Abstract:
Apparatus for applying liquid developer to a latent image-bearing surface and, after image development has been accomplished, for blow-drying the surface. Such apparatus comprises a housing against which the support material is clamped. The housing has a chamber that is open to the support material and which may be selectively interconnected to a source of air under pressure and to a reservoir containing development liquid. When connected with the reservoir of development liquid, a flow defining surface is positioned adjacent to the image-bearing material to form a flow passage for the liquid over the material. An electric potential may be applied to the flow defining surface to provide a development electrode. After development, drying air is introduced into the chamber to remove, squeegie and carry away any fluid remaining on the surface of the support material. Means are provided to wipe the flow defining surface clean of development liquid and to remove that surface from exposure to the drying air. After drying, a member which forms a restricted-flow air passage across the support material is drawn over a surface to wipe such member clean of any extraneous developer components.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is a continuation-in-part of my earlier filed application Ser. No. 763,443, filed on Jan. 28, 1977, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to apparatus for effecting liquid development of discrete latent electrostatic or photographic images. 
     2. Description of the Prior Art 
     It is well known to apply a liquid composition to a surface of a support material for developing latent electrostatic or photographic images thereon. A single liquid, usually referred to as a monobath, can be used to develop latent photographic images, whereas a liquid developer which comprises a liquid carrier and toner particles can be used to develop latent electrostatic images. On the other hand, developer and fixer solutions, as well as water, or various processing gases can be introduced sequentially into the apparatus to develop a photographic latent image in a well known manner. 
     In various types of apparatus known in the prior art, the development liquid can be confined to only the image area of the support material. The support material is clamped in position relative to a processing or developing head to form a development cell, and a single or a number of liquids are then applied sequentially to the surface bearing the latent image. Such processing or developing of a latent image can also include in its cycle of operation, the application to the image area of air for drying the previously applied liquid, or of a liquid which will displace the processing solutions because of its repellent characteristics. Representative prior art U.S. patents of the type described include U.S. Pat. No. 2,582,182 (issued Jan. 8, 1952 to C. M. Tuttle et al), U.S. Pat. No. 3,149,550 (issued Sept. 22, 1964 to Lohse et al) and U.S. Pat. No. 3,936,854 (issued Feb. 3, 1976 to D. S. Smith). 
     According to some prior art apparatus, the development cell includes a first member having an open-end chamber that is interconnected to a reservoir for at least one developing liquid and is provided with sealing means for retaining the developing liquid in proper relation to the image area being developed. The sealing means comprises at least one peripheral member that engages the latent image-bearing surface when the support material is arranged in the developing apparatus. A second member is movable relative to the first member for clamping the image-bearing support material therebetween via the sealing means. The first member is provided with suitable ducts so the developing liquid is directed as a flow over the support material or, more specifically, over the image area and within the confines of the sealing means. After the developing liquid has been applied for developing the latent image, air under pressure can be directed into the chamber to flow over the image area and discharge through a duct or ducts. The application of air under pressure squeegies any remaining liquid off the surface of the support material and carries it away through the ducts in a mist or in a finely atomized condition. 
     In development cells used in photographic and electrographic processes for developing latent images, a problem arises with respect to residual developer compositions (e.g., toner in electrographic processes) which are retained in the cell and build up after a period of time so as to reduce efficiency of the development process. An especially critical developer build-up problem occurs on the development electrode of electrographic processors where toner build-up rapidly occurs and causes electrical field problems from the electrode to the image. As a partial solution to this situation, it has been proposed to provide cross-flow of the developer and the air used to dry the developed image. Air applied to the image surface at right angles to the flow of developer more completely removes residual toner or other residual chemicals. However efficient such cross-flow apparatus, or any other apparatus designed to remove developer from the cell, is, there will still remain some developer in the cell which will build up over a period of time. 
     It has also been recognized that a venturi-forming member in the development cell, spaced closely to the image-bearing surface so as to define a shallow air passage across the surface face, effectively aids in the drying process. Of course, any residual developer build-up on this venturi-forming member would be critical because of its close proximity to the image-bearing surface, resulting in developer and/or air flow patterns on the developed image. 
