DE102007057565A1 - Eddy current mill, rotor and stator, as well as grinding track insert and grinding tool insert for it - Google Patents

Abstract

A stator (ST) is proposed for an eddy-current mill with a grinding gap (MS) defined between the stator (ST) and a rotor (RT), wherein the stator (ST) has a grinding track (20) which separates the grinding gap (MS). outwardly bounded by its conical or cylindrical inner surface (21), which is provided with ribs (26) projecting towards the grinding gap (MS) and extending over the length of the grinding gap (MS). The stator (ST) is characterized in that the ribs (26) of the grinding track (20) in each case in the direction perpendicular to a, by a Aufpunkt (P1) on the respective rib (26) extending imaginary radial plane (E1) around a rib Tilt angle (alpha) inclined. Furthermore, a Mahlbahn insert (20) is proposed, which forms the grinding path (20). Furthermore, a rotor (RT) is proposed for an eddy current mill with a grinding gap (MS) defined between the stator (ST) and a rotor (RT), the rotor (RT) having comminution sections which, during operation of the rotor, have a conical or cylindrical surface (23) strip off and in each case have an at least over a portion of the length of the refining gap (MS) of the lateral surface (23) inwardly extending crushing surface (3) for impacting particles. The stator (ST) is characterized in that the crushing surfaces (3) in each case in a direction perpendicular to an imaginary radial plane (E2) running through a Aufpunkt (P2) on the respective refractive surface around a ...

Description

The The invention relates to an eddy current mill with an intermediate a stator and a rotor defined grinding gap, and a Eddy current stator according to the preamble of claim 1 and an eddy current rotor according to the preamble of Claim 4, one in a housing of such a stator Absorbable grinding track insert according to the preamble of claim 3 and one on a tool carrier of a Such rotor attachable grinding tool insert according to the preamble of claim 6.

Of the Stator has a grinding path, the Mahlspalt outward with their conical or frustoconical or zylinderischen Inner surface limited, which with the Mahlspalt out projecting, over the length of the grinding gap extending ribs, or with a ribbing for crushing and Sliding back is provided by impacting particles. In contrast, the rotor has comminution sections that are in operation of the rotor a conical or cylindrical surface strip off and each one at least over a section the length of the grinding gap from the lateral surface inwardly extending crushing surface for impacting Have particles. The grinding path is often considered one in one provided stator housing can be installed grinding track insert formed, the crushing sections of the rotor than on a provided for tool carrier or Mahlring the rotor attachable grinding tool inserts.

rotates The rotor now at high speed in the stator, wherein the axis of rotation extends approximately in the vertical direction, and Ground material is abandoned from above and in a gap between the Rotor and a cover of the housing to the outside and centrifuged from there into the grinding gap, this millbase is grind between the corrugation of the grinding track and the grinding tools, in which the individual particles depending on the material density and grain size more or less often between grinding track and grinding tools and be hurled forth and thereby broken or smashed.

such For example, eddy-current mills have working speeds of 12,000 rpm and working peripheral speeds on the Mahwerkzeug of 125 m / s, depending on the application, the material properties of the ground material to be comminuted and the desired material parameters of Grinded ground milled different mills with different Diameters, Mahlspaltlängen and widths are used have to.

Eddy current mills of this type are for example from their own patent EP 0787 528 B1 known. There, the stator has a frustoconical grinding path insert with an inwardly directed, axially extending corrugation, which is fixed in a housing of the eddy current mill. On the other side of the refining gap, on the other hand, a rotor which can be driven at high speed is provided which is equipped along the axial direction with a plurality of so-called grinding rings, which are carrier elements for the grinding tools. The grinding rings are in turn equipped along the circumferential direction with a plurality of grinding tools.

task It is therefore an object of the present invention to provide an eddy current mill, or a rotor and a suitable grinding tool insert for it and a stator and a suitable grinding track insert for it to create those achievable with the eddy current mill Milling better to the material properties of the starting material and the desired material parameters of the final material adaptable is.

