Patent Publication Number: US-6215973-B1

Title: Squeegee roller cleaning apparatus for liquid electrophotographic printer

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a squeegee roller cleaning apparatus for a liquid electrophotographic printer and, more particularly, to a squeegee roller cleaning apparatus for a liquid electrophotographic printer having a blade with an improved structure and shape for removing developer remaining between a squeegee roller and a photoreceptor web. 
     2. Description of the Related Art 
     FIG. 1 shows the structure of a conventional liquid electrophotographic printer. Referring to FIG. 1, a development unit of a conventional liquid electrophotographic printer includes a photoreceptor web  10  circulating by being supported by a plurality of rollers  11 , a tray  12  installed under the photoreceptor web  10  for collecting developer remaining after being used for development, a development roller  14  supported by a development frame (not shown) and moving up and down by an elevating means (not shown), a manifold  20  for injecting developer into a gap G (hereinafter, referred to as a development gap) formed between the development roller  14  and the photoreceptor web  10 , a development tank  13  for collecting and holding the developer injected into the development gap G, a development roller cleaning apparatus for removing developer adhering to the outer circumferential surface of the development roller  14 , and a developer removing means for removing developer remaining on the photoreceptor web  10  after being used for the development. 
     The development roller cleaning apparatus consists of a brush roller  18  for cleaning developer adhering to the development roller  14 , by being supported by the development tank  13  and rotating in contact with the development roller  14 , and a development blade  22  having one end in contact with the outer circumference of the development roller  14  and the other end assembled to the body of the manifold  20 , for removing developer remaining between the brush roller  18  and the development roller  14  and transferred to the surface of the development roller  14 . Reference numeral  24  denotes a packing member for discharging developer in the development tank  13  into the tray  12  and reference numeral  26  denotes a stopper for limiting the movement of the packing member  24 . 
     The developer removing means consists of a squeegee roller  15  installed adjacent to the development roller  14  for pressing and removing developer adhering to the photoreceptor web  10 , an air injection nozzle  16  for removing developer by injecting air into a portion where the squeegee roller  15  contacts the photoreceptor web  10 , a squeegee blade  17  for removing developer flowing down along the outer circumference of the squeegee roller  15  while being in contact with the surface of the squeegee roller  15 . 
     During development, the development roller  14  ascends toward the photoreceptor web  10  to maintain the development gap G in the tray  12 . As the development roller  14  moves, the development tank  13  and the manifold  20  are moved upward together. The manifold  20  injects developer into the development gap G and, as the development roller  14  rotates, an area for an electrostatic latent image formed on the surface of the photoreceptor web  10  is developed. Developer carrier adhering to the area for an electrostatic latent image on the photoreceptor web  10  is removed by the developer removing means. 
     In other words, the squeegee roller  15  is in contact with the photoreceptor web  10  and passively rotated thereby in a direction in which the photoreceptor web  10  travels. In doing so, the squeegee roller  15  presses the developer adhering to the electrostatic latent image area so that toner becomes filmy and most of the carrier other than the filmy toner is removed. Here, the air injection nozzle  16  injects air toward the squeegee roller  15 . That is, the carrier squeezed by the squeegee roller  15  flowing along a contact line between the squeegee roller  15  and the photoreceptor web  10  meets the air injected by the air injection nozzle  16  to scatter and fall downward. Here, the blade  17  maintains a state of being separated a predetermined distance from the outer circumferential surface of the squeegee roller  15 . 
     As shown in FIG. 2, after the development mode is terminated, the development roller  14  descends in the tray  12 . As the development roller  14  moves down, the packing member  24  contacting the stopper  26  relatively ascends to open a lower portion of the development tank  13 . Thus, the developer in the development tank  13  is discharged into the tray  12 . 
     However, a drip-line is generated as developer continues to remain between the photoreceptor web  10  and the squeegee roller  15 . The drip-line is generated when developer gathers at a portion where the squeegee roller  15  and the photoreceptor web  10  closely contact each other during development. To remove the drip-line developer, in a state in which the operating speed of the photoreceptor web  10  is reduced, a pressing force of the squeegee roller  15  which presses the photoreceptor web  10  is slightly reduced. Then, by driving the squeegee roller  15  to rotate in the reverse direction to the direction in which the photoreceptor web  10  travels, the drip-line developer is removed due to the rotation of the squeegee roller  15 . The removed developer flows down along the squeegee roller  15  and falls into the tray  12  by being wiped by the blade  17 . The developer falling into the tray  12  is collected on the bottom surface of the tray  12  and supplied to a circulation tank (not shown). 
