GB2220641A

GB2220641A - Ink ribbon cassette

Info

Publication number: GB2220641A
Application number: GB8915628A
Authority: GB
Inventors: Ikutaro Inoue; Yuki Ohishi; Susumu Asakawa
Original assignee: Alps Electric Co Ltd
Current assignee: Alps Alpine Co Ltd
Priority date: 1988-07-11
Filing date: 1989-07-07
Publication date: 1990-01-17
Anticipated expiration: 2009-07-07
Also published as: JPH0212857U; DE3922438A1; IT8920979A0; GB8915628D0; IT1230917B; GB2220641B

Abstract

A thermal transfer printer has a thrusting roller (38) urged towards a pinch roller (34) disposed within or inserted into the casing of a ribbon cassette (23) through an opening (39) formed at the side wall of said casing and the ink ribbon is clamped between the rollers, pinch roller being rotated by a roller driving system, so that the ink ribbon may be run at a constant speed and thus it is possible to peel off the ink ribbon from the sheet of paper, e.g. after a "correct operation". The thrusting roller (38) is carried by a lever which is interconnected to a further lever which is movable between cassette - releasing and - retaining positions. <IMAGE>

Description

1 K1 376 INK RIBBON CASSETTES This invention relates to an ink ribbon

cassette for use in a thermal transfer printer. Such a printer partially fuses ink on an ink ribbon by the action of heat-producing elements in a thermal head and effects printing by transferring fused ink to a sheet of paper. In particular, but not exclusively, the invention relates to an ink ribbon cassette, which is suitable for a thermal transfer printer which can effect a "correct" operation, by which printing on a sheet of paper is erased, and which can peel- off satisfactorily the ink ribbon from the sheet of paper when correction is required.

In the thermal transfer printer described - such a "correct" operation, a above, which can effect "correct" pin, which urges the ink ribbon on a platen behind the thermal head in the forwarding direction of a carriage during correction, is mounted on the carriage so that it can approach and be separated ben through the ink ribbon and the sheet from the plat of paper.

During printing, the "correct" pin is separa-r.ed from the platen. When the ink ribbon, urged on to the sheet of paper located before the pLaten by the thermal head being energized towards t ten, is moved to the side of the thermal head, lihe plat the ink ribbon is peeled off from the sheet of paper so as to move along the side edge of the thermal head, while ink is still in a fused state at the heated position of the ink ribbon. Printing can be effected by transferring the fused ink to the sheet of paper in this way.

On the other hand, during correction, the correct pin is urged on to the platen through a correcting ink ribbon and the sheet of paper. When 1 K1 376 2 - the heat producing elements in the thermal head are opposite a printed letter to be erased on the sheet of paper, the heat producing elements, which are opposite the printed letter to be erased on the sheet of paper, are heated so that the ink of the printed letter on the sheet of paper is fused. Since the affinity of the ink with the ink ribbon is greater than that with the sheet of paper when cooled to be solidified, while the latter is greater than the former when fused, even if the ink of the printed letter on the sheet of paper is fused by heat produced by the thermal head, it is not possible to transfer the ink on the sheet of paper to the ink ribbon, i. the ink ribbon is peeled off from the sheet of Daper, while the ink is still in a fused state. Therefore,. the correct operation can be act that, as described previously, effected by the:E the correct pin is urged on to the platen through the -inued of parer. This is cont nk ribbon and the sheet until the ink on the sheet oL paper, which is fused by heal produce,-' by the thermal- head, is cooled to be solidiffied, and the ink ribbon is peeled off from the sheet of paper after the solidification of the ink so -ansfer the ink on the sheet of' paper to the as to -1k- L ink ribbon.

However, previously, the peeling off of the ink ribbon from the sheet of paper was effected by the winding operation of the ink ribbon accompanied by the rotation of the rewinding bobbin of the ribbon cassette storing the ink ribbon. The rewinding force on the ink ribbon due to the rotation of this rewinding bobbin was not constant, because it deDended on the outer diameter of the ink ribbon wound around the rewinding bobbin. Therefore, there - the rewinding bobbin could slip is a possibility that K1 376 3 and the ink ribbon could not be peeled off from the sheet of paper when the ink is solidified. Thus there was also a problem that, when the ink ribbon cannot be peeled off from the sheet of paper, the ink ribbon is twined round, hence the printing operation as well as the I'correctIl operation is adversely affected.

