Tube fitting with ferrule having recess

Abstract

High localized loading, galling, and high torque forces have been generally eliminated or greatly reduced in a two ferrule tube fitting assembly through suitable modification of the rear ferrule so as to redirect the reaction forces acting between the front ferrule and the drive nut. The rear ferrule has a cylindrical interior wall that closely surrounds the tube end and is provided on the interior cylindrical wall with a circumferentially continuous radial recess that is located between the nose and rear wall of the rear ferrule. The rear ferrule also has a radially external wall that is substantially conical and additionally shaped to extend radially outward toward the enlarged diameter portion or flange of the rear ferrule. The rear ferrule further includes a contoured face on the rear driven surface of the ferrule that engages the drive surface of the drive nut.

1 . A tube fitting comprising: a cylindrical bore for receiving a tube end and a tapered mouth at one end of said bore; a ferrule drive surface; a first ferrule having a first end that extends into said tapered mouth and having a second end with a tapered recess; and a second ferrule having a generally cylindrical interior wall, a tapered forward portion that extends into said tapered recess of said first ferrule, and a driven surface on a rearward portion thereof that engages said ferrule drive surface during pull-up; said second ferrule interior wall having a circumferential recess located between said first and second ends of said second ferrule cylindrical interior wall; said circumferential recess being axially spaced from a front end of said interior wall so a forward cylindrical portion thereof adjoins said front end, said forward cylindrical portion having a diameter no greater than any other portion of said interior wall.  
   
   
       2 - 15 . (canceled)  
   
   
       16 . The tube fitting of  claim 1  wherein said interior wall of said second ferrule includes a rearward cylindrical portion, said recess positioned between said forward and rearward cylindrical portions.  
   
   
       17 . The tube fitting of  claim 16  wherein said rearward cylindrical portion has a larger diameter than said forward cylindrical portion.  
   
   
       18 . The tube fitting of  claim 1  wherein said second ferrule is case hardened over its entire surface.  
   
   
       19 . The tube fitting of  claim 1  wherein said second ferrule driven surface is convex between radially inner and outer portions thereof.  
   
   
       20 . A tube fitting, comprising: 
 a ferrule, said ferrule comprising a main body, said body having a generally cylindrical interior wall, a tapered forward portion that engages a frusto-conical surface during pull up, a driven surface on a rearward portion thereof that engages a drive surface during pull up, said generally cylindrical interior wall having a continuous circumferential recess located between first and second ends thereof, said circumferential recess being axially spaced from said first end so a forward cylindrical portion of said interior wall adjoins said first end, said forward cylindrical portion having a diameter no greater than any other portion of said interior wall, said ferrule being a unitary piece before and after pull up.    
   
   
       21 . The tube fitting of  claim 20  wherein said interior wall includes a rearward cylindrical portion, said recess positioned between said forward and rearward cylindrical portions.  
   
   
       22 . The tube fitting of  claim 21  wherein said rearward cylindrical portion has a larger diameter than said forward cylindrical portion.  
   
   
       23 . The tube fitting of  claim 20  wherein said ferrule is case hardened over its entire surface.  
   
   
       24 . The tube fitting of  claim 20  wherein said driven surface is convex between radially inner and outer portions thereof.  
   
   
       25 . The tube fitting of  claim 20  wherein upon pull-up of the tube fitting on a tube end said ferrule second end is radially spaced from the tube end and a forward edge portion of said ferrule penetrates an outer surface of the tube end.  
   
   
       26 . A tube fitting comprising: a cylindrical bore for receiving a tube end and a tapered mouth at one end of said bore, a ferrule drive surface, a first ferrule having a first end that extends into said tapered mouth and having a second end with a tapered recess; a second ferrule having a generally cylindrical interior wall, a tapered forward portion that extends into said tapered recess of said first ferrule, and a driven surface on a rearward portion thereof that engages said ferrule drive surface during pull-up, said second ferrule interior wall having a continuous circumferential recess located between said first and second ends of said interior wall, said circumferential recess being axially spaced from said first end of said interior wall so a forward extending cylindrical portion thereof adjoins said first end and a rearward extending cylindrical portion thereof extends in a direction toward said second end of said interior wall, said forward cylindrical portion having a diameter less than or equal to said rearward second cylindrical portion.  
   
   
       27 . The tube fitting of  claim 26  wherein said forward and rearward cylindrical portions have different diameters from each other, with said forward cylindrical portion having a smaller diameter.