Abstract:
A recording medium discharge apparatus includes a discharge pusher for discharging a recording medium; and a discharge tray in which the recording medium discharged through the discharge pusher is stacked. The discharge pusher is configured to be capable of conducting electric current, thereby eliminating the static electricity from the recording medium discharged to the discharge tray. For the electric conduction of the discharge pusher, the discharge pusher includes a conductive material. Alternately, an elastic member is made of a conductive material in such a way that a part of the elastic member is extended to a surface of the discharge pusher which comes into contact with the recording medium.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims the benefit of Korean Patent Application No. 2005-96735, filed Oct. 13, 2005 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     Aspects of the present invention relate to a recording medium discharge apparatus and an image forming apparatus using the same, and in particular to a recording medium discharge apparatus adapted to efficiently eliminate static electricity of a recording medium discharged to a discharge tray and an image forming apparatus using the same.  
         [0004]     2. Description of the Related Art  
         [0005]     In an image forming apparatus, such as a copying machine and a printer, an anti-static device is often employed in order to eliminate static electricity from a recording medium electrified while being conveyed within the image forming apparatus. An example of an image forming apparatus provided with an anti-static device as described above is disclosed in Japanese unexamined patent publication No. 2003-212378 and in  FIG. 1 .  
         [0006]     Referring to  FIG. 1 , in a paper loading tray  11 , an anti-static device  19  is installed downstream of a paper-feeding roller  12 . A paper end filler  16  of the anti-static device  19  is arranged to be freely rotated, and an anti-static brush  17  supported by a bracket  18  is rotated clockwise. Through this construction, when a recording medium P 1  enters the device  19 , the paper end filler  16  is pushed and rotated by the recording medium P 1  so that the paper end filler  16  comes into contact with the anti-static brush  17 .  
         [0007]      FIG. 2  shows a document conveying device provided with another conventional anti-static device. Referring to  FIG. 2 , an anti-static mechanism  36  is provided in a document tray in a sheet document reading device of a document reversing type between a document setting tray  31  and a discharge stack tray  32 . Through this construction, it is possible to prevent the repulsion/adhesion of the document caused by frictional static electricity produced as a document  32  is conveyed. The conveying device also includes an image sensor  38  and a contact glass  39 . As described above in relation to  FIGS. 1 and 2 , various types of anti-static devices are provided in order to eliminate static electricity from a recording medium while being conveyed.  
         [0008]      FIG. 3  shows an example provided with another conventional anti-static device. Referring to  FIG. 3 , a print head  51  for forming an image on a recording medium  53 . A platen  55  is provided under the print head  51  so that a recording medium  53  to be formed with an image is seated on the platen  55 . In addition, a feed roller  57  adjacent the platen  55  feeds the recording medium  53  by a predetermined distance. A discharge pusher  61  is provided at a side of the feed roller  57  so as to discharge the recording medium  53  to a discharge tray  59 . The discharge pusher  61  is supported by a coil spring  63 , so that the discharge pusher  61  is returned to its original position by the restoring force of the coil spring  63  after the discharge pusher  61  has discharged the recording medium  53 .  
         [0009]     In addition, in the entrance side of the discharge tray  59 , there is additionally provided an anti-static brush  65 . The anti-static brush  65  comes into contact with the recording medium  53 , thereby eliminating static electricity from the recording medium  53 . However, because the anti-static brush  65  is provided at the entrance side of the discharge tray  59 , there is a problem in that static electricity produced by friction between a recording medium  53  and the discharge tray  59  or between the recording medium  53  and another recording medium already printed and laid on the discharge tray  59  cannot be eliminated, thereby causing poor stacking.  
       SUMMARY OF THE INVENTION  
       [0010]     Aspects of the present invention provide a recording medium discharge apparatus with an improved in anti-static structure.  
         [0011]     Other aspects of the present invention provide an image forming apparatus which uses the recording medium discharge apparatus.  
         [0012]     According to an aspect of the present invention, a recording medium discharge apparatus includes a discharge pusher for discharging a recording medium; and a discharge tray in which the recording medium discharged through the discharge pusher is stacked, wherein the discharge pusher is configured to conduct electric current, thereby eliminating the static electricity from the recording medium discharged to the discharge tray.  
         [0013]     According to an aspect of the present invention, the discharge pusher is formed from a conductive material.  
         [0014]     According to an aspect of the present invention, the recording medium discharge apparatus further includes a conductive member additionally provided on a surface of the discharge pusher which comes into contact with the recording medium.  
