US3435803A - Lifting apparatus - Google Patents

Description

April 1, 1969 J DONALIES 3,435,803

LIFTING APPARATUS Filed Dec. 27, 1965 Sheet of 2 I NVENTOR. DANIEL J. DONALIES ATTORNEYS April 1969 D. J. DONALIES 3,435,803

LIFTING APPARATUS Filed Dec. 27, 1965 Sheet 2 of 2 IN V ENTOR. DANIEL J. DONAL IES ATTORNEYS United States Patent 3,435,803 MFTKNG APPARATUS Daniel I. Donaiies, Rochester, N.Y., assignor to Xerox Corporation, Rochester, N.Y., a corporation of New York Filed Dec. 27, 1965, Ser. No. 516,528 Int. Cl. 1305b /02; G035; /08

US. Cl. 118-637 9 Claims ABSTRACT OF THE DHSCLOSURE This invention relates to transport mechanisms and particularly to apparatus for elevating granular material from a reservoir of such material.

More specifically, the invention relates to apparatus suitable for use in transporting xerographic developer material from a sum or reservoir of developer material to a position to be cascaded over the surface of a xerographic drum.

In the process of xerography, a xerographic plate comprising a layer of photoconductive insulating material on a. conductive backing is given a uniform electrostatic charge over its surface and then, by conventional projection techniques, is exposed to the subject matter to be reproduced. Such an exposure discharges the plate areas in accordance with the light intensity that reaches the plate and thereby creates an electrostatic latent image on or in the photoconductive layer. The latent electrostatic image can be developed by almost any material which is brought into contact with the photoconductive layer and is held thereon electrostatically in a pattern corresponding to the electrostatic latent image. This developed image is usually thereafter transferred to a support surface to which it may be fixed by an suitable means.

A variety of materials may be employed for developing the electrostatic images. However, it has been found preferable to develop line-copy images with a two-component type developing material such as that disclosed in Walkup Patent No. 2,618,551, issued Nov. 18, 1952, which may include a powder or toner of any of a variety of pigmented resins which have been developed for this purpose and a granular carrier material, such as glass, encased in a suitable covering such as, for example, a polymer capable of establishing a desired triboelectric relationship with the toner.

Generally, the latent electrostatic image in the xerographic process is developed into a powder image by cascading the developing material over the surface of the xerographic plate containing the latent electrostatic image. In the two-component developer, the carrier beads and toner powder are mixed together and agitated so that the triboelectric charge is formed on the carrier beads and toner particles to attract them to each other. This combination of carrier beads and toner is referred to herein as developer. The developer material is then elevated to a position where it may be allowed to freely fall or cascade over the surface of the xerographic plate.

In automatic xerographic machines, the xerographic plate is usually in the form of a cylindrical drum, and

Patented Apr. 1, 1969 the developer material is allowed to cascade over a portion of the surface of the drum as the drum rotates. While in moving contact with the surface of the xerographic plate, the developer material deposits the toner on the drum because the electrostatic charge on the plate is greater than the triboelectric charge holding the toner on the carrier beads. The powder remains on the areas of the plate that have the electrostatic charge in image configuration, and the carrier falls from the plate surface and is remixed with the toner and recirculated. Cascade development has been one of the most effective forms of developing systems used in the xerographic process and produces excellent powdered images and has been commercially successful.

In the past, in many of the automatic xerographic machines, the developer has been cascaded over the drum by using a conveyor belt system. Continuous belts are used to transport rectangular buckets which carry the developer from a reservoir to a hopper and dump the contents of each bucket into the hopper. The developer, then, through the force of gravity, cascades down from the hopper and over the xerographic drum, contacting the electrostatic latent image thereon as the developer moves over the drum to form the powdered image by depositing toner on the charged areas.

