Zetec, Inc.

Christopher R Loud

A flexible shaft of nonrigid components for use in pushing an eddy current probe through small diameter pipe bends includes a thin-walled flexible outer sleeve enclosing a data cable helically coiled around a central inner core, typically of braided wire. The inner core is functionally incompressible and inextensible to sustain compressive forces derived from pushing the shaft through a pipe. The outer sleeve supported from within by the data cable and the inner core for sustaining lateral forces of pusher rollers is longitudinally even and smooth to advance the shaft without damage to it.

Flexible shaft with a helically wound data cable supporting a smooth outer sleeve for eddy current probe

In an eddy current probe shaft, a sleeve encloses an inner core of length shorter than the sleeve causing the inner core to curl within sleeve. The inner core includes data cables that typically comprise coaxial cables to which the sleeve is attached at shaft lead and trail ends. The shaft is assembled by stretching the sleeve over the inner core and securing the stretched sleeve to the inner core, the sleeve causing the inner core to curl as the sleeve returns to its unstretched length. Slack thus produced in the inner core, and particularly in the coaxial cables, allows the probe to bend without stressing the coaxial cables and without two coaxial cables within the sleeve moving relative to each other therein eliminating signal drift phenomenon caused by a change in capacitance characteristics of the coaxial cables when insulation of the coaxial cables stretch upon bending.

Prestretched shafet for eddy current probe

A plurality of beads with matching transverse faces and longitudinal bores cooperate to form a bendable shaft with a duct therethrough, held in face-to-face contact with a plurality of elastic bands within the duct. Alternatively, the plurality of bands may comprise a single elastic inner tube. The elastic bands may also mutually overlap to provide redundancy in case a band should break.

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North Bend, WA, United States of America

Christopher R Loud