JP2012126007A - Thermal transfer printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a size of a body by making a platen roller which also functions as a feeding roller movable.SOLUTION: The platen roller 4 changes from a feeding state, a paper conveying state, to a printing state along a moving trajectory regulated by cooperation of a guide hole of a guide member and an enlarged hole of a bearing member. During that time, a meshing state between a driving gear 30 and a platen roller gear 4b is changed. In the printing state, both of them are not meshed, and the platen roller 4 presses a thermal head 9. In the feeding state, both of them are meshed, and the platen roller 4 is driven by rotation by the driving gear 30 as well as the platen roller 4 presses a paper stack 3 from above, thus feeding is performed. In the paper conveying state, the platen roller 4 make no contact with either the thermal head 9 or the paper stack 3.

Description

  The present invention relates to a thermal transfer printer in which a platen roller also functions as a paper feed roller.

  Conventionally, for the purpose of cost reduction and space saving, a thermal transfer type printer in which a platen roller also functions as a paper feed roller is known (Patent Documents 1 and 2 below). This type of printer will be described with reference to FIG.

  FIG. 9 is a cross-sectional view of a conventional printer in which the platen roller also functions as a paper feed roller. This printer includes a thermal head 51, a platen roller 52, and an ink sheet 53. A sheet bundle 54 before printing is stored in the bottom sheet storage section.

  In the printing process, the thermal head 51 and the platen roller 52 heat the thermal head 51 based on the image data while sandwiching the paper and the ink sheet 53 and transporting the paper. An image is formed on the paper by thermally transferring the ink on the ink sheet 53 to the paper by the generated heat.

  The thermal head 51 is fastened and fixed to the head arm member 56. The head arm member 56 can rotate around a shaft 56a, and the thermal head 51 can move up and down by a cam mechanism (not shown). A pressing member 55 is disposed under the sheet bundle 54 before printing, and the pressing member 55 pushes the sheet bundle 54 before printing toward the platen roller 52, thereby urging the sheet bundle 54 toward the platen roller 52. . In this state, the platen roller 52 also functions as a sheet feeding roller by feeding a single sheet by rotating the platen roller 52.

  The fed paper is conveyed between the thermal head 51 and the platen roller 52, the head arm member 56 rotates, the thermal head 51 moves to the platen roller 52 side, and presses the platen roller 52. Thus, thermal transfer is performed.

JP 2002-283635 A JP 7-290775 A

  However, in order to perform good thermal transfer, the thermal head 51 needs a sufficient force to press the platen roller 52. Therefore, the head arm member 56 requires sufficient rigidity and tends to be a relatively large component (see also Patent Document 1). In addition, when a general configuration is adopted in which the ink sheet cassette is inserted from the side of the printer main body, the head arm member 56 is necessarily disposed above the ink sheet cassette. Further, a movable space for the head arm member 56 to move while holding the thermal head 51 is also necessary. For these reasons, there is a problem that a large space is required in the printer main body, leading to an increase in the size of the main body.

  Further, when feeding paper, it is necessary to dispose the pressing member 55 under the paper bundle 54 in order to push up the paper bundle 54 before printing to the platen roller 52 side. It was hindering.

  The present invention has been made to solve the above-described problems of the prior art, and an object of the present invention is to provide a thermal transfer printer capable of reducing the size of the main body by making the platen roller that also functions as a paper feed roller movable. There is to do.

  In order to achieve the above object, the thermal transfer printer according to the present invention includes a thermal head, a storage unit for storing paper, and the thermal head for holding the paper during the printing process by the thermal head, and the storage is performed during paper feeding. A platen roller that functions as a paper feed roller for feeding paper from the printing unit, and the platen roller is moved toward the thermal head during the printing process, and the platen roller is moved toward the storage unit during the paper feeding. And moving means for moving.

  According to the present invention, the main body can be reduced in size by making the platen roller that also functions as a paper feed roller movable.

