DE10059502A1 - Mixture of ultra-fine powder transported through pipe module by exposure to ultrasonic oscillations - Google Patents

Abstract

An assembly transports, doses and mixes ultra-fine (m 10) particles whose advance is induced through modular pipe sections by ultrasonic vibration in the presence of an inert gas or a vacuum. The pipe module is of circular or rectangular cross section. The ultrasonic frequency is in the range f 20 kHz with piezo-ceramic actuators fixed firmly to the pipe module. Each pipe module is fixed to one side of a container. The mass throughput can be raised by the arrangement of a number of pipe modules in series. The modules are capable of driving the particles in a horizontal direction and up an inclined slope.

Description

The invention relates to a device according to the preamble of claim 1.

The handling of highly disperse powders (<10 µm) increasingly includes that continuous conveying, dosing and mixing of fine powder fractions e.g. B. from Metal and ceramic. With regard to security risks, handling and further processing (e.g. Remelting) of the very fine powder, the freedom from oxide of the product is an important factor Quality criterion.

These tasks are performed by a device described below with the Merk paint the claim 1 solved.

The device consists of a modular conveying, dosing and mixing system for Fine fractions of metallic, ceramic and other powders, which are based on the application based on ultrasonic vibrations under an inert gas atmosphere (in which the gas however no funding task takes over) or in a vacuum. The relevant modular pipe conveyor system stem delivers fine powder without oxygen contamination, d. H. without related quality seinbußen. The area of application is to be provided for small quantities and delivery rates, whereby a stable and continuous production operation is possible over longer periods.

The advantages of the invention are:

• - In the possibility of handling very fine powders without gaseous or liquid Additional media
• - resulting in an oxidation-free powder handling z. B. of metal powders,
• - the prevention of wall caking and powder agglomerations in the conveyor route,
• - the possibility of combining powder delivery, metering and mixing.

Description of the execution

The requirements of gas-free conveying, dosing and mixing of very fine powders is due to the gas-free, ultrasonic vibration-induced solid presented here transportation met. The device consists of a modular conveying, dosing and Mixing system for fine fractions of metallic, ceramic and other powders based on the application of ultrasonic vibrations is based on an inert gas atmosphere however, the gas does not take on a pumping task) or in a vacuum. The module in question re pipe conveyor system conveys very fine powder without oxygen contamination, d. H. without this rapid loss of quality. The area of application is for small quantities and delivery rates provide a stable and continuous production operation over longer periods is possible.

The vibration excitation of a tube segment loaded with powder via piezoelectric actuators leads to an elliptical movement of the inner tube wall, as a result of which the powder is transported axially within the tube. The basic arrangement of a conveyor module is shown in Figure 1. Since the processing and handling of the finest solids poses great difficulties due to the increasing interparticle interaction forces with decreasing particle size, the ultrasound-based transport utilizes the dispersing effect of ultrasound to largely prevent wall buildup and agglomerates or their dissolution.

Different actuators can be used to transport the powder in the pipe segments used to generate vibrations. The powder type, shape, medium size and size The external distribution and the loading of the pipe segments with powder are too wide varying parameters.

The vibrations of the pipe wall induced by the piezo elements on the pipe module lead to a transport of the powder within the tube to the side on which the piezo actuators are located. The gas-side formation of an ultrasonic standing wave field prevents agglomeration of the powder fractions (or even dissolves them) and Wall caking in the tube module.

Use of piezoceramic elements to generate vibrations

Due to the approximate volume constancy of piezoceramic elements, one changes rotationally symmetrical piezoceramic body that changes length, too at the same time its diameter. The particular preferred form of vibration can be determined by the Direction of polarization are influenced; the piezo body will move in the direction of its polarization excited, he experiences his increased deflection in this direction. On the other Because of its geometrical shape, each body has one or more resonances frequencies. In the resonance, the deflection of a piezo element increases by a multiple ches, which means that the resonance frequency is much lower Control voltage can achieve the same stroke as with non-resonant control. It is thus possible, by defining the geometric dimensions, the polarization direction and areas and the change in frequency generating fashion.

Piezo actuators as shown in Figure 1 can be used to generate vibrations on a tubular module. B. Piezo rings with electrodes on the lateral surfaces which are radially polarized. Piezo rings with electrodes on the base and top surface that are axially polarized can also be selected. The preferred mode of vibration is that of a change in ring thickness. Piezo tubes with much greater height to wall thickness ratios can also be used. Multiple divided ring actuators are also suitable if appropriate.

tubular modules

All elastic materials, such as. B. also aluminum (we low modulus of elasticity and high thermal conductivity).

Connection options between actuator and tubular module

For the arrangement and fastening of the piezo elements on the pipe segments, different connection options can be selected according to Figure 2:

• - positive connection via fit and / or adhesive connection. For this you can Some piezo rings are used, which are coated on the lateral surfaces and radially polar is standardized. The force is applied via the inner ring surface.
• - Positive connection by a screw connection, two piezo elements can be clamped using clamping rings. For this, piezo rings with coatings are applied Base and top surface with axial polarization used. The force is entered in this Case about the screw elements.

Integration of the conveyor module on a container

To ensure a continuous supply of solids in the conveyor module, for example as a powder-loaded storage container are provided in the side by a hole projects into the tube module. For this, the tube module can be used at one end provided a longitudinal groove and be in a flexibly sealed opening of the storage container be consolidated.

Conveying performance depending on the powder material

The delivery and metering mass flow is based on the frequency and the power entered dependent. In the range of the resonance frequency of the dynamically vibrating system the largest delivery rate can be determined.

An exemplary promotion of the powder fractions listed below was carried out pro without any problems.

Table 2

typical powder material characteristics

The screw connection was used as a connection option between the piezo element and the conveyor module for carrying out the funding studies. The actuators were clamped using clamping nuts and thus connected to the tube module in a force-locking manner. A symmetrical vibration mode of the tube segments is generated by the excitation geometry of the piezo elements used. Figure 3 shows the results of an exemplary fine powder feed in an Al Mg Si 0.5 tube module (da = 40, di = 36, I = 500 mm).

For the finer powders, a minimum size of the power input must be exceeded before the funding process begins. This threshold depends on the material.

Claims (9)

1. Device for conveying, dosing and mixing of very fine particles, characterized in that a gas-free, ultrasonic vibration-induced solids transport is carried out in tube modules. 2. Device according to claim 1, characterized in that the tubular module with circular or rectangular is provided according to the cross section. 3. Device according to claim 1, characterized in that the frequency of the vibration excitation in the Ultra sound range f <20 kHz. 4. The device according to claim 4, characterized in that piezoceramic actuators for vibration be used. 5. The device according to claim 4, characterized in that the connection between the tube module and the Actuators is positively or non-positively executed. 6. The device according to claim 1, characterized in that the tubular module on one side of a container can be adjusted. 7. The device according to claim 4, characterized in that the increase in the delivery and metering capacity by the parallel connection of several modules can be guaranteed. 8. The device according to claim 4, characterized in that the setting of the conveyor line over the rows switching of several modules can be guaranteed. 9. The device according to claim 1, characterized in that the funding module the funding normal and opposite gravity in inclined pipe modules.