# US 10,479,474 B2 · Friction stir welded wingtip torque box > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,479,474 B2 - Document ID: US10479474B2 - Status: Granted - Kind: B2 - Application number: 15/209,974 - Filed: 2016-07-14 - Published: 2018-01-18 - Granted: 2019-11-19 - Earliest claimed: 2016-07-14 - Assignees: The Boeing Company - Applicants: The Boeing Company - Inventors: Michael P. Shemkunas; Kenneth D. Cominsky; Steven S. Heer; David P. Heck; Benjamin D. Smith; John A. Baumann; Matthew D. Uhlman; Burke L. Reichlinger; Eric E. Thomas; James P. Dobberfuhl - Web page: https://patentgrep.com/patent/US10479474B2 ## CPC - B64C 3/18: Spars; Ribs; Stringers - B23K 20/1265: {Non-butt welded joints, e.g. overlap-joints, T-joints or spot welds} - B23K 20/2336: {both layers being aluminium} - B64C 3/182: {Stringers, longerons} - B64C 3/185: {Spars} - B64C 3/20: Integral or sandwich constructions - B64C 3/26: Construction, shape, or attachment of separate skins, e.g. panels - B64C 23/065: {at the wing tips} - B64F 5/10: Manufacturing or assembling aircraft, e.g. jigs therefor - C25D 11/04: of aluminium or alloys based thereon - B23K 2101/12: Vessels - B23K 2103/10: Aluminium or alloys thereof - Y02T 50/10: Drag reduction - B64C: AEROPLANES; HELICOPTERS - B23K: SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM - B64F: GROUND OR AIRCRAFT-CARRIER-DECK INSTALLATIONS SPECIALLY ADAPTED FOR USE IN CONNECTION WITH AIRCRAFT; DESIGNING, MANUFACTURING, ASSEMBLING, CLEANING, MAINTAINING OR REPAIRING AIRCRAFT, NOT OTHERWISE PROVIDED FOR; HANDLING, TRANSPORTING, TESTING OR INSPECTING AIRCRAFT COMPONENTS, NOT OTHERWISE PROVIDED FOR - C25D: PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR - Y02T: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION ## Abstract Provided are wingtip torque boxes and methods of fabricating such boxes using friction stir welding. Specifically, a wingtip torque box may be formed by friction stir welding two monolithic clamshells along their respective spars thereby forming a new monolithic structure. Use of the friction stir welding and monolithic clamshells simplifies the overall fabrication process and yields a robust wingtip torque box that can be bolted on or otherwise attached to an aircraft wing. The wingtip torque box may include internal grid stiffeners and/or external stiffeners that may be also monolithic with other components of the box. For example, the stiffeners may be machined in spars or skin portions of the clamshells during fabrication of clamshells. The wingtip torque box may have a continuous cavity extending between the ends and, in some embodiments, between spars of the box and providing access for performing various operations inside the box. ## Claims ### Claim 1 A wingtip torque box comprising: an upper monolithic clamshell comprising an upper front spar, an upper rear spar, and an upper skin portion extending between the upper front spar and the upper rear spar; a lower monolithic clamshell comprising a lower front spar, a lower rear spar, and a lower skin portion extending between the lower front spar and the lower rear spar, wherein the upper monolithic clamshell and the lower monolithic clamshell form a cavity, wherein the cavity is a continuous cavity that extends between a wing end and a tip end of the wingtip torque box, providing access through the wingtip torque box between the wing end and the tip end, wherein the upper front spar is friction stir welded to the lower front spar at a front friction stir welded joint, and wherein the upper rear spar is friction stir welded to the lower rear spar at a rear friction stir welded joint. ### Claim 2 (depends on 1) The wingtip torque box of claim 1, wherein the upper monolithic clamshell comprises upper internal grid stiffeners extending from the upper skin portion to the cavity, and wherein the lower monolithic clamshell comprises lower internal grid stiffeners extending from the lower skin portion to the cavity, the cavity defined by ends of the upper internal grid stiffeners and the lower internal grid stiffeners. ### Claim 3 (depends on 2) The wingtip torque box of claim 2, wherein the cavity has a height greater than a height of the upper internal grid stiffeners or a height of the lower internal grid stiffeners. ### Claim 4 (depends on 2) The wingtip torque box of claim 2, wherein the upper internal grid stiffeners and the lower internal grid stiffeners are both orthogrid stiffeners. ### Claim 5 (depends on 2) The wingtip torque box of claim 2, wherein the upper internal grid stiffeners and the lower internal grid stiffeners extend between a tip end and a wing end of the wingtip torque box. ### Claim 6 (depends on 1) The wingtip torque box