This conveyor belt device though effective is cumbersome and comprises many elements and parts including a pulley system, continuous conveyor belt, and a miditude of trays. The trays must, of course, be spaced in such a manner as to provide a continuous flow of developer to the hopper so that a continuous flow of developer may be cascaded over the drum containing the electrostatic latent image. A typical prior art device is shown in Lehmann Patent No. 3,105,770, issued Apr. 15, 1960. Since the system must be as wide as the developing drum and must provide enough space for clearance of the belt and trays as they pass the hopper, it is bulky and 0ccupies a large amount of space in an automatic xerographic machine.

It has been found, too, that toner mixing is a problem with the conveyor belt system. In the automatic xerographic machines, toner is added to the carrier beads periodically and uniformly across the entire developer sump to maintain high contrast in developed images. If there is more copyable material forming latent xerographic images on one portion of the drum, toner from the de veloper in the sump supplying that portion of the drum will be depleted more quickly than toner in other portions causing an imbalance of toner across the sump. Further, as the toner is added across the sump, parts of the developer will have more toner than others; and later copies will vary in contrast (intensity of toner applied) across their surface. The conveyor system provides for no side mixing of the two-component developer to avoid the above problem even through side mixing is necessary to maintain toner consistency across the sump. This invention, however, mixes the two-component developer as it brings it to be cascaded over the drum, thereby maintaining consistency.

Triboelectric attraction holds the toner carrier bead in the two-component developer. This attraction is caused and maintained by charges on the particles. This apparatus insures a high triboelectric attraction between the carrier bead and toner powder because friction from the churning and scooping action of this device charges the particles.

The present invention is a practical improvement over the conveyor belt system for delivering developer to the drum containing an electrostatic latent image in a xerographic system in that it is a single piece, therefore requring less maintenance than in the prior art continuous belt and trays arrangement. The device, furthermore, could take up considerably less space than the conveyor belt system and yet function at least as effectively.

This apparatus could be operated at higher speeds than the conveyor system without excessive loss due to spilling and useless throwing of transported material as would tend to occur at higher speeds with the conveyor belt and trays system. As the buckets hit the developer at high speeds, there would be losses due to splashing and throwing of developer. This invention, therefore, provides a needed improvement as a simple one-piece apparatus for carrying the developer in a xerographic development machine to a position where it can be easily cascaded over the electrostatic latent image on the xerographic drum. This invention can also be used to cascade liquids or any solid or liquid developer over the xerographic drum at a variety of speeds and while occupying less space than was previously required to bring the developer material from the reservoir to a position where it could be cascaded over a latent image on the drum.

The functioning of an auger is dependent on the rotation of the screw device which pushes material along its axis. This transport mechanism depends on centrifugal force. As the device is rotated, a force pushes any material located therein and in mechanical contact therewith to the walls of the housing. Such material is held there by friction or slats extending out from the walls. These slats may be parallel to the center axis of the lifting housing or they may be inclined along the wall. Their function is to prevent the material from avoiding the centrifugal force generated on any material in intimate contact with the rotating apparatus. The centrifugal force cooperating with any friction along the sides of the rotating housing hold the material inside against the wall of such housing. If the housing is generally conical in shape, a component of the centrifugal force acts in a direction along the wall of the conical housing forcing any materials held thereon by friction or slats or otherwise up along the walls of the housing. Any conical shaped housing would function with greater or lesser efficiency depending upon the change in radius thereof along its length, as well as the rotational speed thereof. The greater the angle of the housing with a plane perpendicular to the center axis, the greater the efficiency of the device for carrying material up and over the housing wall. The greater the rotational speed of the apparatus, the greater the efficiency of moving the material therein up and over the housing wall.

In several embodiments shown hereinafter, there are slats in the housing that are not inclined along the entire inner surface thereof and are not used as an anger but function merely to cause the material to enter the housing, as well as in the case of two-component developer in xerographic apparatus, to mix the developer and to supply friction which is necessary for the triboelectric forces to cause the two components to cling to each other as described earlier herein.

It is, therefore, an object of this invention to elevate material from a sump of such material.

