An apparatus for supporting a detecting shoe of a sensor for rotation
around a drill pipe stem for detecting identification numbers encoded on
the drill pipe sections of the stem as they are lowered into a borehole.
The apparatus comprises an outer plate means supported for rotation and
having an opening in which is located an inner plate also having an
opening for receiving the drill stem. Arms couple the inner plate to the
outer plate means for rotation therewith and also support the inner plate
for lateral movement in the opening of the outer plate means. The
detecting shoe is coupled to the inner plate by an arm which moves the
shoe against the drill stem for reading purposes. Means also is provided
for operating the shoe arm to move the shoe outward to allow drilling or
other operations to be carried out.