Process for Manufacturing a Tyre Comprising the Step of Marking a Structural Element Thereof

Abstract

A process for manufacturing a tyre includes the following steps: a) providing a carcass structure; b) providing one structural element of the tyre by laying down at least one elongate element of the tyre by laying down at least one elongate element made of crude elastomer material in a position radially external to the carcass structure; c) providing the structural element of the green tyre with one marking by means of an inkjet marking device; d) introducing the green tyre into a moulding cavity; and f) curing the green tyre.

Description

Additional features and advantages of the invention will be better apparent from the following description of some preferred embodiments of tyre manufacturing processes according to the present invention, which description is made, by way of non-limiting example, with reference to the attached drawings, wherein:

FIG. 1 is a partial cross-section view of a pneumatic tyre obtained with a process according to the present invention;

FIG. 2 is a partial schematic plan view of a robotized work station for marking the tread band of a pneumatic tyre in accordance with a process of the present invention;

FIG. 3 is a schematic plan view of a robotized work station for marking the tread band of the pneumatic tyre in accordance with a further embodiment of the process shown in FIG. 2;

FIG. 4 is a schematic perspective view of a robotized work station for marking the tread band of a pneumatic tyre in accordance with a process of the present invention which makes use of a substantially rigid toroidal support.

FIG. 1 shows a partial cross-section view of a tyre 1 comprising a carcass structure 2 obtained with a conventional tyre manufacturing process. In fact, the carcass structure 2 comprises at least one carcass ply 2a, the opposite side edges of which are externally folded up around respective annular reinforcing structures 3, usually known as bead cores.

Alternatively (said embodiment being not shown), each carcass ply 2a has its ends integrally associated with the bead core 3, as disclosed in the European patent EP-928,680 mentioned above.

The bead core 3 is enclosed in a bead 4 defined along an inner circumferential edge of the pneumatic tyre 1 and at which the pneumatic tyre engages on a rim (not shown) forming part of the wheel of a vehicle.

The tyre 1 comprises a pair of sidewalls 7 which are located in axially opposite positions with respect to the carcass structure 2.

The tyre 1 also comprises a tread band 6 in a position radially external to the carcass structure 2. The tread band 6 is made of an elastomeric material into which, at the end of the curing and moulding steps, a raised pattern is formed for the tyre ground contact. In FIG. 1 the tread band 6 is provided with a plurality of grooves 11 which define a plurality of ribs and blocks of the tyre tread pattern.

The tyre 1 further comprises a reinforcing structure 5, usually known as belt structure, which is positioned between the carcass structure 2 and the tread band 6. Preferably, the belt structure 5 includes at least two radially superposed layers 8, 9 of rubberised fabric provided with reinforcing cords, usually of metal material, disposed parallel to each other in each strip and in crossed relationship with the cords of the adjacent strip, preferably symmetrically disposed with respect to the equatorial plane π-π of the tyre. Preferably, the belt structure 5 further comprises, at a radially external position of said belt layers 8, 9, at least one further layer 10 of textile or metallic cords substantially circumferentially disposed, said cords being spirally and coaxially wound at a radially outer position with respect to the belt layers 8, 9.

In the embodiment shown in FIG. 1, the tyre 1 is further provided with a layer 12 of a suitable elastomeric material which is interposed between the tread band 6 and the belt structure 5. Preferably, the layer 12 has the function of improving the adhesion between the tread band 6 and the belt structure 5.

Finally, in tyres of the tubeless type, i.e. devoid of an air inner bladder, a radially internal elastomeric layer 13, i.e. the liner, is present which has imperviousness features to ensure the tyre air-tightness.

With reference to FIGS. 2, 3 and 4, respective work stations are described, generally indicated with reference sign 16 in FIGS. 2 and 3 and with reference sign 17 in FIG. 4, which are provided for manufacturing the tread band 6 and marking it in accordance with the manufacturing process of the present invention.

