Single-sided fasteners

Abstract

The present invention provides a single-sided fastener. The single-sided fastener comprises a bolt portion, a sleeve portion and a tubular insulating sheath. The bolt portion is at least partially received in the sleeve portion. The first end of the sheath is retained on the bolt portion so as to substantially prevent relative axial movement between the first end of the sheath and the bolt portion. The single-sided fastener is movable between a pre-installation configuration and a post-installation configuration, in which the sleeve portion has a first axial position relative to the bolt portion and a predetermined section of the sheath is adjacent to an outer surface of the sleeve portion, and in the post-installation configuration, the sleeve portion has a second different axial position relative to the bolt portion and a predetermined section of the sheath is adjacent to an inner surface of the sleeve portion.

Description

Technical Field

[0001] The present invention relates to a single-face fastener, to a fuel tank fastened together by such a single-face fastener, and to an aircraft comprising such a fuel tank and / or a single-face fastener. Background Art

[0002] There is an increasing trend towards manufacturing aircraft structures from composite materials. In aircraft, composite structures are often fastened to each other and / or to metallic structures using metallic fasteners. Composite materials used for aircraft structures are generally much less conductive than metals, at least under normal operation of the aircraft. If the current density exceeds the current carrying capacity of the joint between the composite structure and the metallic fastener / structure, the charges moving on and in the composite structure may arc from the composite structure to an adjacent metallic fastener or structure.

[0003] When lightning strikes such an aircraft, a large charge is placed on the composite structure. When the charge arcs from the composite structure to the metal fasteners or structure, a very large amount of energy is consumed in a short period of time. The air around the arc is heated by this energy, as is the composite structure. The heating of the composite structure may be sufficient to cause small particles of the composite material to evaporate instantaneously. Alternatively or additionally, particles of the metal fasteners and / or composite material may become hot and break off. The energy of the lightning strike is often sufficient to cause these particles to be ejected in the form of sparks a meter or more from the arc location.

[0004] If such arcing occurs in a fuel tank, there is a risk that a spark could ignite the fuel or any fuel vapours. Aircraft in which the fuel tank is at least partially formed from a composite structure must therefore include mechanisms for preventing ignition of the fuel in the event of a lightning strike. Summary of the invention

[0005] A first aspect of the present invention provides a single-sided fastener. The single-sided fastener includes a bolt portion, a sleeve portion and a tubular insulating sheath. The bolt portion is at least partially received in the sleeve portion. The first end of the sheath is retained on the bolt portion so that relative axial movement between the first end of the sheath and the bolt portion is substantially prevented. The single-sided fastener is movable between a pre-installation configuration and a post-installation configuration, in which the sleeve portion has a first axial position relative to the bolt portion and a predetermined section of the sheath is adjacent to an outer surface of the sleeve portion, and in the post-installation configuration, the sleeve portion has a different second axial position relative to the bolt portion and a predetermined section of the sheath is adjacent to an inner surface of the sleeve portion.

[0006] Optionally, the sheath is elastically deformable.

[0007] Optionally, the sheath is plastically deformable.

[0008] Optionally, the sleeve portion is undeformed in the pre-installation configuration and is deformed in the post-installation configuration.

[0009] Optionally, the sleeve portion has a first axial position relative to the bolt portion in the pre-installed configuration and a second, different axial position relative to the bolt portion in the installed configuration.

[0010] Optionally, in the installed configuration, at least a portion of the boot is sandwiched between the bolt portion and the sleeve portion.

[0011] Optionally, in a pre-installation configuration, the length of a portion of the sleeve adjacent to the outer surface of the sleeve portion is greater than the length of a portion of the sleeve adjacent to the inner surface of the sleeve portion, and in a post-installation configuration, the length of a portion of the sleeve adjacent to the outer surface of the sleeve portion is less than the length of a portion of the sleeve adjacent to the inner surface of the sleeve portion.

[0012] Optionally, in the installed configuration, a second end portion of the boot distal to the first end is sandwiched between the sleeve portion and a structure on which the blind fastener has been installed, such that direct contact between the sleeve portion and the structure is prevented by the boot.

