Abstract:
An internal swage fitting for swaging a tube. The fitting includes a tube connection region with one or more radial grooves and an expansion cavity at the end adjacent to the end of the tube to be swaged. The expansion cavity accommodates flowing tube material during the swaging process with minimal axial pressure on the fitting. The expansion cavity also includes a stop wall to fix the location of the tube in the fitting. The expansion cavity enables swaging of tube materials of relatively high ductility without accounting for setback. It therefore eliminates the need for a collar to establish setback during swaging.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates generally to fittings coupled to tubes by swaging and more particularly to internal swage fittings. 
     A fitting is an auxiliary piece of equipment used to establish a terminus or junction site for a pipe, rod, or tube. In particular, a common use for a fitting is to connect separate tubes together to allow fluid to pass between, preferably without leakage. A fitting is also often used as a closure device to terminate the end of an otherwise open tube. Among many other applications, fittings are used in the aerospace industry to enclose tubes that convey fuel, hydraulic fluids, and the like from one location to another. In those and other critical applications, it is important that the fitting be sufficiently secure about the tube so as to withstand vibration, fluid characteristics and the like without failure. 
     Fittings are often coupled to tubes by welding. Welding can be a time-consuming, costly method of fitting affixation. Further, the weld may not be sufficient to ensure complete coupling and can cause unacceptable stress intensification factor of the tube. Swaging is an alternative mechanical process to join a fitting to a tube without the limitations associated with welding. There are two types of swaging processes: external swaging and internal swaging. External swaging involves the application of a fitting having external surface variations, such as radial or axial lands and grooves, to a tube. The applied fitting is swaged by forging, hammering, or squeezing, such that the external surface configuration is transferred to the interior of the fitting and thus to the tube. The tube is thereby deflected and contorted in the area where it contacts the fitting such that there is a secure coupling of the two. Unfortunately, the transfer of the fitting&#39;s external surface configuration may not be sufficient to establish an adequate coupling, or may cause tube cracking in high cycle fatigue. 
     Internal swaging addresses, in part, some of the problems associated with external swaging. Internal swaging involves the application of a fitting having internal surface variations, again such as lands and grooves, to a tube. The applied fitting is swaged by placing an expander device within the tube and forcing the tube outwardly onto the interior surface of the fitting, or by squeezing the fitting onto the tube. There is a more direct interface between the fitting&#39;s surface configuration and the tube exterior than exists with external swaging. The tube therefore generally conforms more closely to the original surface configuration, resulting in an improved connection between the fitting and the tube. 
     One type of internal swage fitting found to be suitable for some aerospace applications is described in U.S. Pat. No. 4,844,517 issued to Beiley et al. and assigned to Sierracin Corporation of Burbank, Calif. In one configuration, the Beiley fitting includes three or more radial rectangular grooves of specified width and depth dimensions. The groove closest to the end of the tube is of the same design as the other grooves. In another configuration, a series of ramped grooves are combined with a rectangular “end” groove. The rectangular end groove is substantially the same as the rectangular grooves of the first fitting configuration described. That is, the tube butts against it. 
     In commercial use, the Beiley fitting is most suitable for the swaging of tubes made of low ductility material, including Titanium. However, materials of relatively higher ductility, such as stainless steels including SS321, Inconel 625, and other similarly ductile materials, are also used in a wide array of tube applications, including aerospace fluid transfer systems. The materials of higher ductility “flow” to a greater extent than the lower ductility materials under equivalent swaging pressure. The swaging process performed on a low-ductility tube causes the tube to be drawn into the fitting and results in a bulging of the tube at the end groove. The flowing material is forced outwardly toward the fitting, placing significant axial load in that localized area. This bulging of the tube material can cause failure of the fitting as well as undesired changes in tube dimensions. 
     In order to account for the flowing or “sucking in” of the tube into the fitting during the swaging process, it is necessary to set the tube back in relation to the fitting. That is, the tube must be placed in an offset position with respect to the fitting terminus to accommodate the axial and radial flow of the tube material. The swaging process causes the tube to flow and fill into the fitting to make up the setback difference. Since the tube must be completely and securely affixed to the fitting, maintaining the correct setback accurately is important. That is achieved by applying a capture collar about the tube adjacent to the fitting location. The collar must be rigidly but releasably affixed about the tube. Upon completion of the swaging process the collar must be removed. The steps of accurately aligning and applying and removing the collar must be repeated for each fitting applied to each tube of relatively ductile material. Therefore, what is needed is an internal swage fitting that can be used with ductile tubing. What is also needed is such an internal swage fitting that eliminates the need for setback and the use of a setback collar. 
