JPH10258532A - Thermal printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent occurrence of a density unevenness or sheet skew with uniform urging by providing one leaf spring on a printer base, and urging a thermal line head to a round platen by the spring under a predetermined pressure. SOLUTION: A sheet 33 to be transferred is conveyed between a round platen 7 and a thermal line head 18. To urge the sheet 33, a rear surface of a radiation plate 24 of the head 18 set is pressurized by a head urging spring 25 formed of one leaf spring. In a printer set state, one side contact of the head 18 is confirmed by observing an urging distribution state of the head 18 by utilizing a pressure sensitive sheet. If there is the one side contact of the head 18, a position of the spring 25 is delicately moved by a deviation preventive contraction 31 and an urging position regulating hole 30, and regulated by three screws 26, 27, 28 to uniform urging distribution. Alignment of the spring can be simply conducted, and the urging to the sheet become uniform.

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 line head pressing mechanism for stabilizing print quality by uniformizing a load pressing paper inserted between a thermal line head and a round platen. The present invention relates to a thermal printer having the same.

[0002]

2. Description of the Related Art In a general thermal printer, when a paper such as a transfer paper inserted between a thermal line head and a round platen is pressed, one of the thermal line head and the circular platen is pressed by a plurality of coil springs or plate springs. Pressing with a spring.

[0003]

When a plurality of springs are used, a plurality of fixing members for fixing the respective springs and a fixing mechanism for fixing the springs are required, and the size is increased. However, in the conventional printer, a plurality of springs can be used due to a large product size.

On the other hand, at present, due to the spread of portable information terminals and the like, there is an increasing need for small and thin portable thermal printers as output devices.

A small and thin portable thermal printer must be several hundred grams in consideration of portability, and the size of the printer is about 180 mm in width, about 120 mm in depth, and about 22 mm in height.
It has an ultra-compact structure of about mm, and it is difficult to incorporate a plurality of springs or a coil spring having a height as in the related art.

The height of the heat-sensitive line head assembly (5 to 5)
(About 6 mm) and the diameter of the round platen is small (about 9 mm).

[0007] Therefore, a strong pressing may cause deformation. In addition, since the gap between the places where the leaf springs are disposed is as small as about 2 mm, the dimensional accuracy of the tip of the leaf spring cannot be made uniform in the production of the leaf spring, and the pressure distribution due to the variation in the contact position between the leaf spring and the thermal line head. Becomes unstable.

[0008] When the pressure distribution of the head becomes unstable, the pressure on the transfer receiving paper becomes unstable, and when printing is performed, density unevenness occurs in characters and the like, which causes deterioration in print quality.

[0009] In addition, the surface pressure on the surface of the paper also changes when the paper is conveyed, which causes paper skew such that the paper is conveyed obliquely.

[0010] The problem to be solved by the present invention is to eliminate the one-side contact of the thermal line head. Because the thermal printer is small and thin, portable and space-saving inside, when the thermal line head is pressed by the head pressing spring, the pressure distribution of the thermal line head may vary. When the pressure distribution varies, a one-sided contact phenomenon of the heat-sensitive line head occurs, and the printing density is high in the portion hit strongly and the printing density is low in the portion hit lightly.

That is, density unevenness occurs in the printed characters and the like, causing deterioration in print quality.

[0012] Also, in the paper conveyance, the surface pressure against the paper surface changes, which causes paper skew such as the paper being conveyed obliquely.

An object of the present invention is to provide a structure for preventing the above-described uneven print density and paper skew in a printer.

Focusing on the above, the present invention makes it possible to easily align the head pressing spring, to make the thermal line head uniformly press the paper to be printed, to generate unevenness in the density of printed characters, and to obliquely transfer the paper. It is an object of the present invention to provide a small-sized, thin, and highly portable thermal printer in which the occurrence of skew of the transported paper is completely prevented, and the printing quality is good.

[0015]

SUMMARY OF THE INVENTION The object of the present invention is to provide a thermal printer in which a thermal line head and a round platen are provided on a printer base and printing is performed on paper with the thermal line head.
This is achieved by providing a single leaf spring on the printer base and pressing the thermal line head against the round platen with a predetermined pressure by the leaf spring.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIGS. 1, 2, 3 and 4. FIG.

FIG. 1 is a perspective view of a main part showing a mechanism for adjusting a pressing position of a pressing spring of a thermal line head according to the present invention, and FIG. 2 is an exploded perspective view of the thermal printer showing an overall structure of the thermal printer of the present invention. FIG. 3, FIG. 3 and FIG. 4 are cross-sectional perspective views of a main part showing a displacement prevention structure of the pressing position adjusting mechanism in the present invention.

First, the overall structure of the thermal printer of the present invention will be described with reference to FIG.

In FIG. 1, reference numeral 16 denotes a connector for connecting the information processing apparatus with a cable, and print data and the like are transmitted from the information processing apparatus to the printer via the connector 16.

