Abstract:
A portable pneumatic compression riveter consists of a valve, air cylinder and rivet head assembly consisting of an alligator style set of jaws or a c-yoke style jaw set that is used to upset solid rivets used primarily, but not limited to, the aerospace industry. Disclosed is a series of improvements that make the tool lighter, more reliable and safer to operate.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     This invention relates generally to portable pneumatic tools and, more particularly, to compression riveters, used to install solid rivets primarily but not limited to the aerospace industry.  
         [0003]     2. Description of the Related Art  
         [0004]     Portable pneumatic compression riveters are used to install solid rivets to join parts together. They consist of a valve assembly, cylinder assembly with at least one compression chamber and a head assembly consisting of an alligator style set of jaws or a c-yoke style jaw set. An air line with approximately 90 psi compressed air is connected to the valve. The valve is manually actuated by means of a lever allowing compressed air to enter the cylinder assembly. Inside the cylinder, a piston with a seal and a wedge attached to the front is driven forward by the compressed air. The wedge is driven between a set of bearings mounted within the jaws of the rivet head assembly. The wedge forces the pivoting jaw to pivot about a center pin resulting in a squeezing action out on the end of the pivoting jaw as it closes with the fixed jaw. This squeezing action is the means to upset the rivet to join parts together.  
         [0005]     To function most effectively, the valve assembly and cylinder assembly must not leak air. The cylinder material must be both capable of handling the air pressure required to operate the tool and hard enough to resist the wear of the piston. The wedge must be properly aligned with the bearings mounted in the rivet head assembly and capable of handling the resultant forces from upsetting the rivet. A needle roller bearing is typically used with the pivot pin from which the pivoting jaw pivots about. Crushing these needle rollers has long been a limiting factor for this type of tool.  
         [0006]     Another shortcoming of the portable pneumatic compression riveters produced today is the potential for catastrophic failure of the pivoting jaw which can lead to injury or damage to the work being assembled when the forward portion of the pivoting jaw reaches its fatigue limit and breaks off from the attached portion at or around the pivot pin area.  
         [0007]     One of the major reasons for these shortcomings is the need to make the portable pneumatic compression riveter as light as possible for ergonomic reasons. An improved portable pneumatic compression riveter which addresses these problems and shortcomings of earlier work in this field would be an important technological advance.  
         [0008]     It is an object of the invention to provide a portable pneumatic compression riveter which addresses some of the problems and shortcomings of the prior art.  
         [0009]     Another object of invention is to provide such a portable pneumatic compression riveter which addresses cylinder, piston and seal wear issues while contributing to a lighter and more reliable seal design.  
         [0010]     Another object of the invention is to provide such a portable pneumatic compression riveter which allows for a greater misalignment between the wedge and the bearings in the rivet head assembly and further contributes to reducing the weight of the tool.  
         [0011]     Another object of the invention is to provide such a portable pneumatic compression riveter which addresses the problem of crushed needle roller bearings at the pivot pin by utilizing a hardened steel sleeve in place of the needle roller bearing. This further contributes to a lighter, more reliable and compact tool.  
         [0012]     Another object of the invention is to provide such a portable pneumatic compression riveter which reduces the chance of catastrophic failure of the pivoting jaw thus reducing the chance of injury or damage to the work being assembled.  
         [0013]     Another object of the invention is to provide such a portable pneumatic compression riveter which utilizes a composite valve body to further reduce the weight of the tool. How these objects are accomplished will become apparent from the following descriptions and from the drawings.  
       SUMMARY OF THE INVENTION  
       [0014]     Portable pneumatic compression riveters consist of a valve assembly, cylinder assembly with at least one chamber and a head assembly consisting of an alligator style set of jaws or a c-yoke style jaw set. An air line is connected to the valve assembly. The valve is manually actuated by means of a lever allowing air to flow into the cylinder. In the improvement the valve body is of a composite material with an integrated handle improving ergonomics and significantly reducing the weight. The bulkheads separating the chambers in the cylinder assembly are also made of a composite material that seals each chamber with an o-ring and quad-ring. The pistons are also made of a composite material and used with one or more u-rings to seal the piston—cylinder assembly. Use of the u-rings allows the use of an aluminum cylinder with the composite pistons taking most of the wear. The u-rings allow for a significantly larger amount of wear than does a piston with an o-ring; this contributes significantly to extend the service life interval. Further, since composite pistons are used, the cylinder can be made of aluminum without the benefit of hard anodize applied to the interior of the cylinder or using a steel cylinder to address cylinder wear and seal problems.  
