Speed control unit for a pneumatic rotation motor

A speed control unit for a pneumatic rotation motor having a stator with an air inlet passage, and a rotor journalled in the stator, said speed control unit comprising:

• a speed governor including at least two flyweight members, a bias spring, and a valve element displaceable by said flyweight members against said bias spring to restrict air flow through said inlet passage of said stator of said pneumatic rotation motor at motor operation speeds above a predetermined first speed level;
• and
• an overspeed safety device including a flow restricting element which is movably supported in said stator of said pneumatic rotation motor and which is shiftable between a rest position and an active flow restricting position, a spring which biases said flow restricting element toward said active position, a trip element which normally locks said flow restricting element in said rest position, and a speed responsive actuator which is co-rotative with said rotor and which is arranged to release said trip element and free said flow restricting element for movement toward said active position at motor operation speeds above a second predetermined motor speed level;
• wherein said rotor of said pneumatic rotation motor comprises a coaxial blind bore having an open end facing said air inlet passage and in which a mounting structure is provided for movably supporting said flyweight members, said bias spring, and said valve element within said bore;
• wherein said valve element comprises an air flow controlling head located outside said bore;
• and
• wherein said speed responsive actuator comprises an elongate spring element having a first end secured in a coaxial bore in said valve element and having a second end extending out of said valve element, with said elongate spring element being radially supported in an elastically bent shape and being arranged to be exposed to centrifugal action such that when said pneumatic rotation motor attains said second predetermined motor speed level said elongate spring element is further bent by the centrifugal action and said second end of said elongate spring element hits and releases said trip element.