# US 5,706,641 A · Steel cord having layer-twisted structure of helicoidal filaments for reinforcing rubber product > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,706,641 A - Document ID: US5706641A - Status: Granted - Kind: A - Application number: 08/557,915 - Filed: 1995-11-14 - Granted: 1998-01-13 - Earliest claimed: 1994-11-14 - Assignees: Bridgestone Metalpha Corporation - Inventors: Hiroki Ishizaka - Web page: https://patentgrep.com/patent/US5706641A ## CPC - D07B 1/062: {the reinforcing cords being characterised by the strand configuration} - D07B 1/0626: {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} - D07B 1/0633: {having a multiple-layer configuration} - D07B 2201/2021: characterised by their longitudinal shape - D07B 2201/2028: having the same lay direction and lay pitch - Y10S 57/902: Reinforcing or tyre cords - D07B: ROPES OR CABLES IN GENERAL (joining ropes or cables to one another or to other objects B65H69/00, F16G11/00; {mountaineering ropes A63B29/02}; mechanical finishing or dressing of ropes D02J; {braiding D04C}; decorative ropes or cords D04D; suspension cables for bridges E01D19/16; specially adapted for driving, or for being driven by, pulleys or other gearing elements F16G9/00; electric cables or joints insofar as electrical aspects are essential H01B, H01R) - Y10S: TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS ## Abstract A steel cord which is suitable for reinforcing a rubber product and has excellent fatigue resistance. The steel cord has a layer-twisted structure formed by steel filaments respectively having a diameter of 0.15 mm to 0.25 mm. A core of the steel cord is formed by 1 to 4 steel filaments. A least 6 steel filaments are wound around the steel filaments of the core to form at least one layer. When the steel cord is bent from a straight state to a state in which a radius of curvature thereof is d/(17.times.10.sup.-3) wherein d is a diameter in millimeters of each steel filament in an outermost layer of the steel cord, a maximum amount of movement of each steel filament in the outermost layer in a cross-section of the steel cord is less than or equal to (-0.5454d+0.1454).times.10.sup.3 um. The steel cord preferably has a two-layer-twisted structure or a three-layer-twisted structure, and has an arrangement in which the diameters of the steel filaments gradually decrease from the core to the outermost layer. ## Claims ### Claim 1 A steel cord having a layer-twisted structure for reinforcing a rubber product, comprising: a core structure formed by 1 to 4 steel filaments each having a diameter of from 0.15 mm to 0.25 mm, said core structure having a cord axis; and a surrounding structure formed by at least 6 steel filaments each having a diameter of from 0.15 mm to 0.25 mm, said steel filaments being helicoidally twisted around said core structure, said filaments in said surrounding structure forming at least one layer, each layer forming a circumscribed circle defined by the distance between said cord axis and the center of each filament forming said layer, wherein each of said filaments in said surrounding structure has a helicoidal structure having a diameter with a shaping ratio of 80%-90% as measured when being unraveled, the shaping ratio being defined as the ratio of the diameter of said helicoidal structure of each filament to the diameter of the circumscribed circle of the layer including said filament, said shaping ratio being such that the degree of movement of each steel filament in said at least one layer from said cord axis is (-0.5454d+0.1454).times.10.sup.3 .mu.m or less, wherein d is a diameter in millimeters of said filament, as measured when said steel cord is bent from a straight state to a state in which a radius of curvature of said steel cord is d/(17.times.10.sup.-3). ### Claim 2 (depends on 1) A steel cord for reinforcing a rubber product according to claim 1, wherein the number of steel filaments wound around said steel filaments of said core is 6 to 9. ### Claim 3 (depends on 2) A steel cord for reinforcing a rubber product according to claim 2, wherein, given that a diameter of each steel filament of said core portion is represented by dp, and a diameter of each steel filament wound around said steel filaments of said core portion is represented by dq, the relation dp.gtoreq.dq is satisfied. ### Claim 4 (depends on 1) A steel cord for reinforcing a rubber product according to claim 1, wherein the number of steel filaments wound around said steel filaments of said core portion is 6 to 9, and the number of steel filaments wound around said steel filaments wound around said core portion is 11 to 15. ### Claim 5 (depends on 4) A steel cord for reinforcing a rubber product according to claim 4, wherein, given that a diameter of each steel filament of said core portion is represented by dp, a diameter of each steel filament wound around said steel filaments of said core portion is represented by dq, and a diameter of each steel filament wound around said steel filaments wound around said core portion is represented by dr, the relation dp.gtoreq.dq.gtoreq.dr is satisfied. ### Claim 6 (depends on 1) A steel cord according to claim 1, further comprising a rubber soaked into said steel cord at a rubber-soaking ratio of 80% or higher, defined by the ratio of the volume of rubber soaked into the cord to the void formed among the filaments, wherein the number of steel filaments in said surrounding structure is selected to achieve said rubber-soaking ratio. ### Claim 7 A steel cord having a layer-twisted structure for reinforcing a rubber product, comprising: a core structure formed by 1 to 3 steel filaments each having a diameter of from 0.15 mm to 0.25 mm, said core structure having a cord axis; and a surrounding structure formed by at least 6 steel filaments each having a diameter of from 0.15 mm to 0.25 mm, said steel filaments being helicoidally twisted around said steel filaments of said core structure in the same direction and at the same twist pitch as the direction and twist pitch of said steel filaments of said core structure, said filaments in said surrounding structure forming at least one layer, each layer forming a circumscribed circle defined by the distance between said cord axis and the center of each filament forming said layer, wherein each of said filaments in said surrounding structure has a helicoidal structure having a diameter with a shaping ratio of 80%-90% as measured when being unraveled, the shaping ratio being defined as the ratio of the diameter of said helicoidal structure of each filament to the diameter of the circumscribed circle of the layer including said filament, said shaping ratio being such that the degree of movement of each steel filament in said at least one layer from said cord axis is (-0.5454d+0.1454).times.10.sup.3 .mu.m or less, wherein d is a diameter in millimeters of said filament, as measured when said steel cord is bent from a straight state to a state in which a radius of curvature of said steel cord is d/(17.times.10.sup.-3). ### Claim 8 (depends on 7) A steel cord for reinforcing a rubber product according to claim 7, wherein the number of steel filaments wound around said steel filaments of said core portion is 6 to 9. ### Claim 9 (depends on 8) A steel cord for reinforcing a rubber product according to claim 8, wherein, given that a diameter of each steel filament of said core portion is represented by dp, and a diameter of each steel filament wound around said steel filaments of said core portion is represented by dq, the relation dp.gtoreq.dq is satisfied. ### Claim 10 (depends on 7) A steel cord for reinforcing a rubber product according to claim 7, wherein the number of steel filaments wound around said steel filaments of said core portion is 6 to 9, and the number of steel filaments wound around said steel filaments wound around said core portion is 11 to 15. ### Claim 11 (depends on 10) A steel cord for reinforcing a rubber product according to claim 10, wherein, given that a diameter of each steel filament of said core portion is represented by dp, a diameter of each steel filament wound around said steel filaments of said core portion is represented by dq, and a diameter of each steel filament wound around said steel filaments wound around said core portion is represented by dr, the relation dp.gtoreq.dq.gtoreq.dr is satisfied. ### Claim 12 (depends on 7) A steel cord according to claim 7, further comprising a rubber soaked into said steel cord at a rubber-soaking ratio of 80% or higher, defined by the ratio of the volume of rubber soaked into the cord to the void formed among the filaments, wherein the number of steel filaments in said surrounding structure is selected to achieve said rubber-soaking ratio.