These Task is regarding the eddy current mill with the Characteristics of claim 7 solved, with respect to the stator with the features of claim 1, with respect to the Mahlbahn-use with the features of claim 3, in terms of the rotor with the features of claim 4, and with respect to the grinding tool use with the features of claim 6.

at the stator according to the invention extend the ribs the grinding path in each case in the direction perpendicular to a through a Aufpunkt on the respective rib running, imaginary Radial plane inclined by a rib inclination angle.

Of the According to the invention rotor has refractive surfaces on, each in a direction perpendicular to one through a Aufpunkt on the respective refractive surface running, imaginary Radial plane inclined by a Brechflächen inclination angle run. As a radial plane is doing a radial to the axis of rotation referred to the rotor extending plane.

In the eddy current mill according to the invention, the stator according to the invention and, alternatively or in addition, the rotor according to the invention can now be incorporated. In the context of the invention, the grinding path with the inclined ribs can also be formed on a grinding track insert, which is received in a housing of the stator as in known eddy current mills. Likewise, the inclined crushing surfaces may each be provided on separate crushing or grinding tool inserts, which as known per se on a tool carrier ring of the rotor are attachable.

According to the invention succeeds It makes it easy to influence the grinding speed to take an eddy current mill, d. h. that, for example different with one and the same eddy current mill Grinding speeds can be achieved by merely the grinding track insert and / or the tool inserts or Tool carrier rings with the tool inserts be replaced. On one and the same mill can use it different regrinds to Austraggütern with the respectively desired particle size distribution or a regrind to be distinguished in their grain distribution Austraggütern be milled with satisfactory effect, for what so far eddy current mills with different diameters or Mahlspaltlängen had to be provided.

So For example, it would be conceivable to have an eddy-current mill with a range of grinding track inserts, the grinding path inserts with ribs of different Rib inclination angles are provided.

The Inclination angles can differ in their amount but also in their direction, d. H. they can be in or be inclined against the direction of rotation.

Around to define the direction of the inclination angle is in the context of this Registration "inclined in or against the direction of rotation" as "in or inclined counter to the direction of rotation in Mahlspaltlängsrichtung As Mahlspaltlängsrichtung is thereby denotes the direction along the axis of rotation of the rotor, which is the Grinded material fed through the grinding gap to the grinding material feed Mahlgutaustrag takes out.

are the ribs and / or the refractive surfaces thereby against the Direction of rotation inclined, shorten the stay of the Grindings in the grinding gap, because the rebound angle of the ribs or crushing surfaces occurring particles steeper towards Mahlspaltaustritt runs. Are the ribs and / or the refractive surfaces on the other hand tilted in the direction of rotation, the stay extended of the millbase in the grinding gap, because the rebound angle of the on Ripping or crushing surfaces occurring particles shallower Mahlspaltaustritt out runs.

in the former case, so in opposite to the direction of rotation inclined ribs and / or refractive surfaces, becomes a relatively coarse grind achieved with a relatively small amount of fines in the millbase, but where a given by the width of the grinding gap Oberkornbegrenzung is predetermined. This results in a relatively flat grain distribution curve, d. H. There is a relatively small proportion of particles of small grain diameter essentially the same upper grain boundary as straight ribs or crushing surfaces in the ground grinding stock.

A such grain distribution curve is in many applications desired, for example, when a color raw material to color particle flour is to be ground and a slurry of the flour by a too high fines is to be feared. Even with toners for copying machines is a limitation of the grain size asked down, z. B. to 5 microns grain diameter.

In however, many applications will produce the opposite result as desired in the case described above: It should a very fine grinding with a steep grain distribution d. H. relatively few grains of large diameter and a large amount of fines in the crushed regrind can be achieved. This is always required if the regrind is a large one Surface should provide in a small space, such as in rubber powder or granules or in activated carbon powder for Filter applications, etc. For such applications Therefore, the developments of the invention are particularly suitable in which the ribs ribs of the grinding path and / or refractive surfaces the grinding tools are inclined in the direction of rotation.

