Process and drum for looping annular anchoring structures in a process for building tyres for vehicle wheels

Abstract

A process and a drum for looping annular anchoring structures in a process for building tyres for vehicle wheels includes: depositing a loop on a drum including a radially expandable/contractible intermediate annular portion and, in a position axially adjacent to the opposite axial ends of the intermediate annular portion, a pair of radially expandable/contractible lateral annular portions; associating an annular anchoring structure with a radially outer annular surface portion of the loop defined at the intermediate annular portion; and turning up each of opposite end edges of the loop on the annular anchoring structure through the lateral annular portions as a result of a thrusting stress imparted by a respective lateral annular portion of the pair of lateral annular portions because of a synchronous radial movement and a synchronous axial displacement of a respective plurality of circumferentially adjacent first angular sectors.

Claims

1. A process for looping annular anchoring structures in a process for building tyres for vehicle wheels, comprising: depositing a loop on a drum comprising a radially expandable/contractible intermediate annular portion and, in a position axially adjacent to opposite axial ends of said intermediate annular portion, a pair of radially expandable/contractible lateral annular portions; associating an annular anchoring structure with a radially outer annular surface portion of said loop defined at said intermediate annular portion; and turning up each of opposite end edges of said loop on said annular anchoring structure as a result of a thrusting stress imparted by a respective lateral annular portion of said pair of lateral annular portions because of a synchronous radial movement and a synchronous axial displacement of a respective plurality of circumferentially adjacent first angular sectors; wherein during the turning up, the annular anchoring structure is not rotated.

2. The process according to claim 1, wherein said axial displacement is carried out simultaneously with said radial movement.

3. The process according to claim 1, comprising, before depositing said loop, radially expanding at least said intermediate annular portion up to reach an operating diameter that is selected depending on a fitting diameter of a tyre to be built.

4. The process according to claim 3, wherein the radial expansion of at least said intermediate annular portion is carried out simultaneously with at least part of the radial movement of said first angular sectors.

5. The process according to claim 3, wherein the radial expansion of at least said intermediate annular portion is achieved as a result of the synchronous radial movement of a plurality of circumferentially adjacent second angular sectors.

6. The process according to claim 5, wherein the radial movement of each of said second angular sectors is obtained as a result of an elastic thrust exerted on each of said second angular sectors.

7. The process according to claim 1, wherein associating said annular anchoring structure comprises: positioning said annular anchoring structure in a radially outer position with respect to said loop at said intermediate annular portion; and radially expanding at least said intermediate annular portion until a radial thrust is exerted on a radially inner surface of said annular anchoring structure.

8. The process according to claim 7, wherein said radial thrust is an elastic thrust.

9. The process according to claim 1, comprising, at the end of the turning up of said opposite end edges of said loop, axially moving said first angular sectors away from said annular anchoring structure.

10. The process according to claim 9, comprising locking said first angular sectors in a distal axial position with respect to said annular anchoring structure.

11. The process according to claim 10, comprising radially contracting said first angular sectors after said first angular sectors are locked at said distal axial position.

12. The process according to claim 11, comprising, at the end of the radial contraction of said first angular sectors, unlocking said first angular sectors from said distal axial position.

13. The process according to claim 1, wherein an axial elastic thrust is exerted on each of said first angular sectors to achieve an axial displacement thereof towards a middle plane of the drum.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further characteristics and advantages of the present invention will become clearer from the following detailed description of preferred embodiments thereof, made with reference to the attached drawings. In such drawings:

(2) FIG. 1 is a schematic perspective view of a drum in accordance with the present invention;

(3) FIG. 2 is a schematic radial section view of a portion of the drum of FIG. 1 in a first operative configuration thereof;

(4) FIG. 3 is a schematic partial section view of the portion of drum of FIG. 1 in a subsequent operative configuration thereof;

(5) FIG. 4 is a schematic partial section view of the portion of drum of FIG. 1 in an operative configuration subsequent to that of FIG. 3;

