CA2049742A1 - Development apparatus - Google Patents
Development apparatusInfo
- Publication number
- CA2049742A1 CA2049742A1 CA 2049742 CA2049742A CA2049742A1 CA 2049742 A1 CA2049742 A1 CA 2049742A1 CA 2049742 CA2049742 CA 2049742 CA 2049742 A CA2049742 A CA 2049742A CA 2049742 A1 CA2049742 A1 CA 2049742A1
- Authority
- CA
- Canada
- Prior art keywords
- latent image
- charging
- potential
- transporting
- donor roller
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
- G03G15/00—Apparatus for electrographic processes using a charge pattern
- G03G15/06—Apparatus for electrographic processes using a charge pattern for developing
- G03G15/08—Apparatus for electrographic processes using a charge pattern for developing using a solid developer, e.g. powder developer
- G03G15/0806—Apparatus for electrographic processes using a charge pattern for developing using a solid developer, e.g. powder developer on a donor element, e.g. belt, roller
- G03G15/0812—Apparatus for electrographic processes using a charge pattern for developing using a solid developer, e.g. powder developer on a donor element, e.g. belt, roller characterised by the developer regulating means, e.g. structure of doctor blade
Abstract
ABSTRACT OF THE DISCLOSURE
An apparatus in which a latent image is developed with marking particles. The marking particles are transported to the latent image by a donor roller. As the marking particles are being moved to the latent image, they are electrically charged by a blade in contact with the donor roller. An AC potential is applied on the blade. The AC potential is operator adjustable to change the charge on the toner particles. This corrects for changes in the environment and permits the slope of the tone reproduction curve to be optimized for the latent image being developed.
An apparatus in which a latent image is developed with marking particles. The marking particles are transported to the latent image by a donor roller. As the marking particles are being moved to the latent image, they are electrically charged by a blade in contact with the donor roller. An AC potential is applied on the blade. The AC potential is operator adjustable to change the charge on the toner particles. This corrects for changes in the environment and permits the slope of the tone reproduction curve to be optimized for the latent image being developed.
Description
2 ~
PATENT APPLICATION
Attorney Docket No. D/90219 DEVELOPMENT APPARATUS
This invention relates generally to an electrophotographic printing machine, and more particularly concerns a development apparatus employed therein.
In an electrophotographic printing machine, a photoconductive member is charged 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.
Exposure of the charged photoconductive member selectively dissipates the charge thereon in the irradiated area. This records an electrostatic latent image on the photoconductive member corresponding to the informational areas contained within the original document being reproduced. After the electrostatic latent image is recorded on the photoconductive member, the latent image is developed by bringing marking particles into contact therewith. This forms a powder image on the photoconductive member which is subsequently transferred to a copy sheet. The copy sheet is heated to permanently affix the marking particles thereto in image configuration.
Various types of development system have hereinbefore been employed. These systems utilize two component developer material or single component developer material. Two component developer material includes toner particles adhering triboelectrically to carrier granules. A
single component development system uses only toner particles. In many of the single component development systems, the toner particles are conductive. However, the transfer of conductive toner particles to the copy sheet is usually inefficient. In order to overcome this problem, insulating toner particles are frequently employed. When insulating toner particles are utilized, it is necessary to charge these toner particles to the correct polarity. This may be achieved by employing a flexible blade in contact ... .. . . ........... . .
, ' .. ' - ' ... : . ' -' ' ': ' , .
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with a donor roller. As the donor roller transports the toner particles toward the latent image recorded on the photoconductive member, the toner particles pass through a nip defined by the flexible blade and the roll.
The toner particles passing through this nip are triboelectrically charged.
Furthermore, this nip defines the quantity of toner particles being transported on a roller to the latent image recorded on the photoconductive member.
In a printing machine, it would be advantageous to be able to print high quality pictorial and text. It is desirable to print or suppress the gray tones. Furthermore, the printing machine should also be capable of printing continuous tone or half tone pictorial images with a broader range of gray than is currently available. This is of particular significance for development systems having a very steep slope which limits the usefulness of electronic tone reproduction manipulation. In addition, it is desirable to have an operator adjustable system which enables tuning of the toner charge to compensate for environmental changes or any other changes.
The following disclosures appear to be relevant:
US-A-4,459,009 Patentee: Hays et al.
Issued: July 10,1984 US-A-4,523,833 Patentee: Jones Issued: June 18, 1954 US-A-4,619,517 Patentee: Ruhland Issued: October28,1986 US-A-4,707,115 Patentee: Bares Issued: November 17, 1987 .
., -, .
, .
. :
rJ ~ ~
The relevant portions of the foregoing disclosures may be briefly summarized as follows:
US-A-4,459,009 and US-A-4,619,517 disclose a development system having a donor roller which contacts a photoconductive surface to develop a latent image with insulating toner particles. An electrically biased charging roller meters the toner particles to the donor roller and imparts a charge thereon. A doctor blade removes wrong sign toner on tne charging roller. For a positive toner charging system, the voltage applied to the charging roller varies from about + 25 volts to about + 200 volts.
