Downhole tool comprising a rotating part with a torque limiting coupling

Abstract

The invention relates to a downhole tool for use in a petroleum well. The downhole tool () comprises a first part () comprising a driving unit (), and second part () comprising a driven unit (), wherein the drive unit () is configured for driving the driven unit (). The downhole tool () comprises a coupling unit () having an input side (S) coupled with the driving unit () and an output side (S) coupled with the driven unit (), wherein the driving unit () is configured for driving the driving unit () via the coupling unit () comprising a torque limiting coupling having a first operational mode, the coupling unit () transfers all torque from the input side (S) to the output side (S), the coupling unit () further having a second operational mode, wherein the coupling unit () slips such that less torque is transferred form the input side (S) to the output side (S), wherein the second operational mode is automatically activated when the torque load on the input side exceeds a predefined level, and wherein the first operational mode is automatically activated when the torque load on the input side reduces to a level below a further predefined level. The coupling unit () comprises a displacement pump (), wherein the displacement pump () is activated by opening of a pressure-limitation valve (), for facilitating slipping of the coupling unit () when the coupling unit () is switching to the second operational mode, and wherein the displacement pump () is deactivated by closing of the pressure-limitation valve (), for locking the coupling unit () when the coupling unit () is switching to the first operational mode.