Patent Description:
The present disclosure relates generally to the field of permanent mechanical fasteners. More specifically, the present disclosure relates to rivets, which are traditionally used to fasten together two or more metal plates. These include blind rivets applied from one side of a stack of workpieces being joined as well as standard rivets whose installation require access to both sides of the stack of workpieces.

<CIT> discloses a bimetal blind rivet, the head of which rivet is made of a more ductile metal than the rest of the rivet.

JPH0375344A discloses a method of manufacturing a connecting member which is easy to machine and has high strength.

<CIT> discloses a tamper resistant fastener that has a head portion and a bulk-solidifying interlock portion wherein the fastener and the substrate into which the fastener is fitted are permanently fastened via an interlock formed from the interlock portion during the fastening process.

<CIT> discloses a rivet or bolt having a head and a shank portion characterized by a circumferential coating of a ferromagnetic material around a portion of the rivet.

<CIT> discloses a blind river and a rivet mandrel that is connected or can be connected to the tool and is intended for setting the blind rivet. The rivet mandrel can be connected to a designated part of the blind rivet using a rivet setting tool.

One embodiment of the invention relates to a bucked-type rivet assembly according to claim <NUM>. The bucked-type rivet assembly includes a formable member made from an amorphous metal alloy. An anvil configured to facilitate installation of the formable member is at least partially disposed in a channel through the formable member. The anvil includes an interface shaft and an anvil head disposed on a first end of the interface shaft. The formable member is configured to secure a first member in position relative to a second member. The anvil head is configured to plastically deform the formable member proximate to the second member. The anvil head is further configured to separate from the interface shaft upon application of a predetermined tensile force to the interface shaft.

In some embodiments, the bucked-type rivet assembly may form an electrical circuit that includes at least one of the anvil and the formable member.

In some embodiments, the formable member may be heated by exciting the anvil ultrasonically or spinning the anvil rapidly across one or more surfaces of the formable member.

Another embodiment of the invention relates to a method of installation for a bucked-type rivet as per claim <NUM>. Further aspects of the invention are provided in dependent claims <NUM> to <NUM> and <NUM> to <NUM>.

This summary is illustrative only and is not intended to be in any way limiting. Other aspects, inventive features, and advantages of the devices and/or processes described herein, as defined solely by the claims, will become apparent in the detailed description set forth herein, taken in conjunction with the accompanying figures, wherein like reference numerals refer to like elements.

Traditionally, rivets are made from materials that are harder than those being joined. However, the growing use of high-strength alloys has made finding a suitable rivet material problematic. Many of the failure modes typically associated with riveted joints, including excessive tensile stresses, shear stresses, and pull out of the rivet from the joint, may be addressed with improved material properties of the rivet and also better contact force mechanics between the rivet and workpieces being joined.

Referring generally to the figures, a family of rivets is provided. The rivets are made at least partially from an amorphous metal alloy such as bulk metallic glass (BMG). Two types of rivets are provided, including elastic brad-type rivets (e.g., a blind rivet inserted from one side of a stack of workpieces being joined) and standard or bucked-type rivets, which are secured in position by plastically deforming at least one end of the rivet. The design of the elastic brad-type rivets leverages the unique properties of BMG, a material that is able to accommodate large amounts of elastic deformation, to secure together two or more workpieces (e.g., metal plates). The elastic brad-type rivets may be mechanically compressed and inserted through a joining hole in the workpieces. A set of barb-like features on a tail end of each of the brad-type rivets deploys near an outer edge of the joining hole, which locks the rivet in place. Elastic deformation of the tail end of each brad-type rivet results in a tensile force that locks the workpieces together.

Each rivet in a family of bucked-type rivets disclosed herein is secured in place by thermoplastically deforming a portion of the rivet, either on one or both sides of a stack of workpieces. Accordingly, installation procedures generally require access to both sides of the stack of workpieces being joined. A riveting tool or other applicator device is used to facilitate installation of each of the bucked-type rivets. For example, the riveting tool may generate an electrical current through the BMG to rapidly heat the BMG while simultaneously applying a force or pressure to thermoplastically deform a portion of the rivet. This particular bucked-type rivet design lends itself to use with a gas or liquid delivery system to quickly cool the rivet after the forming process is complete.

The riveting tool may interface with a sacrificial piece of material or anvil through which the force is transmitted to the bucked-type rivet. As an alternative to heating the material using an electrical current, the riveting tool may heat the material by spinning the anvil rapidly across the surface of the rivet, applying ultrasonic energy to the anvil, or otherwise mechanically exciting the anvil. The details of the general depictions provided above will be more fully explained by reference to <FIG>.

