Abstract:
A nut-plate riveter which includes multiple pistons which assist in creating a pulling force. The nut-plate riveter provides that spent mandrels are pulled through the tool, thereby avoiding problems in the field. The nut-plate riveter includes a handle and a plurality of pistons disposed in the handle. Cavities are proximate the pistons for pressurizing the pistons, and air supply passages are in communication with the cavities for supplying air to the cavities to pressurize the pistons. A piston rod is engaged with at least one of the pistons, and the piston rod has a longitudinal bore therethrough which is configured to receive a spent mandrel. A deflector fitting may be disposed at an end of the nut-plate riveter.

Description:
RELATED APPLICATION (PRIORITY CLAIM) 
   This application claims the benifit of U.S. Provisional Application Ser. No. 60/441,565, filed Jan. 21, 2003. 

   BACKGROUND 
   This invention generally relates to tools for installing nut-plate rivets, and more specifically relates to a nut-plate riveter which includes multiple pistons in a feed-through mandrel design. 
   Tools are used to install nut-plate rivets. It is advantageous to provide that such tools are lightweight, yet provide the required pulling force on a mandrel for installing a nut-plate rivet. It is also advantageous to provide that such tools are easy to assemble, use and maintain. 
   Many of the tools which are presently commercially available are pneumatic and provide that air pushes a piston in the tool in order to provide the required pulling force on a mandrel which pulls through the rivet. At least one of the tools which is available provides that a plurality of pistons are disposed in the tool, and the plurality of pistons assist (viz-a-viz the air supply) in providing the pulling force. By providing a plurality of pistons, less air pressure is needed to produce the requisite pulling force. 
   Although there is at least one tool presently available which includes multiple pistons, the tool is not configured such that a spent mandrel is automatically pulled through the tool (i.e., away from the nose of the tool). Providing that the spent mandrel is pulled through the tool is advantageous because, otherwise, the spent mandrel must drop out of the front of the tool, and this presents problems. Among other problems, such a design may lead to FOD (Foreign Object Debris) problems in the field, wherein contaminants enter the tool through the front end of the tool, causing the tool to jam, misfunction or break. 
   OBJECTS AND SUMMARY 
   An object of an embodiment of the present invention is provide a nut-plate riveter which is lightweight. 
   Another object of an embodiment of the present invention is provide a nut-plate riveter which is easy to assemble, use and maintain. 
   Yet another object of an embodiment of the present invention is provide a nut-plate riveter which includes a plurality of pistons which assist (viz-a-viz the air supply) in providing a pulling force. 
   Still yet another object of an embodiment of the present invention is provide a nut-plate riveter which includes multiple pistons in a feed-through mandrel design. 
   Briefly, and in accordance with at least one of the foregoing objects, an embodiment of the present invention provides a nut-plate riveter which includes multiple pistons which assist in creating a pulling force. The nut-plate riveter provides that spent mandrels are pulled through the tool, thereby avoiding problems in the field. The nut-plate riveter includes a handle and a plurality of pistons disposed in the handle. Cavities are proximate the pistons for pressurizing the pistons, and air supply passages are in communication with the cavities for supplying air to the cavities to pressurize the pistons. A piston rod is engaged with at least one of the pistons, and the piston rod has a longitudinal bore therethrough which is configured to receive a spent mandrel. A deflector fitting may be disposed at an end of the nut-plate riveter. 

   
     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  is a cross-sectional view of a nut-plate riveter which is in accordance with an embodiment of the present invention, wherein the nut-plate riveter includes two pistons in a pull-through mandrel design; 
       FIG. 2  is an exploded, perspective view of the nut-plate riveter shown in  FIG. 1 ; 
       FIG. 3  is a cross-sectional view of the nut-plate riveter shown in  FIG. 1 , shown in stand-by position, connected to a pulling head; 
       FIG. 4  is an enlarged view of a portion of that which is shown in  FIG. 3 ; 
       FIG. 5  is an enlarged view of another portion of that which is shown in  FIG. 3 ; 
       FIG. 6  is a cross-sectional view taken along line  6 — 6  of  FIG. 5 ; 
       FIG. 7  is similar to  FIG. 5 , but showing the situation when the tool is activated (in the rear position), and showing the spent mandrel; 
       FIG. 8  is an enlarged view of a portion of that which is shown in  FIG. 3 , specifically showing a trigger assembly portion in the standby position; 
       FIG. 9  is a view similar to  FIG. 8 , but showing the trigger depressed; 
       FIGS. 10-14  are sequential views showing operation of the pulling head during actuation of the nut-plate riveter; and 
       FIG. 15  is a cross-sectional view of a nut-plate riveter which is in accordance with another embodiment of the present invention, wherein the nut-plate riveter includes three pistons in a pull-through mandrel design. 
