WO2024141831A1

WO2024141831A1 - Process and apparatus for building tyres for bicycles

Info

Publication number: WO2024141831A1
Application number: PCT/IB2023/062114
Authority: WO
Inventors: Enrico BIRAGHI; Dario GIAMBERSIO; Angelo MAZZUCATO
Original assignee: Pirelli Tyre S.P.A.
Priority date: 2022-12-28
Filing date: 2023-12-01
Publication date: 2024-07-04

Abstract

In building a tyre (2) for bicycles, the deposition of at least one of said components is preceded by a cutting-to-size processing of a semifinished product (20a, 20b, 20c, 20d), which advances in abutment against an advancing plane (P) defined by a conveyor belt (23) comprising a feeding section (24) and a preparation section (25) that are consecutively aligned. The advancement of the semifinished product is stopped and an abutment plate (50) interposed between the feeding section (24) and the preparation section (25) is lifted with respect to the advancing plane (P) together with a cutting section (T) of the semifinished product. A cutting member (51) translates transverse to the semifinished product in order to cut the latter along a cutting line (L). The abutment plate (50), carrying a tail end (B) and a head end (A) of the cut semifinished product, is repositioned coplanar to the advancing plane (P).

Description

Process and apparatus for building tyres for bicycles

The present invention relates to a process for building tyres for bicycles. Also forming the object of the invention is an apparatus for building tyres for bicycles, suitable for the execution of the aforesaid process.

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 building drum used for building the tyre and/or the tyre itself, i.e. to a direction perpendicular to the rotation axis of the building drum/of the tyre and to a direction parallel to the rotation axis of the same respectively.

With the term "application surface" it is intended to indicate a substantially cylindrical surface present in radially outer position with respect to the building drum. When no tyre component is applied on the building drum, the application surface belongs to the actual building drum. In intermediate steps of the building process, the application surface can be represented by the tyre components already applied on the building drum.

The building of a tyre for bicycles usually provides that one or more carcass plies are applied according to a cylindrical configuration around an outer surface of a building drum. A pair of bead cores are fit or applied each around one of the axially opposite terminal flaps of the carcass ply. The terminal flaps are then turned up around the respective bead cores. Then there is the application of a tread band, typically made in strip form of elastomeric material cut-to-size, which is wound around the carcass ply lying against the building drum, in axially centred position respective to the bead cores.

At the end of the winding, the opposite ends of the tread band are slightly superimposed and mutually joined by a head-head junction.

The mutual axial distance between the bead cores remains unchanged in the course of the entire building process, including of the application of the tread band. This aspect of the process represents a particular characteristic that distinguishes the tyres for bicycles from the tyres for motor vehicles. For the latter, in fact, a step of mutual approaching of the bead cores is normally provided in order to shape the carcass structure according to a toroidal configuration during coupling with a belt structure having a diameter greater than that of the bead cores.

Upon completed building, the built green tyre for bicycles is removed from the drum and transferred into a vulcanisation press, in order to be subjected to a treatment of moulding and vulcanisation aimed to determine the structural stabilisation through crosslinking of the elastomeric material present therein, as well as optionally to impart a desired tread design on the tread band.

For example, in the film clip https://youtu.be/e3sHyJKaFMo?t=879 (time counter from 14' 37" to 15' 50" - last viewing 14/12/2022), the sequential deposition is visible of the carcass ply, of the bead cores, of the sidewall reinforcements, of the reinforcements to the beads and of the tread band, for the purpose of building a tyre for bicycles on a building drum. Each of these components is made simultaneously with its deposition from a semifinished product in continuous strip form, coming from a respective feeding group that guides it up to the immediate vicinity of the point of application on the building drum, where an operator provides for the execution of the operations necessary for their application. The application of each component provides that a head end of the respective semifinished product be manually fixed on the deposition surface of the drum, after which the drum completes one or more revolutions around a rotation axis thereof in order to determine the circumferential winding of the semifinished product around the deposition surface. For several components, such as for example carcass ply, sidewall reinforcements, reinforcements bead and tread band, the operator is required to manually operate on the semifinished product and/or on the building drum during winding, in order to facilitate a correct distribution and application of the material.

For the sidewall reinforcements, the operator is also required to manually guide the semifinished product for the purpose of the correct alignment and to manually control the tensioning thereof. At the end of the winding of each component, the rotation of the drum is stopped and the operator must manually cut the semifinished product and join the tail end of the obtained component on the head end previously applied on the deposition surface.

Therefore, at the present state of the art, the assembly operations for the components on the building drum, even if assisted by automatic or semiautomatic feeding systems for the semifinished products, require the use of specialised labour, in order to obtain a correct positioning, distribution, tensioning and/or cutting-to-size of the semifinished products themselves in order to make the components on the building drum.

The Applicant has proposed to automate the above-described present building processes, but the Applicant has observed that the machines and methods normally employed in making tyres for motor vehicles, such as cars and/or motorcycles, cannot be employed in making tyres for bicycles. The building operations of the tyres for bicycles in fact require the preparation and manipulation of extremely slender and delicate manufactured items. Many components, e.g. the liner, the carcass plies, and other textile reinforcement structures can have thicknesses between 0.1 mm and 1 mm, e.g. on the order of 0.3 mm, with width-wise extensions that can reach and exceed values of 450 mm. Also the components in elastomeric material, such as for example the liner, can have thickness within the above-indicated interval, e.g. smaller than 0.35 mm and with width greater than 120 mm. These size characteristics nearly always lead to the use of semifinished products that lack a structural consistency sufficient for allowing the correct handling thereof by the machines normally employed in the building of tyres for motorcycles or cars.

The need to use specialised labour however involves problems relative to a reduced productivity and to a considerable increase of the production costs, in particular where it is necessary to obtain a particular precision and uniformity of production (i.e. repeatability), for example in the production of tyres intended for sports uses, where the structural accuracy is reflected on the performances. Problems are also encountered in terms of safety for the operators, who are often obliged to complete different work operations with their hands in the immediate vicinity and/or in direct contact with the movable parts, with exposure to injury risks.

The Applicant has perceived that by adding a cutting step to the above-described operating sequence, it would be possible to overcome the previously encountered drawbacks.

More precisely, the applicant has found that by separating, from each semifinished product, a piece of appropriate length before proceeding with its application, it is possible to facilitate a correct handling of the materials for the purpose of making the single components of the tyre on the building drum.

In accordance with the present invention, the Applicant has also found that by suitably lifting the semifinished product with respect to an advancing plane thereof in the section traversed by the cutting line, the separation of the piece from the remaining semifinished product with the execution of a precise cut is facilitated, without the limited thickness and reduced consistency of the semifinished product leading to phenomena of stress and/or excessive twisting in the material under the action of the cutting blade.

According to a first aspect the present invention relates to a process for building tyres for bicycles, in which a plurality of components of a tyre being processed are deposited circumferentially around a deposition surface carried by a building drum.

Preferably, provision is made for applying at least one carcass ply around said deposition surface.

Preferably, provision is made for applying a pair of bead cores at a predetermined mutual axial distance around the carcass ply. Preferably, provision is made for turning up axially outer terminal flaps of the carcass ply around the bead cores.

Preferably, provision is made for depositing a tread band around the deposition surface, maintaining the mutual axial distance of the bead cores substantially unchanged.

Preferably, the deposition of at least one of said components is preceded by a cutting-to-size processing of a respective semifinished product in continuous strip form along a cutting line, in order to separate, from the semifinished product itself, a piece having a predetermined cutting length.

Preferably, the cutting-to-size processing comprises positioning the semifinished product with a lower surface thereof in abutment against an advancing plane defined by a conveyor belt comprising a feeding section and a preparation section that are consecutively aligned.

Preferably, the cutting-to-size processing comprises longitudinally advancing the semifinished product along the advancing plane and above an abutment plate interposed between the feeding section and the preparation section.

Preferably, the cutting-to-size processing comprises stopping the advancement of the semifinished product with respect to a cutting plane containing the cutting line and intersecting the advancing plane at the abutment plate, when a head and and a tail end of the semifinished product lies separate from the cutting plane according to a measurement equal to said cutting length.

Preferably, the cutting-to-size processing comprises lifting, with respect to the advancing plane, the abutment plate and a cutting section of the semifinished product arranged thereon. Preferably, the cutting-to-size processing comprises translating, a cutting member transverse to the semifinished product in order to cut the latter along the cutting line.