A printer capable of colour printing is known but in such printer it is necessary to detect the colour of each portion of ink ribbons. Heretofore, the detection is done by rotation of a winding up bobbin to wind up an ink ribbon. The winding up force varies with variation of radius of the ink ribbon as it is wound and of the bobbin and as a result, since a constant run of the ink ribbon is not obtained, detection of colour by a marker is unstable. this invention is to provide The object of a device for peeling off an ink ribbon in a thermal transfer printer, which can solve the problematical -s in a prior art device as described above and point is capable of effecting stably the peeling off of the W ink ribbon from the sheet of paper and stably the detection of an ink of a colour ink ribbon by a marker.

According to the present invention there is provided an ink ribbon cassette for a thermal transfer printer wherein the ink ribbon cassette for a thermal transfer printer is mounted on a carriage movable forward and backward along a platen together with a thermal head and, storing an ink ribbon whose intermediate portion is taken out from a casing so as to be located between the thermal head and a sheet of paper on the platen, a pinch roller contacting with a portion of the ink ribbon introduced into the casing 1 K1 376 after it is taken out therefrom, and said pinch roller is provided with a joint for transmitting rotation of a roller driving system disposed on said carriage, and an opening causing a thrusting roller thrustable on said pinch roller to face the inside of said casing is formed at a side wall of the casing.

Further, an ink ribbon cassette for a thermal transfer printer is characterised. in that in the ink ribbon cassette for a thermal transfer printer mounted on a carriage movable forward and backward along a platen together with a thermal head, and storing an ink ribbon whose intermediate portion is taken out from a casing so as to be located between the thermall head and a sheet of paper on the -en, an opening causing a pinch roll plat -er contacting with a portion of the ink ribbon introduced into the casing after it is taken out therefrom and rotating said casin- is formed Uherewith to face the inside of (D at a bottom wall of the casing, and an opening LD -able on said pinch causing a thrusting roller thrust said casing is formed at roller to 'Lace the inside of a said wall of the casinz-.

-te fol By means o-9 the izn..:: ribbon casset - a thermal transfer printer according to claim 1 or 2 the thrusting roller is th-rusted on the ink roller disposed within or inserted into the casing of said ribbon cassette through the opening formed a-IV the side wall off said casing and the ink ribbon is clamped between both of the rollrs to rotate the pinch roller by the roller driving system, so that run of the ink ribbon being stretched with constant speed is done and thus it is possible to peel off the ink ribbon from the sheet of paper. Therefore, in the case where it is applied to a thermal transfer K1 376 printer capable of doing a correct operation, it is possible to peel off the ink ribbon from the sheet of paper even at the correcting time when it is difficult to peel off the ink ribbon from the sheet of paper. Further, detection of the ink of each of colours of the colour ink ribbons for colour print is done stably due to run of the ink ribbon with constant speed.

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is a plan view illustrating a thermal transfer printer, to which an ink ribbon peeling off device according to this,invention is applied; Figure 2 is a longitudinal cross-sectional C) view of the device indicated in Figure 1; FI.gure 3 is a plan view illustrating the principal part of the thermal transfer printer indicated in Figure 1; FW -r' the device ioUre 4 is a side view o. indicated in Figure 3 viewed from the right; Figure 5 is a scheme illustrating the principal part of the device indicated in Figure 4 in an enlarged scale; and Figure 6 is a plan view of the principal part of the ribbon cassette of another embodiment of this invention.

igures 3 to 5 show a thermal transfer printer, to which the ink ribbon peeling off device according to this invention is applied, and it is supposed there that this thermal transfer printer is of typewriter specification, for example.

