PRINTER

Abstract: Disclosed is a printer having a ribbon cassette (1) with an ink ribbon (3) wound between a feed reel (4) and a take-up reel (5) mounted in a stationary state independ­ ently of a carriage (2), so that the ink ribbon (3) may be let off from the ribbon cassette (1) and is recovered into the ribbon cassette (1) by means of a print head (19) mounted on the carriage (2) along with the movement of the carriage (2) in the printing direction, in which the carriage (2) is provided with a control roller (20) that is disposed on the transfer route of the ink ribbon (3) and is controlled so as to transfer the ink ribbon (3) in the length corres­ ponding to the printing portion at every printing by the print head (19) in the printing action in the direction of the take-up reel (5) and to fix the ink ribbon (3) when the carriage (2) returns or when transferring without print­ ing, and between the reels (4, 5) is disposed a reel control mechanism that applies a rotating force of small torque of such an extent as to slip with respect to the ribbon let-off force by the print head (19) to the both reels (4, 5) in the printing action in the take-up rotating direction, and applies a rotating force of large torque to the both reels (4, 5) when the carriage (2) returns in the take-up rotating direction.

Description: This invention relates to a printer, and more particularly to a printer such as an electro-thermic printer which has a ribbon cassette mounted in a stationary state independently of the carriage, and in which ink ribbon is withdrawn from and recovered on to the ribbon cassette by means of reciprocal motion of a print head mounted on the carriage in the printing direction. In conventional printers using an ink ribbon the ribbon cassette and ribbon take-up mechanism are generally mounted on the carriage together with the print head. This, however, results in the weight of the entire carriage being increased making it hard to move the carriage at high speed. Therefore, in order to move the heavy carriage at high speed, a driving motor of a high output torque is required. This, too, increases the size of the carriage, and accordingly places restrictions on the ribbon cassettes that can be mounted on the carriage. As a means of solving these problems a new mechanism, described in Japanese Laid-Open Patent Publication No. 58-217384 was proposed. In this printer, the ribbon cassette is mounted stationary with respect to the printer and independently of the carriage. Ink ribbon is drawn from the ribbon cassette by the print head mounted on the carriage on motion of the carriage in the printing directions. Although the carriage can be reduced in size and weight and can be moved at high speed because the ribbon cassette is not mounted on it, this type of fixed ribbon cassette encounters technical problems that must be solved. Whenever the carriage is returned to the initial printing position (home position), the take-up side reel is rotated in the take-up direction, and a portion of unused ink ribbon of sufficient length for printing one reciprocal stroke of the carriage is preliminarily wound from the feed reel onto the take-up side reel. The friction member located at the initial printing position for fixing the ink ribbon to the platen during printing is separated from the platen during this operation. The friction member then presses and fixes the ink ribbon to the platen by means of a driving source such as a magnet to define the amount of ink ribbon let-off from the feed side reel. As the carriage is moved in the printing direction the unused ink ribbon previously taken up on the take-up reel is withdrawn and used for printing by the print head. When the carriage reaches the end in the printing direction, it returns during which time the take-up reel is rotated to take-up the used ink ribbon. The operation is then repeated for subsequent printing rows. As a length of ink ribbon sufficient for one reciprocal stroke of the carriage is preliminarily taken up on the take-up side reel and the initial printing portion of this ink ribbon is fixed by the friction member during printing, if non-printing blank portions occur in the printing process the print head is released from the ink ribbon and these portions remain unused and are taken up on the take-up side reel when returning the carriage. The action generally known as ribbon skip does not, therefore occur and, the ink ribbon is consumed unnecessarily. Moreover, since a length of ink ribbon equivalent to one reciprocal stroke of the carriage is preliminarily taken up on the take-up reel side whenever the carriage comes to the initial printing position, it is extremely inefficient, and the take-up diameter of the ink ribbons on both reels changes every moment as the ink ribbon is taken up from the feed side reel to the take-up side reel, so that the rotation control of the motor for taking up the unused ink ribbon preliminarily on the take-up side reel is very difficult. Another printer utilising a stationary ink ribbon mount and movable carriage is described in US 4,621,270. It is an aim of this invention to present a printer capable of feeding the ink ribbon in the ribbon cassette efficiently into the print head provided in