Sheet settling system

Abstract

In a high speed sheet printing or coating machine there is a tendency for the sheets to move about as they are being fed to the datum stops, so that precise registration is not achieved. This is remedied by exerting a damping force which pulls each sheet continuously towards a fixed support surface 12 before and during registration and during printing or coating. The damping force comprises vacuum and/or magnetic forces which settle each sheet rapidly on the fixed support surface as it is fed into contact with the datum stops. The vacuum force is provided by drawing air through an array of holes 26 in the fixed support surface into an underlying chamber 24 evacuated through a pipe 28 by a vacuum pump, and is adjustable either by controlling the flow rate through the pump or by controllably venting the chamber or pipe to atmosphere. The magnetic force is provided by a row of permanent or electro-magnets 22 in the fixed support surface, and can be adjusted by varying their position perpendicular to that surface. Alternatively, in the case of electro-magnets, the magnetic force is adjustable by varying their supply of electrical power.

Dependencies are inferred from the claim text.