(6) FIG. 5 is a schematic partial section view of the portion of drum of FIG. 1 in an operative configuration subsequent to that of FIG. 4;

(7) FIG. 6 is a schematic partial section view of the portion of drum of FIG. 1 in an operative configuration subsequent to that of FIG. 5;

(8) FIG. 7 is a schematic partial section view of the portion of drum of FIG. 1 in an operative configuration subsequent to that of FIG. 6;

(9) FIG. 8 is a schematic partial section view of the portion of drum of FIG. 1 in an operative configuration subsequent to that of FIG. 7.

DETAILED DESCRIPTION OF THE INVENTION

(10) In FIG. 1, reference numeral 100 wholly indicates an exemplifying embodiment of a drum for looping annular anchoring structures in accordance with the present invention. Such looping is carried out in a process for building tyres for vehicle wheels, preferably for automobile wheels.

(11) Preferably, the annular anchoring structures, once looped, are used in building the carcass structures of the aforementioned tyres. In particular, they are positioned in the beads of the tyre and are intended to keep the tyre firmly fixed to the anchoring seat specifically provided in the rim of the vehicle wheel.

(12) An example of an annular anchoring structure intended to be looped on the drum 100 is shown in FIG. 3 and is indicated with reference numeral 10.

(13) The annular anchoring structure 10 comprises a substantially circumferential annular insert 11, also called bead core, and a filling insert 12. The latter is associated with the substantially circumferential annular insert 11 in a radially outer position with respect to the latter.

(14) The looping of the annular anchoring structure 10 comprises the deposition of a loop 5 on the radially outer surface of the drum 100 (FIG. 2), the positioning of the annular anchoring structure 10 in a radially outer position with respect to the drum 100 through a transfer member 500 (FIG. 3), the coupling of the loop 5 with the radially inner surface of the annular anchoring structure 10 (FIG. 4) and the turning up of the opposite edges 5a, 5b of such a loop 5 around the annular anchoring structure 10 so as to completely surround the latter (FIGS. 5-7), thus forming a reinforced annular anchoring structure 15 (FIGS. 6-8). Subsequently, the reinforced annular anchoring structure 15 is picked up by a transfer member, which can for example be the same transfer member 500 used to position the annular anchoring structure 10 on the drum 100.

(15) Preferably, at the end of the looping process the end portions of the end edges 5a, 5b of the loop 5 are offset in the radial direction, for example by at least a few millimetres (preferably by about 5 mm).

(16) The drum 100 can be part of a work station in which there are at least one first storage member for storing annular anchoring structures 10 to be looped and at least one second storage member for storing reinforced annular anchoring structures 15. The aforementioned storage members can be part of a handling line arranged close to the drum 100.

(17) With reference to FIG. 1, the drum 100 extends concentrically to a longitudinal axis X-X.

(18) The drum 100 comprises an intermediate annular portion 110 and, in a position axially adjacent to the opposite axial ends of said intermediate annular portion 110, a pair of lateral annular portions 120a, 120b.

(19) Both the intermediate annular portion 110 and the lateral annular portions 120a, 120b are radially expandable/contractible.

(20) In particular, the intermediate annular portion 110 comprises a plurality of identical angular sectors 111, which are circumferentially adjacent and radially movable synchronously with each other.

(21) Hereinafter, the angular sectors 111 will be identified as intermediate angular sectors. For the sake of simplicity of illustration, in FIG. 1 the reference numeral 111 is associated with only one of the intermediate angular sectors.

(22) Each of the lateral annular portions 120a, 120b comprises a plurality of identical angular sectors 121a, 121b, which are circumferentially adjacent and radially movable synchronously with each other.

(23) Hereinafter, the angular sectors 121a, 121b will be identified as lateral angular sectors. For the sake of simplicity of illustration, in FIG. 1 the reference numerals 121a and 121b are associated with only one of the angular sectors of the lateral annular portion 120a and with only one of the angular sectors of the lateral annular portion 120b, respectively.

