Pneumatic apparatus for the rotation of valve rods

Claim 1

A pneumatic rotary actuator for operation of a valve, comprising: (i) a first casing having a side wall with a cylindrical internal face, and having an end wall with a central hole; (ii) a resilient annular sealing gasket disposed within and secured to the side wall of the casing, said gasket having two diametrically opposed internal expansions so as to define, within said casing, a cavity having an approximately 8-shaped configuration including two half-chambers, said casing side wall including two inlet and outlet ports each opening into a respective one of said half-chambers; (iii) a pin having one end journalled in said central hole of the casing end wall and carrying two radial blades lying in the same plane, and the vertical edges of which blades are in contact with said sealing gasket, said blades dividing each half-chamber into two sectors, said pin having two through-holes disposed on different horizontal parallel planes and oriented so as to provide communication between two opposite sectors of the half-chambers, and (iv) a second casing secured to said first casing and having a central through-hole in which the protruding other end of said pin is journalled.