Joint for conduit with single threaded end

In combination, first and second two-ended metal conduit sections of 10 foot or 20 foot lengths and of weights and diameters ranging from 23.0 lbs. per section to 533.5 lbs. per section and from 2" to 8", and adapted to be connected end-to-end to each other in the field:

• (a) said first conduit section having a circular cylindrical outer wall surface and an axial passage of constant cross-sectional dimensions and configuration, one end of said first conduit section having external thread means thereon and a flat substantially perpendicular end face and said other end of said first conduit section being non-threaded and having a flat substantially perpendicular end face;
• (b) said second conduit section being identical to said first conduit section and having a circular cylindrical outer wall surface equal in diameter to said outer wall surface of said first conduit section and an axial passage of constant cross-sectional dimensions and configurations equal to said axial passage through said first conduit section, one end of said second conduit section having external thread means thereon with a flat substantially perpendicular end face matching and abutting said adjacent flat substantially perpendicular end face of said other non-threaded end of said first conduit section and said other end of said second conduit section being non-threaded and having a flat substantially perpendicular end face;
• (c) a metal coupling sleeve having an end face, said coupling sleeve including female thread means extending from adjacent said end face and constructed and dimensioned to engage said external thread means on said one end of said conduit section;
• (d) each of said conduit sections including in one piece therewith a length of reduced outside diameter extending axially inwardly from said flat substantially perpendicular end face at said other end of said conduit section to form a stop shoulder in said outer wall surface at said non-threaded end said shoulder being substantially perpendicular to the length of the conduit section;
• (e) each of said conduit sections having means providing an annular lock ring groove in said outer wall surface near and spaced axially inwardly from said stop shoulder;
• (f) resilient constrictable lock ring means of spring metal partly in said annular lock ring groove and projecting partially out of said groove;
• and
• (g) abutment means extending radially inwardly on said metal coupling sleeve to define a periphery spaced from the outer diameter of the associated conduit section by a slight clearance adapted to cooperate with said stop shoulder and said projecting part of said lock ring means to permit free rotation of said coupling sleeve on said first conduit section and limited axially inward and axially outward movement of said coupling sleeve along said non-threaded end of said first conduit section so that said coupling sleeve can be threaded onto said externally threaded end of said second conduit section so as to force said end faces of said first and second conduit sections together without rotation of either section and may be backed off said externally threaded end of said second conduit section after said first and second conduit sections are assembled whereby said end face of said coupling sleeve is at least flush with said flat substantially perpendicular end face of said first conduit section to permit said first conduit section to be laterally displaced from said second conduit section without longitudinal movement of either conduit section, said abutment means and said lock ring means being constructed to prevent said lock ring means from being forced inwardly entirely into said annular lock ring groove when said end faces of said first and second conduit sections are forced together;
• (h) the clearance between said periphery defined by said abutment means and the outer diameter of the associated conduit section, being in the order of 0.020" to 0.040" on the diameter sufficient to prevent sections connected by the metal coupling sleeve to be slightly out of axial alignment up to about 1/2.degree. without interfering with the engagement between the female thread means and the coupling sleeve of the internal thread means engageable thereby with one end of a conduit section.