Pneumatic tyre for an agricultural tractor or similar vehicle

(42) Start of patent term: 15.10.1988 (45) Date of issue: 10. 5.1989 (51) Int.Cl? : B60C 11/08

<td>(30) Priority:</td><td>(73) Patent owner:</td>

<td>31. 8.1981 FR 8116676 claims.</td><td>SOCIETE ANONYMOUS DITE: PNEUMATIQUES, CAOUTCHOUC MANUFACTURE ET PLASTIQUES ADHESIVE COLOMBES</td>

<td>(56) Documents:</td><td>F-92700 COLOMBES (FR).</td>

<td>DE-0S2139255 FR-PS1237762 US-PS4254811</td><td></td>

(54) TIRES FOR AGRICULTURAL TRACTORS OR SIMILAR VEHICLES

CQ

AT 388 140

DVR 0078318

Nr.388140

The invention relates to a tire for agricultural tractors or similar vehicles, with a run strip whose raised elements are formed by massive webs spaced from each other in two rows are arranged, which extend in the circumferential direction and the webs see in the axial direction each about a extend the other half of the tread, wherein the webs are alternately offset from one row to the other in the circumferential direction and each formed of two substantially rectilinear segments integrally connected to one another, which form different angles with the Umfangsriehtung.

Such tires are mainly used on light or soft soil.

Treads with such webs are known for example from US-PS No. 3,603,370. The axially inner segment forms at these webs an angle between 15 and 35 °, whereas the axially outer segment forms an angle between 60 and 75 ° with the circumferential direction. However, such a run strip has on light soils inadequate adhesion and on hard floors (roads, etc.) on an insufficient resistance to wear, which is probably due to the general arrangement of the webs and deformations of the tire body (with carcass).

The same applies to an arrangement according to FR-PS No. 1,237,762, in which the rectilinear webs are arranged alternately V-shaped and each extended on the outside of the tire by a transverse segment which is supported on the tire sidewall.

Recently, treads having rectilinearly or slightly curved lands arranged alternately V-shaped have been proposed for radial carcassed tires on which a crown reinforcement (belt) is fitted. However, these tires are also found to have insufficient wear resistance on light soils, especially when these tires are used on the front axle of tractors equipped with two drive axles. It is then absolutely necessary for the tires mounted on the front (drive) axle to have a liability on light or soft soils, which is greater than that of the tires on the rear (drive) axis.

From US-PS No. 4,254,811 a profile is generally known, which is similar to the aforementioned. However, the recessed portions of the tread of the prior art tire are discontinuous and the raised portions are continuous. Therefore, it is not possible, such a tire for agricultural vehicles and the like. to use. In addition, the orders of magnitude of the grooves compared to the projections are extremely low, which also precludes a proper use.

It is an object of the invention to improve the longevity and the behavior of radial tires of the type defined above, in particular when used on tractors with two drive axles.

To achieve this object, the invention provides that the tire has a radial carcass reinforcement in a conventional manner, the Meridiankrümmung is maximum with mounted and normal inflated tire on the tire shoulders, and has a crown reinforcement whose axial width at most equal to 0.9 times, preferably 0.75 to 0.85 times, is the axial width of the tire and which is disposed radially on the outside of and around the carcass reinforcement, and is formed of at least two layers of cables crossed in each layer and crossed from one layer to the other; Forming a circumferential direction of the tire smaller than 30 ° and preferably between 15 and 20 °, the crown reinforcement having a substantially constant meridional curvature from edge to edge which is at most equal to, but preferably less than, the curvature of the tire defined by the reciprocal of half the total diameter, and wherein the carcass reinforcement is along a zone located on the equator is centered and whose width is at least 0.75 times the width of the crown reinforcement, is parallel to the crown reinforcement, and that two successive webs of a same row in the circumferential direction of each other have a distance corresponding to at least 4 times the width of a web, and in that the axially outer segment of the webs extends axially beyond the corresponding edge of the crown reinforcement and at an angle between 85 and 100 ° with the circumferential direction of the tire

No. 3888140, whereas the axially inner segment forms an angle of less than 30 ° with the circumferential direction of the tire, which angle approximates the angles of the radially outer layers of the crown reinforcement, the axially inner segment being the ground in the normal direction of travel in the footprint of the tire before the axially outer segment is to be touched, is connected to the axially outer segment by an intermediate segment, which is preferably curved and extends in the axial direction over a width which is about 0.15 times the axial width of the tire.

