US3149760A - Powder dispensing apparatus - Google Patents

Description

p 22, 1964 R. H. EICHORN ETA]. 3,149,760

POWDER DISPENSING APPARATUS 2 Sheets-Sheet 1 Filed Dec. 23, 1960 MN s m E M ii:..=.::===:: H M eulfig m Q/ 5& w Q m ATTORM EY United States Patent 3,149,760 POWDER DISPENSING APl ARATUS Roger H. Eichorn, Webster, and William G. Lewis, Rochester, N.Y., assignors to Xerox (iorporation, a eorpora= tion of New York Filed Dec. 23, 1960, er. No. 77,955 1 Claim. (Cl. 222-438) This invention relates to improvements in apparatus for dispensing powder or granulated material and, particularly, to improvements in xerographic toner dispensing apparatus.

More specifically, the invention relates to an improved toner dispenser that is particularly adapted for use in a xerographic developing apparatus wherein, in order to develop the electrostatic latent image formed on a xerographic plate, it is required to dust the image with a developer powder, whereby the powder particles are selectively attracted to the charged areas of the plate to form a visible powder particle image of the electrostatic latent image.

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 in tensity which reaches them and thereby creates an electrostatic latent image on or in the plate coating.

Development of the image is effected with developers which comprise, in general, a mixture of a suitable pigmented or dyed electrostatic powder, hereinafter referred to as toner, and a granular carrier material, which latter functions to carry and to generate triboelectric charges on the toner. More exactly, the function of the granular material is to provide the mechanical control to the powder, or to carry the powder to an image surface and, simultaneously, to provide almost complete homogeneity of charge polarity. In the development of the image, the toner powder is brought into surface contact with the coating and is held thereon. electrostatiealiy in a pattern corresponding to the electrostatic latent image. Thereafter, the developed xerographic image is usually transferred to a support material to which it may he fixed by any suitable means.

In the mixture of toner particles and carrier material, 7 V

the toner particles, which are many times smaller than the carrier particles, adhere to, and coat the surface of the carrier particles due to the electrostatic attraction between them. During development, as the powder coated carrier particles roll or tumble over the xerographic plate carrying an electrostatic image of opposite polarity to the charge on the toner, toner particles are pulled away from the carrier by the charged image and deposited on the plate to form a powder image, while the partially denuded carrier particles pass off the plate. As toner powder images are formed, additional toner particles must be supplied to the developer mixture in proportion to the amount of toner deposited on the plate.

It prints, made by the xerographic process, have heavy deposits of toner in image areas of good contrast and non-image areas have a gray veiling, the toner concentration in the developer mixture is too great. If the prints have low contrast images, the quantity of toner par ticlesinthe developer mixture is insufiicient.

In order to continually obtain prints of good quality, the quantity of toner powder in the developer mixture must be held reasonably constant by the addition of toner to the developer mixture in proportion to the amount of toner deposited on the plate.

It is therefore an object of this invention to provide an improved apparatus for dispensing power or granulated material.

Another object of this invention is to provide an improved toner dispenser Whereby accurately metered amounts of toner are added to the developer mixture in a xerographic machine in proportion to the amount of toner used by the machine to make xerographic copy.

A further object of the invention is to provide a toner dispenser which will accurately dispense a given amount of toner powder.

The present invention contemplates an improvement in dispensing devices wherein an automatic metering arrangement is provided to control the rate of discharge from the dispenser.

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

FIG. 1 illustrates schematically a preferred embodiment of a xerographic apparatus adapted for continuous and automatic operation, and incorporating a toner dispenser in accordance with the invention;

FIG. 2 is a top view of a preferred embodiment of the toner dispenser of the invention;

FIG. 3 is an end view of the toner dispenser;

FIG. 4 is a sectional view of the toner dispenser takeri along line 44 of FIG. 2; and

FIG. 5 is an enlarged sectional view illustrating a toner outlet of the toner dispenser.

