EP0045360B1 - Type band for a band printer - Google Patents

Description

The invention relates to a type tape for a type tape printer.

Usual type tape printers (e.g. the IBM type tape printer 3288, 3289) have an all-round type tape, which presents itself as a steel tape with raised print types and tact marks etched out by photochemical means.

The following arrangement of the steel strip in relation to a pressure abutment and the record carrier and ink ribbon to be considered is decisive for the printing of a character: The smooth back of the steel strip moves past the pressure abutment. The ribbon and the recording medium are located in front of the front of the ribbon with the raised printing types. The character imprint in a certain printing position is effected by a printing hammer, which strikes the recording medium and presses it against the ink ribbon, the type of steel ribbon to be printed and the platen.

One of the biggest problems with steel band printers, which has only been partially solved so far, lies in the heavy use of the ink ribbon by the sharp-edged printing types of the steel ribbon, which leads to the soon destruction and uselessness of the ink ribbon.

Again, this disadvantage could only be kept inconspicuous with low printing capacities.

To increase the printing performance, efforts were made to reduce the destructive influence of the sharp-edged printing types on the ink ribbon by subjecting the front side of the ribbon to a polishing process. Character tapes of this type with a polished front have been / are used in type tape printers, e.g. B. of the type IBM 3262 used. The reduction in the destructive force of the previously sharp type edges on the ink sheet is due to the fact that the type edges are slightly rounded by the polishing process.

Such a polishing process turns out to be very complex and expensive and is also very difficult to control. In other words: the polishing process often does not lead to the desired result.

To avoid these disadvantages, it is now an object of the invention to provide a type tape in which the destruction of the ribbon fabric due to the sharp type edges is enormously reduced and which is easy and controllable to manufacture.

This object of the invention is achieved by the measures mentioned in the characterizing part of claim 1.

Further advantageous embodiments of the invention can be found in the subclaims.

• Fig. 1 eine schematische Schnittdarstellung eines zwischen einem Druckwiderlager und einem Druckhammer angeordneten Typenbandes, eines Farbbandes und eines Aufzeichnungsträgers;
• Fig. eine perspektivische Teilansicht der Vorderseite eines Typenbandes mit erhaben herausgeätzten Drucktypen und Taktmarken;
• Fig. 3 eine schematische Schnittansicht durch ein Typenband gemäß der Schnittlinie A-A in Fig. 2;
• Fig. 4 eine schematische Schnittansicht durch ein Typenband mit einer Kunststoffbeschichtung vor Ingebrauchnahme Fig.4A und Fig.4B nach Ingebrauchnahme.

An embodiment of the invention is shown in the drawings and will be described in more detail below. It shows

• Figure 1 is a schematic sectional view of a type tape arranged between a print abutment and a printing hammer, an ink ribbon and a recording medium;
• A perspective partial view of the front of a type tape with raised etched out printing types and timing marks;
• 3 shows a schematic sectional view through a type strip according to section line AA in FIG. 2;
• Fig. 4 is a schematic sectional view through a type tape with a plastic coating before use Fig.4A and Fig.4B after use.

In Fig. 1 is shown in a sectional view how the type tape 1 is arranged opposite the platen 2, the ink sheet 3 and the record carrier 4 and the print hammer 5. To generate a character print, the hammer 5 strikes against the recording medium 4, the ink ribbon 3, the raised etched print type 6 on the front side 1-1 of the type tape 1 and presses the type tape 1 with its rear side 1-2 against the pressure abutment 6. This results in an imprint of type 6 on the recording medium 4. During the imprint, the type ribbon 1 moves in the direction perpendicular to the plane of the drawing, while the ink ribbon 4 remains relatively stationary. At the moment of printing, there is a strong lateral stress on the ribbon, caused by the sharp printing type edges of the character 6. This stress can ultimately lead to destruction of the ribbon tissue, so that - as already indicated - when using »untreated« type ribbons, the ribbons must be replaced frequently.

In Fig. A perspective partial view of the front side 1-1 of the type tape with raised etched out types (6-1, 6-2) and timing marks (6-1-1, 6-2-2) is shown. Excerpts of types H (6-1) and I (6-2) can be seen on the front 1-1 of volume 1. The timing marks assigned to these printing types (6-1-1 and 6-2-2) are also etched out. They are used to synchronize the pressure control.

FIG. 3 shows a sectional illustration of the type tape along the section line A-A according to FIG. 2. It can be seen that the type and timing mark edges (7) are extremely angular, which ultimately has a destructive effect on the ink ribbon. (This sharpness of the print types naturally also applies to the cutting direction indicated by B-B in FIG. 2.)

