US3538887A - Electroscopic toner powder dispenser - Google Patents

Description

United States Patent Ronald Frederick Rueckwald Inventor San Mateo, California Appl. No. 733,879 Filed June 3,1968 Patented Nov. 10, 1970 Assignee Xerox Corporation Rochester, New York a corportion of New York ELECTROSCOPIC TONER POWDER DISPENSER 6 Claims, 2 Drawing Figs.

US. Cl 118/602,

118/637: 198/57: 222/57. 222/163. 222/415 Int. Cl B05C 11/00 Field 01' Search 1 18/7, 602,

637,413,415, 257, 308, 312; 222/55,57, 163, 415: 198/57;30l/(lnq):l17/(1nq) [56] References Cited UNITED STATES PATENTS 1,364,168 l/l92l Willford 198/57 2,429,864 10/1947 Alvord 222/163X 2,940,422 6/1960 Dott 1 18/312 3,079,483 2/1963 'Codichini ll8/637X 3,164,301 1/1965 Hargreaves et a1. 222/415X Primary ExaminerMorris Kaplan Att0rney Ronald Zibelli, Paul M. Enlow,.lames J Ralabate.

Norman E. Schrader and August E. Roehrig, Jr.

ABSTRACT: Apparatus for dispensing electroscopic toner powder into a dynamic developer mixture including a hopper for containing toner powder, pivotally supported from a conveyor unit and adapted to be adjustably positioned relative thereto to form an outlet for regulating the amount of toner powder forwarded by the conveyor belt into contact with the moving developer mixture, the total mixture being dispensed from the conveyor belt into a reservoir within which is disposed developer means,

1 I l l 1 Patented Nov. 10, 1910 f 3,588,887

INVENTOR. I RONALD F. RUECKWALD BYQ Q\ I FIG. 1 5

Patented Nov. 10, 1970 8,538,887

Sheet 2 of 2 FIG. 3

ELECTROSCOPIC TONER POWDER DISPENSER BACKGROUND OF THE INVENTION This invention relates to latent electrostatic image development and in particular to apparatus for maintaining an optimum concentration of electroscopic toner powder in a developer mixture.

More specifically, the invention relates to an electroscopic toner dispenser for metering a quantity of toner powder into a mixture of xerographic or electrographic developer material.

For example, in the electrographic process a sheet of insulating support material, usually paper, on a conductive backing is given an electrostatic charge over its surface in accordance with a desired charge pattern, thereby creating a latent electrostatic image.

Development of the image is effected by developers which comprise, in general, a mixture of suitable pigmented or dyed resin-based powder, hereinafter referred to as toner, and a granular carrier material which functions to generate triboelectric charges on, and to carry the toner powder. More specifically, the function of the carrier material is to provide mechanical control of the toner, or to carry the toner to an image surface and simultaneously provide almost complete homogeneity of charge polarity. In the development of the image, the toner powder is brought into surface contact with the support material and is held thereon by the electrostatic forces in a pattern corresponding to the latent electrostatic image. Thereafter, the developed electrographic image is usually permanently affixed to the support material as by heat fusing.

In the mixture of toner particles and carrier material, the toner particles, which are many times smaller than the carrier material, adhere to and coat the surface of the carrier material due to the triboelectric attraction therebetween. During development, as the toner-coated carrier material is applied to an electrostatic image of opposite polarity to the charge on the toner, toner particles are pulled away from the carrier material by the latent electrostatic image and deposited on the latent electrostatic image bearing support material to form a developed toner-powder image. As toner-power images are formed, additional toner powder must be supplied to the developer mixture to replenish the toner deposited on the support material. The toner material may be of the type disclosed in Carlson US. Pat. No. 2,940,934, wherein the toner particles comprise a finely divided pigmented resin having a particle size less than 20 microns and preferably an average particle size between about 5 and microns and comprising a finely divided uniform mixture of pigment in a nontacky, lowmelting resin. Desirably, the pigment will be a black pigment such as carbon black or other minutely divided carbonaceous pigment.

As the toner powder in the developer mixture is depleted during the development of the latent image on the support surface, more toner powder must be added to maintain a desirable level of copy density. In the event that too much toner powder isadded to the developer mixture, heavy deposits of toner in the image areas in combination with an undesirable deposit of toner in the non-image or background areas results in producing prints of poor contrast with blotchy images or poor resolution.

