FR3051485A1

FR3051485A1 - REINFORCING ELEMENT FOR BANDING, REINFORCED PRODUCT COMPRISING SUCH REINFORCING ELEMENT, BANDAGE COMPRISING SUCH REINFORCING ELEMENT OR REINFORCED PRODUCT, AND METHOD FOR MANUFACTURING SUCH REINFORCING ELEMENT

Info

Publication number: FR3051485A1
Application number: FR1654416A
Authority: FR
Inventors: Bastien Limozin; Philippe Lesoeurs
Original assignee: Michelin Recherche et Technique SA Switzerland; Compagnie Generale des Etablissements Michelin SCA; Michelin Recherche et Technique SA France
Current assignee: Michelin Recherche et Technique SA Switzerland; Compagnie Generale des Etablissements Michelin SCA; Michelin Recherche et Technique SA France
Priority date: 2016-05-18
Filing date: 2016-05-18
Publication date: 2017-11-24
Also published as: WO2017198559A1

Abstract

L'invention concerne un élément de renfort (10) pour bandage comprenant : - un élément filaire (12) comprenant une pluralité de filaments (14), la pluralité de filaments comprenant au moins des filaments (14) externes délimitant au moins en partie une surface externe (24) de l'élément filaire (12), et - une gaine (20) revêtant en partie la surface externe (24) de l'élément filaire (12) réalisée en une composition polymérique thermoplastique, - des interstices externes (38) à l'élément filaire délimités par la paroi interne (22) de la gaine (20) et la surface externe (24) de l'élément filaire (12) délimitée pas les filaments (14) externes, les interstices externes (38) étant essentiellement dépourvus de la composition polymérique thermoplastique, et - des interstices internes (32) à l'élément filaire (12) délimités par la pluralité de filaments (14) étant essentiellement dépourvus de la composition polymérique thermoplastique.The invention relates to a reinforcing element (10) for a bandage comprising: - a wire element (12) comprising a plurality of filaments (14), the plurality of filaments comprising at least external filaments (14) delimiting at least in part a outer surface (24) of the wire element (12), and - a sheath (20) partially coating the outer surface (24) of the wire element (12) made of a thermoplastic polymeric composition, - external interstices ( 38) to the wire element delimited by the inner wall (22) of the sheath (20) and the outer surface (24) of the wire element (12) delimited by the external filaments (14), the external interstices (38). ) being essentially devoid of the thermoplastic polymeric composition, and - internal interstices (32) to the wire element (12) delimited by the plurality of filaments (14) being substantially free of the thermoplastic polymeric composition.

Description

Reinforcement element for a tire, reinforced product comprising such a reinforcement element, a tire comprising such a reinforcing element or reinforced product, and a method of manufacturing such a reinforcing element

FIELD OF THE INVENTION

The field of the present invention is that sheathed reinforcing elements used to strengthen articles or semi-finished rubber products, such as for example bandages, including pneumatic tires. Such sheathed reinforcing elements comprise a wire element, in particular a metallic element, as well as a layer of a thermoplastic polymeric composition sheathing the wire element. The wire element generally comprises an assembly of several filaments, in particular metal monofilaments.

[002] The invention is mainly applicable to heavy vehicles such as "heavy goods vehicles", that is to say subways, buses, agricultural or civil engineering machinery, aircraft or other vehicles for transport or handling.

The present invention relates to a reinforcing element for a tire, a reinforced product comprising such a reinforcing element, a tire comprising such a reinforcing element or reinforced product, and a method of manufacturing such an element. reinforcement for bandage.

STATE OF THE ART

[004] The cladding of a metallic wire element by a layer of thermoplastic polymer composition is known in itself. The sheathing makes it possible to protect one or more metallic wire elements against various external aggressions such as oxidation or abrasion. In addition, the sheathing is performed in order to stiffen the reinforcing elements structurally, to join together if necessary several filaments, and thus to increase their resistance to buckling.

These wire elements and sheathed can then be embedded in elastomer matrices, in particular for bandages, including pneumatic tires, and more particularly to carcass plies of such bandages.

The cladding of a metallic wire element comprising a plurality of filaments is produced so that the layer of thermoplastic polymeric composition penetrates between the filaments of the wire element. Such sheathing said heart of the wire element by the thermoplastic polymeric composition allows impregnation of the thermoplastic polymeric composition and on the one hand, a good adhesion between the metal of the filaments and the thermoplastic polymer composition of the sheath and other on the other hand, a good mechanical anchoring of the sheath in the metallic wire element.

[007] On the one hand, in order to obtain a good interaction between the metal of the filaments and the composition of the sheath, and secondly, in order to promote the penetration of the thermoplastic polymer composition between the filaments, the element Wired is conventionally heat treated prior to the cladding step, for example by heating.

[008] However, the use of a core-impregnated wire element as a reinforcing element of a carcass ply can decrease its performance in endurance bending / compression. Indeed, the temperature of the carcass ply is not homogeneous during the rolling of the bandage. Thus, because of the presence of the sheath, in the highest temperature zones, especially at the shoulder of the bandage, the carcass ply has a lower rigidity due to the softening of the sheath in these high temperature zones. which results in the generation of a small radius of curvature located within the reinforcing element. This small localized radius of curvature generates significant stresses on the wire element, which penalizes the performance of said wire element in endurance.

An object of the invention is to provide a sheathed reinforcing element having improved endurance compared to the sheathed reinforcing element of the state of the art.

