Incremental printing of symbolic information – Thermal marking apparatus or processes – Recording means engaging or holding means
Reexamination Certificate
2002-01-31
2003-03-25
Tran, Huan (Department: 2861)
Incremental printing of symbolic information
Thermal marking apparatus or processes
Recording means engaging or holding means
Reexamination Certificate
active
06538680
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a small-sized thermal printer mounted on a desk-top type electronic apparatus that is installed in a shop or on various portable information devices, and more particularly to a thermal printer having a structure in which, even if a platen roller is of a detachable type, there is no positional displacement between a thermal head and a platen roller during the printing operation.
2. Description of the Related Art
A conventional example of a general small-sized thermal printer provided with a line-type thermal head will now be described with reference to
FIGS. 7
to
10
.
The thermal printer P
2
shown in
FIG. 7
is provided with a platen roller
102
pivoted rotatably to a frame
101
, a head support member
103
provided with a thermal head (not shown in
FIG. 7
) facing the platen roller
102
and a platen spring
104
for giving a biasing force for pressing this head support member
103
against the platen roller
102
.
Also, the thermal printer P
2
of
FIG. 7
is provided with a head-up lever
105
or the like having a cam for moving the above-described head support member
103
apart from the platen roller
102
during the maintenance operations for the paper clog due to paper jam or for replacement of recording paper. The head-up mechanism composed of this head-up lever
105
is a mechanism provided for the purpose of making it possible to manually separate the platen roller
102
and the head support member (thermal head)
103
away from each other by a predetermined distance (for example, at an interval of several millimeters) in order to enable, for example, replacement operation of a thermal sensitive type recording paper or operations for removing paper clog due to paper jam that occurs almost unavoidably.
In the thermal printer P
2
shown in
FIG. 7
, since the platen roller
102
is of a fixed type such that the roller cannot be detached, there is an advantage that the positional precision between the thermal head and the platen roller
102
is high.
Also, a driven gear (not shown in the drawing) to be engaged with a gear train provided with a motor M as a drive source is provided on one side (on the right end side in
FIG. 7
) of the platen roller
102
. Since the roller
102
is of the fixed type as described above, the force applied to the driven gear when the platen roller
102
is rotationally driven may be absorbed by a shaft fastening portion of the platen roller
102
. Thus, there is no problem that the platen roller
102
is lifted during the driving operation to cause positional displacement relative to the thermal head.
Although the thermal printer P
2
has the advantages as described above, the thermal printer has a disadvantage that the operationability in inserting the recording paper is poor. Namely, when the recording paper is to be inserted as described above, the head-up lever
105
is operated to separate the thermal head and the platen roller
102
away from each other by several millimeters and the recording paper is inserted into the gap thus produced. However, insertion of the recording paper is often difficult when the recording paper is curled or its end is folded. Accordingly, there is a demand to improve its structure.
Therefore, a thermal printer P
3
that has a structure such that a platen roller
202
may be detached as shown in
FIGS. 8 and 9
has been developed.
This thermal printer P
3
is composed of a frame
202
having a pair of side wall portions
201
a
and
201
b
arranged to face each other through a predetermined interval in a paper width direction, a head support member
204
for holding a thermal head
203
, a platen roller attaching/detaching mechanism A′ for detachably and rotatably bearing the platen roller
210
by means of the above-described pair of side wall portions
201
a
and
201
b,
a pressing mechanism B′ for bringing the surface of the thermal head
203
into contact with the circumferential surface of the above-described platen roller
210
with predetermined pressing force, a gear transmission mechanism G
1
for transmitting the rotational driving force of the motor M to a driven gear G
2
fixed at one end (at the right end in the drawing) of the above-described platen roller
210
, and so on. In the structural example shown in
FIGS. 8 and 9
, the pressing mechanism B′ is formed integrally with the platen roller attaching/detaching mechanism A′ and they operate as an integral mechanism as a whole.
As shown in
FIG. 9
, the platen roller attaching/detaching mechanism (pressing mechanism B′) A′ is provided with a swing member
300
having a U-shape as a whole and which is slightly wider than the thermal head
203
(head support member
204
). The swing member
300
is provided with a pair of hook-like latch portions
301
to be engaged with both shaft ends (
210
a
and
210
b
) of the platen roller so as to draw the platen roller
210
toward surface of the thermal head
203
, a pair of arm portions
302
for guiding the latch portions
301
to the rear side of the head support member
204
along both sides of the thermal head
203
(head support member
204
), and an elastic member support portion
303
provided at its both ends with arm portions
302
for supporting springs S
10
, S
10
as the spring members and arranged in the width direction in the rear of the head support member
204
. The swing member
300
and the head support member
204
are swingably borne through a support shaft
400
(see
FIG. 10
) provided between the side wall portions
201
a
and
201
b.
Furthermore, a release lever
500
serving as an engagement release means for swinging the swing member
300
itself forwardly so as to release the engagement between the latch portions
301
and the both shaft ends
210
a
and
210
b
of the platen roller
210
is provided in the rear of the swing member
300
(see FIG.
8
).
The thermal printer P
3
having such a structure has such an advantage that, when giving a new supply of the recording paper or the paper clog occurred, the release lever
500
is operated to activate the platen roller attaching/detaching mechanism A′ to remove the platen roller
210
from the frame
202
to thereby make it possible to perform the removal of the paper causing the paper clog, giving a new supply of the recording paper, or the like.
Nevertheless, the thermal printer P
3
shown in
FIGS. 8 and 9
has the above-described advantage, however, the printer suffers from such a disadvantage that the positional displacement between the thermal head
203
and the platen roller
210
can easily occur due to such arrangement that the platen roller
210
is of the detachable type.
Namely, in this thermal printer P
3
, various forces (F
1
, F
2
, and F
3
) as shown in
FIG. 10
are applied to the platen roller
210
and the composite force (F
4
) thereof works in a direction to lift the platen roller
210
. Accordingly, the positions of the thermal head
203
and the platen roller
210
are displaced from each other upon the execution of the printing operation.
More specifically, under the state where the shaft end
210
of the platen roller
210
at which the driver gear G
2
is provided, is being held to the latch portion
301
, the pressing force F
1
to be applied via the thermal head
203
(head support member
204
), the pressing force F
2
to be applied via the arm portion
302
and the latch portion
301
(i.e., the force for drawing the platen roller
210
to the side of the thermal head
203
) and the pressing force F
3
to be applied via the driven gear G
2
due to the drive of the gear transmission mechanism G
1
upon the execution of the printing operation, which works in counterclockwise direction in the drawing, are applied to that shaft end
210
. In particular, a part of the rotational force of F
3
is converted into the force that works in a direction for moving the shaft end
210
b
apart from the latch portion
301
, due to frictional force between the latch portion
3
Adams & Wilks
Seiko Instruments Inc.
Tran Huan
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