It is an object of this invention to improve the xerographic development systems by providing continuous availability of developer to a position where it can be cascaded over the surface of a xerographic drum containing an electrostatic latent image.

A further object of this invention is to reduce the size of xerographic development systems. Yet another object of this invention is to provide a simple one-piece device for delivering two-component developer material to a position for the cascading over a xerographic drum.

Still another object is to provide for improved machine concepts allowing for the production of more efficient and more compact xerographic machines than have been known previously in the art.

These and other objects of this invention are obtained by a generally conical shaped housing partially submerged .4 in a material sump and rotated to cause the material to be forced to the walls of said housing to be drawn by a component of centrifugal force up along the sides of said housing and over the top thereof.

For a better understanding of the invention as well as other objects and further features thereof, reference is had to the following detailed descriptions of the invention to be read in connection with the accompanying drawings, wherein:

FIG. 1 schematically illustrates an embodiment of a xerographic apparatus adapted to continuous and automatic operation, incorporating an optical scanning mechanism and a developer lifting apparatus with a hood.

FIG. 2 illustrates schematically an embodiment of a lifting apparatus incorporating a hopper device.

FIG. 3 is an isometric view of an embodiment of a lifting apparatus with internal structure shown.

FIG. 4 is a partial perspective view of the top of a lifting apparatus with a retrieving hood with portions broken away to show internal structure.

FIG. 5 is another isometric view of an embodiment of a lifting apparatus with internal structure shown.

Referring now to the drawings wherein like numerals designate like parts, there is shown schematically in FIG. 1 a transport mechanism adapted to elevate developer in a xerographic apparatus incorporated into an automatic machine.

The xerographic apparatus comprises a xerographic plate including a photoconductive layer or light-receiving surface on a conductive backing and formed in the shape of a drum, generally designated by numeral 2. The drum is mounted on a shaft journaled in a frame to rotate in the direction indicated by the arrow to cause the drum surface sequentially to pass a plurality of xerographic processing stations.

For the purpose of the present disclosure, the several xerographic processing stations in the path of movement of the drum surface may be described functionally, as follows:

A charging station, preferably located as indicated by reference character A, at which a uniform electrostatic charge is deposited on the photoconductive layer of the xerographic drum. This is generally accomplished by a corona charging device.

Next subsequent thereto in the path of motion of the xerographic drum in exposure station B at which a light for radiation pattern of copy 8 to be reproduced is projected onto the drum surface to dissipate the drum charge in the exposed areas thereof. Thereby a latent electrostatic image of the copy to be reproduced is formed.

Adjacent to the exposure station is a developing station C in which there is positioned a developer apparatus including a container 26 having a lower sump portion for accumulating developing material 12. A conical conveyor 14 having a suitable driving means 16 carries the developing material to a hood 18 where it is cascaded down over, and onto the xerographic drum. Slats 22 in said conical housing cause the developer material to enter said housing. The slats 22 extend below and along the entire length of the housing wall 14 and are at all points parallel to the central axis of the housing wall 14. The hood extends across the length of the drum at the position where the developer begins its cascade.

As the developing material is cascaded over the xerographic drum, toner particles are pulled away from the carrier component of the developing material and deposited on the drum for forming powder images, while the partially denuded carrier particles pass off the drum into the developer container sump. As toner powder images are formed, additional toner particles must be supplied to the developing material in proportion to the amount of toner deposited on the drum. For this purpose, a toner dispenser generally designated 20 is used to replenish toner to the developing material.

Positioned next and adjacent to the developing station is the image transfer station -D at which the xerographic powder image is electrostatically transferred from the drum surface to a transfer material or support surface. This is here accomplished by the corona transfer device 34.

Immediately subsequent to transfer is a stripping device, generally designated 36, for removing the transfer material from the drum surface. After stripping, the powder image may be fused to the transfer material by the fuser 42 and then transported by conveyor 38 to a copy holder 45.

