Abstract:
The self-flaring plastic fitting is generally utilized in coupling one section of tubing to another section of tubing. In the present invention, at least one of the sections of tubing has an end portion with a substantially uniform diameter and a groove about its periphery. The fitting itself includes a fitting body and a fitting nut. The fitting body is provided with a tapered nose section while the fitting nut is provided with a groove engaging device. In assembling the fitting, the end of the section of tubing incorporating the groove is place proximate the tapered nose section of the fitting body while the opposite end of the section of tubing is inserted through the fitting nut. The fitting nut is then pushed towards the fitting body where the groove engaging device of the fitting nut engages the groove of the tubing. As the fitting nut is joined with the fitting body, the fitting nut is drawn over the fitting body and, correspondingly, the tubing is drawn against and over the tapered nose section of the fitting body causing the tubing to flare and a seal to be created between the tapered nose section and tubing.

Description:
FIELD OF THE INVENTION 
     The present invention relates to plastic fittings for joining sections of plastic tubing, and, more particularly, to plastic flare fittings. 
     BACKGROUND OF THE INVENTION 
     Numerous industries use metallic tubes and fittings of copper, stainless steel, steel and various metal alloys where connection of high strength and integrity are needed. Metallic plumbing is very suitable in many applications. However, in certain industries, the fluids conveyed may attack metal components and the metal can contaminate the conveyed fluids, i.e., the semiconductor processing industry. Highly inert fluoropolymers may be utilized for the fittings, tubing, and components in such applications, for example, polytetrafluoroethylene (PTFE), and perfluoroalkoloxy (PFA). To maintain a clean and non-hazardous environment, it is essential that the fittings provided for coupling to sections of tubing are not easily unintentionally disconnected and that the tubing/fitting sealing interface maintains its integrity even under mechanical stress. Various types of fittings are known in the art for these purposes. 
     One common fitting formed from such polymers is the FLARETEK® fitting, available from Fluoroware, Inc., the owner of the instant application. Such fittings provide for a fitting body, with an elongate cylindrical nipple, a threaded portion at the base of the nipple and that completely covers the flared section of the tubing when attached and a fitting nut that is attachable thereto. A flared end portion of tubing is placed over the elongate tapered nose section with the fitting nut thereon. The fitting nut is then threadingly engaged with the fitting body compressing the flared end onto the nipple creating a seal between fitting nut, tubing and fitting body. In order to achieve this seal, the end of the tubing placed over the elongated tapered nose section is flared, prior to assembly, to the shape of the elongate nose tapered section. The flaring of the tubing is achieved by heating the tubing, then shaping the heated tubing into the desired flared configuration by pressing the heated tubing end over an appropriate form, such that the flared shape is retained by the end of the tubing. 
     This step of heating to a temperature sufficient such that the tubing may be permanently deformed and shaping the tubing prior to assembly with the fitting adds time and cost to the overall tubing/fitting assembly process. As such, there is a need for a fitting that is capable of flaring the tubing itself thereby eliminating the need for the heating and shaping of the tubing prior to assembly. The flaring of the tubing is preferably achieved by virtue of the assembly of fitting to tubing and, thus, there is a need that the fitting be readily graspable and, quickly and easily joined. 
     SUMMARY OF THE INVENTION 
     The needs described above are in large measure met by a self-flaring plastic fitting of the present invention. The self-flaring plastic fitting is utilized in coupling a tubing end portion to the fitting. The tubing end portion has a substantially uniform diameter and a groove about its periphery. The fitting itself includes a fitting body and a fitting nut. The fitting body is provided with a tapered nose section while the fitting nut is provided with a groove engaging device. In assembling the fitting, the end of the tubing incorporating the groove is inserted through the nut and is placed confronting the tapered nose section of the fitting body. The fitting nut is then pushed towards the fitting body where the groove engaging device of the fitting nut engages the groove of the tubing. The fitting nut threadingly engages with the fitting body and the fitting nut is drawn inwardly toward the fitting body and, correspondingly, the tubing is drawn against and over the tapered nose section of the fitting body causing the tubing to deform in a flare and a seal to be created between the tapered nose section and flared tubing. 
