Container for a supply of liquid developer
United States Patent [191 Schon et al.  
 [451 Apr. 8, 1975 1 1 CONTAINER FOR A SUPPLY OF LIQUID DEVELOPER [75] Inventors: Klaus Peter Schon,  
 Wiesbaden-Biebrich; I-Ielmut Stieger, Wiesbaden, both of Germany [73] Assignee: Kalle Aktiengesellschaft,  
 Wiesbaden-Biebrich, Germany [22] Filed: May 2, 1973 121] App]. No.: 356,427  
 [30] Foreign Application Priority Data May 5, 1972 Germany 2221974 [52] US. Cl. 355/10 [51] Int. Cl.... 603g 9/04; G03g 13/10; G03g 15/10 [58] Field of Search.... 118/7, 8, 602, 603, DIG. 23;  
 [56] References Cited UNITED STATES PATENTS 1,094,810 4/1914 Rauch 118/7 2,293,201 8/1942 Gaebel 118/7 X 3,369,524 2/1968 Fuhrer 355/10 UX 3.550.520 12/1970 Lucas 95/89 R 3,605,682 9/1971 Groce et al. 118/7 3,658,030 4/1972 Niedier 118/7 3,712,203 1/1973 Kishi 95/89 R Primary E.\&#39;aminerRona1d Feldbaum Attorney, Agent, or Firm-Stevens, Davis, Miller &amp; Mosher .[5 7] ABSTRACT A liquid developer container for an electrophotographic copier which has a housing impervious to liquids, a slidable wall within the housing which subdivides the housing into two chambers, means for moving the slidable wall which can be operated from the outside and on operation change the space ratio between the two chambers, connecting pipes between the two chambers, and an inlet pipe connection and an outlet pipe connection leading into one of the chambers.  
 6 Claims, 3 Drawing Figures SHEETIUEZ PixTENTi-IU PR i97 CONTAINER FOR A SUPPLY OF LIQUID DEVELOPER The present invention relates to a container for a supply of liquid developer for an electrophotographic copying apparatus.  
  It has been known for a long time that charge images may be made visible by means of liquid developers. Where such charge images are developed on re-usable photoconductor layers andthe developed images are then transferred onto paper, a developer may be employed which may be described as consisting substantially of a dispersion of tacky, colored toner particles in a carrier liquid. When using such&#39;developers, serious problems arise in the replenishing of-fthe toner used up by the copies. In order to achieve a satisfactory optical contrast, substantially larger quantities of toner are required than in other processes in which liquid developers are used. The quantity of liquid required for replenis&#39;hing may be of the order of three liters of concentrate per 10,000 copies.  
  It has already been suggested to replace consumed toner by addingthe toner in the form of&#39;a paste to the developer, but this method causes serious problems which hitherto could not be solved in an economically acceptable manner. In particular, a relatively expensive apparatus is&#39;requi&#39;red to distribute the paste&#39;in the develop&#39;er&#39;liquid.  
  It is the object of the present invention to provide a container with a replenishing device for a supply of liquid developer, which container is not too expensive technically, can be replaced relatively easily, guarantees a defined toner concentration while in use, and does not require too much space.  
  According to the present invention, this object is achievedby&#39;a container for a supply of lquid developer which is characterized by i a. a&#39;housing which is impervious to liquids,  
 b. a slidable wall within the housing which subdivides the interior of the housing into two chambers,  
 c.. means for moving the slidable wall which can be :operated from the outside,  
 d. a connecting pipe between the two chambers, and  
 e. an inlet pipe connection and an outlet pipe connection to one of the two chambers.  
  In its simplest embodiment, the connecting pipe between the two chambers consists of a bore in the slidable wall. When the slidable wall is moved, a corresponding portion of the contents of one chamber may be displaced into the other chamber in this manner. No valve is necessary for such a bore, because the bore may be made of such a size that no undesirable mixing of the contents of the two chambers takes place as long as the separating wall is not moved.  
  The ready-for-use developer described above is contained in the chamber equipped with the inlet and outlet pipe connections, and it may-be conveyed from the chamber to the developing station and back to the chamber by means of a circulating pump, for example.  
 Where the housing is of substantially cylindrical 1 shape, the slidable wall may take the form of a movable piston. In this case, the deice for moving the piston may be controlled by the number of copies produced and the piston may travel through a defined stroke for each copy.  
  At least one of the chambers, but preferably both chambers, should be equipped with stirrers which can be operated from the outside of the apparatus. In this case, the container according to thepresent invention may be constructed as a cartridge which is simply inserted into an electrophotographicapparatus, the connection to the inlet and outlet pipes and the mechanical coupling between the drive of the copying apparatus and the means for moving the slidable wall and, possibly, also the driving means for the stirrer or stirrers being made during insertion.  
  In the following, the present invention will be described in further detail by reference to the attached drawing, in which FIG. 1 is a diagrammatic representation of a container according to the present invention which, in this case, forms part of an electrophotographic copying apparatus,  
  FIG. 2 is a further embodiment of the container according to the present invention, and  
  FIG. 3 is an example of still another embodiment of a container according to the present invention.  
