Agitator mill

Abstract

A stirred mill with a container-shaped process unit (2) into which a drive shaft (33) extends, and a rotor (17) with a plurality of tools (30) for transferring energy to grinding aids (31), the process unit (2) having a product inlet (8) and a product outlet (9) through which the product to be ground is fed into and out of the process unit (2), with a motor (3) that drives the drive shaft (33), characterized in that the drive shaft (33) extends from below through a base of the process unit (2) into the vertically oriented process unit (2), and the motor (4) is connected to the drive shaft (33) below the process unit to transfer power to the drive shaft (33), so that the lid can be removed when the process unit (2) is full without having to remove the product or the grinding aids (31).

Description

[0001] The invention relates to a stirred mill with a container-shaped process unit into which a drive shaft extends and a rotor with a plurality of tools to transfer energy to grinding aids. Overview of the field of invention

[0002] Stirred ball mills are used for the comminution and homogenization of solid particles (paints and varnishes) by means of an agitator shaft that intensively moves grinding media. The solid particles are comminuted through impact, pressure, shear, and friction. In principle, stirred ball mills can be distinguished by the horizontal or vertical orientation of the grinding chamber. The grinding media are activated by the agitator shaft, which can be equipped with agitators (tools) such as rods or discs. The grinding chamber is typically filled to a high percentage, e.g., seventy to ninety percent, with grinding media ranging in size from 0.03 to 9 mm in diameter.

[0003] Stirred mills typically comprise a grinding container in which a stirring shaft equipped with grinding elements is arranged, thereby forming a grinding chamber between the grinding container and the stirring shaft, into which the grinding elements extend and into which at least one inlet channel and one outlet channel for ground material open, and a separating device for grinding aids is provided.

[0004] During the grinding process, the product to be ground flows continuously from a product inlet axially to the agitator shaft through the grinding chamber to a product outlet. In the outlet area, the grinding media are then separated from the product stream by means of a separation system.

[0005] In closed stirred ball mills, the throughput and grinding media size are limited by the separation device. This device is designed to reliably retain the grinding media within the milling chamber and must not cause media compression or clogging, even at high throughput rates. Separation devices can be designed as known systems, centrifugal systems, or external separation systems.

[0006] The EP 1943022 B1 patent is based on the task of designing a stirred mill of the generic type in such a way that, particularly when using grinding aids of extremely small diameter, grinding and dispersion with narrow particle distribution is achieved even with only one pass of the material through the stirred mill, without the risk of operational disruptions, in particular due to impact of grinding aids on the protective screen.This is achieved by ensuring that the rotor tools attached to the rotor leave only a small gap to the container wall, that the inner space is designed as a grinding material discharge channel, and that, as devices to prevent the overflow of grinding aids from the grinding chamber into the grinding material discharge channel, the tools attached to the rotor are arranged overlapping each other on a helical line in an area between the grinding aid return channels and the deflection channel in the circumferential direction of the rotor, such that when the rotor is driven in one direction of rotation, they exert an impulse on the grinding aids in the opposite direction to the flow direction.

[0007] A stirred mill is known from EP 0 370 022 B1 (corresponding to US 5,062,577). In this stirred mill, the grinding media are centrifuged from the material-grinding media flow through the grinding media return channels before they reach the protective screen. The protective screen's primary function is to collect worn grinding media that are too light to be directly ejected through the grinding media return channels and to act as a throttling point to create back pressure against the material flow. The agitator is equipped with stirring tools that project into the outer grinding chamber. When using extremely small grinding media, it is not guaranteed that the grinding media will not nevertheless reach the protective screen and clog it over time.Especially when using extremely small grinding media, correspondingly fine protective screens must be used, which in turn can be very easily damaged if grinding media impact them. Conversely, when using grinding media of typical size and processing relatively viscous materials, a partial clogging of the protective screen leads to a significant pressure build-up in the agitator mill, which also disrupts the grinding process.

