Positive seal coupling system

Abstract

A hollow coupling for joining together two pipe ends and having a center, two coupling ends, and an inner profile. The inner profile can include a serrated section having a plurality of threads extending radially around the inner diameter of the coupling, a curved section proximate the serrated section and defining a recess for the deposition of debris and other material during installation of a pipe into the coupling, a smooth section adjacent an end of the coupling and having a diameter slightly less than the outside diameter of a pipe to be inserted into the coupling, and a transition section between the curved section and the smooth section, the transition section having a smooth, rounded profile that minimizes stress concentrations.

What is claimed is: 
     
         1 . A hollow coupling for joining together two pipe ends and having a center, two coupling ends, and an inner profile, the inner profile comprising:
 a serrated section having a plurality of threads extending radially around the inner diameter of the coupling;   a curved section proximate the serrated section and defining a recess for the deposition of debris and other material during installation of a pipe into the coupling;   a smooth section adjacent an end of the coupling and having a diameter slightly less than the outside diameter of a pipe to be inserted into the coupling; and   a transition section between the curved section and the smooth section, the transition section having a smooth, rounded profile that minimizes stress concentrations.   
     
     
         2 . The hollow coupling of  claim 1 , the inner profile further comprising;
 a center section at the center of the coupling proximate the serrated section and having a smooth profile surface.   
     
     
         3 . The hollow coupling of  claim 1 , wherein the threads are inwardly directed toward the center of the coupling. 
     
     
         4 . The hollow coupling of  claim 1 , wherein the threads axe discrete circumferential threads that act as redundant metal to metal seals against a pipe end inserted into the coupling. 
     
     
         5 . The hollow coupling of  claim 4 , wherein at least a portion of the threads are helical threads that penetrate the outer surface of a pipe end inserted into the coupling to create mechanical resistance against separation of the coupling and the pipe. 
     
     
         6 . The hollow coupling of  claim 1 , wherein the inner profile further comprises:
 a pipe end receiving section between the end of the coupling and the smooth section, the diameter of the pipe end receiving section tapered from a diameter larger than the outer diameter of the pipe ends to the diameter of the smooth section.   
     
     
         7 . A hollow coupling for joining together two pipe ends and having an inner profile, the inner profile comprising:
 a plurality of serrations extending over at least a portion of the inner profile;   a first end serration bounding the plurality of serrations at a first end, and providing a transition from a smooth outer surfaces of the inner profile to the serrations; and   a second end serration bounding the plurality of serrations at a second end, and providing a transition from the serrations to a smooth central surface of the inner profile;   the first end serration having a first radius and a second radius, the first radius originating at the smooth surface and curving inwardly toward the axis of the coupling, and the second radius originating from the first radius, and curving away from the axis of the coupling toward the plurality of serrations; and   the second end serration having a first radius and a second radius, the first radius originating at the plurality of serrations and curving away from the axis of the coupling, and the second radius originating from the first radius and curving inwardly toward the axis of the coupling toward the smooth central surface of the profile;   the first and second radii of the first and second end serrations having rounded profiles that reduce stress concentrations in the coupling.   
     
     
         8 . The hollow coupling of  claim 7 , wherein the plurality of serrations are inwardly facing toward a center of the coupling. 
     
     
         9 . The hollow coupling of  claim 7 , wherein a portion of the serrations are helical serrations, and a portion of the serrations are circumferential serrations. 
     
     
         10 . The hollow coupling of  claim 7 , wherein all of the serrations are circumferential serrations. 
     
     
         11 . The hollow coupling of  claim 7 , wherein the plurality of serrations each has a tip that extends inwardly toward the longitudinal axis of the coupling a sufficient distance to engage the pipe ends and create mechanical resistance against the separation of the pipe ends from the coupling. 
     
     
         12 . The hollow coupling of  claim 7 , wherein the first and second radii of the first end serration are about 0.75 inches and about 0.25 inches respectively. 
     
     
         13 . The hollow coupling of  claim 7 , wherein the first and second radii of the second end serration are about 1.5 and about 0.5 inches respectively. 
     
     
         14 . A coupling for joining together pipe ends and having a first side with a first end and a second side with a second end, the coupling having an inner profile comprising:
 first and second serrated sections proximate the center section on the first and second sides of the coupling respectively, the first and second serrated sections having a plurality of threads extending radially around the inner diameter of the coupling;   first and second curved sections proximate the first and second serrated sections respectively, each of the first and second curved sections defining a recess for the deposition of debris and other material during installation of the pipe ends into the coupling;   first and second smooth sections adjacent first and second ends of the coupling, the first and second smooth sections having a diameter slightly less than the outside diameter of the pipe ends to be inserted into the coupling; and   first and second transition sections between the first and second curved sections and the first and second smooth sections respectively, each of the first and second transition sections having a smooth, rounded profile that minimizes stress concentrations.   
     
     
         15 . The hollow coupling of  claim 14 , wherein the inner profile further comprises:
 a center section at the center of the coupling proximate the first and second serrated sections, the center section having a smooth profile surface.   
     
     
         16 . The hollow coupling of  claim 14 , wherein the threads of the first and second serrated sections are discrete circumferential threads that act as redundant metal to metal seals against the pipe ends inserted into the coupling. 
     
     
         17 . The hollow coupling of  claim 16 , wherein at least a portion of the threads of the first and second serrated sections are helical, and penetrate the outer surface of the pipe end inserted into the coupling to create mechanical resistance against separation of the coupling and the pipe. 
     
     
         18 . The hollow coupling of  claim 14 , wherein the threads of the first and second serrated sections are inwardly facing toward a center of the coupling. 
     
     
         19 . The hollow coupling of  claim 15 , further comprising:
 an annular gasket positioned at the center of the coupling for preventing direct contact between the pipe ends when inserted into the coupling, and for forming a redundant seal between the coupling and the pipe ends.   
     
     
         20 . The hollow coupling of  claim 14 , wherein the inner profile further comprises:
 first and second pipe end receiving sections between the first and second ends of the coupling and the first and second smooth sections respectively, the diameter of the first and second pipe end receiving sections tapered from a diameter larger than the outer diameter of the pipe ends at the first and second ends of the coupling to the diameter of the first and second smooth sections.