DRUM MILL

Abstract: The invention relates to a method and an arrangement pertaining to rotary grinding mills (1) of the kind which include a rotatably mounted drum (3) having a first end-wall (5) and a second end-wall (6), a material infeed arrangement (30) and a drum rotating means (60). The material to be ground is introduced into the mill with the aid of an infeed device (31) which delivers material to the drum (3) in a region located between the drum rotating means (60) and the first end-wall (5) of the drum. Ground material is discharged from the mill (1) through a material outfed device (70) mounted adjacent the second end-wall (6) of the drum. The infeed device (31) may have the form of a vane impeller which is adapted to introduce the material into the drum (3) through the medium of mutually communicating openings (37, 12, 10) and through the medium of the first end-wall (5) of the drum. The drum rotating means (60) is suitably a hydraulic motor mounted adjacent the material infeed arragement (30).

Description: DRUM MILL The present invention pertains to a method relating to a rotary grinding mill, in accordance with the preamble of Claim 1. The invention also pertains to an arrangement for carrying out the method. In present-day rotary drum mills used to grind different types of materials, for instance different types of minerals, certain practical problems are encountered in arranging the delivery of material to be ground to the mill in combination, among other things, with the delivery of grinding bodies, for instance grinding rods. The material to be ground is normally introduced to the mill drum through a central opening in one end-wall of the drum, while ground material is normally discharged from the drum through a central opening in the other end-wall thereof. The material to be ground is normally introduced with the aid of a material infeed device in the form, e.g., of an impeller or like device mounted at the first end-wall/infeed end-wall of the drum, while the ground material is normally discharged from the drum with the aid of a so-called drum-tapping screen or some like separator mounted at the other end-wall/outfeed end-wall of the drum, said screen separating ground material from other material and grinding-rod debris, for instance. In some cases, the ground material is dis¬ charged through the outer peripheral surface of the drum, although it is still necessary to provide an opening in the second end-wall of the drum to enable grinding bodies, e.g. grinding rods, to be introduced into the mill. The aforesaid need for readily accessible openings in the two end-walls of the drum has hitherto necessitated the use of relatively complicated and expensive technical solutions, among other things with regard to the means by which the drum is rotated. These relatively complicated drum rotating means have, at times, required the use of relatively complicated and expensive drum bearings. The object of the present invention is to provide a method and an arrangement with which many of the aforesaid problems are solved in an effective arid efficient manner. This object is achieved with a method and an arrangement having the characteristic features set forth in the following method and apparatus Claims. Some of the advantages afforded by the invention are listed below. For instance, a maximum degree of choice is afforded with regard to the design of the arrangement used to discharge ground material from the drum, since the drum drive arrangement is integrated with the mill inlet and thus will have no disturbing influence on the discharge of material from the mill, irrespective of whether the material is discharged through the peripheral wall of the drum or through the opposite end-wall thereof. It is not necessary for the material discharge arrangement to transmit torque from a drive motor. Grinding bodies, such as grinding rods for instance, can be easily delivered to the mill. The invention eliminates the need for complicated speed-varying, rotary drive transmissions, while minimizing the space required by the mill at the same time. The invention also affords technical and economical advantages. The invention will now be described with reference to exemplifying embodiments thereof and also with reference to the accompanying drawings, in which Fig. 1 is a schematic, partly sectioned longitudinal view of a drum mill constructed in accordance with the invention; Fig. 2 is a schematic longitudinal sectional view of the driving arrangement and material infeed arrangement of the mill, said view being shown in larger scale than and from the opposite direction to the view shown in Fig. 1; and Fig. 3 is a schematic sectional view of the material infeed arrangement taken on the line III-III in Fig. 2. Shown in Fig. 1 is a drum mill 1 which includes a drum 3 which rotates on a generally horizontal shaft 2 and which encloses a grinding chamber 4. When necessary, the drum 3 is, of course, lined internally with rubber for instance, and provided with requisite lifters or like devices, even though this has not been shown in the drawings. The drum 3 has a first end-wall 5 and a second end-wall 6. In the illustrated embodiment, the first end- wall 5 functions as an infeed wall and accordingly