Thermal printer having integrally formed paper guide and frame

Description

TECHNICAL FIELD

The present invention relates to a small-sized line thermal printer used for a portable electronic device such as a receipt issuing machine.

BACKGROUND ART

Heretofore, a small-sized line thermal printer is widely used for a portable electronic device such as a receipt issuing machine.

As this type of thermal printer is required to be readily portable, a small-sized, light one is desired.

Therefore, heretofore, a body frame is made of metal such as a thin steel plate and a paper guide made of plastic for guiding recording paper to a printing part between a platen roller and a thermal head is installed as disclosed, for example, in Unexamined Japanese Patent Application No. Hei. 4-140175.

In such a thermal printer, a platen roller

104

and a head support part

103

are secured to a body frame

102

made of plastic as shown in

FIG. 6

, for example. Predetermined printing is executed on thermal recording paper by attaching a thermal head

130

on the side of the platen roller

104

of the head support part

103

so that thermal recording paper is held between the thermal head and the platen roller and by pressing the thermal head

130

attached to the head support part

103

on the platen roller

104

by a torsion coil spring

107

.

There is also another conventional thermal printer in which a body frame is formed integrally with a paper guide from plastic material such as polycarbonate.

However, in such conventional type thermal printers, there are the following problems:

That is, in the case of the above conventional type thermal printers, as the paper guide

121

is made of plastic material, a charge cannot be discharged from the paper guide if thermal recording paper

100

is electrified, and the thermal head

130

may be broken by a spark and others.

Further, as the paper guide

121

is also electrified, there is a problem that the thermal recording paper

100

cannot be guided to the vicinity of the thermal head

130

and the thermal recording paper is hard to insert.

As the platen roller

104

is arranged apart from the bottom of the printer in view of space for gears for driving the platen roller, the paper guide

121

cannot be formed as a part of the body frame

102

. Therefore, as the paper guide

121

is made of another member, the number of parts is increased and as a result, the cost is increased.

Even if the paper guide

121

is formed as a part of the body frame

102

, there is also a problem that it is difficult to increase an angle at which thermal recording paper

100

is wound on the platen roller

104

and precision in feeding paper is not satisfactory.

Furthermore, if the body frame is also made of plastic material as in the other conventional types, the frame must be formed relatively thick to enhance rigidity. As a result, miniaturization cannot be sufficiently achieved.

SUMMARY OF THE INVENTION

The present invention was made in view of the problems and difficulties accompanying the conventional thermal printers. Therefore, an object of the present invention is to provide a thermal printer capable of increasing an angle at which thermal recording paper is wound on a platen roller without generating static electricity.

Another object of the present invention is to provide a thermal printer that is small in size and light in weight, which requires the small numbers of parts and components.

A thermal printer according to the present invention includes a metallic body frame for supporting at least one of a thermal head and a platen roller for holding recording paper in a printing position and a paper guide for guiding the recording paper to the printing position. In the thermal printer of the invention, the paper guide at least in the vicinity of the printing position is integrated, meaning homogeneously formed so as to be a single part, with the body frame.

According to the above constitution, as the paper guide for guiding recording paper to the printing paper is integrated with the metallic body frame, static electricity is discharged via recording paper even if the recording paper is electrified and the paper guide is never electrified. As a result, as no spark is generated between the vicinity of a printing position of the paper guide and the thermal head, the paper guide can be arranged in the vicinity of the printing position and thermal recording paper can be readily and smoothly inserted.

In addition, as the paper guide is not made of plastic material in the case of the present invention, the thickness can be reduced, and as the paper guide is integrated with the body frame, the number of parts can be reduced and as a result, a small-sized, light and low-priced thermal printer can be obtained.

Also, in the case of the present invention, the paper guide in a position in which recording paper is inserted is integrated with the body frame, is bent upward approximately along the width of paper and is provided with a bend-raise portion on which recording paper is slid.

In this case, as static electricity generated on recording paper is discharged via the bend-raise portion by integrating the bend-raise portion which comes in contact with the recording paper with the frame, the carried recording paper can be prevented from being electrified, and any detrimental effect upon the thermal head by static electricity can be prevented.

