Abstract:
A phase controlled sequential gripping tube fitting for gripping a tube therein, the fitting comprising a rear ferrule shaped to receive the tube therein, the rear ferrule having a nose portion and a central body. The tube fitting further comprises a front ferrule having an axially-extending rear portion radially outwardly spaced from the rear ferrule, whereby when the rear ferrule is urged axially in a first direction the rear ferrule grips the tube, and whereby the rear portion of the front ferrule reduces buckling of the rear ferrule.

Description:
This application is a continuation-in-part of U.S. Ser. No. 08/787,967, filed Jan. 23, 1997 now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     The subject invention is directed toward the art of tube fittings and, more particularly, to an improved phase controlled, sequential gripping tube fitting. 
     The general form of tube fitting with which this invention is concerned is described and claimed in the following series of U.S. patents which are incorporated herein by reference: 
     U.S. Pat. No. 2,484,815 issued Oct. 18, 1949 
     U.S. Pat. No. 3,075,793 issued Jun. 29, 1963 
     U.S. Pat. No. 3,103,373 issued Sep. 10, 1963 
     U.S. Pat. No. 4,826,218 issued May 2, 1989 
     U.S. Pat. No. 4,915,427 issued Apr. 10, 1990 
     U.S. Pat. No. 4,915,427 discloses and claims a phase controlled, sequential gripping tube fitting particularly suitable for use on heavy walled tubes. The arrangement disclosed in the patent obtains proper pull-up action in a two ferrule fitting for heavy walled tubes by using ferrules having a relatively heavy and substantial construction including heavily flanged rear end portions. In addition, the coupling nut portion surrounding the ferrules is arranged to closely enclose the flanged rear end portions of the ferrules. 
     While the described arrangement works very satisfactorily, it would be more desirable to obtain equivalent functioning with lighter weight ferrules without relying on the heavy rear flange design. 
     SUMMARY OF THE INVENTION 
     The subject invention provides an arrangement which overcomes the above-discussed disadvantage of the prior design and allows relatively light weight ferrules to perform satisfactorily with heavy walled tubing by controlling and containing the ferrule swaging action in a manner which prevents undesirable ferrule deformation. The design prevents excessive “bear claw” deformation of the rear ferrule and assures that the rear ferrule transmits the necessary driving forces to the front ferrule prior to full engagement of the rear ferrule with the tube. 
     In accordance with a preferred form of the invention, a phase controlled, sequential gripping tube fitting including a main body having a cylindrical tube end receiving opening with a tapered camming mouth forming the entry to the opening has a front ferrule with a tapered forward nose surface in engagement in the camming mouth and a rear surface with a conically tapered recess that extends forwardly toward the nose surface. A rear ferrule having a conically tapered nose is positioned so that the tapered nose extends into the conically tapered recess of the front ferrule. The rear ferrule further includes a rear force engaging surface. Threadedly connected to the main body is a coupling nut engaged with the rear force receiving surface of the rear ferrule to drive the rear ferrule axially forward into the conically tapered rear surface of the front ferrule and produce radial inward movement of the nose portion of the rear ferrule as well as radial inward movement of the nose portion of the front ferrule. The assembly includes an improved arrangement to control outward buckling of the rear ferrule. The arrangement includes a cylindrical central body on the rear ferrule with the central body located between the nose portion and the rear force receiving surface. Associated with the central body is a cylindrical flange portion formed on the front ferrule and extending axially rearwardly therefrom at a location radially outward of the rear recess of the front ferrule. The cylindrical flange has a cylindrical interior surface that closely surrounds the cylindrical central body of the rear ferrule to limit radial outward movement of the rear ferrule or portions thereof. 
     The arrangement between the nose and central body of the rear ferrule and its relationship to the axially rearward extending cylindrical flange on the front ferrule results in containment of the rear ferrule and anchors it against toroidal torsion which can produce the “bear claw” deformation. In addition, it is believed that by moving the contact and force transmission point forwardly into the body of the front ferrule, the front ferrule is driven move smoothly and with less radial deformation. This result can be further enhanced by closely containing the rear portion of the front ferrule by providing the coupling nut with an interior cylindrical surface which substantially engages and closely contains the front ferrule against outward radial deflection. 
     A principal object and primarily advantage of the invention is that it allows the use of lighter weight ferrules than was previously possible when engaging heavy weight tubing. 
     A further object of the invention is the provision of an arrangement for use in a phase controlled, sequential gripping tube fitting to eliminate undesired torsional rotation in the rear ferrule even when a relatively light weight ferrule is used. 
     Yet another object of the invention is the provision of a phase controlled sequential gripping tube fitting that is especially suited for heavy walled tubing but which can also be used for standard weight tubing. 
