REFINING SET

The invention relates to a refining assembly for refining water-suspended pulp fibers between two coaxial refining surfaces which form a refining gap, rotate in relation to each other and are formed by refining bars and grooves extending therebetween. At least one directional component of the refining bars extends radially in relation to the axis of rotation. In order make the refining process more efficient, the refining bars have annular elevations and depressions that run concentrically to the axis of rotation of the refining surfaces and an annular elevation of one refining surface protruding into an annular depression in an opposite refining surface.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a refining assembly, and more particularly, to a refining assembly for refining aqueous suspended fibers.

2. Description of the Related Art

It has been known for a long time to refine cellulose fibers, in other words virgin pulp and/or recycled fibers in order to obtain the desired characteristics in the thus produced fibrous web, in particular in regard to strength, forming and surface properties.

Due to the relatively rapid wear and tear in the case of the refiners used for this purpose, the refining surfaces are formed by replaceable refining sets that are screwed together with the corresponding supporting surface.

To achieve the desired fiber properties, in particular the degree of refining, the refining sets must be adapted as effectively as possible to the pulp that is to be treated—also in order to prevent excessive wear and tear to the sets.

In order to increase the efficiency of fiber treatment, optimal utilization of the available refining surface is strived for.

What is needed in the art is an improvement in the efficiency of fiber treatment.

SUMMARY OF THE INVENTION

According to an embodiment of the invention, a refining assembly for refining aqueous suspended cellulose fibers includes two refining surfaces arranged coaxially to one another and forming a refining gap. The two refining surfaces are configured to rotate relative to one another and are formed by refining bars and grooves extending between them. At least one directional component of the refining bars extends radially relative to an axis of rotation.

According to an embodiment of the invention, the refining bars have annular elevations and depressions that run concentrically to the axis of rotation of the refining surfaces, whereby an annular elevation of one refining surface protrudes into an annular depression of the opposite refining surface.

This forces a shift of part of the cellulose fibers from one refining surface to the opposite refining surface, resulting in a considerable increase in the intensity of the treatment.

In order to maintain the intensity in radial direction, and according to another embodiment of the invention, the distance between the refining bars of the opposite refining surfaces should remain the same in radial direction.

In order to increase efficiency, and accordioning to another embodiment of the invention, additional turbulences and shifts between the refining surfaces can also be achieved in that the grooves have annular elevations and depressions that run concentrically to the axis of rotation of the refining surfaces, whereby an annular elevation of one refining surface protrudes into an annular depression of the opposite refining surface.

To avoid blockages, the distance between the grooves in the opposite refining surfaces should remain the same in radial direction also in this case.

In the interest of an efficient but at the same time gentle fiber treatment it is however advantageous if the radial position of the elevations or respectively depressions in the refining bars corresponds with the radial position of the elevations or respectively the depressions in the grooves of a refining surface.

To minimize wear and tear, the height of the annular elevations or respectively depressions should gradually increase and/or gradually decrease in radial direction.

In an embodiment, the height of the elevations or respectively depressions of the refining bar and the grooves relates to the respective supporting surface for the refining sets that form the refining surface. Depending on the type of refiner, these supporting surfaces for mounting of the refining sets are either flat or conical.

For an intensive turbulence it can however be advantageous if the height of the annular elevation or respectively depression increases in radial direction in one or several increments and or decreases in one or several increments.

Combinations are herein also possible, for example gradually increasing elevations or respectively depressions and incrementally decreasing elevations or respectively depressions, or vice versa.

In one embodiment, and for optimal use of both refining surfaces, elevations and depressions should alternate in both refining surfaces in radial direction.

Depending on the type of fibrous material and the requirements of the treatment thereof it may be sufficient, if elevations and depressions extend only over a partial radial section of the refining surface.

Comprehensive use of the advantages of the invention results however, if the elevations and depressions extend over the entire refining surface.

Moreover, the flow through the refining gap can also be impeded in that at least some grooves are closed off at least partially by barriers. This also intensifies the fiber treatment.

In the final analysis, considerable energy savings can thus be achieved.

DETAILED DESCRIPTION OF THE INVENTION

According toFIG. 1, a refining gap6is formed in the housing of the refining assembly, including a stationary refining surface2that is coupled with the housing and a refining surface3that rotates about a rotational axis7, according to an embodiment of the invention.

The two annular refining surfaces2,3are positioned parallel to one another, wherein the distance between them is generally adjustable.

Rotating refining surface3is herein moved in rotational direction by a shaft16that is rotatably mounted in the housing. Shaft16is driven by a drive that is also located in the housing.

