Patent Publication Number: US-10316998-B2

Title: Conduit fitting subassembly and retaining tool

Description:
RELATED APPLICATIONS 
     This application is a continuation application of continuation application of U.S. Ser. No. 14/509,505, filed on Oct. 8, 2014, titled “Conduit Fitting with Pull-Up Indication”, which is a continuation application of U.S. Ser. No. 13/860,763, filed Apr. 11, 2013, titled CONDUIT FITTING WITH RADIAL CONSTRAINT, now abandoned, which is a continuation of U.S. application Ser. No. 12/718,180, filed Mar. 5, 2010, titled CONDUIT FITTING WITH PULL-UP INDICATION, now issued U.S. Pat. No. 8,439,407, which is a continuation of U.S. application Ser. No. 11/112,800 filed on Apr. 22, 2005 for FITTING FOR TUBE AND PIPE, now issued U.S. Pat. No. 7,695,027, which claims the benefit of U.S. provisional patent application Ser. Nos. 60/564,358 for HARDENED TUBE FITTING filed Apr. 22, 2004 and 60/633,885 for FITTING FOR TUBE AND PIPE filed Dec. 7, 2004, the entire disclosures of which are fully incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     Flareless fittings have been in use for decades for conduits such as tubes and pipes. A flareless fitting is used to connect or join two tube or pipe ends or to connect a conduit end to another assembly such as a tank, a valve, a manifold and so on. The applications are as varied as the types of assemblies with which the fittings are used. One very common type of flareless fitting is a ferrule type fitting. In a ferrule type fitting, one or more ferrules are used to join or connect a conduit end to a fitting member, typically called a fitting body. The fitting body may then be joined to (or be part of) another assembly. In a ferrule type fitting, the ferrule or ferrules must establish a fluid tight seal, particularly under pressure, as well as adequate grip of the conduit and protection against vibration fatigue. High performance fittings, such as are available from Swagelok Company, Solon, Ohio, are capable of withstanding pressures many times the rated pressure of the fitting without leaking, without vibration fatigue and without conduit blow out to the point that the conduit will burst before a seal is compromised or the ferrule(s) can lose their grip on the conduit. 
     Ferrule style fittings have an advantage over other end connections in that they do not rely on any special preparation of the tube or pipe end, other than low cost squaring and deburring. This is because the ferrules create the seals and tube grip. 
     Flareless fittings that use ferrules are commonly used in sophisticated chemical processing apparatus because of their high reliability. For example, in the semiconductor industry, such fittings assure containment of expensive or toxic chemicals. Typically, these applications are high purity and therefore, rely on conduits made of stainless steel or other low corrosion, high strength alloys. 
     Lower cost markets, such as the automotive industry, have their own performance requirements for fluid connections. Most notably, automotive assembly requires simpler assembly procedures. The automotive industry has resisted using ferrule type fittings not only for cost reasons, but also for assembly needs. Ferrules are fairly small annular members that can be dropped or lost in low cost, high throughput facilities. Typical ferrule type fittings are also assembled by what is commonly known as pull-up by turns. Two threaded components, such as a nut and body, enclose the conduit end and one or more ferrules. The assembly is first tightened to a finger tight condition and then a prescribed number of turns, such as one and a quarter or one and a half turns, are used to pull-up the fitting to its final assembled condition. The number of turns is carefully prescribed to prevent over torque or inadequate pull-up. The automotive industry on the other hand typically wants to assemble parts by torque. This allows a simple torque wrench or tool to be used to make the final assembly with the assurance that the fitting has been properly assembled. 
     The next generation of motor vehicles, especially for passenger use, will likely be in the area of alternative fuels such as high pressure hydrogen. The pressure ratings that will be required significantly exceed current rated pressure for ferrule type, flareless fittings (although not the pressure capability of high performance ferrule type, flareless fittings.) For example, it is expected that gaseous hydrogen will need to be contained at a pressure of 15,000 psi (15 ksi). Current flareless tube fittings are rated below 10 ksi. 
     For current high pressure flareless fittings, the material used for the fluid components of the fitting, in at least some applications, must be hardened. To this end, the block of material from which the fitting body is made may be a material hardened by heat treating or, in the example of an austenite stainless steel, may be manufactured from work hardened bar stock. For a straight union fitting, manufacturing the fitting from work hardened bar stock is suitable. More complex configurations, such as elbows and tee shapes, however, require substantially larger blocks of material. For these types of fittings, a substantial amount of material must be removed, which can drive up manufacturing costs. 
     Some threaded tube fittings, on the other hand are made from compact forgings which save material and cost. The use of forged fitting components is well accepted for low pressure applications. The forging process, however, can cause material annealing which eliminates any prior work hardening. Thus, forged components are typically unsuitable for high pressure applications. 
     SUMMARY OF THE INVENTION 
     In accordance with one aspect of the invention, a fitting is provided that will perform at a high pressure rating without compromising leakage, grip and vibration performance achieved by earlier two ferrule tube fittings, even while in some embodiments using lower cost manufacturing processes and materials. In one embodiment, a male fitting component, such as a nut, includes a structure, which constrains a tube gripping device, such as a ferrule or ferrules. As a result, the mating female fitting component need not be formed from a hardened material. The invention thus provides, in accordance with additional aspects, a high pressure fitting that utilizes a fitting body of one material, with a mating nut that is made of a harder material. For example, the body may be annealed stainless steel and the nut may be work hardened stainless steel. This combination can be used in higher pressure applications that can have rated pressures greater than 8 ksi, even greater than 12 ksi. This in part arises from the use of a nut that has a hardness ratio relative to the body of about 1.3:1 to about 2:1 (Vickers scale) or greater. In another embodiment, the ferrules are case hardened, for example by a low temperature carburization process to provide very hard ferrules. In another embodiment, the nut provides a secondary pressure seal against a surface of the fitting body. 
     In accordance with another aspect of the invention, a fitting is provided with a first component that has a portion adapted to constrain a tube gripping device where the exterior of the component is work hardened, for example, in the area of radial constraint. In one embodiment, a selected portion of the fitting is work hardened, for example the female fitting component, by plastically deforming the material on an exterior portion or surface of the female fitting component. Because the selected portion is work hardened, the female fitting component can be initially made from a non-hardened material by forging or casting. In another embodiment, the work hardening provides a more useful configuration to the fitting. For example, the work hardening can include an external thread convolution that allows the fitting to connect with another device or structure. The invention also relates to a method of selectively work hardening, such as by rolling circumferential ridges or threads, for example, on a female threaded fitting component, that may be made initially as a forging. 
