Patent Application
20130180647
The present invention relates to a process and an apparatus for manufacturing a tyre for vehicle wheels.
A tyre for vehicle wheels generally comprises a carcass structure comprising at least one carcass ply formed of reinforcing cords embedded in an elastomeric matrix. The carcass ply has end edges respectively engaged with annular anchoring structures. The latter are arranged in the areas of the tyre usually identified by the name “beads” and each of them is normally formed by a substantially circumferential annular insert on which at least one filling insert is applied, in a radially outer position thereof. Such annular inserts are commonly identified as “bead cores” and have the task of keeping the tyre firmly fixed to the anchoring seat specifically provided in the rim of the wheel, thus preventing, in operation, the radially inner end edge of the tyre coming out from such a seat.
At the beads specific reinforcing structures may be provided having the function of improving the torque transmission to the tyre.
In a radially outer position with respect to the carcass ply a belt structure comprising one or more belt layers is associated, said belt layer being arranged radially one on top of the other and having textile or metallic reinforcing cords with crossed orientation and/or an orientation substantially parallel to the direction of circumferential extension of the tyre.
Between the carcass structure and the belt structure a layer of elastomeric material, known as “under-belt”, can be provided, said layer having the function of making the radially outer surface of the carcass structure as uniform as possible for the subsequent application of the belt structure.
In a radially outer position with respect to the belt structure a tread band is applied, also made of elastomeric material.
Between the tread band and the belt structure a so-called “under-layer” of elastomeric material can be arranged, said under-layer having properties suitable for ensuring a steady union of the tread band itself.
On the side surfaces of the carcass structure respective sidewalls of elastomeric material are also applied, each extending from one of the side edges of the tread band up to the respective annular anchoring structure to the beads.
Throughout the present description and in the subsequent claims, the terms “radial” and “axial” and the expressions “radially inner/outer” and “axially inner/outer” are used with reference to the radial direction and to the axial direction of a forming support. The terms “circumferential” and “circumferentially” instead, are used referring to the annular extension of the forming support.
Throughout the present description and in the subsequent claims, the pressure values here indicated are to be understood as values which refer to the atmospheric pressure.
With particular reference to the area of the tyre identified as “bead”, this is defined by a free end portion of the carcass ply specifically turned up and housing the annular anchoring structure therein.
The Applicant verified that the coupling between the bead core and the carcass ply generally comprises a step, prior to the step of turning up the free end portion of the carcass ply, wherein the filling insert of the bead core is brought. in a contact position with the end edge of the carcass ply by a proper positioning device and a step, simultaneous to the step of turning up the free end portion of the carcass ply, wherein the filling insert of the bead core is laid or pulled down onto the end edge of the carcass ply.
The Applicant focused his attention on those conventional processes wherein the turning up of the free end portion of the carcass ply, and the simultaneous pulling down of the filling insert of the bead core on the end edge of the carcass ply, is carried out as a result of the inflation, up to a predetermined pressure value, of an air chamber specifically provided close to the forming support on which the carcass ply is arranged.
The Applicant observed that in the processes described above, keeping the bead core into position on the end edge of the carcass ply during the turning up of the free end portion of the carcass ply is obtained by only the stickiness of the rubber mixture of the bead core with the rubber mixture of the fabric the carcass ply is made of.
The Applicant noted that such stickiness is not always sufficient to ensure that the desired concentricity between bead core and forming support is maintained. In fact, during the turning up of the free end portion of the carcass ply the bead core is subject to considerable stresses in the radial direction.
The Applicant thus observed that, in order to maintain the desired concentricity between bead core and forming support during the turning up of the free end portion of the carcass ply, it is desirable to achieve a greater consolidation of the bead core on the end edge of the carcass ply during the turning up of the free end portion of the carcass ply.
The Applicant observed, on the other end, that in order to carry out the turning up of the free end portion of the carcass ply, and the simultaneous pulling down of the filling insert of the bead core on the end edge of the carcass ply, by the air chamber the action of the air chamber must not be impaired by the presence of bead core positioning and/or retaining devices.
