JP2024068419A - Printing device and edge detection device - Google Patents

Abstract

[Problem] To provide a printing device and an edge detection device capable of detecting the edge of a backing paper and the edge of a label using one transmission sensor. [Solution] The presence or absence of a backing paper P at the detection position of the transmission sensor 31 changes the amount of light received by the light receiving element 33 relative to the amount of light emitted by the light emitting element 32, so that the edge of the backing paper P can be detected from the change in the amount of received light. Also, the presence or absence of a label L at the detection position of the transmission sensor 31 changes the amount of light received by the light receiving element 33 relative to the amount of light emitted by the light emitting element 32, so that the edge of the label L can be detected from the change in the amount of received light. Since there is a difference between the transmittance of the backing paper P and the transmittance of the label L affixed to the backing paper P, when detecting the edge of the backing paper P, the light emitting element 32 is caused to emit light with a first light emission amount E1, and when detecting the edge of the label L, the light emitting element 32 is caused to emit light with a second light emission amount E2 different from the first light emission amount E1. [Selected Figure] Fig. 6

Description

The present invention relates to a printing device and an edge detection device.

A printer is known that prints images sequentially onto labels arranged in the longitudinal direction on a label paper backing while feeding out a long, rolled label paper.

In one example of this type of printer, in order to determine the print start position for each label, a transmission sensor outputs an electrical signal according to the amount of light that passes through the label paper, and a reflective sensor outputs an electrical signal according to the amount of light reflected by the label paper. The amount of light received by the transmission sensor changes depending on whether a backing paper is present or not, so the transmission sensor can detect the leading edge of the backing paper. The label paper used in this printer also has marks at fixed positions relative to the edge of each label in the transport direction (longitudinal direction of the backing paper). The amount of reflected light changes at the boundary of the marks, so the reflective sensor can detect the edge of the mark. The print start position for the first (leading) label is determined based on the leading edge of the backing paper, and the print start positions for the second and subsequent labels are determined based on the edge of the mark.

JP 2002-47641 A

However, the printer mentioned above requires two detection units: a transmissive sensor and a reflective sensor.

The object of the present invention is to provide a printing device and an edge detection device that can detect the edge of a backing sheet and the edge of a label using a single transmission sensor.

In order to achieve the above object, a printing device according to one aspect of the present invention includes a conveying section that conveys label paper, on which multiple labels are attached to a backing paper in a line in the conveying direction, along a conveying path in the conveying direction; a printing section that prints images on the labels; a transmission sensor including a light-emitting element and a light-receiving element that face each other across the conveying path and that receives light from the light-emitting element with the light-receiving element; and a control section, in which the control section causes the light-emitting element to emit light at a first light emission amount, and detects the edge of the backing paper from a change in the amount of light received by the light-receiving element while the label paper is being conveyed by the conveying section, and causes the light-emitting element to emit light at a second light emission amount different from the first light emission amount, and detects the edge of the label from a change in the amount of light received by the light-receiving element while the label paper is being conveyed by the conveying section.

According to this configuration, multiple labels are affixed to the label paper backing in a row. The label paper is transported along the transport path in the transport direction in which the labels are arranged. The light emitting element and light receiving element of the transmission sensor are arranged on one side and the other side of the transport path, respectively.

The presence or absence of a backing sheet on the optical path from the light-emitting element to the light-receiving element changes the amount of light received by the light-receiving element relative to the amount of light emitted by the light-emitting element, so the edge of the backing sheet can be detected from the change in the amount of light received. Also, the presence or absence of a label on the optical path from the light-emitting element to the light-receiving element changes the amount of light received by the light-receiving element relative to the amount of light emitted by the light-emitting element, so the edge of the label can be detected from the change in the amount of light received. Since there is a difference between the transmittance (degree of transparency) of the backing sheet and the transmittance of the label affixed to the backing sheet, by making the amount of light emitted by the light-emitting element different when detecting the edge of the backing sheet and when detecting the edge of the label, the edge of the backing sheet and the edge of the label can be detected well from the change in the amount of light received by the light-receiving element.

Therefore, a single transmission sensor can be used to detect both the edge of the backing paper and the edge of the label.

In addition, even if the backing paper does not have marks at specific positions for each label, the edges of the backing paper and each label can be detected, so a wide variety of label papers can be used with the printing device.