(24) The synchronous radial movement of the lateral angular sectors 121a is synchronous with the synchronous radial movement of the lateral angular sectors 121b, as described more clearly hereinafter.

(25) The drum 100 also comprises, in a radially inner position with respect to the intermediate angular sectors 111 and to the lateral angular sectors 121a, 121b, a sleeve 101 extending coaxially to the longitudinal axis X-X.

(26) The sleeve 101 is preferably fixed canti-levered on a bearing structure that is not illustrated, so as to allow the annular anchoring structure 100 to be placed in a radially outer position with respect to the drum 100.

(27) As shown in FIG. 2, inside the sleeve 101, and coaxially to the longitudinal axis X-X, a worm screw 102 is provided. The worm screw 102 has a first right-handed axial portion 102a and, on the opposite side with respect to a middle plane M of the drum 100, a second left-handed axial portion 102b.

(28) The screw 102 is supported inside the sleeve 101 by a pair of rolling bearings, not shown. Such a screw 102 can be set in rotation by a suitable motor group, also not shown.

(29) The right-handed axial portion 102a (or the left-handed one 102b) is defined in a radially inner position with respect to the lateral angular sectors 121a, whereas the left-handed axial portion 102b (or the right-handed one 102a) is defined in a radially inner position with respect to the lateral angular sectors 121b.

(30) With reference to FIG. 1, the drum 100 also comprises, in an axially outer position with respect to the lateral annular portions 120a, 120b, respective contrast rings 200a, 200b.

(31) Each contrast ring 200a, 200b is fixedly associated with the sleeve 101 through a plurality of axial brackets 201a, 201b and a plurality of radial brackets 202a, 202b. Preferably, the axial brackets 201a, 201b and the radial brackets 202a, 202b are arranged in an axially outer position with respect to the respective contrast ring 200a, 200b.

(32) Each axial bracket 201a, 201b has an axial end associated with the contrast ring 200a, 200b and an opposite axial end associated with a respective radial bracket 202a, 202b, in turn fixedly associated with the sleeve 101.

(33) The axial brackets 201a, 201b can be fixedly associated with the respective contrast ring 200a, 200b or can be removably associated with the contrast ring 200a, 200b.

(34) In the exemplifying embodiment of the drum 100 shown in FIG. 1, at each contrast ring 200a, 200b there are three axial brackets 201a, 201b and three radial brackets 202a, 202b, all circumferentially spaced apart by 120.

(35) Again with reference to the exemplifying embodiment of FIG. 1, each radial bracket 202a, 202b comprises a plurality of weight reduction holes 203a, 203b (four in the illustrated embodiment) aligned in the radial direction.

(36) For the sake of simplicity of illustration, reference numeral 203a, 203b is associated with only one hole of only one radial bracket 202a, 202b.

(37) Preferably, the radial brackets 202a, 202b are tapered progressively moving in the radially outward direction.

(38) FIGS. 2-8 show the mutual arrangement of an intermediate angular sector 111 and of the two lateral angular sectors 121a, 121b arranged on axially opposite sides with respect to the intermediate angular sector 111 in different operative configurations of the drum 100. The same mutual arrangement can be found, in each of the aforementioned operative configurations, at each of the other circumferentially adjacent angular sectors 111, 121a and 121b of the drum 100.

(39) The lateral angular sectors 121a and 121b are arranged in a mirror-like fashion with respect to the middle plane M of the drum 100.

(40) With reference to FIGS. 2-8, each intermediate angular sector 111 preferably comprises an inverted T-shaped body; it thus preferably comprises a radially outer portion having a predetermined axial length and a radially inner portion having a greater axial length than that of the radially outer portion.

(41) A respective elastic element 113, acting in radial thrust on the intermediate angular sector 111, is arranged in a radially inner position with respect to the intermediate angular sector 111.

