US3659556A

US3659556A - Programmable toner dispenser

Info

Publication number: US3659556A
Application number: US65052A
Authority: US
Inventors: Edward Charles Mutschler
Original assignee: Xerox Corp
Current assignee: Xerox Corp
Priority date: 1970-08-19
Filing date: 1970-08-19
Publication date: 1972-05-02
Anticipated expiration: 1989-05-02
Also published as: CA936681A; FR2102375B1; BE771423A; NL7111221A; FR2102375A1; GB1358448A; DE2141677A1

Abstract

A dispenser for replenishing the toner portion of a mixture of toner and carrier, the mixture developing a latent image formed on an image-bearing surface. A container including spaced-apart side walls is positioned adjacent a rotatable member, the bottom of the side walls being shaped to fit the curvature of the member. The toner is introduced into the container and is dispensed as the member is rotated and at a rate proportional to its speed. In a specific embodiment, the amount of toner dispensed is dependent on the density of the developed image and/or the image printing rate.

Description

United States Patent Mutschler [54] PROGRAMMABLE TONER DISPENSER [72] Inventor: Edward Charles Mutschler, Pittsford, NY.

[73] Assignee: Xerox Corporation, Stamford, Conn.

221 Filed: Aug. 19, 1970 [21] Appl. No.: 65,052

{52] U.S.Cl ..1l8/637,117/17.5

[51] lnt.C1. ..G03g 13/00 [58] Field of Search ..1 18/636, 637; 117/175, 17; 222/414; 198/54, 57

[56] References Cited UNITED STATES PATENTS 51 May 2, 1972 OTHER PUBLICATIONS R. M. Schaffert, Development of Electrostatic Images, Vol. 4 No. 10 March 1962, IBM Technical Disclosure Bulletin.

Cross, l-lider 81. Medley, Magnetic Bnish Developer," Vol. 9 No. 9 February 1967, IBM Technical Disclosure Bulletin Primary Examiner-Mervin Stein Assistant Examiner-Leo Millstein Attorney-James J. Ralabate, John E. Beck and Irving Keschner [5 7] ABSTRACT A dispenser for replenishing the toner portion of a mixture of toner and carrier, the mixture developing a latent image formed on an image-bearing surface. A container including spaced-apart side walls is positioned adjacent a rotatable member, the bottom of the side walls being shaped to fit the curvature of the member. The toner is introduced into the container and is dispensed as the member is rotated and at a rate proportional to its speed. In a specific embodiment, the amount of toner dispensed is dependent on the density of the developed image and/or the image printing rate.

6 Claims, 3 Drawing Figures Patented May 2, 1-972 2 Sheets-Sheet l INVENTOR. EDWA'RD C. MUTSCHLER ATTORNEY Patented May 2, 1 972 3,659,556

2 Sheets-Sheet 2 TO DRUM 34 f 44 Z 2 86 I i 42 rPULSE/CHARACTER PRINTED To DRUM IL 34 PROGRAMMABLE TONER DISPENSER BACKGROUND OF THE INVENTION In the process of xerography, for example, disclosed in Carlson U.S. Pat. No. 2,297,69l issued Oct. 6, 1942, a xerographic plate, comprising a layer of photoconductive insulating material on a conductive backing, is given a uniform electric charge over its surface and is then exposed to the subject matter to be reproduced, usually by conventional projection techniques. This exposure discharges the plate areas in accordance with the light intensity which reaches it 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 suitable pigmented or dyed electrostatic powder, hereinafter referred to as toner, and a granular carrier material which functions to carry and to generate triboelectric charges on the toner. In the development of the image, the toner powder is brought into surface contact with the coating and is held thereon electrostatically in a pattern corresponding to the electrostatic latent image. Thereafter, the developed image is usually transferred to a support material which may be fixed in any suitable means.

In apparatus such as that disclosed in U.S. Pat. No. 3,045,587, character shaped electrodes rather than light patterns are used to record latent electrostatic images. The latent electrostatic images are produced by electrically pulsing symbol shaped electrode elements or an array of electrode pins which are brought in close proximity to an insulating surface, such as a web of insulating material. The images may be developed in the manner described hereinabove with reference to the xerographic process.

In the mixture of developing material comprising toner particles and carrier material, 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 therebetween. During development, as the powder coated carrier particles roll or tumble over the plate or drum carrying an electrostatic image of opposite polarity to the charge of 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 ofi the drum. As toner powder images are formed, additional toner particles must be supplied to the developing material mixture in proportion to the amount of toner deposited on the drum.

