JP2010076136A - Thermal head pressurizing mechanism - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermal head pressurizing mechanism applying head pressure on paper of optional width, symmetrically in the width direction. <P>SOLUTION: The thermal head pressurizing mechanism for pressurizing a thermal head 5 against the paper 7 includes: a shaft 1 which is disposed while taking the width direction of the paper 7 as the axial direction, and has a plurality of cams 2a to 2d; and springs 3a to 3d each disposed between each of the cams 2a to 2d and the thermal head 5. The cam 2 coming in contact with the spring 3 holds the spring 3 between the thermal head 5 and the cam 2, then, the thermal head 5 is energized toward the paper 7, and the positions of the cams 2 coming in contact with the springs 3 and the number of cams 2 coming in contact with the springs 3 are variable in accordance with the rotating angle of the shaft 1. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a mechanism for pressing a thermal head against a sheet, and more particularly to a mechanism for pressing a thermal header that can handle a plurality of sheets having different widths.

  The thermal printer applies pressure to the thermal head to convey the paper and presses it against the platen roller.

  If the pressure at this time is constant, the pressing force per unit length received by the paper increases as the paper width decreases. For this reason, when thin paper is used, the paper may sink into the platen roller, and the thermal head and the platen roller may come into contact with each other and damage the platen roller.

  Further, as in the invention described in Patent Document 1, it is possible to set the head pressure low by a cam, but the pressure distribution is constant, and when a wide head is used, the head is bent. Because of this, it is impossible to apply pressure properly to narrow paper.

Patent Document 2 describes a head pressure adjusting device for a thermal printer that can adjust the head pressure and the head pressing portion in accordance with the width of the printing paper.
JP 2001-180071 A JP 2008-132683 A

  However, since the invention described in Patent Document 2 has a structure in which the paper width is set based on the fixed guide piece, the paper does not pass through the center of the platen roller. Therefore, when the deformation of the thermal head is taken into consideration, as shown in FIG. 5, the sheet is not uniformly sandwiched between the thermal head and the platen roller. That is, the head pressure is asymmetric in the paper width direction. Such a difference in head pressure may not be a problem depending on the paper to be used, but may not be ignored when using a thin and weak paper.

  SUMMARY An advantage of some aspects of the invention is that it provides a thermal head pressing mechanism capable of applying head pressure symmetrically in the width direction to a sheet having an arbitrary width.

  In order to achieve the above object, the present invention provides a thermal head pressing mechanism that presses a thermal head against a sheet, the shaft having a plurality of cams arranged in the width direction of the sheet as an axial direction, and each cam An elastic member disposed between the thermal head and the thermal head, and a cam contacting the elastic member urges the thermal head toward the paper side by sandwiching the elastic member between the thermal head and the thermal head. It is an object of the present invention to provide a thermal head pressing mechanism characterized in that the position and the number of cams in contact with the elastic member are variable according to the rotation angle of the shaft.

  According to the present invention, it is possible to provide a thermal head pressing mechanism capable of applying a head pressure symmetrically in the width direction to a sheet having an arbitrary width.

A preferred embodiment of the present invention will be described. FIG. 1 shows a configuration of a thermal head pressing mechanism according to the present embodiment. The thermal head pressing mechanism includes a shaft 1, a cam 2 (2 a to 2 d), a spring 3 (3 a to 3 d), a rotation angle detection piece 4, a thermal head 5, and a platen roller 6.
A plurality of cams 2a to 2d are attached to the shaft 1 and can be manually rotated. Of the cam 2, the cams 2a, 2d closer to the end have the first shape shown in FIG. 2, and the cams 2b, 2c closer to the center have the second shape shown in FIG. The spring 3 is fixed on the opposite side of the thermal head 5 from the side facing the platen roller 6. The rotation detection piece 4 is a member for detecting the rotation angle of the shaft 1 and includes a mark (slit or the like) whose position changes as the shaft 1 rotates. The thermal head 5 heats the paper 7 sandwiched between the platen roller 6 and prints characters or the like. The platen roller 6 supplies and discharges the paper 7 to and from the printing unit of the thermal head 5.

