Expandable drum for shaping pneumatic tires that comprises a parallelogram-type expander device for retaining the bead wire

A drum (1) for manufacturing a pneumatic tire (2) is provided with a plurality of clamping jaws (12) mounted so as to be movable between a retracted configuration and a deployed configuration which allows the clamping jaws (12) to engage with a bead wire (3) of the tire (2), the clamping jaws (12) being placed, to this end, under the control of a deployment system (13) which comprises an articulated parallelogram (20) having a first, fixed base (25) secured to a shaft (11) and a second, mobile base (26) secured to a clamping jaw (12), and a drive mechanism (30) designed to cooperate with the articulated parallelogram (20) so that it is possible to select and modify the radial position (d26) of the mobile base (26) with respect to the fixed base (25) in order to pass from the retracted configuration to the deployed configuration and vice versa.

BACKGROUND

The present invention relates to the manufacture of pneumatic tyres, in particular pneumatic tyres for heavy-duty vehicles, and more particularly to the field of expansion drums designed to shape the carcass of the pneumatic tyre.

Generally, the carcass of the tyre is produced “flat”, meaning by disposing the various constituents thereof on the circular-base cylindrical surface of a drum. Bead wires, that is to say reinforcing bands, which are generally metallic, are then fitted on this carcass, said bead wires being intended to be integrated into the structure of the bottom region of the pneumatic tyre to make it possible to attach said pneumatic tyre to a rim and retain it thereon.

To subsequently shape the carcass, so as to give said carcass a domed, substantially toric, shape, the drum effects expansion of the central part of the carcass, by inflation or by radial deployment of plates known as “expansion tiles”, and moves the bead wires of the tyre axially towards one another.

The drum is also designed to hold the carcass while a crown block is being secured to the carcass thus shaped, said crown block comprising in particular the tread and one or more reinforcing plies, and while roller-pressing is carried out to expel air and ensure perfect cohesion between said crown block and the carcass.

In order for the bead wires to be held firmly during these operations of shaping the carcass and then of roller-pressing, it is known to use radial clamping devices which comprise a plurality of clamping jaws, said jaws being distributed around the central axis of the drum and mounted so as to be radially movable between a retracted position, close to the axis, which makes it possible to fit the bead wire, loosely, on the drum, and a deployed position in which said jaws engage with the inside diameter of said bead wire in order to exert a centrifugal clamping force on said bead wire.

In order to effect the radial deployment of the clamping jaws, it is in particular known, for example from the document WO-2005/118270, to use wedges that have a bearing surface, known as a “slope”, which is inclined with respect to the central axis, said slope cooperating with a complementary slope provided on the jaw in question. By moving the wedges in translation parallel to the central axis of the drum, for example by means of a pneumatic cylinder, it is thus possible to gradually move the jaws away from the central axis.

In spite of their undeniable robustness, such deployment systems can have a number of drawbacks, however.

Specifically, such deployment systems having wedges are relatively bulky, and need to be positioned axially in the immediate vicinity of the jaws, as close as possible to the region known as the “central region” of the drum, which is comprised axially between the two bead wires and occupied by the carcass intended to be deployed.

However, there is little available space in said central region, which also needs to accommodate the set of plates, known as “expansion tiles”, which are distributed around the circumference of the drum and which are intended to be deployed radially, against the radially inner surface of the carcass, in order to push back said radially inner surface of the carcass so as to shape the latter.

It is all the more difficult to reconcile these imperatives associated with the bulk of the various systems equipping the drum since it is necessary to confer relatively large dimensions on the constituent members of the deployment system, such that said deployment system is capable of generating and supporting significant axial forces, and of converting these axial forces into a centrifugal radial force which has a sufficiently high intensity to prevent, in particular when the carcass is subjected to the roller-pressing operation, any sliding of the constituent elements of said carcass which are situated, and therefore compressed, between the jaw and the bead wire, as is the case in particular for the carcass ply.

Moreover, if the pressure supplying the cylinders actuating the wedges is released, some known deployment systems may sag, and this may have a negative effect on the process of manufacturing the pneumatic tyre, and on the safety of the operator, in particular if pneumatic tyres having large dimensions are being produced, such as tyres intended for heavy-duty vehicles or construction plant vehicles, these therefore integrating particularly large and heavy bead wires.

Next, in spite of the presence of a slope, or even of several successive slopes having different inclinations, it is sometimes difficult to control the intensity and progressive nature of the deployment force that is exerted by means of the wedges against the bead wire and the underlying carcass ply, and this may complicate the control of the drum.

Lastly, to limit wear on the wedges and maintain the quality and precision of the deployment system, it is necessary to make specific provisions with regard to the surface states of the slopes, and to provide suitable lubrication.

The objects assigned to the invention therefore seek to overcome the abovementioned drawbacks and to propose a novel expandable drum which has a clamping device that is not very bulky, performs well, is simple and safe.

SUMMARY

The objects assigned to the invention are achieved by means of a drum intended for manufacturing a pneumatic tyre comprising at least one annular bead wire, said drum having a central axis Z1and being provided with a clamping device which comprises a shaft fitted along the central axis Z1, said shaft bearing a plurality of clamping jaws which are distributed in several angular sectors about said central axis Z1and which are placed under the control of a deployment system which makes it possible to modify the radial distance of said clamping jaws with respect to the central axis Z1such that said clamping jaws define an expandable seat that the deployment system moves alternately from a retracted configuration, in which said expandable seat occupies a first diameter known as the “resting diameter”, which is less than the inside diameter of the bead wire, to a deployed configuration, in which the clamping jaws are radially further away from the central axis Z1than in the retracted configuration, such that the expandable seat extends over a second diameter known as the “clamping diameter”, which is greater than the resting diameter and which allows said expandable seat to engage against the inside diameter of the bead wire and to exert a centrifugal clamping force on said bead wire, said drum being characterized in that the deployment system comprises an articulated parallelogram, the four apexes of which respectively form a first, a second, a third and a fourth pivot, the first pivot and the second pivot being secured to the shaft and positioned respectively at a first radial distance from the central axis Z1and at a second radial distance from the central axis Z1, greater than the first radial distance, so as to define a first base known as the “fixed base” of the articulated parallelogram which extends transversely to the central axis Z1, while the third pivot and the fourth pivot are secured to a clamping jaw and define a second base known as the “mobile base” of the articulated parallelogram, which is kept parallel to the fixed base by a first arm which connects the first pivot to the third pivot so as to define a first side of the articulated parallelogram, and by a second arm which connects the second pivot to the fourth pivot so as to define a second side of the articulated parallelogram, parallel to the first side, and in that the deployment system comprises a drive mechanism designed to cooperate with the articulated parallelogram so that it is possible to select and modify the radial position of the mobile base with respect to the fixed base in order to pass from the retracted configuration to the deployed configuration and vice versa.