(42) Preferably, the elastic element 113 is a compression spring.

(43) In the specific exemplifying embodiment illustrated in FIGS. 2-8, a support body 122 is provided in a radially inner position with respect to each pair of axially adjacent lateral angular sectors 121a, 121b. Such a support body 122 comprises two support body portions 122a, 122b arranged symmetrically on axially opposite sides with respect to the middle plane M of the drum 100. The support body portion 122a is arranged in a radially inner position with respect to the lateral angular sector 121a and the support body portion 122b is arranged in a radially inner position with respect to the lateral angular sector 121b.

(44) Each support body portion 122a, 122b is provided with a hole 123a, 123b extending in the radial direction (FIGS. 5-7). The hole 123a, 123b houses, through a sliding coupling, a respective guide bar 124a, 124b fixedly associated with the sleeve 101 and extending in the radial direction. As a result of the aforementioned sliding coupling the support body 122 can move radially with respect to the sleeve 101.

(45) The hole 123a, 123b has a radially outer portion with reduced diameter, which hereafter is called hole 123a, 123b.

(46) The guide bar 124a, 124b has a spigot 125a, 125b on a radially outer surface thereof (FIGS. 5-7).

(47) In the operative configurations of the drum 100 in which the lateral angular sectors 121a, 121b are radially contracted (FIGS. 2, 3 and 8), the spigot 125a, 125b is housed in the hole 123a, 123b. In the aforementioned figures, such a specific configuration is indicated with the following string of reference numerals: 125a=123a, 125b=123b.

(48) An end portion of a respective lever 140a, 140b is pivoted on each support body portion 122a, 122b. The opposite end portion of the lever 140a, 140b is pivoted at a flange 145a, 145b fixedly associated with a lead nut 146a, 146b coupled with a respective axial portion 102a, 102b of the screw 102.

(49) As a result of the screw-lead nut coupling and of the sliding coupling between support body 122 and guide bar 124a, 124b described above, a rotation of the screw (for example in the clockwise direction, if starting from the operative configuration of FIG. 2 and in the anti-clockwise direction if starting from the operative configuration of FIG. 7) produces a synchronous axial displacement of the flanges 145a, 145b in opposite directions (in particular the flanges 145a, 145b moves one towards the other if starting from the operative configuration of FIG. 2, and the flanges 145a, 145b move away from one other if starting from the operative configuration of FIG. 7) and consequently a synchronous radial displacement of the support body 122 (in particular a radial expansion of the lateral annular portions 120a, 120b if starting from the operative configuration of FIG. 2, and a radial contraction of the lateral annular portions 120a, 120b if starting from the operative configuration of FIG. 7).

(50) As shown in FIG. 2, the support body 122, comprises, in a radially inner position, a shoulder 130 on which a radially inner end of the elastic element 113 is arranged in abutment. Such an elastic element 113 is thus held in compression between the shoulder 130 and the radially inner surface of the intermediate angular sector 111.

(51) Each lateral angular sector 121a, 121b comprises, at an axially inner end thereof, a contact element 127a, 127b preferably made from deformable or elastic material. For the sake of simplicity of illustration the reference numerals 127a and 127b are reproduced only in FIGS. 4 and 6-8.

(52) The contact elements 121a, 121b ensure the continuity of surface contact between loop 5 and annular anchoring structure 10 during the looping of the latter.

(53) A respective elastic element 128a, 128b acts on an axially outer end of each lateral angular sector 121a, 121b. Such an elastic element 128a, 128b axially thrusts the respective lateral angular sector 121a, 121b towards the middle plane M of the drum 100.

(54) Preferably, the elastic element 128a, 128b is a compression spring housed in an axial seat 129a, 129b formed on an axially outer end portion of the lateral angular sector 121a, 121b.

