EP0059923B1 - Mechanism for a mechanical, in particular an electro-mechanical printer for positioning an ink ribbon on different tracks - Google Patents

Abstract

1. A device for a mechanical, preferably electromechanical printing mechanism for setting an ink ribbon in different tracks transversely to its travelling direction on a carrier which can be conveyed in the line direction in the printing mechanism, an ink-ribbon reserve being arranged on said carrier and said ink ribbon being moved past a printing device and through a printing region to an ink-ribbon take-up unit possibly also containing the ink-ribbon reserve, characterized in that said ink-ribbon reserve and said ink-ribbon take-up unit are arranged on a holding device (9) movable on said carrier (2) transversely to the travelling direction of the ink ribbon, said holding device being coupled with a drive unit (13) provided on said carrier (2), the stroke of said drive unit being divided into a plurality of steps corresponding to the number of ink-ribbon tracks (4a, 4b, 5a, 5b) provided.

Description

The invention relates to a device for a mechanical, preferably electromechanical printing unit for setting ink ribbon on different tracks transversely to the running direction on a carrier which can be transported in the line direction in the writing unit, on which a ribbon supply is arranged and the ink ribbon past a printing device through a printing area to one optionally also the ribbon holder containing the ribbon supply is guided.

The setting of different traces of ink ribbons is carried out in printing units for two different reasons. On the one hand, it is important to use color ribbons as evenly or completely as possible, on the other hand, it may be necessary to switch from one color track to the other in the case of two-color inked color ribbons to switch the color of the print. The switching of parallel color traces of ink ribbons is particularly often to be carried out when more than two colors are used in modern electromechanical printing units, so that several ink ribbons are passed parallel to each other at the printing device and each have to be switched to the printing position.

By US-PS 38 41 459 it is already known to bring different color traces or sections of use of an ink ribbon in a printing position in a printing unit of the type considered here in that a ribbon fork leading to the printing position z. B. is pivoted electromagnetically into different positions, whereby the ribbon reaches different heights relative to the printing position. Swivel mechanisms of a similar type are also widely used in typewriters, e.g. To achieve as a Farbumschaltun ^g.

A disadvantage of such swivel devices is that the ribbon, due to its guidance on a relatively long swivel element, moves from one track to another on a circular arc during the adjustment, so that the individual tracks are not guided past the printing point in the same way, but depending on activated track, a position of the ribbon that is oblique to the printing point is caused, which can lead to an uneven font when printing, because the ribbon has a variable distance from the printing device on the one hand and to the recording medium to be printed on the other hand over the height of a character to be reproduced. Disadvantages of this type appear particularly clearly in fast printers which, for. B. work with high-speed needle print heads. Here, a uniform position of the ink ribbon in the printing zone must be ensured, because this high operating frequency of the print head means that the printing process is largely determined by the precise positioning of all sections of an ink ribbon.

If swiveling or tilting mechanisms of the previously known type were used, for example, to switch over the tracks of a plurality of ink ribbons guided one above the other, the disadvantages indicated above would of course increase and very complicated swiveling mechanisms would be required in order to be able to switch over several ink ribbon mutually parallel.

The use of pivotable guide forks is also only possible in those devices in which the ribbon supply and the ribbon holder are coil-shaped and the ribbon is therefore unwound from one spool, passed through the printing area and wound onto the other spool. When using so-called ribbon cassettes, which contain the ribbon supply and the ribbon holder and which, for. B. are simultaneously provided with a rigidly molded guide for the ribbon in the printing area, a switchover of the known type fails. Although it would be possible to tilt such ribbon cartridges, it would also require a quite extensive tilting mechanism, which is only under could take up and switch several cassettes lying on top of each other with considerable effort.

It is an object of the invention to provide, in printing units of the type considered at the outset, the switching of ink ribbon tracks, regardless of the type of ink ribbon guidance, in the simplest but most precise manner so that an unambiguous positioning of an ink ribbon track in the printing area is possible even when several ink ribbons are guided in parallel .

This object is achieved according to the invention for a device of the type mentioned above in that the ribbon supply and the ribbon holder are arranged on a holding device which is displaceably guided transversely to the running direction of the ribbon and is coupled to a drive device provided on the carrier, the movement stroke of which corresponds to the number provided ribbon tracks is divided into several levels.

