Fiber cleaning system for a development system

An apparatus in which an elecrostatic latent image recorded on a photoconductive member is developed with developer material stored in a developer housing. The developer material advances along a path of travel to a development zone closely adjacent to the latent image. A cleaner, positioned in the path of the developer material and spaced from the photoconductive member, cleans contaminants from the developer material without impeding the flow thereof. The cleaner has a multiplicity of fibers disposed in the path of travel of the developer material.

This invention relates generally to an electrophotographic printing 
machine, and more particularly concerns a developer unit in which 
developer material is cleaned to remove contaminants therefrom. 
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 surface. After the electrostatic latent image is recorded 
on the photoconductive surface, the latent image is developed by bringing 
a developer material into contact therewith. Two component and single 
component developer materials are commonly used. A typical two component 
developer material comprises magnetic carrier granules having toner 
particles adhering triboelectrically thereto. A single component developer 
material typically comprises toner particles. Toner particles are 
attracted to the latent image forming a toner powder image on the 
photoconductive surface. The toner powder image is subsequently 
transferred to a copy sheet. Finally, the toner powder image is heated to 
permanently fuse it to the copy sheet in image configuration. 
Single component development systems use a donor roll for transporting 
charged toner to the development nip defined by the donor roll and 
photoconductive member. The toner is developed on the latent image 
recorded on the photoconductive member by a combination of mechanical 
and/or electrical forces. Scavengeless development and jumping development 
are two types of single component development. A scavengeless development 
system uses a donor roll with a plurality of electrode wires closely 
spaced therefrom in the development zone. An AC voltage is applied to the 
wires forming a toner cloud in the development zone. The electrostatic 
fields generated by the latent image attract toner from the toner cloud to 
develop the latent image. In jumping development, an AC voltage is applied 
to the donor roller detaching toner from the donor roll and projecting the 
toner toward the photoconductive member so that the electrostatic fields 
generated by the latent image attract the toner to develop the latent 
image. Single component development systems appear to offer advantages in 
low cost and design simplicity. However, the achievement of high 
reliability and easy manufacturability of the system may present a 
problem. Two component development systems have been used extensively in 
many different types of printing machines. A two component development 
system usually employs a magnetic brush developer roller for transporting 
carrier having toner adhering triboelectrically thereto. The electrostatic 
fields generated by the latent image attract the toner from the carrier so 
as to develop the latent image. In high speed commercial printing 
machines, a two component development system may have lower operating 
costs than a single component development system. Clearly, two component 
development systems and single component development systems each have 
their own advantages. A combination of these systems was described at the 
2nd International Congress on Advances in Non-impact Printing held in 
Washington, D.C. on Nov. 4-8, 1984, sponsored by the Society for 
Photographic Scientists and Engineers. At that time, Toshiba described a 
development system using a donor roll and a magnetic roller. The donor 
roll and magnetic roller were electrically biased. The magnetic roller 
transported a two component developer material to the nip defined by the 
donor roll and magnetic roller. Toner is attracted to the donor roll from 
the magnetic roll. The donor roll is rotated synchronously with the 
photoconductive drum with the gap between them being about 0.20 
millimeters. The large difference in potential between the donor roll and 
latent image recorded on the photoconductive drum causes the toner to jump 
across the gap from the donor roll to the latent image so as to develop 
the latent image. In developer units of this type, performance and 
resulting image quality are dependent upon the presence of contamination 
and debris. Contaminating fibers from many sources are frequently found on 
the photoconductive member. Many of these contaminating fibers migrate 
into the developer unit. In addition, airborne fibers can enter into the 
developer unit. Once in the developer unit, these fibers can be developed 
image wise on the photoconductive member. Scavengeless developer units are 
particularly sensitive to the presence of fibers on the donor roll. These 
fibers and other debris may be caught by the electrode wires. If fibers 
and debris are caught by the electrode wires, the flow of toner particles 
past the electrostatic latent image is sufficiently distorted that 
noticeable non-uniform streak wise deposits of toner are deposited on the 
photoconductive member and subsequently transferred to the copy sheet. 
