GB2179893A

GB2179893A - Multicolour ribbon transfer system

Info

Publication number: GB2179893A
Application number: GB08617173A
Authority: GB
Inventors: Akio Tajima
Original assignee: Seikosha KK
Current assignee: Seikosha KK
Priority date: 1985-07-15
Filing date: 1986-07-15
Publication date: 1987-03-18
Also published as: DE3623841C2; HK11593A; DE3623841A1; GB2179893B; GB8617173D0; KR870001039A; FR2584655B1; KR910006821B1; FR2584655A1

Abstract

A multicolour ribbon transfer system for transferring a ribbon cassette (3) from one position to another with respect to a printing head, the ribbon cassette (3) being provided with a ribbon (5) having a plurality of differently coloured parallel longitudinal bands each of which may be selectively brought to a printing position, the said system comprising spaced apart first and second cassette support members (10,11) having means for engaging opposite ends of the ribbon cassette (3), the first and second cassette support members being movably mounted on fixed structure (6,7,8); a driving motor (9); and transmission means (18,19,21,24 in Figs. 7 and 10) for transmitting drive from the driving motor (9) to the first and second cassette support members (10,11) so as to move the latter, and thus a ribbon cassette (3) carried thereby, over the fixed structure in order to bring a selected coloured band to the said printing position. <IMAGE>

Description

SPECIFICATION Multicolour ribbon transfer system The present invention relates to a multicolour ribbon transfer system for moving a cassette containing a ribbon having a plurality of differently coloured bands, the cassette being movable with respect to a printing head so as to bring a desired colour band into a printing position. Thus the ribbon may be impregnated with different inks in a plurality of colour bands which are parallel to each other and extend longitudinally of the ribbon.

British Patent Specification No. 2,029,i27B discloses an example of a multicolour ribbon transfer system for a serial printer. The system comprises a ribbon shift device provided on a carriage of a printing head. The ribbon shift device is selectively operable to bring any one of a plurality of slender colour bands which are arranged crosswise of a multicolour ribbon between a printing head and a platen.

A set cam means is provided which is engageable with a cam follower of the ribbon shift device for setting the ribbon shift device so as to bring a desired colour band opposite to the printing head in response to the position of the printing head with respect to the left hand margin. A reset cam means is provided which is engageable with the cam follower of the ribbon shift device so as to reset the ribbon shift device before selecting a new shift position. Both the cam means are fixed on a guide shaft of the carriage.

Further, it has also been suggested that a ribbon bearer supporting a pair of ribbon spools with an ink ribbon wound thereon should be transferred to a ribbon colour band opposite to the printing head by a solenoid, and a combination of link and lever is also known (for example, see Japanese Patent Publication No. 16057/1971 and Japanese Patent laid-Open Specification No.

82526/1978).

A dot printer has been used extensively of late both for office application and for personal requirements, and there is a demand that such a printer, even though generally used for printing in black, should optionally have a multicolour printing function. However, the multicolour ribbon transfer systems mentioned above are designed specifically for multicolour printing, their construction is complicated, they employ many parts and require a large space for installation so that they are not suitable for use in an ordinary dot printer.

In the construction of British Patent Specification No. 2,029,327B, the reset cam means corresponds to an initializing mechanism, i.e.

to a mechanism for effecting an initial setting up. However, since the system is such that a ribbon shift is controlled by subjecting the movement of the carriage to the left hand margin to program control, the movement control of the carriage becomes complicated, and further shift and transfer of the ribbon cannot be performed quickly.

As for the constructions suggested in Japanese Patent Publication No. 16057/1971 and in Japanese Patent Laid Open Specification No. 82526/1978, many parts are required which make the constructions complicated and their assembly troublesome. Further, in the case of multicolour ribbon transfer systems of such construction, a detection switch for detecting the colour band of the ribbon opposite to the printing head at an initial position is used in most cases. The detection switch is then normally disposed at a position at which it can be operated by engagement with a member when kept at an initial position of the multicolour ribbon transfer system. However, such a simple configuration of the detection switch may involve the following problems.

