EP2548648B1 - Mill for comminuting of material - Google Patents

Description

The present invention relates to a mill for the comminution of regrind, in particular of wood chips. The mill of the mill has a rotor with a plurality of grinding elements, wherein the rotor is drivable about a rotation axis in a grinding chamber, and wherein the inner wall of the grinding chamber cooperates with the grinding elements to comminute the material to be ground. The grinding chamber has a feed opening and a discharge opening, which allow a feed and discharge of regrind substantially radial with respect to the axis of rotation.

Such a device is for example from the DE 30 20 955 A1 in which it is disclosed that the inner wall of the drum is formed alternately by grinding tracks and screen paths, and further at the highest point of the grinding chamber, an insertion opening is provided. The material to be ground is thus ground both on the grinding tracks and on the screen webs, wherein the openings in the screen webs form a plurality of discharge openings.

From the EP 0 164 489 A2 a device for crushing granular and / or fibrous material is known, wherein in certain embodiments, a grinding between the inner wall of the grinding chamber and grinding elements takes place and in each case a feed opening and a discharge opening are provided which allow feeding and removal of regrind, but rather in more tangential than in the radial direction.

Starting from the first-mentioned prior art, it is the object of the invention to provide a mill for comminution of millbase, which has an increased efficiency, and enables a high throughput of millbase in a short time.

This is achieved in that the feed opening and the discharge opening are each arranged in the lower region of the grinding chamber, that the feed, the highest point of the grinding chamber and the discharge opening are arranged sequentially on the circumference of the inner wall of the grinding chamber in the rotational direction of the rotor, and that the discharge opening is screen-free. The axis of rotation of the rotor is in particular arranged substantially horizontally. Thus, the material to be ground is transported from the feed opening over the highest point of the grinding chamber to the discharge opening. The arrangement of the feed opening and the discharge opening in the lower region of the grinding chamber means that these in the lower two Quadrants the inner wall of the grinding chamber are arranged, and thus the inner wall in the region of its upper two quadrants is available to crush the material to be ground in cooperation with the grinding elements. The pressing force of the ground material to the inner wall of the grinding chamber is effected by the centrifugal forces caused by the rotation of the rotor, which act both on the grinding elements, as well as on the grinding material in motion. In the event that the material to be ground should slow down in the movement along the inner wall of the grinding chamber, the force of gravity acts on the material to be ground, at least in the upper region of the grinding chamber, so that it is moved in the direction of the grinding elements, and is accelerated there again in the circumferential direction. In contrast, with mills that transport the material to be ground, primarily through the lower area of the grinding space, larger unwanted accumulations of ground material, especially at the lowest point of the grinding space, can more easily occur since both the centrifugal force and gravity move the material to be ground there. For this reason, in many such machines, a sieve is arranged in the lower region of the grinding chamber, which on the one hand unfolds a grinding action together with the grinding elements, and on the other hand ensures that insufficiently comminuted material does not leave the grinding chamber. In contrast, the relatively long path between the feed opening and discharge opening according to the invention over the highest point of the grinding chamber allows the ground material to be ground to the desired size until it reaches the discharge opening. Thus, the discharge opening can be configured without a sieve, whereby it is possible that all or almost all the material to be ground, which is located in the region of the discharge opening, is discharged through the discharge opening. This is further enhanced by the fact that the discharge opening is located in the lower region of the grinding chamber, so that in addition to the centrifugal forces and gravity also moves the material to be ground from the grinding chamber into the discharge opening. The screen-free discharge opening has the advantage that it can not be clogged by regrind and thus enables trouble-free and maintenance-free operation.

In particular, the feed opening in the grinding chamber is provided directly after the discharge opening in the direction of rotation of the rotor.

The material to be ground is taken by the grinding elements as soon as it was fed through the feed opening in the grinding chamber and by the centrifugal force to the inner wall of the Mahlraums pressed. Due to the differential speed between the material to be ground and the grinding elements and the frictional forces induced thereby, the grinding of the ground material is effected.

In particular, the mill is designed so that the ground material is transported during the grinding process by the grinding elements from the feed opening over the highest point within the grinding chamber, and then discharged through the discharge opening.

In one embodiment of the invention, the feed opening and the discharge opening are also arranged axially in the same position with respect to the axis of rotation of the rotor. In particular, the feed openings and / or the discharge openings can extend over the entire width of the grinding chamber in the axial direction. Such a design of the feed opening allows a uniform feeding of material to be ground in all areas of the grinding chamber, and such a design of the discharge opening allows safe removal of all ground material from the grinding chamber after passing through the inner wall of the grinding chamber.

