Process and apparatus for building tyres for vehicle wheels

Abstract

An apparatus for building a tyre for a vehicle wheel includes a building drum having at least one first outer circumferential surface, and at least one pair of auxiliary support members removably in engagement with the building drum, each in axial side by side relationship with a respective end of the building drum and having second outer circumferential surfaces extending in the continuation of the first outer circumferential surface so as to support at least one component of the tyre. Each of the second outer circumferential surfaces has at least one non-stick circumferential portion and at least one sticking circumferential portion.

Claims

1. An apparatus for building a tyre for a vehicle wheel, comprising: a building drum having at least one first outer circumferential surface; and at least one pair of auxiliary support members configured to be removably engaged with the building drum, each in axially approached relationship with a respective end of the building drum and having second outer circumferential surfaces extending in a continuation of said first outer circumferential surface for supporting at least one component of the tyre, wherein each of the second outer circumferential surfaces has a plurality of non-stick circumferential portions and a plurality of sticking circumferential portions, the non-stick and sticking portions arranged in an alternating manner along the axial extension of each auxiliary support member and comprising a first sticking circumferential portion having an axial width of between about 20% and about 35% of an overall axial width of one of said auxiliary support members.

2. The apparatus as claimed in claim 1, wherein said first sticking circumferential portion is positioned near a first axial end of the auxiliary support member.

3. The apparatus as claimed in claim 2, wherein each of the second outer circumferential surfaces has a second sticking circumferential portion near a second axial end of the auxiliary support member opposite said first axial end.

4. The apparatus as claimed in claim 3, wherein each of the second outer circumferential surfaces has a first non-stick circumferential portion placed on a first axial end of the auxiliary support member.

5. The apparatus as claimed in claim 4, wherein each of the second outer circumferential surfaces has a second non-stick circumferential portion placed on a second axial end of the auxiliary support member opposite the first axial end.

6. The apparatus as claimed in claim 5, wherein the first sticking circumferential portion and second sticking circumferential portion are separated by a third non-stick circumferential portion.

7. The apparatus as claimed in claim 3, wherein the second sticking circumferential portion has an axial width smaller than or equal to about 15% of an overall axial width of the auxiliary support member.

8. The apparatus as claimed in claim 3, wherein the second sticking circumferential portion has an axial width greater than or equal to about 5% of an overall axial width of the auxiliary support member.

9. The apparatus as claimed in claim 4, wherein the first non-stick circumferential portion has an axial width smaller than or equal to about 15% of an overall axial width of the auxiliary support member.

10. The apparatus as claimed in claim 4, wherein the first non-stick circumferential portion has an axial width greater than or equal to about 5% of an overall axial width of the auxiliary support member.

11. The apparatus as claimed in claim 5, wherein the second non-stick circumferential portion has an axial width smaller than or equal to about 35% of an overall axial width of the auxiliary support member.

12. The apparatus as claimed in claim 1, wherein said plurality of non-stick circumferential portions have a roughness smaller than or equal to about 12 m.

13. The apparatus as claimed in claim 1, wherein said plurality of non-stick circumferential portions comprise a non-stick coating obtained by plasma coating.

14. The apparatus as claimed in claim 1, wherein said plurality of sticking circumferential portions have a roughness greater than or equal to about 12 m.

15. The apparatus as claimed in claim 1, wherein said plurality of sticking circumferential portions have a roughness smaller than or equal to about 15 m.

16. The apparatus as claimed in claim 1, wherein at least one of said plurality of non-stick circumferential portions and at least one of said plurality of sticking circumferential portions define a step therebetween, the thickness of which is between about 5 m and about 50 m.

17. The apparatus as claimed in the claim 16, wherein said thickness is less than or equal to about 20 m.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) This description will be set out hereinafter with reference to the accompanying drawings, given by way of non-limiting example, in which:

(2) FIG. 1 diagrammatically shows, in diametrical section, a step of applying a carcass ply around a building drum provided with two auxiliary support members in accordance with the building process of the present invention;

(3) FIG. 2 is a perspective view to an enlarged scale relative to FIG. 1, of one of the auxiliary support members;

(4) FIG. 3 shows an enlarged portion of one of the auxiliary support members seen in FIG. 1;

(5) FIG. 3a is a further enlargement of FIG. 3;

(6) FIG. 4 shows the portion in FIG. 3 on which tyre components are laid, in accordance with an alternative embodiment of the building process according to the present invention;

(7) FIG. 5 shows to an enlarged scale relative to FIG. 1, a step in which annular anchoring structures are coaxially fitted on the respective end flaps of the carcass ply/plies;

(8) FIG. 6 shows a tyre being processed in the step during which the carcass sleeve is shaped for application of an outer sleeve thereto.

