DE3426477A1 - Chopping mill with scissor-cutting action - Google Patents

Abstract

A chopping mill is described in which the stator blade or rotor blade which take up the entire axial extent of the milling space surrounding the rotor extend inclined with respect to the axis of rotation of the rotor and the chopping edge of each of these blades extends in a warped fashion with respect to the axis of rotation whilst the chopping edges of the respective other blade set extend parallel to the axis of rotation. In the design of this chopping mill according to the invention, each blade which extends inclined with respect to the axis of rotation consists of individual blades which are of equal length and arranged next to one another in a row. Each row of individual blades has a plane which intersects the axis of rotation at the same angle as a common support face, the chopping edges of the individual blades of a row lie in a plane extending parallel to the associated support face and the chopping edge of each individual blade assumes, with respect to the chopping edges of the counterblades, in each case a position in which the change in the blade gap width, brought about by the inclination of the blade, over the length of a chopping edge when the chopping edge of a rotating blade passes by the chopping edge of a fixed blade becomes a minimum.

Description

II. Description

The invention relates to cutting mills, in which to comminuting material is comminuted as a pile by cutting between a fixed and a rotating knife set. It relates in particular to cutting mills according to the generic term of claim 1, d. H. those who work with paper cutting.

Cutting mills that work with paper cutting have compared to the Cutting mills that work with axially parallel cutting edges The advantage is that lower cutting forces are required and the generation of noise during the shredding process is reduced.

From DE-PS 865 249 a cutting mill is known in which the cutting edges of rotor and stator knives are straight and at an angle opposite to the axis of rotation of the rotor are inclined. The cutting edges lie on the surface of two concentric, single-shell rotational hyperboloids, so that fixed and circumferential cutting edges are practically the same over their entire length during the cutting process Have a distance. Depending on the angle of inclination and the length of the cutting edge, however, the cutting angles change along the Cutting edges relatively strong, so that this construction with regard to the cutting angle that can be effectively used in practice only suitable for rotors of short axial length. In addition, the inclined knife a considerable promotion of the goods to a Generate the end wall of the grinding chamber, which is the stronger, the more the angle of inclination of the cutting edges is greater. As a result, overload occurs on one side of the rotor while the other Page there is insufficient utilization. Increased specific energy requirement, uneven running, dust formation and smearing of good on the more exposed front wall of the

Grinding chamber are the result.
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One suitable for cutting mills with any axial length of the rotor Execution shows the FR-PS 2 168 617, after which the cutting edges the stator knife or the rotor knife are axially parallel and the cutting edges of the other set of knives form a helix. You can achieve a constant one Knife gap width and the same cutting angle along the cutting edges, but construction, production and regrinding are complex and very expensive, and also the disadvantageous conveying effect in one direction due to the slope of the helix is retained.

In contrast, the cheap version, in which the helical cutting edge by a straight, the entire axial extension of the rotor is replaced, although it is also known, but here it is an additional factor that the knife gap width when the cutting edge of a rotating knife passes the cutting edge of a stationary knife along the cutting edges changes so significantly that only an unevenly comminuted product is obtained and thin-walled feed material is practically not cut at all will.

The invention is therefore based on the object of such a cutting mill to improve so far that the advantageous properties of the cutting mill according to FR-PS 2 168 617 are largely achieved, that it is easy and cheap to manufacture and its cutting blades allow easy storage and easy to regrind are. Furthermore, mills are to be built with any axial length of the rotor and older mills with axially parallel cutting edges - e.g. B. by replacing the rotor - can be converted to scissor cut.

The task is solved with the characteristic features of the Claim 1. This results in the following advantages:

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- The processing of the common support surface for the individual knives does not cause high costs,

- The difference between the largest and smallest knife gap along the cutting edge of a single knife increases for the practically useful dimensional ratios in which the Angle between the plane containing the support surface of the individual knife and the axis of rotation in the order of magnitude of two or three degrees, in a first approximation reciprocal to the square of the number of individual knives,

- The arrangement can be used without difficulty even in the case of open design Use cutting mill rotors, d. H. those in which the cutting knives are supported by beams that extend over axially perpendicular discs are connected to one another, the outer discs being provided with stub shafts for drive and storage are,

- Rotors of different lengths can with the appropriate graduation be equipped with the same individual knives,

- In the event of damage to the cutting edges, the one to be exchanged Knife size and thus the costs are lower than with long knives,

- The handling of lighter, short blades during assembly is easier and less dangerous,

- Cutting mills with axially parallel cutting edges can be used known knife shapes, as well as the known setting devices, the z. B. allow a presetting of the rotor knives outside of the mill, can be used.

