Abstract:
A pull head for installing pull type fasteners, such as rivetless nut plates. The pull head includes a sleeve, a nosepiece on the sleeve, and an insert which extends from the nosepiece. The insert enters an aperture in a workpiece and centers the pull head relative to the aperture. The insert is shiftable relative to the nosepiece, and preferably includes a taper at its end to facilitate entry into the aperture. The pull head includes jaws which grab and pull on a stem or fastener, and the insert provides that as the stem or fastener is pulled, a surface of the stem or fastener contacts the insert and the insert is pulled along with the stem or fastener. As such, the insert begins in the aperture, but is pulled out of the aperture as the stem or fastener is pulled to effect installation.

Description:
BACKGROUND  
       [0001]     This invention generally relates to tools for installing pull type fasteners, and more specifically relates to such a tool where the tool includes a self-aligning feature.  
         [0002]     Tools for installing pull type fasteners are standard in the industry. Such tools include riveters and other tools which impart a holding or abutment force to a workpiece while imparting a pulling force on a fastener, thereby installing the fastener with regard to the workpiece. Typically, such tools are handheld and are either manual or hydraulically powered. A typical tool used for such an application includes a cylinder which generates a pulling force on a piston. The piston is engageable with a pull head which transfers the pulling force to the fastener. Examples of such tools currently available in the industry include Textron Aerospace Fasteners&#39; G750A hand riveter and G704B power tool, both of which are configured to work with a plurality of pull heads depending on the specific application.  
         [0003]      FIG. 1  illustrates the front portion  10  of a typical pull tool and the components of a typical pull head  12 . As shown, the pull head  12  includes a sleeve  14  which is generally cylindrical having a chamber  16  therein. Disposed in the chamber  16  are a collet  18 , jaws  20 , a jaw follower  22 , a bumper  24  and a spring  26 . An external surface  28  of the sleeve  14  includes threads  30  for receiving a lock nut  32  and threading into a head cylinder  34  at the front portion  10  of the pull tool, while an internal surface  36  of the collet  18  includes threads  38  for threading onto a head piston  40  at the front portion  10  of the pull tool. In use, the pull tool is actuated, causing the head piston  40  to move back relative to the head cylinder  34 , causing the collet  18  to move back relative to the sleeve  14 , and causing the jaws  20  to clamp onto and pull a mandrel or a fastener. This structure and use is conventional and widely known in the industry.  
         [0004]     Rivetless nut plates are also standard in the industry and are typically used in association with fluid tanks, such as fuel tanks or water tanks, for aircraft or the like, for providing a floating, threaded receptacle for receiving a fastener. Some rivetless nut plates are designed such that pull type tools are used to perform the installation. For example, US 2003/0091408 (the publication of U.S. patent application Ser. No. 10/272,721, filed Oct. 17, 2002) discloses a rivetless nut plate where a retainer or attachment sleeve (identified with reference numeral  50  in the Figures of the present application) is positioned in an aperture (identified with reference numeral  52  in the Figures of the present application) in a workpiece (identified with reference numeral  54  in the Figures of the present application), and an enlarged head portion (identified with reference numeral  56  in the Figures of the present application) of a stem (identified with reference numeral  58  in the Figures of the present application) is disposed in the attachment sleeve. Subsequently, a pull tool (such as one which has a front portion  10  such as is shown in  FIG. 1 ) is used to pull on the stem, causing the head portion of the stem to be pulled through a tubular portion of the attachment sleeve, causing the tubular portion to expand and engage side walls of the aperture in the workpiece (as shown in the progression of  FIGS. 5 through 7 , and as shown in the progression of  FIGS. 10 through 12 ).  