According to advantageous developments of the invention, the crown reinforcement has a meridian curvature which is substantially constant from one edge to the other and at most equal but preferably less than the curvature in the circumferential direction (reciprocal of half the total diameter) of the tire; is the carcass reinforcement along an equator centered zone whose width is at least equal to 0.75 times the width of the crown reinforcement, parallel to the crown reinforcement; the crown reinforcement is made up of layers of cables which are crossed in each layer in parallel and from one layer to another at preferably symmetrical angles to the circumferential direction of the tire, these angles being approximately 20 °; In addition to the layers of cables arranged at angles of less than 30 °, the crown reinforcement is formed from at least one layer of parallel cables arranged radially inwardly of the other layers and forming an angle of more than 45 ° with the circumferential direction of the tire form; have the webs, measured at its radially outer surface which is to come into contact with the ground, a practically constant width; have two successive webs of a same row in the circumferential direction a distance from each other, which is at least equal to four times the width of a web; the axially outer web segment projects beyond the corresponding edge of the crown reinforcement in the axial direction by a length which is between 0.1 and 0.2 times the axial width of the tire, the end of this projection being able to form a protuberance protecting the corresponding tire shoulder; the two rows of webs are interleaved into each other on both sides and along the equator in a width which is at most equal to the width of the webs measured at their axially inner ends; the two rows of lands are spaced apart axially on both sides and along the equator at a width at most equal to the width of the lands measured at their axially inner ends; increases the radial height of the lands above the bottom of the tread from the equator to the tread edges; For example, the ratio of the radial height of the tire on its rim to the width of the tire body (as defined below) is between 0.6 and 0.9.

Further features and advantages of the invention will become apparent from the following description of exemplary embodiments and from the drawings, to which reference is made. In the drawings: Fig. 1 is a plan view of a part of a tire according to the invention with part of the reinforcement (carcass and crown reinforcement) exposed; 2 shows a radial section of the tire shown in Fig.l in the plane II-II; 3 and 4 further embodiments of the invention; and Fig. 5 is a diagram for explaining the operation of the invention.

The part of a tread shown in Fig.l comprises solid webs -6- spaced apart in two rows. Each row extends circumferentially and its ridges extend axially about a respective other half of the tread. From one row to the other, the webs -6- are alternately offset in the circumferential direction. The bars -6- of a row are like each other. The webs -6- each have two

Segments -11,12- which are substantially rectilinear or only slightly curved and integrally connected to each other and form different angles A and B with the circumferential direction.

The tire -1- shown in Fig. 2 includes a radial carcass reinforcement -2- and a crown reinforcement -3-. The carcass reinforcement -2- reaches its maximum meridian curvature at the two shoulders when the tire is mounted on the rim and normally inflated, but unloaded.

The crown reinforcement -3- is radially disposed on and around the outside of the carcass reinforcement; its axial width Lj is at most 0.9 times,

Preferably, 0.75 to 0.85 times, the maximum axial width L of the body of the tire -1-, which is achieved between the beads and the protective projections -16- of the shoulders -13-. These projections -16-, which are the subject of a preferred embodiment, are expressly disregarded in the measurement of said width L. The crown reinforcement -3- consists of at least two layers -3 ^, 3₂ - formed by cables which are parallel in each position and from one position -3₁ - to the other situation -3₂ - Are crossed and form at the equator 9 angle C with the circumferential direction of the tire, which are smaller than 30 ° and preferably between 15 and 20 °.

According to the invention, the axially outer segment -11- of the ridges -6- projects axially beyond the corresponding edge of the crown reinforcement -3- and forms an angle B between 85 and 100 ° with the circumferential direction of the tire. The axially inner segment -12- of the webs -6-, which in the normal direction of travel is intended to come into contact with the ground in the footprint -14- of the tire in front of the axially outer segment -11-, is connected to this segment Connected via an intermediate segment -10-, preferably a circular arc with the radius R._J forms. This connecting segment -10- extends according to the invention over an axial width 1 equal to about 0.15 times the axial width L of the tire defined above. The axially inner segment -12- of the webs -6- forms according to the invention with the circumferential direction of the tire at an angle A which is smaller than 30 ° and at the angle C of the outer radial layers -3 ^ 2- of the crown reinforcement - 3- is approximated.

