Patent Description:
Mechanical fasteners (see e.g. <CIT>) are widely used for joining two or more components of a structural assembly. For example, mechanical fasteners are extensively used for joining the structural components of the airframe of an aircraft.

Blind fastener systems are a particular type of mechanical fastener. Blind fastener systems include a core bolt and a sleeve, wherein both the core bolt and the sleeve are inserted into an appropriate bore in a structural assembly and engage the structural assembly from just one side of the structural assembly, without the need for accessing the opposite side of the structural assembly. Therefore, blind fastener systems are particularly suitable for use in applications where access to one side of a structural assembly is difficult or unavailable. Current tooling and installation methods for blind fastener systems are typically quite complex, difficult to manufacture, and challenging to integrate with robotics. These systems specifically struggle with installation at varying (non-normal) angles, installation where sealant is required (which may adhere to, and subsequently jam or plug the internal drive mechanism of the nose piece), and reducing cost.

Accordingly, those skilled in the art continue with research and development efforts in the field of blind fastener systems.

<CIT>, in accordance with its abstract, states: a hydraulic tensioning and release tool for an expansion fastener of a type having an elongate member with a tapered portion for fastening a workpiece, said tool comprising: a sleeve for placement about the tapered portion; one or more cylinders including at least one cylinder for generating compressive force against the workpiece; a release piston for displacing the sleeve and a tension piston for coupling to an end of the elongate member, the tension piston and at least one of the one or more cylinders defining at least one tension chamber and the release piston and at least one of the one or more cylinders defining at least one release chamber; hydraulic ports in fluid communication with said tension chamber and said release chamber for application of hydraulic pressure thereto to displace the tension piston and the release piston for respectively tensioning the elongate member and for releasing the sleeve from the tapered portion; and a tension retaining arrangement for retaining the end of the elongate member in tension subsequent to removal of hydraulic pressure from the tensioning chamber.

<CIT>, in accordance with a machine translation of its abstract, states: blind fastening device for fastening a component to a support wall, in particular a hollow profile, the blind fastening device comprising: - an expansion sleeve with expansion legs; - A sleeve head provided with an opening at one end of the expansion sleeve; - a screw with a threaded section which is guided through the sleeve head provided with the opening and the expansion sleeve, and with a screw head for tightening the screw; - An expanding nut with an internal thread and a conical section which, when the screw is tightened, engages in an opposite end of the expanding sleeve in order to move at least the opposite end of the expanding sleeve essentially radially to expand outwards and thus to anchor the expansion sleeve and - a design of the sleeve head which can be brought into engagement with a holding tool in order to prevent rotation of the sleeve head while the screw is tightened, characterized in that the expanding nut merges at a tapered end of its conical section into a hollow-cylindrical shoulder, the outer diameter of which is the same as the diameter of the opening of the sleeve head of the expanding sleeve is dimensioned with an interference fit, so that it can be pressed into the opening of the sleeve head by tightening the screw.

<CIT>, in accordance with its abstract, states: the invention relates to an anchoring element for anchoring building structures on concrete or solid-brick supporting walls, preferably light-metal substructures for facades. In the case of known anchoring elements, such as expanding dowels, it is aimed to provide a cost-effective anchoring element which can be positioned with simple means and the correct anchoring of which is instantly visible to the workman. For this purpose, an anchoring element, similar to a blind rivet, which has a sleeve and a tensioning pin and which can be anchored in a bore by means of a conventional riveting device, has been provided. The head of the tensioning pin spreads out the sleeve end for anchoring. A marking on the tensioning-pin shank indicates, by virtue of its location after the positioning, the location of the tensioning-pin head and thus the correctly performed or non-performed spreading-out of the sleeve. In the case of an advantageous further development, the predetermined breaking point or, after positioning, the break-off location of the tensioning pin is used as the marking.

<CIT>, in accordance with its abstract, states an anchor bolt assembly comprises a bolt having a cylindrical shank at least a portion of which is screw-threaded, a reduced diameter portion, and a sleeve-expanding portion increasing in diameter from the diameter of the reduced diameter portion to the full shank diameter at <NUM>, and a one-piece expansible sleeve about the bolt portion, the sleeve having a full-length longitudinal slit and an aperture diametrically opposite the slit and nearer to the sleeve end adjacent the shoulder of the bolt, a slit extending from the aperture to the sleeve and adjacent the expander portion of the bolt, and external ribs for engaging the wall of a bore in which the assembly is to be anchored so that the sleeve is held stationary when the bolt is pulled to cause the expander portion to expand the sleeve into wedging engagement with the bore walls. Preferably the bolt portion has a diameter equal to the root diameter of the thread. In its unexpanded form, the sleeve has an outside diameter equal to or slightly less than the full shank diameter, and has a length equal to the length of the bolt portion.

