Dual polarity commutated roll elctrostatic cleaner with acoustic transfer assist

A dual polarity commutated roll attracts toner and debris particles loosened into a particle cloud from the photoreceptor surface by an acoustical horn. The particles are attracted to and adhere to the commutated roll, whether right or wrong sign (i.e. positive or negative), and are removed from the roll, as the roll rotates, by a scraper blade. The particles are collected in a waste container as the particles are removed from the roll surface by the scraper blade. Residual particles that are not attracted to the commutated roll, are removed from the photoreceptor surface by a spots blade. The cleaning system does not contact the photoreceptor, thus, increasing cleaner and photoreceptor life.

BACKGROUND OF THE INVENTION 
This invention relates generally to an electrostatographic copier or 
printer, and more particularly, concerns a cleaning apparatus. 
In an electrophotographic application such as xerography, a charge 
retentive surface (i.e., photoconductor, photoreceptor or imaging surface) 
is electrostatically charged, and exposed to a light pattern of an 
original image to be reproduced to selectively discharge the surface in 
accordance therewith. The resulting pattern 0f charged and discharged 
areas on that surface form an electrostatic charge pattern (an 
electrostatic latent image) conforming to the original image. The latent 
image is developed by contacting it with a finely divided 
electrostatically attractable powder referred to as "toner". Toner is held 
on the image areas by the electrostatic charge on the surface. Thus, a 
toner image is produced in conformity with a light image of the original 
being reproduced. The toner image may then be transferred to a substrate 
(e.g., paper), and the image affixed thereto to form a permanent record of 
the image to be reproduced. Subsequent to development, excess toner left 
on the charge retentive surface is cleaned from the surface. The process 
is well known, and useful for light lens copying from an original, and 
printing applications from electronically generated or stored originals, 
where a charge surface may be imagewise discharged in a variety of ways. 
Ion projection devices where a charge is imagewise deposited on a charge 
retentive substrate operates similarly. 
Although a preponderance of the toner forming the image is transferred to 
the paper during transfer, some toner invariably remains on the charge 
retentive surface, it being held thereto by relatively high electrostatic 
and/or mechanical forces. Additionally, paper fibers, Kaolin and other 
debris have a tendency to be attracted to the charge retentive surface. It 
is essential for optimum operation that the toner remaining on the surface 
be cleaned thoroughly therefrom. 
Conventional cleaning methods for cleaning this residual toner include 
contact cleaners (i.e. cleaners that frictionally contact the imaging 
surface) such as blades and brushes. The contact between these cleaners 
and the surface being cleaned, decrease the wear life of both the cleaner 
and the photoreceptor. This frictional contact can cause tearing and 
chipping to the cleaning blade edge which leads to cleaning failures and 
possible damage to the photoreceptor. The cleaning brushes often develop a 
set due to contact with the imaging surface, that affects the ability of 
the brush to clean the surface. 
The following disclosures may be relevant to various aspects of the present 
invention and may be briefly summarized as follows: 
U.S. Pat. No. 3,257,224 to Jous et al. which discloses a magnetic roller 
that dips into developer powder contained in a trough beneath the roller. 
The iron filings, carrying the toner on their surfaces, adhere in 
brush-like formation to the magnetic poles of the roller and are applied 
in this form by rotation of the roller to the surface of a charged 
electrophotographic material which has been exposed imagewise and is 
traversed over the roller. The toner is attracted electrostatically from 
the magnet to the photoconductive coating of the electrophotographic 
material and a visible image is formed. 
U.S. Pat. No. 4,111,546 to Maret which discloses an electrostatographic 
reproducing apparatus and process that includes a system for 
ultrasonically cleaning residual material from the imaging surface. 
Ultrasonic vibratory energy is applied to the air space adjacent the 
imaging surface to excite the air molecules for dislodging the residual 
material from the imaging surface. Preferably pneumatic cleaning is 
employed simultaneously with the ultrasonic cleaning. Alternatively, a 
conventional mechanical cleaning system is augmented by localized 
vibration of the imaging surface at the cleaning station which are 
provided from behind the imaging surface. 
Xerox Disclosure Journal, volume 18, no.3, May/Jun. 1993, entitled 
"Acoustical Vacuum Cleaner Assist" discloses a high velocity and pressure 
vacuum that subsequently removes particles from the photoreceptor belt. 
The particles being previously dislodged by the vibratory action of an 
acoustical horn against the photoreceptor belt. 
SUMMARY OF INVENTION 
Briefly stated, and in accordance with one aspect of the present invention, 
there is provided an apparatus for cleaning particles from a surface. The 
surface comprises a device, in communication with the surface, for 
loosening the particles from the surface and, a member, positioned 
adjacent the surface, for attracting loosened particles thereto. The 
member including a plurality of segments with adjacent segments being 
opposite polarities for attracting particles having opposite polarities 
thereto.

DETAILED DESCRIPTION OF THE INVENTION 
Referring now to the drawings, where the showings are for the purpose of 
describing a preferred embodiment of the invention and not for limiting 
same, the various processing stations employed in the reproduction machine 
illustrated in FIG. 2 will be briefly described. 
