Fasteners

Abstract

A thread-forming and hole-forming fastener (2) is disclosed. The thread-forming and hole-forming fastener (2) comprises a head (4) and a shank (10) defining a longitudinal axis (L). The shank (10) comprises a shank section (12) and a tip section (14). The shank section (12) extends from the head (4). The tip section (14) extends from the shank section (12) and is opposite the head (4). At least a portion of the shank section (12) is threaded. The tip section (14) is at least partially tapered and defines a tip angle (α). The tip angle (α) is at least 50 degrees.

Description

[Technical field]

[0001] The present invention relates to a thread-forming and hole-forming fastener. The present invention also relates to a method of inserting the fastener into a workpiece and to a joint. [Background technology]

[0002] Fasteners are used to connect parts to one another. Fasteners can be used alone or in combination with other connection methods. Thread-forming fasteners are a type of fastener that forms the material of a workpiece as the thread is created, rather than cutting material from the workpiece to create the thread. When inserting the thread-forming fastener, no material is removed from the workpiece, or a negligible amount of material is removed. Some thread-forming fasteners can also form a hole in the workpiece in which the fastener is placed. The hole is formed at the same time as the thread. Thread-forming fasteners that can also form a hole are sometimes called thread-forming and hole-forming fasteners.

[0003] To insert a thread-forming and hole-forming fastener into a workpiece, the fastener is rotated while in contact with the workpiece such that the workpiece is heated. The fastener is then inserted into the workpiece. The threaded fastener is rotated while inserted into the workpiece, which forms a thread in the workpiece. The quality of the joint formed depends, among other things, on the amount of heat provided to the workpiece.

[0004] It is an object of the present invention to avoid or at least alleviate problems associated with known thread-forming fasteners, whether or not specified herein. Summary of the Invention

[0005] In a first aspect of the invention, a thread-forming and hole-forming fastener is provided. The thread-forming and hole-forming fastener comprises a head and a shank defining a longitudinal axis. The shank comprises a shank section and a tip section. The shank section extends from the head and the tip section extends from the shank section opposite the head. At least a portion of the shank section is threaded. The tip section is at least partially tapered and defines a tip angle, the tip angle being at least 50 degrees.

[0006] Throughout this specification, the term "tip angle" may be understood to refer to the included angle of the tip of a fastener. Tip angle may be understood to refer to the maximum angle between two tangent lines extending through diametrically opposed points of the tip section.

[0007] The shank section may be a cylindrical shank section. The entire shank section may be threaded. The tip section may merge into the shank section by a radius or chamfer.

[0008] The tip angle does not have to be 118 degrees.

[0009] In use, the thread-forming and hole-forming fastener is rotated on a surface of the workpiece to heat the workpiece. Once the workpiece has been heated a predetermined amount, the fastener is threaded into the workpiece by moving the fastener relative to the workpiece in a direction parallel to the longitudinal axis of the fastener. Rotation of the fastener continues while the fastener is threaded into the workpiece. As the fastener is threaded into the workpiece, workpiece material forms along the threads of the shank section, thereby threading the fastener into the workpiece. The quality of a joint created using the fastener depends on the amount the workpiece is heated during fastener insertion. Insufficient heating of the workpiece during the insertion process produces a suboptimal joint. For example, insufficient heating of the workpiece during the insertion process can result in separation of the layers of the workpiece (if the workpiece comprises multiple layers) and / or improper engagement of the fastener threads with the workpiece material. Separation of the layers of the workpiece is sometimes referred to as gap formation.

[0010] The tip section has a tip angle of at least 50 degrees, which advantageously reduces the likelihood of underheating of the workpiece during insertion of the fastener into the workpiece, at least in part due to the contact area between the tip section and the workpiece resulting from the tip angle of at least 50 degrees. Because the likelihood of underheating of the workpiece during insertion of the fastener is reduced, the quality of the joint created using the fastener is improved as compared to when the workpiece is underheated during insertion of the fastener.

[0011] The tip angle may be at least 70 degrees (eg, if no bore is provided at the tip).

[0012] If the tip angle is at least 70 degrees, the likelihood of underheating the workpiece is preferably further reduced.

[0013] The tip section can define a tip section length. The shank section can define a shank section diameter. A ratio of the tip section length to the shank section diameter can be less than or equal to 0.6.

[0014] The ratio of the tip section length to the shank section diameter may be less than or equal to 0.4.

[0015] The tip angle may be less than or equal to 160 degrees.

[0016] Overheating of the workpiece during the insertion process can also produce a suboptimal joint. For example, overheating of the workpiece during the insertion process can result in separation of the layers of the workpiece (if the workpiece comprises multiple layers) and / or improper engagement of the fastener threads with the workpiece material.

[0017] A tip angle of 160 degrees or less reduces the likelihood of overheating of the workpiece during insertion of the fastener into a workpiece, which is at least partially a result of contact due to the contact area between the tip section and the workpiece resulting from a tip angle of 160 degrees or less. Because the likelihood of overheating of the workpiece during insertion of the fastener is reduced, the quality of the joint created using the fastener is improved as compared to when the workpiece is overheated during insertion of the fastener.

[0018] Additionally, a tip angle of 160 degrees or less allows the workpiece material to pass around the fastener instead of being pushed in front of the fastener, which advantageously reduces the possibility of gaps forming during insertion of the fastener into the workpiece.

[0019] The tip angle may be at least 125 degrees. The tip angle may be no greater than 135 degrees.

[0020] When the tip angle is at least 125 degrees and not more than 135 degrees, the likelihood of overheating or underheating is further reduced, thereby further improving the quality of joints made using the fastener.

[0021] The tip angle may be 130 degrees.

[0022] The head may comprise an internal drive configuration. The head may comprise an external drive configuration. The head may comprise a one-way drive configuration. The head may comprise a frangible drive portion. The frangible drive portion may be separable from the fastener after inserting the fastener into a workpiece.

[0023] The tip of the fastener may be conical. The tip of the fastener may be frusto-conical. The tip of the fastener may be radiused.

[0024] The shank section can include a first shank portion adjacent the head. The shank section can include a second shank portion adjacent the tip section.

[0025] The shank section can include a base section. The first shank portion can include a base section.

[0026] The first shank portion may be unthreaded, and the second shank portion may be threaded.

[0027] When the first shank portion is unthreaded, the resistance to fastener insertion is reduced compared to when the first shank portion is threaded. This reduces the amount of force required to insert the fastener into the workpiece. Reducing the force required to insert the fastener into the workpiece advantageously reduces the amount of deflection exhibited by the workpiece during the fastener insertion process, which reduces the likelihood of gap formation occurring. Thus, a better quality joint is produced when the first shank portion is unthreaded and the second shank portion is threaded.

[0028] The first shaft portion may be axisymmetric about the longitudinal axis.

[0029] The first shank portion can include one or more retention features that, in use, can engage a workpiece into which the thread-forming and hole-forming fastener is inserted.

[0030] The one or more retention features may comprise one or more surface irregularities. The one or more surface irregularities may comprise a plurality of protrusions protruding from the first shank portion. The plurality of protrusions may take the form of, for example, ribs and / or hemispheres. The ribs may extend at locations around and / or along the longitudinal axis of the shank.

[0031] When the first shank portion includes one or more retaining features, the likelihood of the fastener coming loose during use is preferably reduced, thereby providing a more robust joint.

[0032] The diameter of the first shank portion may be greater than the diameter of the second shank portion.

[0033] The head may form an undercut.

[0034] When a fastener is inserted into a workpiece, a portion of the workpiece material may be extruded out of the opening formed by the workpiece in a direction opposite to the fastener insertion direction. If the head forms an undercut, this extruded material may be suitably received by the undercut portion of the head. Without the undercut, the extruded material may prevent full insertion of the fastener. Thus, the undercut of the head allows for full insertion of the fastener, thereby resulting in a more robust joint using the fastener.

[0035] The thread-forming and hole-forming fastener may further include a threaded stud extending from the side opposite the underside of the head.

[0036] Advantageously, the threaded stud allows a component to be secured to the fastener, thereby making the fastener more versatile than if the threaded stud were not present.

[0037] The tip section may define an undercut disposed adjacent the shank section.

[0038] When the tip section includes an undercut, the workpiece material deforms into the undercut during the fastener insertion process. This creates an additional area of ​​engagement between the fastener and the workpiece. The additional area of ​​engagement increases the strength of the connection between the fastener and the workpiece compared to when the undercut is not provided. Thus, the undercut allows for a more robust joint to be created using the fastener.

[0039] The pitch diameter of the threads of the shank section may be constant along at least 90% of the length of the shank section.

[0040] The pitch diameter of the threads of the shank section may be constant along at least 75% of the length of the shank section.The pitch diameter of the threads of the shank section may be constant along the entire length of the shank section.

[0041] In a second aspect of the invention, a method of inserting a fastener into a workpiece is provided. The method includes providing a fastener according to the first aspect of the invention, the fourth aspect of the invention, the fifth aspect of the invention or the sixth aspect of the invention. The method further includes providing a workpiece. The workpiece comprises a first surface and a second surface. The second surface is opposite the first surface. The method further includes rotating the fastener about a longitudinal axis of the fastener and contacting the fastener with the first surface of the workpiece to heat the workpiece. The method further includes threading the fastener into the workpiece by moving the fastener and the workpiece relative to each other in a direction parallel to the longitudinal axis of the fastener such that a tip section of the fastener penetrates the first surface. The fastener does not penetrate the second surface of the workpiece.

[0042] The advantages discussed above in relation to the first aspect of the invention apply to this aspect mutatis mutandis.

[0043] The first surface of the workpiece and the second surface of the workpiece do not necessarily form part of the same layer of material of the workpiece. The first surface may be referred to as the upper surface or top surface. The second surface may be referred to as the lower surface or bottom surface.

[0044] Threading the fastener into the workpiece may include forming a thread in the workpiece with the fastener.

[0045] The method may further include providing a die. The second surface may engage the die while the fastener is threaded into the workpiece. The method may include transforming the workpiece material into the die. The workpiece material may be transformed into the die at the same time the fastener is threaded into the workpiece.

[0046] The method may be performed without the use of a die.

[0047] When the second workpiece surface engages with the die while the fastener is being threaded into the workpiece, the workpiece is preferably better restrained compared to when the die is not present. The die can resist the force used to thread the fastener into the workpiece, thereby reducing deflection of the workpiece as the fastener is being threaded into the workpiece compared to when the die is not provided. Deflection of the workpiece can cause, for example, gap formation. In addition, because the force used to insert the fastener into the workpiece can be resisted by the die, the force used can be increased compared to when the die is not provided. Thus, providing a die that the second workpiece surface of the workpiece engages preferably results in a better quality joint.

[0048] The die may include a die recess into which the second surface of the workpiece may deform while the fastener is threaded into the workpiece.

[0049] When the second workpiece surface deforms into the die recess, the shape of the second surface of the workpiece can be controlled by the shape of the die.

[0050] The die recesses may be configured such that the workpiece material does not completely fill the die when insertion of the fastener into the workpiece is completed.

[0051] Configuring the die recesses so that the workpiece material does not completely fill the die when fastener insertion into the workpiece is complete advantageously allows the die to be used with a variety of different workpiece materials, and also reduces the likelihood of the workpiece jamming.

[0052] The die recess may be in the form of a continuous groove or channel.

[0053] The die recess may define a die recess volume. A volume of workpiece material may be displaced while the fastener is threaded into the workpiece. The die volume may be equal to or greater than the volume of the displaced workpiece material.

[0054] The workpiece may comprise a single workpiece layer.

[0055] A single workpiece layer may comprise both the first surface and the second surface of the workpiece.

[0056] The workpiece can include a first layer and a second layer.

[0057] The first layer of the workpiece can comprise a first surface of the workpiece, and the second layer of the workpiece can comprise a second surface of the workpiece.

[0058] At least one of the layers of the workpiece may be made from a metallic material. At least one of the layers of the workpiece may be made from aluminium.

[0059] Both layers of the workpiece may be made from a metallic material. The first layer may be made from aluminum. The second layer may be made from aluminum. The first layer may be made from cast aluminum. The second layer may be made from sheet aluminum. The second layer may be made from cast aluminum. The first layer may be made from sheet aluminum.

[0060] The material of the workpiece may have a tensile strength of at least 300 MPa. The material of the workpiece may have a tensile strength of 550 MPa or less. The material of the workpiece may have a ductility measured as a percent elongation of 10% or less. The material of the workpiece may have a ductility measured as a percent elongation of 5% or less.

[0061] The first workpiece layer can include openings through which the fasteners pass before contacting the workpiece.

[0062] The second workpiece layer may comprise a first surface of the workpiece where the first workpiece layer includes an aperture through which the fastener passes before contacting the workpiece. The diameter of the aperture may be greater than the diameter of the threaded shank section of the thread-forming and hole-forming fastener.

[0063] When a fastener is inserted into a workpiece, some of the workpiece material may be extruded from an opening formed by the workpiece in a direction opposite to the fastener's insertion direction. If the first workpiece layer includes an opening through which the fastener passes before contacting the workpiece, this extruded material may be suitably received between the fastener and the opening. In the absence of an opening, the extruded material may prevent full insertion of the fastener. Thus, the undercut of the head allows for full insertion of the fastener, thereby resulting in a more robust joint using the fastener.

[0064] Some materials may not be compatible with the fastener. This may be, for example, because the fastener is unable to heat the material sufficiently so that the fastener can be threaded into the material. By providing an opening through the first workpiece layer through which the fastener passes before contacting the workpiece, the fastener can connect workpiece layers of different materials, including materials that would otherwise be incompatible with the fastener. This method is therefore more versatile than if no openings were provided.

[0065] The first workpiece layer may be formed of a composite material.

[0066] The first layer may not be provided with openings through which the thread-forming and hole-forming fasteners pass.

[0067] The fastener may include a threaded stud extending from the head side of the shank opposite the shank section. The method may further include fastening a component to the threaded stud.

[0068] The speed at which the fastener is rotated relative to the workpiece may be reduced at least once while the fastener is being threaded into the workpiece.

[0069] After the reduction, the speed at which the fastener is rotated relative to the workpiece may be a non-zero value.

[0070] Reducing the speed at which the fastener is rotated relative to the workpiece allows the workpiece material to better form along with the fastener, and thus, the strength of the connection between the fastener and the workpiece is advantageously improved when the speed at which the fastener is rotated relative to the workpiece is reduced while the fastener is threaded into the workpiece.

