Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B02—CRUSHING, PULVERISING, OR DISINTEGRATING; PREPARATORY TREATMENT OF GRAIN FOR MILLING
  • B02C—CRUSHING, PULVERISING, OR DISINTEGRATING IN GENERAL; MILLING GRAIN
  • B02C17/00—Disintegrating by tumbling mills, i.e. mills having a container charged with the material to be disintegrated with or without special disintegrating members such as pebbles or balls
  • B02C17/16—Mills in which a fixed container houses stirring means tumbling the charge
  • B02C17/161—Arrangements for separating milling media and ground material

Definitions

• the invention relates to an agitator mill with a grinding container and an agitator shaft rotatably arranged therein, which jointly delimit a grinding chamber, a grinding material inlet, a cage which rotates as part of the stirring shaft and is open at one end, and a separating device which is arranged in the cage, holds back unprocessed regrind and, if appropriate, grinding aid contained in the grinding chamber, but allows processed grinding material to flow out to a regrind outlet, the grinding chamber being subdivided into an inlet zone which adjoins the regrind inlet connects and at least a substantial part of its length is axially penetrated by the stirring shaft, and a separation zone which adjoins the inlet zone in the axial direction and is arranged around the cage.
• the separation zone extends over a maximum of 25% of the total length of the grinding chamber; at least 75% of this total length is taken up by the inlet zone.
• the separating device has an effective surface, the size of which is generally between 5% and 10% of the size of the inner surface of the grinding container delimiting the grinding chamber. Information The separating device considerably inhibits the discharge of the ground material from the grinding chamber. The velocity component of the regrind flow in the axial direction of the regrinding container is therefore comparatively low, and there is a high probability that each individual particle of the regrind will be comminuted to the desired size on the long way between the regrind inlet and the separating device.
• the throughput per unit of time is not too great for a given size of the known mill. This is particularly evident in cases in which a single pass of the grinding stock through the grinding chamber of an agitator mill is not sufficient to achieve the desired comminution, and it is therefore necessary to either pump the grinding material through the grinding chamber several times or pump it back and forth several times between a storage container and the grinding chamber.
• the invention is based on the object of significantly increasing the size reduction per unit time in an agitator mill and at the same time achieving a particularly uniform size reduction of the ground material.
• the problem is solved according to the invention starting from an agitator mill of the type described in the introduction in that the separation zone extends over 40% to 80% of the total length of the grinding chamber and the separation device has an effective area, the size of which is at least 20% of that the inner surface of the grinding container which bounds the grinding space.
• the effective area of the separating device is to be understood as that surface of the separating device which is provided with meshes or with annular gaps between separating rings. Due to the comparatively large length of the separation zone and the comparatively large effective area of the separation device, an agitator mill according to the invention is flowed through relatively quickly, so that for each individual regrind particle the likelihood of being adequately crushed in a single pass through the grinding chamber is low. Therefore, the individual particles of the material to be ground have to be conveyed through the grinding chamber on a statistical average much more frequently than in known generic agitator mills before they have undergone the desired comminution.
• the agitator mill according to the invention nevertheless has a significantly higher level Shredding performance is achievable than in known agitator mills of the generic type.
• the uniformity of the comminution is further increased. Because of the short average residence time of the individual regrind particles in the agitator mill, the risk that the regrind is damaged by overheating is generally lower than in the prior art.
• Each of the agitator mills shown has an essentially cylindrical grinding container 10, in which a stirring shaft 12 is mounted coaxially, as well as a grinding material inlet 14 and a separating device 16, to which a grinding material outlet 18 is connected.
• a grinding chamber 20 is formed between the grinding container 10 and the agitator shaft 12 each of the agitator mills shown includes an inlet zone 22 and a separation zone 24.
• the inlet zone 22 contains the regrind inlet 14 (FIGS. 1 and 7 to 11) or it adjoins this in the axial direction (FIGS. 2 to 6).
• the separation zone 24 follows the inlet zone 22 in the axial direction and is arranged around a cage 25 which is formed on the agitator shaft 12, is at least approximately cylindrical, encloses the separation device 16 and is open at one end at the end.
• the length of the separation zone 24 is the same as the length of the cage 25.
• the separating device 16 can be formed by individual separating rings or a mesh screen, is at least approximately cylindrical in all the examples shown and has an effective length which corresponds at least approximately to the length of the cage 25 and thus also to the length of the separating zone 24.
