WO2024213835A1

WO2024213835A1 - Double action impact mill

Info

Publication number: WO2024213835A1
Application number: PCT/FI2024/050171
Authority: WO
Inventors: Hannu Virtanen; Miika Partanen; Miika PULKKINEN
Original assignee: Megatrex Oy
Current assignee: Megatrex Oy
Priority date: 2023-04-14
Filing date: 2024-04-12
Publication date: 2024-10-17
Anticipated expiration: 2025-10-14
Also published as: FI20235423A1; CN121057627A

Abstract

A double-action impact mill (1) comprises a rotor arrangement (2) that has a first side (21) and a second side (13) opposite to the first side (21), a first drive shaft (14) extending outwards from the second side (13) of the rotor arrangement (2), the first drive shaft (14) being in co-operation with at least one ring of the rotor arrangement (2), a second drive shaft (15) extending outwards from the first side (21) of the rotor arrangement (2), the second drive shaft (15) being in co-operation with at least one other ring of the rotor arrangement (2), at least one actuator that is in co-operation with at least one of the drive shafts (14, 15), a feed opening (16), and a discharge (17). The rotor arrangement (2) is configured to be driven from opposite sides (13, 21) of the rotor arrangement (2).

Description

A^DOUBLE^ACTION^IMPACT^MILL FIELD OF THE INVENTION The invention relates to a double-action impact mill. BACKGROUND OF THE INVENTION Document WO 1999054045 discloses a double-action impact mill. Certain materials to be treated in double-action impact mills require high speeds. One of the disadvantages associated with the double-action impact mills is that at high speeds they are prone to breakages. BRIEF DESCRIPTION OF THE INVENTION An object of the present invention is to provide a double-action impact mill so as to alleviate the above disadvantage. The objects of the invention are achieved by a double-action impact mill which is characterized by what is stated in the independent claim. The preferred embodiments of the invention are disclosed in the dependent claims. The invention is based on the idea of dividing driving forces of the dou- ble action impact mill. An advantage of the double-action impact mill of the inven- tion is that it withstands increasing speeds. Another advantage is that sealing of shafts is easier. The double-action impact mill is useful in treating materials such as pulp, especially wood pulp, or nanoparticles. The materials may be treated as dry or wet. In the following, the double-action impact mill is described in a position where it is ready for use. The double-action impact mill comprises a rotor arrangement, a first drive shaft, a second drive shaft, at least one actuator, a feed opening and a dis- charge. The rotor arrangement has a first side and a second side opposite to the first side. The rotor arrangement comprises at least one first ring of the first side of the rotor arrangement and at least one second ring of the second side of the rotor arrangement. The first ring is provided with first blades and the second ring is pro- vided with second blades. The first ring and the second ring intermesh, i.e. the rings follow each other in the direction of the radius of the rotor arrangement. The rotor arrangement may comprise at least two first rings of the first side of the rotor arrangement and at least two second rings of the second side of the rotor arrangement. The first rings are provided with first blades and the sec- ond rings are provided with second blades. The first rings and the second rings intermesh in such a manner that every other ring is the first ring and every other ring is the second ring. The first rings may be integrated in one rotor in such a man- ner that they have the same rotating direction and the same speed, or they may be driven independently. The second rings may be integrated in one rotor in such a manner that they have the same rotating direction and the same speed, or they may be driven independently. The number of the first and second rings may be more than two. Further, the number of the first rings compared to the number of the sec- ond rings may be ±1. The rings may be concentric or eccentric in respect of each other. The first and second rings of the rotor arrangement may be arranged in such a manner that the first rings have been fastened to the top side of the rotor arrangement and the second rings have been fastened to the underside of the rotor arrangement, or vice versa. The first and second rings may also be arranged so that the first rings have been fastened to the left side of the rotor arrangement and the second rings have been fastened to the right side of the rotor arrangement, or vice versa. The preferred alternative at very high speeds is that the first and second rings of the rotor arrangement are arranged in such a manner that the first rings have been fastened to the top side of the rotor arrangement and the second rings have been fastened to the underside of the rotor arrangement, or vice versa. The first drive shaft is in co-operation with at least one ring of the rotor arrangement, i.e. the first drive shaft is arranged to rotate at least one ring of the rotor arrangement. The second drive shaft is in co-operation with at least one ring of the rotor arrangement, i.e. the second drive shaft is arranged to rotate