EP0285602B1 - Method and apparatus for detecting and removing foreign matter from raw cotton - Google Patents

Description

The invention relates to a method according to the preamble of claim 1 and a device according to the preamble of claim 9.

The aim of the invention is to remove foreign fibers from the raw cotton. Foreign fibers can get into the raw cotton through improper removal of the packaging or when picking and collecting the cotton as well as when emptying the bags in the collection point or ginning plant, e.g. the cords with which the sack was tied were cut open, fell onto the floor and with the spilled cotton into the ginn. It is essential for the following considerations that the modern cotton spinning mills work fully automatically in a mixture with automatic removal or milling without supervisory personnel. Therefore, it is also illusory to think about whether one could remove visible foreign bodies manually. In the further processing process, however, such foreign fibers cause essential damage in the finished trade. The frequency of thread breakage in the spinning mill also increases due to such foreign fiber components. In terms of spinning technology, there are no options for safe elimination, which means that these impurities have a particularly negative effect on the rotor spinning process and the yarn quality. Their share of total thread breaks can easily reach 80%. The big problems repeatedly cause the foreign fiber contamination of the cotton in the pure cotton and cotton blended yarn ranges. Since there is no suitable test device with which permanent production checks can be carried out in the Vorwerk with regard to the detection of foreign fibers, this contamination causes considerable damage.

The previous method of checking the raw materials was limited to checking the damage to the packaging or packaging contamination as well as foreign matter or parts within the bale. Since most of the packaging has been damaged and some of the remnants have been pressed into the bale, a better removal of the visible, external bale contamination was necessary. Such devices for detecting foreign matter in bales are e.g. known from FR-A2,571.502. Apart from the fact that a manual cleaning effort of an additional 5 to 10 minutes per bale is required, only large objects can be recognized or eliminated with such foreign matter detection systems; Smaller impurities, which are present in a much larger number, cannot be recognized and interfere with the operation of the system. For the reasons given above, it is clear how important automated foreign fiber detection systems and removal systems are for cotton spinning mills.

As part of the raw cotton disintegration process, the place where the cotton is already relatively well disintegrated should be selected for measurements, but the foreign fiber has not yet been broken down into its individual fiber. Immediately after opening the bale, there are still large proportions of inorganic faulty substances as well as shells, grasses, cotton seeds etc. in the raw cotton. These foreign particles can, however, be easily eliminated with conventional cleaner trains. The later a detection system is used, the fewer false triggers will occur due to the easily removable foreign substances mentioned. However, this requirement contradicts the first requirement for the lowest possible degree of disintegration in order to have the foreign fibers undone.

According to the invention a method of the kind referred to is characterized in that which is to foreign substances to be examined fiber material before irradiation to a flock weight of 10- ¹ to 10- ³ g / flake, preferably g to about 2x1 0- ² / flake, fanned and that X-rays with an acceleration voltage of 5-30 kV, preferably 8-20 kV, in particular 10 kV, are used for radiation.

An inventive device of the type mentioned is characterized in that the X-ray system at a location in Aufschtießungsprozeß is preferably in a calming section, installed at the Aufschließungsgrad the flakes a flock weight of 10- ¹ to 1 0-3g, preferably 2x10 ² g, shows that the X-ray system can be operated with an acceleration voltage of 5-30 kV, preferably 8-20 kV, in particular 10 kV, and that from the foreign body detector, a foreign body detector that removes the foreign matter from the fiber material, preferably at the end of the calming section arranged removal device is controlled. The X-ray device and the associated image recognition device are arranged in order after the processing device for fibers, in particular raw cotton, for example in the course of a cleaner, at a point at which the preferably continuously moved, partially disintegrated fiber, in particular raw cotton, starting from an initial flake weight in one Standard bale is loosened to the flake weight given above The removal device for the foreign fibers can be controlled by the image recognition device.

