Device for applying an elastomeric filler on the bead core of a pneumatic tire

Abstract: The described device comprises a bearing element (2) positioned to engage a bead core and subjected to the action of a friction wheel (7) acting in such a way as to make the bead core rotate around its own axis. Two pressure discs (17, 18) arranged specularly with respect to the lying median plane of the bead core act on opposite sides of a filler (34) to apply the same on the outer peripheral chafer of the bead core while this latter is rotating. The pressure discs lie according to respective planes convergent toward the bead core and divergent in the sense of rotation of the bead core to favour the release of the filler from the pressure discs. The pressure discs are thrust on the filler through a pneumatic cylinder (22) which exerts a constant force on an oscillating support (19) according to an axis parallel to the bead core axis and bearing the discs themselves.

Description: The present invention refers to a device for applying an elastomeric filler on the bead core of a pneumatic tire, of the type comprising a supporting frame, a bearing element rotatably engaged with respect to the frame and positioned to engage rigidly and releasably the bead core of a pneumatic tire, a pair of pressure discs rotatably borne with respect to said frame, positioned symmetrically with respect to the lying median plane of the bead core and having respective mutually facing perimetric projections which act on opposite sides of an elastomeric filler for its application, by a thrust action toward the bead core, along a circumferential outer chafer of the bead core while this latter is rotating around its own axis through actuation means working on the bearing element. As known, the pneumatic tires for motorvehicles in general are always provided, at the bead, with annular elements of metallic material, usually called bead cores, which have mainly the function of supporting the whole pneumatic tire structure. In fact, each bead core is anchored to the carcass of the pneumatic tire through a turn-up formed by the plies provided in the sidewalls of the tire, folded as a book around the section of the bead core. In order to prevent the formation of air pockets between the ply skirts turned-up around the bead core, a suitably shaped filler of elastomeric material is provided along the circumferential chafer of the bead core; said filler has also the task of stiffening the structure of the bead. Recently, apparatuses able to apply the filler on the bead core in a completely automatic manner have been realized. To this end, these apparatuses avail of devices in which the filler, previously cut as a strip of suitable length, is tangentially inserted between two pressure discs coaxially facing that, rotating,apply said strip along the circumferential outer chafer of the bead core while this latter, mounted on a suitable bearing element, is rotate around its own axis. Subsequently, a splicing device operates in such a way as to join the opposite ends of the filler that mutually face according to a "V" configuration in consequence of the difference of diameters according to which the lower and upper zones of the section of the filler are bent. In the devices used at present for applying the filler, the bead core is pulled into rotation by one of the pressure discs. In fact, the pressure discs are rotated by a motor, and one of them has a peripheral portion acting against the bearing element of the bead core to pull it into rotation together with the bead core mounted thereon. Moreover, it is provided that the pressure discs engage the filler through respective perimetric projections obtained on the front of the same so as to get into contact on the opposite sides of the filler itself, in proximity of the portion of base of this latter. The perimetric projections are spaced in a measure slightly smaller than the width of the filler section in the zone where the projections must get into contact. Therefore, when the filler is obliged to pass between the pressure discs suffers such a compression on the sides as to produce a force of reaction that thrusts the filler itself against the outer peripheral surface of the bead core, on which a suitable solution has been previously distributed for providing the adhesion of the filler. From the foregoing it is noted that the known devices for applying the filler reveal some drawbacks. A first drawback consists of the fact that the filler tends to be lifted from the bead core when it is being released from the pressure discs. In fact, owing to the mutual arrangement of the above said perimetric projections, the filler is compressed on the sides when it is inserted between the pressure discs and, therefore it exerts on the perimetric projections an elastic reaction that makes it adhere to the projections themselves. Consequently, the filler is inclined to be removed from the bead core at the points in which the perimetric projections move away from the bead core in consequence of the rotation of the pressure discs. All this can produce several complications in the case in which, for instance owing to a not perfect distribution of the solution on the bead core or in the case in which the solution is not qualitatively satisfactory, the filler should remain attached to the pressure discs instead of adhering to the bead core. In any case, the described solution is not at