When printing, first, the power switch 12
Is turned on, a transfer paper such as a thermal paper or a two-sheet copy paper is inserted through the paper sensor 8 from the paper insertion unit 20,
It is set between the round platen 7 and the thermal line head 18.

Next, the paper supply / discharge switch 13 is pressed, and a paper to be transferred such as thermal paper or two-copy paper is fed by an automatic paper feeding mechanism (hereinafter referred to as "auto loading"), and the paper is caught. Wait for printing to start.

For automatic loading of transfer paper such as thermal paper or two-copy paper, a signal is sent to the control board 4 by pressing a paper feed / discharge switch 13, and a signal is sent from the control board 4 to the line feed motor 10. The feed and the line feed motor 10 are operated. Line feed motor 10
By rotating the round platen 7 via the gear 9, the transfer paper such as thermal paper or two-sheet copy paper is moved between the thermal line head 18 and the round platen 7 to the reference position for cueing.

The transfer of a transfer target paper such as a plain paper printed by transfer using an ink ribbon, a thermal paper whose paper itself is colored by heat or a two-sheet copy paper is performed by a leaf spring (from below) to the thermal line head 18. (Not shown) to press the paper against the round platen 7 to smoothly feed and discharge the paper.

Thereafter, when a print start command is input from the information processing apparatus, the control board 4 rotates the round platen 7 and simultaneously applies heat to a plurality of heating resistors (not shown) of the thermal line head 18. The transferred paper is discharged through the printer cover 3 through the paper guide 19 integrated with the main body upper case 2 while the surface of the transferred paper is colored and printed by the heat, and printing is performed. Let it be completed.

On the control board 4, a CPU 21, a motor drive driver IC, a thermal line head drive IC and the like are arranged.

The heat-sensitive line head 18 and the line feed motor 10 are controlled by the CPU 21.

The printer cover 3 is supported by a release lever 5 and a screw. By tilting the printer cover 3 as shown in the figure, the gap between the heat-sensitive line head 18 and the round platen 7 is enlarged, and when a trouble such as paper jam occurs. It is possible to take out a transfer paper such as a thermal paper or a two-copy paper in which a jam has occurred.

Reference numerals 6a and 6b denote finger guides, which are provided so that the release lever 5 can be smoothly operated when tilted. Reference numeral 14 denotes a power ON / OFF display lamp.

Reference numeral 1 denotes a lower case of the main body, in which a control board 4, a printer main body and the like are disposed. The upper body case 2 is fixed to the lower body case 1 with screws from the back of the printer body.

Reference numeral 15 denotes a secondary battery, which is a driving power source for the control board 4, the line feed motor 10, the thermal line head 18, and the like. The secondary battery 15 is detachable from the upper case 2 of the main body.

An alarm lamp 11 is provided so that the lamp blinks when there is no paper or an abnormality occurs in the printer function.

Reference numeral 22 denotes a paper alignment guide, which is provided integrally with the release lever 5. Paper alignment guide 22
When the paper is fed, the leading edge of the paper is
And has a function of aligning with the contact position of the round platen 7. When the transfer paper such as thermal paper or two-copy paper is fed, a single plate spring applies pressure from below the thermal line head 18 to transfer the transfer paper such as thermal paper or two-copy paper to the round platen. It is designed to be pressed against and transported.

Next, the heat-sensitive line head pressing spring pressing position adjusting mechanism of the present invention will be described with reference to FIG.

The state shown in FIG. 1 shows a state in which a sheet to be transferred such as thermal paper or two sheets of paper is conveyed.

The transfer paper 33 is transported between the round platen 7 and the thermal line head 18. When the transfer paper 33 is pressed, the back surface of the radiator plate 24 of the thermal line head 18 is pressed by a head pressing spring 25 made of a single leaf spring.

The head pressing spring 25 is connected to a printer base 29.
Are screwed into the pressing position adjusting holes 30 by screws 26, 27, and 28.

The round platen 7 is fixed to the side plate 23 by bearings, and is driven to rotate via a gear 9 by a line feed motor (stepping motor).

In the above configuration, the thermal line head 18
As described above, the print quality is degraded if is not uniformly pressed against the transfer receiving paper 33. However, the head pressing spring 25
Of the pressing surface of the heat-sensitive line head 18 or the state of the surface of the heat radiating plate 24 that comes into contact with the pressing surface of the head pressing spring 25, the state of pressing the transfer target paper 33 varies.

This variation in the pressurized state causes density unevenness in printed characters. In places where the pressure is strong, the print density is high, and conversely, the print density is low.

Also, in the transport of paper, the surface pressure on the paper surface changes, causing paper skew such as the paper being transported diagonally.

