Abstract: A robotic manufacturing system includes a track extending along a length of a component of a partially manufactured item, wherein the component has a non-constant longitudinal shape, the track being supported independently of the partially manufactured item. The system includes a jointed member having an elongated arcuate shape, a mount longitudinally movable along the track and configured to receive the jointed member in an articulating manner, and an end effector movably mounted on the jointed member. The jointed member is movable along a portion of the component length in a radial position sympathetic to the non-constant component longitudinal shape. The jointed member is longitudinally movable relative to the mount along its elongated arcuate shape such that the jointed member will move in an arc spaced from and around an outer component surface. A portion of the end effector is movable along a length of the jointed member.

Abstract: An apparatus for connecting a workpiece to a connection element in a form-fit and/or force-fit manner includes a robot for positioning the workpiece, a spindle for connecting the connection element to the workpiece, and a first support to stabilize the workpiece as the connection element is connected to the workpiece. The first support has a contact region substantially in alignment with a spindle longitudinal axis and in contact with the workpiece during connection of the connection element to the workpiece. The contact region has a size which is smaller than 0.01 m2. A second support to stabilize the workpiece as the connection element is connected to the workpiece has a support surface which in a state in which the workpiece is supported in a substantially orthogonal axis relative to the longitudinal axis of the spindle is disposed in a different plane than a support surface of the first support.

Abstract: The present disclosure discloses a method for improving fatigue strength of a workpiece (100). The method comprises positioning the workpiece (100) in a punch and die assembly (102). Operating the punch and die assembly (102) one or more times to imprint surface features (2) on a portion of a surface of the workpiece (100), wherein the surface features (2) induces compressive residual stresses at a sub-surface level of the workpiece (100), and improves the fatigue strength of the workpiece (100).

Abstract: A rivet nut (“rivnut”) installation method and a rivnut structural configuration are disclosed that can be implemented separately in conjunction with one another to serve as an anchor in and/or a workpiece at an installation location. The rivnut installation method involves inserting a rivnut onto an externally threaded mandrel, rotating the mandrel while a free end of the mandrel is in contact with the workpiece, and driving the free end of the mandrel and the rivnut through the workpiece while continuing to rotate the mandrel. The method is particularly useful when the workpiece includes one or more substrate layers composed of a low ductility material such as a polymer composite. The rivnut structural configuration includes the incorporation of an external threading onto at least a portion of a hollow shaft of the rivnut.

Abstract: A tool carrier for a clinching installation, having a housing having a longitudinal axis (L), in which housing a downholder which is impinged by a first compression spring, an outer die which is impinged by a second compression spring, and an inner die which is rigidly connected to the housing are disposed coaxially within one another so as to be routed out of the housing) by way of the free ends of said downholder and dies, is distinguished in that the first compression spring is disposed so as to be coaxial within the second compression spring.

Abstract: The invention relates to a method for producing a component bond (70, 140) comprising: a fastening structure (60, 160) that has at least one component layer (60; 160a, 160b); and a thermoplastic connecting element (10, 110) having a head (12) and a shank (14), in which method the connecting element (10, 110) is driven into the fastening structure (60, 160) under pressure whilst rotating, such that the shank (14) penetrates the fastening structure (60, 160). The connecting element (10, 110), after penetrating the fastening structure (60, 160), is converted by friction into a softened, free-flowing state in a die (44, 144) which is placed against the fastening structure (60, 160) in the opposite direction to the driving direction, resulting in a thicker section (22, 22) that extends beyond the radial extent of some sections of the shank (14). The fastening structure (60, 160) is thus interlockingly held between the head (12) and the thicker section (22, 122).

Abstract: A vehicle wheel comprising a wheel rim with a rim base made from fiber composite material and a wheel disc. The wheel disc is connected to the wheel rim by a connecting element which is guided through a passage of the rim base and is received in the wheel disc. The wheel rim comprises a connecting arrangement with at least one connecting element and a seal element which covers in a complete and hollow manner a part of one or more adjacent connecting arrangements that extends across the rim outer side of the rim base. A circumferential edge of the seal element is glued in air-tight manner to the rim well. Alternatively, the wheel rim comprises a connecting arrangement with a connecting element and a flexible sealing layer made from plastic and completely covers, by coating, a part of the connecting arrangement which extends over the rim outer side of the rim base. An edge region of the flexible seal layer is connected in an air-tight manner to the rim base.