Thus, it is desirable to remove fiber contaminants and debris from the 
flowing developer material. Various type of approaches have been used to 
remove contaminants and particles from developer units as illustrated by 
the following disclosures, which may be relevant to certain aspects of the 
present invention: 
U.S. Pat. No. 4,078,520; 
Patentee: Wilson; 
Issued: Mar. 14, 1978 
U.S. Pat. No. 4,267,245; 
Patentee: Wada; 
Issued: May 12, 1981 
U.S. Pat. No. 4,809,035; 
Patentee: Allen, Jr.; 
Issued: Feb. 28, 1989 
The relevant portions of the foregoing disclosures may be briefly 
summarized as follows: 
U.S. Pat. No. 4,078,520 discloses a developer unit in which developer 
depleted is returned to the sump of the developer housing from the 
photoreceptor by gravity. The depleted developer is directed by a guide 
plate to a screen. The developer impacting the screen passes through the 
screen and through a sensor. The sensor detects toner density and actuates 
a toner dispenser to discharge toner into the sump of the developer 
housing. 
U.S. Pat. No. 4,267,245 described a method of removing foreign material 
from magnetic developers. Magnetic developers are intermittently supplied 
to the peripheral surface of a non-magnetic sleeve. The supplied developer 
travels along the peripheral surface of the sleeve by rotating a magnet. 
Non-contaminated developer is recovered at a position a distance away from 
the supply of developer material. 
U.S. Pat. No. 4,809,035 discloses removing non-magnetic particles from a 
supply of single component magnetic toner descending from a toner hopper. 
Separation is achieved by providing a partly closed unwanted particle 
chamber extending along an entire width of the hopper adjacent and below a 
feed roller and below a hopper outlet. A source of negative air flow is 
established across the entire width of the hopper and across the entire 
length of the unwanted particle chamber so as to draw the unwanted 
particles from the unwanted particle chamber. An air manifold is located 
on the developer unit housing. 
In accordance with one aspect of the present invention, there is provided 
an apparatus for developing a latent image recorded on a surface with 
developer material. The apparatus includes a housing defining a chamber 
storing a supply of developer material. Means are provided for advancing 
the developer material along a path of travel to a development zone 
closely adjacent to the surface so as to develop the latent image recorded 
thereon. Means, spaced from the surface and located in the chamber of the 
housing, clean contaminants from the developer material without 
substantially impeding the advancing developer material. The cleaning 
means comprises a plurality of elongated fibers disposed in the path of 
travel of the developer material. 
Pursuant to another aspect of the present invention, there is provided an 
electrophotographic printing machine of the type in which an electrostatic 
latent image recorded on a photoconductive member is developed to form a 
visible image thereof. The improvement includes a housing defining a 
chamber storing a supply of developer material. Means are provided for 
advancing the developer material along a path of travel to a development 
zone closely adjacent to the photoconductive member so as to develop the 
latent image recorded thereon. Means, spaced from the photoconductive 
member and located in the chamber of the housing, clean contaminants from 
the developer material without substantially impeding the advancing 
developer material. The cleaning means comprises a plurality of elongated 
fibers disposed in the path of travel of the developer material.

While the present invention will be described in connection with a 
preferred embodiment thereof, it will be understood that it is not 
intended to limit the invention to that embodiment. On the contrary, it is 
intended to cover all alternatives, modifications, and equivalents as may 
be included within the spirit and scope of the invention as defined by the 
appended claims. 
Inasmuch as the art of electrophotographic printing is well known, the 
various processing stations employed in the FIG. 1 printing machine will 
be shown hereinafter schematically and their operation described briefly 
with reference thereto. 
Referring initially to FIG. 1, there is shown an illustrative 
electrophotographic printing machine incorporating the development 
apparatus of the present invention therein. 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. Conductive substrate 14 is made 
preferably from an aluminum alloy which is electrically grounded. Belt 10 
moves in the direction of arrow 16 to advance successive portions of 
photoconductive surface 12 sequentially through the various processing 
stations disposed about the path of movement thereof. Belt 10 is entrained 
about stripping roller 18, tensioning roller 20 and drive roller 22. Drive 
roller 22 is mounted rotatably 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. Belt 10 
is maintained in tension by a pair of springs (not shown) resiliently 
urging tensioning roller 20 against belt 10 with the desired spring force. 
Stripping roller 18 and tensioning roller 20 are mounted to rotate freely. 