Preferably, provision is made for repositioning, coplanar to the advancing plane, the abutment plate, carrying a tail end of the cut piece and a head end of the cut semifinished product.

In a further aspect, the invention relates to an apparatus for building tyres for bicycles, comprising a building drum and a deposition group configured for depositing a plurality of components circumferentially around a deposition surface carried by the building drum.

Preferably, said deposition group comprises carcass ply application devices configured for depositing at least one carcass ply around the deposition surface.

Preferably, said deposition group comprises devices for applying a pair of bead cores at a predetermined mutual axial distance around the carcass ply.

Preferably, said deposition group comprises turning up devices configured for turning up axially outer terminal flaps of the carcass ply around the bead cores.

Preferably, said deposition group comprises tread band application devices configured for applying a tread band around the deposition surface, in axially centred position between the bead cores arranged according to said predetermined mutual axial distance.

Preferably, the deposition group comprises at least one preparation unit configured for cutting transversely to size a semifinished product in continuous strip form along a cutting line, in order to separate a piece having a predetermined cutting length from the semifinished product itself.

Preferably, the preparation unit comprises a conveyor belt comprising a feeding section and a preparation section that are consecutively aligned according to an advancing plane transverse to a cutting plane containing the cutting line, and configured for supporting the semifinished product in abutment with a lower surface thereof against the advancing plane itself.

Preferably, the preparation unit comprises devices for controlling the conveyor belt, configured for advancing longitudinally advancing the semifinished product along the advancing plane and stopping the advancement of the semifinished product when a head end of the semifinished product lies separate from the cutting plane according to the measurement equal to said cutting length.

Preferably, the preparation unit comprises an abutment plate interposed between the feeding section and the preparation section of the conveyor at the cutting plane, and movable between a rest position in which it is substantially coplanar to the advancing plane and a work position in which it is lifted with respect to the advancing plane in order to lift with respect to the advancing plane a cutting section of the semifinished product traversed by the cutting plane.

Preferably, the preparation unit comprises a cutting member that is movable transverse to the semifinished product in order to cut the latter along the cutting line.

The Applicant deems that the piece precut-to-size is then more manageable than the semifinished product coming directly from a feeding reel, such that its application can occur in an automated manner with high precision and repeatability, without the risk of causing excessive stresses and/or twisting to the component itself.

It then becomes possible to actuate a suitable automation of the operations aimed for the application of the tread band of a tyre for bicycles on the building drum, facilitating the obtainment of greater precision in the processing, to the benefit of the quality of the final product, the production costs and the safety of the personnel who supervise the production.

The Applicant additionally deems that the lifting executed in proximity to the cutting line allows creating, along the semifinished product, a zone of controlled tensioning that facilitates the execution of the cutting and the separation of the tail end of the obtained piece from the head end of the continuous semifinished product. Thus, the execution of precise cuts is facilitated, even on very thin, not very robust semifinished products, in which the elastomer at the green state which composes them would tend to be easily deformed and create stress (i.e. deformations and consequent localized material accumulations) under the action of a cutting member. The piece precut from the semifinished product is then adapted to be easily translated along the advancing plane up to a zone of application such that the deposition around the building drum can be executed with precision without imposing uncontrolled stretching or twisting on the piece itself.

The Applicant finally deems that the abutment plate employed for determining the lifting of the semifinished product offers a suitable check against the stresses transmitted by the cutting edge of the cutting member to the semifinished product, facilitating the execution of a precise cutting even on semifinished products that are very slender and/or have reduced robustness.

In at least one convenient embodiment, the invention also comprises one or more of the following preferred characteristics. Preferably, during the application of the tread band, an axially central portion of said at least one carcass ply, extended axially through an axial middle line plane equidistant from the bead cores, lies against the deposition surface.

Preferably, the action of lifting comprises retaining the semifinished product on an upper surface thereof opposite the lower surface, along two grip lines side-by-side on sides respectively opposite the cutting plane.

Preferably, the cutting member is brought back to the starting position after the repositioning of the abutment plate.

The mobility of the abutment plate therefore facilitates the execution of a precise processing, preventing undesired interferences between the cutting member and the cut semifinished product during the return to the starting position from determining misalignments of the semifinished product itself with respect to the ideal position for the purpose of its application on the building drum.

Preferably, during the translation of the cutting member, a cutting edge of the cutting member transmits, to the semifinished product, a thrust component directed towards the abutment plate.

Preferably, provision is also made for transmitting vibrations to the cutting member while the semifinished product is cut transversely.

Preferably, said vibrations have ultrasonic frequency. The vibrations, above all if at high frequency such as ultrasonic vibrations, increase the effectiveness of the cutting so as to allow the effective execution thereof on semifinished products of small thickness and limited consistency, limiting the stresses and the consequent deformations induced on the semifinished product itself.

Preferably, the translation of the cutting member occurs in the absence of a direct contact thereof against the abutment plate.

The absence of direct contact optimises the effect of the vibrations transmitted to the cutting member in order to improve the effectiveness thereof.

Preferably, during the translation of the cutting member, an abutment surface of the abutment plate lies separate from a cutting edge of the cutting member according to a measurement not more than 0.1 mm.

Thus, an effective contrast to the thrusts transmitted to the semifinished product is facilitated during the execution of the cutting, opposing uncontrolled deformations of the semifinished product itself.

Preferably, the cutting plane intersects the advancing plane according to a tilted orientation defining, with respect to the advancing plane, a first acute angle with directed vertex directed towards the building drum.

Preferably, the cutting plane intersects the advancing plane according to an orientation perpendicular to the longitudinal extension of the semifinished product.

Preferably, during the execution of the cutting, an action is exerted for blocking the semifinished product with respect to the advancing plane. Hence, undesired movements and/or lateral misalignments of the semifinished product are blocked due to the stresses transmitted during the execution of the cutting.

Preferably, the blocking action is executed upstream of the cutting plane, with reference to the advancement of the semifinished product.

Preferably, the blocking action is exerted downstream of the cutting plane, with reference to the advancement of the semifinished product.

Preferably, the blocking action is exerted against the abutment plate.

The consequent vicinity between the zones of application of the blocking action and the cutting plane reduces the possibility of deformations of the semifinished product due to the cutting member.

Preferably, the blocking action is exerted by at least one thrust plate, acting elastically against the semifinished product.

Preferably, the deposition of said tread band comprises arranging a tread band semifinished product in continuous strip form.

Preferably, the deposition of said tread band comprises subjecting the tread band semifinished product to said cutting- to-size processing.

Preferably, the tread band semifinished product has thickness comprised between 1 mm and 8 mm.

Preferably, the tread band semifinished product has width comprised between 20 mm and 120 mm.

Preferably, said components also comprise an elastomeric base arranged circumferentially around the deposition surface before depositing the tread band. Preferably, the elastomeric base is applied in axially centred position with respect to the bead cores.

Preferably, the deposition of said elastomeric base occurs after the turning up of the terminal flaps.

Preferably, the deposition of said elastomeric base comprises arranging an elastomeric base semifinished product in continuous strip form;

Preferably, the deposition of said elastomeric base comprises subjecting the elastomeric base semifinished product to said cutting-to-size processing.

Preferably, the elastomeric base semifinished product has thickness comprised between 0.5 mm and 1.5 mm.

Preferably, the elastomeric base semifinished product has width comprised between 15 mm and 30 mm.

Preferably, the cutting member is movable along the cutting line from a starting position to an arrival position.

Preferably, the abutment plate is configured for being positioned in the work position before the movement of the cutting member to the arrival position in order to cut the semifinished product.

Preferably, the abutment plate is configured for being positioned in the rest position before the return of the cutting member to the starting position.

Preferably, the preparation unit also comprises an ultrasonic transducer operating on the cutting member in order to transmit an ultrasonic frequency vibration to the latter.

Preferably, the cutting member comprises a blade movable along the cutting direction.

Preferably, the blade has a tilted oriented defining, with respect to the advancing plane, a first acute angle with vertex directed towards the preparation section.

Preferably, the first acute angle has value comprised between 15° and 30°.

Preferably, a cutting edge of the cutting member lies in the cutting plane according to a tilted orientation with respect to the cutting line.

Preferably, the cutting edge forms, in the cutting plane and with respect to the advancing plane, a second acute angle with vertex directed towards said starting position.

Preferably, the second acute angle has value comprised between 5° and 15°.

Preferably, the cutting edge forms, parallel to the advancing plane, a third acute angle with vertex directed towards said starting position.

Preferably, the third acute angle has value comprised between 5° and 25°.