However, the Applicant observed that in the turning up of the free end portion of the carcass ply, the first part of this operation is particularly critical; in fact, during the first part of the turning up, the bead core is subject to stresses in radial direction, which tend to move it from the desired position with respect to the forming support.
The Applicant thus observed that in order to keep the desired concentricity between bead core and forming support a greater consolidation of the bead core on the end edge of the carcass ply during the first part of the turning up of the free end portion of the carcass ply is required.
In this respect, the Applicant perceived that it is possible to increase the anchoring surface between bead core and carcass ply, thus achieving the desired greater consolidation of the bead core on the carcass ply, by starting the turning up of the free end portion of the end edge of the carcass ply while the bead core is still retained into contact with the end edge of the carcass ply against the forming support through a proper positioning device.
More particularly, the Applicant observed that carrying out the inflation of the air chamber in at least two successive time periods allows starting the turning up while the bead core is still kept in contact with the end edge of the carcass ply.
Finally, the Applicant found that carrying out a partial inflation of the air chamber while the positioning device retains the bead core in contact position with the end edge of the carcass ply allows obtaining a first part of the turning up in a condition wherein the bead core is in the desired position with respect to the forming support and the stresses imparted to the bead core during such first part of turning up are effectively opposed. An anchoring is thus obtained between bead core and end edge of the carcass ply which is sufficient to avoid that in the remaining part of the turning up, when the bead core is subject to greater stresses and is retained into position on the carcass ply by only the stickiness of the rubber mixture of the bead core with the rubber mixture of the fabric the carcass ply is made of, the bead core might move from the desired position with respect to the forming support. The desired concentricity between bead core and forming support is thus ensured.
The present invention therefore relates, in a first aspect thereof, to a process for manufacturing a tyre for vehicle wheels, comprising:
The Applicant verified that the present invention allows manufacturing high quality tyres, wherein the position of the bead cores with respect to the forming support is the one desired and defined in the design stage, such position not being altered by the effect of the stresses the bead core is subject to during the turning up of the free end portion of the carcass ply.
According to the invention, the substantial irremovability of the bead core during the turning up of the end edge of the carcass ply is in fact assured either by the fact that a first part of the turning up is carried out while the bead core is retained into contact position with the end edge of the carcass ply by a proper positioning device, and by the fact that the remaining part of the turning up is carried out when, a part of the turning up having been already carried out, the bead core adheres by stickiness onto the end edge of the carcass ply at an extended surface. Carrying out a part of the turning up in a condition wherein the bead core is held in contact position with the end edge of the carcass ply is advantageously made possible by the fact that a partial inflation of the air chamber has been performed.
In a second aspect thereof, the present invention relates to an apparatus for manufacturing a tyre for vehicle wheels, the apparatus comprising:
Advantageously, such an apparatus allows carrying out the process of the present invention discussed above, thus allowing the advantages mentioned above to be achieved.
The present invention, in at least one of the aforementioned aspects, can comprise at least one of the following preferred features.
Preferably, the annular anchoring structure is brought in contact position with the end edge of the carcass ply by the above device for positioning the annular anchoring structure. Advantageously, therefore, retaining the annular anchoring structure in contact position on the end edge of the carcass ply is carried out by the same mechanical member that carries out the positioning of the annular anchoring structure on the aforementioned end edge. Important advantages are thus achieved in terms of construction simplicity of the apparatus that carries out the above process, with a consequent considerable reduction of the production costs.
Preferably, during the partial inflation of said at least one air chamber, a maximum pressure value of between about 0.1 bar and about 0.4 bar is reached. More preferably, said maximum pressure value is of between about 0.2 bar and about 0.3 bar.
Preferably, said at least one air chamber, when it is completely inflated, has a maximum pressure value of between about 0.5 bar and about 1 bar. More preferably, said maximum pressure value is of between about 0.6 bar and about 0.9 bar.