1 is a longitudinal sectional view of a thermal transfer printer according to a first embodiment of the present invention. FIG. 3 is a longitudinal sectional view of the printer in a paper feeding state, a paper transporting state, and a printing state. It is a one part perspective view of a moving mechanism. It is a top view of the component including a moving mechanism, and sectional drawing of the standby state of the moving mechanism along an AA line. It is sectional drawing of the paper feeding state of the moving mechanism in alignment with the AA line of Fig.4 (a), and a printing state. It is the left view of the principal part of the moving mechanism seen from the lower side of FIG. It is a side view of the left guide member. It is a longitudinal cross-sectional view of the paper feed state, paper transport state, and printing state of the printer according to the second embodiment of the present invention. FIG. 6 is a cross-sectional view of a conventional printer in which a platen roller also functions as a paper feed roller.

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

(First embodiment)
1 and 2 are longitudinal sectional views of the thermal transfer printer according to the first embodiment of the present invention. A main body 1 of the printer includes a platen roller 4 that also functions as a paper feed roller. The platen roller 4 is configured to move. In FIG. 1 and FIG. 2, illustration of components constituting a moving mechanism for moving the platen roller 4 is omitted. The moving mechanism will be described later with reference to FIGS. A control unit (not shown) controls the overall operation of the printer.

  First, with reference to FIGS. 1 and 2, the overall schematic configuration will be described together with the printing steps from paper feeding to printing and paper ejection. FIG. 1 shows a standby state before the printing process is started (standby state). FIGS. 2A and 2B respectively show a state during paper feeding and a state during paper conveyance after the paper feeding and before thermal transfer of ink. FIG. 2C shows a state during printing (during thermal transfer). Hereinafter, for the sake of convenience, the left side and the right side of FIG.

  Hereinafter, a state during paper feeding is referred to as a paper feeding state, a state during paper transportation is referred to as a paper transportation state (second state), and a state during printing (during thermal transfer) is referred to as a printing state. A state in which a sheet can be sandwiched between the thermal head 9 and the platen roller 4 is a “first state”, and a state in which paper can be fed by the platen roller 4 is a “third state”.

  As shown in FIG. 1, a casing that covers the printing mechanism inside the main body 1 is configured by the casing cases 2a, 2b, 2c, and 2d. Sheets before printing are stacked in the storage unit 19 at the bottom of the main body 1 to form a sheet bundle 3. In FIG. 1, the sheet bundle 3 is in a fully loaded state. In FIG. 2, the remaining amount of the sheet bundle 3 is drawn with a small amount so that the movement of the platen roller 4 can be easily understood. The housing case 2d is rotated counterclockwise in FIG. 1 about the rotation shaft 2d1, and the sheet bundle 3 can be stored in the storage unit 19.

  A thermal head 9 and an ink sheet cassette 12 are disposed in the upper part of the main body 1. The thermal head 9 is disposed at a fixed position with respect to the main body 1, and has a heating element 9a at the lower part thereof. The ink sheet cassette 12 is a case for protecting the long ink sheet 10 and is configured by connecting a supply side case 12a and a winding side case 12b. The supply side case 12a and the take-up side case 12b are located at positions where the thermal head 9 is sandwiched. A supply-side bobbin 11a is stored in the supply-side case 12a, and a winding-side bobbin 11b is stored in the winding-side case 12b. The ink sheet cassette 12 is provided with a pin 12c for regulating the passage position of the ink sheet 10 between the thermal head 9 and the take-up bobbin 11b.

  In the rear part of the housing, an opening C is formed between the housing case 2a and the housing case 2b. In the front part of the housing, an opening D is formed between the housing case 2a and the housing case 2c. Conveying roller pairs 6 a and 6 b are provided near the rear part in the main body 1. One of the transport roller pairs 6a and 6b is a drive roller, and the other transport roller is a driven roller. A pair of paper discharge rollers 16 a and 16 b are provided at the front of the main body 1. One of the paper discharge roller pairs 16a and 16b is a drive roller, and the other paper discharge roller is a driven roller.

  A grip roller 13 and a pinch roller 14 facing the grip roller 13 are disposed at the center in the front-rear direction of the main body 1. The grip roller 13 is a drive roller connected to a stepping motor (not shown), and can control the feed amount of the paper 3a conveyed one by one by a signal from a control unit (not shown). The pinch roller 14 is a driven roller and is urged by the grip roller 13. A conveyance guide 8 is disposed between the conveyance roller pair 6a, 6b and the rollers 13, 14 in the front-rear direction. A sensor 7 is provided immediately in front of the pair of conveyance rollers 6a and 6b. A sensor 15 is provided immediately in front of the rollers 13 and 14.