[0013] Optionally, the bolt portion comprises two or more separate components.

[0014] Optionally, the first end of the sheath is retained on the bolt portion by mechanical capture of the sheath between the bolt portion and the sleeve portion.

[0015] Optionally, the first end of the sheath is coupled to the bolt portion.

[0016] A second aspect of the present invention provides a fuel tank comprising a first structural member and a second structural member fastened together by the blind fastener according to the first aspect, wherein a sleeve portion of the blind fastener is disposed in a fuel accommodating space of the fuel tank.

[0017] Optionally, the fuel tank is an aircraft fuel tank.

[0018] A third aspect of the present invention provides an aircraft, comprising the single-sided fastener according to the first aspect or the fuel tank according to the second aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0020] Figure 1a is a cross section through a first example blind fastener according to the present invention in a pre-installed configuration;

[0021] Figure 1b is through the installed configuration Figure 1a Cross section of a single-sided fastener;

[0022] Figure 2a is a cross section through a second example blind fastener according to the present invention in a pre-installed configuration;

[0023] Figure 2b is through the installed configuration Figure 2a Cross section of a single-sided fastener;

[0024] Figure 3 is a cross section through an example fuel tank according to the present invention; and

[0025] Figure 4 is a perspective view of an example aircraft according to the present invention. DETAILED DESCRIPTION

[0026] The examples of the present invention described in the following discussion relate to single-sided fasteners. Each single-sided fastener according to the present invention has a bolt portion, a sleeve portion, and a tubular insulating sheath. The bolt portion is at least partially received in the sleeve portion. The first end of the sheath is retained on the bolt portion so that relative axial movement between the first end of the sheath and the bolt portion is substantially prevented. Each single-sided fastener is movable between a pre-installation configuration and a post-installation configuration, in which the sleeve portion has a first axial position relative to the bolt portion and a predetermined section of the sheath is adjacent to an outer surface of the sleeve portion, and in the post-installation configuration, the sleeve portion has a different second axial position relative to the bolt portion, and a predetermined section of the sheath is adjacent to an inner surface of the sleeve portion.

[0027] Sparking between a fastener and the structure to which the fastener is mounted typically occurs beneath the nut (or, in the case of a single-sided fastener, beneath the formed tail). Conventionally, such sparking is prevented by insulating the fastener-structure interface by applying a coating of paint or other insulating material to the structure. However, it has been found that such coatings are often damaged during the process of installing the fastener, thereby requiring inspection of each fastener location in the fuel vapor zone on the aircraft after the fastener is installed. Such inspection is time consuming and is typically not possible in applications where single-sided fasteners have been used (typically because the back of the structure to which the fastener is mounted is not accessible, either for operating the nut or for inspecting the fastener tail and surrounding structure). The single-sided fastener according to the present invention advantageously provides a solution for reliably ensuring that an intact insulating barrier exists between the formed tail of the fastener and the structure after the fastener is installed, thereby preventing the generation of sparks.

[0028] In particular, in the post-installation configuration of the example fastener according to the present invention, the insulating sheath completely covers the area of ​​the sleeve portion of the fastener that would otherwise contact the structural member to which the fastener has been installed. Contact between the sleeve portion and the structural member is thereby prevented, which prevents sparks from being generated between the tail of the fastener and the structural member in the event of a lightning strike. The sheath is sufficiently strong to ensure that the integrity of the sheath is maintained during the process of installing the fastener, thereby eliminating the need to inspect the tail end of the fastener. In addition, the requirement for applying an insulating coating to the structural member is eliminated. Advantageously, the configuration of the fastener according to the present invention allows the sheath to be moved into the desired position due to the normal installation process of the fastener, so that no additional operations are required during the assembly process.

