Patent Description:
Conventionally, a printer that performs printing on a label has been known. For example, in a printer that performs printing on a base sheet on which a plurality of labels are attached at predetermined intervals, the wound base sheet is fed out to a print head such as a thermal head, thereby performing printing on the surface of the label.

Further, in a printer including a mechanism for peeling a printed label from a base sheet, a winding shaft is rotated by a drive source such as a motor, and the base sheet from which the label has been peeled is wound up by the winding shaft. Further, in such a printer, when the printing of the label is completed, a back feed is performed to convey the base sheet in a direction opposite to that at the time of printing so that the next label is returned to the print start position of the print head.

When the back feed is performed, the base sheet wound around the winding shaft is pulled out from the winding shaft while resisting the load caused by a non-exciting torque or the like of the drive source. Therefore, when the back feed is performed, slippage is likely to occur in the conveyance of the base sheet due to the influence of the load, and there is a possibility that the conveyance cannot be accurately performed.

<CIT> describes a label printer that comprises a printing head to implement the printing on a label of a label paper, a feed rotating body to move the label paper during the printing to pass the label through a printing head, a first motor to rotate the rotating body, a peeling body to peel the printed label from the mount, a winding rotating body to move and wind the mount with the label peeled therefrom, a second motor to rotate the rotating body, and a control circuit to control the second motor to rotate the winding rotating body and wind the mount by the torque required for peeling the label from the mount while the label paper is started by starting the rotation of the feed rotating body, the label is started to peel from the mount by the peeling body and moved for a specified distance.

Embodiments of the present invention provide a printer capable of performing a back feed with high accuracy.

In one embodiment, a printer for printing on a label sheet including a plurality of detachable labels, includes a platen roller configured to convey the label sheet, a first motor configured to rotate the platen roller, a print head facing the platen roller and configured to print on a label of the label sheet, a discharge port through which the printed label is discharged and detached, a winding roller for winding the label sheet from which the printed label has been detached, a second motor configured to rotate the winding roller, a drive train by which a rotational force can be transmitted from the second motor to the winding roller, and a processor. The processor is configured to control the first and second motors to rotate in a first direction to convey the label sheet in a forward direction along a conveyance path and control the print head to print on a first label of the label sheet, and after the printed first label is discharged, control the first and second motors to rotate in a second direction that is opposite to the first direction. The drive train disengages the winding roller from the second motor when the second motor is controlled to rotate in the second direction.

According to a first aspect of the invention, it is provided a printer for printing on a label sheet including a plurality of detachable labels, comprising a platen roller configured to convey the label sheet; a first motor configured to rotate the platen roller; a print head facing the platen roller and configured to print on a label of the label sheet; a discharge port through which the printed label is discharged and detached; a winding roller for winding the label sheet from which the printed label has been detached; a second motor configured to rotate the winding roller; a drive train by which a rotational force can be transmitted from the second motor to the winding roller; and a processor configured to control the first and second motors to rotate in a first direction to convey the label sheet in a forward direction along a conveyance path and control the print head to print on a first label of the label sheet, and after the printed first label is discharged, control the first and second motors to rotate in a second direction that is opposite to the first direction, wherein the drive train disengages the winding roller from the second motor when the second motor is controlled to rotate in the second direction.

Optionally, in the printer according to the first aspect of the invention, the drive train includes a one-way clutch by which the rotation force is transmitted from the second motor to the winding roller when the second motor is controlled to rotate in the first direction.

Optionally, in the printer according to the first aspect of the invention, the one-way clutch disengages the winding roller from the second motor when the second motor is controlled to rotate in the second direction.

Optionally, in the printer according to the first aspect of the invention, the drive train further includes a first gear that is connected to the second motor and a second gear that meshes with the first gear and rotates around a shaft to which the one-way clutch is connected to.

Optionally, in the printer according to the first aspect of the invention, the drive train further includes a third gear that is connected to the shaft via the one-way clutch and a fourth gear that meshes with the third gear and is connected to the winding roller.

Optionally, in the printer according to the first aspect of the invention, the processor is configured to control the second motor to rotate in the second direction before controlling the first motor to rotate in the second direction.

Optionally, in the printer according to the first aspect of the invention, the processor is configured to control the second motor to rotate in the second direction at a speed that is greater than a predetermined speed.

Optionally, the printer according to the first aspect of the invention further comprises a torque limiter connected to the winding roller and configured to limit a load torque on the winding roller in a direction opposite to a direction in which the label sheet is wound.

