JPH04244871A - Thermal transfer recording apparatus - Google Patents

Abstract

PURPOSE:To reproduce an image of high quality by a method wherein a paper pressing roller is provided to a paper grasping roller in a freely movable manner so as to obtain a pressure contact state and a pressure contact released state and either one of both rollers is connected to a drive means. CONSTITUTION:Before the formation of a color image on one recording paper P is completed, both end parts of the recording paper P are always held between paper grasping rollers 40 and paper pressing rollers 43 to prevent the shift of the recording paper P. When printing is started, a thermal head 13 comes into contact with a platen roller 11 under pressure at first and, thereafter, the paper grasping rollers 40 and the paper pressing rollers 43 are brought to a pressure contact state. By this constitution, even if the recording paper is slackened or curled when it is fed to a printing part, the recording paper P is printed in a certainly stretched state and no wrinkles are generated in the recording paper P and an image of high quality is reproduced.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal transfer recording apparatus which transfers an image onto recording paper using an ink film coated with heat-melting ink.

0002

2. Description of the Related Art In a thermal transfer recording apparatus, a thermal head is brought into pressure contact with a platen roller via a recording paper and an ink film to reproduce an image on the recording paper. In particular, when reproducing a color image on recording paper, for example, an ink film coated with three colors of ink, yellow, magenta, and cyan, is used and the images are printed one over the other on the recording paper in this order. I try to do that. In this case, after the first color image is printed, it is necessary to return the recording paper to its original position and transport it. Therefore, in order to reproduce a color image with good image quality, it is desirable to prevent the recording paper from shifting with respect to the platen roller until all the color images are printed one on top of the other.

Therefore, as shown in Japanese Patent Laid-Open No. 63-193867, a paper nipping roller is provided at both ends of the platen roller integrally with the platen roller, and a paper presser is movably attached to and released from the pressure contact with the roller. There is a technique in which rollers are provided and both sides of the recording paper are held between a paper nipping roller and a paper pressing roller. In this case, the recording paper is held between the paper nipping roller and the paper pressing roller until the printing operation is completed, and is prevented from shifting in the axial direction with respect to the platen roller. .

As shown in the above-mentioned publication, in a thermal transfer recording device of the type in which paper nipping rollers are provided at both ends of a platen roller, conveyance of recording paper is carried out by these paper nipping rollers and the paper pressed against them. Since this is carried out using a presser roller, in order to improve the conveyance accuracy of the recording paper,
As shown in Japanese Patent No. 73949, there is a paper nipping roller in which the outer circumferential surface of the paper nipping roller is processed with fine irregularities.

[0005]

[Problems to be Solved by the Invention] When such processing is performed or when the paper nipping roller and platen roller are formed from separate members, it is difficult to connect the paper nipping roller and the platen roller to each other. The outer diameter must be set to match with high precision, and it is not easy in practice to manufacture these at low cost. If these outer diameters are different, a distorted image will be formed, making it impossible to reproduce a high-quality image. The reason for this is that during printing, both the platen roller with which the thermal head is in pressure contact, the paper nipping roller and the paper presser roller with which it is in pressure contact,
Since the recording paper will be fed, if the outer diameters of both rollers are different, the portion of the recording paper conveyed by the paper nipping roller and the portion conveyed by the platen roller will be different from each other during printing. This is because the feed amount will be different. Furthermore, even if it is possible to perfectly match the outer diameter of the platen roller and the outer diameter of the paper nipping roller, the platen roller is heated by the thermal head during printing operations, so the platen roller As a result, the outer diameters of the platen roller and the paper nipping roller mutually change. As a result,
The conveyance amount of the recording paper changes depending on the portion where it is conveyed by the platen roller and the portion where it is conveyed by the paper nipping roller, which may cause wrinkles in the recording paper or distortion in the reproduced image.

Therefore, the present invention has been made in view of the problems of the prior art described above, and provides a thermal transfer method that can reproduce high-quality images without causing wrinkles on recording paper or distortion of images. The purpose is to provide a recording device.

