JPH05185668A - Sheet feeding mechanism of thermal transfer printer - Google Patents

Abstract

PURPOSE:To enhance the positioning accuracy of image receiving paper in a sheet feeding mechanism feeding the image receiving paper so as to bend the same along a platen and to simplify the structure around the platen. CONSTITUTION:A paper feed pinch roller 1 is arranged at the position coming into contact with the periphery of the platen 2 on the upstream side of paper feed of a thermal head and a capstan 3 is arranged on the downstream side of paper feed of the thermal head and a motor 5 is fixed to one shaft end of the capstan 3 while a drive gear 6 is fixed to the other shaft end thereof and the shaking gears 7, 8 meshed with the gear 6 to revolve are attached to constitute a planetary gear mechanism 9. A normal rotation gear 11 is attached on the same shaft through an one-way clutch 14 so as not to mutually interfere with a reverse rotation gear 12 through a torque limiter 13 and the drive gear 6 is meshed with the normal rotation gear 11 at the time of paper feed and selectively meshed with the reverse rotation gear 12 at the time of paper return.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal transfer type printer including a thermal head and a platen, such as a copying machine, a facsimile, a word processor, a color hard copy, and the like. It is related to the mechanism.

[0002]

2. Description of the Related Art In a thermal transfer printer capable of printing an image, for example, in order to prevent a print deviation between dots as much as possible, a long ink sheet having at least a width of an image receiving paper and a thermal head are usually used. It is configured to enable line-by-line printing using.

Further, in the case where it is necessary to convey the image receiving paper by bending it along the platen due to the layout of the entire apparatus, conventionally, the structure shown in FIG. 2 has been adopted as an example. In FIG. 2, reference numeral A is a platen,
Here, two paper pressing rollers B, B for bringing the image receiving paper P conveyed from a paper feeding device (not shown) into contact with the periphery of the platen.
Are arranged so as to sandwich the platen A, and ink ribbon guide rollers C, C for guiding the ink ribbon S to the platen surface and a line type thermal head D extending in the platen direction are arranged so as to be able to contact and separate from each other. , During printing (Fig. 2 (a))
The ink ribbon S and the image receiving paper P are pressed against the platen A by the thermal head D in one direction (arrow E in the figure).
Printing is performed for one color while being conveyed in the direction of (1), and when this is completed, the thermal head D is retracted from the platen A (FIG. 2B).
Is reversed and conveyed in another direction (the direction of arrow F in the figure), and printing is performed for the next color in the same manner as the first color.

[0004]

In the printer having the above-described structure, since the image receiving paper P is brought into contact with the platen surface in a wide area, the image receiving paper P can be reciprocally moved with a large frictional force. It is possible to reduce the gap between them as much as possible. However, on the other hand, the line type thermal head D is moved to the platen A when the image receiving paper is returned.
Therefore, there is a problem that the diameter of the platen A is slightly changed between the paper feeding and the paper returning to cause the positional deviation during printing.

That is, since the line type thermal head extending in the entire axial direction of the platen is brought into contact with and separated from the platen, the platen is elastically deformed between printing and returning of the image receiving paper to cause fluctuations in the peripheral speed, resulting in positional displacement. Become. Therefore, the present invention has been made in view of the above points, and provides a novel paper feeding mechanism capable of positioning the image receiving paper with high positioning accuracy and simplifying the structure around the platen. The purpose is to

[0006]

In order to solve the above problems, according to the present invention, a paper feed pinch roller is provided at a position circumferentially in contact with a platen on the upstream side of paper feeding as viewed from the thermal head, and a platen on the downstream side of paper feeding. The capstan is arranged at a position slightly away from the platen, the capstan is connected to the driving means, the forward rotation gear that rotates the platen in the print feed direction is connected to the shaft end of the platen, and the platen is rotated in the paper return direction. The forward rotation gear is sequentially inserted into the platen shaft end through a one-way clutch whose paper feed direction is the lock direction and the reverse rotation gear is sequentially inserted through the torque limiter so that the reverse rotation gears do not interfere with each other. The capstan and the capstan are connected via a transmission mechanism set so that the rotational speeds of the paper feed direction and the paper return direction are different from each other. The forward rotation gear of the platen and the capstan mesh with each other in the forward direction, the reverse gear of the platen meshes with the capstan when the paper is returned, and the peripheral speed VC of the capstan is larger than the peripheral speed VP of the platen during the paper feeding. (VC> VP), and when the paper is returned, the peripheral speed VP ′ of the platen is the peripheral speed V of the capstan.
It was set to be larger than C '(VP'> VC ').

