US3633544A

US3633544A - Turbocloud development

Info

Publication number: US3633544A
Application number: US838951A
Authority: US
Inventors: Ernest A Weiler
Original assignee: Xerox Corp
Current assignee: Xerox Corp
Priority date: 1969-07-03
Filing date: 1969-07-03
Publication date: 1972-01-11
Anticipated expiration: 1989-01-11
Also published as: CA934959A; GB1322363A; DE2033152A1; JPS491218B1

Abstract

A powder cloud development device for developing a latent electrostatic image with toner wherein the toner is conveyed to the latent image area by a forced air system. A development electrode is mounted adjacent the image area to improve development and the electrode includes means to induce turbulence in the flow. A precipitation roller collects the toner in the flow after it passes the image area to control the toner concentration circulating in the device.

Description

United States Patent [72] Inventor Ernest A. Weiler Rochester, N.Y. [21] App1.No. 838,951 [22] Filed July 3, 1969 [45] Patented Jan. 11, 1972 [73] Assignee Xerox Corporation Rochester, N.Y.

[54] TURBOCLOUD DEVELOPMENT 17 Claims, 7 Drawing Figs. [52] U.S. Cl 118/629, 117/17.5,118/312,118/637 [51] Int. Cl G03g 13/08 [50] Field of Search 1 18/629, 627, 637, 308, 312, 309; 117/17.5

[56] References Cited UNITED STATES PATENTS 2,876,737 3/1959 Carlson 118/312X 3,002,849 10/1961 Harmon et a1. 118/308 X POTENTIAL 3,008,826 11/1961 Mott et al. 117/17.5 X 3,336,905 8/1967 Lehmann 118/637 3,357,399 12/1967 Fisher 118/637 3,357,403 12/1967 Donalies 117/17.5 3,367,306 2/1968 Lawes et a1. 1l7/17.5 X 3,370,529 2/1968 Micha1chik..... l17/17.5 3,484,265 12/1969 Swyler 118/637 X Primary Examiner-Mervin Stein Attorneys Donald F. Daley, James J. Ralabate and Robert W. Mulcahy ABSTRACT: A powder cloud development device for developing a latent electrostatic image with toner wherein the toner is conveyed to the latent image area by a forced air system. A development electrode is mounted adjacent the image area to improve development and the electrode includes means to induce turbulence in the flow. A precipitation roller collects the toner in the flow after it passes the image area to control the toner concentration circulating in the device.

BIAS POTENTIAL PMENIEU JAM 1 I872 SHEET 1 [IF 2 BIAS POTENTIAL FIG. 2

BIAS POTENTIAL INVENTOR.

ERNEST A WEILER MQQQM PATENTEU JAN: 1 I972 SHEET 2 OF 2 TURBOCLOUD DEVELOPMENT BACKGROUND OF THE INVENTION This invention relates in general to developing a latent el'ectrostatic image and in particular to an improved powder cloud development device.

More specifically, this invention relates to a powder cloud development device wherein a forced air system carries toner to a latent electrostatic image area by means of a turbulent high-velocity multidirectional airflow to prevent directional development effects. A precipitation roller receives and collects toner after it passes the photoconductor to control the concentration oftoner in cloud.

In the process of xerography, a xerographic plate comprising a layer of photoconductive material on a conductive backing is given a uniform electric charge on its surface and then is exposed to subject matter to be reproduced by various projection techniques. This exposure discharges the plate in accordance with the light intensity reaching it, thereby creating a latent electrostatic image on or in the plate. Development of the image is effected by developers which may comprise, in general, a mixture of suitable, pigmented or dyed resin base powder, hereinafter referred to as toner, which is brought into contact with the plate by various well-known development techniques. During such development of the image, the toner powder is brought into surface contact with the photoconductive coating and is held there electrostatically in a pattern corresponding to the latent electrostatic image. Thereafter, the developed xerographic image may be transferred to a support material to which it may be fixed by any suitable means such as heat fusing.