[0008] From EP 0 504 836 B1, a stirred mill is known in which a pot-shaped rotor is arranged in a cylindrical housing and is provided with through-slots along its length. An inner stator with a protective screen is arranged inside the rotor. Tools are attached to both the rotor and the wall delimiting the grinding chamber in the outer grinding chamber. This stirred mill is not suitable for use with extremely fine grinding media. Furthermore, the problems already described above also occur here.

[0009] From DE 34 37 866 A1 (corresponding to US 5,011,089) a stirred mill is known which has a rotor fitted with paddle-shaped tools on its outer surface. A protective screen is arranged inside the rotor. The rotor consists of axially parallel rods to which the paddle-shaped tools are attached. The material to be ground is fed radially. In this stirred mill, the paddle-like design of the stirring tools does concentrate the grinding media in the area of ​​the container wall; however, defined grinding, especially with extremely small grinding media, and reliable separation of the grinding media without risk of operational disruption are not possible. The material to be ground flows radially through the packing of grinding media, meaning that the material is only exposed to the grinding process over a very short distance.Therefore, only a small amount of grinding progress is achieved with a single pass of the material through the agitator mill.

[0010] From DE 196 38 354 A1 (corresponding to US 5,894,998) a stirred mill of the general type is known in which the protective screen is attached to the pot-shaped rotor and sealed against the inner stator by means of a mechanical seal. The protective screen thus rotates with the rotor, whereby any grinding aids that reach it are additionally flung off.

[0011] From EP 0 546 320 A2 (corresponding to US 5 346 145) a stirred mill is known, on whose rotor tools with conveying surfaces are attached which exert a pulse on the material to be ground and the grinding aids in the direction from the material inlet to the material outlet.

[0012] DE102011010527A1 describes a stirred ball mill with a grinding container and an axially extending stirring shaft in it, which is connected at least at one end to the wall of the grinding container via a rotary feedthrough, wherein a protective disc covering the rotary feedthrough is arranged adjacent to the rotary feedthrough in the grinding container.

[0013] Further mills are from DE102013 111 762 A1, EP 2646160 B1, EP 2907578 B1, EP 3536405 A1, EP 1992412 B1, EP 1724022 B1, EP 1724021 A1, DE 19839210 B4, US 5 330 112 A known. Overview of the invention:

[0014] The object of the invention is to provide an alternative approach that enables a wider range of applications for the mill.

[0015] This problem is solved by the invention according to the features of the claims. Preferred embodiments are defined in the dependent claims.

[0016] The invention comprises a stirred mill with a container-shaped process unit into which a drive shaft extends. A rotor is preferably clamped to the drive shaft. The drive shaft extends from below into the interior of the rotor. The rotor is generally an elongated, round body. This body may have projections, recesses, and internal bores. The rotor body has a corresponding axial bore. The bore is preferably a blind bore, or the end of the bore is closed by an element that allows for a counter-screw connection. The bore or the shaft is cylindrical at its ends so that a clamping connection can be formed. In one possible embodiment, a screw connection is made from above into the head of the shaft, which pulls the shaft into the bore and thus supports a press fit.The rotor is equipped with a multitude of activation pins on its outer surface to transfer energy to grinding aids. These grinding aids are typically metal or ceramic beads, as described above. The activation pins are preferably bolts, particularly made of metal, arranged radially on the outer surface of the rotor. The arrangement of the bolts can vary; for example, staggered, regular, or threaded arrangements are conceivable.

[0017] To ensure the product flows through the processing unit, it has a product inlet and a product outlet through which the product to be ground is fed in and out. The product to be ground is surrounded by a carrier fluid, which is pumped through the processing unit. This is therefore referred to as a wet mill. In the preferred embodiment, the product inlet is located in the lower part of the processing unit and the product outlet in the upper part, so that the product flows from bottom to top through the processing unit, counteracting gravity. In conjunction with this invention, "bottom" is where gravity is stronger and "top" is where gravity is weaker, or where the path to the Earth's center is shorter. Thus, gravity assists the separation of the product and the grinding media, as they are pulled downwards by gravity and therefore kept away from the separation system.

