PRINTING APPARATUS

Abstract: In a printing apparatus wherein a reversible ribbon cassette (7) is detachably installed, provided are means e.g. blocking peace (12) for indicating which side of the ribbon cassette (7) being the side on use and means e.g. projection (6) for detecting whether the side of the ribbon cassette (7) attempted to be reloaded after once removed is the side on use or not based upon the indicating means (12). Thereby, misloading with the not-on-use side of ribbon cassette (7) turned up is prevented and accordingly possibilities of blurred printing caused by use of already used area of the ribbon and/or waste of the ribbon with remaining non-used portion thereon can be avoided. Further, even if the ribbon cassette (7) installed in the apparatus is a multi-use-type one, the possibility of the printing quality being uneven due to the difference in number of times of use in places on the ribbon can also be prevented.

Description: This invention relates to a printing apparatus such as a typewriter and a printer utilized as an output unit of a computer, and more particularly to a printing apparatus in which a ribbon cassette is loaded onto a carriage which is reciprocatively movable along a printing line on a printing paper. Conventionally, there has been such a ribbon cassette as to be reversibly loaded onto the carriage. In other words, the surface of the ribbon contained in the cassette is horizontally seperated in two areas and when the ribbon cassette is loaded on the carriage one side up, one of the areas on the ribbon surface is disposed along the printing line while when it is loaded the other side up the other area is disposed along the printing line. With the above reversible ribbon cassette, however, since there has been no means to indicate which side is now in use, if the ribbon cassette is unloaded from the carriage for some reason before the ribbon reaches one end, an operator very likely misloads the ribbon cassette by putting the reverse side up when resetting the cassette to the printing apparatus. This may cause blurred printing by using the once used area of the ribbon or waste the ribbon cassette which has not yet completely been used. Further, if the ribbon cassette to be installed is a multi-use type one, there is a possibility of the quality of printing being uneven if there is a difference in the number of times of use in places of the ribbon surface. This difference has been frequently caused by reloading the cassette within the reverse (not-in-use) side turned up by mistake after removing the cassette for some reason before the ribbon reaches its one end. US-A-4 264 223 shows a ribbon cassette with an eccentrically mounted knob at one end which, depending on its rotational position can fit into one or other fork defined at each end of a ribbon cassette carriage. It is therefore an object of this invention to provide an improved printing apparatus, wherein a reversible ribbon cassette is utilised, capable of recognising which side of the ribbon cassette be in use even if the ribbon cassette is removed from the apparatus and of ensuring to reload the ribbon cassette with the in-use side thereof turned up. For this purpose, there is provided a printing apparatus wherein a reversible ribbon cassette is detachably installed, which comprises means for indicating which of the two sides of said ribbon cassette is in use and means for detecting whether the side of said ribbon cassette attempted to be reloaded to the use position after being removed is the side in use or not, based upon said indicating means, and wherein reloading of said ribbon cassette is prevented by said indicating means and said detecting means if the side of said ribbon cassette attempted to be reloaded after being removed is not the side in use, the apparatus further comprising a carriage for mounting said ribbon cassette thereon, and wherein said indicating means is provided on said ribbon cassette while said detecting means is provided on said carriage, characterised in that the indicating means comprises a through hole formed on the ribbon cassette and an engaging member movably received within said through hole, and in that said detecting means comprises the surface of the carriage and the vertical portion of said engaging member within said through hole. With the above printing apparatus, when a ribbon cassette removed from the apparatus is to be reloaded, the loaded state of the cassette before the removal can be detected by the detecting means based upon the indicating means and reloading in the same state as before is ensured. The invention will be more clearly understood from the following description, which is given by way of example only, with reference to the accompanying drawings, in which:- Figures 1 and 2 show a thermal printer embodying the invention; Figure 3 is a fragmentary sectional plan view showing a loaded state of a ribbon cassette