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

Abstract

A flexible shaft for use with an eddy current probe includes a flexible outer sleeve enclosing an electrically conducting coaxial cable helically coiled around a central braided wire. The braided wire is functionally incompressible and inextensible to sustain compressive forces derived from pushing the shaft through a pipe. The outer sleeve is longitudinally even accepting rollers of a pusher mechanism frictionally engaging the outer sleeve to advance the shaft without damage to the shaft as a spin motor engages the shaft to rotate the shaft as the pusher mechanism drives the probe into the pipe.

Having described the invention, what is claimed is:  
     
         1 . A flexible shaft for moving a measuring device on a shaft lead end through a pipe, the improvement in the shaft comprising, 
 a flexible outer sleeve running continuously between the measuring device and a shaft tail end,    an inner core flexible in bending but inflexible longitudinally in sustaining compression forces that are derived from pushing the shaft through the pipe without deformation,    an electrically-conducting cable running with the inner core inside the outer sleeve.    
     
     
         2 . The flexible shaft of  claim 1  wherein the outer sleeve comprises a longitudinally even wall surface such that the shaft passes smoothly through rollers of a shaft pusher.  
     
     
         3 . The flexible shaft of  claim 1  wherein the inner core comprises a braided wire cable.  
     
     
         4 . The flexible shaft of  claim 3  wherein the electrically-conducting cable is helically wound around the inner core forming a longitudinally incompressible and inextensible shaft inner structure within the flexible outer sleeve.  
     
     
         5 . The flexible shaft of  claim 4  wherein winds of the cable are spaced apart longitudinally along the wire core.  
     
     
         6 . The flexible shaft of  claim 4  wherein the helically wound cable spaces the wire core from the outer sleeve maintaining the wire core central within the outer sleeve and preventing the wire core from buckling within the outer sleeve.  
     
     
         7 . The flexible shaft of  claim 4  further including a lubric liner around the inner structure providing a reduced friction interface between the shaft inner structure and the outer sleeve.  
     
     
         8 . The flexible shaft of  claim 4  further comprising end caps at each shaft end sealing the shaft inner structure within the outer sleeve and constraining longitudinal movement of the helically wound electrically-conducting cable and inner core within the outer sleeve.  
     
     
         9 . The flexible shaft of  claim 8  wherein the cable passes through the end caps with the end caps centering the braided wire cable in the outer sleeve.  
     
     
         10 . An eddy current probe attached to a flexible shaft lead end, adapted to be driven into a pipe for remote nondestructive testing of the integrity of the pipe, an electrically-conducting cable running from the probe through the shaft to a shaft tail end, the improvement in the flexible shaft comprising, 
 a flexible outer sleeve with a longitudinally even outer surface,    a braided wire cable flexible in bending movement but incompressible and inextensible longitudinally in sustaining compression forces that are derived from pushing the shaft through the pipe without deformation, the electrically-conducting cable helically wound on the wire cable in spacing the wire cable from the outer sleeve maintaining the wire cable central within the outer sleeve and preventing the wire cable from buckling within the outer sleeve, the electrically-conduction cable and the wire cable forming an shaft inner structure within the flexible outer sleeve.    
     
     
         11 . The probe and shaft of  claim 10  further comprising a sheath around the shaft inner structure and within the outer sleeve.  
     
     
         12 . The probe and drive shaft of  claim 10  further comprising end caps at each shaft end sealing the shaft inner structure within and constraining longitudinal movement of shaft members within the outer sleeve.  
     
     
         13 . A flexible shaft with distal and proximal ends comprising, 
 a flexible outer sleeve smooth throughout its outer surface and continuous without surface interruptions between tube proximal and distal ends,    a flexible wire core able to sustain compression forces that are derived from pushing the shaft from its proximal end without deformation,    an electrically-conducting coaxial cable helically wound tightly on the wire core wherein winds of the cable are spaced apart longitudinally along the flexible wire core, the helically wound cable functionally comprising a spacer between the wire core and the outer sleeve that maintains the wire core central within the outer sleeve preventing the wire core from buckling within the outer sleeve.    
     
     
         14 . The flexible shaft of  claim 13  further including a sheath within the outer sleeve around the electrically-conducting coaxial cable and wire core comprising a reduced friction interface to the outer sleeve.  
     
     
         15 . The flexible shaft of  claim 13  wherein the wire core comprises a braided wire cable.  
     
     
         16 . The flexible shaft of  claim 13  further comprising end caps at each shaft end sealing the electrically-conducting coaxial cable and wire core within against potential hostile environmental elements and constraining longitudinal movement of shaft members and centering the wire core within the outer sleeve.  
     
     
         17 . For an eddy current shaft including electrically-conducting data cables along the shaft running from an eddy current probe on the shaft lead end, a method of rotating the eddy current probe on the drive shaft while simultaneously pushing the probe through a pipe, comprising the following steps: 
 a. Enclosing the probe drive shaft with a flexible outer sleeve longitudinally even along its outer surface such that the shaft pusher rollers engaging the shaft do not damage it;    b. Engaging the drive shaft with motorized shaft pusher rollers to drive the shaft into the pipe;    c. Engaging the drive shaft with a spin motor to rotate the shaft as it is being driven through the shaft pusher rollers and into the pipe.    
     
     
         18 . The method of  claim 17  wherein the probe drive shaft comprises, 
 a flexible outer sleeve with a longitudinally even outer surface in accordance with step a. and wherein the probe drive shaft further comprises,  
 a braided wire cable flexible in bending movement but incompressible and inextensible longitudinally in sustaining compression forces that are derived from pushing the shaft through the pipe without deformation, the electrically-conducting cable helically wound on the wire cable in spacing the wire cable from the outer sleeve maintaining the wire cable central within the outer sleeve and preventing the wire cable from buckling within the outer sleeve.