Patent Application
20050028919
The present invention relates to a method for laying reinforcement cords or filaments for tires. More particularly, it relates to the arrangement and the configuration of the reinforcement structure in the sidewalls, the beads and the crown zone of the tire; it also relates to the anchoring of the carcass cords in the bead and the reinforcements of different portions of the bead or the sidewall.
The reinforcement of tires is currently constituted by one or more plies, conventionally referred to as “carcass plies”, “crown plies”, etc. This method of designating reinforcements derives from the manufacturing process, consisting of producing a series of semi-finished products in the form of plies, provided with frequently longitudinal cord reinforcements, which are subsequently assembled to build a tire.
The plies are produced flat, with large dimensions, and are subsequently cut according to the dimensions of a given product. The plies are also assembled, in a first phase, substantially flat. The blank thus produced is then shaped to adopt the toroidal profile typical of tires. The semi-finished products referred to as “finishing” are then applied to the blank, in order to obtain a product ready for vulcanization.
This same conventional process involves the use of a bead wire, used to effect the anchoring or holding of the carcass ply in the bottom zone of the sidewall. Thus, conventionally, a portion of ply is turned up around a bead wire arranged in the bead of the tire. In this manner, anchoring of the carcass ply in the bead is effected.
The fact that this conventional process has become widespread in the industry, despite numerous variants in the manner of producing the plies and assemblies, has lead the person skilled in the art to use a vocabulary modeled on the process; hence the generally accepted terminology, comprising in particular the terms “plies”, “carcass”, “bead wire”, “shaping” to designate the change from a flat profile to a toroidal profile, etc.
However, there are nowadays tires which do not, properly speaking, comprise “plies” or “bead wires” in accordance with the preceding definitions. For example, document EP 0 582 196 describes tires manufactured without the aid of semi-finished products in the form of plies. For example, the cords of the different reinforcement structures are applied directly to the adjacent layers of rubber mixes, the whole being applied in successive layers on a toroidal core having a shape which makes it possible to obtain directly a profile similar to the final profile of the tire being manufactured.
Thus, in this case, there are no longer any “semi-finished products”, nor “plies”, nor “bead wires”. The base products, such as the rubber mixes and reinforcements in the form of filaments, are applied directly to the core. As this core is of toroidal form, the blank no longer has to be shaped in order to move from a flat profile to a profile in the form of a torus.
Furthermore, the tires described in this document do not have the conventional upturn of the carcass ply around a bead wire. This type of anchoring is replaced by an arrangement in which circumferential filaments are arranged adjacent to said sidewall reinforcement structure, the whole being embedded in an anchoring or bonding rubber mix.
There are also processes for assembly on a toroidal core using semi-finished products specially adapted for quick, effective and simple laying on a central core.
Finally, it is also possible to use a mixed process comprising both certain semi-finished products for producing certain architectural aspects (such as plies, bead wires, etc), whereas others are produced from the direct application of mixes and/or reinforcements in the form of filaments.
In the present document, in order to take into account recent technological developments both in the field of manufacture and in the design of products, the conventional terms such as “plies”, “bead wires”, etc, are advantageously replaced by neutral terms or terms which are independent of the type of process used. Thus, the term “carcass-type reinforcement” or “sidewall reinforcement” is valid to designate the reinforcement cords of a carcass ply in the conventional process, and the corresponding cords, generally applied at the level of the sidewalls, of a tire produced in accordance with a process without semi-finished products.
The term “anchoring zone”, for its part, may equally well designate the traditional upturn of a carcass ply around a bead wire of a conventional process or the assembly formed by the circumferential filaments, the rubber mix and the adjacent sidewall reinforcement portions of a bottom zone produced with a process with application to a toroidal core.
The carcass reinforcement of tires is currently constituted by one or more plies, most frequently radial ones, which are turned up about one or more bead wires arranged in the beads. The beads constitute the means which makes it possible to fix the tire on the rim. The rigidity of the bead thus constituted is very great.
For some specific applications in which the tire may for example be subjected to great loads or to violent impacts, etc., it may prove desirable to be able to refine some characteristics such as rigidity, impact strength, etc. Furthermore, in order to facilitate automation of certain steps of the tire manufacturing process, it may prove advantageous to revise the nature and/or the arrangement of some of the constituent elements.
