Tyre carcass fixation

The present invention relates to a tire warp system. In particular, the invention relates to the arrangement of reinforcing warp threads in the sides and feet; also applies to attaching the warp thread to the presser foot.

The state-of-the-art reinforcing matrix solution consists of numerous fibers, most often radial, wrapped around numerous bead wires arranged in the feet. The feet consist of assemblies enabling the tire to be mounted on the rim. The stiffness of the foot formed in this way is very high.

In the state of the art, there is a lack of satisfactory solutions that have the characteristic of increasing stiffness change between the side, which should have high flexibility and the foot, which in contrast should have high stiffness. As a result, the reinforcements that are disposed in this part of the tire inevitably always exhibit some discontinuity: from the farthest end of the warp braid, you suddenly go to the zone without this warp braid, which is inevitably less rigid. To determine, the term radially upward or radially highest means towards the furthest zone from the tire axis and vice versa.

Other concepts of radial matrix are also known in the art to avoid entangling around the bead. By way of example, U.S. Patent No. 815 652, in which it was proposed to create a reinforcing warp starting from one single warp thread, following a particular track from one bead to the other, in such a way that the same warp thread gradually and successively creates reinforcement, which replaces the classic barbed wire. In the known structure, the warp thread forms U-shaped in the sides, the lower part of which is placed in the bead, concentrically in the tire. The lower part U extends in the foot for a certain length of the arch. Place these U-shaped figures as long as necessary, moving them relative to each other until they cover the entire side of the tire. In this way, a structure is obtained in which the reinforcing warp thread is seen radially forming a staircase: the lower part U is not positioned exactly along the circle contained in the plane perpendicular to the axis of the tire. This reinforcement structure adversely affects the precise positioning of the warp thread, and does not ensure very good uniformity of the tire. At present, however, the level of requirements for tires is undoubtedly higher.

The purpose of the present invention is a new arrangement of the reinforcing warp thread in a tire, which ensures a growing change in the flexural stiffness of the tire side as it approaches the bead radially, and furthermore, this system should ensure maximum uniformity of tire reinforcement in the circumferential direction.

Finally, another object of the present invention is to propose a tire reinforcement structure suitable for use in mechanized production.

The carcass arrangement in a tire according to the invention, in which the carcass is arranged on each side of the tire and is mounted in the bead of the tire, the bottom of which is mounted in the seat of the rim,

172 137, each foot monolithically and steplessly connected to the side of the tire, while the sides are connected to the tread, while the warp itself is formed of at least one single warp thread forming the front and return windings, and the foot is reinforced by a circumferentially directed warp thread in that the presser foot has warp threads which are arranged next to each other and form a peripheral system with a loop connecting the front and return windings each time, the front and return windings of the warp threads being arranged radially, and in the foot forming at least one arrangement of peripheral windings, each of which is limited, each sides in the axial direction, through at least one wall of the warp thread circumferentially arranged, with a rubber mixture layer having a hardness above 70 on the Shore A scale between them.

It is preferred that the warp thread is arranged in front and back windings between one foot and the other, passing under the tread.

It is also preferred that in the sides the warp thread is arranged radially and the loops are arranged at an internal level in the lowest part of the walls of the adjacent sheath threads.

It is also preferred that the side parts located just above the rim contact zone and below the maximum external dimension of the tire containing rubber components located on both sides of the tire meet the following relationship:

Σ E, e, (external)

Σ, E, e, (int) “where E, is a module in the radial direction, e, the thickness of each rubber component and outside and inside the warp threads, respectively.

In addition, it is preferred that the layer of the rubber mixture sandwiched between the threads is a mixture containing a synthetic SBR elastomer whose Tg is between -70 and -10 degrees Celsius, representing 40% of the total weight of the layer of the mixture.

A further advantage is that SBR is used together with PB, whose Tg is between -40 and -10 degrees Celsius, the synthetic elastomer content is at least 40% by weight of the total layer, and that the SBR used is in the form of a solution.

A further benefit is that the amount of sulfur in the mixture in the layer is between 5% and 8% of the total weight of the synthetic SBR elastomer.

It is preferred that the layer is formed of an aliphatic polyamide. It is preferred that this layer is formed of polyphenylene oxide. It is also preferred that the layer is formed of formophenolic resin.

It is also preferred that the presser foot comprises circumferentially directed warp threads arranged in a plurality of walls along its entire width, and that in each side the warp thread forms a single peripheral system of radial winding anterior and return, and coming out from one side until joining the bottom of the foot , the system is divided into at least two systems which are increasing axially apart from each other.

It is also preferred that each arrangement arranged in the bead is formed starting from one single warp thread, creating anterior and return windings, and that at the level of the sides two adjacent portions of the warp thread belong to different peripheral systems.

Furthermore, it is preferred that it comprises a wall of threads arranged circumferentially in the side portion located under the equator and that the density of the warp threads arranged circumferentially is less in the side than in the presser foot.