         [0015]     In another aspect of the invention, the wedge is pinned within a clevis that is mounted to the face of the piston. The wedge, driven forward by the compressed air behind the piston, is forced between a set of bearings causing the pivoting jaw to pivot about the center pin resulting in a squeezing action out on the end of the pivoting jaw as it closes with the fixed jaw. In the improvement, the wedge has angled flats on the nose which allow the wedge to self align as it moves forward rather than bind in the rivet head assembly. The wedge&#39;s construction is such that it is pocket milled on both sides creating an I-beam cross section which contributes to a lighter tool.  
         [0016]     In another aspect of the invention, an improvement is made by utilizing a hardened steel sleeve, instead of a needle roller bearing at the pivot pin, to eliminate the problems with crushed needle rollers and also contribute to a lighter, more reliable and compact tool.  
         [0017]     In yet another embodiment of the invention, an improvement is made by adding a hollow recess to the pivoting jaw just above and behind the pivot pin with the purpose of allowing a fatigue crack to propagate into the hollow recess thus preventing a catastrophic failure of the forward portion of the pivoting jaw from becoming a projectile that could cause injury to the operator or damage to the work being assembled.  
         [0018]     Further details of the invention are set forth in the following detailed descriptions and in the drawings.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]      FIG. 1  is a representative side view of an exemplary portable pneumatic compression riveter.  
         [0020]      FIG. 2  is a top elevation view of an exemplary portable pneumatic compression riveter.  
         [0021]      FIG. 3  is a fragmentary sectional view taken along viewing plane  3 - 3  of  FIG. 2  of the portable pneumatic compression riveter prior to the valve&#39;s lever being actuated.  
         [0022]      FIG. 4  is a fragmentary sectional view taken along viewing plane  3 - 3  of  FIG. 2  of the portable pneumatic compression riveter after the valve&#39;s lever is actuated.  
         [0023]      FIG. 5  is an exploded assembly view of the new composite valve body with the integrated handle.  
         [0024]      FIG. 6  is a fragmentary section view taken along viewing plane  3 - 3  of  FIG. 2  of the portable pneumatic compression riveter showing the new composite pistons with u-ring seals.  
         [0025]      FIG. 7  is a fragmentary sectional view taken along viewing plane  3 - 3  of  FIG. 2  of the portable pneumatic compression riveter of the wedge driven between the bearing sets in the rivet head assembly.  
         [0026]      FIG. 8  is a fragmentary sectional view taken along viewing plane  3 - 3  of  FIG. 2  of the portable pneumatic compression riveter showing the pin—clevis—wedge subassembly showing the vertical float of the wedge inside the rivet head assembly.  
         [0027]      FIG. 9  is a top elevation fragmentary sectional view taken along viewing plane  9 - 9  of  FIG. 8  of the pin—clevis—wedge subassembly showing the horizontal float of the wedge inside the rivet head assembly.  
         [0028]      FIG. 10  is a prospective view of the wedge.  
         [0029]      FIG. 11  is a sectional view taken along viewing plane  11 - 11  of  FIG. 8  showing the cross section of the wedge.  
         [0030]      FIG. 12  is a fragmentary sectional view taken along viewing plane  3 - 3  of  FIG. 2  of the portable pneumatic compression riveter showing the pivot pin area of the rivet head assembly.  
         [0031]      FIG. 13  is a fragmentary sectional view taken along viewing plane  3 - 3  of  FIG. 2  of the portable pneumatic compression riveter showing the pivoting jaw with its hollow recess inside the rivet head assembly.  
