Device and method for mixing components of a ceramic starting material

Abstract

The invention relates to a device (2) and a method for mixing components of a ceramic starting material, wherein a flowable powdered ceramic material as a first component can be supplied via a first inlet opening (8) and a flowable powdered additive as a second component can be supplied via at least one further inlet opening (10), each in a meterable manner, to a mixing system (22) in such a way that the first component and the second component mix homogeneously in the mixing system to form a mixed material variably enriched with the additive, which can be supplied as a ceramic starting material for further processing.

Description

[0001] DEVICE AND METHOD FOR MIXING COMPONENTS OF A CERAMIC STARTING MATERIAL

[0002] The invention relates to a device and a method for mixing components of a ceramic starting material.

[0003] DE 21 31 600 A shows a device for producing a mixture of products with a granular, dusty or floury consistency.

[0004] The document DE 696 21 627 T2 shows a plant for mixing thermoplastic polymer pellets.

[0005] EP 3 770 563 A1 shows a plant for weighing and mixing ingredients for asphalt production.

[0006] It is generally known from the state of the art that specific physical or chemical properties can be achieved in ceramic materials through suitable process control or the targeted selection of starting materials. To distinguish them from purely decorative ceramics, such ceramic materials are referred to as technical ceramics. A subgroup of these materials are ceramic materials for medical applications, which are intended to exhibit suitable biocompatibility for use in the human or animal body and often also high strength. These include, for example, dental ceramics, which are used as dental prostheses in the form of a single tooth or a partial or full denture, usually attached to implants inserted into the jawbone. A particularly suitable ceramic material for this purpose is zirconium dioxide.

[0007] Various prior art processes are known for the production of dental ceramic workpieces, such as dental crowns or dentures. These include, for example, the processing of green ceramic, which was described, among other things, in WO 2017 / 202869 A1. Here, a green compact made of a mixture comprising a ceramic powder and a binder system is used. A ceramic shell for dental prostheses can be produced from the green compact. The ceramic shell can be molded and adapted to a substrate before a firing step at temperatures below 1,050°C.

[0008] WO 2018 / 050811 A1 describes a device for functionalization for dental applications and a method therefor, wherein an application device comprises a support for receiving a partially machined dental molding for the production of a dental restoration and a dispensing device for at least partially infiltrating a functionalization material onto the surface of the dental molding.

[0009] Dental prostheses are frequently manufactured using so-called milling blanks, which, however, are often designed with a color gradient to replicate natural teeth. When using a semi-finished product (milling blank), various manufacturing processes are possible. For example, different color or material areas can be pre-pressed, which are then subsequently layered on top of one another to match the color gradient and then pressed again. It is also possible to use a multi-layer pressing process in which the corresponding successive color or material areas are inserted in a pre-mixed form. The mixtures are then transferred one after the other into a press mold, where the poured granules are then pressed together. In addition, pre-compaction can take place to create a more attractive color transition.

[0010] Based on this state of the art, the task now arises to create a device or a method for mixing components of a ceramic starting material, which allows a high production throughput and at the same time enables cost-effective production.

[0011] This object is achieved by the features of independent patent claims 1 and 13. Further advantageous embodiments of the invention are the subject of the subclaims. These can be combined with one another in a technologically expedient manner. The description, particularly in conjunction with the drawings, further characterizes and specifies the invention.

[0012] According to the invention, a device for mixing components of a ceramic starting material is specified, wherein a flowable powdered ceramic material as the first component and a flowable powdered additive as the second component can be metered into a mixing system via a first inlet opening and at least one further inlet opening, so that the first component and the second component mix homogeneously in the mixing system to form a mixture variably enriched with the additive, which can be fed to further processing as a ceramic starting material.

[0013] Accordingly, the device according to the invention produces the mix as a ceramic starting material for further processing, so that it is mixed homogeneously on the one hand, but can also be variably enriched with the additive on the other. In this way, it is possible to achieve a desired composition of the mix due to the dosability when feeding it into the mixing system via the inlet openings. Different procedures for the variable enrichment with the additive are conceivable here. In addition to a graded process control when changing the admixture of the additive, a targeted volume-defined feed of the required amount of additive can generally be achieved, so that material properties of the ceramic starting material are possible that could not be achieved using the layer pressing known from the prior art.Due to the dosability of the supply of the components, reproducible ceramic starting material is created for further processing.

[0014] According to one embodiment of the invention, the ceramic starting material can be further processed into a technical ceramic.

[0015] In general, the device according to the invention is suitable for all flowable ceramic materials in powder form. However, the targeted influencing of the physical or chemical properties of the ceramic material through the addition of additives proves particularly advantageous for technical ceramics. It should be noted here that several additives are typically added to achieve the desired properties. The device according to the invention imposes no restrictions on the type, number, or quantity of additives.