An example of one of the aforementioned techniques for developing the latent image is disclosed in Walkup, U.S. Pat. No. 2,618,551, wherein the toner carried by carrier particles, is rolled or cascaded over the latent electrostatic image bearing surface. The carrier particles in such a system are much larger than the individual toner particles and are selected to be of a material that will form a triboelectric bond between the carrier and the toner. In such a relationship the carrier and toner will acquire an opposite electrostatic charge resulting in the toner being charged to polarity opposite that of the latent charged image. In practice, each carrier has numerous toner particles attracted thereon allowing them to be transported into contact with the photoconductor whereat the greater electrostatic attraction between the two developer components causing toner to be stripped off the carrier and electrostatically bonded to the charged image to effect development thereof. Such a technique is known in the art as cascade development.

Several difficulties are associated with the cascade development process. For example, in developing large image areas the electric field of the image is stronger at the edges than in the center portion. Therefore, the lines of force at the edges are sufficient to attract toner from the carrier, but in the center portion of the image toner is not attracted since the field is not strong enough to overcome the triboelectric attraction between the two components of the developer. Such a phenomenon results in an incomplete development in the central portions of the image while the edges are sufficiently developed.

Cascade development also requires a thorough intermixing of developer after repeated development of an image. If intermixing does not occur, a defect in development referred to as image striations results because of carrier material becoming depleted of toner powder. Normally, toner depletion occurs in cascade development when the carrier and toner materials move past the image in one direction across the photoconductor. Since images normally having varying sized latent image areas to be developed along the direction of flow, repeated development causes the developer flow moving past the more massive image areas to be depleted of toner in a greater amount than the less massive image areas. Elaborate systems for intermixing the developer material is required to overcome this toner depletion difficulty.

In order to overcome the difiiculties presented by the cascade method a technique of developing an image, referred to as powder cloud development, has been given much attention in the prior art. An example of the powder cloud technique is disclosed in Carlson, U.S. Pat. No. 2,928,575, wherein a powder cloud is created by air pressure and a charge placed on the toner by the contact of the cloud on the wall of the powder cloud generator. The charged toner cloud thereupon is moved into the vicinity of the charged image for the development thereof. Accordingly, the powder cloud method alleviates some of the difficulties of large area development because the electrostatic field of the image does not have to compete with the triboelectric attraction between the toner and the carrier as in the cascade system. Therefore, the powder cloud developing system allows the toner to more readily affix to the weaker electrostatic attraction of the central portion of the image.

However, other problems are associated with the use of prior art powder cloud development devices. One disadvantage associated with these developing systems is the ease at which the charged toner will affix to the nonimage or residual charge areas of the photoreceptor. This results in development of what is known as background areas and, therefore, while the prior art powder cloud devices achieve more complete development of solid image areas this method at the same time produces the disadvantage of developing unwanted background areas. In an attempt to prevent development of nonimage or background areas, the prior art has employed the use of a development electrode in the powder cloud device to increase the electric field in image areas in order to attempt to insure that the increased strength of the image field would more readily receive toner to the exclusion of the background areas. However, the use of development electrodes has not completely alleviated the development of nonimage areas and it remains desirable to overcome the background toner deposition problem of the existing powder cloud techniques.

Another attempt in the prior art to solve the aforementioned background development problem has been to create a powder cloud flowing past the image at a sufficient velocity to prevent the toner from being attracted by the weak electric field of the background area while allowing the greater field of the image areas to deflect and attract the toner. It was believed that such a velocity toner flow would prevent background development and at the same time insure adequate toner adherence to the charged laten image. The achievement of high-velocity toner flow, however, has been difficult to obtain as well as making prior art devices more expensive and complex. Further, the generation of high-velocity toner cloud flow conditions in prior art devices has caused directional effects which appear as a streaking of the developed image since the toner passes the photoconductive surface in only one direction. In order to obtain better quality xerographic development, it is necessary to provide a powder cloud device which does not produce streaking of the image as in the prior art.

Satisfactory development by use of a powder cloud device has in the past proven to be expensive and complex. A further reason for this difficulty is the necessity to maintain a controlled dispensing of the toner into the airflow to insure a uniform concentration. If the toner in the cloud is not uniformly dispersed, agglomerates of toner particles are formed which result in uneven development of the charged image. Also, in order to provide economy of operation by powder cloud development, an efficient retrieval of the unused toner must be provided to prevent loss to the outside of the device. Therefore, it becomes desirable to provide a relatively simple powder cloud developing device which renders efficient development of a charged image and overcomes background and directional problems of conventional devices.