     The groove engaging device of the fitting nut may be unitary with the fitting nut or may be distinct therefrom. In the case of a unitary configuration, the groove engaging device preferably comprises an annular collar. In the case of a distinct configuration, the groove engaging device is preferably in the form of a retaining ring. Both fitting body and fitting nut are preferably provided with features for easier grasping and handling, e.g., fitting body is preferably provided with one or more planar surfaces for grasping with a tool while fitting nut is preferably provided with a plurality of winged extensions or knurled or ribbed surfaces for easier grasping and hand assembly. The tapered nose section of fitting the body is preferably of a shortened configuration requiring a minimal flare in the tubing. And, the fitting nut is preferably provided with an intermediate collar with a pinching extension that helps to pinch the formed flare of the tubing against the tapered nose section of the fitting body. 
     The fitting may be part of device or component or may have connection means such as external threads, another self-flaring fitting, or a flange. 
     When used herein “tubing” refers to a section of tubing or a tubular end portion where the tubular end portion is part of a device or component such as a valve or other fitting. Tubing formed of PFA is highly suitable for the self-flaring applications herein. “Portion” when used herein refers to either an integral or distinct and separable member. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a self-flaring fitting with a portion of tubing connected thereto in accordance with the present invention. 
     FIG. 2 is an end view of the self-flaring fitting of FIG.  1 . 
     FIG. 3 is a cross-sectional view of the embodiment of the self-flaring fitting of FIGS. 1 and 2. 
     FIG. 4 is a detailed view of a portion of the self-flaring fitting of FIGS. 1-3. 
     FIG. 4 a  is a side elevational view of groove engaging portions of a fitting nut of the present invention. 
     FIG. 4 b  is a detailed cross-sectional view of the groove of the groove engaging portion of the fitting nut of the present invention. 
     FIG. 5 is a cross-sectional view of an alternative embodiment of the self-flaring fitting of the present invention. 
     FIG. 5 a  is a cross-sectional view of the nut at line  5   a — 5   a  of FIG.  5 . 
     FIG. 6 is a cross-sectional view of another embodiment of a self-flaring fitting of the present invention. 
     FIG. 7 is a across-sectional view of a retaining ring that is used with the self-flaring fitting embodiment of FIG.  5 . 
     FIG. 8 is a perspective view of the retaining ring of the embodiment of FIG.  6 . 
     FIG. 9 is a fluid flow circuit incorporating the self flaring fitting of the invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Each embodiment of the self-flaring fittings of the present invention described herein provides for quicker assembly of fittings to tubing by eliminating the need for prior heating and shaping of the tubing, i.e., to form a flared shape for connecting to the tubing, and by providing a fitting that can manually, quickly, and easily be screwed onto the tubing to form an effective seal. The quick assembly of the self-flaring fitting to tubing is, at least in part, effected by virtue of the short flare of the tubing that is needed and by the reduced number of threads that are necessary to achieve this short flare. 
     Referring to FIGS. 1-6, different embodiments of self-flaring fittings  10  are illustrated. Each generally comprises a fitting body  12  and a fitting nut  14  to provide a self flaring connection to a tubing section end portion  15 . The tubing end portion, fitting nut, and fitting body are all coaxial about axis A. 