BRIEF DESCRIPTION OF THE INVENTION

[010] For this purpose, a bandage reinforcement element is proposed comprising: a wire element comprising a plurality of filaments, the plurality of filaments comprising at least external filaments delimiting, at least in part, an outer surface of the wire element, and a sheath partially coating the outer surface of the wire element made of a thermoplastic polymeric composition, interstices external to the wire element delimited by the inner wall of the sheath and the outer surface of the wire element delimited by the outer filaments , the external interstices being essentially free of the thermoplastic polymeric composition, and interstices internal to the wire element delimited by the plurality of filaments being essentially free of the thermoplastic polymeric composition.

[011] Advantageously, a reinforcing element according to the invention allows a movement of the filaments of the wire element in the sheath, while limiting the interactions between the wire element and the sheath.

[012] Sheath partially coating the outer surface, it is meant that the sheath is in contact with a portion of the outer surface. Thus, the sheath surrounds the entirety of the wire element but only contacts a part, and only a part, of the outer surface of the wire element. In part, therefore, it is meant that the sheath is in contact with a part, and only a part of the outer surface, that is to say that there is a part of the outer surface which is devoid of contact with the sheath.

By filament is meant an elemental monofilament and not an assembly of several elemental monofilaments.

By polymeric thermoplastic composition is meant a composition having a thermoplastic behavior, that is to say having a softening and possibly a melting with the rise in the temperature of the composition.

[015] The reinforcing element according to the invention may also comprise one or more of the following characteristics, considered individually or according to all the possible combinations: the plurality of filaments is arranged in at least one inner layer of Μ> 1 filament (s) ) internal (s) and at least one outer layer of P> 1 external filaments, the outer layer being wound around the inner layer, the internal interstices delimited by the Μ> 1 internal filament (s) and P> 1 external filaments being essentially devoid of the thermoplastic polymeric composition; and / or the P> 1 external filaments are in direct contact with the Μ> 1 internal filament (s); and / or the plurality of filaments of the wire element is arranged in at least one inner layer of Μ> 1 internal filament (s), at least one outer layer of P> 1 external filaments and at least one intermediate layer. of N> 1 intermediate filaments, the intermediate layer of filaments being arranged between the inner layer and the outer layer, the internal interstices delimited by the ou> 1 internal filament (s) and the N> 1 intermediate filaments are essentially free of the thermoplastic polymeric composition and the internal interstices delimited by the N> 1 intermediate and the outer P> 1 filaments are essentially free of the thermoplastic polymeric composition; and / or in the case where M> 1, the filaments of the inner layer are helically wound; and / or the filaments of the outer layer are helically wound around the inner layer or around the intermediate layer; and / or the filaments of the intermediate layer are wound helically around the inner layer; and / or the N> 1 intermediate filaments are in direct contact with the Μ> 1 internal filament (s) and P> 1 external filaments; and / or the outer layer is compact; and / or the plurality of filaments of the wire element is arranged in a single layer of N> 1 external filaments, the central capillary delimited by the N> 1 external filaments being essentially free of the thermoplastic polymeric composition; and / or the N> 1 external filaments are wound helically; and / or each filament is metallic; and / or the diameter of each filament is between 0.1 mm and 0.5 mm; and / or the thickness of the sheath varies from 0.05 mm to 0.5 mm, preferably from 0.10 mm to 0.15 mm; and / or the thermoplastic polymer composition comprises a thermoplastic compound selected from the group consisting of non-elastomeric thermoplastic polymers (TP), thermoplastic elastomers (TPE), vulcanized thermoplastic elastomers (TPV), functionalized thermoplastic elastomers and mixtures thereof. compounds; and / or the sheath having an inner wall, the inner wall is circular or the inner wall is substantially circular so that the surface of the external interstices is smaller than the surface that would have the external interstices in the case of a sheath having a circular inner wall.

[016] The present invention also relates to a reinforced product characterized in that it comprises: an elastomer matrix, and at least one reinforcement element according to the invention, embedded in the elastomer matrix.

[017] In addition, the invention also relates to a tire, characterized in that it comprises a reinforced product according to the invention or a reinforcing element according to the invention.

[018] Such a tire may be pneumatic, that is to say require a gas to support the load applied to it or non-pneumatic, that is to say do not require any gas to support the load that it is applied.

[019] According to one embodiment, the bandage according to the invention comprises a crown surmounted by a tread, two sidewalls, two beads, each side connecting each bead at the top, a carcass reinforcement anchored in each of the beads and extending into the flanks and into the crown, the carcass reinforcement comprising the reinforced product according to the invention or the reinforcement element according to the invention.

Another object of the invention relates to a method of manufacturing a bandage reinforcement element from a wire element comprising a plurality of filaments, the plurality of filaments comprising at least external filaments delimiting at least an outer surface of the wire element, the method comprising a casing step in which the wire element is partially coated with a sheath made of a thermoplastic polymeric composition so that the interstices external to the wire element defined by the inner wall of the sheath and the outer surface of the wire element delimited by the outer filaments are essentially free of the thermoplastic polymeric composition, and the interstices internal to the wire element delimited by the plurality of filaments are essentially devoid of the thermoplastic polymeric composition.

[021] According to one embodiment of the manufacturing method according to the invention, during the casing step, the reinforcing element is at ambient temperature.

[022] Advantageously, the step of tubing the wire element at room temperature avoids penetration of the sheath inside the wire element.

