JP2009107186A - Evaluation apparatus of inkjet recording head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an evaluation apparatus of an inkjet recording head which can surely remove a test pattern formed on a belt via the recording head that is an evaluation object, and which can reuse ink of the collected test pattern. <P>SOLUTION: The evaluation apparatus which evaluates the inkjet recording head has a collecting head 20 that scrapes and collects after the test pattern formed on the belt surface is detected. An ink collecting part 14 sucked by a suction pump 13 is connected to a slit 25 of the collecting head 20. The ink scraped off by a blade 21 travels along the blade 21 and is sucked via an opening 25a. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an ink jet recording head evaluation apparatus that records information by ejecting ink onto a transported recording medium, and in particular, a test pattern is formed on a belt surface by setting the recording head to be evaluated in the apparatus. Thereafter, the present invention relates to an evaluation apparatus including a collection head that collects ink of the test pattern by scraping with a blade.

  The ink jet recording apparatus conveys the recording paper held on the surface of the conveyance belt, and records information by ejecting ink onto the recording paper. A recording head that ejects ink includes a large number of fine ink ejection nozzles in units of pixels, and the many ejection nozzles are likely to be clogged. For this reason, before the recording head is incorporated into the ink jet recording apparatus, ink is ejected from all the ejection nozzles for a certain period of time to evaluate whether the ink is ejected normally.

  In the conventional evaluation method, in order to evaluate whether or not the ink is normally ejected from all the ejection nozzles of the recording head, for example, a solid image test pattern is output on the recording paper conveyed via the belt, and this A test pattern was detected to evaluate missing pixels. In this case, the clerk visually checked the recording paper on which the test pattern was output, judged whether there was a missing pixel, judged the time of occurrence of the defect from the defective position, and observed the actual nozzle with a microscope, resulting in ejection failure. The nozzle was specified.

  In particular, in an evaluation in which ink is ejected continuously for a long time, a test pattern is continuously output using roll paper. In this case as well, an attendant visually confirms the test pattern output on the roll paper to determine the presence or absence of missing pixels and the time of occurrence of a defect. For this reason, enormous time and labor were required for evaluation, and skill was required.

  In order to achieve highly reliable evaluation, high-quality paper that is relatively expensive has been used for the recording paper and roll paper so that the ink does not penetrate into the paper and the test pattern does not bleed. In particular, in the evaluation using the roll paper, it is necessary to periodically replace the roll paper or replenish ink, and there is a problem that the running cost of the evaluation apparatus becomes high.

  Further, when a large amount of roll paper is used, it is necessary to secure an installation space for the roll paper, which causes a problem that the installation space for the apparatus becomes large.

  On the other hand, an evaluation method that does not require a test pattern recording paper is known in which a test pattern is directly output on a belt, the test pattern is detected, and then the test pattern on the belt is removed. , See Patent Document 1). In this method, in order to achieve highly reliable evaluation, it is important to output a high-definition and stable test pattern on the belt and to reliably remove the test pattern output on the belt. In addition, it is preferable that the test pattern ink removed from the belt can be reused.

  However, according to the invention disclosed in this publication, since the belt surface is cleaned using a cleaning roll, the removed ink is highly likely to be re-transferred to the belt, and the ink is reliably removed from the belt surface. Can not. In this method, it is difficult to reuse the removed ink.

  This publication also suggests cleaning using a blade and cleaning using a solvent, but does not describe reusing the removed ink. For example, in the method of removing ink by immersing the belt in a solvent, it is almost impossible to separate the ink removed together with the solvent and reuse it.

  In addition, this publication discloses that a plastic member such as polyimide or a metal is used as the material of the belt. However, when such a plastic member is used, the solvent resistance is poor, and the durability of the belt due to deterioration. Problems arise. For this reason, it is conceivable to use a fluorine-based plastic. However, the water repellency of the belt surface is too good, and ink droplets are connected, making it impossible to perform appropriate evaluation.

Further, when a metal is used for the belt, the solvent resistance is high and the durability is high, but the water repellency is poor, and there is a problem that the ink cannot be sufficiently removed when the ink is removed from the belt surface.
Japanese Patent Laying-Open No. 2005-104147

  An object of the present invention is to provide an evaluation apparatus for an ink jet recording head that can reliably remove a test pattern formed on a belt via a recording head to be evaluated and can reuse the collected ink of the test pattern.

