JPH04298357A - Thermal printer - Google Patents

Abstract

PURPOSE:To provide a thermal printer capable of inexpensively preventing the folding of recording paper, color shift and the detachment of the recording paper from a clamper. CONSTITUTION:By mounting a cylindrical paper guide 21 on the circulating drive pulley shaft 20 of a clamper 10 in a rotatable manner, the folding of recording paper is prevented by the cylindrical paper guide 21 and the difference in feed quantity generated on the pulley shaft 20 is eliminated by the free rotation of the paper guide 21 to prevent color shift and the detachment of the recording paper from the clamper 10.

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 paper guide in a recording paper transport mechanism thereof.

0002

[Prior Art] Figures 3 to 5 are, for example, published in Japanese Patent Application Laid-Open No. 2-2199.
61, in which 1 is a platen roller, 2 is a first pulley rotatably disposed on the shaft 1a on both sides of the platen roller 1, and 3 is a first pulley. A pair of timing belts are hung on a pulley 2, 4 is a second pulley that extends the timing belt 3, 5 is a recording paper, and 6 is an ink sheet, which is supplied with ink for thermal transfer from a supply reel 7. After the ink is thermally transferred, it is wound onto a take-up reel 8. 9 is a thermal head that thermally transfers the ink from the ink sheet 6 onto the recording paper 5 by an electric signal; 10 is a thermal head installed on a bridge 10a installed between the timing belt 3 in parallel with the platen roller 1; A clamper runs in synchronization with the gripping timing belt 3; 11 is a paper detection sensor that detects the leading edge of the recording paper 5; 12 is a paper feeding mechanism that separates and supplies the stacked recording papers 5 one by one; 13 is a paper feeding mechanism 12 14 is a clamper closing mechanism that causes the clamper 10 to grasp the leading edge of the recording paper 5 that has been fed, 14 is a clamper opening mechanism that releases the grip of the clamper 10 immediately before ejecting the recording paper 5 on which printing has been completed, and 15 and 16 are timing belts. 3, a paper guide that holds the recording paper 6 conveyed along 3; 17 is a first motor that is a rotational driving source for the platen roller 1; 18 is a second motor that is a driving source for the second pulley 4; A torque limiter 19 that slips at a predetermined torque is provided between the second pulley 4 and the second motor 18. The rotational speed of the second motor 18 is set so that the running speed of the timing belt 3 is faster than the circumferential speed of the platen roller 1, and the torque limiter 19 constantly slips to absorb the speed difference. The leading end of the recording paper 5 is configured to be pulled by a clamper 10 installed on the timing belt 3 with a predetermined force depending on the torque set by a torque limiter 19. In addition, 20 is the second pulley 4
The radius of the pulley axis is extremely small compared to that of the second pulley 4.

[0003] The operation of the thermal printer configured as described above will be explained. First, before starting the printing operation,
The clamper 10 is located above the clamper closing mechanism 13, and the recording paper 5 is fed from the paper supply mechanism 12.
When the leading end of the recording paper 5 is inserted between the claws of the clamper 10, the clamper closing mechanism 13 is operated to close the clamper 10 and grip the leading end of the recording paper 5, and the platen roller 1 starts rotating in the direction of arrow A. At this time, the thermal head 9 is separated from the platen roller 1, and the clamper 10, which has gripped the recording paper 5 through the gap, is rotated by the torque limiter 19, the second pulley 4, and the timing belt by the rotation of the second motor 18. 3 and reaches the paper detection sensor 11. When the leading edge of the recording paper 5 is detected by the paper detection sensor 11, the thermal head 9 comes into contact with the platen roller 1 and printing starts.

[0004] Then, when the clamper 10 goes around the second pulley 4 and reaches the position of the clamper closing mechanism 13 again,
The thermal head 9 is separated from the platen roller 1, and a clamper 10 is passed between the thermal heads 9 and the ink sheet 6 is set up for the next color at the same time. After that, printing of the second color is started. Similarly, when the third color printing is performed and the color printing is completed, and the clamper 10 reaches the position of the clamper release mechanism 14, the clamper release mechanism 14
is opened to guide the leading edge of the recording paper 5 in the paper ejection direction.