BRIEF DESCRIPTION OF THE FIGURES

[023] Other features and advantages of the present invention will appear on reading the description and the following figures: FIG. 1 is a cross-sectional view of a reinforcing element according to a first embodiment of the invention FIGS. 2 and 3 are cross-sectional views of a reinforcing element according to a second embodiment of the invention, FIG. 4 is a cross-sectional view of a reinforcing element according to a third embodiment. FIG. 5 is a cross-sectional view of a reinforced product according to one embodiment of the invention, FIG. 6 is a cross-sectional view of a reinforced product according to another embodiment of FIG. FIG. 7 is a diagrammatic cross-section of a bandage according to the invention, FIG. 8 represents a step of a method of manufacturing a bandage reinforcement element according to the invention, and FIG. e 9 illustrates flexural stiffness variations of reinforced products according to the invention and of the state of the art as a function of temperature.

[024] It should be noted that these drawings have no other purpose than to illustrate the text of the description and do not constitute in any way a limitation of the scope of the invention.

[025] In the various figures, similar elements are designated by identical references.

DETAILED DESCRIPTION OF THE INVENTION

[026] The subject of the invention is a reinforcing element for a bandage. In particular, Figures 1 to 4 show cross sections of different embodiments of a reinforcing member according to the invention.

[027] A reinforcing element 10 according to the invention comprises a wire element 12 and a sheath 20.

[028] A wire element is an elongate element having a length greater than the dimensions of its cross section, whatever the shape of its cross section. In particular, the cross section may have a circular, oblong, rectangular, square, or even flat shape. The wire element is preferably rectilinear, but may also be non-rectilinear, for example twisted or corrugated.

[029] In particular, the wire element 12 comprises a plurality of filaments 14. More specifically, the wire element comprises an assembly of filaments, the filaments being arranged in one or more concentric layers, the filaments of the same layer being helically wound around the direction of elongation of the wire element. The filaments can be assembled by wiring or twisting. In the case of wiring, the filaments are not twisted about their own axis due to synchronous rotation before and after the point of assembly. In the case of twisting, the filaments undergo both a collective twist and an individual twist around their own axis, which generates a detorsion torque on each of the filaments.

[030] Advantageously, each filament 14 is metallic. Each filament 14 preferably has a diameter of between 0.1 mm and 0.5 mm.

[031] Each filament 14 comprises a metal core, for example steel. According to one embodiment of the invention, each filament 14 comprises a metal coating coating the metal core. The metal coating is for example zinc or brass. According to another embodiment, each filament 14 is devoid of metal coating coating the metal core.

[032] In particular, the plurality of filaments 14 comprises at least external filaments 14 delimiting at least in part an outer surface 24 of the wire element 12. In FIGS. 1 to 4, the outer filaments 14 of the wire element 12 are hatched with the same hatching, different from the hatching of the other filaments of the wire element 12.

[033] The sheath 20 partially covers the wire element 12, and more specifically a portion of the outer surface 24 of the wire element 12. In other words, a portion of the inner wall 22 of the sheath is in contact with a part of the outer surface 24 of the wire element 12, and therefore with a portion of the outer filaments 14 of the wire element 12.

[034] According to one embodiment, the sheath 20 may be in contact with all the external filaments 14 of the wire element 12, as illustrated in FIGS. 1, 3 and 4, or may be in contact with only a portion of the wires. external filaments 14 of the wire element 12, as for example represented in FIG.

[035] According to one embodiment of the invention, the radial thickness of the sheath 20, that is to say the distance between the outer wall 30 of the sheath 20 and the inner wall 22 of the sheath 20, is substantially constant. For example, as shown in Figures 1, 2 and 4, in a cross section of the reinforcing member, the sheath 20 is annular, the inner wall 22 of the sheath being circular. The volume delimited by the outer surface 24 of the wire element 12 and a theoretical circle in which the wire element is circumscribed is filled to less than 10% by the thermoplastic polymer composition. When the inner wall 22 of the sheath is circular, as shown in Figures 1, 2 and 4, the volume defined by the outer surface 24 of the wire element 12 and the theoretical circle circumscribing the wire element is filled to 0 % by the thermoplastic polymeric composition. More precisely, when the inner wall 22 of the sheath is perfectly circular, the inner wall 22 of the sheath corresponds to the theoretical circle in which the wire element 12 is circumscribed.

[036] According to another embodiment of the invention, the radial thickness of the sheath 20 varies. For example, as shown in Figure 3, in a cross section of the reinforcing member, the outer wall of the sheath is circular, and the inner wall of the sheath is substantially circular. The volume delimited by the outer surface 24 of the wire element 12 and the theoretical circle circumscribing the wire element is filled to at most 50% by the thermoplastic polymer composition. Preferably, the volume delimited by the outer surface 24 of the wire element 12 and the theoretical circle circumscribing the wire element is filled to at most 30%, and more preferably to at most 10%, by the thermoplastic polymeric composition. . In other words, the thermoplastic polymeric composition enters the theoretical circle in which the wire element 12 is circumscribed.

[037] Preferably, the sheath has a minimum thickness of 0.05 mm, and a maximum thickness of 0.5 mm. Preferably, the sheath has an average thickness ranging from 0.10 mm to 0.15 mm. In general, the diameter of the reinforcing element is between 1 mm and 1.5 mm.

