SYSTEM FOR ANALYZING AND SORTING A MATERIAL PART

Abstract

The invention relates to a system for analyzing and sorting a material part, in particular a scrap part made of aluminum, comprising: a feed means (110) for transporting the material part (120), a sorting unit (160) which is designed to feed the material part (120) to one of two fractions (F1, F2), a laser device (140) which is designed to generate a plasma (3) on a surface 7A of the material part (120) using a laser beam (5) which propagates along a beam axis (5A), a spectrometer system (1) which is designed to carry out a spectral analysis of a plasma light (3A) emitted from the laser-induced plasma (3) and to generate an output signal in accordance with the result of the spectral analysis that is carried out, anda controller (150) which is designed to receive the output signal and operate the sorting unit (160) on the basis of the output signal and a sorting criterion, whereinthe spectrometer system (1) has a spectrometer (13) and a detection unit (21) which is optically connected to the spectrometer (13), andthe detection unit (21) has an objective (25A, 25B, 25C, 25D) which is paired with a detection cone (35) that forms a plasma detection region (39) in a region (37) overlapping with the laser beam (5). The invention is characterized in that the detection unit (21) has an additional objective (25A, 25B, 25C, 25D) which is paired with an additional detection cone (35) that forms an additional plasma detection region (39) in an additional region (37) overlapping with the laser beam (5). The objectives (25A, 25B, 25C, 25D) are arranged and/or aligned in relation to one another such that the plasma detection region (39) and the additional plasma detection region (39) are arranged in an offset manner along the beam axis (5A) of the laser beam (5) and together form a viewing region (41) of the detection unit (21)

Claims

1. A system for analyzing and sorting a material part, in particular a scrap part made of aluminum, comprising: a feed means for transporting the material part, a sorting unit which is designed to feed the material part to one of two fractions, a laser device which is designed to generate a plasma on a surface 7A of the material part using a laser beam, a spectrometer system which is designed to carry out a spectral analysis of a plasma light emitted form a laser-induced plasma and to generate an output signal in accordance with the result of the spectral analysis that is carried out, and a controller which is designed to receive the output signal and operate the sorting unit on the basis of the output signal and a sorting criterion, wherein the spectrometer system has a spectrometer and a detection unit which is optically connected to the spectrometer, wherein the detection unit has an objective which is assigned a detection cone that forms a plasma detection region in a region overlapping with the laser beam, wherein the detection unit has a further objective which is assigned an additional detection cone that forms an additional plasma detection region in an additional region overlapping with the laser beam, wherein the objectives are arranged and/or aligned in relation to one another such that the plasma detection region and the additional plasma detection region are arranged in an offset manner along the beam axis of the laser beam and together form a viewing region of the detection unit.

2. The system according to claim 1, wherein a plasma detection region is designed in such a way that in the case of a plasma present in the plasma detection region, a measurement share of the plasma light of the associated objective is detected.

3. The system according to claim 1, wherein the detection unit comprises an objective holder that supports a plurality of objectives jointly.

4. The system according to claim 1, wherein the plasma detection regions pass into each other or are arranged spaced from each other along the beam axis.

5. The system according to claim 3, wherein the objective holder provides an optical passage opening through which the beam axis passes.

6. The system according to claim 3, wherein the objective holder comprises a mounting plate which provides several objective mounting openings for receiving a respective objective, and the optical passage opening for the laser beam, wherein the objective mounting openings are distributed around the passage opening.

7. The system according to claim 1, wherein a detection cone extends along an observation axis which runs at an observation angle , wherein the observation angle is between 0 and 90, preferably between 3 and 60, even more preferably between 5 and 25.

8. The system according to claim 1, wherein the spectrometer system comprises a light guiding system which optically connects the detection unit to the spectrometer.

9. The system according to claim 8, wherein the light guiding system provides a number of optical inputs corresponding to the number of objectives, and an optical output, wherein the optical inputs are each designed to receive the measurement share detected with the associated objective and wherein the optical output is designed to output the measurement shares detected with the objectives.

