Transport system for a dot matrix printing mechanism

Abstract

A transport system for a dot matrix printing mechanism including an improved overall design for the transport system and improved designs for individual elements of the system and combinations of elements. The overall design of the present invention uses snap fits extensively throughout for ease of assembly and disassembly, integrates many previously separate parts into one-piece members, employs common part designs wherever possible, and uses single parts to perform multiple functions wherever possible. For example, the striker bar and ribbon frame of the system are combined into one piece and the ribbon cartridge is releasably mounted to the ribbon frame using one end of a latch member while the other end of the latch member is used to bias a pressure roller against the paper advancing roller. The overall design also includes a common drive train interconnected between the moving parts of the system whereby all of the moving parts can be powered by a single motor. Novel individual features are also disclosed including a new pawl arrangement for advancing the paper, cam-follower arrangement for the print head, and bearing design for rotatably supporting the shafts of the transport system. Novel combinations of features disclosed include a ribbon cartridge assembly which automatically positions the ribbon slightly spaced from the platen to receive the paper therebetween, structure in the ribbon cartridge assembly for holding the ribbon taut in front of the platen, and support structure for the ribbon cartridge assembly which holds the ribbon on a bias for longer life.