Automatic sheet feeder

Abstract

An automatic document feeder (ADF) used in a facsimile machine, photocopier or the like. A sheet path from a sheet inlet to outlet is defined by lower, intermediate and upper frames of the ADF. The sheet path is generally shaped like “C” when viewed laterally. The intermediate frame has a pivotable member that can be opened and closed, and a guide member for guiding a sheet passing over a platen glass. An elastic member is provided for biasing the guide member on the platen surface from a turning portion of the C-shaped sheet path. Therefore, it is possible to maintain a clearance between the platen surface and guide member and prevent the sheet from flapping. A retard roller is removably supported by the pivotable member so that replacing and maintenance of the retard roller is simplified. Further, the pivotable member is a one-piece element and made from resin. A plurality of ribs extending in a sheet feed direction are provided near the sheet inlet and/or outlet so that the weight of the automatic document feeder is reduced and movements of the sheets are facilitated.

What is claimed is:  
     
         1 . An automatic sheet feeding apparatus for feeding a sheet from a sheet inlet to a sheet outlet, comprising: 
 a lower frame, an intermediate frame and an upper frame to in combination define a sheet path from a sheet inlet to a sheet outlet, the sheet path extending generally like “C” when viewed laterally, the intermediate frame having at least a pivotable member which can be opened and closed and a guide member for guiding a sheet passing over a platen surface; and    an elastic member for biasing the guide member onto the platen surface from a turning portion of the C-shaped sheet path.    
     
     
         2 . The automatic sheet feeding apparatus as recited in    claim 1   , wherein the guide member is pivotable about a feed roller shaft.  
     
     
         3 . The automatic sheet feeding apparatus as recited in    claim 1   , wherein the pivotable member is made from resin and the platen surface is defined by a platen glass.  
     
     
         4 . The automatic sheet feeding apparatus as recited in    claim 1   , wherein the lower, intermediate and upper frames are integral with each other by fabricating them from a one piece material such as resin.  
     
     
         5 . An automatic sheet feeding apparatus for feeding a sheet from a sheet inlet to a sheet outlet, comprising: 
 a sheet path extending from a sheet inlet to a sheet outlet, and having a generally C shape;    a platen surface located on a downstream side of a turning portion of the C-shaped sheet path;    a first guide member for guiding a sheet from the sheet inlet to the turning portion of the C-shaped sheet path;    a second guide member for guiding the sheet from the turning portion of the C-shaped sheet path to the platen surface;    a third guide member for guiding the sheet from the platen surface to the sheet outlet; and    drive rollers for feeding the sheet along the sheet path, the drive rollers being rotatably supported by the first, second and third guide members respectively, at least the first guide member being pivotable about a shaft of the roller which is supported by the first guide roller.    
     
     
         6 . The automatic sheet feeding apparatus as recited in    claim 5   , wherein the first, second and third guide members are integral with each other by fabricating them from a one piece material.  
     
     
         7 . An automatic sheet feed apparatus comprising: 
 a lower frame, an intermediate frame and an upper frame to in combination define a sheet path extending in a generally like C shape when viewed laterally, the intermediate frame having at least a pivotable member that can be opened and closed and a guide member for guiding a sheet passing over a platen surface, the pivotable member having a recess therein;    a retard roller located in the recess;    a separate roller generally in contact with the retard roller for cooperatively functioning with the retard roller to feed one sheet at a time;    an elastic member located in the recess for exerting an adjustable biasing force directed in a first direction other than a second direction in which the retard roller presses the separate roller; and    a direction change member for receiving the biasing force from the elastic member in the first direction and transferring the biasing force to the retard roller in the second direction.    
     
     
         8 . The automatic sheet feed apparatus as recited in    claim 7   , wherein the direction change member has an L shape with a vertical portion, an angled portion and a horizontal portion when viewed laterally, and is pivotable about the angled portion of the direction change member such that the biasing force acts on the vertical portion of the direction change member and the retard roller is biased by the horizontal portion of the direction change member in the second direction substantially perpendicular to the first direction.  
     
