Title of Invention

A METHOD FOR IDENTIFYING FOREIGN BODIES IN A BASE TEXTILE MATERIAL AND A DEVICE THEREOF

Abstract

The present invention relates to a method for identifying foreign bodies in a base textile material (I, 3, 5), comprising the steps of: subjecting the textile base material to beams (35, 36) which have two defined and different wavelength ranges (AI and A 2); and reflecting the beams (44) by the base material are detected simultaneously and jointly and converted into an electrical signal (18), characterized in that choosing the two wavelength ranges (AI and A 2) such that for the emitted beams (35, 36) sufficient distinctions are expected with respect to the intensity of the reflection on two foreign bodies (FI, F2) to be identified; and distinguishing the two foreign bodies (FI, F2) from each other by means of a limit (41) which lies between values (39, 40) of the electrical signals (18) for both foreign bodies (FI, F2).

Full Text

Method and device for identifying foreign bodies in a textile material The invention relates to a method and to a device for identifying foreign bodies in a base rextile material, wherein the base textile material is subjected to radiation, and the radiation reflected on the base material is detected and converted into an electrical signal. Base textile material is here taken to mean, for example, a fibre composite made of rextile fibres such as a strip, a roving yarn, a yarn made, for example, of cotton or polyester fibres or mixtures thereof, etc. or a composite made of a fibre composite of this type such as a nonwoven, a woven, a knitted fabric, etc. A base textile material is taken to mean a base material which can contain foreign bodies but is predominant in terms of quantity. Such foreign bodies are, for example, foreign fibres in the fibre composite, portions of plastic film.s which, for example, are reduced in size to form narrow^ strips or fibres, vegetable matter (such as husk contents) of the cotton and other unwanted substances, such as hairs, feathers, etc. which can occur as plant components. A method of this type and a device are know^n f rom^ WO 95/29396. Here, the base material, for example a yarn, is irradiated, with white light from one light source or alternately with light of various wavelengths i.e. for example yellow, green or red light from various light sources, against an absorbent background. The light reflected by the base material is detected by at least one receiver which detects the spectrally different portions of the radiation at different times. Therefore, a single receiver can alternately receive the various colours or an individual receiver can be provided for each colour, so all colours are simultaneously detec-ed by different receivers. The receiver or receivers generate (s) a respective electrical signal corresponding to the preferably received wavelength of the radiation. These signals are then .brought into a relation with one another, for example balanced with one another, in order to compensate for unwanted effects. Such an unwanted effect may, for example, be that the reflected light depends not only on the colour of the yarn and of the foreign body but also on the mass, volume or diameter of the yarn. The effect of the mass or the volume, for example, can be eliminated by said balancing, so, for example, only the effect of the colour of ~he yarn can be identified. A foreign body in the material can thus be reliably identified. One drawback of this rriethod, or device is to be seen in that processing of the signals is com^plex as the signals of the individual colour or wavelength fractions have to be separated either in terms of time by a plurali~y cf clocked light sources or in terms of location by filters. The individual signals are then also separately processed and subsequently balanced together or jointly further processed. However with a plurality of different foreign bodies which are spatially distributed in the base material, the known method does not allow the individual foreign bodies to be separately detected, so a distinction can be made between the different foreign bodies in order, for example, to eliminate individual foreign bodies from the base material and to consciously leave others in the base material. It is therefore the object of the invention to avoid said drawbacks and to propose a method and a device allowing different foreign bodies in the base material to be detected in a targeted manner such that they can also be distinguished from one another, so all or only the unwanted foreian bodies can be identified and, for example, eliminated. This opportunity should therefore be provided, in particular, when there is an initial suspicion that two or more different types of foreign body could be present. To achieve this object the starting point is that the extent of the reflection of beams on the base textile material and on possible foreign bodies is at least partially known and that there are differences in the extent of the reflection which result as a function of the wavelength of the beams used. While, for example, the base material cotton has a constant course of reflection as a function of changes in the wavelength of the beams, this does not apply to all possible foreign bodies. It can be that certain foreign bodies have a virtually arbitrary seeming course and at certain wavelengths the reflect as stronalv as the base material but at other wavelengths much less so or much more so. Therefore, depending on the wavelength of the beams, the foreign bodies can also reflect the beams equally strongly or at different strengths. It is advantageous to first of all gain knowledge of how the base material and how the foreign bodies being sought reflect beams in the selected wavelength ranges. It