WO2026082425A1 - Optimised structure of a civil engineering tire - Google Patents

Abstract

A tire (1) for a mine engineering vehicle comprises a protective reinforcement (31) and a working reinforcement (32) radially inside the protective reinforcement (31). The protective reinforcement consists of two protective layers (31) each comprising elastic metal reinforcements, the modulus of extension of which is at least 40 GPa and at most 140 GPa. The diameter of the metal reinforcements of the radially outermost protective layer (311) is at least equal to 2.5 mm and the pitch, in mm, of the metal reinforcements of the radially outermost protective layer (311) is greater than 0.70 * FR/1000 where FR is in N.

Description

Optimized architecture of civil engineering pneumatics

[0001] The present invention relates to a radial tire, intended to equip a heavy vehicle of the civil engineering type, and relates more particularly to the crown reinforcement of a tire for a mining vehicle whether the mine is underground or open pit.

[0002] Radial tires intended to equip a heavy vehicle of the civil engineering type are designated as such in the sense of the standard of the European Tyre and Rim Technical Organisation (European Tyre and Rim Technical Organisation) or ETRTO.

[0003] For example, a radial tire for heavy-duty vehicles of the civil engineering type, as defined by the European Tyre and Rim Technical Organisation or ETRTO standard, is intended to be mounted on a rim whose diameter is at least 25 inches.

[0004] A tire having a geometry of revolution about an axis of rotation, the geometry of the tire is generally described in a meridian plane containing the tire's axis of rotation. For a given meridian plane, the radial, axial, and circumferential directions respectively denote the directions perpendicular to the tire's axis of rotation, parallel to the tire's axis of rotation, and perpendicular to the meridian plane. The circumferential direction is tangent to the circumference.

[0005] In what follows, the expressions "radially inward", respectively

"Radially outside" means "closer" and "further from" the tire's rotation axis, respectively. "Axially inside" and "axially outside" mean "closer" and "further from" the tire's equatorial plane, respectively. The tire's equatorial plane is the plane passing through the middle of the tread and perpendicular to the rotation axis.

[0006] Generally, a tire comprises a tread, intended to come into contact with a ground by means of a tread surface, the two axial ends of which are connected by means of two sidewalls to two beads ensuring the mechanical connection between the tire and the rim on which it is intended to be mounted.

[0007] A radial tire further comprises a reinforcing structure, consisting of a crown structure, radially internal to the tread, and a carcass structure, radially internal to the crown structure.

[0008] The carcass reinforcement of a radial tire for heavy-duty construction vehicles typically comprises at least one carcass layer including reinforcements, generally metallic, coated with a polymeric material of the elastomeric or elastomeric type, obtained by mixing and called the coating compound. A carcass layer includes a main portion, connecting the two beads to each other and generally wrapping, within each bead, from the inside to the outside of the tire around a circumferential reinforcement element, most often metallic, called a bead, to form a inversion. The metallic reinforcements of a carcass layer are substantially parallel to each other and form an angle of between 80° and 90° with the circumferential direction.

[0009] The crown reinforcement of a radial tire for construction equipment comprises a superposition of crown layers extending circumferentially, radially outside the carcass reinforcement. Each crown layer consists of reinforcements, generally metallic, parallel to each other and coated with a polymeric material of the elastomer type or coating mixture.

[0010] Among the top layers, we usually distinguish the protective layers, which are part of the protective reinforcement and radially the outermost, and the working layers, which are part of the working reinforcement and radially located between the protective reinforcement and the carcass reinforcement.

[0011] The protective reinforcement, comprising at least one protective layer for certain applications, but comprising two protective layers for mining vehicles that travel on tracks or in tunnels very often obstructed by stones, sometimes large compared to the size of the tire. These protective layers essentially protect the working layers from mechanical or physico-chemical damage that could propagate radially through the tread towards the inside of the tire. [0012] The protective reinforcement therefore comprises for mining tires two radially superimposed protective layers, formed of elastic metallic reinforcements, parallel to each other in each layer and crossed from one layer to the next, forming, with the circumferential direction, angles of at least 10°.

