EP0568271B1 - Steel cords for reinforcement of rubber articles and pneumatic radial tires - Google Patents
Steel cords for reinforcement of rubber articles and pneumatic radial tires Download PDFInfo
- Publication number
- EP0568271B1 EP0568271B1 EP19930303148 EP93303148A EP0568271B1 EP 0568271 B1 EP0568271 B1 EP 0568271B1 EP 19930303148 EP19930303148 EP 19930303148 EP 93303148 A EP93303148 A EP 93303148A EP 0568271 B1 EP0568271 B1 EP 0568271B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- steel
- cord
- filament
- wrap
- sheath layer
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
Images
Classifications
-
- D—TEXTILES; PAPER
- D07—ROPES; CABLES OTHER THAN ELECTRIC
- D07B—ROPES OR CABLES IN GENERAL
- D07B1/00—Constructional features of ropes or cables
- D07B1/06—Ropes or cables built-up from metal wires, e.g. of section wires around a hemp core
- D07B1/0606—Reinforcing cords for rubber or plastic articles
- D07B1/062—Reinforcing cords for rubber or plastic articles the reinforcing cords being characterised by the strand configuration
-
- D—TEXTILES; PAPER
- D07—ROPES; CABLES OTHER THAN ELECTRIC
- D07B—ROPES OR CABLES IN GENERAL
- D07B1/00—Constructional features of ropes or cables
- D07B1/06—Ropes or cables built-up from metal wires, e.g. of section wires around a hemp core
- D07B1/0606—Reinforcing cords for rubber or plastic articles
- D07B1/062—Reinforcing cords for rubber or plastic articles the reinforcing cords being characterised by the strand configuration
- D07B1/0626—Reinforcing cords for rubber or plastic articles the reinforcing cords being characterised by the strand configuration the reinforcing cords consisting of three core wires or filaments and at least one layer of outer wires or filaments, i.e. a 3+N configuration
-
- D—TEXTILES; PAPER
- D07—ROPES; CABLES OTHER THAN ELECTRIC
- D07B—ROPES OR CABLES IN GENERAL
- D07B1/00—Constructional features of ropes or cables
- D07B1/06—Ropes or cables built-up from metal wires, e.g. of section wires around a hemp core
- D07B1/0606—Reinforcing cords for rubber or plastic articles
- D07B1/062—Reinforcing cords for rubber or plastic articles the reinforcing cords being characterised by the strand configuration
- D07B1/0633—Reinforcing cords for rubber or plastic articles the reinforcing cords being characterised by the strand configuration having a multiple-layer configuration
-
- D—TEXTILES; PAPER
- D07—ROPES; CABLES OTHER THAN ELECTRIC
- D07B—ROPES OR CABLES IN GENERAL
- D07B2201/00—Ropes or cables
- D07B2201/20—Rope or cable components
- D07B2201/2015—Strands
- D07B2201/2023—Strands with core
-
- D—TEXTILES; PAPER
- D07—ROPES; CABLES OTHER THAN ELECTRIC
- D07B—ROPES OR CABLES IN GENERAL
- D07B2201/00—Ropes or cables
- D07B2201/20—Rope or cable components
- D07B2201/2015—Strands
- D07B2201/2024—Strands twisted
- D07B2201/2029—Open winding
- D07B2201/2031—Different twist pitch
-
- D—TEXTILES; PAPER
- D07—ROPES; CABLES OTHER THAN ELECTRIC
- D07B—ROPES OR CABLES IN GENERAL
- D07B2201/00—Ropes or cables
- D07B2201/20—Rope or cable components
- D07B2201/2015—Strands
- D07B2201/2024—Strands twisted
- D07B2201/2029—Open winding
- D07B2201/2031—Different twist pitch
- D07B2201/2032—Different twist pitch compared with the core
-
- D—TEXTILES; PAPER
- D07—ROPES; CABLES OTHER THAN ELECTRIC
- D07B—ROPES OR CABLES IN GENERAL
- D07B2201/00—Ropes or cables
- D07B2201/20—Rope or cable components
- D07B2201/2095—Auxiliary components, e.g. electric conductors or light guides
- D07B2201/2097—Binding wires
- D07B2201/2098—Binding wires characterized by special properties or the arrangements of the binding wire
Definitions
- This invention relates to steel cords used as a reinforcement for rubber articles such as pneumatic tires, industrial belts and the like as well as a pneumatic radial tire comprising a carcass ply comprised of such steel cords and having improved durability.
- tires are well-known.
- tires for trucks and buses or for light trucks generally comprise a carcass ply using cords of two or three layer construction.
- the tensile load of the steel cord lowers during the running of the tire because the sectional area of steel filaments constituting the steel cord is decreased by fretting.
