Single-sided fastener

Abstract

A single-sided fastener includes a head, a shaft having a tail, a tail of the single-sided fastener including the tail of the shaft and a sleeve surrounding the tail of the shaft, and a barrier secured to the tail of the single-sided fastener. The sleeve is configured to expand away from the tail of the shaft to form an expanded sleeve that is forced against a face of a workpiece to sandwich the workpiece between the head and the expanded sleeve. The barrier is configured to be forced against the face of the workpiece to form a sealed covering around the tail of the single-sided fastener.

Description

TECHNICAL FIELD

[0001] The present invention relates to a single-sided fastener, a method of installing a single-sided fastener, and a joint comprising a single-sided fastener. BACKGROUND

[0002] Single-sided (“single face”) fasteners are less prone to outgassing than more conventional double-sided fasteners. The outgassing problem can be addressed to some extent by providing an interference fit between the fastener and the wall of the aperture, but in certain safety-critical environments (such as aircraft fuel tanks) it can be desirable to provide an additional degree of protection.

[0003] US 2019 / 0161206 discloses a spark suppression cap for a single-sided fastener. A sealed cavity is formed between the cap and a structure. The joint is then assembled by inserting the single-sided fastener through an aperture from the opposite side of the structure to the cap. The single-sided fastener is then joined to form the joint. By such an arrangement, the joint can be formed during final assembly and only requires access to one side of the structure. SUMMARY

[0004] A first aspect of the present invention provides a single-sided fastener comprising: a head; a shaft having a tail; a tail of the single-sided fastener comprising the tail of the shaft and a sleeve surrounding the tail of the shaft; and a barrier fixed to the tail of the single-sided fastener, wherein the sleeve is configured to expand away from the tail of the shaft to form an expanded sleeve, the expanded sleeve is forced against a face of a workpiece to sandwich the workpiece between the head and the expanded sleeve, and wherein the barrier is configured to be forced against the face of the workpiece to form a sealed covering around the tail of the single-sided fastener.

[0005] Optionally, the barrier comprises a skirt having a skirt rim, and the skirt is configured to force the skirt rim against the face of the workpiece to form a seal between the skirt rim and the face of the workpiece.

[0006] Optionally, the barrier comprises a cap or sheath having a skirt and a tip, the tail of the single-sided fastener has a side and an end, the side of the tail is covered by the skirt, and the end of the tail is covered by the tip.

[0007] Optionally, the barrier is configured to deform radially towards or away from the tail of the shaft.

[0008] Optionally, the barrier is configured to plastically and / or elastically expand away from the tail of the shaft to form an expanded barrier.

[0009] Optionally, the barrier has a skirt with a skirt rim, the skirt rim is spaced apart from the sleeve by a gap, and the skirt is configured to contract towards the sleeve to at least partially close the gap.

[0010] Optionally, the barrier is secured to the tail of the single fastener by an interference fit, adhesive bond, or snap fit engagement.

[0011] Optionally, the barrier has a top end, and the single fastener further comprises an axial cavity between the top end of the barrier and the tail of the single fastener.

[0012] Optionally, the single fastener further comprises a sealant between the barrier and the tail of the single fastener.

[0013] Optionally, the barrier comprises a skirt, and the single fastener further comprises a pocket between the skirt and the tail of the single fastener.

[0014] Another aspect of the invention provides a method of installing a single fastener, the single fastener comprising: a head; a shaft having a tail; the tail of the single fastener comprising the tail of the shaft and a sleeve surrounding the tail of the shaft; and a barrier secured to the tail of the single fastener, the method comprising the steps of: a) passing the barrier and the tail of the single fastener through a workpiece; and b) tightening the single fastener such that: the sleeve expands away from the tail of the shaft to form an expanded sleeve; the expanded sleeve is forced against a face of the workpiece to sandwich the workpiece between the head and the expanded sleeve, and the barrier is forced against the face of the workpiece such that the barrier forms a sealed covering around the tail of the single fastener.

[0015] Optionally, the barrier comprises a skirt having a skirt rim, and the skirt rim is forced against the face of the workpiece to form a seal between the skirt rim and the workpiece.

[0016] Optionally, when the sleeve expands away from the tail of the shaft to form an expanded sleeve, the barrier elastically or plastically expands away from the tail of the shaft to form an expanded barrier.

[0017] Optionally, the barrier is in an expanded state prior to step a.; in step a., the barrier is in an elastically compressed state as the barrier is passed through the workpiece; and in step a., the barrier at least partially returns towards the expanded state of the barrier after the barrier has passed through the workpiece.

[0018] Optionally, the barrier comprises a skirt, and the single fastener comprises a pocket between the skirt and the tail of the single fastener, wherein, when the single fastener is tightened, uncured sealant flows into the pocket, and the uncured sealant cures in the pocket to bond the skirt to the tail of the single fastener and / or to bond the skirt to the workpiece.