on a carriage; Figure 4 is a partially enlarged front perspective view showing a blocking member on a ribbon cassette and a projection on a carriage; Figure 5 is an exploded view of Figure 4; Figure 6 is a an explanatory front view of Figure 4; Figure 7 is a partially enlarged front perspective view showing still another blocking member; Figure 8 is an exploded view of Figure 7; Figure 9 is a partially sectionally explanatory view of Figure 7; Figure 10 is a partially enlarged front perspective view showing still another blocking member and a recess formed on the carriage. Figure 11 is an exploded view of Figure 10; and Figure 12 is an explanatory view of Figure 10. Description of the Preferred Embodiment Figures 1 and 2 show a thermal printer embodying the invention wherein a horizontally extending platen 1 and a pressing bar 101 are arranged in parallel for supporting and guiding a printing paper P. A printing head unit 102 is reciprocably movably arranged along the axial direction of the platen 1. The printing head unit 102 comprises a carriage 2, a printing head 3 and a ribbon cassette 7. On the carriage 2, as minutely illustrated in Figure 3, the printing head 3 is supported movably between its printing position to abut against the platen 1 as illustrated by solid lines in Figure 3 and a retracted position away from the platen 1 as illustrated by double-dotted lines in Figure 3. On the upper surface of the carriage 2, a fixed shaft 4 and a rotating shaft 5 are mounted. The rotating shaft 5 is provided with a spool engagement portion 5a on its top end and is rotated by a driving source, not shown, to take up a ribbon 8 installed in the ribbon cassette 7. At the center on the upper surface of the front portion of the carriage 2, a projection 6 is provided. The ribbon cassette 7 to be loaded on the carriage 2 is a reversely loadable one. That is, within the ribbon cassette 7, a pair of spools 9, 10 are rotatably disposed at symmetrical positions serving for both taking up and supplying the ribbon 8, and the surface of the ribbon 8 is separated into two areas along a feeding line thereof. The ribbon 8 wound around the spool 9 on the supplying side is adapted to be taken up by the spool 10 on the take-up side through three ribbon guides 14. Close to the ribbon guide 14 located on the center of the ribbon cassette 7, a leaf spring 14a is provided for pressing the ribbon 8 against the ribbon guide 14. When the ribbon cassette 7 is loaded on the carriage 2, the spool 10 is engaged with the spool engagement portion 5a on the rotating shaft 5 while the other spool 9 is loosely fitted on the fixed shaft 4. At the rear end portion of the ribbon cassette 7, a pair of recesses 2b are provided at symmetrical positions. The ribbon 8 is exposed within each of the recess 2b and the printing head 3 is adapted to be located inside the passage of the ribbon 8 within either one of the recesses 2b. At the center of the front side surface of the ribbon cassette 7, a vertically extending recess 11 is formed. The recess 11 opens, as illustrated in Fig. 4 through 6, upside, downside and front side. The size of opening of the recess 11 is formed to be smaller than the size of the interior thereof and to be slightly larger than that of the projection 6 to allow the same to pass therethrough. At the inner side surfaces of the recess 11, a pair of protrusions 11a are opposedly formed at the vertically intermediate position thereof. In the recess 11, a blocking piece 12 having a height approximately half the height of the recess 11 and a width aproximately the same as the width of the interior of the recess 11 is accomodated. This blocking piece 12 is selectively accomodated in one of the inner spaces of the recess 11 divided by the above protrusions 11a and can be moved over the protrusions 11a as illustrated by solid lines and the double-dotted lines in Fig. 6. In Fig. 4, the blocking piece 12 is disposed at the upper space of the recess 11 and therefore the projection 6 can be fitted in the lower space of the recess 11. That is, the ribbon cassette 7 can be loaded on the carriage 2. Then, the rotating shaft 5 is rotated to rotate the spool 10 on the take-up side, whereby the ribbon 8 wound around the spool 9 on the supply side is taken up by the spool 10 on the take-up side through every ribbon guide 14 and the printing head 3, and the printing head 3 is operated, and thus, printing is made on the printing paper P placed on the platen 1 through cooperation of upper half on the ribbon 8, printing head 3 and the platen 1. In order to remove the ribbon cassette 7 from the carriage 2, first, the printing head 3 is transferred to the retracted position illstrated by double-dotted lines in Fig. 3, and in this state, the ribbon cassette 7 is lifted up, whereby the two spools 9, 10 are slipped out of their respective shafts 4, 5 and, at the same time, the projection 6 becomes out of the