Agricultural vehicle tire carcass reinforcement

Abstract

Tire comprising carcass reinforcement (7) comprising turned-up carcass layers (71, 72) and non-turned-up carcass layers (73, 74), each turned-up carcass layer (71, 72) comprising main part (711, 721) wrapped, in each bead (4), from the inside of the tire towards the outside around bead wire (8) of diameter D, to form turn-up (712, 722) of which end (E1, E2) is positioned radially on the outside of radially outermost point E of bead wire (8) at a radial distance (a1, a2), each non-turned-up carcass layer (73, 74) having an end (E3, E4) which is positioned at radial distance (b3, b4) from the radially outermost point of E of bead wire (8), the radial distance (a1, a2) is at least equal to 0.5 times the section height H of the tire and the radial distance (b3, b4) is at most equal to diameter D of bead wire (8).

Claims

1. A tire for a heavy vehicle of a self-propelled agricultural type, comprising: a tread, of width A, connected by way of two sidewalls to two beads configured to provide a mechanical connection to a rim, of width L; a reinforcement comprising a crown reinforcement, radially on an inside of the tread, and a carcass reinforcement, radially on the inside of the crown reinforcement; wherein the carcass reinforcement comprises at least two turned-up carcass layers and at least two non-turned-up carcass layers; wherein each said turned-up carcass layer includes mutually parallel reinforcing elements and comprises a main part wrapped, in each said bead, from the inside of the tire towards an outside around a bead wire, of diameter D, so as to form a turn-up of which an end is positioned radially on the outside of a radially outermost point of the bead wire at a radial distance; wherein each said non-turned-up carcass layer includes mutually parallel reinforcing elements, an end of which is positioned at a radial distance from the radially outermost point of the bead wire, and each non-turned-up carcass layer is not wrapped around any portion of any bead wire; wherein a meridian section of the tire has, in a meridian plane passing through a rotation axis of the tire, a section height H and a section width S; wherein, in each sidewall portion of the tire, a sequence of carcass layers from the outside of the tire to the inside of the tire comprises a turn-up of a first turned-up carcass layer, a first non-turned-up carcass layer, a turn-up of a second turned-up carcass layer, a second non-turned-up carcass layer, a main portion of the second turned-up carcass layer, and a main portion of the first turned-up carcass layer; wherein the radial distance between the end of the turn-up of each turned-up carcass layer and the radially outermost point of the bead wire is at least equal to 0.5 times the section height H of the tire, and wherein the radial distance between the end of each non-turned-up carcass layer and the radially outermost point of the bead wire is at most equal to the diameter D of the bead wire.

2. The tire according to claim 1, wherein the radial distance between the end of the turn-up of each turned-up carcass layer and the radially outermost point of the bead wire is at most equal to 0.85 times the section height H of the tire.

3. The tire according to claim 1, wherein the reinforcing elements of at least one of the carcass layers is made of textile.

4. The tire according to claim 1, wherein the reinforcing elements of at least one of the carcass layers is made of polyester.

5. The tire according to claim 1, wherein the meridian section of the tire has a crown deflection B, and the tread width A is at most equal to 20 times the crown deflection B.

6. The tire according to claim 1, wherein the meridian section of the tire has a crown deflection B, and the tread width A is at least equal to 10 times the crown deflection B.

7. The tire according to claim 1, wherein the section width S of the tire is at most equal to 1.4 times the rim width L.

8. The tire according to claim 1, wherein the section width S of the tire is at least equal to 1.1 times the rim width L.

9. The tire according to claim 1, wherein the tread width A is at most equal to 0.95 times the section width S of the tire.

10. The tire according to claim 1, wherein the tread width A is at least equal to 0.75 times the section width S of the tire.

11. The tire according to claim 1, wherein the tread width A is at most equal to 16 times a crown deflection B.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The features of the invention will be understood better with the aid of FIGS. 1 and 2:

(2) FIG. 1 shows a meridian half-section through a tire for a self-propelled agricultural vehicle according to an embodiment of the invention.

(3) FIG. 2 shows a comparison between the cyclical loads to which a tire according to an embodiment of the invention and a reference tire from the prior art are respectively subjected.

DETAILED DESCRIPTION OF THE DRAWINGS

(4) FIG. 1 shows a meridian half-section through a tire 1 for a heavy vehicle of the self-propelled agricultural type, this meridian half-section not being to scale in order to facilitate the understanding thereof. The axes (XX), (YY) and (ZZ) represent the circumferential, axial and radial directions, respectively. The tread 2, of width A, is connected by way of two sidewalls 3 to two beads 4 that are intended to provide a mechanical connection to a rim 5, of width L. The crown reinforcement 6 is radially on the inside of the tread 2. The carcass reinforcement 7 is radially on the inside of the crown reinforcement 6.

