JPH1120264A - Thermal printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable smooth printing by preventing a contact pressure between a thermal head and a platen roller from becoming excessive. SOLUTION: A rotary supporting part 23 is formed in a state not to obstruct an external force F acting to a thermal head 4 from a platen roller 5 because of a rotational force of the platen roller 5. Moreover, an upstream supporting part 40 is provided at the upper side than the thermal head 4 in a transfer direction of a paper to be a fulcrum when the external force F acts to the thermal head 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal printer having a head holding mechanism capable of pressing a thermal head against a peripheral surface of a platen roller.

[0002]

2. Description of the Related Art FIGS. 2 and 3 show a conventional structure of a thermal printer used as a journal printer. In FIG. 2, reference numeral 1 denotes a printer main body. The printer body 1 includes a paper feeding unit 2, a printing unit 3, and a transport roller (1).
1, 12), a paper winding unit 13, a head cover 15, a head holding means 20, and the like.

[0003] The paper feeding section 2 of the printer main body 1 is formed so as to rotatably hold and feed the roll paper P. The printing unit 3 includes a thermal head 4, a platen roller 5, a head holding unit 20, and the like.
It is covered by the head cover 15.

[0004] The thermal head 4 is formed so that characters and the like can be printed on the roll paper P in cooperation with an ink film (not shown). The platen roller 5 is driven to rotate clockwise in the figure by a drive mechanism 6 (drive motor 7 and power transmission mechanism 8). Further, the head holding unit 20 is configured to move the thermal head 4 to the rotation support portion 23 on the downstream side in the sheet transport direction.
Is formed so as to be rotatable about the platen and to be able to press against the peripheral surface of the platen roller 5.

More specifically, the head holding means 20 holds the thermal head 4 at the rotation support portion 23 and the left end in the drawing, and the right end in the drawing is rotatably supported by the support shaft 24 of the rotation support portion 23. The head support member 21 is formed from a plate 22 mounted on the head support member 21 and an urging spring 26 which is contracted between the ceiling surface of the head cover 15 and presses the thermal head 4 against the platen roller 5. .

The rotation support portion 23 has a support shaft 24 fixed to the printer main body 1 and a hole penetratingly formed at the right end portion of the head support member 21 in the drawing to receive the support shaft 24 so as to be relatively rotatable. And a portion 25.

The head cover 15 is formed to be capable of opening and closing the printer body 1 and covering the thermal head 4 and the head holding means 20 when closed. Specifically, the head cover 15 is provided rotatably about the support shaft 24 and is urged by a spring 16 in a clockwise direction (opening direction) in the figure. This head cover 15
Is formed so as to be locked at the closed position by a locking means (lock mechanism 31).

The lock mechanism 31 includes a lock member (lock lever 32) rotatably provided on the printer main body 1 via a support shaft 35, and a spring for urging the lock lever 32 clockwise in FIG. 33, and an engagement shaft portion 34 provided on the head cover 15 and capable of engaging with the hook portion 32h of the lock lever 32 by the urging force of a spring (16, 33).

Therefore, when the lock lever 32 is rotated counterclockwise against the urging force of the spring 33,
The locking relationship between the hook portion 32h and the engagement shaft portion 34 is released, and the head cover 15 is rotated clockwise by the urging force of the spring 16 to open. With the head cover 15 in the closed position, the lock lever 32
Is rotated clockwise in accordance with the biasing force of the spring 33, the hook portion 32h and the engagement shaft portion 34 are locked, and as a result, the head cover 15 is held at the closed position.

The roll paper P rotatably held by the paper feeding section 2 of the printer body 1 passes through the printing section 3 while being conveyed by the platen roller 5 and conveying rollers (11, 12), etc., and the paper winding section 13 It is wound up. Printing unit 3
Then, characters and the like are printed on the roll paper P by cooperation of the thermal head 4 and the ink film.

[0011]

In the above-described thermal printer, the driving mechanism 6 drives the platen roller 5.
3 is rotated clockwise in FIG. 3, an external force F acts on the thermal head 4 from the platen roller 5 due to the rotational force of the platen roller 5.
Can be decomposed into a component F1 ′ in the direction of a straight line connecting the point of action and the rotation support portion 23, and a component F2 ′ in the direction orthogonal to the line.

Here, the thermal head 4 has the component F
When the thermal head 4 tries to rotate around the rotation support portion 23 by the action of 2 ′, the thermal head 4 bites into the platen roller 5. Therefore, the platen roller 5
, A large reaction force acts from the thermal head 4 side. As a result, a large and unstable contact pressure is generated between the two (4, 5).

When such a situation occurs, the size of the drive mechanism 6 including the drive motor 7 and the like must be increased, which results in an increase in the size of the entire printer and a decrease in print quality.

It is an object of the present invention to provide a thermal printer capable of preventing a contact pressure between a thermal head and a platen roller from becoming excessively large and performing smooth printing.

