Patent ID: 7028785
Filing Date: 2006-04-18
Classification: E21B

Abstract:
1. A pneumatic ground piercing tool, comprising: an elongated hollow body having a front nose and a rear opening; a striker disposed for reciprocation within an internal chamber of the body to impart impacts thereto for driving the body through the ground; a stepped air inlet conduit which cooperates with the striker within the internal chamber of the body to reciprocate the striker and impart blows to a front end wall of the internal chamber under the action of a pressure fluid fed into the rear recess in the striker; a tail assembly mounted in the rear opening of the body having exhaust passages therethrough, at least a potion of each exhaust passage angling radially inwardly to communicate with a central hole at the rear end of the tail assembly whereby exhaust escapes through the central hole, the tail assembly including a tail nut threadedly secured to the body inside the rear opening thereof and having a plurality of threaded, rearwardly opening holes therein, an end cap disposed to fit over the rear opening of the body, the end cap having openings therein in alignment with the threaded holes in the tail nut and forming the central hole through which the air inlet conduit passes; and a plurality of bolts which extend through the openings and are threadedly secured in the threaded holes in the tail nut so that the end cap is securely clamped to the tool body and an axial clamp load is applied to the tail nut.