Hydraulic driving apparatus using a bladder-type accumulator with an improved safety

A hydraulic driving apparatus with a bladder-type accumulator connected to a fluid supply pipe extending from a hydraulic fluid source to at least one actuator, said hydraulic driving apparatus comprising:

• a hydraulic pressure sensor attached to said fluid supply pipe in the vicinity of said bladder-type accumulator;
• and
• a control unit responsive to a detected pressure detected by said hydraulic pressure sensor for controlling said hydraulic fluid source to adjust a fluid flow rate;
• said control unit carrying out the steps of:
• judging, at the start of said hydraulic driving apparatus, an initial gas pressure supplied to said bladder-type accumulator with reference to a gradient of variation of the detected pressure detected by said hydraulic pressure sensor;
• monitoring, during a normal operation of said hydraulic driving apparatus, a difference .DELTA.P between said initial gas pressure and said detected pressure;
• and
• judging occurrence of a trouble when said difference .DELTA.P becomes smaller than a predetermined first difference .DELTA.P1 or when said difference .DELTA.P becomes greater than a predetermined second difference .DELTA.P2, where .DELTA.P2 is greater than .DELTA.P1.