Abstract:
A system and method for electrically isolating conduit connections in a gas line system for residential, commercial or industrial applications. Gas line conduit of standard configuration is cut to length and upset at one end to create an annular flange of increased diameter, which then is machined to a desired configuration having annular ridges and flat and tapered surfaces. The other end of the conduit is machined in a standard thread configuration. The flanged portion of the conduit is then placed in an injection molding machine and receives a non-conductive elastomeric, molded seal thereover which includes a tubular pilot portion. A coupling nut slipped over the conduit may then join the conduit to conventional gas line valves, meters or the like in a completely electrically insulated connection.

Description:
This application claims benefit of provisional No. 60/127,077 filed Mar. 31, 1999. 
    
    
     TECHNICAL FIELD 
     The present invention relates to gas line conduit systems and more particularly to an electrically insulated system which includes an integral union pipe as part of the system, which pipe is electrically insulated at one end for preventing the flow of electricity through the conduit to an earth ground. The invention further relates to the method of manufacture of such system. 
     DISCUSSION OF THE PRIOR ART 
     Gas lines of the type addressed by the teachings of this invention are well known as systems for bringing gas under pressure from underground delivery pipes into an establishment such as a residence or commercial structure, for utilization therein. For purposes of this specification “gas line” is intended to mean any conduit, pipe or similar-type enclosed passageway used to transfer gas under pressure. The gas may be used for any purpose, but most often is used for supplying heating energy, and it is common to utilize natural gas for this purpose. 
     The main gas line is generally buried underground, being brought in from the street or from any other source of supply. It often includes some form of metallic conduit which is capable of conducting electrical current. Once brought into the building, interior piping is utilized to plumb a system. The system might typically comprise a shutoff valve, pressure regulator, gas meter near the point of entry, and further conduits for delivering the gas to the various utilization devices. 
     Undesired electrical current may be generated in these supply systems from a variety of sources, such as for example, the flow of gas itself, which creates distributed electrical potentials. Electrical currents may also result from improper or defective wiring, and the like. Such current may then be transmitted through the interior conduits to the exterior underground line and create an undesirable condition. Such electrical discharges into the earth can create erosion of the supply line and its consequent failure prior to its otherwise predicted lifetime. 
     In the past, insulating fittings such as swivels and unions have been utilized that can be included in gas lines to provide an insulated connection between pipes that carry the combustible gas. Most often, these comprise a threaded coupling which has a union connection at one end which is covered or encapsulated in some manner with nonconductive material to interrupt the metal to metal connection and prevent the flow of electricity. While solving the electrical problem, such devices introduce another threaded joint into the system. Such a joint presents a potential leakage problem due to faulty installation, or more likely due to environmental conditions such as vibration, corrosion or damage by external forces. 
     Another form of insulated gas line conduit is shown in U.S. Pat. No. 5,588,682 in which a length of conduit may be provided with a threaded connection at one end and a flange at the other forming a flange for connection as a union with mating components. The flanged end of the conduit is covered with non-conductive material and serves to isolate the components to prevent conduction of electricity. In this arrangement, a pilot portion is formed at the end of the conduit to guide the conduit in its mating connection with the spud of a component to be connected. A relatively thin layer of non-conducting material thus covers the end of the conduit at the location where the prevention of conduction of electricity is desired. 
     Thus it may be seen that a need exists for a relatively inexpensive, reliable insulating coupling system for metal gas lines, which is not only easy to use and install, but also avoids unwanted electrical conduction and additional threaded connections. 
     SUMMARY OF THE INVENTION 
     The preferred exemplary coupling device and system of the present invention comprises an enclosed metal passageway suitable for transporting a pressurized gas. The passageway carries the gas to or from a gas meter. The system preferably comprises a conduit having a desired preformed configuration and having at one end portion a flange. An insulating resilient seal layer which is preferably a molded nylon piece, covers the flange end portion of the conduit, thereby electrically insulating the flange end portion. The system further has a threaded ring nut which can be moved over the conduit to engage the flange and further engage a component such as a shut off valve, which has a mating, flange-receiving, connector thereon. 
     In use, a threaded nipple, spud or other mating connector of a device having an outer thread is aligned with and pressed against the insulating resilient seal carried on the flanged end of the coupling. A ring nut is then moved over the conduit toward the spud until the open, threaded portion of the ring nut which extends beyond the flange, can be turned to engage the internal threads of the ring nut with the threads of the spud. As the nut is screwed onto the spud, the nut compresses the seal, and holds the flange and spud together, thereby tightly connecting and sealing the conduit to the spud. Thus the seal may act as both an insulator and a seal. 