Referring now to <FIG>, a blind rivet, shown as brad rivet <NUM>, is provided. The brad rivet <NUM> is a permanent mechanical fastener configured to secure two or more workpieces in position relative to one another. There are a wide variety of potential applications for the brad rivet <NUM>. In one embodiment, the brad rivet <NUM> is used to secure a series of metal plates together for the hull of a ship. In other embodiments, the brad rivet <NUM> is used to secure thin aluminum plates together in the construction of an aircraft cockpit and fuselage. The brad rivet <NUM> provides a viable alternative to welding and bolting, particularly for projects where the final weight of the bonded workpieces is a key consideration.

In an illustrative embodiment, the brad rivet <NUM> is configured to secure two workpieces (e.g., steel or aluminum plates, etc.) together in a stack, shown as stack <NUM>. In alternative embodiments, the number of workpieces being joined may be greater. The stack <NUM> includes a first member, shown as first metal plate <NUM> and a second member, shown as second metal plate <NUM>, that are arranged in direct contact with one another. The thickness of each metal plate may vary depending on structural requirements. In the embodiment of <FIG>, the metal plates <NUM>, <NUM> are approximately equal in thickness. As shown in <FIG>, the brad rivet <NUM> is inserted through an aperture <NUM> that extends through each of the first metal plate <NUM> and the second metal plate <NUM>. In the embodiment of <FIG>, the aperture <NUM> includes a first aperture <NUM> disposed in the first metal plate <NUM> and a second aperture <NUM> disposed in the second metal plate <NUM>. Both the first aperture <NUM> and the second aperture <NUM> are circular holes. The first aperture <NUM> has a diameter that is greater than the second aperture <NUM> to accommodate a sleeve <NUM> for the brad rivet <NUM>. In other embodiments, the size and shape of each of the first aperture <NUM> and the second aperture <NUM> may be different.

A variety of suitable amorphous metal alloys may be used for the brad rivet <NUM>. In particular, amorphous metal alloys including BMG alloys and/or crystalline metals characterized by a very large elastic limit and a high tensile strength may be used. Advantageously, BMG alloys with a large elastic limit (the upper range of strain an elastic material can handle before failure) enable the brad rivet <NUM> to be compressed into smaller apertures and deploy into a larger state for maximum gripping/clamping/holding power. A suitable BMG alloy may have an elastic limit of about <NUM>% strain or greater, which is about four times higher than typical crystalline metals. Among various alternatives, the amorphous metal alloy may comprise a zirconium-based BMG alloy or a nickel-based BMG alloy, both of which have a low manufacturing cost. Alternatively, or in addition, it may be desired to have a material with improved fatigue life to avoid failure of the brad rivet <NUM> due to vibration or stress corrosion in atmospheric or more corrosive environments such as seawater.

In the illustrative embodiment shown in <FIG>, the brad rivet <NUM> includes a head portion, shown as head <NUM>, and a tail portion, shown as tail <NUM>, disposed at an opposite end of the brad rivet <NUM>. The brad rivet <NUM> further includes a shaft, shown as cylindrical extension <NUM>, disposed between the head <NUM> and the tail <NUM>. As shown in <FIG>, the head <NUM> of the brad rivet <NUM> is formed in a domed shape having a planar lower surface, shown at flat lower surface <NUM>, that is arranged in contact with an outer surface <NUM> of the first metal plate <NUM>. In other embodiments, the shape of the head <NUM> may be different. For example, the head <NUM> could be in the shape of a rectangle with uniform cross-section. Alternatively, the head <NUM> could be circular with uniform cross-section or any other shape that suitably interfaces with the first metal plate <NUM> and prevents the brad rivet <NUM> from passing through the first aperture <NUM>.

As shown in <FIG>, the tail <NUM> of the brad rivet <NUM> includes two legs, a first leg <NUM> and a second leg <NUM>, which are curved away from one another (e.g., peeled back toward the head <NUM> of the brad rivet <NUM>). In the embodiment of <FIG>, the first and second legs <NUM>, <NUM> are in a shape formed by splitting the cylindrical extension <NUM> along a plane oriented parallel to a longitudinal axis <NUM> of the brad rivet <NUM>, resulting in legs <NUM>, <NUM> that each have a substantially semi-circular cross-sectional shape. Other embodiments may include more legs, each having a similar cross-sectional area. Alternatively one or more legs may be larger or smaller than the other legs.