  FIG. 1 shows a state in which a wide sheet 7 covering almost the entire width of the platen roller 6 is used. In this state, all of the cams 2a to 2d abut against the springs 3a to 3d and compress them. Accordingly, the platen roller 6 is subjected to elastic forces generated by the compressed springs 3a to 3d at a total of four places where the springs 3a to 3d are installed.

  FIG. 3 shows a state in which a narrow paper 7 corresponding to substantially half the width of the platen roller 6 is used. In this state, the shaft 1 is rotated by 90 ° from the state shown in FIG. The rotation angle of the shaft 1 is determined by a mark provided on the rotation angle detection piece 4. In this state, the cams 2b and 2c contact and compress the springs 3b and 3c, but the cams 2a and 2d do not contact the springs 3a and 3d. Therefore, the elastic force generated by the compressed springs 3b and 3c acts on the platen roller 6 at a total of two places where the springs 3b and 3c are installed.

  That is, since only the spring 3 corresponding to the number of the cams 2 in contact with the thermal head 5 biases the thermal head 5, the head pressure can be kept constant regardless of the width of the paper.

  Here, the description has been made on the assumption that the user manually performs the operation of changing the number and position of the cams 2 that rotate the shaft 1 and make contact with the thermal head 5. good. As an example of the configuration for automatic operation, a sensor for detecting the width of the sheet 7 is provided, and the rotation amount of the shaft 1 may be controlled by a stepping motor. However, it is not limited to this configuration.

  Thus, the thermal head pressing mechanism according to the present embodiment can press the thermal head with a constant pressure regardless of the width of the paper.

In addition, the said embodiment is an example of suitable implementation of this invention, and this invention is not limited to this.
For example, in the above-described embodiment, there are two cases where the number and positions of the cams that contact the thermal head are two, but three or more may be selected.
If the number and position of contact with the thermal head are variable, the number and position of the cams are arbitrary.
In addition, when a paper that does not need to pass through the center of the thermal head is applied, as shown in FIG. 4, the cam may be biased to one side of the thermal head and contact the thermal head.
As described above, the present invention can be variously modified.

It is a figure which shows the structure of the thermal head press mechanism which concerns on suitable embodiment of this invention. It is a figure which shows the shape of a cam. It is a figure which shows the structure of the thermal head press mechanism which concerns on suitable embodiment of this invention. It is a figure which shows the structure of the thermal head press mechanism which concerns on suitable embodiment of this invention. In the invention described in Patent Document 2, it is a diagram illustrating a state in which a sheet is non-uniformly sandwiched between a thermal head and a platen roller.

Explanation of symbols

1 Shaft 2 Cam 3 Spring 4 Rotation Angle Detection Piece 5 Thermal Head 6 Platen Roller

Claims (4)

A thermal head pressing mechanism that presses the thermal head against the paper,
A shaft that is arranged with the width direction of the paper as an axial direction and includes a plurality of cams;
An elastic member disposed between each cam and the thermal head;
The cam abutting on the elastic member urges the thermal head toward the paper side by sandwiching the elastic member with the thermal head,
The thermal head pressing mechanism, wherein the position and the number of cams in contact with the elastic member are variable according to the rotation angle of the shaft.   The thermal head pressing mechanism according to claim 1, wherein the cam contacts the elastic member symmetrically with respect to a width direction of the sheet with respect to a center of the thermal head.   3. The thermal head pressing mechanism according to claim 1, wherein a cam closer to the center of the thermal head is in contact with the elastic member in a wider range of the rotation angle of the shaft. Paper width means for detecting the paper width;
4. The thermal head pressing mechanism according to claim 1, further comprising a unit that changes a rotation angle of the shaft according to a detection result of the paper width detection unit. 5.

Images