JPH05155100A - Mechanism for retaining thermal head - Google Patents

Abstract

PURPOSE:To improve the parallelism, positioning precision and pressing force uniformity, etc., of the head and platen by a method wherein the thermal head is retained at a certain degree of freedom in the pressing direction and received image carrying direction, and the relative locations of the head and platen are determined using a positioning plate. CONSTITUTION:A thermal head 1 is fixed on a head attaching frame 2 by a reference hole 10, and a positioning plate 16 is attached to the head attaching frame 2 by a positioning pin 14. The head attaching frame 2 is supported by a hinge pin 3 through a receiving seat 13 which is formed of a material with lubricant property such as polyacetal, etc. A slot 6, in which the hinge pin 13 can move within a specified range in the vertical and lateral directions, is provided in the receiving seat 13. In addition, a preload is added by a pressing spring 9 in order to bring the positioning plate 16 and a bearing 15 into contact assuredly. By the above mentioned constitution, the parallelism, positioning precision and pressing force uniformity of the head and platen can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal head holding mechanism for a thermal transfer type image output apparatus including a thermal head and a platen roller, such as a copying machine, a facsimile, a word processor, a printer and the like.

[0002]

2. Description of the Related Art A conventional thermal head holding mechanism is shown in FIG.
As shown in FIG. 3, the head heater frame 2 having a boss (not shown) fitted into the reference hole 10 provided on the back surface of the thermal head 1 has a platen roller on which the heating resistor arrangement line of the thermal head 1 is arranged. The U-groove positioning portion 7 is designed so as to coincide with the axis of 4. The head mounting frame 2 is provided with an elongated hole portion 6 so as to have a slight degree of freedom in the left-right direction, and at the same time, can be rotated around the hinge pin 3 so that the head can be retracted. There is.

Further, in order to secure the positions of the heat generating resistor and the platen 4, a mechanism is also provided which allows the inner side surface 11 of the U-groove positioning portion 7 to come into contact with the platen shaft 8 without a gap by the preload spring 9. There is also. For example, Japanese Patent Publication Sho 63-
No. 7157, Japanese Examined Patent Publication No. 3-35111, Japanese Unexamined Patent Publication No. 2-295757, Japanese Unexamined Patent Publication No. 3-57674, Japanese Unexamined Patent Publication No. 3-75175, and Japanese Utility Model Laid-Open No. 58-863.
Such a structure is disclosed in Japanese Patent Laid-Open No. 60, Japanese Utility Model Laid-Open No. 62-175925, Japanese Utility Model Laid-Open No. 63-194730, Japanese Utility Model Laid-Open No. 1-30239 and Japanese Utility Model Laid-Open No. 1-175826.

[0004]

However, the holding mechanism of this system has the following problems. When the axis of the platen roller 4 and the axis of the two hinge pins 3 are not parallel, the thermal head 1 is held tilted with respect to the platen roller 4, and the pressing force distribution in the longitudinal direction of the head is made uniform. This is not possible, and density unevenness and blurring occur and print quality deteriorates. When the sliding resistance between the end surface of the elongated hole portion 6 of the head mounting frame 2 and the hinge pin 3 is large, the contact between the inner side surface 11 of the U-groove positioning portion 7 and the platen shaft is not reproducible and the positioning mechanism is reliable. Will not work.

Therefore, the present invention has been made by paying attention to the above points, and includes a positioning mechanism for a thermal head,
The thermal head and the mechanism that absorbs the parallel displacement of the platen are combined, and even if the platen or the head is displaced due to vibration or shock during printing, the thermal relationship between the head and the platen can always be maintained. It is an object to provide a head holding mechanism.

[0006]

In order to solve the above problems, according to the present invention, a head mounting frame for fixing a thermal head and a platen roller are rotated around a rotation supporting shaft independently of the platen roller. The vertical distance between the bearing, which can be mounted on both ends of the platen roller and the outer ring of the bearing, and the contact surface and the line where the heating resistor of the thermal head is arranged is the distance from the center of the bearing to the contact surface. The head positioning plates attached to both ends of the head mounting frame so that the reference surfaces are parallel to each other and the reference planes are parallel to the outer frame of the thermal transfer image output device substantially parallel to the platen roller. Two hinge pins attached are provided, and the width of the hinge pin is about 1.2 to 1.5 times the outer diameter of the hinge pin and the dimension in the longitudinal direction is the hinge pin. The seat of the long hole of about 1.5 to 2 times is molded by lubricious material such as polyacetal bored in outer diameter fixed to the rear ends of the head mounting frame,
A hinge pin is passed through the elongated hole of the seat to be fixed to the outer frame, and in order to bring the positioning plate into contact with the bearing, a spring is locked between the head mounting frame and the outer frame.

