Abstract:
A laser scanning unit and an image forming apparatus employing the laser scanning unit including a light source generating light; a polygon mirror that includes a plurality of reflection mirrors with a polygonal horizontal cross-section, and the polygon mirror rotates to scan the beam from the light source in a main scanning direction, and a light interruption member swinging between a shut position and an open position to selectively block or clear the light path to the polygon mirror according to whether the polygon mirror is operated or not. The light interruption member is swung to the opening position by air pressure generated during an operation of the polygon mirror and returns to the shut position by a restoration force when the polygon mirror stops rotating. The laser scanning unit and the image forming apparatus employing the laser scanning unit include a laser beam interruption structure to prevent body damage of the operators during maintenance and repair and to reduce additional manufacturing costs and installation space.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the priority of Korean Patent Application No. 10-2005-0065672, filed on Jul. 20, 2005, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present general inventive concept relates to a laser scanning unit (LSU) and an image forming apparatus having the same, and more particularly, to an LSU and an image forming apparatus including a simple laser beam interruption structure to prevent injury to an operator performing maintenance and repair.  
         [0004]     2. Description of the Related Art  
         [0005]     In general, laser scanning units (LSUs) are employed in laser printers, digital photocopiers, bar code readers, and facsimiles. The LSU forms a latent image by scanning with a beam deflector and sub-scanning through rotation of a photoreceptor.  
         [0006]      FIG. 1  illustrates a conventional image forming apparatus  50  disclosed in Korean Patent Publication No. 2004-6350. The image forming apparatus  50  includes a developing unit  10  and an LSU  20  facing each other. The LSU  20  scans a light beam on the developing unit  10  to form a latent image. A laser beam interruption device  30  which forms a boundary between the LSU  20  and the developing unit  10  selectively clears or blocks a transmission opening  20 ′ of the LSU  20 . The light interruption member  30  selectively blocks the transmission opening  20 ′ of the LSU  20  and includes a protrusion lever  25  that rises and falls inside the LSU  20 , inclination sliders  21  guiding the protrusion lever  25  when rising and falling, and an operation unit  15  formed on the developing unit  10  to contact and move the protrusion lever  25 . When the developing unit  10  is installed, the operation unit  15  in the upper portion of the developing unit  10  pushes the protrusion lever  25  along the inclination sliders  21  so that an interruption plate  23  coupled to the protrusion lever  25  opens the transmission opening  20 ′ of the LSU  20 . When the developing unit  10  supporting the protrusion lever  25  is removed, the protrusion lever  25  falls downward along the inclination sliders  21  by its own weight and the interruption plate  23  shuts the transmission opening  20 ′. Accordingly, the image forming apparatus is designed such that the laser beam emitted from the LSU  20  is prevented from draining out to the outside when the developing unit  10  is removed or installed.  
         [0007]     According to the conventional image forming apparatus, the operation unit  15  needs to be provided on the developing unit  10  to drive the interruption plate  23  of the LSU  20  to rise and fall. Also, since the transmission opening  20 ′ is shut only when the developing unit  10  is not installed, the transmission opening  20 ′ does not prevent the laser beam from escaping to the outside when the developing unit  10  is mounted.  
       SUMMARY OF THE INVENTION  
       [0008]     The present general inventive concept provides a laser scanning unit (LSU), which has a simplified laser beam interruption structure to reduce manufacturing costs and to simplify the LSU, and an image forming apparatus having the LSU.  
         [0009]     The present general inventive concept also provides an LSU in which a laser beam is interrupted when the LSU stops, regardless of whether a developing unit is detached or attached from or to an image forming apparatus.  
         [0010]     Additional aspects and utilities of the present general inventive concept will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the general inventive concept.  
         [0011]     The foregoing and/or other aspects and utilities of the present general inventive concept may be achieved by providing an LSU including a light source to generate light, a polygon mirror that includes a plurality of reflection mirrors with a polygonal horizontal cross-section to rotate so as to scan the beam from the light source in a main scanning direction, and a light interruption member to swing between a shut position and an open position to selectively block or let pass a light path to the polygon mirror according to whether the polygon mirror is operated or not, wherein the light interruption member is swung to the opening position by an air pressure generated during the operation of the polygon mirror and returns to the shut position by a restoration force when the polygon mirror stops rotating.  