Optionally, in the printer according to the first aspect of the invention, the load torque is greater than an inertial torque on the winding shaft generated by the second motor rotated in the second direction and smaller than an inertial torque on the winding shaft caused by the label sheet conveyed in a reserved direction along the conveyance path opposite to the forward direction.

Optionally, the printer according to the first aspect of the invention further comprises a sensor configured to detect presence or absence of a label in the discharge port, wherein the processor is configured to, when the sensor detects absence of the printed first label after the printed first label is discharged, control the first and second motors to rotate in the second direction.

According to a second aspect of the invention, it is provided a method carried out by a printer that includes a platen roller configured to convey a label sheet, a first motor configured to rotate the platen roller, a print head facing the platen roller and configured to print on a label of the label sheet, a discharge port through which the printed label is discharged and detached, a winding roller for winding the label sheet from which the printed label has been detached, a second motor configured to rotate the winding roller, and a drive train by which a rotational force can be transmitted from the second motor to the winding roller, the method comprising control the first and second motors to rotate in a first direction to convey the label sheet in a forward direction along a conveyance path and control the print head to print on a first label of the label sheet; discharging the printed first label through the discharge port; and control the first and second motors to rotate in a second direction that is opposite to the first direction, wherein the drive train disengages the winding roller from the second motor when the second motor is controlled to rotate in the second direction.

Optionally, in the method according to the second aspect of the invention, the drive train includes a one-way clutch by which the rotation force is transmitted from the second motor to the winding roller when the second motor is controlled to rotate in the first direction.

Optionally, in the method according to the second aspect of the invention, the one-way clutch disengages the winding roller from the second motor when the second motor is controlled to rotate in the second direction.

Optionally, in the method according to the second aspect of the invention, the drive train further includes a first gear that is connected to the second motor and a second gear that meshes with the first gear and rotates around a shaft to which the one-way clutch is connected to.

Optionally, in the method according to the second aspect of the invention, the drive train further includes a third gear that is connected to the shaft via the one-way clutch and a fourth gear that meshes with the third gear and is connected to the winding roller.

Optionally, in the method according to the second aspect of the invention, controlling the second motor to rotate in the second direction before controlling the first motor to rotate in the second direction.

Optionally, in the method according to the second aspect of the invention, (it is further included) controlling the first and second motors to rotate in the second direction includes controlling the second motor to rotate in the second direction at a speed that is greater than a predetermined speed.

Optionally, in the method according to the second aspect of the invention, the printer further includes a torque limiter connected to the winding roller and configured to limit a load torque on the winding roller in a direction opposite to a direction in which the label sheet is wound.

Optionally, in the method according to the second aspect of the invention, the load torque is greater than an inertial torque on the winding shaft generated by the second motor rotated in the second direction and smaller than an inertial torque on the winding shaft caused by the label sheet conveyed in a reserved direction along the conveyance path opposite to the forward direction.

Optionally, the method according to the second aspect of the invention further comprises detecting absence of the printed first label in the discharge port after the printed first label is discharged, wherein the first and second motors are rotated in the second direction upon detection of the absence of the printed first label.

Hereinafter, embodiments will be described in detail with reference to the drawings. The present invention is not limited to the embodiments described below.

<FIG> is a schematic diagram of a label printer <NUM> according to an embodiment. The label printer <NUM> is an example of a printer in the present disclosure.

The label printer <NUM> has a housing <NUM> that stores a label roll LR in which a label sheet LP, which is an example of a print sheet, is wound in a roll shape. On the label sheet LP, a plurality of labels L are attached to a long base sheet M at predetermined intervals (see <FIG>). The label printer <NUM> performs printing on the label L while pulling out the label sheet LP from the label roll LR.

The label printer <NUM> includes conveyance rollers <NUM>, a platen roller <NUM>, a print head <NUM>, an inter-label detection sensor <NUM>, a peeling guide <NUM>, a winding roller <NUM>, and a peeling detection sensor <NUM> inside the housing <NUM>. Further, the label printer <NUM> includes a ribbon holding shaft <NUM>, a ribbon winding shaft <NUM>, and guide shafts <NUM> inside the housing <NUM>.

The conveyance rollers <NUM> include a capstan roller <NUM> and two auxiliary rollers <NUM>. The label sheet LP drawn out from the label roll LR is inserted between the capstan roller <NUM> and the auxiliary rollers <NUM>. The platen roller <NUM> is disposed at a position facing the print head <NUM>. The label sheet LP is inserted between the platen roller <NUM> and the print head <NUM>.

