Printing – Flexible-sheet-securing devices
Reexamination Certificate
2000-05-17
2002-09-03
Evanisko, Leslie J. (Department: 2854)
Printing
Flexible-sheet-securing devices
C101S378000, C101S486000, C101SDIG029
Reexamination Certificate
active
06443065
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to printing presses and more particularly to a plate cylinder for a printing press as well as to a tool and a method for registering plates on the plate cylinder.
2. Background Information
Printing presses may print a continuous web of material, such as paper. A plate cylinder of the printing press may firmly hold or lock-up a flat printing plate, for example a lithographic printing plate. An image to be printed is formed by ink which is transferred from the printing plate to the paper. In offset printing presses the plate first transfers ink to a blanket and then to the paper.
For an image to be printed properly, the plate must be properly registered on the plate cylinder. To permit proper axial registration, the printing plate must be axially movable with respect to the paper or other material to be printed.
In prior art devices, the plate may be fastened first to the plate cylinder and the entire plate cylinder moved axially to provide proper axial register.
For large newspaper and other presses, it often is desirable to have more than one printing plate spaced axially about the plate cylinder, so that, for example, four sections can be printed. It then becomes desirable to be able to register each printing plate independently, so that proper register for each plate can be provided. However, solely moving the plate cylinder does not provide for independent registration.
Moreover, even for single plate cylinders, axial registration devices are often complicated and expensive.
BRIEF SUMMARY OF THE INVENTION
An object of the present invention is to provide a plate cylinder which provides for simple registration of a printing plate. Another alternate or additional object of the present invention is to provide an external registration tool for registering plates on a plate cylinder. Yet another alternate or additional object of the present invention is to provide a simple method for registering printing plates on a plate cylinder. Still another alternate or additional object of the present invention is to provide for independent registration of a plurality of plates on a multi-plate plate cylinder.
The present invention provides a plate cylinder comprising a cylinder body having at least one external slot extending axially with respect to the cylinder body, and at least one register pin slidable by an external registration device within the slot.
A spring element interacting with a rotatable actuator can permit axial movement of the register pins within the slot when the actuator is in a first position, and can lock the register pins in the slot when the actuator is in a second position.
By permitting for an external device to move the pins, the printing plate or press itself does not need to contain the registration mechanism. Thus a simpler and more efficient construction of the plate cylinder can result. In particular at high press speeds, such as 2500 feet per minute or greater, the simpler construction can provide reduced plate cylinder vibrations and improved print qualities.
The plate cylinder is preferably a multi-plate plate cylinder including at least two independently movable register pins.
By permitting each pin to be moved externally and independently from the other pins, simple register of each plate on the plate cylinder can be provided.
The register pin may fit within a slot of the spring element. The spring element preferably comprises two separate springs, one being of low stiffness and the second of higher stiffness. The first low stiffness spring yields a low resistance to sliding the pin, so that a controlled move of the pin can be made. The second spring with a higher stiffness is deformed by a rotation of the actuator. The actuator preferably is an eccentric rod.
The plate cylinder also preferably has location holes or markings for allowing proper placement of the external registration device.
The present invention also provides a printing press comprising a plate cylinder having at least one external slot, the plate cylinder having a register pin slidable in the slot, and an external registration device for sliding the register pin within the slot.
Preferably, the plate cylinder is a multi-plate plate cylinder having a plurality of register pins. The press preferably is a lithographic offset printing press, including a blanket cylinder interacting with the plate cylinder. The simple construction of the plate of the present invention is particularly advantageous when used in combination with a gapless blanket. U.S. Pat. No. 5,429,048 is hereby incorporated by reference herein as an example of an offset lithographic printing press with a removable gapless blanket.
The present invention also provides for an external registration device including a base for attaching to a periphery of a plate cylinder and a pin pusher interacting with a register pin in a slot of the plate cylinder, the pin pusher being axially movable relative to the base.
The base is preferably attached to the plate cylinder using location pins, which interact with location holes in the plate cylinder. Alternately or additionally, the base may be magnetic to be firmly held on the plate cylinder during a registration adjustment.
The pin pusher preferably is movable axially with respect to the base through a nut and screw arrangement. The pin pusher may thus function as a nut by having an internally threaded hole, while an axially extending rod has external threads and function as the screw. An adjustment knob for fine control of the rotational position of the rod can be attached to one end of the rod. Thus by rotation of the adjustment knob, the pin pusher can be axially adjusted to move the registration pin.
The present invention also provides a method for registering plates on a plate cylinder comprising the steps of:
placing an external registration device on a plate cylinder having at least one register pin, and
moving the register pin axially with the external registration device.
The method also preferably includes the step of providing a printing plate having a notch for interacting with the register pin to the plate cylinder, and most preferably to providing a plurality of printing plates to the plate cylinder, the plates being spaced axially apart from one another.
REFERENCES:
patent: 4748911 (1988-06-01), Kobler
patent: 5317971 (1994-06-01), Deye, Jr. et al.
patent: 5379694 (1995-01-01), Haek et al.
patent: 5419248 (1995-05-01), Brotzman
patent: 5429048 (1995-07-01), Gaffney et al.
patent: 5533446 (1996-07-01), Hashimura et al.
Charette William Albert
Dufour Charles Henry
Sposato, Jr. John James
Zlatin Lev
Davidson Davidson & Kappel LLC
Evanisko Leslie J.
Heidelberger Druckmaschinen AG
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