is crucial that the emitted beams have substantially two defined and different wavelength ranges and that the reflected beams are detected simultaneously and j ointly for both wavelength ranges. Defined wavelength range is taken to mean a wavelength range with a certain spectral distribution about a -central wavelength. The defined wavelength range is narrow-band,. A first defined wavelength range of the beams should be selected in a targeted manner such that the beams reflected by the base material provide first values in the electrical signal for at least two different foreign bodies. The values can be any values. A second defined wavelength range should then be selected for the beams such that the reflected beams produce second values in the electrical signal for the foreign bodies. These values are not in the same ratio for the two foreign bodies as in the corresponding electrical signals in the first wavelength range. The power of the beams in the two wavelength ranges should be selected such that the reflected radiation produces different values for the two foreign bodies. This can be achieved with one or more radiation sources which direct beams in these two wavelength ranges cnto the base miaterial/ in which sufficient distinctions can be expected for the two foreign bodies with respect to the intensitv of the reflection. A sincle receiver is used to measure the beam.s fully reflected by the base material. The beams should preferably be mixed; provided they originate from differen- radiation sources, so a homogenised beam mixture strikes the base material. The overall radiation irradiated therefrom is then proportional to the total centriburions of the reflections in the individual wavelength ranges. This total radiation can therefore be simultaneously detected in a single sensor. This also emits a signal which can be used directly, for example to actuate a separating device, with which any portion of the base material which contains unwanted foreign bodies can be rem^oved. The advantages achieved by "he invention are to be seen, in particular, in that certain foreign bodies can thus be searched for in a taraeted manner in a base textile material. It is therefore possible to select which foreign bodies can be purposefully removed and which, if need be, can be left in the base material. If separate and controllable radiation sources are provided, the device can adapt the mode of operation, for example to other foreign bodies which suddenly or gradually remove or supplement the originally present foreign bodies in "he same base m.aterial, in that the intensity of the ceams with the two wavelength ranges is adapted to the changing conditions, The device may thus also be continuously adapted to the needs of the operator or customer. For example, it can thus be determined whether vegetable foreign bodies are to be eliminated or left in the base material. When, owing to the selected design of the device, it is possible to adapt the relative intensity of the beams in the two wavelength ranges, the degree of elimination of the vegetable foreign bodies can also be controlled by adapting the sensitivity of the connected clearer. The invention w^ill be described in more detail hereinafter with the aid of an example and with reference to the accompanying drawings^ in which: Fig. 1, 2 and 3 each show a view of a foreign body in a base material, Fig. 4 shows a simplified view of reflections from the base m.aterial and from the foreign bodies by beams in different wavelength ranges, Fig. 5 shows a schematic and comibined view of the signals generated according to the invention for the base material and for different foreign bodies, Fig. 6 is a schematic view of a device according to the invention and Fig. If 8, 9 and 10 each show a schem.atic view of a portion of the device. The method according to the invention and the device are to be described hereinafter with reference to an example in which the base material is formed by a yarn. Fig. 1 shows a base material or yarn 1 which has a piece of film as the foreign body 2, the film being wound spirally around the yarn. Fig. 2 shows a base material as a strip, nonwoven or yarn 3 which has an accumulation of individual fibres as the foreign body 4, the fibres having a different colour to the base miaterial. Fig. 3 shows a base material as a strip, nonwoven or yarn 5 which has an inclusion or a compacr structure, such as any foreign body, a husk content of the cotton plant, a nep, etc. as the foreign' body 6. Fig. 4 shows a graph with an axis 7 along which values for the wavelength are plotted and an axis 8 along which values for the extent of the reflection of beams are plotted. In this graph various lines are drawn in, namely a line 9 for the base marerial, for exar.pl e cotton, a short interrupted line 10 for a first foreign body Fl and an interrupted line 11 for a second foreign body F2. In order to make the exam.ple approximiate a potentially real task somewhat more concretely, it can, for example, be assumed that the first foreign body Fl could be taken to mean vegetable material and the second foreign body F2 to be taken to mean red fibres made of films. This is to be understood as merely a select:ion of possible examples of foreign bodies. Line 9 corresponds to a reference value for the reflection of the beams on the provided base material alone. Lines 10 and 11 ccnnecr selected points 12, 13 , 14 and 15 which represent measured values of the reflection for a specific wavelength λ1, λ2 • Lines 10 and 11 do not indicate a course of the reflection as a function of the wavelength between the points 12 and 15 bur m.erely serve to make the points which correspond to the same foreign body easier ro identify. Fig. 5 shows schematically a respective portion of