     In accordance with another aspect of the invention, a ferrule type, flareless fitting is provided that can optionally be pulled-up to its final assembled condition by torque rather than by turns. In one embodiment, a male fitting component, such as a nut, includes a structure having a surface that engages a surface on a female fitting component to facilitate pull-up by torque. In another embodiment, a ferrule is provided with a flange that engages a surface on a female fitting component to facilitate pull-up by torque. In yet another embodiment, the nut includes an external surface, for example a surface of a tool engaging portion, that engages an exterior surface on a fitting body. 
     In accordance with another aspect of the invention, a ferrule type flareless fitting is provided that allows for easy installation by providing a single assembly that has one or more ferrules held with a fitting component. In one embodiment, a cartridge nut assembly allows one or more ferrules to be retained securely on a fitting component prior to installation so that the ferrules and the fitting component will not become separated prior to installation. In another embodiment of the invention, a tool is provided which retains the one or more ferrules onto a fitting component prior to installation and is removably during assembly. 
     The invention also provides a fitting with an annealed female body and a male hardened nut in combination with the pull-up by torque functionality. The invention also provides a fitting with pull-up to torque functionality in combination with the functionality of a nut that retains one or more ferrules in an uninstalled condition. The invention also provides a fitting with pull-up to torque functionality in combination with the functionality of the nut forming a seal against the body. The invention also provides a fitting with a female threaded body having at least two tapered or camming surfaces. 
     In accordance with another aspect of the invention, a ferrule type flareless fitting is provided that includes a male nut that is flush with the body or recessed in the body when the fitting is in a pulled-up condition. In one embodiment, a keyed male nut, and corresponding key tool, is provided that has a hex area removed to reduce its overall length. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing features of the present invention will become apparent to one skilled in the art to which the present invention relates upon consideration of the following description of the invention with reference to the accompanying drawings, in which: 
         FIG. 1  is a longitudinal cross-section of an exemplary embodiment of a fitting in accordance with the present invention; 
         FIGS. 1A , B, and C illustrate different thread options for the fitting components of the exemplary fitting shown in  FIG. 1 ; 
         FIG. 2  is an enlarged cross section of a first ferrule of the exemplary fitting shown in  FIG. 1 , 
         FIG. 3  is an enlarged cross section of a second ferrule of the exemplary fitting shown in  FIG. 1 ; 
         FIG. 4  is a cross section of a nut of the exemplary fitting shown in  FIG. 1 ; 
         FIG. 5  is a cross section of the nut of  FIG. 5 , enlarged in the area of the cartridge; 
         FIG. 6  is a cross section of a body of the exemplary fitting shown in  FIG. 1 ; 
         FIG. 7  is a half longitudinal cross-section of the exemplary fitting shown in  FIG. 1  in a finger tight condition, enlarged in the area of the ferrule; 
         FIG. 8  is a half longitudinal cross-section of the exemplary fitting shown in  FIG. 1  in a pulled-up condition, enlarged in the area of the ferrule; 
         FIG. 9  is a graph of illustrative data for torque versus nut displacement for the exemplary fitting shown in  FIG. 1 ; 
         FIG. 10  is a longitudinal cross section of the nut and two ferrules of the exemplary fitting shown in  FIG. 1  where nut and two ferrules are installed on a tool; 
         FIG. 11  is a perspective view of the tool shown in  FIG. 10 ; 
         FIGS. 12A-B  are side cross-sectional views of the exemplary fitting shown in  FIG. 1  illustrating various steps in the use of the tool for making-up the fitting; 
         FIG. 13  is a longitudinal cross-section of another exemplary fitting of the present invention shown in a finger tight condition; 
         FIG. 14  is a half longitudinal cross-section of the exemplary fitting shown in  FIG. 13  in a pulled-up condition, enlarged in the area of the ferrule; 
         FIG. 15  is a cross section of a nut of the exemplary fitting shown in  FIG. 13 ; 
         FIG. 16  is a cross section of the nut of  FIG. 15 , enlarged in the area of the cartridge; 
         FIG. 17  is an enlarged cross section of a first ferrule of the exemplary fitting shown in  FIG. 13 ; 
         FIG. 18  is an enlarged cross section of a second ferrule of the exemplary fitting shown in  FIG. 13 ; 
         FIG. 19  is a longitudinal cross-section of another exemplary fitting of the present invention shown in a finger tight condition; 
         FIG. 20  is a half longitudinal cross-section of the exemplary fitting shown in  FIG. 19  in a pulled-up condition, enlarged in the area of the ferrule; 
         FIG. 21  is a half longitudinal cross-section of another exemplary fitting of the present invention shown in the finger tight condition; 
         FIGS. 22A and 22B  are plan and elevation views of a key tool for use with the exemplary fitting shown in  FIG. 21 ; 
         FIG. 23  is a half longitudinal cross-section of another exemplary fitting of the present invention shown in the pulled-up condition; 
         FIG. 24  is a half longitudinal cross-section of another exemplary fitting of the present invention shown in a finger tight condition, enlarged in the area of the ferrule; 
         FIG. 25  is a half longitudinal cross-section of another exemplary fitting of the present invention shown in a finger tight condition, enlarged in the area of the ferrule. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     While the invention is described herein with specific reference to a variety of structural and material features, such descriptions are intended to be exemplary in nature and should not be construed in a limiting sense. For example, the exemplary embodiments are described primarily in teens of a stainless steel tube fitting for automotive applications. Those skilled in the art, however, will readily appreciate that any one or more of the aspects and features of the invention may be used outside of the automotive industry, can be used with materials other than stainless steel and can be used with many conduits including, but not limited to, tube or pipe. Moreover, many of the aspects of the invention may be used for lower pressure fittings, or the higher rated pressure concepts disclosed herein may be used in a fitting even when the fitting itself will be used in a lower pressure application. Still further, the exemplary embodiments herein illustrate what is commonly known as a female-style fitting, meaning that a female (i.e. internally) threaded component receives and abuts the conduit end. Many aspects of the invention will find application in male-style fittings as will be apparent to those skilled in the art. The invention will also find application for fitting assemblies that do not require threaded connections between the fitting components, for example clamped or bolted fittings may be used. The invention will also find application far beyond the exemplary embodiments herein as to connections that can be made to a wide and ever expansive variety of fluid components including, but not limited to, other conduits, flow control devices, containers, manifolds and so on. 