A reproduction machine, in which the present invention finds advantageous 
use, utilizes a charge retentive member in the form of a photoconductive 
belt 10 consisting of a photoconductive surface and an electrically 
conductive, light transmissive substrate mounted for movement past a 
charging station A, an exposure station B, developer stations C, transfer 
station D, fusing station E and cleaning station F. Belt 10 moves in the 
direction of arrow 16 to advance successive portions thereof sequentially 
through the various processing stations disposed about the path of 
movement thereof. Belt 10 is entrained about a plurality of rollers 18, 20 
and 22, the former of which can be used to provide suitable tensioning of 
the photoreceptor belt 10. Motor 23 rotates roller 18 to advance belt 10 
in the direction of arrow 16. Roller 20 is coupled to motor 23 by suitable 
means such as a belt drive. 
As can be seen by further reference to FIG. 2, initially successive 
portions of belt 10 pass through charging station A. At charging station 
A, a corona discharge device such as a scorotron, corotron or dicorotron 
indicated generally by the reference numeral 24, charges the belt 10 to a 
selectively high uniform positive or negative potential. Any suitable 
control, well known in the art, may be employed for controlling the corona 
discharge device 24. 
Next, the charged portions of the photoreceptor surface are advanced 
through exposure station B. At exposure station B, the uniformly charged 
photoreceptor or charge retentive surface 10 is exposed to a laser based 
input and/or output scanning device 25 which causes the charge retentive 
surface to be discharged in accordance with the output from the scanning 
device. Preferably the scanning device is a three level laser Raster 
Output Scanner (ROS). The resulting photoreceptor contains both 
charged-area images and discharged-area images as well as charged edges 
corresponding to portions of the photoreceptor outside the image areas. 
The high voltage latent image is developed with positive (+) charged 
black toner and is called Charge Area Development (CAD). The low voltage 
latent image is developed with negative (-) charge color toner and 
Discharge Area Development (DAD)!. 
The photoreceptor, which is initially charged to a voltage undergoes dark 
decay to a voltage level. When exposed at the exposure station B it is 
discharged to near zero or ground potential in the highlight (i.e. color 
other than black) color parts of the image. The photoreceptor is also 
partially discharged in the background (white) image areas. After passing 
through the exposure station, the photoreceptor contains charged areas and 
discharged areas which corresponding to two images and to charged edges 
outside of the image areas. 
At development station C, a development system, indicated generally by the 
reference numeral 30 advances developer materials into contact with the 
electrostatic latent images. The development system 30 comprises first and 
second developer apparatuses 32 and 34. The developer apparatus 32 
comprises a housing containing a pair of magnetic brush rollers 35 and 36. 
The rollers advance developer material 40 into contact with the 
photoreceptor for developing the discharged-area images. The developer 
material 40, by way of example, contains negatively charged color toner. 
Electrical biasing is accomplished via power supply 41 electrically 
connected to developer apparatus 32. A DC bias is applied to the rollers 
35 and 36 via the power supply 41. 
The developer apparatus 34 comprises a housing containing a pair of 
magnetic brush rolls 37 and 38. The rollers advance developer material 42 
into contact with the photoreceptor for developing the charged-area 
images. The developer material 42 by way of example contains positively 
charged black toner for developing the charged-area images. Appropriate 
electrical biasing is accomplished via power supply 43 electrically 
connected to developer apparatus 34. A DC bias is applied to the rollers 
37 and 38 via the bias power supply 43. 
Because the composite image developed on the photoreceptor consists of both 
positive and negative toner, a pre-transfer corona discharge member 56 is 
provided to condition the toner for effective transfer to a substrate 
using corona discharge of a desired polarity, either negative or positive. 
Sheets of substrate or support material 58 are advanced to transfer station 
D from a supply tray, not shown. Sheets are fed from the tray by a sheet 
feeder, also not shown, and advanced to transfer station D through a 
corona charging device 60. After transfer, the sheet continues to move in 
the direction of arrow 62 to fusing station E. 
Fusing station E includes a fuser assembly, indicated generally by the 
reference numeral 64, which permanently affixes the transferred toner 
powder images to the sheets. Preferably, fuser assembly 64 includes a 
heated fuser roller 66 adapted to be pressure engaged with a backup roller 
68 with the toner powder images contacting fuser roller 66. In this 
manner, the toner powder image is permanently affixed to the sheet. 
After fusing, copy sheets are directed to catch tray, not shown or a 
finishing station for binding, stapling, collating etc., and removal from 
the machine by the operator. Alternatively, the sheet may be advanced to a 
duplex tray (not shown) from which it will be returned to the processor 
for receiving a second side copy. A lead edge to trail edge reversal and 
an odd number of sheet inversions is generally required for presentation 
of the second side for copying. However, if overlay information in the 
form of additional or second color information is desirable on the first 
side of the sheet, no lead edge to trail edge reversal is required. Of 
course, the return of the sheets for duplex or overlay copying may also be 
accomplished manually. 
Residual toner and debris remaining on photoreceptor belt 10 after each 
copy is made, may be removed at cleaning station F with a cleaning system 
70. The photoreceptor belt 10 is supported by an acoustic transfer assist 
area 130. 