     SUMMARY OF THE INVENTION 
     By the present invention, I have provided liquid development apparatus in which the aforedescribed build-up of residual toner is minimized. In accordance with the invention, those portions of the apparatus wherein developer build-up is especially critical to operation and/or most likely to occur are wiped clean of such build-up from time to time during normal operation of the apparatus. In addition, in apparatus having distinct developing and drying periods, those portions of the apparatus which are necessarily exposed to development liquid during the development period but not during the drying period may be removed from exposure to drying air during the drying period. This reduces the build-up of dried developer compositions on the surfaces so removed. 
     The invention and its objects and advantages will become more apparent by referring to the accompanying drawings and to the ensuing detailed description of the preferred embodiments which follow. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the detailed description of the preferred embodiments of the invention presented below, reference is made to the accompanying drawings in which: 
     FIGS. 1a, 1b and 1c are vertical sectional views of a first embodiment of the present invention showing the apparatus in its &#34;material advancing&#34;, &#34;processing&#34; and &#34;drying&#34; modes, respectively; 
     FIG. 2 is a fragmented vertical sectional view of a second embodiment of the present invention showing the apparatus in its &#34;drying&#34; mode; 
     FIGS. 3a and 3b are fragmented vertical sectional views of a third embodiment of the present invention showing the apparatus in its &#34;material advancing&#34; &amp; &#34;drying modes&#34;, respectively; 
     FIG. 4 is a vertical sectional view of a fourth embodiment of the present invention showing the apparatus in its &#34;park&#34; mode; 
     FIGS. 5a, 5b and 5c are vertical sectional views of a fifth embodiment of the present invention showing the apparatus in its &#34;material advancing&#34;, &#34;processing&#34; and &#34;drying&#34; modes, respectively; 
     FIGS. 6a, 6b and 6c are vertical sectional views of a sixth embodiment of the present invention showing the apparatus in its &#34;material advancing&#34;, &#34;processing&#34; and &#34;drying&#34; modes, respectively. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present description will be directed in particular to elements forming part of, or cooperating more directly with, apparatus in accordance with the present invention. It is to be understood that elements, components and/or sub-components not specifically shown or described may take various forms well known to those skilled in the art. 
     The terms &#34;process&#34;, &#34;develop&#34;, &#34;processing&#34;, &#34;developing&#34;, etc., are to be considered synonomous as used throughout the specification and claims. Also, the term &#34;latent-image-bearing&#34;, used in reference to support or material is meant to include electrostatic as well as photographic material. 
     With particular reference to FIG. 1a, the processing apparatus, designated generally by the numeral 10, comprises a fixed housing 11 and a movable member 12, the latter being actuated into a position to clamp a sheet of latent image-bearing material 13 between housing 11 and member 12. Details of a suitable member 12 and a mechanism for moving it are disclosed in aforementioned U.S. Pat. No. 3,936,854. The disclosure of that patent is specifically incorporated herein by reference. Of course, member 12 may be fixed and housing 11 may be movable, or both may be movable. 
     Image-bearing support material 13 may (1) be a dielectric or (2) comprise a support layer 22 and a light-responsive layer 23. Layer 23 may be a photoconductive or an emulsion layer which can be exposed to provide a single or a plurality of latent images arranged successively in the longitudinal direction of a strip or in an X-Y format on a sheet. Such an exposed material can be processed in a well known manner with a liquid developer, such as toner for an electrostatic image or a monobath or a developer solution, a hypo solution, and finally washing with water for a photographic image. 
     Housing member 11 is provided with an opening 25 to a chamber 26 having entry conduits 28 and 29 and discharge conduits 30 and 31. A recess 32 surrounds opening 25 and a resilient sealing member 33 is arranged and held in the recess. Sealing member 33 can have any predetermined peripheral shape which conforms generally to that of the image area; that is, the sealing member 33 can be square, rectangular, circular or any other shape in accordance with the shape of the image area that is to be developed. Sealing member 33 comprises a mounting portion having an extension that terminates in a lip which engages the peripheral edge of the image area. The lip also serves to engage the surface of layer 23 so sealing member 33, effectively, forms with member 11, chamber 26 into which the processing liquid can be introduced in a manner to be described herein. 