Standard X-ray fluoroscopy devices with high acceleration voltages cannot be used because, as has been established, the foreign fibers to be removed can only be used when a signal is used X-ray tube with an acceleration voltage of approx. 10 kV. An X-ray tube was therefore used, which works with acceleration voltages of 8 - 12 kV. The image of the foreign fibers in the cotton produced in this way provided sufficient contrast to generate a signal with conventionally available image conversion or image scanning systems, which can trigger an elimination mechanism if a certain size of an imaged foreign substance is exceeded. This signal obtained in this way is used (with a time delay and synchronously with the feed speed of the raw cotton) to remove that part of the raw cotton in which the foreign fiber is located, e.g. with a compressed air flow that is activated across the direction of travel of the raw cotton via a compressed air valve , and "shoot out" into a prepared container. In order not to have to put up with too much loss of cotton or in the event of incorrect triggering due to pebbles or organic materials, the content of that container is sorted manually, for example. In this way, foreign fibers down to the order of magnitude of 18 mg could be removed. This corresponds, for example, to a PVC cord with a length of approx. 3 cm and a diameter of approx. 2.5 mm, which is made up of individual threads.

Preferred embodiments of the method and the device according to the invention are clarified in the subclaims, the description and the drawing.

The invention is explained in more detail below on the basis of an exemplary embodiment shown in the drawing.

In the drawing, the disintegration or cleaning process of raw cotton is shown purely schematically in a partial section of a total digestion section. From a schematically indicated bale cutter 19 or a similar device, the raw cotton of delivered bales is processed or removed and loosened in the course of the removal. The usual bales of raw cotton have a weight of about 480 pounds and a volume of a little less than 1 m ³ . This partially loosened cotton may already have preferably 2x10 ² g / flake a flock weight of about 10- ¹ to 10- ³ g / flake. With an air flow generated by a fan 2, the raw cotton is fed via a roller 24 and a fan roller 4, in which further loosening or disintegration takes place, to a calming section 18, in which, for example, seeds, stones or the like. Impurities are excreted. 7 schematically denotes a cleaning device in the calming section 18. The loosened cotton fed to this calming section 18 via a loading shaft 5 and a light barrier 6 is fed at the end of the section via a feed table 8, pressure rollers 9 and feed rollers 10 to a sawtooth roller 11 or separating knives 12 or carding segments 13 which further clean and break up the cotton . The cotton is discharged via the shaft 25, while contaminants are discharged via the shaft 26.

15 designates a density measuring device, which is advantageously an X-ray tube fed by a voltage source 21 or an X-ray transmission device, the optionally fanned beams of which are from a sensor system or an image recording device 14, e.g. Semiconductor image recorders are supplied, which is assigned a processor system or an image evaluation device which, depending on a specific predetermined resolution, emits a trigger signal if the measured density values allow conclusions to be drawn about foreign fibers that exceed a specific dimension. Such a trigger signal is sent via a line 23 to a distance device 17, e.g. a compressed air nozzle, which is thus controlled by the image recording device 14. If the image recording device 14 detects foreign fibers, the removal device 17 is actuated synchronously as a function of time, taking into account the flow velocity of the cotton. If it is a compressed air nozzle, the cotton and the foreign fibers are blown out through a flap 22 into a collecting container 16. From the collection container 16, the raw cotton and the foreign fibers that have been separated out can be further sorted. Instead of a compressed air nozzle for separating contaminated cotton components, an automatically controlled gripper could also be provided.

It should be noted that due to the opposing procedural criteria mentioned at the outset, namely that on the one hand the cotton should be largely open to the elimination of foreign substances, but on the other hand extensive digestion worsens the detection and removal of foreign fibers, which become more and more frayed with further digestion, a compromise had to be made. Accordingly, the detection device according to the invention must be arranged in a region of the raw cotton being conveyed, in which the cotton has been loosened to a theoretical flake weight of 10- ¹ to 10- ³ g / flake, preferably 2x1 0- ² g / flake. It should be noted that the finally loosened, cleaned and digested cotton has a theoretical flake weight, which carries about 5x1 0-7 g / flake.

