Patent Application
20090294024
The present invention relates to a method for manufacturing a tyre for vehicle wheels.
Preferably, but not exclusively, the tyre manufactured with the method of the present invention is a tyre for trucks.
The invention also relates to a method for manufacturing an annular anchoring structure of a tyre for vehicle wheels and an apparatus for making such an annular anchoring structure.
A tyre for vehicle wheels generally comprises a carcass structure comprising at least one carcass ply formed from reinforcement cords incorporated in an elastomeric matrix. The carcass ply has end flaps respectively engaged with annular anchoring structures, arranged in the areas usually identified with the name “beads” and normally each formed from a substantially circumferential annular insert on which at least one filler is applied, in a radially outer position thereof. Such annular structures are commonly referred to as “bead cores” and have the task of keeping the tyre well fixed to the anchoring seat specifically provided in the rim of the wheel, thus avoiding the radially inner end edge of the tyre coming out from such a seat in operation.
In a radially outer position with respect to the carcass structure a belt structure comprising one or more belt layers is associated, said belt layers being arranged radially one on top of the other and having textile or metallic reinforcement 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 can be provided, known as “underbelt”, 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 from elastomeric material like other structural elements making up the tyre.
Between the tread band and the belt structure a so-called “underlayer” of elastomeric material with properties suitable to ensure a steady union of the tread band itself can be arranged.
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.
Conventional manufacturing processes of tyres for vehicle wheels essentially provide that the components of the tyre listed above be firstly made separately from each other, to then be assembled in a subsequent manufacturing step of the tyre.
In particular, with reference to the embodiment of the aforementioned annular anchoring structures, the process for making such annular structures comprises a first manufacturing step of the bead core and a subsequent coating step of the bead core with a reinforcement tape.
A type of bead core known in the field of the manufacture of tyres for vehicle wheels consists of a plurality of adjacent coils of a rubber-coated metal wire assembled in a plurality of layers arranged radially one on top of the other to form an annular element having a predetermined cross section.
Then, the aforementioned reinforcement tape is wound on the bead core thus made. Such a tape comprises a layer of elastomeric material reinforced with one or more textile cords, typically made from nylon.
After the step of coating the bead core with the reinforcement tape a pre-vulcanisation step of the coated bead core can also be carried out to further tighten together the coils that constitute the metallic core of the bead core. After the pre-vulcanisation step a gluing step of the coated and pre-vulcanised bead core is typically carried out, to prepare the bead core to the assembly with the other components of the tyre.
With particular reference to the process for coating the bead core with the reinforcement tape, conventional processes like those described in U.S. Pat. No. 4,097,321 comprise a first loading step of the reinforcement tape on a spool starting from a high-capacity tape collection reel. The spool is then mounted on a bead core coating machine to carry out the winding of the bead core with the reinforcement tape loaded on the spool.
More specifically, U.S. Pat. No. 4,097,321 describes an example of a machine for coating a bead core with a reinforcement tape. Such a machine is provided with a mechanism for holding the bead core and making it rotate at a predetermined speed in a predetermined plane and a device for winding a tape on the bead core. The winding device of the tape comprises a motorised annular wheel on which a spool onto which the reinforcement tape has previously been loaded is mounted. The annular wheel is provided with a slit to allow the positioning of the bead core with respect to the rotational axis of the wheel. The annular wheel is able to rotate about the axis thereof so as to make the spool rotate about the cross-section of the bead core. The rotational speed of the annular wheel is correlated to that of the bead core so as to spirally wind the tape on the bead core. The pitch of the spiral can be varied by changing the rotational speed of the bead core and of the winding device. The machine also comprises a knife to cut the tape after the winding has been completed and the winding device has stopped.
The Applicant has noted that the process for coating the bead core carried out with a conventional machine of the type described above requires, prior to carrying out the step of winding the reinforcement tape onto the bead core, that a loading step of the tape onto the spool and a loading step of the spool onto the machine that will carry out the coating be carried out.
The Applicant has also observed that the spool typically has a limited capacity; in particular, the amount of tape that can be loaded onto the spool is sufficient to wind no more than two/three bead cores, the winding of each bead core generally requiring a large number of revolutions (for example about 80 revolutions) of the spool about the cross-section of the bead core.
