PROCESS AND PLANT FOR PRODUCING TYRES FOR VEHICLE WHEELS

Abstract

A plant and a process for producing tyres for vehicle wheels, includes the steps of: a) building a carcass structure of a green tyre on a first forming drum in at least one carcass structure building line, the carcass structure including at least one carcass ply and a pair of annular anchoring structures; b) building a crown structure of a green tyre on at least one second forming drum in at least one crown structure building line, the crown structure including at least one belt structure and a tread band; c) toroidally shaping the carcass structure assembling it to the crown structure in at least one assembling and shaping work station for the tyre being processed, the assembling and shaping work station being synchronized with the carcass structure building line and with the crown structure building line; wherein each carcass structure is associated with the respective first forming drum whereon it is built up to the end of step c) of shaping and assembling the tyre being processed; and d) moulding and vulcanizing the green shaped tyre in at least one tyre moulding and vulcanizing line separate from said assembling and shaping work station.

Claims

1-102. (canceled)

103. A process for producing a tyre comprising the steps of: a) building a carcass structure of a green tyre on a first forming drum in a carcass structure building line, said carcass structure comprising at least one carcass ply and a pair of annular anchoring structures; b) building a crown structure of a green tyre on a second forming drum in a crown structure building line, said crown structure comprising at least one belt structure and a tread band; c) toroidally shaping said carcass structure by assembling said carcass structure to said crown structure in an assembling and shaping work station to form a shaped green tyre; wherein the carcass structure is associated with the first forming drum up to the end of step c) of shaping and assembling the green tyre; wherein step a) of building the carcass structure comprises sub-step a10) of applying a first portion of sidewalls in a first sidewall building work station of the carcass structure building line; wherein said first portion of sidewalls is applied by winding side by side and/or overlapped coils of a continuous elongated element made of an elastomeric material; wherein said sub-step a10) is the last step of said step a) of building the carcass structure; wherein step b) of building the crown structure comprises at least sub-step b7) of applying a second portion of sidewalls in a second sidewall building work station of the crown structure building line; wherein said second portion of sidewalls is applied by winding side by side and/or overlapped coils of a continuous elongated element made of an elastomeric material; wherein said sub-step b7) is the last step of said step b) of building the crown structure; and d) moulding and vulcanizing the shaped green tyre in a tyre moulding and vulcanizing line separate from said assembling and shaping work station.

104. The process for producing a tyre according to claim 103, further comprising picking up the first forming drum from a drum accumulating work station and placing said first forming drum in said carcass structure building line.

105. The process for producing a tyre according to claim 103, wherein step a) of building the carcass structure further comprises, before sub-step a10), the sub-step of: a1) applying at least one bead reinforcing fabric in a position radially external to the first forming drum.

106. The process for producing a tyre according to claim 105, wherein step a) of building the carcass structure further comprises, before sub-step a10), the sequential sub-steps of: a2) applying at least one first portion of an abrasion-proof element in a position radially external to said first forming drum by winding side by side and/or overlapped coils of a continuous elongated element made of an elastomeric material; a3) applying a liner layer in a position radially external to said first forming drum by winding side by side and/or overlapped coils of a continuous elongated element made of an elastomeric material; a4) applying a sub-liner layer in a position radially external to said liner by winding side by side and/or overlapped coils of a continuous elongated element made of an elastomeric material; a5) applying at least one first carcass ply in a position radially external to the sub-liner layer; and a6) applying a plurality of first intermediate elements to said at least one carcass ply by winding side by side and/or overlapped coils of a continuous elongated element made of an elastomeric material.

107. The process for producing a tyre according to claim 106, wherein step a) of building the carcass structure further comprises, after sub-step a6) and before sub-step a10), the sub-step of: a7) applying a plurality of internal reinforcing elements to said first intermediate elements by winding side by side and/or overlapped coils of a continuous elongated element made of an elastomeric material.

108. The process for producing a tyre according to claim 107, wherein step a) of building the carcass structure further comprises, after sub-step a7) and before sub-step a10), the sequential sub-steps of: a8) applying a pair of annular anchoring structures to the axially opposite ends of said at least one carcass ply by winding side by side and/or overlapped coils of a rubber metal cord; and a9) applying at least one second portion of the abrasion-proof element by winding side by side and/or overlapped coils of a continuous elongated element.

109. The process for producing a tyre according to claim 108, wherein step a) of building the carcass structure further comprises, between sub-step a4) and sub-step a5), the sub-step of: applying a layer of self-sealing material by winding side by side and/or overlapped coils of a continuous elongated element made of an elastomeric material.