Reference is now made to FIG. 1, which shows an elevational view of the 
present invention. As non-transferred residual particles 120 remaining on 
the photoreceptor 10 pass over the ATA (Acoustic Transfer Assist) area 
130, the toner's attraction to the photoreceptor belt 10 is substantially 
lessened due to the high frequency vibrations caused by the acoustical 
horn 140. The operation of an acoustical horn is described, for example, 
in Xerox Disclosure Journal, volume 18, no.3, May/June 1993, and is 
incorporated herein by reference. The invention proposes using a dual 
polarity commutated roll 110 that electrostatically attracts (both right 
and wrong signed) toner, after it has been loosened from the photoreceptor 
10 by the acoustical horn 140. (The horn 140 can be held in contact with 
the photoreceptor 10 by suction.) The high frequency vibration of the 
photoreceptor belt 10 causes the toner particles 120 to form a particle 
cloud between the photoreceptor 10 and the commutated roll 110. The 
voltage potentials on the commutated cleaning roll 110 are adjusted such 
that a more positive attraction (or negative attraction for wrong sign 
toner) is felt by the negatively charged toner on the grounded 
photoreceptor belt. For example, a positive 250 volt potential on positive 
commutations of the cleaning roll create a strong attraction of the 
negatively charged toner setting on the grounded photoreceptor belt 
towards the commutated cleaning roll 110. Conversely, a negative 250 volt 
potential on the negative commutations of the cleaning roll create a 
strong attraction of the positively charged (wrong sign) toner towards the 
commutated cleaning roll. With the assistance of the ATA providing the 
mechanical vibrations necessary to break the bond between the toner and 
the photoreceptor belt and additionally bouncing the toner some distance 
"x" from the photoreceptor belt surface, the attraction of the loose toner 
particles towards the commutated cleaning roll is complete. 
With continued reference to FIG. 1, the commutated roll 110 attracts both 
right and wrong sign toner to adhere to it's surface as it rotates in a 
direction shown by arrow 115. A scraper blade 150 is placed in contact 
with the surface of the commutated roll 110 such that as the commutated 
roll rotates past the scraper blade 150, the particles adhering to the 
surface of the commutated roll 110 are scraped from the surface into a 
waste container (not shown). A vertical cleaner position allows the toner 
to "free fall" into a toner collection container due to gravity 
Any residual toner and/or debris residual particles that are not attracted 
to the commutated roll 110 are removed from the photoreceptor downstream 
from the commutated roll 110 in the direction of motion of the 
photoreceptor. 
The advantage of this apparatus over other cleaning systems is that no 
contact occurs between the commutated roll and the photoreceptor. With no 
contact, the life of the photoreceptor and the commutated roll is 
increased. This device will be used to clean toner from the photoreceptor. 
With continuing reference to FIG. 1, the use of ATA 130 yields greater than 
a 95% transfer efficiency in a cleaner configuration that allows the ATA 
10 to be operated at maximum potential. The acoustical horn 140 can be 
driven at maximum potential because toner registration is not a concern. 
This would allow for larger gaps between the roll 110 and photoreceptor 10 
thus, reducing the need for critical tolerances. The distance "x" of the 
commutated cleaning roll 110 from the surface of the photoreceptor belt 10 
is chosen to minimize the need for critical tolerances. The voltage 
potentials applied to the commutated cleaning roll are optimized such that 
the field strength between the commutated roll and the photoreceptor belt 
are at a maximum and the air break down limit is exceeded. In other words, 
the voltage is high enough to create a strong attraction of the toner from 
the photoreceptor belt towards the commutated roll 110 but not strong 
enough to break down the air between the commutated roll 110 and 
photoreceptor belt 10 and start arcing. For example, the voltage applied 
to the commutated roll 110 is in a range from approximately 100 volts 
(positive or negative) up to the air breakdown limit -100 volts. Thus, the 
voltage potentials and gap width would be chosen to maximize field 
strength and minimize the chance of entering the air breakdown limit. 
This would be considered a non-contact cleaner because no part of the 
cleaner is in contact with the photoreceptor 10 at any time. This 
non-contact cleaner eliminates motion quality problems, reduces 
photoreceptor drag and reduces emissions. In a multi-pass copier (image-on 
-image), this cleaner would not have to retract from the photoreceptor 
belt like conventional contact cleaners. Thus, reducing UMC (Unit 
Manufacturing Cost) and increasing reliability of the cleaner. 
In recapitulation, the dual polarity commutated roll attracts toner and 
debris particles loosened into a particle cloud from the photoreceptor 
surface by an acoustical horn. The particles adhere to the commutated 
roll, whether right or wrong sign, and are removed form the roll, as the 
roll rotates, by a scraper blade. The particles are collected in a waste 
container as the particles are removed from the roll surface by the 
scraper blade. Residual particles not attracted to the commutated roll are 
removed from the photoreceptor surface by a spots blade. 
It is, therefore, apparent that there has been provided in accordance with 
the present invention, a dual polarity commutated roll electrostatic 
cleaner with acoustic transfer assist 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.