US3190264A - Xerographic developing apparatus - Google Patents

Description

June 22, 1965 R. A. HUNT XEROGRAPHIC DEVELOPING APPARATUS Original Filed Nov. 28, 1958 I 2 Sheets-Sheet l FIG. 1

INVENTOR. ROBERT A. HUNT ATTORNEY R. A. HUNT XEROGRAPHIC DEVELOPING APPARATUS Criginal Filed Nov. 28, 1958 June 22, 1965 2 Shets-Sheet 2 OWN INVENTOR. ROBERT A. HUNT ATTORNEY United States Patent 3,190,264 XERtBGRAPHiC DEVELQPHNG APPARATUS Robert A. Hunt, Wiihrahnm, Mass, assignor to Xerox gor poration, Rochester, N. a corporation of New @riginai application Nov. 28, 1953, Ser. No. 776,348. Divided and this application Dec. 14, 1961, ar. No. 159,26d

ll Claim. (Cl. 118-637) This invention relates to improvements in automatic xer-ographic reproduction systems and, particularly, to i1nprovements in systems of this type to facilitate the making of reproductions from microfilm. More specifially, this invention relates to a xer-ographic developing system and is a division of application Serial No. 776,848,

filed November '28, 195 8, in the name of Robert A. Hunt,

now abandoned.

in the process of xerography, for example, as disclosed in Carlson Patent 2,297,691, issued October 6, 1942, a xerographic plate comprising a layer of photoconductive insulating material on a conductive backing is given a uniform electric charge over its surface and is then exposed to the subject matter to be reproduced, usually by conventional projection techniques. This exposure discharges the plate areas in accordance with the light intensity that reaches them, and thereby creates an electrostatic latent image on or in the photoconductive layer. Development of the latent image is effected with an electrostatically charged, finely divided material, such as an electroscopic powder, which is brought into surface contact with the photoconductive layer and is held the-reon electrostaticaliy in a xerographic powder image pattern corresponding to the electrostatic latent image. Thereafter, the developed xcrographic powder image is usually transferred to a support surface to which it may be fixed by any suitable means.

Since the disclosure in Carlson, many improvements have been made in xerographic devices and techniques, within the scope of the basic Carlson invention. As a result, both manual and automatic machines for carrying out xerognaphic reproduction processes are in wide commercial use. The present invention constitutes a further improvement in automatic xerographic processing systems whereby such systems may more readily be ernplayed in integrated data processing systems, particularly those known as unitized data processing systems.

The principal object of the invention is to improve xcrographic developing systems to effect more uniform and consistent development of electrostatic latent images on a xerographic plate.

This and other objects of the invention are attained by means of an improved cascade developing system to form a xerographic powder image of the latent image produced on a xerogr aphic drum.

A preferred form of the invention is shown in the accompanying drawings in which:

l is a perspective view of an automatic xerographic processing system embodying the invention; and

1 16. 2 is a schematic sectional view of the apparatus of the invention.

In the particular embodiment shown in the drawings, the invention is incorporated in a xerographic machine that is a fully automatic, continuous printer for reproducing information contained on microfilm cards. This equipment reproduces copy on a continuous roll of paper, that may have a web width up to 24", from either positive or negative film, in either of two magnification ratios: x or X; whereby microfilm images of different sizes may conveniently be enlarged to the full with of the web. Referring to FIG. 1, the system may be considered to include four distinct sections for housing 3,190,264 Patented June 22, 1965 the several elements thereof, namely, a base section 1, for housing the xerographic drum, the web tensioning and feeding apparatus, as well as the devices for effecting the xerographic functions of plate charging, image transfer, brush cleaning, etc; an upper section 2, for housing the card handling apparatus as well as the bulk of the optical system; an end section 3, secured to the left end of the base section, for housing the xerographic developing apparatus; and a control section 4, mounted on the base section and forward of the upper section, for housing certain of the electrical equipment required in the system and to provide a control panel whereon the operator may set selected ones of a plurality of switches for selecting the desired type of operation.

