CROSS REFERENCE TO RELATED APPLICATIONS

This application is a national phase application based on PCT/IB2014/065339, filed Oct. 15, 2014, which claims the priority of Italian Patent Application No. MI2013A001698, filed Oct. 15, 2013, the content of both applications being incorporated herein by reference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention refers to a method for controlling the laying down of components of tyres on forming drums.

The present invention refers also to an apparatus for controlling the laying down of components of tyres on forming drums.

Description of the Related Art

A tyre for vehicle wheels generally comprises a carcass structure comprising at least a carcass ply having respectively opposite terminal edges engaged to respective anchoring annular structures, generally called “bead cores”, placed in the areas usually identified as “beads”, having an internal diameter substantially corresponding to a so-called “fitting diameter” of the tyre on a respective mounting rim. The tyre also comprises a crown structure comprising at least one belt layers, placed in a radially external position in relation to the carcass ply, and one tread band radially external in relation to the belt layer. A so-called “underlayer” can be interposed between the tread band and the belt layer/s, said underlayer being made of an elastomeric material having properties adapted to ensure a stable coupling of the belt layer/s with the tread band itself. On the side surfaces of the carcass structure, each extending from one of the side edges of the tread band up to the respective anchoring annular structure to the beads, respective sidewalls made of elastomeric material are applied. In the tyres of “tubeless” type, the carcass ply is internally covered by a layer of a preferably butyl-based elastomeric material, usually called “liner” having optimal characteristics of air tightness and extending from one bead to the other.

The term “elastomeric material” intends to indicate a composition comprising at least one elastomeric polymer and at least one reinforcing filler. Preferably such composition comprises also additives such as a cross-linking agent and/or a plasticizer. Thanks to the presence of the cross-linking agent, such material can be cross-linked by heating, so as to form the final article of manufacture.

The “component” of the tyre has to be intended as any functional component of the tyre assembled in the form of a cut-to-size strip (for example: under-liner, liner, carcass ply/ies, belt layer/s, underlayer, tread band, etc.).

The “laying structure” has to be intended as a set comprising a forming drum and a component laid down thereon.

The “main length” of a component laid down on a forming drum has to be intended as the circumferential distance between the first end laid down (also called “head edge”) and the second end laid down (also called “tail edge”) of said component.

In case the two opposite edges of the component laid down overlap, such main length is the circumferential length of the portion of said component laid down having the aforementioned overlapping edges.

In case the two opposite edges of the component laid down are substantially abutting to and matching with each other, such main length is substantially null.

In case the two opposite edges are not in contact with each other, such main length is the circumferential length of the “empty” segment separating the two ends of the component.

The “overall length” of a component has to be intended as the length of the component measured according to the direction along which the component itself moves forward while it is laid down on the forming drum.

WO2013/011396 describes an apparatus for building tyres for vehicle wheels, wherein the forming drum is loaded on a shuttle moving on a guide along a laying line. At each delivery station, at least one semi-finished product is laid down on a radially external surface of the forming drum carried by the shuttle to form at least one component of a tyre.

EP2613122A1 describes a method and an apparatus for detecting shapes such as length and junction dimensions of a strip-shaped element such as a carcass ply and a two-dimensional displacement sensor employed in the detection of the shape of the strip-shaped element.

SUMMARY OF THE INVENTION

The Applicant observed that the techniques of the type shown in EP2613122A1 are limited to provide information representative of the analysis performed on the junction area, without making such information able to act, to some extent, on the building apparatuses of the tyre.

In particular, the Applicant observed that, in order to let such information have an actual practical utility, it is necessary that a human operator intervenes and, according to the information itself, decides to discard the component and/or sets appropriate correction parameters in the preparation stations of the component laid down.

The Applicant verified that, in spite of the use of such systems, the operations of regulation/correction carried out manually are, however, not much reliable.

Indeed, although the starting datum (information representative of the main length of the component laid down and/or of the suitability of the junction) can be considered correct and reliable, the extent of the correction to be made in the subsequent components remains at the full discretion of the operator, and in particular it is based on the experience and on the attention of the latter.

This makes the control and the correction process not reliable enough and makes its results not very replicable.

The Applicant observed also that there are a plurality of parameters on which the operator can act to correct the preparation of the component; this implies that the control that is manually carried out by the operator itself is even more problematic.

The Applicant observed also that the operator has great difficulties in manually managing the correction parameters in plants where different components are prepared and laid down in parallel, and thus there are different machines/stations operating simultaneously that have to be controlled and possibly corrected, such as for example in plants of the type described in the document WO2013/011396 previously described.

The Applicant thus had the intuition that, by adjusting automatically the preparation of the components as a function of the main length detected, it is possible to improve progressively the precision of the positioning of the two ends of each component and, consequently, the structural characteristics of the tyre.

The Applicant also perceived that, by controlling the cutting of the material as a function of the main length detected after the laying down, it is possible to determine accurately the overall length of the subsequent components in order to obtain the desired arrangement of the two ends of the latter.