         [0005]     Typically, those rivetless nut plates which are installed using a pull tool are installed using a pull head  12  such as shown in  FIG. 1  which includes a flat surface which can be held flush against the workpiece  54  during installation. The flat surface helps ensure that installation occurs perpendicular to the surface of the workpiece  54 . While the flat surface of the tool is held against the workpiece, the pull head  12  is inserted into the hole  52  in the workpiece  54  in order to aid in alignment. As such, a proper installation is dependent on the operator&#39;s ability to ensure that the pull head  12  is properly positioned inside the hole  52 . What often occurs is that the pull tool is pressed against the workpiece and the pull head  12  is pressed against one side of the hole  54  (rather than being centered in the hole). As such, installation occurs off center to the hole. Current, widely available pull head designs do not include any means of aligning a rivetless nut plate with regard to a hole, nor include any means for gauging the quality of a drilled hole. Even if the operator takes the time to properly align the pull tool, there remains uncertainty with regard to alignment of the rivetless nut plate with the drilled hole, as well as uncertainty with regard to the quality of the drilled hole.  
         [0006]     Installation of rivetless nut plates requires that the aperture in the workpiece be precise. The difficulty of drilling a hole (i.e., aperture) perpendicular to the surface of a workpiece combined with the difficulty of inserting, aligning and installing the rivetless nut plate relative to the hole often adversely affects the quality of the installation. It is especially difficult to drill a precise hole and thereafter properly align a rivetless nut plate in the hole in situations where thin workpieces are involved, in situations where access is limited (i.e., in tight work spaces), in situations where the aperture in the workpiece is oblong, and in situations where some of the structure surrounding the aperture has been torn out during installation. Generally speaking, when a fastener, such as a rivetless nut plate, is poorly installed, the mechanical properties of the fastener are adversely affected. Therefore, it is important to properly align a fastener, such as a rivetless nut plate, for installation in an aperture.  
       OBJECTS AND SUMMARY  
       [0007]     An object of an embodiment of the present invention is to provide a self-aligning tool for installing pull type fasteners, such as rivetless nut plates.  
         [0008]     Another object of an embodiment of the present invention is to provide a tool which can be used to efficiently align and install pull type fasteners, such as rivetless nut plates, with minimal operator involvement.  
         [0009]     Briefly, and in accordance with at least one of the foregoing objects, an embodiment of the present invention provides a pull head for installing pull type fasteners, such as rivetless nut plates, the pull head is engageable with an installation tool or pull tool and includes a sleeve, a nosepiece on the end of the sleeve, and an insert which extends from an opening in the nosepiece. The insert is configured to enter an aperture in a workpiece and center the pull head relative to the aperture. The insert is shiftable relative to the nosepiece, and preferably includes a taper at its end to facilitate entry into the aperture. The pull head includes jaws which are configured to grab and pull on a stem or fastener, and the insert is configured such that as the stem or fastener is pulled, a surface of the stem or fastener contacts the insert and the insert is pulled along with the stem or fastener. As such, the insert begins in the aperture, but is pulled out of the aperture as the stem or fastener is pulled to effect installation.  
         [0010]     As an alternative, the pull tool may include a spring and a nose which are disposed in an insert, wherein the nose extends through an opening in the insert and is shiftable relative thereto, thereby compressing the spring. The nose is engageable with a rivetless nut plate for example, and the jaws are configured to grab and pull on a stem or fastener. The nose is configured to be pulled along with the stem or fastener, thereby compressing the spring. The insert is configured such that as the stem or fastener is pulled further, the nose becomes fully retracted relative to the insert, and the insert is thereafter pulled along with the stem or fastener and the nose.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]     The organization and manner of the structure and operation of the invention, together with further objects and advantages thereof, may best be understood by reference to the following description, taken in connection with the accompanying drawings, wherein like reference numerals identify like elements in which:  
         [0012]      FIG. 1  is an exploded, cross-sectional view of a conventional pull head and a cross-sectional view of a front portion of a pull tool;  
         [0013]      FIG. 2  is a cross-sectional view of a pull head which is in accordance with an embodiment of the present invention;  
         [0014]      FIG. 3  is an exploded view of some of the components of the pull head shown in  FIG. 2 ;  
         [0015]      FIG. 4  is an exploded view of a spring insert assembly which is shown in  FIG. 3 ;  
         [0016]      FIGS. 5-7  are sequence views which show the pull head of  FIGS. 2 and 3  installing a rivetless nut plate;  
         [0017]      FIG. 8  is a cross-sectional view of a pull head which is in accordance with another embodiment of the present invention;  
         [0018]      FIG. 9  is an exploded view of some of the components of the pull head shown in  FIG. 8 ;  
         [0019]      FIGS. 10-12  are sequence views which show the pull head of  FIG. 8  installing a rivetless nut plate;  
         [0020]      FIG. 13  is an exploded view of a sensing mechanism which can be used in association with a pull head, such as either one of the pull heads shown in FIGS.  2  or  8 ;  
         [0021]      FIG. 14  is a cross-sectional view of the sensing mechanism shown in  FIG. 13 ;  
         [0022]      FIG. 15  shows the sensing mechanism when an aperture is the correct size; and  
         [0023]      FIG. 16  shows the sensing mechanism when an aperture is too large.  
