Patent Application
20230001419
The present invention relates to a portable laboratory scale milling assembly for a ball mill with a housing for refining and separating a substrate and with a collection vessel for retaining the refined substrate, wherein the housing comprises, in vertical order a lid, at least one milling vessel for receiving milling balls and a screen with a refining section and with apertures, and wherein the collection vessel is releasably mounted to a bottom end of the housing, and wherein in the housing an orifice is arranged, wherein in the orifice a valve is arranged for selectively allowing gas to pass between an outside and an inside of the housing in an open position of the valve and to seal the housing against the outside in a closed position of the valve. The present invention also relates to a ball mill with an actuator for holding and moving a milling assembly. Furthermore, the present invention relates to a method for refining a substrate with a milling assembly.
Ball mills of the state of the art are used to refine materials and decrease materials to particle sizes of micron or submicron level. Such refined particles are for instance needed for laboratory analysis testing of material samples. Ball mills usually comprise of a milling jar and a lid. The material to be refined to small particles size is inserted into the milling jar together with milling balls. The milling jar is then closed and optionally sealed. The closed milling jar is than set in motion such that the balls move inside the milling jar. During a milling process the material is exposed to the moving balls and broken down to smaller particles when in contact with the balls and a surface inside the jar. In some applications it is desirable that a maximum size of particles in not exceeded in a material sample. In some cases, it is also desirable, to have a high purity or homogeneity in the material sample and to avoid mixing of unwanted material, components, compounds or elements with the sample.
In the utility model DE 20 2017 107 052 U1 is disclosed a grinding jar and a grinding jar assembly for refining a milling material and/or for separating a milling material from at least a milling body. The utility model discloses a laboratory mill with a grinding jar with multiple grinding fractions vertically arranged above one another. The grinding jar comprises a lid and a bottom jar part. Retaining elements can be clamped between jar parts for separating grinding space fractions from each other. The retaining element can be designed as a strainer. A size of openings in the strainer can decrease from a top to a bottom, such that multiple grinding stages are formed. In operation the grinding bodies decrease a particle size of the milling material and the milling material passes through the openings of the retaining element once a particle size is small enough. According to the teaching the grinding material can be continually decreased in particle size from milling space fraction to milling space fraction. The milling material of a final particle size passes through the openings of a bottom retaining element and can be collected in a bottom jar part. The teaching of the utility model document includes to seal the grinding jar and to clamp the jar parts together. The milling jar assembly allows to decrease a milling material particle size to a very small size and ensure that milling bodies are separated from the milling material. The milling jar assembly also ensures, that the milling material particles are of a minimum size when reaching the bottom jar part.
The document CN 203 750 627 U discloses a milling assembly for a ball mill with a housing for refining and separating a substrate and with a collection vessel for retaining the refined substrate, wherein the housing comprises, in vertical order a lid, a milling vessel for receiving milling balls and a screen with a refining section and with apertures, and wherein the collection vessel is releasably mounted to a bottom end of the housing, and wherein in the housing an orifice is arranged, wherein in the orifice a valve is arranged for selectively allowing gas to pass between an outside and an inside of the housing in an open position of the valve and to seal the housing against the outside in a closed position of the valve.
It is an object of the present invention to provide a means and method to safely mill a substrate to a desired quality.
The object is achieved by a portable laboratory scale milling assembly for a ball mill as taught by claim 1 of the present invention. The object is also achieved by a ball mill according to claim 9. The object is furthermore achieved by a method for refining a substrate with a milling assembly according to claim 10. Advantageous embodiments of the milling assembly, the ball mill and advantageous steps in the method for refining the substrate are disclosed herein.
The invention discloses the technical teaching, that the milling vessel comprises a taper for receiving a sealing screw. The invention also discloses the technical teaching of a ball mill with an actuator for holding and moving a milling assembly. Furthermore the solution to the object lies in an inventive method for refining a substrate with a milling assembly comprising the step of providing a housing with a screen and with a milling vessel with balls, and with the step of inserting a substrate into a milling vessel, and with the step of inserting a sealing screw into a taper in the milling vessel, and with the step of mounting a lid to the milling vessel and sealing the housing with the lid, and with the step of closing at least one valve of an orifice to maintain an atmosphere in the housing, and with the step of milling the substrate by movement of the balls in the milling vessel, wherein the substrate is refined by contact with the balls and wherein the refined substrate passes through apertures in a screen towards a bottom end of the housing, and with the step of collecting the refined substrate in a collection vessel connected to the bottom end of the housing.