• the length of the separating device 16 measured in the axial direction of the agitator shaft 12 is approximately half (FIGS. 1 to 8, 10 and 11) to two thirds (FIG. 9) of the total length of the grinding chamber 20
• the active lateral surface of the separating device 16, which is decisive for the throughput, has an outer diameter which is only slightly smaller than the inner diameter of the cage 25.
• the product length by diameter of the active lateral surface of the separating device 16 is approximately 20% to 25% of the product length by diameter of the inner lateral surface of the grinding container 10.
• the agitator mills shown in FIGS. 1 to 5 and in FIG. 7 to 11 are arranged horizontally, that is to say with a horizontal agitator shaft 12; 6, on the other hand, a standing agitator mill is shown.
• the regrind inlet 14 is formed by bores in the agitator shaft 12. From the beginning to the end of the inlet zone 22, the agitator shaft 12 is slim; their outside diameter is about a quarter to a third of the inside diameter of the grinding container 10. Towards the end of the inlet zone 22, the outside diameter of the agitator shaft 12 steadily increases to about two thirds of the inside diameter of the grinding container 10; the agitator shaft 12 maintains this large diameter in the separation zone 24.
• the part of the agitator shaft 12 arranged in the inlet zone 22 carries agitator elements 26; 1, these are formed by long radial pins which extend up to close to the cylindrical inner wall of the grinding container 10.
• the cage 25 of the agitator shaft 12 arranged in the separation zone 24 likewise carries agitator elements 28 which, however, are formed by short radial pins.
• the grinding chamber 20 is, as indicated in FIG. 1, partially filled with regrind 30 and auxiliary grinding bodies 32.
• the cage 25 has slots 34 which are parallel to the axis and is open on its end face which faces the regrind outlet 18.
• the separating device 16 is formed by a cylindrical sieve which is arranged coaxially with the stirring shaft 12 and is fastened to the grinding container 10.
• a filling body 36 is arranged coaxially with it, which between it and the separating device 16 leaves a relatively narrow annular space 38, which widens towards the grinding material outlet 18.
• the ground material 30 mixed with grinding aids 32 flows from the inlet zone 22 through the separation zone 24 and passes through the open end face of the agitator shaft 12 into its cage 25.
• the grinding aids 32 are thrown outwards through the slots 34 and then repeat their cycle.
• the agitator mill according to FIG. 2 differs from that shown in FIG. 1 essentially in that the ground material inlet 14 is arranged on the end of the grinding container 10 and opens directly into the grinding chamber 20. Furthermore, counter elements 40 in the form of radial pins are fastened to the cylindrical inner wall of the grinding container 10 in the inlet zone 22 and extend between the stirring elements 26 to close to the stirring shaft 12.
• the agitator shaft 12 contains an axial coolant channel 42; This extends from the drive-side end of the agitator shaft 12 on the left in the drawings into the filler body 36 which, according to FIG. 2, is formed integrally with the agitator shaft 12 or is attached to it.
• the separating device 16 is again a cylindrical sieve according to FIG. 2, but, in contrast to FIG. 1, is not attached to the grinding container 10, but rather to the stirring shaft 12, so that the separating device 16 rotates together with the stirring shaft 12.
• the separating device 16 is, to the extent that it corresponds to FIG. 1, attached to the grinding container 10, but according to FIG. 3 it is formed by a ring arrangement with radial gaps arranged between the individual rings.
• the stirring shaft 12 is not provided with stirring elements in the separation zone 24; however, the ring 25 arranged around the separating device 16 ensures, because of its slots 34, that there is sufficient movement of the grinding material 30 and auxiliary grinding bodies 32 in the separation zone 24 for different types of grinding material.
• the embodiment according to FIG. 4 differs from that shown in FIG. 3 primarily in that in the inlet zone 22 on the grinding container 10 between the disk-shaped stirring elements 26, stationary counter-elements 40 are attached, which, as in FIG. 2, are formed by radial rods are. 4, the stirrer shaft 12 has a solid shaft core 44, on which the disk-shaped stirrer elements 26, a spacer sleeve 46 arranged between them and a hollow shaft part 48 carrying the cage 25 are attached.
• the outer contours of the agitator shaft 12 are the same as in FIG. 4 as in FIG. 3; However, the disk-shaped stirring element 26 on the left in FIG.
• the separating device 16 is designed as in FIGS. 3 and 4, but according to FIG. 5 it only has the task of retaining coarse regrind particles and only allowing processed regrind to reach the regrind outlet 18.
• the agitator shaft 12 is mounted in a floating manner in all of the examples shown; a bearing 52 and shaft seal 54 are therefore only, as indicated, arranged at one end of the grinding container 10. At this end or in the vicinity thereof, a drive of conventional design is coupled or can be coupled to the agitator shaft 12.
• the separating device 16 is arranged in each of the agitator mills shown in FIGS. 1 to 5 and in FIGS. 7 to 11 in the half of the grinding container 10 remote from the drive and bearing 52.
• the separating device 16 is arranged in the drive-side half of the grinding container 10 and is connected to the grinding material outlet 18 via a discharge chamber 56 which adjoins the shaft seal 54.