[0071] The reduction in the speed at which the fastener is rotated relative to the workpiece can occur while the tip section is positioned within the second workpiece layer.

[0072] After the reduction, the speed at which the fastener is moved relative to the workpiece may be a non-zero value. The reduction in rotational speed may occur when the tip section is at least 25% of the way through the second workpiece layer.

[0073] Reducing the speed at which the fastener is rotated relative to the workpiece allows the workpiece material to better form along the fastener. A majority of the connection strength between the fastener and the workpiece is a result of the connection between the fastener and the second workpiece layer. Thus, if the speed at which the fastener is rotated relative to the workpiece is reduced while the tip section of the fastener is disposed within the second workpiece layer, the strength of the connection between the fastener and the workpiece is preferably further improved.

[0074] The second surface of the workpiece may include a protrusion into which at least a portion of the tip section of the shank of the fastener is received after the fastener is threaded into the workpiece.

[0075] In a third aspect of the present invention, there is provided a joint. The joint comprises workpieces having a first surface and a second surface. The joint further comprises a fastener according to the first aspect of the present invention, the fourth aspect of the present invention, the fifth aspect of the present invention or the sixth aspect of the present invention. The fastener penetrates the first surface and does not penetrate the second surface.

[0076] The workpiece may comprise a first workpiece layer. The first workpiece layer may comprise a first surface of the workpiece. The workpiece may comprise a second workpiece layer. The second workpiece layer may comprise a second surface of the workpiece. The fastener may at least partially penetrate the second workpiece layer. The fastener may only partially penetrate the second workpiece layer.

[0077] The fastener may be removable from the workpiece. The fastener does not have to be removable from the workpiece.

[0078] The advantages discussed above in relation to the first aspect of the invention apply to this aspect mutatis mutandis.

[0079] The workpiece can include a first workpiece layer having a first surface and a second workpiece layer having a second surface.

[0080] The first workpiece layer can include openings through which the thread-forming and hole-forming fasteners pass.

[0081] The diameter of the opening may be larger than the diameter of the threaded shank section of the thread-forming and hole-forming fastener.

[0082] The first workpiece layer may be formed of a composite material.

[0083] The first layer may not be provided with openings through which the thread-forming and hole-forming fasteners pass.

[0084] The workpiece may comprise a single workpiece layer.

[0085] The thread-forming and hole-forming fastener may further include a threaded stud extending from the side of the head opposite the shank section.

[0086] At least one of the layers of the workpiece may be made from a metallic material. At least one of the layers of the workpiece may be made from aluminium.

[0087] Both of the workpiece layers may be made from a metallic material. The first workpiece layer may be made from aluminum. The second workpiece layer may be made from aluminum. Both of the workpiece layers may be made from aluminum. The first workpiece layer may be made from cast aluminum. The second workpiece layer may be made from sheet aluminum. The second layer may be made from cast aluminum. The first layer may be made from sheet aluminum.

[0088] The material of the workpiece may have a tensile strength of at least 300 MPa. The material of the workpiece may have a tensile strength of 550 MPa or less. The material of the workpiece may have a ductility measured as a percent elongation of 10% or less. The material of the workpiece may have a ductility measured as a percent elongation of 5% or less.

[0089] The head of the thread-forming and hole-forming fastener may be positioned raised from the workpiece. The head of the thread-forming and hole-forming fastener may be positioned substantially flush with the workpiece.

[0090] The second surface may include a protrusion into which the tip section of the fastener is at least partially received.

[0091] In a fourth aspect of the invention, there is provided a thread-forming and hole-forming fastener. The thread-forming and hole-forming fastener comprises a head and a shank defining a longitudinal axis. The shank comprises a cylindrical shank section. The shank comprises a tip section. The cylindrical shank section extends from the head. The tip section extends from the cylindrical shank section. The tip section is opposite the head. At least a portion of the cylindrical shank section is threaded. The fastener further comprises a bore in the tip section extending at least partially along the longitudinal axis.

[0092] The term "thread-forming fastener" is a term known in the art and refers to a fastener that forms threads by deforming the workpiece material instead of cutting threads into the workpiece.

[0093] The bore may extend from the tip of the tip section along the longitudinal axis. The bore may be a through bore. The term "through bore" may be understood to refer to a bore that extends along the entire length of the fastener. The bore may be cylindrical. The bore may be a blind bore.

[0094] The entire shank section may be threaded.

[0095] In the process of inserting thread-forming and hole-forming fasteners into a workpiece, at least a portion of the workpiece's material is displaced by the fastener. The displaced material protrudes from one or more of the workpiece's top surface (i.e., the surface into which the fastener is inserted), the workpiece's bottom surface (i.e., the surface opposite the insertion surface), and one or more intermediate surfaces (i.e., the surfaces at the interface between the workpiece layers). This can result in joint defects such as separation of the workpiece layers, rigid insertion of the fastener due to interference with the protruding material, etc. Such defects compromise the quality of the joint created.

[0096] Because the fastener includes a bore, at least a portion of the workpiece material is received by the bore during and after insertion of the fastener into the workpiece. Thus, the amount of material displaced by the fastener during insertion is reduced compared to when the bore is not provided, thereby reducing the possibility of material protrusion. This advantageously improves joint quality compared to when the bore is not provided.

[0097] The tip section may form a ring leading edge.

[0098] The ring leading edge may define a ring surface.

[0099] When the tip section forms a ring leading edge, the initial contact area between the tip section and the workpiece during the process of inserting the fastener into the workpiece is greater than, for example, when the tip section forms a pointed tip. This increased contact area preferably heats the workpiece more quickly compared to a smaller contact area, thereby making the fastener insertion process more rapid.

[0100] Additionally, during the fastener insertion process, the contact area between the ring leading edge and the workpiece is farther from the fastener's axis of rotation than a fastener with a pointed tip section, so the speed of the ring leading edge is faster than the tip of a pointed tip section for the same rotation speed, which increases the heat delivered to the workpiece during the fastener insertion process, thereby heating the workpiece more quickly compared to a fastener with, for example, a pointed tip section.

[0101] The ring leading edges may be non-coplanar.

[0102] A ring leading edge that is non-coplanar may be understood to mean that at least a portion of the ring leading edge is not in the same plane as another portion of the ring leading edge.

[0103] The ring leading edge may include a number of facets such that the ring leading edge is serrated.

[0104] Because the ring leading edge is non-coplanar, it increases the amount of friction created while inserting the fastener into the workpiece, which reduces the chance of the workpiece becoming underheated during the fastener insertion process.

[0105] The bore may define an inner bore diameter. The bore may define a tapered surface section. The ring leading edge may merge into the bore inner diameter via the tapered surface section.

[0106] The diameter of the ring leading edge may be greater than the diameter of the bore inner diameter. The tapered surface section may comprise a chamfered surface section and / or a radiused surface section.

[0107] The bore may define a bore depth. The tapered surface section may define a tapered surface section depth. A ratio of the tapered surface section depth to the bore depth may be at least 0.1. A ratio of the tapered surface section depth to the bore depth may be at least 0.25. A ratio of the tapered surface section depth to the bore depth may be at least 0.5.

[0108] Because the ring leading edge meets the bore inner diameter with a tapered surface section, stresses on the fastener both during the fastener insertion process and in use are more evenly distributed as compared to alternative transition surfaces between the ring leading edge and the bore inner diameter. More even stress distribution reduces the likelihood of fastener failure, for example as a result of fastener cracking.

[0109] The bore may define an inner bore diameter. The cylindrical shank section may define a shank diameter. A ratio of the shank diameter to the inner bore diameter may be at least 1.5.

[0110] This ratio of shank diameter to bore inner diameter preferably provides sufficient shank material to enable the fastener to withstand the forces required in use, thereby making the fastener more robust.

[0111] The ratio of the shaft diameter to the bore inner diameter may be at least two.

[0112] The shank may define a shank length. The bore may extend along at least 25% of the shank length.

[0113] When the bore extends along at least 25% of the shank length, the amount of workpiece material that can be accommodated by the bore is sufficient such that the likelihood of gap formation occurring during the fastener insertion process is sufficiently reduced.

[0114] The bore may extend along at least 50% of the shank length.

[0115] The bore may extend along up to 25% of the shank length.The bore may extend along up to 10% of the shank length.

[0116] A shallower bore may be desirable for thinner workpieces. With thinner workpieces, less workpiece material is displaced by the fastener because there is less workpiece material to displace. Thus, the depth of the bore may be selected based on the thickness of the workpiece. For harder and / or stronger workpieces, shallower bores may also be used. This is because the likelihood of fastener deformation occurring during fastener insertion increases as the hardness and strength of the workpiece increases. Thus, a bore extending along up to 25% or up to 10% of the shank length provides the advantage of increasing the heat delivered to the workpiece mentioned above while reducing the likelihood of fastener deformation.

[0117] The bore may define a bore surface. The bore surface may define a plurality of surface irregularities.

[0118] When the bore forms a plurality of surface asperities, the surface asperities mate with the workpiece into which the fastener is inserted, which advantageously improves the strength of the connection between the fastener and the workpiece.

[0119] The entire bore may be cylindrical.

[0120] When the bore is entirely cylindrical, the strength of the fastener shank is improved as compared to a bore that includes a tapered section.

[0121] In a fifth aspect of the present invention, a thread-forming and hole-forming fastener is provided. The thread-forming and hole-forming fastener comprises a head and a shank defining a longitudinal axis. The shank comprises a shank section. The shank comprises a tip section. The shank section extends from the head. The tip section extends from the shank section. The tip section is opposite the head. At least a portion of the shank section is threaded. The shank section defines a shank section length. The tip section defines a tip section length. A ratio of the shank section length to the tip section length is at least 2.5. The tip section comprises a plurality of surface asperities.

[0122] The ratio of the shank section length to the tip section length can be calculated by dividing the shank section length by the tip section length.

[0123] The surface irregularities may be in the form of facets.

[0124] The surface irregularities may be in the form of ribs.

[0125] The surface irregularities may be in the form of facets and ribs.

[0126] The plurality of facets may include at least three facets. Each facet may be in the form of a radiused surface section. The facets may be adjacent to one another. The facets may be arranged in an array. The facets may be spaced apart from one another.

[0127] The plurality of ribs may include at least two ribs. The plurality of ribs may include at least three ribs. The plurality of ribs may include six ribs. A portion of the length of the ribs may extend radially (i.e., perpendicular to the longitudinal axis of the fastener). A portion of the length of the ribs may extend circumferentially (i.e., about the longitudinal axis of the fastener). The ribs may extend radially outward from the tip of the tip section. The thickness and / or width of the ribs may be uniform or non-uniform. The thickness of the ribs may be understood to refer to the distance the ribs protrude from the surface of the tip section. The thickness and / or width of the ribs may be minimum at or adjacent to the tip of the tip section. The thickness and / or width of the ribs may be maximum at or adjacent to the tip of the tip section.

[0128] The tip section may be a tapered tip section. The shank section may be cylindrical. The entire shank section may be threaded.

[0129] Each facet of the plurality of facets, or each rib of the plurality of ribs, may extend from a tip of the tip section towards the shank section. Each facet of the plurality of facets, or each rib of the plurality of ribs, may extend from a tip of the tip section to the shank section. Each facet of the plurality of facets may extend radially outward from a tip of the tip section.

[0130] In use, the thread-forming and hole-forming fastener is rotated on a surface of the workpiece to heat the workpiece. Once the workpiece has been heated a predetermined amount, the fastener is threaded into the workpiece by moving the fastener relative to the workpiece in a direction parallel to the longitudinal axis of the fastener. Rotation of the fastener continues while the fastener is threaded into the workpiece. As the fastener is threaded into the workpiece, workpiece material forms along the threads of the shank section, thereby threading the fastener into the workpiece. The quality of a joint created using the fastener depends on the amount the workpiece is heated during fastener insertion. Insufficient heating of the workpiece during the insertion process produces a suboptimal joint. For example, insufficient heating of the workpiece during the insertion process can result in separation of the layers of the workpiece (if the workpiece comprises multiple layers) and / or improper engagement of the fastener threads with the workpiece material. Separation of the layers of the workpiece is sometimes referred to as gap formation.

[0131] Because the tip section includes a plurality of surface asperities, the likelihood of the workpiece underheating during insertion of the fastener into the workpiece is advantageously reduced. The plurality of surface asperities provides a discontinuous contour to the tip section. The discontinuous contour increases the amount of friction between the workpiece and the tip section of the fastener, thereby increasing the amount of heat generated during the fastener insertion process. Because the likelihood of the workpiece underheating during fastener insertion is reduced, the quality of a joint created using the fastener is improved as compared to a case in which the workpiece is underheated during fastener insertion.

[0132] The plurality of facets can include six facets.

[0133] When the plurality of facets includes six facets, heating of the workpiece during fastener insertion is optimized.

[0134] The plurality of facets may include at least two facets. The plurality of facets may include at least four facets.

[0135] Each facet may be in the form of a planar surface section. The facets may be adjacent to one another. The facets may be spaced apart from one another.

[0136] In a sixth aspect of the present invention, there is provided a thread-forming and hole-forming fastener. The thread-forming and hole-forming fastener comprises a head and a shank defining a longitudinal axis. The shank comprises a shank section. The shank comprises a tip section. The shank section extends from the head. The tip section extends from the shank section. The tip section is opposite the head. At least a portion of the shank section is threaded.

[0137] Any feature disclosed in relation to the first, fourth or fifth aspect of the invention may be combined with the sixth aspect of the invention.

[0138] In a seventh aspect of the invention, a method of inserting a fastener into a workpiece is provided. The method includes providing a workpiece comprising a first workpiece layer and a second workpiece layer. The method further includes applying an adhesive to the first and / or second workpiece layers. The method further includes engaging the first and second workpieces with one another such that the adhesive is disposed between the first and second workpiece layers. The method further includes providing a fastener. The fastener includes a head and a shank. The shank defines a longitudinal axis. The shank includes a shank section. The shank includes a tip section. At least a portion of the shank section is threaded. The shank section extends from the head. The tip section extends from the shank section and is opposite the head. The method further includes rotating the fastener about the longitudinal axis and contacting the fastener with the workpiece to heat the workpiece. The method further includes threading the fastener into the workpiece by moving the fastener and the workpiece relative to one another in a direction parallel to the longitudinal axis such that a tip section of the fastener penetrates the first workpiece layer and the adhesive, and the fastener at least partially penetrates the second workpiece layer.

[0139] Due to the adhesive layer, the strength of the connection between the first workpiece and the second workpiece is preferably greater than if the adhesive were not present.