[0013] The working structure, often comprising at least two working layers, serves to encircle the tire and provide it with rigidity and road holding. It withstands both the mechanical stresses of inflation, generated by the tire's inflation pressure and transmitted by the carcass reinforcement, and the mechanical stresses of rolling, generated by the tire rolling on the ground and transmitted by the tread. The crown reinforcement must also resist impacts and punctures, thanks to its intrinsic design, particularly its flexibility and, in particular, that of the protective reinforcement. Furthermore, the tire must have sidewall flex, or drift rigidity under transverse load, to ensure proper vehicle handling on cornering roads.

[0014] The working reinforcement typically comprises two radially superimposed working layers formed of non-extensible metallic reinforcements, parallel to each other within each layer and crossed from one layer to the next, forming, with the circumferential direction, angles preferably of at least 15° and at most 35° so as to resist the transverse forces and a portion of the circumferential forces. The two-layer structure, formed by these two working layers, generally ensures a sufficient level of edge bending for acceptable vehicle behavior.

[0015] To reduce the mechanical inflation stresses transmitted to the working reinforcement, it is known to place a shrink-fit reinforcement radially outside the carcass reinforcement. The shrink-fit reinforcement, whose function is to absorb at least some of the mechanical inflation stresses, improves the durability of the top reinforcement by stiffening it. The shrink-fit reinforcement can be positioned radially inside the working reinforcement, between the two working layers of the working reinforcement, or radially outside the working reinforcement. [0016] In civil engineering applications, the confinement reinforcement may comprise two radially superimposed confinement layers formed of metallic reinforcements, parallel to each other in each layer and crossed from one layer to the next, forming angles of no more than 10° with the circumferential direction. Another embodiment of the confinement reinforcement consists of a circumferential winding of a confinement wire or a continuous confinement strip forming angles of no more than 5° with the circumferential direction.

[0017] With regard to metal reinforcements, a metal reinforcement is mechanically characterized by a curve representing the tensile force (in N) applied to the metal reinforcement as a function of its relative elongation (in %), known as the force-elongation curve. From this force-elongation curve, tensile mechanical characteristics of the metal reinforcement are deduced, such as the structural elongation As (in %), the total elongation at break At (in %), the breaking force Fm (maximum load in N), and the tensile strength Rm (in MPa), these characteristics being measured according to ASTM D 2969-04:2014.

[0018] The total elongation At of the metal reinforcement is, by definition, the sum of its structural, elastic, and plastic elongations (At = As + Ae + Ap), particularly at break, where each of the elongations is non-zero. The structural elongation As results from the relative positioning of the metal wires constituting the metal reinforcement under a small tensile force. The elastic elongation Ae results from the elasticity of the metal of the individual wires constituting the metal reinforcement, the behavior of the metal following Hooke's law. The plastic elongation Ap results from the plasticity, that is, the irreversible deformation, beyond the elastic limit, of the metal of these individual wires. These different elongations, as well as their respective meanings, well known to those skilled in the art, are described, for example, in documents US5843583, W02005/014925, and W02007/090603.

[0019] A tensile modulus, expressed in GPa, is also defined at every point on the force-stretch curve of a metallic reinforcement. This modulus represents the slope of the line tangent to the force-stretch curve at that point. In particular, we call The elastic modulus in extension, or Young's modulus, is the modulus in extension of the linear elastic part of the force-stretch curve.

[0020] Among metallic reinforcements, a distinction is usually made between elastic metallic reinforcements, such as those used in protective layers to prevent the protective layers from absorbing tensile stresses, and non-stretchable or inextensible metallic reinforcements, such as those used primarily in working layers. The important point is that the protective layers be significantly more elastic than the working layers.

[0021] An elastic metal reinforcement, in its unglued state, is characterized by a structural elongation As of at least 0.5% and a total elongation at break At of at least 3%. In addition, an elastic metal reinforcement has a tensile elastic modulus of at most 180 GPa, and usually between 40 GPa and 150 GPa, preferably less than 110 GPa.

[0022] A non-stretchable metal reinforcement is characterized by a total elongation At, under a tensile force equal to 10% of the breaking force Fm, at most equal to 0.2%. Furthermore, a non-stretchable metal reinforcement has an elastic modulus in tension usually between 150 GPa and 200 GPa.