That is to say, even if a detection signal is utilized only at the time of such initialization, the detection switch may be operated unnecessarily and frequently as the ribbon shift is repeated so often. If a mechanical switch like microswitch is used as the detection switch, the frequency with which such a mechanical switch will be serviced is of course limited, and hence the detection switch may have a short life.

Further, in the case of multicolour ribbon transfer systems like those shown in British Patent Specification No.2,029,327B, since the exposed portion of the ribbon in the ribbon cassette is short and the ribbon reciprocates together with the printing head, the inclination of the ribbon will not matter in most cases.

Moreover, if the ribbon cassette is left in position, a laid span of the ink ribbon is required beyond the range in which the printing head is reciprocated. Four colour bands, namely black, blue, red and yellow, are normally formed which are parallel to each other and extend longitudinally of the ink ribbon, and the width of each colour band is rather small as compared with that of each colour band of a twocolour ink ribbon. In such a case, if the ribbon cassette is inclined, the neighbouring colour band, which is not the one which is desired, is capable of coming opposite to the printing head according to the position of the latter.

The inclination of the ribbon cassette may arise from a slight precision error of each component part and may also arise from a slight clearance at a junction.

The object of the present invention is therefore to provide a multicolour ink ribbon transfer system which can be manufactured compactly and at a moderate cost and is preferably such that it can be added to a printer to provide an optional multicolour printing function.

Another object of the invention is to provide a multicolour ribbon transfer system capable of moving a multicolour ribbon quickly.

According to the present invention, there is therefore provided a multicolour ribbon transfer system for transferring a ribbon cassette from one position to another with respect to a printing head, the ribbon cassette being provided with a ribbon having a plurality of differently coloured parallel longitudinal bands each of which may be selectively brought to a printing position, the said system comprising spaced apart first and second cassette support members having means fdr engaging opposite ends of the ribbon cassette, the first and second cassette support members being movably mounted on fixed structure; a driving motor; and transmission means for transmitting drive from the driving motor to the first and second cassette support members so as to move the latter, and thus a ribbon cassette carried thereby, over the fixed structure in order to being a selected coloured band to the said printing position.

Each of the cassette support members is preferably a plate.

The fixed structure preferably comprises spaced apart first and second casings on which the first and second cassette support members are respectively mounted.

The first and second casings may be interconnected by a coupling bar. Moreover, the first and second casings may be provided with means for mounting them detachably on a printer frame.

The transmission means preferably comprises a drive transfer shaft which is driven by the driving motor and which drives the first and second cassette support members by way of first and second drive transfer means.

The drive transfer shaft preferably extends through a recess in the coupling bar.

The first and second drive transfer means preferably comprise first and second drive transfer levers a shaft portion of each of which is mounted on the drive transfer shaft.

Opposite ends of the drive transfer shaft may extend respectively into the first and second casings, the first and second drive transfer levers being respectively disposed in the said first and second casings.

The drive transfer shaft is preferably driven by the driving motor by way of a driving gear.

The driving gear may, for example, be a sector gear.

The driving gear may be arranged to operate a detection switch when the driving gear is in an initial setting position.

The arrangement is preferably such that in operation the driving motor rotates the driving gear through a first angular range, when moving the ribbon cassette to bring each coloured band to its printing position, and through a second angular range, which is outside the first angular range, when the system is initially set up.

Preferably, both the driving gear and the first drive transfer lever are mounted on 'the drive transfer shaft for limited angular movement with respect thereto.

The said second angular range is preferably substantially equal to or slightly smaller than the total limited angular movement through which the driving gear and the first drive transfer lever may be disposed with respect to the drive transfer shaft.

The detection switch may be mounted on an adjusting lever which is mounted for adjustment about the centre of rotation of the driving gear so as to adjust the relative disposition of the detection switch with respect to the driving gear.

