A system for determining torque generated by a motor actuated operator driving a partial turn valve including a torque ring replacing the cover of the operator housing, a frictional shaft coupling member coupling the inner circumferential surface of the drive sleeve within the operator housing to the...http://www.google.de/patents/US5197338?utm_source=gb-gplus-sharePatent US5197338 - System and method for determining torque output of motor actuated valve operators