   

   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. 1-3  illustrate a nut-plate riveter  10  which is in accordance with a first embodiment of the present invention, wherein the nut-plate riveter  10  includes two pistons in a pull-through mandrel design, while  FIG. 15  illustrates a nut-plate riveter  10   a  which is in accordance with a second embodiment of the present invention, wherein the nut-plate riveter  10   a  includes three pistons in a pull-through mandrel design. Regardless of how many pistons are employed, the fact that multiple pistons are used provides that the tool can be lightweight, yet provide the requisite pulling force on a mandrel to install a rivet. Further, the fact that the spent mandrel is pulled through the tool avoids problems and provides that the tool is reliable. 
   The nut-plate riveter  10  illustrated in  FIGS. 1-3  will be described first, and then the nut-plate riveter  10   a  illustrated in  FIG. 15  will be described, pointing out the differences between the two designs, and using like reference numerals to identify like parts. 
   As shown in  FIGS. 1-3 , the nut-plate riveter  10  includes a handle  12  which includes a portion  14  which is configured to be held by a user. A trigger  16  is proximate the handle portion  14  for pressing by the user to actuate the nut-plate riveter  10 . Two pistons  18  and  20  are disposed in the handle  12 , and they are spaced apart from each other. As will be described in more detail below, when the nut-plate riveter  10  is actuated, air pushes on the two pistons  18  and  20  to produce a pulling force on a mandrel  22  (see FIG.  4 ), thereby installing a nut-plate rivet  24 . 
   Starting from the rear of the nut-plate riveter  10  and going forward, the nut-plate riveter  10  includes a mandrel collector bag  26  (see  FIG. 2 ) for collecting spent mandrels which are ejected from the rear of the tool  10 . The mandrel collector bag  26  is configured to fit onto the end  28  of a pin deflector  30 . The pin deflector  30  is generally hollow and has an opening  32  which communicates with the interior of the mandrel collector bag  26  such that spent mandrels  22  can drop from the pin deflector  30 , through the opening  32 , into the mandrel collector bag  26 . 
   A deflector fitting  34  is configured to engage an opposite end  36  of the pin deflector  30 . Specifically, the deflector fitting  34  is generally hollow and cylindrical having a throughbore  38 , and includes a serration or ribs  40  which engage an interior surface  42  of the pin deflector  30 . 
   A retaining ring  44  engages the exterior surface  46  of the deflector fitting  34  as well as engages the interior surface  48  of a rear plug  50 . The rear plug  50  is generally retained in the handle  12  and has an end portion  52  which extends from an aperture  54  in the handle  12  and engages the deflector fitting  34 . A sealing member or o-ring  56  engages an exterior surface of the rear plug  50  and an interior surface of the handle  12 . The rear plug  50  has an end  58  which is configured to receive an end  60  of the rear piston. Proximate the end  58  is a groove  62  for receiving a retaining member or o-ring  64 . The rear piston  18  has a central throughbore  66  along its longitudinal axis. The rear piston  18  includes a groove  68  for receiving a rubber bumper  70  as well as includes a groove  72  for receiving a retaining member or o-ring  74  where the retaining member or o-ring  74  engages an interior surface of the handle  12 . The rubber bumper  70  and rear piston  18  together comprise a rear piston sub-assembly  76 . 
   An end  78  of the rear piston  18  is configured to engage a piston rod  80 . Specifically, as shown, preferably the end  78  of the rear piston  18  includes external threads  82  which threadably engage corresponding internal threads  84  in the piston rod  80 . As shown in  FIG. 6 , the threads  82  are interrupted such that two grooves  86  are provided, thereby providing air passages. The piston rod  80  is generally cylindrical having a central throughbore  88  along its longitudinal axis, and includes orifices  306  which allow the passage of air. A bulkhead  90  engages the exterior surface of the piston rod  80  and contacts a wall  92  (see  FIG. 5 ) in the handle  12 . A retaining member or o-ring  94  is disposed in a groove  96  in the bulkhead  90 , generally between the bulkhead  90  and the piston rod  80 . The bulkhead  90  includes a second groove  98 , and a retaining member or o-ring  100  is disposed in the second groove  98 , disposed generally between the bulkhead  90  and the interior surface of the handle  12 . A retaining ring  102  is disposed in the handle, engaged in a groove  104  provided on the interior surface of the handle  12 . 