110. The process for producing a tyre according to claim 109, wherein step a) of building the carcass structure further comprises, between sub-step a8) and sub-step a9), the sub-step of: applying a plurality of external reinforcing elements to said at least one carcass ply by winding side by side and/or overlapped coils of a continuous elongated element made of an elastomeric material.

111. The process for producing tyres according to claim 108, wherein step a) of building the carcass structure further comprises, between sub-step a8) and sub-step a9), the sub-step of: applying an external ply to said at least one carcass ply.

112. The process for producing a tyre according to claim 108, wherein sub-step a8) of applying the pair of annular reinforcing structures further comprises, the sub-steps of: a8) placing each of the annular reinforcing structures at axially opposite ends of said at least one carcass ply; and a8) folding the ends of said at least one carcass ply onto said at least one carcass ply so as to form flaps that contain said pair of annular anchoring structures.

113. The process for producing a tyre according to claim 108, wherein sub-step a8) of applying the pair of annular reinforcing structures is preceded by step j) of transferring bead cores from a bead core storage work station operatively associated with an annular anchoring structures applying work station of the carcass structure building line.

114. The process for producing a tyre according to claim 103, wherein step b) of building the crown structure, further comprises, before sub-step b7), the sub-step of: b1) applying an under-belt layer in a position radially external to the second forming drum by winding side by side and/or overlapped coils of a continuous elongated element made of an elastomeric material.

115. The process for producing a tyre according to claim 114, wherein step b) of building the crown structure further comprises, before sub-step b7), the sequential sub-steps of: b2) applying a first belt strip in a position radially external to said second forming drum; b4) applying a second belt strip in a position radially external to said first belt strip; b5) applying at least one first layer of textile or metal cords, arranged circumferentially in a position radially external to the second belt strip, and applied at least at axially external portions thereof by winding side by side and/or overlapped coils of a continuous elongated element made of an elastomeric material; and b6) applying at least one tread band in a position radially external to said at least one first layer of textile or metal cords by winding side by side and/or overlapped coils of a continuous elongated element made of an elastomeric material.

116. The process for producing a tyre according to claim 115, wherein step b) of building the crown structure, further comprises, between sub-step b2) and sub-step b4), the sub-step of: b3) laying at least one second intermediate element on the first belt strip by winding side by side and/or overlapped coils of a continuous elongated element made of an elastomeric material.

117. The process for producing a tyre according to claim 103, wherein said second portion of sidewalls of the tyre is applied in a position axially external to said tread band.

118. The process for producing a tyre according to claim 115, wherein sub-step b6) is carried out in at least two tread band assembling work stations by winding side by side and/or overlapped coils of a continuous elongated element made of an elastomeric material.

119. The process for producing a tyre according to claim 115, wherein step b) of building the crown structure further comprises, before sub-step b6) of applying at least one tread band, a sub-step of applying at least one sub-layer on the at least one first layer of textile or metal cords applied in step b5) by winding side by side and/or overlapped coils of a continuous elongated element made of an elastomeric material.

120. The process for producing a tyre according to claim 119, wherein sub-step b6) comprises the application of two tread bands by winding side by side and/or overlapped coils of a continuous elongated element made of an elastomeric material.

121. The process for producing a tyre according to claim 103, further comprising, before step d), transferring the shaped green tyre into a green tyre storing work station operatively associated with the assembling and shaping work station.

122. The process for producing a tyre according to claim 121, further comprising, after transferring the shaped green tyre into a green tyre storing work station, transferring the shaped green tyre to the tyre moulding and vulcanization line.

123. The process for producing a tyre according to claim 103, wherein step c) of shaping and assembling the green tyre comprises the following sub-step: c1) transferring the crown structure from the second forming drum in a position radially external to the carcass structure associated with the first forming drum.

124. The process for producing a tyre according to claim 103, comprising after step a) of building the carcass structure of the green tyre, step a) of transferring and storing a built carcass structure into a work station for storing carcass structures, arranged externally to the carcass structure building line.

125. The process for producing a tyre according to claim 103, comprising, after step a) of building the carcass structure of the green tyre, step a) of transferring and storing a built carcass structure into a drum accumulating work station.

126. The process for producing a tyre according to claim 103, comprising, after step b) of building the crown structure of the green tyre, transferring and storing a built crown structure into a crown structure storing work station.

