Patent Description:
Rivets and other types of fasteners are used in manufacturing to hold workpieces together. Such rivets may hold together metal or other materials and may be high-strength fasteners. In some manufacturing operations, apertures are drilled through workpieces and then rivets are installed in the apertures.

Blind fasteners are traditionally used in the aircraft industry. Such fasteners generally include a nut, a bolt and a sleeve. The nut has a body with a threaded axial bore therethrough. A bolt is threaded in the nut body. A hollow cylindrical sleeve surrounds the bolt between the nut and a head of the bolt. In installation, the fastener is aligned in holes in workpieces. As the bolt is drawn through the bore of the nut, the sleeve is pushed by the bolt head and is deformed against the workpieces thus locking the fastener in position.

Once locked, a portion of the bolt above the workpieces is removed and discarded. This portion typically breaks off from the remainder of the bolt. The surface of the workpiece typically has a resulting protruding tip, pintail, recesses, or other formation so that the installed fastener and the workpiece are not flush. It may be necessary to conduct further operations to make the workpiece and the fastener flush. For example, this may involve shaving off the protruding tip, pintail, or other formation of the remaining fastener after installation which entails considerable man hours or additional automated processes. In addition, the shaving off of the remaining fastener involves repetitive motions that may be required for many fasteners, particularly on large aircrafts. This repetitive motion may contribute to fatigue, human errors, or health and safety concerns if done improperly. Furthermore, each shaving process may allow for increased potential damage to a workpiece, such as an aircraft.

For these and other reasons, there is a need for a fastener which operatively breaks flush with a workpiece and does not result in surface formations. Moreover, there is a need for a more efficient fastener, system, and methods for installing a fastener.

<CIT> suggests a threaded blind fastener adapted to minimize discontinuities on paintable surfaces of the head resulting from clearances between male and female threads.

The following presents a summary of this disclosure to provide a basic understanding of the invention. This summary is intended to neither identify key or critical elements nor define any limitations of embodiments or claims. Furthermore, this summary may provide a simplified overview of some aspects that may be described in greater detail in other portions of this disclosure.

The present disclosure describes a blind fastener as set forth in claim <NUM>.

The foregoing embodiments are merely exemplary of some of the aspects of the invention. Additional features and elements may be contemplated and described herein. Also, features from one of the foregoing embodiments may be combined with features from any of the other foregoing embodiments, as long as they fall within the wording of the appended claims.

The following description and the drawings disclose various illustrative aspects. Some improvements and novel aspects may be expressly identified, while others may be apparent from the description and drawings.

The accompanying drawings illustrate various systems, apparatuses, devices and methods, in which like reference characters refer to like parts throughout.

The invention may be embodied in several forms and the scope of the invention is defined in the appended claims, rather than in the specific description preceding them. All embodiments that fall within the meaning of the claims are therefore intended to be embraced by the claims.

Reference will now be made in detail to exemplary embodiments of the present invention, examples of which are illustrated in the accompanying drawings.

As used herein, the words "example" and "exemplary" mean an instance, or illustration. The words "example" or "exemplary" do not indicate a key or preferred aspect or embodiment. The word "or" is intended to be inclusive rather than exclusive, unless context suggests otherwise. As an example, the phrase "A employs B or C," includes any inclusive permutation (e.g., A employs B; A employs C; or A employs both B and C). As another matter, the articles "a" and "an" are generally intended to mean "one or more" unless context suggests otherwise.

Furthermore, the terms "user," "installer," "technician," and the like are employed interchangeably throughout the subject specification, unless context suggests otherwise or warrants a particular distinction among the terms. It is noted that such terms may refer to human entities or automated components. As such, embodiments may describe a user action that may not require human action.

As used herein, a fastener may refer to various types of rivets, screws, bolts, or the like. Such fasteners may comprise metals, plastics, or other materials. For example, fastener may refer to a cylindrical rivet comprising a metal body (e.g., aluminum, steel, etc.). Moreover, embodiments may refer to a specific type of fastener for simplicity of explanation. As such, disclosed aspects may be applicable to various other types of fasteners.