[038] Advantageously, a movement of the filaments of the wire element in the sheath is possible, and the interactions between the inner filaments of the wire element and the sheath are limited. On the one hand, the lack of impregnation at heart of the wire element by the sheath and secondly, the adhesion between the sheath and the wire element being limited to external filaments, one can thus control the rigidity of the wire element, as well as the movement of the filaments during a cyclic loading of the reinforcing element, for example when the latter is used in a bandage.

The sheath 20 is made of a thermoplastic polymeric composition. Advantageously, the thermoplastic polymeric composition makes it possible to protect the wire element against oxidation. Indeed, the sheath is an effective barrier against corrosive agents likely to penetrate the reinforcing element.

[040] According to one embodiment of the invention, particularly illustrated in Figures 1 to 4, the sheath 20 comprises a single layer consisting of a thermoplastic polymeric composition. According to a variant (not shown), the sheath comprises a plurality of concentric layers, at least the radially innermost layer being made of a thermoplastic polymeric composition. Such sheaths are described in particular in WO2010 / 136389, WO2010 / 105975, WO2011 / 012521, WO2011 / 051204, WO2012 / 016757, WO2012 / 038340, WO2012 / 038341, WO2012 / 069346, WO2012 / 104279, WO2012 / 104280, WO2012 / 104281, WO2013 / 117474 and WO2013 / 117475.

[041] In particular, the thermoplastic polymer composition comprises a thermoplastic compound selected from the group consisting of non-elastomeric thermoplastic polymers (TP), thermoplastic elastomers (TPE), vulcanized thermoplastic elastomers (TPV), functionalized thermoplastic elastomers and mixtures of these compounds.

[042] Preferably, when a non-elastomeric thermoplastic polymer is used, it is chosen from a polyester, a polyamide, a polyketone, a cellulose, a polyphenylene ether or a mixture of these materials. Preferably, a non-elastomeric thermoplastic polymer is chosen from a polyester and a polyamide.

[043] Preferably, the polyester is chosen from a polyethylene terephthalate (PET), a polyethylene naphthalate (PEN), a polybutylene terephthalate (PBT), a polybutylene naphthalate (PBN), a polypropylene terephthalate (PPT) and a polypropylene naphthalate (PPN) and more preferably is polyethylene terephthalate (PET).

[044] The polyamide is preferably an aliphatic polyamide, for example nylon.

[045] Preferably, when a thermoplastic elastomer (TPE) is used, it is a styrenic elastomer (TPS). The thermoplastic elastomer (TPE) may be functionalized and / or unsaturated.

[046] A reinforcing element 10 according to the invention also comprises external interstices 38 and internal interstices 32.

[047] The external interstices 38 to the wire element 12 are delimited by the inner wall 22 of the sheath and the outer surface 24 of the wire element delimited by the outer filaments 14. In other words, an external gap 38 is a space free of material between the sheath 20 and the wire element 12. For example, when the inner wall 22 of the sheath is circular, as shown in FIGS. 1, 2 and 4, a outer gap 38 is delimited by the circle circumscribing the wire element 12, corresponding to the inner wall 22 of the sheath, and the outer surface 24 of the wire element 12.

[048] The interstices internal to the wire element 12 are delimited by the plurality of filaments 14. For example, an internal gap may be a space free of material between two successive layers of filaments or, in the case where the wire element comprises a single layer of N filaments, a free space of material radially internal to the outer layer of filaments.

[049] In particular, the internal interstices 32 and the external interstices 38 are essentially devoid of the thermoplastic polymeric composition. In other words, according to a cross section of the reinforcing element, the internal interstices 32 and the external interstices 38 have a surface totally free of the thermoplastic polymeric composition greater than or equal to 90%. Preferably, at least 95% of the area of the internal interstices 32 is completely free of the thermoplastic polymeric composition, and at least 95% of the area of the external interstices 38 is completely free of the thermoplastic polymeric composition.

[050] A first embodiment of the reinforcing element according to the invention is shown in FIG.

[051] According to this first embodiment, the plurality of filaments 14 is arranged in two layers, an inner layer 16 and an outer layer 18. The inner layer 16 comprises a number M greater than or equal to one of internal filament (s) (s), for example the number M of internal filament 14 is equal to one in FIG. 1. The outer layer 18 comprises a number P strictly greater than one of external fdaments, for example the number P of external filaments 14 is equal to six in Figure 1. In particular, the wire element 12 is a wire element with two layers M + P.

[052] The outer layer 18 is wound around the inner layer 16. Preferably, the outer P filaments 14 are in direct contact with the internal filament (s) 14 or (s). The filaments 14 of the outer layer 18 are wound helically around the inner layer 16. When M> 1, the filaments 14 of the inner layer 16 are helically wound.

[053] Advantageously, the outer layer 18 is compact. More specifically, the filaments 14 of the outer layer 18 are in pairs in contact with each other. Advantageously, a compact outer layer 18 makes it possible to prevent the penetration of the thermoplastic polymer composition between the filaments 14 of the outer layer 18, and consequently into the internal interstices 32 of the wire element 12.

[054] In particular, the outer 30 and inner walls 22 of the sheath are circular. The external interstices 38 to the wire element 12 are delimited by the circle circumscribing the wire element and by the outer surface 24 of the wire element 12.

[055] The internal interstices 32 to the wire element 12 are delimited by the inner layer 16 and the outer layer 18 of filaments 14 of the wire element 12. In particular, the internal interstices 32 are delimited by the or Μ> 1 filament (s) 14 internal (s) and the outer P filaments 14. For example, the internal interstices 32, six in number in Figure 1, are delimited by the inner filament 14 and the six outer filaments 14.