In preferred embodiments thereof, the present invention comprises, before said annular anchoring structure is brought into contact position with the end edge of the carcass ply, displacing said at least one air chamber close to said forming support.
Preferably, the present invention comprises, after completing the inflation of said at least one air chamber, deforming said at least one air chamber to exert a thrust against the end edge of the carcass ply. In this way it is possible to achieve an optimal lying of the turned up end edge on the annular anchoring structure and an advantageous compaction of the bead thus formed, to the advantage of the quality of the tyre obtained and, consequently, the performance thereof.
In particularly preferred embodiments of the present invention, holding the annular anchoring structure in contact position with the end edge of the carcass ply is carried out through a radially outer annular portion of said at least one positioning device and comprises simultaneously moving a radially inner annular portion of said at least one positioning device away from the forming support.
In particular, according to the present invention, when the bead core is moved in contact position with the end edge of the carcass ply, the radially inner annular portion of the positioning device supports the bead core at the inner radial surface of the bead core and pushes it towards the end edge of the carcass ply by acting on the axially outer surface of the bead core together with the radially outer annular portion of the positioning device. The radially outer annular portion of the positioning device then continues to act on the axially outer surface of the bead core to hold it into contact position with the end edge of the carcass ply, while the radially inner annular portion of the positioning device is moved away from the bead core to leave the radially inner surface of the annular anchoring structure free. It is thus possible to carry out the first part of the turning up of the end edge of the carcass ply around the annular anchoring structure.
Preferably, the present invention further comprises, before carrying out the remaining part of turning up the end edge of the carcass ply, moving said radially outer annular portion of said at least one positioning device away from the forming support. It is thus possible to complete the turning up of the end edge of the carcass ply around the annular anchoring structure.
The Applicant noted that when the bead core is not supported by the positioning device anymore, it is firmly anchored by stickiness to the carcass ply at both the side surface thereof facing the forming support and the radially inner surface thereof. Such anchoring is sufficient for preventing undesired movements of the bead core during the remaining part of the turning up. This thanks to the fact that in this part of the turning up the bead core is no longer subject to the same outwards stresses in radial direction whereto it is instead subject in the first part of the turning up. Finally, it is possible in this way to ensure the proper positioning of the bead core in the tyre, to the advantage of quality and performance of the latter.
In preferred embodiments thereof, the present invention, further comprises, before bringing the annular anchoring structure in contact position with the end edge of the carcass ply, pulling the end edge of the carcass ply down towards the rotation axis of the forming support through at least one ply pulling down device.
Preferably, such pulling down is carried out by the ply pulling down device as a result of the movement of the positioning device of the annular anchoring structure towards the forming support along a direction parallel to the rotation axis of the forming support. Clear advantages are thus achieved in terms of construction simplicity of the apparatus that carries out the above process, with a consequent considerable reduction of the production costs.
In the embodiments of the present invention in which said at least one ply pulling down device is used, preferably, before starting the turning up of the end edge around the annular anchoring structure said at least one ply pulling down device is moved away from the forming support.
In particularly preferred embodiments of the present invention, the annular anchoring structure comprises a substantially circumferential annular insert and a filling insert associated in a radially outer position with respect to the substantially circumferential annular insert.
In this case, preferably, before starting the turning up of the end edge of the carcass ply, the filling insert is pulled down on the carcass ply by pushing it against the forming support. This allows obtaining a good anchoring of the annular anchoring structure on the end edge of the carcass ply. Such anchoring is ensured by the stickiness with the rubber mixture of the carcass ply by both the rubber mixture of the substantially circumferential annular insert of the annular anchoring structure and the rubber mixture of the pulled down filling insert.
In the preferred embodiments of the present invention, said at least one air chamber is movable along a direction parallel to the rotation axis of the forming support in a radially inner position with respect to said at least one positioning device.
Preferably, said at least one positioning device is movable along a direction parallel to the rotation axis of the forming support.
In particularly preferred embodiments of the present invention, said at least one positioning device comprises a radially inner annular portion and a radially outer annular portion capable of sliding with respect to one another along said direction parallel to the rotation axis of the forming support.
