Abstract:
An image-forming apparatus includes a developing unit. The developing unit has at least one carrying screw for uniformly distributing toner on a supply roller, a toner container that includes at least one mixing screw and supplies toner to the developing unit, and a toner pressure control device that controls the transfer of the toner by being rotatably mounted in a toner path between the developing unit and the toner container.

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATION  
       [0001]     This application claims the benefit under 35 U.S.C. § 119(a) of Korean Patent Application No. 10-2005-0033542, filed on Apr. 22, 2005, in the Korean Intellectual Property Office, the entire disclosure of which is hereby incorporated by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to an image-forming apparatus. More particularly, the present invention relates to an image-forming apparatus that has a developing unit that includes a toner pressure control device for preventing an increase in toner pressure in the developing unit.  
         [0004]     2. Description of the Related Art  
         [0005]     Generally, an image-forming apparatus prints a desired image on a recording medium by forming an electrostatic latent image on a photosensitive medium using an exposing unit, such as a laser scanning unit (LSU). The electrostatic latent image is developed into a toner image by using toner. The toner image is transferred and fixed on the recording medium by applying heat and pressure.  
         [0006]     According to the type of toner and carrier used, image-forming apparatuses can be generally classified as either wet type apparatuses or dry type apparatuses. A dry type image forming apparatus can be further classified based on whether it has a one-phase developing device or a two-phase developing device.  
         [0007]     An image forming apparatus that has a one-phase developing device forms an image by supplying only toner. In contrast, an image forming apparatus that has a two-phase developing device forms an image by supplying a mixture of toner and a carrier in which toner particles are adhered to the carrier.  
         [0008]     An image-forming apparatus that has a one-phase developing device cleans any toner particles remaining on the surface of a photosensitive medium after developing a toner image thereon with a cleaning device, such as a cleaning blade. The toner particles are then reused in the next developing process.  
         [0009]     An image-forming apparatus that has a two-phase developing device also reuses toner particles recovered from a surface of a photosensitive medium after developing a toner image thereon.  
         [0010]     The above descriptions refer to black and white image formation. When forming a color image, however, toner remaining on the surface of a photosensitive medium cannot be reused since different color toners are mixed on the surface of the photosensitive medium.  
         [0011]     To address this problem, an image-forming apparatus includes a developing unit that develops an electrostatic latent image into a toner image by supplying toner to the photosensitive medium on which the electrostatic latent image is formed. The developing unit receives toner from a toner storage space provided on the developing unit, or receives toner from a separate toner container that is connected to the developing unit.  
         [0012]     The toner transferred to the developing unit is supplied to the photosensitive medium through a developing roller. When toner is continuously supplied to the developing unit and the developing unit is completely filled with toner, the toner pressure in the developing unit may increase. This may cause toner to leak from the developing unit and contaminate peripheral devices in the image-forming apparatus.  
         [0013]     Therefore, there is a need for an image forming apparatus with a device that can prevent an increase in toner pressure in the developing unit by controlling the amount of toner supplied to the developing unit.  
       SUMMARY OF THE INVENTION  
       [0014]     An aspect of the present invention is to address at least the above problems and/or disadvantages and to provide at least the advantages described below. Accordingly, an aspect of the present invention is to provide an image-forming apparatus having a toner pressure control device that prevents an increase in toner pressure in a developing unit by preventing continuous inflow of toner when the developing unit is full of toner.  
         [0015]     According to an aspect of the present invention, an image-forming apparatus comprises a developing unit, a toner container, and a toner pressure control device. The developing unit comprises at least one carrying screw for uniformly distributing toner on a supplying roller, and the toner container comprises at least one mixing screw that supplies toner to the developing unit. The toner pressure control device controls the transfer of the toner by being rotatably mounted in a toner path between the developing unit and the toner container. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]     The above and other objects, features, and advantages of certain exemplary embodiments of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings, in which:  
         [0017]      FIG. 1  is a perspective view of a developing unit and a toner container having a toner pressure control device according to an exemplary embodiment of the present invention;  
         [0018]      FIG. 2  is a perspective view of a developing unit and a toner container having a toner pressure control device according to another exemplary embodiment of the present invention;  
         [0019]      FIG. 3  is a perspective view of a developing unit and a toner container having a toner pressure control device according to still another exemplary embodiment of the present invention;  
         [0020]      FIG. 4  is a perspective view of a developing unit and a toner container having a toner pressure control device according to yet another exemplary embodiment of the present invention; and  
         [0021]      FIG. 5  is a partial perspective view illustrating the operation of the toner pressure control device depicted in  FIG. 4 . 
