EP3384990B1 - Milling arrangement for a basket mill and basket mill - Google Patents

Description

The present invention relates to a grinder for a basket mill according to the preamble of claim 1 and a basket mill.

Basket mills are a subset of agitator ball mills and also known as submersible mills. These mills are used in particular for wet milling of suspensions and pigment pastes, for example in the paint and coatings industry. The grinder consists in known basket mills from a grinding pot with a grinding chamber and balls contained in the grinding chamber. The grinding pot is immersed in a grinding container with the ground material. In operation, the millbase contained in the grinding container is passed through the grinding chamber and the desired grinding process takes place. Since only the millbase contained in the grinding container is ground, basket mills are used for the so-called batch operation by batchwise milling of the material to be ground. Such a basket mill having the features of the preamble of claim 1 is made of EP 0 743 091 A1 known. Further such basket mills are in JP H10 118511 A and GB 2 318 749 A disclosed.

In conventional basket mills has been found that the mixing of the material to be ground in the grinding container is often insufficient and thus requires the processing time to the desired grinding of the material for a relatively long time. Furthermore, when milling millbase with a higher viscosity in conventional basket mills, quality problems have arisen.

It is therefore an object of the present invention to provide a grinder for a basket mill and a basket mill, which leads to a better grinding result in millbase of higher viscosity and / or achieves a shortening of the processing time during milling.

The invention is defined by the features of claims 1 and 18.

In the grinder according to the invention for a basket mill with a grinding pot with a grinding chamber and arranged in the grinding chamber grinding balls, wherein the grinding chamber has a Mahlkammereinlass and a Mahlkammerauslass for the ground material and can be flowed through by the ground material, and with a first conveyor, with the grinding chamber cooperates to produce Mahlgutströmung through the grinding chamber, it is provided that the grinding pot has a bypass flow path, which is flowed through by the material to be ground, bypassing the grinding chamber, wherein a second conveyor with the bypass flow path for generating the Mahlgutströmung by the bypass flow path interacts.

By providing a bypass flow path with the second conveyor, in addition to the flow of the ground material through the grinding chamber, a second flow of the ground material is achieved by the grinding pot, whereby an advantageous mixing of the ground material in the grinding container, in which the grinder is immersed in operation reaches , In operation, ground material is thus conveyed on the one hand into the grinding chamber, in which a thorough mixing of the ground material with the grinding balls takes place, whereby the ground material is ground between the grinding balls. The mixing of the ground material in the grinding chamber can be done for example via a stirrer. On the other hand, there is a parallel flow through the bypass flow path, whereby an advantageous mixing of the ground material is carried out in the grinding container, as an additional circulation of the ground material takes place. The through the bypass flow path For example, the flow of the millbase produced may have a greater volume flow than the flow of the millbase through the grinding chamber. Also, the flow rate of the ground material through the bypass flow path can be greater than the flow rate of the ground material through the grinding chamber.

The provision of a parallel flow through the bypass flow path has been found to be particularly advantageous especially for regrind having a higher viscosity. Under millbase with a higher viscosity is understood to mean a millbase, for example, has a viscosity of> 5000 mPas.

It is preferably provided that the first conveying device is formed by a first pump impeller. The promotion of the ground material for generating the flow through the grinding chamber thus takes place by a rotary drive of the first pump impeller. Thus, the first conveyor can be provided in a structurally simple manner. The first pump impeller may be formed, for example, in the manner of an impeller of a centrifugal pump. The design of the first conveyor as the first pump impeller also has the advantage that the desired flow can be generated with a high efficiency.

