JP2005096229A - Image recording apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image recording apparatus which can easily, inexpensively and accurately carry a recording medium for the image recording apparatus carrying the recording medium by using an annular belt member, without enhancing the accuracy of a mechanical component. <P>SOLUTION: This image recording apparatus comprises: an image recording means for recording an image; a recording-medium carrying means 3 which has the annular belt member 35 laid on a roller for placing and carrying the recording medium 2; a mark recording means for recording a prescribed mark on the belt member 35 by using ink; a mark detecting means 4 for detecting a mark M which is recorded on the belt member 35; a carrying control means for determining the amount of movement of the belt member 35 of the means 3 on the basis of a position wherein the mark detecting means detects the mark M; and a cleaning means 5 for erasing the mark which is recorded on the belt member. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image recording apparatus, and in particular, includes an image recording unit that records an inkjet image by ejecting ink from nozzles onto a recording medium, and a recording medium conveyance unit that includes an annular belt member that conveys the recording medium. The present invention relates to an image recording apparatus.

  2. Description of the Related Art An image recording apparatus that records an inkjet image by ejecting ink from nozzles onto a recording medium that is placed and conveyed on a belt member that is stretched around a roller is known as an inkjet printer.

  In such an image recording apparatus, in general, by ejecting ink from nozzles at a predetermined timing in the process of main scanning a recording head as an image recording means in which a large number of nozzles are arranged in the width direction of the recording medium. After recording an image for one main scan, the belt member is moved by a predetermined distance in the sub-scanning direction orthogonal to the main scanning direction, thereby repeating the operation of conveying the recording medium on the belt member, thereby recording A desired inkjet image is recorded on the medium.

  In such an image recording apparatus, when the recording medium is conveyed by a predetermined distance in the sub-scanning direction by moving the belt member, recording is performed by one main scanning of the recording head unless the movement of the belt member is controlled with high accuracy. White streaks and uneven density occur between the image and the image recorded by the next main scanning, which causes the image to deteriorate.

  For this reason, it is necessary to improve the mechanical accuracy such as improving the diameter accuracy of the roller for conveying the belt member, but it requires advanced and expensive precision processing, especially for large printers that output wide prints. Has a problem that causes a significant increase in cost.

Therefore, conventionally, Patent Document 1 discloses a roller rotation or recording means so as to detect a change in the thickness of the belt member in the circumferential direction and to correct a speed variation of the belt member caused by the change in the thickness. A technique is disclosed in which a recording medium can be conveyed with high accuracy by controlling the recording timing according to.
Japanese Patent No. 2877542

  However, as described in Patent Document 1, in the case of detecting a change in the thickness of the belt member, a detection unit for detecting the thickness, a processing device for performing complex arithmetic control based on the detection signal, and the like In addition, an expensive processing apparatus is required to realize high-speed conveyance, which causes a problem of increasing the cost of the apparatus.

  Therefore, the present invention can easily and inexpensively convey a recording medium in an image recording apparatus that conveys the recording medium using an annular belt member without increasing the accuracy of mechanical parts. It is an object of the present invention to provide an image recording apparatus capable of performing the above.

  The above problems are solved by the following inventions.

  According to the first aspect of the present invention, there is provided an image recording means for recording an image by ejecting ink from nozzles onto a recording medium, and an annular belt member stretched around a roller for placing and transporting the recording medium. Recording medium transporting means, mark recording means for recording a predetermined mark using ink on the belt member, mark detection means for detecting a mark recorded on the belt member, and recording medium transporting means A transfer control means for determining the amount of movement of the belt member in reference to the position where the mark detection means detects the mark, and a cleaning means for erasing the mark recorded on the belt member. An image recording apparatus characterized by the above.

  A second aspect of the present invention is the image recording apparatus according to the first aspect, wherein the image recording unit also serves as the mark recording unit.

  The invention according to claim 3 is characterized in that the ink for recording the mark is at least one kind of ink selected from inks for image recording. It is.

  According to a fourth aspect of the present invention, the mark detection means is means for detecting the mark with light, and at least the reflectance of the belt member and the mark is different. It is an image recording device of description.

