Solid ink jet printers were first offered commercially in the mid-1980""s. One of the first such printers was offered by Howtek Inc. which used pellets of colored cyan, yellow, magenta and black ink that were fed into shape coded openings. These openings fed generally vertically into the heater assembly of the printer where they were melted into a liquid state for jetting onto the receiving medium. The pellets were fed generally vertically downwardly, using gravity feed, into the printer. These pellets were elongated and tapered on their ends with separate rounded, five, six, and seven sided shapes each corresponding to a particular color.
Later solid ink printers, such as the Tektronix Phaser(trademark), the Tektronix Phaser(trademark) 300, and the Jolt printer offered by Dataproducts Corporation, used differently shaped solid ink sticks that were either gravity fed or spring loaded into a feed channel and pressed against a heater plate to melt the solid ink into its liquid form. These ink sticks were shape coded and of a generally small size. One system used an ink stick loading system that initially fed the ink sticks into a preload chamber and then loaded the sticks into a load chamber by the action of a transfer lever. Earlier solid or hot melt ink systems used a flexible web of hot melt ink that is incrementally unwound and advanced to a heater location or vibratory delivery of particulate hot melt ink to the melt chamber.
Basic configurations of a four-color ink loader having independent melt plates have been described in previously issued patents such as, for example, 5,734,402, 5,861,903, and 6,056,394. The disclosures of these patents are hereby incorporated by reference in their entirety.
Embodiments include a solid ink loader for feeding solid ink sticks in a phase change ink jet printer, which includes a first feed channel having a first insertion end and a first melt end for receiving ink sticks and at least one key plate for covering the at least one feed channel. The at least one key plate includes a first plate portion having a first insertion opening for admitting the solid ink sticks into the at least one feed channel, and a first plurality of viewing areas between the insertion opening and the melt end of the at least one channel.