It is preferably provided that the first pump impeller is arranged at Mahlkammerauslass. In other words: The first pump impeller sucks the material to be ground through the grinding chamber. In order to prevent grinding balls from getting into the first pump impeller, provision can be made, for example, for a sieve to be arranged on the grinding chamber outlet, by way of which the grinding balls are retained. The first pump impeller can be designed in particular as a radial pump impeller. The ground material, which flows through the grinding chamber, thus passes in the axial direction on the first pump impeller and is conveyed in the radial direction to the outside. A Such a design has been found to be particularly advantageous, since a recirculation flow can be generated in the Mahlgutbehälter in an advantageous manner. It is preferably provided that the first pump impeller is sealed at a hub region to a housing part of the grinding pot surrounded by the grinding chamber outlet, preferably via a gap seal. This advantageously ensures that the flow coming from the grinding chamber into the pump impeller is discharged radially outward. In a particularly preferred embodiment of the invention it is provided that the pump impeller is designed as a semi-open impeller, wherein the open side, on which the grinding chamber facing side of the impeller is arranged. The first pump impeller can thus be provided with little design effort. The trained as a semi-open impeller first impeller can cooperate advantageously with a housing part of the grinding pot, so that the open side of the half-open impeller is covered and thus the desired flow can be achieved with a high efficiency.

The design of the grinder according to the invention with a first conveyor in the form of a first Pumpenlaufrades also has independent inventive significance and can be realized regardless of the design of the grinding pot of the grinder according to the invention with a bypass flow path. The invention thus also relates to a grinder for a basket mill with a grinding pot with a grinding chamber and arranged in the grinding chamber grinding balls, wherein the grinding chamber has a Mahlkammereinlass and a Mahlkammerauslass for the ground material and can be flowed through by the ground material and with a first conveyor, with the grinding chamber for generating Mahlgutströmung cooperates through the grinding chamber, wherein the first conveyor is formed by a first pump impeller. The first pump impeller may be configured as described above.

In a preferred embodiment of the invention it is provided that the second conveyor is formed by a second pump impeller. Thus, the flow of the ground material through the bypass flow path can be generated in an advantageous manner by a rotary drive of the second pump impeller. Further, the flow through the bypass flow path can be generated with high efficiency.

It can be provided in an advantageous manner that the second pump impeller is disposed at an outlet of the bypass flow path. Thus, the flow through the bypass flow path can be generated via a suction effect of the pump impeller.

The second pump impeller may be formed in the manner of an impeller of a centrifugal pump.

In a particularly preferred embodiment of the invention, it is provided that the second pump impeller is designed as a closed impeller. By means of a closed impeller, a pumping action can be achieved with high efficiency.

It is preferably provided that the first and the second pump impeller have a common drive shaft. In other words, the first and the second pump impeller are driven via a drive shaft, so that the device-technical effort for different drives of the pump impellers is avoided.

It may be provided in an advantageous manner that the second pump impeller acts as a radial pump. For example, the ground material can flow in the region of a hub of the second pump impeller into the pump impeller and be conveyed in the radial direction to the outside.

The invention may advantageously provide that an aperture is arranged at an inlet of the bypass flow path. The flow cross-section of the bypass flow path can be changed via the orifice so that different volume flows through the bypass flow path can be realized with the grinder according to the invention. For example, diaphragms of different sizes can be used. Also, an adjustable aperture can be provided.

In a preferred embodiment of the invention it is provided that the bypass flow path is formed by an annular gap between the grinding basket and a drive shaft for the first and / or the second pump impeller. Thereby, the bypass flow path can be arranged relatively close to the middle of a Mahlgutbehälters, so that in conjunction with, for example, a second pump impeller in the form of a radial pump, a particularly advantageous circulation of the ground material can be achieved by the flow through the bypass flow path.

The invention may advantageously provide that the first and the second pump impeller are formed as a component. Such a configuration of the first and second pump impeller has the particular advantage that only a connection to the drive shaft has to be created. Furthermore, the cost of materials can be kept low because, for example, a disc closing the second pump impeller on one side can simultaneously form the disc of the closed side of the half-open first pump impeller.

