Device and grinding tool for comminuting feed material

Abstract

A device and a plate-like grinding tool for grinding feed material that has a housing extending along an axis of rotation, in which a rotor rotationally driven about the rotation axis is arranged and includes a plurality of axially parallel grinding tools that are surrounded by a stator with stator tools. The effective edges of the grinding tools are arranged radially spaced from the stator tools by forming a grinding gap extending over an axial length of the grinding gap. The material is fed into the grinding gap on an inlet side and exits from the grinding gap on an outlet side. The axially extending effective edges of the grinding tools are divided in the axial direction into at least two first sections, each with a first radial distance from the rotational axis and into at least one second section with a second radial distance from the axis of rotation.

Claims

1. A device for crushing feed material, the device comprising: a housing extending along an axis of rotation; and a rotor arranged in the housing, the rotor being rotationally driven about the axis of rotation, the rotor having over its circumference a plurality of axially parallel grinding tools that are surrounded by a stator with stator tools, axially extending effective edges of the grinding tools being arranged a radial distance from the stator tools by forming a grinding gap thereby extending over an axial length of the grinding gap, wherein the feed material is fed to the grinding gap on an inlet side and emerges from the grinding gap on an outlet side, wherein the axially extending effective edges of the grinding tools are divided into at least two first sections in the axial direction, each having a first radial distance from the axis of rotation, and at least one second section having a second radial distance from the axis of rotation, wherein the at least one second section is arranged between the at least two first sections, wherein the first radial distance is greater than the second radial distance, wherein the axially extending effective edges of the at least two first sections and the axially extending effective edge of the at least one second section are connected with each other via essentially radially extending effective edges, wherein a first one of the grinding tools is adjacent to a second one of the grinding tools, the first one of the grinding tools having a different shape than the second one of the grinding tools and the second one of the grinding tools including two of the at least one second section, and wherein the at least one second section of the first one of the grinding tools is axially offset relative to both of the two of the at least one second section of the second one of the grinding tools.

2. The device according to claim 1, wherein a sum of lengths of all first sections of each of the grinding tools is 60% to 80% of a total axial length of each of the grinding tools.

3. The device according to claim 1, wherein a sum of lengths of all first sections of each of the grinding tools and a sum of lengths of all second sections of each of the grinding tools stand at a ratio of 5:1 to 1:1.

4. The device according to claim 1, wherein an axial length of a single second section of each of the grinding tools comprises 20% to 40% of a total axial length of each of the grinding tools.

5. The device according to claim 1, wherein a radial length of the radially extending effective edges of each of the grinding tools is at most as long as an axial length of the at least one second section of each of the grinding tools that adjoins the radially extending effective edges.

6. The device according to claim 1, wherein a radial length of the radially extending effective edges of each of the grinding tools is at least 5 mm.

7. The device according to claim 1, wherein the axial length of the at least one second section of the first one of the grinding tools and the axial length of the two of the at least one second section of the second one of the grinding tools decreases or increases.

8. The device according to claim 1, wherein the second radial distance of the first one of the grinding tools and the second one of the grinding tools decreases or increases.

9. The device according to claim 1, wherein, at an inlet end of each of the grinding tools, one of the axially extending effective edges comprises a third section having a third radial distance from the axis of rotation, and wherein the first radial distance of each of the at least two first sections of each of the grinding tools is greater than the third radial distance of each of the grinding tools.

10. The device according to claim 9, wherein the third radial distance of the first one of the grinding tools and the second one of the grinding tools, decreases or increases.

11. The device according to claim 9, wherein an axial length of the third section is greater than a radial length of the radially extending effective edges.

12. The device according to claim 9, wherein only one of the grinding tools has another third section provided at an outlet end thereof.

13. The device according to claim 1, wherein the axial offset is at least the sum of 50% of the axial length of the at least one second section of the first one of the grinding tools, where the first one of the grinding tools leads in a direction of rotation, and 50% of the axial length of the at least one second section of the second one of the grinding tools, or is at least the sum of the axial length of the at least one second section of the first one of the grinding tools and of the axial length of the at least one second section of the second one of the grinding tools, where the first one of the grinding tools leads in a direction of rotation.

14. The device according to claim 1, wherein by a displacement of the at least one second section of the first one of the grinding tools and the two of at least one second section of the second one of the grinding tools, a helical path is defined which includes an angle with a surface line of the rotor, wherein the angle is between 10 degrees and 50 degrees.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitive of the present invention, and wherein:

(2) FIG. 1 illustrates a longitudinal section through an inventive device along the line I-I shown in FIG. 2,

(3) FIG. 2 illustrates a partial section through the device shown in FIG. 1 along its line II-II,

(4) FIG. 3 illustrates a sketched representation of an embodiment of the grinding zone of the device with grinding tools shown in FIG. 1, formed by stator tools and grinding tools, the

(5) FIGS. 4a-4d illustrate views of grinding tools, arranged mutually adjacent in the rotor in an embodiment,

(6) FIGS. 5a-5d illustrate views of grinding tools, arranged mutually adjacent in the rotor in an embodiment,

(7) FIG. 6 illustrates a developed view of the rotor portion illustrated in FIG. 4d, showing the material flow, and

(8) FIG. 7 illustrates a view of two grinding tools with an inclined arrangement with respect to a surface line of the rotor.