US-A-4,523,833 describes a development apparatus having a developer roller with the free end portion of a blade resiliently urged into contact therewith. The blade has a plurality of holes. A voltage source is connected to the the blade and creates an electrical field at the holes. By adjusting the level of the voltage source, the intensity of the electrical fieldin the holes is controlled, and, in turn, the quantity of marking particles passing therethrough regulated.
US-A-4,707,115 discloses a development system having a donor roller, which is electrically biased, contacts a photoconductive belt having an electrostatic latent image recorded thereon. A flexible steel blade has the free end thereof contacting the surface of the donor roller to define a nip therebetween through which the particles adhering to the donor roller pass. As the toner particles pass through the nip, the quantity of toner particles is regulated and the toner particles remaining adhering to the donor roller are triboelectrically charged.
Pursuant to the features of the present invention, there is provided an apparatus for developing a latent image with marking particles. The apparatus includes means for transporting the marking particles to the latent image. Means are provided for electrically charging the marking particles being moved to the latent image by the transporting means. Means apply an AC electrical potential on the charging means.
In accordance with another aspect of the present invention, there is provided an electrophotographic printing machine of the type ' ' ' ' , ' ' : ~ ' ' . . - , . -- ~ .
having an electrostatic latent image recorded on a photoconductive member. The improvement in the printing machine includes means for transporting toner particles to the photoconductive member to develop the latent image therewith. Means are provided for electrically charging the toner particles being moved to the latent image by the transporting means. Means apply an AC
electrical potential on the charging means.
Other aspects of this invention are as follows:
An apparatus adapted to develop a latent image with marking particles, including:
means for transporting the marking particles to the latent image;
mean~ for electrically biasing said transporting means;
means for electrically charging the marking particles being moved to the latent image by said transporting means; and operator adjustable means, connected electrically to said charging means, for applying an AC potential and a DC potential on said charging means to adjust the charge on the marking particles, said operator ad~ustable means ad~usting both the AC electrical potential and the DC electrical potential on said charging means independently of said electrical biasing means biasing said transporting means.
An electrophotographic printing machine of the type having an electro~tatic latent image recorded on a photoconductive member, wherein the improvement includes:
means for transporting toner particles to the photoconductive member to develop the latent image therewith;
mean for electrically biasing said transporting means;
- . - -.
:
- . . - .
: . - - ~ , . -: , ., means for electrically charging toner particles being moved to the latent image by said transporting means; and operator adjustable means, connected electrically to said charging means for applying an AC potential and a DC potential on said charging means to adjust the charge on the marking particles, said operator adjustable means adjusting both the AC electrical potential and the DC electrical potential on said charging means independently of said electrical biasing means biasing said transporting means.
Other aspects of the present invention will become apparent as the following description proceeds and upon reference to the drawings, in which:
Figure 1 is a schematic elevational view depicting an electrophotographic printing machine incorporating the development apparatus of the present invention therein;
Figure 2 is a schematic elevational view showing the development apparatus of the Figure 1 printing machine in greater detail; and Figure 3 is an exemplary tone reproduction curve.
While the present invention will hereinafter be described in connection with a preferred embodiment thereof, it will be understood that it i5 not intended to limit the invention to that embodiment. On the contrary, it is intended to cover all alternatives, modifications, and equivalents that may be included within the spirit and scope of the invention as defined by the appended claims.
For a general understanding of the features of the present invention, re~erence i8 made to the drawings.
In the drawlngs, like reference numerals have been used throughout to identify identical elements.
Figura 1 schematically depicts the various components of an illustrative electrophotographic - 4a -' - `:' ' ' ' :
printing machine having the development apparatus incorporating the features of the present invention therein. It will become evident from the following discussion that this development apparatus is equally well suited for use in a wide variety of electrostatographic printing machines, and is not necessarily limited in its ,! ~ , , :
.
2~4~7~
application to the particular electrophotographic printing machine shown herein.
Inasmuch as the art of electrophotographic printing is well known, the various processing stations employed in the Figure 1 printing machine will be shown hereinafter schematically and their operation described briefly with reference thereto.
As shown in Figure 1, the electrophotographic printing machine employs a belt 10 having a photoconductive surface deposited on a conductive substrate. Preferably, the photoconductive surface is made from a selenium alloy with the conductive substrate being made from an aluminum alloy. Other suitable photoconductive materials and conductive substrates may also be employed. Belt 10 is entrained about a pair of opposed, spaced rollers 12 and 14. Roller 14 is rotated by a motor coupled thereto by suitable means such as a drive belt. As roller 14 rotates, belt 10 advances the photoconductive surface, in the direction of arrow 16, through the various processing stations disposed about the path of movement thereof.