In the current art, it is quite difficult to modulate the characteristics of the sidewall and/or of the bead. The sidewall must have great flexibility, and the bead, in contrast, must have great rigidity. Furthermore, the reinforcements which are arranged in this part of the tire always inevitably have a discontinuity: at the level of the radially upper end of the carcass upturn, there is a change without transition into a zone devoid of this carcass upturn, which zone is therefore inevitably less rigid.
Finally, the cost demands are becoming increasingly harsh and require productivity gains which are becoming increasingly difficult to obtain, taking into account the ceaselessly increasing technicality of the products. Any method or device which makes it possible to produce tires at faster rates while maintaining the level of quality is therefore potentially advantageous.
To take into account this environment and these constraints, the invention provides a method for laying cords of a carcass-type reinforcement structure on a tire consisting of arranging at least two filaments on a tire blank so that at least one first and one second filament form, at the level of the crown and the sidewalls, a series of transverse portions extending substantially from one bead of the tire to the other, wherein a single laying head is used which permits substantially simultaneous laying of said at least first and second filaments.
Owing to this method, major productivity gains may be obtained.
Upon the laying of said filaments, said head is preferably arranged relative to the blank of the tire so that the filaments form at least a portion of substantially parallel paths relative to each other.
Given the high laying speeds and the reduced spaces between the filaments, the laying of multiple cords with a single head is particularly advantageous in preventing the cords from being too close to each other, or even touching over certain portions of paths. It is furthermore easier to lay the filaments regularly than if they are laid separately.
The portions of substantially parallel paths are advantageously applied substantially between the crown and the beads.
The sections of substantially parallel paths are advantageously applied in the sidewall, substantially radially externally to the anchoring zone, and preferably substantially radially externally to the equator of each sidewall.
The laying in the form of parallel groups is easiest and most precise structurally starting from the equator and moving towards the crown.
At the level of the beads, U-shaped connections advantageously join together two successive transverse portions of the first filament, and two successive transverse portions of the second filament.
Said laying head preferably provides at least two filament distributors located upstream and preferably in the immediate vicinity of each other.
Advantageously a central core preformed in the image of the profile of a tire is used for assembling in succession the different constituent elements of the tire.
The method according to the invention is particularly suited to the production of tires comprising at least one carcass-type reinforcement structure anchored on either side of the tire in a bead the base of which is intended to be mounted on a rim seat, a crown reinforcement, each bead being extended radially towards the outside by a sidewall, the sidewalls joining, radially towards the outside, a tread, the reinforcement structure comprising:
Such an arrangement comprising substantially parallel groups of filaments makes it possible to produce a multifilament configuration very economically. The groups of cords may be applied substantially simultaneously, for example by means of a single laying head. In this manner, and due to the specific type of architecture according to the invention, it is possible to divide by two or even by three or more the time for laying the reinforcement filaments of carcass type, in particular if the production is effected on a central core preformed in the image of a tire.
Furthermore, the arrangement in substantially parallel groups makes it possible to arrange the filaments very close to one another, thus contributing to increasing the cord density. This has a beneficial effect on a good number of mechanical properties. Thus, for example, it may make it possible to increase the modulus, the tensile strength, etc.
Advantageously, the portions of substantially parallel paths represent at least substantially 25% of the total path of the filaments between the crown and the anchoring zone and preferably between substantially 30% and 80% of the total path of the filaments between the crown and the anchoring zone.
Insofar as the cords are laid in pairs or any other grouped form, the laying time is reduced, thus reducing the cost price.
Advantageously, the portions of substantially parallel paths are provided in the sidewall, substantially radially externally to the anchoring zone, and preferably radially externally to the zone corresponding substantially to the equator of said sidewall. The laying in the form of parallel groups is easiest and most precise structurally starting from the equator and moving towards the crown. Preferably, the equator in question is the one corresponding to the equator of the core on which the different constituent elements of the tire are assembled.
According to another advantageous example, the tire comprises a third filament forming on one hand, at the level of the crown and the sidewalls, a series of transverse portions extending substantially from one bead of the tire to the other, and on the other hand, at the level of the beads, U-shaped connections joining two successive transverse portions of the third filament, the respective paths of the first, second and third filaments being arranged such that, between the crown and the bead, a group of filaments formed by a first, a second and a third adjacent (or successive) filaments form at least a portion of substantially parallel paths.
The laying time can then be divided by three if the cords are laid in groups. The laying density may also be increased, by substantially similar, close paths of the cords of one and the same group.
