Ball mill having spatial unbalance compensation

Abstract

A ball mill is provided comprising at least two milling cup retainers arranged on a machine base plate, each milling cup retainer being designed for a milling cup clamped in the milling cup retainer in a lying position, each milling cup having end-face milling cup ends and a filling of balls as milling bodies and comprising a drive that causes an out-of-phase rotational motion between the milling cup retainers.

Claims

1. A ball mill, comprising: at least two milling cup retainers arranged on a first side of a machine base plate, wherein each milling cup retainer is configured to clamp a milling cup in a lying or slanting position in a central area of each milling cup retainer, each milling cup having end-face milling cup ends and a filling of balls as milling bodies, and wherein each milling cup retainer is connected to separate eccentric shafts disposed on either side of an axis of symmetry of the central area of each milling cup retainer; a drive that causes a rotation of the separate eccentric shafts connected to each milling cup retainer and a rotational motion of each of the at least two milling cup retainers in respective guided rotational motions parallel to a plane coincident with the first side of the machine base plate, wherein a first milling cup retainer of the at least two milling cup retainers rotates along a first rotational path in a first phase and a second milling cup retainer of the at least two milling cup retainers rotates along a second rotational path in a second phase, and wherein the first and second phase are out-of-phase with and opposing one another; and a counterweight disposed on each of the separate eccentric shafts connected to each milling cup retainer on a portion of the separate eccentric shafts disposed on a second side of the machine base plate, wherein the second side of the machine base plate is disposed opposite the first side of the machine base plate, and wherein the separate eccentric shafts each pass through the machine base plate from the first side to the second side.

2. The ball mill of claim 1, wherein the at least two milling cup retainers include more than two milling cup retainers having respective separate eccentric shafts, the more than two milling cup retainers arranged in opposing rotational path pairs on the machine base plate.

3. The ball mill of claim 1, wherein each of the milling cup retainers in a pair of milling cup retainers having opposing rotational paths are disposed opposite one another along a longitudinal axis of the milling cup.

4. The ball mill of claim 1, wherein each of the milling cup retainers in the area of the two milling cup ends is connected to one eccentric shaft each.

5. The ball mill of claimed 1, wherein each of the milling cup retainers comprises a lower part configured to hold a milling cup in a flat or slanting position, wherein the lower part is connected to the separate eccentric shafts of a respective milling cup retainer, and wherein each milling cup retainer comprises an upper part hinged to the lower part and overlapping and clamping the milling cup in the central area.

6. The ball mill of claim 1, wherein the separate eccentric shafts each include a hollow shaft body configured to receive and conduct a cooling medium through and in each milling cup retainer via hollow spaces connected to the hollow shaft body and disposed in each milling cup retainer, and wherein a first eccentric shaft of the separate eccentric shafts is connected to a cooling medium inlet and a second eccentric shaft of the separate eccentric shafts is connected to a cooling medium outlet.

7. The ball mill of claim 6, wherein a hollow space is disposed in a lower part of each milling cup retainer in a connecting area surrounding ends of the separate eccentric shafts as well as in the central area forming a support for the clamped milling cup through which a cooling medium is conducted.

8. The ball mill of claim 7, wherein at least one hollow space is disposed in an upper part of each milling cup retainer, wherein the upper part overlaps the clamped milling cup at a central part of the upper part resting on the clamped milling cup, and wherein the at least one hollow space is connected to the hollow spaces of connecting areas of the lower part through which said cooling medium is to be conducted.

9. The ball mill of claim 1, wherein the counterweight can be re-adjusted according to a mass of the milling cup retainer and the milling cup clamped therein.

10. The ball mill of claim 1, wherein the milling cup ends of the milling cup are flat.

11. The ball mill of claim 1, wherein the milling cup ends of the milling cup are dome-shaped.

12. The ball mill of claim 1, wherein the separate eccentric shafts connected to each milling cup retainer are driven by a common drive element and wherein a compensation clearance is set on one of the separate eccentric shafts between the one of the separate eccentric shafts and the common drive element.