[056] The internal interstices 32 are essentially devoid of the thermoplastic polymeric composition. More specifically, by "substantially" without the thermoplastic polymeric composition, it is meant that at least 90%, and preferably at least 95%, of the surface between the inner layer 16 and the outer layer 18 is completely devoid of thermoplastic polymeric composition . Otherwise, said at most 10%, and preferably at most 5%, of the surface between the outer filaments 14 and the inner filaments 14 comprises thermoplastic polymeric composition.

[057] According to an alternative, the inner wall 22 of the sheath may be substantially circular. In other words, the thickness of the sheath 20 can vary so that the surface of the external interstices 38 is smaller than the surface of the internal interstices 38 when the sheath is circular.

[058] A second embodiment of the reinforcing element according to the invention is shown in FIG.

[059] According to this second embodiment, the plurality of filaments 14 is arranged in at least three layers, an inner layer 16, an intermediate layer 26 and an outer layer 18. The inner layer 16 comprises a number M greater than or equal to one of internal filament (s), for example the number M of internal filament 14 is equal to one in FIG. 2. The intermediate layer 26 comprises a number N strictly greater than one of intermediate filaments, for example the number N The outer layer 18 comprises a number P that is strictly greater than one of external filaments, for example the number P of external filaments 14 is equal to twelve in FIG. 2. In particular, the element Wired wire 12 is a wire element with three layers M + N + P.

[060] According to this embodiment, the intermediate layer 26 is arranged between the inner layer 16 and the outer layer 18. In other words, the outer layer 18 is wound around the intermediate layer 26, and the intermediate layer 26 is wound around of the inner layer 16. Preferably, the N filaments 14 of the intermediate layer 26 are in direct contact with the M filaments 14 of the inner layer 16 and with the P filaments of the outer layer 18. The P filaments 14 of the outer layer 18 are helically wound around the intermediate layer 26 and the N filaments 14 of the intermediate layer 26 are wound helically around the inner layer 16.

[061] Advantageously, the outer layer 18 and the intermediate layer 26 are compact. Advantageously, a compact outer layer 18 makes it possible to prevent penetration of the thermoplastic polymer composition into the internal interstices 34 of the wire element, and a compact intermediate layer 26 makes it possible to prevent penetration of the thermoplastic polymer composition into the internal interstices 36 of the wired element.

[062] As illustrated in Figure 2, the outer gaps 38 to the wire element 12 are delimited by the inner wall 22 of the sheath and the outer surface 24 of the wire element 12, the inner wall 22 of the sheath being circular.

[063] According to this embodiment, the internal interstices 34 to the wire element 12 are delimited by the inner M filaments 14 and N intermediate filaments 14. The internal interstices 36 at the wire element 12 are delimited by the N intermediate filaments 14 and the external P filaments 14. In other words, the internal interstices 34 are delimited by the filaments 14 of the inner layer 16 and the intermediate layer 26, and the internal interstices 36 are delimited by the filaments 14 of the intermediate layer 26 and the outer layer 18.

[064] The internal interstices 34, 36 are essentially free of the thermoplastic polymeric composition. More specifically, by "essentially" without the thermoplastic polymeric composition, it is meant that at least 90%, and preferably at least 95%, of the surface between the inner layers 16, intermediate 26, and outer 18 is completely free of composition thermoplastic polymer. In other words, at most 10%, and preferably at most 5%, of the surface between the outer filaments 14 and the intermediate filaments 14 and the surface between the inner filaments 14 and the intermediate filaments 14 comprises polymeric composition thermoplastic.

[065] An alternative to the second embodiment of the reinforcing element according to the invention is shown in FIG.

[066] In this alternative, the inner wall 22 of the sheath is substantially circular, so that the thickness of the sheath 20, that is to say the distance between the outer wall 30 and the inner wall 22 of the sheath, varies. In other words, in a cross section of the reinforcing element 10, the thickness of the sheath 20 is not radially uniform.

[067] In particular, the space delimited by the outer surface 24 of the wire element 12 and the theoretical circle circumscribing the wire element is filled to at most 50%, preferably at most 30%, and more preferably at most 10% by thermoplastic polymeric composition. As can be seen in FIG. 3, the thermoplastic polymeric composition penetrates into the theoretical circle in which the wire element 12 is circumscribed.

[068] In addition, according to a cross section of the reinforcing element 10, the surface of the external interstices 38 to the wire element 12 shown in FIG. 3 is smaller than the surface of the external interstices 38 to the wire element 12 represented in Figure 2.

[069] A third embodiment of the reinforcing element according to the invention is shown in FIG. 4.

[070] According to this third embodiment, the plurality of filaments 14 is arranged in a single layer of N> 1 external filaments helically wound, for example N = 5 external filaments 14 in FIG. 4. All filaments 14 of FIG. wired element are external filaments. In particular, the wire element 12 is a wired element with a 1 x N layer, also called "open cord".

[071] According to this embodiment, the central capillary 28 is delimited by the N external filaments 14. In particular, the central capillary 28 is an internal gap delimited by the N external filaments 14. The central capillary 28 is essentially free of the thermoplastic polymeric composition.

[072] According to an alternative, the thickness of the sheath 20 varies. In other words, the inner wall 22 of the sheath may be substantially circular, so that the surface of the external interstices 38 is smaller than the surface of the external interstices 38 when the sheath is circular.

