JPH02111575A - Platen driver in thermal printer - Google Patents

Abstract

PURPOSE:To improve a rotation transmission accuracy of a timing belt in printing and to keep the curved part thereof from fatigue and plastic deformation in non-printing by disposing an idler separably from a straight line part of the timing belt set between both pulleys. CONSTITUTION:The tension of a timing belt 6 is changed so as to increase to be more than a set value in printing and return to the normal set value in non-printing. Here, an idler 10 is disposed so as to rotatably come into pressure contact with a straight line part of the timing belt 6, i.e., a part other than curved parts hung on a follower pulley 5 and a drive pulley 7. This idler 10 is rotatably and separably supported by an idler support member 11. Namely, when a printer is in non-printing, the idler support member 11 is shaken to a first position for separating the idler 10 from the timing belt 6 ; when the printer is in printing, the idler support member 11 is shaken to a second position for bringing the idler 10 into pressure contact with the timing belt 6. This contact/separation action of the idler 10 with/from the timing belt 6 is conducted by an idler separating means 12.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a platen drive device for a thermal printer.

[Conventional technology]

Conventionally, as a means for driving the platen drum of a thermal printer, a drive booby is attached to the main shaft of the drive motor, and a slave pulley is attached to the platen drum's spindle, and the drive pulley and the driven boolean are connected to each other. A three-piece platen drive device is used, with a timing belt running between them.

The platen drive device that uses this timing belt as a rotation transmission means does not cause transmission loss due to backlash or slippage unlike other rotation transmission means such as gears or flat belts, so its transmission accuracy is improved, and Because its configuration is relatively simple.

It has the advantage of being able to be installed while making effective use of a small amount of space.

As is well known in thermal printers, the rotational accuracy of the platen drum directly affects the quality of printed information, so the higher the rotational transmission viscosity of the platen drum, the better. In a platen drive device using a timing belt and a pulley, the distance between both pulleys is properly managed, and a predetermined tension is applied to the timing bell 4.

[Problem to be solved by the invention]

By the way, in the above-mentioned platen drive device, the tension applied to the timing belt is about 5% lower than its design value.
It is empirically known that by setting the value relatively large, the accuracy of rotation transmission of the platen drum during printing can be further improved.

However, as mentioned above, if a large tension is always applied to the timing belt, the rotation transmission accuracy of the platen drum during printing can be improved, but when the timing belt is not printing, the tension on the pulley of the timing belt is increased. This causes problems such as the bent portion of the timing bell becoming bent and causing the motor to run out, and repeated bending and stretching of the bent portion due to rotation causing fatigue and plastic deformation, which shortens the life of the timing bell.

[Means to solve the problem]

In order to solve the above-mentioned problem, the present invention disposes an idler so that it can freely approach and separate from the straight part of the timing belt that is passed between both pulleys, and presses the idler against the timing belt during printing. Let me.

When not printing, the idler is arranged to face the timing belt at a position in the front corner.

[For production]

The platen drive device for a thermal printer according to the present invention includes:
During printing, the tension of the timing belt that drives the platen drum is increased by the idler that rotates under pressure compared to the designed one-shift tension, and when not printing, the tension of the timing belt is moved from the timing belt to the front corner, increasing the tension to the design value. The tension is restored.

〔Example〕

As shown in FIG. 1, the thermal printer according to the present invention wraps a recording medium B (not shown) around a platen drum 1, and in this state, a recording sheet is sandwiched between the recording heads 3 and 3.
is brought into pressure contact with the platen drum 1 against the elasticity of the spring 1 by a means (not shown) in contact with the head, and then the platen drum 1 is rotated in the direction of arrow a in FIG. 2 is sent in the direction indicated by the arrow 4.Based on printing information (not shown), the heating section of the recording head 3 is made to generate heat, and the dye contained in the recording sheet 2 is transferred onto the recording medium to form a printed image. is configured to do so.

On the other hand, in FIG. 1, a platen drive that rotates the platen drum 1! The I device is constructed by mounting a driven pulley 5 on a support shaft 1a of a platen drum 1, and mounting a drive pulley 7 for driving this driven pulley 5 via a timing belt 6 on a main shaft 8a of a drive motor 8. ing.

By the way, as described above, in order to improve the accuracy of rotation transmission of the timing belt 6 to the platen drum 1, it is desirable to apply a tension to the timing belt 6 that is larger than the designed tension. However, if this large tension is constantly applied to the timing belt 6, problems such as shortening the life of the timing belt 6 will occur.