Preferably, the cutting member ha a cutting vertex directed towards the abutment plate and configured for operating through the semifinished product, in the absence of direct contact against the abutment plate itself.

Preferably, the cutting vertex is configured for operating through the semifinished product with said lower surface in contact against an abutment surface of the abutment plate.

Preferably, the abutment surface of the abutment plate is spaced from the cutting vertex according to a measurement not greater than 0.1 mm.

Preferably, blocking devices are also provided for the semifinished product with respect to the advancing plane, operating in proximity to the abutment plate. Preferably, said blocking devices are configured for operating on the semifinished product upstream of the cutting plane, with reference to the advancing of the semifinished product.

Preferably, said blocking devices are configured for operating on the semifinished product downstream of the cutting plane, with reference to the advancing of the semifinished product.

Preferably, said blocking devices are configured for pushing the semifinished product against the abutment plate.

Preferably, said blocking devices comprise at least one thrust plate, configured for elastically acting against the semifinished product by means of a terminal edge.

Preferably, the thrust plate is made in the form of an elastically deformable plate.

Preferably, the thrust plate has a plurality of elastically deformable sheets that are respectively parallel and distributed along the terminal edge.

The subdivision of the active edge into deformable sheets allows a more uniform action on the semifinished product, with a spontaneous adaptation of the thrust plate to the cross section profile of the semifinished product itself.

Preferably, the cutting member is movable along a guide having a transverse orientation with respect to the longitudinal extension of the conveyor belt.

Preferably, the cutting member is movable along a guide having a perpendicular orientation with respect to the longitudinal extension of the conveyor belt.

Preferably, the preparation section of the belt feeder is configured for advancing at a speed equal to the feeding section during the transfer of the semifinished product from the feeding section to the preparation section.

Further characteristics and advantages will be more evident from the detailed description of preferred but not exclusive embodiments of a process and relative apparatus for building tyres for bicycles, in accordance with the present invention. Such description will be set forth herein with reference to the enclosed drawings, provided merely for non-limiting purposes, in which:

- figures 1 to 4 schematically show, in radial section, several operating steps aimed for building a green tyre for a bicycle;

- figure 5 shows schematically, in side view, an apparatus for building tyres for bicycles, according to the present invention:

- figure 6 shows a schematic top view of one of the preparation units of a semifinished product constituting part of the present apparatus, in accordance with a first embodiment usable for example for making carcass plies;

- figure 7 shows a detail of the preparation unit of figure 3, with a detail of a cutting group and lifting devices shown in side view;

- figure 8 shows a detail of the preparation unit in the transition zone between a feeding section and a preparation section of a conveyor belt, and showing in front view the cutting group with the lifting devices in lifted position;

- figure 9 shows the detail of figure 8 with the lifting devices in lowered position;

- figure 10 shows a detail of a further preparation unit, with a detail of a cutting group and lifting devices shown in side view in accordance with an embodiment variant;

- figure 11 shows a detail of the preparation unit of figure 10, in the transition zone between a feeding section and a preparation section of a conveyor belt, and showing in front view the cutting group and the lifting devices;

- figure 12 shows a schematic top view of a further preparation unit of a semifinished product constituting part of the present apparatus, in accordance with a further embodiment particularly adapted for example for making tread bands;

- figure 13 shows, in side view, the preparation unit of figure 12, in the transition zone between a feeding section and a preparation section of the conveyor belt;

- figure 14 shows a detail of the preparation unit of figures 12 and 13, showing in front view the cutting group and the lifting devices;

- figure 15 shows a detail of the preparation unit of figures 12 and 14, showing in front view the cutting group and the lifting devices;

- figure 16 shows, in radial section, a structural scheme of a hypothetical tyre for a bicycle.

In figure 5, reference number 1 overall indicates an apparatus for building tyres for bicycles, suitable for actuating a building process according to the present invention.

The present invention is aimed for processing tyres 2 for bicycles, of the type schematically exemplified in figure 16, e.g. for use on road, track, mountain bikes, e-bikes etc.

In tyre 2, the following are identifiable: a radially inner surface 2a, facing substantially towards a geometric rotation axis "X" of the tyre 2, and a radially outer surface 2b facing substantially away from the geometric rotation axis "X".

The tyre 2 for bicycles has a carcass structure 3 comprising at least one carcass ply 4 having mutually parallel cords, incorporated in an elastomeric matrix.

Axially opposite terminal flaps 4a of the carcass ply or plies 4 are engaged to respective bead cores 5, i.e. annular anchoring structures integrated in the zones usually identified with the name of "beads" at which there is the mechanical engagement between the tyre 2 in use conditions and a respective mounting rim.

In radially outer position with respect to the carcass structure 3, a tread band 6 made of elastomeric material is applied.

Preferably, in the carcass structure 3, at least two cord layers having are applied with respectively cross progression. The cords belonging to each layer have an extension tilted according to a predetermined angle, approximately comprised between about 35° and about 55° with respect to circumferential extension direction of the tyre 2. Provision may be made for the presence of two carcass plies 4 that are radially superimposed on each other, each with the respective cords extended along a direction tilted with respect to the circumferential extension of the tyre 2 and according to a tilted orientation with respect to the cords belonging to the other carcass ply 4. Alternatively, as in the illustrated example, provision may be made for a single carcass ply 4 whose terminal flaps 4a, turned up around bead cores 5, are extended at least up to an axial middle line plane M of the tyre 2, such that each defines a further radially outer layer of cords having cross orientation with respect to the cords present in the radially inner layer.

In the tyre 2 for bicycles, provision may however be made for at least one protective band 7 extended circumferentially between the tread band 6 and the carcass structure 3, or between two layers of the carcass ply that are mutually superimposed in radial direction. If present, said at least one protective band 7, whose task is for example that of protecting the tyre 2 from puncture, can have textile structure incorporating cords that are respectively parallel or respectively cross, and preferably has a thickness not greater than about 0.6 mm, preferably comprised between 0.3 mm and 0.6 mm. In one possible embodiment solution, the axial extension of the protective band/bands is smaller than that of the tread band 6, and preferably comprised between 15 mm and 50 mm. In one possible embodiment variant, provision can be made for an enlarged protective band 8, normally termed "bead to bead" whose axial extension is instead greater than that of the tread band 6 and for example comprised between 50 mm and 200 mm, preferably such to terminate axially at each of the bead cores 5. In a further possible non-illustrated embodiment, provision can be made for a first protective band 7 having width smaller than that of the tread band, and an enlarged protective band 8 extended from one of the bead cores 5 to the other.

Between the carcass ply/plies 3 and the tread band 6, an elastomeric base 9 can also be interposed in layer form, preferably in axially centred position with respect to the bead cores and radially inner with respect to the optionally present protective band 7. The elastomeric base can have approximately an axial width comprised between 15 mm and 30 mm, and thickness comprised between 0.5 mm and 1.5 mm.

A radially inner surface of the carcass structure 3 can be coated with a so-called liner 10, composed of an air-impermeable compound layer in which thickness can be approximately comprised between 0.35 mm and 1 mm. The liner 10 is extended from one of the beads to the other, according to an axial extension approximately between 70 mm and 120 mm.

In proximity to the bead cores 5, outside the beads, respective reinforcements bead 11 can also be applied, usually termed "chafers", in the form of textile strips incorporating cords parallel to each other or respectively cross, for the purpose of protecting the beads from contact with the rim of the wheel on which the tyre is mounted. Each reinforcement bead 11 can have a width comprised between 8 mm and 15 mm and a thickness comprised between 0.3 and 1 mm.

Preferably, on the radially outer surface 2b of the tyre 2 for bicycles, portions of carcass ply 4 are identifiable, between the axially outer edges of the tread band 6 and the bead cores 5, such carcass ply 4 portions directly exposed towards the outside environment. The tyre 2 for bicycles in fact typically lacks sidewalls, i.e. layers of elastomeric material applied laterally to the outside of the carcass structure 3, each extended between one of the beads and the respective axially outer edge of the tread band 6. Provision can however also be made for so-called "sidewall reinforcements" 12, each comprising a strip of rubber- coated textile material, incorporating mutually parallel or cross cords with thickness approximately comprised between 0.3 mm and 0.8 mm and extended each between the respective bead and the tread band 6 according to a width comprised between 30 mm and 60 mm.

