Thread guide for an apparatus for manufacturing a filamentary stiffening structure of a tyre, and associated manufacturing apparatus

Abstract

The invention relates to a thread guide for an apparatus for manufacturing a filamentary stiffening structure of a tyre. The thread guide (10) comprises a base (32) and first and second fingers (34) which are supported by the base and are each provided with a guide portion (40) for the thread (14). The guide portions (40) together form a funnel capable of guiding the thread from mutually remote front edges (44) towards closer-together rear edges (46) of the guide portions (40). The closer-together rear edges (46) are curved and delimit between them a passage for the thread having a width greater than or equal to the diameter of the thread. The base (32) defines an opening (52) longitudinally extending the passage for the thread, the transverse dimension of the opening (52) increasing in the direction away from the passage for the thread (14).

Description

[0001] DESCRIPTION

[0002] TITLE: Wire guide for a device for manufacturing a wire stiffening structure for a tire, and associated manufacturing device

[0003] technical field

[0004] The invention relates to the manufacture of tires, and more specifically to the manufacture of a wire stiffening structure for a tire.

[0005] In particular, the invention relates to a wire guide for an apparatus for manufacturing a wire stiffening structure of a tire, and a manufacturing apparatus comprising at least one such wire guide.

[0006] Previous techniques

[0007] In order to improve the behavior, particularly the drift resistance, of pneumatic tires, it is known to implant a stiffening structure within the toroidal inflation cavity that delimits the tire.

[0008] Reference can be made in this regard to the Applicant’s document WO 2020 / 128225-Al.

[0009] The tire described in this document comprises a crown extended radially inward on each side of the tire's median plane by first and second sidewalls, and then by first and second bead ribs designed to contact a mounting support, for example, a rim. Each first and second bead includes a circumferential reinforcing element designed to secure the tire to the mounting support.

[0010] The tire includes an internal surface defining a toroidal cavity for inflating the tire once it is mounted on the mounting support.

[0011] The tire described in these documents includes a stiffening structure comprising first wire stiffening elements extending continuously in the toroidal cavity from the first bead to the apex and second wire stiffening elements extending continuously in the toroidal cavity from the second bead to the apex.

[0012] Each first and second wire stiffening element is attached to each bead from which it extends by a bead interface between the wire stiffening element and a portion of the bead's inner surface. Similarly, each first and second wire stiffening element is attached to the tire's crown by a crown interface between the wire stiffening element and a portion of the crown's inner surface.

[0013] These wire stiffening elements are commonly called "stays." The advantage of using wire stiffening elements is that they result in a low-mass, low-hysteresis stiffening structure. Using identical wire stiffening elements ensures a homogeneous distribution of stress between them.

[0014] However, in order to produce such cable-stayed bandages, the Applicant has developed specific manufacturing equipment.

[0015] In this regard, reference can be made to document WO 2022 / 200718-A1 which proposes a tool with a grooved core for the manufacture of pneumatic tires reinforced by stays which pass through the inflation cavity.

[0016] The tooling described in this document includes a core with groove-type passages intended to receive reinforcement elements, called "stays", which are designed to permanently integrate the structure of the bandage and extend each into the cavity of the bandage by connecting a summit anchor point located in the top of the bandage to a lateral anchor point located in one of the sides or ridges of the bandage.

[0017] The use of such a core allows the stays to be positioned at the desired locations within the volume reserved by the core and consequently in the region of space which will subsequently become the cavity of the bandage after the said bandage has been formed and the core removed.

[0018] We also know from the prior art an apparatus for manufacturing a reinforcement for tires described in document EP 1 426 170-A2. The manufacturing apparatus makes it possible to manufacture the reinforcement from a wire and comprises a frame used in cooperation with a toroidal core on which the reinforcement is progressively built by depositing wire hoops along a desired trajectory.

[0019] The manufacturing apparatus further includes a wire dispensing element, an animation mechanism to transport the wire dispensing element and pressers to apply the wire onto the toroidal form.

[0020] Such a manufacturing device allows the wire to be laid at a variable pitch by varying the rotation speed of the core without changing the working rate of the dispensing element.