In order to maintain the proper proportion of toner to carrier, a toner dispenser is generally provided to replenish the toner manually or automatically.

The rate at which toner is consumed in the developing operation depends both upon the amount of developing material cascaded onto the drum for development of the electrostatic latent image and on the area of the electrostatic latent image to be developed. In high speed electrostatic printers or copiers where toner consumption is high and relatively variable it is desirable to provide a toner dispensing device which is capable of widely variable toning rates. It is also desirable that the toner dispensing device avoid many of the problems associated with prior art devices.

For example, in the prior art vibrating and variable aperture toner dispensing devices, problems such as compacting, agglomeration, etc. of the toner arise.

The amount of toner present in the developing system affects the quality of copy produced. If there is an excess of toner, non-image areas will pick up toner producing undesirable background. If there is a deficiency of toner in the system,

, 3,376,853 discloses a toner concentration control system in the image will not be fully developed and the copy will be weak and light. In order to continually obtain prints of good quality, the quantity of toner powder in the developing material must be varied by adding toner to the developing material in proportion to the amount of toner deposited on the surface to be developed.

Various prior art devices have been proposed to correct the disadvantages listed hereinabove. For example, U.S. Pat. No.

which a conductive plate within a developer housing is used to sense the amount of toner in the housing. Some of the developing material is directed across the conductive plate which is charged by the toner particles and this charge is utilized to charge a capacitor, the discharge of which serves to produce a control signal. The control signal is generated when the amplitude of the signal produced by the toner is below a pre-set level and causes toner particles to be introduced into the machine dispensing system.

In U.S. Pat. No. 3,348,521 the amount of toner dispensed into the developing housing is in accordance with the density of a developed image upon a xerographic plate. A test or comparison electrostatic image is formed or, used in conjunction with xerographic plate. This image is developed along with the image of a document being reproduced by the xerographic machine. A sensing device in the form of a photocell is also provided for receiving light rays reflected from the developed comparison image and this serves to control current flow in a control circuit. A relay is arranged in the circuit and is adapted to connect a toner dispenser motor to a source of electrical power. A mechanical device is activated which imparts repeated or intermittent actuations to a control plate for V dispensing toner into the developer housing.

reliable and capable of dispensing toner over a wide operating range.

SUMMARY OF THE INVENTION The present invention provides apparatus for dispensing toner into a mixture of carrier and toner at a rate that is programmable. A toner container including spaced-apart side walls is positioned adjacent a rotatable member, the bottom of the sidewalls being shaped to fit the curvature of the rotatable member. Toner is introduced into the top of the container and is dispensed, or carried, on the surface of the rotatable member into the developer material mixture. The toner dispensing rate is proportional to the speed and the amount dispensed varies as the number of revolutions of the rotatable member. The speed of the rotatable member may be dependent upon the density of the developed image and/or the rate of image printing. The rotatable member is partially enveloped by the developer material to enable denuded carrier particles to remove the toner formed on the surface of the rotatable member to complete the dispensing cycle.

It is an object of the present invention to provide improved toner dispensing apparatus for dispensing toner at a programmable rate.

It is a further object of the present invention to provide improved toner dispensing apparatus for utilization in high-speed printers or copiers.

It is still a further object of the present invention to provide simple, economical and reliable toner dispensing apparatus which is capable of variable toning rates.

It is a further object of the present invention to provide new and improved toner dispensing apparatus which substantially reduces agglomeration, compacting or caking of the toner.

It is still a further object of the present invention to provide improved toner dispensing apparatus wherein the toner flow rates are directly controllable and can be programmed to follow the density of the developed image and/or the rate of image printing.

DESCRIPTION OF THE DRAWINGS For a better understanding of the invention as well as other objects and further features thereof, reference is made to the following description which is to be read in conjunction with the accompanying drawings wherein:

FIG. 1 is a schematic sectional view of apparatus for dispensing toner in accordance with the teachings of the present invention;

FIG. 2 is a schematic illustration of one embodiment of control circuitry for controlling the amount of toner dispensed in the apparatus illustrated in FIG. 1', and