The apparatus 1 comprises a building drum 13 that is substantially cylindrical, rotatably supported around a horizontal rotation axis X-X thereof. A deposition group overall indicated with 14 in figure 5 provides for depositing a plurality of components of the tyre 2 circumferentially around a deposition surface 15 present on the outside of the building drum 13.

The components are selected by type, number and/or structural and size characteristics as a function of the type of tyre for bicycles under production (road, track, mountain-bike etc.), comprise the carcass ply/plies 4, the bead cores 5, the tread band 6, as well as the possible liners 10, sidewall reinforcements 12, elastomeric base 9, reinforcements bead 11, protective bands 7, 8 etc.

More particularly, as schematised in figures 1 to 4, the building of the tyre 2 for bicycles provides that the carcass ply or plies 4 are deposited according to a cylindrical configuration, by liner/carcass ply application devices 16, 17 that assist with a winding of the carcass ply/plies 4 around the deposition surface 15 present on the outside of the building drum 13. The possible liner 10, indicated with a dash line only in figure 16 for the sake of illustration simplicity, can be deposited on the deposition surface 15 before the application of the carcass ply/plies 4, by said liner/carcass ply application devices 16, 17.

By bead core application devices (not illustrated), a pair of bead cores 5 made for example of composite material with base of natural or synthetic fibres and/or of metal material, are applied at a predetermined mutual axial distance D, each around one of the axially opposite terminal flaps 4a of the carcass ply 4.

Provision can be made that each bead core 5, previously made in the form of a finished component, is first fit around the carcass ply or plies 4 in an axial position corresponding to a circumferential recess 18 optionally arranged on the building drum 13. A slight radial expansion of the building drum 13, for example by levers constituting part of said bead core application devices, determines the application of the bead cores 5 against the carcass ply or plies 4, each at the respective circumferential recess 18.

Alternatively, the bead core application devices can be configured for making each bead core 5 directly on the building drum 13, winding around the carcass ply or plies 4 one or more continuous cords according to a plurality of coils that are axially approached and/or radially superimposed on each other.

Turning up devices 13a (schematically indicated in figure 3) operating at the building drum 13 thus provide a turning up the terminal flaps 4a of the carcass plies 4 around the respective bead cores 5. During the turning up, terminal flaps 4a can be at least partially superimposed on each other, and optionally joined in direct mutual contact.

Tread band application devices 19 assist the application of a tread band 6 around the carcass ply 4, in axially centred position with respect to the bead cores 5. The tread band 6 can be applied in radial superimposition with respect to the turned-up terminal flaps 4a. Upon completed application, the terminal flaps 4a can therefore be partially arranged in axially inner position with respect to axially opposite lateral edges of the tread band 6. During the application of the tread band 6, an axially central portion of said at least one carcass ply 4, extended axially through an axial middle line plane M equidistant from the bead cores 5, lies against the building drum 13 (figure 16) and/or the deposition surface 15.

The tread band 6 is preferably applied, maintaining the mutual axial distance D of the bead cores 5 substantially unchanged. More particularly, the mutual axial distance D between the bead cores 5 preferably remains unchanged in the course of the entire building process, including the application of the tread band 6.

If necessary, the application of the tread band 6 can be preceded by the application of said at least one protective band 7, of the sidewall reinforcements 12, of the elastomeric base 9 in axially centred position with respect to the bead cores 5. The elastomeric base 9 is preferably applied before the turning up of the terminal flaps, while the application of the protective band 7 and/or of the enlarged protective band 8 can occur before or after said turning up, depending on the requirements. The application of the possible reinforcements bead 11 can be executed simultaneously in proximity to each of the beads, before or after the application of the tread band 6.

Upon completed building, the green tyre 2 is removed from the building drum 13 in order to be subjected to other process steps, for example in order to be transferred to a vulcanisation press. For such purpose, the building drum 13 can be radially contracted so as to facilitate the axial removal of the built tyre 2. It is conveniently provided that the deposition of at least one of the aforesaid tyre components is preceded by a cutting-to-size processing of a respective semifinished product 20a, 20b, 20c, 20d in continuous strip form along a cutting line L, in order to separate a piece 21, from the semifinished product itself, having a predetermined cutting length. The piece 21 is subsequently brought to the building drum 13 in order to be applied around the deposition surface 15.

The deposition group 14 for such purpose comprises at least one preparation unit 22a, 22b, 22c, 22d, configured for cutting transversely to size a semifinished product 20a, 20b, 20c, 20d along a cutting line L, in order to separate, from the semifinished product itself, a piece 21 having a predetermined cutting length. More particularly, provision is preferably made for more than one of said preparation unit 22a, 22b, 22c, 22d, each dedicated to the preparation of a respective tyre component. More specifically, in the embodiment of figure 2, in addition to the first preparation unit 22a dedicated for example to the preparation of the liner 10, a second preparation unit 22b and a third preparation unit 22c are also identifiable, respectively dedicated, for example, to the preparation of the carcass ply 4 and of the tread band 6. A fourth preparation unit 22d can be dedicated to the preparation of the sidewall reinforcements 12 or of the reinforcements bead 11. The preparation unit 22a, 22b, 22c, 22d can have a lengthwise extension that is substantially horizontal and/or tilted, and be placed consecutively superimposed one after the other so as to converge towards the building drum 13 from a same side.

Each of the preparation units 22a, 22b, 22c, 22d has a feeding unit Ha, Hb, He, Hd in which the respective semifinished product 20a, 20b, 20c, 20d in continuous strip form is arranged, for example wound in reel form or suitably stored in a container, from which it is progressively drawn during the processing.

Each semifinished product 20a, 20b, 20c, 20d has structural and geometric characteristics adapted for obtaining the respective component to be made and applied on the building drum 13. For example, in the first preparation unit 22a a liner semifinished product 20a made of air-impermeable elastomeric material can be arranged, having thickness approximately comprised between 0.35 mm and 1 mm and width comprised between 70 mm and 120 mm. In the second preparation unit 22b a second semifinished product can be arranged, for example a carcass ply semifinished product 20b, having thickness approximately comprised between 0.3 mm and 0.6 mm and width comprised between 110 mm and 450 mm and incorporating mutually parallel reinforcement cords, tilted according to an angle comprised between 35° and 55° with respect to the longitudinal extension of the semifinished product itself. In the third preparation unit 22c, a third semifinished product can be arranged, for example a tread band semifinished product 20c made of elastomeric material, having thickness approximately comprised between 1 mm and 8 mm and width comprised between 20 mm and 120 mm.

In order to facilitate the description, structural and functional characteristics of the preparation units 22a, 22b, 22c, 22d respectively corresponding to each other will be described hereinbelow only once, mainly with reference to the second preparation unit 22b, but it is intended that they can be indiscriminately applied for each of the preparation units themselves.

In Fig.6 each of the preparation units 22a, 22b, 22c, 22d comprises a conveyor belt 23 having a feeding section 24 and a preparation section 25, that are consecutively aligned in a manner so as to define a substantially horizontal advancing plane P.

Preferably, the feeding section 24 comprises a strip-like feeding belt 26, engaged around a respective first transmission rollers 27. The preparation section 25 comprises in turn a respective strip-like preparation belt 28, engaged around a second transmission rollers 29. Respective upper sections of the feeding belt 26 and of the preparation belt 28 are coplanar and aligned with each other, to define the aforesaid advancing plane P.

Preferably, the feeding section 24 and the preparation section 25 are independently motorised with respect to each other, each at at least one of the respective first transmission rollers 27 and second transmission rollers 29, in order to be able to translate the respective feeding belt 26 and preparation belt 28 at speeds respectively equal or different, depending on the requirements. The conveyor belt 23 is adapted to support the semifinished product 20a, 20b, 20c, 20d coming from the respective feeding unit Ha, Hb, He, Hd, with a lower surface SI thereof in abutment against the advancing plane P, against the preparation belt 28 and/or against the feeding belt 26.

