Patent Document

BACKGROUND OF THE INVENTION 
     Fluid fittings attached by swaging offer certain advantages resulting in extensive use in certain types of installations. An example is the design of U.S. Pat. No. Re. 28,457. However, these fittings require a separate sealing material in grooves and are not suitable for high temperature use. Another prior swaged fitting is shown in U.S. Pat. No. 4,328,982, which is some instances does away with a separate sealing element, providing a metal-to-metal seal. However, again the design is not adapted for extremely high temperature use. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention provides an improved fluid fitting overcoming the problems encountered in the prior art. It is adapted for use in extremely high temperature environments such as in the connections for jet aircraft engines. The fitting provides superior strength at lower temperatures as well. 
     The fitting includes inner and outer sleeves telescoped together so as to provide an annular space adapted to receive the end of a tube. The inner and outer sleeves are secured together by rolling a localized area of the outer sleeve so as to deflect its inner walls around annular ridges on the inner end of the inner sleeve. This is a factory operation. The inner sleeve includes annular grooves in its outer surface which provide lands and sharp corners that dig into the inner wall of the tube when a radial swaging force is applied to the external sleeve. The result is a strong attachment and a metal-to-metal seal. There are spaced longitudinal shallow recesses in the inner wall of the outer sleeve into which the outer surface portions of the tube are deflected when the swaging takes place. This prevents relative rotation between the tube and the fitting. 
     High temperature resistance is assured by proper selection of the coefficients of thermal expansion of the materials of the sleeves and the tube. To achieve this, the inner sleeve should have a greater coefficient of thermal expansion than that of the outer sleeve and the tube. As a result, as temperatures increase the inner sleeve expands at a greater rate than the tube and outer sleeve, and presses more and more tightly against the inner wall of the tube. Similarly, the inner sleeve expands at a greater rate than the outer sleeve and becomes more tightly pressed against the inner wall of the outer sleeve at the location of their attachment. Therefore, the connection and the seal do not deteriorate as temperatures increase, being enhanced instead. 
     The fitting may be made in a variety of forms for coupling tubes together or joining them to other components of a system. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded perspective view of the components of the fitting of this invention; 
     FIG. 2 is a longitudinal section showing the components of the fitting as intially assembled; 
     FIG. 3 is a view similar to FIG. 2, but with the two sleeves attached together; 
     FIG. 4 is a transverse sectional view of the outer sleeve of the fitting, taken along line 4--4 of FIG. 1 and illustrating the longitudinal grooves for preventing rotation of a tube to which the fitting is attached; 
     FIG. 5 is a fragmentary longitudinal sectional view showing a tube inserted into the fitting prior to swaging; 
     FIG. 6 is a longitudinal view of the fitting as completed and swaged to the tube; 
     FIG. 7 is a plan view of a fitting made as a coupling; and 
     FIG. 8 is a plan view of a fitting made as a tee. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The fitting of this invention is made up of two sleeves 10 and 11. The lefthand end of the sleeve 10, as illustrated, is conventional, including a tapered end surface 12 and an exterior shoulder 13 for connection as an ordinary flared fitting. 
     The exterior of the sleeve 10 includes a surface 15 that tapers at a shallow angle to one end 16 of the sleeve. At the inner end of the surface 15 is a relatively long cylindrical surface 17. A curved transition surface 18 connects the surface 17 with a shorter cylindrical part 19 of smaller diameter. Beyond the surface 19 is a second curved transition surface 20 to a still shorter cylindrical portion 21 of narrower diameter adjacent the shoulder 13. 
     Interiorly, the sleeve 10 has a cylindrical portion 22 of constant relatively small diameter adjacent the tapered end surface 12, which connects through a shoulder 23 to a central interior surface 24 of larger diameter. The surface 24 is shorter axially than the surface 22. The sleeve 10 is proportioned so that the shoulder 23 is radially inwardly of the exterior surface 19 of the sleeve and the transition surface 18 on the exterior of the sleeve 10 is outwardly of the internal surface 24. 