DETAILED DESCRIPTION

(9) With reference to the drawings, an apparatus for building tyres for vehicle wheels designed to put into practice a process according to the present invention has been generally identified by reference numeral 1.

(10) Apparatus 1 is intended for manufacture of tyres 2 (FIG. 6) essentially comprising at least one carcass ply 3 preferably internally coated with a layer of impermeable elastomeric material referred to as liner 4. Two annular anchoring structures 5, each comprising a so-called bead core 5a preferably carrying an elastomeric filler 5b at a radially external position, are in engagement with respective end flaps 3a of the carcass ply or plies 3. The annular anchoring structures 5 are integrated close to regions usually identified with the name of beads 6, at which usually engagement between a tyre 2 and the respective mounting rim (not shown) occurs, according to a fitting diameter D0 determined by the inner diametrical sizes of the annular anchoring structures 5 (FIG. 5).

(11) A belt structure 7 is circumferentially applied around the carcass ply/plies 3 and a tread band 8 circumferentially overlaps the belt structure 7. Two sidewalls 9, extending each from the corresponding bead 6 to a corresponding side edge of the tread band 8, are applied to the carcass ply/plies 3, at laterally opposite positions.

(12) Apparatus 1 comprises a substantially cylindrical building drum 10 having two halves 10a supported by a central shaft 11 extending along a geometric axis X-X of the building drum 10. Halves 10a can be axially approached, upon command of a threaded bar 12 for example, that is operatively disposed within the central shaft 11 and carries two threaded portions 12a, 12b, i.e. a right-handed portion and a left-handed portion respectively, each of them engaging one of halves 10a. Halves 10a of the building drum 10 are consequently induced to simultaneously translate in respectively opposite directions along the central shaft 11, following rotations imparted to the threaded bar 12 by an actuator (not shown) that can be operatively coupled to one end of the central shaft 11.

(13) The building drum 10 can further comprise a central section 13 slidably engaging halves 10a and extending in surface continuity relationship relative to said halves so as to define therewith, at a radially external position, a first outer circumferential surface 14 that is substantially continuous.

(14) Each of halves 10a and the central section 13 are made up of respective circumferential sectors that are radially movable between a rest condition (not shown) at which they are moved radially close to the geometric axis X-X to give the building drum 10 an overall diametrical dimension smaller than the fitting diameter D0 of the tyre being processed, in order to enable removal of the tyre 2 being processed from said building drum, and a work condition at which, as shown in the drawings, they extend in circumferential continuity relationship so as to form said outer surface 14 defining an application diameter D1 preferably greater than the fitting diameter D0 (FIG. 5).

(15) The building drum 10 lends itself to be transferred, by at least one robotized arm (not shown) or transfer devices of other type acting on at least one grip end 11a exhibited by the central shaft 11, to one or more work stations to allow accomplishment of different working steps aiming at assembling the tyre 2 being processed.

(16) More particularly, the building drum 10 for instance can be first engaged in a building station 15 (FIGS. 1 to 5) in which a so-called carcass sleeve is made, which comprises the carcass ply/plies coupled to the respective annular anchoring structures 5.

(17) At least one outer handling device (not shown as made in known manner) carries out positioning of the auxiliary support members 16, made in the form of two annular elements for example (FIG. 2), in axially approached relationship with the building drum 10 on axially opposite sides.

(18) The auxiliary support members 16 have respective second outer circumferential surfaces 16a preferably shaped into a substantially cylindrical conformation of substantially the same diameter as the application diameter D1. When approaching has occurred, the second outer circumferential surfaces 16a extend in continuity relationship in the continuation of the first outer circumferential surface 14.

(19) Engagement of the auxiliary support members 16 with the building drum 10 takes place at respective connecting members 17 carried by the building drum 10, made each in the form of a cylindrical sleeve for example, integrally carried by one of halves 10a of the building drum 10 and adapted to be operatively associated with an engagement seat 18 carried by the respective auxiliary support member 16.

(20) Fitting elements, not shown, lend themselves to automatically engage the respective connecting members 17, so as to retain each auxiliary support member 16 in engagement relationship with the building drum 10 also after said members 17 have been disengaged from the aforesaid outer handling device.

(21) The building drum 10 is thus adapted to be transferred, if necessary, between at least one first and one second work unit (not shown) provided in the building station 15, together with the auxiliary support members 16 linked thereto.

