JPS61229578A - Platen mechanism for serial thermal printer - Google Patents

Abstract

PURPOSE:To ensure that a printing surface of a thermal recording paper is constantly maintained in parallel to a serial thermal head and pressed with a uniform pressure, by a construction wherein a rotary shaft of a platen can be turned relatively to a platen support around the same axis as that for a serial thermal head and with the same radius as that for the head so that the head and the platen are brought into contact with each other constantly with uniform pressure. CONSTITUTION:An engaging large diameter part 3a of an end part of the rotary shaft 3 of the platen 4 is engaged in a turning guide groove 9a, and is moved along the groove around the same axis as that for the thermal head 1 with the same radius. Therefore, the relative positions of both of them at the pressure contact part are not changed. The pressure with which the thermal head 1 and the platen 4 are pressed against each other which pressure is generated by forces of both a compression spring 5 and a tension spring 6 remains substantially uniform even when the pressure contact position is changed due to a change of a printing position (the position of the head 1) or deformation of the members, and thermal recording with uniform printed density and favorable quality can be achieved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention provides a serial thermal head that is
The present invention relates to a platen mechanism for a serial thermal printer, which is pressed with equal pressure across a head facing member with a constant Cl't, and can obtain good print quality with uniform print density over the entire paper surface.

[Background of the Invention J] In a conventional serial thermal printer, 1. As shown in FIG. 2, serial number 1 is provided with a heating element at the end of the rotating arm that moves in the serial printing direction. The head 1 is configured to be pressed against the platen 2 by a compression spring 5, and the thermosensitive paper (not shown) is connected to the head 1 and the platen 2.
The area to be printed on the thermal recording paper is sequentially heated by the heating element at the end of the rotating arm of the serial thermal head 1 moving in the serial printing direction, so that printing is performed. It was crawling.

However, in the above-mentioned conventional structure, even if each member is machined with extreme precision using materials with little deformation or bending, the opposing surfaces of the real thermal head 1 and the plug 72 are
ICL so that it can be paralleled correctly anytime and anywhere in the pressure welding state! It was extremely difficult to create. If they are not properly parallel, the print density will be darker in some parts of one character and lighter in other parts. In order to avoid such a situation, the platen 2 was made of a material with higher elasticity than rubber, but this made it possible to ensure that the head and platen were in contact with each other everywhere. What I do is □, but it is not possible to keep the contact pressure between the two constant, and it is not possible to prevent uneven density from occurring within one character or one line of characters.

For this reason, as disclosed in Japanese Patent Application Laid-Open No. 58-56877, a structure as shown in FIG. 5 in which one platen is swingably supported by a platen support via rotating shafts at both ends of the platen is proposed. was suggested.

In FIG. 3, numeral 4 indicates a swingable platen, and numeral 3 indicates the rotation axis of the platen. However, this proposal does not take into account the flatness accuracy of the platen surface or changes in the recording state due to changes in shape due to bending, and there are some issues with regard to the alignment of the Shika Al thermal head and the platen. That was enough.

Figure 4 is a perspective view of the serial thermal printer, in which the serial thermal head 1 moves at high speed from side to side while pressing against the platen surface 7.
-w A/ 11 Takumi, ν. .

The pressure welding line is easy to twist and easy to twist. The m-type platen improves the accuracy of the m-percentage and eliminates the negative effects of torsion.'
j) The platen is bent, as shown by the broken line □ in Fig. 4, and as a result, it hits again.

n5's ``pressure is - wa'', uneven J print density within one line,

” will occur.

[Objective of the Invention] The purpose of the present invention is to expand the printing surface of the thermal recording paper sandwiched between the serial thermal e-head and the platen so that the printed surface of the thermal recording paper is serially parallel to the thermal head. Another object of the present invention is to provide a platen mechanism for a serial thermal printer that can be pressed with a uniform pressure force and can produce high-quality printing without uneven density.

