Labor ball mill

Abstract

The invention relates to a laboratory ball mill, in particular a planetary or centrifugal ball mill on a laboratory scale with a two-point bearing of the grinding station, a cage for inserting and clamping the grinding vessel, an eccentric clamping mechanism for the grinding vessel and a motor drive for clamping and locking the cage.

Description

Field of invention

[0001] The invention relates to a laboratory ball mill, in particular a planetary or centrifugal ball mill on a laboratory scale.

[0002] Background and general description of the invention: Laboratory-scale ball mills are used for a wide range of applications, in particular for crushing and mixing samples and for mechanical alloying.

[0003] In planetary and centrifugal ball mills, grinding bowls are arranged eccentrically to a central axis and move in a circular path around this axis. The rotation of the grinding bowls exerts a radially outward centrifugal force on the material being ground. In a centrifugal ball mill, rotation of the grinding bowl about its own axis relative to the laboratory frame is prevented. In a planetary ball mill, an additional rotation about the grinding bowl axis within the laboratory frame generates a combined circular and rotary motion for the grinding bowl(s).

[0004] In a planetary ball mill, the drive of the grinding bowls causes an absolute rotation of the grinding bowl around its own axis, the receiving or planetary axis. This results in an additional centrifugal force component being generated in a planetary ball mill compared to a centrifugal ball mill. This centrifugal force component is superimposed on the centrifugal force component generated by the rotation of the grinding bowls around the central axis. Finally, the Coriolis force is also effective. These three forces combine to create a force field in the planetary ball mill, to which the grinding balls and the material being ground are subjected.

[0005] With specific dimensions of the rotating parts and specific rotational speeds, trajectories are generated for the grinding balls in a planetary ball mill. The grinding balls then move laterally through the grinding bowl until they strike its inner wall. Afterward, the grinding balls are carried along the inner circumference of the grinding bowl until the resulting force causes the lateral movement described above to occur again, and the grinding balls then perform a flying motion through the grinding bowl. This is also known as the "throwing regime." This allows a planetary ball mill to achieve high grinding performance at higher rotational speeds.

[0006] The forces arising from the rotational movements of the various components, especially in a planetary ball mill, can be relatively high, so that the maximum rotational speed is usually limited by design.

[0007] The applicant has been manufacturing corresponding planetary ball mills on a laboratory scale for decades. An early planetary ball mill of the applicant is known from utility model DE 1 836 885, which comprises planet carriers on which grinding vessels are attached with a clamping device.

[0008] Newer planetary ball mills are manufactured by the applicant under the trademark pulverisette® (series 4 to 7) and are described, for example, in DE 197 12 905, EP 1 945 364, DE 10 2006 047 481, EP 1 945 363, DE 10 2006 047 480, DE 10 2006 047 479, EP 1 933 984, EP 1 933 985, DE 10 2006 047 498, EP 2 010 329, EP 1 981 639 and DE 10 2010 044 254. An overview of the applicant's laboratory mills can also be found on its website at www.fritsch.de.

[0009] British document GB 730 494 proposes a ball mill with a rotating chamber that rotates around its own axis and simultaneously revolves around a stationary axis substantially parallel to its own axis. The distance between the two axes is less than the radius of the chamber. According to GB 730 494, the relatively closely spaced axes are intended to ensure that the load more or less lines the inner wall of the chamber, while a high rate of movement is achieved both relative to the inner wall surface of the chamber and within the chamber itself, through the relative movement of the components—that is, the material to be ground and the grinding balls. The balls are intended to perform a rolling, squeezing motion with respect to the material being ground. A throwing motion is not achievable.

[0010] Despite this limitation regarding the mechanical stress on the components, the mill's construction is complex. For example, the grinding bowl and its lid are attached by a construction using screws and a cross-braced arm.

[0011] Furthermore, a separate external structure mounted on a cylinder is provided to accommodate a roller bearing. This roller bearing surrounds the grinding vessel in the area where the arm cross and the actuating screws for securing the wedges and the lid of the grinding bowl are located, necessitating an extremely large roller bearing. Such a design appears unsuitable for the rotational speeds desired in modern laboratory ball mills. Moreover, inserting and removing the grinding vessel is cumbersome and complicated. Additionally, the clamping force depends on how tightly the user tightens the arm cross, which is a safety concern. Another disadvantage is that the arm cross, with its screws, protrudes upwards, posing a risk of injury to the operator when the mill is rotating.

[0012] From JP 2011-189226 A a platen ball mill with four vessel plates is known, wherein the vessels are arranged between a rotating table and upper support member.

[0013] From JP 2002172342 and JP 2002172343, a so-called vertical ball mill is known, designed for particularly large loads for cleaning contaminated soil. A load of at least 50 kg is mentioned. Furthermore, the upper bearing of the mill apparently has to be removed in order to lift the grinding vessel out of the device with a crane. Additionally, the lid is screwed to the grinding bowl. Both of these features are extremely cumbersome.

[0014] It is evident that the mills described in GB 730 494, JP 2002172342 and JP 2002172343 are not laboratory mills with the specific requirements for such mills, and that such designs cannot be readily transferred to a laboratory mill.

[0015] In laboratory ball mills, the grinding vessels are often inserted into an open-topped mounting device and clamped from above with a spindle. Here, too, the clamping force depends on how tightly the user tightens the spindle. The planetary carriers are mounted on a rotating disc, which can be driven around a central axis. This floating mounting results in high bending stress on the planetary carrier shaft, limiting the achievable grinding capacity. Furthermore, the grinding vessels are clamped using parts that are detached separately, located outside the machine, and then hooked into the respective holder by the user, which carries the risk of operator error.

[0016] EP 1 945 363 discloses a laboratory planetary ball mill with a two-point bearing arrangement in which the center of gravity of the grinding vessel is located between two bearing assemblies. In this design, an upper ball bearing surrounds a cup-shaped housing into which the grinding vessel is inserted axially from above and locked. However, this requires novel and complex grinding vessels with self-locking grinding cup lids and a very large upper bearing. Despite this, the resulting vibrations and forces are still so significant that high mechanical loads occur, which can be counteracted by additional transverse bracing of the grinding vessel, as described in DE 10 2010 044 254.

[0017] The inventors have now set themselves the goal of building a new laboratory ball mill, in particular a centrifugal or planetary ball mill, which can accommodate grinding vessels up to about 500 ml per grinding vessel and achieve an increase in performance compared to previous planetary ball mills with flying bearings.

[0018] The design described in EP 1 945 363 does not appear suitable for this application. While this laboratory planetary ball mill is technically very sophisticated and easy to operate, it is primarily applicable to relatively small grinding vessels on a laboratory scale, e.g., 80 ml. Even at this size, the large upper bearing results not only in high costs but also in increased friction and consequently significant heat dissipation. Increased heat dissipation is particularly undesirable at this point, as process heat dissipation is already difficult. Furthermore, the bearing seal is also problematic because it is very long due to the bearing size. In a planetary or centrifugal ball mill, the bearing not only rotates stationary but is also "flipped" around the central axis, which can force the bearing grease out.

[0019] For larger grinding vessels on a laboratory scale, i.e. typically 160 ml, 250 ml or even 500 ml, this method of holding and clamping the grinding vessels is met with considerable reservations among experts. General description of the invention

[0020] It is therefore an object of the invention to provide a laboratory ball mill, in particular a planetary or centrifugal ball mill on a laboratory scale, which can also be used for large grinding vessels on a laboratory scale, in particular with a size of 160 ml, 250 ml and / or 500 ml, and which enables a high grinding performance.

[0021] Another aspect of the task is to provide such a laboratory ball mill that is easy and efficient for the user to operate, in which, in particular, the insertion and removal of the grinding vessels is quick and convenient, and which nevertheless offers a high level of operational reliability.

[0022] Another aspect of the task is to provide such a laboratory ball mill in which the clamping of the grinding vessel is convenient and reliable and has a reproducible clamping force.

[0023] Another general aspect of the task is to provide a premium laboratory ball mill that meets the highest safety, performance and comfort requirements in many respects.

[0024] The object of the invention is achieved by the subject matter of the independent claims. Advantageous embodiments of the invention are defined in the dependent claims.

[0025] According to the invention, a laboratory-scale ball mill, in particular a planetary or centrifugal ball mill, is provided, in which a support device rotates about a vertical central axis. This orientation is sometimes referred to as a "vertical ball mill". One or more grinding stations or planetary stations are rotatably mounted on the support device about a planetary axis offset parallel to the central axis, wherein each grinding station has a receiving device for at least one grinding vessel that can be filled with material to be ground and grinding media, in particular grinding balls. The receiving device is carried by the support device about the central axis and additionally rotates – usually in the opposite direction to the support device – about the eccentrically mounted planetary axis.Planetary or centrifugal ball mills with only one grinding station, so-called planetary or centrifugal monoball mills, have a mass balancing device with a radially displaceable balancing mass, whereas planetary or centrifugal ball mills with several grinding stations are designed so that the grinding stations are arranged symmetrically around the central axis in order to balance the moments of inertia as well as possible, so that the planetary or centrifugal ball mill has a low imbalance.

[0026] Preferably, the carrier device is driven by a single electric drive motor, e.g. via a belt drive, and the grinding station is driven via a toothed belt drive coupled to the carrier device.

[0027] The support structure, the grinding station, the (belt) drives, and the drive motor are housed in a single unit to meet laboratory safety requirements. The unit has a lid that can be opened when the laboratory ball mill is at rest, allowing access to the grinding stations and the grinding vessels in their holders, i.e., enabling their insertion and removal.

[0028] The grinding vessels for laboratory ball mills consist primarily of a grinding bowl and a grinding bowl lid with a ring seal. The grinding bowl lid is simply clamped axially to the grinding bowl during the grinding process, making it particularly easy and efficient for the user. Furthermore, any excess pressure that often arises, especially during wet grinding processes, can escape safely.

[0029] According to the invention, the receiving device has a cage, in particular a rigid one, in which the grinding vessel is clamped by axial (vertical) clamping. The cage is designed in a plane in which the planetary axis lies, in particular as a rigid closed frame, and comprises at least a lower base section, an upper crossbar, and at least one side wall, which rigidly connects the upper crossbar to the lower base section. The side wall can, for example, be approximately half a cylindrical shell, or, as in the embodiment shown below, two side wall strips opposite the planetary axis are rigidly connected at the top and bottom, respectively, to the upper crossbar and the lower base section. The receiving device, or the cage thus formed, is permanently and rotatably attached to the support device, i.e.,The grinding vessel can be inserted into and removed from the cage when the cage is stored in the device housing on the support device, without the cage needing to be opened or even partially or completely removed.

[0030] The cage is rotatably mounted on the support structure at two axial points: a lower bearing at a first axial position below the lower base section and an upper bearing at a second axial position above the upper crossbar. For the grinding process, the user manually inserts the grinding vessel into the cage, which is thus axially mounted on both sides of the support structure between the lower and upper bearings, without removing the bearings. After grinding, the user manually removes the vessel by opening the housing cover.

[0031] Accordingly, the upper cross-bridge of the rigid cage for receiving the grinding vessel is rotatable with the upper bearing, but fixed to the support device, and remains there when inserting and removing the grinding vessel, i.e., it is not removed for inserting and removing the grinding vessel, which facilitates the insertion and removal of the grinding vessel.

[0032] On the other hand, during the grinding process, the entire grinding vessel, including the grinding bowl lid, as well as the frame-shaped part of the cage, are arranged axially completely between the two bearings, allowing the bearing to absorb high forces and thus enabling high maximum speeds.

[0033] The outer diameter of the grinding vessel can be larger than the inner diameter of the upper and / or lower (ball) bearing. Advantageously, relatively small ball bearings can thus be used on both sides as the upper and / or lower bearing, regardless of the diameter of the grinding vessel, particularly in comparison to EP 1 945 363.

[0034] These smaller ball bearings are more cost-effective and, considering the seal and rolling resistance, have acceptable coefficients of friction. This, in turn, advantageously results in a comparatively reduced heat output during the grinding process. Furthermore, the ball bearing seal is relatively small and can be hurled through the air at high speeds—approximately 800 to 1100 revolutions per minute, depending on the design—as occurs in planetary or centrifugal ball mills, without an unacceptable amount of grease being driven out of the bearing. Additionally, the heat output is reduced, particularly in the upper part of the grinding vessel, which is where the process heat to be dissipated is most pronounced. Despite this, the ball mill can still be designed for grinding vessels large on a laboratory scale.A laboratory ball mill, in particular a planetary or centrifugal ball mill on a laboratory scale, refers specifically to grinding vessels of up to 500 ml, possibly even up to 1000 ml. Large grinding vessels on a laboratory scale are specifically those of 160 ml to 500 ml, possibly even up to 1000 ml, or of 250 ml to 500 ml, possibly even up to 1000 ml.