[0023] The efforts of mining tire manufacturers in the continuous improvement of the reinforcing elements, metallic reinforcements, or cables in the protective layers have significantly improved the puncture resistance of tires from stones present on the ground over which they travel. These failures have clearly decreased, leading to an increase in the frequency of other unexpected failures, which are becoming problematic. This is the case with the formation of a crack that develops at the interface between the outermost radial protective layer and the tread, and which then propagates circumferentially until a portion of the tread detaches, resulting in the tire being removed.

[0024] The inventors have set themselves the objective, for a radial tire for a vehicle of the mining civil engineering type, of reducing the shear forces at the interface between the outermost radially protective layer without deteriorating the performance of resistance to aggressions. [0025] This objective has been achieved, according to the invention, by a tire for mining construction vehicles intended to be mounted on a rim having a diameter at site of at least 25 inches, comprising a tread, the tread height of which is at least 30 mm, and a crown reinforcement, which is radially internal to the tread and radially external to a carcass reinforcement and which comprises crown layers including metallic reinforcements. The crown reinforcement includes a protective reinforcement and a working reinforcement radially internal to the protective reinforcement. The protective reinforcement consists of two protective layers, which are the outermost radially of the crown layers, each of the two protective layers comprising elastic metallic reinforcements having an elongation modulus of at least 40 GPa and at most 140 GPa, embedded in a rubber compound, referred to as the calendering compound, parallel to each other, and having a breaking strength FR. The crown reinforcement comprises at least two working layers, each working layer being radially inner to the protective layers and comprising metallic reinforcements parallel to each other and forming, with the circumferential direction tangent to the circumference of the tire, an angle whose absolute value is at least 17°. The diameter of the metallic reinforcements of the outermost radially protective layer is at least 2.5 mm. Furthermore, the spacing, in mm, of the metallic reinforcements of the outermost radially protective layer is greater than 0.70*FR/1000, where FR is in N.

[0026] The idea is to amplify the characteristics that enabled the metallic reinforcements of the two protective layers to withstand impacts during rolling, such as the diameter of the metallic reinforcements. This is achieved by using metallic reinforcements with a larger diameter than those used in state-of-the-art solutions, while also increasing the spacing and therefore the distance between two reinforcement elements. Indeed, the breaking strength varies with the square of the radius of the reinforcement elements, whereas the distance between two reinforcement elements for the same breaking strength of the protective layer varies linearly with the radius. Thus, since protective layers have reinforcement elements of approximately 2 mm in the state of the art, in the invention, the reinforcement elements of the outermost radial layer should have a diameter of at least 2.5 mm, preferably at least 3 mm, and the spacing, in mm, of the metallic reinforcements of the the outermost radially protective layer is greater than 0.70*FR/1000 where FR is in N, which allows us to maintain a proven protective layer resistance value but with significantly increased rubber bridge sizes between each reinforcement element of the outermost radially protective layer allowing the reduction of shear at the interface of the outermost radially protective layer and the tread.

[0027] By "notch of the metal reinforcements," we mean the distance in mm either between the centers of two directly adjacent metal reinforcements measured perpendicular to the metal reinforcements, or between two right or left edges of cables of two directly adjacent metal reinforcements. This measurement is well known to those skilled in the art and can be taken on a protective layer taken from the tire, by X-ray, or by any other suitable measurement on the cured tire. This formula is derived from experience and tested protective layers considered conclusive regarding puncture problems.

[0028] The invention excludes the possibility that the crown reinforcement may include one or more protective layers other than the two aforementioned protective layers. These two protective layers alone constitute the protective reinforcement, to the exclusion of any other crown layer comprising metallic reinforcements, such as a third protective layer as envisaged in WO2020/229543A1. In practice, these two protective layers are advantageously the only crown layers comprising metallic reinforcements, which are radially interposed between the tread and either the working reinforcement or a reinforcing reinforcement radially external to the working reinforcement.

[0029] It is advantageous for the metallic reinforcements of the outermost radially exposed protective layer to have a diameter of at least 3.0 mm, preferably at least 3.5 mm. Increasing the diameters increases the breaking strength of the metallic reinforcement and therefore the distance between the metallic reinforcements for the same strength of the protective layer. Increasing the distance between the metallic reinforcements of the outermost radially exposed protective layer reduces its circumferential stiffness by increasing the percentage of mixture in the protective layer. Indeed, the breaking strength of the metallic reinforcements increases with As the square of the diameter increases, and while maintaining the same breaking strength of the protective layer, the distance between the reinforcements increases linearly with the diameter. Therefore, by doubling the diameter, the distance between the metal reinforcements can be increased by approximately 3.5 times, thus increasing the calendering mixture ratio and contributing to a decrease in the tire's circumferential stiffness. This allows for a reduction in circumferential stiffness, which influences the failure mode we wish to target.

