Joint restraint assembly
A joint restraint assembly for connecting pipe ends together, or to other objects, which includes a body encircling the pipe. The body has a plurality of cavities adjacent to the pipe with a segment configured to fit into each cavity. One or more threaded bores are disposed through the body into each cavity. A threaded bolt extends through each threaded bore to engage the segment in that cavity, and to pre-load the segment against the pipe when assembled thereon. Mechanical or pressure loading, tending to pull the pipe out of the restraint assembly, causes the segment to self actuate, and the application of increasing load causes a proportional increase to the force engaging the segment to the pipe. The joint restraint assembly reliably accommodates comparatively high levels of mechanical loading and/or pipe internal pressure, and does so without relying upon the limited force produced by the threaded bolt pre-load on the segments at the time of assembly.
1. A method for providing a joint restraint assembly with resistance to pipe pull-out in proportion to the mechanical and/or internal pressure loading applied to a pipe, said method comprising the steps of:
providing a body that encircles the pipe wherein the body has a plurality of cavities and at least one set of a corresponding plurality of threaded bores disposed through said body, said cavities being disposed adjacent the pipe;
disposing a threaded bolt through each of said threaded bores;
disposing a segment within each of said cavities;
pre-loading a first portion of each segment against an outer surface of the pipe by rotating said corresponding bolt disposed in each threaded bore; and
generating a resistance to pipe pull-out forces in proportion to the increased mechanical or internal pressure loading applied to the pipe by pivotal motion of each of said segments, said pivotal motion occurring while losing contact with said threaded bolts; and wherein said step of generating a resistance to pipe pull-out forces comprises permitting said segment to pivot about a second portion that maintains contact with a corner of said cavity, while losing contact with its corresponding bolt, as mechanical or internal pressure loading applied to the pipe increases pipe pull-out forces, said first portion of said segment being driven deeper into the outer surface of the pipe in proportion to the applied mechanical or internal pressure loading, said segment resisting pipe pull-out in proportion to the increased mechanical or internal pressure loading applied to the pipe.
2. The method of claim 1 wherein said step of permitting said segment to pivot about a second portion comprises loading said segment primarily in compression between said body and the outer surface of the pipe.
3. A method for providing a joint restraint assembly with resistance to pipe pull-out in proportion to the mechanical and/or internal pressure loading applied to a pipe, said method comprising the steps of:
providing a body that encircles the pipe wherein the body has a plurality of cavities and at least one set of a corresponding plurality of threaded bores disposed through said body, said cavities being disposed adjacent the pipe;
disposing a threaded bolt through each of said threaded bores;
disposing a segment within each of said cavities;
pre-loading a first portion of each segment against an outer surface of the pipe by rotating said corresponding bolt disposed in each threaded bore; and
generating a resistance to pipe pull-out forces in proportion to the increased mechanical or internal pressure loading applied to the pipe by pivotal motion of each of said segments, said pivotal motion occurring while losing contact with said threaded bolts; and
wherein a second portion of said segment contacts a corner of said cavity and wherein said first portion comprises a cam surface that contacts an outer surface of the pipe and wherein said step of generating a resistance to pipe pull-out forces comprises permitting said segment to pivot about said second portion that maintains contact with the corner of said cavity, while losing contact with its corresponding bolt, as mechanical or internal pressure loading applied to the pipe increases pipe pull-out forces, said cam surface rotating against, but not substantially penetrating, the outer surface of the pipe in proportion to the applied mechanical or internal pressure loading, said segment resisting pipe pull-out in proportion to the increased mechanical or internal pressure loading applied to the pipe.
4. The method of claim 3 wherein said step of permitting said segment to pivot about a second portion comprises loading said segment primarily in compression between said body and the outer surface of the pipe.