  According to a fifth aspect of the present invention, when a necessary conveyance distance of the recording medium at the time of image recording by the recording medium conveyance means is x, a distance y between the mark recording means and the mark detection means is x> y. The mark recording means and the mark detection means are arranged so that the distance of xy, which is a deficiency with respect to the necessary conveyance distance x of the recording medium, is determined by the roller of the recording medium conveyance means. The image recording apparatus according to claim 1, wherein the image recording apparatus is compensated by rotation control.

  A sixth aspect of the present invention is the image recording apparatus according to any one of the first to fifth aspects, wherein the recording medium is a fabric.

  A seventh aspect of the present invention is the image recording apparatus according to any one of the first to sixth aspects, wherein a contact angle between the surface of the belt member and the ink for recording the mark is less than 90 degrees. is there.

  According to the present invention, the recording medium can be transported easily and inexpensively with high accuracy without increasing the precision of mechanical parts in the image recording apparatus in which the recording medium is transported using the annular belt member. Can do.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic diagram of an image recording apparatus according to the present invention, FIG. 2 is a partial plan view thereof, and FIG. 3 is a block diagram of the main part of the image recording apparatus.

  In FIG. 1, reference numeral 100 denotes an image recording apparatus, and 1 denotes a recording head, which includes a single recording head that discharges a single color of ink, and a plurality of recording heads that discharge a plurality of colors such as YMCK, for example. It may be a thing.

  A number of nozzles (not shown) are arranged on the lower surface of the recording head 1 along the direction (left and right direction in the drawing) orthogonal to the main scanning direction (vertical direction with respect to the drawing surface) of the recording head 1. 3, the image data stored in the image memory 7 is read out in a predetermined order, and the head driver 7 is controlled according to the image data. By ejecting ink from each nozzle at a predetermined timing as ink droplets in the form of fine droplets in the downward direction in FIG. An inkjet image is recorded.

  The recording head 1 is mounted on a carriage (not shown), and the carriage moves in both directions along the main scanning direction by a moving means (not shown) so that the recording head 1 reciprocates in the main scanning direction. It has become.

  The recording medium used in the present invention is not particularly limited, such as paper, a resin sheet, and a fabric. Here, an example in which the fabric 2 which is a preferred example in the present invention is used is shown. The cloth 2 as the recording medium is continuously fed out from a roll-shaped original roll (not shown), and the recording medium conveying means 3 disposed opposite the recording head 1 with the cloth 2 interposed therebetween. It is designed to be transported.

  The recording medium conveying means 3 is stretched between a pair of upper rollers 31 and 32 arranged at a predetermined interval, a pair of lower rollers 33 and 34 arranged below the rollers, and the rollers 31 to 34. The belt 2 has a belt member 35, and the fabric 2 is placed on the portion of the belt member 35 spanned by the upper rollers 31 and 32 so that the fabric 2 is smoothed at the portion facing the recording head 1. It is designed to be transported in a state that is maintained in the above state. It should be noted that the number of rollers for passing the belt member 35 may be at least two, and is not limited to the illustrated example.

  The width of the belt member 35 is formed to be wider than the width of the fabric 2, and when the fabric 2 is placed on the belt member 35, as shown in FIG. Each surface of the belt member 35 protrudes.

  Reference numeral 36 denotes a motor for transmitting a rotational driving force to the roller. Here, the motor 36 is connected to the upper roller 31 so that the rotational driving force can be transmitted, and the rotation is controlled by the control unit 6 as shown in FIG. It has become. The recording medium conveying means 3 rotates the upper roller 31 by controlling the rotation of the motor 36, and rotates the belt member 35 in the direction of the arrow, so that the fabric 2 placed on the belt member 35 is removed. Transport.

  Here, the recording head 1 can reciprocate in the main scanning direction over a range wider than the width of the fabric 2, and is determined in advance in the process of main scanning movement in the width direction of the belt member 35. Further, by ejecting ink droplets from at least one nozzle, control is performed so as to record a predetermined mark M (see FIG. 2) on the surface of the belt member 35. Accordingly, the ink for recording the mark M is at least one kind of ink selected from the image recording inks ejected from the recording head 1.

  That is, the recording head 1 is not only an image recording unit but also a mark recording unit, and both are used. The mark recording means for recording the mark M on the surface of the belt member 35 may be configured as a means different from the recording head 1, but in this way the image recording means and the mark recording means are used in combination. Since the ink for recording M is at least one ink selected from the image recording inks ejected from the recording head 1, the number of parts can be reduced and the space can be saved. This is a preferred embodiment.