  In order to achieve the above object, an inkjet recording head evaluation apparatus according to the present invention is an apparatus for evaluating a recording head that records information by ejecting ink, and is relatively opposed to the recording head to be evaluated. A moving belt; a detecting means for detecting a test pattern formed on the belt surface by ejecting ink through the recording head; and an evaluating means for evaluating the recording head based on the test pattern detected by the detecting means And a recovery head that scrapes and recovers the ink of the test pattern recorded on the belt surface by a blade slidably contacted with the belt, and the recovery head is continuous with a base end portion of the blade. A slit that extends in the width direction of the belt at the position and is opened, and a negative pressure is generated through the slit to collect the recovered ink. Is connected to a suction means for sucking.

  According to the above invention, since the negative pressure is generated through the continuous slit at the base end portion of the blade that is in contact with the belt surface and the ink of the test pattern scraped off by the blade is sucked, the test pattern is surely secured. In addition, the ink that has been scraped off can be generally recovered, and the recovered ink can be efficiently reused.

  Since the inkjet recording head evaluation apparatus of the present invention has the above-described configuration and operation, the test pattern formed on the belt can be reliably removed via the recording head to be evaluated, and the collected test pattern The ink can be reused.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a block diagram of an evaluation apparatus 1 that evaluates an ink discharge state of an ink jet recording head 10 (hereinafter simply referred to as a recording head 10) incorporated in an ink jet recording apparatus such as an ink jet printer. In the evaluation apparatus 1, recording heads 10 to be evaluated are sequentially set.

  The evaluation apparatus 1 has an endless belt 2 that moves relatively in a substantially horizontal direction at a position facing the ink discharge end 10a of the set recording head 10. The belt 2 is stretched around a driving roller 4 rotated by a motor 3 at a constant speed in the direction of the arrow shown in the figure, and a driven roller 5 spaced apart from the driving roller 4 in the horizontal direction. The vehicle travels at a constant speed in an arrow T direction (counterclockwise direction in the figure).

  On the downstream side of the recording head 10 along the traveling direction of the belt 2, a camera 6 that functions as the detection means of the present invention is provided. The camera 6 images the surface of the belt 2 illuminated by the illuminating device 7 and detects a test pattern P (described later) formed on the belt surface 2 a via the recording head 10.

  After the test pattern P data detected via the camera 6 is processed by the image processing device 11, only necessary data is selectively stored in the recording computer 12, and the ink ejection state of the recording head 10 is determined. Referenced when evaluating. That is, the image processing apparatus 11 and the recording computer 12 function as the evaluation unit of the present invention.

  Further, two recovery heads 20a and 20b for scraping and recovering the test pattern ink formed on the belt surface 2a are attached to the downstream side of the camera 6 along the moving direction of the belt 2 so as to be separated from each other. It has been. Since these two collection heads 20a and 20b have the same structure, the two collection heads may be collectively referred to as the collection head 20 in the following description.

  The collection head 20 has a plastic plate-like blade 21 that abuts against the belt surface 2a as shown in FIG. 2 representatively of the upstream collection head 20a, and the tip 21a of the blade 21 is connected to the belt surface 2a. The ink of test pattern P is scraped off.

  As shown in FIG. 1, the ink scraped off by each of the collection heads 20a and 20b is collected by the ink collection unit 14 by the suction force of the suction pump 13, and after passing through a filter (not shown), the foreign matter is removed. The recording head 10 is re-supplied via the supply unit 15. The suction pump 13 functions as the suction means of the present invention.

  One of the collection heads 20a on the upstream side in the moving direction of the belt 2 is attached to a position where the blade tip 21a is brought into contact with a relatively flexible portion of the belt 2 that is not wound around the roller. The other collecting head 20b on the downstream side is in a position where the blade tip 21a is brought into contact with a portion of the belt 2 wound around the roller (in this embodiment, a position facing the driven roller 5 via the belt 2). It is attached.

