Title of Invention

"AN APPARATUS FOR THE COMMINUTION OF BULK MATERIALS AND A METHOD THEREOF"

Abstract

This invention relates to a process and an apparatus for the comminution of bulk materials. A rotor (4) comprising impact elements (5) is disposed in the comminution chamber of the apparatus and is surrounded by a screen (6), which has a plurality of deflection elements (7,9) at its surface (6a). The comminution has the character of a pulsating movement with multiple alternation of the feeding and discharge of the product to and from the impact elements, wherein the fine fraction is separated from the total flow.

Full Text

This invention relates to a process and an apparatus for the comminution of bulk materials, particularly cereals, which are used in the mixed animal feedstuffs industry and in milling. A large number of comminution apparatuses is known, in which a rotor, which comprises impact elements and which is surrounded over its entire periphery or only partially by a screen, is disposed in a housing. In these apparatuses the material is fed into a working zone, i.e. into a zone between the impact elements and the inner face of a chamber (screen, impact plate) which surrounds the rotor, and is comminuted there. Since the impact elements are moved directly within the layer of comminuted materials, comminution is dominated by the principle of friction, the ultimate effect of which is manifested in excessive comminution of the particles, in an energy consumption which is too high, and in intensive wear on the impact elements and on the rotor. An apparatus of the aforementioned type is known from DE 1 250 721. This document discloses an impact grinding mill in which rotating impact elements co-operate with a friction- or impact jaw which is disposed between screening plates in a perforated basket. The use of the embodiment according to Figure 4, which comprises a two-armed beater cross and three friction jaws, results in a particularly high energy consumption. GB 1 411 085 discloses an impact mill in which the flow of the material which enters the comminution chamber of the mill is influenced by a special tapered construction of the rotor end. Excess wear on the rotor can thereby be reduced. The object of the present invention is to reduce the energy consumption during comminution, to increase the uniformity of granularity of the finished product, and to increase the service life of the operating elements and of the screen. The apparatus according to the invention comprises a housing which has inlet and outlet nozzles, an impact rotor, and a screen with a plurality of deflection elements which surround the impact rotor. The deflection plates at the periphery of the screen are disposed at a distance from the beaters which is the same or which varies. The deflection elements have a smooth surface at an inclination of 20-80 degrees to the radius, and form a gap with respect to the rotor, the minimum width of which gap is not greater than the diameter of the grains received for processing. The deflection elements are of rotatable construction as regards their inclination to the radius, i.e. they can rotate about a pivot on the screen surface towards said screen surface or in the opposite direction. According to one preferred embodiment, the deflection elements are disposed radially, and form a triangular prism, the lateral edges of which are oriented towards the screen. The deflection elements are thus adjustable along the screen periphery. Due to the possibility of constructing the deflection elements so that they are displaceable along the periphery of the screen surface, uniform wear of the screen is achieved in operation, since segments of the screen which are already worn are thereby covered. On the other hand, when using screens comprising segments of different perforations which are disposed alternately, it is possible to cover screen segments which have the same perforation by the joint displacement of the prismatic operating elements along the screen surface. The granulation of the final product can thereby be predetermined. The grinding or comminution action of the apparatus described above takes place in a working zone between the deflection elements and the impact elements of the rotor and is based on what is termed the principle of impact. On each feeding of the product stream to the impact elements, a single impact into the suspended product occurs. The stream of particles is thereby separated into coarse and fine particles. The coarse particles, which have a high kinetic energy, travel in suspension directly to the next impact element, whereas the fine particles, which have less kinetic energy, travel in suspension around the rotor under the effect of the air stream produced round the rotor, arid continue their movement along the perforated chamber surface and leave the chamber. The fine fraction is thereby separated without being subjected to the joint impact action of the next impact element of the rotor. A pulsating character is thereby imparted to the product stream after it is fed into the comminution chamber, with multiple alternation of the feeding to and discharge from the impact elements. It should also be mentioned that the efficiency of the process is-increased if the material is fed to the rotor at a defined angle. This angle varies within the range of 20-80 degrees to the radius. Accordingly, the present invention relates to an apparatus for the comminution of bulk materials, comprising a housing with inlet and outlet nozzles and with a rotor which is surrounded, over its entire periphery or only partially, by a screen characterised in that deflection elements are rotatably arranged in relation to the radius and that the deflection elements can rotate around a pivot on the screen surface