FIG. 3 is a schematic illustration of another embodiment of control circuitry for controlling the amount of toner dispensed in the apparatus illustrated in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 1 the novel apparatus of the present invention is illustrated. A latent electrostatic charge pattern is placed upon layer of drum 11 by any conventional technique. For example, the latent electrostatic charge pattern may be formed by the basic xerographic process as described in the aforementioned U.S. Pat. No. 2,297,691. A]- ternately, character shaped electrodes as described in U.S. Pat. No. 3,045,587, rather than light patterns may be used to deposit latent electrostatic images, or characters on layer 10. The latent electrostatic images in the latter technique are produced by electrically pulsing the character shaped electrodes or an array of electrode pins which are brought into close proximity to layer 10. Layer 10 in the latter embodiment may comprise an insulator, such as MYLAR, a polyester film sold by the E. I. duPont deNemours Corporation and comprising a film or thin sheet of polyethylene terephthalate. In the first technique, photoconductive insulating layers such as amorphous selenium, zinc oxide, cadmium sulfide and phthalocyanine in a binder may be utilized. Other insulating materials which have the capability of retaining electrostatic charge for a predetermined period of time when charge is applied thereon may be utilized as layer 10 such as polystyrene polyvinyl chloride, cellulose acetate, acrylic polymers, plastic coated paper, pre-dried uncoated papers or any other suitable insulating sheet material.

A development member 12, such as a fibrous brush, rotates about shaft 14 and is mounted on suitable support means. The fibrous brush picks up developer material and applies it to the latent electrostatic characters, or images, on layer 10, thereby developing the images. A transfer donor roller 16 rotates on shaft 18 and is mounted to a suitable support means so that a portion of its surface is in contact with developer material 22 contained in housing 20. The transfer donor roller 16, made for example of metal such as aluminum, transfers developer material 22 to fibrous member 12 which in turn applies it to the charged surface oflayer 10.

The toner, transfer donor roller surface and the fibrous member may be selected from materials arranged in the triboelectric series as set forth in U.S. Pat. No. 3,251,706 in order that the toner will readily adhere to the transfer donor roller and in turn can be picked up by the fibrous member. Thus, the toner, transfer donor roller surface and the fibrous member are arranged in a triboelectric series with positive polarity (the fibrous member) at the top and negative polarity (the toner) at the bottom or vice versa depending on the toner polarity desired. In this manner, any material placed in contact with another which is below it in the triboelectric series will become positively charged and the material below it in the series will become negatively charged. Thus, if a positively charged electrostatic image is to be developed the electroscopic powder must be charged negatively by contact with a brush material which is above it in the series. The negative electroscopic particles will then be deposited upon the positively charged image by electrical attraction.

The electrostatic transfer described hereinabove may be replaced by mechanical transfer of the developer material by utilizing the metal surface of the transfer donor roller surface, the toner being chosen to charge negatively with the fibrous member.

As set forth hereinabove, as the images on medium 10 are developed, the toner contained within housing is depleted.

It is therefore necessary to replenish the toner as the images are developed.

In accordance with the teachings of the present invention, a novel toner dispenser 30 is provided. The toner dispenser comprises two main parts; a hopper or container 32 and a rotatable member 34, such as a cylindrical drum. The hopper 32 includes spaced-apart

side walls

36 and 38 and in the embodiment illustrated, is a bottomless rectangular box with a hinged lid 40. The bottom of the hopper 32 is shaped to fit the curvature of drum 34 to prevent toner particles from escaping therefrom. Clearance between the bottom of hopper 32 and the drum 34 is provided so that the drum 34 may freely rotate. A clearance of approximately 0.015 inches has been successfully utilized. Toner is introduced into hopper 32 when hinged lid 40 is opened. Gravitational forces act on the toner to direct it to the surface of drum 34. Drum 34, when driven by motor 42, dispenses a thin layer of toner, due to centripetal forces, as drum 34 is rotated. In general, the thickness of the dispensed layer is equal to the clearance between the hopper and drum. The toner dispensing rate is proportional to the speed of the drum and therefore the total amount of toner dispensed varies as the number of revolutions of the drum. In order to avoid compactation of the toner, the

side walls

36 and 38 are wider at the bottom than at the top. This keeps the toner aerated and free flowing and prevents compactation of the toner.

Drum 34 is located in the developer material 22 so that depleted carrier particles circulate around its bottom surface thereby wiping off the toner to complete the toner dispensing action.

As shown in FIG. 1, shaft 44 of motor 42 is rotated by applying a source of electrical energy 46 to the motor. FIG. 2 illustrates a specific embodiment of energy source 46 whereby drum 34 is intermittently rotated at a constant speed dependent upon the image density whereas FIG. 3 illustrates another embodirnent of energy source 46 whereby drum 34 is intermit' tently rotated at a constant speed dependent upon the image, or character, printing rate.