[0016] According to a further embodiment of the invention, the ceramic starting material can be further processed into a medical, in particular a dental ceramic, wherein the first component is preferably a ready-to-press granulate in the form of an RTP granulate made of ZrO2.

[0017] The device according to the invention is particularly advantageous for the manufacture of dental products. In particular, it is intended for use in the production of a semi-finished product, also known as a milling blank, in which, starting from a ready-to-press granulate of zirconium dioxide, additives can be added for targeted modification, for example, of the color, in order to create a color-matched dental prosthesis. This is produced from the semi-finished product by milling in the conventional manner. This can be either a dental crown or a denture.

[0018] According to one embodiment of the invention, the first and / or the further component can be fed to the mixing system in a controlled manner via a dosing unit. The dosing units can be controlled via a control unit during feeding to the mixing system.

[0019] As already mentioned above, the dosing capability of adding the first and second components is an important aspect of the reproducible production of the mix as a ceramic starting material for further processing. For this purpose, according to this embodiment, one or more dosing units can be used for adding the components, the dispensing of which can be controlled in a suitable manner. One possible embodiment of a dosing capability can be a screw conveyor, whereby the actual amount fed into the mixing system can be derived from a delivery value of the screw conveyor, which can be calculated from the geometry of the screw conveyor, the bulk density, the rotational speed, and the duration of the feed. Coupling the dosing unit(s) with the control unit enables a correspondingly controlled dispensing of the components.

[0020] According to one embodiment of the invention, the dosing unit is provided with a measuring unit for monitoring the supplied quantity. The measuring unit can be coupled to the control unit.

[0021] Here, the controlled feeding concept described above is expanded to include a measuring unit monitoring the actual amount fed in. This makes it possible to detect any deviations in bulk density, for example, due to inhomogeneities, agglomerates, or uneven distribution in the waste stream, during the ongoing process and dynamically compensate for them via the control unit by adjusting the dosing rate. In addition to a screw conveyor, a piston conveyor or a vibrating conveyor could also be used. Other suitable conveying units are, of course, also possible.

[0022] According to one embodiment of the invention, the mixing system is provided with a downpipe.

[0023] A downpipe represents one possible configuration of the mixing system, with a design similar to a static mixer being envisaged. This is a free-fall mixing process that is expected to achieve a mixing quality sufficient for the implementation of the invention.

[0024] According to one embodiment of the invention, the mixing system is provided with physical, static, or dynamic mixing elements, or generates an air vortex by means of air pressure or performs air mixing combined with an air extraction process.

[0025] To achieve a homogeneous distribution of the various components in the mix, additional mixing elements can be provided to further improve the mixing quality. Different mixing media can be used, and the selection of the mixing media can be easily determined through testing.

[0026] According to one embodiment of the invention, a mixing rod, a vibrating plate, a sieve, or an air vortex system is provided on the downpipe for mixing. Such devices enable an improvement in the mixing quality and can be used in the device according to the invention as required.

[0027] According to one embodiment of the invention, the downpipe is air-conditioned and / or provided with a vibration unit.

[0028] While air conditioning prevents condensation and the formation of agglomerates in the mix, a vibration unit ensures a uniform density of the mix after it leaves the mixing system.

[0029] According to one embodiment of the invention, the mixed material can be fed to a scale after leaving the mixing system.

[0030] In addition to the above-described verification of the actual addition of the components at the input side using the measuring unit, it is also possible to weigh the mix at the output side as it leaves the mixing system to achieve a balance in relation to the process time. This allows the scale to detect the entry of different dosed quantities during the delayed passage through the mixing system and forward this information to the control unit.

[0031] Furthermore, the invention provides a method for mixing components of a ceramic starting material, in particular by means of a device as described above, in which the following steps are carried out: providing a mixing system, metered addition of a first component as a flowable powdered ceramic material and a second component as an additive, mixing the first component and the second component in the mixing system so that the first component and the second component mix homogeneously in the mixing system to form a mixture variably enriched with the additive, and further processing the mixture as a ceramic starting material.

[0032] According to one embodiment of the method according to the invention, the metered feeding is carried out by means of metering units, wherein the metering units are dynamically controlled with respect to a flow rate of the first component or the second component during filling.

[0033] According to a further embodiment of the method according to the invention, the dosing units are provided at the outlet with measuring units which monitor the quantity actually supplied by the dosing units.

[0034] According to a further embodiment of the method according to the invention, the mixed material is fed to a scale after leaving the mixing system.

[0035] According to a further embodiment of the method according to the invention, a control unit controls the dosing units based on the values ​​of the scale.

[0036] According to a further embodiment of the method according to the invention, a control unit controls the dosing units based on the values ​​of the scale and the measuring units.

