JP2840059B2 - Thermal printer - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal printer for printing on paper by a thermal head. 2. Description of the Related Art Conventionally, as shown in FIGS. 6 and 7, a head support 3 to which a thermal head 2 in contact with a platen 1 is fixed and a head pressing plate 30 are rotatable about a support shaft 4. The shaft 31 is slidably fitted on both sides of the head pressing plate 30, the retaining ring 32 is fastened to both ends of the shaft 31 and the washer 33 is fitted, and the lower washer 33 and the head are fitted. The spring 34 is fitted to each of the shafts 31 while being positioned between the pressing plate 30 and the cam 6 is fixedly fitted to the cam shaft 5 parallel to the support shaft 4, and is formed on the outer periphery of the cam 6. Pressing part 7
Presses down the head pressing plate 30 to apply the pressure of the compressed spring 34 to the head support 3, thereby causing the thermal head 2 to resiliently contact the recording medium 10 on the platen 1 as shown in FIG. By retracting the cam 6 from the head pressing plate 30, the thermal head 2 is separated from the platen 1, and at this time, the washer 3 on the shaft 31 is removed.
There is a thermal head holding device that prevents the head pressing plate 30 from coming off from the shaft 31 by 3. [0003] In the conventional apparatus, the thermal head 2 is pressed against the platen 1 by the pressure of a spring 34. A pressing plate 30 is required, and a plurality of shafts 3
1 and a snap ring 32 and a washer 33,
The number of parts increases and the structure becomes complicated. [0004] A platen, a head support rotating about a support shaft, a thermal head fixed to the head support and opposed to the platen, and a base portion are provided.
The free end is fixed to the head support near the spindle.
A leaf spring contacting the head support, and a portion where the thermal head is in contact with the platen at a radius centered on a rotation axis parallel to a rotation axis of the head support.
At the position on the back side of the thermal head facing the
Spring provided with cams which push portion for pressing is formed with. Accordingly, the thermal head is pressed against the platen by transmitting the pressure of the cam from the leaf spring to the head support, but the number of parts is reduced by directly supporting the leaf spring on the head support. achieving simplification, also it can be made uniform contact pressure to the platen at the ends of the thermal head, in particular, pressing by the cam
A thermal head with a leaf spring whose pressure point is in contact with the platen
At the position on the back side of the thermal head facing the portion.
Therefore, even if there is a shape error or assembly error of the leaf spring or cam,
Press the thermal head against the platen with a relatively constant force.
Pressure can be performed . Further, by forming a plurality of pressing portions having different radii from the rotation axis on the cam, a pressing portion for pressing the leaf spring is selected in accordance with the thickness of the recording medium, so that the cam can be pressed against the platen of the thermal head. Adjust the pressing force. FIG. 1 shows a first embodiment of the present invention.
A description will be given based on FIG. 6 and 7 are denoted by the same reference numerals, and description thereof is omitted (the same applies hereinafter). A head support 3 to which the thermal head 2 is fixed is rotatably held by a support shaft 4 and a cam shaft 5
Is fixed to a cam 6 having a pressing portion 7 on the outer periphery.
A base 9 of a leaf spring 8 that contacts the pressing portion 7 of the cam 6 is spot-welded to the upper surface of the head support 3. The support shaft 4 and the cam shaft 5 are held on both sides of the head frame 11 as shown in FIG. Springs 12a are stretched on both sides of the head frame 11 and both sides of the head support 3. Further, a lever 13a is fixed to an end of the cam shaft 5. In such a configuration, when the pressure of the cam 6 is applied to the center of the leaf spring 8, the head support 3
The thermal head 2 pivots downward about the platen 1
The upper recording medium 10 is pressed. At this time, the entire width of one end of the leaf spring 8 is fixed to the head support 3, and the leaf spring 8 is pressed by the cam 6 so that the pressure contact force on the platen 1 at both ends of the thermal head 2 is made substantially equal. As a result, the left and right print qualities can be made the same. When the recording medium 10 is set, the cam 6 is retracted from the head support 3 as shown in FIG. Thus, the head support 3 and the thermal head 2 are separated from the platen 1 by the force of the spring 12a. As described above, by directly fixing the leaf spring 8 for transmitting the pressure of the cam 6 to the head support 3 to the head support 3, the number of components can be reduced and the structure can be simplified. . Next, a second embodiment of the present invention will be described with reference to FIG.