   The front piston  20  engages the piston rod  80  (and specifically a wall  106  thereon) and includes grooves  108 ,  110  for receiving retaining members or O-rings  112 ,  114 —a first retaining member or o-ring  112  is disposed between the front piston  20  and the interior surface of the handle  12 , and a second retaining member or o-ring  114  is disposed between the front piston  20  and the piston rod  80 . A retaining ring  116  engages an exterior surface of the piston rod  80 . 
   An end  118  of the handle  12  is configured to receive a front cap sub-assembly  120  which consists of a front cap  122  and rubber bumper  124 . Specifically, the front cap  122  has external threads  126  which are configured to threadably engage corresponding internal threads  128  on the interior surface of the handle  12 , proximate its front end  118 . The front cap  122  includes a groove  130 , and the rubber bumper  124  is disposed in the groove  130 . The front cap  122  also includes grooves  132 ,  134  for receiving retaining members or o-rings  136 ,  138 —a first retaining member or o-ring  136  is disposed in groove  132  and is disposed generally between the front cap  122  and the interior surface of the handle  12 , and a second retaining member or o-ring  138  is disposed in a groove  134  and is disposed generally between the front cap  122  and the piston rod  80 . 
   An end  140  of the front cap  122  is configured to engage a nose fitting  142 . Specifically, the front cap  122  includes internal threads  144  which are configured to threadably engage corresponding external threads  146  on the nose fitting  142 . The nose fitting  142  also includes internal threads  148 , and the piston rod  80  includes external threads  150 , for engaging a pulling head  200 . 
   One form of pulling head  200  which can be used in connection with the riveter  10  is shown in, primarily, FIGS.  3  and  10 - 14 . As shown, the pulling head  200  includes a sleeve  202  which has corresponding external threads  204  thereon configured to threadably engage the internal threads  148  of the nose fitting  142 . A locknut  206  is disposed on the external threads  204  on the sleeve  202 . A drawbar  208  is disposed in the sleeve  202 . The drawbar  208  has internal threads  210  which are configured to threadably engage the corresponding external threads  150  on the piston rod  80 , and has external threads  212  for threadably engaging corresponding internal threads  214  which are provided in a collet  216 . A jaw follower sub-assembly  218  is disposed generally in the drawbar  208 , and the jaw follower sub-assembly  218  contactably engages a jaw set  220  which engages and pulls on the mandrel  22  during actuation of the riveter  10 . The collet  216  includes an angled cavity  221  therein proximate the jaw set  220 . An end of the jaw follower sub-assembly  220  engages a follower spring  222 , and an end  224  of the follower spring  222  engages an interior surface of the piston rod  80  (see FIG.  7 ). An end  226  of the sleeve  202  provides internal threads  228  which threadably engage corresponding external threads  230  on a nosepiece  232 .  FIGS. 3 ,  4  and  10 - 14  illustrate a test coupon  234  which represents a workpiece. 
   As discussed above, the nut-plate riveter  10  includes a trigger  16 . The trigger  16  is a component of a trigger assembly  236  which includes a valve stem  238  which is received in a bore  240  provided in a valve sleeve  242 . As will be described below when operation of the riveter is discussed, the valve stem includes a plurality of orifices for allowing air flow. An end  244  of the valve stem  242  is received in a corresponding groove  246  in the trigger  16 , and the trigger  16  is secured to the valve stem  238  with a set screw  248 . An opposite end of the valve stem  238  is disposed in the valve sleeve  242 . The valve stem  238  is generally retained in the valve sleeve  242  by a retaining ring  250  and retaining washer  252  which engage the valve sleeve  242 . A pin  254  engages the exterior surface of the valve sleeve  242 . A plurality of retaining members or o-rings  256  are disposed on an exterior surface of the valve sleeve  242 , generally between the valve sleeve  242  and an interior surface of the handle  12 . Additionally, a plurality of retaining members or o-rings  258  are disposed on an exterior surface of the valve stem  238 , generally between the valve stem  238  and an interior surface of the valve sleeve  242 . The handle  12  is configured to receive an air fitting, such as viz-a-viz internal threads  258  which threadably engage corresponding external threads on the air fitting, and inside the handle are channels or cavities which allow air to flow internally through the riveter  10 . 
