Abstract:
A universal offset pulling head assembly for exerting an axial pulling force on a fastener allows the same pulling head assembly to be utilized for a variety of different fastener sizes and types by exchanging a front plate assembly, where the front plate assembly may comprise variable nose pieces according to the type of fastener to be installed. Because the front plate assembly is subject to the most severe wear, other components of the pulling head assembly may continue to be utilized and the front plate assembly discarded. The disclosed pulling head assembly utilizes a stationary guiding member which prevents damage which might otherwise occur because of severe bending moments.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    This invention generally relates to the installation of fasteners, including blind fasteners, and anchoring devices such as rivetless nut plates, which are used in manufacturing, maintenance and repair of aircraft, as well as in countless commercial applications. Such fasteners are installed by placing the fastener into an opening extending through the piece or pieces to be fastened and then applying a load to a male member, known as the break stem, which is initially attached to the fastener. The break stem shears from the fastener body at the end of the installation process upon the application of a predetermined tensile load by an installation tool. 
         [0002]    The invention more specifically relates to fasteners used in confined areas which are usually installed using offset installation equipment. While the idea of offset installation is not new, decreases in the available space for installation results in a concomitant increase in the need for reduced sizing of the installation tool. This increased need has resulted in an increased demand for more compact offset and right-angle pulling heads for operation at concurrently increasing loads. 
         [0003]    Examples of areas which present difficulties in installing fasteners include those which are close to other structures or to an edge, structure obstructed access, and blind access areas, as in the case of an fastener installed in a C-channel. Standard straight pulling head tools are usually unable to install fasteners in such applications. 
         [0004]    Under known practices, pulling heads, including their nose assemblies, are typically custom designed to install fasteners of specific types and sizes. As construction of an aircraft requires the use of hundreds of types and sizes of fasteners, the procurement and use of the corresponding pulling heads can become expensive, unnecessarily complicating the logistics of production and procurement. 
         [0005]    By way of background for pulling heads, U.S. Pat. Nos. 4,796,455 and 6,739,170 B1, both by Rosier, disclose offset nose assemblies, which because of the compact nature and configuration of the nose assembly, increase the applications where use of pulling heads is feasible. However, the devices disclosed by Rosier are dedicated to a single type and size of fastener and are not capable of being reconfigured. As a result, nose assemblies for uncommon types or sizes of fasteners are either unavailable or only available at an increased expense and a longer order lead time than for the more common fasteners. Additionally, because pulling heads tend to jam during operation and prolonged use only exacerbates this tendency, the currently known pulling heads have a relatively short life cycle, as when the active areas of a tool wear out, such that the tool has to be disposed. 
       SUMMARY OF THE INVENTION 
       [0006]    The present application is directed toward an apparatus which addresses the problems identified above. 
         [0007]    The presently disclosed device is a compact re-configurable pulling head which is capable of use for installing a wide variety of fastener types and sizes. This concept decreases the manufacturing cost of the tool, resulting in savings which may be ultimately passed to the consumer of the finished goods. Additionally, because a single pulling head may be utilized for a variety of fastener types and sizes, the number of tools required for manufacturing may be decreased, with concomitant decreases in the logistics of manufacturing, stocking and procurement of the needed tools. 
         [0008]    The disclosed device uses lower cost, easily replaceable wear components and thus can be repaired and refurbished when the use areas are worn as opposed to the entire pulling head being discarded and replaced. 
         [0009]    The disclosed pulling head comprises a housing having a front end and a rear end, a drawbolt having an upper section and a lower section, a drawbolt activation means, a removable front plate, a stationary guiding member, a nose piece, and a break stem gripping means. The front plate is attached to the housing with front plate retention means. The housing comprises a first axis, while the gripping means define a second axis parallel to the first axis. The lower section of the drawbolt, which is disposed within the housing, comprises a guide member engagement surface which slideably engages the stationary guiding member. 
