Incremental printing of symbolic information – Thermal marking apparatus or processes – Specific resistance recording element type
Reexamination Certificate
2000-04-05
2001-11-13
Tran, Huan (Department: 2861)
Incremental printing of symbolic information
Thermal marking apparatus or processes
Specific resistance recording element type
Reexamination Certificate
active
06317150
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a protection cover for a thermal printhead. The present invention also relates to a thermal printhead utilizing such a protection cover.
2. Description of the Related Art
A conventional thermal printhead used in combination with a protection cover is disclosed in JP-A-8(1996)-258309 for example. The conventional printhead includes an elongated head substrate provided with a heating resistor, and a circuit board formed with a predetermined wiring pattern. The circuit board carries a connector electrically connected to the wiring pattern. The head substrate and the circuit board are both mounted on a heat sink. The conventional printhead also includes a protection cover made of synthetic resin. The protection cover is provided for covering the circuit board and part of the head substrate.
The conventional protection cover is made by molding a thermosetting resin such as epoxy. In this way, however, the resulting protection cover tends to deform, for instance, when it cools after being removed from the dies. Thus, it can happen that the finally obtained protection cover may unduly warp downward, with its respective ends raised above its longitudinal center.
Disadvantageously, when the deformed protection cover is used for the conventional thermal printhead, the platen roller may fail to uniformly press a recording paper sheet or transfer ink ribbon onto the protection cover. Consequently, the recording paper sheet and/or the ink ribbon may be unduly strongly pressed onto one (or both) of the longitudinal ends of the protection cover, and therefore torn or wrinkled through the uneven contact with the protection cover.
The above problem may be eliminated by causing the resulting protection cover to have an upwardly warping form, i.e., with its longitudinal center raised above its respective ends. With such an arrangement, the recording paper sheet and/or ink ribbon are relatively strongly pressed onto the central portion of the protection cover only. Thus, the recording paper sheet and/or ink ribbon will not be torn nor wrinkled.
Conventionally, the convex protection cover is formed by using a particularly configured die whose inner surface (shape-defining surface) is upwardly warped in correspondence to the protection cover to be produced. However, it is often quite difficult to process a die to have such a particularly configured inner surface, or even impossible to do so without employing a special processing technique. Thus, forming the upwardly warped protection cover is often time-consuming and/or troublesome, thereby leading to an unduly large cost increase.
SUMMARY OF THE INVENTION
The present invention has been proposed under the circumstances described above, and its object is to provide a protection cover which is free from suffering the above disadvantages.
Another object of the present invention is to provide a thermal printhead utilizing such a novel protection cover.
According to a first aspect of the present invention, there is provided a protection cover for a thermal printhead comprising:
an elongated body having an upper surface and a lower surface; and
first and second bosses formed on said lower surface and spaced from each other longitudinally of the elongated body;
wherein the elongated body is originally flat, but caused to warp for use on the thermal printhead in a manner such that a central portion of said upper surface is raised above end portions of said upper surface.
Since the elongated body of the above protection cover is originally flat, there is no need to prepare a specially configured die for molding the protection cover. Thus, the protection cover of the present invention is produced readily and at a low cost.
In a preferred embodiment, the elongated body may be formed with a first through-hole and a second through-hole which extend through the first boss and the second boss, respectively.
Preferably, the first boss and the second boss may be provided with a first protrusion and a second protrusion, respectively. In this case, the first and the second protrusions may be located between the first and the second through-holes, as viewed longitudinally of the protection cover.
In another preferred embodiment, each of the first and the second bosses may be nonuniform in wall thickness.
According to a second aspect of the present invention, there is provided a thermal printhead comprising:
a circuit board;
a heat sink for supporting the circuit board; and
an elongated protection cover fixed to the heat sink;
wherein the protection cover is provided with at least first and second bosses and caused to warp in a manner such that a central portion of the protection cover is raised above end portions of the protection cover.
Preferably, each of the first and the second bosses may be provided with a protrusion contacting with the circuit board.
Preferably, the thermal printhead of the present invention may further comprise a step member formed on the circuit board. Each of the first and the second bosses may be arranged to overlap on the step member. In this case, the above-mentioned protrusions formed on the first and the second bosses may be omitted. The step member may be a protection layer formed on the circuit board. Alternatively, the step member may be a protrusion formed on the circuit board.
When the above-mentioned protrusions are omitted, each of the first and the second bosses may include an inner part and an outer part, wherein the inner part is closer to the other boss than the outer part is, and the inner part is rendered thicker than the outer part.
Other features and advantages of the present invention will become apparent from the detailed description given below with reference to the accompanying drawings.
REFERENCES:
patent: 5353045 (1994-10-01), Sako
patent: 5739837 (1998-04-01), Nagahata et al.
patent: 5874983 (1999-02-01), Nagahata et al.
patent: 8-258309 (1995-03-01), None
patent: 11-188906 (1999-07-01), None
Nagahata Takaya
Ono Shigeyoshi
Yoshikawa Yasuhiro
Merchant & Gould P.C.
Rohm & Co., Ltd.
Tran Huan
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