# US 12,603,487 B2 · Bushing and manufacturing method therefor > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,603,487 B2 - Document ID: US12603487B2 - Status: Granted - Kind: B2 - Application number: 17/641,639 - Filed: 2020-09-10 - Published: 2022-11-10 - Granted: 2026-04-14 - Earliest claimed: 2019-09-10 - Assignees: Hitachi Energy Ltd - Applicants: Hitachi Energy Ltd - Inventors: Danan Yao; Peirong Cai - Web page: https://patentgrep.com/patent/US12603487B2 ## CPC - H01B 17/26: Lead-in insulators; Lead-through insulators - H02G 3/22: Installations of cables or lines through walls, floors or ceilings, e.g. into buildings - H01B 13/0036: {Details} - H01F 27/04: Leading of conductors or axles through casings, e.g. for tap-changing arrangements - H01B: CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES (selection for magnetic properties H01F1/00; waveguides H01P {; printed circuits H05K}) - H02G: INSTALLATION OF ELECTRIC CABLES OR LINES, OR OF COMBINED OPTICAL AND ELECTRIC CABLES OR LINES - H01F: MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES ## Abstract The present disclosure relates to a bushing and a manufacturing method therefor. The bushing includes a conductive tube and a central tube. The conductive tube is fixedly connected to a bottom connecting assembly and a top connecting assembly. The central tube is fixedly connected to the bottom connecting assembly and the top connecting assembly. The central tube is subjected to a compressive force in an extending direction of the central tube, such that the conductive tube is subjected to a tensile force in an extending direction of the conductive tube. The embodiments of the present disclosure can eliminate or reduce creep or stress relaxation of composites to ensure mechanical properties and sealing performance in a life cycle of the bushing. ## Claims ### Claim 1 A bushing, comprising: a conductive tube fixedly connected to a bottom connecting assembly and a top connecting assembly; and a central tube fixedly connected to the bottom connecting assembly and the top connecting assembly, wherein the central tube comprises a hollow tube that is located inside the conductive tube, and wherein the central tube is subjected to a compressive force in an extending direction of the central tube, such that the conductive tube is subjected to a tensile force in an extending direction of the conductive tube, wherein the central tube and the conductive tube are pre-stressed to maintain engagement with each other under axial loading without applying axial force beyond the top and bottom connecting assemblies. ### Claim 2 (depends on 1) The bushing as claimed in claim 1, wherein the central tube is a metal tube or an alloy tube. ### Claim 3 (depends on 2) The bushing as claimed in claim 2, wherein the bottom connecting assembly comprises: a bottom central tube nut, the central tube being welded to the bottom central tube nut; a bottom nut, the conductive tube being fixedly connected to the bottom nut; and a first bottom bolt via which the bottom central tube nut is fixedly connected to the bottom nut. ### Claim 4 (depends on 3) The bushing as claimed in claim 3, wherein an inner surface of the bottom nut adjacent to the bottom central tube nut is provided with an annular groove adapted to accommodate a first O-ring for sealing. ### Claim 5 (depends on 3) The bushing as claimed in claim 3, further comprising a flange, which is aligned with an outer periphery on an outer side of a projecting rim of the bottom nut and fixedly connected to the bottom nut via a second bolt. ### Claim 6 (depends on 5) The bushing as claimed in claim 5, wherein an outer peripheral surface of the bottom nut adjacent to the flange is provided with an annular groove adapted to accommodate a second O-ring for sealing. ### Claim 7 (depends on 6) The bushing as claimed in claim 6, further comprising a composite insulator, wherein the composite insulator is located outside the conductive tube, and the bottom of the composite insulator is adapted to be sandwiched between the flange and the projecting rim of the bottom nut. ### Claim 8 (depends on 2) The bushing as claimed in claim 2, wherein the top connecting assembly comprises: a top central tube nut, the central tube being fixedly connected to the top central tube nut; a top nut, the conductive tube is fixedly connected to the top nut; and a first top via which the top central tube nut is fixedly connected to the top nut. ### Claim 9 (depends on 8) The bushing as claimed in claim 8, wherein the top connecting assembly further comprises a connecting flange, and the connecting flange is aligned with an outer periphery of the top nut and fixedly connected to the top nut via a second top bolt. ### Claim 10 (depends on 9) The bushing as claimed in claim 9, further comprising a flexible conductive connecting member, wherein the flexible conductive connecting member has a curved shape and is electrically coupled to the connecting flange. ### Claim 11 (depends on 10) The bushing as claimed in claim 10, further comprising: a conductive sleeve electrically coupled to the flexible conductive connecting member, an inner surface of the conductive sleeve being adjacent to an outer surface of the central tube. ### Claim 12 (depends on 11) The bushing as claimed in claim 11, wherein the flexible conductive connecting member comprises a plurality of layers of current-carrying metal members, a part of the inner surface of the conductive sleeve and the outer surface of the central tube has at least one groove, and the at least one groove is adapted to accommodate at least one of an O-ring and a sliding seal. ### Claim 13 (depends on 8) The bushing as claimed in claim 8, further comprising: at least one supporting member located between the central tube and the conductive tube to prevent the central tube from bending in a transverse direction perpendicular to the extending direction of the central tube; and an insulating isolation sleeve located between the top central tube nut and the first top bolt to electrically insulate the top central tube nut from the first top bolt. ### Claim 14 (depends on 2) The bushing as claimed in claim 2, wherein the bottom connecting assembly comprises: a bottom central tube nut, the central tube being welded to the bottom central tube nut; a bottom nut, the conductive tube being fixedly connected to the bottom nut; and a first bottom bolt via which the bottom central tube nut is fixedly connected to the bottom nut. ### Claim 15 (depends on 14) The bushing as claimed in claim 14, wherein an inner surface of the bottom nut adjacent to the bottom central tube nut is provided with an annular groove adapted to accommodate a first O-ring for sealing. ### Claim 16 (depends on 14) The bushing as claimed in claim 14, further comprising a flange, which is aligned with an outer periphery on an outer side of a projecting rim of the bottom nut and fixedly connected to the bottom nut via a second bolt. ### Claim 17 (depends on 16) The bushing as claimed in claim 16, wherein an outer peripheral surface of the bottom nut adjacent to the flange is provided with an annular groove adapted to accommodate a second O-ring for sealing. ### Claim 18 A transformer, comprising: a bushing having: a conductive tube fixedly connected to a bottom connecting assembly and a top connecting assembly; and a central tube fixedly connected to the bottom connecting assembly and the top connecting assembly, wherein the central tube comprises a hollow tube that is located inside the conductive tube, and wherein the central tube is subjected to a compressive force in an extending direction of the central tube, such that the conductive tube is subjected to a tensile force in an extending direction of the conductive tube, wherein the central tube and the conductive tube are pre-stressed to maintain engagement with each other under axial loading without applying axial force beyond the top and bottom connecting assemblies. ### Claim 19 A bushing, comprising: a bottom connecting assembly; a top connecting assembly; an electrically conductive tube connected to the bottom connecting assembly and the top connecting assembly; a central tube connected to the bottom connecting assembly and the top connecting assembly, wherein the central tube comprises a hollow tube that is located inside the electrically conductive tube, and wherein the central tube is subjected to a compressive force in a first direction by the bottom connecting assembly and the top connecting assembly, and the electrically conductive tube is subjected to a tensile force in the first direction by the bottom connecting assembly and the top connecting assembly, wherein the central tube and the conductive tube are pre-stressed to maintain engagement with each other under axial loading without applying axial force beyond the top and bottom connecting assemblies.