[0007]

With the above-described structure, tension is applied between the capstan and the platen during feeding and returning of the image receiving paper to eliminate slack, and the platen and the paper feeding are set when the image receiving paper is set. It is possible to feed the paper with high accuracy by setting the moving distance reference of the image receiving paper with the platen when feeding out a predetermined amount from the joining point of the pinch rollers and with the capstan in other cases.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a top view showing an embodiment of the present invention, and FIG. 3 is a side view showing an embodiment of the present invention. In these drawings, reference numerals 1, 2, 3, and 4 are a paper feed pinch roller, a platen, a capstan, and a grip roller, which are arranged from the upstream side along the image receiving paper conveyance path. In FIG. 3, the image receiving paper follows a path of G → H → I → J → K → L until the trailing edge of the image receiving paper reaches H, and when the return operation is performed thereafter, the image receiving paper is received. The rear end escapes in the direction of H → M.

A motor 5 is connected to one shaft end of the capstan 3 via an appropriate speed reducing means, and a drive gear 6 is fixed to the other shaft end of the capstan 3, where a swing arm is coaxially disposed. A planetary gear mechanism 9 is constructed by attaching 10 so as to rotate with a frictional force capable of being rotated together, and attaching swinging gears 7 and 8 which rotate in mesh with the drive gear 6 at the tip of the swinging arm 10. ing. On the platen shaft on the side where the planetary gear mechanism 9 is arranged, a forward rotation gear 11 is coaxially inserted through a one-way clutch 14 having a print feed direction as a lock direction and a reverse rotation gear 12 is coaxially inserted through a torque limiter 13. When the drive gear 6 rotates in the normal direction, the normal rotation gear 11
The oscillating gear 8 and the reversing gear 12 and the oscillating gear 7 are selectively meshed with each other during reverse rotation.

By the way, the drive gear 6, the planetary gear mechanism 9, and the forward rotation gear 11 and the reverse rotation gear 12 related thereto have a peripheral speed of the platen 2 based on the peripheral speed of the capstan 3 during normal rotation of the capstan 3. Somewhat low, for example 80 ~
95% or slightly higher when reversing, eg 110
The roller diameter and the gear ratio are set so as to be about%.

Hereinafter, description will be made with reference to FIG. A first sheet leading edge detection sensor 20 is provided on the upstream side of the platen 2 in the sheet feeding route of the image receiving sheet thus configured, and a second sheet leading edge detection sensor is provided on the downstream side of the capstan 3 with respect to the sheet feeding. 21 is provided, and a line type thermal head 24 is provided so as to be aligned with the axial direction of the platen 2 so as to be able to come into contact with and separate from the platen.

On the other hand, in the ink sheet system, 30 and 31 are supply reels and take-up reels, respectively, having at least an image receiving paper width, and ink sheets applied by dividing ink in the longitudinal direction are passed through the printing surface of the thermal head 24. It is to be transferred onto image receiving paper. The light emitting element 44,
The light receiving element 45 is a transmissive sensor pair that identifies the color of the ink sheet 46.

Next, the operation of the printer thus configured will be described with reference to FIGS. 4 and 5. When the paper feed signal is input, the thermal head 24 retracts and an interval Δd is formed between the thermal head 24 and the platen 2 to the extent that the image receiving paper P can freely pass therethrough. When the motor 5 rotates in the normal direction in this state, the capstan 3 and the drive gear 6 also rotate in the normal direction, and the planetary gear mechanism 9 connected to this rotates together.
In the state shown in (a), the oscillating gear 8 meshes with the forward rotation gear 11 of the platen 2. As a result, the platen 2 is moved through the one-way clutch 14 to the gears 6, 1
It rotates at a rotation speed determined by 1.