  The platen roller 4 is rotatable about a platen roller shaft 4a that is a rotation shaft. The platen roller shaft 4a extends in the left-right direction (from the front to the back in FIG. 1). A platen roller gear 4b is fastened integrally with the end of the platen roller shaft 4a on the near side in FIG. 1, and the platen roller gear 4b functions as a driven gear.

  The platen roller 4 can be moved in a substantially vertical direction together with the platen roller shaft 4a and the platen roller gear 4b by a moving mechanism described later. The platen roller 4 is the lowest in the paper feeding state (FIG. 2A) in which paper feeding is performed, and is the highest in the printing state by the thermal head 9, that is, in the printing state in which ink is thermally transferred (FIG. 2C). Located in. Accordingly, the state of the platen roller 4 changes between the paper feeding state and the printing state via the paper conveyance state in the middle.

  In the vicinity of the rear portion of the storage portion 19, a drive gear shaft 30 a extends in the left-right direction (from the front to the back in FIG. 1) and is disposed at a position fixed to the main body 1. The drive gear 30 is fastened integrally with the end of the drive gear shaft 30a on the near side in FIG. Both the platen roller gear 4b and the drive gear 30 are located outside the width direction of the sheet bundle 3 (from the front to the rear in FIG. 1), in this example, the front side of the sheet, and the sheet bundle 3 and the conveyed sheet 3a Are arranged at positions where they do not interfere.

  The drive gear 30 rotates in a clockwise direction in FIG. 1 using a stepping motor (not shown) as a drive source. As will be described later, when the platen roller 4 moves, the drive gear 30 and the platen roller gear 4b are engaged with each other and are not engaged. In a state where the two mesh with each other, the rotational torque from the drive gear 30 is transmitted to the platen roller gear 4b, and the platen roller 4 rotates counterclockwise.

  In the printing state (FIG. 2C), the drive gear 30 and the platen roller gear 4 b do not mesh with each other, and the platen roller 4 does not receive rotational torque from the drive gear 30. That is, the platen roller 4 does not rotate even when the drive gear 30 is driven, and is in a state of free rotation. The platen roller 4 is urged by the moving mechanism and presses the thermal head 9. In the paper feeding state (FIG. 2A), the drive gear 30 and the platen roller gear 4 b are engaged with each other, and the platen roller 4 is rotationally driven by the drive gear 30. That is, the platen roller 4 is rotationally driven by driving the drive gear 30 in a state where the platen roller 4 is moved to the paper feeding state by the moving mechanism. The platen roller 4 is urged by an urging force of a tension spring 33 to be described later and presses the sheet bundle 3 from above.

  In the standby state (FIG. 1) and the sheet transport state (FIG. 2B), the platen roller 4 does not contact either the thermal head 9 or the sheet bundle 3. In these states, the engagement state of the drive gear 30 and the platen roller gear 4b is not limited, and the engagement may or may not be engaged.

  When a printing operation is instructed and started in the standby state of FIG. 1, the state of the platen roller 4 and the like transitions as a printing process from a paper feeding state → a paper conveying state → a printing state.

  First, from the standby state of FIG. 1, the platen roller 4 is lowered, and the platen roller gear 4 b is engaged with the drive gear 30 and pressed against the sheet bundle 3. By transmitting rotational torque from the drive gear 30, the platen roller 4 rotates counterclockwise about the platen roller shaft 4a, so that one sheet 3a located on the uppermost surface of the sheet bundle 3 moves backward. Be transported. Then, the leading end of the sheet 3a in the advancing direction hits the inclined surface 5, and the platen roller 4 further rotates, whereby the sheet 3a is conveyed along the inclined surface 5 (FIG. 2A).

  In the middle of the slope 5, a separation portion 5a, which is a gap for preventing heavy running, is provided. The separation unit 5a is a gap corresponding to the thickness of one sheet 3a, so that only one sheet 3a passes downstream.

  When the conveyance proceeds and the sheet 3a is sandwiched between the conveyance roller pairs 6a and 6b, the platen roller 4 rises and separates from the sheet bundle 3. At the same time, the sheet 3a is continuously conveyed backward by the driving force of the conveying roller pair 6a, 6b. Here, the timing at which the platen roller 4 is separated is defined by the sensor 7 detecting the leading edge of the paper 3a (the right edge in FIG. 2B). That is, after the leading edge of the paper 3a is detected, the platen roller 4 is separated after the paper 3a is further transported by a predetermined amount so as to be securely held between the transport roller pairs 6a and 6b. When the sheet is further conveyed, the leading edge of the sheet 3a is once taken out of the printer main body 1 from the opening C on the rear side of the casing (FIG. 2B).

