Patent ID: 6874780

Claim:
A device for controlling delivery of sheets from a stack to a machine for further processing, the stack of sheets having a leading face and a trailing face relative to the machine, the device comprising: a lift operative to raise the stack of sheets; an electric motor operable only in a continuous mode at a variable speed connected to operate the lift; a motor controller for the motor; a vertically movable sheet feeder including a gripping mechanism operative to grip the sheet at the top of the stack for delivery to the machine; a drive mechanism operative to raise and lower the sheet feeder; a first detector located near the uppermost position which can be assumed by the top of the stack, and in an operative relationship to the leading face of the stack, the first detector being operative to generate an output signal representative of the vertical position of the top of the stack; and a computer operative to control the drive mechanism for the sheet feeder; and responsive to the output signal from the first detector, a signal representing the rate at which sheets are fed to the machine by the sheet feeder, and a signal representing the thickness of the sheets to generate a signal for the motor controller representing the variable motor speed.