JP2024068418A - Printing device and label tip sensing device - Google Patents

Abstract

To provide a printing device and a label tip sensing device which can satisfactorily sense that a tip of a first label has reached a sensing position.SOLUTION: A transmission-type sensor 31 makes a light-receiving element 33 receive light from a floodlighting element 32, and outputs a voltage sensing signal corresponding to an amount of the received light. When a label paper LP is conveyed, so that a tip of a mount P is exposed to light from the floodlighting element 32 passing on a conveyance path 15, the light from the floodlighting element 32 is reflected on a tip part of the mount P and diffused. This reduces the amount of received light by the light-receiving element 33, which causes reaching of the tip of the first label L to the sensing position of the transmission-type sensor 31 to be erroneously sensed, although actually the tip of the first label L has reached the sensing position, depending on the reduction amount of the light. Therefore, a slit 35 for adjusting diffusion of light at the tip part of the mount P is arranged between the conveyance path of the label paper LP and the light-receiving element 33.SELECTED DRAWING: Figure 6

Description

The present invention relates to a printing device and a label leading 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.

One example of this type of printer is equipped with a photoelectric sensor that detects the position of the leading edge of each label. In order to determine the print start position for each label, the output signal of the photoelectric sensor changes depending on whether or not a label is present at the detection position of the photoelectric sensor, so it is possible to detect from the output signal of the photoelectric sensor that the leading edge of each label has reached the detection position. Then, the print start position for each label can be determined based on the leading edge of each label.

Japanese Patent Application Laid-Open No. 11-240204

However, when label paper transport begins with the leading edge of the backing paper located upstream of the photoelectric sensor's detection position in the label paper transport direction, the leading edge of the first (leading) label may be detected as reaching the detection position of the photoelectric sensor before it actually does so.

The object of the present invention is to provide a printing device and a label leading edge detection device that can effectively detect when the leading edge of the first label has reached the detection position.

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 affixed to a mount 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 photoelectric sensor that is arranged facing the conveying path and has a light-emitting section that emits light and a light-receiving section that receives light and outputs a detection signal according to the amount of light received by the light-receiving section; and an optical system that adjusts the diffusion of light at the leading end of the mount.

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. A photoelectric sensor for detecting the leading edge of the label is disposed facing the transport path. The photoelectric sensor receives light from the light-emitting section at the light-receiving section and outputs an electrical signal at a level according to the amount of light received.

The transport of the label paper begins with the leading edge of the backing paper positioned upstream in the transport direction relative to the light path from the light projector, and when the leading edge of the backing paper approaches the light path, the light from the light projector is reflected and diffused by the leading edge of the backing paper. This causes a decrease in the amount of light received by the light receiver, and depending on the amount of this decrease or the threshold value set to detect that the leading edge of the label has reached the detection position, it is detected that the leading edge of the first label has reached the detection position before the leading edge of the first (first) label actually reaches the detection position of the photoelectric sensor.

Therefore, an optical system is provided that adjusts the diffusion of light at the leading edge of the backing paper. This makes it possible to reduce the discrepancy between the timing at which the leading edge of the first label is detected as having reached the detection position relative to the timing at which the leading edge of the first label actually reaches the detection position of the photoelectric sensor, and makes it possible to properly detect that the leading edge of the first label has reached the detection position. As a result, by controlling the start of printing on the first label based on the detection that the leading edge of the first label has reached the detection position, it is possible to reduce discrepancies in the printing position of the image on the first label.

In another aspect of the present invention, the label leading edge detection device includes a transport section that transports label paper, on which multiple labels are affixed to a backing paper and aligned in the transport direction, along a transport path in the transport direction; a photoelectric sensor that is arranged facing the transport path and has a light-emitting section that emits light and a light-receiving section that receives light, and outputs a detection signal according to the amount of light received by the light-receiving section; and an optical system that adjusts the diffusion of light at the leading edge of the backing paper.

As with the printing device described above, this label leading edge detection device can reduce the discrepancy between the timing at which the leading edge of the first label actually reaches the detection position of the photoelectric sensor and the timing at which it is detected that the leading edge of the first label has reached the detection position, making it possible to accurately detect that the leading edge of the first label has reached the detection position.