     In the preferred embodiment of the invention, the gas carrying conduit which is to be insulated is a pipe nipple having a thread at one end and an enlarged flange at the other. The flange is machined into a preferred configuration and then encapsulated in an injection molding machine to provide an electrical non-conductive seal thereover. The seal is also of a predetermined configuration and includes not only a sealing portion of substantial thickness, but also an integral pilot portion. The pilot is a tubular extension of the seal beyond the flange on the nipple, and serves to center and guide the nipple and flange toward the sealing surface of the spud, by entering the bore of the spud upon makeup of the connection. 
     A ring nut which is placed over the nipple and slid along the length thereof into engagement with the flange, serves to complete the connection. Interior threads in the nut engage exterior threads of the spud and upon tightening, draw the pilot into the bore, and the flange toward the spud until a sealing engagement is effected. The arrangement of the flange and seal thereby provides surfaces which are engaged by the nut and which contact the spud to provide a non-metallic connection and thus insulation against the flow of electricity. 
     Preferably the flange at the end of the nipple is cold formed into an enlarged flange which is then suited for formation of specific surfaces for retention of the seal, for mechanical retention of the nipple with a mating component, and for the formation of a transverse annular sealing surface, which then serves as a union connection in the makeup of an entire conduit system. After cold forming, the flange is machined to a configuration comprising an inner annular ridge and an outer annular ridge, the two being joined by a central cylindrical section and a tapered or conical section. The central cylindrical section further includes a small intermediate ridge located near the inner ridge. 
     The outer ridge is machined to a diameter to substantially match the mating surface of a component to be joined, and has a flat, transverse face surrounding the bore of the nipple. Extending inwardly from the outer ridge is the conical section, joining the central cylindrical section at a diameter less than the diameter of the outer ridge. The central section extends inwardly to the inner ridge, the latter having a diameter greater than the central section and less than the outer ridge, and which serves as a limit for the seal material which will encapsulate the remainder of the outer flange. The intermediate ridge serves to enhance the grip of the seal. 
     The seal is comprised preferably of an elastomeric material such as nylon, and is joined to the nipple preferably in an injection molding operation. As such the nipple is placed in the molding machine and material extruded over the flange section to completely cover the end of the nipple, externally from the inner flange outwardly over the outer ridge and internally inwardly of the inner ridge. The thickness of the seal is preferably such as to substantially conform to the diameter of the inner ridge and completely cover the conical section and the outer ridge including the transverse sealing face thereof and to form a substantially continuous inner bore for the flange. The seal further includes a tubular portion extending outwardly of the transverse face and integral therewith, forming a pilot to assist in the makeup of the connection. The pilot extends from the inner bore of the nipple axially outward only a short distance to provide a small axial projection and extends radially outward a similar short distance alongside the transverse face of the outer ridge of the flange. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a system with an insulating coupling therein in combination with a supply shutoff valve and other gas line related components, in accordance with the present invention. 
     FIG. 2 is a sectional view of the flange end of a conduit during the forming process, after the end has been cold-formed to shape. 
     FIG. 3 is a perspective view of the flange end of a conduit during the forming process, after the end has been machined to a predetermined configuration. 
     FIG. 4 is a sectional view of the flange end of a conduit after the end has been encapsulated with an elastomeric seal in an injection molding process. 
     FIG. 5 is a perspective view of the entire nipple of the invention with the elastomeric seal molded in place. 
     FIG. 6 is an enlarged partial sectional view of the nipple of FIG.  3 . 
     FIG. 7 is a partially sectioned perspective view of a part of the system of FIG. 1 showing the nipple and shutoff valve portion. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A preferred exemplary embodiment of the invention is shown in FIG.  1  and is generally indicated as  10 . The system  10  includes an inlet conduit  12 , a supply shut-off valve  14 , a nipple  15 , a regulator  16 , preformed conduits  17 ,  18  and a gas meter  20 . Nipple  15  and conduits  17 ,  18  are derived from standard metallic gas pipe and can be of any configuration, being bent as needed to suit the particular installation. In this exemplary embodiment nipple  15  is a straight length of conduit having threads  21  at one end and flange  22  at the other end. 
     The conduits are preferably derived from standard API-5L gas pipe which is a standard ¾ inch, 1 inch, 1¼ inch pipe or the like. In this description all dimensions will be referenced to standard  1  inch size pipe. 