Base section 1 includes tWo side frames that are connected across their tops by a plate 5, whereby the entire system is supported. Suitable cover plates are included to enclose the mechanism and access doors are provided on the front of the machine to facilitate repair and adjustment. Upper section 2 includes suitable cover plates for enclosing the bulk of the card handling apparatus and the optical system, as well as a card magazine 7 for holding microfilm cards from which reproductions are to be made, and a receiving magazine 8 to which cards are ejected after the microfilm image thereon is reproduced. Also included, is a lever 9 whereby the optical system may be set selectively for 15 or 20X magnification ratio. In addition, a handwheel is provided whereby the position of the card magazine may be altered relative to the optical system, in accordance with the longitudinal dimension of the image on the microfilm card. End section 3 is enclosed by a dusttight housing and is pivotally mounted on the base section by suitable hinges 11, whereby the entire end section of the machine may be swung outwardly to permit access to the several elements of the developing system, and to permit convenient access to the surface of the xerographic drum for the purpose of cleaning. The entire structure is specifically arranged to form a light-tight enclosure in the areas of the optical projection system and the xerographic developing system.

GENERAL DESCRIPTION OF SYSTEM (FIG. 2)

Ifor a general understanding of the xerographic processlng system in which the invention is incorporated, reference is had to FIG. 2 in which the various system components are schematically illustrated. As in all xerographic systems based on the concept disclosed in the above-cited Carlson patent, a light image of copy to be reproduced is projected onto the sensitized surface of a xerographic plate to form an electrostatic latent image thereon. Thereafter, the latent image is developed with an oppositely charged developing material to form a xerographic powder image, corresponding to the latent image, on the plate surface. The powder image is then electrostatically transferred to a support surface to which it may be fused by any suitable form of fusing device, whereby the powder image is caused permanently to adhere to the support surface.

In the system disclosed herein, microfilm cards are placed in a card magazine 7 from which they are fed seriatim to a card carriage of a card handling apparatus, generally designated by reference character 15, arranged to the rear of the card magazine assembly. Suitable driving means are provided for the car-d carriage whereby it is caused to move the card past the optical axis of a projection lens system 16 that is illuminated by a projection lamp LMP-3 for the purpose of scanning the microfilm The microfilm card image is projected downwardly through an adjustable objective lens assembly 17 and then reflected upwardly by an adjustable mirr-or element 2h to either of two transverse mirror assemblies 21 or 22, in order to vary the length of the optical path, depending on the magnification ratio employed. From mirror assemblies 21 or 22., the light image is projected downwardly through a variable slit aperture assembly 23 and onto the surface of a Xerographic plate in the form of a drum 24.

Xerographic drum 24 includes a cylindrical member mounted in suitable bearings in the frame of the machine and is driven in a counterclockwise direction by a motor M-Z at a constant rate that is proportional to the scan rate of the microfilm card, whereby the peripheral rate of the drum surface is identical to the rate of movement of the reflected light image. The drum surface comprises a layer of photoconductive material on a conductive baching that is sensitized prior to exposure by means of a screened corona generating device 25, which may be of the type disclosed in Walkup Patent 2,777,957, that is energized from a suitable high potential source.

The exposure of the drum to the light image discharges the photoconductive layer in the areas struck by light, whereby there remains on the drum a latent electrostatic image in image configuration corresponding to the light image projected from the microfilm card. As the drum surface continues its movement, the electrostatic latent image passes through a developing station 26 in which a two-component developing material, which may be of the type disclosed in Walkup Patent 2,638,416, is cascaded over the drum surface.

After developing, the xerographic powder image passes a discharge station 27 at which the drum surface is illuminated by a lamp LMP2, whereby residual charges on the non-image areas of the drum surface are completely discharged. Thereafter, the powder image passes through. an image transfer station 28 at which the powder image is electrostatically transferred to a support surface web 29 by means of a second corona generating device 36 similar to corona charging device 25, mentioned above.