         [0012]     The LSU may further include a housing having an area defining an inner space to contain the light source, the polygon mirror, and the light interruption member and a cover member to couple with the housing to seal the inner space. The light interruption member may be connected to an inside area of the cover member to be able to swing.  
         [0013]     The light interruption member may also include a coupling unit attached to an inner surface of the cover member, a swing unit to extend vertically from an end of the coupling unit and to be swung by the air pressure induced by the polygon mirror, and a shield unit to extend horizontally from an lateral end of the swing unit to interrupt the light to the polygon mirror.  
         [0014]     The light interruption member may also include an elastic body which can be bent according to the air pressure.  
         [0015]     An adhesion medium may be disposed between the coupling unit and the cover member to couple the coupling unit to the cover member. The swing unit may be planar and a main surface of the swing unit may be perpendicular to a circumferential direction of the polygon mirror. The shield unit may be planar and the main surface of the swing unit may be perpendicular to the light path between the light source and the polygon mirror.  
         [0016]     The light interruption member may return to the shutting position by the light interruption member&#39;s elasticity and weight.  
         [0017]     The light interruption member may also include a hinge axis rotatably supported on an inside surface of the cover member, a swing unit to extend vertically from the hinge axis to be swung by the air pressure induced by the polygon mirror; and a shield unit to extend horizontally from a lateral end of the swing unit to interrupt the light path to the polygon mirror.  
         [0018]     The swing unit may be planar, and a main surface of the swing unit may be perpendicular to the circumferential direction of the polygon mirror.  
         [0019]     The shield unit may be planar, and a main surface of the swing unit may be perpendicular to the light path between the light source and the polygon mirror.  
         [0020]     The LSU may further include a hinge bracket connected to the inside of the cover member to support the hinge axis to rotate.  
         [0021]     The shield unit may extend from one side of the swing unit and may extend asymmetrically from the swing unit. The shield unit may also extend from both sides of the swing unit and may be symmetrical about swing unit.  
         [0022]     The foregoing and/or other aspects and utilities of the present general inventive concept may be achieved by providing an image forming apparatus including a laser scanning unit to scan a light signal onto a photoconductive drum to form a latent image, and a developing unit to develop the latent image formed on the photoconductive drum as a visible image on a printing medium, the laser scanning unit including a light source to generate light, a polygon mirror that includes a plurality of reflection mirrors having a polygonal horizontal cross-section to rotate so as to scan the beam from the light source in a main scanning direction, and a light interruption member to swing between a shut position and an open position to selectively block or let pass a light path to the polygon mirror according to whether the polygon mirror is operated or not, wherein the light interruption member is swung to the opening position by an air pressure generated during the operation of the polygon mirror and returns to the shut position by restoration force when the polygon mirror stops.  
         [0023]     The foregoing and/or other aspects and utilities of the present general inventive concept may be achieved by providing a laser scanning unit usable in an image forming unit, including a housing, a light source disposed in the housing to generate light, a mirror unit disposed in the housing to direct the light in a direction, and a light blocking member disposed in the housing between the light source and the mirror unit to selectively block the light according to an operation of the mirror unit.  
         [0024]     The foregoing and/or other aspects and utilities of the present general inventive concept may be achieved by providing an image forming apparatus, including a developing unit to form a latent image and to develop the latent image with a developing agent, and a laser scanning unit to scan light corresponding to the latent image, the laser scanning unit including a housing, a light source disposed in the housing to generate light, a mirror unit disposed in the housing to direct the light in a direction, and a light blocking member disposed in the housing between the light source and the mirror unit to selectively block the light according to an operation of the mirror unit.  
         [0025]     The foregoing and/or other aspects and utilities of the present general inventive concept may be achieved by providing an image forming apparatus, including a light source to generate light in a first direction, a mirror unit to direct the light in a second direction, and a light blocking member to block the light from the light source according to an air pressure generated by an operation of the mirror unit. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0026]     These and/or other aspects and utilities of the present general inventive concept will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:  
         [0027]      FIG. 1  illustrates a conventional image forming apparatus;  
         [0028]      FIG. 2  is illustrates an image forming apparatus according to an embodiment of the present general inventive concept;  
         [0029]      FIG. 3  is a perspective view illustrating a laser scanning unit (LSU) of the image forming apparatus of  FIG. 2  according to an embodiment of the present general inventive concept;  
         [0030]      FIGS. 4 and 5  are perspective views illustrating a light interruption member of the LSU of  FIG. 3 ;  
         [0031]      FIG. 6  is a cross-sectional view taken along line VI-VI of  FIG. 4  illustrating the operation of the light interruption member;  
         [0032]      FIG. 7  is a perspective view illustrating a light interruption member employed in an LSU according to another embodiment of the present general inventive concept; and  
         [0033]      FIG. 8  is a perspective view illustrating a light interruption member employed in an LSU according to another embodiment of the present general inventive concept. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0034]     Reference will now be made in detail to the embodiments of the present general inventive concept, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below in order to explain the present general inventive concept by referring to the figures.  
