Ferrule with relief to reduce galling

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 - 30 . (canceled) 
     
     
         31 . A ferrule for a metal tube fitting, comprising:
 a generally annular one-piece metal body that remains one piece when used in a tube fitting, said body comprising a central and circumferentially continuous cylindrical interior wall that extends through the ferrule from a front end to a back end of said body, a single recess formed in said cylindrical interior wall between said front end and said back end, said cylindrical interior wall having a first portion that is axially forward of said recess and adjoining said front end and a second portion that is axially rearward of said recess and adjoining said back end,   a nose portion with a rearward tapered surface that extends from said front end,   a radially extending flange at said back end of said body, said flange having an end face that provides a ferrule driven surface, and   an outer wall, said outer wall comprising a radially tapered outer wall portion extending from said nose portion to said radially extending flange, said tapered outer wall portion being tapered with a continuously increasing radial dimension in a rearward direction.   
     
     
         32 . The ferrule of  claim 31  wherein said radially tapered outer wall portion is joined to said nose portion with a cylindrical portion of said outer wall. 
     
     
         33 . The ferrule of  claim 31  wherein said single recess is rearward and generally within an axial dimension of said radially extending flange. 
     
     
         34 . The ferrule of  claim 31  wherein said end face is contoured. 
     
     
         35 . The ferrule of  claim 34  wherein said end face is convex. 
     
     
         36 . The ferrule of  claim 31  wherein said body is case hardened over its entire surface. 
     
     
         37 . The ferrule of  claim 31  wherein a portion of said radially tapered outer wall and a portion of said recess define a wall section having a constant thickness t. 
     
     
         38 . The ferrule of  claim 31  wherein said cylindrical interior wall first portion and said cylindrical interior wall second portion have different diameters. 
     
     
         39 . The ferrule of  claim 38  wherein said cylindrical interior wall second portion has a larger diameter than said cylindrical interior wall first portion. 
     
     
         40 . The ferrule of  claim 31  wherein said metal body comprises stainless steel.