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 to a relatively 
high, substantially uniform potential. High voltage power supply 28 is 
coupled to corona generating device 26. Excitation of power supply 28 
causes corona generating device 26 to charge photoconductive surface 12 of 
belt 10. After photoconductive surface 12 of belt 10 is charged, the 
charged portion thereof is advanced through exposure station B. 
At exposure station B, an original document 30 is placed face down upon a 
transparent platen 32. Lamps 34 flash light rays onto original document 
30. The light rays reflected from original document 30 are transmitted 
through lens 36 to form a light image thereof. Lens 36 focuses this 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 12 which corresponds to the 
informational areas contained within original document 30. 
After the electrostatic latent image has been recorded on photoconductive 
surface 12, belt 10 advances the latent image to development station C. At 
development station C, a developer unit, indicated generally by the 
reference numeral 38, develops the latent image recorded on the 
photoconductive surface. Preferably, developer unit 38 includes donor 
roller 40 and electrode wires 42. Electrode wires 42 are electrically 
biased relative to donor roll 40 to detach toner therefrom so as to form a 
toner powder cloud in the gap between the donor roll and photoconductive 
surface. The latent image attracts toner particles from the toner powder 
cloud forming a toner powder image thereon. Donor roller 40 is mounted, at 
least partially, in the chamber of developer housing 44. The chamber in 
developer housing 44 stores a supply of developer material. The developer 
material is a two component developer material of at least carrier 
granules having toner particles adhering triboelectrically thereto. A 
magnetic roller disposed interiorly of the chamber of housing 44 conveys 
the developer material to the donor roller. The magnetic roller is 
electrically biased relative to the donor roller so that the toner 
particles are attracted from the magnetic roller to the donor roller. The 
development apparatus will be discussed hereinafter, in greater detail, 
with reference to FIG. 2. 
With continued reference to FIG. 1, after the electrostatic latent image is 
developed, belt 10 advances the toner powder image to transfer station D. 
A copy sheet 48 is advanced to transfer station D by sheet feeding 
apparatus 50. Preferably, sheet feeding apparatus 50 includes a feed roll 
52 contacting the uppermost sheet of stack 54. Feed roll 52 rotates to 
advance the uppermost sheet from stack 54 into chute 56. Chute 56 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 at transfer station D. 
Transfer station D includes a corona generating device 58 which sprays 
ions onto the back side of sheet 48. This attracts the toner powder image 
from photoconductive surface 12 to sheet 48. After transfer, sheet 48 
continues to move in the direction of arrow 60 onto a conveyor (not shown) 
which advances sheet 48 to fusing station E. 
Fusing station E includes a fuser assembly, indicated generally by the 
reference numeral 62, which permanently affixes the transferred powder 
image to sheet 48. Fuser assembly 62 includes a heated fuser roller 64 and 
a back-up roller 66. Sheet 48 passes between fuser roller 64 and back-up 
roller 66 with the toner powder image contacting fuser roller 64. In this 
manner, the toner powder image is permanently affixed to sheet 48. After 
fusing, sheet 48 advances through chute 70 to catch tray 72 for subsequent 
removal from the printing machine by the operator. 
After the copy sheet is separated from photoconductive surface 12 of belt 
10, the residual toner particles adhering to photoconductive surface 12 
are removed therefrom at cleaning station F. Cleaning station F includes a 
rotatably mounted fibrous brush 74 in contact with photoconductive surface 
12. The particles are cleaned from photoconductive surface 12 by the 
rotation of brush 74 in contact therewith. Subsequent to cleaning, a 
discharge lamp (not shown) floods photoconductive surface 12 with light to 
dissipate any residual electrostatic charge remaining thereon prior to the 
charging thereof for the next successive imaging cycle. 
It is believed that the foregoing description is sufficient for purposes of 
the present application to illustrate the general operation of an 
electrophotographic printing machine incorporating the developer unit of 
the present invention therein. 
Referring now to FIG. 2, there is shown developer unit 38 in greater 
detail. As shown thereat, developer unit 38 includes a housing 44 defining 
a chamber 76 for storing a supply of developer material therein. Donor 
roller 40, electrode wires 42 and magnetic roller 46 are mounted in 
chamber 76 of housing 44. The donor roller can be rotated in either the 
`with` or `against` direction relative to the direction of motion of belt 
10. In FIG. 2, donor roller 40 is shown rotating in the direction of arrow 
68. Similarly, the magnetic roller can be rotated in either the `with` or 
`against` direction relative to the direction of motion of belt 10. In 
FIG. 2, magnetic roller 46 is shown rotating in the direction of arrow 92. 