[0007]

[Means for Solving the Problems] The present invention for achieving the above object includes a platen roller and a thermal head that is movable in pressure contact with the platen roller and in pressure release from the platen roller, and in which the platen roller and the thermal head are movable. In a thermal transfer recording device that conveys an ink film and a recording paper between them to form an image on the recording paper, the platen roller is rotatably mounted on a support shaft, and the thermal head of the support shaft is opposed to the platen roller. A paper holding roller is provided at a position where the recording sheet is not pressed, and a paper pressing roller for holding the recording paper between the paper holding roller and the paper holding roller is provided so as to be movable in and out of pressure contact with the paper holding roller. This is a thermal transfer recording device in which either one of the presser roller and the presser roller is connected to a driving means.

[0008]

[Operation] When a printing operation is performed on recording paper, the recording paper is conveyed by a paper nipping roller and a paper pressing roller that presses against the recording paper via the paper holding roller, and the platen roller carries the recording paper. shall not be involved in the transportation of Therefore, even if the outer diameters of the platen roller and paper nipping roller differ when they are manufactured, or even if the platen roller thermally expands due to printing operations, the conveyance of the recording paper will not be affected by thermal effects. This is achieved by using paper nipping rollers and paper pressing rollers that do not bend the paper, so the recording paper is conveyed with high precision during printing, and high-quality images are printed without distortion or wrinkles on the recording paper. be done.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained in detail below based on the illustrated embodiments. FIG. 1 is a side sectional view showing the main parts of the thermal transfer recording device of the present invention.
are connected to each other, and the support shaft 19 is driven to rotate in both forward and reverse directions by this motor. This support shaft 19 has a platen roller 11 as shown in FIGS. 2 and 3.
are fitted so that they can freely rotate in both forward and reverse directions. Thermal head 1 can swing freely around the mounting shaft 12
3 can be pressed against and released from the platen roller 11. An ink film 16 is conveyed between the thermal head 13 and the platen roller 11, which is fed out from the supply film roll 14 and wound onto the take-up film roll 15. These rolls 14, 15 form the casing 10
It can be attached and detached freely. The illustrated ink film 16 is coated with ink of three colors: yellow, magenta, and cyan in this order. By driving the take-up film roll 15, the ink film 16
is the peeling member 1 provided at the tip of the thermal head 13.
7 and a film winding roller 18, and is wound onto the winding side film roll 15.

A paper feed cassette 20 for storing recording paper is removably attached to the casing 10. In order to take out the recording sheets in the cassette 20 one by one, a paper feed plate 22 is attached to the support shaft 21 so as to be able to swing freely around this support shaft, and a vacuum cup is attached to the tip of the paper feed plate 22 to vacuum suck the recording paper. 23 are provided. When the paper feed plate 22 is oscillated clockwise in FIG. 1 and a sheet of recording paper is adsorbed by the vacuum cup 23, the paper feed plate 22 is returned to its original position shown by the two-dot chain line in the figure. The leading edge of the paper is lifted into position. An auxiliary roller 24 is rotatably mounted at this position, and a support shaft 25
A rotary roller 27 is rotatably attached to the tip of the arm 26, which is swingably provided to the auxiliary roller to sandwich and convey the recording paper. This rotating roller 27 is driven by a conveyance motor M2 connected thereto via a gear or the like. Therefore, the recording paper whose leading end is lifted by the vacuum cup 23 is held between the rotating roller 27 and the auxiliary roller 24 by rotating the arm 26 clockwise, and is conveyed rightward in the figure. In order to guide the conveyance of the recording paper, a lower guide member 30 is installed between the platen roller 11 and the support shaft 25, and an upper guide member 31 is installed above this. Further, a guide plate 32 is fixed to the arm 26 as well.

[0011] In the case shown in the figure, printing of an image on a recording paper is carried out by transporting the recording paper to the forward limit position and then returning the recording paper while transporting it. A guide plate 33 is installed on the right side of the platen roller 11 to guide the recording paper while it is conveyed to the forward limit position. When printing, as described above, the recording paper is returned and conveyed, and in order to detect the leading edge position of the recording paper at that time, the upper guide member 31 is equipped with a leading edge detection sensor S made of a photosensor. is installed. A paper discharge tray 34 is attached above the paper feed cassette 20 to accommodate recording paper after image formation is completed. When the recording paper is discharged toward the paper discharge tray 34, the paper feed plate 22 rotates clockwise to a predetermined position and guides the recording paper with its upper surface.

