Abstract: A device for positioning a sheet separator for a stack of sheets in a sheet feeder includes a drive for the sheet separator operable for moving the latter in two opposite directions. A stop gauge for the rear edge of the sheet stack is slidably supported on an insulating block which is rotatable on the sheet separator. The lower end of the stop gauge is provided with a feeler roller to engage the upper side of the stack, and the opposite end of the stop gauge is provided with a flag cooperating with an inductive switch. The latter switch controls the direction of rotation of the driving motor for the separator. The rotary block controls another switch which stops the motor when the separator attains its desired position. A light barrier switch is arranged at the level of the desired height of the stack and determines the active or inactive condition of the positioning device.

Abstract: A sheet feeding unit includes a stack elevator which raises the top of a supported stack of sheets to infeed height. A sensor senses the position of the top sheets of the stack, to ascertain whether these exhibit improper left or right offset. Depending upon the magnitude and size of the sensed offset, the stack elevator is correctively shifted, to minimize offset at the top of the stack. Although the sensor is located to only one side of the stack, not at both sides of the stack, it is capable of sensing offset in both left and right directions. When the elevator is lowered, for the laying in of a fresh stack, it is automatically brought to a centered position.

Abstract: The stack of sheets is moved towards the distributor at a control velocity corresponding to the distributor operation. If the stack in the operative vicinity of the distributor becomes too low, indicating too slow a stack advance, a mechanical sensor sensing the position of the top of the stack rotates to a position interrupting the signal furnished by the first and second inductive input signal generator. The interruption of the signal results in the furnishing of a second sensor output signal which, at a time determined by a synchronizing signal sets a monostable multivibrator whose output then energizes a relay which in turn applies voltage to a winding of a servomotor moving the arm of a potentiometer in a direction for increasing the speed of advance of the stack.

Abstract: A plurality of rollers each carried on an element pivoted on a support swing back and forth into engagement with respective continuously driven rollers to pinch a sheet delivered between the rollers by means of a vacuum lifter and advance it along a path. A motor on each support can vary the position of the respective movable roller relative to the fixed roller and the pivotal element is insulated from the support but abuts conductively thereagainst in a rest position. A controller connected between the support and the element detects abutment of the two contact surfaces which function as switches and operates a control system that can vary the spacing between each pair of rollers in accordance with the thickness of the sheet being fed to it. A too thick a sheet will push the rollers apart prematurely and open the switch and a too thin sheet will not push them apart before the vacuum lifter releases it.