(55) As shown in FIG. 3, the support body 122 comprises, in a radially outer position, a pair of shoulders 131a, 131b. An axially outer end of a respective elastic element 128a, 128b goes into abutment on each shoulder 131a, 131b. Each elastic element 128a, 128b is thus held in compression between the shoulder 131a, 131b and the axially outer end portion of the lateral angular sector 121a, 121b.

(56) In the operative configuration of the drum 100 shown in FIGS. 2, 3 and 8, as a result of the axial thrust exerted by the elastic element 128a, 128b on the lateral angular sector 121a, 121b, the axially inner end portion of each of the two opposite lateral angular sectors 121a, 121b is in axial abutment against the radially outer portion of the intermediate angular sector 111, thus counteracting the elastic thrust exerted on the lateral angular sectors 121a, 121b by the respective elastic elements 128a, 128b. In such an operative configuration the axially inner end portion of the two opposite lateral angular sectors 121a, 121b is also in radial abutment against the radially inner portion of the intermediate angular sector 111, thus counteracting the elastic thrust exerted on the intermediate angular sector 111 by the elastic element 113 and thus keeping the intermediate angular sector 111 in a position of radial contraction. In this way both the axial displacement of the lateral angular sectors 121a, 121b towards the middle plane M of the drum 100 and the radial expansion of the intermediate angular sector 111 are prevented. Such a radial expansion can, on the other hand, take place, as a result of the thrusting action exerted by the elastic element 113, because of the radial expansion of the lateral angular sectors 121a, 121b.

(57) With reference to FIG. 2, each lateral angular sector 121a, 121b also comprises a radial blind hole 150a, 150b that is open at the radially inner surface thereof. The blind hole 150a, 150b houses, in a radially outer position, an elastic element 151a, 151b and, in a radially inner position, a pin 152a, 152b. The elastic element 151a, 151b thrusts the pin 152a, 152b in the radial direction towards the outside of the blind hole 150a, 150b.

(58) Preferably, the elastic element 151a, 151b is a compression spring.

(59) In the operative configurations of the drum 100 shown in FIGS. 2-6 and 8, the pin 152a, 152b is misaligned with respect to (or outside of) the hole 123a, 123b; therefore, the free end radially inner portion of the pin 152a, 152b abuts against the radially outer surface of the support body 122, which thus exerts a contrast action to the thrust exerted by the elastic element 151a, 151b on the pin 152a, 152b. In such operative configurations the lateral angular sector 121a, 121b is free to slide axially on the support body 122.

(60) The axially outer end of each lateral angular sector 121a, 121b is pivoted at an end portion of a respective balancing lever 160a, 160b. The latter has, at an opposite free end portion thereof, a roller 161a, 161b which can rotate about a rotation axis perpendicular to the axial and radial directions of the drum 100.

(61) The roller 161a, 161b is arranged in a radially inner position with respect to the contrast ring 200a, 200b. Such a roller 161a, 161b is intended to abut on the contrast ring 200a, 200b when the lateral angular sector 121a, 121b is in a condition of maximum expansion (FIG. 7).

(62) During looping, each lever 160a, 160b rotates about two axially outer pivots formed in the support body 122, moving the lateral angular sectors 121a and 121b apart from one another until the pins 152a and 152b, as a result of the thrust exerted by the elastic element 151a, 151b, go inside the holes 123a and 123b. Such a specific configuration is indicated in FIG. 7 with the following string of reference numerals: 152a=123a, 152b=123b.

(63) The two lateral angular sectors 121a and 121b are thus locked in an axially distal position with respect to the middle plane M of the drum 100; this position ensures no interference between the contact elements 127a, 127b with the loop 5 turned up on the annular anchoring structure 10, during the contraction of the drum 100. Such a specific configuration is indicated in FIG. 7 with the following string of reference numerals: 152a=123a, 152b=123b.