     
    
     DESCRIPTION  
       [0024]     While the present invention may be susceptible to embodiment in different forms, there are shown in the drawings, and herein will be described in detail, embodiments thereof with the understanding that the present description is to be considered an exemplification of the principles of the invention and is not intended to limit the invention to that as illustrated and described herein.  
         [0025]      FIG. 2  illustrates a pull head  100  which is in accordance with an embodiment of the present invention, while  FIG. 8  illustrates a pull head  100   a  which is in accordance with another embodiment of the present invention. Both pull heads  100 ,  100   a  are configured to be used with a pull tool to install a pull type fastener, such as a rivetless nut plate, and both are configured to align with an aperture in a workpiece with minimal operator involvement.  
         [0026]     As shown in  FIGS. 2-7 , pull head  100  includes a sleeve  102  and a nosepiece  104  which is threadably engaged in a threaded bore  106  at the end  108  of the sleeve  102 . The sleeve  102  is generally cylindrical and includes a chamber  110 . Disposed in the chamber  110  of the sleeve  102  are a collet  112 , a spring  114  and a spring insert assembly  116 . The collet  112  is generally cylindrical and includes a throughbore  118 . A set of clamping jaws  120 , a jaw follower  122  and a spring  123  are disposed in the collet  112 . An internal surface  124  of the collet  112  includes threads  126  for threading onto the head piston  40  of a pull tool (see  FIG. 1 ), and an external surface  128  of the sleeve  102  includes external threads  130  for threading into a head cylinder  34  of the pull tool (see  FIG. 1 ), wherein the pull tool is configured to drive the head piston  40  back and forth relative to the head cylinder  34 . A nut  132  is provided on the threads  130  on the sleeve  102  for effectively securing the pull head  100  and pull tool together.  
         [0027]     The spring insert assembly  116  includes an insert  140  which is generally cylindrical having a central throughbore  142 . An end portion  144  of the insert  140  preferably includes a taper  146  which is configured to engage a hole  52  in a workpiece  54 , as will be described more fully later herein. The insert  140  includes a shoulder  148  which is configured to engage an internal surface  150  of the nosepiece  104 , as well as a base portion  152  which is configured to engage an internal surface  154  of the sleeve  102 . As such, the insert  140  is generally retained in the nosepiece  104  and sleeve  102 .  
         [0028]     A cap  156  engages the insert  140  proximate an end  158  of the insert  140 , preferably via either a threaded engagement or a press fit. A nose  160  is disposed in the insert  140  and is generally cylindrical having a central throughbore  162 . The nose  160  includes a shoulder  164  which engages an internal shoulder  166  provided in the insert  140 , such that the nose  160  is generally retained in the insert  140 . A spring  168  is disposed in the insert  140 , generally between the nose  160  and the cap  156 .  
         [0029]     To assemble the pull head  100 , first the spring insert assembly  116  is assembled. To assemble the spring insert assembly  116 , the nose  160  is inserted into insert  140 , followed by the spring  168 . Subsequently, the cap  156  is engaged with the insert  140 , such as via a threaded engagement or a press fit. Once the spring insert assembly  116  is assembled, the spring insert assembly  116  is inserted nose  160  first into the sleeve  102 . Then, the spring  114  is positioned behind the spring insert assembly  116 , and the collet  112  is pressed against the spring  114 . Assembly then continues as with other, conventional pull heads—i.e., the jaws  120  and jaw follower  122  are inserted in the collet  112 , and the collet  112  and sleeve  102  are engaged with a pull tool (see  FIG. 1 ).  