[0037] The invention is explained in more detail below with reference to the drawing. It shows:

[0038] Figure 1 is a schematic representation of a device according to the invention, Figures 2A and 2B show a first example of a ceramic component produced with the device from Figure 1 together with a density distribution of the components,

[0039] Figures 3A and 3B show a second example of a ceramic component produced with the device of Figure 1 together with a density distribution of the components, and

[0040] Figure 4 shows a method according to the invention in a flow chart.

[0041] In the figures, identical or identically acting elements are provided with the same reference numerals.

[0042] With reference to Figure 1, an embodiment of a device 2 according to the invention for mixing components of a ceramic starting material is described below. The device 2 is shown in Figure 1 in a schematic view, with only the components relevant to the invention being illustrated. The invention is explained by way of example using the mixing of a ceramic material with an additive. However, it goes without saying that the invention can be extended to include the addition of further additives. In practice, it can be assumed that the device 2 typically processes five additives as admixtures.

[0043] Figure 1 shows that the device 2 has a filling funnel 4, 6 for each of the two substances, which is provided with a corresponding inlet opening 8, 10 for adding the ceramic material as the first component and the additive as the second component. Flowable powdered ceramic material is added as granules via the first inlet opening 8. This can in particular be ready-to-press granules, which are also referred to as RTP granules, made of zirconium dioxide. The second inlet opening 10 can, for example, be used to add a dye as an additive for the ceramic granules. In other embodiments, the additive can be used to specifically influence the physical or chemical properties of the ceramic granules.

[0044] Each of the two filling hoppers 4, 6 is connected to a dosing unit 12, 14, which in the illustrated embodiment can be designed as a screw conveyor. The dosing units 12, 14 each enable the controlled addition of a predetermined amount of the respective substance. For example, based on the activation time of the dosing units 12, 14, the dispensed amount can be determined based on the intrinsic parameters of the screw geometry, bulk density, and speed of the dosing units 12, 14.

[0045] Optionally, one or, as shown, both dosing units 12, 14 are equipped with a measuring unit 16, 18. The measuring units 16, 18 can be used to compare the actual quantity dispensed by the dosing units 12, 14. Both the dosing units 12, 14 and the measuring units 16, 18, if present, are connected to a control unit 20, which controls the dispensing of the substances via the dosing units 12, 14 and, if necessary, incorporates the values ​​from the measuring units 16, 18 into the control system.

[0046] The substances dispensed by the dosing units 12, 14 now enter the actual mixing system 22, which, as shown in Figure 1, is designed in the form of a downpipe which has a feed 24 at its upper end for receiving the substances dispensed by the dosing units 12, 14.

[0047] The mixing system 22 is mounted in a holder 28 with vibration dampening via springs 26. The mixing system 22 can have additional mixing elements 30 that further improve the mixing quality of the two substances. For this purpose, the mixing system 22 can be equipped with physical, static, or dynamic mixing elements 30, or can generate an air vortex using air pressure, or perform air mixing combined with an air extraction process. Additional components, such as a mixing rod, a vibrating plate, a sieve, or an air vortex system, can also be provided as needed.

[0048] The mixing system 22 can be equipped with a vibrator 32 in the downpipe area, which largely prevents the formation of lumps in the mix. The mix 34 leaves the mixing system 22 and is fed to a mold 36, which can be arranged on a scale 38, which can also exchange signals with the control unit 20. However, a pouring shoe can also be used instead of the mold 36. The downpipe area in the mixing system 22 can be air-conditioned.

[0049] The composition of the mixed material 34 fed into the mold 36 can be controlled over a wide range by controlled addition of the admixed substances, so that reproducible starting materials for further processing can be created.

[0050] Figure 2A illustrates the use of device 2 using the example of producing a milling blank. After pressing the mixed material 34 located in the mold 36, the graduated addition of a colorant as an additive via the second inlet opening 10 to the RTP granulate made of zirconium dioxide supplied via the first inlet opening 8 produces a semi-finished product 40 with a color-matched gradient 42, from which a dental crown or denture can be manufactured by machining.

[0051] The color-adjusted curve 42 from Figure 2A is shown again in Figure 2B based on the added quantities M of the two substances. It can be seen that the added zirconium dioxide granulate remains essentially constant according to curve 44, while the additive gradually increases as a color addition according to curve 46.

[0052] Figure 3A shows another use of device 2. Instead of a homogeneous, graded addition of a dye, several layers are created during the production of a component 48 with different additives, for example, to achieve different mechanical properties. The amounts M of the plastic granulate added follow a curve 50 according to Figure 3B, while the addition of the first and second additives follows curves 52 and 54, respectively.

