Patent Publication Number: US-6910252-B2

Title: Apparatus for removing a fastener from a workpiece

Description:
FIELD OF THE INVENTION 
   The present invention relates generally to an apparatus for removing a fastener, such as a bolt, a pin, a rivet or the like, from a corresponding aperture defined by a workpiece and, more particularly, to an apparatus for removing a fastener from a workpiece without damaging the fastener or the workpiece which may be utilized in instances in which the fastener may only be accessed from the head end and, as a result, cannot be punched or pushed out. 
   BACKGROUND OF THE INVENTION 
   From time to time, fasteners, such as bolts, pins, rivets or the like, may need to be removed from various structures in order to partially or completely disassemble the structures. For example, various structures, including aircraft, undergo life cycle testing that requires at least some disassembly at one or more intervals during the lifetime of the structure. Additionally, structures that are involved in accidents may be disassembled during the investigation into the cause and/or the results of the accident. 
   In instances in which fasteners are removed from a structure, the fasteners are preferably removed without damaging either the fastener or the workpiece. In this regard, the structure from which fasteners are removed is frequently reassembled following an inspection and/or the performance of various maintenance activities. As such, it would be desirable, both from a cost and an efficiency standpoint, to reassemble the structure utilizing most, if not all, of the same components. By removing the fasteners without damaging the fasteners or the workpiece, the same fasteners can subsequently be reinstalled without having to rework the workpiece and, in particular, without having to rework the apertures defined by the workpiece in which the fasteners are installed. Moreover, in instances in which fasteners are removed from a structure in order to perform life cycle testing or during an accident investigation, the evidentiary value of the fasteners, as well as the workpiece, is significantly diminished if the condition of the fastener and/or the workpiece is altered or damaged during the disassembly process. 
   Conventional techniques for removing a fastener utilize a drift or a punch to apply axial force to the end of the fastener opposite the head end so as to push the fastener out of the corresponding aperture defined by the workpiece. With respect to a bolt, for example, the nut must first be removed from the threaded end of the bolt and a drift or punch is then utilized to push the bolt out of the corresponding aperture. Depending upon the design of the structure, however, the end of the fastener opposite the head end, such as the threaded end of a bolt, may be relatively inaccessible such that a drift or a punch cannot be utilized to push the fastener out of the corresponding aperture. In these situations, a wrench or the like may oftentimes be inserted from a direction substantially perpendicular to the longitudinal axis of the bolt so as to engage and remove the nut from the fastener. However, the surrounding structure oftentimes prevents access to the threaded end of the bolt with a drift or punch to thereafter remove the bolt. 
   Additionally, some structures may be at least partially forward of relatively soft material, such as aluminum, that may be damaged by the use of a drift or punch, thereby further limiting the use of a drift or punch. Furthermore, some structures may define at least partially threaded apertures that threadably engage the fastener, such as a bolt or the like. In these instances, a drift or punch is also generally inappropriate since attempts to merely push the fastener out of the threaded aperture would be either ineffective and/or would damage the threads defined by the aperture and/or the fastener. 
   In these instances, a fastener must generally be pulled or pried out of the corresponding aperture from the head end of the fastener. In order to pull a fastener out from the head end, a vice grip, pliers or the like are utilized to grasp the head end of the fastener. However, the force required to pull a fastener, such as a bolt, from the corresponding aperture may be substantial due, at least in part, to the generally snug fit of the fastener within the aperture. Moreover, it is generally difficult to securely grasp the head end of the fastener and the vice grip, pliers or the like may tend to slip off if attempts are made to pull the fastener. 
   Depending upon the structure from which the fasteners are extracted, the head end of the fastener may be inaccessible with a vice grip, pliers or the like. In addition, pulling a fastener from the corresponding aperture may damage the head end and/or threads of the fastener as well as the aperture. For example, the pulling force applied to the fastener may serve to misalign the fastener relative to the aperture, thereby damaging the fastener and/or the aperture. As a result of the relatively tight tolerances between the apertures defined by the workpiece and the corresponding fasteners, pulling the fasteners from the corresponding apertures may also induce thread scrubbing of the fastener and, in instances in which the aperture is threaded, of the threaded aperture. 
