FR2536017A1 - Vehicle tyre without an air chamber comprising especially an internal protective layer and a bead protection layer - Google Patents

Abstract

The invention concerns a tyre without an air chamber of radial structure comprising rubberised resistant metal elements and in which there is additionally provided between the internal layer 8 of low permeability to air and the metal carcass a protective layer 13 constituted by a textile material corded with only one or two wires; the rubberised bead protection strip 14 comprises axial thinnings in order to evacuate air from the bead; thus the passage of air from the internal cavity of the tyre 7 into the carcass under the effect of diffusion is reduced in significant proportions and separations between the rubber and metal is avoided; the protective layer moreover serves to make the distribution of the resistant metal elements of the carcass uniform and it improves the service life whilst reducing the costs of materials and of manufacture.

Description

 The present invention relates to a tire for a vehicle without an inner tube, comprising a radial carcass of which at least one layer formed of resistant rubberized metal supports is hooked in each bead on a bead wire and is reinforced by elements incorporated in the bead, a layer arranged at the interior, formed of vulcanizable poly-re of low air permeability and essentially delimiting the internal cavity of the tire containing the compressed air, as well as a protective layer placed between this inner layer and the carcass layer, which s 'extends internally over the entire periphery of the carcass until it is anchored, and a heel protection strip.

 Such tires are provided with a radial carcass, the resistant supports of which advantageously consist of metallic cords.

They surely absorb the high stresses occurring in heavy and light utility vehicles under the effect of the load and the high air pressure existing in the tire.

In order for the compressed air to maintain the necessary pressure and volume permanently in the tire, these vehicle tires have an inner layer formed of a polymer which is advantageous because of its low air permeability. However, over a long period, air still diffuses in the carcass in metallic cables and causes in this zone, because of the high pressure of the gas, its oxygen and humidity content and its behavior in long duration, an oxidation effect and a reduction in the adhesion resistance between the rubber and the steel, which must be avoided in all cases. air having diffused arrives on the path leading to the atmosphere also in the metallic belt layers and it passes on the metallic elements of the beads of the tire before leaving the tire, after a long period, in the zone of flanks. Also this oxidation effect is to be avoided.

To improve the bond between rubber and metal and to make it durable, a whole series of mixed compositions and metallic alloys have been proposed; in this respect, one can cite the specialized articles published in the review "Kautschuk Gummi und Kunststoffe" nO 1i / 1976 pages 749 - 757, nO 4/1978 pages 227 - 232 and the review "Rubber World" September 1980, pages 26 - 30, as well as the German patent application DE-AS 2553 256 and the German patent DE-PS 2164 236. Some of the proposed solutions are very expensive and could not find any application for this reason. We know how to have a filling layer rubber between a carcass and an inner layer
The present invention aims to exert a hindrance on the compressed air and to make it difficult for it to penetrate into the carcass made up of resistant metallic elements. The value of its pressure in the carcass must therefore also be reduced.

 The problem to be solved according to the invention therefore consists in protecting the carcass, the belt and the heels against penetration of compressed air by reducing the passage of air through the carcass so as to thus preserve a great adhesion between the rubberized part and the metallic cables and to avoid separations in the tire without inner tube.

 According to the invention, this result is obtained using a protective layer preventing diffusion between the inner layer and the carcass and additionally this effect is improved by an arrangement of the heel favorable to the escape of air.

 The problem is solved according to the invention in that the protective layer is arranged in the form of a layer of known textile fabric in which the fabric or the cord - depending on the size of the tire - is formed from a single cable or with two wires and in which the wires arranged parallel to each other are arranged with a density of the order of 10 to 120 wires per decimeter, in which case the wires are oriented relative to the equatorial plane by an angle between 70 and 900 The protective layer then extends from one heel to the other, covering the carcass and the heel reinforcement layer up to a radial height which is situated in the area of the carcass extremate. in addition, the rubberized heel protection strip is provided with narrowing zones of axial section distributed peripherally and which serve as vent auxiliaries.