Initially, the photoconductive surface passes through charging station A. At charging station A, a corona generating device 18 charges the photoconductive surface to a relatively high, substantially uniform potential.
Next, the charged portion of the photoconductive surface is advanced through imaging station B. At imaging station B, an original document 20 is positioned face down upon a transparent platen 22.
Imaging of document 20 on platen 22 is achieved by an exposure system which includes a lamp 24, mirror 26, and moving lens 28. The exposure system is a moving optical system. The lamp, mirrors and lens rnove across the original document illuminating incremental widths thereof to form a light image. The light image is projected onto the charged portion of the photoconductive surface. One skilled in the art will appreciate that instead of a light lens optical system, a raster input scanner (RIS) in combination with a raster output scanner (ROS) may be used. The RIS captures the entire image from the original document and converts it to a series of raster scan 2 ~
lines. The RIS contains document illumination lamps, optics,a mechanical scanning mechanism, and a photosensing elerrlent, such as charge coupled device (CCD array). The ROS, responsive to the output from the RIS
performs the function of recording the electrostatic latent image on the photoconductive surface. The RIS lays out the latent image in a series of horizontal scan lines with each line having a certain nurnber of pixels per inch. The ROS may include a laser, rotating polygon mirror blocks, and an modulator. Still another type of exposure system employs only a ROS. The ROS is connected to a computer and the document desired to be printed is transmitted from the computer to the ROS. In all of the foregoing systems, the charged photoconductive surface is selectively discharged to record an electrostatic latent image thereon. Thereafter, belt 10 advances the electrostatic latent image recorded on the photoconductive surface to development station C.
At development station C, a donor roller, indicated generally by the reference numeral 30, receives insulating, non-magnetic toner particles from a toner particle supply reservoir 32. As donor roller 30 rotates, in the direction of arrow 34, toner particles are advanced therewith through a nip defined by a flexible blade 36 having the the free marginal end region thereof in contact therewith. As the toner particles pass through the nip defined by blade 36 contacting donor roller 30, the toner particles thereon are triboelectrically charged. These charged toner particles are transported by donor roller 30 to the electrostatic latent image recorded on the photoconductive surface of belt 10. The electrostatic latent image attracts the toner particles from donor roller 30 to form a powder image thereon.
In addition to triboelectrically charging the toner particles adhering to donor roller 30, blade 36 meters the quantity of toner partitles being advanced to the electrostatic latent image. As shown, one end of blade 36 is mounted fixedly with the free marginal end region thereof being pressed into contact against the exterior circumferential surface of donor roller 30.
Blade 36 is flexible. A voltage source, indicated generally by the reference numeral 38, electrically biases blade 36. Voltage source 38 applies an AC
potential and a DC potential, or an AC potential alone. Voltage source 16 ' .
.
- . . .
, - - - , - - ~ ' ~' '~
. : , ., ~ . ~, :
, - . . . ~ ,- - --.
~7 ~ 2 electrically biases donor roller 30. The AC electrical field changes the average charge level of the toner particles. .Voltage source 38 is operator adjustable. Thus, the machine operator may vary the peak to peak AC
voltage and/or the frequency to obtain the desired toner charge so as to optimize development for the type of document being printed. Further details of the system will be discussed hereinafter with reference to Figures 2 and 3.
With continued reference to Figure 1, after the electrostatic latent image is developed with toner particles, belt 10 advances the toner powder image to transfer station D. At transfer station D, a corona generating device 40 sprays ions onto the backside of copy sheet 42 positioned thereat. This attracts the toner powder image from the photoconductive surface of belt 10 to copy sheet 42. After transfer of the toner powder image to copy sheet 42, copy sheet 42 advances, in the direction of arrow 44, through fusing station E.
Fusing station E includes a heated fuser roller 46 and a back-up roller 48. The toner powder image on copy sheet 42 contacts fuser roller 46.
In this manner, the powder image is permanently affixed to copy sheet 42.
After fusing, copy sheet 42 is advanced by forwarding rollers through a chute to a catch tray where the operator removes the completed copy.
Referring now to Figure 2, the detailed structure of the development apparatus is shown thereat. The development apparatus includes a donor roller, indicated generally by the reference numeral 3û.
Donor roller 30 has a fluoropolymer coating thereon. The coating covers the entire circumferential surface thereof. Generally, the coating has a thickness ranging from about 2 micrometers to about 125 micrometers and preferably ranges from about 10 micrometers to about 50 mi~rometers.