Advantageously, the use of a structure having an articulated parallelogram makes it possible, by virtue of the length of the first arm and second arm, to relocate a part of the deployment system, and more particularly the fixed base of the parallelogram and the portion of the shaft that supports said fixed base and ensures the anchoring thereof at an axial distance from the central region of the drum.

The invention therefore advantageously makes it possible to free up the space in said central region, while providing the deployment system, at a distance from said central region, with secure anchoring which ensures in particular good absorption of the axial forces that are exerted within said deployment system.

Moreover, such an articulated structure reduces the risks of seizing, and limits the needs for material for lubricating or finishing the surfaces of the moving members in question.

In addition, as will be shown below, the use of an articulated parallelogram makes it possible to fit a particularly progressive and powerful drive mechanism, which makes it possible to exert a high-intensity but finely controlled centrifugal radial force on the bead wire.

Similarly, this geometry in the form of a parallelogram is favourable to the fitting of a simple non-return mechanism, which ensures the absence of accidental sagging of the deployment system and of the seat in the event of the energy supply of said deployment system being interrupted or failing.

DETAILED DESCRIPTION

The present invention relates to a drum1intended for manufacturing a tyre2. Said tyre2is preferably a pneumatic tyre2and may be categorized as a pneumatic tyre in the following text.

In a manner known per se, such a tyre2comprises at least one annular bead wire3.

Such a bead wire3is intended to reinforce the part known as the “bottom region” of the tyre2, which makes it possible to attach the tyre to a rim.

The bead wire3forms a circular ring, which is closed on itself about a central axis, known as the “bead-wire central axis” Z3.

D3_in denotes the inside diameter of the bead wire3at rest, in the absence of external stresses that would tend to deform said bead wire by ovalization, twisting, circumferential extension, etc.

Furthermore, the term “mean line” L3could be used to denote the curved line closed on itself, in this case preferably a circular line, which is made up of all of the centres of the cross sections of the bead wire3as considered along said bead wire3, about the central axis Z3of said bead wire.

In a manner known per se, the bead wire3is preferably formed from one or more wires made of a material chosen for its mechanical strength, for example a metal material or a composite material.

The wire(s) may optionally be coated in rubber, individually or as a whole.

According to one possible embodiment, the constituent wires of the bead wire3may be wound in a helix about the mean line L3so as to be interwoven to form a braided torus centred on the bead-wire central axis Z3.

According to another possible embodiment, the wires could be arranged in juxtaposed contiguous turns which are normal to the central axis Z3of the bead wire and which each form a loop about said central axis Z3, as a result each having a diameter equal to or greater than the inside diameter D3_in of the bead wire3.

Preferably, as can be seen inFIGS.1and2, the tyre2comprises two annular bead wires3, namely a first bead wire3_1and a second bead wire3_2, which are disposed on either side of the equatorial plane P_EQ of said tyre2.

By convention, the “central region”1C of the drum1will denote the region of the space which is comprised axially, along the central axis Z1of the drum, between the first bead wire3_1and the second bead wire3_2and which therefore contains, inter alia, the equatorial plane P_EQ of the tyre.

In a manner known per se, the tyre2also comprises a carcass4.

Said carcass4comprises, in a manner known per se, and as can be seen inFIGS.1and2, a carcass ply5which extends from the first bead wire3_1to the second bead wire3_2.

Moreover, the radially inner face of the carcass ply5is preferably covered with a layer of rubber, known as the inner liner6, which is impermeable to the fluid, typically air, used for inflating the pneumatic tyre2.

The tyre2also comprises a crown block7, which has a tread8and reinforcing plies9A,9B provided with mutually parallel reinforcing threads.

Typically, the tyre2could comprise a superposition of at least two reinforcing plies9A,9B referred to as “crossed”, meaning that the reinforcing threads of the first reinforcing ply9A are disposed, with respect to the equatorial line L_EQ of the tyre2, at an angle, known as the “first-ply angle”, which has a sign opposite to the sign of the angle, known as the “second-ply angle”, formed by the reinforcing threads of the second reinforcing ply9B with respect to this same equatorial line L_EQ, such that the threads of the first reinforcing ply9A cross the threads of the second reinforcing ply9B.

As can be seen inFIGS.1to4, the drum1has a central axis Z1.

Said central axis Z1is preferably horizontal, in particular so as to make it easier to fit the constituent members of the tyre2and to handle said tyre2, and to avoid, during the operation of shaping the tyre2, any tendency of the tyre2to deform unevenly, owing to gravity.

The drum1is also provided with a clamping device10.

This clamping device10makes it possible to firmly hold the bead wire3, and the radially underlying carcass ply5, in the desired position during the shaping of the carcass4and then during the operation of fixing the crown block7to said carcass4.

Said step of fixing the crown block7to the carcass4preferably comprises a roller-pressing operation, during which a roller is used to press the crown block7, in particular the shoulders7S of said crown block, onto the carcass4, from the outside of the tyre2, in order to improve the cohesion of the tyre2.

The clamping device10comprises a shaft11, which is preferably cylindrical, and more particularly cylindrical with a circular base, which is fitted on the central axis Z1of the drum, and more preferably centred on said central axis Z1.

As illustrated inFIGS.1to4, said shaft11carries a plurality of clamping jaws12which are distributed in several angular sectors about the central axis Z1and are placed under the control of a deployment system13which makes it possible to modify the radial distance of said clamping jaws12with respect to the central axis Z1.

As a result, said clamping jaws12define an expandable seat14that the deployment system13moves alternately from a retracted configuration, in which said expandable seat14occupies a first diameter known as the “resting diameter” D14_rest, which is less than the inside diameter D3_in of the bead wire3, as illustrated inFIGS.1and3, to a deployed configuration, in which the clamping jaws12are radially further away from the central axis Z1than in the retracted configuration, such that the expandable seat14extends over a second diameter known as the “clamping diameter” D14_clamp, which is greater than the resting diameter D14_rest and which allows said expandable seat14to engage against the inside diameter D3_in of the bead wire3and to exert a centrifugal clamping force F_clamp on said bead wire3, as illustrated inFIGS.2and4.

Of course, the deployment system13will be arranged to as to be able, reciprocally, to return the seat14from its deployed configuration to its retracted configuration, in particular to allow the operator to withdraw the tyre2, preferably an uncured tyre2(that is to say a non-vulcanized tyre), obtained after shaping and roller-pressing, from the drum1, in order for example to then be able to transfer said uncured tyre2into a curing mould.

For the convenience of the description, reference could be made to the retracted configuration and to the deployed configuration both for the drum1as a whole and for all or some of the elements of said drum1that are involved in the changes of configuration, these including in particular the expandable seat14, the clamping jaws12, or all or part of the deployment system13.