     Regulator  16  includes an adapter coupling  24  thereon which directs gas flow therethrough and which may be threaded to nipple  15  and conduit  17  by standard threaded connections. Conduit  18  is joined to conduit  17  by weldment  25  to provide a rigid predetermined spacing therefrom, each of the conduits terminating in respective flanged couplings  27 ,  28  which are spaced to mate with conventional gas meter  20  and to be joined by the respective coupling nuts in a manner well understood in the art. Conduit  18  is described as a 90 degree bend conduit and delivers gas which has been routed through gas meter  20 , to the remainder of the gas system of the installation which might be a home residence or commercial establishment and may be of considerable length and with multiple branches of distribution. 
     All of the components described so far are essentially metallic components and as such are capable of conducting electrical current derived anywhere within the system to inlet conduit  12 , which typically is buried underground and susceptible to corrosion activity, concentrated by electrical discharge into the earth. Nipple  15  of the invention prevents such flow of electricity by the inclusion of a seal  30  at flange  22  which entirely prevents metal to metal contact, thereby interrupting the electrical circuit. Nipple  15  is secured to shut off valve  14  by a nut  31 , such as a metallic valve nut or ring nut, in a union type connection, but is completely isolated from valve  14  and nut  31  by a seal  30  as will be described in greater detail hereinafter. 
     Referring to FIG. 7 there is shown a portion of the system  10  of FIG. 1 in which nipple  15  is connected with shut-off valve  14  with valve nut  31  securing the flange  22  of nipple  15  through the intermediary of seal  30 . Valve  14  includes a boss or spud  32  at one end thereof having exterior threads  34  thereon and a transverse annular sealing face  35  adapted for sealing engagement with the transverse seal face of flange  22 , to be described in greater detail. Valve nut  31  includes mating interior threads and a retaining shoulder  38  inwardly of flange  22 , to draw nipple  15  into secure engagement with valve  14 . It will be apparent that due to the presence of seal  30  no metal to metal connection is established between nipple  15  and valve  14 , thereby preventing the flow of electricity between the components. 
     A method of manufacture of nipple  15  and specific characteristics thereof are described in more detail in FIGS. 2-6. It will be clear however, that nipple  15  is but one form of component that could be utilized according to the teachings of this invention to provide a location for seal  30 , and that similar seals could be established at other conduit connections or in connection with various other components of the system other than at shut-off valve  14 . 
     In FIG. 2 a first stage of manufacture of nipple  15  is depicted at which a length of standard conduit such as API-5L gas pipe is cut off and cold formed at one end to form flange  22  of radially increased diameter. Flange  22  is of generally cylindrical configuration and is preceded by a lead-in taper section  40  from the main body of nipple  15 . Flange  22  includes an outer annular ridge  42  having a seal supporting end face or transverse annular face  44  at the longitudinal outer end thereof surrounding the bore  39  of nipple  15 . A conical surface  45  tapers inwardly from outer ridge  42  to cylindrical upset section  46 , in turn being joined to taper section  40  at step  48 . The interior bore  41  of flange  22  is enlarged from bore  39  and is formed in a continuous contoured configuration to have an enlarged curved section  47 , a reduced curved section  49  and an enlarged spike section  52 , the latter adjacent the outward end of flange  22 . 
     After cold forming, flange  22  is further refined by machining to provide the preferred embodiment of flange  22  depicted in FIG.  3 . Here, upset section  46  is reconfigured to provide an inner annular ridge  50 , and an adjoining central cylindrical section  51 , the latter joining now-enlarged conical surface  45 , which in turn terminates in outer annular ridge  42 . Preferably, central cylindrical section  51  is machined to include an intermediate annular ridge  54  between ridges  42 ,  50  and is positioned closely adjacent to ridge  50 . Intermediate ridge  54  is of lesser radial dimension than ridge  50  and ridge  50  is of less radial dimensions than ridge  42 . An enlarged partial view of the outer machined portion of flange  22  is shown in FIG. 6 to more clearly depict the relative dimensions of the various components of flange  22 . The fully machined flange  22  is shown as well in FIG. 4 in a cross-sectional configuration. 
     As indicated, typical dimensions are related to a one inch size of standard pipe and as such result in an outer ridge  42  diameter of about 1.73 inch, a 45 degree angle to conical surface  45 , an inner ridge  50  diameter of about 1.57 inch and a further reduced central cylindrical section  51  diameter of about 1.50 inch. Central section  51  extends axially about 0.50 inch while inner and outer ridges  50 ,  42  extend about 0.125 inch. Intermediate ridge  54  extends about 0.020 inch radially from central section  51 , is about 0.020 inch in axial extent and spaced about 0.020 inch from inner ridge  50 . 
