JPS6313034Y2 - - Google Patents

Description

[Detailed explanation of the idea]

The present invention relates to an endless type ink ribbon cassette used in a printing device, and relates to an improvement of the roller that feeds the ribbon into the storage chamber. Figure 1 shows the general structure of an endless ribbon cassette. 1 is the cassette case body;
Reference numeral 2 denotes a ribbon storage chamber provided in the case 1, and a pair of rollers 4 and 5 are provided on the entrance side of the ribbon storage chamber for feeding the ribbon 3 into the storage chamber. 4 of these are drive rollers driven from the outside, and arm 6 is attached to this.
A driven roller 5 supported by is pressed by a spring 7. FIG. 2 shows an example of the structure of the drive roller 4, in which a ring 42 made of an elastic body is fitted into a roller body 41 usually made of resin. Note that the driven roller 5 also has the same structure except for the shaft portion. The endless ink ribbon 3 passes between the rollers, is folded in a meandering manner as the rollers rotate, enters the storage chamber 2, is eventually pulled out from the outlet 8, passes through the printing section 9, and returns to the storage chamber again. However, from the user's perspective, the longer the ribbon life, ie, the time to replace the cassette, the better, in terms of cost and effort. The easiest way to meet this demand is to increase the total length of the ink ribbon housed inside. However, since the size of the cassette is restricted by the printing device and cannot be changed, this means that longer ribbons than conventional ones must be packed into the storage chamber of the same volume.
Therefore, in order to achieve this, it is necessary to feed the ribbon into the storage chamber with a larger force than before, that is, to further strengthen the feeding force of the rollers. The problem here is that the feed force exerted by the rollers is generally proportional to the mechanical damage that the ribbon receives from the rollers. In other words, if tooth-shaped grooves or grooves are formed on the surfaces of both rollers, the feeding force will be strengthened, but on the other hand,
The ribbon is easily damaged because it gets caught between the teeth. In addition, permanent deformation (wrinkles) in the form of roller teeth remain in the ribbon, and these wrinkles cause tangles of the ribbon and prevent regular folding, resulting in a reduction in the actual capacity of the storage chamber. In order to avoid this, a simple cylindrical roller with a flat surface without grooves may be used, but this would lack sufficient feeding force and would not serve the original purpose. Conventionally, these two methods or a compromise between them (one roller with grooves and one without grooves) have been used without clear selection criteria, but they can both satisfy the conflicting objectives mentioned above. There was nothing. Therefore, the inventors decided to leave the tooth grooves on the roller in view of the feeding force, and prototyped various tooth grooved rollers in order to develop a tooth profile that would not damage the ribbon. As a result of observation and theoretical analysis of the relationship between the tooth profile of the roller, the wrinkled state of the ribbon fed by the roller, and the state of the ribbon folded in the storage chamber, we found that the tooth profile that would not damage the ribbon was found. It has been found that there is a certain relationship between the specifications and the thickness and material of the ribbon as described below. First, if the ribbon is caught between the elastic ring 42 provided with tooth grooves as shown in FIG. This is thought to depend on the pitch P of the tooth groove and the radius of curvature R of the tooth tip and root. In FIG. 4, which shows an enlarged view of the tooth tip 43, tension and bending stress act on the ribbon 3 bent in close contact with the tooth tip in its length direction.
Distortion occurs accordingly. It is assumed that the thickness of the ribbon 3 is T, and that the ribbon between the angle dθ is initially rectangular, but the length on the inside curves along the tooth profile of the roller without changing, and only the outside stretches, becoming fan-shaped. Then, the inner length (arc) of the ribbon is R・dθ, and the outer length of the ribbon is (T+R)・dθ, so the strain S at the outermost part of the ribbon between the infinitesimal angle dθ is S = (T+R)・dθ−R・dθ/R・dθ =T・dθ/R・dθ ∴S =T/R... If this strain is within the elastic limit and small enough, it will return to its original state. However, otherwise permanent deformation will occur and the result will be wrinkles. Therefore,
The condition for not leaving wrinkles on the ribbon should satisfy the formula. That is, from S=T/R≦K・Sc, T/R≦K・Sc or R≧T/(K・Sc)... Here, Sc means that when tensile stress is applied, the permanent deformation of the ribbon is substantially The amount of strain that begins is a characteristic value unique to each material of the ribbon, and K is a constant. EXAMPLE First, in order to find the compatible range of the pitch P and the constant K, the following experiment was conducted. Assuming that the total tooth height of the tooth groove h = 0.2 mm was constant, elastic rings made of neoprene rubber with an outer diameter of 15 mm and a width of 6 mm were prepared with various pitch P mm of the tooth groove and radius of curvature R of the tooth tip and root. . Next, these rings are attached to rollers 4 and 5, and the pressing force by spring 7 is constant at 400 g, and the width is 13 mm and the thickness is 0.1
When we observed the state of the ribbon after biting the ribbon with mm, Sc = 0.30 and the situation in the storage chamber, we found that in all cases where P > 1 mm, feeding errors occurred, and P ≦
There were good and bad cases with 1mm. Therefore, from the experimental data, those with P=0.94 mm were extracted and shown in Table 1.