3 SUMMARY OF THE INVENTION It is, therefore, an object of this invention to improve development of latent electrostatic charge patterns in image configuration.

Another object of this invention is to improve latent electrostatic image development by preventing the development of background areas of a charged image.

A further object of this invention is to improve latent electrostatic image development by passing a toner powder cloud in multiple directions to prevent directional development effects on the developed image.

Still another object of this invention is to improve powder cloud development by recirculating the powder cloud past the latent electrostatic image to more efficiently utilize the electroscopic toner powder and minimize the air filtration system.

A still further object of this invention is to improve latent electrostatic image development by maintaining the concentration of the toner in a powder cloud development device at a regulated level.

These and other objects are obtained in accordance with the present invention wherein there is provided a powder cloud device which utilizes high-velocity flow created by an air fan to effect development of a latent electrostatic image. Further included in the novel devices disclosed herein is a development electrode adjacent the charged image to create a uniform electrical field emanating therefrom to achieve better solid area development. The electrode is formed to induce turbulence in the toner cloud flow to insure that the toner passes the image in a plurality of directions to prevent directional ef fects or streaking of the developed image. The present invention also includes a precipitation roller which removes toner from the toner cloud after it passes the image to prevent unused toner from being reintroduced to the image thereby producing undesirable background development and to insure that the concentration of the toner in the flow remains at a desired level. The precipitation roller is electrically biased or is constructed of a material that will cause unused toner to adhere to its surface to thereafter be returned to a toner reservoir for redispensing into the airflow.

By utilizing the high-velocity flow of toner powder as in the present invention, the background areas do not attract the toner while the electrostatic charge in the image areas is sufficient to attract and retain the particles thereon. Further, by agitating the flow so that the toner cloud moves past the charged image in multiple directions, the aforementioned streaking problem is prevented. Also, the precipation roller improves development of the charged image since control of toner concentration is achieved to insure that the optimum amount of toner is flowing in the cloud. Therefore, the present invention achieves the desired results of reducing background development, maintaining the concentration of toner at desired levels, preventing development defect characteristics, and other readily apparent advantages with a device that is less expensive and more efficient than prior art powder cloud devices.

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

FIG. 1 is a schematic illustration ofa xerographic reproducing machine utilizing the powder cloud development devices according to the present invention;

FIG. 2 is a perspective illustration of one embodiment of the powder cloud development device according to the present invention;

FIGS. 3, 4 and 5 are perspective illustrations of embodiments of the development electrode utilized in the powder cloud development devices according to the present invention;

FIG. 6 illustrates a schematic diagram of the flow of air in the embodiment shown in FIG. 5 and;

FIG. 7 illustrates a perspective illustration of a second embodiment ofa powder cloud development device according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, there is shown a schematic view of a drum-type xerographic reproducing machine utilizing the present invention. The central element of the apparatus is a photoreceptive drum I mounted on suitable rollers and rotata ble in a conventional direction by a motor M. The drum I is covered on the outer surface 2 with a layer of photoconduc tive insulating material such as vitreous selenium or other suitable surface. A uniform electrostatic charge is placed on the photoconductor surface of the drum by means of a con ventional corona charging device 3. The uniformly charged surface of the drum is then rotated to an exposure means 4, of any well-known type, that exposes the charged image to copy to be reproduced to thereby form a latent electrostatic image of the copy on the photoconductor drum surface.

Following the formation of a latent electrostatic image of the copy, the image on the drum will rotate to a development station 5 (to be described in detail later) to bring the charged image into contact with developer to affix toner powder thereto. After development, the toner image moves to a transfer device 6 and the powder is transferred from the drum to a support material shown as a web of paper 7 or the like which is positioned in contact with the drum by

rollers

8 and 9. A second corona charging device 10 applies a charge to the back of the web to facilitate transfer of the toner in image form. The toner image on the support web then moves past a heating element 11 which affixes the toner to the paper web to form a duplicate of the original copy. A cleaning device 12 contacts the image area of the drum surface as it leaves the transfer device 6 to remove any residual image material from the drum to facilitate reuse of the surface. It should be clear that other modes of charging, exposing, transfer and fusing may be utilized in connection with the present invention, or in a system wherein the photoreceptor is carried by the support material.

