Controls media tension during printing

Abstract

The present disclosure relates to a method for controlling the tension of media during printing. The media is tensioned by supporting an adjustment lever, which is coupled at a first end to a first adjustment arm that moves about a first pivot axis. The tension is provided by resisting a net torque acting on the first adjustment arm. The method includes applying a first setting force to the first adjustment arm to set the net torque acting on the first adjustment arm, and adjusting the first setting force to change the net torque acting on the first adjustment arm.

Description

Background Art

[0001] Some printers that pull media from an input roller, print onto it as it passes through a print station, and then pull it onto an output roller may use a dancer bar coupled to a pivotable arm to control the tension of the media during printing. The tension applied to the media during printing is determined by the net torque acting on the dancer arm, which the media resists as it advances through the printer. The media resists the net torque acting on the dancer arm by supporting it during printing, and thus, the provided tension ensures that the media rolls properly onto the output roller. BRIEF DESCRIPTION OF THE DRAWINGS

[0002] Examples of the present disclosure will be described with reference to the accompanying drawings, in which:

[0003] Figure 1 A side view of an exemplary printer showing control of media tension during printing;

[0004] Figure 2 Shown Figure 1 A side view of an exemplary adjuster in an exemplary printer;

[0005] Figure 3 Shown Figure 1 A perspective view of an exemplary printer;

[0006] Figure 4 Shown for Figure 1 a pair of exemplary adjustment mechanisms in an exemplary printer;

[0007] Figure 5 A flow chart illustrating an exemplary method of controlling tension in media during printing;

[0008] Figure 6 Shown for indication Figure 5 An example of a non-transitory machine-readable storage medium for a method of controlling tension of a medium during printing; and

[0009] Figure 7a and 7b Examples of media including fiducial marks are shown at different times during the printing process. DETAILED DESCRIPTION

[0010] Figure 1A side view of an exemplary printer 1 is shown for controlling the tension of media 8 during printing. Printer 1 includes an input shaft 2 that carries media 8 for printing and an output shaft 4 that collects media 8 once printed. Media 8 may be provided in a roll that is loaded onto or otherwise carried by input shaft 2. Once printed, media 8 can be pulled into a roll around output shaft 4 for subsequent removal.

[0011] The figure shows the path taken by media 8 through this example of printer 1. Media 8 is pulled from input shaft 2 in a clockwise direction (according to the view shown) by drive shaft 6, driven counterclockwise around drive shaft 6 and toward the front of printer 1 past print station 10, which includes the printer head and heat source, from print station 10 downward across the front of printer 1 toward adjustment rod 12, in a counterclockwise direction around adjustment rod 12, and finally pulled upward and in a clockwise direction around output shaft 4. Media 8 is also guided around a number of supports, such as support shaft 18 and support arms 20, which help control the movement of media 8 through printer 1.

[0012] In this example, the input shaft 2, drive shaft 6, adjustment arm 12, and output shaft 4 together control the movement of media 8 through the printer 1. The drive shaft 6 pulls the media 8 from the input shaft 2, and the input shaft 2 applies a braking force to the media 8 to control the tension of the media 8 between the input shaft 2 and the drive shaft 6. As the media 8 is pulled from the input shaft 2 (in this view, the media is pulled from the shaft in a counterclockwise direction), this braking force can be applied by a motor that acts to resist the rotation of the input shaft 2.

[0013] The media 8 passes from the drive shaft 6 through the print station 10, passes under the adjustment bar 12, and is coupled to the output shaft 4. The adjustment bar 12 is supported by the media 8 so that the adjustment bar 12 creates tension in the media 8 between the drive shaft 6 and the output shaft 4.

[0014] The adjustment lever 12 is coupled at a first end to a first adjustment arm 14, which is movable about a first pivot 16. Thus, the adjustment lever 12 can rotate about the first pivot 16 and exert a counterclockwise torque on the adjustment arm 14. As the media passes under the adjustment lever 12 and around and supports the adjustment lever 12, the counterclockwise torque acting on the adjustment arm 14 exerts a downward force on the media 8 and pulls the media from the drive shaft across the front of the printer 1.

[0015] During printing, if the output shaft 4 stops, or in other examples, draws in media 8 at a rate slower than the rate at which the input shaft 2 provides media 8, the length of media 8 between the drive shaft 6 and the output shaft 4 increases, and the adjustment rod 12 drops.

