JPH08310079A - Thermal printer - Google Patents

Abstract

PURPOSE: To clean a platen drum without forming a damage on its outer peripheral face. CONSTITUTION: Radiating fins 14a are formed on a thermal head 14. An air duct 5 with two blow-off passages 25a and 25b is connected with an air feed fan 22. A wind direction shifting plate 26 is set on a branching point for the blow-off passages 25a and 25b. The wind direction shifting plate 26 is rotated by a solenoid 27, and the blow-off passage 25b is blocked during the printing. Wind from the air feed fan 22 is blown to the radiating fins 14a of the thermal head 14 through the blow-off passage 25a to cool forcibly the thermal head 14. The blow-off passage 25a is blocked before and after printing and the wind from the air feed fan 22 is blown to the outer peripheral face of a platen drum 11 through the blow-off passage 25b to clean the platen drum 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal printer, and more particularly to a thermal printer having a platen drum cleaning function.

[0002]

2. Description of the Related Art Thermal printers include a thermal recording type in which a recording sheet is directly colored to record an image and a thermal transfer type in which ink of an ink ribbon is transferred to the recording sheet (image receiving sheet). In these thermal printers, the recording paper is wound around the platen drum. Further, a thermal head in which a plurality of heating elements are formed in a line is arranged on the outer periphery of the platen drum, and is forcibly cooled by the air from the air supply fan while the power of the thermal printer is ON.

In the thermal recording type, the thermal head directly presses the recording paper, and each heating element is selectively heated according to the image data to record an image on the recording paper in a color-developing manner. In the thermal transfer type, the thermal head presses the recording paper via the ink ribbon, and in this state, each heating element is selectively heated to transfer the ink of the ink ribbon to the recording paper.

During the use of the thermal printer, dust may adhere to the outer peripheral surface of the platen drum. When dust adheres to the platen drum, the recording paper in that portion is slightly raised. In the heat-sensitive recording type, the pressing force of the thermal head increases in the raised portion, and the heat transfer coefficient increases. Therefore, even if the amount of heat generated by the heating elements is the same, the amount of heat applied to the recording paper increases, and the color density increases, resulting in uneven density. On the other hand,
In the case of the thermal transfer type, the contact between the recording paper and the ink ribbon is deteriorated and the transfer failure of the ink occurs, so that density unevenness also occurs.

In order to prevent the occurrence of density unevenness due to dust adhering to the platen drum, Japanese Patent Laid-Open No. 61-24877.
It is known to provide a plate-shaped brush on the outer circumference of the platen drum as described in Japanese Patent Laid-Open No. The brush extends in the axial direction of the platen drum, and removes dust attached to the platen drum as it rotates.

[0006]

In the above-mentioned conventional apparatus, in order to obtain sufficient cleaning performance, it is necessary to strongly contact the brush with the outer periphery of the platen drum.
This causes a problem of scratching the platen drum.

It is an object of the present invention to provide a thermal printer which can be cleaned without damaging the outer peripheral surface of the platen drum.

[0008]

To achieve the above object, in a thermal printer according to a first aspect of the present invention, an air supply fan, a direction in which wind from the air supply fan is directed to a thermal head, and an outer periphery of a platen drum. A wind direction switching plate is provided to switch the direction of the wind. When the wind direction switching plate is set on the platen drum side, the wind from the air supply fan is blown to the outer peripheral surface of the platen drum, so that the dust attached to the outer peripheral surface of the platen drum is blown away.

In the thermal printer according to the second aspect, the wind direction switching plate is set on the thermal head side during printing, and air is blown onto the thermal head to cool it. Before and after printing, the wind direction switching plate is set on the platen drum side to clean the platen drum.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, a platen drum 10 is rotatably provided in a frame body 8. The end of the color thermosensitive recording paper 11 is pressed and fixed to the platen drum 10 by the clamper 12. At the time of printing, the platen drum 10 is driven by the pulse motor 13
It is rotated continuously or intermittently in the sub-scanning direction indicated by the arrow. The thermal head 14 is arranged at the print position. As is well known, the thermal head 14 has a large number of heat generating elements arranged in a line in the main scanning direction (axial direction of the platen drum), and each heat generating element generates heat energy according to the density of a pixel. . Further, in order to improve the heat dissipation of the thermal head 14, heat dissipation fins 14a are formed.

A yellow fixing device 15 and a magenta fixing device 16 are sequentially arranged downstream of the thermal head 14. This yellow fixing device 15 has an emission peak of 42.
The magenta fixing device 16 is composed of a 0 nm ultraviolet lamp 17 and a reflector 18, and has an emission peak of 365.
It is composed of an ultraviolet lamp 19 of 1 nm and a reflector 20.

An air supply fan 22 is provided above the frame body 8. A dustproof filter 23 is attached to the intake port of the air supply fan 22 to prevent dust from entering the frame 8. The air supply fan 22 is connected to an air duct 25 provided with two outlet passages 25a and 25b.