[0035] Preferably, the distance between the central axis and the planetary axis is greater than the inner diameter of the grinding vessel, so that the geometric central axis runs outside the interior of the grinding vessel, which can be advantageous for achieving the throwing regime in a laboratory planetary ball mill.

[0036] The lower base section of the cage and the upper crossbar of the cage preferably have bearing journals formed in one piece, with the lower bearing journal of the lower base section extending downwards and the upper bearing journal of the upper crossbar extending upwards. The cage is rotatably mounted outside the cage in the upper and lower bearings by means of these upper and lower bearing journals. This achieves a particularly stable mounting of the cage for absorbing high forces.

[0037] The support device preferably comprises a lower support disc and a bridge structure mounted on the support disc, with the cage arranged axially between the bridge structure and the support disc. For this purpose, the lower bearing is permanently installed in the support disc and the upper bearing in the bridge structure and do not need to be removed for inserting and removing the grinding vessel. This also achieves stable bearing arrangements while minimizing the overall height of the rotating parts within the device housing, which is advantageous for a laboratory mill, as these are typically operated on a table.

[0038] Preferably, the lower base of the cage has a horizontal base plate from which the lower bearing journal extends downwards, so that the base plate and the lower bearing journal form a generally T-shaped cross-section. During the grinding process, the horizontal base plate of the cage rotates directly above the carrier disc, while the lower bearing journal projects axially into the carrier disc. This also keeps the overall height low and prevents the lower bearing from being visible or accessible.

[0039] Preferably, the lower base section is designed as a base tray, and the at least one side wall or side wall strips are rigidly attached to the base tray at their lower axial end and rigidly attached to the upper crossbeam at their upper axial end. This advantageously creates space within the base tray for additional components.

[0040] In particular, the cage has a lateral, i.e. radial, opening through which the grinding vessel can be inserted into and removed from the cage laterally or radially.

[0041] Preferably, the lateral opening for the grinding process is closed by a movable visor, and a back panel is preferably attached to the cage on the opposite side of its circumference. Thus, when the visor is closed, the grinding vessel is completely enclosed by the cage (top, bottom, and circumference), except for recesses. This increases the operational reliability of the ball mill, as the grinding vessel cannot leave the cage when the visor is closed, even if the clamping mechanism of the grinding vessel should loosen during the grinding process. The cage, including the back panel and visor, therefore has a generally cylindrical outline, with the opening occupying at least approximately half of the circumference to provide sufficient space for easy lateral insertion and removal of the grinding vessel.

[0042] The visor is conveniently mounted on the side of the cage so that it can be pivoted upwards to reveal the side opening, which is easy and convenient for the user.

[0043] Preferably, the upward pivoting movement of the visor is spring-loaded, so that the visor automatically pivots upwards when not locked. More preferably, the automatic upward pivoting of the visor is dampened by means of a rotary damper.

[0044] Preferably, the upper crossbeam is designed as a beam-shaped yoke, among other things to leave space in front of or behind the beam-shaped yoke for superstructures on the lid of the grinding vessel. The upper bearing pin extends upwards from the beam-shaped yoke. Furthermore, preferably, the pivoting sight is mounted on the two end faces of the beam-shaped yoke.

[0045] Preferably, the visor and / or the side walls and / or the rear wall have recesses so that air flows around the grinding vessel during rotation. Advantageously, this ensures that a certain degree of air cooling of the grinding vessel is maintained despite the cage being largely closed around it during the grinding process. This remaining air cooling is particularly advantageous because the laboratory ball mill according to the invention can be associated with high rotational speeds, high grinding capacity, and thus significant heat generation.

[0046] Furthermore, the receiving device preferably has a locking mechanism by which the sight is locked for the grinding process, and whose locking state is detected by a control device, so that the grinding process can only be started when the sight is locked. For example, the eccentric shaft described below has a locking tab which locks the sight when the eccentric shaft is rotated. This ensures a high level of operational reliability.

[0047] The grinding vessel is clamped axially within the rigid cage to secure it in the grinding station for the grinding process. If, as in this case, the clamping is sufficiently reliable, it offers the user a particularly simple, quick, and convenient way to secure the grinding vessel in the grinding station. For this purpose, a clamping element is arranged within the cage, which clamps the grinding vessel axially against the lower base or the upper crossbar of the cage. This clamping action secures the grinding container lid against the grinding container, creating a hermetically sealed seal, and simultaneously clamps the grinding vessel firmly, i.e., releasably, within the cage for the grinding process.

[0048] The cage is rigidly and stably designed to absorb the axial forces when the grinding vessel is axially clamped, ensuring that the clamping can withstand high rotational speeds and thus high radial forces. The rigid cage allows the grinding vessel to be held, clamped within the cage, and itself rotatably mounted in the rotary mechanism of the laboratory ball mill. A key advantage is that all clamping forces, in this case the axial forces, are absorbed within the cage and are not transmitted axially to either bearing. This also effectively prevents the other bearing (counter-bearing) from being subjected to a corresponding counterforce.

[0049] Furthermore, the axial position of the upper and lower bearings does not change when the grinding vessel is axially clamped. In particular, the bearings do not need to absorb any axial forces, as the cage or clamping cage absorbs the axial forces during clamping.

[0050] Axial clamping is achieved in particular by means of an eccentric shaft extending transversely to the planetary axis, which is rotatably mounted in the holding device. Compared to axial spindle clamping, this has the advantage that the clamping force is always constant, i.e., reproducible. For the force flow, it would be advantageous to align the yoke and the eccentric shaft parallel to each other. However, for design reasons, it is preferred here to align the eccentric shaft rotated 90° relative to the (clamping) yoke with respect to the planetary axis.

