Abstract:
A pipe fitting in the form of a male coupler and a female coupler both of which have imbedded therein a threaded metallic insert. Both the male coupler and female coupler have a metallic insert that is constructed to define a treacherous path at the surface boundary of the metal insert so as to minimize the possibility of any leakage exteriorly of the coupler from a liquid conducting bore passing through each of the couplers.

Description:
BACKGROUND OF THE INVENTION 
     1) Field of the Invention 
     The field of this invention relates to pipe fittings and more particularly to an interconnecting male coupler and female coupler which are to be connected together in a liquid tight manner between a pair of pipe sections which are slightly axially spaced apart. 
     2) Description of the Prior Art 
     The use of pipe fittings for connecting together a pair of axially spaced apart pipe sections has long been known. In the laying of any liquid conducting pipe, generally the pipe sections come in prescribed lengths, such as twenty feet in length or any other custom required length. When laying of a length of pipe greater or lesser than standard available length, there is therefore required pipe fittings to connect together the joined pipe sections in a liquid tight manner. Normally, for reasons of economics, plastic pipe is being used with greater frequency as opposed to metallic pipe. Plastic pipe has the advantage that it does not rust as does metallic pipe. However, plastic pipe also has the disadvantage in that it is not as strong as metallic pipe and especially in the area of the fittings that interconnect the different sections of pipe, it is difficult to apply a sufficient amount of compressive force in connecting together of the couplers of the fitting in order to achieve a long lasting liquid tight connection. 
     In the past, in order to design a stronger plastic fitting or coupling, it has been common to incorporate one or more metallic members within the fitting that are to be used to establish a high degree of compression in forming of the fitting. Plastic fittings alone have been proved incapable of being torqued sufficiently to produce a leak proof fitting for a long period of time owing to its lesser strength compared to metals. Even after the incorporation of the metallic member, the fundamental problem of a liquid leak proof joint remained to be solved due to the formation of a gap at the surface of metal and plastic interface due to inherent property of plastic to shrink after injection molding. Sometimes this gap formation also occurs during over tightening of the fitting resulting in exterior leaks over a period of time. Inserting bigger sizes of metallic inserts and threading the entire length of metallic inserts, exteriorly or interiorly also adds to the cost which is finally to be borne by end users. Some of these prior art types of fittings require the use of several different parts which requires an assembly procedure of the fitting prior to interconnecting of the male coupler and female coupler of the fitting. 
     If the fitting is constructed totally of plastic, it has been discovered that a totally plastic male coupler and female coupler, when engaged, cannot be tightened sufficiently due to their inherent lesser compression strength than metal fittings to establish sufficient compression that will produce a long lasting liquid tight relationship between a pair of pipe sections. 
     SUMMARY OF THE INVENTION 
     The injection molding of a female coupler and a male coupler with each coupler being imbedded with a metallic insert. Each metallic insert includes a series of threads with these threads to be located at the position to be first engaged when interconnecting the male coupler and the female coupler. The first series of threads in any series of threads are the threads that are subjected to possible damage during engagement and also are subject to damage by an exterior object prior to engagement. Therefore, if these threads could be constructed of metal rather than plastic, the resulting pipe fitting is substantially improved because metal threads are stronger than plastic threads and therefore are damaged less. Each of the metallic inserts establish a boundary or interface with the plastic with this boundary communicating with a fluid conducting bore through the fitting. Inherently, this boundary is subjected to liquid being conducted along the boundary and eventually exiting at an exterior surface of the fitting. In order to minimize this possibility of leakage along this boundary, the metal insert is constructed to include at least one notch, protrusion and groove so as to provide a treacherous path for the leakage thereby minimizing the possibility of leakage. The notch, groove and protrusion also function to provide a tight interconnection between the plastic and the metal to keep the plastic bound tight against the metal. Inherently, after the injection molding process, there is a natural tendency for plastic to shrink and therefore produce a minute gap in the contact area between the plastic and the metal insert. The notch, protrusion and groove facilitate tight interconnection between the plastic surface and the metal surface to minimize the creation of any gap. 
     One of the primary objectives of the present invention is to create a pipe fitting which produces a leak-proof connection between the male coupler and the female coupler of the pipe fitting. 
     Another objective of the present invention is to construct a pipe fitting which is constructed mainly of plastic that utilizes imbedded metal inserts which are positioned at locations of high degree of wear so as to produce not only a long lasting leak-proof pipe fitting but also a pipe fitting to which a greater than normal degree of compression can be applied than if the pipe fitting were constructed solely of plastic. 