Especially good results can be achieved with a tendency of the ribs of the Achieve grinding path. But also with an alternative inclination of the refractive surfaces The grinding tools on the rotor can have an effect on the grain distribution be influenced in the desired direction. Further the effect can be further increased by the fact that both the ribs the grinding path as well as the crushing surfaces of the grinding tools are inclined in the same direction.

In Trying to do this has a range of 10 ° to 30 ° in two possible directions of inclination - ie the Direction of rotation towards or away from the direction of rotation perpendicular to the radial plane inclined - proved to be suitable, wherein Particularly good results have been achieved in a range of 8 ° to 15 ° are.

at the exemplified value of 10 ° up to 12 ° rib inclination angle in the direction of rotation in conventional breaking surfaces the grinding tools could in experiments a desired, achieved very fine grinding of a powdered rubber or granular powder become.

Further advantageous developments will become apparent from the accompanying drawings explained in more detail below, wherein

1 a schematic sectional view of the grinding area of a generic vortex current mill shows;

2 a view of the cross section of a grinding path insert according to an embodiment of the invention in one of the sheet plane in 1 appropriate level;

3 a sectional view taken along one of the line III-III in 1 corresponding line through the stator of an eddy current mill, in which the in 1 shown Mahlbahn insert by the in 2 has been exchanged Mahlbahn insert has been replaced;

4 1 a partial side view of a rotor with a grinding tool insert attached thereto according to a further embodiment of the invention,

5 a side view on the in 4 illustrated grinding tool insert from the in 4 direction indicated by V; and

6 a diagram which qualitatively the cumulative particle distribution over the grain diameter for the generic eddy current mill of 1 , for the eddy current mill with the stator according to the embodiment of the 2 and 3 , as well as for an eddy current mill with oppositely inclined Mahlbahnrippen represents.

First, reference is made to the 1 which shows a schematic representation of the grinding area of a generic eddy current mill. The eddy current mill has a stator ST ', which is a stator housing 22 in which a conical or frustoconical Mahlbahn-use 20 ' taken and a Ringflanschteil 24 is attached. The ring flange part 24 is with the stator housing 22 and the grinding track insert 20 ' , as in 1 indicated, screwed, using washers, the altitude of the grinding path 20 ' can be adjusted, whereby influence on the width of a Mahlspalts designated with MS between the stator ST 'and rotor RT' can be taken. The rotor RT 'rotates about an axis of rotation R, which is at least substantially plumbed to the vertical, so that no gravity-related imbalance occurs. The grinding gap MS is thereby from the stator ST 'on an inner surface 21 the grinding track insert 20 ' limited and on the other hand by the rotor RT 'via an outer circumferential surface 23 of the rotor RT '. The material to be ground then decreases starting from a grinding material feed opening 19 in a cover area of the stator housing 22 via the centrifugal forces generated by the rotating rotor its way to the outside and reaches the grinding gap, which it passes under impact on the grinding gap MS facing surfaces of the rotor RT 'and the stator ST' down.

The grinding path 20 ' In this case, in known vortex-flow mills, there is a corrugation with ribs running in the longitudinal direction of the grinding gap, whereas the rotor RT 'has one or more grinding rings fitted with grinding tools in known eddy current mills along the grinding gap MS, wherein the grinding tools are equipped with refractive surfaces extending in a radial direction to the axis of rotation R.

2 now shows a grinding track insert 20 according to a first embodiment of the invention, which is to replace the in 1 drawn, conventional grinding track insert 20 ' suitable is. The grinding track insert 20 in 2 Although this also has a corrugation. Your ribs 26 but extend at a rib inclination angle α to one through the rotation axis R of the rotor and an intersection point T1 with the respective rib 26 imaginary radial plane E1 (compare also 3 , which the Mahlbahn use 20 in one in the stator housing 22 installed state shows). In 3 are here with dashed lines the top circle diameter and the root diameter of the ribs 26 at the top end of the grinding track insert 20 formed grinding track 20 drawn, with only on the left half of the individual ribs 26 have been drawn.

