JPH0661974B2 - Paper transport method for color thermal printer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to a sheet conveying method in a color thermal printer, and more specifically, a sheet sandwiched between a platen roller and a thermal head is moved forward together with an ink ribbon. The present invention relates to a sheet conveying method applied to a color thermal printer that forms a color image by performing a plurality of operations of returning the sheet and then returning the sheet.

<Prior Art> Conventionally, as a color thermal printer, a timing belt has been used to transmit a rotational force from a main motor pulley to a platen pulley so that a sheet of paper sandwiched between a platen roller and a thermal head is fixed together with an ink ribbon. It is generally adopted that a color image is formed on a sheet by performing a plurality of operations of moving the sheet backward by a distance and then returning only the sheet by a distance equal to the forward distance.

Specifically, a pair of pinch rollers can be pressed against each other with a platen roller interposed therebetween, and a paper feed path from the paper feed cassette to the platen roller and a paper feed path for reciprocating the paper a plurality of times are selected. A configuration provided with a flapper is adopted (see Japanese Patent Laid-Open No. 59-95170).

By adopting the above configuration, when the paper is conveyed from the paper feed cassette to the platen roller, the flapper is driven to select the paper feed path for reciprocating the paper a plurality of times, and the paper is fed. The slack can be removed, and when the paper is reciprocated multiple times thereafter, the different positions of the paper are held by the platen roller and the pair of pinch rollers, and the slack caused by the reciprocation of the paper is retained. To prevent the occurrence of.

<Problems to be Solved by the Invention> In the above-described conventional color thermal printer, when the different positions of the sheet are sandwiched between the platen roller and the pinch roller, the sheet moves forward,
Regardless of the backward movement, the platen roller and the thermal head are brought into pressure contact with each other, so that new slack of the paper does not occur in the so-called transfer area, but the flapper and the pinch roller are In addition to the necessity, it is necessary to move the flapper, bring the pinch roller into contact with and separate from the platen roller, and accurately control the operation timings of the two, which causes a problem that the configuration becomes complicated as a whole.

In addition, when the operation timing is deviated and the pinch roller is pressed against the platen roller before or at the same time as the flapper rotates (if the operating speed of the color thermal printer is increased, it is possible to set the time freely. Frequency, and the above-mentioned operation timing deviation easily occurs)
When carrying from the original paper cassette,
There is no guarantee that the paper will be reliably kept along the platen roller until the leading edge of the paper is nipped between the pinch roller and the platen roller located downstream in the transport direction. In this case, the slack is generated in the sheet nipped by the platen roller and both pinch rollers.

This slack is not promoted even if the paper is reciprocated a plurality of times, but it is not eliminated. Therefore, the slack is centered on the pressure contact position between the platen roller and the thermal head. As to which side the ink ribbon is to be moved to, it is unclear, and when a color image is to be obtained by performing thermal transfer operations a plurality of times from different portions of the ink ribbon, the transfer position for each color will shift,
There is a problem that the quality of the obtained color image deteriorates.

<Object of Invention> The present invention has been made in view of the above problems,
It is an object of the present invention to provide a sheet conveying method in a color thermal printer that can move the sheet forward while the sheet is in contact with the surface of the platen roller without slack.

<Means for Solving Problems> In order to achieve the above-mentioned object, the sheet conveying method of the present invention is provided with a registration roller for supplying the sheet to the upstream side in the sheet conveying direction at the time of sheet setting, A platen roller is provided on the downstream side, and a thermal head that presses / separates from the platen roller and a pinch roller that presses on the downstream side are provided on the upstream side in the above-described conveyance direction. By rotating the driven platen roller,
After transporting the paper until the leading edge of the paper is nipped between the platen roller and the pinch roller, the registration roller is set to the free rotation state, and the platen roller with the thermal head separated from the platen roller, The paper is conveyed by the pinch roller for a predetermined time, and then the thermal head is pressed against the platen roller, and the paper is conveyed by the platen roller and the pinch roller while sandwiching the paper therebetween.

<Operation> In the case of the above-described paper conveyance method, the rotational force is transmitted from the drive source to the platen pulley, the paper sandwiched between the platen roller and the thermal head is moved forward together with the ink ribbon for a predetermined distance, and then the forward movement distance. When the color image is formed on the paper by rotating the paper back and forth by the same distance as the above, the registration roller for feeding the paper and the platen roller to which the thermal head is pressed are rotated. By driving, the paper is conveyed until the leading edge of the paper is nipped between the platen roller and the pinch roller. In that case, in particular, the platen roller and the pinch roller are pressed from the pressure contact position between the platen roller and the thermal head. The leading edge of the paper will move freely without any constraint up to the press contact position with There is a possibility.

Next, the registration roller is allowed to rotate freely, and the platen roller and the pinch roller convey the paper for a predetermined time while the thermal head is separated from the platen roller. Since the resistance is overcome, the platen roller and the pinch roller apply the conveying force to the leading edge of the sheet, so that the sheet can be reliably pressed against the periphery of the platen roller.