     An annular face groove  55  is provided in transverse face  44  of outer ridge  42  to enhance retention of seal  30 . Face groove  55  is on the order of 0.05 inch in radial width and axial depth, is concentric with nipple bore  39  and spaced about 0.09 inch radially inward of the outer surface of outer ridge  42 . 
     Upon completion of the machining, operation nipple  15  is placed in an injection molding machine for forming seal  30  in integral engagement with flange  22  thereof. Nipple  15  with seal  30  thereon is shown in a sectional view in FIG.  4  and in a perspective view in FIG. 5. A view of the assembled nipple  15  and shut-off valve  14  is provided in FIG. 7, as previously described. 
     As best seen in FIG. 4, seal  30  preferably entirely encloses or encapsulates flange  22  from inner ridge  50  on the exterior of flange  22 , over transverse face  44  and over the interior periphery of flange bore  41  to a location closely adjacent nipple bore  39 , axially inwardly of inner ridge  50 . Thus intermediate ridge  54  and cylindrical section  51  are covered by a cylindrical support section  56  of seal  30 , extending axially outwardly to conical retainer section  58  which generally overlies conical surface  45  of nipple  15 . Conical retainer section  58  extends radially and axially outwardly to join outer cylindrical seal flange  60  which generally overlies outer ridge  42  and extends axially beyond transverse face  44  to provide an end face abutting portion or transverse seal face  62 . Seal face  62  is annular and parallels transverse face  44  and terminates at its inner diameter in integral molded pilot  65  which is a tubular axial extension of seal  30  outwardly of seal face  62 . The inner portion of seal  30  is one integral generally tubular section  66  having an inner cylindrical periphery terminating at the end in pilot  65  and extending inwardly toward the inner bore  39  of nipple  15 , terminating at a junction  67  with the inner wall of taper section  40 . The outer periphery of tubular seal section  66  conforms with the inner surface of flange  22  and thus fills curved sections  47 ,  49  (see FIG. 2) as well as spike section  52 . Seal  30  also fills face groove  55  to provide additional stability against relative shifting movement between seal  30  and its support structure, flange  22 . 
     The diameter of support section  56  is approximately the same as that of inner ridge  50  on the order of 1.57 inch, while the outside diameter of outer flange  60  is about 1.85 inch. Outer seal flange  60  extends axially approximately 0.33 inch and pilot  65  extends axially about 0.09 inch from seal face  62 . Pilot  65  has an internal diameter of about 1.10 inch and an external diameter of about 1.24 inch, while the internal diameter (i.e., bore  39 ) of nipple  15  is about 1.05 inch. 
     In makeup of the connection between nipple  15  and valve  14 , as shown in FIG. 7, valve nut  31  is slid over the threaded end of the nipple  15  and brought into engagement with seal  30  on flange  22 . Valve nut  31  includes standard internal threads and a rearward shoulder  38 , being joined by internal conical section  68  having a bevel of 45° which engages the conical retainer section  58  of seal  30  (see FIGS.  4  and  5 ). Nipple  15  is thus drawn into tight engagement with spud  32  with seal face  62  in sealing engagement with the transverse face of spud  32 . In this arrangement, metal to metal contact between valve  14  and nipple  15  is precluded by the interposition of portions of seal  30  to provide electrical isolation in the system. Thus the seal  30  may act as both an insulator and a seal. 
     Thus the electrically insulated conduit and method of the present invention achieves the above stated objectives, eliminates difficulties encountered in the use of prior devices and systems, solves problems and attains the desirable results described herein. 
     In the foregoing description certain terms have been used for brevity, clarity and understanding, however no unnecessary limitations are to be implied therefrom because such terms are used for descriptive purposes and are intended to be broadly construed. Moreover, the descriptions and illustrations herein are by way of examples and the invention is not limited to the exact details shown and described. 
     In the following claims any feature described as a means for performing a function shall be construed as encompassing any means known to those skilled in the art to be capable of performing the recited function, and shall not be limited to the structures shown herein or mere equivalents thereof. 
     Having described the features, discoveries and principles of the invention, the manner in which it is constructed and operated, and the advantages and useful results attained; the new and useful structures, devices, elements, arrangements, parts, combinations, systems, equipment, operations and relationships are set forth in the appended claims.