Preferably, at least one of the drive transfer levers has an adjustment device for adjusting the disposition of the said shaft portion thereof with respect to the remaining portion thereof. The said adjustment device may comprise a U-shaped spring which interconnects said shaft portion and remaining portion, an adjusting screw being provided for adjusting the spacing between the legs of the U-shaped spring. The invention also comprises an assembly comprising a multicolour ribbon transfer system as indicated above and a ribbon cassette which is held in position by and between the said first and second cassette support members, the cassette being provided with a ribbon having a plurality of differently coloured parallel longitudinal bands each of which may be selectively brought to a printing position.

Additionally, the invention comprises a printer provided with the said assembly, the printer having a printer head which is provided with printing means engageable with said ribbon.

The invention is illustrated, merely by way of example, in the accompanying drawings, in which: Figure 1 is a simplified plan view of a preferred embodiment of a multicolour ribbon transfer system according to the present invention, Figure 2 is a front view thereof, Figure 3 is a left side view thereof, partly in section showing how the system is mounted on a printer frame, Figure 4 is an enlarged sectional view taken on the line lV-lV of Fig. 1, Figure 5 is a rear view of a transfer plate forming part of the said embodiment, Figure 6 is an end elevation taken on the line VI-VI of Fig. 5, Figure 7 is a sectional view taken on the line VII-VII of Fig. 9, Figure 8 is a sectioninal view similar to Fig.

7 but with a driving gear and a transfer lever thereof omitted, Figure 9 is a transverse sectional view through a transfer shaft of the said embodiment, Figure 10 is a sectional view taken on line X-X of Fig. 9, Figure ii is an explanatory drawing showing the relationship between a multicolour ribbon and printing elements of a printing head, Figure 12 is a drawing showing the relationship between the said driving gear and the said transfer shaft at the time of the initial setting up of the system and also showing the position of the driving gear corresponding to each ribbon shift position, Figure 13 is a drawing showing the relationship between the said transfer lever and the said transfer shaft at the time of the initial setting up of the system, Figure 14 is a drawing showing the relationship between the said driving gear and the said transfer shaft at an initial position, and Figure 15 is a drawing showing the relationship between the said transfer lever and the said transfer shaft at the initial position.

In Fig. 1 there is shown a printing head 2 which is disposed ahead of a cylindrical platen 1. The printing head 2 is arranged to be reciprocated between arms 3a, 3b of a multicolour ribbon cassette 3, the printing head 2 being moved axially of the platen 1 by means of a carriage (not shown). A record medium 4, such as paper, and an ink ribbon 5, which extends between the arms 3a, 3b of the ribbon cassette 3, are inserted between the platen 1 and the printing head 2. The ink ribbon 5 is an endless member most of which follows a zig-zag path within the cassette 3. The ink ribbon 5 is made to travel counterclockwise, for example, by a ribbon driving device (not shown). As shown in Fig. 2 and in Fig. 3, the ink ribbon 5 has four colour bands 5a to 5d which extend parallel to each other longitudinally of the ink ribbon 5.The colour bands 5a to 5d are impregnated respectively with black, blue, red and yellow inks. A vertical row of printing elements 2b, such as wires or the like, is disposed on a front end surface 2a of the printing head 2 as shown in Fig. 11, and any one of the colour bands 5a to 5d of the ink ribbon 5 can be brought opposite thereto. Fig. 11 shows an initial state, wherein the black colour band 5a is opposite to the row of printing elements 2b. The colour band opposite to the row of printing elements 2b will be transferred into this position as described in detail below by a ribbon transfer system.

This ribbon transfer system in the embodiment shown in the drawings is unitized, and has, as illustrated in Fig. 1, first and second casings 6, 7 on opposite sides of the ribbon cassette 3 and close to the latter. A coupling bar 8, which couples the casings 6, 7 together, extends along a rear side of the ribbon cassette 3. A stepping motor 9, which is used as a driving motor, is provided on the outside of the casing 6. First and second transfer plates 10, 11 are arranged to be moved vertically by the operation of the motor 9, the plates 10, 11 being provided respectively on surfaces of the casings 6, 7 which face each other. Mounting claws 3c to 3e, which are engageable with opposite sides of the ribbon cassette 3, are insertable in various shoulders of the transfer plates 10, 11.Accordingly, the ribbon cassette 3, when placed horizontally between the transfer plates 10, 11, and in engagement with the mounting claws 3c to 3e, will in operation be moved vertically as a result of a vertical movement of the transfer plates 10, 11, whereby a desired colour band of the ribbon 5 can be brought opposite to the row of printing elements 2c shown in Fig. 11.