   In these instances in which the fastener is damaged during its removal, the fastener must generally be replaced prior to reassembly of the structure. Additionally, any apertures that were damaged during the disassembly process must be reworked prior to reassembly of the structure, thereby significantly increasing the time and expense associated with reassembling the structure. 
   As such, it would be desirable to provide an improved tool for removing fasteners from structures without damaging the fasteners or the structure, thereby permitting the structure to be reassembled utilizing the same fasteners with a minimum, if any, rework of the structure. In addition, it would be desirable to provide an improved tool for removing fasteners from workpieces in instances in which the end of the fastener opposite the head end is inaccessible with a drift or a punch. 
   SUMMARY OF THE INVENTION 
   An improved apparatus is provided according to embodiments of the present invention for removing a fastener, such as a bolt, a pin, a rivet or the like, from a corresponding aperture defined by a workpiece which reduces, if not eliminates, damage to the fastener and/or the workpiece that might otherwise be occasioned by conventional disassembly techniques. In this regard, the apparatus of embodiments of the present invention removes the fastener from the head end while maintaining a removal force that is in axial alignment with the fastener and centered on the corresponding aperture defined by the workpiece, thereby avoiding damage to the fastener and the workpiece. By removing the fastener from the head end, the apparatus can remove fasteners in situations in which the other end of the fastener is inaccessible with a drift or a punch. In addition, the apparatus of some embodiments of the present invention rotates the fastener as the fastener is removed from the corresponding aperture, thereby further preventing damage to threaded fasteners and/or threaded apertures, such as by thread scrubbing, during the removal process. In contrast, the apparatus of other embodiments removes the fastener without rotating the fastener, thereby avoiding enlarging the aperture such as in instances in which the fastener is bent, for example. 
   An apparatus for removing a fastener from a corresponding aperture defined by a workpiece includes a pulling plug for engaging the head of the fastener. In instances in which the head of the fastener has a polygonal shape, such as the polygonal head of a bolt, the pulling plug may include a plurality of interior surfaces that are angularly disposed with respect to one another. The angularly disposed interior surfaces of the pulling plug of this embodiment define an interior cavity that receives and mates with the polygonal head of a fastener. 
   The apparatus of the present invention also includes a drive shaft operably connected to the pulling plug. Thus, rotation of the drive shaft also rotates the pulling plug. In instances in which the pulling plug includes a plurality of angularly disposed interior surfaces for mating with the polygonal head of a fastener, rotation of the drive shaft not only rotates the pulling plug, but also the fastener. The apparatus of the present invention further includes a lever member capable of being urged into operable contact with a surface of the workpiece. Advantageously, the lever member is urged into operable contact with the surface of the workpiece so as to push against the surface of the workpiece without gripping or otherwise positively engaging the workpiece. 
   The lever member may therefore have a first end with a shape corresponding to the surface of the workpiece. For example, the first end of the lever member may be disposed at a non-orthogonal angle relative to the drive shaft. The first end of the lever member may include a flange or washer to spread the load over a larger area of the workpiece to avoid damaging the workpiece, a feature particularly attractive for workpieces formed of relatively soft materials. In addition, the first end of the lever may define a notch for accepting the head of another fastener or some other raised feature of the workpiece. The lever member of one embodiment includes an interchangeable end member to permit the shape of the first end to be selectively varied, typically based upon the shape of the workpiece. As such, the apparatus may be utilized in conjunction with workpieces of various shapes with the end member of the lever member generally being selected such that the first end of the lever member has a shape corresponding to that of the surface of the workpiece. 
