Direct cutting-bit drive for deep drilling tools - with working fluid forced between helicoidal surfaces of case and flexible rotor in opposed sections, minimising wear

摘要

A direct drive mechanism for the cutting-bit of tools for drilling at great depth operates on the same principle as a Mono pump. It comprises a case in which rotates a shaft, the case and the shaft being mutually engaged by helicoidal surfaces, one of which is flexible and which form a working chamber through which a working fluid is forced under pressure. The flexible surface is subjected to a fluid pressure with a force directed radially. It is mounted on the shaft as a membranous body fixed at its ends and able to undergo freely the radial displacements in the intermediate zone. The drive is divided into two sections arranged coaxially one behind the other. Each is provided with a working chamber and has an inlet end for the working fluid which is brought to the drive by a central bore. The helicoidal surfaces of the sections have contrary pitches and the working fluid flows through them in opposite directions. The axial pressure forces which are transmitted by the working fluid through the direct drive of the bit to the bit itself are decreased or completely eliminated. The device allows increased power to be applied and gives longer periods of use than existing tools of its type. Because of the contrary pitch of the shaped surfaces of the two working chambers, the rotation and the rotation couple are the same as those of a non-divided drive.