Apparatus and method for making a tube connection
BACKGROUND OF THE INVENTION 
     The present invention is related to apparatus for making a tube connection. More specifically, it is an extension and improvement upon the inventions disclosed in U.S. Pat. Nos. 3,827,727 and 4,061,367. 
     In products which utilize tubing, whether copper, steel, aluminum or other malleable metal, many of the connections are of a permanent nature. At one time, a majority of these connections were made by welding, soldering or brazing the ends of tubing sections together. This was time consuming and costly. The first improvement in the connection of such tubing sections was the flareless fitting. This provided more rapid connection, but did not provide sufficient strength and performance necessary for a great many applications. Further, the cost and weight of the flareless fitting proved a substantial drawback. 
     It is the simultaneous accomplishment of these three goals of low cost, light weight, and high performance which has proved elusive in the design and construction of a permanent connecting device. An innovation in tube connection technology, and the technology upon which this invention is an improvement, is described in U.S. Pat. Nos. 3,827,727; 3,893,720; 4,026,006; and 4,061,367. These patents relate to various designs of sleeve and lockring assemblies which cause deformation and intimate contact between the sleeve and tube section to create a permanent, high performance sealing contact. Nevertheless, the demand for higher performance, lighter weight, and decreased cost has required that the present technology still be improved upon. The present invention provides such an improvement. 
     SUMMARY OF INVENTION 
     The present invention is related to an apparatus for forming a tube connection. The apparatus has a first end comprising a sleeve into which a tube section is initially slidable, and onto which a lockring is forceable; a center portion to stop the movement of the tube and of the lockring; and a second end which may be another sleeve, mirroring the first end, or a plug, an elbow, a reducer or any other fitting or shape which is desired to be permanently attached to the end of a tube section. The sleeve is uniquely shaped to provide, after the tube section is inserted and the lockring forced into place, a reverse taper deformation of the outer sleeve and tube section. &#34;REVERSE TAPER&#34; refers to the deformation being least near the center portion of the apparatus and thereafter generally increasing toward the outer end of the sleeve. This manner of deformation greatly reduces the required installation force while it greatly increases the pullout strength of the tube connection thereby formed. In comparison, this invention reduces the installation forces by as much as fifty per cent (50%) over similar connections, (as described in U.S. Pat. No. 4,026,006), and produces a connection with twice the pull-out strength for a similar size and weight device. Alternatively, utilizing the apparatus of the present invention, the same pull-out strength may be obtained with approximate one-half the size and weight of previous connection apparatus. These savings in size and weight are extremely desirable not only as a reduction in unit cost, but also as a reduction in overall weight of the aircraft or other vehicle in which a vast number of such tube connection apparatus are used. In addition, this manner of deformation causes the tube section to distend slightly thereby creating a preloaded tube connection in which the end of the tube section is forced tightly against the center portion of the device; or, in one embodiment, against an opposing tube section. 
     It is the object of this invention to provide an improved apparatus for making a tube connection, which tube connection will display greater pull-out strength, easier installation, lighter weight, and less cost. Other and additional objects will become apparent upon a reading of the entire specification, drawings and claims. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side view in cross section of the preferred embodiment of the sleeve of the instant invention. A tube section is also shown inserted into the sleeve. 
     FIG. 2 is a side view showing the lockring, sleeve and tube, in cross section, after the lockring has caused deformation of the sleeve and tube. 
     FIG. 3 is an alternate embodiment of the sleeve, also shown as a side view in cross section. 
     FIG. 4 is a side view of the sleeve, with tube inserted. A portion is cut away to show the sleeve and tube in cross-section. 
     FIG. 5 is a similar view, showing the incidence of the lockring onto the sleeve and the resultant deformation of the sleeve and tube. 
     FIG. 6 is a similar view, showing the lockring in final position and the final deformation of the sleeve and tube. 
     FIG. 7 is a plan view of the completed tube connection as formed by the preferred embodiment of the present invention. 
     FIG. 8 is a side view in cross-section showing one embodiment of the center portion. 
     FIG. 9 is a similar view of an alternate embodiment of the center portion. 