Advantageously, the discharge opening is arranged at the substantially lowest point of the grinding chamber. This has the advantage that the gravitational effect acts optimally on the material to be ground in order to remove it from the grinding chamber.

In a preferred embodiment, the angle about the axis of rotation from the feed opening to the discharge opening in the direction of rotation is more than 270 °. This results in a long conveying path along the inner wall of the grinding chamber and thus improved grinding of the ground material.

In particular, the comminution of the ground material takes place primarily or exclusively between the ground elements and the inner wall of the grinding chamber. This is in contrast to ordinary mills in the prior art, in which the grinding additionally takes place between grinding elements and sieve elements, which are mounted above the discharge opening. In particular, the comminution of the material to be ground takes place between ribs on the inner wall and the grinding elements.

Advantageously, the feed opening is arranged in a lower quadrant of the inner wall. Furthermore, in particular, the discharge opening is advantageously arranged in a lower quadrant of the inner wall.

In one embodiment, the grinding chamber has only one feed opening and only one discharge opening. Thus, a defined feeding and removal of ground material can be achieved, whereby a predetermined uniform grinding result can be achieved, namely a certain size of the constituents of the ground material discharged through the discharge opening.

Advantageously, the mill is designed so that almost all regrind or at least the major part of the grind leaves the grinding chamber before completion of a full round through the discharge opening. Thus, the distance of the ground material in the grinding chamber is clearly defined and a uniform and constant comminution of the ground material can be achieved.

In one embodiment, the grinding chamber has a substantially cylindrical shape about the axis of rotation of the rotor. This allows an advantageous interaction with the grinding elements of the rotor. In other embodiments, it is also possible that the grinding chamber is enlarged or reduced in areas, in order to achieve in this area no or a lower grinding action or a higher grinding action.

Advantageously, a plurality of grinding elements are mounted parallel to the rotor in the axial direction. This plurality of grinding elements is further advantageously also attached to a plurality of attachment points in the circumferential direction of the rotor, so that a total of a large number of grinding elements are advantageously fixed in a uniform manner on the rotor, and can cooperate with the inner wall of the grinding chamber for comminuting the ground material.

In a preferred embodiment, the grinding elements are each rotatably mounted on an axis which extends in the axial direction and at a radial distance from the axis of rotation of the rotor. Such an axis allows easy attachment of a variety of grinding elements around them.

In one embodiment, the axes of the grinding elements are held by arranged on the rotor plates whose normal is the axis of rotation of the rotor. These plates are in particular connected to each other by axially extending bolts.

Advantageously, the grinding elements are knives, hammers, beaters or sawing elements. In some embodiments, combinations of the abovementioned grinding elements can also be used in order to achieve the desired grinding result.

In a preferred embodiment, a forced feed is provided which feeds the material to be ground in the radial direction through the feed opening. Characterized in that the feed opening is arranged in a lower region of the grinding chamber, the forced feeding allows to overcome the force of gravity, while the amount of ground material can be accurately determined at the same time. Alternatively, blowers or other funding may be provided.

In a preferred embodiment, the forced feed is a screw conveyor. A screw conveyor allows a continuous and defined feeding of regrind through the feed opening. The defined amount of ground material in turn has an effect on the comminution of the ground material between the inner wall of the grinding chamber and the grinding elements, so that can be controlled and / or adjusted by controlling the feed amount by the screw conveyor directly the grinding result.

Advantageously, the inner wall of the grinding chamber has a plurality of parallel, circumferentially inclined ribs which are arranged at an angle of 30 to 60 ° to the circumferential direction, and in particular at an angle of approximately 42.5 ° to the circumferential direction are arranged. The smaller the angle of the ribs to the circumferential direction, the lower the grinding performance, since then to a large extent a transport of the material to be ground in the direction of the ribs takes place, and to a lesser extent the crushing crossing over the ribs. On the other hand, a small angle has the advantage that a self-cleaning effect occurs, that is, that no regrind accumulates in the ribs. In the defined angular range, there is a compromise between these two properties, with the most advantageous results achieved at an angle of approximately 42.5 °.

In an advantageous embodiment, the ribs are each arranged obliquely in regions in the circumferential direction with angles with opposite signs. This makes it possible that in each of these areas a transport of the ground material takes place in relation to the rotor opposite axial direction, so that the material to be ground during the promotion is not substantially displaced on the inner wall in the axial direction, but only performs a kind of oscillating movement in the axial direction.