[073] The subject of the invention is also a reinforced product comprising the reinforcement element according to the invention. In particular, a cross section of a reinforced product 40 is shown in FIG. 5. A reinforced product according to the invention has a general shape of strip extending in the direction of elongation of the reinforcing element.

[074] The reinforced product 40 comprises an elastomer matrix 42, in which is embedded at least one reinforcing element 10 as described above.

[075] Advantageously, the reinforced product comprises a plurality of reinforcing elements according to the invention. For example, as shown in FIG. 6, the reinforced product 40 may comprise three reinforcing elements 10, the reinforcing elements being aligned.

[076] The subject of the invention is also a tire for a motor vehicle comprising a reinforced product according to the invention, or a reinforcement element according to the invention. Such a tire, here a tire 1 is illustrated in FIG.

[077] According to one embodiment, the tire 1 comprises a crown 2, two sides 3 and two beads 4. The crown 2 is surmounted by a tread (not shown) and, preferably, reinforced by a frame The beads 4 are preferably reinforced by a bead wire 5. Each flank 3 connects each bead 4 to the top 6.

[078] According to one embodiment, a carcass reinforcement 7 is wound around the two rods 5. The carcass reinforcement 7 is anchored in each bead 4. The carcass reinforcement 7 extends in the flanks 3 and until in the top 2. The upturn 8 of the carcass reinforcement 7 is disposed towards the outside of the tire 1, which is represented here mounted on a rim 9.

[079] Advantageously, a bandage according to the invention has improved performance compared to a bandage according to the prior art.

[080] Rolling tests [081] Tests carried out on tires comprising, in the carcass reinforcement, reinforcing elements according to the invention P2, on pneumatic tires comprising reinforcing elements of the state of the tire. technique in which the wire elements are core impregnated PI, and on pneumatic tires comprising wireline elements of the state of the art unsheathed PO, have made it possible to highlight the improved performance of the tire according to the invention. During these tests, during the running of the tires tested, the tires were subjected to stress under extremely demanding conditions, particularly in conditions of high drift, high speed, and high load. The reinforcement elements of the tested bandages comprise a wire element of structure (1 + 6 + 12) × 0.18 mm, that is to say a wire element comprising an internal layer of 1 internal filament, an intermediate layer of 6 intermediate filaments and an outer layer of 12 outer filaments, each filament having a diameter of 0.18 mm. The sheath used for the PO bandage is PA 66 nylon.

[082] The distance traveled by each tire PO, PI and P2 was measured. The results of these tests are collated in Table 1 below and are indicated with respect to the distance traveled by the bandage PO, the value of this reference distance being equal to 100. Thus, a value greater than 100 means that the tested bandage traveled a distance greater than the distance traveled by the PO bandage. Conversely, a value less than 100 means that the bandage tested has traveled a distance less than the distance traveled by the bandage PO.

[083] Table 1

[084] Thus, the pneumatic tire according to the invention P2 has an improved performance of 28% with respect to the pneumatic tire PO comprising non-sheathed wire elements, and an improved performance of 12% with respect to the tire PI including wire elements. impregnated to heart.

[085] Release tests [086] Release tests between the wire element and the cladding were also performed. During these tests, a reinforcing element is prepared comprising a core-impregnated wire element and a reinforcing element comprising a wire element according to the invention. There is a length of 10 cm of each wire element that is sheathed over 5 cm and that is left stripped on 5 cm. The stripped portion of the wire element is passed through a die and the die is abutted against the sheath of the sheathed portion. We fix the die and pull the unsheathed part. We then measure the force required to tear the sheath.

[087] These tests have highlighted that the average force of tearing of a sheath PA 66 of a reinforcing element comprising a wired element of structure (1 + 6 + 12) x 0.18 mm impregnated at heart is 175 N, while the average force of tearing of the same sheath of a reinforcing element according to the invention comprising a wire of the same structure is 45 N.

[088] Thus, these tests show that the force required to tear the sheath of a reinforcing element according to the invention is 3.9 times less than the force required to tear off the sheath of an element. reinforcement whose wired element is impregnated to the heart. Thus, the interaction between the sheath and the wire element within the reinforcing element according to the invention is relatively small, which increases the endurance of the reinforcing element according to the invention.

[089] Fatigue tests in flexion [090] Flexural fatigue tests were also performed on reinforcement elements according to the invention E2, on reinforcing elements of the state of the art in which the wire elements are impregnated El heart, and wire elements of the state of the art unsheathed EO.

[091] These tests are carried out on a dynamic traction machine. Each reinforcing element with a length of 90 mm is pinched between two traction jaws. The initial distance between the two jaws is set at 30 mm. A tensile stress of 10 daN and a displacement in compression of 4 mm are imposed alternately. This traction-compression cycle is carried out until the reinforcement element tested is broken. Sensors measure the number of cycles before failure.

[092] The reinforcing elements of the reinforced products E0, E1, E2 comprise a wire element of structure (1 + 6 + 12) x 0.18 mm. The sheath used for the reinforcing elements E1, E2 is nylon PA 66.

[093] The results of these tests are collated in Table 2 below and are indicated with respect to the number of cycles and the residual repulsion force measured at break of the reinforcing element E0, this number of cycles and the value of this residual repulsion force measured at break being equal to 100. Thus, a value greater than 100 means that the reinforcing element has undergone a number of cycles greater than the number of cycles of the front reinforcement element E0. break. Conversely, a value less than 100 means that the reinforcement element tested has undergone a number of cycles less than the number of cycles of the reinforcement element E0 before failure. Π is the same for the residual repulsion force.