[0016] When the adjustment rod 12 reaches the lower threshold, the output shaft 4 is activated, or in other examples, the output shaft speed is increased, causing the rate at which it pulls the media 8 to increase. Upon activation, the output shaft 4 begins to rotate and pulls the media 8 upward and around the output shaft 4, thereby collecting the media 8 at a rate that exceeds the rate at which the media 8 is being supplied. In doing so, the length of the media 8 between the drive shaft 6 and the output shaft 4 decreases, and the adjustment rod 12 rises.

[0017] When the adjusting rod 12 reaches the upper threshold value, the output shaft 4 is deactivated or slowed down, and the adjusting rod 12 falls again. In this example, the rise and fall of the adjusting rod 12 is a cyclic process.

[0018] In this example, the adjustment arm 12 is detected as having reached a lower threshold and an upper threshold by a sensor, which is a contact sensor in this example, and the output shaft 4 can be activated by an on / off switch in response to the data received by the sensor. In other examples, the position of the adjustment arm can be detected by a different sensor. The sensor can include a proximity sensor, an optical sensor, an angle sensor, any other suitable sensor, or a combination of sensors for detecting or inferring the position of the adjustment arm 14.

[0019] The accuracy of printing on media 8 can depend on the alignment of media 8 and print station 10 during printing, which is facilitated by the tension on media 8 from the support lever. The amount of tension generated in the media by lever 12 depends on the net torque acting on lever arm 14, which is resisted by media 8. This net torque is the sum of the torques acting on the lever arm, excluding the torque caused by the tension in media 8. Therefore, this net torque depends on the weight of lever 12, the weight of lever arm 14, and any other forces acting on the lever arm and their respective distances from pivot 16. This net torque can also include torques applied directly to the pivot, such as braking or rotational forces applied by a motor.

[0020] In this example, the printer 1 includes a first adjuster 22. The first adjuster 22 allows for adjustment of the net torque acting on the first adjustment arm 14. Adjusting the tension in the media 8, for example by reducing the net torque acting on the adjustment arm 14, can be used to reduce or avoid deformation in the media 8 that may occur during printing. The first adjuster 22 can include any suitable device for varying the net torque acting on the first adjustment arm 14, such as a counterweight, a spring, a piston, a motor, a brake, a combination of these, or other elements.

[0021] During printing, uniform and / or non-uniform deformation of the media 8 may occur. Uniform deformation may be deformation in which the media is stretched such that the media increases in length by substantially the same amount along the length between the first and second ends of the adjustment rod 12 (in other words, across the width of the media 8). Non-uniform deformation may be deformation in which the media is stretched such that the media increases in length by different amounts along the length between the first and second ends of the adjustment rod 12. Such deformation may occur in the media during printing due to, for example, high temperatures used to cure the printing ink, moisture from the printing ink, and / or other factors.

[0022] In this example, the first adjuster 22 is coupled to the first adjustment arm 14 to apply a first setting force to the first adjustment arm 14 to set a net torque acting on the first adjustment arm 14. The first adjuster can adjust the first setting force to change the net torque acting on the first adjustment arm 14. Therefore, in one example, the first adjuster 22 can set the initial tension applied by the adjustment rod 12 to the media and change the tension during printing.

[0023] Figure 2 Shown Figure 1 16. A side view of an exemplary adjuster 122 in an exemplary printer of FIG. The exemplary first adjuster 122 shown includes a counterweight 24 that is movable relative to a first pivot 16. A first setting force is determined by an initial position of the counterweight 24 relative to the first pivot 16, and the first setting force is adjusted by moving the counterweight 24 relative to the first pivot 16. In this example, the counterweight 24 is coupled to a threaded rod 26, and in this example, the initial and subsequent positions of the counterweight 24 relative to the pivot 16 are controlled by a motor 30. The motor 30 of this example rotates the threaded rod 26 via gears. The counterweight 24 is not rotatable relative to the threaded rod 26 (e.g., due to a restrictive interaction between the counterweight 24 and the housing, as discussed below). Figure 5 ), and thus, rotation of the threaded rod 26 causes the counterweight 24 to move along the threaded rod 26. Although the movement of the counterweight 24 in this example is due to the action of the motor 30 and the threaded rod 28, in other examples, the counterweight 24 may be moved by other actuators, such as a piston, a transmission, or a linear motor.