Blind fasteners may be used where there is limited operating room, to reduce installation costs, or to reduce installation time in comparison to two-piece non-blind fasteners. Blind fasteners are more readily and cost effectively adapted to automated or robotic installation than would be a two-piece system. For these and other reasons, blind fasteners are considered for non-typical applications wherein access is available but productivity demands and cost concerns drive the use of automation.

A blind fastener may comprise a threaded fastener capable of one-sided installation. To install a blind fastener, a nut and bolt are positioned within an aperture. Some traditional blind fasteners rely on recesses, often cruciform, within the threaded body portion of the fastener to restrain rotation of that component during the installation procedure. Some of these fasteners have a variable "break-off' position of the bolt component relative to the fastener body which is intended to sit flush with the workpiece, such as an aircraft component once installed. When installed, the variable break-off position results in surface features, such as protrusions, pin tails, recesses, or the like. Any portion of the installed blind fastener that protrudes above the surface of the workpiece is removed or reduced by shaving, milling, or similar process to meet aerodynamic stipulations. This additional installation step adds cost and time.

When the fastener results in a recess or sub-flush screw position, aerodynamics can be adversely affected due to parasitic drag created by the void. The inherent void of the recesses relied upon for installation and the variable sub-flush screw position combine to compromise aerodynamics and add labor in terms of preparation for paint and do not present the same opportunity for a relatively seamless finish. For example, when an installed fastener results in a sub-flush finish with a work piece, a user may be required to fill the sub-flush area with a filler material (e.g., resin, epoxy, etc.) or apply multiple layers of paint. In another aspect, the degree to which a breakoff is sub-flush may compromise the integrity of a joint. For instance, the further the breakoff is from the flush surface, the weaker or more compromised the joint may be.

Described embodiments may provide both recess-free and flush break threaded blind fasteners. Such fasteners may comprise aluminum or other materials. Embodiments include a non-threaded area of the bolt at a break-off location to facilitate a smoother cosmetic finish. The aspect of arresting the screw rotation is accomplished by means of interference with a shoulder in the nut element. In another example, a drive nut may comprise a shoulder or other stop structure. It is further noted that an installation tool nose adapter may comprise a shoulder that may arrest movement for break off. In another aspect, the installation tool nose may comprise a textured surface, such as a knurled or breaded surface as described herein.

Exemplary fasteners may include a break groove that fractures a bolt after or during installation. The break groove and the non-threaded portion of the bolt may allow for consistent flush break-off to eliminate secondary shaving, milling or grinding operations, as well as provide reduced cost, reduced time, and improved appearance when painting a workpiece. In another aspect, a flush finish may reduce or eliminate need for filling a void with a filler material or applying multiple layers of paint to a void. Moreover, the drive nut may engage with a shoulder or exposed portion of the nut without engaging with any recesses. This may arrest rotation of the nut during installation. For instance, the drive nut may comprise a knurled or ribbed end that engages the exposed portion of the nut. As such, the exposed portion of the nut may be generally free of any recesses. In examples, the elimination of recesses results in increased material in the head of the nut. This increase in material may reduce potential for fracturing, improve strength of fasteners, increase applications for fasteners, or otherwise result in an improved fastener. For instance, the increased strength of the nut may allow fasteners of particular materials (e.g., aluminum, etc.) to be utilized to fasten parts that experience increased lap sheer strength. Utilization of disclosed fasteners in high stress areas where sheer strength is required may reduce the overall cost as less expensive or difficult to handle materials may be replaced or avoided.

Turning to <FIG>, there is a fastener <NUM> that may provide for a recess-free, flush break when installed in a workpiece. The fastener <NUM> may comprise a blind fastener and may comprise aluminum, steel, or other materials. It is noted that the various components of the fastener <NUM> may comprise the same or different material.