 By these means and protective measures, the passage of air through the metal carcass and the air pressure inside the carcass are significantly reduced. The great adhesion between the rubberized part and the metallic reinforcing elements can thus be preserved in a more permanent manner than before and separations are more surely avoided. The measures taken in this regard already begin during the vulcanization of the raw tire; the air inevitably incorporated during manufacture is then sucked up, as is known and conventional, but it can now however also be advantageously sucked into the section narrowing zones; arranged to be axially thin, the rubberized bead protection band. This air evacuation path is also retained later during the operation of the tire because the air is mainly propagated along parts located inside the protective layer and seeks a favorable path to the atmosphere through the tire beads.

To facilitate the evacuation of air, it is possible to provide vent passages in the rubberized heel protection strip.

 The protective layer existing between the inner layer and the carcass is advantageously formed from a nylon, polyester or aramid fabric.

It can be constituted by cabled wires having for example a dtex of 340/1, 940/2 or 1400/1 or else 1400/2 in the case of nylon 66. Such a protective layer having a lower density of wires according to the circumstances considerably decrease the passage of compressed air in diffusion and it simultaneously reduces the pressure of the air which still penetrates into the carcass These means produce a discharge in the carcass and reduce the diffusion on the path directed towards the carcass. A quality improvement is thus obtained as regards the adhesion of the rubber to the steel because both the vulcanized rubber molecules and the metal molecules, that is to say for example the brass deposited on the steel react with less oxygen and moisture particles in the carcass due to the decrease in air pressure. Thanks to the protective layer, which is advantageous and also inexpensive, which is formed from a cable fabric in accordance with the present invention, it is possible to partially reduce the thickness of the inner layer, which is considerably expensive, by incorporating less percentage of butyl in the rubberized mixture involved in the inner layer.

 In addition, the additional filler layer conventionally used in the past and formed of a rubberized mixture of strong adhesion, placed between the inner butyl layer which has a poor adhesion property and the carcass, can be removed completely or all at least partially.

 Another advantage of the protective layer according to the invention consists in a uniform ordering of the radial and parallel metallic cables of the carcass which is preserved during the production of the raw tire and during vulcanization; in fact, due to the arrangement of the protective layer with fabric threads placed in an orientation-between 70 and 900 relative to the equatorial plane, the metal cords of the carcass do not move as strongly and it is thus possible remedy quality reductions resulting from irregularities and uniformity.

 According to French patent FR-PS 7806 826, it is known that in a tire provided with an air chamber, a protective layer, arranged in the form of an intermediate layer of textile cords, between the layer interior of butyl and the radial carcass in metallic cable. This layer protects the inner butyl layer against penetration of the metal cords delta carcass during the manufacture of the raw tire and it protects the internal cavity of the tire during its use against a sudden loss of air under the action of The known protective layer is made up of cords of nylon or other high-strength materials comprising a very high density of wires per decimeter, these cords being oriented preferably at an angle of about 450 relative to the equatorial plane. This provision is particularly important for a safety tire. The known protective layer is therefore in particular arranged in the form of a rolled up layer comprising a total length of peripheral winding greater than the circumference section. The problem of diffusion of compressed air was not addressed in this patent.

 Other arrangements of the invention relate to different heel structures. One of them relates to the arrangement of the axial section narrowing zones of the rubberized heel protection strip. Such an area can advantageously be provided with through passages improving the air evacuation process in the heel area. In cooperation with this measure, ventilation channels are provided in the corresponding profiled part of the mold, in front of which are placed basic annular elements which penetrate into the rubberized bead protection strip and which thereby ensure that the air is effectively sucked up in the best possible way during vulcanization. The same crossing passages made in the beads of the tire ~ make it, during the operation of the latter, that the air diffusing towards the atmosphere can more easily pass through heels only across the side.

