AU427994B2 - Tank filled with developing liquid in electrophotographic apparatus - Google Patents

Description

ABSTPACT OF THE DISCLOSURE 1 3 71 /7 A tank filled with developing liquid especially for developing electrostatic latent images. A rotatable cylinder mounted in the tank and has such a sucking action as to attract paper, foil or like material having a latent image formed thereon, whereby copies of greater and smaller sizes can be provided effectively by passing along a re- latively long path in the developing liquid. FIELD OF THE INVENTION

This invention relates to a tank filled with de- veloping liquid especially for developing electrostatic latent images. DESCRIPTION OF THE PRIOR ART The known tanks comprises a flat dish, into which paper, foil or like material having a latent image formed thereon is introduced by guide means. These tanks achieve their purposes completely, but are not adapted for use with a photocopying machine which must produce copies at a very high speed. This is because there are the following problems. On the one hand the electrostatic latent image must stay in developing liquid for a predetermined minimum length of time so as to provide a good copy, while on the other hand the copying paper having the latent image thereon must pass through the developing liquid as fast as possible. The latter requirement can be met by providing a sufficiently long path for the image-carrying paper in the liquid. However, this leads to a very large size of the tank. In addition, the long path in the liquid results in an inconvenience that transport rollers must be provided in 2 4 4

17,371/7 the liquid when a larger size of copying paper such as stand- ard format DIN A4 or a smaller size of copying paper such as format DIN AS must be developed. These transport rollers

disposed in the liquid may hamper the development of the latent image. SUMMARY OF THE INVENTION The object of the present invention is to provide a tank through which both a greater size of copy and a smaller size of copy can pass following a relatively long path and with high speed in developing liquid. Such object of the present invention can be achieved by a rotatable cylinder having a sucking action provided with- in the tank so that paper sticks to the cylinder while passing through the liquid. The cylinder is quickly rotatable and moreover, it is free of the possibilities of damaging the paper. The

cylinder directly holds not only a larger size of copying paper but also a smaller size of copying paper. After all, the diameter of the cylinder may be selected to such a level as to provide a minimum length of time for developing an electrostatic latent image at a pre- determined peripheral speed of the cylinder. The paper -voni Lenly sticks at its reverse side to the cylinder. In another arrangement according to the present in- vention, the cylinder comprises a hollow member having grooves formed circumferentially theof, and a motor-driven propeller is provided within the cylinder or at one end thereof. When one end of the cylinder is closed, the solution is continuously forced out of the cylinder into a space surrounding the. -23- 4'7 4 cyl r. cylinder. 17,3 71no The liquid then passes through openings formed in the cylinder and resumes a flow. By the process of this flow, the paper is firmly attracted to the cylinder. The propeller may be of a relatively large size so that it generates a great negative pressure within the cylinder and a great force of circulation at the same time. Such an output could not be attained, for example, by a circulating pump disposed outwardly of the tank because it requires an inlet and an outlet pipe having an excessively large cross section. This propeller also serves conveniently to form a supply means for compensating for the consumption of the developing liquid. This is because, usually in this case, concentrated developing liquid must be continuously supplied to the carrier liquid and of course the former must constantly keep well mixed with the latter.

In still another arrangement according to the pre- sent invention,.the cylinder is provided with external grooves for receiving comb teeth acting as separator means. The invention will now be described by way of ex- ample with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a sectional view of the tank for developing liquid according to the present invention. Figure 2 is a cross-sectional view taken along line II-II of Figure 1.

Figure 3 is a cross-sectional view taken along line III-III of Figure 2. DESCRIPTION OF THE PREFERRED EMBODIMENTS

A tank 1 is filled with developing liquid 2, which 4 79

17,3 71/t is supplied with carrier liquid through a pipe 3 and with concentrated developing liquid through a pipe 4, in accord- ance with the consumption of the developing liquid 2. The lid 5 of the tank 1 is formed with two openings 6 and 7. Through the opening 6, a sheet of paper 9 having an electrostatic latent image formed thereon is introduced by a pair of rollers 8. The sheet of paper 9 has the re- verse side thereof sticking to a cylinder 10 as will be described, and then passes through the developing liquid 2, where the latent image on the sheet of paper is developed. The paper leaves the developing liquid tank 1 through the opening 7 and moves to a drier or, if required, to a printer. The cylinder 10 is hollow and has an open axial end. Openings 12 are formed circumferentially of the cylinder. A propeller 13 driven from a motor 14 is provided at the open end of the cylinder 16. The propeller 13 sucks liquid out of the cylinder and forces the liquid into a space surrounding the cylinder. Thus, the liquid passes through the openings 12 and again into the interior of the cylinder. The propeller 13 generates a relatively great negative pressure within the cylinder, whereby the sheet of paper 9 has its reverse side attracted to the cylinder.. Thus, the paper can be passed through the liquid 2 relatively quickly. The cylinder is shown to be provided with grooves 16, in which comb teeth 17 are fitted so as to separate the sheet of paper from the cylinder 10 and introduce it into the opening 7 after the paper has passed through the liquid. The intense circulation of the liquid caused within the container 1 by the propeller 13 results in an

17,3 717no advantage that when supplied through the pipe 4 the concen- trated liquid is well mixed directly and immediately with the carrier liquid. The cylinder is journalled by means of bearings 20 and 21. A packing ring 22 is provided to pre- vent the outflow of the liquid. When the developing liquid tank is used with an electrophotographic apparatus utilizing the principle of electrostatic image formation, the cylinder is maintained at a constant potential or, if required, at zero potential, so that particles of developer such as toner susJ ended in the liquid may better and faster stick to the electrostat- ically charged surface area of the paper.

6- 4879,

Claims (4)

1 7 .3 71 no The claims defining the invention are as follows:- 1. A developing device comprising: a tank for

containing therein developing liquid; means for carrying in

said tank a copy sheet bearing thereon an electrostatic

latent image; a hollow cylinder, provided rotatably in said

tank so as to immerse at least a part thereof in said develop-

ing solution, having at least one hole in the peripheral

surface of said cylinder; means for discharging the developing

solution provided at one end of said cylinder for attracting

said copy sheet on the peripheral surface of said cylinder;

means for removing said copy sheet from said hollow cylinder;

and means for carrying out said copy sheet from said tank.

2. The developing device according to claim 1,

wherein said means for discharging developing liquid comprises

a propeller supported for rotation in said cylinder and

propeller drive means.

3. The developing device according to claim 1, wherein said hollow cylinder has an end wall on the opposite

end to said one end where aaid discharging means is provided.

4. The developing device according to claim 1, wherein said hollow cylinder comprises at least one peripheral

groove on the outer surface thereof and said copy sheet remov-

ing means comprises an elongate member having an end received in said groove.

The developing device according to claim 1, wherein said hollow cylinder is grounded or maintains a pre-

determined potential. DATED this FOURTH, day of SEPTEMBER, 1972 CANON KABUSHIKI KAISHA Patent Attorneys for the Applicant SPRUSON FERGUSON