The capstan roller <NUM> and the platen roller <NUM> are rotationally driven by a first drive motor <NUM> (see <FIG>), which will be described later. For example, the first drive motor <NUM> rotates the capstan roller <NUM> and the platen roller <NUM> counterclockwise to convey the label sheet LP toward a discharge port <NUM> in -Y direction when printing on the label sheet LP. Further, after the completion of the printing, the first drive motor <NUM> rotates the capstan roller <NUM> and the platen roller <NUM> clockwise and conveys the label sheet LP in the reverse direction, i.e., +Y direction to set the subsequent label L at the print start position.

Hereinafter, the rotation and the rotation direction of the first drive motor <NUM>, the capstan roller <NUM>, and the platen roller <NUM> when the label sheet LP is conveyed in -Y direction are also referred to as "forward rotation". Further, the rotation and the rotation direction of the first drive motor <NUM>, the capstan roller <NUM>, and the platen roller <NUM> when the label sheet LP is conveyed in the +Y direction are referred to as "reverse rotation".

The print head <NUM> is an example of a print unit. The print head <NUM> of the present embodiment is a thermal head in which a plurality of heating elements are aligned. The print head <NUM> prints on the label L of the label sheet LP sandwiched between the platen roller <NUM> and the print head <NUM> by causing the heating elements corresponding to a print pattern to generate heat.

Specifically, an ink ribbon IR is inserted between the platen roller <NUM> and the print head <NUM>. The ink applied to the ink ribbon IR is transferred to the label L on the label sheet LP by the heated print head <NUM>.

Here, the ink ribbon IR is suspended between the ribbon holding shaft <NUM> and the ribbon winding shaft <NUM>. The ribbon holding shaft <NUM> winds an unused portion of the ink ribbon IR in a roll shape. The ribbon winding shaft <NUM> is a shaft for winding a used portion of the ink ribbon IR. The guide shafts <NUM> are guide members for guiding the ink ribbon IR suspended between the ribbon holding shaft <NUM> and the ribbon winding shaft <NUM> to a predetermined position. The ribbon winding shaft <NUM> is rotationally driven in a clockwise direction by a motor (not shown) when printing the label sheet LP, and takes up the ink ribbon IR after printing.

The print head <NUM> is moved up and down by a moving mechanism (not shown) such as a solenoid. Thus, in the label printer <NUM>, it is possible to switch between a state in which the print head <NUM> is in contact with the platen roller <NUM> and a state in which the print head <NUM> is not in contact with the platen roller <NUM>. The print head <NUM> is brought into contact with the platen roller <NUM> at the time of printing on the label sheet LP. The ribbon winding shaft <NUM> winds the ink ribbon IR at a speed corresponding to the conveyance speed of the label sheet LP while printing is performed, and stops winding when the print head <NUM> is not in contact with the ink ribbon.

The inter-label detection sensor <NUM> is provided on a conveyance path of the label sheet LP between the conveyance rollers <NUM> and the platen roller <NUM>. The inter-label detection sensor <NUM> detects a position of a gap between the labels L from the label sheet LP (hereinafter referred to as a label gap). Specifically, the inter-label detection sensor <NUM> detects, as the position of the gap between the labels, a part of the label sheet LP where the light reception level is equal to or higher than a predetermined threshold when the label sheet LP is conveyed. The inter-label detection sensor <NUM> is, for example, a transmissive-type sensor including a light-emitting element and a light-receiving element.

The label printer <NUM> determines the position of the label L from the position of the label gap detected by the inter-label detection sensor <NUM>, and performs position adjustment for positioning the label L at the print start position of the print head <NUM>, adjustment of the printing timing, and the like.

The label sheet LP on which the printing is completed is separated into the base sheet M and the label L in the peeling guide <NUM>. The peeling guide <NUM> is a V-shaped columnar member having two surfaces intersecting each other at an acute angle. The peeling guide <NUM> extends along the X direction. The peeling guide <NUM> bends the label sheet LP conveyed toward the discharge port <NUM> to peel off the label L from the base sheet M. The peeled backing sheet M is wound on the winding roller <NUM>, while the label L peeled off from the backing sheet M is discharged or issued from the discharge port <NUM> provided in the housing <NUM>.

The winding roller <NUM> winds the base sheet M from which the label L has been peeled off. The winding roller <NUM> is rotationally driven by a second drive motor <NUM> (see <FIG>), which will be described later. For example, when printing on the label sheet LP, the second drive motor <NUM> rotates the winding roller <NUM> counterclockwise, and winds the base sheet M (i.e., the label sheet LP) from which the label L has been peeled off onto the winding roller <NUM>.

