DE2148420B2 - METHOD OF APPLYING A BULK VULCANIZABLE STRIP TO THE CARCASS OF A BLANK TIRE OR TIRE TO BE RENOVATED - Google Patents

Description

shafts in other directions, mainly in perpendicular directions, different are. Such a mixture has, in particular, a rate of crystallization which is lower Temperature is higher than with a non-oriented mixture, if the elastomer mixture used is crystallizable. Also shows the X-ray diffraction spectrum of a sample of a molecular oriented elastomer mixture has a far higher degree of crystallization when the mixture is in the preferred Direction is stretched as if the stretch is in a direction perpendicular to it.

According to a preferred embodiment, the method according to the invention is carried out in such a way that that the stretching of the raw strip is carried out by 100 to 300% of its original length.

According to further refinements of the invention, the stretching takes place before or during the application “On the carcass.

According to a further preferred embodiment of the invention, the stretching of the raw strip takes place prior to application to the carcass beyond the final desired elongation and application on the carcass only after the raw tread has reached the desired final The degree of stretching has contracted again.

The application of the raw run strip ens on the carcass is expediently carried out in such a way that one Winding a film made of an elastomer mixture onto the carcass, this film being the same as given above Is subjected to stretching in the running direction. Vulcanization of the pneumatic tire is then carried out if the film has a number of layers corresponding to the desired tread thickness the carcass has been wound up.

In the practical implementation of the method according to the invention, the raw tread can either on a new, still cylindrical or previously cambered carcass, or on the carcass of one retreaded pneumatic tires are applied.

According to the method according to the invention, it is possible in a surprisingly simple and effective manner Wise the tread of a new or retreaded tire with a pronounced anisotropy to provide the properties which, surprisingly, cause the finished pneumatic tire to last longer Runtime, i.e. a higher resistance to wear and tear.

This can possibly be explained as follows:

As already mentioned above, the layer applied to the carcass by the method according to the invention Raw treads have a structural anisotropy, which results in an anisotropy from the inner Structure-producing properties. As a result, there are numerous physical properties such as the modulus of elasticity, the breaking strength and elongation and the electrical resistance, more or less clearly influenced, which then depend on the measuring direction used in each case Differences do not exceed 30%. That which was clearly and with certainty a change learns, on the one hand, is the relative arrangement of the macromolecular chains to one another and / or the accumulation of soot and other admixtures and, on the other hand, the hysteresis loss, which is no longer in is the same in all directions; in addition, this changes the behavior of the pneumatic tire in his Use and other technological characteristics of the tread.

As for the orientation of the macromolecule or the admixtures, there is no doubt that the stretching of the vulcanizable raw tread produces an effect that also applies to the following Vulcanization is retained. It turns out that at a temperature of -25 ° C the tread parts removed from a pneumatic tire manufactured according to the invention crystallized much faster than parts, ίο a mixture made from the same but not subjected to any stretching before being placed on the carcass manufactured tread were removed. This cannot be interpreted otherwise than that the stretching carried out prior to vulcanization orients at least certain parts of the rubber and that vulcanization does not completely eliminate this orientation. It succeeded in some Cut the oriented structure by electron microscopic examination of the structure stretched according to the invention Proof of mixture.

The same conclusion can be drawn from the fact that a sample of the tread is made after vulcanization shows a greater tendency to crystallize if one moves it in the direction of the before vulcanization exerted tension as if the tension was in a direction perpendicular to it was carried out.

Regardless of the mentioned effects on the elastomer mixture, it is not excluded and even likely that the strong tension which the elastomer mixture in a preferred Direction, an orientation effect also on the particles of other components of the mixture, especially the soot particles. The orientation of the chains facilitates their approach, whereby the connecting forces and thus the internal cohesion of the vulcanizate can be improved.

Measurements with a bending meter have shown that a tread applied according to the invention in the case of the deformations generated in the stretching of the same, significantly less Has hysteresis loss than when deforming perpendicular to it. Leave the previously known treads miss this peculiarity and improvement in properties.

On the other hand, an essential factor could also be achieved when using the tires produced according to the invention technical progress can be achieved. A number of tests have been carried out on tires for excavators and if the same test conditions are observed, the runtime is appropriate for wear and tear a weight loss of 5% of the tread is required, averaging 70 Hours for the comparison tires to an average of 120 hours for those made according to the invention Tire rise. Similar findings could be made with pneumatic tires for trucks, where im In the case of a tire produced according to the invention, a weight loss of 5% only after a running time of 225 hours occurred, while with the comparison tire this weight loss of 5% after only one Running time of 150 hours had occurred. Such Extension of the running time from 50 to 100%, which is the case with the tire produced according to the invention found, cannot possibly be accidental, but only as a sign of a profound change in the tread material be interpreted. It should also be noted that this increases the wear resistance of the

Stripes have been improved not only quantitatively but also qualitatively, since the weight loss in the Case of the tire produced according to the invention distributed more evenly on the ga.izen tire.

