Manufacture of radial-carcass tires
This is a continuation of application Ser. No. 28,281, filed Apr. 22, 1970, which in turn was a continuation of Ser. No. 617,658, filed Feb. 21, 1967, both abandoned. 
    
    
     This invention relates to the manufacture of radial-carcass tires and has specific reference to a drum for manufacturing tires of this type. 
     The precision necessary for manufacturing radial carcass tires requires a particular manufacturing procedure; up to now the tire was generally performed on a drum made of flexible material, thus precluding a purely geometrical preformation. 
     In section, a radial tire is characterized by the bead wire position and by the tread postion, forming together an isosceles trapezium. Therefore, during the preformation operation, the drum must necessarily reproduce geometrically this isosceles trapezium. 
     On the other hand, the density of the radial wires must remain constant during the preformation; this is possible only by resorting to a perfectly controlled development, that is, mechanical development. 
     To avoid any detrimental wire elongation some kind of servo-action must be established between the movement of the bead wires towards each other and the tire preformation. If x is the value of this movement, and y the preformation stroke, the relationship x = f y must be obtained. 
     The geometrical-preformation tire manufacturing drum according to this invention meets these requirements, because; 
     1. The bead wires are defined and maintained in the proper position irrespective of the preformation. 
     2. The drum is cylindrically rigid. 
     3. The drum is rigid during the preformation. and the preformation development is a function of the movement of the bead wires towards each other. 
     4. The preformation is definitely geometrical both in development and in section. 
     5. The fabric is turned to its final position after having been shaped, that is, without any distorsion. 
     6. The turning of the tire takes place positively. 
     7. The drum is easily dismounted and extensible to permit the manufacture of several tire sizes. 
     8. It permits the manufacture of 1-ply 2-ply 2-0 or 2-ply 1-1 tires. 
     9. In its original form it permits the non-stop manufacture of tires. 
     10. In a simplified form, this manufacture may be carried out in two half-periods. 
     The device according to this invention comprises means for converting the cylindrical wall of the drum, by a mechanical development respecting the density and regularity of the radial wires, into a regular toroidal wall. 
     To this end, within a hollow shaft driving the drum there is rotatably mounted a screw formed with several threaded sections engaged by two series of internally-threaded or screw sockets or nuts controlling respectively the displacements of brackets sliding on said shaft and controlling crossed arms of equal length which support the preformation sectors, and the synchronous displacements of annular flanges supporting through the medium of bladders a system of metal sectors constituting the deformable structure supporting the tire wall. 
     The pitch of the two series of internally-threaded sockets meshing with said screw are so calculated that the value x of the movement of the bead wires towards each other which is caused by the actuation of the external flanges is a function of the preformation stroke y resulting from the displacement of the aforesaid crossed arms controlled by said sliding brackets. 
     The extensible metal sectors of the supporting structure, which vary in number according to the drum size, consist of flat springs forming a lower sheet having rivoted thereon an upper corrugated sheet consisting of spring elements secured at their ends to rods rigid with the control sector. 
     In its central portion said supporting structure carries cylindrical centering members fitting in the preformation sectors carried by the crossed arms responsive to said sliding brackets. 
     Coil springs are disposed circularly on the outer periphery of the central portion of said metal sectors. 
     The sheet formed by these coil springs is covered with an elastic layer or wall having its ends retained by the control sectors. 
     When the central control screw is rotated, the outer brackets and, therefore, the sectors engaged by the structure supporting the elastic wall, are moved symmetrically towards each other with respect to the drum axis, while the external sliding brackets develop radially, simultaneously and with the same amplitude the preformation sectors, until the structure assumes a continous toroidel configuration on the preformation sector. 
     The device for folding down the plies after the shaping operation comprises essentially flanged sleeves slidably mounted on the drum shaft and maintained at an adjustable relative spacing by screws so as to be carried along by the structure control flanges during their movement in relation to the preformation axis. 
     These flanges carry radial sectors adapted to expand when a suitably disposed air bladder is inflated, said radial sectors supporting peripheral springs adapted to act as support means for the tire bead. 
     Also secured to the flanges controlling the folding movement are pivoted plates hingedly mounted on a table and adapted to wrap the tire on the drum upon completion of the preformation operation. The rotation of the arms producing the folding or turning of the wall is controlled by means of a fluid-actuated cylinder acting upon bearing means. 
    
    
     Other features and advantages of the device constituting the subject-matter of this invention will be described more in detail hereinafter with reference to the accompanying drawings illustrating diagrammatically by way of example a typical form of embodiment of this invention and wherein: 
     FIG. 1 is a diametral section of a half-drum; 
     FIG. 2 is a similar view showing the half-drum after the preformation step and during the turning or folding of the plies and fabric layers; 
     FIG. 3 is a perspective view showing the metal structure of the shaped drum, the elastic wall being removed therefrom; 
     FIG. 4 is a view showing diagrammatically and on a larger scale various details of this structure. 
    