An edge detection device according to another aspect of the present invention includes a conveying section that conveys label paper, on which multiple labels are affixed to a backing paper in a line in the conveying direction, along a conveying path in the conveying direction; a transmission sensor including a light-emitting element and a light-receiving element that face each other across the conveying path and that receives light from the light-emitting element with the light-receiving element; and a control section, in which the control section causes the light-emitting element to emit light at a first light emission amount and detects the edge of the backing paper from a change in the amount of light received by the light-receiving element while the label paper is being conveyed by the conveying section, and causes the light-emitting element to emit light at a second light emission amount different from the first light emission amount and detects the edge of the label from a change in the amount of light received by the light-receiving element while the label paper is being conveyed by the conveying section.

This edge detection device can detect both the edge of the backing paper and the edge of the label using a single transmission sensor, just like the printing device described above.

According to the present invention, it is possible to detect both the edge of the backing paper and the edge of the label using a single transmission sensor.

1 is a cross-sectional view diagrammatically illustrating a configuration of a label printer according to an embodiment of the present invention. FIG. 2 is a block diagram showing a main part of the electrical configuration of the label printer. FIG. 4 is a diagram illustrating the flow of operations of the label printer. 13 is a diagram showing changes in the amount of light received when there is no difference in the amount of light received by the light receiving element between when a label paper backing is present at the detection position of the transmission sensor and when no label paper is present at the detection position. FIG. FIG. 4 is a diagram showing the relationship between the amount of light emitted and the amount of light received by a transmission type sensor. 13A and 13B are diagrams illustrating changes in the amount of light received when there is a difference in the amount of light received by the light receiving element between when a label paper backing is present at the detection position of the transmission sensor and when no label paper is present at the detection position.

The following describes in detail an embodiment of the present invention with reference to the attached drawings.

<Overall configuration of label printer>
1, a label printer 1 (an example of a printing device and an edge detection device) is a device that transports long label paper LP and sequentially prints images on labels L that are arranged in the longitudinal direction of the label paper LP on a backing P of the label paper LP. The label printer 1 has a housing 11 that forms an outer shell, and an outlet 12 for discharging the label paper LP is formed on the side of the housing 11.

The side where the discharge port 12 is formed is defined as the front side of the label printer 1, and the opposite side is defined as the rear side. The top and bottom of the label printer 1 are defined when the label printer 1 is placed on a horizontal surface, and the left and right of the label printer 1 are defined when the label printer 1 placed on the horizontal surface is viewed from the front side. The cross-sectional view shown in Figure 1 is a cross-section of the label printer 1 cut along a cutting plane extending in the front-to-rear direction, viewed from the right side.

The label paper LP is provided in the form of a roll, with the label L facing outwards, wound around a roll core. A roll holder 13 that holds the roll of label paper LP is provided inside the housing 11. The roll holder 13 has a cylindrical shape with a centre line extending in the left-right direction. The roll core of the label paper LP is fitted onto the roll holder 13 and fixed to the roll holder 13, thereby holding the roll of label paper LP in the roll holder 13.

A direction change guide 14 is provided inside the housing 11. The direction change guide 14 is located above and rearward of the roll holder 13 and behind the discharge port 12, and has an arc shape that bulges upward and rearward.

In addition, a transport path 15 is set between the discharge opening 12 and the direction change guide 14 inside the housing 11. The transport path 15 extends linearly from the front end of the direction change guide 14 toward the discharge opening 12.

A transport roller 21 (an example of a transport section) is provided at a position spaced forward from the direction change guide 14. The transport roller 21 is made up of a pair of a drive roller 22 and a driven roller 23. The drive roller 22 and the driven roller 23 are each rotatable about a rotation axis extending in the left-right direction, and their peripheral surfaces abut against each other with the transport path 15 in between. The drive roller 22 is disposed below the transport path 15, and the driven roller 23 is disposed above the transport path 15.

Between the discharge port 12 and the transport rollers 21, and in the vicinity of the discharge port 12, the discharge rollers 24 are provided. The discharge rollers 24 are made up of a pair of a drive roller 25 and a driven roller 26. The drive roller 25 and the driven roller 26 are each provided rotatably about a rotation axis extending in the left-right direction, and their peripheral surfaces abut against each other with the transport path 15 in between. The drive roller 25 is disposed below the transport path 15, and the driven roller 26 is disposed above the transport path 15.