The resting diameter D14_rest that the seat14adopts in the retracted configuration is chosen to be sufficiently smaller than the inside diameter D3_in of the bead wire3first and foremost to allow an operator (this operator either being the rest of an automated robot or a human, optionally assisted by mechanical handling means) to axially fit the bead wire3on the drum1, until said bead wire3is brought, in a loose state, into the desired axial position, with respect to the carcass ply5, along the central axis Z1, before the operation of shaping the carcass4, and then to release the bead wire3and more generally the tyre2, after the operations of shaping the carcass4and fixing the crown block7, in order to allow the operator to withdraw the shaped tyre2from the drum1.

In practice, the resting diameter D14_rest of the seat14will therefore be strictly less than the inside diameter D2_in of the tyre2at rest, that is to say than the diameter of the cylindrical empty space which is situated at the centre of the tyre2and which is delimited radially by said tyre2, and encircled by the bead wire3, in the axial position of the bead wire3in question.

Geometrically, the inside diameter D2_in of the tyre will correspond to the diameter of the free passage section, the circumference of which is delimited by the tyre2, about the central axis Z1, such that this diameter D2_in is considered in a plane normal to the central axis Z1and containing the mean line L3of the bead wire3in question. In practice, the inside diameter D2_in of the tyre corresponds preferably to the narrowest passage section of said tyre2.

It will therefore be noted that, strictly speaking, as can be seen inFIG.1, the inside diameter D2_in of the tyre is strictly less than the inside diameter D3_in of the bead wire3, considered at rest in the absence of tensile elongation of said bead wire3, in as much as said inside diameter D2_in of the tyre likewise depends on the radial thickness of the intermediate layer(s) making up the bottom region2B of said tyre2, which are disposed radially beneath the bead wire3, between the bead wire3and the central axis Z1, and which include in particular the layer formed by the carcass ply5and, if necessary, one or more thicknesses of rubber forming a protective bead around the section of the bead wire3.

However, for the simple convenience of the description, and given the relatively small thickness of these intermediate layers with regard to the inside diameter D3_in of the bead wire3, the inside diameter D2_in of the tyre2could, to a first approximation, be equated in the following text to the inside diameter D3_in of the bead wire.

It will also be noted that, in the deployed configuration, the central axis Z3of the bead wire3coincides preferably with axis the central axis Z1of the drum1.

In the deployed configuration, the clamping diameter D14_clamp of the seat14will of course be chosen so as to generate, on the bead wire3, a sufficient clamping force F_clamp to immobilize the bead wire3with respect to said seat14, and in particular to prevent said bead wire3, and the underlying carcass ply5, from sliding with respect to said seat14along the central axis Z1, during the operations of shaping the carcass4and then fixing the crown block7, and more particularly during the operation of roller-pressing.

It will be noted in this regard that, on account of its intrinsic stiffness, the bead wire3may be considered to be substantially inextensible under circumferential tension along its mean line L3. It is therefore possible to generate a very high centrifugal clamping force F_clamp without otherwise having to extend the circumference of the bead wire3, which therefore, when it is subjected to the clamping force F_clamp, preserves more or less the same inside diameter as the diameter D3_in that it occupied at rest.

In practice, the clamping diameter D14_clamp of the seat14in the deployed configuration is preferably substantially equal to the inside diameter D3_in of the bead wire at rest, taking into account, where appropriate, both interposed thicknesses of rubber and of the carcass ply5, which are situated radially between the bead wire3and the seat14, and the degree of elastic compression of these thicknesses under the clamping force F_clamp.

For the reasons already set out above, it may therefore be considered that the clamping diameter D14_clamp may be equated, for the convenience of the description, to the inside diameter D3_in of the bead wire.

Of course, given the azimuthal distribution of the clamping jaws12about the central axis Z1, the clamping force F_clamp exerted on the bead wire3by the seat14in the deployed configuration is advantageously distributed on either side of the central axis Z1, around the interior circumference of the bead wire3.

In other words, the clamping force F_clamp is multidirectional, in that it is exerted centrifugally in a plurality of radial directions that are distributed, in terms of azimuth about the central axis Z1, within an angular sector which covers overall more than 180 degrees about said central axis Z1.

Thus, in each radial direction considered in terms of azimuth about the central axis Z1, the clamping force F_clamp will result in a first force component oriented in a first direction, which acts on a first sector of the bead wire3, and a second component of opposite sign, which acts on a second sector of the bead wire3diametrically opposite the first sector with respect to the central axis Z3of the bead wire, and which thus balances the first component so as to keep the bead wire3in a constant radial position with respect to the central axis Z1of the drum1.

Such a centrifugal, multidirectional clamping force F_clamp advantageously provides, in the deployed configuration, balanced and relatively uniform clamping, and a self-centring effect of the bead wire3on the central axis Z1of the drum1.

The keeping of the bead wire3on the seat14, and more generally with respect to the drum1, is therefore particularly solid and stable, both axially and radially.

Preferably, the clamping jaws12will be distributed evenly about the central axis Z1, on the circumference of the shaft11, such that the clamping device10will not vary when rotated by approximately N about the central axis Z1, N being the whole number of clamping jaws12.

Preferably, the clamping jaws12are provided, on their radially outer face, as can be seen inFIGS.1to4, with a circumferential housing15, preferably in the form of a V-shaped slot.

Preferably, this circumferential housing15defines the seat14for receiving the bead wire3.

The recessed shape of the circumferential housing15advantageously provides a stable hold, both radially and axially, of the bead wire3within the clamping jaw(s)12in question.

Preferably, a banding strip16, made of elastomer material, will be fitted in the circumferential housing15of the clamping jaws12.

The banding strip16rests against each clamping jaw12by way of its radially inner face16_in, while the radially outer face16_out of said banding strip16then forms the seat14on which the tyre2and the bead wire3come to rest.

Said banding strip16advantageously forms a continuous annular band that is closed about the central axis Z1.

The banding strip16thus creates bridges that ensure continuity of the seat14over the outer perimeter of each clamping jaw12and between the clamping jaws12, thereby making it possible to smooth the circumference of the seat14in spite of the angular division of the clamping jaws12. The seat14thus affords, in the deployed configuration, continuous annular support for the tyre2and the bead wire3.

The passage into the deployed configuration allows the radially outer surface16_out of the banding strip, and therefore more generally the seat14, to hug the interior of the bead wire3around the entire perimeter of said bead wire3. Conversely, in the deployed configuration, the bead wire3therefore rests around the entire circumference of said seat14.

Advantageously, the banding strip16may, by virtue of its intrinsic elasticity, elastically accommodate, by circumferential extension and therefore by adaptation of its diameter, the variations in the diameter D14of the seat14during the passage from the retracted configuration to the deployed configuration, and vice versa.

Moreover, this elasticity of the banding strip16makes it possible, in the manner of a cushion, to adapt and homogenize the centrifugal radial compressive force that the seat14exerts on the bead wire3and the intermediate layers, in particular the carcass ply5, thereby ensuring a relatively flexible hold of the bead wire3and more generally of the tyre2, and therefore avoiding localized damage to the tyre2being caused by an excessive stress concentration.