 In the apparatus shown in FIG. 1, the whole container is designated as 1. It comprises a housing 2 which a is subdivided into the chambers 4 and 5 by a slidable separating wall 3. Chamber 5 is filled with liquid developer which is conveyed, by means of a feed pump 7, from the chamber 5 through the pipe 6 into the developer station of the electrophotographic apparatus, designated in the FIG. as 8. After it has been used for development, the liquid developer is pumped back through the pipe 9 into the chamberS.  
  Chamber 4 contains the developer concentrate, which is 3 to 6 times more concentrated than the developer contained in chamber 5, This means that the same carrier liquids are contained&#39;in both chambers, but that the toner liquids dispersed therein differ in their concentration. A pipe 10 leads from the chamber 4 to a dispersing unit 11 which is connected over a pipe 12 with a tank 13 containing developer concentrate. This tank 13 also is connected to the developer chamber 5 by a pipe&#39;l4.  
  The slidable wall 3 which in the present invention where the housing 2 is cylindrical in shape, consists of a displaceable piston with sealings 15 and 16 may be moved to the right and to the left by a threaded rod operated by driving means 17. The driving means 17 may consist, for example, of a mechanical connection to the drive of a photoconductor drum in the electrophotographic apparatus. Alternatively, the driving means 17 may consist of a separate motor which is controlled either by the number of copies or by a measurement of the toner concentration. By the rotation of the threaded rod 18, the separating wall 3 is moved to the left. Over the dispersing unit 11, the pipe 12, the tank 13, and the pipe 14, the toner concentrate contained in chamber 4 is thereby displaced into the correspondingly enlarged chamber 5. In this manner, no dead volume of unused toner is formed in the developer chamher or in the chamber containing the toner concentrate. Because of the large quantities of liquid involved, this balance of volume is of importance for ectrophotographic apparatuses. The construction according to the a present invention provides a very satisfactory solution A further embodiment of the container according to the present invention is shown in FIG. 2. In this embodiment, a pipe 6 leads from the developer chamber to the electrophotographic apparatus 8 and a pipe 9 leads back to the developer chamber 5. The outside pipes 10, 12, and 14 shown in FIG. 1 are omitted in this embodiment, instead the developer concentrate contained in the chamber 4 is conveyed to the developer chamber 5 simply through two bores 21 and 22 provided in the slidable wall. When the wall 3 is moved downward, toner concentrate flows from the chamber containing the concentrate, i.e., chamber 4, through the bores 21 and 22 into the developer chamber 5. In this embodiment of the container, two stirrers 24 and 25 are provided which are attached to a shaft 23 and serve to mix the contents of chambers 4 and 5, respectively, in order to prevent sedimentation. Further, two guide or operating rods 26 and 27 are provided for displacing the slidable wall or piston 3.  
  Still another embodiment of the device according to the present invention is shown in FIG. 3. In this case, the chamber 4 containing the concentrate is disposed above the developer chamber 5, but in all other respects the device corresponds substantially to the device illustrated by FIG. 2. In this case, too, the piston is provided with two bores 21 and 22 through which the volumes ofchambers 4 and 5 are balanced. In this case, only one stirrer is provided which is installed in the chamber containing the concentrate. The stirrer is capable of being moved upward together with the piston 3. In the zone of the developer chamber 5, the housing 2 has a tapered wall 28. At the bottom of the wall, a pump 7 is provided which conveys the liquid developer through the pipe 6 to the electrophotographic apparatus 8. Through the pipe 9, the liquid developer flows back to the chamber 5. Besides its conveying function, the pump 7 has the function of a stirrer. The pump 7 prevents a sedimentation of the toner in exactly the position where the liquid toner would deposit, i.e., it crushes the enlarged toner drops which are being formed.  
  When measuring the toner concentrate consumed, it was found that, on an average, 0.3 ml of concentrate are spent on a copy of size DIN A 4. A cylindrical container having a circular cross-section of cm diameter and a height of 30 cm, i.e., a volume of about 10 liters, thus necessitates a movement of the piston 3 of approximately 0.01 mm for each copy. Such a movement could be easily produced with the aid of a reduction gear.  
 What is claimed is:  
  1. Container for a supply of liquid developer for an electrophotographic copying apparatus, comprising a. a housing which is impervious to liquids,  
 b. a slidable wall within the housing which subdivides the housing into two chambers,  
 c. this slidable wall consists of a piston means, which is movable by a threaded means operated by driving means from the outside,  
 d. connecting pipes between the two chambers, and  
 e. an inlet pipe connection and an outlet pipe connection leading into one of the chambers.  
  2. The container for a supply of liquid developer according to claim 1, in which the connecting pipe between the two chambers consists of a bore or several bores in the slidable wall.  
  3. The container for a supply of liquid developer according to claim 1, in which the liquid-tight housing is of substantially cylindrical shape and that the slidable wall consists of a piston which is advantageously provided with sealings.  
  4. The container for a supply of liquid developer according to claim 1, in which when the container is inserted into the copying apparatus, the means for moving the slidable wall, which can be operated from the outside, are in connection with the drive for a rotating or circulating re-usable photoconductor employed in the electrophotographic apparatus.  
  5. The container for a supply of liquid developer according to claim 1, in which the housing consists of a first section which substantially defines a first chamber and is of substantially cylindrical shape, and that the remainder of the housing has a tapered wall which at its lowest and narrowest end is provided with a pump.  
  6. The container for a supply of liquid developer according to claim 1, in which at least one of the chambers contains a stirring device which may be operated from the outside.