[0024] The counterweight 24 in this example moves along an axis 26 that is oriented longitudinally through the center of the first adjustment arm 14 and the first pivot 16. In other examples, the axis may be oriented in any other suitable direction.

[0025] The first adjuster 122 in this example is located on the opposite side of the first pivot 16 from the adjustment rod 12. Therefore, the net torque acting on the adjustment arm 14 is less than the net torque that would act on the adjustment arm 14 without the adjuster 22 attached thereto. To reduce the net torque acting on the first adjustment arm 14, the counterweight 24 is moved in a direction away from the first pivot 16.

[0026] In other examples, the first adjuster may be located on the same side of the first pivot axis 16 as the adjustment lever 12. In this case, the net torque acting on the first adjustment arm 14 will be greater than the net torque that would otherwise act on the first adjustment arm without the adjuster 122 attached thereto. In such an example, moving the counterweight 24 in a direction away from the first pivot axis 16 will increase the net torque acting on the first adjustment arm 14.

[0027] In yet other examples, the adjuster 122 may extend across the first pivot axis 16 such that the net moment of the setting may be adjusted to be greater or less than the net moment acting on the adjustment arm 14 without the adjuster 122 attached thereto.

[0028] although Figure 2 The first adjuster 122 shown in FIG. 1 includes a counterweight 24 threaded onto a threaded rod 26, but the first adjuster 22 may include any mechanism that applies a first setting force to the first adjustment arm 14 to set a net torque acting on the first adjustment arm 14 and adjusts the first setting force to change the net torque acting on the first adjustment arm. Other exemplary adjusters may include a counterweight whose position is determined by a spring mechanism or a piston, or may include a motor coupled to the first pivot shaft that controls movement of the first adjustment arm.

[0029] Figure 3 Shows something like Figure 1 1 is a perspective view of an exemplary printer 101 of the printer 1, wherein like features are labeled with like reference numerals, but the medium 8 is not shown. The printer 101 is shown here to include a second adjustment arm 32, which is coupled to the adjustment lever 12 at a second end and is movable about a second pivot 34. In this example, the printer 101 includes a second adjuster 36 coupled to the second adjustment arm 32 to apply a second setting force to the second adjustment arm 32 to set a net moment acting on the second adjustment arm 32, and to adjust the second setting force to change the net moment acting on the second adjustment arm 32.

[0030] In this example, the second adjuster 36 is identical to the first adjuster 22, but in other examples, a different second adjuster may be provided. Providing first and second adjustment arms 14, 32 at each end of the adjustment rod 12 allows for greater support of the adjustment rod 12 and more efficient control of tension across the length of the adjustment rod 12 and, therefore, across the width of the media 8. Providing an adjuster for each of the adjustment arms 14, 32 allows for enhanced control across the length of the adjustment rod 12 and, therefore, across the width of the media 8.

[0031] The exemplary printer 101 includes sensors 15, 35 for detecting characteristics of the medium 8, such as its material, mass or deformation, and a controller 37 for adjusting the first and second setting forces. In this example, the controller 37 is integrated with the controller of the printer 101, but in other examples, the controller can be a separate controller within the printer, or it can be a separate external controller. This adjustment can make the corresponding net torques acting on the first and second adjustment arms equal. In some examples, the characteristics can be properties of the medium itself, properties of the printer (e.g., curing temperature), or properties of the ink. In this example, the sensors 15, 35 are located in an area near the adjustment rod 12, but in other examples, they can be in any suitable position.

[0032] In some examples, to detect uniform deformation in the media, printer 1 may print fiducial marks onto media 8. In some examples, a single fiducial mark having a known dimension (e.g., area, length, or width) may be printed. Once media 8 advances through printer 1, the dimension of the fiducial mark may be detected, and changes in that dimension may be measured.

[0033] If this dimension does not change, or if there is a change below a given threshold, this indicates that the media 8 is substantially undeformed, and therefore, the tension applied to the media 8 by the adjustment rod 12 can remain the same. In this case, the counterweight 24 does not move, and the first and second setting forces are maintained. However, a change in this dimension, or a change above a predetermined threshold, indicates that the media 8 has deformed.