DETAILED DESCRIPTION

(9) FIGS. 1 to 3 show an embodiment of an inventive device 1 in the form of a whirlwind mill, which is used without limitation for fine and very fine comminution of plastics such as thermosets, thermoplastics and elastomers or for grinding of crystalline materials or agglomerates. The device 1 comprises a platform-like machine base 2, which closes at the top with a horizontal mounting plate 3 on which a rotary drive 4 and a support frame 5 are mounted side by side. A cylindrical housing 6 is firmly connected with the support frame 5, which housing axis oriented perpendicular to the mounting plate 3 bears the reference number 7. The housing 6 is axially divided into an inlet-side housing section 8, a central cylindrical housing section 9, and a discharge-side housing section 10.

(10) A rotor 11 with a drive shaft 12 coaxially to the axis 7 is arranged within the housing. The drive shaft 12 is rotatably supported with its lower end section in a lower bearing 13 and with its opposite end section in an upper bearing 14. The end of the drive shaft 12 extending through the mounting plate 3 carries a multi-grooved pulley 15, which is coupled via drive belts 16 with the multi-grooved pulley 17 of the rotary drive 4.

(11) Within the housing 6, an upper supporting disc 18 is located axially perpendicular to the drive shaft 12 and at an axial distance therefrom, a plane-parallel lower supporting disc 19, which rotate with the drive shaft 12. At its periphery, the supporting discs 18 and 19 have position slots for receiving plate-like grinding tools 20 extending axially parallel, which in this way are distributed annularly over the circumference of the rotor 11 and can move during the operation of an inventive device, for example, with a peripheral speed of between about 100 m/sec and 180 m/sec, depending on the product. The angular spacing of the grinding tools 20 over the circumference of the rotor 11 is uniform and in the present embodiment, is three degrees, but may also be four degrees, five degrees or six degrees or more.

(12) The inlet-side housing section 8 downwardly forms the end-face housing closure and has in the region of the axis 7 a concentric inlet opening 21 for the feed material, said opening surrounding the drive shaft 12 over a sparse radial distance. Over the axial thickness of the inlet-side housing section 8, the inlet opening 21 develops into a flat-tapered expansion that in this way forms a distribution space 22 with the lower vertical supporting disc 19, which tapers radially outwards, thus providing acceleration of the feed material in this area. The outlet-side housing section 10 forms the upper end housing closure, where it houses an annular channel 23 extending concentrically to the axis 7, which merges into a material outlet 24 tangentially emerging from the housing section 10.

(13) The central cylindrical housing section 9 accommodates a stator, for which stator tools 35 are arranged on the housing inner periphery, which as a whole form a baffle web and which include a grinding gap 36 (FIG. 3) with the axially extending effective edges of the plate-like grinding tools 20 of the rotor 11.

(14) The feeding of the device 1 with the feed material 37 takes place via a supply channel 38, through which the feed material 37 reaches the housing interior as a gas-solid mixture via the inlet opening 21, where it is accelerated in the distribution space 22 after being deflected in the radial direction to the grinding gap 36. In the milling gap 36, the feed material 37 helically flows about the axis 7 upwards while it is being crushed. Lastly, the sufficiently refined material passes into the annular channel 23, from where it is removed via the material outlet 24 from the device according to the invention.

(15) In order to influence the grinding effect of the grinding tools 20, the effective edge of the grinding tools 20 has a special profile. As can be seen especially in FIG. 3, each grinding tool 20 possesses an effective edge 25 extending axially parallel to the axis 7, which opposes the stator tools 35 while maintaining a radial milling gap 36. The axially extending effective edge 25 is divided into three first sections L1 in the direction of the axis 7, each having a first radial distance R1 from the axis 7, and two second sections L2, each having a second radial distance R2 from the axis 7. Because the second radial distance R2 is less as compared to the first radial distance R1, there is a radial offset of the effective edge 25 in the area of the second sections L2, relative to the effective edge 25 in the region of the first sections L1 in the direction to the axis 7. The first sections L1 and the second segments L2 are each joined together via radially effective edges 26.