After that, the thermal head is brought into pressure contact with the platen roller, and the paper is conveyed by the platen roller and the pinch roller while the paper is sandwiched between them.
The thermal transfer from the ink ribbon can be performed by the thermal head while the paper is pressed against the periphery of the platen roller.

<Examples> Hereinafter, detailed description will be given with reference to the accompanying drawings illustrating examples.

FIG. 6 is a perspective view of a color thermal printer. The printer body is composed of an upper frame (1) and a lower frame (2), and a paper feed cassette (3) is provided at a predetermined position of the upper frame (1). ), Bypass bypass (4), and output tray (5). The paper feed cassette (3) can be removed in order to change the paper size.

FIG. 5 is a schematic view for explaining the internal mechanism of the color thermal printer, in which the paper transport unit (6) is attached at a predetermined position of the upper frame (1) and the lower frame.
The ink ribbon cartridge (7), the thermal head (8), and the thermal head support portion (9) are attached to the predetermined position of (2).

The paper transport section (6) includes a paper feed roller (10a) (10b) and a paper feed path (11
a) (11b), registration roller (12), paper feed path (13), paper feed path switching plate (14), platen roller (15), pinch roller (16), discharge roller (17), reverse feed roller ( 18) and the reverse feed path (19).

If the above configuration is adopted, the paper feed roller (10
a) or the paper feed roller (10b) is selectively rotated to feed the paper (P) from the paper feed cassette (3) or the bypass bypass (4) to feed the paper feed path (11a), or The sheet (P) is conveyed through the sheet feeding path (11b), and the leading end of the sheet is brought into contact with the registration roller (12) in the stopped state, so that the skew feeding is corrected.

After that, by rotating the registration roller (12) at a predetermined timing, the paper feed path (13) and the paper feed path switching plate
Guide the paper (P) between the platen roller (15) and the thermal head (8) through the upper surface of (14), and then platen roller (15)
The paper (P) can be further conveyed along with the rotation of, and guided to the pinch roller (16), and can be further guided to the discharge roller (17) by continuing the conveyance.

Further, when the paper (P) is moved back by a predetermined distance,
The platen roller (15) may be rotationally driven in the opposite direction and the paper feed path switching plate (14) may be rotated upward, so that the paper (P) returned by the platen roller (15) is fed. It is guided to the reverse feed roller (18) through the upper surface of the path switching plate (14) and further to the reverse feed path (19).

Reference numeral (20) is a sensor for detecting the position, color and the like of the ink ribbon (25).

The Ink Ribbon Cartridge (7) above is the Lower Case (21)
, The upper case (22), the feed shaft (23) rotatably housed at both ends of the lower case (21), the winding shaft (24), and both shafts (2
3) It is composed of an ink ribbon (25) whose ends are wound around (24), and the ink ribbon (25) is wound up sequentially by transmitting a rotational force to the winding shaft (24). I am able to Incidentally, (26) is a winding auxiliary roller, and (2
7), (28) and (29) are back tension rollers.

The ink ribbon (25) is formed by sequentially forming a Y (yellow) area, an M (magenta) area, and a C (cyan) area for each predetermined length.

The thermal head (8) is entirely covered with a casing of a material having a high light reflection coefficient such as aluminum, and the heat generating portion is pressed against the platen roller (15). On the downstream side in the paper transport direction,
An ink ribbon separating member for guiding the ink ribbon (25) and the paper (P) and separating them from each other.
(30) is installed.

The thermal head support portion (9) is almost fixed on the upper surface of the fixing member (31) attached at a predetermined position of the lower frame (2) through an acrylide (trade name) (32) as a thrust receiving member. A second moving member that is attached with a first moving member (33) that moves in a horizontal direction and that moves in a substantially vertical direction at a predetermined position of the first moving member (33) via an accuride (trade name) (34). (35) is attached, and a spring (not shown) for urging the second moving member (35) in a predetermined direction is attached,
A solenoid (not shown) for releasing the urging force acting on the second moving member (35) is attached. Then, a thermal head mounting member (37) is rotatably provided at a predetermined position of the second moving member (35) in the width direction (direction parallel to the axis of the platen roller (15)) via the shaft (36). While installing
A receiving member (40) having a groove engageable with the shaft of the platen roller (15) is attached at a predetermined position.

By adopting the above configuration, the platen roller (15)
Of the platen roller (15) by the movement of the first moving member (33) due to the shaft of the engaging member engaging with the groove of the receiving member (40).
It is possible to accurately regulate the pressure contact position between the thermal head (8) and the thermal head (8), and the second moving member (35) is moved to the platen roller side by energizing the solenoid to apply the biasing force of the spring. Then, the thermal head (8) can be brought into pressure contact with the platen roller (15).

The paper (P) transport operation in the color thermal printer having the above-described configuration will be described in detail below with reference to FIGS. 1 to 4.

First, by selectively rotating the paper feed roller (10a) or the paper feed roller (10b), the paper (P) is fed from the paper feed cassette (3) or the bypass bypass (4), and the registration roller ( The leading edge of the paper (P) is corrected by bringing the leading edge into contact with 12).

