초록 ▼

A down-hole signal transmitter includes an annular impeller mounted on a cylindrical casing and arranged to be driven by the mud flow passing along a drill string. Each of the impeller and the casing incorporates two sets of magnets with their poles arranged axially relative to one another such that

A down-hole signal transmitter includes an annular impeller mounted on a cylindrical casing and arranged to be driven by the mud flow passing along a drill string. Each of the impeller and the casing incorporates two sets of magnets with their poles arranged axially relative to one another such that axial movement of the impeller in one direction will tend to be resisted by a force of magnetic repulsion acting between the first set of casing magnets and the second set of impeller magnets and axial movement of the impeller in the opposite direction will tend to be resisted by a force of magnetic repulsion acting between the second set of casing magnets and the first set of impeller magnets. In this way the axial thrust due to the fluid flow is largely taken up. Furthermore the magnetic coupling between the magnet sets in such as to enable driving torque to be transmitted by the impeller to a rotary drive member on which the casing magnets are mounted.

대표청구항 ▼

A down-hole device for producing rotary motion from the mud flow within a borehole comprising a cylindrical casing having its axis aligned with the direction of mud flow, and an annular impeller arranged to be driven by the mud flow and surrounding the casing so as to be coaxial therewith, wherein e

A down-hole device for producing rotary motion from the mud flow within a borehole comprising a cylindrical casing having its axis aligned with the direction of mud flow, and an annular impeller arranged to be driven by the mud flow and surrounding the casing so as to be coaxial therewith, wherein each of the casing and the impeller incorporates at least two magnets, a first of which is closer to one axial end of the impeller and has at least one North pole facing radially outwards and at least one South pole facing radially inwards, and a second of which is closer to the other axial end of the impeller and has at least one South pole facing radially outwards and at least one North pole facing inwards, the impeller and casing magnets being so arranged relative to one another that axial movement of the impeller in relation to the casing in one direction will tend to be resisted by a force of magnetic repulsion acting between the first casing magnet and the second impeller magnet and axial movement of the impeller in relation to the casing in the opposite direction will tend to be resisted by a force of magnetic repulsion acting between the second casing magnet and the first impeller magnet.