Thermal transfer printer

Abstract: A thermal transfer printer in which the number of parts is reduced and in which the ribbon cassette can be transferred in a stable manner includes: a platen (1) arranged in a printing column direction; a carriage (4) arranged so as to be capable of reciprocating along the platen; a ribbon cassette (1) accommodating an ink ribbon in a case main body; a cassette platform (10) mounted on the carriage and equipped with an engagement portion to be engaged with the ribbon cassette; a cassette holder (12) arranged at a position opposite to the cassette platform and having a plurality of cassette holding portions (13) each engaged with the ribbon cassette; a driving mechanism (7) for causing the cassette holder and the cassette platform to be brought into contact with and separated from each other; a cassette transfer mechanism which makes it possible for the ribbon cassette to be transferred between the cassette platform and the cassette holding portion by driving the driving mechanism to cause the cassette holder and the cassette platform to be brought into contact with and separated from each other; and movable members and stationary members for engaging the ribbon cassette which are arranged on the cassette platform and the cassette holding portion.

Description: The present invention relates to a thermal transfer printer of the type in which a desired ribbon cassette is selected from a plurality of ribbon cassettes respectively held by a plurality of cassette holding portions of a cassette holder and in which the selected ribbon cassette is transferred to a cassette platform to perform desired printing. In a common thermal transfer printer, paper and an ink ribbon are arranged before a platen, and, while moving a thermal head mounted on a carriage in a printing column direction in a condition in which the thermal head is held in press contact with the platen through the intermediation of the ink ribbon and the paper, a plurality of heat generating elements are selectively caused to generate heat in accordance with printing signals, whereby the ink of the ink ribbon is melted and transferred to the paper to thereby effect printing. Due to its high printing quality, low noise, low cost, ease of maintenance, etc., such a thermal printer is widely used as an output apparatus for a computer, a word processor, or the like. To make such a thermal transfer printer more convenient to use and achieve a reduction in running cost, there is known, as has been proposed in USP No.5,538,351, a thermal transfer printer in which there is provided a cassette holder holding a plurality of ribbon cassettes containing inks of different colors in cassette holding portions. The cassette holder is arranged opposite to the carriage, and a ribbon cassette having an ink of a desired color is selected from the ribbon cassettes held by the cassette holding portions of the cassette holder. The selected ribbon cassette is transferred from the cassette holding portion to a cassette platform arranged on the carriage to thereby make it possible to perform recording by the thermal head. Fig. 19 schematically shows the construction of the essential part of a cassette holding portion of the cassette holder and the cassette platform of such a conventional thermal transfer printer. In Fig. 19, a ribbon cassette 11 is held by the cassette holding portion 20, and no ribbon cassette 11 is attached to the cassette platform 22. As shown in the drawing, the cassette holding portion 20 is equipped with a pair of arms 20a and 20b for holding the ribbon cassette 11. Around the base portions of these arms 20a and 20b, torsion coil springs (not shown) are wound so that the ribbon cassette 11, held by the cassette holding portion 20, may be reliably held due to the resilient force of the springs, whereby the ribbon cassette 11 is prevented from being detached from the cassette holding portion 20. On the side opposite to the cassette holding portion 20 of the cassette holder, there is arranged a carriage 21, on which there is mounted a cassette platform 22 as shown in Fig. 19 so as to be capable of being brought into contact with and moved away from the cassette holding portion 20. A pair of arms 22a and 22b are arranged on either end of the cassette platform 22. Torsion coil springs (not shown) are wound around the base portions of these arms 22a and 22b so that the ribbon cassette 11 placed on the cassette platform 22 may be constantly held due to the resilient force of these springs, whereby the ribbon cassette 11 is prevented from being detached from the cassette platform 22. The distance between the forward ends of the arms 22a and 22b when the ribbon cassette 11 is not placed on the cassette platform 22 is smaller than the distance between the forward ends of the arms 20a and 20b of the cassette holding portion 20 when the ribbon cassette 11 is being held by the cassette holding portion 20. Further, the distance between the forward ends of the arms 20a and 20b when the ribbon cassette 11 is not being held by the cassette holding portion 20 is smaller than the distance between the forward ends of the arms 22a and 22b of the cassette platform 22 when the ribbon cassette 11 is placed on the cassette platform 22 (See Fig. 19). Next, the operation of transferring the ribbon cassette 11, held by the cassette holding portion 20 of the thermal transfer printer constructed as described above, to the cassette platform 22, will be described. First, as shown in Fig. 19, the cassette platform 22 is moved to a position opposite to the cassette holding portion 20 holding the ribbon cassette 11. In this condition, the cassette platform 22 is moved by a driving means (not shown) so as to approach the cassette holding portion 20. As described above, the distance between the forward ends of the arms 22a and 22b of the cassette platform 22 is smaller than the distance between the forward ends of the arms 20a and 20b of the cassette holding portion 20 when the ribbon cassette 11 being is held by the cassette holding portion 20. Thus, the forward ends of the arms 22a and 22b get inside the arms 20a and 20b of the cassette holding portion 20, and, while moving the arms 20a and 20b apart from each other against the resilient force of the torsion coil springs, enter the cassette holder 20. When the cassette platform 22 further moves toward the cassette holding