WO2001043957A1

WO2001043957A1 - A method for manufacturing reinforcing annular elements for vehicle tyres, and a tyre incorporating inextensible annular inserts manufactured by such a method

Info

Publication number: WO2001043957A1
Application number: PCT/EP2000/012108
Authority: WO
Inventors: Marco Cantu'; Luca Frisiani; Maurizio Marchini
Original assignee: Pirelli Pneumatici S.P.A.
Priority date: 1999-12-15
Filing date: 2000-12-01
Publication date: 2001-06-21
Also published as: AU1861201A

Abstract

Circumferentially inextensible annular elements (6) integrated in the annular structures (7) reinforcing the beads of a tyre (2) are obtained each by the laying of a continuous filiform element (13) according to radially superposed turns (18) extending about the geometric axis of rotation (X) of the tyre itself. The manufacture of each turn (18) entails the formation of a prevalent segment (18a) positioned on a circumferential line perfectly concentric to the axis of rotation (X), on the continuation whereof is formed a transition segment (18b) extending away from or towards the axis of rotation (X) to join the prevalent segment (18a) of the radially contiguous turn (18). Also described is a tyre (2) incorporating reinforcing inserts (6) manufactured according to the invention, and an apparatus (1) for manufacturing the inserts (6).

Description

A Method for Manufacturing Reinforcing Annular Elements for Vehicle Tyres, and a Tyre Incorporating Inextensible Annular Inserts Manufactured by such a Method

The present invention relates to a method for manufacturing reinforcing annular elements for vehicle tyres, of the type comprising the phase of laying at least a continuous filiform element onto a support element, following a laying path substantially concentric to a reference axis, to form concentric turns set radially side by side.

The invention further relates to a tyre incorporating inextensible annular inserts manufactured in accordance with said method, said tyre being of the type comprising a carcass structure having at least a carcass ply presenting axially opposite edges engaged to respective annular structures for reinforcing the beads, each of said annular structures for reinforcing the beads comprising at least a circumferentially inextensible annular insert formed by at least a continuous filiform element extending according to radially contiguous turns substantially concentric to an axis of rotation of the tyre.

The invention also relates to a reinforcing annular element for vehicle tyres, of the kind comprising at least a continuous filiform element extending according to radially contiguous turns substantially concentric to a geometric axis of reference.

The manufacture of the tyres for vehicle wheels entails the formation of a carcass structure substantially composed by one or more carcass plies shaped according to a substantially toroidal configuration and presenting its own axially opposite lateral edges engaged to respective reinforcing annular structures integrating circumferentially inextensible annular inserts, usually known as "bead rings", located in the areas of the tyre usually identified with the name of "beads".

On the carcass structure is applied, in radially external position, a belt structure comprising one or more belt strips shaped as a closed loop, essentially composed by textile or metal cords suitably oriented relative to each other and to the cords belonging to the adjacent carcass plies.

In a position radially external to the belt structure is then applied a tread band, normally comprising a strip of elastomeric material of adequate thickness.

It should be specified that, for the purposes of the present description, the term "elastomeric material" means the rubber compound as a whole, i.e. the set formed by at least a basic polymer suitably amalgamated with reinforcing fillers and process additives of various kinds.

Lastly, on the opposite sides of the tyre being manufactured, a pair of side walls is applied, each of which covers a lateral portion of the tyre lying between a so-called shoulder area, located in proximity to the corresponding lateral edge of the tread band, and a so-called bead located in correspondence with the corresponding bead ring.

Traditional production methods essentially provide for the components of the tyre as listed above to be first manufactured separately from each other, then assembled in a tyre manufacturing phase.

The Applicant's current trend, however is to employ production methodologies which allow to minimise or, possibly, to eliminate the production and storage of semi-finished products.

In practice, the Applicant's research and development are oriented towards new process solutions which allow to manufacture individual components forming them directly on the tyre being manufactured according to a predetermined sequence.