  The mark M recorded on the surface of the belt member 35 can be recorded by ejecting ink droplets while the recording head 1 moves in the main scanning direction, and can be detected by a mark detection means described later. Any form may be used as long as it is, but here, it is recorded as a straight line (line) having a certain length (for example, 1.0 mm) along the main scanning direction. Yes. If the mark M is such a line-shaped mark, the recording can be easily performed only by one main scanning of the recording head 1 and can be accurately detected by a mark detecting means described later, whereby the belt member. The movement of 35 can be performed with high accuracy.

  The position where the mark M is recorded is the surface of the belt member 35 that protrudes from both sides of the fabric 2 and may be at least one of the surfaces. Specifically, the mark detection means to be described later is provided. If it is.

  As shown in FIGS. 1 and 2, a mark detection unit 4 is disposed at a predetermined distance from the recording head 1 on the downstream side of the recording head 1 in the transport direction of the fabric 2. The mark detection unit 4 includes a light emitting element such as an LED that irradiates the surface of the belt member 35 with detection light, and a photodiode that receives the reflected light reflected by the surface of the belt member 35. A change in the amount of light when the detection light applied to the surface of the belt member 35 passes through the mark M described on the moving belt member 35, comprising a reflective optical sensor having a light receiving element. The presence of this mark M is detected by detecting. The detection signal of the mark detection means 4 is output to the control unit 6 shown in FIG.

  The use of the mark detection means 4 for detecting the presence of the mark M using light in this way is a preferable mode because the mark M can be detected at high speed without contact, but in this case, the mark M Therefore, it is preferable that at least the belt member 35 and the mark M, that is, the ink on which the mark M is recorded, have different light reflectivities. The greater the difference in light reflectance, the easier it is for the mark detection means 4 to detect the mark M recorded on the surface of the belt member 35.

  The light reflectance of the belt member 35 and the mark M can be made different by appropriately selecting the material of the belt member 35 and the color of the ink for recording the mark M. It is preferable that the surface is subjected to surface treatment having a wavelength region in which reflection occurs with respect to the emission wavelength of the light emitting element. For example, when the wavelength of the light-emitting element is arbitrary, the surface reflects with respect to all wavelengths, and is visually white, specifically, the surface is white made of silicon or urethane. For example, “Belt type FNB-2E” manufactured by Habasit Japan Co., Ltd. can be used.

  In this case, the ink for recording the mark M on the surface of the belt member 35 may be any ink that absorbs the wavelength of the light emitting element since the surface of the belt member 35 is totally reflected. It is effective for any light emitting element. As another method, the surface may be subjected to surface treatment having a wavelength region in which irregular reflection occurs with respect to the emission wavelength of the light emitting element. As an example of this, the surface of the belt member 35 is preferably uneven, and for example, “belt type FNT-5P” manufactured by Habasit Japan Co., Ltd. can be used. The ink for recording the mark M in this case may be any ink as long as the surface roughness is substantially smooth and reflected by the ink, and in particular, magenta or cyan ink (viscosity 4 cp, surface tension 50 dyne). . As described above, since the light reflectance of the belt member 35 and the mark M is different, the mark detection unit 4 can easily recognize the presence of the mark M.

  Further, in order to ensure that the mark M is recorded on the surface of the belt member 35, the contact angle between the belt member 35 and the ink for recording the mark M is preferably less than 90 degrees. If the angle is less than 90 degrees, the ink on which the mark M has been recorded is fixed on the surface of the belt member 35, and no positional deviation or the like due to the movement of the belt member 35 occurs, and the mark detection means 4 can detect it at the correct position. . When the contact angle is 90 degrees or more, the ink on which the mark M is recorded moves randomly with the movement of the belt member 35 to cause positional displacement, and the mark detection means 4 performs accurate detection. Becomes difficult. Examples of the upper limit value of less than 90 degrees include a belt member 35 subjected to Teflon (registered trademark) processing or the like.

