GB2484958A

GB2484958A - Fastener removal tool

Info

Publication number: GB2484958A
Application number: GB201018186A
Authority: GB
Inventors: Terry Allen
Original assignee: Airbus Operations Ltd
Current assignee: Airbus Operations Ltd
Priority date: 2010-10-28
Filing date: 2010-10-28
Publication date: 2012-05-02
Also published as: GB201018186D0

Abstract

The tool for removing an interference fit sleeve 3 of a sleeved fastener system from a hole 12 in a work piece 13, 14 includes a collet 18 and mandrel 21 assembly 17 moveable between extended and retracted positions for opening and closing jaws 18b of the collet. The assembly 17 is sized to fit inside the sleeve when the collet jaws are closed, the jaws being sized to engage with one end of the sleeve when the jaws are open. A puller device (24, figure 7) includes a body 25 for positioning adjacent the workpiece and drive means 26 for applying a force to the collet and mandrel assembly so as to move the assembly from its extended position to its retracted position in a first action thereby opening the collet jaws, and to move the retracted collet and mandrel assembly relative to the body in a second action. The assembly may include a spring for biasing the assembly to its extended position. The tool is used in a method of removing an interference fit sleeve from a hole in a workpiece from one side of the workpiece.

Description

FASTENER REMOVAL TOOL

FIELD OF THE INVENTION

The present invention relates to a tool for removing an interference fit sleeve of a sleeved fastener system; and to methods for using the tool.

BACKGROUND OF THE INVENTION

Sleeved fastener systems are commonly used to connect workpieces together to form an assembly. A sleeved boh fastener typically comprises a bolt, a sleeve and a collar.

The boh has a head at one end, a blind shaft portion adjacent the head, and a threaded or grooved shaft portion at the opposite, distal end. The blind shaft portion has a greater diameter than the threaded/grooved shaft portion. A grooved pintail extends from the distal end of the boh. The sleeve comprises a hollow tubular shank with either a straight flange for use with a pan head bolt, or an angled flange for use with a countersunk head bolt. Prior to installation, the sleeve has a nominal internal diameter less than the outer diameter of the blind shaft portion of the bolt but greater than, or equal to, the outer diameter of the threaded/grooved shaft portion of the boh. The fastener is supplied for use with the bolt fitted partly inside the sleeve. The collar, as supplied, is substantially tubular with a smooth internal bore. The collar internal diameter is sized to provide a nominal fit over the blind shaft portion of the boh.

Installation of the fastener requires access from both sides of the workpieces to be joined. A nominal hole is formed through the workpieces. The sleeved fastener is installed in the hole from one side. The sleeve shank length is substantially the same as the hole depth, and the nominal hole is sized to accept the fastener sleeve and boh.

A pneumatic puller, for example, is used to pull the bolt through the sleeve by gripping the extended grooved pintail. As the bolt is being pulled through the sleeve, the sleeve expands in the hole because the outer diameter of the blind shaft portion of the boh is greater than the internal diameter of the sleeve. Expansion of the sleeve forms a high interference fit of the sleeve in the nominal hole. The force of the pneumatic puller pulling the bolt through the sleeve causes the head of the boh to seat properly on the outer surface of the assembly. The installed interference fit bolt and sleeve form a fluid tight seal in the hole.

Having pulled the bolt through the sleeve, the threaded/grooved portion of the bolt and pintail are left exposed from the inner surface of the assembly. The collar is then placed over the bolt pintail, up against the inner surface of the assembly. The collar is swaged upon the bolt with a swage gun until the pintail snaps off from the distal end of the bolt at a desired tension to complete the fastener installation.

In some circumstances, e.g. maintenance, inspection, repair, etc., it may be desirable to disassemble the workpieces that have been joined. The collar can be removed from the bolt. The bolt can be relatively easily knocked back until it is substantially flush with the inner surface of the assembly so as to expose the bolt head from the outer surface of the assembly. The bolt can then be removed from the sleeve using a bolt extractor attached to the bolt head. The collar and bolt removal can be carried out as a one-person operation.

