Abstract:
A lockbolt which includes a head portion and a shaft which extends from the head portion. The shaft includes at least a portion which is threaded and has a multi-lobular profile. A collar is swageable onto the multi-lobular threaded portion, and thereafter the lobes provide that the collar does not tend to vibrate loose from the threading. The fact that the section which has a multi-lobular profile is also threaded provides that the collar (or a conventional threaded nut) can be selectively rotatably removed and re-installed on the lockbolt. Before swaging, the collar may initially include a cylindrical bore, or a bore which is multi-faceted, preferably generally corresponding to the profile of the multi-lobular portion of the lockbolt. The lockbolt may also include a frangible pintail, wherein the multi-lobular threaded portion is disposed between the head portion of the bolt and the frangible pintail.

Description:
RELATED APPLICATION (PRIORITY CLAIM) 
   This application claims the benefit of U.S. Provisional Application Ser. No. 60/605,704, filed Aug. 30, 2004. 

   BACKGROUND 
   The present invention generally relates to lockbolts, and more specifically relates to a multi-lobular lockbolt which is configured to be installed vis-a-vis a collar which is swaged onto the bolt. 
   Some conventional lockbolts include a frangible pintail while others do not. As shown in  FIG. 1 , a typical lockbolt  10  which includes a frangible pintail  12  includes: a head  14 , a threaded shaft  16  and a frangible pintail  12  having annular ribs  18 , wherein the head  14  is at one end  20  of the bolt  10 , the frangible pintail  12  is at the other end  22  of the bolt  10 , and the threaded shaft portion  16  is disposed between the head  14  and the frangible pintail  12 . As shown in  FIG. 1 , initially the frangible pintail  12  and threaded shaft  16  is inserted through apertures  24 ,  26  provided in two or more work pieces  28 ,  30 , and a collar  32  is slid onto the bolt  10 , positioned proximate the threaded shaft  16 . Then, as shown in  FIG. 2 , an installation tool  40  is engaged with the collar  32  and the frangible pintail  12 . Specifically, as shown in  FIG. 3 , jaws  41  of the installation tool  40  grip and pull on the pintail  12  (as represented by arrow  42 ) while an anvil  43  of the installation tool  40  pushes down on the collar  32  (as represented by arrows  44 ), causing the collar  32  to swage down onto the bolt  10 . The swaging causes the collar  32  to deform and generally grip onto the threaded shaft portion  16  of the bolt  10 . Once the collar  32  has been swaged, the pintail  12  continues to be pulled until it breaks off, as shown in  FIG. 4 , leaving the bolt  10  installed in the work pieces  28 ,  30 , secured by the collar  32 . Similarly, if the lockbolt is provided as being of the type which does not include a frangible pintail, the threaded portion of the bolt is gripped and pulled as the collar is swaged, and once the collar has been fully swaged, the bolt is released leaving the threads undamaged. 
   Such lockbolts and tools for installing such lockbolts are generally known in the art. For example, a typical tool for installing lockbolts with frangible pintails is disclosed in U.S. Pat. No. 2,114,493, and includes an anvil for swaging the collar and jaws for gripping and pulling on the pintail. 
   The threads of some prior art lockbolts, such as that which is shown in  FIGS. 1-4 , are helical. Regardless of whether the lockbolt includes a frangible pintail or not, the helical threads provide that once the lockbolt has been installed (i.e., the collar has been swaged onto the bolt), the collar can be rotated off of the lockbolt, and thereafter can be threaded back on to the lockbolt (or a new nut threaded onto the lockbolt). A problem associated with providing a lockbolt having standard helical threads is that the collar, once swaged onto the lockbolt, is susceptible to vibrating loose. 
   U.S. Pat. No. 2,531,048 discloses a lockbolt which tends to solve this problem. The lockbolt, instead of including standard helical threads, includes annular ribs. Being annular rather than helical provides that once a collar is swaged onto the ribs, the collar is not susceptible to vibrating loose. However, the lockbolt presents a new disadvantage: once a collar is swaged onto the ribs, the collar must be broken off of the ribs, rather than be rotated off the ribs. As such, the collar cannot be removed and rotated back onto the lockbolt. In fact, due to the ribs being annular, even a new collar cannot be threaded onto the lockbolt. Instead, the swaging process must be repeated to re-secure the lockbolt. 
   OBJECTS AND SUMMARY 
   An object of an embodiment of the present invention is provide a lockbolt which provides that, after installation, a collar does not tend to vibrate loose, yet the collar can be selectively rotatably removed and re-installed on the lockbolt. 
