Tunnel excavator with variable pressure water jets

An excavator comprising:

• an outer cone;
• a center shaft rotatably provided in a shield body in concentric relation to said outer cone;
• an inner cone eccentrically provided on said center shaft to crush excavated materials in cooperation with said outer cone;
• a cutter head provided in front of said inner cone;
• an internally-toothed gear secured to said inner cone, said internally-toothed gear being concentric with said center shaft;
• an externally-toothed gear internally meshed with said internally-toothed gear, said externally-toothed gear being driven to rotate by a driving motor, so that rotation of said externally-toothed gear causes said center shaft to rotate through said inner cone;
• a plurality of water jet spray nozzles provided on said cutter head;
• and
• a multihole compressed water pipe provided in said center shaft, said compressed water pipe communicating with said water jet spray nozzles, wherein said compressed water pipe selectively supplies low-pressure water and high-pressure water such that, during excavation of ground free from obstructions, the low-pressure water is supplied, whereas, during excavation of ground containing obstructions, the high-pressure water is supplied.