Advantageously, the inner wall of the grinding chamber on exchangeable refining plates, wherein the ribs are arranged on the refining plates. This has the advantage on the one hand that the refining plates can be made of a harder material and thus withstand higher loads. On the other hand, however, this also has the advantage that the grinding plates in the mill can be replaced as needed in order to achieve an optimum grinding result for different regrind.

Advantageously, the entire inner wall of the grinding chamber is formed by grinding plates. Thus, the entire inner wall of the grinding chamber contributes to the grinding process, wherein only at the feed opening and the discharge opening no grinding takes place.

In an execution opening, a sieve is provided at a distance from the discharge opening, which is designed to sieve material discharged through the discharge opening. This sieve is arranged so that no residue of regrind can form up to the discharge opening, ie at a significant distance from the discharge opening. It can thus be achieved that, on the one hand, the sieve does not hinder an outflow of ground material through the discharge opening, and, on the other hand, only sufficiently comminuted ground material is provided as the end product.

In particular, the material which is not continuous through the sieve is returned to the feed opening. Thus, this material can be fed to a further grinding process, and is further comminuted accordingly until it has received the desired size.

The object of the invention is further achieved by a mill according to the preamble of the independent claims, in which the comminution of the ground material takes place exclusively between the grinding elements and ribs on the inner wall of the grinding chamber, wherein the discharge opening is screen-free. Thus, it can be prevented by such a mill that sieves clog in a discharge opening, with a high and uniform grinding performance can still be achieved by crushing between the refining elements and the inner wall of the grinding chamber. The aforementioned mill can also be combined with all the aforementioned features.

Finally, the invention also relates to a method for comminution of millbase in a mill with a grinder having a rotor with a plurality of grinding elements, wherein the rotor is driven about an axis of rotation in a grinding chamber, and wherein initially the millbase by a feed opening is supplied in the lower region of the grinding chamber, then crushed by cooperation of the inner wall of the grinding chamber and the grinding elements, while it is transported from the feed opening, over the highest point of the grinding chamber to a discharge opening, and finally the ground material in a substantially radial direction the discharge opening located in the lower region of the grinding chamber is removed, wherein the discharge opening is screen-free.

In particular, the method is characterized in that the millbase is largely discharged through the discharge opening before completion of a full circulation in the grinding chamber. Advantageously, the material to be ground in the radial direction is forcibly fed through the feed opening, in particular by a screw conveyor.

Furthermore, advantageously, the comminution of the ground material takes place exclusively between the ground elements and the inner wall of the grinding chamber.

Figur 1

zeigt eine Schnittansicht der erfindungsgemäßen Mühle von der Seite;

Figur 2

zeigt eine weitere Schnittansicht der erfindungsgemäßen Mühle von der Seite, wobei diese Schnittansicht orthogonal zu der Schnittansicht von Figur 1 ist;

Figur 3

zeigt einen Bereich der Innenwand der erfindungsgemäßen Mühle.

In the following, an advantageous embodiment of the invention will be described with reference to FIGS.

FIG. 1

shows a sectional view of the mill according to the invention from the side;

FIG. 2

shows a further sectional view of the mill according to the invention from the side, this sectional view orthogonal to the sectional view of FIG. 1 is;

FIG. 3

shows a portion of the inner wall of the mill according to the invention.

FIG. 1 shows a mill 1 according to the invention, in particular a hammer mill, in cross section, wherein within a cylindrical grinding chamber, which is bounded by an inner wall 2, a rotor 3 is arranged. The rotor 3 has a central horizontal rotor shaft 4, which about a rotation axis R (see FIG. 2 ) is drivable. The rotor shaft 4 and the rotation axis R extend perpendicular to the plane in FIG FIG. 1 ,

The rotor 3 has a plurality of grinding elements 5, which cooperate with the inner wall 2 in order to grind the grinding stock located in the grinding chamber. Farther the grinding elements 5 also have the function to transport the material to be ground. The grinding elements 5 are pivotally mounted on axles 6, which extend parallel to the rotor shaft 4, that is in the axial direction of the rotor 3, and are arranged at a distance from the rotor shaft 4. In particular, the axes 6 are distributed uniformly around the circumference of the rotor 3 and each have the same radial distance from the rotor shaft 4. The rotor 3 has at least two plates 7, which are arranged on the rotor shaft 4 and in which the axes 6 are arranged. The plates 7 are designed in particular as circular plates whose normal is the axis of rotation R, and in whose center the rotor shaft 4 is arranged. The plates 7 are connected to each other by bolts 8, which extend in the axial direction of the rotor shaft 4.