portion 20, the ribbon cassette 11, which has been held by the arms 20a and 20b of the cassette holding portion 20, is elastically held between the arms 22a and 22b of the cassette platform 22 (See Fig. 20). In this way, the ribbon cassette 11 is transferred from the cassette holding portion 20 to the cassette platform 22. Next, the cassette platform 22, which has thus received the ribbon cassette 11, is brought back to the carriage 21, whereby the desired ribbon cassette 11 is mounted on the carriage 21, thereby making it possible to perform printing by using this ribbon cassette 11 (See Fig. 21). When the printing by using the desired ribbon cassette 11 has been completed, the ribbon cassette 11 is transferred from the cassette platform 22 to the cassette holder 20. This transfer operation will be described below. First, as shown in Fig. 21, the cassette platform 22 mounted on the carriage 21 is moved to a position opposite to the cassette holding portion 20 of the cassette holder holding no ribbon cassette. Then, the cassette platform 22 is moved toward the cassette holding portion 20 by a driving mechanism (not shown). Then, the forward ends of the arms 22a and 22b of the cassette platform 22 are positioned outside the forward ends of the arms 20a and 20b of the cassette holding portion 20 (See Fig. 22). In this condition, the cassette platform 22 is moved toward the cassette holding portion 20. Then, as shown in Fig. 23, the arms 20a and 20b of the cassette holding portion 20 move while outwardly moving the arms 22a and 22b of the cassette platform 22 apart from each other, and the ribbon cassette 11 is transferred from the cassette platform 22 to the cassette holding portion 20. Next, the cassette platform 21 with no ribbon cassette 11 mounted thereon is brought back to the carriage 21 (Fig. 24). When the ribbon cassette 11 has been transferred and the cassette platform 22 with no ribbon cassette 11 mounted thereon has been returned to the carriage 21, the ribbon cassette 11 for next printing is selected, and the above operations of Figs. 19 through 21 are conducted again, whereby a ribbon cassette 11 accommodating an ink ribbon of another color is transferred from the cassette holding portion 20 to the cassette platform 22. In such a conventional thermal transfer printer, to reduce the load of the take-up bobbin when taking up the ink ribbon during printing, the frictional resistance between the reels cassette case, i.e., between the supply reel, around which the ink ribbon is wound, and the take-up reel, and the ribbon cassette case supporting these reels, is made as small as possible, whereby the torque of a motor or the like constituting the driving source for rotating the take-up bobbin is reduced to thereby achieve a reduction in power consumption. However, in this conventional thermal transfer printer, the arms 20a and 20b of the cassette holding portion 20 and the arms 22a and 22b of the cassette platform 22 are formed of materials different from those of the cassette holding portion 20 and the cassette platform 22, respectively. Further, since torsion coil springs (not shown) for elastically holding the ribbon cassette 11 are wound around the arms 20a, 20b, 22a and 22b, the number of parts is rather large, resulting in the cost of the thermal transfer printer being rather high. Further, the large number of parts leads to a poor assembly efficiency. Further, when the ribbon cassette 11 is attached to or detached from the cassette holding portion 20 or the cassette platform 22 for transfer, any positional deviation of the forward ends of the arms 20a, 20b, 22a and 22b may make it impossible for the ribbon cassette 11 to be transferred. For example, there is no problem when, as shown in Fig. 19, the positioning of the cassette platform 22 and the cassette holding portion 20 is effected accurately. However, when the right-hand arm 22a of the the cassette platform 22 is deviated to the outside of the right-hand arm 20a of the cassette holding portion 20, or when the left-hand arm 22b of the the cassette platform 22 is deviated to the outside of the left-hand arm 20b of the cassette holding portion 20, it is impossible for the cassette platform 22 to correctly transfer the ribbon cassette 11, so that it is necessary to provide a positioning sensor (not shown) to effect accurate positioning, resulting in a higher cost. Further, when transferring the ribbon cassette 11 from the cassette holding portion 20 to the cassette platform 22 or from the cassette platform 22 to the cassette holding portion 20, the cassette holder 20 vibrates, so that the ribbon cassette 11 held by the cassette holding portion vibrates, with the result that the above-mentioned reels make some idle running, thereby causing slackness in the ink ribbon wound around the reels. When this ribbon cassette 11, in which the ink ribbon have become slack, is transferred from the cassette holding portion 20 to the cassette platform 22, the slack ribbon may get caught by the platen, the upper portion of the thermal head, etc., so that, when the thermal head is lowered when starting printing, the ink ribbon will get wrinkled, thereby making it impossible for printing to be effected in an appropriate manner. The reader is directed to document EP-A-0703089, in the name of Sharp Kabushiki Kaisha, for a description of a conventional thermal printer. This document discloses a thermal transfer printer comprising: a platen arranged in a printing column direction; a carriage arranged so as to be capable of reciprocating along the platen; a carriage driving mechanism for reciprocating the carriage along the platen; a ribbon cassette accommodating an ink ribbon in a case main body; a cassette platform mounted on the carriage and equipped with engagement portions that comprise two movable members to be engaged with the ribbon cassette; a cassette holder arranged at a position opposite to the cassette platform and having a plurality of cassette holding portions each equipped with cassette engagement portions that comprise a movable member and a stationary member to be engaged with the ribbon cassette; a driving mechanism for causing the cassette holder and the cassette platform to be brought into contact with and separated from each other; a cassette transfer mechanism which makes it possible for the ribbon cassette to be transferred between the cassette platform and the cassette