[0034] As media 8 advances through printer 1, to reduce subsequent deformation of media 8, controller 37 instructs the counterweights 24 in both first and second adjusters 22, 36 to move relative to first and second pivots 16, 34 based on the detected changes, such that the net moments acting on first and second adjustment arms 14, 32 are the same. Consequently, the tension applied by adjustment rod 12 is uniformly adjusted along the length of adjustment rod 12 to correct for the detected deformation. In other examples, rather than measuring the change in the size of the fiducial mark, the expected detection time at a given vertical position can be known, and the actual arrival time can be measured. If there is a difference between the expected arrival time and the actual arrival time, or if the difference is above a given threshold, this indicates substantial deformation of the media. Controller 37 can then instruct the counterweights 24, as described above, to uniformly adjust the tension applied by adjustment rod 12 along its length.

[0035] In some examples, horizontally spaced fiducial marks are printed on the front or back of the media 8. In some examples, horizontally spaced fiducial marks are printed on opposite sides of the media, such as at or adjacent opposite edges of the media. The relative initial positions of the fiducial marks are known at the time of printing, and the relative positions of the fiducial marks are later detected by sensors 15, 35 once the media 8 moves through the printer 1.

[0036] A change in the relative position of the fiducial marks indicates non-uniform deformation of the medium 8 during printing, while no change in the relative position indicates that the tension applied by the adjustment rod 12 does not produce non-uniform deformation.

[0037] If a change in the relative position of the fiducial marker is detected, the controller 37 adjusts the first and / or second setting forces based on the difference between the known relative initial position of the fiducial marker and the detected relative position, thereby reducing non-uniform deformation. For example, the controller 37 may instruct the counterweight 24 in the first adjustment mechanism 22 to move a certain distance from the first pivot 16, and / or instruct the counterweight 24 in the second adjustment mechanism 22 to move a different distance from the second pivot 34. The degree to which the distances differ depends on the magnitude of the detected change. Thus, the tension applied by the adjustment rod 12 varies non-uniformly across the length of the adjustment rod 12, thereby reducing non-uniform deformation in the media 8.

[0038] In some examples, the time at which the fiducial mark is expected to be detected by the sensor may be known or determined, and the detected characteristic may be a difference between the expected detection time and the actual detection time that is above a threshold. If both fiducial marks are detected simultaneously, or earlier or later than expected, this indicates uniform deformation of the medium 8. In such a situation, the counterweights in both the first and second adjusters 22, 36 may be moved based on the detected difference, thereby adjusting the tension uniformly applied by the adjustment rod 12 across its length. This adjustment may cause the net torque acting on the first and second adjustment arms 14, 32 to be the same, or to change by the same amount.

[0039] If the difference between the expected detection time and the actual detection time of the two fiducial marks is different by more than a threshold, it may indicate non-uniform deformation of the media 8. In such a condition, based on the detected difference, the counterweights in either or both of the first and second adjustment mechanisms 22, 36 may then be moved different distances away from the first and second pivots 16, 34, respectively, thereby non-uniformly adjusting the tension applied by the adjustment rod 12 across its length.

[0040] Figure 4 A pair of exemplary first and second adjusters 22, 36 are shown. The first and second adjusters 22, 36 each include a movable counterweight 24. The movable counterweight 24 is coupled to a threaded rod 28 and is non-rotatable relative to the threaded rod 28, such that when the threaded rod 28 is rotated by a gear mechanism 40 operated by a motor 30, the counterweight 24 moves along the threaded rod 28. The threaded rod 28 passes through a housing 29, which forms part of a coupling mechanism 42 for releasably coupling the first and second adjustment mechanisms 22, 36 to the first and second adjustment arms 14, 32.

[0041] The housing 29 of this example is a flat U-shape, and the threaded rod 28 passes through the U-shape and is coupled to the housing at both ends so that the threaded rod 28 can rotate therein. One end of the threaded rod 28 is coupled to a gear mechanism 40, which is in turn coupled to a motor 30 for providing power thereto. The motor 30 can be coupled to a controller. The controller can instruct the motor 30 to rotate the gear mechanism 40, thereby rotating the threaded rod 28 so that the counterweight moves relative to the housing 29. The counterweight 24 is a rectangular prism, one face of which abuts the inner side of the U-shaped housing, thereby preventing the counterweight 24 from rotating relative to the housing. Since the counterweight 24 cannot rotate relative to the housing, the rotation of the threaded rod 28 causes the counterweight 24 to move along the threaded rod 28, and the direction of movement depends on the direction of rotation. Although the counterweight in this example is a rectangular prism, it can be any shape that interacts with the housing to limit its rotation.

