JPH05270019A - Line thermal printer - Google Patents

Abstract

PURPOSE:To prevent unevenness in density of printing and inclination of printed characters in a line thermal printer and reduce costs of members. CONSTITUTION:By providing an allowance for a rotation axis of a thermal head 2, when a platen roller 1 is pressed, in the adjustment in a direction normal to the axis of the platen roller, differences in left and right pressures due to dispersion of a spring 6 are absorbed by the allowance to eliminate the need for adjustment. Further, the vertical dispersion is absorbed by vertically moving an adjustment member 5 so that unevenness in density of printing in left and right directions is prevented and inclination of printed characters is avoided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a line thermal printer, and more particularly to a pressure adjusting mechanism for a line thermal printer used in a handy terminal (POT).

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 3, this type of pressure adjusting mechanism presses the platen roller 1 around the rotation axis of the bracket holding the thermal head 2 to bring the above-mentioned bracket into contact with the thermal head. A fulcrum is provided at the end in the direction orthogonal to the surface, and an eccentric shaft is sandwiched at the other end, and the direction perpendicular to the platen axis is adjusted so that the platen roller and the thermal head uniformly press the eccentric shaft.

[0003]

Since the pressure adjusting mechanism of the conventional line thermal printer described above adjusts only in the direction orthogonal to the platen shaft, as shown in an extreme state in FIG. If the rotary shaft of the thermal head is vertically displaced, there is a drawback in that the printing quality is degraded, such as uneven density due to one-sided contact and the printing is inclined with respect to the recording paper.

Further, if the variation in the positional relationship between the rotary shaft of the thermal head and the platen shaft is eliminated, there is a problem in that the cost of the members becomes high.

[0005]

A line thermal printer of the present invention includes a platen roller for feeding a recording sheet, a thermal head arranged at a position facing the platen roller for printing print data, and a thermal head for the thermal head. Slide pins fixed to the left and right in the platen axis direction,
An adjusting member that regulates the sliding locus of the slide pin and moves up and down, a spring that presses the thermal head and the platen roller in the axial center direction, and the thermal head that is arranged parallel to the platen shaft center and fixes the thermal head And a shaft that operates.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings.

FIG. 1 is a perspective view showing an embodiment of the present invention. FIG. 2 is a side view of the line thermal printer of FIG. 1 viewed from the direction A.

The line thermal printer shown in FIG. 1 comprises a platen roller 1 for feeding a recording paper (not shown), and a thermal head 2 arranged at a position facing the platen roller 1 for printing print data. The thermal head 2 has slide pins 3 fixed to both ends of the platen roller 1 in the axial direction.
Is supported by a shaft 4 having an axis center vertically below a contact surface that can be pressed in the platen axis center and the axis direction. Further, a vertically movable movable adjustment member 5 that abuts the slide pin 3 and determines the sliding direction in the circumferential direction around the shaft 4 is attached to one side of the slide pin 3 on a frame (not shown). Yes, the other side of the slide pin 3 is fixed. The spring 6 presses the thermal head 2 with a torsion spring, and as a result, presses against the platen roller 1.

Next, the operation of this embodiment will be described with reference to FIG.

A play (gap around the shaft 4) is provided between the shaft 4 and the rotary shaft of the thermal head 2. This play is set so that it can be absorbed by considering the worst dimension tolerance due to the axial relationship between the platen roller shaft and the shaft 4. When the spring 6 presses the thermal head 2 against the platen roller 1, the thermal head 2 can be freely displaced within the play, so that the platen roller 1 can be pressed evenly left and right. This eliminates the need for adjustment in the orthogonal direction.

Next, in order to adjust in the vertical direction, the adjustment range of the adjusting member 5 is determined in advance, and the adjusting member 5 is moved in the vertical direction while actually observing the density unevenness and the print inclination. By fixing at the position where the printing inclination is eliminated, the slide pin 3 moves up and down, and eventually the thermal head 2 is displaced, so that the printing quality can be improved.

[0012]

As described above, according to the present invention, the adjustment in the direction orthogonal to the platen roller axis is not necessary and the adjustment in the vertical direction is made. This has the effect of improving the printing quality. In addition, the cost of the member can be reduced by the adjustment without making the dimensional accuracy of the member severe.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of the present invention.

FIG. 2 is a side view of the line thermal printer of FIG. 1 viewed from the A direction.

FIG. 3 is a perspective view of a conventional example.

FIG. 4 is a perspective view showing the problem of the conventional example in an extreme state.

[Explanation of symbols]

 1 Platen roller 2 Thermal head 3 Slide pin 4 Shaft 5 Adjusting member 6 Spring

Claims (1)

[Claims] 1. A platen roller for feeding a recording sheet, a thermal head arranged at a position facing the platen roller for printing print data, and slide pins fixed to the left and right of the thermal head in the platen axis direction.
An adjusting member that regulates the sliding locus of the slide pin and moves up and down, a spring that presses the thermal head and the platen roller in the axial center direction, and the thermal head that is arranged parallel to the platen shaft center and fixes the thermal head A line thermal printer, comprising: