GB2118124A

GB2118124A - Transporting particles

Info

Publication number: GB2118124A
Application number: GB8221204A
Authority: GB
Inventors: James M Hoffman
Original assignee: Xerox Corp
Current assignee: Xerox Corp
Priority date: 1981-07-30
Filing date: 1982-07-22
Publication date: 1983-10-26
Also published as: JPS5827169A; GB2118124B; CA1217044A

Abstract

Apparatus is described for transporting particles as well as apparatus for dispensing particles which incorporates the transporting apparatus. Particle dispensing apparatus as described may be incorporated in developer apparatus of an electrostatographic copier for dispensing toner. An auger (82), coupled to a hopper (78) storing toner particles, dispenses toner particles through apertures (88) substantially uniformly into a developer material. Fibers (96) contact the moving toner particles to induce relative movement between the toner particles and auger (82) in a direction substantially normal to the direction of translation thereof. The fibers (96) also apply a force on the toner particles which prevents the particles clogging during the discharge thereof. <IMAGE>

Description

SPECIFICATION A particle transporting and dispensing apparatus This invention relates to particle transporting apparatus, to particle dispensing apparatus incorporating such transporting apparatus and to development apparatus for an electrophotographic printing machine incorporating such dispensing apparatus.

Generally, the process of electrophotographic printing includes charging a photoconductive member to a substantially uniform potential so as to sensitize the surface thereof. The charged portion of the photoconductive surface is exposed to a light image of an original document being reproduced. This records an electrostatic latent image on the photoconductive member corresponding to the informational areas contained within an original document. After the electrostatic latent image is recorded on the photoconductive member, the latent image is developed by bringing a developer material into contact therewith. This forms a toner powder image on the photoconductive member which is subsequently transferred to a copy sheet. Finally, the powder image is heated to permanently affix it to the copy sheet in image configuration.

A suitable developer material generally comprises carrier granules having toner particles adhering triboelectrically thereto. This twocomponent mixture is brought into contact with the electrostatic latent image recorded on the photoconductive surface. A portion of the toner particles are attracted from the carrier granules to the latent image. These toner particles adhere to the latent image so as to form a powder image on the photoconductive surface.

Various methods have been devised for applying developer material to the latent image.

For example, the developer material may be cascaded over the latent image with the toner particles being attracted from the carrier granules thereto. Other techniques utilize magnetic field producing devices which form brush-like tufts extending outwardly therefrom into contact with the photoconductive surface. In any event, it is apparent that during the development process, toner particles are depleted from the developer material. Thus, additional toner particles must be furnished to the developer materials so as to maintain copy density at a substantially optimum level. Typically, a supply of toner particles is stored in a hopper and periodically or continuously dispensed therefrom into the developer material.

Various approaches have been devised for dispensing toner particles into the developer material. The following disclosures appear to be relevant: U.S. Patent 3659556 describes a development system in which toner particles are dispensed into a developer mixture. An auger drive system transports the developer mixture to a donor roll.

U.S. Patent 4142655 discloses a pair of flexible augers for transporting toner particles from a remote container to a toner dispenser positioned adjacent to the development system.

Japanese Laid-open Publication No.

50-29145 describes a toner container having a rotary driven vaned member located in the opening thereof for dispensing particles into a supply passage. A screw conveyor moves the toner particles to the developing unit.

IBM Technical Disclosure Bulletin, Vol. 1 5, No.

4, September 1972, page 1262, discloses a flexible auger for transporting toner particles from a first station to a second station located within an office copying machine.

Copending U.S. Application No. 104225 discloses a toner particle dispenser having a hopper storing a supply of toner particles therein.

An auger is coupled to the hopper for receiving the toner particles and uniformly dispensing them into the sump of a housing having developer material therein.

From one aspect, the invention consists in apparatus for transporting particles, including: means having an entrance region and at least one exit region for moving particles received at the entrance region and at least one exit region for moving particle received at the entrance region to the exit region; and means for producing relative movement between the particles and said moving means in a direction substantially normal to the direction of movement of the particles between the entrance region and exit region of said moving means so as to advance the particles received at the entrance region to the exit region.

From another aspect, the invention consists in apparatus for dispensing particles, including: means, defining an open ended chamber, for storing a supply of particles therein; means, having an entrance region and at least one exit region, for moving particles received at the entrance region from the open end of the chamber of said storing means; and means for producing relative movement between the particles and said moving means in a direction substantially normal to the direction of movement of the particles between the entrance region and the exit region of said moving means so as to advance the particles received at the entrance region to the exit region for discharge thereat.

From a further aspect, the invention consists in an apparatus for developing an electrostatic latent image recorded on a photoconductive member employed in an electrophotographic printing machine, including means for transporting a developer material of carrier granules and toner particles into contact with the electrostatic latent image, so that a portion of the toner particles are attracted from the carrier granules to the electrostatic latent image to form a toner powder image on the photoconductive member, and particle dispensing apparatus as described above for replenishing the toner particles used in the formation of the toner powder image on the photoconductive member.

In order that the invention may be more readily understood, reference will now be made to the accompanying drawings, in which: Figure 1 is a schematic elevational view depicting an illustrative electrophotographic printing machine incorporating the features of the present invention therein; Figure 2 is a schematic elevational view showing a development system used in the Figure 1 printing machine; Figure 3 is a schematic elevational view illustrating the toner particle dispensing system used in the Figure 2 development system; and Figure 4 is a fragmentary elevational view depicting a portion of the Figure 3 toner particle dispensing system.

Referring to Figure 1 , the electrophotographic printing machine employs a belt 10 having a photoconductive surface 12 deposited on a conductive substrate 14. Preferably, photoconductive surface 12 is made from a selenium alloy with conductive substrate 14 being made from an aluminum alloy which is electrically grounded. Other suitable photoconductive surface and conductive substrates may also be employed.

Belt 10 moves in the direction of arrow 16 to advance successive portions of photoconductive surface 1 2 through the various processing stations disposed about the path of movement thereof. As shown, belt 10 is entrained about stripping roller 1 8, tension roller 20 and drive roller 22. Drive roller 22 is mounted rotatably and in engagement with belt 1 0. Motor 24 rotates roller 22 to advance belt 10 in the direction of arrow 1 6.

Roller 22 is coupled to motor 24 by a suitable means such as a drive belt. Drive roller 22 includes a pair of opposed spaced edge guides. The edge guides define a space therebetween which determines the desired path of movement of belt 10. Belt 10 is maintained in tension by a pair of springs (not shown) resiliently urging tension roller 20 against belt 10 with the desired spring force.

Both stripper roller 1 8 and tension roller 20 are mounted rotatably. These roilers are idlers which rotate freely as belt 10 moves in the direction of arrow 16.

With continued reference to Figure 1, initially a portion of belt 10 passes through charging station A. At charging station A, a corona generating device, indicated generally by the reference numeral 16, charges photoconductive surface 12 of belt 10 to a relatively high, substantially uniform potential.

Next, the charged portion of photoconductive surface 12 is advanced through exposure station B. At exposure station B, an original document 28 is positioned facedown upon a transparent platen 30. Lamps 32 flash light rays onto original document 28. The light rays reflected from original document 28 are transmitted through iens 34 forming a light image thereof. Lens 34 focuses the light image onto the charged portion of photoconductive surface 12 to selectively dissipate the charge thereon. This records an electrostatic latent image on photoconductive surface 1 2 which corresponds to the informational areas contained within original document 28 disposed upon transparent platen 30. Thereafter, belt 10 advances the electrostatic latent image recorded on photoconductive surface 1 2 to development station C.At development station C, a magnetic brush development system, indicated generally by the reference numeral 36, transports a developer mixture of carrier granules and toner particles into contact with the electrostatic image recorded on photoconductive surface 12.

Magnetic brush development system 36 includes a magnetic brush developer roller 38. Magnetic brush developer roller 38 forms a brush of carrier granules and toner particles. The toner particles are attracted from the carrier granules to the electrostatic latent image forming a toner powder image on photoconductive surface 1 2 of belt 10.

The detailed structure of magnetic brush development system 36 will be described hereinafter with reference to Figure 2.

After development, belt 10 advances the toner powder image to transfer station D. At transfer station D, a sheet of support material 40 is moved into contact with the toner powder image. The sheet of support material is advanced to transfer station D by a sheet feeding apparatus, indicated generally by the reference numeral 42. Preferably, sheet feeding apparatus 42 includes a feed roller 44 contacting the uppermost sheet of a stack of sheets 46. Feed roller 44 rotates to advance the uppermost sheet from stack 46 into chute 48.

Chute 48 directs the advancing sheet of support material into contact with photoconductive surface 1 2 of belt 10 in a timed sequence so that the toner powder image developed thereon contacts the advancing sheet of support material at transfer station D.

Transfer station D includes a corona generating device 50 which sprays ions onto the backside of sheet 40. This attracts the toner powder image from photoconductive surface 12 to sheet 40.

After transfer, the sheet continues to move in the direction of arrow 52 onto a conveyor (not shown) which advances the sheet to fusing station E.

Fusing station E includes a fuser assembly indicated generally by the reference numeral 54 which permanently affixes the transferred toner powder image to sheet 40. Preferably, fuser assembly 54 includes a heated fuser roll 56 and a back-up roll 58. Sheet 40 passes between fuser roll 56 and back-up roll 58 with the toner powder image contacting fuser roll 56. In this manner, the toner powder image is permanently affixed to sheet 40. After fusing, chute 60 guides the advancing sheet to catch tray 62 for subsequent removal from the printing machine by the operator.

Invariably, after the sheet of support material is separated from photoconductive surface 12 of belt 10, some residual particles remain adhering thereto. These residual particles are removed from photoconductive surface 1 2 at cleaning station F.

Cleaning station F includes a pre-clean corona generating device (not shown) and a rotatably mounted fibrous brush 64 in contact with photoconductive surface 12. The pre-clean corona generator neutralizes the charge attracting the particles to the photoconductive surface. These particles are cleaned from photoconductive surface 1 2 by the rotation of brush 64 in contact therewith. Subsequent to cleaning, a discharge lamp (not shown) floods photoconductive surface 12 with light to dissipate any residual charge remaining thereon prior to the charging thereof for the next successive imaging cycle.

Referring now to Figure 2, there is shown development system 36 in greater detail. As depicted therat, development system 36 includes a developer roller 38 having a non-magnetic tubular member 66. An elongated magnetic member 68 is positioned interiorly of tubular member 66 and spaced from the interior peripheral surface thereof. Tubular member 66 rotates in the direction of arrow 70 so as to advance the developer material into contact with the electrostatic latent image recorded on photoconductive surface of belt 10. As tubular member 66 rotates in the direction of arrow 70, it passes through the sump of chamber 72 in housing 74. Developer material, disposed in chamber 72, is attracted to tubular member 66 via the magnetic field generated by elongated magnetic member 68.In this manner, the developer material is attracted to tubular member 66 and advances therewith into contact with the electrostatic latent image recorded on photoconductive surface 1 2 of belt 1 0. The electrostatic latent image attracts the toner particles from the developer material. Thus, toner particles are being continually depleted from the developer material. If additional toner particles were not furnished to the developer material, eventually the copies would become progressively lighter and degradate in quality. To this end, a toner particle dispenser, indicated generally by the reference numeral 76, furnishes additional toner particles to chamber 72 of housing 74. Toner particle dispenser 76 includes a hopper 78 storing a supply of toner particles in chamber 80 thereof.

The lower end portion of chamber 80 has an aperture with the entrance port of auger 82 being disposed thereat. Auger 82 includes a tubular member having a plurality of apertures therein and a helical member. As the helical member rotates, it advances the toner particles from hopper 80 along the tube thereof. The toner particles move along the tube and are dispensed through the apertures therein. A multiplicity of fibers engage the moving toner particles to induce slip between the toner particles and helical member in a direction substantially normal to the direction of movement thereof. This prevents the toner particles from only rotating with the helical member and insures that they translate as well.

The detailed structure of toner dispenser 76 will be described hereinafter with reference to Figures 3 and 4.

By way of example, elongated magnetic member 68 is cylindrical and preferably made from barrium ferrite having â plurality of magnetic poles impressed about the circumferential surface thereof. Tubular member 66 is made preferably from aluminum having the exterior circumferential surface thereof roughened.

Referring now to Figure 3, toner particles in chamber 80 of hopper 78 descend into entrance port 84 of auger 82. Auger 82 includes a tubular member 86 extending across chamber 72 (Figure 2) of housing 74 (Figure 2). In this way, toner particles are substantially uniformly discharged across chamber 72 of housing 74. This facilitates the mixing of the toner particles with the denuded carrier granules. Tubular member 86 includes a plurality of substantially equally spaced apertures 88 therein. Helical member 90 is disposed interiorly of tubular member 86. As helical member 90 rotates, toner particles are advanced in the direction of arrow 92. Motor 94 is coupled to helical member 90. Actuation of motor 94 causes helical member 90 to rotate.A multiplicity of substantially flexible fibers extend inwardly from the region of tubular member 86 substantially opposed to the region thereof having apertures 88 therein. The free marginal end region of fibers 96 contact helical member 90. Flexible fibers 96 apply a force on the toner particles substantially normal to the direction of movement thereof. In this way, slip is induced between the toner particles and helical member 90. This insures that the toner particles do not only rotate with helical member 90, but are translated therealong as well. Furthermore, this normal force also prevents the toner particles from clogging apertures 88 in tubular member 86 facilitating the dispensing of the toner particles therethrough.

As shown in Figure 4, flexible fibers 96 are secured to an elongated member 98. Member 98 extends in the direction substantially parallel to the longitudinal direction of tubular member 86.

One end portion of flexible fibers 96 is secured to elongated member 98, via ultrasonic bonding.

Flexible fibers 96 extend downwardly through a slot 100 in tubular member 86. Elongated member 98 is mounted on tubular member 86 and positioned over slot 100. As helical member 90 rotates in the direction of arrow 102, the free marginal end regions 104 of flexible fibers 96 are in engagement therewith. Furthermore, flexible fibers 96 contact the toner particles which are rotating with helical member 90 in the direction of arrow 102. Flexible fibers 96 apply a force to the toner particles in a direction opposite to that of arrow 1 02. This force is substantially normal to the desired direction of translation of the toner particles, indicated by arrow 92 (Figure 3). Thus, slip is induced between the toner particles and helical member 90.It is apparent that if slip is not induced between the toner particles and helical member 90, the toner particles will merely rotate with helical member 90 and not translate in the direction of arrow 92. Hence, it is necessary to induce slippage between helical member 90 and the toner particles to insure the translation thereof in the direction of arrow 92. Furthermore, the force applied on the toner particles by fiber 96 prevents clogging of the exit ports, i.e. apertures 88 in tubular member 86. Clogging and lack of slippage will cause system failure, i.e. clogging and failure to transport the toner particles at a high relative humidity and temperature condition.

By way of example, for a helical member having an outer diameter of about 20.1 millimeters and a minor diameter of about 12.6 millimeters, the fibers are about 6 millimeters long having a clearance of about 1 millimeter from the helical member's minor diameter and extend about 4 millimeters into the tubular member. The fibers extend, in a longitudinal direction, about 232 millimeters. Fiber density is about 30 fibers per centimeters with each fiber being about 0.2 millimeters in diameter. Preferably, each fiber is made from a plastic material.

It is clear that the fibers maintain a shear plane or slip plane in the toner particles adjacent the helical member's minor diameter to control the effective volume of toner particles being transported by the helical member. If the slip plane is largely removed from the helical member's minor diameter, the effective volume of toner particles being transported by the helical member is reduced. This results in radical changes in the rate of dispensing toner particles. These changes are unacceptable in the system. When fibers are not being employed, the rate of dispensing toner particles is greatly reduced at high relative humidity and temperature conditions. Due to the cohesive nature of the toner particles in the operating environment, the slip plane varies radically without the use of fibers. This causes clogging of the dispenser.Furthermore, as the slip plane becomes further removed from the minor diameter of the helical member, the effective volume of toner particles being transported becomes smaller. Testing has shown that without the use of fibers, the dispense rate will be reduced dramatically in stress environmental conditions, i.e. 800 F, 80% relative humidity.

While the present invention has been described as being employed in a toner particle dispensing, it will be appreciated that it may be utilized in any system for moving granular particles from an entrance port to an exit port wherein a helical member is utilized to induce translation of the particles. It is essential that slippage occur between the particles and the helical member to insure translation thereof. The present invention induces slip or relative movement between the helical member and particles to insure translation of the particles.

In recapitulation, it is clear that the dispensing apparatus of the present invention includes a hopper storing a supply of toner particles therein and an auger for dispensing the toner particles substantially uniformly throughout the chamber of a developer housing. In order to provide for the uniform dispensing of the toner particles, slip is induced between the toner particles and the helical member to insure translation of the toner particles along a tubular member having a plurality of substantially equally spaced apertures therein.

