[0001] This invention relates particle dispensing apparatus for furnishing toner particles
to a developer material in a housing which apparatus is particularly suitable for
use in an electrophotographic printing machine.
[0002] Generally, the process of electrophotographic printing includes charging a photoconductive
member to a substantially uniform potential to sensitize the surface thereof. The
charged portion of the photoconductive member 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 the 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 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.
[0003] A suitable developer material frequently comprises carrier granules having toner
particles adhering triboelectrically thereto. This two- component mixture is brought
into contact with the photoconductive surface. 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.
[0004] 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 contacting the photoconductive surface. In any system, it is apparent that
during the development process, toner particles are depleted from the developer material.
Thus, additional toner particles must be furnished to maintain copy density at a substantially
optimum level. In order to produce an efficient printing machine, it is necessary
to conveniently and effectively replace the toner particles used during the formation
of the copies. Hereinbefore, toner particles have been dispensed from a trough or
hopper into the developer material. Frequently, the toner particles are dispensed
in a non-uniform manner. Variations in toner particle dispensing may effect the resultant
copy quality. Various approaches have been devised to dispense toner particles from
a hopper. The following disclosures appear to be relevant:
[0005] US-A-3659556 describes a development system in which toner particles are dispensed
into a developer material. An auger drive system transports the developer material
to a donor roll.
[0006] US-A-4142655 discloses a pair of flexible augers for transporting toner particles
from a remote container to a toner dispenser positioned adjacent the development system.
[0007] Japanese laid-open publication No. 50-29145 describes a toner container having a
rotary driven vaned member located in the opening thereof for dispensing toner particles
into a supply passage. A screw conveyor moves the toner particles to the developing
unit.
[0008] IBM Technical Disclosure Bulletin, Volume 15, 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.
[0009] Particle dispensing apparatus according to this invention is characterised by means
for receiving toner particles from the storing means and a portion of the developer
material from the housing, for intermingling the received toner particles and developer
material with one another and advancing the received toner particles and developer
material to the developer material remaining in the housing.
[0010] The present invention also provides an apparatus for developing an electrostatic
latent image recorded on a photoconductive member, including a housing defining a
chamber for storing a supply of developer material therein, means, disposed in the
chamber of the housing, for transporting developer material into contact with the
photoconductive member to develop the electrostatic latent image recorded thereon,
and particle dispensing apparatus as described above for furnishing toner particles
to developer material in said chamber.
[0011] In order that the present invention may be more readily understood, reference will
now be made to the accompanying drawings, in which:
Figure is a schematic elevational view illustrating an electrophotographic printing
machine incorporating particle dispensing apparatus of the present invention therein;
Figure 2 is a schematic elevational view depicting the development system used in
the Figure printing machine; and
Figure 3 is a fragmentary, side elevational view of the particle dispenser used in
the Figure 2 development system.
[0012] Referring to Figure 1, the electrophotographic printing machine employs a belt 10
having a photoconductive surface 12 deposited on a conductive substrate. Preferably,
photoconductive surface 12 is made from a selenium alloy with conductive substrate
14 being made from an electrically grounded aluminum alloy. Other suitable photoconductive
surfaces and conductive substrates may also be employed. Belt 10 moves in the direction
of arrow 16 to advance successive portions of photoconductive surface 12 through the
various processing stations disposed about the path of movement thereof. As shown,
belt 10 is entrained about a stripping roller 18, tension roller 20 and drive roller
22. Drive roller 22 is mounted rotatably and in engagement with belt 10. Motor 24
rotates roller 22 to advance belt 10 in the direction of arrow 16. Roller 22 is coupled
to motor 24 by 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 stripping roller 18 and tension roller 20 are mounted rotatably.
These rollers are idlers which rotate freely as belt 10 moves in the direction of
arrow 16.
[0013] 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 26, charges photoconductive surface 12 of belt 10 to a relatively
high, substantially uniform potential.
[0014] 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 lens 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 corresponding to the informational areas contained within
the original document on photoconductive surface 12. Thereafter, belt 10 advances
the electrostatic latent image recorded on photoconductive surface 12 to development
station C.
[0015] At development station C, a magnetic brush development system, indicated generally
by the reference numeral 36, transports a developer material of carrier granules and
toner particles into contact with photoconductive surface 12. Magnetic brush development
system 36 includes a developer roller 38 which advances the developer material into
contact with photoconductive surface 12. The developer roller forms a brush comprising
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 12 of belt 10. The detailed structure of magnetic brush development system
36 will be described hereinafter with reference to Figure 2.
[0016] 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 42. Preferably, sheet feeding apparatus 42 includes
a feed roll 44 contacting the uppermost sheet of stack 46. Feed roll 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 12 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.
[0017] Transfer station D includes 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.
[0018] Fusing station E includes a fuser assembly, indicated generally by the reference
numeral 54, which permanently affixes the transfered toner powder image to sheet 40.
Preferably, fuser assembly 54 includes a heated fuser roller 56 and a back up roller
58. Sheet 40 passes between fuser roller 56 and back up roller 58 with the toner powder
image contacting fuser roller 56. In this manner, the toner powder image is permanently
affixed to sheet 40. After fusing, chute 60 guides the advancing sheet 40 to catch
tray 62 for subsequent removal from the printing machine by the operator.
[0019] 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 12 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 generating device neutralizes the charge attracting the particles to the photoconductive
surface. These particles are then cleaned from photoconductive surface 12 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.
[0020] Referring now to Figure 2, there is shown development system 36 in greater detail.
As depicted thereat, 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 periphery 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 12
of belt 10. Magnetic member 68 has a plurality of magnetic poles impressed about a
portion thereof. Thus, as tubular member 66 rotates in the direction of arrow 70,
it passes through the developer material in chamber 72 of 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 12 of belt 10. The electrostatic latent
image attracts some 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 development material, eventually the copies would become
progressively lighter and degradated in quality. The denuded development material
advances with tubular member 66 in the direction of arrow 70 until the magnetic field
produced by elongated magnetic member 68 no longer attracts the material thereto.
At this time, the denuded developer material falls freely from tubular member 66.
Some of the developer material passes into auger 76 of the toner dispenser, indicated
generally by the reference numeral 78. Toner dispenser 78 includes a hopper 80 storing
a supply of toner particles in chamber 82. The lower end portion of chamber 82 has
an opening with auger 84 being positioned thereat. Auger 84 meters precise quantities
of toner particles from chamber 82 of hopper 80. The toner particles are advanced
to auger 76 which intermingles developer material and denuded carrier granules with
the toner particles. Auger 76 substantially uniformly dispenses the mixture of developer
material and t&r.&r particles into chamber 72 of housing 74 to maintain the concentration
of toner particles within the developer material substantially constant. Agitator
88 positioned in chamber 82 of housing 80 rotates to prevent bridging and caking of
the toner particles therein.
[0021] By way of example, elongated magnetic member 68 is a cylindrical member being made
preferably from barrium ferrite having a plurality of magnetic poles impressed about
a portion of the circumferential surface thereof. Tubular member 66 is made preferably
from aluminum having the exterior circumferential surface thereof roughened.
[0022] Turning now to Figure 3, there is shown the detailed structure of toner dispenser
78. As shown thereat, agitator 88 comprises a rectangular frame 90 having shafts 92
extending outwardly therefrom. Shafts 92 are supported in bearings 94 mounted in the
lower portion of hopper 80. One shaft has a gear 96 secured thereto. Auger 84 includes
an enclosure 86 having an entrance port 98 disposed in the opening of hopper 80 so
as to receive toner particles being discharged from chamber 82. Enclosure 86 also
has an exit port 100 for discharging a precisely metered quantity of toner particles
into auger 76. Auger 84 includes a stationary shaft 102 extending in a longitudinal
direction interiorly of enclosure 86. Helical member 104 is entrained about stationary
shaft 102 and is adapted to rotate relative thereto. One end of helical member 104
is secured to shaft 106. Shaft 106 is supported in bearings 108 mounted in enclosure
86. Gear 110 is secured to shaft 106 and meshes with gear 96. Auger 76 includes a
trough 112 having an entrance port 113 coupled to exit port 100 of auger 84. Thus,
toner particles being metered from chamber 82 of hopper 80 are advanced along auger
84 and metered to auger 76. In addition, entrance port 100 receives developer material
and denuded carrier granules from tubular member 66 (Figure 2). This mixture of material
is intermingled and advanced by auger 76 so as to be dispensed substantially uniformly
therefrom into chamber 72 of housing 74 for replenishing the toner particles of the
developer material contained therein. Auger 76 includes a shaft 114 having a helical
member 116 secured thereto. Alternatively, shaft 114 may be omitted in lieu of a helical
coil spring which may be used for auger 76. Helical member 116 is disposed interiorly
of tubular member 112. Bearings 118 support shaft 114 in frame 120. Gear 122 is mounted
on shaft 114 and meshes with gear 110. Motor 124 rotates shaft 114 and, in turn, gear
122. In this way, gears 110 and 96 are also driven so as to rotate helical members
116 and 104 as well as rectangular frame 90.
[0023] In operation, toner particles in chamber 82 of hopper 80 are continuously agitated
by the rotation of frame 90. These toner particles descend through the opening in
hopper 80 into entrance port 98 of enclosure 86. Helical member 104 meters and advances
precise quantities of toner particles to exit port 100. The toner particles then fall
from exit port 100 into entrance port 113 of trough 112. Entrance port 113 also receives
developer material from tubular member 66. This combination of materials is advanced
by helical member 116 along trough 112 so as to be discharged over the downward sloped
edge 126 of trough 112. Inasmuch as trough 112 extends across chamber 72 of housing
74, the combination of toner particles and carrier granules is dispensed substantially
uniformly over front edge 126. The slope of edge 126 of trough 112 is shaped to provide
for substantially uniform dispensing of toner particles along the length of trough
112. This maintains the concentration of toner particles within the developer material
substantially constant.
[0024] In normal operation, motor 124 is continuously energized so as to continuously dispense
toner particles into the chamber of the developer housing. The dispensing rate corresponds
with the usage rate. However, actuation of motor 124 is initiated when the print button
of the printing machine is depressed.
[0025] The intermingling of toner particles with carrier granules and developer material
greatly facilitates the uniformity of dispensing. The carrier granules aid in the
movement of the toner particles. Furthermore, the carrier granules tend to minimize
jamming and clogging of the toner particles as they are being advanced.
[0026] It will be appreciated that a pair of auger systems are not necessarily required
and that a single shaft auger system having different outer and inner diameters and
pitches may be employed in lieu thereof. Thus, there would be one pitch and diameter
in the toner metering zone and a different pitch and diameter in the toner transport
and dispense zone. In addition to facilitating the advancement of the toner particles
during the dispensing operation, the intermingling of the carrier granules therewith
premixes the developer material prior to the dispensing thereof into the chamber of
the housing storing the main supply of developer material.
[0027] 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 metering
precise quantities of toner particles therefrom. The auger advances the toner particles
into a dispensing auger which intermingles a small quantity of developer material
received from the developer roller with the toner particles. This mixture is then
advanced so as to be discharged substantially uniformly into the chamber of the developer
housing for intermingling with the remaining developer material. In this manner, premixing
of the developer material is achieved and the flowability of the toner particles greatly
enhanced.
1. Particle dispensing apparatus for furnishing toner particles to a developer material
in a housing (74), including means (80) for storing a supply of toner particles; and
characterised by means (76) for receiving toner particles from said storing means
(80) and a portion of the developer material from the housing (74), for intermingling
the received toner particles and developer material with one another and advancing
the received toner particles and developer material to the developer material remaining
in the housing (74).
2. Apparatus according to claim 1, wherein said intermingling and advancing means
(76) includes:
means (76) for discharging the received toner particles and developer material into
the remaining developer material in the housing (74); and
means (84) for transporting (80) toner particles from said storing means to said discharging
means (76).
3. Apparatus according to claim 2, wherein said transporting means (84) includes:
an enclosure (86) having an entrance aperture (98) for receiving toner particles from
said storing means (80) and an exit aperture (100) for dispensing toner particles
to said discharging means (76);
a stationary shaft (102) disposed interiorly of said enclosure (86);
a helical member (104) mounted rotatably on said shaft (102); and
means (106) for rotating said helical member (104) relative (102) to said shaft (102)
to transport toner particles received at the entrance aperture (98) of said enclosure
to (100) the exit aperture thereof.
4. Aapparatus according to claim 3, wherein said discharging means (76) includes:
a trough (112) having an entrance port (113) coupled to the exit aperture (100) of
said enclosure (86) with a portion of the entrance port (113) of said trough (112)
being arranged to receive developer material from the housing (74), said trough (112)
having a sloping edge for discharging the received toner particles and developer material
to the remaining developer material in the housing (74);
a helical member (116) mounted rotatably in said trough (112); and
means (114) for rotating said helical member (116) relative to said trough (112) to
move the received toner particles and developer material therealong for discharge
over the sloping edge thereof to the remaining developer material in the housing (74).
5. Apparatus according to claims 1, 2 or 4, further including means (90), operatively
associated with said storing means (80), for agitating the tener particles therein
to facilitate dispensing therefrom.
6. Apparatus for developing an electrostatic latent image recorded on a photoconductive
member, including:
a housing defining a chamber for storing a supply of developer material therein;
means, disposed in the chamber of said housing, for transporting developer material
into contact with the photoconductive member to develop the electrostatic latent image
recorded thereon; and
particle dispensing apparatus according to any preceding claim for furnishing toner
particles to developer material in said chamber.