As an angle at which recording paper is wound on the platen roller can be increased by the bend-raise portion and in addition, the area in which the paper guide and the recording paper are in contact is reduced by the bend-raise portion, a running load is not increased even if the recording paper is wet, the recording paper is smoothly run and high quality printing is enabled.

Further, in the case of the present invention, the paper guide is provided with a step relative to the bottom of the body frame along the direction of the width of recording paper so as to approach the platen roller.

According to the above constitution, the shape along the platen roller of the paper guide can be readily obtained without working so that the paper guide is large-sized, the bend-raise portion provided with desired height can be obtained and hereby, the paper guide high in rigidity and precision can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1

is a plan showing the whole constitution of an embodiment of a thermal printer according to the present invention, is a side view showing the constitution of a printing part in the embodiment and shows a state in which a lever member is pushed down.

FIG. 3

is a side view showing the constitution of the printing part in the embodiment of the present invention,

FIG. 4

is a side view showing the constitution of a driving part in the embodiment, and

FIG. 5

is a side view showing the vicinity of the lever member in the embodiment.

FIG. 6

is a side view showing the constitution of a conventional type thermal printer.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring to

FIGS. 1

to

5

, an embodiment for realizing a thermal printer according to the present invention will be described in detail below.

FIG. 1

is a plan showing a thermal printer equivalent to this embodiment,

FIG. 2

is a side view showing a printing part and shows a state in which a lever member is pushed down and a thermal head presses a platen roller,

FIG. 3

is a side view showing the printing part and a state in which the lever member is pulled up and a thermal head is separated from a platen roller,

FIG. 4

is a side view showing a driving part and

FIG. 5

is a side view showing the vicinity of the lever member.

As shown in

FIG. 1

, a thermal printer

1

is provided with a body frame

2

made of metal such as cold-rolled steel (SPCC), and a printing part

3

. A platen roller

4

and a driving motor

5

for driving the platen roller

4

are attached to the body frame

2

.

The body frame

2

is formed by bending the bottom

2

c

and a pair of side walls

2

a

and

2

b

by sheet metal working. A paper guide

21

described later is formed on the rear side of the body frame

2

. The width of each frame side wall

2

a

and

2

b

is set to a dimension slightly larger than the width of a paper roll described later.

The printing part

3

is constituted by the thermal head

30

and a fixing plate

31

. A predetermined electrode is formed on the surface of the thermal head

30

and is connected to a circuit board (not shown). The thermal head

30

is fixed to a long flat fixing plate

31

made of metal such as a soft iron plate.

Arms

31

a

and

31

b

are bent at both ends of the fixing plate

31

so that each bent width is approximately equal to the inside width of the body frame

2

. These arms

31

a

and

31

b

are attached to a supporting shaft

6

suspended in parallel with the platen roller

4

on both sides of the body frame

2

so that the arms can be turned freely. A torsion coil spring

7

required for the thermal head

30

to press the platen roller

4

is attached to the supporting shaft

6

. In this case, as shown in

FIG. 1

, spring portions

7

b

and

7

c

are formed on both sides of a fitting portion

7

a

in the shape of approximately a letter C in the center of the torsion coil spring

7

. The supporting shaft

6

is attached with it piercing the torsion coil spring

7

. The arms

7

d

and

7

e

of the spring

7

press the fixing plate

31

, and the fitting portion

7

a

is pressed by a supporting portion

2

d

formed from the bottom

2

c

of the body frame

2

. With this arrangement, the thermal head

30

presses the platen roller

4

toward the bottom

2

c

from the top.

A protruded portion

31

c

fitted to a guide portion

80

of a lever member

8

for raising the fixing plate

31

is integrated with the end on the side of the lever member

8

of the fixing plate

31

. The tongue-like protruded portion

31

c

is protruded from one side wall

2

b

of the body frame

2

. The tongue-like protruded portion

31

c

is bent on the reverse side to the side on which the thermal head

30

is fixed and is further provided with a portion for contact for regulating the turning of the lever member

8

.