The label paper LP is pulled from the roll held by the roll holder 13 toward the rear side of the direction change guide 14, and its direction is changed to the front side by aligning it with the direction change guide 14. Then, the leading end of the label paper LP is inserted from the rear side between the drive roller 22 and the driven roller 23 of the transport roller 21.

The drive roller 22 of the conveyor roller 21 and the drive roller 25 of the discharge roller 24 are connected to a transmission path for the rotational force generated by the forward rotation of the motor M (see FIG. 2). When the motor M rotates forward and the rotational force generated by the forward rotation is transmitted to the drive rollers 22 and 25, the drive rollers 22 and 25 rotate counterclockwise when viewed from the right side.

When the label paper LP is passed between the drive roller 22 and driven roller 23 of the transport roller 21 and the drive roller 22 rotates due to the forward rotation of the motor M, the label paper LP is transported along the transport path 15 in the transport direction from the transport roller 21 toward the discharge outlet 12 due to the reaction force of the frictional force generated at the contact point between the circumferential surface of the drive roller 22 and the label paper LP (backing paper P). The driven roller 23 rotates following the movement of the label paper LP.

When the label paper LP is not passed between the drive roller 25 and the driven roller 26 of the discharge roller 24, the driven roller 26 rotates following the rotation of the drive roller 25. When the drive roller 25 and the driven roller 26 are rotating and the leading edge of the label paper LP abuts against the circumferential surface of at least one of the drive roller 25 or the driven roller 26, the label paper LP is pulled between the drive roller 25 and the driven roller 26. The label paper LP then passes between the drive roller 25 and the driven roller 26 while receiving a reaction force of the frictional force generated at the contact point with the circumferential surface of the drive roller 25, and is discharged outside the housing 11 through the discharge port 12.

The roll holder 13 is also connected to a transmission path for the rotational force generated by the reverse rotation of the motor M. When the motor M is reversed and the rotational force generated by the reverse rotation is transmitted to the roll holder 13, the roll holder 13 rotates clockwise as viewed from the right side. As the roll of label paper LP rotates integrally with the roll holder 13, the label paper LP is rewound onto the roll and transported in the opposite direction to the transport direction. At this time, the transport rollers 21 and discharge rollers 24 are in a free rotating state and rotate in response to the movement of the label paper LP.

Between the transport roller 21 and the discharge roller 24, a head 27 (an example of a printing unit) and a CIS (Contact Image Sensor) unit 28 are provided.

The head 27 is disposed above the transport path 15. The head 27 is a line head whose position is fixed. On the underside of the head 27, multiple nozzles are arranged in the left-right direction over a length equivalent to the width of the label L (the length in the direction perpendicular to the transport direction). Specifically, on the underside of the head 27, multiple nozzles are arranged at intervals in the left-right direction to form nozzle rows, and the multiple nozzle rows are parallel in the front-back direction (transport direction), with the nozzles being shifted in the left-right direction between the nozzle rows. The head 27 selectively ejects liquid from the nozzles, and forms dots by depositing droplets on the label L, and prints an image made of dots on the label L.

The CIS unit 28 is disposed above the transport path 15 and in front of the head 27. The CIS unit 28 reads the image printed on the label L. The CIS unit 28 has a built-in light source, a rod lens array, and a linear image sensor. In the linear image sensor, multiple imaging elements (image sensors) are arranged in a row in the left-right direction, which is the main scanning direction. A line of light is irradiated from the light source onto the label L, and the light reflected by the label L enters the linear image sensor through the rod lens array, thereby reading one line of the image printed on the label L in the main scanning direction. Then, while the label L is transported, the image printed on the label L is read line by line, thereby achieving image reading by the CIS unit 28.

A transmission type sensor 31 (an example of a photoelectric sensor) is provided between the transport roller 21 and the head 27. The transmission type sensor 31 includes a light emitting element 32 (an example of a light emitting section) and a light receiving element 33 (an example of a light receiving section), and the light emitting element 32 and the light receiving element 33 are separated into upper and lower parts on either side of the transport path 15 and are arranged on a straight line intersecting the transport path 15. For example, the light emitting element 32 is arranged on the lower side of the transport path 15, and the light receiving element 33 is arranged on the upper side of the transport path 15. The light emitted from the light emitting element 32 passes through the transport path 15 and travels toward the light receiving element 33. The light from the light emitting element 32 is received by the light receiving element 33, and an electrical signal of a signal voltage corresponding to the amount of received light is output from the light receiving element 33 as a detection signal.