The invention may further provide that an agitator is arranged in the grinding chamber. About the agitator, a flow can be generated in the grinding chamber through which an advantageous mixing of grinding balls and ground material and thus the desired grinding action takes place.

It is preferably provided that the agitator is driven via the drive shaft. In other words, the first and second pump impellers and agitator are driven in common via the same drive shaft. Of course, it is also possible that the agitator is driven together only together with one of the two pump impellers and the other pump impeller is driven independently. In one embodiment of the inventive grinder without bypass flow path can be provided that the agitator has a common drive shaft together with the first pump impeller.

The invention can advantageously provide that flow baffles are arranged in the grinding chamber. Via the flow internals, the flow in the grinding chamber can be influenced. The flow installations can lead to a local interruption of the flow, so that advantageously turbulences in the grinding chamber can be achieved, whereby an advantageous grinding result can be achieved.

It can preferably be provided that the flow installations consist of several webs arranged on a peripheral wall, which are arranged parallel to the peripheral wall and project into the grinding chamber. The webs are preferably arranged vertically. In the grinding chamber, for example, by means of a stirrer, a circular flow can be achieved. By arranged on the peripheral wall webs which protrude into the grinding chamber, this circular flow can be interrupted in an advantageous manner and it turbulence can be generated.

It can preferably be provided that between the webs and the peripheral wall in each case a gap is formed. Such configured flow internals have the advantage that on the one hand turbulence in the mixture consisting of grinding balls and ground material in the grinding chamber arise, on the other hand, the flow on the peripheral wall does not tear off completely.

As a result, the mixture contained in the grinding chamber can advantageously be cooled on the peripheral wall, whereby the heat produced by the grinding process can be dissipated in the grinding material in an advantageous manner. This can be done for example by a cooling device in or on the peripheral wall.

The design of the grinder according to the invention with flow fixtures in the grinding chamber also has independent inventive significance and can be realized regardless of the design of the grinder with a bypass flow path or the first pump impeller. The invention thus also provides a grinder for a basket mill with a grinding pot with a grinding chamber and arranged in the grinding chamber grinding balls, wherein the grinding chamber has a Mahlkammereinlass and a Mahlkammerauslass for the ground material and can be flowed through by the ground material and with a first conveyor, with the grinding chamber for generating Mahlgutströmung by the grinding chamber cooperates, before, wherein in the grinding chamber flow baffles are arranged. The flow internals may be formed as previously described.

The invention may also provide advantageously that the grinding pot has a surrounding wall which partially delimits the grinding chamber, wherein the surrounding wall has a cooling device and the cooling device has at least one cooling fluid channel extending in the surrounding wall which extends in a multi-threaded manner in the surrounding wall. By providing at least one cooling fluid channel in the surrounding wall, a particularly advantageous cooling of the surrounding wall and thus of the grinding chamber is possible. In particular, a turbulent flow in the at least one cooling fluid channel can be achieved in an advantageous manner, since in this way a particularly effective cooling can be achieved, whereby a considerable increase in the grinding speed is made possible.

It is preferably provided that, for the flow cross section A _{K of} the at least one cooling fluid channel and the projected milling chamber cross section A _M , which is predetermined by the diameter of the peripheral wall, A _M / A _K > 240. The projected milling chamber cross section is basically a measure of the size the grinding chamber and thus for the performance of the grinder. With greater performance of the grinder and an increased cooling demand is given. It has been found that in the case of customary volume flows of cooling fluid, which are also selected as a function of the size of the grinding chamber, it is advantageously possible to achieve turbulent flow and thus an advantageous cooling effect in cooling fluid passages with flow cross sections which fulfill the specified ratio.

The flow cross section of the at least one cooling fluid channel can be, for example, between 30 and 700 mm ² . Preferably, a cooling fluid channel is provided which, for example, has a rectangular, preferably square, cross-section. The cooling fluid channel with a square cross-section, for example, have side edges of 6 × 6 mm to 25 × 25 mm.

