Abstract:
A developing device which utilizes a development solution having toner particles actuated in the electric field generated by an electromember is provided with a cleaning unit to remove excess toner particles from the surface of the electrode member. The unit includes an air blower which directs air onto the electrode member and blows excess developing solution off the electrode.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a developing device which is employed in a wet type electrophotographic apparatus and the like, more particularly, to a developing device having a development electrode cleaning unit for cleaning the development electrode which is provided with the developing device so that an improved image is obtained through a developing operation executed by the developing device. 
     Conventionally in this type of developing device a development electrode is employed to generate an electric field to propel toner particles included in the developing solution. Without such an electrode it would take a relatively long time to develop an image on a surface of photo-conductive material on which a latent image has been formed simply by dipping the photo-conductive material in the developing solution. Further, if the development electrode is not employed, the image obtained through the developing operation is strongly affected by the so-called &#34;Edge&#34; effect. 
     Thus, the conventional developing device is provided with at least one development electrode, for generating an electric field to propel the toner particles, so as to shorten the time required for obtaining a sufficiently clear image as well as to remove the affect of the Edge effect. The developing device which is provided with a development electrode supplies the developing solution to the development electrode so as to cause the developing solution to contact with the photoconductive material. 
     However, since residual toner is gradually stuck to the surface of the development electrode with each developing operation, the intensity of the electric field generated by the development electrode is weakened. Thus, it becomes necessary to clean the surface of the development electrode. 
     The following two methods for cleaning the surface of the development electrode have been widely employed. 
     (1) Dismounting the development electrode from the developing device and wiping the residual toner stuck to the surface of the development electrode with a piece of cloth or sheet, or 
     (2) Applying a DC(Direct Current) voltage which is the same polarity as that of the toner particles to the development electrode, and simultaneously, vibrating the development electrode with an ultra-sonic wave for removing the residual toner, as disclosed in Japanese Patent Provisional Publication SHO No. 50-1745. 
     However, in the above method (1), it becomes necessary to dismount the development electrode from the developing device in order to clean it. Further, the cleaning operation is complicated and takes much time. 
     On the other hand, in the above method (2), the circuit required for oscillating the ultra-sonic wave is complicated and the total cost of the developing device increases. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the invention to provide an improved developing device utilizing a development electrode and provided with means for cleaning the development electrode to avoid the problem of residual toner sticking. 
     For this purpose, according to the invention, there is provided a developing device utilizing a developing solution including toner particles and comprising at least one development electrode member for generating an electric field to propel said toner particles, said developing device further comprising: 
     means for transporting a material on which said toner particles are to be coated, having a predetermined positional relationship with said development electrode member; and 
     means for blowing air on to a surface of said development electrode member after said material is coated with said toner particles actuated by said development electrode member. 
    
    
     DESCRIPTION OF THE ACCOMPANYING DRAWINGS 
     FIG. 1(A) is a front perspective view of the developing device according to the present invention in a development state; 
     FIG. 1(B) is a front perspective view of the developing device according to the present invention in the cleaning state in which a development electrode is cleaned; and 
     FIG. 2 is a perspective view of the developing device of FIGS. 1(A) and 1(B). 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to the drawings, one embodiment of the developing device according to the present invention is described in the followings. 
     The developing device 1 is structured as shown in FIGS. 1(A) and 1(B). A development electrode 3 is disposed in a concave shape corresponding to the circumferential surface of a drum member 2 for supporting a predetermined material 2a, for example, a photoconductive sheet, on which a desired image is to be developed to a visible image. The development electrode 3 is disposed above a developing solution tank 4 in a manner that the development electrode 3 is always kept away from the circumferential surface of the drum member 2 by a predetermined distance. The development solution tank 4 stores a developing solution 10 in which a plurality of toner particles 10a are included. The developing solution 10 in the developing solution tank 4 is supplied to the development electrode 3 through a feed pipe 5a by a feed pump 5. 
     As shown in FIGS. 1(A) and (B), a slit portion 7 which is slightly longer than the width of the development electrode 3 is disposed rearward by a predetermined distance from the rear edge of the supporting position of the material 2a on the circumferential surface of the drum member 2, and in an axial direction of the drum member 2. An air blower member 8 is provided within the drum member 2 which blows air through an air blow pipe 8a, and the air is blown out to the outside of the drum member 2 through the slit portion 7. The opening for air intake, not shown, of the air blower member 8 is disposed in a predetermined position on the surface of the drum member 2. 