Referring now to FIG. 2, there is illustrated one embodiment of the powder cloud development device 20 at develop ment station 5 according to the present invention. This embodiment of the invention creates a high-velocity cloud of toner powder in a flow of air by utilizing fan 21 which forces air in the direction of the arrows on the drawing through a cloud chute 22. A reservoir 23 oftoner is supported above the chute to retain a supply of toner and the supply is dispensed into the cloud chute by a toner dispensing roller 24 to control the concentration of the toner introduced into the airflow created by the fan 21. Such regulation of the dispensed toner is effected by the rotation of the dispensing roller 24 by suitable means (not shown) to turn at a rate depending on the desired amount of toner concentration. As the roller increases its rotative speed, a larger amount of toner is introduced into the cloud chute by the roller, since the roller carries a fixed amount of toner on its surface and as it rotates faster a greater quantity will be dropped into the chute for any given time interval.

To provide dispensing ofcharged toner into the cloud chute 22 the dispensing roller 24, being constructed of a material which forms a triboelectric relationship between it and the particles, further acts to place an electrostatic charge on the toner. As an alternative manner of charging the toner, the roller may be electrically biased by being connected to a suitable source of electrical potential to place a charge on any toner in contact with the roller 24. A nozzle 25 is provided in the cloud chute immediately upstream of the dispensing roller to increase the velocity of air generated by the fan insuring that the toner is uniformly distributed and carried in the form of a cloud. The cloud chute can be electrically biased to prevent toner from clinging to the chute and to charge any toner particles which were not effectively charged by the dispensing roller. The flow of air carrying the cloud of charged toner particles moves at a high velocity through the cloud chute 22 and is directed through a space between the development electrode 30 and the photoconductive drum 1 bearing the latent charged image on its surface.

The development electrode 30 is a grounded conductive member having a surface in direct confrontation to the charged image and, therefore, alters the lines of electrostatic force emanating from the latent electrostatic image. As the high-velocity charged toner passes between the charged image and the development electrode 30, the relative high speed of the particles prevents toner from depositing on the low-charge background areas while the electrical field of the electrostatic image will attract the toner for development. Therefore, it should be clear tat the cooperation of high-velocity flow and the development of a charged image by preventing deposition of toner in nonimage areas. The development electrode 30 may further increase the field of the charged image and neutralize the background field by being connected to a suitable bias potential which provides still greater control of the development of the image.

To prevent toner loss to the outside of the device, a suitable seal 26 is provided between the development unit and the photoconductor. The seal 26 is desirably constructed of a lowfriction material such as, for example, rabbit fur to prevent abrasion to the photoconductive surface 2. As a further prevention of toner loss, a precipitation roller 31 is rotatably mounted and driven by a suitable means (not shown) beneath an electrically biased baffle 32 to collect unused toner after it passes between the photoconductive surface and the development electrode. The precipitation roller 31 is formed of a material having a triboelectric attraction to the charged toner causing the toner to cling thereto and precipitate out of the airflow. As an alternative manner of attracting the toner, the roller 31 may be connected to a suitable potential of a polarity opposite to the charge on the particles.

The biased baffle 32 is connected to an electrical potential of the same polarity as the charge on the toner to perform the dual function of repelling the toner therefrom to the precipitation roller. The flow of air which has been denuded of toner by the precipitation roller 31 then flows beneath the baffle and up into a duct 33 to be returned in cleaned form to the fan 21 for recirculation. To assure that no toner remains in the return airflow, a suitable filter 34 is provided at the entrance of the duct to remove any toner not already collected by the precipitation roller 31.

The roller is rotatably mounted to rotate by suitable means (not shown) and thus allow the toner collected on the precipitation roller to be scraped from the surface by a suitable scraper 35, such as, for example, a means flexibly biased there against. The removed toner falls into the toner reservoir to be metered into the airflow by the toner dispenser 24. It should, therefore, be apparent that the novel powder cloud device of the embodiment described herein in conjunction with FIG. 2 provides improved development of a latent electrostatic image by preventing deposition of toner in nonimage areas through the utilization of a development electrode and high-velocity toner flow and controls the concentration of the toner in the system by removing unused toner from the airflow prior to recirculation.

