GB1590013A - Tyres - Google Patents

Description

(54) TYRES (71) We, EUTECO Sp.A., an Italian Joint Stock Company, of 11, via Galiani, Milan, Italy do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to improvements in radial tyres.

Radial tyres are known which comprise a carcass formed of one or more plies having reinforcing cords disposed in radial, or substantially radial, planes and a tread, stiffened by a crown reinforcement, the said reinforcement being located between the tread and the carcass and having a width substantially equal to that of the tread.

The plies forming the carcass and the crown reinforcement usually comprise cords of natural or synthetic textile material, or metallic material or fibreglass and in particular the crown reinforcement comprises two or more plies the cords of which usually form angles of from 10 to 300 with the equatorial plane of the tyre.

It is known that when using such tyres on vehicles which travel at high speeds, or which operate at low speed but under heavy load conditions, there can occur separation between the crown reinforcement and the elastomer of the tyre, in correspondence with the end of the cords forming the reinforcement, because of the centrifugal force or as a result of excessive flexing movements.

According to the present invention there is provided a tyre comprising a carcass formed of one or more plies having reinforcing cords disposed in radial, or substantially radial, planes and a crown reinforcement under the tread and having a width substantially equal to the width of the tread, the crown reinforcement comprising two or more superimposed plies, a respective protective ply being folded around each edge of each ply of the crown reinforcement so as to be of U-shape in crosssection, and each protective ply comprising cords of natural or synthetic textile material and having a width as considered unfolded which is less than that of the associated crown reinforcement ply.

Using the tyre according to the invention the said problems associated with separation are avoided, or at least greatly reduced.

In the tyre according to the present invention the following individual characteristics can be identified: - One or more carcass plies comprising cords in radial or substantially radial planes which may be of natural or synthetic textile material, or of metallic material or fibreglass.

- Two or more plies of crown reinforcement comprising cords which may be of natural or synthetic textile material, or of metallic material or fibreglass. These cords may form angles of from 10- to 300 with the circumferential direction.

- Protective plies, equal to twice the number of plies forming the crown reinforcement, the cords of which comprise natural or synthetic textile materials and which in particular may be of aliphatic polyamide such as that known under the commercial name of "nylon".

Therefore, according to the present invention around every edge of every ply of the crown reinforcement a respective protective ply is folded in the form of a U. In this way a number of folds are formed, each fold housing one edge of a ply of the crown reinforcement at the zone where the cords are cut. The number of folds thus formed is accordingly equal to twice the number of plies forming the crown reinforcement.

It has been found that by operating in accordance with the present invention substantial improvements are achieved in the jointing characteristics between the edges of the crown reinforcement plies and the surrounding elastomeric mixture, or indeed, in other words, reductions in phenomena of separation which would occur under high speed or heavy load conditions. These improvements are acheived mainly in the case of crown reinforcements comprising metallic cord plies, expecially of steel and in every case because the edges of each of the plies forming the crown reinforcement are individually protected.

The desirable results which are achieved by operating in conformity with the present invention can probably be attributed to various factors. In the first place, the edges of the superimposed plies, forming the crown reinforcement, are spaced from one another by means of the thickness of the protective plies.

This spacing between the reinforcement plies is more regular and constant than when operating according to the prior art, for example, by means of the use of strips formed only of elas tomer material wound around the edges of the reinforcement plies. In fact an elastomer mixture can undergo a decrease in thickness because of the moulding pressure applied to an almost fluid material during the stage imme diately preceding the vulcanization stage. Such a disadvantage does not arise when one uses protective plies formed of textile materials which, by their very nature, are practically incompressible. Neither, on the other hand, is it easy to keep regular and constant the distance between the edges of the reinforcement plies in those embodiments of the prior art in which the same U-section ply houses the ends of two or more of the said plies.

By operating according to the present invention, there may be provided in a simple and efficient manner a greater distance at the ends of the reinforcement plies , which avoids concentration of the stresses.

The application of the protective plies according to the present invention allows one to achieve particularly favourable results in the case of crown reinforcements formed of metallic material. In fact, protective plies of textile material, especially polyamides, have shown a particularly efficient bonding between materials of characteristics as different as those of metal and the elastomer mixture.

When the separation between the edges of the crown reinforcement ply and the elastomer mixture is mainly due to the centrifugal force (i.e. for tyres for use at high speeds), the cords forming the protective ply are suitably disposed so as to form angles of from 3 to 140 with the equatorial plane of the tyre. In this case, the protective ply folded in the form of an U, forms a slightly extensible ring which opposes the centrifugal force tending to spread apart the edges of the crown reinforcement of the carcass.