However, it is difficult to remove the interference fit sleeve from the hole without damaging the workpiece. Whilst damage to any workpiece is undesirable, it is a particular issue if the workpiece is a composite laminate as delamination can occur around the edge of the hole. The damaged workpiece may need to be repaired or replaced before reassembly, which is undesirable. Alternatively, the sleeve may need to be removed from the workpiece and replaced with a larger diameter sleeved fastener.

Moreover, removal of the sleeve is generally a two-person operation as an extraction device needs to be positioned on the outside of the assembly, whilst a sleeve engagement device needs to be positioned on the inside of the assembly and connected to the extraction device. The increased labour cost of a two-person operation, as compared with a one-person operation, adversely impacts operational efficiency.

SUMMARY OF THE INVENTION

A first aspect of the invention provides a tool for removing an interference fit sleeve of a sleeved fastener system from a hole in a workpiece, the tool comprising: a collet and mandrel assembly moveable between an extended and a retracted position for opening and closing jaws of the collet, the collet and mandrel assembly being sized to fit inside the sleeve when the collet jaws are closed, and the collet jaws being sized so as to engage with one end of the sleeve when the jaws are open; and a puller device having a body for positioning adjacent the workpiece, and drive means for applying a force to the collet and mandrel assembly so as to move the collet and mandrel assembly from its extended position to its retracted position in a first action thereby opening the collet jaws, and to move the retracted collet and mandrel assembly relative to the body in a second action.

A second aspect of the invention provides a method of removing an interference fit sleeve of a sleeved fastener system from a hole in a workpiece, the method comprising: inserting a collet and mandrel assembly inside the sleeve from a fir st side of the workpiece with jaws of the collet closed; opening the jaws of the collet such that they engage with an end of the sleeve on the second side of the workpiece opposite the first; and with the open collet jaws engaged with the end of the sleeve applying a force to the collet and mandrel assembly in a direction substantially coaxial with the sleeve so as to remove the sleeve from the hole on the first side of the The invention is advantageous in that the sleeve removal tool can be used in a one-person operation to remove the fastener sleeve, since the tool can be inserted inside the sleeve, and the tool and sleeve extracted all from the same side of the workpiece.

The collet and mandrel assembly provides accurate control over the maximum diameter of the open collet jaws. Selection of an appropriately sized collet and mandrel assembly can therefore ensure that the open collet jaws are less than, or equal to, the nominal hole diameter such that minimal, or zero, damage to the workpiece occurs as the sleeve is removed.

The collet and mandrel assembly may include a spring for biasing the assembly to its extended position. The collet jaws are preferably resilient and biased to their closed position. The spring therefore preferably balances the resilience of the collet jaws to retained the mandrel against the closed collet jaws.

The tool may include a plurality of the collet and mandrel assemblies of different sizes for removing sleeves of different diameter and/or length. The collet and mandrel assemblies may be interchangeable on the puller device.

The collet and mandrel assembly may include a shaft connected at one end to the mandrel and its opposite end may be threaded for threadingly engaging with the puller device.

The puller device may further include a slider in sliding engagement with the body, and for transmitting the applied force to the collet and mandrel assembly.

The puller device may include a keyway for preventing relative rotation between the puller body and the collet and mandrel assembly.

The drive means may include a screw device for converting rotary motion of a drive shaft into linear motion of the collet and mandrel assembly.

The drive shaft may be mounted in a roller bearing on the body of the puller device.

The drive means may include a power pack. The power pack may be pneumatically, hydraulically or electrically powered, for example.

The method of the second aspect of the invention may form part of a method of removing a sleeved fastener system installed in a workpiece, the installed sleeved fastener system comprising a bolt, a collar and a sleeve, wherein the sleeve has an interference fit with a hole through the workpiece and has a flange on a first side of the workpiece, and wherein the boh has a head on the first side of the workpiece, a blind shaft portion forming an interference fit with the sleeve, and a threaded or grooved shaft portion which receives the collar on the second side of the workpiece, and the method comprising: removing the collar from the boh on the second side of the workpiece; removing the boh from the first side of the workpiece; and removing the sleeve according to the method of the second aspect of the invention.