[0029] Figure 1a and Figure 1b is a cross section through an exemplary blind fastener 1 according to the present invention. The blind fastener 1 can be in a pre-installed configuration ( Figure 1a ) and the installed configuration ( Figure 1b Examples of existing single-sided fasteners to which a sheath may be affixed to form a single-sided fastener according to the present invention include: OSI-Bolt(R) manufactured by Monogram Aerospace Fasteners; Composi-Lok(R) manufactured by Monogram Aerospace Fasteners; Radial-Lok(R) manufactured by Monogram Aerospace Fasteners; Ergotech(R) manufactured by Arconic; and Optiblind(TM) manufactured by Lisi Aerospace.

[0030] exist Figure 1b , a fastener 1 is mounted on a workpiece including a first structural member 14 and a second structural member 15. The first structural member 14 and the second structural member 15 are held together by the fastener 1. Both the first structural member 14 and the second structural member 15 may be formed of a composite material, or both the first structural member 14 and the second structural member 15 may be formed of a metal material, or, it may be the case that one of the first structural member 14 and the second structural member 15 is formed of a composite material and the other of the first structural member 14 and the second structural member 15 is formed of a metal material. In some examples, the first structural member 14 and the second structural member 15 are aircraft structural members. For example, the first structural member 14 may be a wing cover panel, and the second structural member 15 may be a wing spar.

[0031] The fastener 1 comprises a bolt portion 11, a sleeve portion 12 and a tubular insulating sheath 13. The sheath 13 is arranged to surround the bolt portion 11. The bolt portion 11 is at least partially received in the sleeve portion 12. The bolt portion 11 has a head end 111 on which a head is formed. The head has a larger diameter than the other parts of the bolt portion 11. The end of the bolt portion 11 opposite to the head end is referred to as the tail end 112. The sleeve portion 12 can also be considered to have a head end (i.e., the end of the sleeve portion closest to the head of the bolt portion 11) and a tail end (i.e., the end of the sleeve portion closest to the tail end of the bolt portion 11). The bolt portion 11 and the sleeve portion 12 can be formed of any suitable material having material properties suitable for withstanding the operational loads expected to be experienced by the fastener 1. The material of the sleeve portion 12 must also be able to deform in the manner described below during installation of the fastener 1.

[0032] The bolt portion 11 includes two separate parts, namely an inner bolt portion 11a and an outer bolt portion 11b. The inner bolt portion 11a has a shank and a head, and the shank has a substantially constant diameter. The outer bolt portion 11b is hollow and surrounds the head end of the inner bolt portion 11a. The outer bolt portion 11b includes a head section h located around the head of the inner bolt portion 11a, a tapered section t located at the end opposite to the head section, and a shank section s located between the head section h and the tapered section t. The outer bolt portion 11b has an axial length that is significantly smaller than the axial length of the inner bolt portion 11a. In some examples, the outer bolt portion 11b may extend less than half of the axial length of the inner bolt portion 11a. The length of the outer bolt portion 11b may be selected according to the thickness of the workpiece to which the fastener 1 is to be installed. For example, the axial length of the shank section s may be a predetermined amount greater than the thickness of the workpiece.

[0033] The effect of the tapered section t is that the diameter of the bolt portion 11 gradually increases from the diameter of the inner bolt portion 11a to the diameter of the outer bolt portion 11b across the axial length of the tapered section t. This configuration confers several advantages, as will be explained later.

[0034] The diameter of the shank section s is greater than or equal to the diameter of the sleeve section 12 and less than or equal to the diameter of the fastener hole into which the fastener 1 is intended to be installed. The diameter of the sleeve section 12 may be smaller than the diameter of the shank section s so that the sleeve section 12 can be easily inserted into the fastener hole, even in the case where the sheath 13 is provided on the outer surface of the sleeve section 12, such as Figure 1a However, it is advantageous to make the diameter of the shank section s equal to the diameter of the fastener hole so that after installation, close contact between the hole wall and the outer surface of the shank section is achieved. This close contact can prevent sparks from being generated between the fastener 1 and the hole wall.

[0035] Such sparks may occur due to an "edge glow" effect that a composite material may experience when struck by lightning. Thus, the example fastener 1 may be particularly advantageous for applications in which at least one of the first structural member 14 and the second structural member 15 comprises a composite material. It will be appreciated that the configuration of the outer bolt portion 11b facilitates achieving intimate contact between the fastener 1 and the hole wall while also facilitating easy insertion of the fastener 1 into the fastener hole.