The detailed structure of the transfer plate 10 will now be described with reference to Figs. 4 to 6.

As shown in Figs. 5 and 6, locking claws 10a, 10b, which are capable of detachably holding the mounting claws 3c, 3e of the ribbon cassette 3, and a recess 10c, which is capable of receiving and positioning the mounting claw 3d, are formed on the shoulder of the transfer plate 10. Resilient legs 10d, 10d, guide pins 10e, 10e, and a hook 10f are integrally formed so as to project from a rear surface of the transfer plate 10. The legs 10d, 1 Od and the pins 10e, 10e are arranged in one row vertically. As shown in Fig. 4, the guide pins 10e, 10e are slidably mounted in a guide groove 6a formed on an opposite face of the casing 6, and the legs 10d, 10d are locked to an inner edge portion of the guide groove 6a, thereby holding the transfer plate 10 on the opposite face of the casing 6.The hook 10f of the transfer plate 10 is movable in a recessed groove 6b on an inside face of the casing 6, and an energizing spring 12 extends between a hook 6c, which is formed integrally on a lower end portion of the recessed groove 6b, and the hook 10f. Accordingly, the transfer plate 10 is urged downwardly at all times by the force of the spring 12.

A transfer mechanism for transforming a rotation of the motor 9 into a vertical motion of the transfer plate 10 will now be described with reference to Figs. 7 to 10.

As shown in Fig. 7 and in Fig. 8, a motor pinion 14, which is fixed on an output shaft 13 of the motor 9, is disposed in the casing 6. The motor pinion 14 meshes with a gear 16 which is rotatably mounted on a shaft 15 formed integrally with the casing 6. A pinion 17, which is formed integrally with the gear 16, meshes with teeth of a sector shaped driving gear 18. The driving gear 18 is adapted to be reciprocated about the centre line of a transfer shaft 19, the reciprocation of the driving gear 18 being effected by means of the pinion 14, the gear 16 and the pinion 17, and the direction of movement of the driving gear 18 depending upon the direction of rotation of the motor 9. The rotational motion of the driving gear 18 is transferred to the transfer shaft 19.The transfer shaft 19 is inserted, as shown in Fig. 9, into a recess 8a of the coupling bar 8 for coupling the casings 6, 7, opposite end portions of the transfer shaft 19 passing rotatably through the casings 6, 7.

The transfer shaft 19 is non-circular in cross section, and a base portion of the driving gear 18 is fitted non-rotatably in one end portion thereof. The driving gear 18 is urged counterclockwise, as seen in Fig. 7, by an energizing spring 20 which extends between a hook 1 8a which projects from the back of the casing 6 and the hook 6c which projects from a corner of the casing 6. A first transfer lever 21, which is mounted non-rotatably on the transfer shaft 19, is disposed in the casing 6 close to the front surface of the latter, and guide pin 10e of the transfer plate 10 engages in an elongated groove 21 a on a nose portion of the transfer lever 21. Accordingly, rotational motion of the driving gear 18 is transferred to the transfer lever 21 through the transfer shaft 19, thus in operation moving the transfer plate 10 vertically.

A push piece 1 8b is provided for operating a microswitch SW for detecting the position of the ribbon 5. The push piece 1 8b is formed to extend firmly from a rear portion of the driving gear 18. As is shown clearly in Fig. 8 and in Fig. 9, the switch SW is fixed on an adjusting lever 22 which is rotatably mounted on a projection 6d on the inside of the casing 6, i.e. concentrically with the centre of rotation of the driving gear 18, the transfer shaft 19 and the transfer lever 21. The adjusting lever 22 is held on the inside of the casing 6 without being prevented from rotating by virtue of having a circular groove 22a which is concentric with its centre of rotation and which is engaged with a resilient claw 6e formed to protrude firmly from the inside of the casing 6.