The taper and the sealing screw reinforce the cylindrical milling vessel structurally. Furthermore, the taper and sealing screw function as a deflection surface for balls inside the milling vessel and avoid damage to the lid and the orifice in the lid. The deflection surface also causes the ball to frequently come in contact with substrate and the refining section such that the substrate is refined at a high frequency. The application of the taper and the sealing screw in the milling vessel on the top end of the housing thus allows a particularly safe milling operation.
As a preferred embodiment an additional second milling vessel is arranged below the milling vessel. This arrangement allows for consecutively refining substrate to a desired particle size in a controlled environment.
According to another preferred embodiment of the present invention multiple milling vessels are arranged in vertical order below one another. This allows for consecutively refining substrate for instance to submicron level without the need of decreasing aperture size and particle size from one milling vessel to the milling vessel below at a high degree. In other words, the particle size can be decreased gradually in incremental steps.
According to yet another preferred embodiment the housing further comprises a catch basin for attachment of the collection vessel and for guiding refined substrate into the collection vessel, wherein the catch basin is mounted between the milling vessel and the collection vessel. According to another advantage, different sizes of collection vessels can be arranged, in particular when the mating dimensions of collection vessels with different sizes are the same in such a way that collection vessels with different sizes can be mutually exchanged.
The arrangement of a catch basin allows for a small collection vessel by facilitating the catch basin as an adapter piece. A small collection vessel is easy to handle and transported. The use of a catch basin particularly allows to use a screen with a comparatively large diameter and surface. Consequently, an area of the refining section of the screen is large. Consequently, the number of apertures in the screen is high. Consequently, an effective area for the milling and separation of the substrate is large and the milling operation can be performed efficiently and in a short time span.
According to another preferred embodiment of the present invention the screen is arranged, in particular clamped, between the neighboring milling vessel and/or between the milling vessel and the neighboring catch basin. This has the advantage, that an assembling of the milling assembly is eased. The use of equally dimensioned parts, in particular milling vessels, screens and a catch basin of equal or fitting diameter allows to selectively adjust the milling assembly in a modular manner to serve a specific desired milling task. A cleaning of the circular flat screen, the cylindrical tube shaped milling vessel and the round shaped catch basin is eased.
The present invention is also embodied in that the apertures in respective screens decrease in size for consecutively reducing the particle size of the substrate from a top end to the bottom end of the housing. In other words, the apertures in the screen located closest to the top end of the housing features the largest diameter. The screen closest to the bottom end of the housing and the collection vessel features the smallest diameter. The apertures are preferably circular. This allows for instance to hold back substrate, material or particles which are not yet decreased to a desirable size. Material or substrate which cannot be broken to a desired size will not pass the aperture of the respective screen. Consequently, a separation and high purity and homogeneity in the substrate is achieved. Different ball sizes or balls of different material can be used in combination with decreasing diameter of the apertures of respective screens. Thus, a selectively adjustable milling assembly to increase the efficiency of the milling operation is provided.
Advantageously the collection vessel and/or the bottom end of the housing comprises a stopcock for sealing the collection vessel and/or the housing against the outside before detaching the collection vessel from the housing. The stopcock can be arranged in the catch basin. Alternatively, a stopcock can be arranged in the bottom end of the milling vessel next to the collection vessel. In each case the stopcock on one side hinders for instance oxygen or other material to enter into the housing or into the collection vessel. Thus, a reaction of the delicate or sensitive or unstable substrate can be avoided. For instance, an oxidation of the substrate can be avoided. This is particularly critical in view to a substrate with a small particle size with a large surface to volume ratio. Another advantage of the stopcock lies in the fact, that it hinders for instance poisonous or dangerous substrate from leaving the housing or the collection vessel to enter the environment and cause harm or danger to the environment. The stopcock allows to safely retain the substrate inside the housing or inside the collection vessel. The stopcock functions as a safety device for safely transporting the milling assembly or the collection vessel or the housing to a save environment.
In a preferred embodiment the orifice comprises a filter. The filter can be a high efficiency particulate air filter (HEPA). The orifice is arranged in the wall of the housing, in particular in the wall of the milling vessel. The filter may be attached to the wall. The use of such a filter in the orifice avoids harmful material to pass between an inside of the housing and an outside of the housing when the valve of the orifice is in an open position. Also, in case of a defect valve leaking gas is filtered. The filter also avoids contamination of the substrate from gas flowing into the housing through the orifice.