   In operation, the head end of a fastener is engaged by the pulling plug. In this regard, the pulling plug is capable of extending beyond the lever member in order to engage and disengage the fastener. Thereafter, the lever member is moved into contact with the workpiece. The drive shaft is then capable of being retracted in a direction away from the workpiece while the lever member continues to be urged into operable contact with the surface of the workpiece without gripping or otherwise positively engaging the workpiece. As such, the pulling plug is also moved away from the surface of the workpiece as a result of the retraction of the drive shaft in order to remove the fastener from the aperture defined by the workpiece. 
   The lever member generally defines a cylindrical passage through which the drive shaft at least partially extends. Additionally, the lever member may include a collar defining an aperture for snugly receiving the drive shaft. By continuing to urge the lever member into operable contact with the surface of the workpiece while the fastener is being removed from the aperture and by maintaining the desired positional relationship between the lever member and the drive shaft, such as a result of the snug fit of the drive shaft within the aperture defined by the collar of the lever member, the apparatus of the present invention may remove the fastener while maintaining an axis of force centered on the aperture, perpendicular to the workpiece and in-line with the fastener being removed, thereby avoiding damage to the fastener or the aperture. 
   In one embodiment, the lever member and, most commonly, the collar of the lever member, is threadably connected to the drive shaft. According to one removal technique, the drive shaft may be threadably retracted in order move the pulling plug and, in turn, the head end of the fastener away from the surface of the workpiece, while the lever member remains in operable contact with the surface of the workpiece. In the embodiment in which the pulling plug includes a plurality of angularly disposed interior surfaces that define an interior cavity for receiving and mating with the polygonal head of a fastener, the threaded retraction of the drive shaft also rotates and threadably retracts the fastener. By threadably retracting the fastener, the apparatus of this embodiment further avoids damage to the fastener as well as any threaded aperture in which the fastener is installed. In order to facilitate the threaded retraction of the drive shaft, the drive shaft may be rotated by various means including turning the drive shaft with a wrench that engages a nut/lock nut combination that is mounted upon the drive shaft, or rotating the drive shaft with a drive tool. 
   According to another removal technique, the lever member is threadably advanced along the drive shaft. Thus, the fastener is pulled from the workpiece without causing the fastener to rotate. In instances in which the fastener is bent, therefore, this removal technique permits the fastener to be removed without enlarging the aperture. 
   In another embodiment, the lever member does not threadably engage the drive shaft, although the lever member may still include a collar defining an aperture for snugly receiving the drive shaft. In this embodiment, the apparatus may also include a mechanized actuator, such as a pneumatic actuator, a hydraulic actuator, an electric solenoid or the like, for retracting the drive shaft in a direction away from the workpiece. As such, the pulling plug is correspondingly retracted in order to remove the fastener from the aperture defined by the workpiece. In this embodiment, the apparatus may also include a spring for urging the drive shaft and the pulling plug toward the workpiece once the mechanized actuator is deactivated. 
   Accordingly, the apparatus of the present invention permits fasteners to be removed from corresponding apertures defined by a workpiece with less risk of damaging the fasteners and the workpiece than conventional fastener removal techniques. In this regard, the apparatus generally maintains alignment between the fastener and the corresponding aperture during the process of removing the fastener. Additionally, the apparatus may threadably retract fasteners, such as threaded fasteners, in order to facilitate the removal of the fasteners from corresponding apertures defined by the workpiece and to further avoid damage, such as thread scrubbing, to the threaded fastener and/or correspondingly threaded apertures defined by the workpiece. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S) 
     Having thus described the invention in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein: 
       FIG. 1  is a perspective view of an apparatus for removing a fastener according to one embodiment of the present invention following the engagement of the head end of the fastener; 
       FIG. 2  is a cross-sectional view of the apparatus of  FIG. 1 ; 
       FIG. 3  is an end cross-sectional view of the apparatus of  FIGS. 1 and 2 ; 
       FIG. 4  is a cross-sectional view of the apparatus of  FIGS. 1-3  once the lever member has been urged into operable contact with the surface of the workpiece; 
       FIG. 5  is a cross-sectional view of the apparatus of  FIGS. 1-4  once the drive shaft has been retracted during the process of removing the fastener from the workpiece; 
       FIG. 6  is a cross-sectional view of an apparatus according to another embodiment of the present invention in which the lever member is adapted to be threadably advanced relative to the drive shaft; 
       FIG. 7  is a schematic representation of an apparatus for removing a fastener according to another embodiment of the present invention which includes a mechanized actuator for retracting the drive shaft; and 
       FIG. 8  is a perspective view of a lever member having an interchangeable end member that matches the shape of the surface of the workpiece according to one embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The present inventions now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the invention are shown. Indeed, these inventions may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout. 
