Typewriting machines – Platen or platen-moving mechanism – For movement of platen other than for line-spacing
Reexamination Certificate
1999-04-28
2002-01-08
Colilla, Daniel J. (Department: 2854)
Typewriting machines
Platen or platen-moving mechanism
For movement of platen other than for line-spacing
C400S653000, C400S056000
Reexamination Certificate
active
06336760
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a thermal printer, and more specifically, to a thermal printer attached to a POS (Point Of Sales) device.
A thermal printer used in a POS device should be small in size and easy to set a recording sheet. This also applies to a thermal printer incorporated into a portable device.
2. Description of the Related Art
FIG. 1
illustrates an example of a conventional thermal printer. The thermal printer
10
comprises a thermal head
11
and a platen
12
. The thermal printer
10
is incorporated into a sheet holder
13
. The thermal head
11
is separated from the platen
12
by a cam mechanism so as to form a space between the thermal head
11
and the platen
12
. A recording sheet
15
pulled out from a roll
14
is set between the thermal head
11
and the platen
12
.
FIG. 2
illustrates another example of a conventional thermal printer. The thermal printer
20
is formed integrally with a sheet holder device
21
. The sheet holder device
21
comprises a lower box-like member
22
and an open-close upper cover
23
. The upper cover
23
is opened to set a roll
26
into the sheet holder device
21
. The thermal printer
20
comprises a thermal head
24
fixed onto the inner surface of the lower box-like member
22
and a platen
25
attached to the edge of the upper cover
23
. When the upper cover
23
is closed, the platen
25
is in contact with the thermal head
24
. When the upper cover
23
is opened, the platen
25
is separated from the thermal head
24
.
To set a recording sheet, the upper cover
23
is opened, the roll
26
is set, a recording sheet
27
pulled out from the roll
26
is pulled over the front side of the thermal head
24
, and the upper cover
23
is then closed.
In the thermal printer
10
of
FIG. 1
, the thermal head
11
is separated from the platen
12
. Due to a head pressing plate spring provided to the thermal head
11
, the thermal head
11
can move only a limited distance. As a result, it is difficult to form a side sheet passage between the thermal head
11
and the platen
12
. Accordingly, setting a recording sheet
15
between the thermal head
11
and the platen
12
is difficult.
Furthermore, moving the thermal head
11
might result in a deviation of the position of the thermal head
11
when it is returned. Such a positional deviation of the thermal head
11
might cause uneven printing.
To avoid deformation of the rubber platen
12
, the thermal head
11
is kept separate from the platen
12
at the time of shipment of the thermal printer
10
. However, moving the thermal head
11
adds to the force of the head pressing plate spring. If such a condition is maintained for a long period of time, the increased spring force deforms the main body of the thermal printer
10
.
In the thermal printer
20
of
FIG. 2
, when the upper cover
23
is opened, the platen
25
moves. A side space is formed between the platen
25
and the thermal head
24
, so that a recording sheet
27
is easy to set to this printer. However, when the platen
25
is brought back into contact with the thermal head
24
, the platen
25
is substantially moved in the direction of the surface of the thermal head
24
. Even a small fluctuation positioning causes a positional fluctuation of the platen
25
with respect to the heat generating member
24
a
in the thermal head
24
. As s result, uneven printing is often carried out.
Furthermore, since the thermal printer
20
is integrally formed with the sheet holder device
21
, it includes an extra portion for setting the roll
26
. As a result, the thermal printer
20
is large in size.
SUMMARY OF THE INVENTION
The principal object of the present invention is to provide a thermal printer which is free of the above problems.
The object of the present invention is achieved by a thermal printer comprising a thermal head and a platen as a unit. The platen is detachable from the thermal head. The platen is moved from the thermal head so as to form a sheet passage for setting a recording sheet between the thermal head and the platen.
The thermal head is provided with a head pressing plate spring on its rear side, and movements of the thermal head are limited. On the other hand, the platen is not limited in movement. Compared with the thermal head, the platen can be moved a greater distance. Accordingly, a wider sheet passage can be formed by moving the platen instead of moving the thermal head. Thus, feeding a recording sheet into the sheet passage can be easier.
In the thermal printer of this invention, the direction of the platen separating from the thermal head is perpendicular to the surface of the thermal head.
The platen is vertically brought back into contact with the surface of the thermal head. The position of the returned platen might fluctuate with respect to the thermal printer, but the positional relationship between the platen and the thermal head is accurately maintained. Thus, uneven printing can be prevented even after the recording sheet setting is repeated many times.
The object of the present invention is also achieved by a thermal printer which comprises a main body, a thermal head attached to the main body, and platen. The thermal printer and the platen form a unit. The platen is attached to a sheet guide member for guiding a recording sheet between the platen and the thermal head. A sheet roll for holding a recording sheet is also included. A sheet guide member for guiding a recording sheet pulled out from a sheet roll into a space between the platen and the thermal head. The sheet guide member is attached to the main body. By separating the sheet guide member from the thermal head, a sheet passage for transporting a recording sheet between the thermal head and the platen is formed.
In this structure, the inlet path leading to the sheet passage is wider, and setting a recording sheet into the sheet passage is easier.
The object of the present invention is also achieved by a thermal printer which comprises a thermal head attached to a main body and a platen provided with bearings on both ends. The thermal head and the platen form a unit. The bearings of the platen are engaged with flanges on both sides of a sheet guide member for introducing a recording sheet pulled out from a sheet roller into a space between the platen and the thermal head. The platen and the sheet guide member form a platen module. The main body has bearing portions each provided with an opening. The platen module is attached to the main body, with the bearings being engaged with the bearing portions of the main body. By lifting up the sheet guide member of the platen module, the bearings are first rotated in the bearing portions, and the bearings then come out from the bearing portions through the openings. The platen is thus separated from the thermal head, thereby forming a sheet passage for setting a recording sheet between the thermal head and the platen.
By the simple action of lifting up the sheet guide member of the platen module, the platen can be separated from the thermal head.
When the platen is in contact with the thermal head, the bearings and the bearing portions vertically receive the force of the thermal head pressing the platen.
The bearing portions firmly hold the bearings, so that the platen can be fixed without runout.
When the platen is in contact with the thermal head, the bearings are subjected to a rotating force in a direction opposite to the direction of the bearings coming out from the bearing portions through the openings.
By subjecting the bearings to the rotation force in the direction opposite to the direction of the bearings coming out from the bearing portions, the bearings are firmly secured in the bearing portions.
The platen module has a mechanism for click-locking the platen module to the main body when the sheet guide member is lifted up.
In this structure, a recording sheet can be set by both hands, with the platen module being maintained in the lifted position.
The platen module also has a mech
Mori Yukihiro
Sakurai Fumio
Watanabe Sumio
Colilla Daniel J.
Fujitsu Takamisawa Component Limited
Staas & Halsey , LLP
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