[0021] The invention aims to increase the accuracy of wire placement on a core, in particular to enable the manufacture of a wire stiffening structure, especially on a tool with a grooved core of specific manufacture.

[0022] More specifically, the invention aims to enable the manufacture of a wire stiffening structure extending within the toroidal cavity of the tire from the first bead to the second bead, passing through the crown of the tire. This structure is, for example, fabricated on a toroidal core equipped with a plurality of circumferentially distributed grooves formed along inclined planes at various angles of inclination.

[0023] Description of the invention

[0024] The invention relates to a wire guide for an apparatus for manufacturing a wire stiffening structure of a tire, the wire guide comprising a base and first and second fingers supported by the base and each provided with a wire guiding portion.

[0025] The guide portions of the first and second fingers together form a funnel capable of guiding the thread from widely spaced front edges to closely spaced rear edges of said guide portions. The closely spaced rear edges of said guide portions are curved and define a passage for the thread with a width greater than or equal to the thread diameter.

[0026] The base defines an opening extending longitudinally from said passage for the wire, the transverse dimension of the opening increasing as it moves away from said passage for the wire.

[0027] The guide sections of the first and second fingers direct a thread, which is brought between the far front edges, from the front of the thread guide towards the thread passage. The thread thus guided is in contact with one of the guide sections between the far front and near rear edges of the relevant guide section.

[0028] The term "the guide portions of the first and second fingers together form a funnel" means a set of surfaces of the guide portions approaching each other so that a passage between said set of surfaces narrows continuously from a first end to a second end of said passage, regardless of the shape of the funnel thus formed.

[0029] The opening, whose transverse dimensions increase with distance from the wire passage, facilitates the movement of accessories of the manufacturing apparatus, in particular a drive mechanism that moves a wire ejector and a pressure plate. The opening is designed to be positioned opposite a ridge or flank of the core on which the tire is formed.

[0030] According to a first design, the said passage for the wire, which is delimited between the close rear edges of the said guide portion, forms a curved groove.

[0031] Advantageously, the said curved groove is of constant width.

[0032] The curved groove is advantageously shaped like an outer surface of a toroidal core of the manufacturing apparatus in which grooves have been cut, each groove being designed to receive a wire loop to form a wire portion of the tire's wire stiffening structure, in particular a wire portion extending from the apex to a bead or sidewall of the tire. The curved groove is designed to be positioned opposite a wire insertion point in such a cut groove. Advantageously, the width of the curved groove is greater than or equal to the width of such a cut groove.

[0033] According to a second alternative design, the space between the rear edges brought together of said guide portions decreases to a point of passage of the wire at which the distance between the rear edges brought together of said guide portions is minimal.

[0034] At least one of said first and second fingers may include a guide surface opposite the other of said first and second fingers which is inclined with respect to a direction from the front to the back of the wire guide.

[0035] Optionally, said first and second fingers each include a guiding surface facing each other and inclined with respect to the direction from front to back of the wire guide.

[0036] The said guiding surface of the first or second finger may have a surface finish Ra of a value less than or equal to 0.4 pm.

[0037] Such a surface finish Ra is particularly suitable when the wire has an adhesive coating for bonding to the tire rubber. A surface finish Ra of 0.4 pm or less reduces the wire's friction on the guiding surface and allows it to be guided more quickly through the wire channel. By guiding the wire quickly, a more taut wire stiffening structure can be achieved.

[0038] Optionally, the surface of each of the first and second fingers has a surface finish Ra of a value less than or equal to 0.4 pm.

[0039] Advantageously, the distance between the far front edges of said guide portions is at least ten times greater than the wire diameter, preferably at least fifty times greater, and more preferably at least one hundred times greater. Advantageously, a rear surface of the wire guide that has close rear edges is complementary in shape to an outer surface of a toroidal core of the manufacturing apparatus, in particular to an outer surface of a shoulder of said core.

[0040] Thus, the rear surface of the wire guide can be placed as close as possible to the outer surface of the core in order to guide the wire.

