US 4,455,938 AGranted

Dampening apparatus for lithographic press

AssigneeGraph Tech Inc.

InventorJames R. Loudon

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Abstract

The present invention relates to a dampening apparatus for lithographic offset printing presses. A form roller having an ink receptive compressible surface is pressed against a plate on the plate cylinder, and a metering means lying parallel and tangent to the form roller having a relatively incompressible ink receptive surface is pressed against the form roller. A reservoir of dampening solution is maintained above the nip of the form roller and metering roller, and is automatically maintained. Rotation of the form roller results in a metered quantity of solution being fed to the form roller, a portion of that quantity being applied to the lithographic plate, and the excess of that quantity being returned to the supply. The ink applied to the plate is allowed to transfer to both dampener rollers, and the action of the rotating rollers, forced together, on the ink-solution mixture or emulsion, mills that emulsion into essentially uniform small particles which result in quick, thorough, and uniform inking and dampening of the plate.

Claims14

Dependent claims

A dampening apparatus for lithographic printing presses having a plate cylinder around which an offset lithographic printing plate may be mounted, a dampening form roller having an ink receptive surface and mounted parallel and contiguous to said plate cylinder along a first line of tangency, means for positively rotating said form roller in a direction counter to and at the same surface speed as said plate cylinder, a metering roller also having an ink receptive surface extending along a second line of tangency to said form roller on the opposite side thereof from said plate cylinder, the surface of said metering roller being substantially harder than the surface of said form roller, means for rotating said metering roller counter to and at the same surface speed as said form roller, means pressing said metering roller against said form roller and means pressing said form roller against a plate on said plate cylinder such that said rollers define between them a reservoir for dampening solution to which is added ink carried back to said rollers from the plate, whereby there exists a delivery arc on said form roller from said second to said first line of tangency measured in the direction of rotation of said form roller and an uninterrupted solution return arc on said form roller from said first to said second line of tangency in the direction of rotation of said form roller for the mixed ink and dampening solution, and a supply of dampening solution to said reservoir including means for automatically maintaining constant the dampening solution level in said reservoir.

A dampener for an offset lithographic printing press having a plate cylinder on which a lithographic plate can be mounted, said dampener comprising

a frame adapted for mounting on the press adjacent the plate cylinder,
a form roller rotatably supported in said frame for contact with a plate on the plate cylinder,
a metering roller rotatably supported in said frame in pressure contact with said form roller and on the opposite side thereof from the plate cylinder,
seal means mounted on said frame in cooperative relation with said rollers to define a reservoir for dampening solution,
said form roller and said metering roller having ink receptive surfaces and the surface of said metering roller being substantially less resilient than the surface of said form roller,
means for urging said form roller into contact with a plate on the plate cylinder,
means urging said metering roller into contact with said form roller with a force sufficient to compress the form roller surface,
drive means rotating said rollers at one-to-one surface speed with each other and with the plate cylinder,
and means providing a supply of dampening solution to said reservoir,
whereby solution in said reservoir is continually mixed with ink picked up from the plate by the action of the metering and form rollers and the resulting emulsion of solution and ink is applied to the plate by said form roller, the density of ink in the emulsion being directly related to the density of image areas on the plate.

7 more elements

Dependencies are inferred from the claim text.