Abstract: A concrete agitating drum (1) is driven by a hydraulic motor (81). A connection switch-over valve (20) is arranged to have a function to regulate a flow cross-sectional area of pressurized working oil supplied to the hydraulic motor (81) from a variable capacity hydraulic pump (10). The variable capacity hydraulic pump (10) is driven by a combustion engine (60) together with a charge pump (11). When a discharge pressure of the charge pump (11) is low, the connection switch-over valve (20) maintains a small flow cross-sectional area to rotate the agitating drum (1) at a low rotation speed so that fuel consumption of the combustion engine (60) is suppressed to be small. When the discharge pressure of the charge pump (11) becomes high, the connection switch-over valve (20) enlarges the flow cross-sectional area, thereby realizing a rated rotation speed of the agitating drum (1).

Abstract: A variable capacity hydraulic pump (10) drives a concrete agitating drum (1) via a hydraulic motor (81). A hydraulic actuator (14) regulates a discharge flow rate of the hydraulic pump (10) depending on an actuator driving pressure. A load sensing valve (40) generates the actuator driving pressure by reducing a discharge pressure of the hydraulic pump (10) according to a differential pressure between the discharge pressure and a load pressure acting on the hydraulic motor (81). A shut-off valve (20) shuts off supply of the pressurized oil discharged from the hydraulic pump (10) to the hydraulic motor (81). Due to this action, when the differential pressure increases beyond a predetermined differential pressure, an unload valve (30) drains the discharged oil, thereby preventing the hydraulic pump (10) from generating noise due to an excessive increase in the discharge pressure.

Abstract: A concrete agitating drum (1) is driven by a hydraulic motor (81). A connection switch-over valve (20) is arranged to have a function to regulate a flow cross-sectional area of pressurized working oil supplied to the hydraulic motor (81) from a variable capacity hydraulic pump (10). The variable capacity hydraulic pump (10) is driven by a combustion engine (60) together with a charge pump (11). When a discharge pressure of the charge pump (11) is low, the connection switch-over valve (20) maintains a small flow cross-sectional area to rotate the agitating drum (1) at a low rotation speed so that fuel consumption of the combustion engine (60) is suppressed to be small. When the discharge pressure of the charge pump (11) becomes high, the connection switch-over valve (20) enlarges the flow cross-sectional area, thereby realizing a rated rotation speed of the agitating drum (1).

Abstract: An agitating drum driving device comprises a hydraulic motor (81) for rotating an agitating drum (1), and a swash-plate type hydraulic pump (10) connected to a combustion engine (60) to supply pressurized oil to drive the hydraulic motor (81). When the engine rotation speed is not higher than a predetermined speed, the swash-plate angle of a swash-plate (64) is regulated to keep a differential pressure between a pressure of the pressurized oil and a load pressure acting on the hydraulic motor (81) constant. When the engine rotation speed rises above the predetermined speed, the flow rate of the pressurized oil is increased as the engine rotation speed increases while relatively decreasing an increasing rate of the flow rate of the pressurized oil with respect to an increase rate of the engine rotation speed as the engine rotation speed increases.

Abstract: An agitating drum driving device comprises a hydraulic motor (81) for rotating an agitating drum (1), and a swash-plate type hydraulic pump (10) connected to a combustion engine (60) to supply pressurized oil to drive the hydraulic motor (81). When the engine rotation speed is not higher than a predetermined speed, the swash-plate angle of a swash-plate (64) is regulated to keep a differential pressure between a pressure of the pressurized oil and a load pressure acting on the hydraulic motor (81) constant. When the engine rotation speed rises above the predetermined speed, the flow rate of the pressurized oil is increased as the engine rotation speed increases while relatively decreasing an increasing rate of the flow rate of the pressurized oil with respect to an increase rate of the engine rotation speed as the engine rotation speed increases.

Abstract: A variable capacity hydraulic pump (10) drives a concrete agitating drum (1) via a hydraulic motor (81). A hydraulic actuator (14) regulates a discharge flow rate of the hydraulic pump (10) depending on an actuator driving pressure. A load sensing valve (40) generates the actuator driving pressure by reducing a discharge pressure of the hydraulic pump (10) according to a differential pressure between the discharge pressure and a load pressure acting on the hydraulic motor (81). A shut-off valve (20) shuts off supply of the pressurized oil discharged from the hydraulic pump (10) to the hydraulic motor (81). Due to this action, when the differential pressure increases beyond a predetermined differential pressure, an unload valve (30) drains the discharged oil, thereby preventing the hydraulic pump (10) from generating noise due to an excessive increase in the discharge pressure.