Patent Publication Number: US-7717415-B2

Title: Paper feeding device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of Korean Patent Application No. 2003-50490, filed on Jul. 23, 2003, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an image forming apparatus, and more particularly, to a paper feeding device including a paper sensing device which decides whether a sheet of paper is loaded. 
     2. Description of the Related Art 
     In general, an image forming apparatus such as a laser printer, a scanner, and a multi functional peripheral device is an apparatus for forming a visual image by providing a sheet of paper with ink or toner according to data to be printed. 
     The image forming apparatus includes a plurality of sensors on a transfer passage of the paper for sensing whether the paper is transferred smoothly along the transfer passage or not. 
     Especially, one of the sensors is a paper sensing device, which can sense the paper is loaded or not. The paper sensing device senses the paper loading to perform a pre-operation of a paper pickup operation for forming the visual image on the paper. 
     On the other hand, devices having different functions are combined to be a device having multi-functions at present, thus a multi-functional peripheral device combining the devices having different functions such as the printer, scanner, copying machine, and facsimile is developed. 
     The combination of the devices accompanies miniaturization of components, and the components also have multi-functions. 
     Accordingly, in a pickup roller assembly, which picks a sheet of paper up and transfers the paper into the main body, a pickup roller and a sensing device are disposed independently, thus complicating the device and increasing cost due to a lot of components. 
     SUMMARY OF THE INVENTION 
     An aspect of the present invention provides a paper feeding device in which a paper stopper for controlling the position of a front end of a sheet of paper can also perform a function of sensing whether the paper is loaded, thereby to obtain an economic and reliable printing quality. 
     According to an aspect of the present invention, a paper feeding device includes a pickup roller assembly picking a paper up and transferring the paper, a paper sensing device sensing whether the paper is loaded on a sheet of paper feeding board and a stopper controlling the paper so that a front end of the paper is located below the pickup roller. In addition, the paper sensing device includes a sensing unit and a probe unit, which is installed to be rotated with the stopper, turning the sensor unit on/off. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and/or other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the accompanying drawings in which: 
         FIG. 1  is a perspective view of a multi-functional peripheral device including a paper feeding device according to an embodiment of the present invention; 
         FIG. 2  is a partial perspective view of the paper feeding device of  FIG. 1 ; 
         FIG. 3  is a perspective view of a pickup roller assembly of  FIG. 2 ; and 
         FIG. 4  through  FIG. 6  are side cross-sectional views for describing operations of the paper feeding device of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to  FIG. 1  through  FIG. 3 , a multi-functional peripheral device includes a cassette  110 , which is attached/separated to/from a main body  100  on a lower portion of the multi-functional device, for loading papers, a discharging board  120 , through which printed papers are discharged, disposed on an upper portion of the cassette  110 , and a controlling plate  130 , on which buttons for performing required operation by a user are disposed, located on an upper portion of the discharging board  120 . 
     Also, a read-out unit  140  for reading the paper so as to perform a scanning operation and a copying operation, a paper feeding board  151  installed in a paper feeding unit above an upper portion of the read-out unit  140 , with the paper feeding unit being rotatable with respect to the read-out unit  140  to feed the papers, and with a paper feeding unit  150  including a paper feeding device  160 , which provides the read-out unit  140  with the papers to be read, are provided. 
     The paper feeding device  160  includes a pickup roller assembly  162  for picking up the paper and transferring the paper to the read-out unit  140 , a paper sensing device  170  for sensing whether the paper is loaded on the paper feeding board  151  or not, and a stopper  180  for controlling the paper so that the front end of the paper is located in a lower direction of the pickup roller assembly  162 . 
     The pickup roller assembly  162  includes a body  163  having a pickup roller  167 , which is installed on one side of the body  163  to be rotatable with respect to a supporting shaft  168 , and a rotary shaft  164 , which is installed on the other side of the body  163  and supported within the paper feeding unit  150  what is to be rotatable, rotating by a driving power received from a driving unit (not shown) through a gear unit  165 . 
     The pickup roller assembly  162  is covered by an upper frame  161  located thereon, and a lower frame  169  is located on a lower portion of the pickup roller assembly  162 . A slit  169   a  is formed on the lower frame  169  so that the stopper  180  can move thereon. 