   Briefly, and in accordance with at least one of the foregoing objects, an embodiment of the present invention provides a lockbolt which includes a head portion and a shaft which extends from the head portion. The shaft includes at least a portion which is threaded and has a multi-lobular profile. A collar is swageable onto the multi-lobular threaded portion, and thereafter the lobes or high points provide that the collar does not tend to vibrate loose from the threading. The fact that the section which has a multi-lobular profile is also threaded provides that the collar can be selectively rotatably removed and re-installed on the lockbolt (or that a conventional threaded nut can be installed on the lockbolt once the swaged collar has been removed). Before swaging, the collar may initially include a cylindrical bore, or a bore which is multi-faceted, preferably generally corresponding to the profile of the multi-lobular portion of the lockbolt. The lockbolt may also include a frangible pintail, wherein the multi-lobular threaded portion is disposed between the head portion of the bolt and the frangible pintail. The frangible pintail may be provided as having annular ribs. Alternatively, the frangible pintail may be provided as having the same threading as the multi-lobular threaded portion of the lockbolt. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     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: 
       FIG. 1  illustrates a prior art lockbolt having a head, a helically-threaded shaft portion and a frangible pintail, showing a collar positioned proximate the helically-threaded shaft portion, before swaging; 
       FIGS. 2 through 4  illustrate installation of the lockbolt shown in  FIG. 1 ; 
       FIGS. 5 through 7  illustrate installation of a lockbolt which is in accordance with an embodiment of the present invention; 
       FIG. 8  provides a view (similar to a cross-sectional view) of the lockbolt and collar, before swaging, wherein the collar is provided as having a multi-faceted bore; 
       FIG. 9  is similar to  FIG. 8 , but shows the situation where the collar is provided as having a cylindrical bore; 
       FIG. 10  provides a view (similar to a cross-sectional view) of the lockbolt and collar, after swaging; and 
       FIG. 11  is a perspective view of a lockbolt which is in accordance with an alternative embodiment of the present invention. 
   

   DESCRIPTION 
   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. 
     FIGS. 5 through 7  illustrate a lockbolt  100  which is in accordance with an embodiment of the present invention. The lockbolt  100  is similar to the prior art lockbolt  10  shown in  FIGS. 1 through 4  in that the lockbolt  100  includes a head  102 , a threaded shaft  104  and a frangible pintail  106  having annular ribs  108 , wherein the head  102  is at one end  110  of the bolt  100 , the frangible pintail  106  is at the other end  112  of the bolt  100 , and the threaded shaft portion  104  is disposed between the head  102  and the frangible pintail  106 . The difference between the lockbolt  100  shown in  FIGS. 5 through 7  and the prior art lockbolt  10  shown in  FIGS. 1 through 4  resides in the fact that in the lockbolt  100  shown in  FIGS. 5 through 7 , the threaded shaft portion  104  is not merely helically threaded, but rather includes a threaded portion which is multi-lobular or multi-faceted, meaning that the thread includes high points  114  and low points  116  as shown in  FIGS. 8-10 . 
   For example, the threading may be provided as having five lobes or high points (such as is shown in  FIGS. 8-10 ), such as an HP-5 thread as disclosed in U.S. Pat. Nos. 3,875,780 and 3,935,785, both of which are incorporated herein by reference in their entirety. Alternatively, the threading may be provided as having a number of lobes which are more or less than five. For example, the threaded portion may be provided as being quad-lobular (i.e., having four high points), tri-lobular (i.e., having three high points), an oval (i.e., having two high points), etc. 
   Regardless, the fact that the threaded portion  104  of the lockbolt  100  is multi-lobular, having high points and low points, provides that a collar  120 , once swaged onto the lockbolt  10 , does not tend to vibrate off. This is because vibration alone is not enough to cause low points  122  of the swaged collar  120  (see  FIG. 10 ) to move past high points  114  of the multi-lobular portion  104  of the lockbolt  100 . Simultaneously, the fact that the threaded portion  104  is, in fact, threaded and multi-lobular, provides that a collar  120  can be intentionally rotated off the lockbolt  100 , if desired, by using a tool to apply enough torque to the collar  120 . 
     FIGS. 5 through 7  illustrate installation of the lockbolt  100 . The installation process is quite similar to the installation process which is used to install the lockbolt  10  shown in  FIGS. 1 through 4 . To install the lockbolt  100  shown in  FIGS. 5 through 7 , Textron Fastening Systems&#39; Hydro-Electric Power Tool, Model T30 73412-02000, along with Textron Fastening Systems&#39; HydraPac Hydraulic Power Unit, Model HP21 73401-02000, Model HP41 73400-02000 or Model HP51 73404-02000, can be used. Alternatively, some other appropriate installation tool can be used. 
   Initially, the frangible pintail  106  and threaded shaft  104  is inserted through apertures  24 ,  26  provided in two or more work pieces  28 ,  30 , and a collar  120  is placed on the lockbolt  100 , proximate the multi-lobular threaded portion  104 . As shown in  FIG. 8 , the collar  120  can be provided as initially having a throughbore  130  which is multi-lobular or multi-faceted. Preferably, the collar  120  is provided as having a throughbore  130  which has a profile which corresponds to the profile of the multi-lobular portion  104  of the lockbolt  100 . In other words, if the multi-lobular portion  104  of the lockbolt  100  is provided as having five lobes or high points (such as an HP-5 thread), preferably the collar  120  is provided as having a throughbore  130  which has five high points  131  as well. The fact that the collar  120  is provided as having a throughbore  130  which has a profile which corresponds to the profile of the multi-lobular portion  104  of the lockbolt  100  provides for uniform deformation of the collar  120  during swaging. 
