JPH0450124Y2 - - Google Patents

Description

[Detailed description of the invention] [Field of industrial application] This invention moves the paper held between the platen roller and the thermal head forward together with the ink ribbon, and then moves only the paper backward multiple times. In particular, the present invention relates to a color thermal printer that forms a color image on paper.

[Conventional technology]

In this type of color thermal printer,
As shown in Figures 5 and 6, the thermal head a
is configured to be able to switch freely between a state in which it is in pressure contact with the platen roller b and a state in which it is separated from the platen roller b. When moving the paper c and the ink ribbon d forward together, the thermal head a is brought into pressure contact with the platen roller b, When only the ink ribbon d is moved or when only the paper c is moved back (reversely), the thermal head a is separated from the platen roller b to reduce the load.

However, in the above-mentioned conventional example, due to space constraints, etc., even when the thermal head a is separated from the platen roller b and the contact pressure between both a and b is released, as shown by the two-dot chain line in FIG. As seen from the side, the straight line connecting the tip of the ink ribbon separation member e and the upper surface of the thermal head a overlaps the platen roller b, and when only the ink ribbon d is moved, the thermal Even when the head a is separated from the platen roller b, the ink ribbon d comes into contact with the platen roller b.

The ink ribbon d is wound onto a winding shaft (not shown), and a friction clutch is inserted in the rotational drive system for the winding shaft, and a friction clutch is inserted between the thermal head a and the winding shaft. Ink ribbon d between
A winding auxiliary roller is provided to provide resistance to the movement of the ink ribbon d, so that the feeding speed of the ink ribbon d can be kept substantially constant even if the diameter of the portion wound around the winding shaft increases.

[Problem that the invention attempts to solve]

The above conventional example has the following problems.

In other words, when forming a color image or a single color image using an ink ribbon d in which areas of three colors (yellow, magenta, and cyan) or four colors (black and black) are formed in a certain order, the paper supply When only the ink ribbon d is moved to select a desired color area before printing, since the ink ribbon d and the platen roller b are in contact with each other, a large amount of friction occurs between them, and the ink is This placed a large load on the drive section of the ribbon d. Moreover, the coefficient of friction of the ink ribbon d against the platen roller b can be read by a sensor that detects each color area and the colorless area (what color area is formed between each color area) even on the same ink ribbon d. It differs depending on the part marked with the
The ink ribbon d was subjected to irregular braking due to the friction of the platen roller b, and the feeding speed of the ink ribbon d was unstable.

An object of the present invention is to solve the problems of the conventional example described above.

[Means for solving problems]

The technical measures taken by the present invention to achieve the above objectives are as follows. That is, the features of the present invention are that, in the color thermal printer described at the beginning, a first state in which a cover made of a low-friction material is inserted around the platen roller between the platen roller and the thermal head; and a second state in which the thermal head is moved away from between the thermal head and the thermal head, the cover is switched to the first state when the thermal head is separated from the platen roller, and is switched to the first state when the thermal head is pressed against the platen roller. The reason is that a drive mechanism that switches between two states is provided.

[Effect]

According to the above configuration, when the thermal head is separated from the platen roller to move only the ink ribbon, the cover enters between the platen roller and the thermal head, so the ink ribbon is pushed by the cover and the platen roller The platen roller moves in contact with the cover, which has lower frictional resistance than the platen roller.

〔Example〕

Hereinafter, embodiments of the present invention will be described based on the drawings.

FIG. 1 is a longitudinal sectional side view showing an outline of a color thermal printer. In the figure, 1 is a lower frame, 2 is an upper frame pivotably supported upwardly around a horizontal axis 3 with respect to the lower frame 1,
These constitute the printer body. A paper feed set 4, a manual feed bypass 5, and a paper discharge tray 6 are attached to the upper frame 2. Further, a paper transport section 7 is attached to a predetermined position on the upper frame 2, and an ink ribbon cartridge 8, a thermal head 9, and a thermal head support section 10 are attached to predetermined positions on the lower frame 1.