<Main parts of electrical configuration>
As shown in Fig. 2, the label printer 1 includes a controller 41 (an example of a control unit). The controller 41 is, for example, an ASIC (Application Specific Integrated Circuit) and includes a CPU (Central Processing Unit) 42 and a memory 43. The memory 43 includes a rewritable non-volatile memory such as a flash memory, and a volatile memory such as a DRAM (Dynamic Random Access Memory). The non-volatile memory stores programs executed by the CPU 42 and various data. The volatile memory is used as a work area when the CPU 42 executes a program.

The detection signal from the transmission sensor 31 is input to the controller 41.

An encoder 44 is also provided to the drive roller 22 of the transport roller 21, and an encoder signal, which is a pulse signal synchronized with the rotation of the drive roller 22, is input from the encoder 44 to the controller 41. The CPU 42 uses the volatile memory of the memory 43 as a step number counter, and counts the number of pulses of the encoder signal with the step number counter, and can determine the position of the label paper LP from the count number.

The label printer 1 is equipped with a communication interface 45 for communicating with an external terminal such as a PC (Personal Computer). The communication interface 45 may be configured for wired communication with the external terminal via a cable such as a USB (Universal Serial Bus) cable or a LAN (Local Area Network) cable, or may be configured for wireless communication via radio waves. The communication interface 45 is connected to the controller 41.

The controller 41 controls the operation of each part of the label printer 1, such as the head 27 and the motor M, based on signals and data input from the transmission sensor 31, the encoder 44, the communication interface 45, etc.

<Label printer operation>
Although not shown, a power switch for turning on and off the power of the label printer 1 is provided on the housing 11 of the label printer 1. When using the label printer 1, the user operates the power switch to turn on the power of the label printer 1, as shown in FIG.

The user also sets the label paper LP in the label printer 1. That is, the user fits the roll core of the label paper LP roll onto the roll holder 13, fixes the roll core to the roll holder 13, and then pulls the label paper LP from the roll to the rear side of the direction change guide 14. The user then pulls the label paper LP further from the rear side of the direction change guide 14 to the front side along the direction change guide 14. The user then inserts the leading end of the label paper LP from the rear side between the drive roller 22 and driven roller 23 of the transport roller 21, and positions the end of the label paper LP forward of the gap between the drive roller 22 and driven roller 23.

When the label paper LP is set, a tension initialization operation is performed. In the tension initialization operation, the controller 41 (CPU 42) drives the motor M to rotate in the forward direction by a fixed initial rotation amount (S11). The forward rotation of the initial rotation amount of the motor M moves the edge of the label paper LP by a predetermined amount in the conveying direction toward the discharge outlet 12 (hereinafter referred to as the "forward conveying direction"). The initial rotation amount is set so that the forward rotation of the initial rotation amount of the motor M causes the edge of the label paper LP (backing paper P) to reach the detection position of the transmission sensor 31, that is, the position of the optical path from the light emitting element 32 to the light receiving element 33 of the transmission sensor 31, regardless of the position of the edge of the label paper LP set by the user.

Then, the controller 41 reverses the motor M by a fixed, small amount of rotation (S12). By reversing the motor M by a small amount of rotation, the label paper LP is rewound onto the roll, and the end of the label paper LP moves by a fixed amount of rewinding in the direction opposite to the conveying direction (hereinafter referred to as the "reverse conveying direction").

After the motor M has reversed its rotation by the small amount, the controller 41 determines whether or not the end of the backing P of the label paper LP has been detected during the small amount of reversal of the motor M's rotation (S13).

When there is no label paper LP at the detection position of the transmission sensor 31 and light from the light-emitting element 32 of the transmission sensor 31 is not irradiated onto the backing P of the label paper LP, the amount of light received by the light-receiving element 33 becomes maximum, as shown in Figure 4.

When the label L of the label paper LP is not present at the detection position of the transmission sensor 31, but the backing P of the label paper LP is present at the detection position, if the amount of light emitted by the light-emitting element 32 is the same as when the label paper LP is not present at the detection position, the amount of light received by the light-receiving element 33 decreases from a maximum according to the transmittance of the backing P.