<CIT>, in accordance with its abstract, states: rivets, for use in blind holes, have a solid shank with a head coned to fit the 'bottom of the hole as left by the drill. A sleeve is driven by a hollow tool to force its end over the conical surface, and expand it into a chambered out part of the hole. The projecting end of the shank is then riveted over to secure an object, such as the plate, in place. The shank may be of aluminium and the sleeve of steel or both parts may be of aluminium alloys that for the sleeve being harder than that for the shank.

Disclosed are blind fasteners. The invention to which this European patent relates is defined in the appended claims.

In one example, the disclosed blind fastener includes a sleeve having a distal end portion and a proximal end portion and defining a bore. The blind fastener also includes a core bolt at least partially received in the bore of the sleeve, the core bolt defining a core bolt axis and including a body having a distal end portion and proximal end portion axially opposed from the distal end portion, wherein the body is tapered from the distal end portion of the body to the proximal end portion of the body such that the core bolt causes radial expansion of the sleeve when the body is urged relative to the sleeve through the bore along the core bolt axis.

In another example, the disclosed blind fastener includes a sleeve having a distal end portion and a proximal end portion, the sleeve defining a bore. The bore is tapered from the distal end portion to the proximal end portion. The sleeve includes a first metallic material. The blind fastener further includes a core bolt at least partially received in the bore of the sleeve, the core bolt including a second metallic material and defining a core bolt axis. The first metallic material is substantially softer than the second metallic material. The core bolt includes a body having a distal end portion and a proximal end portion axially opposed from the distal end portion. The body is tapered from the distal end portion of the body to the proximal end portion of the body. The blind fastener further includes a stem connected to the proximal end portion of the body.

Also disclosed are methods for installing a blind fastener into a bore in a structure. The blind fastener includes a sleeve and a core bolt at least partially received within the sleeve. The core bolt defines a bolt axis.

In one example, the disclosed method for installing a blind fastener into a bore includes inserting the blind fastener into the bore and pulling the core bolt relative to the sleeve to cause radial expansion of the sleeve.

Other examples of the disclosed blind fasteners and associated methods for installing blind fasteners will become apparent from the following detailed description, the accompanying drawings, and the appended claims. The embodiments shown in <FIG> are for background purposes.

The following detailed description refers to the accompanying drawings, which illustrate specific examples described by the present disclosure. Other examples having different structures and operations do not depart from the scope of the present disclosure. Like reference numerals may refer to the same feature, element, or component in the different drawings.

For the purpose of this disclosure, the terms "coupled," "coupling," and similar terms refer to two or more elements that are joined, linked, fastened, attached, connected, put in communication, or otherwise associated (e.g., mechanically, electrically, fluidly, optically, electromagnetically) with one another. In various examples, the elements may be associated directly or indirectly. As an example, element A may be directly associated with element B. As another example, element A may be indirectly associated with element B, for example, via another element C. It will be understood that not all associations among the various disclosed elements are necessarily represented. Accordingly, couplings other than those depicted in the figures may also exist.

References throughout the present specification to features, advantages, or similar language used herein do not imply that all of the features and advantages that may be realized with the examples disclosed herein should be, or are in, any single example. Rather, language referring to the features and advantages is understood to mean that a specific feature, advantage, or characteristic described in connection with an example is included in at least one example. Thus, discussion of features, advantages, and similar language used throughout the present disclosure may, but do not necessarily, refer to the same example. Referring generally to <FIG>, disclosed is a blind fastener <NUM>. The blind fastener <NUM> includes a sleeve <NUM> and a core bolt <NUM>. The blind fastener <NUM> is configured to couple at least two components to form a structure <NUM> via radial expansion of the sleeve <NUM> upon movement of the core bolt <NUM> relative to the sleeve <NUM>. The blind fastener <NUM> may be generally cylindrical in shape, although other shapes and configurations may be implemented.