  As described above, the first collection head 20a is attached to the belt 2 where the belt 2 is easily bent, and after the ink of the test pattern P is substantially removed with a relatively weak scraping force, the belt back surface is supported by the driven roller 5. The second collection head 20b is attached to the second and the remaining ink is collected with a relatively strong scraping force, so that the remaining ink can be almost eliminated and the ink collection efficiency of the test pattern P can be improved. All ink can be removed reliably.

  FIG. 2 is an enlarged view showing a state in which the recovery head 20a is attached to the belt surface 2a. The collection head 20a is attached to the belt surface 2a with a contact angle θ of 30 ° ± 2 °. The downstream collection head 20b attached at a position facing the driven roller 5 is attached at the contact angle θ described above with respect to the tangential direction of the driven roller 5 at a position where the blade tip 21a contacts the belt surface 2a. ing.

  When the contact angle θ of the blade 21 with respect to the belt 2 is larger than the above-described angle, the blade 21 is liable to bend and damage to the belt surface 2a is increased. On the other hand, when the contact angle θ is smaller than the above-described angle, the contact state of the blade tip 21a with the belt surface 2a becomes unstable, and the ink scraping ability is reduced. For this reason, the collection head 20 is attached with its angle adjusted so that the contact angle of the blade 21 becomes the above-mentioned appropriate angle.

  FIG. 3A shows a view of the collection head 20 viewed from the belt surface 2a side, and FIG. 3B shows the internal structure of the collection head 20 corresponding to FIG. 3A. Is shown schematically. FIG. 3B also shows blocks of configurations 13 and 14 for sucking the collected ink. Hereinafter, the collection head 20 will be described in detail.

  The collection head 20 includes a substantially rectangular plate-shaped blade 21, and an upper housing 22 and a lower housing 24 that sandwich the base end side of the blade 21 from both sides. With the blade tip 21a in contact with the belt surface 2a at the contact angle θ described above and the recovery head 20 attached, the upper housing 22 is positioned above the blade 21 and the lower housing 24 is below the blade 21. To position. As shown in FIG. 2, the tip 21a of the blade 21 protrudes from the tips 22a and 24a of the two housings 22 and 24 toward the belt surface 2a.

  The upper housing 22, not shown in FIG. 3B, is formed in a substantially rectangular plate shape that is slightly larger than the blade 21. The lower housing 24 is also formed in a substantially rectangular plate shape that is substantially the same size as the upper housing and slightly thicker, and has a substantially rectangular recess 25 on the inner surface facing the blade 21. The recess 25 is formed with a slit-like opening 25a extending in the width direction of the belt 2 at the front end 24a of the lower housing 24 facing the belt surface 2a. Is forming. That is, when the collection head 20 is viewed from the belt 2 side (FIG. 3a), the elongated opening 25a of the recess 25 functions as the opening 25a of the slit 25 for sucking ink. In addition, an ink recovery unit 14 connected to the above-described suction pump 13 is connected to the rear end side of the slit 25.

  The blade 21 of the present embodiment has a length in the longitudinal direction along the belt width direction of 50 [mm], a plate thickness of 0.2 [mm], and a length along the lateral direction, that is, Since the blade length is 10 [mm], if there is a gap due to the slit 25 between the blade 21 and the lower housing 24 as described above, the blade 21 bends. For this reason, in the present embodiment, a plurality of ribs 26 for supporting the blade 21 at a plurality of locations are arranged in the slit 25 in a state of being separated from each other. It is sufficient that at least one rib 26 is arranged, and the length and width thereof can be arbitrarily changed, and the tip 26a exposed to the opening 25a of the slit 25 is formed to be tapered.

  Thus, with the recovery head 20 attached to the belt surface 2a at the contact angle θ described above, the detected test pattern P formed on the belt surface 2a is moved to the contact position of the blade tip 21a by the running of the belt 2. When moved, the ink of the test pattern P is scraped off by the blade tip 21a.

  The ink scraped off by the blade tip 21 a is sucked into the opening 25 a of the slit 25 along the inclined lower surface of the blade 21. At this time, a suction force is generated by the suction pump 13 connected to the rear end side of the slit 25, and a negative pressure is generated in the opening 25a. For this reason, almost all of the ink scraped off by the blade tip 21 a is forcibly sucked into the concave portion 25 through the opening 25 a of the slit 25 and collected in the ink collecting portion 14.

