Device for controlling the means delivering sheets to a machine

Abstract

The device comprises a lifting mechanism ( 1 ), a sheet-inserting means, means for detecting the front top level of the stack ( 32 ) connected to a computer acting on an electric motor ( 11 ) of the stack-lifting mechanism ( 1 ), and means for raising the stack ( 4 ). The detector ( 32 ) of the front level of the stack ( 4 ) comprises means for measuring the extent of variations in the level of the stack. The computer is also connected to a source of information ( 17 ) relating to the supply frequency in real time and to the nominal thickness of the sheets. The computer output is connected to a frequency-varying means for controlling the electric motor ( 11 ), the computer being designed so that the value of the signal appearing at its output is characteristic of the difference between the measured level of the stack ( 4 ) and the calculated level.

1 . A device for controlling the means delivering sheets from a stack ( 4 ) to a machine for processing them, comprising at least one mechanism ( 1 ) for lifting the stack, a sheet-inserting means comprising gripping means ( 29 ), means for detecting the upper level of the stack comprising a detector of the front level ( 32 ) of the stack ( 4 ) connected to an input of a computer ( 37 ) acting on at least one electric motor ( 11 ) of the stack-lifting mechanism ( 1 ), and means for raising the stack ( 4 ) in dependence on the upper level, characterised in that the detector of the front level ( 32 ) of the stack ( 4 ) comprises means for measuring the extent of variations in the level of the stack and in that an input of the computer ( 37 ) is also connected to a source of information ( 17 ) relating to the supply frequency in real time and to the nominal thickness of the sheets, and the output of the computer ( 37 ) is connected to at least one frequency varying means ( 42 ) for controlling the electric motor or motors ( 11 ), the computer ( 37 ) being designed so that the value of the signal appearing at its output characterises the difference between the measured level of the stack ( 4 ) and the level calculated on the basis of the said nominal thickness and the said supply frequency and generates a variation in the frequency of the one or more varying means ( 42 ) tending to modify the rate of advance of the motor ( 11 ) in order to make the measured level coincide with a set level.  
     
     
         2 . A device according to    claim 1   , characterised in that the detector ( 32 ) of the front level of the stack ( 4 ) is a linear camera disposed in the vertical direction of the stack.  
     
     
         3 . A device according to    claim 1   , characterised in that the lifting mechanism ( 1 ) is associated with an auxiliary supply means ( 50 ) controlled by a motor ( 53 ) connected to the computer ( 37 ) such that its rate of advance is determined by the same information as used for controlling the one or more electric motors ( 11 ) of the lifting mechanism ( 1 ).