   Additionally, the fact that the collar  120  is provided as having a throughbore  130  which has a profile which corresponds to the profile of the multi-lobular portion  104  of the lockbolt  100  provides that the collar  120  can assist with regard to installation. Specifically, the collar can be placed on the bolt and rotated slightly so that there is an interference fit between portion  104  and the throughbore  130  of the collar. Then, an installation tool can be brought into engagement with the pintail  106  and collar  120  to perform the swaging operation. Alternatively, as shown in  FIG. 9 , the collar  120  can be provided as initially having a throughbore  130  which is cylindrical, or some other shape. 
   Regardless, as shown in  FIG. 5 , an installation tool  140  is engaged with the collar  120  and the frangible pintail  106 . Specifically, jaws  142  of the installation tool  140  grip and pull on the pintail  106  while an anvil  144  of the installation tool  140  pushes down on the collar  120 , causing the collar  120  to swage down onto the bolt  100 , as shown in  FIG. 6 . The swaging causes the collar  120  to deform and generally lock down onto the multi-lobular threaded portion  104  of the bolt  100  ( FIG. 10  provides a view (similar to a cross-sectional view)) of the collar  120  swaged down onto the multi-lobular portion  104  of the lockbolt  100 . 
   Preferably, the installation tool  140  swages only a portion  150  of the collar  120  down onto the threaded portion  104  (see  FIG. 6 ) while the remaining portion  152  remains unswaged, as this renders the assembly easier to assemble and manufacture. Preferably, the portion  152  of the collar  120  which is not swaged includes a hex profiled surface  154  such that a standard hex tool can be used to subsequently remove the collar  120 . Once the collar  120  has been swaged, the pintail  106  continues to be pulled until it breaks off, as shown in  FIG. 7 , leaving the bolt  100  installed in the work pieces  28 ,  30 , secured by the collar  120 . Similarly, if the lockbolt is of the type which does not include a frangible pintail, the threaded portion of the bolt is gripped and pulled as the collar is swaged, and once the collar has been swaged, the bolt is released. 
   Once the collar  120  has been swaged on the lockbolt, and the lockbolt  100  fully installed, secured by the collar  120 , the collar  120  will not tend to vibrate off, due to the multi-lobular profile of the threaded portion  104 . Specifically, vibration alone will not tend to provide that low points  122  of the collar  120  can overcome high points  114  of the multi-lobular portion  104  of the lockbolt  100 , as shown in  FIG. 10 . In other words, the multi-lobular profile of portion  104  provides a certain amount of prevailing torque which tends to resist rotation in response to vibration. At the same time, the collar  120  can be intentionally removed merely by using a tool to apply enough torque (such as by using a hex tool to apply a torque to surface  154 ) such that the low points  122  of the collar  120  overcome the high points  114  of the multi-lobular portion  104  of the lockbolt  100 . 
   Once the collar  120  has been swaged onto the lockbolt  100 , intentional removal of the collar  120  (i.e., rotation of the collar  120  using a tool) causes a thread to be formed in the throughbore  130  of the collar. The thread which is formed in the collar  120  provides that the collar  120  can be easily rotated back onto the threaded portion  104  of the lockbolt  100  after the collar  120  has been intentionally removed therefrom. Subsequently, once the collar  120  has been rotated back onto the lockbolt  100 , it is expected that the fact that the threaded portion  104  of the lockbolt is multi-lobular will result in the collar  120  not tending to vibrate off as much as if the threaded portion  104  of the lockbolt  100  were to be provided as being helically-threaded with standard helical threads, as is provided in the prior art (i.e., lockbolt  10  as shown in  FIGS. 1-4 ). In other words, there is a certain amount of prevailing torque which exists over and beyond what would be provided if portion  104  had a standard helical thread. 
   While it was discussed above that the collar  120  is preferably initially provided with a hex surface  154  to facilitate removal of the collar  120  with a hex tool, the collar  120  can also initially be provided without such a surface, and such a surface can be formed on the collar  120 , by the anvil  144  of the installation tool  140  during the swaging operation. 
     FIG. 11  illustrates a lockbolt  200  which is in accordance with an alternative embodiment of the present invention. The lockbolt  200  is very similar to the lockbolt  100  shown in  FIG. 5 through 7 , the only difference being that the frangible pintail  202  does not include annular ribs, but rather provides a multi-lobular threaded profile similar to the multi-lobular portion  104  of the lockbolt  200  (or lockbolt  100 ). This way, both the portion  104  of the lockbolt which ultimately receives the collar and the pintail portion  202  can be threaded at the same time, using the same thread-forming process. Alternatively, the pintail can be provided as having a helical, non-lobular thread. 
   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.