Printing – Planographic – Rotary machines
Reexamination Certificate
1998-08-04
2001-07-10
Hilten, John S. (Department: 2854)
Printing
Planographic
Rotary machines
C101S147000
Reexamination Certificate
active
06257138
ABSTRACT:
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The invention relates to an offset printing press wherein, as seen in the direction of rotation of a plate cylinder, a first applicator roller is assigned to a dampening unit and a second applicator roller to an inking unit, a bridge roller is in contact with the first and second applicator rollers, and a roller is in contact with the first applicator roller for driving the first applicator roller at the circumferential speed of the plate cylinder or at a different speed.
In a conventional embodiment of this printing press generally known from U.S. Pat. No. 4,724,764, the first applicator roller, as seen in the direction of rotation of the plate cylinder, is driven at a different circumferential speed from the circumferential speed of the plate cylinder, the drive of the first applicator roller preferably effecting a lower circumferential speed. Dirt particles are thereby supposed to be removed from the printing plate due to the wiping effect which occurs. In this conventional construction, the bridge roller also is driven at a different circumferential speed from the circumferential speed of the plate cylinder, so that the second applicator roller, which rotates at the circumferential speed of the plate cylinder, may be braked by the bridge roller. This risk arises, in particular, in the vicinity of the cylinder gap, so that an inking fault may occur after the second applicator roller reengages the printing plate.
SUMMARY OF THE INVENTION
Proceeding from this state of the prior art, it is an object of the invention of the instant application, to provide an offset printing press wherein, during product-dependent supplying of dampening medium and removal of dirt particles from the printing plate, ghosting effects potentially producible by the first or second applicator roller are avoided.
With the foregoing and other objects in view, there is provided, in accordance with the invention, an offset printing press having a plate cylinder and, as viewed in a direction of rotation of the plate cylinder, a first applicator roller assigned to a dampening unit and a second applicator roller to an inking unit, a bridge roller in contact with the first and second applicator rollers, and a roller in contact with the first applicator roller for selectively driving the first applicator roller at the circumferential speed of the plate cylinder and at a different speed, comprising a drive connection of the bridge roller so formed that, when the first applicator roller is driven at a circumferential speed different from that of the plate cylinder, the bridge roller is drivable at the circumferential speed of the plate cylinder.
In accordance with another feature of the invention, the drive connection is between one of the applicator rollers and the bridge roller.
In accordance with another feature of the invention, the drive connection is decouplable when the first applicator roller is driven at the circumferential speed of the plate cylinder.
In accordance with a further feature of the invention, the drive connection comprises a pair of spur gears between the first applicator roller and the bridge roller.
In accordance with a concomitant feature of the invention, one of the spur gears of the pair of spur gears is mounted so as to be decouplable.
According to the invention, there is no differential speed between the bridge roller and the second applicator roller, so that ghosting effects or streaking on the printing plate are avoided. Moreover, there is a differential speed between the first applicator roller and the bridge roller, so that the formation of an emulsion between the dampening medium and ink is improved, and ghosting effects on the first applicator roller are eliminated. In this regard, the drive of the bridge roller may be derived from another roller of the dampening or inking unit or else directly from the printing-press drive. By this construction in accordance with the invention, therefore, dirt particles can be removed from the printing plate in a relatively simple manner, without adversely affecting the inking of the latter.
By the advantageous embodiment of the invention wherein a drive connection is provided between one of the applicator rollers and the bridge roller, it is possible to ensure that the bridge roller will always rotate at the circumferential speed of the plate cylinder, when the first applicator roller has, for example, a lower circumferential speed.
By the further advantageous embodiment of the invention wherein the drive connection is decouplable when the first applicator roller is driven at the circumferential speed of the plate cylinder, there is no differential speed between the participating rollers of the dampening and inking units, so that disturbances or faults are thereby avoided. By the additional advantageous embodiment of the invention wherein the drive connection is formed by a pair of spur wheels between the first applicator roller and the bridge roller, one spur wheel of the pair of spur wheels may be mounted so as to be decouplable, so that faults or malfunctions are avoidable rather simply during the operation of the offset printing press.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in an offset printing press, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
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Cone Darius U.
Greenberg Laurence A.
Heidelberger Druckmaschinen Aktiengesellschaft
Hilten John S.
Lerner Herbert L.
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