Patent ID: 8256539

Claim:
A steerable ground piercing tool, the tool comprising: an elongated outer housing having a lengthwise extending bore; an inner assembly at least in part disposed within the outer housing, the inner assembly comprising; a rotatable chisel having a longitudinally extending shaft at least in part disposed within the housing bore, the chisel having a first end defining an asymmetric tip and a second end defining a first impact surface for receiving a reciprocating action impact to drive the tool through the ground; and a conversion mechanism to selectively convert upon activation thereof at least a first portion of the reciprocating action imparted to the first impact surface into combined reciprocation and rotation of the tool; and a spring assembly disposed at least in part within the tool outer housing to move the rotatable chisel to an at rest state in the absence of imparting of impacts thereon, the spring assembly comprises a spring element within a spring housing disposed about the rotatable chisel, wherein the conversion mechanism comprises: the chisel shaft having a circumference with a series of parallel grooves formed therein and a selected one of the spring housing and the tool outer housing comprises a ratcheting mechanism to interact with the series of parallel grooves formed in the chisel shaft, wherein the ratcheting mechanism comprises: a plurality of contact elements disposed about an inner circumference of the selected one of the spring housing and the tool outer housing with a different one of the contact elements in interaction contact with a different one of the series of parallel grooves formed in the chisel shaft, and wherein the impacts imparted to the second end of the chisel are sufficient to advance the chisel shaft forward and for a first of the contact elements to ride through a first of the grooves and into an adjacent second of the grooves to convert a portion of the reciprocating action imparted to the first impact surface into combined reciprocation and rotation of the tool.