Patent ID: 7467889

Claim:
A concrete agitating drum driving device comprising: a hydraulic motor connected to a concrete agitating drum; a hydraulic pump driven by a combustion engine and causing the hydraulic motor to rotate by supplying pressurized oil thereto; a hydraulic actuator which regulates a flow rate of the pressurized oil in response to an actuator driving pressure; a load sensing valve which generates the actuator driving pressure by reducing a pressure of the pressurized oil to maintain a differential pressure between the pressure of the pressurized oil and a load pressure under which the hydraulic motor operates at a constant level when an engine rotation speed of the combustion engine is not higher than a predetermined speed; and a mechanism which, when the engine rotation speed is higher than the predetermined speed, increases the flow rate of the pressurized oil as the engine rotation speed increases, while relatively decreasing an increase rate of the flow rate with respect to an increase rate of the engine rotation speed as the engine rotation speed increases.