In the embodiment illustrated in FIG. 2, a robotized work station 16 is associated to a conventional manufacturing plant for the production of pneumatic tyres, said conventional plant being not shown in details as known per se.

In such a plant, apparatuses—known per se and not shown—are provided for manufacturing the carcass structure 2 and the annular reinforcing structure 3 associated thereto on a supporting element capable to assume a substantially toroidal configuration, such as for example a manufacturing drum 18, as well as for subsequently forming the belt structure 5 in a radially outer position with respect to the carcass structure 2.

The work station 16 comprises a robotized arm 21, preferably of the anthropomorphic type with seven axes, intended to pick up each drum 18 supporting the carcass structure 2, the annular reinforcing structure 3 and the belt structure 5 from a pick up position 20, defined at the end of a conveyor belt 19 or other suitable transporting means, to a delivery position of the tread band 6.

In FIG. 2, the work station 16 further comprises a delivery member 22 of an extruder 23 which provides for a continuous elongate element 24—having a suitable size in cross-section—which is suitable for manufacturing the tyre tread band 6.

With reference to the work station 16 and to FIG. 2, the tyre manufacturing process comprises a plurality of preliminary steps which are carried out upstream of the work station 16. In particular, the carcass structure 2 comprising the annular reinforcing structure 3 and the belt structure 5 are manufactured and shaped on the drum 18 which assumes and then determines a substantially toroidal shape of the pneumatic tyre under construction. Said drum 18 is then transported by the conveyor belt 19 to the pick up position 20.

In a subsequent step, the robotized arm 21 positions the drum 18 in the delivery position defined at the delivery member 22 of the elongate element 24 intended to obtain the tread band 6.

In such a delivery position, the robotized arm 21 rotates the drum 18 about its rotation axis X-X and carries out a relative displacement between the delivery member 22 and the drum 18 by also imparting to the latter a translational movement along a direction substantially parallel to the aforementioned rotation axis X-X.

Concurrently with the rotation and translation movement of the drum 18, the delivery member 22 delivers the elongate element 24 at a radially outer position with respect to the belt layer 5 so as to form the tread band 6, for instance as disclosed in the European patent EP-928,680 or in the patent application WO 03/070454 in the name of the same Applicant.

The rotation and translation movement of the drum 18 is suitably driven in such a way as to carry out the deposition of at least one strip-like elongate element to form a plurality of coils or windings, which are axially overlapped and/or radially superimposed so as to define the tread band 6.

At the end of the deposition step, the tread band 6 of the green tyre is provided with at least one marking by using an inkjet marking device 40.

According to the embodiment shown in FIG. 2, the inkjet marking device 40 comprises a nozzle 41 which is associated to a pressurized vessel 42 through a hose 43. The pressurized vessel 42 contains the ink which is necessary for providing the tread band with at least one marking, said ink being dispensed under pressure by the nozzle 41.

According to the embodiment of FIG. 2, the inkjet marking device 40 is shown to have only one nozzle 41. However, an inkjet marking device generally comprises at least one printhead which is provided with an array of nozzles, the number of which depends also on the kind of marking to be transferred onto the tyre structural element.

Preferably, an inkjet marking device is suitable for simultaneously providing the tyre structural element with different markings, such as an alpha-numeric identification code and at least one coloured circumferential line, the inkjet marking device being provided with a plurality of printheads (each printhead being provided with an array of nozzles).

For instance, a suitable inkjet printer for carrying out the marking step in accordance with the process of the present invention is the Rea-Jet printer, manufactured by REA Elektronik GmbH.

According to the embodiment of FIG. 2, the inkjet marking device 40 further comprises a control panel 44 by means of which the operator performs the desired set up of the marking device.

In more details, in order to perform the marking of the tread band 6, the robotized arm 21 positions the drum 18 in proximity of the inkjet marking device 40. Successively, the robotized arm 21 rotates the drum 18 about its rotation axis X-X and, concurrently with said rotational movement, the inkjet marking device 40 provides the tread band with the desired marking, e.g. a coloured line or an identification code or both.