In this regard, manufacturing processes have been proposed which are aimed at obtaining determined components of the tyre, such as the tread band, the side walls or others, by depositing on a toroidal support bearing the tyre being manufactured a continuous strip-like element made of elastomeric material having reduced section relative to the one of the component to be obtained, and arranged to form, about the axis of rotation of the tyre, a plurality of turns consecutively set side by side and/or superposed in such a way as to define the component itself in its final configuration. With particular reference to the annular structures reinforcing the beads, the same Applicant has proposed, for instance in European patent applications EP 943421 andEP 928680, for individual circumferentially inextensible annular inserts to be obtained by the circumferential winding of at least a continuous filiform element for multiple consecutive turns, thereby forming a series of turns radially set side by side and concentric to the geometric axis of rotation of the tyre.

The Applicant, however, has noticed that the presence of inserts formed by one or more filiform elements wound in a spiral according to the teachings of the prior art could lead to an imperfect static and/or dynamic balancing of the tyre relative to its own geometric axis of rotation. It was observed that the filiform element wound according to a spiral always entails a certain unbalancing of the mass of the insert formed thereby relative to the axis of rotation.

Based on this observation, a new manufacturing method has been developed, whereby each of the turns formed by the filiform element extends almost over its entire development according to a circumference that is concentric to the axis of rotation of the tyre, or other reference axis, and is joined to the radially interior or radially exterior turn by means of a short transition segment extending, respectively, towards or away from the geometric axis of the tyre. In particular, the subject of the present invention is a new method for manufacturing reinforcing annular elements for vehicle tyres, characterised in that the formation of each of said turns comprises the following phases: forming a prevalent segment of said turn by laying said at least one filiform element according to a laying circumference that is concentric relative to said axis of reference; forming a transition segment of said turn by deviating the filiform element from said laying circumference to a concentric laying circumference.

In a preferential embodiment, the formation of said transition segment is effected simultaneously with the laying of the filiform element in an angular sector whose amplitude, measured in correspondence with the reference axis, has a value of less than 45 ° , and preferably ranging between 5 ° and 30 ° .

Moreover, the formation of the prevalent segment of each turn is preferably performed by actuating the filiform element longitudinally and guiding the filiform element in a stationary application point on said support element, actuated in rotation about said geometric reference axis, the formation of the transition segment being effected by radially displacing the application point of the filiform element on the support element, simultaneously with the rotation of the support element itself.

The invention also relates to a tyre for vehicle wheels, characterised in that each of said turns presents a prevalent segment positioned along a circumferential line concentric to said axis of rotation, and a transition segment extending away or towards said axis of rotation to join the prevalent segment of a radially contiguous turn.

More specifically, the transition segment of each turn opportunely subtends, about the axis of rotation of the tyre, an angular sector whose amplitude has a value of less than 45 ° , preferably ranging between 5 ° and 30 ° .

Advantageously, the continuous filiform element presents a first and a second extremity positioned each in circumferential alignment with the prevalent segment of one of said turns.

In particular, said first and second extremities are respectively arranged in correspondence with an initial point and with a terminal point of the transition segment of at least one of said turns.

Also in accordance with the present invention, a reinforcing annular element for vehicle tyres is proposed, characterised in that each of said turns presents a prevalent segment positioned along a circumferential line concentric to said reference axis, and a transition segment extending away from or towards said reference axis to join the prevalent segment of a radially contiguous turn.

Advantageously, said transition segment of each turn subtends, about said reference axis, an angular sector whose amplitude has a value of less than 45°, preferably ranging between 5° and 30°. In a preferential embodiment, the continuous filiform element has a first and a second extremity positioned each in circumferential alignment with the prevalent segment of one of said turns.

In detail, the first and second extremities are respectively positioned in correspondence with an initial point and with a terminal point of the transition segment of at least one of said turns.

Further features and advantages shall become more readily apparent from the detailed description of a preferred, but not exclusive, embodiment of a method for manufacturing reinforcing annular elements for vehicle tyres, and of a tyre incorporating reinforcing elements manufactured according to the present invention. The description shall be given hereafter with reference to the accompanying drawings, provided solely by way of non limiting indication, in which:

Figure 1 shows a perspective view of an apparatus for manufacturing reinforcing annular elements in accordance with a method forming the subject of the present invention; - Figure 2 is a schematic drawing showing in cross section a tyre undergoing work, in an operative phase in which two circumferentially inextensible annular inserts are manufactured in correspondence with the respective beads;

Figure 3 shows an interrupted view of the area of the transition segments of the turns of a circumferentially inextensible annular insert manufactured on the carcass structure of a tyre;

Figure 4 schematically shows a continuous strip-like element wound about the reference axis in accordance with the subject manufacturing method;

Figure 5 schematically shows a continuous filiform element wound in a spiral according to the prior art about a reference axis.