This invention makes it possible to effectively detect when the leading edge of the first label has reached the detection position.

1 is a cross-sectional view diagrammatically illustrating a configuration of a label printer according to an embodiment of the present invention. 11 is a diagram showing the relationship between a change in the relative position of the label and the light of the transmission sensor and a change in the signal voltage of the detection signal of the transmission sensor. FIG. FIG. 2 is a block diagram showing a main part of the electrical configuration of the label printer. 10 is a flowchart showing the flow of processing executed during printing. 13 is a diagram showing how the signal voltage of the detection signal of the transmission sensor drops below the threshold value when the leading edge of the label paper backing reaches the detection position of the transmission sensor. FIG. FIG. 13 is a diagram showing the change in signal voltage of the detection signal of a transmissive sensor (without slits and with slits) due to the leading edge of a label paper backing reaching the detection position of the transmissive sensor, and the ideal change in signal voltage when there is no diffusion of light at the leading edge of the backing. 13A and 13B are diagrams showing changes in the signal voltage of the detection signal of the transmission sensor when the leading edge of the backing paper of the label paper reaches the detection position of the transmission sensor in a configuration provided with a light diffusion sheet.

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 a label leading edge detection device) is a device that conveys 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 sensor 31 (an example of a photoelectric sensor) is provided between the transport roller 21 and the head 27. The transmission 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). 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 below the transport path 15, and the light-receiving element 33 is arranged above the transport path 15. 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 corresponding to the amount of light received is output from the light-receiving element 33 as a detection signal.

When the light from the light-emitting element 32 is not irradiated onto the backing P of the label paper LP, the amount of light received by the light-receiving element 33 is the greatest, and the signal voltage of the detection signal from the transmission sensor 31 is at its maximum. Also, if the backing P transmits light sufficiently, even if the light from the light-emitting element 32 is irradiated onto the backing P, the amount of light received by the light-receiving element 33 is close to its maximum, and the signal voltage of the detection signal is almost at its maximum.

When the label paper LP is transported in the transport direction on the transport path 15 and the label L comes into contact with the light from the light-emitting element 32, the amount of light received by the light-receiving element 33 decreases, and the signal voltage of the detection signal decreases. Specifically, as shown in FIG. 2, when the leading edge of the label L comes into contact with the light from the light-emitting element 32 to the light-receiving element 33, the amount of light received by the light-receiving element 33 begins to decrease, and the signal voltage of the detection signal begins to decrease. Then, when the label L blocks half of the light from the light-emitting element 32 to the light-receiving element 33, the signal voltage of the detection signal becomes an intermediate value between the maximum and minimum values, and when the label L blocks all of the light from the light-emitting element 32 to the light-receiving element 33, the signal voltage of the detection signal becomes a minimum value.

<Main parts of electrical configuration>
As shown in Fig. 3, 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.

<Printing process>
Before starting printing on the label printer 1, the user pulls out the label paper LP from the roll held in the roll holder 13 and inserts the leading edge of the label paper LP from the rear side between the drive roller 22 and the driven roller 23 of the transport roller 21.

When printing begins, for example, raster data of the image to be printed on each label L is input from an external terminal to the controller 41 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's worth of raster data has been written to the memory 43, the controller 41 begins controlling the head 27 and motor M for printing.

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 (CPU 42) detects that the leading edge of the label L has reached the detection position of the transmissive sensor 31 from the detection signal of the transmissive sensor 31 as shown in FIG. 4 (S1).

As described above, when the label paper LP is transported in the transport direction on the transport path 15 and the leading edge of the label L comes into contact with the light reaching from the light projecting element 32 to the light receiving element 33 of the transmission sensor 31, the signal voltage of the detection signal of the transmission sensor 31 begins to decrease, and when the label L blocks all of the light reaching from the light projecting element 32 to the light receiving element 33, the signal voltage of the detection signal reaches its minimum value. Therefore, when the signal voltage of the detection signal of the transmission sensor 31 decreases to a preset threshold value, it can be detected that the leading edge of the label L has reached the detection position of the transmission sensor 31.