[0036] In the pre-installed configuration, the sleeve portion 12 has a first axial position relative to the bolt portion 11. In particular, the sleeve portion 12 is relatively further away from the head end of the bolt portion 11 (compared to the installed configuration). In the installed configuration, the sleeve portion 12 has a different second axial position relative to the bolt portion 11. In particular, the sleeve portion 12 is relatively closer to the head end of the bolt portion 11. In addition, in the installed configuration, the shape of the sleeve portion 12 is deformed relative to the shape of the sleeve portion 12 in the pre-installed configuration. The sleeve portion 12 is configured to deform into a shape in response to being axially pressed on the trailing end of the outer bolt portion 11b and against the second structural member 15. Figure 1b The tapered section t of the outer bolt portion 11b facilitates the sliding of the sleeve portion 12 on the outer bolt portion 11b when the sleeve portion 12 moves axially toward the head end of the fastener 1 during the installation process. During this axial movement, the head end of the sleeve portion 12 is forced to expand radially by the tapered section t. This expansion can facilitate the deformation of the sleeve portion 12 into Figure 1b The deformed shape after installation is shown in . In the installed configuration of the fastener 1 , the head end of the sleeve portion is expanded where it overlaps the outer bolt portion 11 b (ie, the diameter of the head end of the sleeve portion is increased).

[0037] The deformed shape of the sleeve portion 12 has a larger maximum diameter than the undeformed shape. In the example shown, the maximum diameter of the deformed shape of the sleeve portion 12 is slightly larger than the diameter of the head end of the outer bolt portion 11b. The diameter of the head end of the outer bolt portion 11b and the maximum diameter of the deformed shape of the sleeve portion 12 are each larger than the diameter of the fastener hole 16, which extends through the first structural member 14 and the second structural member 15 and into which the fastener 1 is installed. The diameter of the undeformed shape of the sleeve portion 12 is less than or equal to the diameter of the fastener hole 16. The diameter of the undeformed shape of the sleeve portion 12 can advantageously be slightly smaller than the diameter of the fastener hole 16 so that the sleeve portion 12 and the sheath 13 can be easily inserted into the fastener hole 16. In order to facilitate the deformation of the sleeve portion 12, the sleeve portion 12 may include one or more relatively weak areas or other structural features configured to bend in a controlled manner under the influence of the applied axial pressing force during the installation of the fastener 1.

[0038] In the example shown, the inner bolt portion 11a has threads on its circumferential surface at and / or near the tail end 112. The threads on the inner bolt portion 11a engage with corresponding threads provided on the inner surface of the tail end of the sleeve portion 12. The threaded engagement between the inner bolt portion 11a and the sleeve portion 12 serves to drive relative axial movement between the bolt portion 11 and the sleeve portion 12 in response to relative rotational movement between the inner bolt portion 11a and the sleeve portion 12. The connection between the outer bolt portion 11b and the inner bolt portion 11a is such that the outer bolt portion 11b is substantially prevented from moving relative to the inner bolt portion 11a, and therefore, for the purpose of understanding the installation process, the inner bolt portion 11a and the outer bolt portion 11b can be considered to be an integral bolt portion 11.

[0039] It should be noted that other single-sided fasteners according to the present invention may not include a threaded engagement between the bolt portion and the sleeve portion, and instead may be provided with some other mechanism for driving the relative axial movement of the bolt portion and the sleeve portion. For example, the bolt portion 11 may be configured to be pulled upward by an externally applied pulling force during installation of the fastener 1 while the sleeve portion 12 remains stationary. In other examples, the relative axial movement may be driven in some other manner, such as by rotating or pulling the sleeve portion 12.

