DURING TYRE PRODUCTION

TECHNICAL FIELD

The present invention relates in general to the manufacture of reinforced rubber layers and of vehicle tyres manufactured therewith. More particularly, the present invention relates to the conservation of planarity in continuous reinforced rubber layers prior to final building of the green tyre.

CONTEXT

For tyre manufacturers, efforts aimed at reducing tyre mass have included reducing the thickness of tyre belts made up of multiple plies or layers. Following such efforts, reinforced rubber layers provided for a tyre belt exhibit in a known manner one or more

continuous metal reinforcements (or "reinforcements" or "continuous metallic reinforcements") . Tyres produced with such layers exhibit lower weight and improved rolling resistance. Examples of tyres including such reinforced rubber layers are disclosed in patent publications by the same assignee, WO2015/014574, WO2015/014575, and WO2013/117476.

In order to produce reinforced rubber layers, it is known practice to calender the metal reinforcements between two skim layers of unvulcanized rubber so that reinforced rubber layers are produced. When the green tyre is being built, the resulting layers are cut to the desired size and assembled to form a green tyre. The layers offered for tyre building often exhibit a lack of uniformity or a lack of planarity that can be attributed to the curvature of the metal reinforcements (for example, as demonstrated by the shifting of at least part of one reinforcement with respect to other reinforcements and with respect to the thickness of the rubber) . This curvature may be attributed to numerous causes including, without limitation, a residual torsion in the reinforcement itself and an incorrect orientation of the reinforcements ahead of the

calendering unit. The resulting lack of uniformity makes it difficult to align the reinforcements in adjacent layers during tyre building.

The new materials require increasingly rigid reinforcements, necessitating improvements to material planarity . SUMMARY

One effective proposed solution involves

additional plastic deformation of the reinforced rubber layer and, therefore, of the reinforcement, in a direction that is the opposite to that of the observed curvature. Such a solution is easily implemented in an existing tyre production plant without the need to change the overall operation of the plant.

The present invention relates to a correction installation for ensuring the planarity of a rubber layer reinforced with continuous metallic

reinforcements laid parallel to one another and

extending longitudinally between opposite ends of a rubber layer. The correction installation includes a correction device having a correction roller. This correction roller is an elongate cylindrical component of predetermined diameter with a curved surface along the length of which contact is established between the reinforced rubber layer and the curved surface as the layer passes through the correction installation so that, during the course of a correction process performed by the correction installation, the

reinforcements are spaced uniformly with respect to one another and are also displaced uniformly in such a way that a centre of each reinforcement remains collinear along a defined longitudinal axis through a thickness of the rubber layer.

The correction roller has a centre through which an axis of rotation of the correction roller is defined. The correction roller extends at a

perpendicular angle and rotates about its axis of rotation with respect to a frame supporting the

correction roller.

In certain embodiments, the correction

installation is positioned between an upstream roller that feeds the reinforced rubber layer to the

correction installation and a downstream roller that directs the reinforced rubber layer towards another installation that performs a subsequent step in a calendering line.

In certain embodiments, the correction

installation further includes a roller support that maintains contact with the curved surface of the correction roller so as to distribute a uniform

pressure along the length of the correction roller.

In certain embodiments, the position of the correction roller with respect to the frame is

adj ustable .

A method is also provided for ensuring the

planarity of a reinforced rubber layer.

Further aspects of the present invention will become obvious from reading the following detailed description .

BRIEF DESCRIPTION OF THE DRAWINGS

The nature and various advantages of the present invention will be better understood from reading the following detailed description, and from studying the attached drawings, in which the same reference numerals identify identical elements throughout, and in which:

Figure 1 illustrates a perspective view of one embodiment of a correction installation that forms part of a tyre production system.

Figure 2 is a cross-sectional view of a reinforced rubber layer that is received by the correction

installation of Figure 1.

Figures 3 and 4 are respective partial and cross- sectional views of the correction installation of

Figure 1.

Figure 5 is a diagram of the passage of the reinforced rubber layer with respect to a correction roller of the correction installation of Figure 1.

DETAILED DESCRIPTION

Detailed reference will now be made to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is given for the purposes of explaining, rather than limiting, the invention described. Thus, provision is made for the invention to cover these modifications and alternative forms in so far as they fall within the scope of the attached claims and equivalents thereof.

With reference now to the figures, in which the same numerals identify identical elements, Figure 1 depicts one example of a correction installation 100 that forms part of a tyre production system for producing one or more rubber products that are to be incorporated into one or more vehicle tyres. The correction installation 100 is positioned downstream of a calendering unit (not illustrated) and receives a reinforced rubber layer 10 by way of calendered product having a plurality of metallic reinforcements already incorporated therein. The calendering is performed by calendering methods that are known in the art of tyre production for producing reinforced rubber layers intended for green tyres.

As can be seen also from Figure 2, the reinforced rubber layer 10 includes a plurality of continuous metallic reinforcements 12 having a common geometry. The reinforcements 12, which can include monofilaments or cords, are laid parallel to one another and extend longitudinally between opposite ends of a rubber layer 14. After calendering, the reinforcements 12 should be spaced uniformly with respect to one another and also displaced uniformly in such a way that a centre C12 of each reinforcement remains collinear along a defined longitudinal axis X through a thickness of the rubber layer 14.