A cutting group 30 is adapted to transversely cut the semifinished product 20a, 20b, 20c, 20d in order to separate, from the semifinished product itself, said piece 21 of predetermined length. The cutting group 30 operates along the aforesaid cutting line L, defined by the intersection between the semifinished product 20a, 20b, 20c, 20d and a cutting plane Q transverse to the advancing plane P and entirely intersecting the semifinished product itself, in proximity to a transition zone N between the feeding section 24 and the preparation section 25. The execution of the cutting-to-size processing ensures that, at the start of each operating cycle, the semifinished product 20a, 20b, 20c, 20d has its own head end A positioned at the cutting line L. The execution of a new cutting processing provides that, upon simultaneous activation of the feeding section 24 and of the preparation section 25, the semifinished product 20a, 20b, 20c, 20d is made to longitudinally advance along the advancing plane P and progressively transferred from the feeding section 24 to the preparation section 25. Provision is preferably made that the feeding section 24 and the preparation section 25 advance at equal speed, during the transfer of the semifinished product 20a, 20b, 20c, 20d from the feeding section 24 to the preparation section 25, so as to not subject the semifinished product itself to undesired stresses. Being typically made with green elastomeric material with limited thickness, the semifinished product 20a, 20b, 20c, 20d is in fact rather sensitive to tensile stresses or compression generated by a different of speed between the feeding section 24 and the preparation section 25, which could modify the length and/or the width of the semifinished product itself. Alternatively, it is possible to differentiate, in a controlled manner, the advancing speeds of the preparation section 25 and of the feeding section 24. For example, provision can be made that the preparation section 25 translates at a speed slightly greater than that of the feeding section 24, in order to facilitate a relaxation of the semifinished product 20a, 20b, 20c, 20d or part thereof along the advancing plane P. Photocells, encoders or other suitable control devices 31, operating on the conveyor belt 23 and only schematically indicated since they can be attained in any convenient manner, allow controlling the simultaneous actuation of the feeding section 24 and the preparation section 25, in order to stop the advancement of the semifinished product 20a, 20b, 20c, 20d when its head end A, after having gone beyond the cutting plane Q, reaches a predetermined cutting distance K with respect to the cutting plane itself, as represented in figure 6.

The cutting distance K is correlated to the circumferential extension of the deposition surface 15, for example such that the length of the obtained piece 21 coincides with such circumferential extension. Alternatively, provision can be made that the cutting distance K and the consequent length of the obtained piece 21 be different, e.g. slightly greater, with respect to the circumferential extension of the deposition surface 15, in order to compensate for possible elastic contractions of the material following the execution of the cutting and before the application on the building drum 13.

In proximity to the transition zone N between the feeding section 24 and the preparation section 25, lifting devices 32 also operate, by which the semifinished product 20a, 20b, 20c, 20d is adapted to be spaced from the advancing plane P. When the advancement of the semifinished product 20a, 20b, 20c, 20d has been stopped, the lifting devices 32 engage the semifinished product itself at a cutting section T thereof intersected by the cutting plane Q, and lift it slightly from the advancing plane P so as to facilitate the subsequent execution of the cutting by the cutting group 30. The cutting group 30 is then activated in order to translate transverse to the semifinished product 20a, 20b, 20c, 20d and cut it along the cutting line L, so as to determine the separation of the piece 21 having a desired length corresponding to the cutting distance K delimited between a head end Al thereof, which before belonged to the semifinished product 20a, 20b, 20c, 20d, and a tail end B thereof, obtained by the cutting operation together with a new head end A of the cut semifinished product 20a, 20b, 20c, 20d.

Upon completed cutting, the preparation section 25 is activated in order to advance the piece 21 along the conveyor belt 23 until the head end Al carried by the piece 21 reaches one end of the conveyor belt 23 opposite the feeding unit Ha, Hb, He, Hd, in proximity to the building drum 13.

With a possible translation of the applications devices 16, 17, 19 and/or of the preparation section 25, the head end Al of the piece 21 is positioned on the deposition surface 15 of the building drum 13, and retained thereto for example upon action of suction nozzles arranged on the deposition surface 15 itself, or via adhesion on the latter or on the components previously deposited on the building drum 13. The building drum 13 is then actuated in rotation by a motor 33 or other suitable actuation devices (not illustrated), while the conveyor belt 23, through the preparation section 25, translates the piece 21 at an advancement speed correlated with a peripheral speed of the deposition surface 15, in order to deposit the piece 21 circumferentially around the deposition surface 15.

Measurement devices can be arranged on the conveyor belt 23, such measurement devices optionally integrated - totally or partially - in the aforesaid control devices 31, configured for detecting the length of the piece 21 on the preparation section 25, immediately before its application on the building drum 13. The measurement devices can be combined with a comparator 34 configured for comparing the detected length of the piece 21, with respect to the circumferential extension of the deposition surface 15. The comparator 34 is operatively connected with the aforesaid devices 31 for controlling the conveyor belt 23 and with the motor 33 and/or other devices set to actuate in rotation the building drum 13, in order to modulate the translation speed of the conveyor itself with respect to the peripheral speed of the deposition surface 15. For example, if the length of the piece 21 detected by the measurement devices is slightly different with respect to the circumferential extension of the deposition surface 15, the translation speed of the conveyor belt 23 can be conveniently modulated with respect to the rotation speed of the building drum 13, in order to modify the length of the piece 21 and make it coincide with the circumferential extension of the deposition surface 15.

When the building drum 13 has completed a complete revolution around the rotation axis X-X thereof, the tail end B of the piece 21 is joined with the head end Al previously applied on the deposition surface 15, finalising the application of the tyre component.

The structural specifications of the preparation unit 22a, 22b, 22c, 22d, above all with reference to the lifting devices 32 and to the cutting group 30, can vary as a function of the type of component to be attained.

In figures 6 to 9, one possible embodiment is illustrated that is employed on the second preparation unit 22b configured for making the carcass ply/plies 4. For the sake of description simplicity and coherence, such embodiment will be described herein with reference to the processing of the carcass ply semifinished product 20b. Nevertheless, in addition or as an alternative that described herein, the same embodiment is optionally usable, for example on the first preparation unit 22a for making the liner 10 by processing of the liner semifinished product 20a, and/or for making other components by processing of the respective semifinished products 20a, 20b, 20c, 20d.

As is visible in figure 6, the lifting devices 32 and the cutting group 30 are mounted on a support structure 36 extended transversely above the conveyor belt 23. The support structure 36, e.g. suspended from above at a hinging pin 35, is angularly positionable around a vertical orientation axis Y-Y. The orientation of the support structure 36 depends on that of the cutting plane Q which, for the purposes of the processing of the carcass plies 4, is conveniently tilted with respect to the longitudinal extension of the carcass ply semifinished product 20b. It is therefore possible to modify the angle of the cutting plane Q and of the cutting line L, preferably according to an angle comprised between 35° and 55° with respect to the longitudinal extension of the carcass ply semifinished product 20b, in accordance with the orientation of the cords incorporated in the semifinished product itself.

The lifting devices 32 comprise a plurality of suction cups 37 or grip elements of another type, facing towards the advancing plane P and distributed along two grip lines side-by-side on opposite sides with respect to the cutting plane Q, respectively upstream and downstream with respect to the advancing sense of the carcass ply semifinished product 20b. A pneumatic activation/deactivation circuit leads to the suction cups 37.

By one or more fluid-dynamic cylinders 38 (figure 7), the suction cups 37 are vertically movable with respect to the support structure 36, perpendicular towards and away from the advancing plane P, between a lowered position and a lifted position. In the lowered position, the suction cups 37 act against an upper surface S2 of the carcass ply semifinished product 20b, while the lower surface SI of the latter is in abutment against the advancing plane P, as in figure 9. The suction cups 37 retain the carcass ply semifinished product 20b by exerting attraction forces at the upper surface S2 upon effect of the suction produced through a pneumatic activation/deactivation circuit, not illustrated. By translating towards the lifted position, the suction cups 37 then lift the carcass ply semifinished product 20b from the advancing plane P at the cutting section T, as in figure 8.

For a greater precision in the execution of the cutting, the suction cups 37 respectively arranged on each of the grip lines, lie mutually apart according to a measurement not greater than 20 mm, and the travel completed by them between the lowered position and the lifted position is not greater than 20 mm. The measurement of the lifting is sufficient for allowing the cutting group 30 to penetrate through the carcass ply semifinished product 20b (or other semifinished product) without interfering with the underlying mechanical parts of the conveyor belt 23. The action of lifting also produces a slight tensioning in the cutting section T of the carcass ply semifinished product 20b, which facilitates the separation of the piece 21 along the cutting line L. In the example of figures 6 to 9, the cutting group 30 preferably comprises a cutting member in knife form 39 arranged coplanar with the cutting plane Q. The knife 39 is fixed to a slider 40 movable along a guide 41 integral with the support structure 36 and parallel to the cutting plane Q.

While the carcass ply semifinished product 20b is retained by the suction cups 37 in the lifted position, an actuator, e.g. in threaded bar form 42 and motorised in rotation, moves the slider 40 and the knife 39 carried thereby along the cutting line L, from a starting position to an arrival position, determining the separation of the piece 21 from the carcass ply semifinished product 20b, respectively placed downstream or upstream of the cutting plane Q.