   To assemble the nut-plate riveter, retaining members or o-rings  56 ,  58  are placed in the corresponding grooves on the rear plug  50 . The rear plug  50  is then screwed into the handle  12  using a spanner wrench. Retaining member or o-ring  74  is then is placed into groove  72  on the rear piston  18 , and the rubber bumper  70  is placed in groove  68  provided on the rear piston  18 . The rear piston  18  is then threadably attached to the piston rod  80 . The rear piston  18  is then inserted into the rear plug  50 , which has been threadably engaged in the handle  12 . Retaining member or o-rings  94 ,  100  are inserted into the corresponding grooves  96 ,  98  in the bulkhead  90 . The bulkhead  90  is then inserted into the handle  12  with the piston rod  80  passing through the bulkhead  90 , until the bulkhead  90  sits against wall  92  in the handle  12 . The bulkhead  90  is held in place with retaining ring  102 . 
   Retaining member or o-rings  112 ,  114  are placed in the corresponding grooves  108 ,  110  of the front piston  20 , and the front piston  20  is then inserted into the handle  12  with the piston rod  80  passing through the front piston  20  until the front piston  20  rests against wall  106  on the piston rod  80 . The front piston  20  is held in place with retaining ring  116 . Retaining member or o-rings  136 ,  138  are placed in the corresponding grooves  132 ,  134  in the front cap  122 . The rubber bumper  124  is positioned in the groove  130  provided in the front cap  122 , and this forms the front cap sub-assembly  120 . The front cap sub-assembly  120  is then screwed into the handle  12  until it comes to a stop, with the piston rod  80  passing through the front cap  122 . The nose fitting  200  is then screwed into the front cap sub-assembly  120  until the nose fitting  200  comes to a stop. With this assembly, the piston rod  80  protrudes through the nose fitting  142  (see FIG.  1 ). Retaining ring  44  is placed in the corresponding groove provided on the deflector fitting  34 , and the deflector fitting  34  is then inserted into the rear of the handle  12 , through the rear plug  50  until the retaining ring  44  snaps into place at the corresponding groove provided in the rear plug  50 . The deflector fitting  34  is inserted into the pin deflector  30  so that the serration  40  on the deflector fitting  34  arrests the pin deflector  30 . The mandrel collector bag  26  is then placed over the pin deflector  30  and snapped into place. 
   With regard to assembling the trigger assembly  236 , the retaining members or o-rings  256 ,  258  are placed in the corresponding grooves provided in the valve sleeve  242  and valve stem  238 . The valve stem  238  is then inserted into the valve sleeve  242  with the one end of the valve stem  238  protruding from the valve sleeve  242 . The retaining washer  252  and retaining ring  250  are then inserted in the groove provided in the valve sleeve  242  to restrain the valve stem  238  and hold it in place. The assembled valve is then inserted a corresponding hole  260  provided in the handle  12  and the assembled valve is secured by pin  254 . The protruding end  244  of the valve stem  238  is inserted into a recess  246  provided in the trigger  16  and is held in place by a set screw  248 . Finally, an appropriate air fitting is screwed into the handle  12  (at  258 ). 
   In operation, when pressurized air is introduced at cavity  300  (see FIG.  5 ), the air travels through cavity  302  in the piston rod  80  and escapes into cavity  304  through orifice  306 . This pressurizes both the front piston  20  and rear piston  18 . The air pressure then causes movement of both pistons backwards with amplified force due to the multiple piston arrangement. The pressurized air is trapped in the respective cavities with the appropriate arrangements of o-ring seals. While the pistons  18  and  20  are moving, the air in cavity  308  is vented through orifice  310  in the handle  12 . As shown in  FIG. 9 , simultaneously, air from cavity  310  at the back of the rear piston  18  is routed through cavity  312  to the annulus  314  (see  FIG. 8 ) on the trigger valve and vented through orifice  316  to atmosphere. It is the movement of the multiple pistons that provides the operational force of the tool  10 . As shown in  FIGS. 3 and 4 , the operation swags a collar  24  against a work piece (represented by coupon  234 ) while pulling on a mandrel  22  until the mandrel  22  experiences tensile failure. The spent mandrel  22  is then propelled down the center of the multiple piston arrangements towards the rear of the housing  12  into the collecting bag  26 . The position shown in  FIG. 7  is with the pistons  18  and  20  in the extreme back position. 
