The scotch yoke mechanism is precisely positioned inside a perfectly sealed housing which protects it against corrosion in the most adverse environments. The housing also encompasses a stem thrust support device suitable to withstand the transversal forces generated during rotation and to ensure the proper alignment of the piston rod with the sliding blocks. Low rotational friction is also ensured by means of oversized precise fitted bronze yoke shaft bushings which contribute to extend heavy duty working life span.
The scotch yoke mechanism transforms the linear movement (thrust) of the piston into a 90° rotation (torque). ProControl actuators can be supplied with an inclined scotch yoke (canted) or a symmetric scotch yoke.
The symmetric scotch yoke is normally employed when the valve torque requirements are highest during the intermediate positions of the valves rotation (running), whilst lower at the beginning (valve unseating) and the end (valve reseating) of the valve 90° rotation. The symmetric scotch yoke mechanism is normally used for plug and some ball valve designs.ProControl
The canted scotch yoke is advantageous when the valve torque requirements are highest at the beginning (valve unseating) and the end (valve reseating) of the valve 90° rotation, whilst lowest during the intermediate position (running). The canted scotch yoke mechanism covers most ball and butterfly valve torque requirements.ProControl