Patent Application
20060117869
The present invention relates to a method for metering powders, in particular for the production of combinatorial material libraries and a device for implementing the method.
The discovery and development of new substances and materials is a primary objective of the materials sciences, chemistry, and pharmaceutics. However, the search for suitable compounds is often associated with a great expenditure of time and money. In order to be able to carry out this search more effectively and economically, a systematic method was introduced years ago in pharmaceutics and later in other areas of application, which has become known as “combinatorial chemistry.” In doing so, a number of potentially interesting compounds were produced and analyzed. The advantage of this method is seen in the possibility for automation which allows high throughput in the shortest time.
To produce the material libraries needed for this, for a long time it was necessary to use soluble substances because the only systems that were available for metering substances were those that only allowed the metering of liquids. In materials science in particular, the focus is on the precise metering of for the most part poorly soluble substances in powder or paste form, for example. Furthermore, accurate metering of extremely small quantities of substance increasingly plays a significant role.
A known method for metering powdered substances is to first compress the powder into a pellet which is subsequently penetrated using a suitable hollow punch and the stamped out pellet material is transferred into a vessel for further use. The disadvantage in this method is that it is limited to powders that can be formed into a pellet in a simple manner.
An object of the present invention is to provide a powder metering device and a method for operating the same, which allow automated metering of powders in a simple and accordingly cost-effective manner.
The object of the present invention is achieved by a method and a powder metering device.
The powder metering device of the present invention and the method for operating the same have the advantage that automated metering of powders, in particular for the production of combinatorial material libraries, may be performed in a simple and nonetheless reliable manner. In this context, a metering element is used that has a supply vessel open on one end for taking up the substances to be metered, as well as a plunger which reversibly closes the end of the tubular supply vessel opposite the opening, the opening of the supply vessel for receiving the powder being first plunged into a loose fill, of the powder to be metered previously charged in a metering receiver, in such a way that the edges delimiting the opening of the supply vessel contact a bottom surface of the metering receiver. This ensures that a defined quantity of the previously charged powder is taken up into the supply vessel of the metering element.
It is thus an advantage if the metering element is plunged into the previously charged loose fill at least two times, preferably a plurality of times in direct succession since this causes the powder in the supply vessel to be compacted. This causes a compacted and thus defined quantity of the powder to be metered to be formed within the supply vessel. The powder taken up into the supply vessel is advantageously ejected by an axial movement of the plunger. The ejection is preferably made into a metering vessel which is positioned on scales to monitor the metered quantity of powder.
In another advantageous embodiment, the metering element is stripped after the powder is ejected, by pushing it through an elastic, notched and planar stripping element.
In one particularly advantageous embodiment of the present invention, the supply vessel and/or the plunger have a mount as a point of contact for a mechanical grabber. This allows an automatic mounting and operation of the metering element, for example, by a metering robot. Furthermore, the mount may have a coding for detecting the volume or the diameter of the associated supply vessel.
In another particularly advantageous embodiment, the metering receiver includes a vibrator. This causes the layer thickness of the previously charged loose powder fill to be uniform even as the withdrawal progresses. As an alternative or in addition, the metering receiver has side boundary surfaces slanted in the direction of its bottom surface carrying the fill.
The powder metering device shown in
In order to ensure the closability of supply vessel 12 independently of plunger 16, supply vessel 12 preferably has threads, which are not shown, stamped on the outside wall of supply vessel 12, preferably in the area of its opening.
On its end facing the substance to be metered, plunger 16 preferably includes a gasket 15 which is, for example, mechanically affixed and thus designed to be exchangeable. On its side opposite the substance to be metered, plunger 14 merges into a piston rod 18 which preferably has four suitable ribs for better guidance. Plunger 16 and piston rod 18 are preferably made of stainless steel or a chemically inert polymer such as PTFE or PVC.
To ensure automated metering in a short time cycle, a mount or fitting 26, 28 is provided on the end of supply vessel 12 opposite the opening and/or on the side of plunger 16 or piston rod 18 opposite the substance to be metered, the mount or fitting being used as a point of contact for a mechanical grabber which is not shown.
Furthermore, the powder metering device shown in
The powder metering device shown in
For metering the powder, metering element 10 is essentially positioned over the opening of metering receiver 20 in a step A, opening 14 of metering element 10 being localized primarily vertically over metering receiver 20. In a step B, metering element 10 is then guided using a predetermined force through the opening of metering receiver 20 in an axial direction in such a way that opening 14 of metering element 10 is plunged into fill 22 until the mechanical resistance caused by fill 22 brings the axial movement to a stop. The level of the predetermined force thus controls the insertion depth. Another possibility is to select the predetermined force to be relatively large and to guide metering element 10 through the opening of metering receiver 20 in an axial direction until opening 14 comes into contact with a bottom surface 24 of metering receiver 20 carrying fill 22.
In doing so, the powder to be metered of fill 22 is pressed into the interior of supply vessel 12. Metering element 10 is then moved upwards in an axial direction, preferably until supply vessel 12 is no longer in contact with fill 22 (step C).
This procedure is preferably repeated a plurality of times until the interior of supply vessel 12 is at least largely filled with the powder to be metered and the powder contained in it is strongly compressed. In a last step, metering element 10 is brought into position over a material receptacle of a combinatorial substrate and the metered powder is ejected by an axial movement of plunger 16. The material receptacle may include, for example, a weighing device for monitoring the quantity of metered powder.
In order to cause the powder to drop down after removal and thus form a new homogeneous fill 22, metering receiver 20 preferably has slanted side walls so that the cross section of metering receiver 20 continuously tapers from this opening in the direction of bottom surface 24. As an alternative or in addition, it is possible to couple metering receiver 20 to a vibration device.
If different powders are metered, the powders may be contaminated if one and the same metering element 10 is used. To avoid a contamination or entrainment of powder adhering to the exterior surface of supply vessel 12, a stripping device 30 may also be provided, as is shown, for example, in
For the metering of different powders, an alternative is to assign a separate metering element 10 to each of the powders or powder mixtures to be metered. This effectively prevents the powders from being mixed or contaminated with one another. Should the previously charged powder be an air-sensitive compound, the described metering may be done in a protective gas apparatus, for example, a glove box.
The powder metering device thus includes at least one metering element 10, at least one metering receiver and, if necessary, a grabber, a control unit for controlling the grabber and/or stripping device.
It is possible to provide a plurality of metering elements 10 which differ in particular with respect to the possible metering volume. Despite a different volume of supply vessel 12, the longitudinal dimension of metering elements 10 may be kept largely constant. Different volumes are implemented by the selection of corresponding diameters of supply vessel 12 or by different starting positions of plunger 16 within supply vessel 12. This makes it possible to use metering elements 10 of different metering volumes in succession for metering without the necessity of adapting the mechanical grabber. Furthermore, it is possible to design mounts 26, 28 in such a way that they have an identification marking for identifying the metering volume so that the mechanical grabber is automatically adapted to the corresponding metering volume of the metering element just mounted.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2004 047 464.8 | Sep 2004 | DE | national |