at least one ring of the rotor arrangement. When there are only one first ring and only one second ring the first ring may be in co-operation with the first drive shaft and the second ring may be in co-operation with the second drive shaft, or vice versa. The at least one actuator is in co-operation with at least one of the drive shafts, i.e. the at least one actuator is arranged to generate a driving force to at least one of the drive shafts. The at least actuator may generate the driving force to at least one of the drive shafts either directly or through at least one intermediate shaft. The rotor arrangement is driven from the opposite sides of the rotor arrangement. It means that there is at least the first drive shaft, which extends out- wards from the second side of the rotor arrangement, and the second drive shaft, which extends outwards from the first side of the rotor arrangement and the shafts are driven by at least one actuator. The first and second drive shafts may extend perpendicular to the rotor arrangement. Besides the first and second shafts there may be more shafts that co-operate with at least one ring of the rotor arrangement. The shafts are driven by one or more actuators. The double-action im- pact mill may comprise a first actuator for generating a driving force to at least one ring and a second actuator for generating a driving force to at least one another ring, or the double-action impact mill may comprise only one actuator for generat- ing driving forces to the rings. It is possible that the double-action impact mill com- prises more than two actuators. The actuators may be electric motors. The actua- tors may be driven directly, which is the preferred alternative. Directly driven means in this context that a shaft of an actuator is in direct contact with a shaft of a rotor arrangement, or a shaft that is between the shaft of the actuator and the shaft of the rotor arrangement, or there is a direct drive. The direct contact may be formed e.g. through gears or alike that transfer the driving force directly from one shaft to another shaft. Directly driven includes alternatives wherein speeds of the shaft of the actuator and the shaft of the rotor arrangement are the same, or they are different. Another alternative, although less preferred at very high speeds, is a belt drive. The belt may be a cogged belt or a cone belt, preferably a cogged belt. The feed opening is for feeding the material to be treated. The feed opening may extend through one of the drive shafts, or it may be a separate feed opening. The feed opening may open above or under the rotor arrangement. It is possible that the double-action impact mill comprises more than one feed opening. In the case of more than one feed opening it is feasible that there are at least one feed opening that opens above the rotor arrangement and at least one feed opening that opens under the rotor arrangement. Besides materials to be treated in the dou- ble-action impact mill it is possible that gaseous material, such as nitrogen, is fed to the double-action impact mill. The separate feed opening is the preferred alternative at very high speeds. The separate feed opening may be an inclined tube that feeds material to the nave of the rotor arrangement, or a straight tube that feeds material to the cir- cumference of the rotor arrangement. Material may be fed through the separate feed opening in such a manner that the material flows through an opening / open- ings in a plane of a rotor to the rotor arrangement. The discharge is for discharging the treated material. The discharge may be a tangential opening on a circumference of the rotor arrangement, or the discharge may be through the circumference of the rotor arrangement without any specific opening. In the latter case the rotor arrangement may be placed inside a container. It is also possible to use the feed opening as the discharge and vice versa i.e. it is possible feed a material to be treated through the discharge and suck the treated material out of the rotor arrangement through the feed opening. The rings may rotate at a rotation speed that is between 3000 and 3500 rounds per minute. Even a rotation speed of 10000 or more rounds per minute is possible. It is possible to increase speed from the ordinary speed of 1500 rounds per minute since bearings, such as a bearing of the first drive shaft, withstand high speeds due to the construction described in this text. Each ring may have its own rotation speed. The rotation speeds of the rings are adjustable. In general, each in- dependently driven ring or group of rings may rotate in the same or opposite di- rection in respect of other rings. It is also possible that at least one ring is station- ary, or rotates periodically. A double-action impact mill may be used at very high speeds which may be at least 2000 rounds per minute. The very high speeds are often above 3000 rounds per minute or even above 4000 rounds per minute. A double action impact mill that is used at very high speeds may require a few properties that may be ig- nored at lower speeds. One or more properties explained below may be utilized at very high speeds: Mechanical power transmission shall be arranged directly by a direct drive, or from one shaft to another shaft e.g. through gears since