holding portion by driving the driving mechanism to cause the cassette holder and the cassette platform to be brought into contact with and separated from each other. The present invention has been made with a view toward solving the above problems in the prior art. It is an object of the present invention to provide a thermal transfer printer in which the number of parts is reduced and in which the ribbon cassette can be transferred in a stable manner. According to the present invention there is provided a thermal transfer printer comprising: a platen arranged in a printing column direction; a carriage arranged so as to be capable of reciprocating along the platen; a carriage driving mechanism for reciprocating the carriage along the platen; a ribbon cassette accommodating an ink ribbon in a main case body; a cassette platform mounted on the carriage and equipped with engagement portions that comprise a movable member and a stationary member to be engaged with the ribbon cassette; a cassette holder arranged at a position opposite to the cassette platform and having a plurality of cassette holding portions each equipped with cassette engagement portions that comprise a movable member and a stationary member to be engaged with the ribbon cassette; a driving mechanism for bringing the cassette platform into contact with and separate from the cassette holder; and a cassette transfer mechanism which makes it possible for the ribbon cassette to be transferred between the cassette platform and the cassette holding portion by driving the driving mechanism to bring the cassette platform into contact with and separate from the cassette holder, and by driving and controlling the carriage driving mechanism to move the carriage along the platen. The stationary members may be formed integrally with the cassette platform and the cassette holder. The invention may provide a thermal transfer printer wherein the movable members and the stationary members are arranged at a predetermined interval parallel to the moving direction of the carriage and at opposite positions. The invention may provide a thermal transfer printer wherein elastic members are mounted to the movable members and wherein the movable members are elastically biased towards the stationary members by the elastic members. The present invention may provide a thermal transfer printer wherein the cassette transfer mechanism transfers the ribbon cassette from the cassette holding portion to the cassette platform or from the cassette platform to the cassette holding portion by an operation of moving the cassette platform along the platen relative to the cassette holding portion by the drive and control of the carriage driving mechanism for moving the carriage, and an operation of bringing the cassette platform into contact with and separate from the cassette holding portion. The invention may provide a thermal transfer printer wherein a ribbon take-up bobbin arranged on the carriage and engaged with the take-up reel of the ribbon cassette is rotated in the ribbon take-up direction when transferring the ribbon cassette. Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Fig. 1 is a general perspective view schematically illustrating the construction of a thermal transfer printer in accordance with the present invention; Fig. 2 is an essential-part perspective view illustrating the cassette holding structure of the cassette holding portion of the thermal transfer printer of the present invention; Fig. 3 is a front view of the cassette holding portion of the cassette holder of the thermal transfer printer of the present invention; Fig. 4 is a perspective view of the elastic member of the thermal transfer printer of the present invention; Figs. 5 through 16 are diagrams illustrating the ribbon cassette transferring operation in the thermal transfer printer of the present invention; Figs. 17 and 18 are diagrams illustrating the operation of the elastic members of the cassette holding portion when the ribbon cassette transferring operation is effected in the thermal transfer printer of the present invention; and Figs. 19 through 24 are diagrams illustrating the ribbon cassette transferring operation in a conventional thermal transfer printer. An embodiment of the thermal transfer printer of the present invention will be described with reference to Figs. 1 through 16. As shown in the essential-part perspective view of Fig. 1, in the thermal transfer printer of the present invention, a flat platen 1 is arranged substantially horizontally in the main body of the printer. A guide shaft 2, which extends parallel to this platen 1, connects the side plates (not shown) of the main body case to each other. A carriage 4, which can reciprocate on the guide shaft 2, is arranged over the platen 1 so as to face it. The carriage 4 carries a thermal head 3 which can be brought into contact with and moved away from the platen 1. A plurality of heat generating elements (not shown) are aligned on the thermal head 3. Behind the carriage 4, a toothed belt 5 for causing the carriage 4 to reciprocate on the guide shaft 2 are wound around pulleys (not shown). Further, behind the platen 1, there is arranged a paper feeding mechanism 6 composed of a paper feeding roller 6a and an auxiliary roller 6b, by means of which paper (not shown) is fed between the platen 1 and the thermal head 3. A take-up bobbin 4a and a supply bobbin 4b protrude from the surface of the carriage 4. Further, a cover 4c for protecting the thermal head 3 is provided in the central part of the lower end portion of the carriage 4 (Fig. 1). A lift gear 7 formed of synthetic resin is rotatably arranged on the carriage 4 at a position nearer to the upper end thereof. On the outer periphery of this lift gear 7, there are formed a plurality of screw teeth 7a and screw grooves 7b, which are arranged at equal intervals. Further, in the upper left corner of the carriage 4, a bar-like guide pin 8 formed of metal is arranged. Further, in the right upper corner of the carriage 4, there is arranged a sensor mounting member 9 equipped with a sensor (not shown) for detecting the kind, position, etc. of a ribbon cassette described below. Further, attached to the carriage 4 is a cassette platform 10 capable of carrying a ribbon cassette 11 described below. The cassette platform 10 is movable in a direction perpendicular to the direction of movement of the