In this description, the term thread generally defines both single and multifilament threads or assemblies such as weaves, twists or any other suitable assemblies, irrespective of what material or treatment they have been made of, e.g. surface treatment or coating or pre-treatment wrapping to facilitate adhesion to rubber. The reinforcing warp is built in layers between two walls of the peripherally oriented warp thread with an intermediate rubber connecting layer. The warp is

172 137 called radial if its threads are arranged at an angle of 90 degrees, but in practical use, also at an angle close to 90 degrees.

It is known that in current applications warp fibers are wrapped around a bead. The wire therefore performs the function of attaching the carcass, i.e. absorbing the build-up stress in the carcass strings when loading the tire, for example by pumping. The system described herein provides such a warp function.

In the prior art, the same bead also performs the function of attaching the foot to the rim. The system described here is also capable of providing sufficient attachment.

The subject of the invention will be seen in the embodiments of the drawing, in which Figure 1 is a radial cross section showing essentially one bead and one side of the tire according to the invention; Fig. 2 is a perspective view showing only the arrangement of the reinforcement thread; 3 is a radial section showing a second embodiment of the invention; FIG. 4 - perspective view, in which part of the reinforcement threads is shown arranged in a manner corresponding to the second variant; Fig. 5 is a view showing a third embodiment of the invention in radial section showing the side and foot of the tire.

Figures 1 and 2 show a simpler embodiment. They show various well-known parts of the tire, particularly those related to the present invention, such as side 1 and foot 2. The reinforcing matrix is ​​formed by parts of the 3 warp threads here radially oriented in the sides 1. The 3 warp threads form loops 30 arranged side by side, located in foot 2. Loops 30 are adjacent and do not cross.

When arranging the warp thread in loops, avoid cutting the threads into threads, since their ends are potential weakening of the tire. In fact, the reinforcing thread is essentially a weave; the ends of the weave at the cross-sectional areas expand into many individual threads, spacing apart. In these places, tears inside the tire occur. If the threads are made of textile materials, they are glued to ensure very good adhesion to the rubber. Unfortunately, there is no initial sticking of each end of the weave after cutting, which means that there the rubber does not stick to the cutting site, which often causes tears inside the foot. When deployed herein, this type of inconvenience does not cause concern.

Due to the presence of the loop between the anterior and return winding, it can be seen that the warp is made of a single thread. Of course, the warp may not be manufactured continuously from one single strand. According to the present invention, however, it is good to use a number of threads and place the beginnings and ends of the thread in the tread rather than in the feet.

To ensure perfect assembly of the carcass, a layered foot is made. Inside the foot 2, on one side and on the other side of the windings of the front and return threads 3 warp wall of threads directed peripherally to walls 61 and 62, with a rubber mixture between layer 5 with hardness over 70 Shore A in each at wall 61.62, the 3 warp threads are substantially concentric and superimposed.

It is not necessary to add a rubber mixture that would ensure the impregnation of the 3 warp threads or windings of the threads forming the walls 61 and 62, but the direct contact of the 3 warp threads circumferentially directed with the 3 warp threads directed radially should be prevented. The same type of mixture ensures alignment and connection between 3 warp parts from the same wall, and between different walls of 3 warp threads by impregnation during forming.

The research provided interesting results regarding the usability, for the inside layers of rubber made of a mixture containing a synthetic SBR elastomer used as pure or together with polybutadiene, said SBR has a solidification temperature (Tg) between -70 and -30 degrees Celsius, and said polybutadiene has a Tg between -40 and -10 degrees Celsius, the synthetic elastomer (s) accounts for up to 40% of the total weight of the elastomer, the rest is natural rubber. The considered Tg are measured by differential thermal analysis. The SBR solution is most preferably used.

172 137

For example, a mixture containing a 50% SBR solution having a Tg of -48 degrees Celsius, 50% NR, with the addition of reinforcing components and resins is used to obtain the desired hardness on the Shore A scale. A layer of rubber 5 can be obtained in vulcanized tires , because 3 warp threads and / or threads were wound winding the walls 61, 62 sufficiently wrapped in rubber so that after forming a layer 5 appears, which has just been described.

Instead of rubber-based mixtures as previously mentioned, thermoplastic resins (aliphatic polyamides, polyphenylene oxides) or thermosetting resins (formophenolic resins), which provide sufficient rigidity and viscosity, can also be used.

To obtain a good bonding of the rubber layer 5 simultaneously on the metal strands of the brass walls 61 and 62 and on 3-warp textile threads, and to ensure good adhesion strength to high temperatures, said rubber layer contains a significant amount of sulfur and uses adhesion promoting ingredients (e.g. salts of metallic cobalt or nickel) in well-measured proportions. For example, sulfur is used in an amount of between 5% and 8% of the total weight of the elastomer, and cobalt in an amount of 0.2% of the total weight of the elastomer.

To ensure a very good response to the stresses occurring in the threads under the influence of pumping pressure, it is desirable that said turns are arranged radially at a lower level in the lowest part of the adjacent walls of the circumferentially oriented warp threads.

