Various typewriters are particularly constructed to take a sealed ribbon supply cartridge that contains a ribbon supply spool and a ribbon take-up spool with a run of ribbon that extends exteriorly of the cartridge between the two spools so that it may be engaged in the ribbon guides of the typewriter. The ribbons in such cartridges are single pass ribbons, and the cartridge structure makes them relatively expensive to use. An example of such a typewriter is disclosed in U.S. Pat. No. 3,604,549.
Further, as taught in U.S. Pat. No. 3,604,549 some typewriters have a ribbon advance which is adjustable for use either with a total release ribbon or with a ribbon of the solvent coated plastic transfer matrix type such as that disclosed and claimed in U.S. Pat. No. 3,413,184. The first type of ribbon prints satisfactorily only if there is no overstriking of a previously printed area; whereas, in the case of the plastic transfer matrix ribbon, limited overlapping is permissible. The mechanism disclosed and claimed in U.S. Pat. No. 3,604,549 provides a simple means for adjusting the ribbon advance by means of a vertically movable control member which is spring biased to an elevated position in which the ribbon advance moves the ribbon each time a character is printed. Depressing the control member changes the ribbon advance mechanism to provide the limited overstriking that is permissible with the plastic transfer matrix type ribbon.
As taught in U.S. Pat. No. 3,604,549, the cartridge for the total release ribbon does not touch the vertically movable control member; while the cartridge for the plastic transfer matrix ribbon is built with internal means which depresses the ribbon advance control member when the cartridge is mounted upon the typewriter.