(5) The carcass reinforcement 7 comprises two turned-up carcass layers (71, 72) and two non-turned-up carcass layers (73, 74). Each turned-up carcass layer (71, 72), consisting of mutually parallel reinforcing elements, comprises a main part (711, 721) wrapped, in each bead 4, from the inside of the tire towards the outside around a bead wire 8, of diameter D, so as to form a turn-up (712, 722) of which the end (E.sub.1, E.sub.2) is positioned radially on the outside of the radially outermost point E of the bead wire 8 at a radial distance (a.sub.1, a.sub.2). Each non-turned-up carcass layer (73, 74), consisting of mutually parallel reinforcing elements, has an end (E.sub.3, E.sub.4) which is positioned at a radial distance (b.sub.3, b.sub.4) from the radially outermost point E of the bead wire 8.

(6) Furthermore, at the sidewalls 3, the two non-turned-up carcass layers (73, 74) are axially on the outside of the main parts (711, 721) of the two turned-up carcass layers (71, 72) and axially on the inside of the turn-ups (712, 722) of the two turned-up carcass layers (71, 72). In addition, in the present case, the end (E.sub.3) of the axially outermost non-turned-up carcass layer (73) is interposed between the respective turn-ups (712, 722) of two turned-up carcass layers (71, 72): the non-turned-up carcass layer (73) is said to be sandwiched between the respective turn-ups (712, 722) of the two turned-up carcass layers (71, 72). The end (E.sub.4) of the axially innermost non-turned-up carcass layer (74) is, for its part, interposed between the bead wire 8 and the main parts (711, 721) of the two turned-up carcass layers (71, 72).

(7) The meridian section of the tire has, in a meridian plane passing through the rotation axis of the tire, a section height H and a section width S.

(8) In accordance with the invention, the radial distance (a.sub.1, a.sub.2) between the end (E.sub.1, E.sub.2) of the turn-up (712, 722) of each turned-up carcass layer (71, 72) and the radially outermost point E of the bead wire 8 is at least equal to 0.5 times the section height H of the tire, and the radial distance (b.sub.3, b.sub.4) between the end (E.sub.3, E.sub.4) of each non-turned-up carcass layer (73, 74) and the radially outermost point E of the bead wire 8 is at most equal to the diameter D of the bead wire 8.

(9) FIG. 2 shows two curves that relate respectively to a tire according to the invention, in solid lines, and a reference tire from the prior art, in dotted lines. Each curve shows the cyclical load to which such a tire fitted on the front axle of a self-propelled agricultural vehicle, such as a combine harvester, is subjected. For a tire of the prior art that is inflated to an inflation pressure equal to 1.15, the recommended inflation pressure, the load is initially equal to the recommended load, corresponding to the index 100, then it increases by 70% to the index 170, while the vehicle moves along in the field and harvests, thereby increasing the load on the tire. When the vehicle offloads its cargo, the load decreases to the initial load at the index 100. Thus, loading and unloading cycles of the tire are observed. In the case of the tire according to the invention, inflated to the recommended inflation pressure, the initial load is increased by 20% compared with the initial load on the tire of the prior art, this corresponding to the index 120, and the maximum load reaches the index 186, i.e. an overload of 86%.

(10) The invention has been studied in particular in the case of a tire for a self-propelled agricultural vehicle of the size 800/70 R 32, of which the theoretical aspect ratio HIS between the section height H and the section width S is equal to 0.70. This tire comprises a carcass reinforcement comprising two turned-up carcass layers and two non-turned-up carcass layers, as described in FIG. 1.

(11) The radial distances (a.sub.1, a.sub.2) between the ends (E.sub.1, E.sub.2) of the turn-ups (712, 722) of the turned-up carcass layers (71, 72) and the radially outermost point E of the bead wire 8 are respectively equal to 0.58 times and 0.59 times the section height H of the tire, and thus at least equal to 0.5 times the section height H of the tire. The radial distances (b.sub.3, b.sub.4) between the respective ends (E.sub.3, E.sub.4) of the non-turned-up carcass layers (73, 74) and the radially outermost point E of the bead wire 8 are respectively equal to 0.24 times and 0.0005 times the diameter D of the bead wire 8, and thus at most equal to the diameter of the bead wire 8. The reinforcing elements of all the carcass layers (71, 72, 73, 74) are made of polyester.

(12) The tread width A is equal to 13.35 times the crown deflection B, and thus at most equal to 20 times and at least equal to 10 times the crown deflection B. The section width S of the tire is equal to 1.17 times the rim width L, and thus at most equal to 1.4 times and at least equal to 1.1 times the rim width L. The tread width A is equal to 0.88 times the section width S of the tire, and thus at most equal to 0.95 times and at least equal to 0.75 times the section width S of the tire.

(13) The tests carried out on a tire of the size 800/70 R 32 according to the invention, as characterized above, have shown that the endurance of the carcass reinforcement of this tire, subjected to cyclical loads of between 1.2 times and 1.86 times the recommended load capacity of the reference tire, for a pressure equal to the pressure of the reference tire, was at the same level as that of the carcass reinforcement of the reference tire, subjected to cyclical loads of between 1 and 1.70 times the recommended load capacity of the reference tire, for a pressure equal to 1.16 times the pressure of the reference tire.

(14) The scope of protection of the invention is not limited to the examples given hereinabove. The invention is embodied in each novel characteristic and each combination of characteristics, which includes every combination of any features which are stated in the claims, even if this feature or combination of features is not explicitly stated in the examples.