Referring now in particular to FIG. 3, there is illustrated another form of the development electrode 40 shown in the embodiment of the powder cloud device of FIG. 2. The development electrode is grounded or electrically biased in the manner described in the above description of the development electrode 30 in FIG. 2. The surface of the development electrode 40 in FIG. 3, however, includes a series of hemispheric protrusions 41 which extend into the toner cloud flow as it passes the charged image to effect turbulence in the flow. Such an induced condition of turbulence thereupon will cause the toner to pass the surface to be developed in multiple directions to overcome the streaking effects normally caused by undirectional development. The electrode 40 may further be oscillated or orbited in a direction to and from the drum to produce still more turbulence in the flow for a greater reduction of directional effects in development. Thus, the development electrode having hemispherical protrusions may remain stationary, be oscillated, or be orbited according to the degree of turbulence needed for satisfactory development.

Oscillation of the development electrode may be accomplished by any suitable motor means 42 or oscillation system. As an example, there is illustrated in FIG. 3 a small motor 42 mounted in suitable brackets 43 beneath the surface of the electrode 40. A connecting rod 44 having holes at both ends is pivotally connected at one end to a bracket 46 including a stud which is affixed to the electrode and and at the other end is pivotally connected to a stud 48 mounted on a disc member which is rotated by the motor. The electrode is slidably mounted in brackets 49 which allows it to move to and from the drum according to the combined rotation of the disc and movement of the connecting rod.

Referring now to FIG. 4, there is illustrated still another embodiment of the development electrode 30 shown in FIG. 2, wherein the electrode 50 of FIG. 4 includes tufts 51 of fibers of any suitable material affixed to its surface which extend toward the photoconductive drum. The tufts 51, thereby, cause turbulence in the toner flow to eliminate the previously mentioned directional effects of development. This form of the electrode may also be oscillated to and from the charged image to induce greater turbulence in the flow in the manner described for oscillation of the electrode shown in FIG. 3 or may be orbited in any manner (not shown).

Referring now in particular to FIG. 5, there is illustrated a still further embodiment of the development electrode utilized in the powder cloud device of FIG. 2. The electrode 60 of FIG. 5 includes a surface having alternately oriented, perforated, funnel shape members 61 which are oscillated to and fro in relation to the charged image in the manner described herein in conjunction with the embodiment of FIG. 3. Oscillation of the electrode similarly causes turbulence in the toner flow to alleviate directional development effects as previously discussed. As the funnels are oscillated, an airflow circulation is created through the funnels which acts to increase the turbulence of the flow.

Referring to FIG. 5, there is shown a schematic view of the electrode 60 which illustrates the airflow circulation through the funnels which causes a turbulence in the toner cloud flow allowing the toner to pass the image in more than one direction. The electrode 60 of FIG. 5 is suitably grounded or biased in the manner described in the other embodiments of the development electrode herein disclosed.

Referring now in particular to FIG. 6, there is illustrated an embodiment of a simplified version of the powder cloud development device 20 utilized at development station 5 according to the present invention. A housing 71 is suitably mounted adjacent to the photoconductive surface to be developed and includes therein a conventional transverse blower 72. The transverse blower is a conventional transverse flow fan which creates a significantly higher pressure coefficient than other well-known fans resulting in a higher velocity flow than possible with other types of fans. The transverse fan is suitably mounted in the housing to create a clockwise flow of air around the exterior of the fan as shown by the arrows. The upper portion of the housing includes an opening 73 which is adjacent to the latent image bearing photoconductive surface. As a prevention for the loss of toner to the outside of the device, seals 74 and 75 having low-friction characteristics are mounted between the housing and the photoconductor on both sides thereof. Mounted on the housing adjacent and in confronting relationship to the charged image is a development electrode 76 which is a grounded conductive member or alternatively can be electrically biased in the manner previously discussed in the embodiment of FIG. 2. The clockwise flow created by the transverse blower flows from left to right through the space 77 between the development electrode and the charged image and returns to the transverse fan for recirculation. A suitable toner dispenser 78 is mounted near the bottom of the housing and includes a dispensing roller 79 of the type previously described in conjunction with the powder 5 cloud device of FIG. 2. As toner is dispensed into the flow of air created by the transverse fan, a toner cloud is formed which circulates around the housing and through the space between the photoconductor drum 1 and the development electrode 76 to develop the image on the surface of the pho- 1 toreceptor.