[0040] During the process of installing the fastener 1, the sleeve portion 12 is substantially prevented from rotating relative to the structures 14, 15 in any suitable manner while the bolt portion 11 is rotated relative to the structures 14, 15 and relative to the sleeve portion 12 (e.g., using an installation tool such as a wrench). The direction of rotation of the bolt portion 11 is selected based on the configuration of the thread. Assuming a standard thread is selected, the bolt portion 11 rotates clockwise when the fastener 1 is installed. This relative rotation between the bolt portion 11 and the sleeve portion 12 drives relative axial movement of the bolt portion 11 and the sleeve portion 12 in a direction that causes the sleeve portion 12 to be pressed against the second structure 15. The threads and the bolt head are configured so that sufficient torque can be applied to generate an axial force sufficient to deform the sleeve portion 12 into the deformed shape of the sleeve portion 12.

[0041] The insulating sheath 13 has a first end 131 which may be referred to as a fixed end and a second end 132 which may be referred to as a free end, opposite to the first end 131. The free end 132 of the sheath is free to move relative to the sheath portion 12. The fixed end 131 of the sheath 13 is held on the bolt portion 11 so that relative axial movement between the first end 131 of the sheath and the bolt portion 11 is substantially prevented. Any suitable retaining mechanism may be used to retain the fixed end 131 of the sheath on the bolt portion 11. In the example shown, the fixed end of the sheath 13 is retained on the inner bolt portion 11a by mechanical entrapment of the sheath between the outer bolt portion 11b and the sleeve portion 12. No additional attachment mechanism is required to prevent relative axial movement between the sheath 13 and the bolt portion 11. This can be achieved because an upward force (relative to the force applied by the sleeve 12 to a portion of the sheath 13 adjacent to the tapered section t) is applied to the sheath 13 by the sleeve 12. Figure 1a and Figure 1b ) The component of the axial force is perpendicular to the surface of the tapered section t and therefore serves to press the sheath 13 against this surface.

[0042] In order to retain the fixed end of the sleeve 13 on the bolt portion 11 before installing the fastener 1, the fastener 1 is configured such that the fixed end of the sleeve 13 is tightly sandwiched between the sleeve portion 12 and the inner bolt portion 11a and / or between the sleeve portion 12 and the tapered section t of the outer bolt portion 11b when the fastener 1 is in a pre-installed configuration and no upward axial force is applied to the sleeve 13. In order to further facilitate the retention of the fixed end of the sleeve 13 at a selected axial position on the bolt portion 11, even during installation of the fastener 1, the surface of the sleeve 13 contacting the bolt portion 11 and / or the surface of the bolt portion 11 contacting the sleeve 13 may be configured such that the coefficient of friction between the respective contact surfaces (e.g., compared to the coefficient of friction between the respective contact surfaces of the sleeve 13 and the sleeve portion 12) is relatively high.

[0043] Alternatively, the fixed end may be retained on the bolt portion 11 by bonding or by a different form of mechanical interlocking. For example, mutually interlocking structures may be provided on the fixed end 131 of the sheath and on the outer surface of the bolt portion 11. Suitable mechanisms for retaining the fixed end on the bolt portion 11 include (but are not limited to) interference fits, adhesive bonds, snap-fit ​​joints, thermoplastic welds, fasteners, or other mechanical devices.

[0044] The sheath 13 is deformable so that the sheath 13 can adapt to the deformation of the sleeve portion 12 that occurs during the installation of the fastener 1. In some examples, the sheath 13 is elastically deformable. In other examples, the sheath 13 is plastically deformable. In some examples, due to the stretching of the sheath 13 during the installation process, the length of the sheath 13 in the post-installation configuration can be greater than the length in the pre-installation configuration. The sheath 13 can be formed by any suitable electrical insulating material. For example, the sheath 13 can include a polymer material. The sheath 13 can include a reinforced polymer material. The sheath 13 can include a thermoplastic material. Suitable materials can include nylon, acrylonitrile butadiene styrene (ABS), polyethylene, thermoplastic elastomer (TPE or TPE) or other polymer materials, which are optionally fabric-reinforced. The material of the sheath 13 is selected so that the sheath 13 is strong enough to maintain its structural integrity during the installation of the fastener 1. Preferably, the jacket is as thin as possible while being strong enough to maintain its structural integrity during installation of the fastener and also provide sufficient electrical insulation to prevent sparking between the sleeve portion 12 and the second structure 15 in the event of a lightning strike.