     
         9 . The automatic sheet feed apparatus as recited in    claim 8   , wherein the direction change member has a through hole in the vertical portion of the direction change member such that a user can access the elastic member to adjust elasticity of the elastic member.  
     
     
         10 . The automatic sheet feed apparatus as recited in    claim 7    further including a drive mechanism located in the recess, and a removable cover extending over the recess for closing the recess and defining part of the sheet path.  
     
     
         11 . The automatic sheet feed apparatus as recited in    claim 7    further including at least one first rib for guiding the retard roller in the second direction, and at least one second rib that is integral with the at least one first rib for supporting the direction change member, both the first and second ribs being positioned in the recess.  
     
     
         12 . The automatic sheet feed apparatus as recited in    claim 7    further including a first arm pivotable up and down about one end thereof in the recess for supporting a drive mechanism for the retard roller, and a second arm removably supported at another end of the first arm opposite the one end for supporting the retard roller such that the second arm can pivot up and down about the another end together with the retard roller.  
     
     
         13 . The automatic sheet feed apparatus as recited in    claim 12    further including an intermediate shaft supported by the first arm such that the intermediate shaft extends generally perpendicular to a moving direction of the sheet in the sheet path when viewed from the top, and wherein parts of the drive mechanism upstream of the intermediate shaft are supported by the first arm on one lateral side of the sheet path, and remaining parts of the drive mechanism located downstream of the intermediate shaft until the retard roller are supported by the first and second arms on the opposite lateral side of the sheet path.  
     
     
         14 . An automatic sheet feed apparatus having a sheet inlet and a sheet outlet, comprising: 
 a lower frame, an intermediate frame and an upper flame to in combination define a sheet path extending from a sheet inlet to a sheet outlet, the sheet path being generally shaped like C when viewed laterally, the intermediate frame having at least a pivotable member that can be opened and closed, and a guide member for guiding a sheet passing over a platen surface; and    a sheet discharge roller unit located at the sheet outlet and including a drive roller supported by the lower frame and a driven roller supported by the pivotable member such that the driven roller faces the drive roller and a shaft of the driven roller is rotatably and movably received in a groove formed in the pivotable member, an inlet opening of the groove for receiving the driven roller shaft being smaller than a diameter of the driven roller shaft and having elasticity.    
     
     
         15 . The automatic sheet feed apparatus as recited in    claim 14    further including a spring located on the opposite side with respect to the drive roller for pressing the driven roller shaft toward the drive roller, and wherein when the pivotable member pivots to cause the driven roller to leave the drive roller, the driven roller shaft moves in the groove and a clearance is created between the driven roller shaft and spring.  
     
     
         16 . The automatic sheet feed apparatus as recited in    claim 14   , wherein the sheet inlet of the sheet path is positioned above the sheet outlet, and an upper surface of the pivotable member defines part of the sheet path extending from the sheet inlet and a lower surface of the pivotable member defines part of the sheet path extending to the sheet discharge roller unit.  
     
     
         17 . An automatic sheet feed apparatus having a sheet inlet and a sheet outlet, comprising: 
 a lower frame;    an intermediate frame coupled with the lower frame;    an upper frame coupled with the lower frame via the intermediate frame to define a sheet path extending in a generally C shape when viewed laterally, the intermediate frame having at least a pivotable member that can be opened and closed and a guide member for guiding a sheet passing over a platen surface, the pivotable member being a one piece element made from resin; and    a plurality of ribs formed on the sheet path and extending in a sheet feed direction near at least one of the sheet inlet and outlet.    
     
     
         18 . An apparatus for feeding a sheet from a sheet inlet to a sheet outlet, comprising: 
 means for defining a sheet path from a sheet inlet to a sheet outlet, the sheet path extending generally like “C”, the sheet path defining means having guide means for guiding a sheet passing over a platen surface; and    means for biasing the guide means onto the platen surface.