 The other heel structure involves provisions and arrangements of heel reinforcement elements made of textile cords fabrics formed from identical or thicker threads than those of the protective layer according to the invention. Advantageously, several layers or bands of reinforcing elements are provided which are arranged axially, which reinforce the heel but which, however, serve, on the other hand, in conjunction with the means provided in the rubberized heel protection band, to improve the air evacuation via the tire bead.

Other advantages and characteristics of the invention will be highlighted in the following description, given by way of nonlimiting example, with reference to the accompanying drawings in which
Figure 1 is a radial half-section of a vehicle tire without an inner tube, comprising a protective fabric layer between the inner layer and the radial steel carcass
Figure 2 is an alternative arrangement of the tire bead of Figure 1; and
Figure 3 is a partial plan view taken in the direction-E of Figure 2.

 The vehicle tire 1 is a radial tire with a belt without an inner tube for heavy or light utility vehicles. It essentially consists of the carcass 2, which is formed of radial elements made of steel cords, of the beads 3, of the layer reinforcement in the form of a belt 4> which is made up of several layers of steel cords, the tread 5 and the sidewalls 6.

In accordance with FIG. 1, the internal cavity 7 of the tire is surrounded by the internal layer 8, which consists of a vulcanizable polymer of great air impermeability. Advantageously, this polymer corresponds to halobutyl or bromobutyl rubber. The layer has a thickness
D of about 3 mm It ends respectively in the heel tip at 9 The steel carcass 2, formed of rubber cords of radial steel cords and parallel to each other, is hung in each heel 3 on a rod 10, the carcass end 2a being surrounded axially from the inside to the outside around the rod 10 and ending radially in 2c. The heel rod is formed of steel wires, which are wound radially so as to form a ring of a polygonal cross section, preferably hexagonal. The carcass is inclined at an angle -of 15 relative to the axis of the tire in zone 2b, so that the radially inner base of the bead wire 10. The heel bearing surface li also has this inclination. This heel arrangement is intended for mounting on rims with steep steep shoulders. Additionally, the heel is sufficiently reinforced from the carcass zone 2 to radially above the carcass end 2c, by a layer of steel cord 12.

Between the inner layer 8 and the radial steel carcass 2, a protective layer 13 is provided, which consists of a rubberized textile fabric advantageously formed from materials such as nylon, polyester or aramid. The fabric comprises, in the case where nylon 66 is used with a fineness of yarn or cabled yarn of 940/1 dtex or 940/2 dtex
The fineness of the polyester threads can correspond, for example, to densities of 1100/1 dtex or 1100/2 dtex and the fineness of aramid threads are for example of 550/1 dtex, 550/2 dtex or 840 / 1 dtex. The son has for example a diameter of 0.6 mm and the thickness of the rubberized part is respectively 0.2 mm; a protective layer thickness d of about 1 mm is thus obtained. The protective layer 13 covers the carcass 2 axially outwards until it is anchored in the heel. The protective layer ends at 13a. It reduces, due to its structure and arrangement, the passage of air by diffusion from the internal cavity of the tire to the carcass 2 because the air propagates internally along the protective layer and can escape in the heel area. In addition, thanks to the protective layer provided, the air pressure is reduced inside the steel cord layer of the carcass Consequently, the risk of a decrease in adhesion between the rubberized part and 1-rearing steel after a long period is reduced or slowed down. Separations between rubber and steel are also avoided. The inner layer of butyl rubber 8 is not 100% airtight so that, during the use of the tire, air can enter the inner surface of the protective layer 13. A part of this air slowly penetrates the carcass over time.

On the other hand, air also diffuses from the carcass to the atmosphere. The high proportion of the disturbing air propagates, however - as indicated above internally along the protective layer 13 as far as the bead area of the tire. In this zone, that is to say in the zone of the rim horn (not shown), there is conventionally provided a rubberized strip 14 of heel protection. It comprises in the area 13b of the protective layer axial narrowing of section 14a which are distributed over the periphery. These constrictions can be additionally provided with through passages to improve the evacuation of air.

