JPH0721353U - Printer paper transport mechanism - Google Patents

Abstract

(57) [Summary] [Purpose] To accurately convey multiple types of print paper. In the color thermal transfer printer, when the transfer paper is a normal paper, the cam mechanism shown in (A) is changed from (B) to (C), and the support shaft 16 is rotated to some extent. Not the pinch roller is pressed against the drive roller. On the other hand, O, which has greater rigidity and friction coefficient than paper
In the case of the HP sheet, the cam mechanism shifts from (C) to (D), the support shaft 16 rotates further, and the pinch roller is pressed against the drive roller more strongly. Therefore,
In each case, the transfer paper sandwiched between the rollers is accurately conveyed.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a paper transfer mechanism of a printer suitable for use in a thermal transfer color printer capable of printing on a plurality of types of transfer paper.

[0002]

[Prior art]

 FIG. 3 is a schematic diagram illustrating a paper transport mechanism of a conventional thermal transfer color printer. In the figure, reference numeral 1 denotes a paper cassette in which transfer paper is stored. As the transfer paper, an OHP (over head projector) sheet or the like is used in addition to normal paper. Next, 2 is a paper feed roller for taking out the transferred paper 3 from the paper cassette 1, and includes a feed roller 5, pinch rollers 4 and 6, a platen roller 7, a feed roller 8 and a pinch roller 9, a discharge roller 18 and a pinch roller 19. Is a drive roller and an auxiliary roller for carrying the transfer target paper 3, respectively.

Next, 10 is an ink ribbon supply roller around which an unused ink ribbon 11a is wound, and 14 is an ink ribbon take-up roller 14 around which a used ink ribbon 11b is taken up. . Further, 13 is a guide roller provided in the passage of the ink ribbon. Color inks of 3 to 4 colors are sequentially and repeatedly applied to the ink ribbon 11a in each predetermined region in the longitudinal direction.

Reference numeral 15 denotes a pinch roller lever that is pressed by a pressing unit described below during printing by the thermal head 12 and urges the pinch roller 9 toward the feed roller 8. The pinch roller lever and the pressing unit 15 are provided. FIG. 4 ((A) is a side view, (B) is a rear view), and FIG. 5 shows the structure of a cam mechanism for urging the pressing means. 4 and 5, a plurality of pinch roller levers 15 are loosely fitted to the support shaft 16, and the lever 15 has a curved notch 15a and an inverted U-shaped notch 15b. Parts are formed. Further, the central portion has a recessed shape as shown by a broken line 15c in FIG.

In the feed roller 9, the roller portion 9a is placed at the position of the cutout portion 15a of the pinch roller lever 15, and the projections 9b provided at both ends of the roller portion 9a are cutout portions of the pinch roller lever 15. It is held at a position in contact with the feed roller 8 by being sandwiched by the portion 15b. Further, 17 is a spring formed in a substantially isosceles triangular shape, as shown in the figure, the side corresponding to the bottom is screwed into the chamfered portion 16a of the support shaft 16, and the side corresponding to the apex is the pinch roller lever 15. It touches the central part of the tip of.

Next, in FIG. 5, reference numeral 21 is a cam lever coupled to the support shaft 16, and the protruding portion 21 a thereof is located above the cam 24. The cam 24 makes an eccentric rotary motion via the drive motor 22 and the gear 23, and in conjunction with its vertical motion, the cam lever 21 rotates the support shaft 16 in the direction p or q in the figure. Further, 25 is a cam plate which rotates in synchronization with the cam 24, and the U-shaped sensor SB shows an ON signal when the cam plate 25 is sandwiched and an OFF signal when the cam plate 25 is not sandwiched. Not output to control means. The states of the sensor SB for different positions of the cam plate are shown in FIGS. 6 (A) and 6 (B) when the cam plate 25 is viewed from the gear 23 side.

In the above structure, the transfer paper 3 taken out from the paper cassette 1 by the paper feed roller 2 is conveyed by the feed roller 5 in the direction i in FIG. 3, and is transferred to the feed roller 8 via the platen roller 7. The position reached by the pinch roller 9 is reached. The state of the cam plate 25 at this time is as shown in FIG. 6A, and the sensor SB does not detect the cam plate 25. Since the cam 24 is at the lowest position in the vertical direction, and therefore the overhanging portion 21a of the cam lever 21 is also at the lowest position, the support shaft 16 causes the spring 17 to press the pinch roller lever 15 against the pinch roller 9. It is in a position not to. In this state, no pressure contact force acts between the feed roller 8 and the pinch roller 9.

Next, when a predetermined print start signal is received, the control means drives the drive motor 22 so that the cam 24 rotates in the direction of the arrow from the state shown in FIG. 6 (A). Then, the cam 24 makes an eccentric rotational movement in the direction of the arrow, and the overhanging portion 21a gradually moves upward. With this movement, the support shaft 16 gradually rotates in the direction of p shown in FIG. 4 or 5 via the cam lever 21, and the spring 17 gradually presses the pinch roller lever 15 toward the pinch roller 9.