  At this time, since the lower surface side of the blade 21 is supported by a plurality of ribs 26 extending along the ink suction direction, the blade 21 does not bend even if the blade tip 21a is pressed against the belt surface 2a. The blade tip 21a can be satisfactorily adhered to the belt surface 2a over its entire width, and no ink remains on the belt surface 2a. Further, since the tip of the rib 26 is tapered, the area of the opening 25a of the slit 25 is not narrowed by arranging the rib 26, and the flow of the sucked ink is not hindered.

  By the way, in order to efficiently collect the ink of the test pattern P formed on the belt surface 2a, a negative pressure is applied to the opening 25a of the slit 25 continuous to the base end portion of the blade 21 supported by the rib 26 as described above. In addition to the forced suction of the ink generated, it is important to scrape the ink well from the belt surface 2a. For this reason, in the present embodiment, the belt 2 is made of stainless steel, and the surface roughness Ra of the belt surface 2a is set to 0.02 [μm] or less.

  The surface roughness Ra mentioned here is the arithmetic mean roughness specified in the Japanese Industrial Standard JIS B0601: 2001 “Product Geometrical Specification (GPS) —Surface Properties: Contour Curve Method—Terminology, Definitions, and Surface Property Parameters”. It is.

  In order to improve the peelability of the ink on the belt surface 2a, it is desirable to improve the water repellency of the surface 2a. However, if the water repellency is too good, there is a problem that the ink droplets landed on the belt surface 2a move and the ink droplets are connected to each other. That is, considering the fixability of ink droplets to the belt surface 2a, the water repellency of the belt surface 2a has an appropriate value. In order to improve water repellency, it is conceivable to coat the surface with a fluorine resin or the like. However, since the blade 21 is in sliding contact with the belt surface 2a, the coating tends to peel off, which is not preferable.

  Further, in order to remove the ink on the belt surface 2a satisfactorily, it is desirable that the flatness of the belt surface 2a is high. In other words, if the flatness of the belt surface 2a with which the tip 21a of the blade 21 is in sliding contact is poor, a gap is formed between the blade tip 21a and ink cannot be scraped well. Also in this respect, when the surface is coated, the flatness of the coating surface is easily impaired due to abrasion due to the sliding contact of the blade 21, and it is difficult to obtain the desired surface flatness.

  For this reason, in the present embodiment, considering the solvent resistance, stainless steel that has an appropriate water repellency and that can fix ink droplets well is adopted as the material of the belt 2, and the surface roughness Ra is 0.02. The belt surface 2a was polished so as to be [μm] or less.

  In FIG. 4, a test pattern P is formed on the belt surface 2 a using a stainless steel belt 2 having a surface roughness Ra of 0.02 [μm] or less, and the ink of the test pattern P is removed by the blade 21. The result of examining the state of the belt surface 2a is shown as a graph. At this time, the belt surface 2a after ink removal is imaged through a CCD line sensor (not shown) in which a large number of pixels are arranged in parallel along the belt width direction, and a certain distance along the running direction of the belt 2 is obtained. The value obtained by integrating the data was plotted as the sensitivity of each pixel of the CCD sensor.

  That is, the closer the sensitivity is to zero, the smaller the amount of ink remaining on the belt surface 2a, and the higher the sensitivity, the greater the amount of residual ink. Specifically, it means that there is no residual ink on the belt surface 2a with a sensitivity of 0, and it means that the belt surface 2a is filled with residual ink with a sensitivity of 100.

  From the result of FIG. 4, when a belt having a surface roughness Ra of 0.02 [μm] or less is used as in the present embodiment, the sensitivity of the CCD is 10 or less in each pixel, and the belt surface 2a It can be seen that the cleaning effect is extremely high. That is, it can be seen that the ink of the test pattern P can be effectively removed by increasing the flatness of the belt surface 2a to this extent. In other words, if the amount of residual ink is about this level, there is no fear of affecting the evaluation in the evaluation apparatus 1.

