Abstract:
A tube-fitting-assembly ferrule apparatus and method to secure connections between tubing sections against high pressure, vibration, pulsation, and hammering, by providing a tube-fitting-assembly ferrule which elastically deforms in use, securing the primary circumferential point seal with a shock-absorbing and shape-retaining force.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of my application Ser. No. 14/288,292 filed on May 27, 2014 and entitled “Tube Fitting Assembly,” which issued as U.S. Pat. No. 9,273,808 on Mar. 1, 2016, and which is a divisional of application Ser. No. 13/068,391 filed on May 10, 2011, which issued as U.S. Pat. No. 8,769,798 on Jul. 8, 2014 for a “Tube Fitting Assembly,” the full disclosures of which are incorporated by reference herein and priority of which is hereby claimed. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates generally to the sealing of fittings about tubes and, more particularly, though not exclusively, to the sealing of tubing being a tube gripping member, such as a ferrule. 
     Tube fittings are used to join or connect a tube end to another member, whether that other member be another tube end or a device in fluid communication with the tube end. Generally, tube fittings are designed to withstand operational conditions of the environment where the tube is located, such as pressure, vacuum, pull-out pressure, temperature, pulsation, and/or vibration. Ideally, a tube fitting grips the tube end so as to prevent loss of seal between the tube and another member. A good tube fitting maintains a leak-free connection between the tube and another member. 
     Some tube fittings are designed to be used with plastic tubes, while others are used with metal tubing, such as stainless steel pipes/tubes. While the design criteria for these applications may differ, the basic concepts of this invention may be applicable to both. Typically, stainless steel and other metal tubing is used for high-pressure applications in which the tubing wall thickness is substantial. Such heavy wall tubing is difficult to grip because it is not only hard, but also resistant to deformation. Such physical characteristics make it more difficult to deform the tubing plastically so as to achieve a desired tube grip. 
     Tube fittings usually include an assembly of a tube gripping device, which can be a single or multiple ferrules, and a pull-up member for causing the tube gripping device to be installed on a tube end so as to grip the tube end and create a leak-free seal. The pull-up member can be a threaded nut that is tightly engaged with the body of a member, to which the tubing is connected. The pull-up mechanism most commonly used is a threaded connection of a female threaded nut and a male threaded body component, both of which act upon the ferrule as the nut and the body are threaded together. In such arrangement, the front end of the ferrule is sandwiched between the tube and the body to form a sealing member. 
     Conventional ferrule fittings are inserted into a space between an outer surface of the tubing and an inner surface of the body. The body is formed with a frustoconical camming surface, which a front end of the ferrule contacts. In many known fitting assemblies, the resulting seal is less than adequate, requiring one or more elastomeric seals to prevent leakage of the liquid or gas. 
     The present invention contemplates elimination of drawbacks associated with convention tube fitting, and provides a ferrule seal assembly that effectively seals the interface between the end of the tubing and a body. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       Reference will now be made to the drawings, wherein like parts are designated by like numerals, and wherein: 
         FIG. 1  is a schematic perspective view of the invention; 
         FIG. 2  is a schematic cutaway view of the operation of the invention; 
         FIG. 3  is a side view of embodiments of the invention; 
         FIG. 4  is a perspective view of embodiments of the invention; 
         FIG. 5  is a perspective view of an embodiment of the invention; 
         FIG. 6  is a perspective view of another embodiment of the invention, having cutouts; 
         FIG. 7  is a perspective view of an embodiment of the invention, having a circumferential notch forming a transverse shoulder; 
         FIG. 8  is a perspective view of an embodiment of the invention, having a collar forming a transverse shoulder; and 
         FIG. 9  is a schematic view of different embodiments of the invention in use. 
     
    
    
     SUMMARY OF THE INVENTION 
     It is, therefore, an object of the present invention to provide a ferrule seal assembly that meets high performance characteristics without compromising overall fitting integrity and leak-proof performance, and that minimizes and mitigates the blow-out or blow-off potential of the connection. 
     It is another object of the invention to provide a ferrule seal assembly that is designed for use in high-pressure, vibration, pulsation, and other applications. 