all favourable for a correct application of the filler on the bead core. Another drawback is given by the fact that the pressure discs, in order to pull into rotation the bead core, have necessarily to maintain immovable with respect to the bearing element. This determines an irregular application of the filler when,as often happens, this latter has slight dimensional variations of its section. In particular, when the filler has a section of a measure slightly greater than the nominal one, it is subject to suffer an excessive compression when inserting between the pressure discs. This compression may cause an undesirable elongation of the filler along the zones adjacent to its base If, on the contrary, the filler has a section of a measure slightly smaller than the nominal one, it may happen that said filler is not sufficiently compressed on the bead core during its application. This may cause a not perfect adhesion of the filler on the bead core. Another drawback derives from the fact that the pulling of the bearing element by the corresponding pressure disc takes place according to contact profiles that, nearly always, have radii different from the radius of the outer circumferential chafer of the bead core and from the radius of the perimetric projections positioned to pull the filler. The result is that often the pressure discs pull the filler at a speed different from the speed of the outer perimetric chafer of the bead core, on which the filler leans. This situation, besides not being favourable for a good adhesion of the filler to the bead core, may cause undesirable structural deformations of the filler in its sense of longitudinal development. The main object of the present invention is substantially that of eliminating the drawbacks of the known technique, by realizing a device able to apply the filler on the bead core in a very reliable manner without giving rise to deformations of the filler also in case this latter has, originally, slight dimensional variations in its cross section. This aim and other ones, that will better appear in the present description, are substantially achieved by means of a device for applying an elastomeric filler on the bead core of a pneumatic tire, characterized by the fact that said pressure discs are rotatably idle and released from the driving means and lie according to respective planes which diverge the one with respect to the other in the sense of rotation of the bead core during the application of the filler and converge mutually in direction of the axis of rotation of the bead core. Further characteristics and advantages will grealy appear from the detailed description of a preferred, but not exclusive, embodiment of a device for applying an elastomeric filler on the bead core of a pneumatic tire, according to the present invention, made with reference to the attached sheet of drawing, supplied only by way of non-limiting example, in which: FIGURE 1 - is a broken perspective view of the device according to the invention; FIGURE 2 - shows in front view and in partial section, a pair of pressure discs making part of the device of the invention, during the application of an elastomeric filler on the bead core; FIGURE 3 - shows in lateral view and schematically, the mutual arrangement between the pressure discs and the bearing element of the bead core. With particular reference to figure 1, reference numeral 1 indicates a device for applying an elastomeric filler on the bead core of a pneumatic tire, according to the present invention. In a per se known way, the device 1 is preferably associated with an apparatus, not shown as of no importance for the purposes of the invention, which is suitable for applying elastomeric fillers on bead cores in a completely automatic manner. The device 1 comprises a bearing element 2 (shown only in part) rotatably engaged with an arm 3 connecting this latter with a supporting frame 4. The bearing element 2, in a per se known way, comprises a centering disc 2a positioned to engage a bead core 5 of a pneumatic tire (figure 2) to which a fastening flange 2b is associated; said flange being translable when approaching the disc to provide the fastening of the bead core 5 to the pneumatic tire. Always in a per se known way, it is preferably provided that the arm 3 rotatably supporting the bearing element 2 results on its turn rotatably connected with the supporting frame 4, together with other like arms, to subject the bead core 5 to the next action of the various devices provided in the above mentioned apparatus. On the bearing element 2 there are driving means, indicated altogether with 6, able to rotate the bearing element itself so that the bead core 5 is pulled into rotation around its own axis. Originally, the driving means 6 comprise a friction wheen 7 rotatably engaged with respect to the frame 4 according to an axis parallel to the axis of the bearing element 2. The friction wheel 7 is pulled into rotation by a drive shaft 8 through a motor not shown, and is kept in contact against the peripheral edge of the flange 2b to transmit its own rotary motion to this latter, and therefore to the entire bearing element 2. To this end, as clearly shown in figure 1, it is advantageously provided that the friction wheel 7 is rotatably borne, through the drive shaft 8, by a plate 9 hinged in an oscillating manner to the supporting frame 4 through at least a pin 10 whose axis is substantially parallel