JP2001130086A - Thermal printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal printer in which a pressed contact pressure of a thermal head to a platen can be increased even by a small driving source and a printing quality can be improved. SOLUTION: The thermal printer has a platen 14 with a printing face 14a, a thermal head 4 capable of printing to a recording medium (not shown) and a carriage 1 to which the thermal head 4 is loaded and which can move along the platen 14. The thermal head 4 is supported by a supporting member 5 and made detachable to the platen 14. The supporting member 5 has a head return spring 6 for elastically urging the thermal head 4 in a direction to separate the thermal head from the platen 14. A pressing member 8 can press the supporting member 5 towards the platen 14 against an urging force of the head return spring 6. The supporting member 5 is pressed by the supporting member 8 thereby being moved towards the platen 14, whereby the thermal head 4 is pressed in contact with the platen 14. The thermal head 4 can be directly pressed by the pressing member 8. Therefore, the thermal head 4 can be pressed in contact with the platen 14 by a large pressed contact pressure even when a driving force of a driving source is small.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal printer, and more particularly to a thermal printer capable of increasing a pressure of a thermal head against a platen.

[0002]

2. Description of the Related Art When a conventional thermal printer is described as a thermal transfer printer, although not shown, a carriage having a flat and long platen and capable of reciprocating along the longitudinal direction of the platen is provided. ing. The carriage has a cassette mounting surface formed on an upper surface thereof so that a ribbon cassette can be mounted thereon, and also has a thermal head which can be moved up and down so as to be capable of coming into contact with and separating from a platen. The up / down operation of the thermal head is performed by rotating a motor or the like, which is a driving source, for a heart cam or the like mounted on the carriage. The carriage is provided with a take-up bobbin and a supply bobbin that can be engaged with the take-up reel and the supply reel on the ribbon cassette side.

When the take-up bobbin rotates the take-up reel with the ribbon cassette mounted on the carriage, the ink ribbon printed on the recording paper is taken up on the take-up reel without slack. . To explain the printing operation of such a conventional thermal printer,
First, the platen is separated from the platen (head-up state)
The paper and the ink ribbon are located between the thermal heads.

Then, the thermal head is lowered, and the paper and the ink ribbon are pressed against the platen.
A desired image is printed on paper by moving a carriage along the longitudinal direction of a platen while selectively generating heat in a plurality of heating elements formed on a thermal head according to a print mode. Such conventional thermal printers often print on recording paper of a size ranging from a postcard size to an A4 size. Therefore, even if the pressure applied to the platen of the thermal head is small, the print quality of an image is greatly affected. I never did.

[0005]

However, recent thermal printers require a type of printing on a large-sized recording sheet, for example, a poster, etc. In order to print on such a large-sized recording sheet, there is a demand. The size of the thermal head is increased and the number of line feeds is reduced so as not to lower the printing efficiency. When such a thermal head becomes large in size, the pressure required to press the thermal head against the platen during printing must be increased, and the large-sized thermal head is downed by a conventional heart cam or the like. In this case, a large force could not be transmitted to the thermal head, and the pressure of the thermal head against the platen was insufficient, so that the ink of the ink ribbon could not be properly transferred to the paper, and the print quality could be degraded. .

Further, in recent thermal transfer printers and the like, high-quality print quality equivalent to photographic image quality in full color is required, and even in a printer of a type that prints on a small-size recording paper, a thermal head is required. There is a tendency to increase the press contact pressure against the platen.
In the down operation, it was difficult to obtain a sufficient pressure. Further, in a conventional thermal printer, if the pressure of the thermal head is to be increased, the driving force of a motor or the like as a driving source must be increased, and there is a problem that the driving source becomes large. The present invention has been made in view of the above-described problems, and provides a thermal printer capable of improving the print quality by increasing the pressure of a thermal head against a platen even with a driving source having a small driving force. The purpose is to do. Further, the up / down stroke of the thermal head can be increased, and the replacement of the ink ribbon by the ribbon cartridge is easy.