the carriage. It is another aim of this invention to present a printer capable of performing ribbon skip and transferring the ink ribbon efficiently, in a system in which the ribbon cassette is mounted in a stationary state independently of the carriage. Other objects and further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. It should be understood, however, that the detailed description of and specific examples, while indicating preferred embodiments of this invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. In accordance with a first aspect of the present invention there is provided a printer comprising a ribbon cassette being mounted stationarily on a body of the printer, said ribbon cassette containing a feed reel winding one end of an ink ribbon and a take-up reel winding the other end of said ink ribbon, and a carriage having a print head for printing by using said ink ribbon, said carriage being mounted on said body independently of said ribbon cassette and being movable in a printing direction thereof, characterized in that, said printer further comprises rotating means disposed on said body for applying a first torque to said feed reel in a direction to wind said one end of said ink ribbon and a second torque to said take-up reel in a direction to wind said other end of said ink ribbon during both of printing by said print head and returning of said carriage, and reel control means disposed on said body for controlling said rotating means such that it decreases the respective magnitudes of said first torque and said second torque with respect to a ribbon discharge force of said print head during said printing by said print head, and restores the respective magnitudes of said first torque and said second torque during said returning of said carriage. The said carriage may be provided with a control roller which is disposed on the transfer route of the ink ribbon and is controlled so as to transfer the ink ribbon by a length corresponding to the printing portion in the direction of said take-up reel at every printing action by said print head and to fix the ink ribbon when said carriage returns or when transferring without printing. The reel control mechanism applies a rotating force of small torque to both reels during printing action in the take-up rotating direction so as to allow slip with respect to the ribbon let-off force provided by the printing head. A rotating force of large torque in respective take-up rotation directions is applied to both reels when the carriage returns. During printing the reels of the take-up side and feed side rotate in respective anti-take-up directions by the tensile force of the print head mounted on the carriage on movement of the carriage in the printing direction, and ink ribbon is withdrawn from the ribbon cassette. At this time, since both reels are provided with a rotating force of small torque by the reel control mechanism in the take-up rotating direction tension is maintained in the ink ribbon being withdrawn from the ribbon cassette. When the heating elements of the print head are selectively driven, the thermo-melting ink of the ink ribbon melted in the form of a character pattern is transferred onto the printing paper, and a character is printed. A length of ink ribbon corresponding to the character is transferred across the print head toward the take-up reel by the control roller. During printing action, if non-printing blank portions are continuous, the print head is released from the ink ribbon, and the control roller fixes the ink ribbon while the carriage moves in the printing direction. Ink ribbon is drawn out of the ribbon cassette but does not transfer across the print head. ribbon skip action is thereby effected, and ink ribbon saved accordingly. When the carriage reaches the terminal end in the printing direction, the print head is released from the ink ribbon, and the carriage is returned to the initial printing position while the controller fixes the ink ribbon relative to the print head. The unused portion and printed portion of the ink ribbon are taken up, respectively on the feed reel and take-up reel which are provided with large torques in the respective take-up rotating directions by the reel control mechanism. In accordance with a second aspect of the present invention there is provided a printer comprising means for mounting a ribbon cassette having an ink ribbon wound between a feed reel and a take-up reel; a carriage having a print head for printing on a receptor surface through the ink ribbon mounted independently of the means for mounting a ribbon cassette and being movable relative thereto in printing and return directions; rotatable means for transmitting a first torque to the feed reel and a second torque to the take-up reel of an ink cassette such that tension is maintained in the ink ribbon during printing characterised in that the carriage comprises means for advancing the ink ribbon relative to the print head towards the take-up reel. The present invention will become more fully understood from the detailed description hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention and wherein: Fig. 1 to Fig. 7 refer to one of the embodiments of a printer of this invention, in which: Fig. 1 is a schematic plan view of essential parts; Fig. 2 is a schematic plan view showing the entire printing mechanism; Fig. 3 to Fig 5 are schematic plan views in the printing action, ribbon skip and carriage return, respectively; Fig. 6(a) to (c) are diagrams to show the relationship between ribbon cassette and carriage; and Fig. 7(a) to (d) are timing charts of printing motor, head motor, ribbon control motor, and paper feed motor, respectively. A preferred embodiment of this invention is described in detail below while referring to the drawings. Fig. 1 is a schematic plan view of a ribbon cassette 1 and a carriage 2 which are essential parts of this invention, and Fig. 2 is a schematic drawing showing the entire printing mechanism. In these drawings, a feed reel 4 and a take-up reel 5 of an ink ribbon 3 are disposed parallel, and gears 6, 7 are affixed to these reels 4, 5 as their control mechanism. A prime gear 9 mounted on a motor shaft of a ribbon control motor 8 is meshed with the take-up side gear 7. The rotation of this prime gear 9 is transmitted to the feed side gear 6 by way of a transmission gear 10. By rotation of the prime gear 9 by the ribbon control motor 8 in the direction of the arrow in Fig. 1, a rotating force is provided in the take-up rotating direction on the both reels 4, 5 indicated by arrows in the same drawing, through transmission gear 10 and feed and take-up side gears 6, 7. This rotating force is, during printing action, a small torque so as to allow slip with respect to the draw-out force provided by a print head which is described below. The force becomes a large torque when the carriage 2 returns. The reel torque is set so that the take-up side torque is larger than the feed side torque. The ribbon cassette is mounted in a stationary state being independent of the carriage, on a specified plate 100 of the printer, and is detachable together therewith. The ribbon cassette can be used on both face and back sides, being symmetrical in configuration and having a guide roller (11) for smoothly leading out the ink ribbon outside and a guide part 12 disposed at right and left symmetrical positions, and the ribbon pancake is exchangeable. A ribbon end sensor 13 is provided at a specified position. On the carriage 2, as shown in Fig. 2, a timing belt 17 is wound on a prime side pulley 15 mounted on a printing motor 14 and a guide pulley 16 is applied. The carriage 2 is moved reciprocally in the printing direction along a flat platen 18 by turning the timing belt 17. The carriage 2 is provided with, for example, a print head 19 having a specified number of heating elements disposed in a matrix form and a pair of control roller 20 and a guide roller 21. The print head 19 is disposed so as to be freely rotatable in the arrow direction by a head motor (not shown) located beneath the carriage from one end as the fulcrum, and a printing electrode part composed of said specified number of heating elements is provided at this free end. The pair of control rollers 20 are controlled in rotation so as to feed the ink ribbon 3 by the portion corresponding to the printing length in the direction to the take-up side reel 5 at every printing action of the print head 19 to the recording paper. Three feed rollers 23 rotated by a paper feed motor 22 are attached to the flat platen 18, and a paper end sensor 24 for detecting the end of recording paper sent by each feed roller 23 is provided near a roller shaft 25 of the feed roller 23, and moreover a cassette detection switch 26 to detect whether the ribbon cassette 1 is set in place or not, and a home position switch 27 to detect the return state of the carriage 2 to the initial print position are disposed at specification positions. The operation of the embodiment is explained below while referring to Fig. 3 to Fig. 7. Referring first to Fig. 6, the relation between the ribbon cassette 1 and carriage 2 is explained. When loading the ribbon cassette 1, as shown in Fig. 6(a), the control rollers 20 are spaced from each other at the carriage 2, and the print head 19 is also released from the platen 18. When the ribbon cassette 1 is loaded, the ink ribbon 3 is inserted between the control rollers 20. When the ribbon cassette 1 is set in the specified position on the printed main body, it is detected by the cassette detection switch 26, and the print head 19 turns in the direction of the arrow as shown in Fig. 6(b), and its printing electrode part contacts with the printing paper 28 by way of the ink ribbon 3, while the control roller 20 in the upper position moves to the lower position as indicated by the arrow so as to pin the ink ribbon 3 between the both control rollers 20. At the same time the ribbon cassette 1 is moved from the position indicated by a chain line to the position indicated by solid line, thereby resulting in printing set state. When the printing operation occurs, the carriage 2 on which the print head 19 and control rollers 20 are mounted is ready to move because the ribbon cassette 1 has moved, and releasing the carriage and allowing it to move in the printing direction, rightward in the drawing as shown in Fig. 6(c). The operation is further described below by referring to the timing chart in Fig. 