such an ar- rangement tolerates very high speeds and/or high efficiency. Solid drive shafts are preferred because their sealing and bearing can be made reliably. The rotor ar- rangement shall have horizontal rotors on top of each other, or a horizontal stator and a horizontal rotor on top of each other wherein either the stator or the rotor can be on top. By having the horizontally orientated rotor arrangement material to be processed is evenly distributed in the rotor arrangement that is important in view of balance and wear of the rotor arrangement. Further, feeding to the hori- zontally orientated rotor arrangement is easy because the material to be processed can be fed by using gravitation. Furthermore, when the rotor arrangement is hori- zontally orientated the drive shafts are vertical. The vertical drive shafts are pre- ferred since their bearing load is more easily controllable. In regard to other prop- erties, the double action impact mill for very high speeds may be similar to the dou- ble action impact mill for lower speeds. BRIEF DESCRIPTION OF THE DRAWINGS In the following the invention will be described in greater detail by means of preferred embodiments with reference to the attached drawings, in which Figures 1, 3 to 13 and 15 to 20 show cross-sectional views of double- action impact mills; Figures 2 and 14 show cross-sectional views of rotor arrangements; Figure 21 shows a perspective view of the double-action impact mill of Fig.20; Figure 22 shows a cross-sectional view of a double-action impact mill. DETAILED DESCRIPTION OF THE INVENTION In the following figures each part has a unique number. Therefore, a part described in connection of one figure applies to a part having the same number in connection with another figure when applicable. Figure 1 shows a double-action impact mill 1. The double-action impact mill comprises a rotor arrangement 2 comprising a housing 25, a nave 3 (shown in Fig.2), a first rotor 4 on one side of the rotor arrangement 2 and a second rotor 7 on the other side of the rotor arrangement 2. The first rotor 4 may be on top of the second rotor 7 as shown in Fig. 1 but it is also possible that the first and second rotors 4, 7 are side by side. Orientations of other parts of the double-action mill 1 naturally change according to the orientation of the rotor arrangement 2. The first rotor 4 comprises a first plane 5 and first rings 72, 74 provided with first blades 6 protruding from the first plane 5. The first plane 5 may be hor- izontally orientated. The blades 6 comprise surfaces that crush material to be pro- cessed. The first rotor 4 is arranged to rotate around the nave 3. The second rotor 7 comprises a second plane 8. The second plane 8 may be horizontally orientated. The second rotor 7 is coaxial with the first rotor 4 and comprises second rings 71, 73 provided with second blades 9 protruding from the second plane 8. The blades 9 comprise surfaces that crush material to be processed. The second rotor 7 is arranged to rotate around the nave 3 so that the first rings 72, 74 of the first rotor 4 and the second rings 71, 73 of the second rotor 7 inter- mesh. The second rotor 7 may rotate to the opposite direction in respect of the first rotor 4, or to the same direction. The rotor arrangement 2 comprises a feed opening 16 that begins from a frame 20 on the side 21 of the first rotor 4 and opens to the nave 3 of the rotor arrangement 2. The feed opening 16 may have a diameter of about 100 mm. The feed opening 16 is stationary. The rotor arrangement 2 also comprises a discharge opening 17. The discharge opening 17 may be a tangential opening on a circumference of the first and second rotors 4, 7. The double-action impact mill 1 also comprises a first actuator 10 for generating a driving force to the first rotor 4 and a second actuator 11 for generat- ing a driving force to the second rotor 7. The first and second actuators 10, 11 may be electric motors either directly or through a belt. The belt may be a cogged belt or a cone belt, preferably a cogged belt. There is a body tube 12 extending perpendicular to the second plane 8 on the side 13 of the second rotor 7. The body tube 12 may be supported by a sec- ond frame 22. There are a bearing 24 of the first drive shaft 14 and mechanical seals 23, 27 of the first drive shaft 14 inside the body tube 12. The mechanical seals 23, 27 have small diameters compared to known double-impact mills and therefore, sealing is easier. A first drive shaft 14 is between the first rotor 4 and the first actuator 10. The first drive shaft 14 may extend vertically. The first drive shaft 14 is bear- ing-mounted to the inside of the body tube 12. The first drive shaft 14 may have a diameter of 80 mm, for example. The first actuator 10 rotates a conic gear 18 that rotates a conic gear 28. The conic gear 28 rotates the first drive shaft 14. The conic gears 18, 28 form a pair of conic gears 38. A second drive shaft 15 is between the second rotor 7 and the frame 20. The second drive shaft 15 may extend vertically. The second drive shaft 15 is a hol- low axle that is bearing-mounted to the frame 20 by a bearing 26 and surrounds the feed opening 16. The second drive shaft 15 extends from the second rotor 7 perpendicular to the second plane 8. The second drive shaft 15 may have a