[0015]

According to a first aspect of the present invention, there is provided a head holding means for rotatably holding a thermal head around a rotation supporting portion on a downstream side in a sheet conveying direction and capable of pressing against a peripheral surface of a platen roller. In the thermal printer, the rotary support portion is configured not to withstand an external force acting on the thermal head from the platen roller due to the rotational force of the platen roller, and is further upstream in the sheet transport direction than the thermal head. And an upstream support portion serving as a fulcrum when an external force acts on the thermal head.

In this invention, when the platen roller is rotated, the rotation support portion does not resist external force acting on the thermal head from the platen roller due to the rotation force, and the upstream support portion serves as a fulcrum. .

Since the upstream supporting portion is located upstream of the thermal head in the sheet conveying direction, the thermal head moves around the upstream supporting portion in a direction away from the platen roller when the external force is applied. be able to. Therefore, a large and unstable contact pressure does not occur between the two, and smooth printing can be performed.

According to a second aspect of the present invention, the upstream supporting portion is
A thermal printer is configured to allow the thermal head to move in a direction in which the thermal head comes into pressure contact with the platen roller.

In this invention, the thermal head is prevented from moving in the direction in which the thermal head comes into pressure contact with the platen roller by the upstream support portion so that the contact pressure between them does not become insufficient. Can be pressed with pressure. Therefore, printing can be performed more stably.

According to a third aspect of the present invention, there is provided a printer main body which rotatably holds a thermal head on a rotation support portion on a downstream side in a sheet conveyance direction on a printer main body and presses against a peripheral surface of a platen roller. A head cover provided so as to be openable and closable and capable of covering the thermal head and the head holding means when closed, and a locking means capable of locking the head cover at a closed position, wherein the locking means comprises:
In a thermal printer comprising an engaging shaft provided on a head cover and a locking member provided on a printer main body and capable of engaging with the engaging shaft when the head cover is closed, the rotation support portion is rotated by the rotation of the platen roller. A form that does not resist external force acting on the thermal head from the platen roller due to the force, and an upstream side serving as a fulcrum when an external force acts on the thermal head upstream of the thermal head in the paper transport direction. A support portion, the upstream support portion including the engagement shaft portion, and an engagement receiving portion provided on the head holding means and capable of engaging with the engagement shaft portion; This is a thermal printer formed so as to be allowed to move in a direction in which it comes into pressure contact with a roller.

In this invention, the rotary support portion does not resist external force acting on the thermal head from the platen roller due to the rotational force of the platen roller, and the upstream support portion serves as a fulcrum. Therefore, the thermal head can move around the upstream support portion in a direction away from the platen roller. Therefore, a large and unstable contact pressure does not occur between the two, and smooth printing can be performed.

The engagement shaft and the engagement receiving portion forming the upstream support portion allow the thermal head to move in the direction of pressing against the platen roller. And printing can be performed more stably. Further, since the upstream support portion is formed by using the engagement shaft portion of the locking means, the components can be shared, and the cost can be further reduced.

[0023]

Embodiments of the present invention will be described below with reference to the drawings. As shown in FIG. 1, the basic configuration of this thermal printer is the same as that of the conventional example (FIGS. 2 and 3). When an external force F acts on the thermal head 4 from the roller 5, the thermal head 4 can rotate about the upstream support portion 40 and an excessive contact pressure acts between the two (4, 5). It is configured to be able to prevent that.

Components common to those of the conventional example (FIGS. 2 and 3) are denoted by the same reference numerals, and description thereof will be simplified or omitted.

The rotation support portion 23 is configured so as not to resist external force F acting on the thermal head 4 from the platen roller 5 due to the rotation force of the platen roller 5. Specifically, the head support member 2 forming the rotation support portion 23
One hole 25 is formed considerably larger than the support shaft 24. Therefore, play occurs between the hole 25 of the head support member 21 and the support shaft 24, and when the above-described external force F acts on the thermal head 4, the head support member 21 does not resist and supports the support shaft 24. And move.

The upstream support section 40 is located upstream of the thermal head 4 in the paper transport direction and is formed so as to be a fulcrum when the external force F acts on the thermal head 4. Specifically, the upstream support portion 40 includes an engagement shaft portion 34 of the locking means (the lock mechanism 31) and an engagement receiving portion (42) provided to be able to engage with the engagement shaft portion 34. , And the thermal head 4 is rotatably held. In this embodiment, the engagement receiving portion is a plate 2
2, and is formed with a vertical hole 42 which slidably fits the engaging shaft portion 34 in the vertical direction.

That is, the external force F is applied to the thermal head 4.
Is applied, this external force F can be decomposed into a component F2 in a linear direction connecting the point of action and the upstream support portion 40 and a component F1 in a direction orthogonal to the straight line. Here, the thermal head 4 is moved by the action of the component F1 so that
When the rotation is to be performed about 0 as a fulcrum, the rotation direction is a direction away from the platen roller 5, so that a large contact pressure does not occur between the two (4, 5).

The upstream supporting portion 40 is provided with an urging spring 26.
Does not resist the urging of the head support member 21 by the pressure. Therefore, the contact pressure between the thermal head 4 and the platen roller 5 does not become insufficient.

When the head cover 15 is opened by rotating the lock lever 32 counterclockwise in the figure, the upper end of the vertical hole 42 of the plate 22 and the engaging shaft 34 are locked by the biasing spring 26. The thermal head 4 (head support member 21) is also lifted.

