METHOD FOR ASSEMBLING A TIRE BLANK

Abstract

A method of manufacturing a tire includes steps of: providing a shoulder drum that includes shoulders having a height of at least equal to 25 mm; placing a carcass ply of a green tire on the shoulder drum; providing a winding of circumferential bead reinforcers around each end of the carcass ply, each winding having a number of turns providing a winding of circumferential bead reinforcers against each shoulder of the shoulder drum, each winding being in a spiral; and forming the green tire such that each end of the carcass ply does not have a turnup around the circumferential bead reinforcers, and the circumferential bead reinforcers are positioned in the green tire in a defined layout.

Claims

1-11. (canceled)

12: A method of manufacturing a tire, the method comprising steps of: providing a shoulder drum that includes shoulders each having a height equal to at least 25 mm; placing a carcass ply of a green tire on the shoulder drum; providing an inner winding of circumferential bead reinforcers against each of the shoulders of the shoulder drum, each inner winding being in a spiral, and an outer winding of circumferential bead reinforcers around each end of the carcass ply, each outer winding having a number of turns, wherein the inner and outer windings are provided such that the circumferential bead reinforcers are positioned in the green tire in a defined layout; and forming the green tire such that each end of the carcass ply does not have a turnup around the circumferential bead reinforcers.

13: The method according to claim 12, wherein the height of the shoulders of the shoulder drum is equal to at least 50 mm.

14: The method according to claim 12, wherein axial faces of the shoulders of the shoulder drum form an angle (α) of less than 90° with an axis of the shoulder drum.

15: The method according to claim 14, wherein the angle (α) is between 60 and 80°.

16: The method according to claim 12, wherein the inner and outer windings are provided as annular semi-finished products, and wherein, for each of the inner and outer windings, a ring made from unvulcanized rubber is included and the circumferential bead reinforcers are wound in a spiral.

17: The method according to claim 12, wherein the step of providing the inner and outer windings includes, in succession: placing a first annular semi-finished product against each of the shoulders of the shoulder drum, positioning the carcass ply so that the carcass ply at least partially covers the first annular semi-finished products, and placing a second annular semi-finished product against each end of the carcass ply.

18: The method according to claim 12, wherein, in the step of providing the inner and outer windings, the inner windings are provided by rotating the shoulder drum while laying the circumferential bead reinforcers against the shoulders of the shoulder drum.

19: The method according to claim 18, further comprising a step of winding a strip of unvulcanized rubber on the shoulder drum to form a filler in a lower sidewall of the green tire.

20: The method according to claim 12, wherein, in the step of providing the inner and outer windings, a plurality of windings of circumferential bead reinforcers are superposed in a region forming a lower sidewall of the green tire.

21: The method according to claim 12, further comprising steps of: shaping a carcass of the green tire; and combining the green tire with a crown unit without removing the green tire from the shoulder drum.

22: A tire comprising: a carcass; and circumferential bead reinforcers, wherein the tire is manufactured by a method that includes: providing a shoulder drum that includes shoulders each having a height equal to at least 25 mm, placing a carcass ply of a green tire on the shoulder drum, providing an inner winding of circumferential bead reinforcers against each of the shoulders of the shoulder drum, each inner winding being in a spiral, and an outer winding of circumferential bead reinforcers around each end of the carcass ply, each outer winding having a number of turns, wherein the inner and outer windings are provided such that the circumferential bead reinforcers are positioned in the green tire in a defined layout, and forming the green tire such that each end of the carcass ply does not have a turnup around the circumferential bead reinforcers.

Description

[0029] The following description provides a better understanding of the method according to the invention according to preferred embodiments of the invention and relies on FIGS. 1 to 7 in which:

[0030] FIG. 1 is a schematic view showing in cross section one essential principle of the method according to the invention,

[0031] FIGS. 2 to 4 show a succession of steps of a first embodiment of the method of the invention,

[0032] FIG. 5 shows in cross section a green tire obtained during the course of the method of FIGS. 2 to 4,

[0033] FIG. 6 schematically depicts details of a preferred embodiment of the method of the invention,

[0034] FIG. 7 illustrates an alternative form of the embodiment of FIG. 6.

[0035] In the various figures, elements which are identical or similar bear the same references. The description of the structure and function of these identical or similar elements is therefore not systematically repeated.

[0036] FIG. 1 shows the essential principles of the method according to the invention. The relevant parts of a shoulder drum 2 have been depicted schematically in cross section. The central part of the drum is interrupted in order to make the drawing clearer. Each of the shoulders 21 of the drum and the particular features of the building, according to the method of the invention, of the lower sidewalls 10 of the green tire 1 can thus be seen on a larger scale.

[0037] The drum 2 comprises an axis of rotation A. Each shoulder 21 of the shoulder drum comprises an axial face 22 making an angle α with the axis A of the drum. The angle α is preferably less than 90° and more preferably still comprised between 60 and 80°.

[0038] The shoulders have a height H. This height H is greater than 25 mm according to the invention and preferably greater than 50 mm in particular for assembling tires for utility vehicles (“heavy goods vehicles”), namely tires intended to bear heavy loads under a pressure of at least 5 bar with a load index in excess of 120.