[0140] The fastener may be a fastener according to the first, fourth, fifth or sixth aspect of the invention.

[0141] The fastener may only partially penetrate the second workpiece layer.

[0142] When a fastener only partially penetrates the second workpiece layer, the likelihood of fluid ingress through the second layer is reduced. It is desirable to reduce the likelihood of fluid ingress because the presence of fluid can cause joint defects such as oxidation. Thus, fasteners that only partially penetrate the second workpiece layer preferably provide a more robust joint.

[0143] Additionally, when the fastener only partially penetrates the second workpiece layer, the tip section of the fastener is disposed within the second workpiece layer and does not protrude from the workpiece. This is desirable because a protruding fastener poses a risk of injury to the user and / or damage to the part. Thus, having the fastener only partially penetrate the second workpiece layer preferably provides a safer joint.

[0144] In an eighth aspect of the invention, a method is provided for inserting a fastener into a workpiece. The method includes providing a fastener. The fastener comprises a head and a shank. The shank defines a longitudinal axis. The shank comprises a shank section and a tip section. The shank section is at least partially threaded. The threaded shank section extends from the head. The tip section extends from the shank section and is opposite the head. The method further includes providing a workpiece. The workpiece comprises a first surface and a second surface. The second surface is opposite the first surface. The method further includes rotating the fastener about the longitudinal axis and contacting the fastener with the first surface of the workpiece to heat the workpiece. The method further includes moving the fastener relative to the workpiece at a rate of at least 0.5 mm / sec. The fastener is moved in a direction parallel to a longitudinal axis of the fastener such that the tip section penetrates a first surface of the workpiece and the fastener is threaded into the workpiece. The fastener does not penetrate a second surface of the workpiece.

[0145] The first surface of the workpiece and the second surface of the workpiece do not necessarily form part of the same layer of material of the workpiece. The first surface may be referred to as the upper surface or top surface. The second surface may be referred to as the lower surface or bottom surface.

[0146] The threaded shank may be cylindrical.

[0147] The fastener is moved relative to the workpiece in a direction parallel to the fastener's longitudinal axis at a speed of at least 0.5 mm / sec, thereby reducing the likelihood of overheating of the workpiece. This is because the speed at which the fastener is inserted into the workpiece is sufficient to allow the fastener insertion process to be completed before overheating of the workpiece occurs. It is desirable to reduce the likelihood of overheating of the workpiece because overheating can result in joint defects such as gap formation. Thus, moving the fastener relative to the workpiece in a direction parallel to the fastener's longitudinal axis at a speed of at least 0.5 mm / sec preferably produces a better quality joint as compared to when the fastener is moved at a speed slower than 0.5 mm / sec.

[0148] Additionally, because the fasteners do not penetrate the second surface of the workpiece, the possibility of fluid ingress through the second layer is reduced. Reducing the possibility of fluid ingress is desirable because the presence of fluid can cause joint defects such as oxidation. Thus, fasteners that only partially penetrate the second workpiece layer preferably provide a more robust joint.

[0149] Additionally, because the fastener does not penetrate the second surface of the workpiece, the tip section of the fastener is located within the workpiece and does not protrude out of the workpiece, which is desirable because protruding fasteners pose a risk of injury to the user and / or damage to the part. Thus, having the fastener not penetrate the second surface of the workpiece preferably provides a safer joint.

[0150] The speed at which the fastener is moved relative to the workpiece may be reduced at least once while the fastener is being threaded into the workpiece.

[0151] After the reduction, the speed at which the fastener is moved relative to the workpiece may be a non-zero value.

[0152] Reducing the speed at which the fastener is moved relative to the workpiece allows the workpiece material to better form along with the fastener, and thus, the strength of the connection between the fastener and the workpiece is advantageously improved if the speed at which the fastener is moved relative to the workpiece is reduced while the fastener is threaded into the workpiece.

[0153] The workpiece may comprise a first workpiece layer and a second workpiece layer. The first workpiece layer may comprise a first surface of the workpiece. The second workpiece layer may comprise a second surface of the workpiece. A speed at which the fastener is moved relative to the workpiece may be reduced while a tip section of the fastener is disposed in the second workpiece layer.

[0154] After the reduction, the speed at which the fastener is moved relative to the workpiece may be a non-zero value.

[0155] Reducing the speed at which the fastener is moved relative to the workpiece allows the workpiece material to better form along the fastener. A majority of the connection strength between the fastener and the workpiece is a result of the connection between the fastener and the second workpiece layer. Thus, if the speed at which the fastener is moved relative to the workpiece is reduced while the tip section of the fastener is disposed in the second workpiece layer, the strength of the connection between the fastener and the workpiece is preferably further improved.

[0156] The fastener may be moved relative to the workpiece in a direction parallel to the longitudinal axis of the fastener at a speed of at least 1 mm / sec.

[0157] The fastener may be moved relative to the workpiece in a direction parallel to the longitudinal axis of the fastener at a speed of at least 2 mm / sec.

[0158] In a ninth aspect of the invention, a method for inserting a fastener into a workpiece is provided. The method includes providing a fastener. The fastener comprises a head and a shank. The shank defines a longitudinal axis. The shank comprises a shank section and a tip section. The shank section is at least partially threaded. The threaded shank section extends from the head. The tip section extends from the shank section and is opposite the head. The method further includes providing a workpiece. The workpiece comprises a first surface and a second surface. The second surface is opposite the first surface. The method further includes rotating the fastener about the longitudinal axis and contacting the fastener with the first surface of the workpiece to heat the workpiece. The method further includes threading the fastener into the workpiece by moving the fastener and the workpiece relative to one another in a direction parallel to the longitudinal axis such that a tip of the fastener penetrates the first surface of the workpiece. The fasteners do not penetrate the second surface of the workpiece.Throughout the method, the workpiece temperature remains below the recrystallization temperature of the workpiece material.

[0159] The threaded shank section may be cylindrical.

[0160] Because the workpiece temperature remains below the recrystallization temperature of the workpiece material throughout the method, the fastener is able to better form threads in the workpiece as compared to when the workpiece temperature exceeds the recrystallization temperature of the workpiece material. This is because below the recrystallization temperature, the ductility of the workpiece material is optimized for the fastener to form threads. Above the recrystallization temperature of the material, the workpiece material is too ductile to accurately form threads. Because the threads are better formed, the strength of the connection between the fastener and the workpiece is improved.

[0161] The workpiece may comprise a first workpiece layer and a second workpiece layer. Throughout the method, the material of the first workpiece layer may not intermix with the material of the second workpiece layer.

[0162] In a tenth aspect of the present invention, a joint is provided. The joint comprises a workpiece. The workpiece comprises a first workpiece layer and a second workpiece layer. The joint further comprises an adhesive layer disposed between the first workpiece layer and the second workpiece layer. The joint further comprises a fastener having a hole and thread formed in the workpiece. The fastener extends through the first workpiece layer, the adhesive layer, and at least partially through the second workpiece layer.

[0163] The fastener may extend only partially into the second workpiece layer.The fastener may be threaded into the first workpiece layer.The fastener may be threaded into the second workpiece layer.

[0164] The fasteners may be threaded through all layers of the workpiece. The fasteners may be removable from the workpiece. The fasteners may not be removable from the workpiece.

[0165] In an eleventh aspect of the invention, there is provided a joint. The joint comprises a workpiece. The workpiece comprises a first surface and a second surface. The joint further comprises a thread-forming and hole-forming fastener. The thread-forming and hole-forming fastener comprises a head and a shank. The shank comprises a shank section. The shank comprises a tip section. At least a portion of the shank section is threaded. The shank section extends from the head. The tip section extends from the shank section. The tip section is opposite the head. The fastener penetrates the first surface. The fastener does not penetrate the second surface. The workpiece further comprises a thermo-mechanical affected zone adjacent an interface between the workpiece and the thread-forming and hole-forming fastener.

[0166] The workpiece material in the region of the thermo-mechanical affected zone is harder than the remainder of the workpiece material. The harder workpiece material results in improved joint strength compared to softer workpiece materials. The harder workpiece material in the region of the thermo-mechanical affected zone also improves the ability of the joint to undergo fatigue loading without failure.

[0167] The workpiece may comprise a first workpiece layer. The first workpiece layer may comprise a first surface of the workpiece. The workpiece may comprise a second workpiece layer. The second workpiece layer may comprise a second surface of the workpiece. The fastener may at least partially penetrate the second workpiece layer. The fastener may only partially penetrate the second workpiece layer.

[0168] The workpiece may not include a stir zone. The fastener may be removable from the workpiece. The fastener may not be removable from the workpiece.

[0169] The threaded shank section may be a cylindrical threaded shank section.

[0170] In a twelfth aspect of the present invention, there is provided a joint. The joint comprises a workpiece. The workpiece comprises a single workpiece layer. The workpiece layer comprises a first surface and a second surface. The joint further comprises a thread-forming and hole-forming fastener. The thread-forming and hole-forming fastener comprises a head and a shank. The shank comprises a shank section. The shank comprises a tip section. The shank section extends from the head. The shank section is at least partially threaded. The tip section extends from the shank section and is opposite the head. The fastener penetrates the first surface and does not penetrate the second surface.

[0171] The shank section may be a cylindrical shank section. The fastener may be removable from the workpiece. The fastener may not be removable from the workpiece.

[0172] In a thirteenth aspect of the present invention, there is provided a thread-forming and hole-forming fastener comprising a head and a shank defining a longitudinal axis. The shank comprises a shank section. The shank comprises a tip section. The shank section extends from the head. The tip section extends from the shank section. The tip section is opposite the head. At least a portion of the shank section is threaded. The head is provided with a cutting edge.

[0173] When a fastener is inserted into a workpiece to form a joint, workpiece material may be extruded from the workpiece in a direction opposite to the direction the fastener is being inserted into the workpiece. This is undesirable as the extruded material is prone to corrosion and may lead to failure of the joint. Advantageously, the cutting feature is capable of removing the extruded workpiece material from the workpiece.

[0174] The extruded material is sometimes referred to as excess material.

[0175] The cutting features may be provided on an underside of the head.The cutting features may be provided on a periphery of the head.

[0176] The cutting features may be in the form of one or more ribs. The one or more ribs may include six ribs.

[0177] A portion of the rib length of one or more ribs may extend in a radial direction.A portion of the rib length of one or more ribs may extend in a longitudinal direction.

[0178] The cutting feature may be in the form of one or more teeth. The one or more teeth may include four teeth. At least a portion of each tooth of the plurality of teeth may extend in a radial direction. The one or more teeth may form a portion of a radial periphery of the head.

[0179] The one or more teeth may extend from the underside of the head towards the top of the head.The one or more teeth may extend from the underside of the head to the top of the head.

[0180] In a fourteenth aspect of the invention, a method for inserting a fastener into a workpiece is provided. The method includes providing a fastener according to the thirteenth aspect of the invention. The method further includes providing a workpiece with a first surface and a second surface. The second surface is on an opposite side to the first surface. The method further includes rotating the fastener about a longitudinal axis of the fastener and contacting the fastener with the first surface of the workpiece to heat the workpiece. The method further includes threading the fastener into the workpiece by moving the fastener and the workpiece relative to one another in a first direction, the first direction being parallel to the longitudinal axis of the fastener. The method further includes extruding at least some of the workpiece material from the workpiece in a second direction, the second direction being generally opposite to the first direction. The method further includes removing the extruded material from the workpiece using a cutting edge of a head of the fastener.

[0181] Features disclosed with respect to one aspect of the invention may be combined with features of another aspect of the invention, for example features of any of the first, fourth and / or fifth aspects of the invention may be combined with the sixth aspect of the invention.

[0182] Next, an embodiment of the present invention will be described with reference to the accompanying drawings. [Brief description of the drawings]

[0183] [Figure 1a]1 shows a cross-sectional side view of a fastener according to one embodiment of the present invention. [Figure 1b] FIG. 1b shows a perspective view of the fastener of FIG. [Diagram 2] 1 shows a fastener insertion device for use with any of the fasteners shown. [Diagram 3] 3 shows an enlarged view of the nosepiece of the fastener insertion device of FIG. 2. [Figure 4] 3 illustrates the nosepiece of the fastener insertion device of FIG. 2 during the fastener insertion process. [Diagram 5] 3 illustrates a joint formed using the fastener of FIG. 1 and the fastener insertion device of FIG. 2. [Figure 6] 1 shows the interface of the fastener insertion tool with the die. [Figure 7a] 13 shows a bottom view of a fastener according to a further embodiment of the present invention. [Figure 7b] 7b shows a cross-sectional side view of the fastener of FIG. 7a. [Figure 8] 13 shows a cross-sectional view of a fastener according to a further embodiment of the present invention. [Figure 9] 9 illustrates a joint formed using the fastener of FIG. 8. [Figure 10] 13 shows a cross-sectional view of a fastener according to a further embodiment of the present invention. [Figure 11] 13A-13C show cross-sectional views of joints formed using fasteners according to further embodiments of the present invention. [Figure 12] 13A-13C show cross-sectional views of joints formed using fasteners according to further embodiments of the present invention. [Figure 13] 13 shows a cross-sectional view of a fastener according to a further embodiment of the present invention. [Figure 14] 13A-13C show cross-sectional views of joints formed using fasteners according to further embodiments of the present invention. [Figure 15] 13 shows a cross-sectional view of a fastener according to a further embodiment of the present invention. [Figure 16] 13A-13C show cross-sectional views of joints formed using fasteners according to further embodiments of the present invention. [Figure 17]13A-13C show cross-sectional views of joints formed using fasteners according to further embodiments of the present invention. [Figure 18] 13 shows a cross-sectional view of a fastener according to a further embodiment of the present invention. [Figure 19] 1 shows a perspective view of a fastener according to a further embodiment of the present invention; [Figure 20] 13 shows a cross-sectional side view of a fastener according to a further embodiment of the present invention. [Figure 21] 13A-13C show cross-sectional views of joints formed using fasteners according to further embodiments of the present invention. [Figure 22] 13 shows a cross-sectional side view of a fastener according to a further embodiment of the present invention. [Figure 23] 13 shows a cross-sectional side view of a fastener according to a further embodiment of the present invention. [Figure 24] 1 illustrates a fastener insertion device for use with any of the fasteners disclosed herein. [Diagram 25] 25 shows a detailed view of the fastener insertion device of FIG. 24. [Figure 26] 1 shows the interface of the fastener insertion tool with the die. [Figure 27] 3 illustrates a die for use with the fastener insertion device of FIG. 2. [Figure 28] FIG. 11 is a detailed view of a fastener according to a further embodiment of the present invention. [Figure 29] 13A-13C show cross-sectional views of a fastener and a workpiece according to a further embodiment of the present invention. [Diagram 30] 13A-13C show cross-sectional views of a fastener and a workpiece according to a further embodiment of the present invention. [Diagram 31] 1 shows a fastener according to a further embodiment of the present invention. [Diagram 32] 1 shows a fastener according to a further embodiment of the present invention. [Diagram 33] 1 shows a fastener according to a further embodiment of the present invention. [Diagram 34] 1 illustrates a nosepiece of a fastener insertion device for use with any of the fasteners disclosed herein. [Diagram 35]13 shows a side view of a fastener according to a further embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0184] 1a and 1b show a fastener 2. The fastener 2 comprises a head 4. The head 4 comprises a lower surface 15. The fastener 2 comprises a shank 10. The shank 10 extends from the lower surface 15 of the head 4. The head 4 comprises a driver shape 6, which can be seen in FIG. 1b. The periphery of the driver shape 6 defines a discontinuous profile. In use, the driver shape 6 is engaged by a fastener insertion device, as described in more detail below. The driver shape 6 is an external driver shape. In some embodiments, the driver shape 6 may be an internal driver shape. In some embodiments, the driver shape 6 may be a snap-off driver shape.