     Referring to FIGS. 1 and 2, a first embodiment  300  of a self-flaring fitting is illustrated. The exterior of fitting body  12  typically is generally cylindrical in shape and preferably incorporates one or more planar surfaces  16  or other grasping structure for easier grasping of fitting body  12  during assembly. The non-concealed first portion  17  of the exterior of fitting nut  14  is generally cylindrical in shape but is provided with grasping portions configured as a plurality of winged extensions  18 , which provide for easier grasping and turning of fitting nut  14  during assembly of self-flaring fitting  10 . Each winged extension  18  generally comprises an elongate, substantially planar top face  20  and a pair of elongate, substantially parallel and planar side faces  22  that extend substantially radially outward from a plurality of elongate separator faces  24  generally normal to a pair of substantially parallel end faces  25 ,  26 . The concealed second portion  27 , shown by dashed lines, has external threads, described below with reference to FIGS. 3 and 4. The portion  30  of the fitting body opposite the fitting nut is configured as a threaded nipple with threads  31  indicated by the dashed lines. The portion of the fitting body opposite the fitting nut for the various embodiments of the invention may have any of a variety of configurations including means for connecting to an additional tubing end or component or may be integral with a tubing section or a component, for example, a valve, a tank, a filter, or a pump. 
     Cross-sectional views of self-flaring fitting  10  of FIGS. 1 and 2 are depicted in FIGS. 3,  4 , and  4   a . As shown, fitting body  12  is preferably of a unitary configuration having a fluid flow duct configured as a central bore  310  extending therethrough, an inner body portion  312 , a first end  312 . 2 , and a second end  312 . 4 . Inner body portion  312  comprises a generally radially extending wall  313  with tapered nose  314 , which presents a substantially hollow frustoconical shape, having a wedge shape in cross section, defining the central bore  310 . The nose has a leading tip  315  with a minimal outer diameter d 1 , that is sized to be substantially equal to or less than the tapered inside diameter d 2  at the inside surface  321  of the tubing to be self-flared. A first angular surface  316 , e.g., 45° to the axis, and a second angular surface  317 , define a seat configured as a circular axially extending groove  319  for receiving the tubing end  311  as it self-flares. Wall  318  is threaded at inner surface portion  322  of body portion  312 . 
     Fitting nut  14 , like fitting body  12 , may be of a unitary configuration, and incorporates proximal nut portion  324 . Proximal nut portion  324  is preferably defined by one or a plurality of groove engaging portions  329  configured as an inwardly converging annular collar  330 . The collar  330  is preferably defined by a tapered inner face  332 , a tapered outer face  334  that is substantially parallel to tapered inner face  332 , and a substantially radial front face  336  that extends between inner face  332  and outer face  334 , shown more clearly in FIG. 4 a . Proximal nut portion  324  is further defined by a threaded outer surface portion  340  proximate the converging annular collar  330 , wherein the threads of threaded outer surface portion  340  are designed to interface with the threads of threaded inner surface portion  322  of body portion  312 . Fitting nut  14  further comprises an open interior configured as a central bore  344  that extends from converging annular collar  330  to end face  26 . 
     Groove engaging portions  329  are designed to interface with a groove  380  formed in the outer surface  38  of tubing end portion  15 . As FIGS. 3,  4  and  4   b , depict, tubing  28  has been grooved prior to assembly with a groove tool to preferably create a substantially triangularly-shaped groove  380 . In particular embodiments, the groove  380  in the tubing outer surface  381  has an undercut  385  defined by the substantially surface  381  which is at an angle and to a plane normal to the axis. Of course, other groove shapes and prong shapes may be selected without departing from the spirit or scope of the invention. 
     Front radial face  336  is substantially normal to the axis with optimally a slight angle rearward toward the tubing to provide a locking effect during engagement with the groove in the tubing. Similarly, the groove in the tubing may have a correspondence angle on the substantially radial face  382 , forming an undercut discussed above, whereby the groove engaging members are securely captured within the groove. 
     In securing this first embodiment  300  of self-flaring fitting  10  to tubing, the end of tubing  28  with the groove  380  is inserted through the fitting nut  14  and may be engaged with tapered nose section  314  of fitting body  12 . Fitting nut  14  is pushed toward fitting body  12  until threaded side portion  340  of inner fitting body  324  makes contact with threaded side portion  322  of fitting body  12 . Fitting nut  14  is rotated such that threads of fitting body  12  and threads  385  of fitting nut  14  cooperate to draw fitting nut  14  towards fitting body  12 . 