     In the developer removing means of the development unit having the above structure, the squeegee blade  17  must satisfy the conditions as follows. 
     First, the developer falls downward without a hold up volume phenomenon occurring when the developer is maintained at a contact point between the leading edge of the blade and the squeegee roller, so that developer does not adhere to the surface of the blade. 
     Second, the developer must be completely removed so that the developer does not remain on the surface of the squeegee roller. 
     Third, the blade must not be flipped over to the reverse due to a rotational moment by the rotation of the squeegee roller. That is, as the blade is deformed by the friction with the squeegee roller, the leading edge of the blade must not be lifted, either partially or entirely, from the surface of the squeegee roller. 
     SUMMARY OF THE INVENTION 
     To solve the above problems, it is an objective of the present invention to provide a squeegee roller cleaning apparatus for a liquid electrophotographic printer in which the structure and shape of the blade are improved so that the efficiency in removing the developer remaining between the photoreceptor web and the squeegee roller is increased. 
     Accordingly, to achieve the above objective, there is provided a squeegee roller cleaning apparatus for a liquid electrophotographic printer, which comprises a plate installed at a tray, parallel to the axial direction of a squeegee roller, under a photoreceptor web to be capable of pivoting, a surface-contact blade member supported at the plate so as to selectively surface-contact the outer circumferential surface of the squeegee roller, an elastic spring coupled between the tray and the plate, and a means for making the plate pivot such that the surface-contact blade member can contact or be separated from the outer circumferential surface of the squeegee roller. 
     It is preferred in the present invention that the pivot means comprises a cam member installed at the tray to be capable of rotating so as to contact the plate, and a driving motor for driving the cam member. 
     Also, it is preferred in the present invention that the surface-contact blade member comprises a surface contact portion disposed to be inwardly rounded to the outer circumferential surface of the squeegee roller. 
     Also, it is preferred in the present invention that the radius of the surface-contact portion is less than that of the squeegee roller. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above objective and advantages of the present invention will become more apparent by describing in detail a preferred embodiment thereof with reference to the attached drawings in which: 
     FIG. 1 is a view showing the structure of a conventional liquid electrophotographic printer; 
     FIG. 2 is a view showing the operation of the developer removing means when the development mode is terminated, in the liquid electrophotographic printer shown in FIG. 1; 
     FIG. 3 is a view showing the operation of a developer removing means in a development mode, in a squeegee roller cleaning apparatus for a liquid electrophotographic printer according to the present invention; 
     FIG. 4 is a view showing the operation of the developer removing means when the development mode is terminated, in the squeegee roller cleaning apparatus shown in FIG. 3; and 
     FIG. 5 is a perspective view showing major parts of FIG.  4 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIGS. 3 through 5, a squeegee roller cleaning apparatus for a liquid electrophotographic printer according to the present invention includes a photoreceptor web  100  circulating by being supported by a plurality of rollers  110 , a tray  120  installed under the photoreceptor web  100  for collecting developer remaining after being used for development, a development roller  140  supported by a development frame (not shown) and moving up and down by an elevating means (not shown), a manifold  121  for injecting developer into a gap G (hereinafter, referred to as a development gap) formed between the development roller  140  and the photoreceptor web  100 , a development tank  130  for collecting and holding developer injected into the development gap G, by being supported by the manifold  121 , a development roller cleaning apparatus for removing developer adhering to the outer circumferential surface of the development roller  140 , and a developer removing means for removing developer remaining on the photoreceptor web  100  after being used for development. 
     The development roller cleaning apparatus consists of a brush roller  180  for cleaning developer adhering to the development roller  140 , by being supported by the development tank  130  and rotating in contact with the development roller  140 , and a development blade  122  having one end in contact with the outer circumference of the development roller  140  and the other end assembled to a body of the manifold  121 , for removing developer remaining between the brush roller  180  and the development roller  140  and transferred to the surface of the development roller  140 . Reference numeral  124  denotes a packing member for discharging developer in the development tank  130  into the tray  120  and reference numeral  126  denotes a stopper for limiting the movement of the packing member  124 . 