However, if the leading edge of the backing P of the label paper LP comes into contact with the light from the light-emitting element 32 before the leading edge of the leading label L reaches the detection position, the light from the light-emitting element 32 is reflected and diffused by the leading edge of the backing P. In a configuration in which all of the light traveling straight through the transport path 15 is received by the light-receiving element 33, when the light from the light-emitting element 32 is diffused by the leading edge of the backing P, the amount of light received by the light-receiving element 33 decreases, and the signal voltage of the detection signal from the transmission sensor 31 decreases.

Therefore, depending on the threshold setting, as shown in FIG. 5, the signal voltage that is reduced due to the diffusion of light at the leading edge of the backing paper P may fall below the threshold. In addition, the degree of light diffusion at the leading edge of the backing paper P changes depending on the glossiness of the backing paper P, which changes the amount of reduction in the amount of light received by the light receiving element 33, so it is possible that the signal voltage may fall below the threshold. When the signal voltage falls below the threshold, the controller 41 erroneously detects that the leading edge of the backing paper P has reached the detection position of the transmission sensor 31 as if the leading edge of the label L has reached the detection position.

When the controller 41 detects that the signal voltage of the detection signal of the transmission sensor 31 has dropped to the threshold value and that the tip of the label L has reached the detection position of the transmission sensor 31 (S1: YES), it sets a judgment distance to determine whether the detection is valid or invalid (S2).

The judgment distance is set based on the pitch at which the labels L are arranged (label pitch) and the magnitude of the detection-printing position distance between the detection position of the transmission sensor 31 and the printing position of the head 27. The printing position of the head 27 is, for example, the position at which dots are formed by the nozzles arranged at the most upstream (rearmost) of the head 27 in the transport direction.

While the label L passes the detection position of the transmission sensor 31, the leading edge of the label L is detected to have reached the detection position of the transmission sensor 31 once. Therefore, if the label pitch is less than the distance between the detection and printing positions, the controller 41 sets the label pitch as the judgment distance.

On the other hand, if the label pitch is greater than the distance between the detection and printing positions, while the label paper LP is being transported a distance equal to the label pitch, the leading edge of the label L that has passed the detection position of the transmission sensor 31 will exceed the printing position of the head 27, making it impossible to print an image on that label L. Therefore, when the label pitch is greater than the distance between the detection and printing positions, the controller 41 sets the distance between the detection and printing positions as the judgment distance.

The detection-to-printing position distance between the detection position of the transmission sensor 31 and the printing position of the head 27 is a known value and is stored in the memory 43 of the controller 41. Also, since the label pitch differs depending on the type of label paper LP, the label pitch of the label paper LP used in the label printer 1 is input in advance to the controller 41 from an external terminal via the communication interface 45, for example.

Then, the controller 41 judges whether or not it has again detected that the leading edge of the label L has reached the detection position of the transmission sensor 31 (S3). If it has not detected the leading edge of the label L again at the detection position (S3: NO), the controller 41 judges whether or not the label paper LP has been transported a judgment distance (S4).

If the controller 41 determines that the label paper LP has been transported the determination distance without re-detecting the leading edge of the label L to the detection position (S4: YES), it determines that the arrival detection when the determination distance was set (detection that the leading edge of the label L has reached the detection position of the transmission sensor 31) is valid (S5).

On the other hand, if the controller 41 again detects that the leading edge of the label L has reached the detection position of the transmission sensor 31 while the label paper LP is being transported the determination distance (S3: YES), it invalidates the arrival detection when the determination distance was set and determines that the redetection is valid (S6).

The controller 41 controls printing on the label L by the head 27 based on the detection that is determined to be valid (S7).

To achieve this control, the controller 41 determines the position of the leading edge of the label L based on the detection that is determined to be valid. The controller 41 also sets the printing start position on the label L.

