Semi-rotating single acting pneumatic actuator

Claim 1

A semi-rotating pneumatic actuator comprising a tubular body defining a cylindrical bore housing two valve shutter actuating pistons, each piston being provided with a plurality of blind holes and with opposite portions formed as respective racks meshing with a pinion mounted on an output shaft of said actuator, said two pistons defining a chamber for receiving an operating fluid, two disc members housed in said body, each disc abutting on a respective said piston and having a circular array of apertures registered with said blind holes in said pistons, two flanged disc-shaped spring guides arranged in said body adjacent the ends thereof and rigidly removably coupled thereto, each spring guide having a circular array of apertures registered with said apertures of a said disc member, each said spring guide being further provided with a central through hole having a polygonal portion in which an internally threaded bush is engageable, each said flanged spring guide defining an outer cylindrical seat in which there is received a respective disc shaped end cap having a central through hole through which extends a hollow screw engaged in said bush, said hollow screw having a threaded axial through hole in which is threadedly engaged an adjustment screw on end of which is engageable with the adjacent piston whereby to determine the end of the stroke of the piston, and a plurality of piston biassing springs threaded through the registered holes of said pistons and apertrures of said disc members and spring guides, the outer ends of said springs adjustably abutting against the flat inner face of a respective said end cap.