[0053] A corresponding method according to the invention is illustrated again in Figure 4 using a flow diagram. First, in step 100, a metered addition of a first component as a flowable powdered ceramic material and a second component as an additive takes place. By mixing the first component and the second component in the mixing system 22 in step 102, the first component and the second component mix homogeneously in the mixing system 22 to form a mixed material variably enriched with the additive. Subsequently, in step 104, the mixed material 34 is further processed as a ceramic starting material. The metered addition in step 100 can be carried out by means of metering units 12, 14, wherein the metering units 12, 14 are dynamically controlled with regard to a flow rate of the first component or the second component during filling.Furthermore, in step 100, the dosing units 12, 14 can be provided at the output with measuring units 16, 18, which monitor the quantity actually supplied by the dosing units 12, 14. After leaving the mixing system 22, the mixed material can be fed to the scale 38 in step 102. In this case, it is provided that the control unit 20 controls the dosing units 12, 14 based on the values ​​from the scale 38 and the measuring units 16, 18. The features specified above and in the claims, as well as those shown in the figures, can be advantageously implemented both individually and in various combinations. The invention is not limited to the described embodiments, but can be modified in many ways within the scope of expert knowledge.

[0054] List of reference symbols:

[0055] 2 Device

[0056] 4, 6 filling funnels

[0057] 8, 10 Entrance opening

[0058] 12, 14 Dosing unit

[0059] 16, 18 measuring unit

[0060] 20 Control unit

[0061] 22 Mixed system

[0062] 24 Feed

[0063] 26 springs

[0064] 28 Bracket

[0065] 30 mixing elements

[0066] 32 vibrators

[0067] 34 Mixture

[0068] 36 Shape

[0069] 38 scales

[0070] 40 semi-finished products

[0071] 42 History

[0072] 44 Curve

[0073] 46 Curve

[0074] 48 components

[0075] 50 curve

[0076] 52 Curve

[0077] 54 Curve

[0078] 100 steps

[0079] 102 steps

[0080] 104 steps

Claims

Claims:

1. Device for mixing components of a ceramic starting material, wherein a flowable powdered ceramic material as a first component and a flowable powdered additive as a second component can each be metered into a mixing system via a first inlet opening, such that the first component and the second component mix homogeneously in the mixing system to form a mixture variably enriched with the additive, which can be supplied as a ceramic starting material for further processing.

2. Device according to claim 1, wherein the ceramic starting material can be further processed into a technical ceramic.

3. Device according to claim 1, wherein the ceramic starting material can be further processed into a medical, in particular a dental ceramic, wherein the first component is preferably a pressable granulate in the form of an RTP granulate made of ZrÜ2. 4 Device according to one of claims 1 to 3, wherein the first and / or the further component can be supplied to the mixing system in a controlled manner via a dosing unit.

5. Device according to claim 4, wherein the dosing units are controllable via a control unit during the feeding to the mixing system.

6. Device according to one of claims 1 to 5, wherein the dosing unit is provided with a measuring unit for monitoring the quantity supplied.

7. Device according to claim 6, wherein the measuring unit is coupled to the control unit.

8. Device according to one of claims 1 to 7, wherein the mixing system is provided with a downpipe.

9. Device according to any one of claims 1 to 8, wherein the mixing system is provided with physical, static, or dynamic mixing elements, or generates an air vortex by means of air pressure, or performs an air mixing combined with an air extraction method.

10. Device according to one of claims 8 or 9, wherein a mixing rod, a vibrating plate, a sieve or an air vortex system is provided on the downpipe for mixing.

11. Device according to one of claims 8 to 10, wherein the downpipe is air-conditioned and / or equipped with a vibration unit.

12. Device according to one of claims 1 to 11, wherein the mixture can be fed to a scale after leaving the mixing system.

13. Method for mixing components of a ceramic starting material, in particular by means of a device according to one of claims 1 to 12. 12, in which the following steps are performed: - Providing a mixing system, - Metered addition of a first component as a flowable powdered ceramic material and a second component as an additive, - Mixing the first component and the second component in the mixing system, so that the first component and the second component are in to homogeneously mix the mixture with the additive in the mixing system to create a mixture variably enriched with the additive, and - Further processing of the mixture as a ceramic raw material.

14. Method according to claim 13, wherein the metered supply is carried out by means of metering units, the metering units being dynamically controlled with respect to a flow rate of the first component or the second component during filling.

15. Method according to claim 13 or 14, wherein the dosing units at the output are provided with measuring units that monitor the quantity actually supplied by the dosing units.

16. Method according to claim 15, wherein a control unit controls the dosing units based on the values ​​of the scale and the measuring units.

17. Method according to any one of claims 13 to 16, wherein the mixture is fed to a scale after leaving the mixing system.

18. Method according to claim 17, wherein the control unit controls the dosing units based on the values ​​of the scale.

Images