An ultrasonic transducer 43 can conveniently operate on the cutting group 30 in order to transmit to the latter an ultrasonic frequency vibration that assists with the execution of the cutting. As is more visible in figure 7, the knife 39 of the cutting group 30 preferably has a cutting edge 39a extended in a direction tilted with respect to the advancing plane P so as to form, with respect to the advancing plane itself, an acute angle 0 with vertex directed towards the arrival position, i.e. in the translation sense of the cutting group 30 towards the arrival position. This circumstance ensures that during the execution of the cutting, the cutting edge 39a transmits to the carcass ply semifinished product 20b a vertical thrust component, directed away from the advancing plane P, so as to facilitate the retention action by the suction cups 37. In addition, the end edges of the carcass ply semifinished product 20b and of the piece 21 cut along the cutting line L will tend to be directed upward, so as to limit risks of undesired jamming during the subsequent movement on the advancing plane P.

Also preferably provided that, during the execution of the cutting of the carcass ply semifinished product 20b, the cutting group 30 translates towards the building drum 13. This expedient ensures that possible stresses or other deformations imposed on the material when the cutting edge 39a of the knife 39 encounters the edge of the carcass ply semifinished product 20b tend to be localised on the terminal apex of the tail end B of the cut piece 21, rather than on that of the head end upstream of the cutting line L.

Following the execution of the cutting, the new head end A created on the carcass ply semifinished product 20b just cut is engaged with the suction cups 37 arranged along the grip line upstream of the cutting plane Q. The tail end B of the obtained piece 21 in turn remains retained by the suction cups 37 arranged along the grip line downstream of the cutting plane Q. After the cutting group 30 has reached the arrival position, the suction cups 37 respectively placed upstream and downstream of the cutting plane Q can be brought back to the lowered position, simultaneously or at different times, in order to respectively reposition against the advancing plane P the head end A of the cut carcass ply semifinished product 20b, and the tail end B of the cut piece 21.

Upon completed repositioning, the cutting group 30 can be brought back into the starting position without interfering with the head end A of the cut carcass ply semifinished product 20b and/or with the tail end B of the piece 21.

The cutting plane Q can be advantageously positioned so as to fully intersect the carcass ply semifinished product 20b in a position slightly upstream of the transition zone N between the feeding section 24 and the preparation section 25, such that the cutting group 30 operates above the feeding section 24, adjacent to the transition zone itself. Consequently, with the descent of the suction cups 37 towards the lowered position, the tail end B of the cut piece 21 is deposited on the terminal part of the feeding section 24, leading to the transition zone N. Upon completed repositioning, an actuation of the preparation belt 28 determines the transfer of the tail end B on the preparation section 25, simultaneously with an advancement of the entire piece 21 towards the building drum 13. During this transfer of the tail end B towards the preparation section 25, the feeding belt 26 can remain momentarily inactive in order to facilitate a moving away of the piece 21 from the carcass ply semifinished product 20b.

Alternatively, provision can be made for a simultaneous activation of the feeding belt 26 and of the preparation belt 28, so as to also determine the advancement of the carcass ply semifinished product 20b on the feeding section 24 in order to go beyond the transition zone N and proceed along the advancing plane P at the same preparation section 25. In such case, it is preferable that during the transfer of the tail end B, the piece 21 on the preparation section 25 translates at a speed greater than the advancing speed of the carcass ply semifinished product 20b on the feeding section 24, in order to drive the tail end B on the preparation section 25, facilitating the relaxation of possible stresses and/or other deformations produced during the cutting action, facilitating the moving away thereof from the head end A of the carcass ply semifinished product 20b just cut.

The advancing speeds of the carcass ply semifinished product 20b on the preparation section 25 and on the feeding section 24 can be equalised with respect to each other after the tail end B of the piece 21 has been transferred on the preparation section 25, such that the advancement of the carcass ply semifinished product 20b through the transition zone N can continue uniformly without the same semifinished product being subjected to undesired stretching stresses. It should be observed that that described above for the processing of the carcass ply semifinished product 20b is to be intended as applicable also for any other type of semifinished product 20a, 20b, 20c, 20d being processed.

In figures 10 and 11, one possible embodiment variant is illustrated, employed on the fourth preparation unit 22d configured for making sidewall inserts 12. This embodiment variant is in fact particularly suitable for operating also on semifinished products incorporating reinforcement cords with cross progression, such as for example those typically adapted for making the sidewall reinforcements 12, the reinforcements bead 11, and/or the protective bands 7, 8. For the sake of description simplicity and coherence, the embodiment variant of figures 7 to 9 will therefore be described herein with reference to the processing of only the sidewall insert semifinished product 20d. Nevertheless, in addition or as an alternative to that described herein, the same embodiment is optionally usable, for example, on the first preparation unit 22a and on the second preparation unit 22b for making the carcass ply 4 by processing of the carcass ply semifinished product 20b, and/or for making other components.

This embodiment variant is conceptually similar to that described above, but differs therefrom due to the structural and functional characteristics of the cutting group 30 and of the lifting devices 32. Structural parts and details that are not specified can be made in a manner conceptually analogous to that described above with reference to the embodiment of figures 7 to 9.

In this case, the lifting devices 32 comprise, in place of the aforesaid suction cups 37, a lifting insert 44 arranged on the advancing plane P, flush with the latter, so as to be passed over by the sidewall insert semifinished product 20d passing above it. The lifting insert 44 is shaped substantially as a bar having longitudinal extension parallel to the cutting plane Q. The width of the lifting insert 44 is delimited between an inlet edge 45 directed towards the sidewall insert feeding unit Hd, i.e. in a direction opposite the advancing sense of the sidewall insert semifinished product 20d along the advancing plane P, and an outlet edge 46 directed towards the building drum 13, i.e. in the advancing sense of the sidewall insert semifinished product 20d. Between the inlet edge 45 and the outlet edge 46 is extended above a slide surface 47 having a tilted orientation with respect to the advancing plane P, according to a direction diverging therefrom towards the building drum 13, i.e. along an advancement direction of the sidewall insert semifinished product 20d.

The slide surface 47 is adapted to support the sidewall insert semifinished product 20d while this, during the translation along the advancing plane P, is conducted with its lower surface SI slidably in abutment against the lifting insert 44 itself. The divergent progression of the slide surface 47 ensures that, along the outlet edge 46, a recess 48 is created between the lower surface SI of the sidewall insert semifinished product 20d and the advancing plane P.

The cutting member comprises, in place of the knife 39, a rotating blade 49, having discoidal form and actuated in rotation at high speed around a geometric axis Z-Z thereof parallel to the advancing plane P and orthogonal with respect to the cutting plane Q. The rotating blade 49 lies in the cutting plane Q, and is operatively carried by the respective slider 40 movable along the guide 41. During the execution of the cutting, the rotating blade 49 rotates around the geometric axis Z-Z thereof and translates from the starting position to the arrival position along the guide 41, while with its own peripheral edge 49a it traverses the sidewall insert semifinished product 20d, translating in the recess 48, laterally delimited by the outlet edge 46 of the lifting insert 44.

Preferably, the rotation sense of the rotating blade 49 is selected in a manner such that, at the point of intersection of its cutting edge 39a with the sidewall insert semifinished product 20d, this rotates in the sense opposite its own advancing sense towards the arrival position. Therefore, the action of the rotating blade 49 conveniently tends to move away, from the advancing plane P, the edges of the head end A of the sidewall insert semifinished product 20d just cut and of the tail end B of the obtained piece 21.

Figures 12 to 15 illustrate a possible further embodiment, employed on the third preparation unit 22c configured for making tread bands 6. Also in this case, for the sake of description simplicity and coherence, such further embodiment variant will be described herein with reference to the processing of the tread band semifinished product 20c. Nevertheless, in addition or as an alternative to that described herein, the same embodiment is optionally usable, for example on the first preparation unit 22a for making the liner 10 by processing of the liner semifinished product 20a, of the elastomeric base 9, and/or for making other components by processing of the respective semifinished products 20a, 20b, 20c, 20d.

Also this further embodiment variant is conceptually similar to those described above, and differs therefrom mainly due to the structural and functional characteristics of the cutting group 30 and of the lifting devices 32. Structural parts and details that are not specified can be made in a manner conceptually analogous to that described above with reference to the embodiment of figures 7 to 9.

