Abstract:
A self-flaring fitting assembly for semi-flexible, convoluted tubes or pipes is provided. The inventive fitting assembly, which basically comprises an adaptor, a nut, and a split bushing assembly, eliminates the need for sealing gaskets, is reusable, and further facilitates the ease and speed of installation of semi-flexible piping systems. When used with jacketed tubing, the present inventive fitting assembly is capable of both preventing the undesirable movement of the jacket during installation and assembly and of reducing or eliminating exposure of the tubing located within the fitting assembly to contaminants or corrosive materials found in the surrounding environment.

Description:
RELATED APPLICATION 
     This application is based in part on Provisional Patent Application Ser. No. 60/057,557, filed Aug. 29, 1997. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to fittings for semi-flexible pipes or tubing and, more particularly relates to a self-flaring and self-aligning fitting or fitting assembly that is suitable for use with convoluted metal or plastic tubing. This invention further relates to hose assemblies that employ such fittings. 
     BACKGROUND OF THE INVENTION 
     In 1983, a research and development effort relating to interior fuel gas piping systems was undertaken by the Gas Research Institute (GRI). The objective of this research and development effort was to identify and develop novel piping systems and materials that could serve as viable alternatives to conventional rigid black iron piping systems. 
     As a result of this effort, a piping system was developed that used semi-flexible, convoluted stainless steel tubing (CSST) in combination with elevated gas pressures of up to about 0.03 megapascals (MPa). This piping system offered marked advantages over rigid black iron piping systems. Included among these advantages were ease and speed of installation, elimination of the need for precise and time-consuming onsite measuring, cutting and threading of piping sections, and reduction of the need for certain fittings such as elbows, tees and couplings. One disadvantage that has been identified is increased flow resistance imposed by the tubing convolutions and by smaller internal diameters. This disadvantage has resulted in a requirement for higher system pressures and additional gas pressure regulators upstream of equipment requiring lower gas supply pressures. 
     Fittings that are conventionally used with CSST fuel gas piping, systems require the use of fiber sealing gaskets or the pre-flaring of the ends of the tubing. Fittings that require the use of fiber sealing gaskets are not completely reusable due to the fact that the gasket, which is mechanically compressed between (and possibly adhered to) the tubing and other fitting components, must be replaced. More importantly, the use of such fiber sealing gaskets is problematic in that such gaskets undergo gradual deterioration over time which compromises the integrity of the gas tight seal effected by such fittings. 
     One such prior art fitting is a fitting manufactured and sold by Ward Manufacturing, Blossburg, Pa., under the trade designation WARDFLEX™. The WARDFLEX™ fitting, which is later described in detail, obviates the need for pre-flaring the ends of the tubing and is self-aligning to the extent that it aligns the tubing within the bore of an adaptor. However, the WARDFLEX™ fitting relies upon a fiber gasket to effect a gas tight seal and is not completely reusable. Moreover, this fitting does not serve to prevent the undesirable movement of the tubing jacket during installation and assembly nor does it serve to reduce or eliminate exposure of the tubing located within the fitting to contaminants or corrosive materials found in the surrounding environment. 
     One improvement over this prior art fitting is a fitting manufactured and sold by Mestek, Inc., Westfield, Mass., under the trade designation AUTOFLARE™. The AUTOFLARE™ fitting is self-flaring and comprises: an adaptor, a steel collar inserted in the adaptor for alignment purposes, a nut and a brass split ring. Although the AUTOFLARE™ fitting does not employ a fiber sealing gasket it requires the use of a relatively small and hard to manipulate split ring that adversely impacts upon the ease of assembly. Moreover, this fitting also does not serve to prevent the undesirable movement of the tubing jacket during installation and assembly. In addition, it does not serve to reduce or eliminate exposure of the tubing located within the fitting to contaminants or corrosive materials found in the surrounding environment. 
     It is therefore an object of the present invention to provide a reusable fitting assembly that further facilitates the ease and speed of installation of semi-flexible piping systems. 