     Another objective of the present invention is to construct a pipe fitting which can be manufactured at a cost relatively less expensive than conventional metallic pipe fittings and thereby sold to the ultimate consumer at a relatively inexpensive cost. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an isometric view, partly in cross-section, of the male coupler utilized in conjunction with the pipe fitting of the present invention; 
     FIG. 2 is an isometric view, partly in cross-section, of the female coupler utilized in conjunction with the pipe fitting of the present invention; and 
     FIG. 3 is longitudinal cross-sectional view through an interconnected male coupler and female coupler of the pipe fitting of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring particularly to the drawings, there is shown in FIG. 1 the male coupling  10  of the pipe fitting  12  of the present invention. The pipe fitting  12  is shown in FIG.  3 . The pipe fitting  12  also includes a female coupling  14  which is also shown in the isometric view in FIG.  2 . 
     The male coupling  10  has an annular shaped plastic body  16  with a through bore  18  being centrally formed through the plastic body  16 . The through bore  18  includes an enlarged rear section  20  which forms an annular flange  22  in its connection with the through bore  18 . A pipe section  24  is to be inserted within the enlarged rear section  20  with the forward end of the pipe section  24  to abut against the annular flange  22 . The pipe section  24  is to be fixedly secured to connector  26  which is integral with the body  16 . The threads  28  formed on the exterior surface of the connector  26  are to be used to be connectable to a separate connector fitting, which is not shown, which will function to secure the pipe section  24  to the connector  26 . It is to be understood that the pipe section  24  will be plastic. 
     The male coupling  10  is to be formed by the injection molding process. A metal insert  30  is imbedded within the plastic body  16  with the metal insert  30  actually inserted within the injection molding machine prior to the injection molding of the plastic body  16 . The metal insert  30  has a through bore  32  which is to be aligned with the through bore  18  and also to be of the same diameter as the bore  18 . The metal insert  30  includes a forward threaded end  34  which includes a short series (approximately three in number) of external threads  36 . The plastic body  16  also includes a series (approximately six in number) of external threads  38 . The threads  38  are in alignment with the threads  36  and there is actually a joint  40  formed between the plastic thread on the plastic body  16  and the metal thread on the metal insert  30  at the external of a boundary  42  which comprises the interface between the plastic body  16  and the metal insert  30  with it being understood that this boundary  42  is imbedded within the plastic body  16 . The boundary  42  forms an annular joint  66  that connects with the through bore that is formed by through bores  18  and  32 . The portion of the plastic body  16  that contains the threads  38  is mounted above an enlarged annular portion  44  of the metal insert  30 . From the annular portion  44 , the metal insert  30  forms a plateau section  46  within which is formed an annular groove  48 . The metal insert  30  terminates at an end  50  which extends at a right angle from the plateau section  46 . The end  50  includes a thin annular protrusion  52  which helps to define an inner annular groove  54 . The inner annular groove  54  terminates at an annular ledge  56  which has a chamfered edge  58  which then connects to the enlarged annular portion  44  which forms inside surface of the metal insert  30  that defines the internal through bore  32 . This inside surface of the internal through bore  32  terminates in a chamfered edge  60  which then connects to the outer end  62  of the metal insert  30 . The enlarged annular portion  44  includes an annular notch  64 . This annular notch  64  is located in close proximity to the joint  40 . One of the purposes of the annular notch  64  is to attempt to keep the plastic body  16  into tight connection with the metal insert  30  at the joint  40 . There is a tendency for plastic  16  to slightly shrink after the injection molding process. One of the functions of the notch  64  is to keep the plastic body in tight contact with the metal insert  30  hoping to eliminate or make minimal gap if any at the joint  40 . 
     It is to be understood that liquid is to be conducted through the internal passage  68  of the pipe section  24  and through the through bores  18  and  32 . This means that the liquid will come into contact with the joint  66  and possibly, owing to the inherent tendency for the liquid to creep along the boundary, if given enough time, the liquid can eventually be conducted past the chamfered edge  58 , past annular ledge  56 , through the inner annular groove  54 , past the annular protrusion  52 , across the plateau section  46 , through annular groove  48 , across annular ridge  70  to the enlarged annular groove  44  and possibly across the annular notch  64  to the joint  40 . It is deemed to be exceedingly unlikely that any liquid will eventually end up at joint  40 . But even if it does, the joint  40  will be under compression as the joint  40  is between the threads  36  and  38  and will be secured to an appropriate threaded area of the female coupling  14  and therefore under compression. Normally, there would be a pipe thread tape that will be wound continuously around the threads  36  and  38  in forming the connection with the female coupling  14  which further aids in eliminating the possibility of any leakage from the joint  40 . 