(22) Operating in the building station 15 are auxiliary devices (not shown), adapted to apply components of the carcass sleeve to the building drum 10.

(23) The carcass ply/plies 3 and/or other parts of tyre 2 are preferably made through laying of one or more elementary components. These elementary components are adapted to be used in a suitable amount in order to make up one or more of the above described constituent elements of the tyre, without storage of semifinished products being required.

(24) In more detail, for instance, these auxiliary devices may comprise one or more dispensing devices supplying at least one continuous elongated element of elastomeric material while the building drum 10 is being driven in rotation about its geometric axis X-X, so as to form said liner 4 and/or underliner on the first outer circumferential surface 14 and the second outer circumferential surfaces 16a.

(25) In addition or as an alternative to liner 4 and/or the underliner, the auxiliary devices can be set to form further components on the second outer circumferential surfaces 16a, such as the abrasion-proof element 19 to be incorporated at the beads 6, and/or to lay strip-like elements 20 forming reinforcing fabrics such as the square-woven fabric, and/or, in the case of the so-called run-flat tyres, to lay auxiliary support inserts made of elastomeric material alone (the so-called sidewall inserts) applied onto the respective halves 10a of the building drum 10, so that they are then incorporated at the inside of tyre 2 in the sidewall region 9.

(26) As shown in FIGS. 1, 3, 5 and 6, before laying of liner 4, a continuous elongated element is laid in the form of coils disposed in side by side relationship or radially superposed internally of the second outer circumferential surface 16a, so as to form the abrasion-proof element 19.

(27) According to an alternative construction of the carcass structure, not shown, the abrasion-proof element 19 is laid starting from the first outer circumferential surface 14 of drum 10 as far as the second outer circumferential surface 16a and therefore it lies astride the two above mentioned surfaces 14, 16a.

(28) As shown in FIG. 4, before laying of the abrasion-proof element 19, the strip-like element (forming the square-woven fabric) 20 is fully laid on the second outer circumferential surface 16a.

(29) Subsequently to formation of the above-mentioned components 4, 19, 20, devices not shown as they can be made in any convenient manner, apply the carcass ply/plies 3 around the first outer circumferential surface 14, according to said application diameter D1. Each carcass ply 3 can consist of an article of manufacture in the form of a continuous strip previously cut according to the circumferential extension of the first outer circumferential surface 14 and fed towards the latter, while the building drum 10 is rotating around its geometric axis X-X, so as to cause winding of said strip around said first outer circumferential surface 14.

(30) Alternatively, according to a preferred embodiment, the application devices comprise members for sequentially applying a plurality of strip-like elements disposed transversely of the circumferential extension of the first outer circumferential surface 14, while the building drum 10 is being driven in rotation in a step-by-step movement, in the same manner as described in the U.S. Pat. No. 6,328,084 in the name of the same Applicant, for example.

(31) The carcass ply/plies 3 are then preferably formed directly on the building drum 10, by the strip-like elements applied in mutually approached relationship so as to cover the whole circumferential extension of the first outer circumferential surface 14.

(32) Preferably, the first outer circumferential surface 14 has a smaller axial size than the width of said at least one carcass ply 3, so that the carcass ply/plies 3 laid on the building drum 10 axially protrudes/protrude from the opposite ends of the first outer circumferential surface 14 and appears/appear to be at least partly supported, together with liner 4 and/or the underliner and/or the abrasion-proof element 19 and/or the square-woven fabric 20, by the above mentioned second outer circumferential surfaces 16a belonging to the auxiliary support members 16.

(33) In the embodiment shown in the accompanying drawings, each of the auxiliary support members 16 comprises a tubular body 21 delimiting the engagement seat 18 with the connecting member 17 carried by the building drum 10. When the auxiliary support member 16 is engaged to the building drum 10, the geometric axis X-X of the building drum 10 is coincident with the main axis Y-Y of the tubular body 21.

(34) The auxiliary support member 16 further comprises a radially external cylindrical body 22, spaced apart from and coaxial with the tubular body 21 and connected to the latter through a circular plate 23. The cylindrical body 22 has a first circular edge 24a which approaches the building drum 10 when the auxiliary support member 16 is in engagement with the building drum 10.

(35) The second outer circumferential surface 16a lies on the cylindrical body 22 and has non-stick circumferential portions 25, 25, 25 and sticking circumferential portions 26, 26. Said non-stick circumferential portions 25, 25, 25 and sticking portions 26, 26 have a cylindrical shape coaxial with the main axis Y-Y.