greater diameter than the first drive shaft 14. The feed opening 16 passes the hollow sec- ond drive shaft 15. The second actuator 11 rotates a conic gear 19 that rotates a conic gear 29. The conic gear 29 rotates the second drive shaft 15. The conic gears 19, 29 form a pair of conic gears 38. Figure 2 shows a cross-sectional view of a rotor arrangement 2 that may be placed in the double-action impact mill 1. The rotor arrangement 2 comprises alternating first rings 72, 74, 78 and second rings 71, 73, 79, 81. The first rings be- long to a first rotor 4 and the second rings 71, 73, , 79, 81 belong to a second rotor 7. However, it is possible that the first and second rings are in a different order. It is also possible that at least one of the first rings 72, 74, 78 and/or at least one of the second rings 71, 73, , 79, 81 is/are rotated independently. The first rotor 4 may rotate to one direction and the second rotor 7 may rotate to the opposite direction in respect of the first rotor 4, or both rotors may rotate to the same direction. The first rings 72, 74, 78 comprise first blades 6 and the second rings 71, 73, 79, 81 comprise second blades 9. The first and second blades 6, 9 may be e.g. rectangular, as shown in Fig.2, or triangular. They may be spread radially but other orientations are also possible. The rotor arrangement further comprises a nave 3 and a dis- charge opening 17 that may be a tangential opening as shown in Fig.2. Figure 3 shows a double-action impact mill 1. The double-action impact mill comprises a rotor arrangement 2 comprising a housing 25, a nave 3, a first rotor 4 on one side of the rotor arrangement 2, a second rotor 7 on the other side of the rotor arrangement 2 and a third rotor 30 embracing the first rotor 4 and the second rotor 7. The first rotor 4 may be on top of the second rotor 7 as shown in Fig. 1 but it is also possible that the first and second rotors 4, 7 are side by side. Orientations of other parts of the double-action mill 1 naturally change according to the orientation of the rotor arrangement 2. The first rotor 4 comprises a first plane 5 and first rings 72, 74 provided with first blades 6 protruding from the first plane 5. The first plane 5 may be hor- izontally orientated. The first rotor 4 is arranged to rotate around the nave 3. The second rotor 7 comprises a second plane 8. The second plane 8 may be horizontally orientated. The second rotor 7 is coaxial with the first rotor 4 and comprises second rings 71, 73 provided with second blades 9 protruding from the second plane 8. The blades 9 comprise surfaces that crush material to be processed. The second rotor 7 may be arranged to rotate around the nave 3 to the opposite direction in respect of the first rotor 4 so that the first rings 72, 74 of the first rotor 4 and the second rings 71, 73 of the second rotor 7 intermesh. It is also possible that the rotors 4, 7 rotate to the same direction. The blades 6 of the first rotor 4 and the blades 9 of the second rotor 7 comprise surfaces that crush material to be pro- cessed. The third rotor 30 embraces the first rotor 4 and the second rotor 7. The rotor arrangement 2 comprises a feed opening 16 that begins from a first frame 20 on the side 21 of the first rotor 4 and opens to the nave 3 of the rotor arrangement 2. The rotor arrangement 2 also comprises a discharge opening 17. The discharge opening 17 may be a tangential opening on a circumference of the first and second rotors 4, 7 as shown in Fig.2. The double-action impact mill 1 also comprises a first actuator 10 for generating a driving force to the first rotor 4, a second actuator 11 for generating a driving force to the second rotor 7 and a third actuator 31 for generating a driving force to the third rotor 30. The first, second and third actuators 10, 11, 30 may be electric motors either directly or through a belt drive. There is an body tube 12 extending perpendicular to the second plane 8 on the side 13 of the second rotor 7. The body tube 12 may be supported by a frame 22. A first drive shaft 14 is between the first rotor 4 and the first actuator 10. The first drive shaft 14 may extend vertically. The first drive shaft 14 is bear- ing-mounted to the inside of the body tube 12. There are a bearing 24 of the first drive shaft 14 and mechanical seals 23, 27 of the first drive shaft 14 inside the body tube 12. A second drive shaft 15 is between the second rotor 7 and the first frame 20. The second drive shaft 15 may extend vertically. The second drive shaft 15 is a hollow axle that is bearing-mounted to the first frame 20 and surrounds the feed opening 16. There is a bearing of the second drive shaft 15. The second drive shaft 15 extends from the second rotor 7 perpendicular to the second plane 8. The third rotor 30 comprises a third ability 34 for receiving the driving force of the third actuator 31. The third ability 34 may be a geared surface, such as a geared conical surface that co-operates with a conic gear on a shaft of the third actuator 31. There are a bearing 32 of the third rotor 30 and a mechanical seal 33 of the third rotor 30. The third rotor 30 may rotate to the same or opposite direc- tion in respect of the first rotor 4 or the second rotor 7. Two rotors usually rotate to the same direction and one to the opposite direction. Figure 