According to an illustrative embodiment, each of the first leg <NUM> and the second leg <NUM> include a tail interface, shown as barb <NUM>, configured to engage with the second metal plate <NUM>. Once installed, the barb <NUM> prevents the brad rivet <NUM> from being removed from either the first or second apertures <NUM>, <NUM>. The barb <NUM> is a small projection that extends outward and away from the longitudinal axis <NUM> of the brad rivet <NUM>. For example, the barb may be a sharp point, a ridge configured to dig into a material, a hook shaped extension configured to grab or lock onto an outer edge of a material, or any combination thereof. During installation, the first and second legs <NUM>, <NUM> are held proximate to one another in compression by at least one of the first aperture <NUM> and the second aperture <NUM>. Once the brad rivet <NUM> is inserted past a predetermined point, the first leg <NUM> and the second leg <NUM> deploy (e.g., separate away from one another), latching onto the second metal plate <NUM> at a location that is proximate to an outer edge <NUM> of the second aperture <NUM> (e.g., at a location that is just beyond the outer edge <NUM> or at another anchoring point along an interior surface of the second aperture <NUM>). In the embodiment shown in <FIG>, a separation distance <NUM> between the first leg <NUM> and the second leg <NUM> increases as the head <NUM> of the brad rivet <NUM> moves closer to the outer surface <NUM> of the first metal plate <NUM>.

The brad rivet <NUM> takes advantage of the high elastic limit of BMG in a geometry that can be compressed, inserted through the joining aperture, and secured in position by nature of the resulting forces on the brad rivet <NUM>. The brad rivet is shown in an installed position in <FIG>. In the embodiment of <FIG>, elastic tensile forces generated in the rivet are configured to secure the first member in position relative to the second member. The separation of the first and second legs <NUM>, <NUM> beyond the outer surface of the second metal plate <NUM>, generates a tensile force on the brad rivet <NUM>. This tensile force acts to prevent the first metal plate <NUM> and the second metal plate <NUM> from separating from one another and from separating from the head <NUM> of the brad rivet <NUM>. Although the compressive force acting on the first and second legs <NUM>, <NUM> is reduced when the brad rivet <NUM> is fully installed, there remains an amount of compression that maintains the legs <NUM>, <NUM> in solid contact with the second metal plate <NUM>, even when stresses or vibrations are applied to the joined workpieces.

Advantageously, installation of the brad rivet <NUM> requires access to only one side of the stack <NUM>. In an illustrative embodiment, the brad rivet <NUM> is inserted into the first aperture <NUM> by compressing each of the first leg <NUM> and the second leg <NUM> toward one another (e.g., toward the longitudinal axis <NUM> of the brad rivet <NUM>), thereby reducing the separation distance <NUM> between the first and second legs <NUM>, <NUM> such that an outer diameter of the tail <NUM> is less than an inner diameter of the second aperture <NUM>. There are a variety of tools that may be used to compress the first and second legs <NUM>, <NUM>. In the embodiment of <FIG>, a compressive force is applied by placing a sleeve <NUM>, <NUM> around the tail <NUM>, <NUM> of the brad rivet <NUM>. The sleeve <NUM>, <NUM> is a device configured to position the legs <NUM>, <NUM>, <NUM>, <NUM> before installation of brad rivet <NUM>, <NUM>. For example, the sleeve may be any one of a hollow cylinder, a removable C-clip or clasp, or a combination thereof. The sleeve <NUM>, <NUM> in <FIG> takes the form of a short hollow cylinder. As shown in <FIG>, before inserting the brad rivet <NUM> into the first aperture <NUM>, the sleeve <NUM> is centered on the barbs <NUM> such that the barbs <NUM> contact an inner surface <NUM> of the sleeve <NUM>. Alternatively, the sleeve <NUM> may be disposed on a portion of the tail <NUM> just above the barbs <NUM>, in which case the barbed portion of the tail <NUM> may be used to help center the brad rivet <NUM> with respect to at least one of the first aperture <NUM> and the second aperture <NUM> prior to installation.

As shown in <FIG>, the sleeve <NUM> of the brad rivet <NUM> is configured to facilitate installation of the brad rivet <NUM>. In the embodiment of <FIG>, a diameter of the first aperture <NUM>, shown as first aperture diameter <NUM>, is greater than a diameter of the second aperture <NUM>, shown as second aperture diameter <NUM>. The sleeve <NUM> is configured to engage with the first aperture <NUM>. Additionally, the sleeve <NUM> aligns the brad rivet <NUM> with the center of the first aperture <NUM>. In an illustrative embodiment, a height of the sleeve <NUM> may be less than or equal to a thickness of the first metal plate <NUM> so that the sleeve <NUM> may be fully inserted into the first aperture <NUM>. In other embodiments, the height of the sleeve <NUM> is greater than the thickness of the first metal plate <NUM> and is engageable with both the first aperture <NUM> and a slot <NUM> in the second metal plate <NUM> (thereby aligning the brad rivet <NUM> with the center of the second aperture <NUM>). In yet other embodiments, the brad rivet <NUM> is installed without a sleeve <NUM>. For example, the first aperture diameter <NUM> may be sized to receive a curved edge <NUM> of the barbs <NUM>, the curved edge <NUM> configured to guide each of the first leg <NUM> and the second leg <NUM> together toward the longitudinal axis <NUM> of the brad rivet <NUM> as the tail <NUM> enters the first aperture <NUM>.

