Tread ring for removable tread tires

SWEDEN

<img file="SE352289B_D0001.tif" />

PUBLICATION PAPER No. 352 289 mtc. B 60 c 11/02

PATENTS AND REGISTRATION OFFICE

Patent Application. No. 10365/70 Received on 28 VII 1970 Validity Day on 28 VII 1970

Ans. generally available on 50 In 1971

Ans. published and published on 27 XII 1972 Priority requested from 29 VII 1969 and

III 1970 (Italy, 20 215/69, 21 875/70)

INDUSTRY-PIRELLI SPA, MILANO, ITALY

Inventor t C Magistrini, Monza and L Maiocohi, Moncuoco di Vernate Ombuds S Hammar Wear Drain for Vehicle Dock

The present invention relates to rubber tires with removable wear handling, in particular such rubber tires for pneumatic rings, where the anchoring of the wear ring to the tire body is ensured by the frictional forces resulting from the internal ring pressure.

In such tires, it is known in several patents to provide the wear tire with a system of reinforcing means, the manner of which the device has a decisive influence on the tire's operating characteristics, especially with regard to road holding, steering safety and ride comfort. Thus, in particular, this wear casing exhibits a tensile strength reinforcement consisting of screw-twisted metal wire ropes, oriented substantially parallel to the center circumference of the tire, this reinforcement having the task of counteracting the expansion of the body in order to induce the frictional forces which are to ensure the wear force. However, this reinforcement alone, as is readily apparent, is insufficient to give the tire the many characteristics, which are necessary for it to function satisfactorily during use.

In tire manufacturing, as is well known, the need for a more complicated and reliable reinforcement structure is met by building the tread portion into three layers, the individual layers being oriented in mutually different directions. It has thereby been found possible that by applying two strips of metal wire cloth radially outside the above reinforcement and arranging these strips in such a way that their threads run symmetrically inclined with respect to the middle circumference of the tread, they are distributed by a smaller unevenness or a smaller one. objects on the roadway's caused tensions or stresses over a greater part of the width of the tread and in addition to improve the cross-section of the tread. torsional stiffness, which has a favorable effect on the tire's swing and road holding properties.

However, it has been found that the newly described reinforcing device does not constitute a fully satisfactory solution with regard to the fulfillment of other conditions necessary for the tire to function well under particularly difficult driving conditions, e.g. on poor roadway. In said reinforcing device, the screw-wound reinforcing wire is admittedly protected in the direction of the outside of the tire, but it is not sufficiently protected in the direction of the inside of the tire. Particularly under the influence of impact forces exerted on the tread when it encounters any unevenness on the roadway, the reinforcing or reinforcing device at the impact site reacts in such a way that - although temporarily an inward ring convex rise occurs on the inside of the tire, which distribution of the wire lines which form the reinforcement in the stress area in question. This results in damage to the rubber layer located during the reinforcement and the weakened reinforcement wire eventually weakened so that it can burst. In addition to this, the reinforcement of the tread is ineffective, thereby breaking the ends of the wire can also damage the tire body, resulting in a catastrophic reduction of the entire tire's effective life.

kfen has tried to remedy the above-mentioned inconveniences by placing one of the two strips of metal wire cloth used in conjunction with the main reinforcement, instead of outside of it, in this way the two threaded strips of the reinforcing or reinforcing system will have their threads symmetrically inclined relation to the center circumference of the tread so as to maintain the good characteristics of the tire with respect to stiffness and winding; At the same time, the presence of the wire cloth strip inside the wire reinforcement ensures that the tire is protected even under difficult driving conditions.

However, this device does not, however, provide a complete solution to all the problems that must be taken into account to ensure that the tire operates fully satisfactorily, it can be said to represent a fairly good compromise solution, but at the same time it implies a deterioration of the wear or tear of the tread. , especially where the tire is to be used on bad roads.

A reinforcement system consisting of three layers, consisting mainly of a main reinforcement of twisted metal wire ropes running parallel to the center circumference of the tire and two strips of metal wire cloth, whose threads are symmetrically inclined relative to this periphery, can of course also be obtained in accordance with a third device method. namely, by placing both said strips within said main reinforcement.

However, studies which have now been carried out in this regard did not produce such results that this solution could be shown to have any decided advantages in comparison with the others, as it was found that the thus arranged for the reinforcing system causes the tire to be unacceptable for so-called , edge loop ring. By this term is meant the difficulty of mastering the vehicle as in certain traffic conditions it must be driven with one side wheels on the roadway, where there is a certain height difference between the roadway and the paved roadway, under such conditions the tire has a tendency to meander between the roadway and the roadway. difficult to control way.