Fastener <NUM> generally includes nut <NUM>, bolt <NUM>, sleeve <NUM> and drive nut <NUM>. Fastener <NUM> defines longitudinal axis A and is generally symmetric about longitudinal axis A. Nut <NUM> comprises a body <NUM> with first end <NUM> and second end <NUM>. The body <NUM> may be generally cylindrical extending between the first end <NUM> and the second end <NUM>. First end <NUM> includes head <NUM>. Head <NUM> may be generally frustoconical to allow for installation in a countersunk aperture. Head <NUM> comprises a central bore <NUM> that is non-threaded. Head <NUM> comprises a wrenching surface <NUM> that may be exposed when the fastener is installed in a workpiece, as shown in <FIG>. In an aspect, the wrenching surface <NUM> may be generally level to provide a flush surface with a workpiece once installed. Second end <NUM> may be tapered, angled, or otherwise shaped to engage with sleeve <NUM>. In an example, the second end may comprise a generally frustoconical shape. The shape of the second end <NUM> may allow for sleeve <NUM> to be deformed during installation, as described herein.

The body <NUM> comprises a bore <NUM>. Bore <NUM> comprises threads <NUM>. Threads <NUM> correspond and cooperate with first threaded portion <NUM> of the bolt <NUM>. Bolt <NUM> includes head <NUM>, the first threaded portion <NUM>, recess or break groove <NUM>, second threaded portion <NUM> and non-threaded portion <NUM>. Break groove <NUM> is positioned between the second threaded portion <NUM> and the non-threaded portion <NUM>. In at least one embodiment, the break groove <NUM> is disposed within the non-threaded portion <NUM> such that a first external surface of the bolt <NUM> above the break groove <NUM> is non-threaded and a second external surface of the bolt <NUM> below the break groove <NUM> is non-threaded. First threaded portion <NUM> is positioned between the non-threaded portion <NUM> and the head <NUM>.

It is noted that the second threaded portion <NUM> may extend above the drive nut <NUM>. In some embodiments, a portion of the second threaded portion <NUM> extending above the drive nut <NUM> may not comprise threads and may comprise a wrenching portion, shaft, or the like.

Drive nut <NUM> may comprise an engaging surface <NUM>, internally threaded portion <NUM> and wrenching surface <NUM>. It is noted that the drive nut <NUM> may be hexagonal in shape, cylindrical or otherwise configured for tool engagement. Engaging portion <NUM> may comprise a terminal end of a frustoconical portion <NUM>. The engaging portion <NUM> may operatively interface with wrenching surface <NUM> of the nut <NUM> to rotationally constrain drive nut <NUM> and nut <NUM> together. In an aspect, the engaging portion <NUM> may be a knurled surface of straight, angled or crossed lines on the surface. The knurled surface may prevent rotation of the nut <NUM> as it engages with the wrenching surface <NUM> as described herein.

The first threaded portion <NUM> of the bolt <NUM> comprises a major diameter <NUM>. The major diameter <NUM> is the same or slightly smaller than the diameter of bore <NUM> to allow the first threaded portion to interface with threads <NUM> of the bore <NUM>. The major diameter <NUM> is larger than a diameter <NUM> of bore <NUM>. This acts as a stop as the first threaded portion <NUM> contacts a shoulder <NUM> disposed within the bore <NUM>. The shoulder <NUM> prevents the bolt <NUM> from advancing once the shoulder <NUM> and first threaded portion <NUM> come into contact.

A diameter <NUM> of the non-threaded portion <NUM> may be smaller than the major diameter <NUM> and may be equal to or slightly smaller than head bore diameter <NUM>. This may allow the non-threaded portion <NUM> to pass through the bore <NUM> during installation. In an aspect, the non-threaded portion <NUM> may tightly fit in the bore <NUM> such that the finish after installation is generally flush and smooth.

Turning now to <FIG> these are exemplary views of the fastener <NUM> during various stages of installation in an aperture <NUM> formed through workpieces <NUM> and <NUM>. Fastener <NUM> is disposed within the aperture <NUM>. The aperture <NUM> is provided as generally cylindrical with a frustoconical portion that operatively cooperates with the shape of nut <NUM>.

An installation tool or wrench adapter (not shown) operatively drives the bolt <NUM> at a lead pin <NUM> portion. The lead pin <NUM> extends above the drive nut <NUM> on a non-blind side of installation. The installation tool operatively prevents the drive nut <NUM> from rotating. The drive nut <NUM> contacts the nut <NUM>, such as at the engaging surface <NUM>, as shown in <FIG>, operatively interfacing with wrenching surface <NUM> of the nut <NUM> to rotationally constrain drive nut <NUM> and nut <NUM> together. As described herein, the engaging portion <NUM> may be a knurled surface to prevent or stop the nut <NUM> from rotating. This may allow the sleeve <NUM> to be deformed and form a footprint <NUM> in the back side of the structure providing preload, as shown in <FIG>.