The final station E is a drum cleaning and discharge station at which the drum surface is brushed to remove residual toner particles remaining after image transfer, and at which the drum surface is exposed to a relatively bright light source to effect substantially complete discharge of any residual electrostatic charge remaining thereon.

The remaining drawings and disclosure relate more specifically to improvements in elevating technique afforded by this invention. FIG. 2 schematically shows this invention incorporated in a xerographic apparatus comprising a xerographic plate including a photoconductor plate 48 or light-receiving surface on a conductive backing 50 and formed in the shape of a drum, generally designated by 2, which is mounted on a shaft to rotate in the direction indicated by the arrow to cause the drum surface sequentially to pass a plurality of xerographic processing stations as was more fully enumerated above.

At the developing station, a xerographic developing material 13 is cascaded over the drum surface, whereby toner particles adhere to the electrostatic latent image to form a xerographic powder image in the configuration of the copy to be reproduced.

There is a reservoir or sump 12 of developer material, generally a two-component developer composed of carrier beads and toner; a toner dispenser, generally designated by 20, mounted on container 26; and a developer transport mechanism including an inverted, truncated conical shaped housing 14 with slats 28 extending into the developer reservoir formed by containing 26. A motor 16 is mechanically connected to said conical housing to give it a rotational motion in the direction indicated by the arrow whereby such motion causes the developer from reservoir 12 to move up the walls of the housing 14 and be dispersed into the hopper 19 wherein some is trapped and guided to a position to be cascaded along the photoconductive layer of the drum whereby the toner will form a powder image corresponding to the latent electrostatic image on the photoconductive layer and the excess toner will be dropped back into the reservoir 12. The connection of the motor to the housing in this embodiment is through a center shaft 24, extending through the developer container on which the motor is mounted. The entire developer system is enclosed by container 26.

Referring now to FIG. 3, there is shown an embodiment of the conical lifting device in isometric view with the outer cone surface broken away. This embodiment shows slats of ribs 32 connected to the conical housing 14 and climbing the entire housing at an incline while extending below the housing ir order to scoop and agitate the developer. The opposite sides of the slats are connected to a center shaft 24 which can be connected to a motor means (not shown) in order to rotate the transport mechanism in a manner necesary to cause material therein to move up the wall of the cone to be distributed over the top to a hood or hopper (not shown). Such motion is indicated by the arrow.

Referring now to FIG. 4, which shows the lifting apparatus as embodied in FIG. 1, in conjunction with a hood 18 whereby the hood encompasses an upper portion of the cone housing, the botom of the hood is so formed as to surround but not contact the outer wall of the conical housing 14. Where the housing extends through the hood,

there is a lip or collar 17 on the hood. This prevents any material dispersed from the lifting device from falling through the separation between the housing and the lower hood. The lip runs cooperatively substantially parallel to the cone from the lower plate of the hood upward. The motion of the conical apparatus as indicated by the arrow causes material to be carried up along the sides of the housing to be distributed over the top and into the hood where it is guided by the slope of the lower portion and the sides thereof to a position where it may be put to effective use.

In an embodiment of the device without a hood, such as that shown in FIG. 2, material elevated by the rotational motion of the transport mechanism falls against the sides of the container 26 and is thereby deflected either to the reservoir 12 below or to a hopper 19 extended below the top of the conical housing and included down therefrom toward, for example, a xerographic drum such that developer falling on the hopper will be guided by the hopper to a position above the drum from which it can be cascaded over the drum in the same manner and operation as the device operating with a hood. The hopper extends across the length of the drum to ensure complete and uniform cascade development.

FIG. 5 shows a housing with tapered walls 15, the lower portion of which has a more rapidly increasing distance from the center axis per unit of length of such axis than the upper portion, thus forming a cuplike shape. This housing shape allows for a better, more efficient use of centrifugal force generated by the rotation of such housing around its center shaft 24 by any suitable means (not shown). When the bottom portions of the housing are submerged in a sump of material to be lifted by the housing, the frictional forces and the force of gravity are more easily overcome by the centrifugal force generated through the rotation of the housing since it is easier to cause the material to be thrust to the outer walls than it is to lift the material along such walls. Once momentum is imparted to the material in the sump and contained in the inner, lower portions of the housing, it is somewhat easier to lift the material along the walls since inertia has been overcome. At any given speed of rotation, the centrifugal force is greater as the radius of the system is increased.