towards the screen surface and in the opposite direction. The present invention also relates to a process for operating the apparatus for the above-mentioned comminution of bulk materials, characterised by: a) feeding the pre-comminuted product on to the screen at a defined angle P and at a predetermined velocity, b) the movement of product along the screen with simultaneous separation of the fine fraction and the feeding of the insufficiently comminuted fraction, under the action of the deflection elements, on to the impact elements for further impact, c) multiple repetition of the feeding cycle of the fraction which is still insufficiently comminuted to the rotor, the comminution of this fraction and the conveying thereof to the screen surface. The invention is explained in more detail below with reference to the drawings and to examples of embodiments, where: Figure 1 is a schematic longitudinal view of the impact mill; Figures 2, 2a are schematic side views of the impact mill showing the use of radially disposed deflection elements; Figure 3 is a plan view of the screen comprising segments with different perforations; Figure 4 is a schematic side view of the mill, showing the use of adjustable deflection elements; and Figure 5 is a schematic view showing a detail of a screen comprising an adjustable deflection element. The impact mill shown in Figure 1 consists of a housing 1 which has an inlet nozzle 2 and an outlet nozzle 3. Inside the housing 1 there is a rotor 4 comprising impact elements 5. The rotor is surrounded by a screen 6, on the surface 6a of which a plurality of deflection elements 7,9, which preferably have a triangular cross-section, is disposed. The screen 6 is sub-divided at its periphery into screen segments by the deflection elements 7,9, which are oriented inwards from the screen to the rotor and which have a smooth working face with an inclination in the direction of rotation of the rotor. The angle of inclination to the radius is within the range of 20-80 degrees, and the distance h between the ends of the impact elements 5 and the deflection elements 7,9 is not less than the grain diameter of the starting material. Figures 2 and 2a show a radial design of the deflection elements 9 with lateral edges, which form a triangular prism which is oriented inwards in relation to the screen 6 or to the surface 6a thereof. Figure 3 shows the screen 6, which is sub-divided alternately into segments A and B of different perforations, wherein the triangular prisms cover segments with the same perforation. Figure 4 shows an adjustable arrangement of the deflection elements 7, and Figure 5 shows the directions of rotation of the deflection element 7 to and from the screen 6 about a pivot 80 disposed on the screen surface 6a. The direction of rotation of the rotor 4 can be both clockwise and anti-clockwise. The deflection elements 7,9 are disposed in a ring 10 and can be displaced along the periphery of the screen 6; see Figure 2a in particular. The mill operates as follows: The starting material (uncomminuted cereal) is fed via the inlet nozzle 2 in Figure 1 from two sides to the rotor 4, and under the action of the centrifugal forces Z on the curved rotor path reaches the screen surface 6a or a screen section S (see Figure 2), which is delimited by two successive deflection elements 7 or 9. In this respect, it should be mentioned that the starting material is subjected to partial comminution inside the rotor 4 under the action of the impact elements 5. During its movement along screen 6 as shown in Figure 4, the product arrives at the smooth, inclined surface of the deflection element 7, changes its direction of movement, and is thereby subjected to a single impact of the impact element 5 of the rotor 4. When the product impinges on the impact element 5, it is broken up into particles of different sizes which, under the effect of the inertial forces which are imparted to them on impact, impinge on the next screen section S, which follows the deflection element 7 in the direction of rotation of the rotor 4. During the movement along the screen surface 6a under the action of centrifugal forces and of the air current which is produced by the rotor, a separation of the product is effected according to size. Particles which have passed through the perforations of the screen 6 are discharged from the impact mill as an output product (finished product) via the outlet nozzle 3. The coarser particles, and a certain number of small particles which did not have time to pass through the screen, reach the next deflection element 7, which is situated in the direction of movement of the product. This is followed by a similar process to that described above, with the difference that a stream of product which consists of particles of different sizes moves along the face of the deflection element 7,9. Coarse particles, which have a large supply of kinetic energy, leave the surface at an angle within the range of 20-80 degrees to the radius and encounter a single impact of the rotor 4 in free flight. The fine particles, which have less energy, curve round the deflection element 7,9 and thus reach the next screen section S without the effect of an impact. Directly behind the deflection element 7,9, the small particles thereby reach the screen surface 6a, whilst larger particles impinge on the latter further downstream in the direction of rotation. In this manner, the fine particles cover a longer path along the screen surface 6a until they are next moved by the deflection element 7,9, i.e. there is an increased probability of their passing through the perforations of the screen. At the same time, the coarser particles only have a brief contact with the screen surface 6a, which contributes to the reduction of wear thereof. Each subsequent conveying of product for comminution with the aid of the deflection elements 7,9 differs from the previous step in that the amount of product continuously decreases, because particles of the requisite size are continuously removed through the perforations of the screen 6. This process for the comminution of bulk materials is based on the following principles. 