   With reference to  FIG. 8 , upon release of the trigger  16 , air pressure at cavity  318  pushes the trigger valve outwards and air is introduced into the back of the rear piston  18  through orifice  320  into cavity  322 . Cavity  300  is vented by a connection to atmosphere through the orifice  324  and annulus  314  whereby annulus  314  makes the connection between orifice  324  and atmosphere via orifice  326 . Air is allowed to enter into cavity  308  (see  FIG. 5 ) through orifice  310  so that a vacuum will not be formed behind the front piston  20 . In this way, only the rear piston  18  returns the multiple piston arrangement to the standby position ready for activation. 
   As can be seen from  FIGS. 5 and 7 , the spent mandrel  22  from the swaging operation is allowed to travel through the center of both the front and rear pistons  18 ,  20  to the collector bag  26 , without interfering with the pressurized air that routed around the piston shafts. 
   Actuation of the pulling head  200  during operation of the riveter  10  is best shown in the sequence of view provided in  FIGS. 10-14 . Because the jaw follower sub-assembly  218  is loaded by spring  222 , the nosepiece  232  causes the jaw set  220  to expand in the collet  216 , with each jaw in the two-jaw set maintaining contact with the angled cavity  221  in the front of the collet  216 . With the jaw set  220  expanded, a nut-plate rivet  24  can be inserted into the nosepiece  232  (or removed) with no resistance. The rivet  24  can then be inserted into the materials to be fastened (represented by coupon  234 ). When the trigger  16  is pulled, the front piston rod  80  begins to retract, and the drawbar  208  and collet  216  move away from the nosepiece  232 , which remains stationary in the sleeve  202 . The jaw set  220  is pushed forward in the collet, 216  and closes until it clamps onto the mandrel  22 .  FIG. 10  shows the situation as the jaws  220  have just made contact with the mandrel  22 . The angled cavity  221  in the collet  216  maintains contact with the jaw set  220  and transfers the pulling force load of the tool onto the jaws  220 . As the stroke continues, the mandrel  22  is pulled through the rivet sleeve  24 , which remains held in place in the workpiece  234  by the nosepiece  232 . As shown in  FIG. 12 , the flared end of the mandrel  22  expands the rivet sleeve  24  as it pulls through, causing the rivet sleeve  24  to form a “footprint” on the far side of the workpiece  234  that is larger than the hole in the workpiece  234 . 
   The mandrel  22  is eventually pulled completely through the rivet sleeve (see FIG.  13 ). As the mandrel  22  passes through the rivet sleeve  24 , it also expands the sleeve  24  to fit tightly in the hole. The rivet  24  is installed, and the pulling head  200  is moved away from the workpiece  234  as the trigger  16  is released. The drawbar  208  and collet  216  move forward with the mandrel  22  held in the jaw set  220  until the jaw set  220  engages the nosepiece  232 , which again expands the jaws  220  and releases the mandrel  22 . At this point, another nut-plate rivet  24  can be inserted into the nosepiece  232 . This rivet  24  pushes the mandrel  22  from the previous installation back through the jaw follower sub-assembly  218  (see FIG.  14 ). As the process is repeated, the mandrels  22  move through the tool  10  until they drop into the mandrel collector bag  26 . 
     FIG. 15  illustrates a nut-plate riveter  10   a  very much like that which has been described above, except the riveter  10   a  includes three pistons  18 ,  20 ,  20   a  instead of two. As such, the riveter  10   a  has many of the same parts, but has a longer handle  12   a , an extra bulkhead assembly  400  which includes a bulkhead  90   a , retaining rings  402  and o-rings  404 , an extra piston assembly which includes a piston  20   a  and o-rings  406 , and an extra valve stem  80   a . One having ordinary skill in the art would understand the structure and operation of the riveter  10   a  shown in  FIG. 15  in light of the foregoing detailed description of riveter  10 . 
   Regardless of how many pistons are employed, the fact that multiple pistons are used provides that the tool can be lightweight, yet provide the requisite pulling force on a mandrel to install a rivet. Further, the fact that the spent mandrel is pulled through the tool avoids problems and provides that the tool is reliable. 
   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.