(16) In the present embodiment, the geometrical conditions are selected such, that the sum of the lengths of all the axially extending sections L1 constitutes about 75% of the total axial length L of a grinding tool 20. The ratio of the summed lengths of the first sections L1 to the summed lengths of the second sections L2 is about 3:1. The axial length of a single second section L2 corresponds to about 15% of the total axial length L of a grinding tool 20. The radial length of the edge 26 effective in the radial direction is approximately half as large as the axial length of the subsequent second section L.sub.2.

(17) FIGS. 4a-c show different types of grinding tools 20.1, 20.2, 20.3, adjacent to one another in the rotor 11, as they are generally described in FIG. 3. The arrangement of these different grinding tools 20.1, 20.2, 20.3 in a rotor 11 with a predetermined repetitive sequence is lastly shown in FIG. 4d. With respect to the rotational direction R of the rotor 11, the grinding tool 20.1 is the leading grinding tool and the grinding tool 20.2 the subsequent grinding tool.

(18) The grinding tools 20.1, 20.2 and 20.3 according to FIGS. 4a through 4d have in common that the axially effective edge 25 starts in the inlet-side area with a third section L3. In addition, the grinding tool 20.2 ends as the only one with a third section L3. The axial length of the inlet-side third section L3 is equal in size in all grinding tools 20.1, 20.2 and 20.3. By contrast, the radially effective edge 26.1, 26.2 and 26.3 of the different types of tools adjoining this section L3 is of different lengths. Thus, the radially effective edge 26.1 of the grinding tool 20.1 has the longest length and the radially effective edge 26.3 of the grinding tool 20.3 the shortest length, while the radially effective edge 26.2 has an intermediate length. As a result, the radial distance R3 between the axially extending effective edge 25m in the third section L3 to the rotational axis 7 increases respectively from the grinding tool 20.1 or 20.2 to the grinding tool 20.2 or 20.3.

(19) In addition, the grinding tools 20.1, 20.2 and 20.3 have one (FIG. 4a) or two (FIGS. 4b and 4c) second sections L2 in the axial distance to the inlet-side third portion L3, wherein a second section L2 of the grinding tool 20.1 or grinding tool 20.2 has an axial offset V relative to a second section L2 of the adjacent grinding tool 20.2 or grinding tool 20.3. The radially effective edge 26 of all grinding tools 20.1, 20.2 and 20.3 adjoining the second sections L2 all have a uniform length. Also, as shown in FIGS. 4a-c, the radially effective edges 26 run transversely to the effective edges 25.

(20) The further embodiment according to FIGS. 5a to 5d only differs from the one described under FIGS. 4a to 4d by the higher number of second sections L2. As a result, the number and density of the radially effective edges 26 also increase, so that such a grinding tool 20.1, 20.2, 20.3 is able to more intensively crush the feed material. To avoid repetition, what was stated under FIGS. 4a through 4d applies accordingly.

(21) FIG. 6 represents a developed view of the peripheral portion of the rotor 11 shown in FIG. 4d. It again provides a recurring sequence of the grinding tools 20.1, 20.2 and 20.3 in the circumferential direction. Two adjacent grinding tools 20.1, 20.2, 20.3 each form an axial flow-through chamber in which the feed material moves from the inlet side to the outlet side. The effective edge of all milling components is divided from the inlet side to the outlet side into an inlet-side third section L3, a first section L1, a second section L2 and a first section L1. The grinding tools 20.2 also end outlet-side with a further third section L3, whose effective edge 25 is aligned with the effective edge 25, and the grinding tools 20.3 with a further sequence of a second section L2 and of a subsequent first section L1.

(22) The second segments L2 of two adjacent grinding elements 20.1, 20.2, 20.3 have a uniform axial offset V in the direction toward the outlet side, whereby its arrangement results on lines 39 helically circulating the rotor periphery. The lines 39 enclose with a surface line 40 of the rotor circumference an angle a, which in the present embodiment is approximately 45 degrees.

(23) The flow of the feed material in the area of the rotor 11 is symbolized in FIG. 6 by the arrows 41. It is apparent that the feed material, especially in the second longitudinal sections L2, passes from one chamber to the subsequent chamber, thus traveling in a step-like manner through the rotor 11 to the exit on the outlet side.

(24) Lastly, the subject of FIG. 7 is an embodiment of the invention in which the grinding tools 20 are arranged for controlling the residence time of the feed material in the area of the grinding tools 20, with their effective edge at an angle to a surface line 40 of the rotor circumference. If the outlet side end of the grinding tool 20 is inclined in the rotational direction R (), on impact with the grinding tool 20, the particles of material receive a pulse counter to the general flow of material 41, causing a retaining effect on the flow of material 41. With an opposite inclination (+), however, the particles of material are accelerated on impact with the grinding tools 20 towards the flow of material 41.

(25) The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications and combinations as would be obvious to one skilled in the art are to be included within the scope of the following claims.