carriage 4 (the direction in which it is moved so as to be brought into contact with and separated from a cassette holding portion 13 described below). In that portion of the cassette platform 10 which is nearer to the upper end thereof, there is formed a screw hole 10a. In this screw hole 10a, there are formed screw teeth 10b adapted to be engaged with the screw grooves 7b of the lift gear 7. By rotating the lift gear 7, the cassette platform 10 can be moved in a direction perpendicular to the direction of movement of the carriage 4. Further, on one side of that portion of the cassette platform 10 which is nearer to the upper end thereof, there is provided a guide hole 10k in which a bearing (not shown) is embedded. The guide pin 8 of the carriage 4 is inserted into this guide hole 10k, whereby the guide pin 8 serves as a guide when the cassette platform 10 moves in the direction perpendicular to the direction of movement of the carriage 4. Further, in that portion of the cassette platform 10 which is nearer to the lower end thereof, there are formed a pair of holes 10c and 10d, through which the take-up bobbin 4a and the supply bobbin 4b of the carriage 4 are passed. In the upper corner on the other side of the cassette platform 10, there is formed a rectangular hole 10e, through which the above-mentioned sensor mounting member 9 is passed. Further, in the vicinity of the rectangular hole 10e of the cassette platform 10, there is formed a stationary claw 10g, which is a stationary member formed integrally with the cassette platform 10 by molding. At the forward end of this stationary claw 10g, there is formed a hook-like engagement portion. In the right lower corner of the cassette platform 10 also, there is formed a stationary claw 10h, which is a stationary member formed integrally with the cassette platform 10 by molding. The width dimension of this stationary claw 10h is such that it can be engaged with a protruding portion 11p of an engagement portion 11e of the ribbon cassette 11 described below. Further, at a position opposite to the stationary claw 10h of the cassette platform 10, there is provided a movable claw 10j, which is a movable member spaced apart from the stationary claw 10h by a predetermined distance. The movable claw 10j is formed as a member separate from the cassette platform 10 and rotatable with respect to the cassette platform 10. At the forward end of the movable claw 10j, there is formed a hook-like engagement portion. Further, a protrusion 10m adapted to be engaged with an engagement portion 11f of the ribbon cassette 11 protrudes from the inner side surface of the movable claw 10j. Further, a torsion coil spring (not shown) is wound around the rotation center of the movable claw 10j, and elastically biases the engagement portion at the forward end of the movable claw 10j constantly toward the stationary claw 10h, that is, in the direction of an arrow B. The ribbon cassette 11 accommodates, in a main body case 11a, a long ink ribbon 16 whose end portions are respectively wound around a take-up reel 14 and a supply reel 15. All the ribbon cassettes 11 have the same configuration and the same size irrespective of the color, etc. of the ink ribbon 16 accommodated therein. The take-up reel 14 and the supply reel 15 are rotatably accommodated in the main body case 11a. When the ribbon cassette is mounted on the cassette platform 10, the take-up reel 14 and the supply reel 15 are respectively engaged with the take-up bobbin 4a and the supply bobbin 4b of the carriage 4. By rotating the take-up bobbin 4a, the ink ribbon 16 is taken up by the take-up reel 14. As shown in Fig. 2, a recess 11b is formed in the main body case 11a. When the ribbon cassette 11 is attached to the cassette platform 10 on the carriage 4, the thermal head 3 is inserted into this recess 11b. Further, on the surface on the opposite side of this recess 11b, there is formed an identification marker 11c indicating the kind of ink ribbon 16 accommodated in this ribbon cassette 11. Further, a recess lid is formed at the center of the upper side; engagement portions 11e and 11f are formed on the left and right sides; and chamfered portions 11g and 11h are formed at the upper corners. When the ribbon cassette 11 is mounted to the cassette platform 10, the stationary claw 10g abuts the chamfered portion 11g, and the stationary claw 10h and the movable claw 10j respectively abut the recesses 11e and 11f on either side, the ribbon cassette 11 being engaged by means of the engagement portions. Further, as shown in Fig. 1, at a position opposite to the cassette platform 10 mounted on the carriage 4, there is arranged a cassette holder 12 equipped with a plurality of (four, in the example shown) cassette holding portions 13, at a predetermined distance from the cassette platform 10. The cassette holder 12 is arranged parallel to the direction of movement of the carriage 4. Further, at the lower end of the cassette holder 12, there is provided a stopper portion 12a for restricting downward movement of the ribbon cassette 11 held by the cassette holding portions 13. Thus, the cassette holder 12 has an L-shaped cross section. Further, as shown in Fig. 2, the cassette holding portion 13 of the cassette holder 12 is equipped with a stationary claw 13a, which is a stationary member and whose forward end is divided in two. Hook-like engagement portions are formed at the forward end of stationary claw 13a. The stationary claw 13a, which is integrally formed with the cassette holding portion 13 by molding or the like, protrudes from the cassette holding portion 13. Further, at a position opposite to the stationary claw 13a and at a predetermined distance therefrom, a movable claw 13b, which is a movable member and whose forward end is divided in two, is formed as a member which is separate from the cassette holding portion 13. Hook-like engagement portions are formed at the forward end of the movable claw 13b. The movable claw 13b is rotatable around the base portion thereof. A torsion coil spring (not shown) is wound around the rotation center of this movable claw 13b to constantly bias the engagement portions at the forward end of the movable claw 13b elastically toward the stationary claw 13a, i.e., in the direction of an arrow D. Further, between the stationary claw 13a and the movable claw 13b, there are formed a pair of cassette receiving portions 