US 6,279,962 B1Granted

Safety joint

AssigneeSmith International, Inc.

InventorsBruce McGarian, Valentine H. McGarian

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Abstract

The present invention relates to safety joints which permit separation of a downhole assembly at the location of the joint. The invention provides a safety joint characterized by the provision of auxiliary interconnecting means on a body (2) for interconnecting said body (2) to an auxiliary shaft after removal of a main shaft (3) from said body (2). Axial loading between the auxiliary shaft and said body (2) may be thereby transferred. Furthermore, torque may also be transferred between the auxiliary shaft and said body (2) in a direction opposite to that in which torque may be transferred from the main shaft (3) to said body (2). Thus, the present invention allows a length of downhole assembly located above said body (2) to be removed from a wellbore by rotation of said length of assembly in a first direction and then allows rotation of said body (2) in the same first direction by means of the auxiliary shaft in an attempt to remove a length of assembly stuck in the wellbore downhole of said body (2).

Claims21

Dependent claims

A safety joint for use in a downhole assembly to permit separation of the assembly at the location of the joint, the safety joint comprising:

a body;
means for securing the body to part of the assembly;
a main shaft;
means for securing the main shaft to the remainder of the assembly;
and
main interconnecting means for interconnecting the main shaft and the body to transfer axial loading therebetween and to transmit torque from the shaft to the body in one direction of rotation of the shaft,
the interconnecting means being releasable in response to rotation of the shaft in the opposite direction of rotation to release the shaft from the body;
the safety joint being characterized in that the auxiliary interconnecting means is provided on the body for interconnecting the body to an auxiliary shaft, after removal of the main shaft from the body, to transfer axial loading between the auxiliary shaft and the body and to transfer torque from the auxiliary shaft to the body in the opposite direction of rotation, and
wherein the main interconnecting means comprises a first screw thread on the body for engagement by a corresponding screw thread on the main shaft and a main dog clutch for transmitting torque in one direction of rotation from the main shaft to the body.

6 more elements

Dependencies are inferred from the claim text.