[0019] Yet another aspect of the present application provides a joint comprising: a workpiece; a single-sided fastener comprising: a head; a shaft having a tail; a tail comprising a tail of the shaft and a sleeve surrounding the tail of the shaft; and a barrier secured to the tail of the single-sided fastener, wherein the sleeve has an expanded portion in contact with a face of the workpiece to sandwich the workpiece between the head and the sleeve, wherein the barrier comprises a skirt having a skirt rim in contact with the face of the workpiece to form a sealed cover around the tail of the single-sided fastener, and wherein the skirt rim is held by the tail of the single-sided fastener in a compressed state, causing the skirt rim to exert a sealing force against the face of the workpiece.

[0020] Optionally, the joint further comprises a sealed pocket between the skirt and the tail of the single-sided fastener.

[0021] Optionally, the joint further comprises a cured sealant bonding the skirt to the tail of the single-sided fastener and / or bonding the skirt to the workpiece.

[0022] Yet another aspect of the present application provides an aircraft fuel tank comprising a joint according to the preceding aspect, wherein the aircraft fuel tank has an interior, and the skirt and the tail of the single-sided fastener are located within the interior of the aircraft fuel tank.

[0023] Yet another aspect of the present application provides an aircraft comprising an aircraft fuel tank according to the preceding aspect. BRIEF DESCRIPTION OF DRAWINGS

[0024] Embodiments of the present application will now be described, by way of example, with reference to the accompanying drawings, in which:

[0025] Figure 1 A single-sided fastener according to a first embodiment of the present application is shown;

[0026] Figures 2A-2C A method of installing a single-sided fastener of Figure 1 into a workpiece is shown;

[0027] Figure 3 A single-sided fastener according to a second embodiment of the present application is shown;

[0028] Figures 4A-4C A method of installing a single-sided fastener of Figure 3 into a workpiece is shown;

[0029] Figures 4D-4F A method of installing a single-sided fastener of Figure 3 using a sealant is shown;

[0030] Figure 5 A single-sided fastener according to a third embodiment of the present application is shown;

[0031] Figure 6A Figure 6C shows the... Figure 5 A method for installing single-sided fasteners into a workpiece;

[0032] Figure 7A to Figure 7C A single-sided fastener according to a fourth embodiment of the present invention and a method for installing the single-sided fastener into a workpiece are shown.

[0033] Figure 8 It shows Figure 5 The edge of the barrier component that contacts the surface of the workpiece with a single-sided fastener;

[0034] Figure 9 An alternative barrier element with outwardly curved edges is shown;

[0035] Figure 10 An alternative barrier element with an inwardly curved edge is shown; and

[0036] Figure 11 An aircraft is shown that can be combined with any single-sided fastener of a single-sided fastener. Detailed Implementation

[0037] Figure 1 The single-sided fastener 1 shown includes a metal shaft 3 having an unthreaded body 5, an externally threaded tail 7, and a truncated conical head 9. A pin 11 is attached to the head 9 of the shaft 3. The shaft 3 is surrounded by a metal sleeve 3a. The sleeve includes a truncated conical head 9a surrounding the head 9 of the shaft 3, a cylindrical body 5a surrounding the body 5 of the shaft 3, and a tail 7a surrounding the tail 7 of the shaft 3. The tail 7a of the sleeve 3a has an internal thread that engages with the external thread of the tail 7 of the shaft 3. The head 9a and body 5a of the sleeve 3a are unthreaded.

[0038] In general, the single-sided fastener 1 includes: a head (head 9 of shaft 3 and head 9a of sleeve 3a); a body (body 5a of sleeve 3a and body 5 of shaft 3); and a tail (tail 7 of shaft 3 and tail 7a of sleeve 3a).

[0039] The barrier 13 is fitted to the tail of the single-sided fastener 7 and fixed to the tail 7a of the sleeve 3a. The barrier 13 is an integral part of the single-sided fastener 1—carried by the tails 7 and 7a of the single-sided fastener 1.

[0040] The barrier 13 includes a sheath with a conical tip 17, a cylindrical sheath body 19, and a widened cylindrical skirt 21. The sides of the tail portions 7, 7a of the single-sided fastener 1 are covered by the skirt 21 and the sheath body 19, and the end faces 8 of the tail portions 7, 7a of the single-sided fastener 1 are covered by the cap tip 17.

[0041] As will now be described below with reference to Figures 2A-2C the sleeve 3a is configured such that relative rotation between the threads causes the tail 7a of the sleeve 3a to expand away from the tail 7 of the shaft 3 to form an expanded sleeve having a flange 25 which is forced against the back face 23a of the workpiece 23 to clamp the workpiece between the head 9, 9a of the single-sided fastener and the expanded sleeve. The barrier 13 is also configured to be forced against the back face 23a of the workpiece 23 by the tail 7, 7a of the single-sided fastener 1 to form a sealed covering around the tail 7, 7a of the single-sided fastener.

[0042] First, the single-sided fastener 1 is installed by passing the barrier 13 and the tail 7, 7a of the single-sided fastener 1 through the workpiece 23. The single-sided fastener 1 is shown in Figure 2A partially inserted and in Figure 2B fully inserted.