In this case, it is preferably provided that each cooling channel extends meandering from at least one cooling fluid inlet to a cooling fluid outlet. By such a configuration of the cooling fluid channel or the cooling fluid channels, the entire surrounding wall of the grinding chamber can be cooled in an advantageous manner. In particular, it is possible to cool the entire surrounding wall with only one cooling fluid channel and one cooling fluid access and one cooling fluid outlet. For this purpose, it can be provided, for example, that the cooling fluid access first extends to the lower end of the surrounding wall and then meander-shaped, the cooling fluid channel is guided. At the side opposite the cooling fluid access side, the cooling fluid outlet can then be arranged. In this way, a particularly effective cooling of the surrounding wall and thus the grinding chamber is possible.

The design of the grinder according to the invention with a surrounding wall with a cooling device having a multi-threaded cooling fluid channel also has independent inventive significance and can be implemented independently of the design of the grinding pot of the grinder according to the invention with a bypass flow path. The invention thus also relates to a grinder for a basket mill with a grinding pot having a grinding chamber and arranged in the grinding chamber grinding balls, wherein the grinding chamber has a Mahlkammereinlass and a Mahlkammerauslass for the ground material and can be flowed through by the ground material, and with a first conveyor, the cooperates with the grinding chamber for generating Mahlgutströmung through the grinding chamber, wherein the grinding pot has a surrounding wall which limits the grinding chamber partially, wherein the surrounding wall has a cooling device and the cooling device has at least one extending in the surrounding wall cooling fluid channel, which wound several times in the Surrounding wall extends. The cooling device and the at least one cooling fluid channel can be configured further in the manner described above.

The invention further provides a basket mill with a grinding container and a grinder according to the invention, wherein the grinder is immersed in the grinding container.

Fig. 1

eine schematische Seitenansicht einer erfindungsgemäßen Korbmühle mit Mahlwerk und

Fig. 2

eine schematische Schnittdarstellung des erfindungsgemäßen Mahlwerks der Fig. 1.

In the following, the invention will be explained in more detail with reference to the following figures. Show it

Fig. 1

a schematic side view of a basket mill according to the invention with grinder and

Fig. 2

a schematic sectional view of the grinder of the invention Fig. 1 ,

In Fig. 1 a basket mill 1 according to the invention is shown schematically in side view. The basket mill 1 has a drive 3 and a grinder 5 connected to the drive 3. The grinder 5 is immersed in a milling container 7 shown cut. In the grinding container 7, the material to be ground, for example, a high-solids paint, included.

The grinder 5 is in the Fig. 2 shown schematically in section.

The grinder 5 consists of a grinding pot 9, in which a grinding chamber 11 is formed. The grinding chamber 11 is filled during operation with grinding balls, not shown. The grinding chamber 11 has a grinding chamber inlet 13 and a grinding chamber outlet 15. At the Mahlkammerauslass 15 a sieve 15 a is arranged to retain the grinding balls contained in the grinding chamber 11.

The millbase contained in the grinding container 7 passes through the grinding chamber inlet 13 into the grinding chamber 11 and is mixed here by means of a stirrer 17 with the grinding balls. This creates a turbulent flow in the grinding chamber 11, so that advantageously the material to be ground between the grinding balls is ground.

The flow through the grinding chamber 11 is generated by means of a first conveyor in the form of a first pump impeller 19. The pump impeller 19 is disposed directly on Mahlkammerauslass 15 and formed as a so-called open impeller. The pump impeller 19 consists of a disc 19 a, are applied to the blades 19 b. In a hub region 19 c, the pump impeller 19 is sealed relative to a housing part 9 a of the grinding pot 9, for example via a gap seal. The grist passing through the Mahlkammerauslass 15 is from the blades 19b of the first pump impeller 19 entrained and transported in the radial direction. Thus, the first pump impeller 19 acts as a radial pump.