10. The system according to claim 9, wherein the light guiding system comprises several optical fibers which each provide an optical input and which are combined into a common optical output.

11. The system according to claim 1, wherein the laser device, the spectrometer system and the controller are accommodated in a common housing and form an LIBS module.

12. The system according to claim 1, wherein the feed means is designed to transport the material part along a feeding surface towards the upper section of a chute.

13. The system according to claim 12, wherein the sorting unit is assigned to a lower edge of the chute opposite the upper section of the chute, wherein the sorting unit is designed to feed the material part leaving the chute via the lower edge of the chute to one of two fractions.

Description

[0038] Further features and advantages of the invention will become apparent from the following description with reference to the drawings.

[0039] FIG. 1 shows a schematic representation of the system according to the invention;

[0040] FIG. 2 shows a schematic representation of the operation of the LIBS module according to the invention;

[0041] FIG. 3 shows a further schematic representation of the operation of the LIBS module according to the invention;

[0042] FIG. 4 shows a schematic representation of the LIBS module according to the invention;

[0043] FIGS. 5a, 5b show a first embodiment of a detection unit in a plan and lateral view, respectively;

[0044] FIGS. 6a, 6b show a second embodiment of a detection unit in a plan and lateral view, respectively;

[0045] FIG. 7 shows an enlarged schematic representation of the spectrometer system according to the inventive system of FIG. 1.

[0046] FIG. 1 shows the inventive system 100 in a schematic representation.

[0047] The system 100 is configured to subject a material part 120 to a laser-induced plasma spectroscopy and to sort the material part depending on the result of the spectral analysis, wherein in the illustrated embodiment two fractions F1 and F2 are provided to which the material part 120 can be assigned. Collection points 170, for example in the form of containers, are used to hold the respective fractions F1 and F2.

[0048] As can be seen in the schematic representation according to FIG. 1, the system 100 includes feed means 110 followed by a chute 130. During the intended use, a material part 120 is supplied to the feed means 110. The feed means 110 serves to transport the material part 120 along a feeding surface 111 provided by the feed means to an upper section 131 of the chute 130. The material part 120 is transferred from the feed means 110 to the chute 130 here.

[0049] The feed means 110 can be a vibrated plate. It serves in particular to separate a plurality of material parts 120 supplied to the feed means 110 so that these material parts can be advanced to the chute 130 at distance from each other.

[0050] A material part 120 that has been transferred to the chute 130 goes down the chute 130, following the force of gravity, to the lower edge 132 of the chute which is opposite the upper section 131 of the chute 130. The purpose of the chute 130 is, in particular, to align the material part 120 and to transfer the material part to a defined drop corridor.

[0051] When the material part 120 leaves the chute 130, it moves through the surrounding atmosphere, still in free fall under the action of gravity. It passes the inventive spectrometer system 1. The spectrometer system provides for an analysis of the material part 120, as will be described in more detail below. The spectrometer system 1 generates an output signal corresponding to the result of a spectral analysis that has been carried out. The output signal is supplied to a controller 150 which operates or controls a sorting unit 160 on the one hand depending on this output signal and on the other hand on a sorting criterion. By means of this sorting unit 160, the material part 120 is either deflected in its free fall or there is no deflection. If there is no deflection, the material part 120 reaches the collection point 170 of fraction F2. Otherwise, if sorting takes place by means of the sorting unit 160, the material part 120 reaches the collecting point 170 for fraction F1.

[0052] The spectrometer system 1, which is part of the inventive LIBS module 180, serves the analysis of the composition of the material part 120. Part of the LIBS module 180 are a laser device 140 as well as a controller 150. Preferably, the laser device 140, the spectrometer system 1 and the controller 150 are accommodated in a common housing not further illustrated.

[0053] The laser device 140 on its part consists of further individual components, such as a laser source 9, an optical fiber 9A and focusing optics, as can be seen in particular from the example shown in FIG. 2.