[0043] Next, the single-sided fastener 1 is tightened by a tool (not shown). The tool has a first portion which grips the pin 11 and a second portion which grips the head 9a of the sleeve 3a. The first portion of the tool rotates the pin 11 which in turn rotates the shaft 3. The second portion of the tool holds the head 9a of the sleeve 3a to prevent the sleeve from rotating. Thus, there is relative rotation between the external threads of the tail 7 of the shaft 3 and the internal threads of the tail 7a of the sleeve 3a. This relative rotation drives the tail 7a of the sleeve 3a axially towards the workpiece 23 such that the tail 7a of the sleeve 3a plastically deforms and expands radially away from the tail 7 of the shaft 3 to form an expanded sleeve having a folded flange 25 as shown in Figure 2C . There can be knurling on the sleeve 3a such that the sleeve 3a deforms in a predictable manner.

[0044] As the single-sided fastener 1 is further tightened, the flange 25 is forced against the back face 23a of the workpiece 23 to clamp the workpiece 23 between the head 9, 9a and the expanded sleeve.

[0045] As the sleeve 3a expands away from the tail 7 of the shaft 3, the barrier 13 is configured to expand away from the tail 7 of the shaft 3 to form an expanded barrier having a flared portion 14 of the skirt 21. Thus, as the tail 7a of the sleeve 3a expands away from the tail 7 of the shaft 3 to form an expanded sleeve, the barrier 13 is pushed by the sleeve 3a such that the barrier 13 also expands radially away from the tail 7 of the shaft 3 to form an expanded barrier as shown in Figure 2C . Like the sleeve 3a, the barrier 13 plastically deforms as it expands radially away from the tail 7 of the shaft 3.

[0046] The barrier 13 is typically made of a hard, electrically insulating (non-conductive) material that can be plastically deformed and has a low friction, so that it can easily pass through the workpiece. For example, the barrier 13 can be made of a (reinforced or unreinforced) polymer.

[0047] Figure 2C The expanded barrier 13 is also axially pulled by the tail 7a of the sleeve 3a, so that the flared portion 14 of the skirt 21 is forced against the back face 23a of the workpiece 23 and the barrier 13 forms a sealed covering around the tail 7, 7a of the single-sided fastener 1, thereby providing a spark suppression barrier. The flared portion 14 of the skirt 21 includes a skirt rim 21a that is forced against the back face 23a of the workpiece 23 to form an air-tight seal between the skirt rim 21a and the back face 23a of the workpiece 23. In this case, the rim is the edge of the barrier 13.

[0048] The barrier 13 can be fixed to the tail 7a of the sleeve 3a by interference fit, adhesive bond, thermoplastic welding or snap fit engagement. Alternatively, the barrier 13 can be mechanically retained in a notch or recess in the tail 7a of the sleeve or carried by another component, such as a nut, that is fitted over the tail 7a of the sleeve. Typically, the barrier 13 can be fixed to the tail 7, 7a of the single-sided fastener 1 by any means of connection that prevents the barrier 13 from rotating with the shaft 3 and enables the tail 7, 7a of the single-sided fastener 1 to force the skirt rim 21a against the back face 23a of the workpiece 23.

[0049] Optionally, the sheath body 19 can have internal threads that engage with the external threads of the tail 7 of the shaft 3. In this case, relative rotation drives the sheath body 19 axially towards the workpiece 23. Alternatively, the sheath body 19 can be unthreaded.

[0050] The tool continues to rotate the pin 11 until the single-sided fastener 1 is fully tightened, the increasing torque causing the pin 11 to be sheared off, as shown in Figure 2C .

[0051] In Figure 2CIn the fully tightened joint, the sleeve 3a has a flared flange 25 in contact with the back face 23a of the workpiece 23 to clamp the workpiece 23 between the head 9, 9a and the sleeve 3a, and the skirt rim 21a is in contact with the back face 23a of the workpiece 23 to form a sealed covering of the tail 7, 7a of the single-sided fastener 1. Most of the deformation of the barrier 13 is plastic deformation, but there is also an element that elastically deforms as the fastener is tightened so that the barrier 13 in the fully tightened joint is held in compression by the tail 7, 7a of the single-sided fastener 1. This causes the skirt rim 21a to exert a sealing force against the back face 23a of the workpiece 21, thereby inhibiting gas leakage between the skirt rim 21a and the back face 23a of the workpiece 23.

[0052] The barrier 13 can be flared away from the sleeve 3a to form an air pocket between the barrier 13 and the sleeve 3a. Alternatively, the barrier 13 can remain in close contact with the sleeve 3a so that there is no air pocket, or a minimal air gap can open towards the skirt rim 21a.

[0053] As shown in Figures 2A-2C The fastener 1 is a “single-sided” fastener: that is, a fastener that can be installed into a workpiece and only requires access to one side of the workpiece. The single-sided fastener 1 provides an improvement over the single-sided fastener disclosed in US 2019 / 0161206. In US 2019 / 0161206, the cap had to be secured to the back face of the workpiece in a separate cap installation process before the single-sided fastener was inserted. The single-sided fastener 1 incorporates an integral spark suppression barrier 13, meaning that there is no need to access the back face of the workpiece, and the barrier 13 can be installed in a single installation process along with the rest of the single-sided fastener 13.