    
     The drum a is mounted on a hollow shaft 1 secured by splined coupling 29 to the spindle 28 of the tire making machine, a screw shaft 2 consisting of several threaded sections being mounted within said hollow shaft 1 by means of suitable radial and axial bearings. 
     The splined coupling 20 at one end of screw 2 permits of rotatably driving this screw 2 and therefore the translation of four internally threaded sockets or nuts 3, 3a, 4, 4a. These sockets 3 and 3a, 4 and 4a are disposed symmetrically in relation to the preformation axis. The pitch of sockets 4 and 4a is in such ratio to the pitch of sockets 3 and 3a that the above-mentioned relationship x = f y is obtained. 
     Having thus disclosed the shaft portion the drum will be divided into two separate sections, as follows, for a proper understanding of the disclosure: 
     a. the manufacturing and preformation drum (central portion) 
     b. device for folding the plies and side elements (lateral portions ). 
     MANUFACTURING AND PREFORMATION DRUM 
     It comprises essentially two annular flanges 5 and 5a slidably mounted on the shaft 1 and respensive to the movements of screw sockets 3 and 3a through the medium of driving pins 6. 
     These flanges 5 and 5a support in a suitable peripheral recess an inflatable air bladder 7 capable of giving two stable positions to the metal soctors 8 and 8a  serving the purpose of supporting the carrier structure 35, 36. These metal sectors, of which the number varies as a function of the drum size, are adapted to move radially with a certain stroke controlled by said inflatable air bladder 7. Each sector 8 or 8a carries a flat spring 9 interconnecting these sectors 8 and 8a. This spring consists of heat-treated steel and has the shape shown in FIG. 4. 
     These springs 8 and 8a are rigid with a pair of main component elements 35 and 36 riveted with each other at points 37. Member 35 have hinge-shaped end portions 38 engageable by hinge pins 39 secured to the sector 8 or 8a. Intermediate its ends, the spring 35 has secured thereto a metal centering stud 30 atapted to fit in corresponding cavities of the preformation sector 10. The spring 36 has the contour illustrated with curved ends 40 adapted to fit on a projecting arm of sector 8 or 8a. 
     In the central portion of spring 36 a series of semi-circular cavities 41 are formed to permit the engagement therein of a series of coil springs 42 extending along the complete periphery of the drum. 
     This flexible and extensible metal structure 9, 35 and 36 is covered with an elastic and possibly reinforced layer 11 limiting the extension thereof and retained at its ends in a suitable recess 31 of sectors 6 and 8a. 
     The screw sockets 4 and 4a drive the brackets 12 and 12a by means of driving studs 13. These brackets 12 and 12a carry in the radial direction a series of crossed arms 14 and 15 having strictly the same length. These arms support at their outer ends the preformation sectors 10. 
     DRUM OPERATION 
     As the drum is cylindrical (see FIG. 4), the springs 9 constitute a homogeneous and perfectly rigid assembly since they are held at their central portions by the preformation sectors 10. The drum has a rigid and perfectly cylindrical shape. 
     When the screw 2 is rotated, the flanges 5 and 5a, and therefore the sectors 8 and 8a, are moved symmetrically towards each other with respect to the axis XX. 
     The same rotation of screw 2 causes the corresponding movements of the circular brackets 12, 12a so as to develop radially, simultaneously and with the same amplitude, the preformation sectors 10. The springs 9 then resume a curved configuration such that their developed length remains constant, until a continuous teroidal configuration is obtained at a predetermined maximum diameter. 
     The coil springs 42 constitute a peripherically continuous and definitely homogenous assembly, the elastic wall 11 imparting a smooth and continuous appearance thereto. 
     Thus, the top surface α formed by the assembly of coil springs 42 has a perfectly defined, rigid, smooth and strictly continuous shape. The same applies to the side walls of the drum. 
     In case of a manufacture requiring the provision of a shoulder across the bead of the tire, the sectors 8 and 8a are pushed by the bladder 7 to a diameter greater than the initial diameter. At this stage the preformation operation will take place as described hereinabove. 
     DEVICE FOR FOLDING THE PLIES AND SIDE ELEMENTS 
     Each assembly b comprises essentially a flange 16 in the form of an annular sleeve formed with a portion bent at right angles, slidably mounted on the shaft 1 and maintained at an adjustable mutual spacing by screws 27 so that it can be driven from the flange 8 when the latter is moved towards the preformation axis XX. 
     This flange 10 or 10a carries radial sectors 17, 17a adapted to be moved under the control of an inflatable air bladder 16. The series of sectors 17, 17a is completed by three peripheral springs 33 adapted to support the bead 34 of the tire, so that when the sectors 17, 17a are expanded by inflating said bladders 18 the tire beads 34 are strongly clamped by the peripheral springs 35. 
     Under these conditions the bead 34 of the tire follows exactly the movements of flanges 5 and 5a during the preformation operation. 
     A tray or table 32 or 32a is secured to the flange 16 or 16a. It is adapted to carry a series of flat springs 19, 19a. These springs are hingedly mounted about the point 20 on sectors 17 and 17a and at point 31, at the end of bent levers 23, 23a. These bent levers are each pivoted about a pin 23. Their pivotal movements are controlled by means of an actuator 24 or 24a, acting upon roller 25. This rotation of each bent lever 22, 22a is attended by a vertical enveloping movement of springs 12, 12a as shown in dash-and-dot lines in FIG. 2. The contineous connection between the springs 12 and 12a is obtained through an elastic sheet 26, 26a retained at one end on each spring 20. 
     The manufacture of a radial tire on this device is attended by the following steps: 
     1. The rubber sheets for the side walls are laid upon the folding springs 19, 19a. 
     2. The radial ply is laid upon the drum a. 
     3. The bend wires are laid upon the top of sectors 17, 17a. 
     4. The sectors 17 and 17a are clamped by inflating the air bladder 18. 
     5. Geometrical preformation by rotating the screw 2 and developing the preformation sectors 10, attended by the concomitant movements of springs 33 towards each other. 
     6. The breaker and the tread are laid. 
     7. The sidewall rubber and plies are turned about the two beads with a rolling movement. 
     8. The tire is removed.