Page "Clutch" Paragraph 27

Also known as a slip clutch or safety clutch, this device allows a rotating shaft to slip when higher than normal resistance is encountered on a machine.

An example of a safety clutch is the one mounted on the driving shaft of a large grass mower.

The clutch will yield if the blades hit a rock, stump, or other immobile object.

Motor-driven mechanical calculators had these between the drive motor and gear train, to limit damage when the mechanism jammed, as motors used in such calculators had high stall torque and were capable of causing damage to the mechanism if torque wasn't limited.