[0030] This reduction in shear is even more significant if the combined increase in the diameter of the reinforcing elements and the pitch for an increase in the size of the rubber bridges is accompanied by an increase in the angle between the reinforcing elements of the outermost radially protective layer and the circumferential direction, the absolute value of which is at least 35°, preferably at least 45°, preferably at least 50°, and preferably at least 55°. Typically, the angles of the protective layers are close to the angles of the top layers, between 17° and 35°, for better corrosion resistance. By thus widening the angles of the protective layer, the circumferential stiffness of the protective layer decreases further. This decrease is more than 75% between a protective layer at 25° compared to one at 35°, and even more so at 55°, where the stiffness of the protective layer becomes negligible. From the point of view of other performance, opening the angles further does not matter because the protective layers do not take up tension due to the difference in rigidity of their metallic reinforcements compared to those of the working layers and the shrink-fit layers.

[0031] This modification is acceptable for mining tires, according to the inventors' knowledge, due to the specific conditions of their operation. Indeed, in other applications, objects on the ground that could damage the tire are stones likely to damage the tread or break working layers, but not to puncture the tire. Therefore, the use of large-diameter cables that resist deformation when rolling over the object is possible. This is not the case for applications where the risk of the tire on a The aggression is to drive over an indenter that can puncture the crown reinforcement and lead to a tire puncture.

[0032] To protect all the top layers (working layers, bracing layer, triangulation layer) from the hammering phenomenon caused by rolling on stony soils, it is advantageous that the outermost radially outer protective layer of the top layers has an axial width LPN greater than all the axial widths of the other top layers.

[0033] For the same advantage, preferably the breaking strength FR of the metallic reinforcements of the outermost radially protective layer is greater than 4000 N. This makes it possible to guarantee a distance between the effective reinforcing elements to reduce the shear between the tread and the outermost radially protective layer.

[0034] Advantageously the pitch, in mm, of the metallic reinforcements of the outermost radially protective layer, is less than l.l*FR/1000 where FR is in N. Such an increase in the sizes of the rubber bridges could impair the puncture resistance of the top.

[0035] Advantageously, the protective layers, namely the outermost radially outer protective layer and the innermost radially inner protective layer, are identical in terms of the nature of the metal reinforcements, i.e., same architecture (same number of wires, same assembly, same manufacturing process), same pitch, same calendering mixture, same absolute value of the angle of the metal reinforcements with the circumferential direction, the metal reinforcements being crossed from one protective layer to the other to facilitate manufacturing. In particular, the metal reinforcements of the innermost radially inner protective layer have the same diameter and the same breaking strength as the metal reinforcements of the outermost radially outer protective layer. Similarly, it is advantageous that the pitch of the metal reinforcements of the innermost radially inner protective layer be equal to the pitch of the metal reinforcements of the outermost radially outer protective layer. Thus, it is preferable that the angle formed by the metal reinforcements of the innermost radially inner protective layer be at least 35°, preferably at less than or equal to 45°, preferably less than or equal to 50°, preferably less than or equal to 55°.

[0036] To reduce stress at the interface between the outermost radially protective layer and the rubber compound of the tread directly adjacent to it, it is advantageous for the stiffness of said compound to be close to the stiffness of the calendering compound. Thus, it is preferable that, with the tread directly adjacent to the outermost radially protective layer, the elastic modulus Mal measured at 10% elongation at 23°C of the rubber compound of the tread directly adjacent to the outermost radially protective layer at the center of the tread, be at least equal to 0.65 times the elastic modulus Ma2 measured at 10% elongation at 23°C of the calendering compound of the outermost radially protective layer.