At least one arrangement of cords along a substantially circumferential path is preferably arranged substantially adjacent to said reinforcement structure at the level of the bead.
According to another advantageous example, the portions of substantially parallel paths follow substantially geodesic trajectories, either radial or non-radial.
According to another advantageous embodiment, the “forward” and “return” sections of at least two distinct groups cross so as to form a mesh pattern of cords. For example, the portions of substantially parallel paths are arranged so as to form, on a given side of the tire, a trajectory in the form of circumferentially offset forward and return paths. Said trajectory is advantageously V- or U-shaped. One of the forward or return portions runs along the other forward or return portion of a series of juxtaposed filaments, crossing the filaments. The result of such a configuration is braiding of filaments, crossing at angles which are more or less open according to the radial position and/or according to the respective inclination of each of the filaments.
The tire may then comprise a single ply. Such simplicity of architecture and manufacture, due in particular to the reduction in the number of constituents, makes it possible to reduce the costs.
The method according to the invention is also well suited to the production of tires comprising at least one carcass-type reinforcement structure anchored on either side of the tire in a bead the base of which is intended to be mounted on a rim seat, a crown reinforcement, each bead being extended radially towards the outside by a sidewall, the sidewalls joining, radially towards the outside, a tread, the reinforcement structure comprising:
According to another advantageous example of embodiment, a bead comprises a bead wire around which a portion of the cords is wound. This provides effective and reliable anchoring or holding of the reinforcement structure in the bead. This method of anchoring corresponds to a traditional bead wire, which is widespread in the tire industry. Preferably cords of textile type are used in order to facilitate the formation of the loops.
Advantageously, the tire according to the invention may be manufactured by means of a process for manufacturing a tire in which the different constituent elements are laid turn by turn directly on a core which is for example substantially rigid or inflatable, the profile of which corresponds substantially to that of the final product.
In the case of a tire manufactured using such an automated process in which the different constituent elements are laid turn by turn directly on a core, the profile of which corresponds substantially to that of the final product, the action of laying groups of cords comprising two (or more) cords is particularly advantageous. For example, the result is a great reduction in the laying time for the reinforcement structure.
The present method is also well suited for the production of a tire comprising at least one carcass-type reinforcement structure anchored on either side of the tire in a bead, the base of which is intended to be mounted on a rim seat, a crown reinforcement, each bead being extended radially towards the outside by a sidewall, the sidewalls joining a tread radially towards the outside, the reinforcement structure comprising,
Such an arrangement is optimal for the bottom portion of the sidewall. The zone of excess thickness is reduced to a minimum, there is no risk of contact between the cords, etc. Furthermore, advantageously the zone of substantially parallel paths of the filaments from the sidewall into the upturn loop itself is extended.
Advantageously, the respective paths of the first and second filaments are arranged such that, between the crown and the bead, a group of filaments formed by a first and a second adjacent filament form at least a portion of substantially parallel paths.
Such an arrangement comprising substantially parallel groups of filaments makes it possible to produce a multifilament configuration very economically. The groups of cords may be applied substantially simultaneously, for example by means of a single laying head. In this manner, and due to the specific type of architecture according to the invention, it is possible to divide by two or even by three or more the time for laying the reinforcement filaments of carcass type, in particular if the production is effected on a central core preformed in the image of a tire.
Furthermore, the arrangement in substantially parallel groups makes it possible to arrange the filaments very close to one another, thus contributing to increasing the cord density. This has a beneficial effect on a good number of mechanical properties. Thus, for example, it may make it possible to increase the modulus, the tensile strength, etc.
Advantageously, the portions of substantially parallel paths represent at least substantially 25% of the total path of the filaments between the crown and the anchoring zone and preferably between substantially 30% and 80% of the total path of the filaments between the crown and the anchoring zone.
Insofar as the cords are laid in pairs or any other grouped form, the laying time is reduced, thus reducing the cost price.
Advantageously, the portions of substantially parallel paths are provided in the sidewall, substantially radially externally to the anchoring zone, and preferably radially externally to the zone corresponding substantially to the equator of said sidewall. The laying in the form of parallel groups is easiest and most precise structurally starting from the equator and moving towards the crown. Preferably, the equator in question is the one corresponding to the equator of the core on which the different constituent elements of the tire are assembled.