In figures 12 to 15, the lifting devices 32 comprise an abutment plate 50 interposed in the transition zone N between the feeding section 24 and the preparation section 25 of the conveyor belt 23, at the cutting plane Q. The cutting plane Q in fact intersects the advancing plane P at the abutment plate 50.

The abutment plate 50 is movable between a rest position in which it is substantially coplanar with the advancing plane P, as in figure 13, and a work position in which it is lifted with respect to the advancing plane P, as in figure 14.

When the conveyor belt 23 is activated in order to advance the tread band semifinished product 20c, towards the building drum 13, the semifinished product itself slides above the abutment plate 50, placed in the rest position. After the advancement of the tread band semifinished product 20c has been stopped, following the attainment of the requested cutting distance K between the head end A of the semifinished product itself and the cutting plane Q, the abutment plate 50 is brought into the work position. The tread band semifinished product 20c is therefore lifted with respect to the advancing plane P, at its cutting section T traversed by the cutting plane Q.

The cutting member of the cutting group 30 is attained in blade form 51, rigidly carried by the respective slider 40 movable along the guide 41 in turn integral with the support structure 36, which is extended transverse above the conveyor belt 23. The orientation of the guide 41, transverse and preferably perpendicular with respect to the longitudinal extension of the conveyor belt 23, is such that the cutting plane Q intersects the advancing plane P according to an orientation perpendicular to the longitudinal extension of the tread band semifinished product 20c. In addition the blade 51, and consequently the cutting plane Q, have a tilted orientation defining, with respect to the advancing plane P and to the upper surface S2 of the tread band semifinished product 20c, a first acute angle 01 (figure 14) with vertex directed in the advancing sense of the semifinished product itself, i.e. towards the preparation section 25 and the building drum 13. This tilt facilitates the obtainment of a tilted cut on the head end Al an tail end B of the piece 21 separated from the tread band semifinished product 20c, facilitating the joining on the building drum 13. Preferably, the value of the first acute angle 01 is comprised between 15° and 30°.

The cutting group 30 is adapted to translate from the starting position towards the arrival position by moving the blade 51 along the cutting line L when the abutment plate 50 is in the work position, in order to determine separation of the piece 21 from the respective tread band semifinished product 20c. The execution of the cutting can be facilitated by high-frequency vibrations, preferably ultrasonic, transmitted to the cutting group 30 by the respective ultrasonic transducer 43.

It is also preferably provided that a cutting edge 51a of the blade 51 lies in the cutting plane Q according to a tilted orientation with respect to the cutting line L. At one end of the cutting edge 51a, a cutting vertex 52 directed towards the abutment plate 50 is therefore identifiable. During the execution of the cutting, the cutting edge 51a is extended starting from the cutting vertex 52, away from an abutment surface 50a (figure 12) present on the upper part of the abutment plate 50. More particularly, the cutting edge 51a forms, in the cutting plane Q and with respect to the advancing plane P, a second acute angle 02 (figure 15) with vertex directed towards said starting position. In this manner, the cutting edge 51a is adapted to transmit, to the tread band semifinished product 20c, a thrust component directed towards the abutment plate 50 during the translation of the cutting group 30 towards the arrival position. Preferably, the value of the second acute angle 02 is comprised between 5° and 15°.

In addition, the cutting edge 51a forms, in a plane parallel to the advancing plane P, a third acute angle 03 (figure 12) with vertex directed towards said starting position. In this manner, the penetration of the cutting edge 51a into the tread band semifinished product 20c is facilitated. Preferably, the value of the third acute angle 03 is comprised between 5° and 25°. During the translation of the cutting group 30, the cutting vertex 52 is preferably adapted to operate through the tread band semifinished product 20c in the absence of direct contact between the cutting group 30 and the abutment plate 50 itself. Indeed it is conveniently provided that the abutment surface 50a of the abutment plate 50 lies separate from the cutting vertex 52 of the cutting group 30 according to a measurement not greater than 0.05 mm. It is thus possible to obtain a clean cutting of the tread band semifinished product 20c without determining mechanical interferences between the cutting group 30 and the abutment plate 50, to the benefit of the useful lifetime of the cutting edge 51a and the effectiveness of the ultrasonic vibrations transmitted to the cutting group 30.

Preferably, the action of the cutting group 30 is assisted by blocking devices 53 of the tread band semifinished product 20c with respect to the advancing plane P, operating in proximity to the abutment plate 50. These blocking devices 53 comprise at least one thrust plate configured for acting elastically against the tread band semifinished product 20c by a terminal edge thereof during the execution of the cutting.

More particularly, provision is preferably made for a first thrust plate 54a, and a second thrust plate 54b, operating respectively upstream and downstream of the cutting plane Q and selectively activatable in order to push the tread band semifinished product 20c and consequently exert an action of retention of the semifinished product itself, preferably against the abutment plate 50. Each of the first thrust plates 54a and second thrust plates 54b can be conveniently made in elastically deformable plate form, having a plurality of elastically deformable sheets 55 respectively parallel and distributed along the terminal edge thereof.

Before the action of the cutting group 30 on the tread band semifinished product 20c takes place, the first thrust plate 54a, and the second thrust plate 54b are adapted to be brought from a waiting position, in which they are spaced from the semifinished product itself, above it, as in figure 13, to a thrust position in which they operate against the tread band semifinished product 20c in order to delicately retain it against the abutment plate 50 as in figure 14. The tread band semifinished product 20c is therefore suitably stabilised against the abutment plate 50, and the cutting can be executed without causing undesired lateral movements of the semifinished product itself upon effect of the thrust transmitted by the blade 51.

Upon completed cutting, the first thrust plate 54a and the second thrust plate 54b can return to the waiting position and the abutment plate 50 is brought back to the rest position, so as to reposition, coplanar to the advancing plane P, the tail end B of the cut piece 21 and the new head end A created on the tread band semifinished product 20c that was just cut.

Analogous to that described above, the cut piece 21 is thus adapted to be made to advance towards the building drum 13 upon action of the preparation section 25 of the conveyor belt 23, in order to determine the winding of the tread band around the deposition surface 15 by the tread band application devices 19.

The cutting-to-size processing described above with particular reference to the carcass ply/plies 4, to the sidewall inserts 12, and to the tread band 6 can be conveniently actuated, in addition to or in substitution of at least one of such tyre components, on other components such as for example the liner 10, the elastomeric base 9, the reinforcements bead 11, and/or the protective band/bands 7, 8 optionally provided for in the structural scheme of the tyre 2. For each of these components provision is essentially made to arrange a respective semifinished product 20a, 20b, 20c, 20d in continuous strip form having structural, width and thickness characteristics corresponding to those of the respective tyre component, said semifinished product being subjected to the cutting-to-size processing before its application around the deposition surface 15 of the building drum 13. For the purpose of the processing of components applied in pairs, such as for example the sidewall reinforcements 12, provision can be made for the arrangement of a pair of sidewall reinforcement semifinished products and the simultaneous or independent execution of the cutting-to-size processing on the same, before the simultaneous or independent application of the obtained pieces.

Claims

1. Process for building tyres for bicycles, wherein a plurality of components of a tyre (2) being processed are deposited circumferentially around a deposition surface (15) carried by a building drum (13), wherein the process comprises: applying at least one carcass ply (4) around said deposition surface (15); applying a pair of bead cores (5) at a predetermined mutual axial distance around the carcass ply (4); turning up axially outer end flaps (4a) of the carcass ply (4) around the bead cores (5); applying a tread band (6) around the deposition surface (15), maintaining the mutual axial distance of the bead cores (5) substantially unchanged; wherein the deposition of at least one of said components is preceded by a cutting-to-size processing of a respective semifinished product (20a, 20b, 20c, 20d) in continuous strip form along a cutting line (L), in order to separate, from the semifinished product itself, a piece (21) having a predetermined cutting length; wherein the cutting-to-size processing comprises: positioning the semifinished product (20a, 20b, 20c, 20d) with a lower surface (SI) thereof in abutment against an advancing plane (P) defined by a conveyor belt (23) comprising a feeding section (24) and a preparation section (25) that are consecutively aligned; longitudinally advancing the semifinished product (20a, 20b, 20c, 20d) along the advancing plane (P) and above an abutment plate (50) interposed between the feeding section (24) and the preparation section (25); stopping the advancement of the semifinished product (20a, 20b, 20c, 20d) with respect to a cutting plane (Q) containing the cutting line (L) and intersecting the advancing plane (P) at the abutment plate (50), when a head end (A) of the semifinished product (20a, 20b, 20c, 20d) is spaced from the cutting plane (Q) according to a measurement equal to said cutting length; lifting, with respect to the advancing plane (P), the abutment plate (50) and a cutting section (T) of the semifinished product (20a, 20b, 20c, 20d) arranged thereon; translating a cutting member (51) transverse to the semifinished product (20a, 20b, 20c, 20d) in order to cut the latter along the cutting line (L); repositioning, coplanar with the advancing plane (P), the abutment plate (50), carrying a tail end (B) of the cut piece (21) and a head end (A) of the cut semifinished product (20a, 20b, 20c, 20d).

