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...http://www.google.es/patents/US7255516?utm_source=gb-gplus-sharePatente US7255516 - Method and apparatus for replacement of underground pipe
Method and apparatus for replacement of underground pipe