(64) Each assembly comprising the elastic element 151a, 151b, the pin 152a, 152b, the hole 123a, 123b, the balancing lever 160a, 160b and the contrast ring 200a, 200b defines, in the drum 100, a respective assembly for stopping the axial movement of a respective lateral angular sector 121a, 121b with respect to the support body 122. Such a locking assembly is active in the operative configuration of the drum 100 shown in FIG. 7, corresponding to a condition of maximum expansion of the drum 100.

(65) The axial movement of each lateral angular sector 121a, 121b with respect to the support body 122 is once again possible when, starting from the operative configuration of FIG. 7, after the radial contraction of the support body 122 the spigot 125a, 125b expels the pin 152a, 152b from the hole 123a, 123b, in this way reaching the operative configuration shown in FIG. 8.

(66) Each assembly comprising the elastic element 151a, 151b, the pin 152a, 152b, the hole 123a, 123b and the spigot 125a, 125b defines, in the drum 100, a respective unlocking assembly for unlocking the axial movement of a respective lateral angular sector 121a, 121b with respect to the support body 122.

(67) A preferred embodiment of a process for looping annular anchoring structures 10 in a process for building tyres for vehicle wheels will now be described. Such a process can be carried out using the drum 100 described above.

(68) Initially, the drum 100 is in a configuration of maximum radial contraction, shown in FIG. 1.

(69) The drum 100 is thus radially expanded up to reach an operating diameter that is selected depending on a fitting diameter of a tyre to be built.

(70) Such a radial expansion is achieved as a result of the synchronous and simultaneous radial movement of the intermediate angular sectors 111 and of the lateral angular sectors 121a, 121b. This occurs following a rotation of the screw 102. Such a rotation produces a synchronous axial displacement of the lead nuts 146a, 146b towards one another and, as a result of the consequent displacement of the levers 140a, 140b, a synchronous radial displacement apart from one another (i.e. in a radially outward direction) of the support bodies 122a, 122b and therefore of the lateral angular sectors 121a, 121b associated with them. Such a synchronous radial displacement in turn allows the synchronous radial displacement apart from one another of the intermediate angular sectors 111 as a result of the elastic thrust exerted by the elastic element 113.

(71) The drum 100 is at this point set in rotation about the longitudinal axis X-X by a suitable control device. During such a rotation, the screw 102 is decoupled from the drum and does not rotate, so as to prevent the drum 100 from expanding or contracting radially any further.

(72) During the rotation of the drum 100 the loop 5 is deposited flat on the radially outer surface of the lateral angular sectors 121a, 121b and of the intermediate angular sectors 111 (FIG. 2).

(73) At the end of the deposition of the loop 5 the end edge 5a of the loop is positioned on at least part of each lateral angular sector 121a, the end edge 5b of the loop 5 is positioned on at least part of each lateral angular sector 121b and an intermediate portion of the loop 5 is positioned on each intermediate angular sector 111. Preferably, the position of the loop 5 is asymmetrical with respect to the middle plane M of the drum 100.

(74) At this point, the transfer member 500 carries an annular anchoring structure 10 in a radially outer position with respect to the intermediate portion of the radially outer annular surface of the loop 5 (FIG. 3). The transfer member 500 holds the annular anchoring structure 10 at a lateral surface of the substantially circumferential annular insert 11, for example as a result of a magnetic attraction or by suction.

(75) The annular anchoring structure 10 is carried by the transfer member 500 in a centred position with respect to the middle plane M of the drum 100 and is held in such a position while the drum 100 is radially expanded. Such an expansion proceeds until the drum 100 exerts a predetermined radial thrust on the radially inner surface of the annular anchoring structure 10. The radial expansion of the drum 100 is achieved as a result of the synchronous radial movement of the lateral angular sectors 121a, 121b and of the intermediate angular sectors 111, as described above.