to the axis of the drive shaft 8. A first fluid mechanics control double-acting cylinder 11, fixed with respect to the supporting frame 4, acts on the plate 9 so that the friction wheel 7 is thrust against the flange 2b with a predetermined force, necessary to guarantee the pulling into rotation of the bearing element 2 and the elements connected thereto. Moreover, it is advantageously provided that the drive shaft 8 of the friction wheel 7 crosses rotatably a supporting plate 12 engaged with a small block 13, which bears a plurality of orientation rollers 14, per se known and conventional, whose function will be better cleared up later on. A positioning fluid mechanics double-acting cylinder 15, rigidly connected through a support 16 with the plate 9, works on the supporting plate 12 in such a way that the rollers 14 are thrust with a light load toward the bearing element 2 during the filler application. Moreover, the device 1 comprises a pair of pressure discs 17 and 18 rotatably borne with respect to the supporting frame 4, symmetrically arranged with respect to the median lying plane of the bead core 5 and provided with respective perimetric projections 17a, 18a mutually facing. Originally and advantageously, in accordance with the present invention, the pressure discs 17, 18 are rotatably idle and completely released from the driving means 6: moreover they are mounted in a very particular way with respect to the above said median lying plane of the bead core 5. The discs lie according to respective planes that converge toward the axis of the bearing element of the bead core, as shown in figure 2 in which the device bearing said discs is illustrated at the same point of observation from which one looks at figure 1, i.e. on the front, with the elastomeric filler, indicated with 34, on approaching the observer, as indicated by the arrow F. The opening angle "v" of said planes, of the order of about 10° is preferably comprised between 5° and 15° and of course, with suitable adjusting devices can be made variable instead of fixed, as shown in figure 1. In consequence of said arrangement the above said pair of discs has a zone of minimum mutual distance: said zone is defined by a point P on the edge of each disc in a facing position and opposite to the same point P of the other disc, and it is the zone where the filler 34 suffers the maximum compression between the discs, any other condition being the same. Then, in order to avoid the already mentioned action of tearing from the bead core, that the filler suffers in consequence of the rotation of the pressure discs after leaving the tangent point T between pressure discs and bearing element of the bead core, in accordance with the invention, the common axis passing through the centers of rotation of the two pressure discs is moved in the sense of rotation of the drum 2 so that the point P of minimum distance between the pressure discs does no longer coincide with the tangent point T between said discs and said drum, but is moved backwards (in the sense of rotation) with respect to the above said tangent point T. Said movement, shown diagrammatically in figure 3 is defined by the angle "w" between the diameters "r" and "s" of each disc, passing through point P and T, respectively: the value of the above said angle "w" is conveniently comprised in an interval of more or less 10° about the preferred value of 15°. Substantially, in consequence of said structural arrangement of the various elements of the device according to the invention, the two pressure discs lie according to respective planes which mutually diverge in the sense of rotation of the bead core 5 during the application of the filler (i.e. with reference to figure 2, perpendicularly to the sheet in direction of the observer) and converge the one with respect to the other toward the bead core itself. Moreover, it is provided that the pressure discs 17, 18 are borne by an oscillating support 19, hinged in an oscillating manner with respect to the supporting frame 4 according to an axis parallel to the axis of the bead core 5. Preferably, the oscillating support 19 is connected, through a pin 20, with a bracket 21 secured to the plate 9 that supports the friction wheel 7. Between the plate 9 and the oscillating support 19 there is a double-acting actuator cylinder 22 which thrusts the pressure discs 17, 18 toward the bead core 5 with a force of constant and predetermined entity. As clearly schematized in figure 2, the illustrated example provides that adjusting means 23 be associated with the pressure discs 17, 18 to permit to vary the mutual distance and the orientation around an axis parallel to the axis of the bead core 5. To this end it is provided that a first pressure disc 17 is rotatably engaged with a supporting bracket 24 connected in the lower part with the oscillating support 19, while the second pressure disc 18 is rotatably borne by a mobile small block 25 slidably engaged along at least a guiding rod 26 rigidly mounted on a supporting bracket 24 and extending parallely to the axis of the bead core 5. A threaded bar 27 extending parallely to the guiding rod 26 and crossing in a sliding manner a reference wall 24a of the supporting bracket 24 is secured to the mobile small block 25. An adjusting hand grip 28 engaged during working with the threaded bar 27 and pulled into rotation manually to vary the distance between the pressure discs 17, 18 is