     FIG. 10 is a side view in cross-section of an alternate embodiment of the lockring. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The present invention is preferably embodied in a device for forming a tube joint between two separate tube sections of equal size. The apparatus, then, is broadly symmetrical about centerline A--A. The description, therefore, will be predominantly directed to one end of the apparatus, with reference being made to the components of the second end only when necessary to describe some feature of the invention. It is to be understood, however, that the inventive features contained herein are not restricted to use in a device for connecting two tube sections in a line, but may be used to make a variety of tube joints and connections. The second end of the apparatus could comprise a plug, a reducer, an elbow, a tee, etc. 
     The apparatus of the present invention consists of a sleeve, generally designated 10, a lockring, generally designated 12, and a center portion generally designated 14. The sleeve may be constructed of any malleable metal, such as aluminum, steel, copper, etc.; whereas the lockring is constructed of a metal of considerably higher strength. Sleeve 10 has a hollow interior to allow tube section 16 to slide initially therein. Around the periphery of its hollow interior, sleeve 10 may have sawtooth grooves 20, 21, 22 and 23. These sawtooth grooves are of sufficient size and shape to allow the tube section 16, upon forcing the lockring 12 into position over the exterior of sleeve 10, to be deformed by the &#34;teeth&#34; of said sawtooth grooves while the tube diameter is unaffected within the grooves to provide a gripping action of the outer sleeve 10 upon tube 16. 
     As shown in FIG. 1 the preferred embodiment includes four grooves. The leading groove 20 is substantially equi-diametral to present a sufficiently large surface for easy inspection by micrometer measurement. That diameter is equal to the diameters of grooves 21, 22 and 23 at their greatest point. Therefore, inspection of leading groove 20 will insure proper depth of grooves 21, 22 and 23. Between the grooves are flat lands 26, 27 and 28. The lands 26, 27 and 28 contact and deform the tube section 16 when the lockring 12 is forced onto sleeve 10. 
     At center portion 14 of sleeve 10 is an externally extending stop flange 32 which limits the movement of the lockring 12 onto outer sleeve 10 and an internally extending positioning flange 34 which limits the insertion of tube 16 into sleeve 10 so as to properly center the separate tube sections within sleeve 10 to ensure maximum strength of connection. Two embodiments of positioning flange 34 are shown. In the first embodiment, positioning flange 34 extends radially inward a distance roughly equal the size of the tube wall of tube section 16. This embodiment is shown in FIG. 8. In this embodiment, the tube section ends abut directly against positioning flange 34 and do not come into direct contact with one another. In the alternative embodiment shown in FIG. 9, positioning flange 34 extends a lesser distance radially inward. Using this embodiment of the positioning flange 34, the ends of tube sections 16 may be beveled or shaped so as to allow a substantial portion of the ends of tube sections 16 to come into contact with one another. It should also be noted that the positioning flange 34 could be omitted entirely, allowing the invention to be used for repairing leaks in the tube section. 
     The exterior portion of sleeve 10 has a slight &#34;reverse taper&#34; running from the surface 42 of the sleeve 10 to the center portion 14. In the preferred embodiment, as shown in FIG. 1, this &#34;reverse taper&#34; is achieved by a configuration wherein the exterior diameter of sleeve 10 is uniform for a distance from outer end 36 toward center portion 14 to create a flat surface 38. The exterior diameter of sleeve 10 then increases sharply to create inclined surface 40. In the preferred embodiment, this incline is at a 20° slope. At its greatest point, the exterior diameter is again uniform to create a second flat surface 42. Thereafter, the exterior diameter of sleeve 10 gently decreases, preferrably at approximately a 3° slope, to create a second inclined surface 44. Flat surface 42 and inclined surface 44 create the &#34;REVERSE TAPER&#34; effect unique to this invention. Leading from inclined surface 44 to stop flange 32 is inclined surface 45 to aid the movement of lockring 12 into position at stop flange 32. Immediately adjacent to stop flange 32 is plateau 47 upon which the front of lockring 12 finally rests when lockring 12 is thrust into its final position on sleeve 10. 
     In an alternate embodiment, as shown in FIG. 3, the inclined surface 44 is fitted with steps 46 which tend to hold the lockring 12 in position. 