         [0035]      FIG. 2  is illustrates an image forming apparatus  100  according to an embodiment of the present general inventive concept. Referring to  FIG. 2 , a laser scanning unit (LSU)  200  scans a light signal L into a developing unit  110  and onto a photoconductive drum  111  of the developing unit  110 , and forms a latent image on the photoconductive drum  111 , charged to a predetermined potential by a charge roller  119 . The developing unit  110  includes the photoconductive drum  111  on a circumferential surface of which the latent image is formed by the LSU  200 , a developing roller  113  supplying a toner T to the photoconductive drum and developing a toner image on the photoconductive drum  111  corresponding to the latent image, and a supply roller  115  is placed near the developing roller  113  to supply the toner contained in the toner housing  117  to the developing roller  113 .  
         [0036]     The photoconductive drum  111 , on which the toner image is formed, contacts a transfer roller  130  with a predetermined amount of pressure with a printing medium M therebetween. Thus, the toner image on the photoconductive drum  111  is transferred to the printing medium M, which passes between the photoconductive drum  111  and the transfer roller  130 , and follows a transfer path P. The printing medium M is piled in a first feeding tray  171  or a second feeding tray  173  and then picked up piece by piece by a first pick-up roller  151  or a second pick-up roller  153 , and supplied to the transfer roller  130 . A paper aligner  155  is placed between the first pick-up roller  151  and the transfer roller  130 . The paper aligner  155  feeds and aligns the printing medium so that the toner image can be transferred to a desired spot of the printing medium M.  
         [0037]     A fuser  140  includes a heat roller  141  and a pressure roller  142  closely contacting each other and rotating in opposite directions to each other. As the printing medium M passes through between the heat roller  141  and the pressure roller  142 , toner particles that are adhered to the printing medium M are thermally fused by a predetermined amount of heat and pressure. The printing medium M, on which a visible image is fused, passes between a pair of the feeding rollers  160  and released outside a case  101  onto a face-down tray  102 .  
         [0038]      FIG. 3  is a perspective view illustrating the LSU  200 . Referring to  FIG. 3 , the LSU  200  includes a housing  201  and a cover member  280  facing each other and coupled together to provide an inner space G and optical components contained in the inner space G. The housing  201  contains a scanning optical system scanning a light beam on the photoconductive drum  111  to form a linear latent image, and shields the optical components from external conditions. In general, the housing  201  may be manufactured by injection molding, but its manufacturing method is not limited thereto. An upper portion of the housing  201  is closed by the cover member  280  formed to correspond to the housing  201 , which seals the inner space G. According to the present embodiment of the general inventive concept, a light interruption member  230  is placed at a predetermined position inside the cover member  280 , which will be described in detail later.  
         [0039]     A light source unit  210  is placed at a side of the housing  201  to provide a regularly shaped light beam. The light source unit  210  includes a holder guide  213  in which a lens holder  215  is mounted and a circuit substrate  211  which is combined on the back of the holder guide  213 . An aperture  217  and a cylindrical lens  219  are sequentially disposed in the front of the holder guide  213 . A light emitting device ( 212  of  FIG. 4 ) that emits the light beam is mounted onto the light emitting circuit substrate  211 . The light emitting device  212  may be a light emitting diode (LED) or a laser diode (LD). The light beam emitted from the light emitting device is incident on a side of the lens holder  215  mounted on the holder guide  213 . The lens holder  215  is approximately a hollow cylinder, in which a collimating lens (not shown) is fixed. The collimating lens collimates a divergent light emitted from the light emitting device into a parallel light.  