According to another advantageous example, the tire comprises a third filament forming on one hand, at the level of the crown and the sidewalls, a series of transverse portions extending substantially from one bead of the tire to the other, and on the other hand, at the level of the beads, U-shaped connections joining two successive transverse portions of the third filament, the respective paths of the first, second and third filaments preferably being arranged such that, between the crown and the bead, a group of filaments formed by a first, a second and a third adjacent (or successive) filament form at least a portion of substantially parallel paths.
The laying time can then be divided by three if the cords are laid in groups. The laying density may also be increased, by substantially similar, close paths of the cords of one and the same group.
At least one arrangement of cords along a substantially circumferential path is preferably arranged substantially adjacent to said reinforcement structure at the level of the bead.
According to another advantageous example, the portions of substantially parallel paths follow substantially geodesic trajectories.
According to another advantageous embodiment, the “forward” and “return” sections of at least two distinct groups cross so as to form a mesh pattern of cords. For example, the portions of substantially parallel paths are arranged so as to form, on a given side of the tire, a trajectory in the form of circumferentially offset forward and return paths. Said trajectory is advantageously V- or U-shaped. One of the forward or return portions runs along the other forward or return portion of a series of juxtaposed filaments, crossing the filaments. The result of such a configuration is braiding of filaments, crossing at angles which are more or less open according to the radial position and/or according to the respective inclination of each of the filaments.
The tire may then comprise a single ply. Such simplicity of architecture and manufacture, due in particular to the reduction in the number of constituents, makes it possible to reduce the costs.
According to another advantageous example of embodiment, a bead comprises a bead wire around which a portion of the cords is wound. This provides effective and reliable anchoring or holding of the reinforcement structure in the bead. This method of anchoring corresponds to a traditional bead wire, which is widespread in the tire industry. Preferably cords of textile type are used in order to facilitate the formation of the loops.
Advantageously, the tire according to the invention may be manufactured by means of a process for manufacturing a tire in which the different constituent elements are laid turn by turn directly on a core, the profile of which corresponds substantially to that of the final product, and in which the laying of a first reinforcement structure on a first side of a tire and of a second reinforcement structure on a second side of said tire are effected substantially simultaneously.
In the case of a tire manufactured using such an automated process in which the different constituent elements are laid turn by turn directly on a core, the profile of which corresponds substantially to that of the final product, the action of laying groups of cords comprising two (or more) cords is particularly advantageous. For example, the result is a great reduction in the laying time for the reinforcement structure.
In the present specification, the term “cord” very generally designates both monofilaments and multifilaments, or assemblies such as cables, yarns or alternatively any equivalent type of assembly, and this whatever the material and the treatment of these cords, for example surface treatment or coating or pre-sizing in order to promote adhesion to the rubber, be it treatment before or after the cords are laid.
As a reminder, “radially upwards” or “radially upper” means towards the largest radii.
“Elasticity modulus” of a rubber mix is understood to mean a secant modulus of extension obtained at a uniaxial deformation of extension of the order of 10% at ambient temperature.
A reinforcement or reinforcing structure of carcass type will be said to be radial when its cords are arranged at 90°, but also, according to the terminology in use, at an angle close to 90°.
It is known that in the current art the carcass ply or plies is/are turned up about a bead wire. The bead wire then performs the function of anchoring the carcass, that is to say, takes up the tension which develops in the carcass cords under the action of the inflation pressure. In the configurations described in the present application, which do not use a bead wire of conventional type, the function of anchoring the reinforcement structure of carcass type is also ensured.
It is also known, still in the prior art, that the same bead wire furthermore performs a function of clamping the bead on its rim. In the configurations described in the present application, which preferably do not use a bead wire of conventional type, the clamping function is also ensured, in particular by the windings of circumferential cords closest to the seat.
It goes without saying that the invention can be used by adding other elements to the bead or to the bottom zone of the tire in general, as some variants will illustrate. Likewise, the invention can be used by multiplying the reinforcement structures of the same kind, or even by adding another type of reinforcement structure.