[0045] The sheath 13 is folded back onto the sheath 13 itself around the head end of the sleeve portion 12. The amount by which the sheath 13 is folded back onto the sheath 13 itself differs between the pre-installation configuration and the post-installation configuration. In particular, the length of the sheath 13 adjacent to the outer surface of the sleeve portion 12 (in the axial direction of the fastener 1) is significantly greater in the pre-installation configuration than in the post-installation configuration. Therefore, the length of the sheath 13 adjacent to the inner surface of the sleeve portion 12 is smaller in the pre-installation configuration than in the post-installation configuration. In the pre-installation configuration, the predetermined section 133 of the sheath 13 is adjacent to the outer surface of the sleeve portion 12, while in the post-installation configuration, the predetermined section 133 of the sheath 13 is adjacent to the inner surface of the sleeve portion 12. The fact that the jacket 13 is folded back onto itself in the installed configuration at least to a small extent is advantageous because it ensures that the sleeve portion 12 cannot contact the second structure 15 , thereby ensuring that no sparks will be generated between the sleeve portion 12 and the second structure 15 .

[0046] During the installation of the fastener 1, the surface of the sleeve 13 in contact with the sleeve portion 12 slides relative to the surface of the sleeve portion 12 in contact with the surface of the sleeve 13. In the example shown, the sliding is both axial and rotational. In other examples (for example, in examples where the sleeve portion 12 is not threadedly engaged with the bolt portion 11), the sliding may be only axial. As described above, the bolt portion 11 rotates during the process of installing the fastener 1 while the sleeve portion 12 remains substantially stationary. Since the fixed end 131 of the sleeve 13 is fixedly attached to the bolt portion 11, the sleeve 13 rotates with the bolt portion 11. In addition, as described above, the rotation of the bolt portion 11 causes the sleeve portion 12 to move axially relative to the bolt portion 11 toward the head end of the bolt portion 11. Since the fixed end of the sleeve 13 is fixedly attached to the bolt portion 11, there is relative axial movement between the sleeve 13 and the sleeve portion 12. Therefore, the length of the sheath 13 disposed between the sleeve portion 12 and the bolt portion 11 increases, while the length of the sheath 13 disposed on the outer surface of the sleeve portion 12 decreases. In order to facilitate the relative sliding between the sheath 13 and the sleeve portion 12, the surface of the sheath 13 contacting the sleeve portion and / or the surface of the sleeve portion 12 contacting the sheath 13 may be configured so that there is a low friction coefficient between the contact surfaces. For example, one or both of the sleeve portion 12 and the sheath 13 may include a low friction coating.

[0047] An alternative blind fastener design (not shown) according to the present invention is also contemplated in which the bolt portion is unitary but has substantially the same shape as the combined inner and outer bolt portions 11a and 11b of fastener 1. Such an alternative blind fastener is installed in the same manner as example fastener 1 and provides substantially the same advantages as example fastener 1.

[0048] Figure 2a and Figure 2b is a cross section through a second example fastener 2 according to the present invention. Figure 2a The fastener 2 is shown in a pre-installed configuration, and Figure 2b The fastener 2 is shown in an installed configuration. Figure 2b , the fastener 2 is shown mounted on a workpiece including a first structural member 24 and a second structural member 25 having a Figure 1b 1. The fastener 2 is installed according to the same installation process as the example fastener 1. However, the structure of the fastener 2 differs from the example single-sided fastener 1 of FIG. 1 in certain key aspects. The fastener 2 includes a bolt portion 21, a sleeve portion 22, and a sheath 23, which are substantially the same as the corresponding components of the example fastener 1, except for the differences explicitly described below.

