Bottom sheet feeding apparatus employing a combination slide plate and vacuum valve

Claim 1

A bottom sheet separator-feeder for separating and forwarding sheets seriatim from the bottom of a stack of sheets to be fed, comprising a stack tray for supporting the sheets to be fed, air knife means positioned in front of the stack tray and adapted to provide a layer of air between said tray and the bottom sheet in the stack and the remainder of the sheets in the stack, and vacuum feeding means located within the front portion and in line with the top surface of said tray, said feeding means including a slide plate member having a first surface portion extending along the plane of the bottom surface of said tray and a second surface portion that is sloped down and away from said first surface portion and said tray and extending the width of said tray for bending the front portion of the bottom sheet in the stack down and away from the remainder of the stack, said slide plate member having a plurality of sheet hold down slots in said first and second surface portions and a vacuum plenum arranged for communication with said sheet hold down slots to attract the bottommost sheet in the stack to said slide plate member, said vacuum plenum remaining stationary while said slide plate member is reciprocated to move sheets from under said stack to a take-away position, and including a two position wall connected to said vacuum plenum and positioned with respect to a forward end of said vacuum plenum for blocking air knife flow to the stack during initial sheet acquisition when in a first of said two positions while simultaneously facilitating a higher and faster negative pressure rise below the stack and for allowing full air knife flow to the stack when in the second of said two positions.