[0041] According to the first design in which the passage for the wire forms a curved groove, this curved groove is optionally curved according to the shape of the shoulder of the core. The shoulder of the core is the point of greatest diameter of the grooves cut and is therefore advantageously the point of insertion of the wire into the grooves cut.

[0042] The present invention also relates to an apparatus for manufacturing a wire stiffening structure for a tire, the apparatus comprising:

[0043] - a frame capable of cooperating with a toroidal core which is intended to be mounted on the frame in a rotational manner and on which the wire stiffening structure of the tire is progressively built by depositing hoops of the wire along a desired trajectory for the wire;

[0044] - a wire ejection device in which the wire can slide;

[0045] - a drive mechanism mounted on the frame and configured to move said wire depositing device in a cyclic, back-and-forth motion, bringing it in successive cycles to the vicinity of each of the desired ends for the wire in said trajectory;

[0046] - pressure plates arranged at each end of said trajectory and configured to apply the wire to the core at least at each end of said trajectory; and

[0047] - at least one wire guide as defined previously.

[0048] Optionally, the manufacturing apparatus includes wire guides disposed at each end of said path, each presser at one end of said path being able to extend through the opening of the wire guide at said end of said path to apply the wire to the core. Advantageously, the drive mechanism is configured to move said wire ejection member in a plane, the wire guide being able to guide the wire out of said plane.

[0049] The manufacturing apparatus may include a translation mechanism configured to translate said wire guide at least in an ortho-radial direction of the core.

[0050] This facilitates the alignment of the wire passage with wire insertion points of irregularly distributed circumferential grooves, in particular grooves made along inclined planes at different angles of inclination, each inclined plane being parallel to an axis of rotation of the core.

[0051] Optionally, the manufacturing apparatus includes a memory in which translation coordinates of the translation mechanism associated with angular positions of the core are stored, the translation mechanism being configured to translate said wire guide according to the angular position of the core and the associated translation coordinate.

[0052] Optionally, the manufacturing apparatus includes a core groove position detection device, the translation mechanism being configured to translate said wire guide according to the detected groove position.

[0053] Advantageously, the manufacturing apparatus is capable of implementing a manufacturing process for a wire stiffening structure of a tire comprising at least the positioning of said wire guide so that the wire deposited by said depositing member is guided by said guide portions towards a groove cut into the core, and the application of the wire to the core by a press extending through said opening.

[0054] This manufacturing process may include prior calculation or measurement of the position of said groove cut into the core.

[0055] Brief description of the drawings The present invention will be better understood upon study of the detailed description of embodiments, taken by way of non-limiting examples and illustrated by the accompanying drawings in which:

[0056] [Fig 1] is a perspective view of a device for manufacturing a wire stiffening structure of a tire according to an example of an embodiment of the invention;

[0057] [Fig 2] is a perspective view of a wire guide from figure 1;

[0058] [Fig 3] is a side view of the wire guide in figure 2;

[0059] [Fig 4] is a perspective view of a wire guide according to another embodiment of the invention; and

[0060] [Fig 5] is a schematic view of the determination of the height of the wire guide.

[0061] Detailed description

[0062] Figure 1 illustrates a device for manufacturing 2 a wire stiffening structure of a tire, such a wire stiffening structure being, for example, described in document WO 2022 / 200717-Al.

[0063] The manufacturing apparatus 2 comprises a frame, a wire depositing element 4, a drive mechanism 6, and pressers 8.

[0064] Manufacturing device 2 also includes 10 wire guides which will be described in more detail later.

[0065] The frame cooperates with a toroidal core 12 mounted on the frame in a rotational manner and on which the wire stiffening structure of the tire is progressively built from a wire 14 by depositing hoops of the wire 14 according to a desired trajectory for the wire 14.

[0066] In a non-limiting embodiment, the stiffening structure manufactured by the manufacturing apparatus 2 extends continuously from a first sidewall and / or bead to a second sidewall and / or bead, passing through a vertex of the tire, in particular so as to meander from the first sidewall and / or bead to the second sidewall and / or bead. The wire 14 of the stiffening structure comprises sections extending into a toroidal cavity of the tire. The term "wire" should, of course, be understood in a very general sense, encompassing a monofilament, a multifilament, an assembly such as a cable or twist, or a small number of cables or twists grouped together, regardless of the nature of the material and whether the "wire" is pre-coated with rubber or not.

