Incremental printing of symbolic information – Thermal marking apparatus or processes – Specific resistance recording element type
Reexamination Certificate
2000-09-20
2001-10-23
Tran, Huan (Department: 2861)
Incremental printing of symbolic information
Thermal marking apparatus or processes
Specific resistance recording element type
Reexamination Certificate
active
06307580
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the invention
The present invention relates to a thermal printhead and also a method of making the same.
2. Description of the Related Art
As is well known, a thermal printhead is provided with an elongated heating resistor divided into a multiplicity of heating dots. In operation, the heating dots are selectively energized, so that heat is selectively supplied to transfer ink ribbon or thermosensitive paper for printing required images on recording medium.
Referring to
FIG. 11
of the accompanying drawings which shows a related art (not prior art), a thermal printhead may include a heating resistor unit
31
A, a signal relay unit
34
A and a heat sink
38
supporting these two units. The heating resistor unit
31
A includes a primary substrate
31
which is provided with a heating resistor
32
extending longitudinally of the substrate
31
. A plurality of drive ICs
33
are mounted on the substrate
31
for controlling the operation of the heating resistor
32
based on externally supplied print data. Though not illustrated, a wiring pattern is formed on the substrate
31
for connecting the drive ICs
33
to the heating resistor
32
.
The signal relay unit
34
A includes an auxiliary substrate
34
formed with a predetermined wiring pattern (not shown). This non-illustrated wiring pattern is connected to terminal pads
36
formed on the obverse surface of the substrate
34
. The terminal pads
36
are spaced from each other in the longitudinal direction of the substrate
34
. A connector
37
is attached to the reverse surface of the substrate
34
for making electrical connection between the non-illustrated wiring pattern and an external device or circuit (not shown).
The illustrated thermal printhead also includes a plurality of conductive clip pins
35
for electrically connecting the heating resistor unit
31
A to the signal relay unit
34
A. Each pin
35
is formed with a generally U-shaped portion and a straight lead portion integral with the U-shaped portion. The U-shaped portion is clipped onto a connection terminal (not shown) formed on the primary substrate
31
, while the lead portion is soldered to the relevant one of the terminal pads
36
corresponding to the non-illustrated connection terminal on the substrate
31
.
The thermal printhead having the above arrangement is fabricated in the following manner. First, the heating resistor unit
31
A and the signal relay unit
34
A are prepared. At this stage, the clip pins
35
are attached to the primary substrate
31
of the heating resistor unit
31
A but not connected to the signal relay unit
34
A yet.
Then, as shown in
FIG. 12
, the signal relay unit
34
A is mounted onto a first chuck member
41
. Thereafter, the heating resistor unit
31
A is mounted onto a second chuck member
42
. The first chuck member
41
may be stationary, while the second chuck member
42
may be movable in sliding engagement with the first chuck member
41
in the directions shown by the double head arrow A in the figure.
For positioning the heating resistor unit
31
A to the second chuck member
42
, a plurality of upright pins
43
are provided on the second chuck member
42
. In use, the substrate
31
of the unit
31
A is brought into engagement with the respective pins
33
, as shown in FIG.
12
. The first chuck member
41
, on the other hand, is provided with a positioning piece
46
having an L-shaped cross section, as shown in FIG.
13
. (The positioning piece
46
is omitted in
FIG. 12
for convenience of illustration.) The positioning piece
46
includes an upright contact surface
46
a,
which is brought into engagement with a contact edge
34
a
of the auxiliary substrate
34
. With such an arrangement, the signal relay unit
34
A is positioned relative to the first chuck member
41
.
After the signal relay unit
34
A and the heating resistor unit
31
A are positioned on the first chuck member
41
and the second chuck member
42
, respectively, the second chuck member
42
is moved relative to the first chuck member
41
as shown by the above-mentioned arrow A. In this manner, the lead portion of each clip pin
35
can be aligned with a relevant one of the terminal pads
36
of the signal relay unit
34
A. Then, the lead portion of the clip pin
35
is soldered to the terminal pad
36
.
Finally, the two units
31
A,
34
A are removed from the chuck members to be mounted on the heat sink
38
(FIG.
11
). At this stage, the connector
37
is attached to the auxiliary substrate
34
.
The use of the positioning piece
46
(
FIG. 13
) may suffer from the following drawback.
Specifically, for improving the production efficiency, the substrate
34
and many other identical substrates may be collectively obtained by cutting a large mother board into small pieces. In this case, the contact edge
34
a
of the resulting substrate
34
(and the other three edges as well) may often be formed with burrs due to the cutting operation. As readily understood, such burrs will prevent the substrate
34
from coming into proper contact with the contact surface
46
a
of the positioning piece
46
. This means that the substrate
34
will fail to be positioned accurately relative to the first chuck member
41
, which may result in inaccurate positioning of the clip pins
35
to the terminal pads
36
on the substrate
34
.
Instead of using the illustrated positioning piece
46
, at least two positioning holes
50
may be formed in the auxiliary substrate
34
, as shown in
FIG. 14
, by drilling for example. In this case, the first chuck member
41
may be provided with upright protrusions to be fitted into the positioning holes
50
. With such an arrangement, the auxiliary substrate
34
can be properly positioned on the first chuck member
41
since fewer burrs are formed on the surface of the drilled positioning holes
50
as compared to the contact edge
34
a.
However, as shown in
FIG. 14
, the positioning holes
50
are formed in the wiring pattern-forming region S of the substrate
34
. With such an arrangement, the room for providing the wiring pattern is disadvantageously restricted since the wiring pattern should avoid the location of the positioning holes
50
.
SUMMARY OF THE INVENTION
The present invention has been proposed under the circumstances described above, and its object is to provide a method of making a thermal printhead, whereby the positioning of the heating resistor unit to the signal relay unit can be performed accurately.
According to a first aspect of the present invention, there is provided a method of making a thermal printhead including first and second substrates spaced from each other, the first substrate being provided with a heating resistor. The method comprises the steps of: forming at least one positioning cutout in at least one of the first and the second substrates; positioning the first and the second substrates relative to each other; and establishing electrical connection between the first and the second substrates. The positioning cutout is to be formed at an edge of said one of the first and the second substrates.
Preferably, the positioning cutout may comprise a semi-cylindrical groove. Instead, the positioning cutout may have a triangular or rectangular cross section.
For facilitating the positioning of the substrates, said one of the first and the second substrates may be formed with two positioning cutouts each of which is arranged at an edge of said one of the first and the second substrates.
Preferably, said one of the first and the second substrates may be provided with two longer edges and two shorter edges, in which the two positioning cutouts may be arranged at the shorter edges.
Preferably, the positioning cutout may be formed in the second substrate.
The method of the present invention may further comprise the step of mounting said one of the first and the second substrates onto a position adjusting chuck member provided with a positioning pin to be fitted into the positioning cutout.
Preferably, the electrical connection between the first an
: Rohm Co., Ltd.
Bednarek Michael D.
Shaw Pittman LLP
Tran Huan
LandOfFree
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