     As fitting nut  14  is drawn towards fitting body  12 , converging annular collar  330  engages with groove  380  of tubing  28 , axially pushing the end of tubing  28  over tapered nose section  314  of fitting body  12 . As fitting nut  14  is drawn into fitting body  12 , the end of tubing  28  is forced into a self-flaring configuration over tapered nose section  314  of fitting body  12  and into the tubing end receiving groove  319 . The flare of tubing  28  is securely held in position by virtue of the collar axially compressing the self-flared tubing end  311  into said receiving groove  319  and between the collar and the fitting body. The tubing end is also under radial expansive stress into the flared shape when in the fully engaged connected position. 
     This particular embodiment illustrates the feature of the tubing end portion face  353  seating into the annular, axially inset groove  319  which defines a seat. The tip of the tubing is axially compressed thereby providing additional sealing integrity. 
     Referring to FIG. 4 a , the converging annular collar  330  of the proximal nut portion  324  may have slits  355  defining a plurality of groove engaging portions  329  configured as prongs. Such independent members facilitate radial flexing of the annular collar which is particularly useful when inserting the tubing end therethrough. 
     Referring to FIGS. 5 and 5 a , cross-sectional views of a second embodiment  400  of a cross-section of self-flaring fitting  10  are depicted. As shown, fitting body  12  is preferably of a unitary configuration having a central bore  410  extending therethrough. The unitary configuration of fitting body  12  generally includes an outer collar portion  412 , which may have planar surfaces for grasping, a threaded exterior surface  416 , and a tapered nose portion  418 . 
     Fitting nut  14 , like fitting body  12 , is also preferably of a unitary configuration, and incorporates an proximal nut portion  424 . Proximal nut portion  424  of fitting nut  14  is preferably defined by threaded inner surface portion  440 , wherein the threads are sized to interface with the threads of threaded exterior surface portion  416  of fitting body  12 . Proximal nut portion  424  is further preferably defined by an intermediate inwardly extending inner collar portion  442  that is adjacent threaded inner surface portion  440 . Intermediate inner collar portion  442  includes a tapered cylindrical face  443 , a radial surface  446  that extends to cylindrical face  444 , and a cylindrical bore  448 . Inner collar portion  442  operates as a pinching extension to radially clamp tubing  28  to tapered nose portion  418 . 
     An annular aperture  450  further defines proximal nut portion  424 , and separates inner collar portion  442  from a distal nut portion  454 . Distal nut portion  454  includes one or more groove engaging portions  458  which extend radially inward and axially defining a conveying annular collar  461 . Each groove engaging portion  458  is defined by a tapered outwardly facing surface  462 , an inwardly facing surface  463 , and a nose  464 . The inwardly and outwardly facing surfaces  462 ,  463 , of all the groove engaging portion(s) in combination preferably form frustoconcially shaped surfaces. As shown in FIG. 5 a  the annular collar may have a plurality of slits  466  defining the individual groove engaging portions configured as prongs  458 . Such slits facilitate radial flexing of the groove easing insertion of the tubular end portion through the nut. The converging shape of the groove engaging portions allow substantially axial compressive loading of the gripping members and consequently secure gripping of the tubing by said portions. 
     Groove engaging portion or portions  458  engage a groove  480  formed in tubing  28  to which second embodiment  400  of self-flaring fitting  10  is to be connected. Tubing  28  has been grooved prior to assembly, with a conventional groove tool. 
     In securing second embodiment  400  of self-flaring fitting  10  to tubing  28 , the end  459  of tubing  28  with the groove  480  is inserted through the nut and positioned to confront tapered nose portion  418  of fitting body  12 . Fitting nut  14  is slid down the tubing to threadingly engage the threaded exterior surface portion  416  and is rotated moving same onto fitting body  12 . 