It has been found that the creation of high-velocity toner flow by use of a transverse blower as described herein alleviates the need for a precipitation roller since the flow is 1 moving with such rapid speed that the level of concentration in the flow is not a problem. Further, as a means to place a proper charge on the toner so as to allow it to develop the charged image, the blades of the fan in this embodiment are coated with a suitable material which forms a triboelectric relationship to the toner whereby toner is given a suitable electrostatic charge as it flows through the fan in contact with the blades. The powder cloud device as described in the embodiment of FIG. 7 further can utilize the turbulence inducing electrodes disclosed previously for use in the embodiment of 2 FIG. 2 in order to eliminate any directional or streaking effects caused by the high-velocity flow herein described. The use of such a turbulence-inducing electrode along with the high-velocity conditions created by the transverse fan produces adequate development of the image without the 3 need of a concentration controller and precipitation roller described in the embodiment of FIG. 2.

The novel powder cloud development devices disclosed in conjunction with the present invention will effectively develop a charged image on any photoconductor, as for example, a 3 photoconductor surface on a belt, a web, paper or the like. Further, it is within the scope of the invention to vibrate the development electrode shown in the embodiments of FIG. 2 and FIG. 7 without the use of the particular electrode surfaces described in the embodiments of FIGS. 3 to 5 for the purpose of inducing turbulence in the toner flow.

While the invention has been described with reference to preferred embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents 4 may be substituted for elements thereof without departing from the true spirit and scope of the invention. ln 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.

What is claimed is:

1. An apparatus for developing a support surface bearing a latent electrostatic image with developer material comprising;

a supply of developer material,

fan means for generating a flow of air for carrying developer material to the support surface bearing the l t ntde apz t image conducting means connecting Wfimmnrfieamerwnducting said flow of air past said support surface,

rotatable dispensing means having one portion of the surface thereof communicating with the developer material in said supply and having another portion of the surface thereof communicating with the airflow in said conducting means for rotatably conveying said developer material on the surface of said rotatable dispensing means from 6 said supply to said conducting means for introducing the developer on the surface of said rotatable dispenser to said airflow. and

air return means for directing the airflow back to said fan means after passing the surface to be developed.

2. An apparatus for developing a support surface bearing a latent electrostatic image as in claim l and further including,

a precipitator for removing unused developer material from the air of the flow of air after the airflow passes the surface to be developed.

3. The apparatus of claim 1 wherein the rotatable dispensing means is a roller made of a surface having a triboelectric relationship with the developer material to place an electrostatic charge on the developer material.

4. The apparatus of claim 1 further including an electrically grounded conductive electrode spacedly mounted adjacent the image-bearing surface to cause developer material to flow therebetween.

5. The apparatus of claim 4 wherein the electrode further includes turbulence inducing means for effecting turbulence of the flow of developer material to eliminate directional development effects.

6. The apparatus of claim 5 wherein the turbulence-inducing means is a series of protrusions on the surface of the electrode to extend into the flow of developer material.

7. An apparatus for developing a support surface bearing a latent electrostatic image with developer material comprising;

fan means for creating a flow of air,

dispensing means mounted adjacent said flow of air for introducing electrostatically charged developer material into the flow to be carried thereby,

conveying means connected to the fan means and the dispensing means for directing the flow of air carrying charged developer material past a surface bearing a latent image to be developed, and

receiving means for directing the airflow back to the fan means after passing the surface to be developed, said receiving means including a precipitator for removing unused developer material from the flow after passing the surface to be developed, said precipitator comprising a roller made of a material that forms a triboelectric relationship with the developer material to allow developer to be collected thereon.

8. The apparatus of claim 7 further including a developer reservoir mounted adjacent the roller to receive developer material collected thereon whereby the reservoir supplies developer to the dispensing means.

9. The apparatus of claim 7 wherein the roller includes scraper element adapted to scrape off developer material collected thereon to allow it to be received by the reservoir.

