JP4628859B2 - Thermal head positioning mechanism and thermal printer - Google Patents

Description

  The present invention relates to a thermal printer such as a thermal sublimation printer provided with a platen roller and a thermal head, and a positioning mechanism for positioning the thermal head in the thermal printer.

  FIG. 8A shows a basic configuration of a general thermal printer. The thermal printer shown in FIG. 8A is configured to transfer the ink image onto the recording medium 101 by sandwiching the recording medium (recording paper) 101 and the ink ribbon 102 between the thermal head 104 and the platen roller 103. is there. The thermal head 104 is attached to a rotatable head arm 105.

  When printing is started, the head arm 105 rotates about the rotation shaft 106, and the recording medium 101 and the ink ribbon 102 are sandwiched between the thermal head 104 and the platen roller 103. At this time, the position of the heater line 104 a of the thermal head 104 is positioned with respect to the apex of the platen roller 103 by pressing the thermal head 104 against the positioning member 107.

  The thermal head 104 is pressed against the platen roller 103 by a spring attached to the head arm 105. Since the thermal head 104 is pressed in a direction perpendicular to the tangent line at the apex of the platen roller 103 (that is, the direction toward the axis center of the platen roller 103), the rotation shaft 106 of the head arm 105 is in contact with the apex of the platen roller 103. It is almost on the line. By matching the position of the heater line 104a of the thermal head 104 with the apex of the platen roller 103, uniform pressure is applied to the platen roller 103, and printing with an optimum density on the recording medium 101 becomes possible.

  However, depending on the thickness of the recording medium 101, the position of the heater line 104a of the thermal head 104 may be displaced from the apex of the platen roller 103. In such a case, as schematically shown in FIG. 8B, the pressing force F applied by the spring is a component F1 (the force that sandwiches the recording medium 101 and the ink ribbon 102) toward the axial center of the platen roller 103. And the other component F2. As a result, the force for sandwiching the recording medium 101 and the ink ribbon 102 between the thermal head 104 and the platen roller 103 becomes small, and it becomes impossible to perform printing with an optimum density. In addition, a gap is generated between the thermal head 104 and the positioning member 107. As a result, the positioning accuracy of the thermal head 104 may be lowered, and the print density may be unbalanced.

  Further, if the rotation axis 106 of the head arm 105 is not disposed on the tangent extension at the apex of the platen roller 103, the thermal head 104 is pressed against the tangent of the platen roller 103 at an inclined angle. The dispersion of the pressing force F as described with reference to FIG. 8B occurs, and it becomes impossible to perform printing with an optimal density. As a result, there are many restrictions on the arrangement of the conveyance path (paper path), the insertion port, the paper discharge port, and the like of the recording medium 101, and the degree of freedom in designing the entire thermal printer is reduced.

  Therefore, it has been proposed that the positional relationship between the thermal head and the platen roller be kept constant by replacing the bearing member that supports the positioning shaft provided in the thermal head according to the thickness and material of the recording medium ( For example, see Patent Document 1).

JP 2004-122495 A (page 2-3, FIG. 1)

  However, if the printer component (bearing member) is replaced every time the thickness of the recording medium is changed, there is a problem that the operation becomes complicated. In addition, when the types of recording medium thickness increase, there is a problem that the bearing member corresponding to each must be prepared and the cost increases.

  The present invention has been made to solve the above-described problems, and enables the thermal head to be positioned with respect to the platen roller even when the thickness and type of the recording medium or the conveyance path of the recording medium is changed. The purpose is to obtain a printed image.

  A thermal head positioning device according to the present invention is rotatably provided to a thermal head, and in a certain rotational position, a positioning member that positions the thermal head in a tangential direction of the outer peripheral surface of the platen roller, a thermal head, a platen roller, And a restricting means for restricting the positioning member at the rotational position in a state where at least the recording medium is sandwiched therebetween.