         [0040]     The parallel light collimated by the collimating lens passes through the aperture  217  disposed along the light path and is shaped into a wide light beam in a main scanning direction. Then the parallel light passes through the cylindrical lens  219  disposed next to the aperture  217  and is converged in a sub-scanning direction and focused on a polygon mirror  221 , which will be described later. The main scanning direction indicates the direction in which the light beam is scanned on the photoconductive drum  111  by the polygon mirror  221 , and the sub-scanning direction indicates a rotation direction of the photoconductive drum  111 .  
         [0041]     A second circuit substrate  225  on which the polygon mirror  221  is mounted is placed in a predetermined area of the housing  201  facing the light source unit  210 . The polygon mirror  221  has a plurality of reflection surfaces, and is installed on a rotor of a driving motor  223  to be rotated at a high speed. The light beam incident on the polygon mirror  221  is reflected by the reflection surfaces rotating at the high speed. The light beam is deflected and scanned in the main scanning direction and passes through a scanning optical lens  240 , also called an f-θ lens, to be focused with different magnifications in the main scanning direction. Accordingly, an incident light is focused on the photoconductive drum  111  to form the linear latent image. To this end, the shape of the scanning optical lens  240  varies along the main scanning direction. The light beam focused by the scanning optical lens  240  is reflected by a reflection mirror  251  toward the photoconductive drum  111 . An approximately rectangular window  270  is provided on the lower surface of the housing  201 . The light beam is emitted through the window  270  and scanned onto the photoconductive drum  111  outside the LSU  200 . Further, a synchronization mirror  261  and a light sensor  263 , which receives the light beam reflected by the synchronization mirror  261 , may be placed between the scanning optical lens  240  and the reflection mirror  251 .  
         [0042]     When the cover member  280  is coupled onto a top of the housing  201 , the light interruption member  230  attached to a lower surface of the cover member  280  by an adhering medium  281  is placed on a light path R between the light source unit  210  and the polygon mirror  221 .  FIGS. 4 and 5  are perspective views illustrating the light interruption member  230  of  FIG. 3 . Referring to  FIG. 4 , the light interruption member  230  is attached to the lower surface of the cover member  280  at a predetermined position along the light path R to clear or obstruct the light path R according to an operation of the polygon mirror  221 , and thus prevents the light beam from flowing out in case of an emergency. In an embodiment of the present general inventive concept, the light interruption member  230  is a bent plate. The light interruption member  230  may include a coupling unit  231  attached to the lower surface of the cover member  280 , a swing unit  233  bent from the coupling unit  231  and to extend vertically from the lower surface of the coupling unit  281 , and a shield unit  235  to extend horizontally from an end of the swing unit  233 . A main surface of the swing unit  233  is perpendicular to a circumference of the polygon mirror  221 . The main surface of the swing unit  233  may be parallel to light path R. The swing unit  233  swings along a circumference direction of the polygon mirror  21  due to a circular air flow W about a rotational axis of the polygon mirror  221 . The shield unit  235  is placed on the light path R between the light emitting device  212  and the polygon mirror  221  and selectively clears or obstructs the light path R. The light interruption member  230  may be made of an elastic material such that it can swing between an open position B ( FIG. 6 ) and a shut position A ( FIG. 6 ) through elastic deformation and restoration to its natural state. The elastic material constituting the light interruption member  230  may be selected in consideration of an air pressure generated during the operation of the polygon mirror  221  and the area of the swing unit  233 , and an elastic modulus can be given for the standards for selection.  
         [0043]      FIG. 6  is a cross-sectional view taken along line VI-VI of  FIG. 4  illustrating an operation of the light interruption member  230 . When the laser scanning unit  200  is driven, the airflow W is generated along the circumference of the polygon mirror  221  rotating at the high speed, and the airflow W pushes the swing unit  233  of the light interruption member  230  and swings the light interruption member  230  from the shut position A to the open position B. The swing unit has a surface having a width to receive a force of the airflow. The light interruption member  230  returns to the shutting point B by its own elasticity, and can swing about an axis C, which forms a boundary between the coupling unit  231  and the swing unit  233 . That is, when the polygon mirror  221  does not rotate, the airflow W is not generated so that the force of the airflow on swing unit  233  is removed. When the light path R, which connects the light emitting device  212  and the polygon mirror  221 , is opened by removing the shield unit  233  from the light path R by the light interruption member  230  being moved to the open position B, the light beam emitted from the light emitting device  212  is incident on the rotating polygon mirror  221  and is scanned onto the photoconductive drum  111  to form the latent image. The swing unit  233  may have an angle with the shield unit  235  so that the shield unit  335  moves in a direction having an angle with the light path R, and the swing unit  233  is disposed in a direction to receive the force.  
