EP0154989B1

EP0154989B1 - Thermal transfer printer

Info

Publication number: EP0154989B1
Application number: EP19850102877
Authority: EP
Inventors: Kazuyuki Mashiko; Akiyoshi Hakoyama
Original assignee: Hitachi Ltd
Current assignee: Hitachi Ltd
Priority date: 1984-03-13
Filing date: 1985-03-13
Publication date: 1988-10-19
Also published as: EP0154989A2; JPS60190379A; DE3565654D1; EP0154989A3

Description

Background of the Invention

(1) Field of the Invention

This invention relates to a thermal transfer printer using an inked ribbon according to the precharacterizing part of the claim.

(2) Description of the prior art

In thermal transfer printers of the prior art, it has hitherto been an usual practice to use an inked ribbon having a printing zone with width sized to accommodate one line of characters, symbols, etc, and to use a ribbon sensor which is located in a position corresponding to a sub- stantiallywidthwise central portion of the printing zone of the ribbon for monitoring same.
However, the construction in which the ribbon sensor is located in the position described hereinabove would suffer the disadvantage that when an inked ribbon having a printing zone with width sized to accommodate two lines of characters, symbols, etc., one line superposed above the other, is combined with a ribbon cassette which is used by being turned over, such a ribbon sensor would be impossible to satisfactorily monitor the ribbon with respect to its availability.

Summary of the Invention

This invention has as its object the provision of a thermal transfer printer capable of readily monitoring an inked ribbon having a printing zone with width sized to accommodate two lines of characters, symbols, etc., one line superposed above the other.
This object is achieved by a thermal transfer printer according .to the claim. The aforesaid object of the invention is accomplished by the outstanding feature of the invention that an end mark is provided to an end portion of each line of the inked ribbon, so that the end of the inked ribbon can be sensed by the ribbon sensor with the ribbon cassette is used by being turned over.

Brief Description of the Drawings

Fig. 1 is a perspective view of the thermal transfer printer comprising one embodiment of the invention, showing its external appearance;
Fig. 2 is a top plan view of the ribbon cassette used with the thermal transfer printer shown in Fig. 1, shoowing the interior of the ribbon cassette by removing the top cover;
Fig. 3 is a view showing the ribbon sensor in relation to the inked ribbon contained in the ribbon cassette, in explanation of the operation of the ribbon sensor for monitoring the inked ribbon;
Fig. 4 is a diagram showing one example of the inked ribbon monitoring circuit; and
Fig. 5 is a diagram showing the waveform of the output voltages of the ribbon sensor showing the presence and absence of the available inked ribbon.

