Typewriting machines – Typing by other than type-face or type-die – Thermal
Reexamination Certificate
1998-08-10
2001-02-13
Hilten, John S. (Department: 2854)
Typewriting machines
Typing by other than type-face or type-die
Thermal
C400S120150, C347S185000, C347S195000
Reexamination Certificate
active
06186683
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a recording apparatus, in particular, to a heat transfer recording apparatus using an ink film.
2. Description of the Related Art
A heat transfer recording apparatus such as a printer comprises a platen roller and a thermal head that can be arbitrarily pressed against the platen roller. The recording paper is transferred together with the ink film between the platen roller and the thermal head to allow characters and/or graphic images printed thereon. The ink film has thermally fusing or sublimating type of inks coated on one side thereof. The ink is fused or sublimated to be fixed on the recording paper by means of the heat of the thermal head.
A heat transfer recording apparatus normally preheats its thermal head when forming images on recording paper. The preheating time of the thermal head customarily has been decided based on the temperature of the thermal head detected by means of a thermistor provided immediately above or near the thermal head. The thermistor is not directly detecting the actual thermal head temperature. As a result, when images are recorded on multiple sheets of recording paper successively, it causes a problem that the density of images recorded on recording paper earlier may not be the same as images recorded later because of the delayed response of the thermistor. The problem particularly comes into prominence in the case of half-tone images.
For example, if images are recorded on seven sheets of recording paper successively, the preheating time is set constant as there is no difference in the thermistor detection temperature. However, since the thermal head accumulates heat as time goes, the density of the images on the first to the third sheets are weaker relative to the images on the fourth to the seventh sheets.
SUMMARY OF THE INVENTION
The purpose of the invention is to provide a uniform image quality even when images are formed successively on multiple sheets of recording paper.
One aspect of the present invention is a recording apparatus for forming an image on a recording paper by heating an ink film, the recording apparatus comprising: a temperature detector that detects temperature of a heat source that heats ink films; an accumulated time detector that detects an accumulated time period during which electric power is supplied to the heat source within a prescribed period until up to image forming time; and a preheating time controller that decides a preheating time of the heat source based on a heat source temperature detected by said temperature detector and an accumulated power supply time detected by said accumulated time detector.
Another aspect of the present invention is a recording apparatus for forming an image on a recording paper by heating an ink film, said recording apparatus comprising: a heat source; a heat source controller which controls said heat source so as to generate heat for a prescribed time prior to printing for each recording paper and to generate heat during printing; and a time controller which decides said prescribed time based on a temperature of said heat source and sum of time period during which said heat source generates heat.
The objects, features, and characteristics of this invention other than those set: forth above will become apparent from the description given herein below with reference to preferred embodiments illustrated in the accompanying drawings.
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patent: 5132703 (1992-07-01), Nakayama
patent: 5268706 (1993-12-01), Sakamoto
patent: 63-173669 (1988-07-01), None
Chau Minh
Hilten John S.
Minolta Co. , Ltd.
Sidley & Austin
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