Fluidic actuator

A fluidic, especially pneumatic, positioning drive, especially a valve-positioning drive, comprising:

• a drive element (2) to which pressurized fluid can be admitted;
• and
• a proportional position regulator (3) that regulates the admission of pressurized fluid to the drive element, wherein:
• the position regulator (3) is constructed in two stages, comprising an electrofluidic pilot stage (10) and a fluidic power stage (11);
• the electrofluidic pilot stage (10) comprises an electrical signal input (13), precisely one electromechanical transducer (14) and precisely one proportional valve (16) actuated thereby, with a pressurized-fluid inlet (18), a control-pressure outlet (19) and a vent outlet (20);
• the fluidic power stage (11) comprises two poppet valves (24, 25), which are mounted in a housing (23) and which can be pneumatically actuated via two respective pressure-displacement transducers acting on the valve spindle (28, 29) in question;
• the two pressure-displacement transducers are pressurized from a common control chamber (34), which is disposed in the housing (23) between the poppet valves (24, 25) and is in communication with the control-pressure outlet (19) of the pilot stage (10);
• in the absence of fluidic pressurization, i.e. when the control chamber (34) is unpressurized, a first (24) of the two poppet valves (24, 25) of the power stage (11) is biased into an open position and a second (25) into a closed position;
• the first pressure-displacement transducer associated with the first poppet valve (24) is matched to the second pressure-displacement transducer associated with the second poppet valve (25) in such a way that, during a steady rise of the pressure in the control chamber (34) over a working-pressure range defined by a lower operating pressure (B 1) and an upper operating pressure (B2), the first poppet valve (24) is closed progressively at first and, only after the first poppet valve (24) has been closed completely, is the second poppet valve (25) opened progressively.