[0054] Figure 3 A single-sided fastener 1a is shown fitted with a different barrier 33. This single-sided fastener has many features in common with the single-sided fastener 1 of Figure 1 The same features are given the same reference numerals.

[0055] In this case, the barrier 33 comprises a cap having a flat cap top end 35 and a skirt having a cylindrical portion 39 and a flared portion 41. The skirt 39, 41 has an annular skirt rim 37a. The cylindrical portion 39 of the skirt has an annular seat 39a that contacts the edge of the tail 7a of the sleeve 3a. The sides of the tail 7, 7a of the single-sided fastener 1a are covered by the skirt 39, 41, and the tail 7 of the shaft is covered by the cap top end 35. There is an axial air cavity 34 between the end face of the tail 7 of the shaft and the cap top end 35.

[0056] The annular seat 39a of the skirt can be fixed to the edge of the tail 7a of the sleeve 3a by adhesive bonding, thermoplastic welding or snap-fit engagement. Alternatively, the barrier 33 can be mechanically retained in a notch or recess in the tail 7 of the shaft 3, or carried by another component (such as a nut) which fits over the tail 7a of the sleeve 3a. Typically, the barrier 33 can be fixed to the tail 7, 7a of the single-sided fastener la by any means of attachment which prevents the barrier 33 from rotating with the shaft 3 and enables the tail 7, 7a of the single-sided fastener la to be forced against the back face 23a of the workpiece 23 as shown in Figure 4C

[0057] The skirt rim 37a is spaced from the sleeve 3a by a gap 37b to provide an air pocket 27 between the skirt and the tail of the single-sided fastener. The flared portion 41 of the skirt is configured to elastically contract towards the sleeve 3a to at least partially close the gap 37b, enabling the barrier 33 to be pushed through the workpiece 23 as shown in Figure 4A Figure 4B

[0058] As shown in Figure 4A Figure 4B

[0059] The barrier 33 is typically made of a hard, electrically insulating (non-conductive) material which can elastically deform and has a low friction, so that it can easily pass through the workpiece 23. For example, the barrier 33 can be made of a (reinforced or unreinforced) polymer.

[0060] Figure 4C ​​​​​​In the fully tightened joint, the sleeve 3a has an expanded flange 25 in contact with the back face 23a of the workpiece 23 to clamp the workpiece 23 between the head 9, 9a and the sleeve 3a, and the skirt rim 37a is in contact with the back face 23a of the workpiece 23 to form a sealed cover around the tail 7, 7a of the single-sided fastener la. Most of the deformation of the barrier 33 is elastic deformation, such that the barrier 33 in the fully tightened joint is held in compression by the tail 7, 7a of the single-sided fastener la, and the flared portion 41 of the skirt has an outwardly curved shape, as shown in Figure 4C This causes the skirt rim 37a to exert a sealing force against the back face 23a of the workpiece 23, thereby inhibiting gas leakage between the skirt rim 37a and the back face 23a of the workpiece 23. In Figure 4C the fully tightened joint, the air pocket 27 between the barrier 33 and the tail 7, 7a of the single-sided fastener la is sealed.

[0061] The axial air cavity 34 provides the required clearance to enable the cap to move toward the workpiece 23, as shown in Figure 4B and Figure 4C In an alternative embodiment shown in Figures 4D-4F , the single-sided fastener lb is shown with the axial air cavity 34 filled with a sealant material 38 prior to installation of the cap 33. As the cap moves toward the workpiece 23, the sealant 38 escapes the cavity through a groove in the tail 7, 7a of the fastener and then flows into the air pocket 27 between the skirt and the tail 7, 7a of the single-sided fastener lb, as shown in Figure 4F .

[0062] Tightening the fastener compresses the sealant in the pocket 27 and forces the sealant against the workpiece 23 and / or against the tail 7a of the sleeve, thereby providing enhanced sealing. The sealant in the pocket 27 then cures to bond the cap 33 to the back face 23a of the workpiece 23 and / or to bond the cap to the tail 7a of the sleeve. A small amount of sealant 38 can also remain in the axial cavity 34 at the end of the single-sided fastener, and as the sealant 38 cures, the sealant 38 bonds the cap tip 35 to the end face 8 of the tail 7 of the shaft 3.

[0063] Figure 5 The single-sided fastener 101 shown in Figure 3 is similar to the single-sided fastener la of . Like parts are given like reference numerals and will not be described again.

[0064] The externally threaded tail 7 of the shaft 3 is surrounded by a metal sleeve 103a having an internally threaded tail 107a and an unthreaded body 105a. The internal threads of the tail 107a of the sleeve 103a engage the external threads of the tail 7 of the shaft 3. The head 9 and body 5 of the shaft 3 are surrounded by a collar having a frustoconical head 145, a cylindrical body 147, and a tapered tip 149 with an axial ridge or groove (not shown). The tapered tip 149 fits into the unthreaded body 105a of the sleeve 103a in an interference fit.

