Printing – Planographic – Dampeners
Reexamination Certificate
2002-12-27
2004-09-28
Funk, Stephen R. (Department: 2854)
Printing
Planographic
Dampeners
Reexamination Certificate
active
06796228
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a dampener having a device for precisely metering dampening solution to a plate cylinder in an offset lithograph printing press and, more particularly, to a dampener having a device configured to enable a press operator to finely adjust a roller toward and away from an adjacent roller for precise control of a film of dampening solution that is to be deposited on an offset lithographic printing plate.
2. Background of the Related Art
On a printing press utilizing the offset lithographic method of printing there is typically required a dampener for applying dampening solution to a printing plate to ensure that the non-image area of the plate and, consequently, the non-image area of the printed sheet, is kept clear of ink.
Generally, there are two types of dampeners used on offset lithographic printing presses: ductor-type dampeners and continuous-type dampeners.
Ductor-type dampeners include at least a form roller pressed against and rotating at the same speed as a plate cylinder (press speed) of a printing press, a pan roller rotating at less than press speed for picking up dampening solution from a pan, and a ductor roller that ducts back and forth between the form roller and pan roller. Although still sometimes sold by press manufactures, ductor-type dampeners are less efficient because they are unable to deliver an even film of dampening solution to the printing plate, thereby leading to imperfect ink-water balance and all of the printing conditions associated therewith.
There are basically two types of continuous-type dampeners: pan-type continuous dampeners and seal-type continuous dampeners. Pan-type continuous dampeners come in a wide variety of configurations but can be generally described to include at least a form roller pressed against a plate cylinder and rotating at press speed, a metering roller pressed against the form roller and rotating at press speed, and a pan roller pressed against the metering roller and positioned in a pan for picking up dampening solution Dampening solution is fed to the pan during printing operations. In some configurations the pan roller is rotated at less than press speed through the use of reduction gearing or an adjustable drive motor. Exemplary pan-type continuous dampeners are disclosed in U.S. Pat. No. 3,168,037 to Dahlgren and U.S. Pat. No. 5,158,017 to MacConnell, et al., both of which are incorporated by reference herein.
Seal-type continuous dampeners can be generally described to include at least a form roller pressed against a plate cylinder and rotating at press speed, and a metering roller pressed against the form roller and rotating at press speed. Seals are provided at the ends of the form roller and metering roller to form a reservoir for dampening solution above the nip between the rollers. Dampening solution is fed to the reservoir during printing operations. Exemplary seal-type continuous dampeners are disclosed in U.S. Pat. No. 3,769,909 to Fugman, et al., and U.S. Pat. No. 4,455,398 to Loudon, both of which are incorporated by reference herein.
In contrast to ductor-type dampeners, continuous-type dampeners are preferred because of their superior ability to provide a relatively even film of dampening solution to the plate, and thereby provide much improved ink-water balance.
Continuous-type dampeners, in particular pan-type continuous dampeners, include a number of adjustments to allow an operator to align the rollers so the dampener can provide an even film of dampening solution to the plate cylinder. A particularly critical adjustment is between the metering roller and an adjacent roller since this is where the film of dampening solution emanates. In a pan-type continuous dampener the film of dampening solution can be said to emanate from between the pan roller and the metering roller, and in a seal-type continuous dampener the film of dampening solution can be said to emanate from between the metering roller and form roller. The adjustments in these dampeners are, however, often rather crude and result in diminished print quality. In addition, the adjustments are not always accessible (e.g., they are under a safety guard) to a press operator during print operations. Further, the adjustments often require tools, which make it dangerous to make an adjustment when a press is rotating. Furthermore, because fine-tuning of a print operation takes place while a printing press is printing sample sheets, the efficiency of press operators and the quality of the printing job suffers if the printing press must be stopped each time an adjustment must be made to the dampener.
It will be well appreciated by those of ordinary skill in the art that there are numerous variables that make it necessary for operators to adjust the amount of dampening solution being delivered by a dampener in a printing press. These variables include: changes in ambient temperature between and during print jobs; changes in temperatures on the press during printing (e.g., higher press speeds causes certain press components to heat up); tack and viscosity of the ink; brand and concentration of the fountain solution; type of paper printed (e.g., NCR paper is very absorbent of solution while coated paper is significantly less absorbent of solution); the printing head of the press on which the dampener is mounted; run length of a printing job; age and condition of the rollers on the press; age and condition of the printing press; the operator's experience in adjusting ink flow; the operator's experience in setting roller pressures; and type of printing plate used (e.g., aluminum, polyester). The difficulties in adjusting and, in particular, fine-tuning a dampener severely hinder an operator's ability to overcome these variables.
There is clearly a need in the art for a dampener that includes an adjustment device that will eliminate the problems associated with present-day devices for making an adjustment between a metering roller and an adjacent roller (e.g., form roller, pan roller, intermediate roller.)
SUMMARY OF THE INVENTION
The subject invention discloses a dampener having a device for precisely metering dampening solution in the dampener. The dampener includes a first sideframe and a second sideframe for supporting rollers adjacent a plate cylinder in a printing press. A form roller is rotatably supported by the first and second sideframes in parallel relationship with and contactable with the plate cylinder during printing operations. A metering roller is rotatably supported by eccentric collars, which are rotatably supported by the first and second sideframes. The metering roller is positioned adjacent the form roller so a nip may be formed there between. Seals are pressed against end portions of the form roller and metering roller to form a dampening solution reservoir there between. Dampening solution is supplied to the reservoir during printing operations.
Adjustment devices for adjusting the eccentric collars are included. Each adjustment device includes an arm having a first end and second end. The first end is attached to the eccentric collar so the arm may be used to rotate the eccentric collar to move the metering roller toward and away from the form roller. The second end of the arm includes a threaded pivot. An attachment block is rotatably mounted to the side frame. An adjustment shaft has its first end threadingly engaged with the threaded pivot and its other end rotatingly mounted to the attachment block. By rotating the adjustment shaft the metering roller may be moved toward and away from the form roller. The adjustment device provides for precise metering of dampening solution in the dampener.
Further embodiments and features of the dampener having an adjustment device for precisely metering dampening solution will become readily apparent from the following detailed description taken in conjunction with the drawings.
REFERENCES:
patent: 2795188 (1957-06-01), Williams
patent: 3168037 (1965-02-01), Dahlgren
patent: 3552
Goodwin Lyle
Pudark Arthur
Day International Inc.
Funk Stephen R.
Pillsbury & Winthrop LLP
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