     SUMMARY OF THE INVENTION 
     The above-mentioned needs are met by the present invention, which provides an internal swage fitting that accommodates the flow of high-ductility tube materials. The fitting includes a hollow cylindrical body having an internal surface and an external surface, a tube receiving region and a tube connection region. The internal surface of the body in the tube connection region includes one or more grooves and an expansion cavity for receiving excess material of the tube during a swaging process. The fitting also includes a tube stop wall adjacent to the expansion cavity. A termination end of the tube abuts the tube stop wall when the tube is placed within the cylindrical body. The expansion cavity includes an end wall extending from the tube stop wall and away from the one or more grooves at an angle so as to establish a fill space region for flowing tube material to fill in without applying excessive axial pressure on the fitting. 
     The present invention and its advantages over the prior art will become apparent upon reading the following detailed description and the appended claims with reference to the accompanying drawings. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     The subject matter that is regarded as the invention is particularly pointed out and distinctly claimed in the concluding part of the specification. The invention, however, may be best understood by reference to the following description taken in conjunction with the accompanying drawing figures in which: 
     FIG. 1 is a cross-sectional view of a ferrule (female) swage fitting with the internal configuration of the present invention. 
     FIG. 2 is a cross-sectional view of a ball nose (male) swage fitting with the internal configuration of the present invention. 
     FIG. 3 is a close-up cross-sectional view of the expansion cavity of the internal swage fitting configuration of the present invention. 
     FIG. 4 is a cross-sectional view of the combination of the ferrule and ball nose fittings in assembled relationship with tubes in place prior to swaging. 
     FIG. 5 is a cross-sectional view of the combination of the ferrule and ball nose fittings in assembled relationship with tubes in place subsequent to swaging. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to the drawings wherein identical reference numerals denote the same elements, FIG. 1 illustrates a female (or ferrule) internal swage fitting  10  of the present invention. The fitting  10  is fabricated of any material suitable for the particular application. For example, in the swaging of a tube formed of a ductile material such as SS321 stainless steel, Inconel 625, or the like, the fitting  10  may be fabricated of Titanium or A286. Of course, the fitting  10  may be formed of any material sufficient to cause flow of the tube during the swaging process without substantial distortion of the fitting  10 . 
     The ferrule fitting  10  includes a main hollow cylindrical body  12  having an external surface  14  and an internal surface  16 . The body  12  has a tube receiving region  18  and a tube connection region  20 . The internal surface  16  of the tube connection region  20  of the fitting  10  includes a plurality of radially arranged coupling grooves  22  spaced apart axially by a land  24 . As shown in FIGS. 1 and 3, the tube connection region  20  further includes a radially arranged expansion cavity  26  and a tube stop wall  28 . The tube stop wall  28  blocks forward progression of a tube-to-be-swaged in the fitting  10 . The expansion cavity  26  establishes a location for excess material of the tube to flow during the swaging process. 
     The expansion cavity  26  includes an entry sidewall  30 , a curved fill region  32 , and a backwall  34 . The fill region  32  extends beyond the stop wall  28  to permit excess tube material to flow therein without creating excess axial stress on the fitting  10  at the tube connection region  20 . The backwall  34  is angled away from the stop wall  28  to allow flow material to enter space  36  rather than move directly upward against the internal surface  16  of the fitting  10 . The dimensions of the grooves  22 , the land  24  and the expansion cavity  28  may be selected as a function of the structural characteristics of the tube  12  and the fitting  10 . The angle of the back wall  34  with respect to the tube stop wall  28  may also be selected as a function of the flow characteristics of the tube material and the hoop strength of the fitting  10 . The back wall  34  may be angled away from the stop wall  28  at an angle of between about 10° and about 75° and, in one embodiment at an angle of about 45°. 
     FIG. 2 illustrates a corresponding male (or ballnose) internal swage fitting  40 . The ballnose fitting  40  includes a main hollow body  42  and an external surface  44  and an internal surface  46 . The fitting  40  may be fabricated of a material suitable for swaging a tube of relatively ductile material. For example, the fitting  40  may be fabricated of Titanium or A286. 
     With continuing reference to FIGS. 2 and 3, the body  42  of the fitting  40  has a tube receiving region  48  and a tube connection region  50 . It is to be noted that the housing  42  of the fitting  40  may be of a selectable configuration. However, in order to provide structural reinforcement to the fitting  40  in the tube connection region  50 , it includes a structural region  45 . The structural region  45  is of greater thickness than the remainder of the wall thicknesses of the body  42  to provide hex flats of the fitting  40  to tighten or loosen the fitting on a tube after the fitting  40  has been swaged to a tube. 