[0067] In this description, the term "hoop" refers to a section of wire 14 extending from one point to another within the wire stiffening structure. The set of these hoops forms the wire stiffening structure. Each hoop is designed to extend at least from a bead towards the top of the tire. These hoops can be individualized by cutting the wire 14 during installation, or all connected together within the wire stiffening structure, for example, by loops.

[0068] The removal member 4 includes, for example, an eyelet in which the wire 14 can slide.

[0069] The drive mechanism 6 is mounted on the frame and is capable of moving the wire ejection member 4 in a cyclic, back-and-forth motion, bringing it in successive cycles to the vicinity of each of the desired ends for the wire 14.

[0070] The drive mechanism 6 comprises a main arm 16, a front auxiliary arm 18, and a rear auxiliary arm 20. Each auxiliary arm 18, 20 is articulated on a pivot. The main arm 16 is mounted on one of the auxiliary arms 18, 20 via a pivot and on the other auxiliary arms 18, 20 by a cam follower cooperating with a slot 22.

[0071] The main arm 16 and auxiliary front and rear arms 18, 20 cause the wire removal organ 4 to describe a movement contained in a plane.

[0072] The pressers 8 are arranged at each end of the desired trajectory for the wire 14 and are able to apply the wire 14 to the toroidal core 12 at the ends of the desired trajectory.

[0073] Document EP 1 426 170A2 describes the general operation of the frame, the wire ejection device 4, the drive mechanism 6, and the pressure plates 8. The tire has an internal surface defining its toroidal cavity. The toroidal core 12 comprises an external receiving surface 24 having a shape conjugate to the internal surface of the tire and includes a plurality of grooves 26 extending under the external receiving surface 24 and opening onto the external receiving surface 24. The tire is intended to be molded onto the external receiving surface 24 of the tooling.

[0074] When defining positions, directions, or senses using the terms "radially, axially, circumferentially," or when referring to radii, the reference frame is the toroidal core 12 on which the tire is manufactured, or the tire itself, which amounts to the same thing. The geometric reference axis is the rotation axis R of the toroidal shape.

[0075] The toroidal core 12 comprises an assembly of several monobloc angular sectors arranged in azimuth around the axis of rotation R, according to an alternation of sectors called "keys" 28, preferably designed to be accessible by radially internal approach and to be removed first during the disassembly of the toroidal core 12, and sectors called "vaults" 30, supported and locked in position by the keys 28, and preferably designed to become maneuverable after they have been released by the removal of the keys 28. The vaults 30 form sectors complementary to the keys 28.

[0076] Such an arrangement in monobloc sectors 28, 30 will facilitate demolding, and will also allow the wire 14 to pass locally from the radially outside side of the toroidal core 12, onto the external receiving surface 24 which will receive the components of the bandage wall, which will make it easy to integrate the corresponding portion of the wire 14 into the wall and thus ensure the anchoring of the wire 14 in the top of the bandage.

[0077] Each key 28 here comprises a plurality of key grooves distributed in azimuth around the axis of rotation R according to an angular repetition step, each key groove being made along a radial plane containing the axis of rotation R. Each arch 30 here comprises a plurality of arch grooves distributed around the axis of rotation R, each arch groove being inclined at an angle of inclination forming a non-zero angle with respect to a radial axis, each arch groove being made along an inclined plane parallel to the axis of rotation R of the toroidal core 12, this inclined plane not containing the axis of rotation R of the toroidal core 12.

[0078] In general, the grooves 26 are arranged according to a variable angle of inclination which depends on the dimension of the toroidal core 12.

[0079] This arrangement of the grooves 26 implies that the insertion points of the wire 14 in the grooves 26 are irregularly distributed in azimuth around the axis of rotation R of the toroidal core 12, each insertion point corresponding to the point of greatest diameter of the groove 26 concerned and being located at the shoulder of the toroidal core 12.

[0080] Alternatively, we could provide that the grooves 26 are all identical and inclined in the same direction.