2. Process according to claim 1, wherein the cutting member (51) translates from a starting position and an arrival position during the cutting of the semifinished product (20a, 20b, 20c, 20d) and is brought back into the starting position after the repositioning of the abutment plate (50).

3. Process according to claim 1 or 2, wherein during the translation of the cutting member (51) a cutting edge (51a) of the cutting member (51) transmits, to the semifinished product (20a, 20b, 20c, 20d), a thrust component directed towards the abutment plate (50). 4. Process according to one or more of the preceding claims, also comprising transmitting ultrasonic frequency vibrations to the cutting member (51) while the semifinished product (20a, 20b, 20c, 20d) is transversely cut.

5. Process according to one or more of the preceding claims, wherein the translation of the cutting member (51) occurs in the absence of a direct contact thereof against the abutment plate (50).

6. Process according to one or more of the preceding claims, wherein during the translation of the cutting member (51), an abutment surface (50a) of the abutment plate (50) is spaced from a cutting edge (51a) of the cutting member (51) according to a measurement not greater than 0.1 mm.

7. Process according to one or more of the preceding claims, wherein the cutting plane (Q) intersects the advancing plane (P) according to a tilted orientation defining, with respect to the advancing plane (P), a first acute angle (01) with vertex directed towards the building drum (13).

8. Process according to one or more of the preceding claims, wherein during the execution of the cutting, an action of blocking of the semifinished product (20a, 20b, 20c, 20d) is executed with respect to the advancing plane (P).

9. Process according to one or more of the preceding claims, wherein the action of blocking is executed upstream and downstream of the cutting plane (Q), with reference to the advancement of the semifinished product (20a, 20b, 20c, 20d).

10. Process according to one or more of the preceding claims, wherein the action of blocking is exerted against the abutment plate (50). 11. Process according to one or more of the preceding claims, wherein the deposition of said tread band (6) comprises: arranging a tread band semifinished product (20c) in continuous strip form; subjecting the tread band semifinished product (20c) to said cutting-to-size processing.

12. Process according to claim 11, wherein the tread band semifinished product (20c) has thickness comprised between 1 mm and 8 mm.

13. Process according to one or more of the preceding claims, wherein said components also comprise an elastomeric base (9) circumferentially arranged around the deposition surface (15) before depositing the tread band (6).

14. Process according to claim 13, wherein the deposition of said elastomeric base (9) comprises: arranging a elastomeric base semifinished product in continuous strip form; subjecting the elastomeric base semifinished product to said cutting-to-size processing.

15. Process according to claim 14, wherein the elastomeric base semifinished product (9) has thickness comprised between 0.5 mm and 1.5 mm.

16. Apparatus for building tyres for bicycles, comprising: a building drum (13); a deposition group (14) configured for depositing a plurality of components circumferentially around a deposition surface (15) carried by the building drum (13); wherein said deposition group (14) comprises: carcass ply application devices (16) configured for applying at least one carcass ply (4) around the deposition surface (15); devices for applying a pair of bead cores (5) at a predetermined mutual axial distance around the carcass ply (4); turning up devices (13a) configured for turning up axially outer end flaps (4a) of the carcass ply (4) around the bead cores (5); tread band application devices (19) configured for applying a tread band (6) around the deposition surface (15), in axially centred position between the bead cores (5) arranged according to said predetermined mutual axial distance; wherein the deposition group (14) comprises at least one preparation unit (22a, 22b, 22c, 22d) configured for transversely cutting-to-size a semifinished product (20a, 20b, 20c, 20d) in continuous strip form along a cutting line (L) in order to separate, from the semifinished product itself, a piece (21) having a predetermined cutting length; wherein the preparation unit (22a, 22b, 22c, 22d) comprises: a conveyor belt (23) comprising a feeding section (24) and a preparation section (25) that are consecutively aligned according to an advancing plane (P) transverse to a cutting plane (Q) containing the cutting line (L), and configured for supporting the semifinished product (20a, 20b, 20c, 20d) in abutment with a lower surface (SI) thereof against the advancing plane itself; devices (31) for controlling the conveyor belt (23), configured for longitudinally advancing the semifinished product (20a, 20b, 20c, 20d) along the advancing plane (P) and stopping the advancement of the semifinished product (20a, 20b, 20c, 20d) when a head end (A) of the semifinished product (20a, 20b, 20c, 20d) is spaced with respect to the cutting plane (Q) according to the measurement equal to said cutting length; an abutment plate (50) interposed between the feeding section (24) and the preparation section (25) of the conveyor at the cutting plane (Q), and movable between a rest position in which it is substantially coplanar with the advancing plane (P) and a work position in which it is lifted with respect to the advancing plane (P) in order to lift, with respect to the advancing plane (P), a cutting section (T) of the semifinished product (20a, 20b, 20c, 20d) traversed by the cutting plane (Q); a cutting member (51) movable transverse to the semifinished product (20a, 20b, 20c, 20d) in order to cut the latter along the cutting line (L).

17. Apparatus according to claim 16, wherein the cutting member (51) is movable along the cutting line (L) from a starting position to an arrival position, wherein the abutment plate (50) is configured for being positioned in the rest position before the return of the cutting member (51) to the starting position.

18. Apparatus according to claim 17 or 18, wherein the preparation unit (22a, 22b, 22c, 22d) also comprises an ultrasonic transducer (43) operating on the cutting member (51) in order to transmit, to the latter, an ultrasonic frequency vibration.

19. Apparatus according to one or more of the claims from 16 to 18, wherein the cutting member comprises a blade (51) movable along the cutting direction.

20. Apparatus according to claim 19, wherein the blade (51) has a tilted orientation defining, with respect to the advancing plane (P), a first acute angle (Pl) with vertex directed towards the preparation section (25).

21. Apparatus according to one or more of the claims from 16 to 20, wherein a cutting edge (51a) of the cutting member

(51) lies in the cutting plane (Q) according to an orientation that is tilted with respect to the cutting line (L).

22. Apparatus according to claim 21, wherein the cutting edge (51a) forms, in the cutting plane (Q) and with respect to the advancing plane (P), a second acute angle (02) with vertex directed towards said starting position.

23. Apparatus according to claim 21 or 22, wherein the cutting edge (51a) forms, parallel to the advancing plane (P), a third acute angle (03) with vertex directed towards said starting position.

24. Apparatus according to one or more of the claims from 16 to 23, wherein the cutting member (51) has a cutting vertex

(52) directed towards the abutment plate (50) and configured for operating through the semifinished product (20a, 20b, 20c, 20d), in the absence of direct contact against the abutment plate (50) itself.

25. Apparatus according to claim 24, wherein the cutting vertex (52) is configured for operating through the semifinished product (20a, 20b, 20c, 20d) with said lower surface (SI) in contact against an abutment surface (50a) of the abutment plate (50), the abutment surface (50a) being spaced from the cutting vertex (52) according to a measure not greater than 0.1 mm.

26. Apparatus according to one or more of the claims from 16 to 25, also comprising devices (53) for blocking the semifinished product (20a, 20b, 20c, 20d) with respect to the advancing plane (P), operating in proximity to the abutment plate (50).

27. Apparatus according to claim 26, wherein said blocking devices (53) are configured for pushing the semifinished product (20a, 20b, 20c, 20d) against the abutment plate (50).

28. Apparatus according to claim 26 or 27 wherein said blocking devices (53) comprise at least one thrust plate (54a, 54b) configured for acting elastically against the semifinished product (20a, 20b, 20c, 20d) by a terminal edge thereof. 29. Apparatus according to claim 28, wherein the thrust plate (54a, 54b) is attained in elastically deformable plate form.

30. Apparatus according to claim 28 or 29, wherein the thrust plate (54a, 54b) has a plurality of elastically deformable sheets (55) respectively parallel and distributed along the terminal edge.