Referring to <FIG>, in one or more examples, the blind fastener <NUM> includes a core bolt <NUM> at least partially received in a bore <NUM> of the sleeve <NUM>. The core bolt <NUM> defines a core bolt axis AC and includes a body <NUM> having a distal end portion 122a and proximal end portion 122b axially opposed from the distal end portion 122a. In one example, the body <NUM> is tapered from the distal end portion 122a of the body <NUM> to the proximal end portion 122b of the body <NUM>. The tapered shape of the body <NUM> causes radial expansion of the sleeve <NUM> when the body <NUM> is urged relative to the sleeve <NUM> through the bore <NUM> of the sleeve <NUM> along the core axis AC.

Referring to <FIG>, the taper from the distal end portion 122a of the body <NUM> to the proximal end portion 122b of the body <NUM> is a continuous taper. Referring to <FIG>, in one example, the continuous taper of the body <NUM> has a taper angle Oc defined as the angle between the core bolt axis Ac and a bolt plane defined in the drawings as a bolt line, L<NUM>, coincident with an outside surface <NUM> of the body <NUM> of the core bolt <NUM>. In one example, the angle Oc ranges from about <NUM> degree to about <NUM> degrees. In another example, the continuous taper has a taper angle Oc ranges from about <NUM> degrees to about <NUM> degrees.

In another example, the taper from the distal end portion 122a of the body <NUM> to the proximal end portion 122b of the body <NUM> is a discontinuous taper. For example, the taper from the distal end portion 122a of the body <NUM> to the proximal end portion 122b of the body <NUM> may vary such that it is increased at any portion along the body <NUM> to facilitate breaking near the neck <NUM> of the core bolt <NUM>.

Referring to <FIG>, in one or more examples, the body <NUM> of the core bolt <NUM> is a truncated conical body having a diameter D. The diameter D of the truncated conical body proximate the distal end portion 122a of the body <NUM>, D<NUM>, may be greater than the diameter of the truncated conical body proximate the proximal end portion 122b, D<NUM>. Further, as illustrated in <FIG>, the sleeve <NUM> may be countersunk such that it is chamfered to complement the received core bolt <NUM>.

Referring to <FIG>, in one or more examples, the body <NUM> of the core bolt <NUM> includes a flanged portion <NUM> at the proximal end portion 122b. The flanged portion <NUM> is configured to swage upon installation of the blind fastener <NUM> into a structure <NUM>, see <FIG>. The flanged portion <NUM> of the core bolt <NUM> may be formed by a flange forming tool <NUM>. In one example, the flanged portion <NUM> of the core bolt <NUM> is formed by the flange forming tool <NUM> as the core bolt <NUM> is pulled up. In another example, the flange forming tool <NUM> may spin and/or turn and roll the flanged portion <NUM> of the core bolt <NUM> to maintain the core bolt <NUM> in a desired position.

The body <NUM> causes radial expansion of the sleeve <NUM> when the body <NUM> of the core bolt <NUM> moves along the core bolt axis AC relative to the sleeve <NUM> and into the sleeve <NUM>. The radial expansion of sleeve <NUM> facilitates maintaining the blind fastener <NUM> in a desired position within a structure <NUM>.

Referring to <FIG>, in one or more examples, the blind fastener <NUM> includes a stem <NUM>. Stem <NUM> may be connected to the proximal end portion 122b of the body <NUM>. In one example, the stem <NUM> includes at least one groove <NUM>. Groove <NUM> may be annular, notched, or any other configuration for coupling with a tool. Referring to <FIG>, in another example, the stem <NUM> includes a collared portion <NUM>.

Referring to <FIG>, in one or more examples, the blind fastener <NUM> includes a neck <NUM> abutting the proximal end portion 122b positioned between the body <NUM> and the stem <NUM>. The neck <NUM> may be configured to break apart from the core bolt <NUM> upon being pulled along the core bolt axis AC as the core bolt <NUM> moves, concurrently applying axial force to the sleeve <NUM>, resulting in radial expansion. In one example, the neck <NUM> is substantially cylindrical and has a diameter that is smaller than a diameter proximate the proximal end portion 122b of the core bolt <NUM>, D<NUM>.