Preferably, at least one pulling down device is further provided for pulling down the end edge of the carcass ply towards the rotation axis of the forming support.
Preferably, at least one thrusting device is further provided for thrusting said at least one air chamber against the end edge of the carcass ply.
Preferably, in the embodiments of the present invention in which said annular anchoring structure comprises a substantially circumferential annular insert and a filling insert associated in a radially outer position with respect to the substantially circumferential annular insert, at least one pulling down device is provided for pulling down the filling insert on the end edge of the carcass ply. Such pulling down device is preferably slidingly associated with the device for positioning the annular anchoring structure.
Preferably, the pulling down of the filling insert is carried out while the positioning device of the annular anchoring structure retains the substantially circumferential annular insert in contact position with the end edge of the carcass ply. Advantageously, the undesired movement of the bead core with respect to the forming support is in this way prevented also during the pulling down of the filling insert, with consequent advantages in terms of quality and performance of the tyre to be obtained.
Further features and advantages of the present invention will appear more clearly from the following detailed description of some preferred embodiments of an apparatus and process according to the present invention, made with reference to the attached drawings. In such drawings:
In
In particular, apparatus 100 is used in the manufacturing a carcass structure of the tyre for arranging one or more annular anchoring structures 10 at that region of the carcass structure that will make the tyre bead. Such annular anchoring structures 10 are intended for keeping the tyre well fixed to the anchoring seat specifically provided in the rim of the vehicle wheel.
The manufacturing of the carcass structure of the tyre comprises, at first, laying at least one carcass ply 2 on a substantially cylindrical forming support 50 so that the opposite end edges 2a of the carcass ply project cantilevered from the forming support 50. Subsequently, each annular anchoring structure 10 is associated with each of the opposite end edges 2a of the carcass ply 2.
While this is not shown, in the embodiment illustrated in the attached figures each annular anchoring structure 10 is associated with each end edge 2a of the carcass ply 2 at a respective side shoulder 51 of the forming support 50.
For simplicity of description, the description of apparatus 100 and of the process carried out thereby shall be made hereinafter with reference to only one of the opposite end edges 2a of the carcass ply 2 and to one of the side shoulders 51 of the forming support 50 (thus, referring to only one of the opposite tyre beads). In fact, apparatus 100 is symmetrical in the axial direction and the description made with reference to one of the end edges 2a and to one of the sides 51 of the forming support 50 also applies with reference to the axially opposite end edge and to the axially opposite side of the forming support 50.
The forming support 50 is rotatably mounted about a rotation axis X-X in a totally conventional manner. The structure of the forming support 50 is not described in detail herein since it can be made in any convenient manner by a man skilled in the art. Likewise, the members for supporting and moving the forming support 50 shall not be described as they are totally conventional.
As illustrated in the annexed figures, the annular reinforcing structure 10 comprises at least one substantially circumferential annular insert 11, or bead core, on which at least one filling insert 12 is applied in a radially outer position thereof.
Apparatus 100 comprises a device 110 slidable along a direction x parallel to the rotation axis X-X of the forming support 50, and thus in the two opposite ways of the direction indicated in
As illustrated in
The annular anchoring structure 10 is thus positioned at the desired position on the end edge 2a of the carcass ply 2 by the device 110. Throughout the present description, device 110 shall also be defined as “bead core holding device”.
Device 110 comprises a device 118 for positioning the bead core, the device 118 being extended in a circumferential direction and coaxially to axis X-X of the forming support 50. Such positioning device 118 comprises a radially inner portion 111 for supporting/thrusting the annular anchoring structure 10 and a radially outer portion 112 for thrusting/retaining the annular anchoring structure 10.
As better described hereinafter, the radially inner portion 111 and the radially outer portion 112 of each positioning device 118 are slidable with respect to each other along the direction x parallel to the rotation axis X-X of the forming support 50.