In addition, overtoning by the operator adds to the severity of toner powder accumulation on critical machine components. Thus, it is desirable to regulate the dispensing of toner powder into the developer mixture to keep the quality of the electrographic reproductions at a high level.

Heretofore, various attempts to control the addition of toner powder to a developer mix have generally been directed to the addition of toner powder into a static or substantially stationary quantity of developer material. While such systems are somewhat satisfactory, they have certain obvious shortcomings. For example, when toner powder is added to a static or substantially stationary quantity of developer material, the intermixing of the toner powder with the carrier material becomes very difficult resulting in a deficient triboelectric relationship between the toner powder and carrier. in addition, if the images being reproduced have large solid areas in one portion, then the developer material tends to become depleted of toner powder in this localized area. Furthermore, the time delay required to intermix the additional toner powder into the developer material results in a number of initial prints of poor quality.

In accordance with the present invention, the addition of toner powder into the developer mixture is continually metered and uniformly dispensed into a moving or dynamic developer mixture throughout the width of the developer applicator such that an intermixing of the developer material and the toner powder is achieved resulting in a uniform high quality application of. developer material to the latent electrostatic image on the photoreceptor surface.

SUMMARY OF THE INVENTION It is, therefore, an object of this invention to improve developing latent electrostatic images.

Another object of this invention is to improve electrostatic image developing by controlling the quantity of toner powder added to a developer mixture.

A further object of this invention is to improve electrostatic image developing by maintaining a high degree of intermixing between carrier particles and toner powder.

Still another object of this invention is to improve electrostatic image developing by maintaining a highly intermixed quantity of developer material by dispensing toner powder into a dynamic developer system throughout the width of the developing apparatus.

These and other objects are attained in accordance with the present invention wherein there is provided an electroscopic toner powder dispenser for use in an electrographic facsimile machine, The toner dispenser includes a hopper for retaining a quantity of toner powder pivotably supported adjacent a moving conveyor to form a variable aperture dispensing outlet for adding the toner powder to a dynamic developer system.

DESCRIPTION OF THE DRAWINGS Further objects of this invention together with additional features contributing thereto and advantages accruing therefrom, will be apparent from the following description of one embodiment of the invention when read in conjunction with the accompanying drawings wherein:

FIG. I is a front elevation of an automatic electrographic facsimile transceiver apparatus utilizing the invention of this application;

FIG. 2 is a mechanical schematic representation of the transceiver apparatus of FIG. 1 to better illustrate the use and features of the dispensing apparatus;

FIG. 3 is an enlarged horizontal elevation of a portion of the developer apparatus of the automatic facsimile transceiver with parts broken away to better illustrate the dispensing apparatus of this invention;

FIG. 4 is a front section view of the portion ofthe automatic facsimile transceiver developer apparatus shown in FIG. 3 taken along lines 4-4.

DESCRIPTION OF THE PREFERRED EMBODIMENT ally therealong which form a curvilinear passageway through which a record medium or sheet of electrographic recording material is advanced. A rotatable optical scanner and electrographic recorder turret apparatus 700 is positioned adjacent the passageway to functionally form a scanning-recording station axially positioned along the two semicylindrical surfaces over which the electrographic recording material passes.

When it is desired to transmit the graphic information on the record medium the sheet is advanced to the scanning station 700 whereat electrical signals representative of the graphic information carried thereon are generated as the optical scanner transverses the graphic information on the sheet. When it is desired to receive information from a remote location, the recorder portion of the turret selectively produces electrostatic charge patterns on the electrographic paper record medium, as it is forwarded within the passageway at the recording or scanning station, in response to electrical signals received by the recorder and representative of the graphic information which is desired to be displayed on the record medi- After a latent electrostatic image has been formed on the record medium by the selective deposition of electrostatic charge patterns thereon, the charge patterns representative of the graphic information are rendered visible by means of an electroscopic toner powder developing apparatus 400 which uniformly deposits a quantity of toner powder onto the charged surface of the latent electrostatic image bearing record medium. After the latent image is rendered visible, the toner powder image on the surface of the record medium is permanently affixed thereto to provide a facsimile copy ofthe graphic information thereon.