[0065] Thus, the single-sided fastener 101 includes a head (the head 9 of the shaft and the head 145 of the collar), a body (the body 147 and tip 149 of the collar and the body 5 of the shaft 3), and a tail (the tail 7 of the shaft and the body 105a and tail 107a of the sleeve 103a).

[0066] A barrier 153 fits over the tail 7, 105a, 107a of the single-sided fastener 101 and is secured to the tail 107a of the sleeve 103a. The sides of the tail of the single-sided fastener 101 are covered by the barrier 153. Unlike the previous embodiments, the barrier 153 includes only a flared skirt such that the end face 8 of the tail of the shaft is not covered by the barrier 153.

[0067] The barrier 153 can be secured to the tail 107a of the sleeve 103a by an interference fit, adhesive bond, thermoplastic weld, or snap fit engagement. Alternatively, the barrier 153 can be mechanically retained in a notch or recess in the tail 107a of the sleeve 103a or carried by another component (such as a nut) that fits over the tail 107a of the sleeve 103a. In general, the barrier 153 can be secured to the tail of the single-sided fastener by any connection that prevents the barrier 153 from rotating with the shaft 103 and enables the tail of the single-sided fastener to force the skirt rim 157 against the back face 123a of the workpiece 123.

[0068] The sleeve 103a is configured such that relative rotation between the threads causes the body 105a of the sleeve 103a to expand away from the tail 7 of the shaft 3 to form an expanded sleeve with a folded flange 125 that is forced against the back face 23a of the workpiece 23 to clamp the workpiece between the heads 9, 145 and the flange 125 of the expanded sleeve. The barrier 153 is also configured to be forced against the face of the workpiece 123 by the tail of the single-sided fastener 101 to form a sealed covering around the tail of the single-sided fastener 101.

[0069] As Figure 5As shown in the middle, the barrier 153 is in an expanded state before passing through the workpiece 123. As the barrier 153 passes through the workpiece 123, the barrier 153 is configured to deform radially towards the tail 7 of the shaft 3, such that the barrier 153 is in a resiliently compressed state as it passes through the workpiece 23. Figure 6A The barrier 153 is shown in this compressed state, but it has already started to spring back because most of it has passed through. Then, as shown in Figure 6B, the barrier 153 springs back to its fully expanded state after it has passed through the workpiece 123, reopening the gap between the sleeve 103a and the skirt rim 157.

[0070] In the fully tightened joint, the barrier 153 is held in a compressed state by the tail of the single-sided fastener 101 and has the compressed shape shown in Figure 6C. This causes the skirt rim 157 to exert a sealing force against the back face 23a of the workpiece 23, inhibiting gas leakage between the skirt rim 157 and the back face 23a of the workpiece 23.

[0071] In the fully tightened joint of Figure 6C, there is a sealed pocket of gas 127 between the barrier 153 and the tail of the single-sided fastener 101. This provides a sealed, compressible gas chamber that can inhibit any ignition hazard caused by the fastener 101.

[0072] As the fastener 101 is tightened, the body 105a of the sleeve 103a rides over the tapered tip 149 of the collar, as shown in Figure 6C. The ridge or groove in the tapered tip 149 of the collar grips the body 105a of the sleeve 103a and prevents the sleeve 103a from rotating with the shaft 3.

[0073] In the above embodiments, the single-sided fastener 1, la, 101 is tightened by rotating the shaft 3. Figures 7A to Figure 7C An alternative embodiment is shown in which the single-sided fastener is tightened by pulling the shaft.

[0074] Figures 7A to Figure 7C The single-sided fastener 201 comprises a metal shaft with a removable pin 211, a body 205 and a domed mandrel 207. The shaft is surrounded by a metal sleeve with a head 209a, a body 205a and a tail 207a.

[0075] The single-sided fastener 201 comprises: a head (the head 209a of the sleeve); a body (the body 205a of the sleeve and the body 205 of the shaft); and a tail (the mandrel 207 and the tail 207a of the sleeve).

[0076] As shown in FIG. 7A, the barrier 253 fits over the tail of the single-sided fastener 201 and is secured to the mandrel 207. The barrier 253 includes a cap with a domed cap top end 261 and a flared skirt 263 with a skirt rim 257.

[0077] The domed cap top end 261 can be secured to the mandrel 207 by adhesive bonding or thermoplastic welding. Alternatively, the barrier 253 can be mechanically retained to the mandrel 207, for example by a snap-fit engagement or by a clamp or other fastener.

[0078] As shown in FIGS. 7A to Figure 7C The sleeve is configured such that when the pin 211 is pulled back, the tail 207a of the sleeve is compressed by the mandrel 207, which causes the sleeve to expand away from the shaft to form an expanded sleeve with a flange 225 that is forced against the back face 123a of the workpiece 123 to clamp the workpiece between the head 209a of the single-sided fastener and the flange 225 of the expanded sleeve. The skirt 263 is also configured to be forced against the back face 123a of the workpiece 123 by the mandrel 207 to form a sealed covering around the tail 207, 207a of the single-sided fastener.