By the left and right frames 1A and 1B of this thermal transfer printer a rotating shaft 2 CP K1 376 driven by a motor not shown in the Figure is supported rotatably. A plurality of gum rollers 3, 3,... are displaced by a certain interval in the axial direction on this rotating shaft 2. A fixed guiding member 4 for inserting a sheet of paper not indicated in the Figure is disposed behind these gum rollers 3, inclined under these gum rollers. Further, under these gum rollers 3, a movable guide member 5 having an are-shaped cross-section is disposed movably in a direction where it can approach and separate from the gum rollers 3 by the fact that a guide pin 5A, protruding from the movable guide member 5, slides in a guide groove 4A formed in a fixed guide plate 4. On the rear side surface of this movable guide member 5 there is disposed a holder 6 protruding thereffrom. On this holder 6 a lever 8 energized by a spring is contacted and Uhrusted. Furthermore, on this movable guide member 5 stated above, a pair of fowarding rollers 9,9 having a small diameter are supported rotatably with a certain interval in the peripheral direction of the that they pro' gum rollers 3 stated above so t Urude somewhat towards the gum rollers. ConsequentLY the movable guide member 5 is held to be opposite to the outer periphery of the gum rollers 3 with an extremely small interval by the elastic force of the spring 7 stated above in a state, where each of the forwarding rollers 9 is thrusted on the gum rollers 3.

A platen base plate 10 extending in the horizontal direction and having an approximately L shaped cross-section located before the rotating shaft 2 stated above is supported by the two frames 1A and 1B. The lower end portion of the vertical part 10A of the platen base plate 10 is divided in a 1 K1 376 fork shape and each branch thereof extends, inclined so as to be closer to the rotating shaft 2 with decreasing distance from the lower extremity, and is located freely between a pair of gum rolles 3, 3 adjacent to each other. Further a transversal recessed portion 11 extending in the horizontal direction is formed on the surface of the central portion in the up and down direction in the vertical part 10A of the platen base plate 10, which surface is not opposite to the forwarding roller 9, and a protruding wall 12 extending in the horizontal direction is disposed at the central portion in the up and down direction of the bottom surface of this recessed portion 11. A plane plate shaped platen 13 made of gum, which is freely inserted in the recessed portion 11 stated above and whose rear surface is touched on the protruding wall 12 stated above, is supported rotatably in a vertical plate by the two frames 1A and 1B.

A carriage shaft 14 extending parallel to the axial direction of the forwarding roller 9 is supported by the frames 1A and 13 before the forwarding roller 9 described above and a carriage 15 movable forward and backward in the axial direction of the carriage shaft 14, is supported by this carriage shaft 14. Further, a driven gear 17 and a driving gear 18 are supported rotatably with a certain interval in the movement direction of the carriage 15 on a printer base plate 16 at the neighbourhood of the frames 1A and 1B stated above and a timing belt 19, whose two extremities are attached to the carriage 15, is wound around these driven gear 17 and driving gear 18. In addition, a driving motor 20 driving the driving gear 18 is disposed on the printer base plate 10 at the - K1 376 neighbourhood of the driving gear 18. The driving force of this driving motor 20 is transferred to the driving gear 18 after having been reduced so that the carriage 15 can move forward and backward along the carriage shaft 14 stated above by the drive of this driving gear 18 through the movement of the timing belt 19.

A thermal head mounting table 21, which is opposite the platen 13, is supported movably in the direction along which it can approach and be separated from the platen 13, on the carriage 15 and a thermal head 22, which can approach and be separated from the platen 13 stated above, is mounted on this thermal head mounting table 21. This thermal head 22 is provided with a plurality of heat producing elements arranged at predetermined positions, which are heated selectively according to printing information inputted through a keyboard not shown in the Figlare. Further a cassette stage portion 24, on which a ribbon cassette 23 is located, 4 - is fformed on the carriage:) so that the intermediate p bion of the ink ribbon drawn out from the ribbon casset-te 23 located on this cassette stage portion 24 is positioned between the platen 13 and th-e thermal head 22. In addition, in order that the thermal head 22 can approach or be separated from the platen 13, a motor 25 for moving the thermal head mounting table 21 and at the same time for winding the ink ribbon around a rewinding bobbin in the ribbon cassette 23 is mounted on the carriage 15. In addition, on the carriage 15 at the neighbourhood of the thermal head mounting table 21 there is disposed movably a llcorrectll pin 26 capable of contacting and separating from the platen 13 behind the thermal head 22 in the movement direction (towards the right in Figure 3) of the carriage 15 during printing and correction.