(36) In the embodiment shown not in a limiting sense, three non-stick circumferential portions 25, 25, 25 are disposed in side by side relationship and alternated along the axial extension of the auxiliary support member 16, with two sticking circumferential portions 26, 26.

(37) Preferably, as shown, each of the second outer circumferential surfaces 16a has a first sticking circumferential portion 26 close to a first axial end 27 of the auxiliary support member 16 carrying the circular edge 24a and a second circumferential sticking portion 26 close to a second axial end 28 opposite to said first axial end 27.

(38) Each of the second outer circumferential surfaces 16a further has a first non-stick circumferential portion 25 placed on the first axial end 27 of the auxiliary support member 16, a second non-stick circumferential portion 25 placed on the second axial end 28 of the auxiliary support member 16 and a third non-stick circumferential portion 25 interposed between the first 26 and second 26 sticking circumferential portion.

(39) The first non-stick circumferential portion 25 extends in an axial direction starting from the first circular edge 24a towards the second axial end 28 as far as the first sticking circumferential portion 26. The first sticking circumferential portion 26 extends in an axial direction starting from the first non-stick circumferential portion 25 towards the second axial end 28 as far as the third non-stick circumferential portion 25. The third non-stick circumferential portion 25 extends in an axial direction starting from the first sticking circumferential portion 26 towards the second axial end 28 as far as the second sticking circumferential portion 26. The second sticking circumferential portion 26 extends in an axial direction starting from the third non-stick circumferential portion 25 towards the second axial end 28 as far as the second non-stick circumferential portion 25. The second non-stick circumferential portion 25 extends starting from the second sticking circumferential portion 26 as far as a second circular edge 24b lying on the second axial end 28 of the auxiliary support member 16.

(40) Given the overall width L of the auxiliary support member 16, measured along a direction parallel to the main axis Y-Y, the first non-stick circumferential portion 25 has an axial width L1 included between about 5% and 15% of the overall axial width L of the auxiliary support member 16.

(41) The first sticking circumferential portion 26 has an axial width L.sub.2 included between about 20% and 35% of said overall axial width L of the auxiliary support member 16.

(42) The second sticking circumferential portion 26 has an axial width L.sub.3 included between about 5% and 15% of the overall axial width L of the auxiliary support member 16.

(43) The second non-stick circumferential portion 25 has an axial width L.sub.4 smaller than or equal to about 35% of the overall axial width L of the auxiliary support member 16. The second non-stick circumferential portion 25 therefore can also be absent.

(44) Each of the non-stick circumferential portions 25, 25, 25 must enable relative sliding of the carcass sleeve components of the tyre under processing substantially without offering any resistance.

(45) Preferably, this result is obtained by laying a non-stick coating (containing Teflon, for example) on the cylindrical body 22, preferably using the known plasma-coating technique.

(46) Following laying of the coating, the non-stick circumferential portions 25, 25, 25 preferably have a roughness Ra smaller than or equal to about 12 Each of the sticking circumferential portions 26, 26 must allow the elementary components to be stuck and maintained in place during the starting steps of laying the same on the auxiliary support members 16.

(47) To this aim, these sticking circumferential portions 26, 26 preferably have a roughness Ra included between about 12 m and about 15 m.

(48) The sticking portions 26, 26 are submitted to mechanical machining operations alone without any added material being laid or with laying of added material having mechanical surface features substantially identical (roughness, porosity, hardness) with those of the base surface.

(49) In a preferred embodiment, one or more layers of metal material are added on the whole radially external surface of the cylindrical body 22. These layers have a dual function: ensuring the intimate adhesion of a final non-stick added coating, of Teflon for example, on the non-stick circumferential portions 25, 25, 25; and offering the desired adhesiveness of the sticking circumferential portions 26, 26.

(50) By laying the metal material layers on the non-stick circumferential portions 25, 25, 25 as well, it is also possible to limit the thickness s of the step (FIG. 3a) that is formed between a non-stick circumferential portion 25, 25, 25 and an adjacent sticking circumferential portion 26, 26 to values lower than 50 m. Preferably, this thickness is included between about 5 m and about 20 m.

(51) As shown in FIGS. 1, 3, 5 and 6, a starting end of the continuous elongated element is first stuck to the first sticking circumferential portion 26, which continuous elongated element is subsequently laid in the form of coils disposed in side by side relationship or at least partly radially superposed, to form the abrasion-proof element 19.