[0051] In summary, the invention generally involves the clamping element for axially clamping the grinding vessel, which is no longer removable from the laboratory ball mill by the user, but is permanently integrated into the holding device during normal operation. Furthermore, the clamping element is located in the holding device, particularly below the grinding vessel, and the grinding vessel is axially clamped from below against an upper stop of the holding device, which is formed by the upper crossbar of the rigid cage. This has the advantage of reducing the potential for incorrect operation and positioning the clamping element in the lower region of the support device. This allows the clamping element to be easily concealed from above while still remaining readily accessible for operation. Additionally, the clamping device has a low center of gravity, and the overall height of the grinding station or the holding device can be kept low.Furthermore, the risk of injury can be reduced compared to a tensioning system with a spindle located at the top.

[0052] Preferably, an axially displaceable clamping base is arranged in the base tray, and the eccentric shaft is positioned below the clamping base. The clamping base is then clamped upwards against the grinding vessel by the eccentric shaft by a predefined length, thus axially clamping the grinding vessel within the cage from below against the upper crossbar. Furthermore, the receiving device preferably includes a spring element that is tensioned when the grinding vessel is axially clamped. This has the advantage of generating a predefinable and therefore reproducible axial clamping force. Preferably, the eccentric shaft transmits the clamping force to the clamping base via needle bearings, which support the shaft between the lower base section and the clamping base.

[0053] Preferably, the clamping base is shaped like a trough and holds the bottom of the grinding vessel laterally in a form-fitting manner when the grinding vessel is clamped in the holding device, thereby creating an additional securing for the grinding vessel in the holding device, which is particularly advantageous in the desired combination of high rotational speeds and large grinding vessels on a laboratory scale.

[0054] Preferably, the grinding vessel sits directly on a pressure plate, and the spring element is designed as a disc spring, which is arranged between the pressure plate and the clamping base. This causes the clamping base to be moved axially upwards by the same displacement distance by the eccentric shaft with each clamping operation, thereby tensioning the disc spring. This, in turn, ensures that the disc spring exerts the same, i.e., reproducible, axial spring force on the pressure plate with each clamping operation.

[0055] According to a further preferred embodiment of the invention, the pressure plate has an upwardly extending locking pin which engages positively in a bore in the bottom of the grinding vessel, thereby creating a further securing mechanism for the grinding vessel in the receiving device, which is also particularly advantageous in the desired combination of high rotational speeds and large grinding vessels on a laboratory scale.

[0056] Preferably, the locking pin is drawn downwards into the pressure plate when the clamping element is relaxed and is moved towards the bottom of the grinding vessel by means of the eccentric shaft when clamping is activated. This ensures that the locking pin does not interfere with the lateral insertion of the grinding vessel when relaxed.

[0057] In this respect, the pressure plate has a bore through which the locking pin extends. The pressure plate and the locking pin can be moved axially independently of each other, with the pressure plate being axially tensioned by the disc spring and the locking pin being actuated directly by the eccentric shaft or the clamping base. This advantageously combines a reproducible friction-fit axial clamping of the grinding vessel with at least one positive locking element, so that the fastening of the grinding vessel is easy to handle and yet offers a high degree of operational reliability.

[0058] According to a particularly preferred embodiment of the invention, the ball mill comprises a motor drive for the clamping element, which automatically actuates the clamping of the grinding vessel in the receiving device. Advantageously, the ball mill can thus automatically clamp the grinding vessel, which is convenient for the user and also ensures a consistent and therefore reproducible clamping force for each clamping operation.

[0059] Preferably, the motor of the drive is fixed to the device housing, meaning it does not rotate with the support structure. A coupling device is included for actuating the clamping element, i.e., for tightening and releasing the clamping of the grinding vessel. When the laboratory ball mill is at rest, this coupling device engages the motor drive with the clamping element or the eccentric shaft at a specific rotational orientation of the grinding vessel, allowing the clamping element to be actuated from outside the support structure. This advantageously eliminates the need for electrical leads on the rotating support structure, and even in a mill with multiple grinding stations, only one motor is required.

[0060] In this regard, it is advantageous that the relative rotational speed ratio of the laboratory ball mill is an integer, in particular k = -2 or k = -3, where k is the relative rotational speed ratio. This ensures that the grinding station always occupies the same planetary orientation at a specific insertion and removal position of the support device. The insertion and removal position is preferably the rotational position of the support device in which the grinding station faces the user. In the insertion and removal position, the coupling device can thus connect the motor drive to the clamping element in order to clamp or release the grinding vessel.

[0061] The coupling device preferably comprises a positive-locking coupling in which the coupling parts of the motor drive and the eccentric shaft automatically engage positively when the grinding station is in the insertion and removal position. For this purpose, the positive-locking coupling is, for example, designed as a slot coupling in which a pin extending transversely to the eccentric shaft engages in a slot of a drive shaft extending coaxially to the eccentric shaft when the grinding station is in the insertion and removal position.

[0062] The locking tab, which secures the sight, is preferably attached to an end face of the eccentric shaft and is rotated upwards by the motor drive together with the eccentric shaft to engage in a slot in the sight. The combined actuation of the tensioning and locking mechanisms further increases the operational reliability of the ball mill.

[0063] The invention will now be explained in more detail with reference to exemplary embodiments and the figures, whereby identical and similar elements may be provided with the same reference numerals and the features of the exemplary embodiments may be combined with one another. Brief description of the characters

[0064] They show: Fig. 1 A three-dimensional view of a planetary monoball mill with the housing and sight open, Fig. 2 a three-dimensional view of the planetary monoball mill from Fig. 1 with closed visor and hidden device housing, Fig. 3 a three-dimensional view of the rotating parts of the planetary monoball mill Fig. 1, Fig. 4 a three-dimensional view of the rotating parts of the planetary monoball mill Fig. 1 with closed visor, Fig. 5 a cross-section through the rotating parts of the planetary monoball mill Fig. 3 with relaxed grinding vessel, Fig. 6 a cross-section through the rotating parts of the planetary monoball mill Fig. 4 with a jammed grinding vessel, Fig. 7 an enlarged section from Fig. 5 with relaxed grinding vessel, Fig. 8 an enlarged section from Fig. 6 with a clamped grinding vessel, Fig. 9 a three-dimensional representation of the grinding station with the visor open, Fig. 10 a three-dimensional representation of the grinding station with closed and locked visor, Fig. 11 a cross-section through the milling station along line 11-11 in Fig. 6, Fig. 12 a three-dimensional view of the rotating parts of a planetary ball mill with two grinding stations (planetary duo ball mill). Detailed description of the invention

[0065] Fig. Figure 1 shows a laboratory planetary monoball mill 1 according to the invention, comprising a housing 2. The housing 2 has a lid 4 that can be opened to access the inner grinding chamber 6 of the planetary ball mill 1, in which the support device 8 rotates. In this example, the lid 4 is designed as a rotating lid, but in a simpler embodiment, for example, a hinged lid can be used. In the Fig. In the planetary monoball mill 1 selected as an example, a single grinding station 10 with a grinding vessel 12 is mounted eccentrically rotatably on the support device 8. A mass balancing device 14 is mounted on the support device 8 opposite the grinding station 10 ( Fig. 2-6) arranged to compensate for the moment of inertia of the single grinding station 10.

