Patent ID: 8776667

Claim:
A fluid-dynamic actuator comprising: a cylinder ( 2 ) and a piston ( 3 ), which includes a rod ( 5 ) having a longitudinal axis ( 6 ); the piston ( 3 ) being movable inside the cylinder ( 2 ) along a path of travel ( 9 ) parallel to said axis ( 6 ); the actuator ( 1 ) further including a detection system ( 13 ) for determining a position of the piston ( 3 ) along a path of travel ( 9 ), and wherein said detection system ( 13 ) comprises: a plurality of first grooves ( 14 ), which are machined on an outer surface of respective sections ( 15 ) of the rod ( 5 ) so that respective projections of the first grooves ( 14 ) onto a first plane parallel to the axis ( 6 ) define respective first segments ( 14 a ) parallel to one another and arranged obliquely with respect to a projection of the axis ( 6 ) onto the first plane; a plurality of second grooves ( 17 ), which are machined on an outer surface of the rod ( 5 ) and extend parallel to the axis ( 6 ) for respective lengths such that a respective number of second grooves ( 17 ) run across the outer surface of each of the sections ( 15 ); optical sensing means ( 19 , 21 ) to detect the presence of second grooves ( 17 ) in correspondence with a second plane ( 20 ) transversal to the axis ( 6 ) and fixed with respect to the cylinder ( 2 ) and a first displacement ( 32 ) of the first segments ( 14 a ) along a reading line ( 31 ) defined by an intersection of the second plane ( 20 ) with the first plane, said first displacement ( 32 ) being due to a movement of the piston ( 3 ) along the path of travel ( 9 ); and processing means ( 22 ) to identify the section ( 15 ) of rod ( 5 ) present in correspondence with the second plane ( 20 ) by counting the detected second grooves ( 17 ) and to measure the position of the piston ( 3 ) along the path of travel ( 9 ) as a function of the identified section ( 15 ) and of said first displacement ( 32 ).