127. The process for producing a tyre according to claim 106, further comprising supplying elementary semi-finished products in a work station at sub-step a5).

128. The process for producing a tyre according to claim 127, further comprising preparing the elementary semi-finished products in a semi-finished product preparation line.

129. The process for producing a tyre according to claim 103, further comprising adjusting dimensions of at least one of the first forming drum and the second forming drum.

130. The process for producing a tyre according to claim 129, wherein said adjusting dimensions comprises axial adjustment of the first forming drum.

131. The process for producing a tyre according to claim 129, wherein said adjusting dimensions comprises radial adjustment of the second forming drum.

132. The process for producing a tyre according to claim 103, wherein said first forming drum is transferred from a work station of the carcass structure building line to a next work station by a carriage moving on a travel line.

133. The process for producing a tyre according to claim 103, wherein said second forming drum is transferred from a work station of the crown structure building line to a next work station by means of at least one robotized arm.

134. The process for producing a tyre according to claim 110, wherein at least one of sub-steps a1)-a10) is preceded by a step for transferring the first forming drum into a drum accumulating work station.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0181] Further features and advantages of the invention will appear more clearly from the following description of some preferred examples of production plants and processes according to the invention, made by way of an indicative non-limiting example with reference to the annexed drawings, wherein:

[0182] FIG. 1 shows a schematic layout of a plant for producing tyres for vehicle wheels wherein the process according to a first embodiment of the present invention is carried out; and

[0183] FIG. 2 shows a schematic layout of a plant for producing tyres for vehicle wheels wherein the process according to a second embodiment of the present invention is carried out.

DETAILED DESCRIPTION OF THE INVENTION

[0184] With reference to FIG. 1, reference numeral 1 generally indicates a plant for producing tyres for vehicle wheels according to a first embodiment of the present invention.

[0185] With reference to FIG. 2, reference numeral 1 generally indicates the plant for producing tyres for vehicle wheels according to a second embodiment of the present invention.

[0186] Plant 1, 1 comprises at least one carcass structure building line 2, 2 wherein a carcass structure, comprising at least one carcass ply and a pair of annular anchoring structures, is built on at least one first forming drum 6.

[0187] Such plant 1, 1 further comprises at least one crown structure building line 3, 3 wherein a crown structure, comprising at least one belt structure and as tread band, is built on at least one second forming drum 7.

[0188] Plant 1, 1 is further provided with at least one assembling and shaping work station 4 of the tyre being processed operatively associated with said carcass structure building line 2, 2 and to said crown structure building line 3, 3. Such assembling and shaping work station 4 is suitable for shaping a carcass structure by assembling it to a crown structure so as to obtain a green tyre.

[0189] According to a preferred embodiment of the invention, the carcass structure building line 2, 2, is provided with moving systems for transferring the carcass structure and the first forming drum 6 whereon this has been built from said carcass structure building line 2, 2, to said assembling and shaping line 4. Preferably such moving systems comprise at least one robotized arm 50.

[0190] According to a preferred embodiment of the invention, the crown structure building line 3, 3, is provided with moving systems for transferring the crown structure and the second/third forming drum 7/27 from said crown structure building line 3, 3, to said assembling and shaping line 4. Preferably such moving systems comprise at least one robotized arm 60.

[0191] The assembling and shaping work station 4 is provided with shaping devices, associable to said first forming drum 6, which are suitable for performing the shaping of the carcass structure on the first forming drum 6.

[0192] Such shaping devices are preferably pneumatic or mechanical devices.

[0193] Plant 1, 1 further comprises at least one moulding and vulcanization line 5 of the assembled and shaped tyre wherefrom the finished product is obtained.

[0194] The assembling and shaping work station 4 is provided with transfer devices for transferring the second forming drum 7 or a third forming drum 27 (that will be better illustrated hereinafter) from such work station to the crown structure building line 3 or 3, after the crown structure has been removed therefrom to be associated with the carcass structure.

[0195] The production plant 1, 1 further comprises a drum accumulating work station 0 wherein drums that may be of a different type are stored. Such work station is provided with devices for transferring a first forming drum 6 to the carcass structure building line 2, 2.

[0196] The carcass structure building line 2, 2 comprises a first sidewall building work station 19 provided with devices for applying at least one first portion of sidewalls of the tyre being processed.

[0197] The application of at least one second portion of sidewalls of the tyre being processed is provided in a second sidewall building work station 26 of the crown structure building line 3, 3 by special devices.