  In order for the contact angle between the belt member 35 and the ink for recording the mark M to be less than 90 degrees, at least the surface material of the belt member 35 should have the above contact angle with the ink. The surface of the belt member 35 may be subjected to hydrophilic treatment for improving wettability. For example, the contact angle with the ink may be adjusted to the above value by applying urethane or silicon processing.

  As shown in FIG. 1, a cleaning means 5 for erasing the mark M recorded on the surface of the belt member 35 is disposed on the opposite side (lower side in the figure) of the recording medium conveying means 3 to the recording head 1. Yes. The configuration of the cleaning unit 5 is not particularly limited as long as the mark M can be erased. Here, the cleaning unit 5 includes a cleaning roller 51 that is in contact with the belt member 35 and is driven by the movement of the belt member 35. A part of the cleaning roller 51 is immersed in the cleaning liquid 53 stored in the container 52. As a result, the mark M recorded on the surface of the belt member 35 is washed out and erased by the cleaning roller 51 to which the cleaning liquid 53 is attached. Accordingly, the mark M is erased from the surface of the belt member 35 on the downstream side of the cleaning means 5, and when the mark M moves to the lower side of the recording head 1, a new mark M is recorded at a predetermined timing. . By having this mark erasing function, the circumferential length of the belt member 35 needs to be a multiple of x (described later), which is a necessary transport distance of the fabric 2 that is a recording medium at the time of image recording by the recording medium transport means 3. Therefore, it is not necessary to control the circumferential length of the belt member 35 with high accuracy, and an inexpensive belt member can be used.

  Next, the control operation of the recording medium transport unit 3 in the image recording apparatus 100 will be described.

  FIG. 4 shows the process of the control operation when the mark M is recorded only on one side of the belt member 35 and is detected by one mark detecting means 4 as shown in FIG. Here, the recording head 1 is configured to perform one-time image recording by reciprocating across the width direction of the fabric 2 in a stopped state. During this one-time image recording, the recording is performed. The head 1 is configured to move from the left (initial position) in FIG. 2 to the right (reverse position), and then from the right to the left.

  First, when the belt member 35 is in a stopped state, a mark M is recorded on the surface of the belt member 35 by ejecting ink droplets from any predetermined nozzle of the recording head 1 (S1).

  Next, the recording head 1 records an image by reciprocating across the width direction of the fabric 2 placed on the belt member 35 in a stopped state (S2).

  After the reciprocating movement by the recording head 1, the motor 36 is driven to rotate the roller 31, the belt member 35 is conveyed along the sub-scanning direction at a predetermined speed, and the fabric 2 placed on the belt member 35 is moved. It is conveyed in the sub-scanning direction (S3).

  Due to the sub-scanning movement of the belt member 35, the mark M recorded on the belt member 35 in step S1 eventually passes through the detection range of the mark detection means 4 arranged on the downstream side of the recording head 1, and at this time The presence of the mark M is detected by the mark detection means 4 (S4).

  At the timing when the mark detection means 4 detects the presence of the mark M, the driving of the motor 36 is stopped and the conveyance of the belt member 35 is stopped (S5). Thereby, conveyance of the cloth 2 in the sub-scanning direction is stopped. That is, the movement amount (conveyance distance) of the belt member 35 is determined based on the position where the mark detection unit 4 detects the mark M.

  Next, the recording head 1 records an image by reciprocating across the width direction of the fabric 2 placed on the belt member 35 in a stopped state (S6).

  In the process of returning the recording head 1 to the initial position, the same predetermined timing as described above of the recording head 1 is applied to the surface of the belt member 35 in a stopped state at the timing when the recording head 1 reaches the surface of the belt member 35 beyond the side of the fabric 2. The mark M is recorded by ejecting ink droplets from the nozzles (S7).

  Further, after the reciprocating movement by the recording head 1, the motor 36 is driven to rotate the roller 31, the belt member 35 is conveyed at a predetermined speed along the sub-scanning direction, and the fabric placed on the belt member 35. 2 is conveyed in the sub-scanning direction (S8).

  Due to the sub-scanning movement of the belt member 35, the mark M recorded on the belt member 35 in step S7 eventually passes through the detection range of the mark detection means 4 arranged on the downstream side of the recording head 1, and at this time The presence of the mark M is detected by the mark detection means 4 (S9).

