Patent Abstract:
A nosepiece for use with a pulling head and a riveter for installing blind bolts, primarily the “Unimatic” or “U” type. The nosepiece is preferably made out of two different components (a hard and tough one acting as the interface to the fastener, and a soft, ductile one acting as a shock absorber) and has an active area which is annular and effectively matched to the dimensions of the locking collar of the blind bolt. No tapered surface interferes with the sleeve during installation of the blind bolt. Instead, the active area includes a protrusion which intersects a support surface generally at a ninety degree angle. Providing a minimum or no transition fillet radius from the active area to the support area allows for a minimum length of the active area, providing maximum reinforcement to the active area. It also concentrates the operating stresses in a known area, dispersing them from the critical, working surface of the active area, providing an expected failure mode. A two piece design dissipates the operating stresses away from the active area, moving the unavoidable failures to an internal area of the nosepiece that cannot affect installation of the fastener. This “stress and shock absorption” together with the design features described above leads to superior reliability and dramatic endurance improvements.

Full Description:
BACKGROUND  
       [0001]     The present invention generally relates to nosepieces for use with tools for installing blind bolts, and more specifically relates to a high performance nosepiece for use in such an application.  
         [0002]     Blind bolts are popular fasteners, for example, in the aircraft industry. They are a good alternative to threaded fasteners, providing comparable joint preloads, with a better ability to resist vibration and the benefit of one side installation. A conventional blind bolt  10  is shown in  FIG. 1  and includes a stein  12 , a locking collar  14  and a sleeve  16 . The stem  12  has a head  18  at one end  20  and a serrated portion  22  proximate an opposite end  24 . As shown, the stem  12  extends through the sleeve  16  such that the head  18  of the stem  12  contacts an end  26  of the sleeve  16 .  
         [0003]     While  FIGS. 5-8  relate to the present invention, reference can be made to these Figures with regard to explaining the manner in which a conventional blind bolt is installed. As shown in  FIG. 5 , to install such a blind bolt, the sleeve  16  of the blind bolt  10  is inserted into an aperture  28  in a workpiece  30  (which consists of two or more structures  30   a ,  30   b ), and the jaws  32  of a riveter  40  are used to grip and pull on a serrated stem  12  of the blind bolt. This causes a bulb  42  to form in the blind area  44  of the workpiece  30 , as shown in  FIG. 6 , thereby providing a clamp up load to the workpiece structures  30   a ,  30   b . While the jaws  32  of the riveter  40  pull on the stem  12 , an installation load from the riveter  40  to the fastener  10  is transferred to the locking collar  14  of the blind bolt. This installation load is applied to a very small bearing area, which results in extremely high operating stresses. The high stress applied to the locking collar  14  is desirable, and is part of the installation process of the blind bolt  10 . During installation, the high stresses developed in the locking collar  14  cause deformation of the locking collar  14  into a groove  46  on the stem, as shown in  FIG. 7 , which provides vibration resistance. Upon further pulling on the stem  12  by the riveter  40 , the stern breaks as shown in  FIG. 8  (at the notch  48  shown in  FIGS. 5-7 ), completing the installation of the blind bolt  10 .  
         [0004]     Due to the locking collar  14 , blind bolts such as shown in  FIG. 1  are designed for minimal FOD (foreign object debris), a very desirable feature in the aircraft industry, for example. Other blind bolt designs also include a “shift washer” which is integral with the fastener and which provides the correct interface and installation for the locking collar. Upon installation, the shift washer falls. As such, the shift washer only has to withstand the stresses associated with a single installation. However, in the case of installing a blind bolt  10  such as is shown in  FIGS. 1 and 5 - 8 , the nosepiece of the riveter  40  has to provide the correct interface, set the locking collar  14  reliably and have a decent life and reliability. Furthermore, the nosepiece has to resist tremendous operating stresses, and retain its shape accurately so it can install correctly all fasteners within its lifespan.  
