CN115921041A - Grinding disc and grinding machine - Google Patents

Abstract

The embodiment of the application provides a grinding disc and grinding machine belongs to grinding stirring technical field. The grinding disc is provided with a first material passing hole, the first material passing hole is communicated with the feeding side and the discharging side of the grinding disc along the axial direction of the grinding disc, the wall surface of the first material passing hole comprises a first surface, and the first surface and the axial direction of the grinding disc are mutually inclined so as to prevent grinding media from moving from the feeding side of the grinding disc to the discharging side of the grinding disc. The grinding disc that this application embodiment provided, first surface and grinding disc axial are mutually inclined, and first surface and grinding disc axial are not parallel to each other promptly for first surface can hinder grinding medium from the discharge side removal of the feeding side of grinding disc to grinding disc. Compared with the ground materials such as crude asphalt ores and the like, the grinding medium has lower viscosity and is more easily hindered by the first surface. This helps to alleviate the problem of abrasive media accumulating at the screen, causing severe wear and clogging of the screen.

Description

Grinding disc and grinding machine

Technical Field

The application relates to a grind stirring technical field, especially relates to a grinding disk and machine of grinding.

Background

The raw ore of natural asphalt is generally used after being ground by a grinding machine. In the related art grinding mills, the screen on the discharge side of the grinding mill may be severely worn and clogged during operation, which affects the quality of the ground material and the operating efficiency of the grinding mill.

Disclosure of Invention

In view of the above, it is desirable to provide a grinding disc and a grinding mill to mitigate the extent of screen wear and clogging.

In order to achieve the above object, a first aspect of the embodiments of the present application provides a grinding disc, the grinding disc has a first material passing hole, the first material passing hole is axially communicated with a feeding side and a discharging side of the grinding disc along the grinding disc, a wall surface of the first material passing hole includes a first surface, and the first surface and the grinding disc are axially inclined to each other to block a grinding medium from moving from the feeding side of the grinding disc to the discharging side of the grinding disc.

Further, the first surface is located at a side of the first material passing hole facing away from the rotation direction of the grinding disc, the first surface faces the feeding side of the grinding disc, and the grinding disc rotates to enable the first surface to push at least part of the grinding media moving along the feeding direction back to the feeding side.

Further, the wall surface of the first material passing hole further comprises a second surface, the second surface is located on one side of the first material passing hole facing the rotation direction of the grinding disc, the second surface faces the discharging side of the grinding disc, and the grinding disc rotates to enable at least part of the grinding media to move from the discharging side of the grinding disc to the feeding side of the grinding disc along the second surface.

Furthermore, a first included angle is formed between the extending direction of the first surface and the axial direction of the grinding disc, and the first included angle is 15-45 degrees; and/or a second included angle is formed between the extending direction of the second surface and the axial direction of the grinding disc, and the second included angle is 15-45 degrees.

Further, the first surface extending direction with the abrasive disc axial is first contained angle, the second surface extending direction with the abrasive disc axial is the second contained angle, first contained angle with the second contained angle equals.

Further, the distance between the first surface and the second surface gradually increases in a direction radially outward of the abrasive disc.

Further, the first material passing hole extends along a preset direction, the preset direction is intersected with the axial direction of the grinding disc, and the cross section of the first material passing hole along the preset direction is circular, oval, quincunx or polygonal.

Furthermore, the number of the first material passing holes is multiple, and the first material passing holes are uniformly distributed along the circumferential direction of the grinding disc.

A second aspect of embodiments of the present application provides a grinding mill comprising:

a grinding cylinder;

the rotating shaft is rotationally connected with the grinding cylinder;

the first grinding disc is positioned in the grinding cylinder and connected with the rotating shaft, and the first grinding disc is the grinding disc in any scheme; and

the second grinding disc is positioned in the grinding cylinder and connected with the rotating shaft, the second grinding disc is provided with a second material passing hole, and the wall surface of the second material passing hole is axially parallel to the rotating shaft.

Further, the projected outer contour line of the second grinding disc is the same as or the same as the projected outer contour line of the first grinding disc in the axial projection of the rotating shaft.

Further, along the axial direction of the second grinding disc, the projection outer contour line of the second grinding disc comprises three straight line segments arranged along the circumferential direction of the second grinding disc, and the included angle between the extending direction of at least one straight line segment and the extending directions of two adjacent straight line segments is an acute angle.