     While various aspects of the invention are described and illustrated herein as embodied in combination in the exemplary embodiments, these various aspects may be realized in many alternative embodiments, either individually or in various combinations and sub-combinations thereof. Unless expressly excluded herein all such combinations and sub-combinations are intended to be within the scope of the present invention. Still further, while various alternative embodiments as to the various aspects and features of the invention, such as alternative materials, structures, configurations, methods, devices, software, hardware, control logic and so on may be described herein, such descriptions are not intended to be a complete or exhaustive list of available alternative embodiments, whether presently known or later developed. Those skilled in the art may readily adopt one or more of the aspects, concepts or features of the invention into additional embodiments within the scope of the present invention even if such embodiments are not expressly disclosed herein. Additionally, even though some features, concepts or aspects of the invention may be described herein as being a preferred arrangement or method, such description is not intended to suggest that such feature is required or necessary unless expressly so stated. Still further, exemplary or representative values and ranges may be included to assist in understanding the present invention however, such values and ranges are not to be construed in a limiting sense and are intended to be critical values or ranges only if so expressly stated. 
     Although various embodiments are described herein with specific reference to the fitting components being made of stainless steel, such description 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 metals material for the fitting components, as well as metal tubing materials, including but not limited to 316, 316L, 304, 304L, any austenitic or ferritic stainless steel, any duplex stainless steel, any nickel alloy such as HASTALLOY, INCONEL, MONEL, alloy 825, alloy 625, any precipitation hardened stainless steel such as 17-4PH for example, brass, copper alloys, any carbon or low allow steel such as 12L14 steel for example. An important aspect of the choice of materials is that the tube gripping device preferably should be case or through hardened to a ratio of at least 3.3 and preferably 4 or more times harder that the hardest tubing material that the fitting will be used with. Therefore, the tube gripping device need not be made of the same material as the tubing itself. For example, the tube gripping device may be selected from the stainless steel material noted above, or other suitable materials that can be case hardened, such as magnesium, titanium and aluminum, to name some additional examples. 
     With reference to  FIG. 1 , the fitting  10  includes a first fitting component  12  that can be realized in the form of a female threaded body having internal threads  14 . The first fitting component  12  joins or connects with a second fitting component  16  that can be realized in the form of a male threaded nut having external threads  18  that threadably mate with the threads  14  of the first component  12  when the fitting  10  is made-up or assembled. Different thread options and non-threaded coupling designs may be used for the first and second fitting components. 
       FIGS. 1A , B and C illustrate different thread options for a threaded coupling between the body  12  and nut  16 .  FIG. 1A  illustrates 30° from normal (i.e. 60 degrees included angle) symmetrical thread flanks  19   a  and  19   b .  FIG. 1B  illustrates the optional use of a buttress thread design in which the thread flanks are asymmetrical with one flank  19   a  typically in the range of about 45 degrees and the adjacent flank in the range of about 3 degrees to about 7 degrees from normal. The buttress thread design provides high strength loading on one side to help reduce flaring of the nut during high torque assembly and in high pressure applications.  FIG. 1C  illustrates the use of acme threads wherein the flanks again are symmetrical but of a steeper angle such as about 3 degrees to about 7 degrees from normal. The acme thread design provides higher strength loading uniformly compared to the 60 degrees threads. 
     The fitting  10  further includes a tube gripping device. Ferrules are an example of a tube gripping device and, in this example, two ferrules are included; a front or first ferrule  20  and a back or second ferrule  22 . The fitting, however, can be designed for using a single ferrule or alternative tube gripping device. The nut  16  and ferrules  20 ,  22  fit onto a conduit end T that is received by the body  12 . 
       FIG. 2  is an enlarged cross section of a first or front ferrule of the exemplary fitting shown in  FIG. 1 . The first ferrule  20  is a generally annular part with a generally cylindrical interior wall  24  that slips over the outer surface S of the tube end T (see  FIG. 1 ). The first ferrule  20  has an outer surface  26  that tapers outwardly in a generally conical manner from a forward portion  28  to a rearward portion  30 . The forward portion  28  may include a sharp front edge  32  and a rounded nose portion  34 . The rearward portion  30  includes a frusto-conical recess  36  that forms a camming surface  38 . The tapered outer surface  26  may converge to an axially aligned flange  40  (wherein the axis X is the central longitudinal axis of the conduit and the fitting  10 ). 
       FIG. 3  is an enlarged cross section of a second or back ferrule of the exemplary fitting shown in  FIG. 1 . The second ferrule  22  is a generally annular part with a generally cylindrical interior wall  42  that slips over the outer surface S of the tube end T (see  FIG. 1 ). The second ferrule  22  further includes a nose portion  46  and an axially extending outer surface  44  that extends about a rearward portion  48  of the ferrule. The nose portion  46  includes a sharp front edge  50  and a first tapered portion  52  that extends toward the rear portion  48  from the sharp edge  50  at a rake angle α of about fifteen degrees, for example. The first tapered portion  52  merges or blends to a second tapered portion  54  along a first curved portion  56  such as a radius, for example. The second tapered portion  54  merges or blends to the axial portion  44  at a corner or edge  58  which may alternatively be a radius. The second tapered portion  54  extends at an angle β, such as about thirty-five degrees, for example. 
     The second ferrule  22  further includes a back end portion  60  that has a driven surface  62 . The driven surface  62  extends radially outwardly at an angle δ, such as about five degrees (referenced from normal to the axis X), for example. The driven surface  62  merges or blends with the axial portion  44  along a second curved portion  64 . 