         [0010]    Because the present device has an interchangeable front plate, the front plate can be replaced either when the front plate is excessively worn or, alternatively, when it is desired to install a different type of fastener. Front plates for different fasteners may comprise a integral nose pieces sized for a particular fastener size and type. Alternatively, the nose piece may be removeably attached to the front plate, such that the operator may change out the nose piece as required for the particular fastener. As the front plate and/or the nose piece can be manually replaced by the operator, the same pulling head may be utilized to provide for the installation of different fasteners by simply changing out the front plate and/or the nose piece. 
         [0011]    A consideration for the known offset pulling heads is that operation generates a bending moment which negatively impacts tool performance. If the bending moment is not properly controlled, resulting component failure can occur. Additionally, increasing installation loads as well as increasing offset distance generate increasing bending moments. Improved guiding systems are therefore required to prevent damage caused by the bending moment. Embodiments of the disclosed device comprise an improved guidance mechanism, namely a stationary guide member, to reduce the effects of the bending moment. The stationary guiding member guides the drawbolt during fastener placement and installation, thus ensuring that correct placement and installation of the fastener is not affected by the stress of the bending moment. The guide member may comprise a precision pin having very high surface hardness and thus able to withstand the shearing effects of the bending moments generated during use. The stationary guiding member may be an integral component of the front plate, or attached thereto. When the front plate is attached to the housing of the tool, the guider member is disposed within the housing of the pulling head, providing support to the drawbolt. Additionally, the stationary guiding member provides no threat of harm to the operator or the structure to which the fastener is being installed (such as an aircraft), because the guiding member has no moving or operative protruding parts. 
         [0012]    The front plate retention means can be a threaded fastener of a predetermined size and type of manufacture and more than one fastener may be used, depending upon the desired characteristics and requirements of use. Additionally, the stationary guide member may itself be utilized as means for retaining the front plate to the housing. 
         [0013]    The upper section of the drawbolt comprises gripping means, which may comprise a plurality of jaws. The plurality of jaws grips the break stem of the fastener during installation and transmits the load from the drawbolt to the break stem to shear the break stem. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0014]      FIG. 1  shows an exploded perspective view of an embodiment of the disclosed apparatus. 
           [0015]      FIG. 2  shows a cross sectional view of the embodiment shown in  FIG. 1 . 
           [0016]      FIG. 3  shows a perspective view of the housing and front plate of the embodiment shown in  FIG. 1 . 
           [0017]      FIG. 4  shows perspective view of the front plate of the embodiment shown in  FIG. 1 . 
           [0018]      FIG. 5  shows perspective view of the front plate of  FIG. 4  with the nose piece removed. 
           [0019]      FIGS. 6   a - 6   i  show perspective views of various nose pieces which may be utilized in combination with the front plate shown in  FIG. 5 . 
           [0020]      FIG. 7  shows a partial cross sectional view of the front plate and the drawbolt assembly of an embodiment of the disclosed apparatus in the pre-operative condition. 
           [0021]      FIG. 8  shows a partial cross sectional view of the front plate and the drawbolt assembly of an embodiment of the disclosed apparatus with the drawbolt being activated. 
           [0022]      FIG. 9  shows a perspective view of the jaw members which may be utilized in an embodiment of the disclosed apparatus. 
           [0023]      FIGS. 10   a  through  10   g  show the operational sequence of an embodiment of the disclosed apparatus in the installation of a blind bolt fastener. 
           [0024]      FIGS. 11   a  through  11   d  show the operational sequence of an embodiment of the disclosed apparatus in the installation of a rivetless nut plate installation. 
           [0025]      FIGS. 12   a  through  12   d  show the operational sequence of an embodiment of the disclosed apparatus in the installation of a rivet. 
           [0026]      FIGS. 13 and 13   a  show a sectional view and a perspective view of an alternative embodiment of the disclosed apparatus. 
           [0027]      FIGS. 14 and 14   a  show a sectional view and a perspective view of an alternative embodiment of the disclosed apparatus. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS  
       [0028]    Referring now to the figures,  FIG. 1  shows the major components of an embodiment of the device  10 . As shown, the device  10  generally comprises the housing  12 , the front plate  14  and the drawbolt  16 . The housing  12  and attached front plate  14  are the stationary portions of the device, providing an active area to interface with a fastener during installation. The drawbolt  16  is the mobile part of the device, providing means to grip onto the fastener and providing the pulling force to install the fastener. As shown in  FIG. 2 , the housing  12  is threaded to the head cylinder  18  of a riveter, also referred to herein as the “actuation means.” The drawbolt  16  is operationally connected to the piston  20  of the riveter. 