In a device according to the invention, a special holding device is therefore arranged on the carrier, which does not have to be pivoted or tilted, but is guided on the carrier so as to be displaceable transversely to the running direction of the ink ribbon. This means that each track of one or more ink ribbons guided parallel to one another can be guided through the printing area in a consistently precisely predetermined position, since the movement stroke for the holding device is divided into a corresponding number of stages.

Regardless of the type of guidance of the ribbon on spools or in a cassette, it is possible to arrange several ribbons one above the other, i. H. in the form of a reel or cassette stack. Since this stack can be moved with the holding device through the drive device transversely to the direction of the ribbon, each desired track of several ribbons can be positioned exactly at the prescribed printing point.

The invention thus makes it possible, on the one hand, to use the traces of one or more ribbons uniformly, and on the other hand to switch from one color track to the other in a very simple manner if appropriately colored ribbons are used. So it is possible, for example, to switch to the lower half of the ribbon after using the upper half of the ribbon. B. set different color traces.

Different working principles are conceivable for the drive device which transports the holding device transversely to the running direction of the ink ribbon. A particularly advantageous and simple-working design is characterized in a further development of the inventive concept in that the drive device comprises a cam drive which moves a drive element connected to the holding device by its rotation into a number of positions provided corresponding to the number of ribbon tracks, transverse to the running direction of the ribbon .

The use of a cam drive for the adjustment of the ribbon tracks offers the advantage that a high accuracy of the track adjustment is achieved with the greatest possible simplicity of the drive mechanism. A cam disk, which generates correspondingly different working strokes due to its different distances from the axis of rotation, can have a range of constant distance from the axis of rotation for the working stroke to be achieved in each case, as a result of which a highly precisely controlled drive is not required for its rotation. When the respective range is reached, it is also permissible to run on a drive motor within certain limits without changing the working stroke.

The cam disk drive advantageously comprises two cam disks on a common axis of rotation, one of which actuates the drive element and the other serves as a counterpart for a traction device guided on it, which acts on the holding device in the direction of the first cam disk. This training enables the harmful influence of e.g. B. caused by thermal expansion or other mechanical play tolerances and also ensures a permanent seat of the drive element for the holding device on the first cam, because the holding device is continuously drawn by the traction device guided on the second cam towards the first cam.

The two cams are advantageously designed so that the distances between the curve points of the first cam to the common axis of rotation form constant sums with the distances of the diametrically opposite curve points of the second cam to the common axis of rotation. In this way, constant tensile or compressive stresses are always generated between the drive element for the holding device and the pulling device guided on the second cam disk, so that a consistently accurate compensation of tolerances is ensured over the entire stroke range of the holding device. The drive element and a traction element guided on the second cam plate are expediently on a straight line which runs in the direction of the movement stroke through the common axis of rotation.

If the traction device is connected to the holding device via a tension spring, the constant, firm pressure of the drive element on the first cam plate is further improved, and the tolerance-free guidance is maintained during the lifting movement regardless of signs of wear on the cam plates.

Further designs of a device according to the invention and advantages associated therewith result from the following description of an exemplary embodiment with reference to the figures.

• Fig. 1 die Vorderansicht eines elektromechanischen Druckwerkes gemäß der in Fig. 2 angedeuteten Blickrichtung 1-1 in teilweise gebrochener Darstellung,
• Fig. 2 eine Seitenansicht des Druckwerkes gemäß der in Fig. 1 gezeigten Schnittlinie 2-2 und
• Fig. 3 den Schnitt 3-3 aus Fig. 2.

Show it:

• 1 is a front view of an electromechanical printing unit according to the viewing direction 1-1 indicated in FIG. 2 in a partially broken representation,
• Fig. 2 is a side view of the printing unit according to the section line 2-2 and shown in Fig. 1
• 3 shows section 3-3 from FIG. 2.