Here, as shown in FIG. 5, if the recording paper 5 is in the process of printing when the clamper 10 passes the pulley shaft 20, the recording paper 5 is bent into a dogleg shape on the pulley shaft 20. This causes buckling and paper folding. Also, during printing, the pulley shaft 20 is thin with respect to the second pulley 4, so when the clamper 5 rotates around the second pulley 4, the recording paper 5 becomes slack, causing the clamper on the second pulley 4 to sag. Since the recording paper conveyance amount a of No. 10 is different from the conveyance amount b on the pulley shaft 20 due to the contact between the pulley shaft 20 and the recording paper 5, the recording paper 5 wraps around the pulley shaft 20 and creates tension, so its conveyance is The difference in amount becomes the sliding friction force (resistance force), and the recording paper 5
Slippage occurs between the clamper 10 and the clamper 10, and the conveyance speed tends to change. This may cause an error in the position of the recording paper 5, resulting in color misregistration, or in the worst case, the recording paper 5 may come off the clamper 10.

[0006]

[Problems to be Solved by the Invention] Since the conventional thermal printer is constructed as described above, when the clamper 10 passes the pulley shaft 20, the recording paper 5
Paper folding occurs on 0. Further, the difference between the conveyance amount a of the recording paper 5 on the second pulley 4 and the conveyance amount b on the pulley shaft 20 becomes a resistance force, and the difference between the recording paper 5 and the clamper 10 in order to pull the paper backward. There were problems such as slippage, color misalignment, and detachment of the recording paper 5 from the clamper 10.

The present invention has been made to solve the above-mentioned problems, and provides a thermal printer that can inexpensively prevent recording paper from folding, color misalignment, and recording paper from coming off the clamper. The purpose is to

[0008]

[Means for Solving the Problems] A thermal printer according to the present invention has a cylindrical paper guide rotatably attached to a circulating drive pulley shaft of a clamper.

[0009]

[Operation] The thermal printer according to the present invention prevents paper from folding by attaching a cylindrical paper guide having a radius smaller than that of the second pulley on the pulley shaft of the second pulley. By rotating independently of the shaft, the difference in conveyance amount that occurs on the pulley shaft is eliminated, thereby preventing color misalignment and preventing recording paper from coming off the clamper.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. FIG. 1 is a perspective view of essential parts, and FIG. 2 is a side view of FIG. 1. Parts that are the same as or corresponding to those of the prior art are given the same reference numerals, and their explanations will be omitted. In the figure, 21 is the second
This is a cylindrical paper guide that is rotatably attached to the outer periphery of the pulley 4 without being affected by the pulley shaft 20. The diameter of the paper guide 21 is large enough to prevent the recording paper 5 from folding, and small enough not to get in the way when the clamper 10 passes the second pulley 4.

By providing the paper guide 21 in this manner, when the recording paper 5 passes the second pulley 4 during printing, the paper guide 21 prevents the paper from bending (buckling), thereby preventing the paper from folding. Also, the clamper 1 on the second pulley 4
Although the conveyance amount a of the recording paper 0 and the conveyance amount c on the paper guide 21 are different, the paper guide 21 is
By freely rotating on the paper guide 21, the difference disappears, and the sliding frictional force between the recording paper 5 and the paper guide 21 becomes minute.

0012

As described above, according to the present invention, by attaching a cylindrical rotatable paper guide to the circulation drive pulley shaft of the clamper, it is possible to prevent paper folding of recording paper.
The effect of preventing color misregistration and preventing recording paper from coming off the clamper can be achieved at low cost.

[Brief explanation of drawings]

FIG. 1 is a perspective view of essential parts of a thermal printer showing an embodiment of the present invention.

FIG. 2 is a side view of FIG. 1;

FIG. 3 is a schematic side view showing a conventional thermal printer.

FIG. 4 is a perspective view of the main part of FIG. 3;

FIG. 5 is a side view of the main part of FIG. 4;

[Explanation of symbols]

1 Platen roller 2 First pulley 3 Timing belt 4 Second pulley 5 Recording paper 9 Thermal head 10 Clamper 20 Pulley shaft 21 Paper guide

Claims (1)

[Claims] 1. A thermal printer that forms an image by repeating a printing operation of applying one color each time the recording paper is circulated by circulating the recording paper using a clamper that grips the leading edge of the recording paper, wherein the clamper is driven in a circular manner. A thermal printer characterized by a cylindrical paper guide rotatably attached to a pulley shaft to prevent the recording paper from folding.