The paper transport section 7 includes paper feed rollers 11a, 11
b, paper feed path 12a, 12b, registration roller 1
3, paper feed path 14, paper feed path switching plate 15, platen roller 16, pinch roller 17, discharge roller 1
8, a reverse feed roller 19, and a reverse feed path 20.

The ink ribbon cartridge 8 has a lower case 21, an upper case 22, a feed shaft 23 and a take-up shaft 24 rotatably mounted horizontally on both ends of the lower case 21, and ends on both shafts 23 and 24. It is composed of a wound ink ribbon 25 and the like. The ink ribbon 25 can be sequentially wound by transmitting rotational force to the winding shaft secondary from a drive source (not shown) provided on the printer main body side.
A friction clutch (not shown) is interposed in the rotational drive system for the winding shaft 24. 26 is a winding auxiliary roller, and 27, 28, 29 are back tension rollers. The ink ribbon 25 has regions of three colors, yellow, magenta, and cyan, or four colors including black, for each predetermined length, and between each color region there is a color detection area provided in the printer body. A marked colorless area is formed which is to be read by the sensor 30.

The thermal head 9 is entirely covered with a casing made of a material with a high light reflection coefficient, such as aluminum, and has a heat generating part 9a at a position where it comes into pressure contact with the platen roller 16, and has a heat generating part 9a that is closer to paper transport than the heat generating part 9a. On the downstream side in the direction, an ink ribbon separation member 31 is attached to guide the ink ribbon 25 and paper P and to separate them.

A detailed explanation of the structure of the thermal head support section 10 will be omitted, but by rotating the upper frame 2 downward with respect to the lower frame 1, both ends of the shaft of the platen roller 16 are engaged with the grooves of the receiving member 32. By matching them, the positional relationship between the platen roller 16 and the thermal head 9 is accurately defined. Furthermore, when the paper P and the ink ribbon 25 can be integrally moved forward, a solenoid (not shown) is energized so that the thermal head 9 is pressed against the platen roller 16 by the biasing force of the spring, and only the ink ribbon 25 is moved forward. When moving or reversing only the paper P, the solenoid is demagnetized so that the thermal head 9 descends against the biasing force of the spring and separates from the platen roller 16. It has been done.

Next, before explaining the features of the present invention, the conveyance operation of the sheet P according to the configuration up to this point will be explained based on FIGS. 2A, 2B, and 2C.

First, by selectively rotating the paper feed roller 11a or the paper feed roller 11b, the paper feed cassette 4 is rotated.
Alternatively, the position of the leading edge of the paper P is regulated by feeding the paper P from the manual feed bypass 5 and bringing the leading edge into contact with the registration rollers 13. Therefore, if the paper P is fed diagonally, its orientation is corrected.

After that, at a predetermined timing, the registration roller 1
3, the paper P is supplied to the pressure position between the platen roller 16 and the thermal head 9 via the paper feed path switching plate 15, as shown in FIG. After being separated from the ink ribbon 25 by the ink ribbon separation member 31, the platen roller 16 and the pinch roller 1
It is guided to the contact part with 7.

In this state, while moving the paper P and the ink ribbon 25 forward integrally, the heating section 9 of the thermal head 9
By applying electricity to a, the ink of the ink ribbon 25 melted by the heat generating part 9a is transferred to the paper P, and an image of the first color (for example, yellow) is formed. The paper P is ejected to the paper ejection tray 6, but the conveyance of the paper P is stopped before the trailing edge of the paper P passes the paper feed path switching plate 15.

Next, as shown in FIG. 2B, the paper feed path switching plate 15 rotates upward, and the thermal head
is lowered and separated from the platen roller 16, and the platen roller 16 is driven to rotate in the opposite direction.
The paper P is guided to the reverse feed roller 19 via the paper feed path switching plate 15, and is returned to the reverse feed path 20. The reverse feeding distance of the paper P is set to be equal to the transfer distance between the ink ribbon 25 and the ink ribbon 25, and when the reverse feeding operation is completed, the front end of the paper P is between the platen roller 16 and the pinch roller 17. It remains in a pinched state.

Thereafter, the rotation direction of the platen roller 16 is switched, and as shown in FIG. is formed.