[0007]

As a first means for solving the above problems, a thermal printer according to the present invention comprises:
A platen having a printing surface, a thermal head capable of printing on a recording medium, and a carriage mounted with the thermal head and movable along the platen, wherein the thermal head is supported by a support member and the platen is The support member has a head return spring that elastically urges the thermal head in a direction to separate the thermal head from the platen, and the support member moves the support member against the urging force of the head return spring. A pressing member that can be pressed is provided on the platen side, and the support member is moved to the platen side by pressing of the pressing member, so that the thermal head is pressed against the platen.

The pressing member has a driving force transmitting portion capable of transmitting a driving force from a driving source, and transmits the driving force from the driving source to the driving force transmitting portion to reciprocate the pressing member. To move the support member to the platen side.

The drive source comprises a motor capable of controlling the rotation angle and the number of rotations by controlling the number of steps, the drive force transmission unit comprises a rack, and the rotation of the drive source is controlled by an intermediate gear. The pressing member is transmitted to the driving source transmitting section via the first member to reciprocate the pressing member.

The pressing member has a pressure contact pin which is reciprocally movable by a pressure contact spring, and the support member can be pressed by the pressure contact pin by reciprocation of the pressing member.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a thermal printer according to the present invention will be described as a thermal transfer printer, for example. First, as shown in FIG. 1, the thermal printer of the present invention is provided with a carriage 1 that can reciprocate in the directions of arrows A and B. The carriage 1 has a plate-shaped frame 2, and the frame 2 is moved along a longitudinal direction of a platen 14, which will be described later, by a driving force of a driving motor (not shown) including an AC servomotor disposed on the back side. Reciprocating movement (in the directions of arrows A and B). A vertically long head pressing mechanism 3 is disposed in the center of the frame 2 in the vertical direction in the figure.
Is attached. As shown in FIGS. 2 and 3, the head press-contact mechanism 3 is provided with a support member 5 for supporting the lowermost thermal head 4, and the thermal head 4 is moved up and down by a platen 14 which will be described later. Can be moved away from.

The support member 5 is elastically urged in a direction to separate the support member 5 from the platen 14 as shown in FIG.
The head return spring 6 as shown in FIG. A protrusion 5b is formed on the upper surface 5a of the support member 5 so as to protrude therefrom. A pressing member 8 is disposed above the support member 5 so as to contact the protrusion 5b. This pressing member 8
The support member 5 can be reciprocated vertically in the drawing.
Of the lower platen 1 against the urging force of the head return spring 6
It can be pressed to the four sides. The pressing member 8 has a cylindrical holder 9, and the inside of the holder 9 is formed in a cavity (not shown), and a press contact pin 8 a is disposed inside the cavity. The upper and lower ends of the press-contact pin 8a protrude from the holder 9 and are supported by the holder 9 so as to be reciprocally movable in the vertical direction in the figure.

A pressure spring (not shown) composed of a compression coil spring is disposed inside the cavity of the holder 9, and the pressure pin 8a is always moved downward by the pressure spring.
It is elastically biased to the side. The urging force of the pressure contact spring (not shown) is set to be larger than the urging force of the head return spring 6 that elastically urges the support member 5 upward.

The pressing pin 8a of the pressing member 8 has a lower end protruding from a lower portion of the holder 9 and a convex portion 5b of the supporting member 5.
Is pressed. The support member 5 and the pressing member 8 are supported by a rear guide plate 10 shown in FIG. 3 and are independently movable up and down. The holder 9 is mounted on a mounting member 11, and the mounting plate 11 is supported by a guide plate 10 so that the pressing member 8 can move up and down.

The mounting member 11 has a driving force transmitting portion 11a composed of a rack capable of transmitting the driving force of the driving source 12, and the driving force of the driving source 12 is transmitted to the driving source transmitting portion 11a. The pressing member 8 reciprocates. Then, by the movement of the pressing member 8 to the platen 14 side,
The pressing member 8 presses the support member 5 and the thermal head 4
Is pressed against the platen 14.