         [0044]     The light interruption member  230  returns to an erect posture in the shut position A by light interruption member&#39;s own elasticity and weight when the polygon mirror  221  stops operating, and obstructs the light path R between the light emitting device  212  and the polygon mirror  221 . That is, as the polygon mirror  221  stops rotating, the airflow W around the polygon mirror  221  stops, and the light interruption member  230  is moved to the shutting point A by its own elasticity and weight. Since the light interruption member  230  selectively clears and obstructs the light path according to whether the polygon mirror  221  is operated or not, an injury due to exposure to a laser beam when the developing unit  110  is attached or detached for maintenance and repair of the image forming apparatus is prevented. In particular, in the present embodiment of the general inventive concept, the laser beam is interrupted when the polygon mirror  221  stops, and thus higher safety standards can be achieved compared to the prior art in which a laser beam is interrupted only when the developing unit  110  is removed. Further, since the beam interruption structure is simplified compared to the prior art, manufacturing costs are reduced and the entire image forming apparatus can be simplified. The swing unit  233  and the shield unit  235  may be formed in a monolithic body.  
         [0045]      FIG. 7  is a perspective view illustrating a light interruption member  330  employed in an LSU according to another embodiment of the present general inventive concept. Referring to  FIG. 7 , the light interruption member  330  includes a hinge axis  331 , a swing unit  333  vertically extending downward from the hinge axis  331 , and a shield unit  335  horizontally extending from an end of the swing unit  333 . The hinge axis  331  is rotatably supported on the cover member  280  and the light interruption member  330  rotates around the hinge axis  331 . A hinge bracket  381  is coupled onto an inside surface of the cover member  280 . A screw hole  381 ″ is formed in the hinge bracket  381 , and a screw member (not shown) passes through the screw hole  381 ″ and is coupled to the cover member  280 . The hinge axis  331  is inserted in hinge holes  381 ′ formed in the hinge bracket  381  to be rotatable. The light interruption member  330  of the present embodiment pivots around the hinge axis  331  in the cover member, and thus can be a rigid body instead of an elastic body. Also, elastic deformation is not required during the operation of the light interruption member, and thus the light interruption member  330  can operate smoothly even when the air pressure generated by the polygon mirror is relatively low.  
         [0046]      FIG. 8  is a perspective view illustrating a light interruption member  430  employed in the LSU  200  according to another embodiment of the present general inventive concept. The light interruption member  430  includes a hinge axis  431 , a swing unit  433  vertically extending from the hinge axis  431  downward, and a shield unit  435  horizontally extending from an end of the swing unit  433 . A hinge bracket  481  is coupled onto the inside surface of the cover member  280 . A screw hole  481 ″ is formed in the hinge bracket  481 , and a screw member (not shown) passes through the screw hole  481 ″ and is coupled to the cover member  280 . The hinge axis  431  is inserted in hinge holes  481 ′ formed in the hinge bracket  481  to be rotatable. Since the shield unit  435  in the present embodiment of general inventive concept is extended symmetrically about the swing unit  433 , when the polygon mirror  221  stops operating, the light interruption member  430  falls to a vertical position in which it is balanced due to its symmetry, and interrupts the light path R. The light path R intersects the center of the light interruption member  430 , and a sufficient margin is secured to align the light interruption member  430  with the light path R which connects the light emitting device  212  and the polygon mirror  221 . Therefore, precise alignment of the light interruption member  430  is not required, and thus alignment can be easier.  
         [0047]     The laser scanning unit and the image forming apparatus of the present general inventive concept includes a light interruption member which selectively interrupts a laser beam according to an operation of a polygon mirror to prevent an injury to the user due to exposure to the laser beam when the polygon mirror stops operating. In particular, since the laser beam is interrupted when the polygon mirror is stopped, higher safety standards are satisfied compared to the prior art, in which the laser beam is interrupted only when the developing unit is removed. Further, a structure of the laser beam interruption member is simple, thus reducing the manufacturing costs and simplifying an entire image forming apparatus.  
         [0048]     Although a few embodiments of the present general inventive concept have been shown and described, it will be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the general inventive concept, the scope of which is defined in the appended claims and their equivalents.