[0066] The grinding station 10 has a receiving device 16 for receiving the grinding vessel 12 consisting of grinding cup 12a and grinding cup lid 12b. In the Fig. In the embodiment shown in Figures 1-11, the grinding vessel 12 has a capacity of 500 ml, which is already a relatively large grinding vessel for a laboratory planetary ball mill, and the support device 8 rotates at a maximum speed of approximately 800 revolutions per minute. These are relatively demanding requirements for a laboratory planetary ball mill. However, the invention can also be used for laboratory planetary ball mills with medium-sized grinding vessels, e.g., 250 ml or 160 ml, or even smaller grinding vessels.

[0067] Referring to Fig. Figure 12 shows the rotating parts of a symmetrically constructed planetary duo ball mill, wherein two grinding stations 10 are opposite each other with respect to the central axis 20, so that their moment of inertia is compensated. The present invention is therefore not limited to planetary mono ball mills ( Fig. 1-11) is limited, but is equally suitable for laboratory ball mills 1 with multiple grinding stations 10, e.g. two ( Fig. 12), four or any other number of grinding stations. The invention is described below using an example in the form of a planetary monoball mill 1 ( Fig. 1-11) explained, wherein the grinding stations 10 in laboratory ball mills 1 with several grinding stations 10 are identically designed.

[0068] Referring to the Fig. The support device 8 comprises two disc-shaped blocks 18 and 19, bolted together, in the form of a pulley 18 and a support disc 19. A drive motor 5 rotates the support device 8 about the central axis 20 via a V-belt 7 over the pulley 18, causing the grinding station 10 with the support disc 19 to rotate in a circular path around the central axis 20. A toothed belt drive 22, coupled to the belt drive of the pulley 18, additionally drives the self-rotation of the grinding station 10 about the planetary axis 24, which is mounted eccentrically to the central axis 20, so that the grinding station 10 rotates about the central or sun axis 20 and simultaneously also about its own planetary axis 24. In this embodiment of a planetary ball mill, the two directions of rotation are opposite.

[0069] The central axis 20 is rigidly attached to the housing base plate 32. The support device 8 is rotatably mounted on the stationary central axis 20, which is designed as a bearing journal, by means of two ball bearings 28, 30.

[0070] The coupled belt drive 22 comprises a first toothed belt pulley 26, which is mounted between the two ball bearings 28, 30 on the central axis 20, and a second toothed belt pulley 27, by means of which the self-rotation of the grinding station 10 about the planetary axis 24 is driven via a toothed belt 31. The speed ratio of the self-rotation of the grinding station 10 about the planetary axis 24 relative to the rotation about the central axis 20 (so-called relative speed ratio k) is an integer. In the present planetary monoball mill, k = -2; in planetary multiball mills with several grinding stations, k = -3 can be advantageous. Due to the integer speed ratio k, the grinding station 10 is always in the same orientation at the front loading and unloading position, which is advantageous in the Fig. The position shown in 1-6 is under the (open) rotating housing cover 4.

[0071] How best to in the Fig. As shown in Figures 9-11, the receiving device 16 comprises a rigid cage 34, which consists of a lower base section 36, an upper cross-bridge designed as a yoke 38, and two side walls 40. The elongated, strip-shaped side walls 40 are attached at their respective upper ends 40a to the end faces 38a, 38b of the yoke 38, in this example by welding. The side walls 40 are also firmly connected at their lower ends 40b to the lower base section 36, in this example by welding, so that the cage 34 forms a rigid frame, in this example substantially rectangular in cross-section, which has a cross-section of Fig. 11 The grinding vessel 12 is completely enclosed on both lateral sides as well as top and bottom, i.e., viewed from the side, in a ring-like manner. The rigid cage 34 serves on the one hand to receive the grinding vessel, but on the other hand also to absorb the clamping forces when the grinding vessel 12 is clamped in the rigid cage 34.

[0072] The lower base section 36 and the yoke 38 each have a bearing journal 42, 44, which extends in opposite directions, i.e., downwards and upwards respectively, coaxially to the planetary axis 24. The downwardly and upwardly extending bearing journals 42, 44 are integrally formed with the lower base section 36 and the yoke 38, respectively. The grinding station 10 is rotatably mounted on the support device 8 about the planetary axis 24 by means of ball bearings 46, 48 on the bearing journals 42, 44. This means that the receiving device 16, or the cage 34, is mounted at two axial positions, both of which are axially opposite and located completely outside the grinding vessel 12 or even outside the cage 34. The rigid cage 34 for clamping the grinding vessel 12 is therefore mounted between the two ball bearings 46, 48. This two-point mounting above and below the grinding vessel 12 orThe rigid cage 34 effectively absorbs the forces occurring during the grinding process, yet relatively small standard ball bearings can be used for both bearings 46 and 48, since the diameter of the bearing journals 42 and 44 is considerably smaller than that of the grinding vessel 12. Thus, the inner diameters of the ball bearings 46 and 48 are smaller than the outer diameter of the grinding vessel 12. As will be explained in more detail below, the grinding vessel 12 is no longer inserted into the grinding station 10 from above, as in previous laboratory ball mills, but radially to the planetary axis 24, i.e., from the side. Therefore, the cage 34 can be designed as a rigid cage, and the yoke 38 of the cage 34 is not removed by the user for inserting and removing the grinding vessel 12, but rather is a fixed component of the rigid cage 34 that cannot be detached by the user during normal operation.

[0073] Referring to Fig. In figures 5-8, the lower bearing 46 is mounted in the support disc 19 and the upper bearing 48 in a bridge structure 50, the bridge structure 50 being rigidly connected to the support disc 19. In other words, the cage 34 with the grinding vessel 12 is rotatably mounted at the top of the bridge structure 50 and at the bottom of the support disc 19. Due to the relatively large axial distance between the two bearings 46 and 48, with the grinding vessel 12 positioned entirely between them, very high centrifugal forces can be absorbed. Nevertheless, neither the yoke 38 nor the upper bearing 48 needs to be removed to remove or insert the grinding vessel 12.

