Pneumatic impact tool for pipe insertion

A pneumatic impact tool, comprising:

• a body including a sleeve, a nose section fitted over a front end of the sleeve, an end cap in engagement with a rear end of the sleeve, and a tying device engaging the nose section and end cap for clamping the sleeve therebetween;
• a striker disposed for reciprocation within an internal chamber of the sleeve to impart impacts to the nose section for driving the body forward, the striker having a rearwardly opening recess and a rear radial passage through a wall enclosing the recess, a front end portion having a bearing thereon for sliding engagement with the internal chamber and passages permitting flow of pressure fluid to a front, variable-volume pressure chamber ahead of the striker, and a rear end portion having a bearing thereon rearwardly of the radial passage for sliding engagement with the internal chamber;
• an air distributing mechanism for effecting reciprocation of the striker, the air distributing mechanism including a stepped air inlet conduit which cooperates with the striker within the internal chamber of the body to impart blows to a front end wall of the internal chamber under the action of a pressure fluid fed into the rear opening in the striker, followed by reverse movement of the striker upon passage of the rear radial passage past a front edge of a step of the stepped air inlet conduit, and exhaust of compressed air upon passage of the rear radial passage past a rear edge of the step of the stepped air inlet conduit;
• and
• a tail assembly mounted in a rear end opening of the body that secures the striker and air distributing mechanism in the body, the tail assembly including a tail nut having an outer flange that is rigidly clamped between a rear end of the sleeve and the end cap to secure the tail nut to the body, the tail nut having a central lengthwise opening extending therethrough in which the air inlet conduit is mounted and having exhaust passages for exhaust of compressed air.