As shown in Figs. 3, 8 and 9, a resilient head 23a of an adjusting shaft 23 has a split groove which is disposed on the outside of the casing 6 at a position opposite to a nose portion of the adjusting lever 22. A cylinder 6f (Fig. 8) is secured to the inside of the casing 6 so as to surround the adjusting shaft 23. Knurling (not shown) is provided on the inner peripheral surface of the cylinder 6f this knurling being engageable with a resilient arm 23b of the adjusting shaft 23 so as to keep the adjusting shaft 23 at a desired position for adjustment.

An eccentric pin 23c (Fig. 7), which projects from the adjusting shaft 23, engages in an elongated groove 22b on a nose portion of the adjusting lever 22. Thus the adjusting lever 22 is rotatable around the projection 6d by the eccentric pin 23c as a result of turning the adjusting shaft 23, thereby adjusting the positional relationship between the push piece 18b of the driving gear 18 and the switch sW.

A transfer mechanism in the casing 7 will now be described with reference to Figs. 9 and 10.

A second transfer lever 24, which is disposed in the casing 7 has a cylinder 24b coupled to its rear end portion through a Ushaped spring 24a. The cylinder 24b is nonrotatably mounted on an end portion of the transfer shaft 19. An adjusting screw 25 passes through a projection 24c which extends from the cylinder 24b. The adjusting screw 25 is screwed into a projection 24d on an end portion of the spring 24a. The degree of opening of the U-shaped spring 24a can be adjusted by turning the adjusting screw 25, and thus a nose portion of the transfer lever 24 can be adjusted so as to alter its position.

The transfer plate 11 which is adjacent to the side of the casing 7 has a form which is symmetrical with respect to the transfer plate 10 and is held on the side of the casing 7 in a similar structure. That is, as shown in Fig.

10, the transfer plate 11 has locking claws 1 lea, 1 ib which are capable of detachably gripping the mounting claws 3c, 3e of the ribbon cassette 3.

The transfer plate 11 also has a recess 11 C which is capable of positioning the mounting claw 3d. Resilient legs 11 d, 1.1 d, guide pins 11 e, 11e and a hook ill are formed to project integrally from a rear portion of the transfer plate 11. The legs 1 it, 1 1d and the guide pins 11 e, 11 e are arranged in one vertical row. The guide pins 11 e, 11 e are slidably mounted in a guide groove 7a formed on the inside of the casing 6, and the legs 11 d, lid are locked to an inner edge portion of the guide groove 7a, thereby holding the transfer plate 11 to the inside of the casing 7.

The hook 11 f of the transfer plate 11 is movable in a recessed groove 7b on the inside of the casing 7. An energizing spring 26 extends between a hook 7c, which projects firmly from a lower end portion of the recessed groove 7b, and the hook 11 f. Accordingly, the transfer plate 11 is urged downwardly at all times by the force of the spring 26. A guide pin lie of the transfer plate 11 engages in an elongated groove 24e formed on a nose portion of the transfer lever 24.

Consequently, the transfer plate 11 is moved vertically as a result of the transfer lever 24 being moved by the transfer shaft 19.

The multicolour ribbon transfer system which is unitized as described above can be mounted detachably at a predetermined position on a printer frame 28 which supports the platen 1 and other parts, as shown in Fig. 3.

The multicolour ribbon transfer system can be so mounted by means of locking claws 27a, 27b which are formed integrally on the lower surface of each of the casing 6 and 7. A connector 29 is provided on a front end surface of the casing 6 for connecting both the motor 9 and the switch SW for detecting the position of the ribbon 5 to a control circuit (not shown).