An agitator 48 may be provided for creating a turbulence in the developer material for preventing caking or agglomeration of the toner and to provide a continuous supply of developer material to the donor roller 16. In order to rapidly deliver developer material to donor roller 16, an auger drive system 50 is provided. The auger drive system comprises auger 52, gearing mechanism 54, and motor 56 for driving gearing mechanism 54. The gearing mechanism 54 is coupled to auger 52, the rotation of auger 52 transporting the replenished developer material from the area of drum 34 to the area of housing 20 adjacent donor roller 16.

It should be noted that although layer 10 is illustrated as being formed on drum 11, it is obvious that layer 10 could comprise a sheet or web which is transported past brush 12. In addition, a magnetic brush instead of the fibrous, or fur, brush described hereinabove may be utilized if the latent image is of a negative polarity. Here, instead of carrier particles, an iron powder, which is low in the triboelectric series, is mixed with a low melting pigment resin toner high in the series, which donates electrons to the iron powder, the toner taking on a positive electrostatic charge. The mixture is picked up by the magnetic brush and is swept across the surface of layer 10 to transfer the toner to the negative electrostatic latent image on the surface of layer 10. The magnetic brush is generally composed of a mass of very small iron particles which tend to link up into fibers in the presence of a magnetic field. The iron bristles of the magnetic brush orient themselves along the lines of magnetic force forming a structure which plays the same role as the fibers of the fur brush. When the magnetic carriertoner mixture is picked up by the magnet, the brush is formed of the charged toner particles clinging in random fashion to the iron particle bristles. The developing action of the magnetic brush is similar to the fur brush.

Referring now to FIG. 2, there is shown one embodiment of the energization means 46 shown in FIG. 1 wherein the amount of toner dispensed is dependent on the density of the developed image on layer 10.

In operation, as drum 1] is rotated, the latent electrostatic image thereon is developed by the technique described hereinabove. The developed image is transported by normal rotation of drum 1 1 past sensing device 60. The sensing device 60 includes a lamp shield and a lamp L-l which when energized, is adapted to project light rays onto a portion of the developed image on the drum surface at an angle relative thereto. The sensing device 60 also includes a photocell P-l which is adapted to scan the light rays reflected from the drum surface directed thereon by the light rays emanating from the lamp L-l. The relative positioning of the photocell is such that it will receive light rays reflected from a portion of the developed image. Suitable support means, not shown, may be utilized for mounting the lamp and photocell adjacent drum 11. The amount of light reaching the photocell is determined by the density of the developed electrostatic image as it is scanned by the photocell. The output of the photocell, as is well known, is proportional to the amount of light reaching the photocell. The output of the photocell is coupled to input terminal 70. Capacitor 72 is coupled across terminal 70 and stores a small amount of electrical charge corresponding to the output of photocell 60. A grounded resistor 71 shunts capacitor 72 via switch 74, switch 74 being in the open position. Switch 74 is controlled by relay 76 in a manner described hereinbelow. Capacitor 72 is coupled to signal sensor, or threshold device, 80 which in turn is connected to amplifier 82. Amplifier 82 is utilized to amplify the signal produced by the threshold device 80 and to drive or energize relay 86 having a normally open switch S-l associated therewith. Upon energization of the relay 86, switch S-l closes and source of potential energizes motor 42, thereby rotating member 34 and dispensing toner in a manner described hereinabove.

The charge built up on capacitor 72 is discharged into threshold device 80, the device being selected to generate an output signal when the capacitor discharge, or input signal, applied thereto is beyond a pre-set adjustable level corresponding to a predetermined image density. When the input signal, corresponding to the density of the image on layer 10, is below the pre-set level, an output signal is not produced by the threshold device 80. The output signal is applied to relay 86 via amplifier 82, closing switch S-1 and energizing motor 42. Energization of motor 42 rotates member 34, thereby dispensing toner in small evenly spaced quantities which will effect the density of the developed image in the matter of a few dispensing cycles.

Relay 76 is operated by applying a pulse thereto, the pulse being generated (by means not shown) for each increment of rotation of the rotatable member 34. When relay 76 is operated, switch 74 is closed, and a small amount of charge on capacitor 72 is discharged to ground via resistor 71.

Motor 42 operates intermittently at a constant speed, a speed slightly greater than that needed to supply toner at the highest likely demand rate.

To provide the light rays that must reach the photocell P-l from the developed image on drum 11, the light source L-l is connected to a suitable battery 66 with a manually actuable on-off switch 68 for the lamp. The light source is arranged at an angle relative to the axis of the photocell so that their respective axis intercept on the surface of layer 10.