Apparatus 100 further comprises a device 120 for pulling down the end edge 2a of the carcass ply 2 towards axis X-X of the forming support 50. Such pulling down is required, in the embodiment shown in the attached drawings, for allowing the bead core holding device 110 to approach the forming support 50 in order to position the annular anchoring structure 10 at the desired position on the end edge 2a of the carcass ply 2. Throughout the present description, device 120 shall also be defined as “ply pulling down device”.
As shown in
Device 120 comprises a plurality of ply pulling down members 128 (only one of which is shown in the attached figures) arranged adjacent to each other in the circumferential direction and coaxially to axis X-X of the forming support 50.
Each ply pulling down member 128 comprises a plurality of blades 121 (only one of which is illustrated in the attached figures), partially overlapping in the circumferential direction. In particular, the blade of a ply pulling down member is partially overlapped to the adjacent blade of the same member and the circumferentially outer blades of two circumferentially consecutive ply pulling down member 128 are arranged so as to be also partially overlapped in the circumferential direction.
Blades 121 are preferably made of elastically bending material and are shaped so that, at rest, they take on as a whole an open corolla-like configuration, that is a configuration expanded in radial direction.
When stressed in radial direction, blades 121 on the other hand may take on, as a whole, a closed or radially contracted configuration.
During sliding of the ply pulling down device 120 with respect to the bead core holding device 110, blades 121 are thrust by the ply pulling down device 120 towards a radially inner position with respect to the positioning devices 118 (
In the embodiment illustrated in the annexed figures, blades 121 are held in their radially contracted configuration by the thrust exerted in the radial direction by the positioning devices 118 of the bead core holding device 110, and more in particular by the radially inner portion 111 of such device 110 (
In the particular embodiment shown here, apparatus 100 further comprises a device 130 for pulling down the filling insert 12 on the carcass ply 2.
Device 130 comprises a plurality of filling insert pulling down members 138 (only one of which is shown in the attached figures) each provided with a respective roller 131. Roller 131 slides on a radially outer surface of the radially outer portion 112 of each positioning device 118.
Rollers 131 are arranged side by side in the circumferential direction coaxially with respect to the axis X-X of the forming support 50.
Each roller 131 is elastically associated with the respective positioning device 118, as described for example in WO 2009/063264 to the same Applicant.
As shown in
Preferably, as shown in
Alternative embodiments are provided for apparatus 100 of the present invention, wherein device 130 for pulling down the filling insert 12 is defined by a continuous ring which is axially slidable with respect to the bead core holding device 110 and having a side profile with a shape matching that of the annular anchoring structure 10 when filling insert 12 is pulled down, as described for example in the aforementioned document WO 2009/063264.
As better described hereinafter, alternative embodiments of apparatus 100 of the present invention are also provided wherein no positioning device is used at all for pulling down the filling insert 12 on the carcass ply 2.
Apparatus 100 further comprises a device 140 suitable for turning up the end edge 2a of the carcass ply 2 about the annular anchoring structure 10 in order to form a turned up end portion of the carcass ply 2 having the annular anchoring structure 10 therein. Throughout the present description, device 140 shall also be defined as “turning up device”.
Device 140 is slidable parallel to axis X-X with respect to the bead core holding device 110 and to the ply pulling down device 120 in the two opposite ways of the direction indicated by arrow H in
Device 140 is arranged in a radially inner position with respect to the device 120 for pulling down the end edge 2a of the carcass ply 2.
As shown in the annexed figures, device 140 comprises an air chamber 141 whose free ends are associated respectively with two axially adjacent annular elements 142, 143. Such air chamber 141 is intended to be inflated in two successive time periods to achieve the turning up of the end edge 2a of the carcass ply 2, according to the following description.