[0198] The carcass structure building line 2, 2 comprises at least two of the following work stations: [0199] a work station for applying a reinforcing fabric 8 provided with devices for applying at least one bead reinforcing fabric on a first forming drum 6; [0200] a first abrasion-proof application work station 9 provided with devices for applying at least one first portion of an abrasion-proof element in a position radially external to said first forming drum 6; [0201] a liner application work station 11 provided with devices for applying a liner layer in a position radially external to said first forming drum 6; [0202] a sub-liner application work station 12 provided with devices for applying a sub-liner layer in a position radially external to said liner; [0203] a ply application work station 13 provided with devices for applying at least one first carcass ply in a position radially external to the sub-liner layer; [0204] a work station for applying first intermediate elements 14 provided with devices for applying a plurality of first intermediate elements at the carcass plies; [0205] an internal reinforcing element application work station 15 provided with devices for applying a plurality of internal reinforcing elements at said first intermediate elements; [0206] a annular anchoring structures applying work station 16 provided with devices for applying at least one pair of annular anchoring structures to the axially opposite ends of said at least one carcass ply; [0207] a second abrasion-proof application work station 18 provided with devices for applying at least one second portion of the abrasion-proof element; [0208] a first sidewall building work station 19 provided with devices for applying at least one first portion of sidewalls of the tyre being processed.

[0209] Advantageously, the above first intermediate elements are applied by winding side by side and/or overlapped coils of a continuous elongated element of elastomeric material. The presence of elastomeric material between the textile cords of the carcass ply/plies and the above internal reinforcing elements exhibiting metal cords (having sharp edges due to the angled laying thereof), prevents contact between the latter and the carcass ply itself preventing the possible onset of cracks in the tyre operation.

[0210] In both embodiments of the present invention shown in the figures, the carcass structure building line 2, 2 comprises each of the above work stations. The latter are sequentially arranged along two parallel travels run by the first forming drum 6 in opposite directions.

[0211] In particular, in the second embodiment shown in FIG. 2, the work station for applying intermediate elements 14, the work station for applying internal reinforcing elements 15 and the annular anchoring structures applying work station 16 are integrated in an integrated unit 36.

[0212] The carcass structure building line 2 of the production plant 1, according to the first embodiment of the invention, beside the above work stations comprises also a work station for applying self-sealing material 10 provided with devices for applying a layer of self-sealing material in a position radially external to said sub-liner layer. As can be seen in FIG. 1, said work station for applying self-sealing material 10 is arranged downstream the first sub-liner application work station 12.

[0213] The carcass structure building line 2, 2 may also comprise a external reinforcing elements applying work station 17 which is provided with devices for applying a plurality of external reinforcing elements at the carcass plies. Such external reinforcing elements applying work station 17 is arranged downstream the annular anchoring structures applying work station 16.

[0214] In the second embodiment, said external reinforcing elements applying work station 17 is integrated in the integrated unit 36 of the carcass structure building line 2.

[0215] According to an alternative embodiment, not shown in the figures, the carcass structure building line 2, 2 comprises, alternatively to said external reinforcing elements applying work station 17, a work station for applying an external ply which is provided with devices for applying an external ply at the carcass ply/plies. Such work station for applying an external ply is arranged downstream the annular anchoring structures applying work station 16.

[0216] Similarly to the external reinforcing elements applying work station 17, such work station may be integrated in said integrated unit 36 of the carcass structure building line 2.

[0217] The annular anchoring structures applying work station 16 of the carcass structure building line 2, 2 is also provided with devices for folding the ends of the carcass plies on the plies themselves, so as to form flaps that contain said annular anchoring structures.

[0218] According to the first embodiment, the production plant 1 further comprises a bead core storing work stations 32 suitable for forming the annular anchoring structures of the tyre being processed. Such bead core storing work stations 32 is operatively associated with the annular anchoring structures applying work station 16 and arranged in the proximity thereof.

[0219] As shown in FIG. 2, said second abrasion-proof application work station 18 and said first sidewall building work station 19 are comprised in a carcass structure completing unit 33.

[0220] The latter also comprises devices for transferring the first forming drum 6 from the carcass structure building line 2 into the completion unit 33 itself. In other words, such transfer devices pick up the first forming drum 6 from one of the above travel lines for transferring it to the completion unit 33 where the carcass structure is completed.

[0221] Said devices for transferring the first forming drum 6 in the carcass structure completing unit 33 comprise a robotized arm 44.

[0222] The latter is also suitable for transferring the first forming drum 6 to the travel line once the carcass structure has been completed.

