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1. (WO1998050720) THREADED CONNECTION FOR ENHANCED FATIGUE RESISTANCE

Pub. No.:    WO/1998/050720    International Application No.:    PCT/US1998/007657
Publication Date: Fri Nov 13 00:59:59 CET 1998 International Filing Date: Wed Apr 15 01:59:59 CEST 1998
IPC: E21B 17/042
E21B 17/08
F16L 15/04
F16L 15/06
Applicants: GRANT PRIDECO, INC.
Inventors: EVANS, Ed
DeLANGE, Richard
BUSTER, Jerry, L.
Title: THREADED CONNECTION FOR ENHANCED FATIGUE RESISTANCE
Abstract:
A threaded connection for improving fatigue resistance to cyclic loading is disclosed. The threaded connection (10) basically comprises a pair of interlocking members (12, 16) having corresponding radially inner (52) and radially outer (50) spiral threads thereon, each spiral thread including a spiral compression flank (56, 68) and a spiral tension flank (58, 64) wherein at least one of the spiral compression flanks (56, 68) and spiral tension flanks (58, 64) on the inner spiral threads are in planar engagement with a corresponding spiral compression flank (56, 68) and spiral tension flank (58, 64) on the outer spiral thread. Axial spacing between the tension flanks (58, 64) and the compression flanks (56, 68) on the radially inner and radially outer spiral threads further define a stress reducing spiral root surface (60, 62) on at least one of the radially inner (52) and radially outer (50) threads and a corresponding crest surface (54, 66) on the other radially inner and radially outer spiral threads.