[0081] Each wire guide 10 is positioned so that the wire 14 deposited by the depositing member 4 is guided in a groove 26 of the toroidal core 12.

[0082] Each wire guide 10, illustrated more visibly in figures 2 and 3, comprises a base 32 and first and second fingers 34 supported by the base 32.

[0083] The base 32 is provided with a folded portion 36 and two connecting portions 38, each connecting portion 38 extending on one side one of the first and second fingers 34 and on the other side the folded portion 36 of the base 32.

[0084] The first and second fingers 34 are each provided with a guide portion 40 for the wire 14. The guide portions 40 of the first and second fingers 34 together form a funnel suitable for guiding the wire 14 deposited by the depositing member 4.

[0085] The guide portion 40 of each of the first and second fingers 34 comprises an inclined guide surface 42 which is opposite the other finger 34 and which extends between a front edge 44 and a rear edge 46. The front edge 44 is located radially outside the rear edge 46. The wire 14 is deposited by the depositing member 4 from the front to the rear of the wire guide 10. Each guide surface 42 is inclined with respect to the direction from the front to the rear of the wire guide 10. When the wire guide 10 is viewed from the side, the tangent to each guide surface 42 and the direction from front to rear form an angle whose value increases from the rear edge 46 towards the front edge 44 of the guide surface 42 in question.

[0086] The inclined guide surfaces 42 of the first and second fingers 34 move towards each other from the far-off front edges 44 of the guide surfaces 42 to the near-rear edges 46 of the guide surfaces 42 to form the funnel. The distance between the far-off front edges 44 is strictly greater than the distance between the near-rear edges 46. A passage cross-section of the funnel defined by the first and second fingers 34, in particular by the guide surfaces 42 of the first and second fingers 34, decreases continuously from the front to the rear of the wire guide 10, in particular from the far-off front edges 44 to the near-rear edges 46.

[0087] The wire guide 10 is thus able to guide the wire 14 out of the plane described by the removal member 4.

[0088] The rear edges 46 close to the guide portions 40 are curved and delimit between them a passage for the wire 14 which is presented here in the form of a curved groove 48.

[0089] The curved groove 48 has a width greater than or equal to the diameter of the wire 14, and here has a constant width which is less than three times the width of a groove 26 of the toroidal core 12.

[0090] The rear surface of the wire guide 10 is curved to follow the outer shape of the toroidal core 12. More precisely, the rear surface, which has closely spaced rear edges 46, is complementary in shape to a portion of the outer surface 24 of the toroidal core 12, and even more precisely to the outer surface 24 of the shoulder 50 of the toroidal core 12. The curved groove 48 is contained within a radial plane containing the axis of rotation R. The base 32 of the wire guide 10 defines an opening 52 extending longitudinally from the curved groove 48. The opening 52 extends transversely between the connecting portions 38 of the base 32, and longitudinally between the guiding portions 40 of the wire guide 10 and the bent portion 36 of the base 32. The transverse dimension of the opening 52, namely the dimension between the connecting portions 38 of the base 32, increases from the curved groove 48, towards the folded portion 36 of the base 32.

[0091] The shape and position of the opening 52 facilitate the movement of the depositing organ 4 which radially bypasses the wire guide 10 from the distal end of the distant front edges 44 towards the folded portion 36 of the base 32 in order to deposit the wire 14 in the funnel formed by the guiding surfaces 42 of the first and second fingers 34.

[0092] The shape and position of the opening 52 also facilitate the movement of the presser 8 arranged on the same side of the toroidal core 12 as the wire guide 10 considered, this presser 8 engaging in the opening 52 of the wire guide 10 considered in order to press the wire 14 at one end of the desired trajectory for the wire 14.

[0093] In order to increase the tolerance of the positioning of the wire guide 10 relative to the dispensing member 4, and to guide the wire 14 from many trajectories of the wire guide 10, the distance between the front edges 44 away from the guiding portions 40 is at least ten times greater than the diameter of wire 14, preferably at least fifty times greater, and more preferably at least one hundred times greater.