• the stirring elements 26 are accordingly attached to or in the vicinity of the free end of the stirring shaft 12.
• the agitator shaft 12 is slim only in the area of the bearing 52 and shaft seal 54 up to the beginning of the inlet zone 22; Here it has a diameter of the order of a quarter to a third of the inside diameter of the grinding container 10.
• a cone 58 belonging to the stirring shaft 12 begins at a short distance axially inside the shaft seal 54 and has a cone 58 with a complementarily conical inner end wall 60 of the grinding container 10 conical friction gap 62 limited.
• the area of the conical friction gap 64, near the shaft seal 54, opens the regrind inlet 14.
• a conical friction gap 64 of approximately the same width adjoins the conical friction gap 62 and extends to the end of the inlet zone 22.
• the ground material 30 is activated in the friction gaps 62 and 64 by friction between the walls of the grinding container 10 and the stirring shaft 12 that delimit these friction gaps.
• the agitator shaft 12 has an outer diameter that is somewhat smaller than the largest diameter of the cone 58.
• FIG. 8 agrees with FIG. 7 in that the outer diameter of the agitator shaft 12 increases greatly axially within the shaft seal 54 at a short distance.
• the stirring shaft 12 has an outer diameter which is approximately two thirds of the inner diameter of the grinding container 10.
• the stirring shaft 12 carries stirring elements 26 in the form of relatively short radial pins.
• Counter-elements 40 also in the form of short radial pins, but attached to the inner wall of the grinding container 10, are only present in the inlet zone 22; the entire separation zone 24 around the separation device 16 is free of such counter elements 40.
• the agitator mill according to FIG. 9 corresponds to that shown in FIG. 7 in the design of the cone 58 and the inner end wall 60 of the grinding container 10; thus a conical friction gap 62 and a cylindrical friction gap 64 are also present here.
• the cylindrical friction gap 64 is, however, much shorter since the cone 58 ends with a collar 66 which is narrow in the axial direction and immediately behind it, according to FIG. 9 on the right thereof, the cage 25 begins. the outside diameter of which is considerably smaller than that of the bundle 66.
• the length of the cage 25, and thus the separation zone 24, is approximately three quarters of the length of the grinding chamber 20.
• the cage 25 is covered with pin-shaped stirring elements 28, between which the Grinding container 10 fastened, likewise pin-shaped counter elements 40 project radially inwards.
• ground material 30 and auxiliary grinding body 32 are activated relatively strongly in the separation zone 24;
• the ⁇ o activated grinding auxiliary bodies 32 are, however, prevented with certainty by the collar 66 from reaching the area of the grinding material inlet 14. As a result, this is particularly well protected against wear.
• the cage 25 is divided into three regions which adjoin one another in the axial direction, namely a region 66 which begins near the open cage end and which has axially parallel, radially continuous slots 34, a closed central area 68, which is completely free of such slots, and an area 70 which is distant from the open end of the cage and in which radially continuous axially parallel slots 34 are provided.
• the closed central region 68 of the cage 25 is approximately half as long as the separation zone 24.
• the cage 25 is completely closed not only in its central region 68, but also in its region adjacent to the open end of the cage; radially continuous, axially parallel slots 34 or other openings, through which auxiliary grinding bodies 32 can emerge from the cage 25, are only arranged in the region 70 which is distant from the open end of the cage and which extends around the end region 72 of the separating device 16.
• the cage 25 shown in FIGS. 10 and 11 it is possible to improve the uniformity of the flow around the relatively long and large-area separating device 16 and thereby further increase the comminution rate per unit of time.
• Ground material 30 and auxiliary grinding body 32 are prevented from radially flowing through the cage 25 in its central region. There, only one of radial components can thus be essentially free. Flow take place. It has been found that precisely in this way blockages in the annular space 38 between the separating device 16 and the inner wall of the cage 25 are avoided and the efficiency of the separating device is largely used over its entire length under all usual operating conditions.

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• Engineering & Computer Science (AREA)
• Food Science & Technology (AREA)
• Crushing And Grinding (AREA)

Applications Claiming Priority (4)

Publications (1)

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ID=25875826

Family Applications (1)

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Cited By (6)

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Citations (3)

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• 1989
  • 1989-11-16 DE DE3938171A patent/DE3938171C1/de not_active Expired - Fee Related
  • 1989-12-04 EP EP89122340A patent/EP0376001B1/de not_active Expired - Lifetime
  • 1989-12-04 DE DE8989122340T patent/DE58904209D1/de not_active Expired - Lifetime
  • 1989-12-27 WO PCT/EP1989/001608 patent/WO1990007378A1/de unknown
  • 1989-12-27 JP JP2501624A patent/JP2680738B2/ja not_active Expired - Lifetime

Patent Citations (3)

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