[0185] The head 4 defines an undercut 8. The undercut 8 is disposed adjacent to and extends around the shank 10. The undercut 8 can receive material from a workpiece during use, as described in more detail below. In some embodiments, the undercut 8 need not be present. In the absence of the undercut 8, the undersurface 15 of the head 4 can be generally planar.

[0186] The shank 10 comprises a shank section 12. The shank section 12 comprises a base section 11. The base section 11 of the shank section 12 extends from the head 4 of the fastener 2. The shank 10 comprises a tip section 14. The base section 11 is generally disposed within the undercut 8 of the head 4. However, in some embodiments, a portion of the base section 11 may extend beyond the underside 15 of the head 4. In such embodiments, the base section may taper toward the shank section 12 (as shown). The shank section 10 defines a shank section diameter SD. The shank section diameter SD may be referred to as a minor diameter. The shank section diameter SD may exclude the diameter of the base section 11. The shank section diameter SD is determined, for example, by the required connection strength provided by the fastener. The diameter of the shank section 10 may be at least 2 mm. The diameter of the shank section 12 may be no more than 10 mm. The diameter of the shank section 12 may be at least 3 mm. The diameter of shank section 12 may be 8 mm or less. The diameter of shank section 12 may be 4 mm, such that fastener 2 is an M4 fastener. The diameter of shank section 12 may be 5 mm. The diameter of shank section 12 need not be an integer number. For example, the diameter of shank section 12 may be 4.5 mm. Shank section 12 defines a longitudinal axis L.

[0187] The shank section 12 is threaded. Thus, the shank section 12 may be referred to as a threaded shank section. The threads of the shank section 12 define a thread diameter TD. The thread diameter TD may be referred to as the major diameter. The thread diameter TD is generally constant along the length of the shank section. In some embodiments, the thread diameter TD of the shank section 12 may be generally constant along at least 50% of the length of the shank section. In some embodiments, the thread diameter TD may be generally constant along at least 75% of the length of the shank section. In some embodiments, the thread diameter TD may be generally constant along at least 90% of the length of the shank section. In some embodiments, the threads of the shank section 12 may include a tapered section adjacent the tip section 14. The shank section 12 is generally cylindrical. Although in FIG. 1a the entire shank section is shown as threaded, in some embodiments, at least a portion of the shank section 12 may be threaded. The fastener 2 may be made of any suitable material. For example, the fastener 2 may be made of steel. The fastener 2 may be provided with a coating, which may be, for example, a zinc-nickel coating.

[0188] The tip section 14 extends from the shank section 12. In some embodiments, the tip section 14 can be joined to the shank section 12 by a radius. In some embodiments, the tip section 14 can be joined to the shank section 12 by a chamfer. The tip section 14 is disposed at an end of the shank section 12 opposite the head 4. The tip section 14 defines a tip section length TL. In some embodiments, the ratio of the tip section length TL to the thread diameter TD of the shank section 12 can be 0.6 or less. In some embodiments, the ratio of the tip section length TL to the thread diameter TD of the shank section 12 can be 0.4 or less. The ratio of the tip section length TL to the thread diameter TD of the shank section 12 can be calculated by dividing the tip section length TL by the thread diameter TD. The ratio of the tip section length TL to the thread diameter TD can be selected based on, for example, the thickness of the workpiece as a whole and / or the thickness of an individual layer of the workpiece. The ratio of the tip section length TL to the thread diameter TD can be proportional to the thickness of the workpiece.

[0189] The tip section 14 is tapered. The tip section 14 defines a tip angle α. The term tip angle may be understood to refer to the included angle of the tip of the tip section 14. The tip angle α is at least 50°. The tip angle α may be at least 70°. The tip angle α may be equal to or less than 160°. The tip angle α may be at least 125° and equal to or less than 135°. The tip angle α may not be equal to 118°. In the illustrated embodiment, the tip section 14 is conical. However, in other embodiments, the tip section 14 may be any other tapered shape, such as a frustoconical or radiused. When the tip section 14 is frustoconical or any other tapered shape, the tip angle α is the angle between diametrically opposed points on the tapered surface of the tip section 14. Regardless of the shape of the tip section 14, the tip angle α is the maximum angle defined between two tangents extending through diametrically opposed points of the tip section 14. The points to which the tangents extend are located at corresponding points along the longitudinal axis L. If the tip section 14 is radiused, the tip section may be generally dome-shaped. If the tip section 14 is dome-shaped, the dome may be a pointed dome. If the tip section 14 is radiused, the radius of the tip section may be at least 2 mm. The radius of the tip section 14 may be no greater than 15 mm. The radius of the tip section 14 may be at least 5 mm. The radius of the tip section may be no greater than 10 mm. The tip section 14 defines a tip 19. The tip 19 defines an end point of the tip section 14. The tip 19 is in the form of a point. In other embodiments, for example, if the tip section 14 is frusto-conical, the tip 19 may be in the form of a flat surface section.

[0190] Fastener 2 is a thread-forming and hole-forming fastener. The term thread-forming fastener is a term known in the art and refers to a fastener that forms a thread by deforming the workpiece material instead of cutting a thread in the workpiece and removing workpiece material. Fastener 2 forms a thread rather than cutting a thread in the workpiece by the geometry of the thread on shank section 12 and by the process by which the fastener is inserted into the workpiece, as described in more detail below. The term hole-forming fastener is a term known in the art and refers to a fastener that forms a hole in the workpiece by deforming the workpiece material instead of cutting a hole in the workpiece.

[0191] FIG. 2 illustrates an insertion device 16 capable of inserting fasteners 2 into a workpiece 17. In some embodiments, fasteners 2 may be inserted into the workpiece 17 using a handheld fastener insertion device. In FIG. 2, the workpiece 17 comprises a first workpiece layer 18 and a second workpiece layer 20. The first workpiece layer 18 may be referred to as a top layer of the workpiece 17. The second workpiece layer 20 may be referred to as a bottom layer of the workpiece 17. The first workpiece layer 18 forms a first surface 34 of the workpiece 17. The first surface 34 may be referred to as a top surface of the workpiece 17. The second workpiece layer 20 forms a second surface 36 of the workpiece 17. The second surface 36 of the workpiece 17 is opposite the first surface 34 of the workpiece 17. The second surface 36 may be referred to as a bottom surface of the workpiece 17. In some embodiments, the workpiece 17 may comprise a single workpiece layer. If workpiece 17 comprises a single workpiece layer, the single workpiece layer comprises the first surface 34 and the second surface 36 of the workpiece. In other embodiments, workpiece 17 may comprise three, four, or more workpiece layers. If workpiece 17 comprises more than two workpiece layers, second workpiece layer 20 may still be the bottom workpiece layer. A layer disposed between first workpiece layer 18 and second workpiece layer 20 may be referred to as an intermediate layer.

[0192] The first workpiece layer 18 and the second workpiece layer 20 may be made of any suitable material. The first workpiece layer 18 and the second workpiece layer 20 may be made of a metallic material. In this embodiment, the first workpiece layer 18 and the second workpiece layer 20 are made of aluminum. The first workpiece layer 18 is made of cast aluminum. The second workpiece layer 20 is made of sheet aluminum. In some embodiments, the first workpiece layer 18 may be made of sheet aluminum. In some embodiments, the second workpiece layer 20 may be made of cast aluminum. When one or both of the first workpiece layer 18 and the second workpiece layer 20 are made of cast aluminum, the diameter of the shank section 12 may be larger than other materials. This is because the fastener 2 is typically inserted into the flange portion of the workpiece, and the flange of a cast workpiece is typically larger than, for example, a sheet workpiece. Thus, the cast workpiece provides more workpiece material into which the fastener 2 can be inserted. The material of the first and / or second workpiece layer 18,20 may have a tensile strength of at least 300 MPa. The material of the first and / or second workpiece layer 18,20 may have a tensile strength of 550 MPa or less. In some embodiments, the material of the first and / or second workpiece layer 18,20 may have a tensile strength of at least 100 MPa. In some embodiments, the material of the first and / or second workpiece layer 18,20 may have a tensile strength of 1000 MPa or less. The material of the first and / or second workpiece layer 18,20 may have a ductility measured as a percent elongation of 10% or less. The material of the first and / or second workpiece layer 18,20 may have a ductility measured as a percent elongation of 5% or less.

[0193] The insertion device 16 comprises a shaft 22. The shaft 22 is driven by a first actuator 24 and a second actuator 25. The first actuator 24 is an electric motor. In some embodiments, the first actuator 24 may be a pneumatic cylinder. In some embodiments, the first actuator 24 may be a pneumatic-hydraulic actuator or an electro-hydraulic actuator. The first actuator 24 is configured to rotate the shaft 22 about a longitudinal axis of the shaft (not shown in FIG. 2). The second actuator 25 is a pneumatic cylinder. In some embodiments, the second actuator 25 may be an electric motor. In some embodiments, the second actuator 25 may be a pneumatic-hydraulic actuator or an electro-hydraulic actuator. The second actuator 25 is configured to move the shaft 22 in an axial direction, which is a direction parallel to the longitudinal axis of the shaft. The shaft 22 can engage with the drive feature 6 of the fastener 2 such that rotation of the shaft 22 also results in rotation of the fastener 2. The insertion device 16 includes a nosepiece 26. The fastener 2 is received within the nosepiece 26 prior to insertion of the fastener.

[0194] In some embodiments, the workpiece 17 is not supported on a second workpiece surface by the fastener insertion device 16 while the fastener is being inserted into the workpiece. This is sometimes referred to as single-sided insertion. Figure 2 shows the fastener insertion device 16 performing single-sided insertion. The method of inserting the fastener 2, or any other fastener disclosed herein, into a workpiece may be a single-sided insertion method.

[0195] The fastener insertion device 16 may include a C-frame (not present in FIG. 2). The C-frame may also be referred to as a C-clamp. A C-frame may be provided in which the workpiece 17 is supported on a first workpiece surface and a second workpiece surface while the fastener is inserted into the workpiece. This may be referred to as a double-sided insertion. Thus, the method of inserting the fastener 2, or any other fastener disclosed herein, into the workpiece may be a double-sided insertion method. Double-sided insertion allows the fastener 2 to resist the force of being inserted into the workpiece 117. This reduces deflection of the workpiece compared to single-sided insertion. Reduced deflection of the workpiece is advantageous as it reduces the possibility of damage to the workpiece and / or joint defects such as gap formation.

[0196] 2 shows the insertion device 16 immediately prior to inserting the fastener 2 into a workpiece 17. The insertion device 16 may be any suitable commercially available insertion device. For example, the insertion device 16 may be an Atlas Copco KFLOW® system available from Atlas Copco IAS GmbH, Geretsried, Germany.

[0197] FIG. 3 illustrates the nosepiece 26 of the fastener insertion device 16 prior to insertion of the fastener 2. The shaft 22 includes an end portion 28. The end portion 28 of the shaft 22 includes a bore 30. The bore 30 extends into the end portion 28. The bore 30 provides the end portion 28 of the shaft 22 with a fastener engagement portion 32. The shape of the fastener engagement portion 32 is complementary to the driver shape 6 of the fastener 2. The fastener engagement portion 32 is configured to engage with the driver shape 6 of the head 4 of the fastener 2. In FIG. 3, the head 4 of the fastener 2 is received within the bore 30 of the end portion 28 of the shaft 22. Thus, rotation of the shaft 22 also results in rotation of the fastener 2. Similarly, axial translation of the shaft 22 results in translation of the fastener 2 along its longitudinal axis (not shown in FIG. 3). When fastener 2 is received in fastener-engaging portion 32 , the longitudinal axis of fastener 2 is coaxial with the longitudinal axis of shaft 22 .

[0198] A method of inserting the fastener 2 into the workpiece 17 will now be described. Although the method will be described with respect to the fastener 2, the method applies to all embodiments of the fastener described herein. Starting from the position shown in FIG. 3, the nosepiece 26 is engaged with the first surface 34 of the workpiece 17. The shaft 22, and thus the fastener 2, is then rotated about its longitudinal axis (not shown in FIG. 3) such that the fastener is rotated about its longitudinal axis. The shaft 22 rotates, for example, at a speed of 3000 rpm. In some embodiments, the shaft 22 can rotate at a speed of at least 500 rpm and / or not more than 12000 rpm. In some embodiments, the shaft 22 can rotate at a speed of at least 1000 rpm and / or equal to 6000 rpm. In some embodiments, the shaft can rotate at a speed of not more than 9000 rpm. In some embodiments, the shaft 22 can rotate at a speed of 6000 rpm. In some embodiments, the shaft 22 can rotate at a speed of 9000 rpm. The speed at which the shaft 22 rotates may be determined, for example, by the hardness of the material from which the workpiece 17 is made. The required rotation speed of the shaft 22 generally increases as the hardness of the material from which the workpiece 17 is made increases. Although FIG. 3 shows the fastener 2 spaced apart from the workpiece when the rotation of the shaft 22 begins, in some embodiments, the fastener 2 may be in contact with the workpiece 17 before the rotation of the shaft 22 begins. While the shaft 22 rotates, the shaft 22 is moved along an axial direction until the tip 19 of the fastener 2 contacts the first surface 34 of the workpiece 17. When the tip 19 contacts the first surface 34 of the workpiece 17, the axial movement of the shaft 22, and therefore the fastener 2, is paused. While the movement of the shaft 22 is paused, the shaft may apply a load to the fastener 2. The load applied by the shaft 22 to the fastener 2 may extend in the axial direction. Thus, the load applied by the shaft 22 to the fastener 2 may be referred to as an axial load. The load applied to the fastener 2 by the shaft 22 may be 250N.Rotation of the shaft 22, and therefore the fastener 2, continues while the fastener 2 is in contact with the first surface 34 of the workpiece 17. This causes the workpiece 17 to heat up. This is due to friction between the tip section 14 of the fastener 2 and the first surface 34 of the workpiece 17. When the shaft 22 exerts an axial load on the fastener 2, the amount of friction generated between the tip section 14 of the fastener 2 and the first surface 34 of the workpiece 17 is greater than when the fastener is not subjected to an axial load.