recess 11. Thereafter, if the removed ribbon cassette 7 is reloaded onto the carriage 2 without being turned over, the projection 6 is again fitted into the recess 11, and thus, the reloading of the ribbon cassette 7 onto the carriage 2 is allowed. From the fact that the reloading is allowed as described above, it is certainly acknowledged that the loaded state of the ribbon cassette 7 is the same as that before the removal. If it is attempted to reload the ribbon cassette 7 with the reverse side turned up by mistake, then the projection 6 on the carriage 2 comes in abutment with the blocking piece 12 within the recess 11 and thereby the projection 6 is prevented from entering into the recess 11. As a result, the reloading of the ribbon cassette 7 is prevented, and from the fact that the reloading is prevented, it is certainly acknowledged that it has been attempted to load the ribbon cassette 7 with the opposite side up which is different from that before the removal. Now, in order to use another area of the ribbon 8 by loading the ribbon cassette 7 with the reverse side turned up, the blocking piece 12 is shifted against the resilience of the protrusions 11a into the lower space of the recess 11, and, after the blocking piece 12 has moved across the protrusions 11a and the protrusions 11a are restored to their original state, the blocking piece 12 is stably held at its lower position inside the recess 11 by the protrusions 11a and the peripheral portions of the opening of the recess 11. Thus, the ribbon cassette 7 is allowed to be loaded with its reverse side turned up, and at the same time, it is prevented from being loaded with its original side turned up. Figures 7 to 9 show a further modification wherein a blocking rod 22 is vertically slidably received in a through-hole 21 provided at the centre of the front portion of the ribbon cassette 7. On the inner peripheral surface of the through-hole 21, formed are a pair of engaging grooves 21a, 21b at a predetermined vertical interval. On the other hand, an engaging flange 22a formed of a resilient material to be engaged with the engaging groove 21a or 21b is provided at the vertically intermediate position on the outer periphery of the blocking rod 22. That is, when the engaging flange 22a is engaged with the upper engaging groove 21a, the blocking rod 22 is held at its first position and one end thereof is projected out of the original side surface of the ribbon cassette 7 as illustrated by solid lines in Figure 9. On the other hand, the engaging flange 22a is engaged with the lower engaging groove 21b, the same is held at its second pcsition where the other end of the blocking rod 22 is projected out of the reverse side surface of the ribbon cassette 7 as illustrated by double-dotted lines in Figure 9. Accordingly, when the ribbon cassette 7 loaded as above is once removed from the carriage 2 and then the ribbon cassette 7 is to be reloaded, if the same is going to be loaded with the reverse side turned up, the end portion of the blocking rod 22 projected out of the original side surface of the ribbon cassette 7 comes into abutment with the upper surface of the carriage 2 whereby the reloading of the ribbon cassette 7 is prevented. It is, of course, allowed to reload the ribbon cassette 7 with the reverse side turned up if the blocking rod 22 is pressed downwardly to put it into its second position illustrated in Figure 9 by double-dotted lines where the flange 22a thereof is engaged with the lower groove 21b. Figures 10 to 12 show still other modifications wherein a recess 23 is formed on the upper surface of the front portion of the carriage 2, which is put at slightly rightwardly shifted position from the centre, while a blocking rod 25 is initially held in a through-hole 24 formed in the front central position of the ribbon cassette 7. Inner space of the through-hole 24 is substantially separated by opposedly protruded vertical ribs 24a,24b,24c made of a resilient material into two sections symmetrically formed about the centre line of the ribbon cassette 7. The blocking rod 25 has an upper end 25a and lower end 25b protruding out of the original and reverse surfaces of the ribbon cassette 7, respectively. On the other hand, the blocking rod 25 is provided with two pairs of opposedly protruding flange portions 25c,25d at a predetermined vertical interval which are adapted to be engaged with guide grooves 24d,24e formed on the inner wall of the ribbon cassette 7 to prevent the blocking rod 25 from slipping out of the through-hole 24. The blocking rod 25 has to be slid against resilience of the vertical ribs 24a,24b,24c to be switched between two areas inside the through-hole 24 as illustrated by solid lines and double-dotted lines in Figure 12. In the state as shown in Figure 10, the blocking rod 25 is disposed at the right-hand section and the downwardly projected end 25b of the blocking rod 25 can be fitted