Pneumatic excavator

摘要

PCT No. PCT/US98/04968 Sec. 371 Date Dec. 2, 1999 Sec. 102(e) Date Dec. 2, 1999 PCT Filed Mar. 13, 1998 PCT Pub. No. WO98/40568 PCT Pub. Date Sep. 17, 1998A portable excavator having a tube to point a supersonic gas stream at a buried object. The excavator includes a movable member disposed within the conduit to pulse gas passing through the conduit and a supersonic gas nozzle at the exit of the conduit. Compressed gas delivered to the conduit exits the nozzle in a pulsed manner at two to three Hz. The movable member includes a piston which blocks gas from flowing through the conduit by the biasing force of a spring. When the force to the pressure differential across the piston exceeds the biasing force, the piston moves and allows gas to flow through the conduit until the force from the pressure differential across the piston is less than the biasing force.