The selection of suitable dimensional proportions when applying the teaching of the invention with regard to process-related requirements prepares a designer for cutting grooves with average Expertise no difficulties, so that precise measurements can be dispensed with here.

To further reduce the cutting forces it is proposed that Support surfaces of two successive ones in the circumferential direction of the grinding chamber Execute rows of single knives with the same angle of inclination but opposite direction of inclination. This achieves that the always present in cutting mills with scissors cut promotion of the material to an end wall of the grinding chamber out constantly Direction changes so that there is an even distribution of material along the cutting edges. The specific energy requirement is lower and the run is smoother, dust formation and smearing of material on a grinding chamber front wall are avoided. This arrangement is preferred used in cutting mills where the cutting edges of the rotor knives are inclined to the axis of rotation and the cutting edges of the stator knives run axially parallel.

But it is also possible to use the support surfaces of the individual rows of knives in groups in the circumferential direction of the grinding chamber successively with the same angle of inclination, but the opposite direction of inclination. This arrangement is particularly advantageous for granulators, in which the cutting edges of the rotor knives are axially parallel and the cutting edges of the stator knives are inclined to the axis of rotation, because here the individual stator knife group in a common knife carrier can be used, which is processed outside of the mill and together with the already set stator knives as fully assembled knife block can be built into the grinder.

The cutting knives used as individual knives are preferably given Uniformly ground cutting edges with the same wedge angle. This is, for example, 90 ° for the stator knives and 55 ° for rotor knives, as is common with cutting mills with axially parallel cutting edges.

In certain cases, however, it can be due to the inclination of the individual knives It may be necessary to grind the individual knives in a row differently while maintaining the same wedge angle in order to to maintain uniform cutting ratios over the entire axial extent of the grinding chamber. In this case it is an advantage if the cutting edges are ground so that in the installed state for each individual knife in the middle of its cutting edge the the same rake angle and the same clearance angle results, with the prerequisite that the cutting edges of a row of knives are in a common Lie level.

The invention is to be explained in more detail on the basis of exemplary embodiments. Show it
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1 shows a cross section through a cutting mill with inclined rotor knives and axially parallel stator knives,

FIG. 2 schematically shows the arrangement of a rotor knife according to FIG.

3 shows the arrangement according to FIG. 2 in plan, but strongly distorted, 4 shows a cross section through a cutting mill with axially parallel axes

Rotor knives and inclined stator knives.

In the figures, components of the same type are denoted by the same item numbers.

In the mill housing of the cutting mill 1 according to FIG. 1, which consists of the upper housing part 2 and the lower housing part 3, the rotor 4 is mounted rotatably about the horizontal axis of rotation 5. Each of the rotating rotor knives 6 here consists of three individual knives 6 ', 6 ¹¹ , 6' ^{11 of} equal length arranged in a row next to one another (FIGS. 2 and 3, which show the arrangement of the rotor knife shown in FIG. 1 on the rotor 4 at the top left) . These individual knives are attached to the common support surface 7 on the rotor 4 with the aid of the bar 8 and screws (not shown here), the support surface 7 being part of a plane 9 which defines the axis of rotation 5 at the angle 10 (here 2.5 °) cuts. The cutting edges of the individual knives 6 ′, 6 ¹ ′, 6 ^IM lie in a plane that runs parallel to the support surface 7. The rotor knives 6 work together with the stator knives 11 used in the upper housing part 2, which have cutting edges running parallel to the axis of rotation 5. The lower boundary of the grinding chamber 12 surrounding the rotor forms the sieve 13. The rotor is made up of individual bars 14 which are connected to one another via the axially perpendicular end disks 15, these being provided with shaft journals 16 for storage and drive.