[0007]

With the above-described structure, the head mounting frame is held movably in the vertical and horizontal directions within a certain range, and the positioning plate is always in contact with the bearings in the horizontal direction during printing. The relative position of the resistor arrangement line and the platen is kept constant.

Further, the vertical direction is regulated by the platen, and the uniformity of the pressing force of the head on the platen is ensured. Therefore, the head positioning mechanism and the head platen parallel support mechanism are combined.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a side view showing an embodiment of the present invention, and FIG. 3 is a front view showing an embodiment of the present invention. In FIG. 1, the head mounting frame 2 has a boss (not shown) that fits into a reference hole 10 provided on the back surface of the thermal head 1.
The positioning pin 14 for restricting the mounting position of the positioning plate 16 is provided so as to strictly control the mutual positional relationship. Then, the thermal head 1 passes through the reference hole 10
It is fixed to the bottom surface of the head mounting frame 2 by screwing or the like, and positioning plates 16 are fixed to both side surfaces of the head mounting frame 2 via positioning pins 14, and the positioning reference surface 12 of the positioning plate 16 is a bearing. It is in contact with 15. This bearing 15 is, as shown in FIG.
The platen roller 4 is pivotally attached to both ends.

Further, receiving seats 13 having elongated holes 6 are fixed to both sides of the rear end of the head mounting frame. The seat 13 is molded using a resin having excellent slidability such as polyacetal or oil-containing polyacetal. In particular, the dimension of the elongated hole is, as shown in FIG. 4, the diameter d of the hinge pin 3.
In contrast, the width is 1.2 to 1.5d and the length is 1.5 to 2d,
There is play in the vertical and horizontal directions. Further, since the head mounting frame 2 is preloaded in the printing direction by the preload spring 9, the positioning reference plane 1 of the positioning plate 16 is used.
The spring force acts in a direction in which the bearing 2 and the bearing 15 are always in contact with each other.

With the above construction, the positioning plate 16 always contacts the outer ring of the bearing 15 during printing by the action of the spring force of the preload spring 9 and the frictional force of the thermal head 1 and the ink sheet (not shown). Positioning plate 1 due to contact
Positioning reference surface 1 which is a contact surface between the bearing 6 and the bearing 15.
Since the vertical distance from 2 to the placement line of the heating resistor is always constant, even if the platen roller 4 shifts in the horizontal direction due to vibration of the device driving source, for example, at the time of shipping or head replacement, the positioning plate 16 is The print position of the thermal head 1 can be aligned with the normal position of the thermal head 1 and the platen roller 4 in order to move the thermal head 1 in unison with the above. Even if occurs, the thermal head 1 and the platen 4 can perform the printing operation while maintaining an appropriate positional relationship.

Further, the distances L _{1 and} L ₂ between the shaft center 17 of the platen roller 4 and the center lines 18 and 19 of the hinge pins 3 are error ε (due to the influence of hole position tolerance and mounting tolerance as shown in FIG. ≠ 0), but if the play between the seat 13 and the hinge pin 3 is 0.2d to 0.5d larger than this ε, the thermal head 1 will be parallel to the platen 4 as shown in FIG. As a result, a uniform pressing force can be obtained between the thermal head 1 and the platen roller 4 without adjustment.

[0013]

As described above, according to the present invention, it is not necessary to adjust the relative positions of the thermal head and the platen, and even if the thermal head and the platen are displaced due to the vibration of the apparatus, the thermal head There is an effect that the printing position and the platen can always be printed while maintaining an appropriate positional relationship.

Further, even if the processing accuracy and the mounting accuracy of the components are somewhat poor, the thermal head and the platen roller are automatically aligned to keep the pressing roller in parallel with each other so that the pressing force is evenly distributed and high-quality printing is performed for a long time. It also has the effect of making it possible.

[Brief description of drawings]

FIG. 1 is a side view showing an embodiment according to the present invention.

FIG. 2 is a side view showing a conventional example.

FIG. 3 is a front view showing an embodiment according to the present invention.

FIG. 4 is a dimensional drawing of a seat according to the present invention.

[Explanation of symbols]

 1 Thermal Head 2 Head Mounting Frame 3 Hinge Pin 4 Platen 9 Preload Spring 10 Reference Hole 12 Positioning Reference Surface 13 Seat 15 Bearing 16 Positioning Plate

Claims (1)

[Claims] 1. A thermal transfer image output device including a thermal head and a platen roller, wherein the head mounting frame for fixing the thermal head and the platen roller can be rotated independently of the platen roller around a rotation supporting shaft. The bearing vertically attached to both shaft ends of the platen roller and the outer ring of the bearing are in contact with each other, and the vertical distance between the contact surface and the arrangement line of the heating resistor of the thermal head is the contact from the center of the bearing. Holding a thermal head having a head positioning plate attached to both ends of the head mounting frame so that the shape is regulated so as to be equal to the distance to the surface, and the reference surfaces are parallel to each other. mechanism.