In further reference is made to the 4 and 5 ,

With 1 is a grinding tool insert according to a further embodiment of the invention designated and a total of 28 a Mahlring, which two carrier plates 5 . 6 has, between those over the circumference of the grinding ring 28 distributes a variety of grinding tool inserts 1 are attached. The Mahlring 28 is doing a rotor hub 29 attached and is with the rotor hub 29 Part of the total designated RT rotor. The rotor can, as in the case shown, only one Mahlring 28 or along the Mahlspalts several rows of grinding tools 1 and accordingly a plurality of grinding rings arranged one above the other on the hub 28 ,

With R is again the predetermined direction of rotation of the rotor and thus the attached Mahlrings 28 marked, with L the Mahlspaltlängsrichtung. It can be seen that the grinding tool insert 1 on the pointing in the direction of rotation R of the rotor side with a 3 has designated refractive surface on which impinge the bouncing from the lying on the other side of the refining grinding track particles and are to be smashed, so that the millbase is ground to fine powder. The breaking surface 3 is on its radial outside of a sharp edge 4 limited, which is easy to the axis of rotation of the rotor which in turn corresponds to the cone slope of the grinding path, so that the width of the grinding gap is constant.

The edges 4 the on the Mahlring 28 arranged grinding tool inserts strip the in 1 With 21 Designated lateral surface from which encloses the grinding gap MS from the inside, when the rotor ST is installed in the eddy current mill shown there. The breaking surface 3 is inclined at a refractive surface inclination angle β of 11.25 ° with respect to a radial plane E2, which passes through the axis of rotation R. For the sake of clarity alone, the plane E2 for the figure was chosen such that the point P2 is no longer on the refractive surface 3 lies, but on an imaginary, the refractive surface extending plane. However, this does not matter for the determination of the angle β.

The grinding tool insert 1 has a wing-shaped crushing section 10 on, which with a sleeve-shaped attachment portion 9 is soldered. The sleeve-shaped attachment portion 9 or sleeve section 9 is between the carrier plates 5 . 6 inserted. The carrier plates 5 . 6 have through holes that are to the sleeve section 9 of the respective milling tool insert 1 aligned. Through the sleeve section 9 and the associated through holes is a bolt 8th performed, which has a mother 12 the grinding tool insert 1 at the grinding ring 28 attached. By a more or less strong suit of the mother can be a more or less easy or stiff rotation of the grinding tool 1 around the through the bolt 8th reach the axis of rotation S formed.

This is the grinding tool use 1 according to the illustrated advantageous embodiment, pivotally mounted or oscillating on the rotor RT, wherein the pivot axis S advantageously extends axially parallel to the axis of rotation of the rotor. However, this could also be inclined by a few degrees, for example by the degree of conical inclination of the grinding path to the axis of rotation or in the direction of the refractive surface inclination angle β. Due to the high rotational speed of the rotor RT in eddy current mills of the generic type, the grinding tool insert is used 1 held in its working position, as long as only the ground material to be ground in the grinding gap is located. If, on the other hand, a hard foreign object strikes the milling tool insert, it can pivot out of its working position and thereby avoid the foreign body. Even if it is no longer possible to continue grinding after the penetration of such a foreign body, it is still possible to limit the damage to the mill, since now the operators are given the opportunity to switch off the mill before the foreign body smashes one or more grinding tools and thus still causes greater damage.