- the decrease of sectional area in some filaments constituting the steel cord becomes conspicuous, such filaments are apt to undergo breakage as a result of tensile shock or repetitive bending. Once these filaments are broken, tensile stress in the other filaments increases to promote fatigue breakage of the cord. Therefore, in order to increase the durability of the cord, it is required to avoid a part of the steel filaments constituting the steel cord becoming prematurely broken as compared with the remaining steel filaments, and it is desirable that the tensile loads of all filaments in the cord are equally lowered.
- the present inventor has made studies with respect to steel cords formed by spirally winding a wrap steel filament around a steel cord of layer twisting structure for stably preventing the lowering of tensile load in the steel filaments (filament diameter: 0.15-0.25 mm) constituting the steel cord used in a carcass ply during the running of a tire, and found that the lowering of tensile load in the steel filaments constituting the outermost layer of the steel cord is extremely large and that a main factor in the lowering of tensile load is a fretting phenomenon with the wrap filament.
- the inventor has made studies with respect to steel cords formed by removing the wrap filament, which is the main factor in the lowering of tensile load, for preventing the occurrence of fretting around the wrap filament, and confirmed that the fretting is certainly removed to control the lowering of tensile load of the steel filament, but the restraining property of the cord is poor due to the absence of the wrap filament and furthermore when the cord is excessively bent, the steel filaments constituting the cord are scattered and finally broken when abnormal force is applied to the steel filaments. In the latter case, the life at break of the cord is largely decreased as compared with the cord stabilized by wrapping the cord with the wrap filament. As a result, in order to prevent the decrease of the cord life based on the application of extreme bending force, it becomes required to restrain the cord with the steel filament in any form.
- the inventor has made further studies with respect to the steel cord of layer twisting structure and discovered that it is advantageous to prevent the lowering of tensile load in the steel filaments of the outermost layer by controlling the application of abnormal force to the steel filament while maintaining the restraint of the filaments constituting the cord when a large bending force is applied to the cord and mitigating the fretting between the wrap filament and the steel filaments constituting the outermost layer of the cord, and as a result the invention has been accomplished.
- a steel cord for the reinforcement of rubber articles formed by twisting 1 to 4 steel filaments as a core and at least one sheath layer comprised of a plurality of steel filaments arranged around the core, provided that the twisting pitch of at least one sheath layer is different from that of a remaining sheath layer adjacent thereto or that of the core, and wherein wrap steel filament is spirally wound around a sheath layer located at an outermost side of the steel cord in the same twisting direction as in one said sheath layer.
- a pneumatic radial tire comprising a carcass ply of a radial structure toroidally extending between a pair of bead portions and containing steel cords therein, said steel cord being formed by twisting 1 to 4 steel filaments as a core and at least one sheath layer comprised of a plurality of steel filaments arranged around the core, provided that the twisting pitch of at least one sheath layer is different from that of a remaining sheath layer adjacent thereto or that of the core, and wherein a wrap steel filament is spirally wound around a sheath layer located at an outermost side of the steel cord in the same twisting direction as in the said sheath layer.
- the wrap steel filament is wound around the outermost sheath layer at a twisting pitch of 2-6 mm.
- the resistance to corrosion fatigue is improved and also the lowering of tensile load of the cord due to fretting between the outermost sheath layer and the wrap steel filament can be controlled while maintaining the restraint of the steel filaments in the cord.
- Figs. 1 and 2 are sectionally shown embodiments of steel cord for the reinforcement of rubber articles according to the invention having layer twisting structures of 3+9+1 and 1+6+12+1, respectively.
- numeral 1 is a core comprised of one or three steel filaments
- numeral 2 is a sheath layer comprised of a plurality of steel filaments arranged adjacent to each other around the core 1.
- the sheath layer 2 is comprised of nine steel filaments in Fig. 1 and six steel filaments in Fig. 2.
- a second sheath layer 3 comprised of twelve steel filaments is arranged around the sheath layer 2 in the embodiment of Fig. 2.
- numeral 4 is a wrap steel filament spirally wound around the outermost sheath layer in the same twisting direction as in the outermost sheath layer.
- Fig. 3 is sectionally shown a third embodiment of the steel cord according to the invention having a layer twisting structure of 3+9+15+1, in which a second sheath layer 3 comprised of 15 steel filaments is arranged around a first sheath layer 2 comprised of 9 steel filaments.
- a steel cord having a layer twisting structure of 3+8+13+1 may be used as a modification of this embodiment.
- the non-uniform lowering of tensile load in the steel filaments is due to the fact that the wrap steel filament is twisted in the direction opposite to the twisting direction of the steel filaments in the outermost sheath layer. Since the twisting direction of the wrap steel filament is different from that of the steel filaments in the outermost sheath layer, the contact area therebetween becomes small and the contact pressure per unit area is large.
- torsion is applied to the carcass ply cord at a ground contact portion of the tire in the axial direction of the cord.