Thereafter, as shown in FIG. 1, the sheet feeding path switching plate (14) is rotated downward by rotationally driving the registration roller (12), so that the platen rollers pressed against each other are pressed.
Guide the paper (P) between the (15) and the thermal head (8).

In this case, when the front end of the paper (P) is sandwiched between the platen roller (15) and the thermal head (8), the front end moves freely without any restriction. It is conceivable that the paper (P) is slack.

Then, by continuing the rotation drive of the platen roller (15) to further convey the paper (P), the leading end is guided by the ink ribbon separating member (30), and the platen roller (15) is guided.
It is guided to the nip point between (15) and the pinch roller (16).

In this case, since the leading end of the paper (P) is simply guided by the ink ribbon separating member (30), as shown in FIG. Based on the state of being along the ink ribbon separating member (30) and pressed against the surface of the platen roller (15),
It is in the same state as when sagging occurs.

The tip of the platen roller (15) and pinch roller (1
After being sandwiched between the platen roller (6) and the platen roller (15) as shown in FIG. 3, the thermal head (8) is separated from the platen roller (15) and the registration roller (12) is allowed to rotate freely. Since only 15) is rotationally driven, the registration roller (12) acts as a resistance, and the paper (P) can be surely brought into a state of being pressed against the surface of the platen roller (15). It should be noted that during this period, since no carrying force acts on the ink ribbon (25), only the slack of the paper (P) can be eliminated.

After eliminating the slack of the paper (P) and pressing it against the periphery of the platen roller, as shown in FIG. 4, the thermal head (8) is pressed against the platen roller (15), and the paper is in between. (P) and the ink ribbon (25) are sandwiched, and while the rotational force is transmitted to the platen roller (15), the heating element of the thermal head (8) is energized, whereby the ink ribbon (25) The paper (P) and the ink ribbon (25) can be conveyed while thermal transfer is performed, and the thermal transfer position can be accurately controlled without being affected by slack.

By carrying out the above operation, the paper (P) is conveyed by a predetermined distance (the rear end of the paper (P) is fed by the paper feed path switching plate (14).
The platen roller (1
By rotating 5) in the opposite direction (counterclockwise in the figure), the paper (P) can be moved back by a distance equal to the thermal transfer distance.

After performing the reverse feeding operation for the predetermined distance as described above,
The paper (P) can be moved forward by transmitting the driving force so that the platen roller (15) rotates in the opposite direction (clockwise in the drawing).

Hereinafter, by repeating the reciprocating operation of the paper (P) in response to the thermal transfer operation of each color from the ink ribbon (25), it is possible to obtain a high-quality color image without color misregistration.

<Effects of the Invention> As described above, according to the present invention, even when the leading end portion is sandwiched between the platen roller and the pinch roller in a state where the paper is not pressed against the periphery of the platen roller, Since it is possible to perform thermal transfer with a thermal head after it is pressed against the surroundings,
The unique effect that a high-quality color image without color misregistration can be obtained.

[Brief description of drawings]

1 to 4 are schematic views of a main part for explaining a sheet conveying operation, FIG. 5 is a schematic view showing an internal mechanism of a color thermal printer, and FIG. 6 is an external perspective view. (8) …… Thermal head, (12) …… Registration roller, (15) …… Platen roller, (16) …… Pinch roller, (25) …… Ink ribbon, (P) …… Paper

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuo Nakamura 1-2-2 Tamatsukuri, Higashi-ku, Osaka City, Osaka Prefecture Mita Industrial Co., Ltd. (72) Makoto Ohsaku 1-2-2 Tamatsukuri, Higashi-ku, Osaka City, Osaka No. Mita Industry Co., Ltd. (72) Inventor Hiroyuki Arima 1-2-2 Tamatsukuri, Higashi-ku, Osaka City, Osaka Prefecture Mita Industry Co., Ltd.

Claims (1)

[Claims] 1. A rotational force is transmitted from a driving source to a platen pulley, and a sheet of paper sandwiched between a platen roller and a thermal head is moved forward together with an ink ribbon for a predetermined distance, and then only the paper is moved by a distance equal to the forward movement distance. In a color thermal printer that forms a color image on paper by performing multiple reciprocating operations, a registration roller is provided to supply the paper to the upstream side in the paper transport direction when setting the paper, and the downstream side thereof A platen roller is provided on the upstream side, and a thermal head that presses / separates from the platen roller on the upstream side and a pinch roller that presses on the platen roller on the downstream side are used. By rotating the driven platen roller, the leading edge of the paper After the paper is conveyed until it is nipped between the roller and the pinch roller, the registration roller is set to the free rotation state, and the thermal head is separated from the platen roller. Paper in a color thermal printer characterized in that the paper is carried for a predetermined time, and then the thermal head is brought into pressure contact with the platen roller and the paper is carried by the platen roller and the pinch roller while the paper is sandwiched between them. Transport method.