     It is a further object of the invention to provide a ferrule seal assembly that employs a single or multiple ferrules. 
     These and other objects of the invention are achieved through the provision of a tube fitting assembly, which comprises a cylindrical tube having an exterior surface, a longitudinal axis, and a tube end. The tube has a circumferential notch formed in the exterior surface adjacent the tube end. The notch is defined by a curved surface and a transverse surface, which extends substantially perpendicularly to the longitudinal axis of the tube. 
     The fitting assembly also comprises a first tube fitting member having an inner bore and an internally threaded end, said first tube fitting member being configured to receive the tube within the inner bore. A second tube fitting member has a central aperture extending through a length thereof, the second fitting member comprising an externally threaded end. A tube gripping member is mounted for sliding movement along exterior surface of the tube. The tube gripping member has a tapered front end configured to fit into the notch, when the second tube fitting member is pulled up, and seal the tube end. 
     The first tube fitting member can be a valve component, a conduit, a manifold, or any other device. The second tube fitting member is an externally threaded nut that partially fits into the bore of the first tubing member when pulled up. The tube gripping member is a ferrule with sufficient plasticity, allowing the front end of it to be deformed while being fitted into the notch. The flexing ability of the ferrule allows a partial bending of the ferrule sealing portion, which moves into a sealing contact with the tube end. 
     The notch on the tube body is partially defined by a curved or arcuate exterior surface of the tube. An arcuate camming surface is formed opposite the tube arcuate surface along the inner bore of the body, or the first tube fitting member. A space is defined between the arcuate surfaces of the tube and the body, and the tube gripping member, or ferrule fits tightly into said space when forced into a sealing position by the pulling up of the externally threaded nut. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIG. 1  and all figures generally, the tube-fitting-assembly method  100  and the tube-fitting-assembly ferrule apparatus  10  are shown in use schematically. 
     The invention is used with tubing, usually high-pressure tubing subject to vibrating, pulsating, or pounding, characterized by a tube channel  201  defined by a one or more tube-wall sections  202 . The tubing sections are connected to other tubing sections or ultimately to devices by the operation of threaded sockets  203  and threaded plug-nuts  204 . The end of the tube-wall section  202  is terminated with a section sealing surface  205  that seals against a socket sealing surface  206  that is built in to the threaded socket  203 . The resulting seal is a point seal that circles the tube channel. It is this point seal that will be subjected to vibrating, pulsing, and pounding during normal operation of the tube assembly. 
     The invention provides a transverse shoulder  20  on the tube-wall section  202  near the section sealing surface  205 . The transverse shoulder  20  provides a circumferential contact surface that will directly transmit sealing pressure to the section sealing surface  205 . Referring briefly to  FIG. 7 , in an embodiment, the transverse shoulder  20  is created by removing a circumferential notch  21  of material from the tube-wall section. Referring briefly to  FIG. 8 , in another embodiment, the transverse shoulder  20  is created by adding a collar  22  to the tube section, creating a circumferential ledge  23 . This collar  22  could be machined or constructed into the tube section, or could be added as a threaded, welded, pressed, or otherwise attached separate piece. 
     Referring to  FIG. 3  &amp;  FIG. 5 , the tube-fitting-assembly ferrule  10  has a ferrule body  11  and a ferrule forward face  12 . In use, the ferrule forward face will make circumferential contact with, and be compressed against, the transverse shoulder, and the ferrule body  11  will elastically deform so as to constrict or tighten the inner surface of the ferrule body against the tube and to expand or bulge the outer surface of the ferrule body against the inside of the threaded socket. When the angled ferrule forward face  12  is forced against the transverse shoulder  20 , the angle promotes the constricting and bulging deformations at the desired places. Optionally, a groove or swale  13  can be made in the ferrule body  11  to provide a weakened area to further promote the desired deformations. 