  On the other hand, FIG. 5 shows the result of examining the state of the belt surface 2a after ink removal when a belt having a surface roughness Ra of about 0.05 [μm] is used, and FIG. The result of examining the state of the belt surface 2a after ink removal when a belt having a surface roughness Ra of about 0.1 [μm] is used is shown. Needless to say, the data in FIGS. 5 and 6 were obtained under the same conditions as in FIG. 4 except that the surface roughness Ra of the belt surface 2a was varied.

  According to this, when a belt having a surface roughness Ra of about 0.05 [μm] is used, as shown in FIG. 5, there are seven places with high sensitivity, and a lot of ink remains in this portion. I understand that. Although the highest sensitivity is about 50, it is conceivable that the ink color is other than black or the sensitivity is lower than the actual color due to lighting conditions, etc., and actually the belt surface 2a at this part affects the evaluation. It is considered that a large amount of ink remains to the extent given.

  Further, when a belt having a surface roughness Ra of about 0.1 [μm] is used, as shown in FIG. 6, there are 10 or more high portions with high sensitivity, and there are many in almost all regions of the belt surface 2a. It can be seen that the ink remains. It can also be seen that the minimum level of sensitivity is increased in all pixel data. This means that the ink remains thin over the entire belt surface 2a.

  As described above, when ink remains on the belt surface 2a, even if there is an ink discharge defective portion in actual evaluation, it is impossible to evaluate ink loss at that portion, and it becomes impossible to perform highly reliable evaluation.

  For this reason, in the present embodiment, the stainless steel belt 2 is used, and the surface roughness Ra is set to 0.02 [μm] or less.

  As described above, according to the present embodiment, using the stainless steel belt 2 having good ink fixability and easy peeling, and having a low surface roughness, the blade tip 21a is placed on the belt surface 2a with an appropriate contact angle θ. The two recovery heads 20 that are brought into contact with each other are arranged apart from each other in the running direction of the belt 2, and the ink scraped off by each recovery head 20 is sucked by the suction pump 13 and recovered by the ink recovery unit 14. After the test pattern P is formed and detected on the belt surface 2a, the test pattern P on the belt surface 2a can be reliably removed, the ejection state of the recording head 10 can be evaluated well over a long period of time, and ink recovery The efficiency can be increased, the recovered ink can be reused, and the running cost of the evaluation apparatus 1 can be reduced.

  Next, an evaluation method of the recording head 10 using the above-described evaluation apparatus 1 will be described with reference to FIGS. 8 to 10 together with the flowchart shown in FIG.

  First, as shown in step 1 in FIG. 7, the evaluation apparatus 1 applies a test pattern P having a predetermined shape to the surface 2 a of the belt 2 that travels at a constant speed via the recording head 10 to be evaluated. Output.

  Although the output timing of the test pattern P varies depending on the type of evaluation (such as continuous ejection for a long time), it is not necessary for the evaluation apparatus 1 to manage this timing or output a trigger signal. In the present embodiment, as shown in FIG. 8B, a rectangular test pattern P of a solid image extending over substantially the entire width of the belt 2 is formed on the belt surface 2a.

  At this time, the image processing apparatus 11 waits for the test pattern P to be conveyed to the imaging area 6a of the camera 6 (step 2) (state of FIG. 8a), and confirms that the test pattern P has reached the imaging area 6a. As a trigger (step 2; YES) (state of FIG. 8b), data output of each pixel along the belt width direction of the captured image is started (step 3).

  Here, it is assumed that a camera 6 having a large number of CCDs arranged in parallel in the width direction of the belt 2 is used. At this time, the image processing apparatus 11 detects the test pattern P at intervals of 10 [msec] until the rear end in the transport direction of the test pattern P passes through the imaging area 6a of the camera 6 as shown in FIG. Output data.

  The recording computer 12 sequentially compares the data output from the image processing apparatus 11 with the previous data (step 4) and only when the data is different from the previous data (step 4; NO), the data is shown in FIG. It is stored in a data table showing an example (step 5). That is, the same data as the previous data is not stored in the data table (step 6). As a result, only the minimum necessary data is stored in the data table.

  FIG. 9 shows an example of data when the defective ejection portion S of the test pattern P ′ having a missing pixel as shown in FIG. 10 is detected. That is, as shown in FIG. 10, when the test pattern P ′ having the defective ejection portion S with missing pixels is conveyed, the data in which the defective ejection portion S is detected has two edges A and B as shown in the graph of FIG. Will have.

