PNEUMATIC TIRE WITH REINFORCING BELT

Abstract: This invention relates to a pneumatic tire incorporating a reinforcement belt comprising two superposed unfolded median plies (P,Q) and two laterally disposed folded marginal plies (R,R′). The folded plies each forms two superposed flaps, with the corresponding flaps of each marginal ply being sub­ stantially aligned. In all embodiments of the invention at least one pair of corresponding opposite laterally disposed flaps align with one (Q) of the unfolded median pies (P,Q), and the lateral areas of the other unfolded median ply (P) are surrounded by the folded plies (R,R′).

Description: Pneumatic tire with reinforcing belt This invention relates to pneumatic tires and more particularly to an improved reinforcement belt construction for a pneumatic tire. A reinforcement belt such as disclosed in my U.S. patent NO 4.034.791 includes two flat unfolded plies comprised of metallic reinforcement filiform elements coated with natural or synthetic rubber and two folded over plies with filiform elements likewise coated and made of a synthetic textile material such as an aromatic polyamide or an aramide known under the trademark Kevlar. As used herein the term "filiform elements" relates to cable cords, strands, filaments and monofilaments. The unfold¯ ed plies predominate in the median area of the reinforcement belt whereas each lateral area of the belt is predominated by a folded over ply that forms two confronting flap portions. Each flap portion of one folded ply in one lateral area aligns with a corresponding flap portion of the other folded ply in the other lateral area of the reinforcement belt. The folded and unfolded plies are arranged such that one of the unfolded plies is an extension of one set of aligned flaps in each of the folded over plies. Under this arrangement the reinforcement belt has, at the various points.along its crosswise width, at least two and at the most three layers or thicknesses of superpositioned plies. A reinforcement belt structure of the type described provides adequate transverse rigidity and also substantially reduces the likelihood of separation and/or tearing of the lateral edges of the belt. Such a belt is also relatively economical to manufacture because the plies that incorporate relatively costly reinforcement elements do not extend over the entire width of the belt as is the case with certain known reinforcement belt structures. While the reinforcement belt of the present invention is of a different construction than the belt disclosed in my U.S. Patent ND 4.034.791 it provides benefits similar to those already described for my prior belt construction. It is an object of this invention to provide a pneumatic tire having an improved novel reinforcement belt construction that provides an optimum amount of transverse rigidity in the median area of the belt and an optimum amount of flexibility in the lateral area of the belt. The present invention relates to a pneumatic tire wherein an annular reinforcement belt surrounds a carcass intermediate the carcass and the tread in substantially symmetrical relationship to an equatorial plane of the tire. The reinforcement belt, in crosssection, comprises two crosswise spaced, opposite, laterally disposed plies each folded to form a pair of superposed flap portions having ends directed toward the equatorial plane of the tire. Homologous ends of the flap portions are aligned and have respective predetermined crosswise spacings therebetween. A first unfolded ply of the reinforcement belt is disposed intermediate a first pair of opposite laterally disposed flaps in alignment with the ends of the flaps, enabling the flaps to form terminal extensions of the first unfolded ply. A second unfolded ply which is of greater crosswise extent than the first unfolded ply is surrounded in the lateral area of the belt by the folded over plies. This arrangement of folded and unfolded plies provides at least two and at the most three layers of ply material at various points along the crosswise width of the reinforcement belt. Thus in each embodiment the folded over plies surround the lateral areas of only one of the unfolded plies, and the filiform elements of the folded over plies have substantially more flexibility than those of the unfolded plies. In at least one embodiment of the invention the first unfolded ply is disposed radially beyond, with respect to the axis of rotation of the tire, the second unfolded ply. In other embodiments of the invention the first unfolded ply is disposed radially internally of the second unfolded ply. The crosswise extents of the superposed folded over flap portions need not be equal. Moreover the aligned folded over flap portions that form terminal extensions of the first unfolded ply can be of greater or lesser crosswise extent than the aligned folded over flap portions that do not form extensions of the first unfolded ply. In the accompanying drawings in