The step of removing the bolt may include knocking the bolt back until it is substantially flush with the second side of the workpiece, and then removing the bolt from the first side of the workpiece using a bolt extractor.

The sleeved fastener system may include a pan head, or countersunk, bolt and a corresponding sleeve flange.

The workpiece may be made of composite material, e.g. a laminate of carbon or glass fibre reinforced plastic. Alternatively, the workpiece may be metallic, e.g. Aluminium, or Titanium, or any other suitable material.

The collet and mandrel assembly may be sized such that the maximum diameter of the jaws when open is less than or equal to the nominal diameter of the hole in the The workpiece may be part of an aircraft, e.g. an aircraft wing box, or fuselage.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described with reference to the accompanying drawings, in which: Figure 1 illustrates a sleeved fastener system comprising a sleeve partially received on a boh having a removable pintail, and a collar for swaging onto the bolt; Figure 2 illustrates the sleeved fastener system being installed in a hole in a workpiece and in particular shows the bolt having been pulled through the sleeve so as to expand the sleeve within the hole to an interference fit, and the collar placed over the threaded/grooved portion of the bolt ready for swaging; Figure 3 illustrates the sleeved fastener system installed in the workpiece; Figure 4 illustrates the sleeved fastener system being removed from the workpiece and in particular shows the boll being removed from inside the sleeve; Figure 5 illustrates a collet and mandrel assembly of a sleeve removal tool in accordance with the invention being inserted inside the sleeve held in the workpiece, with the collet and mandrel assembly in an extended state such that the collet jaws are closed; Figure 6 illustrates the collet and mandrel assembly in a retracted state such that the collet jaws are open to engage with one end of the sleeve; and Figure 7 illustrates the sleeve removal tool comprising a puller device and the collet and mandrel assembly engaged with the sleeve, ready to pull the sleeve from the

DETAILED DESCRIPTION OF EMBODIMENT(S)

Figure 1 illustrates a sleeved fastener system 1 comprising a high interference threaded pull bolt 2, a sleeve 3, and a collar 4. The high interference threaded pull boll 2 is similar to that described in US patent LTSSO1 8920. The bolt 2 shown in Figure 1 is of a pan head type with a pan head 5, and the sleeve 3 has a corresponding straight flange 6. A variant of this sleeved fastener system includes a countersunk head bolt which cooperates with a sleeve having an angled flange.

The bolt 2 has a blind shaft portion 7 at one end adjacent to the head 5, and a threaded or grooved (ringed) shaft portion 8 at the other end. The outer diameter of the threaded/grooved portion 8 is less than the inner diameter of the sleeve 3, whilst the outer diameter of the blind portion 7 has a diameter greater than the inner diameter of the sleeve 3.

As shown in Figure 1, the sleeved fastener is supplied with the bolt 2 received inside the sleeve 3. The bolt 2 further comprises an integrally formed pintail 9 extending from the distal end of the bolt 2 via a fracture collar 10. The pintail 9 is ribbed for engagement with a pull tool, as will be described in detail below. The pintail 9 has an outer diameter less than the inner diameter of the sleeve 3. The collar 4 has a smooth internal bore 11 for swaging engagement with the threaded/grooved portion 8 of the bolt 2.

Figure 2 illustrates the sleeved fastener system 1 being installed in a hole 12 formed in a pair of workpieces 13, 14 to be joined together. The hole 12 has an internal nominal diameter for receiving the as-supplied sleeve 3 with a clearance fit. The sleeve 3 is inserted in the hole 12 with the bolt head S initially sitting well above the sleeve flange 6 (as shown in Figure 1).

A pull tool (not shown) is positioned against an inner surface 15 of the workpieces 13, 14 to be joined and attached to the pintail 9 of the boll 2. The pull tool is used to pull the bolt 2 through the sleeve 3. As the bolt 2 moves through the sleeve 3 a taper 7a located between the threaded/grooved portion 8 and the blind portion 7 of the bolt swells the sleeve 3 to form a high interference fit between the blind portion 7 of the bolt 2 and the inner surface of the sleeve 3, and a high interference between the outer surface of the sleeve 3 and the bore of hole 12 in the workpieces 13, 14.