[0074] The lower bearing journal 42 has a projection 52 with a slightly reduced diameter below the lower bearing 46. This projection extends further downwards, and the toothed belt pulley 27 is attached to this projection to drive the grinding station 10 rotationally around the planetary axis 24. Thus, the lower base section 36, together with the integral bearing journal 42, forms a T-shape in cross-section. The bearing journal 42 extends through the carrier disc 19, both to be supported in the carrier disc 19 by means of the lower bearing 46 and so that the projection 52 with the toothed belt pulley 27 protrudes downwards from the carrier disc 19 to drive the toothed belt 22 below the carrier disc 19.

[0075] Referring again to Fig. 9-10 The cage 34 has a visor 56 by means of which a lateral opening 54 of the cage can be closed. When the visor 56 is open, the grinding cup 12 can be removed and inserted transversely to the planetary axis 24, i.e. horizontally through the opening 54. For this purpose, the visor 56 is rotatably mounted on the end faces 38a, 38b of the yoke 38 or there on the outside of the side cheeks 40, so that the visor 56 can be pivoted upwards to release the lateral opening 54 ( Fig. 9). For the grinding process, the visor 56 is closed ( Fig. 10), so that the cage 34 together with the closed visor 56 and a back wall 58 forms a protective cage enclosed circularly around the planetary axis 24, so that the grinding vessel 12 cannot fly out of the grinding station 10, even if the tension should loosen or even come loose.

[0076] Referring again to Fig. 11. The bearing and fastening elements 60a, 60b, by means of which the sight 56 ​​is rotatably mounted on the end faces 38a, 38b of the yoke 38, serve not only for bearing but also for the automatic, spring-loaded, damped opening of the sight 56. In the illustrated example, a rotary spring 92 is installed in an end-face bore of the yoke 38 on the right bearing and fastening element 60a, which automatically pushes the sight open by spring force, and a rotary damper 93 is installed in an end-face bore of the yoke 38 on the left bearing and fastening element 60b, which dampens the sight movement when opening.

[0077] Referring again to the Fig. 7-8 The grinding vessel is clamped from below against the grinding bowl base 12c by an eccentric shaft 62. The eccentric shaft 62 is mounted in a transverse bore in a downwardly extending pin 71 of a clamping base 70. The pin 71 engages in a corresponding coaxial bore 43 in the bearing pin 42 of the lower base part 36.

[0078] The eccentric shaft 62 is further supported against the clamping base 70 by two needle bearings 64, the needles 66 of the bearings 64 running on the eccentric shaft 62, while the outer ring 68 of the bearings 64 rests against the underside of the clamping base 70 and is moved back and forth against it during the stroke. The eccentric shaft 62 thus transmits the axial height change to the clamping base 70 via the two needle bearings 64, which are designed for a load of 20 kN.

[0079] The clamping base 70 is positioned above the lower base section 36, which does not preclude the edge 37 of the lower base section 36 from extending beyond the clamping base 70. The lower base section 36 is even specifically designed as a base tray, which also laterally supports the clamping base 70. The clamping base 70, also called a spring lifter, raises a pressure plate 74 in the form of a pressure disc by means of a spring assembly, which in this example comprises two disc springs 72. The use of one or more disc springs 72 has proven advantageous, as disc springs are well-suited to the requirements given here with regard to spring stiffness and the available installation space. In this example, two identical disc springs stacked in opposite directions are used to double the travel distance while maintaining the same clamping force. This allows for better handling of length tolerances, so that they have virtually no effect on tension differences.

[0080] The pressure plate 74, in turn, lifts the inserted grinding vessel 12 first against the pressure yoke 38, which acts as a stop for the grinding vessel lid 12b, until all axial gaps in the system are eliminated. During further clamping, the seal 76 between the grinding vessel 12a and the grinding vessel lid 12b is compressed. Once this seal is compressed to a rigid height stop, the clamping base compresses the disc spring 72 over the remaining clamping travel of the eccentric shaft 62 to generate the actual axial clamping force for the grinding vessel in the rigid cage 34. This clamping force is reproducible due to the reproducible axial travel by means of the eccentric shaft 62, i.e., it is identical for each clamping operation.

[0081] In general, the bearing journals 42, 44 which run coaxially to the planetary axis 24, as well as the clamping element, in this example the eccentric shaft 62, are integrated on or in the rigid cage 34.

[0082] In this example, the eccentric shaft 62 has an eccentricity of approximately 1.5 mm. The eccentric shaft 62 is rotated approximately 180° and extended beyond its pivot point to create self-locking in the clamped state. Thus, the clamping assembly has a clamping travel of approximately 3 mm, which is transferred to the clamping base 70. Of this, approximately 0.5 mm is provided as a system gap to allow for easy insertion and removal of the grinding vessel. The seal 76 requires approximately 0.3 to 0.4 mm of clamping travel to be compressed. Therefore, the remaining approximately 2 mm of clamping travel is available for clamping the grinding vessel via the disc spring 72.

[0083] The clamping base 70 is trough-shaped and houses the disc spring 72 and the pressure plate 74 within its interior. In the fully clamped state, the rim 77 of the clamping base 70 projects axially upwards slightly beyond the base of the grinding vessel 12, thus creating an additional positive fit with the base 12c of the grinding vessel 12. In other words, in the clamped state, the rim 77 of the clamping base 70 slightly engages the base 12c of the grinding vessel 12 on its underside. Furthermore, the eccentric shaft 62 moves a coaxial locking pin 78, which engages positively in a bore 80 in the base 12c of the grinding vessel 12 and additionally centers the grinding vessel 12 in the receiving device 16. A radially shallow groove 82, which opens centrally into the bore 80, guides the grinding vessel 12 during lateral insertion and removal.

[0084] The grinding vessel 12 is therefore secured in the rigid cage 34 by two positive locking mechanisms 12c, 77 and 78, 80 in addition to the clamping force, so that the grinding vessel cannot be removed from this position even if there were no axial clamping force sufficient for a radial frictional locking mechanism.