Donor roller 30 may be made from any suitable material including, for example, aluminized Mylar coated with the fluoropolymer coating, a seamless extruded polymer sleeve coated with a polymer containing a conductive additive such as carbon black and overcoated with a fluoropolymer, or a bare electroformed nickel sleeve having a fluoropolymer coating thereover. Toner supply reservoir 32 has a supply of : ~ ` ~ ' . , .
toner particles 50 therein. The supply of toner particles 50 in reservoir 32 are weakly charged particles. Flexible blade 36 has the free end region 52 thereof contacting the surface of donor roller 30 to define a nip therebetween throug~ which the particles adhering to donor roller 30 passO In this way, as donor roller 30 rotates int he direction of arrow 34, toner particles 50 are advanced through nip 52. As the toner particles pass through the nip, the quantity of toner particles is regulated and the toner particles remaining adhering to donor roller 30 are triboelectrically charged. By way of example, blade 36 may be made from a strip of flexible steel. Donor roller 30 i-~electrically biased to a ~uitable magnitude and polarity by voltage source 16. Preferably, donor roller 30 is electrically biased from about +75 volts to about +350 volts, or from about -75 volts to about -350 volts. In this way, the toner particles adhering to donor roller 30 are electrostatically attracted to the latent image recorded on the photoconductive surface of belt 10.
Further details of a development apparatus of the type describQd herein are disclosed in U.S. ~atent No.
4,4~9,009 issued in 1984 to Hays et al. Blade 36 is electrically biased by voltage source 38 to an AC
potential and a DC potential or an AC potential alone.
Voltages and spacings to be chosen to limit the peak electric field in the nip to less than the Paschen limit for air break down. By way of example, blade 36, which i8 coated, is alectrically biased to an AC potential of 4,000 volts peak to peak at a fre~uency of 2,400 HZ and at 100 volt~ DC. Alternatively blade 36 may be electrically biased to 4,000 volts peak-to-peak at a frequency of 1,000 HZ and 0 volts DC. Alternatively, a rod may be used in lieu of a blade for charging/metering toner particles on donor roller 30.
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. . . - -: : . -. ~ -. , .
Referring now to Figure 3, there is shown a graph of the toner reproduction curve. The slope of this curve is adjustable by the operator selecting the appropriate AC bias applied on charging blade 36.
Adjusting the AC electrical bias on blade 36 changes the average charge level of the toner, thereby changing the slope of this curve. This enables printing or suppressing, as the case may be, of gray tones. By selecting the appropriate - 8a -..` ~ \.
..
' ~ . :
7 ~ 2 AC bias on charging blade 36, continuous tone or half tone pictorial images with a broad range of gray may be printed. In addition, by being able to adjust the toner charge, the toner charge may be adjusted for environmental conditions or other reasons. Furthermore, it has been found that the use of an AC bias increases the toner particle agitation in the metering/charging nip. This agitation reduces the toner size and/or charge distribution effects preventing the occurrence of history effects such as lower or higher density development.
In recapitulation, it is clear that the the developer unit of the present invention employs an electrically biased charging blade. An AC
potential is applied on the charging blade. The potential is adjustable to change the charge on the toner particles. In this way, the slope of the tone reproduction curve may be adjusted to optimize development of the latent image.
- It is, therefore, evident that there has been provided inaccordance with the present invention, a development system which satisfies the aims and advantages hereinbefore set forth. While this invention has been described in conjunction with a preferred 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.
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PATENT APPLICATION
Attorney Docket No. D/90219 DEVELOPMENT APPARATUS
This invention relates generally to an electrophotographic printing machine, and more particularly concerns a development apparatus employed therein.
In an electrophotographic printing machine, a photoconductive member is charged 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.
Exposure of the charged photoconductive member selectively dissipates the charge thereon in the irradiated area. This records an electrostatic latent image on the photoconductive member corresponding to the informational areas contained within the original document being reproduced. After the electrostatic latent image is recorded on the photoconductive member, the latent image is developed by bringing marking particles into contact therewith. This forms a powder image on the photoconductive member which is subsequently transferred to a copy sheet. The copy sheet is heated to permanently affix the marking particles thereto in image configuration.
Various types of development system have hereinbefore been employed. These systems utilize two component developer material or single component developer material. Two component developer material includes toner particles adhering triboelectrically to carrier granules. A
single component development system uses only toner particles. In many of the single component development systems, the toner particles are conductive. However, the transfer of conductive toner particles to the copy sheet is usually inefficient. In order to overcome this problem, insulating toner particles are frequently employed. When insulating toner particles are utilized, it is necessary to charge these toner particles to the correct polarity. This may be achieved by employing a flexible blade in contact ... .. . . ........... . .
, ' .. ' - ' ... : . ' -' ' ': ' , .
2 ~ t~
with a donor roller. As the donor roller transports the toner particles toward the latent image recorded on the photoconductive member, the toner particles pass through a nip defined by the flexible blade and the roll.
The toner particles passing through this nip are triboelectrically charged.
Furthermore, this nip defines the quantity of toner particles being transported on a roller to the latent image recorded on the photoconductive member.
