Ball joint apparatus and method of fabrication

Abstract

A ball joint apparatus for a pressurized fluid line includes a bellows and a pair of opposed tube portions to accommodate limited flexure between the tube portions. The apparatus also includes an annular ball element positioned over one of the tube portions and an annular housing member mounted on the other tube portion and overlapping the ball member. As initially formed, the overlapping end of the housing member is open and of a diameter exceeding the maximum diameter of the ball member to permit ease of assembly. After the component parts are in position and welded as desired, the apparatus is placed in a hydraulic press and the open end of the housing member is necked down by a swaging process to establish bearing contact with the ball member. Alternative arrangements of the apparatus are provided for use with stainless steel tubing and with titanium tubing.

What is claimed is:  
     
         1 . A metal ball joint assembly for permitting limited flexure in attached pressurized fluid lines comprising: 
 first and second tubular sections extending on opposite ends of a central bellows which is capable of limited flexure to accommodate differences in axes angles of said tubular sections; and    a housing surrounding and constraining said bellows to flexure within predetermined angle limits, said housing comprising:    an inner annular element of a first selected arcuate shape varying in diameter along its length from a first end shaped to match the diameter of the first tubular section to a second end of enlarged diameter suitable for overlapping said bellows; and    an outer annular element of a second selected arcuate shape varying in diameter from a first end shaped to match the diameter of the second tubular section to an intermediate section of enlarged diameter exceeding the maximum diameter of the inner annular element and then to a necked-down section of reduced diameter at a second end, the intermediate section and the neckeddown section overlapping and enclosing the second end of said inner element,    the inner and outer annular elements having portions of said arcuate shapes matching in curvature to provide adjacent bearing surfaces which remain in sliding contact during flexure of the bellows.    
     
     
         2 . The apparatus of    claim 1    wherein said adjacent bearing surfaces comprise an inner surface of a portion of the outer element and an outer surface of a portion of the inner element which are maintained in supporting contact during flexure of the bellows.  
     
     
         3 . The apparatus of    claim 2    whereby said adjacent bearing surfaces are coated with a lubricant to reduce friction over the extent of surface contact.  
     
     
         4 . The apparatus of    claim 1    further including first and second pressurized fluid lines respectively connected to first and second tubular sections in fluid communication therewith.  
     
     
         5 . The apparatus of    claim 4    wherein said connections comprise welded joints between the first and second tubular sections and corresponding ones of the pressurized fluid line sections.  
     
     
         6 . The apparatus of    claim 1    wherein the inner and outer elements include a common transition portion having a generally arcuate shape adapted to provide said bearing surfaces.  
     
     
         7 . The apparatus of    claim 6    wherein the inner and outer annular elements include overlapping sections which are parallel to respective first and second tubular sections and which at least partially overlap said bellows.  
     
     
         8 . The apparatus of    claim 7    wherein said inner element partially overlaps said bellows and said outer element completely overlaps said bellows and extends to partially overlap said inner element.  
     
     
         9 . The apparatus of    claim 1    wherein said outer element includes a lip portion at the termination of the necked-down section, said lip portion being generally parallel to the axis of the associated tubular section.  
     
     
         10 . The apparatus of    claim 1    wherein said metal is stainless steel throughout the extent of said assembly.  
     
     
         11 . The apparatus of    claim 1    wherein said metal is titanium throughout the extent of said assembly and the assembly is structurally configured for welding to pressurized fluid lines which are fabricated of titanium.  
     
     
         12 . The apparatus of    claim 1    including, in addition, a first annular restraint collar positioned along said first tubular section to be overlapped by said inner annular element.  
     
     
         13 . The apparatus of    claim 12    wherein said first annular restraint collar is welded at a first end to said first tubular section at its point of connection with one end of the central bellows.  
     
     
         14 . The apparatus of    claim 13    wherein said first annular restraint collar is flared at a second end to contact and support the inner annular element.  
     
     
         15 . The apparatus of    claim 14    wherein contact of the flared end of the first annular restraint collar with the inner surface of the inner annular element is established in the region of the bearing surfaces between the inner and outer annular elements.  
     
     
         16 . The apparatus of    claim 1    wherein said bellows is formed as an extension of a pressurized fluid line at one end of the bellows.  
     
     
         17 . The apparatus of    claim 16    wherein the inner annular element is not attached to the associated pressurized fluid line but is maintained in position against sliding along said associated pressurized fluid line by an annular restraint collar which is welded to said fluid line near one end and flared outwardly at the other end to contact the inner surface of said inner annular element and support the inner annular element in a fixed position on said associated pressurized fluid line.  
     
     
         18 . The apparatus of    claim 17    further including a second annular restraint collar positioned at the end of said bellows remote from said first-mentioned annular restraint collar for providing support to the outer annular element.  
     