Meanwhile, the transfer levers 21, 24 are fitted non-rotatably on the driving shaft 19 with a fine clearance. However, the clearance may not necessarily be exactly the same between the transfer levers 21, 24 on both end portions of the driving shaft 19 due to a manufacturing error of an individual part or for some other reason. If the driving shaft 19 is a long one, as in the embodiment shown in the drawings, the driving shaft 19 itself may give rise to torsion. Such torsion could cause a difference in the height position (vertical position) between the left and right transfer plates 10, 11. Consequently, the ribbon cassette 3 or the ink ribbon 5 could be brought to a position in which it is at an angle to the direction in which the printing head 2 moves.However, any such inclination of the ribbon cassette 3 or ink ribbon 5 to the said direction can be adjusted so that the ribbon cassette 3 or ink ribbon 5 is made parallel to the said direction by turning the adjusting screw 25 an appropriate amount so as to adjust the degree of opening of the U-shaped spring 24a.

The initial setting up of the muiticolour ribbon transfer system shown in the drawings will now be described.

When printing in black, red, blue and yellow the driving gear 18 will be respectively positioned at P, to P4 as shown in Fig. 12. The angles between the positions P1 and P2, P2 and P3, and P3 and P4 are f),. 03, and ft3 re- spectively. In the illustrated embodiment, the position P, is an initial position in which the black colour band 5a is opposite to the printing head 2. In the ribbon shift for colour transfer during the printing operation, the driving gear 18 is reciprocated to rotate through a first angle ft which represents the total of the angles Oi, fit2, fit3.

The initial setting up of the multicolour ribbon transfer system may, for example, be carried out when the printer is closed down. In this case, the driving gear 18 may at this stage be disposed at any one of the positions P1 to P4.

However, the driving gear 18 is rotated clockwise to a position P0 shown in Fig. 12.

The position P0 is a position displaced clockwise from the position P, by a second angle 00, and the detection switch SW is closed at the position P0 by the push piece 18b of the driving gear 18.

In order to keep the transfer lever 21 motionless and thus to keep the ribbon cassette 3 still even if there is any displacement of the driving gear 18 from the position P, to P0 or reversely thereof, the clearance at the fitting zones between the driving gear 18 and the transfer shaft 19 and between the transfer shaft 19 and the transfer lever 21 is utilized positively in the illustrated embodiment as follows.

As shown clearly in Figs. 12 to 15, a substantial clearance exists both between a shaft hole 18c of the driving gear 18 and the transfer shaft 19 and between a shaft hole 21b of the transfer lever 21 and the transfer shaft 19, and the clearance permits relative plays of said parts through relief angles ssl, ss2- Fig. 14 and Fig. 15 show relative positional relationships between the driving gear 18 and the transfer shaft 19 and between the transfer shaft 19 and the transfer lever 21 at an initial position (in which the ribbon cassette 3 is at its lowermost position) where the black colour band 5a is opposite to the printing head 2.

The driving gear 18 is urged counterclockwise by the spring 20 shown in Fig. 7. Therefore there will be play as illustrated between the driving gear 18 and the transfer shaft 19 at the initial position of Fig. 14. Then, the transfer lever 21 is urged clockwise as seen in Fig.

15 by virtue of the fact that the guide pin 10e of the transfer plate 10 is urged downwardly by the spring 12 as shown in Fig. 4. Therefore there will be play between the transfer lever 21 and the transfer shaft 19 as shown in Fig. 15.

Accordingly, when the driving gear 18 is rotated clockwise as seen in Fig. 14 by the driving motor 9 in order two achieve the initial setting up of the transfer system,~ the transfer shaft 19 does not move until the driving gear 18 has rotated through the angle fi1, after which rotation of the driving gear 18 causes similar rotation of the transfer shaft 19. However, during the time that the transfer shaft 19 is being rotated through the angle ss2, the transfer shaft 19 merely turns idly in the shaft hole 21b of the transfer lever 21 and thus the transfer lever 21 does not move. The detection switch SW is closed when the driving gear 18 has been rotated through the angle 1+ss2)=00 (as indicated by a full line in Fig.