       FIGS. 4-5  illustrate a cross section of a nut of the exemplary fitting shown in  FIG. 1 . The nut  16  has an overall cylindrical configuration defining a central bore  66  that receives the tube end T during assembly. The nut  16  has a front end  68  that defines a socket, recess or cage  70 . The socket  70  is defined by a cylindrical first portion  72  and a frusto-conical portion  74  that tapers radially inwardly towards a back end  75  of the nut  16 . The frusto-conical portion  74  forms a drive surface that contacts the driven surface  62  of the second or back ferrule during pull-up. The drive surface  74  is formed at an angle τ, such as about fifteen degrees, for example. Because the angle τ is different from the angle δ, the driven surface  62  of the back ferrule  22  initially contacts the drive surface  74  at the outer radius  64  (see  FIG. 7 ). The difference angle Φ, where Φ=τ−δ, assures that the initial contact between the nut  16  and the second ferrule  22  is radially spaced from the tube end T; thus, the contact between the driven and the drive surfaces  62 ,  74  is not a flush. 
     The socket  70  is formed within an axially extending and generally cylindrical wall or cartridge  76 . The cartridge  76  is sized to retain the back ferrule  22  and at least a portion of the rearward portion  30  of the front ferrule  20  therein, to form a nut and ferrule assembly or cartridge nut assembly  78  (see  FIG. 10 ). The term cartridge as used herein is a shorthand reference to the concept of a fitting component, in this example a male threaded nut  16  having a structure that can retain one or more ferrules therewith even when the assembly is uninstalled with the mating fitting component. Thus, the cartridge nut assembly  78 , which includes the cartridge nut  16  and one or more ferrules  20 ,  22 , may be used to retain the ferrules and nut together when the assembly is either uninstalled or only installed in the body  12  in a finger tight condition. 
     Many different techniques may be used to retain the ferrule or ferrules  20 ,  22  within the cartridge nut  16  prior to final pull-up or even initial assembly into the mating fitting component. For example, a non-contaminating glue or adhesive may be used to hold the ferrules  20 ,  22  in place, with the glue releasing its grip under the force of pull-up. Alternatively, the cartridge wall  76  may be slightly crimped radially inwardly to retain the ferrules  20 ,  22  therein. Still further, an adhesive may be used that breaks down into a lubricant upon pull-up to help reduce pull-up torque. In another embodiment disclosed herein, a tool is used to hold the parts together as an assembly  78  (see  FIG. 10 ). 
     With reference to  FIG. 5 , the cartridge  76  may include a tapered portion  82  that tapers radially outwardly towards the back end  75  of the nut  16 . The tapered portion  82  extends at an angle θ, such as for example about forty-five degrees. 
     The nut  16  further includes a tool engagement portion  80  that allows a torque wrench or other tool to be used to tighten and pull-up the fitting  10 . The tool engagement portion  80  in the exemplary embodiment of  FIG. 1  is realized as a hex portion  80 . The tool engagement portion  80  can be formed in variety of ways. For example, the nut  16  may include a key hole that allows a corresponding keyed wrench to be used to tighten and pull-up the fitting, as described in relation to  FIGS. 21-22 . 
     The nut  16  may further include a neck  77  of somewhat reduced outer diameter between the threads  18  and the tool engagement portion  80 . The neck  77  may be used to provide an intrinsic gauging function to verify proper pull-up for both pull-up by torque and pull-up by turns. By intrinsic gauging is meant a structure or feature associated with the fitting itself (as contrasted with a separate tool or gauge) that provides an indication to the assembler that the fitting has been properly assembled and pulled up. A large variety of structures or features can perform the intrinsic gauging function, some examples of which are disclosed in International Application No. 03/07739 and U.S. patent application Ser. No. 10/711,353, and U.S. Pat. No. 6,640,457 B2, the entire disclosures of which are fully incorporated herein by reference. A gap gauge may also be used in a known manner to confirm proper pull-up of the fitting  10 . 
     With reference to  FIG. 6 , the female threaded body  12  is a generally cylindrical part centered on the axis X. The body  12  has an opening  83  at a forward end  84  adapted to receive the tube end T. A central bore  86  extends through the body  12  and forms a port  88  which defines a fluid flow path. The port  88  may be used to establish fluid communication with another part such as a valve, tee, elbow, manifold, etc. It should be noted that although the female threaded fitting component  12  is shown as a separate stand alone part, the features of the component by which it can make a fluid connection with the male threaded fitting component could, alternatively, be incorporated into a bulk body  85  such as a manifold, valve, pump, tank, and so on, commonly referred to as a fluid port. 
     The female body further includes a counterbore  89  that forms a shoulder  90 . The tube end T bottoms against the shoulder  90  when received by the body  12 . The counterbore  89  may have a slight taper to it to help form a seal about the tube end T upon pull-up of the fitting  10 . 
     The female fitting component  12  further includes a first tapered surface, such as for example frusto-conical surface  92  and a second tapered surface, such as for example frusto-conical surface  94 . The first frusto-conical surface  92  forms a first or ferrule camming surface in the body  12  and may be axially adjacent the forward end of the counterbore  89 . The second frusto-conical surface  94  forms a second or cartridge camming surface in the body  12  and may be axially adjacent or near the forward end of the first camming surface  92 . The first or ferrule camming surface is formed at an angle α. The angle α may be selected to optimize the camming action with the nose portion  34  of the first ferrule  20 . In typical two ferrule and one ferrule fittings, this angle is about twenty degrees but may be any suitable value from about 10 degrees to about forty-five degrees. 
     The second or cartridge camming surface  94  is formed at an angle ρ. In this example, the angle is about forty-five degrees, but this angle is not required. The angles σ and ρ may be the same or different from each other. In the illustrations herein, the angles are different, therefore there is a radial step  96  that joins the two camming surfaces  92 ,  94 . This step may be radial or may have its own angle or taper or other profile as needed. 
     The body  12  further includes female threads  14  which threadably mate with the threads  18  on the male nut  16 . It should be noted that the body  84  may also be formed into a cap by closing off or eliminating the port  86 , such as for example can be used to cap the end of a fluid line. The body  12  may be provided with hex flats to facilitate holding the body while the nut  16  is being tightened down during pull-up. Of course, pull-up involves relative axial translation between the fitting components, the nut  16  and body  12 , in this case effected by relative rotation between the nut and body, regardless of which fitting component is being held and which is being turned. In a non-threaded coupling, pull-up involves relative axial translation between the two fitting components by means other than two threaded components, such as for example two components forced together by a clamping device. 