         [0015]     According to an aspect of the present invention, the discharge pusher is supported by a conductive spring connected so that the spring extends to the surface of the discharge pusher.  
         [0016]     According to an aspect of the present invention, the spring is a coil spring.  
         [0017]     According to another aspect of the present invention, there is provided an image forming apparatus comprises: a print head for forming a given image on a recording medium; a feed roller for feeding the recording medium a predetermined distance; a discharge pusher for discharging the recording medium with the formed image; and a discharge tray in which the recording medium discharged through the discharge pusher is stacked, wherein the discharge pusher conducts electric current, to eliminate the static electricity from the recording medium discharged to the discharge tray. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]     The above and other aspects and/or features of the present invention will be more apparent and more readily appreciated from the description for certain embodiments of the present invention taken with reference to the accompanying drawings, in which:  
         [0019]      FIG. 1  shows a construction of a conventional anti-static device;  
         [0020]      FIG. 2  shows a document conveying device having another conventional anti-static device;  
         [0021]      FIG. 3  shows a document conveying device having another conventional anti-static device;  
         [0022]      FIG. 4A  schematically shows an ink-jet printer  100  provided with an anti-static structure according to an embodiment of the present invention;  
         [0023]      FIG. 4B  shows a state of discharging a recording medium as the discharge pusher shown in  FIG. 4A  is operated; and  
         [0024]      FIGS. 5A and 5B  show the operating states of a recording medium discharge apparatus provided with an anti-static device according to an embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS  
       [0025]     Hereinbelow, the embodiments of the present invention are described in detail with reference to accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below in order to explain the present invention by referring to the figures.  
         [0026]      FIG. 4A  schematically shows an ink-jet printer  100  provided with an anti-static structure according to an embodiment of the present invention, and  FIG. 4B  shows a state of discharging a recording medium  101  as the discharge pusher shown in  FIG. 4A  is operated. Referring to  FIGS. 4A and 4B , an ink-jet printer  100  comprises a recording medium supply unit  110  for supplying the recording medium  101 . A feeding unit  130  feeds the recording medium  101  received from the recording medium supplying unit  110  into the printer  100 . An image forming unit  150  prints an image on the recording medium  101  while the recording medium  101  is fed by the feeding unit  130 . A recording medium discharge unit  170  discharges the recording medium  101  with the image printed by the image forming unit  150  to a discharge unit  185  (see  FIGS. 5A and 5B ). A driving unit  190  reciprocally moves the image forming unit  150 .  
         [0027]     The recording medium supply unit  110  comprises an automatic paper-feeding tray  111  for receiving recording medium  101 , and a pickup roller (not shown) for transmitting the recording medium  101  received in the automatic paper-feeding tray  111  toward the feeding unit  130 . However, it is understood that other feeding devices can be used and that manual feeding can be used instead of or in addition to the recording medium supply unit  110 .  
         [0028]     The image forming unit  150  comprises a cartridge  153 . A print head  151  for injecting ink droplets is attached to the bottom of the cartridge  153  (as shown in  FIGS. 5A and 5B ). The cartridge  153  is mounted on a carriage  161  to be conveyed according to the movement of the carriage  161  in left and right directions (as indicated by arrow G), thereby forming an image on a recording medium  101  fed through the recording medium supply unit  110 . However, it is understood that other image forming units  150  can be used using more or fewer cartridges and that the image forming unit  150  can be for laser and/or ink jet printing.  
         [0029]     The driving unit  190  comprises a motor  101 . A driving pulley (not shown) is connected to the motor  191 . A driven pulley  193  is installed opposite to the driving pulley. A timing belt  195  is installed around peripheral surfaces of the driving pulley and the driven pulley  193 . A guide rod  197  movably supports the carriage  161  along direction G. However, other driving arrangements can be used and need not be used in other aspects using other image forming units  150 .  
         [0030]     The recording medium discharge unit  170  comprises discharge pushers  171 . The pushers  171  rotate by receiving power from a gear train (not shown in the drawings). As the power is transmitted through the gear train, the discharge pushers  171  rotate as shown in FIGS.  4 B through  5 B, thereby feeding the recording medium  101  formed with an image on the top side thereof. Upon completing the feeding movement, the discharge pushers  171  are returned to their original position by the restoring force of elastic members  173 . While multiple pushers  171  are shown, it is understood that a single pusher  171  could be used.  
