DE2709578A1 - Bead of pneumatic tires - Google Patents

Description

MANITZ. FINSTERWALD & GRÄMKOW

* »Munich, 04.03.77 P / 3A'r-D 2237

DUKLOP LIMITED
Dunlop House, Ryder Street, bt.James's, London SW 1, England

Bead of pneumatic tires

The invention particularly relates to the bead of a pneumatic tire a belted tire.

Radial tires include a plurality of circumferentially spaced reinforcing threads, each located in a radial plane of the tire between two in Axially spaced apart tire beads extend and are wound around these ridges.

In the manufacture of a radial tire, the reinforcing threads are arranged to form a substantially cylindrical structure with the ends of the threads extending longitudinally of the structure and looped around the beads provided at each end of the group of threads. The thus arranged tire components are when the tire is completed _f reshaped from the substantially cylindrical shape into the toroidal shape required and thereby the encryption

709837/0813 _ _? _

DR. C. MANITZ · DIPL.-INC. M. FINSTERWALD DIPL. - IN CW GRAMKOW ZENTRALKASSE BAYER. VOLKSBANKF ^

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Strengthening threads made them differ from the original Axial position in a substantially radial position with respect to a lateral cross-section through the finished tire to move.

The beads usually comprise bead wires _t embedded in rubber and the aforesaid movement of the reinforcing threads tends to cause a disturbance in the cross-sectional shape of the bead. The disruption which makes the manufacture of products of constant quality difficult can essentially be avoided by precuring the rubber bead. The use of pre-vulcanized beads, however, requires additional preparatory work so that a good bond between the bead and the adjacent rubber material is achieved during the vulcanization of the tire. This preparatory work represents additional manufacturing costs.

In accordance with the present invention, a tire bead is included

/ et

WuI dead wires that are embedded in a rubber compound, the a mixture of natural chew and a styrene-butadiene copolymer with a bound styrene content of at least percent by weight, as specified by the British Standard Mr. UiS 1673 Section 5 · 1 described method will.

The bead strips and the mixture enveloping them can be provided with a cover layer which also consists of the same Mixture can exist, as it is used for the sheathing of the bead wires, so that the resulting bead has an outer cross-sectional shape which allows the relative movement between the bead and the others during tire manufacture Components of the tire, for example the reinforcing threads occurs, which are wound with their ends around a bead.

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The invention also provides a pneumatic tire incorporating one according to the invention Contains tire bead and a pneumatic tire which is produced by a method according to the invention.

The invention is explained below, for example, with reference to the drawing described; in the drawing shows:

FIG. 1 bead wires embedded according to the invention in a rubber mixture, and FIG

Figures 2-7 each in cross section the bead structure according to Figure in different cross-sectional shapes, covered with additional Layers of the enveloping mixture to form bead arrays of various overall cross-sectional shapes to achieve.

In a preferred embodiment of the invention shown in Figure 1, the polymer content of the rubber mixture 10, in which the bead seams 11 are embedded, equal parts of natural rubber and a styrene-butadiene copolymer with high Styrene content. A resin precursor, e.g. B. phenolformaldehyde and ΗΜΓ (hexamethylenetetramine) is preferably also included. The resin precursor prevents the vulcanized from softening Mixture at temperatures during the working conditions occur during manufacture.

Examples of suitable mixtures with and without precursors are given below;

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Natural rubber

Styro1-butadiene copolymer (87.5% bound styrene) carbon black (N 375 ASTI ^ standard) insoluble sulfur sulfenamide accelerator (e.g. Santocure from Monsanto) zinc oxide

Stearic acid

paraffinic oil (e.g. Dutrex BT)

precondensed ehenol-formaldehyde resin (e.g. GEJ 448 Schenactady Midland)

Hexamethylenetetramine (HMP)

Hydrocarbon resin (e.g. Escorez from Esso)

without prior
runner with before
runner 50 50 50 50 55 55 1.60 1.60 1.00 1.00 5.00 5.00 2.00 2.00 10.00 10.00 - 6.00 - 0.50

6.00

During the deformation of the arranged components to the required Ring shape for the finished tire will be a disorder The cross-sectional shape of the bead prevented by the embedding mixture, dajs is sufficiently stiff to withstand forces exerted by the movement the reinforcement thread and the other components located around the bead assembly is caused to withstand.

The high styrene styrene-butadiene copolymer found in the The mixture contained enables a treatment at the processing temperatures and also results in plastic, non-deforming Ambient temperature properties that maintain the bead shape while the tire is being molded.

During the subsequent vulcanization of the tire, this

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Contains bead, the butadiene units of the styrene-butadiene copolymer cross-linked with natural rubber with a high styrene content and the mixture in the tire bead combines with the adjacent rubber mixture of the tire. The styrene units cannot be networked and are therefore retained as "mobile groups, i.e. they have a higher degree of freedom. As a result a thermoplastic phase is introduced into the mixture, which prevails at low temperatures and creates a stiff state in the mixture. At higher temperatures the networked units of natural rubber and prevail of butadiene and result in an elastic phase.

Surprisingly, it has been found that the special combination of natural rubber and styrene-butadiene copolymer with a high styrene content causes the advantageous properties mentioned. An examination of the phenomenon _

/ the mixture indicates that this result is due to the fact that at normal ambient temperatures behaves like a plastic substance.

Figure 2 shows a bead structure which corresponds to that of Figure 1, however, a uniform cover layer 12 made of the same material as the wire wrapping mixture 10 contains.

Figure 3 illustrates a bead assembly in which an arrangement of bead wires 13 is disposed in a mixture 10 of hexagonal cross section, wherein the wires are encased in a cover layer 14 having a cross-section of varying thickness around the circumference, so that the resulting Has bead circular cross-section.

FIG. 4 shows a bead wire arrangement with an irregular cross section, which is enclosed in a cover layer 15 of varying thickness, so that the resulting bead has an elliptical cross section.

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Figures 5 and 6 each show changes in the structures Figure 3 or 4, with one of the surfaces 16, 17 of the hexagonal Wire bundle has an angle to a direction which is perpendicular to a plane containing the bead stands so that the wire assembly is evenly supported when placed on a wheel rim with a complementary tire Angle is raised. The angle can typically be in the Be of the order of 15 °.

Figure 7 illustrates a WuIstdrahtanordnung group having irregular cross section which is encased within a covering layer 18, which in turn so changes in its strength that results in a further changing of the structure of FIG M-.

Although a mixture is specifically mentioned, the natural rubber and high styrene styrene-butadiene copolymer are the same Contains weight ratio, the content of natural rubber and styrene-butadiene copolymer with a high styrene content in the mixture in its relative proportions between 10:90 to 70:30 parts by weight, regardless of whether or not a resin precursor is used.

It is thus shown that the present invention meets the need eliminates the need to use pre-vulcanized beads and thus a considerable saving in manufacturing costs results.

- patent claims -

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Claims (3)

Pat ent a η claims (1.jBeifenwulst with bead wires in a rubber mixture ν / are embedded, indicated by a Mixture of natural rubber and styrene-butadiene copolymer with a bound styrene content of at least 32 percent by weight, determined according to the method described in British Standard No. BS 1673 Section 5 · 1. 2. tire bead according to claim 1, characterized net that the bead wires and the rubber mixture with a cover layer made of the same rubber mixture in which the bead wires are embedded. 3. Pneumatic tire, characterized by a bead according to one of the preceding claims. 709837/0813