The Applicant has therefore found that in conventional processes and machines of the type described above it is necessary to periodically replace the empty spool with a loaded spool. The loading/unloading steps of the spool onto/from the deposition machine, being carried out manually by the operator, require a certain intervention time that implies an increase in the overall time used by the machine to carry out the complete coating of the bead cores.
The Applicant has realised that it is possible to automate the coating step of the bead core by eliminating the loading/unloading steps of the spool onto/from the machine, thus decreasing the overall time taken by the machine to carry out the complete coating of the bead cores.
In particular, the Applicant has found that the aforementioned loading/unloading steps of the spool can be eliminated by making the wheel that carries out the winding of the reinforcement tape onto the bead core works as a spool that is loaded during a first step of the winding.
The present invention therefore relates, in a first aspect thereof, to a method for manufacturing a tyre comprising a carcass structure having at least one carcass ply associated with axially opposite annular anchoring structures, said method comprising the steps of:
Advantageously, the method of the present invention comprises a bead core coating step that, unlike conventional coating processes, does not provide for the execution of any manual loading/unloading step of the spool onto/from the machine used to carry out the coating of the bead core. Indeed, the method of the present invention provides for the execution of a loading step of the reinforcement tape onto the same deposition member that carries out the winding of the bead core and during at least part of the step of winding the bead core. The deposition member thus acts itself as a spool whilst it carries out the winding of the tape onto the bead core. Therefore it is not necessary to provide for the interruption of the winding step to replace the spool.
The Applicant also observes that the tape deposition member advantageously has a tape accumulation speed much higher than that of the spool; it is thus possible to accumulate on such a deposition member an amount of tape per unit time much greater than that which can be accumulated in a conventional spool used in conventional processes.
In a second aspect thereof, the present invention relates to a method for manufacturing an annular anchoring structure of a tyre for vehicle wheels, comprising the steps of:
Such a method can be carried out in the method for manufacturing a tyre of the present invention described above and thus has the advantageous characteristics discussed above with reference to the aforementioned method for manufacturing the tyre.
In a third aspect thereof, the present invention relates to an apparatus for manufacturing an annular anchoring structure for a tyre for vehicle wheels, comprising a bead core support device and a tape deposition member movable with respect to said bead core support device to wind a reinforcement tape onto a bead core, wherein during the winding of the reinforcement tape onto the bead core said tape deposition member also acts as a tape loading member.
Such an apparatus allows the coating step of the method for manufacturing a tyre of the present invention to be carried out. Such an apparatus therefore allows the advantageous characteristics discussed above with reference to the aforementioned method for manufacturing the tyre to be achieved.
The present invention, in at least one of the aforementioned aspects, can have the following preferred and/or advantageous characteristics.
In a preferred embodiment of the method of the present invention, the steps of winding the reinforcement tape onto the bead core and of loading the reinforcement tape onto the tape deposition member are carried out through the same rotational movement of the tape deposition member about a respective rotational axis. In this way, advantageously, a substantial structural and functional simplification is achieved with respect to conventional coating processes and/or machines, where the steps of winding the tape onto the bead core and of loading the tape onto the spool took place through different and specifically provided devices and/or members.
In particular, in the method of the present invention, preferably, the step of loading the reinforcement tape onto the tape deposition member is carried out during a first part of the step of winding the reinforcement tape onto the bead core. In this way, advantageously, a substantial reduction of the time taken to carry out the winding of the bead core is achieved with respect to conventional coating processes and/or machines, where the steps of winding the tape onto the bead core and of loading the tape onto the spool took place one after the other following loading of the spool onto the machine.
In preferred embodiments of the method of the present invention, the step of loading the reinforcement tape onto the tape deposition member comprises the step of continuously drawing the reinforcement tape from a tape collection reel arranged adjacent to the tape deposition member. Advantageously, the tape deposited on the bead core is thus drawn directly from the high-capacity tape collection reel, i.e. without using any spool.
Preferably, a cutting step of the reinforcement tape is also carried out so as to interrupt the drawing of the tape from said tape collection reel once the winding of the bead core is completed.
More preferably, the cutting step of the reinforcement tape is carried out after the tape deposition member has carried out a predetermined number of revolutions about the respective rotational axis. As already stated, the Applicant has verified that, advantageously, the number of revolutions that the deposition member must carry out to completely wind a bead core is substantially lower than that carried out by the spool in conventional processes and machines, with a consequent saving of time and increasing of production capacity.