Donor roller 40 is preferably made from anodized aluminum. 
Developer unit 38 also has electrode wires 42 which are disposed in the 
space between the belt 10 and donor roller 40. A pair of electrode wires 
are shown extending in a direction substantially parallel to the 
longitudinal axis of the donor roller. The electrode wires are made from 
one or more thin (i.e. (50 to 100.mu. diameter) stainless steel wires 
which are closely spaced from donor roller 40. The distance between the 
wires and the donor roller is approximately 25.mu. or the thickness of the 
toner layer on the donor roll. The wires are self-spaced from the donor 
roller by the thickness of the toner on the donor roller. The ends of the 
wires are supported by the tops of end bearing blocks which may also 
support the donor roller for rotation. The wire extremities are attached 
so that they are slightly below a tangent to the surface, including toner 
layer, of the donor structure. Mounting the wires in such a manner makes 
them insensitive to roll runout due to their self-spacing. 
As illustrated in FIG. 2, an alternating electrical bias is applied to the 
electrode wires by an AC voltage source 78. The applied AC establishes an 
alternating electrostatic field between the wires and the donor roller 
which is effective in detaching toner from the surface of the donor roller 
and forming a toner cloud about the wires, the height of the cloud being 
such as not to be substantially in contact with the belt 10. The magnitude 
of the AC voltage is relatively low and is in the order of 200 to 600 
volts peak at a frequency rangig from about 3 kHz to about 10 kHz. A DC 
bias supply 80 which applies approximately 300 volts to donor roller 40 
establishes an electrostatic field between photoconductive surface 12 of 
belt 10 and donor roller 40 for attracting the detached toner particles 
from the cloud surrounding the wires to the latent image recorded on the 
photoconductive surface. At a spacing ranging from about 10.mu. to about 
40.mu. between the electrode wires and donor roller, an applied voltage of 
200 to 600 volts produces a relatively large electrostatic field without 
risk of air breakdown. The use of a dielectric coating on either the 
electrode wires or donor roller helps to prevent shorting of the applied 
AC voltage. Blade 82 strips all of the toner from donor roller 40 after 
development so that magnetic roller 46 meters fresh toner to a clean doner 
roller. A DC bias supply 84 which applies approximately 100 volts to 
magnetic roller 46 establishes an electrostatic field between magnetic 
roller 46 and donor roller 40 so that an electrostatic field is 
established between the donor roller and the magnetic roller which causes 
toner particles to be attracted from the magnetic roller to the donor 
roller. Metering blade 86 is positioned closely adjacent to magnetic 
roller 46 to maintain the compressed pile height of the developer material 
on magnetic roller 46 at the desired level. Magnetic roller 46 includes a 
non-magnetic tubular member or sleeve 88 made preferably from aluminum and 
having the exterior circumferential surface thereof roughened. An 
elongated multiple magnet 90 is positioned interiorly of and spaced from 
sleeve 88. Elongated magnet 90 is mounted stationarily. Motor 100 rotates 
sleeve 88 in the direction of arrow 92. Developer material is attracted to 
sleeve 88 and advances therewith into the nip defined by donor roller 40 
and magnetic roller 46. Toner particles are attracted from the carrier 
granules on the magnetic roller to the donor roller. Scraper blade 91 
removes denuded carrier granules and extraneous developer material from 
the surface of sleeve 88. 
With continued reference to FIG. 2, augers, indicated generally by the 
reference numeral 94, are located in chamber 76 of housing 44. Augers 94 
are mounted rotatably in chamber 76 to mix and transport developer 
material. The augers have blades extending spirally outwardly from a 
shaft. The blades are designed to advance the developer material in the 
axial direction substantially parallel to the longitudinal axis of the 
shaft. 
