Ratchet wheel 1 is keyed to shaft 6 and rigidly attached to gear 2 which meshes with rack 3. Rack 3 is attached to the typewriter carriage. A constant torque is applied to wheel 1 about fixed axis A (see View II). As a key is struck, member 5 turns counterclockwise (see View I), movable pawl a is disengaged from a tooth space of wheel 1, being replaced by pawl b (see View III) so that ratchet wheel 1 cannot rotate. As soon as pawl a disengages wheel 1, it is turned by spring 4 to the position shown in View III. As member 5 swings back clockwise (see View I), pawl b is disengaged from the tooth space and ratchet wheel 1 is thereby released, but in turning it engages movable pawl a which is near the next tooth space. Thus, ratchet wheel 1 can only turn through an angle corresponding to one tooth.
$2787$RG,FD$