Patent ID: 9568125
Date: 2017-02-14
CPC Classifications: E21B,F16L

Claim:
1. A threaded joint for steel pipes comprising: a pin and a box, the pin having a male thread and a lip comprising: the box having a female thread, a sealing surface and a shoulder surface, the male thread being interengaged with the female thread, the sealing surface of the pin being in sealing contact with the corresponding sealing surface of the box, the shoulder surface of the pin being arranged at an end face of the pin, the sealing surface of the pin being located on a pipe end side near the male thread, the nose portion existing between the sealing surface and the shoulder surface, said nose portion not contacting a portion of the box facing said the nose portion of the pin, wherein the shoulder surface of the pin comprises two distinct adjacent surfaces, in that the corresponding shoulder surface of the box facing the shoulder surfaces of the pin comprises two distinct adjacent surfaces, said main shoulder surfaces of the pin and box being disposed so as to prevent a radially inward deformation of the lip, said sub shoulder surfaces of the pin and the box being disposed so as to limit a radially outward deformation of the lip, said main shoulder surface of the pin having a greater radial dimension than said sub shoulder surface of the pin, at least said main shoulder surface of the pin being in axial abutment with at least the corresponding main shoulder surface of the box, wherein at least a part of the nose portion of the pin has an outside peripheral surface which is not in prolongation of the sealing surface of the pin and the sealing surface of the pin, the outside surface of the nose portion of the pin and sub shoulder surface of the pin are not aligned and wherein the sealing surface of the box, the inner surface of the portion of the box facing the outside surface of the nose portion of the pin and the sub shoulder surface of the box are not aligned, and further wherein the sub shoulder surfaces of the pin and the box do not contact each other in a normal tightened state, where the normal tightened state means that the pin and the box are tightened to reach a proper tightening torque, and wherein when compared to the normal tightened state, higher compressive load is acting or an excessive tightening torque is applied, the sub shoulder surfaces contact and suppress outward deformation of the lip.