When the leading edge of the backing paper P comes into contact with the light traveling straight from the light-projecting element 32 of the transmission sensor 31, the light is diffused, and the signal voltage of the detection signal of the transmission sensor 31 drops. After that, when the leading edge of the backing paper P passes through the light traveling straight from the light-projecting element 32, the light diffusion stops, and the amount of light received by the light-receiving element 33 increases. However, if the leading edge of the label L comes into contact with the light traveling straight from the light-projecting element 32 before the leading edge of the backing paper P passes through the light, the amount of light received by the light-receiving element 33 drops due to light blocking by the label L. Therefore, before the leading edge of the label L actually reaches the detection position of the transmission sensor 31, the signal voltage drops below the threshold, and the controller 41 detects the arrival of the leading edge. As a result, a deviation occurs in the position of the leading edge of the label L determined by the controller 41, compared to an ideal case where there is no light diffusion at the leading edge of the backing paper P.

As shown in FIG. 6, a slit plate 34 (an example of an aperture) is provided between the transport path 15 and the light receiving element 33. The slit plate 34 has a slit 35 formed therein for reducing the diameter (front-rear width) of the light received by the light receiving element 33. The slit 35 has a slit length in the left-right direction that is longer than the diameter of the light (light passing through the transport path 15) emitted by the light projecting element 32, and a slit width in the front-rear direction that is shorter than the diameter of the light emitted by the light projecting element 32.

Because the slit plate 34 is provided, even if the leading edge of the backing paper P is exposed to the light from the light-emitting element 32 passing through the transport path 15 and the light from the light-emitting element 32 begins to diffuse at the leading edge of the backing paper P, the amount of light received by the light-receiving element 33 is not affected by the diffusion of light at the leading edge of the backing paper P until the leading edge of the backing paper P is exposed to the light traveling straight from the light-emitting element 32 through the slit 35 to the light-receiving element 33. However, when the leading edge of the backing paper P is exposed to the light traveling straight from the light-emitting element 32 through the slit 35, the light is diffused and the signal voltage of the detection signal of the transmission sensor 31 decreases. After that, when the leading edge of the backing paper P passes through the light passing through the slit 35, the diffusion of light ceases, so the amount of light received by the light-receiving element 33 increases, but when the leading edge of the label L is exposed to the light, the amount of light received by the light-receiving element 33 decreases due to the light blocking by the label L. Therefore, the controller 41 detects the leading edge of the label L before it actually reaches the detection position of the transmission sensor 31. As a result, compared to an ideal case where there is no diffusion of light at the leading edge of the mount P, the amount of deviation is smaller than in a configuration where the slit plate 34 is not provided, but there is still a deviation in the position of the leading edge of the label L as determined by the controller 41.

The amount of deviation depends on the diameter of the light received by the light receiving element 33 (the width of the slit 35). The controller 41 sets an offset distance according to the diameter of the light received by the light receiving element 33, i.e., sets an offset distance equal to the amount of deviation, and for the first label L at the top, sets the print start position to a position that is a fixed distance plus the offset distance from the leading edge of the label L. For the second label L, the controller 41 sets the print start position to a fixed distance from the leading edge of the label L.

Then, based on the position of the leading edge of the label L, the controller 41 determines the timing at which the print start position on the label L reaches the print position of the head 27, and causes the head 27 to start printing an image on the label L at that timing.

<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. A transmission sensor 31 for detecting the leading edge of the label L is disposed facing the transport path 15. The transmission sensor 31 receives light from a light-emitting element 32 with a light-receiving element 33, and outputs a detection signal with a voltage corresponding to the amount of light received.

When the label paper LP is transported and the leading edge of the backing paper P comes into contact with the light from the light-emitting element 32 passing through the transport path 15, the light from the light-emitting element 32 is reflected and diffused by the leading edge of the backing paper P. As a result, the amount of light received by the light-receiving element 33 decreases, and before the leading edge of the label L actually reaches the detection position of the transmission sensor 31, the signal voltage of the detection signal of the transmission sensor 31 falls below the threshold value, and the controller 41 detects that the leading edge of the first (leading) label L has reached the detection position.