     It can thus be seen that the overall path of any leakage of liquid from joint  66  to joint  40  comprises an exceedingly treacherous path formed by the numerous contortions of the series of notches and grooves on the metal insert  30 . Additionally, it is to be noted that the threads  36  are located outside of the threads  38 . It is the threads  36  that are initially engaged with the threads  38  then being subsequently engaged. The threads  36  are subject to a greater amount of wear than the threads  38 . Also, prior to engagement of the male coupling  10 , it is the threads  36  that are most likely to incur damage by an exterior structure. The fact that the threads  36  are metal, and therefore are of a harder material than the threads  38 , the threads  36  are therefore least likely to be damaged. 
     Referring particularly to FIGS. 2 and 3 of the drawings, the female coupling  14  includes a plastic body  72  which has a through bore  74 . The through bore  74  has an enlarged rear section  76 . Between the rear section  76  and the through bore  74  is an annular flange  78 . A pipe section  80  is to be mounted within the rear section  76  with the forward end of the pipe section  80  abutting against the annular flange  78 . The pipe section  80  has an internal passage  82  through which liquid is to flow. Liquid is to flow between the internal passage  82 , the internal through bore  32 , the through bore  18 , and into the internal passage  68 . The rear section  76  is formed within the plastic body of a connector  84  which is integral with the plastic body  72 . The threads  86  are to be usable in a manner similar to the usage of the threads  28  in order to securely fix in position the pipe section  80  in conjunction with the connector  84  in a liquid-tight manner. 
     Imbedded within the plastic body  72  is a metal insert  88 . Metal insert  88  has a forward threaded end  92  which has a series (approximately three in number) of internal threads  94 . The plastic body  72  also includes a series of internal threads  96 . The metal insert  88  has a boundary or interface in conjunction with the plastic body  72  which forms a joint  98  between the threads  94  and  96 . From the joint  98 , the interface is formed into an extended annular portion  100  within which is located an annular notch  102 . The extended annular portion  100  then terminates at a thin annular protrusion  104  of an end  106 . The end  106  is then formed into a plateau section  108  which located at a right angle to the end  106 . Within the plateau section  108  is an annular groove  110 . The annular groove  110  connects with an annular ridge  112 . The annular ridge  112  then connects with forward threaded  92  forming a joint  114  at the forward end  116  of the female coupling  14 . 
     One of the functions of the notch  102  is that after the injection molding process, shrinking tends to occur of the plastic body  72 . The presence of the notch  102  in close proximity to joint  98  will hopefully keep the joint  98  tight. Actually, the annular groove  110 , notch  102  and annular ridge  112  is to increase the grip between the plastic body  72  and metal insert  88  and to prevent any gap due to shrinkage of plastic after injection molding. Groove  110  provides additional space where the plastic can flow during injection molding thereby providing extra bonding between plastic and metal causing increased overall strength of the female coupler  14 . This extra bonding will also prevent the slippage between plastic body  72  and inserted metal insert  88  during tightening of the fitting  12 . Annular groove  48 , annular notch  64  and annular ridge  70  provided on metal insert  30  has two purposes: first to make the leakage path longer and second to increase the grip between and plastic body and metal insert. Any liquid passing through the bores  82 ,  74 ,  32 ,  18  and  68  in either direction is unlikely to come in contact with joint  98  as female threads of female coupling will be covered by male threads of male coupling and will be under compression. Since the liquid film cannot enter at joint  98 , there is no possibility for creeping of liquid film past notch  102 , through extended annular portion  100 , across annular extension  104 , past plateau  108  and finally through the joint  114  to be disposed of in the ambient exteriorly of forward end  116 . 
     It is again to be noted that the forward threaded end  92  comprises the first series of threads that are to be engaged relative to the female coupler  14 . Again, the threads of the forward threaded end  92  are the threads that are most likely to be damaged prior to engagement. Also, when the male coupler  10  is engaged with the female coupler  14 , the compressive force is divided between forward threaded ends  34  and  92  of male coupler  10  and female coupler  14  respectively. 
     Referring particularly to FIG. 3 of the drawings, it can be readily observed that the connection of the female coupler  14  and the male coupler  10  is to produce the pipe fitting  12  of this invention. Part of the external threads  38  lockingly engage with internal threads  94  and external threads  36  lockingly engage with part of the internal threads  96 .