     It is a more particular object to provide a self-aligning and self-flaring fitting assembly that eliminates the need for sealing gaskets and that, when used with jacketed tubing, is capable of both preventing the undesirable movement of the jacket during installation and assembly and of reducing or eliminating exposure of the tubing located within the fitting assembly to contaminants or corrosive materials found in the surrounding environment. 
     It is a further object of the present invention to provide a hose assembly that employs such a fitting assembly. 
     SUMMARY OF THE INVENTION 
     In accordance with these objects, the present invention provides: 
     a self-aligning and self-flaring fitting assembly for semi-flexible, convoluted pipes, which comprises: 
     an adaptor having a pipe receiving bore, which comprises: a first section having a diameter; a second section having a reduced diameter; and an internal stop shoulder intermediate thereto which prevents the pipe from passing completely through the adaptor; 
     a nut having a pipe receiving bore and a stop shoulder; 
     adjustable interengaging means on the nut and on the first section of the adaptor for moving the nut in threaded engagement towards the adaptor; and 
     a spilt bushing assembly having a bore and comprising: at least two alignable and substantially arcuate bushing sections that, when assembled together, define an opening; at least two spaced internal ribs that serve to lock the bushing sections in place on an end of a convoluted pipe; a first end which is engageable with the internal stop shoulder of the adaptor; and a second end which is engageable with the stop shoulder of the nut; 
     wherein, when the bushing sections of the split bushing assembly are assembled on an end of a convoluted tube or pipe that has been inserted through the nut, such that the internal ribs of the split bushing assembly engage circumferential grooves on the convoluted pipe, and when the convoluted pipe end with the bushing sections assembled thereon is inserted into the first section of the adaptor and the nut moved in threaded engagement towards the adaptor, a first convolution on the end of the convoluted pipe is compressed between the internal stop shoulder of the adaptor and the first end of the split bushing assembly in a flared configuration while each internal rib of the split bushing assembly sealably contacts a circumferential groove on the convoluted pipe. 
     The present invention also provides a hose assembly that employs the inventive fitting assembly. 
     The foregoing and other features and advantages of the present invention will become more apparent from the following description and accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a cross-sectional view of a prior art convoluted pipe fitting manufactured and sold Ward by Manufacturing, Blossburg, Pa., under the trade designation WARDFLEX™; 
     FIG. 2 is a cross-sectional view of a partially assembled fitting assembly constructed in accordance with a preferred embodiment of the present invention; 
     FIG  3  is a cross-sectional view of the fitting assembly of FIG. 2 that has been fully assembled; and 
     FIG. 4 is a cross-sectional view of another preferred embodiment of the present invention that employs a termination fitting. 
     FIG. 5 is a cross-sectional view of a fully assembled fitting assembly positioned on a jacketed, reinforced convoluted tube in accordance with a preferred embodiment of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The present inventive pipe fitting assembly will be described hereinbelow mainly in association with interior fuel gas piping systems. However, the invention is not so limited. The inventive pipe fitting assembly can also be used for any convoluted hose application including, but not limited to, those applications dedicated to the transfer of chemicals, liquid petroleum, water and steam. 
     Moreover, although the inventive fitting assembly is described hereinbelow mainly in conjunction with convoluted stainless steel tubing or CSST, any type of semi-flexible tubing that can accommodate a wide variety of corrosive or aggressive fluids is envisioned, including, but not limited to, semi-flexible tubing made from thermoplastic, metal or metal alloy materials such as olefin-based plastics (e.g., polyethylene (PE)), fluorocarbon polymers (e.g., polytetrafluoroethylene (PTFE)), carbon steel, copper, brass, aluminum, titanium and nickel alloys. 