13c, which protrude from the surface of the cassette holder 12, to hold the ribbon cassette 11 on the ribbon cassette holding portion 13 in a condition in which it is separated from the surface of the cassette holder 12 by a predetermined distance. Further, protrusions 13d are formed at the forward ends of the cassette receiving portions 13c to restrict upward displacement of the ribbon cassette 11. Further, as shown in the plan view of Fig. 3, two bottomed mounting holes 13e and 13f are formed in a line F, which is substantially the center line of the cassette holding portion 13. In the inner surfaces of the mounting holes 13e and 13f, on the center line F at positions nearer to the stationary claws 13a, there are formed, in the depth direction of the mounting holes 13e and 13f, protrusions 13g and 13h with an arcuate cross-sectional configuration and a predetermined height. Further, elastic members 17 are forced into the mounting holes 13e and 13f. When the ribbon cassette 11 is held by the cassette holding portion 13, the elastic members 17 abut the inner walls 14b and 15b of the bobbin engagement holes 14a and 15a of the take-up reel 14 and the supply reel 15 of the ribbon cassette 11 to effect elastic biasing. These elastic members 17 are formed of a soft material, such as rubber, which is easily deformed by slight external forces and quickly restored to the former shape when there is no external force. Fig. 4 shows the configuration of the elastic member 17. As shown in the drawing, it has a cylindrical base portion 17a having substantially the same outer diameter as the bobbin engagement holes 14a and 15a of the take-up reel 14 and the supply reel 15 of the ribbon cassette 11. On the base portion 17a, there are formed a plurality of circumferential wedge-like protrusions 17b. Thus, the elastic member 17 can be easily forced into the mounting hole 13e, 13f. However, once forced in, it cannot be easily taken out of the mounting hole 13e, 13f due to the above-mentioned protrusions 17b. Further, a longitudinal expanding slot 17c, provided on the outer periphery of the base portion 17a and having a predetermined width, extends up to a position near the center of the base portion 17a. Further, a substantially semi-cylindrical protrusion 17f having an outer wall 17e extending along the periphery of the base portion 17a is formed at an end of an upper surface 17d of the base portion 17a. The outer wall 17e of this protrusion 17f has substantially the same arcuate configuration as the outer periphery of the base portion 17a. Since the outer diameter of the protrusion 17f is smaller than the diameter of the bobbin engagement holes 14a and 15a of the reels 14 and 15 of the ribbon cassette 11, the insertion of the reels 14 and 15 of the ribbon cassette 11 into the bobbin engagement holes 14a and 15a can be effected with ease. Further, a plurality of longitudinal serrations extend from the upper end of the protrusion 17f to a level which corresponds to substantially half the height of the protrusion 17f. When forcing the base portion 17a of the elastic member 17 into the mounting hole 13e, 13f of the cassette holding portion 13, the protrusion 13g, 13h of the mounting hole 13e, 13f is engaged with the expanding slot 17c of the elastic member 17, and then the elastic member 17 is forced into the mounting hole 13e, 13f. Thus, the serrated outer wall 17e of the protrusion 17f always faces the movable claw 13b of the cassette holding portion 13. Further, the protrusion 17f has an expanding slot 17g extending in the height direction provided in the outer wall 17e thereof. The expanding slot 17g, which has a predetermined width, extends outwardly in the direction opposite to the expanding slot 17c of the base portion 17a from a position near the axis of the base portion 17a to a level that is the same as the surface 17d of the base portion 17a. Further, the entire outer periphery of the base portion 17a of the elastic member 17 is embedded in the mounting hole 13e, 13f, and only the protrusion 17f protrudes beyond the mounting hole 13e, 13f. The ribbon cassette 11, which is held by the cassette holding portion 13, constructed as described above, is longitudinally pressurized by the resilient force of the torsion coil spring of the movable claw 13b toward the stationary claw 13a, and engaged by the operation of the engagement portions at their forward ends. In the vertical direction, the ribbon cassette 11 is positioned by the protrusions 13d of the cassette receiving portions 13c and the stopper portion 12a of the cassette holder 12. Thus, if vibrations, etc. are applied to the thermal transfer printer from outside, the ribbon cassette 11 is not detached from the cassette holding portion 13. While in Fig. 1 the cassette platform 10 is detached from the carriage 4, in actual use, the cassette platform 10 is movably mounted to the carriage 4, the lift gear 7, which is the driving mechanism for causing the cassette platform 10 and the cassette holding portion 13 to come into contact with and moved away from each other, being in screw engagement with the screw hole 10a of the cassette platform 10. When the cassette platform 10 is moved toward the cassette holding portion 13 by rotating the lift gear 7, the cassette platform 10 hits the cassette receiving portions 13c of the cassette holding portion 13 and the movement toward the cassette holding portion 13 is stopped before the cassette platform 10 is detached from the lift gear 7, so that there is no concern that the cassette platform 10 will be detached from the lift gear 7. In the condition in which the ribbon cassette 11 is being held by the cassette holding portion 13, the identification mark 11c of the ribbon cassette 11 is at a position opposite to a sensor (not shown) mounted to the sensor mounting member 9 of the carriage 4. This identification mark 11c is read by the sensor mounted to the sensor mounting member 9 while moving the carriage 4, whereby the kind of ribbon cassette 11 is discriminated. In this thermal transfer printer P, constructed as described above, the ribbon cassette 11 is transferred from the cassette holding portion 13 to the cassette platform 10, and, conversely, from the cassette platform 10 to the cassette holding portion 13. This transferring operation will be described with reference to the schematic diagrams, Figs. 5 through 16. First, the case will be