[0054] As will be still explained in more detail with particular reference to FIGS. 2 and 3, the spectrometer system 1 comprises a detection unit 21, which in turn provides several objectives. A detection cone 35 is assigned to each of these objectives, which form a plasma detection region 39 in a region overlapping with the laser beam 5. These plasma detection regions 39 are arranged offset to one another along the beam axis of the laser beam 5 and together form a viewing region 41 of the detection unit 21. The viewing region 41 is therefore composed of the individual plasma detection regions 39, whereby the detection region covered by the detection unit overall is defined.

[0055] FIG. 2 shows a schematic overview of a spectrometer system 1 for spectral analysis of a plasma light 3A emitted by a laser-induced plasma 3 (schematically indicated as a filled circle). Detectable plasma light 3A is, for example, in the wavelength range of UV light, visible light, near infrared light and/or infrared light; in particular, detectable plasma light can be in the spectral range of approximately 190 nm to approximately 920 nm. In the case of LIBS, the plasma 3 is generated by means of a laser beam 5 on a surface 7A of a sample 7.

[0056] To generate the laser beam 5, which may be a pulsed laser beam for example, the spectrometer system 1 comprises a laser beam source 9. The laser beam source 9 is designed to provide the laser beam parameters required for plasma generation. The laser beam 5 is supplied, for example, via an optical fiber 9A of focusing optics 11 and focused by the latter onto the surface 7A of the sample 7 (material part 120 according to FIG. 1). The focusing optics 11 can be designed in particular as a laser head component with a focusing function, such as an active laser component acting in particular on the spectrum or the pulse duration or the pulse length. The laser beam 5 propagates between the focusing optics 11 and the sample 7 along a beam axis 5A. Exemplary focus diameters (1/e.sup.2 beam diameter at the beam waist) and focus lengths (double Rayleigh lengths) are in the range from <50 m to >250 m and in the range from <5 mm to >1000 mm, respectively.

[0057] In particular, laser parameters can be set/selected in such a way that a region in which plasma generation can take place (also referred to as the ignition region) extends along the beam axis, for example over a length in the range from approx. 5 mm to approx. 50 mm, for example over a length of 10 mm, 20 mm or 30 mm.

[0058] FIG. 2 schematically shows a focus zone 11A elongated along the beam axis 5A, as it is formed in the region of the surface 7A of the sample 7. The plasma 3 forms on the surface of the sample 7A due to the interaction of the laser radiation with the material. With LIBS, the usual dimensions (average diameter) of a plasma 3 are in the range of e.g. 0.1 mm to 5 mm (depending on the sample material and laser parameters).

[0059] The spectrometer system 1 further comprises an optical spectrometer 13 for spectral analysis of the plasma light 3A. The optical spectrometer 13 is shown as a grating spectrometer in FIG. 2 as an example. In general, the spectrometer 13 comprises at least one dispersive element 13A, e.g. a grating, a prism or a grating prism, and a pixel-based detector 13B onto which the plasma light impinges in a spectrally expanded manner. Spectral components of the plasma light 3A to be analyzed are assigned to the pixels of the detector 13B. The detector 13B outputs intensity values of the irradiated pixels to an evaluation unit 15, usually a computer including a processor and a memory. The evaluation unit 15 outputs a measured spectral distribution 17 and compares it with stored reference spectra, for example, in order to assign the elements contributing to the plasma light 3A to the plasma light 3A and thus to the sample 3 being analyzed and to output them as the result of the spectral analysis.

[0060] In the spectrometer 13, a (spectrally dependent) beam entrance for the plasma light to be analyzed is defined by an entrance aperture 19, usually an entrance slit 19A.

[0061] The spectrometer system 1 further comprises a detection unit 21 with an objective holder 23 and a plurality of objectives 25A, 25B, 25C which are held by the objective holder 23. As an example, three objectives are shown in the Figures, two in the image plane and one behind it. The number of objectives used can be selected depending on spatial and optical parameters as well as parameters of the material of the sample to be examined; it is, for example, in the range from 2 to 20, for example 4, 5, 8, 9 or 15 objectives.