     The body  12  may also include a work hardened portion  81  formed generally radially outward of the ferrules  20 ,  22 . In addition to being radially outward of the tube gripping device  20 ,  22 , the amount and location of work-hardening can be selected, as appropriate, for a given application. The work hardened portion preferably extends from the forward end  84  of the fitting body  12  to at least a location radially outward of the radial step  96 . The work hardening portion, however, may extend, for example, to a location radially outward of the rearward end of the first camming surface  92  or extend the entire length of the exterior surface of the body  12 . The work hardening is accomplished by plastically deforming the material on an exterior portion of the fitting component  12 . The material can be plastically deformed in a variety of ways. For example, the work hardening may be accomplished by creating a series of generally rolled circumferential ribs or by rolling an exterior male thread  98  on the fitting body  12 . 
       FIGS. 7 and 8  illustrate the fitting  10 , enlarged in the area of the ferrules, in a finger tight condition and a pulled-up condition, respectively. In the finger tight condition of  FIG. 7 , the first or front ferrule nose portion  28  is positioned partially within the camming mouth formed by the ferrule camming surface  92 . Note that the back ferrule  22  engages the drive surface  74  of the nut  16  at the difference angle Φ. This assures that during pull-up the back end portion  60  of the second ferrule  22  will move or remain radially outward from the outer surface S of the tube end T. At the same time, the nose portion  46  of the back ferrule  22  is plastically deformed so that the sharp edge  50  bites or indents into the tube surface S, producing a strong tube gripping shoulder  100  and a fluid tight seal. The ferrule nose  46  also hinges so that a portion  102  of the cylindrical wall  42  is radially compressed against the tube wall surface S to swage or collet the back ferrule  22  against the surface axially spaced from the bite  100 . This region of high radial compression and colleting of the back ferrule  22  provides excellent protection of the bite or indent  100  from vibration. The back ferrule  22  thus is designed to hinge in deformation and effect upon pull-up the colleting region  102  between the bite or indent  100  and the back end  60  of the ferrule while having the back end portion  60  moved radially outward or kept radially outward from the outer surface S of the tube end T. The exact location of the colleting region  102  will be determined by, among other things, the size of the ferrule  22 . In some cases, the collet region  102  can be adjacent the bite or indent  100  while in other cases the colleting region may occur axially spaced from the bite or indent. The collet region  102  may in some case be further characterized by a convex profile that swages the tube end. 
     The relative axial translation between the two fitting components  12 ,  16  is performed so that the forward tapered surface  82  of the cartridge  76  contacts and cams against the second tapered surface  94  of the body  12 . The contact between the cartridge  76  and the v surface  94  produces a coining like action so that the cartridge tapered surface  82  forms a strong fluid tight seal against the camming surface  94 . At the same time, the front ferrule surface, especially at the radius  34 , forms a seal against the first camming surface  92 . The front ferrule  20  may optionally swage or bite into the tube wall S to provide tube grip. 
     The primary functions of the ferrules  20 ,  22  are to create fluid tight seals and tube grip, along with resistance to fatigue from outboard system induced vibration. The front ferrule  20  is used primarily to provide a fluid tight seal against the body  12  and the tube outer surface S, while the back ferrule  22  is used for a back-up seal against the tube outer surface S and to provide excellent tube grip. The particular geometry and operation of the ferrules, or a single ferrule in such applications, can be selected as required for a particular application and dependent on the types of materials being used. The back ferrule  22 , for example, may be provided with one or more recesses in the interior cylindrical wall  42  of the ferrule, and the driven surface  62  of the ferrule may be contoured. Still further, one or both of the ferrules  20 ,  22  may be case hardened, for example by a low temperature carburization process to provide very hard ferrules that are corrosion resistant. The case hardening may be applied over a portion or all of the ferrule surface. A number of issued patents disclose such case hardening and geometry concepts that may be applied to the ferrules, such as U.S. Pat. Nos. 6,629,708; 6,547,888; 6,165,597; and 6,093,303 issued to the assignee of the present invention, the entire disclosures of which are fully incorporated herein by reference, as well as PCT International Publication Nos. WO 02/063195A2 and WO 02/063194A3 also incorporated herein by reference. Such patents and the concepts therein, however, are exemplary in nature as to the present invention and should not be construed in a limiting sense. Many different case hardening processes and a wide variety of geometric configurations may be used to properly control the plastic deformation of the ferrules during pull-up to assure adequate seal and tube grip. 
     Under elevated pressures, for example 15 ksi, the tube wall will tend to be radially expanded, pushing outward on the ferrules  20 ,  22 . The cartridge  76  serves to radially contain the ferrules  20 ,  22  and prevent loss of seal and tube grip. Note that the body  12  does not constrain much if any of the front ferrule  20 . The stress of containing the front ferrule  20  radially under pressure is achieved by the cartridge  76 , as is the case with the back ferrule  22 . This is significant for reasons that will be discussed hereinbelow. Note further, particularly in  FIG. 1 , that the optional work hardened exterior  81  will also function to contain higher pressure by radially constraining and supporting the cartridge  76  in an assembled condition. 
     Upon pull-up, when the cartridge  76  engages the second camming surface  94  in the body  12 , not only will the cartridge form a seal against fluid pressure, but the assembler will also notice a sharp and dramatic increase in pull-up torque.  FIG. 9  is a graph of illustrative data for torque versus nut  16  displacement. Note that in region A the torque rises somewhat slowly and steadily as a result of the ferrules  20 ,  22  plastically deforming while biting into the tube T and camming against the body camming surface  92  and the front ferrule camming surface  38 . As soon as the cartridge  76  contacts the second camming surface  94  in the body  12 , however, the torque in region B increases sharply and dramatically. By selecting an appropriate torque value that corresponds to proper pull-up, the fitting  10  can be pulled-up by torque rather than by turns. Thus, a simple torque wrench can be used to make-up the fitting  10 . Note from  FIG. 9  that the cartridge concept provides a very tight or steep torque to nut displacement ratio. This is in significant contrast to prior fittings wherein the torque gradually increases as the ferrules defoun. Since too many factors can influence the gradual torque readings, torque cannot always be used to accurately gauge proper pull-up of prior fittings. Instead prior fittings typically are pulled-up by counting turns or displacement of the nut relative to the body. For example, region A in  FIG. 9  shows that torque can increase rather little over significant displacement of the nut relative to the body, thus preventing torque from correlating well with turns or displacement. 
