Small-bore tunnel-driving machine

摘要

The device is used for digging a horizontal bore or small diameter tunnel in the ground. It has a pointed front end (1) which may be pushed through soft ground and has a cylindrical housing (2). The housing contains a longitudinally sliding percussion piston (3) which knocks against the inside of the pointed front end to drive it forward. The piston contains control air passages and has a hollow rod (10) inside it, admitting air from a compressed air supply (13). There are further control passages (4) and ports (9) for release of used air.