     Still other advantages and benefits of the invention will become apparent to those skilled in the art upon a reading and understanding of the following detailed description. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention may take physical form in certain parts and arrangements of parts, a preferred embodiment and method of which will be described in detail in this specification and illustrated in the accompanying drawings which form a part hereof, and wherein: 
     FIG. 1 is a partial side elevational view in cross section of a coupling device which employs a female coupling nut; 
     FIG. 2 is a view similar to FIG. 1 with a tube member inserted into the coupling and the coupling components made up to a finger-tight relationship; 
     FIG. 3 is a view like FIG. 1 but showing the fitting in its made up condition with the ferrules in their tube gripping positions; and, 
     FIG. 4 is a greatly enlarged view of the circled portion of FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawings wherein the showings are for the purposes of illustrating the preferred embodiment of the invention only and not for purposes of limiting same, the FIGS. 2 and 3 generally show a coupling body  10  with a tubular member  12  associated therewith and received therein. Suitable gripping and sealing engagement between the body  10  and the tube member  12  is achieved through the use of a coupling nut  14  and a ferrule arrangement  16 . 
     In the subject arrangement, the coupling body  10  has a first end  20  and an associated second end (not shown). It should be understood that the coupling body could be associated with any type of second end or associated structure and could be formed directly on a fluid flow device, such as a valve or the like. As can be appreciated, however, the coupling body  10  includes an internal flow passage  22  that joins with a cylindrical bore  24  extending axially inward of the first end  20 . The bore  24  is preferably coaxial with the internal flow passage  22  and the juncture between bore  24  and flow passage  22  provides a radial end wall or shoulder  26 . The diameter of counterbore  24  is, as can be seen from FIGS. 2 and 3, sized so as to closely but slidably receive the end of the tube  12 . The shoulder  26  provides an inward limit stop for the tube  12  and locates the tube end relative to the ferrule arrangement  16 . An outer counterbore  28  extends from counterbore  24  to the outer end of the fitting body and has a generally conical shape expanding radially outwardly to define a tapered, conical camming mouth about the bore  24 . 
     The coupling nut  14  is preferably of hex-shaped exterior configuration and has a central bore that is threaded as illustrated at  30  and cooperates with external threads  32  formed about the exterior of the body  10  on the first end  20 . The coupling nut  14  acts to drive the ferrule arrangement  16  into its sealed and gripping relationship in a manner subsequently to be described. For the present, it should be noted that the axial outer end of the coupling nut  14  includes a central bore  34  that is sized so as to closely encircle the exterior of the tube  12 . Referring in particular to FIGS. 1 and 4, the details and preferred construction for the ferrule arrangement  16  can best be understood. In particular, the assembly includes a front ferrule  36  and a rear ferrule  38 . The front ferrule  36  has a central through opening  40  which is cylindrical in shape and sized so as to closely but slidably receive the tube  12 . The exterior of the ferrule  36  is of tapered configuration as shown and tapers at an angle α only slightly less than the taper angle of the camming mouth  28 . Preferably the angle α is in the range of about 10° to 30°. The corresponding angle of the camming mouth is generally slightly greater, as shown. The tapered outer surface  42  extends substantially the length of the ferrule from the nose  44  to adjacent the rear surface of the ferrule. The rear surface of the front ferrule  36  includes a conically tapered rear force receiving surface  46  that is inclined or tapered at an angle in the range of, for example, about 40° to 50° generally as shown. 
     Cooperating with the front ferrule is the second or rear ferrule  38  which has a central through opening  50  that generally corresponds in diameter to the central through opening  40  of the front ferrule  36 . This opening  50  is also arranged so as to closely but slidably receive the tube  12 . The forward or axial inner end  52  of the rear ferrule  38  is tapered so as to generally correspond to the taper of the force receiving recess  46  of the front ferrule. The rear ferrule  38  is preferably a unitary, annular ferrule, and does not have a split or a gap formed therein. Axially rearward of the inner or nose end  52  of ferrule  36  is a central body section  54  of cylindrical configuration. The axial outermost or right-hand end of the ferrule  38  is of slightly greater diameter as seen at  56  to define a radially extending end flange having a cylindrical radial outer side face  57 . A counterbore  58  within the coupling nut  14  is sized and arranged so as to enclose the flange defined by portion  56  of ferrule  38 . In addition, a slightly tapered or inclined end wall  60  on ferrule  38  is arranged to correspond with the angled inner shoulder  62  of the nut  14  and act as a force receiving surface when the nut  14  is tightened to body  10  to move the ferrules to their tube gripping and sealing position shown in FIG.  3 . 