A wind direction switching plate 26 is provided at the branch point of the outlet passages 25a and 25b. The wind direction switching plate 26 is rotated by the solenoid 27 and closes either one of the outlet passages 25a and 25b. Outlet passage 25a
The air that has entered the radiator fins 14 of the thermal head 14.
The thermal head 14 is forcibly cooled by being sprayed on a. The blowout passage 25b is provided in order to blow off dust adhering to the outer peripheral surface of the platen drum 11.
The wind speed is increased by narrowing the tip and facing the outer peripheral surface. On the opposite side of the air supply fan 22, an exhaust fan 28 for discharging dust blown from the platen drum 10 and discharging hot air of the thermal head 14.
Is provided.

The system controller 31 controls the drive of the solenoid 27 and also controls the respective parts in sequence. Reference numeral 30 is a keyboard.

The operation of the above configuration will be described. When the power is turned on, the air supply fan 22 and the exhaust fan 28 start rotating. Since the wind direction switching plate 26 closes the blowout passage 25a as shown by the solid line in FIG. 1, the wind from the air supply fan 22 is blown toward the outer peripheral surface of the platen drum 10 through the blowout passage 25b, and the platen drum The outer peripheral surface of 10 is cleaned. Dust adhering to the outer peripheral surface of the platen drum 10 is dropped and exhausted by the exhaust fan 28.

When the print start switch of the keyboard 30 is pressed, a print start signal is sent to the system controller 31 and the color thermosensitive recording paper 11 is fed. At the same time, the system controller 31 operates the solenoid 27 to rotate the wind direction switching plate 26 to the position indicated by the alternate long and short dash line, thereby closing the blowout passage 25b. The wind from the air supply fan 22 is blown against the cooling fins 14a of the thermal head 14 through the discharge passage 25a to cool the thermal head 14.

The tip of the color thermosensitive recording paper 11 is the clamper 1
After being fixed at 2, the platen drum 10 starts rotating. When the front end of the color thermosensitive recording paper reaches the thermal head 14 during the rotation of the platen drum 10, a yellow image is thermally recorded line by line. The portion on which the yellow image is thermally recorded is irradiated with ultraviolet rays of about 420 nm from the fixing device 15 for yellow and is fixed.

At the second rotation of the platen drum 10, a magenta image is thermally recorded line by line, and is fixed by an ultraviolet ray of about 365 nm from the magenta fixing device 16. At the third rotation of the platen drum 10, a cyan image is thermally recorded line by line. In this way, a full-color image is recorded on the color thermosensitive recording paper 11 by the three-color frame sequential method.

When printing is completed, the clamper 12 releases the clamp. When the platen drum 10 rotates in this state, the thermal head 14 causes the color thermosensitive recording paper 11 to rotate.
Is pressed against the platen drum 10, the color thermosensitive recording paper 11 rotates together with the platen drum 10. As a result, the color thermosensitive recording paper 11 is held by the clamper 12
The paper passes through the bottom and is ejected. After the color thermosensitive recording paper 11 is discharged, the system controller 31 sets the solenoid 27.
Since the air is turned off, the outlet passage 25a has the wind direction switching plate 2
Closed by 6. The air from the air supply fan 22 is blown to the outer peripheral surface of the platen drum 10 through the discharge passage 25b, and the outer peripheral surface of the platen drum 10 is cleaned. Therefore, since the platen drum is air-blown before feeding and after discharging, the color thermosensitive recording paper is not wound around with the dust adhering to the outer peripheral surface of the platen drum, and it is possible to prevent density unevenness from occurring. You can

In the above embodiment, the air is blown from the air supply fan to the outer peripheral surface of the platen drum that is stopped for cleaning. However, immediately before the print start switch is operated and paper is fed. The platen drum may be rotated once and cleaning may be performed by blowing air from the air supply fan to the entire outer peripheral surface of the platen drum during this rotation.

The present invention can be applied to a thermal transfer color printer using an ink ribbon, in addition to the thermal recording type. Further, in addition to the line printer, it can be used for a serial printer in which a thermal head reciprocates in the sub scanning direction. If a large size wind direction switching plate is used, the duct 25 can be omitted.

[0022]

As described in detail above, according to the thermal printer of the present invention, it is possible to switch between the direction in which the air from the air supply fan is directed to the thermal head and the direction in which it is directed to the outer peripheral surface of the platen drum. Since the wind direction switching plate is provided, both the forced cooling of the thermal head and the cleaning of the platen drum can be performed. Further, since the cleaning of the platen drum is performed without contact, the platen drum is not damaged.

Since the thermal head is forcibly cooled during printing and the platen drum is cleaned before or after printing, the platen drum can be cleaned using the cooling air supply fan of the thermal head.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a thermal printer of the present invention.

[Explanation of symbols]

 10 Platen Drum 11 Color Thermal Recording Paper 14 Thermal Head 22 Air Supply Fan 26 Wind Direction Switching Plate

Claims (2)

[Claims] 1. In a thermal printer for recording by recording a thermal head on a recording paper wound around a platen drum, an air supply fan, a direction in which wind from the air supply fan is directed to the thermal head, and an outer periphery of the platen drum. A thermal printer, which is provided with a wind direction switching plate that switches to a direction in which it faces the surface. 2. The thermal printer according to claim 1, wherein the wind direction switching plate switches to the thermal head side during printing, and switches to the platen drum side before and after printing.