The drive source 12 comprises a motor capable of controlling the rotation angle and the number of rotations by controlling the number of steps.
1a, an intermediate gear 13 is disposed, and the rotation of the drive source 12 is transmitted to the driving force transmission unit 11a via the intermediate gear 13, and the pressing member 8 reciprocates in the vertical direction of arrows C and D. It is movable. Therefore, by changing the rotation ratio between the intermediate gear 13 and the drive source 12, a large pressing force can be transmitted to the pressing member 8 with a small driving force.
When the pressing member 8 reciprocates, the pressing pin 8a presses the convex portion 5b of the support member 5, and the support member 5 moves toward the platen 14 against the elastic force of the head return spring 6. The thermal head 4 is pressed against the platen 14 at a predetermined pressure.

A long platen 14 having a flat printing surface 14a having a printing range E of a predetermined dimension is provided at a position on the lower side of the drawing opposite to the thermal head 4. . The platen 14 is supported at both ends in the longitudinal direction by a support plate 14c, and is rotatable by a predetermined angle. That is, the thermal head 4 is placed on the platen 1
4, the platen 14 has a self-tuning structure that rotates following the surface of the thermal head 4 on which a plurality of heating elements (not shown) are formed.

On the surface of the frame 2 of the carriage 1, a rotatable take-up bobbin 17 protrudes near the upper right corner of the frame 2, and a rotatable supply bobbin near the upper left corner of the frame 2. 18 are protruded. The take-up bobbin 17 is engaged with a take-up reel 20 around which the ink ribbon 19 is wound, and the supply bobbin 18 is engaged with a supply reel 21 around which the ink ribbon 19 is wound. I have.

Each of the bobbins 17 and 18 is independently rotatable by a motor 23 connected via a joint 22. Then, a take-up reel 20 in which the ink ribbon 19 is wound around the take-up bobbin 17
And the supply reel 21 around which the ink ribbon 19 is wound around the supply bobbin 18 is engaged.
By rotating the respective bobbins 17 and 18 in a counterclockwise direction, the ink ribbon 19 is wound from the supply reel 21 to the take-up reel 20. When all of the ink ribbons 19 have been used, the take-up reel 20 and the supply reel 21 around which the ink ribbon 19 is wound are wound by a ribbon cartridge (not shown) using a ribbon cartridge (not shown).
7 and the supply bobbin 18 so as to be exchangeable.

Between the take-up bobbin 17 and the supply bobbin 18, a plurality of, for example, twelve rollers 24 facing the ribbon transport path are rotatably arranged on the frame 2 in the present embodiment. ing. The plurality of rollers 24
Among them, some of the rollers 24 are swingable, so that a back tension can be applied to the ink ribbon 19 being wound. Therefore, the ink ribbon 19 at the time of printing is used.
It is designed to prevent failure due to slack. The back tension applied to the ink ribbon 19 by the part of the rollers 24 causes the back tension on the lower side of the ribbon transport path.
The back tension applied to the ink ribbon 19 is controlled such that the back tension applied to the ink ribbon 19 has a predetermined size, without being measured by the two tension sensors 25, 25.

In the middle portion of the ribbon transport path, the ink ribbon 19 is routed around a plurality of rollers 24 so as to contact the thermal head 4. Also,
A rotatable paper feed roller 26 is disposed behind the platen 14 shown in FIG. 1, and the paper feed roller 26 is rotated to move a recording medium (not shown) between the thermal head 4 and the platen 14. Can be transported.

The printing operation of the thermal printer according to the present invention will be described. First, the thermal head 4 is raised, and the carriage 1 is moved in the direction of arrow B.
The thermal head 4 is positioned at the printing start position at the end of the printing range of the platen 14. In this state, the drive source 12 is rotated by a predetermined number of steps to move the pressing member 8 downward in the figure. Then, the pressing pin 8a elastically biased by the pressing spring (not shown) directly presses the support member 5, and
The support member 5 moves toward the platen 14 against the urging force of the head return spring 6. Then, the thermal head 4 supported by the support member 5 presses the recording medium on the platen via the ink ribbon 19.

