US3442254A - Electrostatic developer - Google Patents

Description

May 6, 1969 HBDEO AKIYYAMA ET AL 3,442,254

ELECTROSTATIC DEVELOPER Filed Aug. 28, 1967 Sheet of 2 NVENTORS 6 worse AKIYAMA MAURICE H. ARTAUD HIDEO AKIYAMA ET AL 3,442,254

ELECTROSTATIC DEVELOPER May 6, 1969 Filed Aug. 28, 1967 Sheet '2 of 2 FIG. 3

INVENTORS HIDEO AKIYAMA MAURICE H. ARTAUD 3,442,254 ELECTROSTATlC DEVELOPER llidco Alriyama, Los Angeles, and Maurice H. Artaud, Torrance, Calih, assignors to The National Cash Register Company, Dayton, Ohio, a corporation of Maryland Filed Aug. 28, 1967, Ser. No. 663,681 lint. Cl. BtlSh /02; 623d 5/08 U.S. Cl. 118-637 An electrostatic developing unit having a perforate guide member for receiving a substrate on which there is formed discriminate areas of electrostatic charge. A spray nozzle is positioned to direct a spray of an electrostatic developing solution pumped from a supply tank onto the guide member to pass through the perforations therein until intercepted by the substrate. The electrostaticallycharged pigment contained in the solution is attracted to the discriminately-charged areas of the substrate. The remainder of the solution flows off the substrates and through the perforated guide member to be funneled back into the supply reservoir. The developed substrate is passed from the unit through a drying station for driving off any remaining solvent. The supply tank is preferably comprised of the bottles used for storing and shipping the developing solution, which bottles can be rapidly interchanged to provide fresh solution to the unit HISTORY OF INVENTION This invention relates to an electrostatic developer unit useful for developing a latent image formed by the discriminate application of an electrostatic charge on a sub strate surface.

Very briefly, the most common use for electrostatic developing units such as contemplated by the present invention is in photocopy printing. A paper substrate provided with a sensitized coating is passed through an electrostatic discharge unit, tag, a corona charging unit, where the entire coating is electrosatically charged. The coating of the paper substrate is then exposed to an imagebearing light beam wherein the light is blocked out of the image portions. In the areas of the coating exposed to light, i.e., the brackground areas, the electrostatic charge is neutralized. Thus, when the substrate is passed through the developing unit, the oppositely-charged pig ment particles of the developing solution are attracted only to the image areas.

Although the photocopy printing process has been the subject of many developments, there are still problem areas where improvement is needed. Developing techniques used in many of the printing processes involve the application of the developing dyes from a liquid solution where a drying step is required. Because drying causes undersirable time delays, it is important to minimize the degree of wetting of the substrate. Also, during the developing process it is important to maintain consistency of contrast between the dark image areas and light baclo ground areas.

An example of a prior art apparatus for providing a development process for photocopy printing is disclosed in Ostensen U.S. Patent No. 3,249,088, entitled Developing Tank Unit For Electrostatic Printing." The Ostensen device provides a concave lower guide member in which a circulating pool of the developing solution is formed. The guide member directs the substrate through the pool and the pigment is attracted to the charged areas as described above.

3,442,254 Patented May 6, 1969 in the Ostensen process, because the substrate which is generally comprised of a paper sheet with a sensitized coating is immersed in the liquid solution, significant wetting occurs which requires considerable drying.

Handling of equipment wherein such developing apparatus is contained is also a problem. The solution must be periodically replaced or fortified which necessitates the pouring of the liquid from a storage container into the supply tank of the apparatus. The process is cumbersome and inconvenient with spillage occurring frequently.

It is thus an object of the present invention to provide a developing apparatus that will reduce the extent of wetting of the substrate to shorten the drying period, and to provide means to facilitate more convenient handling.

In general, the preferred apparatus of the present invention comprises a perforated guide member that directs the paper substrate past a spray nozzle. The developing solution is pumped through an outlet tube connected to a supply bottle and through the spray nozzle which directs a spray of the solution onto the image-bearing surface of the paper substrate. The spray runs off of the paper substrate and through the perforated guide member into a funnel. The tunnel directs the solution through a return tube that is fastened to the supply bottle. When the solution needs to be changed, the tubes are merely disconnccted from the bottle and connected to a fresh bottle. Whereas only one side of the paper substrate is wetted with the solution, the drying period is substantially shortened.

The above advantages, as well as other advantages of the invention, will become more apparent by reference to the following detailed description and drawings wherein: v

FIG. 1 is a schematic view illustrating a micro-image viewing and printing apparatus incorporating the present invention;

FIG. 2 is an enlarged perspective view with parts broken away showing an electrostatic developing unit generally shown in FIG. 1:

FIG. 3 is a cross-sectional view of the electrostatic developing unit of FIG. 2; and

FIG. 4 is a partial view of the electrostatic developing unit showing an alternate form of the guide means.