Therefore, in the platen driving device according to the present invention, the first I2
As shown in Idler 10. Idler support member 11
The tension and relaxation mechanism of the timing belt 6, which is made up of the idler 1 and the control means 12, increases the tension of the timing belt 6 more than its design value (approximately 50% increase) when printing 5, and normally when not printing. Vary the value so that it returns to the design value.

Here, the idler 10 is located at a straight portion of the timing bell 1.6, that is, a portion other than the curved portion formed by the driven pulley 5 and the driving pulley 7, and is arranged to rotate under pressure. This idler 1011. Idler support member 11
It is supported in a manner that allows it to rotate freely and to be detachable from the brackets.

That is, the idler support member 11 is pivotally connected to a shaft ILa implanted in a side plate (not shown) of the printer body to which the drive motor 8 and the like are fixed.
By swinging the idler support member 11 about the fulcrum, the idler 10 is brought into contact with the timing bell)-G. Here, the idler support member 11 is
A tight spring 1 hung on the end of the eyelash 10 side
3, the idler 10 is swung to a first position where the idler 10 is separated from the timing belt 6 during normal operation, that is, when the printer is not printing. J! toward the first position of the idler support member 11 by this spring 13! ! The reason is that the elasticity of this spring 13 is applied to another spring 14 applied between the other end of the idler support member II and the idler contact/separation means 12.
It is stopped by balancing the elasticity of .

On the other hand, when the printer is printing, the idler support member 11 is connected to the second
is swung to the position. The operation of bringing the idler 10 into contact with the timing belt 6 is performed by an idler contact/separation means 12. That is, the idler contact/separation means 12 in this embodiment includes a solenoid 12a and a solenoid drive circuit 12b that turns off the solenoid 12a when the printer is not printing and turns on the solenoid 12a when printing.
It is made up of. Therefore, when the printer is not printing, the solenoid 12a is turned off, the idler support member 11 faces the first position as described above, and the idler 10 is separated from the timing belt 6. As a result, the tension of the timing belt 6 is relaxed to a normal (three-value) level that does not cause plastic deformation or the like.

On the other hand, as described above, when the printer starts printing, the solenoid 12a is turned on through the solenoid drive port 12b. As a result, the idler support member 11 is swung counterclockwise in FIG. 1 against the elasticity of the spring 13, and is moved to a second position where the idler 10 is in pressure contact with the timing belt 6 as shown in FIG. In the face of this, this idler lO
Due to the pressure contact, the timing bell (6) is bent and tensed, and a tension larger than its design value is applied to this timing bell (6). Here, as described above, the increase value of the tension applied to the timing belt 6 during printing can be set by the amount of deflection δ of the timing belt 6 due to the pressure contact of the idler 10. The amount of deflection δ is determined by the pressing force of the idler against the timing belt 6 due to the springs 1 and 1, and the spring 13 and the timing belt during non-printing.・It is determined by the reaction force due to the tension in 6.

Therefore, by appropriately setting the amount of deflection δ in advance based on the above-mentioned specifications, the tension of the timing belt 6 can be varied by the tangential movement of the idler 10 with respect to the timing belt 6.

In this embodiment, a solenoid is used as the idler contact/separation means, but the idler support member 11 may be oscillated by a rotating eccentric cam.

Further, the idler contact/separation means may be constructed so that the head contact means of the recording/rad 3 and the idler support member 11 are interlocked via a link.

Further, it is preferable that the surface of the idler 10 that comes into pressure contact with the timing belt 6 is the outer circumferential surface of the timing belt 6, but it may be the inner circumferential surface depending on the arrangement space.

Further, the idler may be roller-shaped, pulley-shaped, or ball-shaped.

Further, the idler support member 11 is configured to move the idler 10 linearly with respect to the timing belt 6 (a
may be completed.

〔Effect of the invention〕

The platen drive device for a thermal printer according to the present invention includes:
The timing belt that rotates the platen drum improves the accuracy of rotation transmission during printing and improves the quality of printed images, and prevents fatigue and plastic deformation of the curved portion of the timing belt when not printing. This can extend the life of the timing belt.

[Brief explanation of drawings]

FIG. 1 is a side view of a sales outlet of an embodiment of the present invention, and FIG. 2 is a schematic side view showing the operating state of the embodiment.

Claims (1)

[Claims] In a thermal printer having a platen drive device that transmits the rotation of a drive pulley of a drive motor by a timing belt to a driven pulley of a platen drum, an idler that rotates in pressure contact with a straight portion of the timing belt;
an idler support member that supports the idler so as to be able to move toward and away from the timing belt; and an idler support member that faces the idler at a first position that separates the idler from the timing belt when the thermal printer is not printing. A platen drive device for a thermal printer, comprising: idler contact/separation means for causing the idler support member to face a second position for bringing the idler into pressure contact with the timing belt during printing.