Patent ID: 6923270
Filing Date: 2005-08-02
Classification: E21B

Abstract:
1. A reversible, 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, the striker having a rearwardly opening recess and a rear radial passage through a wall enclosing the recess, a front portion having a front bearing thereon for sliding contact with a first inner surface of the body and passages permitting flow of pressure fluid to a front, variable-volume pressure chamber ahead of the striker, and a rear portion having a rear bearing thereon rearwardly of the radial passage for sliding contact with a second inner surface the body; 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, followed by reverse movement of the striker when the rear radial passage moves past a front edge of the step of the stepped air inlet conduit, and exhaust of compressed air when the rear radial passage moves past a rear edge of the step of the stepped air inlet conduit; a tail assembly mounted in the rear opening of the body that secures the air inlet conduit in the body, wherein the tail assembly has 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; and a mechanism that reverses the direction of travel of the tool by causing the striker to impact against the tail assembly instead of the front end wall of the internal chamber of the body.