in the recess 23 of the carriage 2, whereby the ribbon cassette 7 is loaded on the carriage 2 with its original side turned up. Accordingly, when the ribbon cassette 7 loaded as above is once removed from the carriage 2 and then the ribbon cassette 7 is reloaded onto the carriage 2, loading with the original side turned up is allowed because the downwardly protruded end 25b of the blocking rod 25 is fitted into the recess 23. On the other hand, if it is attempted to reload the ribbon cassette 7 with the reverse side turned up by mistake, the upwardly protruding end 25a then comes into abutment with the upper surface of the carriage 2 since the protruding end 25a of the blocking rod 25 is positioned leftward of the centre of the carriage 2 when the ribbon cassette 7 is turned over. Thus, reloading of the ribbon cassette 7 is prevented unless the blocking rod 25 is shifted to the left-hand section as indicated by double-dotted lines in Figure 12. As described above, according to the present invention, if the ribbon cassette is going to be reloaded with the reverse side up after it is removed from the carriage, the ribbon cassette is prevented from reloading, while reloading is allowed without any difficulties if the same side as before removal is turned up. Thus, it is certainly acknowledged whether the side turned up for reloading is the same side as before removal or not, and thereby blurred printing by the use of once used areas of the ribbon and/or waste of the ribbon which has not yet completely been used can be avoided. Moreover, according to the present invention, even in case the ribbon cassette is a so-called multi-use type one wherein the same area of the ribbon surface is repeatedly used for printing, the possibility of the print quality being uneven depending upon the area of the ribbon to be used due to the difference in the number of times of use thereof can also be prevented. This invention is not restricted to the above-described embodiments, but further modifications may be made without departing from the scope of the invention.

Claims: A printing apparatus wherein a reversible ribbon cassette (7) is detachably installed, which comprises means (11,12) for indicating which of the two sides of said ribbon cassette is in use and means (6) for detecting whether the side of said ribbon cassette (7) attempted to be reloaded to the use position after being removed is the side in use or not, based upon said indicating means (11,12), and wherein reloading of said ribbon cassette (7) is prevented by said indicating means (11,12) and said detecting means (6) if the side of said ribbon cassette (7) attempted to be reloaded after being removed is not the side in use, the apparatus further comprising a carriage (2) for mounting said ribbon cassette (7) thereon, and wherein said indicating means (11,12) is provided on said ribbon cassette (7) while said detecting means (6) is provided on said carriage, characterised in that the indicating means (11,12) comprises a through hole (11) formed on the ribbon cassette and an engaging member (12) movably received within said through hole, and in that said detecting means (6) comprises the surface of the carriage (2) and the vertical portion of said engaging member (12) within said through hole. Apparatus according to claim 1, wherein said through hole (21) is provided with a pair of engaging portions (21a,21b) on the inner surface thereof at a predetermined vertical interval, and the engaging member (22) is provided with a portion (22a) at a vertically intermediate position to be selectively engaged with one of said engaging portions (21a,21b), in order to project out of said at least one side of the ribbon cassette (7), and said detecting means comprises the cassette mounting surface of said carriage (2). Apparatus according to claim 1, wherein said through hole (24) is horizontally defined to provide two holding spaces and the engaging member (25) is to be selectively accommodated in one of said holding spaces, both ends (25a,25b) of said engaging member (25) protruding out of the surfaces of said ribbon cassette (7), and wherein said detecting means comprises a recess (23) formed on said carriage (2) to receive therein one of said protruded ends (25a,25b) of said engaging member (25) if said engaging member is accommodated in the corresponding one of said holding spaces. Apparatus according to claim 1, wherein said through-hole (11) vertically defines two holding spaces, said engaging member is a blocking member (12) to be selectively accommodated in one of said holding spaces, and said detecting means comprises a projection (6) formed on said carriage (2) to be received in the other of said holding spaces when said ribbon cassette (7) is loaded.

Inventors: NONOMURA, YOSHIHITO, TAKAGI, KAZUHIKI
Applicants: BROTHER KOGYO KABUSHIKI KAISHA
Application year: 1987
Main classification: B41J35
IPC codes: B41J35, B41J32