US 4,285,605 AGranted

Escapement mechanism and backspace mechanism for a moving paper carriage typewriter having dual pitch capability

AssigneeInternational Business Machines Corporation

InventorsEdward R. Lloyd, Raymond M. Marowski

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Abstract

A mechanism which will function to allow the escapement of the carriage of a typewriter in one of two predetermined escapement pitches and be capable of backspace operation from a single backspace input for both pitches regardless of which escapement pitch is selected. Escapement ratchets for the two selected pitches are combined, together with a backspace ratchet. Each of the escapement ratchets are engageable by an escapement pawl and the engagement of a pawl with a particular ratchet will determine the pitch within which the escapement system will function. A backspace ratchet is combined with the escapement ratchets and fixedly attached thereto to provide the backspace drive. The backspace ratchet is selectably engageable by the backspace pawl for causing rotation in the opposite direction of that normally utilized for escapement. All motion of the escapement ratchets or backspace ratchet is transmitted through a pinion mounted to the ratchet assembly and, in turn, is transmitted to the paper carriage rack.

Claims3

Dependent claims

An escapement and backspace apparatus for a dual pitch typewriter having a carriage, a printing means, means for selecting characters on said printing means,

said carriage associated with said typewriter to translate relative thereto:
escapement means for defining the positions of said carriage with respect to said typewriter and for moving said carriage through said positions in stepwise manner, in a selected one of a plurality of predetermined escapement pitches, said escapement means comprising, a plurality of escapement ratchets, each defining a separate escapement pitch, and a backspace ratchet, said ratchets associated to rotate together, the ratchet teeth on said backspace ratchet subtending an arc equal to the lowest common divisor of the angles subtended by the teeth on said escapement ratchets;
an escapement pawl operatively associated with each of said escapement ratchets,
means for withdrawing said escapement pawls from said escapement ratchets and thereafter releasing said escapement pawls for re-entry into the next tooth of said escapement ratchets,
operator controlled means for rendering all but one of said escapement pawls inoperative;
and a backspace pawl operative to engage said backspace ratchet and rotate said backspace ratchet in a backspacing direction by an arcuate increment greater than the arc subtended by the largest arc between teeth on said escapement ratchets.

3 more elements

Dependencies are inferred from the claim text.