R.r. Donnelley and Sons Company

Andres Peekna

Michael Choi

Ronald A Banike

Christopher J Sensmeier

David G DeVries

In accordance with the invention, a magnetic cylinder and image plate or blanket carrier plate of magnetic material are provided for printing. The cylinder has a peripheral surface and the image plate or carrier plate is wrapped around the cylinder with an inner surface of the plate being in direct contact with the cylinder peripheral surface. The blanket and carrier plate are subject to circumferential movement around the cylinder as the blanket is subject to localized pressure from another cylinder in a nip, plus forces due to ink tack. The cylinder peripheral surface is defined by circumferentially spaced, axially extending ridges for suppressing local sliding by surface gripping with the plate inner surface.

Magnetic cylinder with surface gripping

Magnetic cylinders with an image plate or an offset blanket carrier plate have annular pole pieces and magnets which maximize either the resistance of the plate to peel-off or the attractive force intensity with a nominal displacement of the plate from the cylinder for typical operating conditions. The plates are precurved, preferably with a radius slightly less than the cylinder radius.

Magnetic cylinders with image plate or blanket for offset printing

A magnetic cylinder and plate for offset printing. The cylinder has annular magnets and pole pieces. The magnetic circuit is completed through a printing plate. The magnetic flux substantially saturates the pole pieces and plates. The area ratio of the pole pieces to the magnets is greater than about 0.45 to 1 and preferably about 0.6 to 1. In assembling the magnets and cylinder, the magnets are wrapped into slots between the pole pieces. The magnets are angularly displaced so that the leading magnet is positioned between the pole pieces before it is in proximity to the trailing magnet and demagnetization of the magnets is minimized.

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Hinsdale, IL, United States of America

Andres Peekna