[0223] The crown structure building line 3, 3 according to the present invention comprises a work station for applying an under-belt layer 20 provided with devices for applying an under-belt layer on the second forming drum 7.

[0224] Said crown structure building line 3, 3 may further comprise the following work stations operatively arranged in line: [0225] a first belt applying work station 21 provided with devices for applying at least one first belt strip in a position radially external to said second forming drum; [0226] a second intermediate elements laying work station 22 provided with devices for laying at least one second intermediate element on the first belt structure; [0227] a second belt applying work station 23 provided with devices for applying a second belt strip in a position radially external to said first belt strip; [0228] a cord application work station 24 provided with devices for applying at least one first layer of cords, arranged circumferentially on the radially external belt strip, applied at least at the axially external portions thereof; [0229] at least one tread band assembling work station 25 provided with devices for applying at least one tread band in a position radially external to said cord layer; [0230] a second sidewall building work station 26 provided with devices for building at least one second portion of sidewalls in a position axially external to the tread band.

[0231] Advantageously, the above second intermediate elements are applied by winding side by side and/or overlapped coils of a continuous elongated element of elastomeric material. The presence of elastomeric material covering the axial ends of at least two overlapped belt strips may be useful in tyres for very high performance vehicles, since it prevents the onset of cracks at the axial ends of the belts that could generate due to the considerable efforts a tyre of this type is subject to.

[0232] In the embodiment of the present invention illustrated in FIG. 1, the crown structure building line 3 comprises each of the work stations, which are sequentially arranged so as to form a loop crossed by the second forming drum 7, preferably in clockwise direction.

[0233] According to the embodiment shown in FIG. 2, the crown structure building line 3 comprises: [0234] a first unit 34 for the partial building of the crown structure, wherein the crown structure is partially built on the second forming drum 7, comprising an under-belt layer application work station 20, a first belt application work station 21, an intermediate element laying work station 22 and a second belt application work station 23; [0235] a second unit 35 for the partial building of the crown structure, wherein the crown structure is completed on a third forming drum 27, geometrically different from the second forming drum 7, comprising a cord application work station 24, at least two tread band assembling work stations 25 and a second sidewall building work station 26; [0236] a crown structure transferring work station 28 from the second forming drum 7 of the first unit 34 for partially building the crown structure to the third forming drum 27 of the second unit 35 for partially building the crown structure.

[0237] The crown structure transferring work station 28 is arranged between the first unit 34 for the partial building of the crown structure and second unit 35 for the partial building of the crown structure.

[0238] The third forming drum 27 comprises a convex forming surface. In other words, the forming surface is not flat, but curved so as to shape the crown structure.

[0239] The second belt applying work station 23 of the crown structure building line 3, 3 is also provided with devices for applying a third belt strip in a position radially external to said second belt strip.

[0240] The crown structure transferring work station 28 also comprises devices for turning the ends of the first belt strip on the second belt strip or of the first belt strip on the second and third belt strip.

[0241] The crown structure building line 3, 3 comprises, downstream the cord application work station 24, a sub-layer application work station provided with devices for applying at least one sub-layer of the tread band in a position radially external to the cord layer.

[0242] The crown structure building line 3, according to one embodiment illustrated in FIG. 1, preferably comprises six work stations for building a tread band 25.

[0243] The production plant 1, 1, according to the present invention, comprises a green tyre storing work station 30 operatively associated with the assembling and shaping work station 4 and to the moulding and vulcanization line 5 of the tyre.

[0244] Said green tyre storing work stations 30 is arranged between the assembling and shaping work station 4 and the moulding and vulcanization line 5 and is provided with devices for transferring the green tyre to the moulding and vulcanization line 5.

[0245] Plant 1, 1 comprises devices for transferring the green tyre from the assembling and shaping work station 4 to the green tyre storage work station 30, preferably the above devices comprise a robotized arm 29.

[0246] The green tyre assembling and shaping work station 4 comprises: [0247] at least one stand-by position of the second forming drum 7 or of the third forming drum 27; [0248] devices for transferring the crown structure for transferring it to a position radially external to the carcass structure associated with the first forming drum 6.

[0249] Plant 1, 1, according to one embodiment of the invention not shown in the figures, comprises a work station for storing carcass structures positioned externally to the carcass structure building line.

[0250] As an alternative, the carcass structure storage work station may coincide with the drum accumulating work station 0 of the carcass structure building line 2, 2.