  The image processing apparatus 11 outputs the data detected via the camera 6 to the recording computer 12 as it is, but the recording computer 12 always compares the input data with the previous data. For this reason, the recording computer 12 stores the changed data including the edges A and B in the data table based on the fact that the data is different before and after the detection of the edges A and B.

  Specifically, in this case, the recording computer 12 compares the previous information N-1 that does not include the information on the edges A and B with the information N that includes the information on the edges A and B. Based on the difference, the information N is stored in the data table. The data stored in the data table is also associated with information regarding the date and time when the event occurred.

  For this reason, when actually evaluating the ejection state of the recording head 10, the detected data is referred to by referring to the data table when the test pattern P formed on the belt surface 2a is detected via the recording head 10. Based on the changed time and the changed pixel, it is possible to determine a defective discharge location such as a missing pixel. In this case, since data for evaluation judgment is selectively stored as compared to verifying all detected data, it is possible to easily evaluate the recording head 10 without requiring enormous data processing. Is possible. For example, when there is no missing pixel and data relating to the edges A and B as described above is not detected, there is no data to be stored in the recording computer 12, and therefore the evaluation becomes very easy.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the above-described embodiments. For example, you may delete some components from all the components shown by embodiment mentioned above.

1 is a block diagram showing an ink jet recording head evaluation apparatus according to an embodiment of the present invention. The enlarged view for demonstrating the attachment state with respect to the belt of the collection | recovery head integrated in the evaluation apparatus of FIG. The front view for demonstrating the structure of the collection | recovery head of FIG. 2, (a), and a block diagram (b). 2 is an evaluation graph of residual ink when the surface roughness of a belt incorporated in the evaluation apparatus of FIG. 1 is 0.02 [μm] or less. An evaluation graph of a belt having a surface roughness of 0.05 [μm] for comparison. An evaluation graph of a belt having a surface roughness of 0.1 [μm] for comparison. The flowchart for demonstrating operation | movement of the evaluation apparatus of FIG. Operation | movement explanatory drawing for demonstrating the detection method of a test pattern. The figure which shows an example of the data memorize | stored in the computer for recording. Operation | movement explanatory drawing for demonstrating the method to detect the pixel omission of a test pattern.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Evaluation apparatus, 2 ... Belt, 6 ... Camera, 10 ... Recording head, 11 ... Image processing apparatus, 12 ... Recording computer, 13 ... Suction pump, 14 ... Ink collection part, 15 ... Ink supply part, 20 ... Collection Head, 21 ... Blade, 21a ... Tip, 25 ... Slit, 25a ... Opening, 26 ... Rib, 26a ... Tip, P ... Test pattern.

Claims (7)

An evaluation apparatus for evaluating an ink jet recording head that records information by discharging ink,
A belt that moves relative to the recording head to be evaluated;
Detecting means for detecting a test pattern formed on the belt surface by discharging ink through the recording head;
Evaluation means for evaluating the recording head based on the test pattern detected by the detection means;
A recovery head for scraping and recovering the ink of the test pattern recorded on the belt surface by a blade slidably contacted with the belt;
The recovery head has a slit that opens in the width direction of the belt at a position continuous to the base end portion of the blade, and generates a negative pressure through the slit to suck the recovered ink. An evaluation device connected to the suction means.   2. The recovery head according to claim 1, further comprising at least one rib extending along the suction direction of the ink so as to support the blade in order to prevent the blade from bending. The evaluation device described.   The evaluation apparatus according to claim 2, wherein the end of the rib exposed at the opening of the slit is tapered.   The evaluation apparatus according to claim 1, wherein the recovery head is disposed at two positions spaced apart from each other on the downstream side of the recording head along the moving direction of the belt.   The said collection | recovery head of the downstream along the conveyance direction of the said belt among these two collection | recovery heads is arrange | positioned in the position facing the roller which wound the said belt. Evaluation device.   The evaluation apparatus according to claim 1, wherein the belt is made of stainless steel.   7. The evaluation apparatus according to claim 6, wherein the surface roughness Ra of the belt is 0.02 [μm] or less.

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