Further, the first grinding disc is circular in shape.

Further, the number of the first grinding discs is multiple, the first grinding discs are arranged along the axial direction of the rotating shaft, and at least one second grinding disc is arranged between every two adjacent first grinding discs.

Further, of the first and second grinding discs, the first grinding disc is closest to the discharge side of the mill and/or the second grinding disc is closest to the feed side of the mill.

The grinding disc provided by the embodiment of the application has the advantages that the first surface and the axial direction of the grinding disc are mutually inclined, namely the first surface and the axial direction of the grinding disc are not parallel to each other, so that the first surface can prevent grinding media from moving from the feeding side of the grinding disc to the discharging side of the grinding disc. Compared with the ground materials such as crude asphalt ores and the like, the grinding medium has lower viscosity and is more easily hindered by the first surface. This helps to alleviate the problem of abrasive media accumulating at the screen, causing severe wear and clogging of the screen.

Drawings

FIG. 1 is a schematic view of the structure of a grinder in the embodiment of the present application;

FIG. 2 is a schematic structural view of a first polishing disk according to an embodiment of the present disclosure;

FIG. 3 is a schematic view of a second polishing disk according to an embodiment of the present disclosure;

fig. 4 is a schematic structural diagram of the first polishing disk and the second polishing disk connected to the rotating shaft in the embodiment of the present application.

Description of reference numerals: a grinding cylinder 1; a rotating shaft 2; a first abrasive disc 3; a first material passing hole 31; a first surface 311; a second surface 312; a transition surface 313; a rounded corner 314; a second abrasive disk 4; a second material passing hole 41; the direction of rotation of the grinding disc 5.

Detailed Description

It should be noted that, in the present application, technical features in examples and embodiments may be combined with each other without conflict, and the detailed description in the specific embodiment should be understood as an explanation of the gist of the present application and should not be construed as an improper limitation to the present application.

Before describing the embodiments of the present application, it is necessary to analyze the causes of the screen mesh which may be seriously worn and blocked in the related art, and to obtain the technical solution of the embodiments of the present application through reasonable analysis.

In the related art, a grinder includes a grinding cylinder containing a grinding medium therein. After the grinding material enters the grinding cylinder through the feeding side, the grinding medium and the grinding material are ground in the grinding cylinder. The hardness of the ground material is lower than that of the grinding medium, and the volume of the ground material particles is reduced after grinding. The ground grinding material is discharged from the grinding cylinder through the discharge side. The grinding machine further comprises a separator and a rotating shaft connected with the grinding cylinder in a rotating mode, the separator is connected to one end, facing the discharging side, of the rotating shaft, the separator is provided with a screen, the screen is used for filtering grinding materials, the grinding materials with small particle size are discharged from the discharging side, and the grinding materials with large particle size continue to be ground in the grinding cylinder. In the working process of the grinding machine, the grinding materials to be ground continuously enter the grinding cylinder, and the grinding media easily flow towards the discharge side under the action of the feeding thrust of the grinding materials. The grinding media have high hardness and large particle volume and are easy to accumulate at the screen, so that the screen is seriously abraded and blocked.

The embodiment of the present application provides a grinding machine, please refer to fig. 1, the grinding machine includes a grinding cylinder 1, a rotating shaft 2, a first grinding plate 3 and a second grinding plate 4, the rotating shaft 2 is rotatably connected to the grinding cylinder 1, the first grinding plate 3 is located in the grinding cylinder 1 and connected to the rotating shaft 2, and the second grinding plate 4 is located in the grinding cylinder 1 and connected to the rotating shaft 2.

In one embodiment, referring to fig. 1, the rotating shaft 2 is disposed along the axial direction of the grinding cylinder 1. So set up, can make the grinding material obtain even abundant grinding, guarantee that the grinding material granule through grinding is even.

The first polishing disc 3 according to the embodiment of the present application is any one of the following polishing discs.

Referring to fig. 2, the polishing disc provided in the embodiment of the present application has a first material passing hole 31, the first material passing hole 31 is axially connected to the feeding side and the discharging side of the polishing disc, a wall surface of the first material passing hole 31 includes a first surface 311, and the first surface 311 and the polishing disc are axially inclined to each other to prevent the grinding medium from moving from the feeding side of the polishing disc to the discharging side of the polishing disc. So arranged, the first surface 311 and the grinding disc are axially inclined to each other, so that the first surface 311 is able to hinder grinding medium from moving from the feed side of the grinding disc to the discharge side of the grinding disc. The grinding media has a lower viscosity than ground materials such as raw natural asphalt, and is more likely to be hindered by the first surface 311. The grinding medium can be effectively prevented from accumulating at the screen, so that the screen is seriously abraded and blocked.

