PURPOSE: To prevent impaction to a working machine by sufficiently reducing the turning speed of a swivel base by a method in which before the set turning position against the vehicle of the swivel table is reached, the amount of oil to a turning oil- pressure motor is regulated in such a way that when the turning speed is great and the turning angular speed is small, the circuit to the turning oil-pressure motor is closed.
CONSTITUTION: A solenoid valve 15B is provided between oil paths for an oil-pressure motor 3 for driving a swivel table and a switching valve 10 for the swivel table, and an oil amount regulating valve 15B is provided between an oil-pressure pump P and the switching valve 10. A detector 16 for the turning position against the vehicle of the swivel table, setters 17 and 18 for the turning position against the vehicle of the swivel table, and a detector 19 for the operating state of the turn-switching valve are provided. A detector 27 for the acceleration of the swivel table and a detector 28 for the turning speed are also provided. Before the set turning position of the swivel table is reached, by the outputs of each detector, the valve 15A is automatically moved toward the reduction of oil amount. When the acceleration is small and the turning speed is great, the valve 15B is automatically closed and the speed of the swivel table is sufficiently reduced at the set positions.
TABUCHI YOSHINOBU
TSUDA AKIRA
TSUTSUMI MASAHIRO
IKEDA KAZUSHIGE