- torsional force is applied in a direction opposite to the twisting direction of the steel filaments in the outermost sheath layer, if the twisting direction of the wrap steel filament is opposite to the twisting direction of the steel filaments in the outermost sheath layer, torsional force is created in a direction of tightening the twisting direction of the wrap steel filament and hence a relative movement between the wrap steel filament and the steel filaments in the outermost sheath layer occurs.
- the twisting direction of the spiral wrap steel filament restraining the steel cord of layer twisting structure is made in the same direction as the steel filaments of the outermost sheath layer, whereby the contact area between the steel filaments in the outermost sheath layer and the wrap steel filament is increased and the contact pressure therebetween is decreased. Further, even if torsional force is applied to the cord, the relative movement between the steel filaments in the outermost sheath layer and the wrap steel filament reduces and hence the reduction of sectional area in the steel filaments of the outermost sheath layer and the lowering of tensile load accompanied therewith are controlled.
- the steel filaments are restrained by the wrap steel filament, even when the cord is extremely bent, the steel filaments constituting the cord are not scattered and hence the breaking life of the cord is not lowered even when abnormal force is applied to a part of the steel filaments.
- the filament diameter may be the same or different between the core and the sheath.
- the twisting pitch of the steel filaments in the outermost sheath layer is the same as that of the spiral wrap steel filament, there is caused movement of the wrap steel filament into the outermost sheath layer, so that it is necessary that the twisting pitch of the steel filaments in the outermost sheath layer is different from that of the wrap steel filament.
- the invention is particularly preferable to apply the invention to a steel cord having a layer twisting structure of 3+8+1 in view of the cord durability. That is, when the invention is applied to rubber penetration type cords having a gap between the steel filaments in the sheath layer, if a large bending force is applied to the cord under a low internal pressure, the movement of the steel filaments becomes small because rubber penetrates into the inside of the cord and hence the resistance to cord breaking-up is improved.
- Steel cords are prepared as shown in Table 1 and applied to a carcass ply of a radial tire for trucks and buses having a tire size of 11/70R22.5 14PR at an end count of 22.0 cords/5 cm.
- the fretting depth and cord breakage under large bending force are measured by running such a tire on a drum under the following test conditions:
- steel cord of Comparative Example 1 having a layer twisting structure of 3+9+1 and a wrap steel filament of Z-lay (control)
- steel cord of Comparative Example 2 having a layer twisting structure of 3+9 and no wrap steel filament
- steel cord of Example 1 having a layer twisting structure of 3+9+1 and a wrap steel filament of S-lay according to the invention.
- the measured results are shown in Table 1.
- the steel filaments of the outermost sheath layer corresponding to two cords are taken out from the tire after the running under usual conditions and broken through a tensile test. Then, the broken sections of these filaments are observed by means of a microscope to measure a fretting depth h shown in Fig. 4 when the section of the original steel filament is circle.
- the fretting depth is evaluated by an index value according to the following equation:
- Steel cords are prepared as shown in Table 2 and applied to a carcass ply of a radial tire for trucks and buses having a tire size of 11/70R22.5 14PR at an end count of 20.0 cords/5 cm.
- the fretting depth and cord breakage under large bending force are measured in the same manner as in Example 1 by running such a tire on a drum under the same conditions as in Example 1.
- steel cord of Comparative Example 3 having a layer twisting structure of 1+6+12+1 and a wrap steel filament of Z-lay (control)
- steel cord of Comparative Example 4 having a layer twisting structure of 1+6+12 and no wrap steel filament
- steel cord of Example 2 having a layer twisting structure of 1+6+12+1 and a wrap steel filament of S-lay according to the invention.
- the measured results are shown in Table 2.
- the twisting pitch of the core is considered to be infinite.
- Steel cords are prepared as shown in Table 3 and applied to a carcass ply of a radial tire for trucks and buses having a tire size of 11/70R22.5 14PR at an end count of 19.8 cords/5 cm.
- the fretting depth and cord breakage under large bending force are measured in the same manner as in Example 1 by running such a tire on a drum under the same conditions as in Example 1.
- steel cord of Comparative Example 5 having a layer twisting structure of 3+9+15+1 and a wrap steel filament of S-lay (control)
- steel cord of Comparative Example 6 having a layer twisting structure of 3+9+15 and no wrap steel filament
- steel cord of Example 3 having a layer twisting structure of 3+9+15+1 and a wrap steel filament of Z-lay according to the invention.
- the measured results are shown in Table 3.
- Steel cords are prepared as shown in Table 4 and applied to a carcass ply of a radial tire for trucks and buses having a tire size of 11/70R22.5 14PR at an end count of 31.8 cords/5 cm.
- the fretting depth and cord breakage under large bending force are measured in the same manner as in Example 1 by running such a tire on a drum under the same conditions as in Example 1.
- steel cord of Comparative Example 7 having a layer twisting structure of 3+8+1 and a wrap steel filament of Z-lay (control)
- steel cord of Comparative Example 8 having a layer twisting structure of 3+8 and no wrap steel filament
- steel cord of Example 4 having a layer twisting structure of 3+8+1 and a wrap steel filament of S-lay according to the invention.