In Fig. 1, an electromechanical printing unit is shown in front view and partially broken view, the platen roller 1 (FIG. 2) not being recognizable according to the viewing direction 1-1 indicated in FIG. 2. The printing unit is held between two side boards 35 and 36, which belong to a device frame. Between these side boards 35 and 36, two guide rods 7a and 7b are held, on which by means of guide rollers 6a and 6b (Fig. 2) a carrier 2 is guided so that it is known per se by a drive not shown in Fig. 1 Guide rods 7a and 7b can be transported in order to produce a print line running parallel to the guide rods 7a and 7b on a recording medium which is arranged on the platen roller 1 shown in FIG. 2. For this purpose, the carrier 2 carries, in addition to a holding device 9 still to be described, a print head 3, which in the exemplary embodiment shown is a needle print head and can produce characters on a recording medium with printing needles (not shown) in a printing area 4c.

The carrier 2, which can also be referred to as a carriage with regard to its guidance with guide rollers 6a and 6b on the guide rods 7a and 7b, carries the holding device 9 on guide rods 27a and 27b which are screwed to the holding device 9 at 30a and 30b and are guided on the carrier 2 in guide bushes 28a and 28b, so that the holding device 9 can be raised or lowered in the vertical direction with respect to the illustration in FIG. 1.

The holding device 9 is designed as a support plate on which two ink ribbon cassettes 4 and 5 are held one above the other. These ribbon cartridges 4 and 5 can be designed, for example, according to US Pat. No. 4,213,715. They are held on the holding device 9 in that they are attached to stud bolts 10 which can be provided with locking grooves in a manner known per se in order to hold the ribbon cassettes 4 and 5 in place. To maintain a predetermined distance between the ribbon cassettes 4 and 5, spacers 11 of predetermined thickness are provided. In addition, the ink ribbon cassettes 4 and 5 are held on the holding device 9 by means of a spring clip 12.

The ink ribbons contained in the ink ribbon cassettes 4 and 5 are passed through guide channels provided on the ink ribbon cassettes 4 and 5 and integrally connected to them after exiting the respective ink ribbon cassette 4 and 5, respectively, then reach a printing area, which is shown in FIG. 1 at 4c , and are then returned to the respective ribbon cassette 4 or 5. In Fig. 1 it is indicated that the ribbon in the upper ribbon cassette 4 has two tracks 4a and 4b and the ribbon in the lower ribbon cassette 5 has two tracks 5a and 5b. These tracks can be colored differently, but it is also possible to provide ribbon tracks of the same color. Obviously, not only ribbon cassettes, but also open ribbon supply and ribbon take-up spools can be provided on the holding device 9, for which purpose then only the corresponding receiving axes for such spools would have to be provided on the holding device 9 designed as a support plate.

If the ink ribbon of the lower ink ribbon cassette 5 is to be arranged in the printing area 4c, the holding device 9 on the carrier 2 is to be moved upwards until the area 5c of the lower ink ribbon comes to the position where the printing area 4c is shown in FIG. 1 is. The two areas 4c and 5c are formed by windows in a pressure point guide 9a connected to the holding device 9, into which the respective ink ribbon is inserted from above when the respective ink ribbon cassette 4 or 5 is placed on it. The respective window releases the ink ribbon guided past it so that the printing needles of the wire print head 3 hit the ink ribbon and its color can be transferred to the recording medium.