In an illustrative embodiment, a driving tool (e.g., a hammer or other driving tool configured to force the tail <NUM> of the brad rivet <NUM> into the second aperture <NUM>) is used to secure the brad rivet <NUM> in position relative to the metal plates <NUM>, <NUM>. A method of installation for the brad rivet <NUM> includes inserting the sleeve <NUM> into the first aperture <NUM> and using the driving tool to force the tail <NUM> of the brad rivet <NUM> out of the sleeve <NUM> and into the second aperture <NUM> (e.g., by repeatedly contacting the head <NUM> of the brad rivet <NUM> with the driving tool). During installation, the sleeve <NUM> remains fixed in position relative to the metal plates <NUM>, <NUM>. Installation of the brad rivet <NUM> is complete once the flat lower surface <NUM> of the head <NUM> contacts the first metal plate <NUM>.

In an illustrative embodiment (not shown), at least one of the first aperture diameter <NUM> and the second aperture diameter <NUM> may be larger than an outer diameter of the cylindrical extension <NUM> between the head <NUM> and the tail <NUM> of the brad rivet <NUM>. This additional space (e.g., a small annular gap between the brad rivet <NUM> and the workpieces being joined) is at least partially accommodated by the large amount of elastic displacement of the first and second legs <NUM>, <NUM> of the brad rivet <NUM>.

<FIG> show an illustrative embodiment of a brad rivet <NUM> including a head portion, shown as head <NUM>, that is configured to deform elastically. As shown in <FIG>, the head <NUM> of the brad rivet <NUM> is formed in a domed shape having a planar lower surface, shown as flat lower surface <NUM>. The brad rivet <NUM> includes a pair of legs, a first leg <NUM>, and a second leg <NUM>, disposed on a tail portion, shown as tail <NUM>, of the brad rivet <NUM>. Prior to installation, as shown in <FIG>, each of the first leg <NUM> and the second leg <NUM> are compressed together toward a longitudinal axis for the brad rivet <NUM> by a sleeve <NUM>.

The methods used for the installation of the brad rivet <NUM> of <FIG> may also be used for the installation of the brad rivet <NUM> of <FIG> shows the same brad rivet <NUM> as <FIG>, after joining the first metal plate <NUM> and the second metal plate <NUM>. As shown in <FIG>, the first leg <NUM> and second leg <NUM> are deployed (e.g., separated from one another) beyond an outer edge <NUM> of the second aperture <NUM>. The first leg <NUM> and the second leg <NUM> contact the outer edge <NUM> of the second aperture <NUM>, preventing the brad rivet <NUM> from being pulled back through the second aperture <NUM>.

In the embodiments of <FIG>, a portion of the elastic tensile force generated within the brad rivet <NUM> results from deformation of the head <NUM>. During installation of the brad rivet <NUM>, as shown in <FIG>, a portion of the head <NUM> deforms elastically, resulting in recessed portion, shown as dimple <NUM>, in the head <NUM>. As the head <NUM> returns to its original geometry (shown in <FIG>), the metal plates <NUM>, <NUM> are brought together by the elastic tensile forces generated in the brad rivet <NUM>. In other words, the combined deformation of the head <NUM> and the first and second legs <NUM>, <NUM> generates an elastic tensile force within the brad rivet <NUM> that compresses the metal plates <NUM>, <NUM> together between the head <NUM> and the tail <NUM>.

Yet another illustrative embodiment of a brad rivet <NUM> is shown in <FIG>. As shown in <FIG>, the brad rivet <NUM> includes a head <NUM> and a tail <NUM>, each including a set of deformable legs. A first leg <NUM> and a second leg <NUM> are disposed proximate to the tail <NUM> of the brad rivet <NUM>, while a third leg <NUM> and a fourth leg <NUM> are disposed proximate to the head <NUM>. Like the brad rivets <NUM>, <NUM> of <FIG>, each of the legs <NUM>, <NUM>, <NUM>, <NUM> includes an interface feature configured to engage with the second metal plate <NUM>. Each of the first leg <NUM> and the second leg <NUM> of the brad rivet <NUM> includes a tail interface, shown as tail barb <NUM>, while each leg <NUM>, <NUM> on the head <NUM> of the brad rivet <NUM> includes a head interface, shown as head barb <NUM>. The brad rivet <NUM> also includes a pulling member, shown as breakstem <NUM> (see <FIG>), centered between the third leg <NUM> and the fourth leg <NUM>. As shown in <FIG>, the breakstem <NUM> extends away from the tail <NUM> of the brad rivet <NUM> along a longitudinal axis <NUM> of the brad rivet <NUM>.