The platen roller

4

is respectively attached to the both side walls

2

a

and

2

b

of the body frame

2

via platen bearings

41

a

and

41

b

so that the platen roller can be rotated freely. As shown in

FIGS. 1 and 4

, the torque of the rotation shaft

50

of the driving motor

5

is transmitted to a gear

9

fixed at one end of the platen shaft

40

of the platen roller

4

via gears

10

,

11

and

12

. The driving motor

5

is connected to a circuit board not shown via a lead wire

51

and a connector

52

.

The lever member

8

for switching between pressure upon or release from the platen roller

4

by the thermal head

30

is attached to the other end of the platen roller

4

so that the lever member can be turned freely. The lever member

8

is made of resin such as polycarbonate and the guide portion

80

is formed in the vicinity of the center of the turning.

As shown in

FIGS. 2 and 5

, the guide portion

80

is formed approximately in a circular arc and is provided with a guide face

80

a

which extends from the center of the turning toward a grip

81

of the lever member

8

. As shown in

FIG. 5

, slight clearance is formed between the guide face

80

a

of the guide portion

80

and the protruded portion

31

c

of the fixing plate

31

in a state in which the lever member

8

is pushed down. A concave portion

80

b

for fitting with the protruded portion

31

c

of the fixing plate

31

is formed at the end on the side of the grip

81

of the guide portion

80

.

As shown in

FIGS. 2 and 3

, the paper guide

21

for guiding paper S extended from thermal recording paper rolled cylindrically to a printing position in which the thermal head

30

and the platen roller

4

come in contact is formed on the rear side of the bottom

2

c

of the body frame

2

with a part of the bottom

2

c

of the body frame

2

bent.

An introducing portion

21

a

along the shape of the platen roller

4

is formed by curving the paper guide

21

on the side of the platen roller

4

. In this case, the end

21

c

of the introducing portion

21

a

enters the vicinity of a part in which the thermal head

30

and the platen roller

4

come in contact, that is, the vicinity of the printing position.

As shown in

FIG. 1

, grooves

24

and

25

are respectively formed on both sides at the end on the rear side of the paper guide

21

and a bend-raise portion

21

b

is formed in a part between these grooves

24

and

25

so that the bend-raise portion is protruded on the side of the platen roller

4

. The bend-raise portion

21

b

is extended approximately in parallel with the platen roller

4

, that is, in the direction of the width of paper S and is formed by bending for example so that the section is approximately in the shape of a mountain.

Referring to

FIG. 2

, the paper guide

21

is provided with an introducing portion

21

a

and a bend-raise portion

21

b

. The bend-raise portion

21

b

is subjected, for instance, to a drawing process, so that the paper guide

21

is slightly raised relative to the bottom

2

c

. That is, the paper guide

21

is provided with a step h relative to the bottom

2

c

so as to approach the platen roller

4

.

As shown in

FIG. 2

, the top of the bend-raise portion

21

b

is formed so that the top is approximately as high as the lower part of the platen roller

4

.

In this embodiment constituted as described above, when paper S is installed, the grip

81

of the lever member

8

is grasped by an operators fingers and raised. As a result, the guide face

80

a

of the guide portion

80

of the lever member

8

and the protruded portion

31

c

of the fixing plate

31

come in contact, the fixing plate

31

is raised as the lever member

8

is turned and pressure upon the platen roller

4

by the thermal head

30

is released. When the lever member

8

is further raised, the protruded portion

31

c

of the fixing plate

31

is fitted to the concave portion

80

b

of the guide portion

80

of the lever member

8

and as shown in

FIG. 3

, the lever member

8

is fitted with the grip

81

of the lever member

8

standing relative to the bottom

2

c

of the body frame

2

. In this state, the end of paper S is inserted between the platen roller

4

and the introducing portion

21

a

of the paper guide

21

from the rear side of the paper guide

21

.