K1 376 A roller shaft 27 extending in the up and down direction is supported rotatablY on the carriage 15 on the rear end side in the movement direction of the carriage 15 during printing and correction, as indicated in detail in Figures 1 and 2, so that this roller shaft 27 is inserted into openings 29 formed coaxially at corner portions of the upper wall 28A and the lower wall 28B of the easing 28 of the ribbon cassette 23. The roller shaft 27 stated above extends below the carriage 15 stated above and on the part of this roller shaft 27 below this carriage 15 there is mounted a toothed wheel 30, which is connected with the motor 25 through a series of special toothed wheels not shown in the Figure and rotably driven by the drive of the motor 25. Thus, said roller sha-.Lu 27 serves as a joint for transmitting rotation of a roller driving system. Further, within the casing 28 of the ribbon cassette 2 23 there is disposed a sleeve 31 supported rotatably on the upper wall 28A and the lower wall 28B described above. A plurality of key grooves 32, 32,... are for-med with a certain interval in the -oer.-'p'--,eral direction on the inner peripheral surface of this sleeve 31. On the other hand, on the outer peripheral surface of the roller shaft 27 stated above there are disposed a plurality of keys 33, 33r... protruding there-Prom, each of which can be inserted into each of the key grooves 32 so that the sleeve 21 is rotated together with the roller shaft 27 in one body by engaging the sleeve 31 with the roller shaft 27.

On the outer periphery of the sleeve 31, there is mounted a pinch roller 34, whose surface portion is made of a material having a relatively K1 3705 10 great friction coefficient, so that the ink ribbon not shown in the Figure is rewound on the rewinding bobbin 35 along the outer periphery of this pinch roller 34 from the thermal head 22 stated above. Further a first rotating shaft 36 extending in the up and down direction is supported rotatably on the carriage 15 at the neighbourhood of the roller shaft 27 so as not to hinder the loading of the ribbon cassette 23 on the cassette stage portion 24. On the upper portion of this first rotating shaft 36 there is mounted a bracket 37 so as to be able to rotate together with the first rotating shaft 36 in one body. A thrusting roller 38 facing on the pinch roller 34 is supported rotatably by this bracket 37 and this thrusting roller 38 is so constructed that a part thereof 'Laces the interior of the easing 28 through an opening 39 formed in a side wall 28C of the easing 28 state7d above so as to be able to be jointed with the pinch roller 34 stated above.

-e 40, A cam plat which can rotate together with the first rotating shaft 36 in one body, is mounted on the lower end portion of this first rotating shaft. 306 and an are-shaped reverse cam groove 41 is formed on this cam plate 40. Further, between this cam plate 40 and the carriage 15) stated above there is mounted a helical spring 42 energizing this cam plate 40 in the clockwise direction in Figure 1, i.e. in the direction, along which the thrusting roller 38 is urged on the pinch roller 34. In addition, a second rotating shaft 43, extending similarly, is supported rotatably on the carriage 15 at a position adjacent to the first rotating shaft 36 and a lever 44 is secured to the lower end portion of this second rotating shaft 43 so as to be able to rotate together with this second rotating shaft 43 in K1 376 - 11 one body. A pin 45, which can slide in the reverse cam groove 41 formed in the cam Plate 40 stated above, is disposed on the extremity portion of this lever 44, protruding therefrom. In this case, concerning the position of the arc-shaped reverse cam groove 41 and that of the second rotating shaft 43 stated above, which is the rotation centre of the lever 44, the distance between the end portion of the reverse cam groove 41 in the counterclockwise direction in Figure 1 and the second rotating shaft 43 is somewhat longer than the distance between the end portion of the reverse cam groove 41 in the clockwise direction and the second rotating shaft 43. Consequently, when the lever 44 is rotated in the clockwise direction, the cam plate 40 is rotated together with the bracket 37 in the counterclockwise direction from the state indicated in Figure 1 against the elastic force o. the helical spring 42 by -ween the position the difference in the distance bet of the reverse cam groove 41 in the peripheral direction and the second rotating shaft 43 and the thrusting roller 38 is separated f.rm the pinch roller 31 1+.