1. Pre-comminution of the starting material (whole cereal grains), which is fed to the interior space of the rotor 4, and its simultaneous acceleration to a defined velocity; 2. Further conveying of the pre-comminuted product, at a defined angle and at a predetermined velocity, on to the screen 6; 3. Movement of product along the screen 6 or screen surface 6a which surrounds the rotor 4, with simultaneous separation of the fine fraction and feeding of the insufficiently comminuted fraction, under the action of the inclined deflection elements 7 which are disposed on the screen 6, for further impact by the impact elements 5; 4. Multiple repetition of the feeding cycle of the fraction which is still insufficiently comminuted to the rotor 4, comminution of this fraction and further conveying thereof to the screen surface 6a. In addition, the principle of comminution of this impact mill is based on comminution without the direct co-operation of the rotor 4 and screen 5 [sic]; this is manifested in a reduction of the energy consumption and in an increase in the service life of the impact elements. It should be mentioned that the perforated surface of the chamber is at a distance from the rotor which is necessary to prevent the rotor being capable of exerting impacts on the product which is to be by-passed. The process exhibits its best efficiency if the product is fed to the rotor at a defined angle. This angle must fall within the range of 20-80 degrees to the radius. List of Reference Numerals 1 Housing 2,3 Inlet and outlet nozzles 4 Rotor 5 Impact elements 6 Screen 6a Screen surface 7,9 Deflection elements 8 Motor 10 Ring at the periphery of the screen 80 Pivot of the deflection element at the screen surface A Working zone G Comminuted material h Distance between the deflection elements and the impact elements of the rotor S Screen sections a Angle of inclination of the deflection element to the radius PI P2 Double arrows showing the deflection of the material towards and away from the impact elements Z Centrifugal forces P Angle which determines the feed of product to the rotor. WE CLAIM: 1. An apparatus for the comminution of bulk materials, comprising a housing (1) with inlet and outlet nozzles (2,3) and with a rotor (4) which is surrounded, over its entire periphery or only partially, by a screen (4) characterised in that deflection elements (7,9) are rotatably arranged in relation to the radius and that the deflection elements can rotate around a pivot (80) on the screen surface (6a) towards the screen surface and in the opposite direction. 2. An apparatus as claimed in claim 1, wherein the deflection elements (7) have a smooth working face with an angle of inclination a within the range of 20-80 degrees to the radius. 3. An apparatus as claimed in claim 1, wherein the deflection elements (9) are disposed radially and form a triangular prism, the lateral edges of which are oriented towards the screen (6). 4. An apparatus as claimed in any one of the preceding claims, wherein the distance between the deflection elements (7,9) and the impact elements (5) of the rotor (4) does not exceed the grain size diameter of the starting material. 5. An apparatus as claimed in any one of claims 1 to 4, wherein the deflection elements (7,9) are displaceably disposed along the screen periphery (6). 6. An apparatus as claimed in claims 1, 3 or 5, wherein the screen (6) has segments with different perforations. 7. An apparatus as claimed in claims 3, 5 and 6, wherein the lateral edges of the triangular prisms each cover segments with identical perforations. 8. An apparatus as claimed in claim 5, wherein the deflection elements (7,9) are displaceable along a ring (10) at the periphery of the screen surface (6a). 9. A process for operating the apparatus for the comminution of bulk materials as claimed in claim 1, characterised by: a) feeding the pre-comminuted product on to the screen (6) at a defined angle ß and at a predetermined velocity, b) the movement of product along the screen with simultaneous separation of the fine fraction and the feeding of the insufficiently comminuted fraction, under the action of the deflection elements (7,9), on to the impact elements (5) for further impact, c) multiple repetition of the feeding cycle of the fraction which is still insufficiently comminuted to the rotor (4), the comminution of this fraction and the conveying thereof to the screen surface (6a). 10. A process as claimed in claim 9, wherein the angle ß can vary within the range of 20-80 degrees to the radius. 11. An apparatus for the comminution of bulk materials substantially as hereinbefore described with reference to the accompanying drawings. 12. A process for the comminution of bulk materials substantially as hereinbefore described with reference to the accompanying drawings.

Documents:

541-del-1998-abstract.pdf

541-del-1998-claims.pdf

541-del-1998-correspondence-others.pdf

541-del-1998-correspondence-po.pdf

541-del-1998-description (complete).pdf

541-del-1998-drawings.pdf

541-del-1998-form-1.pdf

541-del-1998-form-13.pdf

541-del-1998-form-19.pdf

541-del-1998-form-2.pdf

541-del-1998-form-3.pdf

541-del-1998-form-4.pdf

541-del-1998-form-6.pdf

541-del-1998-gpa.pdf

541-del-1998-pct-210.pdf

541-del-1998-pct-338.pdf

541-del-1998-pct-409.pdf

541-del-1998-petition-137.pdf

541-del-1998-petition-138.pdf

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