Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
2002-01-30
2004-10-12
Knable, Geoffrey L. (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S130700, C156S132000, C156S133000, C152S562000
Reexamination Certificate
active
06802923
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a process for manufacturing a tire comprising a carcass reinforcement, the reinforcement elements of which are radial in the sidewalls and oblique to the circumferential direction in the region of the crown reinforcement. It also relates to the tires obtained by said process.
BACKGROUND OF THE INVENTION
Tires of the radial type, and more precisely the non-vulcanized toric blanks thereof, are commonly manufactured by a process comprising two distinct phases. In the first phase, the cylindrical blank of the carcass reinforcement is manufactured on a cylindrical building drum. The blank comprises, inter alia, the carcass reinforcement itself, the rubbers and reinforcements internal to the carcass reinforcement, and all of the elements forming the beads, these elements being the bead wires, the profiled elements and bead filler layers and bead reinforcement armatures. In a second phase, the cylindrical blank of the carcass reinforcement is shaped, dilated to adopt a toric form, on which form there will then be laid the elements constituting the crown reinforcement, the profiled elements and rubber layers separating the crown reinforcement from the carcass reinforcement, as well as the tread. The toric, non-vulcanized tire blank is then introduced into a vulcanization mold, the blank undergoing slight additional shaping to end up with the final dimensions of the tire.
The two-phase manufacturing process for radial tires has for a long time been considered as the only one which can be used industrially, despite the fact that, if compared to the single-phase (or -stage) process used for cross-ply tires, the two-stage process involves additional, more complex, more costly equipment, more labor, and consequently a necessarily higher cost price.
That is why it has always been considered advantageous to be able to manufacture radial tires by a single-stage process and using the traditional equipment for manufacturing cross-ply tires. Such single-stage process consists of assembling, on one and the same drum, all of the constituents of the tire blank in a practically cylindrical shape.
To the extent that the reinforcement elements of the carcass reinforcement are elements which are radial over the entire meridian length and that the crossed reinforcement elements of the crown reinforcement create a triangulation with the elements of the carcass reinforcement, the shaping of the cylindrical blank to arrive at a toric blank is practically impossible, unless a certain number of tricks are used such as lubricating the different layers and/or plies by means, for example, of zinc stearate in powdered form or in solution in a solvent, or the laying between the carcass reinforcement and the crown reinforcement of a large pad of rubber mix. These tricks having more drawbacks than advantages.
French Patent 1 413 102, noting that the portion of the radial carcass reinforcement located radially to the inside of the crown reinforcement might be superfluous, describes a tire comprising a carcass reinforcement anchored in each bead to an inextensible annular element and formed of independent reinforcement elements. The independent reinforcement elements are arranged, firstly, radially or substantially radially between the bead and the crown reinforcement and, secondly, with an orientation which moves substantially away from the radial orientation over at least an axial portion of the region in which the crown reinforcement extends. The carcass reinforcement is finished off by a crown reinforcement, and the simplest solution consists in having a crown reinforcement composed of a single crown ply formed of reinforcement elements, the angle of orientation of which relative to the circumferential direction is of a sign opposite to that formed by the elements of the carcass reinforcement in its oblique portion. Such a tire structure can be produced by the one-stage manufacturing process. The carcass ply is arranged on a building drum, the radial reinforcement elements of the carcass ply being placed substantially parallel to the generatrices of the drum. The bead wires are then put in place and the edges of the carcass ply are turned up around the bead wires and bead filler rubbers to form the carcass ply upturns. Then the crown ply is laid, the direction of the crown reinforcement elements forming a suitable angle with those of the carcass ply, and the two plies, carcass and crown, are caused to adhere. Then the cylindrical blank thus obtained is shaped by bringing together the bead wires and inflating the membrane of the building drum. The reinforcement elements of the carcass ply and those of the crown ply adopt a new angular configuration depending on the starting angles and the shaping ratio in the zone where the two plies are superposed, whereas the carcass ply elements substantially retain their radial orientation in the sidewalls.
Although the foregoing process can effectively make it possible to obtain blanks having a plurality of carcass reinforcement plies and a plurality of crown reinforcement plies, the reinforcement elements of the plies can only have two angular orientations (−&bgr;, +&ggr;) or (+&bgr;, −&ggr;) at the crown, without such orientations being identical (&bgr;≠&ggr;). The process, therefore, does not make it possible, firstly, to obtain a tire having a single crown ply which is exempt from excessive lateral thrust at 0° drift, and, secondly, to have a tire which is effective in all travelling configurations, owing to the fact that the orientation of the elements of the different plies does not result in the creation of the slightest axial zone with the presence of a triangulated reinforcement. It is true that the cited reference proposes a solution for overcoming the last-mentioned disadvantages, i.e., it is possible to add to the structure described another crown ply, the reinforcement elements of which have an orientation of a sign which is opposite to that of the reinforcement elements of the first ply. The laying of the second crown ply, however, is only effected, according to the process described, in a second stage after shaping to the final diameter of the toric blank, that is to say, a process identical to the process for manufacturing a blank having a true triangulated reinforcement.
SUMMARY OF THE INVENTION
It is an object of the invention to overcome the foregoing disadvantages and to provide a tire produced by a process very close to a one-stage process, and which makes it possible to obtain either a tire having a crown ply, the reinforcement elements of which form the angle opposite to that of the elements of the radially subjacent carcass with the circumferential direction, or a tire having a crown reinforcement with plies of reinforcement elements which are crossed from one ply to the next, or a tire having a partially triangulated crown reinforcement.
According to the invention, a process for manufacturing a tire comprising a carcass reinforcement which is radial in the sidewalls and the reinforcement elements of which form with the circumferential direction and radially beneath a crown reinforcement, which is composed of at least one layer of reinforcement elements forming an angle ⊥&ggr;
2
with said direction, an angle ∓&bgr;
2
over a width L, includes initially manufacturing a cylindrical blank comprising all of the components of the tire by at least the following steps:
a) at least one carcass reinforcement ply formed of radial reinforcement elements is laid on the central part of diameter D of a cylindrical building drum;
b) the annular bead elements, which are inextensible and have an internal diameter D
3
, the profiled elements and bead filler rubbers, the bead reinforcement armatures, are laid, and the edges of the carcass ply are turned up to form the carcass upturns;
c) the central part of the carcass ply is subjected to an angular variation of its reinforcement elements by pre-shaping on the drum, passing from the diameter D to a greater diameter D
Ahouanto Michel
Bestgen Luc
Knable Geoffrey L.
Michelin Recherche et Technique SA
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