The breakstem <NUM> is configured to engage with an applicator device to facilitate installation of the brad rivet <NUM>. A method of installing the brad rivet <NUM> includes engaging each of the tail barbs <NUM> with the second metal plate <NUM> proximate to the outer edge <NUM> of the second metal plate <NUM>. This may be accomplished by first securing a sleeve (not shown) along the length of the brad rivet <NUM>, the sleeve configured to compress the each of the legs <NUM>, <NUM>, <NUM>, <NUM> toward the longitudinal axis <NUM> of the brad rivet <NUM>. In an illustrative embodiment, the sleeve <NUM> is a hollow cylinder that extends along the entire length of the brad rivet <NUM> (e.g., the sleeve oriented such that a central axis of the sleeve is substantially parallel to the longitudinal axis <NUM>). In an illustrative embodiment, the inner diameter of the sleeve is approximately the same as the first and second aperture diameters <NUM>, <NUM>. The method includes centering the central axis of the sleeve <NUM> with respect to a central axis of the first aperture <NUM> and ejecting the brad rivet <NUM> from the sleeve <NUM> directly into the first and second aperture <NUM>, <NUM>.

The method further includes pulling back on the breakstem <NUM> (e.g., away from the tail <NUM> of the brad rivet <NUM> in a direction perpendicular to an outer surface <NUM> of the first metal plate <NUM>), which compresses the first leg <NUM> and the second leg <NUM> together toward the longitudinal axis <NUM> of the brad rivet <NUM>. The brad rivet <NUM> elongates as a separation distance <NUM> between the first leg <NUM> and the second leg <NUM> decreases. This process continues until each of the third leg <NUM> and the fourth leg <NUM> engage with the first metal plate <NUM> proximate to an edge of the first metal plate <NUM>, shown as upper edge <NUM>. The method concludes by separating the breakstem <NUM> from the brad rivet <NUM>, by bending, twisting, or upon application of a predetermined force by the applicator device.

In the illustrative embodiment shown in <FIG>, the head interface for each leg <NUM>, <NUM> of the brad rivet <NUM> includes a plurality of barb-like features. As shown in <FIG>, the head interface further includes a second head barb <NUM> disposed just below head barb <NUM> on the tail facing side of the head barb <NUM>. Similar to head barb <NUM>, the second head barb <NUM> is a small projection that extends away from either the third leg <NUM> or fourth leg <NUM> in a direction that is substantially perpendicular to one of the third leg <NUM> and the fourth leg <NUM>. Using multiple head barbs <NUM>, <NUM> permits the brad rivet <NUM> to be tightened by discrete amounts during installation. Among the various benefits, multiple head barbs <NUM>, <NUM> allow a single brad rivet <NUM> design to accommodate workpieces of varying thickness. Using multiple head barbs <NUM>, <NUM> also provides a mechanism for adjustment of the tensile forces that secure the workpieces together.

In various illustrative embodiments, the method of installation of the brad rivet <NUM>, <NUM> may be different. For example, transferring the brad rivet <NUM>, <NUM> from the sleeve into one of the first and second apertures <NUM>, <NUM> may be greatly simplified in an embodiment where a user is provided access to both sides of the stack <NUM> of joined workpieces. Furthermore, the length and geometry of the sleeve may be altered depending on the material properties and geometry of the brad rivet <NUM>, <NUM>.

A variety of geometries are contemplated for the head interface. In one embodiment, the head interface takes the form of a saw tooth pattern along a surface of each of the third leg and fourth leg. In another embodiment, the head interface is formed in the shape of a hook or another geometry that is configured to latch or engage with the first metal plate <NUM>.