         [0005]     Two nosepiece designs  50 ,  80  which are currently available in the industry are shown in  FIGS. 2 and 3 . As shown, both designs provide a long, slender, conical active area  52 ,  82  to interface with the locking collar  14 . The fact that the active areas  52 ,  82  are conical provides that the active area  52 ,  82  interferes with an end surface  54  (identified in  FIG. 5 ) of the sleeve  16  of the blind bolt  10 . As a result, low nosepiece reliability and life are associated with both of these designs, and these issues are well known. In fact, the industry has tried over the years to eliminate these shortcomings, without success. The most significant improvement was the use of some exotic materials (like Vasco 350). However, the tool life improvement was incremental and reliability did not improve significantly.  
         [0006]     Reliability of the designs shown in  FIGS. 2 and 3  is low because at high levels of stress and not enough support of the active area  52 ,  82 , any minor deviation or material, surface or heat treat flaw can cause part failure. As a result, the manufacturing tolerances surfaces and heat treat requirements are very tight, thereby making manufacturing very costly and causing high rejection rates.  
         [0007]     Furthermore, the life of one of the nosepieces  50 ,  80  shown in  FIGS. 2 and 3  can vary from a few installations (i.e., under ten) to a few hundred installations, and virtually identical nosepieces can have very different life expectancies, making the product very unreliable.  
         [0008]     Finally, the designs shown in  FIGS. 2 and 3  provide inconsistent and poor dimensional stability; they can also have several forms of failure that become very difficult to detect during operation. Therefore, if the nosepieces are not inspected carefully prior to being re-used, while the nosepiece appears to be in good condition, the dimensional changes may cause faulty fastener installation, a very undesirable outcome.  
       OBJECTS AND SUMMARY  
       [0009]     An object of an embodiment of the present invention is to provide an improved nosepiece for use with a riveter for installing blind bolts.  
         [0010]     Another object of an embodiment of the present invention is to provide a nosepiece which provides a dramatically improved tool life, better reliability and better dimensional stability.  
         [0011]     Yet another object of an embodiment of the present invention is to provide a nosepiece which provides a positive visual indication of structural failure.  
         [0012]     Briefly, and in accordance with at least one of the foregoing objects, an embodiment of the present invention provides a nosepiece which has an active area which is annular and effectively matched to the dimensions of the locking collar of a blind bolt which the nosepiece is configured to install. The active area is configured to provide that no tapered surface interferes with the sleeve during installation of the blind bolt. Instead, the active area includes a protrusion which intersects a support area at a ninety degree angle. The transition from the protrusion to the support area surface may provide a fillet. Providing a minimum or no transition fillet radius from the active area to the support area allows for a minimum length of the active area, providing maximum reinforcement to the active area. It also concentrates the operating stresses this area, dispersing them from the critical, working surface of the active area, providing an expected failure mode. In other words, by providing a minimum or no transition fillet radius from the active area to the support area, the operating stresses are concentrated in this area. As such, when there is structure failure, such failure tends to occur at this location, causing the part to chip, thereby providing a positive, very easy visual indication of the working condition of the nosepiece. Preferably, an external surface of the nosepiece is threaded such that the nosepiece can be threaded into a riveter. Also, preferably a rear surface of the nosepiece is tapered and is configured to engage and spread open the jaws of a riveter, such that the stem of a blind bolt can be readily inserted into the riveter through a bore in the nosepiece, without the jaws interfering.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]     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:  
         [0014]      FIG. 1  illustrates a conventional blind bolt;  
         [0015]      FIGS. 2 and 3  illustrate prior art nosepiece designs;  
         [0016]      FIG. 4  illustrates a nosepiece which is in accordance with an embodiment of the present invention;  
         [0017]      FIGS. 5-8  provide a sequence of cross-sectional views, showing the nosepiece of  FIG. 4  being used in association with a riveter to install a blind bolt such as is shown in  FIG. 1 ;  
         [0018]      FIG. 9  illustrates a two component nosepiece configuration which is in accordance with an alternative embodiment (for dramatically improved performance) of the present invention;  
         [0019]      FIG. 10  illustrates the nosepiece of  FIG. 9 , after significant use; and  
         [0020]      FIGS. 11-13  illustrate the same body being used with three different inserts to install different size blind bolts.  