[094] Table 2

[095] These results show that the residual repulsion force of the reinforcement element according to the invention E2 is much greater than the residual repulsion force of the reinforcement element E0 and of the same order of magnitude as that of the reinforcement element E0. El reinforcing element. Surprisingly, the number of cycles that can undergo the reinforcing element according to the invention E2 is much greater than the number of cycles that can undergo the reinforcing elements E0 and El, demonstrating a stamina largely improved.

[096] Flexural stiffness tests as a function of temperature [097] Bending stiffness tests as a function of temperature were also performed on reinforced products according to the invention R2 and on reinforced products comprising reinforcing elements of the state of the art in which the wire elements are impregnated at heart RI. Since the rigidity of the thermoplastic polymeric composition evolves as a function of temperature, a reinforced product comprising non-sheathed wire elements of the prior art RO is taken as a reference.

[098] The reinforcing elements of the reinforced products RO, RI, R2 comprise a wire element of structure (1 + 6 + 12) x 0.18 mm. The sheath used for reinforced products RI, R2 is PA 66 nylon.

[099] Each tested reinforced product comprises reinforcing elements arranged alternately with each other in a pitch of 1.7 mm and embedded in an elastomeric matrix usually used as a calender composition. Each reinforced product is in the fired state, i.e., the elastomeric matrix has been vulcanized. Each tested reinforced product has the shape of a specimen measuring 10 x 20 cm.

[100] Each test piece is fixed on one side to a fixed pivot and on the other side to a pivot mounted to move in translation in a slide. A torsion torque of the same force and opposite direction is applied to each of the pivots. The pivot mounted movable then approaches the fixed pivot and a constant radius of curvature is obtained along the specimen. As a function of the radius of curvature, the bending stiffness of the test piece is determined.

[101] In order to determine the variation of the bending stiffness as a function of temperature, the measurement is reproduced at different temperatures.

[102] The evolution of the bending stiffness Rf as a function of the temperature T is shown for the reinforced products R0, R1, R2 in FIG. 9.

[103] The reinforced product comprising unsheathed wire elements R0 has a substantially constant flexural stiffness Rf of 23 daN / mm2, irrespective of the temperature. The flexural stiffness Rf of the reinforced product R0 comprising the unsheathed wire elements is represented by the straight line I in FIG. 9. The obliquely hatched zone in FIG. 9 illustrates the flexural rigidity Rf supplied to the elastomer matrix by the elements. wired unsheathed.

[104] The reinforced product according to the invention R2 has a flexural stiffness Rf decreasing with the temperature and greater than the bending stiffness Rf of the reinforced product RO. The bending stiffness Rf of the reinforced product according to the invention R2 is represented by line III in FIG. 9. The vertically hatched area in FIG. 9 illustrates the excess of flexural rigidity Rf supplied to the elastomer matrix by the sheath. relative to the flexural stiffness Rf provided by the only unsheathed wire elements of the reinforced product RO.

[105] The reinforced product comprising core impregnated wire elements RI has a flexural stiffness Rf decreasing with temperature and greater than the flexural stiffness Rf of the reinforced products RO and R2. The flexural stiffness Rf of the reinforced product RI is represented by line II in FIG. 9. The hatched area horizontally in FIG. 9 illustrates the excess of flexural rigidity Rf supplied to the elastomer matrix by the impregnation at the core of the sheath with respect to the flexural rigidity Rf provided by the sheathed wire elements of the reinforced product according to the invention R2.

[106] These tests have shown that the higher the temperature, the greater the flexural stiffness Rf of the reinforced products R1 and R2 is close to the flexural stiffness Rf of a reinforcement product comprising unsheathed wire elements. The reinforced product according to the invention R2 has the advantage of having a lower flexural stiffness Rf than the reinforced product comprising wire elements impregnated with core R1. A posteriori, the inventors at the origin of the invention explain that, in the reinforced product comprising wire elements impregnated core Rl, the movement of the filaments of the wire element in the sheath are blocked by the impregnation heart of the thermoplastic polymeric composition. In the reinforced product according to the invention RO, the movement of the filaments of the wire element in the sheath is possible, which has the effect of reducing the flexural stiffness Rf of the reinforced product according to the invention R2. In addition, the difference in bending stiffness Rf of the reinforced product according to the invention R2 with the bending stiffness Rf of the reinforced product RO as a function of the temperature is lower than the difference in bending stiffness Rf of the reinforced product according to the prior art R1 with the bending stiffness Rf of the reinforced product RO with the temperature. In fact, the bending stiffness Rf of the reinforced product comprising wire elements impregnated with a core R1 varies from 24.5 daN / mm 2 from 20 ° C. to 110 ° C., whereas the flexural stiffness R.sub.f of a reinforced product according to FIG. The invention varies from 10 daN / mm 2 from 20 ° C to 110 ° C. A small difference in bending stiffness Rf as a function of the temperature thus makes it possible to avoid the generation of a small radius of curvature located along the reinforcing element.

[107] The invention also relates to a method of manufacturing a reinforcing element for tire as described above.

[108] The manufacturing method includes a supply step in which a wire element and a sheath are provided. In particular, the wire element comprises a plurality of filaments comprising at least external filaments delimiting an outer surface of the wire element. The sheath is made of a thermoplastic polymeric composition as described above.

[109] The manufacturing method comprises a casing step, during which the wire element of the sheath is partially coated so as to form a reinforcing element according to the invention.