All the details of embodiment are given in the following description, supplemented by FIGS. 1 to 22, in which:
a to 1d illustrate a first example of a method which permits the manufacture of tires such as those described in FIGS. 3 onwards, with the substantially simultaneous laying of at least two cords;
a to 2c illustrate an example of a second method which permits the manufacture of tires such as those described in FIGS. 15 onwards, with the substantially simultaneous laying of at least two cords;
d illustrates an example of a second method which permits the manufacture of tires such as described in FIGS. 15 onwards, with the substantially simultaneous laying of at least two cords, but with laying means different from those illustrated in
a and 3b are radial sections showing essentially the sidewalls, the beads and the crown of a first and a second form of embodiment of a tire according to the method of the invention;
a, 13b and 13c are meridian profiles of a variant comprising a conventional bead wire, for example formed of a metal or composite cable;
a, 14b and 14c illustrate, by means of perspective views of a section through a portion of a tire capable of being manufactured according to the method of the invention, examples of paths of a reinforcement structure in a group in relation to a circumferential anchoring structure;
a, 22b and 22c illustrate, by means of perspective views of a section of a portion of a tire capable of being manufactured according to the method of the invention, examples of paths of a reinforcement structure in a group in relation to a circumferential anchoring structure.
In the different figures, identical reference numerals are used in order to identify similar elements.
a to 1d illustrate an example of a method which permits the manufacture of tires such as those described in the following figures (in particular FIGS. 3 to 14), with the substantially simultaneous laying of at least two cords 50. Using this method facilitates obtaining portions of substantially parallel paths. Storage or supply means make it possible to bring in two, three (or even more) cords which are to be applied to a first layer of rubber mix formed substantially in the image of the profile of the final product. Before application, the cords are arranged in the immediate vicinity of each other at distances corresponding substantially to the distance provided between the cords of one and the same group. For application of the cords against the mix, the laying means moves in space, for example from one bead to the other, along the path which the cords to be laid have to follow in the tire.
Thus, a group of cords is guided by a laying means for application along a predefined path. The laying may be effected either by guiding the group to a substantially infinitesimal distance from the product intended to receive the cords, or by compaction or by application of a laying force by means of a suitable tool until it comes into contact with the rubber mix previously applied. This mix is preferably adhesive, thus enabling the group of cords to be retained or held in place once slight contact is produced between the cords and the rubber mix. The group is therefore guided from one bead of the tire to the other, moving over the sidewalls and the crown. Once laid as far as a radially lower portion of a bead, thus forming a “forward” section, the group of cords is guided so as to move circumferentially or angularly, to enable the group of cords to move over the profile in a path substantially adjacent to the “forward” portion to form a “return” section, extending as far as the opposite bead.
a to 1d diagrammatically illustrate a mechanism which makes it possible to lay groups of cords such as described above. Reserves 60 of cords enable the laying mechanism to be supplied. The latter comprises a series of guide means 53, 54 (preferably as many means as there are cords to be laid), which are preferably mobile from one side of the tire to the other, actuated by a control means 50, 51, 52. In the example illustrated, the control means comprises a motor 50 and transport elements 51 and 52, such as, for example, a slider which moves on a rail, enabling the guide means 53, 54 for the cords 5 grouped for example in twos or threes (as illustrated) to be moved in space.
b shows the development of the path several moments later, when a connection has been produced, the guide 54 re-ascends along the sidewall in order to lay another section, circumferentially spaced apart from the previous one.
c illustrates the same tire, when the slider arrives at the opposite side; the guide 54 carries the cords into the region of the shoulder. The laying along the opposite sidewall and the production of the corresponding connections is effected similarly to that previously described for the first sidewall.
d illustrates the return of the slider 51 and guide means in order to produce a new “forward” section.
According to an advantageous variant, the distance between the cords before laying is variable or adjustable, so to as make it possible to lay the cords with larger or smaller inter-cord spaces depending on the types of products, or even with variable spaces on one and the same product, for example as a function of the position on the profile.
a to 2c illustrate another example of a method which permits the manufacture of tires such as those described in the following figures (in particular 15 to 22), with the substantially simultaneous laying of at least two cords 50. Using this method facilitates obtaining portions of substantially parallel paths. Storage or supply means make it possible to bring in two, three (or even more) cords which are to be applied to a first layer of rubber mix formed substantially in the image of the profile of the final product to be brought in. Before application, the cords are arranged in the immediate vicinity of each other at distances corresponding substantially to the distance provided between the cords of one and the same group. For application of the cords against the mix, the laying means moves in space, for example from one bead to the other, along the path which the cords to be laid have to follow in the tire.