[0037] It is advantageous that, when the metallic reinforcements of the two protective layers have a peripheral layer of strands, the peripheral layer of strands of the metallic reinforcements of the protective layers be desaturated. “Desaturated layer” means that the diameter of the strands relative to the perimeter where said peripheral strands are arranged is such that there is sufficient space between each strand to allow the calendering compound to penetrate the metallic reinforcement in order to protect all of these metallic reinforcements from corrosion. Indeed, saturated cables are not penetrated by gum, and if a crack forms in the calendering compound down to the peripheral layer of the metallic reinforcement, then water can enter the reinforcement and move within it, causing corrosion along its entire length. With a penetrated cable whose outer strand layer is desaturated, the crack reaches the metal reinforcement but does not allow water to penetrate it, let alone circulate through it, as the metal reinforcement is impregnated with the calendering mixture. It is interesting that the same principle applies to the metal reinforcements of the working layers; namely, since the metal reinforcements of the working layers have an outer strand layer, the outer strand layer of the metal reinforcements of the working layers is desaturated.

[0038] The features of the invention are illustrated by the schematic figure 1, not shown to scale, with reference to a tire of size 29.5R29. [0039] Figure 1 shows a meridional section of a tire 1 for heavy-duty vehicles of the civil engineering type comprising a crown reinforcement 3, radially internal to a tread 2 and radially external to a carcass reinforcement 4. The crown reinforcement 3 comprises, radially from the outside in, a protective reinforcement 31, a working reinforcement 32 and a reinforcing reinforcement 33. The protective reinforcement comprises two protective layers 311 and 312 comprising elastic metallic reinforcements coated in an elastomeric material or coating or calendering mixture, parallel to each other and forming angles respectively Al 11 and Al 12, with a circumferential direction XX' tangent to the circumference of the tire, the protective layers being crossed from one protective layer to the next. The working reinforcement 32 comprises two working layers 321, 322 whose respective metal reinforcements are embedded in an elastomeric material, parallel to each other and forming angles of 24° with the circumferential direction XX', and are intersected from one working layer to the next. The confinement reinforcement 33 comprises two confinement layers 331, 332 whose respective metal reinforcements, embedded in an elastomeric material, are parallel to each other and forming angles of between 5° and 10° with the circumferential direction XX', and are intersected from one confinement layer to the next.

[0040] The invention was tested or evaluated on tires of sizes 29.5R29, 24.00R35, 27.00R49, and 50/80R57. The reference tires are commercially available tires. The reference cable for the Michelin® brand tires used as references is an E24.26 elastic cable made of 24 steel wires of 0.26 mm diameter with an elongation modulus of 80 GPa. Its diameter is 1.97 mm and its breaking strength is 2550 N. These reinforcing elements are desaturated, and therefore the calendering compound penetrates to the core of the reinforcing elements. This cable is used at a 2.5 mm pitch, resulting in a 0.53 mm inter-cable spacing, for a layer strength of 1020 N/mm² within a protective layer. It utilizes two crossed layers to create a very fine mesh, suitable for certain heavy equipment tires on construction sites where nails, screws, and other sharp, thin objects are present that could puncture a tire. This type of object is not particularly dangerous for mining tires, whose tread thickness is generally greater than the length of such objects, which are also... These tires are not commonly found in underground or surface mines. For example, the tread depth of mining tires is greater than 30 mm and often exceeds 90 mm. The protective layers of these tires have reinforcing elements that form an angle of 24° with the circumferential direction. These reinforcing elements are intersecting from one protective layer to the next. For these tires, these protective layers have significantly improved peak impact performance, resulting in excellent impact resistance. However, while this improved performance has significantly reduced tire shrinkage due to peak impacts, it has also revealed another failure mode that is becoming increasingly common: the formation of circumferential pockets between the protective layer and the tread.

[0041] The invention was implemented using a reinforcing element 52.26 composed of 52 wires, each 0.26 mm in diameter, with an extension modulus of 68 GPa. These reinforcing elements are elastic and desaturated so that the calendering compound penetrates to the core of the reinforcing elements. They have a diameter of 3.1 mm and a breaking strength of 6050 N. They were installed at a spacing of 5.9 mm to provide a protective layer strength equivalent to that of the test piece, but with a 2.8 mm inter-wire spacing. Furthermore, the angle of the reinforcing elements of the outermost radially protective layer of the tires according to the invention with the circumferential direction is 50°.

[0042] The invention was tested in three modes: straight-line driving, braking, and tire drifting. Since the tires were of different sizes, the same braking force (Fx) and drift thrust (Fy) ratios relative to the nominal load were applied. During straight-line driving, the forces Fx and Fy were negligible, and the load (Fz) was equal to the tire's nominal load. During drifting, a Fy/Fz ratio of approximately 20% was used, and for braking, a Fx/Fz ratio of approximately 15% was used.