- the measured results are shown in Table 4.
- the steel cord according to the invention has such a layer twisting structure that the wrap steel filament is spirally wound around the outermost sheath layer in the same direction as in the steel filaments of the outermost sheath layer.
- the fretting between the steel filaments of the outermost sheath layer and the wrap steel filament is decreased and also the lowering of tensile load in the steel filaments of the cord becomes equal to improve the cord life, so that the tire durability can considerably be improved.
Description
- This invention relates to steel cords used as a reinforcement for rubber articles such as pneumatic tires, industrial belts and the like as well as a pneumatic radial tire comprising a carcass ply comprised of such steel cords and having improved durability.
- As rubber articles reinforced with steel cords, tires are well-known. Among them, tires for trucks and buses or for light trucks generally comprise a carcass ply using cords of two or three layer construction.
- It is usual that the tensile load of the steel cord lowers during the running of the tire because the sectional area of steel filaments constituting the steel cord is decreased by fretting. In this case, if the decrease of sectional area in some filaments constituting the steel cord becomes conspicuous, such filaments are apt to undergo breakage as a result of tensile shock or repetitive bending. Once these filaments are broken, tensile stress in the other filaments increases to promote fatigue breakage of the cord. Therefore, in order to increase the durability of the cord, it is required to avoid a part of the steel filaments constituting the steel cord becoming prematurely broken as compared with the remaining steel filaments, and it is desirable that the tensile loads of all filaments in the cord are equally lowered.
- Attention is drawn to the disclosure of EP-A-0 373 593, in particular to the prior art cords shown in figures 5 and 6 thereof.
- It is an aim of the present invention to improve the durability of steel cords by equally lowering the tensile loads of the steel filaments in the steel cord due to decrease of filament sectional area through fretting during running when the steel cords are applied to a rubber article, particularly the carcass ply of the radial tire for trucks and buses.
- The present inventor has made studies with respect to steel cords formed by spirally winding a wrap steel filament around a steel cord of layer twisting structure for stably preventing the lowering of tensile load in the steel filaments (filament diameter: 0.15-0.25 mm) constituting the steel cord used in a carcass ply during the running of a tire, and found that the lowering of tensile load in the steel filaments constituting the outermost layer of the steel cord is extremely large and that a main factor in the lowering of tensile load is a fretting phenomenon with the wrap filament.
- Furthermore, the inventor has made studies with respect to steel cords formed by removing the wrap filament, which is the main factor in the lowering of tensile load, for preventing the occurrence of fretting around the wrap filament, and confirmed that the fretting is certainly removed to control the lowering of tensile load of the steel filament, but the restraining property of the cord is poor due to the absence of the wrap filament and furthermore when the cord is excessively bent, the steel filaments constituting the cord are scattered and finally broken when abnormal force is applied to the steel filaments. In the latter case, the life at break of the cord is largely decreased as compared with the cord stabilized by wrapping the cord with the wrap filament. As a result, in order to prevent the decrease of the cord life based on the application of extreme bending force, it becomes required to restrain the cord with the steel filament in any form.
- Under the above circumstances, the inventor has made further studies with respect to the steel cord of layer twisting structure and discovered that it is advantageous to prevent the lowering of tensile load in the steel filaments of the outermost layer by controlling the application of abnormal force to the steel filament while maintaining the restraint of the filaments constituting the cord when a large bending force is applied to the cord and mitigating the fretting between the wrap filament and the steel filaments constituting the outermost layer of the cord, and as a result the invention has been accomplished.
- According to a first aspect of the invention, there is provided a steel cord for the reinforcement of rubber articles formed by twisting 1 to 4 steel filaments as a core and at least one sheath layer comprised of a plurality of steel filaments arranged around the core, provided that the twisting pitch of at least one sheath layer is different from that of a remaining sheath layer adjacent thereto or that of the core, and wherein wrap steel filament is spirally wound around a sheath layer located at an outermost side of the steel cord in the same twisting direction as in one said sheath layer.
- According to a second aspect of the invention, there is provided a pneumatic radial tire comprising a carcass ply of a radial structure toroidally extending between a pair of bead portions and containing steel cords therein, said steel cord being formed by twisting 1 to 4 steel filaments as a core and at least one sheath layer comprised of a plurality of steel filaments arranged around the core, provided that the twisting pitch of at least one sheath layer is different from that of a remaining sheath layer adjacent thereto or that of the core, and wherein a wrap steel filament is spirally wound around a sheath layer located at an outermost side of the steel cord in the same twisting direction as in the said sheath layer.
- In a preferred embodiment of the invention, the wrap steel filament is wound around the outermost sheath layer at a twisting pitch of 2-6 mm. When the steel cords according to the invention are applied to the carcass ply of a pneumatic radial tire, the resistance to corrosion fatigue is improved and also the lowering of tensile load of the cord due to fretting between the outermost sheath layer and the wrap steel filament can be controlled while maintaining the restraint of the steel filaments in the cord.
