Deep Foundation Excavator

A deep foundation excavator comprising a self-propelled vehicle body and a working mechanism provided on the vehicle body, wherein

• the working mechanism comprises:
• a boom provided on the vehicle body;
• an arm provided on a tip end of the boom;
• a bucket lifting and opening/closing device provided on the arm;
• and a clamshell bucket liftably provided on the arm and excavating a pit by a lifting operation and an opening/closing operation with the bucket lifting and opening/closing device, wherein
• the bucket lifting and opening/closing device comprises:
• a lifting cylinder provided on the arm;
• a first lifting sheave and a first opening/closing sheave moving in a length direction of the arm with the lifting cylinder;
• a second lifting sheave separated from the first lifting sheave and provided on the arm;
• a second opening/closing sheave separated from the first opening/closing sheave and provided on the arm;
• an opening/closing cylinder moving the second opening/closing sheave relative to the first opening/closing sheave;
• a lifting rope whose one end is mounted on the arm and whose other end is mounted on the clamshell bucket, and whose intermediate portion is looped around the first lifting sheave and the second lifting sheave;
• and
• an opening/closing rope whose one end is mounted on the arm and whose other end is mounted on the clamshell bucket, and whose intermediate portion is looped around the first opening/closing sheave and the second opening/closing sheave, wherein
• the arm has a first opposing surface and a second opposing surface that are opposite in a direction perpendicular to the length direction of the arm, wherein
• the first lifting sheave and the second lifting sheave are disposed on an outer side surface of the first opposing surface, and
• the first opening/closing sheave, the second opening/closing sheave and the opening/closing cylinder are disposed on an outer side surface of the second opposing surface.