         [0030]     Thereafter, in use, the pull tool is positioned over a hole  52  that has been prepared for fastener installation, and the nose  160  is extended through the hole  52  and the pull tool is pressed against the workpiece  54 . As the pull tool is pressed against the workpiece  54 , the hole  52  in the workpiece  54  encounters the taper  146  on the insert  140  and the hole  52  moves upwards along the taper  146 . The taper  146  works to align the pull head  100  concentrically to the hole  52 . Then, the mandrel  58  of an assembled rivetless nut plate, such as the rivetless nut plate disclosed in US 2003/0091408 (the publication of U.S. patent application Ser. No. 10/272,721, filed Oct. 17, 2002), which is hereby incorporated by reference in its entirety, is inserted into the extruding nose  160  (see  FIG. 5 ), and the sleeve  50  of the rivetless nut plate is pressed firmly against the nose  160 . The firm press ensures that the rivetless nut plate fits over the end of nose  160 . By fitting around the nose  160 , the rivetless nut plate becomes concentric with the pull head  100  and the hole  52 . Preferably, the throughbore  162  of the nose  160  and the end  180  of the nose  160  are provided as being consistent with the geometry of the mandrel  58  and the attachment sleeve  50 , respectively, of the rivetless nut plate such that a good fit can be achieved between the nose  160  of the pull head  100  and the attachment sleeve  50  and mandrel  58  of the rivetless nut plate (i.e., the mandrel  58  fits well in the nose  160 , and the attachment sleeve  50  of the rivetless nut plate fits well over the nose  160 ).  
         [0031]     When the pull tool is actuated, the mandrel  58  is pulled. Specifically, the jaws  118  lock onto the mandrel  58  as the collet  112  is pulled back and the mandrel  58  is pulled back along with the collet  112 . At first, the insert  140  does not move back. Instead, the insert  140  is held flush against the internal surface  150  of the sleeve  102  as a result of compression by the spring  114 . The nose  160  retracts first against the spring  168  within the spring insert assembly  116 . The inner geometry of the nose  160  interacts with the mandrel base  182  (see  FIG. 6 ) and serves to guide the rivetless nut plate through the center of the hole  52 . The nose  160  retracts until the inner spring  168  is completely compressed. When the nose  160  is fully retracted, the retainer  50  of the rivetless nut plate will be at the surface of the hole  52  as shown in  FIG. 6 . The collet  112  would have retracted far enough to allow the compressed spring  168  to relax and releases the insert  140 . Installation thereafter continues as has been conventional. The mandrel  58  is pulled through the retainer  52 , expanding the retainer into the workpiece  54  and completing the installation as shown in  FIG. 7 . The result is a self-aligned installation that was not dependent on operator skill.  
         [0032]     The pull head  100   a  shown in  FIGS. 8-12  is very much like the pull head  100  previously described. Hence, like reference numerals are used to identify like parts. The pull head  100   a  provides that, instead of including a spring insert assembly  116  and a spring  114 , the pull head  100   a  includes an insert  140   a  (without including springs  114 ,  168  and an end cap  156 ). While this embodiment lacks the spring action and lost motion which is provided by the previous embodiment, the insert  140   a  still provides a centering function with regard to a hole  52  in a workpiece  54 . Preferably, like the insert  140  of pull head  100 , the insert  140   a  of pull head  100   a  also includes a taper  146   a.    
         [0033]     To assemble the pull head  100   a , the insert  140   a  and collet  112  are inserted into the sleeve  102 . Assembly then continues as with other, conventional pull heads—i.e., the jaws  120 , jaw follower  122  and spring  123  are inserted in the collet  112 , and the collet  112  and sleeve  102  are engaged with a pull tool.  
