PURPOSE: To improve safety by making it store the operating time and the number of operating times of a signal generator as the upper limit values corresponding to the period in which the device is usable, and in the case that the accumulated value exceeds this, by stopping the change control of the maximum value of circuit pressure.
CONSTITUTION: This is provided with a circuit pressure changing means, which enables the maximum value of the circuit pressure supplied from a hydraulic pump 2 to a hydraulic cylinder 8 to be changed or limited, and a signal generator 17, which generates a signal for operating this circuit pressure changing means. Next, the supposed operating time of a signal generator 17 corresponding to the period in which a hydraulic driving device is usable and the number of operating times are stored in advance as the limit time and the limit number of times. And, the actual operating times and number of times of the signal generator 17 are accumulated, and in the case that these exceed the limit values stored in the storage part, the change control of the maximum value of the circuit pressure by the circuit pressure changing means is stopped by a controller 16.
YASUDA TOMOHIKO
KATSUKI KIMIO
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