[0079] The skirt 263 is in an expanded state before passing through the workpiece 123. When the skirt 263 passes through the workpiece 123, the skirt 263 is configured to deform radially towards the tail of the single-sided fastener such that the skirt 263 is in a resiliently compressed state as it passes through the workpiece 123. Then, as shown in FIG. 7A, the skirt 263 springs back to its expanded state after it has passed through the workpiece 123, thereby reopening the gap between the sleeve 207a and the skirt rim 257.

[0080] In the fully tightened joint of Figure 7C , the sleeve has an expanded flange 225 in contact with the back face 123a of the workpiece 123 to clamp the workpiece between the head 209a and the flange 225, and the skirt rim 257 is in contact with the back face 123a of the workpiece to form a sealed covering around the tail 207, 207a of the single-sided fastener 201. The skirt 263 in the fully tightened joint is held in a compressed state by the tail of the single-sided fastener. This causes the skirt rim 257 to exert a sealing force against the back face 123a of the workpiece 123, thereby inhibiting gas leakage between the skirt rim 257 and the back face 123a of the workpiece 123.

[0081] In the fully tightened joint of Figure 7C , there is a sealed gas pocket 227 between the barrier 263 and the tail of the single-sided fastener. This provides a sealed, compressible gas chamber that can inhibit any ignition hazard caused by the fastener.

[0082] In the above described embodiments, the edge of the skirt 21, 41, 153, 263 provides a skirt rim which contacts the back face of the workpiece. As an example, Figure 8 An example of a skirt rim 157 in a fully tightened joint of Figure 6C is shown.

[0083] In other embodiments, the edge of the skirt can be bent back inwards or outwards to form a rim with a lip. Figure 9 An example of a lip 158a bent outwards is shown, and Figure 10 An example of a lip 158b bent inwards is shown. In both cases, the lip is bent back so that the edge of the skirt does not contact the workpiece. In this case, the skirt rim is the base 157a, 157b of the lip which contacts the back face of the workpiece.

[0084] In the above described embodiments, the shaft 3, 103, 203, 205, 207 and the sleeve 3a, 103a, 203a, 205a, 207a are generally made of a metal material. The barrier 13, 33, 153, 253 is generally made of a different material to the shaft 3, 103, 203 and a different material to the sleeve 3a, 103a, 203a. Figures 4A-4C Figures 4D-4F Figure 6A In the embodiments of Figures 6C and 7A to Figure 7C In the above described embodiments, the barrier 13, 33, 153, 263 springs back to its fully expanded state after passing through the workpiece. However, it is not necessary for this to happen - in other words, the barrier 13, 33, 153, 263 can only partially spring back. In this case, the flange 25, 125, 225 pushes the skirt radially as the sleeve expands.

[0085] In the above described embodiments, the shaft 3, 103, 203, 205, 207 and the sleeve 3a, 103a, 203a, 205a, 207a are generally made of a metal material. The barrier 13, 33, 153, 253 is generally made of a different material to the shaft 3, 103, 203 and a different material to the sleeve 3a, 103a, 203a.

[0086] The barrier is preferably made of an electrically insulating material, such as a polymer material.

[0087] By way of example, the barrier 13, 33, 153, 263 can be made of nylon, acrylonitrile butadiene styrene (ABS), polyethylene, thermoplastic elastomer (TPE or TPE), or another polymer material, optionally fabric-reinforced.

[0088] In the above described embodiments, the barrier 13, 33, 153, 263 forms a sealed covering around the tail of the single-sided fastener. This enables the barrier 13, 33, 153, 263 to suppress any ignition hazards (such as sparking or jets of hot gas / particles) which are generated at the single-sided fastener. If there is a sealed air pocket 27, 127, 227, this provides a sealed, compressible gas chamber which can suppress any ignition hazards.

[0089] ​​The single-sided fastener 1, 1a, 1b, 101, 201 can be used for any application, but most preferably the single-sided fastener is used for an aircraft, such as the aircraft 70 shown in Figure 11 The wings 72 of the aircraft include fuel tanks, one of which is indicated at 74 in Figure 11 The upper and lower boundaries of the fuel tank are provided by the upper and lower skins of the wing, and the front and rear boundaries are provided by the front and rear spars of the wing. In the above embodiments, the barrier and the tail of the single-sided fastener can be located within the interior of the fuel tank, such that the barrier suppresses a fire hazard within the full tank. The interior 75 of the fuel tank 74 is shown in Figure 2C , Figure 4C , Figure 4F , FIG. 6C, and Figure 7C

[0090] For ease of illustration, the workpiece is illustrated as a single component 23 in Figures 2A-2C , Figures 4A-4F and Figure 6A through FIG. 6C, but in practice the workpiece typically includes a pair of components joined together by the single-sided fastener, as represented by the two-component workpiece 123 in FIGS. 7A through Figure 7C For example, the two components of the workpiece can be a wing skin and a wing rib, a wing spar and a wing rib, or a wing spar and a wing skin.

