JPH1120246A - Printing mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure a correct print gap, being set by the position of a positioning roller and a platen, between the printing face of a medium and the forward end of a print head by shifting the platen downward by an amount corresponding to the thickness of the medium when the medium enters into the nip between the platen and the positioning roller. SOLUTION: When a medium P is carried rightward through rotation of a carry roller R, the medium P enters into the nip between a platen 11 and a positioning roller 18. Consequently, the platen 11 and the positioning roller 18 are turned by the medium P in the carrying direction of medium and the platen 11 is moved downward by an amount corresponding to the thickness (t) of the medium P along a guide hole 14a while resisting against an urging member (e.g. a coil spring) 15a held by a holder 16. Consequently, a correct print gap being set by the position of the positioning roller 18 and the platen 11 is ensured between the printing face of the medium P and the forward end of a print head. Printing is effected under that state by means of the print head while carrying the medium P.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printing mechanism for adjusting a printing gap according to the thickness of a printing medium.

[0002]

2. Description of the Related Art As shown in FIG. 5, a printing mechanism of a type in which a print medium P is transported between a print head 1 and a platen 2 by a transport roller R and printed is provided with a thickness t of the print medium P.
In some cases, it is necessary to adjust an interval between the print head 1 and the platen 2 to secure an appropriate print gap g between the print surface of the print medium P and the print head 1. An example of a mechanism for adjusting the print gap is as follows. The platen 2 is connected to the rack 2 a, the pinion 3, and the torque limiter 4.
And is provided so as to be able to move up and down freely. At the time of adjusting the printing gap, the platen 2 is raised by the motor 5. When the platen 2 presses the print medium P against the print head 1 with the pressing force specified by the torque limiter 3 and stops, the motor 5 is rotated in reverse to lower the platen 2 from the stop position by a distance corresponding to the print gap g.

[0003]

In the above-described conventional mechanism, every time printing is performed on a print medium, the transport of the print medium is temporarily stopped, and the platen is raised and lowered to adjust the print gap. Since it takes time, there is a limit to the number of print media that can be processed per unit time. Also, the mechanism and control for raising and lowering the platen tend to be complicated. The present invention has been made based on such circumstances, and an object thereof is to provide a printing mechanism having a simple configuration capable of printing more printing media per unit time.

[0004]

According to a first aspect of the present invention, there is provided a printing mechanism, comprising: a printing head; a roller-shaped platen which rotates together with a printing medium conveyed in a printing direction; And a platen supporting means that constantly urges in a direction approaching the print head, and is rotatably supported by a frame that holds the print head, and has an appropriate print gap from a tip position of the print head. And a positioning roller provided such that a nip surface with the platen is formed at a position corresponding to a distance between the printing medium and the nip between the platen and the positioning roller to perform printing. It is characterized by. According to the above configuration, when the medium enters the nip between the platen and the positioning roller, the platen
The medium is moved downward by the thickness of the medium against the urging force of the platen supporting means. An appropriate print gap set by the position of the positioning roller and the platen is secured between the print surface of the medium and the tip of the print head.

According to a second aspect of the present invention, there is provided a printing mechanism including a print gap adjusting means for supporting a position of a positioning roller with respect to a print head in an adjustable manner. According to the above configuration, by adjusting the position of the positioning roller with respect to the print head by the print gap adjusting means, the print gap can be arbitrarily adjusted according to, for example, the paper quality of the medium.

According to a third aspect of the present invention, there is provided a printing mechanism, further comprising a support means for movably supporting a print head and a positioning roller in a direction parallel to an axis of a platen.
It is characterized in that it is rotatably supported in at least both the printing direction of the printing medium and the direction perpendicular to the printing direction. According to the above configuration, the position of the print head with respect to the print medium can be moved in the transport direction of the print medium, that is, in the direction perpendicular to the print direction.

[0007]

Next, the present invention will be described with reference to the drawings. 1 is a front view showing a configuration of a printing mechanism according to an embodiment of the present invention, FIG. 2 is an enlarged view of a portion A in FIG. 1, and FIG. 3 is a side view of FIG. It is.
1 to 3, the same or corresponding members as those in FIG. 5 showing the conventional example are denoted by the same reference numerals, and description thereof will be omitted.