It would be conceivable between the carrier plates 5 . 6 and the sleeve section 9 To insert washers of a good sliding material, if the frictional forces are to be reduced, so that when hitting a hard foreign body or the like on the wing-shaped crushing section 10 or wing section 10 easier return from the aligned in the radial direction working position of the grinding tool succeeds. If, in contrast, an increased resistance force of the grinding tool against sliding back is desired, this could be accomplished via an annular spring, which is attached on the one hand to one or both carrier rings and on the other hand to the grinding tool insert. With the help of the above measures, the mobility of the rotation is thus adjustable.

The grinding tool insert 1 Thus, according to the hardness or other properties of the ground material can be either loosely oscillating on the rotor RT or fastened executed or, if caused by the rotational speed of the rotor RT centrifugal force for comminuting the ground material is insufficient or, if the grinding tool use 1 would otherwise pivot out of its working position, be biased in this working position on the rotor RT to be fastened or be fastened.

The wing section 10 can consist of a hard metal, whereas the sleeve-shaped attachment portion 9 can be made of a standard structural steel. In this way, on the one hand, the attachment portion 9 material rather be simpler or cheaper designed as the crushing section 10 ,

Alternatively, a grinding tool insert to be used for a particular grinding stock could also consist overall of a material corresponding to this millbase, if, for example, minimal abrasion and a high degree of freedom of metal of the pulverized powder are important (eg in the case of luminescent powder) made of ceramic , For example, Al ₂ O ₃ , when it comes to a particularly abrasion-resistant and abrasion-resistant surface of the grinding tool for very abrasive grinding materials (for example, dolomite with quartz foreign inclusions) of hard metal, on the other hand, it depends on a non-toxic abrasion, for example in the food industry, made of stainless steel.

In the illustrated embodiment, the crushing portion 10 doing with the attachment section 9 soldered. Instead of soldering the wing section 10 with the attachment section 9 would be any other type of connection, z. B. gluing or screwing the two sections 9 . 10 of the grinding tool insert 1 conceivable with each other.

However, it would also be conceivable to attach an alternating plate to the crushing section, as described for example in the European patent application EP 0 1 413 357 A1 has already been proposed, and to manufacture this crushing plate from a specific material associated with the crushing process and the support plate holding the crushing plate integral with the attachment portion of a different material. It could also exchange plates with different Brechflächen-inclination angles may be provided, in which case by equipping the crushing plate holding universal carrier sections of the grinding ring recorded grinding tool inserts with crushing plates of another Brechflächen inclination angle, the eddy current mill could be converted to crush another grist. Finally, it would also be conceivable to form the support sections holding the crushing plate in one piece or as part of the respective grinding ring, so that the grinding tool inserts merely consist of the alternating plates.

Also it would be conceivable, pointing in the direction of rotation of the rotor Crushing surface of the grinding tool by a coating on Forming crushing portion, for example, a hard material coating (For example, tungsten carbide, TiC-TaC or even diamond) and the Milling tool use otherwise in one piece from a cheaper To produce material.

Of the 6 let the different slopes of the grain distribution in 3 eddy current mills take, where there on the abscissa, the cumulative grain distribution in volume percent (Vol-%) is given over the diameter D on the ordinate.

With G _-10 , a grain distribution curve of an eddy current mill is shown, the Mahlbahn in Mahlbahnlängsrichtung by 10 ° against the direction of rotation inclined ribs, with G _o the cumulative grain distribution curve of the same eddy current mill with a grinding path with conventional ribs, and with G _10, the cumulative grain distribution curve of the eddy current mill with a grinding track whose ribs are inclined by 10 ° to the direction of rotation.

As you can see G _{-10 has} the flattest course, ie the smallest fines content in the material to be ground, whereas G _{10 has} the steepest gradient, ie the largest fines content in the material to be ground.

It can also be seen that, despite the different steepnesses, the same upper grain boundary OK is present, whereas the smallest grain diameter UK ₁₀ , UK _o , UK _-10 vary. In _G-10 the smallest grain diameter UK _-10 are substantially larger than the smallest grain diameter UK ₁₀ at G _10th

Also, the limit diameters D40 ₁₀ , D40 _o , D40 _-10 and D60 ₁₀ , D60 _o , D60 _-10 , where 40% and 60% of the grinding stock volume are reached, vary due to the different steepness of the grain distribution curves G ₁₀ , G _o , G _-10 strong.

