Patent ID: 8448936
Filing Date: 2013-05-28
Classification: B65H,Y10S

Abstract:
1. An automatic document feeder for feeding plural documents, said automatic document feeder comprising: a sheet input tray for placing said plural documents, wherein said plural documents comprise a first document and a second document; a transfer channel; a sheet pick-up module for feeding said plural documents that are placed on said sheet input tray into said transfer channel; a retard roller arranged under said sheet pick-up module and contacted with said second document, so that a first frictional force or a second frictional force between said retard roller and said second document is generated, wherein said second frictional force is smaller than said first frictional force, wherein said retard roller comprises: a thickness detecting module disposed above said transfer channel for detecting a thickness of said plural documents, thereby generating a thickness-detecting signal; and a controlling unit in communication with said thickness detecting module and said sheet pick-up module for controlling a rotating direction of said sheet pick-up module, wherein if said thickness of said plural documents is smaller than or equal to a thickness threshold value, said sheet pick-up module is controlled by said controlling unit to continuously rotate in a first rotating direction, and a document frictional force between said first document and said second document is smaller than said first frictional force, so that said first document is allowed to be fed into said transfer channel, wherein if said thickness of said plural documents is greater than said thickness threshold value, said sheet pick-up module is controlled by said controlling unit to continuously rotate in a second rotating direction, and said second frictional force is smaller than said document frictional force, so that said plural documents are returned to said sheet input tray, wherein under control of said controlling unit, after said sheet pick-up module is rotated in said second rotating direction for a delaying time, said sheet pick-up module is rotated in said first rotating direction to feed said plural documents into said transfer channel.