     In another embodiment, as shown in FIG. 4, the &#34;REVERSE TAPER&#34; is accomplished by a series of externally projecting ribs. First rib 48 is the first rib which lockring 12 encounters as lockring 12 is forced into position toward stop flange 32 on sleeve 10. Rib 48 has inclined surface 52 on the side of rib 48 which faces the onslaught of lockring 12. This is to facilitate the movement of lockring 12 over rib 48. On the opposite side of rib 48 from inclined surface 52, is an abrupt shoulder 54. The abrupt shoulder 10 restrains movement of the lockring 12 after lockring 12 has been forced onto sleeve 10. Sleeve 10 has a second external rib 56, which like rib 48, extends about the total periphery of periphery of sleeve 10, and is located between rib 48 and stop flange 32. Second rib 56 has a similar incline surface 57 to aid the motion of lockring 12 and an abrupt shoulder 60. The external radius of second rib 56 is slightly but significantly less than the similar dimension of first external rib 48. Sleeve 10 has a third external rib 62, located between second external rib 56 and stop flange 32. Like external ribs 48 and 56, rib 42 has an inclined surface 64 and an abrupt shoulder 66. The external radius of third rib 62 is slightly but significantly less than the similar dimension of second rib 56. The amount by which the external radii of ribs 48, 56 and 62 successively decrease is such as to produce the approximately 3° &#34;REVERSE TAPER.&#34; 
     Turning now to lockring 12, it will be seen that lockring 12 is broadly a frustum in longitudinal cross-section. Front beveled edge 68 aids lockring 12 as it encounters inclined surface 40, (or ribs 48, 56, and 62), and plateau 47. Following beveled edge 68 is flat area 70. Flat area 70 is located such that it is positioned over substantially the total exterior surface of surfaces 40, 42 and 44, (or ribs 48, 56 and 62) when locking 12 is forced into final position against stop flange 32. Lockring 12 has an abrupt shoulder 72 which aids in maintaining lockring 12 in position. In one embodiment of lockring 12, shown in FIG. 10, a trailing surface 74 is included to eliminate a potential stress point at abrupt shoulder 72. 
     A tube connection is formed by sliding tube section 16 into sleeve 10. The tube section 16 is initially easily slidable within sleeve 10, however, the size of sleeve 10 is such as to eliminate much of the free space between tube section 16 and the interior surface of outer sleeve 10 without restricting the free slidability of tube section 16 within sleeve 10. Positioning flange 34 restricts the movement of tube section 16 within sleeve 10 and causes the tube end 16 to be centrally located within sleeve 10. Lockring 12 is then forced over sleeve 10, causing sleeve 10, and concomitantly therewith, tube section 16, to deform. Because of the configuration of the sleeve 10, the sleeve and the tube section 16 are deformed to the greatest extent at surface 42, (or rib 48). They are deformed a lesser amount nearer center portion 14. This produces a reverse taper in the deformation of sleeve 10 and tube section 16. As the tube 16 is deformed, it is forced into sawtooth grooves 20, 21, 22 and 23. Sawtooth grooves 18 then provide a gripping function tending to hold tube section 16 within sleeve 10. 
     By deforming tube section 10 in this manner, tube section 16 undergoes a &#34;toothpaste tube&#34; effect, whereby tube section 16 is slightly but significantly distended. As the opposing tube section 16 is likewise distended, the adjoining tube sections 16 are forced, under a substantial load, into intimate contact with positioning flange 34 or with one another, depending upon the embodiment of positioning flange 34 being utilized. In either embodiment, a crevice free joint is obtained which substantially eliminates cleaning and corrosion problems. 
     A line connecting the interior edges of the sawtooth grooves of the deformed sleeve, and a line connecting the same grooves prior to deformation, form an angle, designated B in FIG. 2, of approximately 3 degrees. As can readily be seen, in order for tube section 16 to be withdrawn from sleeve 10 once lockring 12 has been forced into position thereby deforming sleeve 10 and tube 16, that amount of tube 16 between surface 40 (or first rib 48) and positioning flange 32 would need to be further deformed. This 3 degree &#34;REVERSE TAPER&#34; significantly increases the pullout strength of the tube connection formed by this invention. 
     Thus, an improved apparatus for making a tube connec-tion has been described and disclosed. It will, however, be clear to those skilled in the art that many modifications of the embodiment here described are possible. Therefore, the invention is not to be limited except by the spirit and scope of the appended claims.