In this way, precise quantities of toner particles are metered from the apertures substantially uniformly across the developer housing.

Claims

1. An apparatus for transporting particles, including: means having an entrance region and at least one exit region for moving particles received at the entrance region to the exit region; and means for producing relative movement between the particles and said moving means in a direction substantially normal to the direction of movement of the particles between the entrance region and exit region of said moving means so as to advance the particles received at the entrance region to the exit region.

2. An apparatus according to Claim 1, wherein said producing means includes means for inducing slip between said moving means and the particles in the direction substantially normal to the direction of movement of the particles between the entrance region and exit region of said moving means.

3. An apparatus according to Claim 1 or 2, wherein said moving means includes: a substantially tuuular member having an entrance port for receiving particles and at least one exit port; and elongated helical member disposed interiorally of said tubular member; and means for rotating said helical member to move particles along said tubular member for the entrance port to the exit port.

4. An apparatus according to Claim 3, wherein slip inducing means includes a multiplicity of flexible fibers extending in a longitudinal direction radially and inwardly along said tubular member with the free region of said fibers contacting the particles.

5. An apparatus according to Claim 4, wherein: said tubular member includes an elongated slot extending in a direction substantially parallel to the longitudinal axis thereof; and said slip inducing means includes an elongated member having one end of said fibers secured thereto, said elongated member being mounted on said tubular member so that said fibers secured thereto extend through the slot in said tubular member with the free region of said fibers contacting the particles therein.

6. An apparatus according to Claim 1, wherein said producing means applies a force on the particles in a direction substantially normal to the direction of movement of the particles between the entrance region and exit region of said moving means so as to minimize clogging of the exit region by particles.

7. An apparatus for dispensing particles, including: means, defining an open ended chamber, for storing a supply of particles therein; means, having an entrance region and at least one exit region, for moving particles received at the entrance region from the open end of the chamber of said storing means; and means for producing relative movement between the particles and said moving means in a direction substantially normal to the direction of movement of the particles between the entrance region and the exit region of said moving means so as to advance the particles received at the entrance region to the exit region for discharge thereat.

8. An apparatus according to Claim 7, wherein said producing means includes means for inducing slip between said moving means and the particles in the direction substantially normal to the direction of movement of the particles between the entrance region and exit region of said moving means.

9. An apparatus according to Claim 7 or 8, wherein said moving means includes: a substantially tubular member having an entrance port in communication with the opened end of the chamber of said storing means for receiving particles therefrom and a plurality of substantially equally spaced apertures therein for dispensing particles therefrom; an elongated helical member disposed interiorally of said tubular member; and means for rotating said helical member to move particles along said tubular member for discharge from the apertures therein.

10. An apparatus according to Claim 9, wherein slip inducing means includes a multiplicity of flexible fibers extending in the longitudinal direction radially inwardly along said tubular member with the free region of said fibers contacting the particles.

11. An apparatus according to Claim 10, wherein: said tubular member includes an elongated slot extending in a direction substantially parallel to the longitudinal axis in the region of the circumferential surface thereof opposed from the region of the dispensing apertures therein; and said slip inducing means includes an elongated member having one end of said fibers secured thereto, said elongated member being mounted on said tubular member so that said fibers secured thereto extend through the slot in said tubular member with the free region of said fibers contacting the particles therein.

12. An apparatus according to Claim 7, wherein said producing means applies a force on the particles in a direction substantially normal to the direction of movement of the particles between the entrance region and exit region of said moving means so as to minimize clogging of the exit region by the particles being discharged thereat.

1 3. An apparatus for dispensing particles, constructed, arranged and adapted to operate substantially as hereinbefore described with reference to the accompanying drawings.

14. An apparatus for developing an electrostatic latent image recorded on a photoconductive member employed in an electrophotographic printing machine, including means for transporting a developer material of carrier granules and toner particles into contact with the electrostatic latent image so that a portion of the toner particles are attracted from the carrier granules to the electrostatic latent image forming a toner powder image on the photoconductive member; and apparatus for dispensing particles according to any of claims 7 to 1 3 for replenishing the toner particles used in the formation of the toner powder image on photoconductive member.