12). However, the transfer lever 21 remains still at this time. An initializing signal of the detection switch SW is then Fed to the control circuit. After the detection switch SW is closed, the motor 9 is reversed until the state reverts to that shown in Fig. 14. Accordingly, the transfer lever 21 is kept still and the ribbon cassette 3 is left at the lowermost position even though the driving gear 18 is displaced from the position P, to P0 and from the position P, to P0 during the initial setting up.

The above example merely relates to one preferred embodiment of the invention, and various changes and modifications may be made. For example, the transfer lever 21 may be arranged to operate at the time of the initial setting up even though the relief angles fi1, ss2 are reduced to zero or thereabouts.

As will be appreciated, in the multicolour ribbon transfer system shown in the drawings, the pair of casings 6, 7 are disposed opposite to both the end portions af the multicolour ribbon cassette 3 and both the casings 6, 7 are coupled through the coupling bar 8. Transfer plates 10, 11 which can be moved vertically or so as to rock are provided on sides of the casings 6, 7 which face each other, and the transfer shaft 19 which interlocks both the casings 6, 7 passes through the recess 8a in the coupling bar 8. Opposite portions of the multicolour ribbon cassette 3 are carried by the transfer plates 10, 11 so that different ribbon colour bands can be brought to the printing position. Such a ribbon transfer system can therefore be constructed compactly, and the construction is simplified so as to make assembly easy.Since the ribbon transfer system can be installed in a limited space, the multicolour printer for which it is designed can be miniaturized. In addition, it is easy to meet the market demand for a multicolour printing function and the latter can be provided at a moderate cost.

Furthermore, the position of the multicolour ribbon 5 can be changed quickly, and the detection switch SW for detecting the position of the ribbon 5 is not operated at the time of a normal ribbon shift but is operated only at the time of the initial setting up of the system. Consequently, wear is reduced to the minimum. A multicolour ribbon transfer system of high reliability can thus be provided.

Further, since a level adjusting device constituted by the parts 24a, 25 is also provided for the ribbon cassette 3, any inclination of the ribbon 5 can be removed without the need to ensure particularly high standards of precision of the individual parts, and the adjusting device is very simple in construction so that it can be provided in a limited space and at moderate cost.

Claims

1. A multicolour ribbon transfer system for transferring a ribbon cassette from one position to another with respect to a printing head, the ribbon cassette being provided with a ribbon having a plurality of differently coloured parallel longitudinal bands each of which may be selectively brought to a printing position, the said system comprising spaced apart first and second cassette support members having means for engaging opposite ends of the ribbon cassette, the first and second cassette support members being movably mounted on fixed structure; a driving motor; and transmission means for transmitting drive from the driving motor to the first and second cassette support members so as to move the latter and thus a ribbon cassette carried thereby over the fixed structure in order to bring a selected coloured band to the said printing position.

2. A system as claimed in claim 1 in which each of the cassette support members is a plate.

3. A system as claimed in claim 1 or 2 in which the fixed structure comprises spaced apart first and second casings on which the first and second cassette support members are respectively mounted.

4. A system as claimed in claim 3 in which the first and second casings are interconnected by a coupling bar.

5. A system as claimed in claim 3 or 4 in chich the first and second casings are provided with means for mounting them detachably on a printer frame.

6. A system as claimed in any preceding claim in which the transmission means comprises a drive transfer shaft which is driven by the driving motor and which drives the first and second cassette support members by way of first and second drive transfer means.

7. A system as claimed in claim 4 and in claim 6 in which the drive transfer shaft extends through a recess in the coupling bar.

8. A system as claimed in claim 6 or 7 in which the first and second drive transfer means comprise first and second drive transfer levers a shaft portion of each of which is mounted on the drive transfer shaft.

9. A system as claimed in any of claims 3-5 and in claim 8 in which opposite ends of the drive transfer shaft extend respectively into the first and second casings, the first and second drive transfer levers being respectively disposed in the said first band second casings.