As successive electrostatic latent images are developed, the toner 
particles within the developer material are depleted. A toner dispenser 
(not shown) stores a supply of toner particles. The toner dispenser is in 
communication with chamber 76 of housing 44. As the concentration of toner 
particles in the developer material is decreased, fresh toner particles 
are furnished to the developer material in the chamber from the toner 
dispenser. The augers in the chamber of the housing mix the fresh toner 
particles with the remaining developer material so that the resultant 
developer material therein is substantially uniform with the concentration 
of toner particles being optimized. In this way, a substantially constant 
amount of toner particles are in the chamber of the developer housing with 
the toner particles having a constant charge. The developer material in 
the chamber of the developer housing is magnetic and may be electrically 
conductive. By way of example, the carrier granules include a low 
permeability magnetic core having a thin layer overcoat with layer of 
resinous material. The toner particles are made from a resinous material, 
such as a vinyl polymer, mixed with a coloring material, such as chromogen 
black. The developer material comprise from about 95% to about 99% by 
weight of carrier and from 5% to about 1% by weight of toner. However, one 
skilled in the art will recognize that any suitable developer material 
having at least carrier granules and toner particles may be used. 
Developer material advances with tubular member 88 in the direction of 
arrow 92. Toner particles advance with donor roller 40 in the direction of 
arrow 68. Any contaminants and/or debris move with the toner particles and 
developer material in the direction of arrows 92 and 68. The toner 
particles, developer material, contaminants and debris flow through a 
cleaner, indicated generally by the reference numeral 102. Cleaner 102 
includes a multiplicity of fibers 104 mounted on a support 106. Support 
106 is mounted removably on a side wall of developer housing 44. By way of 
example, support 106 may be mounted slidably in rails secured to the side 
wall housing 44. In this way, an operator may readily remove cleaner 102 
from developer housing 44 at selected maintenance intervals. Fibers 104 
have hooks at the free ends thereof. The hooks are oriented with the bent 
end pointing up against the direction of flow of the toner particles, 
developer material, contaminants and debris. Thus, cleaner 102 is oriented 
vertically. However, there are many other orientations and positions which 
will operate equally satisfactorily depending upon the configuration of 
the developer housing. Further details of cleaner 102 are shown in FIG. 3. 
Turning now to FIG. 3, cleaner 102 is shown in greater detail. Cleaner 102 
is shown oriented vertically with the toner particles, developer material, 
contaminants and debris flowing in the direction of arrow. Fibers 104 
orient themselves with their Stokes diameter (usually their maximum 
dimension) perpendicular to the flow direction. This offers the maximum 
probability of capture by the hooks on the free ends of fibers 104. In 
general, the cleaner should be mounted in near vertical position so that 
developer material and toner particles can flow easily, thereby 
maintaining a high flux of contaminated developer material flowing through 
it. The hooks offer some impedance, but do not totally inhibit the flow. 
Therefore, cleaner 102 can be mounted at an orientation other than the 
vertical depending upon the flow angle of the developer material, the pile 
density of the fibers, their diameter and length. Fibers have a hook part 
of the type decribed herein are made and sold under the registered 
trademark "Velcro". These fibers and their method of manufacture are 
described more fully in U.S. Pat. Nos. 2,717,437 and 3,009,235, the 
relevant portions thereof being hereby incorporated into the present 
application. Cleaner 102 is woven to form a strong backing sheet of fabric 
with a loop pile made of monofilaments of a heat settable material such as 
"Nylon" a registered trademark. The loop pile is heat set and thereafter 
each separate loop is cut transversely of one leg at a point below the 
crest of the loop so as to form an individually vertically disposed hook 
from each loop. The backing sheet is adhesively secured to support 106. 
In recapitulation, it is evident that the developer unit of the present 
invention includes an operator removable cleaner positioned in the path of 
flow of the developer material to remove contaminants and debris 
therefrom. The cleaner includes a multiplicity of fibers secured to a 
rigid support. Each fiber has a hook on the free end thereof. In this way, 
the fibers trap contaminants while permitting the developer material to 
flow freely therethrough. The support is mounted slidably on a wall of the 
developer housing. 
It is, therefore, apparent that there has been provided in accordance with 
the present invention, a developer unit that fully satisfies the aims and 
advantages hereinbefore set forth. While this invention has been described 
in conjunction with a specific embodiment thereof, it is evident that many 
alternatives, modifications, and variations will be apparent to those 
skilled in the art. Accordingly, it is intended to embrace all such 
alternatives, modifications and variations that fall within the spirit and 
broad scope of the appended claims.