     Angling the camming surface  94 , such as at the angle ρ, allows the fitting  10  to be re-made. Each remake of the fitting  10  progresses the cartridge subassembly further into the body for each re-make, even if only slightly. For very sharp torque increases, the angle ρ may approach ninety degrees (relative to the axis X). This alternative arrangement would provide a dramatic increase in torque for pull-up by torque, but in some cases may lessen the ability to remake the fitting  10  after the initial pull-up. 
     Referring to  FIG. 8 , as well as the alternative embodiment of  FIGS. 14 and 21  for example, the contact between the cartridge forward surface  82  and the body tapered surface  94  to effect pull-up by torque also produces a radial support of the body for the cartridge after pull-up. This feature of these embodiments when used further facilitates the use of the fitting at higher pressures along with the pull-up by torque functionality. 
     Other embodiments may be used to effect pull-up by torque rather than having the cartridge  76  engage the body  12 . For example, a ferrule can be designed to engage the body in a manner to effect pull-up by torque, as described below with regard to  FIGS. 19-20 . In addition, any two generally radial surfaces of the nut  16  and the body  12  can be designed to engage upon proper pull-up of the fitting  10  to provide the sharp torque increase. For example, an exterior surface on the fitting body may be designed to engage an exterior surface of the nut upon complete pull-up. These surfaces, as with the camming surface  94  and cartridge tapered surface  82 , may be angled to allow for remake of the fitting. 
     A fitting in accordance with the invention may be used in pressure applications below 12 ksi, even 8 ksi, but more notably may be used as a higher pressure rated fitting above 8 ksi, even above 12 ksi. A number of features and aspects of the invention relate to the ability of the fitting to withstand higher rated pressures, as will now be discussed. 
     Unlike traditional female style fittings, the invention provides a fitting  10  in which the ferrules  20 ,  22 , and especially the front ferrule  20 , are radially constrained against pressure by the male fitting component rather than the female fitting component. In other words, the front ferrule  20  engages with the camming surface  92  in a manner similar to prior female fitting designs, but is radially constrained and held against pressure by the cartridge  76 . 
     For fittings that are made of stainless steel, the nut  16  can be a work hardened part, such as can be machined from bar stock, for example, because it must be strong enough to constrain the ferrules  20 ,  22  under higher pressures. The female body  12 , however, does not need to be a formed from work hardened material because it is not necessarily utilized to protect the ferrules  20 ,  22  under pressure. Therefore, the body  12  may be formed from an annealed material, such as by forging or casting, for example. Forming the fitting body  12  by forging or casting, for example austenite stainless steel, can be significantly less expensive than forming it by machining from hardened bar stock. This is especially true if the fitting body is (or is part of) a complex shape, such as a tee or an elbow. As a result, significant cost savings can be realized with the present invention. Further, austenite stainless steel, which cannot be hardened by heat treating, can be utilized to form the body without needing to work harden the steel. Forming the body from austenite stainless steel is advantageous in many applications due to its excellent corrosion resistance. 
     The ability to provide a fitting  10  that can function at higher pressure rating or working pressures with an annealed body also greatly expands its available applications. For example, the fitting body  12  can be formed by providing a female port in a variety of fluid components that are made of softer annealed metals, such as pump housings, cylinder heads, manifolds, tanks, and so on. Still a further alternative embodiment, however, provides that the body  12  may also be formed from work hardened material or have a portion of the body work hardened, if so required, particularly for even higher pressure ratings or working pressures. 
     Selectively work hardening a portion of the fitting body  12  makes the fitting withstand high internal pressures without deformation or damage that would cause leakage of the fitting  10 . Thus, selectively work hardening the fitting body provides a similar advantage to not utilizing the body to protect the tube gripping device  20 ,  22  under pressure. Specifically, the body  12  may be formed from an annealed material, rather than hardened bar stock. Doing so results in a fitting  10  that can function at higher pressure rating or working pressures but be realized at a significant cost savings over prior high pressure fittings. 
     If, for example, the fitting  10  is to be rated at 15 ksi, then it is, by industry convention, tested typically under hydraulic pressure up to and exceeding four times that pressure rating (a 4-to-1 tube grip performance factor), or 60 ksi. A statistically significant number of fittings are tested up to and exceeding 60 ksi to reliably predict with high confidence that the fitting will go to at least four times the prospective working pressure without leakage. Applicants have found that the fitting  10  in accordance with the present invention can hold pressures up to about 75 ksi and greater, thus providing at least a 5-to-1 tube grip performance factor. Thus, selectively work hardening a portion of the fitting  10  also allows the use of a relatively soft forging for the fitting body  20 . 
     As described hereinabove, the fitting  10  may be selectively work hardened by plastically deforming a portion  81  of the fitting. A portion of the fitting  10 , radially outward of the ferrules  20 ,  22 , is work hardened by rolling a set of circumferential ribs or an external male thread  98  on the fitting body  12 . The work hardening can be performed concurrently with the machining of the fitting body  12  or other part. Specifically, a piece, such as the fitting body  12 , is typically machined on a multiple spindle machine having multiple index positions at which various machining operations are done sequentially. With one of these operations being the rolling of the ribs or thread  98 , to work harden the fitting body  12 , the body need not be subjected to a separate work operation (off the one machine) to harden it. The part  12  can be loaded once onto the machine, machined including the work hardening to form the thread  98 , then unloaded. 
     In addition, the male thread  98  that may be formed in the work hardening process can provide a more useful configuration to the fitting  10 . In particular, the thread  98  can be used to attach certain fitting enhancements to the fitting  12 . For example, one or more lock nuts can be threaded onto the male thread  98  to further strengthen the fitting  10 . Additional examples can include using the thread  98  to mount the fitting body  12  to a panel or to attach a means that can support the tube T, assist retaining the tube in the fitting  10 , assist attenuating the effects of outside tube vibration, or other functions. 
     The higher pressure rating, 15 ksi or higher, may be further achieved with the fitting  10  disclosed herein because of the ability to case harden or carburize the ferrules. This allows the ferrules  20 ,  22  to bite and seal against work hardened conduits such as for example heavy walled tubing or ⅛ hard or strain hardened material that is needed for higher pressure applications. The fitting  10  provides a back ferrule  22  that has substantial bulk material to make the ferrule stronger in gripping the conduit as well as being able to bite into the conduit. Still further, the seal formed by the cartridge  76  against the second camming surface  94  provides a secondary or backup seal to the body seal formed by the front ferrule  20  against the first camming surface  92 . The cartridge seal against the second camming surface  94  may be facilitated by use of the softer annealed body. 