It should be explained that the first surface 311 and the grinding disk are axially inclined to each other, i.e. the first surface 311 and the grinding disk are axially not parallel to each other.

In one embodiment, with continued reference to fig. 2, the first surface 311 is located at a side of the first material passing hole 31 facing away from the rotation direction 5 of the grinding disc, the first surface 311 faces the feeding side of the grinding disc, and the grinding disc rotates to make the first surface 311 push at least a part of the grinding media moving along the feeding direction back to the feeding side. This arrangement enables first surface 311 to generate a thrust towards the feed side during rotation of the grinding disc, which helps to alleviate the accumulation of grinding media at the screen and thus helps to alleviate problems of wear and clogging of the screen by the grinding media.

It should be noted that the grinding medium has a lower viscosity than ground material such as raw natural asphalt ore and is more likely to flow toward the feed side by the thrust force of the first surface 311.

It should be noted that the feeding direction is directed from the feeding side to the discharging side.

In one embodiment, with continued reference to fig. 2, the wall of the first material passing hole 31 further includes a second surface 312, the second surface 312 is located at a side of the first material passing hole 31 facing the rotation direction 5 of the grinding disc, the second surface 312 faces the discharge side of the grinding disc, and the grinding disc rotates to move at least a portion of the grinding media from the discharge side of the grinding disc to the feed side of the grinding disc along the second surface 312. So set up, the grinding disk rotation can make second surface 312 produce towards the suction of feed side, and relative ground materials such as natural asphalt raw ore, grinding medium viscosity is lower, flows to the feed side under the effect of second surface 312 more easily. This helps to alleviate the accumulation of grinding media at the screen, and thus helps to alleviate problems of wear and clogging of the screen by the grinding media.

In one embodiment, the second surface 312 may optionally be parallel to the axial direction of the polishing disk.

It should be noted that the shapes of the first surface 311 and the second surface 312 are not limited.

In one embodiment, the first surface 311 may have a wave shape, a step shape, a saw-tooth shape, a circular arc shape, or a flat surface.

In one embodiment, the second surface 312 may have a wave shape, a step shape, a saw-tooth shape, a circular arc shape, or a flat surface.

In one embodiment, with reference to fig. 2, the first surface 311 and the second surface 312 are both planar.

In an embodiment, referring to fig. 2, the extending direction of the first surface 311 forms a first included angle with the axial direction of the polishing disc, and the first included angle is 15 ° to 45 °. So set up, on the one hand can guarantee that first surface 311 produces stronger hindrance effect to the flow of discharge side to the grinding medium, and on the other hand can guarantee that the grinding material is smoothly flowed in first punishment in advance hole 31. Illustratively, the first included angle is 22.5 °, 15 °, 30 °, or 45 °.

It should be noted that the extending direction of the first surface 311 is from the inner side of the first surface 311 to the outer side, the inner side of the first surface 311 is a side close to the rotating shaft 2, and the outer side of the first surface 311 is a side away from the rotating shaft 2.

In an embodiment, referring to fig. 2, the first surface 311 is a plane, and an included angle between the first surface 311 and the axial direction of the polishing disc is a first included angle.

In an embodiment, referring to fig. 2, the extending direction of the second surface 312 forms a second included angle with the axial direction of the polishing disc, and the second included angle is 15 ° to 45 °. So set up, on the one hand can guarantee that second surface 312 produces stronger hindrance effect to the flow of grinding medium to the delivery side, on the other hand can guarantee that the grinding material flows smoothly in first punishment in advance hole 31. Illustratively, the second included angle is 22.5 °, 15 °, 30 °, or 45 °.

It should be noted that the extending direction of the second surface 312 is directed from the inner side of the first surface 312 to the outer side, the inner side of the first surface 312 is a side close to the rotating shaft 2, and the outer side of the first surface 312 is a side away from the rotating shaft 2.

In one embodiment, referring to fig. 2, the first surface 312 is a plane, and an included angle formed between the first surface 312 and the axial direction of the polishing disc is a first included angle.