With reference to the aforementioned figures, the reference number 1 indicates in its entirety an apparatus for manufacturing reinforcing annular elements for vehicle tyres, in accordance with a method constituting the subject of the present invention. The apparatus 1 and the method implemented thereby are suitable for being opportunely used within the scope of manufacturing vehicle tyres in accordance with manufacturing processes of the kind described for instance in the publications EP 943421, EP 928680 and/or in the European patent applications EP 988300762.5, EP 99830685.6, all in the name of the same Applicant, according to which the manufacture of each component of the tyre is accomplished on a manufacturing line by working at least a basic semifinished product, supplied in a predetermined quantity depending on the tyre model to be manufactured.

A tyre undergoing work on the apparatus 1 is schematically indicated as 2 in Figure 2. By way of indication, the tyre 2 presents a carcass structure 3 formed by at least a carcass ply 4 having axially opposite terminal edges engaged to reinforcing annular structures 5 integrated in the circumferentially interior areas of the tyre 2, usually identified by the name of "beads". Each reinforcing annular structure 5 comprises one or more circumferentially inextensible annular inserts 6 and one or more filling inserts 7 coupled to the carcass ply 4.

Within the scope of the manufacture of the tyre 2, the formation of the carcass ply 4 can advantageously be accomplished by the sequential laying of pre-cut strip-like elements 4a, 4b consecutively set side by side in mutual circumferential alongside relationship on the external surface of a toroidal support 8 whereon at least a layer of elastomeric material, usually known as

"liner" 9, has previously been formed, for instance as described in the publication EP 928680 and in the European patent application 98830662.7, in the name of the same Applicant. The manufacture of the tyre 2 entails the execution of further work phases, such as the application of a belt structure in a position radially external to the carcass structure 3, the application of a tread band in a position radially external to the belt structure and the application of side walls on the opposite sides of the belt structure 3, phases which are not further described herein as they are not relevant for the purposes of the invention.

Within the scope of this manufacturing process, the apparatus 1 is suitable for manufacturing the circumferentially inextensible annular inserts 6 integrated in respective annular structures reinforcing the beads 5 comprised in the carcass structure 3.

For this purpose, the apparatus 1 essentially comprises a support device 10 able to engage removably the toroidal support 8 in correspondence with an attachment hold 8a coaxially projecting from opposite parts relative thereto. To the support device 10 are associated a gear motor 11 or equivalent devices for actuating the rotation of the toroidal support 8 about its own geometric axis X. A pair of laying organs 12 operate on the opposite sides of the toroidal support 8 to support each the application of a continuous filiform element 13 coming for instance from a feeding reel or directly from a strainer or from other convenient feeding devices, not shown herein as they are not relevant for the purposes of the mvention. The continuous filiform element 13, preferably coated by a thin layer of elastomeric material, is preferably constituted by a single metal wire having a diameter ranging, by way of indication, between 0.7 mm and 1.3 mm, but may comprise a plurality of thinner threads, parallel or twisted in the form of a cord, made of metallic or synthetic material. More in particular, for this purpose it is possible to use a cord made of metallic material with multiple strands mutually twisted, preferably in counter direction, i.e. one that is opposite to the direction of torsion between the individual wires of each strand. In this case, a metallic cord with 7x4x0.28 conformation is preferred, i.e. a cord composed of seven strands, each constituted by four steel wires with a diameter of 0.28 mm. Alternatively, it is possible to use a textile cord having a tensile strength that is comparable to that of the metallic cord described above. In this case, the use of the aramidic fibre is preferred, and still more preferably the one commercially known as Kevlar®. Each laying organ 12 essentially comprises an arm 14 bearing a terminal roller 15 or other kind of application device, oriented according to an axis that is radial relative to the axis of rotation X of the toroidal support 8 and able to act in thrusting relationship against the toroidal support itself to apply the rubber-coated filiform element 13 and make it adhere against the terminal edge of the carcass ply 4 or other previously formed component of the tyre 2. To the arm 14 of each laying organ 12 are also associated further guide and/or transmission elements (not shown) to bring the filiform element 13 to the terminal application roller 15, as well as a cutting unit operating upstream of the terminal roller itself to cut the continuous filiform element 13 during the final phase of application.

