This invention relates to ribbon storage devices and particularly to ribbon storage devices of the type commonly called ribbon cartridges or cassettes especially useful for printing machines.
Ribbon cartridges are known in the art where an endless ink ribbon is stacked in uniform folds in a storage chamber by a packing mechanism. The packing mechanism may be external to the ribbon cartridge or may be part of it. The ribbon is drawn from one end of the ribbon stack and fed past recording heads, for example, by the packing mechanism or other means. Such devices are described in U.S. Pat. Nos. 539,683; 764,342; 1,063,289 and 2,685,357, as well as the abovecited related patent application. A known advantage of uniformly-stacked ribbon over randomly stuffed ribbon such as shown in U.S. Pat. Nos. 3,989,132 and 3,974,906 is that storage space is more efficiently used thereby increasing the available supply of storable ribbon. Further advantages of a uniformly folded ribbon are realized in the reduction in hangups and jams within the cartridge which produce wide variations in the tension applied to the ribbon often experienced with randomly stuffed ribbon masses.
In order to provide a uniform ribbon stack, it is necessary for the ribbon to be contained and supported on both ends as well as the outer edges, otherwise the stack can collapse thereby causing bunching or tangling of the ribbon, especially where the ribbon has been used over a long period. The approach shown in the cited patents is to virtually fill the cartridge to the very point of exit. This, however, has been found to cause hangups or jamming at the exit to the cartridge. The problem is aggravated by changes in physical characteristics of the ribbon resulting from its extended use. It has been found that these changes cause the length of the ribbon stack to vary during use, thus the packing mechanism experiences variations in the back pressure which can affect the uniformity of the folding operation. Creasing, curling, uneven wear occuring during extended use, along with and/or the degradation in the uniformity of folding are considered causes for the variation in the length of the ribbon stack and the variation in the back pressure.