[0085] Referring again to the Fig. 5-8 The clamping of the grinding vessel 12 in the rigid cage 34 is motorized. For this purpose, the ball mill 1 has a motor 84, which is fixedly attached to the device housing 2 outside the support device 8. The motor 84 drives a drive shaft 86, which is slotted 88 at its inner end in order to be able to couple to a transverse pin 90 attached transversely to the eccentric shaft 62 when the grinding station is in the Fig. The insertion and removal positions shown in Figures 1-6 and the correct rotational orientation are crucial. This can be described as a slotted coupling or a coupling consisting of a claw 88 and a blade 90. The eccentric shaft 62 can then be rotated via the motor 84 to automatically clamp the grinding vessel axially or to automatically release the clamping force.

[0086] This design has the advantage that only a single motor 84 is required, even if the ball mill 1 has several grinding stations 10. The motor 84 is a standard geared motor from Bosch and generates a torque of 30 Nm at the drive shaft 86 and thus on the eccentric shaft 62. With the clamping mechanism shown, an axial clamping force of approximately 12 kN can be achieved.

[0087] The described design has the further advantage that the force generated when the clamping mechanism is released does not have to be absorbed by the user, but is automatically absorbed by the clamping motor 84.

[0088] In addition to the axial clamping and the positive locking mechanisms that secure the grinding vessel in the rigid cage, the rigid cage also features the sight 56 ​​and the rear wall 58 as a further securing element, so that the cage 34 is circularly enclosed around the planetary axis 24 when the sight 56 ​​is closed. The cage 34 thus fulfills a dual function: firstly, to absorb the axial clamping force, and secondly, to completely enclose the grinding vessel 12 when the sight 56 ​​is closed (including circular enclosure). However, the sight 56 ​​and the rear wall 58 have recesses 56a and 58a, respectively, to ensure sufficient air cooling of the grinding vessel 12.

[0089] To make the ball mill 1 even more convenient to use, the clamping mechanism is automatically triggered by the sight 56 ​​as follows. With the sight 56 ​​open, the user inserts the grinding vessel 12 into the cage 34 from the side and closes the sight 56 ​​manually by pivoting it downwards. This tensions the rotary spring 92, which is mounted in the yoke 38 on the sight bearing 60a. The position of the closed sight 56 ​​is automatically detected by the ball mill 1, and a control unit 94, in response to the closed sight 56, activates the geared motor 84 to rotate the eccentric shaft 62 and clamp the grinding vessel 12 in the cage 34. Simultaneously, a locking tab 96, attached to the motor-side end face 62a of the eccentric shaft 62, is rotated upwards ( Fig. 4, Fig. 6, Fig. 8, Fig. 10) and engages in a groove 98 in the sight 56 ​​to lock it. The locking mechanism automatically releases the rotation of the grinding station 10 on the carrier device 8.

[0090] How best to Fig. As can be seen in Figure 3, the locking tab 96 locks the grinding station 10 against rotation relative to the carrier device 8 in the lower rotational position, in which the sight 56 ​​is not locked, thereby locking the entire rotary mechanism due to the coupled drives 7, 19 and 22.

[0091] Once the visor 56 is locked, it can be released by the user. The housing cover 4 then closes at the user's request via the control panel 100, and the grinding process begins.

[0092] The clamping mechanism with the eccentric shaft 62 is further designed such that the sight 56 ​​opens automatically when the locking tab 96 releases the locking mechanism.

[0093] After the grinding process, the carrier device 8 automatically moves the grinding station 10 into the insertion and removal position and locks the rotary mechanism there. Furthermore, the ball mill 1 automatically opens the housing cover 4 after the grinding process. Depending on the user setting, the cover either remains locked initially or opens automatically immediately. Three control programs are available for this: a) Stop-End-Open, i.e. everything is stopped, the mechanism locks and the cup holder immediately releases automatically. b) Stop-end-allow, i.e. everything is stopped, the mechanism is locked, but the sight 56 ​​remains locked so that the grinding vessel 12 remains under tension, which is particularly useful if the grinding vessel needs to cool down first, for example to counteract the so-called "spitting". c) Stop-End-Careful Up, i.e., as in a), but to minimize any spitting, the clamping of the grinding vessel is opened very slowly. The rotary damper 93 on the sight pivot bearing 60b further dampens the upward pivoting movement of the sight 56 ​​caused by the rotary spring 92 on the sight pivot bearing 60a, so that it also pivots slowly upwards.

[0094] In this example, the eccentric shaft 62 is rotated by 180° between the relaxed position (locking tab 96 down) and the tensioned position (locking tab 96 up), which has the advantage that the locking tab 96 can be used in a simple way both to lock the sight 56 ​​and to lock the rotation of the grinding station 10 on the support device 8.

[0095] Referring to Fig. In section 11, the eccentric shaft 62 and the beam-shaped yoke 38 are rotated by 90° with respect to the planetary axis 24. This allows the sight 56 ​​to be mounted on the yoke 38 and to pivot forward in the insertion and removal position, since in this position the yoke runs transversely relative to the user and the eccentric shaft points towards the user, who is standing in front of the ball mill 1. In other words, in the insertion and removal position, the yoke 38 runs transversely to the central axis 20, whereas the eccentric shaft 62 runs radially to the central axis 20. This allows the geared motor 84, located in the front area of ​​the ball mill 1, to engage with the eccentric shaft 62 in the insertion and removal position. Fig. 5-6).

[0096] Because the motor 84 does not rotate with the carrier device 8, even in a multi-station ball mill, e.g., with two, four, or more grinding stations 10, each grinding station can be operated in the insertion and removal position by one and the same geared motor 84. For this purpose, the ball mill 1 electronically rotates the desired grinding station into the front insertion and removal position upon a corresponding input from the user at the control panel 100.

[0097] A sunshade 102, which rotates with the carrier device 8, is rigidly connected to the carrier disc 19. The sunshade 102 is located approximately at the level of the grinding bowl base 12c and thus optically covers the lower part of the grinding station 10, in particular the eccentric shaft 62, the slotted coupling 88, 90, and the geared motor 84. The sight 56 ​​is flush with the sunshade 102, and the grinding station has a planetary cover 106 that is also horizontally flush with the sunshade 102 and rotates with the grinding station 10 around the planetary axis 24 in an opening 104 of the sunshade 102. The planetary cover 106 has a slot 108 through which the locking tab extends upwards to lock the sight 56.