     As fitting nut  14  is drawn towards fitting body  12 , groove engaging portion or portions  458  of inner fitting portion  424  engages groove  480  of tubing  28 . This facilitates the forcing of tubing  28  over tapered nose portion  418  of fitting body  12  into a self-flaring configuration. The flare of tubing  28  is securely held in position by virtue of the groove engaging portion(s)  458 /groove  480  interface and by inner collar portion  442  pinching tubing  28  against tapered nose portion  418  of fitting body  12 ; the pinching effect and sealing effect is increased as fitting nut  14  is tightened towards stop ring  414 . The fitting can be configured to have the radial face  481  provide a stop for the leading surface of the tip  459  of the end of the tubing at an optimal tightness of the fitting. 
     The embodiment of FIG. 5 with the intermediate collar portion of the nut provides additional sealing integrity in that the flared end of the tubing is radially compressed between the nose and said intermediate collar portion. Although said collar portion is shown as integral with the nut, it could also be distinct separable component assembleable into the nut. 
     Referring to FIGS. 6,  7 , and  8 , a third embodiment  500  of a of self-flaring fitting  10  is depicted. The cross-sectional view of FIG. 6 illustrates the interior configuration of fitting body  12  and fitting nut  14 . As shown, fitting body  12  is preferably a unitary configuration having a central bore  510  extending therethrough. The unitary configuration of fitting body  12  generally includes an outer flange portion  512 , a threaded portion  516 , and a tapered nose portion  518 . Note that the outside diameter of the tapered nose portion  518  is ideally slightly less than the inside diameter of the tubing to be joined. The tip  519  of the nose portion  518  is configured to wedge under and slide inside the tubing section. 
     Fitting nut  14  incorporates a proximal nut portion  524 . Proximal nut portion  524  of fitting nut  14  is preferably defined by an internally threaded portion  540 , wherein the threads of internally threaded portion  540  are sized to interface with the threads of threaded portion  516  of fitting body  12 . Proximal nut portion  524  is further preferably defined by an intermediate collar portion  542  that is proximate internally threaded portion  540 . Intermediate collar portion  542  includes a converging bore  544 , a radially extending surface  546  that is substantially perpendicular to the fitting axis, and a frustoconical surface  548  that may be at approximately  45  degrees, to substantially cylindrical face  544 . Intermediate collar portion  542  preferably operates as a pinching extension to compress and seal tubing  28  to tapered nose portion  518 . Said compression is primarily radial and is also axial. 
     An annular recess  550  is positioned in the distal nut portion  543 , and is positioned between intermediate collar portion  542  and a distal collar portion  554  of inner nut portion  524 . Distal collar portion  554  includes a substantially cylindrical bore  556 , extending from end face  26 , and an annular groove  560  defined by a first surface  562  and a second surface  564 . 
     In this embodiment the groove engaging portion  572  is comprised of a retaining ring, a separate cross-section of which is provided in FIG. 7, is adapted to fit within annular groove  560  while a proximal portion  574  of retaining ring  572  has a radially extending face and extends radially inward to grip with the tubing  28 . Retaining ring  572  has a distal portion  570  with a bore  571  having an inside diameter which is suitably approximately the same as the outside diameter of the tubing. The bore at the proximal portion converges and is preferably provided with a triangularly-shaped tip  576 . Of course, other tip shapes may be used without departing from the spirit or scope of the invention. Retaining ring  572  may be formed of rigid fluoropolymers such as PEEK or carbon filed TEFZEL®, an ETFE polymer available from Dupont. 
     Retaining ring  572  is sized to interface with a groove  580  that is preferably formed in a tubing  28  to which the self-flaring fitting  10  is to be connected. The tubing  28  has been grooved prior to assembly, with a grooving tool known in the art to create a triangular-shaped groove  580  at approximate distance from the end of the tubing. Of course, other groove shapes may be selected without departing from the spirit or scope of the invention. 
