Incremental printing of symbolic information – Thermal marking apparatus or processes – Specific resistance recording element type
Reexamination Certificate
2000-07-25
2001-05-22
Tran, Huan (Department: 2861)
Incremental printing of symbolic information
Thermal marking apparatus or processes
Specific resistance recording element type
C347S209000
Reexamination Certificate
active
06236422
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a thermal printhead for use in a facsimile or a printer as a printing means for example. It also relates to a protective cover for protecting drive ICs and wiring patterns or the like provided on the thermal printhead.
BACKGROUND ART
A prior-art thermal printhead is disclosed for example in JP-A-8-258309. The disclosed thermal printhead includes a heat sink plate, a head substrate, and a circuit board. The head substrate and the circuit board are bonded to the heat sink plate with an adhesive. The head substrate has an upper surface on which a heating resistor and a plurality of drive ICs are mounted. The circuit board carries a connector for external connection and has an upper surface provided with a wiring pattern for connecting the drive ICs to the connector.
The thermal printhead further includes a protective cover formed of a synthetic resin. The protective cover is so provided as to cover the wiring pattern on the circuit board and the drive ICs on the head substrate. The protective cover has a lower surface which is integrally formed with a plurality of engagement pawls. By flexing the protective cover widthwise appropriately, the engagement pawls are brought into engagement with the circuit board and the head substrate, thereby mounting the protective cover onto the thermal printhead. Conversely, the protective cover may be removed from the thermal printhead by disengaging the engagement pawls from the circuit board and the head substrate.
The prior art thermal printhead has the following problems. As described above, since the protective cover mounted onto the circuit board and the head substrate is flexed, it tends to restore to its natural state, exerting a force on the circuit board and the head substrate to separate them from the heat sink plate. As a result, the circuit board and the head substrate may be partially lifted from the heat sink plate.
Further, mounting the protective cover in such a flexed state onto the thermal printhead may cause another problem. In printing, a printing paper and/or an ink ribbon is pressed against the heating resistor on the head substrate by a platen roller. At that time, the protective cover which is undesirably flexed widthwise comes into contact with the printing paper and/or the ink ribbon strongly at a particular portion or portions. As a result, the printing paper and/or the ink ribbon may be broken or wrinkled.
DISCLOSURE OF THE INVENTION
It is, therefore, an object of the present invention to provide a thermal printhead which eliminates or alleviates the problems of the prior art described above.
Another object of the present invention is to provide a protective cover which can be advantageously used in such a thermal printhead.
In accordance with a first aspect of the present invention, there is provided a protective cover for use with a thermal printhead including a heat sink plate formed with a plurality of fixing holes, a head substrate, and a circuit board, the protective cover comprising: a main body having an obverse surface and a reverse surface; and a plurality of pins extending from the reverse surface; wherein each of the pins is designed for press-fitting into a respective one of the fixing holes.
With the structure described above, the protective cover is carried on the heat sink plate. Accordingly, it is possible to prevent the head substrate and the circuit board from being separated from the heat sink plate.
The pins may be integrally formed on the main body. Alternatively, the pins may be formed separately from the main body and then bonded to the main body.
Preferably, each of the pins may be formed with at least one slit facilitating press-fitting of the pin into a respective one of the fixing holes.
In a preferred embodiment, the protective cover further includes a plurality of engagement pawls for engaging the head substrate, and each of the engagement pawls is integrally formed on the main body.
Each of the engagement pawls may extend in the same direction as the pins.
The protective cover may further include a plurality of protrusions projecting from the reverse surface of the main body, and each of the protrusions is provided adjacent to one of the engagement pawls.
In accordance with a second aspect of the present invention, there is provided a thermal printhead comprising: a heat sink plate formed with a plurality of fixing holes; a head substrate carried on the heat sink plate and provided with a heating resistor and a plurality of drive ICs; a circuit board carried on the heat sink plate and formed with a predetermined wiring pattern; and a protective cover for covering the circuit board, the protective cover having a main body including an obverse surface and a reverse surface; wherein the protective cover has a plurality of pins extending from the reverse surface of the main body, each of the pins being designed for press-fitting into a respective one of the plurality of fixing holes in the heat sink plate.
In accordance with a third aspect of the present invention, there is provided a protective cover for use with a thermal printhead including a heat sink plate, a head substrate, and a circuit board, the protective cover comprising an elongated main body including an obverse surface and a reverse surface, wherein the main body is warped so that a longitudinally central portion of the main body is located higher than other portions of the main body.
With such an arrangement, a printing paper and/or an ink ribbon comes into contact with the central portion of the protective cover relatively strongly. As a result, it is possible to prevent the printing paper and/or the ink ribbon from being broken or wrinkled.
The protective cover may further include a plurality of first engagement pieces protruding from the reverse surface of the main body for engagement with the circuit board.
The protective cover may further include a plurality of protrusions protruding from the reverse surface of the main body for engagement with the heat sink plate.
The protective cover may further include a plurality of second engagement pieces protruding from the reverse surface of the main body for engagement with the head substrate.
The protrusions may be integrally formed on the main body.
In accordance with a fourth aspect of the present invention, there is provided a thermal printhead comprising: a heat sink plate; a head substrate carried on the heat sink plate and provided with a heating resistor and a plurality of drive Ics; a circuit board carried on the heat sink plate and formed with a predetermined wiring pattern; and a protective cover for covering the circuit board, the protective cover having an elongated main body including an obverse surface and a reverse surface; wherein the main body is warped so that a longitudinally central portion of the main body is located higher than other portions of the main body.
In a preferred embodiment, the protective cover is provided with a plurality of protrusions for engagement with the heat sink plate.
Preferably, the circuit board is formed with a plurality of through-holes for allowing passage of the protrusions.
The protective cover may be provided with a plurality of first engagement pieces protruding from the reverse surface of the main body for engagement with the circuit board.
The circuit board may include cutouts for engagement with the first engagement pieces.
The protective cover may be provided with a plurality of second engagement pieces protruding from the reverse surface of the main body for engagement with the head substrate.
Other objects, features and advantages of the present invention will become clearer from the description of embodiments given below with reference to the accompanying drawings.
REFERENCES:
patent: 5739837 (1998-04-01), Nagahata et al.
patent: 5-162348 (1993-06-01), None
patent: 8-258309 (1996-10-01), None
patent: 9-94988 (1997-04-01), None
patent: 11-188906 (1999-07-01), None
Nagahata Takaya
Yokoyama Eiji
Yoshikawa Yasuhiro
Bednarek Michael D.
Pittman Shaw
Rohm & Co., Ltd.
Tran Huan
LandOfFree
Thermal printhead and protective cover used for the same does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Thermal printhead and protective cover used for the same, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Thermal printhead and protective cover used for the same will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2474666