Thus, a group of cords is guided by a laying means for application along a predefined path. The laying may be effected either by guiding the group to a substantially infinitesimal distance from the product intended to receive the cords, or by compaction or by application of a laying force by means of a suitable tool until it comes into contact with the rubber mix previously applied. This mix is preferably adhesive, thus enabling the group of cords to be retained or held in place once slight contact is produced between the cords and the rubber mix. The group is therefore guided from one bead of the tire to the other, moving over the sidewalls and the crown.
Once laid as far as a radially lower portion of a bead, thus forming a “forward” section, the group of cords is guided so as to move circumferentially or angularly, to enable the group of cords to move over the profile in a path substantially adjacent to the “forward” portion to form a “return” section, extending as far as the opposite bead.
Furthermore,
a illustrates an example of displacement of the guide means of one side of the tire. Guiding as close as possible of the profile as far as the level of the bead makes it possible to effect advantageously precise, regular laying. The guide means bring the cords into the bottom position; a relative angular displacement between the guides 54 and the tire being assembled makes it possible to move the cords in translation to form the connections 11. In order to do this, the guide means 54 are advantageously driven in rotation on themselves, so as to form the connections 11, for example using a second motor means 56.
To facilitate the respective positionings between the sidewall [of] the laying members, it may also be arranged that, during the rotation of the guide means 54, either the tire undergoes a rotation of several degrees, or the guide 54 is displaced along the bottom zone, or a combination of both. According to an advantageous variant, such as illustrated, a press element 55 exerts a slight pressure against the base of the cords before shaping the connections. Thus any accidental sliding or displacement of the cords during laying is avoided.
b shows the development of the path several moments later, when a connection has been produced, and the guide 54 re-ascends along the sidewall in order to lay another section, circumferentially spaced apart from the previous one.
c illustrates the same tire, when the slider arrives at the opposite side; the guide 54 carries the cords into the region of the shoulder. The laying along the opposite sidewall and the production of the corresponding connections is effected similarly to that previously described for the first sidewall.
According to an advantageous variant, the distance between the cords before laying is variable or adjustable, so to as make it possible to lay the cords with larger or smaller inter-cord spaces depending on the types of products, or even with variable spaces on one and the same product, for example as a function of the position on the profile.
d illustrates an advantageous variant in which the guide means 54 are arranged on an arm or multi-axis robot capable of displacing said means 54 along the path of the filaments 5. The forward 14 and return 15 sections and the connections 11 are arranged and produced similarly to what has been discussed for
a, 3b and 4 illustrate a first example of embodiment of a tire 1 capable of being manufactured according to the method of the invention. The main constituent elements are clearly visible in
In the radially inner portion of the sidewalls 3, there are located beads 4, provided for mounting on a rim of suitable form and dimensions.
In order to ensure perfect anchoring of the reinforcement structure, preferably a stratified composite bead is produced. Within the bead 4, between the cord alignments of the reinforcement structure, there are arranged circumferentially oriented cords 80. These are arranged in a stack 81 as in the drawings, or in a plurality of adjacent stacks, or in packets, or in any suitable arrangement, depending on the type of tire and/or the desired characteristics.
The radially inner end portions of the reinforcement structure 5 cooperate with the beads. There is thus created anchoring of these portions in said beads so as to ensure the integrity of the tire. In order to promote this anchoring, the space between the circumferential cords and the reinforcement structure is occupied by a bonding rubber mix. It is also possible to provide for the use of a plurality of mixes having different characteristics, delimiting a plurality of zones, the combinations of mixes and the resultant arrangements being virtually unlimited. However, it is advantageous to provide for the presence of a mix of high elasticity modulus in the zone of intersection between the arrangement of cords and the reinforcement structure. By way of non-limitative example, the elasticity modulus of such a mix may reach or even exceed 15 to 25 MPa, and even in some cases reach or even exceed 40 MPa.
This mix of high modulus is advantageously arranged so as to be in direct contact with the adjacent portions of the reinforcement structure 5. In the conventional configurations, a carcass ply (cord impregnated in a layer of rubber mix) is applied. There therefore results a thin intermediate layer of mix of lower modulus which is located between the mix of high modulus and the portion of reinforcement structure. With direct contact, and therefore without the presence of this thin layer of mix of lower modulus, the impact of the presence of the mix of high modulus in the zone is amplified. In fact, the traditional thin layer of lower modulus causes losses of energy, which may cause deterioration of the mechanical properties.