     In securing first embodiment  500  of self-flaring fitting  10  to tubing  28 ,the tubing  28  is inserted through fitting nut  14 , and the end of tubing  28  with groove  580  is placed facing tapered nose portion  518  of fitting body  12 . To the extent that is possible, tubing  28  is manually started over tapered nose portion  518 . The nut  14  is pushed toward fitting body  12  until threaded side portion  516  of fitting body  12  makes contact with threaded side portion  546  of fitting nut  14 . Fitting nut  14  is preferably then manually rotated such that threads of fitting body  12  and fitting nut  14  act to draw fitting nut  14  towards stop ring  514 . 
     As fitting nut  14  is drawn towards stop ring  514 , tip  576  of proximal portion  574  of retaining ring  572  engages groove  580  of tubing  28 . The engagement of tip  576  with groove  580  facilitates the drawing of tubing  28  further over tapered nose portion  518  of fitting body  12  to force the end of tubing  28  into a self-flaring configuration over tapered nose portion  518  of fitting body  12 . The flare of tubing  28  is securely held in position by virtue of the tip  576 /groove  580  interface and by virtue of lower wall  548  of intermediate collar portion  542  pinching tubing  28  against tapered nose portion  518  of fitting body  12 ; the pinching effect is increased as fitting nut  14  is drawn towards stop ring  514 . 
     It should be noted that the embodiments disclosed provide for fluid flow ducts in the fitting which are substantially of the same diameter, and thus are as the tubing end portion to be joined. Preferably, the minimal cross-sectional area of flow duct, typically defined by the diameter d 1 , will be at least 85% of the area of the tubing end portion, defined by diameter d 2 . 
     Referring to FIG. 9, a fluid flow circuit  600  suitable for the invention herein is illustrated with circuit components  610 ,  612 ,  614  including a valve  612  with a connection means  618  comprising a flange. Component  610  may be, for example, a source of highly caustic fluid. The component  614  may be, for example, equipment for semiconductor processing. The components are all formed of chemically inert materials. The self-flaring coupling provides coupling means to connect particular components  612 ,  614  through unprepared tubing  613  with a high level of integrity both from a fluidic seal perspective and a mechanical strength perspective. 
     Moreover, the various aspects of the embodiments of the invention herein may be used with aspects of the inventions disclosed in copending applications, owned by the owner of this application, Ser. Nos. 09/590,544, 09/590,328 filed on the same date as this application and with the same inventors. These applications, entitled Torque Confirmation Fitting and Plastic Fitting for Flared Tubing, are hereby incorporated herein by reference. 
     In the preferred embodiments, the tubing and all or substantially all of the fitting will be formed from fluoropolymers, for example PFA. In particular embodiments, where the groove engaging portion is a distinct member, other more rigid materials, preferably chemically inert materials, i.e. PEEK, may be appropriate. For the self-flaring of the tubing to be effective for forming a secure mechanical and fluidic seal, the tip of the tubing needs to radially deform. Associated with the flaring of the tubing end, the tapered nose of the fitting body will typically show some radial compression. Operations may be performed on the tip of the tubing to facilitate this deformation or the initial engagement with the tapered nose and still be within the scope of this invention. For example, shaping the tip by rounding or removing the corner between the bore of the tubing and face of the tubing, or reducing the wall thickness at the tip by removing material from the interior or exterior surfaces, can facilitate initial insertion of the tapered fitting nose and the self flaring. Also, several annular exterior grooves may be utilized with several axially spaced groove engaging members to accomplish the gripping of the tubing by the nut. Such multiple grooves would facilitate utilizing grooves of lesser depth for providing the same axial compression of the tubing by the nut. In addition, warming the tip of the tubing to temporarily reduce its tensile strength and facilitate the flaring deformation when and as the fitting is assembled is also contemplated. 
     In certain applications different portions of the fitting body may be formed from differing materials and combined by simple assembly or in some configurations overmolding may be appropriate. See U.S. Pat. No. 5,837,180 assigned to owner of this application, and hereby incorporated by reference. 
     The present invention may be embodied in other specific forms without departing from the spirit of the essential attributes thereof; therefore, the illustrated embodiments should be considered in all respects as illustrative and not restrictive, reference being made to the appended claims rather than to the foregoing description to indicate the scope of the invention.