In a printing machine, it would be advantageous to be able to print high quality pictorial and text. It is desirable to print or suppress the gray tones. Furthermore, the printing machine should also be capable of printing continuous tone or half tone pictorial images with a broader range of gray than is currently available. This is of particular significance for development systems having a very steep slope which limits the usefulness of electronic tone reproduction manipulation. In addition, it is desirable to have an operator adjustable system which enables tuning of the toner charge to compensate for environmental changes or any other changes.
The following disclosures appear to be relevant:
US-A-4,459,009 Patentee: Hays et al.
Issued: July 10,1984 US-A-4,523,833 Patentee: Jones Issued: June 18, 1954 US-A-4,619,517 Patentee: Ruhland Issued: October28,1986 US-A-4,707,115 Patentee: Bares Issued: November 17, 1987 .
., -, .
, .
. :
rJ ~ ~
The relevant portions of the foregoing disclosures may be briefly summarized as follows:
US-A-4,459,009 and US-A-4,619,517 disclose a development system having a donor roller which contacts a photoconductive surface to develop a latent image with insulating toner particles. An electrically biased charging roller meters the toner particles to the donor roller and imparts a charge thereon. A doctor blade removes wrong sign toner on tne charging roller. For a positive toner charging system, the voltage applied to the charging roller varies from about + 25 volts to about + 200 volts.
US-A-4,523,833 describes a development apparatus having a developer roller with the free end portion of a blade resiliently urged into contact therewith. The blade has a plurality of holes. A voltage source is connected to the the blade and creates an electrical field at the holes. By adjusting the level of the voltage source, the intensity of the electrical fieldin the holes is controlled, and, in turn, the quantity of marking particles passing therethrough regulated.
US-A-4,707,115 discloses a development system having a donor roller, which is electrically biased, contacts a photoconductive belt having an electrostatic latent image recorded thereon. A flexible steel blade has the free end thereof contacting the surface of the donor roller to define a nip therebetween through which the particles adhering to the donor roller pass. As the toner particles pass through the nip, the quantity of toner particles is regulated and the toner particles remaining adhering to the donor roller are triboelectrically charged.
Pursuant to the features of the present invention, there is provided an apparatus for developing a latent image with marking particles. The apparatus includes means for transporting the marking particles to the latent image. Means are provided for electrically charging the marking particles being moved to the latent image by the transporting means. Means apply an AC electrical potential on the charging means.
In accordance with another aspect of the present invention, there is provided an electrophotographic printing machine of the type ' ' ' ' , ' ' : ~ ' ' . . - , . -- ~ .
having an electrostatic latent image recorded on a photoconductive member. The improvement in the printing machine includes means for transporting toner particles to the photoconductive member to develop the latent image therewith. Means are provided for electrically charging the toner particles being moved to the latent image by the transporting means. Means apply an AC
electrical potential on the charging means.
Other aspects of this invention are as follows:
An apparatus adapted to develop a latent image with marking particles, including:
means for transporting the marking particles to the latent image;
mean~ for electrically biasing said transporting means;
means for electrically charging the marking particles being moved to the latent image by said transporting means; and operator adjustable means, connected electrically to said charging means, for applying an AC potential and a DC potential on said charging means to adjust the charge on the marking particles, said operator ad~ustable means ad~usting both the AC electrical potential and the DC electrical potential on said charging means independently of said electrical biasing means biasing said transporting means.
An electrophotographic printing machine of the type having an electro~tatic latent image recorded on a photoconductive member, wherein the improvement includes:
means for transporting toner particles to the photoconductive member to develop the latent image therewith;
mean for electrically biasing said transporting means;
- . - -.
:
- . . - .
: . - - ~ , . -: , ., means for electrically charging toner particles being moved to the latent image by said transporting means; and operator adjustable means, connected electrically to said charging means for applying an AC potential and a DC potential on said charging means to adjust the charge on the marking particles, said operator adjustable means adjusting both the AC electrical potential and the DC electrical potential on said charging means independently of said electrical biasing means biasing said transporting means.
Other aspects of the present invention will become apparent as the following description proceeds and upon reference to the drawings, in which:
Figure 1 is a schematic elevational view depicting an electrophotographic printing machine incorporating the development apparatus of the present invention therein;
Figure 2 is a schematic elevational view showing the development apparatus of the Figure 1 printing machine in greater detail; and Figure 3 is an exemplary tone reproduction curve.
While the present invention will hereinafter be described in connection with a preferred embodiment thereof, it will be understood that it i5 not intended to limit the invention to that embodiment. On the contrary, it is intended to cover all alternatives, modifications, and equivalents that may be included within the spirit and scope of the invention as defined by the appended claims.
For a general understanding of the features of the present invention, re~erence i8 made to the drawings.
In the drawlngs, like reference numerals have been used throughout to identify identical elements.