10. A system as claimed in any of claims 6-9 in which the drive transfer shaft -is driven by the driving motor by way of a driving gear.

11. A system as claimed in claim 10 in which the driving gear is a sector gear.

12. A systems as claimed in claim 10 or 11 in which the driving gear is arranged to operate a detection switch when the driving gear is in an initial setting position.

13. A system as claimed in any of claims 10-12 in which in operation the. driving motor rotates the driving gear through a first angular range, when moving the ribbon cassette to bring each coloured band to its printing position, and through a second angular range, which is outside the first angular range, when the system is initially set up.

14. A system as claimed in claim 8 or 9 and in any of claims 10-13 in which both the driving gear and the first drive transfer lever are mounted on the drive transfer shaft for limited angular movement with respect thereto.

15. A system as claimed in claim 13 and in claim 14 in which the said second angular range is substantially equal to or slightly smaller than the total limited angular movement through which the driving gear and the first drive transfer lever may be disposed with respect to the drive transfer shaft.

16. A system as claimed in claim 12 or in any claim appendant thereto in which the detection switch is mounted on an adjusting lever which is mounted for adjustment about the centre of rotation of the driving gear so as to adjust the relative disposition of the detection switch with respect to the driving gear.

17. A system as claimed in claim 8 or in any claim appendant thereto in which at least one of the drive transfer levers has an adjustment device for adjusting the disposition of the said shaft portion thereof with respect to the remaining portion thereof.

18. A system as claimed in claim 17 in which the said adjustment device comprises a U-shaped spring which interconnects said shaft portion and remaining portion, an adjusting screw being provided for adjusting the spacing between the legs of the U-shaped spring.

19. A muiticolour ribbin transfer system substantially as herein before described with reference to and as shown in the accompanying drawings.

20. An assembly comprising a multicolour ribbon transfer system as claimed in any preceding claim and a ribbon cassette which is held in position by and between the said first and second cassette support members, the cassette being provided with a ribbon having a plurality of differently coloured parallel longitudinal bands each of which may be selectively brought to a printing position.

21. A printer provided with an assembly as claimed in claim 20, the printer having a printer head which is provided with printing means engageable with said ribbon.

22. A multicolour ribbon transfer system including a first and second casings disposed opposite to both side end portions of a multicolour ribbin cassette provided with a multicolour ink ribbon having a plurality of colour bands divided parallel longitudinally thereof, and a coupling bar through which both the casings are coupled, which are characterized in that:: first and second transfer plates capable of bearing both side end portions of said multicolour ribbon cassette are installed movably on each opposite face of said first and second casings; a driving motor and a first transfer mechanism for shifting said first transfer plate in interlocking with rotations thereof so as to face any one of said colour bands of the ribbon cassette on a printing head are provided on said first casing; a transfer shaft driven through said first transfer mechanism passes said coupling bar and its end portion comes into said first and second casings; and a second transfer mechanism for shifting said second transfer plate in interlocking with said transfer shaft is provided on said second casing.

23. The multicolour ribbon transfer system as defined in claim 22, said first transfer mechanism further comprising: a driving gear rotated within the range of a first angle normally by said driving motor and then rotated as far as the position of a second angle exceeding the range of said first angle at the time of initialization; said transfer shaft fitted non-rotatably in said driving gear relatively to rotation; a transfer lever fitted non-rotatably in said transfer shaft relatively to displacement and shifting said transfer plates; a detection switch operated by said driving gear when said driving gear is rotated as far as the position of the second angle exceeding the range of said first angle at the time of initialization, and detecting a colour band of said multicolour ribbon opposite to the then printing head.

24. The multicolour ribbon transfer system as defined in claim 23, wherein a U-shaped spring is formed integrally on at least one of said transfer levers, and an adjusting screw for adjusting an opening is provided on the Ushaped spring.

25. Any novel integer or step, or combination of integers or steps, hereinbefore described and/or as shown in the accompanying drawings, irrespective of whether the present claim is within the scope of, or relates to the same or a different invention from that of, the preceding claims.