   Referring now to  FIG. 1 , an apparatus  10  for removing a fastener  12  from a corresponding aperture defined by a workpiece  14  is depicted. The apparatus is capable of removing a variety of fasteners such as bolts, pins, rivets and the like. Regardless of the type of fastener, the fastener has a head end  16  that is accessible while the fastener is installed in the corresponding aperture defined by the workpiece. For example, the fastener may include a head end that sits upon or is recessed relative to the surface of the workpiece. In either instance, the head end is larger than the shaft  18  of the fastener that extends through the corresponding aperture. Additionally, the apparatus is capable of removing fasteners from a wide variety of workpieces, including workpieces formed of metal and composite materials. In one embodiment, the apparatus is utilized to remove fasteners from an airframe assembly. However, the apparatus may be utilized to remove fasteners from a wide variety of other structures, if so desired. 
   Regardless of the type of structure, the workpiece  14  advantageously defines one or more apertures through which corresponding fasteners  12  extend. In instances in which the fasteners are threaded, such as bolts, the apertures may also be at least partially internally threaded. While the aperture may have a greater length than the fastener in some circumstances, a fastener generally completely extends through the aperture such that the head end  16  of the fastener is seated upon or recessed within one surface of the workpiece while the other end of the fastener extends beyond the opposed surface of the workpiece. For bolts or other threaded fasteners, a nut may also be threadably engaged on the end of the bolt opposite the head end. 
   In order to remove the fastener  12 , such as during disassembly of the structure for life cycle testing, an accident investigation or for any other reason, the apparatus  10  of the present invention initially engages the head end  16  of the fastener. In this regard, the apparatus includes a pulling plug  20  for engaging the head end of the fastener. As shown in  FIGS. 1 and 2 , and as explained more fully below, the pulling plug may extend beyond the remainder of the apparatus to engage the fastener. In one embodiment, the pulling plug has a generally cylindrical shape that defines a passage extending lengthwise therethrough. A first end  22  of the pulling plug, namely, the end of the pulling plug proximate the workpiece  14 , defines a lengthwise extending slot or opening  24  for receiving the head end of the fastener. Thus, the first end of the pulling plug is not completely cylindrical, but, instead, has a generally U-shape. The slot defined by the first end of the pulling plug opens into an internal cavity that is sized and shaped to receive the head end of the fastener. In instances in which the head end of the fastener has a polygonal shape, such as the polygonal head of a bolt, the first end of the pulling plug may include a plurality of interior surfaces angularly disposed with respect to one another so as to define an interior cavity having a polygonal shape that matches and engages the polygonal head end of the fastener. 
   The first end  22  of the pulling plug  20  proximate the workpiece  14  also includes an inwardly extending flange. This flanged end of the pulling plug also defines an opening therethrough which is sized to be smaller than the internal cavity. In particular, the opening defined by the flanged end of the pulling plug is sized to be smaller than the head end  16  of the fastener  12 , but slightly larger than that portion of the shaft  18  of the fastener proximate the head end. As such, the pulling plug can engage the fastener such that the head end of the fastener is disposed within the internal cavity defined by the pulling plug, and the flanged end of the pulling plug is disposed beneath the bead end of the fastener and between the head end of the fastener and the surface of the workpiece such that the shaft of the fastener extends through the opening defined by the flanged end of the pulling plug. Thus, force applied by the pulling plug in a direction away from the surface of the workpiece would be applied to the fastener via the engagement of the head end of the fastener by the flanged end of the pulling plug. 