4 shows a double-action impact mill 1. The double-action impact mill 1 comprises a first actuator 10 for generating a driving force to the first rotor 4 and the second rotor 7. The first actuator 10 may be an electric motor either di- rectly or through a belt. The belt may be a cogged belt or a cone belt, preferably a cogged belt. A first drive shaft 14 is between the second rotor 7 and the first actua- tor 10. The first drive shaft 14 may extend vertically. The second rotor 7 comprises rings 71, 73. A second drive shaft 15 is between the first rotor 4 and the first actuator 10. The first rotor 4 comprises rings 72, 74. The second drive shaft 15 may extend vertically. The second drive shaft 15 is a hollow axle that surrounds the feed open- ing 16. The feed opening 16 passes the hollow second drive shaft 15. There are intermediate shafts between the shaft of the first actuator 10 and the first drive shaft 14 and there are also intermediate shafts between the shaft of the first actuator 10 and the second drive shaft 15. Fig. 4 shows three intermediate shafts, namely shafts 35, 36 and 37. Each shaft 35, 36, 37 are provided with abilities for receiving the driving force of the first actuator 10. The abilities may be a pair of conic gears 38. Arrows in Fig.4 show directions of rotation of the conic gears. The first actuator 10 rotates a conic gear 39 that rotates a conic gear 40. The conic gear 40 rotates the shaft 35 that rotates conic gears 41 and 45 arranged on the shaft 35. The shaft 35 may be vertical. The conic gear 41 rotates a conic gear 42 that in turn rotates the shaft 36 and a conic gear 18. The shaft 36 may be horizontal. The conic gear 18 rotates a conic gear 28 and the first drive shaft 14. The first drive shaft 14 rotates the second rings 71, 73 of the second rotor 7. The conic gear 45 rotates a conic gear 46. The conic gear 46 rotates the shaft 37. The shaft 37 may be horizontal. The conic gear 19 rotates a conic gear 29 and the second drive shaft 15. The second drive shaft 15 rotates the first rings 72, 74 of the first rotor 4. Fig. 4 shows a situation where the first drive shaft 14 and the second drive shaft 15 rotate to opposite directions. Fig.5 shows a double-impact mill 1 that is similar to that of Fig.4 but the first drive shaft 14 and the second drive shaft 15 rotate to the same direction. Figure 6 shows a double-action impact mill 1. The double-action impact mill 1 comprises a first actuator 10 for generating a driving force to the second rotor 7. The first actuator 10 may be an electric motor either directly or through a belt. The belt may be a cogged belt or a cone belt, preferably a cogged belt. The double-action impact mill comprises a second actuator 11 for gen- erating a driving force to the first rotor 4. The second actuator 11 may be an electric motor either directly or through a belt. The belt may be a cogged belt or a cone belt, preferably a cogged belt. A first drive shaft 14 is between the second rotor 7 and the first actua- tor 10. The first drive shaft 14 may extend vertically. A second drive shaft 15 is between the first rotor 4 and the second ac- tuator 11. The second drive shaft 15 may extend vertically. The second drive shaft 15 is a hollow axle that surrounds the feed opening 16. The second drive shaft 15 extends from the first rotor 4 perpendicular to the rotor arrangement 2. The sec- ond drive shaft 15 may have a greater diameter than the first drive shaft 14. The feed opening 16 passes the hollow second drive shaft 15. The shafts of the actuators 10, 11 and the first and second drive shafts 14, 15 are provided with abilities for receiving the driving force of the first actuator 10 and the second actuator 11. The abilities may be a pair of conic gears 38. Arrows in Fig.6 show directions of rotation of conic gears. The first ac- tuator 10 rotates a conic gear 18 which rotates a conic gear 28 arranged on the first drive shaft 14. The first drive shaft 14 rotates the rings 71, 73 of the second rotor 7. The second actuator 11 rotates a conic gear 19 which rotates a conic gear 29 arranged on the second drive shaft 15. The second drive shaft 15 rotates the rings 72, 74 of the first rotor 4. Fig.7 shows a double-impact mill 1 that is similar to that of Fig.6 except that the feed opening 16 is inside the first drive shaft 14, i.e. the double-impact mill 1 is fed underneath. Fig.8 shows a double-impact mill 1 that is similar to that of Fig.6 except that there are two feed openings 16, namely one feed opening 16 that passes the hollow second drive shaft 15 and one feed opening 16 that passes the hollow first drive shaft 14. Fig.9 shows a double-impact mill 1 that is similar to that of Fig.6 except that the first actuator 10 and the second actuator 11 are arranged differently. The first actuator 10 rotates the first drive shaft 14 that rotates rings 71, 73. The second actuator 11 rotates the second drive shaft 15 that rotates rings 72, 74. The second actuator 11 rotates a cylindrical gear 47 that rotates a cylindrical gear 48. The cy- lindrical gears form a pair of cylindrical gears 51. Fig. 10 shows a double-impact mill 1 that comprises three rotors, namely the first, second and third rotors 4, 7, 75. The first actuator 10 rotates a conical gear 18 that rotates conical gears 28, 54. The conical gear 