[Table] Note* ○: Good, ×: Poor with many disturbances From these results, it was found that there is no problem if the boundary that can be accommodated without trouble has a T/R of 2.5, that is, a radius of curvature of 0.04 mm or more. Also, the constant K is Sc=0.3, T/
From the formula R = 2.5, it became 8.3. That is, the necessary and sufficient condition for orderly folding and storage is that the tooth space specifications satisfy the following formulas and expressions, and this is the gist of the present invention. R≧T/(8.3×Sc) ... P≦1mm ...Next, in order to see the influence of the ribbon specifications, the conditions other than the ribbon were as in the previous section, and the ribbon alone was 20mm wide, 0.12mm thick, and Sc= When tested instead of 0.37 ribbon (base fabric was 66 nylon as in the previous case),
Similarly, if P > 1 mm, all feed defects will occur, and P
There were good cases and bad cases for ≦1 mm. Therefore, data for P=0.94 mm were extracted from the experimental data and are shown in Table 2. The conclusion drawn from this result is the same as the conclusion in the previous section.

[Table] Note* ○: Good, ×: Poor with a lot of disorder The same results were obtained for each, but as can be seen from Figure 4 and the above explanation, the relationship between bending and strain is similar to the length perpendicular to the page of the figure, that is, the width of the ribbon. Since they are unrelated, this result is theoretically acceptable. Above, an embodiment has been described with respect to one of the objects of the present invention, which is not to damage the ribbon.Next, an embodiment regarding the feeding force of the ribbon, which is another object of the present invention, will be described. First, as in the above example, it is made of neoprene and has an outer diameter.
An elastic ring of 15 mm and width of 6 mm was prepared, and the smooth ring with no grooves on its surface was designated as A. Further, the same ring with tooth grooves of h = 0.17 mm, P = 0.8 mm, and R = 0.08 mm was designated as B. The thickness of the ribbon to be tested is 0.1mm, same as in the above example, so ring B
The dimensions of the tooth space satisfy the formula and the conditions of the formula. Next, first, as comparative examples, we will compare a combination of ring A with no tooth grooves on both the driving side and driven side, and a combination in which the driving side is replaced with ring B with tooth grooves. Cassette case 1 for 3 types of combinations using B
When the ribbon was fed, the compression force was measured as the tension acting on the ribbon. The measurement results and the condition of the ribbon sent are shown in Table 3. As is clear from this result, even though the effects on the ribbon are the same, there is a large difference in the feeding force.
According to the present invention, it has been found that a significantly higher feeding force can be obtained than before without damaging the ribbon.

[Table] In implementing the present invention, if the radius of curvature of the tooth tip does not have a single value, the minimum point should satisfy the formula. In addition, the shape of the tooth groove is
It is not limited to the shape shown in the figure. As for the hardness of the elastic ring, a hardness of 55 according to the vulcanized rubber physical testing method (JIS: K6301) was used in the above-mentioned embodiments, but a hardness of 30 to 80 is suitable. As detailed above, according to the present invention, it is possible to design an optimal feed roller for each ribbon used, and as a result, a ribbon cassette that does not cause trouble even when storing a longer ribbon than before can be obtained. is,
The user's request for extending the life of the cassette can be met.

[Brief explanation of the drawing]

Fig. 1 is a diagram illustrating the internal structure of the ribbon cassette, and Fig. 2 is a drawing illustrating the structure of the ribbon driving roller.
Figure 3 is a cross-sectional view of the tooth profile provided on the surface of the roller.
FIG. 4 is an explanatory diagram showing a state in which a ribbon is attached to the tip of the tooth. 1...Cassette case, 2...Storage room, 3...
Ribbon, 4, 5...roller, 7...spring, 42...elastic ring.

Claims (1)

[Scope of Claim for Utility Model Registration] In an endless ribbon cassette for printing, which is provided with a pair of rollers that sandwich the ink ribbon at the entrance of the ink ribbon storage chamber, and is configured to fold the ink ribbon into the storage chamber by driving the rollers, An endless ribbon cassette for printing, characterized in that the roller is made of an elastic material, and the specifications of the tooth grooves provided on the surface of the roller are within the range specified by the following formula and formula. R≧T/(8.3×Sc) ... P≦1mm ... where T: Thickness of the ink ribbon, Sc: Amount of strain at which permanent deformation of the ribbon begins due to tensile stress, R: Curvature of the tip of the roller groove tooth radius, P: pitch of the tooth groove provided on the roller, 8.3: constant.