Hereinafter, the rotation and the rotation direction of the second drive motor <NUM> and the winding roller <NUM> when the label sheet LP is wound are referred to as "forward rotation". Further, the rotation and the rotation direction of the second drive motor <NUM> and the winding roller <NUM> when rotating in the direction opposite to the forward rotation are referred to as "reverse rotation". The rotational direction of the winding roller <NUM> at the time of the forward rotation corresponds to the winding direction of the label sheet LP.

The peeling detection sensor <NUM> is installed in the vicinity of the discharge port <NUM>, and detects the presence or absence of the label L peeled off from the base sheet M. The peeling detection sensor <NUM> is, for example, a transmissive-type sensor including a light-emitting element and a light-receiving element.

When the peeling detection sensor <NUM> detects the label L, the label printer <NUM> pauses the conveyance and printing of the label sheet LP. When a user removes the label L from the discharge port <NUM>, the peeling detection sensor <NUM> detects that the label L does not exist. When it is detected by the peeling detection sensor <NUM> that the label L does not exist, the label printer <NUM> resumes the conveyance and printing of the label sheet LP.

Specifically, when resuming printing, the label printer <NUM> causes the label sheet LP to be conveyed by a predetermined amount in a direction opposite to the conveyance direction at the time of printing, in order to return the next label L following the label L that has been peeled off to the print start position of the print head <NUM>. When the label printer <NUM> completes the conveyance in the reverse direction, the label printer <NUM> prints on the next label L, and issues the label L on which the printing is completed from the discharge port <NUM>. Hereinafter, the conveyance of the label sheet LP at the time of printing is referred to as "feed", and its conveyance direction is referred to as "feed direction". Further, the conveyance for returning the label sheet LP to the print start position is also referred to as "back feed", and its conveyance direction is referred to as "back feed direction".

Next, a hardware configuration of the label printer <NUM> will be described with reference to <FIG> is a hardware block diagram of the label printer <NUM>.

As illustrated in <FIG>, the label printer <NUM> includes a CPU (Central Processing Unit) <NUM>, a ROM (Read Only Memory) <NUM>, and a RAM (Random Access Memory) <NUM>.

The CPU <NUM> is a processor for controlling the label printer <NUM>. The ROM <NUM> stores various programs. The RAM <NUM> temporarily stores programs and various types of data. The CPU <NUM>, the ROM <NUM> and the RAM <NUM> are connected via a bus and the like. The CPU <NUM>, the ROM <NUM>, and the RAM <NUM> constitute a control unit <NUM>. That is, the CPU <NUM> of the control unit <NUM> executes a control process related to the operation of the label printer <NUM> in accordance with a control program <NUM> stored in the ROM <NUM> or a storage unit <NUM> described later and loaded onto the RAM <NUM>.

The storage unit <NUM> is a non-volatile memory such as an HDD (Hard Disc Drive) or a flash memory in which the storage data is held even when the power is turned off. The storage unit <NUM> stores the control program <NUM> for controlling the operation of the label printer <NUM>. Further, the storage unit <NUM> stores various pieces of setting information related to the operation of the label printer <NUM>.

The control unit <NUM> is connected to a controller <NUM> that controls input and output of data via the bus or the like. The controller <NUM> is connected to the first drive motor <NUM>, the second drive motor <NUM>, and the like in addition to the above-described print head <NUM>, the inter-label detection sensor <NUM>, and the peeling detection sensor <NUM>.

The first drive motor <NUM> is a drive source for the conveyance rollers <NUM> (e.g., the capstan roller <NUM>) and the platen roller <NUM>. The second drive motor <NUM> is a drive source of the winding roller <NUM>. The first drive motor <NUM> and the second drive motor <NUM> are, for example, stepping motors. Here, the first drive motor <NUM> functions as a conveyance unit that conveys the label sheet LP in the feed direction (i.e., the forward direction) and the back feed direction (i.e., the reverse direction) together with the conveyance rollers <NUM> and the platen roller <NUM> described above.

In the present embodiment, the drive source of the conveyance rollers <NUM> and the platen roller <NUM> is the first drive motor <NUM>, but a drive source may be provided for each roller. In the present embodiment, at least the conveyance rollers <NUM>, the platen roller <NUM>, and the winding roller <NUM> are driven by different driving sources.

The controller <NUM> outputs the detection results of the inter-label detection sensor <NUM> and the peeling detection sensor <NUM> to the control unit <NUM>. In addition, the controller <NUM> receives an instruction from the control unit <NUM> and controls the operation of each unit of the label printer <NUM>. For example, the controller <NUM> controls the operations of the first drive motor <NUM> and the second drive motor <NUM> to feed the label sheet LP at a predetermined conveyance rate or back feed the label sheet LP at a predetermined conveyance rate.

