Thermal printer unit and thermal printer

Details Thermal printer unit and thermal printer Thermal printer unit and thermal printer

2001-06-18

2004-01-27

Colilla, Daniel J. (Department: 2854)

Typewriting machines

Platen or platen-moving mechanism

For movement of platen other than for line-spacing

C400S120160, C347S220000

Reexamination Certificate

active

06682239

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a thermal printer unit and a thermal printer, and, in particular, to a thermal printer unit and a thermal printer applied to a portable terminal apparatus and a POS (Point Of Service) apparatus, and employing rolled paper.
For a printer of a portable terminal apparatus or a POS apparatus, increase in printing speed and easy exchange of printing paper are demanded. In order to deal with these requests, a line thermal printer employing rolled paper as printing paper is used.
2. Description of the Related Art
FIG. 1
shows a line thermal printer
10
in the related art.
FIG. 2
shows a general configuration of the line thermal printer
10
shown in FIG.
1
.
FIGS. 3A
,
3
B and
3
C illustrate operation of a platen roller and a thermal head of the line thermal printer
10
shown in FIG.
1
.
The line thermal printer
10
is of a clam-shell-type, and has a body
11
and a cover
13
supported by a shaft
12
on the body
11
. The body
11
has a paper roll containing part
11
a
in which a paper roll is contained, and, also, has the thermal head
15
incorporated therein together with a head pressing spring
14
. The platen roller
16
is supported on an extending end of the cover
13
. In the body
11
, grooves
18
in which a shaft
17
of the platen roller
16
is fitted are formed. Each of these grooves
18
has a shape of a vertically extended straight line and has an opening
18
a
at the top thereof, as shown in FIG.
3
A.
The line thermal printer
10
enters a condition, shown in
FIGS. 2 and 3C
, such that the printer
10
can perform printing as a result of: the cover
13
being opened; the paper roll
20
having a paper end
21
thereof unwound partially being contained in the paper roll containing part
11
a
; the unwound paper end
21
being drawn out so as to pass in front of the thermal head
15
; and the cover
13
being closed. That is, at the last stage of closing the cover
13
, the platen roller
16
comes into contact with the thermal head
15
and pushes it out, the shaft
17
enters the grooves
18
, and, the platen roller
16
reaches a position shown in
FIGS. 2 and 3C
, as shown in
FIGS. 3A and 3B
. In this condition, the head pressing spring
14
presses the thermal head
15
onto the platen roller
16
by a force F
1
(functioning as a head pressure), and the paper end
21
is sandwiched between the thermal head
15
and platen roller
16
, as shown in FIG.
2
. Further, the platen roller
16
and cover
13
are locked together in a condition in which the shaft
17
of the platen roller
16
is fitted into the grooves
18
and are pressed onto the bottoms of the grooves
18
by the above-mentioned force F
1
.
As the necessity arises, the paper roll
20
is exchanged after the cover
13
is opened as a result of the end of the cover on the side of the platen roller
16
being pulled up with a strong force.
In this line thermal printer
10
, when the cover
13
is opened, a wide space is formed between the thermal head
15
and platen roller
16
, and, thereby, exchange of the paper roll
20
can be easily performed. Further, the cover
13
is locked through the operation of closing the cover
13
, and the lock is released as a result of the cover
13
being pulled up. Accordingly, any other special locking operation or lock releasing operation is needed to be performed. Accordingly, the printer
10
is convenient in operation thereof.
There is a possibility that a portable terminal apparatus is knocked or dropped by accident during handling thereof. Accordingly, the line thermal printer which is incorporated in the portable terminal apparatus is required to have a strong locking mechanism such that the cover
13
is prevented from being opened by accident, even when the portable terminal apparatus is knocked or dropped.
As shown in
FIG. 3C
, in the above-mentioned line thermal printer
10
, the cover
13
is locked or prevented from opening by the force F
1
. Accordingly, in order to achieve the stronger locking mechanism as mentioned above, it is necessary to increase the force F
1
applied by means of the head pressing spring
14
.
However, when the force F
1
is increased, the head pressure may become larger than a proper head pressure. Thereby, the printing quality may be degraded, the thermal head
15
may be easily worn so as to have a shorter life, and so forth.
In contrast to this, when it is demanded that the locking of the cover be easily released, the above-mentioned force F
1
applied by the head pressing spring
14
is to be decreased. However, when the force F
1
is decreased, the head pressure may become lower than the proper one, and, as a result, the print becomes faint.
Further, the thermal head
15
is inclined in the direction of the grooves
18
as shown in
FIG. 2
so that the force F
1
is directed obliquely downward. Thereby, at the last stage of closing the cover
13
, the platen roller
16
may come into contact with a top corner
15
a
of the thermal head
15
strongly, as shown in FIG.
3
A. Thereby, the platen roller
16
may be harmed.
FIG. 11
shows a line thermal printer unit
130
incorporated in another clam-shell-type line thermal printer in the related art. In the line thermal printer unit
130
, a thermal head assembly
132
is incorporated into a frame
131
, and, also, a platen roller assembly
133
is incorporated into the frame
131
detachably.
On the bottom of the frame
131
, a photosensor
134
for detecting roll paper is mounted, and, also, a mechanical switch
135
for detecting that the platen roller assembly is mounted at a proper position is mounted on a side wall of the frame
131
. A detecting knob part
135
a
of the mechanical switch
135
projects into a depressed receiving part
138
of the frame
131
used for mounting the platen roller assembly
133
therein. A flexible cable
136
extends from the photosensor
134
, while a normal covered cable
137
extends from the mechanical switch
137
.
In this thermal printer unit
130
, because the frame
131
has not an enough space therein, the mechanical switch
135
is mounted on the outer wall of the frame
131
. Accordingly, the substantial lateral length of the line thermal printer unit
130
becomes larger by the mechanical switch
135
than that of the frame
131
itself.
Further, as the photosensor
134
and mechanical switch
135
are components different in type therebetween, the manufacturing costs thereof are high.
Further, works of wiring the flexible cable
136
and covered cable
137
, which are different in type therebetween, are troublesome, accordingly.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a thermal printer unit and a thermal printer in which the above-described problems are solved.
A thermal printer unit according to the present invention comprises:
a thermal head assembly; and
a platen roller,
wherein:
the thermal head assembly comprises:
a frame having platen roller receiving parts receiving both ends of the platen roller, respectively;
a thermal head mounted on the frame; and
a spring member mounted on the frame and applying a head pressure to the thermal head,
wherein each platen roller receiving part comprises:
a vertical groove part having an opening at the top thereof;
a horizontal groove part extending from the bottom of the vertical groove part in a direction such as to be away from the thermal head; and
a projection part formed relatively by the vertical groove part and horizontal groove part, located above the horizontal groove part, and projecting from a depth part of the horizontal groove part toward the thermal head, and
wherein both ends of the platen roller are inserted into the horizontal groove parts of said platen roller receiving parts, respectively, and, also, are pressed by the spring member via the thermal head into the depth parts thereof, respectively.
In this configuration, both ends of the platen roller are loaded into the depth parts of the horizontal groove parts of the platen rol

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