When a label L of the label paper LP is present at the detection position of the transmission sensor 31, even if the amount of light emitted by the light-emitting element 32 is the same as when the label paper LP is not present at the detection position, the amount of light from the light-emitting element 32 that passes through the label paper LP is drastically reduced, and the amount of light received by the light-receiving element 33 drops significantly from a maximum to a minimum.

Therefore, when the label paper LP is transported in the reverse transport direction from a state in which the edge of the backing paper P is located forward of the detection position of the transmission sensor 31, the controller 41 can determine that the edge of the backing paper P has been detected when the signal voltage of the detection signal of the transmission sensor 31 (the signal voltage according to the amount of light received by the light receiving element 33) drops to a preset threshold value for detecting the edge of the backing paper.

However, when the transmittance of the backing paper P is close to 1, depending on the setting of the light emission amount of the light-emitting element 32, even if the backing paper P reaches the detection position of the transmission sensor 31, the amount of decrease in the amount of light received by the light-receiving element 33 is small, and the signal voltage corresponding to the amount of light received does not decrease to the threshold value for detecting the end of the backing paper, so the end of the backing paper P cannot be detected. Therefore, when the label paper LP is transported in the reverse transport direction, the rear end (downstream end in the reverse transport direction) of the foremost (leading) label L that reaches the detection position of the transmission sensor 31 is erroneously detected as the end of the backing paper P. As a result, the label paper LP stops with the rear end of the foremost label L located at the home position that is almost the same as the detection position of the transmission sensor 31, and the end of the backing paper P not located at the home position.

Therefore, when the controller 41 detects the edge of the backing paper P, it causes the light-emitting element 32 of the transmission sensor 31 to emit light at the first light emission amount E1. As shown in FIG. 5, the first light emission amount E1 is the light emission amount of the light-emitting element 32 when the light-emitting element 32 is increased from a predetermined amount and the light-receiving element 33 receives a saturated amount of light in a state where the label paper LP (backing paper P) is not present at the detection position of the transmission sensor 31 (on the optical path from the light-emitting element 32 to the light-receiving element 33).

By making the light emitting element 32 emit light at the first light emission amount E1, as shown in FIG. 6, when the label paper LP is not present at the detection position of the transmission sensor 31, the amount of light received by the light receiving element 33 is maximum, and when the liner P is present at the detection position of the transmission sensor 31, the amount of light received by the light receiving element 33 is light reception amount R1. Therefore, when the label paper LP is transported in the reverse transport direction from a state in which the end of the liner P is located forward of the detection position of the transmission sensor 31, and the end of the liner P reaches the detection position of the transmission sensor 31, the signal voltage according to the amount of light received by the light receiving element 33 increases from the signal voltage according to the amount of light received R1, which is smaller than the liner end detection threshold, to the maximum. Therefore, the controller 41 can detect the end of the liner P.

When the controller 41 determines that the edge of the backing paper P has not been detected (S13: NO), it reverses the motor M by a small amount of rotation (S12) and determines whether or not the edge of the backing paper P has been detected during the small amount of reversal of the motor M (S13). As a result, the reversal of the small amount of rotation of the motor M is repeated until the controller 41 determines that the edge of the backing paper P has been detected during the small amount of reversal of the motor M.

When the controller 41 determines that the edge of the backing paper P has been detected during the small amount of rotation reversal of the motor M (S13: YES), it repeats the small amount of rotation reversal of the motor M until the edge of the backing paper P reaches a home position set downstream in the reverse conveying direction from the detection position of the transmission sensor 31. Then, the controller 41 ends the small amount of rotation reversal of the motor M at the timing when the edge of the backing paper P reaches the home position (S14).

In this way, the motor M is repeatedly rotated in the small amount until the controller 41 determines that the end of the backing paper P has been detected during the small amount of rotation of the motor M. When the controller 41 determines that the end of the backing paper P has been detected during the small amount of rotation of the motor M, the label paper LP is transported in the reverse transport direction until the end of the backing paper P reaches a home position set downstream in the reverse transport direction from the detection position of the transmission sensor 31. This causes the label paper LP to stop with its end located at the home position, and the label paper LP does not slip out from between the drive roller 22 and driven roller 23 of the transport roller 21 to the rear.

When printing (a print job) begins, for example, raster data of the image to be printed on each label L is input to the controller 41 from an external terminal via the communication interface 45 along with a print command. The raster data is data of a raster image, and is written to an image memory area set in the memory 43. When at least one page of raster data has been written to the memory 43, the printing operation of printing the image on the label L can be started. During the printing operation, the controller 41 rotates the motor M in the forward direction (S21) and controls the operation of the head 27.