     Specific reference is now made to FIG. 1, which depicts a prior art fitting, marketed under the trade designation WARDFLEX™, which is shown generally at  100 . The WARDFLEX™ fitting  100  is used in conjunction with jacketed, convoluted tubing  102  and is basically comprised of: an adaptor  104 ; a nut  106 ; adjustable interengaging means  108  on the nut  106  and on the adaptor  104 ; a split retainer  110 ; and a fiber sealing gasket  112 . The adaptor  104  has a pipe receiving bore  114  and a first section  116  and a second “reduced diameter” section  118  separated by a perpendicular stop shoulder  120 . The nut  106  has a pipe receiving bore  122  and a “reduced diameter” first end  124 , while the split retainer  110  has a bore  126 , two opposing arcuate sections  128   a, b  (not shown); three contiguous internal ribs  130   a, b, c;  and a first end  132  that is engageable with the “reduced diameter” first end  124  of the nut  106 . 
     When assembling the WARDFLEX™ fitting  100  on the jacketed tubing  102 , the jacket is first cut back from the end so as to expose at least seven convolutions on tubing  102 . The exposed end is then fed through the nut  106  and the split retainer  110  positioned thereon three convolutions back from the end. In particular, the internal ribs  130   a, b, c  of split retainer  110  each fit against and conform to circumferential grooves located between convolutions  134   a, b, c, d  of the jacketed tubing  102 . The fiber sealing gasket  112  is then fixed in position against the stop shoulder  120  of adaptor  104  and the nut  106  moved in threaded engagement toward the adaptor  104 . As the nut  106  moves toward the adaptor  104 , the three convolutions located between the split retainer  110  and the gasket  112  become compressed and thereby assumably form a gas tight seal. In the resulting fitting assembly, the jacket is not secured or locked in place by fitting  100  and the split retainer  110  is mechanically compressed only against the exposed end of tubing  102 . 
     As will be readily evident to those skilled in the art, non-metal, fiber gaskets must be handled carefully in order to avoid contamination and to prevent cutting or scoring the gaskets during assembly or damage resulting thereto from overtightening the fitting assembly. Moreover, fiber gaskets are adversely affected by weather, moisture and freeze/thaw cycles and therefore fitting assemblies that employ such fiber gaskets must be monitored to assure maintenance of gas tight seals. 
     Referring now to FIG. 2, a partially assembled fitting assembly constructed in accordance with a preferred embodiment of the present invention is shown generally at  10 . The inventive fitting assembly  10  is shown in conjunction with jacketed, convoluted tubing  12  and is basically comprised of: an adaptor  14  having a pipe receiving bore  16 , which comprises: a first section  18  having a diameter a; a second section  20  having a reduced diameter b; and a radially inwardly extending interior stop shoulder  22 ; a nut  24  having a bore  26  and a stop shoulder  28 ; adjustable interengaging means  30  on the nut  24  and on the first section  18  of the adaptor  14  for moving the nut  24  in threaded engagement toward the adaptor  14 ; and a split bushing assembly  32  having a bore  34 , which comprises: a pair of oppositely disposed, alignable, substantially arcuate and semi-circular bushing halves  36   a, b  (not shown) that when assembled together, define a circular opening; at least two spaced internal ribs  38   a, b  that serve to lock bushing halves  36   a, b  in place on an end of tubing  12 ; a first end  40  which is engageable with the radially inwardly extending internal stop shoulder  22  of the adaptor  14 ; and a second end  42  which is engageable with the stop shoulder  28  of the nut  24 . As will be readily apparent to those skilled in the art, internal ribs  38   a, b  are adapted to engage circumferential grooves on convoluted tubing  12 . Opposed bushing halves  36   a, b  engage the same grooves, which extend circumferentially around the tubing  12 . In this manner, the bushing halves  36   a, b  are substantially locked in place over the end of tubing  12 . 
     The second section  20  of adaptor  14  may adopt any configuration necessary to adapt it to the respective piping system. For example, second section  20  may adopt a step or normal “T”, 45° or 90° configuration. 
     Moreover, nut  24  may also be modified to adopt any necessary configuration. For example, and as best shown in FIG. 4, the nut  24  can be modified to accommodate a termination fitting  46 . In particular, nut  24  may further comprise a first section  48  capable of threadably engaging termination fitting  46 . 
