Joint for oil well drilling pipe

Claim 1

In a joint for connecting metallic pipe sections comprising a male member provided with a thread formed on a frusto-conical outer surface, and a female member provided with a mating thread formed on a frusto-conical inner surface of said female member, said female member having a shoulder positioned at the inner end of the threads thereon, which shoulder limits the penetration of said male member into said female member due to the abutment of the end of said male member against said shoulder, and which shoulder is provided with an annular groove defined by a frusto-conical inner surface which inclines inwardly of said female member as it approaches the tip of said shoulder, and an outer surface encircling said inner surface, said male member having a lateral surface adjacent the inner end thereof which is spaced by a first lateral clearance from the encircling portion of said female member, the improvement according to which: said female member is a composite member comprising a sleeve and a false male member, said sleeve being provided with two female threads positioned on frusto-conical surfaces, each of which is inclined outwardly as it approaches one of the two ends of the sleeve, one of which female threads is the thread mating with said male member and separably receives said male member, while the other female thread permanently grips mating threads on said false male member, said shoulder being formed at the end of said false male member and a second lateral clearance being provided between the shoulder-carrying end of said false male member and the part of said threaded sleeve encircling it.