In order to print an image on each label L with good positional accuracy, the controller 41 needs to know the position of the leading edge of each label L.

When printing an image on the label L, the controller 41 detects the leading edge of the label L from the detection signal of the transmission sensor 31.

When the label paper LP is transported in the forward transport direction from a state in which the backing P of the label paper LP is present at the detection position of the transmission sensor 31, and the leading edge of the label L reaches the detection position, the amount of light received by the light receiving element 33 decreases. Therefore, when the signal voltage of the detection signal of the transmission sensor 31 (signal voltage according to the amount of light received) decreases to a preset threshold value for detecting the label end, the controller 41 can determine that the leading edge of the label L has been detected.

However, when the light emitting element 32 of the transmission sensor 31 emits the first light emitting amount E1, as shown in FIG. 5, the amount of light received by the light receiving element 33 of the transmission sensor 31 drops from the amount of light received R1 to the amount of light received R2 in response to the leading edge of the label L reaching the detection position of the transmission sensor 31. For example, during tension initialization, the controller 41 reads the signal voltage corresponding to the amount of light received R1 when the backing paper P is present at the detection position of the transmission sensor 31 and the signal voltage corresponding to the amount of light received R2 when the label L is present at the detection position, and sets the label end detection threshold to the intermediate value of these signal voltages. If the amount of drop R1-R2 in the amount of light received by the light receiving element 33 is small, there is a risk that the signal voltage will not drop below the label end detection threshold even when the leading edge of the label L reaches the detection position due to the influence of the change in the signal voltage of the detection signal of the transmission sensor 31 and the attitude of the label paper LP, and the detection accuracy of the leading edge of the label L will decrease. The same applies when the user inputs a label edge detection threshold value corresponding to the label paper LP from an external terminal to the controller 41.

Therefore, during printing, the controller 41 causes the light-emitting element 32 of the transmission sensor 31 to emit light at the second light emission amount E2. The second light emission amount E2 is the amount of light emitted by the light-emitting element 32 when the amount of light received by the light-receiving element 33 becomes saturated by increasing the amount of light emitted by the light-emitting element 32 from a predetermined amount in a state where there is no label L but a backing paper P at the detection position of the transmission sensor 31 (on the optical path from the light-emitting element 32 to the light-receiving element 33), and is greater than the first light emission amount E1.

By making the light emitting element 32 emit light at the second light emission amount E2, when there is no label paper LP but a backing paper P at the detection position of the transmission sensor 31, the amount of light received by the light receiving element 33 is maximum, and when a label L is present at the detection position of the transmission sensor 31, the amount of light received by the light receiving element 33 is R3. Therefore, when the leading edge of the label L reaches the detection position of the transmission sensor 31, the amount of light received by the light receiving element 33 drops from maximum to R3, and the signal voltage according to the amount of light received becomes equal to or less than the label end detection threshold. Therefore, the controller 41 can determine that the leading edge of the label L has been detected when the signal voltage of the detection signal of the transmission sensor 31 drops to the label end detection threshold.

The controller 41 controls printing by the head 27 on the label L based on the detection of the leading edge of the label L that has reached the detection position of the transmission sensor 31. That is, the controller 41 sets the print start position on the label L to a position a certain distance away from the leading edge of the label L, determines the timing at which the print start position reaches the printing position of the head 27 from the current position of the leading edge of the label L, and causes the head 27 to start printing an image on the label L at that timing.

When all of the raster data input from the external terminal to the controller 41 has been printed on the label L, the controller 41 stops the motor M and stops the operation of the head 27. This ends the printing operation.

After the printing operation is completed, if the label printer 1 has an auto-cutting function that separates the portion of the label paper LP with the printed label L from the remaining portion, the label paper LP is cut by the auto-cutting function (S31: Cut). If the label printer 1 does not have an auto-cutting function, the user separates the portion of the label paper LP with the printed label L, and then inputs information that the label paper LP has been cut to the controller 41 from an external terminal or an operation panel (not shown) provided on the label printer 1.