The destructive influence of the sharp type and clock mark edges is now avoided by coating the drawing tape with a plastic, preferably with a material containing polytetrafluoroethylene (PTFE). PTFE is e.g. B. known under the trade name »TEFLON« from Dupont.

From a technological point of view, such a coating is no longer a problem. However, such coatings have hitherto only been carried out for flat parts, in order, for example, B. to prevent food from sticking to frying pans or saucepans or to achieve a certain lubricating effect with parts sliding past one another (carburettor bearings in automobiles).

Even specialists considered it impossible and doubtful that coating the irregular relief-like type tape surface with raised etched-out printing types and timing marks could lead to the desired satisfaction of the task.

4A and B show schematic sectional representations of a type strip before and after use, which was coated with a PTFE-containing material. The cutting line would correspond to B-B of FIG. 2 if the type strip shown there had been coated.

The metallic cut surface is heavily hatched, while the cut surface is only slightly hatched by the layer 12 containing PTFE.

Immediately after the coating, the PTFE-containing material is not only deposited on the locations 8 between the type elevations 6-1 and clock mark elevations 6-2, but also at locations 9 on the type surface to be printed, as well as embankment-like at locations 10 on both sides of the types - or time stamp surveys.

After the use of type tape 1, the material containing PTFE deposited in the areas 9 is rubbed off in the shortest possible time (with high printing performance after a few cycles); it also partially attaches to the embankments 11 (Fig. 4B). From this representation it can be seen that, compared to the representation according to FIG. 3, the effective type and clock mark edges are no longer so sharply formed (embedded in material containing PTFE) and therefore can no longer have such a destructive effect on the ribbon fabric.

The PTFE-containing layer must also contain certain additives (resins) that guarantee the abrasion resistance of the layer. Such admixtures to achieve a higher abrasion resistance are commercially available (eg as »TEFLON S«, registered trademark of the Dupont company). The application of pure PTFE required e.g. B. for reasons of liability on the base material, a previous sandblasting and a high temperature. However, both of these boundary conditions would not be acceptable, particularly for type bands. In the case of steel ribbons for type ribbon printers, the layer containing PTFE is applied by spraying with a subsequent moderate heat treatment.

As a result of the surface tension of the sprayed-on PTFE-containing emulsion - as can also be seen from FIGS. 4A and 4B - there are ramp-like embankment-like contours on the flanks of the type or clock mark elevations, which promote the sliding of the type ribbon on the ink ribbon. Lateral carry-over of the ribbon is enormously reduced compared to an uncoated, but polished type ribbon. As a result of the coating, the mechanical destruction of the ribbon fabric is reduced to such an extent that the service life of the ribbon is at least doubled for new type ribbons.

Furthermore, the contamination occurring in the area of the type tape is reduced, since fewer type fibers and colored particles are entrained by the type tape in coated type tapes and are only transported to a small extent due to the anti-adhesive properties of the layer surface.

During the continuous use of coated type tapes (after several million lines), the layer containing PTFE is of course also slightly removed. At the same time as this removal, however, there is also a rounding of the type or clock mark edges, so that there is no destructive effect on the ink sheet, as would be the case from the start with an uncoated and polished band.

The coating on the front of the type tape also leads to a reduction in wear on the surface of the type tape, which is due to the formation of a thin film of the PTFE, which is also to be understood as a dry lubricant, both on the type surfaces to be printed and on the fabric of the ink sheet.

The use of a PTFE-containing layer for the relief-like type tape surface, taking into account the particular type of stress that occurs with impact printers, led to the surprising result that the destructive influence of the formerly sharp type and clock mark edges on the ink cloth fabric could be reduced enormously.

Furthermore, during the partial abrasion of the PTFE-containing layer, after several million print lines, there is a gradual, ribbon-friendly rounding off of the type or clock mark edges, as could not be achieved by a polishing process that is difficult to control. As a result, the destructive influence of sharp-edged printing type and timing mark edges on the ink sheet is not given at any time when a coated type tape is used.

Claims (3)

1. Type belt for type belt printer, characterized in that the type belt (1) is coated with a synthetic material (12).

2. Arrangement as claimed in claim 1, characterized in that the coating material contains polytetrafluoroethylene (PTFE).

3. Arrangement as claimed in claim 1 or 2, characterized in that the type belt (1) with the print types (6) protruding therefrom (1) in a manner known per se, is covered with coating material (12) of such a thickness that toward the edge of the print type surface the coating material is arranged like a slope (11) forming a flattened slope crest.

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