[0018] Furthermore, the invention comprises a motor, preferably a three-phase motor, which drives the drive shaft. A key aspect of the invention is that the drive shaft extends from below through a base of the process unit into the vertically oriented process unit, and the motor is connected to the drive shaft below the process unit to transmit power to the drive shaft. This allows the lid to be removed when the process unit is full, without having to remove the product or the grinding media. Gravity provides support in this case, as the beads are held back from the separation system. This makes it easier to replace worn or clogged parts. Different sieve sizes can also be applied to the material being ground. The sieve can thus become progressively smaller during the grinding process.

[0019] In possible embodiments, the motor is arranged parallel to, preferably laterally to, the process unit, so that the motor's axis of rotation is parallel to the drive shaft. In this case, power transmission can be achieved via drive belts and pulleys located below the process unit. Chains, gears, or transmissions are also conceivable. Other motor arrangements are also possible.

[0020] In one possible embodiment, the cover can be removed from the process unit by releasing locking mechanisms. The cover is preferably attached to the edge or a flange of the process unit's outer casing with screws or nuts. Appropriate seals are provided to ensure a sufficient seal.

[0021] In one possible embodiment, at least two covers are provided, and the fastening means of the process unit are designed such that the covers are interchangeable. Interchangeable means that only bolts or screws need to be loosened, without having to replace any other structural parts inside or outside the process unit. Thus, by replacing the cover, it is possible to switch between a dynamic and a static separating device without having to empty the process unit or change the rotor; in particular, the grinding aids or the product do not need to be removed. The rotor is designed so that it does not collide with either cover after they have been replaced.

[0022] In one possible embodiment, the lid or a flange arranged on the lid can be removed upwards to change the screen without emptying the process unit or changing the rotor; in particular, the grinding aids or the product do not need to be removed. In the static separator, the lid can also be equipped with a flange that allows access to the screen without removing the entire lid. This flange can be opened using appropriate quick-release fasteners, granting access to the screen. This allows the screen to be replaced, cleaned, or exchanged for a finer screen.

[0023] In one possible embodiment, the separating device is connected to the removable cover, so that removing the cover also removes the separating device. This allows the entire separating device to be removed upwards at once by loosening screws, bolts, or fasteners outside the process unit. Working inside the process unit is therefore unnecessary, thus facilitating a cleaner working environment.

[0024] Due to the connection between the lid and the separating device, the product outlet is formed in the lid and is located downstream of the separating device in the direction of product flow. The product outlet typically originates centrally from the lid and is directed upwards and to the side. Other configurations are possible.

[0025] In addition to activation pins on the rotor, one possible embodiment also provides radially arranged activation pins on the stator, which is located on the inside of the process unit, extending into the spaces between spaced activation pins of the rotor.

[0026] In addition, in one possible embodiment, the rotor may have activation pins in an axial direction in the bottom area and / or on the top, pointing upwards and / or downwards.

[0027] This results in a more intensive stimulation of the grinding aids.

[0028] In one possible embodiment, the rotor has a central recess at its upper end, facing the cover and provided with a circumferential wall into which the separating device, attached to the cover, extends from above. The separating device can be designed as a tubular screen extending downwards from the cover into the process unit. To reduce the overall height, the rotor has a corresponding recess so that it rotates around the screen unit, which is statically arranged inside the rotor and surrounded by the circumferential wall.

[0029] In one possible embodiment of the rotor, return openings are formed in the circumferential wall, extending from the central recess towards the stator to guide the grinding media back into the space between the stator and rotor. These openings facilitate the return of the grinding media, which are transported back by the centrifugal force generated by the rotor. Preferably, the return openings do not run completely radially, but rather at an oblique angle or bent in the direction of rotation, thus achieving a pump-impeller effect similar to that of a jet pump.