[0251] Likewise, plant 1, 1 comprises a crown structure storing work stations 41.

[0252] At least one between the ply application work station 13, the first belt application work station 21, the second belt application work station 23 and the cord application work station 24 is operatively associated with at least one unit for supplying elementary semi-finished products 37 in the respective work stations.

[0253] In both embodiments shown in the figures, all of the above work stations are operatively associated with and arranged close to respective units for supplying elementary semi-finished products 37.

[0254] The elementary semi-finished products preferably comprise continuous elongated elements of elastonieric material, strips of elastomeric material generally called strip-like elements containing two or more textile or metal cords, single rubber metal cords, therein.

[0255] In the work stations illustrated above, the above elementary semi-finished products may be wound by side by side and/or overlapped coils, for example in the case of continuous elongated elements that contribute to the forming of liners, sub-liners, sub-layers, fillers in the bead zone, sidewalls, tread band, or in the case of single rubber metal cord that contributes to the forming of bead cores or of the cord layer at zero degrees in the belt structure. As an alternative, such semi-finished products may be laid reciprocally side by side, especially in the case of strip-like elements that for example contribute to forming carcass plies, belt strips, and some types of reinforcing elements.

[0256] As shown in FIG. 1, the plant according to the invention may comprise a line for preparing elementary semi-finished products 31 suitable for being supplied in at least one between the carcass structure building line 2 and the crown structure building line 3.

[0257] The plant 1, 1 for producing tyres comprises devices for adjusting the shape and/or the dimensions of at least one between the first forming drum 6, the second forming drum 7 and the third forming drum 27.

[0258] According to preferred embodiments, the first forming drum 6 is adjustable in axial direction and the second forming drum 7 is adjustable in radial direction.

[0259] The carcass structure building line 2, 2 is preferably provided with devices for transferring the first forming drum 6 from a work station of the same carcass structure building line 2, 2 to the next work station which preferably comprise a carriage moving on a travel line. Such carriage moves on the travel lines stopping at work stations wherein the tyre must be processed.

[0260] Likewise, the crown structure building line 3, 3 is provided with devices for transferring the second forming drum 7 from a work station of the same crown structure building line 3, 3 to the next work station. These devices preferably comprise at least one robotized arm 38. The latter picks up the drum from a work station and carries it into the next work station.

[0261] According to the second embodiment, the crown structure building line 3 is provided with devices for transferring the third forming drum 27 from a work station of the second unit 35 for partially building the crown structure to the next work station which preferably comprise at least one robotized arm 38.

[0262] According to the present invention, the moulding and vulcanization line 5 of the shaped green tyre comprises at least two vulcanizing units 39. Each of said vulcanizing units 39 comprises at least one vulcanizing die 40 wherein a tyre is moulded and vulcanized in a known manner.

[0263] In production plant 1, according to one embodiment of the invention, said vulcanizing units 39 are ten. Each vulcanizing unit 39 comprises two vulcanizing dies 40.

[0264] In production plant 1, according to a different embodiment of the invention, said vulcanizing units 39 are five. Each vulcanizing unit 39 comprises two vulcanizing dies 40.

[0265] With reference to the production plant 1, 1 illustrated in FIGS. 1 and 2, two preferred embodiments of a production process according to the invention shall now be described.

[0266] According to a step a), a carcass structure of a green tyre, comprising at least one carcass ply and a pair of annular anchoring structures, is built on a first forming drum 6 in at least one carcass structure building line 2. The robotized arm 50 carries the carcass structure built and associated with the forming drum 6 thereof to the assembling and shaping line 4. Said carcass structure building line 2, according to the invention, works at a production rate equal to t1.

[0267] According to a step b), a crown structure of a green tyre, comprising at least one belt structure and a tread band, is built on at least one second forming drum 7 in at least one crown structure building line 3. The robotized arm 60 carries the crown structure built and associated with the forming drum 7 thereof to the assembling and shaping line 4. Said crown structure building line 3, according to the invention, works at a production rate equal to t2.

[0268] The process according to the invention, according to a step c), provides the toroidal shaping of said carcass structure for building it to said crown structure, in at least one assembling and shaping line 4 of the tyre being processed, which is operatively associated with said carcass structure building line 2 and to said crown structure building line 3. Said assembling and shaping work station 4, according to the invention, works at a production rate equal to.

[0269] The production process finally provides a step d) of moulding and vulcanizing the shaped green tyre in at least one tyre moulding and vulcanization line 5.