FIG. 2 shows an enlarged example of a specific example of the platen roller 11 shown in FIG. 1. As shown in FIG. The length L of the platen roller 11 rotatably fitted to the support shaft 19 is set to be approximately the same as the width dimension of the ink film 16. Two paper nipping rollers 40 are integrally fixed to the support shaft 19 on both sides of the platen roller 11. These paper nipping rollers 40 are made of a highly hard material, have a high friction coefficient on their outer peripheral surfaces, and have a diameter set to be approximately the same as the diameter of the platen roller 11. Furthermore, in order to increase the frictional resistance of the paper nipping roller 40, ceramic particles or particles of a hard material such as diamond or tungsten may be uniformly coated with an adhesive or welded. The coating may be applied by means such as the following. In that case, the particle size of the hard material such as diamond is 50 to 15
It is desirable to set it to about 0 μm, and more preferably to set it to about 75 to 125 μm. If the particle size of the particles is too small, it will not be possible to obtain the conveyance force for recording paper such as plain paper or OHP paper, and conversely, even if the particle size is increased, the conveyance force will not increase much, and the conveyance traces of the paper nipping rollers will not be obtained. Since it is noticeable on the back side of the recording paper, the particle size was set as described above. Furthermore, it is desirable to plate the surface of the paper nipping roller to prevent coated particles from falling off and improve the durability of the paper nipping roller.

As shown in FIG. 2, two support shafts 41 are fixed to the casing 10 so as to face each other, and a support arm 42 is swingably attached to each support shaft 41. ing. A paper presser roller 43 is rotatably attached to the tip of each of these support arms 42 and can be brought into and out of pressure contact with the paper nipping roller 40 . A torsion coil spring 44 attached to each support arm 42 applies a pressing force to the paper pressing roller 43 toward the paper nipping roller 40 via the side of the recording paper. Paper holding roller 40 of paper pressing roller 43
In order to release the pressure contact with each arm 42
An actuator 46a of a solenoid 46 engages with a pin 45 fixed to the pin 45. The recording paper is held by paper nipping rollers 40 on both sides from the start to the end of printing.
Since the ink film 16 is held between the ink film 16 and the paper pressing roller 44, the ink film 16 has a width larger than that of the ink film 16.

FIG. 3 shows the platen roller 11 shown in FIG.
The platen roller 11 has a hollow cylindrical shape, and the support shaft 1 is supported by a bearing 35.
It is rotatably attached to 9. Further, the platen roller 11 has a hollow cylindrical roller base 11m and a rubber portion 11n laminated on the outer circumferential surface of the roller base 11m. The paper nipping roller 40 is fixed to the support shaft 19 and rotates together with the support shaft 19. Therefore, the platen roller 11 and the paper nipping roller 40 can rotate independently.

FIG. 4A shows a state in which the paper nipping roller 40 and the paper pressing roller 43 rotate the paper nipping roller 40 clockwise in the figure to transport the recording paper P forward. Further, FIG. 4(B) shows the state in which the paper nipping roller 40 is reversed and the thermal head 13 is in pressure contact with the recording paper P.
This shows the state in which it is being returned and transported. In this way, the forward conveyance and return conveyance of the recording paper P is performed by driving the paper nipping roller 40 by the motor M1, and the platen roller 11 does not participate in the conveyance of the recording paper P.

FIG. 5 is a block diagram showing the control section of the above-mentioned thermal transfer recording apparatus, and includes a central processing unit (CPU) 5.
0 is a print switch 5 that commands the start of printing.
1. Image memory 5 in which image data to be reproduced is stored
2. In order to detect the position of the leading edge of the recording paper, signals are input from the leading edge detection sensor S provided on the upper guide member 31 described above, the film sensor 53 that detects the position of the ink applied to the ink film 16, etc. It has become so. Further, from the CPU 50, a roller drive motor M that rotationally drives the paper nipping roller 40 via the support shaft 19 is provided.
1, a conveyance motor M2 that drives the rotating roller 24,
In order to swing the thermal head 13, a head swing mechanism 54 composed of, for example, a cam mechanism, a head drive mechanism 55 that sends image data to the thermal head 13, and a paper feeder that drives the arm 26 and paper feed plate 22. A control signal is sent to the mechanism 56 and a film drive mechanism 57 for driving the take-up roll 15 and transporting the ink film 16.