A further annular element 144 is provided in a axially outer position with respect to the two annular elements 142, 143 for supporting the air chamber 141 at the bottom when it is inflated (
As schematically illustrated in the attached figures, apparatus 100 further comprises a control circuit 150 controlled by a microprocessor P. Such control circuit 150 acts on the positioning device 118 and on the turning up device 140 for defining a first operating configuration, wherein the air chamber 141 is in a partially inflated configuration and the positioning device 118 (in particular, the radially outer portion of such device) retains the annular anchoring structure 10 in a proximal contact position with the end edge 2a of the carcass ply 2 (
According to the present invention, when the air chamber 141 is in the partially inflated configuration, a maximum pressure value of between about 0.1 bar and about 0.4 bar, preferably equal to about 0.2 bar, is reached therein. On the other hand, when the air chamber 141 is in the completely inflated configuration, a maximum pressure value of between about 0.5 bar and about 1 bar, preferably comprised between about 0.6 bar and about 0.9 bar, is reached therein.
Apparatus 100 of the present invention further comprises a device 160 for thrusting the air chamber 141 against the end edge 2a of the carcass ply 2.
Such device 160 comprises an annular element 161 slidable parallel to axis X-X (direction x) between a rest position wherein it is in a distal position with respect to the air chamber 141 (
As mentioned above, in alternative embodiments of apparatus 100 (not shown), the device 130 for pulling down the filling insert 12 is not provided. In this case, the pulling down of the filling insert 12 on the carcass ply 2 takes place after the complete inflation of the air chamber 141 as a result of the action exerted on the inflated air chamber 141 by the annular element 161 of the thrusting device 160. In other words, the pulling down of the filling insert 12 on the carcass ply 2 takes place simultaneously with the deformation of the inflated air chamber 141 caused by the annular element 161 of the thrusting device 160.
A preferred embodiment of a process for manufacturing a tyre in accordance with the present invention shall now be described, wherein such process can be carried out through apparatus 100 described above. In particular, the part relating to the manufacture of the carcass structure of the tyre shall be described.
At first, as illustrated in
Subsequently, as shown in
Subsequently (
The axial movement of the bead core holding device 110 causes the movement of blades 121 along the curved broken line indicated with C in
Subsequently, as shown in
In particular, such pulling down takes place, at first, by exerting a predetermined thrust on a radially inner annular portion of the side surface 12a of the filling insert 12 and then, by axially moving rollers 131 towards the forming support 50, thus exerting such thrust on a progressively greater portion of the side surface 12a of the filling insert 12 starting from the aforementioned radially inner annular portion along all the radial extension of the side surface 12a.
Subsequently, as illustrated in
At this point, while always keeping the radially outer annular portion 112 of each positioning device 118 of the bead core holding device 110 pushed on the substantially circumferential annular insert 11 against the side shoulder 51 of the forming support 50 (arrow F′), the air chamber 141 is partially inflated up to a predetermined maximum pressure value, preferably comprised between about 0.1 bar and about 0.4 bar, so as to carry out a first part of the turning up of the end edge 2a of the carcass ply 2 around the annular anchoring structure 10.
Subsequently, as shown in
After the complete inflation of the air chamber is carried out, the thrusting device 160 is axially moved until it is brought close to the forming support 50. In such position, the annular element 161 comes into contact with the air chamber 141 and, deforming the latter, it causes a thrust action of the air chamber 141 against the end edge 2a of the carcass ply 2 previously turned up on the annular anchoring structure 10 (
In the embodiment of the present invention in which no specific device (such as for example device 130 described above) is used for achieving the pulling down of the filling insert 12 on the carcass ply 2 before starting the turning up of the end edge 2a of the carcass ply 2 around the annular anchoring structure, the pulling down of the filling insert 12 on the carcass ply 2 takes place simultaneously with the above-described deformation of the inflated air chamber 141 by the action of the annular element 161 of the thrusting device 160.
Of course a man skilled in the art can make further modifications and changes to the invention described above in order to meet specific and contingent application requirements, modifications and changes which fall in any case within the scope of protection as defined by the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| MI2010A001760 | Sep 2010 | IT | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/IB11/02277 | 9/26/2011 | WO | 00 | 3/21/2013 |
| Number | Date | Country | |
|---|---|---|---|
| 61388452 | Sep 2010 | US |
