way of example in FIG. 12, the stepped coating 35 extends to a top end of the refiner bar 30. In a variant, the stepped coating 35 may extend to a point below the top end of the refiner bar 30 so as to leave a small uncoated portion at the top end of the refiner bar 30. In a variant, the refiner bar 30 may have a variable coating that tapers from the second step to the top end of the refiner bar 30.
[0063] In the embodiment depicted by way of example in FIG. 12, the surface that is coated with the stepped coating 35 is a leading surface of the refiner bar 30. In another embodiment, the stepped coating 35 may be on a trailing surface of the refiner bar 30. In yet another embodiment, the stepped coating 35 may be on both sides of the refiner bar 30, i.e. on both the leading surface and on the trailing surface. In the latter case, the stepped coatings 35 on the leading surface and trailing surface may be the same or they be different, either different in coating geometry or different in coating material.
[0064] In the embodiment depicted by way of example in FIG. 12, the second portion of the bar height having the second coating thickness is taller than the first portion of the bar height having the first coating thickness. In another embodiment, the first and second portions may have the same dimensions in the axial direction (same height-wise dimension). In yet another embodiment, the first portion may be taller than the second portion.
[0065] In the embodiment depicted by way of example in FIG. 12, the first and second portions (first and second steps) abut each other such that there is no axial (height-wise) gap between the first and second steps. In a variant, there may be a gap between the first and second steps. In another variant, there may be a transition zone with a variable coating (e.g. a linearly variable coating or parabolically variable coating) in the transition zone.
[0066] In the embodiment depicted by way of example in FIG. 13, the stepped coating 35 may be stepped in a radial direction. In the embodiment depicted by way of example in FIG. 13, every refiner bar 30 has a stepped coating 35. In this example embodiment, the stepped coating 35 has a first coating thickness along a first portion of the bar length and a second coating thickness along a second portion of the bar length.
[0067] In the embodiment depicted by way of example in FIG. 13, the refiner bar 30 has an uncoated portion extending from a radially inner end of the refiner bar 30 to the stepped coating 35. In another embodiment, the stepped coating 35 covers the entire leading surface of the refiner bar 30 (such that there is no uncoated portion).
[0068] In the embodiment depicted by way of example in FIG. 13, the stepped coating 35 extends to a radially outer end of the refiner bar 30. In a variant, the stepped coating 35 may extend to a point radially inward of the full bar length so as to leave a small uncoated portion at the radial end of the refiner bar 30. In another variant, the portion at the radial end of the refiner bar 30 may have a variable coating that tapers from the second step to the radially outer end of the refiner bar 30.
[0069] In the embodiment depicted by way of example in FIG. 13, the surface that is coated with the stepped coating 35 is a leading surface 32 of the refiner bar 30. In another embodiment, the stepped coating 35 may be on a trailing surface of the refiner bar 30. In yet another embodiment, the stepped coating 35 may be on both sides of the refiner bar 30, i.e. on both the leading surface and on the trailing surface. In the latter case, the stepped coatings 35 on the leading surface and trailing surface may be the same or they be different, either different in coating geometry or different in coating material.
[0070] In the embodiment depicted by way of example in FIG. 13, the first portion of the bar length having the first coating thickness is longer than the second portion of the bar length having the second coating thickness. Alternatively, the first portion of the bar length having the first coating thickness is shorter than or equal to the second portion of the bar length having the second coating thickness.
[0071] In the embodiment depicted by way of example in FIG. 13, the first and second portions (first and second steps) abut each other such that there is no radial gap between the first and second steps. In a variant, there may be a radial gap between the first and second steps. In another variant, there may be a transition zone with a variable coating (e.g. a linearly variable coating or parabolically variable coating) in the transition zone.
[0072] Although the embodiments of FIGS. 12 and 13 show the stepped coating 35 in either axial or radial directions of the refiner bar 30, the refiner bar 30 may have stepped coatings 35 that are stepped in both the axial and radial directions on the same surface of the refiner bar 30. For example, the leading surface 32 of the refiner bar 30 could have a first step that is axially inward and radially inward, a second step that is axially outward and radially inward, a third step that is axially inward and radially outward and a fourth step that is axially outward and radially outward. In this example, all four steps may have different coating thicknesses.
[0073] FIGS. 14-19 depict various other examples of stepped coatings on refiner bars in accordance with further embodiments of the invention. The relative thicknesses and relative heights of the steps of the stepped coatings are meant to be exemplary only.
