Thermal transfer printer without printing displacement

Typewriting machines – Typing by other than type-face or type-die – Thermal

Reexamination Certificate

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Details

C400S124020

Reexamination Certificate

active

06227730

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a thermal transfer printer, specifically to a thermal transfer printer that acquires an appropriate contact pressure of the thermal head in correspondence with a printing mode, and produces a good printed image without making printing displacement when printing on a printed medium in different printing modes.
2. Description of the Prior Art
Generally, the thermal transfer printer, pressing a thermal head onto a platen through an ink ribbon and a printed medium such as a printed paper and moving a carriage along the platen, drives a heating element of the thermal head selectively on the basis of printing data, and transfers ink of the ink ribbon onto the printed medium, thus performing printing of a desired image. And, such a thermal transfer printer has been widely employed as an output device for computers or word processors because of its high quality of printed images, low noise, low cost, easiness of maintenance, etc.
FIG.
3
and
FIG. 4
illustrate major parts of a thermal transfer printer in general.
FIG. 3
is a perspective view of a carriage, and
FIG. 4
is a plan view of the drive system of the carriage in FIG.
3
.
In FIG.
3
and
FIG. 4
, on a carriage
5
capable of freely reciprocating along a platen
2
is disposed a motor
14
that drives a mechanism for contacting and detaching a thermal head
6
with a plurality of thermal elements arrayed (not illustrated) to and from the platen
2
and a mechanism for taking up an ink ribbon. A pinion
15
on the output of the motor
14
is engaged with a transfer gear
16
. The transfer gear
16
is engaged with a gear
18
formed on the circumference of a cam
17
. On the upper side of the cam
17
is formed a cam groove
19
for contacting and detaching the head, and on the lower side thereof is formed a cam groove
20
for taking up the ribbon.
And, a vertical support shaft
21
is installed on the carriage
5
near the platen
2
. A substantially T-letter shaped head lever
22
constituting the mechanism for contacting and detaching the head is attached to the support shaft
21
so as to freely swing, serving the support shaft
21
as the fulcrum. A head mount
23
facing to the platen
2
is fastened on a part of the head lever
22
near the platen
2
. The thermal head
6
is mounted on a plane of the head mount
23
facing to the platen
2
, and a stopper
24
is projected on the head mount
23
with a specific distance from the rear side of the head mount
23
.
Further, a head pressing lever
25
of substantially L-letter shape is attached to the support shaft
21
so as to freely rock, serving the support shaft
21
as the fulcrum. On one end of the head pressing lever
25
, a pin
26
is projected which is engaged in the cam groove
19
of the cam
17
for contacting and detaching the head. The other end of the head pressing lever
25
is located between the rear side of the head mount
23
on the head lever
22
and the stopper
24
, and a spring holding part
27
is formed upright on the other end of the head pressing lever
25
. Further, a high contact pressure spring
28
is intervened between the spring holding part
27
and the head mount
23
. The energizing force of this high contact pressure spring
28
maintains a state that the head pressing lever
25
is in contact with the stopper
24
on the head lever
22
. In this state, the head pressing lever
25
and the head lever
22
are integrally swung by the rotation of the cam
17
.
And, the carriage
5
includes a drive gear
30
that is able to freely rotate with the support shaft
31
as the rotation center, which is engaged with a rack
29
formed on the main body of the printer not illustrated. A low contact pressure spring
32
having a lower spring pressure than the high contact pressure spring
28
is bridged between the support shaft
31
and the head lever
22
, so as to constantly give to the head lever
22
an energizing force that presses the thermal head
6
toward the platen
2
.
Further, the support shaft
31
has a swing plate
33
attached thereon, which is able to freely swing with the support shaft
31
as the fulcrum. A pin
34
is projected on one end of this swing plate
33
, which is engaged in the cam groove
20
for taking up the ribbon formed on the lower side of the cam
17
. A support shaft
35
is projected on the other end of the swing plate
33
, and a transfer gear
36
engaged with the drive gear
30
is attached to this support shaft
35
to freely rotate.
Furthermore, a take-up bobbin
7
and a supply bobbin
8
for the ink ribbon are provided on the carriage
5
. As shown in
FIG. 4
, a take-up gear
37
engaged with the transfer gear
36
is coaxially attached on the lower side of the take-up bobbin
7
through a friction mechanism not illustrate d. And, a second take-up bobbin
38
and a second supply bobbin
39
are provided on the carriage
5
. A second take-up gear
41
is coaxially attached on the lower side of the second take-up bobbin
38
through a friction mechanism not illustrated, which is engaged through a transfer gear
40
with the take-up gear
37
on the take-up bobbin
7
. The take-up bobbin
7
and the second take-up bobbin
38
are each driven to rotate by the engagement of the transfer gear
36
with the take-up gear
37
, which is effected by the swing of the swing plate
33
. And, the second supply bobbin
39
is installed on the carriage
5
through a friction mechanism not illustrated.
Further, as shown in
FIG. 5
, a first cam position
19
a
, a second cam position
19
b
, a third cam position
19
c
, and a fourth cam position
19
d
are formed in the cam groove
19
of the cam
17
for contacting and detaching the head, in such a manner that the radii from the rotation center of these cam positions
19
a
,
19
b
,
19
c
,
19
d
are each made into different dimensions r1, r2, r3, r4 within specific ranges of rotation angle. The curve of the cam is formed flat and parallel in each range of the cam positions
19
a
to
19
d
,as shown in FIG.
6
.
And, by controlling the rotation of the motor
14
in correspondence with the printing mode such as the printing using the thermally fused ink ribbon, the printing using the metallic ink ribbon, or the printing using the thermally sublimed ink ribbon, the rotation angle of the cam
17
is controlled, the cam positions of the cam groove
19
for contacting and detaching the head that the pin
26
on the head pressing lever
25
is engaged with are selected, and thereby the thermal head
6
is made to give an appropriate contact pressure to the platen
2
.
That is, the fourth cam position
19
d
in the cam groove
19
for contacting and detaching the head is the head-up position where the thermal head
6
is detached from the platen
2
, the third cam position
19
c
is the low contact pressure position where the printing is made with the lowest contact pressure, the first cam position
19
a
is the high contact pressure position where the printing is made with the highest contact pressure, and the second cam position
19
b
is the intermediate contact pressure position where the printing is made with the intermediate contact pressure between the highest and the lowest. And, in the printing mode using the thermally sublimed ink ribbon, the low contact pressure position is selected, where the pin
26
on the head pressing lever
25
is located at the third cam position
19
c
in the cam groove
19
for contacting and detaching the head; in the printing mode using the metallic ink ribbon, the intermediate contact pressure position is selected, where the pin
26
on the head pressing lever
25
is located at the second cam position
19
b
in the cam groove
19
; and in the printing mode using the thermally fused ink ribbon, the high contact pressure position is selected, where the pin
26
on the head pressing lever
25
is located at the first cam position
19
a
in the cam groove
19
, where the thermal head
6
is given the highest contact pressure.
Furthermore, a

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