In view of these problems, the present invention provides a pressure-sensitive paper (a paper that develops color when a certain load is applied to the paper, and a paper that produces a color density difference due to a difference in pressure) when the printer is assembled.
By checking the pressure distribution state of the heat-sensitive line head 18 and confirming the contact of the heat-sensitive line head 18, if there is a contact of the heat-sensitive line head 18, the position of the head pressing spring 25 is squeezed to prevent displacement. It is delicately moved by 31 and the pressing position adjusting hole 30 and is adjusted by three screws 26, 27 and 28 to obtain a uniform pressing distribution.

FIG. 3 shows that when the head pressing spring 25 is positioned, the head pressing spring 25 is
8 is a cross-sectional perspective view of a main part in which a shift preventing throttle 31 is provided on a part of the printer base 29 so that the printer base 29 can be quickly set in parallel with the printer 8; FIG.

FIG. 4 is a sectional perspective view of a main part in which a slit 32 for preventing displacement is provided in a part of the printer base 29 so that the position can be set quickly when the head is pressed against the head pressing spring 25 as in FIG.

With the structure shown in FIGS. 3 and 4, the positioning of the head pressing spring 25 can be easily performed.

[0045]

As described above, according to the present invention, the positioning of the head pressing spring can be easily performed, the pressure applied to the paper on which the thermal line head is printed becomes uniform, and the occurrence of density unevenness of printed characters and It is an object of the present invention to provide a small-sized, thin, and highly portable thermal printer in which the occurrence of paper skew in which the transfer paper is conveyed obliquely is completely prevented, and the printing quality is good.

[Brief description of the drawings]

FIG. 1 is a perspective view of a main part showing a thermal line head pressing spring pressing position adjusting mechanism of the present invention.

FIG. 2 is an exploded perspective view showing the overall structure of the thermal printer of the present invention.

FIG. 3 is a cross-sectional perspective view of a main part showing a heat-sensitive line head pressing spring alignment structure with a squeeze for preventing displacement according to the present invention.

FIG. 4 is a perspective view of an essential part showing a heat-sensitive line head pressing spring positioning structure at a slit for preventing displacement according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Lower case, 2 ... Upper case, 3 ... Printer cover, 4 ... Control board, 5 ... Release lever, 6a ... Finger guide (left), 6b ... Finger guide (right), 7 ... Round platen, 8 ... Paper sensor, 9: gear, 10: line feed motor, 11: alarm lamp, 12: power switch, 1
Reference numeral 3 indicates a paper supply / discharge switch, 14 indicates a power ON / OFF indicator lamp, 15 indicates a secondary battery, 16 indicates a connector, 17 indicates thermal paper and two-copy paper, 18 indicates a thermal line head, 19 indicates a paper guide, and 20 indicates paper. Insertion part, 21 CPU, 22 guide for paper alignment, 23 side plate, 24 radiator plate, 25 head pressing spring, 26, 27, 28 screw, 29 printer base, 30 pressure adjustment hole, 31: squeezing for preventing displacement, 32: slit for preventing displacement, 33: transfer paper.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tomoharu Kitakishi 1-1-1, Higashitaga-cho, Hitachi City, Ibaraki Prefecture Within Tachitaga Engineering Co., Ltd. (72) Inventor Akira Akutsu 1-chome, Higashitaga-machi, Hitachi City, Ibaraki Prefecture No. 1 Hitachi Taga Engineering Co., Ltd. (72) Inventor Toshimitsu Gomida 1-1-1, Higashitagacho, Hitachi City, Ibaraki Pref.

Claims (7)

[Claims] 1. A thermal printer in which a thermal line head and a round platen are provided on a printer base and printing is performed on paper by a thermal line head, wherein a single leaf spring is provided on the printer base, and the thermal line head is provided by the leaf spring. A thermal printer configured to press a round platen with a predetermined pressure. 2. The thermal printer according to claim 1, wherein said leaf spring imparts its acting force to the center of said thermal line head or in the vicinity thereof. 3. A thermal printer in which a thermal line head and a round platen are provided on a printer base and printing is performed on paper by the thermal line head. A press position adjusting mechanism is provided on a printer base for fixing a pressing spring of the thermal line head. Thermal printer. 4. A thermal printer according to claim 3, wherein the press position adjusting mechanism includes a screw, and a plurality of press position adjusting holes provided at regular intervals in the printer base in parallel with the thermal line head. Printer. 5. The thermal printer according to claim 3, wherein the pressure position adjusting holes are evenly provided at intervals of about 2 to 3 mm. 6. The thermal printer according to claim 1, wherein a side of the pressing spring fixing portion of the thermal line head is in contact with a side surface of the thermal line head in parallel with the thermal line head. Or a thermal printer with grooves or slits. 7. The thermal printer according to claim 1, wherein the size of the printer is about 180 mm or less,
A thermal printer having a depth of about 120 mm or less, a height of about 22 mm or less, a round platen diameter of about 10 mm or less, and a weight of several hundred grams.