The slats 30 function in the same manner as they did in the previously described embodiment; that is, they agitate the material to be lifted, they cause more material to enter the housing, and they assist in maintaining the necessary contact between the material and the rotating housing in order that the centrifugal forces and components thereof may act on the material to cause it to rise up the inner wall of the housing to be dispersed over the top thereof in the same manner as previously described.

It is understood and expressly stated that this device is not limited to use with a two-component xerographic developer system but functions equally as well with a granular material or a liquid. The lifting device would properly function with or without a hood and can be activated by any means for supplying rotation to it. While the invention has been described with reference to the structures disclosed herein, it is not confined to the details set forth; and this application is intended to cover such modifications or changes as may come within the purposes of the improvement or the scope of the following claims.

What is claimed is:

1. In a system for developing latent xerographic images on a continuously moving sensitized plate where a granular developer material is continually transported from a sump to be cascaded in a substantially uniform quantity over the latent xerographic image, the improvement for accomplishing such transport comprising a container capable of holding a quantity of granular developer material and having an opening adapted to receive a xerographic plate,

a housing having tapered outer walls increasing in distance from its center axis from its lower portion to its upper portion,

means to cause the granular developer in said container to enter said housing and remain in mechanical con tact therewith,

means to rotate said housing whereby such rotation causes the granular developer material within said housing to be thrust against the wall thereof by centrifugal force and climb the wall of said housing, and

guide means positioned above said housing and adapted to catch and guide said granular developer forced over the top of said housing for cascading over the latent xerographic image on a sensitized plate.

2. The apparatus of claim 1 wherein said means to cause the granular developer to enter said housing from said sump comprises slats inclined along the entire wall of and extending below said housing.

3. The apparatus of claim 1 wherein said hood comprises an upper plate covering the top of said conical housing, a lower inclined plate extending below the top of, and surrounding, said housing in close spaced relation and inclined downward toward the sensitized plate containing the latent xerographic image, a sealing wall between said upper and lower plates having an opening adapted to receive said sensitized plate whereby developer thrown from said housing is trapped in said hood and guided to said plate.

4. The apparatus as in claim 3, wherein said lower inclined plate contains a lip in intimate contact therewith at every portion where said lower plate surrounds said housing in close spaced relation, said lip being in a cooperatively parallel relation to said housing.

5. The apparatus of claim 1 wherein said housing is cuplike in shape so that the reaction due to centrifugal force at the housing walls on the material within the housing in a direction along the walls is greater in the lower portion of the housing than the upper portion.

6. The apparatus of claim 1, said housing having conical outer walls.

7. The apparatus of claim 1 wherein said guide means includes a hood positioned above said housing and adapted to catch and guide said granular developer forced over the top of said housing.

8. The apparatus of claim 1 wherein the lower portion of said housing diverges from the center thereof more rapidly per unit length of housing than the upper portions thereof.

9. The apparatus of claim 1 wherein said housing is cup-like in shape.

References Cited UNITED STATES PATENTS 843,275 2/1907 Huntley 103-99 913,179 2/ 1909 Wemette 103-99 1,020,382 3/ 1912 Alpha 103-91 1,238,139 8/1917 Hayes 103-99 2,671,405 3/ 1954 Stoors 103-99 3,075,459 1/1963 Hoelzer et a1 103-99 X 3,158,509 11/1964 Hudson 118-637 3,253,821 5/1966 Jamison 103-100 XR 3,334,613 8/1967 Young 118-633 3,369,524 2/ 1968 Fuhrer 118-637 PETER FELDMAN, Primary Examiner.

Us. 01. X.R.

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