     The developer removing means consists of a squeegee roller  150  installed adjacent to the development roller  140  for pressing and removing developer adhering to the photoreceptor web  100 , and a blade assembly  170  for removing the developer flowing down along the outer circumference of the squeegee roller  150  while being in contact with the surface of the squeegee roller  150  in a drip-line removing mode. 
     The blade assembly  170  includes a plate  171  supported by the tray  120  and a surface-contact blade member  175  installed at the plate  171 . The tray  120  is fixed to the main body of the printer for collecting developer after being used for the development and supplying the developer to a circulation tank (not shown). 
     The plate  171  is installed parallel to the lengthwise direction of a rotation shaft  152  of the squeegee roller  150  (see FIG. 5) to face the squeegee roller  150 . Also, the plate  171  is installed to be capable of pivoting by a pivot means with respect to a hinge shaft  173  having both ends fixed to side surfaces  128  of the tray  120 . 
     The surface-contact blade member  175  is installed at the side surface of the plate  171  which faces the squeegee roller  150 . Also, the surface-contact blade member  175  has a surface contact portion  176  which is inwardly rounded to comform to the outer circumferential surface of the squeegee roller  150 . The surface contact portion  176  has first and second tangential portions  182  and  184  whose end portions are operative to contact the outer circumference of the squeegee roller  150 . The radius R 2  of the surface contact portion  176  is preferably smaller than the radius R of the squeegee roller  150  (see FIG.  4 ). 
     The lower portion of the plate  171  is coupled to a protrusions  129  formed at both side surfaces  128  of the tray  120  by elastic springs  177  such as compression springs. The elastic spring  177  elastically bias the surface-contact blade member  175  to be pressed against the outer circumference of the squeegee roller  150  by a restoring force thereof. 
     The pivot means includes a cam member  179  supported by both side surfaces  128  of the tray  120  and rotating to allow the plate  171  to contact or be separated from the squeegee roller  150 . The cam member  179  is driven by a driving motor  178 . 
     In the operation of the squeegee roller cleaning apparatus for a liquid electrophotographic printer according to a preferred embodiment of the present invention, referring to FIG. 3, during development, the development roller  140  supported to the development tank  130  ascends toward the photoreceptor web  100  in the tray  120  maintaining the development gap G from the photoreceptor web  100 . Then, the manifold  121  injects developer into the development gap G. The development roller  140  presses the developer to adhere to an area for an electrostatic latent image of the photoreceptor web  100 . Here, the brush roller  180  in the development tank  130  contacts the development roller  140  to clean the developer remaining on the surface thereof. The brush roller  180  rotates in a direction identical to that of the development roller  140 . The blade  122  removes developer remaining between the brush roller  180  and the development roller  140  to be transferred to the surface of the development roller  140 . The removed developer is collected in the development tank  130  and stored therein temporarily. 
     Developer adhering to the electrostatic latent image area of the photoreceptor web  100  is squeezed by being pressed by the squeegee roller  150  to make the toner filmy. Most of the carrier except for the filmy toner falls into the tray  120 . Here, the squeegee roller  150  is passively driven by the circulating photoreceptor web  100  and accordingly rotated in the same direction as the circulating direction of the photoreceptor web  100 . The liquid carrier squeezed by the squeegee roller  150  flows along the contact line between the squeegee roller  150  and the photoreceptor web  100  and is blown by air injected by the air injection nozzle  160  to fall. 
     When the cam member  179  is rotated by driving the driving motor  178 , the plate  171  pivots clockwise on the hinge shaft  173 , overcoming an elastic force of the elastic springs  177 . Then, the surface-contact blade member  175  is separated a predetermined distance from the outer circumferential surface of the squeegee roller  150 . The reason for separating the surface-contact blade member  175  from the squeegee roller  150  so as not to contact it, is to prevent lowering of the rotation speed of the squeegee roller  150  due to contact of the surface-contact blade member  175  and the squeegee roller  150  so that damage to an image formed on the electrostatic latent image area on the photoreceptor web  100  can be prevented. 