[0049] The bolt portion 21 is a single integral component, rather than including an inner bolt portion and an outer bolt portion. In addition, the shape of the bolt portion 21 is different from the overall shape of the bolt portion 11. The bolt portion 21 has a head 211 that is substantially the same as the head 111 of the bolt 11 and a shank 212 extending from the head 211. The shank 212 has a first portion a adjacent to the head 211, the first portion a having a relatively large diameter. The second portion b forms the remainder of the shank 212 and has a relatively small diameter. The diameter of the second portion b is smaller than the diameter of the first portion a by at least the thickness of the sleeve 22. When the fastener 2 is in Figure 2a In the pre-installed configuration shown in , the diameter of the second portion b can be smaller than the diameter of the first portion a by the combined thickness of the sleeve 22 and the sheath 23.

[0050] The axial length of the first portion a is equal to the thickness of the workpiece formed by the first structural member 24 and the second structural member 25. The diameter of the first portion a is greater than or equal to the diameter of the sleeve portion 22, and the diameter of the first portion a is less than or equal to the diameter of the fastener hole 26, and the fastener 2 is intended to be installed in the fastener hole 26. The diameter of the sleeve portion 22 may be smaller than the diameter of the first portion a so that the sleeve portion 22 can be easily inserted into the fastener hole, even in the case where the sleeve 23 is provided on the outer surface of the sleeve portion 22. As with the example fastener 1, it is advantageous in this example to make the diameter of the first portion a equal to the diameter of the fastener hole so that a close contact between the hole wall and the outer surface of the first portion a is achieved after installation to prevent sparks from being generated between the fastener 2 and the hole wall.

[0051] The fixed end portion 231 of the sheath 23 is bonded to the second portion b of the shaft 212 using any suitable bonding agent.

[0052] Installation of an example fastener 2 on a workpiece and the movement of the sleeve 23 during installation Figure 2b The deformation of the installed configuration shown in FIG. 1 is substantially the same for fastener 2 as for fastener 1. The only significant difference is that shank 212 does not include a tapered section over which sleeve 23 necessarily expands. Instead, the deformation of sleeve 23 is entirely caused by the buckling of sleeve 23, which occurs when sleeve 23 is axially pressed against the step between first portion a and second portion b of shank 212. The installed configuration of fastener 2 is substantially the same as for fastener 1. Figure 1a The installed configuration of the fastener 1 shown in FIG. 1 is substantially similar, except that the head end of the sleeve portion 22 is not expanded.

[0053] Figure 3is a cross section through a fuel tank 30. The fuel tank 30 includes a first structural member 34a and a second structural member 34b, which are fastened together by a single-sided fastener 3 of the present invention. The fuel tank 30 is schematically represented and is not shown to scale. In particular, for ease of description, the fastener 3 is shown to be significantly larger than it would be in actual application relative to the rest of the fuel tank.

[0054] The one-sided fastener 3 shown is Figure 1a to Figure 1b The example fastener 1 has the same design, but the single-sided fastener 3 can be any single-sided fastener according to the present invention. The first structural member 34a is a first end of an integral fuel tank wall member, and the second structural member 34b is a second end of an integral fuel tank wall member. However, other examples in which the first structural member 34a and the second structural member 34b are included in separate components are possible. The first structural member 34a and the second structural member 34b can have any of the features of the example first structural members 14, 24 and the second structural members 15, 25 described above. The fuel tank wall member is configured so that when the first structural member 34a and the second structural member 34b are fastened together, the fuel tank wall member defines an enclosed space 36 suitable for storing fuel. The enclosed space 36 can be referred to as a fuel holding space (even though in some operating states of the fuel tank, there may actually be no fuel held therein). In some examples, the first structural member 34a and the second structural member 34b can be fastened together by a plurality of single-sided fasteners 3 according to the present invention. In some examples, the fuel tank 30 is an aircraft fuel tank.