Then, as shown in FIG. 6B, when the sensor SB detects the cam plate 25 and supplies an ON signal to the control means, the control means stops the drive motor 22 and the cam 24 is in this state. Stop in the state shown in. In this state, the pinch roller protrusion 9b sandwiched by the notch 15b of the pinch roller lever 15 is pressed, and each pinch roller 9 is pressed against the feed roller 8. As a result, the transfer paper 3 is held between the feed roller 8 and the predetermined pressure. Then, the feed roller 8 rotates by a predetermined angle to convey the transferred paper 3 to a predetermined printing start position, and the thermal head 12 is pressed against the platen roller 7 by a spring (not shown).

Then, as the feed roller 8 and the discharge roller 18 rotate, the transferred paper 3 is conveyed in the direction m in the figure, and the heating element on the thermal head 12 causes the first ribbon of the ink ribbon 11 a A portion of the color ink corresponding to the print data is thermally transferred to the transfer paper 3.

Next, the thermal head 12 is returned to its original position and the feed rollers 8 and 5 rotate in the opposite direction to superimpose the second color ink on the transfer paper 3 for thermal transfer. The transfer paper 3 is conveyed in the direction of j in the figure, and the transfer paper 3 is returned to the printing start position described above. Then, similarly, the second color ink is thermally transferred onto the transfer paper 3. Further, the same operation is performed for the third or fourth color inks, whereby characters, images and the like are color printed on one sheet of transfer paper 3.

As described above, in the case of printing color inks of a plurality of colors in an overlapping manner, if the transfer accuracy of the transfer target paper is poor, the printing positions of the color inks are displaced from each other, which is a so-called dot shift phenomenon. Occurs. Printed images with misaligned dots have poorer hue and legibility of characters. Therefore, in order to improve the conveyance accuracy of the transferred paper 3, microprotrusions (diameter: 10 μm) (not shown) are formed on the entire outer peripheral surface of the feed roller 8, which increases the friction coefficient and increases the pinch roller. The mutual pressure contact with 9 is increased.

[0013]

[Problems to be solved by the device]

 In the paper transport mechanism described above, the pressing force of the pinch roller lever 15 against the pinch roller 9 during printing is kept constant by the cam mechanism that operates based on the detection signal of the sensor SB. However, ordinary paper or OHP sheet as the transfer paper has different rigidity and friction coefficient. Therefore, for example, for an OHP sheet, a large conveying force is required as compared with the case of paper, and the pressing force of the pinch roller lever 15 needs to be further increased. However, if the position of the sensor SB and the shape of the cam plate 25 are changed so that the appropriate pressing force is applied to the OHP sheet, an excessive pressing force is applied to the paper this time, and the paper is pressed. There arises a problem that a dent mark due to the minute projections of the feed roller 8 is attached to one surface.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a paper transport mechanism of a printer that can accurately transport a plurality of types of printing paper.

[0015]

[Means for Solving the Problems]

 In order to solve the above problems, in the present invention, a drive roller, a pinch roller rotatably provided, a paper discrimination sensor for discriminating the type of print paper, and a discrimination output by the paper discrimination sensor described above. An urging member for urging the pinch roller toward the drive roller with a force corresponding to the type of the print paper based on the signal.

[0016]

[Action]

 According to the above configuration, the type of the printing paper is discriminated by the paper discrimination sensor, and the biasing member biases the pinch roller toward the drive roller with a force corresponding to the type of the printing paper based on the discrimination signal. Therefore, it is possible to accurately convey a plurality of print sheets having different rigidity and friction coefficient.

[0017]

【Example】

 An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic view for explaining a paper transport mechanism of a thermal transfer printer according to an embodiment of the present invention. The parts common to the respective parts in FIG. 3 are designated by the same reference numerals and the description thereof will be omitted. In FIG. 1, a sensor SA is provided between the feed roller 8 and the discharge roller 18 in the passage of the transfer paper 3, sandwiching the passage. In this sensor SA, the light projecting portion and the light receiving portion face each other, and the light emitted from the light projecting portion is received by the light receiving portion via the transfer paper. When the transfer paper is the above-mentioned paper and OHP sheet, there is a large difference in the amount of light received by the light receiving section.

Next, FIG. 2 (A) is a partial view of the cam mechanism in this embodiment, and the portions common to the respective portions in FIG. 5 are designated by the same reference numerals and the description thereof will be omitted. In FIG. 2, a sensor SC is newly provided in addition to the conventional sensor SB for detecting a cam plate. 2B to 2D are views of the cam plate 25 as viewed from the gear 23 side similarly to FIG. 6, and show the states of the sensors SB and SC for different positions of the cam plate. is there.