[Summary of the invention]

In order to achieve the above purpose, the present shoulder not only supports the platen in a swinging manner, but also supports the hemorrhoid supporting the platen (
The platen rotation axis is carved in the platen support body □ so that it can be rotated 9 times around the circumference of the same axis as the 7-server □ marhead with the same □-゛ radius. Engage the platen rotation shaft with the guide groove, support the platen on the platen support □, pull the platen rotation shaft toward the thermal head by the tension spring, and then The inner magnetic head □ is in a state where it is rotated, and the pressure between the serial thermal head and the platen is always evenly distributed using a compression spring. It is pushed towards the platen, but the platen mechanism is pulled towards the thermal head by the tension spring, so that the 'thermal□ head and platen pressure contact position'
This is because the force of the compression spring is strong in response to movement and the force of the tension spring is weak in the state of movement, or vice versa. [Embodiment of the Invention] Fig. 1 is a side view of essential parts of an embodiment of the present invention, where 1 is a serial thermal head, and 5 m is an engagement of the end of the platen rotating shaft 3, as can be seen from Fig. 4. Large amount.

Diameter part, 4 is swingable grating, 5 is compression/spring, 6 company tension spring, 9 is platen support, 9m is platen support #
A rotation guide groove is carved in the rotation guide groove Kf8 for engagement at the end of the platen rotating shaft. Zhou l゛【
゛It moves on the same radius, therefore, the thermal
Although both the platen 4 and the platen 4 move, the relative positions of the two at the pressure points □ do not change. Also, from Figure 1, the compression spring 5 stretches and the pushing force weakens. In the state where the spring is floating, the tension spring 6 is stretched and the pulling force is strong, and on the other hand, when the compression spring 5 is compressed and the pushing force is not strong, It is important to note that the tension spring 6 returns and contracts, weakening the pulling force.
The pressure contact between the thermal head 1 and the platen 4, which is caused by the force of both the compression spring 5 and the tension spring 6, is such that the pressure contact position is the printing position (serial/summar head position). ) or deformation of parts, etc., the t grain is equalized, and a thermal recorder with uniform printing density can be obtained.

In addition, unlike when using a rubber platen, there is no need to increase the contact force between the thermal head and the platen, so less motor power is required to feed the paper, and there is less wear and tear on the thermal head. It becomes less.

〔Effect of the invention〕

As explained above, with the single-print fRI/c, it is possible to obtain high-quality printing with extremely high print density within one character and one printing line, as well as reduce paper feeding power and thermal・
Secondary effects such as reduced head wear can also be obtained.

4, WKe) flll single & aE11 Figure 1 is a side view of the main part of an embodiment of the present invention, Figure 1ll1 is a side view of the main part of a conventional fixed platen type serial thermal printer, and 3rd @ is a side view of the main part of a conventional fixed platen type serial thermal printer. FIG. 4 is a perspective view of a conventional swinging platen type serial thermal printer.

1. Serial thermal head, 2. Fixed blade platen, 3. Platen rotation axis.
5 &...Large diameter part for retaining the platen rotating shaft, 4...
・Swinging platen, 5...compression spring, 6.
...Tension spring, 7...Platen surface, 8...Standing platen, 9...Platen support, 9m...
Rotation guide groove.

;jP1 figure t'21 't''31fl 3t'4 figure

Claims (1)

[Claims] The serial thermal head has a heating element at the end of the rotating arm that moves in the serial printing direction, and is pressed against the platen by a compression spring.Thermal recording paper is sandwiched between the platen and the thermal recording paper for printing. In a serial thermal printer, the platen has rotating shafts protruding from both ends, and this platen rotating shaft is carved into the platen support so that it can rotate at the same radius around the same axis as the thermal head. The platen is engaged with the rotation guide groove, and the platen is supported by the platen support so that it can swing freely and the center of this swing can rotate at the same radius around the same axis as the thermal head, and further, A platen mechanism for a serial thermal printer characterized in that the platen rotating shaft is rotated toward the thermal head by a tension spring so that the platen is always in pressure contact with the thermal head with approximately the same pressure.