     As pointed out hereinabove, the processing apparatus can be utilized for the processing or developing of either an electrostatic or photographic latent image. However, the apparatus that has been illustrated is used primarily for the development of an electrostatic image. Normally, the apparatus is associated with peripheral apparatus which provides the plurality of exposed areas on support material 13. These latent images are arranged in successive areas on a strip of material or in an X-Y direction on a sheet of material. In either case, the image area is separated from the adjacent area or areas, so as to provide a peripheral area in which the sealing means can engage the material without endangering or injuring any part of the latent image area per se. Consequently, the strip or sheet of material is positioned between member 12 and housing 11 and movable member 12 is then moved into a position in which the image area is surrounded by lip 33 and clamped to housing 11 in a sealed relationship. 
     Within chamber 26, a pair of slide valves 40 and 42 are arranged to travel vertically as shown in FIGS. 1a-1c under the control of suitable moving means, such as hydraulic cylinders 44 and 46, respectively. Slide valves 40 and 42 have respective cavities 48 and 50 to provide selective communication between conduits 28, 29, 30 and 31 and opening 25. Another opening 52 in slide valve 40 has a flexible strip of spring steel 53 secured at 53a to form a venturi passage to be explained hereinafter. Spring means (not shown) are provided to resiliently urge slide valves 40 and 42 toward conduits 28, 29 and 30. 
     OPERATION 
     Generally, when movable member 12 is withdrawn from housing member 11 (or vise versa) so that image-bearing member 13 may be moved therebetween, the movable elements within housing 11 are in a &#34;material advancing&#34; position as shown in FIG. 1a. In that configuration, developer which enters cavity 50 via conduit 29, is blocked by slide valve 42 from further travel. Looking at slide valve 40, it can be seen that air entering cavity 48 via conduit 28 flows out conduit 30 without entering chamber 26. 
     Now, after member 12 has moved to form a seal between support material 13 and sealing member 33, hydraulic cylinder 46 is activated to move slide valve 42 upwardly as viewed in FIG. 1a to the position shown in FIG. 1b, permitting the developing liquid to move from cavity 50, over the latent-image-bearing surface of layer 23 and into chamber 26. The liquid may be introduced at a controlled velocity to limit turbulence at the surface of the layer 23, rising vertically through cavity 50 and forcing ahead of it any air or other gas that might be in the cavity. As the liquid developer approaches the development zone, it moves around a flow defining surface 54 of slide valce 42, over the top of slide valve 42 and, by gravity, into discharge conduit 31. An electrical potential from a source 55 may, in the case of electrographic processing, be applied to surface 54 of slide valve 42, via conductive housing member 11, so that that surface acts in a known manner as a development electrode. After the image has been developed by the movement of the development liquid over the image-bearing surface, slide valve 42 is returned to its FIG. 1a position, thereby blocking further flow of developer into the development zone. Any developer liquid in chamber 26 may now drain from the chamber through conduit 31. Upon its return to its FIG. 1a position, development electrode surface 54 scrapes against the boundary edge of opening 25 and is thereby wiped clean of substantially all developer build-up which may have formed thereon during the development period. 
     Next, hydraulic cylinder 44 may be activated to move slide valve 40 from its FIG. 1a position to that shown in FIG. 1c, thereby permitting pressurized air, entering housing 11 through conduit 28, to flow over the image surface in a direction opposite to that of the flow of the processing liquid; namely, in a downward vertical direction. At the same time, any excess liquid that may have adhered to the image area or any of the surfaces within the member 11 will be exhausted via conduit 31. The air that is introduced via duct 28 is preferably warmed in order to provide a maximum drying effect. It can be seen that while drying air is flowing through chamber 26, development electrode surface 54 is in contact with an inner wall of housing 11 so that any liquid developer which might not have been wiped from the electrode surface is not exposed to the drying air. Accordingly, the amount of developer caking on the electrode is substantially reduced. 
     As slide valve 40 moves to its FIG. 1c position, venturi-forming member 53 moves into opening 25 to reduce the free space within opening 25. Venturi-forming member 53 serves to further define the flow path for drying air now passing from conduit 28, through cavity 48, around venturi 53 and back out conduit 30. 