  According to the present invention, the thermal head can be accurately positioned in the tangential direction of the platen roller even when the type and thickness of the recording medium or the conveyance path of the recording medium is changed. Accordingly, the pressure contact force of the thermal head with respect to the platen roller can be kept constant, and it becomes possible to perform printing with an optimum density. Further, since there are less restrictions on the arrangement of the platen roller and the thermal head and the conveyance path of the recording medium, the degree of freedom in designing the thermal printer is increased.

  Further, by configuring the positioning member to be rotatable, it is possible to prevent interference between the positioning member and the platen roller when the thermal head is moved.

Embodiment 1 FIG.
1 and 2 are side views showing a main part of a thermal printer provided with a thermal head positioning mechanism according to Embodiment 1 of the present invention. FIG. 3 is a schematic diagram showing an example of the overall configuration of a thermal printer including the thermal head positioning mechanism according to Embodiment 1 of the present invention.

  As shown in FIG. 1, the thermal printer includes a platen roller 3 that is rotationally driven by a motor (not shown), and a thermal head 4 that is disposed to face the platen roller 3. The thermal head 4 is formed by forming a heater line 4a composed of a large number of heating elements on the surface of the support substrate on the platen roller 3 side. A number of heating elements constituting the heater line 4 a are arranged in a line in the direction of the rotation axis of the platen roller 3.

  A recording medium (recording paper) 1 and an ink ribbon 2 are sandwiched between the thermal head 4 and the platen roller 3 and are conveyed from the right side to the left side in the drawing. In the following description, the direction in which the recording medium 1 and the ink ribbon 2 are transported (the direction from the right side to the left side in the figure) is referred to as the transport direction. Further, the upstream side (right side in the figure) in the transport direction is called rear, and the downstream side (left side in the figure) is called front.

  As shown in FIG. 3, a recording medium roller 21 that holds the recording medium 1 and a ribbon roller 23 that holds the ink ribbon 2 are arranged behind the thermal head 4 and the platen roller 3 (right side in the figure). Yes. Further, a winding roller 24 for winding the ink ribbon 2 is disposed in front of the thermal head 4 and the platen roller 3 (left side in the figure). The recording medium 1 is pulled out from the recording medium roller 21, passes between the thermal head 4 and the platen roller 3, and then discharged through the discharge outlet 13. The ink ribbon 2 is pulled out from the ribbon roller 23, passes between the thermal head 4 and the platen roller 3, and is then wound around the take-up reel 24.

  As shown in FIG. 1, a head arm 5 is provided to move the thermal head 4 in a direction toward and away from the platen roller 3. The head arm 5 is supported so as to be rotatable about a rotation shaft 6 provided behind the platen roller 3 (upstream in the conveying direction). The rotation shaft 6 extends substantially parallel to the rotation shaft of the platen roller 3. The head arm 5 is configured to rotate between a lower position where the thermal head 4 is pressed against the platen roller 3 (FIG. 1) and an upper position where the thermal head 4 is separated from the platen roller 3 (FIG. 2). Has been.

  A rotatable cam (drive member) 10 is attached to the head arm 5. The cam 10 is an eccentric cam that rotates about a rotation shaft 10a, and is rotated by a motor (not shown).

  A support member 9 is provided adjacent to the lower side of the cam 10. The support member 9 is moved in the direction approaching the platen roller 3 and the opposite direction by contacting the cam 10. The support member 9 has a flat plate portion 91 that is substantially parallel to the support substrate of the thermal head 4, and the cam 10 comes into contact with the upper surface on the front side of the flat plate portion 91. The support member 9 further includes a leg portion 92 that extends substantially vertically from the lower surface on the front side of the flat plate portion 91.

  The elastic member 7 is fixed to the bottom surface of the leg portion 92 of the support member 9. The bottom surface of the elastic member 7 is fixed to the top surface of the thermal head 4. As the elastic member 7, a damper, a spring, or the like can be used. The leg portion 92, the elastic member 7 and the thermal head 4 of the support member 9 are fixed to each other by screws or the like. When the elastic member 7 is compressed, the interval between the flat plate portion 91 of the support member 9 and the thermal head 4 is shortened (interval C1 shown in FIG. 1), and when the elastic member 7 is extended, the support member 9 The distance between the flat plate portion 91 and the thermal head 4 becomes longer (the distance C2 shown in FIG. 2).