described in which the ribbon cassette 11 held by the cassette holding portion 13 of the cassette holder 12 is transferred to the cassette platform 10 to which no ribbon cassette 11 is attached. First, the carriage 4 is moved along the platen 1, and the identification mark 11c of the ribbon cassette 11 held by each cassette holding portion 13 is read by the sensor 9a mounted to the sensor mounting member 9 of the carriage 4, whereby the kind of ribbon cassette 11 is identified, and a ribbon cassette 11 accommodating an ink ribbon 16 of a desired color is selected before the carriage 4 is stopped. The positional relationship between the cassette platform 10 and the selected cassette holding portion 13 at this time is such that the engagement portion of the movable claw 10j of the cassette platform 10 is positioned outside the engagement portion of the movable claw 13b of the cassette holding portion 13. That is, the carriage 4 is stopped at a position where the movable claw 10j and the stationary claw 10h of the cassette platform 10 are somewhat deviated from the movable claw 13b and the stationary claw 13a of the cassette holding portion 13 (Fig. 5). Next, the lift gear 7 is rotated to move the cassette platform 10 toward the cassette holding portion 13 (in the direction of the arrow b) to a position where the engagement portion at the forward end of the movable claw 10j of the cassette platform 10 and the engagement portion at the forward end of the movable claw 13b of the cassette holding portion 13 cross each other. Next, when the carriage 4 is moved in the direction of the arrow c along the platen 1, the engagement portion of the movable claw 10j of the cassette platform 10 abuts the end portion of the ribbon cassette 11, and the movable claw 10j rotates in the direction of the arrow A against the resilient force of the torsion coil spring (not shown) (Fig. 7). At this time, the cassette platform 10 is moved in the direction of the arrow c until the stationary claw 10h of the cassette platform 10 is positioned outside the stationary claw 13a of the cassette holding portion 13. Next, the lift gear 7 of the carriage 4 is rotated again to further move the cassette platform 10 toward the cassette holding portion (in the direction of the arrow d) to thereby cause the ribbon cassette 11 to be held between the cassette platform 10 and the cassette holding portion 13. Then, the movable claw 10j of the cassette platform 10, which has been in contact with one end portion of the main body case 11a of the ribbon cassette 11 is further rotated in the direction of the arrow A, and the surface of the cassette platform 10 abuts the surface 11m of the ribbon cassette 11, with the result that the movement of the cassette platform 10 toward the cassette holding portion 13 (in the direction of the arrow d) is stopped (Fig. 8). When, in this condition, the carriage 4 (the cassette platform 10) is moved in the reverse direction (in the direction of the arrow e) along the platen 1, the movable claw 13b of the cassette holding portion 13 rotates in the direction of the arrow C (outwards), and the engagement portion of this movable claw 13b is detached from the end portion of the main body case 11a of the ribbon cassette 11. At the same time, the engagement portion of the stationary claw 13a of the cassette holding portion 13 is also detached from the other end portion of the ribbon cassette 11, with the result that the base portion of the V-shaped movable claw 13b becomes vertical. When the base portion of the movable claw 13b of the cassette holding portion 13 becomes vertical, the movable claw 13b of the cassette holding portion 13 does not further rotate in the direction of the arrow C. Thus, if the cassette platform 10 moves in the direction of the arrow e, the ribbon cassette 11 is stopped at the base portion of the movable claw 13b which has become vertical, and does not move any further in the direction of the arrow e. Due to this arrangement, only the cassette platform 10 moves in the direction of the arrow e, until the engagement portion of the stationary claw 10h of the cassette platform 10 is engaged with the protrusion 11p of one recess 11e of the ribbon cassette 11. The engagement portion of the movable claw 10j of the cassette platform 10 rotates in the direction of the arrow B due to the resilient force of the torsion coil spring to engage with the other recess 11f of the main body case 11a of the ribbon cassette 11, whereby the ribbon cassette 11, which has been held by the cassette holding portion 13, is transferred to the cassette platform 10 (Fig. 9). That is, the carriage 4 is moved in the direction of the arrow e along the platen 1 to cancel the engagement of the ribbon cassette 11 with the engagement portions of the movable member 13b and the stationary member 13a of the cassette holding portion 13, and, at the same time, the ribbon cassette 11, which has thus been released from the engagement, is transferred to the engagement portions of the movable claw 10j and the stationary claw 10h of the ribbon cassette platform 10 to which no ribbon cassette 11 is mounted. Then, the lift gear 7 is rotated in the reverse direction to move the cassette platform 10 away from the cassette holding portion 13 (in the direction of the arrow f), with the result that the ribbon cassette 11 is engaged with the stationary claw 10h and the movable claw 10j of the cassette platform 10 and separated from the cassette holding portion 13 to be returned to a predetermined position on the carriage 4, whereby the transfer from the cassette holding portion 13 to the cassette platform 10 is completed (Fig. 10). When the cassette platform 10 is returned to the predetermined position on the carriage 4, the take-up bobbin 4a and the supply bobbin 4b of the carriage 4 shown in Fig. 1 are engaged with the take-up reel 14 and the supply reel 15 of the ribbon cassette 11. Then, the carriage 4 supported by the guide shaft 2 moves along the platen 1, whereby printing is made possible. Next, described will be the operation of transferring the ribbon cassette 11 from the cassette platform 10 to the cassette holding portion 13 for the purpose of replacing the ribbon cassette 11 attached to the cassette platform 10 with another ribbon cassette 11. First, the cassette platform 10 with the ribbon cassette 11 mounted thereto is moved to the position of a cassette holding