It should be noted that the sizes of the first included angle and the second included angle are selected according to the material of the grinding medium, the shape of the grinding medium particles and the volume of the particles.

In one embodiment, the material of the grinding media may be cast iron, alloy, alumina, silicon carbide, ceramic, or the like.

In one embodiment, the shape of the grinding medium may be one or a combination of more than one of a round ball, a truncated cone, a cylindrical ball and a short round rod.

In an embodiment, referring to fig. 2, the first included angle and the second included angle are equal. Thus, the first material passing hole 31 can be conveniently machined and manufactured.

In one embodiment, referring to fig. 2, the first material passing hole 31 is a cylindrical through hole. So set up for first punishment in advance hole 31 can be through mould stamping forming. Specifically, the axial direction of the first material passing hole 31 and the axial direction of the grinding disc are a third included angle, and the first included angle, the second included angle and the third included angle are equal in size.

In an embodiment, with reference to fig. 2, the wall surface of the first material passing hole 31 further includes a transition surface 313, and the transition surface 313 is connected between the first surface 311 and the second surface 312.

In one embodiment, with continued reference to fig. 2, the transition surface 313 and the first surface 311 have rounded corners 314 at their junctions, which help to alleviate the accumulation of polishing material and polishing media at the edges of the first material passing holes 31.

In one embodiment, with continued reference to fig. 2, the transition surface 313 and the second surface 312 have rounded corners 314 at their junctions, which help to alleviate the accumulation of polishing material and polishing media at the edges of the first material passing holes 31.

In one embodiment, with continued reference to fig. 2, the distance between the first surface 311 and the second surface 312 increases gradually along the radial direction of the polishing disc. So set up, can enough guarantee first surface 311 and second surface 312 to the barrier effect of grinding medium, be favorable to grinding material to pass through first material through hole 31 again.

Specifically, in an embodiment, with reference to fig. 2, a plane of the inner side of the first surface 311 and the rotation axis of the polishing disc is referred to as a first reference plane, and an outer side of the first surface 311 is far away from the first reference plane along the direction 5 departing from the rotation direction of the polishing disc. The plane of the inner side of the second surface 312 and the rotation axis of the grinding disc is called a second reference plane, and the outer side of the second surface 312 is far away from the second reference plane along the rotation direction 5 of the grinding disc.

In one embodiment, the first material passing hole 31 extends along a predetermined direction, the predetermined direction is axially intersected with the polishing disc, and a cross section of the first material passing hole 31 along the predetermined direction is circular, elliptical, quincunx or polygonal.

In an embodiment, referring to fig. 2, the number of the first material passing holes 31 is multiple, and the multiple first material passing holes 31 are uniformly arranged along the circumferential direction of the grinding disc. So set up, can enough make the smooth and easy flow of grinding material, can alleviate the accumulation of grinding medium in screen cloth department again effectively.

In an embodiment, with reference to fig. 2, the number of the first material passing holes 31 is preferably 6 to 8. Illustratively, the number of the first material passing holes 31 is 8.

In one embodiment, referring to fig. 3, the second polishing disk 4 has a second material passing hole 41, and a wall surface of the second material passing hole 41 is axially parallel to the rotating shaft 2. So set up for the second material passing hole 41 can not produce great hindrance to the flow of grinding material, leads to the work efficiency of grinding machine to be lower, thereby makes first abrasive disc 3 mutually support with second abrasive disc 4 and can enough alleviate the accumulation of grinding medium in screen cloth department effectively and can guarantee the work efficiency of grinding machine again.

In an embodiment, referring to fig. 2 to 4, the projected outer contour of the second polishing disk 4 is different from the projected outer contour of the first polishing disk 3 in shape when projected along the axial direction of the rotating shaft 2. So set up, be convenient for grind material and grinding medium and form the torrent at the in-process that flows, make the grinding material obtain abundant grinding.

In one embodiment, the projected outer contour of the second grinding disk 4 and the projected outer contour of the first grinding disk 3 may have the same shape in the axial projection of the rotating shaft 2.

In one embodiment, the second polishing disk 4 may have an oval, quincunx, or polygonal shape.