[0039] The key constituent parts of the green tire 1 at this stage of tire building and, in particular, those of the lower sidewalls 10 are clearly visible in FIG. 1. The carcass ply 3 covers the entire drum, from one lower sidewall to the other. An inner liner 4 is visible on the inside of the carcass ply. In each lower sidewall, the carcass ply is positioned between two bundles of circumferential bead reinforcers. Outer reinforcers 11 can be distinguished here from inner reinforcers 12. Each of the said bundles of circumferential reinforcers is made up of a spiral winding of several turns of a filamentary reinforcer which turns are laid against the axial face 22 of the shoulder of the drum, namely parallel thereto. Viewed in cross section, each bundle may, as here, take the form of a single layer or of several layers. Rubber profiled elements 13 and 14 protect both the circumferential reinforcers and the carcass ply, by preventing any direct contact between them and with the external environment of the lower sidewall. This is also referred to as the “lower sidewall filler”.

[0040] The carcass ply 3 therefore has no turnup around the circumferential bead reinforcers. It is simply held between the two bundles of reinforcers. At this stage in the method, the lower sidewall is complete and it will be appreciated that the circumferential bead reinforcers and also the volumes of rubber are already in position in the green tire in their substantially definitive layout, namely substantially in the layout they will have in the finished tire after it has been moulded. Such a lower sidewall therefore experiences no significant deformation or rotation, either during shaping or during use of the finished tire.

[0041] After the method step depicted in FIG. 1, the drum can be extracted from the green tire. The green tire can then be picked up on another support before being shaped (namely before being inflated to adopt its toroidal shape) and before receiving the crown reinforcers and the tread.

[0042] FIGS. 2 to 4 depict a preferred embodiment of the method of the invention in which the later steps of the tire building are performed on the same drum 2 as was used for the steps depicted in FIG. 1. For the sake of simplicity, the central part of the drum has not been depicted.

[0043] FIG. 2 therefore shows the green tire blank 1 in the state of FIG. 1, namely with the carcass and lower sidewalls assembled on the shoulder drum 2. In FIG. 3, the green tire remains connected to the drum by its lower sidewalls 10 while the length of the drum is gradually reduced (the shoulders of the drum move closer to one another) while an internal pressure forces the carcass to adopt a toroidal shape and then to press itself firmly against the inside of a crown ring 5. The crown ring may combine all the crown reinforcers and the tread in a way known per se in the field of tire building. FIG. 4 corresponds to the moment at which the green tire is completely assembled and shaped, ready to be separated from the drum and then placed in the vulcanizing mould.

[0044] As FIGS. 3 and 4 show, and so as to allow the green tire built on the shoulder drum 2 to be shaped when the shoulders 21 move closer together, the shoulders 21 of the shoulder drum 2 have a height H that is less than the height of the sidewalls of the shaped green tire. According to the invention, and whatever the type of tire being built, the shoulders 21 of the shoulder drum 2 have a height H smaller than the height of the sidewalls of the future tire.

[0045] FIG. 5 shows the complete green tire separated from the drum and ready to be moulded.

[0046] FIG. 6 illustrates a preferred embodiment of the method of the invention, in which embodiment the circumferential bead reinforcers are prepared in the form of annular semi-finished products comprising the said reinforcers wound in a spiral associated with an unvulcanized rubber ring intended to fill the lower sidewall. These subassemblies 1311 and 1412 are thus easy to handle a little like the bead wires in the conventional method. In order to obtain the lower sidewall architecture described in the preceding figures, the method here consists in placing a first semi-finished ring 1412 against the axial face 22 of each shoulder of the drum, and then in folding the ends of the carcass ply 3 over this inner ring before placing a second semi-finished ring 1311 over each of the ends of the carcass ply 3. It will be appreciated that other designs of tire can be obtained according to the invention by varying the number and type of semi-finished rings placed on each side of the carcass. The carcass reinforcement may also be made up of two or more superposed plies between which such annular semi-finished products may also be interposed in the lower sidewall.

[0047] Another way of forming the spiral-winding of the filamentary reinforcer may be to lay a bare filament and a strip of rubber according to the method described in the patent application published under number WO2006/067069. In that case, the rubber profiled elements 13 and 14 are preferably produced by a great many turns of the strip of rubber. FIG. 7 illustrates this alternative form. The circumferential reinforcers 11 and 12 comprise several turns of filament wound in situ during the rotation of the drum and associated over several layers with a strip of rubber wound according to the same principle, at the same time or not as described in document WO2006/067069. It will be appreciated that, in a similar way to FIG. 6, the interior part (12, 14) of the lower sidewall is produced against the drum, and then the carcass ply 3 is folded over this first subassembly before the exterior part (11, 13) is produced on top of the carcass. This figure also illustrates the case of a plurality of layers of reinforcers as mentioned hereinabove.

[0048] The method of the invention makes it possible to manufacture, in a way which is simple and therefore industrially robust, tires the lower sidewall of which is lightweight, strong and plays only a very small part in the rolling resistance of the tire.

[0049] Within the context of the invention, any suitable type of filamentary reinforcer can be used for the circumferential windings, for example a monofilament or a metal cord, a textile thread (such as an aramid or hybrid cord) or an inorganic thread (glass fibre).