[0270] According to the invention, each carcass structure is associated with the respective first forming drum 6 whereon it is built up to the end of step c) of shaping and assembling of the tyre being processed and, in steady operation, t1 and t2 are comprised in the range 0.9 {tilde over (t)}-1.3 {tilde over (t)}.

[0271] According to a preferred embodiment of the invention, t1 and t2 are comprised in the range 0.931 {tilde over (t)}-1.15.

[0272] Even more preferably, t1 and t2 are comprised in the range 0.97 {tilde over (t)}-1.1 {tilde over (t)}.

[0273] The case wherein {tilde over (t)}, t1 and t2 are substantially equal, that is, when t1 and t2 are comprised in the range 0.99 {tilde over (t)}-1.01 {tilde over (t)}, is particularly preferred.

[0274] According to preferred embodiments, {tilde over (t)} is comprised between 60 and 80 s and more preferably, {tilde over (t)} is comprised between 65 and 75 s.

[0275] For example, if {tilde over (t)}=70, t1 and t2 are comprised between 63 and 91 s. More preferably, t1 and t2 are comprised between 65.1 and 80.5 s, and even more preferably t1 and t2 are comprised between 67.9 and 77 s, which allows optimum management of the process for producing tyres according to the invention. In this way, in fact, considerable stand-by time from the production point of view are not provided.

[0276] According to preferred embodiments, the process also comprises the step z) of picking up a first forming drum 6 from a drum accumulating work station 0 and placing it in said carcass structure building line 2.

[0277] Step a) of building the carcass structure comprises sub-step a10) of applying at least one first portion of sidewalls of the tyre being processed in a first sidewall building work station 19 of the carcass structure building line 2.

[0278] Step b) comprises sub-step b7) of applying at least one second portion of sidewalls of the tyre being processed in a second sidewall building work station 26 of the crown structure building line 3.

[0279] Preferably, step a) also comprises sub-step a1) of applying at least one bead reinforcing fabric in a position radially external to the first forming drum 6.

[0280] According to preferred embodiments, said step a) of building the carcass structure may further comprise the sequential sub-steps of:

[0281] a2) applying at least one first portion of an abrasion-proof element in a position radially external to said first forming drum 6;

[0282] a3) applying a liner layer in a position radially external to said first forming drum 6;

[0283] a4) applying a sub-liner layer in a position radially external to said liner;

[0284] a5) applying at least one first carcass ply in a position radially external to the sub-liner layer;

[0285] a6) applying a plurality of first intermediate elements at the carcass ply/plies.

[0286] Step a) comprises, after sub-step a6), the further sub-step a7) of applying a plurality of internal reinforcing elements as said intermediate elements.

[0287] Afterwards, the further sequential sub-steps may be provided:

[0288] a8) applying at least one pair of annular anchoring structures to the axially opposite ends of the carcass ply/plies;

[0289] a9) applying at least one second portion of the abrasion-proof element;

[0290] a10) applying at least one first portion of sidewalls of the tyre being processed.

[0291] According to the embodiment of the invention carried out in plant 1 of FIG. 1, step a) of building the carcass structure comprises, between sub-step a4) and sub-step a5), the sub-step of: [0292] applying a layer of self-sealing material.

[0293] According to preferred embodiments of the process of the invention, step a) of building the carcass structure comprises, between sub-step a8) and sub-step a9), the sub-step of applying a plurality of external reinforcing elements at the carcass ply/plies.

[0294] Such sub-step may be replaced by the sub-step of applying an external ply at the carcass ply/plies.

[0295] Sub-step a8) of application of the annular reinforcing structures comprises the following sub-steps:

[0296] a8) placing the annular reinforcing structures at the axially opposite ends of the carcass ply/plies; and

[0297] a8) folding the ends of the carcass ply/plies onto the plies themselves so as to form flaps that contain said annular anchoring structures.

[0298] The same sub-step a8) is preferably preceded by a step j) of transferring bead cores suitable for forming said annular anchoring structures from a bead core storage work station 32 operatively associated with the annular anchoring structures applying work station 16 of the carcass structure building line 2.

[0299] Step a) of building the carcass structure may comprise, before sub-step a9) of applying the second portion of the abrasion-proof element, sub-step a9) of transferring the first forming drum 6 into a carcass structure completing unit 33 comprising a second abrasion-proof application work station 18 and a first sidewall building work station 19, as shown in FIG. 2.

[0300] Said sub-step a9) of transferring the first forming drum 6 into the carcass structure completing unit 33 is preferably carried out by a robotized arm 44.