Therefore, as an example of an optical system that adjusts the diffusion of light at the tip of the mount P, a slit plate 34 having a slit 35 is provided. Even if the tip of the mount P comes into contact with the light from the light-emitting element 32 passing through the transport path 15 and the light from the light-emitting element 32 begins to be reflected and diffused at the tip of the mount P, the amount of light received by the light-receiving element 33 is not affected by the diffusion of light at the tip of the mount P until the tip of the mount P comes into contact with the light traveling straight from the light-emitting element 32 through the slit 35 to the light-receiving element 33. And, since the diameter (width in the front-rear direction) of the light traveling straight through the slit 35 to the light-receiving element 33 is small, the tip of the mount P quickly passes through the light. Therefore, by providing the slit plate 34, the time required for the tip of the mount P to pass through the light received by the light-receiving element 33 is shorter than in a configuration in which the slit plate 34 is not provided.

When the leading edge of the backing paper P passes through the light received by the light receiving element 33, the diffusion of light ceases and the amount of light received by the light receiving element 33 increases. If the time required for the leading edge of the backing paper P to pass through the light received by the light receiving element 33 is short, the leading edge of the backing paper P can be made to pass through the light before the leading edge of the label L comes into contact with the light received by the light receiving element 33. This makes it possible to delay the timing at which the amount of light received by the light receiving element 33 decreases due to light blocking by the label L compared to a configuration in which the slit plate 34 is not provided, and makes it possible to bring the timing at which the leading edge of the first label is detected as having reached the detection position of the transmission sensor 31 closer to the timing at which the leading edge of the first label actually reaches the detection position.

As a result, it is possible to accurately detect that the leading edge of the first label L has reached the detection position, and based on the detection that the leading edge of the first label L has reached the detection position, the start of printing on the first label L is controlled, thereby reducing the amount of deviation in the printing position of the image on the first label L.

In addition, an offset distance is set according to the diameter of the light received by the light receiving element 33, and for the first label L at the top, a position that is a fixed distance plus the offset distance from the tip of the label L is set as the print start position. For the second label L, a position that is a fixed distance from the tip of the label L is set as the print start position. This allows the print start position for each label L to be set at a fixed position relative to the tip of the label L, allowing images to be printed on each label L with good positional precision.

Furthermore, when it is detected that the leading edge of the label L has reached the detection position of the transmission sensor 31, a judgment distance is set to determine whether the detection is valid or invalid. If the leading edge of the label L is detected again while the label paper LP is transported the judgment distance from the time when the judgment distance was set, the previous detection is invalidated and the subsequent redetection is valid. On the other hand, if the leading edge of the label L is not detected again while the label paper LP is transported the judgment distance from the time when the judgment distance was set, the detection at the time when the judgment distance was set is valid. Then, based on the detection that is determined to be valid, the printing on the label L by the head 27 is controlled. This makes it possible to further suppress the erroneous detection that the leading edge of the backing paper P has reached the detection position as the leading edge of the first label L having reached the detection position, and to more effectively detect that the leading edge of the first label L has reached the detection position.

The judgment distance is set to the label pitch or the distance between the detection and printing positions.

While the label L passes the detection position of the transmission sensor 31, the leading edge of the label L is detected to have reached the detection position of the transmission sensor 31 once. Therefore, by setting the judgment distance to the label pitch, it is possible to prevent the leading edge of the next label L from being detected to have reached the detection position while the label paper LP is transported the judgment distance after the leading edge of the label L is detected to have reached the detection position.

However, if the label pitch is greater than the distance between the detection and printing positions, while the label paper LP is being transported a distance equal to the label pitch, the leading edge of the label L that has passed the detection position of the transmission sensor 31 will exceed the printing position of the head 27, making it impossible to print an image on the label L. This inconvenience can be avoided by setting the distance between the detection and printing positions as the judgment distance when the label pitch is greater than the distance between the detection and printing positions.

<Other embodiments>
Instead of the slit plate 34, as shown in Fig. 7, a light diffusion sheet 36 that diffuses the light from the light projecting element 32 may be provided between the transport path 15 and the light projecting element 32 of the transmission sensor 31. The light from the light projecting element 32 passes through the light diffusion sheet 36, so that the light intensity distribution becomes more uniform. As a result, it is possible to prevent a large decrease in the amount of light received by the light receiving element 33 when the leading edge of the backing paper P approaches the optical path from the light projecting element 32. Therefore, as in the configuration in which the slit plate 34 is provided, it is possible to prevent the leading edge of the backing paper P from reaching the detection position from being erroneously detected as the leading edge of the first label L reaching the detection position, and it is possible to properly detect that the leading edge of the first label L has reached the detection position.