     When the pickup roller assembly  162  receives the driving power through the gear unit  165  from the driving unit (not shown), the rotary shaft  164  rotates. A clutch  166  installed on the rotary shaft  164  moves the body  163  using the rotating force of the rotary shaft  164  toward the lower direction, that is, toward the lower frame  169  centering around the rotary shaft  164 . The pickup roller  167  is moved toward the lower direction with the body  163 . Here, the pickup roller  167  receives the driving force from the rotary shaft  164  through a driving force transfer device (not shown) and rotates to contact and feed the paper from the paper feeding board  151 . 
     The paper sensing device  170  includes a probe unit  171  fixedly installed on one end of the supporting shaft  168 , and a sensor unit  172  fixedly installed on the upper frame  161 . Preferably, the sensor unit  172  comprises a light emitting unit  172   a  radiating the light and a light receiving unit  172   b  receiving the light radiated from the light emitting unit  172   a , which are disposed with a predetermined distance from each other. 
     The probe unit  171  blocks the light radiated from the light emitting unit  172   a  toward the light receiving unit  172   b  by locating between the light emitting unit  172   a  and the light receiving unit  172   b , or makes the light radiated from the light emitting unit  172   a  go to the light receiving unit  172   b  by being out of between the light emitting unit  172   a  and the light receiving unit  172 , thereby the sensor unit  172  is turned on/turned off to sense the paper. 
     According to an aspect of the present invention, an optical sensor is used as the sensor unit  172 , however, a contact type sensor that is turned on/off by contacting the probe unit  171  or various modifications can be used as the sensor unit  172 . 
     The stopper  180  comprises a stopping unit  181 , which is installed to slide in the slit  169   a  formed on the lower frame  169 , having one side fixed on both ends of the supporting shaft  168  and the other side extending toward the lower frame  169 , and a suspending unit  182  installed on the upper frame  161  and selectively coupled to a suspending step  183  disposed on the supporting shaft  168  to stop the rotation of the supporting shaft  168 . 
     Operations of the paper feeding device having above structure according to the present invention will be described with reference to accompanying figures. 
       FIG. 4  shows a status that the paper is not provided to the paper feeding board  151  according to an aspect of the present invention. Referring to  FIG. 2  and  FIG. 4 , the probe unit  171  is located between the light emitting unit  172   a  and the light receiving unit  172   b  of the sensor unit  172 , thus blocking the light radiated from the light emitting unit  172   a  going to the light receiving unit  172   b . Since a status where the light receiving unit  172   b  receives the light radiated from the light emitting unit  172   a  is referred to as a turned-on status, and a status where the light radiated from the light emitting unit  172   a  is blocked is referred to as a turned-off status, the status shown in  FIG. 4  is the turned-off status. On the other hand, the suspending step  183  is separated a predetermined distance from the suspending unit  182 . 
     Referring to  FIG. 2  and  FIG. 5 , when the paper (P) is loaded on the paper feeding board  151  and the front end of the paper pushes the stopping unit  181  toward the direction represented by an arrow, the stopping unit  181  rotates in a clockwise direction to rotate the supporting shaft  168 . Here, the probe unit  171  is located between the light emitting unit  172   a  and the light receiving unit  172   b , and escaped therefrom when the supporting shaft  168  rotates, then the sensor unit  172  is turned on and decides that the paper P is loaded on the paper feeding board  151 . 
     On the other hand, when the suspending step  183  is suspended by the suspending unit  182 , the stopping unit  181  prevents the paper P from proceeding toward the direction represented by the arrow. 
     Referring to  FIG. 2  and  FIG. 6 , when the rotary shaft  164  rotates, the body  163  rotates in a clockwise direction centering around the rotary shaft  164 , and the pickup roller  167  approaches the paper P. Here, the suspending step  183  is separated from the suspending unit  182 , and the stopping unit  181  slides along a guide  169   b.    
     The pickup roller  167  rotates by the rotating force received from the rotary shaft  164  to pick up and transfer the paper. 
     As described above, according to the paper feeding device of the present invention, since the probe unit for turning the sensor unit on/off is operated with the stopper, the number of components can be reduced, thus reducing the cost and stabling the quality of product. 
     While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.