Alternatively (said embodiment being not shown), at the end of the tread band deposition step, the robotized arm 21 discharges the drum 18—supporting the green tyre—on a conveyor means. Successively, a rotating transferring apparatus, e.g. a manipulator, takes the drum 18 from the conveyor means and positions the drum 18 in proximity of the inkjet marking device 40 so that the step of providing the tyre tread band with a desired marking can be carried out as disclosed herein above.

At the end of the marking step, the manufacturing process according to the present invention can comprise the step of storing the finished green tyre before the moulding and curing steps are performed.

Alternatively, at the end of the marking step, the green tyre supported on the drum 18 is transported—in a way known per se and not shown in the figures—to the subsequent work stations of the plant, e.g. the moulding and curing work stations.

According to a variant of the previous embodiment of the process of the present invention, said embodiment being shown in FIG. 3, a substantially cylindrical auxiliary drum 18′ is used on which the belt structure 5 is assembled. The auxiliary drum 18′ is moved substantially in the same way as the drum 18 previously illustrated.

More precisely, the auxiliary drum 18′ is positioned in proximity of the delivery member 22 of an extruder 23; subsequently, an elongate element 24 of elastomeric material is delivered by the delivery member 22 onto the belt structure 5, preferably carrying out a relative displacement between the delivery member 22 and the auxiliary drum 18′ so as to form the tread band 6.

Subsequently, the auxiliary drum 18′ is positioned in proximity of the inkjet marking device 40 so that a marking is provided to the tyre tread band as disclosed with reference to the embodiment of FIG. 2.

At the end of the deposition of the tread band 6, the belt structure-tread band assembly is associated to the remaining components of the tyre which have been manufactured on a different manufacturing drum. Therefore, the final assembling of the green tyre and the subsequent shaping thereof allow to obtain the finished green tyre which is suitable for being moulded and cured.

These preferred embodiments (shown in FIGS. 2 and 3) of the process according to the invention have an advantageous and effective application when it is desired to exploit a conventional production line, making use of at least one manufacturing drum on which the semi-finished products, which shall constitute the pneumatic tyre, are at least partially formed, said conventional production line being integrated with a final robotized work station for manufacturing the tread band.

In the embodiment illustrated in FIG. 4, a work station intended to manufacture the tread band 6 of the pneumatic tyre 1 is generally indicated with reference sign 17.

The work station 17 is associated to a highly automated plant for manufacturing pneumatic tyres, or for carrying out part of the working operations foreseen in the production cycle of the pneumatic tyres, said plant being not illustrated in details. Further details on such a manufacturing process are, for example, described in the European patent EP-928,680 mentioned above.

According to said process, the manufacturing of the different structural components of the pneumatic tyre 1 are carried out directly on a support 28, substantially toroidal and preferably substantially rigid, having an outer surface 28a, 28b which is substantially shaped according to the inner configuration of the pneumatic tyre.

Within such a plant, robotized work stations (not shown in FIG. 4) are also present for manufacturing on the toroidal support 28 the carcass structure 2 comprising the annular reinforcing structure 3 and for the subsequent formation of the belt structure 5, at a radially outer position with respect to the carcass structure 2.

The work station 17 comprises a robotized arm known per se, generally indicated with reference sign 29 and preferably of the anthropomorphic type with seven axes, intended to pick up each support 28 carrying the carcass structure 2, the annular reinforcing structure 3 and the belt structure 5 from a pick up position 30, defined at the end of two supporting arms 36, 37 of a trestle 31 or other suitable supporting means, to a delivery position of the tread band 6.

More specifically, the delivery position of the tread band 6 is defined at a delivery member 35 of an extruder 34 which provides for at least one continuous elongate element (not shown in FIG. 4) for obtaining the tread band 6.

Further structural and functional details of the robotized arm 29 are described, for example, in the International patent application WO 00/35666 in the name of the same Applicant.