An additional illustrative embodiment of a brad rivet <NUM> is generally depicted in <FIG>. Again, the brad rivet <NUM> includes a head portion, shown as head <NUM> and a tail portion, shown as tail <NUM>, which is disposed on an opposite end of the brad rivet <NUM> as the head <NUM>. As shown in <FIG>, the head <NUM> and tail <NUM> are separate components that engage with one another via a threaded interface <NUM>. Like the brad rivets <NUM>, <NUM> of <FIG>, the head <NUM> of the brad rivet <NUM> is formed in a domed shape having a planar lower surface, shown at flat lower surface <NUM>. During installation, the flat lower surface <NUM> is brought into contact with the outer surface <NUM> of the first metal plate <NUM>. The threaded interface <NUM> includes a threaded extension <NUM> disposed centrally on the flat lower surface <NUM> of the head <NUM>. The threaded extension <NUM> is received within a threaded hole <NUM> on the tail <NUM>.

In the embodiment of <FIG>, the tail <NUM> and head <NUM> of the brad rivet <NUM> are both made from BMG, although the head is not configured to deform elastically. Alternatively, the head may be made from another material (e.g., a steel alloy, etc.). Again, the tail <NUM> includes a first leg <NUM> and a second leg <NUM> that are configured to elastically deform or deploy on an opposite end of the stack <NUM> of workpieces once inserted into the aperture <NUM>. As shown in <FIG>, the tail <NUM> extends through the second aperture <NUM> and a portion of the first aperture <NUM>. In other embodiments, the tail <NUM> extends through only a portion of the first aperture <NUM>.

Advantageously, the tensile forces generated by the brad rivet <NUM> of <FIG> may be easily adjusted via the threaded interface <NUM> after installation. In an illustrative embodiment, the head <NUM> may include a fastener interface configured to engage with a fastening tool. In one embodiment, the fastener interface is one of a variety of types of screw drive (e.g., hex, slot drive, etc.). In another embodiment, the head <NUM> is a hex head cap screw or another type of bolt.

An illustrative embodiment of a bucked-type rivet assembly, shown as rivet assembly <NUM>, is provided in <FIG>. The rivet assembly <NUM> includes a formable member, shown as rivet piece <NUM> and an anvil, shown as forming piece <NUM>. The forming piece <NUM> is configured to be received within a channel <NUM> of the rivet piece <NUM>. The rivet piece <NUM> is shown isolated from the forming piece <NUM> in <FIG>, while the forming piece <NUM> is shown isolated from the rivet piece <NUM> in <FIG>.

As shown in <FIG>, the rivet piece <NUM> includes a head portion, shown as head <NUM>, disposed on a first end of a shaft, shown as cylindrical extension <NUM>. In an illustrative embodiment, the rivet piece <NUM> is formed as a single piece from an amorphous metal alloy. As with the brad rivets shown in <FIG>, and <FIG>, the head <NUM> of the rivet piece <NUM> is formed in a domed shape having a planar lower surface, shown at flat lower surface <NUM>, that is configured to contact one of the first metal plate <NUM> and the second metal plate <NUM> (also see <FIG>). The cylindrical extension <NUM> of the rivet piece <NUM> has an outer diameter that is sized to fit within both the first aperture <NUM> and the second aperture <NUM> simultaneously.

A variety of suitable amorphous metal alloys may be used for the rivet piece <NUM>. Amorphous metal alloys having a reasonably large thermoplastic processing window or supercooled liquid region are particularly appealing for this application. The subcooled liquid region (ΔTx) is defined as a separation (e.g., temperature difference) between a temperature (Tx) associated with the onset of crystallization and the glass transition temperature (Tg). Suitable amorphous metal alloys may include a BMG alloy having a subcooled liquid region ΔTx = Tx - Tg within a range between about <NUM> and <NUM> or greater. Other possible candidates include titanium, iron, and nickel-based BMG alloys. Yet other possible candidates include zirconium-based BMG, which may be alloyed with one, or a combination of, copper, nickel, titanium, aluminum, and beryllium. The zirconium BMG may also be alloyed with one or more group three elements as minor alloying additions such as Yttrium and Scandium to improve the viability of commercial-scale production.

In the embodiment of <FIG> and <FIG>, the forming piece <NUM> is configured to be at least partially disposed in an opening, shown as channel <NUM>, that extends along a central axis of the rivet piece <NUM>. As shown in <FIG>, the forming piece <NUM> includes an interface shaft, shown as puller shaft <NUM> having a first end and a second end. The forming piece <NUM> also includes an anvil head, shown as forming head <NUM>, disposed on a first end of the puller shaft <NUM>. A portion of the puller shaft <NUM> is configured to separate from the forming piece <NUM> upon application of a predetermined tensile force to the puller shaft <NUM>. A separation point, shown as notch <NUM>, is disposed at an axial position along the length of the puller shaft <NUM> proximate to the forming head <NUM>. The notch <NUM> is configured to weaken the puller shaft <NUM> so that it breaks upon application of a predetermined force. The notch <NUM> may be any one of a variety of different geometries; for example, the notch <NUM> may be a v-shaped channel, a u-shaped channel, a rectangular channel, or any combination thereof. In the illustrative embodiment of <FIG> and <FIG>, the notch <NUM> is a v-shaped channel that extends around the perimeter of the puller shaft <NUM>.