The control unit <NUM> is connected to a communication unit <NUM> via the bus or the like. The communication unit <NUM> is a network interface circuit that communicates with an external device such as an information processing device via a communication line (not shown). For example, the communication unit <NUM> acquires a print instruction and print data to be printed on the label L from such an external device. The communication line may be a wired communication line or a wireless communication line.

The hardware configuration of the label printer <NUM> is not limited to the configuration of <FIG>. For example, the label printer <NUM> may include an operation unit for receiving an operation from a user, a display unit for displaying various types of information, and the like.

In the label printer <NUM> having the above-described configuration, the control unit <NUM> controls each unit of the label printer <NUM> by executing the control program <NUM>, and performs printing while conveying the label sheet LP. Hereinafter, a printing operation of the label printer <NUM> will be described with reference to <FIG>.

For example, when printing of print data is instructed via the communication unit <NUM>, an operation unit (not shown), or the like, the control unit <NUM> drives the first drive motor <NUM> and the second drive motor <NUM> via the controller <NUM> to cause the conveyance rollers <NUM>, the platen roller <NUM>, and the winding roller <NUM> to rotate forward. Accordingly, the label sheet LP drawn out from the label roll LR is conveyed toward the discharge port <NUM>.

When a gap between labels is detected by the inter-label detection sensor <NUM> as the label sheet LP is conveyed, the control unit <NUM> receives a detection signal via the controller <NUM>. Next, the control unit <NUM> specifies, for example, a print timing at which printing is performed by the print head <NUM> based on a predetermined conveyance speed of the label sheet LP and an arrangement position of the print head <NUM> in the conveyance path.

Subsequently, the control unit <NUM> applies a voltage to the heating elements of the print head <NUM> via the controller <NUM> to print an image (e.g., a character string or the like) corresponding to the print data on the label L of the label sheet LP based on the specified print timing.

<FIG> is a diagram for explaining a printing operation of the label printer <NUM>. In <FIG>, among the parts shown in <FIG>, the platen roller <NUM>, the print head <NUM>, the inter-label detection sensor <NUM>, the peeling guide <NUM>, the winding roller <NUM>, and the peeling detection sensor <NUM> are shown for illustration purpose, and the same applies to <FIG>.

In <FIG>, among labels La, Lb, Lc arranged on the label sheet LP, the leading end of the preceding label La is conveyed to the position of the print head <NUM> (i.e., the print start position). Further, an arrow direction indicated by a solid line in the drawing indicates a conveyance direction of the label sheet LP to be fed. The fed label sheet LP is folded back by the peeling guide <NUM> and is wound up by the winding roller <NUM>.

When the printing of the label L is completed, the control unit <NUM> controls the rollers <NUM> and <NUM> to convey the label sheet LP in the feeding direction. When the label L peeled off by the peeling guide <NUM> is detected by the peeling detection sensor <NUM> along with the conveyance of the label sheet LP, the control unit <NUM> receives the detection signal via the controller <NUM>. Next, the control unit <NUM> stops the conveyance of the label sheet LP.

<FIG> shows that printing of the label La shown in <FIG> is completed and the label La is conveyed to the discharge port <NUM>. In <FIG>, the control unit <NUM> stops feeding and waits until the label La is removed.

In the condition of <FIG>, the user removes the label La discharged from the discharge port <NUM>. <FIG> shows the state in which the label La is removed from the state in <FIG>. When the label La is removed, the peeling detection sensor <NUM> detects that there is no label La.

In the state shown in <FIG>, the leading end of the label Lb following the label La has passed through the print head <NUM>. Therefore, as shown in <FIG>, the control unit <NUM> returns the leading end of the label Lb to the print start position of the print head <NUM> by back feeding the label sheet LP by a predetermined amount. Note that an arrow direction indicated by a broken line in the drawing indicates a conveyance direction of the label sheet LP to be back-fed.

Then, when printing on the label L is continuously performed, the control unit <NUM> performs printing on the label Lb while feeding the label sheet LP as described with reference to <FIG>. When printing is performed after the label Lc, the operations of <FIG>, <FIG> are repeatedly executed.

Incidentally, when back feeding the label sheet LP, the first drive motor <NUM> is rotated in reverse, and the label sheet LP (i.e., the base sheet M) wound up by the winding roller <NUM> is pulled out. At this time, the first drive motor <NUM> draws the label sheet LP wound on the winding roller <NUM> from the winding roller <NUM> while resisting the loads caused by the non-exciting torque or the like of the second drive motor <NUM>. Therefore, when the back feed is performed, slippage is likely to occur in the conveyance of the label sheet LP due to the effect of the loads, and there is a possibility that the conveyance cannot be accurately performed.