includes a central opening 10 through which material is fed into the drum. The end-wall 5, or infeed end-wall, supports a first hollow tubular shaft or trunnion 11 whose centre bore 12 communicates with the material infeed opening 10. The tubular shaft 11 is journalled for rotation relative to a stand 7 or foundation surface by means of a first journal bearing 13, including, for instance, a roller bearing and carried by the stand 7. In the illustrated embodiment, the end-wall 6 functions as a material discharge end-wall and accordingly has a central opening 20 through which ground material is discharged. The end-wall 6, or material discharge end-wall, supports a second hollow tubular shaft or trunnion 21 whose centre bore 22 communicates with the material outfeed opening 20. The tubular shaft 21 is mounted for rotation relative to the frame 7 or foundation by means of a second journal bearing 23, which includes, for instance, a roller bearing and which is supported by the frame 7 or foundation surface. A material infeed arrangement 30 is mounted adjacent the infeed wall 5. The infeed arrangement 30 can be driven for rotation and includes a material infeed device 31 in the form of a so-called vane impeller having vanes or blades 32 ' which are curved forwardly in the intended direction of rotation and which are carried by a rear impeller wall 33 and independently by a respective front vane wall 34. The front edges of respective vane walls 34 are referenced 35 in Fig. 3 and the rear edge 36 of the vane wall coincides with the rear edges of the vanes 32. As a result of this construction, when the infeed arrangement 30 including the vane wheel or impeller 31 is driven in the intended direction A, the vanes 32 will function as scoops which scoop-up material that is fed into the co-rotating outer casing 40 of the infeed arrangement 30, this material being fed-in/advanced by virtue of the rotary movement of the impeller 31, through inlet openings 37 in the tubular hub 38 of the impeller and into the centre bore 12 of the tubular shaft 11, and from there through the infeed opening 10 and into the drum 3 for grinding. The hub 38 of the impeller wheel 31 is connected to the hollow-tubular shaft 11 so that the impeller 31 and the outer casing 40 will accompany the rotary movement of the drum 3 and the shaft 11. In the illustrated embodiment, the outer casing 40 is integral with the impeller 31 and, similar to the impeller, is fixedly carried by the shaft 11. The outer casing 40 has a conical inlet part 41 and a cylindrical mantle part 42, the shape and dimension of which are adapted for coaction with the impeller 31. Those parts of the outer casing 40 and the impeller 31 of the infeed arrangement 30 that are subjected to wear are conveniently covered with wear-resistant material, such as rubber, for instance. At its outer end remote from the drum 3, the impeller hub 38 supports a shaft end 50 fitted with an end plate 51 which blocks the outer end of the centre bore in the hub 38, so that material will enter through the openings 37 in the hub 38 and from there through the holes 12 and 10 and into the grinding chamber 4 of the mill 1. The drum 3, the material infeed arrangement 30 and the vane impeller 31 are rotated by means of a drive motor 60, which is • suitably encapsulated, wherein the rotor part 61 of the motor is fixedly connected to the shaft end 50, for instance by means of a suitable key or spline coupling. The stator 62 of the drive motor 60 is secured against rotation relative to the stand 7 or foundation, for instance by means of a locking arm 63 or like device. The material to be ground in the mill is delivered to the infeed arrangement 30 through the medium of a material delivery tube or chute 65 which discharges into the outer casing 40 of the arrangement 30, an imagined material level being indicated by the level line 66. In the illustrated embodiment, the mill 1 carries at its outfeed wall 6 a material discharge device, in the illustrated case a so- called rotary drum-tapping screen 70, which is attached to the tubular shaft 21 and which has a central opening 71 which communicates with the grinding chamber 4 through the openings 22 and 20. Ground material leaves the " grinding chamber through openings in the mantle surface 72 of the screen 70, while grinding body debris, for instance grinding rod debris, departs through a free end 73 of the screen 70. Naturally, the screen 70 may have any desired form, depending upon prevailing requirements. The illustrated drive device 60 will suitably have the form of a hydraulic motor, although other types of drive motors may also be used within the scope of the invention, for instance stepped-down electric motors. However, a hydraulic motor is extremely suitable, because of its excellent starting properties and its low speeds, which enable the motor to be connected directly to the shaft end 50 without requiring the provision of intermediate, speed-varying transmission elements. The function of the drum mill 1 will now be described in more detail. The drive motor 60 rotates the material infeed arrangement 30, including the vane impeller 31, the drum 3 and the material screening device 70, in the direction A. The material to be ground is delivered to the