  In FIGS. 1 and 2, the deformation amount (compression amount and stretch amount) of the elastic member 7 is exaggerated for easy understanding of the operation principle, but it is not necessary to have such a large deformation amount. .

  One positioning lever (positioning member) 8 is attached to each end face of the thermal head 4 (that is, both end faces of the platen roller 3 in the rotation axis direction). The positioning lever 8 is attached to the thermal head 4 so as to be rotatable about a rotation shaft 8a. The rotation shaft 8 a is an axis parallel to the rotation axis of the platen roller 3.

  An engagement hole 93 with which one end of the positioning lever 8 can be engaged is formed at a substantially central portion of the flat plate portion 91 of the support member 9 described above. As shown in FIG. 1, when the distance between the thermal head 4 and the flat plate portion 91 of the support member 9 is close to C <b> 1, the positioning lever 8 is engaged with the engagement hole 93 of the thermal head 9. On the other hand, as shown in FIG. 2, the positioning lever 8 is disengaged from the engagement hole 93 of the flat plate portion 91 in a state where the distance between the thermal head 4 and the flat plate portion 91 of the support member 9 is widened to C2.

  A guide member 14 having an inclined surface is provided between the flat plate portion 91 and the leg portion 92 of the support member 9. When the distance between the thermal head 4 and the flat plate portion 91 of the support member 9 is narrowed from C2 to C1, the guide member 14 is in sliding contact with the end of the positioning lever 8 and engages the positioning lever 8 along the inclined surface. Guide to hole 93.

  An abutting member 11 that abuts against the positioning lever 8 in a state where the positioning lever 8 is engaged with the engaging hole 93 is provided on the upper surface (the surface facing the flat plate portion 91 side) of the thermal head 4.

  A coaxial ring 12 provided coaxially with the platen roller 3 is attached to both ends in the axial direction of the platen roller 3. The positioning lever 8 comes into contact with the outer peripheral surface of the coaxial ring 12 in a state where the positioning lever 8 is engaged with the engagement hole 93 described above.

  FIG. 4 shows an example of the mounting structure of the cam 10 and the support member 9 described above. The rotating shaft 10a of the cam 10 is attached to an attachment frame 95 fixed to the head arm 5, for example. The support member 9 is guided by a rail 96 provided on the mounting frame 95 so as to be movable toward and away from the platen roller 3, and is urged toward the cam 10 by a spring member (not shown). Yes. Note that the mounting structure shown in FIG. 4 is merely an example, and any structure that can ensure the contact between the cam 10 and the support member 9 may be used.

  Next, the positioning operation of the thermal head 4 in the present embodiment will be described. Before the start of printing, the head arm 5 is in the upper position shown in FIG. 2 and the thermal head 4 is spaced upward from the platen roller 3. In this state, the positioning lever 8 is not engaged with the engagement hole 93 of the support member 9 and is rotatable about the rotation shaft 8a. The elastic member 7 is stretched in the thickness direction, and the support member 9 supports the thermal head 4 via the elastic member 7. The distance between the flat plate portion 91 of the support member 9 and the thermal head 4 extends to C2.

  At the start of printing, the cam 10 is rotated and the head arm 5 is further lowered to the lower position shown in FIG. When the head arm 5 is lowered, the moving member 9 and the thermal head 4 are lowered, and the thermal head 4 is pressed against the platen roller 3. Further, as the cam 10 rotates, the support member 9 moves downward, and the distance between the flat plate portion 91 of the support member 9 and the thermal head 4 (which is already in pressure contact with the platen roller 3) is reduced to C1. Accordingly, the positioning lever 8 rotates along the guide member 14 of the support member 9 and engages with the engagement hole 93.