The efficiency therefore depends on the fact that the cords are anchored to the radially innermost face and to the radially outermost face of the end of each reinforcement ply, thus giving rise to a stronger overall structure with maximum values in correspondence with the area in which the cords of the protective ply form the fold.

When the separation between the end of the crown reinforcement ply and the elastomer mixture is due essentially to heavy load conditions, the cords forming the proctive ply conveniently form angles of 450 to 900 with the equatorial plane of the tyre.

It is known that in the more common case of metallic crown reinforcements one observes, after short periods of operation, small separations between the free ends of the cords forming the plies of the said reinforcement which have no galvanic coating because of the cutting and the surrounding elastomer. These small separations are the origins of separations of greater importance. The application of the protective plies makes it possible to limit this undesirable phenomenon in an efficient manner, in consequence of the decrease of the relative movements between the elastomer mixture and the cords of the crown reinforcement. In fact, at the most critical point one has the presence of a fold of material less rigid than the steel, in which the cords possess optimum bonding characteristics with the elastomer mixture.

The invention will now be illustrated with reference to the accompanying drawings, in which: Figure 1 illustrates in cross section a tyre according to the present invention; Figure 2 illustrates on an enlarged scale one half of a crown reinforcement ply having a protective ply folded in a U around its edge; Figure 3 shows in plan the disposition of the cords of a protective ply with respect to the disposition of the cords of a crown reinforcement ply.

With more particular reference to Figure 1, the numeral 1 indicates the tread, 2 the side walls, 3 a radial carcass ply, 4 an internal rubber protective strip and 5 the bead cores around which the ply 3 is wound.

In the same Figure Al and A2 show the plies of the crown reinforcement each having a protective ply folded around each edge thereof in the form of a U. More particularly, the protective plies P1 and Pal', applied to the reinforcement ply Al and the protective plies P2 and P2' applied to the reinforcement ply A2 are folded such that each limb of the U has a length which can vary from 5 to 305S with respect to the total width of the reinforcement ply.

Furthermore, each protective ply can be symmetrically folded and therefore each limb of the U has substantially the same length, or can be folded asymmetrically, thus presenting different limb lengths. In the latter case, configurations are possible in which the free ends of the plies assume a suitable staggering, the amount of such staggering having a maximum value equal to 15 mm.

In a typical embodiment of the present invention the protective plies are formed of a polyamide fabric (commercial name "nylon") having a yarn count of 940 X 2 dtex, containing 12 cords per centimeter, counted in a direction perpendicular to that of the cords themselves.

Moreover, the fabric is rubberized with an elastomer mixture which is conveniently identical or similar to that used for the rubberization of the metal fabrics forming the reinforcement plies Al and A2.

The protective plies are cut at an angle of 8" and have an unfolded width of 35 mm.

Figure 2 shows diagramatically and on an enlarged scale one half of the reinforcement ply Al of Figure 1 and at the right end of the said reinforcement ply the protective ply P1 is applied.

By way of example, the latter is formed of a polyamide fibre fabric (as defined hereabove) having an unfolded width of 35 mm.

Furthermore, the part L1 of the ply P1, adhering to the radially innermost surface has a length equal to 20 mm, whilst the part LE, adhering to the outermost surface of the ply A1, has a length of 15 mm. Thus the staggering between the two parts is equal to 5 mm and furthermore the two parts form the fold C which contains one edge of the reinforcement ply Al.

Figure 3 shows in plan a protective ply folded around one edge of a crown reinforcement ply.

In this case, the parts of the protective ply, which adhere to the two upper and lower surfaces of the reinforcement ply, have a length indicated by L in the Figure.

Moreover, the cords forming the protective ply form an angle with the equatorial plane of the tyre, the said plane being parallel to the fold formed by the parts themselves and the said angle assuming values of from 3 to 140 or from 45 to 90 , when the casing is used for tyres intended for high speeds or for high loads respectively .

With further reference to Figure 3 the cords forming the protective ply pass from one edge K to the other edge K' forming the fold C, which in the case under discussion is located halfway along the path between K and K'.

This fold encloses and surrounds the ends of the cords of the reinforcement ply, and Figure 3, for the sake of simplicity, shows only two of these cords indicated by the letters M and N.

The cords of the reinforcement ply form, moreover, angles with the equatorial plane of the tyre which usually assume values of from 100 to 300 in conformity with the prior art.

WHAT WE CLAIM IS: 1. A tyre comprising a carcass formed of one or more plies having reinforcing cords disposed in radial, or substantially radial, planes and a crown reinforcement under the tread and having a width substantially equal to the width ofthe tread, the crown reinforcement comprising two or more superimposed plies, a respective protective ply being folded around each edge of each ply of the crown reinforcement so as to be of U-shape in cross-section, and each protective ply comprising cords of natural or synthetic textile material and having a width as considered unfolded which is less than that of the associated crown reinforcement ply.