         [0029]    Housing  12  has a front end  22  and a rear end  24 . The front end  22  and the rear end  24  of the housing  12  define a first axis A 1  as shown in  FIG. 2 . Drawbolt  16  comprises an upper section  26  and a lower section  28 , the lower section  28  disposed within the housing  12 . The drawbolt  16  is connected to an actuation member  30 , which in turn is operated by the actuation means for axial movement of the drawbolt  16  relative to the housing  12  and along the first axis A 1 . 
         [0030]    The upper section  26  of the drawbolt  16  comprises a gripping means, such as jaws  32  which are disposed within jaw housing  34 . Jaws  32  are biased forward within jaw housing  34  by biasing means such as a spring  36  (or a rubber grommet) which is retained by plug  38 . Jaws  32  are in axial alignment with the central axis of nose piece  40 , thereby defining a second axis A 2 , as shown in  FIG. 2 . The second axis A 2  is parallel to the first axis A 1 . 
         [0031]    Front plate  14  is removably attached to the front end  22  of housing  12  with retention means such as screw  66  or other suitable fastener which typically will allow for changing of the front plate on site by the operator. The front plate  14  may comprise a nose piece  40  having an aperture  42 . However, as shown in  FIGS. 13 and 13   a,  the nose piece  40  may, alternatively, be attached to an alternative embodiment of housing  12 ′. The axis of the aperture  42  coincides with the second axis A 2 . The front plate  14  further comprises a stationary guiding member  44 , which may be set within a counter-bore  64 , where the stationary guiding member  44  axially extends into the housing  12  when the front plate is attached to the housing. The lower section  28  of drawbolt  16  comprises a guide member engagement surface  46  which slideably engages a portion of the stationary guiding member  44  as the drawbolt  16  axially moves relative to the housing  12 , as indicated by the arrow shown in  FIG. 2 . Guide member engagement surface  46  may comprise a portion of the inside surface of an aperture axially extending through the lower section  28  of drawbolt  16  as shown in  FIG. 1 . 
         [0032]    During the operating cycle of the installation tool, the drawbolt  16  is precisely guided by the stationary guiding member  44 . Stationary guiding member  44  is preferably manufactured from tough and durable materials having a very hard surface. Stationary guiding member  44  serves multiple functions. It provides accurate location of front plate  14  with respect to housing  12 . It provides accurate location of the drawbolt  16  with respect to nose piece  40 , which is critical for the correct installation of a fastener. The stationary guiding member  44  guides the drawbolt  16  during operation, protecting the assembly against the destructive effects of the bending moments generated during fastener installation. 
         [0033]      FIG. 3  shows a perspective view of an embodiment of housing  12  with front plate  14  attached with screw or other suitable fastener  66 . Front plate  14  further comprises nose piece  40 . Nose piece  40  is the component which interfaces with the fastener during installation, and is typically a high wear component. As shown in  FIG. 3 , stationary guiding member  44  may be pressed flush into the front plate  14 . Housing  12  and front plate  14  are maintained in a generally stationary position during the operational cycle of the installation tool.  FIG. 4  shows a perspective view of an embodiment of front plate  14  detached from housing  12 , showing stationary guiding member  44 , which is in axial alignment with first axis A 1 . The distance L 1  between first axis A 1  and second axis A 2  defines the offset of the pulling head. Nose piece  40  and stationary guiding member  44  are typically pressed into front plate  14 . However, it is to be appreciated that other means of attaching either component to the front plate  14  may be utilized, such as threads, or, alternatively, the nose piece and/or stationary guiding member  44  may be integral components of front plate  14 . Alternatively, as shown in  FIGS. 13 and 13   a,  nose piece  40  may be attached to an alternative embodiment of housing  12 ′. 