The arm 14 of each laying organ 12 is borne by a first guide structure 16 movable according to a first direction of actuation "L", preferably parallel to the axis of rotation X of the toroidal support 8. The first guide structure 16 is in turn movable on a second guide structure 17, along a second direction "N" preferably orthogonal to the first direction of actuation "L". These motions are reflected in corresponding movements of the terminal application roller 15.

Each arm 14 is also preferably able to swivel about an axis of oscillation "K" orthogonal relative to the directions of actuation "L" and "N".

A programmable electronic control unit, not shown because it can be obtained in any opportune manner by the person versed in the art, controls the actuation of each terminal application roller 15 along the first and second direction of actuation "L" and "N", and about the axis of oscillation "K", as well as the actuation of the toroidal support 8 about its own axis of rotation X, interpolated with the movements of terminal application rollers. Actuation control by the electronic control unit can advantageously be carried out according to pre-set programs, selectable on each occasion according to the geometric and dimensional characteristics of the tyre 2 undergoing work, which can for instance be determined through an identification code, for instance of the barcode type, associated to the toroidal support 8 and readable by a suitable reading unit associated for instance to the support device 10. To manufacture each of the circumferentially inextensible reinforcing annular inserts 6, it is essentially provided for the terminal application roller 15 of each laying organ 12 to be brought in thrusting relationship against the external surface of the toroidal support 8 to determine the application of a first extremity of the continuous filiform element 13 against the respective terminal edge of the carcass ply 4 or other component of the tyre 2 previously formed on the toroidal support itself.

Simultaneously or immediately after the application of the first extremity of the continuous filiform element 13, the toroidal support 8 is actuated in rotation about its own geometric axis X. Simultaneously with said rotatory motion, the terminal application roller 15 of each laying organ 12 is moved radially towards or away from the geometric axis of rotation X, in such a way as to cause the continuous filiform element 13 to be laid according to a path substantially concentric to the axis of rotation X, thereby forming a plurality of concentric turns 18 set radially side by side, as Figure 2 clearly shows. Advantageously, the formation of each of the turns 18 is accomplished essentially in two distinct phases. It is provided for a prevalent segment 18a of each turn 18 to be formed by laying the filiform element 13 according to a laying circumference that is concentric relative to the axis of rotation X. For this purpose, each arm 14 is maintained motionless during the rotation of the toroidal support 8, so that the filiform element 13 actuated longitudinally in the direction of the terminal application roller 15 is guided thereby on the support element 8 in an application point that is stationary relative to the geometric axis of rotation X. This situation is maintained until the turn 18 is almost completely formed, by way of indication until the toroidal support 8 completes a rotation of at least 315 ° about the geometric axis X.

The formation of the prevalent segment of the turn 18 is preceded or followed by the formation of a transition segment 18b, carried out by suitably actuating the arm 14 of each laying organ 12, in such a way as to displace radially the terminal application roller 15, and hence the application point of the continuous elongated element 13, relative to the geometric axis of rotation X simultaneously with the rotation of the toroidal support 8. In this way, the filiform element 13 is deviated from the laying circumference of the prevalent segment 18a, to be brought on a new laying circumference, concentric to the first, whereon the prevalent segment 18a of the contiguous turn 18 shall be formed.

Preferably, the formation of the transition segment 18b is conducted simultaneously with the laying of the filiform element 13 according to an angular sector, indicated as " " in Figure 3, whose amplitude measured in correspondence with the axis of rotation X preferably ranges between 5 ° and 30°, and in any case not exceeding 45 ° .

Preferably, the laying of the continuous filiform element 13 starts with the formation of the prevalent segment 18a of the radially external turn of the insert 6 being manufactured.

During the laying of the last turn 18, i.e. the innermost turn in the example described, the continuous elongated element 13 is cut at a predetermined linear distance from the first extremity thereof, measured along the development of the elongated element itself for instance by means of an encoder associated to the terminal roller 15 or to one of the guide rollers positioned on the arm 14 of the respective laying organ 12.