Abstract: A preform for a carbon-carbon composite including a plurality of fibrous layers stacked and needled-punched together to form the preform in the shape of an annulus having an inner radial section and an outer radial section. Each fibrous layer includes a respective plurality of fabric segments comprising at least one of carbon fibers or carbon-precursor fibers. At least one fibrous layer includes a first fabric segment forming at least a portion the inner radial section, the first fabric segment defining a first segment bisector and a first fiber orientation angle, and a second fabric segment forming at least a portion the outer radial section, the second fabric segment defining a second segment bisector and a second fiber orientation angle, where the first and second segment bisectors are radially aligned and the first fiber orientation angle is different than the second fiber orientation angle.

Abstract: An energy storage device includes: an electrode assembly including stacked plates, and a positive electrode current collector joined to the stacked plates, wherein the electrode assembly and the positive electrode current collector include a joined portion where the electrode assembly and the positive electrode current collector are joined to each other with a concavo-convex structure where either one of the electrode assembly and the positive electrode current collector projects toward the other of the electrode assembly and the positive electrode current collector, and an outer periphery of the joined portion has a non-circular shape as viewed in a stacking direction of the plates in the joined portion.

Abstract: A clearance ? between an inner peripheral surface of an attachment hole of an attachment tongue and an outer peripheral surface of a valve shaft is set to be smaller than an allowable displacement amount ? in an axial direction of a valve with respect to the attachment tongue. When a condition is satisfied in which the outer peripheral surface of the valve shaft comes into contact with a front-side periphery and a back-side periphery of the attachment hole of the attachment tongue, and in which a top surface of a valve body comes into contact with a back surface of the attachment tongue, a waste gate valve is constituted so that a metal washer becomes non-contact with a front surface of the attachment tongue.

Abstract: A method for evaluating installation of blind rivets including measuring the “cycle time” represented “y0”, transmitting sound waves through the blind rivet installed in the structure, measuring the “travel time” represented “x0”, relating “travel time” and “cycle time”, and obtaining a pair of times (x0,y0), providing a time relation pattern establishing a borderline between an area of suitable rivets and an area of unsuitable rivets, the border represented y=f(x), so for cycle time values greater than y=f(x), it is considered a “suitable area”, for cycle time values less than y=f(x), it is considered an “unsuitable area”, representing pair (x0,y0) in the graphic representation and verifying if the value of y0 is greater or less than the value of y=f(x0), classifying installation of the rivet as suitable or unsuitable according to the verification.

Abstract: Embodiments described herein provide a flexible electromagnetic clamp that may be utilized to provide an adjustable clamping force to a wide variety of non-planar surfaces. One embodiment comprises an electromagnetic clamp that includes a pair of electromagnetic members and a current source. The electromagnetic members are disposed on opposing sides of an assembly to be clamped. Each electromagnetic member includes a flexible bladder that includes ferromagnetic filings, an electrical winding wrapped around the bladder, and a flexible sleeve wrapped around the electrical winding and the bladder. The electrical winding generates a magnetic field across the bladder that is based on an applied current. The current source is electrically coupled to each electrical winding and controls a clamping force applied by the electromagnetic members to the assembly based on the applied current.

Abstract: The present disclosure provides a multi-leaved core damping disk comprising an annular-shaped first disk half, an annular shaped second disk half, and a multi-leaved core axially aligned with, and disposed therebetween.

Abstract: A blind riveting apparatus (1) comprises a motor (3), and a clamp (31) for gripping the mandrel of a blind rivet, the clamp being movable substantially along the axis of the rivet. The apparatus further comprises a first transmission (51) configured to transfer rotary motion of the motor (3) to the clamp (31) when engaged; and a second transmission (52) configured to convert rotary motion of the motor (3) to linear motion of the clamp (31), and thereby retract the clamp (31) to pull on the mandrel, when engaged. A transmission control apparatus is arranged to selectively adjust the degree of engagement of at least one of the first (51) and second (52) transmissions, the transmission control apparatus comprising a variable-influence brake or clutch (58). Methods of blind riveting, and further pieces of blind riveting apparatus, are also disclosed.

