Printer

A printer includes a supply shaft wound with unused film including contrast agent, a winding shaft wound with used film including used contrast agent, rotation-speed detector for detecting a rotation speed of the supply shaft, and remaining-amount detector for determining an amount of unused film from the detected rotation speed detected. In the printer, the remaining amount of unused film such as ink film, roll paper or the like can be determined accurately.

FIELD OF THE INVENTION

The present invention relates to a printer used in, for example, a facsimile and a printing apparatus.

BACKGROUND OF THE INVENTION

A conventional thermal transfer printer for a facsimile, a printing apparatus or the like using-ordinary paper as printing paper uses a heat-melting ink film.

FIG. 10schematically illustrates a method for detecting an amount of ink film remaining in the conventional printer, and FIG.11andFIG. 12schematically illustrate respective rotation speeds of an ink-film-winding shaft of the conventional printer.

As shown inFIG. 10, printing paper1undergoes printing using heat-melting ink film2. The amount of ink film2remaining in printer3is detected based on the detected rotation speed of winding shaft4.

Ink film2fed from supply shaft5passes between thermal transfer head6and platen roller7to be wound around take-up shaft4at a constant speed. Consequently, the rotation speed of winding shaft4is high when the amount of ink film2wound around winding shaft4is small as shown inFIG. 11, and is low when the amount of ink film2wound around winding shaft4is large as shown in FIG.12.

In order to detect a variation in the above-described rotation speed, remaining-amount detector9detects the remaining amount of ink film2. In remaining-amount detector9, the rotation speed, which is detected by rotation-speed detector8disposed at winding shaft4, is related with the remaining amount of ink film2.

In conventional printer3, when the rotation speed of winding shaft4is high as shown inFIG. 11, rotation-speed detector8can detect the rotation speed accurately. Accordingly, the remaining amount of ink film2can be detected accurately. When the rotation speed of winding shaft4is low as shown inFIG. 12, however, rotation-speed detector8cannot detect the rotation speed accurately. Thus, the remaining amount of ink film2is hardly detected accurately.

In other words, the amount of ink film2remaining sufficiently is detected accurately, although being allowed to be detected roughly. However, the remaining amount of ink film2, upon being small cannot be detected accurately, although being to be detected accurately. Consequently, a warning for the remaining amount of ink film2must be given early for safety.

SUMMARY OF THE INVENTION

A printer includes a supply shaft wound with an unused film having contrast agent, a winding shaft wound with a used film having used contrast agent, a rotation-speed detector for detecting a rotation speed of the supply shaft, and a remaining-amount detector for detecting an amount of the unused ink film from the detected rotation speed.

In the printer, the remaining amount of the unused film such as ink film, roll paper or the like can be detected accurately.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In a printer of a first exemplary embodiment performing thermal transfer printing with ink film or thermal recording paper, a rotation speed of a supply shaft increases with consumption of the ink film or thermal recording paper, and the rotation speed of the supply shaft is accordingly detected accurately. That is, a remaining amount of the ink film or thermal recording paper corresponding to the rotation speed of the supply shaft can be detected accurately as the remaining amount approaches zero.

The first embodiment will be detailed with reference toFIGS. 1-9.

FIG. 1schematically illustrates a method for detecting a remaining amount in the printer in accordance with the first embodiment. FIG.2andFIG. 3illustrate a rotation speed of the ink-film-supply shaft of the printer.FIG. 4is a schematic diagram of the ink-film-supply shaft and a rotation-speed detector of the printer.FIG. 5schematically illustrates a magnet mounted to the supply shaft of the printer. FIG.6andFIG. 7illustrate states of a reed switch turned on and off of the printer.FIG. 8shows signal pulses from the reed switch of the printer.FIG. 9schematically illustrates a method for detecting an amount of thermal recording paper remaining in a printer.

InFIG. 1, the printer of the first embodiment includes thermal transfer head16, platen roller17, rotation-speed detector18for detecting a rotation speed of the ink film supply shaft, and remaining-amount detector19A for detecting the remaining amount of ink film12based on the detected rotation speed. An ink film roll device for accommodating ink film12in roll form includes ink film12, supply shaft14wound with unused ink film12and winding shaft15for winding up used ink film12.

As shown inFIG. 1, printing paper11, upon being ordinary paper11, is printed with heat-melting ink film12. Printer13of the first embodiment differs from a conventional printer in that the remaining amount of ink film12remaining is determined based on the detected rotation speed of supply shaft14.

A speed with which ink film12fed from supply shaft14passes between thermal transfer bead16and platen roller17to be wound around winding shaft15is constant. Therefore, the rotation speed of supply shaft14is low when the amount of ink film2remaining on supply shaft14is large as shown in FIG.2. The rotation speed of supply shaft14is high when the amount of ink film12remaining on supply shaft14becomes small as shown in FIG.3. In the printer of the present embodiment, the remaining amount of ink film12is determined accurately since being determined based on the rotation speed of supply shaft14. This rotation speed is detected accurately by rotation-speed detector18since the rotation speed of supply shaft14is high when the remaining amount of film is small.

In remaining-amount detector19A, the rotation speed of supply shaft14preliminary corresponds to the remaining amount of ink film12. Remaining-amount detector19A determines the remaining amount of ink film12based on the detected rotation speed.