Furthermore, the elastic stress, of the centripetal constriction type, that the banding strip16exerts on the clamping jaws12advantageously brings about an effect of cohesion and self-centring of the clamping jaws12as a whole with respect to the central axis Z1, and also generates a return force which makes it easier for said clamping jaws12, and the deployment system13, to return from the deployed configuration to the retracted configuration.

According to one embodiment variant, which may be implemented in particular if the drum1does not have a banding strip16, provision could be made, in order to exert a self-centring force for returning each clamping jaw12to the retracted configuration, of an annular return spring, which could for example be housed in an annular attachment groove18that is provided in said clamping jaw12, centred on the central axis Z1, and separate from the circumferential housing15forming the seat14, as can be seen inFIGS.3and4.

It will be noted that the clamping device1is preferably dimensioned such that the banding strip16and/or, respectively, the annular return spring housed in the attachment groove18, is already preloaded, under elastic circumferential tension, when the clamping device10is in the retracted configuration, and that the intensity of this tensile stress increases when passing from the retracted configuration to the deployed configuration.

By permanently keeping the banding strip16, and/or, respectively, the annular return spring, under tension, and therefore not in a loose state, a situation is avoided in particular in which said banding strip16, or, respectively, said return spring, does not slip out of the circumferential housing15, or, respectively, out of the attachment groove18, of the clamping jaws12.

Of course, the banding strip16could have any appropriate sectional shape.

Preferably, said banding strip16could be arranged so as to have an annular groove17forming the seat14, which makes it possible to receive the bead wire3.

Advantageously, the radially outer face16_out of the banding strip16will thus have a recessed seat14profile, which will form a stable receptacle for the bead wire3.

According to the invention, the deployment system13comprises an articulated parallelogram20, the four apexes of which respectively form a first pivot21, a second pivot22, a third pivot23and a fourth pivot24.

The respective axes of rotation of these four pivots are preferably mutually parallel, and preferably disposed perpendicularly to a reference plane, known as the “sagittal plane” PS, which contains the central axis Z1and which thus preferably divides the drum1into two parts that are substantially if not exactly symmetric to one another.

This sagittal plane PS corresponds here to the section plane used forFIGS.1,2,3and4.

Among other advantages, a structure in the form of an articulated parallelogram20is very simple, undeniably lightweight, and relatively compact with regard to the amplitude of the movements allowed by such a structure.

As can be seen clearly inFIGS.3and4, the first pivot21and the second pivot22are secured to the shaft11and positioned respectively at a first radial distance d21from the central axis Z1and at a second radial distance d22from the central axis Z1, said second radial distance d22being greater than the first radial distance d21, so as to define a first base25known as the “fixed base”25of the articulated parallelogram20, said fixed base25extending transversely to the central axis Z1, while the third pivot23and the fourth pivot24are secured to a corresponding clamping jaw12and define a second base26known as the “mobile base”26of the articulated parallelogram20.

It will be noted that, within the fixed base25, the first pivot21is, and remains (whether in the retracted configuration, in the deployed configuration, during the passage from the retracted configuration to the deployed configuration, or vice versa), closer to the central axis Z1than the second pivot22. Similarly, within the mobile base26, the third pivot23is, and remains, radially closer to the central axis Z1than the fourth pivot24, in the retracted configuration, in the deployed configuration, or during the passage from one of these configurations to the other.

The mobile base26is kept parallel to the fixed base25by a first arm27which connects the first pivot21to the third pivot23so as to define a first side27A of the articulated parallelogram20, and by a second arm28which connects the second pivot22to the fourth pivot24so as to define a second side28A of the articulated parallelogram20, parallel to the first side27A.

The “first side”27A denotes here, regardless otherwise of the shape of the first arm27that is used to materially connect the first pivot21to the second pivot23, the straight-line segment which, geometrically, joins the first pivot21to the third pivot23, and more particularly the straight-line segment that is perpendicular to and intersects the axes of the first pivot21and of the third pivot23and which thus joins, in the sagittal plane PS, the centre of rotation of the first pivot21to the centre of rotation of the third pivot23, that is to say which joins the first apex of the articulated parallelogram20to the third apex of the articulated parallelogram20.

Similarly, the “second side”28A denotes, mutatis mutandis, the straight-line segment which geometrically joins the second apex of the articulated parallelogram20, and therefore the centre of rotation of the second pivot22, to the fourth apex of the articulated parallelogram20formed by the centre of rotation of the fourth pivot24.

It will be noted that the shape of the first arm27, or, respectively, the shape of the second arm28, may vary without departing from the scope of the invention.

This being the case, by simplicity of construction, the first arm27and the second arm28will preferably be straight, and therefore mutually parallel, so as to coincide with the first side27A, and, respectively, with the second side28A, at least in the abovementioned sagittal plane PS, as is illustrated inFIGS.1,2,3and4.

On account of the arrangement in the form of a parallelogram, the length of the fixed base25, which is equal to the centre-to-centre spacing between the first pivot21and the second pivot22, is equal to the length of the mobile base26, which corresponds for its part to the centre-to-centre spacing between the third pivot23and the fourth pivot24.

Similarly, the length of the first side27A defined by the first arm27, which is equal to the centre-to-centre spacing between the first pivot21and the third pivot23, is also equal to the length of the second side28A which corresponds to the centre-to-centre spacing between the second pivot22and the fourth pivot24.

By way of indication, the length of said first side27A and second side28A, which depends in particular on the permitted size of the drum1and on the diameter of the portion known as the “seat” of the bottom region2B of the tyre2, which is intended to rest on the rim, may be between 120 mm and 200 mm, preferably between 140 mm and 180 mm, and for example equal to 152 mm.

The arrangement of the articulated parallelogram20according to the invention, with a fixed base25which extends transversely to the central axis Z1, or perpendicularly to said central axis Z1, advantageously makes it possible to position the fixed part of said articulated parallelogram20, namely the fixed base25secured to the shaft11, at an axial distance from the mobile base26, and therefore at an axial distance from the clamping jaws12and from the central region1C of the drum, and to keep said fixed base25at an axial distance from said clamping jaws12and from the central region1C of the drum during the passage from the retracted configuration to the deployed configuration.

Thus, a significant part of the volume occupied by the deployment system13is situated outside the central region1C of the drum1.

According to a preferred arrangement of the invention, the length of the fixed base25, that is to say the centre-to-centre spacing between the first pivot21and the second pivot22, is strictly less than the length of the first side27A, that is to say the centre-to-centre spacing between the first pivot21and the third pivot23.

In other words, the first and second bases25,26preferably form the short sides of the articulated parallelogram20, while the first and second arms27,28define the long sides of said articulated parallelogram20.

Such an arrangement makes it possible to minimize the radial size of the deployment system13, while favouring the axial offset of the fixed base25with respect to the mobile base26which carries the clamping jaw12, since the distance of said axial offset depends on the length chosen for the first side27A.