The grinding pot 9 also has a bypass flow path 21 through which the material to be ground can flow, bypassing the grinding chamber 11. The bypass flow path 21 has an inlet 23 and an outlet 25. To generate the flow through the bypass flow path 21, a second conveyor in the form of a second pump impeller 27 is provided. The second pump impeller 27 is disposed at the outlet 25 of the bypass flow path 21 and formed as a so-called closed impeller. The second pump impeller 27 has a first disc 27a and a second disc formed by the disc 19a of the first pump impeller 19. Thus, the first pump impeller 19 and the second pump impeller 27 are formed as one component. Between the first disc 27a of the second pump impeller 27 and the disc 19a of the first pump impeller 19, blades 27b are arranged. The millbase flowing through the bypass flow path 21 passes through the outlet 25 into a pump inlet 27 c of the second pump impeller 27, which is located in the hub region of the second pump impeller 27. By the blades 27b of the second pump impeller 27 of this regrind is transported in the radial direction, so that the second pump impeller 27 acts as a radial pump.

The first and second pump impeller 19,27 are driven by a common drive shaft 29, with the in Fig. 1 shown drive 3 is connected. The common drive shaft 29 may be formed, for example, as a hollow shaft.

The agitator 17 has a flange 17 a, via which the agitator 17 is also connected to the common drive shaft 29. With others Words: The first pump impeller 19, the second pump impeller 27 and the agitator 17 are driven by the common drive shaft 29.

The bypass flow path 21 is formed through an annular gap formed between the common drive shaft 29 and the grinding pot 9 so that the inlet 23 of the bypass flow path 21 passes through the flange portion 17 a of the agitator 17. The flange portion 17 has not shown connecting webs with the common drive shaft 29.

In the grinding chamber 11 flow internals in the form of webs 31 are arranged, which extend parallel to the peripheral wall 33 in a vertical direction and project into the grinding chamber 11. The webs 31 are distributed uniformly in the circumferential direction in the grinding chamber 11 and each form a gap 34 to the peripheral wall 33. The webs 31 act as a so-called flow breaker, so that the circulating in the grinding chamber 11 flow of ground material and grinding balls against the webs 31st bounce and thus generate turbulence. The columns 34 cause the flow along the peripheral wall 33 does not tear off completely, so that caused by the peripheral wall 33 cooling of the ground material in the grinding chamber 11 can be carried out in an advantageous manner.

The circumferential wall 33 is formed by a surrounding wall 9b of the grinding pot 9. To generate the cooling effect on the circumferential wall 33, a cooling device 35 is arranged in the surrounding wall 9b, which consists of a cooling fluid channel 37 arranged in the surrounding wall 9b. The cooling fluid channel 37 extends meandering in the surrounding wall 9b. Via a cooling fluid access 39, the cooling fluid channel 37 is supplied with cooling fluid. For this purpose, the cooling fluid access 39 is first connected to a lower portion 37a of the cooling fluid channel 37, and the cooling fluid channel 37 extends in a meandering manner to a cooling fluid outlet 41.

The flow cross-section of the cooling fluid channel 37 is selected so that there is a turbulent flow with conventional volume flows of cooling fluid. It has been found that with conventional volumetric flow rates of cooling fluid, a ratio of the projected grinding chamber base cross section formed by the area enclosed by the peripheral wall 33 to the flow area of the cooling fluid channel 37 of at least 240, usually a turbulent flow, can be generated in the cooling fluid channel 37 an advantageous cooling effect takes place.

By the grinder 5 according to the invention various advantages can be realized in a basket mill. By the flow through the bypass flow path 21 and bypassing the grinding chamber 11, an additional circulation is achieved in the Mahlgutbehälter 7, whereby the processing time, in particular regrind can be shortened by higher viscosity. By providing a first conveyor for generating the flow through the grinding chamber 11 in the form of a first pump impeller 19, a flow through the grinding chamber 11 is achieved in an advantageous manner and with high efficiency.