In an embodiment, referring to fig. 3 and 4, along the axial direction of the second polishing disk 4, the projected outer contour line of the second polishing disk 4 includes three linear segments arranged along the circumferential direction of the second polishing disk 4, and an included angle between the extending direction of at least one linear segment and the extending direction of two adjacent linear segments is an acute angle. So set up, can have great clearance between the edge of second abrasive disc 4 and the grinding vessel 1, be convenient for grind smooth and easy flow of material in grinding vessel 1. The second grinding disc 4 and the first grinding disc 3 are matched for use, so that the accumulation of grinding media at the screen mesh can be relieved, and the grinding machine has high working efficiency.

In an embodiment, referring to fig. 2 to 4, along the axial direction of the second polishing disk 4, the projected outer contour line of the second polishing disk 4 includes three linear segments arranged along the circumferential direction of the second polishing disk 4, and an included angle between the extending direction of at least one linear segment and the extending direction of two adjacent linear segments is an acute angle. The first abrasive disc 3 is circular in shape. With this arrangement, the gap between the edge of the first polishing disk 3 and the polishing drum 1 is small, and the first material passing hole 31 is matched to greatly obstruct the flow of the polishing medium to the discharge side. And because the second grinding disc 4 can not generate larger obstruction to the flow of the grinding materials, the mutual matching of the first grinding disc 3 and the second grinding disc 4 can not only improve the grinding effect of the grinding machine, but also ensure the working efficiency of the grinding machine.

In an embodiment, along the axial direction of the second grinding disk 4, the projected outer contour line of the second grinding disk 4 may optionally include a plurality of straight line segments arranged along the circumferential direction of the second grinding disk 4.

In an embodiment, referring to fig. 4, a projection profile of the second polishing disc 4 along the axial direction of the rotating shaft 2 is located within a projection profile of the first polishing disc 3 along the axial direction of the rotating shaft 2. With this arrangement, the effect of the first polishing disk 3 on the flow of the polishing medium to the discharge side can be improved.

In one embodiment, referring to fig. 4, the diameter of the first polishing disk 3 is the same as the diameter of the circumscribed circle of the second polishing disk 4.

In an embodiment, referring to fig. 4, the number of the first polishing discs 3 is multiple, the multiple first polishing discs 3 are arranged along the axial direction of the rotating shaft 2, and at least one second polishing disc 4 is disposed between two adjacent first polishing discs 3. So set up, can make the flow of milling material in grinding vessel 1 more even, and be convenient for milling material and grinding medium form the torrent at the in-process that flows, make the milling material obtain abundant grinding.

In one embodiment, a plurality of first polishing discs 3 are disposed in close proximity.

In one embodiment, with continued reference to fig. 4, the second grinding disk 4 is located closest to the feed side of the mill, of the first grinding disk 3 and the second grinding disk 4. So set up, can guarantee that the in-process that the grinding material got into the machine of grinding can not receive great hindrance to can guarantee the work efficiency who grinds the machine.

It is to be explained that the larger particles of the unground ground material are more hindered during the flow. If, of the first 3 and second 4 grinding discs, the first grinding disc 3 is located closest to the feed side of the mill, the first grinding disc 3 will create a strong obstacle to the grinding material.

In one embodiment, with continued reference to fig. 4, the first grinding disk 3 is the closest to the discharge side of the grinder among the first grinding disk 3 and the second grinding disk 4. So set up for the first grinding disk 3 that is closest to the mill discharge side is less apart from the mill discharge side, can be better alleviate the gathering of grinding medium at the screen cloth.

It should be explained that the first grinding pan 3 accumulates less grinding media near the discharge side and subsequently accumulates more grinding media in the feed direction. Thus, the smaller the distance of the first grinding disc 3 closest to the discharge side of the mill from the screen, the less grinding medium accumulates at the screen.

In an embodiment, referring to fig. 4, the number of the first polishing discs 3 is three. So set up for grinding medium is in the flow process to the ejection of compact side, through three first abrasive disk 3 in proper order, can be better alleviate the gathering of grinding medium in screen cloth department. In addition, the three first grinding discs 3 do not generate large obstruction to the flow of the grinding materials in the grinding cylinder 1, and the working efficiency of the grinding machine can be ensured.

In an embodiment, referring to fig. 4, two second polishing discs 4 are disposed on the left side of the leftmost first polishing disc 3, two second polishing discs 4 are disposed between the middle first polishing disc 3 and the leftmost first polishing disc 3, and one second polishing disc 4 is disposed between the rightmost first polishing disc 3 and the middle first polishing disc 3. So set up, can enough guarantee that the grinding material smoothly flows, can alleviate the condition that grinding medium piles up in screen cloth department effectively again.