Most preferably, when the 3 warp thread forms the front and return windings from one bead 2 to the other bead of the tire under the tread. Various tire reinforcement assemblies are not part of the present invention. It is enough to indicate that they can be produced by all methods of appropriate reinforcement, such as by threads arranged in a manner forming a triangular ring. In addition, of course, a very rigid rubber mixture can be placed in the tread in the manner used to create the tie layer on the tie rod of classic tires. This rubber of the connecting layer can be arranged on one and / or the other side of the reinforcing matrix.

While the tire mounted on the rim for which it is intended, tolerates various deformations, the zone of contact with the rim, i.e. the part of the bead located under the rim's edge, is subjected to virtually no deformation. The highest part of the side, i.e. generally between the maximum outer dimension and the center of the side of the tire, bends enough to give the tire the necessary flexibility.

In order to ensure the smoothest passage possible between the zone in contact with the rim and the maximum outer dimension of the tire above the zone of contact with the rim and below the equator, the rubber components located on one and the other side of the carcass meet the following relationship:

Σ 15, e, (external)

Σ, E, e, (int) ~ where E1 is a module in the radial direction, e, the thickness of each rubber component and outside 70 and inside 71 warp threads respectively. If there are numerous layers of braids in this part of the warp, only the components on the outside of the 3 outermost warp threads and inside the 3 inner warp threads respectively are relevant for the application of this formula.

When the modulus of each of the components used is comparable, it means that it is possible to move the warp as far as possible from the inside of the side 1. It is also possible to use more flaccid rubbers (i.e. with a smaller module) from the inside of the side. This provides the right compromise between tire strength and comfort offered.

172 137

In Figs. 3, 4 and 5 it can be seen that in each side 1, the 3 warp thread forms a single circumferential system of the portion of the 3 warp threads circumferentially spaced apart, whereby starting from one side to attach to foot 2, the warp is divided into two systems circumferential radial threads 31.32 stepping apart gradually, axially one from the other. Each peripheral arrangement of the radial threads is limited, as described above, on each side by a wall of threads directed peripherally with a layer of rubber between them as described above. The system 31 is bounded by the walls 61 and 62, the system 32 is bounded by the walls 62 and 63. All the walls of the circumferentially directed threads are formed as spiral coils. It is preferred that the central wall 62 rises radially higher than the side walls 61 and 63.

In this way, a path arrangement is obtained which appears very clearly in the perspective of Fig. 4, where it can be clearly seen that the different arrangements are separated by the walls of the circumferentially directed thread.

Of course, more than two peripheral systems of radial threads that are radially spaced apart may be used. In this case, each system is formed starting from one single warp thread, creating anterior and return windings. Parts of the thread from different systems are arranged in such a way that in the sides 1 two adjacent threads 3 warp were elements of other systems in the foot 2. In other words, threads from different systems are interwoven together in the side, but not in the foot 2 in such a way that also there the threads of each system do not cross.

This second variant is particularly interesting because, at the level of the side of the tire 1, there is exactly one circumferential arrangement of a part of the radial thread (in exactly one layer). This provides great flexibility for the sides: it reduces the stiffness of the deformation of the side 1 when the tire expands, because such a structure remains thin, much thinner than when there are two warp coils, as in the technologies currently used.

As the foot 2 approaches, the warp threads 3 split into two peripheral systems, which gradually separate from each other, of course you can adjust the height at which this separation is to take place in many systems, placing the rubber inside the selected height.

In this way, the deformation rigidity increases. In addition, it is divided by two number of parts of radial warp threads in one arrangement within the foot, relative to the number of parts of radial warp threads in one single arrangement in the side, which is particularly interesting because the area at the height of the foot is much smaller, there is a lot less space to place 3 warp threads in the pattern than in side 1. Such displacement of the warp threads facilitates precise laying in place with good rubber impregnation.

Fig. 5 shows a third embodiment of the invention. Inside foot 2, peripheral threads of warp thread 64 and 65 are added. Between the warp threads 3 there is only a very thin layer of rubber, i.e. layers not wider than the diameter of the thread of the coil or systems.

In the same figure it can be seen that there are portions of thread 66 directed radially towards the top in part of side 1 located under the equator. This makes it possible to give the course of various forms a natural balance of the radially expanded matrix. You can also precisely shape the tire while it is inflated on the wheel. You can also use threads from nature in the sides and foot or inside them. Preferably, the density of the circumferentially directed 3 warp threads is lower in the sides 1 than in the feet 2. It is desirable that the change in density occurs in an increasing manner to ensure the smoothest passage between the bead and the side 1 of the tire.

It can be seen that the structure of the reinforcement proposed for the radial matrix enables a progressive evolution of stiffness between the side and foot. This structure provides the tire with a great opportunity to regulate stiffness and its evolution by simply changing the density of the circumferentially directed threads and possibly the number of peripheral systems of the radial threads in the bead, and by changing the type of thread.

The proposed structure does not present any discontinuity in reinforcement, which is very beneficial for tire durability, and also leads to greater tire comfort.

To position the reinforcing threads as precisely as possible, it is preferable to manufacture the tire on a rigid core that imposes the form of the inner cavity of the tire. Placed on the core, in the order required by the final architecture, all tire components that are unfolded directly at their destination, without shaping at any time during manufacture. In this case, the tire may be shaped and vulcanized as described in US 4,899,892.

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