This invention relates generally to ink jet printing apparatus of a type suitable for printing addresses on preprinted documents, such as magazines, newspapers and the like. Prior art systems for such purposes have generally employed electrostatic printers or other devices for printing a strip of labels. The printed labels then have been applied to the magazines or newspapers by a suitable label application device. A typical prior art apparatus for feeding preprinted documents and applying such labels thereto is disclosed in Ridenour U.S. Pat. No. 2,606,681.
An example of a prior art system which feeds preprinted documents and prints addresses directly thereon is disclosed in Erikson et al U.S. Pat. No. 4,122,457. The Erikson system utilizes a plurality of ink jet printing nozzles which are oscillated back and forth across a moving document to print lines of characters. The printing speed of the jets limits each jet to a printing output rate of about 250 characters per second. This translates into a document feed rate of only about 125 ft./min., which is much too slow for many applications.
It is well known that ink jet printing can be carried out at much faster speeds than the upper limit mentioned above in connection with the Erikson system. Printers for such high speed printing may generate rows of closely spaced jets, which may be stimulated, charged, deflected, and selectively caught as taught in Mathis U.S. Pat. No. 3,701,998. Such print heads are commercially employed for business forms printing and routinely print documents as they are being transported at a speed of 600 ft./min. Still higher speed applications are described in Frey U.S. Pat. No. 3,913,719 which teaches an ink jet printing apparatus operating in combination with a conventional newspaper printing press.
Heretofore the above mentioned high speed ink jet printers have not been used for addressing purposes due to their relatively high cost and also due to the fact that the industry already has a large investment in conventional addressing systems of the general type described in Ridenour U.S. Pat. No. 2,606,681. Such conventional addressing systems are able to address documents at a reasonably fast speed, but the requirement for off-line printing of address labels and the application of such labels to the documents has been both cumbersome and expensive.