FIGS. 6 to 8 are diagrams showing operating states of the above-mentioned thermal transfer recording apparatus, in which the thermal head 13 is separated from the platen roller 11 and the paper pressing roller 43 is separated from the nipping roller 40. , the recording paper P is auxiliary roller 2
4 and a pressure roller 27 that presses against the paper. At this time, the ink film 16 is also separated from the platen roller 11. FIG. 6(A) shows a state in which the recording paper P has reached the position of the platen roller 11, that is, the printing section. At this time, as shown in FIG. 8(A), the recording paper P is curled or loosened. There may be a situation.

Next, as shown in FIG. 6(B), when the thermal head 13 is pressed against the platen roller 11, the center of the recording paper P is first pressed, and as shown in FIG. 8(B), the recording paper P is pressed. slack is removed. With the curl or looseness of the recording paper removed in this way, the image shown in Figure 6 (
C) As shown, the paper pressing roller 43 is connected to the paper nipping roller 40.
press against. As a result, as shown in FIG. 8(C), both sides of the recording paper P are pressed down. Then, when the rotating roller 27 is separated from the auxiliary roller 24, as shown in FIG.
As shown in A), the restraint of the recording paper P by these rollers 24 and 27 is released. Furthermore, as shown in FIG. 7(B), the thermal head 13 is released from the pressure contact with the platen roller 11. As a result, the recording paper P is restrained only by the paper nipping roller 40 and the paper pressing roller 43 pressed against it. In this state, to position the ink film 16, that is, to print a first color yellow image on the recording paper P, the roll 15 is driven to position the leading edge of the yellow-applied portion. At the same time, when the support shaft 19 is rotated by the motor M1, the paper nipping roller 40 integrated therewith is driven in the direction shown by the arrow, and the presser roller 43 is also driven to rotate.

After the recording paper P is conveyed to the predetermined advance limit position by these rollers 40 and 43, the thermal head 13 is moved to the platen roller 1 as shown in FIG. 7(C).
Printing is performed in a state where it is in pressure contact with 1. During printing, the recording paper P is conveyed back. That is, during the conveyance shown in FIG. 7C, printing is performed using the so-called return printing method, with the trailing edge as the leading edge. At this time, the paper nipping roller 40 is rotated counterclockwise by the support shaft 19, and when the leading edge detection sensor S detects the leading edge of the recording paper, printing is started.

As described above, if a color image is to be formed on the recording paper P using three color inks, first a yellow image is formed while the recording paper P is being conveyed back, and then a yellow image is formed on the recording paper P again. is conveyed forward, and then the magenta image is printed over the yellow image while the recording paper P is conveyed back. Furthermore, a cyan image is superimposed and transferred in the same manner. Until the formation of a color image on one sheet of recording paper P is completed, both sides of the recording paper P are always held between the paper nipping roller 40 and the paper pressing roller 43.
The recording paper P does not shift. Moreover, when printing starts, the thermal head 13 first comes into pressure contact with the platen roller 11, and then the paper holding roller 43 comes into pressure contact with the paper nipping roller 40, so that the recording paper is fed even to the printing section. If the recording paper is loose when
Even if it is curled, the recording paper is definitely stretched,
Printing will be performed, and the recording paper will be wrinkle-free and a high-quality image will be reproduced.

The illustrated embodiment shows a case where an image is reproduced by a field sequential method using inks of three colors, but inks of these intermediate colors are applied in accordance with the inks of these colors. An ink film having ink portions of six colors in total may be used, or an ink film having black ink portions may be used. Further, in this case, the present invention can be applied not only to the case of reproducing a color image using the frame sequential method but also to the case of reproducing a monochrome image. Furthermore, although the illustrated embodiment shows a case in which an image is reproduced on the recording paper when it is conveyed backward, the present invention can also be embodied in a case where an image is reproduced when the recording paper is conveyed forward. It is possible.

FIG. 9 is a diagram showing another type of platen roller 11, in which a holding member 3 fixed to a support shaft 19 is shown.
A friction plate 38 is attached to 6 via a spring member 37, and this friction plate 38 contacts a friction plate 39 fixed to the platen roller 11, thereby forming a torque limiter. As a result, when a difference in rotation occurs between the paper nipping roller 40 and the platen roller 11, slipping occurs between the two friction plates 38 and 39. Therefore, a predetermined load is applied to the platen roller 11, and the influence of the conveying force of the ink ribbon during printing can be reduced, making it possible to reproduce a higher quality image.