The support surface to which the powder image is transferred may be of any convenient type and is obtained from a supply roll 31 and is fed over suitable guide and tensioning rolls and directed into surface contact with the drum in the immediate vicinity of transfer corona generating device 36. After transfer, the support surface is separated from the drum surface and guided through a suitable heat fusing apparatus 32, whereby the powder image is permanently afiixed to the support surface. Thereafter, the support surface is fed over a further system of guide and tensioning rolls and onto a take-up roll 33 that is driven by motor M3.

After transfer, the Xerographic drum surface passes through a cleaning station 34 at which its surface is brushed by a cleaning brush assembly 35, rotated by a motor M-4, whereby any residual developing material remaining on the drum is removed. Thereafter, the drum surface passes through a second discharge station 36 at which it is illuminated by a fluorescent lamp LMP-l, whereby the drum surface in this region is completely flooded with light to remove any electrostatic charge that may remain thereon. Suitable light traps are provided in the system to prevent any light rays from reaching the drum surface, other than the projected microfilm image, during the period of drum travel immediately prior to sensitization by corona generating device 25 until after the drum surface is completely passed through the developing station 26.

DEVELOPING SYSTEM (FIG. 2

In order to effect development of the electrostatic latent image formed on the Xerographic drum, the invention includes an improved developing system that is particularly adapted to effect uniform and consistent development,

regardless of drum width, and is specially suited to effect development on the 24" wide drum employed on the Xerographic reproduction apparatus disclosed herein. in addition, the developing system is structurally arranged to facilitate maintenance thereof and to permit ready access to the xerographic drum for periodic cleaning.

As mentioned above, the entire developing system is contained in end section 3 of the apparatus that is formed of a plurality of sheet metal plates that are integrally connected to provide a completely dust-tight housing and are arranged to be mounted on hinges fixed on base section 1 so that the entire developing system may be swung outwardly from the machine to afford access thereto and to the Xerographic drum.

In prior Xerographic processing devices, it was customary to provide a developing system having a vertical conveyor apparatus to transport developing material from a collecting point to a system of chutes whereby the material could be directed into contact with the Xerographic drum. in such devices the vertical conveyor usually included relatively narrow conveyor buckets which necessitated lifting the developing material to a substantial height and then distributing it through an elaborate chute system in order to effect proper developing material distribution on the drum surface. in the present invention the vertical conveyor system includes relatively wide buckets that are arranged parallel to the Xerographic drum axis and have a transverse length approximately equal to three-quarters of the width of the drum surface.

in the specific arrangement wn, conveyor system includes a plurality of transverse buckets 2.46 that are horizontally supported between two endless belts 247 on opposite sides of the developer system housing and extend over pulleys 248 and 249 that are fixed respectively on transverse shafts 25% and 251. For actuating the conveyor system, upper shaft 25% is driven through a belt 252 by a motor M-5 that rotates constantly while the machine is in operation.

The developing material conveyed upwardly by the conveyor system is discharged onto an inclined plate 253 that extends transversely across the entire developing system structure, and extends downwardly to a point at which it forms a transverse slit orifice in conjunction with a sheet metal plate 254 of the developer system housing. The slotforrned by plates 253 and 254 is of sufficient width to pert. i; an adequate flow of developing material into contact with the Xerographic drum surface, but is suiiiciently narrow to impede the progress of the developing material and cause it to back up on plate 253 to form a substantial reserve of developing material while the machine is in operation. Thus, since rate of developer flow is a function of slot width rather than head of material, a uniform flow of developing material is maintained at all times. For convenience of maintenance, an access door 255 is hinged in an aperture in plate and, together with plate 253, forms a substantia ly continuous surface for transporting developing material.

To minimize undesired bouncing of the developing material within the system, a curved baffle plate 256 is 60 secured along the lower edge of plate 253 and extends transversely across the machine in spaced relation to the Xerographic drum. The spacing is such as to permit complete freedom of movement of the developing material between the plate and the Xerographic drum, and the outward curve of plate is effective to guide substantially all of the developing material downwardly onto an inclined transverse plate 257, whereby the developing material is guided into a collecting bin 25% formed by the cover plates of the apparatus wherein it may conveniently 70 be scooped by conveyor buckets 246.