[0055] Figure 4 An example aircraft 400 including a one-sided fastener (not visible) according to the present invention is shown, with the aircraft 400 having a pair of wings 402 attached to a fuselage 401. Each wing 402 includes a structural wing box formed by a front spar, a rear spar, an upper cover plate, and a lower cover plate. Any two or more of the wing box components may be integrally formed. At least some of the joints between the wing box components may include one or more one-sided fasteners according to the present invention. Each wing box at least partially defines a fuel containment space, and thus may have a Figure 3In the case where the joint between the wing box components forms part of the wall of the fuel containment space, any fastener included in the joint extending into the fuel containment space can advantageously be a single-sided fastener according to the present invention (such as the example fastener 1 or the example fastener 2 described above). In addition, the aircraft 400 may include one or more additional fuel tanks. Any such additional fuel tanks may include structural members fastened together by one or more single-sided fasteners according to the present invention. The aircraft shown is a commercial passenger aircraft, but the above discussion is equally applicable to any other type of aircraft or indeed to any other vehicle that includes a fuel containment space defined by structural members fastened together.

[0056] Although the invention has been described above with reference to one or more examples or embodiments, it will be appreciated that various changes or modifications may be made without departing from the scope of the invention as defined in the appended claims.

[0057] Although the present invention has been described above primarily in the context of fixed-wing aircraft applications, the present invention may also be advantageously adapted for use in a variety of other applications, including but not limited to applications in vehicles such as helicopters, drones, trains, automobiles, and spacecraft.

[0058] Where the term "or" has been used in the foregoing description, the term should be understood to mean "and / or" unless explicitly stated otherwise.

Claims

1. A single-sided fastener, comprising: Bolt part; a sleeve portion, wherein the bolt portion is at least partially received within the sleeve portion; A tubular insulating sheath, characterized in that a first end of the sheath is retained on the bolt portion such that relative axial movement between the first end of the sheath and the bolt portion is substantially prevented; wherein the blind fastener is movable between a pre-installed configuration and a post-installed configuration, In the pre-installed configuration, the sleeve portion has a first axial position relative to the bolt portion, and a predetermined section of the jacket is adjacent to an outer surface of the sleeve portion; and In the installed configuration, the sleeve portion has a second, different axial position relative to the bolt portion, and the predetermined section of the jacket is adjacent to an inner surface of the sleeve portion, Therein, the sheath is folded back onto the sheath itself around the head end of the sleeve portion.

2. The one-sided fastener according to claim 1, wherein: The sheath is elastically deformable.

3. The one-sided fastener according to claim 1, wherein: The sheath is plastically deformable.

4. A blind fastener according to any preceding claim, wherein: The sleeve portion is undeformed in the pre-installation configuration and is deformed in the installed configuration.

5. The single-sided fastener according to any one of claims 1 to 3, wherein: In the installed configuration, at least a portion of the boot is sandwiched between the bolt portion and the sleeve portion.

6. The single-sided fastener according to any one of claims 1 to 3, wherein: In the pre-installation configuration, the length of the portion of the sheath adjacent to the outer surface of the sleeve portion is greater than the length of the portion of the sheath adjacent to the inner surface of the sleeve portion, and in the post-installation configuration, the length of the portion of the sheath adjacent to the outer surface of the sleeve portion is less than the length of the portion of the sheath adjacent to the inner surface of the sleeve portion.

7. The single-sided fastener according to any one of claims 1 to 3, wherein: In the installed configuration, a second end portion of the sheath remote from the first end portion can be sandwiched between the sleeve portion and a structure on which the blind fastener has been installed, so that direct contact between the sleeve portion and the structure can be prevented by the sheath.

8. The single-sided fastener according to any one of claims 1 to 3, wherein: The bolt portion comprises two or more separate components.

9. The single-sided fastener according to any one of claims 1 to 3, wherein: The first end of the sheath is retained on the bolt portion by mechanical entrapment of the sheath between the bolt portion and the sleeve portion.

10. The single-sided fastener according to any one of claims 1 to 3, wherein: The first end portion of the sheath is coupled to the bolt portion.

11. A fuel tank, comprising a first structural member and a second structural member fastened together by the single-sided fastener according to any one of claims 1 to 10, wherein: The sleeve portion of the blind fastener is disposed in a fuel accommodating space of the fuel tank.

12. The fuel tank according to claim 11, wherein The fuel tank is an aircraft fuel tank.

13. An aircraft comprising the single-face fastener according to any one of claims 1 to 10 or the fuel tank according to claim 11 or claim 12.

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