1. Field of the Invention
The invention relates to flexographic printing press for printing on corrugated board sheet.
2. Description of the Prior Art
A schematic diagram of a conventional flexographic printing press of a general type is shown in FIG. 1 and a plan view in section of an ink roll portion of the press shown in FIG. 1 is shown in FIG. 2.
In the flexographic printing press shown in FIG. 1, a material 1 to be printed is passed between a printing cylinder or roll 3 to which a form plate 2 is attached, and a receiving roll 4 to thereby subject the material 1 to printing.
Flexographic ink 7 is supplied to an ink reservoir formed by a doctor roll 5 and an anilox roll 6.
The doctor roll 5 is driven at a predetermined speed, which is lower than the peripheral speed of the anilox roll 6, by a worm reducing electric motor 8 via sprocket wheels 9, 10 and a chain 11 to transfer ink uniformly to the anilox roll 6.
The anilox roll 6 is driven by the printing roll 3 at the same peripheral speed as the printing roll 3 via a gear 13 containing a one-way clutch 12 therein.
Accordingly, as the operational speed, i.e. the number of revolution per minute of the printing cylinder 3, is increased, the number of revolution per minute of the anilox roll 6 is increased. As a result, the flow rate of ink passed between the doctor roll 5 and anilox roll 6 is increased in accordance the hydrostatic law so that the amount of ink transferred to the surface of the anilox roll 6 is increased.
Consequently, the flow rate of ink varies depending upon the operational speed of the printing cylinder.
This causes variations in thickness of printed matter. When the printing cylinder is rotated at a high speed, ink is transferred to the form plate at an unduly high rate so that beautiful printed matter can hardly be obtained. Moreover, such printed matter is not dried in a short time.