The pull tool pulls the bolt through the sleeve 3 until the pan head 5 of the bolt 2 is seated properly against the sleeve flange 6, which in turn seats properly against the outer surface 16 of the workpieces 13, 14. The boh 2 and sleeve 3 of the sleeved fastener form a fluid tight high interference fit in the hole 12. The collar 4 is placed over the exposed pintail 9 and pushed up to the surface 15. A swage gun (not shown) is placed over the pintail 9 and up to the collar 4. As the swaging action of the swage gun grips the grooved pintail 9, and with the force pushing up onto the collar 4, the collar 4 is swaged onto the threaded/grooved portion 8 of the bolt 2. The swage gun keeps applying pressure until the tensile limit of the fracture collar 10 is reached at which point the pintail 9 snaps off from the distal end of the bolt 2 to complete the fastener installation. Figure 3 illustrates the installed sleeved fastener system.

In one embodiment, the component 13 is an aircraft wing cover and the component 14 is a wing box rib, or spar. The components 13 and 14 are formed of laminate composite material, such as carbon fibre reinforced plastic, for example. The fluid tight seal created by the high interference fit fastener 1 is particularly beneficial since the interior volume of an aircraft wing is typically used as a fuel tank.

In order to disassemble the workpieces 13, 14 it is necessary to remove the installed fastener. First, the collar 4 is removed and then the boh 2 can be knocked back until the distal end of the boh 2 is substantially flush with the inner surface 15 of the workpieces 13, 14, as shown in Figure 4. A bolt extractor (not shown) can then be positioned against the outer surface 16 of the workpieces 13, 14 and used to extract the bolt 2 from inside the sleeve 3 by engagement with the underside of the pan head 5 and pulling in the direction of arrow F. This then leaves the sleeve 3 still forming a high interference fit with the bore of hole 12.

Figure 5 illustrates a collet and mandrel assembly 17 of a sleeve removal tool in accordance with the invention being inserted inside the sleeve 3 for removing the sleeve 3 from the hole 12 in the workpieces 13, 14. The collet and mandrel assembly 17 includes a collet 18 having a collet body 18a and a set of integrally formed collet jaws 18b formed by creating slits 19 in a tapered distal end 18c of the collet 18. The collet jaws 1 8b are arranged around the circumference of the generally tubular collet 18.

Each of the collet jaws 1 8b has a flange 1 8d extending substantially radially outwardly from the distal, free end of each collet jaw I 8b. The inward taper of the distal end 1 8c of the collet 18 creates a "closed" position for the collet jaws 18b. In the closed position the outer diameter dl of the collet jaws 1 8b is less than or equal to the outer diameter d2 of the body 18a of the collet 18.

The collet 18 further comprises a cylindrical portion l8e integrally formed with the body 1 8a and disposed at the proximal end of the collet and mandrel assembly 17.

The cylindrical portion 1 8e has a central bore 1 8f. The central bore 1 8f receives a shaft 20 connected to a mandrel 21. The mandrel comprises a solid cylindrical portion 21a and a frusto-conical portion 21b terminated in an end stop 12c.

The mandrel 21 is slidably disposed inside the collet 18 such that the collet and mandrel assembly 17 is movable between an extended position (as shown in Figure 5) in which the frusto-conical portion 21b of the mandrel extends beyond the collet jaws 1 8b such that the collet jaws 1 8b are closed, and a retracted position in which the frusto-conical portion 21b of the mandrel is retracted inside the collet jaws 1 8b so as to force the collet jaws 18b to expand to an "open" position. The end stop 21c prevents the collet jaws 1 8b from being opened beyond the limit where the end stop 21c contacts the flanges 18d of the collet jaws 18b. The shaft 20 is integrally formed with the mandrel 21.

The outer diameter of the cylindrical portion 21a of the mandrel 21 is sized such that the collet jaws 1 8b are biased against the cylindrical surface of the mandrel when the collet jaws 1 8b are in the closed position. The outer diameter of the collet and mandrel assembly 17 in its extended position with the collet jaws 1 8b closed is sized such that the collet and mandrel assembly 17 may be freely inserted inside the interference fit sleeve 3 installed in the workpieces 13, 14.