[0091] In the above embodiments, the barrier is fixed to the sleeve and / or to the tail of the shaft. In other embodiments, the barrier can be fixed to another portion of the tail of the single-sided fastener.

[0092] In the above embodiments, the barrier is configured to be forced against the face of the workpiece by the tail of the single-sided fastener to form a sealed covering around the tail of the single-sided fastener. In other embodiments, the barrier can be forced against the face of the workpiece by another component of the single-sided fastener.

[0093] In the above embodiments, the head of the single-sided fastener is part of the shaft or part of the sleeve. In other embodiments, the head of the single-sided fastener can be provided by another component.

[0094] In some of the above embodiments, the tail of the shaft has external threads, the sleeve has internal threads that engage the external threads of the tail of the shaft, and the sleeve is configured such that relative rotation between the threads causes the sleeve to expand away from the tail of the shaft to form an expanded sleeve. In other embodiments such as FIG. 7A, the sleeve and the shaft can be threadless.

[0095] ​In the above embodiments, the barrier includes a skirt having a skirt rim, and the skirt rim is forced against the back face of the workpiece to form a seal between the skirt rim and the back face of the workpiece. In other embodiments, the skirt can be rimless, or another component of the barrier can be forced against the back face of the workpiece.

[0096] In some of the above embodiments, the barrier includes a cap or sheath that is fixed to the tail of the single fastener. In these embodiments, the cap or sheath includes a top end and a skirt, the tail of the single fastener has a side and an end, the side of the tail is covered by the skirt, and the end of the tail is covered by the top end. That is, the cap or sheath completely covers the tail of the single fastener. In other embodiments (e.g., FIG. 6C), the barrier can include only a skirt, such that only a portion of the tail of the single fastener is covered by the barrier.

[0097] In the above embodiments, the barrier is configured to expand (plastically and / or elastically) away from the tail of the shaft as the sleeve expands away from the tail of the shaft to form an expanded barrier. In other embodiments, the barrier can not expand during installation.

[0098] In the above embodiments, the barrier is configured to deform (plastically or elastically) radially toward or away from the tail of the shaft. In other embodiments, the barrier can not deform during installation.

[0099] In the above embodiments, the barrier has a skirt with a skirt rim that is spaced apart from the sleeve by a gap. Optionally, the barrier is configured to contract toward the sleeve to at least partially close the gap. This makes it easier to insert the barrier through the workpiece.

[0100] In the above embodiments, the barrier is fixed to the tail of the single fastener by an interference fit, adhesive bond, snap-fit engagement, thermoplastic weld, or fastener or other mechanical device. In general, any type of connection that enables the barrier to be pulled into sealing engagement with the back face of the workpiece by the tail of the single fastener can be used.

[0101] In some of the above embodiments, the single fastener has an axial cavity, typically a gas cavity 34, between the top end 35 of the barrier and the end face 8 of the tail of the single fastener. This can provide the required void to enable the barrier to move axially during installation.

[0102] In one of the above embodiments, the single fastener includes a sealant, typically an uncured sealant, between the barrier and the tail of the single fastener. In other embodiments, the single fastener is free of sealant.

[0103] In some of the above embodiments, the barrier includes a skirt and the single-sided fastener further includes a pocket 27, 127, 227 between the skirt and the tail of the single-sided fastener. The pocket can be an air pocket, and the air pocket can be sealed in the installed joint.

[0104] In the above embodiments, the single-sided fastener is tightened by rotating or pulling the shaft. In other embodiments, the single-sided fastener can be tightened in some other way, such as by rotating or pulling a sleeve or another component of the single-sided fastener.

[0105] In the above embodiments, the expansion sleeve includes a folded bulb or flange. Alternatively, the expansion sleeve can have a different geometry.

[0106] In the above embodiments, the barrier is held in the compressed state by the tail of the single-sided fastener, which causes the skirt rim to exert a sealing force against the face of the workpiece. In other embodiments, the skirt rim can be in contact with the workpiece without exerting a sealing force.

[0107] In some embodiments, the barrier is in an expanded state before it passes through the workpiece; the barrier is in a resiliently compressed state as it passes through the workpiece; and the barrier at least partially returns toward its expanded state after it has passed through the workpiece. In other embodiments, the barrier is not compressed as it passes through the workpiece.

[0108] Examples of suitable single-sided fasteners that can have a barrier sheath, barrier cap, or barrier skirt affixed to form a single-sided fastener according to the present application include the OSI-Bolt(R) manufactured by Monogram Aerospace Fasteners; the Composi-Lok(R) manufactured by Monogram Aerospace Fasteners; the Radial-Lok(R) manufactured by Monogram Aerospace Fasteners; the Ergotech(R) manufactured by Arconic; and the Optiblind(TM) manufactured by Lisi Aerospace.

[0109] Where the word "or" appears in the preceding text, this is to be interpreted as meaning "and / or" so that the items in question need not be mutually exclusive and can be used in any appropriate combination.

[0110] While the application has been described above with reference to one or more preferred embodiments, it will be understood by those skilled in the art that various changes in form and details can be made therein without departing from the spirit and scope of the application as defined in the following claims.

