System for operating a fluid actuator

System for driving an actuator which comprises:

• a chamber,
• a shutter of an injection nozzle for molten material for injection molding, and
• a piston that is
• movable/translatable inside the chamber following the action on the piston of a pressurized fluid, and
• connected to the shutter,
• the system being configured to adjust/vary the stroke of the shutter and comprising a device or means for forcing the transfer of a predetermined amount of fluid between the outside and inside of the chamber,
• wherein the amount of fluid is determined before sending it to the actuator or extracting it from the actuator,
• so as to bring/move the shutter from a closing position, in which there is no passage of molten material, towards an opening position, in which there is passage of molten material, by injecting the predetermined amount of fluid from the outside into the chamber or by injecting the predetermined amount of fluid from the chamber towards the outside, and/or
• so as to bring/move the shutter from an opening position, in which there is passage of molten material, towards a closing position, in which there is no passage of molten material, by extracting the predetermined amount of fluid from the chamber or by injecting the predetermined amount of fluid into the chamber, respectively.