- The invention will be further described with reference to the accompanying drawings, wherein:
- Fig. 1 is a diagrammatically sectional view of a steel cord having a layer twisting structure of 3+9+1;
- Fig. 2 is a diagrammatically sectional view of a steel cord having a layer twisting structure of 1+6+12+1;
- Fig. 3 is a diagrammatically sectional view of a steel cord having a layer twisting structure of 3+9+15+1; and
- Fig. 4 is a schematic view illustrating a fretting depth h.
- In Figs. 1 and 2 are sectionally shown embodiments of steel cord for the reinforcement of rubber articles according to the invention having layer twisting structures of 3+9+1 and 1+6+12+1, respectively. In Figs. 1 and 2, numeral 1 is a core comprised of one or three steel filaments, while
numeral 2 is a sheath layer comprised of a plurality of steel filaments arranged adjacent to each other around the core 1. Thesheath layer 2 is comprised of nine steel filaments in Fig. 1 and six steel filaments in Fig. 2. Further, asecond sheath layer 3 comprised of twelve steel filaments is arranged around thesheath layer 2 in the embodiment of Fig. 2. In Figs. 1 and 2, numeral 4 is a wrap steel filament spirally wound around the outermost sheath layer in the same twisting direction as in the outermost sheath layer. - In Fig. 3 is sectionally shown a third embodiment of the steel cord according to the invention having a layer twisting structure of 3+9+15+1, in which a
second sheath layer 3 comprised of 15 steel filaments is arranged around afirst sheath layer 2 comprised of 9 steel filaments. As a modification of this embodiment, there may be used a steel cord having a layer twisting structure of 3+8+13+1. - In the conventional layer-twisted steel cord, the non-uniform lowering of tensile load in the steel filaments, particularly lowering of tensile load in the steel filaments of the outermost sheath layer, is due to the fact that the wrap steel filament is twisted in the direction opposite to the twisting direction of the steel filaments in the outermost sheath layer. Since the twisting direction of the wrap steel filament is different from that of the steel filaments in the outermost sheath layer, the contact area therebetween becomes small and the contact pressure per unit area is large.
- During the running of a tire, torsion is applied to the carcass ply cord at a ground contact portion of the tire in the axial direction of the cord. When the torsional force is applied in a direction opposite to the twisting direction of the steel filaments in the outermost sheath layer, if the twisting direction of the wrap steel filament is opposite to the twisting direction of the steel filaments in the outermost sheath layer, torsional force is created in a direction of tightening the twisting direction of the wrap steel filament and hence a relative movement between the wrap steel filament and the steel filaments in the outermost sheath layer occurs. Therefore, when such a relative movement is caused under a large contact pressure, the reduction of sectional area in the steel filaments of the outermost sheath layer is promoted by the wrap steel filament and hence the tensile load of the steel filaments in the outermost sheath layer lowers.
- According to the invention, the twisting direction of the spiral wrap steel filament restraining the steel cord of layer twisting structure is made in the same direction as the steel filaments of the outermost sheath layer, whereby the contact area between the steel filaments in the outermost sheath layer and the wrap steel filament is increased and the contact pressure therebetween is decreased. Further, even if torsional force is applied to the cord, the relative movement between the steel filaments in the outermost sheath layer and the wrap steel filament reduces and hence the reduction of sectional area in the steel filaments of the outermost sheath layer and the lowering of tensile load accompanied therewith are controlled. Moreover, since the steel filaments are restrained by the wrap steel filament, even when the cord is extremely bent, the steel filaments constituting the cord are not scattered and hence the breaking life of the cord is not lowered even when abnormal force is applied to a part of the steel filaments.
- If the twisting direction is the same between the spiral wrap steel filament and the steel filaments in the outermost sheath layer, the filament diameter may be the same or different between the core and the sheath. On the other hand, if the twisting pitch of the steel filaments in the outermost sheath layer is the same as that of the spiral wrap steel filament, there is caused movement of the wrap steel filament into the outermost sheath layer, so that it is necessary that the twisting pitch of the steel filaments in the outermost sheath layer is different from that of the wrap steel filament.
- Moreover, it is possible to wind the wrap steel filament in the same twisting direction as in the steel filaments of the outermost sheath layer by properly controlling the preforming ratio and torsion (residual torsional stress) of the wrap steel filament without obstructing the operability (curling after the cutting).
- It is particularly preferable to apply the invention to a steel cord having a layer twisting structure of 3+8+1 in view of the cord durability. That is, when the invention is applied to rubber penetration type cords having a gap between the steel filaments in the sheath layer, if a large bending force is applied to the cord under a low internal pressure, the movement of the steel filaments becomes small because rubber penetrates into the inside of the cord and hence the resistance to cord breaking-up is improved.
- The following examples are given in illustration of the invention and are not intended as limitations thereof.