A micro-image viewing and printing apparatus that utilizes the present invention is schematically illustrated in FIG. 1. A transparency 10 containing the micro-images is sandwiched between two glass plates 12. A light source 14 projects a light beam l t through a condensing lens 116 which directs the beam through the micro-image and into a projection lens 13. The image-bearing beam 14' is then reflected off a first mirror 20 toward a second mirror 22 which reflects the beam onto a rear viewing screen 23. The process and apparatus as generally described are similar to the process and apparatus specifically disclosed in the commonly assigned U.S. application, Scr. No. 554,001, filed in the names of Akiyama and Slockwell on May 31, 1966, entitled "Micro-Image Display Apparatus."

in the present system, a third mirror 21 is mounted for pivotal movement by a motor 25 to intercept and shift the beam away from the first mirror 20 and onto a fourth mirror 24. The fourth mirror 24 is positioned to reflect the beam toward a fifth mirror 26 which reflects the beam onto an exposure plane defined by an endless belt 28. A solenoid actuated shutter 31 is positioned with respect to the projection lens 18 to block the light beam 14' to permit exposure at the exposure plane only on command and for a specified time period.

A guideway 30 comprising a feed hopper 32, channel members 3d, and feed rollers 36 is adapted for moving a specially treated paper substrate through an electrostatic charging unit 38. The charging unit 38 produces an electrostatic charge on the paper substrate and the paper substrate is then directed by guide member 40 onto the endless belt 28. A suitable paper substrate for the above process is disclosed in Greig US. Patents Nos. 3,052,539 and 3,052,540, and a suitable electrostatic charging unit is disclosed in Giaimo, Jr., US. Patent No. 2,922,883.

The endless belt 28 is adapted to receive the electrostatically-charged paper substrate and to move the paper into position for exposure by the image-bearing light beam 14'. The paper substrate is held onto the endless belt 28, as for example, by providing vent openings 29 in the belt with suction means (not shown) for drawing the paper substrate tightly against the endless belt. An appropriate timing mechanism provides for the proper positioning of the paper substrate before the solenoid actuated shutter 31 exposes the paper substrate for the desired period of time. Various timing mechanisms are available for accomplishing the above which are well known to the art and, accordingly, they are not disclosed herein.

Upon exposure, the endless belt 28 moves the paper substrate through guide 42 into engagement with ingress rollers 44. The paper substrate is directed through an electrostatic developing unit 46 (to be described in detail in a later section) and egress rollers 48 receive the paper substrate with the developed image thereon and direct it through guide 50 into a receiving tray 52.

DEVELOPING UNIT Referring to FIGS. 1 and 2, an electrostatic developing solution 53 such as LX27-89A available from Philip A. Hunt Corporation is contained within the bottle 54, which may be the bottle in which the solution is contained when received from the supplier. A dip tube 56 is inserted through a cap 58 into the solution contained in the bottle. A pump 60 is connected to the dip tube 56 and is adapted to draw solution through the dip tube 56 and pump it through a hose 62 to a spray nozzle 64.

Referring to FIGS. 2 and 3, an upper guide member 66 and a lower guide member 68 cooperate to form a concave pathway for the paper substrate from the ingress rollers 44 to the egress rollers 48, e.g., see FIG. 2 where a paper substrate 70 is shown being passed through the pathway provided by the upper and lower guide members.

Said upper end and lower guide members 66 and 68 are sufiiciently perforated whereby the flow of solution from the spray nozzle 64 can pass freely through the guide members during the periods when there is 'no paper substrate between them. For example, the guide members may be constructed from a continuous screen sheet. The guide members and spray nozzle are mounted in a housing 72 that forms an enclosure for the developing process. The bottom wall 74 of the housing 72 is formed into a funnel whereby with the center recessed, as shown, the solution is caused to flow toward a central outlet 76. A return hose 78 carries the solution (by gravitational flow) back to the supply bottle 54.

It will be seen that with the pump 60 shut off, the solution will drain into the bottle 54 to permit handling of the apparatus with little chance for the solution to spill out.

OPERATION In the operation of the equipment described above, an operator visually identifies the dcsircd micro-image to be copied by properly positioning the micro-image-bearing transparency so that the desired micro-image is visible on the screen 23 (see FIG. 1). Mirror 21 is then pivoted over the projection lens 18 and solenoid actuated shutter 31 is closed to block the light beam 14. A paper substrate 70 is then placed on the feed hopper 32 and manually moved into contact with the first of feed rollers 36. The paper substrate 70 is then moved by the succeeding feed rollers 36 through the guideway 30 formed by the channel members 34 into the electrostatic charging unit 38. The entire surface of one side of the paper substrate '70 is electrostatically charged therein. The movement of the paper substrate 70 is continued around the guide member 40 and onto the endless belt 28.