Of course, deviations and modifications of the illustrated embodiment are possible without departing from the scope of the invention. In particular, the above embodiments may be combined as desired within the scope of the invention. Furthermore, it would also be conceivable, the refractive surface 3 to form with a bag.

at the eddy current mills according to the invention The ribs or the refractive surfaces each extend vertically Direction to one by one Aufpunkt on the respective rib or refractive surface running, imaginary radial plane to inclined a ridge or Brechflächen inclination angle. That is, the ridge slope angle, below the respective rib or crushing surface to the radial plane runs, is measured in the normal direction to the radial plane.

The refractive surfaces 3 but can not be made only in the direction along the Mahlspalts to the radial plane E2. A hiring in the manner of an indexable insert in the direction of a radial plane about an axis parallel to the axis of rotation of the rotor extending axis would be conceivable.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• EP 0787528 B1 [0005]
• EP 01413357 A1 [0043]

Claims (10)

Stator (ST) for an eddy-current mill with a grinding gap (MS) defined between the stator (ST) and a rotor (RT), the stator (ST) being a grinding track ( 20 ) having the milling gap (MS) outwardly with its frustoconical or cylindrical inner surface ( 21 ), which project towards the grinding gap (MS), extending over the length of the grinding gap (MS) ribs ( 26 ), characterized in that the ribs ( 26 ) of the grinding track ( 20 ) in each case in the direction perpendicular to one through a Aufpunkt (P1) on the respective rib ( 26 ), considered radial plane (E1) extend inclined by a rib inclination angle (α). Stator (ST) according to claim 1, characterized that the rib inclination angle (α) is 5 ° to 30 °, preferably 8 ° to 15 °, for example 10 °. Grinding track insert ( 20 ), suitable for receiving in a dedicated stator housing ( 22 ) of a stator (ST) of an eddy current mill, characterized in that it comprises the grinding track ( 20 ) according to one of claims 1 or 2 forms. Rotor (RT) for an eddy-current mill with a grinding gap (MS) defined between the stator (ST) and a rotor (RT), the rotor (RT) comminution sections ( 1 ), which in the operation of the rotor has a frusto-conical or cylindrical outer surface ( 23 ) and at least over a portion of the length of the grinding gap (MS) of the lateral surface ( 23 ) inwardly extending refractive surface ( 3 ) for impacting particles, characterized in that the refractive surfaces ( 3 ) in each case in the direction perpendicular to an imaginary radial plane (E2) running through an attachment point (P2) on the respective refractive surface, extend inclined by a refractive surface inclination angle (β). Rotor (RT) according to claim 4, characterized that the refractive surface inclination angle (β) is 5 ° to 30 °, preferably 8 ° to 15 °, for example 10 °. Grinding tool insert ( 1 ) for mounting on a tool carrier ring ( 28 ) of a rotor (RT) of an eddy-current mill, characterized in that it comprises a comminution section ( 1 ) according to claim 4 or 5 forms. Eddy current mill with a grinding gap (MS) defined between a stator (ST) and a rotor (RT), characterized in that the stator (ST) drives the grinding track ( 20 ) according to one of claims 1 to 3 and / or the rotor (RT) the crushing sections ( 1 ) according to one of claims 4 to 6. An eddy current mill according to claim 7, characterized in that the ribs ( 26 ) and / or the refractive surfaces ( 3 ) in Mahlspaltlängsrichtung (L) seen against the direction of rotation (R) are inclined. Eddy current mill according to claim 7, characterized that the ribs and / or the refractive surfaces exit from the grinding gap seen from inclined in the direction of rotation. Radial plane radial to a rotation axis (R) of the rotor (RT). frustoconical = conical