- Steel cords are prepared as shown in Table 1 and applied to a carcass ply of a radial tire for trucks and buses having a tire size of 11/70R22.5 14PR at an end count of 22.0 cords/5 cm. The fretting depth and cord breakage under large bending force are measured by running such a tire on a drum under the following test conditions:
- Speed:
- 60 km/hr
- Internal pressure:
- 8 kgf/cm2 (usual running)
1 kgf/cm2 (running under large bending force) - Load:
- JIS 100% load (usual running)
JIS 40% load (running under large bending force) - As the steel cord, there are used steel cord of Comparative Example 1 having a layer twisting structure of 3+9+1 and a wrap steel filament of Z-lay (control), steel cord of Comparative Example 2 having a layer twisting structure of 3+9 and no wrap steel filament, and steel cord of Example 1 having a layer twisting structure of 3+9+1 and a wrap steel filament of S-lay according to the invention. The measured results are shown in Table 1.
- The steel filaments of the outermost sheath layer corresponding to two cords are taken out from the tire after the running under usual conditions and broken through a tensile test. Then, the broken sections of these filaments are observed by means of a microscope to measure a fretting depth h shown in Fig. 4 when the section of the original steel filament is circle. When an average of the measured values h is a fretting depth of the cord, the fretting depth is evaluated by an index value according to the following equation:
- Index =
- fretting depth of test tire/ fretting depth of control x 100
- The presence or absence of cord breakage is measured by taking out the steel cords from the tire after the running over a distance of 10,000 km under the large bending force.
Table 1 Comparative Example 1 Comparative Example 2 Example 1 Twisting structure 3+9+1 3+9 3+9+1 Twisting direction S/S/Z S/S S/S/S Twisting pitch 6.0/12.0/3.5 6.0/12.0 6.0/12.0/3.5 Filament diameter (mm) (1) core, sheath 0.23 0.23 0.23 (2) wrap 0.15 - 0.15 Fretting depth 100 - 8 Cord breakage none * presence none * * : no filament breakage - Steel cords are prepared as shown in Table 2 and applied to a carcass ply of a radial tire for trucks and buses having a tire size of 11/70R22.5 14PR at an end count of 20.0 cords/5 cm. The fretting depth and cord breakage under large bending force are measured in the same manner as in Example 1 by running such a tire on a drum under the same conditions as in Example 1.
- As the steel cord, there are used steel cord of Comparative Example 3 having a layer twisting structure of 1+6+12+1 and a wrap steel filament of Z-lay (control), steel cord of Comparative Example 4 having a layer twisting structure of 1+6+12 and no wrap steel filament, and steel cord of Example 2 having a layer twisting structure of 1+6+12+1 and a wrap steel filament of S-lay according to the invention. The measured results are shown in Table 2. Moreover, when the core is comprised of a single steel filament, the twisting pitch of the core is considered to be infinite.
Table 2 Comparative Example 3 Comparative Example 4 Example 2 Twisting structure 1+6+12+1 1+6+12 1+6+12+1 Twisting direction -/S/S/Z -/S/S -/S/S/S Twisting pitch ∞/6.0/12.0/3.5 ∞/6.0/12.0 ∞/6.0/12.0/3.5 Filament diameter (mm) (1) core, sheath 0.20 0.20 0.20 (2) wrap 0.15 - 0.15 Fretting depth 100 - 13 Cord breakage none * presence none * * : no filament breakage - Steel cords are prepared as shown in Table 3 and applied to a carcass ply of a radial tire for trucks and buses having a tire size of 11/70R22.5 14PR at an end count of 19.8 cords/5 cm. The fretting depth and cord breakage under large bending force are measured in the same manner as in Example 1 by running such a tire on a drum under the same conditions as in Example 1.
- As the steel cord, there are used steel cord of Comparative Example 5 having a layer twisting structure of 3+9+15+1 and a wrap steel filament of S-lay (control), steel cord of Comparative Example 6 having a layer twisting structure of 3+9+15 and no wrap steel filament, and steel cord of Example 3 having a layer twisting structure of 3+9+15+1 and a wrap steel filament of Z-lay according to the invention. The measured results are shown in Table 3.
Table 3 Comparative Example 5 Comparative Example 6 Example 3 Twisting structure 3+9+15+1 3+9+15 3+9+15+1 Twisting direction S/S/Z/S S/S/Z S/S/Z/Z Twisting pitch 5.5/10.5/15.5/3.5 5.5/10.5/15.5 5.5/10.5/15.5/3.5 Filament diameter (mm) (1) core, sheath 0.175 0.175 0.175 (2) wrap 0.15 - 0.15 Fretting depth 100 - 17 Cord breakage none * presence none * * : no filament breakage - Steel cords are prepared as shown in Table 4 and applied to a carcass ply of a radial tire for trucks and buses having a tire size of 11/70R22.5 14PR at an end count of 31.8 cords/5 cm. The fretting depth and cord breakage under large bending force are measured in the same manner as in Example 1 by running such a tire on a drum under the same conditions as in Example 1.