   As best shown in  FIG. 3 , the passage extending lengthwise through the pulling plug  20 , including the interior cavity and the opening defined by the inwardly extending flange of the first end  22  of the pulling plug, is preferably centered. As such, the apparatus  10  can apply relatively equal force across the width of the head end  16  of the fastener  12  to further assist in the extraction of the fastener in an axial direction so as to avoid damage to the fastener and/or the corresponding aperture. 
   The apparatus  10  also includes a drive shaft  28 . The drive shaft may be at least partially threaded. In one illustrated embodiment that will be described below, the drive shaft is threaded along its entire length to permit fasteners  12  having a wide variety of lengths to be extracted. However, other embodiments of the apparatus of the present invention include a drive shaft in which only portions are threaded or in which the drive shaft is unthreaded along its entire length. 
   The drive shaft  28  is connected, generally at a first end, to the pulling plug  20 . Although the drive shaft may be connected to the pulling plug in various manners, the first end of the drive shaft may be threaded as illustrated in  FIGS. 1 and 2  such that the drive shaft may threadably engage the pulling plug. In the illustrated embodiment, for example, the second end of the pulling plug, opposite the flanged end, defines an internally threaded portion for engaging the drive shaft. As described below, the threaded first end of the drive shaft that engages the pulling plug advantageously has threads of the opposite orientation from other threaded portions of the drive shaft, i.e., left-handed threads as opposed to right-handed. By engaging the pulling plug with threads of the opposite orientation, the pulling plug and the drive shaft remain connected during the threaded retraction of the drive shaft during extraction of a fastener  12 . While the drive shaft is shown to be threadably attached to the pulling plug in the illustrated embodiment, the drive shaft and the pulling plug may be integrally formed or otherwise attached in other embodiments. By threadably attaching or otherwise removably attaching the pulling plug to the drive shaft, however, the versatility of the apparatus  10  of this embodiment of the present invention is enhanced since pulling plugs that are designed to receive and engage fasteners having head ends  16  with different sizes and shapes can be alternatively threadably attached to the drive shaft. In embodiments in which both the drive shaft and the fastener are threaded, the threads of the drive shaft also generally have the opposite orientation to the threads of the fastener being removed. 
   The apparatus  10  of the present invention also includes a lever member  30  for operably contacting the surface of the workpiece  14  during the removal of a fastener  12 . In the illustrated embodiment, the lever member has a cylindrical shape and defines an internal passage centered within the lever member through which at least a portion of the drive shaft  28  extends. In addition, the pulling plug  20  is advantageously disposed within one end of the internal passage defined by the lever member while the fastener  12  is being removed. In order to prevent the flanged first end  22  of the pulling plug from spreading radially outwardly during the process of removing the fastener and thereby potentially allowing the head end  16  of the fastener to become disengaged from the pulling plug, the lever member preferably defines the internal passage to be shaped and sized to closely approximate the exterior shape and size of the pulling plug. In one embodiment in which both the lever member and the pulling plug have a generally cylindrical shape, the inner diameter of the lever member is about 0.005 inch to 0.010 inch larger than the exterior diameter of the pulling plug. 
   As shown in  FIGS. 1-5 , the lever member  30  may include a flanged end  42  for operably contacting the workpiece  14 . The flanged end extends radially outwardly from the cylindrical portion of the lever member. Thus, the flanged end effectively spreads the forces applied by the apparatus  10  to the workpiece over a greater area of the workpiece. The spreading of the forces provided by the flanged end of the lever member is particularly advantageous in instances in which the workpiece is formed of a relatively soft material, such as aluminum, that may otherwise be damaged by the forces generated during the fastener removal process. Although the lever member depicted in  FIGS. 1-5  is of a unitary or integral design, the flanged end of the lever member may be interchangeable as described below in conjunction with the embodiment of  FIG. 8  in order to mate with a variety of differently shaped workpieces. While the flanged end of the lever member is advantageous as described above, the lever member need not include the flanged end and the end may, instead, have the same shape and profile as the remainder of the cylindrical lever member, if desired. 