Specifically, the label sheet LP is back-fed by the fixed amount of conveyance so that the next label L reaches the print start position of the print head <NUM>, but there is a possibility that the actual amount of conveyance varies due to the slippage of the roller conveyance. In this case, the printing position on the label L is displaced, and thus there is a possibility that the printing accuracy is lowered.

It should be noted that there is a method of adjusting the position based on the detection result by back feeding the label sheet LP to a position detectable by the inter-label detection sensor <NUM>. However, such a method increases the total amount of conveyance, and thereby reducing printing performance.

The label printer <NUM> of the present embodiment includes a drive train for accurately back feeding the label sheet LP without decreasing printing performance. Hereinafter, the drive train included in the label printer <NUM> will be described with reference to <FIG>.

<FIG> are diagrams illustrating an example of a drive train <NUM> related to the rotational drive of the winding roller <NUM>. <FIG> show the winding roller <NUM> as viewed from the Z direction.

The winding roller <NUM> includes a winding shaft <NUM> serving as a rotation shaft, and a sleeve <NUM> provided around the winding shaft <NUM>. The winding shaft <NUM> is an axis of the winding roller <NUM> and is rotatable in the axial direction. The sleeve <NUM> is formed of a material such as rubber, and is provided around the winding shaft <NUM>.

The winding shaft <NUM> is rotationally driven by the driving force of the second drive motor <NUM> via the drive train <NUM> illustrated in <FIG>.

The drive train <NUM> is provided between the winding roller <NUM> and the second drive motor <NUM>. The drive train <NUM> includes a first gear <NUM>, a second gear <NUM>, a shaft portion <NUM>, a third gear <NUM>, a fourth gear <NUM>, and a one-way clutch <NUM>. The first gear <NUM> is provided, for example, on the rotation shaft of the second drive motor <NUM> and rotates by the driving force of the second drive motor <NUM>. The first gear <NUM> meshes with the second gear <NUM>. The second gear <NUM> includes the shaft portion <NUM>. The third gear <NUM> is attached to the shaft portion <NUM>. The third gear <NUM> meshes with the fourth gear <NUM> fixed to the end of the winding shaft <NUM>.

The third gear <NUM> is attached to the shaft portion <NUM> via the one-way clutch <NUM>. The one-way clutch <NUM> is a clutch mechanism that transmits a rotational force to the third gear <NUM> at the time of feeding, and shuts off the drive from the third gear <NUM> at the time of back feeding.

In the above-described configuration, when feeding the label sheet LP, the second drive motor <NUM> rotates the drive train <NUM> in the first direction (i.e., the direction indicated by the solid arrow in <FIG>) under the control of the control unit <NUM>. In this case, the driving force of the second drive motor <NUM> is transmitted to the winding shaft <NUM> via the first gear <NUM>, the second gear <NUM>, the third gear <NUM>, and the fourth gear <NUM>, and causes the winding roller <NUM> to rotate forward. Thus, the winding roller <NUM> performs a winding operation of the fed label sheet LP.

On the other hand, when the label sheet LP is back-fed, the label sheet LP wound on the winding roller <NUM> is pulled out by the reverse rotation of the platen roller <NUM>, so that the winding roller <NUM> is also reversed. At this time, the drive train <NUM> receives the rotational force rotating in the second direction opposite to the first direction (i.e., the direction indicated by the broken line arrow in <FIG>), but since the one-way clutch <NUM> is in the idling state by the second drive motor <NUM>, the winding roller <NUM> rotates independently from the first gear <NUM>, the second gear <NUM>, and the second drive motor <NUM>.

It is preferable that the second drive motor <NUM> is reversed prior to the reversal of the first drive motor <NUM> in order to achieve the idling condition of the one-way clutch <NUM> when the label sheet LP is back-fed.

Specifically, the idling state of the one-way clutch <NUM> is achieved when the control unit <NUM> drives the second drive motor <NUM> in reverse prior to the reverse driving of the first drive motor <NUM>. More specifically, the control unit <NUM> drives the second drive motor <NUM> in reverse such that a first rotational speed n1 of the shaft portion <NUM> generated by pulling out the label sheet LP by the back feed and a second rotational speed n2 of the shaft portion <NUM> generated by the reverse drive of the second drive motor <NUM> are n1 < n2. Further, although the first rotational speed n1 of the shaft portion <NUM> generated by pulling out the label sheet LP varies depending on the quantity of the label wound around the winding roller <NUM>, the control unit <NUM> drives the second drive motor <NUM> in reverse so as to satisfy n1 < n2 relation under any condition. This causes the one-way clutch <NUM> to idle.