- As the steel cord, there are used steel cord of Comparative Example 7 having a layer twisting structure of 3+8+1 and a wrap steel filament of Z-lay (control), steel cord of Comparative Example 8 having a layer twisting structure of 3+8 and no wrap steel filament, and steel cord of Example 4 having a layer twisting structure of 3+8+1 and a wrap steel filament of S-lay according to the invention. The measured results are shown in Table 4.
Table 4 Comparative Example 7 Comparative Example 8 Example 4 Twisting structure 3+8+1 3+8 3+8+1 Twisting direction S/S/Z S/S S/S/S Twisting pitch 5.5/10.5/3.5 5.5/10.5 5.5/10.5/3.5 Filament diameter (mm) (1) core, sheath 0.21 0.21 0.21 (2) wrap 0.15 0.15 0.15 Fretting depth 100 - 8 Cord breakage none * presence none * * : no filament breakage - As mentioned above, the steel cord according to the invention has such a layer twisting structure that the wrap steel filament is spirally wound around the outermost sheath layer in the same direction as in the steel filaments of the outermost sheath layer. When such steel cords are applied to the carcass ply of a radial tire, the fretting between the steel filaments of the outermost sheath layer and the wrap steel filament is decreased and also the lowering of tensile load in the steel filaments of the cord becomes equal to improve the cord life, so that the tire durability can considerably be improved.
Claims (4)
- A steel cord for the reinforcement of rubber articles formed by twisting 1 to 4 steel filaments as a core (1) and at least one sheath layer (2,3) comprised of a plurality of steel filaments arranged around the core, provided that the twisting pitch of at least one sheath layer is different from that of a remaining sheath layer adjacent thereto or that of the core, and wherein a wrap steel filament (4) is spirally wound around a sheath layer located at an outermost side of the steel cord, characterized in that said wrap steel filament (4) is wound in the same twisting direction as in the said sheath layer.
- A steel cord as claimed in claim 1, characterized in that said wrap steel filament (4) is wound around said outermost sheath layer at a twisting pitch of 2-6 mm.
- A steel cord as claimed in claim 1 or 2, characterized in that said cord has a layer twisting structure selected from 3+9+1, 3+8+1, 1+6+12+1 and 3+9+15+1 types.
- A pneumatic radial tire comprising a carcass ply of a radial structure toroidally extending between a pair of bead portions and containing steel cords therein, characterized in that said steel cord is as claimed in any of claims 1 to 3.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP10774292 | 1992-04-27 | ||
JP107742/92 | 1992-04-27 |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0568271A1 EP0568271A1 (en) | 1993-11-03 |
EP0568271B1 true EP0568271B1 (en) | 1996-06-19 |
Family
ID=14466812
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP19930303148 Expired - Lifetime EP0568271B1 (en) | 1992-04-27 | 1993-04-22 | Steel cords for reinforcement of rubber articles and pneumatic radial tires |
Country Status (3)
Country | Link |
---|---|
EP (1) | EP0568271B1 (en) |
DE (1) | DE69303222T2 (en) |
ES (1) | ES2090867T3 (en) |
Families Citing this family (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR2795751A1 (en) | 1999-06-29 | 2001-01-05 | Michelin Soc Tech | MULTILAYER STEEL CABLE FOR PNEUMATIC CARCASS |
FR2833277A1 (en) * | 2001-12-07 | 2003-06-13 | Michelin Soc Tech | METAL CABLE USABLE FOR REINFORCING A CARCASS FRAME OF A TIRE AND A PNEUMATIC TIRE |
FR2843361B1 (en) * | 2002-08-07 | 2005-04-08 | Otico | REINFORCEMENT CABLE FOR SOFT FILLER WITHOUT END |
JP5692749B2 (en) * | 2011-02-24 | 2015-04-01 | 株式会社ブリヂストン | Steel cords for rubber article reinforcement and rubber-steel cord composites |
Family Cites Families (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB720149A (en) * | 1952-06-17 | 1954-12-15 | Dunlop Rubber Co | Improvements in or relating to pneumatic tyres |
JP2659072B2 (en) * | 1988-12-16 | 1997-09-30 | 住友電気工業株式会社 | Steel cord for rubber reinforcement |
JPH0811872B2 (en) * | 1990-11-29 | 1996-02-07 | 株式会社ブリヂストン | Steel cord and pneumatic radial tire for reinforcing rubber articles |
-
1993
- 1993-04-22 DE DE1993603222 patent/DE69303222T2/en not_active Expired - Fee Related
- 1993-04-22 ES ES93303148T patent/ES2090867T3/en not_active Expired - Lifetime
- 1993-04-22 EP EP19930303148 patent/EP0568271B1/en not_active Expired - Lifetime
Also Published As
Publication number | Publication date |
---|---|
DE69303222D1 (en) | 1996-07-25 |
EP0568271A1 (en) | 1993-11-03 |
DE69303222T2 (en) | 1996-12-05 |
ES2090867T3 (en) | 1996-10-16 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
EP2065511B1 (en) | Rubber reinforcing steel cord and pneumatic radial tire | |
EP0460705B1 (en) | Steel cords for the reinforcement of rubber articles | |