<FIG> illustrates a not claimed exemplary embodiment of a blind fastener <NUM> that includes a sleeve <NUM> that may comprise a cut out, recess, or other space <NUM> for receiving an insert <NUM>. The blind fastener <NUM> may include the same or similar components as the blind fastener <NUM>, such as a nut <NUM>, bolt <NUM>, and drive nut <NUM>. The insert <NUM> may comprise plastic or other material. The insert <NUM> may assist in formation of the footprint <NUM> during installation. The functioning of such an insert <NUM> may comprise a tensile strength generally less than the tensile strength of the sleeve <NUM>. For example, the tensile strength of the insert <NUM> may be about <NUM>% to <NUM>% of the tensile strength of the sleeve <NUM>. The dimensions of the insert <NUM> may be varied such that the insert <NUM> is completely or partially disposed within the cavity. It is further noted that the insert <NUM> may comprise a monolithic construction or may consist of two or more pieces.

As described herein, bolt <NUM> may comprise two or more thread sizes with the smaller thread contributing to a reduced area <NUM> where exposed at the nut head upon torsional break-off at the completion of the installation process. During installation, the bolt <NUM> travels towards the installation tool and bottoms out on the nut shoulder <NUM>. The non-threaded area <NUM> is then exposed and breaks off at the break groove <NUM> allowing a smooth shank, exposed with no thread profile, to provide an improved flush appearance as shown in <FIG>. In <FIG>, the drive nut <NUM> and lead pin <NUM> is broken off from the other portions of fastener <NUM>. <FIG> shows a perspective, cross-sectional view of the fastener <NUM> installed in the workpieces.

Turning to <FIG>, there are additional views of the break groove <NUM>. In examples, the break groove <NUM> may be cut at an angle <NUM> defined between a first wall <NUM> and a second wall <NUM>. The angle <NUM> may be between m and n degrees, where m and n are numbers. For instance, m may be <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, etc. In another example, n may be <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, etc. In at least one example, the angle <NUM> may be generally <NUM> degrees. In some embodiments, <NUM> degrees has shown to produce unexpectedly improved results that result in clean or flush breaks during the installation. In another aspect, the first wall <NUM> may be generally planar or flat relative a work piece when installed and the second wall <NUM> may extend at angle <NUM> from the first wall <NUM>. It is further noted that the vertex <NUM> between the first side <NUM> and the second side <NUM> may be curved, chamfered, or otherwise shaped.

It is noted that some embodiments may include a drive nut comprising a stop feature, in addition to the shoulder <NUM>. This may allow the throw-away portion of the fastener to provide a stop. For instance, the drive nut <NUM> may comprise a shoulder disposed therein. The shoulder may stop advancement of the bolt <NUM> such that the bolt cannot further advance. In an aspect, the shoulder may stop the bolt <NUM> when the non-threaded portion <NUM> is exposed. The bolt <NUM> may break off with a flush, recess-free finish.

Turning to <FIG>, there is a system <NUM> comprising an installation tool <NUM> and a not claimed blind fastener <NUM>. It is noted that the blind fastener <NUM> may comprise the same or similar components as the blind fastener <NUM> or <NUM>, such as a nut <NUM>, bolt <NUM>, and sleeve <NUM> or <NUM>. Blind fastener <NUM>, however, does not comprise a drive nut. Instead, the installation tool <NUM> may be coupled with or comprise a head <NUM> adapted to interface with the bolt <NUM>. For instance, the installation tool <NUM> may include a surface <NUM> that may be a knurled surface of straight, angled or crossed lines. The surface <NUM> may comprise other knurls or other formations to prevent rotation of the nut <NUM> as it engages with the installation tool <NUM> as described herein.