Even more preferably, after the step of cutting the reinforcement tape, the step of winding onto the bead core the reinforcement tape loaded on the tape deposition member and not yet deposited on the bead core is carried out. In accordance with the present invention, advantageously, the tape loaded on the deposition member is used to complete the winding of the bead core. The complete winding of the tape onto the bead core thus takes place through a continuous process that can be easily automated.
Preferably, to carry out the coating step of the bead core the bead core is positioned with respect to the tape deposition member in such a way that a cross-section of the bead core is placed at a rotational axis of the tape deposition member. More preferably, a free end of the reinforcement tape is associated with the bead core at said cross-section of the bead core. Advantageously, the aforementioned operations are carried out automatically.
Even more preferably, in the coating step of the bead core the tape deposition member and the bead core are moved simultaneously about respective rotational axes so as to wind the reinforcement tape onto the bead core and simultaneously load the reinforcement tape onto the tape deposition member. Advantageously, the fact that the winding onto the bead core and the loading of the tape onto the deposition member to allow the winding to be completed after the cutting step are carried out simultaneously allows a substantial reduction in the processing time (and therefore a substantial increase in production capacity) with respect to conventional processes.
Preferably, in the aforementioned step of simultaneously moving the tape deposition member and the bead core the tape deposition member is moved at a first predetermined rotational speed about the respective rotational axis and the bead core is moved at a second predetermined rotational speed about a respective rotational axis. More preferably, during the winding of the tape onto the bead core said first and second predetermined rotational speeds are kept constant, so as to obtain a homogeneous and uniform coating on the entire bead core.
Preferably, the bead core support device of the apparatus of the present invention comprises at least one bead core support roller adapted to act upon an inner annular surface portion of the bead core to support the bead core with respect to the tape deposition member. More preferably, the bead core support device further comprises at least one bead core locking roller substantially parallel to said at least one bead core support roller, adapted to cooperate with said at least one bead core support roller to lock the bead core in position with respect to the tape deposition member. Even more preferably, the bead core support device further comprises at least one side bead core support roller positioned with respect to said at least one bead core support roller in a position such as to provide the bead core with a lateral support for a side surface portion of the bead core arranged at a side axially opposite the inner annular surface portion of the bead core supported by said at least one bead core support roller.
In the preferred embodiments thereof, the apparatus of the present invention comprises a first rotation command group of said tape deposition member about a respective rotational axis.
Preferably, said first command group comprises an electric motor and first motion transmission members between the electric motor and the tape deposition member.
In the preferred embodiments thereof, the apparatus of the present invention further comprises a second rotation command group of said bead core about a respective rotational axis.
Preferably, said second command group comprises second motion transmission members from the aforementioned electric motor to said at least one bead core support roller.
In the apparatus of the present invention, preferably, the tape deposition member comprises an annular wheel having an opening to allow the positioning of a cross-section of the bead core inside the annular wheel.
Preferably, said at least one bead core support roller is arranged inside said annular wheel so as to position said cross-section of said bead core at a rotational axis of said annular wheel.
In a particularly preferred embodiment of the apparatus of the present invention, the tape deposition member comprises a plurality of first rollers associated with said annular wheel.
Preferably, said first rollers are arranged one after the other along a first circumference of said annular wheel. More preferably, said first rollers have respective rotational axes substantially parallel to the rotational axis of the annular wheel. Advantageously, the aforementioned rollers allow the winding of the tape onto the bead core and, simultaneously, the winding of the tape onto the tape deposition wheel during a first step of the winding of the tape onto the bead core.
In the aforementioned particularly preferred embodiment, the apparatus of the present invention further comprises a second roller associated with said annular wheel at a tape inlet zone. Preferably, such a second roller has a respective rotational axis inclined by a predetermined angle with respect to the rotational axis of said annular wheel. Advantageously, this roller angularly deviates the tape directly towards the bead core so as to orientate it correctly with respect to the cross-section of the bead core to be coated.
In a preferred embodiment of the apparatus of the present invention, said tape inlet zone is defined in said annular wheel at said opening.
In a second preferred embodiment of the apparatus of the present invention, said tape inlet zone is defined in said annular wheel at the axially opposite side with respect to said opening. Advantageously, with this arrangement the tape coating machine does not have any members at the access zone of the bead core inside the annular wheel.