Preferably, the laying of the last turn 18 ends immediately before the start of the formation of the transition segment 18b thereof. Of this turn 18, therefore, only the prevalent segment 18a positioned concentrically to the axis of rotation X shall be measurable, the turn 18 lacking the transition segment 18b.

By so doing, the continuous elongated element 13 advantageously presents its opposite extremities located respectively in correspondence with an initial point and with a terminal point of the transition segment 18b of at least one of the turns 18. In particular, the first extremity of the elongated element 13 is situated in correspondence with the initial point of the transition segment 18b belonging to the first of the turns 18, i.e. to the radially outermost turn 18. The second extremity of the elongated element 13 is in turn situated in correspondence with the terminal point of the transition segment 18b belonging to the next-to-last turn 18.

The present invention achieves important advantages.

It is noted that the laying accomplished according to the subject method allows to attain a better distribution of the masses of each annular insert 6 relative to the geometric axis of rotation X of the tyre 2, eliminating the problems deriving from the mass imbalances inevitably connected with the laying conducted according to the prior art.

The better to highlight this advantageous aspect, Figures 4 and 5 show in schematic fashion the laying obtainable respectively according to the subject method and according to the state of the art. It should be observed that in these 5 figures the dimensions of the filiform element 13 are considerably enlarged, and the diameter of the laying circumferences of the turns 18 was purposely reduced relative to the actual situation. From Figure 5, one can easily note that the laying accomplished according to the prior art determines a certain imbalance relative to the geometric axis of rotation X or other reference axis, since the barycentric l o axis "P" of the insert 6 formed by the turns 18 is offset relative to the axis X, by an amount corresponding to half the radial distribution pitch of the turns themselves.

The same situation cannot be observed in Figure 4, where the turns 18 extend in a manner that is perfectly concentric to the geometric axis X

15 practically along the totality of their development. In this circumstance, the possible barycentric imbalance is represented exclusively by the absence of material in the areas indicated as "Z" in Figure 4, delimited on the continuation of the extremities of the elongated element 13 in correspondence with the transition segments 18b. The maximum extent of this imbalance therefore

20 corresponds to the mass of a segment of the filiform element 13 having a length equal to the circumferential extension of one of the transition segments 18b, and has a practically negligible value, which can be completely eliminated by reducing the circumferential extension of the transition segments 18b to zero, i.e. manufacturing radially oriented transition segments 1 lb.

25 It should also be observed that, although described with particular reference to the manufacture of circumferentially inextensible annular inserts 6 integrated in the structures reinforcing the beads 5, the invention can be implemented to manufacture any reinforcing annular element to be integrated in the structure of a tyre, particularly wherever an optimal balancing is required relative to the geometric axis of rotation X of the tyre itself, or any other reference axis.

It should also be noted that the manufacture of such reinforcing annular elements can also be accomplished separately from the other components of the tyre being manufactured, on a toroidal support 8 or on a support element of another kind.

Claims

1. A method for manufacturing reinforcing annular elements of vehicle tyres, comprising the phases of laying at least a continuous filiform element (13) on a support element (8), according to a laying path substantially concentric to a reference axis (X), to form concentric turns (18) set radially side by side, characterised in that the formation of each of said turns (18) comprises the following phases: forming a prevalent segment ( 18a) of said turn ( 18) laying said at least one filiform element (13) according to a laying circumference concentric relative to said reference axis (X); forming a transition segment (18b) of said turn (18) by deviating the filiform element (13) from said laying circumference to a concentric laying circumference.

2. A method as claimed in claim 1, wherein the formation of said transition segment (18b) is accomplished simultaneously with the laying of the filiform element (13) in an angular sector (α) whose amplitude, measured in correspondence with the reference axis (X), presents a value of less than 45°.

3. A method as claimed in claim 1, wherein the formation of said transition segment (18b) is accomplished simultaneously with the laying of the filiform element (13) in an angular sector ( ) whose amplitude, measured in correspondence with the reference axis (X), has a value ranging between 5 ° and 30°.