Claims

1. A single-sided fastener, comprising: a head; a shaft having a tail; a tail of the single-sided fastener comprising the tail of the shaft and a sleeve surrounding the tail of the shaft; and a barrier fixed to the tail of the single-sided fastener, wherein the sleeve is configured to expand away from the tail of the shaft to form an expanding sleeve that is forced against a face of a workpiece to clamp the workpiece between the head and the expanding sleeve, wherein the barrier is configured to be forced against the face of the workpiece to form a sealed covering around the tail of the single-sided fastener, and wherein the barrier comprises a skirt having a skirt rim, the barrier forms a flared portion of the skirt as the single-sided fastener is rotated, and the skirt is configured to force the skirt rim against the face of the workpiece to form a seal between the skirt rim and the face of the workpiece.

2. The single-sided fastener of claim 1, wherein, the barrier comprises a cap or sheath having a skirt and a tip, the tail of the single-sided fastener has a side and an end, the side of the tail is covered by the skirt, and the end of the tail is covered by the tip.

3. The single-sided fastener of claim 1 or 2, wherein, the barrier is configured to deform radially toward or away from the tail of the shaft.

4. The single-sided fastener of claim 1 or 2, wherein, the barrier is configured to plastically and / or elastically expand away from the tail of the shaft to form an expanding barrier.

5. The single-sided fastener of claim 1 or 2, wherein, the skirt rim is spaced apart from the sleeve by a gap, and the skirt is configured to contract toward the sleeve to at least partially close the gap.

6. The single-sided fastener of claim 1 or 2, wherein, the barrier is joined to the tail of the single-sided fastener by an interference fit, adhesive bond, or snap fit.

7. The single-sided fastener of claim 1 or 2, wherein, the barrier has a tip, and the single-sided fastener further comprises an axial cavity between the tip of the barrier and the tail of the single-sided fastener.

8. The single-sided fastener of claim 1 or 2, further comprising a sealant between the barrier and the tail of the single-sided fastener.

9. The single-sided fastener of claim 1 or 2, wherein, the single-sided fastener further comprises a pocket between the skirt and the tail of the single-sided fastener.

10. A method of installing a single-sided fastener, the single-sided fastener comprising: a head; a shaft having a tail; a tail of the single-sided fastener comprising the tail of the shaft and a sleeve surrounding the tail of the shaft; and a barrier fixed to the tail of the single-sided fastener, the method comprising the steps of: a. passing the barrier and the tail of the single-sided fastener through a workpiece; and b. tightening the single-sided fastener such that: i. the sleeve expands away from the tail of the shaft to form an expanding sleeve; ii. the expanding sleeve is forced against a face of the workpiece to clamp the workpiece between the head and the expanding sleeve; and iii. the barrier is forced against the face of the workpiece such that the barrier forms a sealed covering around the tail of the single-sided fastener, wherein the barrier comprises a skirt having a skirt rim, and the skirt rim is forced against the face of the workpiece to form a seal between the skirt rim and the workpiece.

11. The method of claim 10, wherein, The barrier member elastically or plastically expands away from the tail of the shaft to form an expanded barrier member when the sleeve expands away from the tail of the shaft to form the expanded sleeve.

12. The method of claim 10 or 11, wherein, The barrier member is in an expanded state prior to step a.; in step a., the barrier member is in an elastically compressed state when the barrier member passes through the workpiece; and in step a., after the barrier member has passed through the workpiece, the barrier member at least partially returns toward the expanded state of the barrier member.

13. The method of claim 10 or 11, wherein, The single-sided fastener includes a pocket between the skirt and the tail of the single-sided fastener, wherein, when the single-sided fastener is tightened, uncured sealant in an axial cavity between a top end of the barrier member and the tail of the single-sided fastener flows into the pocket, and the uncured sealant cures in the pocket to bond the skirt to the tail of the single-sided fastener and / or to bond the skirt to the workpiece.

14. A joint, comprising: a workpiece; a single-sided fastener, the single-sided fastener including a head, a shaft having a tail, a tail including the tail of the shaft and a sleeve around the tail of the shaft, and a barrier member secured to the tail of the single-sided fastener, wherein the sleeve has an expanded portion in contact with a face of the workpiece to clamp the workpiece between the head and the sleeve, wherein the barrier member includes a skirt having a skirt rim in contact with the face of the workpiece to form a sealed covering around the tail of the single-sided fastener, and wherein the skirt rim is held in a compressed state by the tail of the single-sided fastener, causing the skirt rim to exert a sealing force against the face of the workpiece.

15. The joint of claim 14, further comprising a sealed pocket of air between the skirt and the tail of the single-sided fastener.

16. The joint of claim 14 or 15, further comprising cured sealant bonding the skirt to the tail of the single-sided fastener and / or to the workpiece.

17. An aircraft fuel tank comprising the joint of claim 14, 15 or 16, wherein, The aircraft fuel tank has an interior, and the skirt and tail of the single-sided fastener are located within the interior of the aircraft fuel tank.

18. An aircraft, comprising the aircraft fuel tank of claim 17.

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