With reference to the work station 17 described above and to FIG. 4, the further preferred embodiment of the process for manufacturing a pneumatic tyre in accordance with the present invention is described herein below.

In details, said process comprises a plurality of preliminary steps which are carried out upstream of the work station 17 by means of a plurality of robotized stations, the latter providing for the manufacturing of the carcass structure 2, the annular reinforcing structure 3 and the belt structure 5 which are successively transported—supported on the toroidal support 28—to the pick up position 30.

In a subsequent step, the robotized arm 29 positions the toroidal support 28 in proximity of the delivery position defined at the delivery member 35 which provides for the elongate element intended to form the tread band 6.

In such a delivery position, the robotized arm 29 rotates the support 28 about its rotation axis X-X and carries out a relative displacement between the delivery member 35 and the support 28 also imparting to the latter a translational movement along a direction substantially parallel to the aforementioned rotation axis X-X.

Simultaneously with the rotation and translation movement of the support 28, the delivery member 35 delivers—by means of the extrusion 34—the elongate element at a radially outer position with respect to the belt layer 5 so as to form the tread band 6.

Preferably, the delivery of the elongate element is carried out by forming a plurality of coils axially arranged side-by-side and/or radially superposed so as to define the tread band 6.

In a subsequent step, the robotized arm 29 positions the support 28 in proximity of an inkjet marking device (not shown in FIG. 4) so that the desired marking is applied onto the tyre tread band according to the steps sequence described with reference to the embodiments of FIGS. 2 and 3.

At the end of the tread band deposition step, the green tyre is completed by transporting the support 28 to the subsequent work stations of the plant, e.g. the moulding and curing work stations.

This different preferred embodiment (shown in FIG. 4) of the process according to the invention has, in particular, an advantageous and effective application when it is desired to use production techniques which allow to minimize, or possibly eliminate, the production and storage of the semi-finished products, for example by adopting process solutions which allow to make the individual components by directly applying them on the pneumatic tyre being manufactured according to a predetermined sequence by means of a plurality of robotized work stations.

The manufacturing process of the present invention offers some major advantages compared to the known art.

First of all, since the inkjet printing system is a non-contact process, the marking step according to the process of the present invention does not cause the elongate element—which form a tyre structural element—to be deformed by pressure, so that the drawbacks mentioned above can be avoided.

Secondly, the inkjet printing system allows that a controlled amount of ink, in the form of fine droplets, reaches the outer surface of the tyre structural element according to a direction which is substantially perpendicular to the outer surface. This aspect, in combination with the fact that the inkjet printing system is a non-contact process, avoids that ink penetration may occur below the windings of the elongate element which form the tyre structural element to be marked. Moreover, the spraying technique and the controlled ink amount which can be transferred onto the tyre structural element, are particularly advantageous for carrying out a discontinuous marking of the tyre, said spraying technique avoiding that ink droplets can be erroneously applied to the tyre.

Furthermore, thanks to the fact that the inkjet printing system is a non-contact process, the marking is effectively and reliably performed notwithstanding irregularities which may be present on the outer surface of the tyre structural element such as, for instance, the overlapping regions of the adjacent windings of the elongate element which form the tyre structural element. Therefore, the process according to the present invention ensures a high quality of the marking, both in case a code or a line have to be provided onto the tyre structural element.

Moreover, the inkjet printing system further contributes to confer high flexibility to the tyre manufacturing process. In fact, thanks to the electronic control of the nozzles of the printheads, it is possible to simply and quickly modify the marking, e.g. the character to be printed out, the writing size and/or format, the predetermined path between two successive markings, the marking colour. These changes can be carried out by modifying the set up of the nozzles or of a part thereof by means of a terminal which is operated by the technical people responsible for carrying out the tyre manufacturing process. Therefore, important structural modifications—e.g. substitution of the printing devices like the marking applicators mentioned above—of the printing system can be avoided.