For the purposes ofthe present disclosure, reference will be had primarily to use of the facsimile transceiver apparatus in the receive mode of operation, although it is to be understood that the transceiver unit is designed to function both as a transmitter and a receiver. When the automatic electrographic facsimile transceiver apparatus 100 is operated in the receiver mode, sheets of electrographic recording material 105 upon which the graphic information is to be recorded, are placed into the machine on a record material tray 102 located at the front ofthe machine and directly beneath a second copy support tray 101 utilized when the transceiver apparatus is operated in the transmit mode. The record sheets 105 are advanced from the tray 102 by means of an automatic sheet feeder and are transported into the passageway defined between inner platen assembly 500 and outer platen assembly 5550 by means of a sheet transport generally designated 350. The electrographic recording sheets are forwarded into position within the passageway defined between the inner and outer platen assemblies 500 and 550, respectively, and then advanced to the scanner-receiver area by a paper drive mechanism generally designated 600. At the scan-receive turret 700, and upon receipt of suitable electrical control pulses, the paper drive 600 is removed from engagement with the electrographic recording sheet and a stepping drive mechanism 630 engaged therewith to advance the copy sheet at a controlled speed past the scanner-receiver 700.

Information is recorded upon the electrographic record sheet 105 by means of an electrographic recording stylus supported on the rotating turret assembly 700 for rotation therewith to selectively charge an increment of the electrographic recording material, in response to electrical control signals, as the recording material is advanced thereover. The information desired to be recorded on the copy sheet 105, is received by the transceiver apparatus, decoded through appropriate electrical circuitry, and utilized to energize the electrographic recording stylus in the turret assembly 700. In response to these electrical control pulses, the record or copy sheet 105 is clectrographically charge in image patterns corresponding to the information coupled into the transceiver upparatus, Upon completion of the recording process, the copy sheet 105 is advanced by the stepping drive assembly 650 over a magnetic brush developer unit 400 whereat the latent electrostatic charge pattern on the sheet is rendered visible by application of the electroscopic toner powder particles which adhere to the record sheet in the charged areas. After the latent electrostatic image on the record sheet has been rendered visible by the electroscopic toner powder, the copy sheet is further advanced along the curvilinear path to a fusing apparatus generally designated 800 at which point the electroscopic toner powder particles are fused to the copy sheet to create a permanent facsimile copy of the graphic information displayed on the support material. After the toner powder image has been permanently affixed to the record sheet, the sheet is advanced to a sheet transport 900 whereat the completed facsimile copy is forwarded out of the machine and into the copy receive tray 103 located a the front portion of the transceiver.

As shown in HO. 1, the developing unit 400 is appropriately supported adjacent the passing electrographic support material 105 in a manner such that the developer material contained thereon contacts the support material for the development of the latent electrostatic image by the application of electroscopic toner powder. The developing unit 400 includes a rotatable magnetically-permeable drum 420 supported within the developer unit housing on a shaft 430 for rotation about a plurality of permanent magnets 4,50. The magnets 450 are supported internally of the developing drum 4320 and adjacent to the path of drum travel throughout approximately three quarters of the drums internal peripheral surface. In this manner, developer material including magnetic carrier particles, e.g., iron filings, is attracted onto the surface of developing drum 420 and carried thereby through the development zone to the point whereat the magnetic field from magnets 4150 is insufficient to hold the developer material to the drum surface allowing the toner powder depleted developer material to fall from the drum surface onto the conveyor 321 of toner dispenser 300. For further details of the specific construction of developing unit 400 reference is made to copcnd: ing U. S. Pat. application Development Apparatus Ser. No. 823,878 filed May l2, 1969, in the name of Ronald F. Rueckwald.

The toner powder dispenser 300 includes a hopper or container 310 for holding a quantity of electroscopic toner powder to be dispensed into the developer mixture to replenish the toner powder used to develop latent electrostatic images on the clectrographic support material 105, and a conveying apparatus 320 for removing a quantity of toner powder from the container 310 and forwarding the powder through a toner powder replenishing zone whereat the developer mixture utilized in developing a latent electrostatic image falls from the developing drum 420 onto the toner powder laden conveyor belt 321 to be intermixed therewith and thereafter conveyed to a sump 444 whereat the toner-replenished developer material is recirculated by the developing drum 420. The dispensing apparatus 300 is supported within the developer unit 400 between front and rear frame plates 447 and 448, respectively, by means of a pair of brackets 323 secured to the bottom plate 449 of the developer unit and the frame 322 ofthe conveying apparatus 320.