Figura 1 schematically depicts the various components of an illustrative electrophotographic - 4a -' - `:' ' ' ' :
printing machine having the development apparatus incorporating the features of the present invention therein. It will become evident from the following discussion that this development apparatus is equally well suited for use in a wide variety of electrostatographic printing machines, and is not necessarily limited in its ,! ~ , , :
.
2~4~7~
application to the particular electrophotographic printing machine shown herein.
Inasmuch as the art of electrophotographic printing is well known, the various processing stations employed in the Figure 1 printing machine will be shown hereinafter schematically and their operation described briefly with reference thereto.
As shown in Figure 1, the electrophotographic printing machine employs a belt 10 having a photoconductive surface deposited on a conductive substrate. Preferably, the photoconductive surface is made from a selenium alloy with the conductive substrate being made from an aluminum alloy. Other suitable photoconductive materials and conductive substrates may also be employed. Belt 10 is entrained about a pair of opposed, spaced rollers 12 and 14. Roller 14 is rotated by a motor coupled thereto by suitable means such as a drive belt. As roller 14 rotates, belt 10 advances the photoconductive surface, in the direction of arrow 16, through the various processing stations disposed about the path of movement thereof.
Initially, the photoconductive surface passes through charging station A. At charging station A, a corona generating device 18 charges the photoconductive surface to a relatively high, substantially uniform potential.
Next, the charged portion of the photoconductive surface is advanced through imaging station B. At imaging station B, an original document 20 is positioned face down upon a transparent platen 22.
Imaging of document 20 on platen 22 is achieved by an exposure system which includes a lamp 24, mirror 26, and moving lens 28. The exposure system is a moving optical system. The lamp, mirrors and lens rnove across the original document illuminating incremental widths thereof to form a light image. The light image is projected onto the charged portion of the photoconductive surface. One skilled in the art will appreciate that instead of a light lens optical system, a raster input scanner (RIS) in combination with a raster output scanner (ROS) may be used. The RIS captures the entire image from the original document and converts it to a series of raster scan 2 ~
lines. The RIS contains document illumination lamps, optics,a mechanical scanning mechanism, and a photosensing elerrlent, such as charge coupled device (CCD array). The ROS, responsive to the output from the RIS
performs the function of recording the electrostatic latent image on the photoconductive surface. The RIS lays out the latent image in a series of horizontal scan lines with each line having a certain nurnber of pixels per inch. The ROS may include a laser, rotating polygon mirror blocks, and an modulator. Still another type of exposure system employs only a ROS. The ROS is connected to a computer and the document desired to be printed is transmitted from the computer to the ROS. In all of the foregoing systems, the charged photoconductive surface is selectively discharged to record an electrostatic latent image thereon. Thereafter, belt 10 advances the electrostatic latent image recorded on the photoconductive surface to development station C.
At development station C, a donor roller, indicated generally by the reference numeral 30, receives insulating, non-magnetic toner particles from a toner particle supply reservoir 32. As donor roller 30 rotates, in the direction of arrow 34, toner particles are advanced therewith through a nip defined by a flexible blade 36 having the the free marginal end region thereof in contact therewith. As the toner particles pass through the nip defined by blade 36 contacting donor roller 30, the toner particles thereon are triboelectrically charged. These charged toner particles are transported by donor roller 30 to the electrostatic latent image recorded on the photoconductive surface of belt 10. The electrostatic latent image attracts the toner particles from donor roller 30 to form a powder image thereon.
In addition to triboelectrically charging the toner particles adhering to donor roller 30, blade 36 meters the quantity of toner partitles being advanced to the electrostatic latent image. As shown, one end of blade 36 is mounted fixedly with the free marginal end region thereof being pressed into contact against the exterior circumferential surface of donor roller 30.
Blade 36 is flexible. A voltage source, indicated generally by the reference numeral 38, electrically biases blade 36. Voltage source 38 applies an AC
potential and a DC potential, or an AC potential alone. Voltage source 16 ' .
.
- . . .
, - - - , - - ~ ' ~' '~
. : , ., ~ . ~, :
, - . . . ~ ,- - --.
~7 ~ 2 electrically biases donor roller 30. The AC electrical field changes the average charge level of the toner particles. .Voltage source 38 is operator adjustable. Thus, the machine operator may vary the peak to peak AC
voltage and/or the frequency to obtain the desired toner charge so as to optimize development for the type of document being printed. Further details of the system will be discussed hereinafter with reference to Figures 2 and 3.
With continued reference to Figure 1, after the electrostatic latent image is developed with toner particles, belt 10 advances the toner powder image to transfer station D. At transfer station D, a corona generating device 40 sprays ions onto the backside of copy sheet 42 positioned thereat. This attracts the toner powder image from the photoconductive surface of belt 10 to copy sheet 42. After transfer of the toner powder image to copy sheet 42, copy sheet 42 advances, in the direction of arrow 44, through fusing station E.