The application of the aforementioned ball mill with an actuator allows for an efficient milling operation. A milling result is reproducible with an automated ball mill with an actuator.
The conduct of the aforementioned inventive method for refining the substrate with the milling assembly has the advantage, that a safe refinement in a controlled environment without the need to process or contact the substrate even until finally retained in the collection vessel is achieved.
A further preferred method step, comprises setting a desired atmosphere in the housing by evacuating or inserting a gas into the housing through the orifice. This for instance allows for controlling a chemical reaction or to avoid a chemical reaction during the milling process. The contamination of a substrate from gas can be avoided by performing a milling operation under vacuum. Also, the processing of gas contaminated from the substrate during the milling operation inside the housing can be avoided by applying a vacuum to the housing.
Yet another preferred method step, comprises the step of opening a valve to flush refined substrate particles towards the collection vessel. This can particularly be achieved by opening the valve of the orifice in the top end of the housing, particularly in the lid and letting gas pass into the vacuum of the housing. This allows for an effective milling operation without remainders of substrate particles left in the housing. This has the advantage, that a cleaning operation and handling of remaining substrate is decreased.
A further preferred method step, comprises the step of closing a stopcock in the collection vessel and/or closing a stopcock in the bottom end of the housing for sealing the inside against the outside before removing the collection vessel from the housing. This allows to avoid a dangerous material to enter the environment from the inside of the collection vessel or from the inside of the housing. This also avoids for instance gas or particles or material from the environment and the outside to enter into the inside of the housing or the inside of the collection vessel.
In yet another application the orifices can be used to clean the housing inside by flushing air from one orifice to another orifice and through the housing. In yet another application a continuous flow of gas through the housing between one orifice at a bottom end of the housing and one orifice at the top end of the housing can cause movement of particles and facilitate refinement and sieving. Depending on the gas a drying or moisting of substrate can be achieved.
In an application gas may be circulated in a closed loop between two orifices through the housing. In this setup the inside of the housing is a part of the closed loop and another part of the closed loop lies on the outside of the housing, wherein the two orifices are connected by a tube on the outside.
The aforementioned components as well as the claimed components and the components to be used in accordance with the invention in the described embodiments, are not subject to any special exceptions with respect to their size, shape, material selection and technical concept such that the selection criteria known in the pertinent field can be applied without limitations.
The circular and flat lid 12 features an orifice 19 with a valve 20. The orifice 19 is located in the center of the circular lid 12. An additional orifice 19 with a valve 20 is arranged in the milling vessel 13 and the catch basin 21 respectively. The milling vessel 13 comprises a socket 28 for connection with an here not depicted actuator arm of a ball mill. The top end milling vessel 13 comprises a taper 26 with a hole for receiving a sealing screw 27. The taper is a disk with a decreasing thickness of materiel towards the hole in the center. The flat circular screens 15 comprise of apertures 17 and a refining section 16. The catch basin 21 of the housing 10 features an outlet 32 in the bottom end 18 of the housing 10. In the outlet 32 arranged is a stopcock 24 for sealing the housing 10. The collection vessel 11 also comprises a stopcock 24 for sealing the collection vessel 11. The collection vessel 11 is connectable to the outlet 32 by a screw connection. The outlet 32 and the collection vessel 11 feature threads 33, such that the collection vessel 11 can be screwed onto the outlet 32. The circular top end of the catch basin 21 features a flange 31. The cylindrical top end milling vessel 13 and the cylindrical bottom end milling vessel 13 also feature flanges 31 at their respective top ends and bottom ends. The clamping means 29 may connect the lid 12 and the milling vessel 13 by encompassing the flange 31 and the lid 12 and clamping them together. A connection between the milling vessels 13 and a connection between the milling vessel 13 and catch basin 21 can be realized by the clamping means 29 encompassing two respective neighboring flanges 31. The milling vessels 13 are of cylindrical shape. A height of the milling vessel may be 15 cm a diameter of the milling vessel may be 7 cm. The clamping means 29 comprises a lever 37 for tightening and closing the clamping means 29 around a circumference of the flanges 31 and the lid.