     
    
     DESCRIPTION  
       [0021]     While the present invention may be susceptible to embodiment in different forms, there is shown in the drawings, and herein will be described in detail, an embodiment 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.  
         [0022]      FIG. 4  illustrates a nosepiece  100  which is in accordance with an embodiment of the present invention. As shown, the nosepiece  100  has an active area  102  which includes an annular protrusion  104 . The protrusion  104  is effectively matched to the dimensions of the locking collar  14  of a blind bolt  10  which the nosepiece  100  is configured to install. The active area  102  is configured to provide that, unlike the designs shown in  FIGS. 2 and 3 , no tapered surface interferes with surface  54  of the sleeve  16  of the blind bolt  10  during installation. Instead, the active area  102  includes a protrusion  104  which intersects a support area  106  at generally a ninety degree angle. The transition from the protrusion  104  to the intersecting, support area  106  may provide a fillet, and the support area  106  has an outer edge  108  which may also be rounded. An external surface  110  of the nosepiece  100  is threaded such that the nosepiece  100  can be threaded into a riveter  40 , and more specifically into a pulling head which is engaged with a riveter  40 . Specifically, the nosepiece  100  can be engaged with, for example, the following pulling heads: H955 pulling head, H9055 pulling head or a right angle pulling head such as the H866-3, 4, 5 or 6 pulling head, each of which is commercially available from Cherry Aerospace®. Also, the following riveters, for example, can be used: the G746a power riveter, the G747 power riveter, the G704B riveter, the G30 hand riveter or the G750A hand riveter, each of which is commercially available from Cherry Aerospace®. The riveter, pulling head and nosepiece can also be used to install, for example, Cherrylock® A Code fasteners, which are also commercially available from Cherry Aerospace®.  
         [0023]      FIGS. 5-8  provide a sequence of cross-sectional views, showing the nosepiece  100  of  FIG. 4  being used in association with a riveter  40  to install a blind bolt  100  such as is shown in  FIG. 1 . As shown, the nosepiece  100  has a throughbore  112  for receiving a stem  12  of the blind bolt  10 , and the surface  106  which intersects with the annular protrusion  102  has an outside diameter (dimension  120  in  FIG. 5 ) which is larger than both the inside diameter (dimension  122  in  FIG. 6 ) and outside diameter (dimension  124  in  FIG. 8 ) of the protrusion  102 . Also, as shown in  FIG. 5 , preferably a rear surface  130  of the nosepiece  100  is tapered and is configured to engage and spread open the jaws  32  of the riveter  40 , such that the stem  12  of the blind bolt  10  can be readily inserted into the riveter  40 , through the bore  112  in the nosepiece  100 , without the jaws  32  interfering.  
         [0024]     To install the blind bolt  10 , the sleeve  16  of the blind bolt  10  is inserted into an aperture  28  in a workpiece  30 , as shown in  FIG. 5 , and the stem  12  of the fastener  10  is inserted into the nosepiece  100 , such that the annular protrusion  102  contacts the locking collar  14  of the fastener  10 . Then the riveter  40  is actuated, causing the jaws  32  of the riveter  40  to grip and pull on the serrated stein  12  of the blind bolt  10 . This causes a bulb  42  to form in the blind area  44  of the workpiece  30 , as shown in  FIG. 6 , thereby providing a clamp up load to the workpiece structures  30   a ,  30   b . While the jaws  32  of the riveter  40  pull on the stem  32 , an installation load from the riveter  40  to the fastener is transferred by the nosepiece  100  to the locking collar  14  of the blind bolt  10 . This installation load is applied to a very small bearing area, which results in extremely high operating stresses. The high stress applied to the locking collar  14  is desirable, and is part of the installation process of the blind bolt  10 . During installation, the high stresses developed in the locking collar  14  cause deformation of the locking collar  14  into a groove  46  on the stem  12 , as shown in  FIG. 7 , which provides vibration resistance. Upon further pulling on the stein  12  by the riveter  40 , the stein  12  breaks as shown in  FIG. 8 , completing the installation of the blind bolt  10 .  