The optimum embodiment of the present invention is characterized in that the following improvements are made to the color thermal printer having the above configuration.

That is, as shown in FIGS. 3 and 4, a cover 33 made of a low-friction material such as metal or hard synthetic resin is inserted around the platen roller 16 between the platen roller 16 and the thermal head 9. 1st
(see FIG. 4) and a second state (see FIG. 3) in which it exits from between the platen roller 16 and the thermal head 9.
More specifically, both ends 3 of the cover 33 are attached to a shaft 34 concentric with the shaft of the platen roller 16.
3a is pivotably supported around the shaft 34. Then, attach this cover 33 to the thermal head 9.
A drive mechanism 35 is provided which switches to the first state when the thermal head 9 is separated from the platen roller 16 and switches to the second state when the thermal head 9 comes into pressure contact with the platen roller 16. The drive mechanism 35 may be an electric one using a solenoid or the like to switch between the first and second states in synchronization with the movement of the thermal head 9; In the example, it is configured by links that pivotally connect both ends 33a of the cover 33 and both sides of the thermal head 9, and the cover 33 is switched between the first and second states in conjunction with the movement of the thermal head 9. It is configured to take place.

According to the above embodiment, when the paper P and the ink ribbon 25 are integrally moved forward, the thermal head 9 is in pressure contact with the platen roller 16, so the cover 33 is moved as shown in FIG. In, the first
in a state. Therefore, the ink ribbon 25 is attached to the paper P.
At the same time, it is held between the thermal head 9 and the platen roller 16, and thermal transfer can be performed without any trouble.

When only the ink ribbon 25 is to be moved to select a desired color area in a state where no paper P is supplied between the thermal head 9 and the platen roller 16, the thermal head 9 is first lowered, Since the cover 33 is separated from the platen roller 16, the cover 33 is switched to the second state in conjunction with this. As a result, the ink ribbon 25
As shown in the figure, the cover 33 is pushed down and contact with the platen roller 16 is cut off. The ink ribbon 25 moves in contact with the cover 33 instead of the platen roller 16, but since the cover 33 is made of a low-friction material, the friction is small and the winding of the ink ribbon 25 is prevented. The removal can be carried out smoothly and at a stable speed using a slight driving source.

[Effect of idea]

The present invention has the above-described configuration, and when the thermal head is separated from the platen roller to move only the ink ribbon, the cover enters between the platen roller and the thermal head, so the ink ribbon is pushed by the cover. The contact with the platen roller is cut off, and the cover moves in contact with the cover, which has lower frictional resistance than the platen roller.

Therefore, there is an effect that the ink ribbon can be wound smoothly and at a stable speed using a small driving source.

[Brief explanation of the drawing]

1 to 4 show an embodiment of the present invention,
Figure 1 is a longitudinal side view showing an overview of the color thermal printer, Figure 2 A, B, and C are schematic views of the main parts explaining the paper conveyance operation, and Figure 3 is the main part when the thermal head is pressed against the platen roller. FIG. 4 is a side view of the main part in a state where the thermal head is separated from the platen roller. Fifth
This figure and FIG. 6 are side views of main parts showing a conventional example. 9... Thermal head, 16... Platen roller, 33... Cover, 35... Drive mechanism, P...
Paper.

Claims (1)

[Claims for Utility Model Registration] (1) By moving the paper sandwiched between the platen roller and the thermal head forward together with the ink ribbon, and then moving only the paper back several times, color is printed on the paper. In a color thermal printer that forms an image, a cover made of a low-friction material is placed around the platen roller in a first state in which it enters between the platen roller and the thermal head, and in a first state in which it exits from between the platen roller and the thermal head. and a second state in which the thermal head is separated from the platen roller, and a drive mechanism is provided for switching the cover to the first state when the thermal head is separated from the platen roller and to switch the cover to the second state when the thermal head is pressed against the platen roller. A color thermal printer characterized by: (2) Utility model registration claim (1) characterized in that the drive mechanism is configured to switch the cover between the first and second states in conjunction with the movement of the thermal head. The color thermal printer described in .