In this state, a plurality of heating elements (not shown) of the thermal head 4 are selectively heated according to the print mode, and the carriage 1 is moved along the platen 14 in the direction of arrow A. Ink ribbon 19
Is transferred to a recording medium, and a desired image is printed on the recording medium. In the thermal printer of the present invention, the support member 5 for supporting the thermal head 4 is directly pressed by the pressing member 8 so as to press the thermal head 4 against the platen 14. The pressure of the thermal head 4 can be increased, and the thermal head 4 of a large size can be pressed against the platen 14 with an appropriate pressure to print a high-quality image on a recording medium.

[0024]

As described above, according to the present invention, a pressing member capable of pressing the supporting member against the platen against the urging force of the head return spring is provided, and the supporting member is pressed by the pressing member. By moving the thermal head to the platen by moving it to the platen side, the supporting member that directly supports the thermal head can be pressed by the pressing member, and even if the thermal head becomes large, small drive It is possible to provide a thermal printer capable of pressing the thermal head against the platen with a large pressure by using a driving source of force. Further, since the up / down stroke of the thermal head can be made large, the replacement of the ink ribbon by the ribbon cartridge becomes easy.

The pressing member has a driving force transmitting portion capable of transmitting a driving force from a driving source, and transmits the driving force from the driving source to the driving force transmitting portion to reciprocate the pressing member. The support member is moved to the platen side, so that the reciprocating movement of the pressing member can be directly transmitted to the support member supporting the thermal head, and the thermal head is pressed against the platen with a large pressure contact pressure. can do.

The drive source comprises a motor capable of controlling the rotation angle and the number of rotations by controlling the number of steps, the drive force transmission unit comprises a rack, and the rotation of the drive source is controlled by an intermediate gear. Is transmitted to the drive source transmission unit via the drive unit, so that the pressing member is reciprocated.Thus, a large driving force is applied to the pressing member by increasing the size of the intermediate gear even with a driving source having a small driving force. Can be transmitted. That is, it is possible to provide a thermal printer capable of pressing the thermal head against the platen with a large pressure using a driving source having a small driving force.

The pressing member has a pressure contact pin which is reciprocally movable by a pressure spring. The support member can be pressed by the pressure contact pin by reciprocation of the pressing member, so that the platen undulates or warps. Even if there is a pressure contact, it is possible to absorb variations in the pressure of the thermal head due to undulation or warping by the pressure spring.

[Brief description of the drawings]

FIG. 1 is a perspective view of a main part of a thermal printer according to the present invention.

FIG. 2 is a front view of a head pressing mechanism according to the present invention.

FIG. 3 is a side view of a head pressure contact mechanism according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Carriage 2 Frame 3 Head press-contact mechanism 4 Thermal head 5 Support member 5a Upper surface 5b Convex part 6 Head return spring 8 Pressing member 8a Press-contact pin 9 Holder 10 Guide plate 11 Mounting member 12 Drive source 13 Intermediate gear 14 Platen 14a Printing surface 17 winding Removal bobbin 18 Supply bobbin 19 Ink ribbon

Claims (4)

[Claims] A platen having a printing surface; a thermal head capable of printing on a recording medium; and a carriage mounted with the thermal head and movable along the platen. The support member has a head return spring that elastically biases the thermal head in a direction to separate the thermal head from the platen. The support member opposes the biasing force of the head return spring. A pressing member capable of pressing the support member against the platen is provided, and the support member is moved toward the platen by pressing of the pressing member, so that the thermal head is pressed against the platen. A thermal printer. 2. The pressing member has a driving force transmitting portion capable of transmitting a driving force from a driving source, and transmits the driving force from the driving source to the driving force transmitting portion to reciprocate the pressing member. 2. The thermal printer according to claim 1, wherein the support member is moved to move the support member toward the platen. 3. The drive source comprises a motor capable of controlling the rotation angle and the number of revolutions by controlling the number of steps, the drive power transmission unit comprises a rack, and the rotation of the drive source is controlled by an intermediate gear. 3. The thermal printer according to claim 2, wherein the pressing member is reciprocated by being transmitted to the driving source transmitting unit via a driving member. 4. The pressure member has a pressure contact pin that is reciprocally movable by a pressure contact spring, and the support member can be pressed by the pressure contact pin by reciprocation of the pressure member. The thermal printer according to 1, 2, or 3.