[0199] Rotation of the shaft 22, and therefore the fastener 2, continues until a predetermined amount of heat has been supplied to the workpiece 17. Heating of the workpiece 17 causes the material of the workpiece 17 to soften (reduce hardness). However, the material of the workpiece 17 does not melt. Throughout the fastener insertion process, the workpiece 17 remains below the recrystallization temperature of the workpiece material. The recrystallization temperature of a material is typically 40-50% of the melting temperature of the material. The recrystallization temperature may vary depending, for example, on whether the material has undergone any cold deformation (i.e., deformation of the material that does not increase the temperature of the material). Aluminum alloys typically have recrystallization temperatures of 340°C to 400°C, and magnesium alloys typically have recrystallization temperatures of 300°C to 400°C. Because the material of the workpiece 17 remains below the recrystallization temperature, the fastener insertion process is a warm forming process. During the fastener insertion process, the material of the workpiece 17 remains below its recrystallization temperature so that the material of the workpiece 17 is not softer than if the material of the workpiece was above its recrystallization temperature. This preferably allows the fastener 2 to form threads in the workpiece 17 during the fastener insertion process. Throughout the fastener insertion process, the materials of the first workpiece layer 18 and the second workpiece layer 20 do not intermix with each other. However, slight intermixing of the materials of the first workpiece layer 18 and the second workpiece layer 20 may occur.

[0200] Once the predetermined amount of heat is provided to the workpiece 17, the shaft, and therefore the fastener 2, is moved axially such that the fastener 2 enters the workpiece 17. The load applied to the fastener 2 while it enters the workpiece 17 is at least 500 N. In some embodiments, the load applied to the fastener 2 while it enters the workpiece 17 is 20 kN or less. In some embodiments, the load applied to the fastener 2 while it enters the workpiece 17 is at least 2 kN. In some embodiments, the load applied to the fastener 2 while it enters the workpiece 17 is 15 kN or less. In some embodiments, the load applied to the fastener 2 while it enters the workpiece 17 is 10 kN or less. In some embodiments, the load applied to the fastener 2 while it enters the workpiece 17 is 5 kN or less. In some embodiments, the load applied to the fastener 2 while it enters the workpiece 17 is at least 1 kN. In some embodiments, the load applied to the fastener 2 while it penetrates the workpiece 17 is at least 3 kN. As the number of workpiece layers increases, a higher load may be required. In addition, the load used may be proportional to the hardness of the material from which the workpiece 17 is made. Other factors may be considered when determining the load applied to the fastener 2 during this stage of the fastener insertion process. This causes the fastener 2 to thread into the workpiece 17. FIG. 4 shows the insertion device 16 and fastener 2 while the tip 19 of the fastener 2 is in contact with the first surface 34 of the workpiece 17. The speed at which the shaft 22, and therefore the fastener 2, is moved axially is at least 0.5 mm / sec. Because the shaft 22 moves at a speed of at least 0.5 mm / sec, the possibility of overheating the workpiece during the fastener insertion process is reduced. This is to ensure that by moving the fastener 2 at this speed, the fastener insertion process is completed before the workpiece 17 overheats. Workpiece 17 may be considered overheated when the temperature of the workpiece exceeds the recrystallization temperature of the material from which the workpiece is made.In some embodiments, the shaft 22 can move axially at a rate of at least 1 mm / sec. In some embodiments, the shaft 22 can move axially at a rate of at least 2 mm / sec. The speed at which the shaft 22 moves axially may be determined at least in part by the ductility of the material from which the workpiece 17 is made. The speed at which the shaft 22 moves axially may be faster for more ductile workpiece materials. The speed at which the shaft 22 moves axially may be slower as the ductility of the material from which the workpiece 17 is made decreases. The speed at which the shaft 22 moves axially may also be determined at least in part by the amount of heat provided to the workpiece 17 by the fastener 2. The more heat provided to the workpiece 17 by the fastener, the faster the speed at which the shaft 22 moves axially.

[0201] In some embodiments, the speed at which the shaft 22 is moved axially while the fastener 2 is being screwed into the workpiece 17 may be reduced at least once. The reduction in speed may be such that the axial speed of the shaft 22 is non-zero after the reduction. The reduction in speed at which the shaft 22 is moved axially may be such that after the reduction, the axial speed of the shaft 22 is at least 50% of the speed of the shaft in this direction before the reduction. The reduction in speed at which the shaft 22 is moved axially may be such that after the reduction, the shaft moves axially a distance equal to or less than the pitch distance of the thread of the shank section 12 of the fastener 2 per revolution of the shaft. Advantageously, this reduces the possibility of the thread formed in the workpiece 17 by the fastener 2 being stripped. Stripped threads are undesirable, for example, as this may cause insufficient joint strength. The term "pitch distance" may be understood to refer to the distance between corresponding points of the thread of the shank section. If the rate at which the shaft 22 moves axially is such that the shaft moves axially a distance that is less than the pitch distance of the threads on the shank 12 of the fastener 2 per revolution of the shaft, the material of the workpiece 17 is preferably soft enough so that the threads reform in the workpiece with each revolution of the shaft 22, and therefore the fastener 2. A reduction in the axial speed of the shaft 22 may occur when the tip 19 of the fastener 2 is placed in the second workpiece layer 20. A reduction in the axial speed of the shaft 22 may occur when the tip 19 contacts the second workpiece layer 20. The position of the tip 19 may be determined, for example, by monitoring the position of the shaft 22 and determining the amount the shaft has moved axially.

[0202] As the fastener 2 is moved axially, the material of the workpiece 17 is deformed along the tip section 14 and shaft section 12 of the fastener 2. The material of the workpiece 17 is deformed into the threads of the shank section 12. Thus, threads are formed in the material of the workpiece 17 so that the fastener 2 is screwed into the workpiece 17. In addition, an opening (or hole) is formed in the workpiece 17 through which the fastener 2 is received. The axial movement of the shaft 22, and therefore the fastener 2, continues until the tip section 14 is disposed within the second workpiece layer 20. The axial movement of the shaft 22, and therefore the fastener 2, stops before the tip 19 of the fastener 2 penetrates the second surface 36 of the workpiece 17. Thus, when the fastener insertion process is completed, the tip 19 of the fastener 2 is disposed within the second workpiece layer 20 of the workpiece 17. Additionally, once the fastener insertion process is complete, the underside 15 of the head of the fastener 2 contacts the first surface 34 of the workpiece 17 .

[0203] In some embodiments, the speed at which the shaft 22 is rotated about its longitudinal axis, and therefore the speed at which the fastener 2 is rotated about its longitudinal axis, may be reduced at least once while the fastener 2 is being threaded into the workpiece 17. The reduction in the rotational speed may be such that the rotational speed of the shaft 22 is non-zero after the reduction. The reduction in the speed at which the shaft 22 rotates is such that the rotational speed of the shaft 22 after the reduction is at least 50% of the rotational speed of the shaft 22 before the reduction. In some embodiments, the reduction in the speed at which the shaft 22 rotates is such that the rotational speed of the shaft 22 after the reduction is at least 30% and / or no more than 70% of the rotational speed of the shaft 22 before the reduction. The reduction in the rotational speed of the shaft 22 may occur when the tip 19 of the fastener 2 is disposed in the second workpiece layer 20. The reduction in the rotational speed of the shaft may occur when the tip 19 contacts the second workpiece layer 20. The rotational speed of the shaft 22 after the reduction may be, for example, 300 rpm.

[0204] After the reduction in the rotational speed, the amount of heat supplied to the workpiece 17 is reduced relative to the amount of heat supplied to the workpiece 17 before the reduction. This also reduces the temperature of the material of the workpiece 17. As the temperature of the material of the workpiece 17 decreases, the torque required to rotate the shaft 22 at a constant or approximately constant rotational speed increases. In addition, the torque required to rotate the shaft 22 at a constant or approximately constant rotational speed increases when the lower surface 15 of the head 4 of the fastener 2 contacts the first surface 34 of the workpiece 17. The torque required to rotate the shaft 22 is monitored throughout the fastener insertion process. When the torque required to rotate the shaft 22 reaches a predetermined value, the shaft 22, and therefore the fastener 2, stops rotating. The predetermined torque value at which the shaft 22 stops rotating may be at least 3 Nm. The predetermined torque value at which the shaft 22 stops rotating may be no more than 30 Nm. The predetermined torque value at which the shaft stops rotating may be at least 10 Nm. The predetermined torque value at which shaft 22 stops rotating may be 20 Nm or less. The predetermined torque value at which shaft 22 stops rotating may be 10 Nm. The magnitude of the predetermined torque may be determined, for example, by the required connection strength and / or the material from which workpiece 17 is made.

[0205] FIG. 5 shows a joint 38 resulting from the process of inserting the fastener 2 into the workpiece 17. The head 4 of the fastener 2 is raised from the workpiece 17. In other words, the head 4 protrudes beyond the first surface 34 of the workpiece 17. In some embodiments, the head 4 may be flush with the workpiece. A head is flush with the workpiece 17 if the head 4 is approximately flush with the first surface 34 of the workpiece 17. The fastener 2 is removable from the joint 38. In some embodiments, the fastener 2 may not be removable. Whether the fastener 2 is removable from the joint 38 is determined by the function of the fastener in use. The bottom surface 15 of the head 4 of the fastener 2 engages the first surface 34 of the workpiece 17. The tip section 14 of the fastener 2 is disposed within the second workpiece layer 20. The tip section 14 does not penetrate the second surface 36 of the workpiece 17. Thus, tip section 14 of fastener 2 only partially penetrates second workpiece layer 20. As a result of the fastener insertion process, second workpiece layer 20 now includes a protrusion 40 because fastener 2 has displaced a volume of workpiece 17 material. Protrusion 40 extends from second surface 36 of workpiece 17. Tip 19 of fastener 2 is disposed within protrusion 40. No portion of tip section 14 of fastener 2 penetrates second surface 36 of workpiece 17.

[0206] Because the temperature of workpiece 17 does not exceed the recrystallization temperature of the material of workpiece 17 throughout the fastener insertion process, joint 38 comprises a thermo-mechanically affected zone (TMAZ). The thermo-mechanically affected zone is characterized by the material of workpiece 17 being subjected to both heating and mechanical shear during the fastener insertion process. The thermo-mechanically affected zone is located adjacent the interface between workpiece 17 and fastener 2.

[0207] The quality of the joint produced using the insertion process depends on the amount of heat provided to the workpiece 17 during the fastener insertion process. Underheating or overheating of the workpiece during the fastener insertion process can result in joint defects. Examples of such joint defects are improper engagement between the threads of the shank section 12 of the fastener 2 and the workpiece 17, or separation of the first workpiece layer 18 from the second workpiece 20. Separation between the first workpiece layer 18 and the second workpiece layer 20 is sometimes referred to as gap formation. Gap formation is undesirable because it allows environmental materials, such as water, to enter the joint and damage the joint. The amount of heat provided to the workpiece 17 during the fastener insertion process depends on the tip angle α of the tip section 14 of the fastener 2. The tip angle α of the fastener 2 in this embodiment can be optimized within a range of at least 50° to provide an optimized amount of heat to the workpiece 17. The optimum tip angle α depends at least on the ductility of the material of the workpiece 17, the hardness of the material of the workpiece 17, the speed at which the fastener is inserted during the fastener insertion process, and the speed at which the fastener is moved axially during the fastener insertion process. This reduces the likelihood of under- or over-heating the workpiece 17 during the fastener insertion process compared to fastener tip angles α outside the range of tip angles α of the present embodiment.

[0208] In some embodiments, the fastener insertion process may include applying an adhesive to the first and / or second workpiece layers 18, 20. The adhesive is applied to the first and / or second workpiece layers 18, 20 before the workpiece 17 is provided to the fastener insertion device 16. The adhesive may be applied as a liquid paste layer or a film layer. The adhesive is applied to the areas of the first workpiece layer 18 and the second workpiece layer 20 where the fastener 2 will be inserted. The first workpiece layer 18 and the second workpiece layer 20 are then engaged with one another. Once the first workpiece 18 and the second workpiece 20 are engaged with one another, the adhesive is disposed between the first workpiece layer 18 and the second workpiece 20. The fastener insertion process then continues as described above, with the fastener passing through the adhesive layer. If an adhesive is applied, the joint resulting from the fastener insertion process includes an adhesive layer disposed between the first workpiece layer and the second workpiece layer.

[0209] The fastener insertion device 16 does not require a die. If the fastener insertion device 16 does not include a die, the method of inserting the fastener 2 into the workpiece 17 may be single-sided or double-sided insertion. The absence of a die may be particularly useful, for example, when the workpiece 17 is a box section, or when the point in the workpiece where the fastener 2 is inserted is not accessible from both sides by the fastener insertion device. In these cases, single-sided insertion may be appropriate. However, a double-sided insertion method may also be used. The absence of a die may also be beneficial for thicker workpieces (e.g., workpieces having a total thickness of at least 6 mm). This is because a thicker workpiece can better accommodate the volume occupied by the fastener.

[0210] FIG. 24 illustrates the fastener insertion apparatus 16 without a die, in which the second surface of the workpiece (not shown) is supported on the lower arm 29 of a C-frame 35. Thus, the fastener insertion apparatus 16 of FIG. 24 allows for double-sided insertion of the fastener. FIG. 25 illustrates a detailed view of the lower arm 29 of the C-frame 35. The lower arm 29 of the C-frame 35 includes a die holder 37. A stem of a die (not shown) is receivable in the die holder 37. Double-sided insertion of the fastener can be performed with or without a die received in the die holder 37.