The printing procedure in each of the above-mentioned embodiments will be explained with reference to the flowcharts shown in FIGS. 10 and 11.

When the power of the thermal transfer recording device is turned on, C
The PU 50 and each member constituting the device are initialized in step 60. At this time, the thermal head 13 is separated from the platen roller 11, the solenoid 46 is not energized, and the paper pressing roller 43 is in pressure contact with the paper nipping roller 40. In order to reproduce the image on recording paper in this state,
If it is determined in step 61 that the operator has turned on the print switch 51, first, in step 62, the solenoid 46 is energized and the paper pressing roller 43 is separated from the paper nipping roller 40. Next, the paper feeding operation in step 63 is executed, and the recording paper is transferred to the paper feeding cassette 20 by the rocking movement of the paper feeding plate 22 and the vacuum suction of the vacuum cup 22.
After being taken out from inside, the arm 26 rotates and the rotating roller 27 comes into pressure contact with the auxiliary roller 24.

In this state, in step 64, the motor M
2 rotates normally, the rotating roller 27 rotates clockwise, and the recording paper P is conveyed forward. This state corresponds to FIG. 6(A). If it is determined in step 65 that the recording paper has reached the forward limit position, the conveyance motor M2 is stopped (step 66). The fact that the forward limit position has been reached is determined when a predetermined period of time has elapsed since the tip detection sensor S changed from off to on. In step 67, a cam mechanism (not shown) is operated to first press the thermal head 13 against the platen roller 11. This case corresponds to FIG. 6(B). Then step 6
8, the solenoid 46 is de-energized and the state shown in FIG.
), the paper pressing roller 43 is moved between the paper holding rollers 4 and 4.
Press it to 0.

In step 69, the arm 26 is returned to its original position, the rotating roller 27 is separated from the auxiliary roller 24, and
The state shown in FIG. 7(A) is set. Furthermore, the value N of the number of times of printing is reset to zero in step 70, and step 7
In step 1, the pressure contact of the thermal head 13 is released. This state corresponds to FIG. 7(B). Under this state, the recording paper P is transported forward by driving the roller drive motor M1 to rotate normally in step 72. If it is determined in step 73 that the leading edge detection sensor S is turned off, this means that the leading edge detection sensor S has detected the trailing edge of the recording paper P, and the roller drive motor M1 is immediately stopped in step 74. , in step 75, the thermal head 13 is brought into pressure contact. This state corresponds to FIG. 7(C).

Printing is executed in this state. First, in step 76, the number of times of printing is incremented by 1, and in step 77, a printing operation is performed. This printing operation is performed by sending an image signal from the image memory 52 to the thermal head 13 while rotating the paper nipping roller 40 counterclockwise by reversing the roller drive motor M1. Once the first color image has been printed, the determination in step 78 is NO, and steps 71 to 77 are executed again. In this case, when the determination in step 78 is YES, step 79 is executed, and the arm 26 is swung and the rotating roller 27 is pressed against the auxiliary roller 24 . Furthermore, the pressure contact of the thermal head 13 is released, the solenoid 46 is energized, and the paper pressing roller 43 is separated from the paper nipping roller 40 (steps 80 and 8).
1).

Further, if it is determined in step 83 that the motor M2 is reversed to reverse the rotation roller 27 in step 82, and that the recording paper P is discharged toward the tray 34 in step 83, then step 84 is performed. to stop motor M2. In this way, the formation of an image on one sheet of recording paper is completed.