  At the timing when the mark detection means 4 detects the presence of the mark M, the drive of the motor 36 is stopped and the conveyance of the belt member 35 is stopped (S10). Thereby, conveyance of the cloth 2 in the sub-scanning direction is stopped.

  Thereafter, a desired image is recorded on the surface of the fabric 2 by repeating the same operation as described above according to the image data.

  In FIG. 5, as shown in FIG. 6, the marks M1 and M2 are recorded on both sides of the belt member 35 and detected by the mark detection means 4A and 4B arranged on both sides of the fabric 2, respectively. The process of operation is shown. Here, the recording head 1 is similar to the above in that the recording head 1 reciprocates across the width direction of the fabric 2 in a stopped state, but one image recording is performed for each forward and backward operation. In this mode, the fabric 2 is conveyed by a predetermined distance between the forward movement and the backward movement.

  First, when the belt member 35 is stopped, an ink droplet is ejected from one of the predetermined nozzles of the recording head 1 onto the one surface of the belt member 35 to record the mark M1 (S20).

  Next, the recording head 1 records an image by moving in one direction (forward movement) over the width direction of the fabric 2 placed on the belt member 35 in a stopped state (S21).

  After the forward movement by the recording head 1, the motor 36 is driven to rotate the roller 31, the belt member 35 is conveyed along the sub-scanning direction at a predetermined speed, and the fabric 2 placed on the belt member 35 is moved. It is conveyed in the sub-scanning direction (S22).

  Due to the sub-scanning movement of the belt member 35, the mark M1 recorded on the surface of the belt member 35 in step S20 eventually passes through the detection range of one mark detection means 4A arranged on the downstream side of the recording head 1. At this time, the presence of the mark M1 is detected by the mark detection means 4A (S23).

  At the timing when the mark detection means 4A detects the presence of the mark M1, the driving of the motor 36 is stopped and the conveyance of the belt member 35 is stopped (S24). Thereby, conveyance of the cloth 2 in the sub-scanning direction is stopped.

  The ink droplets are ejected from the predetermined nozzle of the recording head 1 onto the other surface of the belt member 35 before the image recording by the next backward operation is started when the belt member 35 is stopped. The mark M2 is recorded (S25).

  Next, the recording head 1 records an image by moving (reverse operation) in the opposite direction over the width direction of the fabric 2 placed on the belt member 35 in a stopped state (S26).

  Further, after the backward operation by the recording head 1, the motor 36 is driven to rotate the roller 31, the belt member 35 is conveyed at a predetermined speed along the sub-scanning direction, and the fabric placed on the belt member 35. 2 is conveyed in the sub-scanning direction (S27).

  Due to the sub-scanning movement of the belt member 35, the mark M2 recorded on the belt member 35 in the above step S25 eventually passes through the detection range of the other mark detection means 4B arranged on the downstream side of the recording head 1, At this time, the presence of the mark M2 is detected by the mark detection means 4B (S28).

  At the timing when the mark detection means 4B detects the presence of the mark M2, the driving of the motor 36 is stopped and the conveyance of the belt member 35 is stopped (S29). Thereby, conveyance of the cloth 2 in the sub-scanning direction is stopped.

  Thereafter, the process returns to step S20 and a desired image is recorded on the surface of the fabric 2 by repeating the same operation as described above according to the image data.

  According to the present invention, the mark M (M1, M2) is recorded on the surface of the belt member 35 that is outside the region of the cloth 2 that is the recording medium, and the belt 2 is conveyed, thereby causing the cloth 2 to be conveyed. Since the conveyance is stopped at the timing when the mark M (M1, M2) is detected and image recording is performed, the mark detection means 4 (4A, 4B) detects the mark M (M1, M2). Thus, only the time error that stops is required, and there is no need to improve mechanical accuracy such as roll diameter accuracy, and inexpensive and highly accurate conveyance can be performed. In particular, in the case of a large printer that outputs a wide print, such improvement in mechanical accuracy causes a significant increase in cost, and thus the present invention exhibits a particularly remarkable effect.

  Even if the belt member 35 makes one round in the above operation, only the mark M (M1, M2) newly recorded by the recording head 1 is erased because the mark M (M1, M2) is erased by the cleaning means 5. Is detected by the mark detection means 4 (4A, 4B), and the problem of erroneous detection does not occur.