The configuration will be described with reference to FIGS. The print head 1 is fixed to a frame 10a of a housing. The roller-shaped platen 11 has both ends of a support shaft 12 rotatably supported by bearings 13a and 13b having a built-in bearing. Frames 10a, 10
b is provided with guide holes 14a and 14b formed of vertically long holes shown by broken lines in FIG.
Bearings 13a, 13 provided in shapes corresponding to a, 14b
3b is inserted. Therefore, the platen 11
The print head 1 is supported vertically along the guide holes 14a and 14b, that is, freely movable toward and away from the print head 1.

Slightly below the center of the guide holes 14a and 14b, biasing members 15a and 15 made of coil springs are provided.
b are held by the frames 10a, 16b.
10b. Urging members 15a, 1
5b is stretched to the holders 16a and 16b in a state where the lower portions of the bearings 13a and 13b are urged upward. Therefore, the platen 11 is constantly urged in the direction approaching the print head 1 by the two urging members 15a and 15b.

A positioning roller 18 is rotatably supported at the tip of an arm 17 fixed to the frame 10a of the housing. As shown in FIG.
Is an appropriate print gap g from the tip position of the print head 1.
Are provided so that a nip surface with the platen 11 is formed at a position corresponding to the distance.

The operation of the above configuration will be described.
When the medium P is transported in the direction of arrow F by the transport roller R, the medium P enters the nip between the platen 11 and the positioning roller 18. As shown in FIG. 2, when the medium P enters the nip, the platen 11 and the positioning roller 18
Is rotated by the medium P in the same direction as the transport direction (printing direction). At this time, the platen 11 is moved downward by the thickness t of the medium P against the urging forces of the urging members 15a and 15b. As a result, an appropriate print gap g set by the positions of the positioning roller 18 and the platen 11 is secured between the print surface of the medium P and the tip of the print head 1. In this state, printing can be performed by the print head 1 while transporting the medium P in the direction of arrow F.

As described above, according to the above-described embodiment, unlike the conventional mechanism, every time printing is performed on a medium, it is not necessary to perform an operation for securing an appropriate print gap prior to the printing operation. Printing can be performed with an appropriate print gap secured only by transporting to the nip between the platen and the positioning roller. Therefore, the time required for the printing process can be significantly reduced. In addition, a mechanism for raising and lowering the platen by a driving source such as a motor and control for raising and lowering operation are not required, and a simple mechanism can be used, so that cost can be reduced.

The frames 10a, 10a of this embodiment
0b, bearings 13a, 13b, guide holes 14a, 14b,
The urging members 15a and 15b and the holders 16a and 16b constitute "platen supporting means" that supports the platen so as to be able to freely move toward and away from the print head and constantly urges the platen in a direction approaching the print head.

In the above-described embodiment, the print head 1 is fixed. However, as in other embodiments described below, the print head 1 is moved in a direction perpendicular to the transport direction (print direction). It is also possible to perform printing.

FIG. 4 is a side view showing a main part of another embodiment. The support means for the platen 11 is the same as in the above-described embodiment, and is not shown. The print head 1 is fixed to a carriage 20. The carriage 20 is slidably supported by two guide bars 21 and 22 extending in a direction parallel to the axis of the platen 11. The guide bar 22 is located behind the guide bar 21 on the paper surface of FIG.

The upper part of the carriage 20 has gears 23, 24
The roller 24 is reciprocated along the axial direction of the platen 11 (the direction of the arrow H) when one of the rollers 24 is rotationally driven by a drive source such as a motor (not shown). It is becoming like.

At the lower part of the carriage 20, an arm 27 to which a positioning roller 26 is fixed is vertically moved (in the direction of arrow V).
Is provided with a support portion 28 for slidably supporting. The tip of a screw 29 screwed to the support portion 28 is rotatably held by the arm 27. Therefore, by rotating the screw 29, the vertical position of the arm 27, that is, the position of the positioning roller 26 with respect to the print head 1 can be variably set.