In the herein illustrated example, the fibrous suspension that is to be refined and which contains cellulose fibers1runs via an infeed through the center into refining gap6between the two refining surfaces2,3.

The fibrous suspension passes interacting refining surfaces2,3in radially outward direction and exits the adjacent annulus through an outlet.

Means that are generally known with which power is generated in order to press the two refining surfaces2,3against one another are not illustrated.

Both refining surfaces2,3are respectively formed by several refining disks14,15as illustrated inFIG. 2that extend respectively over a circumferential segment of the corresponding refining surface2,3and which are also referred to as refining sets.

Refining disks14,15that are arranged closely adjacent next to one another provide a continuous refining surface2,3in circumferential direction. Refining disks14,15respectively are mounted on a flat supporting surface17.

As illustrated inFIG. 2, refining disks14,15and thus also refining surfaces2,3are formed by a plurality of radially progressing refining bars4and grooves5between them.

The cross section of refining bars4which are also referred to as blades is generally rectangular. However, the scope of the present invention covers other shapes.

Grooves5between refining bars4also have a rectangular cross section and serve as flow channels for the fibrous suspension. The groove depth is generally between 2 and 20 mm.

So that the groove width does not become too large in radially outward direction at a constant and uniform width of refining bars4, refining bars4can be split or newly added in radial direction10.

According to an embodiment of the invention, refining bars4have annular elevations8and depressions9that run concentrically to axis of rotation7of refining surfaces2,3, whereby an annular elevation8of one refining surface2,3protrudes into an annular depression9of opposite refining surface2,3.

Due to elevations8and depressions9, turbulences are caused in the fibrous suspension that is to be treated. Moreover, when flowing through refining gap6, the fibrous suspension is forced at least partially to shift between refining surfaces2,3.

The result is increased efficiency in refining.

FIGS. 3 to 6illustrate various arrangements of refining surfaces2,3, according to other embodiments of the invention. Regardless of said arrangements however, the distance between refining bars4of opposite refining surfaces2,3, and the distance between grooves5of opposing refining surfaces2,3in radial direction10is the same.

InFIG. 6, grooves5have a constant height above supporting surface17in radial direction10, according to an embodiment of the invention. This means that the height of refining bars4relative to the groove bottom changes in radial direction10.

In contrast thereto, grooves5contribute to the turbulence in the examples illustrated inFIGS. 3 to 5. This means that also grooves5have annular elevations11and depressions12that run concentrically to axis of rotation7of refining surfaces2,3, whereby an annular elevation11of one refining surface2,3protrudes into an annular depression12of opposite refining surface2,3.

To avoid blockages due to constrictions, the radial position of elevations8or respectively depressions9of refining bars4corresponds with the radial position of elevations11or respectively depressions12of grooves5of a refining surface2,3.

InFIGS. 3 to 5—viewed in radial direction—the height of refining bars4above the groove bottom is the same.

It is for example however also possible that the height of grooves5relative to supporting surface17in radial direction10fluctuates less than the height of refining bars4relative to supporting surface17.

In the interest of a homogeneous treatment during flow, elevations8,11and depressions9,12alternate in all arrangements and on both refining surfaces2,3in radial direction10.

In one embodiment, refining surfaces2,3are to be designed depending upon cellulose fibers1that are to be treated and according to the requirements of such treatment.

FIG. 3illustrates one design wherein the height of annular elevation8,11or respectively depression9,12on both refining surfaces2,3as well as on refining bars4and grooves5gradually increases and gradually decreases in radial direction10.

InFIG. 6only the height of refining bars4changes gradually relative to supporting surface17.

As shown inFIGS. 4 and 5, to further increase the level of turbulence, the height of annular elevation8,11or respectively depression9,12increases or decreases in radial direction10in one (FIG. 4) or several (FIG. 5) increments. In the case of several increments—as illustrated inFIG. 5—the transitions can progress perpendicular to the direction of flow.

In the case of only one increment between elevation8,11and depression9,12a slanted transition is to be recommended for minimization of wear and tear, according toFIG. 4.

In general, elevations8,11and depressions8,12extend over the entire refining surface2,3.

In many cases however—as can be seen inFIGS. 1 and 2—it is sufficient if elevations8,11and depressions9,12extend only over a partial radial section of refining surface2,3.

Additionally, barriers13can also intensify the fiber treatment, according toFIG. 5. Said barriers13close off grooves5completely or partially and can thus also support the shifting of the fibrous suspension between refining surfaces2,3.