The Applicant thus found that, by sending a signal generated as a function of the main length detected to a preparation station adapted to prepare said component, and by regulating said preparation station on the basis of the information contained in said signal, the precision of the positioning of the ends of the components subsequently laid down can be remarkably improved.

In accordance with a first aspect, the invention refers to a method for controlling the laying down of components of tyres on forming drums.

Preferably said method comprises sending a first electromagnetic radiation incident on a first laying structure comprising a forming drum and a first component of a tyre laid down on said forming drum.

Preferably said method comprises detecting at least one corresponding first reflected radiation.

Preferably said method comprises determining, as a function of said first reflected radiation a first parameter representative of a first main length of said first component.

Preferably said method comprises comparing said first parameter with one or more pre-stored reference parameters.

Preferably said method comprises generating a first correction signal as a function of said comparison.

Preferably said method comprises sending said first correction signal to at least one preparation station of said first component to regulate the preparation of further components.

In accordance with another aspect, the invention refers to an apparatus for controlling the laying down of components of tyres on forming drums.

Preferably said apparatus comprises an emission device to send a first electromagnetic radiation incident on a radially external surface of a first laying structure comprising a forming drum and a first component of a tyre laid down on said forming drum.

Preferably said apparatus comprises a detection device to detect at least one corresponding first reflected radiation.

Preferably said apparatus comprises a processing unit.

Preferably said processing unit is configured for determining, as a function of said first reflected radiation, a first parameter representative of a first main length of said first component.

Preferably said processing unit is configured for comparing said first parameter with one or more pre-stored reference parameters.

Preferably said processing unit is configured for generating a first correction signal as a function of said comparison.

Preferably said processing unit is configured for sending said first correction signal to at least one preparation station adapted to prepare said first component to regulate the preparation of further components.

The Applicant believes that, in this way, the correction technique applied to the preparation station adapted to prepare the components to be laid down is more accurate and reliable, as it is substantially independent of high variable and unpredictable factors such as the ability, the attention and the experience of the operator in charge of the control of the plant.

In particular, the overall length of the components that will have to be laid down can be corrected as a function of the inaccuracies detected at the ends of the component already laid down.

In accordance with one or more of the aforementioned aspects, the invention comprises one or more of the following preferred characteristics.

Preferably, a queue is arranged comprising one or more auxiliary components ready to be laid down on said forming drum, said auxiliary components being prepared by said preparation station before receiving said first correction signal.

Preferably, each one of said auxiliary components is waited to be laid down on, and afterwards removed from, said forming drum.

Preferably a second component is identified and laid down on said forming drum after said auxiliary components, said second component being prepared by said preparation station after receiving said first correction signal.

Preferably, when said second component is laid down on said forming drum, a second electromagnetic radiation is sent being incident on a second laying structure comprising said forming drum and said second component laid on said forming drum.

Preferably, at least one corresponding second reflected radiation is detected.

Preferably, a second parameter representative of a second main length of said second component is determined as a function of said second reflected radiation.

Preferably, a second correction signal is generated as a function of said first parameter and of said second parameter.

Preferably said second correction signal is sent to said preparation station.

Preferably, when said second component is laid down on said forming drum, said emission device is activated to send a second electromagnetic radiation incident on a second laying structure comprising said forming drum and said second component laid down on said forming drum.

Preferably, a second parameter representative of a second main length of said second component is detected as a function of a second reflected radiation detected by said detection device.

Thus it is possible to further improve the precision of the positioning of the ends of the component laid down, and in particular the main length of the component itself.

The Applicant observed, indeed, that a series of factors such as, for example, the conditions wherein the plant operates, the temperature of the workplace which is not always constant, the fact that the reels of material from which the components are obtained cannot be identical to one another, the wear and the lengthening of the belts transporting the semi-finished products, etc., can provoke a drift of the preparation station adapted to prepare the components, namely a condition wherein the behaviour of the devices that are part of said preparation station progressively deviates from the expected one.

Furthermore, with the aim of minimizing the idle time between the component deposition step and the subsequent operation, a queue of components is created before the latter are laid down on the forming drums.

This implies that once a determined correction is set for the preparation station, yet a certain number of components (equal to the number of components forming the queue) will be laid down before the effects of such correction are visible.

The Applicant observed in this regard that, for several reasons, the exact number of the components forming a queue is not always known to the operator.

Firstly, the operator does not know the instant in time when the components are cut before being put in the queue; in other words, the operator cannot know if the correction inserted in a certain instant is applied also to components that, in that instant, are not part of the queue, yet, but that are about to be cut, or if such components have already been cut and thus the number of components in the queue will increase in a very short time.

Furthermore, different types of components and different types of materials imply queues comprising different quantities of components, so that the operator can hardly know and/or remember the exact number of components that form each queue.

In addition to this, in plants that are at least partially automated, such as the one of the type described in WO 2013/011396, different types of components may be made in parallel in the same plant, so that the same operator is in charge of controlling different lines simultaneously wherein the queues comprise different quantities of components. The Applicant thus observed that the operator, after having set a determined correction, cannot identify with a reasonable reliability which are the components where such correction had an effect, and he/she cannot understand if the inaccuracy previously detected was substantially corrected or if, on the contrary, it is necessary to further refine the adjustment.