         [0031]      FIGS. 5A and 5B  show the operation of the recording medium discharge unit  170  with an anti-static device according to an embodiment of the present invention. Referring to  FIGS. 5A and 5B , a platen  181  is provided under the print head  151 . The recording medium  101  is seated on the platen  181  so that printing is performed on the top side of the recording medium  101 . A feed roller  131  of the feeding unit  130  adjacent the platen  181  to convey the recording medium  101  to be printed with the image by a predetermined distance, and a discharge pusher  171  is installed in a side of the feed roller  131  to discharge the recording medium  101  to a discharge tray  185 .  
         [0032]     While shown discharging to the discharge tray  185 , it is understood that the discharge can be any stacking or sorting area and need not be to a separate tray as shown, and the area need not be external to a housing if the stacking area is internal to the image forming unit  150 . Moreover, it is understood that other discharge units  170  can be used which convey the recording medium  101  other than through pushing using the pushers  171 .  
         [0033]     The discharge pusher  171  is elastically supported by a coil spring  173   a , which is an example of an elastic member  173 . Upon completing the operation of discharging the recording medium  101 , the discharge pusher  171  is returned to its original position by the restoring force of the coil spring  173   a . As shown, the discharge pusher  171  is configured to perform an anti-static function according to an aspect of the invention. That is, at least one of the discharge pushers  171  is configured to eliminate static electricity produced by the friction of the recording medium  101 , thereby preventing a stacking error caused when the recording medium  101  is stacked in the discharge tray  185  with static electricity. It is possible to configure the discharge pusher  171  so that the discharge pusher  171  itself performs a grounding function, to provide a separate ground member to perform the grounding function, or combinations thereof.  
         [0034]     If the at least one discharge pusher  171  is configured so that the discharge pusher itself performs the grounding function, all or a portion of the discharge pusher  171  is formed from a—conductive material (such as metal) and is connected to a ground according to an aspect of the invention. If a separate ground member is additionally provided to one or more of the discharge pushers  171 , a conductive member is additionally provided on at least a portion of the surface  171   a  of the discharge pusher  171  and is connected to the ground.  
         [0035]      FIGS. 5A and 5B  show an example for providing a separate ground member and where the elastic member  173  implements the grounding function. The elastic member  173  a conductive coil member  173   a . Here, one end  173   a ′ of the coil spring  173   a  is projected on the recording medium contact surface  171   a  of the discharge pusher  171  to come into contact with the recording medium  101 , thereby implementing an anti-static function.  
         [0036]     The coil spring  173   a  is tensioned by the discharge pusher  171  rotated by the driving force provided for feeding the recording medium  101 . If the discharge of the recording medium  101  is completed and the driving force exerted to the discharge pusher  171  is released, the coil spring  173   a  returns the discharge pusher  171  to the state shown in  FIG. 5A  by its restoring force. However, it is understood that other mechanisms can be used to bias the pusher  171  and that the spring  173   a  can be otherwise located.  
         [0037]     While described as using the tension member  173  as a conductive grounding element, it is understood that additional ground paths can be created using a conductive hinge about which the pusher  171  rotates.  
         [0038]     As described above, according to aspects of the present invention, it is possible to obtain an advantage of efficiently eliminating static electricity of a recording medium by forming a discharge pusher for discharging the recording medium from a conductive material or extending a coil spring for elastically supporting the discharge pusher to a surface which comes into contact with the recording medium, so that an anti-static function can be implemented until the recording medium is completely discharged to a discharge tray.  
         [0039]     As the effect of eliminating static electricity is improved as described above, it is possible to prevent a stacking error caused by the repulsion or adhesion of a recording medium caused static electricity.  
         [0040]     Moreover, if a coil spring is used to implement the anti-static function, the number of components can be reduced because it is not needed to use a separate anti-static device as in the prior art.  
         [0041]     It is understood that the instant invention can be implemented in a wide variety of image forming devices, such as inkjet and laser printer devices, faxes, and copiers, and can be used in multifunction devices that further scan and/or fax in addition to forming images. Moreover, it is understood that aspects of the invention can be used in non-image forming devices in which paper or other media are automatically stacked, such as sorting and stacking machines, folding machines, and other like devices.  
         [0042]     Although representative embodiments of the present invention have been shown and described in order to exemplify the principle of the present invention, the present invention is not limited to the specific embodiments. It will be understood that various modifications and changes can be made by one skilled in the art without departing from the spirit and scope of the invention as defined by the appended claims and equivalents thereof. Therefore, it shall be considered that such modifications, changes and equivalents thereof are all included within the scope of the present invention as defined in the claims.