     A rounded shoulder 26 connects the surface 24 to an additional interior cylindrical surface 27 of still greater diameter. The surface 27 connects to a surface 28 of slightly larger diameter, which forms the entrance to the fitting at the end 16. There are, in addition, three equally spaced axially extending broached slots 29 in the surface 27 which carry the diameter of the entrance surface 28 to their inner ends, which are spaced from the shoulder 26. These slots provide an anti-rotational affect when the fitting is swaged onto a tube, as discussed below. 
     This construction provides the sleeve 10 with a thinner wall at the surfaces 27 and 28 then the wall on the opposite side of the shoulder 26. The sleeve 10 has its greatest wall thickness beyond the shoulder 23. 
     The sleeve 11 is of smaller diameter than the sleeve 10 and of lesser wall thickness. It is made of a material having a greater coefficient of thermal expansion than that of the sleeve 10. The material of the sleeve 11 also is harder than that of the sleeve 10, and has a higher yield strength. The sleeve 11 includes a first cylindrical interior surface 31 adjacent one end 32, and a longer cylindrical surface 33 that connects to the surface 31 and is of slightly larger diameter. The surface 33 extends all the way to the opposite end 34 of the sleeve 11. 
     Exteriorly, the sleeve 11 has a rounded exterior edge that leads to a cylindrical exterior surface 36 adjacent the end 34. An annular groove 37 interrupts the surface 36 inwardly of the end 34. A short distance from the annular groove 37 is a much wider annular groove 38, which is of the same depth as the groove 37. This leaves a land 39 between the grooves 37 and 38. At the end 32 of the sleeve 11 is an exterior annular enlargement that includes a tapered outer end wall 40 and a tapered inner end wall 41 that connects to the inner end part of the surface 36 beyond the wide groove 38. The enlargement is provided with a shallow arcuate annular groove 42 in its outer periphery. The intersections of the surfaces 40 and 41 with the surface of the groove 42 produce two closely spaced annular ridges. 
     Initially the sleeve 11 is positioned within the sleeve 10, as shown in FIG. 2, with the sleeve end 32 intermediate the ends of the sleeve 10, abutting the interior shoulder 23 of the sleeve. The end 34 of the sleeve 11 is adjacent but recessed axially inwardly of the end 16 of the outer sleeve 10. A compressive force then is applied to the sleeve 10 at the surface 91, rolling this portion of the sleeve radially inwardly to attach the sleeves 10 and 11 together, as seen in FIG. 3. This deflects the exterior surface 19 inwardly to the level of the exterior surface 21 of the sleeve 10, causing the material of the inner wall of the sleeve 10 at the surface 24 to be deflected inwardly into the annular groove 42 and around the annular ridges defined by the end enlargement of the sleeve 11. Thus, the material of the sleeve 10 is deflected inwardly around the tapered surface 40 and the end 32 of the sleeve 11, as well as being deflected around the tapered surface 41. This forms a secure attachment and a fluid seal between the two sleeves. 
     The tube 43, to be attached to the fitting, is introduced into the annular space 44 between sleeves 10 and 11, as seen in FIG. 5. The end 45 of the tube 43 is advanced past the land 39 of the sleeve 11, normally being positioned adjacent the shoulder 26 that connects the internal diameter portions 24 and 27 of the sleeve 10. Preferably the parts are proportioned so that the tube 43 can enter the space between the sleeves 10 and 11 freely, yet without much clearance. The materials of the components of the fitting are selected so that the inner sleeve 11 has a coefficient of thermal expansion greater than that of the tube 43. The coefficient of thermal expansion of the sleeve 10 may be less than that of the tube 43. 