The arrangements of cords may be put together and manufactured in several ways. For example, a stack 81 may advantageously be formed of a single cord wound (substantially at zero degrees) in a spiral over several turns, preferably from the smallest diameter towards the largest diameter. A stack may also be formed of a plurality of concentric cords laid one in another, so that rings of gradually increasing diameter are superposed. It is not necessary to add a rubber mix to ensure the impregnation of the reinforcement cord, or circumferential windings of cord.
In order to position the reinforcement cords as accurately as possible, it is very advantageous to build the tire on a rigid support, for example a rigid core which imposes the shape of its inner cavity. There are applied to this core, in the order required by the final architecture, all the constituents of the tire, which are arranged directly in their final position, without the profile of the tire having to be turned up or folded over during building. This building may for example use the devices described in Patent EP 0 580 055, and also in French application 00/01394, for the laying of the carcass reinforcement cords, and in document EP 0 264 600 for the laying of the rubber compositions. The tire may be molded and vulcanized as set forth in U.S. Pat. No. 4,895,692.
The first and second filaments are arranged circumferentially in similar manner, but in slightly offset circumferential positions, so as not to be superposed over great lengths. As illustrated in
In each of the sections 14 and 15, the groups each comprise at least a portion of substantially parallel paths 16, in which the two adjacent filaments of one and the same group move along substantially parallel trajectories.
In these two examples, the circumferential distance between two adjacent filaments or filaments of one and the same group 10 is less than the distance between two adjacent filaments each belonging to two distinct groups.
Due to the substantially radial trajectories of the cords, which in fact are similar to substantially meridian trajectories, for a given pitch P, the circumferential distance between two adjacent groups of cords varies substantially regularly between the bottom zone and the region of the crown of the tire. Most frequently, due to the smaller radius in the bottom zone of the tire, the filaments there are closer to each other. As the crown is approached, the radius becomes larger and the filaments then have more circumferential space between them. FIGS. 4 to 9 clearly show this context since these are projections in the plane of arrangements which are intended to occupy a spatial position such that the crown zone is on a first radius R and the zone of the bead 4 is positioned on another radius r which is smaller than the first radius R. The substantially toric form of a tire makes this type of variation of radius inevitable. It is therefore unthinkable in practice to have a constant inter-cord distance between R and r.
The present invention goes against this teaching since the distance between two cords is maintained over a given portion, by forming groups. In return, the distance between the cords of two adjacent groups varies substantially between the radial positions R and r so as to compensate for the parallel portions of the groups.
Industrial production rates and productivity constraints are nowadays such that very high manufacturing speeds are required and mean that the regularity of laying is not absolute. The mechanical demands of the product furthermore tolerate a certain margin as far as accuracy is concerned, without in any way adversely affecting the final quality. Thus, according to the invention, a tire may comprise cord arrangements having cord trajectories, the regularity of which is not as absolute as that illustrated in the figures.
FIGS. 10 to 12 illustrate various examples of embodiment in which groups of cords are arranged along different paths of “bias” type.
a illustrates another variant of configuration of “bias” type in which groups of two cords 5 follow substantially geodesic paths. The connections 11 occupy either similar radial positions, or alternatively slightly offset positions. Depending on the laying process used, the latter configuration may possibly have several advantages. Thus, for example, if the two cords of the group are laid simultaneously, it is possible to pass around a single fixing point located substantially between the two connections 11.
In the examples illustrated in FIGS. 10 to 12, the groups of cords 5 comprise portions 16 of substantially parallel paths extending substantially from one bead of the tire to the other. According to various variants (not shown), these portions 16 may be limited, for example from one equator to the other, or from any point of a first sidewall towards a symmetrical point on the other sidewall.
a, 13b and 13c are meridian profiles of a variant comprising a conventional bead wire 20, for example formed of a metal or composite cable. In 11a, the cords 5 can be seen passing along a central core against which the various constituent elements of the tire are applied in succession. The cord passes from one bead 4 to the other and is extended radially internally relative to the bead wire 20. The arrangements of the cords 5 in groups 10, in “forward” 14 and “return” 15 portions forming connections 11 and crossings 12 at the level of the beads may, at this stage of manufacture, be comparable or similar to those shown in FIGS. 3 to 13. Thus, the connections and crossings 11 and 12 may be located radially internally to the bead wire 20.