     The invention, however, is not limited to use with stainless steel materials. For example, the automotive industry, especially for alternative fuel vehicles, may decide to pursue carbon steel rather than stainless steel for various fittings and conduits. The invention provides advantages in the use of carbon steel as well, even though carbon steel can be hardened by annealing. These advantages include but are not limited to the cartridge concept for easier assembly (to be described further hereinbelow), providing a seal with the cartridge against the body, and providing a fitting that can be pulled up to torque rather than by turns. 
       FIG. 10  is a longitudinal cross section of the nut  16  and two ferrules  20 ,  22  of the exemplary fitting shown in  FIG. 1  where nut and two ferrules are installed on a tool  103 . The tool  103  provides a convenient way to hold the cartridge nut  16  and one or more ferrules  20 ,  22  together as a single assembly  78  prior to make-up of a fitting  10 . Thus, the assembly  78  and tool  103  together provide a single unit  104  that can be installed in a mating fitting component, such as for example the female fitting component  12 , so that an assembler only needs to handle two fitting parts. As a result, there are no loose ferrules to assemble, and the ferrules can be installed at the manufacturer to avoid installation errors. Other techniques for providing a cartridge nut assembly such as the use of an adhesive have been described hereinabove. 
       FIG. 11  illustrates a perspective of an exemplary embodiment of the tool  103 . With reference to  FIGS. 10 and 11 , the tool  103  includes a head  105  that can be manually gripped or can be gripped by a simple tool such as pliers. The tool  103  is a single plastic element but other materials may be used as required. Flexible fingers  106   a  and  106   b  extend from the head  105  and include at their respective distal end, a raised lip  107   a  and  107   b . The lips  107   a,b  and head  105  define a slot or carriage  108  onto which the cartridge nut  16  and the ferrules  20 ,  22  can be installed. The flexible fingers  106   a,b  radially compress enough to allow the nut  16  and then the ferrules  20 ,  22  to move over the lips  107   a,b  toward the head  105 . Once past the lips  107   a,b , the fingers  106   a,b  snap back outward, thus retaining the ferrules  20 ,  22  and nut  16  together on the tool  103  as a single assembly  78 . 
       FIGS. 12A and 12B  illustrate various steps in the use of the tool  103  to make up the fitting  10 . To make up the fitting  10 , the assembly  78  is inserted into the female body  12  and the assembler can easily use finger pressure to rotate and threadably engage the nut  16  and the body  12  (or rotate the nut into a female port in another body). As the nut  16  is threaded into the body  12 , the lips  107   a,b  will engage a surface inside the body  12 , in this case the first camming surface  92 . Further axial displacement of the assembly  78  and tool  103  into the body  12  causes the fingers  106   a,b  to be radially compressed due to a camming action against the body  12 . 
     The continued axial displacement of the assembly  78  and tool  103  causes the fingers  106   a,b  to compress sufficiently for the lips  107   a,b  to be dimensionally smaller than the inside diameter of the ferrules  20 ,  22  and the nut  16 . The tool  103  thus self disengages from the ferrules. When this occurs, the tool  103  can be easily extracted from the assembly  78  and body  12 . Note that the tool  103  can be easily adapted to any size fitting, and also can be color coded or provided with other indicia to indicate information about the assembly  78 , such as the size, materials, pull-up torque and so on. For example, a groove  109  or other suitable marking, indicia or structure may be provided on the tool  103  to provide a visual indication to the user that the fitting has been adequately made up in the finger tight position to allow easy removal of the tool. 
       FIGS. 13-18  illustrate another exemplary fitting of the present invention. Many of the functional features of this embodiment are similar to the above embodiment except as otherwise noted. The exemplary fitting  110  of  FIGS. 13-18  includes a female threaded body  112  and a male threaded nut  114 . The body  112  includes a first camming surface  116  and a second camming surface  118 . The second camming surface  118  engages with an angled surface  120  on the interior end  122  of a cartridge  124  formed as part of the nut  114  during pull-up ( FIG. 14 ). The angle θ of the surface  120  may be about forty-five degrees relative to the central longitudinal axis X of the fitting  110 , but other angles may be used as required. In this embodiment, however, the cartridge  124  includes a tapered or conical wall  126  that forms a tapered socket  128  for a back ferrule  130  and at least a portion of a front ferrule  132 . The tapered socket  128  provides for easier withdrawal of the nut  114  during disassembly because the ferrules can disengage from contact with the wall  126  during withdrawal of the nut. The wall  126  may taper at an angle ε of about five to about twenty degrees relative to a central longitudinal axis X but other angles may be used as required. The back ferrule  130  may include a tapered outer wall portion  134  to facilitate disassembly, and the front ferrule  132  may also include a tapered outer wall portion  136 . The back and front ferrule tapered outer walls  134 ,  136  may be formed at an angle suitable to achieve the desired effect, for example, about five to about twenty degrees relative to the axis X, but other angles may be used as needed. Thus, the invention contemplates a cartridge design in which upon disassembly the entire assembly of the nut  114  and two ferrules  130 ,  132  can be withdrawn or where the nut can be separately removed. The inclusion of a tapered socket may be especially useful for higher pressure applications because the ferrules will not bind or “weld” to the socket wall upon pull-up or application of high pressure. The ferrules will disengage from the tapered socket wall as the nut is withdrawn so that torque will not be applied to the ferrules during disassembly. This will help assure that a proper remake of the fitting can be effected. 
       FIGS. 19 and 20  illustrate another embodiment of the present invention wherein  FIG. 19  is a longitudinal cross-section of a fitting in a finger tight position and  FIG. 20  illustrates the fitting in the pulled-up position. In this embodiment the fitting  150  includes a nut  152  and body  154  that may be similar in design to the embodiments described herein above. In this embodiment, however, the axial length  155  of the cartridge  156  is shortened because the cartridge  156  is only being used to retain the back ferrule  158 . The front ferrule  160  is no longer contained within the cartridge  156 . A tool, similar to the tool shown in  FIGS. 10-12 , may be used to maintain a single component assembly as in the above described embodiments. 