[0062] The spectrometer system 1, in particular the detection unit 21, further comprises an optical light guiding system 27 which optically connects the objectives 25A, 25B, 25C to the spectrometer 13. The light guiding system 27 provides a plurality of optical inputs 29, each optically associated with one of the objectives 25A, 25B, 25C, and a functional optical output 31 (common to the objectives) optically associated with the entrance aperture 19.

[0063] Each of the objectives 25A, 25B, 25C is arranged to detect a measurement share 33 of the plasma light 3a and comprises at least one focusing optical element, such as a converging objective or a concave mirror. A detection cone 35 is assigned to each of the objectives 25A, 25B, 25C. The beam axis 5A runs through the detection cones 35, wherein the detection cones 35 have a set minimum size in the region of the laser beam 5. Each detection cone 35 comprises a plasma detection region 39 in an overlap region with the laser beam 5 which is assigned to the corresponding objective 25A, 25B, 25C. For example, the detection cones 35 have a length from an entrance aperture of an objective to the laser beam in the range from 200 mm to 400 mm. In FIG. 2, for example, the plasma 3 is generated in the plasma detection region 39 of the objective 25B, so that the associated measurement share 33 of the plasma light 3A is detected by the objective 25B and imaged onto the associated optical input 29 of the light guiding system 27. Measurement shares 33 detected by one or more objectives are guided by the optical light guiding system 27 to the common optical output 31 and coupled through the entrance aperture 19 into the optical system 13 for spectral analysis.

[0064] FIG. 2 shows an example of three objectives 25A, 25B, 25C which are arranged azimuthally distributed around the beam axis 5A. The objectives 25A and 25B are located on opposite sides of the beam axis 5A and are therefore directed towards the beam axis 5A from opposite sides. The objective 25C is directed towards the beam axis 5A from behind. A further objective (not shown in FIG. 2) can, for example, be directed at the beam axis 5A from the front or be directed at the focus zone 11A along the beam axis 5A with the aid of a beam splitter. To illustrate this, the detection cones 35 are shown in FIG. 2 with a dashed line running conically towards the beam axis 5A, the focus zone 11A, the plasma 3 and the plasma detection regions 39 being shown exaggerated in comparison to the detection cones 35 for illustration.

[0065] FIG. 3 shows a mounting plate 23A of the detection unit 21 of the LIBS system to illustrate the arrangement and alignment of the objectives 25A, 25B, 25C. For stationary mounting of the objectives, the mounting plate 23A has objective mounting openings for receiving the objectives 25A, 25B, 25C. The objective mounting openings are each arranged at a radial distance from the beam axis 5A and are designed for an inclined alignment of the objectives 25A, 25B, 25C to the beam axis 5A. To illustrate the inclined alignment, observation axes 35A of the objectives 25A, 25B, 25C are at an observation angle to the beam axis 5A.

[0066] To achieve the multifocal concept, the objectives 25A, 25B, 25C are fixed in the mounting plate 23A (generally arranged and aligned in the holder 23) in such a way that the plasma detection regions 39 are offset along the beam axis 5A. In particular, for comparable observation angles , the offset in the direction of the beam axis 5A can be achieved by varying the radial distance of the objectives 25A, 25B, 25C from the beam axis 5A (optionally with varying insertion). As an example, different radial distances R1 and R2 for the objectives 25A and 25B are indicated in FIG. 3. Alternatively (optionally with a comparable radial spacing), the observation angle of at least some of the objectives can be adapted to the desired offset of the plasma detection regions 39 in the direction of the beam axis 5A (see e.g. FIG. 6B). Mixed forms in the configuration are also possible.