In this state, when one sheet of image-receiving paper 47 is pulled out from a paper feeding device (not shown) and the leading edge is conveyed to the first sheet leading edge detecting sensor 20, a signal from the sensor 20 is output ( FIG. 4 (a)). From this time, when the paper is fed by the length corresponding to the distance from the junction of the platen 2 and the paper feed pinch roller 1 to the predetermined amount from the sensor 20 (FIG. 4B), the thermal head Moves down to bring the image receiving paper 47 together with the ink sheet S into pressure contact with the platen 2 (FIG. 4C). As a result, the image receiving paper 4
7 is guided by the platen 2 and the thermal head 24,
It is caught in the capstan 3 and the grip roller 4.

By the way, since the peripheral speed of the capstan 3 is set to be higher than the peripheral speed of the platen 2 when the capstan 3 is in the normal rotation state, the one-way connected to the platen 2 in this state. Clutch 14
Acts as an overrunning clutch and loses the power transmission function to the platen, and the platen 2 rotates freely at a speed corresponding to the conveyance speed of the image receiving paper 47 regulated by the capstan 3. Further, when the leading edge of the image receiving paper 47 reaches the leading edge detecting second sensor 21 (see FIG. 4).
(D)) The motor 5 is temporarily stopped, and at the same time, the thermal head 24 retracts and separates from the platen 2. When the motor 5 rotates in the reverse direction in this state, the planetary gear mechanism 9 moves to
The oscillating gear 7 meshes with the reversing gear 12 at the end of the platen shaft while rotating to the position shown in (b). In this state, the peripheral speed of the platen 2 becomes higher than the peripheral speed of the capstan 3. Therefore, the image receiving paper 47 is pulled back while the conveyance speed is regulated by the peripheral speed of the capstan 3 and at the same time the tension determined by the slip torque of the torque limiter 13 provided on the platen 2 and the platen diameter is applied. ..

By the above process, the motor 5 is temporarily stopped at the time when the front end of the image receiving paper is pulled back by the distance to the limit of being added to the capstan 3 and the grip roller 4 (FIG. 5 (a)), and then the thermal head. Drop 24. As a result, the ink sheet 46 and the thermal head 24 are brought into pressure contact with the image receiving paper 47 set to a constant tension. At this stage, when a print signal is input, the motor 5 rotates in the forward direction to perform paper feeding at a specified speed, and the thermal head 24 performs printing in line units (FIG. 5).
(B)). In this printing process, the oscillating gear 8 meshes with the forward rotation gear 11 of the platen 2 and the driving speed via the transmission mechanism of the platen 2 becomes lower than the peripheral speed of the capstan 3. The capstan 3 is rotated without being subjected to a rotational force, so that the capstan 3 is rotated at the same speed as the moving speed of the image receiving paper 47.
The printing is executed with a constant tension applied to.

Printing for the first color is completed (see FIG. 5).
(C)), a return signal is output from a host device (not shown). As a result, the thermal head 24 retracts and a space is formed between the platen 2 and the thermal head 24, and the motor 5 reversely rotates in this state. In this case, since the peripheral speed of the platen 2 is faster than that of the capstan 3, the torque limiter 13 generates a constant slip torque. As a result, the slack of the image receiving paper 47 between the capstan 3 and the platen 2 is removed. From the time when the front end of the image receiving paper 47 passes the sensor 21, the image receiving paper 47 is returned by a certain distance and set at the cueing position (FIG. 5A). In parallel with this paper returning process, the ink ribbon 46 is wound to set the portion of the second color ink. When such preparation is completed, the same process as described above (FIG. 5 (b) → (c) →
Printing is performed for the third color through (a)).

Further, in the case of printing characters, for example, in the case of printing in black, when there is a black ink portion in addition to the three primary colors, the time when the second tip detection sensor 21 detects By setting the return amount from the distance to the platen (FIG. 5D), the length of the unprintable area at the upper end can be reduced as much as possible.