[0030] In one possible embodiment, a clamping element is arranged in the recess, which clamps the rotor to the drive shaft, the upper end of which extends into the recess. The drive shaft thus ends just below the bottom of the recess and is clamped to the rotor there.

[0031] In one possible embodiment, the product inlet is located in the bottom area or in the lower surface of the process unit, so that the product to be ground flows from bottom to top through the stirred mill.

[0032] In one possible embodiment, the dynamic separating device is driven by one or more drivers attached to the rotor. The drivers extend upwards from the rotor and engage in a corresponding receptacle, thus eliminating the need for a separate drive. However, it is also possible to provide a separate drive to achieve different rotational speeds.

[0033] In one possible embodiment, the process unit has an outer casing that extends around the stator and forms a stator cooling chamber with a cooling water inlet and outlet. Typically, the cooling water flows from bottom to top through the stator cooling chamber, mirroring the product flow.

[0034] In one possible embodiment, the base of the process unit features a cooling chamber that extends around the drive shaft, with a cooling water inlet and outlet. This allows for different cooling temperatures and also provides better separation of the components, thus simplifying manufacturing for the replacement of internal wear parts.

[0035] In one possible embodiment, the rotor could also be designed as a cooled variant by introducing the cooling medium into the rotor from below through the drive shaft. Character description

[0036] The following describes the figures of the possible embodiments.

[0037] It shows Figure 1 The mill from the side with a partially transparent housing, and the components drive, V-belt and process unit; Figure 2 a section through the process unit along the shaft; Figure 3 a cut through the process unit along the shaft, whereby the sieve was removed individually, from the lid upwards; Figure 4 where the lid is equipped with a dynamic separating device. Description of a detailed embodiment

[0038] The Figure 1 The inventive mill is shown from the side, with the housing being partially translucent.

[0039] A process unit 2 and a motor 3 (preferably a three-phase motor) are arranged parallel to each other on a machine stand 1, such that their axes of rotation are parallel to each other. The motor shaft points downwards and is fitted with a motor pulley 4.

[0040] Process unit 2 also has a V-belt pulley 6, which is formed on the underside. Both V-belt pulleys are connected to each other via a V-belt 5.

[0041] A bearing 7 is designed as a table-like structure laterally to the motor housing. The process unit 2 is arranged on this bearing, and a drive shaft 33 extends through the bearing, connecting to the V-belt pulley 6 on one side and to a rotor 17 located in the process unit 2 on the other. The motor thus drives the rotor in the process unit.

[0042] Above storage unit 7 is a product inlet 8, which allows product to flow into the bottom area of ​​process unit 2. The product to be ground is pumped against gravity from bottom to top towards the lid of process unit 2. The product to be ground is suspended in a carrier fluid and is pumped through the process unit along with this fluid. The product outlet 9, from which the product to be ground emerges, is located in the area of ​​the lid.

[0043] To prevent overheating of the product being ground, two cooling water chambers are provided. These can also be combined into one. The first stator cooling chamber 19 is located in the wall area of ​​the process unit 2. A cooling water inlet 10 for a stator 16 is provided for this purpose. The process unit 2 is preferably double-walled, with an outer jacket 14 and an inner jacket that serves as the stator 16. The stator cooling chamber 19 is flooded with cooling fluid from bottom to top and the fluid is also pumped through it in this direction. A corresponding cooling water outlet 11 is located in the upper area of ​​the process unit.

[0044] Furthermore, a floor cooling chamber 20 is formed in the floor to cool the bearing of the drive shaft 33 and the material being ground in the floor area. For this purpose, a cooling water inlet 12 and a cooling water outlet 13 are formed in the floor.