Referring to <FIG>, in one or more examples, the blind fastener <NUM> may include a cap <NUM>. In one example, the cap <NUM> is integral with the core bolt <NUM>. In another example, the cap <NUM> is threadedly engageable with the core bolt <NUM>, see <FIG>. The cap <NUM> may be substantially flush with an inner surface <NUM> of the structure <NUM> upon installation. In another example, the cap <NUM> may be offset from the inner surface <NUM> of the structure <NUM> upon installation. The sleeve <NUM> buckles along a flanged portion <NUM> and forms a lip along the inner surface <NUM> between the cap <NUM> and the structure <NUM>, see <FIG>.

Referring to <FIG>, in one or more example, sleeve <NUM> has a distal end portion 110a and a proximal end portion 110b. Sleeve <NUM> further defines a bore <NUM> configured to receive core bolt <NUM>. In one example, sleeve <NUM> defines a sleeve axis As. The bore <NUM> of the sleeve <NUM> is tapered from the distal end portion 110a to the proximal end portion 110b of the sleeve <NUM>. The taper may be continuous from the distal end portion 110a to the proximal end portion <NUM>10b. The continuous taper of the sleeve <NUM> may be substantially the same as the continuous taper of the core bolt <NUM>.

Still referring to <FIG>, in one or more examples, the continuous taper of the sleeve <NUM> has a sleeve taper angle ΘS that is defined by the angle between a sleeve axis AS and a sleeve plane defined in the drawings as a sleeve line, L<NUM>, coincident with an inside surface <NUM> of the sleeve <NUM>. In one example, the continuous taper has a sleeve taper angle Os ranging from about <NUM> degree to about <NUM> degrees. In another example, the continuous taper has a sleeve taper angle Os ranging from about <NUM> degrees to about <NUM> degrees. In yet another example, referring to <FIG>, the continuous taper has a sleeve taper angle Os that is substantially the same as a taper angle Oc of the core bolt <NUM>.

Referring to <FIG> and <FIG>, the sleeve <NUM> includes a flanged portion <NUM> at the distal end portion 110a. The flanged portion <NUM> may be sized and shaped to receive the distal end portion 122a of the body <NUM> of the core bolt <NUM> and the cap <NUM> of the blind fastener <NUM>. For example, the cap <NUM> may be similarly chamfered to mate with the flanged portion <NUM> of the sleeve <NUM>. The flanged portion <NUM> of the sleeve <NUM> may swage over the inner surface <NUM> of the structure <NUM> upon pulling of the core bolt <NUM> along the core bolt axis AC for retention of the blind fastener <NUM> upon installation, see <FIG>.

Referring to <FIG>, in one or more examples, the sleeve <NUM> may have a lower flanged portion <NUM>. In one example, the lower flanged portion <NUM> is chamfered. The lower flanged portion <NUM> may be sized and shaped to accommodate a flanged portion <NUM> of the core bolt <NUM> upon installation of the blind fastener <NUM>. Similarly, the sleeve <NUM> may be a protruding head sleeve, see <FIG>.

In one non-limiting example, the blind fastener <NUM> includes a sleeve <NUM> having a distal end portion 110a and a proximal end portion 110b. The sleeve <NUM> defines a bore <NUM>. The bore <NUM> is tapered from the distal end portion 110a to the proximal end portion 110b. The sleeve <NUM> includes a first metallic material.

The blind fastener <NUM> further includes a core bolt <NUM> at least partially received in the bore <NUM> of the sleeve <NUM>. The core bolt <NUM> includes a second metallic material and defines a core bolt axis AC. The first metallic material has a hardness that is substantially softer than the hardness of the second metallic material. The core bolt <NUM> includes a body <NUM> having a distal end portion 122a and a proximal end portion 122b axially opposed from the distal end portion 122a. The body <NUM> is tapered from the distal end portion 122a of the body <NUM> to the proximal end portion 122b of the body <NUM>. The blind fastener <NUM> further includes a stem <NUM> connected to the proximal end portion 122b of the body <NUM>.

In one or more examples, the core bolt <NUM> of blind fastener <NUM> includes a second metallic material and the sleeve <NUM> includes a first metallic material. In one example, the first metallic material is substantially different from the second metallic material. The first metallic material may have a hardness that is different than a hardness of the second metallic material. The first metallic material may be at least <NUM>% softer than the second metallic material. In another example, the first metallic material may be at least <NUM>% softer than the second metallic material. The materials of the core bolt <NUM> and sleeve <NUM> of the fastener <NUM> may be selected based upon one or more desired material properties, such as hardness, tensile strength, elongation, yield strength, and the like. Material hardness, for example, may be measured by Brinell, Rockwell, Vickers, or any other suitable means of determining material hardness. Material hardness may change based upon the material composition used for each component of the blind fastener <NUM>.