rhe base material or, in particular, of a yarn with a firsr foreign body Fl and a second foreign body F2. Electrical signals 16 and 17 generated by reflection are indicated for radiations λ1, λ2. A signal 18 results for mixed beams which consist of two wavelength ranges λ1 and λ2. the horizontal portions of these signals correspond to values for the reflection of the radiation on the pure base material or on the uncontaminated yarn, while downwardly pointing deflections correspond to values for the reflection as can be generated by foreign bodies. The causes and significance of the individual deflections are to be discussed in more detail in conjunction with the description of the mode of operation of the invention. Fig. 6 shows a simplified view of a device for carrying out the method according to the invention. This consists of a radiation source 19, a receiver 20 for the radiation 44. reflected on the base material 1, 3, 5 and an evaluating unit 21 for the electrical signals emitted by the receiver 20, The radiation source 19 can also be connected to a controller 22. The radiation source 19 consists, for example, of an LED as a source for beams with a first wavelength and a further LED as a source for beams with a second wavelength. An, if need be, metered supply for the two sources or switching on or off of one source takes place via the controller 22. Fig. 7 shows as an embodiment for a radiation source 19 a light-emitting diode 23 known per se (called an LED, as is known) with a chip 2 4 which can irradiate beams in a preferably first defined wavelength range and, additionally, beams in a second defined wavelength range even if at different strength. Fig. 8 shows a light-emitting diode 25 with two chips 26 and 27 mounted in the same housing, each chip 26, 27 radiating with its own wavelength and also having its own rerminals 28, 29 for this purpose. Fig. 9 shows as an embodiment for a radiation source 19 two light-emitting diodes 30a and 30b arranged side-by-side, each of which is suitable for beamtS in its own defined wavelength range. Fig. 10 shows as the radiation source 19 two light-emitting diodes 31 and 32 connected in series, the light-em.itting diode 32 being designed as a "chip-LED". The mode of operation of the invention is as follows: If, for example, it is a matter of identifying a first foreign body Fl in a base material 1, 3, 5 a wavelength range λ1or λ2 is selected according to Fig. 4, in which "he foreign body reflects the emitted beams sufficiently strongly that an electrical signal is produced which differs sufficiently from that of the base material. This would certainly be the case for the foreign body is represented by lines 10 and 11 at λ2. The electrical signal 16 which is produced in the process and which quantifies the reflection for beams with λ1 results, according to Fig. 5, in a large deflection or value 33 for the foreign material Fl and a likewise very large deflection or value 34 for the foreign material F2. This means that in this case the foreign bodies Fl and F2 can be easily identified. However, in practice it is difficult to distinguish between Fl and F2 because of rhe small difference between the deflections or values 3 3 and 34. By looking at Fig. 4, it can be seen that with a radiation source 19, which emits beams with a wavelength Xz, it will be difficult' to distinguish the foreign bodies Fl and F2 from each other and also from the base material, as line 9 characterises. A signal course 17 in Fig. 5; as is to be expected at the output of the receiver 20, with deflections or values 37 and 38, confirms this . However, if a radiation source 19 according to the invention is used, which can emit beams 35, 36 at two different wavelength ranges, a signal course 18 may thereby be achieved at the output of the receiver 20. Beams with the two wavelength ranges λ1 and λ2 result in a deflection or value 39 for the foreign body Fl and in a deflection or value 40 for the foreign body F2. It can immediately be identified that, in comparison to the signal course 16, the deflections 39 and 44 for the foreign bodies Fl and F2 differ more from each other than rhe deflections 33 and 34 of the signal course 15. Therefore, ir is possible here to set a limit 41 between zhe maximum values or deflections 39 and 40 to discriminate between the foreign bodies Fl and F2. If the limit 41 is exceeded by the signal course 18 foreign bodies Fl are identified. If, in addition, the limit 42 below the value or deflection 40 is stipulated, it can be established whether signal 18 is indicating foreign body Fl only, foreign body F2 only or both foreign bodies Fl and F2. In other words, the foreign bodies Fl and F2 are identified together when the signal 18 exceeds the limit 42. Foreign bodies Fl are identified when "che signal 18 exceeds the limit 41. It is thus possible to detect foreign bodies Fl and F2 separately. In this cas'e, the signal course 18 is based on the assumption that, for example, 30% of the beams have the wavelength X2 and the remainder the wavelength With said method it is therefore possible, as shown, to either identify the foreign bodies Fl alone or else the foreign bodies Fl and F2 together. It is also possible to make the relative intensity of the two wavelength ranges selectable in order to thus eliminate, for example, vegetable matter to a variably selectable extent. To carry out the method, the device shoulc preferably be provided with a radiation source 19, wherein the power of the beams in one wavelength range can be controlled in comparison to the other wavelength range. This may be easily achieved with radiation sources, as shown by Fig. 6 to 10, and a controller 22 designed for this purpose. 