Abstract: A rivet setting machine is provided. In another aspect, a linear displacement sensor directly senses and detects a position of a rivet-setting punch relative to a nosepiece of a rivet setting machine. A further aspect provides a control system and software instructions for sensing the relative position of a punch and nosepiece used by a programmable controller to determine and monitor a rivet setting position without use of a force sensor, motor current/voltage sensor, or a rotation sensor.

Abstract: A riveting system is operable to join two or more workplaces with a rivet. In another aspect of the present invention, a self-piercing rivet is employed. Still another aspect of the present invention employs an electronic control unit and one or more sensors to determine a riveting characteristic and/or an actuator characteristic.

Abstract: A fastener carrier for fasteners for use in a riveting system, said carrier comprising at least one holding zone and at least one release zone, wherein said holding zone holds a fastener in a stored position and said release zone releases said fastener from said carrier, said holding zone having a diameter smaller than said release zone.

Abstract: A blind rivet is adapted for fastening two members, each member having a plurality of fastening holes arranged in corresponding positions. The inner diameter of the holes in the second member are greater than the inner diameter of the holes in the first member to compensate for positioning errors that may occur during machining. The blind rivet includes a rivet body having a sleeve, a rivet head, and a through hole; a mandrel having an elongated stem and a head; and a washer. The washer is arranged around the outer circumferential surface of the sleeve in the rivet body and adjacent to the rivet head. The members to be fastened are fastened between the enlarged end of the sleeve and the washer.

Abstract: A headrest assembly for an aircraft seat includes a headrest frame having a body portion, a top member interconnected with the headrest frame, a spring clip member interconnected with the top member, a bracket member with a locking rivet, and a headrest tube having a longitudinal slot. The top member includes a plurality of elongated slots and the bracket member is coupled to the headrest frame. The headrest tube is configured to receive the locking rivet in the longitudinal slot in a locked position and thereby lock the headrest tube to the headrest frame.

Abstract: A method of forming a fastener may include inserting a blank precursor into a bore of a forming die having an enlarged bore portion. The method may further include applying a first axial compression force to the blank precursor, and forming a cold-worked head section and an enlarged shank portion on the blank precursor corresponding to the enlarged bore portion. The enlarged shank portion may have a nominal shank portion extending therefrom. The method may additionally include inserting the nominal shank portion into a bore of a final reduction die, applying a second axial compression force to the enlarged shank portion, and urging the enlarged shank portion into the bore of the final reduction die. The method may also include reducing a cross-sectional area of the enlarged shank portion by approximately 2 to 5 percent to form a cold-worked shank section.

Abstract: A beverage bottle handling machine construction method for constructing a beverage bottle handling machine, such as a beverage bottle cleaning machine, a beverage bottle treating machine, and a beverage bottle shrink wrapping machine in a beverage bottling plant and container handling machines corresponding to the beverage bottle handling machine. The abstract of the disclosure is submitted herewith as required by 37 C.F.R. §1.72(b). As stated in 37 C.F.R. §1.72(b): A brief abstract of the technical disclosure in the specification must commence on a separate sheet, preferably following the claims, under the heading “Abstract of the Disclosure.” The purpose of the abstract is to enable the Patent and Trademark Office and the public generally to determine quickly from a cursory inspection the nature and gist of the technical disclosure. The abstract shall not be used for interpreting the scope of the claims.

Abstract: A method of manufacturing a custom sized plastic tote lighter in weight than heretofore known custom sized plastic totes is provided. The method comprises separating an injection molded tote into upper and lower portions by cutting the injection molded tote. A sleeve or middle portion of plastic material is secured to the upper and lower portions of the injection molded tote to create a custom sized plastic tote of a desired height. Alternatively, portions of different injection molded totes may be used to create a custom sized plastic tote. The sleeve may be made from different materials and may be made of multiple pieces.

Abstract: In a method of supplying connecting elements to a processing unit, in which the connecting elements are placed in readiness by a supply unit and conveyed individually by a passage to a loading device arranged on the processing unit, the conveyance of the connecting elements takes place in two separate steps, a first step in which the connecting elements are individually conveyed by the supply unit into a intermediate reservoir arranged near the loading device, and a second step in which a single connecting element at a time is conveyed from the intermediate reservoir into the loading device of the processing unit. Specifically, at least two different connecting elements are picked up by the intermediate reservoir, and of the several connecting elements accommodated in the intermediate reservoir an arbitrary one determined by the processing operation is selected for the second step and conveyed to the loading device.