Then, the control unit <NUM> causes the one-way clutch <NUM> to idle, and then causes the first drive motor <NUM> to reverse-rotate to back feed the label sheet LP by a predetermined amount. As a result, the control unit <NUM> conveys the next label L to the print start position of the print head <NUM>.

In the idling state of the one-way clutch <NUM>, since the winding roller <NUM> is unloaded, there is a possibility that slack occurs in the base sheet M due to the inertia of the rotation at the end of the back feed. Therefore, for example, as shown in <FIG>, a torque limiter <NUM> that generates a constant load torque in rotation in the second direction may be added to the drive train <NUM> or the like of the winding roller <NUM> to apply an appropriate load to prevent the occurrence of slack.

<FIG> is a diagram illustrating another configuration example of the drive train of the winding roller <NUM>. <FIG> shows an example in which the torque limiter <NUM> is provided at the end of the winding shaft <NUM> that is different from the shaft end where the fourth gear <NUM> is provided. It is assumed that a load torque T1 of the torque limiter <NUM> is set to be T2 < T1 < T3 where T2 is an inertial torque generated in the winding roller <NUM> by the reverse drive of the second drive motor <NUM> and T3 is a torque generated in the winding roller <NUM> by the pull-out of the label sheet LP. As a result, the torque limiter <NUM> adds, to the winding roller <NUM>, a load smaller than the torque T3 generated from the conveying force of the conveyance roller <NUM> and the platen roller <NUM> at the time of the back feed. At the end of the back feed, the torque limiter <NUM> applies a higher load to the winding roller <NUM> than the rotational moment of inertia (i.e., the inertial torque T2) remaining in the reversed winding roller <NUM>. Therefore, in the label printer <NUM>, back feed can be performed without causing slack in the base sheet M.

With the above-described configuration, the label printer <NUM> can perform back feeding of the label sheet LP without being affected by the loads of the second drive motor <NUM>, so that it is possible to accurately align the label sheet with the print start position by the back feeding. Therefore, the label printer <NUM> can accurately perform printing on the label L.

Next, an operation of the label printer <NUM> will be described with reference to <FIG> is a flowchart illustrating an example of an operation performed by the label printer <NUM>.

First, the control unit <NUM> drives the first drive motor <NUM> and the second drive motor <NUM> in the forward direction to convey the label sheet LP including the label L to the print start position (step S11). When the label L reaches the print start position, the control unit <NUM> drives the print head <NUM> to print the label L (step S12).

When the printing is completed, the control unit <NUM> conveys the label sheet LP toward the discharge port <NUM> (step S13). As a result, the printed label L is discharged from the discharge port <NUM> in a state in which a part of the label L is peeled off from the base sheet M by the peeling guide <NUM>.

Next, the control unit <NUM> waits until the label L is removed based on the detection result of the peeling detection sensor <NUM> (step S14; No). Upon detecting that the label L has been removed (step S14; Yes), the control unit <NUM> proceeds to step S15 in order to back feed the label sheet LP.

The control unit <NUM> drives the second drive motor <NUM> in reverse to idle the one-way clutch <NUM> of the drive train <NUM> (step S15). Next, the control unit <NUM> drives the first drive motor <NUM> in reverse to back feed the label sheet LP by a predetermined amount of conveyance in order to position the subsequent label L at the print start position (step S16). It is assumed that the control unit <NUM> drives the second drive motor <NUM> in reverse so that the first rotational speed n1 of the shaft portion <NUM> generated by pulling out the label sheet LP and the second rotational speed n2 of the shaft portion <NUM> generated by the reversing drive of the second drive motor <NUM> are n1 < n2 to each other.

Subsequently, the control unit <NUM> determines whether to finish printing (step S17). For example, when it is instructed to continuously print on a plurality of labels L, the control unit <NUM> determines to continue printing (step S17; No), and returns the process to step S12. Then, the control unit <NUM> performs printing on the next label L positioned at the print start position.

Further, for example, when the designated number of labels L are printed, the control unit <NUM> determines that the printing is finished (step S17; Yes), and ends the present process.

As described above, the label printer <NUM> of the present embodiment includes, between the winding roller <NUM> and the second drive motor <NUM>, the drive train <NUM> that transmits the rotational force in the winding direction in which the label sheet LP is wound on the winding roller <NUM>, and sets the rotational force in the direction opposite to the winding direction to the idling state. Further, the label printer <NUM> drives the second drive motor <NUM> to rotate forward while the label sheet LP is being conveyed in the feed direction, and when the printed label L is discharged from the discharge port <NUM>, the label sheet LP is conveyed by a predetermined amount in the back feed direction.