     In this example, the front ferrule  160  includes an enlarged radially extending flange  162 . The flange  162  is sized to fit within a bore  164  of the fitting body  154 . The flange  162  further includes a driven rear surface  166  and a seal surface  168  at a forward portion  169  of the flange. The seal surface  168  extends at an angle θ, such as about forty-five degrees, for example. The seal surface  168  engages a first camming surface  170  of the body  154  during pull-up. This provides a dependable secondary pressure seal and pull-up to torque design similar in function to the engagement of the front end of the cartridge of the above embodiments. 
     The driven surface  166  in this example is generally radial and engages the front end  172  of the cartridge  156  during pull-up so that the cartridge directly drives the front ferrule  160  forward. The back ferrule  158  also drives the front ferrule  160  forward until the cartridge  156  engages the front ferrule flange  162 . The front ferrule  160  further includes a tapered nose portion  174  that engages a second camming surface  176  of the body  154 . The flange  162  may be appropriately dimensioned so that the flange is supported by the body wall  178 , particularly under pressure. The body  154 , thus, may be formed of work hardened raw material, or may have work hardening selectively applied to an annealed body. 
       FIG. 21  is a half longitudinal cross-section of another exemplary fitting of the present invention shown in the finger tight condition. In this embodiment, the fitting  180  includes a body  182  and ferrules  184 ,  186  that may be similar in design to the embodiments described hereinabove. In this embodiment, however, fitting  180  includes a different nut  188 . The nut  188  has a generally cylindrical configuration that defines a passage  190  for receiving a tube end T. The nut  188  has an external thread  192  for engagement with the internal thread  194  of a female fitting component, such as the fitting body  182 , for example. The nut  188  has a rear face or outer face  196  that includes a key hole  198 . The key hole  198  is adapted to receive a key tab  200  of a keyed wrench  202 . 
     With reference to  FIG. 22 , the keyed wrench  202  has an elongated handle portion  203  with a generally rectangular cross-section. The cross-sectional shape of the handle portion  203  can be other than rectangular. For example, the handle portion  203  could have an oval or circular cross section. The key tab  200  extends from the handle portion  203  at about a right angle. The key tab  200  may extend from the handle portion  203  at an angle other than a right angle, though a right angle is preferred. The key tab  200  is adapted to mate with the key hole  198  to allow the key wrench  202  to rotate the nut  188  sufficiently to pull-o the fitting  180 . 
     The key wrench  202  also includes a clearance opening  204  extending along a central axis  206  of the handle portion  203 . The clearance opening  204  is sized and positioned to allow the key wrench  202  to straddle the conduit and engage the nut  188  without the tube interfering. 
     The length of the nut  188  is selected so that, when the nut is fully screwed into the fitting body  182 , the rear face  196  of the nut  96  is flush with the end of the body  182 , or is recessed. There is no standard hex configuration projecting from the fitting body  182 . As a result, the chance of inadvertent loosening or removal of the nut  188  is reduced since the ability to disassemble the fitting  180  is restricted to only those personnel that have the specific keyed wrench  202 . In addition, providing different positions for the key hole  198  on the nut  188  may allow specific products (sizes, etc.) to be manufactured in combination with specific wrenches. 
     Further, because the nut  188  does not project from the fitting body  182 , the assembled fitting  180  is smaller. This can be beneficial in applications in which space is at a premium, for example, automotive applications. Finally, the nut  188  is also beneficial as it may allow for cost reduction, since the complete nut can be silver plated (for lubrication of the threads  192 ) without the need to selectively plate the threads or to strip plating off of the hex area (as is done for standard female nuts) for cosmetic effect. Thus, silver platting can be accomplished by dipping the entire nut  188 . 
       FIG. 23  is a half longitudinal cross-section of another exemplary fitting of the present invention shown in the pulled-up condition. In this embodiment, the fitting  210  includes a body  212 , a nut  216 , and ferrules  220  and  222  that may be similar in design to the embodiments described hereinabove. In this embodiment, however, body  212  includes an exterior camming surface  224  that engages a tapered surface  226  on the nut  216  upon proper pull-up. The exterior camming surface  224  may be located on a forward end  228  of the body  212 . The tapered surface  226  of the nut  216 , tapers outward from the axis X away from the body  212 . The tapered surface  226  may be located, for example, on a tool engagement portion such as a hex portion  230 . 
       FIG. 24  is a half longitudinal cross-section of another exemplary fitting of the present invention shown in the finger tight condition. In this embodiment, the fitting  250  includes a body  252 , a nut  256 , and a first ferrule  260  that may be similar in design to the embodiments described hereinabove. In this embodiment, however, the nut  256  includes an integral ferrule  262  that can either replace the first ferrule  260  or, as shown in  FIG. 24 , function as a second ferrule. The geometry of the integral ferrule  262  (such as, for example, a tapered outer surface portion  264 , radius portions  266  and  268 , a nose portion  270 , and so on) is selected so as to effect an appropriate radially inward hinging action of the integral ferrule in response to the nose portion being driven into a camming surface, such as a camming surface  272  on a rearward portion  274  of the first ferrule  260 . The concept of a integral ferrule utilized in a fitting has been disclosed in International Publication Number WO 02/063194A2, the entire disclosure of which is fully incorporated herein by reference. The publication and the concepts therein, however, are exemplary in nature as to the present invention and should not be construed in a limiting sense. 
       FIG. 25  is a half longitudinal cross-section of another exemplary fitting of the present invention shown in the finger tight condition. In this embodiment, the fitting  280  includes a body  282 , a nut  286 , and a first ferrule  290  that may be similar in design to the embodiments described hereinabove. In this embodiment, however, the nut  286  includes a separable ferrule  292  that can either replace the first ferrule  290  or, as shown in  FIG. 25 , function as a second ferrule. The separable ferrule  292  is attached to the nut  286  by a frangible web portion  294 . Upon partial pull-up of the fitting  280 , the separable ferrule  292  engages a camming surface, such as a camming surface  296  on a rearward portion  298  of the first ferrule  290 , and breaks off or separates from the nut  286 . Once separate, the separable ferrule  292  functions similar to the ferrules described in the embodiments hereinabove. The concept of a separable ferrule utilized in a fitting has been disclosed in International Publication Number WO 02/063195A2, the entire disclosure of which is fully incorporated herein by reference. The publication and the concepts therein, however, are exemplary in nature as to the present invention and should not be construed in a limiting sense. 
     The invention has been described with reference to the preferred embodiments. Modification 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.