In one example, the first metallic material includes a ferrous metal. In another example, the first metallic material includes a non-ferrous metal. In yet another example, the first metallic material may include one or more of titanium, aluminum, copper, bronze, beryllium, nickel, tin, steel, or any combination thereof. In one example, the first metallic material is corrosion resistant. In another example, the first metallic material provides electromagnetic energy (EME) protection. In one non-limiting example, the blind fastener <NUM> includes Inconel™. The use of non-metallic materials is also contemplated and such use will not result in a departure from the scope of the present disclosure.

In one example, the second metallic material includes a ferrous metal. In another example, the second metallic material includes a non-ferrous metal. In yet another example, the second metallic material may include one or more of titanium, aluminum, copper, bronze, beryllium, nickel, tin, steel, or any combination thereof. In one example, the second metallic material is corrosion resistant. In another example, the second metallic material provides EME protection. In one non-limiting example, the second metallic material includes Inconel™. The use of non-metallic materials is also contemplated and such use will not result in a departure from the scope of the present disclosure.

Referring to <FIG>, in one or more examples, disclosed is a method <NUM> for installing a blind fastener <NUM>, as shown and described herein, into a bore <NUM> in a structure <NUM>. The blind fastener <NUM> includes a sleeve <NUM> and a core bolt <NUM> at least partially received within the sleeve <NUM>, the core bolt <NUM> defining a core bolt axis AC, see <FIG>.

Referring to <FIG>, the method <NUM> includes inserting <NUM> the blind fastener <NUM> into the bore <NUM> of the structure <NUM>. In one example, the inserting <NUM> includes inserting both the sleeve <NUM> and core bolt <NUM> simultaneously into the bore <NUM> of the structure <NUM>. The inserting <NUM> engages the structure <NUM> from just one side, without the need for accessing the opposing side of the structure <NUM>. The inserting <NUM> may be performed manually, may be automated, or a combination thereof.

Still referring to <FIG>, the method <NUM> includes applying <NUM> an axial force to the sleeve <NUM> to immobilize the sleeve relative to the structure <NUM>. In one example, the method <NUM> incudes, during the applying <NUM>, pulling <NUM> the core bolt <NUM> relative to the sleeve <NUM> to cause radial expansion of the sleeve <NUM>. The pulling <NUM> may be performed manually, may be automated, or a combination thereof.

The pulling <NUM> may be achieved, for example, by operatively coupling a tool <NUM> to the core bolt <NUM>, the tool <NUM> configured to pull the core bolt <NUM> along the core bolt axis AC. The tool <NUM> may include any movement mechanism, such as an actuator, configured to pull the core bolt <NUM> along the core bolt axis AC. Applying <NUM> axial force occurs simultaneously with the pulling <NUM> as the tapered core bolt <NUM> moves along the core bolt axis AC and presses against the sleeve <NUM> into structure <NUM>.

In one example, the core bolt <NUM> includes a stem <NUM> and the method <NUM> includes gripping <NUM> the core bolt <NUM> prior to the pulling <NUM>. The gripping <NUM> may be performed manually, may be automated, or a combination thereof. The gripping <NUM> may include moving a tool <NUM> into engagement with the stem <NUM> of the blind fastener <NUM>. In one example, the tool <NUM> includes a locking collar <NUM> configured to engage with the stem <NUM> of the blind fastener <NUM>. The stem <NUM> may include a groove <NUM>, a collared portion <NUM>, or any other feature to facilitate engagement of the tool <NUM>, or locking collar <NUM>, with the blind fastener <NUM>. The locking collar <NUM> may be operatively coupled with a movement mechanism of the tool <NUM>, such as an actuator, configured to pull the locking collar <NUM> along the core bolt axis AC.

The core bolt <NUM> of the blind fastener <NUM> includes a cap <NUM>. The cap <NUM> protruded from the structure <NUM> after the pulling <NUM>, see <FIG>. The cap <NUM> abuts the buckled portion of the sleeve <NUM> along the inner surface <NUM> of the structure <NUM> after the pulling <NUM>, upon installation. In yet another example, the cap <NUM> is substantially flush with an inner surface <NUM> of the structure <NUM> after the pulling <NUM>, see <FIG>.