   As described below, the apparatus  10  is preferably designed such that the pulling plug  20  is capable of extending beyond the lever member in order to engage the head end  16  of the fastener  12  prior to removal operations as shown in  FIGS. 1 and 2 , and to be disengaged from the head end of the fastener once the fastener has been removed from the workpiece  14 . The relative positions of the lever member and the pulling plug may be altered during the process of removing the fastener from the workpiece, however, by moving the lever member toward and into operable contact with the workpiece so as to surround and support the pulling plug during the process of removing the fastener from the workpiece, as shown in  FIGS. 4 and 5 . 
   In operation, the pulling plug  20  engages the head end  16  of the fastener  12  as shown in  FIGS. 1 and 2 , and the lever member  30  is then moved into operable contact with the surface of the workpiece  14  as shown in FIG.  4 . By thereafter moving the drive shaft  28  and, in turn, the pulling plug in a direction away from the surface of the workpiece, while maintaining the lever member in operable contact with the surface of the workpiece, the fastener may be extracted as shown in FIG.  5 . The apparatus  10  of the present invention provides for the drive shaft and the pulling plug to be retracted while the lever member is maintained in operable contact with the workpiece in various manners. In the embodiment depicted in  FIGS. 1-5 , the lever member threadably engages the drive shaft in such a manner that rotation of the drive shaft causes the drive shaft and, in turn, the pulling plug to be retracted relative to the surface of the workpiece while maintaining the lever member in operable contact with the workpiece. In this embodiment, the lever member includes a collar  32  that is internally threaded. As depicted, the collar may be integral with the remainder of the lever member and may be disposed at one end of the lever member, such as the end of the lever member opposite the workpiece. Alternatively, the collar may be disposed at other locations along the length of the lever member so long as the collar remains rearward of the pulling plug once the pulling plug has been retracted relative to its fullest extent to the lever member. In this regard, in order to have the versatility to extract fasteners having a length ranging from a relatively short length to a much longer length, the lever member should have a length such that the spacing between the collar of the lever member and the pulling plug, once the lever member has been disposed in operable contact with the workpiece, is approximately equal to the maximum length of the fasteners that the apparatus is designed to extract less the cumulative thickness of the head end of the fastener and the flanged first end  22  of the pulling plug. 
   As mentioned above, the drive shaft  28  may be threaded along its entire length. In alternative embodiments, however, only that portion of the drive shaft is threaded that will threadably engage the collar  32  of the lever member  30 . In this embodiment, the length of the threaded portion of the drive shaft that threadably engages the collar of the lever member should have a sufficient length such that the lever member can be threadably retracted to permit the pulling plug to engage the head end of the fastener and can thereafter be threadably advanced into operable contact with the workpiece  14 . 
   In any event, the lever member  30  and the collar  32  of the lever member is advantageously threaded in the opposite direction or sense than the threaded end portion of the drive shaft that engages the pulling plug  20 . Thus, the pulling plug rotates with the drive shaft as the drive shaft is threadably retracted, while the lever member remains in operable contact with the surface of the workpiece  14 . 
   The drive shaft  28  also advantageously includes an engagement element to permit the drive shaft to be engaged and rotated, such as to move the pulling plug  20  and, in turn, the fastener  12  in a direction away from the surface of the workpiece  14 . In the illustrated embodiment, for example, the nut and lock nut combination  34  are threaded onto the drive shaft. The nut and lock nut combination may then be engaged by a wrench or the like and turned so as to threadably retract the drive shaft. Alternatively, the drive shaft may have a head  35 , typically disposed on the end of the drive shaft opposite the pulling plug. The head of the drive shaft of this embodiment may be engaged by a mechanized socket wrench or other drive tool, for example, to facilitate the threaded retraction of the drive shaft. 