[0067] In general, the observation angle can be in the range from 0 (via beam splitters along the laser beam) to 90 (observation orthogonal to the laser beam). The observation angles shown by way of example in the context of the disclosure are in the range from 5 to 15, for example in the range from 5 to 10. The observation axes 35A of neighboring objectives 25A, 25B, 25C approach the beam axis 5A from different azimuthal directions (azimuthal angle in the plane perpendicular to the beam axis 5A). In the case shown in FIG. 3, the observation angles are comparable for all objectives and do not deviate from each other by more than e.g. 5 or 1 (deviation given e.g. by permitted manufacturing tolerances of the objective mounting openings and objectives). However, the radial distances to the beam axis 5A vary in the arrangement shown in FIG. 3. Accordingly, comparable spectra can be recorded from the plasma detection region 39 of the different objectives for a sample at different positions of the surface of the sample along the beam axis 5A (corresponding to different measurement constellations in the context of a measurement process), for example from objective 25B in the case of a surface profile according to the solid line (surface 7A of sample 7 from FIG. 2) or from objective 25A in the case of a surface profile according to the dotted line 7A or from objective 25C in the case of a surface profile according to the dashed line 7A.

[0068] As indicated in FIG. 3, the plasma detection regions 39 together form a viewing region 41 of the detection unit 21. The viewing region 41 extends along the beam axis 5A in the region of the focus zone 11A.

[0069] A measuring depth along the beam axis 5A is assigned to each of the plasma detection regions 39. In FIG. 3, the measuring depth corresponds, for example, to a diameter of the circles that illustrate the plasma detection regions 39. For an objective, the measurement depth is a specific characteristic that is given by optical parameters such as the focal length and aperture of the objective as well as by the arrangement and orientation of the objective (e.g. geometric position parameters of the objective with respect to the beam axis 5Adistance and angle). For example, the plasma detection regions 39 can each extend along the beam axis 5A over a measurement depth of approximately 5 mm to 15 mm, in particular over a measurement depth of approximately 5 mm to approximately 12 mm. In some embodiments, the plasma detection regions 39 can extend along the beam axis 5A over 1/10 to of the viewing region 41. In FIG. 3, the plasma detection regions 39, which are arranged offset along the beam axis 5A in the multifocal concept, are spaced at a distance D in the order of magnitude of the measuring depth (here approx. twice the diameter of the plasma detection regions 39) as an example. Alternatively, the plasma detection regions 39 can be adjacent to each other or partially overlap (for example in the range of 10% of the measuring depth). In this way, the objectives can capture plasma light from different sections of the viewing region 41 along the beam axis 5A.

[0070] Furthermore, FIG. 3 shows an optional protective window 43A that can be provided in the area of an optical passage opening 43 in the mounting plate 23A in order to be able to direct the laser beam through the holder 23 and past the objectives 25A, 25B, 25C onto the sample.

[0071] FIG. 4 shows a perspective view of an exemplary LIBS measuring head 51 that is connected to a laser beam source via an optical fiber 9A. The holder 23 of the LIBS measuring head 51 comprises a longitudinal support plate 23B, to which an attachment for the optical fiber 9A and the focusing optics 11 (laser head with beam shaping) is provided on the input side. The optical spectrometer 13 is also attached to the longitudinal support plate 23B, and the mounting plate 23A is provided for the four objectives 25A, 25B, 25C, 25D (generally n>1-fold entrance optics). The objectives 25A, 25B, 25C, 25D are set up to detect measurement shares of plasma light from plasma detection regions 39 that are arranged offset to each other along the beam axis 5A and to supply them to the spectrometer 13 for spectral analysis via the light guiding system 27 (for example a fiber bundle with n>1 inputs and a functional output-n-on-1 fiber bundle). As an example, FIG. 4 shows two optical fibers 45 of the light guiding system 27, which optical fibers optically connect the objectives 25B and 25C to the common spectrometer 13. The light guiding system 27 can be used to combine the measurement shares in the spectrometer 13 (or optionally before coupling into the spectrometer 13) for a measurement process.

[0072] The n-fold observation of the viewing region with several (four in FIG. 4) objectives allows a significant increase in the depth of field, given by the juxtaposition of the plasma detection regions of the objectives. This makes it possible to efficiently analyze structured, uneven samples on the surface. Furthermore, the sample is viewed from different angles, which reduces shadowing effects. The detected measurement shares are combined at a common output of the light guiding system (sum of all observations) and fed to a common spectral analysis.

[0073] An n-on-1 fiber bundle allows several objectives to be fed into one spectrometer, wherein several n-on-1 bundles can be used for feeding into several spectrometers.