General As shown, the xerographic apparatus comprises a xerographic plate including a photoconductive layer or lightreceiving surface on a conductive backing and formed in the shape of a drum, generally designated by numeral 26, which is 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 xer-ographic processing stations in the path of movement of the drum surface may be described functionally as follows:

A charging station, at which a uniform electrostatic charge is deposited on the photoconductive layer of the xerographic drum;

An exposure station, at which a light or radiation pattern of copy .to' be reproduced is projected onto the drum image are cascaded over the drug surface, whereby the toner particles adhere to the electrostatic latent image to form a xerographic powder image in the configuration of the copy to be reproduced; Y v

'A transfer station, at which the Xerographic powder image is electrostatically transferred from the drum sur-' face to a transfer material or support surface; and;

A drum cleaning and discharge station, at which the drum surface is first charged and then brushed to remove residual toner particles remaining thereon 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 charging station is preferably located as indicated by reference character A in the schematic illustration of the apparatus. In general, the charging apparatus or corona charging device 21 includes a corona discharge array of one or more dischargeelectrodes that extend transversely across the drum surface and are energized from a high potential source and are substantially enclosed within a shielding member.

Next subsequent thereto in'the path of motion of the xerographic drum is an exposure station E. This exposure station may be one of a number of types of mechanisms or members such as desirably an optical scanning or projection system or the like designed to project a line copy image onto the surface oft he photoconductive xerographic drum from a suitable original.

The optical scanning or projection assembly consists of a copyboard in the shape of a drum, hereinafter referred to as copy drum 22, which is adapted to support copy to be reproduced and arranged to rotate in lightprojection relation to the moving light-receiving surface of the xerographic plate. Uniform lighting is provided by suitable lamps attached to a slotted light reflector 23 mounted adjacent to the copy drum.

A light shield 24 adapted to protect the xerographic plate from extraneous light is positioned adjacent to the surface of the xerographic plate. A slot aperture 26 in the light shield extends transversely to the path of movement of the light-receiving surface of the xerographic drum 26 to permit reflected rays from the copy drum to be directed against a limited transverse area of the light-receiving surface as it passes therebeneath.

To enable the optical system to be enclosed within a relatively small cabinet, a folded optical system including an object mirror 26, a lens 27, and an image mirror 28 is used in the preferred embodiment of the apparatus.

Copy fed through paper guides 31 to the copy drum is removably secured thereon by a suitable gripper mechanism for movement therewith in timed relation to the movement of the xerographic drum whereby a flowing image of the copy is projected onto the xerographic drum. The copy is held against the surface of the copy drum by means of guides 32 and 33, the latter also preventing the trailing edge of the copy from contacting the web cleaner 54. After the copy is scanned it can be released from the copy drum to be transported out of the machine by copy feed out roller 34 coacting with the peripheral surface of the copy drum to forwarc the copy through copy guide 30.

Adjacent to the exposure station is a developing station C in which there is positioned a developer apparatus 35 including a developer housing having a lower or sump portion for accumulating developer material as. Mounted within the developer housing is a motor driven buckettype conveyor used to carry the developer material previously supplied to the developer housing to the upper portion of the developer housing from where the developer material is cascaded over a hopper chute onto the drum.

As the developer material cascades over the drum, toner particles of the developer material adhere electrostatically to the previously formed electrostatic latent image areas onthe drum to form a visible xerographic powder image;-the remaining developer material falling off the peripheral surface of the drum into the bottom of the developer housing. Toner particles consumed during the developing operation to form the xerographic powder images/are replenished by a toner dispenser 37 mounted within the developer housing.

raaveo Positioned next adjacent to the developing station is the image transfer station D which includes suitable sheet feeding mechanism adapted to feed sheets of paper successively to the xerographic drum in coordination with the presentation of the developed image on the drum at the transfer station. The sheet feeding mechanism includes a sheet source such as a tray 41 for a plurality of sheets of a suitable support material, that is, sheets of paper or the like, a separating roller 42 adapted to feed the top sheet of the stack of support material to a sheet conveyor mechanism 43 having paper grippers 44 there on which carry the sheet support material into contact with the rotating xerographic drum in coordination with the appearance of a developed image at the transfer station.

The transfer of the xerographic powder image from the drum surface to the support material is effected by means of a corona transfer device 45 that is located at or immediately after the point of contact between the support material and the rotating xerographic drum. The corona transfer device 45 is substantially similar to the corona discharge device that is employed at the charging station in that it also includes an array of one or more corona discharge electrodes that are energized from a suitable high potential source and extend transversely across the drum surface and are substantially enclosed with a shielding member. In operation, the electrostatic field created by the corona transfer device is effective to tack the transfer material electrostatically to the drum surface and simultaneously with the tacking action, the electrostatic field is effective to attract the toner particles comprising the xerographic powder image from the drum surface and cause them to adhere electrostatically to the surface of the support material.