Next, the operation of this embodiment will be described. In the above-described structure, when the new transfer paper 3 reaches the position between the feed roller 8 and the pinch roller 9 and the print start signal is output from the control means, the cam 24 moves to the position shown in FIG. 2), the cam plate 25 is detected by the sensor SB. At this time, the sensor SC remains off. As a result, the transfer paper 3 is pressed with the same pressing force as in the conventional case, and is then conveyed to a predetermined print start position.

Next, the light emitted from the light projecting section of the sensor SA is received by the light receiving section through the transferred paper 3, and the detection signal corresponding to the received light amount is output to the control means. The control means sets a predetermined threshold level for this light amount, and when the light amount is smaller than the threshold level, for example, when the transferred paper 3 is paper, the thermal head 12 immediately starts the printing operation. . Then, the transfer paper 3 (paper) is nipped by the feed roller 8 and the pinch roller 9 by the above pressing force and conveyed. In this case, the pressing force has an appropriate magnitude for the sheet, and the dent mark due to the minute protrusions of the feed roller 8 does not stand out on the sheet after printing.

On the other hand, when the amount of received light is larger than the threshold level, for example, when the transfer target paper 3 is an OHP sheet, the control means causes the cam 24 to further change from the current state shown in FIG. 2C. The drive motor 22 is driven so as to rotate in the direction of the arrow. As a result, the projecting portion 21a moves further upward, so that the support shaft 16 is gradually rotated further in the p direction via the cam lever 21. Along with this movement, the spring 17 further presses the pinch roller lever 15 toward the pinch roller 9. Then, as shown in FIG. 2D, when the sensor SC detects the cam plate 25 and supplies an ON signal to the control means, the control means stops the rotation of the drive motor 22.

In this state, the cam 24 is at the highest position in the vertical direction, and the support shaft 16 is in a position where the spring 17 presses the pinch roller lever 15 against the pinch roller 9 most. Then, the projection 9b of the pinch roller sandwiched between the notches 15b is pressed with a larger pressing force than in the case of the above-described paper, and each pinch roller 9 is pressed against the feed roller 8 more strongly. Then, the printing operation by the thermal head 12 is started, and the transfer paper 3 (OHP sheet) is nipped by the feed roller 8 and the pinch roller 9 and conveyed. In this case, the pressing force between the two rollers is appropriate for the OHP sheet, and the OHP sheet having rigidity and frictional force larger than that of the sheet is accurately conveyed.

As described above, according to this embodiment, the sensor SA determines the type of the transfer target paper (paper or OHP sheet), and the transfer target paper is nipped and conveyed with an appropriate pressing force. As a result, there is an effect that transfer accuracy of the transfer target paper is good, color printing is performed favorably, and there is no concern that a noticeable dent is formed on the paper or the like.

In this embodiment, the pressing force of the pinch roller 9 is set in two steps by the sensors SB and SC, but the present invention is not limited to this, and the number of such paper discriminating sensors is used. The number of steps that can be set can be increased by increasing the number of steps and the shape of the cam plate.

Further, in this embodiment, the pressing force of the pinch roller with respect to the feed roller is controlled by using the cam mechanism (and the leaf spring), but the present invention is not limited to this, and any other biasing means may be used. It is possible to do. Further, the mounting method and the number of feed rollers are not limited to those shown in this embodiment. Further, the paper transport mechanism of the printer according to the present invention is not limited to the color thermal transfer printer, and is considered to be effective when applied to various printers.

[0026]

[Effect of device]

 As described above, according to the present invention, the paper discriminating sensor outputs the discrimination signal for discriminating the type of the printing paper, and the pinch roller is directed toward the drive roller with an appropriate force for each printing paper based on the discrimination signal. It is possible to accurately convey multiple types of print paper.

[Brief description of drawings]

FIG. 1 is a schematic view illustrating a paper transport mechanism of a thermal transfer color printer according to an embodiment of the present invention.

FIG. 2 is a view for explaining the configuration and operation of the cam mechanism according to the embodiment.

FIG. 3 is a schematic diagram illustrating a paper transport mechanism of a conventional thermal transfer color printer.

4A and 4B are a side view and a rear view of a pressing mechanism of a pinch roller 9 in FIG.

FIG. 5 is likewise a perspective view of a pressing mechanism for the pinch roller 9 and a cam mechanism for moving the pressing mechanism.

FIG. 6 is a diagram illustrating the operation of the cam mechanism of FIG.

[Explanation of symbols]

 3 Print Paper 8 Feed Roller (Drive Roller) 9 Pinch Roller 15 Pinch Roller Lever (Biasing Member) 17 Spring (Biasing Member) SA Sensor (Paper Discrimination Sensor)

Claims (1)

[Scope of utility model registration request] 1. A drive roller, a rotatably provided pinch roller, a paper discriminating sensor for discriminating the type of print paper, and a discriminating signal output from the paper discriminating sensor for determining the type of the print paper. And a biasing member that biases the pinch roller toward the drive roller with a corresponding force.