It is further noted that the head <NUM> may comprise a stop feature, in addition to the shoulder <NUM>. This may allow the throw-away portion of the fastener to provide a stop. For instance, the head <NUM> may comprise a shoulder disposed therein. The shoulder may stop advancement of the bolt <NUM>. In an aspect, the shoulder may stop the bolt <NUM> when the non-threaded portion <NUM> is exposed. The bolt <NUM> may break off with a flush, recess-free finish.

In view of the subject matter described herein, methods that may be related to various embodiments may be better appreciated with reference to the flowchart of <FIG>. While the not claimed method(s) are shown and described as a series of blocks, it is noted that associated methods or processes are not limited by the order of the blocks unless context suggests otherwise or warrants a particular order. It is further noted that some blocks and corresponding actions may occur in different orders or concurrently with other blocks. Moreover, different blocks or actions may be utilized to implement the methods described hereinafter. Various actions may be completed by one or more of users, mechanical machines, automated assembly machines (e.g., including one or more processors or computing devices), or the like.

Turning now to <FIG>, there is a method <NUM> that may provide for installation of a fastener as described herein. It is noted that an installation tool may be utilized for installing the fastener. The installation tool may be automated or may be applied by a user. The installed fastener may be similar or identical to embodiments described herein.

At <NUM>, the method provides a fastener (e.g., fastener <NUM>) in a workpiece. The fastener may comprise a bolt, a sleeve, a nut, and a drive nut. The bolt may comprise one or more threaded portions. The one or more threaded portions may comprise different thread dimensions. In another aspect, the bolt may comprise a non-threaded portion disposed between threaded portions. The bolt may additionally or alternatively comprise a break groove.

At <NUM>, the method comprises rotating a bolt of the fastener. Rotation of the bold may comprise rotating a lead pin or screw via an installation tool. The installation tool may comprise an automated tool or a handheld tool.

At <NUM>, the method comprises preventing rotation of the nut with the drive nut. For instance, the installation tool may prevent the drive nut from rotating. The drive nut may comprise a knurled surface that interfaces with the nut to prevent rotation of the nut.

At <NUM>, the method comprises preventing the fastener from advancing with the use of a shoulder of the drive nut. The shoulder is disposed within a bore of the nut. As the fastener passes through the bore, the shoulder prevents a wider portion of the fastener from passing beyond the shoulder.

At <NUM>, the method may include breaking off the drive nut and lead pin or screw. The portion of the fastener remaining in the workpiece may comprise a recess-free, flush surface with the workpiece.

Claim 1:
A fastener (<NUM>) comprising:
a nut (<NUM>) comprising a body (<NUM>), a first end (<NUM>), and a second end (<NUM>), wherein the body (<NUM>) comprises an internally threaded bore (<NUM>) having a first diameter, and the second end (<NUM>) comprises a head (<NUM>) comprising a wrenching surface (<NUM>), and a bore (<NUM>) comprising a second diameter (<NUM>);
a bolt (<NUM>) comprising a bolt head (<NUM>), a first threaded portion (<NUM>), a second threaded portion (<NUM>), and a non-threaded portion (<NUM>), wherein the non-threaded portion (<NUM>) is disposed between the first threaded portion (<NUM>) and the second threaded portion (<NUM>), and wherein the first threaded portion (<NUM>) comprises different dimensions than the second threaded portion (<NUM>); and
a sleeve (<NUM>) disposed between the bolt head (<NUM>) and the nut (<NUM>);
wherein the bolt (<NUM>) passes through the sleeve (<NUM>) and the nut (<NUM>); and
the first threaded portion (<NUM>) comprises a major diameter (<NUM>) that is less than or equal to the first diameter such that the first threaded portion (<NUM>) of the bolt <NUM> can interface with the threads (<NUM>) of the internally threaded bore (<NUM>); and
characterized in that:
the first diameter is different from the second diameter (<NUM>);
the bore (<NUM>) of the second end (<NUM>) of the nut (<NUM>) is non-threaded; and
the major diameter (<NUM>) is larger than the second diameter (<NUM>) of the bore (<NUM>) so as to create a shoulder (<NUM>) configured to prevent the bolt (<NUM>) from advancing when the first threaded portion (<NUM>) comes into contact with the shoulder (<NUM>).