A removal prevention lever 46 is secured to the upper end portion of the second rotating shaft 43 stated above so as to be able to rotate together with this second rotating shaft 43 in one body and a stopper 47 facing on the upper side of the ribbon cassette 23 loaded on the cassette stage portion 24 oP the carriage 15 to prevent for the ribbon cassette 23 to be taken-off is disposed on the upper end portion of this removel prevention lever 46, protruding therefrom so as to extend in the horizontal direction. This removal prevention lever 46 is so constructed that when the lever 44 stated K1 376 above is rotated in the clockwise direction from the state indicated in Figure 1, the stopper 47 is rotated so as to be evacuated from the position above the ribbon cassette 23 to the side.

Referring to Figures 3 to 5, supporting levers 48A and 48B, each of which is chevron-shaped, are mounted coaxially pivotably on the outer sides of the two frames 1A and 1B, obliquely upward from the rotating shaft 2 on the carriage 15 side from the centre of the rotating shaft 2 stated above. Between the extremities of the two supporting levers 48A and 48B there is hung a round guide bar 49 extending parallel to the rotating shaft 2. As indicated in detail in Figure 3, this guide bar 49 is constructed so as to pivot in the forward and backward directLon of the printer between the state where the centre of the shaft is positioned approximately right above the thermal head mounting table 21 in order to touch on a part of the sheet of paper protruding upward from the platen 13 and to guide the sheet of paper so that the printe,' surface thereof is turned upward, and the state where it is positioned on the ribbon cassette 23 so as not to touch on the part of the sheet of paper protruding upward from the platen 13. Further, the guide bar 49 is so constructed that it can be held stably in the two states described above by the frames 1A and 1B as well as by well-known holding means such as a clip stop not shown in the Figure, disposed between the supporting levers 48A and 48B. Further, an operating protrusion 50 for rotating the guide bar 49 is disposed on one of the supporting levers 48B, protruding there- from.

A cylindrical cam follower 51 extending parallel to the rotating shaft 2 and protruding outward from the frame 1B stated above is secured to 1 1 K1 376 the lever 8 stated above. On the other hand, at the end portion of the rotating shaft 2 stated above there is disposed pivotably a cam lever 52 for rotating a holder 6 so as to move between a position, where movable guide members 5 are contacted with a gum roller 3 by the fact that it rotates until the cam surface 53 reaches the lowest position, and a position where they are separated from the gum roller 3. Further, an operating protrusion 54 for rotating thin cam lever 30 is disposed at the extremity portion of the cam lever 52 stated above, protruding therefrom.

The operation of the apparatus is described below.