         [0034]      FIG. 5  depicts the front plate  14  with the nose piece  40  removed, showing aperture  52  into which nose pieces  40  of different configurations may be set. It is this feature which allows a single pulling head to be utilized for a large variety of different fasteners and sizes. By changing either front plate  14  or, alternatively, changing the nose piece  40  in the front plate or housing  12 ′, the same pulling head may be utilized for many different fasteners. In addition, because the front plate  14  comprises the high wear components of the device, a worn front plate may be discarded while the remaining components of the pulling head have remaining service life.  FIGS. 6   a  through  6   i  depict a variety of embodiments of the nose piece  40  which may be disposed within aperture  52  of front plate  14 . The nose piece  40  may be pressed into the aperture  52  or otherwise attached to the front plate  14 . Front plate  14  is attached to housing  12  with retention means which are inserted through attachment aperture  54  of front plate  14 . 
         [0035]      FIGS. 7 through 9  show detailed views of the configuration of jaws  32  As shown in  FIG. 9 , jaws  32  may comprise three segments which, when assembled comprise a conical front shape. This conical shape matches the internal shape of the drawbolt cavity  56 . The angle of the front of the jaws  32  affects the engagement of the jaws onto the stem  100  of a fastener member, and the disengagement of the jaws from the stem. Nose piece  40  comprises a conical back end  58  which, when the drawbolt  16  is in the forward position as shown in  FIG. 7 , pushes jaws  32  slightly back, compressing spring  36  or other biasing means and opening the jaws for receiving stem  100  (not shown). When the actuation means is activated, as illustrated in the active area detail  FIG. 8 , drawbolt  16  begins to move backward away from the nose piece  40  and the front of the jaws  32  disengage from the conical back end  58  of the nose piece, at which point the jaws are urged forward by spring  36  or other biasing means, such as an elastic element. In moving forward against the front of the drawbolt cavity  56 , the jaws  32  are forced closed by the conical shape of the drawbolt cavity  56 , thereby locking onto stem  100 . When the actuation means is deactivated, the drawbolt  16  moves forward against the conical back end  58  of the nose piece  40  thereby releasing jaws  32  from the stem  100 . 
         [0036]    It has been found that the angle for the front of the jaws  32 , and the matching angle of the drawbolt cavity  56  should exceed forty-five degrees and that the optimal angle is sixty degrees, as depicted in  FIG. 7 . The use of a sixty degree angle has been found to be optimum for high performance, increased life of the jaws  32  and drawbolt  16 , and rapid engagement/disengagement of the jaws with stem  100 , especially when installing fasteners requiring high installation loads. A more standard angle of 36 degrees may also be used. 
         [0037]    As illustrated in the examples provided below, the disclosed invention provides the ability to utilize a single pulling head to install completely different sizes and varieties of fasteners simply by changing out the front plate  14  and/or the nose piece  40 . While three different examples are provided below, it is to be appreciated that the applications for the presently disclosed invention apply to many other types of fasteners and the following applications are provided as examples only rather than an exhaustive list of applications. 
         [0038]      FIGS. 10   a  through  10   g  show the stages of installation of a blind bolt fastener with an embodiment of the device  10 .  FIG. 10   a  shows the initial stage of installation with the blind fastener  102  placed in an aperture in the structure  104 . The device  10  has previously been equipped with a front plate  14  and/or nose piece  40  specific to the fastener  102  to be installed. With jaws  32  held in an open position by the conical back end  58  of the nose piece  40 , the nose piece is positioned onto the fastener stem  100  as shown in  FIG. 10   b.  The trigger of the riveter is pressed, causing the drawbolt  16  to pull away from the conical back end  58  of nose piece  40  as shown in  FIG. 10   c.  Once jaws  32  have been pulled away from the conical back end  58  of nose piece  40 , the jaws  32  are urged forward by spring  36  against the conical shape at the front of the drawbolt cavity  56  which forces the jaws to close and lock onto stem  100 . Once the jaws  32  have fully engaged stem  100 , the stem is pulled toward the pulling head, thereby forming bulb  106  on the blind side of the structure  104 . As illustrated in  FIG. 10   e,  when the required load is reached, nose piece  40  deforms the locking collar  108  (best shown in  FIG. 10   a ) of the blind fastener  102  by wedging the locking collar between the sleeve  110  of the fastener and the stem  100 , thereby fully installing the blind fastener. Once the blind fastener  102  is fully installed, additional load applied by the installation tool breaks stem  100 , such that a stem remnant  100 ′ remains in the jaws  32  as shown in  FIG. 10   f . As shown in  FIG. 10   g,  when the trigger of the installation means is released, the drawbolt  16  returns to its original position and the jaws  32  are released by engaging the conical back end  58  of the nose piece  40 . The stem remnant  100 ′ is thereby released by the jaws  32  but not ejected. When the nose piece  40  is placed over the next fastener stem  100  to be installed, the stem remnant  100 ′ is pushed out of the jaws  32  through an opening in plug  38  into deflector  60 . 