The invention is explained using an exemplary embodiment shown in the drawings. It shows

Fig. 1 would be a schematic representation of a winder raw treads to be applied to the carcass,

2 shows a radial section through a tire before the vulcanization of the raw tread and

3 shows a radial section through the tread of a tire in an enlarged representation in its final shape after vulcanization.

Fig. 1 shows a carcass 1 of a pneumatic tire during the application of a raw tread. The carcass 1 can be a new carcass or a carcass prepared for retreading. The carcass 1 is mounted on a rim 2 and is inflated by means of a tube to a pressure of about 1 kp / cm ^2. The rim 2 with the carcass 1 is set in rotation by means of an electric motor 3. The speed of the electric motor 3 is regulated by means of a follower roller 4 in order to keep the peripheral speed V _{x of} the carcass 1 constant.

The raw tread is wound up by continuously winding a rubber sheet 10 in a spiral shape the carcass 1 is made. The rubber sheet 10 contains those indicated below in parts by weight Substances:

Smoked Sheets 1 100

Stearic acid 2

HAF carbon black 50

Zinc oxide 5

N-Cyclohexylbenzothiazylsulfonamide 1

Phentyl- / 3-naphthylannine 1

Plasticizer 5

Sulfur 2

The rubber film 10 produced on a calender is pulled off a roll 15. She has in this process section a thickness of 2 mm. The roller 15 is with the help of a friction roller 16 in The direction of the arrow rotated. An intermediate layer made of a fabric or polyethylene 17 separates the successive layers of the rubber film 10 from one another. When unwinding the Roll 15, the intermediate layer 17 is wound onto a drum 18 driven by a motor.

From the column 15 the rubber foil 10 arrives in a compensating reservoir 19 which stores the rubber foil 10 under low tension in a variable section, so that the roll 15 can continue to be unwound between two raw tread application operations. Between the compensation reservoir 19 and the carcass 1, the rubber film 10 runs over driven rollers 20, 21 and 22, which give the rubber film 1 (1 a constant linear speed V _a , which is significantly lower than the peripheral speed V _{1 of} the carcass 1. Between the rollers 20, 21, 22 and the carcass 1, the rubber sheet 10 is therefore subject to stretching, as a result of which its length changes in the ratio V _x IV _n . On the roller 21 there are knives 24 which, according to a set program, either have a central part or two lateral parts Cut out parts of the rubber sheet 10, depending on which profile is to be given to the raw running strip.

In the case of the mixture indicated above, the following initial and final dimensions result for the stretching of the rubber sheet 10:

Initial thickness 20 mm

Final thickness about 11 mm

Initial width 650 mm

Final width 450 mm

Degree of elongation 2.7 (i.e. 170% stretching)

Winding speed 18 m / min.

When a number of layers of the rubber film 10 has been applied to the carcass 1, which for Production of the desired raw strip are required, the speed of the electric motor 3 increased for a short moment to an additional permanent stretching of the rubber film 10 between the carcass 1 and the roller 22 to produce. The rubber sheet 10 can then be cut off. Remove the carcass 1 with the raw tread and place a new carcass 1 on the rim 2. The tension of the rubber sheet 10 promotes the adherence of each turn to the preceding one during winding and the elimination of air between the rubber sheet 19 and the carcass 1.

After the carcass 1 has been provided with the raw tread, vulcanization takes place. You can do it Proceed in a conventional manner for a new tire by placing the tire in a die brings in and then vulcanizes it. But you can also do it in the usual way for a retreading procedure, namely bring the tire into a container or boiler, where it is heated with flowing steam is vulcanized, after which the tread profile is formed with the help of cutting tools.

Fig. 2 shows a pneumatic tire before vulcanization. A carcass 30 contains reinforcement 31 wrapped around bead cores 32. In addition, a crown reinforcement 33 and a raw tread 34 are provided. As can be seen, the raw tread 34 consists of a spiral superposition of a large number of turns 36, all of which run parallel and have the same thickness. Fig. 3 shows the apex of the same tire after vulcanization. The introduction of a profiling 37 in the raw tread changes the course and the thickness of the windings 36 somewhat, mainly in the vicinity of those zones in which the mixture has flowed under the action of heat. The layer structure of the tread 35 can be clearly seen, however. If the tire is profiled after vulcanization, the layered structure of the tread 35 reveals the permanent parallel course of the windings 36 (FIG. 2). Several rubber foils 10 can be wound up under different tensions and changes in length. It is also possible to change the tension according to any law during winding. During winding, a tension 6u in the longitudinal direction may be superimposed on a tension in the transverse direction. The magnitude of the stresses and elongations can be much greater or lesser than in the example described. It is essential. that the raw tread 34 experiences a great stretching either before or during winding and that it is vulcanized in a strongly tensioned and stretched state, which is retained after winding.