which various embodiments of the invention are illustrated; Figure 1 is a simplified schematic frtmentary sects ional view of a pneumatic tire incorporating one embodiment of the present invention; Figures 2-4 are simplified schematic representations of reinforcement belt constructions incorporating further embodiments of the present invention, the belt construction being disassociated from the tire environment for purposes of clarity; and Figure 5 shows a prior art reinforcement belt construction. Referring to Figures 1-5 the letter A designates the radially external side of the reinforcement belt with respect to the axis of rotation of the tire and the letter B designates its radially internal side. Reference number 1 represents the equatorial plane of the tire and the reinforcement belt. In Figures 1-4 the letter P generally designates an unfolded ply of relatively large width extending over substantially the entire width of the reinforcement belt. The letter Q designates 2unfolded ply of relatively lesser width than the unfolded ply P. The unfolded plies P and Q are formed of rubber coated metallic filiform elements selected to impart a desired predetermined crosswise rigidity to the reinforcement belt. The letters R and R' in Figures 2-4 respectively designate the folded over plies in the lateral areas of the reinforcement belt. The plies R and R' are formed of rubber coated filiform reinforcement elements having substantially greater flexibility than the filiform elements of the unfolded plies. Any type of sufficiently flexible filiform elements can be used such as formed of metal, preferably steel, or a natural or artificial textile material, fiberglass; or an aromatic polyamide or aramide such as the type of material designated by the trademark Kevlar. In the Figure 2 embodiment the relatively narrow unfolded ply Q1 forms an extension of radially internal flaps 3 and 3' respectively of the folded over plies R1 and R'1. The unfolded ply Q1 is disposed radially internally of the relatively wide unfolded ply P1 and the folded over plies R1 and R'1 surround the lateral areas 4 and 4' of the unfolded ply P1. The radially internal flaps 3 and 3' have a greater crosswise extent than the radially external flaps 2 and 2'. It will be noted that it is possible to select filiform reinforcement elements having substantial differences in flexibility and/or elasticity even though made of the same constituent material. For example, filiform elements made of steel can have a modulus of elasticity varying from approximately 1,000 to 20,000 kilograms per sq. mm. Thus by selecting predetermined structures of filiform elements made of steel, the unfolded plies can be made relatively rigid and the folded over plies relatively flexible. Accordingly the filiform elements of the flies P1 and Q1 are formed of heavy steel cable cords. Each cable cord comprises a strand of four wires having a diameter of 0.25 mm. The filiform elements of the folded over plies R1 and R'1 are formed of fine, flexible steel cable cords each cord comprising four strands of three wires having a diameter of 0.15 mm. In the Figure 3 embodiment the radially internal flaps have a lesser crosswise extent than the radially external flaps. The folded over plies R2 and R'2 are formed of aramide filiform elements such as known under the trademark Kevlar. The filiform reinforcement elements of the unfolded plies P2 and Q2 are substantially the same as those of the plies P1 and Q1. In the Figure 4 embodiment the unfolded ply Q3 is radially external of the unfolded ply P3 and forms an extension of the radially external flaps. The filiform reinforcement elements of the unfolded plies P3 and Q3 are substantially the same as those of Figures 2-3 whereas the filiform reinforcement elements of the folded over plies R3 and R'3 can be made of Kevlar material as described for the Figure 2 embodiment. Figure 5 shows a prior art reinforcement belt structure comprising a flat ply 2 and a folded over ply r whose extremities surround the lateral edges of the flat ply p. The filiform reinforcement elements of the plies 2 and r are made of steel with the elements of the ply 2 being formed of coarse steel cable cords to provide a desired transverse rigidity to the belt. The filiform elements of the ply r are relatively flexible steel cable cords. In comparing the belt structure of Figure 5 with the embodiment of Figure 2 it will be noted that the Figure 2 reinforcement belt has greater transverse rigidity than the Figure 5 reinforcement belt without sacrificing the desired flexibility at the lateral end portions of the belt. The Figure 2 embodiment also permits a reduction in manufacturing costs because the relatively heavy steel cable cords that constitute the armature of a ply such as Q1 are substantially less expensive than the relatively flexible steel cable cords used throughout the folded over ply r of the Figure 5 reinforcement belt that is known in the art.