-e the ribbon At first, in order to locat cassette 23 on the cassette stage portion 24 of the carriage 15, the pin 45 of the lever 44 is positioned at the end portion in the clockwise direction of the reverse cam groove 41 of the cam groove 40 in Figure 1 and the stopper 47 of the removal prevention lever - a refuge position as indicated by 46 is posi-tuioned at an imaginary line in Figure 1I and at the same time the bracket 37 of the thrusting roller 38 is positioned also at a refuge position as indicated by an imaginary line in Figure 1. In such a state, when the ribbon cassette 23 is located in the cassette stage portion 24, the ink ribbon exposed before the ribbon cassette 23 is positioned before the thermal head 22. At the same time, the roller shaft 27 disposed on the thermal head mounting table 23, protruding therefrom, is inserted in the sleeve 31 of the pinch roller 34 through the opening 29 formed in a K1 376 the lower wall 28B of the ribbon cassette 23 and a state, where the sleeve 31 can be rotated together with the roller shaft 27 in one body, is realised by the fact that each of the keys 33 of the roller shaft 27 is imaged with each of the key grooves 32. At this time, the removal prevention lever 46 is rotated counterclockwise in Figure 1 and the stopper 47 thereof is faced on the upper side of the ribbon cassette 23 so that the ribbon cassette 23 is not rickety because of vibrations. Further, the lever 44, which rotates together with this removal prevention lever 46 as one body, is also rotated counterclockwise by the counterclockwise rotation of the removal prevention lever 46 and the pin 45 thereof reaches the end portion in the countercloc'_.,wise direction o"' the reverse cam groove 41 formed in the cam plate 40. At this time, the cam te 40 is rotated clockwise and the thrusting p I at roller 38 supported by the bracket 37 rotating together with this cam plate 40 in one body is faced -1 1 the cas4 -oar-I.-Ly on the interior o- -ng 28 of the ribbon casselutue 23 through the side wall 28C. of the casing 28 by the action of the helical spring 42 so as to - the pinch roller 34 and to hold the.ink ribbon thrust th.

therew;LV On the other hand, in order to position the paper, the two supporting levers 48A and 48B sheet o-IL -ed to positions indicated by imag4 are rotat -nary lines in Figure 4 by laying a finger on the o erating C) p protrusion 50 so that the guide bar 49 is positioned above the ribbon cassette 23, where it cannot be contacted with the sheet of paper, and at the same time each of the forwarding rollers 9 is kept in the state, where it is separated from the gum roller 3, by the fact that the cam lever 52 is rotated by 1 K1 376 laying . a finger on the operating protrusion 54 and the lever 8 is rotated counterclockwise from the state indicated in Figure 4 against the elastic force o" the spring 7.

-LI In this state the sheet of paper not shown in the Figure is inserted between the gum roller 3 and the movable guide member 5 from the fixed guide plate 4 and positioned so that the extremity side of the sheet of paper protrudes above the platen 13. At this positioning of this sheet of paper, since the guide bar 27 is located at the refuge position, where it cannot be contacted with f paper, it is possible to effect easily the sheet o.1 -ioning of the sheet of paper.

the posit Once the positioning of the sheet of paper has been terminated in the manner described above, 14 the two suppor.Lng levers 48A and 48B are rotated to the Dos Uions indicated by full lines in Figure 4 by laying a finger on the operating protrusion 50 so t - a position, which is that the Eaide bar 49 is kept at somewhat devia-.ed from the position right above the p'aten 13 towards the carriage 15. At the same time, the cam'Lever 52 is rotated in the direction opposite 'ous one by laying a finger on the to the prev. CD operating protrusion 54 and the lever 8 is rotated so that the forwarding ro"Ller 9 is thrusted on the gum roller 3 by the elastic force of the Spring 7. Then, since the paLt of the sheet of paper before the printing is put between the gum roller 3 and the forwarding roller 9, it is possible to forward the sheet of paper by driving the motor not shown in the Figure to rotate the gum roller 3.

In such a state, when printing information is inputted through a keyboard not shown in the Figure, current in the form of a pulse is made to flow through the motor 25 mounted on the carriage 15 a K1 376 for every input of the printing information and the thermal head 22 is thrusted on the platen through the ink ribbon and the sheet of paper by moving the thermal head mounting table 21. At this time, since the platen 13 is freely rotatable in a vertical plane, it is positioned closely to the thermal head. Then, in the state where the thermal head 22 is moved towards the platen 13 through the ink ribbon and the sheet of paper, the heat producing elements in the thermal head 22 are heated selectively, depending on the inputted printing information and the ink, at the position where the ink ribbon is in contact with the heat producing elements which are heated, is fused 2' paper. After that, and transferred to the sheet o-IC to f' a plilse is made t current in the form o -low through the driving motor 20 and the carriage 15 is moved through the movement of the timing belt 19, corresponding to the letter to letter space set along the carriage shaft 14 so as to be positioned, corresponding to the succeeding input. The motor 25 -e-I in one direction in is driven so as to be rotat synchronism with this movement of the carriage l-.