The Applicant thus believes that, by generating the second correction signal as a function of said first parameter and of said second parameter, it is possible to further improve the precision and the reliability of the corrections made to the preparation station.

Preferably, generating said second correction signal as a function of said first parameter comprises generating said second correction signal as a function of said first correction signal.

Thus it is possible to progressively correct the functioning of the preparation station, keeping the correction previously made into consideration.

Preferably, when each one of one or more auxiliary components is laid down on said forming drum, an auxiliary electromagnetic radiation is sent being incident on an auxiliary laying structure comprising said forming drum and said auxiliary component laid down on said forming drum.

Preferably, at least one corresponding auxiliary reflected radiation is detected.

Preferably, a respective auxiliary parameter representative of the main length of said auxiliary component laid on said building drum is determined as a function of said auxiliary reflected radiation.

Preferably, said second correction signal is generated as a function of also said auxiliary parameter.

Thus it is possible to make corrections to the preparation station also as a function of the positioning of the ends of the components laid down before the first correction signal could produce its effects.

Preferably an identification parameter is received being representative of a type and/or of a material at least of said first component.

Preferably a first algorithm associated to said identification parameter is selected. Preferably, at least said first parameter is determined on the basis of said first algorithm. Thus it is possible to determine the first parameter using an appropriate algorithm for the type of component laid down and/or for the material which the latter is made of. Preferably, said second parameter is determined on the basis of said first algorithm. Preferably, said one or more auxiliary parameters are determined on the basis of said first algorithm.

Preferably a second algorithm associated to said identification parameter is selected. Preferably, at least said first correction signal is generated on the basis of said second algorithm.

Thus the correction made to the preparation station can be determined appropriately according to an algorithm selected as a function of the type of component that was laid down.

Preferably, said second correction signal is generated on the basis of said second algorithm.

Preferably, waiting that each one of said auxiliary components is laid down on, and afterwards removed from, said forming drum comprises determining a number N representative of how many auxiliary components are included in said queue.

Preferably, waiting that each one of said auxiliary components is laid down on, and afterwards removed from, said forming drum comprises verifying that N auxiliary components are laid down on and subsequently removed from said forming drum.

Preferably, in order to wait that each one of said auxiliary components is laid down on, and afterwards removed from, said forming drum, said processing unit is configured to determine a number N representative of how many auxiliary components are included in said queue.

Preferably, in order to wait that each one of said auxiliary components is laid down on, and afterwards removed from, said forming drum said processing unit is configured to verify that N auxiliary components are laid down on and subsequently removed from said forming drum.

Preferably, said number N of auxiliary components in said queue is determined as a function of said identification parameter.

Preferably, a displacement parameter is determined as a function of said identification parameter.

Preferably, as a function of said displacement parameter, at least one emission device and one detection device are displaced adapted to emit at least said first incident electromagnetic radiation and to receive said first reflected electromagnetic radiation, respectively.

Thus the detection of the reflected radiations can be optimized, since the position of the emission device and of the detection device is determined as a function of the type of component that was laid down and/or of the material which the latter is made of. Preferably said displacement occurs along a direction substantially parallel to a rotation axis of said forming drum.

Preferably, a time parameter is determined representative of a waiting time of said second component after being prepared by said preparation station and before being laid down on said forming drum.

Preferably, said second correction signal is generated as a function of said time parameter.

Thus it is possible to make corrections of controlled extent in case the component had to wait for a long time between the building and the laying down.

The Applicant noticed in fact that the physical/geometrical characteristics of the awaiting component can vary over time. In particular, the Applicant noticed that, in the course of time, the dimensions of the component tend to reduce to a certain extent, as a function, for example, of the environmental characteristics and of the specific characteristics of the material which the component is made of. Such variations, although substantially imperceptible from a macroscopic point of view, may however affect remarkably the main length of the component, once the latter is laid down on the forming drum. The Applicant verified that the corrections based on the detection of such main length do not bring any improvement of the functioning of the preparation station, and, on the contrary, they contribute to generate noise in the control data, thus slowing down the convergence of the system towards an optimal functioning. The Applicant thus verified that, by decreasing the extent (or the intensity) of the correction set as a function of the waiting time of the component of which the main length is detected, it is possible to improve the quality of the corrections made and to speed up the convergence towards satisfactory operating condition.

Preferably said second correction signal is configured so as to provoke in said preparation station a modification whose amount is substantially monotonous decreasing in relation to the increase of said waiting time.

Preferably said emission device and said detection device are mounted on a support structure and are movable along one or more respective guides substantially parallel to a rotation axis of said forming drum.

Preferably at least an actuator active on said emission device and/or on said detection device is provided to move the latter along said one or more guides.

Preferably said processing unit is configured to receive an identification parameter representative of a type and/or of a material of at least said first component.

Preferably said processing unit is configured to command said at least an actuator as a function of said identification parameter.

Accordingly the apparatus according to the invention can adapt in an optimal way to components having different characteristics, thus improving the quality of the detection performed and, consequently, the quality of the corrections made.