In this embodiment, the paper feeding device automatically feeds the image receiving paper, but it is clear that the same effect can be obtained when the image receiving paper is manually set. ..

[0020]

As described above, according to the present invention,
A paper feed pinch roller is placed at a position circumferentially contacting the platen upstream of the moving path of the image receiving paper, and a capstan is placed at a position slightly downstream from the platen on the paper feed downstream side as viewed from the thermal head. Is connected to the drive means, and the forward rotation gear that rotates the platen in the print feed direction at the shaft end of the platen and the reverse rotation gear that rotates the platen in the paper return direction do not interfere with each other. Through a one-way clutch in which the lock direction is the lock direction, and the reverse rotation gear is sequentially inserted into the platen shaft end through the torque limiter, and the platen and the capstan have different rotation speeds in the paper feeding direction and the paper returning direction. Since it is connected via the transmission mechanism set as above, it is possible to drive fine adjustment of the feed speed between the paper feed rollers by one drive source. And ability to unnecessary complex sequences, a large place to contribute to miniaturization and simplification of the apparatus.

Further, when the image receiving paper is set, when the front end of the image receiving paper is conveyed by a predetermined amount from the joining point between the platen and the paper feed pinch roller, the thermal head is almost pressed to guide the image receiving paper to the capstan. Therefore, it is possible to improve the positioning accuracy of the print start position of the image receiving paper, and to improve the print quality particularly in the case of multicolor printing.

Furthermore, since either the capstan or the platen can be selected as the print start position at the front end of the image receiving paper, the initial margin in normal printing can be achieved without degrading the print quality in multicolor printing. It is possible to reduce it as much as possible.

[Brief description of drawings]

FIG. 1 is a top view of an embodiment of the present invention.

FIG. 2 is a side view showing a conventional example.

FIG. 3 is a side view of an embodiment of the present invention.

FIG. 4 is a diagram illustrating a paper feeding operation.

FIG. 5 is a diagram illustrating a paper feeding operation.

FIG. 6 is an explanatory view of a power transmission mechanism.

[Explanation of symbols]

 1 Paper Feed Pinch Roller 2 Platen 3 Capstan 4 Grip Roller 6 Drive Gear 7 Swing Gear 8 Swing Gear 10 Swing Arm 11 Forward Gear 12 Reverse Gear 13 Torque Limiter 14 One Way Clutch 20 Paper Lead Detection Sensor 21 Paper Lead Detection Sensor 24 Thermal head 46 Ink sheet 47 Image receiving paper

Claims (3)

[Claims] 1. A thermal transfer printer including a thermal head and a platen, wherein a paper feed pinch roller is disposed at a position that is in circumferential contact with the platen on the upstream side of the paper feed when viewed from the thermal head, and further downstream when viewed from the thermal head. Side, a capstan is arranged at a position slightly away from the platen, the capstan is connected to a driving means, and a forward rotation gear that rotates the platen shaft end in the print feed direction and a paper return direction are rotated. The reverse rotation gears are coaxially arranged so that they do not interfere with each other, the forward rotation gears are connected to the platen shaft end via a one-way clutch that locks the paper feed direction, and the reverse rotation gears are connected via a torque limiter. Inserting, connecting the platen and the capstan via a transmission mechanism with different rotation speeds in the paper feeding direction and the paper returning direction, In the direction, the forward rotation gear of the platen and the capstan mesh with each other, the reverse rotation gear of the platen and the capstan mesh with each other when the paper is returned, and the peripheral speed of the capstan becomes larger than the peripheral speed of the platen when the paper is fed. A paper feed mechanism for a thermal transfer printer, wherein the peripheral speed of the platen is set to be higher than the peripheral speed of the capstan when returning the paper. 2. When the image receiving paper is first set, when the front end of the image receiving paper is fed by a predetermined amount from the joining point of the platen and the paper feed pinch roller, the thermal head is almost pressed to the vicinity of the platen to receive the image. The paper feeding mechanism according to claim 1, which guides a paper conveyance path to a capstan. 3. The paper feeding mechanism according to claim 1, wherein the printing start position of the image receiving paper can be selected to be either a position meshed with the capstan or a position near the platen.