By providing the webs 31 in the grinding chamber 11 turbulence in the grinding chamber 11 are produced in an advantageous manner, whereby also a reduction of the processing time can be achieved.

Due to the configuration of the cooling device as in the surrounding wall 9b extending cooling fluid channels 37, in which a turbulent flow is generated, the cooling capacity is significantly increased, so that a significant increase in the grinding speed can be made without an unacceptable heat input into the material to be ground.

Claims (15)

1. Grinding assembly (5) for a basket mill (1) having a grinding shell (9) with a grinding chamber (11) and with grinding balls arranged in the grinding chamber (11), wherein the grinding chamber (11) comprises a grinding chamber inlet (13) and a grinding chamber outlet (15) for the grinding stock and is configured for the throughflow of the grinding stock, and with a first conveyor means which cooperates with the grinding chamber (11) for generating a grinding stock flow through the grinding chamber (11),
   characterized in that
   the grinding shell (9) comprises a bypass flow path (21) which the grinding stock can flow through while bypassing the grinding chamber (11), wherein the grinding gear (5) comprises a second conveyor means which cooperates with the bypass flow path (21) to generate the grinding stock flow through the bypass flow path (21).
2. Grinding assembly of claim 1, characterized in that the first conveyor means is formed by a first pump impeller (19), wherein the first pump impeller (19) is preferably arranged at the grinding chamber outlet (15).
3. Grinding assembly of claim 2, characterized in that the first pump impeller (19) is sealed, preferably by a gap seal, in a hub region (19c) from a housing part (9a) of the grinding shell (9), which surrounds the grinding chamber outlet (15).
4. Grinding assembly of one of claims 1 to 3, characterized in that the first pump impeller (19) is configured as a semi-open impeller, wherein the open side is arranged on the side of the impeller facing to the grinding chamber (11).
5. Grinding assembly of one of claims 1 to 4, characterized in that the second conveyor means is formed by a second pump impeller (27), wherein the second pump impeller (27) is preferably arranged at an outlet (25) of the bypass flow path (21).
6. Grinding assembly of claim 5, characterized in that the second pump impeller (27) is configured as a closed impeller.
7. Grinding assembly of one of the preceding claims, characterized in that the first and the second pump impeller (19, 27) have a common drive shaft (29).
8. Grinding assembly of one of the preceding claims, characterized in that the first and the second pump impeller (19, 27) are configured as one component.
9. Grinding assembly of one of claims 7 or 8, characterized in that an agitator assembly (17) is arranged in the grinding chamber (11), wherein the agitator assembly (17) is preferably driven via the common drive shaft (29).
10. Grinding assembly of one of claims 1 to 9, characterized in that flow fixtures are arranged in the grinding chamber (11).
11. Grinding chamber of claim 10, characterized in that the flow fixtures are formed by a plurality of webs (31) arranged at a circumferential wall (33) of the grinding chamber (11), which are arranged in parallel with the circumferential wall (33) and protrude into the grinding chamber (11).
12. Grinding assembly of claim 11, characterized in that a gap (34) is formed between the webs (31) and the circumferential wall (33), respectively.
13. Grinding assembly (5) of one of claims 1 to 12, characterized in that the grinding shell (9) comprises a surrounding wall (9b) which delimits the grinding chamber (11) in part, wherein the surrounding wall (9b) comprises a cooling device (35), and the cooling device (35) comprises at least one cooling fluid channel (37) extending in the surrounding wall (9b), which channel extends in the surrounding wall (9b) with multiple windings.
14. Grinding assembly of claim 13, characterized in that each cooling fluid channel (37) extends in a meandering shape, starting from at least one cooling fluid inlet (39) to a cooling fluid outlet (41).
15. Basket mill (1) comprising a grinding container (7) and a grinding assembly (5) of one of claims 1 to 14, wherein the grinding assembly (5) is adapted to be plunged/immersed into the grinding container (7).

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