Abstract: A method of manufacturing a custom sized plastic tote lighter in weight than heretofore known custom sized plastic totes is provided. The method comprises separating an injection molded tote into upper and lower portions by cutting the injection molded tote. A sleeve or middle portion of plastic material is secured to the upper and lower portions of the injection molded tote to create a custom sized plastic tote of a desired height. Alternatively, portions of different injection molded totes may be used to create a custom sized plastic tote. The sleeve may be made from different materials and may be made of multiple pieces.

Abstract: A blind rivet setting method enables a modified step approach to grip and pull multiple diameters of blind rivet mandrels to fracture, easily feed the remaining spent mandrel portion through a blind rivet tool, and collect and more efficiently dispose of substantially shortened spent mandrel portions when a blind rivet mandrel collection system is utilized.

Abstract: An electric riveter capable of rivet pre-pulling includes an operating unit, a controlling unit, a driving unit, and a clamping unit. The controlling unit controls the driving unit according to the way in which a user operates the operating unit, the clamping unit is driven by the driving unit to move between an initial position, a pre-pulling position, and a severing position. The operation method for the electric riveter entails: providing a rivet when the clamping unit is at the initial position; operating the operating unit in a first operation mode to move the clamping unit to the pre-pulling position and clamp the rivet; and operating the operating unit in a second operation mode to move the clamping unit to the severing position and sever the rivet. Accordingly, the rivet is prevented from falling off during the operation process, thereby enhancing ease of use of the electric riveter.

Abstract: A manufacturing method employing a robotic assembly system includes first and second fastener system components that are positioned by a robotic assembly on opposite sides of at least two structural pieces that are to be fastened together. The first system component includes a particular tool of a plurality of different types of tools, where the particular tool installs a particular fastener of a plurality of different types of fasteners. Each tool includes a block or base of magnetic material with a passageway opening for the fastener associated with the tool passing through the base. The robotic assembly positions the tool against one side of the structural pieces to be fastened, and positions an electromagnet assembly on the opposite side of the structural pieces. Activating the electromagnet assembly clamps the structural pieces together. With the fastener positioned in a hole through the structural pieces, the tool is activated to install the fastener between the structural pieces.

Abstract: A drive assembly for a torque converter is provided. The drive assembly includes a turbine shell and a damper assembly fixed to the turbine shell by at least one rectangular rivet. A method of forming a drive assembly for a torque converter is also provided. The method includes fixing a turbine shell and a damper assembly together by a plurality of rectangular rivets.

Abstract: A product comprising a front body hinge pillar adaptor component and a method for adding an adaptor component to a standard front body hinge pillar to accommodate various styles of windshields and A-pillars.

Abstract: A number of variations may include a product including a secondary dash including a center portion constructed and arranged to be attached to a primary dash of a vehicle.

Abstract: A beverage bottle handling machine construction method for constructing a beverage bottle handling machine, such as a beverage bottle cleaning machine, a beverage bottle pasteurization machine, and a beverage bottle shrink wrap machine in a beverage bottling plant. The abstract of the disclosure is submitted herewith as required by 37 C.F.R. §1.72(b). As stated in 37 C.F.R. §1.72(b): A brief abstract of the technical disclosure in the specification must commence on a separate sheet, preferably following the claims, under the heading “Abstract of the Disclosure.” The purpose of the abstract is to enable the Patent and Trademark Office and the public generally to determine quickly from a cursory inspection the nature and gist of the technical disclosure. The abstract shall not be used for interpreting the scope of the claims. Therefore, any statements made relating to the abstract are not intended to limit the claims in any manner and should not be interpreted as limiting the claims in any manner.

Abstract: The method and device provided herein relates to the field of screwed joints for panels and, in particular, for sandwich panels used in aerospace applications. It relates to a method for attaching a headless rivet nut to a wall of such a panel. The method comprises: injecting a predetermined quantity of adhesive into a blind hole made in the wall of the panel; fitting the headless rivet nut onto a rivet nut setting tool, the rivet nut setting tool comprising a pierced anvil and a mandrel passing through the anvil, the mandrel being screwed into the rivet nut so as to press the rivet nut onto the anvil; positioning the headless rivet nut in the blind hole, the anvil coming to press against the wall of the panel; setting the rivet nut so as to squeeze the wall of the panel between the anvil and a flange formed by deformation of the rivet nut.