Examples of the subject matter disclosed herein may be described in the context of aircraft manufacturing and service method <NUM> as shown in <FIG> and aircraft <NUM> as shown in <FIG>. During pre-production, the method <NUM> may include specification and design (block <NUM>) of aircraft <NUM> and material procurement (block <NUM>). During production, component and subassembly manufacturing (block <NUM>) and system integration (block <NUM>) of aircraft <NUM> may take place. Thereafter, aircraft <NUM> may go through certification and delivery (block <NUM>) to be placed in service (block <NUM>). While in service, aircraft <NUM> may be scheduled for routine maintenance and service (block <NUM>). Routine maintenance and service may include modification, reconfiguration, refurbishment, etc. of one or more systems of aircraft <NUM>.

Each of the processes of the method <NUM> may be performed or carried out by a system integrator, a third party, and/or an operator (e.g., a customer). For the purposes of this description, a system integrator may include, without limitation, any number of aircraft manufacturers and major-system subcontractors; a third party may include, without limitation, any number of vendors, subcontractors, and suppliers; and an operator may be an airline, leasing company, military entity, service organization, and so on.

As shown in <FIG>, aircraft <NUM> produced by the method <NUM> may include airframe <NUM> with a plurality of high-level systems <NUM> and interior <NUM>. Examples of high-level systems <NUM> include one or more of propulsion system <NUM>, electrical system <NUM>, hydraulic system <NUM>, and environmental system <NUM>. Any number of other systems may be included. Although an aerospace example is shown, the principles disclosed herein may be applied to other industries, such as the automotive industry. Accordingly, in addition to aircraft <NUM>, the principles disclosed herein may apply to other vehicles, e.g., land vehicles, marine vehicles, space vehicles, etc..

The disclosed blind fasteners and associated methods for installing blind fasteners shown or described herein may be employed during any one or more of the stages of the method <NUM>. For example, components or subassemblies corresponding to component and subassembly manufacturing (block <NUM>) may be fabricated or manufactured in a manner similar to components or subassemblies produced while aircraft <NUM> is in service (block <NUM>).

Also, one or more examples of the systems, methods, or combination thereof may be utilized during production stages (block <NUM> and block <NUM>), for example, by substantially expediting assembly of or reducing the cost of aircraft <NUM>. Similarly, one or more examples of the systems or method realizations, or a combination thereof, may be utilized, for example and without limitation, while aircraft <NUM> is in service (block <NUM>) and/or during maintenance and service (block <NUM>).

The disclosed blind fasteners and associated methods for installing blind fasteners are described in the context of an aircraft. However, one of ordinary skill in the art will readily recognize that the disclosed blind fasteners and associated methods for installing blind fasteners may be utilized for a variety of applications. For example, the disclosed blind fasteners and associated methods for installing blind fasteners may be implemented in various types of vehicles including, e.g., helicopters, watercraft, passenger ships, automobiles, and the like.

Claim 1:
A blind fastener (<NUM>) comprising:
a sleeve (<NUM>) comprising a distal end portion (110a), a proximal end portion (110b), and a flanged portion (<NUM>) at the distal end portion (<NUM>10a), wherein the sleeve defines a bore (<NUM>); and
a core bolt (<NUM>) at least partially received in the bore (<NUM>) of the sleeve (<NUM>), the core bolt (<NUM>) defining a core bolt axis (AC) and comprising a body (<NUM>) and a cap (<NUM>), wherein the body has a distal end portion (122a) and a proximal end portion (122b) axially opposed from the distal end portion (122a), wherein the body (<NUM>) is tapered from the distal end portion (122a) of the body (<NUM>) to the proximal end portion (122b) of the body (<NUM>) such that the core bolt (<NUM>) causes radial expansion of the sleeve (<NUM>) when the body (<NUM>) is urged relative to the sleeve (<NUM>) through the bore (<NUM>) along the core bolt axis (Ac);
wherein the cap (<NUM>) and flanged portion (<NUM>) are arranged such that the sleeve (<NUM>) buckles along the flanged portion (<NUM>) to form a lip which abuts the cap when the body (<NUM>) is urged relative to the sleeve (<NUM>) through the bore (<NUM>) along the core bolt axis (Ac).