     Of particular importance to the invention is the relationship between the rear of the front ferrule and the forward, cylindrical body portion  54  of the rear ferrule  38 . In particular, it will be seen that the front ferrule  36  includes an axially rearwardly extending cylindrical flange portion  66  that defines a cylindrical bore  68  leading to the force receiving inclined surface  46 . This flange portion  66  preferably extends along a significant length of the rear ferrule, or the cylindrical body portion  54 , to radially constrain the rear ferrule. The flange portion  66  may extend less than half along the cylindrical body portion. However, other lengths of the flange  66 , such as greater than half the length of the cylindrical body portion, or about one fourth of the length of the rear ferrule  54 , or other varying lengths, may still be utilized. The flange portion  66  preferably has a thickness sufficient to prevent buckling of the central body portion  54 . Accordingly, the flange portion  66  is preferably thicker than the body portion  54  to prevent outward buckling of the central body portion, and in one embodiment the central body  54  is less than about two-thirds of the thickness of the flange portion  66 . As can be seen in FIG. 4, the outer diameter of the flange portion of the front ferrule  36  is radially outward of the rear ferrule. Thus in the illustrated embodiment the front ferrule  36  has an outer diameter greater than the rear ferrule  34 . 
     As best shown in FIG. 4, the flange portion  66  of the front ferrule  36  is radially spaced from the central body portion  54  of the rear ferrule  38 . A ferrule gap  77  is located therebetween. The ferrule gap  77  helps to prevent frictional forces and stresses from building up between the flange portion and the central body portion during makeup of the fitting. This enables the ferrules to slide relatively smoothly during make-up. Although the nose  52  of the rear ferrule  38  engages the force receiving surface  46  of the front ferrule  36  during make up, the spacing between the ferrules at the ferrule gap  77  is preferably maintained during makeup. If there is buckling of the rear ferrule, the rear ferrule may distort slightly into the ferrule gap  77  before the flange portion  66  arrests the buckling of the rear ferrule. However, when there is no buckling, during normal make up the gap  77  is maintained. It should be noted that the width of the ferrule gap  77  in FIG. 4 is exaggerated for ease of illustration. 
     Additionally, it should be noted that there is within the nut member  14  a second counterbore  70  that is sized and arranged so as to closely enclose the rear end diameter of the front ferrule and constrain its radial outward movement during the tightening of the nut member  14  to the tube gripping position. In this way, both the front ferrule and the rear ferrule are radially constrained by the nut member while the nose portion of the rear ferrule is further constrained and guided by the counterbore  68  in the rear of the front ferrule  36 . By so guiding and constraining the rear ferrule at both the axial inner and outer ends, it is caused to move progressively inward while it drives the front ferrule into its gripping position. This controlled movement prevents torsional twisting and constrains the gripping movement to avoid “bear clawing” or the over deflection or rolling of the nose portion of the rear ferrule. In addition, by so moving the force receiving surface of the front ferrule inwardly of the rear face, there appears to be a better ability of the rear ferrule to constrain and control the forces applied thereto. 
     FIG. 3 shows the components after the nut member  14  has been moved from the finger tight position of FIG. 2 to the “made-up,” fully engaged tube gripping position. It is important to note that the length of central section  54  of rear ferrule  38  is related to the counterbore  58  of the coupling nut  14  and the cylindrical bore  68  so as to prevent any possibility of engagement between the end face  66   a  of flange portion  66  and end face  70   a  of second counterbore  70  (see FIG.  4 ). This assures that gap G is maintained at all times, even after makeup of the fitting as seen in FIG.  3 . By maintaining the gap G, a spring action is retained by the ferrules. This assures a seal is maintained throughout thermal cycling and vibration. Also, it permits subsequent remake of the fitting. The gap G in the disclosed embodiment is located between the end face  66   a  of the front ferrule and the end face  70   a  of the coupling nut  14 . However, the gap may be located between other elements, such as between the front ferrule and the rear ferrule, depending upon the particular arrangement and shapes of the components in the tube coupling. Although the components surrounding the gap may vary, it is preferable that the gap be sized and located so as to allow for deformation of the front ferrule  36  and rear ferrule  34 . As the fitting is repeatedly made up, the front ferrule  36  and/or the rear ferrule  34  may plastically deform such that the front ferrule moves into the gap G. The rear ferrule may be compressed, or the front ferrule may acted upon such that the flange portion  66  is urged into the gap. The gap G provides an axially-extending space into which the ferrule may deform to allow repeated make ups of the fitting. There may be deformation of the ferrules after each make-up of the fitting, and the gap G accommodates the accumulated deformations. The gap preferably is large enough to accommodate significant deformation of the ferrule, and preferably extends axially a significant distance relative the central body portion  56  of the rear ferrule  38 . In one embodiment, the gap extends about one-third the length of the central body portion  56 . 
     The invention has been described with reference to the preferred embodiment. Obviously, modifications and alterations will occur to others upon a reading and understanding of this specification. It is intended to include all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.