     
         19 . The apparatus of    claim 18    wherein said second annular restraint collar is flared at one end to maintain contact with a portion a the outer annular element over a section of increasing diameter extending from the first end of said outer annular element.  
     
     
         20 . The apparatus of    claim 19    wherein the second annular restraint collar is welded in a sandwich configuration between an extension of the bellows and the first end of said outer annular element.  
     
     
         21 . The apparatus of    claim 1    wherein the necked-down portion of the outer annular element terminates in a collar which is generally parallel to the axis of the outer annular element to provide added support against deformation by forces between said bearing surfaces during flexure of the assembly.  
     
     
         22 . A metal ball joint assembly for permitting limited flexure in attached pressurized fluid lines comprising: 
 first and second tubular sections extending on opposite ends of a central bellows which is capable of limited flexure to accommodate differences in axes angles of said tubular sections; and    a housing surrounding and constraining said bellows to flexure within predetermined angle limits, said housing comprising:    first and second arcuate annular elements having mating arcuate portions structurally configured to hold said elements together, one partially within the other, in a slidable partially spherical joint, the mating arcuate portions of said first and second elements having adjacent bearing surfaces to permit ready flexure of said central bellows within an allowable range;    the second arcuate annular element having a neckeddown portion adjacent an end opposite the first arcuate annular element to hold said first element against separation from said second element.    
     
     
         23 . The apparatus of    claim 22    wherein said adjacent bearing surfaces are coated with a lubricant to reduce friction over the extent of surface contact.  
     
     
         24 . The apparatus of    claim 22    wherein the necked-down portion of the second annular element terminates in a lip portion which is generally parallel to the axis of the second annular element to provide added support against deformation by forces between said bearing surfaces during flexure of the assembly.  
     
     
         25 . The apparatus of    claim 24    further including a first restraint collar which is welded in position adjacent one end of the bellows and which has a flared portion extending outwardly to contact the first arcuate annular element in the vicinity of said bearing surfaces.  
     
     
         26 . The apparatus of    claim 25    further including a second flared restraint collar near the end of the bellows remote from said first flared restraint collar, said second restraint collar being fixed in position and maintaining contact with said second annular element to provide support for said second annular element.  
     
     
         27 . The method of fabricating a ball joint assembly for installation in a pressurized fluid line to permit limited flexure between adjacent portions of said line, the method comprising the steps of: 
 assembling a bellows between a pair of tube portions for attachment in a pressurized fluid line;    forming an annular ball member having an outer end of reduced diameter to match the diameter of a first one of the tube portions and an inner end of enlarged diameter suitable for overlapping the bellows;    sliding the ball member into position overlapping the bellows;    forming an annular housing member having a first end of reduced diameter matching the diameter of the second tube portion and a second end having a diameter exceeding the outer diameter of the ball member;    sliding the housing member along the second tube portion to a position where the second end overlaps an arcuate portion of the ball member between the inner and outer ends;    welding the first end of the housing member and the outer end of the ball member to the respective adjacent tube portions; and    placing the thus-assembled combination in a hydraulic press and rotating the combination to swage the second end of the housing member radially inward to make contact with the outer surface of the ball member in the region of the arcuate portion thereof while developing an axially extending lip to provide additional strength to said assembly.    
     
     
         28 . The method of fabricating a ball joint assembly for installation in a pressurized fluid line to permit limited flexure between adjacent portions of said line, the method comprising the steps of: 
 assembling a bellows between a pair of tube portions for attachment in a pressurized fluid line;    forming an annular ball member having an outer end of reduced diameter to match the diameter of a first one of the tube portions and an inner end of enlarged diameter suitable for overlapping the bellows;    forming a first annular restraint member configured to maintain the position of the bellows and support the ball member;    sliding the first annular restraint member onto the first tube portion to a position adjacent the bellows;    welding the first annular restraint member to the first tube portion to retain it in position adjacent the bellows;    sliding the ball member onto the first tube portion to a position overlapping the first annular restraint member and the bellows;    forming an annular housing member having a first end of reduced diameter matching the diameter of the second tube portion and a second end having a diameter exceeding the outer diameter of the ball member;    forming a second annular restraint member configured to provide support for a selected portion of the housing;    sliding the second annular restraint member onto the tubular extension adjacent the bellows on the side remote from the first annular restraint member;    sliding the housing member along the second tube portion to a position adjacent the second annular restraint member such that the second end overlaps the arcuate portion of the ball member between the inner and outer ends;    forming a necked-down collar of the second tube member and inserting the collar into the bellows extension;    welding the collar, the bellows extension, the second annular restraint member and the first end of the housing member together; and    placing the thus-assembled combination in a hydraulic press and rotating the combination to swage the second end of the housing member radially inward to make contact with the outer surface of the ball member and the first annular restraint member in the region of the generally arcuate portion thereof.