[0211] In some embodiments, a die may be provided during the fastener insertion process. Figure 6 shows a further embodiment of a joint 138 having a die 135. The die 135 forms part of a fastener insertion device (not shown) and may be provided, for example, on an opposite side of a C-clamp (or other clamp) from the punch of the fastener insertion device. The die is receivable in a die holder in the lower arm of the C-clamp.

[0212] The die 135 forms a die recess 137. The die recess 137 defines a die recess volume. The die recess 137 includes a base surface 139. The die recess 137 includes a sidewall 141. In the illustrated embodiment, the die recess 137 is generally cylindrical. In other embodiments, the die recess 137 may be any suitable shape. For example, the die recess may be frusto-conical.

[0213] During the fastener insertion process, the die 135 engages the second surface 136 of the workpiece 117. The die 135 engages the second surface of the workpiece 117 throughout the fastener insertion process. The die 135 contacts the second surface 136 of the workpiece 117 before the fastener 2 contacts the workpiece 117. As described above, when the fastener 2 is inserted into the workpiece 117, at least a portion of the material of the workpiece 117 is displaced. When the die 135 is provided, the displaced workpiece 117 material deforms into the die recess 137. The volume of the die recess 137 may be equal to or greater than the volume of the workpiece material displaced during the fastener insertion process.

[0214] FIG. 26 shows an alternative die 235. The die 235 is similar to the die 135. The die 235 differs from the die 135 in that the die recess 237 does not include a base surface. The die recess 237 includes side walls 241. Because the die recess 237 does not include a base surface, the deformation of the workpiece material in the direction in which the fastener is inserted into the workpiece is not limited compared to a die recess that includes a base surface. The deformation of the workpiece material is shaped by the side walls 241 of the die recess 237. The die can include a surface that is located at or toward the bottom end of the recess, which is spaced apart from the second surface of the workpiece in use. In this configuration, the second surface does not contact the base surface during the fastener insertion process.

[0215] FIG. 27 illustrates a further alternative die 335. The die 335 can be used with the fastener insertion apparatus 2 illustrated in FIGS. 2-4. The die 335 is in the form of a die table. The die table 335 includes a plurality of die recesses 337. When the die 335 is used to insert fasteners into a workpiece, a nosepiece of a fastener insertion apparatus (not shown) is positioned over one of the die recesses 337. The die 337 allows for multiple fasteners to be inserted into different locations of a workpiece without moving the workpiece (not shown). In some embodiments, the die recesses 337 of the die table can take the form of a continuous channel or groove that extends along the length or width of the die table.

[0216] In some embodiments, the fastener can include a plurality of surface irregularities. Figures 7a and 7b show such an embodiment of fastener 102. Similar numerals are used for fastener 102 as for fastener 2. In this embodiment, tip section 114 is shown as frustoconical. However, in other embodiments, the tip section may be conical. Because tip section 114 is frustoconical, tip 119 of the tip section forms a planar surface section.

[0217] 1 in that the tip section 114 of the fastener 102 includes a plurality of surface irregularities 142 (only one of which is labeled in FIG. 6). In the illustrated embodiment, the surface irregularities are in the form of facets 142. In the illustrated embodiment, the plurality of facets 142 includes six facets. However, in other embodiments, the plurality of facets 142 can include any suitable number of facets. In some embodiments, the plurality of facets 142 can include at least two facets. In some embodiments, the plurality of facets 142 can include at least four facets. In some embodiments, the plurality of facets 142 can include nine facets or less. In some embodiments, the plurality of facets 142 can include eight facets or less. The optimal number of facets in the plurality of facets 142 can be determined by, for example, the desired fastener insertion time (i.e., the time required to insert the fastener into a workpiece) and the material properties of the workpiece into which the fastener 102 is to be inserted. As the number of facets increases, the amount of heat provided to the workpiece during the fastener insertion process also increases. When the workpiece is made of aluminum, the optimal number of facets is preferably six. This is to minimize the possibility of the workpiece being overheated or underheated. The facets 142 are arranged in an array. Thus, the facets 142 are distributed around the longitudinal axis of the fastener 2. In the illustrated embodiment, the facets 142 are adjacent to one another. However, in other embodiments, the facets of the facets 142 may be spaced apart from one another. When the facets of the facets 142 are spaced apart from one another, a radiused surface section may be disposed between the facets. Each facet of the facets 142 is in the form of a planar surface section. However, in other embodiments, each facet of the facets 142 may be in the form of a radiused surface section.

[0218] FIG. 7b illustrates a cross-sectional side view of the fastener 102. The tip section 114 defines a tip section length TL. The tip section length TL extends along a direction parallel to the longitudinal axis L of the fastener 102. The shank section 112 defines a shank section length SL. The shank section length SL extends along a direction parallel to the longitudinal axis L of the fastener 102. The shank section length SL extends from the lower surface 115 of the head 104 to the tip section 114 of the fastener 102. The ratio of the shank section length SL to the tip section length TL is at least 2.5. In some embodiments, the ratio of the shank section length SL to the tip section length TL may be at least 3. In some embodiments, the ratio of the shank section length SL to the tip section length TL may be at least 3.5. In some embodiments, the ratio of the shank section length SL to the tip section length TL may be at least 2. The ratio of the shank section length SL to the tip section length TL can be determined, for example, by the required connection strength provided by the fastener 102 and / or the total thickness of the workpiece into which the fastener 102 is inserted. A larger ratio of the shank section length SL to the tip section length TL increases the connection strength by providing more threads to secure to the workpiece 17. The ratios of the shank section length to the tip section length disclosed herein may be applied to all embodiments of the fasteners disclosed herein.

[0219] Referring again to FIG. 7a, each facet of the plurality of facets 142 extends from the tip 119 toward the shank section 112. In particular, each facet of the plurality of facets 142 extends from the tip 119 to the shank section 112. However, in some embodiments, each facet of the plurality of facets 142 may not extend to the shank section 112, but may instead extend from the tip 119 toward the shank section 112. In this case, a surface section is disposed between the plurality of facets 142 and the shank section 112. Whether the plurality of facets 142 extend to the shank section 112 may be determined by the material from which the workpiece is made. The plurality of facets 142 that extend to the shank section 112 provide more heat to the workpiece compared to when the plurality of facets 142 do not extend to the shank section 112. The tip angle α of the fastener 102 varies about the longitudinal axis L of the fastener. The tip angle α of the fastener 102 is determined by the smallest angle between two diametrically opposed points on the tip section 112 .

[0220] As discussed above, the method of inserting fastener 2 applies to each of the fasteners disclosed herein, as discussed above. In use, the multiple facets advantageously reduce the likelihood of a workpiece becoming underheated during insertion of fastener 102 into the workpiece. The facets of multiple facets 142 increase the amount of friction between tip section 114 and the workpiece (compared to a rotationally symmetric tip section). This increased friction increases the amount of heat generated between the tip section and the workpiece, thereby reducing the likelihood of a workpiece becoming underheated while fastener 102 is being inserted. Because the likelihood of a workpiece becoming underheated during insertion of fastener 102 is reduced, the quality of joints made using fastener 102 is improved (compared to joints made using fasteners not having multiple facets).

[0221] In some embodiments, the surface irregularities may be in the form of ribs. Such an embodiment is shown in FIG. 28. The ribs 2142 provide the same advantages as the facets 142. The ribs 2142 include four ribs. However, in some embodiments, the ribs 2142 may include at least two ribs and / or up to six ribs. A portion of the length of each rib of the ribs 2142 extends radially (i.e., perpendicular to the longitudinal axis L of the fastener 2102). The ribs 2142 extend from the tip 2119 of the tip section 2114. A portion of the length of each rib of the ribs 2142 extends circumferentially (i.e., centered about the longitudinal axis L of the fastener 2102). The thickness and / or width of the ribs 2142 may be uniform or non-uniform. The thickness of the ribs 2142 may be understood to refer to the distance the ribs protrude from the surface of the tip section 2114. The thickness and / or width of the ribs 2142 may be smallest at or adjacent to the tip 2119 of the tip section 2114. The thickness and / or width of the ribs 2142 may be largest at or adjacent to the tip 2119 of the tip section 2114. In some embodiments, the multiple surface irregularities can include two or more facets and one or more ribs.

[0222] In some embodiments, the fastener may include a fixing point. In some embodiments, the fixing point is in the form of a stud. Preferably, when the fastener includes a stud, the fastener insertion device does not include a die. This is because when the fastener includes a stud, the point of the workpiece where the fastener is inserted is often not accessible to the die. However, the fastener insertion device may include a die when the fastener includes a stud. FIG. 8 illustrates an embodiment of a fastener 202 that includes a fixing point. For fastener 202, similar numbers are used as for fastener 2,102. Fastener 202 differs from fastener 2,102 in that fastener 202 further includes a stud 246. However, the tip angle of fastener 202 may correspond to the tip angle of fastener 2. Similarly, tip section 214 may include multiple facets.

[0223] The stud 246 extends from an upper surface 244 of the head 204 of the fastener 202. The upper surface 244 is opposite the lower surface 215 of the head 204. The stud 246 is threaded. The stud 246 is generally cylindrical. The stud 246 extends along a longitudinal axis L of the fastener 202. The stud 246 allows a component, such as an electrical contact, to be secured to the fastener 202. The stud 246 defines a diameter. The diameter of the stud 246 need not be the same as the diameter of the shank section 212. The diameter of the stud 246 may be at least 2 mm. The diameter of the stud 246 may be no greater than 10 mm. The diameter of the stud 246 may be at least 3 mm. The diameter of the stud 246 may be no greater than 8 mm. The diameter of the stud 246 may be no greater than 10 mm. The diameter of the stud 246 may be at least 3 mm. The diameter of the stud 246 may be 8 mm or less. The diameter of the stud 246 does not have to be an integer. For example, the diameter of the stud 246 may be 4.5 mm.

[0224] In some embodiments, the fastening point may be in the form of a loop extending from the top surface 244 of the fastener 202, for example.

[0225] 9 illustrates fastener 202 being inserted into workpiece 217, thereby forming joint 238. In the illustrated embodiment, workpiece 217 comprises a first workpiece layer 218. First workpiece layer 218 is the only workpiece layer of workpiece 217. However, in other embodiments, workpiece 217 may comprise multiple workpiece layers. Because first workpiece layer 218 is the only workpiece layer, first workpiece layer 218 comprises workpiece first surface 234 and workpiece second surface 236.

[0226] In some embodiments, the fastener may include a bore. Figure 10 illustrates such an embodiment of a fastener 302. Similar numbers are used for fastener 302 as for fasteners 2, 102, and 202. Although not shown, fastener 302 may also include a stud extending from a top surface 344 of head 304 of fastener 302.

[0227] The fastener 302 includes a bore 348. The bore 348 extends within the tip section 314 of the fastener 302. The bore 348 extends along a direction parallel to the longitudinal axis L of the fastener 302. The shank 310 defines a shank length ZL. The bore 348 defines a bore depth BD. A ratio of the bore depth BD to the shank length ZL may be at least 0.25. In other words, the bore 348 extends along at least 25% of the shank length ZL. The tip section 314 includes a ring leading edge 350. The shank length ZL extends from the lower surface 315 of the head 304 to the ring leading edge 350. The ring leading edge 350 may form a ring surface. In the illustrated embodiment, the ring leading edge 350 is planar. However, in some embodiments, the ring leading edge 350 may be non-planar. In such an embodiment, the ring leading edge 350 may be serrated. Having the ring leading edge 350 serrated reduces the possibility of underheating the workpiece during the fastener insertion process. The bore forms a bore surface 355. In some embodiments, the bore surface 355 may form a plurality of surface asperities. The surface asperities may be in the form of tabs, ribs, and / or protrusions, for example. When the bore surface 355 forms a plurality of surface asperities, the surface asperities interlock with the workpiece into which the fastener 302 is inserted, thereby improving the strength of the connection between the fastener 302 and the workpiece.

[0228] The tip angle α of the tip section 314 is at least 50°. Because the fastener 302 includes a bore 348 and thus the tip section 314 forms the ring leading edge 350, the initial contact area between the fastener 302 is greater for a constant tip angle than if the bore 348 were not present. This allows the tip angle α of the tip section 314 of the fastener 302 to be reduced compared to if the bore is not present, since the increased contact area increases the amount of heat delivered to the workpiece during use. Thus, if a bore is present, the fastener can perform well when the tip angle is at least 50°, for example, and if a bore is not present, the fastener can perform well when the tip angle is at least 70°, for example.

[0229] The bore 348 defines an inner bore diameter d. The ratio of the shank diameter to the inner bore diameter d may be at least 1.5. This preferably provides sufficient material in the shank section 312 to enable the fastener 302 to withstand the forces required in use. In some embodiments, the ratio of the shank diameter to the inner bore diameter d may be at least 2.

[0230] The ring leading edge 350 merges into the bore inner diameter d by a tapered surface section 352. The tapered surface section 352 comprises a chamfered surface section 354. The angle between diametrically opposed points of the chamfered surface section 354 is at least 25 degrees. The angle between diametrically opposed points of the chamfered surface section 354 is no greater than 45 degrees. The chamfered surface section 354 is adjacent to the ring leading edge 350. The tapered surface section 352 comprises a radiused surface section 356. The radiused surface section 356 is adjacent to the chamfered surface section 354. The radiused surface section 356 is adjacent to the bore inner diameter d. In some embodiments, the tapered surface section 352 may comprise only one of the chamfered surface section 354 and the radiused surface section 356. In some embodiments, the chamfered surface section 354 may be adjacent to the bore inner diameter d and the radiused surface section 356 may be adjacent to the ring leading edge 350. In some embodiments, the entire bore 348 may be cylindrical.

[0231] During the fastener insertion process, a volume of workpiece material is displaced by the fastener 304. The presence of the bore 348 preferably reduces the amount of workpiece material displaced during the fastener insertion process because the volume of workpiece material is received by the bore, thereby reducing the amount of workpiece material displaced by the fastener 302. Because the bore 348 extends along at least 25% of the shank length, the amount of material displaced by the fastener 302 during the fastener insertion process is sufficient such that the likelihood of workpiece layers separating is reduced. The tapered surface section 352 preferably facilitates the deformation of the workpiece material into the bore 348. The geometry of where the ring leading edge 350 meets the bore inner diameter preferably more evenly distributes the stresses experienced by the fastener 302, and particularly the shank 310, during the fastener insertion process.