Moreover, since the marking of the tyre structural element is preferably carried out successively to the deposition step of the elongate element which form the tyre structural element, especially in the case the latter is the tyre tread band, the marking step occurs when the elastomeric material is substantially warm. Said aspect is particularly advantageous for the reason that the heat possessed by the elastomeric material contributes in evaporating the ink solvent so that the ink can strongly adhere to the elastomeric material.

Claims

1-28. (canceled)

29. A process for manufacturing a tyre comprising the steps of: providing a carcass structure having at least one carcass ply associated with at least one annular reinforcing structure;providing at least one structural element of a green tyre by laying down at least one elongate element made of crude elastomer material in a position radially external to said carcass structure;providing said at least one structural element of the green tyre with at least one marking by means of an inkjet marking device;introducing the green tyre into a moulding cavity; andcuring the green tyre.

30. The process according to claim 29, wherein said at least one structural element is a tyre tread band.

31. The process according to claim 29, wherein said at least one structural element is a tyre sidewall.

32. The process according to claim 29, wherein said at least one structural element is a tyre tread band and a tyre sidewall.

33. The process according to claim 29, further comprising the step of providing a belt structure in a position radially external to said carcass structure.

34. The process according to claim 29, wherein the step of providing at least one structural element is carried out by winding at least one elongate element.

35. The process according to claim 34, wherein the step of winding comprises the step of forming a plurality of coils axially arranged side-by-side and/or radially superposed.

36. The process according to claim 29, wherein the step of providing the carcass structure is carried out on a manufacturing drum.

37. The process according to claim 29, wherein the step of providing the belt structure is carried out on a manufacturing drum or on an auxiliary drum.

38. The process according to claim 36 or 37, further comprising the step of positioning said drum in proximity of a delivery member.

39. The process according to claim 38, further comprising the step of delivering the at least one elongate element by means of said delivery member.

40. The process according to claim 39, wherein the step of delivering is performed while carrying out a relative displacement between the delivery member and the drum.

41. The process according to claim 39, wherein the step of delivering is performed while rotating the drum about its rotation axis.

42. The process according to claim 40, wherein the relative displacement between the delivery member and the drum is carried out by imparting to the drum a translational movement along a direction substantially parallel to its rotation axis.

43. The process according to claim 29, further comprising the step of positioning a manufacturing drum or an auxiliary drum in proximity of the inkjet marking device.

44. The process according to claim 29, wherein the step of providing said at least one structural element with at least one marking is performed while rotating a manufacturing drum or an auxiliary drum about its rotation axis.

45. The process according to claim 29, wherein the step of providing the carcass structure comprises the steps of producing and assembling the carcass structure on a toroidal support.

46. The process according to claim 33, wherein the step of providing the belt structure comprises the steps of producing and assembling the belt structure on a toroidal support.

47. The process according to claim 45 or 46, wherein the toroidal support is substantially rigid.

48. The process according to claim 45 or 46, further comprising the step of positioning said toroidal support in proximity of a delivery member.

49. The process according to claim 48, further comprising the step of delivering the at least one elongate element by means of said delivery member.

50. The process according to claim 49, wherein the step of delivering is performed while carrying out a relative displacement between the delivery member and the toroidal support.

51. The process according to claim 49, wherein the step of delivering is performed while rotating the toroidal support about its rotation axis.

52. The process according to claim 50, wherein the relative displacement between the delivery member and toroidal support is carried out by imparting to the toroidal support a translational movement along a direction substantially parallel to its rotation axis.

53. The process according to claim 45, further comprising the step of positioning the toroidal support in proximity of the inkjet marking device.

54. The process according to claim 45, wherein in the step of providing said at least one structural element with at least one marking is performed while rotating the toroidal support about its rotation axis.

55. The process according to claim 29, wherein the inkjet marking device comprises at least one printhead.

56. The process according to claim 55, wherein the printhead is provided with at least one nozzle.