10. An apparatus for developing a support surface bearing a latent electrostatic image with developer material comprising;

fan means for creating a flow of air,

receiving means for directing the airflow back to the fan means after passing the surface to be developed, said receiving mean s includin g a precipitator fo rremoving unused developer material from the flow after passing the surface to be developed, said precipitator including a roller coupled to a bias potential of opposite polarity than the charge on the developer to attract developer thereto.

11. An apparatus for developing a support surface bearing a latent electrostatic image with developer material comprising;

fan means for creating a flow of air,

dispensing means mounted adjacent said flow of air for in troducing electrostatically charged developer material into the flow to be carried thereby,

conveying means connected to the fan means and the dispensing means for directing the flow of air carrying charged developing material past a surface bearing a latent image to be developed, and

receiving means for directing the airflow back to the fan means after passing the surface to be developed, said receiving means including a precipitator for removing unused developer material from the flow after passing the surface to be developed and a baffle member coupled to an electrical bias potential as the same polarity as the charge on the developer material to repel developer material therefrom to the precipitator.

12. An apparatus for developing a support surface bearing a latent electrostatic image with developer material comprising;

fan means for creating a flow of air,

dispensing means mounted adjacent said flow of air for introducing electrostatically charged developer material with the flow to be carried thereby,

conveying means connected to the fan means and the dispensing means for directing the flow of air carrying charged developing material past a surface bearing a latent image to be developed,

an electrically grounded conductive electrode spacedly mounted adjacent the image-bearing surface to cause developer material to flow therebetween, said electrode including turbulence inducing means for effecting turbulence of the flow of developer material to eliminate directional development effects and said turbulence inducing means includes a series of tufts of fibers mounted on the surface of the electrode to extend with the flow of developer material, and

receiving means for directing the airflow back to the fan means after passing the surface to be developed.

13. An apparatus for developing a support surface bearing a latent electrostatic image with developer material comprising;

fan means for creating a flow of air,

conveying means connected to the fan means and the dispensing means for directing the flow of air carrying charged developing material past a surface bearing a latent image to be developed.

an electrically grounded conductive electrode spacedly mounted adjacent the image-bearing surface to cause the developer material to flow therebetween, said electrode including turbulence inducing means for effecting turbulence of the flow of developer material to eliminate directional development effects, said turbulence inducing means including vibrating means connected to the electrode to move the electrode to and from the image bear ing surface, and

14. The apparatus of claim 12 wherein the electrode includes a surface of alternatively directed perforated funnels to create an additional airflow through the perforations to effect turbulence of the flow of developer material.

15. In an apparatus for developing a support surface bearing a latent electrostatic image with developer material including a developer flow generator for moving charged developer in a fluid flow medium past an image bearing surface to be developed, the improvement therein comprising a turbulence inducing means mounted adjacent the developer material flow passing the image-bearing surface to be developed to prevent directional development effects, said turbulence-inducing means including an electrically grounded development electrode, said development electrode being vibrated relative to the image-bearing surface to be developed to induce turbulence.

16. The device of claim 15 wherein the electrode includes a series of elements extending into the developer material flow to create turbulence therein.

17. In an apparatus for developing a support surface bearing a latent electrostatic image with developer material including a developer flow generator for moving charged developer in a fluid flow medium past an image bearing surface to be developed, the improvement therein comprising a turbulence inducing means mounted adjacent the developer material flow passing the surface bearing the latent electrostatic image to be developed to prevent directional development effects, said turbulence inducing means including;

an electrically grounded development electrode for repelling charged developer in the developer material flow, and means for oscillating said development electrode relative to said image bearing surface for inducing turbulence in the developer material flow as said developer material flow passes the surface bearing the latent electrostatic image.

Claims

1. An apparatus for developing a support surface bearing a latent electrostatic image with developer material comprising; a supply of developer material, fan means for generating a flow of air for carrying developer material to the support surface bearing the latent electrostatic image, conducting means connecting with said fan means for conducting said flow of air past said support surface, rotatable dispensing means having one portion of the surface thereof communicating with the developer material in said supply and having another portion of the surface thereof communicating with the airflow in said conducting means for rotatably conveying said developer material on the surface of said rotatable dispensing means from said supply to said conducting means for introducing the developer on the surface of said rotatable dispenser to said airflow, and air return means for directing the airflow back to said fan means after passing the surface to be developed.

