US 4,383,777 AGranted

Torque-limiting carriage return knock-off mechanism

AssigneeInternational Business Machines Corporation

InventorsDouglas H. Eskew, Raymond M. Marowski, Danny R. Sevy

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Abstract

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.

Claims7

Dependent claims

In a typewriter with a moving paper carriage, a carriage return mechanism for returning said carriage to a line beginning position, said carriage return mechanism comprising:

a carriage return cord;
a carriage return cord drum having said carriage return cord attached at one end thereof to said drum;
a first arbor, said arbor attached to said carriage return cord drum in driving relationship;
a normally disengaged clutch spring engageable with said arbor;
a second arbor, said clutch spring attached to and driven by said second arbor;
clutch control means for engaging and disengaging said clutch with and from said first arbor;
carriage return cord tension sensing means coupled to said clutch control means and responsive to predetermined cord tensions for operating said clutch control means;
a drive input means;
a deformable resilient torque transmission means interconnecting said drive input means and said second arbor for transmitting the motion of said input means to said second arbor, while allowing limited relative movement therebetween, and for absorbing loads during deformation, thereby preventing peak initial carriage return cord tensions from prematurely operating said clutch control means.

6 more elements

Dependencies are inferred from the claim text.