[0094] In order to quickly guide the wire 14 into the groove 26 of the toroidal core 12, each guiding surface 42 of the first and second fingers 34 has a surface finish Ra of a value less than or equal to 0.4 pm.

[0095] With reference to Figure 2, the manufacturing apparatus 2 further includes a translation mechanism 54 for each wire guide 10 in an ortho-radial direction of the toroidal core 12. The translation mechanism 54 is capable of translating the wire guide 10 independently of the drive mechanism 6. More specifically, the folded portion 36 of the wire guide 10 in question is connected to the relevant translation mechanism 54.

[0096] The toroidal core 12 is mounted on the frame in a rotational manner, however some of the grooves 26 of the toroidal core 12 are made along inclined planes which are parallel to the axis of rotation R of the toroidal core 12. Thus, the angular position for the insertion of the wire 14 varies from one groove 26 to another of the toroidal core 12 depending on the angle of inclination of the inclined planes along which the grooves 26 of the toroidal core 12 are made.

[0097] By changing the translational position of the wire guide 10, and without changing the regular rotational movement of the toroidal core 12 or the regular movement of the dispensing member 4, the movement of the wire 14 is corrected so that the wire 14 is guided by the wire guide 10 in the groove 26 of the toroidal core 12.

[0098] The second embodiment shown in Figure 4 differs from the first embodiment of the wire guide shown in Figures 1 to 3 in that the passage for the wire 14, delimited by the rear edges 46 close to the guide portions 40, does not form a curved groove of constant width. In this example, the space between the rear edges 46 close to the guide portions 40 decreases until a point 55 of the wire 14 passes through it, at which point the distance between the rear edges 46 close to the guide portions 40 is minimal.

[0099] The passage point 55 is of a width greater than or equal to the diameter of the wire 14, for example less than three times the width of a groove 26 of the toroidal core 12. The opening 52 of the base 32 of the wire guide extends from the passage point 55 of the wire.

[0100] Other forms of passage for the wire can be considered as alternatives, particularly depending on the shape of the grooves in the toroidal core for which the wire guide is intended to be used.

[0101] With reference to Figure 5, the manufacturing apparatus 2 includes a memory 56 in which translation coordinates of the translation mechanism 54 associated with angular positions of the toroidal core 12 are stored. These translation coordinates are, for example, calculated based on a theoretical model of the toroidal core 12 and the theoretical arrangement of the grooves 26 on the keys 28 and arches 30. More precisely, these coordinates are, for example, calculated based on the azimuth of the grooves 26 of the toroidal core 12, the angles formed by the inclined planes for manufacturing the grooves 26, and the radius of the toroidal core 12. These coordinates may, moreover, take into account an assembly clearance of the keys 28 and arches 30.

[0102] The manufacturing device 2 also includes a processor 58 capable of controlling the translation mechanism 54 as a function of the angular position of the toroidal core 12 and translation coordinates contained in the memory 56.

[0103] In order to further improve the accuracy of the positioning of the wire guide 10 relative to the groove 26 of the toroidal core 12, the manufacturing apparatus 2 is equipped with a detection device 60 for the position of grooves 26 of the toroidal core 12.

[0104] The detection device 60 includes, for example, an optical detection device such as an optical fiber. The detection device 60 is positioned opposite the toroidal core 12, in particular opposite the shoulder 50 of the toroidal core 12, in order to detect the angular position of the grooves 26 of the toroidal core 12 and to associate these positions with angular positions of the toroidal core 12.

[0105] The processor 58 is capable of performing a calculation, based on the detected angular positions of the grooves 26 of the toroidal core 12 and the angular positions of the toroidal core 12, to determine the translation coordinates of the wire guide 10 and associate them with the angular positions of the toroidal core 12.

[0106] The processor 58 is capable of controlling the translation mechanism 54 according to the detected position of the groove 26 of the toroidal core 12.

[0107] In the examples shown, the wire guide 10 comprises first and second fingers 34 that are symmetrical to each other. Alternatively, the wire guide 10 could comprise first and second fingers 34 that are different from each other, particularly depending on the architecture of the toroidal core 12 when the wire 14 comes into contact with a single guide portion 40.