If paper S is printed, the grip

81

of the lever member

8

is grasped and pushed down on the rear side. As a result, the fitting between the protruded portion

31

c

of the fixing plate

31

and the concave portion

80

b

of the guide portion

80

of the lever member

8

is released and as shown in

FIG. 2

, the fixing plate

31

is pressed upon paper S on the platen roller

4

by the pressure of the torsion coil spring

7

. In this state, the thermal head

30

is driven, the platen roller

4

is rotated to carry paper S and predetermined printing is executed on the paper S.

According to this embodiment constituted as described above of the present invention, as the paper guide

21

provided with the introducing portion

21

a

for guiding paper S in a direction in which the paper S is wound on the platen roller

4

is integrated with the metallic body frame

2

, static electricity is discharged via the body frame even if the paper S is electrified and the paper guide

21

is never electrified. As a result, as no spark is generated between the end

21

c

of the introducing portion

21

a

and the thermal head

30

and the end of the introducing portion can be arranged extremely near the platen roller

4

, paper S can be readily and smoothly inserted.

In the case of this embodiment, as paper S and the bend-raise portion

21

b

of the paper guide

21

are always in contact when the paper S is printed, static electricity generated on the paper S is released via the bend-raise portion

21

b

and the paper S is never electrified. As a result, any bad effect upon the thermal head

30

by static electricity can be prevented.

Further, as the area in which paper S and the paper guide

21

are in contact is small because the paper is in contact with only the bend-raise portion

21

b

, a running load between the paper S and the paper guide

21

can be reduced if the paper S is wet. In addition, as an angle at which paper S is wound on the platen roller

4

is increased by the bend-raise portion

21

b

and ability in feeding paper is enhanced, high quality printing by the smooth running of the paper S is enabled.

Furthermore, as the paper guide

21

is provided with a step h relative to the bottom

2

c

of the body frame

2

so that clearance between the paper guide and the platen roller

4

is reduced, the introducing portion

21

a

in a shape along the platen roller

4

and the bend-raise portion

21

b

formed so that it is high as desired can be readily obtained without increasing a size of the paper guide

21

and hereby, the paper guide

21

high in rigidity and precision can be obtained.

Moreover, in the case of this embodiment, as plastic material is not used for the material of the paper guide

21

, the paper guide can be thinned, and the thermal printer can be miniaturized.

Also as the paper guide

21

is integrated with the body frame

2

, the number of parts is reduced and the cost can be reduced.

In addition, in this embodiment, as the thermal head

30

can be separated from the platen roller

4

by raising the lever member

8

, an interval between the thermal head

30

and the platen roller

4

can be increased, and the platen roller

4

can be readily cleaned.

The present invention is not limited to the above embodiment and various variation is allowed.

For example, the shape, the thickness and others of the introducing portion and the bend-raise portion respectively formed in the paper guide are not limited to those in the above embodiment, design can be varied within the scope of the present invention and the shape, the material and others of the body frame may be also varied suitably.

APPLICABILITY TO INDUSTRY

As described above, the thermal printer according to the present invention is useful for a printer for a portable electronic device such as a receipt issuing machine and is particularly suitable for using as a small-sized line thermal printer.