     Next the fitting is swaged to complete the attachment to the tube 43. This is accomplished by applying an external compressive force by a radial swaging tool on the surface 17 of the sleeve 10. This forces the surface 17 radially inwardly until it is of substantially the same diameter as that of the surface 19 of the sleeve 10. As this occurs, the inner wall of the sleeve 10 presses against the tube 43, which is forced inwardly against the outer surface of the sleeve 11. The latter experiences some deflection but resists the inward compression sufficiently to cause the inner surface of the tube 43 to be deflected inwardly around the land 39 and against the surface of the sleeve 11 at the grooves 37 and 38. As a result, the corners 47 and 48 at either end of the land 39 are caused to dig into the inner surface of the tube 43. Similarly, the corner 49 at the outer end of the groove 37 of the sleeve 11 becomes embedded in the inner surface of the tube 43. This creates metal-to-metal seals at the locations of these corners, effectively preventing the leakage of fluid along the inner surface of the end part of the tube 43. At the same time, the deflection of the tube securely attaches it to the sleeve 11. 
     The exterior of the tube 43 is forced into the three spaced broached grooves 29, which prevents rotation of a tube relative to the sleeves 10 and 11. 
     The inner sleeve 11, being of relatively hard material with a high yield strength, can resist the compression force of the swaging so that the tube deflects as described above. The relatively thin wall of the sleeve 11 maximizes the internal diameter of this sleeve so that the fitting will not unduly restrict the flow of fluid. The outer sleeve 10, being more malleable than the inner sleeve and of lesser yield strength, can compress the tube in the swaging operation and hold it inwardly against the sleeve 11. The malleability of the sleeve 10 assists the fitting in withstanding bending forces on the tube to which it is attached. 
     The fitting is well suited for use at elevated temperatures, such as in the environment of jet aircraft engines. As the components become elevated in temperature, the sleeve 11 becomes pressed even more tightly against the inner wall of the tube 43. This comes about from the coefficients of thermal expansion of these elements. The sleeve 11, by having a greater coefficient of thermal expansion than that of the tube 43, will maintain an increasing outward pressure against the inner wall of the tube as temperatures rise. Similarly, because the sleeve 11 has a greater coefficient of thermal expansion than that of the sleeve 10, it will have a greater outward force against the sleeve 10 at the connection between the two as temperatures rise. The tube 43 can be made to increase its force against the outer sleeve 10 when the latter is made of a material having a smaller coefficient of thermal expansion than that of the tube. Thus, the fitting does not lose its properties at elevated temperatures, always being mechanically held together securely with an effective metal-to-metal seal. 
     Performance under flexure is improved significantly by the application of a thin coating of dry film lubricant 50 on the bore entrance surface 28 of the sleeve 10. The lubricant will impregnate the surface 28, filling in low spots to provide a uniform and smooth surface. Metal-to-metal contact between the sleeve 10 and the tube 43 is avoided at the zone where the dry lubricant is present. As a result, the fitting does not scuff the tube at the surface 28 under vibration and greatly extended tube life is obtained. Without the lubricant, the roughness from normal machining of the surface 28 may produce stress risers on the tube 43 that can lead to tube failure under vibration. Only a very thin film of lubricant is needed, most of it penetrating the surface 28. A solid film extreme environment dry lubricant, such as a molybdenum disulfide base mixed with graphite, of a total thickness of 0.0005 inch, is effective up to 1100° F. 
     In addition to flexing, the fitting also withstands severe tensile loads, impulse loads and other adverse conditions. 
     Although shown in the previously described embodiment as used in conjunction with a conventional flared fitting at one end, a fitting manufactured in accordance with this invention may have many other configurations. For example, as shown in FIG. 7, the fitting 51 is a coupling, both ends of which are to receive tube ends just as did the right-hand end portion of the fitting as illustrated in FIGS. 1-6. After swaging the tubes will be connected together. 
     FIG. 8 shows one of the other embodiments of the invention, this time as a tee 52. 
     The foregoing detailed description is to be clearly understood as given by way of illustration and example only, the spirit and scope of this invention being limited solely by the appended claims.

Technology Category: 4