The position of the cutting edge of each individual knife with respect to the cutting edges of the counter knife, i.e. here the stator knife 11, is determined by shifting each individual knife on the support surface 7 in such a way that the outer corners of its cutting edge meet the surface of the (imaginary) envelope cylinder 17 touch that the cutting edges of axially parallel rotor knives would describe with the smallest possible knife gap to the stator knives. This then means here that the outer corners of the cutting edges of the closely spaced individual knives 6 ', 6 ¹¹ , 6 ¹¹¹ forming a rotor knife 6 lie on the circumference of an elongated ellipse 18, which by intersecting the plane determined by the cutting edges of the individual knives with the above-mentioned envelope cylinder 17 arises, which thus runs parallel to the support surface 7.

This ensures that the change in the knife gap width over the cutting edge length caused by the knife inclination Each individual knife passes the cutting edge of the stator knife becomes to a minimum. With the construction described here, there is a change in the knife gap width for each Individual knives of a maximum of 0.07 mm, i.e. H. this value is still within the usual range for axially parallel knives permissible tolerance limit of 0.1 mm.

Adjusting the individual knives, which are basically constructed in the same way are like knives of cutting mills with axially parallel cutting edges, can therefore in a known manner with the help of usual setting! B. a preset allow the rotor knife outside of the granulator.

As can be clearly seen from FIG. 1, the bearing surfaces are 7 two consecutive ones in the circumferential direction of the grinding chamber 12 Rows of the individual knives to the axis of rotation 5 at the same angle, but inclined in opposite directions.

The cutting mill 1 shown in Fig. 4 differs from that described above essentially in that the cutting edges of the rotor knives 6 are parallel and the cutting edges of the stator knives 11 run inclined to the axis of rotation 5. The stator knives 11, which each consist of individual knives strung together, are divided into two groups, and each group is used in a common knife carrier 19 or 20. Within a knife group are the contact surfaces of all individual knives under the same Angle inclined to the axis of rotation 5, but the inclination of one group is opposite to the other. By using the removable knife carriers 19, 20, manufacture and assembly are very simplified because they take place outside the mill and the knife carriers with the already set stator sneezes built into the upper part of the housing 2 of the cutting mill 1 as a fully assembled knife block can be.

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Claims (5)

Patent application from ALPINE Aktiengesellschaft, Augsburg for a cutting mill with scissors cut I. Claims 1. Cutting mill for comminuting various types of material by cutting between stationary stator knives fastened in the mill housing and rotating rotor knives arranged on a rotor rotatably mounted in the mill housing, the stator knives or rotor knives occupying the entire axial extent of the grinding chamber surrounding the rotor being inclined to the axis of rotation of the rotor run and the cutting edge of each of these knives is skewed to the axis of rotation, while the cutting edges of the other set of knives run parallel to the axis of rotation, characterized in that each knife (6) inclined to the axis of rotation (5) is made up of individual knives of equal length arranged in a row next to one another (6 ', 6 ¹¹ , 6 ¹¹¹ ) is that each row of the individual knives has a plane (9) that cuts the axis of rotation at the same angle (10) as a common support surface (7), that the cutting edges of the individual knives of a row in a parallel for the corresponding edition surface extending plane and that the cutting edge of each individual knife with respect to the cutting edges of the counter knife (11) assumes a position in which the knife gap caused by the knife inclination change over the cutting edge length when the cutting edge of a rotating knife passes the cutting edge • a stationary Knife becomes a minimum. 2. Cutting mill according to claim 1, characterized in that that the bearing surfaces (7) of two rows of individual knives following one another in the circumferential direction of the grinding chamber (12) have the same angle of inclination, but opposite inclination. 3. Cutting mill according to claim 1, characterized in that that the bearing surfaces (7) of the individual rows of knives follow one another in groups in the circumferential direction of the grinding chamber have the same angle of inclination, but opposite inclination. 4. Cutting mill according to one of claims 1 to 3, characterized in that all individual knives have a unit have borrowed ground cutting edge with the same wedge angle. 5. Cutting mill according to one of claims 1 to 3, characterized in that with a constant wedge angle due to the different grinding of the cutting edges in one Row of individual knives arranged next to one another are for each individual knife in the installed state in the middle of its cutting edge the same rake angle and the same clearance angle result.