Semi-automatic hydraulic excavator

A semi-automatic hydraulic excavator which includes a boom, an arm and a bucket having a movable bottom, said excavator comprising:

• an arm control means for controlling the arm of said excavator automatically and manually;
• a bucket control means for controlling the bucket of said excavator automatically and manually and;
• one or more additional control means for manually controlling additional elements of the excavator, wherein the additional control means includes means for rotating the excavator under control of a rotation lever, means for moving the bucket bottom under control of a bottom lever and means for moving the boom under control of a boom lever;
• detection means for producing signals representing rotation lever directional movement, bottom lever movement and boom lever movement;
• an automatic control circuit which controls, upon detection of a signal corresponding to the fact that said excavator has completed a predetermined work procedure, said arm control means and said bucket control means to place them in an automatic control mode;
• wherein said automatic control circuit logically combines signals from the detection means respectively corresponding to the facts that the rotation lever is operated in one direction, said rotation lever is then operated in the reverse direction, the bottom lever is operated and that the boom lever is operated downward;
• said arm control means being designed to control said arm during the automatic control mode so that an arm angle thereof becomes coincident with a fixed preset value corresponding to an original excavation posture, said bucket control means being designed to control said bucket during the automatic control mode so that a bucket angle thereof becomes coincident with a preset value corresponding to the original excavation posture, whereby, upon completion of dumping work, said bucket is swiftly brought back to the original excavation posture by simultaneous manual operation of the additional control means and automatic operation of the arm control means and bucket control means.