The forming head <NUM> is configured to plastically deform the tail <NUM> of the rivet piece <NUM>. In an illustrative embodiment, the forming piece <NUM> is made from an electrically conductive material having a larger cross-sectional area than the rivet piece <NUM> along the path of current flow to reduce Joule heating within the forming piece <NUM>. The forming piece <NUM> may also be made from a material with a higher melting point than the BMG to prevent the forming piece <NUM> from plastically deforming with the tail <NUM> and/or before the tail <NUM>.

A variety of different materials may be used for the forming piece <NUM>, including steels and hard copper beryllium alloys, both of which have electrical conductivities that are higher than BMG. Suitable steel alloys may have electrical conductivities of approximately <NUM>% of the International Annealed Copper Standard (IACS) or greater, whereas suitable copper beryllium alloys may have electrical conductivities within a range between <NUM>-<NUM>% IACS or greater. Both of these alloy families also have relatively high thermal conductivity, which is necessary in order to quench the BMG back down below the glass transition temperature (Tg) before devitrification can occur. Another example of a suitable materials for the forming piece <NUM> are aluminum alloys. Among other benefits, aluminum alloys tend to be less expensive, have lower hardness, but higher electrical and thermal conductivities for more efficient and faster heating and cooling operations. Although aluminum alloys are not as hard as copper or steel alloys, above Tg the BMG alloys significantly soften and become viscous, so although wearing and deformation of the anvil will occur over time, the aluminum based forming piece <NUM> could potentially be a more economical solution in some implementations. More complex designs for the forming piece <NUM> are also feasible to deliver the electrical current more efficiently to the BMG. For example, a very high electrical conductivity pathway (such as a wire) could be incorporated into a pocket and/or opening disposed in the forming piece to deliver the electrical current directly to the surface of the rivet instead of requiring the current to travel through the forming piece <NUM> for heating. The high conductivity pathway may be insulated from the forming piece <NUM>. Alternatively, the forming piece <NUM> may be configured such that a portion of the current flows through the forming piece <NUM>, while simultaneously a portion of the current flows through the high electrical conductivity pathway.

The forming head <NUM> of <FIG> and <FIG> is formed in a U-shape when viewed in cross-section, whose ends curve back toward the puller shaft <NUM>. In other embodiments, the forming head <NUM> may be formed in a T-shape when viewed in cross-section (see <FIG>), or another shape that suitably forms the rivet piece <NUM> around the outer edge <NUM> of the second aperture <NUM>. As shown in <FIG>, a second end of the puller shaft <NUM>, opposite the forming head <NUM>, is configured to be received within the channel <NUM>. As shown in <FIG>, the second end of the puller shaft <NUM> extends beyond the head <NUM> of the rivet piece <NUM> along a central axis of the rivet piece <NUM> and is configured to be received within an applicator device, shown as rivet tool <NUM> (see <FIG>).

A flow diagram of a method <NUM> of installing a rivet assembly is shown in <FIG>, according to an illustrative embodiment. The rivet assembly may be the same or similar to the rivet assembly <NUM> described with reference to <FIG>. For simplicity, similar numbering will be used to identify similar components. The method <NUM> is illustrated conceptually in <FIG>. The method <NUM> includes inserting the cylindrical extension <NUM> of the rivet piece <NUM> through the first aperture <NUM> and the second aperture <NUM>, at <NUM>, such that the flat lower surface <NUM> of the head <NUM> contacts an outer surface <NUM> of the first metal plate <NUM>. The method <NUM> further includes inserting the forming piece <NUM> into the channel <NUM> of the rivet piece <NUM> from an opposite side of the stack <NUM> (e.g., from the second metal plate <NUM> toward the first metal plate <NUM>), at <NUM>, such that the forming head <NUM> is brought into contact with the cylindrical extension <NUM>.

A variety of techniques may be used to deform the rivet piece <NUM> using the forming piece <NUM>. For example, the rivet piece <NUM> may be heated to a forming temperature based on the size and material composition of the rivet piece <NUM> and then deformed using the forming piece <NUM>. In order to heat the rivet piece <NUM>, the rivet tool <NUM> (see <FIG>) may incorporate resistive heaters or another suitable heating device. Alternatively, the rivet tool <NUM> may be configured to rapidly excite the forming piece <NUM> while it is in contact with the rivet piece <NUM>. For example, the rivet tool <NUM> may be configured to excite the forming piece <NUM> using ultrasonic energy. Alternatively, the rivet tool <NUM> may be configured to rapidly spin the forming piece <NUM> to generate heat at the interface between the forming piece <NUM> and the rivet piece <NUM>.