CD the mo-' -Perred to This rotational drive o-. Lor is trans the roller shaft 27 through a series of special toothed wheels not shown in the Figure and the pinch roller 34, against which the thrusting roller is urged, is rotated with a constant speed so that the ink ribbon, which has justl passed through the thermal head 22, is stretched and peeled Off from the sheet of paper. This ink ribbon, which has been peeled off from the sheet of paper, is wound by the rewinding bobbin 35 through the pinch roller 34 and the thrusting roller 38. Since the thermal Uransfer printer is of typewriter specification, the thermal head 22 is separated frDm the platen 13 principally a 1 K1 376 - 17 for every input, but in the case where the input is effected with a high speed, the thermal head 22 is held to be in the state, where it is thrusted on the platen 13.

Printing is effected, as described above, corresponding to the printing information inputted through the keyboard, and when printing for one line is terminated, the carriage 15 is returned along the carriage shaft 14 by the drive in the reverse direction of the driving motor 20 in the state, where the thermal head 22 is separated from the platen 13.

At this time the rotating shaft 2 is driven so as to be rotated by the drive of the motor not shown in the Figure so that the sheet of paper is,forwarded for one line. -Printing of the succeeding line is effected by inputting newly corresponding printing - of the information through the keyboard. The part -en becomes sheet of paper protruding above the plat longer, as the printing advances in this way. However, when thisprotruding length of the sheet of - of paper reaches a certain value, since the sheet - the printing sur' paper is guided so that Lace is - of paper is turned upward by the fact that the sheet contacted with the guide bar 49, the sheet of paper is unlikely to become instable for example by being fluttered by wind.

Further, in order to dismount the ribbon ' the cassette 23 from the cassette stage portion 24 o-IL carriage 15, the removal prevention lever 46 is rotated clockwise to the position indicated by the imaginary line in Figure 1 so that the stopper 47 thereof is located at the refuge position and at the same time the lever 44 is rotated in the same -" the direction in synchronism with this rotation o. removal prevention lever 46. In this way, the 0 K1 376 -ion of the reverse cam groove 41 formed in the posit cam plate 40, in which the pin 40 is inserted, is varied and the cam plate 40 and the bracket 37 are rotated counterclockwise in Figure 1 so that the thrusting roller 38 is evacuated to the exterior of the casing 28 of the ribbon cassette 23. It is sufficient to lift the ribbon cassette 23 upward thereafter.

In order to effect the correct operation to erase the ink on the predetermined portion of the printing on the sheet of paper, the ribbon cassette storing the ink ribbon for the correction is loaded on the cassette stage portion 24 of the carriage 15 in the same way as described previously and the removal prevention lever 46 is rotated so that fluttering of the ribbon cassette 23 is prevented by the stopper 47 thereof. At the same time, the thrusting roller 38 is urged towards the pinch roller - of paper and the carriage 15 are 34 and the sheet moved so that printing to be erased is opposite the bhermal he-id 22. Thereafter the motor 25 mounted on the carriage 15 is driven so that the thermal head 22 and the correct pin 26 approach the platen 13 through the ink ribbon and the sheet of paper. The ink of -ing the the printing to be erased is fused by heat corresponding heat producing elements in the thermal head 22. Thereafter, when the carriage 15 is moved and the ink in the fused state is deviated to the side of the thermal head 22, since at this correct 30 operation the correct pin 26 is moved towards the platen 13 through the ink ribbon and the sheet of paper, the ink in the fused state is deviated to the side of the thermal head while being put between the sheet of paper and the ink ribbon and cooled to be solidified there.Although the affinity of the ink 1 K1 376 with the sheet of paper is stronger than that with the ink ribbon in the fused state, when it is cooled to be solidified, the affinity with the ink ribbon becomes stronger than that with the sheet of paper. Therefore, the solidified ink is transferred to the ink ribbon, which is stretched at a position beyond the correct pin 26 by the pinch roller 34 driven to be rotated in synchronism with the movement of the carriage 15 so as to be peeled off from the sheet of paper and consequently the printing on the sheet of paper is erased.

