Typewriting machines – Typing by other than type-face or type-die – Thermal
Patent
1996-04-08
1998-07-07
Hilten, John S.
Typewriting machines
Typing by other than type-face or type-die
Thermal
40012017, 347197, 347198, B41J 2315
Patent
active
057758204
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a thermal printer which carries out printing by thermally transferring ink of an ink ribbon to print paper using a thermal head.
BACKGROUND ART
An image printing mechanism of a thermal printer comprises a thermal head including a plurality of heating elements arranged in rows, and a platen against which the heating elements of the thermal head are detachably pressed. The thermal head is pressed against the platen by a head pressing mechanism which presses the thermal head against the platen. Such a thermal printer is usually provided with a paper feeding mechanism for feeding print paper between the thermal head and the platen, and a ribbon transporting mechanism for transporting an ink ribbon between the thermal printer and print paper. Where the thermal printer is assembled as a line printer, the heating elements of the thermal head are arranged in the direction of primary scanning while the print paper and the ink ribbon are fed in the direction of secondary scanning by means of the paper feeding mechanism and the ribbon transporting mechanism. In the thermal printer having such a construction, the paper feeding mechanism feeds the print paper in synchronism with the feeding of the ink ribbon by the ribbon transporting mechanism. Further, the heating elements of the thermal head are selectively heated in synchronism with these feeding mechanisms. As a result, ink from the ink ribbon is selectively transferred to the print paper, so that dot-matrix images are formed.
Synchronization in feeding action between the print paper and the ink ribbon connotes that the ink ribbon is transported in accordance with the amount of travel of the print paper. However, in some cases, the print paper is fed without forming an image. The feeding of the ink ribbon in this case results in wastage of the ink ribbon. To prevent this, some printers are provided with a press releasing mechanism which drives the thermal head using a solenoid so as to move it away from the platen. The print paper is fed while the thermal head is separated from the platen, whereby only the print paper is fed without moving the ink ribbon. More specifically, this type of thermal printer is provided with a solenoid whose rod advances or recedes when energized. The solenoid is disposed with its rod facing in the direction orthogonal to the direction of the movement of the thermal head, and the rod is linked to a movable end of the thermal head. With this arrangement, the energizing of the solenoid causes the rod to advance or recede, so that the other end of the thermal head is pulled in the direction opposite to the platen. As a result, the platen moves away from the thermal head.
Drawbacks in the prior art will now be explained. The solenoid is elongated in the direction in which the rod advances or recedes. For this reason, the space occupied by the solenoid and the thermal head is L-shaped, and the area of that occupied space becomes increased. This results in a large-sized thermal printer. Particularly, the solenoid interrupts a transporting path for the ink ribbon, and this significantly restricts the degree of freedom with which the ink ribbon transporting path can be arranged.
Another problem of the prior art is that the thermal printer becomes large since a large-sized solenoid becomes necessary to provide large drive torque for drawing the thermal head against the pressing force of the head pressing mechanism.
A further problem of the prior art is that the rod of the solenoid must be connected to the thermal head after attachment of the solenoid to the printer when the press releasing mechanism is used. This makes the assembling work of the printer complicated.
An object of the present invention is to provide a compact thermal printer.
Another object of the present invention is to provide a thermal printer which is easy to be assembled.
A further object of the present invention is to provide a thermal printer which facilitates the setting of print paper.
DISCLOSURE OF THE INVENTION
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Matsushita Izumi
Sugimoto Kazuaki
Yukawa Chiaki
Hilten John S.
Kabushiki Kaisha TEC
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