13. The ball mill of claim 12, wherein a toothed washer is disposed on an end of each of the separate eccentric shafts opposite the connected milling cup retainers, wherein the common drive element is a revolving toothed belt engaging with teeth of the toothed washer, and wherein a width of tooth spaces between the teeth of the toothed washer is greater than a width of teeth on the toothed belt.

14. The ball mill of claim 13, wherein all of the separate eccentric shafts of the milling cup retainers arranged on the machine base plate are driven by the common drive element and wherein the compensating clearance is set on only one of the separate eccentric shafts connected to a single milling cup retainer.

15. The ball mill of claim 1, wherein the first rotational path of the first milling cup retainer causes the first milling cup retainer to rotate in a first rotational direction, and wherein the second rotational path of the second milling cup retainer causes the second milling cup retainer to rotate in the first rotational direction.

Description

(1) The drawing illustrates an embodiment of the invention described below, wherein show:

(2) FIG. 1 a partial perspective view of a ball mill comprising two milling cup retainers,

(3) FIG. 2 a schematic lateral view of a milling cup retainer with a milling cup clamped in the same

(4) FIG. 3a-c a bottom view of the eccentric shafts assigned to the two milling cup retainers together with the drive medium

(5) The ball mill 10 shown in FIG. 1 as a whole comprises a housing 11 (not shown in full) on the upper side of which a machine base plate 12 is arranged for two milling cup retainers 13 to be installed, with one milling cup each clamped in the same. Each of the milling cup retainers 13 comprises a lower part 14 being provided two external connecting areas 16 with a central area 15 serving as bearing surface for a milling cup to be clamped. On one of the connecting areas 16 an upper part 17 overlapping the middle area 15 of the milling cup retainer 13 is swivel mounted around a swivel axis 18, arranged on the connecting area 16, wherein, within the context of the illustrated embodiment, the upper part 17 can be locked with the other connecting area 16 of the lower part 14 on the face opposite of the swivel axis 18 by means of a locking device 19 being operated by a locking lever 20. Alternatively a locking mechanism using a screw joint can also be employed, such as a clamping mechanism using screws and a suitable clamping bracket. The upper part 17 of the milling cup retainer 13 overlaps the middle area 15 of the lower part 14 too, forming a bearing surface for a milling cup retainer with a center section 22, wherein the shape of the middle area 15 of the lower part 14 as well as the center section 22 of the upper part 17 is adapted to the outer contour of the milling cup to be clamped in the milling cup retainer 13.

(6) In the housing 11 a motor 21 is provided, protruding upwardly above the machine base plate 12, which drives the two milling cup retainers 13 arranged on the machine base plate 12 by means of a drive mechanism provided below the machine base plate 12.

(7) As illustrated in FIGS. 1 and 2, two eccentric shafts 25 serve as drive for each of the two milling cup retainers 13, which in each case are connected to the two connecting areas 16 of each of the milling cup retainers 13, thus being joined to the same. Each eccentric shaft 25 comprises a drive section 26 located below the machine base plate 12 and a connecting section 27 projecting over the machine base plate 12 defined in the corresponding connecting area 16 of the milling cup retainer 13. The sections 26 and 27 of each of the eccentric shafts 25 are arranged offset to one another in order to provide the eccentricity, which in the illustrated embodiment is equal. For mounting the drive section 26 of the eccentric shafts 25, bearings 29 are provided below the machine base plate 12, while between the connecting sections 27 of the eccentric shaft 25 and the connecting areas 16 of the respective lower part 14, of each milling cup container 13 connected to the same, bearings 30 are arranged.

(8) Moreover, as illustrated in FIG. 2, a milling cup 23 is placed in the middle area 15 of the corresponding lower part 14 of a milling cup retainer 13 and clamped in the milling cup retainer 13 by means of the upper part 17 spanning the lower part 14 of the milling cup retainer 13.

(9) When the two drive sections 26 of the two eccentric shafts 25 having the same eccentricity are put in rotation by means of the driving mechanism driven by the motor 21, the milling cup 23 being clamped in the milling cup retainer 13 in a lying position moves on a circular path because the two external connecting areas 16, each connected to an eccentric shaft itself are moving on a circular path.