     
    
       [0022]     Throughout the drawings, the same drawing reference numerals will be understood to refer to the same elements, features, and structures.  
       DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS  
       [0023]     The matters defined in the description such as a detailed construction and elements are provided to assist in a comprehensive understanding of the exemplary embodiments of the invention. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the exemplary embodiments described herein can be made without departing from the scope and spirit of the invention. Also, descriptions of well-known functions and constructions are omitted for clarity and conciseness.  
         [0024]      FIG. 1  is a perspective view of a developing unit and a toner container having a toner pressure control device according to an exemplary embodiment of the present invention.  
         [0025]     Referring to  FIG. 1 , a developing unit  110  and a toner container  120  are connected to each other so that a toner inlet  116  disposed in a developing unit housing  111  and a toner outlet  126  disposed in a toner container housing  121  correspond to each other. The toner container  120  may be connected at a predetermined angle with respect to the developing unit  110  to facilitate the transfer of toner from the toner container  120  to the developing unit  110 .  
         [0026]     A portion of the developing unit  110  includes a developing roller  112 , a supplying roller  113 , and a plurality of carrying screws  114  and  115 . The developing roller  112  is exposed to the outside of the developing unit housing  111 , and is rotatably mounted on the developing unit housing  111 . The developing roller develops an electrostatic latent image formed on a photosensitive medium (not shown) into a toner image by supplying toner to the photosensitive medium. The supplying roller  113  supplies toner to the developing roller  112  and is mounted substantially parallel to the developing roller  112 . The carrying screws  114  and  115  are rotatably mounted in the developing unit housing  111  and carry toner to the supplying roller  113 . The carrying screws  114  and  115  carry toner in the developing unit housing  111  in a lengthwise direction of the supplying roller  113 .  
         [0027]     The carrying screws  114  and  115  carry the toner in the developing unit housing  111  by rotating in opposite directions to each other as indicated in  FIG. 1 .  
         [0028]     The toner container  120  (which is filled with toner) is detachably mounted to the developing unit  110 , and includes a plurality of mixing screws  122  and  123  to prevent the toner from hardening.  
         [0029]     A toner pressure control device  130  is mounted on the toner inlet  116  of the developing unit  110  to control the amount of toner being transferred to the developing unit  110  from the toner container  120 . The toner pressure control device  130  allows the toner to flow into the developing unit  110  when the developing unit  110  is not full with toner. However, the toner pressure control device  130  limits the flow of toner into the developing unit  110  by blocking the toner outlet  126  when the developing unit  110  is full with toner. In this way, the toner pressure control device  130  prevents an increase of toner pressure in the developing unit  110 .  
         [0030]     The toner pressure control device  130  includes a pressure control plate  132  that is mounted on a rotation axis  131  disposed substantially parallel to the supplying roller  113  in the toner inlet  116  to block or open the toner inlet  116 .  
         [0031]     The pressure control plate  132  is mounted to contact an opening unit  124 . The opening unit  124  has a conical shape and is formed on the mixing screw  122  mounted nearest to the toner outlet  126 . Accordingly, when the opening unit  124  contacts the pressure control plate  132 , the pressure control plate  132  rotates toward the developing unit  110 . Then, the toner inlet  116  is opened by the pressure of toner entering into the developing unit  110  from the toner container  120 .  
         [0032]     In another exemplary embodiment of the present invention, the pressure control plate  132  does not contact the opening unit  124 , and the pressure control plate  132  is opened by the pressure of toner transferring from the toner container  120  to the developing unit  110  since the toner container  120  is mounted in an inclined position with respect to the developing unit  110 .  
         [0033]      FIG. 2  is a perspective view of a developing unit and a toner container having a toner pressure control device according to another exemplary embodiment of the present invention.  