5y appropriately configuring the controller 22 it can also be ensured that the beams in at least one wavelength range can be switched on and off. The operator can thus also easily adjust -the unit to the base material or to other foreign bodies. When processing cotton into yarn it can be important to restrict the number of interventions in a varn clearer known per se. These interventions are made during che production of yarn using yarn clearers known per se, in particular with the cutting element cherecf. However, i:: should be taken into account that the more foreign bodies that are identified and eliminated, the m.ore frequently-the production machine, i.e. the spinning frame or bobbin winding machine, is stopped. Therefore it is important to decide which foreign bodies are to be tolerated and which are to be cut out. This can be done, for example, in that a decision is made in advance on which foreign bodies in the end product are actually harmful and which are not. For example, vegetable matter is undesired as the foreign body but is also quite harmless as, for example, it does not impair the dyeability of the yarn and therefore cannot be easily identified in the woven. Beams in a wavelength range between 520 and 570 mm are suitable for identifying other foreign bodies, such as green, red or blue polypropylene film as the foreign body and for discriminating the vegetable matter. The polypropylene film would then substantially correspond zo the foreign body F2; the vegetable matter, on the other hand, to the foreign body Fl, with reference to the embodiments of Fig. 4 and 5. Beams, for example, with a wavelength in the infrared range are suitable for the second wavelength range Λ2 . pi" If the device 43 for eliminating the foreign bodies from the base material, such as a yarn clearer known per se, is provided, this can be activated by the evaluating unit 21 as soon as the limit 41, 42 previously stored therein, for example in a processor, is reached or exceeded. The limits can be input into the evaluating 21 via an input device. During the production of yarn, as can be assumed in.this example, production can be optimised in this way such that a clear distinction can be made as to which foreign bodies are destructive, such that these are allowed to be removed, and this also always means that the production, i.e. the spinning head or the winding head, stands still for the time required for removal. If, therefore, it is clarified before production which foreihn bodies are likely to the present in the base material and which foreign bodies are actually to be removed, the quality of the product can be increased thereby, on one hand, and, on the other hand, the production output is maintained in that, for exam.ple, the cutting rate of the yarn clearer is limited. If foreign bodies are to be identified in a roving yarn, strip or in a flat woven insread of in a yarn, as shown, then this merely has an effect on the dimensioning of the radiation sources and the receiver, but in particular on the device for cutting our the foreign bodies, if such a device is available. Claims 1. Method for identifying foreign bodies in a base textile material (1, 3, 5), wherein the textile base material is subjected to beams (35, 36) and the beams (44) reflected by the base material are detected and converted into an electrical signal, characterised in that the emitted beam.s (35, 36) , substantially have two defined and different wavelength ranges (λ1 and λ2) snd the reflected beams are detected simultaneously and jointly from the two wavelength ranges. 2. Method according to claim 1, characterised in that the first defined wavelength range (λ1) of the beamS is selected such that the beams reflected by the base material with foreign bodies provides first values (33, 34) in the electrical signal for at least two different foreign bodies (Fl, F2), in that a second defined wavelength range (λ2) is selected such that the reflected beams produce an electrical signal with two values (37, 38) for the same foreign bodies (Fl, F2) , which values are not in the same ratio for the two foreign bodies as in the corresponding electrical signals in the first wavelength range. 3. Method according to claims 1, characterised in that to distinguish one foreign body, a limit (42) is provided for the electrical signal which lies between values (39, 40) for the electrical signal of the first foreign body and of the second foreign body. 4. Method according to claim 1, characterised in that the power of the beams in one wavelength range can be controlled in comparison to the other wavelength range. 5. Method according to claim 1, charac~erised in that the beams can be switched on and off in at least one wavelength range. 6. Method according to claim 1, characterised in that beams with a wavelength in the infrared range are selected for one wavelength range. 7. Method according to claim 1, characterised in that one wavelength range is provided for distinguishing disruptive foreign bodies in a yarn as the base textile material. 8. Device according to claim 1, characterised by a radiation source (19) for beams (35, 36) in at least two wavelength ranges and a receiver (20) fcr measuring the beams (44) fully reflected by the base material. 9. Device according to claim 8, characterised in that a light-emitting diode (23, 25) is used as the radiation source, which radiates in two different wavelength ranges . 10. Device according to claim 8, characterised in that two light-emitting diodes (30a, 30b or 31, 32) are used as the radiation source, each of which radiates in a wavelength range which is different from that of the other light-emitting diode. 11. A method for identifying foreign bodies substantially as herein described with reference to the accompanying drawings.

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