     The internal surface  46  of the tube connection region  50  of the fitting  40  includes a plurality of radially arranged coupling grooves  22  spaced apart axially by a land  24 . The tube connection region  50  further includes a radially arranged expansion cavity  26  and a tube stop wall  28 . The tube stop wall  28  blocks forward progression of a tube-to-be-swaged in the fitting  40 . The expansion cavity  26  establishes a location for excess material of the tube to flow during the swaging process. 
     The expansion cavity  26  includes an entry sidewall  30 , a curved fill region  32 , and a backwall  34 . The fill region  32  extends beyond the stop wall  28  to permit excess tube material to flow therein without creating excess axial stress on the fitting  40  at the tube connection region  50 . The backwall  34  is angled away from the stop wall  28  to allow flow material to enter space  36  rather than move directly upward against the internal surface  16  of the fitting  40 . The dimensions of the grooves  22 , the land  24  and the expansion cavity  28  may be selected as a function of the structural characteristics of the tube  12  and the fitting  40 . The angle of the back wall  34  with respect to the tube stop wall  28  may also be selected as a function of the flow characteristics of the tube material and the hoop strength of the fitting  40 . The back wall  34  may be angled away from the stop wall  28  at an angle of between about 10° and about 75° and, in one embodiment at an angle of about 45°. 
     When two tubes are to be coupled together in a swaging process, the ferrule fitting  10  and the ballnose fitting  40  are arranged in relation to the tubes in a manner shown in FIG. 4. A first tube  52  is inserted into the tube-receiving region  18  of the ferrule fitting  10 . It is directed toward the tube stop wall  28  of the fitting  10  until it comes in contact with that surface. A second tube  54  is inserted into the tube-receiving region  48  of the ballnose fitting  40 . It is directed toward the tube stop wall  28  of the fitting  40  until it comes in contact with that surface. The fitting  10  is then swaged onto the tube  52  and the fitting  40  swaged onto the tube  54  using conventional swaging methods. The conventional swaging methods may include the use of either a roller swage or a bladder swage and mandrel inserted into the fitting/tube combination and removed upon completion of the swaging process. 
     The fittings  10  and  40  are shown in FIG. 4 in adjacent relation to one another prior to swaging. However, the respective tubes and fittings may be swaged apart from one another and then brought into communication with one another prior to final assembly. It can be seen that the wall thicknesses of the tubes  52  and  54  are substantially uniform and straight prior to swaging. The swaging process, as shown in FIG. 5, causes the tubes to distort in the vicinity of the grooves  22  and the expansion cavity  26  and a portion of the tube material to flow into those regions. The design of those regions of the internal fittings  10  and  40  allow the tube material in those regions to flow in a suitable direction without placing excess axial stress on the fittings. In addition, the stop  28  halts further inward movement of the tubes. 
     FIG. 5 illustrates one embodiment of the joining together of two tubes swaged with the internal swage fittings of the present invention. In particular, a threaded nut  56  is applied to fitting threads  58  of the fitting  40  to Ser. No. 09/668,940 13DV-13662 draw the two fittings together. A ballnose receiving mating surface  62  of the fitting  10  is placed in contact with a ferrule entering mating surface  60  of the fitting  40 . The nut  56  is then tightened onto the fitting  40 . The fitting  10  is drawn toward the fitting  40  because a ferrule capture wall  64  of the body  12  is grabbed by nut flange  66  as the nut  56  is threaded onto the fitting  40 . The threading action fixes the two fittings together. In the embodiment of the present invention shown in FIG. 5, the tubes  52  and  54  are securely coupled together so that fluid may pass between the two. It is to be noted that an alternative embodiment of the ballnose fitting  40  may be used as a termination of the tube  54  without coupling to another tube. 
     The internal swage fittings shown and described including the expansion cavity  26  enable reliable swaging of tubing of relatively high ductility without placing excessive axial force on those fittings. Further, expansion cavity  26  in combination with the stop wall  28  eliminates sucking in of the tube during the swaging process. Setbacks are no longer required and, therefore, collars and collar application and removal steps are eliminated. 
     The foregoing has described an improved internal swage fitting. While specific embodiments of the present invention have been described, it will be apparent to those skilled in the art that various modifications thereto can be made without departing from the spirit and scope of the invention as defined in the appended claims.