  When the conveyance further proceeds and the sensor 7 detects the rear end (left end in FIG. 2B) of the sheet 3a in the traveling direction, the pair of conveyance rollers 6a and 6b rotate in the reverse direction. Then, this time, the end which was the rear end of the sheet 3a becomes the top, passes the upper surface of the conveyance guide 8 forward, and is conveyed to the thermal head 9 side.

  When the conveyance of the sheet advances, the leading end (left end in FIG. 2C) of the sheet 3a is sandwiched between the grip roller 13 and the pinch roller 14, and the downstream sensor 15 detects the leading end of the sheet 3a. The conveyance of the sheet 3a is temporarily stopped. Then, the platen roller 4 is pressed against the thermal head 9 side, and the paper 3a and the ink sheet 10 are sandwiched between the thermal head 9 and the platen roller 4 and are in pressure contact with each other (FIG. 2C). At this time, since the platen roller gear 4b does not mesh with the drive gear 30, the platen roller 4 becomes a driven roller and rotates as the paper 3a is conveyed.

  The paper 3a is conveyed downstream by the rotation of the grip roller 13, and at the same time, the ink sheet 10 is taken up by the rotation of the take-up bobbin 11b, and the paper 3a and the ink sheet 10 are conveyed synchronously. While the ink sheet 10 and the paper 3a are sandwiched between the thermal head 9 and the platen roller 4, the heating element 9a of the thermal head 9 generates heat based on the information of the image data. As a result, the ink on the ink sheet 10 is thermally transferred to the paper 3a, and images such as characters are formed.

  Here, in the case of full-color printing, a full-color image is formed by repeatedly superposing three colors of yellow, magenta, and cyan and performing thermal transfer. When the first color thermal transfer is completed, the grip roller 13 is rotated in the reverse direction, and the downstream end (the left end in FIG. 2C) of the paper 3a is temporarily returned to the printing start position, and then the grip roller 13 is rotated forward. The thermal transfer for the second and subsequent colors is started. When the three-color thermal transfer is completed, the protective film is finally overcoated by the same thermal transfer, and printing is completed. After printing is completed, the sheet 3a is sandwiched between the pair of discharge rollers 16a and 16b, and discharged from the opening D on the front side of the housing to the outside of the main body 1.

  When the next printing operation is to be continued after the printing is completed, the platen roller 4 transitions from the printing state to the paper feeding state. However, when there is no next printing schedule, the platen roller 4 changes from the printing state to the standby state.

  Next, the configuration of a moving mechanism that moves the platen roller 4 will be described with reference to FIGS.

  FIG. 3 is a perspective view of a part of the moving mechanism. FIG. 4A is a top view of a component including a moving mechanism. 4 (b), 5 (a), and 5 (b) are cross-sectional views of the moving mechanism along the line AA in FIG. 4 (a), showing a standby state, a paper feeding state, and a printing state, respectively. ing.

  The moving mechanism includes a bearing member (holding portion) 22, an arm member 23, a lever member 24, a lever rotating shaft 25, a lever shaft 26, a cam 27, a cam shaft 27a, a compression spring 28, and a platen roller guide member 29. Is done. As shown in FIG. 4A, the platen roller guide member 29 (hereinafter also abbreviated as “guide member 29”) is disposed on the left and right sides of the sheet bundle 3 in the width direction of the sheet bundle 3. Fixed to.

  As shown in FIGS. 3 and 4B and the like, the bearing member 22 has a long hole 22a that is long in the front-rear direction, and the platen roller shaft 4a is rotatable in the long hole 22a and is relatively relative to the front-rear direction. It is inserted freely in the displacement. The arm member 23 has a level difference in the middle in the front-rear direction, the rear half is high, and a horizontal portion 23a. The front half of the arm member 23 is lowered, and the bearing member 22 is fixed on the tip 23c.