As the paper gripper mechanism continues to move forward in its closed circuit, it will strip the support material from the xerographic drum and carry it to a fixing device, such as, for example, heat fuser 46, whereat the developed and transferred xerographic powder image on the support material is permanently fixed thereto.

After fusing, the finished copy is preferably discharged from the apparatus at a suitable point for collection externally of the apparatus. To accomplish this there is provided a pair of delivery rolls 47 and 48 by means of which the copy is delivered to a copy holder after it is released by the gripper mechanism. Suitable cam means are provided at the receiving and delivery stations of the conveyor mechanism to actuate the paper gripper at these stations to receive or discharge a sheet of support material.

The next and final station in the device is a drum cleaning station E whereat any powder remaining on the xerographic drum after the transfer step is removed and whereat the xerographic drum is flooded with light to cause dissipation of any residual electrical charge re maining on the xerographic drum.

To aid in the removal of any residual powder remaining on the xerographic drum there is provided a corona precleaning device 51 that is substantially similar to the corona discharge device that is employed at charging station A. Removal of residual powder from the xerographic drum is effected by means of a web cleaner device 54 adapted to continuously feed a clean fibrous web material into wiping contact with the xerographic drum. As shown, the web material 55 is taken from a supply roll 56 and transported around a cleaning roll 57, preferably made of rubber, around a guide plate 58 to be wound on a take-up or rewind roll 61.

Any residual electrical charge remaining on the xerographic drum is dissipated by light from a fluorescent lamp 62, mounted in a suitable bracket above the xerographic drum, a suitable starter being provided for energizing the fluorescent lamp.

Suitable drive means drive the xerographic drum, the copy drum, and the sheet conveyor mechanism at predetermined speeds relative to each other, and to efiect operation of the paper separator roll, and the web cleaner mechanism, the latter being driven at a speed whereby relative movement between the xerographic drum and the web material is effected. Suitable drive means are also provided for effecting operation of the conveyor mechanism and toner dispenser of the developing apparatus assembly.

It is believed that the foregoing description is sufficient for the purposes of this application to show the general operation of a xerographic reproducing apparatus. For further details concerning the specific construction of the xerographic apparatus shown, reference is made to copending application, Serial No. 77,954, filed concurrently herewith on December 23, 1960, in the name of Eichorn et a1.

Toner Dispenser As the developing mixture is cascaded over the xerographic drum, toner particles are electrostatically pulled away from the carrier component of the developer material and deposited on the drum to form xerographic powder images, while the partially denuded carrier particles pass off the drum into the reservoir. As toner powder images are formed, additional toner particles must be supplied to the developing mixture in proportion to the amount of toner deposited on the drum. To supply additional toner particles to the developer mixture, a toner dispenser is used to accurately meter toner to the developer mixture and is mounted in the developer housing through a suitable opening formed in the top, back portion of the outer shell.

Referring now in particular to FIGS. 2 to 5, inclusive, which illustrate a preferred embodiment of the toner dispenser 37, the toner dispenser of the invention includes a container for toner formed as a box having a top plate 241 to which is secured as by spot welding, two depending end plates 242 having a lower convex shaped portion, and cut-out portions centrally located therein, a depending left-hand bearing plate 243 and an enclosure or base plate 244 formed to match the contour ofthe end plates. The container is closed at one end by dust cap 245 and at its other end by right-hand bearing plate 246 and the elements attached thereto as described in greater detail hereinafter.

The container is supported by means of the top plate 241 adapted to rest on the top portion of the outer shell of the developer housing, with a suitable gasket or seal 247 sandwiched therebetween, the container being held in position by screws 232 passing through the top plates and threaded into the outer shell of the developer housing.

The top plate is provided with an inlet opening 248 through which toner may be deposited within the con tainer, the inlet opening being closable by means of cover 251 pivotally secured by hinge 252 to the top plate, the hinge being secured at one end to the cover plate and at its other end to the top plate. 253 encircles the outer edges of the cover in position to contact the top plate, so that, when the cover is closed the gasket is pressed against the top plate by means of the spring clips 227 pivotally secured to the outer shell of the developer housing.

A gasket 6 266 on shaft 256. Axial alignment of the beater shaft is maintained at one end by hearing housing cover 271 mounted on the bearing housing 264A secured to the right-hand bearing plate, and at its other end by screw 272 threaded through dust cap 245 and secured by lock nut 273.