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0032]     Referring first to  FIGS. 1, 2 ,  3  and  4  an exemplary portable pneumatic compression riveter is depicted which includes a valve assembly  14 , cylinder assembly  16  with more than one chamber (3 chambers in this representation identified here as chambers  1 ,  2  and  3 ), and a rivet head assembly  17 .  FIGS. 1, 2 ,  3  and  4  show the compression riveter fitted with an al1igator set of jaws  10 . The exemplary portable pneumatic compression riveter includes the preferred embodiments disclosed in this document.  FIG. 3  shows the compression riveter prior to the lever  15  on the valve assembly  14  being actuated with the alligator jaw set  10  open.  FIG. 4  shows the compression riveter with the lever  15  on the valve assembly  14  actuated and the alligator jaw set  10  closed. When the lever  15  is released the alligator jaw set  10  opens and the compression riveter resets as shown in  FIG. 3 .  
         [0033]     Additionally,  FIG. 5  shows the composite valve body  12  with the integrated handle. The composite valve body  12  is made of a composite material and houses the valve sleeve assembly  21 . The lever  15  is used to actuate the valve sleeve assembly  21  inside the composite valve body  12 .  
         [0034]     Referring additionally to  FIGS. 3, 4  and  6  the unidirectional composite pistons  7  and bi-directional composite piston  8  each have u-ring seals  9  with the bi-directional piston having two u-ring seals  9  installed opposing each other. When the lever  15  is actuated, compressed air enters the first and successive chambers (chambers  1 ,  2  and  3  in this representation) in the cylinder assembly  16  building pressure behind the stationary composite bulkheads  6  sealed with o-rings  5  and quad rings  11 . The pistons  7  and  8  are driven forward forcing the wedge  25  pinned in the clevis  27  attached to the lead piston  7  into the rivet head assembly  17 . As a result, the pistons  7  and  8  rub against the cylinder wall  18 . The composite pistons  7  and  8  act as traditional wear rings and protect the cylinder wall  18  from excessive damage. The u-ring seals  9  allow for as much as 0.060 wear, in this example, to the piston&#39;s  7  and  8  outside diameter while still maintaining a full seal. This greatly exceeds the amount of dimensional change that a conventional o-ring—piston—cylinder arrangement in this type of tool can have and maintain its seal.  
         [0035]     Refer to  FIGS. 7, 8  and  9  where the wedge  25  is driven between the bearings  28  and  29  on the rivet head assembly  17 .  FIG. 8  shows the hole  23  in the wedge  25  is larger than the pin  30  diameter in the clevis  27  allowing “vertical float”  38  to compensate for any misalignment of the wedge  25  with the bearings  28  and  29  positioned in the rivet head assembly  17 . Refer additionally to  FIGS. 8 and 9  where the width of the back of the wedge  25  at its attach point to the clevis  27  where the pin  30  attaches them is narrower than the clevis&#39;  27  width. This allows for “horizontal float”  39  to compensate for any misalignment of the wedge with the rivet head assembly  17 . Referring also to  FIG. 10  an angled flat  40  on the front of the wedge  25  allows the wedge  25  to self align without binding as it moves forward into the rivet head assembly  17 . Additionally, refer to  FIGS. 8 and 11  where a cross section of the wedge  25  is presented. This light but rigid wedge design contributes to a significant reduction in the weight of the wedge  25  and contributes to a lighter compression riveter.  
         [0036]      FIG. 12  shows a sectional view of the pivot area  33  of the rivet head assembly  17 . In the center is a hardened steel sleeve  35  that slip fits into the pivoting jaw  31  and is joined together with the fixed jaw  32  with a slip fit pivot pin  34 . The hardened steel sleeve  35  avoids the problems encountered with a needle roller bearing in this application and contributes to a lighter more reliable and compact compression riveter.  
         [0037]      FIG. 13  shows another embodiment of the improvement to the portable pneumatic compression riveter where the pivoting jaw  31  has a hollow recess  36  behind the pivot pin  34 . The hollow recess  36  provides a safe zone to arrest a crack in the pivoting jaw  31  propagating from the pivot area  33 . This hollow recess  36  helps prevent a catastrophic failure caused by a crack propagating unchecked from the pivot area  33  allowing the forward portion of the pivoting jaw  31  to become a projectile. The hollow recess  36  also contributes to a lighter tool.  
         [0038]     While the principles of the improvements have been shown and described in connection with preferred embodiments, it is to be understood clearly that such embodiments are by way of example and are not limiting.