Preferably, the fixed base25extends in a plane substantially normal to the central axis Z1of the drum1, for example forming an angle of between −5 degrees and +5 degrees with respect to the plane normal to said central axis Z1, and particularly preferably in a plane exactly normal to said central axis Z1.

In addition to the fact that such a transverse, or radial, orientation of the fixed base25, and therefore of the mobile base26which is parallel to the latter, helps to free up the central region1C of the drum, as indicated above, such an arrangement makes it possible to move the clamping jaw12along a path that is substantially radial with respect to the shaft11during the passage from the retracted configuration to the deployed configuration, and makes it easier to generate a clamping force F_clamp comprising a centrifugal component, perpendicular to the central axis Z1, which has a high strength.

Furthermore, preferably, the inclination angle A27formed, with respect to the central axis Z1, by the first side27A of the articulated parallelogram20, which joins the first pivot21to the third pivot23, remains between −15 degrees and +15 degrees, preferably between −10 degrees and +6 degrees, during the passage from the retracted configuration to the deployed configuration and vice versa.

It will of course be the same for the inclination angle, which is identical given the parallelism, formed by the second side28A with respect to the central axis Z1.

By convention, the inclination angle A27could be measured between the central axis Z1and the first side27A, or, respectively, the second side28A, in the sagittal plane PS which is normal to the respective axes of rotation of the pivots21,23connected by said side27A, and which contains the central axis Z1.

The inclination angle A27will, by convention, be counted as negative when the first arm27tilts in a convergent manner towards the central axis Z1, that is to say gets closer to said central axis Z1with increasing distance from the first pivot21towards the third pivot23and the central region1C of the drum, such that said first arm27follows a downward slope, as can be seen inFIGS.1and3, and, by contrast, the inclination angle A27will, by convention, be counted as positive when the first arm27diverges from the central axis Z1as it gets progressively further away from said central axis Z1with increasing distance from the first pivot21towards the third pivot23and the central region1C, such that said first arm27follows an upward slope, as can be seen in particular inFIG.4.

Advantageously, by disposing and confining the first side27A, and therefore in this case the first arm27, and consequently likewise the second side28A parallel to said first side27A, in a substantially axial orientation, more or less parallel to the central axis Z1of the drum, it is possible:both to move the fixed base25axially away from the mobile base26and therefore from the central region1C of the drum1, by an offsetting distance which is more or less equal to the length of the first side27A, such that full advantage is taken of the length of the first arm27to realize this axial offset,and to keep the undesired axial displacement of the mobile base26with respect to the shaft11, during the pendular pitching movement of the first and second arms27,28, which allows the passage from the retracted configuration to the deployed configuration, below a predetermined tolerance threshold, for example fixed at 0.5 mm (five tenths of a millimetre).

As regards this last point, it will specifically be noted that, ideally, it is desired for the movement of the clamping jaws12that is necessary on passing from the retracted configuration to the deployed configuration not to have a negative effect, or at the very least not to have a significant negative effect, on the axial position of the bead wire3with respect to the shaft11, in particular such that the clamping operation does not cause any deformation or destabilization of the constituent elements of the carcass4. In this regard, a movement of the clamping jaws12that is as perpendicular as possible with respect to the central axis Z1, and therefore virtually radial or strictly radial, will preferably be sought.

More particularly, the passage from the retracted configuration to the deployed configuration can be considered to take place via an intermediate configuration, known as the “partially deployed configuration”, in which the mobile base26is further away from the central axis Z1than in the retracted configuration, and which corresponds to the stage at which the seat14comes into contact with the tyre2so as to start to exert a supporting action on the bead wire3, and then to continue when the radial spacing of said mobile base26with respect to the central axis Z1is increased, and therefore so is the clamping force exerted on the bead wire3, until the final configuration is reached, namely the fully deployed configuration, to which the desired clamping force F_clamp corresponds.

The axial displacement of the seat14, and therefore of the bead wire3is thus intended to be minimized during the passage, which will be denoted “clamping travel”, from the intermediate, partially deployed configuration to the final, fully deployed configuration, that is to say between the moment at which the seat14of the clamping jaw12comes into contact with the bottom region2B and starts to act on the bead wire3and the moment at which the seat14, which has remained in contact with the bottom region2B, reaches the deployed position, which corresponds to the desired clamping of the bead wire3.

For this reason, a maximum limit will preferably be imposed on the axial displacement allowed during the passage from the retracted configuration to the deployed configuration, and more particularly during the abovementioned clamping travel.

By way of indication, and as indicated above, this limit may be fixed for example at 0.5 mm (five tenths of a millimetre).

By way of indication, the limit to axial displacement allowed during the clamping travel, from the intermediate configuration to the fully deployed configuration, will preferably be fixed at 0.1 mm (one tenth of a millimetre).

The configuration of the articulated parallelogram20, and in particular the length of the first and second sides27A,28A, and their starting and finishing inclination angle A27with respect to the central axis Z1, will be adapted as a result, as is explained below.

Particularly preferably, the articulated parallelogram20is designed such that the inclination angle A27changes sign during the passage from the retracted configuration to the deployed configuration, and more preferably during the clamping travel, meaning that the first side27A and the second side28A, during this deployment movement, tilt so as to reverse the orientation of their pitching inclination with respect to the central axis Z1, and therefore pass through an intermediate configuration in which said first and second sides27A,28A are parallel to the central axis Z1, and in which the inclination angle A27is zero.

Structurally, this manifests itself in the fact that, in the retracted configuration, the third pivot23is situated at a radial distance d23from the central axis Z1that is less than the (fixed) radial distance d21at which the first pivot21is located (FIG.3), such that said third pivot23is closer to the central axis Z1than the first pivot21, while in the deployed configuration, the third pivot23is located at a radial distance d23from the central axis Z1that is greater than the radial distance21at which the first pivot21is located (FIG.4), such that the third pivot23is further away from the central axis Z1than the first pivot21.

The deployment movement of the mobile base26, and then the return retraction movement, and more preferably the portion of these movements that corresponds specifically to the clamping travel (and then to the corresponding return movement), therefore follows a circular arc that is advantageously distributed on either side of the extremum formed by the passage through the zero inclination angle A27, this having the effect of minimizing the axial displacement.

Specifically, the component of axial displacement which is generated by the first part of the deployment movement, during which the first side27A leaves the starting position that it occupies in the retracted configuration, or more particularly in the partially deployed configuration, said starting position corresponding by convention to a negative inclination angle A27, in order to adopt an intermediate position parallel to the central axis Z1, that is to say the part of the movement during which the inclination angle A27is reduced (in terms of absolute value) in order to arrive at a zero inclination, is compensated at least partially by the component of axial displacement, in the opposite direction, which is generated during the second part of the deployment movement, when the first side27A leaves the intermediate position parallel to the central axis and increases its inclination angle A27in order to reach the non-zero inclination (in this case positive by convention) which corresponds to the deployed configuration (clamping configuration).