[0301] According to preferred embodiments of the process of the invention, step b) of building the crown structure comprises sub-step b1) of applying an under-belt layer in a position radially external to the second forming drum 7.

[0302] Step b) may also comprise the further sequential sub-steps of:

[0303] b2) applying at least one first belt strip in a position radially external to said second forming drum;

[0304] b3) laying at least one second intermediate element on the first belt structure;

[0305] b4) applying a second belt strip in a position radially external to said first belt strip;

[0306] b5) applying at least one first layer of textile or metal cords, arranged circumferentially in a position radially external to the radially external belt strip, and applied at least at the axially external portions thereof;

[0307] b6) applying at least one tread band in a position radially external to said cord layer;

[0308] b7) applying at least one second portion of sidewalls of the tyre being processed in a position axially external to said tread band.

[0309] Sub-step b6) is preferably carried out in at least two tread band assembling work stations 25. In particular, in the embodiment of the process of the invention, carried out in plant 1 of FIG. 1, such sub-step b6) is carried out in six tread band assembling work stations 25, whereas in a different embodiment, carried out in plant 1 of FIG. 2, such sub-step b6) is carried out in two tread band assembling work stations 25.

[0310] According to said different embodiment illustrated in FIG. 2, step b) of building the crown structure comprises, after sub-step b4), the sub-step of transferring the partially built crown structure from said second forming drum 7 whereon it is partially built to a third forming drum 27, into a crown structure transferring work station 28 of the crown structure building line 3.

[0311] Sub-step b4), according to a preferred embodiment, comprises the application of a third belt strip in a position radially external to the second belt strip. In that case, said step b) of building the crown structure comprises, before the sub-step of transferring the partially built crown structure, the sub-step of turning the ends of the first belt strip on the second belt strip or of the first belt strip on the second and on the third belt strip.

[0312] Step b) of building the crown structure comprises, before sub-step b6) of building the tread band, the sub-step of applying at least one sub-layer of the tread band on the cord layer applied before.

[0313] In such solution, said sub-step b6) comprises the application of two layers of tread band.

[0314] Before step d), according to preferred embodiments, the process comprises the step e) of transferring the shaped green tyre into a green tyre storing work stations 30 operatively associated with the assembling and shaping work station 4.

[0315] After such step e), a step f) of transferring the shaped green tyre to the tyre moulding and vulcanization line 5 is provided.

[0316] The step c) of shaping and assembling the green tyre comprises the sub-step c1) of transferring the crown structure from the second/third forming drum 7/27 whereon it has been built in a position radially external to the carcass structure associated with the first forming drum 6.

[0317] After the step a) of building the carcass structure of the green tyre, there is provided a step a) of transferring and storing the built carcass structure into a work station for storing carcass structures arranged externally to the carcass structure building line 2, or a step a) of transferring and storing the built carcass structure into the drum accumulating work station 0.

[0318] Likewise, after the step b) of building the crown structure of the green tyre, there may be provided a step b) of transferring and storing the built crown structure into a crown structure storing work stations 41.

[0319] According to preferred embodiments, the process for producing tyres provides that at least one between sub-steps a5), b2), b4) and b5) comprises the pre-step g) of supplying elementary semi-finished products in the respective work stations.

[0320] The process further comprises the additional step h) of preparing elementary semifinished products in a semi-finished product preparation line 31.

[0321] There is further provided a step i) of adjusting the dimensions of at least one between the first forming drum 6, the second forming drum 7 and the third forming drum 27.

[0322] In the preferred embodiments, said step i) comprises the axial adjustment of the first forming drum 6 and the radial adjustment of the second forming drum 7.

[0323] The first forming drum 6 is preferably transferred from a work station of the carcass structure building line 2 to the next work station by a carriage moving on a travel line.

[0324] Preferably, the second/third forming drum 7/27 is transferred from a work station of the crown structure building line 3/3 to the next work station by at least one robotized arm 38.

[0325] The process finally provides that at least one of sub-steps a1)-a10) is preceded by a step for transferring the first forming drum 6 into the drum accumulating work station 0 for making up for any failures or changes in the production requirements.

[0326] Within the scope of the present description above and in the following claims, all numerical values indicating amounts, parameters, percentages and so on are always to be deemed as preceded by the term about, if not otherwise stated. Moreover, all numerical value ranges include all possible combinations of the maximum and minimum numerical values and all possible intermediate ranges, besides those specifically indicated in the text.