Typewriter ribbon drive with constant ribbon stepping - controlled by guides limiting engagement between pawl and ratchet wheel

摘要

Typewriter has an ink ribbon drive wherein the ribbon spool is mounted on a ratchet wheel (1) which is rotated by a pawl (9) activated in response to any one typing impression. To ensure that the ratchet mechanism does not affect impression strength of the type (as may occur during ribbon reversal), and to ensure that the ribbon advance is the same at each activation, there are provided two guides (33, 35) arranged so that after a predetermined part of the stroke of the pawl the one guide (33) frees the pawl for engagement with the ratchet wheel and the other guide (35) withdraws the pawl again after a predetermined progress of the whee.