[110] The wire element is coated in part of the sheath so that the interstices external to the wire element delimited by the inner wall of the sheath and the outer surface of the wire element delimited by the outer filaments are essentially free of of the thermoplastic polymeric composition, and such that the inner interstices of the wire element delimited by the plurality of filaments are essentially free of the thermoplastic polymeric composition.

[111] The method according to the invention is implemented by means of a casing device shown in FIG. 8. The casing device 44 comprises a guide 46 of the wire element 12 as well as an extrusion head 48 allowing extrusion of the thermoplastic polymeric composition in the form of a ring 50 around the wire element 12 at the outlet of the guide 46. The device comprises a suction system 52 arranged to create a depression between the ring 50 and the wire element 12 so as to press the sheath around the wire element 12. The ring 50 of thermoplastic polymer composition is driven in motion by the wire element 12. At the outlet of the extrusion head 48, reinforcing element 10, that is to say the wire element 12 sheathed, is cooled to a temperature between 5 ° C and 70 ° C, preferably between 5 ° C and 20 ° C, with air or other cold gas, or by passing through a water bath followed by drying stage.

[112] Advantageously, during the casing step, the reinforcing element 10 is at ambient temperature. Indeed, the wire element 12 is stored wound around a storage coil, and is unrolled so as to be passed through the casing device 44. The wire element 12 is not preheated before the step of casing, so as not to promote the impregnation at heart of the wire element 12 by the thermoplastic polymeric composition.

[113] In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that different features are cited in different dependent claims does not indicate that a combination of these features can be advantageously contemplated. Any reference sign in the claims should not be interpreted as limiting the scope of the invention.

Claims

A bandage reinforcing member (10) comprising: a wire member (12) comprising a plurality of filaments (14), the plurality of filaments including at least external filaments at least partially defining an outer surface (24) of the wire wired element (12), a sheath (20) partially coating the outer surface (24) of the wire element (12) made of a thermoplastic polymeric composition, external interstices (38) to the wire element delimited by the inner wall (22) of the sheath (20) and the outer surface (24) of the wire element (12) delimited by the outer filaments (14), the outer interstices (38) being substantially free of the thermoplastic polymeric composition, and internal interstices (32) to the wire element (12) delimited by the plurality of filaments (14) being substantially free of the thermoplastic polymeric composition.

The reinforcing element (10) according to claim 1, wherein the plurality of filaments (14) is arranged in at least one inner layer (16) of Μ> 1 internal filament (s) (14) and at least one outer layer (18) of P> 1 outer filaments (14), the outer layer (18) being wrapped around the inner layer (16), the inner interstices (32) delimited by the Μ> 1 filament (s) ) (14) internal (s) and P> 1 external filaments (14) being essentially free of the thermoplastic polymeric composition.

A reinforcing element (10) according to claim 1, wherein the plurality of filaments (14) of the wire element (12) is arranged in at least one inner layer (16) of Μ> 1 filament (s) ( 14), at least one external layer (18) of P> 1 external filaments (14) and at least one intermediate layer (26) of N> 1 intermediate filaments (14), the intermediate layer (26) being arranged between the inner layer (16) and the outer layer (18), the internal interstices (34) delimited by the Μ> 1 filament (s) (14) inteme (s) and the N> 1 filaments (14) Intermediates are essentially free of the thermoplastic polymeric composition and the internal interstices (36) delimited by the N> 1 intermediate filaments (14) and the outer P> 1 filaments (14) are essentially free of the thermoplastic polymeric composition.

A reinforcing element (10) according to claim 1, wherein the plurality of filaments (14) of the wire element (12) is arranged in a single layer of N> 1 external filaments (14), the central capillary ( 28) delimited by the N> 1 external filaments (14) being essentially free of the thermoplastic polymeric composition.

The reinforcing element (10) according to any one of claims 1 to 4, wherein the thermoplastic polymeric composition comprises a thermoplastic compound selected from the group consisting of non-elastomeric thermoplastic polymers (TP), thermoplastic elastomers (TPE) , vulcanized thermoplastic elastomers (TPV), functionalized thermoplastic elastomers and mixtures of these compounds.

6. Reinforced product (40), characterized in that it comprises: an elastomer matrix (42), and at least one reinforcing element (10) according to any one of the preceding claims, embedded in the matrix of elastomer (42).

7. Bandage (1), characterized in that it comprises a reinforced product (40) according to the preceding claim or a reinforcing element according to any one of claims 1 to 5.

8. Bandage (1) according to claim 7, comprising a crown (2) surmounted by a tread, two sidewalls (3), two beads (4), each side (3) connecting each bead (4) to the top (2), a carcass reinforcement (7) anchored in each of the beads (4) and extending into the flanks (3) and into the apex (2), the carcass reinforcement (7) comprising the reinforced product (40) or the reinforcing element (10).

A method of manufacturing a bandage reinforcing member from a wire element comprising a plurality of filaments, the plurality of filaments comprising at least external filaments at least partially delimiting an outer surface of the wire element, the method comprising a casing step during which the wire element is partially coated with a sheath made of a thermoplastic polymeric composition so that the interstices external to the wire element delimited by the inner wall of the sheath and the outer surface of the wire element delimited by the outer filaments are substantially free of the thermoplastic polymeric composition, and the internal interstices of the wire element delimited by the plurality of filaments are substantially free of the thermoplastic polymeric composition.

10. The manufacturing method according to the preceding claim, wherein during the casing step, the reinforcing element is at room temperature.