 Such an arrangement has been shown in FIGS. 2 and 3. The axial section narrowing 14 ′ a of the rubberized strip 14 ′ for protecting the heel is widened by a vent passage taking the form of a recess 15. The recesses 15 of a sector are visible in FIG. 3. They are distributed at intervals over the periphery; they are formed by the auxiliary vent means existing on the tire molds (base rings) (not shown).

 In accordance with FIG. 2, the protective layer 13 ′ is arranged and arranged in a manner similar to that indicated in FIG. 1. Between this layer and the radial steel carcass 2 ′, three bands are however provided, for example of textile cable fabric 16,17,18 having stepped ends and serving as heel reinforcing elements.

They form, in conjunction with the bead vent means, an additional auxiliary to promote the evacuation of air from the tubeless tire.

 The ends of the protective layer 13 ′ may, instead of being disposed axially outside the heel reinforcement elements, also be placed internally between the carcass end 2a and the first layer of axially inner fabric 16. Also , this arrangement contributes to establishing a favorable air evacuation path in the heel area. However, it is essential in this case that the protective layer according to the invention extends from one heel to the other and increases in significant proportions the difficulty of crossing the compressed air towards the carcass, in order -d '' avoid disruptive influences on reducing the adhesion of rubber to metal.

Claims (8)

 1.- Tire for a vehicle without an inner tube, comprising a radial carcass, at least one layer of which is made of resistant, rubberized metal supports (2) is hooked in each bead on a bead wire (10) and is reinforced by elements incorporated in the bead (12), a layer (8) arranged inside, formed of vulcanizable polymer of low air permeability and essentially delimiting the internal cavity (7) of the tire containing the compressed air, as well as a protective layer ( 13) placed between this inner layer and the carcass layer, and extending internally over the entire periphery of the carcass until it is anchored, and a heel protection strip (14), characterized in that the protective layer (13 ) is arranged in the form of a layer of known rubberized textile fabric, in which the fabric consists of a single or two-wire cord and where the wires are arranged with a density of the order of 10 to 120 wires per decimeter (measured in the heel area) and make an angle of between 70 and 900 with respect to the equatorial plane (XX) and in that the protective layer (13) extends axially outward to a radial height corresponding to the area of the end carcass (2a, 2c).  2. A tire according to claim 1, characterized in that the protective layer (13) consists of fabric and cabled in nylon, polyester or aramid son.  3.- A tire according to one of claims 1 and 2, characterized in that the rubberized bead protection strip (14) has axial section narrowing zones (14a) distributed over the periphery.  4.- A tire according to one of claims 1 to 3, characterized in that the rubberized bead protection strip (14,14 ') has vent passages (15) in the region of the section narrowing zones ( 14a)  5. A tire according to claim 4, characterized in that the vent passage is arranged in the form of a groove (15 ') in the section narrowing zone (14a).  6. A tire according to one of claims 1 to 5, comprising at least one bead reinforcement layer (12) consisting of rubberized steel cord elements, which is arranged axially outward relative to the carcass end (2a) characterized in that the protective layer (13) is axially and externally in contact with the heel reinforcement layer (12) over a significant part of its radial length and is connected to the vent passage ( 15).  7.- A tire according to one of claims 1 to 6, characterized in that, instead of the steel bead reinforcement strip (12), there are provided several axial reinforcement strips (16,17, 18) fabric of textile cords, in particular nylon, polyester and / or aramid cords, arranged in a tiered fashion and surrounded on the outside by the protective layer (13 ').  8.- A tire according to claim 7, characterized in that the end of the protective layer (13 ') is disposed between the end of the casing (2a) and the set of reinforcement strips (16, 17, 18) .