Referring now to FIG. 3, a second embodiment of the energization means 46 shown in FIG. 1 is illustrated wherein the amount of toner dispensed is also dependent on a desired, or predetermined image density. However, in this embodiment the measured, or actual, image density on the surface of layer is selected to be dependent on the character printing rate. The control circuitry shown in FIG. 3 is substantially identical to the circuitry shown in FIG. 2, the input to terminal 70 being different in each case. In the circuitry of FIG. 3, an electrical pulse is generated for each character printed and applied to input terminal 70, capacitor 72 storing a small amount of electrical charge for each character printed. The control circuitry operates on the input signal applied to terminal in the same manner as described with reference to FIG. 2. The fact that image density is related to the character printing rate is obvious since toner is depleted as each characteris developed.

While the invention has been described with reference to its preferred embodiments, 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.

What is claimed is:

1. A toner dispensing device for use in apparatus for developing latent electrostatic images formed on a surface, said apparatus including means for applying developer materialto said images thereby producing powdered images on said surface comprising:

a container for the toner, the sides of said container being wider at the bottom than at the top,

means for dispensing toner from the container into a reservoir containing a mixture of developer material for replenishing the developing material with toner, said dispensing means comprising a rotatable member adjacent the bottom of said toner container, said rotatable member being cylindrically shaped and the bottom of said container being shaped to fit the curvature of said cylindrical member, the rotation of said member dispensing said toner to said developer material,

drive means coupled to said member for rotating said member at a predetermined speed, and

means for selectively energizing said drive means, whereby said member is rotated at said predetermined speed, the amount of toner dispensed varying as the number of revolutions of said rotatable member.

2. The device as set forth in claim 1 wherein said cylindrical member is partially enveloped by said developer material.

3. The device as set forth in claim 2 wherein said drive means is energized when the density of said developed image is below a predetermined image density.

4. A system for developing latent electrostatic images formed on an image-bearing surface including means for applying developer material to said images thereby producing developed images on said surface comprising:

a toner container, said container including first and second spaced apart side walls and an opening at the bottom of said container for allowing toner to exit therefrom, the bottom of said toner container being shaped to fit the curvature of a cylindrically shaped member positioned adjacent thereto, and the space between said side walls being greater at the bottom of said side walls than at the top,

means for dispensing toner from said container into a reservoir containing a mixture of developer material, said dispensing means comprising a rotatable cylindrical member positioned adjacent said bottom opening,

drive means coupled to said member for rotating said member at a predetermined speed,

means for selectively energizing said drive means whereby said member is rotated at said predetermined speed, the amount of toner dispensed varying as the number of revolutions of said rotatable member, and

means for circulating said developer material between said reservoir and said applying means.

5. The system as set forth in claim 4 wherein said cylindrical member is partially enveloped by said developer material.

6. The device as set forth in claim 5 wherein said drive means is energized when the density of said developed image is below a predetermined image density.

Claims

1. A toner dispensing device for use in apparatus for developing latent electrostatic images formed on a surface, said apparatus including means for applying developer material to said images thereby producing powdered images on said surface comprising: a container for the toner, the sides of said container being wider at the bottom than at the top, means for dispensing toner from the container into a reservoir containing a mixture of developer material for replenishing the developing material with toner, said dispensing means comprising a rotatable member adjacent the bottom of said toner container, said rotatable member being cylindrically shaped and the bottom of said container being shaped to fit the curvature of said cylindrical member, the rotation of said member dispensing said toner to said developer material, drive means coupled to said member for rotating said member at a predetermined speed, and means for selectively energiziNg said drive means, whereby said member is rotated at said predetermined speed, the amount of toner dispensed varying as the number of revolutions of said rotatable member.

4. A system for developing latent electrostatic images formed on an image-bearing surface including means for applying developer material to said images thereby producing developed images on said surface comprising: a toner container, said container including first and second spaced apart side walls and an opening at the bottom of said container for allowing toner to exit therefrom, the bottom of said toner container being shaped to fit the curvature of a cylindrically shaped member positioned adjacent thereto, and the space between said side walls being greater at the bottom of said side walls than at the top, means for dispensing toner from said container into a reservoir containing a mixture of developer material, said dispensing means comprising a rotatable cylindrical member positioned adjacent said bottom opening, drive means coupled to said member for rotating said member at a predetermined speed, means for selectively energizing said drive means whereby said member is rotated at said predetermined speed, the amount of toner dispensed varying as the number of revolutions of said rotatable member, and means for circulating said developer material between said reservoir and said applying means.