  As shown in FIG. 4B, a compression spring 28 is interposed between the horizontal portion 23 a of the arm member 23 and the distal end portion 24 a of the lever member 24. Further, the distal end portion 24 a of the lever member 24 is positioned on the protruding portion 23 b that protrudes from the left and right end portions of the rear end of the front half of the arm member 23. In the paper transporting state, standby state, and paper feeding state, the leading end 24 a comes into contact with the projecting portion 23 b by the biasing force of the compression spring 28, so that the lever member 24 is fixed to the arm member 23. It becomes a state. Both the arm member 23 and the lever member 24 are pivotally supported by the lever rotation shaft 25. The lever rotation shaft 25 is pivotally supported by the left and right guide members 29. Therefore, as long as the distal end 24a is in contact with the protrusion 23b, when the lever member 24 rotates about the lever rotation shaft 25, the arm member 23 is also interlocked with the lever member 24, and both rotate together like a seesaw. Move.

  A lever shaft 26 extending in the left-right direction connects the rear ends of the left and right lever members 24 (FIG. 3). The rear end of the lever member 24 is always urged upward by a tension spring 33 having one end fixed to the main body 1 (FIG. 4B). Therefore, the platen roller shaft 4a is always urged in the downward rotation direction (counterclockwise in FIG. 4B) around the lever rotation shaft 25 via the arm member 23 and the bearing member 22. .

  A cam shaft 27a extending in the left-right direction is disposed immediately behind the lever shaft 26 (FIG. 3). The cam shaft 27 a is pivotally supported with respect to the main body 1. The left and right cams 27 are fixed to a cam shaft 27a and rotate integrally. One of the left and right cams 27 is connected to a drive gear that uses a stepping motor (not shown) as a drive source. By controlling the driving of the stepping motor by a control unit (not shown), the rotation angle of both cams 27 is controlled, and the cam surface 27b of each cam 27 can be pressed against the lever shaft 26 or retracted. Thereby, the position of the platen roller 4 is controlled via the lever member 24 and the arm member 23.

  At the time of paper feeding, as shown in FIG. 5A, the cam 27 is positioned at the initial position rotated clockwise. Then, the lever shaft 26 is lifted upward together with the rear end (end portion on the cam 27 side) of the lever member 24 biased by the tension spring 33, and the platen roller 4 is lowered with the lever rotation shaft 25 as a fulcrum. The platen roller 4 presses the uppermost surface of the sheet bundle 3 by the urging force of the tension spring 33. The bearing member 22 and the tip 23c of the arm member 23 are located away from the sheet bundle 3 in the width direction of the sheet bundle 3 (vertical direction in FIG. 4A) and do not interfere with each other.

  During conveyance, the cam 27 rotates counterclockwise from the initial position against the urging force of the tension spring 33, and the cam surface 27 b pushes down the lever shaft 26. Then, the lever member 24 and the arm member 23 are rotated clockwise around the lever rotation shaft 25, and the platen roller 4 is slightly raised. The platen roller 4 is separated from the uppermost surface of the sheet bundle 3.

  At the time of printing, the cam 27 further rotates counterclockwise from the paper conveyance state, and the cam surface 27b further pushes down the lever shaft 26. Then, the lever member 24 and the arm member 23 rotate about the lever rotation shaft 25 in the clockwise direction of FIG. As shown in FIG. 5B, when the platen roller 4 comes into contact with the thermal head 9, the bearing member 22 cannot be displaced thereafter, so that the compression spring 28 is contracted by the amount of rotation of the lever member 24. It will be. Therefore, in the printing state, the lever member 24 pushes up the arm member 23 via the compression spring 28, thereby pressing the platen roller 4 against the thermal head 9. In order to perform good thermal transfer during printing, the platen roller 4 needs to be pressed against the thermal head 9 with a predetermined force, which is realized by controlling the compression amount of the compression spring 28 by the rotation angle of the cam 27. .

  In FIG. 5B, the protrusion 23b of the arm member 23 and the tip 24a of the lever member 24 are separated from each other, and the compression spring 28 is in a paper feeding state (FIG. 5A) or a standby state (FIG. 4B). )) Is shown in a more compressed state.

  FIGS. 6A and 6B are a left side view and a right side view of the main part of the moving mechanism as seen from the lower side and the upper side of FIG. 4A, respectively. FIG. 7 is a side view of the left guide member 29. In the left guide member 29 appearing in FIGS. 6A and 7, an insertion port 29 a for inserting the ink sheet cassette 12 is formed. The other parts of the configuration are common to the left and right guide members 29.