(10) In as far as two milling cup retainers 13 together with their respective milling cups 23 are arranged on the machine base plate 12, the directions of movement of the two milling cups 23 on their respective circular paths are oriented each in opposing directions of movement together with opposing phases of motion in such a manner, that, when the ball mill 10 is in operation, the centrifugal forces acting on the milling cup retainers 13 with their clamped milling cups 23 are compensated above the machine based plate 12.

(11) Since with this arrangement the centrifugal forces compensate each other on the plane, in which the milling cup retainers rotate, but the moments having alternating direction of rotation around a vertical axis remain on this plane, each of the eccentric shafts 25 is provided an additional counterweight 28 in the drive section 26 located below the machine plate 12 with the same being arranged on the face opposite the connecting area 16 of the milling cup retainer 13 located above the machine base plate 12 in relation to the longitudinal axis of the individual eccentric shafts 25. Thus, forces are balanced effectively on each of the eccentric shafts 25 during the circular movement of the milling cup retainer 13 connected to the same, which due to the fact, that two milling cup retainers 13 driven in counter rotation and phase opposition together with the connected eccentric shafts 25 are designed in the same manner, at the same time compensating the above described moment at the vertical axis on which the milling cup retainers 13 rotate as well as moments which are lying in this plane and which are initially caused by the centrifugal forces of the milling cup retainers 13 and the counter weights 28.

(12) In order to provide cooling to the milling cup 23 during operation of the ball mill, the two eccentric shafts 25 are designed having an inner boring 31 as hollow-bored shafts. Accordingly, the two connecting areas 16 facing each other as well as the middle area 15 of the lower part 14 connecting the same are provided hollow spaces 32 which by means of a sealing element 33 fixed at the upper end of each of the eccentric shafts 25 and a sealing surface 34 formed on the milling cup retainers 13 serving as counter sealing element of the sealing element 33 are connected to the borings 31 of the two eccentric shafts 25. In this manner a gaseous or liquid cooling medium introduced into one of the two eccentric shafts 25 can flow via the corresponding eccentric shaft 25 and hollow spaces 32 provided in the lower part 14 to the eccentric shaft 25 connected on the opposite side to the milling cup retainer 13 as well as be discharged from the same. Accordingly, in the illustrated embodiment a cooling medium inlet 36 is provided on the lower end of the left eccentric shaft 25 and a cooling medium outlet 37 is provided on the right eccentric shaft. By designing the middle area 22 of the upper part 17 of each milling cup retainer 13 as having a hollow space 35 and by connecting the same to the hollow spaces 32 of the bottom part 14 it is ensured, that the cooling medium being introduced into the bottom part 14 of the milling cup retainer flows also through the upper part 17 of each retainer. In this manner the milling cup 23 is enclosed by cooled components allowing the temperature inside the milling cup 23 to be restricted during the crushing process.

(13) FIG. 3a illustrates the driving concept according to the invention, wherein a revolving toothed belt 39 driven by a toothed lock washer 40 drives all four eccentric shafts 25 assigned to the milling cup retainers 13 as described in FIGS. 1 and 2. For this purpose, the toothed belt 39 wound around the lock washer 40 of the drive is guided over deflection rollers 42 and wound on the outside around the toothed washers 41 arranged on the ends of the eccentric shaft 25, with the teeth 43 of the toothed belt 39 engaging with the tooth gaps 44 of the toothed washers 41. In order to prevent the eccentric shafts 25 and the toothed belt 39 getting jammed during operation of the mill, a compensation play 38 is set on one of the two eccentric shafts 25 between the eccentric shafts 25 and the toothed belt 39. As illustrated in FIG. 3b, on one of the two toothed washers 41 the width of the tooth gap 44 is larger than the width of the teeth 45 of the toothed belt 39 resulting in the desired compensation play 38. On the other hand, as illustrated in FIG. 3c, the teeth 43 of the toothed belt 39 of the other eccentric shaft assigned to the same milling cup retainer 13 are completely engaged with the tooth gaps 44 of the corresponding toothed washer 41. The same configuration has also been realized for the two eccentric shafts 25 of the other milling cup retainer, which has not been illustrated here.

(14) The features, claims, summary and drawings, disclosed in the above description of the invention can be used individually or in any combination for realizing said invention.