   In instances in which the fastener  12  is removed by threadably retracting the drive shaft  28  and the interior cavity of the pulling plug  20  engages the head end  16  of the fastener, the fastener will rotate in unison with the drive shaft. The rotation may actually help to remove the fastener by, in effect, lifting the fastener from the aperture. In some instances, however, the apparatus  10  preferably removes the fastener without causing the fastener to rotate. For example, fasteners that are bent are desirably removed without causing the fastener to rotate since the rotation of the fastener will enlarge the aperture. In these instances, the lever member may be threadably advanced while the drive shaft is prevented from rotation. The threaded advancement of the lever member also causes the drive shaft and the pulling plug to be moved away from the surface of the workpiece, thereby extracting the fastener. To facilitate the threaded advancement of the lever member, the collar  32  of the lever member may have flats such as by being turned as shown in  FIG. 6  in order to have a square, hexagonal or other polygonal shape that may be engaged by a wrench or the like. Additionally, a bushing  33  may be disposed between the collar and the cylindrical portion of the lever member so as to permit relative rotation of the collar with respect to the cylindrical portion of the lever member. 
   Alternatively, the drive shaft  28  may be unthreaded along either its entire length or at least a majority of its length. In this embodiment, the lever member  30  does not threadably engage the drive shaft. However, the lever member generally still includes a collar  32  defining an opening that snugly receives the drive shaft such that the lever member remains centered and aligned about the drive shaft. In this embodiment, as depicted in  FIG. 7 , the pulling plug  20  is again attached to or integral with one end of the drive shaft. The other end of the drive shaft may be engaged by a mechanized actuation mechanism  36 , such as a hydraulic actuator, a pneumatic actuator or an electric solenoid as schematically depicted in FIG.  7 . In operation, the mechanized actuation mechanism retracts the drive shaft in a direction away from the surface of the workpiece  14 . The apparatus of this embodiment also includes a fixed element  38  for engaging the lever member, such as the collar of the lever member, and preventing corresponding retraction of the lever member. As the drive shaft is retracted, therefore, the first end of the lever member operably engages the surface of the workpiece such that further retraction of the drive shaft removes the fastener  12  from the aperture defined by the workpiece. As shown, the apparatus of this embodiment may also include a return spring  40  such that upon deactivation of the mechanized actuation mechanism, the drive shaft is again extended such that the pulling plug extends beyond the lever member. 
   As also shown in  FIG. 7 , the end of the lever member  30  that is proximate the workpiece  14  may include a radially extending flange, such as a radially outwardly extending flange  42 , to distribute the force that the apparatus  10  will apply to the workpiece over a broader area of the workpiece. Additionally, the flanged end of the lever member may have a shape that matches the shape of the surface of the workpiece surrounding the fastener  12  to be extracted such that the fastener is maintained in an aligned relationship with the corresponding opening defined by the workpiece while the fastener is being removed, thereby avoiding damage to the fastener and/or the opening. As such, the flanged end of the lever member may not lie within a plane perpendicular to the longitudinal axis of the drive shaft  28 . Instead, the flanged end of the lever member can be disposed at a non-orthogonal angle to the longitudinal axis defined by the drive shaft, and may have a non-planar shape to match the shape of curved workpieces. Still further, the flanged end of the lever member may define one or more notches for receiving the head end of other fasteners or other features that extend outwardly from the surface of the workpiece that are located in the proximity of the fastener to be removed. Thus, the apparatus of the present invention is capable of removing fasteners from workpieces having various different shapes. 