[0045] As in the Figures 2 and 3The barrel-shaped process unit 2, as shown, comprises the outer shell 14, within which the stator 16 is formed at a distance. The stator cooling chamber 19 is arranged between the two. A grinding chamber 18 is formed around the stator 16, in the center of which the rotor 17 rotates.

[0046] The process unit is closed off at the bottom by a process unit floor 21, to which the floor cooling room 20 borders.

[0047] The outer shell 14 is usually connected to the process unit base 21.

[0048] Furthermore, a bead drain plug 32 is provided in the bottom of the process unit to drain the grinding aids 31 downwards.

[0049] The bearing housing serves as a support for the process unit base. For this purpose, a flange connection 22 of the process unit is used on the bearing housing. The process unit is attached to the flange connection 23 by means of a fastener 23.

[0050] The process unit is limited at the top by an upper grinding chamber lid 15 with a receptacle for a sieve unit / static separating device.

[0051] The Figures 2 and 3 The images show a grinding chamber lid with sieve in both the installed and removed positions.

[0052] Figure 4 In contrast, a dynamic separation device is shown. The grinding chamber lid has a bore in which the sieve unit 26 is arranged. The sieve unit in turn has a sieve cover 27 and a sieve 28 adjoining it.

[0053] The removable fasteners 29 and 24 allow both the grinding chamber lid and the sieve unit to be removed, replaced or cleaned.

[0054] Both the stator wall and the rotor are equipped with circumferentially arranged activation pins 30, formed at a right angle to the axis of rotation. These pins extend into the space between the stator and rotor to interlock and thus transfer the rotational energy to the grinding aids 31. The activation pins can even be located in the base or on the top of the rotor and can be oriented downwards or upwards, as shown in the diagram. Figures 2-4 show.

[0055] The rotor indicates how Figure 3 As can be clearly seen, a central recess 41 is located in the upper area, into which the sieve extends when the device is in operation. This increases the sieve area while maintaining a compact design.

[0056] To allow grinding aids that are in direct contact with the sieve to be returned to the grinding chamber, the rotor has return openings 25 in its upper area. These are arranged at intervals around the circumference and extend from the upper edge of the recess 41 to its lower edge.

[0057] The drive shaft 33 extends almost to the underside of the central recess 41 through a rotor hub 34. The drive shaft 33 is connected to the rotor hub 34 by a clamping piece 35 formed at the bottom of the central recess 41. The rotor casing (item 31) then extends around the rotor hub and can be integrally or detachably connected to it.

[0058] The Figure 4Figure 1 shows an embodiment of the invention in which the upper grinding chamber lid 36 is designed with a dynamic separating device 40 with a friction gap 37. The invention can be converted within a short time without emptying the process unit. Only the lid needs to be replaced.

[0059] Driver 38 transmits the rotary motion from the rotor to the dynamic gap or dynamic separating device, in which two rings are arranged close together, one of these rings rotating. The ground product is guided through this gap.

[0060] The outlet 39 and the bearing housing of the dynamic separating device are formed in the grinding chamber lid. Reference symbol list

[0061] 1 Machine stand 2 Process unit 3 Three-phase motor 4 Motor pulley 5 V-belt 6 Process unit pulley 7 Bearing 8 Product inlet 9 Product outlet 10 Stator cooling water inlet 11 Stator cooling water outlet 12 Base cooling water inlet 13 Base cooling water outlet 14 Outer casing 15 Upper grinding chamber cover, housing for screen unit / static separator 16 Stator 17 Rotor 18 Grinding chamber 19 Stator cooling chamber 20 Base cooling chamber 21 Base of process unit 22 Flange connecting process unit to bearing housing 23 Process unit mounting to item 22 24 Mounting of items 15 & 36 25 Return opening in rotor for grinding aids 26 Screen unit / static separator 27 Screen cover / cover for static separator 28 Screen 29 Mounting of item26 30 Activation pin 31 Grinding aid body 32 Bead drain plug 33 Drive shaft 34 Rotor hub 35 Clamping piece 36 Upper grinding chamber cover, housing for dynamic gap / dynamic separating device 37 Friction gap 38 Driver (transmits the rotary motion from the rotor to the dynamic gap) 39 Outlet / bearing housing of the dynamic separating device 40 Dynamic separating device 41 Central recess rotor.