FIG. 12 is a diagram showing a portion corresponding to FIG. 3 of a thermal transfer recording device according to another embodiment, and FIG. 13 is a diagram showing a recording paper P printed by this thermal transfer recording device. In FIG. 12, members common to those shown in FIG. 3 are given the same reference numerals. Figure 13
As shown in , this recording device records the following on the recording paper P.
A character display area A, such as character information, and a code information display area B are printed, and a paper nipping roller 40 and a paper pressing roller 4 are used in the area between these display areas A and B.
3, the recording paper P is conveyed in the direction shown by the arrow. Therefore, a paper nipping roller 40 is fixed to the center of the support shaft 19, and a paper pressing roller 43 can be brought into and out of pressure contact with the paper nipping roller 40. The thermal heads include a first thermal head 13a for printing the character display area A, and a second thermal head 13b for printing the code information display area B.
It consists of two rollers, located on both sides of the paper nipping roller 40 and the paper pressing roller 43. Similarly, the platen rollers are rotatably mounted via bearings 35 so that the first and second platen rollers 11a and 11b each rotate freely relative to the support shaft 19 in correspondence with the thermal head. and are located on both sides of the paper nipping roller 40, respectively. In this case, the ink film also has the code 1
Since two display parts are used as shown in 6a and 16b, both display parts can be printed in different colors, or one display part can be printed with magnetic ink. In this way, the axial position and number of each of the platen roller and paper nipping roller, which are rotatably attached to the support shaft 19, can be set arbitrarily, and the thermal The position of the head, etc. can also be set arbitrarily.

Furthermore, in each of the above-mentioned embodiments, the paper nipping roller 40 provided on the support shaft 19 is driven, and the paper pressing roller 43 that presses against it is not driven but driven. However, the driving side and the driven side may be reversed to drive the paper pressing roller 43. In that case, not only the platen roller but also the paper nipping roller will be rotatably fitted to the support shaft.

[0031]

As described above, according to the present invention, in a thermal transfer recording paper device of the type in which a paper nipping roller is provided coaxially with a platen roller, the support shaft for coaxially supporting these rollers is Attach the platen roller so that it can rotate freely,
The recording paper is conveyed by a paper nipping roller and a paper pressing roller that presses the recording paper against it, and the platen roller is not involved in conveying the recording paper, so that the recording paper can be easily printed. The recording paper can be transported with the desired precision without being affected by the heat of the thermal head even when the recording paper is being transported, preventing wrinkles from occurring during the transport process of the recording paper, and reproducing high-quality images on the recording paper. It became possible to do so.

[Brief explanation of the drawing]

FIG. 1 is a side view showing the main parts of a thermal transfer recording device according to an embodiment of the present invention;

FIG. 2 is an enlarged exploded perspective view showing the platen roller and paper nipping roller shown in FIG. 1;

[Fig. 3] is a sectional view showing the main part of Fig. 1;

FIG. 4 is a perspective view showing a state in which recording paper is being conveyed;

[
FIG. 5 is a block diagram showing a control circuit of the thermal transfer recording device;

FIG. 6 is a side process diagram showing the operating process of the thermal transfer recording device shown in FIG. 1;

FIG. 7 is a side process diagram showing the operating process of the thermal transfer recording device shown in FIG. 1;

FIG. 8 is a front process diagram showing the operating process of the thermal transfer recording device shown in FIG. 1;

FIG. 9 is a sectional view showing a main part of a thermal transfer recording device according to another embodiment;

FIG. 10 is a flowchart showing the operating procedure of the thermal transfer recording device shown in FIG. 1;

11 is a flowchart showing the operating procedure of the thermal transfer recording device shown in FIG. 1,

FIG. 12 is a sectional view showing a main part of a thermal transfer recording device according to still another embodiment of the present invention;

13 is a plan view showing recording paper printed by the apparatus shown in FIG. 12. FIG. 11, 11a, 11b... platen roller, 13, 13a
, 13b... Thermal head, 16, 16a, 16b... Ink film, 19... Support shaft, 20... Paper feed cassette, 2
4... Auxiliary roller, 27... Rotating roller, 40... Paper nipping roller, 43... Paper pressing roller, P... Recording paper.

Claims (1)

[Claims] [Claim 1] A thermal head having a platen roller and a thermal head that is movable to press against and release the pressure from the platen roller,
In a thermal transfer recording device that conveys an ink film and a recording paper between the platen roller and the thermal head to form an image on the recording paper, the platen roller is rotatably mounted on a support shaft, and the support shaft A paper nipping roller is provided at a position where the thermal head does not face the thermal head, and a paper pressing roller for nipping the recording paper between the paper nipping roller and the paper nipping roller is provided so as to be movable in and out of pressure contact with the paper nipping roller; A thermal transfer recording device in which either one of the paper nipping roller and the paper pressing roller is connected to a driving means.