[0043] The reduction of maximum shear in the rubbers entering the tread at the interface with the outermost radially protective layer is on average for the different tires of the order of 25% and can reach 70%. With a more flexible protective layer at increasing angles, while maintaining the same level of rupture strength, we should achieve crown impact resistance equivalent to that of control tires. With such a significant reduction in shear deformation at the interface between the outermost radial protective layer and the tread, resistance to pocketing should be correspondingly improved. Thus, the invention enables an improvement in crown strength for mining tires.

Claims

Demands 1. Tyre (1) for mining construction equipment intended to be mounted on a rim having a diameter at site of at least 25 inches, comprising: - a tread (2) with a tread height of at least 30 mm, and - a crown reinforcement (3), which is radially internal to the tread (2) and radially external to a carcass reinforcement (4), and which comprises crown layers (311, 312, 321, 322, 331, 332) comprising metallic reinforcements, wherein the crown reinforcement (3) comprises a protective reinforcement (31) and a working reinforcement (32) radially internal to the protective reinforcement (31), wherein the protective reinforcement (31) consists of two protective layers (311, 312) which are the outermost radially external crown layers of the crown layers, each of the two protective layers comprising elastic metallic reinforcements, having a modulus of extension of at least 40 GPa and at most 140 GPa, embedded in a rubbery compound, called calendering compound, parallel to each other, and having a breaking strength FR, wherein the reinforcement of apex comprises at least two working layers (321, 322), each working layer (321, 322) being radially internal to the two protective layers (311, 312) and comprising metallic reinforcements, parallel to each other and forming, with the circumferential direction (XX’) tangent to the circumference of the tire, an angle whose absolute value is at least equal to 17°, in which the diameter of the metallic reinforcements of the outermost radially external protective layer (311) is at least equal to 2.5 mm, and in which the pitch, in mm, of the metallic reinforcements of the outermost radially external protective layer (311) is greater than 0.70*FR/1000 where FR is in N. 2. Tire (1) according to claim 1, wherein the metallic reinforcements of the outermost radially protective layer (311) form, with a circumferential direction (XX') tangent to the circumference of the tire, a APN angle whose absolute value is at least equal to 35°, preferably at least equal to 45°, preferably at least equal to 50°, preferably at least equal to 55°. 3. Pneumatic (1) according to any one of the preceding claims, wherein the metallic reinforcements of the outermost radially protective layer (311) have a diameter of at least 3 mm, preferably at least 3.5 mm. 4. Pneumatic (1) any one of the preceding claims, wherein the breaking strength FR of the metallic reinforcements of the outermost radially protective layer (311) is greater than 4000 N. 5. Pneumatic (1) according to any one of the preceding claims, wherein the pitch, in mm, of the metallic reinforcements of the outermost radially protective layer (311) is less than 1.1 *FR/1000 where FR is in N. 6. Pneumatic (1) according to any one of the preceding claims, wherein the metallic reinforcements of the innermost radially protective layer (312) have the same diameter and breaking strength as the metallic reinforcements of the outermost radially protective layer (311). 7. Pneumatic (1) according to any one of the preceding claims, wherein the pitch of the metal reinforcements of the innermost radially protective layer (312) is equal to the pitch of the metal reinforcements of the outermost radially protective layer (311). 8. Pneumatic (1) according to any one of the preceding claims, wherein the angle formed by the metallic reinforcements of the innermost radially protective layer (311) is at least equal to 35°, preferably at least equal to 45°, preferably at least equal to 50°, preferably at least equal to 55°. 9. A tire (1) according to any one of the preceding claims, wherein the tread (2) is directly adjacent to the outermost radially outer protective layer (311), and wherein the elastic modulus Mal measured at 10% elongation at 23 °C of the rubber compound of the tread (2) directly adjacent to the outermost radially outer protective layer, at the center of the tread, is at least equal to 0.65 times the - 16 - elastic modulus Ma2 measured at 10% elongation at 23 °C of the calendering mixture of the outermost radially outer protective layer (311). 10. Pneumatic (1) according to any one of the preceding claims, wherein the metallic reinforcements of the two protective layers (311, 312) are desaturated.