2. An apparatus for developing a support surface bearing a latent electrostatic image as in claim 1 and further including, a precipitator for removing unused developer material from the air of the flow of air after the airflow passes the surface to be developed.

7. An apparatus for developing a support surface bearing a latent electrostatic image with developer material comprising; fan means for creating a flow of air, dispensing means mounted adjacent said flow of air for introducing electrostatically charged developer material into the flow to be carried thereby, conveying means connected to the fan means and the dispensing means for directing the flow of air carrying charged developer material past a surface bearing a latent image to be developed, and receiving means for directing the airflow back to the fan means after passing the surface to be developed, said receiving means including a precipitator for removing unused developer material from the flow after passing the surface to be developed, said precipitator comprising a roller made of a material that forms a triboelectric relationship with the developer material to allow developer to be collected thereon.

10. An apparatus for developing a support surface bearing a latent electrostatic image with developer material comprising; fan means for creating a flow of air, dispensing means mounted adjacent said flow of air for introducing electrostatically charged developer material into the flow to be carried thereby, conveying means connected to the fan means and the dispensing means for directing the flow of air carrying charged developer material past a surface bearing a latent image to be developed, and receiving means for directing the airflow back to the fan means after passing the surface to be developed, said receiving means including a precipitator for removing unused developer material from the flow after passing the surface to be developed, said precipitator including a roller coupled to a bias potential of opposite polarity than the charge on the developer to attract developer thereto.

11. An apparatus for developing a support surface bearing a latent electrostatic image with developer material comprising; fan means for creating a flow of air, dispensing means mounted adjacent said flow of air for introducing electrostatically charged developer material into the flow to be carried thereby, conveying means connected to the fan means and the dispensing means for directing the flow of air carrying charged developing material past a surface bearing a latent image to be developed, and receiving means for directing the airflow back to the fan means after passing the surface to be developed, said receiving means including a precipitator for removing unused developer material from the flow after passing the surface to be developed and a baffle member coupled to an electrical bias potential as the same polarity as the charge on the developer material to repel developer material therefrom to the precipitator.

12. An apparatus for developing a support surface bearing a latent electrostatic image with developer material comprising; fan means for creating a flow of air, dispensing means mounted adjacent said flow of air for introducing electrostatically charged developer material with the flow to be carried thereby, conveying means connected to the fan means and the dispensing means for directing the flow of air carrying charged developing material past a surface bearing a latent image to be developed, an electrically grounded conductive electrode spacedly mounted adjacent the image-bearing surface to cause developer material to flow therebetween, said electrode including turbulence inducing means for effecting turbulence of the flow of developer material to eliminate directional development effects and said turbulence inducing means includes a series of tufts of fibers mounted on the surface of the electrode to extend with the flow of developer material, and receiving means for directing the airflow back to the fan means after passing the surface to be developed.

13. An apparatus for developing a support surface bearing a latent electrostatic image with developer material comprising; fan means for creating a flow of air, dispensing means mounted adjacent said flow of air for introducing electrostatically charged developer material into the flow to be carried thereby, conveying means connected to the fan means and the dispensing means for directing the flow of air carrying charged developing material past a surface bearing a latent image to be developed. an electrically grounded conductive electrode spacedly mounted adjacent the image-bearing surface to cause the developer material to flow therebetween, said electrode including turbulence inducing means for effecting turbulence of the flow of developer material to eliminate directional developmeNt effects, said turbulence inducing means including vibrating means connected to the electrode to move the electrode to and from the image bearing surface, and receiving means for directing the airflow back to the fan means after passing the surface to be developed.

17. In an apparatus for developing a support surface bearing a latent electrostatic image with developer material including a developer flow generator for moving charged developer in a fluid flow medium past an image bearing surface to be developed, the improvement therein comprising a turbulence inducing means mounted adjacent the developer material flow passing the surface bearing the latent electrostatic image to be developed to prevent directional development effects, said turbulence inducing means including; an electrically grounded development electrode for repelling charged developer in the developer material flow, and means for oscillating said development electrode relative to said image bearing surface for inducing turbulence in the developer material flow as said developer material flow passes the surface bearing the latent electrostatic image.