At this correction, since the peeling off off the ink ribbon from the sheet of paper is effected in the state where the ink is solidified a stronger force is required for the peeling off of the ink ribbon during correction than that required during printing, for which the ink ribbon is peeled off from the sheet of paper when the ink is in the fused state. However, since that peeling off of the ink ribbon is effected by means of the pinch roller 34 rotated with a constant speed and the thrusting roller 38, it is possible to peel off stably the ink ribbon with a constant tensile force with respect to a prior dev4ce, in which the peeling off of the ink -ion of the rewinding ribbon is effected by the rotat bobbin 35 in the ribbon cassette 23. Furthermore, according to this embodiment, since the outer peripheral surface portion is made of a material having a relatively great friction coefficient, it is possible to peel off more stably the ink ribbon from the sheet of paper without slipping the ink ribbon.

This invention is not restricted to the embodiment described above, but various modifications are possible.

For example, in the embodiment described K1 376 - 20 above, the pinch oller 34 may be mounted directly on 't 27 and the pinch roller 34 may be so the roller sha4L constructed that it faces the interior of the easing 28 of the ribbon cassette 23 through the opening 29 formed in the lower wall 28B of the casing 28 of the ribbon cassette 23, when the ribbon cassette 23 is located on the cassette stage portion 24 of the carriage 15. Even in such a construction the thrusting roller 38 may be constructed similarly to that in the embodiment described above. In this case, it is necessary to dispose a plurality of guide pins 55, 55,... guiding the ink ribbon R, as indicated in Figure 6, in the casino 28 of the ribbon C) -ed cassette 23, at the neighbourhood of the insert part of the pinch roller 34 so that the ink ribbon can be contacted with the outer periphery of the pinch roller 34, when the pinch roller 34 is inserted in the casing 28 of the ribbon cassette 23.

Furthermore, this invention can be applied also to genera-, thermal transfer printers, in which no correct operation is effected.

As explained above, according to this invention, since the ink ribbon is peeled off from 2' paper by putting the ink ribb.on between the sheet of the pinch roller positively driven and the thrusting roller so as to stretch the ink ribbon, it is possible to effect stably the peeling off of the sheet of paper and thus a practical effect can be obtained that situations such as entanglement of the ink ribbon can be obviated beforeheand and further practical effect that detection of the colour ink ribbons for colour print is done stably due to run of the ink ribbon with constant speed, is obtained.

1 K1 376

Claims

1. An ink ribbon cassette for a thermal transfer printer, mountable on a carriage movable forward and backward along a platen together with a thermal head, the cassette including an ink ribbon whose intermediate portion is taken out from a casing so as to be located between the thermal head and a sheet of paper on the platen, a pinch roller contacting with a portion of the ink ribbon introduced into the casing after it is taken out therefrom, the pinch roller having a joint for transmitting rotation of a roller driving system disposed on said carriage, and an opening causing a roller, urgeable against the pinch roller, to face the inside of the casing formed at a side wall of the casing.

2. An ink ribbon cassette for a thermal tr .ansfer printer mountable on a carriage movable forward and backward along a platen together with a thermal head, the cassette including an ink ribbon -er.mediate portion is taken out from a casing whose int so as to be located between the thermal head and a - of paper on the platen, wherein an opening, sheet causing a pinch roller to contact a portion of the ink ribbon introduced into the casing after it is taken out therefrom and rotating therewith to face the inside of said casing is formed at a bottom wall off the casing and an opening causing a roller, urgeable against the pinch roller, to face the inside ot" said casing, is formed at a side wall of the casing.

3. A thermal transfer printer, including an ink ribbon cassette as claimed in Claim 1 or Claim 2.

4. A thermal transfer printer substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawings.

Published 1989 at The Patent Offl- ce. State House. 66."71 RWh Holborn, London WClR 4TP Further copies maybe obtained from The Patent Office. Sales Branch, St Mary Cray, Orpington, Kent BR5 3RD. Printed by Multiplex techniques ltd, St Mary Cray, Kent, Con. 1/87