Paper feeding unit for preventing multiple feeding

Abstract

A paper feeding unit for substantially preventing multiple feeding is provided. The paper feeding unit includes a paper feeding cassette that stores printing mediums, and a knock-up plate rotatably disposed in the paper feeding cassette and on which the printing mediums are loaded. A knock-up spring applies an elastic force to the knock-up plate. A protruding portion, which is formed by protruding the knock-up plate, has a friction force with the printing medium loaded thereon greater than the friction force between printing mediums. Accordingly, multiple feeding is substantially prevented, and the manufacturing and assembly costs are reduced.

1 . A paper feeding unit, comprising: 
 a paper feeding cassette that stores printing mediums to be supplied by a pick-up roller to a main frame of an image forming apparatus;    a knock-up plate rotatably disposed in the paper feeding cassette and on which the printing mediums are loaded;    a knock-up spring that applies an elastic force to the knock-up plate toward the pick-up roller; and    a protruding portion formed by protruding the knock-up plate at a position facing the pick-up roller and of which friction force with the printing medium loaded thereon is greater than the friction force between the printing mediums.    
   
   
       2 . The paper feeding unit according to  claim 1 , wherein the protruding portion is formed by a blanking process of the knock-up plate.  
   
   
       3 . The paper feeding unit according to  claim 2 , wherein the protruding portion has a protrusion degree less than about 0.2 mm with respect to the surface of the knock-up plate.  
   
   
       4 . The paper feeding unit according to  claim 3 , wherein the protruding portion is formed in a portion of the knock-up plate that is depressed in the opposite direction with respect to the pick-up roller.  
   
   
       5 . The paper feeding unit according to  claim 1 , wherein at least two protruding portions are arranged on left and right sides of the knock-up plate with respect to a pick-up direction of the printing medium so that a configuration of the protruding portions on the left side is symmetrical to a configuration of the protruding portions on the right side.  
   
   
       6 . The paper feeding unit according to  claim 1 , wherein the surface of the protruding portion is subject to an embossing process.  
   
   
       7 . The paper feeding unit according to  claim 1 , wherein the protruding portion includes one or more squares having a hole in the center thereof.  
   
   
       8 . The paper feeding unit according to  claim 7 , wherein at least one of the squares having a hole in the center thereof is inclined with respect to a pick-up direction of the printing medium.  
   
   
       9 . A paper feeding unit, comprising: 
 a paper feeding cassette that stores printing mediums to be supplied by a pick-up roller to the main frame of an image forming apparatus;    a knock-up plate that is rotatably disposed in the paper feeding cassette and on which the printing mediums are loaded;    a knock-up spring that applies an elastic force to the knock-up plate towards the pick-up roller; and    a protruding portion disposed on the knock-up plate using an outsert molding method at a position facing the pick-up roller and of which a friction force with the printing medium loaded thereon is greater than the friction force between the printing mediums.    
   
   
       10 . The paper feeding unit according to  claim 9 , wherein the protruding portion has a protrusion degree less than about 0.2 mm with respect to the surface of the knock-up plate.  
   
   
       11 . The paper feeding unit according to  claim 10 , wherein the protruding portion is formed in a portion of the knock-up plate that is depressed in the opposite direction with respect to the pick-up roller.  
   
   
       12 . The paper feeding unit according to  claim 9 , wherein at least two protruding portions are arranged on left and right sides of the knock-up plate with respect to a pick-up direction of the printing medium so that a configuration of the protruding portions on the left side is symmetrical to a configuration of the protruding portions on the right side.  
   
   
       13 . The paper feeding unit according to  claim 9 , wherein the surface of the protruding portion is subject to an embossing process.  
   
   
       14 . The paper feeding unit according to  claim 9 , wherein the protruding portion includes one or more squares having a hole in the center thereof.  
   
   
       15 . The paper feeding unit according to  claim 14 , wherein at least one of the squares having a hole in the center thereof is inclined with respect to a pick-up direction of the printing medium.  
   
   
       16 . A paper feeding unit, comprising: 
 a paper feeding cassette storing printing mediums to be supplied by a pick-up roller to a main frame of an image forming apparatus;    a knock-up plate rotatably disposed in the paper feeding cassette and having an upper surface on which the printing mediums are loaded;    a knock-up spring applying an elastic force to a lower surface of the knock-up plate to bias the knock-up plate toward the pick-up roller; and    a protruding portion disposed on the knock-up plate and facing the pick-up roller, the friction force between the protruding portion and the loaded printing medium is greater than the friction force between the printing mediums.    
   
   
       17 . The paper feeding unit according to  claim 16 , wherein the protruding portion is formed by protruding the knock-up plate.  
   
   
       18 . The paper feeding unit according to  claim 17 , wherein the protruding portion is formed by a blanking process of the knock-up plate.  
   
   
       19 . The paper feeding unit according to  claim 16 , wherein the protruding portion is formed using an outsert molding method.  
   
   
       20 . The paper feeding unit according to  claim 16 , wherein the protruding portion has a protrusion height less than about 0.2 mm with respect to the upper surface of the knock-up plate.  
   
   
       21 . The paper feeding unit according to  claim 20 , wherein the protruding portion is formed in a portion of the knock-up plate that is depressed in the opposite direction with respect to the pick-up roller.  
   
   
       22 . The paper feeding unit according to  claim 16 , wherein at least two protruding portions are arranged on left and right sides of the knock-up plate with respect to a pick-up direction of the printing medium so that a configuration of the protruding portions on the left side is symmetrical to a configuration of the protruding portions on the right side.  
   
   
       23 . The paper feeding unit according to  claim 16 , wherein the surface of the protruding portion is subject to an embossing process to increase the friction coefficient.  
   
   
       24 . The paper feeding unit according to  claim 16 , wherein the protruding portion includes one or more squares having a hole in the center thereof.  
   
   
       25 . The paper feeding unit according to  claim 24 , wherein at least one of the squares having a hole in the center thereof is inclined with respect to a pick-up direction of the printing medium.