28 rotates the first drive shaft 14 that rotates ring 71. The conical gear 54 rotates a third drive shaft 56 that rotates ring 73 of the third rotor 75. The second actuator 11 rotates a conical gear 19 that rotates a conical gear 29. The conical gear 29 rotates the second drive shaft 15 that rotates rings 72, 74 of the first rotor 4. The rings 71, 73 rotate to opposite directions. The speed and direction of rotation of the first rotor 4 is independent on the speed and direction of rotation of the rings 71, 73. The double-action impact mill 1 comprises a feed opening 16 through the second drive shaft 15. Fig.11 shows a double-action impact mill 1 that comprises three rotors, namely the first, second and third rotors 4, 7, 75. The first actuator 10 rotates a conical gear 18 that rotates a conical gear 28. The conical gear 28 rotates the first drive shaft 14 that rotates a ring 71 that belongs to the second rotor 7. The second actuator 11 rotates a conical gear 19 that rotates a conical gear 29. The conical gear 29 rotates the second drive shaft 15 that rotates the rings of the first rotor 4, e.g. rings 72 and 74. The third actuator 31 rotates a conical gear 63 that rotates a conical gear 60. The conical gear 60 rotates the third drive shaft 56 that rotates a ring 73 that belongs to the third rotor 75. Speeds and directions of rotation of the first, second and third actuators 10, 11, 56 are independent on each other. The feed opening 16 is through the sec- ond drive shaft 15. Fig.12 shows a double action impact mill 1 that comprises four rotors, namely the first, second, third and fourth rotors 4, 7, 75, 76. The first actuator 10 rotates a conical gear 18 that rotates a conical gear 28. The conical gear 28 rotates the first drive shaft 14 that rotates a ring 71 of the second rotor 7. The second actuator 11 rotates a conical gear 19 that rotates a conical gear 29. The conical gear 29 rotates the second drive shaft 15 that rotates a ring of the first rotor 4, e.g. ring 72. The third actuator 31 rotates a conical gear 63 that rotates a conical gear 60. The conical gear 60 rotates the third drive shaft 56 that rotates a ring 73 of the third rotor 75. The fourth actuator 64 rotates a conical gear 65 that rotates a conical gear 66. The conical gear 66 rotates the fourth drive shaft 67. The fourth drive shaft 67 rotates a ring 74 of the fourth actuator 64. Speeds and directions of rotation of the first, second, third and fourth actuators 10, 11, 56, 67 are independent from each other. The feed opening 16 is through the second drive shaft 15. Figs. 13 and 14 show a double-action impact mill 1 that is similar to that of Fig.6 except that the first and second rotors 4, 7 are not concentric but eccentric. Rings of the first rotor 4, i.e. rings 72 and 74, have been moved slightly so that they are not concentric with a nave 3. It is possible to move rings 71 and 73 as well. Fig. 13 shows one example how to arrange power transmission in connection with ec- centric rings but other layouts, which are shown in the figures above, are also pos- sible. Fig. 15 shows a double-action impact mill 1 that is fed through a feed opening 16 placed directly above a rotor arrangement 2. Thus, the double-action impact mill 1 of Fig.15 is not fed through any axle. Fig.15 shows one example how to arrange power transmission in connection with the feed opening 16 of Fig.15 but other layouts, which are shown in the figures above, are also possible. Fig.16 shows a double-action impact mill 1 where a rotor arrangement 2 discharges to a container 77. Fig.16 shows one example how to arrange power transmission in connection with the container 77 of Fig.16 but other layouts, which are shown in the figures above, are also possible. Fig.17 shows a double-action impact mill 1 that is similar to that of Fig. 6 except that the first rotor 4 has only one ring 72 and the second rotor 7 has only one ring 71. Fig.18 shows a double-action impact mill 1 that is similar to that of Fig. 12 except that the rotor arrangement 2 comprises more rings. The double action impact mill 1 that comprises four rotors, namely the first, second, third and fourth rotors 4, 7, 75, 76. The first actuator 10 rotates a conical gear 18 that rotates a con- ical gear 28. The conical gear 28 rotates the first drive shaft 14 that rotates a ring 71 of the second rotor 7. The second actuator 11 rotates a conical gear 19 that rotates a conical gear 29. The conical gear 29 rotates the second drive shaft 15 that rotates a ring of the first rotor 4, e.g. ring 72. The third actuator 31 rotates a conical gear 63 that rotates a conical gear 60. The conical gear 60 rotates the third drive shaft 56 that rotates rings 73, 79 of the third rotor 75. The fourth actuator 64 rotates a conical gear 65 that rotates a conical gear 66. The conical gear 66 rotates the fourth drive shaft 67. The fourth drive shaft 67 rotates rings 74, 78 of the fourth actuator 76. Speeds and directions of rotation of the first, second, third and fourth rotors 4,7, 75, 76 are independent from each other. The feed opening 16 is through the second drive shaft 15. Fig.19 shows a double-action impact mill 1 that is similar to that of Fig. 6 except that the feed opening 16 is from the side, i.e. the feed opening 16 is oblique. The double action impact mill 1 of