4. A method as claimed in claim 1 , wherein the formation of the prevalent segment (18a) of each turn (18) is accomplished by longitudinally actuating the filiform element (13) and guiding the filiform element in a stationary application point on said support element (8), actuated in rotation about said geometric reference axis (X), the formation of the transition segment (18b) being accomplished by radially displacing the application point of the filiform element (13) on the support element (8), simultaneously with the rotation of the support element itself.

5. A tyre for vehicle wheels, comprising a carcass structure (3) having at least a carcass ply (4) presenting axially opposite edges engaged to respective annular structures reinforcing the beads (5), each of said annular structures reinforcing the beads (5) comprising at least a circumferentially inextensible insert (6) formed by at least a continuous filiform element (13) extending according to radially contiguous turns (18) substantially concentric to an axis of rotation (X) of the tyre (2), characterised in that each of said turns (18) presents a prevalent segment (18a) positioned along a circumferential line concentric to said axis of rotation (X), and a transition segment (18b) extending away from or towards said axis of rotation (X) to join the prevalent segment ( 18a) of a radially contiguous turn.

6. A tyre as claimed in claim 5, wherein the transition segment (18b) of each turn (18) subtends, about the axis of rotation (X) of the tyre (2), an angular sector ( ) whose amplitude presents a value of less than 45°.

A tyre as claimed in claim 5, wherein the transition segment (18b) of each turn (18) subtends, about the axis of rotation (X) of the tyre (2), an angular sector ( ) whose amplitude presents a value ranging between 5° and 30°.

8. A tyre as claimed in claim 5, wherein said continuous filiform element 5 (13) presents a first and a second extremities each arranged in circumferential alignment with the prevalent segment (18a) of one of said turns (18).

9. A tyre as claimed in claim 8, wherein said first and second extremities are respectively positioned in correspondence with an initial point and with a l o terminal point of the transition segment (18b) of at least one of said turns (18).

10. A tyre as claimed in claim 5, wherein said at least one continuous filiform element (13) comprises a single metallic wire.

15 11. A tyre as claimed in claim 10, wherein said metallic wire has a diameter ranging between 0.7 mm and 1.3 mm.

12. A tyre as claimed in claim 5, wherein said at least one continuous filiform element (13) comprises at least a metallic cord with multiple strands 0 mutually twisted in counter direction.

13. A tyre as claimed in claim 12, wherein said metallic cord is a 7x4x0.28 cord.

5 14. A tyre as claimed in claim 5, wherein said at least one continuous filiform element (13) comprises at least a textile cord made of aramidic fibre.

15. A reinforcing annular element for vehicle tyres, comprising at least a continuous filiform element (13) extending according to radially contiguous turns (18) substantially concentric to a geometric reference axis (X), characterised in that each of said turns ( 18) presents a prevalent segment (18a) positioned along a circumferential line concentric to said reference axis (X), and a transition segment (18b) extending away from or towards said reference axis (X) to join the prevalent segment (18a) of a radially contiguous turn (18).

16. An annular element as claimed in claim 15, wherein the transition segment (18b) of each turn (18) subtends, about said reference axis (X), an angular sector ( ) whose amplitude has a value of less than 45°.

17. An annular element as claimed in claim 15. wherein the transition segment (18b) of each turn (18) subtends, about said reference axis (X), an angular sector (α) whose amplitude has a value ranging between 5 ° and 30 ° .

18. An annular element as claimed in claim 15. wherein said continuous filiform element (13) presents a first and a second extremities each arranged in circumferential alignment with the prevalent segment ( 18a) of each of said turns (18).

19. An annular element as claimed in claim 18, wherein said first and second extremities are respectively positioned in correspondence with an initial point and with a terminal point of the transition segment (18b) of at least one of said turns (18).

20. An annular element as claimed in claim 15, wherein said at least one continuous filiform element (13) comprises a single metallic wire.

21. An annular element as claimed in claim 20, wherein said metallic wire presents a diameter ranging between 0.7 and 1.3 mm.

22. An annular element as claimed in claim 15, wherein said at least one continuous filiform element (13) comprises at least a metallic cord with multiple strands mutually twisted in counter direction.

23. An annular element as claimed in claim 22, wherein said metallic cord is a 7x4x0.28 cord.

24. An annular element as claimed in claim 15, wherein said at least one continuous filiform element (13) comprises at least a textile cord made of aramidic fibre.