         [0039]      FIGS. 11   a  through  11   d  show the stages of installation of a rivetless nut plate (“RNP”) assembly  202  with an embodiment of the device  10 . The RNP assembly  202  is a different type of fastener from blind fastener  102 , because access is available on the other side of the structure  204 . As shown in  FIG. 11   a,  nose piece  40  is placed over mandrel  200 , with the nose piece penetrating the structure  204 . When the actuation means are activated, the draw bolt  16  pulls away causing the jaws  32  to clamp down on mandrel  200 . The retainer of the RNP assembly  202  is pulled into the structure  204 , and the mandrel  200  begins to collapse expanding the retainer into the structure as shown in  FIG. 11   c.  Continued load applied to the mandrel  200  causes it to detach from the RNP assembly  202 ′, leaving a mandrel remnant  200 ′ in jaws  32 . As shown in  FIG. 11   d,  the mandrel remnant  200 ′ is returned to the front of the tool where it may be manually ejected. 
         [0040]      FIGS. 12   a  through  12   d  show the stages of installation of a rivet-type fastener  302  with an embodiment of the device  10 . As shown in  FIG. 12   a,  nose piece  40  is placed over rivet stem  300 , with the nose piece  40  abutting the head of the rivet. When the actuation means are activated, the draw bolt  16  pulls away causing the jaws  32  to clamp down on rivet stem  300 . As the rivet stem  300  is pulled backward by drawbolt  16 , a shear ring  308  on the stem collapses the sleeve of the rivet  302  forming bulb  306 . As the rivet stem  300  continues to move through the sleeve of the rivet  302 , the shear ring  308  shears off of the stem, allowing a locking collar  310  to contact the driving anvil  62  at the front of nose piece  40 . The locking collar  310  fills the recessed area between the rivet stem  300  and the sleeve which secures them together. Continued pulling by the drawbolt  16  causes the rivet stem  300  to fracture from the rivet fastener. 
         [0041]    Because different application may present access issues, the geometry of the front plate  14  of the pulling head may impact whether the tool is suitable for use in the application. Therefore, the following embodiments of the invention present modified front plate arrangements having different profiles. These embodiments may also present advantages to an operator not realized by the embodiments disclosed above, such as easier or faster field replacement of the front plate. In addition, the following embodiments discuss modifications to the stationary guide member  44  which may, in a particular application, be desirable. 
         [0042]      FIGS. 13 and 13   a  show an alternative embodiment of the pulling head  10 ′. In this embodiment, the short front plate  14 ′ comprises a stationary guiding member  44 ′ in the form of a dowel pin, but the nose piece  40  is retained in housing  12 ′ rather than in front plate  14  as shown in the other embodiments. Front plate  14 ′ further comprises fastener  66 ′. 
         [0043]      FIGS. 14 and 14   a  show an alternative embodiment of the pulling head  10 ″. In this embodiment, stationary guiding member  44 ″ functions as a retention means for attaching front plate  14 ″ to the housing  12 ″ in addition to the existing fastener  66 ″. 
         [0044]    While the above is a description of various embodiments of the present invention, further modifications may be employed without departing from the spirit and scope of the present invention. Thus the scope of the invention should not be limited according to these factors, but according to the claims to be filed in the forthcoming utility application.