Abstract: Provided is a manufacturing method of a bending module that forms a plurality of joint members by press-processing sheet material, with each joint member having a joint member body, a connection protrusion and a wire guide protrusion having a wire guide hole formed at one side corner of the joint member body, and connection protrusion is formed at another side corner of the joint member body. The wire guide protrusions are folded with respect to the joint member bodies; a joint member assembly is formed by arranging the plurality of joint members in parallel and connecting neighboring connection members to connect the joint members together; the joint member assembly are bent to a ring shape; and each joint member is connect to each other by welding corners thereof.

Abstract: A tacking fastener for securing workpieces together to form a temporary assembly is provided that includes a stem and a sleeve. The stem includes a proximal end portion, a central portion, and a distal end portion. The stem further includes a head disposed at the proximal end portion, the head defining a distal face having a gripping feature. The sleeve includes a flange disposed at the distal end portion, the flange defining a proximal face having a gripping feature. The sleeve is disposed around the stem and configured to form a tacking rivet upon installation of the tacking fastener. The sleeve is plastically deformed during installation to form a plurality of bulbs, thereby being capable of securing workpieces of varying grip length. The stem and the tacking rivet remain within the workpieces after the workpieces are secured.

Abstract: A method for forming a joint using a self-piercing rivet includes the steps of: positioning the sheet material over a die and providing a rivet having a substantially cylindrical shank and a head, the shank having a central blind bore and an annular piercing end spaced from said head. The ratio of the difference between the outside and inside diameters of the shank in the region around the bore to the outside diameter of the shank is in the range 0.47 to 0.52. The method also includes positioning a rivet over the sheet material at a position opposite the die and using a punch to set the rivet and force it into the sheet material such that it pierces the upper surface thereof and such that the shank deforms outwardly to interlock with the material but without penetration to the die side of the material.

Abstract: An apparatus and method are provided for feeding a connecting element into a processing position of a joining apparatus. The apparatus includes a singulation slide for separating and feeding a connecting element. The singulation slide has a through-hole running in an axial direction for accommodating the connecting element, and the through-hole is partially defined by two leg segments. The singulation slide includes a base segment and the transition from the base segment to each of the leg segments is designed so that the leg segments are flexible in a radial direction.

Abstract: Provided are a method for splitting longitudinally an end part of a metal plate or a metal rod having a rectangular, polygonal, or elliptical shape, in which the length of incision in the split portion can be freely adjusted and smooth split face can be formed; a metal part manufactured by such method; and a method for bonding such metal part.

Abstract: A conventional blind rivet tool with modified nose housing, i.e., a rivet gun with replaceable and interchangeable nosepieces, facilitates feeding and setting of multiple diameters of blind rivets with substantially shortened exposed mandrel portions extending beyond the head flange of the rivet, all while maintaining blind rivet performance and reducing total installed blind rivet costs. A rivet with a reduced exposed mandrel protrusion relative to conventional and standardized mandrels can be enabled and more easily fed through the tool.

Abstract: A rivet setter that can efficiently and smoothly perform, and reduce the takt time for a rivet setting operation. The rivet setter can be configured to set a rivet sequentially fed from a rivet supplying means by inserting the rivet into apertures formed at predetermined positions on workpieces. The rivet setter can have delivery paths for delivering the rivet one by one by sliding the rivet down to a settable position and can have a hanging support portion formed in the settable position in the tip end of the delivery path for supporting the head of rivet and for hanging the rivet shank downward. The rivet setter can be configured to enable the rivet to be set in the apertures of the workpieces by moving the hanging support portion substantially horizontally while keeping the rivet suspended in the hanging support portion and inserted into the apertures of the workpieces.

Abstract: A LED lighting device is disclosed, which includes a LED lighting source, a printed circuit board, a heat sink and a transparent cover. The LED lighting source is provided on the printed circuit board, and the cover is attached to the heat sink for protecting the LED lighting source and the printed circuit board. The LED lighting device further includes a rivet made of plastics, which is used to fix the printed circuit board to the heat sink.

Abstract: Disclosed are a method and a device for the connection of two components indirectly or directly in an overlap joint, wherein component sections located in the overlap are pressed together for each drilling procedure by means of a clamping unit formed from a pressure application device on the drilling machine side and a guide on the component side, such that any penetration of chips between the component sections is prevented and temporary connecting elements can be dispensed with.