Preferably, the apparatus of the present invention comprises a support frame of said annular wheel and a plurality of third rollers associated with said frame at a second circumference outside said first circumference. Advantageously, the rollers arranged on the second circumference keep in position the tape wound on the first rollers of the annular wheel by counteracting the centrifugal force which such a tape is subjected to due to the high rotational speed of the annular wheel.
More preferably, said third rollers have respective rotational axes substantially parallel to the rotational axis of said annular wheel.
Preferably, the apparatus of the present invention further comprises a tape feeding group arranged upstream of said annular wheel to pull the reinforcement tape from one tape collection reel and feed it to said annular wheel.
More preferably, said tape feeding group comprises a guide member of said tape in said tape inlet zone. Even more preferably, said guide member comprises a fourth roller arranged in a position which is tangential to an envelope of said first rollers during the rotation of said annular wheel about the respective rotational axis. Such a fourth roller, advantageously, contributes to orientating the tape in the optimal way with respect to the cross-section of the bead core to be coated.
In the preferred embodiment thereof, the apparatus of the present invention comprises a pressing device of a free end of said reinforcement tape on said bead core.
Preferably, the apparatus of the present invention further comprises a cutting device of said reinforcement tape. Preferably, said cutting member acts upon the tape without needing to interrupt the winding step of the tape onto the bead core.
Further characteristics and advantages of the present invention shall become clearer from the following detailed description of a preferred embodiment of an apparatus and of a method in accordance with the present invention, given as a non-limiting example with reference to the attached drawings. In such drawings:
a to 4n schematically show a sequence of a coating step of the bead core carried out with the apparatus of
In
The bead core 100 is adapted to be associated with an end flap of a carcass ply of the tyre during its manufacture.
In an example embodiment, illustrated schematically in
The pitch of the helicoid defined by the tape 200 on the bead core is preferably selected so as to make the adjacent coils of the helicoid partially lie on top of one another. Such a pitch is preferably kept constant along the entire bead core.
The reinforcement layer 200, preferably, comprises a fabric incorporated in a matrix of elastomeric material.
In a preferred embodiment, the fabric of the reinforcement layer 200 comprises one or more textile cords of nylon, preferably nylon 942, whereas the matrix of elastomeric material is natural and synthetic rubber based.
After the step of coating the bead core 100 with the reinforcement tape 200 the bead core 100 is subjected to a pre-vulcanisation process to tighten together the coils 111 that constitute the metallic core 110 of the bead core 100. After the pre-vulcanisation step a gluing step of the coated and pre-vulcanised bead core 100 is carried out, to prepare the bead core to the tightening with the other components of the tyre. Such a gluing step, for example, can comprise a further coating step of the bead core with a reinforcement tape, such a step being totally identical to that carried out before pre-vulcanisation.
With reference to the example embodiment of the apparatus 1 of the present invention shown in
The reinforcement tape 200 is drawn from a high-capacity tape collection reel 300 supported by a suitable support member 310 positioned near to the tape deposition member 20.
The apparatus 1 comprises, upstream of the tape deposition member 20, a tape feeding group 400. The group 400 pulls a free end of the reinforcement tape 200 from the tape collection reel 300 and feeds it to the tape deposition member 20. An appropriate pressing device (not illustrated) presses such a free end on an outer surface portion of the bead core 100 previously positioned in the apparatus 1 to thus be able to begin the winding step. The pressing device then releases the free end of the tape 200 when winding has begun.
In the example illustrated in
The apparatus 1 also comprises, upstream of the tape deposition member 20, a cutting device 500 of the tape 200. Such a device 500 comprises, in particular, a blade 501 adapted to cut the tape 200 downstream of the moving roller 410 and upstream of the guide roller 413 in an end step of the coating operation of the bead core 100, as shall be described hereafter in the present description.
The position of the support member 310 of the tape collection reel 300 with respect to the deposition member 20 can be different to the one illustrated, in which case the positions of the feeding group 400 and of the cutting device 500 shall also be different. For example,
The tape deposition member 20 comprises an annular wheel 21 rotatably associated with a support frame 210, visible in
In the example illustrated in
The annular wheel 21 is made to rotate about its rotational axis by an electric motor 25, through appropriate motion transmission members operatively arranged between the electric motor 25 and the annular wheel 21. In the example illustrated in
The annular wheel 21, at a circumferential portion thereof, has a plurality of rollers, all indicated with 30, having respective rotational axes substantially parallel to the rotational axis of the annular wheel 21 and arranged one after the other on a substantially circumferential line defined in said annular wheel 21. For the sake of clearness of the figures, in
As shall be described hereafter, the rollers 30 act as support elements of the tape 200 accumulated in the wheel 21 during a first part of the step of winding the tape 200 onto the bead core 100.