  The guide member 29 is also formed with a rail-shaped guide hole (regulator) 29b. The end portions of the platen roller shaft 4 a are inserted into and engaged with the guide holes 29 b of the left and right guide members 29. When the platen roller shaft 4a moves, the guide hole 29b regulates the position of the platen roller shaft 4a in a direction (front-rear direction) parallel to the conveyance direction of the paper 3a during printing. As will be described in detail later with reference to FIG. 7, the guide hole 29b and the elongated hole 22a of the bearing member 22 cooperate to move the trajectory of the platen roller shaft 4a (and hence the platen roller 4) in the direction perpendicular to the platen roller shaft 4a. (RA, RB) is defined.

  Positioning pins 9b are fixed to the thermal head 9 (FIGS. 4A, 6 and 7). The positioning pin 9b is fitted in a positioning hole (not shown) of the guide member 29. As described above, the position of the thermal head 9 and the platen roller 4 is regulated by a single member called the guide member 29, so that the thermal head 9 and the platen roller 4 can be accurately aligned, thereby improving the printing quality. Can contribute.

  As shown in FIG. 7, the guide hole 29b can be roughly classified into a lower region 29bA and an upper region 29bB from the shape thereof. In FIG. 7, the arc locus RA has a radius r between the axis (distance) between the platen roller shaft 4 a and the drive gear shaft 30 a in a state where the drive gear 30 and the platen roller gear 4 b of the platen roller 4 are engaged with each other. This is a locus drawn around the axis center of the drive gear shaft 30a. The locus RB is a straight line in the vertical direction from the point on the arc locus RA toward the heating element 9a of the thermal head 9. The lower region 29bA is formed in an arc shape along the arc locus RA, and the upper region 29bB is formed in a straight line shape or a substantially straight line shape along the locus RB. The lower area 29bA and the upper area 29bB are smoothly connected at the intersection of the arc locus RA and the locus RB.

  When the platen roller shaft 4a moves through the lever member 24, the arm member 23, and the bearing member 22 by the rotation of the cam 27, the platen roller shaft 4a can be displaced in the longitudinal direction in the elongated hole 22a of the bearing member 22. is there. As a result, the platen roller shaft 4a can move in the guide hole 29b following the arc locus RA and the locus RB.

  The platen roller shaft 4a is positioned in the lower region 29bA in the paper feeding state (FIGS. 2A and 5A), and the upper region in the printing state (FIGS. 2C and 5B). Located near the top of 29bB. In the paper transporting state (FIG. 2B) and the standby state (FIGS. 1 and 4B), it is located at a predetermined position in the range from the upper portion of the lower region 29bA to the upper region 29bB. A trajectory that is continuous between the arc trajectory RA and the trajectory RB is a moving trajectory of the platen roller 4 (platen roller shaft 4a).

  In a state where the platen roller shaft 4a is engaged with the lower region 29bA, the axis center of the platen roller shaft 4a is on the arc locus RA. Therefore, the platen roller gear 4b and the drive gear 30 can mesh appropriately, and the rotational torque from the drive gear 30 is transmitted to the platen roller gear 4b.

  Here, as the paper feeding is repeated, the uppermost position of the sheet bundle 3 changes according to the remaining amount of the sheet bundle 3 in the storage unit 19, and the contact position of the platen roller 4 with the sheet bundle 3 is full of the sheet bundle 3. It gradually changes from the state to the last one. In the paper feeding state, the center of the platen roller shaft 4a is positioned on the arc locus RA, so that the distance between the platen roller shaft 4a and the drive gear shaft 30a is kept constant at the radius r. Since the movement trajectory of the platen roller 4 is defined in this manner, the platen roller gear 4b and the drive gear 30 are always meshed at any position in the paper feeding state, and an appropriate paper feeding operation is ensured. The length of the lower area 29bA is set such that the platen roller 4 can sufficiently follow the change in the uppermost position until the sheet bundle 3 is fully loaded.

  When the sheet feeding state is changed to the sheet conveying state, the axis center of the platen roller shaft 4a is located in the range from the upper part of the arc locus RA to the lower part of the locus RB. Depending on the set position at that time, the engagement between the platen roller gear 4b and the drive gear 30 may be insufficient or may not be engaged.