Description of the preferred Embodiment

A preferred embodiment of the invention will now be described by referring to the accompanying drawings.
Referring to Fig. 1, a plurality of shafts 4 are joined at opposite ends to side plates 1 and 2 for supporting a carriage 5 thereon for sliding movement. The carriage 5 supports thereon a ribbon cassette 7 that can be used by being turned over and a thermal head 15. An inked ribbon 16 having a printing zone with width sized to accommodate two lines of characters, symbols, etc., are containing in the ribbon cassette 7.
The carriage 5 is driven by a carriage motor 8 through a timing belt 10 for movement leftwardly and rightwardly in Fig. 1.
A line feed motor 11 transmits a driving force to a gear 12 supported by a shaft of a platen 18 to feed a printing sheet 14. Alternatively, the printing sheet 14 can be fed manually by turning a platen knob 13. The numeral 19 designates a sheet guide.
By moving a release lever 20 forwardly and rearwardly, sheet keep rollers 17 slidably supported by a shaft 3 can be moved between a position in which they are maintained in pressing engagement with the surface of the printing sheet 14 would on the platen 18 and a position in which they are out of engagement with the surface of the printing sheet 14.
The numeral 6 designates a home position sensor, and the numeral 9 a flat cable for passing a electric current to the thermal head 15.
The home position sensor 6, carriage motor 8, line feed motor 11, thermal head 15 and a ribbon sensor 21 subsequently to be described is controlled by a central processing unit (CPU) 23 serving as a control unit.
The thermal transfer printer of the aforesaid construction is of a one-way printing system in which printing is performed only when the carriage 5 moves rightwardly. When the carriage 5 moves rightwardly, the inked ribbon 16 is taken up; the inked ribbon 16 is not taken up when the carriage 5 moves leftwardly.
The ribbon cassette 7 that can be used by being turned over contains, as shown in Fig. 2, the inked ribbon 16 having a printing zone with width sized to accommodate two lines of characters, symbols, etc., one line superposed above the other.
The ribbon cassette 7 is formed, as shown in Fig. 2, at its top surface and bottom surface with openings C and D for receiving the ribbon sensor 21. The ribbon sensor 21 mounted to the carriage 5 is removably inserted in the openings C and D. In Fig. 2, the ribbon sensor 21 is shown as being inserted in the openings D.
The thermal head 15 is inserted in a cutout A formed in the ribbon cassette 7. In this case, the lower half-portion G of the inked ribbon 16 shown in Fig. 3 is used for performing printing.
When the printing operation using the lower half-portion G of the inked ribbon 16 is finished, the ribbon cassette 7 is turned over, and the thermal head 15 is inserted in the cutout B formed in the ribbon cassette 7.
Since the thermal head 15 is rigidly secured to the carriage 5, an upper-half portion F of the inked ribbon 16 as shown in Fig. 3 is switched to a lower position and used for performing printing when the ribbon cassette 7 is turned over.
In a thermal transfer printer using the ribbon cassette 7 of the aforesaid construction, the ribbon sensor 21 described hereinabove monitors the inked ribbon 16 in such a manner that, as shown in Fig. 3, it is positioned against the lower half-portion of the inked ribbon 16 to see if there is still a space in the printing zone in which printing can be performed.
More specifically, the inked ribbon 16 has a ribbon end mark E attached to an end portion of the inked ribbon 16 where the lower half-portion G ceases to exist. The ribbon end mark E may be provided by doing without the application of an ink to the end portion of the inked ribbon 16, so that the ribbon sensor 21 will sense the absence of ink.
Fig. 4 shows one example of the inked ribbon monitoring circuit including the ribbon sensor 21 which produces a voltage V,. The voltage V, becomes a voltage V_H when the sensor 21 is positioned against a portion of the inked ribbon 16 to which the ink is applied, and becomes a voltage V_L when it is positioned against a portion of the inked ribbon 16 having the end mark E (where no ink is applied to the ribbon). Thus, the different voltages V_H and V_L are transmitted through a voltage comparator 22 to the CPU 23.
When the ribbon cassette 7 is turned over after the end mark E is sensed following a printing operation performed on the lower half-portion G of the inked ribbon 16 as shown in Fig. 3, the upper half-portion F shown in Fig. 3 will now be used as the lower half-portion on which printing is performed. By providing an end mark E similar to the end mark E attached to the end portion of the half-portion G shown in Fig. 3 to an end portion of the half-portion F, it is possible for the ribbon sensor 21 to sense the absence of the ink in a portion of the inked ribbon 16 where the half-portion F ends in the same manner as it senses the absence of the ink in the portion of the inked ribbon 16 where the half-portion G ends as described hereinabove.
If the thermal transfer printer is of a type in which printing is performed on an upper half-portion of the inked ribbon 16 by means of the thermal head 15, then monitoring of the inked ribbon is performed by arranging the ribbon sensor 21 to be positioned against the upper half-portion of the inked ribbon 16 and sense the absence of the ink in the same manner as described hereinabove by referring to the use of the lower half-portion of the inked ribbon 16 for printing purposes.
In the embodiment shown and described hereinabove, the ribbon end mark E has been shown and described as being provided by doing without the application of an ink on either end portion of the inked ribbon 16. However, the invention is not limited to this specific form of the end mark, and the end mark E may be applied by any known means, such as the provision of a projection or application of silver paper.
In the embodiment shown and described hereinabove, the ribbon sensor 21 has been described as being mounted to the carriage 5. However, when the thermal transfer printer is of a type in which the ribbon cassette does not move in synchronism with the carriage, the ribbon sensor may be mounted to one of the side plates as is the case with a home position sensor.
From the foregoing description, it will be appreciated that the invention provides means for readily and positively sensing the absence of a printing zone on the inked ribbon contained in a ribbon cassette that can be used by being turned over. This is conductive to a fall in running costs which is the greatest advantage offered by the ribbon cassette that can be used by being turned over.

Claims

A thermal transfer printer comprising:
a platen (18) supporting a printing sheet (14);

a carriage (5) mounted for reciprocatory movement lengthwise of the platen (18);

a thermal head (15) supported by the carriage (5);

a plurality of heat generating elements mounted in the thermal head (15);

an inked ribbon cassette (7) detachably attached to the carriage (5);

a pair of ribbon cores located in the inked ribbon cassette (7) for rotation; and

an inked ribbon (16) wound on the pair of ribbon cores and extending therebetween, said inked ribbon (16) being interposed between the printing sheet (14) on the platen (18) and the thermal head

(15) supported by the carriage (5) and, as the thermal head (15) forces the inked ribbon (16) against the printing sheet (14), performing printing of characters, symbols, etc., on the printing sheet (14) by transferring ink from the inked ribbon (16) to the printing sheet (14) by heat generated by the heat generating elements;

said inked ribbon (16) being provided at an end portion thereof with a ribbon end mark (E); and a ribbon sensor (21) is provided for monitoring the inked ribbon (16) for sensing the presence of the ribbon end mark (E).

characterized in that, said inked ribbon (16) is constructed to have a printing zone of a size large enough to accommodate two lines of characters, symbols, etc., one line superposed above the other, whereby one half-portion (G) of the printing zone is used for printing characters, symbols, etc., along one line to the end of the inked ribbon (16) as it is wound on one of the pair of ribbon cores and the other half-portion (F) of the printing zone is used, after the inked ribbon cassette (7) is turned over following completion of printing on the one half-portion (G) of the printing zone, for printing characters, symbols, etc., winding the inked ribbon on the other ribbon core, said inked ribbon (16) being provided at the ends of both half- portions (F, G) with a ribbon end mark (E).