[0108] In the examples shown, the wire guide 10 is made from a single piece. Alternatively, it is possible to form the wire guide by assembling several separate pieces or parts.

Claims

DEMANDS 1. Wire guide (10) for an apparatus for manufacturing (2) a wire stiffening structure of a tire (4), the wire guide (10) comprising a base (32) and first and second fingers (34) supported by the base (32) and each provided with a wire (14) guiding portion (40), characterized in that: - the guide portions (40) of the first and second fingers (34) together form a funnel capable of guiding the wire (14) from front edges (44) far apart from each other to rear edges (46) close together of said guide portions (40); - the rear edges (46) close to said guide portions (40) are curved and delimit between them a passage for the wire (14) having a width greater than or equal to the diameter of the wire (14) - the base (32) defines an opening (52) extending longitudinally said passage for the wire (14), the transverse dimension of the opening (52) increasing as it moves away from said passage for the wire (14).

2. Wire guide (10) according to claim 1, in which said passage for the wire (14), which is delimited between the rear edges (46) brought together from said guide portions (40), forms a curved groove (48).

3. Wire guide (10) according to claim 2, wherein said curved groove (48) is of constant width.

4. Wire guide (10) according to any one of claims 1 to 3, wherein at least one of said first and second fingers (34) comprises a guiding surface (42) opposite the other of said first and second fingers (34) which is inclined with respect to a direction from the front to the back of the wire guide (10), said first and second fingers (34) in particular each comprising a guiding surface (42) opposite each other and inclined with respect to the direction from the front to the back of the wire guide (10).

5. Wire guide (10) according to claim 4, wherein said guiding surface (42) of the first or second finger (34) has a surface finish Ra of a value less than or equal to 0.4 pm, the surface of each of the first and second fingers (34) has a surface finish Ra of a value less than or equal to 0.4 pm.

6. Wire guide (10) according to any one of claims 1 to 5, wherein the distance between the leading edges (44) away from said guide portions (40) is at least ten times greater than the wire diameter (14), preferably at least fifty times greater, more preferably at least one hundred times greater.

7. Wire guide (10) according to any one of claims 1 to 6, in which a rear surface of the wire guide (10) which is provided with the rear edges (46) brought together is of complementary shape to an outer surface (24) of a toroidal core (12) of the manufacturing apparatus (2), in particular to an outer surface (24) of a shoulder (50) of said core (12).

8. Apparatus for manufacturing (2) a wire stiffening structure for a tire (4), the apparatus (2) comprising: - a frame suitable for cooperating with a toroidal core (12) which is intended to be mounted on the frame in a rotational manner and on which the wire stiffening structure of the tire (4) is progressively built by depositing hoops of the wire (14) along a desired trajectory for the wire (14); - a wire ejection device (6) in which the wire (14) can slide; - a drive mechanism (8) mounted on the frame and configured to move said wire depositing member (6) in a cyclic, back-and-forth motion, bringing it in successive cycles to the vicinity of each of the desired ends for the wire (14) in said trajectory; - pressure points (8) arranged at each end of said trajectory and configured to apply the wire (14) to the core (12) at least at each end of said trajectory; and - at least one wire guide (10) according to any one of claims 1 to 7.

9. Manufacturing apparatus (2) according to claim 8, wherein the drive mechanism (8) is configured to move said wire dispensing member (6) in a plane, the wire guide (10) being able to guide the wire (14) out of said plane.

10. Manufacturing apparatus (2) according to claim 8 or 9, comprising a translation mechanism (54) configured to translate said wire guide (10) at least in an ortho-radial direction of the core (12). 1 1. Manufacturing apparatus (2) according to claim 10, comprising a memory (56) in which are stored translation coordinates of the translation mechanism (54) associated with angular positions of the core (12), the translation mechanism (54) being configured to translate said wire guide (10) according to the angular position of the core (12) and the associated translation coordinate.

12. Manufacturing apparatus (2) according to claim 10 or 11, comprising a device for detecting the position of grooves (26) of the core (12), the translation mechanism (54) being configured to translate said wire guide (10) according to the detected position of the groove (26).

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