Swivelling working vehicle

Claim 1

A working vehicle capable of swivelling comprising: a swivel base (2) having a working implement (6), a hydraulic motor (3) for swivelling the swivel base, an actuator valve (10) for controlling the hydraulic motor in opposite directions and stopping the hydraulic motor, an angle sensor (18) for detecting an angle of the swivel base relative to the vehicle body, a setting adjuster (19) for setting a stopping position (θf) of the swivel base relative to the vehicle body, detector means (17) for detecting operating conditions of the actuator valve, said actuator valve including flow control valve means for controlling flow rate of hydraulic oil supplied to the hydraulic motor, forward and reverse braking valves (14) which prevent a momental rotation of said swivel base when in a stationary position, forward and reverse relief valves (15) for cushioning said swivel base during stopping, and control means (20) adapted to receive signals from the angle sensor, the setting adjuster and the detector means and to transmit signals to the actuator valve and to the flow control valve to swivel the swivel base at a predetermined speed, said control means having a first swivel speed computing function to provide a first speed accelerated with swivelling of the swivel base, a second swivel speed computing function to provide a second speed decelerated as the swivel base approaches a stopping position, a third swivel speed computing function to provide a third, predetermined constant speed as a maximum permissible speed over an entire swivel range of the swivel base, a swivel speed setting function to set the slowest swivel speed at an angular position of the speeds provided by the first to third computing functions to be the swivel speed for that angular position, and an overrun correcting function to provide a correcting swivel speed for returning to the stopping position when an overrun of the swivelling is detected.