In the illustrative embodiment of <FIG>, the rivet piece <NUM> is heated, at <NUM>, by passing current through an electrical circuit that includes the puller shaft <NUM>, the forming head <NUM>, and the rivet piece <NUM>, arranged in series. The electrical circuit is completed by the rivet tool <NUM> (see <FIG>), which is in contact with both the puller shaft <NUM> and the head <NUM> of the rivet piece <NUM>. As shown in <FIG>, the puller shaft <NUM> is separated from the rivet piece <NUM> by an annular gap <NUM> and an insulating layer, shown as layer <NUM>, that is disposed on a surface of the forming piece, shown as cylindrical outer surface <NUM>. The layer <NUM> prevents the electrical circuit from shorting across the annular gap between the forming piece <NUM> and the rivet piece <NUM> during the heating stage.

In the method <NUM> of <FIG>, the rivet tool <NUM> (see <FIG>) is configured to pull on the second end of the forming piece <NUM> while simultaneously passing a current through the electrical circuit, at <NUM>. Among other benefits, the method of using an electrical current to heat the rivet piece <NUM> is fast, controllable, and heats the rivet piece <NUM> directly rather than indirectly. Once heated, the rivet piece <NUM> begins to thermoplastically deform proximate to the interface between the rivet piece <NUM> and the forming head <NUM>, compressing together each of the metal plates <NUM>, <NUM>. The method <NUM> further includes breaking the interface shaft, at <NUM>. As shown in <FIG>, the notch <NUM> in the puller shaft <NUM> is dimensioned so that at a known load the forming head <NUM> separates from the puller shaft <NUM>. The forming piece <NUM> is then removed from the rivet assembly <NUM>, leaving behind the rivet piece <NUM>. In the embodiment of <FIG>, the current is switched off to allow the rivet piece <NUM> to cool to a hardened fully amorphous state prior to or during separation of the forming head <NUM> from the puller shaft <NUM>.

A gas or liquid delivery system (not shown) may be coupled to the rivet tool <NUM> to help quench the rivet piece <NUM> after the heating stage. Among other benefits, a rapid quench prevents devitrification of the BMG during the cooling stage. The rivet tool <NUM> may be configured to provide and circulate a stream of gas (e.g., nitrogen, an inert gas, etc.) or liquid (e.g., water) through the annular gap <NUM> between the forming piece <NUM> and the rivet piece <NUM>. The rivet tool <NUM> may be configured to administer the gas or liquid beginning at approximately the same time as the current is switched off or just before the current is switched off to shorten the overall duration of the installation process.

In an illustrative embodiment, the rivet piece <NUM> may be configured to thermoplastically deform on both sides of the stack <NUM> to achieve very low profiles of the rivet piece <NUM> on either side of the stack <NUM>. For example, in an illustrative embodiment the rivet piece <NUM> is a shaft (e.g., a solid shaft of approximately the same geometry as the aperture <NUM>) that is deformed by placing a forming head against the rivet piece <NUM> on either side of the stack <NUM> (e.g., placing a first forming head of a first forming piece against the rivet piece <NUM> proximate to the second metal plate <NUM>, and placing a second forming head of a second forming piece against the rivet piece <NUM> proximate to the first metal plate <NUM>). Among other benefits, forming the rivet piece <NUM> from both sides creates a joint with as little gap as possible (e.g., a hermetic seal) between the rivet piece <NUM> and both the metal plates <NUM>, <NUM>. Furthermore, unlike traditional steel rivets whose microstructure is altered during the forming process, the heated BMG may be readily formed into a variety of shapes without altering the material properties (e.g., strength, etc.) of the BMG.

Claim 1:
A bucked-type rivet assembly (<NUM>) comprising:
a formable member (<NUM>) made from an amorphous metal alloy, the formable member having a channel (<NUM>); and
an anvil (<NUM>) at least partially disposed in the channel, the anvil comprising:
an interface shaft (<NUM>); and
an anvil head (<NUM>) disposed on a first end of the interface shaft;
wherein:
the formable member is configured to secure a first member (<NUM>) in position relative to a second member (<NUM>);
the anvil head is configured to plastically deform the formable member proximate to the second member; and
the anvil head is configured to separate from the interface shaft upon application of a predetermined tensile force to the interface shaft.