Next, the operation of this embodiment will be described. When the platen roller 5 is rotated clockwise in FIG. 1 during printing, an external force F acts on the thermal head 4 from the platen roller 5 due to the rotational force as described above. The rotation support part 23 does not oppose, and the upstream support part 40 becomes a fulcrum.

Here, since the upstream supporting portion 40 is located on the upstream side of the thermal head 4 in the sheet conveying direction, the thermal head 4 to which the external force F has acted moves from the platen roller 5 with the upstream supporting portion 40 as a fulcrum. It can rotate in the escape direction. Therefore, both (4,5)
There is no large and unstable contact pressure between them,
Printing can be performed smoothly.

According to this embodiment, when the upstream supporting portion 40 is provided and the external force F acts on the thermal head 4 from the roller 5 due to the rotational force of the platen roller 5, the thermal The head 4 has an upstream supporting portion 40
Is formed so as to be rotatable with the fulcrum as a fulcrum, so that an excessive contact pressure is prevented from acting between the two (4, 5), thereby enabling smooth printing.

The upstream support portion 40 is formed by a vertical hole 42 formed in the plate 22 on the head support member 21 side and the engagement shaft portion 34, and the biasing spring 26 biases the thermal head 4. Therefore, the thermal head 4 can be pressed against the platen roller 5 with a predetermined pressure. Therefore, printing can be performed more stably.

Further, since the upstream support portion 40 is formed by using the engagement shaft portion 34 of the existing locking means (lock mechanism 31), the cost can be further reduced.

[0035]

According to the first aspect of the present invention, the rotary support portion is configured not to withstand an external force acting on the thermal head from the platen roller due to the rotational force of the platen roller, and the paper is made smaller than the thermal head. Since the upstream support portion is provided on the upstream side in the transport direction as a fulcrum when an external force acts on the thermal head, it is possible to prevent an excessive contact pressure from acting between the two and perform smooth printing.

According to the second aspect of the invention, the thermal head can be pressed against the platen roller with a predetermined pressure because the upstream support portion is configured to allow the thermal head to move in the direction in which the thermal head is pressed against the platen roller. Therefore, the same effect as that of the first aspect can be obtained, and printing can be performed more stably.

According to the third aspect of the present invention, the rotary support portion is configured not to withstand the external force acting on the thermal head from the platen roller due to the rotational force of the platen roller, and the paper transport direction is higher than the thermal head. An upstream supporting portion is provided on the upstream side as a fulcrum when an external force acts on the thermal head. The upstream supporting portion includes an engaging shaft portion and an engaging receiving portion. Since it is formed so as to be allowed to move in the pressing direction, it is possible to produce a smoother and more stable printing by generating a sufficient contact pressure between the two, and further sharing by using parts. Cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining an embodiment of the present invention.

FIG. 2 is an overall configuration diagram for explaining a conventional configuration of a thermal printer.

FIG. 3 is a view for explaining a positional relationship between a platen roller and a head holding unit.

[Explanation of symbols]

 REFERENCE SIGNS LIST 3 printing unit 4 thermal head 5 platen roller 6 drive mechanism 15 head cover 20 head holding unit 23 rotation support unit 31 lock mechanism (locking unit) 32 lock lever (locking member) 34 engagement shaft unit 40 upstream support unit 42 vertical hole (Engagement receiving part)

Claims (3)

[Claims] 1. A thermal printer comprising a head holding means for rotatably holding a thermal head around a rotation support portion on a downstream side in a sheet conveyance direction and capable of pressing against a peripheral surface of a platen roller. The thermal head is configured not to withstand the external force acting on the thermal head from the platen roller due to the rotational force of the platen roller, and the external force acts on the thermal head upstream of the thermal head in the sheet transport direction. A thermal printer comprising an upstream supporting portion serving as a fulcrum. 2. The thermal printer according to claim 1, wherein the upstream supporting portion is configured to allow the thermal head to move in a direction in which the thermal head comes into pressure contact with the platen roller. 3. A head holding means which holds the thermal head rotatably around a rotation support portion on the downstream side in the sheet conveying direction on the printer main body and presses against the peripheral surface of the platen roller, and is provided on the printer main body so as to be openable and closable. A head cover, which is capable of covering the thermal head and the head holding means when closed, and locking means capable of locking the head cover at a closed position, wherein the locking means includes an engagement shaft provided on the head cover; A thermal printer, which is provided on a printer main body and includes an engagement shaft portion and an engagement member capable of engagement when the head cover is closed, wherein the rotary support portion is moved from the platen roller by the rotation force of the platen roller. Not to withstand the external force acting on the head, and to the upstream side of the thermal head in the sheet transport direction. Maruheddo the upstream support portion serving as a fulcrum when the external force acts provided to,
The upstream support portion includes the engagement shaft portion and an engagement receiving portion provided on the head holding means and capable of engaging with the engagement shaft portion, and a direction in which the thermal head is in pressure contact with the platen roller. Thermal printer formed to be acceptable to move to.