         [0034]     Thereafter, in use, the pull tool is positioned over a hole that has been prepared for fastener installation, and the end  190  of the insert  140   a  is extended through the hole  52  (see  FIG. 10 ) and the pull tool is pressed against the workpiece  54 . As the pull tool is pressed against the workpiece, the hole  52  in the workpiece  54  encounters the taper  146   a  on the insert  140   a  and the hole moves upwards along the taper  146   a . The taper  146   a  works to align the pull head  100   a  concentrically to the hole  52 . Then, the mandrel  56  of an assembled rivetless nut plate (or not a mandrel, but some other fastener) is inserted into the insert  140   a , and the rivetless nut plate is pressed firmly against the end  190  of the insert  140   a . The firm press ensures that the rivetless nut plate fits over the end  190  of the insert  140   a . By fitting around the end  190  of the insert  140   a , the rivetless nut plate becomes concentric with the pull head  100   a  and the hole  52 . Preferably, the insert  140   a  is provided as being consistent with the geometry of the rivetless nut plate such that the mandrel  56  fits well in the insert  140   a , and the attachment sleeve  50  of the rivetless nut plate fits well over the end  190  of the insert  140   a.    
         [0035]     When the pull tool is actuated, the mandrel  56  is pulled. Specifically, the jaws  120  lock onto the mandrel  56  as the collet  112  is pulled back and the mandrel  56  is pulled back along with the collet  112 . The mandrel  56  pulls the insert  140   a  back with it (see  FIG. 11 ). The inner geometry of the insert  140   a  interacts with the mandrel base and serves to guide the rivetless nut plate through the center of the hole  52 . The mandrel  56  is pulled through the retainer  50 , expanding lobes of the retainer into the workpiece  54  and completing installation as shown in  FIG. 12 . The result is a self-aligned installation that was not dependent on operator skill.  
         [0036]     Either pull head  100 ,  100   a  provides a novel solution to the industry&#39;s problem of installing rivetless nut plates into thin structures. The installation tools that are currently being used are using pull heads that result in too many unacceptable installations. The unacceptable installations are tearing into and biting the structure surrounding a hole during installation.  
         [0037]     The pull heads described above and illustrated in  FIGS. 2-12  provide that a pull tool will be able to align itself to the hole, align the fastener to the hole, and recognize and, if necessary, prohibit installation into poor quality drilled holes (i.e., undersized or oversized holes). First, the addition of an angled taper at the tip of the pull head concentrically guides the hole in the structure to the pull head during installation even if the pull tool is not held firmly against the structure during installation.  
         [0038]     Second, preferably a portion of the nose or insert is configured to protrude through the hole prior to installation. This protrusion ensures that the rivetless nut plates, or other general pull type fasteners, are aligned to the center of the pull tool. The protrusions are circular cylinders with an inner curved geometry at the tip that is able to fit in between the rivetless nut plate attachment sleeve and the rivetless nut plate mandrel in order to keep the rivetless nut plate concentrically aligned to the installation tool during installation.  
         [0039]     Third, the cylindrical protrusions can serve to verify that minimum or maximum hole size requirements are fulfilled prior to installation. If the hole size is too small, the cylindrical protrusion will not fit through the hole, prohibiting installation. The addition of a sensing element  200 , as shown in  FIGS. 13-16 , on the outer diameter  202  of the cylindrical protrusion  203  (such as the nose  160  of pull head  100 , or the insert  140   a  of pull head  100   a ) can serve to detect if the hole size is too large. The sensing element  200  may be composed of two or more tiny spherical balls  204  housed within the outer diameter of the cylindrical protrusion  203  at equal intervals. As shown in  FIG. 14 , the spherical balls  204  are held above the surface  205  of the cylindrical protrusion  203  with relaxed springs  206  in order to form an outer diameter (i.e., dimension  208 ) that equals the maximum allowable hole size. When pressure is applied to the spherical balls  204  as shown in  FIG. 15 , the springs  206  compress and the sensing element  200  activates. Thus, the sensing element  200  activates during installation so long as the hole  52  in the workpiece  54  is not oversized, as shown in  FIG. 16 . If the sensing element  200  does not activate, preferably a warning signal (as represented by arrow  210 ) is sent to the operator, such as a bright red light or an installation lock that would prevent the release of the installation tool trigger.  
         [0040]     While embodiments of the present invention are shown and described, it is envisioned that those skilled in the art may devise various modifications of the present invention without departing from the spirit and scope of the disclosure.