         [0025]     As shown in  FIGS. 5-8 , the active area  104  is annular, short and stubby, with a minimum fillet radius at the transition to the support area  106 . Since the fillet radius would interfere with the setting of the locking collar to the full depth, this portion has to be compensated by increasing the length of the protrusion  102  (i.e., the extent to which the protrusion  104  extends from the support area  106 ). By keeping this to a minimum, the feature is as stubby as necessary. The dimensions of the protrusion  102  (i.e, the inside diameter (dimension  122  in  FIG. 5 ) and the outside diameter (dimension  124  in  FIG. 8 ) closely match the fastener dimensions, providing maximum bearing surface for the active area. The protrusion length (i.e., the extent to which the protrusion  104  extends from the support area  106 ) of the annular active area  104  closely matches the maximum standard requirement for setting the locking collar  14 . As such, during installation, the fastener  100  is precisely guided and centered during installation and by keeping corner breaks of the work surface to an absolute minimum.  
         [0026]     Providing a minimum or no transition fillet radius from the active area  104  to the support area  106  allows for a minimum length of the active area, providing maximum reinforcement to the active area. It also concentrates the operating stresses in this area, dispersing them from the critical, working surface of the active area, providing an expected failure mode. In other words, by providing a minimum or no transition fillet radius from the active area  104  to the support area  106 , the operating stresses are concentrated in this area. As such, when there is structure failure, such failure tends to occur at this location, causing the part to chip, thereby providing a positive, very easy visual indication of the working condition of the nosepiece. Furthermore, the two piece embodiment displaces most of the stress from this area to an area inside of the softer body, acting as a shock absorber, increasing the life of this design dramatically.  
         [0027]     The short, stubby design provides excellent support to the stress area, keeping the active area rigid. Buckling and radial plastic deformation of the annular area are not possible. The only failure mode allowed by the current design is compressive (axial), and that can be controlled very well by the mechanical properties of the material used, and by using a two piece design to further reduce the stresses in the active area.  
         [0028]     The nosepiece area  106  behind the active annular feature  104  is quite sizeable by comparison, able to absorb considerable shock and provide the much needed hoop (radial) strength. Corner breaks at the outside diameter/inside diameter of the annular active area are minimal, to keep the load bearing area as large as possible.  
         [0029]     The nosepiece  100  shown in  FIGS. 4-8  provides dramatically improved tool life (such as 600 to 1200 installations), good reliability (in extensive tests, all nosepieces such as is shown in  FIGS. 4-8  had similar life expectancy, within reasonable margins) and dimensional stability (the design is very rigid, with very little or no dimensional changes being possible over the life of the nosepiece).  
         [0030]     Furthermore, the nosepiece  100  shown in  FIGS. 4-8  is configured to provide a positive visual indication of structural failure. This is because, in operation, the stress is concentrated in a known area, away from the working surface, and that is precisely where failure occurs. When that happens, the material in the stressed area chips away, providing an excellent visual indication of the failure. By comparison, the designs  50 ,  80  illustrated in  FIGS. 2 and 3  do not behave consistently, progressively deforming over the life of the nosepiece. As such, if the nosepieces are not inspected carefully prior to being re-used, and a nosepiece has suffered dimensional changes, there could be faulty fastener installation.  
         [0031]     In an alternative embodiment, significantly improving the life and reliability of this design, the annular area  104  can be a separate component made out of a different material and to higher precision requirements, pressed or otherwise mounted into the body of the nosepiece. This option is represented by the dotted line  140  in  FIG. 8 .  