rotatably connected with the reference wall 24a. Advantageously the supporting bracket 24 has a top wall 24b of curvilinear development which is secured under an arcuate plate 29 integral with the oscillating support 19. The arcuate plate 29, countershaped to the top wall 24b, develops around an axis parallel to the axis of the bead core 5 and arranged substantially at the level of the axes of the pressure discs 17 and 18. The top wall 24b is preferably engaged with the arcuate plate 29 through at least a threaded piston-pin 30 which crosses in a sliding manner a respective opening 31 obtained in the arcuate plate to be engaged with a threaded nut 32 suitale for fixing the positioning of the supporting bracket 24. By unloosing the nut 32 and moving the piston-pin along the opening 31 it is advantageously possible to place the bracket 24 around the center of curvature of the arcuate plate 29, and in such a way, to adjust simultaneously the orientation of the pressure discs 17 and 18 around an axis parallel to the axis of the bead core 5, for instance around the common axis passing through the centers of rotation of the discs 17 and 18, i.e. to vary the value of the angle "w". After what described as regards the structure of the device forming the object of the invention, the working of the same is the following one. Following the engagement of the bead core 5 between the centering disc 2a and the fastening flange 2b, the friction wheel 7, thrust against the peripheral edge of the flange itself by the action of the fluid-mechanics cylinder 11, is pulled into rotation so as to determine the pulling of the bead core with a rotary motion in the sense of the arrow 33 of figure 1. Contemporaneously, the elastomeric filler 34, in the form of a strip, is inserted, through known and therefore not illustrated feeding means, between the pressure discs 17, 18 and the bead core 5 as shown in figure 2. More particularly, the filler 34 having a section substantially triangular of a quite accentuated height, is engaged between the perimetric projections 17a, 18a of the pressure discs 17, 18 that, placed at a predetermined distance from one another through the adjusting means 23 and thrust toward the bead core 5 by the action of the second cylinder 22, get into contact on the sides of the filler in proximity of the base of the same, so that the filler is thrust with its base against the perimetric outer chafer of the bead core 5, on which an adhesive solution has been previously distributed. Therefore, the filler 34 adheres to the bead core 5 and is pulled by this latter into the rotation given by the friction wheel 7. While the filler 34 is dragged by the bead core 5, the same passes through the pressure discs 17 and 18 which apply it on the bead core and, consequently, through the orientation rollers 14 which, in a per se known way, are oriented in such a way as to oblige the filler itself to effect an undulated path. On following said path, the filler suffers repeated deformations, especially in the zones farther from the bead core 5 which causing its yield, take care that the filler itself maintains a symmetric orientation with respect to the median plane of the bead core 5. Advantageously, the mutual orientation of the pressure discs 17 and 18 is such that the distance between the perimetric projections 17a, 18a in the zones of contact with the filler 34 increases progressively in the sense of rotation of the bead core 5. Therefore, the elastic reactions of the filler on the perimetric projections 17a, 18a, consequent to the compression exerted on the sides of the filler by the pressure discs 17, 18 will result defined in the zones in which the initial insertion of the filler between the pressure discs takes place. On the contrary, these elastic reactions will reduce progressively, up to nullify on getting near the zone in which the filler 34 now applied on the bead core 5, disengages from the pressure discs 17 and 18. The possibility that the filler 34 by moving away from the bead core 5 is dragged by friction into the zones in which the perimetric projections 17a, 18a rotating around the axis of the respective pressure discs 17, 18 move away from the bead core 5, is thus eliminated. Moreover, and advantageously, as the force by which the pressure discs 17 and 18 act on the filler 34 is due to the action of the actuator cylinder 22, said force can maintain a predetermined and constant value even if the section of the filler 34 should have slight dimensional variations in the various points of its longitudinal development. This eliminates the possibility of structural deformations of the filler or an inefficacious application of the same on the bead core in consequence of the above said dimensional variations of the section of the filler. The present invention achieves thus the aimed purposes. As described above, it is noted that the device forming the object of the invention is able to eliminate the drawbacks of the known technique, permitting an effective and reliable application of the filler on the bead core, without producing any structural and/or dimensional variation on the filler itself. To this end, it is also considered that, as the pressure discs 17 and 18 are entirely released from the driving means 6, the device of the invention is also able to guarantee that the pulling of the filler 34 takes place at a speed exactly identical to the peripheral speed of the bead core 5.

