Pneumatic actuator.

摘要

A pneumatic actuator comprises a cylindrical cell (1) through which a normally laminar flow of air from a source (6) passes between an inlet jet (2) and an outlet jet (3) to provide an output pressure in outlet pipe (8). The cell (1) includes a piezo-electric element (9) arranged, in response to a suitably modulated oscillating electrical signal, to produce an acoustic signal that disturbs the laminar flow whereby air exhausts through exhaust ports (4) and the output pressure in the pipe (8) falls. The differing pressure outputs in the pipe (8) may be used to control the state of a pneumatic device such as a valve. The electrical signal is produced by a photo-diode (10), via a matching circuit (11), in response to a suitably modulated optical control signal generated by a laser source (12) and transmitted to the photo-diode (10) along a fibre optic cable (13). An actuator of the invention has extremely fast response times compared to prior pneumatic actuators, typically of the order of 5 milliseconds.