Sheet-size detecting mechanism

Abstract

A sheet-size detecting mechanism includes a sheet holder composed of a paper tray and a paper guide. The mechanism also includes a logic board and a sensor module. Adjusting the width of the paper guide corresponding to the sheet width may cause a lot of digital information to be generated due to relative motion between the logic board and the sensor module. Then the sheet-size may be determined accordingly.

What is claimed is:  
     
         1 . A sheet-size detecting mechanism comprising: 
 a plate having a facing surface and a bottom which is located in opposite to the facing surface;    a logic board having a plurality of feature sections on a surface thereof and the logic board being located at the bottom of the plate;    a sensor module located at the bottom of the plate, and    at least one paper guide movably mounted to the plate, the logic board being movable relative to the sensor module, the sensor module generating signals by relative movements between the feature sections and the sensor module.    
     
     
         2 . The mechanism as claimed in  claim 1 , wherein the logic board is connected to the paper guide.  
     
     
         3 . The mechanism as claimed in  claim 1 , wherein the sensor module is connected to the paper guide.  
     
     
         4 . The mechanism as claimed in  claim 1 , wherein the feature sections on the logic board are plurality of ribs and gaps are defined between the ribs.  
     
     
         5 . The mechanism as claimed in  claim 1  further comprising sensors on the facing surface of the plate.  
     
     
         6 . The mechanism as claimed in  claim 1 , wherein the sensor module is composed of plurality of sensing units.  
     
     
         7 . The mechanism as claimed in  claim 6 , wherein each sensing unit is composed of two sensors between which a passage is defined.  
     
     
         8 . The mechanism as claimed in  claim 1 , wherein the feature sections of the logic board are recesses.  
     
     
         9 . The mechanism as claimed in  claim 1 , wherein the feature sections of the logic board are holes.