Claims: Device for applying an elastomeric filler on the bead core of a pneumatic tire comprising: a supporting frame; a bearing element (2) rotatably engaged with respect to the frame and positioned to engage rigidly and releasably a bead core of a pneumatic tire; a pair of pressure discs (17, 18) rotatably supported with respect to said frame, arranged symmetrically with respect to the median lying plane of the bead core and having respective perimetric projections (17a, 18a) mutually facing which act on opposite sides of an elastomeric filler (34) to apply it, by means of a thrust action toward the bead core (5), along an outer circumferential chafer of the bead core while this latter is rotate around its own axis through driving means working on the bearing element, characterized by the fact that said pressure discs (17, 18) are rotatably idle and released from the driving means and lie according to respective planes that diverge the one with respect to the other in the sense of rotation of the bead core (5) during the application of the filler and converge mutually in the direction of the axis of rotation of the bead core. Device according to claim 1, characterized by the fact that said angle of convergence between the planes of said pressure discs is comprised between 5° and 15°. Device according to claim 1, characterized by the fact that said pressure discs are engaged with an oscillating support (19) hinged with respect to the supporting frame according to an axis parallel to the axis of rotation of the bead core and on which at least a fluid mechanics cylinder (22) acts to thrust with a force of predetermined and constant entity the pressure discs toward said bead core. Device according to claim 3, characterized by the fact that the pressure discs (17, 18) are connected with the oscillating support (19) through a supporting bracket (24) having a top wall of curvilinear development engaged with an arcuate plate (29) integral with said oscillating support and countershaped to said top wall, said supporting bracket being positioned around the center of curvature of the arcuate plate to adjust simultaneously the orientation of the pressure discs around an axis parallel to the axis of the bead core. Device according to claim 4, characterized by the fact that said axis parallel to the axis of the bead core is the common axis passing through the centers of rotation of said discs and that said orientation with respect to said axis is adjustable in an interval of 25°. Device according to claim 3, characterized by the fact that a first pressure disc (17) is rotatably engaged with a supporting bracket (24) secured to said oscillating support (19) and a second pressure disc is engaged with a mobile small block (25) engaged in a sliding manner along at least a guiding rod (26) integral with the supporting bracket (24) and extending parallely to the axis of the bead core, a threaded bar (27) being associated with said mobile small block and extending parallely to the guiding rod and crossing in a sliding manner said supporting bracket (24) to be engaged during working with an adjusting hand grip (28) rotatably connected with the supporting bracket itself and capable of being pulled into rotation to adjust the distance between the pressure discs. Device according to claim 6, characterized by the fact that said driving means comprise a friction wheel (7) pulled into rotation and working against a peripheral edge of the bearing element (2) to pull into rotation the bead core (5). Device according to claim 7, characterized by the fact that said friction wheel (7) is rotatably engaged with a plate (9) hinged to the supporting frame according to an axis parallel to the axis of rotation of the bead core and on which at least a fluid mechanics cylinder (11) acts to thrust the friction wheel against the bearing element of the bead core.

Inventors: PIZZORNO AUGUSTO, PIZZORNO, AUGUSTO
Applicants: PIRELLI, PIRELLI COORDINAMENTO PNEUMATICI S.P.A.
Application year: 1989
Main classification: B29D30
IPC codes: B29D30