Abstract: A downhole tool (100) for generating pressure pulses in a drilling fluid comprising an elongate body (107, 127) and a plurality of blades (116) spaced around the body. The blades are each divided into an independent front section (116a) and rear section (116b), forming a set of front sections and a set of rear sections, at least one of the set of front sections and the set of rear sections being mounted for rotation and being angularly displaceable relative to each other between a first position in which the sections are aligned and a second position in which the rear sections obstruct fluid flow between the front sections to generate a pressure pulse. The tool includes a first set of driving blades in front of the blades (116) for generating a torque on the blade sections, the driving blades being curved in a first direction, and an escapement means (129) which is radially movable to permit stepwise rotation of the blade sections, and thus to move the blade sections between the first and second positions.

Abstract: A downhole tool for generating pressure pulses in a drilling fluid comprising an elongated body and a plurality of blades spaced around the body. The blades are each divided into an independent front section and rear section, forming a set of front sections and a set of rear sections, at least one of the set of front sections and the set of rear sections being mounted for rotation such that the front and rear sections are angularly displaceable relative to each other between a first position in which the sections are aligned and a second position in which the rear sections obstruct fluid flow between the front sections to generate a pressure pulse. The tool includes a means for generating a torque on the blade sections, and an escapement means which is radially movable to permit stepwise rotation of the blade sections, and thus to move the blade sections between the first and second positions.

Abstract: A downhole MWD tool for generating pressure pulses in a drilling fluid comprises an elongate body for positioning in a drill collar and a plurality of blades spaced around the body. Each blade is divided into an independent front section and rear section one of the front and rear sections being mounted on a rotatable shaft such that the front and rear sections are angularly displaceable relative to one another between a first position in which the sections are aligned and a second position in which the rear blades obstruct fluid flow between the front sections to generate a pressure pulse. A hydraulic actuator is operable to rotate the shaft, and is powered by the pressure difference in the drilling fluid between an upstream end of the tool and a position downstream of the tool.