  The positioning lever 8 stands substantially vertically with respect to the support substrate of the thermal head 4 in a state where the positioning lever 8 is engaged with the engagement hole 93 of the support member 9, and is a contact member provided on the thermal head 4. 11 and a coaxial ring 12 attached to the platen roller 3. As a result, the thermal head 4 can be positioned in the front-rear direction, that is, in the tangential direction at the contact point (here, the apex) with the platen roller 3, and the heater line 4 a can be accurately pressed against the apex of the platen roller 3.

  The recording medium 1 and the ink ribbon 2 are sandwiched between the thermal head 4 and the platen roller 3, and the platen roller 3 is rotated so that each heating element constituting the heater line 4 a of the thermal head 4. Generates heat according to the image information, whereby an ink image is formed on the recording medium 1.

  After printing, the head arm 5 is raised and the thermal head 4 is separated upward from the platen roller 3. Further, the cam 10 rotates to release the urging force of the support member 9 and the elastic member 7 returns to the extended state, and the distance between the flat plate portion 91 of the support member 9 and the thermal head 4 is increased to C1. As a result, the positioning lever 8 is released from the engagement hole 93 and is rotatable.

  According to the thermal head positioning mechanism configured as described above, the thermal head 4 is moved by the action of the positioning means (positioning lever 8) and the regulating means (cam 10, support member 9, contact member 11 and guide member 14). It is positioned in the tangential direction at the contact point with the platen roller 3. Furthermore, the thermal head 4 is pressed against the platen roller 3 in a direction perpendicular to the tangential direction by the elastic member 7. As a result, a uniform and sufficient pressure contact force is applied between the thermal head 4 and the platen roller 3, and printing with an optimum density becomes possible.

  Here, the effect of this embodiment will be described in comparison with the prior art. FIG. 5 is a diagram schematically showing a pressure contact state between the thermal head 104 and the platen roller 103 in a conventional thermal printer. FIG. 6 is a diagram schematically showing a pressure contact state between the thermal head 4 and the platen roller 3 in the present embodiment.

  As shown in FIG. 5, in the conventional thermal head positioning mechanism, when the rotating shaft 106 (FIG. 8) of the head arm 105 is not on the tangent line at the contact C between the thermal head 104 and the platen roller 103, The pressing force Fa of the platen 104 on the platen roller 103 acts in a direction inclined with respect to the tangent at the contact C. As a result, the pressing force Fa of the thermal head 104 against the platen roller 103 is dispersed, and the force Fa1 for actually sandwiching the recording medium and the ink ribbon (not shown in FIG. 5) is smaller than the pressing force Fa. It becomes impossible to print at a high density.

  On the other hand, in the present embodiment described above, the thermal head 4 is positioned with high accuracy in the front-rear direction with respect to the apex of the platen roller 3 as shown in FIG. A pressure contact force Fa can be applied in the direction of heading. Therefore, a uniform and sufficient pressure contact force is applied between the thermal head 4 and the platen roller 3, and printing with an optimum density is possible.

  Further, in the present embodiment described above, as shown in FIG. 6B, even when the thermal head 4 is pressed against a point other than the apex of the platen roller 3, the thermal head 4 is connected to the contact C. Positioning in the tangential direction and press-contacting in a direction orthogonal to the tangential direction can be performed. As a result, the pressing force Fa of the thermal head 4 against the platen roller 3 acts in a direction perpendicular to the tangent at the contact C, and dispersion of the pressing force Fa can be prevented. Therefore, when the conveyance path of the recording medium 1 is changed, or when the position of the rotation shaft 6 of the head arm 5 is changed, the thermal head 4 may be configured to be in pressure contact with other than the apex of the platen roller 3. Printing with optimal density can be performed.

  Furthermore, in the present embodiment, even if the thickness of the recording medium 1 is arbitrarily changed, the thermal head 4 is in contact with the platen roller 3 because the difference in thickness is absorbed by the elastic deformation of the elastic member 7. Pressing is performed in a direction perpendicular to the tangent line in C, and printing with an optimum density can be performed.