Since the two ink ribbons shown in Fig. 1 together have four individual tracks 4a, 4b, 5a and 5b, the holding device 9 must be able to be brought into four different positions in the vertical direction, in order to each one of these tracks 4a, 4b, 5a and 5b To assign printing needles of the needle print head 3. For this purpose, a drive device 13 is provided under the carrier 2, which is driven by an electric motor 18. The electric motor 18 and the drive device 13 are mounted on a frame which is formed by side plates 14 which are connected to one another via bolts 14a. In Fig. 1, the one side plate 14 of this frame is shown broken, so that a cam 15 behind it can be seen, which can be rotated on an axis 17 mounted in the side plates 14. For this purpose, the drive motor 18 is coupled to the axis of rotation 17 via a gear transmission with gear wheels 19. 1 shows, the cam disc 15 has four sections I, 11, 111, IV, which have a continuously increasing distance from the axis of rotation 17. A driving roller 21 is guided on the cam plate 15 and is mounted on a lifting plate 20 which is rigidly connected to the holding device 9. If the cam disc 15 rotates counterclockwise in the direction of the arrow shown in FIG. 1, the driving roller 21 will pass from section 1 of the cam plate 15 into section 11, so that this no longer causes the ribbon track 4a but the ribbon track 4b in the printing area 4c is arranged. When the cam disc 15 rotates further, the driving roller 21 reaches the sections 111 and IV, so that the holding device 9 is then raised further via the lifting plate 20 and the ribbon sections 5a and 5b reach the printing area 4c. By switching on the drive motor 18 for a respectively measured time, the holding device 9 with the ribbon cassettes 4 and 5 arranged thereon is each conveyed to a height which corresponds to the desired positioning of an ink ribbon track 4a, 4b, 5a, 5b in the printing area 4c. In Fig. 1, a gear transmission 29 with a drive motor is shown below the lower ribbon cassette 5 on a carrier element 9b connected to the holding device 9, through which the ribbons can be transported in a manner not shown during the printing operation.

FIG. 2 shows a representation of the printing unit in accordance with the section 2 shown in FIG. 1, in which the assignment of the ink ribbon track 4a to the printing area can be seen particularly clearly, ie it is at one point directly opposite the platen roller 1 arranged. In addition, a toothed drive belt 8 is shown, which is not shown in FIG. 1 for a better overview and which is used to transport the carrier 2 in the printing line direction in a manner known per se. It can also be seen in which way the two ink ribbon cassettes 4 and 5 are held on the holding device 9 by the spring clip 12, which is anchored to the holding device 9 at 12a.

In the frame formed with the two side plates 14 and the bolts 14a, the gear transmission with the gears 19 in coupling with the drive motor 18 and the first cam plate 15, on which the driving roller 21 is guided, can be seen. Arranged parallel to the lifting plate 20 is a pulling rail 23, which is connected at its upper end to the holding device 9 via a pulling spring 24, which is anchored to it at 24a.

The tension spring 24 is anchored to this at 24b. At the lower end of the pull rail 23, a driving roller 22 is provided, which is guided on a second cam 16. This second cam 16 sits on the axis of rotation 17 of the first cam 15 and serves to guide the driving roller 22 during the rotation of the first cam 15 so that the tension on the holding device 9 in the downward direction is as constant as possible via the tension rail 23 and the tension spring 24 is exercised so that the driving roller 21 is always pressed sufficiently against the cam 15 and the holding device 9 is always guided firmly and tolerance-free during its lifting movement. The shape of the second cam disk 16 relative to the first cam disk 15, as well as the mutual assignment of the driver rollers 21 and 22, is described below with reference to FIG. 3.

FIG. 2 also shows a clock disk 26 arranged on the axis of rotation 17 of the two cam disks 15 and 16, which has slots which are translucent at regular intervals in a manner not shown. This clock disk 26 is assigned to an optical signaling device 25, which contains a light source and a light sensor and can generate signals when passing the translucent slots of the clock disk 26, which signals are fed to a control device 40 for the drive motor 18. If the control device switches on the drive motor 18 upon receipt of a switchover command for the ribbon tracks 4a, 4b, 5a, 5b, it can determine the desired position of a ribbon track to be set in each case in a manner known per se, with the respective position determined by counting pulses from the reporting device 25 Compare the position and switch off the drive motor 18 when the target position is reached, since the target position then matches the actual position. Controls of this type are known per se and therefore do not need to be explained in more detail here.

In Fig. 3, the shape of the two cams 15 and 16 and the assignment of the driving rollers 21 and 22 actuated with them is shown in a partial view. The cam disc 15 has the shape already explained with reference to FIG. 1, so that it enables the setting of four different ribbon tracks. The pull rail 23 is now arranged so that the driving roller 22 held at its lower end on an axis 22a lies on a common straight line with the driving roller 21, this line running through the center of the axis of rotation 17 of the two cams 15 and 16. In order to enable a relative movement of the pull rail 23 and the lifting plate 20, the pull rail 23 is provided with an elongated hole 23a in the region of the axis of rotation 17 and the lifting plate 20 for the driving roller 22 with a slot 20b in the region of the axis 22a.

