| 摘要 |
The keylevers, trip levers and sublevers of a powered type action arrangement are pivotally supported on common pivot rods and mounted in a single mounting bracket with the keylevers biased to a rest position by springs urging the trip levers against the keylevers. The normal rest position of the keylevers and keylever movement necessary to initiate printing are determined by a stop member limiting the movement of the trip levers, and the stop member has a cam-shaped cross-sectional configuration and is rotatable so as to vary the distance of keylever movement necessary to effect printing. The keylever depression is resisted by leaf springs secured to the mounting bracket for engagement by the trip levers, and the resisting pressure may be varied by a pressure adjusting mechanism for moving the leaf springs relative to the trip levers. Each depression of a keylever pivots the associated trip lever to move a cam carried on the associated sublever into engagement with a rotating power roll for driving the corresponding type bar in a printing movement. The engagement of the cams with the power roll is limited by a stop member which is part of an impression control mechanism, and the position of the stop member may be adjusted to uniformly vary the impact intensity of all the type bars. After a cam is disengaged from the power roll, the momentum imparted to the type bar continues its printing movement toward the platen against the urging of a return spring connected to the sublever for returning it to a rest position. The impact intensity of each type bar may be individually varied by controlling the tension of the return spring, and the mounting bracket has a plate with a plurality of holes associated with each type action for enabling the return spring to be stretched to different distances. To prevent the type bars from undergoing a printing movement when a carriage supporting the platen is in a left margin position, a bail is pivoted into blocking relation with the cams for restricting engagement with the power roll.
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