Printer media pick apparatus

Abstract

A method is disclosed for picking media in inkjet printers using a non-linear system, so that only a single sheet of media is drawn into the printer for printing. Inkjet printers operate by drawing media into the printer for printing. Two coil springs, arranged in parallel, support the pressure plate to bring media stack in contact with the pick roller. At full media stack, both coils are compressed; at low media stack, only one spring is compressed, the other is uncompressed, thus providing sufficient contact pressure between media and pick roller.

We claim:  
     
         1 . A media pick apparatus comprising: 
 a pick roller  10  for picking media;    a pressure plate  11  for supporting media; and    a system for exerting a predetermined non-linear force on the pressure plate  11  to maintain a non-linear pressure between media on the pressure plate  11  and the pick roller  10 .    
     
     
         2 . The apparatus recited in  claim 1 , wherein the system further comprises: 
 a compressible system having a working principle based on one of air, liquid or material property, or a combination thereof.    
     
     
         3 . The apparatus recited in  claim 1 , wherein the system further comprises: 
 a coil spring having non-linear characteristics.    
     
     
         4 . The apparatus recited in  claim 1 , wherein the system further comprises: 
 two coil springs of different characteristics.    
     
     
         5 . The apparatus recited in  claim 4 , wherein 
 the two coil springs are arranged in parallel.    
     
     
         6 . A method of feeding media sheets into a printer having a pressure plate  11  supporting the media sheets against a pick roller  10 , the method comprising: 
 moving a pressure plate  11  to bring a first media sheet into contact with the pick roller  10 , including exerting a first force by a system on the pressure plate  11  against the pick roller  10 ;  
 feeding the first media sheet into the printer by rotating the pick roller  10  and contacting the first media sheet through friction means; and  
 after feeding the first media sheet, moving the pressure plate  11  to bring a second media stack into contact with the pick roller  10 , including exerting a second force by the system on the pressure plate  11  against the pick roller  10 , wherein the first force and the second force in combination produce non-linear characteristics.