     When an image on the photoconductive material 2a is developed, the material 2a is held at a predetermined position on a circumferential surface of the drum member 2, the material being rotated along with the drum member 2. As the drum member 2 is rotated, the surface of the material 2a is evenly charged by a charge unit, not shown. After that, the surface of the material 2a is exposed by an exposure unit, not shown, in accordance with an image to be developed, thereby, a latent image corresponding to the image is formed on the surface of the material 2a. After that, the material 2a is moved in close to the development electrode 3 as the drum member rotates. 
     Just before the material 2a is moved close to the development electrode 3, the feed pump 5 starts a feeding operation of the developing solution 10 in the developing solution tank 4 to the development electrode 3. Thus, the material 2a on which the latent image has been formed is dipped into the developing solution 10 fed from the developing solution tank 4, on the development electrode 3, and thereby the latent image is developed into a visible image. 
     After the trailing end of the material 2a has passed above the development electrode 3, the feed pump 5 stops its operation, and thereby the feed operation of the developing solution 10 from the developing solution tank 4 ceases. 
     However, in this state, due to surface tension of the liquid and so forth, unnecessary developing solution 10 remains on the surface of the development electrode 3. After it remains for a long time, the toner particles 10a are gradually stuck to the surface of the development electrode 3, thereby dirtying the electrode surface and degrading the quality of the image to be developed. 
     To avoid the above problem, as shown in FIG. 1(A), a slit portion 7 is provided downstream of the material 2a along a rotating direction of the drum member 2. In this structure, after the trailing end of the material 2a  has passed on the development electrode 3, the slit portion 7 approaches the development electrode 3 as the drum member 2 rotates, and the air blower member 8 starts its operation blowing out air through the slit portion 7 from the air blow pipe 8a. In this state, when the drum member 2 rotates and the slit portion 7 passes above the development electrode 3, any developing solution 10 staying on the surface of the development electrode 3 is blown off by the air from the slit portion 7, as shown in FIG. 1(B). The developing solution 10 flows down to the developing solution tank 4 from the surface of the development electrode 3 and thereby the surface of the development electrode 3 is cleaned. After the slit portion on the surface of the drum member 2 has passed above the development electrode 3 as the drum member 2 rotates, the air blower member 8 stops its operation and the cleaning operation of the development electrode 3 is completed. As described above, each time the material 2a is dipped in the developing solution 10 on the development electrode 3, the developing solution 10 remaining on the surface of the development electrode 3 is blown off thereby the surface of the development electrode 3 is always cleanly maintained. 
     As shown in FIG. 2, the side edge parts 7a, 7a of the slit portion 7 are provided at a predetermined angle for the direction along which the drum member 2 is rotated. In this structure, the developing solution 10 on the surface of the development electrode 3 is surrounded by air from the edge parts 7a, 7a of the slit portion 7 and a central part 7b, which is slightly longer than the width of the development electrode 3, disposed perpendicular to the direction along which the drum member 2 rotates. The side edge parts 7a, 7a are bent in the rotating direction of the drum member 2, and the air blown from the edge side parts 7a, 7a form a wall of air with the air blown from the central part 7b of the slit portion 7. Therefore, the developing solution 10, splashed from the surface of the development electrode 3 by the air, is surrounded by the air and it becomes possible to prevent an any unnecessary scattering of the development solution 10 from the surface of the development electrode 3. 
     The developing device according to the present invention is not limited to the above embodiment. For example, in the embodiment described above, although a photoconductive sheet is used as the material on which a latent image is formed, the material may be the usual sheet and the drum member a photoconductive drum member. In addition, it may be considered that the material is integrally provided with the supporting member, i.e., the drum member in the above embodiment. Further, although the air is blown through the slit portion from the air blower member in the above embodiment, it is also possible to structure that the slit portion is connected through an open/close valve to a compressed air source instead of the air blower member and the air is blown in accordance with an open-close operation of the valve. 
     Furthermore, with respect to a shape of the slit portion, although the central part of the slit portion is provided perpendicular to a direction of the drum member, it is also possible to structure the slit portion in a curve shape or in a &#34;V&#34; shape without a portion perpendicular to a rotating direction of the drum member. 
     In the above embodiment, the drum member is used for supporting a material on which an image is formed. However, it is also possible to employ a plate shape member for supporting the material. In addition, instead of the rotating drum member, it is possible to employ a structure in which the development electrode is moved to the member for supporting the material on which the image is formed, or both is movable with each other.