In order to limit the amount of developing material in collecting bin 258, the apparatus includes a catch baffle plate 259 that extends transversely across the entire developing system housing and has its lower edge spaced 5 from the surface of plate 257 to control the flow of developing material into the collecting bin. By this arrangement the amount of developing material in bin 258 cannot exceed the height of the lower edge of battle 259. Developing material in excess of this level backs up on the incline of plate 257 and is contained by the vertical face of baffle plate 259 to replace the developing material removed from bin 258 by buckets 246. In etfect, plates 257, 259 and the adjoining side plates for the developer system form a discharge bin for the developing material as it is continuously cascaded over the drum surface. By this means it is possible to keep a substantially constant supply of developing material in the collecting bin and to maintain a substantially constant load on the conveyor system.

In order to replenish the developing material with toner particles as these are expended in the formation of xerographic powder images, the apparatus includes a toner dispensing mechanism 260 that is disclosed in detail and claimed in my copending application Serial No. 776,976, filed November 28, 1958, now Patent No. 3,013,703. Toner dispenser 260 is supported on a suitable bracket 261 in the developing system housing, and is driven from shaft 250 via belt 262, pulley assembly 263 and belt 264.

In operation, the toner dispenser functions to sift toner material onto the developing material that has cascaded over the xerographic drum surface. In order to ensure uniform distribution of new toner, the toner dispenser extends horizontally substantially across the drum surface and functions to distribute a uniform flow of toner particles throughout its entire width, in accordance with the dispensing rate required.

To ensure adequate mixing of the toner particles with the developing material, at least a portion of them are caused to deposit on curved bafile plate 256. To cause these particles to be mixed with the remaining developing material, a narrow slot 255a is formed in access door 255 on guide plate 253 whereby a portion of the material supported by plate 253 is caused to pass through the slot and over the surface of plate 256 thereby flushing the toner particles into the developing material supply at the bottom of the housing.

What is claimed is:

In an xerographic developing system for cascading developing material onto the surface of a xerographic plate, the combination of a collecting bin for containing developing material,

a conveyor for elevating developing material from the collecting bin,

an inclined chute arranged to receive the material from the conveyor and to transport the material to the surface of the xerographic plate,

said chute having a slot formed thereon through which portions of the material fall,

a discharge bin arranged below the xerographic plate for receiving the material as it is cascaded over the xerographic plate,

said collecting bin and said discharge bin being arranged to eflfect gravity feed of the developing material from the discharge bin to the collecting bin,

said discharge bin including a baflle means positioned between the same and the collecting bin for limiting the quantity of developing material fed from the discharge bin to the collecting bin,

a xerographic toner dispenser positioned above said collecting bin and in discharging relationship thereto for dispensing toner therein, and

a deflecting plate arranged between said chute and said collecting bin and below the slot formed therein for receiving said portions of developing material as they fall through said slot, said deflecting plate extending into the path of dispensing toner and being adapted to direct said portions into contact with the toner being dispensed into said collecting bin whereby the dispensed toner becomes mixed with some of the material.

References Cited by the Examiner UNITED STATES PATENTS 1,696,171 12/28 Lipsius 118--312 XR 2,173,032 9/39 Wintermute 118-312 XR 2,395,903 3/46 Nordquist 118-249 XR 2,633,780 4/53 Watson 118-349 XR 2,810,364 10/57 McArthur et al. 118301 2,990,278 6/61 Carlson 117--17.5 XR 3,011,474 12/61 Ulrich 11717.5 XR 3,013,342 12/61 Huber et al. 118-637 XR 3,043,685 7/62 Rosenthal 117-17.5 XR 3,045,587 7/62 Schwertz 117-175 XR 3,053,962 9/62 Cerasani et al 117--17.5 XR

WILLIAM D. MARTIN, Primary Examiner. RICHARD D. NEVIUS, Examiner,

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