[0232] The bore 348 defines a bore depth. The bore depth extends from the ring leading edge 350 towards the head 304 in a direction parallel to the longitudinal axis L of the fastener 302. The tapered surface section 352 defines a tapered surface section depth. The tapered surface section depth extends from the ring leading edge 350 towards the head 304 of the fastener 302 in a direction parallel to the longitudinal axis L of the fastener 302. The ratio of the tapered surface section depth to the bore depth is at least 0.1. In some embodiments, the ratio of the tapered surface section depth to the bore depth is preferably at least 0.2. A ratio of the tapered surface section depth to the bore depth of at least 0.2 provides a gradual transition between the ring leading edge 350 and the bore inner diameter d. This provides a more uniform stress distribution in the tip section 314 during the fastener insertion process, thereby reducing the possibility of defects occurring during the insertion of the fastener 302 into a workpiece. In some embodiments, the ratio of tapered surface section depth to bore depth may be at least 0.5.

[0233] In some embodiments, the fastener may not be removable from the workpiece into which it is inserted. Figure 11 illustrates such an embodiment of fastener 402. Similar numbers are used for fastener 402 as for fasteners 2, 102, 202, and 302. Fastener 402 may include a bore, a stud, multiple facets, and / or a tip angle according to previous embodiments described herein.

[0234] The shank section 412 includes a first threaded portion 458. The first threaded portion 458 is adjacent to the tip section 414. The shank section 412 includes a second threaded portion 460. The shank section 412 includes a flat portion 462. The flat portion 462 is sometimes referred to as a horizontal thread gap. The flat portion 462 is disposed between the first threaded portion 458 and the second threaded portion 460. FIG. 11 shows the fastener 402 being inserted into a workpiece 417, thereby forming a joint 438. The flat portion 462 separates the first threaded portion 458 and the second threaded portion 460 from one another. This prevents the fastener 402 from being removed from the workpiece 417 by rotating the fastener 402 in a direction opposite to the threads of the shank section 412. This is because the material of the workpiece 417 interferes with the second threaded portion 460 and prevents the fastener from turning. During the fastener insertion process, the material of the workpiece 417 softens due to the heat supplied to the material. The softening of the material of the workpiece 417 causes the material of the workpiece to deform along the first threaded portion 458 and the second threaded portion 460. In some embodiments, the pitch distance, thread angle, and / or diameter of the first threaded portion 458 may be equal to or greater than the pitch distance, thread angle, and / or diameter of the second threaded portion 460. In some embodiments, the pitch distance and / or diameter of the first threaded portion 458 may be equal to or less than the pitch distance and / or diameter of the second threaded portion 460.

[0235] In some embodiments, at least a portion of the shank section of the fastener shank is not threaded. FIG. 12 illustrates an embodiment of a fastener 502 as inserted into a workpiece 517, thereby forming a joint 538. Similar numbers are used for fastener 502 as for fasteners 2, 102, 202, 302, and 402. In this embodiment, the driver geometry 506 of the head 504 of fastener 502 is an internal driver geometry. However, driver geometry 506 may be an external driver geometry, etc. Fastener 502 may include any of the features disclosed in connection with the previous embodiments described herein.

[0236] The shank section 512 comprises a first shank portion 570. The shank section 512 comprises a second shank portion 572. The first shank portion 570 is adjacent to the head 504 of the fastener 502. The first shank portion 570 comprises the base section 511 of the shank section 512. The second shank portion 572 is adjacent to the first shank portion 570 and the tip section 514. The first shank portion 570 is unthreaded. The second shank portion 572 is threaded. Because only a portion of the shank section 510 is threaded, the force required to insert the fastener 502 into a workpiece is reduced compared to if the entire shank section was threaded. This is because the resistance to insertion of the fastener is reduced compared to if the entire shank section 510 was threaded (because there is less surface area in contact with the workpiece).

[0237] In some embodiments, the fastener may include one or more retention features that, in use, engage with a workpiece into which the fastener is inserted. FIG. 13 illustrates an embodiment of such a fastener 602. Similar numerals are used for the fastener 602 as in the previous embodiments of fasteners described herein. A first shank portion 670 of the fastener 602 is non-threaded. A second shank portion 672 is threaded. The first shank portion 670 includes a plurality of protrusions 674 (only one of which is labeled in FIG. 13). The plurality of protrusions 674 are arranged in an array. A plurality of cavities 675 are alternately disposed between the plurality of protrusions 674. The plurality of protrusions 674 includes six protrusions. However, in other embodiments, the plurality of protrusions may include any suitable number of protrusions. The plurality of protrusions 674 do not extend radially beyond the threads of the second shank portion 672. In some embodiments, the plurality of protrusions 674 may protrude radially beyond the threads of the second shank portion 674. In the illustrated embodiment, the protrusions of the plurality of protrusions 674 extend parallel to the longitudinal axis L of the fastener 602. In other embodiments, the protrusions of the plurality of protrusions may twist about the longitudinal axis L of the fastener 602. When the plurality of protrusions is twisted about the longitudinal axis L of the fastener 602, the protrusions of the plurality of protrusions 674 extend in a direction parallel to the longitudinal axis L of the fastener 602, centered about the longitudinal axis L of the fastener 602.

[0238] When inserted into a workpiece (not shown in FIG. 13 ), the material of the workpiece deforms along the plurality of protrusions 674 and into the cavities of the plurality of cavities 675. The material of the workpiece at least partially fills the cavities of the plurality of cavities 675. Thus, in use, the plurality of protrusions 674 engage the workpiece into which the fastener is inserted. Thus, rotation of the fastener 602 after insertion is prevented by the interaction between the plurality of protrusions 674 and the material of the workpiece. Thus, the plurality of protrusions 674 can be referred to as retention features. In some embodiments, only one protrusion need be provided. Thus, the fastener 602 comprises one or more retention features. In some embodiments, the one or more retention features may be in the form of a rib extending, for example, about or in a direction parallel to the longitudinal axis L of the fastener 602.

[0239] In some embodiments, the tip section of the fastener may form an undercut. Such an embodiment is shown in FIG. 14. Similar numerals are used for the fastener 702 as for the previous fasteners disclosed herein. FIG. 14 shows the fastener 702 being inserted into a workpiece 717, thereby creating a joint 738. The maximum diameter of the tip section 714 of the shank 710 is greater than the diameter of the shank section 712 of the shank 710. Thus, an undercut 776 is formed by the tip section 714. The undercut 776 is located adjacent the shank section 712. Due to the undercut 776, the amount of interference between the fastener 702 and the workpiece 717 is increased compared to when the undercut 776 is not provided. This increase in interference between the fastener 702 and the workpiece 717 increases the strength of the connection between the fastener 702 and the workpiece 717.

[0240] In some embodiments, the fastener may include a washer. Such an embodiment is shown in FIG. 15. Similar numerals are used for the fastener 802 as in the previous embodiments disclosed herein. The fastener 802 may include any of the features described with reference to the previous embodiments. The fastener 802 includes a washer 878. The washer 878 engages the underside 815 of the head 804 of the fastener 802. The provision of the washer 878 reduces the possibility of the fastener rotating during use (i.e., after the joint is formed). Rotation of the fastener 802 during use is undesirable as it may result in the fastener loosening. Thus, the provision of the washer 878 results in a more robust joint. The washer 878 may be configured such that, during use, the washer seals against the head 804 of the fastener 802 and the workpiece (not shown in FIG. 15). The seal may be a water-tight seal such that water or other liquids cannot pass under the head 804 of the fastener during use. The presence of water under the fastener head 804 is undesirable as it can lead to corrosion. The washer 878 may be made from aluminum. Forming the washer 878 from aluminum may be particularly preferred when the fastener 802 is formed from steel and the workpiece is formed from magnesium. Forming the washer 878 from aluminum prevents the formation of galvanic corrosion cells.

[0241] In some embodiments, the diameter of the shank of the fastener need not be uniform along the length of the shank. Such a fastener 902 is shown in FIG. 16. The fastener 902 uses similar numbers as the fasteners of the previous embodiment. FIG. 16 shows a fastener 902 being inserted into a workpiece 917, thereby creating a joint 938. The fastener 902 can include any of the features described with reference to the previous embodiment. In this embodiment, the diameter of the first shank portion 970 is larger than the diameter of the second shank portion 972. In other embodiments, the diameter of the second shank portion 972 can be larger than the diameter of the first shank portion 970. The geometry of the shank section 912 in this embodiment displaces less material of the workpiece 917 compared to a fastener having a constant diameter shank. Additionally, axial loads applied to the fastener 902 during the fastener insertion process can be reduced compared to a fastener having a constant diameter shank. This advantageously reduces the likelihood of the workpiece 917 cracking as a result of the fastener insertion process. Because the likelihood of the workpiece 917 cracking is reduced, the fastener 917 advantageously produces a more robust joint. Additionally, because less material is displaced by the fastener 917, there is reduced resistance to deformation by the workpiece 917 compared to a fastener having a constant diameter shank. Thus, if the axial load applied to the fastener 902 is equal to the axial load applied to a fastener having a constant diameter shank, the time it takes to insert the fastener into the workpiece 917 is reduced. Thus, this results in a more efficient fastener insertion process.

[0242] In some embodiments of the method of inserting fasteners, the method can include providing an opening in the first workpiece layer. This can be particularly suitable when the workpiece includes layers of different materials. In particular, when the workpiece layer or layers in which the opening or openings are provided are not easily shaped. When the workpiece includes one or more intermediate layers, the method can also include providing an opening in at least one or more intermediate layers. The method may include providing an opening in all of the intermediate layers. The openings provided in the first workpiece layer may be referred to as pre-holes. FIG. 17 shows a joint 1038 resulting from such a method. As can be seen, the first workpiece layer 1018 includes an opening 1090. The opening 1090 can be provided using any known method, such as machining. In this embodiment, the second workpiece layer 1020 includes the first surface 1034 of the workpiece 1017. The material from which the first workpiece layer 1018 is made may be, for example, a composite material. The material from which the first workpiece layer 1018 is made may also be any other low ductility material.

[0243] The shape of at least a portion of the aperture may correspond to the shape of the fastener. FIG. 29 illustrates an embodiment in which the shape of the aperture 1990 corresponds to the shape of the head 1904 of the fastener 1902. FIG. 30 also illustrates an embodiment in which the shape of the aperture 2090 corresponds to the shape of the head 2004 of the fastener 2002. In FIGS. 29 and 30, the shape of a portion of the aperture 1990, 2090 corresponds to the shape of the underside 1915, 2015 of the head 1904, 2004 of the respective fastener 1902, 2002. The aperture may be sized for the fastener to be inserted into the workpiece 1917, 2017. The size of the aperture 1990, 2090 for the fastener 1902, 2002 can be selected based on, for example, the material from which the workpiece 1917, 2017 is made. For example, a larger aperture can be used for a harder and / or stronger workpiece. In FIG. 29 , the size of the aperture 1990 corresponds to the size of the portion of the fastener 1902 that is received by the first workpiece layer 1918. That is, the ratio of the size of the aperture 1990 to the size of the portion of the fastener 1902 that is received by the first workpiece layer 1918 is 1:1. In FIG. 30 , the size of the aperture 2090 is 25% of the size of the portion of the fastener 2002 that is received by the first workpiece layer 2018. That is, the ratio of the size of the aperture 2090 to the size of the portion of the fastener 2002 that is received by the first workpiece layer 2018 is 1:4. In general, the ratio of the size of the aperture to the size of the portion of the fastener that is received by the first workpiece layer may be at least 1:4 and / or at most 1:1 and / or at most 2:1.

[0244] In some embodiments, when the method includes providing an opening in the first workpiece layer 1018, the method may further include centering the fastener 1002 relative to the opening 1090. Centering the fastener 1002 relative to the opening 1090 may be performed using a machine vision system. The machine vision system may form part of a fastener insertion device (not shown in FIG. 17). The machine vision system is configured to identify the opening 1090 and determine the center of the opening. This information is then provided to the fastener insertion device. The fastener insertion device then adjusts the position of the fastener 1002 such that the fastener is centered relative to the opening 1090. After centering the fastener 1002 relative to the opening 1090, the longitudinal axis L of the fastener is approximately coaxial with the central axis of the opening (not shown in FIG. 17). The central axis of the opening 1090 is an axis that extends along the center of the opening.

[0245] Centering the fastener 1002 relative to the aperture 1090 advantageously reduces the likelihood of the fastener contacting a surface of the aperture during the fastener insertion process. Contact between the fastener 1002 and a surface of the aperture is undesirable as it can result in an improperly inserted fastener. Centering the fastener 1002 results in a consistently formed joint.

[0246] The method of inserting the fasteners into the workpiece 1017 is otherwise the same as that described above. The provision of the openings 1090 allows for the use of fasteners to connect the first workpiece layer 1018 to the second workpiece layer 1020 when the first workpiece layer 1018 is made from a material that is not easily moldable.

[0247] In some embodiments, the drive shape of the fastener may be an internal drive shape. FIG. 18 shows a fastener 1102 in which the drive shape 1106 is an internal drive shape. This allows the fastener 1102 to be approximately flush with a first surface of the workpiece (not shown in FIG. 18) after insertion into the workpiece. The internal drive shape may be hexagonal or have some other suitable shape (the same applies to the external drive shape). Because the drive shape 1106 is an internal drive shape, the diameter of the head 1104 is reduced compared to a fastener with an external drive shape. This allows the fastener 1102 to be used in narrower workpieces (not shown in FIG. 18) compared to a fastener with an external drive shape without the head 1104 overhanging the workpiece. This drive shape and other internal drive shapes can be used in combination with other fastener embodiments.

[0248] In some embodiments, the fastener can include one or more retaining features. FIG. 19 illustrates a further embodiment of a fastener 1202 including one or more retaining features. In this embodiment, the one or more retaining features are in the form of a plurality of recesses 1292 (only one of which is labeled in FIG. 19). In some embodiments, only at least one recess need be provided. In the illustrated embodiment, the plurality of recesses 1292 includes four recesses. In other embodiments, the plurality of recesses 1292 may include any suitable number of recesses. For example, the plurality of recesses 1292 may include at least two recesses. In some embodiments, the plurality of recesses 1292 may include four or fewer recesses. In some embodiments, the plurality of recesses 1292 may include six or fewer recesses. The recesses 1292 extend into the shank section 1212 of the fastener 1202. The recesses 1292 extend toward the longitudinal axis L of the fastener 1202. The plurality of recesses 1292 extend in a direction parallel to the longitudinal axis L of the fastener 1202. In some embodiments, the plurality of recesses 1292 may extend at least partially around the longitudinal axis L of the fastener 1202.