of claim 1, wherein the upper monolithic clamshell comprises upper external stiffeners extending from the upper front spar away from the cavity, wherein the lower monolithic clamshell comprises lower external stiffeners extending from the lower front spar away from the cavity. ### Claim 7 (depends on 6) The wingtip torque box of claim 6, wherein the upper external stiffeners comprise upper vertical portions extending perpendicular to the front friction stir welded joint, and wherein the lower external stiffeners comprise lower vertical portions extending perpendicular to the front friction stir welded joint. ### Claim 8 (depends on 1) The wingtip torque box of claim 1, wherein the upper skin portion and the lower skin portion define an airfoil shape of the wingtip torque box. ### Claim 9 (depends on 1) The wingtip torque box of claim 1, wherein the upper monolithic clamshell comprises an upper wing attachment plate, wherein the lower monolithic clamshell comprises a lower wing attachment plate, and wherein each of the upper wing attachment plate and the lower wing attachment plate comprises fastener openings. ### Claim 10 (depends on 9) The wingtip torque box of claim 9, wherein each of the fastener openings comprises a first cylindrical opening extending substantially perpendicular to a plane defined by the upper wing attachment plate or by the lower wing attachment plate, wherein each of the fastener openings further comprises a second cylindrical opening extending substantially perpendicular to a plane defined by the upper skin portion or by the lower skin portion. ### Claim 11 (depends on 9) The wingtip torque box of claim 9, wherein the upper wing attachment plate and the lower wing attachment plate are coplanar. ### Claim 12 (depends on 9) The wingtip torque box of claim 9, wherein the upper wing attachment plate and the lower wing attachment plate are substantially perpendicular to the front friction stir welded joint and to the rear friction stir welded joint. ### Claim 13 (depends on 1) The wingtip torque box of claim 1, wherein the wingtip torque box comprises aluminum. ### Claim 14 (depends on 1) The wingtip torque box of claim 1, wherein a material composition of the wingtip torque box is substantially uniform throughout an entire volume of the wingtip torque box. ### Claim 15 A method of fabricating a wingtip torque box, the method comprising: aligning an upper monolithic clamshell and a lower monolithic clamshell relative to each other, wherein the upper monolithic clamshell comprises an upper front spar, an upper rear spar, and an upper skin portion extending between the upper front spar and the upper rear spar; wherein the lower monolithic clamshell comprises a lower front spar, a lower rear spar, and a lower skin portion extending between the lower front spar and the lower rear spar, friction stir welding the upper front spar and the lower front spar thereby forming a front friction stir welded joint extending between the wing end and the tip end; and friction stir welding the upper rear spar and the lower rear spar thereby forming a rear friction stir welded joint extending between the wing end and the tip end, wherein the upper monolithic clamshell and the lower monolithic clamshell form a cavity, wherein the cavity is a continuous cavity that extends between a wing end and a tip end of the wingtip torque box, providing access through the wingtip torque box between the wing end and the tip end. ### Claim 16 (depends on 15) The method of claim 15, wherein friction stir welding the upper front spar and the lower front spar and friction stir welding the upper rear spar and the lower rear spar are performed in sequence. ### Claim 17 (depends on 15) The method of claim 15, wherein friction stir welding the upper front spar and the lower front spar at least partially overlaps in time with friction stir welding the upper rear spar and the lower rear spar. ### Claim 18 (depends on 15) The method of claim 15, further comprising, after friction stir welding the upper front spar and the lower front spar, removing an end of the upper front spar and an end of the lower front spar corresponding to a path end of friction stir welding. ### Claim 19 (depends on 15) The method of claim 15, further comprising forming fastener openings in an upper wing attachment plate of the upper monolithic clamshell and in a lower wing attachment plate of the lower monolithic clamshell. ### Claim 20 (depends on 15) The method of claim 15, further comprising, after friction stir weld anodizing the wingtip torque box. ### Claim 21 (depends on 7) The wingtip torque box of claim 7, wherein each of the upper vertical portions is collinear to one of the lower vertical portions.