portion 13 holding no ribbon cassette. At this time, the cassette platform 10 is moved such that the cassette platform 10 and the cassette holding portion 13 are brought into a positional relationship in which the engagement portion of the movable claw 10j of the cassette platform 10 with the ribbon cassette mounted thereon is on the inner side of the engagement portion of the movable claw 13b of the cassette holding portion 13 holding no ribbon cassette (Fig. 11). Next, the lift gear 7 is rotated to move the cassette platform 10 toward the cassette holding portion 13 (in the direction of the arrow b). At this time, the cassette platform 10 is brought close to the cassette holding portion 13 until the engagement portion of the movable claw 10j of the cassette platform 10 and the engagement portion of the movable claw 13b of the cassette holding portion 13 cross each other (Fig. 12). Then, in this condition, the carriage 4 is moved in the direction of the arrow e. Then, the engagement portion of the movable claw 13b of the cassette holding portion 13 abuts one end of the main body case of the ribbon cassette 11, and the movable claw 13b rotates in the direction of the arrow C (outwards) against the resilient force of the torsion coil spring (not shown), that is, so as to move away from the stationary claw 13a, with the result that the base portion of this movable claw 13, which has a V-shaped configuration, becomes vertical. Like the movable claw 10j of the cassette platform 10 described above, the movable claw 13b of the cassette holding portion 13 does not further rotate outwards when the base portion thereof has become vertical (Fig. 13). Next, the lift gear 7 is rotated to further move the cassette platform 10 toward the cassette holding portion 13 (in the direction of the arrow d) so that the ribbon cassette 11 may be held between the cassette platform 10 and the cassette holding portion 13. Then, one side surface of the ribbon cassette 11 abuts the vertical base portion of the movable claw 13b of the cassette holding portion 13, and the surface 11n of the ribbon cassette 11 abuts the surfaces of the cassette receiving portions 13c of the cassette holding portion 13, and the movement of the cassette platform 10 toward the cassette holding portion 13 is stopped (Fig. 14). When the cassette platform 10 is moved in the direction of the arrow c, the ribbon cassette 11 abuts the stationary claw 13a of the cassette holding portion 13, and the engagement portion of this stationary claw 13a engages one side portion of the main body case 11a of the ribbon cassette 11. At the same time, the movable claw 13b of the cassette holding portion 13 is also rotated in the direction of the arrow D by the resilient force of the torsion coil spring (not shown), and engages the other end portion of the ribbon cassette 11. When, in this condition, the cassette platform 10 is further moved in the direction of the arrow c, the base portion of the movable claw 10j of the cassette platform 10 abuts one end portion of the ribbon cassette and rotates outwards in the direction of the arrow A against the resilient force of the torsion coil spring, with the result that the engagement portion of this movable claw 10j is detached from the main body case 11a of the ribbon cassette 11. At the same time, the engagement portion of the stationary claw 10h is also detached from the ribbon cassette 11, and the ribbon cassette 11 is transferred from the cassette platform 10 to the cassette holding portion 13. In this way, by moving the carriage 4 along the platen 1, the cassette platform 10 is moved, and the ribbon cassette 11, which has been engaged with the engagement portions of the movable member 10j and the stationary member 10h of the cassette platform 10, is brought into a non-engagement state. Further, this non-engaged ribbon cassette 11 is engaged with the movable claw 13b and the stationary claw 13a of the cassette holding portion 13, whereby the transfer of the ribbon cassette 11 is effected (Fig. 15). Then, the screw gear 7, serving as the driving mechanism, is rotated in the reverse direction to move the cassette platform 10 in the direction of the arrow f, and the cassette platform 10 is moved away from the cassette holding portion 13 to return it to the predetermined position on the carriage 4. Then, the cassette holding portion 13, which has held no ribbon cassette 11, holds the ribbon cassette 11, thus completing the transfer of the ribbon cassette 11 from the cassette platform 10 to the cassette holding portion 13 (Fig. 16). As shown in detail in Figs. 17 and 18, when the ribbon cassette 11 is transferred, as a result of the movement of the ribbon cassette 11 in the direction of the arrow C, the take-up reel 14 and the supply reel 15, which have been on the surfaces 17d of the elastic members 17, are detached from the surfaces 17d, and the outer walls 17e of the protrusions 17f abut the movable claw 16b side of the inner peripheral surfaces 14b and 15b of the bobbin holes 14a and 15a and elastically biased. As a result, the protrusions 17f of the elastic members 17 impart a rotational load to the take-up reel 14 and the supply reel 15, so that, if vibrations are applied to the ribbon cassette 11, the reels 14 and 15 make no idle running, and no slackness is generated in the ink ribbon 16. Further, if the pressurizing force of the take-up reel 14 and the supply reel 15 is applied to the protrusions 17f of the elastic members 17, the elastic members 17 are not rotated to cause positional deviation of the protrusions 17f since the protrusions 13g and 13h of the mounting holes 13e and 13f (See Fig. 3) are engaged in the expanding slots 17c of the base portions 17a. Further, due to the expanding slots 17g formed in the protrusions 17f of the elastic members 17, the protrusions 17f easily undergo elastic deformation, and, if the pressurizing force of the take-up reel 14 and the supply reel 15 is applied to the protrusions 17f, they can easily undergo elastic deformation, so that the engagement of the ribbon cassette 11 can be effected without a hitch. Further, since a plurality of serrations are formed on the outer walls 17e of the protrusions 17f of the elastic members 17, elastic biasing can be reliably effected if there are a plurality of engagement protrusions on the inner peripheral surfaces 14b and 15b of the bobbin engagement holes 14a and 