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

For example, in the above embodiment, a configuration was described in which a transmission sensor 31 was provided and it was detected that the leading edge of the label L had reached the detection position of the transmission sensor 31. However, a reflective sensor may be provided above the transport path 15 and it may be detected that the leading edge of the label L has reached the detection position of the reflective sensor.

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, for example, to a device that reads an image printed on a label L to detect the leading edge of the 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 34: Slit plate 35: Slit 36: Light diffusion sheet 41: Controller L: Label LP: Label paper P: Backing paper

Claims (12)

a conveying section that conveys a label sheet, on which a plurality of labels are arranged in a conveying direction on a backing sheet, along a conveying path in the conveying direction;
a printing unit that prints an image on the label;
a photoelectric sensor that is disposed facing the transport path, has a light projecting unit that emits light and a light receiving unit that receives light, and outputs a detection signal according to an amount of light received by the light receiving unit;
and an optical system that adjusts the diffusion of light at the leading end of the mount. 2. The printing device according to claim 1,
A printing apparatus, wherein the optical system is a diaphragm that reduces a light diameter. 2. The printing device according to claim 1,
A printing device, wherein the optical system is a light diffusion sheet that diffuses the light from the light projecting unit. The printing device according to any one of claims 1 to 3,
A control unit,
The control unit is
Detecting that the leading edge of the label has reached a detection position of the photoelectric sensor from a detection signal of the photoelectric sensor;
The printing device controls printing on the label by the printing unit based on the detection of the arrival at the detection position. 5. The printing device according to claim 4,
The control unit is
For the first label, a print start position is determined to be a position that is a fixed distance from the leading edge of the label plus an offset distance according to the diameter of the light received by the light receiving unit;
For the second and subsequent labels, a position that is the fixed distance from the leading edge of the label is determined as a print start position. 5. The printing device according to claim 4,
The control unit is
a determination distance is set for determining whether the detection is valid or invalid at the time when the arrival of the leading edge of the label is detected;
if the arrival of the leading edge of the label is detected again while the medium is being transported the determination distance by the transport unit from the time when the determination distance was set, the previous detection is determined to be invalid and the subsequent redetection is determined to be valid;
if the arrival of the leading edge of the label is not detected again during the time period from when the determination distance is set until the medium is conveyed by the conveying unit over the determination distance, the detection at the time when the determination distance was set is determined to be valid;
The printing device controls printing on the label by the printing unit based on the detection determined to be valid. 7. The printing device according to claim 6,
The labels are provided at a constant label pitch in the transport direction,
The control unit sets the determination distance to the label pitch. 7. The printing device according to claim 6,
the printing unit is disposed downstream of the photoelectric sensor in the transport direction,
The control unit sets the determination distance to be equal to or less than a detection-printing position distance between a detection position by the photoelectric sensor and a printing position by the printing unit. 7. The printing device according to claim 6,
The labels are set at a constant label pitch in the conveying direction,
the printing unit is disposed downstream of the photoelectric sensor in the transport direction,
When the label pitch is less than a detection-printing position distance between a detection position by the photoelectric sensor and a printing position by the printing unit, the control unit sets the determination distance to the label pitch. 10. The printing device according to claim 9,
When the label pitch is greater than the distance between the detection and printing positions, the control unit sets the determination distance to the distance between the detection and printing positions. 2. The printing device according to claim 1,
The photoelectric sensor is a transmission type sensor in which the light emitting section and the light receiving section are arranged on a straight line with the transport path in between. a conveying section that conveys a label sheet, on which a plurality of labels are arranged in a conveying direction on a backing sheet, along a conveying path in the conveying direction;
a photoelectric sensor that is disposed facing the transport path, has a light projecting unit that emits light and a light receiving unit that receives light, and outputs a detection signal according to an amount of light received by the light receiving unit;
and an optical system that adjusts the diffusion of light at the leading end of the backing paper.

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