Hydraulically pulsed indexing system for sleeve-type core barrels

摘要

A coring tool, which includes a flexible wire mesh in which the core is disposed, includes a mechanism for maintaining tension on the wire mesh sleeve which then seizes the core disposed within the sleeve, and which serves to retain the core and maintain it under tension. The sleeve is maintained under tension by tensile force transmitted to the sleeve through a stripper tube. The stripper tube is axially disposed through a piston ratchet assembly connected to a piston slidable within the drill string. The piston is resiliently urged upward within the drill string by a return spring but is longitudinally forced downward within the drill string and advanced downwardly with respect to the stripper tube by an increase in pressure within the drill string thereby compressing the return spring. The piston ratchet assembly prevents the piston from moving longitudinally upward with respect to the stripper tube and thereby allows the resilient force of the preloaded spring to be applied through the piston and piston ratchet assembly to the stripping tube as a tensile force on the wire mesh sleeve. A fixed ratchet assembly is provided within the coring tool to prevent any downward movement of the stripper tube through the fixed ratchet assembly thereby maintaining tension on the stripper tube while the piston is being advanced in response to an increase in fluidic pressure.