Fig.19 is suitable for processing at very high speeds. The double-action impact mill 1 comprises a first actuator 10 for generating a driving force to a second rotor 7. The first actuator 10 may be an elec- tric motor that drives a first drive shaft 14. The double-action impact mill comprises a second actuator 11 for gen- erating a driving force to the first rotor 4. The second actuator 11 may be an electric motor that drives a second drive shaft 15. A first drive shaft 14 is solid, i.e. it is not hollow, and it is between the second rotor 7 and the first actuator 10. The first drive shaft 14 extends vertically. A second drive shaft 15 is solid, i.e. it is not hollow, and it is between the first rotor 4 and the second actuator 11. The second drive shaft 15 extends ver- tically. The second drive shaft 15 extends from the first rotor 4 perpendicular to the rotor arrangement 2. The shafts of the actuators 10, 11 and the first and second drive shafts 14, 15 are provided with abilities for receiving the driving force of the first actuator 10 and the second actuator 11. The abilities directly transmit the driving force from one shaft to another shaft. The abilities may be a pair of conic gears 38, or a similar pair of cylindrical gears 51 that are shown in Fig.9. The above-mentioned feature of Fig.9 may be applied in connection with the first and second drive shafts 14, 15, or only in connection with either of the drive shafts 14, 15. Possibilities to transmit driving forces, which can also be applied in con- nection with high speeds, are shown in Figs.4, 5, 6, 7, 8, 10, 11, 12, 13, 15, 16, 17, and 18 provided that the drive shafts 14, 15 are solid, i.e the feed opening 16 is not through one of the drive shafts 14, 15. In Fig.19, it is shown that the first actuator 10 rotates a conic gear 18 which rotates a conic gear 28 arranged on the first drive shaft 14. The first drive shaft 14 rotates the rings 71, 73 of the second rotor 7. The second actuator 11 ro- tates a conic gear 19 which rotates a conic gear 29 arranged on the second drive shaft 15. The second drive shaft 15 rotates the rings 72, 74 of the first rotor 4. Fig.20 shows a double-action impact mill 1 that is similar to that of Fig. 6 except that both rotors 4, 7 have only one ring 71, 72 and the feed opening 16 is a separate opening on the circumference of the rotor arrangement 2. An advantage of the double-action impact mill 1 of Fig.20 is that the circumferential speed may be higher. The double-action impact mill 1 of Fig. 20 is suitable for use at high speeds because drive shafts 14, 15 are solid, a feed opening 16 is outside the shafts and the driving forces are directly transmitted from one shaft to another shaft. The double-action impact mill 1 of Fig.20 may have more than one feed opening 16, and the feed openings may open from above and/or under of the rotor arrangement. Multiple materials may be fed so that each material may be fed through one feed opening in such a manner that they do not become mixed until in the rotor arrangement. It is also possible that gaseous materials, such as steam, is fed through at least one of the openings. Fig.21 shows a perspective view of the double-action impact mill 1 of Fig.20. Figure 22 shows a double-action impact mill 1. The double-action im- pact mill 1 comprises a first actuator 10 for generating a driving force to the second rotor 7. The first actuator 10 may be an electric motor that is directly driven. The double-action impact mill comprises a second actuator 11 for gen- erating a driving force to the first rotor 4. The second actuator 11 may be an electric motor that is directly driven. A first drive shaft 14 is between the second rotor 7 and the first actua- tor 10. The first drive shaft 14 may extend vertically. A second drive shaft 15 is between the first rotor 4 and the second ac- tuator 11. The second drive shaft 15 may extend vertically. The second drive shaft 15 extends from the first rotor 4 perpendicular to the rotor arrangement 2. The shafts of the actuators 10, 11 and the first and second drive shafts 14, 15 are provided with abilities for receiving the driving force of the first actuator 10 and the second actuator 11. The abilities may be a pair of conic gears 38. The first actuator 10 rotates a conic gear 18 which rotates a conic gear 28 arranged on the first drive shaft 14. The first drive shaft 14 rotates the rings 71, 73 of the second rotor 7. The second actuator 11 rotates a conic gear 19 which ro- tates a conic gear 29 arranged on the second drive shaft 15. The second drive shaft 15 rotates the ring 72 of the first rotor 4. The rotor arrangement 2 comprises a plane 5 of the first rotor 4. The plane 5 has a nave 3. The plane 5 is not solid but it is provided with openings 44. Radially extending bars 43 or alike may join the nave 3 and the ring 72 of the first rotor 4. Material may be fed through a feed opening 16 in such a manner that the material flows through the opening 44 / openings 44 in the plane 5 of the rotor 4 to the rotor arrangement 2. It will be obvious to a person skilled in the art that, as the technology advances, the inventive concept can be implemented in various ways. The inven- tion and its embodiments are not limited to the examples described above but may vary within the scope of the claims.