Then, the controller 41 reverses the motor M (S32). The reverse rotation of the motor M transports the label paper LP in the reverse transport direction. While reversing the motor M, the controller 41 determines from the detection signal of the transmission sensor 31 whether or not the edge of the backing paper P of the label paper LP has been detected. At this time, the controller 41 causes the light-emitting element 32 of the transmission sensor 31 to emit light at the first light emission amount E1.

When the controller 41 determines that the end of the backing paper P has been detected while the motor M is rotating in the reverse direction, it continues to rotate the motor M in the reverse direction until the end of the backing paper P moves from the detection position of the transmission sensor 31 to the home position. The controller 41 then stops the motor M when the end of the backing paper P reaches the home position (S33). This causes the label paper LP to stop with its end located at the home position. Therefore, when new printing is performed with the label paper LP still set, it is possible to start conveying the label paper LP in the forward conveying direction from a state in which the end of the label paper LP is located at the home position without performing a tension initialization operation.

If the label printer 1 does not have an auto-cut function and the portion of the label paper LP with the printed label L is not cut off within a specified time from the end of the printing operation, the controller 41 reverses the motor M by a certain amount so that the print start position of the first label L among the labels L on which an image has not yet been printed is located at the print position of the head 27. This ensures that when new printing is performed with the label paper LP still set, printing starts from the first label L among the unprinted labels L, preventing an image from being printed on top of the printed label L.

<Action and effect>
As described above, multiple labels L are affixed in a row to the backing P of the label paper LP. The label paper LP is transported in the transport direction, which is the arrangement direction of the labels L, along the transport path 15. The light-emitting element 32 and the light-receiving element 33 of the transmission sensor 31 are arranged opposite each other with the transport path 15 in between.

Depending on the presence or absence of the backing paper P at the detection position of the transmission sensor 31 (on the optical path from the light emitting element 32 to the light receiving element 33), the amount of light received by the light receiving element 33 relative to the amount of light emitted by the light emitting element 32 changes, and the signal voltage of the detection signal of the transmission sensor 31 changes according to the change in the amount of received light, so that the end of the backing paper P can be detected from the change in signal voltage. Also, depending on the presence or absence of the label L at the detection position of the transmission sensor 31, the amount of light received by the light receiving element 33 relative to the amount of light emitted by the light emitting element 32 changes, and the signal voltage of the detection signal of the transmission sensor 31 changes according to the change in the amount of received light, so that the end of the label L can be detected from the change in signal voltage. Since there is a difference between the transmittance (light transmittance) of the mount P and the transmittance of the label L affixed to the mount P, when detecting the edge of the mount P, the light-emitting element 32 is caused to emit light at a first light emission amount E1, and when detecting the edge of the label L, the light-emitting element 32 is caused to emit light at a second light emission amount E2 different from the first light emission amount E1. This allows the controller 41 to properly detect the edge of the mount P and the edge of the label L from the change in signal voltage according to the change in the amount of light received by the light-receiving element 33.

In addition, even if the backing paper P does not have marks at fixed positions for each label L, the edges of the backing paper P and each label L can be detected, so a wide variety of label papers LP can be used with the printing device.

The first light emission amount E1 is set to a light emission amount smaller than the second light emission amount E2. Specifically, the first light emission amount E1 is set to the light emission amount of the light-emitting element 32 when the light-receiving element 33 receives a saturated light amount by increasing the light emission amount of the light-emitting element 32 from a predetermined amount in a state where the backing P is not present at the detection position of the transmission sensor 31. As a result, even if the transmittance of the backing P is close to 1, there is a large difference between the light-receiving amount when the backing P is not present at the detection position of the transmission sensor 31 and the light-receiving amount when the backing P is present at the detection position. Therefore, the controller 41 can accurately determine the presence or absence of the backing P on the optical path and accurately detect the edge of the backing P.

After the label paper LP is set in the label printer 1, a tension initialization operation is performed before printing on the label L begins, and the edge of the backing paper P is detected during the tension initialization operation. In the tension initialization operation, the label paper LP is transported a predetermined distance in the forward transport direction, and then the label paper LP is transported in the reverse transport direction. When the edge of the backing paper P is detected, transport of the label paper LP in the reverse transport direction is stopped at the timing when the edge of the backing paper P reaches the home position. This allows the edge of the label paper LP (backing paper P) to be positioned at the home position. Therefore, transport of the label paper LP can be started from a state in which the edge of the label paper LP is positioned at the home position, and printing of an image on the label L can be started.