A description will be given based on FIG. In this embodiment, two pressing portions 1 having different radii from the cam shaft 5 are provided on the outer periphery of the cam 6.
2 and 13 are formed. Therefore, as shown in FIG. 4, when printing on a label 14 affixed to a backing paper, the label 14 is thin and soft, such as about 0.15 mm. Press the thermal head 2
Can be set weaker against the label 14. Also, as shown in FIG. 5, when printing on the tag paper 15, the tag paper 15
Since the plate spring 8 is pressed by the pressing portion 13 having a large radius because it is thick and hard such as 5 mm, the tag paper 15 of the thermal head 2 is pressed.
Can be set relatively high. Therefore, the pressure contact force of the thermal head 2 can be set to an optimum value depending on the printing medium, whereby the printing quality can be improved. conventionally,
Since the pressing force is set in accordance with the thick tag paper 15 so that the pressing force of the thermal head 2 is not insufficient, when the thin label 14 is used, the pressing force is too strong and the life of the thermal head 2 is shortened. However, in this embodiment, the life of the thermal head 2 can be extended. Since the present invention is constructed as described above, the thermal head is pressed against the platen as a structure for transmitting the pressure of the cam from the leaf spring to the head support. by fixing the can be simplified in structure by reducing the number of parts, also, the thermal
Uniform pressure contact with the platen at both ends of the head
In particular, the point pressed by the cam is
Wherein the round head opposes the portion in contact with the platen
Because it is located on the back side of the thermal head,
With a relatively constant force, even if there is a shape error or assembly error
The thermal head can be pressed against Latin
Furthermore, by forming a plurality of pressing portions having different radii from the rotation axis on the cam, a pressing portion for pressing the leaf spring is selected according to the thickness of the recording medium, and the pressure contact force of the thermal head is adjusted. As a result, it is possible to improve the print quality and extend the life of the thermal head.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view of a printing state showing a first embodiment of the present invention. FIG. 2 is a side view showing a state where a thermal head is separated from a platen. FIG. 3 is an exploded perspective view thereof. FIG. 4 is a side view showing a second embodiment of the present invention and showing a state of printing on a thin recording medium. FIG. 5 is a side view showing a state in which printing is performed on a thick recording medium. FIG. 6 is a side view showing a printing state of a conventional example. FIG. 7 is a side view showing a state where a thermal head is separated from a platen of a conventional example. [Description of Signs] 1 platen 2 thermal head 3 head support 4 support shaft 6 cam 7 pressing unit 8 leaf spring 12 pressing unit 13 pressing unit

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B41J 25/308-25/316 B41J 2/32

Claims (1)

(57) [Claims] Platen and a head support member which rotates the support shaft as a fulcrum, a thermal head opposed to the platen is fixed to the head support, the f in the vicinity of the base is the supporting shaft
Free end abuts on the head support
A leaf spring which, said located radially on around the head support of the pivot axis parallel to the rotation axis Samaruhe'
The thermal element facing the part where the plate contacts the platen
Thermal printer, wherein said leaf spring cam and good Li Cheng the pressing portion for pressing is formed at a position on the back side of the head. 2. Platen and a head support member which rotates the support shaft as a fulcrum, a thermal head opposed to the platen is fixed to the head support, the f in the vicinity of the base is the supporting shaft
Free end abuts on the head support
And a thermistor positioned on different radii about a rotation axis parallel to a rotation axis of the head support.
The head facing the portion where the head contacts the platen.
The leaf spring at the position on the back side of the
A cam having a plurality of pressing portions selectively pressed by pressure
Thermal printer, characterized in that the I and Li Cheng.