         [0034]     Referring to  FIG. 2 , the developing unit and the toner container have substantially identical configurations to the developing unit  110  and the toner container  120  depicted in  FIG. 1 . However, the toner pressure control device  230  of  FIG. 2  is different from the toner pressure control device  130 .  
         [0035]     The toner pressure control device  230  includes a pressure control plate  232  rotatably mounted on a rotation axis  231  which is substantially parallel to the supplying roller  113  in the toner inlet  116 . The toner pressure control device  230  also includes a rotation control plate  233  vertically connected to the pressure control plate  232  and disposed to contact the opening unit  124 .  
         [0036]     The opening unit  124  opens when the rotation control plate  233  rotates the pressure control plate  232  toward the developing unit  110  in contact with the opening unit  124 , thereby facilitating the flow of toner into the developing unit  110 .  
         [0037]     The pressure control plate  232  rotates due to the pressure of toner when the developing unit  110  is full with toner, and the toner inlet  116  can be blocked when the pressure control plate  232  rotates toward the toner container  120  since the rotation control plate  233  bends when it contacts the opening unit  124 . To allow this bending, the rotation control plate  233  may be formed of a soft material, such as rubber or fiber.  
         [0038]      FIG. 3  is a perspective view of a developing unit and a toner container having a toner pressure control device according to still another exemplary embodiment of the present invention.  
         [0039]     Referring to  FIG. 3 , the developing unit and the toner container have substantially identical configurations to the developing unit  110  and the toner container  120  depicted in  FIG. 1 . However, the toner pressure control device  330  of  FIG. 3  is different from the toner pressure control device  130  of  FIG. 1   
         [0040]     The toner pressure control device  330  includes a pressure control plate  332  that blocks or opens the toner inlet  116 . The pressure control plate  332  is rotatably mounted on a rotation axis  331  in the toner inlet  116 . The rotation axis  331  is slanted at a predetermined angle with respect to the supplying roller  113 .  
         [0041]     The slant of the rotation axis  331  by a predetermined angle with respect to the supplying roller  113  allows the toner transferred by the rotation of the carrying roller  115  to reach the pressure control plate  332 . This increases the contact area between the toner that is transferred to the pressure control plate  332  by the carrying roller  115  and the pressure control plate  332 .  
         [0042]      FIG. 4  is a perspective view of a developing unit and a toner container having a toner pressure control device according to yet another exemplary embodiment of the present invention, and  FIG. 5  is a partial perspective view illustrating the operation of the toner pressure control device depicted in  FIG. 4 .  
         [0043]     Referring to  FIG. 4 , the developing unit and the toner container have substantially identical configurations to the developing unit  110  and the toner container  120  depicted in  FIG. 1 . However, the toner pressure control device  430  of  FIG. 4  is different from the toner pressure control device  130  of  FIG. 1 .  
         [0044]     The toner pressure control device  430  includes a pressure control plate  432  rotatably mounted on a rotation axis  431  in the toner inlet  116  and slanted at a predetermined angle with respect to the supplying roller  113 . A rotation control plate  433  is vertically connected to the pressure control plate  432  and disposed to contact the opening unit  124 .  
         [0045]     The rotation axis  431  is slanted at a predetermined angle with respect to the supplying roller  113 . The rotation axis  431  may be inclined parallel to an outer circumference of the opening unit  124  so that the toner transferred by the rotation of the carrying roller  115  can reach the pressure control plate  432 . This increases the contact area between the toner transferred to the pressure control plate  432  by the carrying roller  115  and the pressure control plate  432 . The rotation control plate  433  is preferably formed of a soft material, such as rubber or fiber.  
         [0046]     As depicted in  FIG. 5 , when the developing unit  110  is full of toner, the pressure control plate  432  rotates in a counter clockwise direction due to the pressure (see arrows in  FIG. 5 ) of the toner in the developing unit  110 . When the rotation control plate  433  rotates toward the toner container  120 , the rotation control plate  433  bends when contacting the opening unit  124 , thereby blocking the toner inlet  116 .  
         [0047]     As described above, an image-forming apparatus according to the present invention can regulate toner pressure in the developing unit to prevent leakage of toner from the developing unit and prevent peripheral elements from being contaminated with toner.  
         [0048]     While the invention has been shown and described with reference to certain exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.