[0074] The exemplary embodiment in the detection unit 21 shown in FIG. 3 is further illustrated with reference to FIGS. 4A and 4B. FIG. 5 shows a top view of the mounting plate 23A. The optical passage opening 43 in the center allows the laser beam to pass through (laser beam axis 5A). Four objective mounting openings 53A, 53B, 53C, 53D are arranged azimuthally around the passage opening 43 with varying radial distances to the beam axis 5A. They are equally distributed azimuthally, so that two objective mounting openings are located opposite each other in pairs. In the perspective view of FIG. 5B, four identical objectives 25A, 25B, 25C, 25D are inserted into the objective mounting openings 53A, 53B, 53C, 53D. The objectives 25A, 25B, 25C, 25D have been inserted into the objective mounting openings 53A, 53B, 53C, 53D to different degrees so that, depending on the radial distance, the associated plasma detection regions 39 are arranged next to each other in the direction of the beam axis and thus form the depth-of-field viewing region 41 of the detection unit 21.

[0075] An alternative embodiment is illustrated in FIGS. 6A and 6B. In the top view of the mounting plate 23A, four objective mounting openings 55A, 55B, 55C, 55D can be seen, which are arranged symmetrically at the same radial distance from the passage opening 43 and equally distributed around it. As indicated in the perspective view of FIG. 6B, the offset of the plasma detection regions 39 in the direction of the beam axis 5A is caused by different observation angles of the objectives 25A, 25B, 25C, 25D used. For example, at a radial distance of 30 mm, the observation angles can be in the range of 3 to 15, so that the viewing region 41 is formed at a distance of approximately 100 mm from the mounting plate 23A. In the case of different viewing angles (and optionally viewing heights), the detected spectral distributions can vary with a large-volume plasma, but these differences in the spectral distributions are negligible in particular for a small-volume plasma, as it is usually generated for the LIBS, since essentially the entire plasma lies in a plasma detection region 39.

[0076] FIG. 7 once again shows a detailed view of the system 100 according to the invention as shown in FIG. 1. It can be seen here that material parts are provided which are different in their composition, namely material parts 120B made of plastic and material parts 120A made of aluminum. In the manner described above, the spectrometer system 1 according to the invention can be used for sorting in such a way that the material parts 120A are separated from the material parts 120B. For this purpose, if a plastic material part 120B is detected, it is ejected by the sorting unit 160. For this purpose, the sorting unit 160 has an air pressure nozzle by means of which a plastic part 120B can be ejected from the stream of material parts. As a result of such sorting, separated material parts 120B made of plastic on the one hand and material parts 120A made of aluminum on the other hand accumulate at the collection points 170.

TABLE-US-00001 List of reference signs 1 spectrometer system 3 plasma 3A plasma light 5 laser beam 5A beam axis 7 sample 7A surface 7A dotted line 7A dashed line 9 laser beam source 9A optical fiber 11 focusing optics 11 focus zone 13 optical spectrometer 13A dispersive element 13B detector 15 evaluation unit 17 spectral distribution 19 entrance aperture 19A entrance slit 21 detection unit 23 objective holder 23A mounting plate 23B longitudinal support plate 25A objective 25B objective 25C objective 25D objective 27 light guiding system 29 optical input 31 optical output 33 measurement share 35 detection cone 35A observation axes 37 overlap region 39 plasma detection region 41 viewing region 43 optical passage opening 43A protective window 45 optical fiber 51 LIBS measuring head 53A objective mounting opening 53B objective mounting opening 53C objective mounting opening 53D objective mounting opening 55A objective mounting opening 55B objective mounting opening 55C objective mounting opening 55D objective mounting opening 57A objective mounting opening 57B objective mounting opening 57C objective mounting opening 57D objective mounting opening D distance R1, R2 radial distances observation angle 100 system 110 feed means 111 feeding surface 120 material part 120A aluminum part 120B plastic part 130 chute 131 upper section 132 lower edge 140 laser device 150 controller 170 collection point 180 LIBS module