     Contemplated materials for use in making adaptor  14 , nut  24 , and split bushing assembly  32  include thermoset resins such as phenolics, acrylics and epoxies, thermoplastic resins such as polyamides, styrenic polymers (e.g., ABS) and fluorocarbon polymers (e.g., PTFE), and metal and metal alloy materials such as carbon steel, copper, brass, aluminum, titanium, stainless steel and nickel alloy. In a preferred embodiment adaptor  14 , nut  24  and bushing assembly  32  are made of a brass alloy. The above-referenced components, namely—adaptor  14 , nut  24  and split bushing assembly  32  are available from Titeflex Corporation, 603 Hendee Street, Springfield, Mass. 01139-0054 under the product designation GASTITE® fitting assembly and having product part number XRFTG. 
     When assembling the inventive fitting assembly  10  on the jacketed tubing  12 , the tubing  12  is cut to a desired length allowing approximately 2.54 centimeters (cm) for the fitting assembly  10 . The tubing  12  is preferably cut in a circumferential groove or recessed area on convoluted tubing  12 . The jacket is then cut back or stripped from the end of the tubing  12  so as to expose two convolutions  44   a, b  thereon. The nut  24  is then slid over tubing  12  and the split bushing assembly  32  positioned on the end thereof such that rib  38   a  fits against and conforms to the recessed area located between convolutions  44   a  and  44   b  and rib  38   b  contacts the jacket on tubing  12  between convolutions  50   a  and  50   b.  As best shown in FIG. 3, the end of the tubing  12  having the split bushing assembly  32  positioned thereon is inserted into the first section  18  of adaptor  14 . The nut  24  is then moved in threaded engagement toward the adaptor  14  causing rib  38   a  to lock the jacket on tubing  12  between convolutions  50   a  and  50   b  thereby effecting a contaminant resistant seal while also causing convolution  44   a  to become compressed between the internal stop shoulder  22  of the adaptor  14  and the first end  40  of the split bushing assembly  32  resulting in a gas tight seal while adopting a flared configuration. By cutting the tubing  12  in a circumferential groove or recessed area, any rough edges or areas remaining on the metal as a result of cutting do not interfere with or adversely affect the gas tight seal that results from the assembly of the present inventive fitting  10 . In a more preferred embodiment, fitting assembly  10  employs at least one piloting or self-alignment means. Such piloting means include, but are not limited to, configuring the split bushing assembly  32  such that its outer diameter approximates diameter a of the first section  18  of adaptor  14 , thereby ensuring that tubing  12  is aligned properly within adaptor  14  for a uniform flare and a gas tight seal. In addition to the benefits described hereinabove, the design of inventive fitting assembly  10  obviates the need for special tools to assemble the fitting. Two wrenches, a utility knife and a standard tube cutter are the only tools necessary to assemble the fitting  10  on convoluted tubing  12  and to effect safe, gas-tight connections. During the tightening process only the nut  24  is rotated which serves to facilitate installations in confined spaces. Moreover, fitting,  10  relies upon a superior metal-to-metal seal and not upon fiber gaskets and their drawbacks. In addition, when fitting  10  is used in conjunction with jacketed, convoluted tubing, the split bushing assembly  32  serves to avoid unintended movement of the jacket (i.e., jacket “pull-back”) during installations in confined spaces and serves to reduce or eliminate exposure of the unjacketed end portion of the tubing  12  to contaminants found in the surrounding environment by sealing against the jacket on tubing  12 . 
     It should be understood by those skilled in the art that obvious modifications can be made to the present inventive fitting assembly  10  without departing from the spirit of the invention. For example and as shown in FIG. 5, modifications to fitting assembly  10  that are necessitated by the use of convoluted tubing in conjunction with reinforcing layers  52 , such as metal braid reinforcing layers, and optionally, protective jackets, such as polyvinyl chloride (PVC) or PE protective jackets, are considered to be within the scope of the present invention.