(52) As shown in FIG. 4, before laying the abrasion-proof element 19, a starting end of the strip-like element is stuck to the first sticking circumferential portion, which strip-like element is then wound up to form the square-woven fabric 20.

(53) As shown in FIGS. 1, 3, 4, 5 and 6, stuck to the second sticking circumferential portion 26 are the end flaps 3a of the strip-like elements disposed transverse to the circumferential extension of the first outer circumferential surface 14 and designed to form the carcass ply/plies 3.

(54) When formation of the carcass ply/plies 3 has been completed, the auxiliary support members 16 are disengaged from the respective connecting members 17. This disengagement can be for example obtained with the aid of the aforesaid outer handling device, by an action involving axial moving apart from the respective halves 10a of the building drum 10 so as to remove the second outer circumferential surfaces 16a from the abrasion-proof element 19, and/or liner 4, and/or square-woven fabric 20 and/or carcass ply/plies 3.

(55) When disengagement is over, the auxiliary support members 16 can remain in engagement with the outer handling device, ready for being used again in a new working cycle.

(56) During disengagement, a moving-apart force depending on the tyre size and type is applied to each of said auxiliary support members 16. This force is included between about 10 kg and about 150 kg and in any case is preferably lower than 100 kg.

(57) Removal of the auxiliary support members 16 makes it possible, after possible transfer of the building drum 10 to another working unit, to fold down the end flaps 3a of the carcass ply/plies 3 applied around the building drum, towards the geometric axis X-X of the building drum itself, for instance with the aid of rollers or other devices not shown as they can be made in any convenient manner.

(58) Locating members, not shown as they can be made in known manner, carry out fitting of each of the annular anchoring structures 5 coaxially around one of the end flaps 3a of the carcass ply/plies 3 folded down towards the geometric axis X-X, locating it in axial abutment relationship against the corresponding half of the building drum 10 (FIG. 5).

(59) When the locating operation has been completed, turning-up members, not shown, turn up each of the end flaps 3a around the respective annular anchoring structure 5, so as to stabilise engagement of same with the carcass ply/plies 3 giving rise to formation of said carcass sleeve.

(60) When engagement of the annular anchoring structures 5 is over or concurrently with this operating step, application of at least one portion of the sidewalls 9 can be carried out.

(61) The building drum 10 carrying the carcass sleeve is then preferably transferred to a location 29 (FIG. 6) external to the building station 19, for receiving and engaging an outer sleeve 30 integrating the belt structure 7, preferably already coupled to the tread band 8.

(62) The outer sleeve 30 having an inner diameter D2 greater than the winding diameter D1, can be prepared in advance by formation or winding of one or more belt layers adapted to make the belt structure 7 on an auxiliary drum (not shown), and subsequent winding of the tread band 8 on the belt structure 7 carried by the auxiliary drum. More particularly, building of the tread band 8 can be carried out by feeding means supplying a continuous elongated element of elastomeric material that is applied, in the form of coils disposed in side by side relationship and/or at least partly radially superposed, onto the belt structure 7 carried by the auxiliary drum, while the latter is being driven in rotation. According to an alternative embodiment, at the end at least one portion of the sidewalls 9 can be build on the outer sleeve 30.

(63) The outer sleeve 30 thus formed is adapted to be removed from the auxiliary drum, for instance by means of a transfer ring 31 or other suitable devices that will then dispose it to a coaxially centred position around the carcass sleeve carried by the building drum 10.

(64) Then, shaping devices act on the building drum 10 to shape the carcass sleeve into a toroidal configuration, so as to cause application of same against a radially internal surface of the outer sleeve 30.

(65) The shaping devices can for instance comprise said actuator (not shown) designed to drive the threaded bar 12 in rotation to cause mutual axial approaching of halves 10a of the drum and, consequently, of the annular anchoring structures 5 of the carcass sleeve. Preferably, the shaping devices further comprise inflating members, not shown, adapted to feed a working fluid into the carcass sleeve and cause radial expansion thereof by inflation, during mutual approaching of the annular anchoring structures 5.

(66) Then at least one auxiliary shaping member 32 (only diagrammatically shown in FIG. 6) is preferably engaged to the building drum 10, which auxiliary member is suitable for being integrated with the shaping devices to enable the shaping step of the carcass sleeve to be carried out.

(67) When the shaping step has been completed, the building drum 10 can be possibly transferred to at least one additional working station (not shown).

(68) At the end of building, tyre 2 can be removed from the building drum 10 after disengagement of the auxiliary shaping members 32 and radial contraction of said drum, to be submitted to a vulcanisation and moulding step to be carried out in any convenient manner.