2. A tyre according to claim 1 wherein the protective plies comprise aliphatic polyamide cords.

3. A tyre according to claim 1 or 2 wherein the cords of the protective plies form angles of 3 to 140 with the equatorial plane of the tyre.

4. A tyre according to claim 1 or 2 wherein the cords of the protective plies form angles of 45" to 900 with the equatorial plane of the tyre.

5. A tyre according to any one of the preceding claims wherein the protective plies are coated with an elastomer mixture identical to or similar to that used for the crown reinforcement plies.

6. A tyre according to any one of the preceding claims wherein each limb of each Ufolded protective ply has a length which is 5 to 30% of the total width of the reinforcement ply to which the protective ply is applied.

7. A tyre according to any one of the preceding claims wherein each protective ply is folded such that each limb of the U-folded ply is of substantially the same length.

8. A tyre according to any one of claims 1 to 6 wherein each protective ply is folded such that the limbs of the U-folded ply have different lengths having a difference of up to 15 mm.

9. A tyre according to any one of the preceding claims wherein the cords of the crown reinforcement plies form angles of 10 to 30 with the equatorial plane of the tyre.

10. A tyre substantially as described herein with reference to and as illustrated in Figures 1 to 3 of the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (10)

**WARNING** start of CLMS field may overlap end of DESC **. is applied. By way of example, the latter is formed of a polyamide fibre fabric (as defined hereabove) having an unfolded width of 35 mm. Furthermore, the part L1 of the ply P1, adhering to the radially innermost surface has a length equal to 20 mm, whilst the part LE, adhering to the outermost surface of the ply A1, has a length of 15 mm. Thus the staggering between the two parts is equal to 5 mm and furthermore the two parts form the fold C which contains one edge of the reinforcement ply Al. Figure 3 shows in plan a protective ply folded around one edge of a crown reinforcement ply. In this case, the parts of the protective ply, which adhere to the two upper and lower surfaces of the reinforcement ply, have a length indicated by L in the Figure. Moreover, the cords forming the protective ply form an angle with the equatorial plane of the tyre, the said plane being parallel to the fold formed by the parts themselves and the said angle assuming values of from 3 to 140 or from 45 to 90 , when the casing is used for tyres intended for high speeds or for high loads respectively . With further reference to Figure 3 the cords forming the protective ply pass from one edge K to the other edge K' forming the fold C, which in the case under discussion is located halfway along the path between K and K'. This fold encloses and surrounds the ends of the cords of the reinforcement ply, and Figure 3, for the sake of simplicity, shows only two of these cords indicated by the letters M and N. The cords of the reinforcement ply form, moreover, angles with the equatorial plane of the tyre which usually assume values of from 100 to 300 in conformity with the prior art. WHAT WE CLAIM IS:

1. A tyre comprising a carcass formed of one or more plies having reinforcing cords disposed in radial, or substantially radial, planes and a crown reinforcement under the tread and having a width substantially equal to the width ofthe tread, the crown reinforcement comprising two or more superimposed plies, a respective protective ply being folded around each edge of each ply of the crown reinforcement so as to be of U-shape in cross-section, and each protective ply comprising cords of natural or synthetic textile material and having a width as considered unfolded which is less than that of the associated crown reinforcement ply.

2. A tyre according to claim 1 wherein the protective plies comprise aliphatic polyamide cords.

3. A tyre according to claim 1 or 2 wherein the cords of the protective plies form angles of 3 to 140 with the equatorial plane of the tyre.

4. A tyre according to claim 1 or 2 wherein the cords of the protective plies form angles of 45" to 900 with the equatorial plane of the tyre.

5. A tyre according to any one of the preceding claims wherein the protective plies are coated with an elastomer mixture identical to or similar to that used for the crown reinforcement plies.

6. A tyre according to any one of the preceding claims wherein each limb of each Ufolded protective ply has a length which is 5 to 30% of the total width of the reinforcement ply to which the protective ply is applied.

7. A tyre according to any one of the preceding claims wherein each protective ply is folded such that each limb of the U-folded ply is of substantially the same length.

8. A tyre according to any one of claims 1 to 6 wherein each protective ply is folded such that the limbs of the U-folded ply have different lengths having a difference of up to 15 mm.

9. A tyre according to any one of the preceding claims wherein the cords of the crown reinforcement plies form angles of 10 to 30 with the equatorial plane of the tyre.

10. A tyre substantially as described herein with reference to and as illustrated in Figures 1 to 3 of the accompanying drawings.