The positioning roller 26 has a configuration in which a ball-shaped roller that rotates in all directions is provided. Therefore, even when the carriage 20 moves in the axial direction of the platen 11 or when the medium P is transported in the printing direction, the carriage 20 can smoothly rotate with respect to the medium P. Since the ball-shaped roller of the positioning roller 26 has a small area in contact with the medium P, if the pressing force per unit area is large and may possibly affect the medium P, two positioning rollers 26 or two It suffices to provide two or more of them to distribute and reduce the load applied to the medium P.

The arm 27, the support 28 and the screw 29 constitute a print gap adjusting means 30 for supporting the position of the positioning roller with respect to the print head in an adjustable manner.

On the other hand, the carriage 20, the guide bar 21,
The support means 31 for supporting the print head and the positioning roller movably in a direction parallel to the axis of the platen is constituted by the gear 22, gears 23 and 24 and the timing belt 25.

According to the above-described configuration, the print head 1 can be slid along the axial direction of the platen 11, so that printing can be performed on the medium P at the position moved in the axial direction of the platen 11. Can be.

The position of the positioning roller 26 with respect to the print head 1 is variably set by the screw 29, so that a print gap g secured between the print surface of the medium P and the print head 1 can be arbitrarily set. Value can be adjusted. Therefore, an appropriate print gap g can be arbitrarily set according to the paper quality of the medium P.

The positioning roller is not limited to the one using the above-mentioned ball-shaped roller. The positioning roller 18 shown in FIGS.
A well-known support mechanism that rotatably supports an axis in a direction perpendicular to the printing surface of the image may be used.

[0024]

According to the printing mechanism of the first aspect, printing can be performed while securing an appropriate printing gap only by transporting the medium to the nip between the platen and the positioning roller. Therefore, the time required for the printing process can be significantly reduced. In addition, a mechanism for raising and lowering the platen by a driving source such as a motor and control for raising and lowering operation are not required, and a simple mechanism can be used, so that cost can be reduced.

According to the printing mechanism of the present invention, the position of the positioning roller with respect to the print head is adjusted by the print gap adjusting means, so that the print gap can be arbitrarily adjusted according to, for example, the paper quality of the medium. it can.

According to the printing mechanism of the third aspect, the position of the print head with respect to the print medium can be moved in the transport direction of the print medium, that is, in the direction perpendicular to the print direction.

[Brief description of the drawings]

FIG. 1 is a front view showing an embodiment of a printing mechanism of the present invention.

FIG. 2 is an enlarged view of a portion A in FIG.

FIG. 3 is a side view of FIG.

FIG. 4 is a side view showing another embodiment.

FIG. 5 is a configuration diagram illustrating an example of a conventional mechanism.

[Explanation of symbols]

 Reference Signs List 1 print head 11 platen 18, 26 positioning roller 15a, 15b biasing member 16a, 16b holder 30 print gap adjustment means 27 arm 28 support part 29 screw 31 support means 20 carriage 21, 22 guide bar 23, 24 gear 25 timing belt P Medium t Medium thickness g Print gap

Claims (3)

[Claims] 1. A print head, a roller-shaped platen that rotates together with a print medium conveyed in a print direction, and a platen that supports the platen so that the platen can be freely moved toward and away from the print head, A platen supporting means that is constantly energized, and is rotatably supported by a frame that holds the print head, and is located at a position separated from the tip end position of the print head by a distance corresponding to an appropriate print gap. A printing mechanism comprising: a positioning roller provided so as to form a nip surface; and printing by sandwiching the print medium between the nip of the platen and the positioning roller. 2. The printing mechanism according to claim 1, further comprising print gap adjusting means for supporting the position of the positioning roller with respect to the print head in an adjustable manner. 3. A print head and a positioning means for supporting a positioning roller movably in a direction parallel to an axis of a platen, wherein the positioning roller is provided in at least any one of a printing direction of a printing medium and a direction perpendicular to the printing direction. 3. The printing mechanism according to claim 1, wherein the printing mechanism is also rotatably supported.