The apparatus 1 also comprises a deviating roller 31 associated with the annular wheel 21 at the tape inlet zone 200 into the wheel 21. In particular, the different position of the deviating roller 31 in the two different embodiments illustrated respectively in
The deviating roller 31 has a respective rotational axis inclined by a predetermined angle with respect to the rotational axis of the annular wheel 21. Such an angle is selected according to the pitch of the tape winding helicoid that one wishes to be obtained on the bead core 100.
Preferably, the guide roller 413 is arranged in a position which is tangential to the envelope of the rollers 30 during the rotation of the annular wheel 21 about the respective rotational axis so as to orientate the tape 200 in the optimal way with respect to the cross-section 101 of the bead core 100 to be coated.
With reference to
Above the support roller 11 of the bead core 100 a bead core locking roller 12 is provided arranged with the respective rotational axis parallel to the rotational axis of the support roller 11. The bead core locking roller 12 acts in abutment on an outer side surface portion of the bead core 100 at the cross-section 101 supported by the support roller 11 and cooperates with said roller 11 to lock the bead core 100 in position with respect to the annular wheel 21. Preferably, the outer surface of the locking roller 12 fits onto the outer profile of the bead core 100.
The bead core support device 10 further comprises a lateral support roller 13 for the bead core positioned so as to provide the bead core 100 with a lateral support at a side surface portion 102 of the bead core 100 arranged at a side axially opposite the cross-section 101 supported by the support roller 11. The rotational axis of the lateral support roller 13 is substantially perpendicular to the rotational axis of the bead core 100.
The support roller 11 is made to rotate by appropriate motion transmission members operatively arranged between the electric motor 25 and the support roller 11. In the example illustrated in
Preferably, the rotational speed of the bead core 100 and of the annular wheel 21 are controlled and correlated with each other so as to make a winding with constant pitch. Regarding this, the apparatus 1 comprises a control device (not illustrated) of the aforementioned speeds. Such a control device, in particular, keeps the variation in speed between the aforementioned speeds constant during the entire winding step of the tape onto the bead core.
As shown in
The apparatus 1 described above thus makes it possible, in a method for manufacturing a tyre comprising a carcass structure having at least one carcass ply associated with axially opposite annular anchoring structures, to manufacture one of such annular anchoring structures. The apparatus 1, in particular, makes it possible to carry out the step of coating the bead core with the reinforcement tape 200.
In operation and in the method for coating the bead core 100, with reference to
The reinforcement tape 200 is then drawn from the tape collection reel 300 actuating the tape feeding group 400. The group 400, through the moving roller 410, pulls a free end of the reinforcement tape 200 from the tape collection reel 300. Such a free end is fed to the annular wheel 21, after having been orientated correctly through the guide roller 413 and the deviating roller 31.
The pressing device presses such a free end of tape on the outer surface of the cross-section 101 of the bead core 100 positioned at the rotational axis of the annular wheel 21, making it adhere to it.
Such a step is shown in
Then the step of winding the tape 200 onto the bead core begins. During an initial part of the winding step, the pressing device remains active on the tape 200 which is being deposited on the bead core 100 whilst the bead core 200 and the annular wheel 21 are made to rotate about the respective axes with controlled and constant speeds. As shown in the sequence of
Thereafter the pressing device deactivates (
The apparatus 1 is set up so that after the annular wheel 21 has completed a predetermined number of revolutions sufficient to allow the complete winding of the bead core, the blade 501 of the cutting device 500 is activated to cut the reinforcement tape 200 (
Once all of the tape 200 loaded on the annular wheel has been applied onto the bead core 100, the bead core is unloaded from the apparatus 1 and the end flap of the tape 200 wound on the bead core is laid down by hand on the bead core.
The bead core winding step is then finished and the apparatus 1 is ready to carry out the coating of a new bead core.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/IT2005/000763 | 12/23/2005 | WO | 00 | 7/15/2009 |
