Printing – Planographic – Rotary machines
Reexamination Certificate
2000-12-28
2002-12-31
Colilla, Daniel J. (Department: 2854)
Printing
Planographic
Rotary machines
C101S177000, C101S217000, C101S232000, C101S246000
Reexamination Certificate
active
06499395
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an offset printing machine, and more particularly, to sheet transfer from a sheet feed cylinder to an impression cylinder and from the impression cylinder to a sheet discharge portion.
Multiple color offset printing machines are known for printing in multiple colors. For example, Japanese Patent Application Publication Toku-Hyou-Hei-9-510410 discloses a four color offset printing machine in which a single impression cylinder, a single sheet discharge mechanism, a single sheet feed conveyor (feeder), a single sheet feed cylinder (sheet transfer 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 driven by rotation of the impression cylinder.
Each plate cylinder is formed 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 formed with a plate for one specific color, and a different color is associated with each plate. Therefore, a total of four plates for four different colors are formed 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, 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 printing machine 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 colors 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 twice rotation of the sheet feed cylinder. However, when a sheet is transferred from the sheet feed cylinder to the impression cylinder, each time one of the impression cylinder pawls holding a sheet at an outer periphery of the impression cylinder intersects with sheet feed cylinder pawls for holding a sheet to the outer periphery of the sheet feed cylinder, a sheet cannot be maintained at the outer periphery of the impression cylinder for more than a single rotation of the impression cylinder.
Further, each of the impression cylinder pawls protrudes radially outwardly from the outer peripheral surface of the impression cylinder, and the sheet feed cylinder pawls protrude radially outwardly from the outer peripheral surface of the sheet feed cylinder. Also, recesses are formed in the section of the impression cylinder and the sheet feed cylinder that confronts the protruding pawls. Therefore, when the pawls of the sheet feed cylinder and the impression cylinder intersect without transferring a sheet, that is, for maintaining a sheet on the peripheral surface of the impression cylinder, the pawl provided to the sheet feed cylinder and protruding toward the corresponding recess on the impression cylinder pushes the sheet held on the impression cylinder, and possibly tears the sheet.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an offset printing machine capable of maintaining a sheet held on the impression cylinder without damaging the sheet by the pawl on the sheet feed cylinder when the pawl on the sheet feed cylinder relatively passes through the pawls on the impression cylinder and when there is no need to transfer a sheet from the sheet feed cylinder to the impression cylinder.
This and other objects of the present invention will be attained by an offset printing machine for forming an image on a sheet including a plate cylinder, a blanket cylinder, an impression cylinder, impression cylinder grippers, a sheet feed cylinder, a sheet feed cylinder gripper, an improved sheet feed side impression cylinder gripper drive mechanism, and an improved sheet feed cylinder gripper drive 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 is 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 a peripheral length equal to the circumferential length of the color region and the color section. The impression cylinders are provided at the outer peripheral surface of the impression cylinder and are movable along with the rotation of the impression cylinder. Each impression cylinder gripper
Aoyama Hideo
Liang Dong
Tsuji Yoshiyuki
Colilla Daniel J.
Ryobi Ltd.
Sughrue & Mion, PLLC
LandOfFree
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