The inventors have now, quite surprisingly, come up with a reinforcing or reinforcing device, by means of which it is possible to produce a removable wear tire for rubber tires, which provides the tire with such operating characteristics that they in all respects fulfill the requirements set out above.

This is achieved by a removable tread of the kind stated in the preamble of the following claim 1, mainly through the device specified in the characterizing part of this claim.

The term elastically extensible metal wire ropes in the present specification refers to ropes which, when embedded in rubber, exhibit an apparent modulus of elasticity for tensile loads less than ½ / 10 of the tensile breaking limit of at most 3500 kp / mm.

The metal wire ropes forming the third auxiliary layer, located outside the main reinforcement, can be elastically extensible due to their special structure; wire lines of this kind, for example, are those whose cardamases and the like, respectively. the parts and threads are all twisted in the same direction and which have no central core, the twisting direction of the parties and threads being the same as the threads themselves. According to a particularly suitable embodiment of the invention, the lines of the three additional reinforcing layers with the middle periphery of the tread form an angle of between 10 and 30 °; this design can bring significant advantages in terms of the effective life of the tire and is therefore especially intended for those cases where the main problem is to obtain a tire that lasts as long as possible.

Another suitable embodiment of the invention is characterized in that the width of the extra reinforcement layer radially outside the main reinforcement does not exceed the width of the main reinforcement itself, but not less than 40% of the latter width.

Further, the device according to the invention is preferably characterized in that the angle of inclination relative to the center circumference of the tread of the radially outside the main reinforcement layer's lines has the same sign as the angle of inclination of the lines in the two additional reinforcing layers which are located within the main reinforcement.

It has been found that the presence of the third auxiliary layer outside the reinforcement has a decisive influence on the tread's way of handling during driving, by cooperating very effectively with the other layers of the reinforcement or reinforcement system described. Thus, a pneumatic tire provided with such wear tire has very good characteristics with regard to driving safety, road holding and ride comfort and lacks the disadvantages mentioned above with known tires of the type in question.

An exemplary embodiment of the invention will now be described in more detail with reference to the accompanying drawing, in which;

Fig. 1 in cross-section and with parts broken away shows a tire provided with wear according to the invention, while Fig. 2 shows a part of tread one developed in accordance with Fig. 1 and with parts broken away to illustrate cord bearings etc. within the body itself. tread.

In Fig. 1, a tire is shown in the dimensions 12. 00 R 20 and consists of a tire body 2 and a wear track 1 which is removably mounted on it.

The tread line i is provided in its interior with a reinforcement 3, consisting of screw-twisted metal wire ropes, laid in a single layer with the individual ropes (see fig. 2) running approximately parallel to the tire and the tire respectively. tread center circumference. The rope used may, for example, have a structure according to the designation 7 (7X3) / 0.15 and a diameter of 2, 70 mm, whereby the designation 7 (7x3) / 0, 15 in the present case is intended to indicate that each rope is made up of seven cardboard parts, each consisting of seven parts, each with three threads, the diameter of which is 0, 15 mm.

The reinforcement has a width L of 205 mm. Two additional reinforcing layers 4 and 5 are embedded in the wear path radially within the reinforcing layer.

Both of these layers are formed by mutually parallel metal wire ropes which are symmetrically inclined with angles θ'resp. In relation to the center circumference of the tread. 8, both of which should be about 20 °. These extra layers have a width L 'of 210 mm, which is thus slightly larger than the width L. of the reinforcement 3.

Another additional reinforcing layer 6, also formed by mutually parallel metal wire cables, is embedded in the tread radially outside the main arrangement layer 3. This outer layer is also composed of mutually parallel metal wire cables, which with the center circumference of the tread form an angle Y of about 20 °. the same angle as the angle a. The extra layer 6 has a width L, which constitutes about 80% of the main arm ring even 3 width L and thus amounts to about 165 mm.

The lines in the two extras for the reinforcing layers 4 and 5 have the structural designation 7X3 / 0, 15 and 0.90 mm diameter, with the designation 7X3 / 0, 15 in this case indicating that each rope is made up of seven parts on each of three threads; each wire has a diameter of 0.15 mm. The lines in the outer reinforcement layer 6 have the structural designation 3x7 / 0, 175 (three parts each of seven threads), and, as mentioned, are struck with the same twisting direction for both the seven threads in each party and for the three parties; they have a diameter of i, 10 mm. These ropes have an apparent modulus of elasticity, for tensile stresses less than l / l 0 of the tensile stress limit, equal to 2200 kp / mm⁴.