Fusing station E includes a heated fuser roller 46 and a back-up roller 48. The toner powder image on copy sheet 42 contacts fuser roller 46.
In this manner, the powder image is permanently affixed to copy sheet 42.
After fusing, copy sheet 42 is advanced by forwarding rollers through a chute to a catch tray where the operator removes the completed copy.
Referring now to Figure 2, the detailed structure of the development apparatus is shown thereat. The development apparatus includes a donor roller, indicated generally by the reference numeral 3û.
Donor roller 30 has a fluoropolymer coating thereon. The coating covers the entire circumferential surface thereof. Generally, the coating has a thickness ranging from about 2 micrometers to about 125 micrometers and preferably ranges from about 10 micrometers to about 50 mi~rometers.
Donor roller 30 may be made from any suitable material including, for example, aluminized Mylar coated with the fluoropolymer coating, a seamless extruded polymer sleeve coated with a polymer containing a conductive additive such as carbon black and overcoated with a fluoropolymer, or a bare electroformed nickel sleeve having a fluoropolymer coating thereover. Toner supply reservoir 32 has a supply of : ~ ` ~ ' . , .
toner particles 50 therein. The supply of toner particles 50 in reservoir 32 are weakly charged particles. Flexible blade 36 has the free end region 52 thereof contacting the surface of donor roller 30 to define a nip therebetween throug~ which the particles adhering to donor roller 30 passO In this way, as donor roller 30 rotates int he direction of arrow 34, toner particles 50 are advanced through nip 52. As the toner particles pass through the nip, the quantity of toner particles is regulated and the toner particles remaining adhering to donor roller 30 are triboelectrically charged. By way of example, blade 36 may be made from a strip of flexible steel. Donor roller 30 i-~electrically biased to a ~uitable magnitude and polarity by voltage source 16. Preferably, donor roller 30 is electrically biased from about +75 volts to about +350 volts, or from about -75 volts to about -350 volts. In this way, the toner particles adhering to donor roller 30 are electrostatically attracted to the latent image recorded on the photoconductive surface of belt 10.
Further details of a development apparatus of the type describQd herein are disclosed in U.S. ~atent No.
4,4~9,009 issued in 1984 to Hays et al. Blade 36 is electrically biased by voltage source 38 to an AC
potential and a DC potential or an AC potential alone.
Voltages and spacings to be chosen to limit the peak electric field in the nip to less than the Paschen limit for air break down. By way of example, blade 36, which i8 coated, is alectrically biased to an AC potential of 4,000 volts peak to peak at a fre~uency of 2,400 HZ and at 100 volt~ DC. Alternatively blade 36 may be electrically biased to 4,000 volts peak-to-peak at a frequency of 1,000 HZ and 0 volts DC. Alternatively, a rod may be used in lieu of a blade for charging/metering toner particles on donor roller 30.
~.
,. : . . :
: . .
.. . .
. . . - -: : . -. ~ -. , .
Referring now to Figure 3, there is shown a graph of the toner reproduction curve. The slope of this curve is adjustable by the operator selecting the appropriate AC bias applied on charging blade 36.
Adjusting the AC electrical bias on blade 36 changes the average charge level of the toner, thereby changing the slope of this curve. This enables printing or suppressing, as the case may be, of gray tones. By selecting the appropriate - 8a -..` ~ \.
..
' ~ . :
7 ~ 2 AC bias on charging blade 36, continuous tone or half tone pictorial images with a broad range of gray may be printed. In addition, by being able to adjust the toner charge, the toner charge may be adjusted for environmental conditions or other reasons. Furthermore, it has been found that the use of an AC bias increases the toner particle agitation in the metering/charging nip. This agitation reduces the toner size and/or charge distribution effects preventing the occurrence of history effects such as lower or higher density development.
In recapitulation, it is clear that the the developer unit of the present invention employs an electrically biased charging blade. An AC
potential is applied on the charging blade. The potential is adjustable to change the charge on the toner particles. In this way, the slope of the tone reproduction curve may be adjusted to optimize development of the latent image.
- It is, therefore, evident that there has been provided inaccordance with the present invention, a development system which satisfies the aims and advantages hereinbefore set forth. While this invention has been described in conjunction with a preferred 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.
., .
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.
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: :
. . : -.:
- ,. .. .
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.. : . . . '. .'. ~ , ' ~ ' -. , . : .,, . ~ .. .. ..