Figure 6 illustrates the collet and mandrel assembly 17 in its retracted state after having been inserted inside the sleeve 3. Having been inserted inside the sleeve 3 with the collet jaws 1 Sb closed such that the collet jaw flanges 1 Sd have passed through to the other side of the sleeve 3, the collet and mandrel assembly 17 is moved to its retracted position so as to open the collet jaws 1 8b.

With the collet jaws I 8b open, the outer diameter of the collet jaw flanges I 8d is greater than the internal diameter of the sleeve 3, but less than the nominal diameter of the hole 12 in the workpieces 13, 14. The flanges 18d of the collet jaws 18b therefore engage with one end of the sleeve 3 but do not contact the workpieces 13, 14.

The collet jaws 1 Sb are biased to their closed position and so the mandrel 21 is biased to its extended position owing to the frusto-conical portion 2 lb of the mandrel 21. A tension spring 22 is provided for acting against the sprung bias of the collet jaws l8b such that the mandrel 21 is securely retained within the collet 18. The proximal end of the shaft 20 is threaded for receiving a nut 23. Application of a pulling force in the direction of arrows D acts to remove the sleeve from the workpieces 13, 14 in a two-step action.

In a fir st step the collet and mandrel assembly 17 is moved from its extended position to its retracted position thereby opening the collet jaws 1 Sb so as to engage with one end of the sleeve 3. When the mandrel end stop 21c bears against the collet jaws lSb continued pulling action in the direction of arrows P pulls the collet and mandrel assembly 17 and the sleeve 3 with which the collet jaws 1 Sb are engaged in the direction of arrows P thereby removing the sleeve 3 from the hole 12 in the The pulling force for moving the collet and mandrel assembly 17 and the sleeve 3 is provided by a puller device 24 shown in Figure 7. The puller device 24 includes a puller body 25 including a substantially tubular portion 25a, a foot portion 25b extending substantially perpendicular to the longitudinal axis of the cylindrical portion 25a at a distal end of the puller body 25, and a proximal end 25c. The puller body 25 houses a screw device 26 for converting rotary motion of a drive shaft 27 into linear motion of a slider 28 slidably disposed within the puller body 25 and engaged with the collet and mandrel assembly 17 via the nut 23. Mounted on an outer surface of the proximal end 25c of the puller body 25 is a roller bearing 29 and a nut 30.

The slider 28 engages with a keyway segment 31 disposed inside the puller body and in fixed relation with the puller body 25 so as to prevent relative rotation between the slider 28 and the puller body 25.

Application of a torque to the shaft 27 causes linear movement of the slider 28 within the puller body 25 and corresponding application of force in the direction of arrows P (see Figure 6) to the collet and mandrel assembly 17 connected to the puller device 24.

The annular foot 25b of the puller body 25 bears against the outer surface 16 of the workpieees 13, 14 over a relatively large surface area so as to avoid damage to the The torque may be applied to the puller device either manually, e.g. using a spanner or the like, or using a power pack. In a preferred embodiment, a pneumatic power pack such as is commonly known in the art may be used. Alternatively, any suitable power pack, e.g. one that is hydraulically or electrically powered, may be used.

The sleeve removal tool in accordance with this invention can be used to safely and efficiently remove the sleeve 3 from the workpieces 13, 14, and requires access from only one side of the workpieces 13, 14. In the examples given above, where the components 13, 14 form part of an aircraft wingbox such that the outer surface 16 is an outer aerodynamic surface of the aircraft wingbox, and the inner surface 15 is an interior surface of an integral wing fuel tank, the sleeve removal tool in accordance with this invention is particularly advantageous since it is not necessary to gain access to the interior of the fuel tank in order to remove the sleeve and therefore the sleeve removal may be carried as a one person operation.

Although in the embodiments described above the workpieces 13, 14 are of composite material it will be appreciated that the invention may be applied to removal of sleeves of sleeved fasteners from metallic workpieces or workpieces made of other materials.