An upper milling chamber 34 is formed between the wall 40 of the top end milling vessel 13, the deflection surface 36 and, the screen 15 clamped between milling vessel 13 at the top end 23 and the milling vessel 13 at the bottom end 18. A lower milling chamber 35 is formed between the wall 40 of the bottom end milling vessel 13, the screen 15 clamped between milling vessel 13 at the top end 23 and the milling vessel 13 at the bottom end 18, and the screen 15 clamped between the milling vessel 13 at the bottom end 18 and the catch basin 21. The screen 15 of the upper milling chamber 34 and the screen 15 of the lower milling chamber 35 at the bottom end 18 comprise of the apertures 17 and the refining sections 16 respectively. The upper milling chamber 34 and the lower milling chamber 35 is filled with milling balls 14 and the substrate 22 to be refined. In a first step before the milling operation the substrate 22 is filled into the upper milling chamber 34 from a top end 23 through the hole in the taper 26. In a second step the sealing screw 27 is screwed into the hole of the taper 26. In a further step the lid 12 is mounted to the top end milling vessel 13 by the clamping means 29. In a further step the housing 10 is evacuated through the orifice 19 such that the sealed milling assembly 1 is set under vacuum. During the evacuation process filters 25 of the orifice 19 filter the gas sucked from the inside 38 of the housing 10 such that no substrate, particles or harmful components or material in the gas enter the outside 39 of the housing 10. In a subsequent step the valves 20 of the orifice 19 are set to a closed position to maintain the vacuum. During the milling operation the milling assembly 1 is set in motion, such that the balls 14 move and refine the substrate 22 by breaking it up into particles under contact with the balls 14 and under contact with the refining section 16 of the screen 15. The diameter of the apertures 17 in the screen 15 of the upper milling chamber 34 is larger than the diameter of the apertures 17 in the screen 15 of the lower milling chamber 35. Once the substrate 22 is broken down to a particle size which allows a passage through the aperture 17 of the screen 15 of the upper milling chamber 34 by gravity, it will fall into the lower milling chamber 35. The particles of the substrate 22 in the lower milling chamber 35 are again refined. Once the particles have a size small enough to pass through the apertures 17 in the screen 15 of the lower milling chamber 35 the particles of the substrate 22 will fall into the catch basin 21. Then the particles of the substrate 22 will fall or slide further into the collection vessel 11 under the influence of gravity and movement from the actuator. This ensures, that only particles of a size smaller than the diameter of the apertures 17 of the lower milling chamber 35 are collected. Furthermore, it is ensured that the substrate 22 is separated from the milling balls 14 in the milling process. These two aspects are not achievable with a conventional milling jar, where only by statistical probability and the original quality of the substrate 22 a particle size is determined. The aforesaid separation of milling balls 14 from the substrate 22 is also not possible with a conventional milling jar.
During the milling operation the stopcock 24 of the outlet 32 of the catch basin 21 and the stopcock 24 of the collection vessel 11 are open, such that the refined substrate particles 22 can fall through the outlet 32 into the collection vessel 11. Once the substrate 22 is entirely refined and has passed the upper milling chamber 34, the lower milling chamber 35, the catch basin 21 and is collected in the collection vessel 11 the stopcock 24 of the outlet 32 is closed and the stopcock 24 of the collection vessel 11 is closed. After closing of the stopcock 24 of the catch basin 21 and after closing of the stopcock 24 of the collection vessel 11, the collection vessel 11 can be screwed of the catch basin 21. With the closed stopcock 24 the refined substrate 22 remains in a vacuum and is sealed from the outside 39. This has the advantage, that an undesirable reaction between the particles of the substrate 22 and the environment, in particular air is avoided. This also has the advantage that a contamination of the environment outside 39 with the refined particles of the substrate 22 is avoided.
In an alternative operation the sealing screw 27 is not screwed into the taper 26. This allows that remaining particles of the substrate 22 can be flushed into the collection vessel 11 by setting the valve 20 of the orifice 19 in the lid 12 from the close position of the valve 20 to the open position of the valve 20. In the open position of the valve 20 air from the outside 39 flows into the housing 10 due to the low pressure from the vacuum. With inflowing air remaining particles of the substrate 22 are flushed towards and into the collection vessel 11.
The orifice 19 in particular in the lid 12 may feature an adapter arrangement with an exchangeable coupling part for a tubing with different sizes. This makes possible that tubes with different sizes and diameters can be attached to the orifice 19.
| Number | Date | Country | Kind |
|---|---|---|---|
| 19212227.3 | Nov 2019 | EP | regional |
This application is the U.S. National Stage of PCT/EP2020/075854 filed on Sep. 16, 2020, which claims priority to European Patent Application 19197740.4 filed on Sep. 17, 2019, the entire content of both are incorporated herein by reference in their entirety.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2020/082654 | 11/19/2020 | WO |