15a. Further, in another embodiment, the elastic members 17 do not abut the inner peripheral surfaces 14b and 15b of the bobbin engagement holes 14a and 15a to effect elastic biasing. Instead, they may abut, for example, end surfaces of the take-up reel 14 and the supply reel 15 to elastically bias the take-up reel 14 and the supply reel 15. As described above, in the thermal transfer printer of the present invention, stationary and movable members for engaging the ribbon cassette 11 are arranged on both the cassette platform and the cassette holding portion, and the stationary members are integrally formed with the cassette platform and the cassette holding portion, so that the number of parts can be reduced, thereby making it possible to provide a low-cost thermal transfer printer. Further, the stationary and movable members are arranged in a direction parallel to the direction of movement of the carriage and opposed to each other at a predetermined distance, and the engagement portions of the movable members are elastically biased toward the stationary members, so that the ribbon cassette can be reliably engaged with the cassette platform or the cassette holding portion. Thus, if external vibrations, etc. are applied to the thermal transfer printer, the ribbon cassette is not detached from the cassette platform or the cassette holding portion. Further, the ribbon cassette is transferred from the cassette holding portion to the cassette platform or from the cassette platform to the cassette holding portion through a combination of the operation of moving the cassette platform and the cassette holding portion relative to each other in the direction of movement of the carriage and the operation of causing the cassette platform and the cassette holding portion to come into contact with and move away from each other, so that, if the opposing positions of the cassette platform are somewhat deviated with respect to the cassette holding portion at the time of transferring, the transfer of the ribbon cassette can be effected without a hitch. Thus, there is no need to provide a positioning sensor for performing the positioning of the carriage, thereby achieving a reduction in price. Further, elastic members adapted to abut and elastically bias the reels of the ribbon cassette when the ribbon cassette is held are mounted to the cassette holding portion, so that, if external vibrations are applied to the thermal transfer printer to cause the cassette holding portion holding the ribbon cassette to vibrate, it is possible to prevent the reels from rotating since the elastic members impart rotational load to the reels of the ribbon cassette. Thus, there is no concern that slackness will be generated in the ink ribbon, and it is possible to prevent the ribbon from getting caught by the thermal head, etc. when the ribbon cassette is transferred. Further, since the protrusions of the elastic members abut and elastically bias the movable claw side of the inner peripheral surfaces of the bobbin engagement holes of the reels of the ribbon cassette, the protrusions of the elastic members reliably pressurize the inner peripheral surfaces of the bobbin engagement holes of the reels due to the pressurizing force of the movable claw of the cassette holding portion, so that it is possible to reliably prevent the reels from making idle running, thereby preventing slackness from being generated in the ink ribbon.

Claims: A thermal transfer printer comprising: a platen (1) arranged in a printing column direction; a carriage (4) arranged so as to be capable of reciprocating along the platen; a carriage driving mechanism for reciprocating the carriage along the platen; a ribbon cassette (11) accommodating an ink ribbon (16) in a main case body; a cassette platform (10) mounted on the carriage and equipped with engagement portions that comprise a movable member (10j) and a stationary member (10h) to be engaged with the ribbon cassette; a cassette holder (12) arranged at a position opposite to the cassette platform and having a plurality of cassette holding portions (13) each equipped with cassette engagement portions that comprise a movable member (13b) and a stationary member (13a) to be engaged with the ribbon cassette; a driving mechanism (7) for bringing the cassette platform into contact with and separate from the cassette holder; and a cassette transfer mechanism which makes it possible for the ribbon cassette to be transferred between the cassette platform and the cassette holding portion by driving the driving mechanism to bring the cassette platform into contact with and separate from the cassette holder, and by driving and controlling the carriage driving mechanism to move the carriage along the platen. A thermal transfer printer according to Claim 1, wherein the stationary members are formed integrally with the cassette platform and the cassette holder. A thermal transfer printer according to Claim 1 or 2, wherein the movable members and the stationary members are arranged parallel to the direction of movement of the carriage and at opposite positions at a predetermined interval. A thermal transfer printer according to any preceding claim, wherein elastic members (17) are mounted to the movable members and wherein the movable members are elastically biased toward the stationary members by the elastic members. A thermal transfer printer according to any preceding claim, wherein the cassette transfer mechanism transfers the ribbon cassette from the cassette holding portion to the cassette platform or from the cassette platform to the cassette holding portion by an operation of moving the cassette platform along the platen relative to the cassette holding portion by the drive and control of the carriage driving mechanism for moving the carriage, and an operation of bringing the cassette platform into contact with and separate from the cassette holding portion. A thermal transfer printer according to any preceding claim, wherein a ribbon take-up bobbin (4a) arranged on the carriage and engaged with the take-up reel (14) of the ribbon cassette is rotated in the ribbon take-up direction when transferring the ribbon cassette.

Inventors: ISHITOBI YUUSAI, UEDA KAZUO, YOROZU HIDEKI, ISHITOBI, YUUSAI, UEDA, KAZUO, YOROZU, HIDEKI
Applicants: ALPS ELECTRIC CO LTD, ALPS ELECTRIC CO., LTD.
Application year: 1998
Main classification: B41J17
IPC codes: B41J32, B41J35