The bearing housings 258, 258A, 264 and 264A inserted through apertures formed in the bearing plates, are secured to their respective bearing plates as by peening over the edges of the bearing housing. Dust seals 267 and 265 encircle shafts 256 and 261, respectively, within the bearing housings to protect the bearings mounted therein from the toner particles.

The brush 255 is positioned so that as it is rotated the bristles of the brush contact the lower curved portion of the container to brush toner particles toward the apertures 254 to fall therethrough.

This size of the apertures are chosen to accommodate freely the particle size of toner or other granular material to be dispensed. However, an interesting characteristic of these minute powder particles is that under certain conditions they will agglomerate or pack together so tightly that they literally become a solid mass. This condition probably occurs when there is substantially no aeriform fluid surrounding the powder particles, a condition which will occur when there is sufficient powder in a pile to force the aeriform fluid out of the bottom layer of the powder particles in the pile. The agglomera tion of the powder particles may also be effected as a result of cold flow, that is, although the particles may not be at a sufliciently high temperature to fuse together, they may be sutficiently viscous to cause the particles to weakly adhere to each other.

In the operation of the toner dispenser, a supply of toner powder is placed within the container which forms a reservoir for the toner powder. tained within the container, even though the apertures in the bottom wall of the container are larger in diameter than the largest dimension of any particle of toner, because the toner particles will aglomerate, for the reasons described previously, to form a bridge or breakable seal across the apertures. Of prime importance to the operation of this toner dispenser is the fact that the brush is located relative to the bottom of the container, such that there is a slight deflection of the bristles of the brush as they wipe across'the aperture area. This action of the brush will bring toner to the apertures and as the bristles of the brush pass over the apertures the bristles will slightly project into the apertures to force toner therethrough. Thus, as the brush is rotated at a relatively slow speed by suitable drive mechanism, operatively connected to the extension shaft 274 threaded into the righthand end of shaft 256, the individual bristles of the brush will carry particles of toner to the apertures to be forced therethrough by the bristles of the brush.

It is apparent that any' number of apertures may be provided for the discharge of toner, but for a given number of apertures of a predetermined size the dispensing rate will be dependent upon the speed of operation of the Toner placed in the container is dispensed through apertures 254 inv the lower portion of the base plate by means of cylindrical brush 255 secured to the threaded portions of drive shaft 256 journaled in bearings 257 and 257A mounted in bearing housings 258 and 258A secured to the right-hand bearing plate 246 and the lefthand bearing plate 243. The brush is secured axially against the shoulder of the drive shaft 256 by means of retaining ring 259 positioned in a suitable groove provided in the drive shaft.

A beater shaft 261 carrying a wire beater arm 262 secured thereto is journaled in bearings 263 and 263A mounted in bearing housings 264 and EMA and driven by gear 265 attached thereto which meshes with gear brush.

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 improvements or the scope of the following claim.

What is claimed is: A toner dispenser including a container having an arcuate trough portion extending longitudinally across the bottom thereof, said arcuate trough portion being provided with a plurality of spaced apart apertures in the bottom of said arcuate trough portion, said container being adapted to hold a supply of toner to be dispensed and said apertures being of a size to prevent the normal flow of toner therethrough,

Toner powder is re- 7 a brush having bristles thereon journaled for rotation in said container With said bristles in interference contact only with the bottom portion of said arcuate trough portion,

agitator means journaled for rotation in said container above said brush with the axis of rotation of said agitator means being substantially parallel to the axis of rotation of said brush,

drive means connected to said brush for rotating said brush whereby as said brush is rotated the bristles of said brush will carry toner to said apertures and whereby as said brush is rotated said bristles as they travel over said aperture Will extend into said apertures to force t0ner therethrough,

and driven means connected to said brush and to said agitator means to rotate said agitator means at a speed greater than the rotative speed of said brush.

References Cited in the file of this patent UNITED STATES PATENTS Clawson Dec. 21, 1858 Wolfe June 21, 1904 Bow Mar. 15, 1921 Singletary Nov. 21, 1950 Farley Aug. 25, 1953 Theme Feb. 3, 1959 Fisher Oct. 27, 1959 Waller Dec. 29, 1959 FOREIGN PATENTS France July 6, 1955

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