MEASURING ARRANGEMENT AND METHOD FOR DETERMINING PROPERTIES OF A MATERIAL TO BE EXTRUDED WHILE A SCREW-EXTRUSION PROCESS IS BEING CARRIED OUT

Abstract

In a measuring arrangement for determining properties of a material to be extruded while an extrusion process is being carried out in an extruder, at least one extruder screw is rotatably mounted in a tubular guide in a barrel and is connected to a rotary drive. Material to be extruded is fed to the tubular guide at one end and is removed as finish-extruded material at an oppositely arranged discharge. Arranged at measuring positions at predeterminable defined intervals on the wall of the tubular guide along the longitudinal axis of the extruder screw are multiple first sound transducers, which are designed for the detection of sound waves that are generated during the extrusion process by the extrusion process as process noises and/or are emitted by a second sound transducer, arranged at one end of the tubular guide, in the direction of the longitudinal axis of the extruder screw and into the material to be extruded that is conveyed through a mixing chamber present in the tubular guide.

Claims

1-7. (canceled)

8. A measuring arrangement for determining properties of a material to be extruded while an extrusion process is being carried out in an extruder, comprising: at least one extruder screw rotatably mounted in a tubular guide in a barrel, said at least one extruder screw is connected to a rotary drive and material to be extruded can be fed to the tubular guide at one end and can be removed as finish-extruded material at an oppositely arranged discharge, and multiple first sound transducers arranged at measuring positions at predeterminable defined intervals on a wall of the tubular guide along the longitudinal axis of the extruder screw, said multiple first sound transducers adapted for the detection of sound waves that are generated during the extrusion process by the extrusion process as process noises and/or are emitted by a second sound transducer, arranged at one end of the tubular guide, in the direction of a longitudinal axis of the at least one extruder screw and into the material to be extruded that is conveyed through a mixing chamber present in the tubular guide.

9. The measuring arrangement according to claim 8, wherein the second sound transducer is arranged in the region of the end of the tubular guide which is arranged in the conveying direction of the material to be extruded before or at the start of the extrusion process.

10. The measuring arrangement according to claim 8, wherein the multiple first sound transducers are arranged distributed in different angular orientations over the circumference of the tubular guide.

11. The measuring arrangement according to claim 8, wherein active surfaces of the first acoustic transducers couple to the material to be extruded in the interior of the tubular guide via a protective and adjustment window or a protective layer.

12. A method for determining properties of a material to be extruded while an extrusion process is being carried out using a measuring arrangement according to claim 8, in which transit times and/or amplitudes of sound waves are detected in a frequency-resolved manner via the first sound transducers and properties of the material to be extruded are determined via an electronic evaluation unit in respective process zones, which are arranged along the conveying direction of the material to be extruded.

13. The method according to claim 12, wherein a cross-correlation with detected sound measurement signals which have been detected between two first sound transducers each arranged at different measuring positions and a pulse transmission function of the sound measurement signals which have been detected at said two measuring positions is thus obtained.

14. The method according to claim 12, wherein mean values, standard deviations, distribution functions and their higher moments of the detected sound wave measurement signals are taken into account.

Description

[0061] In the drawings:

[0062] FIG. 1 in a schematic representation, an example of a measuring arrangement in accordance with the invention

[0063] FIG. 2 detail A from FIG. 1 on an enlarged representation.

[0064] FIG. 1 shows an example of a measuring arrangement in accordance with the invention on an extruder 7. In this example, a screw 4 is rotatably mounted in a tubular guide 5 and is driven by a rotary drive, not shown.

[0065] Material 1 to be extruded is introduced via a feeder into a mixing chamber arranged inside the tubular guide 5 and formed by means of a gap between the inner wall of the tubular guide and the outer wall of the screw 4. In the case of two screws which rotate around axes of rotation aligned parallel to one another and are arranged next to one another, the volume in the gap between the outer surfaces of the screws is added to the mixing chamber.

[0066] The material to be extruded is conveyed through the tubular guide 5 to the exit 6 by means of the rotation of the screw.

[0067] In this example, four first sound transducers 3 are arranged on the outer wall of the tubular guide 5, with which sound transducers sound waves can be detected. The four first sound transducers 3 are connected to the electronic evaluation unit, with which a frequency-resolved evaluation of the sound waves detected at the measuring positions of the first sound transducers 3 is carried out, by means of lines routed through channels from the extruder 7 to an electronic evaluation unit (not shown).

[0068] In the example shown, a second sound transducer 2 is arranged in the tubular guide 5 in the region of the rotary drive of the screw 4 (not shown), with which second sound transducer sound waves are emitted into the screw 4 and the material 1 to be extruded. In this case, sound waves of different frequencies can be emitted, taking into account the respective material 1 to be extruded. However, the frequency can also be selected such that it is optimized for a specific measuring position at which a first sound transducer 3 is arranged. For this purpose, the properties of the material 1 to be extruded in the associated process zone and/or the interval between the second sound transducer 2 and the corresponding first sound transducer 3 arranged there can be taken into account.

[0069] The evaluation of the sound wave measurement signals detected by meas of the first sound transducers 3 is as follows:

[0070] At any given time, t.sub.i, i=1, . . . N [0071] Filtering the measurement signals to remove any high-frequency noise. [0072] Cross-correlating the measurement signals from different first sound transducers 3 in order to obtain the pulse transfer functions between the measuring positions at which the first sound transducers 3 are arranged. As an alternative to this, a direct evaluation of the individual measurement signals without cross-correlation or alternatively a statistical evaluation of the individual measurement signals with regard to the moments of their distribution can be carried out. [0073] In the case of cross-correlation and direct signal evaluation, a spectral analysis of the frequency-dependent transit times and amplitudes or, alternatively, a non-spectral cumulative analysis can be carried out. [0074] Comparing the measurement results that were detected at different measuring positions (direct and statistical evaluation) or the measurement results resulting from cross-correlation between different measuring positions. [0075] Establishing the correlation of the measurement results to relevant process parameters using prerecorded calibration curves; optionally, temporal changes in the measurement results in the ongoing process can be taken into account without prior calibration.