Torque-limiting carriage return knock-off mechanism

摘要

A carriage return device utilizing a spring clutch and shock unloader spring is disclosed in conjunction with a cord tension sensing mechanism for detecting the cord tension increases when the paper carriage of a typewriter ceases to move and the carriage return drive mechanism continues to operate. It is desirable to disengage the drive mechanism at that point rather than to cause frictional wear or overloading of the motor pending a predetermined amount of driving time prior to disengagement. Upon the cord tension reaching a preset value, the clutch pawl will disengage the drive clutch and prevent further wear of the clutching arrangement. To prevent premature disengagement of the clutch, a shock unloading pretensioned spring is incorporated in the drive unit to absorb the initial shocks of clutch engagement and the forces experienced during acceleration of the paper carriage.