EP0719889B1 (en) | Steel cords for the reinforcement of rubber article | |
US5396942A (en) | Pneumatic radial tires with core-sheath steel belt cords | |
EP0752325A1 (en) | Pneumatic radial tire | |
EP0488735B1 (en) | Steel cords for rubber reinforcement and pneumatic radial tires using the same | |
EP0834613B1 (en) | Rubber article reinforcing steel cord and pneumatic tire | |
EP1344864B1 (en) | Steel cord, method of making the same and pneumatic tire including the same | |
EP0669421B1 (en) | Steel cords for the reinforcement of rubber articles and pneumatic radial tires using the same | |
EP0568271B1 (en) | Steel cords for reinforcement of rubber articles and pneumatic radial tires | |
JP3187601B2 (en) | Steel cord for reinforcing rubber articles and pneumatic radial tire | |
JPH1128906A (en) | Pneumatic radial tire | |
US5871603A (en) | Pneumatic tires with organic or inorganic fiber cord bead core | |
JPH07117406A (en) | Pneumatic radial tire for heavy load | |
EP1001074B1 (en) | Steel cords for the reinforcement of rubber articles and pneumatic tires | |
JP3529875B2 (en) | Steel cord for reinforcing rubber articles and pneumatic radial tire | |
JPH09209281A (en) | Steel cord for reinforcing rubber and radial tire using the same | |
JPH10280288A (en) | Steel cord for reinforcing rubber and radial tire for heavy duty using the same | |
JPH10131065A (en) | Steel cord for reinforcing rubber article and radial tire for heavy load using the same | |
JPH05279975A (en) | Pneumatic radial tire | |
JPH08176977A (en) | Rubber-reinforcing steel ford and radial tire using the same | |
JPS6241338A (en) | Steel cord for reinforcing rubber article |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
PUAI | Public reference made under article 153(3) epc to a published international application that has entered the european phase |
Free format text: ORIGINAL CODE: 0009012 |
|
AK | Designated contracting states |
Kind code of ref document: A1 Designated state(s): BE DE ES FR GB IT |
|
17P | Request for examination filed |
Effective date: 19931018 |
|
17Q | First examination report despatched |
Effective date: 19950116 |
|
GRAH | Despatch of communication of intention to grant a patent |
Free format text: ORIGINAL CODE: EPIDOS IGRA |
|
GRAA | (expected) grant |
Free format text: ORIGINAL CODE: 0009210 |
|
AK | Designated contracting states |
Kind code of ref document: B1 Designated state(s): BE DE ES FR GB IT |
|
ITF | It: translation for a ep patent filed |
Owner name: MARIETTI E GISLON S.R.L. |
|
REF | Corresponds to: |
Ref document number: 69303222 Country of ref document: DE Date of ref document: 19960725 |
|
ET | Fr: translation filed | ||
REG | Reference to a national code |
Ref country code: ES Ref legal event code: FG2A Ref document number: 2090867 Country of ref document: ES Kind code of ref document: T3 |
|
REG | Reference to a national code |
Ref country code: ES Ref legal event code: FG2A Ref document number: 2090867 Country of ref document: ES Kind code of ref document: T3 |
|
PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: FR Payment date: 19970409 Year of fee payment: 5 |
|
PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: GB Payment date: 19970414 Year of fee payment: 5 |
|
PLBE | No opposition filed within time limit |
Free format text: ORIGINAL CODE: 0009261 |
|
STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT |
|
PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: ES Payment date: 19970428 Year of fee payment: 5 Ref country code: DE Payment date: 19970428 Year of fee payment: 5 |
|
26N | No opposition filed | ||
PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: BE Payment date: 19970612 Year of fee payment: 5 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: GB Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 19980422 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: ES Free format text: LAPSE BECAUSE OF EXPIRATION OF PROTECTION Effective date: 19980423 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: FR Free format text: THE PATENT HAS BEEN ANNULLED BY A DECISION OF A NATIONAL AUTHORITY Effective date: 19980430 Ref country code: BE Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 19980430 |
|
BERE | Be: lapsed |
Owner name: BRIDGESTONE CORP. Effective date: 19980430 |
|
GBPC | Gb: european patent ceased through non-payment of renewal fee |
Effective date: 19980422 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: DE Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 19990202 |
|
REG | Reference to a national code |
Ref country code: FR Ref legal event code: ST |
|
REG | Reference to a national code |
Ref country code: ES Ref legal event code: FD2A Effective date: 20000601 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: IT Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20050422 |