[0074] FIG. 14 is a cross-sectional view of a refiner filling piece 20 having stepped coatings 35 on the refiner bars 30 in which the stepped coatings 35 comprise three steps in accordance with another embodiment of the invention. In this example, each stepped coating 35 covers the entirely leading surface of the refiner bar. In this example, the height of each step of the three steps is the same. In a variant, the steps may have different heights. In this example, the difference in thickness between the first and second steps is the same as the difference in thickness between the second and third steps. In a variant, the difference in thickness between the first and second steps is not the same as the difference in thickness between the second and third steps.
[0075] FIG. 15 is a cross-sectional view of a refiner filling piece 20 having stepped coatings on the refiner bars 30 in which the stepped coatings 35 comprise three steps above an uncoated lower portion in accordance with another embodiment of the invention. In other words, the stepped coating may begin at a point higher than the base, e.g. the midpoint, at a tenth of the height, an eighth of the height, a sixth of the height, a fifth of the height, a quarter of the height, a third of the height, three-quarters of the height, etc.
[0076] FIG. 16 is a cross-sectional view of a refiner filling piece 20 having stepped coatings 35 on the refiner bars 30 in which the stepped coatings 35 comprise two steps above and below uncoated portions in accordance with another embodiment of the invention. In this example, the stepped coating 35 begins at a point above the base and terminates at a point below the top of the refiner bar. The uncoated portions may be equal in height or different in height.
[0077] In other embodiments, the refiner bar 30 may comprise a combination of stepped coatings and variable coatings. For example, the refiner bar 30 may have a variable coating over a first portion that increases linearly in an axial or radial direction, then a stepped coating having a first thickness over a second portion and a second thickness over a third portion. Alternatively, the refiner bars may have stepped coating and then a variable coating. The variable coating may increase in an axial or radial direction. Alternatively, the variable coating may decrease in the axial direction or in the radial direction.
[0078] FIG. 17 is a cross-sectional view of a refiner filling piece 20 in which the refiner bars 30 have both stepped coatings 35 and linearly variable coatings 34 in accordance with another embodiment of the invention. In this example, the linearly variable coatings 34 taper from the upper edge of the stepped coatings 35 to the top of the refiner bars.
[0079] FIG. 18 is a cross-sectional view of a refiner filling piece 20 in which the refiner bars 30 have both stepped coatings 35 and nonlinearly variable coatings 34 in accordance with another embodiment of the invention. In this example, the nonlinearly variable coatings are parabolically shaped. In this example, the nonlinearly variable coatings extend from the upper edge of the stepped coatings to the top of the refiner bars.
[0080] FIG. 19 is a cross-sectional view of a refiner filling piece 20 in which the refiner bars 30 have stepped coatings 35 on both the leading surfaces 32 and the trailing surfaces 38. In FIG. 19, the stepped coatings 35 on both the leading surfaces 32 and the trailing surfaces 38 are identical. However, in a variant, the stepped coatings 35 on the leading surfaces 32 may be different than the stepped coatings 35 on the trailing surfaces 38. For example, the stepped coatings 35 on the leading surfaces 32 may be thicker than the stepped coatings 35 on the trailing surfaces 38. Alternatively, the number of steps on the leading surfaces 32 may be different from the number of steps on the trailing surfaces 38. Alternatively, the coating materials on the leading and trailing surfaces may be different.
[0081] FIG. 20 is a perspective view of a refiner bar 30 showing gaps G between steps 35a, 35b and 35c of a stepped coating 35 in accordance with another embodiment of the invention. The dimensions and proportions of the steps and gaps G are merely illustrative of the concept. The gap between the first and second steps may be the same as or different than the gap between the second and third steps. There may be two steps, three steps, four steps or five or more steps.
[0082] For the purposes of interpreting this specification, when referring to elements of various embodiments of the present invention, the articles a, an, the and said are intended to mean that there are one or more of the elements. The terms comprising, including, having, entailing and involving, and verb tense variants thereof, are intended to be inclusive and open-ended by which it is meant that there may be additional elements other than the listed elements.
[0083] This invention has been described in terms of specific embodiments, implementations and configurations which are intended to be exemplary only. Persons of ordinary skill in the art will appreciate that many obvious variations, refinements and modifications may be made without departing from the inventive concept(s) presented in this application. The scope of the exclusive right sought by the Applicant is therefore intended to be limited solely by the appended claims.