Dispensing of the toner powder into the developer mixture is regulated by the adjustable positioning of the hopper 310 relative to the conveyor belt 321 of the conveying apparatus 320. Hopper 310 comprises a hollow rectangular housing open at the top for addition of toner powder and at the bottom for the dispensing of toner powder in cooperation with conveyor belt 321 into the developer mixture. The hopper is appropriately secured, as by welding, to a pivot shaft 324 pivotable in a pair of brackets 325 secured to the frame of conveyor apparatus 320. A spring 332, secured at one end to hopper 310 and at its other end to a frame plate 446 of the developer unit, biases the hopper in a clockwise direction (as seen in FIG. 1) against a threaded adjustable stop 333 whereby the spacing between the bottom of hopper 310 and the top run of conveyor belt 321 can be adjusted by rotating the hopper on pivot shaft 324 by means of turning the knob of adjustable stop 333. The positioning of hopper 310 relative to conveyor belt 321 defines an aperture through which toner powder passes on the conveyor belt, the quantity of powder dispensed being determined by the spacing between these elements for a given constant linear velocity of the conveyor belt.

The conveying apparatus 320 includes a frame 322, supported from bottom frame plate 449 of the developer unit by means of the pair of brackets 323, positioned adjacent developer drum 420 such that developer material falling therefrom will fall onto the toner powder laden conveyor belt as it emerges from beneath hopper 310. The belt is supported about idler roller 326 and drive roller 327 each roller being rotatably supported in'conveyor frame 322. Idler roller 326 is adjustably supported in frame 322 by means of a tension bracket 328 to maintain the conveyor belt 321 in a predetermined stressed configuration. The drive roller 327 is rotatably supported in frame 322 and driven by means of an electric motor MOT-l appropriately supported from the developer unit 400 and connected to drive roller 327 by means of a sleeve coupling 351.

As developing drum 420 rotates within the developer housing the developer mixture which passes out of the magnetic field from magnets 450 is no longer held on developing drum 420 and, therefore, falls from the drum surface onto the toner powder laden conveyor belt 321 positioned adjacent thereto. A pair of baffles 329 are supported from each side of conveyor frame 322 and extend perpendicular to the surface of conveyor belt 321 to constrain the developer mixture onto the conveyor belt to ensure mixing of the toner powder with the toner powder depleted developer mixture. After the developer mixture has been replenished with toner powder, the mixture is conveyed to a developer sump from where the replenished developer mixture is recycled for image development.

While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the true spirit and scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teaching of the invention without departing from its essential teachings.

lclaim: Apparatus for use in dispensing electroscopic toner powder into a moving quantity of developer material including:

developing means for applying a quantity of developer material to a latent electrostatic image and having a sump portion to retain the developer material therein;

said developing means adapted to forward a'quantity of developer material including electroscopic toner powder through a path of movement in operative contact with a latent electrostatic image whereat the toner powder is depleted from the developer material and the remaining developer material passed into said sump portion;

a conveyor comprising an endless belt supported upon a plurality of rollers and adapted for rotation in a path of movement such that a portion thereof intercepts said remaining developer material prior to its passage into said sump portion; and

container means for holding a quantity of electroscopic toner powder and having an opening therein positioned adjacent another portion of said endless belt and forming an outlet therewith for toner powder contained within said container means to be dispensed therefrom, whereby toner powder is brought into contact with said remaining developer material for mixing therewith.

2. The apparatus of claim 1 including means to vary the position of said container means relative to said endless belt such that the outlet formed therebetween is adjustable to vary the quantity of toner powder forwarded by said endless belt into contact with said remaining developer material.

3. The apparatus of claim 2 wherein said means to vary the position of said container includes a control stop positionable to vary the outlet formed between said container means and said endless belt.

4. The apparatus of claim 2 wherein said container means is supported from said conveyor.

5. The apparatus of claim 4 wherein said container means is biased into contact with an adjustable control'stop to vary the pivotal position of said container relative to said endless belt for defining the toner powder outlet formed therebetween.

6. The apparatus of claim 1 including baffle means supported from said conveyor and positioned to guide said remaining developer material into contact with said toner powder forwarded by said endless belt.

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