During printing, the leading edge of each label L is detected while the label paper LP is transported in the forward transport direction. Therefore, based on the detection of the leading edge of the label L, the head 27 can be made to start printing an image on the label L at the timing when the print start position of the label L reaches the print position of the head 27.

<Modification>
Although one embodiment of the present invention has been described above, the present invention can be embodied in other forms.

For example, the head 27 is not limited to a configuration that prints images using an inkjet recording method, but may be a configuration that prints images using a thermal transfer method or a configuration that prints images using an electrophotographic method.

In the above embodiment, the label printer 1 was taken up. However, the present invention is not limited to the label printer 1, and may be applied to, for example, a device that reads an image printed on a label L to detect the edge of a backing sheet P and the edge of a label L.

In addition, various design modifications can be made to the above-mentioned configuration within the scope of the claims.

1: Label printer 15: Transport path 21: Transport roller 27: Head 31: Transmission sensor 32: Light emitting element 33: Light receiving element 41: Controller E1: First light emission amount E2: Second light emission amount L: Label LP: Label paper P: Backing paper

Claims (9)

a conveying section that conveys a label sheet, on which a plurality of labels are affixed to a backing sheet in a conveying direction, along a conveying path in the conveying direction;
a printing unit that prints an image on the label;
a transmission sensor including a light emitting element and a light receiving element facing each other across the transport path, the light from the light emitting element being received by the light receiving element;
A control unit,
The control unit is
causing the light emitting element to emit light at a first light emission amount, and detecting an edge of the backing paper from a change in the amount of light received by the light receiving element while the conveying unit is conveying the label paper;
a light-emitting element that emits light at a second light emission amount different from the first light emission amount, and detects an edge of the label from a change in the amount of light received by the light-receiving element while the label paper is being transported by the transport unit. 2. The printing device according to claim 1,
A printing device, wherein the first amount of light emitted is less than the second amount of light emitted. 3. The printing device according to claim 2,
A printing device in which the first light emission amount is the light emission amount of the light-emitting element when the light emission amount of the light-emitting element is increased from a predetermined amount and the light received by the light-receiving element becomes saturated when the backing paper is not present on the optical path from the light-emitting element to the light-receiving element. 4. The printing device according to claim 3,
The control unit of the printing device increases the light emission amount of the light-emitting element from a predetermined amount when the backing paper is not present on the optical path from the light-emitting element to the light-receiving element before the printing unit starts, and sets the light emission amount of the light-emitting element when the light received by the light-receiving element becomes saturated to the first light emission amount. The printing device according to any one of claims 1 to 4,
The control unit causes the light-emitting element to emit light at the first light emission amount before the printing unit starts printing, thereby detecting an edge of the mount. 6. The printing device according to claim 5,
The control unit is
causing the conveying unit to convey the label paper in one direction of the conveying direction, and causing the printing unit to print an image on the label;
a conveying unit that conveys the label paper a predetermined amount in one of the conveying directions before the printing unit starts printing, and then conveys the label paper in the other direction in the conveying direction while causing the light-emitting element to emit the first light emission amount to detect the end of the backing paper. The printing device according to any one of claims 1 to 4,
The control unit is
causing the conveying unit to convey the label paper in one direction of the conveying direction, and causing the printing unit to print an image on the label;
A printing device that detects an edge of the label by causing the light-emitting element to emit light at the second light emission amount during printing by the printing unit. The printing device according to any one of claims 1 to 4,
The control unit is
causing the conveying unit to convey the label paper in one direction of the conveying direction, and causing the printing unit to print an image on the label;
a conveying unit that conveys the label paper in the other direction in the conveying direction while causing the light-emitting element to emit light at the first light emission amount, thereby detecting an end of the backing paper. a conveying section that conveys a label sheet, on which a plurality of labels are affixed to a backing sheet in a conveying direction, along a conveying path in the conveying direction;
a transmission sensor including a light emitting element and a light receiving element facing each other across the transport path, the light from the light emitting element being received by the light receiving element;
A control unit,
The control unit is
causing the light emitting element to emit light at a first light emission amount, and detecting an edge of the backing paper from a change in the amount of light received by the light receiving element while the conveying unit is conveying the label paper;
an edge detection device that causes the light-emitting element to emit light at a second light emission amount different from the first light emission amount, and detects the edge of the label from a change in the amount of light received by the light-receiving element while the label paper is being transported by the transport unit.

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