[0042] The coupling mechanisms 42 are adapted so that they can be removably coupled to the first and second adjustment arms. The coupling mechanisms 42 have a recess 39 for positioning around the first or second pivot of the first or second adjustment arm 14, 32, respectively, and a hanger 41 for supporting the first and second arms 14, 32, respectively. Thus, the first and second adjustment mechanisms can be retrofitted to a printer by fitting the hanger 41 under and around the first and second adjustment arms 14, 32, and fitting the recess over the first and second pivots 16, 34. The motor 30 can then be communicatively coupled to a controller which in turn is coupled to a sensor for detecting deformation of the medium. The controller can be Figure 3 The controller 37 described in the embodiment of the present invention and the sensor may be Figure 3 Sensors 15, 35 described in.

[0043] Figure 5 An exemplary method of controlling the tension of media during printing is shown, where the media is tensioned by supporting an adjustment lever that is coupled at a first end to a first adjustment arm that moves about a first pivot and at a second end to a second adjustment arm that moves about a second pivot, with tension being provided by resisting a net moment acting on the first and second adjustment arms.

[0044] The method includes applying a first setting force 44 to a first adjustment arm to set a net torque acting on the first adjustment arm, and applying a second setting force 44 to a second adjustment arm to set a net torque acting on the second adjustment arm. The first and second setting forces can be applied by coupling movable counterweights to the first and second adjustment arms at desired distances from the first and second pivot axes, respectively. This can be done automatically in response to detected or input characteristics of the media or printer, or it can be done manually by a user. The first and second setting net torques can be equal, which allows the adjustment rod to apply uniform tension on the media, or the first and second setting net torques can be different. If each movable counterweight has an equal weight, the first and second setting net torques can be equalized by moving each counterweight to the same distance from the first and second pivot axes.

[0045] The method also includes printing 46 two reference marks, one on either side of the face of the medium. The reference marks can be printed at regular or irregular intervals throughout the printing process, and the position of each reference mark can be recorded. These reference marks can be of any shape, such as lines, dots, QR codes, or features of the printed medium itself. In other examples, the reference marks can be pre-printed on the medium. The method also includes detecting 48 the reference marks once they advance through the printer and measuring the change in the position of the reference marks. Either as an absolute position or relative to another mark, the change in the position of the reference mark from its expected position can indicate that deformation of the medium has occurred. The degree to which the position of the reference mark differs from the expected position is then used to calculate the expected change in net torque, and therefore, the change in tension applied by the adjustment arm, in order to reduce or avoid subsequent deformation.

[0046] The method further includes adjusting 50 the first and second setting forces to change the net moments acting on the first and second adjustment arms, respectively. The controller may calculate the desired first and second setting forces based on the change in length of the fiducial marker to correct or reduce the detected deformation and instruct the first and second adjusters accordingly. If the first and second adjusters include movable counterweights, the first and second setting forces may be adjusted by moving the counterweights relative to the first and second pivots, respectively.

[0047] Figure 6 An example of a non-transitory machine-readable storage medium 52 is shown. The non-transitory machine-readable storage medium 52 is encoded with instructions 54 that are executable by a processor to perform Figure 5 method.

[0048] Figure 7a An example of a medium 8 is shown that includes fiducial marks 60, 61 printed at predetermined locations. In this case, the fiducial marks 60, 61 are printed adjacent to opposite edges of the medium along a first axis 62 such that they are at the same longitudinal position on the medium 8. The relative positions of the fiducial marks are known, and their positions relative to the first axis are also known.

[0049] Figure 7b An example of media 8', fiducial marks 60', 61', and first axis 62' is shown after media 8 has moved through the printer. In this example, first axis 62' indicates the intended positions of fiducial marks 60', 61', and it can be seen that both fiducial marks 60, 61 have moved from their intended positions on first axis 62'. It is also apparent that the relative positions of the fiducial marks have changed, with fiducial mark 60' moving further away from axis 62' than fiducial mark 61'.