(76) At this point the transfer member 500 leaves the annular anchoring structure 10 and the turning up of the end edges 5a, 5b on the opposite lateral surfaces of the annular anchoring structure 10 can begin (FIGS. 4-6). Such a turning up is achieved as a result of the radial expansion of only the lateral annular portions 120a, 120b of the drum 100 and of the simultaneous synchronous axial movement of the lateral angular sectors 121a, 121b.

(77) The radial expansion of the lateral annular portions 120a, 120b is obtained as a result of the synchronous radial movement of only the lateral angular sectors 121a, 121b.

(78) The synchronous radial movement of the lateral angular sectors 121a, 121b is obtained as described above.

(79) The radial movement of the intermediate angular sectors 111, on the other hand, is prevented by the radial contrast force exerted by the annular anchoring structure 10 against the elastic thrust of the elastic element 113, which contracts (FIGS. 5 and 6).

(80) The simultaneous synchronous axial movement of the lateral angular sectors 121a, 121b is obtained, while the lateral angular sectors 121a, 121b radially displace outwards, as a result of the axial thrust exerted by the elastic element 128a, 128b against the annular anchoring structure 10.

(81) During the radial movement and the simultaneous axial movement of the lateral angular sectors 121a, 121b, the contact elements 127a, 127b thrust the end edges 5a, 5b of the loop 5 against the lateral surfaces of the annular anchoring structure 10, until the operative configuration shown in FIG. 6 is reached, in which the annular anchoring structure 10 is completely surrounded by the loop 5. A reinforced annular anchoring structure 15 is thus obtained.

(82) A further synchronous radial movement of the lateral angular sectors 121a, 121b is at this point prevented by the contact between rollers 161a, 161b and respective contrast rings 200a, 200b. In particular, the radial thrust of the rollers 161a, 161b on the contrast rings 200a, 200b causes a rolling of the rollers 161a, 161b on the radially inner surface of the contrast rings 200a, 200b, a consequent displacement of the balancing levers 160a, 160b and a consequent axial displacement of the lateral angular sectors 121a, 121b away from the reinforced annular anchoring structure 15, overcoming the elastic thrust exerted by the elastic elements 128a, 128b.

(83) During such axial displacement the pins 152a, 152b of the lateral angular sectors 121a, 121b, thrusted by the respective elastic elements 151a, 151b, slide on the radially outer surface of the support body 122 until the operative configuration shown in FIG. 7 is reached, in which the pins 152a, 152b go inside the holes 123a, 123b, preventing any further axial displacement of the lateral angular sectors 121a, 121b.

(84) At this point the direction of rotation of the screw 102 is reversed, thus obtaining a radial contraction of the lateral annular portions 120a, 120b of the drum 100 as a result of the synchronous radial movement of the lateral angular sectors 121a, 121b in a radially inward direction.

(85) The aforementioned radial contraction proceeds until the spigots 125a, 125b provided on the guide bars 124a, 124b thrust the pins 152a, 152b out from the holes 123a, 123b and the lateral angular sectors 121a, 121b are pushed once again by the respective elastic elements 128a, 128b towards the middle plane M of the drum 100.

(86) Thereafter, the transfer member 500 picks the reinforced annular anchoring structure 15 up and the drum 100 is contracted until the operative configuration shown in FIG. 8 is reached. Such a radial contraction is produced by a further radial movement of the lateral angular sectors 121a, 121b in a radially inward direction and, from the time when the latter go into radial abutment on the intermediate angular sectors 111, from a simultaneous radial movement of the intermediate angular sectors 111 in a radially inward direction.

(87) The transfer member 500 can thus withdraw the reinforced annular anchoring structure 15 from the drum 100, which is thus ready to proceed with the looping of another annular anchoring structure according to the process described above.

(88) The Applicant estimates for the entire looping process described above a cycle time of about 40-50 seconds.

(89) Of course, a man skilled in the art can bring further modifications and variants to the invention described above in order to satisfy specific and contingent application requirements, said variants and modifications in any case being within the scope of protection as defined by the following claims.