     When slide valve 40 moves from its FIG. 1a position to its FIG. 1c &#34;drying&#34; position, there may be some residual amount of liquid developer in chamber 26. This residual developer will form a thin coating on venturi-forming member 53 and will be hardened by the drying air. After repeated cycles of the apparatus, enough developer components will likely have been deposited on the venturi-forming member to at least partially obstruct the passage of drying air. 
     In order to minimize such build-up, by the present invention, venturi-forming member 53 wipes against an edge 56 of housing member 11 each time slide valve 40 moves from its FIG. 1c position to its FIG. 1a position. 
     Other Embodiments 
     FIG. 2 is a fragmented view of another embodiment of the present invention showing the apparatus in its &#34;drying&#34; mode. Apparatus not shown may take the form shown in FIG. 1c. In fact many parts shown are the same as in FIG. 1c and have been identified by the same reference numerals. 
     Actually the difference between the FIG. 2 embodiment and that of FIG. 1c is in the manner that the venturi is formed. Slide valve 60 is provided with a rigid venturi-forming member 62 pivoted at 64 and urged in a clockwise direction as shown by a leaf spring 66. Operation of the apparatus as shown in FIG. 2 is substantially the same as in FIGS. 1a-1c. Note that corner 56a of housing 11 will wipe along venturi-forming member 62 as slide valve 60 moves upwardly. Member 60 has been called a slide valve in this embodiment for consistency. However, it will be noted that when it is in its upper position, air entering through conduit 28 will not be valved off, but will instead flow past the venturi-forming member into chamber 26 to exhaust out the top of that chamber. 
     Yet another form of the present invention is shown in FIGS. 3a and 3b wherein a venturi is formed of a surface of slide valve 70 rather than with a separate member movably mounted in the slide valve. A wall 72 of housing 11 is inclined so that when slide valve 70 moves from its FIG. 3a position to its &#34;drying&#34;, FIG. 3b position, edge 74 restricts the air flow in the manner of a venturi. As the slide valve returns to its FIG. 3a position, its lower surface 76 is wiped by edge 56a in the manner of the previous embodiments. 
     It is not necessary to valve off the developer inlet during drying, and in the embodiment shown in FIG. 4, I have provided a bypass cavity 80 in the wall of housing 11 to permit developer to be circulated continuously around slide valve 42, through conduit 31 and back to the reservoir when slide valve 42 is in the position shown. 
     Still another embodiment of my invention is shown in FIGS. 5a, 5b and 5c, wherein a single slide valve 86 having three stop positions is shown. In the position shown in FIG. 5a development liquid at conduit 29 enters chamber 88 and is blocked from further movement. Drying air entering conduit 28 passes through chamber 90 and is exhausted through conduit 30. For development, slide valve 86 moves to the position shown in FIG. 5b, and for drying, the slide valve moves from the FIG. 5a position to that shown in FIG. 5c. 
     In some instances, it may not be desirable to return development liquid removed from the chamber directly to the supply sump. For instance, developer which was in the chamber and exposed to drying air is more likely to have clumps or other impurities therein which might cause clogging problems. Therefore, I have provided means, shown in FIGS. 6a, 6b and 6c for separating, from the reusable development liquid, development liquid removed from the chamber during the drying cycle. The latter may be discarded or filtered and reused. 
     As in the FIGS. 5a-5c embodiment, the FIGS. 6a-6c embodiment includes but a single slide valve 96. In brief, when the slide valve is in its FIG. 6a position, drying air entering through conduit 28 passes through chamber 97 and exits through conduit 30, while development liquid cannot pass beyond chamber 98. In its &#34;developing&#34; mode, slide valve 96 has moved upwardly so that liquid entering through conduit 29, passes through chamber 98, over the image-bearing surface, through a passage 100 and back to the sump through another conduit 102. 
     When slide valve 96 moves downwardly to its FIG. 6c, &#34;drying&#34; mode, conduit 29 is again blocked and chamber 97 communicates drying air inlet conduit 28 with the image-bearing surface. Now, as mentioned above, it is desirable that any development liquid remaining in the housing member be removed to a separate receptacle for either discarding or further processing before being returned to the sump. A conduit 104 receives such liquid. 
     The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.