  Further, in the prior art, if the position of the rotation shaft 106 of the head arm 105 (FIG. 8) is changed or the recording medium conveyance path is changed, the pressure contact force Fa as shown in FIG. It is difficult to freely change the layout, and as a result, there is a restriction that the position of the paper discharge port 13 cannot be changed, for example.

  On the other hand, in this embodiment, even when the thermal head 104 is pressed against a point other than the apex of the platen roller 103 (FIG. 6B), it is possible to perform printing with an optimum density. The layout can be freely changed. As a result, for example, the position of the sheet discharge outlet 13 can be changed as shown in FIG. 7, and the degree of freedom in design is increased. Also in this case, since it is not necessary to perform large part replacement or the like compared to before the layout change, the manufacturing cost of the thermal printer can be reduced.

  In the present embodiment, since the positioning lever 8 is in contact with the coaxial ring 12 of the platen roller 3, accurate positioning based on the position of the platen roller 3 becomes possible.

  Furthermore, in the present embodiment, the restricting means for restricting the position of the positioning lever 8 is constituted by the cam 10, the support member 9, the abutting member 11 and the guide member 14, so that the occupied space is small and the structure is simple. The thermal head 4 can be positioned with respect to the platen roller 3.

  In the above-described embodiment, the thermal sublimation type thermal printer in which the recording medium and the ink ribbon are sandwiched between the thermal head 4 and the platen roller 3 has been described. Other thermal printers may be used as long as they are provided.

It is a side view which shows the principal part of the thermal printer provided with the thermal head positioning mechanism which concerns on one embodiment of this invention. It is a side view which shows the principal part of the thermal printer provided with the thermal head positioning mechanism which concerns on one embodiment of this invention. 1 is a schematic diagram illustrating an example of an overall configuration of a thermal printer including a thermal head positioning mechanism according to an embodiment of the present invention. It is a side view which shows an example of the attachment structure of the cam and support member in the thermal head positioning mechanism which concerns on one embodiment of this invention. It is a schematic diagram for comparing and explaining the effect of the thermal head positioning mechanism according to the embodiment of the present invention. It is a schematic diagram for comparing and explaining the effect of the thermal head positioning mechanism according to the embodiment of the present invention. 1 is a schematic diagram illustrating a layout example of an overall configuration of a thermal printer including a thermal head positioning mechanism according to an embodiment of the present invention. It is a side view which shows the basic composition of the conventional thermal printer.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Recording medium, 2 Ink ribbon, 3 Platen roller, 4 Thermal head, 4a Heater line, 5 Head arm, 6 Rotating shaft, 7 Elastic member, 8 Positioning member, 9 Support member, 10 Cam member, 11 Contact member, 12 Coaxial ring, 14 Guide member, 91 Flat plate part, 92 Leg part, 93 Engagement hole.

Claims (6)

A thermal head positioning mechanism used in a thermal printer that sandwiches at least a recording medium between a thermal head and a platen roller to form an image on the recording medium,
A positioning member that is rotatably provided on the thermal head, and positions the thermal head in a tangential direction of the outer peripheral surface of the platen roller at a certain rotation position;
A thermal head positioning mechanism comprising: a regulating means for regulating the position of the positioning member at the rotational position in a state where at least a recording medium is sandwiched between the thermal head and the platen roller. The regulating means is
A support member that supports the thermal head via an elastic member;
A drive member for moving the support member in a direction approaching the platen roller;
A guide member for guiding the positioning member to the rotational position when the drive member moves the support member in a direction approaching the platen roller;
The thermal head positioning mechanism according to claim 1, further comprising: an abutting member that abuts on the positioning member when the positioning member reaches the rotation position.   The thermal head positioning mechanism according to claim 2, wherein the driving member is a cam attached to an arm that supports the thermal head.   4. The thermal head positioning mechanism according to claim 1, wherein the positioning member is in contact with a ring provided coaxially with the platen roller at the rotation position. 5.   A thermal printer comprising the thermal head positioning mechanism according to any one of claims 1 to 4.   The thermal printer according to claim 5, wherein a direction in which the thermal head faces the outer peripheral surface of the platen roller can be arbitrarily set.

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