The resultant axial displacement of the mobile base26with respect to the shaft11between the retracted configuration and the deployed configuration is therefore minimized, if not substantially eliminated, while the useful radial displacement of said mobile base26may be significant.

It will also be noted that the radial displacement of the mobile base26, and therefore the radial displacement of the seat14, which corresponds to the clamping travel, may in practice be relatively small, in particular on account of the virtually inextensible nature of the bead wire3, which makes it possible to rapidly increase the clamping force with a radial displacement of small amplitude, as soon as contact of the seat14is established with the bottom region2B. By way of indication, said radial displacement corresponding to the clamping travel could thus be between 2 mm and 10 mm, for example around 4 mm.

If a length of the sides27A,28A of the articulated parallelogram20is considered to be equal to 152 mm, as indicated above, a radial displacement of 4 mm corresponds to an angular travel (change in inclination angle A27) of around 3 degrees.

If this angular travel of 3 degrees, corresponding to the desired clamping travel, is distributed evenly with respect to the horizontal (i.e. with respect to the direction given by the central axis Z1), the angular displacement of the arms27,28with respect to the horizontal position, known as the “neutral position”, will therefore be +/−1.5 degrees.

The axial displacement of the mobile base26, and therefore of the seat14and of the bead wire3, when said mobile base26travels through this arc of 3 degrees passing through the horizontal position, is equal to the difference between, for the one part, the radius of said arc, namely the length L_27A of the side27A, which corresponds to the axial position in which said mobile base26is located with respect to the fixed base25when the arm27is horizontal, and, for the other part, the projection of this same side27A onto the horizontal when said side27A has tilted through 1.5 degrees with respect to the horizontal in order to reach the deployed configuration.

Thus, in the above example, the axial displacement will be: L_27A−L_27A*cos(1.5 degrees), or, for a side length L_27A of 152 mm, an axial displacement of 0.052 mm, much lower than the limit of 0.1 mm set out above.

The deployment system13comprises of course a drive mechanism30which is designed to cooperate with the articulated parallelogram20in order for it to be possible to select and modify the radial position d26of the mobile base26with respect to the fixed base25, in order to pass from the retracted configuration to the deployed configuration, and vice versa, to return from the deployed configuration to the retracted configuration.

The drive mechanism30could move the mobile base26by deforming the articulated parallelogram20, i.e. by modifying the geometric shaping of the articulated parallelogram in a controlled manner by appropriately varying the angles at the apex of the articulated parallelogram20, by virtue of the relative mobility conferred by the first, second, third and fourth pivots21,22,23,24.

To this end, the drive mechanism30could comprise any suitable driving member31, for example a cylinder40, preferably a pneumatic cylinder, placed under the dependence of a suitable control unit, for example an electronic computer.

Preferably, said driving member31will drive a mobile member32, such as a slider32, in relative axial displacement, along the shaft11and the central axis Z1, with respect to the axial position, fixed on the shaft11, of the first and second pivots21,22.

Thus, the deployment system13could be actuated, and more particularly the shaping of the articulated parallelogram20modified to pass from the retracted configuration to the deployed configuration, or vice versa, without it being necessary to axially move the articulated parallelogram20as a whole, and more particularly by keeping the first and second pivots21,22, and therefore the fixed base25, in a fixed axial position on the shaft11, set back from the central region1C of the drum1.

To deploy the seat14, all that will be necessary will be to axially displace the slider32, which is less bulky than the articulated parallelogram20as a whole, with respect to said articulated parallelogram20, in this case by moving said slider32away from the (preferably common) axial position of the first and second pivots21,22and moving said slider32axially towards the central region1C.

Preferably, each clamping jaw12, independently of the other clamping jaws12, comprises its own individual deployment system13, placed in the angular sector in question of the shaft11, about the central axis Z1.

The different deployment systems13, thus distributed—like the clamping jaws12that they actuate—in a star arrangement about the central axis Z1, could advantageously be coordinated, and in particular synchronized, by means of a single control unit, which will control the drive mechanism(s)30associated with the different clamping jaws12.

Furthermore, the shaft11is preferably mounted so as to be movable in translation on the drum1, along the central axis Z1, so as to be able to move the bead wire3, which is carried by the seat14installed on said shaft11, towards the equatorial plane P_EQ of the tyre2during the shaping step.

This movement of the shaft11axially towards the equatorial plane P_EQ of the tyre2is advantageously separate from and independent of the radial, or virtually radial, movements of the deployment system13and more particularly the radial, or virtually radial, movements of the mobile bases26of the articulated parallelograms20.

It is thus possible to first of all clamp the bead wire3by radially deploying the clamping jaws12and then, once the bead wire3has been secured to the shaft11by the centrifugal clamping force F_clamp, to axially displace the bead wire3,3_1so as to move it towards the equatorial plane P_EQ, and the other bead wire3_2, so as to shape the carcass4.

According to a preferred feature which may constitute a wholly separate invention, in particular in combination with any deployment system13or any elevator system using an articulated parallelogram20mounted on a support of the shaft11type or any other appropriate support, similar by convention to a shaft11and extending in a direction considered to be a central axis Z1, wherein said articulated parallelogram20is used in connection with the deployment of a drum1for building pneumatic tyres or for any other application, the deployment system13comprises:a slider32which is guided on the shaft11, preferably in translation, so as to be able to move, under the control of a driving member31, such as a cylinder40having a piston41, at least along an axial movement component that is parallel to the central axis Z1,a pusher33which is secured to the mobile base26of the articulated parallelogram20and which has, with respect to the slider32and to the central axis Z1, a convex curved ramp34,a connecting shoe35which is carried by the slider32, which has a concave cradle36with which the ramp34of the pusher33cooperates in sliding contact, and which is mounted on the slider32in a tilting manner by means of a pivot known as the “pitch pivot”37so as to be able to adapt its inclination with respect to the central axis Z1depending on the position of said connecting shoe35along the ramp34of the pusher33,
such that a movement of the slider32on the shaft11along the central axis Z1is converted by the sliding of the connecting shoe35on the ramp34of the pusher33into a variation in the radial distance d33of the pusher33from the central axis Z1, and therefore into a corresponding variation in the radial distance d26of the mobile base26of the articulated parallelogram20with respect to the central axis Z1.

For the convenience of depiction, the radial distance d26of the mobile base from the central axis Z1may be equated to the radial distance d23of the third pivot, and more particularly of the axis of said third pivot23, from the central axis Z1, since said third pivot23is part of said mobile base26.

The axis of the pitch pivot37is advantageously parallel to the axes of the first, second, third and fourth pivots21,22,23,24, and therefore normal to the sagittal plane PS.

As indicated above, the slider32is moved on the shaft11relative to the axial position, which is fixed with respect to said shaft11, of the first and second pivots21,22, and therefore relative to the axial position, fixed with respect to the shaft11, of the fixed base25.