7. When the power is turned on at time t1 in Fig. 7(b), the head motor rotates the print head 19 in the direction to contact with the platen 18 as shown in Fig. 7(b), and immediately the print head 19 is rotated in the direction to be separated from the platen 18. After the printing electrode part of the print head 19 is thus released from the ink ribbon 3, at time t2, the printing motor 14 is rotated reversely as shown in Fig. 7(a), and the carriage 2 is moved toward the initial printing position, and, at time t3, when the carriage 2 returns to the initial printing position, the printing motor 15 slightly rotates in normal direction to set the carriage 2 in the specified initial printing position. At the same time, as shown in Fig. 7(c), the ribbon control motor 8 is rotated to move the ink ribbon 3 by a specified length. Then, at time t4, the head motor rotates to move the print head to the platen 18 side, and the print head 19 is pressed on the recording paper 28 through the ink ribbon 3, so as to be ready to print. At time t5, printing action is started, and the printing motor 14 is put in normal rotation as shown in Fig. 7(a), and the carriage 2 moves in the printing direction as shown in Fig. 3. At this time, a rotating force in the arrow direction in the drawing is applied to the prime gear 9 by means of the ribbon control motor 8, and the feed side and take-up side gears 6, 7 are rotated in the direction to take up the ink ribbon 3 as indicated by the arrow in the same drawing. However, as shown in Fig. 7(c), since only a small voltage of about half of rating is applied to the ribbon control motor 8, the reel torques of the both reels 4, 5 are small, and are effective to apply tension to the ink ribbon 3 so that the ink ribbon 3 can run stably and remain taut. Besides, at every printing action by the print head 19, the control rollers 20 rotate in the arrow direction in Fig. 3 to transfer the ink ribbon 3 by the portion corresponding to the printing length in the direction of the take-up reel 5, and when not printing, that is, when the carriage 2 moves, the ink ribbon 3 is held and fixed to draw out the ink ribbon 3 from both reels 4, 5. At time t6, when a printing blank signal is fed, as shown in Fig. 7(b), the head motor rotates the print head 19 in the direction to be separated from the platen 18. The quantity of rotation at this time is, as obvious from Fig. 7(b), about half of the usual rotation, and the printing electrode part of the print head 19 is slightly spaced from the recording paper 28 as shown in Fig. 4. At the same time, the ribbon control motor 8 stops rotating. In consequence, as shown in Fig. 7(a), the carriage 2 is moved in the printing direction as indicated by the arrow in Fig. 4 by the rotation of the printing motor 14, and, at this time, since the control rollers 20 are holding and fixing the ink ribbon 3, the ink ribbon 3 is drawn out from both reels 4, 5. That is, a ribbon skip action is effected, and the ink ribbon 3 is saved. When this ribbon skip action ends at time t7, the head motor rotates as shown in Fig. 7(b), and the printing electrode part of the print head 19 is pressed again, as the head motor rotates, to the recording paper 28 by way of the ink ribbon 3, and a small voltage is applied to the ribbon control motor 8 at time t8, and tension is applied again to the both reels 4, 5, thereby continuing the printing action. At time t9, when the carriage 2 reaches the printing end position, the rotation of the printing motor 14 stops as shown in Fig. 7(a), and at time t10 the head motor rotates slightly as shown in Fig. 7(b) to space the print head 19 slightly from the recording paper 28 as shown in Fig. 5, so that the rotation of the ribbon control motor 8 once stops. Next, at time t11, as shown in Fig. 7(c), the ribbon control motor 8 is rotated by a specified rotating force, and immediately at time t12 the printing motor 14 is rotated reversely to return the carriage 2 as shown in Fig. 5. At this time, the both control rollers 20 are pinching and fixing the ink ribbon 3, and the unused and used ink ribbons are taken up on the both reels 4, 5. By the home position sensor 27, at time t13, the rotation of the printing motor 14 is stopped as shown in Fig. 7(a), and later at time t14 the rotation of the ribbon control motor 8 stops as shown in Fig. 7(c). At t15, the head motor rotates as shown in Fig. 7(b) to move the print head 19 to the specified position, thereby opening a specified space against the recording paper 28, and at time t16 the paper feed motor 22 rotates as shown in Fig. 7(d), and the recording paper 28 is fed. As described herein, according to the printer of this invention, aside from the advantages of the ribbon cassette fixed type, such as high speed, small size, and use of large-sized ribbon cassette, since the ink ribbon can be transferred by the portion of the printing length by the print head at the time of printing by the newly installed control rollers, there is no loss in ribbon take-up, and faster operation is realized, and moreover the ribbon skip action which was difficult in the conventional ribbon cassette type can be easily effected, and the ink ribbon can be saved, so that great economical effects can be obtained.

