Abstract: A method for installation of an underground pipe includes an initial step of boring a pilot hole through the ground at a predetermined grade angle by extending a drill string having a steerable boring bit mounted thereon through the ground. Upon reaching an end location for the pilot hole, the bit is removed from the drill string, and an expander having a diameter greater than the pilot hole is attached to the drill string, which expander is backed by an impact device such as a pneumatic impactor including a striker that delivers repeated impacts to a rearwardly facing surface of the expander, and by a pipe drawn along behind the expander. The expander is pulled back through the pilot hole at the grade angle while the impactor is operated to aid progress of the expander through the ground and pull the pipe into place behind the expander.

Abstract: A ground piecing tool includes a housing and an air distributing mechanism that reciprocates a striker to impact a chisel shaft in response to a supply of compressed fluid including a fluid inlet tube mounted in the bore of the striker having a radial port, a rear end of the inlet tube being in communication with the distributing mechanism, wherein the housing and chisel shaft cooperate to define a front chamber that decreases in volume as the chisel moves forward relative to the housing, and wherein the chisel shaft has a radial passage therein that conducts compressed fluid from the radial port of the inlet tube to the front chamber, which is configured to form an air spring.

Abstract: A pneumatic ground piercing tool includes a tail assembly including a tail nut and tail cap, the tail cap having a plurality of discharge ports for exhausting spent compressed air, the discharge ports opening into an annular space between a rearwardly opening recess of the tail cap and an air supply conduit such that the exhaust ports are shielded by a side wall of end cap from plugging when the ground piecing tool is operated in reverse mode.

Abstract: An impactor for use with a directional boring machine for replacement of underground pipes includes a bursting head having a rearwardly opening recess and a front end opening that communicates with the recess. An inlet pipe is connected at its front end to a distal end of the drill string and extends into the recess of the bursting head through the front end opening. A striker is mounted for sliding movement along the inlet pipe, and a distributing mechanism responsive to pressure fluid supplied through the drill string and inlet pipe causes the striker to reciprocate in the rearwardly opening recess of the head to deliver forward impacts against the bursting head. The striker and distributing mechanism are mounted in a tubular housing, and a pulling connection is provided by which the impactor can be pulled by the drill string while the striker is delivering impacts against the head in the same direction as a pulling force exerted by the drill string.

Abstract: A method of the invention uses a pneumatic ground piercing tool having a reversing mechanism with a supplemental air line capable of supplying compressed air for reverse operation to a radial port in the air distributing mechanism. This radial port is located between a pair of bearing surfaces on the step of the air inlet conduit, and when pressurized by the supplemental air line, causes the front pressure chamber to receive compressed air earlier than normal, shifting the stroke of the striker rearwardly so that the tool operates in reverse. Such a method includes the steps of operating the tool in forward mode by supplying compressed air to the first air hose, and operating the tool in reverse mode by supplying compressed air to the second air hose while permitting partial venting of the front pressure chamber through the first air hose.

Abstract: The invention provides a method for reversing an impact boring tool of the type having a reversing mechanism actuated by rotation of the compressed air supply hose that enters the tool through a rear end opening. This method includes the initial step of connecting the air supply hose to the tool using a quick-release coupling device including tubular male and female members which are coupled together, one of the members being mounted on the end of the air supply hose and the other mounted on an air inlet conduit of the tool, the coupling device further having a locking sleeve and a ball seated in a first pit in one of the members and configured for insertion into a second pit in the other of the members as the locking sleeve moves over the ball, the locking sleeve being biased to a locked position wherein the ball is seated in both pits thereby preventing rotation of one member relative to the other as well as disengagement of one member from the other.

Abstract: A pneumatic ground piercing tool according to the invention has a reversing mechanism provided as part of the air distributing mechanism. Such a tool includes an elongated tubular housing having a rear opening, a head assembly including an anvil, a striker disposed for reciprocation within an internal chamber of the housing to impart impacts to a rear impact surface of the anvil for driving the body through the ground, an air distributing mechanism for effecting reciprocation of the striker, and a tail assembly mounted in a rear end opening of the housing that secures the striker and air distributing mechanism in the housing. In one embodiment, the outer bushing of the valve sleeve can slide a short distance relative to the air supply tube and has an intermediate radial port which selectively communicates with the air supply conduit. The valve sleeve also includes a detent mechanism for securing the air supply tube in its forward or reverse position.