Of course, the angular position of the slider32on the shaft11in terms of azimuth about the central axis Z1is indexed with respect to said shaft11, such that the angular position in terms of azimuth of the slider32coincides with the angular position in terms of azimuth of the corresponding mobile base26.

The centres of curvature of the cradle36and of the ramp34, and more particularly said centres of curvature considered in the sagittal plane PS, will both be oriented on the same side with respect to the interface between the cradle36of the connecting shoe35and the ramp34of the pusher33, and situated radially, with respect to the central axis Z1, beyond the centre of the pitch pivot37.

Preferably, said centres of curvature of the cradle36and of the ramp34will be coincident, such that the respective curvatures of the cradle36and of the ramp34are identical, and such that the cradle36thus perfectly hugs the ramp34.

Preferably, the cradle36will have, in particular in the sagittal plane PS, a curvature of constant sign, meaning it will not have a reversal of curvature, and the same will go for the ramp34, which will preferably have a curvature of constant sign, and of the same sign as the curvature of the cradle36.

Particularly preferably, the radius of curvature of the cradle36, in particular in the sagittal plane PS, will be constant, such that the cradle36is in the shape of a circular arc.

More generally, the cradle36will preferably form a portion of a straight circular-base cylinder, the generatrix of which is parallel to the axis of the pitch pivot37, parallel to the axis of the first, second, third and fourth pivots21,22,23,24, and therefore normal to the sagittal plane PS.

Similarly, the ramp34will preferably be in the shape of a circular arc, along a portion of a circular-base cylinder, the generatrix of which is parallel to the axis of the pitch pivot37, and therefore normal to the sagittal plane PS, and the radius of curvature of which is preferably equal to that of the cradle36.

Advantageously, the use of a curved interface geometry between the cradle36and the complementary ramp34makes it possible to convert, in an effective, progressive, and well-controlled manner, the axial force which is generated by the driving member31, and which tends to axially move the slider32, in this case in the direction of the equatorial plane P_EQ, into a radial force, in this case into the centrifugal clamping force F_clamp.

In particular, it is possible to progressively generate, but nevertheless to rapidly increase, the radial clamping force F_clamp, by using for this purpose an axial travel of the slider32of relatively short extent, thereby making it possible to preserve a compact, although powerful, deployment system13.

This curved interface between the cradle36and the ramp34also provides a large contact surface area, which ensures great stability and makes it possible to generate a particularly high radial component of clamping force F_clamp, while allowing better control of the contact pressures and the associated phenomena of friction or of deformation.

In this regard, it will be noted that it is possible to use, in particular to produce the shoe35and more particularly the cradle36, a copper-based alloy, for example a bronze, which will make it possible to establish a metal/metal contact with the ramp34, this being highly resistant to compression but only putting up little frictional resistance to the sliding movement of the cradle36on the ramp34, and which will therefore not require maintenance or additional lubrication.

The use of a curved geometry and the control of the associated friction also makes it possible, as will be described in detail below, to define an irreversibility threshold, from which the slider32and the shoe35occupy, with respect to the ramp34and the bead wire3, a self-immobilizing position in which they prevent the spontaneous return of the slider32under the force exerted by the bead wire3on the seat34in reaction to the clamping force F_clamp, and thus lock the deployment system13in the deployed configuration.

Preferably, the slider32is driven by a driving member31formed by a cylinder40, preferably a pneumatic cylinder, which has a piston41mounted in a movable manner in a sleeve42.

Such a cylinder40advantageously makes it possible to generate, relatively simply, a significant axial thrust force, which is then converted into a radial clamping force F_clamp by the above-described driving mechanism30.

Advantageously, the axial thrust force could be all the higher since it is possible, by virtue of the cylinder40being offset away from the central region1C of the drum, made possible by the arrangement in the form of a parallelogram that is the subject of the invention, to provide a sleeve42and a piston41which have a section, and therefore a useful surface exposed to pressure, which is particularly large.

The cylinder40could preferably be an annular cylinder, centred on the central axis Z1, the piston41of which, which is also annular, could advantageously simultaneously actuate several deployment mechanisms13, and therefore several clamping jaws12, or even all of the clamping jaws12distributed around the circumference of the drum1.

Preferably, as can be seen inFIGS.3and4, the slider32can be carried by the piston41, while the fixed base25of the articulated parallelogram20is fixed to the sleeve42of the cylinder40.

Such an arrangement advantageously combines compactness, simplicity and robustness.

The creation of the sealing between the piston41and the sleeve42is likewise simplified, since this sealing can be obtained for example by means of simple scraper seals43,44, for example O-rings or lobed seals, in this case centred on the central axis Z1. Said seals43,44are advantageously housed in grooves that are concentric with the central axis Z1.

Furthermore, the static sealing between the shaft11and the cylinder head of the cylinder31, and consequently between the sleeve42and the shaft11, is preferably provided by an O-ring45, as can be seen inFIG.3.

According to a preferred feature, which may constitute a wholly separate invention, regardless otherwise of the arrangement of the deployment system13, and for example independently or in combination with an articulated parallelogram20according to the invention, the deployment system13has a non-return locking arrangement50, which is activated during the passage from the retracted configuration to the deployed configuration, so as to prevent any spontaneous return to the retracted configuration from the deployed configuration.

More particularly, said non-return locking arrangement50allows the deployment system13to withstand the action exerted by the bead wire3on the seat14, under the effect of gravity and/or as a reaction to the clamping force F_clamp.

Advantageously, such a non-return locking arrangement50makes it possible, on account of its self-locking action, to keep the bead wire3in position, clamped and centred on the deployed seat14, even if the driving member31stops being activated, and, more particularly, even if the energy supply of said driving member31is interrupted, deliberately or otherwise, for example if the pressure supply of the cylinder40is interrupted.

Thus, energy can be saved and operational safety can be increased, since it is possible, as soon as the deployed configuration has been reached and the non-return locking arrangement50has been activated, to release the force exerted by the driving member31, without any risk of the deployment system13sagging.

Once the non-return locking arrangement50has been activated, the unlocking of the deployment system13should be brought about, that is to say intentionally carried out, to allow the return to the retracted configuration.

According to one possible implementation, the non-return locking arrangement50is obtained by a toggle effect, during which the travel of the slider32is provided such that, during the passage from the retracted configuration to the deployed configuration, the centre of the pitch pivot37carried by said slider32reaches, and preferably crosses, the imaginary plane, known as the “force plane” PF, which is normal to the central axis Z1and which contains the closed contour, known as the “mean line” L3, formed by all of the centres of the cross sections of the bead wire3as considered along said bead wire3, about the central axis Z1.

In practice, the centripetal constriction force which is exerted by the bead wire3on the deployed seat14, in reaction to the centrifugal clamping force F_clamp, is in fact contained substantially in this force plane PF, situated vertically in line with the annular groove17.