If this condition is met, the device according to the invention could, for example, already be arranged immediately after the bale cutter, since such devices can already flocculate the cotton in such a way that that this flake weight range specified according to the invention is reached. If, for example, instead of a bale cutter 19, another raw cotton feed device is provided in order to feed the raw cotton to the cleaning train, the device according to the invention is arranged at a different location at which the desired flake weight reduction is present, for example only after one or more cleaning stages. The selection of the voltage of the X-ray tube was also important, since a voltage that is too low or too high does not result in a usable signal and only through the mutual coordination of the X-ray voltage and the degree of volume flocculation can be obtained recognizable and evaluable evaluation signals indicating foreign fibers.

Plastic fibers and plastic cords can be optimally separated with the device according to the invention or with the method according to the invention. It is essential for the method that the path irradiated by the X-ray beam, i.e. the space through which the cotton flakes flow has a dimension (a) which is approximately 3-15 cm in size, preferably approximately 9 cm. Rectangular channels or round channels with the above dimensions could be used as the radiation depth or radiation diameter. It is important that the loosened fiber flakes are tight at the measuring location or without gaps in order to ensure an essentially constant output level for the density measurement. With the flake weight provided according to the invention, this is achieved with the specified dimensions of the measuring path depth.

Theoretical calculations for the optimal layer thickness of the material to be irradiated resulted in a layer thickness or penetration depth of approx. 10 cm. In order to obtain a density fluctuation that can be detected by inexpensive image processing systems, the signal-to-noise ratio should be as high as possible (approx. 2: 1). It follows from this that the layer to be penetrated by the rays may not contain more mass of raw fiber material than the mass of the foreign body to be searched for. This means that the smaller the dimension of the foreign fiber to be determined, the thinner the layer of the loosened material must be.

From experience, through previous manual sorting in textile companies, it is known that approximately 80% of the framing fibers to be removed have a diameter of approximately 2.5 mm. In the case of a foreign fiber made of plastic, it was therefore possible to calculate that the layer thickness may be approximately 8 cm under the mentioned boundary conditions of the signal strength.

The thinner the fibers have been guided past the radiometer or the smaller the depth of radiation, the thinner the foreign fibers that can still be recognized. However, this means, with a constant throughput of raw fiber material, through a cleaner train, a widening of the necessary channel or an increase in the speed at which the image recognition system has to work.

For constructional reasons, the width of a search device should not exceed a value of approx. 1 m, e.g. conventional cleaner trains that have this width can be used for installation.

The above shows that, in theory, even the thinnest foreign fibers could be discovered, e.g. by reducing the throughput through a cleaning unit, but economically an optimum channel width of 5-10 cm should be chosen.

It is advantageous if, in order to determine a locally delimitable increase in density due to foreign fibers, e.g. Plastic cords, sensor elements are used in a one-line or multi-line arrangement, the preferably square or circular dimension of which is in the order of the minimum dimension of the weakest foreign fiber to be detected, the signals corresponding to the density fluctuations being fed to an electronic evaluation system.

Claims (14)

1. A method and an apparatus for detecting and removing foreign matter from fibrous material, in particular from raw cotton,in which the fibrous material is conveniently continuously fed to an electron beam or X-ray transmission densimeter device and continuously examined as to density fluctuations and density increases detected and clearly locally delimitated against surrounding density, as, for instance, foreign fiber areas containing plastics material cords, are defined and such areas are removed from the fibrous material, characterized in that the fibrous material to be examined as to foreign matter is loosened preceding irradiation to a flock weight of 10-¹ to 10-³g/flock, preferably to about 2 x 1 0-²g/flock and that X-ray radiation with an accelerating potential of 5 to 30 kV, preferably 8 to 20 kV, in particular 10 kV, is employed for irradiation.