Claims

1. A thermal printer comprising:a thermal head and a platen roller, both for holding recording paper in a printing position therebetween, a metallic sheet defining a metallic body frame for supporting at least one of said thermal head and said platen roller, the metallic sheet comprising a bent portion defining a metallic paper guide in the vicinity of said printing position, for guiding said recording paper to said printing position.
2. A thermal printer according to claim 1, wherein:said paper guide is formed as a single inseparable unit with said body frame in a position in which said recording paper is inserted; and said paper guide is provided with a bend-raise portion extended approximately in the direction of the width of said recording paper, bent upward and on which said recording paper is slid.
3. A thermal printer according to claim 2, wherein: said bend-raise portion is formed as a single inseparable unit at a part of the paper guide where the roller paper (s) is inserted.
4. A thermal printer according to claim 1, wherein said thermal head is disposed on a bottom part of said body frame for printing a paper;said paper is urged against said thermal head by said platen roller and said roll paper is urged against said platen roller by said thermal head.
5. A thermal printer according to claim 1, further comprising:a spring urging the thermal head toward the platen roller.
6. A thermal printer comprising:a thermal head and a platen roller, both for holding recording paper in a printing position therebetween, a metallic sheet defining a metallic body frame for supporting at least one of said thermal head and said platen roller, the metallic sheet comprising a bent portion defining a metallic paper guide in the vicinity of said printing position, for guiding said recording paper to said printing position, said paper guide being provided with a step relative to the bottom of said body frame at both ends in the direction of the width of said recording paper so as to approach said platen roller.
7. A thermal printer comprising:a thermal head and a platen roller, both for holding recording paper in a printing position therebetween, a metallic sheet defining a metallic body frame for supporting at least one of said thermal head and said platen roller, the metallic sheet comprising a bent portion defining a metallic paper guide in the vicinity of said printing position, for guiding said recording paper to said printing position, said paper guide is formed as a single inseparable unit with said body frame in a position in which said recording paper is inserted; said paper guide is provided with a bend-raise portion extended approximately in the direction of the width of said recording paper, bent upward and on which said recording paper is slid; and said paper guide is provided with a step relative to the bottom of said body frame at both ends in the direction of the width of said recording paper so as to approach said platen roller.
8. A thermal printer comprising a sheet defining a body frame for supporting at least one thermal head and a platen roller for holding recording paper in a printing position between them, the sheet comprising a bent portion defining a paper guide for guiding said recording paper to said printing position, wherein:both of said body frame and said paper guide are electrically conductive.
9. A thermal printer comprising:a thermal head; a platen roller contactable with the thermal head, and an electrically conductive sheet defining a body frame supporting at least one of the thermal head and the platen roller, the electrically conductive sheet comprising a bent portion defining an integral, inseparable paper guide that is electrically conductive and that extends to the vicinity of a position where the platen roller is contactable with the thermal head.
10. A thermal printer according to claim 9, wherein the body frame has a bent-raise portion that is bent upward from a bottom of the body frame, and that is elongated along the platen roller.
11. A thermal printer according to claim 10, wherein a minimal distance between the platen roller and the bottom of the body frame is substantially equal to a maximum distance between the bent-raise portion and the bottom of the body frame.
12. A thermal printer according to claim 9, wherein the paper guide is raised upward from a bottom of the body frame by a step.
13. A thermal printer according to claim 9, further comprising:a spring by which the thermal head and the platen roller are urged against each other.
14. A thermal printer according to claim 9, further comprising:a spring urging the thermal head toward the platen roller.
15. A thermal printer according to claim 9, wherein the paper guide is partially curved.

Priority Claims (1)

Number	Date	Country	Kind
9-005012	Jan 1997	JP

PCT Information

Filing Document	Filing Date	Country	Kind	102e Date	371c Date
PCT/JP98/00148		WO	00	9/14/1998	9/14/1998

Publishing Document	Publishing Date	Country	Kind
WO98/30396	7/16/1998	WO	A

US Referenced Citations (10)

Number	Name	Date
4425047	Narushima	Jan 1984
4683478	Suzaki et al.	Jul 1987
5342131	Nakajima et al.	Aug 1994
5541635	Wills et al.	Jul 1996
5618117	Yoshida et al.	Apr 1997
5820068	Hosomi et al.	Oct 1998
5833380	Hosomi et al.	Nov 1998
5846003	Mori et al.	Dec 1998
5902059	Asai et al.	May 1999
6118469	Hosomi	Sep 2000

Foreign Referenced Citations (6)

Number	Date	Country
54-19007	Feb 1979	JP
57-177755	Nov 1982	JP
60-105573-A	Jun 1985	JP
61-219671-A	Sep 1986	JP
04-1658841-A	May 1992	JP
4-140175	May 1992	JP

Thermal printer having integrally formed paper guide and frame

Information

Patent Number

Date Filed

Date Issued

Inventors

Original Assignees

Examiners

Agents

CPC

US Classifications

Field of Search

US