. Gripping means, as for example vacuum drawing means located behind the endless belt, grips and holds the paper substrate 70 to the endless belt 28. The movement of the belt is controlled so as to move the paper into position for the desired exposure. The solenoid actuated shutter 31 is then opened to permit the imagebearing light beam to be directed onto fourth mirror 24 to be reflected from fifth mirror 26 onto the electrostatically-charged surface of the paper substrate 70. Light neutralizes the electrostatic charge so that the only areas of the surface that remain charged are the areas corresponding to the image (i.e., those areas where the light of the light beam have been shielded by the image contained on the transparency 10).

After the proper period of exposure, the solenoid actuated shutter 31 is closed and the endless belt 28 moves the paper substrate 70 through guide 42 into engagement with ingress rollers 44. The paper is then moved by ingress rollers 44 into the concave pathway formed by upper and lower guide members 66 and 68 (see FIGS. 2 and 3). As the paper is passed under the spray nozzle 64, the paper substrate intercepts the flow of the solution from the nozzle and forms a shallow pool of the solution'on the surface of the paper substrate. Buildup of the pool is avoided by reason of the solution flowing to the edges and spilling oil the paper substrate to continue on through the lower guide member 68 as indicated by "arrows 53 in FIG. 2. Thus, the solution does not subment particles contained in the solution having an opposite charge to the charge on the paper substrate are attracted to the image areas of the paper substrate to produce a visable image. The paper substrate is moved by the ingress rollers 44 into engagement with egress rollers 48 to be directed through guideway 50 into the receiving tray 52.

It will be understood that the apparatus as described above is merely an example of the invcnainon and is not intended in any way to restrict the scope of the invention. For example, the apparatus may be modified whereby instead of forming a substantially concave pathway for the paper substrate to travel through the developing unit, the upper and lower guide members 66 and 68 may be formed into a straight or almost straight pathway as illustrated in FIG. 4. It will be understood that a very shallow pool of the solution will be formed on the surface of the paper in this alternate embodiment of the invention by reason of the surface tension embodied in the solution. Also, rather than forming upper and lower guides 66 and 68 from a continuous screen sheet, one or both may be provided, for example, by a plurality of individual rods, formed and assembled to provide the desired guideway for the paper substrate while permitting free llow of the developing solution lhcrclhrough.

What isclaimed is:

1. An electrostatic developing unit comprising a perforated concave guide means for guiding a flexible substrate with a curvature through the developing unit, one surface of said substrated having discriminate areas that are electorstatically charged, and means for directing a spray of a developing solution downwardly onto the concave guide means, said perforated concave guide means being comprised of mating upper and lower guide members adapted to permit free passage of the developing solution therethrough and being further adapted to guide the substrate under the spray of developing solution to form thereon at the bottom of the curvature a shallow, continuously circulated pool of the solution.

2. An electrostatic developing unit as defined in claim 11 wherein the perforated concave guide means is comprised of upper and lower cylindrically concave screen sheeting.

3. An electrostatic developing unit for producing a visible image on a paper substrate surface by the depositing of electrostatically-charged pigment particles from a developing solution onto oppositely charged image areas of the paper substrate surface comprising, a housing, a spray nozzle positioned over an opening in the top of the housing adapted to spray developing solution into the opening, a guideway for the paper substrate mounted to the housing and spanning across the opening, said guideway being comprised of mating upper and lower guide members perforated to permit the developing solution from the spray nozzle to pass freely into the housing, and said guideway adapted to guide an electrostaticallycharged paper substrate under the spray nozzle vto intercept the flow of developing solution to form a shallow pool of the solution on the top surface of the paper substrate while the under surface remains relatively dry, to thereby provide for the depositing of pigment contained in the solution onto the charged image areas of the substrate surface, a reservoir for containing a quantity of the developing solution, pumping means for pumping solution from the reservoir to the spray nozzle, and return means for directing the solution sprayed into the housing back to the reservoir.

4. An electrostatic developing unit as defined in claim 3 wherein the mated upper and lower perforated guideway members are cylindrically concave whereby a shallow pool of the developing solution formed on the paper substrate at the bottom of the curvature formed by the concave guideway is caused to flow over the surface of the paper substrate as the paper substrate is guided through the guideway.

5. An electrostatic developing unit as defined in claim 4- wherein each of the upper and lower guide members is comprised of a continuous screen sheet.

6. An electrostatic developing unit as defined in claim 4 wherein the concave guideway is comprised of cooperating concave formed rods.

References Cited UNITED STATES PATENTS 3,124,484 3/1964 Magnusson 118637 3,137,225 6/1964 Cuthbert -89 3,139,808 7/ 1964 Ritzerfeld et a1 95-89 3,155,546 11/1964 Dirks 118637 3,202,526 8/1965 Ostensen 1l737 3,242,902 3/1966 Ulary 118637 3,359,945 12/1967 Hasting et a1. 118637 PETER FELDMAN, Primary Examiner.

U.S. Cl. X.R.

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