The inner wall 2 of the grinding chamber substantially corresponds to the inner wall of a hollow cylinder, which is arranged around the rotation axis R of the rotor 3. The inner wall 2 is formed by a plurality of refining plates 9, which with ribs 10 (see FIG. 3 ) are provided. The grinding elements 5 are each arranged so that they can comminute the millbase in cooperation with the refining plates 9 of the inner wall 2 of the grinding chamber.

The rotor shaft 4 is driven clockwise as in FIG. 1 is shown by the arrow. The grinding chamber has a feed opening 11, which is arranged in the lower left quadrant of the inner wall 2 of the grinding chamber. The feed opening 11 is a direct opening into the grinding chamber and has no sieve or similar elements. Ground material is introduced by a forced feed 12 in the form of a screw conveyor through the feed opening 11 into the grinding chamber. The feed direction of the ground material into the grinding chamber is in particular radial with respect to the axis of rotation R of the rotor 3. The ground material enters the space between the rotor 3 and the inner wall 2 and is taken along by the grinding elements 5 in the clockwise direction along the inner wall 2. The material to be ground is thus conveyed from the feed opening 11 in the direction of the highest point of the grinding chamber. The centrifugal forces cause the ground material to come into contact with the inner wall 2 and is ground by the grinding elements 5 in cooperation with the inner wall 2. Starting from the highest point of the grinding chamber, the material to be ground is transported further along the upper right quadrant and the lower right quadrant of the inner wall 2 of the grinding chamber, until it finally leaves the grinding chamber through a discharge opening 13.

The discharge opening 13 is arranged at the lowest point of the grinding chamber, so that the material to be ground leaves the grinding chamber under the action of gravity. Accordingly, the discharge port has a relatively large cross section and has no screen or the like in it. Thus, the material to be ground is conveyed from the feed opening 11 about 315 ° about the axis of rotation R through the grinding elements 5 along the inner wall 2 of the grinding chamber until it leaves the grinding chamber through the discharge opening 13. Only insignificant or no parts of the ground material are conveyed on the path between discharge opening 13 and feed opening 11. As in FIG. 1 can be seen, the discharge opening 13 and the feed opening 11 are close to each other, so that the Mahlstrecke between feed opening 11 and discharge opening 13 is designed as long as possible in the clockwise direction.

After the discharge opening 13, the material to be ground falls through a shaft 14 and is optionally passed through a sieve, not shown, so that unwanted large components of the material to be ground again the forced feed 12 can be supplied.

In FIG. 2 the mill 1 is also shown in a side sectional view, wherein now the rotor shaft 4 extends horizontally in the plane of the drawing. For driving the rotor shaft, a drive 15, in particular an electric motor, is provided, which is connected to the rotor shaft 4 via a coupling 16. The rotor shaft 4 is mounted on both sides in rolling bearings 17, 18. On the rotor shaft 4, a plurality of the plates 7 are spaced apart in the axial direction, wherein a central and an outer plate 7 have a greater thickness than the remaining plates 7. The plates 7 are connected to the bolts 8, which has a plurality of notches for Have fixing the plates 7. The individual segments of the bolt 8 are connected by a long screw.

The grinding elements 5 are mounted on the axes 6, which are held by the plates 7. Between the grinding elements 5 spacer elements are provided to hold the grinding elements in a defined axial position. The spacer elements may be configured integrally with the grinding elements 5.

In FIG. 3 Finally, a section of the inner wall 2 of the grinding chamber is shown, wherein it can be seen that the inner wall 2 is formed by a plurality of refining plates 9, which are fastened by means of screws. The screws are provided in recessed openings of the refining plates 9. The individual refining plates 9 each have Ribs 10 which extend at an angle to the circumferential direction, in this case at an angle of 42.5 °. In one preferred embodiment, the refining plates 9 can each be arranged in different orientations, that is to say in the present case, the middle refining plate would be designed so that its ribs 10 would be in the same orientation extends at an angle with opposite signs to the other two refining plates. As a result, it can be prevented that a conveying effect of the ground material occurs in the axial direction.

As an alternative to the configuration of the inner wall 2 with refining plates 9, the ribs 10 can also be provided integrally in the inner wall of the mill. An advantage of the design with refining plates 9, however, is that the refining plates 9 can be easily changed and thus different embodiments of ribs 10 can be provided for different grinding applications, as well as worn refining plates can be replaced.

The mill is particularly suitable for the milling of wet wood chips, which is not a fine grinding mill but a pre-grinding mill. The chips are then forwarded, for example, for further processing in a dryer. In particular, the rotor is driven at 1,500 revolutions per minute.