   The flanged end  42  of the lever member  30  may be interchangeable. As shown in  FIG. 8 , for example, the flanged end of the lever member may be disengagable from the remainder of the lever member. In the illustrated embodiment, the flanged end of the lever member may be threadably engaged to the remainder of the lever member, although the flanged end may be removably attached to the remainder of the lever member in other manners. While a single flanged end of the lever member is depicted in  FIG. 8 , the lever member could include multiple flanged ends; each having a different shape and/or being disposed at a different angle relative to the longitudinal axis defined by the drive shaft  28 . Thus, during the removal of a fastener  12 , the flanged end that best matches the shape of that portion of the workpiece  14  in the vicinity of the fastener may be selected and attached to the remainder of the lever member. If the shape of the workpiece in the vicinity of another fastener that is to be thereafter removed is different, a different flanged end that better matches the shape of the workpiece may be selected, the prior flanged end may be disengaged from the remainder of the lever member and the newly selected flanged end installed in its place. For purposes of illustration, the flanged end of the lever member depicted in  FIG. 8  also defines a notch for accommodating the head ends of other fasteners or other raised features on the workpiece. 
   In operation, the lever member  30  is generally initially positioned such that the pulling plug  20  extends therebeyond. In the embodiment depicted in  FIGS. 1 and 2 , for example, the lever member may be threadably retracted on the drive shaft  28  so that the pulling plug extends therebeyond. Also, as an initial matter, the end of the fastener opposite the head end  16  may be tapped toward the workpiece  14  so as to be flush with the surface of the workpiece. By tapping the end of the fastener in this manner, the head end of the fastener is generally positioned slightly above and spaced from the front surface of the workpiece. As such, the pulling plug can be positioned so as to receive the head end of the fastener within the internal cavity defined by the pulling plug. As shown in  FIG. 4 , the lever member  30  is then positioned so as to operably engage the surface of the workpiece  14 , such as by being threadably advanced along the drive shaft  28  until the end of the lever member contacts the surface of the workpiece. Thereafter, the drive shaft may be retracted such that the pulling plug  20  and, in turn, the fastener  12  is likewise retracted in a direction away from the surface of the workpiece as shown in  FIG. 5 , thereby removing the fastener from the workpiece. As described above, the drive shaft can be retracted in various manners, including the threaded retraction of the drive shaft or the retraction of the drive shaft by a mechanized actuation mechanism  36  of various types. 
   In instances in which the head end  16  of the fastener  12  has a polygonal shape, the interior cavity defined by the pulling plug  20  also generally has a corresponding polygonal shape. As such, rotation of the drive shaft  28  and, in turn, the pulling plug also causes the fastener to rotate as a result of the engagement of the polygonal head of the fastener within the polygonally shaped interior cavity defined by the pulling plug. This rotation of the fastener during the removal process is generally advantageous for threaded fasteners since the rotation reduces, if not eliminates, thread scrubbing of the threads of the fastener and/or internal threads within the opening defined by the workpiece. Additionally, the rotation of the threaded fastener assists in the removal of the fastener such as by seemingly lifting the fastener from the opening. 
   Alternatively and with reference to  FIG. 6 , the drive shaft  28  may be retracted by threadably advancing the lever member  30  along the drive shaft while preventing the drive shaft from rotating. As such, the fastener  12  may be removed without causing the fastener to be rotated. While rotation of the fastener is advantageous in some circumstances as described above, it is sometimes desirable to removed the fastener without subjecting the fastener to rotation, such as in instances in which a bent fastener is being removed and any rotation of the fastener would undesirably enlarge the aperture. 
   As such, the apparatus  10  of the present invention is capable of removing a wide variety of fasteners  12 . Advantageously, the apparatus of the present invention maintains the fastener in axial alignment with the corresponding opening defined by the workpiece  14  such that the fastener is removed in a manner that reduces, if not eliminates, damage to the fastener and the workpiece. Moreover, the apparatus of the present invention is capable of removing fasteners in situations in which the end of the fastener opposite the head end  16  is relatively inaccessible such that the fastener is not suitable for removal by use of a drift or a punch as in conventional fastener removal techniques. Moreover, the controlled removal of a fastener provided by the apparatus of the present invention permits fasteners to be removed from workpieces formed of a variety of materials including softer materials, such as aluminum, that might otherwise be damaged by conventional fastener removal techniques. 
   Many modifications and other embodiments of the inventions set forth herein will come to mind to one skilled in the art to which these inventions pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the inventions are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.