In an embodiment, referring to fig. 4, a central axis of the first polishing disk 3 coincides with an axis of the rotating shaft 2.

According to the structure, the rotating shaft 2 can rotate stably in the working process of the grinding machine.

In one embodiment, referring to fig. 4, the central axis of the second polishing disk 4 coincides with the axis of the rotating shaft 2.

According to the structure, the rotating shaft 2 can rotate stably in the working process of the grinding machine.

The various embodiments/implementations provided herein may be combined with each other without contradiction.

The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims (14)

1. A grinding disc, characterized in that the grinding disc is provided with a first material passing hole, the first material passing hole is communicated with the feeding side and the discharging side of the grinding disc along the axial direction of the grinding disc, the wall surface of the first material passing hole comprises a first surface, and the first surface and the grinding disc are mutually inclined in the axial direction so as to prevent grinding media from moving from the feeding side of the grinding disc to the discharging side of the grinding disc.

2. An abrasive disc according to claim 1, characterized in that the first surface is located at the side of the first material passage opening facing away from the direction of rotation of the abrasive disc, which first surface is facing the feed side of the abrasive disc, and the abrasive disc is rotated such that the first surface pushes at least part of the grinding media moving in the feed direction back to the feed side.

3. The grinding disc of claim 2 wherein the wall of the first material passing hole further comprises a second surface on a side of the first material passing hole facing the direction of rotation of the grinding disc, the second surface facing the discharge side of the grinding disc, the grinding disc rotating to move at least a portion of the grinding media along the second surface from the discharge side of the grinding disc to the feed side of the grinding disc.

4. The abrasive disc according to claim 3, wherein the first surface extending direction forms a first included angle with the axial direction of the abrasive disc, and the first included angle is 15 ° to 45 °; and/or a second included angle is formed between the extension direction of the second surface and the axial direction of the grinding disc, and the second included angle is 15-45 degrees.

5. A grinding disc according to claim 3, wherein the first surface extension direction and the axial direction of the grinding disc form a first angle, the second surface extension direction and the axial direction of the grinding disc form a second angle, and the first angle and the second angle are equal.

6. A grinding disc according to claims 3-5, characterized in that the distance between the first and second surfaces increases gradually in the direction radially outwards of the grinding disc.

7. The grinding disc according to any one of claims 1 to 5, wherein the first material passing hole extends along a predetermined direction, the predetermined direction axially intersects with the grinding disc, and a cross section of the first material passing hole along the predetermined direction is circular, elliptical, quincunx, or polygonal.

8. The grinding disc of any one of claims 1 to 5, wherein the number of the first material passing holes is multiple, and the multiple first material passing holes are uniformly arranged along the circumferential direction of the grinding disc.

9. A grinding mill, characterized in that it comprises:

a grinding cylinder;

the rotating shaft is rotationally connected with the grinding cylinder;

a first grinding disc positioned in the grinding cylinder, wherein the first grinding disc is connected with the rotating shaft, and the first grinding disc is the grinding disc according to any one of claims 1 to 8; and

the second grinding disc is positioned in the grinding cylinder and connected with the rotating shaft, the second grinding disc is provided with a second material passing hole, and the wall surface of the second material passing hole is axially parallel to the rotating shaft.

10. A grinding mill according to claim 9, characterized in that the projected outer contour of the second grinding disc is of the same or different shape as the projected outer contour of the first grinding disc, as projected in the axial direction of the shaft.

11. A grinding mill according to claim 10, characterized in that the projected outer contour of the second grinding disc, in the axial direction of the second grinding disc, comprises three straight segments arranged circumferentially of the second grinding disc, and the angle between the extension direction of at least one of the straight segments and the extension direction of two adjacent straight segments is acute.

12. A grinding mill according to claim 11, characterized in that the first grinding disc is circular in shape.

13. A grinding mill according to any one of claims 9 to 12 wherein there are a plurality of said first grinding discs arranged axially along said shaft, at least one said second grinding disc being provided between adjacent ones of said first grinding discs.

14. A grinding mill according to claims 9 to 12, characterized in that of the first grinding pan and the second grinding pan, the first grinding pan is the one closest to the discharge side of the grinding mill and/or the second grinding pan is the one closest to the feed side of the grinding mill.

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