[0249] The plurality of recesses 1292 extend along the entire length of the shank section 1212. In some embodiments, the plurality of recesses may extend partway along the shank section 1212. In some embodiments, the plurality of recesses 1292 may extend only along the first shank portion 1270. In some embodiments, the plurality of recesses 1292 may extend only along the second shank portion 1272. The plurality of recesses 1292 may be referred to as a vertical thread gap. Due to the plurality of recesses 1292, the fastener 1202 cannot be removed from the workpiece into which the fastener is inserted. This is due to interference between the plurality of recesses and the material of the workpiece.

[0250] In some embodiments, the fastener may include one or more secondary locking features. The one or more secondary locking features may be in the form of one or more surface irregularities. FIG. 20 illustrates an embodiment of a fastener 1302 that includes one or more secondary locking features. In the illustrated embodiment, the one or more secondary locking features are in the form of threads 1394 on the underside 1315 of the head 1304 of the fastener 1302. The direction of the threads 1394 is the same as the direction of the threads of the shank section 1312. In some embodiments, the direction of the threads 1394 may be opposite to the direction of the threads of the shank section 1312. In other embodiments, the one or more retention features may be in the form of any other type of surface irregularities, such as protrusions and / or ribs. When inserted into a workpiece (not shown in FIG. 20), the threads 1394 engage the workpiece, thereby further securing the fastener 1302 to the workpiece. The one or more secondary locking features preferably reduce the likelihood of the fastener 1302 loosening when subjected to vibration loads. Thus, one or more secondary fastening features preferably produce a more robust joint.

[0251] In some embodiments, if a die is provided during the fastener insertion process, the die may be a ring die. Such an embodiment is shown in FIG. 21. In FIG. 21, the fastener 702 is secured to the workpiece 1417. However, any of the fasteners described herein may be used in combination with a ring die. FIG. 21 shows a joint 1438 in combination with a ring die 1495. The ring die 1495 includes a cavity 1496. The ring die 1495 includes a protrusion 1497. The protrusion 1497 is ring-shaped and is provided as a lip around the cavity 1496. During the fastener insertion process, the protrusion 1497 forces material of the workpiece 1417 into the threads of the fastener 702. Additionally, if the fastener includes an undercut 776, the protrusion 1497 forces material of the workpiece 1417 into the undercut 776 of the fastener 702. Advantageously, this improves the engagement between the fastener 702 and the material of the workpiece 1417. The improved engagement between the fastener 702 and the material of the workpiece 1417 advantageously improves the strength of the connection between the fastener 702 and the workpiece 1417.

[0252] As mentioned above, in some embodiments, the tip section of the shank may be radiused. Such an embodiment is shown in FIG. 22. As can be seen, the tip section 1514 is radiused. The tip 1519 of the tip section 1514 is pointed. In some embodiments, the tip 1519 of the tip section 1514 may be radiused. The tip section 1514 defines a tip angle α. The tip angle α is the angle between a first tangent line T1 and a second tangent line T2. The first tangent line T1 and the second tangent line T2 extend through diametrically opposite points of the tip section 1514. The point through which the first tangent line T1 extends is co-located along the longitudinal axis L of the fastener 1502 as the point through which the second tangent line T2 extends. The position of the point where the first tangent line T1 extends and the position of the point where the second tangent line T2 extends are positions where the angle between the first tangent line T1 and the second tangent line T2 is at a maximum value.

[0253] As mentioned above, the fastener may be provided with a generally cylindrical bore. Such an embodiment is shown in FIG. 23. As can be seen, the bore 1648 of the fastener 1602 is generally cylindrical. The tip angle α of the tip section 1614 is the angle between diametrically opposed points of the tip section 1614. The tip angle α in FIG. 23 is measured between a first tangent line T1 and a second tangent line T2. The first tangent line T1 and the second tangent line T2 extend through diametrically opposed points of the tip section 1614.

[0254] FIG. 31 illustrates a further embodiment of the fastener 1802. The fastener 1802 includes a bore 1848. The bore 1848 is conical. In other non-illustrated embodiments, the bore 1848 may be frustoconical, cylindrical, or any other suitable shape. The ratio of the bore depth BD to the shank length ZL may be up to 0.25. That is, the bore depth BD may be up to 25% of the shank length ZL. In some embodiments, the bore depth may be up to 10% of the shank length ZL. The bore depth BD may be selected based on, for example, the hardness of the workpiece into which the fastener 1802 is inserted, the strength of the workpiece, and / or the thickness of the workpiece. A bore depth BD that is shallower compared to the shank length ZL may be particularly suitable for harder, stronger, and / or thinner workpieces. The provision of the bore provides a ring-shaped initial contact area between the fastener 1802 and the workpiece. This increases the speed at which portions of the fastener 1802 contact the workpiece as compared to a point contact area. By increasing this speed, more heat is delivered to the workpiece by the fastener 1802 and less time is taken to heat the workpiece.

[0255] In some embodiments, the fastener may be capable of removing excess or extruded workpiece material. When the fastener is inserted into the workpiece, the workpiece material may be extruded from the workpiece in a direction opposite to the fastener insertion direction. When extruded, the workpiece material is in a softened state, but not in a liquid state. This excess material is undesirable as it may be susceptible to corrosion and lead to joint failure. FIG. 32 shows an embodiment of a fastener 2202 capable of removing excess workpiece material. In this embodiment, the head 2204 of the fastener 2202 is provided with a number of cutting edges 2297 (only one of which is labeled in FIG. 32). In general, the cutting edge or edges do not need to be sharp, since the extruded material is softened as it is cut by the cutting edge or edges of the fastener. Each cutting edge 2297 forms part of a respective tooth 2298 (only one of which is labeled in FIG. 32). The teeth 2298 extend from a circumference 2299 of the head 2204. The plurality of teeth 2298 includes four teeth 2298, and thus four cutting edges 2297. However, in some embodiments, the head 2204 can include at least one tooth and / or up to six teeth, each tooth being provided with a respective cutting edge. FIG. 33 illustrates an alternative embodiment of a fastener 2302 including a plurality of cutting edges 2397. Each of the cutting edges 2397 forms a portion of a respective rib of a plurality of ribs 2398. The ribs 2398 are provided on a lower surface 2315 of the head 2304. The plurality of ribs 2398 includes five ribs, and thus five cutting edges 2397 are provided. However, in some embodiments, the head 2304 can include at least one rib and / or up to six ribs, each rib being provided with a respective cutting edge. The number of teeth 2298 or ribs 2398, and therefore the number of cutting edges 2297, 2397, can be selected based on, for example, the hardness of the material of the workpiece into which the fastener 2202 is inserted.

[0256] If cutting edges 2297, 2397 are present, which may be the case for any of the embodiments disclosed herein, the method of inserting a fastener into a workpiece may further include using one or more cutting edges to cut extruded or excess material from the workpiece. Cutting of excess workpiece material may occur after the fastener is threaded into the workpiece. However, it is not necessary for the threads to be fully formed before cutting of excess workpiece material begins.

[0257] In FIG. 33 , the ribs of the plurality of ribs 2398 are provided with a radius. The ribs of the plurality of ribs are generally rounded. The ribs 2398 can cut through the extruded material from the workpiece during the fastener insertion process as the extruded material softens. In some non-illustrated embodiments, each of the ribs of the plurality of ribs 2398 can define a respective apex. If provided, the apex forms a cutting edge for each rib.

[0258] In some embodiments, the nosepiece of an insertion device used to insert any of the above fasteners may be capable of removing excess workpiece material. FIG. 34 illustrates an embodiment of such a nosepiece 2426. The nose includes a plurality of cutting edges 2497 (only one of which is visible in FIG. 34). The plurality of cutting edges 2497 includes two cutting edges. The two cutting edges are diametrically opposite one another. In some embodiments, the nosepiece 2426 can include at least one cutting edge and / or up to four cutting edges.

[0259] Although a number of specific embodiments of the present invention have been described above, features of each embodiment may be combined. For example, a fastener may comprise a bore for fastener 302 and a stud for fastener 202. FIG. 35 illustrates an embodiment of a fastener 1702 that combines features of the above-mentioned embodiments. Fastener 1702 comprises a first threaded portion 1658 and a second threaded portion 1760. Fastener 1702 further comprises a retention feature in the form of a number of protrusions 1774. The number of protrusions are disposed between first threaded portion 1558 and second threaded portion 1760. The pitch distance of the threads of first threaded portion 1758 is less than the pitch distance of the threads of second threaded portion 1760.

[0260] While specific embodiments of the invention have been described above, it will be appreciated that the invention may be practiced otherwise than as described. The above description is intended to be illustrative and not limiting. Thus, it will be apparent to one skilled in the art that modifications may be made to the invention as described without departing from the scope of the claims set out below.

Claims

1. a head and a shank defining a longitudinal axis, the shank comprising a shank section and a tip section, the shank section extending from the head and the tip section extending from the shank section opposite the head; At least a portion of the shank section is threaded; the tip section is at least partially tapered and defines a tip angle, the tip angle being at least 50 degrees. Thread forming and hole forming fasteners.

2. 2. The thread forming and hole forming fastener of claim 1, wherein said tip angle is at least 70 degrees.

3. 3. The thread forming and hole forming fastener of claim 1 or 2, wherein the tip section defines a tip section length, the shank section defines a shank section diameter, a ratio of the tip section length to the shank section diameter is less than or equal to 0.

6.

4. The thread forming and hole forming fastener of any one of claims 1 to 3, wherein the tip angle is 160 degrees or less.

5. The thread forming and hole forming fastener of any one of claims 1 to 4, wherein the tip angle is at least 125 degrees and no more than 135 degrees.

6. 6. The thread forming and hole forming fastener of any one of claims 1 to 5, wherein the shank section comprises a first shank portion adjacent the head and a second shank portion adjacent the tip section.

7. 7. The thread forming and hole forming fastener of claim 6, wherein said first shank portion is unthreaded and said second shank portion is threaded.

8. 8. The thread-forming and hole-forming fastener of claim 6 or 7, wherein the first shank portion includes one or more retention features, which, in use, engage a workpiece into which the thread-forming and hole-forming fastener is inserted.

9. A thread-forming and hole-forming fastener according to any one of claims 6 to 8, wherein the diameter of the first shank portion is greater than the diameter of the second shank portion.

10. A thread-forming and hole-forming fastener according to any one of claims 1 to 9, wherein the head forms an undercut.

11. The thread-forming and hole-forming fastener of any one of claims 1 to 10, further comprising a threaded stud extending from a side opposite the underside of the head.

12. The thread-forming and hole-forming fastener of any one of claims 1 to 11, wherein the tip section forms an undercut disposed adjacent the shank section.

13. The thread-forming and hole-forming fastener according to any one of the preceding claims, wherein the pitch diameter of the threads of the shank section is constant along at least 90% of the length of the shank section.

14. 1. A method of inserting a fastener into a workpiece, comprising: Providing a fastener according to any one of claims 1 to 13; providing a workpiece having a first surface and a second surface, the second surface being opposite the first surface; rotating the fastener about a longitudinal axis of the fastener and contacting the fastener with the first surface of the workpiece to heat the workpiece; threading the fastener into the workpiece by moving the fastener and the workpiece relative to one another in a direction parallel to the longitudinal axis of the fastener such that the tip section of the fastener penetrates the first surface; Including, The method, wherein the fastener does not penetrate the second surface of the workpiece.

15. 15. The method of claim 14, wherein threading the fastener into the workpiece comprises forming a thread in the workpiece with the fastener.

16. 16. The method of claim 14 or 15, further comprising the step of providing a die, wherein the second surface engages the die while the fastener is being threaded into the workpiece.

17. 17. The method of claim 16, wherein the die includes a die recess, and the second surface of the workpiece deforms into the die recess while the fastener is threaded into the workpiece.

18. 20. The method of claim 17, wherein the die recess defines a die recess volume, a volume of workpiece material is displaced while the fastener is threaded into the workpiece, and the die volume is greater than or equal to a volume of the displaced workpiece material.

19. The method of any one of claims 14 to 18, wherein the workpiece comprises a single workpiece layer.

20. The method of any one of claims 14 to 18, wherein the workpiece comprises a first layer and a second layer.

21. 21. The method of claim 20, wherein at least one of the layers of the workpiece is made from a metallic material, optionally wherein at least one of the layers of the workpiece is made from aluminum.

22. 22. The method of claim 20 or 21, wherein the first workpiece layer includes an opening through which the fastener passes before contacting the workpiece.

23. The method of claim 22 , wherein the first workpiece layer is formed of a composite material.

24. 24. The method of any one of claims 14 to 23, wherein the fastener further comprises a threaded stud extending from the head side of the shank opposite the shank section, the method further comprising the step of fastening a component to the threaded stud.

25. A method according to any one of claims 14 to 24, wherein the speed at which the fastener is rotated relative to the workpiece is reduced at least once while the fastener is being threaded into the workpiece.

26. 26. The method of claim 25 when dependent on claim 20, wherein reducing the speed at which the fastener is rotated relative to the workpiece occurs while the tip section is positioned within the second workpiece layer.

27. 27. The method of any one of claims 14 to 26, wherein the second surface of the workpiece comprises a protrusion into which at least a portion of the tip section of the shank of the fastener is received after the fastener is threaded into the workpiece.

28. a workpiece having a first surface and a second surface; A fastener according to any one of claims 1 to 13. wherein the fastener penetrates the first surface and does not penetrate the second surface.

29. 30. The joint of claim 28, wherein the workpiece comprises a first workpiece layer having the first surface and a second workpiece layer having the second surface.

30. 30. The joint of claim 29, wherein the first workpiece layer includes an opening through which the thread-forming and hole-forming fastener passes.

31. 31. The joint of claim 29 or 30, wherein the first workpiece layer is formed of a composite material.

32. 30. The joint of claim 28, wherein the workpiece comprises a single workpiece layer.

33. A joint as claimed in any one of claims 28 to 32, wherein the thread-forming and hole-forming fastener further comprises a threaded stud extending from a side of the head opposite the shank section.

34. A joint according to any one of claims 28 to 33, wherein at least one of the workpiece layers is made from a metallic material, optionally at least one of the workpiece layers is made from aluminium.

35. 35. The joint of any one of claims 28 to 34, wherein the heads of the thread-forming and hole-forming fasteners are positioned raised from the workpieces or the heads of the thread-forming and hole-forming fasteners are positioned substantially flush with the workpieces.

36. A joint as claimed in any one of claims 28 to 34, wherein the second surface comprises a protrusion into which the tip section of the fastener is at least partially received.

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