  When transitioning from the paper transport state to the printing state, the axis center of the platen roller shaft 4a moves upward along the locus RB, and in the printing state, it is positioned near the top of the locus RB. Then, the engagement between the platen roller gear 4b and the drive gear 30 is completely disengaged, and the platen roller 4 is in a state of pressing the thermal head 9. The platen roller 4 is a driven roller that follows the conveyance of the sheet 3a.

  According to the present embodiment, the guide hole 29b of the guide member 29 and the elongated hole 22a of the bearing member 22 cooperate to move the platen roller 4 in the direction perpendicular to the axial direction of the platen roller shaft 4a (circular arc). A trajectory RA and a trajectory RB) are defined. The platen roller 4 transits to a paper feeding state, a paper transporting state, and a printing state according to this movement trajectory. The platen roller 4 presses the uppermost surface of the sheet bundle 3 in the paper feeding state, and the platen roller gear 4b and the drive gear 30 mesh with each other, so that the paper feeding operation can be performed reliably. On the other hand, in the printing state, the platen roller 4 presses the thermal head 9 without the platen roller gear 4 b and the drive gear 30 meshing with each other.

  Thus, first, the platen roller 4 also functions as a paper feed roller, so that space saving is achieved. Further, since the platen roller 4 is movable and can be displaced between a position for pressing the thermal head 9 and a position for feeding paper, the thermal head 9 may not be configured to be movable. This eliminates the need for an arm or the like for holding the thermal head 9 and a movable / retracting space for them, and allows the printer body 1 to be downsized.

  In the paper feeding state, the position of the platen roller 4 follows the change in the uppermost position of the sheet bundle 3 according to the remaining amount of the sheet bundle 3 in the storage unit 19 by the urging force of the tension spring 33. In addition, the distance between the platen roller shaft 4a and the drive gear shaft 30a is kept constant at the radius r. As a result, the sheet bundle 3 can be pressed in a state in which the rotational driving force at the time of paper feeding is kept constant, so that it is not necessary to provide a mechanism for urging the sheet bundle 3 from below. Thinning is possible.

  The thermal head 9 is fixed to the guide member 29, and a guide hole 29b for regulating the position of the platen roller shaft 4a is provided in the guide member 29. Thereby, since the relative positioning of the thermal head 9 and the guide hole 29b is performed, the movement trajectory of the platen roller 4 becomes accurate.

  By the way, the guide hole 29b is formed in a rail shape as a restricting portion that restricts the position of the platen roller shaft 4a in the front-rear direction. However, it is not limited to this. For example, in order to make the axis center of the platen roller shaft 4a follow the arc locus RA during the transition from the paper feeding state to the printing state, at least the rear edge 29bA1 (FIG. 7) of the lower region 29bA. The corresponding part should just exist. This is because the drive gear 30 is present on the front side of the platen roller gear 4b, so that the forward movement of the platen roller shaft 4a is restricted.

  Further, since the platen roller gear 4b is disengaged from the drive gear 30, in order to shift from the arc locus RA to the locus RB, at least the portion corresponding to the front edge 29bB1 (FIG. 7) in the upper region 29bB is present. It only has to exist. In addition to this, when the platen roller 4 presses the thermal head 9, the platen roller 4 can be positioned with respect to the thermal head 9 by securing a contact surface for pressing back and forth of the platen roller shaft 4 b. It becomes.

  Furthermore, the upper region 29bB does not need to extend linearly, and the upper region 29bB may be formed so that the locus RB extends toward the outside of the arc locus RA. Therefore, it may be somewhat curved.

  Further, the portion corresponding to the guide hole 29b as a restricting portion for restricting the position of the platen roller shaft 4a in the front-rear direction is not necessarily provided in the guide member 29, and is provided in a portion fixed to the main body 1. Just do it.

(Second Embodiment)
8A to 8C are longitudinal sectional views of a printer according to the second embodiment of the present invention. In the second embodiment, in contrast to the first embodiment (FIG. 2 and the like) described above, the conveyance roller pair 6a, 6b and the sensor 7 are eliminated, and the conveyance guide 31 and the sensor 32 are provided. However, other configurations are the same.