Claims: A printer comprising a ribbon cassette (1) being mounted stationarily on a body of the printer, said ribbon cassette containing a feed reel (4) winding one end of an ink ribbon (3) and a take-up reel (5) winding the other end of said ink ribbon, and a carriage (2) having a print head (19) for printing by using said ink ribbon, said carriage being mounted on said body independently of said ribbon cassette and being movable in a printing direction thereof, characterized in that, said printer further comprises rotating means (9) disposed on said body for applying a first torque to said feed reel in a direction to wind said one end of said ink ribbon and a second torque to said take-up reel in a direction to wind said other end of said ink ribbon during both of printing by said print head and returning of said carriage, and reel control means (8) disposed on said body for controlling said rotating means such that it decreases the respective magnitudes of said first torque and said second torque with respect to a ribbon discharge force of said print head during said printing by said print head, and restores the respective magnitudes of said first torque and said second torque during said returning of said carriage. The printer according to claim 1, wherein said carriage further has control rollers (20) for transferring said ink ribbon in a length corresponding to a printing portion of every printing by said print head during said printing by said print head and for selectively gripping said ink ribbon to hold and said ink ribbon stationary relative to said print head. The printer according to claim 2, wherein said control roller is adapted to grip said ink ribbon during said returning of said carriage. The printer according to claim 2 or 3, wherein said control roller is adapted to grip said ink ribbon when a blank is encountered during said printing by said print head, and said reel control means further controlling said rotating means to fail to apply said first torque and said second torque to said feed reel and said take-up reel, respectively, when a blank is encountered during said printing. A printer comprising means for mounting a ribbon cassette (1) having an ink ribbon (3) wound between a feed reel (4) and a take-up reel (5); a carriage (2) having a print head (19) for printing on a receptor surface through the ink ribbon mounted independently of the means for mounting a ribbon cassette and being movable relative thereto in printing and return directions; rotatable means (9) for transmitting a first torque to the feed reel and a second torque to the take-up reel of an ink cassette such that tension is maintained in the ink ribbon during printing characterised in that the carriage comprises means (20) for advancing the ink ribbon (3) relative to the print head (11) towards the take-up reel (5). A printer according to claim 5 wherein the printer further comprises control means (8) for providing first and second torques of first respective magnitudes during printing such that ribbon is withdrawn from the cassette on movement of the carriage in the printing direction and for providing first and second torques of second respective magnitudes such that ink ribbon is taken up by the feed and take-up reels during carriage return, the second respective magnitudes being greater than the first respective magnitudes. A printer according to claim 5 or claim 6, wherein said means for advancing comprises control rollers (20) selectively for advancing the ink ribbon relative to the printing head for each successive printing operation and gripping said ink ribbon to hold said ink ribbon stationary relative to said printing head. A printer according to claim 7, wherein said control rollers select to grip said ink ribbon during carriage return. The printer according to claim 7 or claim 8, wherein said control rollers select to grip said ink ribbon when a printing blank signal corresponding to a printing blank is encountered and wherein said reel control means is responsive to the printing blank signal to fail to provide said first and second torques to said feed reel and said take-up reel, respectively.

Inventors: YAMAGUCHI, KOUZOU
Applicants: SHARP KABUSHIKI KAISHA
Application year: 1988
Main classification: B41J33
IPC codes: B41J33, B41J35, B41J32