[0050] Deviations of the two marks from their expected positions may indicate a combination of uniform deformation of the media, and changes in their relative positions may indicate non-uniform deformation. In such a situation, a controller receiving sensor data indicating such deviations from the expected positions may change the net torque on the adjustment arms on each side of the adjustment rod to reduce the net torque and, thereby, attempt to reduce deformation. To reduce non-uniform deformation, the net torque acting on the adjustment arms on one side of the reference marks 60, 60' may be reduced more than the net torque acting on the adjustment arms on one side of the reference marks 61, 61'.

[0051] While deformation has been discussed based on comparing the position of a fiducial marker to an expected position or to other fiducial markers, deformation can be detected by directly detecting deviations in the dimensions of the fiducial marker itself, or by using an image sensor and analyzing a printed image. Any detected deformation can be used as a basis for adjusting the net torque on the adjustment arm.

Claims

1. A method for controlling the tension of a medium during printing, wherein the medium is tensioned by supporting an adjustment lever, wherein the adjustment lever is coupled at a first end to a first adjustment arm that moves about a first pivot and at a second end to a second adjustment arm that moves about a second pivot, wherein the tension is provided by resisting a net moment acting on the first adjustment arm and resisting a net moment acting on the second adjustment arm, the method comprising: applying a first setting force to the first adjustment arm to set the net moment acting on the first adjustment arm; adjusting the first setting force to change the net moment acting on the first adjustment arm; applying a second setting force to the second adjustment arm to set the net moment acting on the second adjustment arm; as well as adjusting the second setting force to change the net moment acting on the second adjustment arm, Wherein, the first setting force and the second setting force are automatically adjusted based on the characteristics of the medium.

2. The method according to claim 1, wherein The characteristic of the medium is detected, and the first setting force and the second setting force are adjusted so that the respective net moments acting on the first adjustment arm and the second adjustment arm are the same.

3. The method according to claim 2, wherein: Two horizontally spaced fiducial marks are printed on the media, and the first and second setting forces are adjusted based on a difference between a relative initial position of the fiducial marks and a relative position of the fiducial marks at a later time.

4. The method according to claim 1, wherein The first and second setting forces are applied by coupling movable counterweights to the first and second adjustment arms, respectively, and the first and second setting forces are adjusted by moving the counterweights relative to the first and second pivots, respectively.

5. A printer comprising: Adjustment lever; a first adjustment arm coupled to the adjustment rod at a first end and movable about a first pivot axis; a first adjuster coupled to the first adjustment arm to apply a first setting force to the first adjustment arm to set a net torque acting on the first adjustment arm, and to adjust the first setting force to change the net torque acting on the first adjustment arm; a second adjustment arm coupled to the adjustment rod at a second end and movable about a second pivot axis; a second adjuster coupled to the second adjustment arm to apply a second setting force to the second adjustment arm to set a net torque acting on the second adjustment arm, and to adjust the second setting force to change the net torque acting on the second adjustment arm; as well as A controller for adjusting the first setting force and the second setting force according to the method of any one of claims 1 to 4. The printer according to claim 5 , wherein: The first adjuster includes a movable counterweight, and the first setting force is adjusted by moving the counterweight relative to the first pivot.

7. The printer according to claim 6, wherein The movable counterweight is coupled to the threaded rod and is non-rotatable relative to the threaded rod such that when the threaded rod is rotated by a gear mechanism operated by a motor, the counterweight moves along the threaded rod.

8. The printer according to claim 5, wherein The printer includes a sensor for detecting a characteristic and a controller for adjusting the first setting force and the second setting force so that corresponding net moments acting on the first adjustment arm and the second adjustment arm are equal.

9. The printer according to claim 5, wherein The printer includes a sensor for detecting a relative difference between an initial relative position and a subsequent relative position of two horizontally spaced reference marks printed on the medium, and a controller for adjusting the first and second setting forces based on the relative difference.

10. The printer according to claim 9, wherein The first and second adjusters are removably coupled to the first and second adjustment arms, respectively.

11. A non-transitory machine-readable storage medium encoded with instructions executable by a processor to operate the printer according to any one of claims 5 to 10 in accordance with the method according to any one of claims 1 to 4.

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