Hydraulic control system and method for a bucket shake operation in a work machine with a hydraulic pump and unloader valve

A control system for a machine,

• the machine including:
• a hydraulic pump for supplying hydraulic pressure to a supply line;
• a bucket;
• at least one bucket actuator operable by the hydraulic pressure to tilt the bucket between an upwardly facing, rack position and a downwardly facing, dump position;
• and
• at least one user control operable by a user to produce control signals, the control signals including a bucket shake control signal;
• the control system including:
• an unloader valve having an unloader valve actuator, the unloader valve being openable in use to relieve the hydraulic pressure from the supply line to unload the hydraulic pump, and closable by the unloader valve actuator;
• a load sensing line arranged to apply a pressure signal, responsive to demand for hydraulic power, to the unloader valve actuator, to close the unloader valve to maintain the hydraulic pressure in the supply line;
• and
• a bucket control valve operable, in use, by the control signals to apply the hydraulic pressure from the supply line to the at least one bucket actuator;
• the bucket control valve being operable, in use, responsive to the bucket shake control signal to cause the at least one bucket actuator to perform a bucket shake operation, the bucket shake operation being a repeated movement of the bucket, alternately towards the rack and dump positions, to shake debris from the bucket;
• wherein the control system is arranged to maintain a constant pressure signal in the load sensing line, to maintain the unloader valve constantly in a closed condition, for a duration of the bucket shake operation.