  FIGS. 8A, 8B, and 8C show a paper feeding state, a paper transporting state, and a printing state, respectively. However, in the paper conveyance state of FIG. 8B, the conveyance direction of the paper 3a is switched from the front to the rear in the middle.

  In the paper feeding state (FIG. 8A), the platen roller 4 presses the sheet bundle 3. The conveyance guide 31 has a guide shape that guides the sheet 3 a toward the thermal head 9. When the leading edge of the fed sheet 3 a is directed forward and is sandwiched between the grip roller 13 and the pinch roller 14, the platen roller 4 is separated from the sheet bundle 3, and the sheet bundle 3 and the thermal head 9. It stops at a position where it does not contact either of them (FIG. 8B).

  When the paper 3a is once transported to the downstream side by the rotational driving of the grip roller 13, and the rear end (the right end in FIG. 8B) of the paper 3a passes the sensor 32, the grip roller 13 rotates in the reverse direction. The paper 3a is conveyed backward (to the right in FIG. 8B). Thereafter, when the front end (left end in FIG. 8B) of the sheet 3a is detected by the sensor 15 in the vicinity of the grip roller 13, the platen roller 4 moves so as to press against the thermal head 9 (FIG. 8 ( c)).

  From this state, the rotation direction of the grip roller 13 becomes normal again, and the sheet 3a is conveyed forward (to the left in FIG. 8C) together with the ink sheet 10. Then, when the heating element 9a of the thermal head 9 generates heat based on the image data, the ink is thermally transferred to the paper 3a and an image is formed.

  According to the present embodiment, the main body 1 of the printer can be reduced in size. Moreover, since the pair of transport rollers 6a and 6b is not required as compared with the first embodiment, it is possible to further contribute to size reduction and cost reduction.

  Although the present invention has been described in detail based on preferred embodiments thereof, the present invention is not limited to these specific embodiments, and various forms within the scope of the present invention are also included in the present invention. included. A part of the above-described embodiments may be appropriately combined.

4 Platen Roller 4a Platen Roller Shaft 4b Platen Roller Gear 9 Thermal Head 22 Bearing Member 29 Platen Roller Guide Member 29b Guide Hole 30 Drive Gear 30a Drive Gear Shaft 33 Tension Spring

Claims (6)

Thermal head,
A storage section for storing paper;
A platen roller that functions as a paper feed roller for sandwiching paper with the thermal head at the time of printing processing by the thermal head and feeding paper from the storage unit at the time of paper feeding;
A thermal transfer printer comprising: a moving unit that moves the platen roller toward the thermal head during the printing process and moves the platen roller toward the storage unit during the paper feeding.   The moving means changes from a first state in which a sheet can be sandwiched between the thermal head and the platen roller to a third state in which paper can be fed by the platen roller via a second state. The platen roller is moved. At this time, the platen roller is moved substantially linearly from the first state to the second state, and from the second state to the third state, the circle is moved. The thermal transfer printer according to claim 1, wherein the thermal transfer printer is moved in an arc shape.   When the platen roller is moved by the moving unit, the platen roller has a defining unit that defines a moving trajectory of the platen roller so that the platen roller transitions from the first state to the third state. The thermal transfer printer according to claim 2.   A driven gear provided on a rotation shaft of the platen roller; and a drive gear capable of rotating the platen roller by meshing with the driven gear, and in the third state, 4. The thermal transfer printer according to claim 2, wherein the drive gear meshes with each other, and the driven gear and the drive gear are separated from each other and do not mesh with each other in the first state. 5.   The thermal transfer printer according to claim 4, wherein the platen roller rotates freely in the first state. When the platen roller is moved by the moving means, the paper is fed by the platen roller through the second state from the first state where the thermal head and the platen roller can hold the paper. Defining means for defining a movement trajectory of the platen roller to move to a possible third state;
A driven gear provided on the rotation shaft of the platen roller;
A drive gear capable of rotationally driving the platen roller by meshing with the driven gear;
In the third state, the defining means is configured so that the driven gear and the driving gear mesh with each other, and in the first state, the driven gear and the driving gear are separated from each other so as not to mesh with each other. Further, from the second state to the third state, the movement trajectory of the platen roller has a constant distance between the axis center of the platen roller and the axis center of the drive roller. The thermal transfer printer according to claim 1, wherein the thermal transfer printer is defined to have an arc shape.

Images