In 13b, there can be seen the upturn of the cord 5, first of all against the radially inner portion of the bead wire 20, then against the axially outer portion of this bead wire, in order substantially to surround or envelop the latter. The upturned portion 22 advantageously comprises the connections and crossings 11 and 12.
As shown in
a illustrates a perspective view of the form of embodiment shown in
b and 14c illustrate variants of
FIGS. 15 to 22 illustrate other examples of tires which can be produced advantageously by means of the method according to the invention. The base elements are similar and laid similarly to what has been mentioned previously for the examples of FIGS. 3 to 14. On the other hand, the arrangement of the filaments differs somewhat in the portion of the bottom zone of the tire.
According to a first example (
The first and second filaments are arranged circumferentially in similar manner, but in slightly offset circumferential positions, so as not to be superposed over great lengths. As illustrated in
In the case in which more than two connections are present, they are positioned successively from a first, radially outer, connection to a second, then a third, etc, always more towards a radially inner position. Thus a sort of multi-connection arrangement is formed, with an external connection inside of which is located one or more internal connections, all arranged one in another.
Beyond the connection, the group of cords follows its trajectory towards the crown, forming a second “return” section 15. The succession or alternation of connections from one bead to the other is such that a first connection formed on a first internal filament 5 in a first bead is arranged radially externally in the second bead, for a circumferential position substantially close to the first connection. This is illustrated clearly in FIGS. 15 to 22.
In each of the sections 14 and 15, the groups each comprise at least a portion of substantially parallel paths 16, in which the two adjacent filaments of one and the same group move along substantially parallel trajectories.
In these two examples, the circumferential distance between two adjacent filaments or filaments of one and the same group 10 is less than the distance between two adjacent filaments each belonging to two distinct groups.
Due to the substantially radial trajectories of the cords, which in fact are similar to substantially meridian trajectories, for a given pitch P, the circumferential distance between two adjacent groups of cords varies substantially regularly between the bottom zone and the region of the crown of the tire. Most frequently, due to the smaller radius in the bottom zone of the tire, the filaments there are closer to each other. As the crown is approached, the radius becomes larger and the filaments then have more circumferential space between them. FIGS. 15 to 22 clearly show this context since these are projections in the plane of arrangements which are intended to occupy a spatial position such that the crown zone is on a first radius R and the zone of the bead 4 is positioned on another radius r which is smaller than the first radius R. The substantially toric form of a tire makes this type of variation of radius inevitable. It is therefore unthinkable in practice to have a constant inter-cord distance between R and r.
The present invention goes against this teaching since the distance between two cords is maintained over a given portion, by forming groups. In return, the distance between the cords of two adjacent groups varies substantially between the radial positions R and r so as to compensate for the parallel portions of the groups.
Industrial production rates and productivity constraints are nowadays such that very high manufacturing speeds are required and mean that the regularity of laying is not absolute. The mechanical demands of the product furthermore tolerate a certain margin as far as accuracy is concerned, without in any way adversely affecting the final quality. Thus, according to the invention, a tire may comprise cord arrangements having cord trajectories of a regularity which is less than that illustrated in the figures.
FIGS. 19 to 21 illustrate various examples of embodiment in which groups of cords are arranged along different paths of bias type.
The angle φ may vary for example between 5 and 45 degrees, according to the case. The left-hand portion of
In the examples illustrated in FIGS. 19 to 21, the groups of cords 5 comprise portions 16 of substantially parallel paths extending substantially from one bead of the tire to the other. According to various variants (not shown), these portions 16 may be limited, for example from one equator to the other, or from any point of a first sidewall towards a symmetrical point on the other sidewall.
a illustrates a perspective view of the form of embodiment shown in
b and 22c illustrate variants of
The variant of
This axial separation makes it possible to place a larger number of cords even when the radius is small. The mechanical properties such as rigidity may also be optimized. As illustrated in 22c, in this variant, the “forward” 14 and “return” 15 portions of a group of cords 15 are advantageously spaced and separated by at least one “forward” and/or “return” portion of another group of cords. In addition to being spaced axially, successive sets of connections 11 may also be offset radially, for example forming groups of two connections, each group being spaced radially from another, as illustrated in
| Number | Date | Country | Kind |
|---|---|---|---|
| 01/17136 | Dec 2001 | FR | national |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/EP02/14721 | Dec 2002 | US |
| Child | 10880407 | Jun 2004 | US |