         [0032]      FIG. 9  illustrates a nosepiece  200  which is in accordance with an alternative embodiment of the present invention. The nosepiece  200  consists of two separate components—a body  202  and an insert  204  which is pressed into the body  202 . An external surface  206  of the body  202  includes threads  208  so that the nosepiece  200  can be threaded into a pulling head used with a riveter, such as the pulling head  40  shown in  FIGS. 5-8 , much like nosepiece  100 . The body may also be made press fit into the pulling head. The body  202  preferably includes a hex-shaped portion  210  for engagement with a tool, and includes a stepped central throughbore  212  in which the insert  204  is pressed. The throughbore  212  in the body  202  preferably includes an increased diameter portion  214  which receives an increased diameter portion  216  of the insert  204 . The insert  204  also includes a central throughbore  218 , and includes a front end surface profile  220  which provides an active area  222  that intersects a support area  224  at generally a ninety degree angle, much like nosepiece  100 . Preferably, like nosepiece  100 , a rear surface  226  of the insert  204  of the nosepiece  200  is tapered or conical and is configured to engage and spread open the jaws  32  of the riveter  40 , such that the stem  12  of a blind bolt  10  can be readily inserted into the riveter  40 , through the bore  218  in the insert  204 , without the jaws  32  interfering.  
         [0033]     While the insert  204  is made out of a very hard and tough material, such as Maraging 350, to resist the tremendous installation loads and shocks developed during tool operation, the body  202  is made out of a much softer, ductile material, such as a low alloy steel, acting as a shock absorber to the insert  204  which is pressed into the body  202 .  
         [0034]     During use, the fact that the body  202  is softer than the insert  204  provides that the body  202  allows the insert  204  to embed into the body  202  slightly with each cycle, transferring most of the shock load away from the active area  222  of the insert  204 . The unavoidable failure is therefore transferred to the softer body  202 , to an area that will not impede the proper performance of the nosepiece  200 , improving significantly the life of the nosepiece  200  by deflecting shocks away from the active area  222 . As an example, as shown in  FIG. 9 , the insert  204  may initially protrude from the body  202  by 0.064 inches (dimension  230  in  FIG. 9 ). However, as an example, as shown in  FIG. 10 , after significant use the insert  204  may embed into the body  202  by as much as 0.010 inches, causing the insert  204  to only end up protruding from the body  202  by 0.054 inches (dimension  230  in  FIG. 10 ), and a deformation bulb  232  may end up forming in the body.  
         [0035]     A shoulder  234  is provided on the insert  204 , and the shoulder  234  provides a visual indication of the status of the nosepiece  200 . For example, the nosepiece  200  may be used as long as the shoulder  234  is above or flush with a front surface  236  of the body, and the active area  222  is in good condition (i.e., has no fractures or deformations).  
         [0036]     As discussed above, a rear surface  226  of the insert  204  is tapered or conical and is configured to engage and spread open the jaws of a riveter. Since the jaws of a conventional riveter are very hard with sharp edges, and the body  202  is made of soft material, the back end of the body  202  cannot be used to open the jaws because this would result in premature wear. To avoid this issue, the rear surface  226  of the harder insert  204  is configured to engage and open the jaws instead.  
         [0037]     Preferably, the nosepiece  200  is configured such that it is designed modular so that one body  202  can take multiple size inserts. For example,  FIGS. 10, 11  and  12  show the same body  202  receiving three different sized inserts—an insert  204  for accommodating a—8 blind bolt (see  FIG. 10 ), an insert  204   a  for accommodating a—6 blind bolt (see  FIG. 11 ), and an insert  204   b  for accommodating a—5 blind bolt (see  FIG. 12 ). This keeps production cost down and simplifies product structure. Additionally, due to this feature the insert could be pressed directly into the body of a pulling head when space constraint is a big issue.  
         [0038]     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.

Technology Classification (CPC): 8