The crown reinforcement -3 has a very small meridional curvature 1 / R, which is substantially constant from one edge to the other. The curvature is at most equal to the curvature in the circumferential direction, which is equal to, but preferably less than, the reciprocal of half the total diameter of the tire. Along a zone centered on the equator and having an axial width at least equal to 0.75 times the width Lj of the crown reinforcement, the carcass reinforcement -2- is parallel to this crown reinforcement -3-. Preferably, the layers are -3₁₅3₂- The crown reinforcement -3- arranged symmetrically at angles of about 20 ° to the circumferential direction of the tire.

According to the invention, the crown reinforcement -3- is formed of at least two layers of cables which are inclined at less than 30 ° to the circumferential direction. These layers -3 ^ 3₂ - According to the invention are arranged under the tread, as well as in a preferred embodiment in which the crown reinforcement -3- beyond at least one layer (not shown) of parallel cables which form an angle of more than 45 ° with the circumferential direction of the tire , According to the invention, the axially inner segments -12- of the webs -6- are substantially parallel to these layers -3_} 3₂- Oriented, which have an inclination of less than 30 °, ie parallel to the orientation, according to which the crown reinforcement -3- or the belt works. Thus, it can be assumed that the substantially longitudinally oriented segments 12 of the webs 6 are optimally held by the underlying belt and are very resistant to wear on both hard and light soils. These practically longitudinally oriented segments -12- can also more easily penetrate into light or soft soils. This results in improved lateral displacement of the earth and course keeping, especially on sloping soils. On the other hand, the layers oriented at less than 30 ° give -3j, 3_?- The tire according to the invention a practically cylindrical apex, which experiences in the ground contact zone -14- only a small contraction.

The axially outer, substantially transversely oriented segments -11- project beyond the corresponding edge of the crown reinforcement -3- by a length d which is between 0.1 and 0.2 times the axial width L of the tire as defined above. The end of this projection can form a projection which extends beyond the axial width L of the tire and is intended to protect the corresponding tire shoulder. The end portions of the substantially transverse segments -11- of the webs -6- are thus fixedly connected to the radial carcass reinforcement -2-, especially where it reaches its maximum curvature. Due to the almost rectangular contour -14- the ground contact area on the ground

No. 3,888,140 to the crown reinforcement according to the invention, the substantially transverse segments -11- of the webs -6- engage the lightweight bottom over their entire axial extent, and not at their connecting element -10- for connection to the substantially longitudinal one Segment -12-, as with a Kreuzkarkassenreifen with elliptical

Contact patch -15- is the case that is also shown in Figure 5 for comparison. Furthermore, the underlying, substantially longitudinal layers -3j, 3 act₂ - In the immobilization of the curved connecting elements -10- of the webs -6- in the longitudinal direction with.

The webs 6 formed according to the invention preferably have a virtually constant

Width e measured at the radially outer surface to be in contact with the ground. The distance between two successive webs -6- of a same row in the circumferential direction is at least equal to 4 times the width e of a web -6-.

Depending on whether the longitudinal adhesion and the wear resistance or the self-cleaning effect of the tread according to the invention is to be increased, it is favorable, the axially outer ends of the webs -6- axially outward (Figure 4) or inwardly (Fig.3 ), whereas in the embodiment shown in Fig. 1 these ends are aligned in the equatorial plane, which is illustrated by its section line -9-. The axial distance 1 (Fig.4) or the axial width 1 of the interleaving (FIG. 3) should expediently not exceed the width e of the webs -6- which is measured on the axially inner segment -12-, the webs -6- remaining in each case separated from one another ,

As can be seen from Figure 2, the meridional curvature of that surface of the webs -6-, which is to come into contact with the ground, less than that of the crown reinforcement -3-. The radial height of the webs -6- over the bottom of the barrel strip thus increases from the equator to the edges of the tread toward, these edges are determined by the axially outer ends of the webs -6-.