Sheet feeder

Abstract

The invention concerns an apparatus for forward transferring sheet-like objects from a stack, said apparatus including separate lifting elements gripping by suction to the upper surface of the sheet-like object situated top-most on the stack. The gripping elements are positioned in a row extending over the stack of the sheet-like objects in transversal direction with respect to the forward direction of the sheet-like object. The suction effect of the lifting elements is individually controlled by means of a control device including a light source creating a substantially line-shaped illumination pattern over the top of the stack. The illumination of the light source is focused substantially parallel to the lifting element row, at an inclined angle to the surface plane of the sheet stack. Camera means for observing the illumination pattern forwards information about the uniformity of the uppermost layer of the stack for controlling the gripping elements.

1 . An apparatus for forwarding transfer sheet-like objects from a stack, said apparatus including separate lifting elements positioned in a row extending over the stack in transversal direction with respect to a forwarding transfer direction from the stack, said lifting elements being connected to a vacuum means and equipped with an opening/closing/means for each element for releasable gripping by suction to the upper surface of the sheet-like object lying top-most in the stack and to be transferred from the stack, and transfer elements for transferring the lifted sheet-like object from the stack, wherein the apparatus further includes a control device including a light source creating a substantially line-shaped illumination pattern focused substantially parallel to the lifting element row, at an inclined angle to the plane of the top surface of the sheet stack, and a camera means for observing the illumination pattern, the gripping operation of the lifting elements being individually controlled by means of said control device 
     
     
         2 . The apparatus according to  claim 1 , wherein the lifting elements are located adjacent to each other and form a suction line extending in transversal direction substantially over the total width of the stack. 
     
     
         3 . The apparatus according to  claim 1 , wherein the lifting means comprise a slide actuator means for controllably opening and closing the suction effect, respectively. 
     
     
         4 . The apparatus according to  claim 2 , wherein the lifting means comprise a slide actuator means for controllably opening and closing the suction effect, respectively.