The circumference of the cam disk 16 is now dimensioned such that the sum of the distances between the driving rollers 21 and 22 from the common axis of rotation 17 of the two cam disks 15 and 16 is constant. In this way it is ensured that when the lifting plate 20 is lifted by the cam plate 15, the distance between the driving roller 22 and the common axis of rotation 17 becomes smaller as the distance between the driving roller 21 and the common axis of rotation 17 increases. It is thereby achieved that the tension rail 23 pulls the holding device 9 downward under largely uniform loading of the tension spring 24 and the driving roller 21 always lies evenly against the cam disk 15. Any tolerances that can be caused, for example, by stretching or by play due to wear of the cam disks 15 and 16 or other mechanical elements are compensated for, so that a lifting and lowering movement of the holding device 9 which is always free of play can be achieved.

As can be seen, the cam disc 15 has a largely constant distance from the axis of rotation 17 in the region of the sections 1, 11, 111 and IV, as a result of which a certain inaccuracy of the drive device 13 or a running of the drive motor 18 after shadowing can be accepted. The position of an ink ribbon track 4a, 4b, 5a, 5b once reached is then maintained regardless of such drive tolerances.

Claims (10)

1). A device for a mechanical, preferably electromechanical printing mechanism for setting an ink ribbon in different tracks transversely to its travelling direction on a carrier which can be conveyed in the line direction in the printing mechanism, an ink-ribbon reserve being arranged on said carrier and said ink ribbon being moved past a printing device and through a printing region to an ink-ribbon take-up unit possibly also containing the ink-ribbon reserve, characterized in that said ink-ribbon reserve and said ink-ribbon take-up unit are arranged on a holding device (9) movable on said carrier (2) transversely to the travelling direction of the ink ribbon, said holding device being coupled with a drive unit (13) provided on said carrier (2), the stroke of said drive unit being divided into a plurality of steps corresponding to the number of ink-ribbon tracks (4a, 4b, 5a, 5b) provided.

2). A device as set forth in claim 1, characterized in that said drive unit (13) comprises a cam drive unit (15, 16) which by its rotation moves a drive element (21) connected with said holding device (9) into a number of positions transversely to the travelling direction of the ink ribbon (4, 5) corresponding to the number of ink-ribbon tracks provided. 3). A device as set forth in claim 2, characterized in that said cam drive unit includes two cam plates (15, 16) on a common axis of rotation (17), one of said cam plates actuating the drive element (21) and the other cam plate serving as a counterpart for a pulling device (22, 23) guided on it, said pulling device biasing said holding device (9) towards said first cam plate (15).

4). A device as set forth in claim 3, characterized in that the distances between the cam points of said first cam plate (15) and the common axis of rotation (17) add up to a constant sum with the distances between the diametrically opposed cam points of said second cam plate (16) and the common axis of rotation (17).

5). A device as set forth in claim 3 or 4, characterized in that said drive element (21) and a pulling element (22) guided on said second cam plate lie on a straight line extending through said common axis of rotation (17) in the direction of the stroke.

6). A device as set forth in claim 5, characterized in that said drive element (21) and said pulling element (22) are rollers which roll along the respective cam plate (15, 16).

7). A device as set forth in any of claims 3 to 6, characterized in that said pulling device (22, 23) is joined to said holding device (9) by way of a tension spring (24).

8). A device as set forth in any of claims 3 to 7, characterized in that said common axis of rotation (17) is coupled with a rotatable, preferably electro-optical indicating unit (25, 26), the signals of said indicating unit being feedable as position indicating signals to a control unit (40) for an electric motor (18) being mounted on said carrier (2) and driving said drive unit (13).

9). A device as set forth in claim 8, characterized in that said electric motor (18) is coupled with said common axis of rotation (17) by way of a gear drive (19).

10). A device as set forth in any of the foregoing claims, characterized in that said holding device (9) has a supporting plate for the ink-ribbon reserve and the ink-ribbon take-up unit, said supporting plate being guided on said carrier (2) by means of guide rods (27a, 27b) extending in the direction of the stroke.

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