The distance between the individual grinding elements 5 in the form of hammers is approximately 3 mm in the axial direction.

The refining plates 9 are made of hardened material, and can be exchanged in the mill 1.

The inner wall 2 is occupied in particular continuously with grinding elements 9. Due to the underlying discharge opening 13 no aspiration of the mill is necessary. The fact that the discharge opening 13 is screen-free, this can be made smaller than a discharge opening 13 with sieve, which should provide a corresponding discharge performance. Thus, with a sieve-free discharge opening 13, a larger proportion of the inner wall of the grinding chamber with the grinding elements 9 cooperate. In addition, mills show the sieves in the discharge opening quickly wear in the sieves, and are therefore in need of maintenance.

The grinding elements 5 are designed in particular as hammers, namely as metal plates with a perforation, which are plugged onto the axles.

Claims (15)

1. Mill (1) for the grinding of grist, in particular wood chips, with a grinder having a rotor (3) with a plurality of grinding elements (5), wherein the rotor (3) can be driven in a grinding area about an axis of rotation (R), wherein the internal wall (2) of the grinding area cooperates with the grinding elements (5) to grind the grist, and wherein the grinding area has a feed-in opening (11) and a discharge opening (13) which enable essentially radial feed-in and discharge of grist relative to the axis of rotation (R), characterised in that the feed-in opening (11) and the discharge opening (13) are each arranged in the lower region of the grinding area, the feed-in opening (11), the highest point in the grinding area and the discharge opening (13) are arranged in sequence at the circumference of the internal wall (2) of the grinding area in the direction of rotation (R) of the rotor (3) and the discharge opening (13) is free of sieves.
2. Mill according to claim 1, wherein the mill (1) is designed such that during the grinding process the grist is transported through the grinding elements (5) from the feed-in opening (11) via the highest point within the grinding area and then dispensed through the discharge opening (13).
3. Mill according to either claim 1 or claim 2, wherein the feed-in opening (11) and the discharge opening (13) are arranged axially at the same height relative to the rotational axis (R) of the rotor (3).
4. Mill according to any one of the preceding claims, wherein the discharge opening (13) is arranged on the essentially lowest point of the grinding area.
5. Mill according to any one of the preceding claims, wherein the angle of the feed-in opening (11) to the discharge opening (13) about the axis of rotation (R) in the direction of rotation is more than 270 degrees.
6. Mill according to any one of the preceding claims, wherein the grinding of the grist is carried out exclusively between the grinding elements (5) and the internal wall (2) of the grinding area.
7. Mill according to any one of the preceding claims, wherein the grinding area only has one feed-in opening and (11) only one discharge opening (13).
8. Mill according to any one of the preceding claims, wherein the mill (1) is designed such that almost all of the grist or at least the majority of the grist leaves the grinding area before the completion of a full cycle by the discharge opening (13).
9. Mill according to any one of the preceding claims, wherein the grinding elements (5) are each rotatably mounted on an axis (6) which extends in an axial direction and at a radial distance to the axis of rotation (R) of the rotor (3).
10. Mill according to any one of the preceding claims, wherein a forced feeder (12) is provided which feeds the grist through the feed-in opening (11) in a radial direction.
11. Mill according to claim 10, wherein the forced feeder (12) is a screw conveyor.
12. Mill according to any one of the preceding claims, wherein the internal wall (2) of the grinding area has several ribs (10) arranged in parallel, at an angle to the circumferential direction, which ribs are arranged at an angle of 30 to 60 degrees to the circumferential direction, and in particular are arranged at an angle of approximately 42.5 degrees to the circumferential direction.
13. Mill according to any one of the preceding claims, wherein a sieve is provided at a distance from the discharge opening (13), which sieve is designed to sieve the material discharged through the discharge opening (13).
14. Mill according to claim 13, wherein the mill (1) is designed to feed the material which does not pass through the sieve back to the feed-in opening (11).
15. Method for the grinding of grist in a mill (1) with a grinder having a rotor (3) with a plurality of grinding elements (5), wherein the rotor (3) is driven in a grinding area about an axis of rotation (R), and wherein initially the grist is fed through a feed-in opening (11) in the lower region of the grinding area, then it is ground by means of cooperation of the internal wall (2) of the grinding area and the grinding elements (5) while it is transported from the feed-in opening (11) via the highest point in the grinding area to a discharge opening (13), and wherein finally the grist is fed in an essentially radial direction through the discharge opening (13) in the lower region of the grinding area, wherein the discharge opening (13) is free of sieves.

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