Claims

CLAIMS 1. A double-action impact mill (1) comprising - a rotor arrangement (2) that has a first side (21) and a second side (13) opposite to the first side (21), the rotor arrangement comprises at least one first ring (72, 74, 78) of the first side (21) of the rotor arrangement (2) and at least one second ring (71, 73, 79) of the second side (13) of the rotor arrangement (2), the first ring is provided with first blades (6) and the second ring is provided with second blades (9), the first ring and the second ring intermesh, - a first drive shaft (14) extending outwards from the second side (13) of the rotor arrangement (2), the first drive shaft (14) being in co-operation with at least one ring of the rotor arrangement (2), - a second drive shaft (15) extending outwards from the first side (21) of the rotor arrangement (2), the second drive shaft (15) being in co-operation with at least one other ring of the rotor arrangement (2), - at least one actuator that is in co-operation with at least one of the drive shafts (14, 15), - a feed opening (16), and - a discharge (17), wherein the rotor arrangement (2) is configured to be driven from op- posite sides (13, 21) of the rotor arrangement (2). 2. The double-action impact mill according to claim 1, characterized in that the rotor arrangement comprises at least two first rings (72, 74, 78) of the first side (21) of the rotor arrangement (2) and at least two second rings (71, 73, 79) of the second side (13) of the rotor arrangement (2), the first rings and the second rings intermesh in such a manner that every other ring is the first ring and every other ring is the second ring. 3. The double-action impact mill according to claim 2, characterized in that the first drive shaft (14), which is driven by a first actuator (10), is in co-oper- ation with the rings (72, 74) of the first side (21) of the rotor arrangement (2) and the second drive shaft (15), which is driven by a second actuator (11), is in co-op- eration with the rings (71, 73) of the second side (13) of the rotor arrangement (2). 4. The double-action impact mill according to claim 2, characterized in that the first drive shaft (14), which is driven by a first actuator (10), is in co- operation with the rings (71, 73) of the second side (13) of the rotor arrangement (2) and the second drive shaft (15), which is driven by the first actuator (10), is in co-operation with the rings (72, 74) of the first side (21) of the rotor arrangement (2). 5. The double-action impact mill according to claim 2, characterized in that the first drive shaft (14), which is driven by a first actuator (10), is in co-oper- ation with the rings (71, 73) of the second side (13) of the rotor arrangement (2) and the second drive shaft (15), which is driven by a second actuator (11), is in co- operation with the rings (72, 74) of the first side (21) of the rotor arrangement (2). 6. The double-action impact mill according to claim 2, characterized in that the first drive shaft (14), which is driven by a first actuator (10), is in co-oper- ation with one ring (71) of the second side (13) of the rotor arrangement (2); the second drive shaft (15), which is driven by a second actuator (11), is in co-opera- tion with the rings (72, 74) of the first side (21) of the rotor arrangement (2) and the third drive shaft (56), which is driven by the first actuator (10), is in co-opera- tion with one ring (73) on the second side (13) of the rotor arrangement (2). 7. The double-action impact mill according to claim 2, characterized in that the first drive shaft (14), which is driven by a first actuator (10), is in co-oper- ation with one ring (71) of the second side (13) of the rotor arrangement (2); the second drive shaft (15), which is driven by the second actuator (11), is in co-oper- ation with the rings (72, 74) of the first side (21) of the rotor arrangement (2) and a third drive shaft (56), which is driven by a third actuator (31), is in co-operation with one ring (73) of the second side (13) of the rotor arrangement (2). 8. The double-action impact mill according to claim 2, characterized in that the first drive shaft (14), which is driven by a first actuator (10), is in co-oper- ation with one ring (71) of the second side (13) of the rotor arrangement (2); the second drive shaft (15), which is driven by a second actuator (11), is in co-opera- tion with the one ring (72) of the first side (21) of the rotor arrangement (2); a third drive shaft (56), which is driven by a third actuator (31), is in co-operation with one ring (73) of the second side (13) of the rotor arrangement (2) and a fourth drive shaft (67), which is driven by a fourth actuator (64), is in co-operation with one ring (74) of the first side (21) of the rotor arrangement (2). 9. The double-action impact mill according to claim 8, characterized in that the third drive shaft (56) is in co-operation with more than one ring of the first side (21) of the rotor arrangement (2). 10. The double-action impact mill according to claim 8 or 9, character- ized in that the fourth drive shaft (67) is in co-operation with more than one ring of the second side (13) of the rotor arrangement (2). 11. The double-action impact mill according to any preceding claim, characterized in that the feed opening (16) extends through the first drive shaft (14) and/or the second drive shaft (15), or is a separate opening. 12. The double-action impact mill according to any preceding claim, characterized in that the rings (71, 72, 73, 74, 78, 79, 81) are concentric. 13. The double-action impact mill according to any preceding claim 1 to 11, characterized in that at least one of the rings (71, 72, 73, 74, 78, 79, 81) is eccentric. 14. The double-action impact mill according to any preceding claim, characterized in that the discharge (17) is a tangential opening at the circumfer- ence of the rotor arrangement (2). 15. The double-action impact mill according to any preceding claim 1 to 13, characterized in that the discharge (17) is through the circumference of the rotor arrangement (2) in such a manner that the rotor arrangement (2) is config- ured to discharge directly to a container (77). 16. The double action impact mill according to claim 1, characterized in that the first side (21) is a top side and the second side (13) is an underside. 17. The double action impact mill according to claim 1, characterized in that the double action impact mill comprises a first actuator (10) having a shaft and a second actuator (11) having a shaft. 18. The double action impact mill according to claim 17, characterized^ in that the shaft of the first actuator (10) is in direct contact with the first drive shaft (14) and the shaft of the second actuator (11) is in direct contact with the second drive shaft (15) through abilities on the shafts. 19. The double action impact mill according to claim 18, characterized in that the abilities are gears. 20. The double action impact mill according to claim 18 or 19, charac- terized in that the first and second drive shafts (14, 15) are solid. 21. The double action impact mill according to any preceding claim 16 – 20, characterized in that the feed opening (16) is outside the first and second drive shafts (14, 15).