As a result, the label printer <NUM> can back feed the label sheet LP without being affected by the loads of the second drive motor <NUM>, so that the back feed can be accurately performed. Therefore, since the label printer <NUM> can accurately align the label L to the print start position by the back feed, it is possible to improve the printing accuracy on the label L. Further, in the label printer <NUM>, it is possible to suppress the amount of conveyance at the time of the back feed, and it is possible to improve the throughput.

In addition, the label printer <NUM> drives the second drive motor <NUM> in reverse prior to the back feed of the label sheet LP. Further, the label printer <NUM> drives the second drive motor <NUM> in reverse so that the second rotational speed n2 of the shaft portion <NUM> generated by the reverse drive of the second drive motor <NUM> is larger than the first rotational speed n1 of the shaft portion <NUM> generated by the pull-out of the label sheet LP. As a result, the one-way clutch <NUM> of the drive train <NUM> can be in the idling state prior to the back feed of the label sheet LP, and thus the back feed is performed in a state where the second drive motor <NUM> is unloaded.

Further, the label printer <NUM> further includes the torque limiter <NUM> that adds, to the winding roller <NUM>, a load that is smaller than the torque generated in the winding roller <NUM> by pulling out the label sheet LP at the time of the back feed and is larger than the moment of inertia of the rotation remaining in the winding roller <NUM> at the time of the end of the back feed. As a result, the label printer <NUM> can perform the back feed without causing slack in the base sheet M, and thus it is possible to prevent the occurrence of a conveyance abnormality such as a meandering of the base sheet M.

It is to be noted that the above-described embodiments can be appropriately modified and implemented by changing a part of the configuration or the function of the label printer <NUM>. Therefore, in the following, some modifications according to the above-described embodiments will be described as other embodiments. Note that, in the following, differences from the above-described embodiments will be mainly described, and detailed descriptions of the same points as those described above will be omitted. Further, the modification examples described below may be implemented individually or in combination as appropriate.

In the above-described embodiments, the drive train <NUM> is configured with four gears and the one-way clutch <NUM> is provided in the third gear <NUM>, but the configuration of the drive train <NUM> is not limited to this. For example, the drive train <NUM> may comprise one to three, or five or more gears. Further, the one-way clutch <NUM> may be provided in any of the gears constituting the drive train <NUM>, and may be provided in, for example, the second gear <NUM> described with reference to <FIG>.

In the above-described embodiments, as described in the flowchart of <FIG>, the back feed is performed before the printing is finished, but the present invention is not limited thereto, and the back feed may not be performed when the printing is finished. In this case, the label printer <NUM> may perform the step S15 and the step S16 at the time of resuming the printing, thereby performing the back feed at the print start position. Further, the label printer <NUM> may perform back feed the label sheet LP to a position at which the labels L are detectable by the inter-label detection sensor <NUM> when a printing is resumed.

The program executed by the label printer <NUM> of the above-described embodiments is stored in advance in the ROM <NUM>, the storage unit <NUM>, or the like. The program executed by the label printer <NUM> of the above-described embodiments may be recorded on a non-transitory computer-readable recording medium such as a CD-ROM, a flexible disk (FD), or a CD-R, DVD (Digital Versatile Disk) in an installable format or an executable format.

Claim 1:
A printer (<NUM>) for printing on a label sheet (LP) including a plurality of detachable labels (L), comprising:
a platen roller (<NUM>) configured to convey the label sheet (LP);
a first motor (<NUM>) configured to rotate the platen roller (<NUM>) ;
a print head (<NUM>) facing the platen roller (<NUM>) and configured to print on a label (L) of the label sheet (LP);
a discharge port (<NUM>) through which the printed label (L) is discharged and detached;
a winding roller (<NUM>) for winding the label sheet (LP) from which the printed label (L) has been detached;
a second motor (<NUM>) configured to rotate the winding roller (<NUM>);
a drive train (<NUM>) by which a rotational force can be transmitted from the second motor (<NUM>) to the winding roller (<NUM>) ; and
a processor (<NUM>),
characterized in that
the processor (<NUM>) is configured to:
control the first and second motors (<NUM>, <NUM>) to rotate in a first direction to convey the label sheet (LP) in a forward direction along a conveyance path and control the print head (<NUM>) to print on a first label (L) of the label sheet (LP), and
after the printed first label (L) is discharged, control the first and second motors (<NUM>, <NUM>) to rotate in a second direction that is opposite to the first direction, wherein
the drive train (<NUM>) disengages the winding roller (<NUM>) from the second motor (<NUM>) when the second motor (<NUM>) is controlled to rotate in the second direction.