Importance

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Abstract

A high resolution ink jet printer includes a rotating drum and a pair of ink jet heads scanned along a substrate carried by the drum in a direction parallel to the axis of the drum. The heads are driven by a lead screw coupled to the drum drive shaft and a control unit controls the rate of drop ejection from the printheads at a rate corresponding to the rate of encoder signals received from an encoder coupled to the drum drive draft. One printhead receives and ejects drops of black, magenta, cyan and yellow high-density inks and the other printhead ejects drops of black, magenta and cyan low-density inks along with another ink which may be a different color or black ink of a different density. High resolution and high print quality are assured by accurate control of the distance between the drum support shaft and the drum surface and also between the drum support shaft and a carriage support rail on which the printhead is supported as it moves adjacent to the drum surface. For hot melt ink, a heater is provided adjacent to the drum surface to maintain the drum surface temperature at a constant level below the melting point of the ink and a housing surrounding the printer has a controlled temperature zone to maintain the ambient temperature about 10.degree. C. below the drum temperature.

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First Claim