Claims

1. Agitator bead mill with a container-shaped process unit (2) into which a drive shaft (33) extends, and a rotor (17) with a plurality of tools (30) for transferring energy to grinding media (31), wherein the process unit (2) has a product inlet (8) and a product outlet (9) through which the product to be ground is fed into and out of the process unit (2), with a motor (3) which drives the drive shaft (33), wherein the drive shaft (33) extends from below through a process unit bottom into the vertically oriented process unit (2), and the motor (3) is connected to the drive shaft (33) below the process unit in order to transmit power to the drive shaft (33), so that a cover (15) can be removed when the process unit (2) is filled without having to remove the product or the grinding media (31), wherein the product inlet is formed in the lower region of the process unit so that the liquid product to be ground flows from bottom to top through the agitator bead mill against the force of gravity, characterized in that - that at least two covers are provided, and fastening means of the process unit are designed so that the covers are interchangeable, and by replacing the cover, it is possible to switch between a dynamic separator and a static separator without having to empty the process unit or change the rotor (17), in particular, the grinding media or the product do not have to be removed, and / or - that a dynamic separator (40) is driven by one or more drag elements (38) from the rotor.

2. The agitator bead mill according to the preceding claim, characterized in that the cover (15, 27, 36) can be removed from the process unit by loosening fastening means.

3. The agitator bead mill according to one of the preceding claims, characterized in that a screen can be removed upwards individually or together with the cover without having to empty the process unit or change the rotor (17), in particular, the grinding media (31) or the product do not have to be removed.

4. The agitator bead mill according to claim 2 or 3, characterized in that the separator (40, 26) is connected to the removable cover so that removing the cover also removes the separator.

5. The agitator bead mill according to one of claims 2-4, characterized in that the product outlet is formed in the removable cover (15, 27, 36) and is arranged downstream of the separator in the direction of flow of the product.

6. The agitator bead mill according to one of the preceding claims, characterized in that the rotor (17) is formed on the outside with radially arranged activation pins (30).

7. The agitator bead mill according to the preceding claim, characterized in that the process unit is formed on an inner side as a stator (16) with radially arranged activation pins (30) extending into spaces between spaced activation pins (30) of the rotor.

8. The agitator bead mill according to one of the preceding claims, characterized in that the rotor (17) has a central recess (41) at its upper end, which faces the cover and is provided with a circumferential wall into which the separator (28) attached to the cover extends from above.

9. The agitator bead mill according to the preceding claim, characterized in that the circumferential wall has return openings (25) which extend from the central recess towards the stator in order to guide the grinding media back into the space between the stator and the rotor.

10. The agitator bead mill according to one of claims 8 or 9, characterized in that a clamping piece (35) is arranged in the recess, which clamps the rotor to the drive shaft, the upper end of which extends into the recess, and / or a screw connection is used as a fixation.

11. The agitator bead mill according to one of the preceding claims, characterized in that the motor (3) is arranged to the side of the process unit (2), preferably with its axis of rotation parallel to that of the drive shaft (33), and is connected to the drive shaft via power transmission means (4, 5, 6).

12. The agitator bead mill according to one of the preceding claims, characterized in that the process unit has an outer jacket (14) which extends around the stator and forms a stator cooling chamber (19) with a stator coolant inlet (10) and a stator coolant outlet (11).

13. The agitator bead mill according to one of the preceding claims, characterized in that the process unit bottom has a bottom cooling chamber (20) which extends around the drive shaft (33), with a bottom coolant inlet (12) and a bottom coolant outlet (13).

Images