Advantageously, the puller device 24 is adapted to be connected to a variety of collet and mandrel assemblies of different sizes such that the same puller device can be used with a variety of interchangeable collet and mandrel assemblies for removal of sleeves of different dimensions. The user simply needs to disconnect one collet and mandrel assembly of a given size from the puller device and reconnect a different collet and mandrel assembly of a different size.

Although the invention has been described above with reference to one or more preferred embodiments, it will be appreciated that various changes or modifications may be made without departing from the scope of the invention as defined in the appended claims.

Claims

Claims 1. A tool for removing an interference fit sleeve of a sleeved fastener system from a hole in a workpiece, the tool comprising: a collet and mandrel assembly moveable between an extended and a retracted position for opening and closing jaws of the collet, the collet and mandrel assembly being sized to fit inside the sleeve when the collet jaws are closed, and the collet jaws being sized so as to engage with one end of the sleeve when the jaws are open; and a puller device having a body for positioning adjacent the workpiece, and drive means for applying a force to the collet and mandrel assembly so as to move the collet and mandrel assembly from its extended position to its retracted position in a first action thereby opening the collet jaws, and to move the retracted collet and mandrel assembly relative to the body in a second action.
2. A tool according to claim I, wherein the collet and mandrel assembly includes a spring for biasing the assembly to its extended position.
3. A tool according to claim 1 or 2, including a plurality of the collet and mandrel assemblies of different sizes for removing sleeves of different diameter and/or length, and wherein the collet and mandrel assemblies are interchangeable on the puller device.
4. A tool according to any preceding claim, wherein the collet and mandrel assembly includes a shaft connected at one end to the mandrel and its opposite end is threaded for threadingly engaging with the puller device.
5. A tool according to any preceding claim, wherein the puller device further includes a slider in sliding engagement with the body, and for transmitting the applied force to the collet and mandrel assembly.
6. A tool according to any preceding claim, wherein the puller device includes a keyway for preventing relative rotation between the puller body and the collet and mandrel assembly.
7. A tool according to any preceding claim, wherein the drive means includes a screw device for converting rotary motion of a drive shaft into linear motion of the collet and mandrel assembly.
8. A tool according to claim 7, wherein the drive shaft is mounted in a roller bearing on the body of the puller device.
9. A tool according to any preceding claim, wherein the drive means includes a power pack.
10. A tool according to claim 9, wherein the power pack is pneumatically, hydraulically or electrically powered.
11. A method of removing an interference fit sleeve of a sleeved fastener system from a hole in a workpiece, the method comprising: inserting a collet and mandrel assembly inside the sleeve from a first side of the workpiece with jaws of the collet closed; opening the jaws of the collet such that they engage with an end of the sleeve on the second side of the workpiece opposite the first; and with the open collet jaws engaged with the end of the sleeve applying a force to the collet and mandrel assembly in a direction substantially coaxial with the sleeve so as to remove the sleeve from the hole on the first side of the
12. A method of removing a sleeved fastener system installed in a workpiece, the installed sleeved fastener system comprising a bolt, a collar and a sleeve, wherein the sleeve has an interference fit with a hole through the workpiece and has a flange on a first side of the workpiece, and wherein the bolt has a head on the first side of the workpiece, a blind shaft portion forming an interference fit with the sleeve, and a threaded or grooved shaft portion which receives the collar on the second side of the workpiece, and the method comprising: removing the collar from the bolt on the second side of the workpiece; removing the bolt from the first side of the workpiece; and removing the sleeve according to the method of claim 11.
13. A method according to claim 12, wherein the step of removing the bolt includes knocking the bolt back until it is substantially flush with the second side of the workpiece, and then removing the boh from the first side of the
14. A method according to claim 12 or 13, wherein the sleeved fastener system includes a pan head, or countersunk, boh and corresponding sleeve flange.
15. A method according to any of claims 11 to 14, wherein the workpiece is made of composite material, preferably a laminate of fibre reinforced plastic.
16. A method according to any of claims 11 to 15, wherein the collet and mandrel assembly is sized such that the maximum diameter of the jaws when open is less than or equal to the nominal diameter of the hole in the workpiece.