Rotation of gear 1 is transmitted through gears 2, 3, 4, 5 and 6 to gear segment 7, which is supported on and turns about fixed knife-edge A. Turning motion of gear segment 7 is converted into translational motion of link 8. Spring 9 eliminates backlash in the gearing. To prevent the force of spring 9 from leading to unintentional downward motion of link 8, gear 6 has a friction washer (not shown) which counterbalances the force of spring 9 by means of a frictional torque.
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