infeed arrangement 30 through the delivery tube 65, wherein as the vane impeller 31 rotates it feeds material into the drum 3 through the openings 37, 12 and 10, as indicated in broken flow arrows in Fig. 2. When wishing to feed grinding bodies, e.g. grinding rods for instance into the drum, it is necessary to stop rotation of the mill 1 temporarily, by temporarily stopping the drive motor 60, therewith enabling the grinding rods to be introduced into the drum 3 through the free end 73 of the screen 70 and through the openings 71, 22 and 20. The ground material leaves the mill 1 through the openings 20 and 22 and through openings in the mantle surface 72 of the screen 70. The construction solution afforded by the invention in which the drive motor 60 is mounted adjacent to or essentially within the material infeed arrangement 30 in a manner which will have no negative influence on the function of the infeed arrangement thus enables grinding bodies, e.g. grinding rods, to be introduced easily into the mill from the non-feed end of the mill 1, without having any disturbing influence on any form of drive arrangement mounted at said non-feed end. The inventive positioning of the drive motor also provides practically unlimited choice with regard to the position and design of the material discharge arrangement 70. The inventive positioning of the drive motor also provides a wide variation in choice with regard to the design and positioning of the journal bearings 13 and 23. For instance, it is conceivable to journal the drum 3 on external bearings, by supporting the drum on a group of rotatably journalled rollers serving as bearing means. Naturally, the design details of the material infeed arrangement 30 can be varied. One non-limiting example in this regard is that the impeller vane configuration 31 can be changed, as can also the configuration of the outer casing 40. It is also conceivable for the outer casing to be supported on a stand or foundation structure stationarily in relation to a rotating impeller. It is also conceivable to place the drive motor 60 externally of the outer casing 40, or at a greater distance from the vane impeller 31, for instance by extending the shaft end 50. Naturally, the direction in which the material delivery tube 65 connects tό ~ the infeed arrangement can also be changed when required or desirable. The invention is therefore not restricted to the illustrated and described exemplifying embodiments thereof, since changes and modifications can be made thereto within the scope of the following Claims.

Claims: CLAIMS 1. A method relating to a rotary grinding mill (1) of the kind which includes a rotatably journalled drum (3) having a first end-wall (5) and a second end-wall (6) , a material infeed arrangement (30) and a drum rotating drive means (60) , characterized by introducing the material to be ground into the mill with the aid of an infeed device (31) which delivers said material to the drum (3) in a region located between the drive means (60) and the first drum end-wall (5) . 2. A method according to Claim 1, characterized by discharging ground material from the mill (1) through an outfeed device (70) mounted adjacent the second drum end-wall (6) . 3. An arrangement relating to rotary grinding mills (1) of the kind which include a rotatably journalled drum (3) having a first end-wall (5) and a second end-wall (6) , a material infeed arrangement (30) and a drum rotating means (60) , characterized in that an infeed device (31) is adapted to feed material into the drum (3) through the medium of mutually communicating openings (37, 12, 10) and through the medium of the first end-wall (5) ; and in that the drive means (60) is mounted adjacent the material infeed arrangement (30) . 4. An arrangement according to Claim 3, characterized in that the first end-wall (5) of the drum (3) supports a first hollow shaft (11) which is mounted adjacent the infeed device (31) and the drum rotating means (60) . 5. An arrangement according to Claim 3 or Claim 4, characterized in that the second end-wall (6) of the drum (3) supports a second hollow shaft (21) which is mounted adjacent a material discharge device (70) . 6. An arrangement according to Claim 4 or Claim 5, characterized in that the drum rotating means (60) is a hydraulic motor whose rotor (61) is mounted on the first hollow shaft (11) . 7. An arrangement according to any one of Claims 4-6, characterized in that the drum rotating means (60) is mounted adjacent the first hollow shaft (11) in the absence of speed varying transmission elements. 8. An arrangement according to any one of Claims 5-7, characterized in that the drum (3) is mounted for rotation about its longitudinal axis (2) by means of a first journal bearing (13) which rotatably carries the first hollow shaft (11) , and by means of a second journal bearing (23) which rotatably carries the second hollow shaft (21) . 9. An arrangement according to any one of Claims 3-8, characterized in that the infeed device (31) is a vane impeller.

Inventors: HANSSON KURT, JEDBORN ALF, HANSSON, KURT, JEDBORN, ALF
Applicants: HANSSON KURT, JEDBORN ALF, PROING HANSSON & JEDBORN AB, HANSSON, KURT, JEDBORN, ALF
Application year: 1995
Main classification: B02C17
IPC codes: B02C17