[0098] The arrangement of the eccentric shaft 62 or, more generally, of the axially length-changing clamping element below the grinding vessel 12, more precisely between the bottom 12c of the grinding cup 12a and the lower bottom part 36 of the cage 34, is therefore not only advantageous for reasons of space with regard to the arrangement of the geared motor 84.

[0099] In the illustrated embodiment, both the axially length-changing clamping element in the form of the eccentric shaft 62 and the spring element in the form of the disc spring 72 are located below the grinding vessel 12. However, it is also conceivable to separate these two elements locally and, for example, to leave the eccentric shaft 62 at the bottom and to arrange the spring element 72 above the grinding vessel 12, or between the grinding bowl lid 12b and the yoke 38.

[0100] In summary, a premium laboratory ball mill is provided with an axial two-point bearing of the grinding station(s), a rigid cage for inserting and clamping the grinding vessel, an eccentric clamping mechanism for the grinding vessel, and a motorized drive for the clamping and locking of the cage.

[0101] The invention therefore comprises several aspects that, while advantageously interacting with one another, could each constitute an independent invention. This applies in particular to the two-point mounting of the grinding station, the cage for inserting and clamping the grinding vessel, the clamping mechanism for the grinding vessel, and the motorized drive for the clamping and, if applicable, locking of the cage.

[0102] In principle, it is evident that the features of the exemplary embodiments, regardless of whether they are disclosed in the description, the claims, the figures or otherwise, also individually define essential components of the invention, even if they are described together with other features.

[0103] Furthermore, the embodiments described above are to be understood as examples, and the invention is not limited to these, but can be varied in many ways without leaving the scope of protection of the claims.

Claims

[1] Laboratory ball mill (1), in particular planetary or centrifugal ball mill on laboratory scale, comprising a support device (8) which is rotatably mounted about a central axis (20), at least one grinding station (10) with a receiving device (16) for at least one grinding vessel (12) that can be filled with grinding material and grinding media, wherein the receiving device (16) is rotatably mounted about an offset planetary axis (24) relative to the support device (8) and is carried by the latter about the central axis (20), a drive (7, 18) for the carrier device (8), a drive (22) for the grinding station (10), a device housing (2) which contains the support device (8), the grinding station (10) and the drives and includes a housing cover (4) which can be opened when the laboratory ball mill (1) is at rest, wherein the receiving device (16) comprises a cage (34) with a lower base part (36), an upper crossbar (38) and at least one side wall (40) which connects the upper crossbar (38) to the lower base part (36), wherein the support device (8) comprises a lower support disc (19) and a bridge structure (50) attached to the support disc (19) and the cage (34) is rotatably mounted on the bridge structure (50) with a lower bearing (46) at a first axial position below the lower bottom part (36) in the support disc (19) and with an upper bearing (48) at a second axial position above the upper cross bridge (38) and the grinding vessel (12) can be inserted into the cage (34) mounted in this way by the user for the grinding process and can be removed by the user after the grinding process when the housing cover (4) is open, wherein the upper bearing (48) is permanently installed in the bridge structure (50) and is not removed for inserting and removing the grinding vessel (12), so that the upper cross bridge (38) with the upper bearing (48) is rotatably but not detachably mounted on the bridge structure (50) during normal operation and remains firmly attached to the cage (34) when inserting and removing the grinding vessel (12). [2] Laboratory ball mill (1) according to one of the preceding claims, wherein the outer diameter of the grinding vessel (12) is larger than the inner diameter of the lower and / or the upper bearing (46, 48). [3] Laboratory ball mill (1) according to one of the preceding claims, wherein the lower bottom part (36) of the cage (34) has a lower bearing journal (42) extending axially downwards and / or the upper cross bridge (38) of the cage (34) has an upper bearing journal (44) extending axially upwards, wherein the lower bearing journal (42) is mounted in the lower bearing (46) and the upper bearing journal (44) is mounted in the upper bearing (48). [4] Laboratory ball mill (1) according to one of the preceding claims, wherein the lower bottom part (36) of the cage (34) has a horizontal base plate from which the lower bearing pin (42) extends downwards and the horizontal base plate of the cage (34) rotates directly above the carrier disk (19), while the lower bearing pin (42) projects axially into the carrier disk (19). [5] Laboratory ball mill (1) according to one of the preceding claims, wherein the lower bottom part (36) is designed as a bottom tray and wherein the at least one side cheek (40) is rigidly attached to the bottom tray with its lower axial end and rigidly attached to the upper cross bridge (38) with its upper axial end. [6] Laboratory ball mill (1) according to one of the preceding claims, wherein the cage (34) has a lateral opening (54) through which the grinding vessel (12) can be inserted laterally into the cage (34) and removed again. [7] Laboratory ball mill (1) according to claim 6, wherein the lateral opening (54) for the grinding process can be closed by a movable visor (56). [8] Laboratory ball mill (1) according to claim 7, wherein the sight (56) is mounted laterally on the cage (34) so ​​as to pivot upwards in order to release the lateral opening (54) by pivoting upwards the sight (56). [9] Laboratory ball mill (1) according to claim 7 or 8, wherein the grinding vessel is enclosed on all sides by the cage (34) when the visor (56) is closed, so that the grinding vessel (12) cannot leave the cage (34). [10] Laboratory ball mill (1) according to one of the preceding claims, wherein the visor (56) and / or the side walls have recesses to allow cooling of the grinding vessel (12) during rotation during the grinding process. [11] Laboratory ball mill (1) according to one of the preceding claims, wherein a clamping element (62) is arranged in the cage (34) which clamps the grinding vessel (12) axially against the lower bottom part (36) or the upper cross bridge (38) of the cage (34) in order to clamp the grinding cup lid (12b) against the grinding cup (12a) and to hermetically seal the grinding vessel (12) and to clamp the grinding vessel (12) firmly in the cage (34) for the grinding process, wherein the cage (34) is rigid and absorbs the axial forces when axially clamping the grinding vessel (12). [12] Laboratory ball mill (1) according to one of the preceding claims, wherein the axial position of the lower and upper bearings (46, 48) does not change when the grinding vessel (12) is axially clamped. [13] Laboratory ball mill (1) according to one of the preceding claims, wherein an eccentric shaft (62) extending transversely to the planetary axis (24) is rotatably mounted in the receiving device (16), by means of which the axial clamping of the grinding vessel (12) is effected.

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