Down-hole devices for imparting rotary motion

Abstract From the Canadian patent

A T I O N, "Down-hole Devices for Imparting Rotary Motion" ABSTRACT OF THE DISCLOSURE, 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, and an annular stator fixed to the casing upstream of the impeller. The stator has blades canted in one sense relative to the mud flow direction whereas the impeller has blades parallel to the mud flow direction. The stator blades thereby cause the mud flow to impact on the impeller blades at such an angle that a small or negligible thrust results at the impeller bearings. It is therefore possible to ensure a long service life for the bearings.