2. A method according to claim 1, wherein the loosening of the fibrous material to a flock weight of 10-¹ to 10-³ g, preferably 2 x 10-² g, is effected in the course and by appropriate control of the removing operation of the fibrous material from a raw fiber bale, for instance by means of a bale breaker.

3. A method according to claim 1 or 2, wherein the signals corresponding to the density fluctuations are fed to an electronic evaluation system and the foreign fiber areas defined by the evaluation system are removed , controlled by the evaluation system and preferably time-lagged and synchronous with the advance motion,from the partially broken up or loosened raw fibrous material, in particular the raw cotton, for instance by expelling by means of a compressed air jet, removal by grab or the like.

4. A method according to any one of the claims 1 to 3, wherein the density measurement is carried out on a transport line, for instance air conveyor or conveyor belt, in the location in which the individual, optionally discontinuously supplied flocks are accumulated or made to pass in such a manner that interposed cavities are eliminated and a largely continuous material flow with homogeneous surface density is created.

5. An apparatus for breaking up fibrous material as well as detecting and removing foreign matter from fibrous material, in particular from raw cotton, with a breaking-up device to which the fibrous material freed of packing material is fed, with a contactlessly operating foreign body detector (14, 15), in particular for detecting foreign fibers, monitoring the conveying path of the fibrous material during the breaking-up operation, the foreign body detector (14, 15) being formed as a transmission densimeter with an electron beam or X-ray device, for carrying out the method according to any one of the claims 1 to 4, characterized in that the X-ray device is installed at a location in the breaking-up process, preferably in a smoothing line (18), in which the breaking-up degree of the flocks yields a flock weight of 10-¹ to 10-³ g, preferably of 2 x 10-², that the X-ray device is operable at an accelerating potential of 5 to 30 kV, preferably of 8 to 20 kV, in particular 10 kV, and that a removing means (17) removing the foreign bodies from the fibrous material and controlled by the foreign body detector (14, 15) is disposed downstream from the foreign body detector (14, 15), preferably at the end of the smoothing line (18).

6. An apparatus according to claim 4 or 5, wherein the transmission densimeter device contains one or a plurality of sensor element(s) sensitive to X-ray or electron irradiation, optionally in single-line or multiple-line arrangement, preferably disposed perpendicularly to the conveying direction, whose sensor resolution corresponds to the minimum dimensions of the smallest foreign body to be detected

7. An apparatus according to claim 6, wherein the sensors are disposed behind a collimator, conveniently in the housing shield, for eliminating the contrast deterioration caused by scattering.

8. An apparatus according to claim 6 or 7, wherein an electronic evaluation system (14), conveniently an image processing system, is connected to the sensor elements.

9. An apparatus according to any one of the claims 4 to 8, wherein the evaluation system (14) is coupled with the removing device (17, 22) and the removing device (17, 22) is controlled by the evaluation system (14).

10. An apparatus according to any one of the claims 4 to 9, wherein the removing device (17, 22) consists of a compressed air system or a grab.

11. An apparatus according to any one of the claims 4 to 10, wherein the evaluation system comprises a trigger unit with optionally adjustable thresholds for the optionally displayable density measuring signals generated by foreign bodies and transmitted by the sensors.

12. An apparatus according to any one of the claims 4 to 11, wherein a computer circuit is connected to the irradiation device for determining the respective change in density of the fibrous material moving past the irradiation device and the computer circuit is connected to the removing device for actuating the same.

13. An apparatus according to any one of the claims 4 to 12, wherein the densimeter device is disposed on a smoothing line between a bale breaking-up device for the raw cotton, for instance a bale breaker, and the next following breaking-up device, for instance a carding and removing knife device.

14. An apparatus according to any one of the claims 4 to 13, wherein a collecting container for discarded foreign fibers and raw cotton forming part of a final sorting means is associated with the removing device.

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