  In the image recording apparatus 100 described above, the nozzle for recording the mark M (M1, M2) on the surface of the belt member 35 and the mark detection means 4 (4A) for detecting the mark M (M1, M2). 4B), the case where the fabric 2 is disposed so that the fabric 2 is equal to the transport distance x required at one time in the sub-scanning direction for image recording (x = y) has been described. It is also preferable to set the distance y between the mark recording nozzle and the mark detection means 4 (4A, 4B) such that x and y satisfy x> y.

  That is, as shown in FIG. 7, when the distance y between the mark recording nozzle and the mark detection means 4 (4A, 4B) is set such that x and y satisfy x> y, In the state where the mark detection means 4 (4A, 4B) detects the mark M (M1, M2) and the conveyance of the belt member 35 is stopped, the distance of xy with respect to the desired conveyance distance x of the fabric 2 is reduced. Run short. Since the distance x is known in advance, the control unit 6 uses the position where the mark M (M1, M2) is detected as a reference, and a drive signal corresponding to the shortage (xy) distance. To the motor 36, the roller 31 is rotationally controlled, and the belt member 35 is transported at a feeding speed reduced by the distance xy.

  The conveyance for the distance xy is controlled by the number of pulses applied to the motor 36 when a stepping motor is used as the motor 36. Although not shown, a rotary encoder may be arranged coaxially with the rotation axis of the roller 31 and controlled by the number of pulses when the rotary encoder is read.

  Controlling the conveyance of the belt member 35 in this way has the following effects. That is, in the case of x = y, in addition to the time error, the motor 36 is stopped immediately after detecting the mark M. Therefore, when the conveyance speed is high according to the law of inertia, the predetermined distance is exceeded and the conveyance is performed. There is an upper limit on speed. However, in the case of x> y, it is possible to eliminate the influence of inertia by increasing the conveyance speed at the distance of y and decreasing the speed by the distance of xy. That is, it is possible to obtain a high conveyance speed and a high-accuracy conveyance amount, and to overcome the conflicting problems of improving the printing speed and improving the image quality.

Schematic diagram of an image recording apparatus according to the present invention Partial plan view of an image recording apparatus according to the present invention Configuration block diagram of main parts of image recording device Process diagram showing an example of control operation when a mark is detected by the mark detection means Process diagram showing another example of control operation when mark is detected by mark detection means Partial plan view of another image recording apparatus A figure explaining other examples of control operation

Explanation of symbols

1: Recording head 2: Fabric (recording medium)
3: Recording medium conveying unit 31-34: Roller 35: Belt member 36: Motor 4, 4A, 4B: Mark detecting unit 5: Cleaning unit 51: Cleaning roller 52: Container 53: Cleaning liquid 6: Control unit 7: Image memory 8: Head driver

Claims (7)

Image recording means for recording an image by ejecting ink from nozzles onto a recording medium;
A recording medium conveying means having an annular belt member stretched over a roller for placing and conveying the recording medium;
Mark recording means for recording a predetermined mark using ink on the belt member;
Mark detection means for detecting a mark recorded on the belt member;
A conveyance control unit that determines a movement amount of the belt member in the recording medium conveyance unit with reference to a position where the mark detection unit detects the mark;
An image recording apparatus comprising: cleaning means for erasing the mark recorded on the belt member.   2. The image recording apparatus according to claim 1, wherein the image recording unit also serves as the mark recording unit.   The image recording apparatus according to claim 1, wherein the ink for recording the mark is at least one kind of ink selected from inks for image recording.   4. The image recording apparatus according to claim 1, wherein the mark detection means is means for detecting the mark with light, and at least the reflectance of the belt member is different from that of the mark.   The mark recording is performed such that a distance y between the mark recording unit and the mark detection unit satisfies x> y, where x is a required conveyance distance of the recording medium during image recording by the recording medium conveyance unit. And the mark detection means are arranged, and a distance corresponding to xy, which is a shortage with respect to the necessary conveyance distance x of the recording medium, is compensated by rotation control of the rollers of the recording medium conveyance means. The image recording apparatus according to claim 1.   The image recording apparatus according to claim 1, wherein the recording medium is a fabric.   The image recording apparatus according to claim 1, wherein a contact angle between the surface of the belt member and the ink for recording the mark is less than 90 degrees.

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