     The constricting and bulging deformations undergone by the ferrule body  11  are elastic deformations, at least in part, depending upon the specific materials used in a given embodiment. The elasticity of the deformation, which can also be analyzed as stress, imparts a spring-like character to the deformed ferrule body  11 , which functions similarly to an automobile shock absorber, and absorbs pulsations or hammering in the tubing, thereby maintaining the integrity of the circumferential point seal by reducing the tendency of the section sealing surface  205  and the socket sealing surface  206  to create a gouge or groove one against the other under pulsations of higher pressure, eventually compromising the integrity of the seal. Additionally, where such gouging or grooving occurs, the spring action presses the section sealing surface  205  and the socket sealing surface  206  more tightly together, restoring the integrity of the seal. 
     The shock-absorbing function of the elastically deformed ferrule body  11  can be complemented by a gripping function, or optionally a secondary-sealing function. Where the deformed ferrule body constricts around the tube-wall section  202  and bulges against the inner surface of the threaded socket  203 , gripping surfaces are formed. These gripping surfaces strengthen the connection generally, and also provide a mechanism for a portion of vibration, pounding, or hammering stress to be transferred to such gripping surfaces through the shock-absorbing transfer through the deformed ferrule body  11 . Optionally, such gripping surfaces can be designed to form a secondary seal. 
     Referring to  FIG. 4  &amp;  FIG. 6 , optionally, a number of cutouts  14  can be placed in the ferrule forward face  12  in order to promote or allow for deformation. Such notches might be needed for embodiments where the interaction of the size of the ferrule and the hardness of the chosen material create some resistance to the desired deformation. 
     Referring to  FIG. 1 ,  FIG. 2 , &amp;  FIG. 9 , in use, the invention provides a tube-fitting-assembly ferrule  10  having a ferrule body  11  and a ferrule forward face  12 , which encircles a tube-wall section  202 . The tube-wall section is placed into a threaded socket  203  and a threaded plug-nut  204  is installed behind the ferrule and into the threaded socket  203 . The tightening of the threaded plug nut forces the ferrule forward face  12  against the transverse shoulder  20 , which both (a) forces the section sealing surface  205  against the socket sealing surface  206  to form a circumferential point seal, and (b) deforms the ferrule body so that it constricts against the tube-wall section  202  and bulges against the inner wall of the threaded socket  203 . 
     The tube-fitting-assembly ferrule  10  forms an exceptionally strong mechanical resistance to vibrations, pulsation, or pressure tending to break connection between the body and the tube. In many embodiments, the constricting and bulging deformations provide both (a) additional gripping surfaces and (b) a secondary seal. All embodiments provide an additional sealing pressure resulting from the elastic or partially elastic deformation of the ferrule body, because the elastically deformed ferrule body can absorb additional stress from pulsations of higher pressure, and can become less deformed, and “spring back” during pulsations of lower pressure. 
     In accordance with this invention, an efficient tube fitting is provided using a ferrule seal assembly. As the ferrule acts against the curved camming surface of a female threaded body, the ferrule forms additional annular seals at the front end of the ferrule. The features of this invention are particularly advantageous when the tube has high hardness characteristics and biting techniques, when the ferrule bites into the tube, are difficult to apply. 
     The components of the ferrule sealing assembly can be made of a noncorrosive material such as stainless steel, although identification of the material is intended to be exemplary in nature and should not be construed in a limiting sense. Those skilled in the art will readily appreciate that the invention may be realized using any number of different types of metal materials for the fitting components, as well as metal tubing materials, including ferritic stainless steel, any duplex stainless steel, any nickel alloy, any precipitation hardened stainless steel, brass, copper alloys, any carbon alloy steel, or other suitable materials. Furthermore, the ferrule sealing assembly need not be made of the same material as the tubing itself. 
     Although a number of aspects of the invention are described herein as being incorporated into the exemplary embodiments, such description should not be construed in a limiting sense. For any particular application the various aspects of the invention may be used as required in different combinations and sub-combinations thereof. Furthermore, although the present disclosure describes and/or illustrates a number of design choices and alternative embodiments, such descriptions are not intended to be and should not be construed as an exhaustive list of such choices and alternatives. 
     Many changes and modifications can be made in the present invention without departing from the spirit thereof. I, therefore, pray that my rights to the present invention be limited only by the scope of the appended claims.