Consequently, said force plane PF constitutes a locking threshold in that, when the slider32moves sufficiently along the shaft11, parallel to the central axis Z1, in order that the centre of the pitch pivot37passes from one side of said force plane PF to the other, the torque exerted, about the pitch pivot37, by the reaction of the bead wire3against the seat14, and therefore the torque exerted against the connecting shoe35and the slider32, changes sign.

If a stop is provided in order to limit the travel in translation of the slider32on the shaft11in the direction of the equatorial plane P_EQ, or a stop is provided in order to limit the tilting travel, in this case in the clockwise direction inFIGS.3and4, of the connecting shoe35on the slider32via the pitch pivot37, this change in sign, which tends to bring about reversal of the pitching movement of the connecting shoe35, has the effect of firmly immobilizing the connecting shoe35against the slider32, and consequently of locking the ramp34, the pusher33, and the clamping jaw12carried by the latter in position.

According to another possible implementation, the non-return locking arrangement50is obtained by friction, by an appropriate arrangement of the pitch pivot37, of the cradle36and of the ramp34of the pusher33, which is chosen such that, when the axial position of the slider32reaches a threshold known as the “locking threshold”, which is sufficiently close (as can be seen inFIG.4) to the axial position of an imaginary plane, known as the “force plane” PF, which is normal to the central axis Z1and which contains the closed contour, known as the “mean line” L3, formed by all of the centres of the cross sections of the bead wire3as considered along said bead wire3, about the central axis Z1, the resultant force, which results from the stresses exerted on the seat14and which is exerted at the interface between the cradle36of the connecting shoe35and the ramp34of the pusher33, is kept confined inside the friction cone of said interface.

To this end, it may be possible in particular, depending on the constituent materials of the cradle36and of the ramp34, and therefore depending on the coefficient of friction between these elements, and depending on the dimensions of the bases25,26and sides27A,28A of the articulated parallelogram20, to choose appropriate dimensioning and an appropriate geometric arrangement of the pitch pivot37, of the travel of the slider32, and of the radius of curvature of the cradle36and of the ramp34, so as to make it possible, once the slider32has reached or passed the locking threshold, to prevent the ramp34from sliding in the cradle36, at least in the direction of a return to the retracted configuration.

As a result, in the deployed configuration, the slider32cannot be spontaneously sent backwards, towards the position that said slider32occupies in the retracted configuration, just under the action exerted by the bead wire3on the seat14, such that said slider32remains interposed radially, as do the connecting shoe35and the pusher33, between the clamping jaw12, and more particularly the mobile base26, for the one part, and the central axis Z1of the drum1for the other part, thereby making it possible to ensure the continuity of support of the clamping jaw12, and therefore of the seat14, against the bead wire3.

In order to bring about the unlocking of the deployment system13, in order to return the seat14from the deployed configuration to the retracted configuration, it may be possible for example to apply a slight negative pressure to the chamber of the cylinder40in order to return the piston41and the slider32, in this case axially away from the central region1C of the drum, sufficiently to unlock said deployment system13.

In a variant, provision could be made for the cylinder40to be a double-acting cylinder comprising, axially on either side of the piston41, for the one part a first chamber, known as the “deployment chamber”, intended to be pressurized to pass the piston41, the slider32and more generally the deployment system13from the retracted configuration to the deployed configuration, as indicated above, and, for the other part, on the other side of the piston41, a second chamber, known as the “return chamber”, intended to be pressurized to bring about the unlocking of the deployment system13and the return of the piston41, the slider32and more generally the deployment system13to the retracted configuration. Such a solution will make it possible to take advantage, if necessary, of a greater unlocking and return force.

In the case of a non-return locking arrangement50having a toggle, this active bringing about of unlocking, in this case for example by the application of negative pressure to the deployment chamber of the cylinder40and/or the pressurization of the return chamber of said cylinder40, will have the effect of returning the slider32below the locking threshold of said toggle, in this case typically by returning said slider32so as to make it cross back over the force plane PF in the opposite direction to the locking direction, that is to say by moving said slider32axially away from the equatorial plane P_EQ and the central region1C.

Respectively, in the case of a non-return locking arrangement50having a friction cone, this active bringing about of unlocking will have the effect of reconfiguring the geometric disposition of the slider32, of the connecting shoe35and of the ramp34, and therefore of reconfiguring the friction cone at the interface considered, so as to allow the ramp34of the pusher33to slide on the cradle36of the sliding shoe35in the direction of a return to the retracted configuration.

Of course, if the non-return locking arrangement50adopts a different form, for example that of a ratchet acting mechanically on one of the mobile elements of the deployment system13in order to prevent said mobile element from moving in the direction of a return to the retracted configuration, appropriate unlocking means could be provided, such as a connecting rod, which will make it possible to retract the ratchet on demand in order to release the mobile element held by said ratchet, and thus to free up the deployment system13.

It will also be noted that, advantageously, once the non-return locking arrangement50has been unlocked, the elastic constriction force that is exerted by the banding strip16, or if appropriate by the annular return spring, on the clamping jaws12assists the return movement of the deployment system13into the retracted configuration.

Furthermore, as can be seen inFIG.5, the first arm27and/or the second arm28of the articulated parallelogram20may preferably comprise at least two side members51,52which each connect together the two pivots21,23, and22,24, respectively, connected by the arm27,28in question, said side members51,52being held together by one or more crosspieces53.

Such a structure, of the lattice beam type, advantageously confers excellent rigidity on the arm27,28, while preserving the lightweight nature thereof.

It also allows the arm27to form a yoke, thereby ensuring precise and stable guidance of said arm27on its pivots21,23, giving said arm a plurality of points of contact distributed along the axis of each of said pivots21,23.

Of course, preferably, the drum1could comprise, as schematically indicated by way of dashed lines inFIG.2, a first shaft11_1and a second shaft11_2which are mounted so as to move in translation along the central axis Z1and are each provided with an expandable seat14_1,14_2, such that it is possible to shape the pneumatic tyre2by clamping a first bead wire3_1on the expandable seat14_1of the first shaft11_1and a second bead wire3_2on the expandable seat14_2of the second shaft11_2and then by moving the two shafts11_1,11_2axially towards one another so as to move the two bead wires3_1,3_2carried by said shafts11_1,11_2axially towards one another.

Said shafts11_1,11_2will thus be mounted so as to be movable in opposition, such that each can move the bead wire3_1,3_2that they carry towards the equatorial plane P_EQ and thus, during the shaping operation, to force or accompany the movement that makes it possible to curve the carcass4in order to attach the crown block7to said carcass4and then to carry out the roller-pressing operation.

The deployment systems13, preferably having an articulated parallelogram20, which are carried by each of said shafts11_1,11_2could be as described above.

Of course, the invention is in no way limited only to the abovementioned exemplary embodiments, a person skilled in the art being notably capable of isolating or freely combining one or another of the above-described features with one another, or of substituting equivalents therefor.