Abstract: A retention clip assembly to join individual panels with aligned pilot holes comprises a body having an enlarged flange and a generally cylindrical leg defined by a plurality of spaced leg segments surrounding a pin insertion hole. The leg segments are separated by spaced slits and define a central passage. A pin having an enlarged head and an elongate shaft is slidable in the central passage. It engages cam projections on the interiors of the leg segments and expands the segments to secure the body to the panels. The pin includes flexible fingers having radially outer surfaces spaced apart a distance greater than the body leg deformable toward the pin shaft. The flexible fingers pass through the body flange and expand after surpassing the pilot holes in the panels. The flexible fingers slide in diametrically opposed slits, contact the edges of the pilot holes and stabilize the clip assembly within the pilot holes.

Abstract: A riveting device for the riveting of components in an overlap joint, with an upper tool for driving a rivet into a rivet hole passing through the components, and with a lower tool as a dolly, which has a deforming section for purposes of plastically deforming the end of a rivet shaft driven through the rivet hole, wherein the riveting device has a magazine with a feed device for purposes of feeding a rivet into a shot passage of the upper tool, an actuator for purposes of accelerating the rivet introduced into the shot passage of the upper tool in the direction of the components, and an adjustment system for purposes of aligning the shot channel with the rivet hole. Also disclosed is a method for the riveting of components in an overlap joint.

Abstract: An elastic retaining assembly for matable components includes a first component having a first surface. Also included is a second component having a second surface and a third surface, wherein the second component is configured to be mated with the first component. Further included is a receiving feature formed proximate an engagement side of the second component and defining a pin perimeter surface. Yet further included is an elastically deformable pin operatively coupled to, and extending away from, the first surface, wherein the elastically deformable pin is formed of an elastically deformable material to elastically deform proximate the pin perimeter surface upon contact with the receiving feature.

Abstract: Fastener delivery apparatus for automatically selecting and delivering fasteners such as rivets to a setting tool. The fasteners are pre-loaded in a package and dispense via at least one fastener delivery tube that interconnects the setting tool to a fastener feeder device. The fastener feeder device releases selected fasteners from the package into the delivery tube. The fasteners are transportable individually or in groups in the tube from the feeder device to the tool.

Abstract: The present invention relates, amongst other things, to a punch-in element having a hollow head part of larger transverse dimension and a hollow shaft part of smaller transverse dimension which projects away from one side of the head part, wherein a ring-like sheet metal contact surface is formed at the said side of the head part and surrounds the shaft part, with a plurality of ribs at the outer periphery of the shaft part which extend in the axial direction along the shaft part from the sheet metal contact surface to close to the free end of the shaft part. A pre-installation component, a component assembly and a method is also claimed.

Abstract: A composite part defining a button shaped protrusion and including fibers reinforcing a resin matrix throughout the part. The fibers may be in the form of a woven mat or in the form of loose fibers that are deposited in a mold. Methods of making the composite part with a woven mat or loose fibers being provided in the button shaped recess that defines a void in the fiber reinforced composite part at a predetermined location where a self-piercing rivet is to be inserted.

Abstract: A method of assembling a piston plate and cover for a torque converter comprising the steps of: installing a shimming leaf into the cover; installing a rivet comprising a rivet head and a rivet body into a piston plate hole; supporting the rivet head with the shimming leaf; and expanding the rivet body into the piston plate hole. The method includes a shimming leaf assembly, wherein the shimming leaf assembly comprises the shimming leaf and a pivot, wherein the shimming leaf is rotatable about the pivot.

Abstract: A hybrid light fixture housing comprising a roll formed or press fabricated metal housing substrate having ceiling interface side members formed from aluminum extrusion processes attached thereto. The ceiling interface side members may comprise a single extruded clip member configured to clip around the ends of the sidewalls of the housing substrate or a first backing bar piece secured to the housing substrate and a second ceiling trim member secured to the housing substrate and the backing bar.

Abstract: A method for producing a connector, in particular for repair, in particular in the field of aviation and aerospace, including the steps of: providing a base layer; attaching a first layer of fibre composite material having a first rigidity to the base layer; attaching a second layer of fibre composite material having a second rigidity to the first layer, offset therefrom, the second rigidity being greater than the first rigidity; and riveting the first layer to the base layer and riveting the second layer to the first layer and to the base layer.