Examples of suitable reinforcements include, without limitation, reinforcements made from micro- alloyed carbon steel (0.9% carbon and 0.2% chrome) of UHT type having a breaking strength (Rm) of the order of 3650 MPa (breaking force of 258 N) and a total elongation at break (A _t ) of 2.3% (Rm and At being measured under tension in accordance with ISO standard 6892 of 1984) . Each reinforcement 12 may be any

individual steel reinforcement that has an extent in cross section (diameter or thickness) that exceeds 100 ym. The metallic reinforcements may have any suitable cross-sectional geometry.

The rubber layer 14 includes a conventional composition for the calendering of tyre belt plies and its thickness may be suited to the belt in which it will be used. The rubber layer 14 may be manufactured from a diene rubber, namely from any elastomer that is derived at least in part from a diene monomer. This diene elastomer may be selected from the group

consisting of polybutadienes (BRs) , natural rubber (NR) , synthetic polyisoprenes (IRs), butadiene

copolymers, isoprene copolymers and blends of these elastomers, such copolymers being selected from the group consisting of butadiene-styrene copolymers

(SBRs) , isoprene-butadiene copolymers (BIRs) , isoprene- styrene copolymers (SIRs) and isoprene-butadiene- styrene copolymers (SBIRs) .

A rubber composition selected for the rubber layer 14 may contain one or more diene elastomers and one or more additives commonly used in the rubber matrices intended for tyre manufacture. Such additives include, without limitation, carbon black, silica, coupling agents, anti-ageing agents, antioxidants, plasticizers, extension oils, plasticizing resins with a high glass transition temperature (higher than 30°C), agents that facilitate the processing (processability) of the compositions in the raw state, tackifying resins, anti- reversion agents, methylene acceptors and donors, reinforcing resins, known adhesion-promoting systems of the metal salt type, or a crosslinking or vulcanization system. A person skilled in the art will know how to adjust the formulation of the rubber composition in order to derive properties desired for a specific tyre.

Referring once again to Figure l,the correction installation 100 may be positioned between an upstream roller 20 that feeds the reinforced rubber layer 10 from the calendering unit to the correction

installation and a downstream roller 22 that directs the layer 10 towards another installation that performs a subsequent step in the calendering line (for example, a treatment installation or a storage installation) . It is understood that a production system with rollers 20, 22 is provided by way of example and that the

correction installation 100 can be adapted for use in existing production systems having different

configurations .

Referring once again to Figure 1 and also to

Figures 3 and 4, the correction installation 100 receives the reinforced rubber layer 10 as a calendered product that passes through the correction installation 100 via a correction device. The direction of passage is indicated in Figure 1 by the arrows A.

The correction device includes a correction roller 106 that is an elongate cylindrical component of predetermined diameter Dio6- The diameter D106 is

selected according to the properties of the materials of the reinforcement 12. The correction roller 106 has a curved surface 106a along the length of which contact is established between the reinforced rubber layer 10 and the curved surface as the layer passes through the correction installation 100.

The correction roller 106 has a centre C106 through which an axis of rotation of the correction roller is defined. The correction roller 106 extends at a

perpendicular angle and rotates about its axis of rotation with respect to a frame 109 supporting the correction roller. The position of the correction roller 106 with respect to the frame 109 is adjustable according to the properties of the reinforced rubber layer 10. These properties may include the properties of the materials of the reinforcement 12 and the thickness of the rubber layer 14.

Referring again to Figure 4 and also to Figure 5, an angular relationship is illustrated with respect to the deformation of the reinforcements 12 as the

reinforced rubber layer 10 gradually passes along an offset path through the correction installation 100. With the support of the correction roller 106, the reinforced rubber layer referred to as 10 wraps around the curved surface 106a of the correction roller 106. The points of tangency of the rubber layer with respect to the correction roller help to define an angle of wrap Θ of the layer. A portion of the rubber layer extending from the points of tangency helps to define an included angle β. For a given radius of the

correction roller 106 and a given angle β, the rubber layer will engage with the curved surface 106a over a contact length Lio. The correction roller is positioned in such a way that it guarantees that there will be enough tension on the layer to achieve the correction.

Referring again to Figures 3 and 4, a roller support 110, which is optional, may support the

correction roller 106 in a position such that the reinforced rubber layer 10 wraps uniformly around the curved surface 106a. In one embodiment, the roller support 110 maintains contact with the curved surface 106a of the correction roller 106 so as to distribute a uniform pressure along the length of the correction roller. In this way, the uniformity of the contact between the correction roller 106 and the entire width of the reinforced rubber layer 10 is ensured.

Referring once again to Figure 2, during a

correction process performed using the correction installation 100, the longitudinal and vertical alignment of the reinforcements 12 is ensured in such a way that a maximum tolerance for a displacement Di ₂ , measured between each reinforcement centre C ₁ 2 and the longitudinal axis X of the rubber layer 14, does not exceed a predetermined tolerance for the particular rubber layer when assembled. Upon leaving the

correction installation 100, the reinforced rubber layer 10 exhibits a sufficient planarity that

facilitates its assembly with another layer during subsequent steps in the tyre production, this assembly no longer being impeded by offsets between one or more metallic reinforcement ( s ) at the extremities of adjacent rubber layers.

The terms "at least one" and "one or more" are used interchangeably. The ranges given as lying

"between a and b" encompass the values of "a" and "b".

Although particular embodiments of the disclosed apparatus have been illustrated and described, it will be appreciated that various changes, additions and modifications can be made without departing from either the spirit or scope of the present description.

Therefore, no limitation should be imposed on the scope of the invention described, apart from those set out in the appended claims.