Claims: Claims of patent 1. Pneumatic tire comprising an annular carcass having a radially outerlying crown portion, a tread constituting an annular cover surrounding the crown portion of said carcass, and an annular reinforcement belt interpositioned between the crown portion of said carcass and said tread, characterized in that said reinforcement belt has marginal end portions in cross-section, and comprises in cross-section a pair of opposite, laterally disposed, crosswise spaced, first and second plies of a first cord material, each of said first and second plies being folded to form two respective flap portions having ends directed toward an equatorial plane of the tire and respective folded margins directed away from said equatorial plane, one of the flap portions of each said first and second folded plies and at least a portion of the other said respective flap, being superposed, a first ply of second cord material having opposite terminal ends being disposed between homologous ends of one of the pairs of corresponding opposite, laterally disposed flap portions such that one pair of opposite, laterally disposed flap portions extends laterally beyond corresponding terminal ends of said first ply of said second cord material in substantial alignment with said corresponding opposite terminal ends, and a second ply of said second cord material being disposed adjacent said first ply of said second cord material and having opposite terminal ends, respectively disposed between the superposed flap portions of the first and second folded plies, such that the reinforcement belt has at least two layers of ply thickness at various points along its crosswise width and three layers of ply thickness where the folded over flap portions are superposed. 2. Pneumatic tire according to claim 1, characterized in that said first and second cord materials comprise filiform elements, the filiform elements of said first cord material being substantially more flexible than the filiform elements of said second cord material. 3. Pneumatic tire according to claim 2, characterized in that said filiform elements of said first cord material are formed of metal. 4. Pneumatic tire according to claim 3, characterized in that said filiform elements of said first cord material are formed of steel. 5. Pneumatic tire according to claim 4, characterized in that said filiform elements of said first# cord material are formed of relatively fine steel cord whereas the filiform elements of said second cord material are formed of relatively coarse steel cord. 6. Pneumatic tire according to claim 1, . characterized in that said filiform elements of said first cord material comprise nonmetallic cords and said filiform elements of said second cord material comprise metallic wire cords. 7. Pneumatic tire according to claim 6, characterized in that said nonmetallic cord material is formed of an aromatic polyamide identified by the trademark Kevlar. 8. Pneumatic tire according to claim 1; characterized in that said reinforcement belt is symmetrical with respect to the equatorial plane of said tire. 9. Pneumatic tire according to claim 1, characterized in that homologous ends of the first and second pairs of corresponding opposite, laterally disposed flap portions are crosswise aligned. 10. Pneumatic tire according to claim 1, characterized in that said second ply of said second cord material is of greater crosswise extent than the first ply of said second cord material. 11. Pneumatic tire according to claim 1, characterized in that said second ply of said second cord material is disposed radially internal of said first ply of said second cord material. 12. Pneumatic tire according to claim 1, characterized in that said second ply of said second cord material is disposed radially external of said first ply of said second cord material. 13. Pneumatic tire according to claim 1, characterized in that the crosswise extent of each flap of the other pair of corresponding opposite, laterally disposed flap portions is greater than the crosswide extend of each flap of said one pair of corresponding opposite, laterally disposed flap portions. 14. Pneumatic tire according to claim 13, characterized in that said one pair of corresponding opposite, laterally disposed flap portions is disposed radially inwardly of said other pair of corresponding opposite, laterally disposed flap portions. 15. Pneumatic tire according to claim 14, characterized in that second ply of said second cord material is of greater crosswise extent than the first ply of said second cord material and is disposed radial ly inward of the first ply of said second cord material. 16. Pneumatic tire according to claim 14, characterized in that the second ply of said second cord material is of greater crosswise extent than the first ply of said second cord material and is disposed radially outward of the first ply of said second cord material. 17. Pneumatic tire according to claim 13, characterized in that said one pair of corresponding opposite, laterally disposed flap portions is disposed radially outwardly of said other pair of corresponding opposite, laterally disposed flap portions. 18. Pneumatic tire according to claim 17, characterized in that the second ply of said second cord material is of greater crosswise extent than the first ply of said second cord material and is disposed radially outward of the first ply of said second cord material. 19. Pneumatic tire according to claim 17, characterized in that the second ply of said second cord material is of greater crosswise extent than the first ply of said second cord material and is disposed radially inward of the first ply of said second cord material.

Inventors: MIRTAIN, HENRI JEAN
Applicants: PNEU UNIROYAL ENGLEBERT
Application year: 1979
Main classification: B60C9
IPC codes: B60C9