Printing – Multicolor – Rotary machines
Reexamination Certificate
2000-12-01
2003-03-18
Colilla, Daniel J. (Department: 2854)
Printing
Multicolor
Rotary machines
C101S232000
Reexamination Certificate
active
06532869
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an offset printer, and more particularly, to a multiple color printer provided with a sheet feed mechanism for feeding a sheet or other print medium to a sheet feed cylinder.
A multiple color offset printers are known for printing in multiple colors. For example, Japanese Patent Application Publication Toku-Hyou-Hei-9-510410 discloses a four color offset printer in which a single impression cylinder, a single sheet discharge mechanism, a single sheet feed conveyor (feeder), a single sheet feed cylinder, two blanket cylinders, two plate cylinders, and ink roller groups for four colors are provided.
A sheet feed mechanism including the sheet feed conveyor and the sheet feed cylinder is adapted for supplying a sheet to a surface of the impression cylinder. The impression cylinder has an outer peripheral surface where the sheet is held. The sheet discharge mechanism is adapted to remove the sheet from the surface of the impression cylinder. The blanket cylinders are adapted to press the sheet against the impression cylinder to form an ink image on the sheet.
The outer peripheral surface of the impression cylinder is provided with grippers, each gripper having a pawl at its tip for holding a sheet. The impression cylinder is equally divided into three segments for holding each sheet at each segment, and is driven by a drive motor. Axes of the blanket cylinders and the paper feed cylinder are disposed in parallel with the axis of the impression cylinder, and outer peripheral surfaces of the blanket cylinders and the paper feed cylinder are in contact with the outer peripheral surface of the impression cylinder. The blanket cylinders, the sheet feed conveyer, the sheet feed cylinder, and the sheet discharge mechanism are rotated by rotation of the impression cylinder.
Each plate cylinder is provided with a plate at its outer peripheral surface. The axes of the two plate cylinders are disposed in parallel with the axes of the two blanket cylinders, and each plate cylinder is in contact with a corresponding blanket cylinder, so that each plate cylinder is rotated by the rotation of the corresponding blanket cylinder. The outer peripheral surface of each plate cylinder is equally divided into two plate segments, and each plate segment has a peripheral length equal to that of each segment of the impression cylinder. Each plate segment is provided with a plate for one specific color, and a different color is associated with each plate. Therefore, totally four plates for four different colors are provided in the two plate cylinders.
Each ink roller group is adapted for supplying ink to the plate on the plate cylinder. Two groups of ink rollers are provided for one plate cylinder so as to supply inks of two colors. Therefore, totally four groups of ink rollers are provided for supplying inks of four different colors. The ink rollers have axes in parallel with the axis of the plate cylinder, and are in contact with the plate cylinder. The ink rollers are rotated by the rotation of the plate cylinder.
In this way, in the offset printer capable of performing four color printing with the two blanket cylinders, each sheet is printed with two colors during each single rotation of the impression cylinder, and printing of the additional two color is performed during the second rotation of the impression cylinder. That is, each sheet is held on the impression cylinder for two rotations thereof, and thereafter must be released from the impression cylinder by the sheet discharge mechanism. If each sheet is supplied to the impression cylinder at every single rotation of the impression cylinder, it becomes impossible to perform four color printing with respect to each sheet. To avoid this, a sheet is supplied to every other segment of the impression cylinder. For example, if a sheet is supplied to a first segment, then, a sheet is not supplied to a second segment, but a sheet is supplied to a third segment. The supplied sheet is held on the impression cylinder until completion of two rotations thereof and is then discharged from the impression cylinder by the sheet discharge mechanism.
No specific arrangement is proposed in the Japanese patent application publication No. Toku-Hyou-Hei 9-510410 for supplying a sheet to every other segment of the impression cylinder.
One conceivable arrangement is to design the outer peripheral length of the sheet feed cylinder equal to the peripheral length of each segment of the impression cylinder, and supply a sheet to the impression cylinder at every second rotation of the sheet feed cylinder. To this effect, it is necessary to supply sheet to the sheet feed roller every second rotation thereof. Because a single sheet must be transferred to the impression cylinder at every second rotation of the sheet feed cylinder, if a sheet is supplied to the sheet feed roller at every single rotation thereof, two sheets must be held at the outer surface of the sheet feed roller, or else a first sheet already held at the sheet feed cylinder must be released therefrom when the sheet feed roller receives a subsequent sheet. In the latter case, the sheet supplying system may operate abnormally.
In another aspect, when the sheet is to be supplied to the impression cylinder, orientation of the sheet and lateral position of the sheet are important factors. To this effect, a sheet abutment mechanism (a front lay mechanism) for adjusting the orientation of the sheet and a sheet lateral position control mechanism for adjusting the lateral position of the sheet are conventionally provided at positions upstream of the sheet feed cylinder. However, no detailed arrangement has been proposed for driving the sheet abutment mechanism and the sheet lateral position control mechanism in order to supply sheet to the impression cylinder at every second rotation of the sheet feed cylinder.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a multiple color offset printer having a sheet feed mechanism capable of supplying each sheet from the sheet feed cylinder to the impression cylinder at a desired timing.
This and other objects of the present invention will be attained by an improved multiple color offset printer for forming a multiple color image on a sheet including a plate cylinder, a blanket cylinder, an impression cylinder, a sheet feed cylinder, a sheet feed cylinder gripper, a feeder board, and a swing mechanism. The plate cylinder is rotatable about its axis and has an outer peripheral surface equally divided in a circumferential direction into at least two color regions. An ink image is formed on each color region, and each color region has an equal circumferential length. The blanket cylinder is rotatable about its axis and has an outer peripheral surface in contact with the color regions and equally divided in a circumferential direction into at least two color sections. Each ink image on each color region is transferred to each color section, and each color section has an equal circumferential length. The impression cylinder is rotatable about its axis and has an outer peripheral surface on which the sheet is held and transferred. Each color section is in contact with the outer peripheral surface of the impression cylinder for transferring each ink image on each color section onto the sheet. The outer peripheral surface of the impression cylinder is equally divided into a plurality of segments each having peripheral length equal to the circumferential length of the color region and the color section. The sheet feed cylinder is rotatable about its axis and has an outer peripheral surface on which a sheet is held and transferred and in contact with the outer peripheral surface of the impression cylinder for transferring the sheet to the impression cylinder. The outer peripheral surface of the sheet feed cylinder has a peripheral length equal to each peripheral length of each segment of the impression cylinder. The sheet feed cylinder gripper is provided at the outer peripheral surface of the s
Aoyama Hideo
Tahara Naritoshi
Tsuji Yoshiyuki
Colilla Daniel J.
Ryobi Ltd.
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