Fail-safe motor-driven cylinder for lifting apparatus

For use with lifting apparatus, a motor-driven cylinder including:

• a frame;
• a motor supported fixedly in said frame and having a rotatable shaft;
• screw means having intermeshed internally and externally threaded members;
• torque transmission means coupled between said rotatable shaft and said externally threaded member of said screw means;
• said torque transmission means including torque sensing means movable from a first position in the presence of torque transmission between said shaft and said screw means to a second position in the absence of troque transmission between said shaft and said screw means;
• braking means carried by said torque sensing means and operative upon the movement of said torque sensing means to said second position to prevent rotation of said internally threaded member in said screw means;
• and,
• load coupling means coupled to said screw means;
• said torque sensing means including first and second intermeshed helical gears coupled between said rotatable shaft of said motor and said screw means, said first and second helical gears, when transmitting torque, producing a force in the direction of said first position of said torque sensing means.

For use with lifting apparatus, a motor-driven cylinder including:

• a frame;
• a motor supported fixedly in said frame and having a rotatable shaft;
• screw means having intermeshed internally and externally threaded members;
• torque transmission means coupled between said rotatable shaft and said externally threaded member of said screw means;
• said torque transmission means including torque sensing means movable from a first position in the presence of torque transmission between said shaft and said screw means to a second position in the absence of torque transmission between said shaft and said screw means;
• braking means carried by said torque sensing means and operative upon the movement of said torque sensing means to said second position to prevent rotation of said internally threaded member in said screw means;
• and,
• load coupling means coupled to said screw means;
• said torque sensing means including first and second intermeshed helical gears coupled between said rotatable shaft of said motor and said screw means.