     FIG. 4 shows the operation of the developer removing means when the development mode is terminated, in the squeegee roller cleaning apparatus according to the preferred embodiment of the present invention. Referring to the drawing, the development roller  140  descends toward the bottom of the tray  120 , together with the development tank  130 . Next, the packing member  124  is moved up by the stopper  126  to open the bottom surface of the development tank  130 . Then, the developer in the development tank  130  flows down on the bottom surface of the tray  120  through an opening where the packing member  124  is disposed. As the bottom surface of the tray  120  is inclined at a predetermined angle with respect to the widthwise direction of the photoreceptor web  100 , the developer flows downward along the inclined surface and is provided to the circulation tank (not shown). 
     After development is terminated, developer remaining at a contact point A between the photoreceptor web  100  and the squeegee roller  150  remains so that a drip-line is generated. That is, part of the developer having been squeezed by the squeegee roller  150  does not fall but continues to remain at the contact point A between the side of the squeegee roller  150  and the photoreceptor web  100 . The drip-line should be removed periodically to maintain a clear image. 
     To achieve the above purpose, the squeegee roller  150  is lowered so that a rotational load applied to the photoreceptor web  100  by a pressing force by the squeegee roller  150  is reduced, and the squeegee roller  150  is reversely rotated thereafter. 
     Simultaneously, the driving motor  178  is rotated so that the cam member  179  is rotated counterclockwise. Then, the plate  171  pivots counterclockwise toward the outer circumference of the surface-contact blade member  175  by a restoring force of the elastic springs  177  so that the surface contact portion  176  of the surface-contact blade member  175  contacts the outer circumferential surface of the squeegee roller  150 . Here, the space between the outer circumferential surface of the squeegee roller  150  and the surface contact portion  176  disappears as the surface contact portion  176  completely contacts the outer circumferential surface of the squeegee roller  150  by a restoring force of the elastic springs  177 . This is because the radius R 2  of the surface contact portion  176  is formed to be relatively less than the radius R 1  of the squeegee roller  150  so that the contact surface between the first and second tangential portions  182  and  184  can firmly contact the outer circumferential surface of the squeegee roller  150  and the surface-contact blade member  175  is formed of a soft material. 
     Thereafter, developer remaining at one side of the squeegee roller  150  flows along the circumference of the squeegee roller  150  as the dotted arrow shown in FIG. 4 indicates. Developer is wiped by the surface-contact blade member  175  and prevented from being carried further along the outer circumferential surface of the squeegee roller  150 . That is, the developer is completely removed by being wiped at the first tangential portion  182  as the outer circumferential surface of the squeegee roller  150  and the surface contact portion  176  are completely in contact with each other. Accordingly, the developer flows down by being guided along a rounded portion R of the surface-contact blade member  175 . Thus, the hold up volume phenomenon of developer remaining between the outer circumference of the squeegee roller  150  and the first tangential portion  182  can be prevented. The developer falling by being blocked by the surface-contact blade member  175  is collected in the tray  120  and discharged to the circulation tank (not shown). 
     As the plate  171  biased by the elastic springs  177  pivots on the hinge shaft  173 , the first tangential portion  182  of the surface contact portion  176  is prevented from being lifted, either partially or entirely, from the surface of the squeegee roller  150  as the surface-contact blade member  175  is deformed due to the friction with the squeegee roller  150  by a rotational moment of the squeegee roller  150 . 
     As described above, the squeegee roller cleaning apparatus for a liquid electrophotographic printer according to the present invention includes a blade member which surface-contacts corresponding to the outer circumferential surface of the squeegee roller so that the generation of a hold up volume generated at the contact point between the blade member and the squeegee roller is reduced, thereby preventing the developer from adhering thereto. 
     Also, as developer does not remain on the surface of the squeegee roller, efficiency in cleaning is improved. The blade member is prevented from being turned over due to the rotational moment by the rotational driving of the squeegee roller. Consequently, efficiency in removing developer remaining between the photoreceptor web and the squeegee roller can be improved. 
     It is noted that the present invention is not limited to the preferred embodiment described above, and it is apparent that variations and modifications by those skilled in the art can be effected within the spirit and scope of the present invention defined in the appended claims.