Claims (8)
1. An apparatus adapted to develop a latent image with marking particles, including:
means for transporting the marking particles to the latent image;
means for electrically biasing said transporting means;
means for electrically charging the marking particles being moved to the latent image by said transporting means; and operator adjustable means, connected electrically to said charging means, for applying an AC potential and a DC potential on said charging means to adjust the charge on the marking particles, said operator adjustable means adjusting both the AC electrical potential and the DC electrical potential on said charging means independently of said electrical biasing means biasing said transporting means.
means for transporting the marking particles to the latent image;
means for electrically biasing said transporting means;
means for electrically charging the marking particles being moved to the latent image by said transporting means; and operator adjustable means, connected electrically to said charging means, for applying an AC potential and a DC potential on said charging means to adjust the charge on the marking particles, said operator adjustable means adjusting both the AC electrical potential and the DC electrical potential on said charging means independently of said electrical biasing means biasing said transporting means.
2. An apparatus according to Claim 1, wherein said transporting means includes a donor roller.
3. An apparatus according to Claim 2, wherein said charging means includes a blade having free marginal end region contacting said donor roller to define a nip through which the marking particles pass.
4. An apparatus according to Claim 1, wherein said charging means meters the quantity of marking particles being moved by said donor roller to the latent image.
5. An electrophotographic printing machine of the type having an electrostatic latent image recorded on a photoconductive member, wherein the improvement includes:
means for transporting toner particles to the photoconductive member to develop the latent image therewith;
means for electrically biasing said transporting means;
means for electrically charging toner particles being moved to the latent image by said transporting means; and operator adjustable means, connected electrically to said charging means for applying an AC potential and a DC potential on said charging means to adjust the charge on the marking particles, said operator adjustable means adjusting both the AC electrical potential and the DC electrical potential on said charging means independently of said electrical biasing means biasing said transporting means.
means for transporting toner particles to the photoconductive member to develop the latent image therewith;
means for electrically biasing said transporting means;
means for electrically charging toner particles being moved to the latent image by said transporting means; and operator adjustable means, connected electrically to said charging means for applying an AC potential and a DC potential on said charging means to adjust the charge on the marking particles, said operator adjustable means adjusting both the AC electrical potential and the DC electrical potential on said charging means independently of said electrical biasing means biasing said transporting means.
6. A printing machine according to Claim 5 wherein said transporting means includes a donor roller.
7. A printing machine according to Claim 6, wherein said changing means includes a blade having free marginal end region contacting said donor roller to define a nip through which the marking particles pass.
8. A printing machine according to Claim 5, wherein said charging means meters the quantity of marking particles being moved by said donor roller to the latent image.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US60108890A | 1990-10-22 | 1990-10-22 | |
| US601088 | 1990-10-22 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2049742A1 true CA2049742A1 (en) | 1992-04-23 |
Family
ID=24406180
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2049742 Abandoned CA2049742A1 (en) | 1990-10-22 | 1991-08-23 | Development apparatus |
Country Status (3)
| Country | Link |
|---|---|
| EP (1) | EP0482867A3 (en) |
| JP (1) | JPH04260074A (en) |
| CA (1) | CA2049742A1 (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0577077B1 (en) * | 1992-06-30 | 1998-09-09 | Sharp Kabushiki Kaisha | Developing device and method |
| US5307124A (en) * | 1992-11-20 | 1994-04-26 | Eastman Kodak Company | Development method and apparatus including toner pre-charging capability |
| JPH08220875A (en) * | 1995-02-20 | 1996-08-30 | Tec Corp | Developing device |
| DE19819390A1 (en) * | 1997-07-03 | 1999-01-07 | Heidelberger Druckmasch Ag | Developing electrostatic latent image on image carrier with single component insulative toner |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS53113551A (en) * | 1977-03-15 | 1978-10-04 | Fuji Photo Film Co Ltd | Developing device |
| JPS5543562A (en) * | 1978-09-22 | 1980-03-27 | Ricoh Co Ltd | Developing method |
| JPS58129445A (en) * | 1982-01-28 | 1983-08-02 | Toshiba Corp | Copying device |
| JPS59220771A (en) * | 1983-05-31 | 1984-12-12 | Canon Inc | Combination copying machine and printer |
| JPS60103371A (en) * | 1983-11-11 | 1985-06-07 | Fuji Xerox Co Ltd | Developing device of electrophotographic copying machine |
| US4707115A (en) * | 1986-08-28 | 1987-11-17 | Xerox Corporation | Device for cleaning a charging member |
| JPH01144075A (en) * | 1987-11-30 | 1989-06-06 | Mita Ind Co Ltd | Developing device |
-
1991
- 1991-08-23 CA CA 2049742 patent/CA2049742A1/en not_active Abandoned
- 1991-10-15 JP JP3266430A patent/JPH04260074A/en active Pending
- 1991-10-21 EP EP19910309719 patent/EP0482867A3/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| EP0482867A3 (en) | 1992-11-19 |
| JPH04260074A (en) | 1992-09-16 |
| EP0482867A2 (en) | 1992-04-29 |
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| Date | Code | Title | Description |
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| EEER | Examination request | ||
| FZDE | Dead |