Rotation-speed detector18of the printer in accordance with this embodiment includes, as shown inFIG. 4, reed switch18a for detecting a magnetic field and counter18b for counting the number of states of reed switch18a turned on and off.

In the present embodiment, magnet holder21integrally formed with magnet20is inserted, as shown inFIG. 5, into an opening at one end of supply shaft14. Specifically, holder21is fixed into the opening by press fitting, an adhesive or ultrasonic welding. The other end of supply shaft14is provided with a supply gear.

As shown inFIGS. 6 and 7, reed switch18a is turned on and off thorough detecting a change of direction of a magnetic force line generated by magnet20mounted in supply shaft14. Reed switch18a is turned on when the direction of the magnetic force line directing from a north pole to a south pole of magnet20is parallel with an axis of reed switch18a, as shown in FIG.6. When magnet20rotates in half, changing from the state shown inFIG. 6to reverse the positions of the north and south poles, reed switch18a is also turned on since the direction of the magnetic force line directing from the north pole to the south pole of magnet20is parallel with the axis of reed switch18a.

When the direction of the magnetic force line directing from the north pole to the south pole of magnet20is perpendicular to the axis of reed switch18a, as shown inFIG. 7, reed switch18a is turned off. When magnet20rotates in half, changing from the state shown inFIG. 7to reverse the positions of the north and south poles, reed switch18a is also turned off since the direction of the magnetic force line from the north pole to the south pole of magnet20is perpendicular to the axis of reed switch18a.FIG. 8shows signal pulses corresponding to the on/off states of reed switch18a in a single revolution of magnet20. The number of peaks or troughs of the signal pulses is directly proportional to the number of revolutions of magnet20.

The number of revolutions per unit time of magnet20represents the rotation speed of supply shaft14. The rotation speed can be determined by counting the number of signal pulses (i.e., the number of peaks or troughs) corresponding to the on/off states of reed switch18a per unit time with counter18b. The more the number of on/off states per unit time of reed switch18a, the less error in the rotation speed of supply shaft14, and the more accurately the rotation speed can be determined. The rotation speed of supply shaft14increases as the remaining amount of ink film12decreases. Thus, the remaining amount of ink film12is determined more accurately when ink film12is nearly used up than when ink film12start to be used.

In other words, when the remaining amount of ink film12is sufficient and thus may be determined roughly, the amount can be determined less accurately. In the present embodiment, as the remaining amount of ink film12approaches zero, the remaining amount of ink film12is determined more accurately. Accordingly, the time for replacing ink film12can be determined accurately when the remaining amount of ink film12is small. Therefore, the printer of this embodiment may generate a warning of the remaining amount of ink film12right before ink film12runs out.

Whether ink film12is placed in printer13or not can be determined through determining whether supply shaft14rotates or not. This enables rotation-speed detector18to be a substitute for a detector of ink film12.

Further, in the present embodiment, remaining-amount detector19A judges that the rotation speed detected by detector18exceeds a predetermined speed and then issues a notification of this result to reporting unit19B for display this result at a display screen of display19C. At this moment, an alarm may be sounded simultaneously with this display by a sound generator (not shown).

A thermal transfer printer may employ thermal recording paper23as recording paper.FIG. 9shows thermal transfer printer22employing the thermal recording paper in roll form. Printer22includes, similarly to the first embodiment, thermal transfer head16, platen roller17, rotation-speed detector18for detecting a rotation speed of a supply shaft and remaining-amount detector19A for determining a remaining amount of ink film or the thermal recording paper based on the detected rotation speed detected. Unused thermal recording paper23is wound around supply shaft24.

The remaining amount of thermal recording paper23can be determined through detecting the rotation speed of supply shaft24. As mentioned in above, rotation-speed detector18detects the rotation speed of supply shaft24, and remaining-amount detector19A determines the remaining amount of thermal recording paper23.

Thermal recording paper23generally has, at an ending portion thereof, a colored part functioning as an index of the remaining amount. This allows the remaining amount of thermal recording paper23to be detected roughly at about three levels according to the second embodiment.

As described in above in the present embodiment, the rotation speed of the thermal recording paper supply shaft is detected, and the remaining-amount detector determines the remaining amount of thermal recording paper based on the rotation speed. Thus, the smaller the remaining amount is, the more accurately the remaining amount is determined. Therefore, the printer can issue a warning of the remaining amount at an appropriate time right before the thermal recording paper is used up.

Further, similarly to remaining-amount detector19A of the first embodiment, remaining-amount detector19A of this embodiment judges that the rotation speed detected by detector18exceeds a predetermined speed and provides a notification of this result to reporting unit19B for display this result at a display screen of display19C, and an alarm may be sounded simultaneously with this display by a sound generator (not shown).

Many modifications may be made from the art of the present invention and are not described specifically herein. However, these modifications are intended to fall within the scope of the present invention.

For example, the rotation-speed detector of the first embodiment includes the magnet mounted to the supply shaft to detect the rotation speed. However, the present invention is not so limited to it, and the rotation speed may be detected by a mechanical detector, e.g. a switch, an optical detector, or other electromagnetic detector.

The same advantage can be obtained when the ink film and the thermal recording paper used in the printers of the first and second embodiments are replaced by a printing member accommodated in roll form and including contrast agent added or applied thereto.